In recent years a strong demand has arisen for spin-on carbon (SOC) materials compatible with high-temperature processes. This requirement is to enable usage of high-temperature SOC (HTSOC) materials in integration schemes utilizing chemical vapor deposition (CVD) and/or atomic layer deposition (ALD) processes. In addition to compatibility with the high-temperature deposition processes, planarization requirements and/or chemical-mechanical polishing compatibility are often critical. To answer these new challenging requirements, we have developed a family of HTSOC materials that fulfills these critical needs. In this paper we present a successful development of pattern transfer process using our HTSOC with EUV lithography. We also present the capability of the HTSOC to be used as a mandrel in self-aligned double patterning (SADP) utilizing high-temperature CVD deposition of the spacer. The properties of the next-generation HTSOC materials that enable these processes will be discussed in detail and compared to previous HTSOCs material, conventional low-temperature SOCs, as well as amorphous carbon (aC).

Lithography track performance capabilities have been rapidly expanding through the years and have reached such a level of sophistication that focusing on classic metrics such as throughput, yield, cleanliness, and process stability is no longer enough. Currently, in addition to these traditional efforts, track manufacturers are developing advanced hardware features that can help resist suppliers achieve the stringent patterning requirements currently in place. Via this holistic approach, resist and track vendors can have an extensive collaboration and explore together various lithographic performance improvement opportunities. In this work, we investigate the capability of novel hardware solutions currently available on our SCREEN DT-3000 coat-develop track system to reduce EUV resist defectivity. The potential of using these innovative features to favorably modify the surface of different photoresists was deeply explored, and new enhanced process alternatives for different material types were successfully identified. We hereby present our work using a DT-3000 track and EUV NXE:3400C scanner to improve defectivity levels of aggressive 16nmhp L/S patterns.

Line edge roughness in chemically amplified EUV resists is strongly determined by the heterogeneity of the resist and the chemical processes between exposure and etching. A direct visualization of the chemical changes during development would obviously help to quickly optimize this process. However, no current technique has the sensitivity and spatial resolution to allow such metrology without adversely affecting the resist chemistry. Here, we show the potential of IR-AFM to follow the chemical processes in resist without causing chemical changes.

This talk will discuss efforts to pattern and utilize liquid metals as conductive inks for stretchable, soft, and reconfigurable electronics. Alloys of gallium have metallic conductivity, yet have low viscosity, low toxicity, and negligible volatility. Despite the large surface tension of the metal, it can be patterned into non-spherical 2D and 3D shapes due to the presence of an ultra-thin oxide skin that forms on its surface.

Augmented reality (AR) technologies that enable the overlay of digital information on the real world are widely anticipated to be the next wave of computing platforms. For a truly immersive AR experience, the AR glasses should be lightweight, comfortable, stylish, socially acceptable, and efficient that can be worn all day. Traditional optical devices are very bulky and are not suitable for head mounted displays (HMDs) for AR glasses. Hence, there is an increasing interest in developing nano-optics based devices that are significantly smaller and lighter than the conventional devices. Materials innovation is one of the key pillars that could enable the fabrication of such lightweight devices. In this talk, the impact of new materials like highly transparent, high refractive index (HRI) substrates, litho and patterning materials for device fabrication and permanent optical materials to develop all-day wearable AR glasses will be discussed.

Pattern collapse and photoresist scumming reduce lithographic quality with detrimental consequence on the process window, etching and pattern transfer. As extreme ultraviolet (EUV) lithography patterning moves to smaller and smaller technology nodes, these phenomena become increasingly dominant. In this work, we propose a three-interface model that accounts for the collapse and wiggling during development (due to developer infiltration) and rinse and drying (due to capillary force). We introduce a metric W3 (dependant on photoresist thickness, pitch, CD, and linewidth roughness) and demonstrate experimentally that W3 of exposed materials predicts scumming while the W3 of unexposed materials predicts collapse and wiggling.

The continued miniaturization of integrated circuit features has been made possible through multilayer patterning processes where different etch steps transfer the patterned photoresist image through various hardmasks to the underlying substrate. Wet etchants, such as the aqueous mixture of ammonium hydroxide and hydrogen peroxide known as SC-1 (Standard Clean -1), are often used for the selective removal of metal surfaces (i.e. TiN) from the substrate. To ensure that this metal removal is indeed selective, organic underlayers are used to protect the metal surface in regions where metal removal is unwanted. Unfortunately, these harsh basic and oxidative conditions are often incompatible with many underlayers which result in their delamination from the substrate, exposing and damaging the metal surface. Here we report our work on improving the SC-1 wet etch resistance of an underlayer coated over TiN. By increasing the film’s binding to the metal surface and decreasing its brittleness through polymer design or additive choice, we improve the time for film delamination in an SC-1 bath from 1 minute to over 20 minutes. Furthermore, we have developed a new method to evaluate SC-1 resistance by quantifying TiN removal by measuring the amount of titanium leached into the solution during wet etching by using inductively coupled plasma mass spectrometry (ICP-MS). We demonstrate with this method and XSEM images that TiN can be removed if the film does not act as a sufficient barrier to prevent SC-1 penetration, even if no film delamination is observed, which will be used to optimize future underlayer formulations.

