Modulated scatterometry
An apparatus for scatterometry measurements is disclosed. The apparatus includes a modulated pump source for exciting the sample. A separate probe beam is directed to interact with the sample and the modulated optical response is measured. The measured data is subjected to a scatterometry analysis in order to evaluate geometrical sample features that induce light scattering.
1. An apparatus for evaluating a sample have light diffracting features comprising:
an intensity modulated energy source for periodically exciting the sample;
a probe beam directed to reflect off the sample in the region which has been periodically excited;
a detector for monitoring the probe beam after interaction with the sample and generating output signals; and
a processor for filtering the output signals to determine the modulated optical scattering of the light and wherein the modulated optical scattering response is analyzed according to a scatterometry analysis to evaluate the light diffracting features on the sample.
2. An apparatus as recited in claim 1 wherein said probe beam is polychromatic and detector generates output signals as a function of wavelength.
3. An apparatus as recited in claim 2 wherein the detector and processor operate as a reflectometer.
4. An apparatus as recited in claim 2 further including an analyzer and wherein the processor determines the change in polarization state of the probe beam.
5. A method for evaluating a sample have light diffracting features comprising the steps of:
periodically exciting a region on the sample;
directing a probe beam of radiation to reflect off a portion of the region which has been periodically excited;
monitoring the probe beam after interaction with the sample and generating output signals; and
filtering the output signals to determine the modulated optical scattering of the light and wherein the modulated optical scattering response is analyzed according to a scatterometry analysis to evaluate the light diffracting features on the sample.
6. A method as recited in claim 5 wherein said probe beam is polychromatic and the output signals are generated as a function of wavelength.
7. A method as recited in claim 6 wherein the monitoring and filtering step measure the modulated changes in the intensity of the probe beam.
8. A method as recited in claim 6 wherein the monitoring and filtering step determines the modulated changes in polarization state of the probe beam.
9. A method as recited in claim 5 further including the step monitoring the probe beam after interaction with the sample during a period when the sample is not being periodically excited and using the results to further evaluate the sample.