DRY ETCH DAMAGE IN GAAS METAL-SEMICONDUCTOR FIELD-EFFECT TRANSISTORS EXPOSED TO INDUCTIVELY-COUPLED PLASMA AND ELECTRON-CYCLOTRON-RESONANCEAR PLASMAS

The effects of Ar plasma exposure on transconductance, channel sheet r esistance, output resistance, and gate contact ideality factor of GaAs metal-semiconductor field-effect transistors (MESFETs) were investiga ted using two different high-density plasma sources, namely inductivel y coupled plasma and electron resonance plasma. Ion-induced damage is found to be reduced at moderate source powers (similar to 200 W) becau se of the reduction in cathode dc self-bias and hence ion energy, but at higher source powers the increase in ion flux produces significant deterioration of the device performance. Careful attention must be pai d to both ion flux and ion energy in order to minimize ion-induced dam age. Due to their relatively low channel doping levels, MESFETs are fo und to be more sensitive to plasma damage than devices with very heavi ly doped component layers such as heterojunction bipolar transistors. (C) 1997 American Vacuum Society.