Patent Publication Number: US-2019186032-A1

Title: Composition for cobalt plating and method for forming metal wiring using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2017-0172046, filed on Dec. 14, 2017, and Korean Patent Application No. 10-2018-0155422, filed on Dec. 5, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The following disclosure relates to a composition for cobalt plating and a method for forming a metal wiring using the same, and more particularly, to a composition for cobalt plating that suppresses thermal expansion of the metal caused by the high temperature of the process to achieve excellent high-temperature stability, thereby resulting in prevention of deformation of a substrate even without any structural modification of the substrate or additional processing, and a method for forming a metal wiring using the same. 
     BACKGROUND 
     In accordance with the recent tendency of electronic devices to become lighter, thinner, and smaller, electronic components such as semiconductors, printed circuit boards (PCBs), and the like, constituting the electronic devices, are required to have high density and high integration. Thus, various studies have been conducted to reduce the size of semiconductors while simultaneously improving the performance thereof. 
     A semiconductor chip is subjected to repeated thermal treatments such as annealing during a metal lamination process and a post-process. However, when the process is repeatedly performed at high temperature and room temperature, stress occurs due to a damascene structure and thermal expansion of the metal material filled in a via hole, thereby resulting in substrate deformation problems such as warping, extrusion, and the like. These problems may cause thermal mismatch between laminated chips, thus leading to defects such as poor connection, deterioration of electrical conductivity, and the like. 
     To this end, Korean Patent Publication No. 10-1095055 discloses a method of forming a via hole in a substrate for attenuating thermal stress in the via hole and then forming a bulb hole in the via hole by an isotropic etching method. 
     In the above-described patent, it is attempted to improve the thermal stability in view of the structural property, but the method of adding a structure for mitigating volumetric expansion inside a via has a problem in that it makes the hole forming process complicated. 
     Patent Literature: KR10-1095055 
     SUMMARY 
     An embodiment of the present disclosure is directed to providing a composition for cobalt plating capable of achieving excellent high-temperature stability using a carbonaceous material having a low coefficient of thermal expansion and high thermal conductivity, and a method for forming a metal wiring using the same. 
     All of the above objects and other objects of the present disclosure can be achieved by the present disclosure described below. 
     To achieve the above-mentioned problem, the present invention provides a composition for cobalt plating comprising: a) 0.1 to 30% by weight of a cobalt salt; b) 0.001 to 5% by weight of chloride or hydrochloric acid; c) 0.01 to 10% by weight of boric acid; d) 0.001 to 1% by weight of a carbonaceous material; and e) a residual amount of a solvent. 
     Further, the present invention provides a method for forming a metal wiring comprising a step of forming a cobalt thin film on a substrate using the composition for cobalt plating of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a SEM image of a cross-section of a substrate manufactured in Example 1 of the present disclosure. 
         FIG. 2  is a SEM image of a cross-section of a substrate manufactured in Comparative Example 1 of the present disclosure. 
         FIG. 3  is an image showing a cross-section of the substrate manufactured in Example 1 of the present disclosure measured with an energy dispersive X-ray analyzer. 
         FIG. 4  is an image showing a cross-section of the substrate manufactured in Comparative Example 1 of the present disclosure measured with an energy dispersive X-ray analyzer. 
         FIG. 5  is an image of the substrate manufactured in Example 1 of the present disclosure taken by SEM after a durability test. 
         FIG. 6  is an image of the substrate manufactured in Comparative Example 1 of the present disclosure taken by SEM after a durability test. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a composition for cobalt plating of the present disclosure and a method for forming a metal wiring using the same are described in detail. 
     The present inventors studied to solve a problem in that the metal filled in a wiring groove of a substrate thermally expands during high-temperature processes, and as a result, found that when a composition for cobalt plating comprises a carbonaceous material, excellent high-temperature stability is achieved due to a low coefficient of thermal expansion, thus completing the present disclosure based on this finding. 
     The composition for cobalt plating of the present disclosure is characterized by comprising: a) 0.1 to 30% by weight of a cobalt salt; b) 0.001 to 5% by weight of chloride or hydrochloric acid; c) 0.01 to 10% by weight of boric acid; d) 0.001 to 1% by weight of a carbonaceous material; and e) a residual amount of a solvent. In this case, there is an effect of suppressing thermal expansion of the metal occurring during a post-treatment high-temperature process, thereby resulting in prevention of deformation of a substrate even in the absence of any structural modification is of the substrate or additional processing. 
     a) Cobalt Salt 
