Circuit board cleaning method

Abstract

In one embodiment, a substrate cleaning method is provided that can reduce residues during cleaning after peeling off a resin mask. [Solution] This disclosure relates in one embodiment to a method for cleaning a substrate, comprising the following steps 1 and 2. Step 1: A step of peeling off a resin mask from a substrate having a copper-containing metal layer and a resin mask on its surface using a resin mask peeling solution composition. Step 2: A step in which the substrate treated in Step 1 is washed with an aqueous solution with a pH of 8 or higher.

Description

Technical Field

[0001] The present disclosure relates to a method for cleaning a substrate and a method for manufacturing an electronic component.

Background Art

[0002] In recent years, in personal computers and various electronic devices, power consumption has been reduced, processing speed has been increased, and miniaturization has advanced. Wiring such as package substrates mounted on these devices has become finer year by year. For forming such fine wiring and connection terminals such as pillars and bumps, the metal mask method has been mainly used so far. However, due to its low versatility and difficulty in coping with the miniaturization of wiring and the like, it is being changed to other new methods.

[0003] As one of the new methods, a method using a resin mask, also called a dry film resist, is known. In this method, a metal seed layer is formed by electroless plating on an insulating substrate. Subsequently, the metal seed layer is laminated with a resin mask, a pattern is formed by exposure and development processing, and copper wiring and tin bumps are formed by electroplating. The resin mask remaining on the substrate is finally peeled off and removed, and an alkaline peeling liquid composition is used at that time.

[0004] For example, Patent Document 1 proposes a treatment liquid used for removing a resist, which is at least one of a resist film and residues of the resist film. Patent Document 2 proposes a method for manufacturing a semiconductor device substrate including a step of peeling an organic underlayer film in which part or all of a silicon-containing film used as an ion implantation mask remains, using a peeling liquid. Patent Document 3 proposes a rinse liquid used for cleaning (rinsing) a substrate after treating residues after ashing in a treatment of a substrate subjected to dry etching and ashing using a photoresist pattern provided on the substrate as a mask, and a method for treating the substrate using the same.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-52186 [Patent Document 2] Japanese Patent Publication No. 2016-51094 [Patent Document 3] Japanese Patent Publication No. 2001-222118 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the cleaning process for substrates with a resin mask, the resin mask is usually removed with a stripping solution, followed by cleaning (e.g., acid cleaning). Even after this post-cleaning process (hereinafter also referred to as "post-cleaning"), residues of components from the stripping solution composition (e.g., metal corrosion inhibitors) may remain on the substrate. If components such as metal corrosion inhibitors remain on the substrate, it may adversely affect subsequent processes after the cleaning process for substrates with a resin mask (e.g., metal seed layer removal (also known as seed layer etching)).

[0007] Therefore, this disclosure provides a substrate cleaning method that can reduce residues during cleaning after peeling off a resin mask, and a method for manufacturing electronic components. [Means for solving the problem]

[0008] This disclosure relates, in one embodiment, to a method for cleaning a substrate, comprising the following steps 1 and 2. Step 1: A step of peeling off a resin mask from a substrate having a copper-containing metal layer and a resin mask on its surface using a resin mask peeling solution composition. Step 2: A step in which the substrate treated in Step 1 is washed with an aqueous solution with a pH of 8 or higher.

[0009] This disclosure relates, in one embodiment, to a method for manufacturing electronic components, including a cleaning method according to this disclosure.

[0010] This disclosure relates, in one embodiment, to a cleaning solution for use in step 2 of a substrate cleaning method of this disclosure, the cleaning solution containing an inorganic alkaline compound, further containing metal ions other than alkali metal ions, wherein the content of the metal ions is 1 ppb or more and 100 ppm or less, and the pH is 8 or higher. [Effects of the Invention]

[0011] According to this disclosure, in one embodiment, a method for cleaning a substrate is provided that can reduce residues during cleaning after peeling off a resin mask with a peeling solution composition. [Modes for carrying out the invention]

[0012] This disclosure is based on the finding that when a resin mask is removed from a substrate having a copper-containing metal layer and a resin mask on its surface using a stripping solution, and then washed with an inorganic alkaline compound, it is possible to reduce residues in the post-cleaning process (improve low residue in post-cleaning).

[0013] In other words, in one embodiment, this disclosure relates to a method for cleaning a substrate (hereinafter also referred to as "the cleaning method of this disclosure") which includes the following steps 1 and 2. Step 1: A step of peeling off a resin mask from a substrate (hereinafter also referred to as "object to be cleaned") having a copper-containing metal layer and a resin mask on its surface using a resin mask peeling solution composition (hereinafter also referred to as the "peeling step"). Step 2: A step in which the substrate processed in Step 1 is washed with an aqueous solution with a pH of 8 or higher (hereinafter also referred to as the "post-washing step").

[0014] According to this disclosure, in one or more embodiments, a substrate cleaning method is provided that can reduce residue during cleaning after resin mask removal (improve the low residue retention during post-cleaning). Furthermore, by using the cleaning method of this disclosure for cleaning electronic components such as electronic circuit boards having a resin mask, high-quality electronic components can be obtained with a high yield.

