Patent ID: 7494936

Claim:
A method for electrochemical etching of a semiconductor material using positive potential dissolution (PPD) in alkaline etching solutions without the need for toxic hydrogen fluoride, said method comprising: subjecting one of: a polished material and an as-cut semiconductor material to an etching solution; positively biasing said material at atypically highly positive (anodic) potentials in a voltage range between approximately plus 20 volts and plus 55 volts relative to a reference saturated calomel electrode (SCE); and etching in the trans-passive range of potentials in which passivity breaks down and fast etching occurs, wherein said fast etching is defined as any rate faster than 5 microns per minute; and specifically controlling and directing illumination by light incident upon the positively biased polished/as-cut semiconductor material surface contacted and wetted by an alkaline etching solution free from toxic hydrogen fluoride such that the specifically controlled and directed illumination of the positively biased semiconductor material surface contacted and wetted by the etching solution increases the value of the anodic current density of the semiconductor material from practically zero at the passivity state to approximately 5000 mA/cm 2 , and such that the application of positive biasing at atypically highly positive (anodic) potentials in said voltage range, combined with specifically controlling of the semiconductor material surface contacted and wetted by the etching solution, is applied for a necessary and sufficient period of time to enable a positive synergistic effect on the rate and extent of etching of the semiconductor material, and therefore, on the type of etched semiconductor material formed therefrom.