Power Semiconductor Devices with Barrier Layer to Reduce Substrate Up-Diffusion and Methods of Manufacture

Abstract

A method for controlling the thickness of an expitaxially grown semiconductor material includes providing a semiconductor substrate that is doped by dopants of a first type; forming a buffer layer atop the semiconductor substrate, the buffer layer being doped with dopants of a second type that has much less diffusivity relative to that of dopants of the first type and forming the expitaxially grown layer atop the buffer layer to a desired thickness. The buffer layer, which acts to counter an up-diffusion of the dopants of the first type from the substrate into the epitaxially grown layer, can be doped with arsenic or carbon or both arsenic and carbon. A semiconductor device includes the buffer layer to counter an up-diffusion of the dopants of the first type from the substrate into the epitaxially grown layer.

1 - 180 . (canceled) 
     
     
         181 . A method for controlling the thickness of an expitaxially grown semiconductor material, comprising:
 providing a semiconductor substrate that is doped by dopants of a first type;   forming a buffer layer atop said semiconductor substrate, the buffer layer being doped with dopants of a second type that has much less diffusivity relative to that of dopants of the first type; and   forming the expitaxially grown layer atop said buffer layer to a desired thickness.   
     
     
         182 . The method of  claim 181  wherein the buffer layer is doped with Arsenic. 
     
     
         183 . A method for controlling the thickness of an expitaxially grown semiconductor material, comprising:
 providing a semiconductor substrate that is doped by dopants of a first type;   forming a barrier layer atop said semiconductor substrate, the barrier layer having a composition including carbon; and   forming the expitaxially grown layer atop said buffer layer to a desired thickness,   wherein, the barrier layer acts to counter an up-diffusion of the dopants of the first type from the substrate into the epitaxially grown layer.   
     
     
         184 . The method of  claim 183  wherein the step of forming the barrier layer comprises growing a layer of silicon carbide. 
     
     
         185 . The method of  claim 183  wherein the step of forming the barrier layer comprises implanting carbon dopants into a surface of the semiconductor substrate. 
     
     
         186 . A method for controlling the thickness of an expitaxially grown semiconductor material, comprising:
 providing a semiconductor substrate that is doped by dopants of a first type;   forming the expitaxially grown layer atop said semiconductor substrate to a desired thickness;   forming a well region inside the epitaxially grown layer, the well region having dopants of a second type that have opposite conductivity to the dopants of the first type; and   forming a diffusion barrier layer at a junction between the expitaxially grown layer and the well region,   wherein, the barrier layer acts to counter diffusion dopants between the well region and the epitaxially grown layer.   
     
     
         187 . The method of  claim 186  wherein the step of forming a diffusion barrier layer comprises implanting carbon atoms through a window defining the well region. 
     
     
         188 - 235 . (canceled) 
     
     
         236 . The method of  claim 182  wherein the buffer layer is further doped with carbon. 
     
     
         237 . The method of  claim 181  wherein the buffer layer is doped with both arsenic and carbon. 
     
     
         238 . The method of  claim 181  wherein the buffer layer is formed directly on top of the semiconductor substrate. 
     
     
         239 . The method of  claim 181  wherein the epitaxially grown layer is formed directly on top of the buffer layer. 
     
     
         240 . A method for controlling the thickness of an expitaxially grown semiconductor material, comprising:
 providing a semiconductor substrate that is doped by dopants of a first type;   forming a barrier layer atop said semiconductor substrate, the barrier layer having a composition including carbon and arsenic; and   forming the expitaxially grown layer atop said barrier layer to a desired thickness,   wherein, the barrier layer acts to counter an up-diffusion of the dopants of the first type from the substrate into the epitaxially grown layer.   
     
     
         241 . The method of  claim 240  wherein the step of forming the barrier layer comprises growing a layer of silicon carbide. 
     
     
         242 . The method of  claim 240  wherein the step of forming the barrier layer comprises implanting carbon and arsenic dopants into a surface of the semiconductor substrate 
     
     
         243 . The method of  claim 240  wherein the barrier layer is formed directly on top of the semiconductor substrate. 
     
     
         244 . The method of  claim 240  wherein the epitaxially grown layer is formed directly on top of the barrier layer. 
     
     
         245 . A method for controlling the thickness of an expitaxially grown semiconductor material, comprising:
 providing a semiconductor substrate that is doped by dopants of a first type;   forming a first layer atop said semiconductor substrate, the first layer having a composition including carbon;   doping the first layer with arsenic to form a barrier layer; and   forming the expitaxially grown layer atop the barrier layer to a desired thickness,   wherein, the barrier layer acts to counter an up-diffusion of the dopants of the first type from the substrate into the epitaxially grown layer.   
     
     
         246 . The method of  claim 245  wherein the step of forming the first layer atop said semiconductor substrate comprises growing a layer of silicon carbide. 
     
     
         247 . The method of  claim 245  wherein the first layer is formed directly on top of the semiconductor substrate. 
     
     
         248 . The method of  claim 245  wherein the epitaxially grown layer is formed directly on top of the first layer. 
     
     
         249 . A method of making semiconductor device comprising:
 providing a semiconductor substrate that is doped by dopants of a first type;   forming a buffer layer atop said semiconductor substrate, the buffer layer being doped with dopants of a second type that has much less diffusivity relative to that of dopants of the first type;   forming a drift region of a first conductivity type and a desired thickness atop said buffer layer;   forming a well region having a second conductivity type opposite the first conductivity type and extending above the drift region;   forming an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material; and   forming source regions having the first conductivity type formed in the well region adjacent the active trench.   
     
     
         250 . The method of  claim 249  wherein the buffer layer is doped with arsenic. 
     
     
         251 . The method of  claim 249  wherein the buffer layer is further doped with carbon. 
     
     
         252 . The method of  claim 249  wherein the buffer layer is doped with both arsenic and carbon. 
     
     
         253 . The method of  claim 249  wherein the buffer layer is formed directly on top of the semiconductor substrate. 
     
     
         254 . The method of  claim 249  wherein the drift region is formed directly on top of the buffer layer. 
     
     
         255 . The method of  claim 249  further comprising forming a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region. 
     
     
         256 . A semiconductor device comprising:
 a semiconductor substrate that is doped by dopants of a first type;   a buffer layer formed atop said semiconductor substrate, the buffer layer being doped with dopants of a second type that has much less diffusivity relative to that of dopants of the first type;   a drift region of a first conductivity type and a desired thickness atop said buffer layer;   a well region extending above the drift region and having a second conductivity type opposite the first conductivity type;   an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material; and   source regions having the first conductivity type formed in the well region adjacent the active trench.   
     
     
         257 . The semiconductor device of  claim 256  wherein the buffer layer is doped with arsenic. 
     
     
         258 . The semiconductor device of  claim 256  wherein the buffer layer is further doped with carbon. 
     
     
         259 . The semiconductor device of  claim 256  wherein the buffer layer is doped with both arsenic and carbon. 
     
     
         260 . The semiconductor device of  claim 256  wherein the buffer layer is formed directly on top of the semiconductor substrate. 
     
     
         261 . The semiconductor device of  claim 256  wherein the drift region is formed directly on top of the buffer layer. 
     
     
         262 . The semiconductor device of  claim 256  further comprising a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region.