Schottky rectifier

Abstract

A semiconductor rectifier includes a semiconductor substrate having a first type of conductivity. A first layer, which is formed on the substrate, has the first type of conductivity and is more lightly doped than the substrate. A second layer having a second type of conductivity is formed on the substrate and a metal layer is disposed over the second layer. The second layer is lightly doped so that a Schottky contact is formed between the metal layer and the second layer. A first electrode is formed over the metal layer and a second electrode is formed on a backside of the substrate.

What is claimed is: 
     
         1 . A method of fabricating a rectifier comprising:
 providing a semiconductor body of a first conductivity type;   forming a first layer on the substrate, said first layer having the first type of conductivity and being more lightly doped than the substrate;   forming a second layer over the substrate, said second layer having a second type of conductivity, said second type of conductivity being opposite to said first type of conductivity;   forming a metal layer over the second layer, wherein the second layer is lightly doped so that a Schottky contact is formed between the metal layer and the second layer; and   forming a first electrode over the metal layer and a second electrode on a backside of the substrate.   
     
     
         2 . The method of  claim 1 , wherein forming the second layer includes implanting or diffusing a dopant of the second type into the first layer. 
     
     
         3 . The method of  claim 1 , further comprising:
 forming at least one trench in the first layer;   lining a bottom and sidewalls of the at least one trench with a dielectric layer; and   filling the at least one trench with a conducting material.   
     
     
         4 . The method of  claim 3 , wherein forming at least one trench in the first layer is performed before forming the metal layer. 
     
     
         5 . The method of  claim 1 , wherein forming the second layer includes forming the second layer to achieve a desired tradeoff between on-state performance and switching performance. 
     
     
         6 . The method of  claim 1 , wherein the second layer has a doping concentration less than that needed to form an Ohmic contact between the metal layer and the second layer. 
     
     
         7 . The method of  claim 1 , wherein the second layer is formed in the first layer. 
     
     
         8 . The method of  claim 1 , wherein forming a second layer comprises forming the second layer by implantation or diffusion into the first layer. 
     
     
         9 . The method of  claim 1  wherein the second layer is formed on the first layer. 
     
     
         10 . The method of  claim 3  wherein the second layer is formed in the first layer and is adjacent to at least one side of the trench. 
     
     
         11 . The method of  claim 10  wherein the second layer is adjacent to both sides of the trench. 
     
     
         12 . The method of  claim 3  wherein the at least one trench comprises a plurality of trenches formed in the first layer and the second layer is formed in the first layer between select pairs of trenches. 
     
     
         13 . The method of  claim 3  wherein the second layer is formed in the first layer between each pair of trenches. 
     
     
         14 . The method of  claim 1  wherein the silicide layer is formed at an interface between the metal layer and second layer. 
     
     
         15 . The method of  claim 12  wherein the second layer is formed between only some pairs of adjacent trenches. 
     
     
         16 . The method of  claim 15  wherein a TMBS is present in parts of the device that do not include the second layer. 
     
     
         17 . The method of  claim 5  wherein the plurality of trenches are present only in parts of the rectifier having conventional TMBS cells, and wherein the second layer is present as a planar structure in a remaining active area of the device. 
     
     
         18 . The method of  claim 1 , wherein the metal layer is disposed directly over the second layer.