Method for pre-treating the surface of a substrate

Abstract

A method for pre-treating the surface of a substrate before subsequent electroless copper deposition, comprising: a) a step of preparing a substrate including an active surface on a non-conductive material, wherein the active surface has an activator, and the activator includes a catalytic metal; b) a step of contacting the active surface with a pre-treatment aqueous solution for pre-treatment to obtain a pre-treated surface, wherein the pre-treatment aqueous solution contains or consists of copper ions, an inorganic acid, and a reducing agent, and the pH of the pre-treatment aqueous solution is less than 6, provided that the reducing agent is capable of reducing copper ions at an alkaline pH but not at a pH less than 6; an aqueous stock composition, and its use for preparing a pre-treatment solution for pre-treating a substrate including an active surface on a non-conductive material, wherein the active surface has an activator, and the activator includes a catalytic metal used for subsequent electroless copper deposition onto the pre-treated surface.

Description

Technical Field

[0001] The present invention relates to a method for pretreating the surface of a substrate, an aqueous stock composition, and its use for preparing a pretreatment solution for surface pretreatment. The method is particularly suitable for use in the electroless deposition of copper onto a subsequently pretreated surface.

Background Art

[0002] The wet chemical deposition of a metal or metal alloy layer onto a surface has been customary in the art for many years. This wet chemical deposition can be achieved by electrolytic or electroless plating of the metal. Electroless plating is the controlled autocatalytic deposition of a continuous film of metal without the assistance of an external supply of electrons. In contrast, electrolytic plating requires such an external supply of electrons. These methods are very important in the electronics industry and are used, among other applications, in the manufacture of printed circuit boards, semiconductor devices, and similar articles.

[0003] In the manufacture of printed wiring boards (PCBs), an electroless copper plating bath is used to deposit copper onto an active surface having structures such as through-holes and circuit paths, for example, as a base for subsequent electrolytic copper plating. Activation can be performed by a catalytic metal, for example, in the form of palladium particles or palladium-based colloids. Surface activation is necessary to make non-conductive surfaces susceptible to the influence of a catalytic metal for subsequent electroless metal plating. The electroless metal plating is used, for example, for the deposition of copper as a base for further electroless or electrolytic plating of copper, nickel, gold, silver, and other metals as required. A typical electroless copper plating bath contains a copper compound, a complexing agent for copper ions, a reducing agent, and various additional compounds that make the bath more stable, regulate the plating rate, and / or enhance the gloss of the copper deposit.

[0004] JP2015147987A relates to electroless copper plating on a non-electrically conductive substrate material, and more particularly to an electroless copper plating method in which catalyst supply is performed as a pretreatment instead of using an aqueous copper colloidal catalyst solution and palladium, which is commonly used for activation. After this pretreatment, a further electroless copper plating solution is applied to the first copper catalyst layer.

[0005] EP 3 578 683 B1 relates to an electroless copper plating bath for depositing at least a copper or copper alloy layer on the surface of a substrate, a method for depositing at least a copper or copper alloy layer on the surface of a substrate using the electroless plating bath, and a kit of parts for providing the electroless copper plating bath of the invention.

[0006] While many such electroless plating compositions have been successfully used, the metallization industry still has a need to improve electroless copper plating to provide a uniform plating layer for subsequent plating processes and to avoid the formation of voids in through-holes and circuit paths. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] JP2015147987A [Patent Document 2] EP 3 578 683 B1 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Therefore, an object of the present invention is to provide a means for improving the surface of a substrate for use in subsequent improved electroless copper plating, which results in a uniform plating result on the surface.

[0009] Furthermore, an object of the present invention is to improve the surface of a substrate in terms of homogeneity and / or efficiency, so that it can be used for subsequent electroless copper deposition after the activation of the surface of the object to be treated.

[0010] Another object of the present invention is to provide a means for pre-treating a surface before subsequent electroless copper deposition. Therefore, when the surface is treated with an electroless metal plating bath, the metal or metal alloy coating is not left incomplete and is therefore satisfactory.

