Sic semiconductor device having pn junction interface and method for manufacturing the sic semiconductor device

Abstract

A method for manufacturing a semiconductor device capable of reducing an ON resistance. In the present invention, a drift layer is formed on a substrate. An ion implanted layer is formed in a surface of the drift layer. A surplus carbon region is formed in the drift layer. The drift layer is heated. In a case where the surplus carbon region is formed, the surplus carbon region is formed in a region deeper than an interface between the ion implanted layer and the drift layer. In a case where the drift layer is heated, impurity ions of the ion implanted layer are activated to form an activation layer, and interstitial carbon atoms are dispersed toward the activation layer.

1 . A method for manufacturing a semiconductor device, comprising:
 a drift layer formation step of forming a drift layer of a first conductivity type on a silicon carbide semiconductor substrate;   an ion implanted layer formation step of implanting impurity ions being impurities of a second conductivity type in a surface of said drift layer to form an ion implanted layer in which said impurity ions are implanted;   a surplus carbon region formation step of implanting interstitial carbon inducing ions that induce carbon between lattices in said drift layer to form a surplus carbon region having surplus interstitial carbon atoms; and   a heating step of heating said drift layer after said ion implanted layer formation step and after said surplus carbon region formation step, wherein   said surplus carbon region formation step implants said interstitial carbon inducing ions in a region deeper than an interface between said ion implanted layer and said drift layer to form said surplus carbon region, and   said heating step heats said drift layer to activate said impurity ions implanted in said ion implanted layer in order to form an activation layer of the second conductivity type while said heating step heats said drift layer to disperse said interstitial carbon atoms toward said activation layer.   
     
     
         2 . The method for manufacturing a semiconductor device according to  claim 1 , wherein said surplus carbon region formation step implants said interstitial carbon inducing ions on the deeper region side within 500 nm from the interface between said ion implanted layer and said drift layer to form said surplus carbon region. 
     
     
         3 . The method for manufacturing a semiconductor device according to  claim 1 , wherein said surplus carbon region formation step implants said interstitial carbon inducing ions from the surface of said drift layer. 
     
     
         4 . The method for manufacturing a semiconductor device according to  claim 1 , further comprising a substrate removal step of removing said silicon carbide semiconductor substrate before said surplus carbon region formation step,
 wherein said surplus carbon region formation step implants said interstitial carbon inducing ions from a back surface of said drift layer.   
     
     
         5 . The method for manufacturing a semiconductor device according to  claim 1 , wherein said surplus carbon region formation step implants said interstitial carbon inducing ions being carbon to form said surplus carbon region. 
     
     
         6 . The method for manufacturing a semiconductor device according to  claim 1 , wherein said surplus carbon region formation step implants said interstitial carbon inducing ions having an implantation surface density of 1×10 13  cm −2  to 1×10 16  cm −2  and implantation energy of 10 keV to 10 MeV to form said surplus carbon region. 
     
     
         7 . The method for manufacturing a semiconductor device according to  claim 1 , wherein said surplus carbon region formation step implants said interstitial carbon inducing ions having an implantation surface density higher than a density of carrier traps in the interface between said ion implanted layer and said drift layer to form said surplus carbon region. 
     
     
         8 . The method for manufacturing a semiconductor device according to  claim 1 , wherein said ion implanted layer formation step implants said impurity ions being aluminum, boron, phosphorus, or nitrogen to form said ion implanted layer. 
     
     
         9 . The method for manufacturing a semiconductor device according to  claim 1 , wherein said heating step heats said drift layer at a temperature in a range of 1400° C. to 1800° C. 
     
     
         10 . A method for manufacturing a semiconductor device, comprising:
 a drift layer formation step of forming a drift layer of a first conductivity type on a silicon carbide semiconductor substrate;   an ion implanted layer formation step of implanting impurity ions being impurities of a second conductivity type in a surface of said drift layer to form an ion implanted layer in which said impurity ions are implanted;   a substrate removal step of removing said silicon carbide semiconductor substrate;   a protective film formation step of forming a protective film at least on a surface of said ion implanted layer after said substrate removal step;   a thermal oxide film formation step of forming a thermal oxide film on the surface of said drift layer and a back surface of said drift layer after said protective film formation step;   a film removal step of removing said protective film and said thermal oxide film; and   a heating step of heating said drift layer after said ion implanted layer formation step, wherein   said thermal oxide film formation step forms said thermal oxide film to cause interstitial carbon atoms to be ejected into said drift layer, and   said heating step heats said drift layer to activate said impurity ions implanted in said ion implanted layer in order to form an activation layer of the second conductivity type.   
     
     
         11 . The method for manufacturing a semiconductor device according to  claim 10 , wherein said ion implanted layer formation step implants said impurity ions being aluminum, boron, phosphorus, or nitrogen to form said ion implanted layer. 
     
     
         12 . The method for manufacturing a semiconductor device according to  claim 10 , wherein said heating step heats said drift layer at a temperature in a range of 1400° C. to 1800° C. 
     
     
         13 . The method for manufacturing a semiconductor device according to  claim 10 , wherein said thermal oxide film formation step forms said thermal oxide film at a temperature in a range of 1000° C. to 1500° C.