Preferential etching of InP through photoresist masks.

Photoresist etch mask undercutting problems have been studied for the etching of v-grooves in InP(100) substrates for channelled substrate laser growth. The relationship between the photoresist mask undercutting and the impurity contents (HF, HBr, and H sub 2 0 sub 2) in the etchant were studied. The fluoride anion in the etchant causes the separation of the photoresist from the oxidized InP surface and results in excessive undercutting.