[0011] Another objective is to improve subsequent electroless copper plating by avoiding copper ion depletion, particularly at the start of the subsequent electroless copper deposition, thereby enabling an improved copper coating of the subsequent electroless copper deposition layer. In particular, it is to provide a surface pretreatment method for obtaining surface structures such as through-holes and circuit boards in which the number of voids is reduced, especially after pretreatment, when copper is deposited on the surface of the substrate. [Means for solving the problem]

[0012] The present invention solves the problems of the prior art and provides, according to an independent claim, a method for pre-treating the surface of a substrate, an aqueous stock composition, and the use of an aqueous stock composition for preparing a pre-treatment solution for pre-treating a surface before subsequent electroless copper deposition of copper onto a pre-treated surface.

[0013] In this regard, the present invention, in a first embodiment, is a method for pre-treating the surface of a substrate to be used for subsequent electroless copper deposition, a) A step of preparing a substrate containing an active surface on a non-conductive material, wherein the active surface contains an activator, and the activator contains a catalytic metal; b) A step of obtaining a pre-treated surface by contacting the active surface with a pre-treatment aqueous solution for pretreatment, wherein the pre-treatment aqueous solution is - Copper ions, preferably Cu 2+ ion, - Inorganic acids, preferably sulfuric acid or hydrochloric acid, and - Reducing agent, preferably formaldehyde Includes or consists of The pH of the pretreatment aqueous solution is less than 6, preferably 1 to 5. However, provided is a method including a step on the condition that the reducing agent can reduce copper ions at an alkaline pH but cannot reduce copper ions at a pH less than 6.

[0014] In a further aspect, the present invention is an aqueous stock composition for preparing a pretreatment solution for pretreatment of a substrate including an active surface on a non-conductive material, wherein the active surface has an activator, and the activator - copper ions having a concentration of 700 to 900 mmol / L, preferably Cu 2+ ions, - an inorganic acid having a concentration of 100 to 600 mmol / L, preferably 200 to 400 mmol / L, preferably selected from sulfuric acid or hydrochloric acid, - optionally, a reducing agent having a concentration of 700 to 3300 mmol / L, preferably formaldehyde contains or consists of these, and preferably contains a catalytic metal used for subsequent electroless copper deposition, the pH of the aqueous stock composition is less than 6; However, provided is an aqueous stock composition on the condition that an optional reducing agent can reduce copper ions at an alkaline pH but cannot reduce copper ions at a pH less than 6.

[0015] In still a further aspect, the present invention relates to the use of the above aqueous stock composition for preparing a pretreatment solution for pretreatment of a substrate including an active surface on a non-conductive material, wherein the active surface has an activator, and the activator preferably contains a catalytic metal used for subsequent electroless deposition of copper on the pretreated surface.

[0016] The features will become apparent to those skilled in the art by describing exemplary embodiments in detail with reference to the accompanying drawings.

Brief Description of the Drawings

[0017] [Figure 1] It is an image showing the result of the copper plating experiment after pretreatment of the present invention.

Mode for Carrying Out the Invention

[0018] The terms “electroless copper deposition bath”, “electroless copper plating bath”, and “aqueous electroless copper deposition bath” have the same meaning unless otherwise stated.

[0019] In the following description of embodiments of the present invention, singular terms may include the plural unless the context clearly indicates otherwise.

[0020] The pretreatment aqueous solution is intended to pretreat the active surface of the substrate before applying the subsequent electroless copper deposition process in order to enhance the formation of the subsequent plated copper layer deposited from the electroless copper deposition bath. Therefore, the pretreatment aqueous solution is also referred to as an “enhancing solution”. Both terms are used in this description.

[0021] By the method of the present invention, it is possible to improve the copper coating of the subsequent electroless deposited copper layer on the activated and pretreated surface of the substrate, and the number of voids in the surface structure, particularly through-holes and circuit paths after pretreatment, when copper is deposited on the surface, is reduced.

[0022] Although not wishing to be bound by theory, during normal electroless copper deposition without pretreatment, the amount of copper ions reduced on the surface of the substrate and / or in the immediate vicinity of the surface is considered to be depleted at the start of electroless copper deposition. As a result, the plating layer becomes non-uniform, and voids occur in the surface structure, particularly through-holes and circuit paths.

