Ruthenium catalyst processing and oxidation for scalable complementary metal-oxide-semiconductor-compatible metal-assisted chemical etch

Background: Metal-assisted chemical etching (MacEtch) of Si is a catalyst-based etch technique that has demonstrated better performance at attaining high-aspect ratio structures than reactive ion etching but developing a complementary metal-oxide-semiconductor (CMOS)-compatible process is an ongoing challenge. Ruthenium (Ru) is a highly desirable catalyst for CMOS manufacturing but is too catalytically active. Aim: To create a scalable Ru MacEtch process, the Ru catalyst must be tailored to have lower activity. Ru catalyst patterning must consider CMOS compatibility and fidelity of large area, nanoscale pattern transfer. Approach: The catalytic activity of Ru and MacEtch uniformity is tailored through optimization of Ru deposition and oxidation with CMOS-compatible patterning. Results: This report contains an entirely CMOS-compatible process for MacEtch of Si with feature dimensions down to 50 nm. To our knowledge, this is the first example of patterning a catalyst for MacEtch using dry etch processing. It also demonstrates that oxidation of the Ru catalyst can significantly reduce its catalytic activity and allow for a 100% increase in patterned area without porosity compared with previous publications. Conclusion: A drop-in replacement to plasma etching is demonstrated for CMOS devices and CMOS-compatible foundries. Catalyst design parameters such as deposition rate and heat treatment have a great influence on MacEtch performance. (c) 2024 Society of Photo-Optical Instrumentation Engineers (SPIE)