Plasma Enhanced Deposition Of Silicon-Nitride For Use As An Encapsulant For Silicon Ion-Implanted Gallium-Arsenide

Silicon nitride films have been produced by plasma enhanced chemical vapour deposition using silane and ammonia as the reactant gases in a Plasma-Therm PK1250PD machine. The compositions of the films have been investigated as a function of the silane to ammonia flow rate ratio used for deposition, using infra-red transmission and Auger electron spectroscopies. These techniques indicated that the plasma deposited films were silicon-rich and contained hydrogen. The oxygen content of the films was below the detection limit of Auger electron spectroscopy implying that it was less than 1%. Silicon ion-implanted semi-insulating gallium arsenide has been annealed using an approximately 1000 Å thick film of plasma deposited silicon nitride as an encapsulant. This capped annealing technique has achieved 70% activations of 4×10 12 cm −2 , 200 keV silicon implants with sheet Hall mobilities of 4000 cm 2 V −1 s −1 at room temperature. Free carrier concentration and Hall mobility profiles are presented. Unimplanted semi-insulating gallium arsenide samples have also been capped annealed in the same manner and maintained a sheet resistivity of greater than 10 7 ohm/square after annealing.