JP2008045156A - Surface treatment agent for copper or copper alloy surface, and treatment method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment agent for copper or a copper alloy with which sufficient adhesion between the surface of copper or a copper alloy composed of a vapor deposited layer or an electroless plated layer and a photosensitive resin (photoresist) can be secured. <P>SOLUTION: The surface treatment agent for copper or a copper alloy is composed of an aqueous solution comprising one or more kinds of heterocyclic compounds expressed by formula in Figure, and further having the pH of ≤4; wherein, R<SP>1</SP>to R<SP>4</SP>denote each independently a nitrogen atom or a carbon atom. In this case, when at least one selected from R<SP>1</SP>to R<SP>4</SP>denotes a carbon atom, hydrogen for holding the carbon atom may be substituted or may not be substituted. Further, R<SP>1</SP>and R<SP>2</SP>and/or R<SP>3</SP>and R<SP>4</SP>can form a condensed ring together with the other carbon ring or heterocyclic ring. The carbon ring or heterocyclic ring in this case may have a lower alkyl group as a substituent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface treatment agent and a surface treatment method for the surface of copper or a copper alloy such as a printed wiring board.

  Pre-treatment of copper or copper alloy to form photosensitive resin (photoresist) in the manufacturing process of printed wiring board that forms plating resist or etching resist with photosensitive film on copper or copper alloy and performs patterning In general, physical polishing such as buff polishing or chemical polishing such as soft etching is generally adopted. In addition to the purpose of activating the surface of copper or a copper alloy, these pretreatments for polishing can be performed with a photosensitive resin (photoresist) by an anchor action caused by roughening the surface of the copper or copper alloy. Has the effect of improving adhesion. However, physical polishing and chemical polishing are difficult due to the thinning of the substrate itself having an insulating layer or the thinning of the copper or copper alloy itself (deposition layer or electroless plating layer) that forms a photosensitive resin (photoresist). Since the number of cases has increased, the number of cases where the activation treatment of copper or copper alloy is changed to rust removal with dilute sulfuric acid has increased. Further, in recent years, due to the fine lines and reduction of the pattern to be formed, the dilute sulfuric acid activation treatment has caused problems in the adhesion of the plating resist or the etching resist with the photosensitive resin (photoresist), and the productivity is decreasing. Is the situation. More specifically, a photosensitive resin (photoresist) formed on copper or a copper alloy is developed with an aqueous solution such as sodium carbonate after exposure, and the developed pattern is used as a plating resist or etching resist in the next step. However, if the resist adhesion cannot be ensured in the plating step or the etching step, the plating step treatment agent or the etching step treatment agent may be submerged, so that a desired patterning shape cannot be obtained. In particular, since a copper or copper alloy deposition layer or electroless plating layer formed as a conductive film on an insulating layer cannot be thinly polished, establishment of a method for chemically improving the adhesion to a photosensitive resin (photoresist) Is required.

JP-A-11-43778 discloses an aqueous solution containing a compound selected from aminotetrazole and aminotetrazole derivatives (first aqueous solution) or a compound selected from aminotetrazole and aminotetrazole derivatives and aminotriazole and aminotriazole derivatives. A copper surface treatment method is described in which an aqueous solution containing a compound to be bonded (second aqueous solution) is applied to a copper surface to which a resin having a glass transition temperature of 150 ° C. or higher is bonded. However, in this document, in order to maintain adhesiveness with a resin having a high glass transition temperature, the copper surface is roughened by physical polishing or chemical polishing before being brought into contact with the first aqueous solution or the second aqueous solution. Whether or not the adhesion between the copper surface and the resin is improved by the first aqueous solution or the second aqueous solution without roughening the copper surface by physical polishing or chemical polishing. Is not clearly shown.
JP 11-43778 A

  As described above, in the prior art, copper or a copper alloy composed of a vapor deposition layer or an electroless plating layer cannot be physically polished or chemically polished because it is a thin layer. There has been a problem that sufficient adhesion to a plating resist or etching resist by resist) cannot be secured. This invention is made | formed in view of such a condition, The processing agent for copper or copper alloy which can ensure sufficient adhesiveness of the copper or copper alloy surface, and photosensitive resin (photoresist), and copper or copper It is an object of the present invention to provide an alloy surface treatment method.

