Scatterometer including an internal calibration system
First Claim
1. A scatterometry system comprising:
- a light source configured to emit a light beam of predefined optical characteristics;
a detector configured to receive a light beam and output a signal indicative of optical characteristics of the received light beam;
a substrate holder configured to receive and position a substrate so as to receive the light beam from said light source and scatter a portion of the light beam to said detector; and
a pitch calibration station including a pitch calibration standard to provide measurement data indicative of the current system status.
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Accused Products
Abstract
A scatterometer system comprises a pitch calibration station that allows the monitoring of a tool status of the scatterometry system without involving a user'"'"'s interaction. The pitch calibration station comprises a pitch calibration standard, for example in the form of a grid pattern that may conveniently be evaluated on the basis of a reference data library. By providing the pitch calibration station, the measurement process may easily be adapted to include reference measurements on a regular basis so as to increase the reliability of measurement values obtained by scatterometry. In one particular example, a corresponding set of instructions for performing the calibration measurement may be implemented into a self-test routine of the scatterometry system.
30 Citations
27 Claims
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1. A scatterometry system comprising:
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a light source configured to emit a light beam of predefined optical characteristics;
a detector configured to receive a light beam and output a signal indicative of optical characteristics of the received light beam;
a substrate holder configured to receive and position a substrate so as to receive the light beam from said light source and scatter a portion of the light beam to said detector; and
a pitch calibration station including a pitch calibration standard to provide measurement data indicative of the current system status. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of monitoring a status of a scatterometry system, the method comprising:
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providing a pitch calibration standard;
establishing a reference data library for said pitch calibration standard;
obtaining measurement data of said pitch calibration standard; and
comparing said measurement data with said reference data library to assess the status of the scatterometry system. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
an initialization of the scatterometry system, an elapse of a predefined time interval, a completion of a predefined number of measurement cycles and an external request for a calibration measurement.
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13. The method of claim 11, wherein obtaining measurement data and comparing said measurement data with the reference data library is carried out during a self-test routine of the scatterometry system.
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14. The method of claim 11, wherein comparing the measurement data with the reference data library includes assessing whether a difference of the reference data and the measurement data is within a predefined allowable range.
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15. The method of claim 14, further comprising indicating an invalid tool status when said difference is outside of said predefined allowable range.
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16. The method of claim 14, further comprising storing a value indicative of said difference to establish a tool history.
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17. The method of claim 11, wherein said light source, said detector and said substrate holder are provided in the form of one of an ellipsometer and a photometer.
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18. The method of claim 11, wherein said pitch calibration standard is a grid pattern.
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19. The method of claim 16, wherein establishing said tool history includes determining at least one of an average value and a standard deviation of a plurality of values indicative of differences between measurement data and the reference data library of previously performed measurements with said pitch calibration standard.
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20. The method of claim 19, wherein said reference data library is updated on the basis of the tool history.
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21. The method of claim 16, wherein one or more correction values are established on the basis of the tool history.
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22. A method of operating a scatterometer, the method comprising:
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starting a self-test routine of the scatterometer, the self-test routine including;
obtaining measurement data from a pitch calibration standard;
comparing said measurement data with reference data characterizing the pitch calibration standard; and
indicating that the scatterometer is acceptable for performing measurements when a result of said comparison is within a predefined allowable range. - View Dependent Claims (23, 24, 25, 26, 27)
an initialization of the scatterometer, an external request, an elapse of a predefined time interval and a completion of a predefined number of measurement cycles.
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24. The method of claim 22, further comprising storing said comparison result to establish a tool history.
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25. The method of claim 24, further comprising updating said reference data on the basis of the tool history.
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26. The method of claim 25, further comprising measuring a substrate and evaluating measurement data of said substrate on the basis of substrate reference data and said tool history.
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27. The method of claim 22, further comprising indicating an invalid tool status when said comparison result is outside of a predefined allowable range.
Specification