Patent ID: 8093920

Claim:
A method for determining steady state diffusion length of minority carriers, L 0 , in semiconductor wafer, from the measurement of at least two diffusion length values L 1 and L 2 , under non-steady state conditions at frequencies ω 1 , and ω 2 , respectively, the method comprising: illuminating a wafer surface with light, which is modulated at a first frequency, ω 1 ; monitoring first surface photovoltage signals of the wafer during illumination with the light modulated at the first frequency; determining a first diffusion length, L 1 , based on the first surface photovoltage signals; illuminating a wafer surface with light, which is modulated at a second frequency, ω 2 , where the first and second frequencies are different; monitoring second surface photovoltage signals of the wafer during illumination with the light modulated at the second frequency; determining a second diffusion length, L 2 , based on the second surface photovoltage signals; and calculating a third diffusion length, L 3 corresponding to a third frequency, ω 3 , different from the first and second frequencies, based on a relationship relating diffusion length at different frequencies.