Minority carrier lifetime measurement in epitaxial silicon layers

The minority carrier lifetime is measured in the silicon epitaxial layer. The lifetime is 8.0 ms in an as-received n/n epitaxial layer. This time is due to the carrier recombination at the Si surface. A lifetime of 120 ms is obtained after passivation of the epitaxial layer surface. Since this lifetime is affected largely by the carrier recombination al the substrate, lifetime of the epitaxial layer cannot be measured directly even by measurement as a wavelength of 520 nm. Therefore. the lifetime can be determined only by subtracting the lifetime of the substrate water from the observed value. This measurement and calculation give a minority carrier lifetime of an n-epitaxial layer as 450 mu s. This lifetime is much greater than that of the substrate. However, it deviates widely within a wafer, for instance, from 102 to 450 mu s. However, the origin of the lifetime deviation is not clear. This lifetime measurement technique makes it possible to deposit a high quality and uniform epitaxial layer by improving the deposition conditions.