A manufacturing process for analog and digital gallium arsenide integrated circuits

A process for manufacturing small-to-medium scale GaAs integrated circuits is described. Integrated FET´s, diodes, resistors, thin-film capacitors, and inductors are used for monolithic integration of digital and analog circuits. Direct implantation of Si into > 10⁵Ω.cm resistivity substrates produces n-layers with ± 10-percent sheet resistance variation. A planar fabrication process featuring retained anneal cap (SiO2), proton isolation, recessed Mo-Au gates, silicon nitride passivation, and a dual-level metal system with polyimide intermetal dielectric is described. Automated on-wafer testing at frequencies up to 4 GHz is introduced, and a calculator-controlled frequency domain test system described. Circuit yields for six different circuit designs are reported, and process defect densities are inferred.