[0023] Surprisingly, by contacting the activated surface with the pretreatment aqueous solution of the present invention, it was found that at least copper ions and a reducing agent were deposited on the resulting pretreatment surface. Due to the acidic pH, the reduction of copper ions did not begin at this point, and the pretreatment surface was prepared for further treatment. In other words, the reducing agent can reduce copper ions in an alkaline environment, but if this is the main or only difference in the solution composition, it cannot reduce copper ions at a pH of less than 6, preferably less than 5, more preferably in the pH range of 1 to 5, most preferably less than 2, or in the pH range of 1 to 2. Therefore, by contacting the resulting pretreatment surface with the subsequently applied alkaline electroless copper plating bath, the aforementioned problem can be overcome, and the reducing agent on the pretreatment surface becomes active.

[0024] The pretreatment aqueous solution preferably does not contain nickel ions or cobalt ions that have been intentionally added as functional compounds. In this context, intentionally added compounds mean that the compound is not added as a required compound in the solution, and if present due to being drawn in from another source, the compound does not have a functional effect on the pretreatment solution.

[0025] The pre-treated aqueous solution also preferably does not contain any further organic additives such as wetting agents, surfactants, or stabilizers, in addition to the reducing agent mentioned, which may be an organic reducing agent, and an optional complexing agent, which may be an organic complexing agent.

[0026] In a preferred embodiment of the present invention, the pretreatment aqueous solution used in this method consists of copper ions, an inorganic acid for pH adjustment, and a reducing agent, wherein the pH of the pretreatment aqueous solution for obtaining the pretreated surface is less than 6; provided that the reducing agent is capable of reducing copper ions at an alkaline pH but not at a pH less than 6.

[0027] The substrate is preferably a substrate whose surface has a structure such as through-holes and circuitry, or a substrate whose surface at least a portion of the surface is metallized with a copper layer. The substrate is preferably a substrate for manufacturing integrated circuits (IC substrate) or a substrate for manufacturing printed circuit boards (printed circuit board material).

[0028] The surface of the substrate to be treated with the pretreatment solution of the present invention includes an active surface on a non-conductive material, the surface having an activator thereon, the activator containing or being a catalytic metal such as copper, silver, gold, palladium, platinum, rhodium, cobalt, ruthenium, iridium in the form of a pure metal or a mixed metal colloid, preferably the activator contains a palladium colloid. The active surface after activation with the catalytic metal usually becomes a metal spot with an island-like structure rather than a separate metal layer on the surface of the substrate. During activation, it is possible to sensitize the substrate before the deposition of the metal or metal alloy onto the substrate. This can be achieved by the adsorption of the catalytic metal onto the surface of the substrate.

[0029] In this context, "pure" means that only one type of metal forms the metal colloid. Alternatively, "pure" means that the metal content of the catalyst metal is at least 98 wt%, and more preferably at least 99 wt%.

[0030] The substrate comprises a non-conductive (insulating) material, preferably a non-metallic material, more preferably a plastic and / or resin. The resins and plastics include insulating materials typically used in the electronics industry, which are metallized. The resins and plastics are preferably selected from epoxy, e.g., epoxy resins, isocyanate resins, bismaleimidotriazine resins, and phenylene resins; polyester, e.g., polyethylene terephthalate (PET), polyimide (PI), polytetrafluoroethylene, acrylonitrile-butadiene-styrene (ABS) copolymer, polyamide (PA), polycarbonate (PC), and mixtures and blends of the aforementioned.

[0031] The organic polymer more preferably comprises a polyimide resin or an epoxy resin, and the polyimide resin may be modified by the addition of polysiloxane, polycarbonate, polyester, etc. The epoxy resin may be a glass-filled epoxy substrate material comprising a combination of epoxy resin and glass filler, or a high glass transition temperature glass-filled epoxy substrate material, which has been modified to have low thermal expansion and a high glass transition temperature.

[0032] The organic polymer may include fillers, such as glass fillers or silica fillers. Preferred glass fillers are preferably selected from borosilicate glass, quartz glass, silica glass, and fluoride glass. The sizes of the different fillers range from 0.01 μm to 5 μm in diameter, and preferably the average diameter is 0.5 μm.

[0033] This method can be used in vertical and horizontal plating apparatuses. Preferably, this method is used in a vertical plating apparatus, where the substrate is transported by a transport device and processed through the processing module of the plating apparatus.

[0034] The copper ion of the present invention, preferably Cu 2+ The ions can be obtained from any suitable water-soluble copper salt. Non-limiting examples include copper sulfate or copper chloride.

