Abstract:
A plating apparatus includes a bath configured to reserve a plating solution for plating a substrate and a holder configured to hold the substrate. The bath includes an anode electrode provided inside the bath. The holder includes a cathode electrode for applying a voltage to the substrate. The bath is equipped with first and second discharge portions. The plating apparatus includes a first path, a supply path, a second path and a flow rate control valve. The first path circulates the plating solution, which is discharged from the first discharge portion, to the bath. The supply path supplies the plating solution, which is provided from the first path, into the bath. The second path provides the plating solution, which is discharged from the second discharge portion after flowing on the anode electrode, to the first path. The flow rate control valve controls a flow rate of the plating solution flowing from the second path to the first path.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a plating apparatus for use in a plating process for manufacturing semiconductor devices.  
         [0003]     2. Description of the Related Art  
         [0004]     Some of conventional plating apparatuses are known as facedown type plating apparatuses. The facedown type plating apparatus adopts a form (referred to as facedown form) of arranging a substrate such as silicon wafer above a plating solution bath and forms a plated layer such as a copper layer on the substrate. In the facedown type plating apparatus, there is provided the plating solution bath having an anode electrode disposed at the bottom thereof and a plating solution filled therein. The substrate is arranged such that the surface thereof, on which plating treatment is executed, faces the solution surface of the plating solution. In the facedown type plating apparatus, the plating treatment is executed by applying voltage between the substrate and the anode electrode in this condition. The facedown form has been increasingly widely used since it is advantageous in, for example, downsizing the plating apparatus.  
         [0005]     Hereinafter, a conventional plating apparatus will be described.  FIG. 1  shows a configuration of the conventional plating apparatus  101  in a cross sectional view. Referring to  FIG. 1 , the conventional plating apparatus  101  includes a plating treatment chamber  102 , a tank  103 , a pump  104 , and a constant current power source  105 . The tank  103  holds a plating solution flowed out from the plating treatment chamber  102 . The pump  104  circulates the plating solution held in the tank to the plating solution chamber  102 . The pump  104  circulates the plating solution through the tank  103  and the plating treatment chamber  102 . The constant current power source  105  supplies DC current to wafer holders  111  and an anode contact plate  119 , which are described later.  
         [0006]     Referring to  FIG. 1 , the plating treatment chamber  102  includes the wafer holders  111  for holding a wafer  107  and a plating treatment chamber inner bath  112  for holding the plating solution. The plating treatment chamber  102  is provided with circulation drains  113 , which are connected to the plating treatment chamber inner bath  112  via respective anode chamber drain nozzles  114 . The plating treatment chamber inner bath  112  includes the anode contact plate  119 , an anode  115 , a membrane  117 , and a diffuser plate  118 . The plating treatment chamber inner bath  112  configures an anode chamber  121  between the anode  115  and the membrane  117 . Similarly, the plating treatment chamber inner bath  112  configures a membrane diffuser plate chamber  122  above the membrane  117 .  
         [0007]     The anode contact plate  119  supplies to the anode  115 , a current outputted from the constant current power source  105 . The anode  115  acts as a bottom electrode in correspondence with the current supplied via the anode contact plate  119 . The membrane  117  filters additive decomposition products contained in the plating solution. The diffuser plate  118  supplies the plating solution to the wafer  107  such that the plating solution flows uniformly to the wafer  107 .  
         [0008]     As a plating solution supply path, a plating solution supply nozzle  116  is configured which penetrates through the anode contact plate  119 , the anode  115 , and the membrane  117 . Referring to  FIG. 1 , the plating solution supplied into the membrane diffuser plate chamber  122  passes through the diffuser plate  118  and then is discharged through the circulation drains  113 . The plating solution supplied into the anode chamber  121  is discharged from the circulation drains  113  via the anode chamber drain nozzles  114  provided for the anode chamber  121 .  
