Silicon Nitride in Compound Semiconductor Integrated Circuits (ICs)

Abstract

Silicon nitride is applied in monolithic, integrated, digital, and analog circuits composed of FETs, diodes, resistors, and thin-film capacitors on compound semiconductor substrates. Silicon nitride can be used as a mask for implanting Si to produce n-type layers and for implanting hydrogen to achieve isolation by generating radiation damage. It can also be used for encapsulating before annealing, providing recessed Mo-Au gates, and for passivation [1,2]. ICs on GaAs with a high degree of integration are fabricated by the same technique by preparing patterned multilayers consisting of a silicon nitride layer sandwiched with a silicon oxide and a PSG layer prior to annealing and preparing contacts and gate contacts [3]. Highspeed, ion-implanted GaAs ICs are annealed using a silicon nitride oxide layer for encapsulation. The silicon nitride oxide layer is deposited in a mixture of SiH₄, NH₃, and 0₂ at 923 K. The subsequent annealing is performed at 1073 K [4]. Alternatively, GaAs specimens are coated with a silicon nitride oxide layer, patterned, implanted with silicon ions, encapsulated with a silicon nitride layer, and annealed to prepare high-speed GaAs ICs [5].