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Elimination of Conical Studs by Silylation Process

IP.com Disclosure Number: IPCOM000101961D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Jacobs, SL: AUTHOR [+4]

Abstract

Conical stud formations have been observed on wafers processed with plasma nitride film as a barrier layer. These mis-shapen studs may be eliminated by use of a silylation process.

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Elimination of Conical Studs by Silylation Process

       Conical stud formations have been observed on wafers
processed with plasma nitride film as a barrier layer. These
mis-shapen studs may be eliminated by use of a silylation process.

      Conical-shaped studs (Fig. 1) are observed to occur during
wafer processing when plasma nitride film (SiXN4) is employed as a
lift-off barrier.  Plasma nitride film is a preferred barrier layer
over resin glass which, while not evidencing conical studs, has been
found to contribute to increased cycle time and rework cost.  The
proper stud shape 12 is shown in Fig. 2 where resin glass is employed
as the barrier layer.  The conical studs are believed to result from
outgassing of solvents retained in the underlay material during metal
evaporation.  By means of the process described below, plasma nitride
film is used together with standard lift-off procedures, to eliminate
conical studs. Fig. 3 is a sketch of an SEM of an isolated stud after
the 10-step process as follows:
1)   Coat polyimide underlay on a wafer, using a double-coat
     technique, followed by a post application bake.
2)   A coating of about 1.3 mm positive resist exposed to
     1.3 mm low UV is followed by a soft bake for 5 minutes.
3)   Expose with a mask.
4)   Develop.
5)   Silylation for 6 minutes.
6)   RIE in oxygen.
7)   Bake.
8)   Preclean BHF dip for 10 seconds.
9)   Stud metal evaporation process followed by lift-off
  ...