2024 IITC Conference Program

TUESDAY, JUNE 4, 2024

Session 1: Conference Kick-off, Awards Program & Keynote
Chair: Zhihong Chen (Purdue University)

8:15 – 8:25
Welcome
Zhihong Chen – Purdue

8:25 – 8:35
Award Program – Best Papers 2023
Chairs: Zhihong Chen (Purdue University) & Stefan Schulz (TU Chemnitz)

8:35 – 9:25
Keynote – Technology Innovations to Fuel 1T Transistors

Hemanth Jagannathan – IBM

Artificial intelligence (AI) is transforming our world and the demand for computing capability is increasing at an unprecedented pace. Here we will talk about semiconductor technology innovations in logic, memory, and advanced packaging to meet this ever-growing demand in the era of AI. Transistor architecture breakthroughs and integrated circuits interconnects innovations have enabled tens of billions of transistors onto a chip the size of a fingernail. In addition, chiplet and advanced packaging technology will help accelerate technology and design innovation to integrate over 1 trillion transistors onto a single package before the end of 2030. By Increasing the number of transistors on a single package, we can make AI hardware more powerful and more energy efficient.

9:25 – 9:45 Coffee Break

Session 2: Advanced Interconnects I

Chairs: Paul Besser (Entegris) & Tatsuya Usami (Rapidus)

9:45 – 10:15

2.1 Advanced interconnect capacitance and interface engineering beyond 1.4nm Logic Devices (Invited)

Kang Sub Yim, Jong Min Baek, Hoon Seok Seo – Samsung Electronics

As device miniaturization progresses, the importance of parasitic capacitance and resistance of interconnects in logic devices is increasing in terms of performance and low-power product implementation. In recent devices below 1.4 nanometers, not only the intrinsic properties of the materials but also the interface characteristics have a significant impact on the overall interconnect performance, so specialized engineering is required. In this study, we improved resistance and capacitance through material and process development in a direction that improves interface characteristics, and secured results that improve reliability.

10:15 – 10:45

2.2 Breaking Barriers: Innovations in MOL and BEOL Interconnects for Advanced Semiconductor Technology (Invited)

Gaurav Thareja – Applied Materials

10:45 – 11:05

2.3 Airgap Integration in MP18 Two-Level Semi-damascene Interconnects with Fully Self-aligned Vias

Gilles Delie, Gayle Murdoch, Giulio Marti, Anshul Gupta, Chen Wu, Alicja Lesniewska, Anton Gavrilov, Ivan Ciofi, Souvik Kundu, Stefan Decoster, Seongho Park, Zsolt Tokei – IMEC

Airgap integration in 18 to 26 nm metal pitch (MP) two-metal level semi-damascene interconnects with fully self-aligned vias (FSAV) on 300 mm wafers is reported. The first metal layer (Mx) is patterned using EUV-SADP with subsequent direct metal etch of the Ru film. Airgap is integrated at a targeted height of 4-6 nm below the top metal lines allowing for FSAV compatibility. 80% of kelvin vias landing on Mx at MP18 meet the <50 ohm resistance target specification and 40% of them meet the via-to-line leakage target of <100 pA. The airgap line-to-line capacitance is found to be 40% lower compared to the dielectric gap fill reference.

11:05 – 11:25

2.4 Process Control for the Modification of Ruthenium Resistivity in Scaled Subtractive Interconnects

Jack Rogers, Hirokazu Aizawa, Nicholas Joy, Rinus Lee, Kenichi Imakita, Hojin Kim, Toru Hisamatsu – TEL Technology Center, America, LLC

For advanced interconnect nodes, finding a new low-resistivity, barrier-independent material to replace copper becomes critical as pitch scaling reaches less than 20nm due to the poor scaling of barrier/liner films necessary for copper metallization leading to increased resistivity. Materials like ruthenium are promising replacement interconnects since they can be barrier-less and have good electrical properties at narrow wire dimensions. However, ruthenium film properties can vary depending on the underlayer and film deposition conditions. Optimization of the ruthenium deposition process is therefore necessary to provide a sufficient advantage over copper.  Film grain size and orientation both impact resistivity, and the modification of these parameters is discussed and presented in this report.

11:25– 11:45

2.5 Interface engineering for performance and reliability boosting of logic devices

Jong Min Baek, Suhyun Bark, Yeonggil Kim, Minchul Ahn, Geun Tae Yun, Deokyoung Jung, Hoon Seok Seo, Sungsoo Kim, Kyuhee Han, Youngwoo Cho, EunJi Jung, Taehong Ha, Kang Sub Yim, Sunjung Kim – Samsung Electronics

As the width of interconnects decreases, it is getting more crucial to figure out and handle interfacial phenomena, which is called as interface engineering, to ensure device performance and reliability. In this study, we investigated various interactions among metal to metal and metal to dielectric interfaces in interconnect structure with regard to electrical characteristics related to resistance, capacitance, and reliability. As a result, it enabled to improve in resistance by ~30% and capacitance by ~5% via recently developed and optimized process conditions in sub-2nm logic devices.

11:45- 12:05

2.6 Ion Beam Deposition of Epitaxial 0001 In-Plane and Out-of-Plane Low-Resistivity Ruthenium for Interconnect Applications

Rutvik J. Mehta, Yuejing Wang, Frank Cerio, Robert Caldwell, Christopher J. Jezewski, I-Cheng Tung, Jimmy Wang, Matthew V. Metz – Veeco Instruments, Inc., Intel Corporation

Ruthenium with favorable resistivity scaling effects is a promising candidate for nanometer scale interconnects. An anisotropic transport phenomenon results in a predicted orientation dependence for ruthenium with resistivity perpendicular to the basal 0001 planes expected to be significantly lower than along the basal planes, but such films are challenging to deposit. We report the first deposition of epitaxial [0001] in-plane ruthenium thin films using a Veeco IBD300™ Ion beam deposition (IBD) tool. IBD with the highest sputter energy and fine-scale control of deposition energetics enables ideal microstructures for metal thin films. IBD of ruthenium achieve epitaxial [0001] in-plane and out-of-plane thin films in the as-deposited state with back-end-of-the-line (BEOL) compatible thermal budget. Electrical measurements of the as-deposited IBD ruthenium thin films shows ultra-low-resistivity and attractive thickness scaling. These results establish the combination of ion beam deposition and ruthenium as a promising approach for the next generation of integrated device interconnects.

12:05 – 1:20 Lunch

Session 3: Reliability & Failure Analysis
Chairs: Kuan-Neng Chen (National Yang Ming Chiao Tung University) & Munehiro Tada (Keio University)

1:20– 1:40

3.1 Intrinsic Reliability of High Capacitance Density Topographic MIM

Christopher Perini, James Palmer, Shahriar Imam, Neena Gilda, Che-yun Lin, Rahim Kasim, James Waldemer, Chris Pelto – Intel Corporation

Addressing the ever-increasing demand for efficient power integrity requirements necessitated the advent of on-die decoupling capacitors. These capacitors provide high dynamic current throughout switching workloads and reduce power supply droop during microprocessor operation. In this paper, we demonstrate a high reliability Metal-Insulator-Metal (MIM) decoupling capacitor on patterned topography with best-in-class capacitance density, implementable in a standard BEOL stack. Conduction behavior through the HiK dielectric is investigated along with complete characterization of Time Dependent Dielectric Breakdown (TDDB). The MIM capacitor reliability exhibits an intrinsic lifetime of >10 years at 1.32 V operation at 125oC. In addition, this process demonstrates excellent low extrinsic defect density and meets standard JEDEC environmental Reliability requirements. The combination of high capacitance and robust reliability of the integrated topographic MIM process significantly enhances the efficiency of on-chip power delivery and protects against power supply noise.

1:40– 2:00

3.2 Investigation of Cu barrier properties of 1-nm-thick PVD-Co(W) films as a single liner/barrier in next-generation ULSI-Cu interconnect

Yubin Deng, Takeshi Momose, Yukihiro Shimogaki – University of Tokyo

In this study, a quantitative evaluation of Cu barrier properties with different thicknesses and compositions of ultrathin physical vapor deposited (PVD) Co(W) films was conducted through a comprehensive analysis using the modified time-lag method. Compared to the 20-nm-thick PVD-Co(W) films, which crystallized after annealing, the PVD-Co(W) films with 1~3-nm-thickness remained amorphous and exhibited enhanced barrier properties. The amorphous structure of the thinner films improved the barrier properties by eliminating the grain boundaries as the primary diffusion path for Cu atoms. More importantly, a 1-nm-thick PVD-Co(W) film with a W composition of 35 at. % exhibited exceptional Cu diffusion barrier properties, surpassing other compositions. This superior performance can be attributed to the high thermal stability that preserves the amorphous structure and overall integrity of the film, resulting from the optimal atom packing. This film also displayed the lowest Cu diffusivity (D) and highest activation energy (Ea = 2.5 eV) among all the investigated barrier candidates. In addition, ultrathin PVD-Co(W) films can function effectively as both a barrier against Cu diffusion and an oxygen diffusion block, underscoring their application superiority to Cu interconnects in next-generation ultra-large-scale integration (ULSI) devices. 

