Abstract:
There is a method and apparatus for plating in which electroless copper plating is performed in a contact hole and an interconnect trench on a minute scale of a semiconductor integrated circuit device, and a plating structure. Organic material originated from an organic gas carried over from the preceding step is removed from the inner surface of a blind hole, thereafter the surface of the barrier layer is subjected to predetermined pretreatments comprising a hydroxylation treatment, a coupling treatment, a Pd colloidal solution treatment and the like, and following the pretreatments, electroless plating with copper is effected desirably under influence of ultrasonic waves. Hence, a uniform, good quality plating layer is formed inside and outside the hole and a CMP processing following the plating is performed with ease.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for plating, and a plating structure and for example, to a method and apparatus that are preferable for forming a copper interconnection in a contact hole or an interconnect trench, and an interconnect structure in a semiconductor integrated device. 
     BACKGROUND OF THE INVENTION 
     Al (aluminum) interconnects have conventionally been formed in fine contact holes or interconnect trenches of a high density integrated circuit fabricated on a semiconductor wafer (hereinafter referred to as wafer). The Al interconnects, however, have exposed a tendency to be increasingly replaced with Cu (copper) interconnects because of its limited resistance to electromigration. As Cu interconnection techniques in the contact holes and interconnect trenches, a so called Damascene approach that comprises a process in which Cu interconnection material is filled into the openings by electroplating and unnecessary portions of the interconnection material are removed by polishing using a CMP (Chemical Mechanical Polishing) technique has been regarded as having great promise in the future for reduction in manufacturing cost of a semiconductor device since there is no need to fill spaces between interconnects with an interlayer insulating film. Further, an interconnect can be formed in an opening with a high aspect ratio. 
     FIGS. 1 to  4  are sectional views schematically showing a copper interconnection process by means of a Damascene technique (here, a dual Damascene technique). 
     That is, in the process shown in the figures, insulating layers  34  and  35 , such as layers made of SiO 2 , are stacked on copper interconnects  32   a  and  32   b  (on whose upper and lower surface barrier layers  33  are provided) which are formed on a wafer  31  by etching or the like. Thereafter, a contact hole  36  and interconnect trenches  37  are formed by etching or the like and copper interconnects are formed by electroplating copper which constitutes as interconnection material. In the interconnection process, a seed layer  39  that serves as nuclei for plating is formed in the contact hole  36  and interconnect trench  37  as shown in FIG. 2 after a barrier layer  38  is formed as shown in FIG.  1 . Following formation of the seed layer, a copper electroplating layer  40  is formed as shown in FIG. 3 (which is an enlarged sectional view of a region in the vicinity of the contact hole  36  of FIG. 2) and the electroplating layer  40  is polished off to form an copper interconnect  43  in the contact hole  36  as shown in FIG.  4 . In addition, a copper interconnect similar to that in the contact hole  36  is simultaneously formed in the interconnect trench  37  as well. 
     However, a recess  42  and a seam  41  are apt to occur respectively on and in the interconnect as shown in the figures. Associated with this phenomenon, there arise problems such as items (1) to (4) which will be shown as follows: (1) Since an electroplating film is deposited on the surface of the wafer  31  and, especially, in the vicinity of the mouth of the blind hole (contact hole)  36  with priority assigned thereto, there arise limitations that the minimum of a diameter D of the blind hole  36  is 0.25 μm and the highest aspect ratio thereof is of the order of 5. (2) Filling by electroplating into the blind hole  36  is possible by selecting an effective combination of additives. However, when the additives are selectively combined so as to electroplate a small diameter blind hole, an almost flat surface finish is obtained in a wide mouthed trench, whereas a swollen surface finish is formed at the top of a small diameter blind hole; that is, a flat surface finish is hard to acquire in a small diameter blind hole, which entails more difficulty in planarization by CMP. (3) As shown in FIG. 2, when the seed layer  39  is formed, the seed layer  39  is not formed on the sidewall of the blind hole  36  in a uniform thickness, but rather the layer  39  is apt to be formed thick on the upper surface and areas in the vicinity of the respective mouths of the blind hole  39  and interconnect trench  37 . Such spatial thickness distribution of the seed layer  39  with a large dispersion, in turn, is a cause for a spatial thickness dispersion in electroplating. (4) Further, when electroplating is performed in an apparatus of a rotary electrode type, a thickness variation along a diameter is recognized: the state is such that an 8 inch diameter wafer has a variation of the order of 3% and a 12 inch diameter wafer has a variation of the order of 5%, which acts as a difficult factor in globally uniform planarization across the entire surface of a wafer. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is accordingly an object of the present invention to provide a method and apparatus for plating with high productivity by means of which plating an interconnection with uniformity, high quality and high planarity can be achieved even in a hole with a high aspect ratio and over a large area plating region, and a plating structure. 
