Patent Application
20140360865
This application claims priority to Japanese Patent Application No. 2013-119744 filed Jun. 6, 2013, the entire contents of which are hereby incorporated by reference.
A soluble anode made of phosphorus-containing copper (hereinafter referred to as “phosphorus-containing copper anode”) is widely used in a known type of copper electroplating apparatus which performs copper plating of a substrate surface by immersing a substrate such as a semiconductor wafer, held by a substrate holder, in a plating solution. When using a phosphorus-containing copper anode, it is common practice to perform dummy plating by applying a voltage between a dummy substrate and the phosphorus-containing copper anode to produce a thin film, called a black film, uniformly on the surface of the phosphorus-containing copper anode before applying a voltage between a substrate and the phosphorus-containing copper anode to perform copper plating of the substrate surface. This operation can suppress the production of monovalent copper, thereby preventing formation of sludge.
When copper plating is performed with the use of the phosphorus-containing copper anode, a black film may peel off the surface of the anode during the progress of copper plating and may be suspended in a plating solution. The black film suspended in the plating solution, if it is attached to a substrate, may cause a defect in the substrate.
To address the problem, an apparatus has been proposed in which an enclosure is formed by an anode cup and a membrane, and an anode (ion source material) is disposed in the enclosure (see U.S. Pat. No. 6,126,798).
A plating apparatus has been proposed which comprises an anode chamber and a cathode chamber that are separated by a porous transmissive bather of a multi-layer structure which allows permeation of metal ions therethrough but does not allow permeation of non-ionic organic additives (see U.S. Pat. No. 6,527,920). A plating apparatus has also been proposed which uses an anode having an average grain size of at least 50 μm and containing phosphorus in a concentration of at least 200 ppm, and uses a membrane which separates an anode chamber and a cathode chamber and which allows permeation of metal ions therethrough while preventing permeation of particles larger than 0.05 μm (see U.S. Pat. No. 6,821,407).
A method for producing an anode which has an average grain size of not more than 30 μm and can prevent detachment of a black film has been proposed. This method involves the steps of subjecting a phosphorus-containing copper ingot, having a copper purity of at least 99.99%, a phosphorus concentration of 300 to 1000 ppm and an oxygen content of not more than 10 ppm, to hot forging at an initial temperature of 600 to 900° C. (see Japanese laid-open patent publication No. 2012-57186). Further, a technique has been proposed which involves the steps of bubbling an electrolytic solution in an anode bag, in which an anode is housed, with air or oxygen gas so as to keep the amount of dissolved oxygen in the electrolytic solution at a level of not less than 5 ppm, thereby preventing the growth/detachment of a black film on/from the surface of the anode (see Japanese laid-open patent publication No. 201146973).
It is generally difficult to produce a firm black film in a manner as not to peel off the underlying surface of the phosphorus-containing copper anode. Moreover, use of a fairly complicated construction is generally required in order to prevent a black film, which has peeled off a phosphorus-containing copper anode, from adhering to a substrate. In particular, a very complicated structure will be needed to completely prevent a black film from adhering to a substrate.
It is therefore a first object to provide a copper electroplating apparatus which can stably retain a black film on a surface of a soluble anode of phosphorus-containing copper, thereby minimizing an amount of the black film that peels of the soluble anode.
It is a second object to provide a copper electroplating apparatus which, even if a black film peels off a soluble anode of phosphorus containing copper, can prevent the black film from being attached to a substrate more reliably with a relatively simple construction.
Embodiments, which will be described below, relates to a copper electroplating apparatus, and more particularly to a copper electroplating apparatus in which a substrate such as a semiconductor wafer, held by a substrate holder, is immersed in a plating solution to form e.g., connecting bumps or interconnects of copper on a surface of the substrate, or to perform through-hole copper plating of the substrate.
In an embodiment, a copper electroplating apparatus comprises: a plating bath configured to hold a plating solution therein; a soluble anode of phosphorus-containing copper to be immersed in the plating solution held in the plating bath; a substrate holder configured to hold a substrate and dispose the substrate at a position opposite the anode while immersing the substrate in the plating solution held in the plating bath; a substrate holder transport device configured to transport the substrate holder holding the substrate; an anode bag that surrounds the anode, the anode bag being formed of mesh; a regulation plate configured to regulate an electric field, the regulation plate having an opening and being disposed between the anode and the substrate held by the substrate holder; and a diaphragm disposed so as to close the opening of the regulation plate, the diaphragm being configured to allow permeation of metal ions therethrough and not allow permeation of additives contained in the plating solution.
Even if a black film peels off the soluble anode of phosphorus-containing copper (phosphorus-containing copper anode) and floats in the plating solution, the movement of the black film toward the substrate can be doubly blocked by the anode bag and the diaphragm. This makes it possible to substantially completely prevent the black film from attaching to the surface of the substrate.
In an embodiment, the anode of phosphorus-containing copper has a phosphorus concentration in a range of 1800 to 2700 ppm by mass and an average copper grain size in a range of 15 μm to 45 μm.
It has been verified from an experiment that a firm black film, having a uniform thickness and which hardly peels off, is produced on the surface of an anode made of phosphorus-containing copper (or a phosphorus-containing copper anode) when the anode has a phosphorus concentration in the range of 1800 to 2700 ppm, preferably in the range of 2000 to 2700 ppm.
