EFFECTS OF THE ETCHMASK PROPERTIES ON THE ANISOTROPY RATIO IN ANISOTROPIC ETCHING OF (100)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/H2O solution. The mechanical stress induced in the silicon substrate by a n LPCVD-Si3N4 etchmask has been analysed by 3D finite element analysis . It is shown that the rise of the mechanical stress at the edges of e tchmask openings is mainly affected by the thickness of the LPCVD-Si3N 4 etchmask. The effect of the mechanical stress on the anisotropy rati o was experimentally determined. It has been found that the anisotropy ratio decreases with increasing LPCVD-Si3N4 etchmask thickness. Furth ermore the use of SiO2/LPCVD-Si3N4 double-layer etchmasks resulted in rough {111} side wall surfaces and a lower anisotropy ratio.