In-situ detection of thin-metal interface using optical interference
AssigneeLam Research Corporation
InventorSundar Amartur
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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.
Claims18
A method for detecting an endpoint during a chemical mechanical polishing process, comprising the operations of:
- illuminating a portion of a surface of a wafer with broad band light;
- receiving reflected spectrum data corresponding to a plurality of spectrums of light reflected from the illuminated portion of the surface of the wafer;
- calculating a sum of peak magnitudes occurring in a Fourier Transform of wave-numbers obtained from the reflected spectrum data;
- and
- determining an endpoint based on the sum of peak magnitudes.
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 corresponding to a plurality of spectrums of light reflected from the illuminated portion of the surface of the wafer;
- logic that calculates a sum of peak magnitudes occurring in a Fourier Transform of wave-numbers obtained from the reflected spectrum data;
- and
- logic that determines an endpoint based on the sum of peak magnitudes.
A system for detecting an endpoint during a chemical mechanical polishing process, comprising:
- a polishing pad having a pad slot;
- a platen having a platen slot, the platen slot capable of aligning with the pad slot during particular points of the chemical mechanical polishing process;
- a broad band light source for illuminating a portion of a surface of a wafer through the platen slot and the pad slot;
- an optical detector for receiving reflected spectrum data corresponding to a plurality of spectrums of light reflected from the illuminated portion of the surface of the wafers;
- logic that calculates a sum of peak magnitudes occurring in a Fourier Transform of wave-numbers obtained from the reflected spectrum data;
- and
- logic that determines an endpoint based on the sum of peak magnitudes.
Dependencies are inferred from the claim text.