Methods and systems for creating or performing a dynamic sampling scheme for a process during which measurements are performed on wafers
Various methods and systems for creating or performing a dynamic sampling scheme for a process during which measurements are performed on wafers are provided. One method for creating a dynamic sampling scheme for a process during which measurements are performed on wafers includes performing the measurements on all of the wafers in at least one tot at all measurement spots on the wafers. The method also includes determining an optimal sampling scheme, an enhanced sampling scheme, a reduced sampling scheme, and thresholds for the dynamic sampling scheme for the process based on results of the measurements. The thresholds correspond to values of the measurements at which the optimal sampling scheme, the enhanced sampling scheme, and the reduced sampling scheme are to be used for the process.
1. A method for sampling wafers during a measurement process, comprising:
designing a plurality of sampling schemes for the measurement process, wherein the sampling schemes comprise one or more parameters of measurements to be performed on wafers by a measurement tool during the measurement process, and wherein the one or more parameters of the measurements for at least two of the sampling schemes are different and determined prior to use of the sampling schemes;
triggering one of the plurality of sampling schemes for the wafers; and
activating the triggered sampling scheme such that the measurements are performed on the wafers during the measurement process using the triggered sampling scheme, wherein said designing, said triggering, and said activating are performed using a computer system.
2. The method of claim 1 , wherein said designing comprises:
performing measurements on substantially all wafers in at least one lot at substantially all measurement spots on said substantially all wafers;
determining, based on results of the measurements performed on said substantially all wafers, an optimal sampling scheme, an enhanced sampling scheme, and a reduced sampling scheme; and
determining thresholds, based on the results of the measurements, that will be used to trigger the optimal sampling scheme, the enhanced sampling scheme, and the reduced sampling scheme.
3. The method of claim 1 . wherein said designing comprises designing the plurality of sampling schemes based on results of measurements performed on substantially all wafers in at least one lot at substantially all measurement spots on said substantially all wafers, and wherein the wafers for which the triggered sampling scheme is activated are in a lot other than the at least one lot.
4. The method of claim 1 , wherein said designing comprises designing the plurality of sampling schemes based on results of measurements performed on substantially all wafers in at least one lot at substantially all measurement spots on said substantially all wafers, wherein the results of the measurements comprise raw measurement data, and wherein the method further comprises applying an absolute value or regression filter to the raw measurement data before designing the plurality of sampling schemes based on the raw measurement data.
5. The method of claim 1 , wherein said designing comprises designing the plurality of sampling schemes based on results of measurements performed on substantially all wafers in at least one lot at substantially all measurement spots on said substantially all wafers and based on information from one or more tools that performed one or more processes on said substantially all wafers.
6. The method of claim 1 , wherein said designing comprises designing the plurality of sampling schemes based on results of measurements performed on substantially all wafers in at least one lot at substantially all measurement spots on said substantially all wafers and based on historical process control data for one or more processes performed on said substantially all wafers.
7. The method of claim 1 , wherein said designing comprises designing the plurality of sampling schemes based on an optimization criterion and one or more constraints external to the measurement process.
8. The method of claim 1 , wherein said designing comprises determining direct thresholds to be used for said triggering.
9. The method of claim 1 , wherein said triggering is initiated by comparing results of measurements performed on substantially all wafers in at least one lot at substantially all measurement spots on said substantially all wafers to direct thresholds.
10. The method of claim 1 , wherein said triggering is initiated by comparing statistical properties of results of measurements performed on substantially all wafers in at least one lot at substantially all measurement spots on said substantially all wafers to direct thresholds.
11. The method of claim 1 , wherein said triggering is initiated by comparing historical process control data to direct thresholds.
12. The method of claim 1 , wherein said triggering is initiated by comparing data from one or more metrology tools or one or more process tools to direct thresholds.
13. The method of claim 1 , wherein said designing comprises determining non-direct thresholds to be used for said triggering.
14. The method of claim 1 , wherein said triggering is initiated by comparing time data to non-direct thresholds.
15. The method of claim 1 , wherein said triggering is initiated by comparing process tool quality control data to non-direct thresholds.
16. The method of claim 1 , wherein said triggering is initiated by comparing production floor or material planning data to non-direct thresholds.