Effect of CVD-SiO/sub 2/ film on reliability of GaAs MESFET with Ti/Pt/Au gate metal

The effect of CVD-SiO/sub 2/ films on the reliability of GaAs MESFET with Ti/Pt/Au gate metal was investigated. It was found that the mean time to failure (MTTF) of MESFET with 350/spl deg/C-depositied SiO/sub 2/ was only about one-seventh of that of the ones with 440/spl deg/C-SiO/sub 2/. It was also found that, in the storage test at 300/spl deg/C for 24 hours, diffusion of Pt into GaAs was accelerated when the SiO/sub 2/ deposition temperature was lower than 380/spl deg/C. FT-IR spectra indicated that the lower deposition temperature leads to a higher concentration of the residual hydrogen in SiO/sub 2/. Thermal differential spectrometry (TDS) demonstrated that hydrogen in SiO/sub 2/ could migrate even below 300/spl deg/C. In conclusion, the residual hydrogen in SiO/sub 2/ causes the degradation phenomena.