Reactive ion etching of via holes for GaAs HEMTs and MMICs using Cl/sub 2//BCl/sub 3//Ar gas mixtures

Summary form only given, as follows. A process for through-the-wafer via hole connections to each individual source contact for power high electron mobility transistors and monolithic microwave integrated circuits has been developed using reactive ion etching in Cl/sub 2//BCl/sub 3//Ar gas mixtures. Placing vias in this manner eliminates the need for source airbridges, which minimizes source inductance and results in increased gain and efficiency. The GaAs etch rate and resultant etch profiles have been studied as functions of bias voltage, gas mixture, flow rate, via mask dimension, and etch time. Due to the formation of an etch-inhibiting coating on the via sidewalls, the process produces remarkably smooth and anisotropic profiles. Rectangular vias as small as 15 /spl mu/m wide by 55 /spl mu/m long on 50 /spl mu/m thick substrates are routinely etched in our production process with an average etch rate of around 0.3 /spl mu/m/min.