As quantum computers based on superconducting qubit processors scale, cryogenic microwave components in the qubit control and readout chain must be appropriately tested and qualified to ensure consistent and high-fidelity quantum computation. However, the intersection of superconducting cryogenics and microwave electronics is a new domain with limited technical and commercial expertise. In this paper we validate a TaaS (testing-as-a-service) framework using an organizational workgroup model that consists of (1) a commercial Test House, (2) standard temperature Component Manufacturer, (3) Academic Partner, and (4) System Integrator to demonstrate a scalable model for the qualification of cryogenic microwave components. The goal of this model is to secure the supply chain and support the rapid growth of Quantum Computing (QC) technologies. The component test vehicle presented in this paper is a low-noise amplifier (LNA) which is a crucial component in the cryogenic chain to ensure adequate signal-to-noise of the qubit readout. We devise standard test metrics and protocols by which LNA performance is measured, including key parameters such as gain and flatness, reflection and isolation, operating bandwidth, and noise figure. We present details of the cryogenic testbed customized for LNA qualification, outline test methodologies, and present a suite of standard processes that are used to systematize data collation and reporting. The testbed is validated by reproducing parameters of a pre-characterized LNA. Its value is demonstrated by characterizing a proof-of-concept cryogenic LNA prototype. Finally, we describe the extension of our TaaS framework toward testing at scale for various active and passive cryogenic components used in QC.

The Quantemol database (QDB) provides cross sections and rates of processes important for plasma models; heavy particle collisions (chemical reactions) and electron collision processes are considered. The current version of QDB has data on 28 917 processes between 2485 distinct species plus data for surface processes. These data are available via a web interface or can be delivered directly to plasma models using an application program interface; data are available in formats suitable for direct input into a variety of popular plasma modeling codes including HPEM, COMSOL, ChemKIN, CFD-ACE+, and VisGlow. QDB provides ready assembled plasma chemistries plus the ability to build bespoke chemistries. The database also provides a Boltzmann solver for electron dynamics and a zero-dimensional model. Thesedevelopments, use cases involving O2, Ar/NF3, Ar/NF3/O2, and He/H2O/O2 chemistries, and plans for the future are presented.

We report a design methodology for creating high-performance photonic crystals with arbitrary geometric shapes. This design approach enables the inclusion of subwavelength shapes into the photonic crystal unit cell, synergistically combining metamaterials concepts with on-chip guided-wave photonics. Accordingly, we use the term “photonic metacrystal” to describe this class of photonic structures. Photonic metacrystals exploiting three different design freedoms are demonstrated experimentally. With these additional degrees of freedom in the design space, photonic metacrystals enable added control of light-matter interactions and hold the promise of significantly increasing temporal confinement in all-dielectric metamaterials.

Switching of phase change memory (PCM) materials between crystalline and amorphous phase with electrical pulses and optical properties make it an important candidate for storage class memory and neuromorphic computing. However, PCM materials can be sensitive to air exposure during integration, therefore in-vacuo RIE and encapsulation is important to provide the required oxygen diffusion barrier. Low temperature SiN deposition can be used for low thermal budget integration schemes provided a good film conformality is achieved and damage or etching to the PCM elements is mitigated. In this work, ammonia- (NH3-) free, plasma enhanced chemical vapor deposition (PECVD) SiN films deposited at 40°C (microwave plasma) and 200°C (inductively coupled plasma), are compared and wet etch rates and optical properties are evaluated. NH3-free SiN films were deposited using SiH4, N2, H2, and Ar as source gases. Tuning the plasma parameters during encapsulation we observed simultaneous selective etching of GST and controlled SiN film deposition. Hydrogen and argon addition to the plasma mixture provided the main control knob for in-situ GST trimming during deposition, avoiding any type of elemental or structural damage to the GST films.

Through‐silicon via etch (TSV) is critical to current and future advanced packaging schemes. For heterogeneous integration approaches in particular, where modular components are tightly packed together, these processes play an integral role. While etch processes for silicon appear well understood and the frontiers of plasma etch have led us to advanced cyclic processes for device fabrication such as atomic layer etching, TSV applications are fundamentally different due to their relative size and aspect ratio targets. Unlike small-scale etching, TSV feature etching has not shown exponential change over time. To achieve TSV targets such as high etch rate, high aspect ratio, and clean profiles to support filling, known solutions are employed such as cryogenic wafer temperatures, alternative hard mask schemes, and extremely short gas cycle times; these solutions require specialized equipment and/or a more complex integration scheme. We explore the creation of high-aspect ratio, diffusion-limited TSV etches with high PR selectivity (<50:1) and high aspect ratios while simultaneously aiming for a high etch rate all while using non-cryogenic temperatures and a standard photoresist mask. A focus on sidewall profile and sidewall damage is maintained.

