Fabrication of a heterojunction bipolar transistor with integrated MIM capacitor

Abstract

In the present invention, a semiconductor device is formed which includes an MIM capacitor located on the upper surface of a heterostructure from which the emitter, base and collector sections of a nearby HBT are defined. In this way the capacitor and HBT share a substantially common structure, with the base and emitter electrodes of the HBT fashioned from the same metal layers as the upper and lower capacitor plates, respectively. Furthermore, as the insulator region of the capacitor is formed prior to definition of the HBT structure, the dielectric material used can be deposited by means of a plasma enhanced process, without damaging the HBT structure.

1 . A method of fabricating a semiconductor device, comprising the steps of: 
 forming a lower plate and an insulator section of a metal-insulator-metal (MIM) capacitor on an upper surface of a heterostructure located on a semi-insulating substrate, the material of the lower plate and underlying heterostructure being common to an electrode and substructure of an emitter section of a heterojunction bipolar transistor (HBT) subsequently defined in the process on another section of the device;    forming a base electrode of the HBT and an upper plate of the MIM capacitor from a commonly deposited metal layer; and,    defining base and collector sections of the HBT in layers of the heterostructure located beneath the emitter section.    
     
     
         2 . A method according to  claim 1 , in which the step of forming the insulator section of the MIM capacitor comprises the sub-step of depositing a dielectric material by a plasma-enhanced deposition process.  
     
     
         3 . A method according to  claim 1 , further comprising the step of etching down to the semi-insulating substrate a section of the heterostructure between the location of the HBT and the location of the capacitor.  
     
     
         4 . A method according to claims  1 , further comprising the step of forming a resisitor on another section of the device, wherein a contact for the resistor is formed from a commonly deposited metal layer from which a section of the HBT or MIM capacitor is formed.  
     
     
         5 . A method according to claims  1 , further comprising the step of depositing a passivation layer over at least a section of the device by means of a non-plasma-enhanced deposition process.  
     
     
         6 . A method for forming a device, comprising: 
 forming a lower plate and an insulator section of a metal-insulator-metal (MIM) capacitor on an upper surface of a heterostructure located on a semi-insulating substrate, the material of the lower plate and underlying heterostructure being common to an electrode and substructure of an emitter section of a heterojunction bipolar transistor (HBT) subsequently defined in the process on another section of the device;    forming a base electrode of the HBT and an upper plate of the MIM capacitor from a commonly deposited metal layer;    defining base and collector sections of the HBT in layers of the heterostructure located beneath the emitter section; and    forming a resistor having a contact formed from a commonly deposited metal layer from which a section of at least one of the HBT and the MIM capacitors are formed.    
     
     
         7 . The method of  claim 6 , further comprising: 
 etching a section of the hetereostructure between the area containing the HBT and the area containing the MIM capacitor, said section etched to the semi-insulating substrate.    
     
     
         8 . The method of  claim 6 , further comprising: 
 depositing a passivation layer over at least a section of the device using a non-plasma enhanced deposition process.    
     
     
         9 . The method of  claim 6 , wherein the HBT is electrically connected to a plate of the MIM capacitor.  
     
     
         10 . The method of  claim 6 , wherein the semi-insulating substrate comprises a layer of InP.  
     
     
         11 . The method of  claim 6 , wherein the hetereostructure comprises layers of epitaxially grown InP/InGaAs materials.