KR20140090145A

KR20140090145A - Formaldehyde-free electroless copper plating solution

Info

Publication number: KR20140090145A
Application number: KR1020147008668A
Authority: KR
Inventors: 에디트 슈타인헤우저; 잔드라 뢰젤러; 슈테파니 비제; 탕 캄 라이 응우옌; 루츠 슈탐프
Original assignee: 아토테크더치랜드게엠베하
Priority date: 2011-10-05
Filing date: 2012-10-01
Publication date: 2014-07-16
Also published as: JP6180419B2; CN104040026A; WO2013050332A8; EP2764135A2; JP2014528517A; US20140242264A1; TWI557271B; WO2013050332A3; WO2013050332A2; KR101953940B1; TW201323654A; CN104040026B

Abstract

The present invention relates to a process for the preparation of polyoxyalkylene glycols, which comprises a copper ion source, a glyoxylic acid source as a reducing agent and at least one polyaminodisuccinic acid or at least one polyaminominosuccinic acid as the complexing agent or at least one polyaminodisuccinic acid and at least one polyamino mono Succinic acid, as well as the electroless copper plating method using the aqueous solution and the use of the solution for plating the substrate.

Description

FORMALDEHYDE-FREE ELECTROLESS COPPER PLATING SOLUTION <br> <br> <br> Patents - stay tuned to the technology FORMALDEHYDE-FREE ELECTROLESS COPPER PLATING SOLUTION

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

Electroless plating is a controlled autocatalytic deposition of continuous metal film, without external electron supply assistance. The non-metallic surface may be pretreated to make it receptive or catalytic for deposition. All or selected portions of the surface may be suitably pretreated. The main components of the electroless copper bath are copper salts, complexing agents, reducing agents and, as optional components, alkali and additives, for example as stabilizers. The complexing agent is used to chelate the deposited copper and prevent precipitation of copper from solution (i. E., Hydroxides, etc.). Chelated copper makes copper available as a reducing agent to convert copper ions to metal form.

A conventional electroless copper bath used formaldehyde as a reducing agent. Formaldehyde is the most important and well established reducing agent of conventional electroless copper plating processes. In 1987, formaldehyde was classified as a possible human carcinogen by the US Environmental Protection Agency. In June 2004, the International Agency for Research on Cancer (IARC) classified formaldehyde as a human carcinogen. As a result, formaldehyde electroless copper baths have been developed to meet safety and occupational hygiene requirements.

US 4,617,205 discloses a composition for electroless deposition of copper, comprising a complexing agent, such as EDTA, capable of forming a complex with copper ions, a glyoxylate as a reducing agent, and a copper with a stronger copper copper oxalate complex .

US 7,220, 296 discloses an electroless plating bath comprising a water-soluble copper compound, a glyoxylic acid and a complexing agent which may be EDTA.

US 20020064592 discloses an electroless bath comprising a copper ion source, glyoxylic acid or formaldehyde as a reducing agent, and EDTA, tartrate or alkanolamine as a complexing agent.

US 20,080,223,253 silver, copper salt, formaldehyde, para-formaldehyde, glyoxylic acid, NaBH _4, KBH _4, NaH ₂ P0 _2, hydrazine, formaldehyde, glucose and that may be selected in such a polysaccharide, and the group consisting of mixtures thereof A reducing agent and a reducing agent such as ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), cyclohexanediamine tetraacetic acid, diethylenetriaminepentaacetic acid, and tetrakis (2-hydroxypropyl) ethylenediamine (Also referred to as " Quadrol ", a trademark of BASF), which is an electroless copper plating solution.

A disadvantage of EDTA, HEDTA, tetrakis (2-hydroxypropyl) ethylenediamine, and other related complexing agents is the lack of biodegradability.

The performance of the copper plating solution is generally unpredictable and strongly depends on the molar ratio of its constituents, in particular the complexing agent and reducing agent, and its constituents.

An object of the present invention was to provide an electroless copper plating solution free of formaldehyde.

Another object was to provide an electroless copper plating solution having improved performance, for example an improved copper deposition rate.

Another object of the present invention was an electroless copper plating solution using a biodegradable complexing agent for copper.

Another objective was that the formaldehyde-free copper plating solution should meet the criteria for formaldehyde electroless copper baths. It should be suitable for both horizontal and vertical processes where end products are used, for example, in advanced technologies, such as HDI (High Density Interconnect) PCBs and IC boards (IC = integrated circuits, PCB = printed circuit boards) . The solution should also be suitable for the manufacture of displays.

The present invention provides an electroless copper plating solution,

- a source of copper ions,

As a reducing agent, a source of glyoxylic acid, and

As the complexing agent, at least one polyamino dicosuccinic acid, or at least one polyamino-aminosuccinic acid, or a mixture of at least one polyaminodisuccinic acid and at least one polyaminomonosuccinic acid,

The molar ratio of the complexing agent to the copper ion is in the range of 1.1: 1 to 5: 1.

One or more of the above-mentioned objects are achieved by an electroless copper plating solution according to claim 1 (hereinafter abbreviated as "solution ") or by advantageous embodiments as described in the dependent claims and the detailed description.

The solution of claim 1 is formaldehyde free and shows improved copper deposition rates. A deposition rate of 0.15 to 1.0 占 퐉 / 10 minutes, 0.15 to 1.5 占 퐉 / 10 minutes, or even 0.15 to 2.0 占 퐉 / 10 minutes may be reached.

Advantages of this new formaldehyde copper bath are good bath performance, bath stability, good coverage, high deposition rate and low blistering tendency. Formaldehyde, an important bath component, is replaced by a non-toxic reducing agent.

The molar ratio of the complexing agent polyaminodisuccinic acid or polyaminomonosuccinic acid to copper ion leads to beneficial properties of the plating solution, as further described in the following and in the Examples, which include inhibited copper hydroxide precipitation, bath stability , And inhibited blister formation in the copper plating process.