In an embodiment, a copper electroplating apparatus comprising: plating bath configured to hold a plating solution therein; a soluble anode of phosphorus-containing copper to be immersed in a plating solution held in the plating bath; a substrate holder configured to hold a substrate and dispose the substrate at a position opposite the anode while immersing the substrate in the plating solution held in the plating bath; a substrate holder transport device configured to transport the substrate holder holding the substrate; a first anode bag that surrounds the anode, the first anode bag being formed of mesh; a second anode bag that surrounds the first anode bag, the second anode bag being formed of mesh which is finer than the first anode bag; and a regulation plate configured to regulate an electric field, the regulation plate having an opening and being disposed between the anode and the substrate held by the substrate holder.
Even if a black film peels of the soluble anode of phosphorus-containing copper (phosphorus-containing copper anode) and floats in the plating solution, the movement of the black film toward the substrate can be doubly blocked by the first anode bag and the second anode bag. This makes it possible to substantially completely prevent the black film from attaching to the surface of the substrate.
In an embodiment, a copper electroplating apparatus comprising: a plating bath configured to hold a plating solution therein; a soluble anode of phosphorus-containing copper to be immersed in a plating solution in the plating bath; a substrate holder configured to hold a substrate and dispose the substrate at a position opposite the anode while immersing the substrate in the plating solution in the plating bath; a substrate holder transport device configured to transport the substrate holder holding the substrate; a regulation plate configured to regulate an electric field, the regulation plate having an opening and being disposed between the anode and the substrate held by the substrate holder; a diaphragm disposed so as to close the opening of the regulation plate, the diaphragm being configured to allow permeation of metal ions therethrough and not allow permeation of additives contained in the plating solution; a shield box which separates an interior of the plating bath into an anode chamber in which the anode and the diaphragm are disposed and a cathode chamber in which the substrate, held by the substrate holder, is disposed, the shield box having an opening, which is closed with the diaphragm, at a position opposite the opening of the regulation plate; and a plating solution discharge line configured to discharge the plating solution from a bottom of the anode chamber.
Even if a black film peels off the soluble anode of phosphorus-containing copper (phosphorus-containing copper anode) and floats in the plating solution, the plating solution, containing the black film can be discharged from the bottom of the anode chamber. In addition, the diaphragm can block the floating black film from moving from the anode chamber into the cathode chamber. Thus, the black film can be substantially completely prevented from attaching to the surface of the substrate.
According to the above-described embodiments, the use of the anode made of phosphorus-containing copper (phosphorus-containing copper anode) having a phosphorus concentration of 1800 to 2700 ppm, preferably 2000 to 2700 ppm, makes it possible to produce a firm black film, having a uniform thickness and which hardly peels off, on the surface of the anode.
Even if a black film peels of a soluble anode of phosphorus-containing copper (phosphorus-containing copper anode), the copper electroplating apparatus, with a relatively simple construction, can substantially completely prevent the black film from adhering to the surface of the substrate.
Embodiments of the present invention will now be described with reference to the drawings. The same reference numerals are used in the following figures and description to refer to the same or like members, components, etc., and a duplicate description thereof will be omitted.
The substrate loading unit 20, a storage vessel 24 for storing (and temporarily storing) substrate holders 18 therein, a pre-wetting bath 26 for immersing the substrate in pure water, a pre-soaking bath 28 for etching away an oxide film formed on a surface of a conductive layer, such as a seed layer, of the substrate, a first cleaning bath 30a for cleaning the surface of the pre-soaked substrate, together with the substrate holder 18, with a cleaning liquid (e.g., pure water), a blow bath 32 for removing the cleaning liquid from the cleaned substrate, a second cleaning bath 30b for cleaning the plated substrate, together with the substrate holder 18, with a cleaning liquid (e.g., pure water), and a copper plating unit 34 are arranged in this order. The copper plating unit 34 includes an overflow bath 36 and a plurality of plating bath 38 surrounded by the overflow bath 36. Each plating bath 38 is configured to receive one substrate therein and perform plating, e.g., copper plating, on the surface of the substrate that is immersed in a plating solution held in the plating bath 38.
Located lateral to the above baths, there is provided a substrate holder transport device 40, driven e.g., by a linear motor, for transporting the substrate holder 18, together with a substrate, between the baths. The substrate holder transport device 40 has a first transporter 42 for transporting a substrate between the substrate loading unit 20, the storage vessel 24, the pre-wetting bath 26, the pre-soaking bath 28, the first cleaning bath 30a, and the blow bath 32, and a second transporter 44 for transporting the substrate between the first cleaning baths 30a, the second cleaning bath 30b, the blow bath 32, and the copper plating unit 34. The substrate holder transport device 40 may only include the first transporter 42, without the second transporter 44.
Paddle drive devices 46 are provided each for driving a paddle 232 (shown in
The substrate loading unit 20 includes a flat stage plate 52 which is laterally slidable along rails 50. Two substrate holders 18, parallel to each other, are placed horizontally on the stage plate 52. One substrate is transferred between one substrate holder 18 and the substrate transport device 22, and then the stage plate 52 is slid laterally so that the other substrate is transferred between the other substrate holder 18 and the substrate transport device 22.
