Pump and probe type second harmonic generation metrology
Various approaches to 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.
1. A method of optical interrogation comprising:
applying pumping radiation across an entire semiconductor wafer using a pump optical source;
providing probing radiation to a first location on the wafer using a probe optical source;
raster scanning the probing radiation or the wafer;
providing probing radiation to a second location on the wafer using the probe optical source;
detecting a Second Harmonic Generation (SHG) effect signal at the first and second locations generated by at least one of the pumping radiation and the probing radiation using an optical detector; and
a) obtaining the SHG effect signal less than 10 seconds after applying at least one of the pumping radiation and the probing radiation at the first or second locations or b) varying a wavelength of the pumping radiation to detect a region wherein the SHG effect signal suddenly changes in slope to determine a threshold injection carrier energy.
2. The method of claim 1 , further comprising applying the pumping radiation and the probing radiation with a variable time offset relative to one another to enable determination of one or more material parameters, the variable time offset being associated with energy of at least one of the probing radiation or the pumping radiation.
3. The method of claim 1 , comprising: a) obtaining the SHG effect signal within less than 10 seconds after applying at least one of:
the pumping radiation and the probing radiation, and b) applying the pumping and probing radiation with a variable time offset relative to one another to enable determination of material parameters not otherwise attainable with application of probing radiation only or pumping and probing radiation without the variable time offset.
4. The method of claim 1 , comprising: a) obtaining the SHG effect signal within less than 10 seconds after applying at least one of the pumping radiation and the probing radiation, b) applying the pumping and probing radiation with a variable time offset relative to one another to enable determination of material parameters, and c) varying a wavelength of the pumping radiation to detect a region wherein the SHG effect signal suddenly changes in slope to determine threshold injection carrier energy.
5. The method of claim 1 , comprising: a) obtaining the SHG effect signal within less than 10 seconds after applying at least one of:
the pumping radiation and the probing radiation and b) varying a wavelength of the pumping radiation to detect a region wherein the SHG effect signal suddenly changes in slope to determine threshold injection carrier energy.
6. The method of claim 1 , comprising: a) applying the pumping and probing radiation with a variable time offset relative to one another to enable determination of material parameters, and b) varying a wavelength of the pumping radiation to detect a region wherein the SHG effect signal suddenly changes in slope to determine threshold injection carrier energy.
7. The method of any of claims 1 , wherein the SHG effect signal is obtained in less than 6 seconds after applying at least one of the pumping radiation and the probing radiation.
8. The method of any of claims 1 , wherein the SHG effect signal is obtained in less than 1 second after applying at least one of the pumping radiation and the probing radiation.
9. The method of any of claims 1 , wherein the SHG effect signal is obtained in less than 10 nanoseconds after applying at least one of the pumping radiation and the probing radiation.
10. The method of claim 1 , wherein the pumping radiation has an average optical power greater than about 100 mW.
11. The method of claim 1 , wherein the pumping radiation has an average optical power less than about 10 W.
12. The method of claim 1 , wherein the pumping radiation has a wavelength between about 80 nm and about 1000 nm.
13. The method of claim 1 , wherein the probing radiation has an average optical power less than about 150 mW.
14. The method of claim 1 , wherein the probing radiation has a peak optical power greater than about 10 kW.
15. The method of claim 1 , wherein the probing radiation has a peak optical power less than about 1 GW.
16. The method of claim 1 , wherein the probing radiation has a wavelength between about 100 nm to 2000 nm.
17. The method of claim 1 , wherein the pump optical source comprises a UV flash lamp.
18. The method of claim 1 , wherein the pump optical source comprises a pulsed laser.
19. The method of claim 1 , wherein the SHG effect signal is obtained less than 10 seconds after applying at least one of the pumping radiation and the probing radiation.
20. The method of claim 1 , wherein the wavelength of the pumping radiation is varied to detect a region wherein the SHG effect signal suddenly changes in slope to the threshold injection carrier energy.
21. A method of optical interrogation comprising:
applying pumping radiation from a pump optical source across an entire semiconductor wafer;
applying probing radiation from a probing optical source to a first location on the wafer;
raster scanning the probing radiation or the wafer;
applying probing radiation from the probing optical source to a second location on the wafer;
detecting a Second Harmonic Generation (SHG) effect signal generated by at least one of the pumping radiation and the probing radiation at the first and second locations using an optical detector;
varying a wavelength of the pumping radiation; and
determining a characteristic of the detected Second Harmonic Generation (SHG) effect signal in the presence of at least one of the pumping and probing radiation.
22. A method of optical interrogation comprising:
applying pumping radiation energy from a pump optical source across an entire semiconductor wafer;
applying probing radiation energy from a probing optical source to a first location on the wafer;
raster scanning the probing radiation energy or the wafer;
applying probing radiation energy from the probing optical source to a second location on the wafer;
detecting a Second Harmonic Generation (SHG) effect signal at the first and second locations using an optical detector;
varying energy of the pump radiation; and
identifying an inflection point in the SHG effect signal associated with a threshold injection carrier energy.