US 7,406,394 B2 · Spectra based endpointing for chemical mechanical polishing

Abstract

Methods and apparatus for spectrum-based endpointing. An endpointing method includes selecting two or more reference spectra. Each reference spectrum is a spectrum of white light reflected from a film of interest on a first substrate and has a thickness greater than a target thickness. The reference spectra is selected for particular spectra-based endpoint determination logic so that the target thickness is achieved when endpoint is called by applying the particular spectra-based endpoint logic. The method includes obtaining two or more current spectra. Each current spectrum is a spectrum of white light reflected from a film of interest on a second substrate when the film of interest is being subjected to a polishing step and has a current thickness that is greater than the target thickness. The method includes determining, for the second substrate, when an endpoint of the polishing step has been achieved.

Claims17

Dependent claims

A computer program product, tangibly stored on machine readable medium, the product comprising instructions operable to cause a processor to:

select two or more reference spectra, each reference spectrum representing a spectrum of light reflected from a film of interest on a first substrate when illuminated with white light;
obtain two or more current spectra, each current spectrum being a spectrum of light reflected from a film of interest on a second substrate when illuminated with white light, the film of interest on the second substrate being subject to a polishing step, and the two or more current spectra being obtained from a single platen rotation of the polishing step;
calculate differences between the current spectra and the reference spectra to generate a plurality of differences for the single platen rotation;
select a smallest difference from the plurality of differences;
and
determine, for the second substrate, whether an endpoint of the polishing step has been achieved, the determining being based on the smallest difference.

3 more elements

A computer program product, tangibly stored on machine readable medium, the product comprising instructions operable to cause a processor to:

select two or more reference spectra, each reference spectrum representing a spectrum of light reflected from a film of interest that is on a first substrate and that has a thickness greater than a target thickness, the reference spectra being selected for particular spectra based endpoint determination logic so that the target thickness is achieved when endpoint is called by applying the particular spectra based endpoint logic;
obtain two or more current spectra, each current spectrum being a spectrum of light reflected from a film of interest that is on a second substrate, is subject to a polishing step and has a current thickness that is greater than the target thickness, wherein the instructions to obtain current spectra include instructions to obtain current spectra for each revolution of a platen used in the polishing step;
determine, for the second substrate, whether an endpoint of the polishing step has been achieved, the determining being based on the reference spectra and the current spectra, including calculating a difference between each of the reference spectra and each of the current spectra and generating a difference trace that includes multiple points, each of which represents the smallest of the differences calculated for a revolution of the platen;
and
call the endpoint when one of the differences reaches a threshold value.

2 more elements

Dependencies are inferred from the claim text.

Spectra based endpointing for chemical mechanical polishing

Life of this patent

Spectra based endpointing for chemical mechanical polishing

Life of this patent

Abstract

Claims17