In one embodiment of the invention, the molar ratio of glyoxylic acid to complexing agent is less than 4.6: 1. As can be seen in the present invention, such molar ratio has an advantageous effect on the copper deposition quality on the substrate, such as, for example, coverage, backlighting and passivation. Also advantageous molar ratios of glyoxylic acid to complexing agent, especially EDDS, are 4.5: 1 or less, 4.2: 1 or less, 4.0: 1 or less, 3.8: 1 or less, and 3.6: The preferred lower limit of the molar ratio of glyoxylic acid to complexing agent, particularly EDDS, is 0.45: 1, or 0.7: 1, 1: 1 or 2: 1. Thus, the preferred range for the molar ratio of glyoxylic acid to complexing agent, in particular EDDS, is 0.45: 1 to 4.5: 1, 0.45: 1 to 4.2: 1, 0.45: 1 to 4.0: 1, 0.45: Or 0.45: 1 to 3.6: 1. Other preferred ranges are 1: 1 to 4.5: 1, 1: 1 to 4.2: 1, 1: 1 to 4.0: 1, 1: 1 to 3.8: 1, or 1: 1 to 3.6: Another preferred range of molar ratios of glyoxylic acid to complexing agents, especially EDDS, is 2: 1 to 4.5: 1, 2: 1 to 4.2: 1, 2: 1 to 4.0: Or 2: 1 to 3.6: 1. The ratio relates to the molar amount of the complexing agent, which means the total molar amount of the complexing agent, if more than one complexing agent is used. The molar concentration of the glyoxylic acid is preferably at least as high as the molar concentration of copper in the solution, and more preferably higher. Therefore, the molar ratio of glyoxylic acid to Cu is preferably 1: 1 or more, preferably 1.5: 1 or more, more preferably 2: 1 or more.

Polyaminodisuccinic acid and polyamino monosuccinic acid show very good or even high biodegradability. The plating solution of the present invention can be prepared by dissolving or dissolving a mixture of ethylenediaminetetraacetic acid (EDTA), N'- (2-hydroxyethyl) -ethylenediamine-N, N, N'-triacetic acid (HEDTA) Propyl) ethylenediamine.

The solution according to the invention and the process according to the invention are preferably used for the coating of printed circuit boards, chip carriers and semiconductor wafers or else other circuit carriers and interconnect devices. The solution is used especially in printed circuit boards and chip carriers, and also in semiconductor wafers, plating copper surfaces, trenches, blind micro vias, through-hole vias (through holes) and similar structures.

In particular, solutions of the present invention or processes of the present invention may be applied to surfaces, such as trenches, blind microvias, through-hole vias, and comparable structures, on a surface in a printed circuit board, chip, carrier, wafer, and various other interconnect devices. As shown in FIG. As used herein, the term "through-hole via" or "through hole" includes through-hole vias of all kinds and includes so-called "through silicon vias" in silicon wafers.

Other applications expected for solutions include metallization for display applications. At this point, copper is deposited on a glass substrate, in particular a flat glass surface. Wet electroless copper deposition on glass substrates is advantageous compared to metal sputtering processes used to date. The advantages that can be achieved with wet electroless deposition compared with the sputtering technique are that the internal stress is reduced, the bending of the glass substrate is reduced, the equipment maintenance is reduced, the metal is used effectively, and the material waste is reduced to be. Moreover, a high copper deposition rate is achieved with the solution of the invention in glass substrates, especially glass substrates that are pre-treated with relatively few metal seeds.

The solution of the present invention is an aqueous solution. The term "aqueous solution" means that the predominant liquid medium, which is a solvent in solution, is water. Also water-miscible liquids, such as, for example, water-miscible alcohols and other polar organic liquids, may be added.

The solution of the present invention may be prepared by dissolving all components in an aqueous liquid medium, preferably water.

The solution contains, for example, a copper ion source which may be any water soluble copper salt. Copper, for example, but not limited to, copper sulfate, copper chloride, copper nitrate, copper acetate, copper methane sulfonate _{((CH 3 0 3 S)} 2 Cu), copper hydroxide; Or as a hydrate thereof.

The electroless copper bath using the above-described reducing agent preferably uses a relatively high pH, usually 11-14, or 12.5-14, preferably 12.5-13.5, or 12.8-13.3. The pH is generally controlled by potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), ammonium hydroxide or tetramethylammonium hydroxide (TMAH). Thus, the solution may contain a source of hydroxide ions, for example, but not exclusively, as one or more of the compounds described above. If a solution of alkaline pH is desired and the pH is not yet in the alkaline range by other constituents, for example a hydroxide source is added.

The use of potassium hydroxide is particularly preferred because of the high solubility of potassium oxalate. Oxalate anions are formed in the solution by oxidation of the glyoxylic acid used as a reducing agent.

Glyoxylic acid is a reducing agent for reducing copper ions with elemental copper. As used herein, the term "glyoxylic acid" includes glyoxylic acid as well as glyoxylic acid. In the solution, there may be a glyoxylic acid and a glyoxylate ion which are inferred. The exact nature of the species, acid or salt present will depend on the pH of the solution. The same applies to other weak acids and weak bases.

The term "source of glyoxylic acid" includes glyoxylic acid and all compounds that can be converted to glyoxylic acid in aqueous solution. The aldehyde containing acid in aqueous solution equilibrates with its hydrate. A suitable source of glyoxylic acid is dihaloacetic acid, such as dichloroacetic acid, which is hydrolyzed in an aqueous medium with hydrates of glyoxylic acid. Alternative glyoxylic acid sources are bisulfite adducts, such as hydrolyzable esters or other acid derivatives. Bisulfite adducts may be added to the composition and formed in situ. The bisulfite adduct may be made of glyoxylate, and bisulfite, sulfite or metabisulfite.

One or more additional reducing agents, such as for example phosphorous acid, glycolic acid or formic acid, or salts of the acids mentioned above, may be added if desired. However, the solution of the present invention does not contain formaldehyde. Thus, the solution is free of formaldehyde. The additional reducing agent is preferably an agent that acts as a reducing agent but can not be used as a sole reducing agent (see US 7,220,296, col. 4, I. 20-43 and 54-62). Additional reducing agents are also called "enhancers" in this sense.

