Etch rates and morphology of silicon ( h k l) surfaces etched in KOH and KOH saturated with isopropanol solutions

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Silicon wafers with (1 1 0), (3 3 1), (3 1 1) and (2 1 1) crystallographic orientations etched in KOH and KOH saturated with isopropyl alcohol solutions have been studied. Etch rates of selected ( h k l ) planes were estimated by direct etch depth measurements. The effects of IPA additive on etch rates, hillocks formation and surface roughness of considered planes were analysed. It was shown that IPA affects the planes of ( h h l )-type, causing both their etch rate reduction and surface quality improvement. IPA addition to KOH solution does not reduce etch rates of ( h l l )-type planes but results in bulky hillocks formation on the whole etched area. The type of IPA interaction with different crystallographic planes probably depends on bond configuration on a particular plane.