[0035] The concentration of copper ions in the pretreatment solution is preferably 20 to 270 mmol / L, more preferably 30 to 135 mmol / L, and most preferably 55 to 75 mmol / L.

[0036] The concentration of the inorganic acid is preferably 10 to 100 mmol / L, more preferably 20 to 50 mmol / L.

[0037] The inorganic acid is preferably selected from sulfuric acid or hydrochloric acid, more preferably from sulfuric acid.

[0038] In a preferred embodiment, the inorganic acid is sulfuric acid having a concentration of 10 to 100 mmol / L (relative to 50% by mass of aqueously diluted sulfuric acid in a completely diluted solution).

[0039] The pH of the pretreatment aqueous solution is preferably 1 to 5, more preferably 1 to 4, and most preferably 1 to 2.

[0040] In one embodiment, an organic acid, preferably an alkanoic acid, more preferably formic acid, may be further added to the pretreatment aqueous solution. The organic acid preferably has a concentration of 10 to 100 mmol / L.

[0041] In one embodiment of the pretreatment solution used, the reducing agent capable of reducing copper ions at an alkaline pH but not at a pH below 6 is selected from glyoxylic acid and / or formaldehyde. Preferably, the reducing agent is formaldehyde. Preferably, when formaldehyde is used, the pH is 1 to 5, more preferably 1 to 2.

[0042] The concentration of the reducing agent in the pretreatment solution is preferably 80 to 320 mmol / L, more preferably 120 to 280 mmol / L.

[0043] The pretreatment solution preferably contains a complexing agent suitable for complexing copper ions in the pretreatment solution, preferably Cu 2+ It contains a complexing agent suitable for complexing ions.

[0044] While complexing agents in the pretreatment solution are not strictly necessary, they can improve plating performance and efficiency. The complexing agent preferably has a concentration of 4-60 mmol / L.

[0045] In one embodiment, the complexing agent is preferably selected from ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), (ethylenedinitrile)-tetra-2-propanol (also known as Quadrol), and (2R,3R,4S)-pentane-1,2,3,4,5-pentol (also known as xylitol), and tartaric acid. In a preferred embodiment, the complexing agent is tartaric acid.

[0046] The following specific examples of pretreatment solutions have proven particularly effective in avoiding voids in the subsequently deposited copper layer.

[0047] In one embodiment, in the pretreatment solution, - Cu 2+ The concentration is 20-270 mmol / L; - The concentration of the reducing agent is 80-320 mmol / L; - If present, the concentration of the optional complexing agent used, preferably tartaric acid, is 4-60 mmol / L, and the pH is adjusted to less than 6 by an inorganic acid.

[0048] A preferred concentration of an inorganic acid, preferably sulfuric acid, that can be combined with the aforementioned concentration range is 10 to 100 mmol / L, more preferably 20 to 50 mmol / L.

[0049] A preferred concentration of hydrochloric acid that can be combined with these concentration ranges is 10–100 mmol / L.

[0050] In a preferred embodiment, in the pretreatment solution, - Cu 2+ The concentration is 30-135 mmol / L; - The concentration of the reducing agent is 80-320 mmol / L; - If present, the concentration of the optional complexing agent used, preferably tartaric acid, is 7-30 mmol / L, and the pH is adjusted to less than 6 by an inorganic acid.

[0051] A preferred concentration of sulfuric acid that can be combined with these concentration ranges mentioned above is preferably 20 to 50 mmol / L.

[0052] In one embodiment of the pretreatment solution, the pH of the pretreatment solution is adjusted to 1-5, preferably 1-4, and more preferably 1-2.

[0053] Pretreatment of the surface with a pretreatment solution can be carried out by various methods, such as immersion or rinsing, without limitation. Pretreatment of the surface with a pretreatment solution is preferably carried out by immersing the surface in the pretreatment solution. The preferred immersion time is 0.5 to 3 minutes. The temperature of the pretreatment solution is preferably in the range of 20 to 35°C.

[0054] The method of the present invention is preferably suitable for subsequent electroless copper deposition using an alkaline electroless copper plating bath, and preferably the electroless copper plating bath is applied directly after obtaining a pre-treated surface in step b).

