Browse Prior Art Database

Integrated Capacitors and Resistors for Double Polysilicon Bipolar Transistors

IP.com Disclosure Number: IPCOM000112167D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Bronner, GB: AUTHOR [+2]

Abstract

Modern bipolar processes need both on chip capacitors and on chip resistors for a number of circuits. Adding these can add significant complexity and area. Disclosed here is a structure that allows the natural integration of capacitors and resistors into a double polysilicon bipolar transistor. The emitter polysilicon layer is used as one plate of the capacitor. Another polysilicon layer is deposited and used as both the other plate of the capacitor and for polysilicon resistors.

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Integrated Capacitors and Resistors for Double Polysilicon Bipolar
Transistors

      Modern bipolar processes need both on chip capacitors and on
chip resistors for a number of circuits.  Adding these can add
significant complexity and area.  Disclosed here is a structure that
allows the natural integration of capacitors and resistors into a
double polysilicon bipolar transistor.  The emitter polysilicon layer
is used as one plate of the capacitor.  Another polysilicon layer is
deposited and used as both the other plate of the capacitor and for
polysilicon resistors.

      In a conventional bipolar transistor process two layers of
polysilicon are used.  The first layer is doped p+ and used to
contact the base region of the transistor.  The second layer is doped
n+ and forms the emitter of the transistor.  In this invention a
third layer of polysilicon is added which acts as both a thin film
resistor or one plate for the on-chip capacitor.  Capacitors are
formed between two layers of polysilicon, similar to the manner used
in stacked capacitor DRAM structures.  One capacitor plate is the n+
polysilicon used for the emitter contact.  After this is defined, a
thin insulator is formed and a second layer of doped polysilicon is
deposited, patterned and etched.  This third polysilicon layer is
used as both a capacitor plate and elsewhere as polysilicon
resistors.  The capacitor dielectric acts as etch stop allowing the
third layer of polysilicon to be removed...