Abstract: An invention for detecting an endpoint during a chemical mechanical polishing (CMP) process is provided. A reflected spectrum data sample is received that corresponds to a plurality of spectrums of light reflected from an illuminated portion of the surface of a wafer. The reflected spectrum data sample is normalized using a normalization reference comprising a first reflected spectrum data sample obtained earlier during the CMP process. In addition, the normalization reference is updated during the process using a second reflected spectrum data sample obtained earlier during the CMP process. The second reflected spectrum data sample is obtained after the first reflected spectrum data sample. In this manner, an endpoint is determined based on optical interference occurring in the reflected spectrum data.

Abstract: An invention is provided for detecting an endpoint during a chemical mechanical polishing (CMP) process. A reflected spectrum data sample is received that comprises a plurality of values corresponding to a plurality of spectrums of light reflected from an illuminated portion of a surface of a wafer. The reflected spectrum data sample is decomposed into noise sub-space values and signal sub-space values, and the noise sub-space values are truncated. In addition, outside spectrum data is extrapolated using a linear combination of the values of the reflected spectrum data sample. In this manner, an endpoint can be determined based on optical interference occurring in the reflected spectrum data.

Abstract: An invention for detecting an endpoint during a chemical mechanical polishing (CMP) process is provided. A reflected spectrum data sample is received that corresponds to a plurality of spectrums of light reflected from an illuminated portion of the surface of a wafer. The reflected spectrum data sample is normalized using a normalization reference comprising a first reflected spectrum data sample obtained earlier during the CMP process. In addition, the normalization reference is updated during the process using a second reflected spectrum data sample obtained earlier during the CMP process. The second reflected spectrum data sample is obtained after the first reflected spectrum data sample. In this manner, an endpoint is determined based on optical interference occurring in the reflected spectrum data.

Abstract: An invention is provided for removing a top wafer layer during a CMP process. Time series data is collected based on a reflected wavelength from a top layer of a wafer. A Fourier Transform is applied to the time series data, and a frequency of peak intensities in the Fourier Transform of the time series data is analyzed to determine a peak magnitude in the frequency. A first removal rate of the top layer is determined based on the peak magnitude in the frequency, and a current thickness of top layer is calculated based on the first removal rate. The CMP process is discontinued when the current thickness of the top layer is equal to or less than a target thickness, and a separate polishing process is performed to remove an additional portion of the top layer. In one aspect, the separate polishing process can be based on a soft endpoint detection process having second removal rate that is lower than the first removal rate.

Abstract: An invention is disclosed for an optical endpoint detection system that utilizes optical interference to determine when a metal layer has reached a thin metal zone during a CMP process. A portion of a surface of a wafer is illuminated with broad baned light source. Then, reflected spectrum data corresponding to a plurality of spectrums of light reflected from the illuminated portion of the surface of the wafer is received. An endpoint is then determined based on optical interference occurring in the reflected spectrum data, which is a result of phase differences in light reflected from different layers of the wafer, and occurs when the top metal layer is reduced to the thin metal zone.