     The cobalt salt may be, for example, one or more selected from the group consisting of cobalt sulfate, cobalt nitrate, and cobalt acetate. In this case, the cobalt salt is reduced and precipitated as a cobalt metal through an electrochemical reaction to form a metal wiring. 
     The cobalt salt may have an amount of, for example, 0.1 to 30% by weight, 0.1 to 20% by weight, or 0.5 to 15% by weight, and more preferably 5 to 15% by weight with respect to the composition for cobalt plating. Within this range, an excellent effect of reducing the cobalt and precipitating it as cobalt metal to form the metal wiring is be achieved. 
     For example, the cobalt metal may have a coefficient of thermal expansion of 12×10 −6 ° C. to 15×10 6 ° C., or 13×10 −6 ° C. to 14×10 −6 ° C., and within this range, expansion of the metal at a high temperature easily occurs. 
     The coefficient of thermal expansion means the ratio between the thermal expansion and temperature of an object under a constant pressure, and the coefficient of thermal expansion in the present disclosure is measured according to ASTM D696. 
     The cobalt salt may have a concentration of, for example, 80 to 250 g/L or 100 to 150 g/L, and within this range, the effect of reducing the cobalt and precipitating it as cobalt metal through the electrochemical reaction is excellent. 
     b) Chloride or Hydrochloric Acid 
     The chloride may be, for example, cobalt chloride. In this case, there is an advantageous effect in manufacturing a composition for cobalt plating having an excellent plating performance. 
     The cobalt chloride, for example, may be dissociated into chloride ions in an aqueous solution state in a plating solution, wherein the chloride ions may have a concentration of, for example, 10 to 1,000 ppm, or 1 to 150 ppm with respect to the composition for cobalt plating. Within this range, there is an effect in that a uniform plating film without the inclusion of foreign materials is achieved. 
     The chloride may have an amount of, for example, 0.001 to 5% by weight, 0.01 to 4% by weight, and more preferably 0.05 to 2% by weight with respect to the composition for cobalt plating. Within this range, there is an effect in that a uniform plating film without the inclusion of foreign materials is achieved. 
     The chloride may be replaced with, for example, hydrochloric acid. In this case, there is an effect in that the electrical conductivity is excellent. 
     c) Boric Acid 
     The boric acid serves to prevent the deposition of cobalt hydroxide, which may be formed when the local pH near an electrode surface increases during plating. 
     The boric acid may have an amount of, for example, 0.01 to 10% by weight, 0.05 to 7% by weight, and more preferably 0.1 to 5% by weight with respect to 100% by weight of the composition for cobalt plating. Within this range, there is an excellent effect of constantly maintaining and controlling the pH of the composition for cobalt plating. 
     The boric acid may have a concentration of, for example, 1 to 100 g/L, 2 to 50 g/L, or 10 to 35 g/L. Within this range, the effect of adjusting the pH of the composition for cobalt plating and maintaining it at a constant level is excellent. 
     D) Carbonaceous Material 
     The carbonaceous material may be one or more selected from the group consisting of carbon black, activated carbon, expanded graphite, graphene, carbon nanotube, carbon fiber, and graphite, and more preferably may be graphene oxide or carbon nanotube. In this case, there is an effect in that excellent high-temperature stability is achieved through lowering of the coefficient of thermal expansion of the composition for cobalt plating. 
     The carbonaceous material may have a coefficient of thermal expansion of 1×10 −6 ° C. to 5×10 6 /° C., or 2×10 −6 /° C. to 4×10 −6 /° C. Within this range, there is an effect in that the high-temperature stability is excellent, thus resulting in easy application to semiconductor chips. 
     The graphene is, for example, a two-dimensional material made by forming a hexagonal lattice structure of carbon atoms. In this case, the thermal properties and physical properties are very outstanding. 
     The graphene can be obtained, for example, by performing reduction treatment on graphene oxide, wherein the reduction may be performed under an inert atmosphere, specifically, under an N 2  atmosphere at 50 to 400° C. or at 100 to 200° C. for 15 to 100 minutes, or for 30 to 60 minutes. 
     Within this range, the oxide graphene is reduced and converted to graphene, and there is an effect of lowering the coefficient of thermal expansion of the composition for cobalt plating. 
     The flake size of the graphene oxide may be, for example, 0.01 to 30 microns, 0.1 to 10 microns, and more preferably 0.1 to 7 microns. Within this range, there is an effect of achieving excellent high-temperature stability by lowering the coefficient of thermal expansion of the composition for cobalt plating. 
     The size of the graphene oxide can be measured by Atomic Force Microscope (AFM), or Transmission Electron Microscope (TEM). 
     The thickness of the graphene oxide may be, for example, 0.2 to 100 nm, 0.3 to 30 nm, and more preferably 0.34 to 15 nm. Within this range, excellent thermal and physical properties are achieved. 
     In the present disclosure, the thickness of graphene may be measured by AFM. 
     The graphene oxide can be, for example, a single atomic layer, multiple atomic layers, or a mixed layer thereof, preferably with a composition of 50% or more, 50 to 99%, or 70 to 90% of a single atomic layer. In this case, there is an effect of achieving excellent high-temperature stability. 