[0015] While the detailed mechanism of action by which the effects of this disclosure are manifested remains unclear, it is presumed to be as follows. Conventionally, the common method for removing residues from the substrate surface, including the outermost layer of metal, was to clean the substrate with an acid capable of dissolving the metal. However, some of the residues have low solubility in acid and may remain on the substrate surface even after conventional acid cleaning. One such residue is metal corrosion inhibitors, which are originally dissolved in strongly alkaline stripping solutions and exhibit high solubility in alkalis. Therefore, in the cleaning method of this disclosure, by using a highly soluble alkaline compound as the cleaning solution after resin mask stripping, it is considered possible to easily remove residues derived from the stripping solution composition (for example, residues of metal corrosion inhibitors) remaining on the substrate. However, this disclosure does not have to be interpreted as being limited to this mechanism.

[0016] In this disclosure, a resin mask is a mask formed using a resin as a component, which functions as a protective film, for protecting the surface of a material from treatments such as etching, plating, and heating. Examples of resin masks include, in one or more embodiments, a resist layer after exposure and development, a resist layer subjected to at least one of exposure and / or development (hereinafter also referred to as "exposed and / or developed"), or a cured resist layer. Furthermore, in one or more embodiments, the resin mask is formed using a resist whose physical properties, such as solubility in a developer solution, change when exposed to light or electron beams. Resists are broadly classified into negative and positive types based on their reaction method with light or electron beams. Negative resists have the characteristic of decreasing solubility in a developer solution when exposed, and the layer containing a negative resist (hereinafter also referred to as the "negative resist layer") is used as a resin mask in the exposed area after exposure and development. Positive resists have the characteristic of increasing solubility in a developer solution when exposed, and the layer containing a positive resist (hereinafter also referred to as the "positive resist layer") has the exposed area removed after exposure and development, and the unexposed area is used as a resin mask. By using a resin mask with such characteristics, it is possible to form fine connection parts of circuit boards such as metal wiring, metal pillars, and solder bumps. As the resin material for forming the resin mask, in one or more embodiments, a film-like photosensitive resin, a resist film, or a photoresist can be mentioned. General-purpose resist films can be used. In one or more embodiments, the resin mask is a copper or tin plating mask for use in copper or tin plating treatment.

[0017] The cleaning method of the present disclosure is a cleaning method for cleaning a substrate (object to be cleaned) having a copper-containing metal layer and a resin mask on its surface. In the present disclosure, cleaning of a substrate having a copper-containing metal layer and a resin mask on its surface includes peeling the resin mask from the substrate having the resin mask using a stripping liquid composition, and post-cleaning the substrate after resin mask peeling. Peeling of the resin mask may include removal and / or dissolution of the resin mask. In one or more embodiments, the cleaning method of the present disclosure is used for cleaning before seed layer etching (a step before the metal seed layer removal step). In one or more embodiments, the cleaning method of the present disclosure is used in the manufacturing process of electronic components (electronic substrates such as printed circuit boards and package substrates).

[0018] [Object to be cleaned] In one or more embodiments, the object to be cleaned is a substrate having a copper-containing metal layer and a resin mask on its surface. In one or more embodiments, the substrate having a copper-containing metal layer and a resin mask on its surface has undergone a process of performing at least one of soldering and plating using the resin mask. In one or more embodiments, the copper-containing metal layer is a copper plating layer. The copper plating layer can be formed, for example, by electroless copper plating. In one or more embodiments, the copper-containing metal layer is used as a metal wiring. Examples of the thickness of the copper-containing metal layer include 3 μm to 30 μm. Examples of the substrate include an insulator plate, a film, and the like.

[0019] Examples of the objects to be cleaned include, in one or more embodiments, manufacturing intermediates of electronic components (electronic substrates such as printed circuit boards and package substrates). In one or more embodiments, these manufacturing intermediates are produced in a modified semi-additive process (MSAP). Examples of electronic components include printed circuit boards and package substrates. The manufacturing intermediates are intermediate products in the manufacturing process of the electronic components, and include intermediate products after resin mask treatment. Specific examples of objects to be cleaned include, for example, electronic components on which wiring, connection terminals, etc., are formed on the substrate surface by undergoing a process of at least one of the following: soldering using a resin mask and plating (copper plating, aluminum plating, nickel plating, tin plating, etc.). In this disclosure, soldering means creating solder in areas on the substrate where a resin mask is not present and forming solder bumps by heating. In this disclosure, plating means performing at least one type of plating process selected from copper plating, aluminum plating, nickel plating, and tin plating on areas on the substrate where a resin mask is not present. Areas where a resin mask is not present refer to the parts of a resist pattern (a resin mask in the shape of a pattern) formed by developing a resin mask laminated to a substrate, where the resin mask has been removed by the developing process.

[0020] In one or more embodiments, the object to be cleaned is a substrate having a resist pattern (a resin mask in the shape of a pattern) formed by developing a resin mask laminated to the substrate, and having undergone at least one of the processes of soldering and plating. For example, the object to be cleaned may be a substrate having a portion where a hardened resist layer is formed on the substrate in the presence of a resin mask, and a portion where solder bumps or a plating layer are formed in the portion where a resin mask is not present.

