Spatially resolved characterisation of silicon as-cut wafers with photoluminescence imaging

The characterisation of silicon as-cut wafers is important for process control in the solar cell production, since it can serve as starting material quality inspection and give information about a change of material properties caused by different process steps. In particular spatially resolved characterisation tools such as Photoluminescence Imaging are useful as an information source. Due to the low signal in a luminescence image of an as-cut wafer a major problem is superimposed excitation reflection light when the detection occurs from the front side of the wafer. We present a method which eliminates the spurious reflection contribution by a special image correction. The image correction is based on the measurement of the reflection topology of the as-cut wafer surface separately from the luminescence intensity.