JP2009299128A - Electroplating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroplating apparatus capable of forming a dense conductive body free from the generation of voids even if a via hole has small diameter and large aspect ratio. <P>SOLUTION: The electroplating apparatus 6 is provided with a plating bath 8 storing a plating liquid 7, a cathode electrode 9 immersed in the plating bath 8 and provided with a power feed ring 18 for fixing a plating body 1 on the main surface and electrically connected to a wiring 2 formed on the plating body 1, an anode electrode 12 provided so as to face the cathode electrode 9 for energizing the plating liquid 7, a current shielding plate 11 having a through-hole 17 and provided between the anode electrode 12 and the cathode electrode 9, a reserve tank 15 storing the excess plating liquid 7 from the plating bath 8 and a convection nozzle 13 circulating the plating liquid 7 in the plating bath 8 by feeding the plating liquid 7 in the reserve tank 15 from the bottom of the plating bath 8 and is provided with a stirring means 10 for further stirring the circulated plating liquid 7 between the current shielding plate 11 and the cathode electrode 9. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electroplating apparatus for filling openings such as wirings and via holes formed on a printed wiring board or a semiconductor wafer by plating.

  Recently, in electronic materials such as semiconductor wafers and printed wiring boards, copper is used in various parts as a metal having good electrical characteristics and capable of various processing methods. A plating method is frequently used as a method of forming copper on such an electronic material. In particular, in recent years, a gap between wirings and the like formed on the surface of an electronic material has been actively filled by plating.

  For example, a gap between wirings, a via hole, or the like is embedded in a groove structure such as a minute via hole or a trench formed on the surface of a semiconductor wafer by copper plating on a printed wiring board. In general, the technique of embedding wiring and via holes by plating is called via fill plating technique, and the difficulty is defined by the aspect ratio (depth / via hole diameter). When the aspect ratio is 1 or more, voids are formed in the via holes. It is said that it is easy to occur.

  Therefore, a new plating solution can be constantly supplied to the inside of the via hole by developing a plating solution that can control the plating speed inside and outside the via hole and forcibly circulating it using a pump etc. The generation of voids was suppressed.

For example, Patent Documents 1 to 3 are known as prior art document information relating to the invention of this application.
JP 2005-307259 A JP 2006-249478 A JP-A-8-1000029

  In the above plating apparatus, the plating solution is forcibly circulated in the plating tank, but the plating solution flows along the wafer surface as the diameter of the via hole becomes smaller and the aspect ratio becomes larger. Therefore, the plating solution does not enter and stays in the via hole, so that the supply of metal ions is stopped, and as a result, voids are easily generated.

  Therefore, an object is to reliably infiltrate and agitate the plating solution even in the small-diameter via hole.

  In order to achieve the above object, the present invention provides a plating tank storing a plating solution, a wiring immersed in the plating tank, fixing the object to be plated on the main surface, and the wiring formed on the object to be plated. A cathode electrode provided with a power supply means for connection, an anode electrode provided opposite to the cathode electrode, for supplying current to the plating solution, and having a through hole provided between the anode electrode and the cathode electrode A current tank, a reserve tank for storing excess plating solution from the plating tank, and a convection nozzle for convection of the plating solution in the plating tank by supplying the plating solution in the reserve tank from the bottom. An electroplating apparatus provided with stirring means for further stirring the convected plating solution between the current shielding plate and the cathode electrode.

  In the electroplating apparatus according to the present invention, a cathode electrode and an anode electrode are immersed substantially vertically in a plating tank storing a plating solution, and electrically connected to the cathode electrode on the main surface of the cathode electrode. After fixing a to-be-plated body, it is an electroplating apparatus which forms and fills a plating film in the wiring and via hole which were formed in the said to-be-plated body by supplying with electricity between these cathode electrodes and anode electrodes. The plating tank includes a convection nozzle that convects the plating solution in the plating tank by spraying upward the excess plating solution stored in the reserve tank at the bottom, and from the main surface of the cathode electrode, that is, from the object to be plated. Stirring means that can swing and reciprocate vertically and horizontally at a certain distance is provided, so that the plating solution that convects along the surface of the object to be plated from the bottom is stirred by disturbing the flow. Can do. Therefore, even for via holes with a small diameter and a large aspect ratio, a new plating solution can be infiltrated and supplied as needed. As a result, openings such as wiring and via holes can be formed with dense plating that does not generate voids. There exists an effect which can be filled with a conductor in a part.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example in which a conductor layer is filled in an opening formed on an object to be plated using the electroplating apparatus in the present embodiment. 1A is a front view for explaining the shape of the opening, and FIG. 1B is a cross-sectional view taken along the line A-AA in FIG.

