Radiation imagery chemistry: process – composition – or product th – Stripping process or element
Reexamination Certificate
1998-11-24
2001-07-17
Gulakowski, Randy (Department: 1746)
Radiation imagery chemistry: process, composition, or product th
Stripping process or element
C134S042000, C510S174000, C510S176000, C216S095000
Reexamination Certificate
active
06261735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to a composition and method for removal of probing ink and negative photoresist polymer residue from a substrate, such as a silicon wafer. Mixtures including anisole, organic sulfonic acids, and aliphatic hydrocarbons containing 9 to 13 carbon atoms are used to strip hard to remove materials such as probing ink and cross-linked negative photoresist polymer residue. The composition and method achieve improved removal of these materials while significantly reducing metal corrosion.
2. Brief Description of the Prior Art
In the manufacture of semiconductor microcircuits it is necessary to mark defective microchips during the final electrical testing with an epoxy or polyurethane based ink on the finished silicon wafer to distinguish bad dies from the good dies. After the electrical test is done, sometimes it may be deemed necessary to clean the ink off the silicon wafer because of a wrong electrical test program, because bonding pads were misprobed, or for other reasons. This allows the silicon wafer be retested or reprobed with the necessary corrections. Conventional solvents such as alcohols, ketones and esters, or more aggressive heterocyclic solvents such as n-methyl pyrrolidone do not remove hard baked and cured epoxy type probing ink even at elevated temperatures and long process times.
Highly acidic or alkaline solutions and strong oxidizing agents on the other hand, such as fuming nitric acid, sulfuric acid/hydrogen peroxide, and tetramethyl ammonium hydroxide or other alkaline solutions may be effective in removing the ink, but they create corrosion difficulties and stain or destroy the sensitive alloys such as Al/Cu/Si in bonding pad areas of the wafer.
It is therefore highly desirable to provide an environmentally friendly ink removing process and a corresponding composition which in a reasonably short process time cleans only the cured probing ink without leaving any residue, and that is also safe to use on sensitive metal layers.
The present invention is also useful for removal of negative photoresist. Prior art resist removers are described in U.S. Pat. Nos. 4,165,294 and 4,992,108. These patents also describe organic sulfonic acids suitable for use in the present invention, and to that extent their disclosures are incorporated herein by reference.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a composition and method for removing probing ink and cross-linked negative photoresist polymer residue which is low in toxicity and nonhazardous to the user and the environment.
Another object of this invention is to provide a composition that works more quickly than conventional commercially available strippers or solvent for probing ink and negative photoresist removal.
A further object of this invention is to provide a composition for probing ink and negative photoresist removal which is not corrosive to sensitive alloys and does not adversely effect the sensitive bonding pad areas of a semiconductor wafer.
Briefly, the preferred embodiment of the present invention utilizes a mixture of anisole (methoxybenzene, C
6
H
5
—O—CH
3
), an alkylarylsulfonic acid, and aliphatic hydrocarbons containing 9 to 13 carbon atoms to remove probing ink and negative photoresist from a substrate with reduced metal corrosion.
DESCRIPTION OF THE PREFERRED EMBODIMENT
This invention provides a composition and method for removing probing ink and cross-linked negative photoresist polymer residue from semiconductor wafers, while reducing corrosive action of the composition on sensitive metal layers. The stripping composition is comprised of from 60% to 85% by weight anisole and from 15% to 40% by weight of an alkylarylsulfonic acid. The composition is preferably free of toxic materials such as phenols and chlorinated hydrocarbons.
An aliphatic hydrocarbon may be added to the composition, with a preferred composition comprising from 25% to 60% by weight anisole, 20% to 60% by weight alkylaryl sulfonic acid having 12-20 carbons, and 20% to 40% by weight aliphatic hydrocarbons containing from 9 to 13 carbon atoms. While the composition with just anisole and the sulfonic acid is the most effective for ink and photoresist removal, the addition of the hydrocarbon component reduces volatility of the composition and results in a longer bath life while still providing effective removal.
REFERENCES:
patent: 4165294 (1979-08-01), Vander Mey
patent: 4992108 (1991-02-01), Ward et al.
patent: 5612303 (1997-03-01), Takayanagi et al.
patent: 1-114846 (1989-05-01), None
Gulakowski Randy
Jaffer David H.
Olsen Allan
Pillsbury & Winthrop LLP
Silicon Valley Chemlabs, Inc.
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