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LASER Endpoint System

The LASER Endpoint System LEP400 can be used for finding an end point during plasma etching. It sends in LASER light through a top view port on the etch chamber down onto the sample. The light reflects from the surface and is is detected by the LEP400. The reflected signal has an intensity that depends in the layer thicknesses and refractive indexes of the layers on the sample. Reflections some the different interfaces between the sample layers interferes and therefore the intensity varies as the top layer is getting thinner during the etch (unless that top layer is opaque). This can be used to find the endpoint between two layers and it can also be used to certain thickness down in one of the layers.

A detailed manual describing how to due this is uploaded here: