JP6030848B2 - Electroless copper plating bath and electroless copper plating method - Google Patents

Description

  The present invention relates to an electroless copper plating bath and an electroless copper plating method. More specifically, the present invention relates to an electroless copper plating bath that does not contain formaldehyde and can be used near neutral, and an electroless copper plating bath using the electroless copper plating bath. The present invention relates to an electrolytic copper plating method.

  In conventional electroless copper plating baths, formaldehyde is used as a reducing agent for copper ions. However, formaldehyde has a high vapor pressure, and it has been pointed out that the working environment is deteriorated due to irritating odors and that the carcinogenicity has an adverse effect on the human body. ing. In addition, since the electroless copper plating bath using formaldehyde is strongly alkaline, it tends to damage the object to be plated and cause deterioration, and it can be used effectively for metals such as aluminum or aluminum alloys. It was not possible and its use was limited.

  On the other hand, as described in Patent Document 1, for example, an electroless copper plating bath using amine borane or a derivative thereof without using formaldehyde as a reducing agent has been proposed. This amine borane is a reducing agent that can be used under neutral to weakly alkaline pH conditions, prevents deterioration of the object to be plated, and can be used with high safety.

  However, this amine borane has a problem that the reducing power is very high and the plating bath is easily decomposed. So far, there has been no electroless copper plating bath solution having good bath stability and high practicality while containing this amine borane as a reducing agent.

  In addition, when formaldehyde is used as a reducing agent, the formaldehyde exhibits a strong reducibility selectively on metal surfaces such as palladium and copper, while the reducing action in the plating bath is weak. Precipitation to places other than (metal) was difficult to occur. In contrast, borane compounds such as dimethylamine borane are strong enough to reduce water to hydrogen and reduce metal ions to metal not only on the metal but also in the plating bath. There was a problem in that the selectivity to the surface was low, and the particles protruded out of the pattern and precipitated.

JP 2001-131761 A

  Therefore, the present invention has been made in view of the above-described conventional situation, and does not use formaldehyde, can be used under a pH condition near neutral, and improves the plating bath stability, An object is to provide an electroless copper plating bath capable of forming a plating film having a good film thickness while suppressing out-of-pattern precipitation, and an electroless copper plating method using the electroless copper plating bath. .

  As a result of intensive studies in order to solve the above-described object, the present inventors have determined that out-of-pattern precipitation is achieved by controlling the balance between the promotion and suppression of plating deposition in a formaldehyde-free electroless copper plating bath. It was found that a plating film having a good film thickness can be formed while effectively suppressing the above, and the present invention has been completed.

That is, the electroless copper plating bath according to the present invention is an electroless copper plating bath having a pH of 4 to 9, which contains a water-soluble copper salt and aminoborane or a substituted derivative thereof as a reducing agent and does not contain formaldehyde. It contains polyaminopolyphosphonic acid as an agent, an anionic surfactant, an antimony compound, and a nitrogen-containing aromatic compound, and the concentration of the antimony compound is 1 to 4 mg / L.

  The electroless copper plating method according to the present invention is characterized in that a copper plating film is formed on a substrate using the electroless copper plating bath.

  According to the present invention, it can be used under pH conditions near neutral, and plating can be performed without damaging the object to be plated. In addition, plating deposition outside the pattern can be effectively suppressed, and a plating film having a good film thickness can be formed. This makes it possible to easily perform plating without providing a barrier layer or the like on a base material such as aluminum or an aluminum alloy, and can be suitably used for manufacturing a semiconductor wafer or the like.

It is a graph which shows the relationship between the antimony density | concentration in an electroless copper plating bath, and a deposit film thickness. It is a graph which shows the relationship between the antimony density | concentration in an electroless copper plating bath, and a deposit film thickness.

Hereinafter, specific embodiments of the electroless copper plating bath and the electroless copper plating method according to the present invention (hereinafter referred to as the present embodiment) will be described in detail in the following order.
1. 1. Electroless copper plating bath 2. Electroless copper plating method Example

<< 1. Electroless copper plating bath >>
The electroless copper plating bath according to the present embodiment is a so-called formaldehyde-free plating bath that does not contain formaldehyde, and includes a water-soluble copper salt and aminoborane or a substituted derivative thereof as a reducing agent, and has a pH of 4 ~ 9 electroless copper plating bath. The electroless copper plating bath is characterized by containing polyaminopolyphosphonic acid as a complexing agent, an anionic surfactant, an antimony compound, and a nitrogen-containing aromatic compound.