As shown in
The second holding member 58 includes a base portion 60 and a ring-shaped seal holder 62. The seal holder 62 is made of vinyl chloride so as to enable a retaining ring 64, which will be described later, to slide well. An annular substrate-side sealing member 66 is fixed to an upper portion of the seal holder 62. This substrate-side sealing member 66 is placed in pressure contact with a periphery of the surface of the substrate W to seal a gap between the substrate W and the second holding member 58 when the substrate W is held by the substrate holder 18. An annular holder-side sealing member 68 is fixed to a surface, facing the first holding member 54, of the seal holder 62. This holder-side sealing member 68 is placed in pressure contact with the first holding member 54 to seal a gap between the first holding member 54 and the second holding member 58. The holder-side sealing member 68 is located at the outer side of the substrate-side sealing member 66.
As shown in
The seal holder 62 has a stepped portion at a periphery thereof, and the retaining ring 64 is rotatably mounted to the stepped portion through a spacer 65. The retaining ring 64 is inescapably held by an outer peripheral portion of the first mounting ring 70a. This retaining ring 64 is made of a material (e.g., titanium) having high rigidity and excellent acid and alkali corrosion resistance and the spacer 65 is made of a material having a low friction coefficient, for example PTFE, so that the retaining ring 64 can rotate smoothly.
Inverted L-shaped dampers 74, each having an inwardly projecting portion and located at the outer side of the retaining ring 64, are provided on the first holding member 54 at equal intervals along a circumferential direction of the retaining ring 64. The retaining ring 64 has, on its outer circumferential surface, outwardly projecting portions 64b arranged at positions corresponding to positions of the dampers 74. A lower surface of the inwardly projecting portion of each damper 74 and an upper surface of each projecting portion 64b of the retaining ring 64 are inclined in opposite directions along the rotational direction of the retaining ring 64 to form tapered surfaces. A plurality (e.g., three) of upwardly projecting protrusions 64a are provided on the retaining ring 64 at predetermined positions along the circumferential direction of the retaining ring 64. The retaining ring 64 can be rotated by pushing and moving each protrusion 64a from a lateral direction by means of a rotating pin (not shown).
With the second holding member 58 open, the substrate W is inserted into the central portion of the first holding member 54, and the second holding member 58 is then closed through the hinge 56. Subsequently the retaining ring 64 is rotated clockwise so that each projecting portion 64b of the retaining ring 64 slides into the inwardly projecting portion of each damper 74. As a result, the first holding member 54 and the second holding member 58 are fastened to each other and locked by engagement between the tapered surfaces of the retaining ring 64 and the tapered surfaces of the dampers 74. The lock of the second holding member 58 can be released by rotating the retaining ring 64 counterclockwise to disengage the projecting portions 64b of the retaining ring 64 from the inverted L-shaped dampers 74. When the second holding member 58 is locked in the above-described manner, the downwardly-protruding portion of the substrate-side sealing member 66 is placed in pressure contact with the periphery of the surface of the substrate W. The substrate-side sealing member 66 is pressed uniformly against the substrate W to thereby seal the gap between the periphery of the surface of the substrate W and the second holding member 58. Similarly, when the second holding member 58 is locked, the downwardly-protruding portion of the holder-side sealing member 68 is placed in pressure contact with the surface of the first holding member 54. The sealing holder-side sealing member 68 is uniformly pressed against the first holding member 54 to thereby seal the gap between the first holding member 54 and the second holding member 58.
A protruding portion 82 is formed on the upper surface of the first holding member 54 so as to protrude in a ring shape with a size corresponding to a size of the substrate W. The protruding portion 82 has an annular support surface 80 which contacts a periphery of the substrate W to support the substrate W. The protruding portion 82 has recesses 84 arranged at predetermined positions along a circumferential direction of the protruding portion 82.
A pair of outwardly-projecting holder hangers 90 is provided on the ends of the first holding member 54 of the substrate holder 18. These holder hangers 90 serve as a support when the substrate holder 18 is transported and when the substrate holder 18 is supported in a suspended state. A hand lever 92 extends between the holder hangers 90 on both sides. The substrate holder transport device 40 is configured to grip the hand lever 92 to thereby hold the substrate holder 18. In the storage vessel 24, the holder hangers 90 are placed on an upper surface of a surrounding wall of the storage vessel 24, whereby the substrate holder 18 is suspended in a vertical position. When transporting the substrate holder 18 from the storage vessel 24, the holder hangers 90 of the suspended substrate holder 18 are gripped by the first transporter 42 of the substrate holder transport device 40. Also in the pre-wetting bath 26, the pre-soaking bath 28, the cleaning baths 30a, 30b, the blow bath 32, and the copper plating unit 34, the substrate holder 18 is held in a suspended state with the holder hangers 90 placed on a surrounding wall of each bath.
As shown in
The electrical contacts 88, which are to be electrically connected to the electrical conductors 86, are secured to the seal holder 62 of the second holding member 58 by fastening tools 89, such as screws. Each of the electrical contacts 88 has a leaf spring-like contact portion located at the outer side of the substrate-side sealing member 66 and projecting inwardly. This spring-like contact portion is springy and bends easily. When the substrate W is held by the first holding member 54 and the second holding member 58, the contact portions of the electrical contacts 88 come into elastic contact with the peripheral surface of the substrate W supported on the support surface 80 of the first holding member 54.
