JP6388910B2 - Electroless copper plating solution - Google Patents

Description

  The present invention relates to an electroless copper plating solution, a method of electroless copper plating using the electroless copper plating solution, and the use of the electroless copper plating solution for plating a substrate.

  Electroless plating is a controlled autocatalytic deposition of a continuous metal film without the assistance of an external supply of electrons. Non-metallic surfaces can be pretreated to be receptive for deposition or to be catalytic. All parts of the surface or selected parts can be appropriately pretreated. The main components of the electroless copper bath are copper salts, complexing agents, reducing agents, and optional components such as alkaline components and additives such as stabilizers. The complexing agent is used to chelate the copper to be deposited and prevent copper from precipitating out of solution (ie, precipitating as a hydroxide or the like). Copper chelation results in an effective copper state for the reducing agent that converts copper ions into a metallic form.

  Patent Document 1 discloses a composition for electroless deposition of copper. It has copper ions, glyoxylic acid as reducing agent, and complexing agents such as EDTA that can form complexes with copper that are stronger than copper oxalate complexes.

  U.S. Patent No. 6,057,032 teaches an electroless plating bath having a complexing agent such as a water soluble copper compound, glyoxylic acid and EDTA.

  U.S. Patent No. 6,057,031 discloses an electroless bath having a copper ion source, glyoxylic acid or formaldehyde as a reducing agent and EDTA, tartrate or alkanolamine as a complexing agent.

  The performance of the copper plating solution is difficult to predict and strongly depends on its constituents, in particular the complexing and reducing agents and on the molar ratio of the constituents.

US 4,617,205 US7,220,296 US2002 / 0064592

  An object of the present invention is to provide an electroless copper plating solution with improved performance, particularly with improved copper deposition rate. It is a further object of the present invention to provide an electroless copper plating solution for obtaining copper deposits having low roughness.

The present invention
A copper ion source,
-As a reducing agent or source of reducing agent and-as a complexing agent,
i) N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine or a salt thereof and ii) N ′-(2-hydroxyethyl) -ethylenediamine-N, N, N′-triacetic acid or a salt thereof The electroless copper plating solution containing the combination containing these is provided.

  The complexing agent combination may further comprise iii) ethylenediaminetetraacetic acid or a salt thereof.

  N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine is abbreviated below as “Quadroll”, a trademark of BASF Corporation.

  Ethylenediaminetetraacetic acid is referred to below as “EDTA”.

  N '-(2-hydroxyethyl) -ethylenediamine-N, N, N'-triacetic acid is referred to below as "HEDTA".

  In one embodiment, the electroless copper plating solution preferably does not contain cyclohexanediaminetetraacetic acid (CDTA) in the range of 0.1 mM to 5.5M. In other embodiments, the electroless copper plating solution preferably does not contain any CDTA.

  One or more of the above objects are achieved by the electroless copper plating solution of claim 1 (hereinafter abbreviated as “solution”) or by the advantageous embodiments described in the dependent claims and specification. While the copper plating solution of the present invention exhibits improved copper deposition, it is possible to achieve low roughness of the copper surface, which is extremely important for the performance of certain electronic devices. Due to the higher degree of deposition, a better thickness of the copper layer can be achieved in the same process time.

  The solution according to the invention and the method according to the invention are preferably also used for coating printed circuit boards, chip carriers and semiconductor wafers, or for coating other circuit carriers and connection elements. The solution is used in particular for printed circuit boards and chip carriers for plating surfaces, trenches, blind microvias, through-hole vias and similar structures with copper, but also for semiconductor wafers.

  In particular, the solution of the present invention or the method of the present invention can be applied on the surface to equivalent structures in trenches, blind microvias, through-hole vias and printed circuit boards, chips, carriers, wafers and various other connecting elements. Can be used for copper deposition. As used herein, the term “through-hole via” or “through-hole” encompasses all types of through-hole vias, including so-called “through-silicon vias” in silicon wafers.

  Another application for the solutions of the present invention to be used with beneficial effects is that of flat substrates formed from glass, ceramic or plastic, preferably metal coatings on those substrates having a large surface area (Metallization). For example, there are all kinds of displays such as TFT-displays and liquid crystal displays (LCDs). As mentioned above, low roughness of the copper surface can be achieved with the solution of the present invention. This effect is particularly advantageous in display applications because the copper layer is manufactured with good conductivity.

