Low damage dry etching of III–V compound semiconductors using electron cyclotron resonance discharges

Abstract

Electron cyclotron resonance (ECR) discharges are characterized by low ion energies ( ≤ 15 eV) and high densities of active species. This makes them excellent candidates for high rate, low damage dry etching of III–V semiconductors. We have investigated the use of ECR discharges of CH 4/H 2/Ar for etching InP, InGaAs, AlInAs and GaAs as a function of additional rf biasing of the sample, and in this article present the InP results. In contrast to the results with conventional reactive ion etching (RIE), ECR discharges lead to very shallow (~ 20 Å) damaged layers on these materials and much less disruption of the electrical quality of the etched surface. For example, RIE of InP leads to nonstoichiometric, In-rich surfaces to which one cannot make a Schottky contact. Removal of at least 150 Å of material is required before the integrity of the surface is restored. We have been able to achieve excellent rectifying contacts on ECR-etched InP without the need for wet chemical treatment of the surface. Optical and chemical analysis of the ECR etching shows that it clearly is a low damage process relative to the more conventional dry etch methods.