Browse Prior Art Database

Self-Aligned Polysilicon Emitter Process

IP.com Disclosure Number: IPCOM000099356D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Bracchitta, JA: AUTHOR [+4]

Abstract

This process for making a self-aligned emitter for a bipolar transistor is incorporated into a standard complementary metal oxide silicon (CMOS) process. Benefits of the process include minimizing masking steps, providing a planar surface for subsequent processing, and minimizing the contact area between the polysilicon contact plate and emitter junction.

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Self-Aligned Polysilicon Emitter Process

       This process for making a self-aligned emitter for a
bipolar transistor is incorporated into a standard complementary
metal oxide silicon (CMOS) process.  Benefits of the process include
minimizing masking steps, providing a planar surface for subsequent
processing, and minimizing the contact area between the polysilicon
contact plate and emitter junction.

      Referring to Fig. 1, standard polysilicon gate CMOS processing
is used through junction formation and then a layer 10 of reflowable
glass is applied over silicon nitride layer 12.  Other features and
materials shown are layer 14 titanium silicide over polysilicon shape
16 having oxide sidewall insulation 18, silicided metal 20 over
junctions 22 in an N-well 24.  Photomasking and anisotropic etching
are used to open an area over polysilicon shape 16 where an emitter
is to be formed.

      To achieve the cross section shown in Fig. 2, polysilicon 16
and silicide 14 are selectively removed. Next, base and emitter
implants are performed to form base junction 32.  Then, oxide
sidewall spacers 26 are formed by conformal deposition, followed by
anisotropic etching. Conformal deposition of doped polysilicon 28,
followed by planarization, forms emitter plate 28.  The doping
material is out-diffused from polysilicon 28 to form emitter junction
30.  Emitter plate 28 contacts emitter junction 30 in a very small
area.  Standard processing is resumed by deposit...