     The carbon nanotube may be, for example, a one-dimensional material in which a carbon atom layer is rolled up in a tube shape. In this case, outstanding thermal and physical properties are achieved. 
     The carbon nanotube may have, for example, a diameter of 1000 nm or less or 10 to 1000 nm, and a length of 10 nm or more, or 10 to 1000 nm. In this case, there is an effect of suppressing thermal expansion of the metal occurring during the process, thereby resulting in prevention of deformation of a substrate. 
     The carbon nanotube may be, for example, a single-walled carbon nanotube or a multi-walled carbon nanotube. In this case, the high-temperature stability is excellent. 
     The carbon nanotube may have, for example, a diameter of 50 nm or less, or 1 to 50 nm, and a length of 90 nm or more, or 90 to 1000 nm. In this case, there is an effect of suppressing thermal expansion of the metal occurring during the process, thereby resulting in prevention of deformation of a substrate. 
     In the present disclosure, the diameter and length of the carbon nanotube can be measured through a transmission electron microscope (TEM). 
     The carbonaceous material may be, for example, 0.001 to 1% by weight, 0.001 to 0.5% by weight, or more preferably 0.005 to 0.2% by weight with respect to the composition for cobalt plating. Within this range, the effect of improving thermal stability is excellent, and agglomeration and precipitation do not occur, thereby resulting in excellent stability of the composition for cobalt plating. 
     e) Solvent 
     The composition for cobalt plating may comprise, for example, a solvent. The solvent may be, for example, water or a polar organic solvent. In this case, it may be compatible with the components of the present disclosure and may have excellent ease of processing and storage stability. 
     The water may be, for example, distilled water. In this case, it may have excellent compatibility with the components of the present disclosure and allow the effects of the present disclosure to be manifested well. 
     The polar organic solvent may be, for example, one or more selected from the group consisting of esters such as methyl formate, ethyl formate, methyl acetate, dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, butyrolactone, and the like; nitriles such as acetonitrile, benzonitrile, and the like; nitro compounds such as nitromethane, nitrobenzene, and the like; amides such as N,N-dimethylformamide, N,N-diethylformamide, N-methylpyrrolidinone, and the like; sulfoxides such as dimethyl sulfoxide, and the like; sulfones such as dimethyl sulfone, tetramethylene sulfone, and other sulfonic acids, and the like; and oxazolidinone such as N-methyl-2-oxazolidinone, and the like. 
     The content of the solvent is not particularly limited, and may be, for example, a residual amount, excluding the components in the composition for cobalt plating, and can be appropriately adjusted in consideration of workability, stability, and the like, of the composition for cobalt plating of the present disclosure. 
     f) Other Additives 
     The composition for cobalt plating according to the present disclosure may further comprise, for example, 0.0001 to 0.1% by weight, or 0.001 to 0.08% by weight of one or more additives selected from the group consisting of accelerators, retarders and leveling agents. In this case, there is an advantage in that voids or seams do not occur when the metal is filled in a wiring groove of the substrate. 
     The accelerator may be, for example, a sulfo group-containing compound. In this case, there is an effect of increasing the rate at which cobalt is reduced, thereby resulting in an increase in the cobalt filling rate. 
     The sulfo group-containing compound may be, for example, one or more selected from the group consisting of disodium 3,3′-dithiobis(1-propanesulfonate), bis(3-sulfopropyl)disulfide, mercaptoethane sulfonic acid, 3-mercapto-1-propanesulfonic acid, 3-N,N-dimethlyaminodithiocarbamoyl-1-propanesulfonic acid, and a C1-C20 alkyl sulfonic acid, and preferably disodium 3,3′-dithiobis(1-propanesulfonate). In this case, there is an effect of increasing the rate at which cobalt is reduced, thereby resulting in an increase in the cobalt filling rate. 
     The accelerator may have a concentration of, for example, 0.5 to 200 μM, or 4 to 50 μM. Within this range, there is an effect of increasing the cobalt filling rate. 
     For example, the retarder may be one or more selected from the group consisting of polyethylene glycol, polypropylene glycol, poly(ethylene glycol-co-propylene glycol), polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol, polyvinyl alcohol, polyethylene oxide, stearyl alcohol polyglycol ether, stearic acid polyglycol ester, oleic acid polyglycol ester, nonylphenol polyglycol ether, octanol polyalkylene glycol ether, and octanediol bis-(polyalkylene glycol ether). In this case, there is an effect of suppressing the movement of cobalt ions and adjusting the rate at which cobalt is reduced to control the cobalt filling rate and to prevent the formation of voids or seams during the filling, thereby resulting in improvement of reliability. 
     The retarder may have a concentration of, for example, 1 to 200 μM or 20 to 100 μM. Within this range, there is an effect of suppressing the movement of cobalt ions and adjusting the cobalt filling rate so that the cobalt filling rate is controlled. 
