Techniques for reduction in surface roughness and aperture size effect for XeF/sub 2/ etching of Si

Abstract

Low etching pressure and high temperature on silicon substrate successfully decrease the etched surface roughness and the aperture effect which represent challenges toward the application of silicon etching with XeF/sub 2/ to MEMS fabrication. Etched roughness and aperture effect are extremely high and limit factors for the design rules of MEMS devices. In order to express an extent of the aperture effect, an uniformity of etched depth is defined as followed: (depth at 25 /spl mu/m)/(depth at 175 /spl mu/m)/spl times/100%. By lowering the charge pressure from 390 to 65 Pa, the etched roughness decreased from 870.8 and 174.4 /spl Aring/ and the uniformity improved from 71.3 to 88.7%. By heightening the substrate temperature from 300 to 440 K, the etched roughness decreased from 151.4 and 44.5 /spl Aring/ and the uniformity increased from 71.3 to 91.6%. These results will allow us to design with less constraints and expand the field of applications of XeF/sub 2/ etching to MEMS.