Hetero-bipolar transistor and method for producing the same

Abstract

A semiconductor device provided with a substrate made of material except for semiconductors and having thermal conductivity greater than that of the semiconductor material. The semiconductor device provides, on the support, a metal layer, a primary mesa, and electrodes formed on the primary mesa. The metal layer, which is in contact with the primary mesa, may be made of at least one of tungsten (W), molybdenum (Mo), and tantalum (Ta) with a thickness of the 10 to 60 nm.

1 . A semiconductor device, comprising:
 a metal layer provided on a support;   a semiconductor stack provided on the metal layer; and   electrodes provided on the semiconductor stack,   wherein the metal layer is made of one of tungsten (W), molybdenum (Mo), and tantalum (Ta) with a thickness of 10 to 60 nm.   
     
     
         2 . The semiconductor device of  claim 1 ,
 wherein the metal layer has a thickness of 10 to 50 nm.   
     
     
         3 . The semiconductor device of  claim 1 ,
 wherein the support has thermal conductivity greater than those of semiconductor layers constituting the semiconductor stack.   
     
     
         4 . The semiconductor device of  claim 3 ,
 wherein the support has the thermal conductivity of 100 to 3000 W/m/K.   
     
     
         5 . The semiconductor device of  claim 4 ,
 wherein the support is made of one of aluminum nitride (AlN), silicon (Si), silicon carbide (SiC), and diamond (C).   
     
     
         6 . The semiconductor device of  claim 3 ,
 wherein the support has a thickness of 20 to 200 μm.   
     
     
         7 . The semiconductor device of  claim 1 ,
 wherein the metal layer covers at least a portion of a side of the semiconductor stack.   
     
     
         8 . The semiconductor device of  claim 7 ,
 wherein the semiconductor stack includes a sub-collector layer, a collector layer provided on the sub-collector layer, a base layer provided on the collector layer, an emitter layer provided on the base layer, and a emitter contact layer provided on the emitter layer, and   wherein the metal layer covers a side of the sub-collector layer.   
     
     
         9 . The semiconductor device of  claim 1 , wherein the semiconductor stack includes at least two emitter layers in a top of the semiconductor stack, the at least two emitter layers being isolated from each other. 
     
     
         10 . A method of producing a semiconductor device, comprising steps of:
 growing a plurality of semiconductor layers to from a semiconductor stack on a semiconductor substrate;   forming a first adhesive layer on the semiconductor stack;   bonding a temporary support made of non-semiconductor material to the first adhesive layer;   removing the semiconductor substrate from the semiconductor stack to expose a surface of the semiconductor stack;   forming a second adhesive layer on the exposed surface of the semiconductor stack;   bonding a support to the second adhesive layer; and   removing the temporary support from the semiconductor stack,   wherein the support has thermal conductivity greater than thermal conductivities of semiconductor layers constituting the semiconductor stack.   
     
     
         11 . The method of  claims 10 ,
 wherein at least one of the step of bonding the temporary substrate to the first adhesive layer and the step of bonding the support to the second adhesive layer is carried out by atomic diffusion bonding (ADB).   
     
     
         12 . The method of  claim 11 ,
 wherein the step of the ADB is carried out continuous to the step of forming the first adhesive layer or the step of forming the second adhesive layer without exposing the first adhesive layer or the second adhesive layer to an atmosphere.   
     
     
         13 . The method of  claim 10 ,
 wherein at least one of the step of forming the first adhesive layer and the step of forming the second adhesive layer includes a step of forming a metal layer made of at least one of tungsten (W), molybdenum (Mo), and tantalum (Ta) by sputtering.   
     
     
         14 . The method of  claim 10 ,
 further including a step of etching a portion of a lowermost semiconductor layer in the semiconductor stack to form a step in the semiconductor stack after removing the semiconductor substrate but before the step of forming the second adhesive layer, and   wherein the step of forming the second adhesive layer includes a step of covering the step in the semiconductor stack by the second adhesive layer.   
     
     
         15 . The method of  claim 10 ,
 wherein the step of forming the first adhesive layer includes a step of covering a whole side surface of the semiconductor stack by a metal layer made of at least one of tungsten (W), molybdenum (Mo), and tantalum (Ta).   
     
     
         16 . The method of  claim 10 ,
 further including a step of removing a periphery of the semiconductor stack before the step of forming the first adhesive layer,   wherein the step of forming the first adhesive layer includes a step of forming the first adhesive layer so as to cover a top of the semiconductor stack and a side of the semiconductor stack that is exposed by the removal of the peripheral of the semiconductor stack.   
     
     
         17 . The method of  claim 16 ,
 further including a step of, after the step of removing the temporary support, removing the first adhesive layer covering the top and the side of the semiconductor stack.   
     
     
         18 . The method of  claim 17 ,
 further including steps of, after the step of removing the first adhesive layer,   sequentially etching a portion of the semiconductor stack to form an emitter mesa, a portion of the semiconductor stack to form a base mesa, and a portion of the semiconductor stack to form a collector mesa, and   forming electrodes on the semiconductor stack.