Osakpolo Isowamwen, Nathan Marchack, Devi Koty, Qingyun Yang, Hien Nguyen, Steve Molis, Scott Lefevre, Marco Hopstaken, Andy Metz, Jeff Shearer, Robert Bruce
The recent passing of the CHIPS act has highlighted the semiconductor industry as a driver of innovation. Simultaneously, environmental legislation regarding per- and polyfluoroalkylated substances (PFAS) usage has become a major focus in both the US and EU, which has potential implications for many hydro- and perfluorocarbon (HFC/PFC) gases currently used in semiconductor manufacturing. High-aspect ratio (HAR) etch processes are a critical component of two high-growth manufacturing areas (packaging and solid-state memory), however, they are significant consumers of HFC/PFC chemistries due to the vertical scale of the features involved. This paper analyzes reduced gas flow effects in a HAR through-silicon via (TSV) etch process, with the aim of improving the sustainability of future processes through an improved mechanistic understanding. We demonstrate a cyclic C4F8 /SF6 TSV process with ~90% ER and comparable sidewall roughness using 50% of the SF6 flow rate and 60% of the passivation time. We also show through TOF-SIMS analysis a depth dependence of the sulfur and fluorocarbon concentrations on the TSV sidewall which varies with gas flow rate, providing further insight into the mechanisms associated with HAR etching.
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.
The progress of three potential DSA applications, i.e. fin formation, via shrink, and pillars, were reviewed in this paper. For fin application, in addition to pattern quality, other important considerations such as customization and design flexibility were discussed. An electrical viachain study verified the DSA rectification effect on CD distribution by showing a tighter current distribution compared to that derived from the guiding pattern direct transfer without using DSA. Finally, a structural demonstration of pillar formation highlights the importance of pattern transfer in retaining both the CD and local CDU improvement from DSA. The learning from these three case studies can provide perspectives that may not have been considered thoroughly in the past. By including more important elements during DSA process development, the DSA maturity can be further advanced and move DSA closer to HVM adoption.
It has been shown that high charge mobility in solution-processible organic semiconductor-based field effect transistors
is due in part to a highly parallel π-π stacking plane orientation of the semiconductors with respect to gate-dielectric. Fast
solvent evaporation methods, generally, exacerbate kinetically random crystal orientations in the films deposited,
specifically, from good solvents. We have investigated solubility-driven thin film structures of thiophene derivative
polymers via spin- and drop-casting with volatile solvents of a low boiling point. Among volatile solvents examined,
marginal solvents, which have temperature-dependent solubility for the semiconductors (e.g. methylene chloride for
regioregular poly(3-alkylthiophene)s), can be used to direct the favorable crystal orientation regardless of solvent drying
time, when the temperature of gate-dielectrics is held to relatively cooler than the warm solution. Grazing-incidence X-ray
diffraction and atomic force microscopy strongly support that significant control of crystal orientation and mesoscale
morphology using a "cold" substrate holds true for both drop and spin casting. The effects of physiochemical post-modificaiton
on film crystal structures and morphologies of poly(9,9-dioctylfluorene-co-bithiophene) have also been
investigated.
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