Method and apparatus for detecting a planarized outer layer of a semiconductor wafer with a confocal optical system
First Claim
1. A method of planarizing a first side of a semiconductor wafer with a polishing system, comprising the steps of:
- polishing said first side of said wafer in order to remove material from said wafer;
moving a lens of a confocal optical system between a number of lens positions so as to maintain focus on said first side of said wafer during said polishing step;
determining a rate-of-movement value based on movement of said lens during said moving step; and
stopping said polishing step if said rate-of-movement value has a predetermined relationship with a movement threshold value.
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Abstract
A method of planarizing a first side of a semiconductor wafer with a polishing system includes the step of polishing the first side of the wafer in order to remove material from the wafer. The method also includes the step of moving a lens of a confocal optical system between a number of lens positions so as to maintain focus on the first side of the wafer during the polishing step. The method further includes the step of determining a rate-of-movement value based on movement of the lens during the moving step. Moreover, the method includes the step of stopping the polishing step if the rate-of-movement value has a predetermined relationship with a movement threshold value. An apparatus for polishing a first side of a semiconductor wafer is also disclosed.
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Citations
10 Claims
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1. A method of planarizing a first side of a semiconductor wafer with a polishing system, comprising the steps of:
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polishing said first side of said wafer in order to remove material from said wafer;
moving a lens of a confocal optical system between a number of lens positions so as to maintain focus on said first side of said wafer during said polishing step;
determining a rate-of-movement value based on movement of said lens during said moving step; and
stopping said polishing step if said rate-of-movement value has a predetermined relationship with a movement threshold value. - View Dependent Claims (2, 3, 4, 5)
said polishing step includes the step of rotating said wafer with a wafer motor, and said stopping step includes the step of idling said wafer motor if said rate-of-movement value has said predetermined relationship with said movement threshold.
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4. The method of claim 1, wherein:
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said polishing step includes the step of rotating a wafer carrier so as to urge said wafer into contact with a polishing platen, and said confocal optical system is positioned such that an incident light beam emitting therefrom is directed through an opening defined in said polishing platen so as to impinge upon said first side of said wafer.
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5. The method of claim 1, wherein said moving step includes the step of moving an objective lens of said confocal optical system between said number of lens positions so as to maintain focus on said first side of said wafer during said polishing step.
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6. An apparatus for polishing a first side of a semiconductor wafer, comprising:
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a polishing system which operates to polish said wafer, said polishing system having (i) a polishing platen which includes a polishing surface, and (ii) a wafer carrier which is configured to (a) engage said wafer by a second side of said wafer, and (b) apply pressure to said wafer in order to press said wafer against said polishing surface of said polishing platen;
a confocal optical system having a movable objective lens, said confocal optical system being configured to move said objective lens between a number of lens positions so as to maintain focus on said first side of said wafer during polishing of said wafer; and
a controller electrically coupled to said confocal optical system, wherein said controller is configured to (i) determine a rate-of-movement value based on movement of said objective lens during polishing of said wafer, and (ii) terminate operation of said polishing system so as to cease polishing of said wafer in response to determination that said rate-of-movement value has a predetermined relationship with a movement threshold value. - View Dependent Claims (7, 8, 9, 10)
said wafer motor is operable in (i) a polishing mode of operation in which said wafer motor rotates said wafer carrier, and (ii) an idle mode of operation in which said wafer motor is idle, and said wafer motor is positioned in said idle mode of operation if said rate-of-movement value has said predetermined relationship with said movement threshold.
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8. The apparatus of claim 6, wherein:
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said polishing platen has an opening defined therein, and said confocal optical system is positioned such that an incident light beam emitting therefrom is directed through said opening defined in said polishing platen so as to be impinged upon said first side of said wafer.
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9. The apparatus of claim 8, wherein:
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said confocal optical system includes a confocal laser system, said incident light beam includes an incident laser beam generated by said confocal laser system, and said confocal laser system is positioned such that said incident laser beam is directed through said opening defined in said polishing platen so as to impinge said incident laser beam on said first side of said wafer.
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10. The apparatus of claim 6, wherein said controller is further configured to terminate operation of said polishing system so as to cease polishing of said wafer in response to determination that said rate-of-movement value is less than said movement threshold value.
Specification