  As described above, the electroless plating bath according to the present embodiment does not contain a reducing agent used under strong alkaline pH conditions such as formaldehyde and glyoxylic acid, and can be used in neutral to weakly alkaline conditions. Alternatively, a substituted derivative thereof is used as a reducing agent. Thereby, the metal base material used as a to-be-plated object is not damaged like the strong alkaline plating bath which used formaldehyde etc. as a reducing agent. Therefore, it can be suitably used as a plating bath for forming a plating film on a semiconductor wafer made of, for example, aluminum or an aluminum alloy, and a good plating film can be formed.

  By the way, when aminoborane or a substituted derivative thereof is used as a reducing agent, the plating bath is easily decomposed due to its extremely strong reducing power, and precipitation outside the pattern formed on the substrate that is the object to be plated occurs. There is a problem that the pattern selectivity is low. However, in the electroless copper plating bath according to the present embodiment, the polyaminopolyphosphonic acid as the complexing agent, the anionic surfactant, the antimony compound, and the nitrogen-containing aromatic compound are included. Therefore, it is possible to increase the stability of the plating bath and to control the balance between the promotion and suppression of plating deposition and to form a plating film with a good film thickness with high pattern selectivity. Can be made.

  According to such an electroless copper plating bath, for example, on a metal substrate such as aluminum or aluminum alloy, magnesium or magnesium alloy, and without providing a barrier layer or the like for preventing out-of-pattern precipitation, good extruding A simple plating film can be easily formed, and can be suitably used, for example, in the manufacture of semiconductor wafers.

<Aqueous copper salt>
Examples of the water-soluble copper salt include copper sulfate, copper nitrate, copper chloride, copper acetate, copper citrate, copper tartrate, copper gluconate, and the like. Two or more kinds can be mixed and used at an arbitrary ratio.

  As a density | concentration of water-soluble copper salt, it can be 0.005-0.5 mol / L as a copper concentration, for example, It is preferable to set it as 0.01-0.5 mol / L, 0.05-0.1 mol / L is more preferable. If the concentration of the water-soluble copper salt is less than 0.005 mol / L, the deposition rate becomes slow and the plating time becomes longer, which is not economical. On the other hand, if the concentration exceeds 0.5 mol / L, the amount of squeeze increases and the cost increases, and the plating solution becomes unstable. In addition, nodules and roughness are likely to occur, and pattern properties are degraded.

<Reducing agent>
Examples of the amine borane or substituted derivative thereof as a reducing agent include dimethylamine borane, tert-butylamine borane, triethylamine borane, and trimethylamine borane.

  Amine borane or substituted derivatives thereof are reducing agents that can be used in neutral to weakly alkaline conditions. Therefore, unlike plating baths using aldehyde-based reducing agents such as formaldehyde and glyoxylic acid, they are not used in strong alkalinity. Can be prevented. Moreover, like an aldehyde-type reducing agent, a working environment can be worsened and the bad influence with respect to a human body can be excluded, and safety can be improved.

  The concentration of amine borane or a substituted derivative thereof as a reducing agent is preferably 0.01 to 0.5 mol / L.

<Complexing agent>
The electroless copper plating bath according to the present embodiment contains polyaminopolyphosphonic acid as a complexing agent. Polyaminopolyphosphonic acid can easily complex copper ions efficiently in the vicinity of neutrality, and can suppress the decomposition of the plating bath and enhance the stability.

  Specifically, examples of the polyaminopolyphosphonic acid include N, N, N ′, N′-ethylenediaminetetrakis (methylenephosphonic acid), nitrilotris (methylenephosphonic acid), diethylenediaminepenta (methylenephosphonic acid), and diethylenetriamine. Examples include penta (methylenephosphonic acid), bis (hexamethylenetriaminepenta (methylenephosphonic acid)), glycine-N, N-bis (methylenephosphonic acid), and the like.

  Although it does not specifically limit as a density | concentration of polyamino polyphosphonic acid as a complexing agent, It is preferable to set it as 0.01-1 mol / L. If the concentration is less than 0.01 mol / L, copper ions cannot be complexed sufficiently and the plating bath may become unstable. On the other hand, if the concentration exceeds 1 mol / L, the amount of pumping increases and the cost increases. Moreover, it is not economical because the deposition rate of copper becomes slow and the plating time becomes long. Furthermore, there is a possibility that the underlying film is damaged and deteriorated.