[0021] The resin mask may be, for example, a negative-type resin mask or a positive-type resin mask. In this disclosure, a negative-type resin mask is formed using a negative-type resist, and an example of this is an exposed and / or developed negative-type resist layer. In this disclosure, a positive-type resin mask is formed using a positive-type resist, and an example of this is an exposed and / or developed positive-type resist layer.

[0022] [Process 1: Peeling Process] Step 1 in the cleaning method of this disclosure is a step (peeling step) of peeling off a resin mask from a substrate (object to be cleaned) having a copper-containing metal layer and a resin mask on its surface using a resin mask peeling liquid composition. In one or more embodiments, the peeling step includes bringing the object to be cleaned into contact with the resin mask peeling liquid composition.

[0023] In step 1, methods for removing the resin mask from the object to be cleaned using the resin mask removal solution composition, or for bringing the resin mask removal solution composition into contact with the object to be cleaned, include, for example, immersing the object to be cleaned in a cleaning bath containing the resin mask removal solution composition, spraying the resin mask removal solution composition onto the object to be cleaned (shower method), and an ultrasonic cleaning method in which ultrasonic waves are irradiated during the immersion. The resin mask removal solution composition can be used for cleaning as is without dilution. Examples of objects to be cleaned include those described above. For example, immersion times can range from 1 minute to 10 minutes, or even from 3 minutes to 6 minutes. For example, spraying times can range from 1 minute to 10 minutes, or even from 3 minutes to 6 minutes.

[0024] In step 1, it is preferable to irradiate the resin mask peeling solution composition with ultrasound when it comes into contact with the object to be cleaned, in order to easily exhibit the peeling and cleaning power of the resin mask peeling solution composition, and it is more preferable that the ultrasound is of a relatively high frequency. From the same viewpoint, the irradiation conditions for the ultrasound are preferably, for example, 26 to 72 kHz and 80 to 1500 W, and more preferably 36 to 72 kHz and 80 to 1500 W.

[0025] The temperature of the resin mask stripping liquid composition used in step 1 is preferably 40°C or higher, more preferably 50°C or higher, from the viewpoint of easily exhibiting the stripping and cleaning power of the resin mask stripping liquid composition, and preferably 70°C or lower, more preferably 60°C or lower, from the viewpoint of reducing the impact on the organic resin-containing substrate.

[0026] <Composition for removing resin mask used in step 1> The resin mask stripping liquid composition used in step 1 may, in one or more embodiments, contain one or more components selected from the group consisting of hydroxide (component A), alkanolamine (component B), organic solvent (component C), and water (component D), or it may contain all of these. In addition, the resin mask stripping liquid composition used in step 1 may, in one or more embodiments, contain a metal corrosion inhibitor. The following describes the components contained in the resin mask release solution composition.

[0027] (Component A: Hydroxide) The hydroxide (hereinafter also referred to as "component A") contained in the resin mask release solution composition used in step 1 can be at least one selected from aliphatic quaternary ammonium hydroxides and inorganic metal hydroxides. Component A may be one type or a combination of two or more types.

[0028] Examples of aliphatic quaternary ammonium hydroxides include quaternary ammonium hydroxides represented by the following formula (I). The aliphatic quaternary ammonium hydroxide may be a single type or a combination of two or more types. [ka] In the above equation (I), R 1 , R 2 , R 3 and R 4 Each of these groups is independently at least one selected from a methyl group, an ethyl group, a propyl group, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. Quaternary ammonium hydroxides represented by formula (I) are salts consisting of a quaternary ammonium cation and a hydroxide, and include, for example, at least one selected from tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, 2-hydroxyethyltrimethylammonium hydroxide (choline), 2-hydroxyethyltriethylammonium hydroxide, 2-hydroxyethyltripropylammonium hydroxide, 2-hydroxypropyltrimethylammonium hydroxide, 2-hydroxypropyltriethylammonium hydroxide, 2-hydroxypropyltripropylammonium hydroxide, dimethylbis(2-hydroxyethyl)ammonium hydroxide, diethylbis(2-hydroxyethyl)ammonium hydroxide, dipropylbis(2-hydroxyethyl)ammonium hydroxide, tris(2-hydroxyethyl)methylammonium hydroxide, tris(2-hydroxyethyl)ethylammonium hydroxide, tris(2-hydroxyethyl)propylammonium hydroxide, tetrakis(2-hydroxyethyl)ammonium hydroxide, and tetrakis(2-hydroxypropyl)ammonium hydroxide. Among these, from the viewpoint of improving resin mask removal performance, it is preferable that component A contains tetramethylammonium hydroxide (TMAH).

[0029] Examples of inorganic metal hydroxides include alkali metal hydroxides, and from the viewpoint of improving resin mask removal (peelability), at least one selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide is preferred, with potassium hydroxide being the most preferred among these. The inorganic metal hydroxide may be a single type or a combination of two or more types.

[0030] From the viewpoint of improving resin mask removal performance, component A preferably contains an aliphatic quaternary ammonium hydroxide, and more preferably contains tetramethylammonium hydroxide (TMAH). The content of aliphatic quaternary ammonium hydroxide in component A is preferably 0.5% by mass or more, more preferably 1.5% by mass or more, even more preferably 2.5% by mass or more, and even more preferably 3.5% by mass or more.

