Pump and probe type second harmonic generation metrology

Abstract

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 optically interrogating a surface, the method comprising
 applying pumping radiation to a surface to be interrogated using a pump optical source;   providing probing radiation to the same surface using a probe optical source;   detecting a Second Harmonic Generation (SHG) effect signal 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, b) applying the pumping and probing energy with a variable time offset relative to one another to enable determination of one or more material parameters or c) varying a wavelength of the pump energy to detect a region wherein the SHG signal suddenly changes in slope to determine threshold injection carrier energy.   
     
     
         2 . The method of  claim 1 , wherein the variable time offset is associated with energy of at least one of the probing radiation and 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 energy 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 energy with a variable time offset relative to one another to enable determination of material parameters, and c) varying a wavelength of the probing energy to detect a region wherein the SHG 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 c) varying a wavelength of the probing energy to detect a region wherein the SHG signal suddenly changes in slope to determine threshold injection carrier energy. 
     
     
         6 . The method of  claim 1 , comprising: b) applying the pumping and probing energy with a variable time offset relative to one another to enable determination of material parameters, and c) varying a wavelength of the probing energy to detect a region wherein the SHG 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 .- 27 . (canceled) 
     
     
         28 . A method of optical interrogation of a hetero-interface substrate, the method comprising:
 applying pumping radiation from a pump optical source to a surface;   applying probing radiation from a probing optical source to the same surface at a temporal offset;   detecting a Second Harmonic Generation (SHG) effect signal generated by at least one of the pumping radiation and the probing radiation using an optical detector; 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.   
     
     
         29 .- 37 . (canceled) 
     
     
         38 . A method of optical interrogation of a hetero-interface substrate, the method comprising:
 applying pumping radiation energy from a pump optical source to a surface;   applying probing radiation energy from a probing optical source to the same surface;   detecting a Second Harmonic Generation (SHG) effect signal generated by at least one of the pumping radiation and the probing radiation using an optical detector;   varying energy of the pump radiation; and   identifying an inflection point in the SHG signal associated with a threshold injection carrier energy.   
     
     
         39 .- 107 . (canceled)