Effect of bias sputtering on W and W-Al Schottky contact formation and its application to GaAs MESFETs

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.