Increasing an electrical resistance of a resistor by nitridization

Abstract

A method for increasing an electrical resistance of a resistor. A semiconductor structure that includes the resistor is placed in a chamber that includes a gas including nitrogen-containing molecules at an nitrogen concentration. A fraction F of an exterior surface of a surface layer of the resistor is exposed to the nitrogen-comprising molecules. A portion of the surface layer is heated at a heating temperature. A combination of the nitrogen concentration and the heating temperature is sufficient to nitridize the portion of the surface layer by reacting the portion with the nitrogen-containing molecules. Heating the portion of the surface layer includes directing a beam of radiation or particles into the portion of the surface layer heat the portion of the surface layer. The portion of the surface layer is nitridized by being reacted with the nitrogen-containing molecules such that an electrical resistance of the resistor is increased.

1 . A method for increasing an electrical resistance of a resistor, comprising the steps of:
 providing a semiconductor structure that includes the resistor;   placing the semiconductor structure in a chamber, wherein the resistor includes a surface layer having an exterior surface;   including a gas within chamber, wherein the gas includes nitrogen-comprising molecules at an nitrogen concentration;   exposing a fraction F of the exterior surface of the surface layer to the nitrogen-comprising molecules;   heating a portion of the surface layer at a heating temperature, wherein an exterior surface of said portion consists essentially of the fraction F of the exterior surface of the surface layer, and wherein a combination of the nitrogen concentration and the heating temperature is sufficient to nitridize the portion of the surface layer by reacting said portion with the nitrogen-comprising molecules, wherein heating the portion of the surface layer includes directing a beam into the portion of the surface layer such that the beam causes the heating of the portion of the surface layer, and wherein the beam is selected from the group consisting a beam of radiation and a beam of particles; and   nitridizing the portion of the surface layer by reacting said portion with the nitrogen-comprising molecules such that an electrical resistance of the resistor is increased, wherein an exterior surface of said portion consists essentially of the fraction F of the exterior surface of the surface layer.   
   
   
       2 . The method of  claim 1 , wherein the beam is the beam of radiation, and wherein the radiation includes a laser radiation. 
   
   
       3 . The method of  claim 2 , wherein F<1. 
   
   
       4 . The method of  claim 2 , wherein F=1. 
   
   
       5 . The method of  claim 2 , wherein the laser radiation is a pulsed laser radiation. 
   
   
       6 . The method of  claim 2 , further comprising generating the laser radiation by a laser whose spot size is less than a surface area of the exterior surface of the surface layer. 
   
   
       7 . The method of  claim 1 , wherein the beam is the beam of particles. 
   
   
       8 . The method of  claim 7 , wherein the beam of particles is a beam of electrons. 
   
   
       9 . The method of  claim 7 , wherein the beam of particles is a beam of protons. 
   
   
       10 . The method of  claim 7 , wherein the beam of particles is a beam of ions. 
   
   
       11 . The method of  claim 1 , wherein said nitridizing results in a thickness of the nitridized portion of the surface layer being an increasing function of an energy flux of the beam. 
   
   
       12 . The method of  claim 1 , wherein a dimension of the exterior surface of the surface layer is no smaller than a smallest surface area on which the beam could be focused. 
   
   
       13 . The method of  claim 1 , wherein the gas is a flowing gas. 
   
   
       14 . The method of  claim 1 , wherein the gas is a non-flowing gas. 
   
   
       15 . The method of  claim 1 , wherein the method further comprises:
 predetermining a target resistance R t  and an associated tolerance ΔR t  for the electrical resistance of the resistor; and   testing the resistor during the nitridizing step to determine whether the electrical resistance of the resistor is within R t ±ΔR t .   
   
   
       16 . The method of  claim 15 , wherein if during the testing step the electrical resistance of the resistor is determined to not be within R t ±ΔR t  then the method further comprises:
 iterating such that each iteration of the iterating includes additionally executing the exposing and nitridizing steps and additionally testing the resistor during the nitridizing step to determine whether R 2 ″ is within R t ±ΔR t , wherein R 2 ″ is a latest value of the electrical resistance of the resistor as determined by said testing; and   ending the iterating if R 2 ″ is within R t ±ΔR t  or if (R 2 ″−R 1 ) (R t ″R 2 ″)<0, wherein R 1  is a latest value of the determined electrical resistance of the resistor immediately prior to said testing.   
   
   
       17 . The method of  claim 15 , wherein said ending the iterating comprises satisfying R 2 ″ being within R t ±ΔR t . 
   
   
       18 . The method of  claim 17 , wherein the method further comprises determining from a calibration curve the time of exposure that results in the electrical resistance of the resistor being within R t ±ΔR t  as a result of said nitridizing, and wherein said nitridizing is performed for the determined time of exposure. 
   
   
       19 . The method of  claim 15 , wherein said ending the iterating comprises satisfying (R 2 ″−R t ) (R t −R 2 ″)<0. 
   
   
       20 . The method of  claim 15 , wherein said testing comprises continuously testing the resistor during the nitridizing step.