（式中、Ｒ¹〜Ｒ⁴はそれぞれ独立して窒素原子又は炭素原子を表す。ここで、Ｒ¹〜Ｒ⁴のうちの少なくとも一つが炭素原子を表すときには、当該炭素原子が保持する水素は置換されていてもよく又は置換されていなくてもよい。さらに、Ｒ¹とＲ²及び／又はＲ³とＲ⁴は、他の炭素環又は複素環と共に縮合環を形成することができる。この場合の炭素環又は複素環は置換基として低級アルキル基を有していてもよい。）
によって表される１種以上の複素環式化合物を含有し、しかもｐＨが４以下である水溶液からなる銅又は銅合金用表面処理剤を提供する。 To solve this problem, the following formula:

(In the formula, R ^{1 to} R ⁴ each independently represent a nitrogen atom or a carbon atom. Here, when at least one of R ^{1 to} R ⁴ represents a carbon atom, the hydrogen held by the carbon atom is In addition, R ¹ and R ² and / or R ³ and R ⁴ may form a condensed ring together with other carbocycles or heterocycles. The carbocycle or heterocycle in this case may have a lower alkyl group as a substituent.
The surface treatment agent for copper or copper alloy which consists of the aqueous solution which contains 1 or more types of heterocyclic compounds represented by these, and is pH 4 or less is provided.

  Further, the present invention is characterized in that the surface treatment agent for copper or copper alloy and the surface of copper or copper alloy are brought into contact with each other, and then a resist layer made of a photosensitive film is formed on the surface. An alloy surface treatment method is also provided.

  According to the surface treatment agent or the surface treatment method of the present invention, the copper or copper alloy surface is activated without etching even if it is copper or a copper alloy comprising a vapor deposition layer or an electroless plating layer at a pH of 4 or less, And since the 1 or more types of heterocyclic compound contained in the said processing agent adheres to the surface of the said activated copper or copper alloy, sufficient of the surface of the said copper or copper alloy, and photosensitive resin (photoresist) Good adhesion can be secured.

  According to this invention, even if it is copper or a copper alloy which cannot perform physical polishing and chemical polishing, the adhesiveness of the surface of the said copper or copper alloy and photosensitive resin (photoresist) can be improved. The treatment agent and treatment method for copper or copper alloy of the present invention are suitable for the production of a printed wiring board in which fine wire adhesion of a photosensitive resin (photoresist) is required.

  The surface treatment agent for copper or copper alloy of the present invention is characterized by comprising an aqueous solution containing one or more heterocyclic compounds described below and having a pH of 4 or less. That is, the pH of 4 or less promotes the adhesion of the heterocyclic compound to copper or a copper alloy, and as a result, the adhesion between the surface of the copper or copper alloy and the photosensitive resin (photoresist) is improved. Can do. Although it is not clear why the heterocyclic compound adheres to the copper or copper alloy surface when the pH is 4 or less, it is usually an oxide layer film (monovalent copper and divalent copper) of several to tens of angstroms. When copper or a copper alloy covered with a layer is immersed in a treatment solution having a pH of 4 or less, imino hydrogen of the heterocyclic compound reacts with the monovalent copper in the process of slightly reducing the oxide film. This is thought to be due to adhesion. In addition, the pH of the aqueous solution is 3.5 or less, more preferably 3.0 or less.

On the other hand, if the pH of the aqueous solution exceeds 4, the solubility of the heterocyclic compound is lowered, or the adhesion of the heterocyclic compound to the copper or copper alloy surface is lowered. I can't get it. Moreover, in the aqueous solution exceeding pH 4, copper and a copper alloy cannot be activated, and since these adhesion reactions are remarkably suppressed, sufficient effects cannot be obtained.