The second holding member 58 is opened and closed by a not-shown pneumatic cylinder and by a weight of the second holding member 58 itself. More specifically, the first holding member 54 has a through-hole 54a, and a pneumatic cylinder is provided so as to face the through-hole 54a when the substrate holder 18 is placed on the stage plate 52. The second holding member 58 is opened by extending a piston rod of the pneumatic cylinder through the through-hole 54a to push up the seal holder 62 of the second holding member 58 through a pushing rod. The second holding member 58 is closed by its own weight when the piston rod is retracted.
A shield box 108 is disposed in the substrate processing chamber, so that the interior of the substrate processing chamber is separated into the anode chamber 110 inside the shield box 108 and the cathode chamber 112 outside the shield box 108. The bottom plate 100 has first plating solution passage openings 100a that provide fluid communication between the cathode chamber 112 and the plating solution distribution chamber 104. The bottom plate 100 further has a second plating solution passage opening 100b located below the anode chamber 110. The shield box 108, at its bottom, has a plating solution passage opening 108a formed at a position corresponding to the second plating solution passage opening 100b. The plating solution distribution chamber 104 communicates with the anode chamber 110 via the second plating solution passage opening 100b and the plating solution passage opening 108a.
When a substrate W is held by the substrate holder 18, the peripheral portion of the substrate W is liquid-tightly sealed with the sealing members 66, 68, while a front surface (to-be-plated surface) of the substrate W is exposed. The substrate W, held by the substrate holder 18, is immersed in the plating solution in the cathode chamber 112 and set in a vertical position.
The plating solution used in this embodiment is an acidic copper sulfate plating solution comprising sulfuric acid, copper sulfate, a halide ion and the following organic additives: a plating accelerator comprising SPS (bis(3-sulfopropyl) disulfide); a suppressor comprising PEG (polyethylene glycol); and a leveler comprising PEI (polyethylene imine). A chloride ion is preferably used as the halide ion.
The overflow bath 36 for receiving the plating solution that has overflown the edge of the plating bath 38 is provided around the plating bath 38. One end of a circulation line 122, which is provided with a pump 120, is coupled to the bottom of the overflow bath 36, and the other end of the circulation line 122 is coupled to the bottom of the plating solution distribution chamber 104. The plating solution that has been collected in the overflow bath 36 is introduced into the plating solution distribution chamber 104 by the actuation of the pump 120. A gap is provided between a lower end of the shield plate 106 and the bottom of the plating solution distribution chamber 104. Therefore, the flow of the plating solution, flowing out of the circulation line 122, is divided by the shield plate 106 into a flow toward the anode chamber 110 and a flow toward the cathode chamber 112. Thus, a part of the incoming plating solution passes through the first plating solution passage openings 100a of the bottom plate 100 and flows into the cathode chamber 112, while the remainder of the plating solution passes through the second plating solution passage opening 100b of the bottom plate 100 and the plating solution passage opening 108a of the shield box 108 and flows into the anode chamber 110.
The plating solution that has flowed into the cathode chamber 112 overflows the edge of the plating bath 38 into the overflow bath 36. The plating solution that has flowed into the anode chamber 110 flows out of the shield box 108 through an opening (not shown) provided at a top portion of a side wall of the shield box 108, and also flows into the overflow bath 36. The plating solution in the anode chamber 110 does not directly flow into the cathode chamber 112.
Located downstream of the pump 120, a constant-temperature unit 124 for regulating a temperature of the plating solution at a predetermined temperature (e.g., 25° C.), and a filter 126 for removing foreign matter (e.g., having a diameter of not less than 0.1 μn) contained in the plating solution are attached to the circulation line 122. A drain line 128 is connected to the bottom of the plating bath 38.
A disk-shaped soluble anode of phosphorus-containing copper (hereinafter referred to as “phosphorus-containing copper anode”) 130, having approximately the same size as the substrate W and held by an anode holder 132, is set in a vertical position in the anode chamber 110. This phosphorus-containing copper anode 130 is immersed in the plating solution in the anode chamber 110 when the plating bath 38 is filled with the plating solution. The substrate W, held by the substrate holder 18, is immersed in the plating solution held in the cathode chamber 112. The substrate W is disposed in the cathode chamber 112 such that it faces the phosphorus-containing copper anode 130.
In this embodiment a material (phosphorus-containing copper) having a copper purity of 99.69% by mass and a phosphorus concentration of 2660 ppm by mass (hereinafter referred to simply as ppm) is used for the phosphorus-containing copper anode 130. The phosphorus concentration of the phosphorus-containing copper anode 130 is in the range of 1800 to 2700 ppm, preferably in the range of 2000 to 2700 ppm. The phosphorus-containing copper anode 130 of this embodiment has a sulfur concentration of 50 ppm and a nickel concentration of 100 ppm. The average copper grain size of the phosphorus-containing copper anode 130 is 35 μm in this embodiment, preferably in the range of 15 μm to 45 μm, more preferably in the range of 30 μm to 40 μm.
The copper grain size is preferably not only small but also uniform. If the grain boundary is large, partial detachment of grains can occur due to selective or preferential progress of dissolution of the pain boundary. On the other hand, if the grain boundary is too small, it is difficult to produce a uniform crystal structure. From this viewpoint, the average copper grain size of the phosphorus-containing copper anode 130 is preferably in the range of 15 μm to 45 μm, more preferably in the range of 30 μm to 40 μm.
