Browse Prior Art Database

Double Poly Self Aligned NPN Bipolar Transistor Structure

IP.com Disclosure Number: IPCOM000122648D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 91K

Publishing Venue

IBM

Related People

Barmak, K: AUTHOR [+4]

Abstract

Disclosed is a process to fabricate a double-poly self-aligned NPN bipolar transistor structure. This process eliminates the dummy emitter stack required in the NTX structure (1). It also eliminates the extrinsic-base implant required in the ETX process (2), which can cause dislocations in the silicon-germanium active base. This process is compatible with either ion-implanted or epitaxial-base structures and is described below for an epitaxial base, lightly-doped emitter structure.

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Double Poly Self Aligned NPN Bipolar Transistor Structure

      Disclosed is a process to fabricate a double-poly
self-aligned NPN bipolar transistor structure.  This process
eliminates the dummy emitter stack required in the NTX structure (1).
It also eliminates the extrinsic-base implant required in the ETX
process (2), which can cause dislocations in the silicon-germanium
active base.  This process is compatible with either ion-implanted or
epitaxial-base structures and is described below for an epitaxial
base, lightly-doped emitter structure.

      After growth of the collector epitaxial layer, the isolation
and reach-through are formed.  Then the p+ epitaxial base is
deposited, followed by a thin n-type epitaxial emitter layer.  Next,
in-situ phosphorus-doped amorphous silicon is deposited by the
dopant.  A TiN/TiSi2 stack can also be deposited at this point for
devices with offset emitter contact.  An oxide/nitride stack is then
deposited by PECVD (Fig. A).

      The emitter and non-device areas are then lithographically
defined, and the nitride and oxide are etched.  The next step is a
reactive ion etch that etches N++ poly selectively to N silicon.
This etch is a chlorine-based etch that has a selectivity >15:1.
This etch stops in the N epitaxial layer (Fig. B).  By controlling
the degree of overetch, the etch-bias can be used to produce emitters
with dimensions smaller than the lithographic critical dimension.
Because of the selectivity of the etch, there is no penet...