A pH of 4 or less can be achieved with one or more acids selected from inorganic and organic acids. Here, the term “inorganic acid” refers to an acid formed by combining an acid group containing nonmetal such as Cl, S, N, P, and B with hydrogen, specifically hydrochloric acid, hypochlorous acid. Sulfuric acid, sulfurous acid, nitric acid, nitrous acid, orthophosphoric acid, phosphorous acid, pyrophosphoric acid, metaphosphoric acid, boric acid and the like. Although there is no restriction | limiting in particular in the inorganic acid which can be used for the surface treating agent for copper or copper alloy of this invention, Nitric acid, a sulfuric acid, phosphoric acid, boric acid, etc. are preferable. This is because these inorganic acids particularly promote the adhesion reaction of the heterocyclic compound to copper. In the present invention, the term “organic acid” refers to an organic compound having an acidic property, and specifically includes carboxylic acid, sulfonic acid, sulfinic acid, and the like. In the present invention, in particular, carboxylic acid and sulfonic acid can be used. Here, the term “carboxylic acid” refers to a compound in which a hydrocarbon hydrogen atom is replaced by “—COOH”, and the term “sulfonic acid” refers to a hydrocarbon hydrogen atom that is a sulfone group (—SO ₃ H ). The carboxylic acid that can be used is not particularly limited, but acetic acid, glycolic acid, citric acid, gluconic acid and the like are preferable. The sulfonic acid that can be used is not particularly limited, but methanesulfonic acid, ethanolsulfonic acid, phenolsulfonic acid, toluenesulfonic acid and the like are preferable. In addition, it is also possible to add sodium hydroxide, potassium hydroxide, aqueous ammonia, or a salt of these inorganic acids or organic acids as appropriate to adjust the pH.

によって表される５員環複素環式化合物であることができる。この式において、Ｒ¹〜Ｒ⁴はそれぞれ独立して窒素原子又は炭素原子を表す。一具体例では、Ｒ¹〜Ｒ⁴の全て又はいずれかは炭素原子を表し、しかも当該炭素原子上の水素原子は置換されていない。この場合の５員環複素環式化合物の例としては、ピロール、ピラゾール、イミダゾール、トリアゾール、テトラゾールなどが挙げられる。 The heterocyclic compound contained in the aqueous solution has the following formula:

Can be a 5-membered heterocyclic compound represented by In this formula, R ^{1 to} R ⁴ each independently represent a nitrogen atom or a carbon atom. In one specific example, all or any of R ^{1 to} R ⁴ represents a carbon atom, and a hydrogen atom on the carbon atom is not substituted. Examples of the 5-membered heterocyclic compound in this case include pyrrole, pyrazole, imidazole, triazole, tetrazole and the like.

In another embodiment of the present invention, at least one of R ^{1 to} R ⁴ in the above formula represents a carbon atom, and the hydrogen held by at least one of the carbon atoms is a certain substituent. Has been replaced. Here, examples of the substituent include a group containing at least one hetero atom selected from nitrogen, oxygen and sulfur, a C _{1 to} C ₆ alkyl group, an aryl group, and the like. Examples of the group containing one or more heteroatoms include a hydroxy group, an alkoxy group, and an amino group. In this case, an amino group is most preferable. Preferred alkyl groups include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl and the like and isomers thereof. More preferred alkyl groups are a methyl group, an ethyl group and an isopropyl group. A preferred aryl group is a phenyl group. Examples of 5-membered heterocyclic compounds having these substituents include 5-aminotetrazole, 3-amino-1,2,4-triazole, 3,5-dimethylpyrazole, 2-isopropylimidazole, and 5-phenyl. Examples include tetrazole.

In another specific example, in the above formula, R ¹ and R ² and / or R ³ and R ⁴ can form a condensed ring together with other carbocycles or heterocycles. Here, a benzene ring is mentioned as an example of another carbocyclic ring. Examples of other heterocycles include 5-membered or 6-membered rings containing one or more heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur. Specific examples of the condensed ring compound include indole, indazole, benzimidazole, benzotriazole, carbazole and condensed rings of the 5-membered ring and other heterocyclic rings, which are condensed ring compounds of the 5-membered ring and a benzene ring. Some puddings, carbolines, etc. Preferred fused ring compounds are indole, indazole, benzimidazole and benzotriazole. Moreover, these condensed ring compounds may have one or more substituents. Examples of substituents include those described for the substituted derivatives of the 5-membered ring compounds or lower alkyl groups such as methyl groups. An example of the condensed ring compound having the substituent is 5-methylbenzotriazole.

