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Broadly-Controllable Resistance Thin-Film Resistors for VLSI

IP.com Disclosure Number: IPCOM000104355D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Edelstein, DC: AUTHOR

Abstract

There is a need for thin film resistors on bipolar logic chips with sheet resistances (R[s]) above 1 K&omc./[_] as pulldowns and for bias networks for the current-switches in the logic gates. Ion implanted resistors suffer from large stray capacitances, and will not be used in the future. Doped polysilicon thin film resistors will be used, but it becomes difficult to control the properties to the tolerances needed when the required R[s] exceeds ~1 K&omc./[_]. For complementary bipolar circuits where PNP transistors are also used, there is a need for resistors with R[s] <= 10 K&omc./[_], which is not possible for short-dimensioned polysilicon resistors. To get sufficient resistances, the polysilicon resistors often take up significant area in the logic cells, impacting integration density.

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Broadly-Controllable Resistance Thin-Film Resistors for VLSI

      There is a need for thin film resistors on bipolar logic chips
with sheet resistances (R[s]) above 1 K&omc./[_]  as pulldowns and
for bias networks for the current-switches in the logic gates.  Ion
implanted resistors suffer from large stray capacitances, and will
not be used in the future.  Doped polysilicon thin film resistors
will be used, but it becomes difficult to control the properties to
the tolerances needed when the required R[s]  exceeds ~1
K&omc./[_].  For complementary bipolar circuits where PNP transistors
are also used, there is a need for resistors with R[s] <= 10
K&omc./[_], which is not possible for short-dimensioned polysilicon
resistors.  To get sufficient resistances, the polysilicon resistors
often take up significant area in the logic cells, impacting
integration density.  Thick film resistors made from polymer pastes
are already in use for packaging and printed circuit board
applications, but this technique is not compatible with VLSI
dimensions.

      Disclosed is a thin film resistor methodology which uses
polyimide thin films.  In the case of BPDA-PDA, films from a few 100
A  to over 1 &mu.m have been shown to have very reproducible
electrical characteristics.  The dielectric constant, conductivity,
and dielectric loss may all be tailored by varying the film thickness
and/or irradiating with uv light [*] or ion bombardment to increase
the DC conductivity, at leas...