  The electroless copper plating solution of the present invention can be beneficially used for copper deposition on glass substrates, particularly glass substrates having a large surface area such as glass plates. The glass substrate is used in the application of the display as described above, but is not particularly limited. The wet electroless copper deposition on the glass substrate by the solution as described above is beneficial compared to the metal sputtering method that has been used previously. The advantages achievable with wet electroless copper deposition compared to sputtering technology are, among other things, reduced internal stress and bending of the glass substrate, reduced equipment maintenance, effective use of metal, reduced waste, during the manufacturing process In temperature reduction.

  Furthermore, the electroless copper plating solution of the present invention can be beneficially used for plating a glass substrate, particularly a glass plate of a display.

  In any case, general wet electroless deposition usually results in a rougher metal surface than the sputtering method. In the case of display manufacturing, the rough metal surface causes poor switching properties, in particular undesirably prolonged switching times. Therefore, in display manufacturing, it is necessary to prepare a metal layer having a roughness within a range that can be achieved by sputtering. Surprisingly, the electroless copper plating solution of the present invention can prepare a metal layer with a high degree of precipitation and at the same time have a low roughness within the range achieved by the sputtering method.

  More specifically, the substrate for display manufacture is activated by a metal seed layer for subsequent deposition of the metal layer to build the necessary circuits and switching elements. Therefore, the metal seed layer already has future patterns of circuits and switching elements that include small and / or isolated activation regions as well as combinations of small and wider activation regions. Displayed. A high degree of copper deposition on glass substrates, in particular glass substrates with small and / or isolated activation regions, is achieved with the solution according to the invention. In addition, the solution of the present invention is capable of depositing a metal layer with a uniform thickness and at the same time with a high degree of deposition in a small activated region and a wider activated region.

  The solution of the present invention is an aqueous solution. The term “aqueous solution” means that the common liquid medium that is the solvent in the solution is water. In addition, other liquids miscible with water, such as alcohol and other polar organic liquids, can be added.

  Solutions of the present invention can be prepared by dissolving all components in an aqueous liquid medium, preferably water.

The solution contains a copper ion source, eg, any water soluble copper salt. Copper can be added, for example, as copper sulfate, copper chloride, copper nitrate, copper acetate, copper methanesulfonate ((CH ₃ O ₃ S) ₂ Cu), copper hydroxide or hydrates thereof, to which It is not limited.

  The reducing agent works to reduce copper ions and provides metallic copper for plating. Examples of the reducing agent include, but are not limited to, formaldehyde, glyoxylic acid, hypophosphite, hydrazine and borohydride. Preferred reducing agents are formaldehyde and glyoxylic acid.

  The term “reducing agent source” refers to a substance that converts to a reducing agent in solution. The source of the reducing agent is, for example, a reducing agent precursor that is converted into a reducing agent. Examples relating to glyoxylic acid are described below.

  In view of safety, health and environmental requirements, a particularly preferred reducing agent is glyoxylic acid. Formaldehyde is a very important and well-established substance in a general electroless copper plating method, but is classified as a substance having a high possibility of human carcinogenesis. Thus, in one embodiment, the electroless aqueous copper plating solution contains glyoxylic acid or a glyoxylic acid source. In this embodiment, the solution of the present invention does not contain formaldehyde, or the solution of the present invention is, in other words, formaldehyde free.

  The term “glyoxylic acid source” also includes all compounds that can be converted to glyoxylic acid in aqueous solution, eg precursors. A preferred precursor is dichloroacetic acid. Glyoxylic acid is a reducing agent for reducing copper ions to elemental copper. Glyoxylic acid and glyoxylate ions may be present in the aqueous solution. The term “glyoxylic acid” as used herein also includes their salts. The exact nature of the species, acid or salt present depends on the pH of the aqueous solution. The same considerations apply to other weak acids and weak bases.

