Process for coating a substrate with metallic layer

Details Process for coating a substrate with metallic layer Process for coating a substrate with metallic layer

1994-06-28

2001-05-22

Nguyen, Nam (Department: 1753)

Stock material or miscellaneous articles

All metal or with adjacent metals

Composite; i.e., plural, adjacent, spatially distinct metal...

C428S674000, C428S626000, C204S192140

Reexamination Certificate

active

06235411

ABSTRACT:

DESCRIPTION
1. Technical Field
The present invention is concerned with coating polyimides of the diaryl dianhydride type with a metallic layer and particularly is concerned with providing a layer of chromium followed by a layer of copper on the substrate.
The present invention finds special applicability in the fabrication of metallized integrated circuit substrates.
2. Background Art
Polyimides are commonly employed in the electronics industry.
For instance, in the packaging of semiconductor chips, polyimide films are often used as flexible substrates or coated onto rigid substrates such as ceramics. In such instances, a pattern of metallic conductors is formed on the polyimide. Often, the conductors are at least two layers of metal being a layer of chromium followed by a layer of copper. In many instances, an additional outer layer of chromium is employed.
After deposition, the metal layers are imaged into circuits by means of photolithographic operations. Depending on the use of the circuit, the polyimide may or may not be imaged either before or after the formation of the circuit. The adhesion between the metal layers and polyimide is crucial to circuit reliability. In particular, problems have occurred resulting in lifting up of the copper line from the underlying polyimide substrate rendering the carrier unsuitable for its intended purpose.
Accordingly, the importance of improving the adhesion between such substrates and the metallic layers cannot be overemphasized.
SUMMARY OF INVENTION
The present invention is concerned with improving the adhesion of chromium layer followed by a copper layer on a polyimide substrate.
In particular, according to the present invention, the adhesion between the polyimide layer and chromium-copper layers is enhanced by depositing a layer of about 5 to about 200 angstroms of chromium by sputtering at a rate of about 4 angstroms/second or less, followed by depositing a layer of copper. It has been found pursuant to the present invention that the improved adhesion is achieved for substrates of polyimides obtained from diaryldianhydride and a diamine, by the control of the deposition rate of the chromium.


REFERENCES:
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patent: 4702963 (1987-10-01), Phillips et al.
patent: 4720401 (1988-01-01), Ho et al.
patent: 4863808 (1989-09-01), Sallo
patent: 4886681 (1989-12-01), Clabes et al.
patent: 4915494 (1990-04-01), Shipley et al.
patent: 4956197 (1990-09-01), Babu et al.
patent: 5055358 (1991-10-01), Livingston et al.
Skeist “Handbook of Adhesives” 2nd Ed. (1977) Van Nostrand, pp 597-599, 612-613.

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