Wafer metrology techonologies

Abstract

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 .- 39 . (canceled) 
     
     
         40 . A system for optically interrogating a surface, comprising
 a pump optical source configured to emit pumping radiation;   a probe optical source configured to emit probing radiation;   at least one optical detector configured to detect second harmonic generated light by at least one of the pumping radiation and the probing radiation;   an optical device for introducing a variable time offset between the pumping and the probing radiation; and   a processor configured to determine a characteristic of the detected second harmonic generated light.   
     
     
         41 . The system of claim  1 , wherein the pump optical source comprises a UV flash lamp. 
     
     
         42 . The system of claim  1 , wherein the pump optical source comprises a laser. 
     
     
         43 . The system of  claim 42 , wherein the pump optical source comprises a pulsed laser. 
     
     
         44 . The system of claim  1 , wherein the probe optical source comprises a pulsed laser. 
     
     
         45 . The system of  claim 40 , wherein the pulsed laser is selected from nanosecond, picosecond and femtosecond lasers. 
     
     
         46 . The system of  claim 44 , wherein the pulsed laser comprises a tunable wavelength laser. 
     
     
         47 . The system of claim  1 , wherein the optical detector is selected from a photomultiplier tube, a CCD camera, an avalanche detector, a photodiode detector, a streak camera and a silicon detector. 
     
     
         48 . The system of claim  1 , wherein the system is configured to obtain the second harmonic generate light in less than 10 seconds after applying at least one of the pumping radiation and the probing radiation. 
     
     
         49 . The system of  claim 48 , wherein the system is configured to obtain the second harmonic light in less than 1 second after applying at least one of the pumping radiation and the probing radiation. 
     
     
         50 . The system of claim  1 , wherein the optical device for introducing a variable time offset is a shutter. 
     
     
         51 . The system of  claim 50 , wherein the shutter is an optical shutter selected from a Kerr cell and a Pockels cell. 
     
     
         52 . The system of  claim 50 , wherein the shutter is a mechanical shutter. 
     
     
         53 . The system of  claim 50 , wherein the shutter is configured to introduce a time offset between about 1 millisecond and about 60 seconds. 
     
     
         54 . The system of claim  1 , wherein the optical device is a programmable optical delay. 
     
     
         55 . The system of claim  1 , wherein the processor is configured to obtain a time dependence of the detected second harmonic generated light in less than 10 seconds after applying at least one of the pumping radiation and the probing radiation. 
     
     
         56 . The system of claim  1 , wherein the processor is configured to determine a characteristic of the detected second harmonic generated light including a reduction in intensity of the detected second harmonic generated light in the presence of pumping energy. 
     
     
         57 . The system of claim  1 , wherein the processor is configured to determine a characteristic of the detected second harmonic generated light including an increase in intensity of the detected second harmonic generated light in the presence of pumping energy. 
     
     
         58 . A system for optically interrogating a surface, comprising
 a pump optical source configured to emit pumping radiation;   a probe optical source configured to emit probing radiation;   at least one optical detector configured to detect second harmonic generated light by at least one of the pumping radiation and the probing radiation; and   a controller configured to obtain information from part of the second harmonic generated light produced less than 10 seconds after applying at least one of the pumping radiation and the probing radiation.   
     
     
         59 .- 65 . (canceled) 
     
     
         66 . A system for optically interrogating a surface, comprising
 a pump optical source configured to emit pumping radiation;   a probe optical source configured to emit probing radiation with variable energy;   an optical detector configured to detect second harmonic generated light by at least one of the pumping radiation and the probing radiation; and   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.   
     
     
         67 .- 321 . (canceled)