2:00– 2:20

3.3 Assessing Impact of Non-Uniform Localized Heating on Reliability

Yoon Jo Kim, Edwin B. Ramayya, Lei Jiang, Jason Jopling, Rahim, Kasim – Intel Corporation

Moore’s Law-driven technology improvements have led to a significant increase in power density across a multitude of market segments, from mobile to HEDT (high-end desktop) and servers. This, in turn, has led to an increase in both spatial and temporal thermal non-uniformity across the chip. In this paper, thermally-induced reliability risks due to localized heating (thermomigration and thermal fatigue) were experimentally investigated. Novel test structures as well as experiments were devised to assess these risks. Thermomigration risks were demonstrated to be low at power densities up to 370C/µm. The assessment of local thermal fatigue risks for contact- M4 layers indicated that they exhibited no failures through up to 10 billion thermal cycles, within peak temperature ranges of 220°C to 280°C.

2:30– 2:40

3.4 Highly Reliable Ruthenium-Cobalt Binary Liner for Advanced Node Cu interconnect

Gyuho Myeong, Junki Jang, Kihyun Kim, Jaeho Lee, Eunyoung Park, Hoyun Jeon, Kyounghee Nam, Eunji Jang, Chin Kim, Doowhan Park, Rak-Hwan Kim, Jeonghoon Ahn and Jongho Lee – Samsung Electronics

In this paper, alternative Ruthenium-Cobalt Binary Liner (RCBL) instead of conventional Co liner with atomic layer deposition (ALD) TaN barrier metal was studied. ab initio simulation shows Co liner has various phases with different Cu wettability and its phase ratio with high wettability increases with Ru substrate rather than Ta substrate. Additionally, adhesion between barrier metal and liner increases in RCBL as lattice mismatch decreases. As a result reduction in 87% of Cu void and 14% of line resistance were achieved in relatively thin RCBL with high Cu wettability compared to conventional Co liner process. Manufacturability and reliability of RCBL process were also confirmed with logic chip yield and time dependent dielectric breakdown (TDDB) measurement of foundry product for advanced node.

2:40– 3:00

3.5 Impact of ESD Events on TSV Liner Reliability

Emmanuel Chery, Michele Stucchi, Stefan, Van Huylenbroeck, Eric Beyne – IMEC

In this work, 0.7µm via-last TSV arrays were pre-stressed with a series of ten 60 V ESD pulses. Their liner reliability performances were subsequently investigated though voltage ramp stresses with various ramp rates to assess the impact of the ESD pre-stress on the dielectric properties. The breakdown voltage and leakage current of pre-stressed structures is unaffected by the ESD events.

3:00 – 3:20 Coffee Break

Session 4: Metrology & BEOL Integration
Chairs: Mark Zaleski (Micron) & John Zhu (Qualcomm)

3:20– 3:50

4.1 Resolving nanoscale composition fluctuations and defects in advanced interconnects: a crucial step to comprehend thin film resistivity (Invited)

Claudia Fleischmann – IMEC

With the introduction of new materials in the interconnect domain, we need to screen and control a broader range of material properties down to the (sub)nanometer length scale to realize low resistivity. This work will demonstrate how we can leverage Atom Probe Tomography and Positron Annihilation Spectroscopy for that purpose, as these methods allow to measure the spatially resolved composition and to identify point defects, respectively. The potential of each method will be highlighted by curated application examples, complemented with a brief introduction of each technique.

3:50– 4:10

4.2 Advanced Black Diamond® for <2nm BEOL Low k Integration

Bo Xie, Rui, Lu, Orlando Trejo, Akansha Singh, Michael Haverty, Lauren Bagby, Kent Zhao, Lakmal Kalutarage, Monika Jamieson, Chi-I Lang, Chandru Ramalingam, Li-Qun Xia – Applied Materials

The scaling of <2nm technology node is extremely challenging.  It demands a robust low k for BEOL integration due to the reduced cross-sectional area of metal wires which increases the resistance-capacitance (RC) of BEOL interconnects. Realizing this aggressive pitch is challenged by variability and mechanical stability issues and an increasing process flow complexity. The electrical and mechanical property requirements of low k dielectrics are crucial though to enable a variety of new process innovations, scaling boosts, and new conductors for interconnect scaling.

4:10– 4:30

4.3 Low-Resistivity Subtractive-Etched W Lines and Highly Reliable High Aspect Ratio Fully Self-Aligned Vias for 3D Flash Memory

Mitsuhiko Noda, Genki Sawada, Seiya Hirano, Sota Araki, Atsushi Rikukawa, Yusuke Goki, Katsumi Yamamoto, Toshiyuki Sasaki, Daichi Nishikawa, Toshiyuki Morita, Masayoshi Tagami, Norio Ohtani, Masaru Kito – Kioxia Corporation

A novel process integration of low-resistivity subtractive-etched tungsten (W) interconnect and high aspect ratio fully self-aligned vias (HAR-FSAV) have been developed for 3D flash memory. The low-resistivity W line is achieved through surface treatment after the subtractive etching process. The HAR-FSAV is constructed by introducing a stacked interlayer dielectric structure and optimizing upper via etching condition. These technologies are promising for shrinking the interconnects of 3D flash memory in the future.

4:30– 4:50

4.4 A novel single damascene process for via metal corrosion-free interconnects in advanced nodes

Koichi Motoyama, Dominik Metzler, Jennifer Church, Hosadurga Shobha, Haojun Zhang, Huai Huang, Kisik Choi – IBM Research

Via metal corrosion during via CMP is one of the major process challenges for S/D (single damascene) interconnects. Thus, the detailed mechanism of via metal corrosion during via CMP have been investigated and a novel via process has been proposed to demonstrate via metal corrosion-free S/D interconnects. The via metal corrosion-free S/D interconnect could achieve improved viachain yield and enhanced EM (electromigration) performance compared to D/D (dual damascene) interconnect due to an ideal via profile and better Cu fill capability.

WEDNESDAY, JUNE 5, 2024

Session 5: Keynote
Chair: Nick Lanzillo (IBM)

8:15 – 9:05
Keynote – Materials Challenges for the Semiconductor Industry

Dr. James O’Neill – Entegris

Session 6: Advanced Interconnects II
Chair: Kang Sub Yim (Samsung)

9:05 – 9:35
6.1 Advanced Logic Interconnect:  Challenges and Potential Solutions (Invited)

Harsono Simka – Samsung Electronics

9:35 – 9:55
6.2 A Rapid Process for Vapor-deposited MOF as low-k dielectrics seamless gap fill for M1 and M2 Interconnects

Dipayan Pal; Naeun Yang, Harsono Simka, Andrew Kummel – UC San Diego, Samsung Electronics

A rapid novel process of vapor phase ZIF-8 MOF deposition is reported with commercially viable process time (15 min only) at 160C CVD temperature. This is the fastest reported vapor process to form a MOF film, and it was enabled by the high processing temperature and a low background H2O environment. Both high aspect ratio gap fill and multiple aspect ratio gap fill were demonstrated; this is the first report of multiple aspect ratio gap fill with no residual ZnO remaining. Parallel plate capacitors were fabricated, and k value was estimated to be ~2.6, and the devices were stable over months. Applications can be found in BEOL, FEOL device fabrication, packaging, and three-dimensional heterogeneous integration (3DHI).

9:55 – 10:15
6.3 Exploration of Barrier Materials for Cu2Mg/SiO2 and resistivity scaling of twinned Cu2Mg (Student Paper)

Toshihiro Kuge, Masaya Iwabuchi, Mansour Moinpour, Ravi Kanjolia, Masataka Yahagi, Junichi Koike – Tohoku University, EMD Electronics

Cu2Mg shows a slow resistivity increase with decreasing film thickness below 10 nm. However, Mg has a strong tendency to react with dielectric oxide and degrade the property of the interconnect structure. This work explored a barrier material to prevent the reaction and to find a reason to maintain a low resistivity below the film thickness of less than 10 nm. The results showed a good barrier property of 1nm Mo, 2nm Ru, and 2 nm Y2O3, which agreed well with thermodynamic calculation. The good resistivity scalability was attributed to easy twinning tendency in a C15 cubic Laves phase.

10:15 – 10:35 Coffee Break

Session 7: Materials & Unit Process I
Chairs: Soo-Hyun Kim (Ulsan National Institute of Science and Technology) & Benjamin Lilienthal-Uhlig (Fraunhofer)

10:35 – 11:05
7.1 Atomic Layer Deposition of Molybdenum for barrierless metallization of Vias and Lines (Invited)

Jans Willem Maes – ASM

To keep increasing integrated circuit density the pitch of interconnects must reduce further. To achieve this, metals with a low resistivity and high melting point are preferred that do not require any diffusion barriers or liners for adhesion or for film nucleation. In recent years, Atomic Layer Deposition (ALD) processes have been developed that enabled to explore the use of Molybdenum for various types of interconnects. In this work we will discuss various of these studies. The combined results show that ALD deposited Molybdenum is a very promising solution for barrierless metallization of scaled vias and lines.

Void free filling of 20 nm wide high aspect ratio trenches in SiO2 was shown using a conformal ALD deposition process [Gupta; 1, 2]. Adhesion of Molybdenum deposited directly on SiO2 was studied by 4-point bending and was found strong enough for successful CMP without using any liner [Hosseini; 3]. TCR measurements on the Molybdenum lines indicated an effective resistivity of ~11 uOhmcm without applying post metal anneals. Adding anneals resulted in further grain growth, reduction of resistivity and elimination of the seam without observing delamination issues. Molybdenum vias on top of the lines showed a via resistance matching the value predicted from device modeling, indicative of successful preclean and filling of the via.