  In addition to the reducing agents described above, one or more additional reducing agents such as hypophosphorous acid, glycolic acid, formic acid, salts of these acids may be added. The additional reducing agent is preferably an agent that acts as a reducing agent but cannot be used as a sole reducing agent (eg, US 7,220,296, column 4, lines 20-43 and 54- (See line 62). In this sense, further reducing agents are also referred to as “enhancing agents”.

  The electroless copper bath using the reducing agent described above is preferably at a relatively high pH, usually 11-14, preferably 12.5-13.5, potassium hydroxide (KOH), sodium hydroxide (NaOH), It is usually adjusted with lithium hydroxide (LiOH), ammonium hydroxide, or quaternary ammonium hydroxide, such as tetramethylammonium hydroxide (TMAH). Thus, the solution may include a source of hydroxide ions, such as but not limited to one or more of the compounds listed above. For example, if an alkaline pH of the solution is desired, and if the pH is not already in the alkaline range by other components, a hydroxide source is added.

  Preference is given to using potassium hydroxide. When glyoxylic acid is employed as the reducing agent, it is advantageous to use potassium hydroxide because of the high solubility of potassium oxalate. Oxalate anions are formed in solution by oxidation of glyoxylic acid. Therefore, potassium hydroxide is particularly preferred for the stability of the solution of the present invention.

  The solution of the present invention further comprises a mixture of quadrol of complexing agent i) or a salt thereof and HEDTA of complexing agent ii) or a salt thereof. The mixture of the complexing agent i) Quadrol or a salt thereof and the complexing agent ii) HEDTA or a salt thereof may further comprise the complexing agent iii) EDTA or a salt thereof. Adding Quadrol or a salt thereof to complexing agent ii) or a mixture of complexing agent ii) and complexing agent iii) effectively increases copper precipitation. Prior to the invention of the present invention, it was observed that an increase in metal deposition rate was accompanied by an increase in metal surface roughness. Surprisingly, in the present invention, a copper surface having a high copper deposition rate and low roughness is obtained.

  Quadrol, HEDTA or EDTA salts may be any suitable water-soluble salt. The counter ion of the salt of Quadrol, HEDTA or EDTA is preferably selected from alkali metal ions, alkaline earth metal ions and ammonium ions. More preferably, the counter ion of the salt of Quadrol, HEDTA or EDTA is selected from lithium ion, sodium ion, potassium ion, magnesium ion, calcium ion and ammonium ion.

  The solution of the present invention is free of harmful co-metals. The solution of the present invention is particularly free of nickel. Nickel forms a more stable complex than copper with the complexing agent used here. Thus, nickel reduces copper complex formation, adversely affects copper deposition, or prevents copper deposition. In addition, the presence of nickel in the plating bath leads to unwanted nickel deposition that must be specifically avoided in display manufacturing.

  In one embodiment of the solution of the invention, the molar ratio of complexing agent to copper ions is 1: 1 to 10: 1, preferably 1: 1 to 8: 1, with respect to the total molar amount of all complexing agents. More preferably 2: 1 to 8: 1, more preferably 2: 1 to 5: 1, still more preferably 1.5: 1 to 4: 1, most preferably 2: 1 to 4: 1. With respect to the total molar amount of all complexing agents, the molar ratio of complexing agent to copper ions is defined as the ratio of the total molar amount of all complexing agents to the molar amount of copper ions. The total molar amount of all complexing agents means the sum of the individual molar amounts of all complexing agents. “All complexing agents” can be a mixture of complexing agent i) and complexing agent ii) or a complexing agent i), a mixture of complexing agent ii) and complexing agent iii). For example, the amount of complexing agent is also defined as an equivalent amount. One equivalent is the amount of complexing agent that completely complexes the amount of copper ion provided. In the case of Quadrol, HEDTA and EDTA or their salts, 1 equivalent of complexing agent corresponds to a molar ratio of complexing agent to copper ions of 1: 1. In the case of Quadrol, HEDTA and EDTA, a molar ratio of complexing agent to copper ion of 1: 1 to 10: 1 means that the equivalent of complexing agent based on copper is 1 to 10. .

  Lower amounts of complexing agent lead to instability of the plating bath or precipitation does not begin. Higher amounts of complexing agents based on copper not only lead to higher plating bath concentrations, but also reduce plating bath life and lead to instability. Using the ranges indicated above leads to a beneficial combination of high copper deposition rate and low roughness.

