Microfabrication by mask-maskless wet anisotropic etching for realization of multilevel structures in {100} oriented Si

Step-like structures oriented along 〈110〉 or 〈100〉 directions on {100} oriented Si substrates are first etched with mask following maskless etching in 30 wt. % KOH solution in water at 80 °C. The step structures investigated by maskless etching are convex prismatic edges bounded by {100} and {111} planes for 〈110〉 oriented steps or only {100} planes for 〈100〉 oriented steps. Experimental results are used to verify the nature of {hkl} cutting planes that are developed at the convex corners of the steps during maskless anisotropic etching. From analytical relations and experimental results, the ratio between the etching rates for the {hkl} (fast-etching plane at the edge step) and {100} planes is found for both step orientations.