Charge decay measurement systems and methods

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. 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 .- 120 . (canceled) 
     
     
         121 . A method of optical interrogation of a sample material, the method comprising:
 charging the material at a sample site with radiation to a first charging level;   reducing the intensity of the charging radiation;   obtaining multiple charge state decay measurements at the sample site by directing an interrogating optical beam at the sample site at different times after reducing the intensity of the charging radiation to provide decay curve data; and   determining a characteristic of the decay curve data to determine a parameter of the sample material,   wherein the multiple charge state decay measurements are obtained within  1  second after reducing the intensity of the charging radiation.   
     
     
         122 . The method of  claim 121 , wherein determining a characteristic of the decay curve data includes determining a shape of the decay curve data. 
     
     
         123 . The method of  claim 121 , wherein the parameter is selected from at least one of: a charge carrier density, a trap charge density, an occupied trap density, a carrier injection threshold energy, a charge carrier lifetime, a charge accumulation time, and trapping cross-section. 
     
     
         124 . The method of  claim 121 , further comprising obtaining charge state decay measurements at another sample site at different times after reducing the intensity of the charging radiation to provide the decay curve data. 
     
     
         125 . The method of  claim 124 , further comprising charging the material at another sample site with radiation to a second charging level. 
     
     
         126 . The method of  claim 125 , wherein the first and the second charging level are same. 
     
     
         127 . The method of  claim 125 , wherein the first and the second charging level are different. 
     
     
         128 . A system for optical interrogation of a sample material, the system comprising:
 an optical source capable of charging the material at a sample site with charging radiation to a first charging level;   a detection system capable of obtaining multiple charge state decay measurements at the sample site at different times after reducing the intensity of the charging radiation to provide a decay curve data; and   a processor capable of determining a characteristic of the decay curve data to determine a parameter of the sample material,   wherein the multiple charge state decay measurements are obtained within 1 second after reducing intensity of charging radiation.   
     
     
         129 . The system of  claim 128 , wherein the detection system is capable of obtaining the multiple charge state decay measurements at the sample site at different times in less than  50  milliseconds after reducing the intensity of the charging radiation to provide a decay curve data. 
     
     
         130 . The system of  claim 128 , wherein the detection system is capable of obtaining the multiple charge state decay measurements at the sample site at different times in less than 1 millisecond after reducing the intensity of the charging radiation to provide a decay curve data. 
     
     
         131 . The system of  claim 128 , wherein the detection system is capable of obtaining the multiple charge state decay measurements at the sample site at different times in less than 500 microseconds after reducing the intensity of the charging radiation to provide a decay curve data. 
     
     
         132 . The system of  claim 128 , wherein the optical source comprises at least one of: a UV flash lamp, a laser and a pulsed laser. 
     
     
         133 . The system of  claim 128 , wherein the detection system comprises a probe beam; and a detector capable of detecting a second harmonic generation (SHG) signal associated with the probe beam. 
     
     
         134 . The system of  claim 133 , wherein the probe beam is emitted by a pulsed laser.