  In other embodiments, with respect to the total molar amount of all complexing agents, the molar ratio of complexing agent to copper ions is 3: 1 to 8: 1, preferably 3: 1 to 5: 1, more preferably 3: 1 to 4: 1. Using these ranges leads in particular to a beneficial combination of high copper deposition rate and low roughness. Excellent reproducibility, excellent reproducible copper deposition and a very uniform thickness of the copper layer can be obtained.

  In one embodiment, the ratio of the molar amount of complexing agent i) to the molar amount of complexing agent ii) is from 1: 0.05 to 1:20, preferably from 1: 0.1 to 1:10, more preferably Is 1: 1 to 1: 5, more preferably 1: 1 to 1: 4, most preferably 1: 2 to 1: 4. The ratio of the molar amount of complexing agent i) to the molar amount of the mixture of complexing agent ii) and complexing agent iii) (complexing agent i): [complexing agent ii) + complexing agent iii)]) is 1: 0.05 to 1:20, preferably 1: 0.1 to 1:10, more preferably 1: 1 to 1: 5, more preferably 1: 1 to 1: 4, most preferably 1: 2. ~ 1: 4.

  The molar amount of the mixture of complexing agent ii) and complexing agent iii) ([complexing agent ii) + complexing agent iii)]) is the individual mole of complexing agent ii) and complexing agent iii). The total amount.

  In another embodiment, the ratio of the molar amount of complexing agent i) to the molar amount of complexing agent ii) is 1: 0.05 to 1: 5, preferably 1: 0.05 to 1: 3, more preferably. Is 1: 0: 1 to 1: 2. The ratio of the molar amount of complexing agent i) to the molar amount of the mixture of complexing agent ii) and complexing agent iii) (complexing agent i): [complexing agent ii) + complexing agent iii)]) is The ratio is 1: 0.05 to 1: 5, preferably 1: 0.05 to 1: 3, more preferably 1: 0.1 to 1: 2.

  In another embodiment, the ratio of the molar amount of complexing agent i) to the molar amount of complexing agent ii) is 1: 5 to 1:20, preferably 1: 7 to 1:15, more preferably 1: 7. ~ 1: 10. The ratio of the molar amount of complexing agent i) to the molar amount of the mixture of complexing agent ii) and complexing agent iii) (complexing agent i): [complexing agent ii) + complexing agent iii)]) is 1: 5 to 1:20, preferably 1: 7 to 1:15, more preferably 1: 7 to 1:10.

  Using the ranges indicated above leads to a beneficial combination of high copper deposition rate and low roughness.

  In one embodiment, the electroless aqueous copper plating solution comprises i) N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine (Quadrol) or a salt thereof and ii) N ′ as a complexing agent. Contains a combination comprising-(2-hydroxyethyl) -ethylenediamine-N, N, N'-triacetic acid (HEDTA) or a salt thereof.

  In a further embodiment, the electroless aqueous copper plating solution comprises i) N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine (Quadrol) or a salt thereof, ii) N ′ as a complexing agent. -(2-hydroxyethyl) -ethylenediamine-N, N, N'-triacetic acid (HEDTA) or salt thereof and iii) ethylenediaminetetraacetic acid (EDTA) or salt thereof.

In one embodiment, the solution of the present invention contains the following types of ingredients in the following concentrations:
Copper ion: 1 to 5 g / l (corresponding to 0.016 to 0.079 mol / l), preferably 2.0 to 3.0 g / l;
Reducing agent: 0.027 to 0.270 mol / l, preferably 2 to 20 g / l of glyoxylic acid, or 0.8 to 8.5 g / l of formaldehyde;
Complexing agent (total amount of all complexing agents): 5-50 g / l, preferably 20-40 g / l, more preferably 20-30 g / l.

The solution of the present invention has further components such as additives such as stabilizers, surfactants, rate control additives, fine grain additives, pH buffers, pH adjusters, enhancers. (It is not essential and contained). Such additional components are described, for example, in the following references, which are incorporated herein in their entirety by indicating these references:
US 4,617,205 (especially disclosure of column 6 line 17 to column 7 line 25)
US 7,220,296 (especially disclosure of column 4, line 63 to column 6, line 26)
US 2008/0223253 (see especially paragraph 0033, paragraph 0038).

