Base for a NPN bipolar transistor

Abstract

An improved base for a NPN bipolar transistor. The base region is formed with Boron and Indium dopants for improved beta early voltage product and reduced base resistance.

1 . A method of forming a base region in an NPN transistor, the method comprising: 
 diffusing Boron dopants through a select region of working surface of a substrate; and    implanting Indium dopants through the select region of the working surface of the substrate.    
     
     
         2 . The method of  claim 1 , wherein a peak concentration of Indium dopants are formed deeper from the working surface of the substrate than a peak concentration of the Boron dopants.  
     
     
         3 . The method of  claim 1 , wherein the Boron dopants have a gaussian profile with a peak concentration approximate the working surface of the substrate.  
     
     
         4 . The method of  claim 1 , wherein the location of the Indium dopants is approximately determined by implant.  
     
     
         5 . The method of  claim 1  wherein the indium dopants have approximately a Gaussian profile with the peak concentration below the working surface.  
     
     
         6 . The method of  claim 1 , wherein the ratio of Boron dopants to Indium dopants is selected to achieve a desired beta temperature coefficient.  
     
     
         7 . A method of forming a base region in an NPN transistor, the method comprising: 
 epitaxially growing the base region with Boron and Indium dopant profiles.    
     
     
         8 . The method of  claim 7 , wherein a peak concentration of Boron dopants adjacent a base-emitter junction is grown greater than a peak concentration of Indium dopants and a peak concentration of Indium dopants at a base-collector junction is grown greater than the concentration of Boron dopants.  
     
     
         9 . A method of forming a NPN transistor, the method comprising: 
 forming a collector in a substrate with N conductivity type dopants, the substrate having a working surface;    forming a base region in the collector adjacent the working surface of the substrate with P conductivity type dopants, wherein the P type conductivity type dopants are both Boron and Indium dopants; and    forming an emitter region in the base region adjacent the working surface of the substrate with the N conductivity type dopants.    
     
     
         10 . The method of  claim 9 , wherein forming the Boron and Indium dopants in the base region further comprises: 
 diffusing the Boron dopants; and    implanting the Indium dopants.    
     
     
         11 . The method of  claim 9 , wherein at least one of the Boron and Indium dopants formed in the base region further comprises: 
 diffusing the dopants.    
     
     
         12 . The method of  claim 9 , wherein at least one of the Boron and Indium dopants formed in the base region further comprises: 
 implanting the dopants.    
     
     
         13 . The method of  claim 9 , wherein the forming the Boron and Indium dopants in the base further comprises: 
 epitaxially growing the base and incorporating the Boron and Indium dopants in the base during the epitaxial growth.    
     
     
         14 . The method of  claim 9 , wherein the concentration of Boron dopants adjacent a base-emitter junction is greater than the concentration of Indium dopants to set base resistance of the NPN transistor with the Boron dopants.  
     
     
         15 . The method of  claim 9 , wherein the concentration of Indium dopants at a base-collector junction is greater than the concentration of Boron dopants to achieve relatively high early voltage that is set by the Indium dopants.  
     
     
         16 . The method of  claim 9 , wherein a peak concentration of Indium dopants are formed deeper from the working surface of the substrate than a peak concentration of the Boron dopants.  
     
     
         17 . The method of  claim 9 , wherein the Boron dopants have a gaussian profile with a peak concentration approximate the working surface of the substrate.  
     
     
         18 . The method of  claim 9 , wherein the location of the Indium dopants is approximately determined by implant.  
     
     
         19 . The method of  claim 9  wherein the Indium dopants have approximately a Gaussian profile with the peak concentration below the working surface.  
     
     
         20 . The method of  claim 9 , wherein the collector N conductivity type is made with a low density of dopants and the emitter N type conductivity type is made with a high density of dopants.  
     
     
         21 . The method of  claim 20 , further comprising: 
 forming a collector contact a select distance from the emitter adjacent the working surface of the substrate, the collector contact having N conductivity type with a high density of dopants.    
     
     
         22 . A method of forming a base region in a NPN transistor, the method comprising: 
 introducing a select amount of Indium dopants to the base region; and    introducing a select amount of Boron dopants to the base region, wherein the ratio of the select amount of the Indium dopants to the select amount of Boron dopants is selected to determine the beta temperature coefficient of the NPN transistor.    
     
     
         23 . The method of  claim 22 , wherein introducing the Boron and Indium dopants in the base region further comprises: 
 diffusing the Boron dopants; and    implanting the Indium dopants.    
     
     
         24 . The method of  claim 22 , wherein at least one method of introducing the Boron and Indium dopants in the base region further comprises: 
 diffusing the dopants.    
     
     
         25 . The method of  claim 22 , wherein at least one method of introducing the Boron and Indium dopants in the base region further comprises: 
 implanting the dopants.    
     
     
         26 . The method of  claim 22 , wherein the introducing of the Boron and Indium dopants in the base further comprises: 
 epitaxially growing the base and incorporating the Boron and Indium dopants in the base during the epitaxial growth.