     According to one aspect of the present invention , there is provided a method for plating in which at least a hole is plated with a metal, comprising: a first step of removing organic material existent in a plating region; a second step of hydrophilizing a surface of the plating region after the first step; a third step of bonding a coupling agent with the surface hydrophilized by the second step; a fourth step of bonding a catalytic metal with the coupling agent at the surface after the third step; a fifth step of exposing the catalytic metal to activate after the fourth step; and a sixth step of electrolessly plating the activated surface after the fifth step. 
     According to a method for plating of the present invention, when at least a hole, such as a blind hole, is plated as a plating region, since organic material existent in a plating region is removed and the surface is hydrophilized, further a catalytic metal is bonded with a coupling agent that is bonded with the surface, and the surface is exposed, activated and then electrolessly plated, plating is effected uniformly at the mouth, bottom and sidewall of the hole and further no seed layer is required, which is different from a conventional electroplating. Hence, not only a flat surface but a hole with a high aspect ratio can be plated in a uniform manner with a good quality and in addition, a plating layer with high flatness can be formed at the top part of the hole. Therefore, polishing following the plating is easy to be effected and electroless plating can be conducted directly after the polishing without either physical surface roughening or a heat treatment (see JP 93-101974 A), thereby enabling a method for plating with high productivity to be provided. 
     According to another aspect of the present invention, there is provided an apparatus for plating in which at least a hole is plated with a metal, comprising: a pretreatment section which performs a first step of removing organic material existent in a plating region, a second step of hydrophilizing a surface of the plating region after the first step, a third step of bonding a coupling agent with the surface hydrophilized by the second step, a fourth step of bonding a catalytic metal with the coupling agent at the surface after the third step, and a fifth step of exposing the catalytic metal to activate after the fourth step; and an electroless plating section which performs a sixth step of electrolessly plating the activated surface after the fifth step. According to the present invention, there can be provided an apparatus for electroless plating with good reproducibility since the apparatus is based on the above described method for plating, which apparatus comprises the pretreatment section and electroless plating section. 
     According to still another aspect of the present invention, there is provided a plating structure that is formed by plating at least a hole with a metal, wherein a coupling agent is bonded with a hydroxylated surface of a plating region, a catalytic metal is bonded with the coupling agent and an electroless plating layer is formed on the surface with the catalytic metal interposed therebetween. According to the present invention, since an electroless plating layer is formed based on the method for plating, an excellent plating structure is provided. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a sectional view schematically showing a step of electroplating according to a conventional example. 
     FIG. 2 is a sectional view schematically showing another step of electroplating according to the conventional example. 
     FIG. 3 is a sectional view schematically showing still another step of electroplating according to the conventional example. 
     FIG. 4 is a sectional view schematically showing a further step of electroplating according to the conventional example. 
     FIG. 5 is a sectional view schematically showing a step of electroless plating according to an embodiment of the present invention. 
     FIG. 6 is a sectional view schematically showing another step of electroless plating according to the embodiment of the present invention. 
     FIG. 7 is a sectional view schematically showing still another step of electroless plating according to the embodiment of the present invention. 
     FIG. 8 is a sectional view schematically showing a further step of electroless plating according to the embodiment of the present invention. 
     FIG. 9 is a sectional view schematically showing still a further step of electroless plating according to the embodiment of the present invention. 
     FIG. 10 is a sectional view schematically showing an example of an apparatus for electroless plating according to an embodiment of the present invention. 
     FIG. 11 is a sectional view schematically showing another example of an apparatus for electroless plating according to the embodiment of the present invention. 