Polyaminodisuccinic acid is a compound having two or more nitrogen atoms, two of the nitrogen atoms are bonded to a succinic acid (or salt) group, and preferably only two nitrogen atoms are attached to one succinic acid (or salt) Lt; / RTI > As used herein, the term succinic acid includes its salts. The compound has at least two nitrogen atoms and, because of the commercial availability of the amine, preferably has about 10 or fewer nitrogen atoms, more preferably about 6 or less, most preferably 2 nitrogen atoms. Most preferably the nitrogen atom to which the succinic acid moiety is not attached is replaced by a hydrogen atom. More preferably, the succinic acid group has a nitrogen atom at the end, most preferably each nitrogen also has a hydrogen substituent. The term " terminal " means the first or last nitrogen atom present in the compound, regardless of other substituents. Another definition of terminal nitrogen is primary amine nitrogen before the succinic acid moiety is attached. The terminal nitrogen is transferred to the secondary amine nitrogen after the succinic acid moiety is attached. Because of the steric hindrance of two succulents in one nitrogen, it is preferred that each nitrogen bearing the succinic group has only one such group. The remaining bonds in the nitrogen having a succinic acid group are preferably hydrogen or an alkyl or alkylene group (linear, branched or cyclic, including a cyclic structure joining more than one nitrogen atom or more than one of the single nitrogen atoms, Linear or both), or these groups have ether or thioether linkages, all preferably having 1 to 10 carbon atoms, more preferably 1 to 6, most preferably 1 to 3 carbon atoms, most preferably hydrogen . Preferred alkyl groups include methyl, ethyl and propyl groups. More preferably, the nitrogen atom is linked by an alkylene group, wherein the alkylene groups preferably each have 2 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, even more preferably 2 to 8, 6 carbon atoms, i.e. ethylene, propylene, butylene, pentylene or hexylene. The polyaminodisuccinic acid compound preferably has at least about 10 carbon atoms, preferably up to about 50, more preferably up to about 40, and most preferably up to about 30 carbon atoms. The term "succinic acid" is used herein for its acid and salt; Salts include metal cations (e.g., potassium, sodium) and ammonium or amine salts.

The polyaminodisuccinic acid useful in the practice of the present invention is (preferably) substituted with a group that is unsubstituted or inertly substituted and that does not undesirably interfere with the activity of the polyaminodisuccinic acid in the selected application. Such inert substituents include alkyl groups (preferably having from 1 to 6 carbon atoms); An aryl group (preferably having from 6 to 12 carbon atoms) containing an arylalkyl group and an alkylaryl group, an alkyl group being preferred among these, and a methyl group and an ethyl group being preferred among the alkyl groups.

The inert substituent is suitable for an alkylene group between any part of the molecule, preferably a carbon atom, more preferably an alkylene group, for example between an nitrogen atom or a carboxylic acid group, most preferably between nitrogen groups .

Preferred polyaminodisuccinic acids are ethylenediamine-N, N'-disuccinic acid (EDDS), diethylenetriamine-N, N "-disuccinic acid, triethylenetetramine- Hexamethylene diamine N, N'-dodecanoic acid, tetraethylenepentamine-N, N "" -disuccinic acid, 2-hydroxypropylene-1,3-diamine-N, N'- Diamine-N, N'-disuccinic acid, 1,3-propylenediamine-N, N "-disuccinic acid, cis-cyclohexanediamine-N, N'-disuccinic acid, transcyclohexanediamine-N, Succinic acid, and ethylene bis (oxyethylene nitrilo) -N, N'-disuccinic acid. The preferred polyaminodisuccinic acid is ethylenediamine-N, N'-disuccinic acid.

Such polyaminodisuccinic acid can be prepared, for example, by the process disclosed in Kezerian et al., US Patent 3,158,635, which is incorporated herein by reference in its entirety. Kezerian et al. Discloses reacting maleic anhydride (or an ester or salt) with a polyamine corresponding to the desired polyaminodisuccinic acid under alkaline conditions. The reaction generates a number of optical isomers, for example, the reaction of ethylenediamine with maleic anhydride is carried out using three optical isomers [R, R], [S, S] and [S, R] ethylenediamine disuccinic acid ) Due to the presence of two asymmetric carbon atoms in the ethylenediamine disuccinic acid. This mixture is used as a mixture or alternatively by means of the state of the art to obtain the desired isomer (s). Alternatively, the [S, S] isomer can be obtained from inorganic chemistry, V.7, (1968), pp. Is prepared by the reaction of a compound such as 1,2-dibromoethane with an acid such as L-aspartic acid as described by Neal and Rose in "Stereospecific Ligand and its Complex of Ethylenediamine Disuccinic Acid" .

The polyaminomonosuccinic acid is a compound in which the succinic acid (or salt) moiety has at least two nitrogen atoms attached to one of the nitrogen atoms. Preferably the compound has at least two nitrogen atoms and, because of the commercial availability of the amine, preferably has about 10 or fewer nitrogen atoms, more preferably about 6 or less, most preferably 2 nitrogen atoms. The remaining nitrogen atoms, i. E. Those not attached to the succinic acid moiety, are preferably substituted with hydrogen atoms. Although the succinic acid moiety may be attached to any amine, the succinic acid group is preferably attached to the terminal nitrogen atom. By term, it refers to the first or last amine present in the compound, regardless of other substituents. Another definition of terminal nitrogen is primary amine nitrogen before the succinic acid moiety is attached. The terminal nitrogen is transferred to the secondary amine nitrogen after the succinic acid moiety is attached. The remaining bonds in the nitrogen having a succinic acid group are preferably hydrogen or an alkyl or alkylene group (linear, branched or cyclic, including a cyclic structure joining more than one nitrogen atom or more than one of the single nitrogen atoms, Linear or both), or these groups have ether or thioether linkages, all preferably having 1 to 10 carbon atoms, more preferably 1 to 6, most preferably 1 to 3 carbon atoms, most preferably hydrogen . Preferred alkyl groups include methyl, ethyl and propyl groups. In general, the nitrogen atom is linked by an alkylene group, each containing 2 to 12 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 8, most preferably 2 to 6 carbon atoms, Ethylene, propylene, butylene, pentylene or hexylene. The polyamino monosuccinic acid compound preferably has at least about 6 carbon atoms, preferably at most about 50, more preferably at most about 40, and most preferably at most about 30 carbon atoms. The polyaminomonosuccinic acid useful in the practice of the present invention is (preferably) not substituted or inertly substituted as described above for the polyaminodisuccinic acid compound.