[0031] The content of component A in the resin mask peeling liquid composition used in step 1 is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 4% by mass or more, from the viewpoint of improving resin mask removal (peelability) and suppressing copper corrosion. Similarly, it is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less. If component A is a combination of two or more types, the content of component A refers to the total content of those types. If component A contains an aliphatic quaternary ammonium hydroxide, the content of the aliphatic quaternary ammonium hydroxide in the resin mask peeling solution composition used in step 1 is preferably 0.5% by mass or more, more preferably 1.5% by mass or more, even more preferably 2.5% by mass or more, and from the viewpoint of improving resin mask removal (peeling) and suppressing copper corrosion, preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less. If the aliphatic quaternary ammonium hydroxide is a combination of two or more types, the content of the aliphatic quaternary ammonium hydroxide refers to the total content of those types. If component A contains an inorganic metal hydroxide, the inorganic metal hydroxide content in the resin mask peeling solution composition used in step 1 is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and from the viewpoint of improving resin mask removal (peelability) and suppressing copper corrosion, preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less. If the inorganic metal hydroxide is a combination of two or more types, the inorganic metal hydroxide content refers to their total content.

[0032] In this disclosure, "content of each component in the resin mask stripping solution composition" means the content of each component at the time of use (during the stripping treatment), that is, at the time when the resin mask stripping solution composition is first used for the resin mask stripping treatment. In this disclosure, the content of each component in the resin mask stripping solution composition can be considered as the amount of each component blended in the resin mask stripping solution composition in one or more embodiments.

[0033] (Component B: Alkanolamine) Examples of the alkanolamine (amino alcohol) (hereinafter also referred to as "component B") contained in the resin mask release solution composition used in step 1 include compounds represented by the following formula (II). Component B may be one type or a combination of two or more types. [ka]

[0034] In the above equation (II), R 5 R represents a hydrogen atom, a methyl group, an ethyl group, or an aminoethyl group. 6 R represents a hydrogen atom, a hydroxyethyl group, a hydroxypropyl group, a methyl group, or an ethyl group. 7 This represents a hydroxyethyl group or a hydroxypropyl group.

[0035] Component B can be, for example, at least one selected from monoethanolamine (MEA), monoisopropanolamine, N-methylmonoethanolamine, N-methylisopropanolamine, N-ethylmonoethanolamine, N-ethylisopropanolamine, diethanolamine, diisopropanolamine, N-dimethylmonoethanolamine, N-dimethylmonoisopropanolamine, N-methyldiethanolamine, N-methyldiisopropanolamine, N-diethylmonoethanolamine, N-diethylmonoisopropanolamine, N-ethyldiethanolamine, N-ethyldiisopropanolamine, N-(β-aminoethyl)ethanolamine, N-(β-aminoethyl)isopropanolamine, N-(β-aminoethyl)diethanolamine, and N-(β-aminoethyl)diisopropanolamine. Among these, from the viewpoint of improving resin mask removal performance, it is preferable that component B contains monoethanolamine (MEA).

[0036] The content of component B in the resin mask removal liquid composition used in step 1 is preferably 1% by mass or more, more preferably 6% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of improving resin mask removal performance and suppressing copper corrosion, and similarly, preferably 18% by mass or less, more preferably 16% by mass or less, and even more preferably 14% by mass or less. If component B is a combination of two or more types, the content of component B refers to the total content of those types.

[0037] (Component C: Organic solvent) The organic solvent contained in the resin mask peeling solution composition used in step 1 (hereinafter also referred to as "component C") may be one type or a combination of two or more types. Component C may be at least one solvent selected from glycol ethers and aromatic ketones in one or more embodiments. Examples of glycol ethers include compounds having a structure in which ethylene glycol is added to an alcohol having 1 to 8 carbon atoms in 1 to 3 moles. Specific examples of glycol ethers include at least one selected from diethylene glycol monobutyl ether (BDG), ethylene glycol monobenzyl ether, diethylene glycol monohexyl ether, ethylene glycol monophenyl ether, and diethylene glycol diethyl ether. Examples of aromatic ketones include acetophenone. Among these, component C is preferably glycol ether, and more preferably diethylene glycol monobutyl ether (BDG), from the viewpoint of improving resin mask removal performance.

[0038] The content of component C in the resin mask removal liquid composition used in step 1 is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and from the viewpoint of improving resin mask removal performance, it is preferably 15% by mass or less, more preferably 13% by mass or less, and even more preferably 10% by mass or less. If component C is a combination of two or more types, the content of component C refers to the total content of those types.

[0039] (Component D: water) In one or more embodiments, the water contained in the resin mask peeling solution composition used in step 1 (hereinafter also referred to as "component D") may be ion-exchanged water, RO water, distilled water, pure water, ultrapure water, etc.

