Application of the Infrared Lasers to Contactles.s Measurement of Minority Carrier Lifetime and Wafer Process Evaluation

Abstract

A microwave contactless technique is described for measuring the minority carrier lifetime of semiconductor wafer, using the light emitting diodes as the carrier injection source. The minority carrier which is injected in wafer which is placed 40mm from the waveguide end is measured by the reflection signal of microwave. The minority carrier lifetime which is obtained from the reflection microwave signal decay is compaired with that obtained by the JIS (Japan Industrial Standard) method. The spatial resolution of the lifetime measurement is considered to be about 200, μm∅, from measurement using a LED with optical fiber system, which is equal to the diameter of the injected light beam plus diffusion length. Minority carrier lifetime is measurable in 0.054 ohm- cm silicon wafer, which is carrier injected by YAG laser. Physical parameters relative to the excess carrier such as diffusion constants and bulk lifetime are also measured by this contactless method.