Going beyond the limited design freedoms of traditional photonic crystals, we experimentally show how photonic metacrystals exploit the inclusion of subwavelength dielectric scatterers in the unit cell to deterministically modify k-space and real space profiles.

IBM Research recently announced that 2nm node Nanosheet Technology is able to deliver superior density, power and performance compared to today’s 7nm FinFET technology in mass production. To enable 2nm node Nanosheet Technology, advanced patterning solutions are required. Dimensional compression drives the need for advanced patterning solutions including wider use of extreme ultraviolet (EUV) lithography. This also creates higher in feature aspect ratios, which in turn creates additional challenges during plasma etch. As aspect ratios continue to increase, difficulty with in-feature ion, radical, and volatile species transport during plasma etch presents an exceptional challenge. Dimensional scaling and wider use of EUV increases the need for further reduction of critical dimension (CD) variability, including line edge and line width roughness. The introduction of 3-dimensional gate all around nanosheet architecture has introduced an additional unique set of patterning challenges to address for coming technology nodes. When combined with dimensional scaling there is a clear need for novel advanced patterning process solutions to enable future nodes. In this presentation a variety of these challenges and the impact they will have on device and node scaling will be introduced and reviewed.

We demonstrate a novel process for building a Resistive RAM (ReRAM) stack which reduces the forming voltage (V-form) and increases the switching resistance, both characteristics that are important ingredients for the use of ReRAM in scalable analog compute for AI. Utilizing this process, we explore analog switching characteristics above 100k and demonstrate 4-bit programming at Rmax = 1M. Utilizing the same writing characteristics, CIFAR-10 inference simulation shows 90% accuracy, comparable to the full precision model accuracy.

The scientific study of plasma discharges and their material interactions has been crucial to the development of semiconductor process engineering and, by extension, the entire microelectronics industry. In recent years, the proliferation of the big data business model has led to heightened interest in technology candidates with the potential to supplant CMOS architectures in critical metrics such as computational capacity or power consumption. These novel technologies share many common material elements with existing logic and memory devices, but the impact of mass fabrication techniques on their performance is largely unknown due to differences in the underlying physics of their operation. Two components are thus vital to this endeavor: fundamental evaluation of any emerging plasma process interactions and the ability to tailor any aspect of the plasma process necessary to produce the desired specifications. In this article, we review relevant advances in the study of plasma-induced damage mechanisms as well as characterization methods such as diagnostic probes and simulation tools. We also provide an outlook for the application of techniques such as plasma doping, area-selective etch/deposition, and heterogeneous integration. The frontiers of any new computing paradigms can only be explored through a focus on atomic scale engineering, and progress in the field of plasma science supplies the necessary toolset.

In the ideal case, plasma-enhanced atomic layer etching enables the ability to not only remove one monolayer of material but also leave adjacent layers undamaged. This dual mandate requires fine control over the flux of species to ensure efficacy, while maintaining an often arduously low ion energy. Electron beam-generated plasmas are well-suited for etching at low ion energies as they are generally characterized by highly charged particle densities (1010–1011 cm−3) and low electron temperatures (<1.0 eV), which provide the ability to deliver a large flux of ions whose energies are <5 eV. Raising the ion energy with substrate biasing thus enables process control over an energy range that extends down to values commensurate with the bond strength of most material systems. In this work, we discuss silicon nitride etching using pulsed, electron beam-generated plasmas produced in argon-SF6 backgrounds. We pay particular attention to the etch rates and selectivity versus oxidized silicon nitride and polycrystalline silicon as a function of ion energy from a few eV up to 50 eV. We find the blanket etch rate of Si3N4 to be in the range of 1 A/s, with selectivities (versus SiO2 and poly-Si) greater than 10:1 when ion energies are below 30 eV.

Phase Change Memory (PCM) materials can be damaged during plasma exposure leading to changes in phase transition behavior. Etch-induced damage and crystallization properties of GeSbTe (GST) were evaluated as a function of substrate temperature, plasma chemistry, and plasma exposure time. Enhanced damage formation is related to selective elemental depletion and non-volatilized etch residue retention in the near surface region. These experiments validate literature findings that crystallization time increases with reduction in film thickness for GST samples capped with a thin SiO2 film, indicating the presence of a modified layer which serves as an interface layer material. A direct comparison of passivating properties of hydrofluorocarbon and hydrocarbon on GST can be more conclusive with a fine tuning of film thickness and an evaluation of total residue retention with depth profiling.