  The surface treating agent for copper or copper alloy of the present invention can contain one or more of the heterocyclic compounds listed above.

  The compounding amount of the heterocyclic compound is preferably in the range of 0.005 to 3% by weight as the total amount, and more preferably in the range of 0.01 to 2% by weight as the total amount, but is not limited thereto. In addition, if the said compounding quantity is less than 0.001 weight%, the adhesiveness to copper or a copper alloy will fall, and sufficient effect will not be acquired, but if it exceeds 3 weight%, an effect will be saturated and it will be uneconomical.

  The treatment of the copper or copper alloy surface is carried out in such a manner that the aqueous solution of the present invention is uniformly attached to the surface of the copper or copper alloy by dipping or spraying. The copper or copper alloy to be treated preferably consists of an electroless layer or a vapor deposition layer. Specifically, the treatment is performed at a treatment temperature in the range of room temperature to 40 ° C. for a treatment time of 5 to 120 seconds. After this treatment step, a water washing and drying step is performed. In addition, the said water washing and drying are enough for a general water washing and drying process.

  After this drying step, a photosensitive resin (photoresist) is laminated on the surface of copper or copper alloy treated with the surface treating agent, exposed, and developed with an alkaline solution to form a resist surface. At this time, the adhesion between the surface of the copper or copper alloy treated with the surface treating agent of the present invention and the photosensitive resin is significantly improved as compared with the prior art. Although the theory that the adhesion between the surface of copper or a copper alloy and a photosensitive resin (photoresist) is improved by the adhesion of one or more heterocyclic compounds is not clear, a photosensitive resin composed of acrylic acid and / or methacrylic acid In the process of exposing the (photoresist), the heterocyclic compound acts as a binder component between the surface of the copper and copper alloy and the photosensitive resin (photoresist), thereby improving the adhesion in the next step. It is thought that it will improve remarkably.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.

(Adhesion test)
The results of Examples and Comparative Examples are shown in Table 1. The evaluation is performed by observing the resist residual area at the tape peeling portion, where ◯ indicates no resist peeling, Δ indicates a resist peeling area of less than 5%, and x indicates a resist peeling area of 5% or more.