  Stabilizers are compounds that stabilize the electroless plating solution against unnecessary outplating in the bulk solution. The term “outplating” means undesired and / or uncontrolled copper deposition, for example, at the bottom of the reaction vessel or other surface. The function of stabilization is, for example, a substance that acts as a catalyst poison (for example, a compound containing sulfur or another chalcogenide) or a compound that forms a cuprous complexing agent, that is, a compound that suppresses the formation of cuprous oxide. Fulfilled by.

The solution of the present invention may contain one or more stabilizers. Suitable stabilizers include, but are not limited to, dipyridyl (2,2′-dipyridyl, 4,4′dipyridyl), phenanthroline, mercapto-benzothiazole, thiourea and its derivatives, NaCN, KCN, K ₄ [ Cyanides such as Fe (CN) ₆ ], polymers such as Na ₂ S ₂ O ₃ , K ₂ S ₂ O ₃ , thiocyanate, iodide, ethanolamine, polyacrylamide, polyacrylate, polyethylene glycol or polypropylene glycol , And copolymers thereof.

  In another aspect, the present invention relates to an electroless copper plating method, the method comprising contacting the substrate with the electroless copper plating solution described above.

  For example, the substrate may be dipped or dipped in the solution of the present invention. In the method, the entire surface of the substrate or only selected portions can be plated with copper.

  During use, it is preferred to stir the solution of the present invention. In particular, work-agitation and / or solution agitation can be used.

  The method of the present invention is carried out for a time sufficient to produce the required thickness of deposit, which will depend on the particular application.

  One anticipated application of the method of the present invention is the preparation of printed circuit boards. Electroless deposition of copper based on the method of the present invention is particularly applicable for through-plating of holes, surfaces, trenches, blind microvias in printed circuit boards. By using the present invention, double sided boards or multilayer boards can be plated whether rigid or flexible.

  The method of the present invention is useful for preparing electroless copper deposits having thicknesses in the range of 0.05 μm to 10 μm, preferably in the range of 0.1 μm to 10 μm, 0.1 μm to 5 μm, 0.5 μm to 3 μm. is there. The thickness of the copper layer is measured with a white light interferometer as described in the examples.

  The method of the present invention produces a copper layer having a roughness (expressed as a root mean square roughness parameter) on the substrate of 5 nm to 60 nm, preferably 5 nm to 55 nm, more preferably 10 nm to 45 nm. The resulting roughness is 30% than the method using only complexing agent ii), the method using only complexing agent iii) or the method using only a mixture of complexing agent ii) and complexing agent iii). -60%, preferably 40-50% lower. Here, the term “only” means that no Quadrol is added. The roughness of the copper layer is measured with a white light interferometer as described in the examples.

  The substrates widely used in printed circuit board manufacture are most often epoxy resins or epoxy glass composites. However, other substrates, particularly phenolic resins, polytetrafluoroethylene (PTFE), polyimide, polyphenylene oxide, bismaleimide triazine (BT) resin, cyanate ester and polysulfone can be used.

  Apart from the application of the method in printed circuit board manufacture, it can be found useful for plating substrates made of glass, ceramic or plastic, for example ABS, polycarbonate, polyimide or polyethylene terephthalate.

In another embodiment of the method of the invention, the substrate is a substrate made of glass, ceramic or plastic, preferably a substrate also having a large surface area. A large surface area means an area of at least 1 m ² , preferably at least 3 m ² , more preferably at least 5 m ² . In another embodiment, a wide surface area is preferably ^{1m 2 ~9m} 2, more preferably ^{3m 2 ~9m} 2, more preferably ^{3m 2 ~6m} 2, even more preferably ^{5m 2 ~6m} 2. The substrate preferably has a flat surface. The term “flat” means a roughness (Sq or RMS) of a few nanometers. The preferred roughness is measured as RMS and is 5-30 nm. The roughness measurement method and explanation of the terms “Sq” and “RMS” are given in the examples.

