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Isolation Field Implant Process Technology for CMOS

IP.com Disclosure Number: IPCOM000107183D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 3 page(s) / 75K

Publishing Venue

IBM

Related People

Kotecha, H: AUTHOR [+3]

Abstract

The typical CMOS process technology uses two separate photo levels to define the isolation levels and field implant areas. As the two photo levels must be aligned to one another, overlay alignment tolerances must be included in the circuit design layout. These tolerances necessarily increase the size of the circuit.

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Isolation Field Implant Process Technology for CMOS

       The typical CMOS process technology uses two separate
photo levels to define the isolation levels and field implant areas.
As the two photo levels must be aligned to one another, overlay
alignment tolerances must be included in the circuit design layout.
These tolerances necessarily increase the size of the circuit.

      This article describes a process to combine the two separate
photo levels in a single photo exposure step and thereby increase the
density of the circuit.  Following pad nitride deposition, a photo
level comprised of a multi-level resist layer is formed.  The
multi-level resist layer as depicted in Fig. 1, is preferably formed
by using two reticles to expose the photoresist layer.  The
reticle-to-reticle alignment is less than 0.025 mm, resulting in an
essentially self-aligned structure.  As shown in Fig. 1, the areas
where the N-well regions reside and the active areas of the P type
regions are not exposed. The P type isolation areas receive a full
exposure dose and the isolation areas of the N-well layers receive a
partial dose.  When developed, the full-dose regions are completely
developed out, while the partial-dose regions are left with a partial
height of resist.

      Next, the pad nitride in the P type isolation areas is etched,
stopping on the underlying pad oxide layer.  The field implant is
performed to introduce boron into the isolation areas of the P type
regions....