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Polish Scrap Revival

IP.com Disclosure Number: IPCOM000109258D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 5 page(s) / 222K

Publishing Venue

IBM

Related People

Koblinger, O: AUTHOR

Abstract

During the backpolishing of an insulator with filled studs, its surface is partly damaged or the insulator is removed to such an extent that the minimum insulator thickness across the entire substrate is less than a nominal value. Misalignment and material problems are a bar to using an additional insulator and repeating the process sequence (fabricating the studs, filling them and surface polishing).

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Polish Scrap Revival

       During the backpolishing of an insulator with filled
studs, its surface is partly damaged or the insulator is removed to
such an extent that the minimum insulator thickness across the entire
substrate is less than a nominal value.  Misalignment and material
problems are a bar to using an additional insulator and repeating the
process sequence (fabricating the studs, filling them and surface
polishing).

      A process is described, by which the studs, after application
of an additional insulator, are bared such that the metal lines on
the insulator, partly adjacent to the studs, extend across a reduced
insulator thickness for only a few micrometers and that anywhere else
they are electromagnetically decoupled.  As a result, there is no
loss of electrical performance.

      The process is particularly suitable for repairing insulator
damage (grooves, scratches, tool marks, removal of too much material)
caused by polishing.

      As the electrical wiring extends across the entire substrate,
the insulator thickness must be maintained in full for
electromagnetic decoupling.

      In the described process, too small an insulator thickness
(say, 6 microns) is accepted at locations where no electrical
connection is made through the insulator, i.e., the studs.  Anywhere
else, the insulator is rebuilt in full or to a thickness exceeding
the minimum value (8 microns) by depositing an additional insulator.
The additional insulator, consisting of polyimide, increases the
insulator thickness and removes grooves, scratches, tool marks, and
the like from the insulator surface.

      In the next step, vias are produced in the additional
insulator, baring the studs, while leaving the electrically relevant
portion of the insulation unchanged.  For this purpose, a process,
such as RIE, is used which permits checking the depth of the vias in
the insulator, i.e., adjacent to the studs.
Example 1 (Fig. 1)

      On top of an insulator that is too thin (6 microns) (Fig. 1A),
an additional insulator of a thickness of 3 microns is deposited
(Fig. 1B), so that the virtual insulator thickness is about 1 micron
above the desired minimum value.  Then, photoresist is applied (Fig.
1C), exposed and developed (Fig. 1D).  The photo process is carried
out such that a resist angle of about 60 to 70o is obtained.  By
oxygen RIE, the additional insulat...