  In a special embodiment, the substrate is a glass substrate, preferably a glass plate. The glass substrate, in particular a glass plate, can be used for the application of TFT displays, for example liquid crystal displays. Therefore, the glass substrate specifically meets specifications used in display applications, such as thickness and smoothness. Preferred glass is alkali-free, for example, alkali-free borosilicate glass.

  The glass substrate can be pretreated, for example with a metal seed, before the method of the invention is carried out. Further details are described below.

  In one embodiment of the method of the invention, the method is carried out in the temperature range of 20-60 ° C, preferably 30-55 ° C. In the present invention, it was shown that when Quadrol is used as a complexing agent in combination with other complexing agents, copper deposition can be performed at a lower temperature than when Quadrol is not used. Despite the low temperature, the deposition rate is higher than in a bath without Quadrol.

  The surface of the substrate, ie the substrate to be plated with copper, in particular a non-metallic surface, is within the scope of the prior art (eg as described in column 8 of US Pat. No. 4,617,205) It may be pretreated by means to be more receptive or autocatalytic for copper deposition. The entire surface or selected portions on the surface can be pretreated. However, pretreatment is not necessary in all cases and depends on the type of substrate and its surface. Within the scope of the pretreatment, it is possible to impart sensitivity to the substrate prior to the deposition of electroless copper on the substrate. This can be achieved by adsorbing a catalytic metal (such as a noble metal, such as palladium) on the surface of the substrate.

  The pretreatment process is highly dependent on parameters such as the substrate, the desired application and the desired properties of the copper surface.

An exemplary and non-limiting pretreatment process, particularly for printed circuit board laminates and other suitable substrates, may have one or more of the following steps:
a) Optionally, clean and condition the substrate to increase adsorption. Cleaners remove organics and other residues. The cleaner may also include additional materials (conditioners) that prepare the surface for the next activation step, i.e., increase the adsorption of the catalyst to a more uniformly activated surface.
b) Etching to remove oxide from the copper surface, especially from the inner layer in the hole. This can be done by persulfate or peroxide based etch systems.
c) Contact with a pre-dip solution such as hydrochloric acid solution or sulfuric acid solution. The pre-dip solution optionally contains an alkali metal salt such as sodium chloride.
d) Contact with an activator solution containing a noble metal, preferably a colloidal or ionic catalyst metal such as palladium, to cause catalysis on the substrate surface. The pre-dip of step c) serves to protect the activator from drag-in and contamination (optionally, especially when the activator contains an ionic catalytic metal).
e) contacting with a reducing agent, wherein the metal ions of the ionic activator are reduced to elemental metals (or when the activator contains a colloidal catalytic metal).
f) contacting with the promoter, in which case the components of the colloid, for example protective colloid, are removed from the catalytic metal.

  In another type of pretreatment process, a permanganate etch step is used. The so-called Desmear process is a multi-stage process that is a swelling step, a permanganate etching step and a reduction step. A swelling agent employed in the swelling step is prepared by mixing an organic solvent. During this process, drill smear and other impurities are removed from the surface of the substrate. A high temperature of 60-80 ° C. promotes penetration of the swelling agent, resulting in a swollen surface. Therefore, a stronger effect of the subsequently applied permanganate solution is possible during the permanganate etching process. Thereafter, the reducing agent solution in the reducing step removes manganese dioxide generated during the permanganate etching step from the surface. The reducing agent solution includes a reducing agent and may optionally include a conditioner.

  The Desmear process can be combined with the above steps. The desmear process can be performed prior to step a) of the pretreatment step described above, or the desmear process can be performed instead of steps a) and b) of the pretreatment step described above.

  In metallization for display applications, and in pretreatment processes that are particularly suitable for metallization of glass substrates, the surface is simply contacted with a predip solution or activator solution, followed by the solution of the present invention. Contacted with. Contact with the cleaning solution and adhesion enhancer prior to the pre-dip step is an optional step that can be performed previously.

