Second Harmonic Generation (SHG) optical inspection system designs
Second Harmonic Generation (SHG) can be used to interrogate a surface of a sample such as a layered semiconductor structure. The SHG based sample interrogation systems may simultaneously collect different polarization components of the SHG signal at a time to provide different types of information. SHG imaging systems can provide SHG images or maps of the distribution of SHG signals over a larger area of a sample. Some such SHG imaging systems employ multiple beams and multiple detectors to capture SHG signals over an area of the sample. Some SHG imaging systems employ imaging optics to image the sample onto a detector array to form SHG images.
1. A system for characterizing a sample using second harmonic generation, the system comprising:
a sample holder configured to support a sample;
an optical source configured to direct a light beam onto said sample to produce second harmonic generation from said sample;
an array beam generator configured to generate a plurality of beams using the light beam received from the optical source;
a focusing lens configured to focus light from said optical source onto said sample;
a scanner disposed in an optical path between the array beam generator and the focusing lens, the scanner configured to scan the plurality of the beams received from the array generator over the sample, by redirecting them;
an optical detection system configured to receive second harmonic generated light from said sample, said optical detection system comprising at least one detector array;
a translation stage configured to translate said sample with respect to said optical source and said at least one detector array;
projection optics configured to project a 2D array of beams of second harmonic generation light from said sample onto said at least one detector array; and
processing electronics configured to receive signals from said at least one detector array;
wherein the scanner scans the plurality of beams over separate regions of the sample in parallel and in a first direction and the translation stage scans the sample in a second direction perpendicular to the first direction, and
wherein the system generates a map of a distribution of the second harmonic generated light over an area on the sample by combining data received from the detector array.
2. The system of claim 1 , wherein said at least one detector array comprises a 2-D array.
3. The system of claim 1 , wherein said at least one detector array comprises a CCD array.
4. The system of claim 1 , wherein said at least one detector array comprises a time dependent integration device.
5. The system of claim 1 , wherein said projection optics is configured to image the sample onto said at least one detector array.
6. The system of claim 1 , wherein said projection optics comprises an imaging lens, said at least one detector array being disposed at a conjugate image plane of said sample.
7. The system of claim 1 , wherein said translation stage comprises an x-y translation stage.
8. The system of claim 1 , further comprising at least one polarization beamsplitter disposed so as to receive second harmonic generated light from said sample, said polarization beamsplitter configured to separate light into first and second polarization components and to direct said first and second polarization components to first and second detector arrays, respectively.
9. The system of claim 8 , wherein said first and second polarization components are s and p polarizations, respectively.
10. The system of claim 1 , wherein the scanner comprises one or more mirrors or reflective surfaces.
11. The system of claim 1 , wherein the array beam generator comprises an acousto-optic modulator.