[0055] Therefore, in one embodiment, the method of the present invention further includes the step of pre-treating the surface with a pre-treatment solution, and then electrolessly depositing copper onto the pre-treated surface to obtain an electroless spectrometry-deposited copper surface. Preferably, the electroless spectrometry is performed after surface pre-treatment without any intermediate rinsing steps. It has been found that avoiding intermediate rinsing steps reduces the number of voids in the deposited metal layer.

[0056] After obtaining a copper surface by electroless copper deposition on a pre-treated surface, this method preferably further includes electrolytic copper deposition.

[0057] If the method includes surface pretreatment and subsequent copper deposition, it may be called a pretreatment and copper deposition method, or simply a method for copper deposition.

[0058] In one embodiment, after pretreatment, electroless metallization is performed using an aqueous electroless copper deposition bath for the electroless extraction of copper, and the bath contains copper ions, preferably Cu 2+The bath contains ions, complexing agents such as tartaric acid, and reducing agents such as formaldehyde, and the pH of the bath is 9 to 14, preferably >10, more preferably 11 to 14, and most preferably 13 to 14. This pH range can be achieved by the presence of an appropriate amount of NaOH or KOH. An appropriate amount means an amount suitable for achieving the desired pH. The electroless copper deposition bath may or may not contain nickel ions. Suitable electroless copper plating bath compositions are Printoganth MV TP2 and MV Plus, which can be purchased from Atotech Deutschland GmbH & Co. KG. The concentration of copper ions in this electroless copper bath composition is preferably in the range of 1 g / l to 10 g / L, more preferably 2 g / l to 5 g / l. Thus, at least one reducing agent can convert copper(I) ions and / or copper(II) ions present in this composition into elemental copper. The concentration of at least one reducing agent in the electroless copper bath used is preferably in the range of 0.02 mol / l to 0.3 mol / l, more preferably 0.054 mol / l to 0.2 mol / l, and even more preferably 0.1 mol / l to 0.2 mol / l. Preferably, the electroless copper bath contains at least one complexing agent for copper ions, such as a hydroxycarboxylic acid such as tartaric acid. Preferably, the concentration of the complexing agent is in the range of 0.004 mol / l to 1.5 mol / l, more preferably 0.02 mol / l to 0.6 mol / l, and even more preferably 0.04 mol / l to 0.4 mol / l.

[0059] In this embodiment, the pretreatment solution (enhancement solution) used in the pretreatment by the method of the present invention has the same components as the following bath for electrolytic extraction of copper, Cu 2+ The solution contains an inorganic acid and a reducing agent. If the pretreatment solution contains a complexing agent, preferably the same complexing agent used in the bath for electroless copper deposition is used. A preferred complexing agent is tartaric acid. The difference between the pretreatment solution and the bath for electroless copper deposition (also called an electroless copper plating bath) is that i) the bath for electroless copper deposition contains further organic additives known for such baths, and ii) the pretreatment solution has a lower (acidic) pH than the alkaline bath for electroless deposition.

[0060] Our experiments have shown that not all reducing agents can reduce copper ions to metallic copper in solutions with a pH of less than 6. In other words, if the reducing agent is, for example, formaldehyde and / or glyoxylic acid, copper ions are not reduced in such solutions with a pH of less than 6.

[0061] Generally, electroless alkaline copper plating baths used contain stabilizers, solvents, wetting agents, and further optional components such as functional additives, e.g., brighteners, accelerators, inhibitors, and anti-coloring agents. Such baths and components are known in the art.

[0062] The electroless copper plating bath may further include a source of nickel ions, a source of cobalt ions, and mixtures thereof, while the pretreatment solution does not contain any nickel ions, cobalt ions, or mixtures thereof.

[0063] In one embodiment, the method of the present invention includes a further pretreatment step before the step of obtaining the active surface by pretreatment of a substrate containing an active surface on a non-conductive material with a pretreatment solution, wherein the active surface contains an activator, the activator contains a catalyst metal, and the pretreatment step is - An optional step (i) of treating the surface with an aqueous solution of an alkaline cleaning agent containing ethanolamine; - Step (ii) of treating the surface of step (i) with an aqueous etching cleaning agent containing persulfate; - An optional step (iii) in which the surface of step (ii) is treated with a pre-immersion solution; - Preferably, the surface of step (iii) is treated (iv) with an activating solution containing a catalyst metal, such as copper, silver, gold, palladium, platinum, rhodium, cobalt, ruthenium, or iridium, in the form of a pure metal or a mixed metal colloid; and - If the activator solution contains metal ions, step (v) is performed by treating the surface of step (iv) with the reducer solution. It includes them in this order.