  A resist 3 was applied onto the wiring 2 provided on the object 1 to be plated such as a semiconductor wafer or a printed circuit board using a spin coater, and the resist 3 was exposed and developed to form a pattern having openings 4. And the columnar conductor 5 which fills the inside of the opening part 4 is formed by forming and growing the conductor layer from the bottom surface 4a of the opening part 4 by the electroplating apparatus of the present embodiment.

  The conductor 5 is used, for example, as a via hole for electrically connecting the wirings between layers or as a wiring formed on the substrate 2. In this embodiment, the opening 4 provided in the resist 3 has a rectangular shape composed of a long side 4b and a short side 4c. The short side 4c is 20 to 40 μm, and the long side 4b is 1.5 times the short side 4c. As described above, the thickness 3a of the resist 3 is further set to 30 to 79 μm. The aspect ratio is defined as the ratio of the short side 4c to the thickness 3a (depth) of the resist 3 and is about 4 at the maximum.

  FIG. 2 is a cross-sectional view for explaining the electroplating apparatus 6 in one embodiment of the present invention.

  In the center of the plating tank 8 storing the plating solution 7, a cathode electrode 9 for immersing the plating object 1 and supplying power to the wiring 2 (FIG. 1) for plating is immersed. On both sides of the electrode 9, a stirring means 10, a current shielding plate 11, and an anode electrode 12 are arranged in this order.

  A convection nozzle 13 is disposed at the bottom of the plating tank 8, and the plating solution 7 in the reserve tank 15 is sprayed upward from the convection nozzle 13 via the pump 14, thereby plating in the plating tank 8. The liquid 7 is forced to convection in the direction of arrow B. Then, the excess plating solution 7 overflowing from the plating tank 8 is recovered again to the reserve tank 15 through the drain 16. The plating solution 7 is managed with the plating solution 7 collected in the reserve tank 15, and is maintained and managed so that the components, pH, and the like are within a certain range.

  The cathode electrode 9, the current shielding plate 11, and the anode electrode 12 described above each have a flat plate shape, and are immersed in the plating solution 7 in parallel at regular intervals.

  The current shielding plate 11 is provided with a through hole 17 smaller than the outer shape of the object to be plated 1 fixed on the cathode electrode 9, and current flowing between the cathode electrode 9 and the anode electrode 12 is covered by the through hole 17. The plated body 1 is shielded or rectified so as to concentrate on a predetermined location.

  FIG. 3A is a front view of the cathode electrode 9 viewed from the C-CC direction of FIG. In the present embodiment, the four objects 1 to be plated are fixed to both main surfaces of the cathode electrode 9 via the feed ring 18. FIG. 3B is a cross-sectional view taken along the line D-DD of FIG. 3A, and both main surfaces of the cathode electrode 9 are provided with recesses 9a substantially equal to the thickness of the object 1 to be plated, After the object to be plated 1 is placed in the recess 9 a, the main surface of the cathode electrode 9 and the wiring 2 provided on the object to be plated 1 are electrically connected via the power supply ring 18. In addition, in order to prevent that the side surface and back surface of the to-be-plated body 1 are plated, an insulating layer is formed at least on the bottom surface and side surface of the recess 9a.

  4 is an example of the stirring means 10 provided between the cathode electrode 9 and the current shielding plate 11, and is a front view seen from the E-EE direction of FIG.

  The agitation means 10 of the present embodiment includes an agitation paddle 20 composed of a plurality of first bars 19 provided substantially vertically at regular intervals, and a motor 21 that drives the agitation paddle 20 horizontally and vertically. Yes. Thus, when the stirring paddle 20 is provided substantially vertically, the drive motor 21 reciprocates a certain distance in the horizontal direction, that is, from the front to the back in FIG. By doing so, the flow of the plating solution 7 sprayed from the convection nozzle 13 and convecting along the surface of the object to be plated 1 can be disturbed and stirred. As a result, even if the opening 4 has a small diameter and a large aspect ratio (FIG. 1), the plating solution 7 can enter and be supplied and agitated. 7 can circulate to fill and form the dense conductor 5 (FIG. 1) without voids.

  The motor 21 is connected to the agitation paddle 20 via an eccentric cam or the like. For example, the rotation of the agitation paddle 20 by one rotation of the motor 21 reciprocates or swings.

  FIG. 5 is a front view for explaining another example of the stirring means 10.