     The leveling agent prevents the formation of voids caused by blocking an entrance of the wiring groove in accordance with the rapid growth of a plating layer due to the concentration of an electric field at the entrance of the wiring groove when the composition for cobalt plating of the present disclosure is filled in the wiring groove on the substrate. 
     Examples of the leveling agent may comprise one or more selected from the group consisting of polyimine, polyamine, polyethyleneimine, alkylated polyethyleneimine, polyvinylpyridine, polyvinylpyrrolidone, pyrrole, 2-mercaptothiazoline, 4-mercaptopyridine, ethylenethiourea, thiourea, pyrazole, polyaniline, imidazole, triazole, tetrazole, pentazole, benzimidazole, benzotriazole, oxazole and benzoxazole. In this case, there is an excellent effect of preventing the via hole or trench from being blocked first. 
     The leveling agent may have a concentration of, for example, 1 to 200 μM or 10 to 80 μM. Within this range, there is an effect of preventing the via hole or trench from becoming clogged first. 
     Composition for Cobalt Plating 
     The composition for cobalt plating may further comprise conventional additives such as a surfactant, a reducing agent, chloride ions, a defoaming agent, and the like. In this case, the additives which may be employed are not particularly limited as long as they are commonly used in the technical field of the present disclosure. 
     The composition for cobalt plating may have a pH of, for example, 2 to 9, 2 to 5, or 7 to 9. Within this range, the plating performance is excellent. 
     Method for Forming Metal Wiring 
     The method for forming a metal wiring of the present disclosure may comprise, for example, a step of forming a cobalt thin film on a substrate using the composition for cobalt plating of the present disclosure. In this case, there is an excellent effect of suppressing thermal expansion of the metal occurring during high-temperature processes, thereby resulting in prevention of deformation of a substrate even without any structural modification of the substrate or additional processing. 
     The step of forming the cobalt thin film may be performed, for example, by electroplating, and the electroplating method is not particularly limited, but for example, may be performed using a plating apparatus which comprises a plating bath containing a composition for plating, a substrate holder supporting a substrate serving as a negative electrode, a positive electrode having an opposite electrode with respect to the substrate holder, and a current source for supplying a current. 
     The electroplating may be, for example, a method of performing pretreatment on a substrate and then immersing the substrate in a composition for cobalt plating, wherein the pretreatment may be, for example, a method of performing alkaline degreasing, hydrophilization treatment, acid activity, or the like. 
     The electroplating may be performed, for example, with a current density of 0.1 to 15 ASD, or 1 to 7 ASD. Within this range, when electroplating is performed using the composition for cobalt plating of the present disclosure, deformation of the substrate can be significantly prevented due to the thermal stability in a subsequent high-temperature post-treatment process. 
     The electroplating may be performed, for example, at 10 to 80° C., or 20 to 35° C. Within this range, when electroplating is performed using the composition for cobalt plating of the present disclosure, deformation of the substrate can be significantly prevented due to thermal stability in a subsequent high-temperature post-treatment process. 
     The substrate may be, for example, one selected from the group consisting of a silicon substrate, a silicon-germanium substrate, a metal oxide single crystal substrate, a silicon on insulator (SOI) substrate, a germanium on insulator (GOI) substrate, and a copper substrate. In this case, there is an effect of preventing the substrate from being deformed even in the absence of any structural modification of the substrate or additional processing. 
     The substrate may have a structure of, for example, a through silicon via (TSV), a damascene, redistribution layer (RDL), or under bump metallurgy (UBM) structure. In this case, a via hole or a trench is formed and the inside thereof is filled with a conductive material, thereby resulting in the achievement of good physical and electrical connection between semiconductor chips. 
     The TSV, damascene, RDL, or UBM above refers to the method of transmitting an electrical signal between the chips by forming the via hole or the trench vertically penetrating the semiconductor chips when the wirings are formed in the chip, and when the semiconductor chips are stacked. 
     The via hole or trench may have, for example, a depth of 0.03 to 500 μm, a width of 0.007 to 500 μm, and an aspect ratio of 1:0.01 to 1:150, preferably 1:0.1 to 1:0.60, or 1:3 to 1:10. Within this range, there is an effect of preventing the substrate from being deformed even in the absence of any structural modification of the substrate or additional processing. 
     The aspect ratio means the width/depth ratio. 
     The materials used in the Examples and Comparative Examples below are as follows:
         Cobalt salt: Cobalt Sulfate (CoSO 4 *7H 2 O)   Chloride: Cobalt Chloride (CoCl 2 )   Accelerators: SPS (Disodium 3,3′-Dithiobis(1-propanesulfonate)   Retarders: PEG (Polyethylene glycol), PEG(Polyethylene glycol)-block-PPG(Polypropylene glycol)-block-PEG(Polyethylene glycol)   Leveling Agents: Polyethylenimine, Benzotriazole   Carbonaceous Material: Graphene Oxide with a flake size of 0.2 to 5 microns, an atomic layer of 70% or more, and a thickness of 0.34 to 5 nm.       

