EFFECT OF OXYGEN ON SI ETCH PROFILE USING DC SF6 PLASMA MICROMACHINING

Abstract

Plasma etching with tapered profile structure (high aspect ratio structures) in silicon is an important step in manufacturing capacitors for memory devices and integrated components of microelectromechanical systems. In these applications, the goal is to etch an isotropic deep features with high etch rates and with tapered profile while maintaining good uniformity. This study presents a utilization of SF6/O2 glow discharge plasma in silicon etching. The effects of etching gas (SF6) pressure and addition of oxidation gas ratio on the etching rates have been investigated. In plasma etching; the balance between feature sidewall passivation and feature bottom etching lead to anisotropic etching. Since plasma etching process depends on the chemical reaction, its rate is dependant on the diffusion rate of the reactive species generated by the plasma to the etch front and the etch products away from the etch front which affected by the sidewall passivation. Results show that in such plasma process, both etching and passivation reactions occur at the same time. These etching and passivation reactions lead to taper etch profiles when O2 ratio was 10%. Visualization of profiles for N-type and poly-type Si wafers using optical microscopy is complimented by plasma etching rate. Key words: SF6plasma, micro etching, taper profile.