Browse Prior Art Database

Deep Trench Vertical PNP for Complementary Bipolar/BiCMOS

IP.com Disclosure Number: IPCOM000109079D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 3 page(s) / 144K

Publishing Venue

IBM

Related People

Warnock, J: AUTHOR

Abstract

Disclosed is a process for a vertical pnp which can be integrated very easily into a standard high-performance npn process, using only one additional lithography masking level.

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This is the abbreviated version, containing approximately 52% of the total text.

Deep Trench Vertical PNP for Complementary Bipolar/BiCMOS

       Disclosed is a process for a vertical pnp which can be
integrated very easily into a standard high-performance npn process,
using only one additional lithography masking level.

      With the present state of the art, it is generally difficult to
integrate a high-performance vertical pnp transistor into a standard
high-performance bipolar (npn) process.  The number of additional
lithography mask steps can range from 4 to 8, new technology elements
may be required, and there is a large increase in the process
complexity associated with the addition of the vertical pnp.  Lateral
pnp's are more easily added to the npn process, but they offer lower
performance (1-3 GHz compared to 20-40 GHz for a vertical pnp), and
worse parasitic capacitances.

      Disclosed here is a process which circumvents many of the
problems involved with conventional vertical pnp integration.  The
process is new in that it features a self-aligned vertical pnp
fabricated at the bottom of a deep trench, instead of being
fabricated near the silicon surface as in conventional processes.
This removes the necessity of creating  patterned buried layers for
npn and pnp subcollectors, and allows the pnp to be formed with only
one additional lithography masking level in  almost any npn process.
However, the resulting pnp has a collector which is common to the
substrate, limiting somewhat its applications. The base and emitter
contacts use standard procedures adapted for the structure described
here.  A process flow is described in detail below.

      Using a standard deep trench etch process, trenches are etched
as shown in Fig....