     EXAMPLES 
     Example 1 
     Plating Treatment Process 
     A silicon wafer coated with copper having a size of 30 mm×30 mm was prepared and subjected to a pretreatment process. Then, the wafer was immersed in a cobalt plating solution, and a current was applied with a current density of 4.0 ASD to perform plating. Here, the temperature of the cobalt plating solution was maintained at 30° C., and stirring was continuously performed throughout the plating process using a rotating disk. As the cobalt plating solution acting as a virgin makeup solution (VMS), a solution containing 10.0 part by weight of cobalt sulfate (CoSO 4 *7H 2 O), 5.0 parts by weight of boric acid (H 3 BO 3 ), 1.0 parts by weight of cobalt chloride (COCl 2 ), 0.005 parts by weight disodium 3,3′-dithiobis(1-propanesulfonate) (SPS), 0.01 parts by weight of polyethylene glycol (PEG), 0.005 parts by weight of polyethylenimine, 0.05 parts by weight of graphene oxide, and a residual amount of distilled water (DIW), was used. 
     Reduction Treatment Process 
     The silicon wafer on which the cobalt plating was formed was subjected to a reduction treatment at 300° C. for 60 minutes in an N 2  atmosphere to reduce the graphene oxide to graphene. 
     Example 2 
     Example 2 was performed in the same manner as in Example 1, except that 0.02% by weight of PEG(polyethylene glycol)-block-PPG(polypropylene glycol)-block-PEG(polyethylene glycol) was used instead of 0.01% by weight of PEG (Poly ethylene glycol, and 0.005% by weight of benzotriazole was used instead of polyethylenimine. 
     Example 3 
     Example 3 was performed in the same manner as in Example 1, except that no other additives (accelerators, retarders and leveling agents) were added to the cobalt plating solution. 
     Comparative Example 1 
     Comparative Example 1 was performed in the same manner as in Example 1, except that the graphene oxide was not added to the cobalt plating solution and the reduction treatment was not performed. 
     Test Example 
     The plating properties of Examples 1 to 3 and Comparative Example 1 were measured by the following methods, and results thereof are shown in the drawings and Tables 1 and 2 below. 
     Confirmation of formation of graphene oxide
         SEM: Cross sections of the manufactured substrates were photographed by SEM. Results thereof are shown in  FIG. 1  (Example 1) and  FIG. 2  (Comparative Example 1). Unlike in  FIG. 2 , it could be confirmed from the circled portion of  FIG. 1  that a black carbon material was formed on the substrate.   Energy dispersive X-ray analyzer (EMAX X-ray Detector): Cross sections of the manufactured substrates were measured using an energy dispersive X-ray analyzer (EX-250 manufactured by HORIBA, Ltd.). Results thereof are shown in Table 1 below, and the measurement portions are shown in  FIG. 3  (Example 1) and  FIG. 4  (Comparative Example 1).       

