Browse Prior Art Database

All Plated Single Stud Cu or Au or Sn/Pb or Combination of Two to Produce Straight Walls

IP.com Disclosure Number: IPCOM000114833D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Doss, SK: AUTHOR [+3]

Abstract

Disclosed is a thick photoresist (40 microns) process which produces vertical stud walls when plated. This process eliminates the stud mushrooming produced using the conventional thin resist plating process.

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All Plated Single Stud Cu or Au or Sn/Pb or Combination of Two to
Produce Straight Walls

      Disclosed is a thick photoresist (40 microns) process which
produces vertical stud walls when plated.  This process eliminates
the stud mushrooming produced using the conventional thin resist
plating process.

      The current copper stud plating process produces thick studs 40
microns high with 20 microns of mushroomed copper around all four
sides of the plated stud.  In this process photoresist only 7 microns
thick is applied.  Consequently, only the first 7 microns of the
plated copper studs have straight walls.  The remaining 33 microns of
the stud are mushroomed.  The resulting stud structure is responsible
for the alumina overcoat voids that occur under the stud mushroom.
The straight wall studs produced by the proposed thick resist process
eliminate the alumina voids due to the absence of the shadowing
effect of the overhanging stud mushroom.

      Also the thick resist process eliminates one mask step by
plating an all gold or a combination of copper and gold, or copper
and tin/lead stud in a single mask step.

      Excellent adhesion properties for the straight-walled studs
using both a single material or a combination of materials have been
demonstrated.  These studs also showed no alumina recision around the
studs as a result of the overcoating and lapping process.