[0064] Step (i) is preferably carried out at 50°C to 70°C for 3 to 7 minutes. In a preferred embodiment, the detergent comprises 10 to 20 g / L of sodium hydroxide and 10 to 16 g / L of ethanolamine (MEA).

[0065] Step (ii) is preferably carried out at 25°C to 40°C for 1 to 2 minutes. In a preferred embodiment, the detergent contains 100 to 150 g / L of sodium persulfate and 30 to 45 g / L of sulfuric acid.

[0066] An optional step (iii) in which the surface of step (ii) is treated with a pre-immersion solution. The pre-immersion solution preferably comprises a pH adjuster, preferably sulfuric acid and / or sodium bisulfate, and a nonionic surfactant, preferably a polyethylene glycol (PEG) compound, more preferably PEG 1500 MW or PEG 10,000 MW.

[0067] The pre-immersion solution can be acidic or alkaline.

[0068] Preferably, step (iv) treats the surface of step (iii) with an activator solution containing a metal, metal colloid, or metal ions containing the compound. The activator solution is applied to the surface of the nonconductive layer, preferably the surface is treated with a palladium activator solution, and a palladium ion layer is deposited on the surface of the nonconductive layer of step (iv). Other useful activator solutions known in the art may include metal colloids containing copper, nickel, and alloys such as palladium-tin.

[0069] The palladium activator solution contains at least one source of palladium ions. Furthermore, the solution may also contain sources of other metal ions, such as sources of ruthenium ions, rhodium ions, palladium ions, osmium ions, iridium ions, platinum ions, copper ions, silver ions, nickel ions, cobalt ions, gold ions, and mixtures thereof. The palladium ions and the further metal ions are adsorbed on the surface of the substrate.

[0070] (v) The process of treating the substrate in step (iv) is carried out with a palladium reducing solution if a palladium activator solution is used, and the palladium ion layer precipitated in step (iv) is converted into a metallic palladium layer.

[0071] The step of treating the surface of a substrate containing at least palladium ions is carried out in a solution containing at least one reducing agent selected from the group consisting of boron-based reducing agents, a source of hypophosphate ions, hydrazine and hydrazine derivatives, ascorbic acid, isoascorbic acid, a source of formaldehyde, glyoxylic acid, a source of glyoxylic acid, glycolic acid, formic acid, sugars, and salts of the aforementioned acids, which is suitable for reducing metal ions adsorbed on the surface of the substrate to a metallic state (at least palladium ions).

[0072] Further optional steps of the method of the present invention are one or more cleaning steps, in particular a desmear process known in the art.

[0073] The following embodiments relate to aqueous stock compositions of the present invention. The aqueous stock compositions are intended to be used to prepare pretreatment solutions for pretreatment of a substrate comprising an active surface on a nonconductive material, wherein the active surface has an activator, and the activator comprises a catalytic metal.

[0074] In one embodiment, the aqueous stock composition is prepared in the amounts listed below.

[0075] Aqueous stock composition, 15-50 g / L (calculated based on 96% mass of H2SO4), preferably 20-35 g / L. 100-400 g / L of CuSO4x 5H2O, and Optionally, 13 to 55 g / L of a complexing agent, preferably tartaric acid. Includes or consists of The pH of the aqueous stock composition is less than 6.

[0076] A reducing agent capable of reducing copper ions at an alkaline pH but not at a pH below 6 may be added to an aqueous stock composition, or may be provided separately for preparing a pretreatment solution for pretreatment of the substrate surface prior to subsequent electroless copper deposition. When the reducing agent is added directly to the aqueous stock composition, the added reducing agent, preferably formaldehyde and / or glyoxylic acid, more preferably formaldehyde, has a final concentration of 25 to 120 g / L in the aqueous stock composition. When the reducing agent is added separately to a pretreatment solution for pretreatment of the substrate surface prior to subsequent electroless copper deposition, the concentration of the reducing agent in the reducing agent stock solution is 25 to 120 g / L and is diluted in the same way as the aqueous stock composition for preparing the pretreatment solution for pretreatment of the substrate surface prior to subsequent electroless copper deposition.