     FIG. 12 is a sectional view schematically showing still another example of an apparatus for electroless plating according to the embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Below, description will be given of preferred embodiments of the present invention with reference to the accompanying drawings: 
     Describing about the surfaces of a plating region in a method and apparatus for plating and a plating structure according the present invention, tantalum nitride as barrier layers  3  and  7  are respectively provided, in advance, on the surface of a copper interconnect  2  at the bottom of a hole  6  that serves as a contact hole (in addition, likewise, another barrier layer  3  is provided on the lower surface thereof, which is shown with an imaginary line, and which will not be shown in the following figures), as shown in FIG. 5, and on the surface of the sidewall of the hole  6  and an insulating film  5  as shown in FIG.  6 . Contaminating materials classified into organic material originating from an organic gas included in a small amount in the air inside a vacuum apparatus or/and a clean room used in a previous process are in many cases adsorbed on the barrier layers as a monomolecular film. Therefore, it is desired that after the barrier layer  7  constituted of tantalum or its compounds, for example tantalum nitride, is formed on the surface of at least the hole, the surface of the barrier layer is oxidized in order to remove the organic material, as a pretreatment. It is further desired that subsequent to the treatments, the surface is treated with an oxidizing agent to be hydroxylated; following the hydroxylation, the hydroxylated surface is reacted with a silane coupling agent or a titanate coupling agent including an atom or an atomic group that is easy to form a coordinate bond with a metallic component of a protective agent for a colloid of a catalytic metal. The resulting surface of the reaction is treated with a colloidal solution of the catalytic metal to have the metal component in the protective agent for the colloid of the catalytic metal to form a coordinate bond with a functional group of the silane coupling agent or titanate coupling agent. After treatment with the colloidal solution, the protective agent in excess that remains without formation of the coordinate bond is removed to expose the catalytic metal and activate the metal. Finally, the activated surface is treated with an electroless plating solution including a chelating agent and a reducing agent without alkali metal therein thereby, completing electroless plating with copper or nickel. 
     Since no contaminating organic material film more than one molecule thick, as a basic nature, attaches on the surfaces of wafers in actual device production, a process is only required in which a wet treatment is given to the wafer using an ozone/water mixture of 0.5 PPM or more in ozone concentration and preferably, in the range of 5 to 15 PPM in ozone concentration at room temperature at a flow rate in the range of 1 to 30 1/min for a time in the range 10 sec to 20 min in a spin cup as shown on FIGS. 10 and 11, as a removal treatment for the attaching organic material on the barrier layer. In the wet treatment, a form of a nozzle is not specific and if ultrasonic waves are applied to the ozone/water mixture through a running water ultrasonic nozzle whose wet surface portion is constituted of PTFE (polytetrafluoroethylene), stainless, titanium or the like, the wet treatment is more effective and a treatment time can be reduced. In addition to the above described treatment, the removal of an organic material contaminant may be effected, as a pretreatment, by a dry treatment such as an ozone treatment under ultraviolet irradiation, oxygen plasma ashing treatment and others. 
     In the above described hydroxylation, the surfaces of the barrier layer  7  and the metal or/and its compound constituting of the interconnect at the bottom of the hole  6 , which are shown in FIG. 6, are oxidized in water, thereby the surfaces are hydrophilized and —OH groups are effectively formed on the surfaces. Hence, if the hydroxylation treatment is an ozone/water mixture treatment, it is most desirable that the hydroxylation treatment and the organic material removal treatment occur concurrently. However, when the organic material removal treatment is of the dry type, as the hydroxylation treatment, any material may be used or any treatment may be adopted as far as the material or the treatment has a capability of oxidize a metal or its compound constituting a barrier layer. The hydroxylation treatment is exemplified as follows: an ozone/water mixture treatment similar to the treatment in the organic material removal treatment, a sulfuric acid/hydrogen peroxide treatment, a hypochlorous acid treatment, an ammonium permanganate treatment and others. 
     A treatment in which the —OH group that is formed in the hydroxylation treatment and a coupling agent are reacted with each other to form a chemical bond may be effected using a silane coupling agent or a titanate coupling agent, which is most desirably adopted since the coupling agents have a capability of forming a coordinate bond with tin which protects a Pd colloidal catalyst that is used in the next process, by an amino group and a thiol group located in a hydrocarbon molecular chain or/and at the opposite end from an Si atom or a Ti atom in the hydrocarbon molecular chain of the coupling agents. Further, the surface that has been treated by a silane coupling agent or a titanium coupling agent has a surface irregularity of recess/projection corresponding to a size of a bonded molecule of a coupling agent and thereby is made rough as much. Therefore, the coupling treatment can be said to have sufficiently been performed if the coupling agent treated surface can retain a hydrophilicity at a level at which a colloidal catalytic metal used in the next process is adsorbed on the treated surface. Such silane coupling agent and titanium coupling agent are represented by compounds that have a group such as —OH group, —COOH group or —OR group, wherein R indicates an alkyl group, in the molecular chain or at an end thereof. 
