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Two Step Emitter Poly & Silicide Process for Advanced Bipolar Transistor

IP.com Disclosure Number: IPCOM000122066D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 59K

Publishing Venue

IBM

Related People

Mei, SN: AUTHOR [+2]

Abstract

For very small emitter openings, the deposition of a relatively thick (1800 A~ used by conventional process) polysilicon layer can narrow or totally fill the opening, causing non-uniform doping when the polysilicon is implanted and emitter drive-in anneal done out of it.

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Two Step Emitter Poly & Silicide Process for Advanced Bipolar Transistor

      For very small emitter openings, the deposition of a relatively
thick (1800 A~ used by conventional process) polysilicon layer can
narrow or totally fill the opening, causing non-uniform doping when
the polysilicon is implanted and emitter drive-in anneal done out of
it.

      A process to minimize the so-called narrow-emitter-effect has
been developed.  This novel process describes a thin (300 to 600 A~)
polysilicon deposition and an As I/I (10 -30 KeV, 8E15/cm2) are
followed by a thicker (1500-1200 A~) polysilicon and As I/I (30 KeV,
2E16/cm2) to form polysilicon emitter for advanced self-aligned
double poly bipolar transistor.

      In the conventional process the narrow-emitter-effect can be
observed through the ECS punch-through voltage measurement as shown
in Table 1.  In the case of standard ion-implanted polysilicon
emitter contacts, the ECS punch-through voltages are 4.2V and 5.1V
for emitter sizes of 1.5mm x 1.5mm and 0.5mm x 1.0mm, respectively,
giving WBVECS of 0.9V.  The results suggests that shallower emitter
junctions are formed on transistors with narrow emitter widths.  This
narrow-emitter-effect can be attributed to the fact that the vertical
surfaces of the emitter polysilicon on the edges of the emitter are
not doped by the implantation.  Since the diffusivity of arsenic in
polysilicon is much higher than in single crystalline silicon, the
arsenic from the i...