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Chemical/Mechanical Polishing Process for Polyimide Planarization

IP.com Disclosure Number: IPCOM000113921D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Chow, M: AUTHOR [+4]

Abstract

Polyimide is useful as a low dielectric insulating material for VLSI interconnection. Current methods to planarize the polyimide on top of the topographic surfaces are achieved by a dry etchback with a layer of sacrificial planarizing material such as resist, polystyrene, epoxy, etc. However, the degree of planarization by using these techniques is always limited by many factors, such as film coating uniformity, dry etch process and pattern density.

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Chemical/Mechanical Polishing Process for Polyimide Planarization

      Polyimide is useful as a low dielectric insulating material for
VLSI interconnection.  Current methods to planarize the polyimide on
top of the topographic surfaces are achieved by a dry etchback with a
layer of sacrificial planarizing material such as resist,
polystyrene, epoxy, etc.  However, the degree of planarization by
using these techniques is always limited by many factors, such as
film coating uniformity, dry etch process and pattern density.

      A chemical/mechanical polish method proposed here was found not
only capable of planarizing the polyimide, but also polishing
tungsten with a similar rate.  Therefore, it is possible with this
approach, to simultaneously polish polyimide and tungsten studs
enhancing the cost effectiveness of the process, as it avoids two
separate steps of polishing W and polyimide.

      It was demonstrated that the optimum polishing result can be
obtained by using a slurry with DI water, etchant and alumina
abrasive in conjunction with a Suba 500 pad at 5 psi.  Removal rates
of polyimide and tungsten are about 220nm/min.  Different variables,
such as pad softness, polish pressure and slurry mixtures were
examined to improve the removal rate and to reduce the surface
scratching.  By reducing the pressure from 15 to 5 psi the scratching
level was significantly reduced.  If the scratching persists another
layer of polyimide is spun on top of alread...