High-Aspect-Ratio Parallel-Plate Microchannels Applicable to Kinetic Analysis of Chemical Vapor Deposition

A method is proposed to fabricate a high-aspect-ratio (HAR) microchannel with a microscopic gap and AR of more than 1000:1 applicable to a test structure for kinetic analysis of chemical vapor deposition (CVD). It has a parallel-plate structure and is formed concisely by sticking a planar Si substrate and a patterned Si or silicon-on-insulator (SOI) substrate fabricated by single-step etching, by clamping them. The resulting feature exhibits a uniform gap and smooth surface morphology along its depth. When CVD is conducted into this HAR microchannel, the sticking probability (η) of film-forming species can be detected by analyzing the film thickness gradient. The use of a microchannel with an AR of 1000:1 enables the elucidation of η values from 1 down to the order of 10−7. A kinetic analysis of SiC-CVD from methyltrichlorosilane and H2 is thus performed. It is found that conformal SiC-film growth occurred inside the HAR microchannel, where one of the film-forming species is revealed to have extremely low η around 10−6. The present study demonstrates that the developed HAR microchannel is a solution to access the overall reaction kinetics of CVDs, including film-forming species with extremely low η.