OPTICAL-DETECTION AND DYNAMICS OF SURFACE TRANSIENT PROCESSES IN PLASMA CVD OF HYDROGENATED AMORPHOUS-SILICON

By in situ diagnosis using p-polarized light reflection from an a-Si:H growing surface, we have verified the so-called growth zone, i.e. the transient topmost atomic layers, and analyzed its relaxation process quantitatively. A stabilized He-Ne laser was linearly p-polarized and impinged on an rf plasma depositing a-Si:H surface and the reflected l ight intensity was measured by a photodiode. A slight and gradual chan ge was detected in the reflected light intensity when the film deposit ion was halted by turning off the plasma. The observed reflection patt ern including this slight and clear change can be well simulated by ta king into account the presence and relaxation of the growth zone with its refractive index and the absorption coefficient lower than those o f the bulk network. The relaxation rate increased with an increase of substrate temperature. During this relaxation stage, the growing surfa ce layer is considered to be densified by liberating hydrogen into the rigid bulk amorphous network.