Logic technologies require zero defectivity patterning to meet yield targets in high volume manufacturing. The migration to EUV lithography has introduced substantial new challenges in demonstrating defect-free patterning due to the introduction of radiation chemistry to the exposure process, limitations of the photosensitive resist materials, and photon shot noise inherent in shorter wavelength radiation. Achieving zero EUV patterning defects for the pitches required at leading-edge technology nodes is extremely challenging, as the defect sources involve multiple factors including resist and stack material properties, process variabilities, and photon stochastics. At SPIE 2020, Lam Research introduced our dry photoresist and dry development technology, which breaks the tradeoffs between dose, roughness, and defect performance. To achieve zero EUV patterning defects, we have engineered a holistic approach to co-optimize the complete EUV patterning flow with key differentiating steps such as dry photoresist deposition, post-exposure bake (PEB), dry development, and pattern transfer etch. The dry photoresist provides a simple, homogeneous, and stable composition of metal oxide network after deposition, EUV exposure, and PEB. The materials contrast of dry photoresist is enhanced by proprietary PEB to obtain the best selectivity for dry development and downstream pattern transfer etch. Unlike wet develop, dry develop allows us to tune the conditions during the pattern development process to provide optimum dry photoresist integrity and mitigate any residue for best patterned defect performance. We have demonstrated best-in-class defect performance with co-optimized patterning processes from resist deposition to pattern transfer. We first demonstrate 300mm blanket wafer performance after coat, bake and dry develop, where our post-develop defect performance is < 10 particles/wafer, 99% being defects consistent with our lab tool baseline defectivity. On patterned wafers using both P30 and P28 line/space large area macros, our dry photoresist shows no nanobridge or line break defects (sizes 10nm) are detected by e-beam inspections (scan area ~ 40mm2). A nanobridge defect density < 0.01/cm2 after pattern transfer etch is demonstrated by bright field inspections of whole wafers (scan area ~ 100cm2).

Perfluorooctane sulfonate, PFOS, was previously widely used in photolithography, but it and other long-chain acids had to be phased out due to concerns about their bioaccumulation potential and toxicity. A number of replacement chemicals are now used, including short-chain and emerging per- and polyfluoroalkyl substances (PFAS) such as perfluorobutane sulfonate (PFBS), fluorinated ethers, and non-PFAS alternatives. A wide variety of replacement chemistries have been used or proposed, ranging from simple small-molecule acids to complex fluorinated polymers. A major challenge in finding suitable alternatives is to balance performance with the need to avoid regrettable substitutions, which can lead to continuing harm to workers, communities, and ecosystems, and leave producers in positions of regulatory uncertainty. Assessment of PFAS continues to be limited by lack of data on hazard properties. Despite decades of growing interest, data on bioaccumulation potential and toxicity exist for only a handful of them. Based on the lack of available data, there is a clear need for scientifically sound assessments of both fluorinated and non-PFAS chemicals if they are to be adopted as alternatives. Yet a chemical-by-chemical approach to such evaluation is both time- and resource-intensive. Our group is developing a molecular dynamics-based framework to evaluate the relative hazards of PFAS and non-PFAS alternatives in comparison with substances like PFOS that are known to be problematic in their bioaccumulation and toxicity profiles. Molecular dynamics is used to predict the strength PFAS association with a variety of proteins selected for their contribution to the bioaccumulation potential and specific toxic mechanisms of PFAS, including fatty acid transport proteins, serum albumin, and thyroid hormone receptors. The individual predicted are then combined within a weighted score framework to rank substances by an overall hazard score (Figure 1). This is similar to existing approaches to evaluate neutral organic substances based on their persistence, bioaccumulation, and toxicity (PBT) profiles, but this is the first such attempt to focus on PFAS-specific properties. Upcoming work will further validate this hazard-ranking scheme using a zebrafish embryo toxicity assay for substances that are available for analysis, compared to benchmark chemicals like PFOS.