Preferred polyaminomonosuccinic acids are ethylenediamine monosuccinic acid, diethylenetriamine monosuccinic acid, triethylenetetramine monosuccinic acid, 1,6-hexamethylenediamine monosuccinic acid, tetraethylenepentamine monosuccinic acid, 2hydroxypropylene-1, Propylene diamine monosuccinic acid, 1,3-propylene diamine monosuccinic acid, cis cyclohexanediamine monosuccinic acid, trans-cyclohexanediamine monosuccinic acid, and ethylene bis (oxyethylene nitrile) . A preferred polyaminomonosuccinic acid is ethylenediamine monosuccinic acid.

Such polyaminomonosuccinic acids can be prepared, for example, by the process in Bersworth et al., US Pat. No. 2,761,874, which is incorporated herein by reference, and as disclosed in Kokai Tokkyo Koho JP 57,116,031. Generally, Bersworth et al. Disclose reacting alkylenediamines and dialkylenetriamines under mild conditions with maleic esters (in the alcohol) under mild conditions to generate amino derivatives of N-alkyl substituted aspartic acids. The reaction generates a mixture of R and S isomers.

In one embodiment, when the solution contains a mixture of polyaminodisuccinic acid and polyamino monosuccinic acid, the polyamino substituent of the polyaminodisuccinic acid and the polyamino monosuccinic acid is preferably the same. Thus, for example, if the polyamino dicosuccinic acid is ethylenediamine-N, N'-disuccinic acid, then the polyamine monosuccinic acid is ethylenediamine monosuccinic acid.

In a preferred embodiment, ethylenediamine-N, N'-disuccinic acid (EDDS) is used as a complexing agent. EDDS is a preferred complexing agent because of its high biodegradability. Other electroless copper baths with biodegradable complexing agents as tartrate typically use toxic co-metallic nickel. It has been found that toxic co-metals can be avoided in the present invention. Thus, the solution of the present invention is free of toxic co-metals. The solution of the present invention is preferably free of nickel.

The present inventors have found that a significantly improved copper deposition rate is obtained in the solutions of the present invention, including glyoxylic acid and EDDS. This is an unexpected result because in the comparative example using formaldehyde, the copper deposition is not improved or only slightly improved when the formaldehyde-EDDS-combination is compared to formaldehyde-EDTA.

The term "EDDS" includes racemic EDDS or all its optically active isomers, such as (S, S) -EDDS, and salts and derivatives thereof. Preferably the term refers to (S, S) -EDDS or a salt thereof. EDDS may also be prepared by the process of PCT / GB94 / 02397. In the solution, ethylenediamine disuccinic acid and ethylenediamine disuccinate ion may be present depending on the pH of the solution.

In one embodiment, the solution of the invention contains a copper ion, preferably a complexing agent that is EDDS, and a glyoxylic acid at the following concentrations:

1 to 5 g / l corresponding to Cu-ions: 0.016 to 0.079 mol / l,

5 to 50 g / l corresponding to 0.034 to 0.171 mol / l of complexing agent,

Glyoxylic acid: 2 to 20 g / l corresponding to 0.027 to 0.270 mol / l

The solution of the present invention more preferably contains a complexing agent, which is a copper ion, preferably EDDS, and glyoxylic acid at the following concentrations:

Cu-ions: 2 to 3 g / l corresponding to 0.031 to 0.047 mol / l

20 to 40 g / l corresponding to 0.068 to 0.137 mol / l of complexing agent,

Glyoxylic acid: 2 to 20 g / l corresponding to 0.027 to 0.270 mol / l

In the present invention, the molar ratio of the complexing agent to the copper ion, which in this context means the total amount of complexing agent (s) (i.e., the molar sum of all complexing agents, if more than one complexing agent is used) is from 1.1: : 1, more preferably 1.5: 1 to 5: 1. When such molar ratios are used, that is, complexing agents, especially EDDS, are used in molar excess over copper, the solutions of the present invention have shown better performance. In the present invention it is shown that when a glyoxylic acid is used as a reducing agent, a complexing agent of at least 1.1: 1, in particular EDDS, copper, is needed to complex the copper ion. Molar ratios of less than 1: 1 lead to precipitation of copper hydroxide and copper plating is not possible. On the other hand, molar ratios in excess of 5: 1 lead to bath instability and high blister formation on the substrate surface in the copper plating process.

In a further embodiment, the molar ratio of complexing agent to copper ion in this context, which means the total amount of complexing agent (s), is in the range from 2: 1 to 5: 1, more preferably from 3: 1 to 5: 1. This embodiment is particularly advantageous when the copper bath is agitated during deposition, and is particularly advantageous when air is agitated and additional reducing agents (also referred to as "enhancers") are used in addition to glyoxylic acid, and further reducing agents are preferably glycolic acid, Phosphoric acid, or formic acid, and most preferably glycolic acid.

The solutions of the present invention may, but need not, include additional components such as stabilizers, surfactants, additives such as rate controlling additives, atomizing additives, pH buffers, pH adjusting agents and enhancers. Such additional components are described, for example, in the following references, which are incorporated by reference in their entirety: U.S. 4,617,205 (especially from col. 6, I.17 ~ col.7, I. 25), US 7,220,296 4, I 63 to col 6, I 26), US 2008/0223253 (especially paragraph 0033 and paragraph 0038).