  Yet another method often used for glass substrates may be performed in the following step prior to copper plating: the glass surface to be plated has a metal seed layer. The metal seed layer can be brought to the surface by sputtering techniques. A typical seed is a layer composed of copper, molybdenum, titanium, or a mixture thereof. The pretreated glass surface is contacted with an activator solution containing a noble metal, preferably an ionic catalytic metal such as paradymium, which causes catalysis. The ionic catalytic metal is reduced on the surface by the seed metal. In this method, the addition of further reducing agents may be omitted. This method is particularly used for copper plating of glass substrates for display applications.

  A typical pretreatment process, or individual steps thereof, may be combined with alternative pretreatment processes if deemed necessary.

  In a further aspect, the present invention provides a display such as a printed circuit board, wafer, integrated circuit substrate, molded circuit component (MID) component, liquid crystal display or plasma display, in particular a display for electronic devices and TV, a display component, Or the use of an electroless copper plating solution as described above for the plating of plastic parts such as plastic parts for functional or decorative purposes.

The invention is explained in more detail by the following examples. These examples are set forth to illustrate the invention, but should not be construed as limiting the invention.

Figure 3 shows the effect of a combination of Quadrol and a further complexing agent EDTA on the copper thickness and roughness of the plating process. Figure 3 shows the effect of the combination of Quadrol and the further complexing agent HEDTA on the copper thickness and roughness of the plating process.

Roughness measurement method:
Optical roughness meter / white light interferometer (Model MIC-520, ATOS, Germany) is used to measure the thickness of electroless plated copper layer (height difference between reference plate and plating pattern) and surface roughness. used. A white light interferometer is an optical microscope known to those skilled in the art that projects a target area of a sample onto a CCD camera. The interfering objective lens mounted on the internal beam splitter is used to project a highly accurate reference mirror on the CCD camera. To superimpose both images, a spatially resolved fringe image is created to show a high difference image between a very flat reference mirror and the sample of interest. A vertical scanning scheme is used to image samples with a wide altitude distribution, so that the fringe images of the area of interest are as a series of images within different distances of the sample-objective. Visualized. A complete three-dimensional image is created from these data. By using this method, uneven images in the range of 60 μm × 60 μm to 1.2 mm × 1.2 mm can be recorded with vertical resolution in the range of several nanometers (nm).

  The unevenness data is used to measure the surface roughness expressed as the root mean square roughness parameter, abbreviated as Rq or RMS in the surface shape (shape roughness parameter), and Sq in the surface unevenness (area roughness parameter). Abbreviated as The meaning of Rq is the same as the meaning of RMS. Rq has the meaning defined in DIN EN ISO 4287 (German and English version of 1998, Chapter 4.2.2), and Sq is ISO25178-2 (4.1.1) dated April 2012. The meaning defined in Chapter).

  In addition, the unevenness data is also used to calculate the thickness of the plated copper layer based on the height difference between the substrate surface (reference plate) and the surface of the plated metal pattern. To calculate the relief image, layer thickness and surface roughness, an optical roughness meter / white light interferometer (Model MIC-520, ATOS, Germany) with computer software, micromap 123, version 4.0. (Micromap) is installed.

  The measurement form was Focus 560M. The concavo-convex image was measured with an objective lens having a magnification of 10 times and an eyepiece lens having a magnification of 2 times. The concavo-convex image was measured in the range of 312 μm × 312 μm and composed of 480 × 480 points.

Example 1: Combination of Quadrol and further complexing agent Substrate: alkali-free borosilicate glass, 0.7 mm thick, sputtered copper seed layer.
Preprocessing:
1. Alkali cleaner 40 ° C / 1 min2. 2. Rinse with water 3. Sulfuric acid pre-dip solution, room temperature (RT) / 20 seconds 4. Ion Pd activator (exchange reaction of Cu and Pd) RT / 2 minutes Rinsing with water In producing an electroless copper plating solution, a combination of Quadrol / EDTA (comparative example) and a combination of Quadrol / HEDTA (examples of the present invention) were employed as complexing agents. Quadrol was added at 0 g / l, 2.7 g / l and 5.4 g / l, respectively. Cu ²⁺ ions were added as CuSO ₄ ^* 6H ₂ O. The pH of the bath was 13.2 at 21 ° C.

