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Browse Prior Art Database

Method to Make Precision Resistors And Capacitors in a Conventional BICMOS Process

IP.com Disclosure Number: IPCOM000121139D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

El-Kareh, B: AUTHOR [+2]

Abstract

Precision resistors and capacitors are made by depositing and patterning thin films used in a conventional bipolar metal oxide silicon (BICMOS) process technology. The structures are defined on thick oxide field regions without added complexity to the conventional BICMOS process. The resulting passive devices have sufficient precision to allow their use in analog BICMOS circuits.

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This is the abbreviated version, containing approximately 71% of the total text.

Method to Make Precision Resistors And Capacitors in a Conventional
BICMOS Process

      Precision resistors and capacitors are made by depositing
and patterning thin films used in a conventional bipolar metal oxide
silicon (BICMOS) process technology.  The structures are defined on
thick oxide field regions without added complexity to the
conventional BICMOS process.  The resulting passive devices have
sufficient precision to allow their use in analog BICMOS circuits.

      Referring to Fig. 1, metal oxide silicon field-effect
transistor (MOSFET) region 10 and capacitor or resistor (C/R) device
region 12/14 are shown after field oxide 16 and gate dielectric 18
are formed on silicon substrate 20.  Heavily doped thin polysilicon
layer 22, oxide layer 24 and nitride layer 26 are deposited and
devices are defined by standard lithography and etching techniques.
During this step, layers 22, 24, and 26 are also removed from bipolar
regions (not shown).

      A mask normally used to define emitter openings over base
regions in bipolar devices (not shown) is also used to selectively
remove layers 26 and 24 over regions of polysilicon layer 22, which
are to be contacted later, as shown in Fig. 2.

      Fig. 3 shows that MOSFETs and passive devices are completed at
the same stage of processing.  This also applies to bipolar
structures which are not shown.  Second highly doped polysilicon
layer 28 is deposited and makes contact with polysilicon layer 22 in
regi...