Lateral etching and filling of high aspect ratio nanometer-size cavities for silicon device structures

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We study a process technique involving SiO2 lateral etching coupled with amorphous Si (α-Si) refilling as a possible alternative to improve performance and lower costs for bipolar complementary metal–oxide semiconductor technologies. We investigated the lateral etching of oxide layers with thicknesses between 50 and 2.5 nm confined between a Si substrate and a multilayer stack composed of polycrystalline Si, WSix, and Si3N4. We found that the lateral etching of SiO2 proceeds even with the smallest thickness (2.5 nm) to create extremely small cavities. The etch extent (fixed time) dependence with SiO2 thickness suggests that capillary action may be an important mechanism. Using standard amorphous Si deposition techniques, we refilled all the small cavities without void formation as witnessed from transmission electron micrographs.