Bottom-up deposition provides seam-free filling and potentially larger grain size. Using an area selective ALD approach 10.5 nm CD vias in dual damascene structures in low-k were filled successfully with Molybdenum [van der Veen, 4]. Via resistance was in the range expected from modeling. Reliability studies on barrierless Molybdenum films in planar capacitor structures demonstrate the absence of Molybdenum drift into various dielectric at relevant stressing conditions [3]. Electromigration studies at elevated temperature show a robust behavior of Molybdenum interconnects at high currents [2, 4].

Acknowledgement: We thank A. Gupta, M. Hosseini, M.H. van der Veen, all from imec.

References, all from joint imec-asm work: [1] A. Gupta et.al., IEDM 2021, p 22.5.1-22.5.4; [2] A. Gupta et.al., IITC 2022, p 58-60; [3] M. Hosseini et.el., IITC 2022, p 145-147; [4] M.H. van der Veen et.al. IITC 2023, p 1-3.

11:05 – 11:35
7.2 Interconnects Patterning: Novel Innovations and Challenges (Invited)

Florian Gstrein – Intel

11:35 – 11:55
7.3 Two Metal Level Semi-Damascene Interconnects for Superconducting Digital Logic

Sara Iraci, Ankit Pokhrel, Daniel Perez Lozano, Jean-Philippe Soulie, Sujan Kumar Sarkar, Rajendra Kumar Saroj, Yann Canvel, Vincent Renaud, amey walke, Bart Kenens, Blake Hodges, Seifallah Ibrahim, Trent Josephsen, Benjamin Huet, Gayle Murdoch, Min-Soo Kim, Sabine O’Neal, Quentin Herr, Anna Herr, Zsolt Tőkei – IMEC

In this paper we present a superconducting two-metal level (2ML) BEOL unit process based on NbxTi(1-x)N (NbTiN) that was developed in imec’s 300 mm pilot line using a semi-damascene flow and 193i lithography. The unit process features direct-metal-etch wires with minimum critical dimension (CD) of 50 nm and shallow planarized vias with minimum CD of 80 nm deposited at 420 C, compatible with CMOS BEOL dielectrics. Normalized line resistance of 50 nm NbTiN wires show that 95% of the devices meet the expected resistance 800-1200 Ω/µm consistent with blanket films resistivity. Low temperature measurements show that NbTiN wires and vias have a critical temperature of 12-13.5 K and a critical current density of 80-113mA/µm2.

11:55 – 12:15
7.4 Barrier-Less W Metallization Processes for Low-Resistance Contacts at Sub-3 nm Logic Devices

Seongdong Lim, Seongheum Choi, Jeongik Kim, Byungchul Kang, Daeun Kim, Yeji Song, Donghyun Kim, Sanghoon Uhm, Chunghwan Shin, Taehong Ha – Samsung Electronics

The low-resistance of middle of line (MOL) contacts has been highlighted as critical for high-performance logic devices. Tungsten (W) has been widely used in MOL, but the relevantly required barrier materials (e.g. TiN) prevented achieving low resistance contacts as the dimension shrinks down. The replacement of high resistance barrier by an enhanced PVD W technology with an excellent step coverage allowed barrier-less W process, but a limited gap-fill performance of PVD W alone is still challenging for ultra-high aspect ratio contacts at sub-3 nm logic devices. In this study, a novel fabrication route of low-resistance barrier-less W contacts has been freshly demonstrated by reinforcing the combination of PVD W and CVD W with an adoption of nucleation process. The result of ASTAR TEM analysis exhibits a single crystallographic orientation in each contact, which is desirable for the low resistivity and reliability. Furthermore, the nucleation-assisted barrier-less W shows dramatically reduced contact resistance compared to the conventional W metallization with barrier, which resulted in significant gain of AC performance in logic devices. The suggested barrier-less W metallization process is strongly believed to be more efficiently applicable to high-performance sub-3 nm logic devices.

12:15 – 1:30 Lunch

Session 8: Contacts to CMOS Devices & Novel/Emerging Technologies
Chair: Philippe Rodriguez (CEA-Leti) & Todd Ryan (Intel)

1:30 – 2:00
8.1 Programmable Optics Based on Copper Interconnects for Lidar, Communications, Optical Computing, and Beyond (Invited)

Gleb Akselrod – Lumotive

Light Control Metasurface (LCMTM) devices using Cu pillars as resonators have been successfully developed and commercialized for the first time for solid-state optical beam steering in 3D sensing applications. In contrast to conventional Cu interconnect applications in logic or memory devices where Cu is used because of its low resistivity and great electromigration performance, Cu is chosen as the pillar material in the LCMTM device thanks to its excellent optical properties. The Cu pillars are fabricated using conventional Cu damascene processes followed by patented integration scheme to remove the dielectric material between Cu lines. The solid-state beam steering is achieved by applying different voltage patterns to the Cu pillars without any mechanical moving parts, leading to superior reliability performance. The LCMTM device can generate a wide field of view (FOV) beam steering larger than 160o. The beam can be steered from one direction to another direction within microseconds. The unique capability of the LCM device combined with low costs of the fabrication process make it a leading candidate for 3D sensing lidar applications. Furthermore, the LCMTM device has the potential in a wide range of new applications such as optical communications, computing, and beyond.

2:00 – 2:30
8.2 BEOL based memristive devices and circuits for energy efficient artificial neural networks (Invited)

Sven Zimmerman – Fraunhofer ENAS

2:30 – 2:50
8.3 Front-side Integration of Middle-of-line Stacked Contacts for Monolithic CFET

Victor Vega Gonzalez, Karen Stiers, Cassie Sheng, Steven Demuynck, Camila Toledo de Carvalho Cavalcante, Lucas Petersen Barbosa Lima, Thomas Chiarella, Juergen Boemmels, Tanushree Sarkar, Nathali Franchina Vergel, Dunja Radisic, Roger Loo, erik rosseel, Clement Porret, Geert Mannaert, Subhobroto Choudhury, Vincent Brissonneau, Emmanuel Dupuy, Anthony Peter, Nicolas Jourdan, Jean-Philippe Soulie, Takahiro Hakamata, Ainhoa Romo Negreira, Robert Clark, Kevin vandersmissen, Farid Sebaai, Pallavi Puttarame Gowda, Ju Geng Lai, Sunil Kumar Sanjeevi, Andrea Mingardi, Chan BT, Alfonso Sepulveda Marquez, Robert Langer, Il Gyo Koo, Efrain Altamirano Sanchez, katia devriendt, Paulina Rincon Delgadillo, Frederic Lazzarino, jerome mitard, Jef Geypen, Dmitry Batuk, Yi Fan Chen, Frederik Verbeek, Frank Holsteyns, Sujith Subramanian, Zsolt Tokei, Naoto Horiguchi, Serge Biesemans – IMEC

Complementary FET (CFET) is a device where n- and p-MOS transistors are stacked. In consequence, the source and drain metal contacts also need to be stacked. In this work, we investigate the high aspect-ratio (AR) patterning and metallization required for the formation of metal contacts in the monolithic CFET integration. The bottom contact is processed first by patterning deep trenches in between gates with AR > 13, CD = 17 nm and with a pitch of 60 nm. Subsequently, these high AR trenches are metalized, polished, and etched back. Afterwards, proper dielectric isolation needs to be in place before building the top contact. Finally, routing vias and the first BEOL layer are implemented all through the front side of the wafer for electrical tests.

2:50 – 3:10
8.4 200nm-pitched, Superconducting Nb Interconnects for Cryo-CMOS Application

Noriyuki Iguchi, Hideaki Numata, Masamitsu Tanaka, Koichiro Okamoto, Takahisa Tanaka, Ken Uchida, Hiroki Ishikuro, Toshitsugu Sakamoto, Munehiro Tada – NanoBridge Semiconductor, Inc., Nagoya University, The University of Tokyo, Keio University

A 200nm-pitched, superconducting niobium (Nb) interconnects with TiN protecting layer are fabricated on a 300-mm wafer for cryo-CMOS used in Quantum State Controller (QSC) application. The developed Nb interconnects show superior superconductivity with a Tc of 7.8 K and a record-high Jc of 64MA/cm2 at 4.2 K, which is high enough to local interconnects used in a cryo-CMOS circuit. For the first time, the SPICE simulation, using a 65nm-node cryogenic (4K) PDK with a technology file including Nb superconducting interconnects, estimates 40% improvement in signal delay in a typical use case. This result indicates that a cryogenic CMOS operation power can be reduced by the superconducting interconnects, as the operating voltage can be lowered while maintaining the same operation speed as that with the Cu interconnects.

3:10 – 3:30
8.5 Fabrication of Superconducting Nb Airbridges in a 300 mm Pilot Line for Quantum Technologies

Danny Wan, Massimo Mongillo, Yann Canvel, Daniel Perez Lozano, Bert Tobback, Tsvetan Ivanov, Antoine Pacco, Xiaoyu Piao, Shana Massar, Anton Potocnik, Kristiaan De Greve – IMEC

Superconducting Nb airbridges were fabricated in imec’s 300 mm pilot line utilizing an advanced production toolset. An optimized process flow, which does not rely on liftoff or shadow evaporation, results in high airbridge yield across full wafers, and is compatible with trilayer-based superconducting qubit fabrication methods. Airbridges integrated with resonators were characterized at millikelvin temperatures, showing that the addition of airbridges has minimal contribution to microwave losses. This work demonstrates that airbridges can be incorporated into foundry compatible qubit fabrication flows.