Analyses of unit process trace data are critical components of modern semiconductor manufacturing process control. While process development environments share many characteristics with manufacturing environments, development tools and processes may not be suitable candidates for the deployment of traditional trace analytics such as FDC applications. Here we describe the adaptive use of large scale, proactive process trace monitoring and reactive root cause analytics for supporting development operations. The large-scale monitoring application we have deployed is comprehensive in scope and scale and focusses on monitoring the stability of a chamber over time. The reactive root cause application we have deployed automatically searches large trace data spaces to identify trace data elements with potentially interesting relationships to variations in on-wafer measurements and is designed to handle the small sample sizes encountered frequently in development operations.

Plasma etch residue formation and its removal from silicon nitride (SiN) films deposited at 200ºC, 480ºC and 700ºC is explored. X-Ray Photoelectron Spectroscopy (XPS) measurements showed that SiN contains more nitrogen (N) and less oxygen (O) with increasing deposition temperature. SiN films were etched in an Inductively Coupled Plasma (ICP) reactor in a halogen/hydrofluorocarbon (H:HFC) gas mixture; the carbon (C) containing species in the resulting residue films were studied as a function of the H:HFC ratio in the plasma. Post-plasma etch cleaning methods of the SiN surface were compared, these included: wet treatment with diluted hydrofluoric acid (dHF), sputtering with argon (Ar) plasma, and combined dHF and Ar plasma. After etch, Secondary Ion Mass Spectroscopy (SIMS) and XPS data showed formation of fluorocarbon (FC) films on SiN. FC film thickness after etch was estimated from XPS to reach up to 2 nm. Ultimately the SiN etch rate was shown to drop with increasing deposited C thickness while the lower nitrogen content in the SiN film (i.e. 200ºC) led to higher etch rate, which is in good agreement with literature. Ar plasma sputter turned out to be the most effective way of cleaning C residues: C surface content after Ar sputter was reduced to or below the reference data (unetched sample). In terms of wet treatment, an optimized chemistry was identified (AltChem) and post-RIE cleaning was more efficient than dHF in reducing C surface concentrations.

Extreme ultraviolet (EUV) lithography has emerged as the next generational step in advancing the manufacturing of increasingly complex semiconductor devices. The commercial viability of this new lithographic technique requires compatible photoresist (PR) materials that satisfy both the lithographic and etch requirements of good feature resolution, chemical sensitivity, a low line edge roughness, and good critical dimension uniformity. Achieving the decreased feature pitches of modern processing nodes via EUV lithography places a limit on the available photoresist thickness for a pattern transfer process. Therefore, etch processes are required to maximize the etching selectivity of a hard mask material, such as SiO2, to an EUV photoresist. In this work, the authors evaluated the ability of an atomic layer etching (ALE) process to maximize the SiO2/EUV PR etching selectivity. Through the flexible parameter space available in an ALE process, the authors evaluated the etching behaviors as a function of the ALE parameters of ion energy, etch step length, fluorocarbon (FC) deposition thickness, and precursor gas type. The authors found that the interaction between the energetic argon ion bombardment and a deposited FC layer produces a modified surface layer on the PR material that can strongly control the PR etch rate and even produce an etch stop under some conditions. Under the same processing conditions, the etching behavior of SiO(2)continues unimpeded, thus resulting in a high overall SiO2/PR etching selectivity. Secondary characterization using x-ray photoelectron spectroscopy and atomic force microscopy was used to support the conclusions derived from the ellipsometric modeling based on the surface chemistry evolution and determine the impact of the ALE process on the surface roughness of the EUV PR, respectively. Additionally, attenuated total reflection Fourier-transform infrared spectroscopy was used to track the impact on specific functional groups within the PR composition from both the argon ion bombardment and FC deposition components of the ALE process. The ALE-based PR etching concept established in this work serves as a foundation for both the understanding of the impacts of an ALE process on an EUV PR material and for future works, employing an ALE process for PR-based pattern transfer.