[0040] The content of component D in the resin mask stripping liquid composition used in step 1 can be the remainder after excluding component A, component B, component C, and optional components (metal corrosion inhibitors, other components) described later. Specifically, from the viewpoint of improving resin mask removal performance and suppressing copper corrosion, the content of component D in the resin mask stripping liquid composition used in step 1 is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more. Furthermore, from the viewpoint of improving resin mask removal performance, it is preferably 98% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0041] (Metal corrosion inhibitor) The resin mask stripping liquid composition used in step 1 may, in one or more embodiments, contain a metal corrosion inhibitor. The resin mask stripping liquid composition used in step 1 may, in one or more embodiments, contain component A, component B, component C, and component D, and further contain a metal corrosion inhibitor. Examples of metal corrosion inhibitors (inhibitors) that can inhibit copper corrosion include thiazoles or their derivatives, compounds having an imidazole skeleton, and compounds having a triazole skeleton. Examples of thiazoles or their derivatives include thiazole, benzothiazole, mercaptobenzothiazole (MBT), aminobenzothiazole (ABT), etc., and from the viewpoint of inhibiting copper corrosion, it is more preferable to include mercaptobenzothiazole (MBT). Examples of compounds having an imidazole skeleton include compounds having a benzimidazole skeleton, such as benzimidazole (BI), 5-methylbenzimidazole (MBI), and 5,6-dimethylbenzimidazole (DMBI). Examples of compounds having a triazole skeleton include benzotriazole (BTA), 1-methylbenzotriazole (MBTA), tolyltriazole (TTA), and 5,6-dimethylbenzotriazole (DMBTA). These metal corrosion inhibitors (inhibitors) may be used individually or in combination of two or more types.

[0042] If the resin mask stripping liquid composition used in step 1 contains a metal corrosion inhibitor, the content of the metal corrosion inhibitor in the resin mask stripping liquid composition is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, relative to the total amount (100% by mass) of the resin mask stripping liquid composition, from the viewpoint of inhibiting copper corrosion, and preferably 0.5% by mass or less, more preferably 0.3% by mass or less, from the viewpoint of ease of removal of the metal corrosion inhibitor by post-washing and reduction of residue on the substrate. From the viewpoint of inhibiting copper corrosion, ease of removal of the metal corrosion inhibitor by post-washing and reduction of residue on the substrate, the content of the metal corrosion inhibitor in the resin mask stripping liquid composition is preferably 0.05% by mass or more and 0.5% by mass or less, more preferably 0.1% by mass or more and 0.3% by mass or less. If there is a combination of two or more metal corrosion inhibitors, the content of the metal corrosion inhibitors refers to their total content.

[0043] (Other ingredients) The resin mask stripping solution composition used in step 1 may further contain other components as needed, in addition to the components described above. Examples of other components include those commonly used in resin mask stripping solutions (cleaning agents for resin mask stripping), such as alkaline agents other than components A and B, amines other than component B, solvents other than component C, surfactants, chelating agents, thickeners, dispersants, rust inhibitors, polymer compounds, solubilizers, antioxidants, preservatives, defoaming agents, and antibacterial agents.

[0044] The pH of the resin mask stripping solution composition used in Step 1 is preferably 10 or higher, more preferably 12 or higher, even more preferably 13.3 or higher, even more preferably 13.5 or higher, and even more preferably 14.0 or higher, from the viewpoint of improving resin mask removal efficiency. In this disclosure, the pH of the resin mask stripping solution composition is the value at 25°C and can be measured using a pH meter, specifically by the method described in the examples.

[0045] The resin mask release liquid composition used in step 1 may be a so-called one-component type, where all components are pre-mixed and supplied to the market, or a so-called two-component type, where the components are mixed at the time of use.

[0046] The resin mask stripping liquid composition used in step 1 can be manufactured in one or more embodiments by blending component A, component B, component C, component D, and optionally a metal corrosion inhibitor and other components in a known manner. For example, the resin mask stripping liquid composition used in step 1 may consist of at least component A, component B, component C, and component D. In this disclosure, "blending" includes mixing component A, component B, component C, component D, and optionally the above-mentioned metal corrosion inhibitor and other components simultaneously or in any order. In the production of the resin mask release liquid composition used in Step 1, the preferred blending amount of each component can be the same as the preferred content of each component of the resin mask release liquid composition used in Step 1 described above.

[0047] The resin mask stripping solution composition used in step 1 may be in a form that can be used directly for the resin mask stripping treatment, or it may be prepared as a concentrate to the extent that it does not impair storage stability by causing separation or precipitation. The concentrate of the resin mask stripping solution composition can be used after diluting it so that each component has the above-mentioned content (i.e., the content during the resin mask stripping treatment). The concentrate of the resin mask stripping solution composition can also be used by adding each component separately at the time of use. In this disclosure, "at the time of use" or "during the resin mask stripping treatment" of the concentrate of the resin mask stripping solution composition refers to the state in which the concentrate of the resin mask stripping solution composition has been diluted.

[0048] [Step 2: Post-cleaning step] Step 2 in the cleaning method of this disclosure is a step (post-cleaning step) in which the substrate treated in Step 1 (substrate after resin mask removal) is cleaned with an aqueous solution with a pH of 8 or higher (hereinafter also referred to as the "post-cleaning solution"). In one or more embodiments, Step 2 is a step prior to the metal seed layer removal step. Furthermore, if there is a step between step 1 and step 2 in which the substrate after the resin mask has been removed comes into contact with water, then the object to be cleaned (post-cleaned) in step 2 is the substrate after contact with water.