3:30 – 3:50 Coffee Break

Session 9: DTCO & Advanced Interconnects III
Chair: Susumu Matsumoto (Tower Partners Semiconductor)

3:50 – 4:20
9.1 What Role Could 2D Materials Play in the Semiconductor Industry? (Invited)

Eric Pop – Stanford University

This talk will present my (biased) perspective on whether two-dimensional (2D) materials could play a role in the semiconductor industry. It is important to recognize that 2D materials may only be good for applications where their ultrathin nature gives them distinct advantages, such as flexible electronics [1], light-weight solar cells [2], or nanosheet transistors [3]. I will focus on 2D materials for 3D heterogeneous integration of electronics, which has major advantages for energy-efficient computing [4]. Here, 2D materials could be monolayer transistors with ultralow leakage [5] (due to larger band gaps than silicon), used to access high-density memory [6]. Results from our group [3,7] and others [8] have shown monolayer 2D transistors with good performance, which cannot be achieved with sub-nanometer thin conventional semiconductors, and the 2D performance could be further boosted by strain engineering [9] and improved contacts [7]. I will also describe some unconventional applications, using 2D materials as thermal insulators [10], heat spreaders [11], and thermal transistors [12]. These could enable control of heat in “thermal circuits” analogous with electrical circuits. Combined, these studies reveal fundamental limits and some key applications of 2D materials, which take advantage of their unique properties.

 

Refs: [1] A. Daus et al., Nat. Elec. 4, 495 (2021). [2] K. Nassiri Nazif, et al., Nat. Comm. 12, 7034 (2021). [3] C. English et al., IEDM, Dec 2016. [4] M. Aly et al., Computer 48, 24 (2015). [5] C. Bailey et al., EMC (2019). [6] A. Khan et al. Science 373, 1243 (2021). [7] C. McClellan et al. ACS Nano 15, 1587 (2021). [8] S. Das et al., Nat. Elec. 4, 786 (2021). [9] I. Datye et al., Nano Lett. 22, 8052 (2022). [10] S. Vaziri et al., Science Adv. 5, eaax1325 (2019). [11] C. Koroglu & E. Pop, IEEE Elec. Dev. Lett. 44, 496 (2023). [12] M. Chen et al., 2D Mater. 8, 035055 (2021).

4:20 – 4:40
9.2 A design approach for ultra-low-k dielectric organosiloxane polymers

Hanna Luusua, Thomas Gädda, Jagadish Salunke, Zhongmei Han, Heli Kekkonen, Juha Rantala, Hsiaokang Chang, Hsin-Yen Huang, Ting-Ya Lo, Gary Liu  – PiBond Oy, Taiwan Semiconductor Manufacturing Company

Capacitance reduction is crucial for advanced interconnect scaling. Decreasing dielectric constant of inter layer dielectric (ILD) and inter metal dielectric (IMD) contributes significantly to the decrease of capacitance. Spin-on organosiloxane polymers have many advantages as ILD and IMD materials, including high thermal stability, easy processing, and dielectric constant (k) lower than 3. For further k reduction, introduction of porosity is the most common strategy to achieve k< 2.7. However, highly porous materials can suffer from e.g. poor mechanical properties, resulting in several integration challenges. We have demonstrated a material design approach for low-k organosiloxane dielectric polymers, enabling ultra-low-k (<2.5) spin-on thin films without introducing porosity to material. 4:40 – 5:00 9.3 Investigation of Graphene Cap Formation on NiAl by Low Temperature Thermal CVD (Student Paper)

Yumehito Temmyo, Jean-Philippe Soulie, Christophe Adelmann, Zsolt Tokei, Kazuyoshi Ueno – Shibaura Institute of Technology, IMEC

In order to suppress the increase in resistivity due to surface oxidation of NiAl thin films, we developed a process for forming a graphene cap on the NiAl surface with using an ultra-thin Ni layer and the optimized thermal CVD at 400 C. Although Ar-plasma cleaning of NiAl surface was found to promote the CVD reaction at the surface, CNT-like features were formed due to non-uniform Ni on the NiAl surface. A 2 nm Ni layer on NiAl can promote a uniform deposition of carbon film with the optimized CVD condition of lower thermal budget and higher precursor supply.  There was no increase in the resistivity of optimized C/Ni/NiAl film during annealing in the air up to 400°C.

Poster Session and Conference Reception (5:30 – 8:00)

Posters
Chair: Fumihiro Inoue (Yokohama National University) & Chris Wilson (IMEC)

 

P1. Redefining 2-Level Semi-Damascene Interconnect Technology: Benchmarking three different Fully Self-aligned Via options

Giulio Marti, Gilles Delie, Gayle Murdoch, Anshul Gupta, Souvik Kundu, Stefan Decoster, Olalla Varela Pedreira, Alicja Lesniewska, Yannick Hermans, Bart Kenens, Fulya Ulu Okudur, Seongho Park, Zsolt Tokei – IMEC

This study highlights the effectiveness of a novel two-metal-level semi-damascene integration approach using fully self-aligned pillar-vias (FSAV) for interconnects ranging from 18 to 26 nm metal pitch. We employ EUV-SADP-SIM patterning scheme and direct metal etch of Ru to demonstrate the proof of concept on 300 mm wafers on 300mm wafers. This integration not only gives lower via resistance than the previously reported schemes but also promise lowers capacitance between the two metal layers. Furthermore, it significantly widens the via litho and etch process window, making it more attractive for advanced semiconductor manufacturing.

P2. Self-aligned 8nm T2T as cell boundary in the middle-of-line

Philippe Marien, Yannick Hermans, Subhobroto Choudhury, Souvik Kundu, Stefan Decoster, Fulya Ulu Okudur, Naveen Reddy, Bart Kenens, Nicolas Jourdan, Gilles Delie, Giulio Marti, Chen Wu, Victor Vega Gonzalez, Gayle Murdoch, Seongho Park, Zsolt Tokei – IMEC

In order to achieve tight, 8 to 12 nm cell boundaries, Ru direct metal etch can be used to split a larger via into two opposite facing smaller vias and create a tight metal line tip-to-tip (T2T) at the cell boundary. This is obtained by self-aligning the Ru direct metal etch to the tightest metal layer above. This technique of splitting a via and creating a T2T with zero line extension is promising for cell boundary definition of complementary FET. In this work, we will discuss lithography overlay and via CD process window definition to achieve the improved morphological and electrical results. For 8 nm T2T, we have obtained a 55% leakage current yield. Additionally, for 10 and 12 nm T2T, a leakage current yield of above 90% was achieved.

P3. Demonstration of MP18-26nm Ru Semi-Damascene Spacer-is-Dielectric SADP Integration

Chen Wu, Stefan Decoster, Vincent Renaud, Yannick Hermans, Philippe Marien, Giulio Marti, Nancy Heylen, Bart Kenens, Syamashree Roy, Fulya Ulu Okudur, Quoc Toan Le, Naveen Reddy, Alfonso Sepulveda Marquez, Gilles Delie, Anshul Gupta, Alicja Lesniewska, Gayle Murdoch, Seongho Park, Zsolt Tőkei – IMEC

This work presents a novel Spacer-is-Dielectric (SID) SADP Ru semi-damascene integration scheme by using metal-based core and gap hard masks. More than 70% yield in tested line resistance and line-to-line leakage, especially in MP18 structures, confirm the flow feasibility. The tested MP18 structures show a median line resistance of 720 Ω/µm and a clean line-to-line leakage with breakdown voltages in the range of 12-14V.

P4. Technology benchmarking of copper electromigration using a grain-sensitive simulation framework (Student Paper)

Ahmed S. Saleh, Kristof Croes, Hajdin Ceric, Ingrid De Wolf, Houman Zahedmanesh – IMEC

A calibrated simulation framework for the analysis of electromigration (EM) in nano-interconnects, incorporating the intricate influence of microstructure, is presented. Different technology options were benchmarked for EM performance, taking copper texture and microstructural changes with scaling into account. Specifically, the impacts of metal cap and copper doping were simulated for a constant line height of 80nm and for linewidths between 20 and 100nm. An almost linear increase in normalized lifetime was observed for aspect ratios of 1 and above. An increase ranging from 10x to 100x was gained by using a metal cap for aspect ratios below 2. However, its effectiveness strongly weakened with decreasing CD with almost no EM lifetime gain for 20nm CD. Doping elements that lower grain boundary diffusivity were found to be more effective at these small dimensions.

P5. Patterning process and electrical yield optimization at the limits of single exposure EUV 0.33 NA: a pitch 26nm damascene process

Victor M. Blanco Carballo, Kevin Vandersmissen, Bart de Wachter, Kathleen Nafus, Yannick Feurprier, Thiam arame, Alex Hsu, Cyrus Tabery, Jan Doise, Peter De Schepper – IMEC, TEL, ASML, Inpria

In this work we have developed a single layer short loop damascene process to evaluate and optimize patterning performance of pitch 26nm single exposure 0.33 NA EUV. An electrical readout of 1m long meanders and forks-forks is used to compare the different processes and evaluate the amount of resist defects leading to shorts or opens. For the best process a full wafer combo yield of 99.7% is achieved (edge excluded) equivalent to 12 defects/cm2

P6. Interconnect Delay Modeling of Critical Paths in Angstrom Nodes (Student Paper)

Francesco Dell’Atti, Anita Farokhnejad, Odysseas Zografos, Pieter Weckx, Julien Ryckaert, Paul Heremans – IMEC

This work provides a methodology to analyze and model critical path interconnections of physically implemented digital designs in Angstrom nodes. The Elmore delay computation is applied to the detailed interconnect topology to provide a block-level statistical assessment of dominant parameters such as wire and via resistance (R), as well as wire and pin capacitance (C), on interconnect performance. Our methodology can rapidly assess the impact of back-end-of-line (BEOL) materials, interconnect geometries, and scaling boosters on the interconnect delay of complex digital designs, enabling fast turn-around time for Design-Technology Co-optimization (DTCO) loops. The model predicts delays with 1.3 percent of maximum mean error, standard deviations below 3 percent, and 23x speedups compared to conventional Static-Timing-Analysis (STA) sensitivity analyses.

