Spatially resolved lifetime imaging of silicon wafers by measurement of infrared emission
The measurement of infrared absorption of excess carriers is a successful technique by which images of the excess free carrier density and recombination lifetime in silicon can be generated. Carrier density imaging (CDI) has recently been developed as a powerful tool by which one obtains such images. This article analyzes both the effect due to absorption and emission of infrared radiation by excess carriers in silicon. The former effect is the basis of the existing CDI technique whereas this article describes a lifetime measurement technique based on the latter effect. Both methods allow one to obtain lifetime images with high spatial resolution on the order of seconds and measure actual lifetimes. These techniques are contactless and nondestructive. The emission CDI mode facilitates the measurement of low-lifetime wafers on the order of seconds.