<Anionic surfactant>
The electroless copper plating bath according to the present embodiment contains an anionic surfactant. By containing an anionic surfactant, the stability of the plating bath can be improved.

  The detailed mechanism for improving the stability of the plating bath is not clear, but by adding an anionic surfactant, the anionic surfactant is adsorbed on the fine metal particles produced in the plating bath, and further grain growth occurs. This is considered to have an effect of helping dissolution of the fine particles by the complexing agent and other additives described above. In addition, it is considered that inhibiting the metal fine particles generated in the plating bath from aggregating and growing due to the dispersion effect of the anionic surfactant is also a factor for improving the bath stability.

  On the other hand, since the cationic surfactant has too high absorptivity on the surface of the metal fine particles, it inhibits plating deposition (the cationic surfactant once adsorbed on the surface is difficult to separate from the surface). In addition, nonionic surfactants have a lower adsorptivity to metal fine particles and a weak effect of improving bath stability compared to anionic surfactants and cationic surfactants. In addition, since the electroless copper plating bath has a high salt concentration, the nonionic surfactant is liable to generate cloudiness due to a lower cloud point. Furthermore, since the nonionic surfactant has a higher foaming property when its concentration is increased, it is difficult to increase the concentration in order to improve bath stability.

  Specifically, as the anionic surfactant, an alkylcarboxylic acid surfactant, a sodium salt of β-naphthalene sulfonic acid formalin condensate (for example, Demol N manufactured by Kao Corporation, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Naphthalenesulfonate formaldehyde condensates such as labeline series), sodium polyoxyethylene lauryl ether sulfate (for example, Emar 20C manufactured by Kao Corporation) and polyoxyethylene alkyl ether sulfate triethanolamine (for example, Kao Corporation) ) Emul 20T, etc.) polyoxyalkylene ether sulfate, sodium dodecyl sulfate (for example, Emar 10G manufactured by Kao Corporation), triethanolamine dodecyl sulfate (for example, Emar TD manufactured by Kao Corporation) and dodecyl Ammonium sulfate (for example, Emer manufactured by Kao Corporation) Higher alcohol sulfate esters or salts thereof, sodium dodecylbenzenesulfonate (for example, Neoperex GS manufactured by Kao Corporation, Lipon LH-200 manufactured by Lion Corporation, Daiichi Kogyo Seiyaku Co., Ltd.) Monobenzene Y-100, etc.) and linear alkylbenzene sulfonate sodium (for example, Neogen S-20F manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) or the like, sodium dialkylsulfosuccinate (for example, Kao ( Perex OT-P manufactured by Adeka Co., Ltd., Adeka Coal EC series manufactured by ADEKA Co., Ltd.), disodium lauryl sulfoi succinate (for example, Neo Haitenol LS manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) For example, Alkylsulfosuccine such as Neocor SW-C manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Ester surfactant, polyoxyethylene alkyl sulfosuccinic acid or a salt thereof (for example, Neo Hightail S-70 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), monoalkyl phosphate ester or a salt thereof (for example, ADEKA manufactured by ADEKA Corporation) PS / CS / TS series, phosphanol series manufactured by Toho Chemical Industry Co., Ltd.), polyoxyethylene tridecyl ether phosphate (for example, Prisurf A212C manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and polyoxyethylene Polyoxyethylene alkyl ether phosphoric acid such as lauryl ether phosphate (for example, Prisurf A208B manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) or the like, α-olefin sulfonic acid or salt thereof (for example, Daiichi Kogyo Seiyaku ( And Neogen AO-90, etc.).

  Although it does not specifically limit as a density | concentration of an anionic surfactant, It is preferable to set it as 0.01-2000 mg / L. If the concentration is less than 0.01 mg / L, the effect as a stabilizer cannot be sufficiently obtained, and the plating bath may become unstable. In addition, nodules and roughness are likely to occur. On the other hand, if the concentration exceeds 2000 mg / L, the foamability becomes too high. Moreover, the washability in a post-process falls and waste liquid and waste water treatment become difficult.

<Antimony compound>
The electroless copper plating bath according to the present embodiment contains an antimony compound. By adding an antimony compound in this way, it is possible to improve the deposition rate and suppress the protrusion by balancing the effect of promoting the precipitation of plating due to the underpotential deposition phenomenon and the effect of inhibiting the precipitation due to the catalyst poisoning effect associated with the adsorption of antimony. Can be obtained.

