Micromachining of p-type 6H-SiC by electrochemical etching

Abstract

In order to structure p-type single-crystal 6H-SiC wafers for micro-electro-mechanical systems (MEMS) applications, electrochemical etching at a constant current density is used. In this paper, first, a suitable mask with a Poly/SiO2/SiC scheme is used for a long-time electrochemical etching of p-type 6H-SiC in a dilute HF solution. Etching rates and etched profiles with different concentrations (1, 2, 4, 8%) of the HF solution and different current densities (50, 100, 150 mA/cm(2)) are investigated in order to optimise the etching process. An HF concentration between 2 and 4% and a current density between 50 and 100 mA/cm(2) are suggested to obtain a smooth etching surface and a uniform etching profile. With these process parameters, the etching rate is found to be between 0.40 and 0.95 mum/min. A circular structure with a depth of 200 mum is demonstrated for further MEMS applications. (C) 2003 Elsevier B.V. All rights reserved.