Advanced and reliable GaAs/AlGaAs ICP-DRIE etching for optoelectronic, microelectronic and microsystem applications

Abstract

We investigate the parameter optimization for micron-scale etching by Inductive Coupled Plasma - Deep Reactive Ion Etching (ICP-DRIE) of GaAs/AlGaAs semiconductor heterostructures. Although dry etching approaches have been reported in the literature using a broad variety of plasma etch tools, there is still need to meet the majority of microsystems dry etching requirements. The etch process family studied here, is dominated by the relative pressures of BCl3 (Boron trichloride) and Cl2 (Chlorine) gases. The influence of using a BCl3/Cl2/Ar/N2 mixture at different pressures has been investigated: A small addition of N2 (Nitrogen) is very effective inducing sidewall protection when using photoresist masks. The etch profile quality has been characterized as a function of the plasma process and of the etched feature sizes. The desired etch characteristics for GaAs/AlGaAs heterostructures can be achieved by controlling the various process parameters with good reliability, high selectivity, and – simultaneously – high etch rates and sidewall verticality. Etch rates from 1 to over 5.5μm/min have been obtained. The selectivity with optical photoresist varies from 2.3 to 16. The presented results can be valuable for a wide range of applications involving fabrication of micro-electro-mechanical-systems or Micro Optoelectronic Mechanical Systems.