Improvements in method and apparatus for determining minority carrier diffusion length

The constant-magnitude steady-state surface photovoltage (SPV) method for determining the minority carrier diffusion length L is in principle an excellent technique. It has, however, recevied relatively limited use because of practical difficulties in carrying out the required measurements. This paper describes an improved measurement system that virtually eliminates these difficulties and allows a rapid straightforward determination of L. These measurements in silicon monitor wafers have enabled a routine quality control check on many factory processing steps, particularly those that are carried out at high temperature and have the potential for significantly degrading L.