Patent Document ID: 7982867
Application ID: 12767339
Patent Flag: 1

Claim One:
1. A method for generating a profile of the carrier concentration in a semiconductor wafer as a function of depth comprising the steps of: measuring the modulated optical reflectivity of a test wafer and generating output signals in response thereto, said measurements being obtained by periodically exciting the wafer with an intensity modulated pump beam having an energy and modulation frequency sufficient to create thermal and plasma waves that effect the reflectivity of the wafer and monitoring the modulated optical reflectivity changes with a separate probe beam, said measurements being obtained for at least two different separations between the pump and probe beam spots on the wafer; creating a theoretical model of the wafer; calculating an optical response of the model using an initial set of parameters and comparing the calculated optical response to the generated output signals and iterating the parameters of the model until the differences between the calculated optical response and the output signals is minimized; determining a carrier concentration depth profile based on the results of the iteration; and displaying or storing the depth profile.