Double HBT base metal micro-bridge

Abstract

A heterojunction bipolar transistor (HBT) device structure is provided which facilitates the reduction of the base-collector capacitance and a method for making the same. The base-collector capacitance is decreased by fabricating a base micro-bridge connecting a base contact to a base mesa on the HBT. The base micro-bridge is oriented along about one of 001, 010, 00{overscore (1)}, and 0{overscore (1)}0 direction to a major flat of the wafer. The HBT device employs a phosphorous based collector material. During removal of the phosphorous based collector material, the base layer is undercut forming the micro-bridge, successfully removing the collector and sub-collector material below the bridge due to the orientation of the micro-bridge. The removal of collector and sub-collector material reduces the base-collector junction area, and therefore reduce the base-collector junction capacitance.

1 . A heterojunction bipolar transistor (HBT) device comprising: 
 an intrinsic HBT portion formed from a stacked layer having a subcollector region, a collector region disposed above the subcollector region, a base mesa disposed above the collector region and an emitter disposed above the base mesa;    a base contact portion having a base contact disposed away from the intrinsic HBT portion; and    a conductive bridge that connects the base mesa with the base contact, the conductive bridge oriented at about one of a 001, 010, 00{overscore (1)}, and 0{overscore (1)}0 direction with respect to a major flat of the wafer, the conductive bridge exposing convex edges along at least a portion of one side of the HBT device.    
   
   
       2 . The HBT device of  claim 1 , the collector region formed from a phosphorous based material.  
   
   
       3 . The HBT device of  claim 2 , the phosphorous based material being one of Indium Phosphide (InP) and Indium Gallium Phosphide (InGaP).  
   
   
       4 . The HBT device of  claim 2 , the base mesa formed from an arsenic based material.  
   
   
       5 . The HBT device of  claim 4 , the arsenic based material being one of Indium Gallium Arsenide (InGaAs), Indium Aluminum Arsenide (InAlAs), Indium Gallium Aluminum Arsenide (InAlGaAs), Gallium Arsenide Antimonide (GaAsSb) and Gallium Arsenide (GaAs).  
   
   
       6 . The HBT device of  claim 1 , the base contact portion formed from a stacked layer having a subcollector region, a collector region disposed above the subcollector region, a base mesa disposed above the collector region and the base contact disposed above the base mesa.  
   
   
       7 . The HBT device of  claim 1 , further comprising an opening below the conductive bridge between the collector regions of the base contact portion and the intrinsic HBT portion.  
   
   
       8 . The HBT device of  claim 1 , the opening extends between the subcollector regions of the base contact portion and the intrinsic HBT portion below the conductive bridge.  
   
   
       9 . An integrated circuit comprising the HBT device of  claim 1 .  
   
   
       10 . The HBT device of  claim 1 , the conductive bridge oriented at about one of 001, 010, 00{overscore (1)}, and 0{overscore (1)}0 direction with respect to a major flat of a wafer during fabrication of the HBT device.  
   
   
       11 . A heterojunction bipolar transistor (HBT) device fabricated on a semiconductor wafer having a major flat, the HBT device comprising: 
 an intrinsic HBT portion formed from a stacked layer having a subcollector region, a phosphorous based collector region disposed above the subcollector region, an arsenic based base mesa disposed above the phosphorous based collector region and an emitter disposed above the arsenic based base mesa;    a base contact portion having a base contact disposed away from the intrinsic HBT portion; and    a connecting bridge that electrical connects the base mesa with the base contact, the connecting bridge oriented at about one of 001, 010, 00{overscore (1)}, and 0{overscore (1)}0 direction with respect to the major flat of the wafer during fabrication.    
   
   
       12 . The HBT device of  claim 11 , the intrinsic HBT portion, the base contact portion and the connecting bridge aligned at about one of 001, 010, 00{overscore (1)}, and 0{overscore (1)}0 direction with respect to the major flat of the wafer during fabrication.  
   
   
       13 . The HBT device of  claim 11 , the connecting bridge having at least one side with a convex geometric surface, such that the connecting bridge is undercut during at least one of a collector etch and a subcollector etch.  
   
   
       14 . The HBT device of  claim 11 , the phosphorous based material being one of Indium Phosphide (InP) and Indium Gallium Phosphide (InGaP).  
   
   
       15 . The HBT device of  claim 14 , the arsenic based material being one of Indium Gallium Arsenide (InGaAs), Indium Aluminum Arsenide (InAlAs), Indium Gallium Aluminum Arsenide (InAlGaAs), Gallium Arsenide Antimonide (GaAsSb) and Gallium Arsenide (GaAs).  
   
   
       16 . The HBT device of  claim 15 , the subcollector formed from one of a phosphorous based material or an arsenic based material.  
   
   
       17 . The HBT device of  claim 11 , the base contact portion formed from a stacked layer having a subcollector region, a collector region disposed above the subcollector region, a base mesa disposed above the collector region and the base contact disposed above the base mesa and an opening below the connecting bridge between the collector regions of the base contact portion and the intrinsic HBT portion, the opening formed during at least one of a collector etch and a subcollector etch that undercuts the connecting bridge.  
   
   
       18 . The HBT device of  claim 11 , the intrinsic HBT portion having a cantilever base contact structure.  
   
   
       19 - 27 . (canceled)