[0049] In one or more embodiments, the post-cleaning step includes contacting the substrate after the resin mask has been removed with an aqueous solution with a pH of 8 or higher. Examples of cleaning methods for post-cleaning in step 2 include immersion cleaning, ultrasonic cleaning, agitation cleaning, and spray cleaning, with spray cleaning being preferred among these. Therefore, in one or more embodiments, step 2 preferably includes spraying an aqueous solution with a pH of 8 or higher onto the substrate treated in step 1 (the substrate after the resin mask has been removed).

[0050] In step 2, the cleaning time for post-cleaning, or the time for contacting the substrate with an aqueous solution of pH 8 or higher after peeling off the resin mask, is preferably 60 seconds or less, more preferably 45 seconds or less, and even more preferably 30 seconds or less, from the viewpoint of minimizing damage to the substrate after peeling off the resin mask, and preferably 1 second or more, more preferably 5 seconds or more, and even more preferably 10 seconds or more, from the viewpoint of removing residue from the substrate after peeling off the resin mask.

[0051] The temperature of the aqueous solution with a pH of 8 or higher used for post-cleaning in step 2 is preferably 15°C or higher, more preferably 20°C or higher, and even more preferably 25°C or higher, from the viewpoint of removing residue from the substrate after peeling off the resin mask, and from the viewpoint of minimizing damage to the substrate after peeling off the resin mask and suppressing the volatilization of the aqueous solution used for post-cleaning, it is preferably 40°C or lower, more preferably 35°C or lower, and even more preferably 30°C or lower.

[0052] In step 2, the change in thickness of the copper-containing metal layer on the substrate before and after post-cleaning [(thickness of the copper-containing metal layer before post-cleaning) - (thickness of the copper-containing metal layer after post-treatment)] is preferably 500 nm or less, preferably 100 nm or less, and more preferably 10 nm or less. The maximum copper ion concentration in the aqueous solution with a pH of 8 or higher after post-washing in step 2 is preferably 1000 ppm or less, preferably 500 ppm or less, and more preferably 100 ppm or less. The copper ion concentration in the aqueous solution with a pH of 8 or higher after post-washing can be measured using inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0053] <Aqueous solution with a pH of 8 or higher (post-wash solution) used in step 2> In step 2, the aqueous solution with a pH of 8 or higher (post-cleaning solution) preferably contains an inorganic alkali compound in one or more embodiments, from the viewpoint of removing the metal corrosion inhibitor by post-cleaning and reducing residue on the substrate. In one or more embodiments, the post-cleaning solution is an aqueous solution obtained by diluting an inorganic alkali compound with water. Examples of inorganic alkali compounds include ammonium hydroxide (ammonia) and alkali metal hydroxides. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide. The inorganic alkali compound may be one type or a combination of two or more types. As for the aqueous solution with a pH of 8 or higher (post-cleaning solution) used in step 2, ammonia aqueous solution, sodium hydroxide aqueous solution, etc., are preferred from the viewpoint of removing the metal corrosion inhibitor by post-cleaning and reducing residue on the substrate. If the aqueous solution with a pH of 8 or higher (post-washing solution) used in step 2 is an aqueous ammonia solution, the concentration of the aqueous ammonia solution is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of post-washing properties, and preferably 25% by mass or less, and more preferably 20% by mass or less, from the viewpoint of post-washing properties and volatility. When the aqueous solution with a pH of 8 or higher (post-cleaning solution) used in step 2 is an aqueous sodium hydroxide solution, the concentration of the aqueous sodium hydroxide solution is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, from the viewpoint of post-cleaning performance, and from the viewpoint of post-cleaning performance and suppression of damage to the substrate, it is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. The pH of the aqueous solution (post-cleaning solution) used in step 2, with a pH of 8 or higher, is preferably 8 or higher, more preferably 9 or higher, and more preferably 10 or higher, from the viewpoint of the removal of the metal corrosion inhibitor by post-cleaning and the reduction of residue on the substrate.

[0054] The aqueous solution with a pH of 8 or higher (post-washing solution) used in step 2 contains, in one or more embodiments, metal ions (e.g., copper ions, etc.) in a concentration of approximately 1 ppb to 100 ppm, in addition to metal ions (e.g., sodium ions, potassium ions) derived from the raw materials (inorganic alkali compounds). This small amount (approximately 1 ppb to 100 ppm) of metal ions is thought to have a buffering effect, stabilizing the etching of the workpiece during washing after the resin mask is removed. Therefore, the aqueous solution with a pH of 8 or higher used in step 2 further contains metal ions other than alkali metal ions, and the content of these metal ions is between 1 ppb and 100 ppm. Furthermore, in other embodiments, this disclosure relates to a cleaning solution for use in step 2 of the substrate cleaning method of this disclosure, which contains an inorganic alkali compound and further contains metal ions other than alkali metal ions, wherein the content of the metal ions is 1 ppb or more and 100 ppm or less, and the pH is 8 or higher. The concentration of metal ions other than alkali metal ions in the cleaning solution can be measured using ICP-MS or the like, and specifically can be measured by the method described in the examples. In step 2, the aqueous solution with a pH of 8 or higher (post-washing solution) can be reused in one or more embodiments. When the post-washing solution is reused, metal ions originating from the object being washed may accumulate. In step 2, in one or more embodiments, the post-washing solution is replaced with a new one when the content of metal ions other than alkali metal ions in the post-washing solution exceeds 100 ppm, or before it exceeds 100 ppm.

