In this study, we evaluate the electrical characteristics of the SOI layer made by the wafer bonding method using a laser/microwave method. We use a He-Ne laser pulse for the photoconductivity modulation method and a semiconductor laser diode for the photoconductivity decay method as the carrier injection light source. The detected signal intensity at the void area decreases as compared with that at the center area of the SOI layer where there are no voids. The positions of the voids revealed by the proposed method are in good agreement with those by X-ray topography. We also measure the lifetime by the photoconductivity decay method using a laser diode. The lifetime at the void area is much shorter than that at the center area. It is considered that the decrease in the detected signal intensity at the void area is due to reduction in the minority carrier lifetime.

This paper describes a new evaluation technique for Si surfaces. A laser/microwave method using two lasers of different wavelengths for carrier injection is proposed to evaluate Si surfaces. With this evaluation system, the effect of impedance mismatching between the microwave probe and the Si wafer can be eliminated. These lasers used in this experiment are He-Ne (wavelength633 nm, penetration depth3 µm) and YAG lasers (wavelength1060 nm, penetration depth500 µm). Using a microwave probe, the amount of injected excess carriers can be detected. These carrier concentrations are mainly dependent on the condition of the surface, when carriers are excited by the He-Ne laser, and the condition of the bulk region, when carriers are excited by the YAG laser. We refer to microwave intensities detected by the He-Ne and YAG lasers as the surface-recombination-velocity-related microwave intensity (SRMI) and bulk-related microwave intensity (BRMI), respectively. We refer to the difference between SRMI and BRMI as relative SRMI (R-SRMI), which is closely related to the surface condition. A theoretical analysis is performed and several experiments are conducted to evaluate Si surfaces. It is found that the R-SRMI method is better suited to surface evaluation then conventional lifetime measurements, and that the rdliability and reproducibility of measurements are improved.

A laser/microwave method using two lasers of different wavelengths for carrier excitation is proposed to evaluate Si surfaces. These constitute a He-Ne laser (wavelength=633 nm, penetration depth=3 µm) and a YAG laser (wavelength=1060 nm, penetration depth=500 µm). Using a microwave probe, the amount of excited carriers can be detected. The carrier concentration is mainly dependent on the condition of the surface when carriers are excited by the He-Ne laser, as well as on the condition of the bulk region when carriers are excited by the YAG laser. Microwave intensities detected under the He-Ne and the YAG lasers illumination are referred to as the surface-recombination-velocity-related microwave intensity (SRMI) and the bulk-related microwave intensity (BRMI), respectively. The difference between SRMI and BRMI is called relateve SRMI (R-SRMI), and is closely related to the condition of the surface and surface active region. We evaluate the surfaces of the samples after plasma and wet etching to remove the photoresist layer. And we evaluate the surfaces of the samples after heat or HF treatment which is done to recover the damage introduced by plasma etching. It was found that the R-SRMI method is better suited to surface evaluation than conventional lifetime measurements.