JPS61243447A - Formation of pattern - Google Patents

Abstract

PURPOSE:To enhance adhesion of a fine pattern, such as LSI, by oxidizing a copper surface in advance and then forming a polyimide pattern. CONSTITUTION:The copper surface is oxidized in an atmosphere of air or oxygen, at >=100 deg.C. For example, copper is deposited by sputtering on a ceramic substrate heated at about 120 deg.C, the copper surface is coated with a polyimide precursor, and further, with a positive type photoresist layer, exposed through a mask, developed, and etched in succession, and finally, heated to form a polyimide pattern. The oxidation treatment of the copper surface permits adhesion between the polyimide film and the copper surface to be remarkably strengthened.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for forming a polyimide pattern with excellent adhesiveness on a copper surface, and is particularly applicable to circuit modules for LSI towers, hybrid ICs, etc. The present invention relates to a method that can be used to significantly improve the adhesion between copper, which is a wiring layer, and polyimide, which is an insulating layer.

[Conventional technology]

Conventionally, when patterning polyimide on various substrates, methods for improving wettability and adhesion with the substrate include pre-treating the substrate with a silane coupling agent, or using polyimide and/or polyimide precursors. A method of blending a silane coupling agent into a composition is known.

However, when the substrate is copper, sufficient adhesion cannot be obtained by using these silane coupling agents. For example, in the case of a fine line pattern with a width of about 2I1 X lines, leakage of the etching solution and developer to the interface was observed, and it could not be said that the pattern had sufficient adhesion under severe handling conditions. As a result, the Pressure Cunker Test (PCT)
), or when used in a soldering bath or dry heat above 300°C, the interface between the copper surface and the polyimide layer would peel, making it impractical in terms of reliability. .

[Problem that the invention seeks to solve]

The present invention relates to a method that eliminates the above-mentioned drawbacks and can form a pattern having good adhesion even in a 2-line width using an extremely easy process.

[Means for solving problems]

That is, the present invention relates to a method for forming a polyimide pattern on a copper surface, which is characterized in that the copper surface is subjected to an oxidation treatment in advance.

The copper surface referred to in the present invention refers to copper foil used in printed wiring boards, etc., a substrate with a copper surface obtained by electroless copper plating, electrolytic plating, or sputtering, or a copper surface commonly called a copper plate. These are copper plates etc. obtained by rolling.

Examples of the polyimide pattern in the present invention include polyimide patterns obtained from polyimide precursors and polyimide patterns obtained from solvent-soluble polyimide, and examples of pattern forming methods include photolithography, screen printing, and the like.

As a polyimide precursor, the general formula (A) [in the formula, X is a (2+n)-valent carbocyclic group or a heterocyclic group, Y is a (2
+m) a valent carbocyclic group or a group containing number 1 or more, W is a group that can react with the carbonyl group of -C0OR to form a ring when ROH is removed by heat treatment, n is 1 or 2, m is 0.1 or 2, and C0OR and Z are in an ortho position or an override position with respect to each other. ] Examples include polymers having repeating units represented by the following.

Typically, tetracarboxylic acid anhydrides such as pyromellitic anhydride, benzophenonetetracarboxylic anhydride, biphenyltetracarboxylic anhydride, hydrates and 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone are used. Representative examples include polyimide precursors produced by condensation of diamines such as , 4,4'-diaminodiphenylmethane, and methyl, ethyl, propyl, and esters thereof, but are not limited thereto.

A typical example of this polyimide precursor is Bailarin■
(manufactured by DuPont) and PIQ■ (manufactured by Hitachi Chemical). Another example is polyimide silicon PIX @ (manufactured by Hitachi Chemical), which is partially copolymerized with a silicon compound. These are non-photosensitive polyimide precursors, and a predetermined pattern can be formed by applying them to a substrate, converting part or all of them into polyimide by heating, and etching the polyimide using a photoresist.

Further, there is a photosensitive polyimide precursor in which R in the general formula (A) is a group having a carbon-carbon double bond and is bonded to the main chain through a chemical bond.