It has been verified from an experiment that a firm black film, having a uniform thickness and which hardly peels off, is produced on the surface of the phosphorus-containing copper anode 130 when the anode 130 has a phosphorus concentration in the range of 1800 to 2700 ppm, preferably in the range of 2000 to 2700 ppm.
In particular, the experiment was conducted using the phosphorus-containing copper anode 130 comprising the above-described components and using two types of plating solutions (first plating solution and second plating solution) containing different additives. Dummy plating was carried out for one hour at a cathode current density of 2 ASD (A/cm2) to produce a black film on the surface of the anode. Subsequently, plating was carried out for two hours at a cathode current density of 3 ASD. Thereafter, shower rinsing (3.5 L/min) was performed on the black film on the anode by applying a shower perpendicularly onto the black film from a shower head disposed at a distance of 30 cm. During the shower rinsing, the black film was photographed every 10 seconds so that the state of the black film was examined. The examination results have showed that in both cases of the first plating solution and the second plating solution, an underlying material the anode) was not exposed even after the shower rinsing was carried out for 90 seconds and that no peeling of the black film from the underlying material (i.e., the anode) was observed.
A comparative experiment was conducted in the same manner as the above-described experiment except for using a phosphorus-containing copper anode having a phosphorus concentration of 400 to 500 ppm. As a result, the underlying material (anode) became exposed after carrying out the shower rinsing for 30 seconds in the case of using the first plating solution, and after carrying out the shower rinsing for 20 seconds in the case of using the second plating solution, and peeling of the black film from the base (anode) was observed in both cases. An additional comparative experiment was conducted in the same manner as the above-described experiment except for using a phosphorus-containing copper anode having a phosphorus concentration of 400 to 600 ppm. As a result, the underlying material (anode) became exposed after carrying out the shower rinsing for 10 seconds in the case of using the first plating solution, and 20 seconds in the case of using the second plating solution, and peeling of the black film from the base (anode) was observed in both cases.
A regulation plate 134 for regulating the distribution of electric potential in the plating bath 38 is disposed in the plating bath 38. This regulation plate 134 is located between the phosphorus containing copper anode 130 and the substrate holder 18 disposed in the plating bath 38. In this embodiment the regulation plate 134 has a cylindrical portion 136 and a rectangular flange portion 138, with an opening 134a which is formed by an inner circumferential surface of the cylindrical portion 136. The regulation plate 134 is made of polyvinyl chloride which is a dielectric material. The size of the opening 134a, i.e., the diameter of the inner circumferential surface of the cylindrical portion 136, is set to be capable of sufficiently restricting broadening of the electric field. The cylindrical portion 136 has a predetermined axial length.
The shield box 108 has an opening 108b at a position corresponding to the cylindrical portion 136 of the regulation plate 134. The flange portion 138 of the regulation plate 134 is located in the anode chamber 110, and the cylindrical portion 136 of the regulation plate 134 is fit into the opening 108b. An anode-side end of the cylindrical portion 136 lies in the anode chamber 110. A diaphragm 142 is fixed to the anode-side end of the cylindrical portion 136 by an annular fixing plate 140. The diaphragm 142 is disposed so as to entirely cover the inner circumferential surface of the cylindrical portion 136, i.e., the opening 134a of the regulation plate 134 in its entirety. The diaphragm 142 is comprised of a cation exchange membrane or porous membrane which allows permeation of metal ions therethrough but does not allow permeation of additives contained in the plating solution. A commercially-available product “Yumicron” (Yuasa M&B CO., Ltd.) is an example of such a porous membrane.
A gap between the flange portion 138 of the regulation plate 134 and the inner surface of the shield box 108, a gap between the flange portion 138 and the diaphragm 142, and a gap between the faxing plate 140 and the diaphragm 142 are sealed with sealing members (not shown), respectively.
A water-permeable mesh anode bag 144, which surrounds the phosphorus-containing copper anode 130 and is secured to the plating bath 38, is disposed in the anode chamber 110. Examples of the anode bag 144 may include a polypropylene mesh having a thread-to-thread spacing of 40 μm to 50 μm and a permeability to a copper sulfate plating solution of 20 mL/cm2/sec, a polypropylene mesh having a thread-to-thread spacing of 10 μm to 15 μm and a permeability to a copper sulfate plating solution of 1.25 mL/cm2/sec, and a polypropylene mesh having a thread-to-thread spacing of 1 μm and a permeability to a copper sulfate plating solution of 0.6 mL/cm2/sec. An upper end of the anode bag 144 lies at a position higher than the opening for overflowing the plating solution in the anode chamber 110.
According to this embodiment, the phosphorus-containing copper anode 130 is surrounded by the water-permeable mesh anode bag 144 and, in addition, the anode-side end of the opening 134a of the regulation plate 134 is entirely covered with the diaphragm 142. Therefore, even if a black film peels of the phosphorus-containing copper anode 130, the black film does not enter the cathode chamber 112. Thus, it is possible to substantially completely prevent the black film from adhering to the surface of the substrate W.
The black film that has peeled of the phosphorus-containing copper anode 130 is suspended in the plating solution in the anode chamber 110. The movement of the black film into the cathode chamber 112 can be doubly blocked by the anode bag 144 and the diaphragm 142. The plating solution in the anode chamber 110, containing the suspended black film, is delivered via the overflow bath 36 to the filter 126, where foreign matter including the black film is removed. The plating solution is then returned to the cathode chamber 112 and the anode chamber 110.