         [0009]     Here, as for the conventional plating treatment chamber  102 , when the plating treatment is executed on the wafer  107  which is set on the wafer holders  111 , the plating solution is supplied from the plating solution supply nozzle  116  at a rate of 61/min. During the plating treatment, a current of 1 to 10 A is supplied to the anode  115  for approximately two to five minutes.  
         [0010]     Japanese Laid Open Patent Application (JP-P-2001-316887) discloses a face down type plating apparatus. United States Patent Document (U.S. Pat. No. 6,890,416) discloses another plating apparatus. The another plating apparatus is provided with a pump, anode chamber and membrane diffuser plate chamber. The rotation rate and stroke of the pump is increased to control the flow rates of plating solution flowing to the entire of the anode chamber, membrane diffuser plate chamber and surface of a wafer to be plated.  
         [0011]     To form a thick copper (Cu) film by plating the wafer  107  with copper, as described above, it is required to provide a current of approximately 10 A for a long period of time. In this case, Cu concentration in the plating solution flowing on the anode  115  may become high. A small flow rate of the plating solution flowing on the anode  115  in this condition may cause deposition of crystals of copper sulfate on the anode  115 . The crystals of copper sulfate on the anode  115  increase the electric resistance between the plating solution and the anode  115 . This may make it difficult to maintain the current of approximately 10 A for a long period of time, which may in turn result in failure to perform an appropriate plating treatment.  
         [0012]     Conventionally, a power supply, which can supply high voltage, has been used as the constant current power source to secure desired current, thereby coping with the problem of the increased resistance.  
         [0013]     In formation of the thick Cu film, the flow rate of the plating solution flowing on the anode  115  has been increased by increasing the amount of the plating solution supplied to the plating treatment chamber  102 . As described above, when the thicker film is formed by plating, it is required to increased flow rate of the plating solution flowing on the anode  115  (in order to prevent Cu deposition on the anode).  
         [0014]     As for the plating apparatus disclosed in United States Patent Document (U.S. Pat. No. 6,890,416), the pump increases the flow rate of the plating solution and thereby enables suppressing the deposition of crystals of copper sulfate on an anode of the plating apparatus.  
       SUMMARY  
       [0015]     It has now been discovered that an increased amount of the plating solution to be supplied results in an increased amount of the plating solution flowing to the surface of the membrane  117 . Thus, the plating solution flowing on the surface of the wafer  107  flows faster. This may make it difficult to form a plated film with a uniform film thickness over the surface of the wafer  107 . Moreover, the increased amount of the plating solution raises the consumption of various components contained in the plating solution, resulting in the increased cost for plating the wafer.  
         [0016]     In an aspect of the present invention, a plating apparatus includes a plating treatment bath and a substrate holder. The plating treatment bath is configured to reserve a plating solution for plating a substrate. The substrate holder is provided above the plating treatment bath and configured to hold the substrate such that the substrate can rotate in a horizontal plane. The plating treatment bath includes an anode electrode provided inside the plating treatment bath. The substrate holder includes a cathode electrode for contacting the substrate to apply a voltage to the substrate. The plating apparatus includes a first flow path, a supply path, a second flow path and a flow rate control valve. The first flow path is configured to circulate the plating solution, which is discharged from the plating treatment bath via a first discharge portion, to the plating treatment bath. The supply path is configured to supply the plating solution, which is provided from the first flow path, into the plating treatment bath. The second flow path is configured to provide the plating solution, which is discharged from the plating treatment bath via a second discharge portion after flowing on the anode electrode, to the first flow path. The flow rate control valve is provided between the first flow path and the second flow path. The flow rate control valve is configured to control a flow rate of the plating solution provided from the second flow path to the first flow path.  
         [0017]     In this case, the flow rate control valve controls the flow rate of the plating solution flowing along the second flow path such that the deposition of copper sulfate crystals on the anode electrode can be suppressed. Moreover, the flow rate control valve adjusts its valve opening not to increase a flow speed of the plating solution flowing along the substrate surface.  
