Gallium nitride materials including thermally conductive regions

Abstract

The invention includes providing gallium nitride materials including thermally conductive regions and methods to form such materials. The gallium nitride materials may be used to form semiconductor devices. The thermally conductive regions may include heat spreading layers and heat sinks. Heat spreading layers distribute heat generated during device operation over relatively large areas to prevent excessive localized heating. Heat sinks typically are formed at either the backside or topside of the device and facilitate heat dissipation to the environment. It may be preferable for devices to include a heat spreading layer which is connected to a heat sink at the backside of the device. A variety of semiconductor devices may utilize features of the invention including devices on silicon substrates and devices which generate large amounts of heat such as power transistors.

1 . A semiconductor structure comprising: 
 a substrate;    a gallium nitride material device region having a crack level of less than 0.005 micron/micron 2  and formed over the substrate;    a heat spreading layer formed over the substrate, the heat spreading layer having a greater thermal conductivity than that of the gallium nitride material region and capable of conducting heat generated in the gallium nitride material device region; and    a heat sink.    
     
     
         2 . The semiconductor structure of  claim 1 , wherein the heat spreading layer is formed between the substrate and the gallium nitride material region.  
     
     
         3 . The semiconductor structure of  claim 1 , wherein the heat spreading layer comprises a compound of the group consisting of group III nitrides and silicon carbide.  
     
     
         4 . The semiconductor structure of  claim 1 , wherein the heat spreading layer comprises Al x Ga (1-x) N, wherein x>0.5.  
     
     
         5 . The semiconductor structure of  claim 1 , wherein the heat spreading layer has a thermal conductivity greater than or equal to about 1.7 W/m 2 ·K.  
     
     
         6 . The semiconductor structure of  claim 1 , wherein the heat spreading layer is in direct contact with the gallium nitride material region.  
     
     
         7 . The semiconductor structure of  claim 1 , wherein the heat sink extends from a surface of the semiconductor structure.  
     
     
         8 . The semiconductor structure of  claim 7 , wherein the heat sink extends from a backside of the semiconductor structure.  
     
     
         9 . The semiconductor structure of  claim 7 , wherein the heat sink extends from a topside of the semiconductor structure.  
     
     
         10 . The semiconductor structure of  claim 1 , wherein the heat sink extends to a heat generating region within the semiconductor structure.  
     
     
         11 . The semiconductor structure of  claim 1 , wherein the heat sink has a surface exposed to the environment.  
     
     
         12 . The semiconductor structure of  claim 1 , wherein the heat sink is in contact with the heat spreading layer.  
     
     
         13 . The semiconductor structure of  claim 1 , wherein the heat sink comprises a thermally conductive material deposited in a via.  
     
     
         14 . The semiconductor structure of  claim 1 , wherein the heat sink comprises a channel.  
     
     
         15 . The semiconductor structure of  claim 1 , wherein the heat sink comprises a layer.  
     
     
         16 . The semiconductor structure of  claim 1 , wherein the gallium nitride material region includes a plurality of gallium nitride material layers.  
     
     
         17 . The semiconductor structure of  claim 1 , wherein the semiconductor structure forms a transistor.  
     
     
         18 . The semiconductor structure of  claim 1 , wherein the gallium nitride material region is substantially free of cracks.  
     
     
         19 . The semiconductor structure of  claim 1 , wherein the gallium nitride material layer is monocrystalline.  
     
     
         20 . The semiconductor structure of  claim 1 , wherein the heat sink comprises a via.  
     
     
         21 . The semiconductor structure of  claim 1 , comprising a silicon substrate.  
     
     
         22 . The semiconductor structure of  claim 1 , further comprising an electrical contact formed on the semiconductor structure.  
     
     
         23 . A method of forming a semiconductor structure comprising: 
 forming a heat spreading layer over a substrate;    forming a device structure comprising a gallium nitride material region having a crack level of less than 0.005 micron/micron 2  over the substrate; and    forming a heat sink associated with the semiconductor structure,    wherein the heat spreading layer has a greater thermal conductivity than that of the gallium nitride material region and is capable of conducting heat generated by the device structure.    
     
     
         24 . The method of  claim 23 , wherein forming the heat sink comprising etching a via extending from the surface of the semiconductor structure.  
     
     
         25 . The method of  claim 23 , further comprising processing the semiconductor structure to form a transistor.  
     
     
         26 . The method of  claim 23 , further comprising processing the semiconductor structure to form a light emitting device.  
     
     
         27 . A method of operating a semiconductor device comprising: 
 operating a semiconductor device comprising a gallium nitride material region formed over a silicon substrate;    transmitting heat generated by the device through a heat spreading layer formed over the substrate; and    dissipating heat generated by the device through a heat sink associated with the semiconductor device.    
     
     
         28 . The method of  claim 27 , wherein the device is a transistor.  
     
     
         29 . The method of  claim 27 , wherein the heat sink comprises a channel.  
     
     
         30 . The method of  claim 27 , further comprising passing a cooling medium through the channel.