Patent ID: 8795029
Filing Date: 2014-08-05
Classification: B24B,G01B,H01L

Abstract:
1. An endpoint detection method, comprising: processing an outer surface of a substrate, the processing changing a thickness of a layer at the outer surface over time; during processing, directing an incident light beam through a window in an opaque metal body onto the surface being processed; receiving at a detector of a monitoring system a reflected light beam from the substrate through the window and generating a signal from the detector, the reflected light beam being a combination of at least a reflection from the outer surface and a reflection from an inner surface of the layer on a side of the layer opposite the outer surface; generating in the monitoring system a signal based on the reflected light beam received at the detector, wherein the signal generated in the monitoring system is a time-varying cyclic signal that varies as the thickness of the layer varies over time with a period of the cyclic signal determined by an index of refraction of the layer and a wavelength of the light beam; detecting a processing endpoint by detecting from changes in the cyclic signal that a portion of a cycle of the cyclic signal has passed as a trigger to halt processing, the portion being less than a full cycle of the cyclic signal; and halting processing upon detecting the processing endpoint.