     It is desired that a tin atom of stannous chloride which is a protective agent for the Pd colloid is reacted with an amino group or a thiol group in the silane coupling agent or the titanate coupling agent to form a coordinate bond by a treatment using a colloidal solution of a catalytic metal protected by stannous chloride, for example palladium (hereinafter also referred to as Pd), thereby making the palladium colloid bonded with the surfaces. That is, the Pd colloidal solution which is protected by stannous chloride is made to act on the wafer  1  which has been treated by the above described coupling agent and thereby, the tin atoms in the Pd colloid can react with the amino groups or thiol groups of the silane coupling agent or the titanate coupling agent on the wafer  1  to form coordinate bonds and as a result, attain strong bonds of Pd colloid with the surface. 
     In this case, any type of Pd colloidal catalyst can be adopted if the catalyst is like, Catalyst 9F made by Shipley Co., Ltd. However, since the Pd colloidal catalyst is used in a semiconductor process, a Pd colloidal catalyst whose protective agent is stannous chloride is preferred. 
     Excess stannous chloride that is not participated in coordinate bond with the surface of the wafer  1  is removed through cleaning by an aqueous solution such as one of HBF 4  (boron fluoride) or H 2 SO 4  (sulfuric acid) to expose Pd, thus completing a pretreatment. An activating agent including HBF 4  like Accelerator  19  made by Shipley Co., Ltd. is most preferred for cleaning/removal in terms of quality and performance. On the other hand, a sulfuric acid based activating agent like Accelerator  240 , which is similar to Accelerator  19 , is more preferred since the activating agent is better from the viewpoint of environmental protection, although the agent is somewhat problematic in terms of quality and performance. 
     When the Pd colloidal solution is made simply to act on the wafer  1 , the Pd colloid is only adsorbed on the wafer  1 . Hence, in this situation, there arises a problem that the activation treatment cannot be performed by applying ultrasonic waves, since Pd is removed if ultrasonic treatment is applied. However, when a wafer is pretreated with a silane coupling agent or a titanate coupling agent including —NH 2  group or —SH group, as described above, and thereafter a Pd colloid is reacted with such a group to form a coordinate bond, Pd firmly attaches onto the surface since a chemical bond arises and therefore, the activation treatment can be performed while applying ultrasonic waves. In this case, even a blind hole with an aspect ratio as high as 1:4 or more and a diameter as small as 0.3 μm or less is treated with sufficient effectiveness and uniform plating can be attained even in a hole with an aspect ratio of 1:10 and a diameter of 0.18 μm. 
     The above described pretreatment is conducted in one cup and for the reason, a spin cup apparatus as shown in FIGS. 10 and 11 in which many kinds of treatment can be performed is preferred, whereas a dipping bath type as shown in FIG. 8 can be used as well. 
     The above described pretreatment for electroless plating can be applied for not only an interconnection process for a semiconductor wafer as described above, but a surface treatment for a metal or an inorganic object of every kind, which enables strong, precise plating with a high coating capability to be realized with no physical surface roughening treatment applied. 
     In this case, an electroless plating liquid including the following compounds is desirably employed: a salt of copper or nickel; an amphoteric ion type chelating agent such as glycin; a chelating agent in the form of an ammonium salt such as ammonium succinate; a reducing agent such as ammonium hypophosphite; and a non-ionic type surfactant, a cationic surfactant, and an anionic surfactant in the form of an ammonium salt. That is, in order to prepare an electroless plating liquid, a salt of copper or nickel; an amphoteric ion type chelating agent such as glycin; and a chelating agent in the form of an ammonium salt such as ammonium succinate and ammonium malic acid are mixed and pH of the mixture is adjusted by adding aqueous ammonia, and the resultant mixture is further mixed with a reducing agent including no alkali metal ion such as ammonium hypophosphite, hypophosphorous acid, ammonium borohydride, hydrazine and formalin and further with as a surfactant, a non-ionic type surfactant; a cationic surfactant; and an anionic surfactant in the form of an ammonium salt. 