  The underpotential deposition phenomenon is because the target metal (copper) is promoted by the electrons released when the added element (antimony) is once reduced and then immediately re-dissolved as ions. This is a phenomenon in which metal is deposited at a potential lower than the theoretically calculated deposition potential.

  Specifically, for antimony compounds, the concentration effect on the deposition rate of the plating metal is convex, that is, the concentration is too low or too high, the precipitation rate is slow, and there is a concentration that maximizes the deposition rate. To do. Therefore, an inhibitory action appears on the edge of the pattern where the antimony is likely to be adsorbed (edge part), and an accelerating action mainly appears at the edges other than the edge where the antimony is difficult to adsorb. It is considered that the spread of plating deposition can be suppressed.

  Here, the relationship of the deposition rate of the plating metal depending on the concentration transition of the antimony compound will be described more specifically with reference to specific experimental examples.

First, as Experimental Example 1, a sample formed by patterning a TiN film on an Al—Si alloy sputter formed on a silicon wafer and then subjected to double zincate treatment according to a conventional method was subjected to electroless copper plating having the composition shown below. An electroless copper plating treatment was performed by immersing in a bath for 1 hour to form a copper plating film on the pattern.
[Electroless copper plating bath composition]
Ethylenediaminetetra (methylenephosphonic acid): 0.08 mol / L
Copper (copper sulfate / pentahydrate): 0.063 mol / L (4 g / L as copper concentration)
Dimethylamine borane: 8 g / L
Sodium lauryl sulfate: 20 mg / L
o-phenanthroline: 4 mg / L
Antimony oxide: See Table 1 below (as antimony concentration)
pH: 7.7
Bath temperature: 60 ° C

  Then, the film thickness of the formed plating film, the amount of precipitation outside the pattern (the amount of protrusion), and the plating appearance were examined. Table 1 below shows the measurement results. Further, FIG. 1 shows the change of the deposited film thickness with respect to the antimony concentration in the electroless copper plating bath. In Table 1 below, “bridge” in the protrusion evaluation indicates a state where the patterns are connected by plating protrusion, and “edge galling” in the appearance evaluation is the outer peripheral portion of the substrate / pad. This shows that the phenomenon that the film thickness of the film becomes thinner has occurred. A negative protrusion value means that no plating is deposited on the pattern edge due to edge galling and the base is exposed.

  When plating is performed under the conditions of the plating bath composition and the base in Experimental Example 1 described above, as shown in Table 1, in the case of no addition of antimony or in the case of a low concentration and in the case of a high concentration, the plating deposition rate becomes slow, It can be seen that as the plating film thickness is reduced, precipitation abnormality occurs at the pattern edge. On the other hand, when the antimony concentration is moderate in the concentration range of Table 1, a plating film having a good film thickness is formed, and the spread of plating deposition outside the pattern and edge galling are suppressed. I understand.

  Next, as Experimental Example 2, a ceramic substrate patterned with a nickel film was immersed in an electroless plating bath having the same composition as that of Experimental Example 1 for 1 hour with a palladium-substituted sample according to a conventional method. Then, an electroless copper plating treatment was performed to form a copper plating film on the pattern. That is, the relationship of the plating metal deposition rate due to the transition of the concentration of the antimony compound when the condition of the base to be plated was changed was examined. The antimony oxide concentration (as antimony concentration), which is a constituent of the plating bath, was changed as shown in Table 2 below.

  Then, the film thickness of the formed plating film, the amount of precipitation outside the pattern (the amount of protrusion), and the plating appearance were examined. Table 2 below shows the measurement results. Further, FIG. 2 shows the change of the deposited film thickness with respect to the antimony concentration in the electroless copper plating bath. The terms relating to evaluation in Table 2 below are the same as in Table 1 above.

  As shown in Table 2, even when the base conditions are changed, when no antimony is added, when the concentration is low, and when the concentration is high, the plating deposition rate becomes slow, the plating film thickness decreases, and the pattern edge It can be seen that precipitation anomalies have occurred. On the other hand, when the antimony concentration is medium in the concentration range of Table 2, a plating film having a good film thickness is formed, and the spread of plating deposition outside the pattern and edge galling are suppressed. I understand.

  As shown in Experimental Examples 1 and 2 as described above, although depending on the plating bath composition, plating base conditions, stirring conditions, etc., the deposition rate becomes slow even if the concentration is too low or too high. It can be clearly seen that there is a tendency that there is a concentration range where the speed is maximum. And, in the concentration range where the deposition rate is maximum, an inhibitory action appears on the pattern edge (edge part) where antimony is likely to be adsorbed, and an accelerating action mainly appears at the edge other than the edge where antimony is difficult to adsorb. It can be seen that the spread (protrusion) of the plating deposition outside the pattern can be suppressed while forming a plating film having a good film thickness.

