Browse Prior Art Database

Low Thermal Budget Emitter Process for High Performance Bipolar Devices

IP.com Disclosure Number: IPCOM000120215D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Blouse, J: AUTHOR [+8]

Abstract

Disclosed is a low thermal budget emitter formation process for high performance bipolar devices. The method proposed uses chemical vapor deposition (CVD) to deposit a thin (& 500 o) layer of in-situ doped (ISD) amorphous silicon, followed by in-situ densification and in-situ deposition of a thicker layer (Z 1500 o ) of ISD polysilicon to form a composite emitter structure. The structure is then annealed at temperatures & 600~C for several hours, followed by a rapid thermal anneal (RTA) at 1050~C for 20 seconds, to completely crystallize the amorphous layer and activate the dopants.

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Low Thermal Budget Emitter Process for High Performance Bipolar Devices

      Disclosed is a low thermal budget emitter formation
process for high performance bipolar devices.  The method proposed
uses chemical vapor deposition (CVD) to deposit a thin (& 500 o)
layer of in-situ doped (ISD) amorphous silicon, followed by in-situ
densification and in-situ deposition of a thicker layer (Z 1500 o )
of ISD polysilicon to form a composite emitter structure.  The
structure is then annealed at temperatures & 600~C for several hours,
followed by a rapid thermal anneal (RTA) at 1050~C for 20 seconds, to
completely crystallize the amorphous layer and activate the dopants.

      In general, crystallized amorphous silicon is found to have
larger grain sizes than annealed CVD polysilicon, and hence higher
conductivity.  Complete crystallization is possible if a single
crystalline surface is used as the seed layer.  Since dopants are
incorporated during the deposition, a conventional high temperature
drive-in is not required for junction formation.  Crystallized
amorphous silicon has high carrier mobilities and stable material
properties which make it suitable for use as an emitter in bipolar
transistors.  The low temperature of both the deposition and solid
phase crystallization (& 600~C) makes this process compatible with
thin base homojunction and heterojunction devices.  The resulting
structure is shown in the figure.

      An example of such an emitter formation...