Electron cyclotron resonance plasma etching of InP in CH4/H2/Ar

Plasma etching of InP in a microwave (2.45 GHz) electron cyclotron resonance (ECR) CH4/H2/Ar discharge has been investigated as a function of additional radio frequency (rf, 13.56 MHz) self-biasing of the sample. The etch rate of InP in a 1 mTorr, 250 W CH4/H2/Ar (5/15/7) ECR discharge increases linearly with applied rf bias, from 50 Å min−1 at 0 V to 350 Å min−1 at 200 V. Etching under ECR conditions alone yields smooth surface morphologies, while additional rf biasing of the discharge leads to In droplets remaining on the surface. This appears to be a result of preferential removal of P by the high atomic hydrogen density in the discharge. The room-temperature photoluminescence intensity from InP is reduced by approximately an order of magnitude after ECR etching, but is restored after removal of ∼20 Å from the surface by wet chemical etching. Gold Schottky contacts on InP samples etched under ECR conditions only yield barrier heights of 0.48 eV and ideality factors of 1.1, essentially identical to those on wet-etched control samples. ECR etching performed with an additional 100 V rf bias yields diodes with barrier heights of 0.44 eV and ideality factors of 1.6. Removal of ∼20 Å of the surface on these samples restores the values to those obtained on the control material.