  Therefore, by adding an antimony compound having a predetermined concentration to the plating bath in this way, the deposition rate can be improved based on the balance between the effect of promoting plating deposition and the effect of inhibiting the deposition due to the catalytic poison effect accompanying the adsorption of antimony. The effect of suppressing protrusion can be obtained and pattern selectivity can be enhanced, and a plating film having a good film thickness with suppressed protrusion can be formed.

  As described above, the specific amount (concentration) of the antimony compound varies depending on the constituent components (plating composition) of other plating baths, the conditions of the base, the stirring conditions, and the like. Although it is preferable to change appropriately, for example, it is 0.1-20 mg / L, Preferably it is 0.5-10 mg / L, More preferably, it can be 1-4 mg / L.

  The antimony compound is not particularly limited as long as it is a water-soluble compound that dissolves in the plating bath. For example, antimony oxide, antimony chloride, and the like can be used.

<Nitrogen-containing aromatic compound>
The electroless copper plating bath according to the present embodiment contains a nitrogen-containing aromatic compound.

  Conventionally, nitrogen-containing aromatic compounds such as 2,2'-bipyridyl and 1,10-phenanthroline have been used as stabilizers for plating baths and film property improving agents. However, although the detailed mechanism is not clear, by adding a nitrogen-containing aromatic compound to the electroless copper plating bath according to the present embodiment, the nitrogen-containing aromatic compound acts as an accelerator for promoting the plating metal. To come.

  Specifically, as this nitrogen-containing aromatic compound, imidazole or its substituted derivative, pyrazole or its substituted derivative, oxazole or its substituted derivative, thiazole or its substituted derivative, pyridine or its substituted derivative, pyrazine or its substituted derivative, pyrimidine Or substituted derivatives thereof, pyridazine or substituted derivatives thereof, triazine or substituted derivatives thereof, benzothiophene or substituted derivatives thereof, benzothiazole or substituted derivatives thereof, 2,2′-dipyridyl, 4,4′-dipyridyl, nicotinic acid, nicotinamide Pyridine such as picolines and lutidines or substituted derivatives thereof, quinoline such as hydroxyquinoline or substituted derivatives thereof, 3,6-dimethylaminoacridine, proflavine, acridine acid, quinoline-1,2-dicarboxylic acid and the like. Gin or substituted derivatives thereof, uracil, uridine, thymine, 2-thiouracil, 6-methyl-2-thiouracil, pyrimidine such as 6-propyl-2-thiouracil or substituted derivatives thereof, 1,10-phenanthroline, neocuproin, bathophenanthroline, etc. Phenanthroline or a substituted derivative thereof, and purines such as aminopurine, adenine, adenosine, guanine, hydantoin, adenosine, xanthine, hypoxanthine, caffeine, theophylline, theobromine, aminophylline, or substituted derivatives thereof.

  Although it does not specifically limit as a density | concentration of a nitrogen-containing aromatic compound, It is preferable to set it as 0.01-1000 mg / L. When the concentration is less than 0.01 mg / L, the effect as an accelerator cannot be obtained, and the speed becomes slow and the plating time becomes long, which is not economical. In addition, copper deposition in the initial stage may be deteriorated, resulting in damage to the base substrate or unprecipitated portions. On the other hand, when the concentration exceeds 1000 mg / L, the deposition rate becomes too high, resulting in a rough film. In addition, nodules and roughness are likely to occur, and pattern properties are reduced. Furthermore, the plating bath may become unstable.

<Other conditions>
The pH of the plating bath is pH 4.0 to 9.0, preferably pH 5.0 to 9.0, more preferably pH 6.0 to 8.0. As described above, in the electroless copper plating bath according to the present embodiment, aminoborane or a substituted derivative thereof that can be used under neutral to alkaline conditions is contained as a reducing agent. From this, it can be used in the range of pH 4.0-9.0, and can perform a plating process without giving a damage with respect to the base material which is a to-be-plated thing.

  Here, when the pH is less than 4.0, natural consumption of the reducing agent increases, leading to an increase in cost, and the plating bath becomes unstable. On the other hand, when pH becomes larger than 9.0, the damage to the base material used as a to-be-plated object will become large.

