Non-contact measurements of the minority carrier recombination lifetime at the silicon surface

Minority carrier recombination lifetime is one of the basic parameters that can provide information regarding the condition of the silicon substrate at various stages of the device manufacturing process. The key challenge is to effectively separate surface region effects from the bulk and to determine the minority carrier lifetime that is selectively related to the surface region of the silicon. This paper reviews requirements, physical principles, and implementation of the non-contact measurement of the minority carrier recombination lifetime, which is controlled solely by the characteristics of the silicon surface and sub-surface region. The method is based on a short wavelength, low light intensity, and high modulation frequency ac-SPV. Examples of experimental results using a commercial system developed to implement such methodology are discussed.