         [0018]     The present invention is effective in optimally controlling only the flow rate of the plating solution flowing to an anode chamber without changing the amount of the plating solution to be supplied. That is, the present invention enables a variable flow rate of the plating solution flowing to the anode chamber while keeping constant the flow rate of the plating solution flowing on a surface of the wafer. The present invention enables a plating treatment for forming plated films of various thickness from thin film thickness to thick film thickness while keeping constant the flow rate of the plating solution flowing on the surface of the wafer.  
         [0019]     According to the present invention, when a thin film is plated, a flow rate of the plating solution flowing on the anode electrode can be reduced to smaller flow rate than when a thick film is plated. The reduction in the flow rate of the plating solution can suppress the consumption of additives and also increase in cost.  
         [0020]     According to the present invention, a plating treatment can be executed without configuring a constant current power source that can supply high voltage. This permits execution of an appropriate plating treatment without increasing facility-related costs.  
         [0021]     According to the present invention, an increase in a flow speed of the plating solution on the wafer surface can be suppressed to thereby provide a plated film of uniform film thickness over the surface of the wafer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:  
         [0023]      FIG. 1  is a sectional view illustrating a configuration of a conventional plating apparatus;  
         [0024]      FIG. 2  is a sectional view illustrating a configuration of a plating apparatus according to a first embodiment of the present invention; and  
         [0025]      FIG. 3  is a sectional view illustrating a configuration of a plating apparatus according to a second embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purpose.  
         [0027]     The embodiments of the present invention will be described below with reference to the accompanying drawings. The embodiments to be described below refer to, as an example, a case where a plating apparatus  1  according to the present invention is an apparatus which plates a silicon wafer with copper to thereby form the Cu film. This does not mean that the present invention is only applicable to plating treatment for forming the Cu film.  
       First Embodiment  
       [0028]      FIG. 2  is a sectional view that illustrates configuration of a plating apparatus  1  according to the first embodiment of the present invention. Referring to  FIG. 2 , the plating apparatus  1  of the first embodiment includes a plating treatment chamber  2 , a tank  3 , a pump  4 , a constant current power source  5 , and flow rate control valves  6 .  
         [0029]     The plating treatment chamber  2  is a treatment bath in which the plating treatment on a wafer  7  is executed. The plating treatment chamber  2  reserves a plating solution for use in performing the plating treatment on the wafer  7 . The tank  3  holds the plating solution discharged from the plating treatment chamber  2 . The pump  4  supplies the plating solution held in the tank  3  to the plating treatment chamber  2 . Thus, the plating solution discharged from the plating treatment chamber  2  returns to the plating treatment chamber  2 . This enables circulative supply of the plating solution. The constant current power source  5  provides an electric power required for the plating treatment performed by the plating treatment chamber  2 . The flow rate control valve  6  controls the flow rate of the plating solution flowing to the anode chamber while keeping constant the flow rate of the plating solution flowing on the wafer surface.  
         [0030]     Referring to  FIG. 2 , the plating treatment chamber  2  includes a plating treatment chamber inner bath  12 . The plating treatment chamber  2  is also provided with circulation drains  13 . Wafer holders  11  hold the wafer  7 . As shown in  FIG. 2 , the wafer holders  11  are in contact with the wafer  7  which is arranged with the surface thereof subjected to plating treatment facing downward. The wafer holders  11  hold the wafer  7  such that the wafer  7  can rotate. The wafer holders  11  are connected to the constant current power source  5  via a first node N 1 .  
         [0031]     Inside the plating treatment chamber inner bath  12 , an anode  15  is configured. As shown in  FIG. 2 , the anode  15  is connected to an anode contact plate  19 , which is provided outside the plating treatment chamber inner bath  12 . The anode contact plate  19  is connected to the constant current power source  5  via a second node N 2 . Therefore, the anode  15  acts as an anode electrode (bottom electrode) in correspondence with a current supplied via the anode contact plate  19 .  