The copper plating unit 34 of this embodiment is provided with a bubbling device 150 for supplying a gas, such as air or an inert gas (e.g., N2 gas), into the plating solution in the anode bag 144 to form bubbles in the plating solution. The bubbling device 150 includes a bubbling pipe 152 having a large number of jet ports its an upper area, and a gas supply line 154 communicating with the bubbling pipe 152. The bubbling pipe 152 extends horizontally along the surface of the phosphorus-containing copper anode 130 and is disposed in the anode bag 144. The gas supply line 154 is provided with a filter 156 for removing foreign matter from the gas flowing through the gas supply line 154.
The bubbling device 150 is provided optionally. The black film can be made to more hardly peel off the phosphorus-containing copper anode 130 by supplying, by means of the bubbling device 150, the gas, such as air or an inert gas (e.g., N2 gas), into the plating solution to form the bubbles in the plating solution existing on the surface of the phosphorus-containing copper anode 130 in the anode bag 144.
The agitating paddle 232 as an agitating tool for agitating the plating solution existing between the substrate holder 18 and the regulation plate 134 is disposed in the cathode chamber 112 of the plating bath 38. The agitating paddle 232 is located between the substrate holder 18 and the regulation plate 134, disposed in the plating bath 38, and extends vertically. By reciprocating the agitating paddle 232 parallel to the substrate W to agitate the plating solution during plating of the substrate W, a sufficient amount of copper ions can be supplied uniformly to the surface of the substrate W.
As shown in
It is preferred that a Width and the number of slits 232a be determined such that each strip-shaped portion 232b is as narrow as possible insofar as it has the necessary rigidity so that the strip-shaped portions 232b between the slits 232a can efficiently agitate the plating solution and, in addition, the plating solution can efficiently pass through the slits 232a.
The copper plating unit 34 is provided with a plating power source whose positive electrode is connected via a conducting wire to the phosphorus-containing copper anode 130 and whose negative electrode is connected via a conducting wire to the surface of the substrate W when plating of the substrate W is performed.
A sequence of plating process steps of performing copper electroplating of the surface of the substrate W using the copper electroplating apparatus shown in
At the start-up of the copper electroplating apparatus, dummy plating is performed by applying a voltage between a dummy substrate and the phosphorus-containing copper anode 130 to produce a black film on the surface of the phosphorus-containing copper anode 130. As described above, a firm black film, having a uniform thickness and which hardly peels off, is produced on the surface of the phosphorus-containing copper anode 130 by performing the dummy plating with the use of the anode 130 having a phosphorus concentration in the range of 1800 to 2700 ppm, preferably in the range of 2000 to 2700 ppm, and an average copper grain size in the range of 15 μm to 45 μm, preferably in the range of 30 μm to 40 μm.
One substrate is taken by the substrate transport device 22 out of the cassette 10 mounted on the cassette table 12, and the substrate is placed on the aligner 14 that aligns an orientation flat or a notch in a predetermined direction. After the alignment, the substrate is transported to the substrate loading unit 20 by the substrate transport device 22.
On the other hand, two substrate holders 18 housed in the storage vessel 24 are simultaneously gripped by the first transporter 42, and transported to the substrate loading unit 20. The substrate holders 18 are lowered into a horizontal position and are simultaneously placed on the stage plate 52 of the substrate loading unit 20. Then the two air cylinders are actuated to open the second holding members 58 of the two substrate holders 18.
The substrate is inserted by the substrate transport device 22 into the substrate holder 18 positioned on the center side, and the air cylinder is reversely actuated to close the second holding member 58. The second holding member 58 is then locked by means of a locking/unlocking mechanism (not shown). After the completion of loading of the substrate to the one substrate holder 18, the stage plate 52 is slid laterally, and a substrate is loaded into the other substrate holder 18 in the same manner. Thereafter, the stage plate 52 is returned to its original position.
The substrate W is fixed to the substrate holder 18 with its front surface (to-be-plated surface) exposed in the opening of the substrate holder 18. To prevent intrusion of the plating solution into the internal space of the substrate holder 18, the gap between the peripheral portion of the substrate W and the second holding member 58 is sealed with the substrate-side sealing member 66, and the gap between the first holding member 54 and the second holding member 58 is sealed with the holder-side sealing member 68. The substrate W, at a sealed portion not in contact with the plating solution, is electrically connected with the electrical contacts 88. The conducting wires extending from the electrical contacts 88 are connected to the connecting terminal 91 of the substrate holder 18. Therefore, an electric current can be supplied to a conductive layer, such as a seed layer, of the substrate W by connecting a power source to the connecting terminal 91. The substrate loading unit 20 has a sensor for sensing the electrical contact between the substrate W, held by the substrate holder 18, and the electrical contacts 88. The sensor, when it detects poor contact between the substrate W and the electrical contacts 88, outputs a signal to a controller (not shown).
The two substrate holders 18, each holding a substrate, are transported from the substrate loading unit 20 to the pre-wetting bath 26 by the first transporter 42 of the substrate holder transport device 40. The first transporter 42 lowers the substrate holders 18 to immerse the substrates, together with the substrate holders 18, in a pre-wetting liquid (e.g., pure water) in the pre-wetting bath 26.
