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In this work the photo-conductance decay (PCD) technique is used to measure the effective carrier lifetime in 160 nm-180 nm thick active layers of silicon-on-insulator (SOI) substrates both SIMOX and bonded. Study was carried out using 405 nm excitation wavelength featuring 200 nm absorption depth in silicon which was selected to coincide with the thickness of the active layers in the SOI wafers studied. The results obtained indicate the effectiveness of PCD methodology adopted for this study in the measurements of the minority carrier lifetime in Si active layers in SOI substrates. They demonstrate differences between PCD characterization of bulk and SOI wafers which are related to the confinement of the depletion region within the Si active layer in the latter case making its electrical properties less sensitive to the variation of the surface chemical condition. On the other hand, the process related physical changes in the SOI surface morphology were readily detectable by PCD measurements. Furthermore, the specific outcome of this investigation is the result indicating higher minority carrier lifetime in the Si active layer of bonded SOI wafers as compared to SIMOX wafers used in this study.

This experiment is concerned with photoconductive decay (PCD) measurements devised specifically for the purpose of characterization of the near-surface region of semiconductor substrates. The method was tested through the measurements of the germanium wafers for which the surface was roughened in a controlled fashion, and multi-crystalline silicon wafers with textured surfaces. The near-surface lifetime of minority carriers and carrier mobility were reduced as the Ge surface roughness increased, and increased for mc-Si as saw damage was removed by chemical treatment. These results demonstrate a direct correlation between condition of the semiconductor surface and the electrical parameters measured. It is postulated that the PCD method using temporary contact can be effectively used to monitor the condition of semiconductor surfaces during device processing.