P7. Ion Beam Deposition of Low-Resistivity Tungsten and Molybdenum for Interconnect Applications

Rutvik Mehta, Yuejing (Crystal) Wang, Ashish Kulkarni, Robert Walko, Paul Turner, Frank Cerio, Robert Caldwell – Veeco Instruments, Inc.

Refractory metals like tungsten and molybdenum with favorable resistivity scaling effects are promising candidates for nanometer scale interconnects for memory and logic. Ion beam deposition with the highest sputter energy and fine-scale control of deposition energetics enables metal thin films with ideal microstructures. Tungsten and molybdenum thin films deposited by ion beam deposition on 300mm wafers show large grained fully (110)-aligned microstructures presaging low-resistivity independent of the underlying substrates. Unlike other deposition approaches which require additional inserted layers and show underlayer dependence, ion beam deposition achieves lower resistivity in the as-deposited state independent of the underlying substrate. Resistivity versus thickness curves of ion beam deposited tungsten and molybdenum films shows ultra-low resistivity in the as-deposited state with scaling effects qualitatively similar to that of corresponding epitaxial films. These results establish the application of ion beam deposition of refractory metals as a very promising approach towards low-resistivity interconnects for the next generation of integrated devices.

P8. Formation of Lateral-Type High-Tc Superconductor Josephson Junction by Helium Ion Microscopy

Shinichi Ogawa, Tetsuro Misawa, Kosuke Kurushima, Yuji Otsuka, Yukinori Moritta, Chiharu Urano – National Institute of Advanced Industrial Science and Technology, Toray Research Center, Inc.

This paper presents, for the first time, the results of investigating the dependence of ion dose and temperature on the formation of Josephson junctions via helium ion irradiation of YBa2Cu3O7-; high-temperature superconductor thin films. Helium ion microscopy technology was employed for the helium ion irradiation. Our observations reveal that the characteristics of Josephson junctions can be controlled by the dose of helium ions. Converging the helium ion beam to a diameter of 0.35 nm, with an acceleration voltage of 30 kV, and an irradiation dose in the order of 1E17/cm2, demonstrates the formation of excellent lateral-type thin film Josephson junctions.

P9. Selective Co ALD for Chiplet-to-Wafer and Wafer-to-Wafer Bonding (Student Paper)

Cheng Hsuan Kuo, Madison Manley, Dipayan Pal, Rohan Sahay, Ravi Kanjolia, Mansour Moinpour, Jacob Woodruff, Jeffrey Spiegelman, Muhannad Bakir, Andrew Kummel – UCSD, Georgia Institute of Technology, EMD Electronics, RASIRC

Cyclic clean treatment by using strong oxidant: HOOH and reductant: N2H4 ¬was developed for Cu cleaning which can be applied in the inverse hybrid metal bonding process. Compared to UHV anneal at higher temperature (415C), cyclic clean process is only performed at 340C with lower surface impurities. Also, highly selective Co ALD is deposited on metal Cu but not on SiO2 even after 1000 ALD cycles.

P10. Enhancement of electromigration performance of molybdenum nanowires by CoMo capping (Student Paper)

Sijie Gu, Haijun Cheng, Chun-Feng Hu, Xin-Ping Qu Ping – Fudan University

The electromigration performance of the Mo nanowires with different capping layers is measured. Results show that the CoMo capped Mo nanowires show better electromigration performance than that of the ones capped with Si3N4 or SiO2. It is found that the CoMo capping layer can effectively protect the Mo film from oxidation as well as nitridation, which is the main reason for the improved EM performance of the Mo nanowires.

P11. Data Analytics to Identify Improved Low k Films

William Entley, Achtyl Jennifer, Robert Ridgeway – EMD Electronics

This paper investigates the development of as deposited dense low k films with high mechanical strength, crucial for advanced semiconductor manufacturing. Over 1100 unique low k films from seventeen precursors were deposited and analyzed, focusing on mechanical properties. The study used a Design of Experiments (DOE) approach to maximize mechanical strength of each precursor. Data analytics were used to analyze and sort the low k films to identify precursors that had the highest mechanical strength at a given value of the dielectric constant. This was done by extracting the Pareto Frontier, representing films with the highest mechanical strength at varying dielectric constants, for each precursor. Results showed significant variation in mechanical strength among precursors, with two novel precursors exhibiting superior performance compared to DMDMOS, an industry standard precursor. Analysis of the carbon distribution in the films provided insight into mechanical strength variations. This research highlights the potential of tailored precursor design to meet the demanding requirements of dense low k films in advanced semiconductor nodes.

P12. Halogen Free Low Temperature ALD Mo-based Films for Interconnects Applications

Aein Babadi, Randall Higuchi, Mike Savo, Charlene Chen, Bhushan Zope, Sergei Ivanov – EMD Electronics

Molybdenum-based films synthesized by low temperature atomic layer deposition (ALD) from different organometallic halogen free Molybdenum precursors. The film’s average composition was investigated and correlated with their nanoscale structures and electrical transport properties. A high work function N-rich MoN film with low carbon contamination was demonstrated in comparison with MoC/MoCN films with low resistivity. The precursor composition dependence of film’s properties leads to a low resistivity MoC film as well as selective deposition of Mo films on metallic substrates.

P13. Surface Characterization and Modification for Cu/SiCN Hybrid Bonding (Student Paper)

Kenta Hayama, Kohei Nakayama, Ryosuke Sato, Yutetsu Kamiya, Ken Harada, Masahiro Yokoyama, Yasuhiro Kawase, Fumihiro Inoue – Yokohama National University, Mitsubishi Chemical Corporation

Hybrid bonding is an ideal bonding scheme for achieving finer interconnect pitch in multiple applications. To ensure high yielding, the pre-bonding surface preparation is a crucial process step as hybrid bonding requires surface uniformity of Cu pad. In this study, the influence of P-CMP cleaning and the effect of N2 plasma activation on Cu pad were investigated. The P-CMP alkaline cleaning solution can remove BTA residues. Furthermore, the plasma activation turns the Cu surface without any carbon related residues even with 15 sec process time. These results suggest an optimized surface condition for fine-pitch hybrid bonding.

 

P14. Low contact resistance copper-copper bonding with selective electroless plating cobalt interlayer

Yun-Hao Shao, Zihong Ni, Gui Chen, Hao Wang, Xin-Ping Qu – Fudan university

Low temperature metal direct bonding is very challenging in 3D interconnect technical. In this work, self aligned Co layer is selectively deposited on the copper line by electroless plating as an interlayer for Cu-Cu bonding. The direct bonding between Cu/Co is performed without a chemical mechanical polishing process at 250C; in ambient. An intact bonding interface is observed and a specific contact resistance of 5.5×10^-7 Ω·cm^2 is obtained. Through a special surface treatment, the specific contact resistance can achieve 3.8×10^-8 Ω·cm^2, which is lower than that of Cu-Cu bonding with PVD Co interlayer.

P15. Cyclic Etching of Mo Nanowires

Ivan Erofeev, Antony Winata Hartanto, Harold Philipsen, Antoine Pacco, Muhaimin Mareum Khan, Zainul Aabdin, Frank Holsteyns, Utkur Mirsaidov – National University of Singapore, IMEC

We show that a uniform recess of polycrystalline Mo films and nanowires can be achieved using a cyclical two-step method: isotropic oxygen plasma-based surface oxidation followed by selective etching of this oxide layer. The oxidation step fully defines the recess depth, and the low facet dependence of plasma oxidation ensures its uniformity. Our study describes the parameters (RF power, gas pressure, and exposure time) that affect and control the uniformity of oxidation of patterned Mo nanowires. We showed that using highly selective oxide etching, we can perform multiple etching cycles with a typical etch rate of 1-2 nm per cycle, depending on the RF power. Due to plasma isotropy, this approach can be implemented for a controlled uniform etching of large vertical stacks of metal nanostructures.

P16. Characterization of Siliconcarbonitride bonding layer for plasma activated direct fusion bonding

David Doppelbauer, Christoph Floetgen, Ignacio Gabriel Vicente Gabàs, Serena Iacovo, Steven Brems, Eric Beyne, Jiri Duchoslav, Heiko Groiss – EV Group E. Thallner GmbH, IMEC, Johannes Kepler University Linz

In the scope of this work, a comprehensive study of plasma treated Silicon carbonitride (SiCN) dielectric bonding surfaces on Si wafers is presented. PECVD grown films were investigated by means of variable angle spectroscopic ellipsometry (VASE) and angle-resolved x-ray photoelectron spectroscopy (ARXPS) before and after plasma activation. Based on ARXPS depth-profiling data, an ellipsometry model was developed, allowing for non-destructive characterization of the plasma effect on the SiCN bonding surfaces. Oxidation processes and intermediate mixture phase layers between the grown oxide and the SiCN layer were observed and correlated to plasma specific characteristics as measured by current-voltage probes. The plasma activation effect was further evaluated after bonding of SiCN wafer pairs in terms of bonding energy. Plasma characteristic parameters correlate well with oxide thickness after plasma activation and bonding energy.

