Silicon Nitride Final Passivation for GaAs Metal Semi-Conductor Field Effect Transistors (MESFETs) Packaged in Plastic Mold

A highly reliable SiNx final passivation film for GaAs metal semi-conductor field effect transistor (MESFETs) packaged in plastic mold has been developed. The addition of He to N2 for the carrier gas in plasma enhanced chemical vapor deposition (PE-CVD) has been found effective to reduce both stress and pinholes and to significantly improve the resistance to moisture of the SiNx film. Rutherford back scattering (RBS), hydrogen forward scattering (HFS) and FT-IR analyses demonstrated that the SiNx with less pinhole has fewer hydrogen atoms in the film. Regarding the FETs housed in the SOT-89 mold package, no failure was observed up to 1000 h in the 85°C–85% relative humidity (RH) reverse bias test.