Importance

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Abstract

Circularly polarized light is used to detect an end point of a thin film layer. Collimated light is passed through a polarizing filter and a polarizing beam splitter resulting in light which is almost entirely linearly polarized in a first direction. This first direction polarized light is passed through a quarter wave retarder and is converted to circularly polarized light. The circularly polarized light is reflected off of a surface having a thin film layer and passes back through the quarter wave retarder. This reflected circularly polarized light is converted by the quarterwave retarder into linearly polarized light having a second direction. This second direction polarized light is easily isolated by passing it back through the beam splitter. The light may then be analyzed by end-point detection circuitry and the end-point of the film layer detected.

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First Claim