P17. Investigation of the enlargement of Ru grains and failure modes analysis in microsecond UV laser annealing

Zeinab Chehadi, Richard Daubriac, Lu Lu, Karim Huet, Zsolt Tokei, Leonardo Cancellara, Fuccio Cristiano, Louis Thuries– LASSE-Screen, LAAS-CNRS, ScreenSPE, IMEC

Interconnects based on Ru has been considered as a promising candidate to replace Cu-based interconnects for the future technology nodes thanks to its low bulk resistivity , its short electron mean free path (e-MFP) and the possibility to have a barrier-less integration. In this work, we demonstrate that µs UV Laser Annealing (UV- LA) is an interesting process strategy to reduce the metal line resistance by enlarging grains in thin Ru films. A method based on numerical simulations has been proposed to optimize the LA conditions to lower the Ru film resistivity close to the bulk one, while avoiding the apparition of structural damages such as wrinkles or buckling.

P18. Nano-chemical characterization of SiO2 and Cu surfaces for Cu-Cu hybrid bonding

Padraic O’Reilly, Beihang Yu, Cheng Hsuan Kuo, Andrew Kummel, Ricardo Ruiz, Sung I. Park – Molecular Vista, Inc., Lawrence Berkeley National Laboratory, UCSD

Infrared photo-induced force microscopy (IR PiFM), which combines non-contact atomic force microscopy and infrared spectroscopy (AFM IR), is applied to precisely characterize the surface chemical state of the silicon oxide and copper. Based on an AFM platform, the technique can monitor the topographical condition (flatness of the dielectric as well as the recession of the Cu pads) in addition to the surface chemistry (absence of unwanted molecules and the presence of desired surface termination), both with ~ 5 nm lateral resolution and monolayer sensitivity, to characterize the suitability of the samples for successful Cu-Cu hybrid bonding.

P19. 300mm Wafer-scale ALD-grown MoS2 for Cu diffusion  barrier

Thong Ngo, Angelica Zacatzi, Yuanqiu Tan, Daniel Lee, Anand Wankis, Nguyen Vu, Ravi Kanjolia, Mansour Moinpour, Zhihong Chen – EMD Electronics, Purdue University

Cu has served as the interconnect metal in various chip generations, typically accompanied by a TaN/Ta diffusion barrier/liner. The size-scaling demand for future nodes requires thinning down TaN/Ta bi-layer. The thickness of TaN/Ta has reached the limit of its barrier/liner capability, necessitating the exploration of alternative diffusion barrier/liner materials. In this paper, we report the 300mm wafer-scale atomic layer deposited MoS2 as a promising candidate for Cu diffusion barrier/liner interconnect. MoS2 was deposited on thermal SiO2 substrate at the temperatures ranging from 200-550 °C. Good conformality of MoS2 was demonstrated on high aspect ratio structure. The resistivity of Cu/MoS2/SiO2 stack is lower than that of Cu/SiO2 stack. Time dependent dielectric breakdown of Cu/MoS2/SiO2 will be discussed and benchmarked with Cu/Ta/TaN/SiO2.

P20. Investigation of the Low Dielectric Constant Properties of SiOx/AlOx Nanolaminate Film (Student Paper)

Xinyu Wang, Jing Mu, James Huang, Yunil Cho, Kesong Wang, Dipayan Pal, Ajay Yadav, T. Wong Keith, Ellie Yieh, Srinivas Nemani, Andrew Kummel – UC San Diego, Applied Materials

Low-k materials play a pivotal role in semiconductor technologies, primarily due to their capability to enhance signal transmission speed and reduce power consumption. This study investigates a series of novel low-k (<2.5) SiOx/AlOx nanolaminate films with smooth surfaces deposited on Si substrates via a dual-temperature thermal chemical vapor deposition (CVD) process. The low dielectric constant value achieved by the nanolaminate is ascribed to its porous nature. Additionally, incorporating carbon into the nanolaminate structure greatly enhanced the atmospheric stability of the film by making it hydrophobic. P21. Enhanced process control for plasma triggered oxide growth in plasma activated wafer bonding

Christoph Floetgen, Ignacio Gabriel Vicente Gabàs, David Doppelbauer – EV Group E. Thallner GmbH

In Plasma Activated Wafer Bonding (PAWB) the plasma process modifies the surface conditions of a substrate, allowing for low-temperature annealing of the wafers to be bonded. Despite its critical role in the PAWB process, plasma treatment is often insufficiently characterized. In this study, electrical plasma parameters are recorded during the plasma activation process using current-voltage probes at the plasma chamber electrodes. These parameters are then correlated with bonding quality metrics like the plasma-triggered oxide growth on Si and the bond strength after annealing. As will be shown, particularly the oxide thickness grown after plasma activation can be determined by a simple functional correlation to plasma characteristic electrical parameters connected to the total dose of ions impinging on the wafer surface. This allows for potential enhanced process control, specifically in the light of the industry’s current and future challenges of shrinking device nodes.

P22. Metal-metal contact resistance measurements (Student Paper)

Poyen Shen, Daniel Gall – Rensselaer Polytechnic Institute

The contact resistance at metal-metal (W, Mo, Ru, Co, TiN) interfaces is determined using a new method based on blanket superlattice thin films where the resistivity  parallel to the interfaces is measured as a function of superlattice period  to quantify the electron interface scattering. Epitaxial W(001)/Mo(001) superlattices show a continuous resistivity increase from 7.10 to 8.62 µΩ-cm with decreasing  = 50-1.7 nm, indicating a contact resistance of 2.6×10-16 Ω-m2. Ru/Co multilayers show a much more pronounced increase from 15.0 to 47.5 µΩ-cm with  = 60-2 nm which is attributed to atomic intermixing leading to an interfacial Ru-Co alloy with a high measured  = 61 µΩ-cm and a Ru-Co contact resistance for interfaces deposited at 400 °C of 9.1 ×10-15 Ω-m2. Ru/TiN and Co/TiN interface resistances are dominated by the high for TiN, and are therefore proportional to the TiN thickness.

P23. Wafer-Level Electrochemical Deposition and Processing of Nanotwinned Cu RDL

Chih-Hao Hsia, SungHo Park, Soichi Watanabe, Marco Arnold, Zaid El-Mekki, Martine Delande, Ehsan Shafahian, Punith Kumar M. K. Gowda, Herbert Struyf, Aleksandar Radisic – BASF, IMEC

We have successfully performed wafer-level (300 mm) fabrication of highly (111) oriented nanotwinned copper (nt-Cu) Redistribution layers (RDL) using through-resist electrochemical deposition on barrier/seed combinations such as TiW/Cu, TaN/Cu, and TaN/Ta/Cu.    We have examined physical-chemical properties of nt-Cu and explored possible challenges in post-plating processing of these structures.  After photoresist removal, nt-Cu lines were analyzed using Scanning electron microscopy (SEM) and Focused ion beam (FIB) techniques.  Within wafer (WIW) and within die (WID) feature height uniformity were measured using profilometry and Cu losses in the plated lines upon wet-etch of the Cu seed were examined using automated SEM measurements.

 

P24. Mechanistic and Performance Aspects for Co-designed Process Technology to Enable Mo as the Next Generation Conductor

Michael White, Kevin Dockery, Paul Besser, Daniela White, Bryan Hendrix, Don Frye, Maryam Farmand, Jun Liu, Das Atanu, Jason Seabold, Fernando Hung – Entegris

PVD and CVD molybdenum (Mo) wafers/coupons were prepared and analyzed by various techniques including XPS, electrochemistry, impedance spectroscopy, AFM, Zeta Potential, Raman as well as ATR FTIR spectroscopies. The surface chemistry was then correlated with performance parameters such as the static etch and polishing rates/profile in addition to the defectivity after Planarcore® brush cleaning using with Entegris ML slurries and AG-Mo series PCMP cleaners.

P25. The investigation of Ar plasma treatment on the contact resistance between metal-metal by a simple metal bonding simulation approach

Gui Chen, Yun-Hao Shao, Xin-Ping Qu – Fudan University

Reducing the direct metal bonding temperature is a challenge for 3D metal bonding. We present a simple fabrication process using the two-step PVD Cu / Co on the PVD Co / Cu surface with a vacuum break followed by annealing to simulate the real metal-metal bonding. Based on this approach, without critical requirement of cleanliness of the bonding surface, the parameters which impacts the bonding temperature and interface specific contact resistance can be efficiently find out. In this work, we first used this approach to choose the correct Kevin structure to measure the low contact resistance, and then the effects of Argon plasma activation of the Co layer, which is used as an interlayer for Cu-Cu bonding, were investigated. It is found that the Ar plasma activation can result in uniform Co3O4 layer formation and effectively reduce contact resistance.

P26. Doping Effects in Grain Boundaries of Tungsten: Insights from First-Principle Study (Student Paper)

Yeongjun Lim, Mincheol Shin – Korea Advanced Institute of Science and Technology

As semiconductor device sizes shrink to the nanometer scale, the sharp increase in resistance due to grain boundary and surface scattering poses uncertainties regarding the continued use of copper as an interconnect material. In pursuit of alternatives, tungsten has emerged, but its high resistance due to scattering remains a challenge. This study investigates the effects of grain boundary doping, a potential method for reducing resistance, through first-principle simulations combining density functional theory (DFT) and non-equilibrium Green’s function (NEGF) method. Our simulations reveal that grain boundary doping with certain impurities can effectively reduce resistivity in specific coincidence site lattice grain boundaries of tungsten interconnects.