[0055] In one or more embodiments, the cleaning method of the present disclosure may include a step between step 1 and step 2 in which the substrate treated in step 1 is brought into contact with water. In one or more embodiments, the cleaning method of the present disclosure may include a step of bringing the substrate cleaned in step 2 into contact with water after step 2. Here, methods for bringing the substrate (the substrate processed in step 1, the substrate cleaned in step 2) into contact with water include, for example, immersing the substrate in a tank of water to bring it into contact with the water, or spraying water onto the substrate to bring it into contact with the water. The contact time between the substrate (the substrate processed in step 1 and the substrate cleaned in step 2) and water is preferably, for example, 10 seconds or more and 60 seconds or less. The steps of bringing the substrate processed in step 1 into contact with water, and bringing the substrate cleaned in step 2 into contact with water, may, in one or more embodiments, include drying the substrate after contact with water. Examples of drying methods include air blow drying.

[0056] [Manufacturing methods for electronic components] This disclosure relates, in one embodiment, to a method for manufacturing electronic components (hereinafter also referred to as the "electronic component manufacturing method of this disclosure"), including the cleaning method of this disclosure. The electronic component manufacturing method of this disclosure is a method for manufacturing electronic components that, in one or more embodiments, includes a step (hereinafter also referred to as the "cleaning step") of cleaning a substrate (object to be cleaned) having a copper-containing metal layer and a resin mask on its surface using the cleaning method of this disclosure. The cleaning method in the cleaning step may be the same as the cleaning method of this disclosure described above. The object to be cleaned may be the object to be cleaned described above. In one or more embodiments, the method for manufacturing electronic components of the present disclosure may include a step of performing at least one of soldering and plating treatments using a resin mask on the electronic component, such as a printed circuit board or a packaged circuit board, before the cleaning step. In one or more embodiments, the method for manufacturing an electronic component of the present disclosure may include a step of etching a copper-containing metal layer after the cleaning step. According to the method for manufacturing electronic components of this disclosure, by using the cleaning method of this disclosure, it is possible to obtain a substrate that reduces residue during cleaning after peeling off the resin mask (improving low residue in post-cleaning performance), thereby enabling the manufacture of highly reliable electronic components. [Examples]

[0057] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited in any way by these examples.

[0058] 1. Preparation of resin mask release solution composition A resin mask release solution composition (pH: 14.0) was prepared by mixing each component shown in Table 1 in the amounts (mass %) and effective content listed in Table 1, and then stirring the mixture. Note that the amount of water in Table 1 includes the amount of water contained in aqueous solutions of hydroxides, etc.

[0059] The following materials were used to prepare the resin mask release solution composition. (Component A) TMAH: Tetramethylammonium hydroxide [Manufactured by Showa Denko Corporation, concentration 25%] (Component B) MEA: Monoethanolamine [Manufactured by Nippon Shokubai Co., Ltd.] (Component C) BDG: Butyl diglycol [manufactured by Nippon Emulsifier Co., Ltd., diethylene glycol monobutyl ether] (Component D) Water [Pure water with a purity of 1 μS / cm or less, produced using the G-10DSTSET pure water system manufactured by Organo Corporation] (Metal corrosion inhibitor) MBT: 2-mercaptobenzothiazole [manufactured by Tokyo Chemical Industry Co., Ltd.]

[0060] [Method for measuring the pH of a resin mask release solution composition] The pH of the resin mask release solution composition at 25°C was measured using a pH meter (Toa Denpa Kogyo Co., Ltd., HM-30G), and the value was obtained 3 minutes after immersing the pH meter electrode in the resin mask release solution composition.

[0061] [Table 1]

[0062] 2. Preparation of the post-washing solution composition Inorganic alkali compounds or acid compounds were diluted with water to prepare the post-cleaning solution compositions for Examples 1-3 and Comparative Example 1, with the compositions shown in Table 2. The amounts (mass %) and effective content of each component in the post-cleaning solution compositions are shown in Table 2. Note that the amount of water in Table 2 includes the amount of water contained in the alkaline aqueous solution or acid aqueous solution.

[0063] The following were used to prepare each post-washing solution composition. (Inorganic alkali compounds) Ammonia water: Ammonia aqueous solution [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., concentration 28%] NaOH: Sodium hydroxide aqueous solution [Manufactured by Ishida Chemical Industries Co., Ltd., concentration 48%] (acid compound) Sulfuric acid: Sulfuric acid aqueous solution [Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., concentration 95%] (Water for dilution) Water [Pure water with a purity of 1 μS / cm or less, produced using the G-10DSTSET pure water system manufactured by Organo Corporation]

[0064] [Method for measuring the pH of a post-wash solution composition] The pH of the post-washing solution composition at 25°C was measured using a pH meter (Toa Denpa Kogyo Co., Ltd., HM-30G), and the value was obtained 3 minutes after immersing the pH meter electrode in the post-washing solution composition.