         [0032]     The circulation drains  13  are configured in the plating treatment chamber  2 , and each serve as a flow path for circulating the plating solution flowing out from the plating treatment chamber inner bath  12 . As shown in  FIG. 2 , the plating apparatus  1  according to the present embodiment configures a plating solution circulating flow path  8  (first flow path) with the circulation drains  13 , the tank  3 , and the pump  4 .  
         [0033]     The plating treatment chamber inner bath  12  described above includes anode chamber drain nozzles  14 , a plating solution supply nozzle  16 , a membrane  17 , and a diffuser plate  18 . The anode chamber drain nozzle  14  is an outlet port for discharging the plating solution contained in an anode chamber  21 . As shown in  FIG. 2 , the anode chamber drain nozzles  14  according to the present embodiment are connected to the flow rate control valves  6 . The membrane  17  filters additive decomposition products contained in the plating solution. The diffuser plate  18  supplies the plating solution such that the plating solution flows uniformly to the wafer  107 .  
         [0034]     The plating solution supply nozzle  16  is a plating solution supply path in the plating apparatus  1  according to the present embodiment. The plating solution supply nozzle  16  penetrates through the anode contact plate  19 , the anode  15 , and the membrane  17 . As shown in  FIG. 2 , the plating solution supplied into a membrane diffuser plate chamber  22  passes through the diffuser plate  18 , and is discharged from the circulation drains  13 . The plating solution supplied into the anode chamber  21  is supplied from the anode chamber drain nozzles  14 , which are provided in the anode chamber  21 , to the circulation drains  13  via the flow rate control valves  6 .  
         [0035]     As described above, in the plating treatment for forming the Cu film or the like, it is required to reduce the amount of the plating solution flowing to the membrane diffuser plate chamber  22  to appropriately form the Cu film. In order to prevent formation of crystals of copper sulfate or the like on the anode  15  in this condition, the plating apparatus  1  according to the present embodiment is provided with the anode chamber drain nozzles  14  of large nozzle diameter size. The anode chamber drain nozzles  14  of large nozzle diameter size ensure a sufficient amount of the plating solution flowing to the anode chamber drain nozzles  14 . That is, the large nozzle diameter size of the anode chamber drain nozzles  14  reduces the flow resistance of the nozzles  14 , thereby permitting a sufficient amount of the plating solution to flow to the anode chamber drain nozzles  14 .  
         [0036]     Here, the flow rate control valve  6  according to the present embodiment controls valve opening such that the flow rate of the plating solution flowing through the anode chamber drain nozzle  14  is between 60 and 100 ml/min. An experiment has proved that, in the plating treatment for forming the Cu film or the like, controlling this flow rate between 60 and 100 ml/min provides favorable results. That is, controlling the flow rate of the plating solution flowing through the anode chamber drain nozzle  14  between 60 and 100 ml/min by use of the flow rate control valve  6  prevents the Cu concentration in the plating solution flowing on the anode  15  from becoming high. In the plating apparatus  1  according to the present embodiment, the flow rate control valves  6  controls the flow late of the plating solution. Thus, the plating apparatus  1  suppresses formation of the crystals of copper sulfate on the anode  15  and thus prevents an increase in the electrical resistance between the anode  15  and the plating solution.  
         [0037]     The flow rate control valve  6  can vary the flow rate of the plating solution flowing to the anode chamber  12  while keeping constant the flow rate of the plating solution flowing on the surface of the wafer  7 , thereby avoiding stagnation of the flow on the anode  15 . Thus, upon formation of the thicker Cu film, deposition of copper sulfate on the anode  15  is suppressed. The plating apparatus  1  can form an appropriate Cu film. On the other hand, upon formation of a thinner Cu film, the flow rate of the plating solution flowing on the anode  15  can be reduced smaller than that for forming the thicker Cu film. Thereby, the plating apparatus  1  suppresses the consumption of additive and thus increase in the cost.  
         [0038]     In this condition, the flow rate of the plating solution supplied to the membrane diffuser plate chamber  22  is controlled at an optimum level, thus permitting the thickness of the film to be uniform over the surface of the wafer  7 . Further, there is no increase in the electrical resistance, thus permitting configuration of the plating apparatus which forms the appropriate Cu film without being provided with a power supply which can supply high voltage. This permits reduction in the costs spent on facilities for the plating apparatus.  