[0077] The following embodiments relate to the use of the aqueous stock composition of the present invention for preparing a pretreatment solution for pretreatment of the activated surface of a substrate used for subsequent electrolytic copper emission of copper onto an activated and pretreated surface. The aqueous stock composition of the present invention is also called a “reinforced stock solution”.

[0078] In one embodiment, the stock aqueous solution is diluted with water when preparing the pretreatment solution. A preferred dilution ratio is in the range of 6 to 24, preferably 6 to 12. The pH is controlled to be less than 6, preferably 1 to 5, most preferably 1 to 2.

[0079] In one embodiment, a reducing agent, preferably formaldehyde, is added when preparing the pretreatment solution. Preferably, the reducing agent is supplied into the reducing agent stock composition. Both the aqueous stock composition and the reducing agent stock composition can be mixed and then diluted. The dilution ratio of the resulting stock composition is the quotient between the final volume obtained (volume of aqueous stock composition, and optionally volume of reducing agent stock composition, and volume of added water) and the volume used of the aqueous stock composition and optionally volume of the reducing agent stock composition. For example, if the final volume is 1000 ml and the volume used of the aqueous stock composition (including the reducing agent) is 85 ml, the dilution ratio is 1000 / 85 = 11.8.

[0080] The present invention will be illustrated below with reference to the following drawings and non-limiting embodiments. [Examples]

[0081] 1. Preparation of stock solution An aqueous stock composition having the following components and concentrations was prepared. The components were diluted with deionized water.

[0082] Aqueous stock composition

[0083] [Table 1]

[0084] Reducing agent stock composition

[0085] [Table 2]

[0086] The final pH was less than 2.

[0087] 2. Preparation of pretreatment solution The above stock composition was diluted with deionized water to prepare a pretreatment solution. The pH was less than 2.

[0088] 2.1 Pretreatment solution 1: 85 ml of aqueous stock composition and 15 ml of formaldehyde stock solution were diluted with water to a final volume of 1000 ml. The pH was approximately 1.

[0089] 2.2 Pretreatment solution 2: 170 ml of stock aqueous solution and 30 ml of formaldehyde stock solution were diluted with water to a final volume of 1000 ml. The pH was approximately 1.

[0090] 2.2 Pretreatment solution 3: 42.5 ml of stock aqueous solution and 7.5 ml of formaldehyde stock solution were diluted with water to a final volume of 1000 ml. The pH was approximately 2.5.

[0091] The concentration in mmol / L is half the concentration of each component compared to pretreatment solution 1.

[0092] 3. Plating experiment First, the substrate surface of each substrate was treated in the following order with a cleaning solution, etching cleaning solution, pre-immersion solution, activator solution, and reducer solution, with an intermediate rinsing step. Details are shown in the table below. The substrate was immersed in each of the solutions.

[0093] Next, the surface was treated with the different pretreatment solutions 1 / 2 / 3 prepared in Example 2, and without any pretreatment solution. The substrate was immersed in each of the pretreatment solutions.

[0094] The surface was metallized with copper by immersion in an electroless copper bath, both after and without pretreatment, without an intermediate rinsing step.

[0095] [Table 3]

[0096] The following substrates were used a) Sample "60" (60 μm × 60 μm VIA) b) Sample "75" (75 μm × 75 μm VIA)

[0097] Figure 1 shows the results of plating experiments using different substrates and different pretreatment solutions.

[0098] For both substrates, the best results in minimizing voids after copper plating were obtained with pretreatment solution 1, which was prepared by diluting 85 ml of the stock composition of Example 1 and 15 ml of the formaldehyde stock composition (28 wt%) with water to a final volume of 1000 ml. The results for pretreatment solution 1 are shown in column 1 / "POR Reinforcer" for each substrate.

[0099] With no pretreatment (column 2 / "w / o strengthening agent") and pretreatment solution 3 (column 3 / "half-concentration strengthening agent"), the void density is significantly higher.

[0100] In substrate a) ("60"), good results were also obtained with pretreatment solution 2 (row 4 / "double the amount of reinforcing agent"), which may be due to the smoother surface of substrate b) ("sample 75") and the fact that other dimensions of VIAs (vertical interconnects) may lead to better solution exchange.

