A silicon containing antireflection coating (SiARC) can effectively suppress standing waves when the photoresist thickness is limited, but the relationship between polymer structures and optical parameters is not clear. High-silicon-content polysiloxanes were synthesized by sol–gel processing, and SiARC was prepared by spin-coating method. The influence of Si/Ph on the optical parameters (n and k values) of SiARC was investigated. Finally, the effect of silicon content on the etching rate of fluorine ion and oxygen ion was studied.