Stabilizers are compounds that stabilize the electroless plating solution for unwanted outplating in bulk solutions. The term "out-plating" means an unspecific and / or uncontrolled deposition of copper. Reduction of copper (II) is not indefinite in the entire bath and must occur only on the desired substrate surface. The stabilizing function can be achieved, for example, by a material that acts as a catalyst poison (e.g., a sulfur or other chalcogenide containing compound) or by a compound that forms a copper (I) Ⅰ) Suppresses the formation of oxides.

Suitable stabilizers include, but are not limited to, dipyridyl (2,2'-dipyridyl, 4,4'dipyridyl), phenanthroline, mercapto-benzothiazole, thiourea or diethyl-thiourea , Cyanide such as NaCN, KCN, K ₄ [Fe (CN) ₆ ], thiocyanate, iodide, ethanolamine, mercapto-benzotriazole, Na ₂ S ₂ O ₃ , Amides, polyacrylates, polyethylene glycols, or polymers such as polypropylene glycols and their copolymers, and include 2,2'-dipyridyl (abbreviated as "DP"), diethyl- thiourea, K ₄ [ Fe (CN) ₆ ], NaCN and mercapto-benzothiazole are particularly suitable.

In one embodiment, the stabilizer is selected from cyanide-free stabilizers, primarily for environmental and occupational hygiene reasons. Thus, the solution of the present invention is preferably free of cyanide. In this connection, 2,2'-dipyridyl is the preferred stabilizer. Dipyridyl is preferably added in an amount of 1 to 10 mg / L.

European application EP1876262 discloses an electroless copper bath containing at least one thiocarboxylic acid as an essential ingredient. The thio compound mentioned in EP1876262 comprises a compound having the formula HS- (CX1) r- (CHX2) s-COOH, X1 is -H or -COOH; X2 is -H or -SH; r and s are positive integers, r is 0 to 2, or 0 or 1; s is 1 or 2; Specific examples of the thio compounds mentioned in EP1876262 include thioglycolic acid, thiopropionic acid, thiomalic acid and dithiodysuccinic acid. According to EP1876262 this thiocarboxylic acid is compatible with glyoxylic acid and its salts and stabilizes the electroless copper composition by preventing the formation of copper oxide. The required minimum amount of thio compound according to EP1876262 is 0.01 ppm. In the present invention, as generally and concretely mentioned in EP1876262, the performance of the electroless copper bath has been shown to be better when the thiocarboxylic acid component is avoided or at least below the limits mentioned in EP1876262. As mentioned generally and specifically in EP1876262, trace amounts of thiocarboxylic acid may also be present if the amount is less than 0.01 ppm. However, it is preferred that the thiocarboxylic acid is not added to the solution of the invention, i. E. The bath does not contain any thiocarboxylic acid as generally and specifically mentioned in EP1876262.

In another aspect, the invention is directed to an electroless copper plating process comprising contacting the substrate with an electroless copper plating solution as described above.

For example, the substrate may be dipped or immersed in the solution of the present invention. In the process, only the entire surface or only a selected portion of the substrate may be plated with copper.

The solution is preferably stirred during use. In particular, work-and / or solution-agitation may be used. A preferred type of agitation is air agitation of the solution. Air agitation may be achieved by forming bubbles through the solution during use.

The process will be carried out for a sufficient time to produce an adherend of the required thickness, eventually depending on the particular application.

One anticipated use of the invention would be particularly suitable for the manufacture of printed circuit boards. The electroless deposition of copper according to the process of the present invention can be used particularly for through plating of holes, surfaces, trenches, blind microvias in printed circuit boards. Double-sided or multi-layer substrates (rigid or flexible) may be plated according to the present invention.

The process of the present invention may be useful for providing electroless copper adducts having a thickness in the range of 0.1 to 25 [mu] m, preferably 0.25 to 3 [mu] m.

Substrates commonly used in printed circuit board manufacturing are most often epoxy resins or epoxy glass composites. However, other materials may be used, particularly phenolic resin, polytetrafluoroethylene (PTFE), polyimide, polyphenylene oxide, bismaleate triazine resin (BT resin), cyanate ester and polysulfone.

In addition to the process uses in the manufacture of printed circuit boards, it can be used in the production of plastic, such as acrylonitrile butadiene styrene (ABS) and polycarbonate; Ceramics, and glass. &Lt; RTI ID = 0.0 > [0040] < / RTI >

In one embodiment of the process of the present invention the process is carried out at a temperature of from 20 to 60 캜, preferably from 20 to 55 캜, more preferably from 20 to 50 캜, even more preferably from 20 to 45 캜, and most preferably from 20 to 40 캜 Temperature. This embodiment is very advantageous because it requires a higher temperature for good plating performance, especially a sufficient copper deposition rate, for formaldehyde-based solutions according to the prior art.

The surface of a substrate to be plated with copper, in particular a non-metallic surface, can be modified by means known to those skilled in the art (e. G., The United States 4,617,205, as described in col 8). All or selected portions of the surface may be pretreated. However, pretreatment is not necessary in all cases and depends on the type of substrate and surface. Within the pretreatment, the substrate can be sensitized before depositing electroless copper on the substrate. This may be accomplished by adsorption of a catalysed metal (e.g., a noble metal, such as palladium) on the surface of the substrate.

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

An exemplary, non-limiting pretreatment process, particularly for printed circuit board laminates and other suitable substrates, comprises the following steps:

a) contacting the substrate with an activator solution containing a noble metal, preferably a colloidal or ionically catalyzed metal such as palladium, to cause the surface of the substrate to be catalysed,

And optionally, especially if the activator contains an ionically catalysed metal,

b) contacting the substrate with a reducing agent, wherein the metal ion of the ionic activator is reduced to a metal element,

Alternatively, if the activator contains a colloidal catalyzed metal,

c) contacting the promoter with a substrate, wherein the component of the colloid, for example the protective colloid, is removed from the catalysed metal.

