PHOTOELECTROCHEMICAL ETCHING OF SEMICONDUCTORS

Photoelectrochemical (PEC) etching of III-V semiconductors has been us ed to fabricate unique structures in electronic and photonic devices, such as integral lenses on light-emitting diodes, gratings on laser st ructures, and through-wafer via connections in field-effect transistor s. The advantages and characteristics of PEC etching are reviewed, and the extension of this processing technique to silicon is addressed, T hree-dimensional structures are of great interest in silicon for elect ronic and micromechanical devices. Silicon is a challenging material t o PEG-etch because the oxides formed during etching inhibit the dissol ution rate and decrease the spatial resolution. In addition, the long carrier lifetime permits holes to react at unilluminated sites. Nonaqu eous solvents provide a processing environment where oxides do not int erfere with the spatial resolution and free fluoride is no longer need ed in the dissolution of silicon.