Non-destructive characterization techniques for SOI substrates

Silicon-on-insulator (SOI) is very promising for submicron CMOS due to low parasitic capacitance, higher potential speed, and ease of isolation. The major requirements for the starting material are: 1) thin Si layers, 2) low active defect densities, 3) highly uniform layers, and 4) good crystalline and electrical quality. Since the variation in these parameters from wafer-to-wafer and run-to-run can be substantial, it is beneficial to qualify the starting wafers as much as possible before using them in circuit runs. An arsenal of characterization techniques has been developed to do this, emphasizing non-contact, non-destructive methods as much as possible. The methods discussed include: spectroscopic ellipsometry, automatic defect counting, photoluminescence scanning, and surface photovoltage response measurement