     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                   
                   
                   
                 Comparative 
               
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Element 
                   
                 Element 
                   
                 Element 
                   
                 Element 
               
               
                 Elements 
                 wt % 
                 Ratio % 
                 wt % 
                 Ratio % 
                 wt % 
                 Ratio % 
                 wt % 
                 Ratio % 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 C k 
                 21.33 
                 52.95 
                 20.59 
                 50.07 
                 16.12 
                 45.64 
                 — 
                 — 
               
               
                 o k 
                 5.32 
                 9.92 
                 7.94 
                 14.50 
                 3.85 
                 8.18 
                 — 
                 — 
               
               
                 Co k 
                 73.35 
                 37.12 
                 71.47 
                 35.43 
                 80.03 
                 46.18 
                 100 
                 100 
               
               
                 Total 
                 100.00 
                 100.00 
                 100.00 
                 100.00 
                 100.00 
                 100.00 
                 100.00 
                 100.00 
               
               
                   
               
            
           
         
       
     
     As shown in Table 1, it could be confirmed that the contents of C and O atoms of Examples 1 to 3 increased, and thus it could be appreciated that the black material formed on the substrate was graphene. 
     Durability Test 
     The manufactured substrates were subjected to thermal treatment at 350° C. for 60 minutes in an N 2  atmosphere and the results thereof are shown in  FIG. 5  (Example 1) and  FIG. 6  (Comparative Example 1). In  FIG. 5 , no change was observed in the surface of the substrate, but in  FIG. 6 , it could be confirmed that cracks and desorption of the substrate occurred. 
     Surface Resistance Test 
     In order to measure the surface resistivity of the manufactured substrates, surface resistance values of the center and four edges were measured and averaged using a 4-point probe method. The surface resistance values were measured before and after the thermal treatment on the above-manufactured substrates at 350° C. for 60 minutes under the N 2  atmosphere, and results thereof are shown in Table 2 below. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Comparative 
               
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 1 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Resistance 
                 −5.5% 
                 −6.2% 
                 −7.4% 
                 −13.1% 
               
               
                 increase/decrease rate 
               
               
                 after heat treatment 
               
               
                   
               
            
           
         
       
     
     As shown in Table 2, in the substrate of Examples 1 to 3 according to the present disclosure, it could be confirmed that the thermal expansion of the cobalt metal occurring during the high-temperature process was suppressed, and thus the surface resistance increase/decrease rate after the high-temperature heat treatment was low. On the contrary, in Comparative Example 1 in which no graphene was formed, it could be confirmed that the surface resistance increase/decrease rate was −13.1%, which was more than two times higher than that in Example 1. 
     According to the present disclosure, there are provided a composition for cobalt plating capable of achieving excellent high-temperature stability using a carbonaceous material having a low coefficient of thermal expansion and high thermal conductivity, and a method for forming a metal wiring using the same.