Method and apparatus for determining concentration of defects and/or impurities in a semiconductor wafer

A method of determining a concentration of defects and/or impurities in a semiconductor wafer comprising:

• (a) causing a first current value to flow in a semiconductor wafer having a substrate of semiconducting material;
• (b) exposing the semiconductor wafer to a pulse of light whereupon electron-hole pairs generated in the semiconductor wafer in response to the light pulse cause the current to increase to a second value;
• (c) after termination of the pulse of light, determining a rate of change of the current from the second value toward the first value;
• and
• (d) determining a concentration of defects and/or impurities in the semiconductor wafer as a function of the rate of change.

A system for determining a concentration of defects and/or impurities in a semiconductor wafer comprising:

• means for causing a first current value to flow in a semiconductor wafer having a substrate of semiconducting material;
• means for exposing the semiconductor wafer to a pulse of light to generate electron-hole pairs in the semiconductor wafer that cause the current to increase to a second value;
• means for determining a rate of change of the current from the second value toward the first value after termination of the light pulse;
• and
• means for determining a concentration of defects and/or impurities in the semiconductor wafer as a function of the rate of change from the second current value to the first current value.