In situ Raman spectroscopy of the selective etching of antimonides in GaSb/AlSb/InAs heterostructures

The in situ real-time monitoring of the selective etching of semiconductor structures with a Raman microprobe system is demonstrated for the first time. The technique that is applied to GaSb/AlSb/lnAs heterostructures allows the accurate timing of the etching as well as a study of the chemistry of the etching process and can be applied to many problems in the processing of compound semiconductors. During etching of AlSb a surface layer rich in Sb builds up that slows down the etch rate, whereas GaSb is etched without producing this residue layer. The different etching behaviour of AlSb and GaSb is confirmed by measurements of the etching depth in patterned samples by means of a Dektak stepper. The origin of the antimony layer is explained.