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  Plating apparatus and plating methodUSPTO Application #: 20060081478Title: Plating apparatus and plating method Abstract: A plating apparatus employs a dipping method with good gas-bubble releasability and, by regulating the flow of plating solution in a plating tank, can enhance the in-plane uniformity of a thickness of a plated film. The plating apparatus includes a plating tank for holding a plating solution, a plating solution jet nozzle having a slit-like plating solution jet orifice for jetting the plating solution toward a surface to be plated of an object to be plated disposed in the plating tank, and a plating solution supply section for supplying the plating solution to the plating solution jet nozzle. (end of abstract) Agent: Wenderoth, Lind & Ponack, L.L.P. - Washington, DC, US Inventors: Tsuyoshi Sahoda, Tsutomu Nakada, Nobutoshi Saito, Junichiro Yoshioka, Fumio Kuriyama, Masunobu Onozawa USPTO Applicaton #: 20060081478 - Class: 205148000 (USPTO) Related Patent Categories: Electrolysis: Processes, Compositions Used Therein, And Methods Of Preparing The Compositions, Electrolytic Coating (process, Composition And Method Of Preparing Composition), Agitating Or Moving Electrolyte During Coating The Patent Description & Claims data below is from USPTO Patent Application 20060081478. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a plating apparatus and a plating method for plating a surface (surface to be plated) of a substrate, such as a semiconductor wafer, and more particularly to a plating apparatus and a plating method useful for forming embedded interconnects by embedding a conductive material (interconnects material), such as copper or silver, in interconnects recesses, such as fine trenches and via holes, provided in a surface of a semiconductor wafer, or for forming bumps (protruding electrodes), to which package electrodes or the like are electrically connected, on a surface of a semiconductor wafer. [0003] The plating apparatus and the plating method of the present invention are also useful for embedding of via holes in the production of an interposer or a spacer, for example, which has, in its interior, a large number of vertically-penetrating via plugs and is used for so-called three-dimensional mounting of e.g. a semiconductor chip. [0004] 2. Description of the Related Art [0005] In a tape automated bonding (TAB) or flip chip, for example, it has been widely conducted to deposit copper, solder, nickel or multi-layered materials thereof at prescribed areas (electrodes) on the surface of a semiconductor chip having interconnects, thereby forming protruding connecting electrodes (bumps). Such bumps electrically connect the semiconductor chip with package electrodes or TAB electrodes electrically. There are various methods for forming these bumps, including electroplating method, printing method, and ball bump method The electroplating method has become in wide use due to its relatively stable performance and capability of forming fine connections, in view of the recent tendency to increasing number of I/O terminals on semiconductor chips and to finer pitch. [0006] The electroplating method includes a spurting or cup method in which a substrate, such as a semiconductor wafer, is positioned horizontally with a surface (surface to be plated) facing downward and a plating solution is spurted from below; and a dipping method in which the substrate is placed vertically in a plating tank and immersed in a plating solution, while a plating solution is supplied from the bottom of the plating tank and is allowed to overflow the tank. According to the dipping method of electroplating, bubbles, which can adversely affect the quality of the plating, are easily removed and the footprint is small. The dipping method is therefore considered to be suited for bump plating in which holes to be filling by the plating are relatively large and which requires a fairly long plating time. [0007] In recent years, instead of using aluminum or aluminum alloys as a material for forming interconnects circuits on a semiconductor substrate, there is an eminent movement towards using copper (Cu) that has a low electric resistivity and high electromigration resistance. Copper interconnects are generally formed by filling copper into fine interconnects recesses provided in a surface of a substrate. Various techniques for forming such copper interconnects are known, including CVD, sputtering, and plating. According to any such techniques, a copper film is formed in a substantially entire surface of a substrate, followed by removal of unnecessary copper by performing chemical mechanical polishing (CMP). [0008] FIG. 1 shows a conventional electroplating apparatus that employs a dipping method. The electroplating apparatus 600 includes a plating tank 602 for holding therein a plating solution 601, and an overflow tank 604 for holding the plating solution that has overflowed the upper end of the overflow weir 603 of the plating tank 602. In the plating tank 602, a substrate W, which is held by a substrate holder 605, and an anode 606, both immersed in the plating solution 601, are disposed vertically and opposite to each other at a predetermined distance. Paddles (stirrers) 607 are disposed vertically between the substrate W and the anode 606. The paddles 607 are mounted to a paddle shaft 608. The paddle shaft 608 can be reciprocated parallel to the substrate W so as to stir the plating solution in the plating tank 602. [0009] The plating solution 601, after filling the plating tank 602, overflows the overflow weir 603 and flows into the overflow tank 604, and is discharged from the overflow tank 604. The plating solution 601 then passes through a circulation pump 609, a constant-temperature unit 610 and a filter 611, all provided in a circulation line 612, and again flows into the plating tank 602 from its bottom. The plating solution 601 circulates in this manner. A plating power source 613 is connected to the substrate W and the anode 606 to apply a direct-current voltage between the substrate W and the anode 606, and pass a plating current from the anode 606 to the substrate W, thereby forming a plated film on the surface of the substrate W. The plating solution between the substrate W and the anode 606 is stirred by the paddles 607 during plating in order to form a uniform plated film (see, for example, Japanese Patent Laid-Open Publication No. 2004-162129). [0010] As described above, in the conventional plating apparatus that employs a dipping method, the