Examples 1-3
The aqueous solutions having the compositions of Example Nos. 1 to 3 shown in Table 1 were adjusted with ion-exchanged water to a constant temperature of 35 ° C. Substrates having a copper deposited film with a thickness of approximately 1 μm were immersed in these aqueous solutions for 20 seconds, and then the substrate was washed with water and dried. Thereafter, a photosensitive resin (photoresist) Phototec RY-3215 manufactured by Hitachi Chemical Co., Ltd. is laminated on the dried copper surface, exposed at 65 mJ / cm ² , and minimally developed with 1 wt% sodium carbonate. Development was carried out in twice the time to form a resist surface with a line / space of 40 μm / 40 μm. Next, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. Thereafter, a tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Examples 4-6
The aqueous solutions having the compositions of Example Nos. 4 to 6 shown in Table 1 were adjusted with ion-exchanged water and kept at a constant temperature of 25 ° C. Substrates having an electroless copper plating film with a thickness of approximately 0.5 μm were immersed in these aqueous solutions for 15 seconds, and then the substrate was washed with water and dried. Thereafter, a photosensitive resin (photoresist) ALPHA NIT225 manufactured by Nichigo-Morton Co., Ltd. is laminated on the dried copper surface, exposed at 100 mJ / cm ² , and a minimum development time of 2 with 1 wt% potassium carbonate. Development was performed in a double time to form a resist surface having a line / space of 40 μm / 40 μm. Next, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. Thereafter, a tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Examples 7-9
The aqueous solutions having the compositions of Example Nos. 7 to 9 shown in Table 1 were adjusted with ion-exchanged water and kept at a constant temperature of 30 ° C. A substrate having an electroless copper plating film having a thickness of about 1 μm was immersed in these aqueous solutions for 10 seconds, and then the substrate was washed with water and dried. Thereafter, a photosensitive resin (photoresist) Phototec RY-3215 manufactured by Hitachi Chemical Co., Ltd. is laminated on the dried copper surface, exposed at 65 mJ / cm ² , and minimally developed with 1 wt% sodium carbonate. Development was carried out in twice the time to form a resist surface with a line / space of 40 μm / 40 μm. Next, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. Thereafter, a tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Examples 10-12
An aqueous solution having a composition of Example Nos. 10 to 12 shown in Table 1 was adjusted with ion-exchanged water and kept at a constant temperature of 25 ° C. A substrate having an electroless copper plating film with a thickness of about 1.5 μm was immersed in these aqueous solutions for 25 seconds, and then the substrate was washed with water and dried. Thereafter, a photosensitive resin (photoresist) ALPHA NIT225 manufactured by Nichigo-Morton Co., Ltd. is laminated on the dried copper surface, exposed at 100 mJ / cm ² , and minimum development time with 1% by weight of potassium carbonate. Development was performed in twice the time to form a resist surface with a line / space of 40 μm / 40 μm. Next, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. The tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Examples 13-14
The aqueous solutions having the compositions of Example Nos. 13 to 14 shown in Table 1 were adjusted with ion-exchanged water and kept at a constant temperature of 25 ° C. A substrate having an electroless copper plating film with a thickness of about 1.0 μm was immersed in these aqueous solutions for 25 seconds, and then the substrate was washed with water and dried. Thereafter, a photosensitive resin (photoresist) ALPHA NIT225 manufactured by Nichigo-Morton Co., Ltd. is laminated on the dried copper surface, exposed at 100 mJ / cm ² , and minimum development time with 1% by weight of potassium carbonate. Development was performed in twice the time to form a resist surface with a line / space of 40 μm / 40 μm. Next, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. The tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Comparative Example 1
A substrate having a copper vapor deposition film with a thickness of about 1 μm was immersed in 5% sulfuric acid prepared with ion exchange water for 20 seconds, then washed with water and dried. Dry the copper surface by Hitachi Chemical Co., Ltd. of the photosensitive resin (photoresist) Photec RY-3215 was laminated, exposed at 65 mJ / cm ^2, 2 times the minimum developing time 1 wt% of sodium carbonate Development was performed over time to form a resist surface with a line / space of 40 μm / 40 μm. Next, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. Thereafter, a tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Comparative Example 2
A substrate having an electroless copper plating film having a thickness of about 0.5 μm was immersed in 5% sulfuric acid prepared with ion exchange water for 20 seconds, then washed with water and dried. The dried copper surface is laminated with a photosensitive resin (photoresist) ALPHA NIT225 manufactured by Nichigo-Morton, exposed at 100 mJ / cm ² , and twice the minimum development time with 1% by weight of potassium carbonate. And a resist surface having a line / space of 40 μm / 40 μm was formed. Next, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. Thereafter, a tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Comparative Examples 3-6
An aqueous solution having a composition of Comparative Example Nos. 3 to 6 shown in Table 1 was adjusted with ion-exchanged water to a constant temperature of 30 ° C. A substrate having an electroless copper plating film with a thickness of about 1 μm was immersed in these aqueous solutions for 20 seconds, then washed with water and dried. The dried copper surface is laminated with a photosensitive resin (photoresist) ALPHA NIT225 manufactured by Nichigo-Morton, exposed at 100 mJ / cm ² , and twice the minimum development time with 1 wt% sodium carbonate. And a resist surface having a line / space of 40 μm / 40 μm was formed. Subsequently, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. Thereafter, a tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Comparative Example 7
An aqueous solution having the composition of Comparative Example No. 7 shown in Table 1 was adjusted with ion-exchanged water and kept at a constant temperature of 25 ° C. A substrate having an electroless copper plating film with a thickness of approximately 1.0 μm was immersed in this aqueous solution for 25 seconds, and then the substrate was washed with water and dried. Thereafter, a photosensitive resin (photoresist) ALPHA NIT225 manufactured by Nichigo-Morton Co., Ltd. is laminated on the dried copper surface, exposed at 100 mJ / cm ² , and minimum development time with 1% by weight of potassium carbonate. Development was performed in twice the time to form a resist surface with a line / space of 40 μm / 40 μm. Next, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. The tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

