Effect of coating and plasma treatments on the induced coupled plasma-reactive ionic etching of boron-doped diamond for microelectromechanical systems (MEMS) applications

Abstract

Induced coupled plasma etching was performed on poly-crystalline boron-doped diamond (BDD) films synthesized by microwave assisted chemical vapor deposition (MWCVD). Effects of the input power and of the gas composition and pressure on etching performances have been investigated. A basic aluminium layer and a new hybrid material have been studied as protecting film for the patterning. Best conditions to get high etch rates were a gas ratio Ar/O₂ of 27% (vol.) under 10 mTorr at 200 W (input power). Aluminium (Al) masking induced un-intentional whiskers formation which was removable using CHF₃ as a reactive gas with the drawback to lower the process selectivity. In order to get both a high etching rate and a high selectivity, a hybrid material based on an organic/mineral resin was then used as the masking material. This performing photoresist film allowed etching a 3.6-μm-thick BDD film at 200 nm min⁻¹.

Keywords:

• BDD film
• Al coating
• hybrid photoresist coating
• whiskers density
• diamond etching