NONSELECTIVE WET CHEMICAL ETCHING OF GAAS AND ALGAINP FOR DEVICE APPLICATIONS

The nonselective wet chemical etching of AlGaInP and GaAs in pure iodi c (HIO3) acid and in hydrochloric acid (HCl) associated different oxid ant agents has been evaluated. The pure iodic acid is nonselective bet ween III-V phosphides and arsenides. Unfortunately, the etch of GaAs r esults in a very rough morphology and an etch rate 10 times greater th an on AlGaInP. The mixing of HCl with different oxidants such as H2O2 gives a nonselective etchant.:However H2O2 dissociates HCl to form chl orine which produces a wide evolution of the etch rate with time incom patible with the reproducibility necessary for device technology. This phenomenon is easily explained and solved using oxidant agents such a s KIO3, K2Cr2O7 Added to HCI, they give chemically stable solutions bu t unfortunately they give rise to a strong undercut of the AlGaInP und er the GaAs. The iodic acid is also a strong oxidant. Therefore a dilu ted solution of(HCI, HlO(3), H2O) is proposed which gives an evolution of the etch rate between 300 and 3000 Angstrom/min with water dilutio n, a good stability in the time, and similar etch rates on the two mat erials with very good morphologies. Applied to heterostructure no unde rcut of the AlGaInP is observed. (C) 1998 American Vacuum Society.