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Blanket CVD Tungsten Deposition Process for Filling Vias with an Undercut

IP.com Disclosure Number: IPCOM000120698D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 39K

Publishing Venue

IBM

Related People

Bhattacharya, S: AUTHOR [+3]

Abstract

Disclosed is a process for the prevention of delamination of blanket CVD tungsten films in vias with an undercut and sputtered Ti/W or TiW alloy adhesion layers during the via-fill by a blanket CVD-W process.

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Blanket CVD Tungsten Deposition Process for Filling Vias with an
Undercut

      Disclosed is a process for the prevention of delamination of
blanket CVD tungsten films in vias with an undercut and sputtered
Ti/W or TiW alloy adhesion layers during the via-fill by a blanket
CVD-W process.

      CVD-W films exhibit poor adhesion to an oxide substrate.  To
improve adhesion, various adhesion promoting layers, such as
sputtered Ti/W, TiW alloy, Ti/TiN and in-situ deposited WSix, are
used.  Since sputtered films are not conformal, the undercut regions
on the bottom of a via will have very little, if any, of the
sputtered adhesion layer.  CVD tungsten films, when deposited by H2
reduction of WF6 on such structures with Ti/W bilayer or with any of
the above-mentioned sputtered layers, start delaminating at the
undercut region during the earlier stages of W deposition.  This
delamination occurs because the WF6 attacks the Ti in the sputtered
film.  If the tungsten deposition is continued further, tensile
stresses in the tungsten film cause it to curl away from the surface
of the vias.  These vias when viewed from the top show mound-like
structures.

      The tungsten film delamination and subsequent mound-like
structure formation was eliminated when a thin initial CVD tungsten
layer (1500-2000Ao was deposited by SiH4 or by a mixture of SiH4 and
H2 reduction of WF6.  The vias were subsequently filled by normal H2
reduction of WF6 in order to achieve a good confor...