The effect of DC bias on the sputter-deposition of W and W-Al on GaAs substrates was investigated. By applying a negative bias to the substrate, the concentration of impurities in the metals and at the interface, such as oxygen, was reduced, and the characteristics of the Schottky contact were improved with respect to the barrier height, the n-value and the uniformity. These results are explained by the reverse sputtering effect for the substrate. This technique was applied to the gate formation of GaAs MESFETs, and the uniformity of the threshold voltage distribution within a 2-inch wafer was much improved.

I{e investigated the effect of DC bias on the sputter-deposition of I{ and I{-Al on the GaAs substrates. By applying a negative bias to the substrate, we found that the concentration of impurities in the netal and at the interface were reduced, and the characteristics of the Schottlcy contact were improved with respect to the barrier height, the n-value and tire uniforrnity, which was due to the reverse sputtering effect on the substrate. This technique was applied to the gate formation of GaAs MESFEIs, and the uniformity of the threshold voltage within a 2 inch wafer rras much improved.