Detection system for chemical-mechanical planarization tool

Abstract

Methods and apparatus are provided for endpoint detection in a chemical mechanical planarization (CMP) process. Reflectance spectra data is taken periodically in different areas of a surface of a semiconductor wafer during a chemical mechanical planarization process. Three different reflectance spectra are identified to determine a status of the CMP process. A first reflectance spectra data corresponds to light reflected predominately from a layer of material on the surface of the semiconductor wafer. A second reflectance spectra corresponds to the layer of material being thinned such that the second reflectance spectra is modified by an underlying layer of material. A third reflectance spectra corresponds to light reflected predominately from the underlying layer of material.

Description

TECHNICAL FIELD [0001] The present invention generally relates to the chemical mechanical planarization of semiconductor wafers, and more particularly relates to the detection of an end point of a chemical mechanical planarization process. BACKGROUND [0002] A flat disk or “wafer” of single crystal silicon is the basic substrate material in the semiconductor industry for the manufacture of integrated circuits. Semiconductor wafers are typically created by growing an elongated cylinder or boule of single crystal silicon and then slicing individual wafers from the cylinder. The slicing causes both faces of the wafer to be extremely rough. The front face of the wafer on which integrated circuitry is to be constructed must be extremely flat in order to facilitate reliable semiconductor junctions with subsequent layers of material applied to the wafer. Also, the material layers (deposited thin film layers usually made of metals for conductors or oxides for insulators) applied to the wafer...

AI Technical Summary

Problems solved by technology

The slicing causes both faces of the wafer to be extremely rough.

Nonplanar surfaces create poor optical resolution of subsequent photolithography processing steps.

Poor optical resolution prohibits the printing of high-density lines.

Another problem with nonplanar surface topography is the step coverage of subsequent metallization layers.

If a step height is too large there is a serious danger that open circuits will be created.

Excessive removal of overburden from the front surface of the wafer, whether a raw sheet film, or an STI, metal or dielectric layer structure on the front wafer surface, may damage the wafer.

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