The photosensitive groups introduced into the polyimide precursor through chemical bonds are typically groups with carbon-carbon double bonds that can be trimerized or polymerized by light, such as vinyl groups, allyl groups, and acrylic groups. , a group having a methacrylic group, a cinnamyl group, a maleimide group, and the like.

Forms of chemical bonds include ester bonds, amide bonds,
There are ionic bonds, etc., and methods for introducing them are described in U.S. Pat.
The method disclosed in Japanese Patent No. 145794 can be applied. As a photosensitive polyimide precursor obtained by such a method, an example of the former is Selectilanx HTR.
-2■ (manufactured by Merck & Co., Ltd.), and a representative example of the latter is Photonice UR-3100■ (manufactured by Toshi).

Photosensitive compounds that are mixed for the purpose of imparting or, if necessary, improving photosensitivity to a polyimide precursor and/or a photosensitive polyimide precursor in which a photosensitive group is introduced into the polyimide precursor through a chemical bond, include: Examples of the sensitizer include, but are not limited to, the following.

Benzophenone, benzophenones such as 4,4'-bis(dimethylamino)benzophenone, benzoin ether or anthraquinone or thioxanthone derivative, 1
-Phenyl-1,2-propanedione-2-(o-ethoxycarbonyl)-oxime and other oximes, 2,6-bis-(4'-diethylaminobenzal)-cyclohexanone and other bisazides I! , mercapto compounds such as 1-phenyl-5-mercaptotetrazole, and biimidazoles such as 2,4.5-triphenylimidazolyl dimer.

In addition, the following are good examples of photosensitive monomers, but the invention is not limited thereto.

Trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, pentaerythritol diacrylate, pentaerythritol dimethacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, 3-mercaptopropionic acid, thioglycol Mercapto compounds such as acids, maleimides such as phenylsulfonylmaleimide, isocyanates such as ethyl isocyanate methacrylate.

It is preferable to add 0.1 to 50 parts by weight of these additives to 100 parts by weight of the photosensitive polyimide precursor.

As a solvent, N-methylpyrrolidone, γ-butyrolactone, N,N'-dimethylacetamide, N,N'-
Dimethylformamide is a good example.

A typical method for coating the substrate is by using a spinner.

In the case of a photosensitive polyimide precursor, unlike a non-photosensitive polyimide precursor, there is an advantage that a pattern can be directly formed without using a photoresist.

A photosensitive polyimide precursor is applied onto a substrate having a copper surface using a spinner, and the solvent is removed by drying. Next, ultraviolet rays are irradiated through a photomask, followed by development and rinsing to remove unexposed areas and form a predetermined pattern. By thermosetting this pattern and converting it into polyimide, a polyimide pattern with excellent heat resistance, electrical properties, etc. can be formed.

Examples of the polyimide used in the present invention include bismaleimide polyimide (typical examples include Kelimide (manufactured by Mitsui Petrochemical) and BT resin (Mitsubishi Gas Chemical)), polyimide having an acetylene group at the end (THERMID),
(manufactured by National Cornstarch)], solvent-soluble polyimide (XU-218 (manufactured by Ciba Geigy)), and the like.

The polyimide used in the present invention is a photosensitive polyimide in which R in the polyimide precursor represented by the general formula [A] is a group having a carbon-carbon double bond, and is directly bonded to the polymer main chain through an ester bond. Particularly preferred.

When R in the general formula [A] is hydrogen and a photosensitive polyimide precursor with ionic bonding mixed with dimethylaminoethyl methacrylate is used, it is preferable to provide a titanium or chromium layer on the copper surface by sputtering or the like. By providing the titanium layer and the chromium layer, it is possible to prevent the generation of scum due to the formation of a complex between copper and the polyimide precursor in the unexposed area.

