THE FORM OF ETCH RATE MINIMA IN WET CHEMICAL ANISOTROPIC ETCHING OF SILICON

Etching of monocrystalline silicon in alkaline based solutions leads t o a deep minimum in the etch rate crystallographically oriented along (111). The details of the form of the minimum (angular dependence of t he etch rate) are investigated and discussed in a framework of steps o riginating from spontaneous nucleation and from misorientation of the crystal face exposed to the etchant. As a result, the etch rate minimu m is characterized by a narrow flat portion that reflects the density of nuclei, and the temperature dependence of the width has an activati on energy equal to 1/3 of the nucleation barrier.