Next, the two substrate holders 18 holding the substrates are transported from the pre-wetting bath 26 to the pre-soaking bath 28 by the first transporter 42. In the pre-soaking bath 28, a surface oxide film of each substrate is etched away, thereby exposing a clean metal surface. Thereafter, the substrate holders 18 holding the substrates are transported to the first cleaning bath 30a by the first transporter 42. In the first cleaning bath 30a, the substrates and the substrate holders 18 are cleaned with a cleaning liquid supplied into the first cleaning bath 30a. Pure water or a chemical solution can be used as the cleaning liquid.
The substrate holders 18, holding the cleaned substrates, are transported from the first cleaning bath 30a to the copper plating unit 34 by the second transporter 44 of the substrate holder transport device 40. The substrate holders 18 are lowered by the second transporter 44 into the plating baths 38, and are suspended from the tops of the plating baths 38. The second transporter 44 of the substrate holder transport device 40 sequentially repeats the above operations to sequentially transport substrate holders 18, each holding a substrate, to the plating baths 38 of the copper plating unit 34.
After the substrate holders 18 are set in all the plating baths 38, copper plating of each substrate is canned out in each plating bath 38 in the following manner. While circulating the plating solution between the plating bath 38 and the overflow bath 36 through the circulation line 122, copper plating of the surface of the substrate is carried out by applying a plating voltage between the phosphorus-containing copper anode 130 and the substrate in the plating bath 38. During plating, each substrate holder 18 is suspended and fixed with the holder hangers 90 supported on the top of the plating bath 38, and an electric current is supplied from the plating power source to a conductive layer, such as a seed layer, through the electrical conductors 86 and the electrical contacts 88. During plating of the substrate, the agitating paddle 232 reciprocates parallel to the surface of the substrate by means of the paddle drive device 46 and, as necessary, bubbles are formed in the plating solution by means of the bubbling device 150.
Even if, during the copper plating, a black film peels off the phosphorus-containing copper anode 130 and is suspended in the plating solution in the anode chamber 110, the movement of the black film into the cathode chamber 112 is doubly blocked by the anode bag 144 and the diaphragm 142. The black film can therefore be substantially completely prevented from adhering to the surface of the substrate.
Upon completion of the copper plating, the application of the plating voltage, the supply of the plating solution, the reciprocation of the paddle, and the bubbling of the plating solution are stopped. Thereafter, two substrate holders 18, each holding a plated substrate, are simultaneously gripped by the second transporter 44 and are transported to the second cleaning bath 30b, where the substrate surfaces, together with the substrate holders 18, are cleaned with a cleaning liquid.
The substrate holders 18, holding the cleaned substrates, are transported from the second cleaning bath 30b to the blow bath 32 by the second transporter 44. In the blow bath 32, air or nitrogen gas blows liquid droplets from the surfaces of the substrates held by the substrate holders 18, thereby drying the substrates.
The two substrate holders 18 after dried in the blow bath 32 are transported to the substrate loading unit 20 by the first transporter 42, and are placed on the stage plate 52 of the substrate loading unit 20. The second holding member 58 of the substrate holder 18 at the center side is unlocked by means of the locking/unlocking mechanism, and the air cylinder is actuated to open the second holding member 58. The substrate transport device 22 removes the substrate from the substrate holder 18, and transports the substrate to the spin rinse drier 16, where the substrate is spin-dried (drained) by high-speed rotation. The dried substrate is returned to the cassette 10 by the substrate transport device 22.
After or in parallel with the substrate is returned to the cassette 10, the stage plate 52 is slid laterally and the substrate is removed from the other substrate holder 18. The substrate is then spin-dried by the spin rinse drier 16, and the dried substrate is returned to the cassette 10 by the substrate transport device 22.
A polypropylene mesh having a thread-to-thread spacing of 20 μm may be used as the first anode bag 162. A mesh which is finer than the first anode bag 162, e.g., a polypropylene mesh having a thread-to-thread spacing of 1 μm, is used as the second anode bag 164. Upon replacement of the phosphorus-containing copper anode 130, the first anode bag 162, together with the anode holder 132, is pulled away from the plating bath 38 to be replaced with a new one.
According to this embodiment, a relatively large black film that has peeled of the surface of the phosphorus-containing copper anode 130 and is floating in the plating solution in the anode chamber 110, is blocked from passing through the first anode bag 162. A relatively small black film that has passed through the first anode bag 162 is blocked from passing through the second anode bag 164. In this manner, a black film suspended in the plating solution is substantially completely prevented from moving from the anode chamber 110 into the cathode chamber 112.
According to this embodiment, the plating solution flows into the anode chamber 110 after foreign matter is removed from the plating solution by the pre-filter 170. A black film that has peeled off the surface of the phosphorus-containing copper anode 130 and is suspended in the plating solution held in the anode chamber 110 gradually sinks, due to its own weight, toward the bottom of the anode chamber 110. The plating solution at the bottom of the anode chamber 110, containing a considerable amount of black film, is discharged from the bottom of the anode chamber 110 through the plating solution discharge line 176.
The circulation line 122 branches, at a point downstream of the filter 126, into a first branch line 200A and a second branch line 200B. The first branch line 200A extends into the anode chamber 110, while the second branch line 200B extends in the plating solution distribution chamber 104. The pre-filter 170 is provided in the first branch line 200A, so that foreign matter in the plating solution flowing in the first branch line 200A is removed by the pre-filter 170. The plating solution that has passed through the second branch line 200B is released into the plating solution distribution chamber 104.