       Second Embodiment  
       [0039]     Hereinafter, referring to the drawings, a second embodiment of the present invention will be described.  FIG. 3  is a sectional view that illustrates configuration of the plating apparatus  1  according to the second embodiment of the present invention. In the drawing used for the following description, components provided with the same numerals as those in the first embodiment have the same configuration and operation as those in the first embodiment. Therefore, the descriptions for the overlapping components are omitted from the following description.  
         [0040]     Referring to  FIG. 3 , in the plating apparatus  1  according to the second embodiment, the pump  4  in the plating solution circulating flow path  8  is provided with an anode chamber pump  31  and a membrane diffuser plate chamber pump  32 . The plating solution supply nozzle  16  includes a membrane diffuser plate chamber plating solution supply nozzle  33  and anode chamber plating solution supply nozzles  34 . As shown in  FIG. 3 , the anode chamber pump  31  is connected to the anode chamber plating solution supply nozzles  34 . The membrane diffuser plate chamber pump  32  is connected to the membrane diffuser plate chamber plating solution supply nozzle  33 .  
         [0041]     The anode chamber plating solution supply nozzle  34  supplies the plating solution to the anode chamber  21 . The membrane diffuser plate chamber plating solution supply nozzle  33  supplies the plating solution to the membrane diffuser plate chamber  22 . As shown in  FIG. 3 , the membrane diffuser plate chamber plating solution supply nozzle  33  and the anode chamber plating solution supply nozzles  34  are configured independently from each other. Here, the anode chamber pump  31  supplies the plating solution to the anode chamber plating solution supply nozzles  34 , and the membrane diffuser plate chamber pump  32  supplies the plating solution to the membrane diffuser plate chamber plating solution supply nozzle  33 . Therefore, controlling the flow rates of the plating solution supplied by the anode chamber pump  31  and the membrane diffuser plate chamber pump  32  permits highly accurate control of flow rates of the plating solution flowing in the anode chamber  21  and in the membrane diffuser plate chamber  22 .  
         [0042]     The plating apparatus  1  according to the second embodiment can control independently the flow rates of the plating solution supplied to the anode chamber  21  and the membrane diffuser plate chamber  22 . This permits supplying a minimum necessary amount of the plating solution to each of the chambers, thus achieving cost reduction by suppressing the plating solution consumption.  
       Third Embodiment  
       [0043]     Hereinafter, referring to the drawings, a third embodiment of the present invention will be described. The plating apparatus  1  according to the third embodiment is provided with the plating solution supply nozzle  16  having outlet ports of nozzle diameter sizes such that the plating solution flows through the anode chamber drain nozzle  14  at a flow rate of 60 to 100 ml/min. In this case, the plating solution supply nozzle  16  controls the nozzle diameter size of the outlet port for supplying the plating solution to the membrane diffuser plate chamber  22  or controls the nozzle diameter size of the outlet port for supplying the plating solution to the anode chamber  21 . Thus, the plating solution supply nozzle  16  controls the flow rate through the anode chamber drain nozzle  14 . The plating apparatus  1  according to the third embodiment, when the flow rate of the plating solution discharged from the anode chamber drain nozzle  14  is desired to be fixed, can control the flow rate of the plating solution flowing through the anode chamber drain nozzle  14  while suppressing an increase in the facility-related costs. Moreover, providing the flow rate control valve  6  described above permits variably controlling, with higher accuracy, the flow rate of the plating solution flowing through the anode chamber drain nozzle  14 .  
         [0044]     The plurality of embodiments described above can be practiced in combination within the range consistent with the configuration and operation thereof. The flow rate control valve of the present invention maybe provided with, for example, a flow meter and thereby may control the valve.  
         [0045]     It is apparent that the present invention is not limited to the above embodiment, but may be modified and changed without departing from the scope and spirit of the invention.