Claims

1. A method for pre-treating the surface of a substrate, a) A step of preparing a substrate including an active surface on a non-conductive material, wherein the active surface has an activator, and the activator includes a catalytic metal; b) A step of obtaining a pre-treated surface by contacting the active surface with a pre-treatment aqueous solution for pretreatment, wherein the pre-treatment aqueous solution is - Copper ions, - Inorganic acids, and - Reducing agent This includes or consists of these: The pH of the aforementioned pretreatment aqueous solution is less than 6. However, the reducing agent is capable of reducing copper ions at an alkaline pH, but is not capable of reducing copper ions at a pH of less than 6. Methods that include...

2. The method according to claim 1, wherein the pretreatment solution contains a complexing agent suitable for complexing copper ions in the pretreatment solution.

3. The method according to claim 2, wherein the complexing agent has a concentration of 4 to 60 mmol / L.

4. In the aforementioned pretreatment solution, - The concentration of copper ions is 20 to 270 mmol / L, preferably 30 to 135 mmol / L, more preferably 55 to 75 mmol / L. - The concentration of the reducing agent is 80 to 320 mmol / L. The method according to claim 1 or 2.

5. The method according to any one of claims 1 to 4, wherein the inorganic acid has a concentration of 10 to 100 mmol / L, more preferably 20 to 50 mmol / L.

6. The method according to any one of claims 1 to 5, further comprising the step of electrolessly depositing copper onto the pre-treated surface to obtain an electroless copper-deposited surface.

7. The method according to claim 5, wherein electroless copper deposition is performed directly after surface pretreatment without any intermediate steps such as rinsing or drying of the pretreated surface.

8. The electroless copper deposition is carried out using an aqueous electroless copper deposition bath, and the bath contains copper ions, preferably Cu 2+ The method according to claim 5 or 6, comprising ions, a complexing agent, and a reducing agent, wherein the pH of the bath is 9 to 14, preferably 13 to 14.

9. The method according to any one of claims 1 to 8, wherein the catalyst metal is copper, silver, gold, palladium, platinum, rhodium, cobalt, ruthenium, or iridium in the form of a pure metal or a mixed metal colloid.

10. The process includes a further pretreatment step before the step of pretreatment of the surface, preferably a non-conductive surface, with the further pretreatment step being: - An optional step (i) of treating the surface with an aqueous solution of an alkaline cleaning agent containing ethanolamine; - Step (ii) of treating the surface of step (i) with an aqueous etching cleaning agent containing persulfate; - An optional step (iii) in which the surface of step (ii) is treated with a pre-immersion solution; - Preferably, step (iv) of treating the surface of step (iii) with an activator solution containing a catalyst metal, a mixed metal colloid, or metal ions; and - If the activator solution contains noble metal ions, step (v) is performed by treating the surface of step (iv) with a reducer solution. The method according to any one of claims 1 to 9, comprising or consisting of in this order.

11. The method according to any one of claims 1 to 10, wherein the pretreatment solution does not contain intentionally added nickel ions and cobalt ions.

12. An aqueous stock composition for preparing a pretreatment solution for pretreatment of a substrate containing an active surface on a nonconductive material, wherein the active surface has an activator, and the activator is - Copper ions having a concentration of 700 to 900 mmol / L, preferably Cu 2+ ion, - An inorganic acid having a concentration of 100 to 600 mmol / L, preferably 200 to 400 mmol / L, preferably selected from sulfuric acid or hydrochloric acid. - Optionally, a reducing agent having a concentration of 700 to 3300 mmol / l, preferably formaldehyde. A catalyst metal comprising or consisting of these, The pH of the aqueous stock composition is less than 6; An aqueous stock composition, provided that the optionally selected reducing agent is capable of reducing copper ions at an alkaline pH, but is not capable of reducing copper ions at a pH of less than 6.

13. In the liquid composition, copper ions, preferably Cu 2+ The aqueous stock composition according to claim 12, further comprising a complexing agent suitable for complexing ions, preferably 160 to 200 mmol / L of tartaric acid.

14. Use of the aqueous stock composition according to claim 12 or 13 for preparing a pretreatment solution for pretreatment of a substrate having an active surface on a nonconductive material, wherein the active surface has an activator, and the activator includes a catalytic metal, as specified in any one of claims 1 to 11.

15. The use according to any one of claims 12 to 14, wherein the reducing agent is preferably formaldehyde and / or glyoxylic acid, and is added when preparing the pretreatment solution.

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