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Reconditioning of Titanium Nitride Surfaces for Good Resist Adhesion

IP.com Disclosure Number: IPCOM000103103D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 68K

Publishing Venue

IBM

Related People

Dorleans, FF: AUTHOR [+3]

Abstract

Thin titanium nitride films (300 to 600 A) have been used as anti-reflective layers to improve dimensional control when printing resist images on metal surfaces. Typically, a titanium nitride (TiN) layer is sputter deposited in situ on top of the metal surface. If the metal is subsequently to be patterned by reactive ion etching (RIE), the resist mask must first be hardened to withstand the high temperatures encountered in the RIE process. If rework is required after the hardening step, the resist must be stripped by exposure to an oxygen plasma, i.e., by ashing.

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Reconditioning of Titanium Nitride Surfaces for Good Resist Adhesion

      Thin titanium nitride films (300 to 600 A) have been used as
anti-reflective layers to improve dimensional control when printing
resist images on metal surfaces.  Typically, a titanium nitride (TiN)
layer is sputter deposited in situ on top of the metal surface.  If
the metal is subsequently to be patterned by reactive ion etching
(RIE), the resist mask must first be hardened to withstand the high
temperatures encountered in the RIE process.  If rework is required
after the hardening step, the resist must be stripped by exposure to
an oxygen plasma, i.e., by ashing.

      Our experiments have shown that the adhesion of the new layer
of photoresist to the TiN is severely degraded, demonstrated by the
following experiment.  Wafers with fresh TiN surfaces were oxygen
ashed under standard conditions for 30 minutes (the time typically
used for complete resist removal); additional TiN wafers were not
ashed.  A positive photoresist composed of a diazoquinone sensitizer,
a novolac resin, and a suitable casting solvent was then spun onto
all wafers and baked at 85~C for 30 minutes; the resist thickness
after the bake was 1.4 microns.  The wafers were exposed using a
projection printer and a mask with long lines that are prone to
lifting if adhesion is unsatisfactory.  After 8 minutes of immersion
in a sodium metasilicate-based developer the ashed surfaces showed
severe adhesion failure and the...