     As described above, a chelating agent, a reducing agent (as ammonium hypophosphite), and a surfactant (as an anionic surfactant in the form of an ammonium salt) are in the forms of an ammonium salt and pH is adjusted using aqueous ammonia and a desirable composition of an electroless plating liquid is as follows: 
     copper chloride or nickel chloride: 10 to 100 g/l (copper sulfate, nickel sulfate, copper sulfamate or nickel sulfamate may be used instead) 
     gycin: 2 to 50 g/l (another amphoteric ion type chelating agent such as other amino acids may be used instead) 
     ammonium succinate: 2 to 50 g/l (ammonium salts such as ones of malic acid, succinic acid, malonic acid and formic acid may be used instead) 
     ammonium hypophosphite: 2 to 50 g/l (hypophosphorous acid, formalin, hydrazine, ammonium borohydride and the like may be used instead) 
     aqueous ammonia: 5 to 200 ml/l (pH is adjusted to a necessary value in the range of 6 to 12) 
     ammonium lauryl sulfate: 0.1 to 20 mg/l (a cationic surfactant is used when pH is acidic, an anionic surfactant when pH is basic and a non-ionic surfactant when pH is either acidic or basic) 
     In such a manner, it is desired to use an electroless plating liquid added with a salt of a catalytic metal such as nickel, cobalt, palladium and gold which serve as a plating reaction accelerator in an amount of 10 ppm or more. 
     Further, a treatment in a wet state is desirably performed under an influence of ultrasonic waves during the above described steps. In order to make the wet treatments effective, each wet treatment is desirably effected as follows: the apparatus of a spin cup type shown in FIGS. 10 and 11 or the apparatus of a dipping bath type shown in FIG. 12 is used, each step described above is conducted in one chamber, a treatment liquid is distributed over a plating object while rotating the object, or alternatively the object is dipped in the treatment liquid and the object is heated at a predetermined temperature. With the apparatuses in use, each step is made possible to be performed and in such a way, a series of steps including a pretreatment and electroless plating can be implemented. FIGS. 10 and 11 are schematic views of the same apparatus. In the apparatus, a turn table  15  that is supported on a shaft  14  and in which a heater is embedded is provided in a cup  13 , a predetermined liquid is supplied to a wafer (which indicates a wafer in a fabrication stage of an integrated circuit in FIGS. 10 to  12 )  1  that is held on the turn table  15  through a nozzle  18  ( 18   a  indicates a water cleaning nozzle that can be changed over to O 3 ,  18   b  a hydroxylation nozzle,  18   c  a coupling nozzle,  18   d  a Pd colloidal catalyst nozzle and  18   e  an activation liquid nozzle) disposed above the wafer  1 , and a cleaning water is further supplied from a rear-surface water cleaning nozzle  19  disposed below the wafer. Further, an air pressure caused by rotation of the turn table  15  is discharged from an exhaust port  17 , and cleaning water supplied and others are discharged from a drainage port  16 . FIG. 10 shows a pretreatment process and arrow marks below the respective nozzles  18   a  to  18   e  indicate supply of treatment liquids through the nozzles  18   a  to  18   e  in respective steps. FIG. 11 shows an electroless plating step and a reference mark  18   a  indicates a warm pure water nozzle,  18   b  an electroless plating liquid nozzle and arrow marks below the nozzles indicate supply of treatment liquids in the respective steps. Further, in order to enable effective electroplating to be performed, a heater  20  embedded in the turn table  15  is controlled in the range of 30 to 90° C. so as to supply a heated plating liquid. 
     Further, FIG. 12 is a schematic view of a dipping bath type apparatus and in the apparatus, a treatment liquid  28  is supplied from a pipe  22  into a dipping bath  21  that is provided with an ultrasonic vibrator  23  at the bottom thereof. An overflowing liquid  28  once flows down in a receiver  24  as shown with an arrow and then is discharged from a drainage port  25 . A wafer  1  is held on a wafer holding section  27  of a right-angle rotary mechanism  26  and dipped in the treatment liquid  28 , wherein a predetermined treatment liquid  28  is supplied according to each step to perform the corresponding predetermined treatment. 
     Both of the apparatuses can be used broadly in the range of temperature from room temperature to 90° C., though depending on a value of pH. The liquids are very stable in all the temperature range and do not decompose in all the temperature range. In order not to contaminate each treatment liquid, the spin cup which can be sealed is desirably employed. However, if the top of the dipping bath is sealed with a film or the like stuck on the top, the dipping bath can be used while preventing a treatment liquid from being contaminated. In both types, ultrasonic waves are desirably utilized and while a wavelength may be arbitrary, a high frequency of 1 MHz or higher is desirably used since a diameter of a blind hole is as small as 1 μm or less. In the process, a cleaning water or a circulated water with 1% or less dissolved oxygen in content is desirably used after each step. That is, oxidation of a plating film is prevented from occurring and a high electric conductivity can be maintained by using the cleaning water and the circulated water with dissolved oxygen in content of 1% or less. Further, a baking treatment is desirably applied after electroless plating. That is, since crystals in an electroless plating film is small in size and further, there arises a closed seam  9  in a plating region in a hole as shown in FIG. 7, though no void occurs therein, the baking treatment is effected at 300 to 500° C. in an inactive gas atmosphere or vacuum so that the seam  9  can be erased as shown in FIG.  8 . 
