DRY ETCHING OF SUBMICRON GRATINGS FOR INP LASER STRUCTURES COMPARISON OF HI/H2, CH4/H2 AND C2H6/H2 PLASMA CHEMISTRIES

Three different discharge chemistries for dry etching of gratings in InP laser structures have been investigated. Each type of plasma (Hl/H2, CH4/H2, C2H6/H2) yields controllable etch rates that are constant with etching time. Lower DC self-biases can be used with Hl/H2 because of the greater volatility of the group III etch products. The C2H6/H2 mixture produces excessive polymer deposition on the photoresist mask at process pressures greater-than-or-equal-to 10 mTorr The rectangular shape of the gratings is preserved during overgrowth by organo-metallic vapour phase epitaxy.