  The pH of the plating bath can be adjusted, for example, by containing a pH adjusting agent such as sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide.

  The temperature of the plating bath is not particularly limited, but is 20 to 90 ° C, preferably 40 to 80 ° C, and more preferably 60 to 70 ° C. When the bath temperature is less than 20 ° C., the deposition rate becomes slow and the plating time becomes long, which is not economical. On the other hand, when the bath temperature exceeds 90 ° C., the deposition rate becomes too fast, resulting in a rough film, and warping of the substrate may occur due to thermal contraction of the film after plating. In addition, nodules and roughness are likely to occur, and pattern properties may be reduced. Furthermore, the plating bath becomes unstable and the natural consumption of the reducing agent increases, leading to an increase in cost.

  As described above, the electroless copper plating bath according to the present embodiment is an electroless copper plating bath that contains aminoborane or a substituted derivative thereof as a reducing agent and does not contain formaldehyde. A phosphonic acid, an anionic surfactant, an antimony compound, and a nitrogen-containing aromatic compound are included. According to this electroless copper plating bath, since it can be used in the vicinity of neutrality, it does not damage the object to be plated, and is good even for an object to be easily deteriorated such as aluminum. Plating treatment can be performed.

  Moreover, according to this electroless copper plating bath, the stability of the plating bath can be improved and the balance between the promotion and suppression of plating deposition can be controlled, so that plating outside the pattern protrudes. On the other hand, it is possible to form a plating film having a desired good film thickness without causing edge galling or the like.

  Thereby, for example, without providing a barrier layer or the like for preventing out-of-pattern precipitation on aluminum or aluminum alloy or magnesium or magnesium alloy, it is possible to easily form a good plating film without protrusion, for example, It can be suitably used in the production of semiconductor wafers.

  Moreover, since the balance between the promoting action and the suppressing action of plating deposition can be controlled as described above, the formed plating film becomes smooth, and for example, the peel strength of wire bonding can be improved. Also, the appearance of the plating film is very good.

≪2. Electroless copper plating method >>
Next, an electroless copper plating method using the above-described electroless copper plating bath will be described. As the electroless plating method, a known method can be used. In addition, a known method can be applied to the catalyst application process when a catalyst application process or the like is necessary as the pretreatment.

  As described above, the temperature during the electroless copper plating treatment is performed by controlling the bath temperature of the electroless copper plating bath to 20 to 90 ° C, preferably 40 to 80 ° C, and more preferably 60 to 70 ° C.

  Moreover, it does not specifically limit as electroless copper plating processing time, What is necessary is just to set suitably so that it may become a desired film thickness. Specifically, for example, it can be about 30 seconds to 15 hours.

  In addition, when performing the electroless copper plating process, as a result of the progress of the plating process, copper ions are reduced to metallic copper by the reducing agent and deposited on the substrate, resulting in the concentration of copper ions in the plating solution and the reducing agent. The concentration will decrease and the pH will also change. Therefore, continuously or periodically, the electroless copper plating solution is supplemented with a water-soluble copper salt, reducing agent, complexing agent, or other additive as a copper ion source, and the concentration thereof is kept constant. It is preferable to keep it within the range.

  The electroless copper plating bath is preferably stirred by a method such as air bubbling as necessary.

  Specifically, as an electroless copper plating method using the above-described electroless copper plating bath, for example, a zincate (zinc) is applied to a substrate made of aluminum or an aluminum alloy, magnesium or a magnesium alloy without providing a barrier layer. After performing the (replacement) process, an electroless copper plating process is performed using the electroless copper plating bath described above. In the electroless copper plating method according to the present embodiment, since the out-of-pattern precipitation can be effectively suppressed as described above, it is possible to easily form a good plating film without providing a barrier layer or the like. it can.

  Alternatively, as another example of the electroless copper plating method, for example, a thin film containing copper, nickel, palladium, platinum, tungsten, molybdenum, rhodium, titanium, tantalum, or the like is substituted with palladium, platinum, copper, or the like. After performing the activation treatment, the electroless copper plating treatment is performed using the above-described electroless copper plating bath.

  Alternatively, after the above-described activation treatment, a reduction treatment is performed with a treatment liquid containing borane or a substituted derivative thereof, and then an electroless copper plating treatment is performed using the above-described electroless copper plating bath.

≪3. Examples >>
Hereinafter, specific examples of the present invention will be described. Note that the present invention is not limited to any of the following examples.

