Process Monitoring for a-Si:H Materials and Interfaces


Real time ellipsometry results are presented which have been useful in characterizing nucleation, interface formation, and surface modification for hydrogenated amorphous silicon (a-Si:H) thin films and device structures. Earlier studies of the effect of deposition procedure on a-Si:H nucleation are reviewed, and new data on plasma-enhanced CVD p-type a-Si:H are discussed. Changes in the initial microstructural coalescence are observed when gas phase concentrations of 0.2% B2H6 are added to SiH4 to obtain the p-type films. When depositing p-type a-Si:H on undoped a-Si:H at 180°C and 250°C. ellipsometry allows detection of film formation at the rate of a few monolayers/minute by CVD (in the absence of plasma excitation) from the doping gas mixture. CVD requires both SiH4 and B2H6 in the gas. Other interesting aspects of this process are presented. Finally, in situ ellipsometry is applied with H2 plasmas and ion beams to study near-surface Si-Si bond breaking and etching. A common effect of many of these treatments is a reduction in the density of Si-Si bonds in the film bulk by 6–8%.

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Collins, R.W., Cavese, J.M. Process Monitoring for a-Si:H Materials and Interfaces. MRS Online Proceedings Library 118, 19 (1988).

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