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Etchstop Material for Reactive Ion Etching

IP.com Disclosure Number: IPCOM000121713D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Goldblatt, RD: AUTHOR [+5]

Abstract

One of the processes for circuit definition for the fabrication of multilayer thin film structures is reactive ion etching of polyimide followed by metal backfilling. During reactive ion etching of polyimide, the etch rate is not always uniform. In order to improve the uniformity of etching and achieve consistent depth of trench, a suitable etchstop is required under the polyimide layer. An etchstop material for this purpose should be (1) resistant to plasma etching, (2) compatible with past and future polyimide layers, and (3) comparable to the polyimide in terms of thermal stability and solvent resistance. In the present disclosure, a new type of etchstop material, based on metal-phthalocycanines (MPTCs) is described along with the techniques to use this material to meet these requirements.

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Etchstop Material for Reactive Ion Etching

      One of the processes for circuit definition for the
fabrication of multilayer thin film structures is reactive ion
etching of polyimide followed by metal backfilling. During reactive
ion etching of polyimide, the etch rate is not always uniform.  In
order to improve the uniformity of etching and achieve consistent
depth of trench, a suitable etchstop is required under the polyimide
layer.  An etchstop material for this purpose should be (1) resistant
to plasma etching, (2) compatible with past and future polyimide
layers, and (3) comparable to the polyimide in terms of thermal
stability and solvent resistance.  In the present disclosure, a new
type of etchstop material, based on metal-phthalocycanines (MPTCs) is
described along with the techniques to use this material to meet
these requirements.

      MPTCs are very thermally stable and can be sublimed at Z 600~C
without decomposition.  They are also resistant to oxidation by
oxygen plasma.  Even when oxidized, MPTCs leave metal oxide films on
the surface which will reduce etch rates dramatically.  These
material are quite chemically stable as well.

      Because of the resistance of MPTCs to almost any solvent, it is
difficult to dissolve these materials. However, they can be dispersed
in a polymer solution by appropriate means, e.g., ball milling.  A
carefully prepared dispersion of MPTCs in polyamic acid solution can
be easily spun on a substrate.  Th...