Preferably, the additional steps which may optionally be carried out in any combination before step a) are as follows:

i. Cleaning and conditioning the substrate to increase adsorption. With detergent, organic and other residues are removed. The detergent may also contain additional substances (conditioners) that prepare the surface for the activation step, i. E., Increase the adsorption of the catalyst and lead to a more uniformly activated surface.

Ii. Etching the substrate to remove oxide from the surface of the copper, especially from the inner layer in the hole. This may be done by a per sulfate or peroxide based etching system.

Iii. Contacting the substrate with a pre-dip solution such as a hydrochloric acid solution or a sulfuric acid solution, optionally also with an alkali metal salt such as sodium chloride in a pre-dip solution. Pre-dip acts to protect the active agent from drag-in and contamination.

In other types of pretreatment processes, the permanganate etching step is used. A so-called desmear process using a permanganate etching step is described in the appended examples. The smear removal process may be combined with the steps described above. In particular, the smear removal process may be performed before step a) of the above-described pretreatment process, or before step i) to step iii) mentioned above when at least one of the steps i) to iii) is performed. The smear removal process may also be performed instead of step i) and step ii).

In a pretreatment process particularly suited for metallization of a display substrate and metallization of a glass substrate, the surface is contacted with the solution of the present invention only after contact with the pre-dip solution and the activator solution. Pre-dipping step Contact with pre-cleaning solution and adhesion promoter is an optional step that may be performed in advance.

Another process often used for glass substrates may be performed with the following steps prior to copper plating: the glass surface to be plated shows metal particles as seeds. The metal particles may be provided on the surface by a sputtering technique. Exemplary seeds are particles composed of copper, titanium, molybdenum, zirconium, aluminum, chromium, tungsten, niobium, tantalum or mixtures or alloys thereof. Other seeds may be metal oxides or mixed metal oxides such as, for example, indium tin oxide. This process can also be used on plastic substrates such as, for example, substrates made of polyethylene terephthalate.

The pretreated glass surface is contacted with an activator solution containing a noble metal, preferably an ionically catalyzed metal such as palladium, to allow the surface to be catalyzed. The ionically catalysed metal is reduced on the surface by the seed metal. In this process, the addition of additional reducing agent may be omitted. This process is particularly used for copper plating of glass substrates for display applications.

The exemplary preprocessing process, or its single steps, may be combined into an alternative pre-processing process if deemed necessary.

In a further aspect, the present invention provides a method of manufacturing a printed circuit board, a wafer, an integrated circuit substrate, a MID (molded interconnect device) component, a display, such as a liquid crystal display, a TFT- display, a plasma display, an electroluminescent display (ELD) Electroless as described above for the plating of micromechanical displays (ECD), in particular electronic devices or displays for TVs, display components, flat sensors, such as X-ray imaging devices, or plastic parts, for example plastic parts for functional or decorative applications To the use of a copper plating solution.

Hereinafter, the present invention will be described in more detail by the following examples. This embodiment is described in order to clearly show the present invention, but should not be construed as limiting the present invention.

Figure 1 shows the steps of a smear removal multistage process for cleaning the surface.
Figure 2 shows the steps of a through hole plating process for activation.
3 shows a reference sample for backlight measurement, showing the results of D1 to D10.
Figure 4 shows copper thickness in a glass substrate using a bath with different complexing agents.

Example

Way

Backlight Method:

The through-hole coverage of electroless copper plating can be evaluated using an industry standard backlight test where the electroless plated specimens are cut to ensure that the incomplete coverage area can be detected with bright spots when viewed through a strong light source. [United States 2008/0038450 A1].

The quality of the copper deposit is determined by the amount of light observed under a conventional optical microscope.

Backlight measurement results are given on a scale from D1 to D10, where D1 means the worst and D10 the best. A reference sample showing the results from D1 to D10 is shown in Fig.

One. Example

Bath composition

Configuration table

Operating temperature: 38 ~ 50 ℃

Deposition rate: about 0.6 탆 / 10 min.

Job Description

In this embodiment, the test sample is treated with a conventional smear removal process to clean the hole wall surface and the inner layer copper surface. In addition, the resin surface is roughened to achieve good copper adhesion.

The smear removal process is a multistage process having the steps shown in Fig.

The swelling agent is made up of a mixture of organic solvents. During this step drill smears and other impurities are removed. Temperatures as high as 60-80 < 0 > C promote penetration of the swelling agent leading to the swollen surface. Thus, a stronger attack of the permanganate solution to be applied later is possible. The reducing solution (reaction conditioner) then removes the manganese dioxide produced during the permanganate step from the surface.

In the PTH (through-hole plating) process, a nonconductive material is prepared for copper deposition. The activation step of the PTH process is shown in FIG.

The detergent is used to remove organics and condition the surface for the next activation step.

The etch cleaner removes the oxide from the surface of the copper inner layer at the hole. The material used as an etchant is selected from a mixture of sulfuric acid and hydrogen peroxide, or from peroxodisulfate, or from peroxomonosulfate. The etching cleaning solution may also contain an additive and / or a stabilizer in addition to the etching component.

Activation of the panel and hole surfaces with palladium occurs in active agents containing colloidal or ionically catalyzed metals, such as noble metals, preferably palladium, which catalyze the surface. In one possible set-up, the active agent contains palladium ions that are complexed by an organic ligand. A pre-dip pre-dip must protect the active agent from dragging and contamination.

The last step in the activation process is the reducing agent. Where the palladium ions are reduced to elemental palladium with high catalytic activity. After the reducing agent step, electroless copper deposition is performed with the solution of the present invention. The reducing agent is used in combination with an ionic metal compound as an activator. It uses a reducing agent such as hypophosphite, borane, aminoborane.

For electroless copper deposition, the bath composition was achieved by adding the bath component to the appropriate volume of water in the order shown schematically in Table 1. Air agitation was used. The operating temperature varied from 38 to 50 ℃. In addition, the deposition time was set to 10 to 60 minutes to achieve the required copper thickness.

