Wafer metrology technologies
Various approaches can be used to interrogate a surface such as a surface of a layered semiconductor structure on a semiconductor wafer. Certain approaches employ Second Harmonic Generation and in some cases may utilize pump and probe radiation. Other approaches involve determining current flow from a sample illuminated with radiation. Decay constants can be measured to provide information regarding the sample. Additionally, electric and/or magnetic field biases can be applied to the sample to provide additional information.
1. A system for optically interrogating a surface, comprising:
a probe optical source configured to direct probing radiation to the surface;
a UV flash lamp configured to direct UV light to the surface;
at least one optical detector configured to detect second harmonic generated light produced by the probing radiation directed on the surface in the presence of the UV light;
a scanning stage configured to enable scanning said probing radiation across multiple locations on the surface; and
a controller configured to obtain second harmonic generation measurements from the second harmonic generated light detected by the at least one optical detector,
wherein said system is configured to be part of a semiconductor fabrication or production line,
wherein said controller is configured to obtain second harmonic generation measurements from the second harmonic generated light less than 10 seconds after applying the probing radiation.
2. The system of claim 1 , wherein the probe optical source comprises a laser.
3. The system of claim 1 , wherein the probe optical source comprises a pulsed laser.
4. The system of claim 3 , wherein the pulsed laser is selected from nanosecond, picosecond and femtosecond lasers.
5. The system of claim 4 , wherein the pulsed laser comprises a tunable wavelength laser.
6. The system of claim 1 , wherein the at least one optical detector is selected from a photomultiplier tube, a CCD camera, an avalanche detector, a photodiode detector, a streak camera and a silicon detector.
7. The system of claim 1 , wherein the probing radiation has a peak optical power greater than about 10 kW.
8. The system of claim 1 , wherein the controller is configured to obtain second harmonic generation measurements from the second harmonic generated light produced between 1 second and 100 milliseconds after applying the probing radiation.
9. The system of claim 1 , further comprising processing electronics configured to detect a region of discontinuity in the second harmonic generated light to determine threshold injection carrier energy as the energy of the probing radiation is varied.
10. The system of claim 1 , wherein said system is part of a semiconductor fabrication or production line.
11. The system of claim 1 , wherein the UV light has an energy from 1 Joule to 10 kilojoules per flash.
12. The system of claim 1 , wherein the scanning stage comprises an x-y stage.
13. The system of claim 1 , wherein the scanning stage comprises a rotational stage.
14. The system of claim 1 , further comprising an Equipment Front End Module (EFEM) configured to accept a wafer comprising the surface.
15. The system of claim 1 , wherein a peak power of the UV light is less than a threshold peak power for generating second harmonic light and average power of the UV light is above a threshold power for charging the surface.
16. A method of optically interrogating a surface, the method comprising:
providing probing radiation to the surface, using a probe optical source, to optically interrogate the surface;
providing UV light to the surface using a UV flash lamp,
detecting a second harmonic generated signal generated by the probing radiation, in the presence of UV light, using an optical detector; and
obtaining second harmonic generation measurements from the detected second harmonic generated signal less than 10 seconds after applying the probing radiation.
17. The method of claim 16 , wherein said surface is on a semiconductor wafer in a semiconductor fabrication or production line.
18. The method of claim 17 , further comprising an Equipment Front End Module (EFEM) configured to accept a wafer comprising the surface.
19. The method of claim 16 , wherein a peak power of the UV light is less than a threshold peak power for generating second harmonic light and average power of the UV light is above a threshold power for charging the surface.