Method for fabricating a semiconductor device

Abstract

A method for fabricating a semiconductor device includes forming a first semiconductor layer on a front side of the semiconductor substrate. Additional semiconductor layers may be formed on a font side of the first semiconductor layer. The substrate is subsequently removed. In some embodiments, one or more additional semiconductor layers may be formed on the back side of the first semiconductor layer after the semiconductor substrate has been removed. Additionally, in some embodiments, a portion of the first semiconductor layer is removed along with the semiconductor substrate. In such embodiments, the first semiconductor layer is subsequently etched to a known thickness. Source regions and device electrodes may be then be formed.

1 . A method for fabricating a semiconductor device, the method comprising: 
 forming a semiconductor substrate;    forming a first semiconductor layer on a front side of the semiconductor substrate; and    removing the semiconductor substrate after the formation of the first semiconductor layer.    
   
   
       2 . The method of  claim 1 , wherein the semiconductor device is an insulated-gate bipolar transistor.  
   
   
       3 . The method of  claim 2 , wherein the semiconductor device is a DMOS insulated-gate bipolar transistor.  
   
   
       4 . The method of  claim 2 , wherein the semiconductor device is a UMOS insulated-gate bipolar transistor.  
   
   
       5 . The method of  claim 1 , wherein the semiconductor substrate is formed from silicon-carbide.  
   
   
       6 . The method of  claim 5 , wherein the first semiconductor layer is formed on a silicon side of the semiconductor substrate.  
   
   
       7 . The method of  claim 5 , wherein the first semiconductor layer is formed on a carbon side of the semiconductor substrate.  
   
   
       8 . The method of  claim 1 , wherein the first semiconductor layer is epitaxially grown on the front side of the semiconductor substrate.  
   
   
       9 . The method of  claim 1 , wherein the first semiconductor layer is a drift semiconductor layer having a first concentration of first type impurities that is less than a second concentration of first type impurities of the semiconductor substrate.  
   
   
       10 . The method of  claim 1 , wherein the first semiconductor layer has a thickness of about one micrometer.  
   
   
       11 . The method of  claim 1 , wherein the semiconductor substrate is removed using a chemical mechanical polishing process.  
   
   
       12 . The method of  claim 1 , further comprising forming a second semiconductor layer on a front side of the first semiconductor layer, wherein the first semiconductor layer has a first concentration of first type impurities and the second semiconductor layer has a second concentration of second type impurities.  
   
   
       13 . The method of  claim 1 , further comprising forming a second semiconductor layer on a back side of the first semiconductor layer after the semiconductor substrate has been removed.  
   
   
       14 . The method of  claim 1 , wherein the first semiconductor layer forms a bottom semiconductor layer of the semiconductor device after the semiconductor substrate has been removed.  
   
   
       15 . The method of  claim 1 , wherein the first semiconductor layer forms a top semiconductor layer of the semiconductor device after the semiconductor substrate has been removed.  
   
   
       16 . The method of  claim 1 , wherein removing the semiconductor substrate comprises removing a portion of the first semiconductor layer.  
   
   
       17 . The method of  claim 16 , wherein a second semiconductor layer is formed on a front side of the first semiconductor layer prior to the removing step.  
   
   
       18 . The method of  claim 16 , further comprising determining a thickness of the first semiconductor layer subsequent to the removing step.  
   
   
       19 . The method of  claim 18 , wherein determining a thickness of the first semiconductor layer comprises determining a thickness of the first semiconductor layer using a trench length measure technique.  
   
   
       20 . The method of  claim 18 , wherein determining a thickness of the first semiconductor layer comprises determining a thickness of the first semiconductor layer based on a sheet resistivity of the first semiconductor layer.  
   
   
       21 . The method of  claim 18 , wherein determining a thickness of the first semiconductor layer comprises extrapolating an conductivity of the first semiconductor layer to a value of about zero.  
   
   
       22 . The method of  claim 18 , further comprising etching the first semiconductor layer to a known thickness based on the determined thickness.  
   
   
       23 . A method for fabricating an insulated-gate bipolar transistor, the method comprising: 
 forming a semiconductor substrate;    forming a drift semiconductor layer on a front side of the semiconductor substrate;    forming a drain layer on a front side of the drift semiconductor layer; and    removing the semiconductor substrate.    
   
   
       24 . The method of  claim 23 , wherein forming a semiconductor substrate comprises forming a silicon-carbide semiconductor substrate.  
   
   
       25 . The method of  claim 24 , wherein forming a drift semiconductor layer comprises forming a drift semiconductor layer on a silicon side of the semiconductor substrate.  
   
   
       25 . The method of  claim 24 , wherein forming a drift semiconductor layer comprises forming a drift semiconductor layer on a carbon side of the semiconductor substrate.  
   
   
       26 . The method of  claim 23 , wherein the drift semiconductor layer is doped with first type impurities and the drain semiconductor layer is doped with second type impurities.  
   
   
       27 . The method of  claim 23 , further comprising forming a first source region and a second source region in the drift semiconductor layer subsequent to the removing step.  
   
   
       28 . The method of  claim 27 , further comprising forming a first source contact on a front side of the first source region, a second source contact on a front side of the second source region, a gate oxide on a back side of the first semiconductor layer, and a gate contact on a front side of the gate oxide.  
   
   
       29 . The method of  claim 23 , further comprising forming a drain contact on a front side of the drain semiconductor layer.  
   
   
       30 . The method of  claim 23 , further comprising forming an additional semiconductor layer on a back side of the drift semiconductor layer subsequent to the removing step.  
   
   
       31 . A method for fabricating an insulated-gate bipolar transistor, the method comprising: 
 forming a semiconductor substrate;    forming a first semiconductor layer on a front side of the semiconductor substrate;    forming a second semiconductor layer on a front side of the first semiconductor layer; and    removing the semiconductor substrate and a portion of the first semiconductor layer.    
   
   
       32 . The method of  claim 31 , further comprising forming a third semiconductor layer on a front side of the second semiconductor layer.  
   
   
       33 . The method of  claim 31 , further comprising determining a thickness of the first semiconductor layer subsequent to the removing step.  
   
   
       34 . The method of  claim 33 , wherein determining a thickness of the first semiconductor layer comprises determining a thickness of the first semiconductor layer using a trench length measure technique.  
   
   
       35 . The method of  claim 33 , wherein determining a thickness of the first semiconductor layer comprises determining a thickness of the first semiconductor layer based on a sheet resistivity of the first semiconductor layer.  
   
   
       36 . The method of  claim 33 , wherein determining a thickness of the first semiconductor layer comprises extrapolating a conductivity of the first semiconductor layer to a value of about zero.  
   
   
       37 . A method for fabricating a semiconductor device on a semiconductor substrate, the method comprising: 
 forming a first semiconductor layer on a front side of the semiconductor substrate;    forming a second semiconductor layer on a front side of the first semiconductor layer;    removing the semiconductor substrate; and    processing the semiconductor device after the removing step to form an insulated-gate bipolar transistor.    
   
   
       38 . The method of  claim 37 , wherein the first and the second semiconductor layers are formed from a silicon-carbide material.