<Examination of composition of electroless copper plating bath>
First, in Examples 1 to 2 and Comparative Examples 1 to 10 shown below, the composition of the electroless plating bath was changed, and the film thickness of the plating film and the amount of precipitation outside the pattern (extruding amount) were examined. .

[Example 1]
(Electroless copper plating bath composition)
Ethylenediaminetetra (methylenephosphonic acid): 0.08 mol / L
Copper (copper sulfate / pentahydrate): 0.063 mol / L (4 g / L as copper concentration)
Dimethylamine borane: 8 g / L
Sodium lauryl sulfate: 20 mg / L
o-phenanthroline: 4 mg / L
Antimony oxide: Antimony concentration 2mg / L
pH: 7.7
Bath temperature: 60 ° C

(Electroless copper plating method)
After forming a pattern with a TiN film on an Al-Si alloy sputter formed on a silicon wafer, a sample subjected to double zincate treatment according to a conventional method is immersed in an electroless copper plating bath having the above composition for 1 hour. Electrolytic copper plating treatment was performed to form a copper plating film on the pattern.

(Evaluation)
About the formed plating film, the plating film thickness was measured from the height difference measurement before and after the plating treatment by a laser microscope. As a result, the formed plating film had a good film thickness of 5.3 μm, and the protrusion from the pattern was almost 5 μm.

[Example 2]
(Electroless copper plating bath composition)
Glycine-N, N-bis (methylenephosphonic acid): 0.13 mol / L
Copper (copper sulfate / pentahydrate): 0.063 mol / L (4 g / L as the copper concentration)
Dimethylamine borane: 8 g / L
Sodium lauryl sulfate: 20 mg / L
2,9-dimethyl-1,10-phenanthroline: 2 mg / L
Antimony oxide: Antimony concentration 2mg / L
pH: 7.7
Bath temperature: 60 ° C

(Electroless copper plating method)
After forming a pattern with a TiN film on an Al-Si alloy sputter formed on a silicon wafer, a sample subjected to double zincate treatment according to a conventional method is immersed in an electroless copper plating bath having the above composition for 1 hour. Electrolytic copper plating treatment was performed to form a copper plating film on the pattern.

(Evaluation)
About the formed plating film, the plating film thickness was measured from the height difference measurement before and after the plating treatment by a laser microscope. As a result, the formed plating film had a good film thickness of 5.3 μm, and the protrusion from the pattern was almost 5 μm.

[Comparative Example 1]
The electroless copper plating bath composition was subjected to electroless copper plating in the same manner as in Example 1 except that no antimony compound was added, and a copper plating film was formed on the pattern.

  As a result, the thickness of the formed plating film was 2.6 μm, which was thinner than those in Examples 1 and 2, and the protrusion from the pattern was 15 μm. Thus, plating deposition was suppressed, and a large amount of protrusion deposition was caused, resulting in very low pattern selectivity.

[Comparative Example 2]
The electroless copper plating bath composition was subjected to electroless copper plating in the same manner as in Example 1 except that lead 2 mg / L was added instead of antimony 2 mg / L, and a copper plating film was formed on the pattern. It was.

  As a result, the thickness of the formed plating film was 2.2 μm, which was thinner than those of Examples 1 and 2, and the protrusion from the pattern was 12 μm. Thus, plating deposition was suppressed, and a large amount of protrusion deposition was caused, resulting in very low pattern selectivity.

[Comparative Example 3]
The electroless copper plating bath composition was subjected to electroless copper plating treatment in the same manner as in Example 1 except that thallium 0.3 mg / L was added instead of antimony 2 mg / L, and a copper plating film was formed on the pattern. Formed.

  As a result, the thickness of the formed plating film was 1.8 μm, which was very thin compared to Examples 1 and 2. Further, the amount of protrusion from the pattern was large, and the connection between the patterns (bridge) occurred due to the protrusion, so that the amount of protrusion could not be measured. Thus, plating deposition was suppressed, and a large amount of protrusion deposition was caused, resulting in very low pattern selectivity.

[Comparative Example 4]
The electroless copper plating bath composition was subjected to electroless copper plating in the same manner as in Example 1 except that sodium lauryl sulfate was not added to form a copper plating film on the pattern.

  In Comparative Example 4, the plating bath was decomposed during the plating process, and the plating process could not be performed normally.

[Comparative Example 5]
The electroless copper plating bath composition was subjected to electroless copper plating in the same manner as in Example 1 except that o-phenanthroline was not added to form a copper plating film on the pattern.

