HEMT VLSI technology using nonalloyed ohmic contacts

The authors propose HEMT (high electron mobility transistor) VLSI technology using nonalloyed ohmic contacts. For large integration levels, nonalloyed ohmic contacts have two advantages. One is their extremely short ohmic length, and the other is that direct connection between source/drain and gate can be made with the same metal. The propagation delay time of a ring oscillator with one-metal simultaneous formation of the source/drain and gate was 37 ps/gate (L/sub g/=0.9 mu m), comparable to that of conventional HEMT ring oscillators. The number of contact holes in a six-transistor basic memory cell was eight using a conventional technique and was reduced to three using the new technique. The memory cell size was reduced to 21.5*21.5 mu m/sup 2/, which may be the smallest area ever reported for a GaAs SRAM (static random access memory).<>