Method for determining the doping profile of a partially activated doped semiconductor region

Abstract

A method is disclosed for determining the inactive doping concentration of a semiconductor region using a PMOR method. In one aspect, the method includes providing two semiconductor regions having substantially the same known as-implanted concentration but known varying junction depths. The method includes determining on one of these semiconductor regions the as-implanted concentration. The semiconductor regions are then partially activated. PMOR measures are then performed on the partially activated semiconductor regions to measure (a) the signed amplitude of the reflected probe signal as function of junction depth and (b) the DC probe reflectivity as function of junction depth. The method includes extracting from these measurements the active doping concentration and then calculating the inactive doping concentration using the determined total as-implanted concentration and active doping concentration. The method may also include extracting thermal diffusivity, refraction index, absorption coefficient, and/or SRHF lifetime from these measurements.

1 . A method of determining the inactive doping concentration of a semiconductor region using a photomodulated optical reflectance (PMOR) method, the method comprising:
 providing a set of at least two semiconductor regions having substantially the same known as-implanted concentration but known varying junction depth;   determining on at least one of these semiconductor regions the as-implanted concentration;   partially activating the at least two semiconductor regions;   measuring by a photomodulated optical reflectance (PMOR) technique on the partially activated semiconductor regions the signed amplitude of the reflected probe signal as a function of junction depth and for at least two laser separation values;   measuring by a PMOR technique on the partially activated semiconductor regions the DC probe reflectivity as a function of junction depth;   extracting from these measurements the active doping concentration thereby assuming crystal mobility; and   calculating the inactive doping concentration using the determined total as-implanted concentration and active doping concentration.   
     
     
         2 . The method according to  claim 1 , further comprising extracting thermal diffusivity, refraction index, absorption coefficient, and/or Shockley-Reed-Hall lifetime from these measurements. 
     
     
         3 . The method according to  claim 1 , wherein the PMOR technique is a high-modulation-frequency PMOR technique providing a signal in-phase with modulation signal and a signal with a 90° phase difference with respect to the probe laser beam. 
     
     
         4 . The method according to  claim 3 , wherein the modulation frequency of the pump laser beam is in the Mhz range. 
     
     
         5 . The method according to  claim 1 , wherein the semiconductor regions have an integrated concentration of about 1e20 cm −3  or higher. 
     
     
         6 . A method of determining the effect and/or efficiency of an annealing process on physical properties of a doped semiconductor region, the method comprising:
 (a) providing at least one sample of the doped semiconductor region;   (b) determining the doping profile of the at least one sample;   (c) applying an anneal process to the at least one sample; and   (d) extracting the selected physical property from the annealed sample according to the method of  claim 1 .   
     
     
         7 . The method according to  claim 6 , further comprising:
 repeating processes (a) to (d) for another sample wherein another anneal process is applied; and   correlating the variation in the physical property to the variation in the anneal processes.   
     
     
         8 . The method according to  claim 6 , wherein the physical property is selected from the group of: thermal diffusivity, complex refraction index, absorption coefficient, and/or Shockley-Reed-Hall lifetime. 
     
     
         9 . A method of determining the inactive doping concentration of a semiconductor region using a photomodulated optical reflectance (PMOR) method, the method comprising:
 providing at least two semiconductor regions having substantially the same as-implanted concentration but different known junction depths, wherein the semiconductor regions being not annealed;   performing a photomodulated optical reflectance (PMOR) technique on at least one of these semiconductor regions to determine the as-implanted concentration;   partially activating the at least two semiconductor regions;   performing a PMOR technique on the partially activated semiconductor regions for at least two different laser separation values to measure the signed amplitude of the reflected probe signal as a function of the junction depth and the DC probe reflectivity as a function of the junction depth;   determining based on these measurements the active doping concentration; and   calculating the inactive doping concentration using the determined total as-implanted concentration and the active doping concentration.   
     
     
         10 . A system for determining the inactive doping concentration of a semiconductor region using a photomodulated optical reflectance (PMOR) method, the system comprising:
 means for providing a set of at least two semiconductor regions having substantially the same as-implanted concentration but different known junction depth;   means for determining on at least one of these semiconductor regions the as-implanted concentration;   means for partially activating the at least two semiconductor regions;   means for measuring by a photomodulated optical reflectance (PMOR) technique on the partially activated semiconductor regions the signed amplitude of the reflected probe signal as a function of junction depth and for at least two laser separation values;   means for measuring by a PMOR technique on the partially activated semiconductor regions the DC probe reflectivity as a function of junction depth;   means for extracting from these measurements the active doping concentration thereby assuming crystal mobility; and   means for calculating the inactive doping concentration using the determined total as-implanted concentration and active doping concentration.   
     
     
         11 . A system for determining the inactive doping concentration of a semiconductor region using a photomodulated optical reflectance (PMOR) method, the system comprising:
 a providing module configured to provide a set of at least two semiconductor regions having substantially the same as-implanted concentration but different known junction depth;   a determining module configured to determine on at least one of these semiconductor regions the as-implanted concentration;   an activating module configured to partially activate the at least two semiconductor regions;   a measuring module configured to measure by a photomodulated optical reflectance (PMOR) technique on the partially activated semiconductor regions (a) the signed amplitude of the reflected probe signal as a function of junction depth and for at least two laser separation values, and (b) the DC probe reflectivity as a function of junction depth;   an extracting module configured to extract from these measurements the active doping concentration thereby assuming crystal mobility, and   a calculating module configured to calculate the inactive doping concentration using the determined total as-implanted concentration and active doping concentration.   
     
     
         12 . The system according to  claim 11 , further comprising an extracting module configured to extract thermal diffusivity, refraction index, absorption coefficient, and/or Shockley-Reed-Hall lifetime from these measurements. 
     
     
         13 . The system according to  claim 11 , wherein the semiconductor regions have an integrated concentration of about 1e20 cm −3  or higher. 
     
     
         14 . The system according to  claim 11 , wherein the PMOR technique is a high-modulation-frequency PMOR technique providing a signal in-phase with modulation signal and a signal with a 90° phase difference with respect to the probe laser beam. 
     
     
         15 . The system according to  claim 14 , wherein the modulation frequency of the pump laser beam is in the Mhz range.