In-situ detection of thin-metal interface using high resolution spectral analysis of optical interference
AssigneeLam Research Corporation
InventorSundar Amartur
Life of this patent
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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.
Claims20
A method for detecting an endpoint during a chemical mechanical polishing (CMP) process, comprising the operations of:
- receiving a reflected spectrum data sample comprising a plurality of values corresponding to a plurality of spectrums of light reflected from an illuminated portion of a surface of a wafer;
- extrapolating outside spectrum data using a linear combination of the values of the reflected spectrum data sample;
- and
- determining an endpoint based on optical interference occurring in the reflected spectrum data.
An endpoint detection apparatus for detecting an endpoint during a chemical mechanical polishing process, comprising:
- a broad band light source for illuminating a portion of a surface of a wafer;
- an optical detector for receiving reflected spectrum data sample comprising a plurality of values corresponding to a plurality of spectrums of light reflected from the illuminated portion of the surface of the wafer;
- logic that extrapolates outside spectrum data using a linear combination of the values of the reflected spectrum data sample;
- and
- logic that determines an endpoint based on optical interference occurring in the reflected spectrum data.
A method for detecting an endpoint during a chemical mechanical polishing (CMP) process, comprising the operations of:
- receiving a reflected spectrum data sample comprising a plurality of values corresponding to a plurality of spectrums of light reflected from an illuminated portion of a surface of a wafer;
- decomposing the reflected spectrum data sample into noise sub-space values and signal sub-space values;
- truncating the noise sub-space values;
- extrapolating outside spectrum data using a linear combination of the values of the reflected spectrum data sample;
- and
- determining an endpoint based on optical interference occurring in the reflected spectrum data.
Dependencies are inferred from the claim text.