As the oxidation treatment method used in the present invention, the copper surface is
Examples include a method of heating the copper surface to 0° C. or higher and then oxidizing the copper surface in air or an oxygen atmosphere, or a method of physically depositing CuO or CutO by sputtering. A particularly preferred method is a wet method in which CuO is formed using an aqueous solution of NaC10□ or H20□.

In the method of oxidizing a copper surface according to the present invention, when conducting conductors in the upper and lower layers through via holes, it is preferable to remove oxides on the copper surface. The preferred method for removal is immersion in an aqueous ammonium persulfate solution and so-called quick etching.
Examples of methods include firing in a furnace in a reducing atmosphere such as hydrogen or sputtering in an argon or reducing gas atmosphere.

Next, the present invention and its effects will be explained using Examples, but the present invention is not limited thereto.

Example 1 50x50x0.5mm ceramic substrate (96.0%
Copper was deposited using a sputtering device while heating the alumina to 120°C. This substrate was cooled under an oxygen atmosphere. Bilalin 0PI-2555 was coated onto this ceramic substrate having a copper oxide surface using a spin coater.
(manufactured by DuPont) and subsequently heated at 140° C. for 30 minutes in a clean open to obtain a 5- coating film. A positive photoresist AZ-1350J (
2.5.10.15.2 after drying
AZ using a mask with lines & spaces of 0ts
-1350J was exposed. Next, developer MP-312 (
AZ-1350J and Baylarin P at Sibley Co., Ltd.
I-2555 was developed and etched. After washing with water, it was heated at 400°C for 30 minutes to perform polyimidation.

The substrate with the obtained pattern was placed in boiling water at 100° C., and after boiling for 2 hours, the adhesiveness was measured by a tape peel test. Microscopic observation of the pattern after the tape peeling test showed good adhesion with no problems such as peeling off of the etched areas.

Comparative Example 1 Bilarin PI-255 was deposited on a substrate with a copper surface in the same manner as in Example 1 except that the substrate temperature during sputtering was room temperature and the extraction atmosphere was changed to air.
5 patterns were formed. This pattern was heated to 400℃, 3
When heated for 0 minutes, part of the pattern peeled off and curled.

Comparative Example 2 After applying an aminosilane coupling agent (VM-651 manufactured by DuPont) on a substrate and performing pretreatment,
Bilarin PI-2555 was applied and buttered in the same manner as in Comparative Example 1.

Although no peeling of the pattern was observed when heated at 4QO°C for 30 minutes, this pattern was heated in the same manner as in Example 1.
After being immersed in boiling water for an hour, a tape peeling test was performed, and all of the thin line portions of 10 μm or less of the pattern were peeled off.

Example 2 Thickness 35. The copper foil of u was immersed in Q-bond (manufactured by Muromachi Chemical Co., Ltd.) whose main component was NaC10□ at 90° C. for 3 minutes.

As a result of analyzing the surface with ESCA, it was confirmed that it had changed to CuO. On this fJ foil, a photosensitive polyimide precursor Selectirafx 1 (TR-2) solution (manufactured by Merck & Co., Ltd.) was applied to a thickness of 50 μm using an applicator.

After drying on a hot plate at 70° C. for 3 hours, the photosensitive polyimide precursor was directly exposed using a mask having a 1 m square zebra pattern, developed with N-methylpyrrolidone, and rinsed with isopropyl alcohol. This substrate was heated at 400° C. for 2 hours to form polyimide. After continuing heat treatment in PCT at 2 atmospheres for 6 hours,
Visual inspection and tape peeling test were conducted, but no problems such as peeling of the pattern occurred, and sufficient adhesion was confirmed even after immersion in a 280° C. solder bath for 3 minutes.

〔Effect of the invention〕

The present invention makes it possible to significantly improve the interlayer adhesion of conductors and insulating layers made of fine patterns in circuit modules for mounting electronic components such as LSIs and ICs, and hybrid ICs with copper wiring, thereby improving reliability. was able to be granted.

Claims (1)

[Claims] A method for forming a polyimide pattern on a copper surface, the method comprising oxidizing the copper surface in advance.