Surface oxide formation inhibiting the etch of a tantalum nitride (TaN) film was controlled through step pressure modulation and H2 addition in a Cl2/Ar based plasma-assisted cyclic etch process. Sources contributing to the oxidation of the film included the mask materials, specifically the silicon-containing antireflective coating, as measured by optical emission spectroscopy. Surface analysis of etched films by secondary ion mass spectroscopy showed the presence of a modified surface layer ∼2 nm thick with localized oxygen concentrations 0.02 and 0.003 that of the control sample (without and with H2 addition, respectively). Reduced Ta–O bonding observed via x-ray photoelectron spectroscopy as a result of H2 addition was found to enhance etch rate uniformity of both blanket and patterned films. Minimization of redeposited oxidized TaN on the mask sidewalls of patterned samples was achieved using this etch process and by controlling the lithographic stack composition.

Monitoring vacuum ultraviolet (UV/VUV) emission in plasma systems is challenging as it requires specialized diagnostic systems or sensors to be compatible with these devices. This study addresses different reactor configurations and plasma chemistries with various levels of UV emission and their effects on a known set of polymers. First, the effect of He plasma treatment of organic underlayer (NFC-1400) and e-beam resist (hydrogen silsesquioxane) on line-space patterning of polysilicon at sub-100 nm pitch was investigated. By applying He plasma exposure, both before and after patterning of the optical underlayer, a significant improvement in line edge roughness (LER) from 2.5 to 1.4 nm was observed. To understand the plasma treatment mechanisms, polymers were exposed to synchrotron VUV light at 62 nm (or 20.0 eV), which coincides with the He VUV emission range (50–60 nm), followed by etching of poly-Si, and were found to have similar LER results. The refraction index measurements for both the optical underlayer and the e-beam resist revealed the key finding that the polymers absorption maxima corresponded exactly to the wavelength of ∼60 nm. Second, the impact of inductively coupled and microwave plasma configurations on etch rates and chemical properties of photoresists were investigated. Identifying specific photon-induced modifications on polymers can help detect UV/VUV emission in the plasma and decouple ion and photon effects on materials. Poly(methyl methacrylate) and poly(4-vinylphenol)-based photoresists were exposed to argon (Ar) and nitrogen (N2) plasmas. Surface and elemental analyses confirmed that plasma effects on chemical modifications, surface roughness, and etch rate were significantly higher for poly(methyl methacrylate) compared to poly(4-vinylphenol)-based photoresists. Detailed elemental and molecular structure analyses of these polymers showed relatively higher damage to both species caused from the inductively coupled plasma, which is ultimately correlated with a higher UV/VUV emission.

The early work of John Coburn and Harold Winters revealed a synergistic effect in ion-enhanced Si etching by the concurrent irradiation of Ar+ and XeF2. This finding provided an important foundation for the development of plasma dry etching processes. The experimental results of Coburn and Winters also found effects that are useful for the development of atomic layer etching (ALE) processes characterized by a self-limited etch rate. ALE approaches are widely established and can be utilized in either directional or isotropic etching by employing proper surface modification and product removal steps. Nevertheless, the development of material selective ALE processes is still limited. An approach that combines substrate-selective deposition with etching opens a new processing window for selective ALE. The authors studied the deposition behavior of mixtures of methane (CH4) with trifluoromethane (CHF3) and mixtures of methane with octafluorocyclobutane (C4F8) on HfO2 and Si surfaces. The experimental results show that a CH4/C4F8 mixture produces a comparable fluorocarbon (FC) deposition thickness on both HfO2 and Si during the deposition step. In contrast, a CH4/CHF3 mixture deposits an FC film on Si, whereas it fluorinates the HfO2 surface with negligible FC deposition. Utilizing these behaviors allows for an ALE process based on CH4/CHF3 for selective removal of HfO2 over Si. Surface characterization data that provide mechanistic insights into these processes are also provided and discussed.

This document is a joint response by scientists from the Princeton Plasma Physics Laboratory, IBM T. J. Watson Research Center and Applied Materials, Inc. to the DOE Office of Science (DOE-SC) Request for Information: Basic Research Initiative for Microelectronics (https://www.federalregister.gov/documents/2019/07/12/2019-14869/request-for-information-basic-research-initiative-for-microelectronics). Specifically, we propose DOE-SC to include the following topics in their consideration for future solicitations on Microelectronics: 1) The development of a real-time monitoring and in-situ diagnostic techniques that can provide information on plasma, substrate surface, and interaction between both during atomic precision processing of complex materials for the most advanced microelectronic devices with applications to high performance computing and artificial intelligence, and 2) The development of experimentally validated modeling tools to predict processing dynamics including plasma, chemical and material processes involved.