[0065] [Copper ion concentration in the post-washing solution composition] After preparation, the washing solution compositions were sampled, diluted with water, and the amount of copper ions was measured by ICP analysis (Agilent Technologies, Agilent 5110 ICP-OES). The copper ion content in the washing solution compositions of Examples 1-3 and Comparative Example 1 was 0.1 ppm.

[0066] 3. Evaluation of post-cleanability of Examples 1-3 and Comparative Example 1 Using the test pieces described below, treatment with the prepared stripping solution compositions was carried out according to the procedure below, and the post-cleaning properties of the prepared post-cleaning solution compositions for Examples 1-3 and Comparative Example 1 were evaluated. [Test piece] A test piece (50mm x 50mm) was obtained by electroless plating onto an insulating substrate, consisting of a solid substrate with a copper plating layer (thickness: 3μm) on its surface and a dry film layer on top of it. [Treatment with a stripping solution composition] 2.5 L of the stripping solution composition was prepared and heated to 60°C. This solution was then sprayed for 4 minutes (pressure: 0.03 MPa, spray distance: 80 mm) onto a test piece with copper plating on its surface, while circulating it through a box-type spray cleaning machine equipped with a full-cone nozzle (J020, manufactured by Ikeuchi Co., Ltd.) as the spray nozzle. Finally, the test piece was sprayed with pure water and rinsed for 30 seconds. The treatment using the above-described stripping solution composition is intended for the stripping process in "the process of stripping a resin mask from a substrate having a copper-containing metal layer and a resin mask on its surface" (Step 1). [Post-washing (Step 2)] Test pieces treated with the stripping solution composition were sprayed for 10 seconds (pressure: 0.03 MPa, spray distance: 80 mm) using 2.5 L of the post-cleaning solution composition (temperature: 25°C) described in Examples 1-3 and Comparative Example 1, while circulating in a box-type spray cleaning machine equipped with a full-cone nozzle (J020, manufactured by Ikeuchi Co., Ltd.) as a spray nozzle (post-cleaning). After that, the test pieces were rinsed with pure water for 30 seconds and finally dried with nitrogen blow. The surface elemental concentration (N / Cu ratio) of the dried test pieces was measured using an X-ray photoelectron analyzer (PHI Quantera SXM, ULVAC-PHI, Inc.). A lower N / Cu value indicates less residue adhering to the test piece surface and better post-cleanability. Here, if the N / Cu value is less than 0.3, it is judged to have good post-cleanability and is indicated as "1" in Table 2. If the N / Cu value is 0.3 or higher, it is judged to have poor post-cleanability and is indicated as "0" in Table 2. The results are shown in Table 2.

[0067] [Table 2]

[0068] As shown in Table 2, Examples 1-3, which used an inorganic alkaline compound for post-cleaning, showed superior post-cleaning performance compared to Comparative Example 1, which used an acidic compound for post-cleaning. [Industrial applicability]

[0069] According to this disclosure, a substrate cleaning method is available that can reduce residues during cleaning after peeling off a resin mask from a substrate having a copper-containing metal layer and a resin mask on its surface (improving the low residue retention during post-cleaning). Furthermore, by using the cleaning method of this disclosure, it is possible to improve the performance and reliability of manufactured electronic components and increase the productivity of semiconductor devices.

Claims

1. A method for cleaning a circuit board, comprising the following steps 1 and 2. Step 1: A step of peeling off a resin mask from a substrate having a copper-containing metal layer and a resin mask on its surface using a resin mask peeling solution composition. Step 2: A step in which the substrate processed in Step 1 is washed with an aqueous solution with a pH of 8 or higher.

2. The washing method according to claim 1, wherein the aqueous solution with a pH of 8 or higher used in step 2 contains an inorganic alkaline compound.

3. The washing method according to claim 2, wherein the aqueous solution with a pH of 8 or higher used in step 2 further contains metal ions other than alkali metal ions, and the content of the metal ions is 1 ppb or more and 100 ppm or less.

4. The cleaning method according to claim 1, wherein the resin mask stripping liquid composition used in step 1 contains a metal corrosion inhibitor.

5. The cleaning method according to claim 1, wherein the resin mask stripping liquid composition used in step 1 contains one or more components selected from the group consisting of hydroxide (component A), alkanolamine (component B), organic solvent (component C), and water (component D).

6. The cleaning method according to claim 1, further comprising a step of bringing the substrate processed in step 1 into contact with water between step 1 and step 2.

7. The cleaning method according to claim 1, further comprising the step of bringing the substrate cleaned in step 2 into contact with water after step 2.

8. The cleaning method according to claim 1, wherein step 2 includes spraying an aqueous solution with a pH of 8 or higher onto the substrate treated in step 1.

9. The cleaning method according to claim 1, wherein step 2 is a step prior to the metal seed layer removal step.

10. A method for manufacturing an electronic component, comprising a method for cleaning a substrate according to any one of claims 1 to 9.

11. A cleaning solution for use in step 2 of the method for cleaning a substrate according to any one of claims 1 to 9, It contains an inorganic alkali compound, Furthermore, it contains metal ions other than alkali metal ions, and the content of the said metal ions is 1 ppb or more and 100 ppm or less. A washing solution with a pH of 8 or higher.

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