P27. The feasibility of the lateral wet-etching on TiN layers in 3D multilayer stack structure

Jiao Jin, Jiabao Sun, tuo xin, Weidu Qin, Chaoyang Guan, wenjun chen, Chao Tian, Baodong Han, Hongbo Sun, Chao Zhao – Beijing Superstring Academy of Memory Technology

3D Memory Device is manufactured based on dielectric materials of SiOx and SiN vertically multilayer stacked semiconductor structures. Atomic Layer Deposition (ALD) have homogeneous step coverage of sidewalls and bottom with high aspect ratios in achieve 3D structure. But existing inherently void defect in lateral pocket layers. The worse uniformity and profile appeared after wet lateral etch along with pre-process layer seam, affecting seriously the storage properties of the device and lead to slower transfer speeds. In this study, Oxide Trim (wet isotropic etching SiOx) provides a new strategy for wet lateral etching TiN thin films by ALD technology of seam issue. The trumpet shaped opening between the stacked layers formed by twice lateral wet etching SiN promoted the seam inward after deposition, potential increasing the filler metal density in the seal and improving the BL uniformity using wet chemical of high etching selectivity for TiN to SiOx/SiN.

P28. Proposal for Improved Electrical Efficiency through Thermal Modeling of Interconnect Structure (Student Paper)

Taeyeong Hong, Seul Ki Hong – Seoul National University of Science & Technology

This study investigated the modeling of heat and current distribution in interconnect structure used in semiconductor systems based on their shapes, utilizing Finite Element Method (FEM) simulations. The research aims to optimize power efficiency in interconnect structures by securing the modeling of heat and current distribution through experimental validation, confirming the integrity of the models. In interconnect structures, the current density increases as the contact area for current flow at the junction of metal lines and vias narrows, leading to a temperature rise due to Joule heating. The need for scaling down exacerbates the issue as the dimensions need to be progressively reduced, conforming to the specifications of both lower and upper components, causing a reduction in the width of the conductors. The temperature increase due to Joule heating is inevitable with this reduced area, and it ultimately leads to the destruction, directly impacting the reliability of the entire system. The experimental results provide considerations for reliability when significantly scaling down interconnect structures in current semiconductor systems. Furthermore, these findings can be widely applied to research aimed at developing interconnect structures that enhance reliability.

P29. Lateral Metal Deposition and the Formation of Interconnection

Weidu Qin, Jiabao Sun, Jiao Jin, Chao Tian, Chaoyang Guan, Hongbo Sun, Chao Zhao – Beijing Superstring Academy of Memory Technology

With the development of semiconductor technology, the device architecture has developed from two-dimensional stacking to three-dimensional stacking, which makes it difficult to deposit interconnected metal films in multi-layer stacking structures. In order to obtain higher quality interconnection films, we used atomic layer deposition (ALD) and WET ETCH process to form TiN metal films in a multilayer stacked lateral structure. After WET ETCH, a straight profile was obtained and a seam-control TiN film was formed. This method shows good potential in depositing high-quality thin films and forming metal interconnections in multi-layer stacked devices.

P30. Thermally Conductivity Study of One Micron AlN Deposition by Bipolar High Power Impulse Magnetron Sputtering (Student Paper)

Ping Che Lee, Mcleod Aaron, Mingeun Choi, Vaca Diego, Satish Kumar, Andrew Kummel – UCSD, Georgia Institute of Technology

High Power Impulse Magnetron Sputtering (HIPIMS) has emerged as a promising technique for the deposition of thin films with superior properties. In this study, HIPIMS was combined with a positive target bias (Kick voltage) process to enhance AlN film quality further. Aluminum Nitride (AlN) thin films were deposited using this method and characterized using Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). The thermal properties of the films were investigated using Frequency Domain Thermoreflectance (FDTR). The results show that the HIPIMS plus Kick process significantly improves the film quality, leading to enhanced thermal conductivity (112 W/ m·K) compared to conventional techniques. This work demonstrates the potential of HIPIMS in producing high-quality thin films with improved thermal properties, making it suitable for various applications in electronics and thermal management.

THURSDAY, JUNE 6, 2024

Session 10: Keynote
Chair: Mansour Moinpour (EMD Electronics)

8:15 – 9:05
Keynote – Memory Technology: Status and Scaling Perspective

Dr. Nirmal Ramaswamy – Micron

Session 11: 3D Packaging & Integration
Chair: Arup Saha (ASML) & Harsono Simka (Samsung)

9:05 – 9:35
11.1 High Performance 3D Flash Memory based on CBA (CMOS Directly Bonded to Array) Technology (Invited)

Shigeki Kobayashi – Kioxia

We applied CBA (CMOS directly bonded to array) technology to BiCS FLASHTM generation 8, and demonstrated superior performance: a program throughput of 205MB/s with the triple level cell, a read time of 40s, and an interface speed of 3.2Gbps. The CBA advantages are discussed on a viewpoint of interconnect technology. On-pitch-SGD (OPS) technology is also introduced as a newly developed technology to achieve the memory density of more than 18Gb/mm2 in BiCS FLASHTM generation 8.

9:35 – 10:05
11.2 Reconfigured Wafer-on-Wafer 3D Integration with Meta Bonding Technologies (Invited)

Takafumi Fukushima – Tohoku University

Reconfigured Wafer-on-Wafer (RWoW) 3D integration is an advanced multichip-to-wafer 3D integration method that employs massively parallel assembly techniques. The critical steps involve temporary bonding to carrier wafers and the transfer of multiple chips from these carrier wafers to target wafers. Fukushima et al. have termed carrier wafers using self-assembly with liquid surface tension with known good dies (KGDs) as “Reconfigured Wafers.” Initially, various 1st-layer KGDs equipped with microbumps are sorted from different device wafers post-testing. These KGDs are then self-assembled on a carrier wafer and temporarily bonded in a face-down manner. Subsequently, the carrier wafers are aligned and bonded to the respective target interposer or IC device wafers, which feature an identical microbump design to the self-assembled KGDs. Similar innovative technologies, such as “Collective Bonding” and “Reconstructed Wafers” have appeared later.

The bonding between KGDs and target wafers employs microbump-to-microbump bonding or direct/hybrid bonding, followed by detachment of the KGDs from the carrier wafers and their transfer to the target wafers. The ensuing steps include underfilling and multi-chip thinning, encompassing backside grinding/CMP and TSV/microbump formation. The final stage involves vertically stacking these KGDs in layers by repeating the multi-chip transfer processes. We call the advanced chip/wafer bonding technology “Meta Bonding” such as fine-pitch microbump bonding, ultrafine-pitch hybrid bonding, and DSA bonding and more. for coming future high-performance and multi-functional 3D and heterogeneous holistic systems including BSPDN, C-FET (Complementary Field-Effect Transistor), and Photonic/Quantum/DNA/Molecular IC etc.

10:05 – 10:35
11.3 3D Stacking Technology Challenges for High Bandwidth Memory (HBM) (Invited)

Ho Young Son – SK Hynix Semiconductor

Co-Authors:  Seungchul Han, Sangyong Lee, Ki-Ill Moon and Kangwook Lee

The exponential growth of generative AI is revolutionizing both human experience and the semiconductor industry. In parallel, high bandwidth memory (HBM) technology has emerged as a key driver leading the unprecedented growth of AI industry and catalyzing major advancements in memory technology. HBM was initially embraced in graphics applications due to its superior bandwidth, power efficiency, density, and compact footprint when compared to conventional FCBGA packages. This technology utilizes through-silicon vias (TSVs) and micro-bumps to vertically interconnect multiple chips, which include a base die and 4 to 16 DRAM dies.

As the demand on the HBM with greater bandwidth and capacity continues to grow, significant technical challenges arise in the 3-dimensional vertical stacking technology. Some of these challenges include thin die handling and thermal management, resulting from increased power and chip count. However, our innovative MR+MUF (mass reflow and molded underfill) technology provides a solution to these obstacles. This technology not only offers enhances thermal dissipation capability but also offers cost-effectiveness and reliable mechanical reliability of advanced memory product. This paper presents the MR+MUF package technology and outlines its solutions for thin die handling, fine pitch bump joining, and narrow gap filling. Moreover, while micro-bump joining is limited in its stacked chip count and thermal dissipation capabilities, Cu-Cu hybrid bonding has emerged as a promising alternative, offering superior thermal dissipation and compatibility for higher chip stacks over 16Hi. Despite the numerous advantages of hybrid bonding in multi-thin die stacks for HBM, there are several significant hurdles to its implementation, particularly in terms of thermal management and dimensional considerations. In this paper, we propose potential solutions to these challenges and explore the solution to overcome the hurdles of chip-to-wafer hybrid bonding for future HBM applications.

10:35 – 10:55
11.4 Study and Control of the Distortion Induced by the Bonding Process for BSPDN Approaches

Karine Abadie, Ivanie Mendes, Marie-Line Pourteau, Fournel Frank, Hadi Hijazi, Balan Viorel, Richard Van Haren, Suwen Li, Blandine Minghetti, Leon Van Dijk, Mart Baars, Laurent Michaud, Thomas Plach, Gernot Probst – Université Grenoble Alpes, CEA-leti, ASML, EV Group

With the development of the Back-Side Power Delivery Network (BSPDN), new challenges and specifications in terms of alignment for subsequent exposure steps arise. Indeed, for 2-nm node technology this requires a very fine correction of the distortion induced by all the process steps on the transferred thin layer. One process step in particular seems to have a predominant effect on this aspect: the bonding. This paper introduces the methodology developed at CEA-Leti in collaboration with ASML and EV Group, to characterize the distortion induced by the direct bonding process step at global and local scale. The integration flow simulates BSPDN approach, considering a thin silicon layer to be transferred to another substrate, and allows developing innovative immersion scanner correction strategies.

