REAL-TIME, INSITU MONITORING OF SURFACE-REACTIONS DURING PLASMA PASSIVATION OF GAAS

Real-time, in situ observations of surface chemistry during the remote plasma passivation of GaAs is reported herein. Using attenuated total reflection Fourier transform infrared spectroscopy, the relative conc entrations of -As-O, -As-H, -H2O, and -CH2 bonds are measured as a fun ction of exposure to the effluent from a microwave discharge through N H3, ND3, H-2, and D2. The photoluminescence intensity (PL) from the Ga As substrate is monitored simultaneously and used qualitatively to est imate the extent of surface state reduction. It was found that, while the -CH(x)(x = 2,3) and -As-O concentrations are reduced rapidly, the rates at which the -As-H concentration and the PL intensity increase a re relatively slow. The concentration of -H2O on the GaAs surface incr eases throughout the process as surface arsenic oxides and the silica reactor walls are reduced by atomic hydrogen. These observations sugge st that removal of elemental As by reaction with H at the GaAs-oxide i nterface limits the passivation rate.