Signal processing for in situ monitoring of the formation or removal of

Abstract

The deposition material on, or removal of material from, an article, such as on an exposed surface of an intermediate integrated circuit structure, is optically monitored. The processes that are so monitored include the formation of a dielectric layer on a semiconductor wafer, and the removal of material from such a layer by planarization, polishing, or etching, a process of chemical-mechanical-polishing (CMP) being given as an example. A resulting optical signal is detected and processed in real time to provide information of the progress of the material formation or removal and an indication when an end point has been reached. The optical signal being processed varies sinusoidally as a result of interference between light reflected from a surface being operated upon and light reflected from some other surface. A differential or integral of this signal is formed to provide additional peaks and valleys that are detected in order to obtain data points from the signal every one-quarter period. This allows a very early determination of the amount of material being added or removed, the rate that this is occurring, and the like, which determinations are repetitively updated as more signal data points are acquired. This information can be provided to an individual who is operating the processing equipment, and/or can be used to directly control the processing equipment.