Deep single step vertical ICP–RIE etching of ion beam sputter deposited SiO2/Si multilayer stacks

•Vertical etching of an ion beam sputtered SiO2/Si multilayer stack is presented.•The stack was etched with a single step C4F8 and O2 based ICP–RIE process.•A profile of 90° and smooth sidewalls were the result of the vertical etching.•A deposition technique of a durable, defect free, steep Cr hard mask is described.•Selectivity between the multilayer stack and Cr hard mask was 77:1.

Deep vertical etching of a 10 μm thick SiO2/Si multilayer stack is presented. The stack was deposited by ion beam sputtering. To etch the stack, an octafluorocyclobutane (C4F8)–oxygen (O2) based inductively coupled plasma - reactive ion etching (ICP–RIE) process was developed. The recipe shows very similar etching rates for silicon dioxide (SiO2) and silicon (Si); thus it can be implemented as a simple one step etching process. In order to protect the stack properly during the etching, a durable hard mask is required. Investigations of the deposition of such a mask, using chromium (Cr) deposited by electron beam physical vapour deposition (EBPVD), are also presented.

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