The substrate was contacted with each of the above plating solutions at 45 ° C. for 12 minutes each. The sample of the deposited copper layer was analyzed by the method described in the measurement mode “Focus 560 M”. The results are shown in Table 1 and Table 2 below. 1 and 2 show graphs of the results obtained.
Table 1: Quadrol / EDTA combinations

Table 2: Quadrol / HEDTA combinations

  Residence time means the contact time between the substrate and the electroless copper plating solution.

  The Quadrol / EDTA combination (Table 1, Figure 1) or Quadrol / HEDTA combination (Table 2, Figure 2) has a copper thickness when the same process time is selected compared to EDTA alone or HEDTA alone, respectively. To increase. The addition of Quadrol shows the result that the precipitation rate increases while the roughness of the deposited copper layer is significantly reduced. When Quadrol is added to a solution already contained in HEDTA, the roughness related to the precipitation rate is lower than when Quadrol is added to a solution already contained only in EDTA.

Example 2: Comparative example The substrate used in Example 1 was pretreated in the same manner as in Example 1. The electroless copper plating solution was prepared in the same manner as in Example 1. The copper plating solution contained a combination of complexing agents Quadrol and HEDTA in a molar ratio of 1:20. The total molar amount of the complexing agent was changed based on the molar ratio of copper ions as shown in Table 3. As a stabilizer, a mixture of cyanide and sulfur compound was added.

  Two pretreated substrates (Samples A and B) were contacted with the individual plating solutions described above for 10 minutes each at 45 ° C. A sample of the deposited copper layer was analyzed as in Example 1. The results are shown in Table 3.

Table 3: Various ratios of complexing agents to copper ions

  Both electroless copper plating solutions deposited copper with a high deposition rate, but the roughness of the obtained copper layer was very high. In addition, the electroless copper plating solution was unstable when Quadrol and HEDTA were used in a molar ratio to copper ions of 0.5: 1. When Quadrol and HEDTA were used in a molar ratio to 11: 1 copper ions, the deposited copper layer showed rough growth and swelling.

Claims (14)

-Copper ion source-reducing agent or reducing agent source, and-as a complexing agent,
i) N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine or a salt thereof; ii) N ′-(2-hydroxyethyl) -ethylenediamine-N, N, N′-triacetic acid or a salt thereof And a ratio of the total molar amount of all complexing agents to copper ions is 1: 1 to 10: 1 .   The electroless aqueous copper plating solution according to claim 1, wherein the complexing agent combination further comprises iii) ethylenediaminetetraacetic acid or a salt thereof.   The electroless aqueous copper plating solution according to claim 1 or 2, wherein the ratio of the total molar amount of all complexing agents to copper ions is 1: 1 to 8: 1.   The electroless aqueous copper plating according to any one of claims 1 to 3, wherein the ratio of the molar amount of the complexing agent i) to the molar amount of the complexing agent ii) is from 1: 0.05 to 1:20. solution.   Electroless electrolysis according to claim 2 or 3, wherein the ratio of the molar amount of complexing agent i) to the molar amount of the mixture of complexing agent ii) and complexing agent iii) is from 1: 0.05 to 1:20. Aqueous copper plating solution.   The electroless aqueous copper plating solution according to any one of claims 1 to 5, wherein the reducing agent is selected from glyoxylic acid and formaldehyde.   An electroless copper plating method comprising contacting the substrate with the electroless aqueous copper plating solution according to any one of claims 1 to 6.   The electroless copper plating method according to claim 7, wherein the substrate is a base material made of glass, ceramic, or plastic. Wherein the substrate is a glass board, an electroless copper plating method according to claim 7 or 8. The electroless copper plating method according to claim 7, wherein the substrate has a surface area of at least 5 m ² . Producing a copper layer having a thickness of 0.5μm~3μm on the substrate, an electroless copper plating method of any one of claims 7 to 10. The electroless copper plating method according to any one of claims 7 to 11 , wherein a copper layer having a roughness of 5 nm to 60 nm expressed as a root mean square roughness parameter is produced on the substrate. Printed circuit board, an integrated circuit board, wafer, molded circuit component, a display, for plating the display parts or plastic parts, the use of electroless aqueous copper plating solution according to any one of claims 1 to 6. For plating glass board, the use of electroless aqueous copper plating solution according to any one of claims 1 to 6.

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