Bath Features

Deposition rate (measured in FR4 material, e.g. Matsushita MC 100 EX): about 0.6 [mu] m / 10 min.

Blistering tendency (tested material: ABF GX-92 from Ajinomoto): low or none

Coverage (both FR4 and GX-92): Good

Color (FR4 and GX-92 quantum): Samman Pink

The backlight is tested in copper-clad FR4 with through-holes.

Plated Example

The test panel goes through the smear removal process (see table below).

Smear removal process

Activation process based on ionic activator system:

Activation process

Examples of configurations for the copper bath are described in the following table.

Embodiment of bath composition

Operating temperature: 38 ℃

Deposition rate: 0.6 탆 / 10 min

Blistering tendency: None

Coverage: Good

Backlight D8

Color: Saman Pink

2. Comparative Example : HEDTA Glyoxylic acid or several biodegradable Complexing agent Glyoxylic acid

Comparative Example 2.1: HEDTA ( N ' - (2-hydroxyethyl) - Ethylenediamine -N, N, N ' - Triacetic acid )

Bath composition

Operating temperature: 45 ℃

Deposition rate: 0.5 탆 / 10 min

Backlight: D7

Bath stability: Good

Coverage: Good

Color: Saman Pink

Disadvantages: Non-biodegradable complexing agents

Comparative Example 2.2: biodegradable sorbitol

Bath composition

Operating temperature: 60 ℃

Deposition rate: 0.3 탆 / 10 min

Backlight: D8

Bath stability: Low

Coverage: Good

Color: Saman Pink

Disadvantages: Low deposition rate

Comparative Example 2.3: Biodegradable K- Na - Tartrate

Bath composition

Operating temperature: 38 ℃

Deposition rate: 0.3 탆 / 10 min

Backlight: D8 ~ D9

Bath stability: Low

Blistering trend: low

Coverage: Good

Color: Saman Pink

Disadvantages: high complexing agent concentration and low deposition rate

Comparative Example 2.4: Biodegradability Gluconic acid

Bath composition

Operating temperature: 50 ℃

Deposition rate: 0.4 탆 / 10 min

Backlight: D4 ~ D5

Bath stability: Very low

Coverage: Bad

Color: Salmon pink, slightly dark

Disadvantages: poor copper deposition and very low bath activity

summary:

When glyoxylic acid was used as a reducing agent, conventional biodegradable complexing agents such as tartrate could no longer satisfy the bath requirement. Glyoxylic acid and the biodegradable complexing agents according to the comparative examples tested above showed low deposition rates and / or high concentrations of complexing agent were required. In addition, the tested biodegradable complexing agents exhibited no copper deposit or poor results for coverage, deposition rate and blistering tendency. On the other hand, (S, S) -ethylenediamine-N, N'-disuccinic acid ((S, S) -EDDS) was biodegradable and met the plating industry requirements. The solution of the present invention containing EDDS was characterized by its good bath performance, good coverage, high deposition rate and low blistering tendency. Due to the strong complexing nature of EDDS, the stability of the copper bath of the present invention is much better than when it has other biodegradable complexing agents.

3. Example : Having different reducing agents EDDS versus EDTA compare

3.1 Glyoxylic acid as a reducing agent Example

3.1.1 Bath composition 1: Glyoxylic acid / EDDS Of the present invention

Operating temperature: 38 ℃

Deposition rate: 0.8 탆 / 10 min

Backlight: D6

Bath stability: Good

Coverage: Good

Color: Saman Pink

Blistering: No blistering

3.1.2 Bath composition 2: Glyoxylic acid / EDTA Have Comparative Example

Operating temperature: 38 ℃

Deposition rate: 0.4 탆 / 10 min

Backlight: D4

Bath stability: Good

Coverage: bad, passivation can be observed

Color: Salmon pink, slightly dark

Blistering: None

result:

When comparing Example 3.1.1 with Example 3.1.2, the copper plating bath containing EDDS was twice as fast as the EDTA containing bath for the copper deposition rate under the same plating conditions. Moreover, good coverage with EDDS has been achieved.

3.2 With formaldehyde as reducing agent Comparative Example

3.2.1 Bath composition 3: Formaldehyde / EDDS Have Comparative Example

Operating temperature: 38 ℃

Deposition rate: 1.1 탆 / 10 min

Backlight: D7

Bath stability: Good

Coverage: Good

Color: Saman Pink

Blistering: No blistering

3.2.2 Bath composition 4: Formaldehyde / EDTA Have Comparative Example

Operating temperature: 38 ℃

Deposition rate: 0.9 탆 / 10 min

Backlight: D6

Bath stability: Low

Coverage: Bad, slight passivation

Color: Salmon pink, slightly dark

Blistering: Yes

result:

Baths with EDDS / formaldehyde exhibit slightly higher deposition rates than those with EDTA / formaldehyde. However, when EDTA was replaced by EDDS (see Example 3.1.1 and Example 3.1.2), the increase in deposition rate was much lower than with glyoxylic acid. Thus, in baths with formaldehyde, EDDS is similar or slightly better than EDTA. However, when having a glyoxylic acid as a reducing agent, EDDS shows much better results than EDTA (an increase in deposition rate of about 100%), which was unpredictable in the prior art.

4. Example : Different concentrations of Complexing agent EDDS And copper

Molar ratio EDDS: change in Cu

Bath composition

Copper 3.0 g / l

Complexing agent: EDDS 12 to 101 g / l

Alkali: KOH 7.2 g / l

Stabilizer: 2,2'-dipyridyl 0.004 g / l

Reductant: glyoxylic acid 8 g / l

Operating temperature: 36 ° C

Test results

Deposition rate: 0.6 탆 / 10 min

The molar ratio EDDS: Cu of 1.1: 1 is required to at least complex the copper ions in the alkaline solution. A molar ratio of less than 1.1: 1 leads to the precipitation of copper hydroxide. Therefore, copper plating is not possible.

A molar ratio of greater than 5: 1 leads to bath instability and high blister trend in PCB materials. The deposited color is dark salmon pink and the backlight is at the required value of D7.