The plating solution containing a black film joins the circulation line 122 at the point upstream of the pump 120, and is sent to the constant-temperature unit 124 and to the filter 126 by the pump 120. The black film is removed from the plating solution by the filter 126. In addition, since the plating solution discharge line 176 for discharging the plating solution from the anode chamber 110 is separated from the second branch line 200B extending to the cathode chamber 112, the black film can be substantially completely prevented from entering the cathode chamber 112.
Even if the black film sinks due to its own weight, the pre-filter 170 can prevent the black film from intruding into the plating solution distribution chamber 104. Therefore, the black film does not enter the cathode chamber 112 via the plating solution distribution chamber 104.
As with the embodiment shown in
This embodiment makes it possible to reduce the amount of the black film contained in the plating solution in the anode chamber 110 and prevent the black film suspended in the plating solution from entering the cathode chamber 112. In order to ensure appropriate permeability to the plating solution, the pre-filter 170 has a mesh coarser than the diaphragm 142. Instead of the pre-filter 170, a backflow prevention valve or a check valve may be used to prevent the plating solution in the anode chamber 110 from flowing back into the plating solution distribution chamber 104.
In the embodiment shown in
In operation, while the liquid level of the plating solution in the anode chamber 110 is kept within a predetermined range based on an output signal of the liquid level sensor 192, the plating solution is supplied into the anode chamber 110 through the plating solution supply line 182 which branches of from the circulation line 122, and pure water is supplied to the plating solution in the anode chamber 110 through the pure water supply line 184. The plating solution is discharged from the bottom of the anode chamber 110 through the plating solution discharge line 190.
Also in this embodiment, a black film floating in the plating solution in the anode chamber 110 gradually sinks, due to its own weight, toward the bottom of the anode chamber 110. The plating solution at the bottom of the anode chamber 110, containing a considerable amount of the black film, is discharged from the anode chamber 110 through the plating solution discharge line 190. This operation can reduce the amount of the black film contained in the plating solution in the anode chamber 110 and can substantially completely prevent the black film suspended in the plating solution from entering the cathode chamber 112.
The double mesh anode bags are constituted by a coarse first anode bag 162 and a second anode bag 164 which is finer than the first anode bag 162. The second anode bag 164 is disposed so as to surround the first anode bag 162. The anode bags 162, 164 are each formed of a water-permeable polypropylene mesh. Such double anode bags 162, 162 can trap both a relatively large black film and a relatively small black film in two stages, thereby preventing clogging of the diaphragm 142.
In this embodiment, the anode chamber 110 is configured to only hold the plating solution therein and does not basically allow the plating solution to overflow the anode chamber 110. A relief shoot 240 is provided on the side wall of the shield box 108 that defines the anode chamber 110. The relief shoot 240 communicates with the top area of the anode chamber 110 and extends from the anode chamber 110 into the overflow bath 36. Even if the plating solution overflows the anode chamber 110, the plating solution flows through the relief shoot 240 into the overflow bath 36. Thus, even if the plating solution flows out of the anode chamber 110, the plating solution will not directly enter the cathode chamber 112.
A pure water supply line 184 and a plating solution discharge line 190 are coupled to the anode chamber 110. The plating solution discharge line 190 extends downwardly from the bottom of the anode chamber 110. The plating solution discharge line 190 is provided with a drain valve 241. When the drain valve 241 is opened, the plating solution in the anode chamber 110 is discharged through the plating solution discharge line 190. The plating solution flowing in the plating solution discharge line 190 is not recovered, and is discarded as liquid waste.
A black film suspended in the plating solution in the anode chamber 110 gradually sinks due to its own weight toward the bottom of the anode chamber 110. The plating solution at the bottom of the anode chamber 110, containing a considerable amount of the black film, is discharged, due to its own weight, from the anode chamber 110 through the plating solution discharge line 190. This operation can reduce the amount of the black film contained in the plating solution in the anode chamber 110 and can prevent the black film suspended in the plating solution from entering the cathode chamber 112.
A plating solution supply line 244 is coupled to the top of the anode chamber 110. This plating solution supply line 244 is not used to supply the plating solution to the anode chamber 110 during plating of a substrate, but used solely to initially supply the plating solution to the anode chamber 110 before the start of plating, i.e., used solely to prepare the plating bath. The plating solution supply line 244 is provided with a first supply valve 246 and a second supply valve 247 located downstream of the first supply valve 246. The circulation line 122 is connected to the plating solution supply line 244 at a branch point 249 located between the first supply valve 246 and the second supply valve 247, so that a part of the plating solution, flowing in the plating solution supply line 244, flows into the circulation line 122. The first supply valve 246 and the second supply valve 247 are usually closed. Only at the time of preparation of the plating bath, the first supply valve 246 and the second supply valve 247 are opened to supply the plating solution to the anode chamber 110 through the plating solution supply line 244 and to also supply the plating solution to the cathode chamber 112 through the circulation line 122.
While the embodiments have been described above, it should be understood that the present invention is not limited to the embodiments described above, and is capable of various changes and modifications within the scope of the inventive concept as expressed herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-119744 | Jun 2013 | JP | national |
