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

BackgroundMetal-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.AimTo 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.ApproachThe catalytic activity of Ru and MacEtch uniformity is tailored through optimization of Ru deposition and oxidation with CMOS-compatible patterning.ResultsThis 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.ConclusionA 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.