Uncontrolled copper adducts in the beaker can be found after electroless copper plating with bath 6 (molar ratio EDDS: Cu of 6: 1). Bath stability is insufficient.

5. Example : Glyoxylic acid versus different molar ratio EDDS The plating solution

EDDS vs. glyoxylic acid of different molar ratios in the electroless copper bath are tested as shown in the following table.

Bath composition:

Moles and mass of Cu, complexing agent and reducing agent

The test panel undergoes an activation process based on the smear removal process (Table 2) and the ionic activator system (Table 3) as described in Example 1.

The following parameters were applied for electroless plating in an electroless copper bath:

- T = 38 DEG C

- Dummy plating: 10-15 minutes

- Exposure time: 10 minutes

Tested materials: In addition to GX-92 (short smear removal: 2 ', 4', 4 ') and FR4 already described in Example 1, test panels made of the following materials were used.

ABS (short smear removal: 2 ', 4', 2 ') for testing coverage and passivation;

R1755C for backlight test (smear removal: 5 ', 10', 5 ').

In the following table, deposition test results are shown.

Bath stability decreases after one day in all baths. The next day precipitation of copper hydroxide occurs. To improve bath stability, a ratio of EDDS to copper of at least 1.1: 1 is recommended. However, this experiment shows the effect of the molar ratio of glyoxylic acid: EDDS on copper substrate quality on the substrate.

The test shows that the copper deposition quality decreases as the concentration of the glyoxylic acid increases. Due to the higher glyoxylic acid concentration in the electroless copper bath, the copper-glyoxylic acid complex is expected to form competitively with the Cu-EDDS complex and the glyoxylic acid also acts as a complexing agent instead of the reducing agent.

Although the concentration of the glyoxylic acid is high enough to serve as both parts (complexing agent and reducing agent), the reduction process using the copper-glyoxylic acid complex appears to be performed erroneously. Formation of the copper-glyoxylic acid complex leads to bath instability with passivation on the copper coating material. Wherein the passivation causes the copper surface to become inactive for the electroless copper plating process; The electroless copper plating process is terminated at the passive surface. Copper deposition quality decreases when the molar ratio of glyoxylic acid: EDDS is greater than 4.6: 1. Initial reactivity, copper coverage and passivation depend on the molar ratio of glyoxylic acid: EDDS.

Complexing agents play an important role in the electroless copper plating process. The reduction process is not possible with all of the complexing agents. The complexing agent EDDS forms a complex with copper which can be easily reduced. The coating quality (coverage, backlight) is very good at a ratio of glyoxylic acid: EDDS of less than 4.6: 1, especially 3.6: 1 or less.

6. Example : Thiocarboxylic acid Experiment using

Comparison of EDTA and EDDS with and without thiocarboxylic acid

Thioglycolic acid is used as the thiocarboxylic acid in the experiment.

Test schedule with different bath composition

Operating temperature: 55 ℃

Test results

Thioglycolic acid leads to dark colored electroless copper deposition. The deposition rate decreases with the use of thioglycolic acid in electroless copper baths.

7. Example : Different Complexing agent Which uses a copper bath having On the substrate Copper Adhesion

Sample: Glass with sputtered Ti / Cu seed

Pretreatment:

The copper thickness results obtained for the different complexing agents are shown in FIG.

Claims

As an electroless copper plating aqueous solution,
- source of copper ions,
As a reducing agent, a source of glyoxylic acid, and
As the complexing agent, at least one polyamino dicosuccinic acid, or at least one polyamino-aminosuccinic acid, or a mixture of at least one polyaminodisuccinic acid and at least one polyaminomonosuccinic acid,
Wherein the molar ratio of complexing agent to copper ions is in the range of 1.1: 1 to 5: 1.

The method according to claim 1,
Wherein the molar ratio of the glyoxylic acid to the complexing agent is less than 4.6: 1.

3. The method according to claim 1 or 2,
Wherein the molar ratio of the complexing agent to the copper ions is in the range of 1.5: 1 to 5: 1.

4. The method according to any one of claims 1 to 3,
An electroless copper plating aqueous solution containing less than 0.01 ppm of thiocarboxylic acid.

5. The method according to any one of claims 1 to 4,
Wherein the complexing agent is at least one polyaminodisuccinic acid.

6. The method according to one of claims 1 to 5,
The complexing agent is ethylenediamine-N, N'-disuccinic acid (EDDS), an electroless copper plating aqueous solution.

7. The method according to any one of claims 1 to 6,
Wherein the aqueous solution further comprises one or more stabilizers.

8. The method of claim 7,
The stabilizer may be selected from the group consisting of dipyridyl, phenanthroline, mercapto-benzothiazole, thiourea or derivatives thereof, cyanide, thiocyanate, iodide, ethanolamine, mercapto-benzotriazole, Na ₂ S ₂ 0 ₃ , polyacrylamides, polyacrylates, polyethylene glycols or polypropylene glycols or copolymers thereof. An electroless copper plating aqueous solution.

9. The method according to any one of claims 1 to 8,
Wherein the electroless copper plating aqueous solution further comprises a source of hydroxide ions.

10. The method according to any one of claims 1 to 9,
Wherein the electroless copper plating aqueous solution contains a second reducing agent in addition to glyoxylic acid.

11. The method of claim 10,
Wherein the second reducing agent is selected from the group of salts of phosphoric acid, glycolic acid, formic acid, and salts of the acids.

1. An electroless copper plating method comprising:
11. A method of electroless copper plating comprising contacting a substrate with an electroless copper plating aqueous solution according to one of the preceding claims.

13. The method of claim 12,
Lt; RTI ID = 0.0 > 20-60 C. < / RTI >

11. Use of an electroless copper plating aqueous solution according to one of claims 1 to 11 for plating printed circuit boards, integrated circuit boards, wafers, molded interconnect devices, displays or plastic parts.

Use of an electroless copper plating aqueous solution according to one of claims 1 to 11 for plating glass substrates, in particular glass substrates for displays.