As a result, the protrusion from the pattern was as small as 0.5 μm, but the plating film thickness was as extremely thin as 1.2 μm, and the plating rate was significantly reduced.
[Comparative Example 6]
For the electroless copper plating bath composition, electroless copper plating treatment was performed in the same manner as in Example 1 except that 0.5 g / L of polyethylene glycol (PEG) # 1000 was added instead of 20 mg / L of sodium lauryl sulfate. A copper plating film was formed on the pattern.

  In Comparative Example 6, the plating bath was decomposed during the plating process, and the plating process could not be performed normally.

[Comparative Example 7]
The electroless copper plating bath composition was subjected to electroless copper plating in the same manner as in Example 1 except that bismuth 2 mg / L was added instead of antimony 2 mg / L, and a copper plating film was formed on the pattern. It was.

  As a result, although the film thickness of the formed plating film was as good as 4.4 μm, it was not possible to measure the amount of protrusion because the connection (bridge) between patterns occurred due to the protrusion of the plating outside the pattern. It was.

[Comparative Example 8]
The electroless copper plating bath composition was the same as in Example 1 except that 0.08 ml / L of diethylenetriaminepentaacetic acid was added instead of 0.08 mol / L of ethylenediaminetetra (methylenephosphonic acid). And a copper plating film was formed on the pattern.

  In Comparative Example 8, copper plating was not deposited, and corrosion of the Al—Si alloy spatter forming the pattern occurred.

[Comparative Example 9]
An electroless copper plating treatment was performed in the same manner as in Example 1 except that an electroless copper plating bath having the following composition was used, and a copper plating film was formed on the pattern.

(Electroless copper plating bath composition)
Ethylenediaminetetraacetic acid: 0.08 mol / L
Copper (copper sulfate, pentahydrate): 0.0315 mol / L (2 g / L as the copper concentration)
Formaldehyde: 2g / L
Polyethylene glycol (PEG) # 1000: 1 g / L
2,2 ″ -dipyridyl: 20 mg / L
pH: 13.2 (adjusted with NaOH)
Bath temperature: 60 ° C

  In Comparative Example 9, the Al—Si alloy sputter was dissolved, and plating could not be performed normally. This is presumably because the plating bath uses formaldehyde as a reducing agent and is highly alkaline, so that the damage to the substrate has increased.

[Comparative Example 10]
An electroless copper plating treatment was performed in the same manner as in Example 1 except that an electroless copper plating bath having the following composition was used, and a copper plating film was formed on the pattern.

(Electroless copper plating bath composition)
Ethylenediaminetetraacetic acid: 0.08 mol / L
Copper (copper sulfate, pentahydrate): 0.0315 mol / L (2 g / L as the copper concentration)
Glyoxylic acid: 6 g / L
Polyethylene glycol (PEG) # 1000: 1 g / L
2,2 ″ -dipyridyl: 20 mg / L
pH: 13.2 (adjusted with NaOH)
Bath temperature: 60 ° C

  In Comparative Example 10, the Al—Si alloy sputter was dissolved and plating could not be performed normally. This is considered that the plating bath uses glyoxylic acid as a reducing agent and is highly alkaline like formaldehyde, so that the damage to the base material has increased.

Claims (7)

An electroless copper plating bath having a pH of 4 to 9, which contains a water-soluble copper salt and aminoborane or a substituted derivative thereof as a reducing agent and does not contain formaldehyde,
Containing a polyaminopolyphosphonic acid as a complexing agent, an anionic surfactant, an antimony compound, and a nitrogen-containing aromatic compound ,
An electroless copper plating bath , wherein the concentration of the antimony compound is 1 to 4 mg / L. 2. The electroless copper plating bath according to claim 1, wherein the electroless copper plating bath has a pH of 6.0 to 8.0. The electroless copper plating bath according to claim 1 or 2 , wherein the concentration of the polyaminopolyphosphonic acid is 0.01 to 1 mol / L. The anionic surfactant concentration is, electroless copper plating bath according to claim 1 to 3, wherein the a 0.01~2000mg / L.   The electroless copper plating bath according to any one of claims 1 to 4, wherein the concentration of the nitrogen-containing aromatic compound is 0.01 to 1000 mg / L.   An electroless copper plating method, wherein a copper plating film is formed on the substrate using the electroless copper plating bath according to claim 1. The electroless copper plating method according to claim 6, wherein the base material is aluminum, an aluminum alloy, magnesium, or a magnesium alloy.

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