10:55 – 11:15
11.5 Bonding induced distortion in wafer-to-wafer bonding applications: how the scanner and Yieldstar can enable 3D integration

Victor M. Blanco Carballo, Vincent Renaud, Serena Iacovo, Anne Jourdain, Alex Hsu, Yun-Heng Tseng, Cyrus Tabery, Etienne De Poortere – IMEC, ASML

In this work, we have developed a two-layer short loop process on device wafers to study the distortion fingerprint induced by a wafer-to-wafer bonding process. The alignment grid is used to characterize the after-bonding wafer deformation. Alignment modeling and optimization was performed to reduce the expected backside process overlay to below 5nm as well as the wafer-to-wafer variability.

11:15 – 11:35 Coffee Break

Session 12: Materials & Unit Process III
Chair: Tom Mountsier (LAM Research)

11:35 – 11:55
12.1 Low Resistance Stacked Via Metallization for Future Interconnects

Marleen H. van der Veen, Anita Farokhnejad, Akhilesh Kumar Mandal, Herbert Struyf, Seongho Park, Zsolt Tőkei – IMEC

We present stacked via and wire resistance predictions to find low resistive via metallization schemes that improve the system performance for sub-2 nm nodes. Implementing Ru vias with Cu wires at EUV patterned levels can give up to 60% resistance reduction. The circuit benefit of using Ru vias is determined with enhanced ring oscillator (RO) simulations. The Ru-Cu hybrid metallization in V2-M5 EUV printed layers gives a 10% frequency improvement as compared to stacks with semi damascene (SD) Ru and dual damascene (DD) Cu. The implementation of the selective Ru on Cu is demonstrated in metal pitch (MP) MP21-MP24 DD structures with yielding chains and vias that meet their resistance target.

11:55 – 12:15
12.2 Selective CVD Ru on W by sequential small molecule inhibitor treatments

Kai-Hung Yu, Ryota yonezawa, Hirokazu Aizawa, Wajda Cory, kawasaki Hiroaki, Mayersky Joshua, Suzuki Hidenao – TEL Technology Center, America, LLC

This paper presents a method of sequential surface treatments that effectively extends the selectivity of metal deposition onto desired metal surfaces and suppresses undesired nuclei defects. Two different types of Small Molecule Inhibitors (SMIs) were used in this paper to demonstrate that Chemical Vapor Deposition CVD Ruthenium can be deposited on W metal surface selective to SiO2 dielectric surface. A Chemical Mechanical Planarization (CMP) process exposed both W and SiO2 on top of patterned surfaces which was then used for testing the concept of Area Selective Deposition (ASD). Whole wafer In-Line electrical Test (ILT) results were used to demonstrate the selectivity loss. Undesired nuclei defects on the SiO2 surface correspond to an increase in the measured leakage current.

12:15 – 12:35
12.3 Dielectric Relaxation in HfO2/Al2O3 MIM Capacitors

Jeff Gambino, Vincent McGahay, Gyana Biswal, Akihiro Hasegawa, Michael Cook, Thomas Long, Karen Barker, David Price, Rick Mauritzson – Onsemi

Dielectric relaxation has been measured in HfO2/Al2O3 MIM capacitors.   The dielectric relaxation current exhibits a weak temperature dependence, with activation energies ranging from ~ 0.067 eV (20 msec after voltage pulse) to ~0.15 eV (2 sec after voltage pulse).    It is proposed that the initial dielectric relaxation is from electron emission from shallow traps, whereas the later dielectric relaxation is from emission from deep traps.

12:35 – 1:50 Lunch

Session 13: DTCO & Advanced Interconnects IV
Chair: Chris Wilson (IMEC) & Marco Arnold (BASF)

1:50 – 2:20
13.1 Backend-Compatible On-Chip DC-DC Converters

Sunbin Deng, Jungyoun, Kwak, Junmo Lee, Shimeng Yu, Suman Datta – Georgia Tech

In this work, we have developed back-end-of-line (BEOL)-compatible on-chip DC-DC converters using amorphous oxide semiconductor (AOS) power transistor technology. Simulation results of these converters have shown a high efficiency of approximately 83%, holding promise for efficient power delivery in heterogeneous three-dimensional integrated circuits.

2:20 – 2:50
13.2 Towards a comprehensive solution for future interconnects

Gert Leusiak – TEL

2:50 – 3:10
13.3 Ligand Engineering to Machine learning: Optimizing Ru ALD for Ultrathin Film Deposition

Jay Chiu, Isiah Liu, Chang-Won Lee, Guo Liu, Bhushan Zope – EMD Electronics, a business of Merck KGaA, Darmstadt

This study demonstrated our significant advancements in H2-based thermal Ru ALD, using novel Ru precursors, RuEM8 and RuEM10, which enable fabrication of ultra-thin Ru films with: excellent continuity at thicknesses as low as 3 nm, over 99% conformality, greater than 99 wt.% purity, and bulk resistivity reduced to 15 uΩ·cm. Such attributes position them as prime candidates for interconnect applications. Those breakthroughs were built on our strategic innovations: (1) A Machine-learning guided DoE methodology for high-efficiency ALD process optimization. (2) Smoothing-agent post-treatment to improve continuity via modulating Ru surface diffusion. (3) tailored ligands as “in-situ” inhibitors to facilitate 2D Ru growth. This showcased the combination of chemistry domain knowledge and machine learning forms the basis of a high-efficiency ALD precursor development methodology.

3:10 – 3:30
13.4 Modeling of Via Resistance considering Spatially-Resolved Conductivity and Temperature-Dependence (Student Paper)

Xinkang Chen, Sumeet Gupta – Purdue University

This paper presents a physics-based via resistance model featuring spatially-resolved conductivity due to surface scattering based on the Fuchs-Sondheimer (FS) theory, grain boundary scattering based on Mayadas-Shatzkes (MS) theory and temperature dependence incorporated in bulk conductivity, spatially-resolved FS (SRFS) and MS models. Based on this comprehensive modeling approach, we develop a 3D simulation framework for copper-based tapered via structure with Ta liner and TaN barrier to evaluate the via resistance. Our results show that the temperature-sensitivity of via resistance mainly stems from the bulk conductivity of copper. Utilizing our physics-based SRFS model, we confirm that the resistance due to surface scattering has a negligible temperature-dependence across a wide range of specularity and interconnect dimensions.

3:30 – 3:50 Coffee Break

Session 14: Materials & Unit Process III
Chair: Axel Preusse (Global Foundries)

3:50 – 4:10
14.1 Improvement of Ru-Co Liner for void-free Cu interconnect in extremely small pitch

hehsang Ahn, Seungwook Lee, Hoyun Jeon, Wonhyuk Hong, EunJi Jung, Taehong Ha – Samsung Electronics

While development in Copper (Cu) processes can contribute to Cu fill enhancement, optimizing the properties of the Liner can also be a significant role in Cu reflow characteristics. Therefore, this study aimed to improve Cu fill through the enhancement of the Ruthenium (Ru) and cobalt (Co) liner, particularly on 3nm-scale Cu interconnects. The surface morphology of the RuCo liner, which appears as the Co thickness increases, was improved through Atomic Layer Deposition (ALD)-like deposition of Co layer and plasma treatment between liner layers. This work provides the way to improve RuCo liner through process enhancements, resulting in a 80% reduction in void formation and enhancing Cu reflow characteristics. In addition, it was confirmed that the improved RuCo liner generates less voids depending on between chemical mechanical planarization (CMP) step to BM seed step.

4:10 – 4:30
14.2 Atomic Layer Deposition of TiN in Horizontal Vias Using Hydrazine as Nitrogen Precursor (Student Paper)

Jannick Fammels, Ping Che Lee, Dipayan Pal, Julian Pilz, Dmytro Solonenko, Jeffrey Spiegelman, Andrew Kummel – University of California, San Diego; Silicon Austria Labs, RASIRC

With decreasing feature size and changes in 3D DRAM and NAND architecture, TiN diffusion barriers for Cu and W metallization must become thinner and extremely conformal in horizontal structures. Titanium tetrachloride (TiCl4) and anhydrous hydrazine (N2H4) are promising precursors for low resistivity TiN atomic layer deposition (ALD). In this work these precursors were investigated for developing a particle free TiN ALD process with extremely high conformality in horizontal vias.

4:30 – 4:50
14.3 Ultra Low-k Properties of Atomic Layer Deposited Amorphous Boron Nitride for Futuristic Inter Metal Dielectric (Student Paper)

Inkyu Sohn, Taejin Choi, Jaewon Kim, Hyungjun Kim – Yonsei University, Samsung Electronics

Here, we report 4 nm thick a-BN films deposited by plasma enhanced atomic layer deposition (PE-ALD) with ultralow k values of 1.43 (close to that of air, k = 1) at operation frequencies of 1 MHz. The growth per cycle (GPC) is confirmed to be ~0.12 A/cycle at 350 C; and the thickness of synthesized film linearly increased with the number of ALD cycles. The RMS roughness is only 1.23 nm even at 30 nm thick of a-BN which indicates the formation of smooth surface of our ALD process. Also, XPS shows the stoichiometric a-BN and TEM, XRD, Raman confirms the amorphous nature of BN. Our results demonstrate that ALD a-BN process holds the potential for application in the realization of next-generation 3D integrated devices.