     By means of the above described method and apparatus for plating, the plating can be performed in a case where a diameter of the hole is 0.25 μm or less and an aspect ratio is 5 or higher and as actual results, a case where a diameter of the hole is 0.13 μm and an aspect ratio is 10 or higher has been established, which suggests a possibility that a hole with a smaller diameter and a higher aspect ratio is electrolessly plated with success. 
     According to the embodiment described above, a uniform, rigid electroless plating film can be formed throughout its entire surface on a barrier layer such as a layer made of Ti or a compound thereof, Ta or a compound thereof, or the like with neither a physical surface roughening treatment nor a high temperature heat treatment, and a high quality plating film of low oxygen content can be obtained in a blind hole in a state in which no void arises in company with a seam, the seam is erased by a heat treatment after the plating and a high degree of crystallinity is ensured. 
     Further, an OH group on the surface of a wafer or the like forms a chemical bond (covalent bond) with a silane coupling agent or a titanate coupling and a Pd particle forms a chemical bond (coordinate bond) with the surface. Therefore, an adhesive force of the electroless plating film to the surface is strong in principle and not only activation but electroless plating can be effected using ultrasonic waves with no bubble generation in the treatment liquids, which has conventionally been impossible to be done. 
     Consequently, an electroless plating film can be formed in a blind hole 0.25 μm or less in diameter and 5 or higher in aspect ratio using copper or nickel. 
     Further, a film with a uniform thickness across the surface can be formed on wafers of either 8 and 12 inch in diameter as well. Since the surface of a wafer after the plating has a recess as small as 0.1 μm or less in depth at the top of a blind hole when a plating film thickness is, for example, 0.5 μm, a CMP process in the next step can be conducted with ease as shown in FIG.  9 . 
     It should be noted that a method for electroless plating of the present invention is excellent in thickness uniformity and fine feature coverage of a plating film and such a feature is the result of various contrivances described above, which has not been obtainable by simply employing a conventional electroless plating technique. That is, in the case of simply employing a conventional electroless plating technique, the surface roughening is not effected and a Pd catalyst does not adhere to a flat surface sufficiently with the result that the plating is not successful since an adhesive force is weak. In addition to such an inconvenience, fine bubbles generate as a result of a side reaction during the electroless plating, which makes the conventional technique not suitable for plating in a small blind hole. Furthermore, since alkali metal ions such as Na are included in salts of organic acids used as a chelating agent for electroless plating, a reducing agent and a pH adjusting liquid, the conventional technique is not suitable for a semiconductor process. In a method for electroless plating of the present invention, it is apparent that none of the above described faults occur. 
     It should be noted that the embodiment is possible to be altered in various ways based on a technical concept of the present invention. 
     For example, oxidizing agents, reducing agents, and other treatment liquids are not limited to those described above, but each of them can be replaced one with an equivalent capability. Further, an apparatus for plating is not limited to those shown in FIGS. 10 and 12 but the apparatuses can be replaced with equivalents in terms of performance. Further, an object of electroplating is not limited to a dual Damascene interconnect structure and a single Damascene interconnect structure used in an integrated circuit on a semiconductor wafer, but can be applied to various other kinds of interconnection and in addition, to all other plating items. 
     As described above, according to the present invention, when at least a hole like a blind hole is plated as a plating region, organic material existent on the plating region is removed and the surface is hydrophilized, then a catalytic metal is bonded with a coupling agent that is bonded with the surface, and the catalytic metal is exposed to activate, which is followed by electroless plating on the surface. Hence, according to the electroless plating, uniform plating is effected at the mouth and on the bottom and sidewall while no seed layer is required, which makes the electroless plating of the present invention different from a conventional electroplating. For the reasons, a uniform, good quality plating film can be achieved not only on a flat surface but in a hole with a high aspect ratio, wherein the top part of the hole can be filled with a plating layer of a high flatness. Accordingly, since polishing after the plating is easy to be conducted and direct electroless plating can be effected with neither physical surface roughening nor a heat treatment, a method for plating and a plating structure with high productivity can be provided.