paddles 607 are reciprocated parallel to the substrate W during plating to stir the plating solution between the substrate W and the anode 606 in order to form a uniform plated film. However, since the plating solution 601 is supplied from the bottom of the plating tank 602 and is caused to overflow the upper end of the overflow weir 603, a flow of the plating solution 601 is created. The flow of the plating solution 601 strongly affects the formation of a plated film, which imposes a limitation on the in-plane uniformity of the plated film. The same holds also for an electroless plating apparatus. [0011] FIG. 2 shows another conventional electroplating apparatus that employs a dipping method. The electroplating apparatus includes a plating tank 312a for holding therein a plating solution, and a vertically-movable substrate holder 314a for detachably holding a substrate W with its peripheral portion sealed watertightly and its front surface (surface to be plated) exposed. In the plating tank 312a, an anode 324, which is held by an anode holder 326, is disposed vertically. Further, a regulation plate 328 having a central hole 328a, composed of a dielectric material, is disposed such that when a substrate W, held by a substrate holder 314a, is disposed opposite the anode 324, it is positioned between the anode 324 and the substrate W. [0012] In operation, the anode 324, the substrate W and the regulation plate 328 are immersed in the plating solution in the plating tank 312a while the anode 324 is connected via a conducting wire 330a to the anode of a plating power source 332 and the substrate W is connected via a conducting wire 330b to the cathode of the plating power source 332. Due to the potential difference between the substrate W and the anode 324, metal ions in the plating solution receive electrons from the surface of the substrate W, whereby the metal deposits on the substrate W and forms a plated film (metal film). [0013] According to this plating apparatus, the regulation plate 328, having the central hole 328a, is disposed between the anode 324 and the substrate W, disposed opposite the anode 324, in order to regulate the electric potential distribution in the plating tank 312a with the regulation plate 328. This makes it possible to regulate to some extent the thickness distribution of the plated film formed on the surface of the substrate W. [0014] FIG. 3 shows yet another conventional electroplating apparatus that employs a dipping method. This electroplating apparatus differs from the embodiment shown in FIG. 2 in that a regulation plate is not provided, but a ring-shaped dummy cathode (dummy electrode) 334 is provided such that it surrounds the periphery of a substrate W held by the substrate holder 314a. Upon plating, the dummy cathode 334 is connected via a conducting wire 330c to the cathode of the plating power source 332. [0015] According to this plating apparatus, the uniformity of a metal film formed on the surface of the substrate W can be improved by regulating the electric potential of the dummy cathode 334. [0016] FIG. 4 shows yet another conventional electroplating apparatus that employs a dipping method. This electroplating apparatus differs from the embodiment shown in FIG. 2 in that a regulation plate is not provided, but a paddle shaft (stirring mechanism) 336, located above the plating tank 312a, is disposed between the substrate holder 314a and the anode 324 in parallel to them. A plurality of stirring paddles (stirrers) 338 is suspended substantially vertically from the lower surface of the paddle shaft 336. During plating, the paddles 338 are reciprocated parallel to the substrate W by the paddle shaft 336 so as to stir a plating solution in the plating tank 312a. [0017] According to this plating apparatus, by reciprocating the paddles 338 parallel to the substrate W by the paddle shaft 336, the flow of the plating solution along the surface of the substrate W can be uniformized (directionality of the flow of plating solution eliminated) over the entire surface of the substrate W. This enables the formation of a plated film having a uniform thickness over the entire surface of the substrate W. [0018] It has generally been quite difficult with conventional plating apparatuses to securely fill in via holes having a high aspect ratio and a large depth, such as those having a diameter of 10 to 20 .mu.m and a depth of 70 to 150 .mu.m, provided in a substrate, with a metal film by plating while preventing the formation of defects, such as voids, in the metal film. [0019] For example, when filling in via holes having a high aspect ratio of not less than 1 and a large depth with a metal film by plating by using, for example, the plating apparatus shown in FIG. 4, and carrying out plating while strongly stirring a plating solution by the paddles 338, the flow of plating solution will not reach the bottoms of the via holds. Thus, as shown in FIG. 5, when carrying out plating under such conditions on a surface of a barrier layer 344 covering an insulating film 342 in which a via hole 340 is provided, plating deposition progresses preferentially around the open end of the via hole 340, whereby the open end can be closed up with a metal film (plated film) 346 and a void 348 can be formed in the metal film 346 embedded in the via hole 340. [0020] On the other hand, there is a demand for an apparatus which itself is of a simple structure and has an easily-maintained structure or mechanism. The plating apparatus shown in FIG. 3, for example, needs operations for adjustment of the dummy electrode and removal of the plated metal that has adhered to the dummy electrode. A plating apparatus, which is free from such a complication in operation or maintenance and is easier to handle and maintain, is now in demand. [0021] In carrying out electroplating, the plating rate can be increased by increasing the current density during plating. Merely increasing the current density, however, could cause plating problems such as burnt plating, plating defects, passivation in a surface of an anode, etc. SUMMARY OF THE INVENTION [0022] The present invention has been made in view of the above situation in the related art. It is therefore a first object of the present invention to provide a plating apparatus and a plating method which employ a dipping method with good gas-bubble releasability and which, by regulating the flow of plating solution in a plating tank, can enhance the in-plane uniformity of a thickness of a plated film. Continue reading... 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