Increasing an electrical resistance of a resistor by nitridization

Abstract

A method for increasing an electrical resistance of a resistor. A fraction F of an exterior surface of a surface layer of a resistor of a semiconductor structure is exposed to the nitrogen-comprising molecules. An anodization electrical circuit is formed and includes: a DC power supply, an electrolytic solution including nitrogen, and the resistor partially immersed in the electrolytic solution. The DC power supply is activated and generates a voltage output, that causes an electrolytic reaction in the electrolytic solution near the resistor. The electrolytic reaction generates nitrogen ions from the nitrogen in the electrolytic solution. The fraction F is exposed to the nitrogen ions. A portion of the surface layer is nitridized by being reacted with the nitrogen ions at a temperature above ambient room temperature 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;   forming an anodization electrical circuit which includes: a DC power supply, an electrolytic solution comprising nitrogen, the resistor partially or totally immersed in the electrolytic solution such that a fraction F of an exterior surface of a surface layer of the resistor is immersed in the electrolytic solution, and a cathode partially immersed in the electrolytic solution, wherein the resistor is electrically coupled to a positive terminal of the DC power supply such that the resistor serves as an anode, and wherein the cathode is electrically coupled to a negative terminal of the DC power supply;   activating the DC power supply such that the DC power supply generates a voltage output, wherein the voltage output causes an electrolytic reaction in the electrolytic solution near the resistor, and wherein the electrolytic reaction generates nitrogen ions from the nitrogen in the electrolytic solution;   exposing the fraction F of the exterior surface of the surface layer of the resistor to the nitrogen ions; and   nitridizing a portion of the surface layer by reacting said portion with the nitrogen ions at a temperature above ambient room temperature 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 a dimension of the resistor does not exceed about 1 micron. 
   
   
       3 . The method of  claim 1 , wherein F<1. 
   
   
       4 . The method of  claim 1 , wherein F=1. 
   
   
       5 . The method of  claim 1 , wherein the resistor includes an electrically resistive material selected from the group consisting of polysilicon, amorphous silicon, titanium, tantalum, tungsten, aluminum, silver, copper, nitrides thereof, silicides thereof, and alloys thereof. 
   
   
       6 . The method of  claim 1 , wherein the resistor partially immersed in the electrolytic solution. 
   
   
       7 . The method of  claim 1 , wherein the resistor totally immersed in the electrolytic solution. 
   
   
       8 . 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 .   
   
   
       9 . The method of  claim 8 , 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.   
   
   
       10 . The method of  claim 8 , wherein said ending the iterating comprises satisfying R 2 ″ being within R t ±ΔR t . 
   
   
       11 . The method of  claim 10 , 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. 
   
   
       12 . The method of  claim 8 , wherein said ending the iterating comprises satisfying (R 2 ″−R t )(R t −R 2 ″)<0. 
   
   
       13 . The method of  claim 8 , wherein said testing comprises continuously testing the resistor during the nitridizing step.