Granted Patent B2

US 8,260,446 · App. 12/699,014 · Granted Sep 4, 2012

Assignee: Applied Materials, Inc.

Abstract

Claims (16)

1. A computer-implemented method, comprising:

storing a library having a plurality of reference spectra, each reference spectrum of the plurality of reference spectra having a stored associated index value, each index value representing a time during a polishing operation at which the reference spectrum of the plurality of reference spectra with the associated index value is expected to be observed;

measuring a sequence of spectra in-situ during polishing of a substrate to obtain measured spectra, wherein each stored associated index value was generated prior to polishing of the substrate;

binning spectra from the measured spectra into two or more radial zones;

for each measured spectrum of the sequence of spectra, finding a best matching reference spectrum from the plurality of reference spectra to generate a sequence of best matching reference spectra;

determining the associated index value for each best matching spectrum from the sequence of best matching reference spectra to generate a sequence of index values;

fitting a linear function to the sequence of index values; and

halting the polishing either when the linear function matches or exceeds a target index or when the associated index value from the determining step matches or exceeds the target index,

wherein the steps of finding a best matching reference spectrum to generate a sequence of best matching reference spectra, determining an associated index value for each best matching spectrum from the sequence of best matching reference spectra to generate a sequence of index values and fitting a linear function to the sequence of index values are performed for each of the two or more radial zones independently of one another.

2. The method of claim 1 , wherein a first of the two or more radial zones is an inner zone and a second of the two or more radial zones is an annular zone.

3. The method of claim 1 , further comprising adjusting a polishing rate in at least one radial zone of the two or more radial zones.

4. The method of claim 3 , wherein adjusting the polishing rate comprises causing an endpoint to occur when an entirety of the substrate has a flat surface.

5. The method of claim 1 , wherein determining the associated index value for each best matching spectrum from the sequence of best matching reference spectra to generate a sequence of index values includes determining associated index values from two different libraries of reference spectra to generate two corresponding sequences of index values.

6. The method of claim 5 , wherein fitting a linear function to the sequence of index values includes fitting a linear function to each sequence of index values that corresponds to each library to obtain two different linear functions, the method further comprising:

for each zone, determining which of the linear functions has a better goodness of fit to the corresponding sequence of index values.

7. The method of claim 6 , wherein halting polishing includes halting polishing when the linear function with the better goodness of fit to the index trace for each zone matches or exceeds the target index value.

Assignments (1)

Continuity (11)