Hydrogenation and defect creation in GaAs-based devices during high-density plasma processing

摘要

The effects of Inductively Coupled Plasma (ICP) and Electron Cyclotron Resonance (ECR) H_2 plasmas on GaAs metal semiconductor field effect transistors (MESFETs), high electron mobility transistors (HEMTs) and heterojunctionbipolar transistors (HBTs) have been measured as a function of ion flux, ion energy and process pressure. The chemical effects of hydrogenation have been compared to direct physical bombardment by Ar plasmas under the same conditions. Si dopant passivation in MESFETs and HEMTs and C base-dopant passivation in HBTs produces much larger changes in sheet resistance, breakdown voltage and device gain or transconductance than Ar ion bombardment and suggests that H_x-containing plasma chemistries (CH_4/H_2 for semiconductor etching, SiH_4 for dielectric deposition, CHF_3 for dielectric etching) should be avoided, or at least the exposure of the surface minimized. In some cases the device degradation is less for higher source power conditions, due to the suppression of cathode de self-bias and hence ion energy.