1. A light source comprising a first component light source, said component light source comprising:
N LEDs, each LED having a light emitting chip in a package, said light emitting chip emitting light in a forward direction and light in a side direction, wherein N>1, said light generated in said forward direction being determined by a drive signal coupled to that LED, a portion of said light in said side direction leaving said package;
a photo-detector; and
a collector positioned to direct a portion of said light in said side direction that leaves said package of each of said LEDs onto said photo-detector, said photo-detector generating N intensity signals, each intensity signal having an amplitude related to the intensity of said light emitted in said side direction by a corresponding one of said LEDs.
2. The light source of claim 1 wherein the intensity of light in said side direction is a fixed fraction of the intensity of light in said forward direction.
3. The light source of claim 1 wherein said collector is circularly symmetric.
4. The light source of claim 1 wherein said collector is cylindrical, said LEDs being arranged along a line parallel to an axis of said collector.
5. The light source of claim 1 wherein each of said LEDs emits light at a wavelength that is different from the wavelengths at which the others of said LEDs emit light.
6. The light source of claim 5 wherein said photo-detector comprises N photodiodes for measuring light received through N wavelength filters, each wavelength filter passing light from one of said LEDs.
7. The light source of claim 1 wherein N=2.
8. The light source of claim 1 wherein N=3.
9. The light source of claim 1 wherein said first component light source comprises a bus and a first interface circuit for controlling N signals, each signal determining a light intensity to be generated in said forward direction by a corresponding one of said LEDs, said interface circuit further coupling said N intensity signals to said bus in response to a control signal identifying said first interface.
10. The light source of claim 9 comprising a second component light source, said second component light source comprising:
N LEDs, each LED having a light emitting chip in a package, said light emitting chip emitting light in a forward direction and light in a side direction, wherein N>1, said light generated in said forward direction being determined by a drive signal coupled to that LED, a portion of said light in said side direction leaving said package;
a photo-detector;
a collector positioned to direct a portion of said light in said side direction that leaves said package of each of said LEDs onto said photo-detector, said photo-detector generating N intensity signals, each intensity signal having an amplitude related to the intensity of said light emitted in said side direction by a corresponding one of said LEDs and a second interface circuit for controlling N signals, each signal determining a light intensity to be generated in said forward direction by a corresponding one of said LEDs in said second component light source, said interface circuit further coupling said N intensity signals to said bus in response to a control signal identifying said second interface.
11. The light source of claim 10 further comprising a feedback controller connected to said bus, said feedback controller utilizing said intensity signals of each of said component light sources to control said drive signals.
12. A method for illuminating a device with light from a plurality of LEDs, each LED having a light emitting chip in a package, said light emitting chip emitting light in a forward direction and light in a side direction, said light generated in said forward direction being determined by a drive signal coupled to that LED, a portion of said light in said side direction leaving said package, said method comprising:
collecting a portion of said light in said side direction from each of said LEDs;
measuring the intensity of said collected light for each of said LEDs to generate a measured intensity value for each of said LEDs;
controlling said drive signals of said LEDs to maintain each of said measured intensity values at a target value.
13. The method of claim 12 wherein said light in said forward direction is used to illuminate said device.
14. The method of claim 12 wherein one of said LEDs emits light of a color different from the light emitted by another one of said LEDs.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of controlling polishing, comprising:
storing a sequence of default values;
polishing a substrate;
monitoring the substrate during polishing with an in-situ monitoring system;
generating a sequence of measured values from measurements from the in-situ monitoring system;
combining the sequence of measured values with the sequence of default values to generate a sequence of modified values;
fitting a function to the sequence of modified values; and
determining at least one of a polishing endpoint or an adjustment for a polishing rate based on the function.
2. The method of claim 1, wherein for each measured value from the sequence of measured values there is an associated default value from the sequence of default values.
3. The method of claim 2, wherein combining the sequence of measured values with the sequence of default values comprises for each measured value calculating a weighted average of the measured value and the associated default value.
4. The method of claim 3, comprising storing a first timestamp for each measured value from the sequence of measured values, and a second timestamp for each default value from the sequence of default values.
5. The method of claim 4, comprising determining a matching default value from the sequence of default values for each measured value, and wherein determining the matching default value includes determining the second timestamp that matches the first timestamp.
6. The method of claim 4, wherein the first timestamp comprises a measurement time, a number of platen rotations, or an ordinal position in the sequence of measured values.
7. The method of claim 3, comprising receiving user input selecting the weighting value for the calculation of the weighted average.
8. The method of claim 7, wherein a same weighting value is used for the calculation of the weighted average for every measured value from the sequence of measured values.
9. The method of claim 3, comprising dynamically determining a weighting value for the calculation of the weighted average.
10. The method of claim 9, wherein dynamically determining the weighting value comprises fitting a second function to the sequence of measured values, determining a goodness of fit of the second function to the sequence of measured values, and determining the weighting value based on the goodness of fit.
11. The method of claim 9, wherein monitoring the substrate comprises receiving a measured spectrum from the in-situ monitoring system, and wherein generating the sequence of measured values comprises finding a best matching reference spectrum from a plurality of reference spectra.
12. The method of claim 11, wherein dynamically determining the weighting value comprises determining a difference between the measured spectrum and the best matching reference spectrum, and determining the weighting value based on the difference.
13. The method of claim 9, wherein a same weighting value is used for the calculation of the weighted average for every measured value from the sequence of measured values.
14. The method of claim 9, comprising calculating a weighting value for each measured value.
15. The method of claim 1, wherein the in-situ monitoring comprises an optical monitoring system or an eddy current monitoring system.
16. The method of claim 1, wherein polishing the substrate comprises rotating a platen, and the sequence of measured values comprises one measured value per rotation of the platen.
17. The method of claim 1, comprising storing a target value and determining a polishing endpoint by calculating a time at which the function equals the target value.
18. The method of claim 1, comprising determining a value of the function at a time T0 at which the polishing parameter is adjusted, and wherein determining the adjustment comprises calculating a desired polishing rate based on the value of the function.