Effects of the etchmask properties on the anisotropy ratio in anisotropic etching of silicon in aqueous KOH

The objective of the present study is to investigate the influence of the etchmask properties on anisotropic etching of silicon in a KOH/O solution. The mechanical stress induced in the silicon substrate by an LPCVD- etchmask has been analysed by 3D finite element analysis. It is shown that the rise of the mechanical stress at the edges of etchmask openings is mainly affected by the thickness of the LPCVD- etchmask. The effect of the mechanical stress on the anisotropy ratio was experimentally determined. It has been found that the anisotropy ratio decreases with increasing LPCVD- etchmask thickness. Furthermore the use of /LPCVD- double-layer etchmasks resulted in rough side wall surfaces and a lower anisotropy ratio.