Comparative Example 8
The aqueous solution of Comparative Example No. 8 shown in Table 1 was adjusted with ion-exchanged water to a constant temperature of 30 ° C. A base material having an electroless copper plating film having a thickness of about 0.5 μm is immersed in a 5 wt% sulfuric acid aqueous solution for 1 minute, and then sufficiently washed with water. Soaked for 2 seconds, then washed with water and dried. The dried copper surface is laminated with a photosensitive resin (photoresist) ALPHA NIT225 manufactured by Nichigo-Morton, exposed at 100 mJ / cm ² , and twice the minimum development time with 1 wt% sodium carbonate. And a resist surface having a line / space of 40 μm / 40 μm was formed. Subsequently, the substrate was immersed in 2N hydrochloric acid at a constant temperature of 50 ° C. for 1 minute, and further immersed in 2N sulfuric acid at a constant temperature of 30 ° C. for 1 hour. Thereafter, a tape was pressure-bonded to the resist surface and peeled off in the vertical direction. Resist adhesion was confirmed with a microscope.

  As shown in Table 1, it was confirmed that the adhesion between the surface of copper or copper alloy and the photosensitive resin (photoresist) was improved by the present invention.

Claims (7)

The following formula:

(In the formula, R ^{1 to} R ⁴ each independently represent a nitrogen atom or a carbon atom. Here, when at least one of R ^{1 to} R ⁴ represents a carbon atom, the hydrogen held by the carbon atom is In addition, R ¹ and R ² and / or R ³ and R ⁴ may form a condensed ring together with other carbocycles or heterocycles. The carbocycle or heterocycle in this case may have a lower alkyl group as a substituent.
A surface treatment agent for copper or copper alloy comprising an aqueous solution containing at least one heterocyclic compound represented by the formula (1) and having a pH of 4 or less. In the above formula, at least one of R ^{1 to} R ⁴ represents a carbon atom, and hydrogen held by at least one of the carbon atoms is a hydroxy group, an alkoxy group, an amino group, or a C _{1 to} C ₆ alkyl. The surface treatment agent for copper or copper alloy according to claim 1, which is substituted with a substituent selected from the group consisting of a group and an aryl group.   Heterocyclic compounds are pyrrole, pyrazole, imidazole, triazole, tetrazole, indole, indazole, benzimidazole, benzotriazole, 5-aminotetrazole, 3-amino-1,2,4-triazole, 3,5-dimethylpyrazole, 2 The surface treatment for copper or copper alloy according to claim 1 or 2, characterized in that it is selected from the group consisting of -isopropylimidazole, 5-phenyltetrazole and 5-methylbenzotriazole and combinations of two or more thereof. Agent.   The surface treating agent for copper or copper alloy according to any one of claims 1 to 3, comprising at least one acid selected from the group consisting of inorganic acids and organic acids.   The inorganic acid is selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid and boric acid, and the organic acid is a group consisting of acetic acid, glycolic acid, citric acid and gluconic acid and methanesulfonic acid, ethanolsulfonic acid, phenolsulfonic acid and toluenesulfonic acid. The surface treatment agent for copper or copper alloy according to claim 4, wherein the surface treatment agent is selected from the group consisting of:   The surface treatment agent for copper or copper alloy according to any one of claims 1 to 5 is brought into contact with the surface of copper or copper alloy, and then a resist layer made of a photosensitive film is formed on the surface. A method for treating a copper or copper alloy surface.   The copper or copper alloy surface treatment method according to claim 6, wherein the copper or copper alloy is an electroless layer or a vapor deposition layer of copper or a copper alloy.