  The difference from FIG. 4 is that a plurality of second bars 22 are provided at equal intervals so that the stirring paddle 20 is orthogonal to the first bars 19. Thus, when the stirring paddle 20 is constituted by the first and second crosspieces 19 and 22 orthogonal to each other, the reciprocating motion is performed at a constant distance in the vertical direction (vertical direction in FIG. 2) in addition to the horizontal direction. Or it is swung. By doing so, it becomes possible to disturb the flow of the plating solution 7 sprayed from the convection nozzle 13 and further stir, and as a result, the denser conductor 5 can be filled into the opening 4. In addition, although the cross-sectional shape of the 2nd crosspiece 22 is a triangle, a quadrangle | tetragon, etc., the conductor 5 can be formed most uniformly by providing the opening part 4 anywhere in the to-be-plated body 1 by selecting a square. did it.

(Example 1)
FIG. 6 shows the results of conducting electroplating using the above-described electroplating apparatus 6 and examining the copper sulfate concentration and void generation rate in the plating solution 7. First, by conducting a beaker experiment, the diameter of the opening 4 formed on the 4-inch wafer as the object 1 to be plated 1 is electroplated to a diameter of 15 μm, a depth of 30 μm, and an aspect ratio of 2 to form a conductor. An attempt was made to optimize the composition of the plating solution in which no voids were generated. After plating, a part of the upper portion of the resist 3 was removed by polishing, and using an X-ray fluoroscope (manufactured by Shimadzu Corporation), voids in the conductor 5 formed at 90 locations in the wafer surface were individually observed.

  First, at a copper sulfate concentration of at least 220 g / L or more, the void generation rate was zero. Since copper sulfate does not dissolve at 260 g / L or more, the optimum concentration at which no void is generated is 225 g / L. As for the sulfuric acid and chlorine ion concentrations, no voids are generated even when the sulfuric acid concentration is 50 g / L and the chlorine ion concentration is 50 mg / L in the normal copper sulfate plating bath composition. However, the concentrations of additive inhibitors, accelerators and smoothing agents have a significant effect on the void generation rate. As the additive, Top Lucina FA manufactured by Okuno Seiyaku was used. Similarly, as a result of examining the combination, FA-1 (inhibitor) 6 ml / L, FA-2 (accelerator) 1.5 ml / L, FA-3 (smoother) 13 ml / L was the optimum condition. . This additive formulation is FA-2 (suppressor) 5 ml / L, FA-2 (accelerator) 0.4 ml / L, FA-3 (smoother) 6 ml / L, FA-2, FA-3 is slightly increased. The optimum plating conditions are shown below.

[Plating solution composition]
Copper sulfate pentahydrate: 225 g / L
Sulfuric acid: 50 g / L
Chlorine: 50 mg / L
Additive Top Lucina FA-1 (Okuno Pharmaceutical Co., Ltd.): 6ml / L
Additive Top Lucina FA-2 (Okuno Pharmaceutical): 1.5ml / L
Additive Top Lucina FA-3 (Okuno Pharmaceutical): 13ml / L
Current density: 2 A / dm ²
Liquid temperature: 25 ° C
(Example 2)
Next, the relationship between the rocking condition of the stirring paddle 20 and the void generation rate was examined. FIG. 7 shows the results of studying the rotation speed and void generation rate of the motor 21 of the stirring means 10 using the electroplating apparatus 6 of the present embodiment. The composition of the plating solution 7 and the plating conditions were as shown in Example 1, and the void generation rate was 0 by setting the rotation speed of the motor 21 to 20 rpm or more.

  The shape of the opening 4 examined this time is that the short side 4c of the opening 4 is 20 μm, the depth 3a is 30 μm, the aspect ratio is 1.5, and from the above results, the rotational speed of the motor 21 is 20 rpm or more. It is assumed that a new plating solution 7 is infiltrated and supplied so as to sufficiently supplement copper ions consumed by the formation of the conductor layer in the opening 4.

  Further, when the convection nozzle 13 is turned off, even if the agitation paddle 20 is swung at 30 rpm, some voids are generated. Therefore, it is considered essential to convect the plating solution 7. However, if the flow velocity of the convection nozzle 13 is too fast, the conductor 5 grows conformally inside the opening 4, so that a small amount of the plating solution 7 is adjusted as needed.

  In the above liquid composition, the number of rotations of the motor 21 was set to 30 rpm, the openings 4 having different diameters, depths, and aspect ratios were formed, and electroplating was performed. The void generation rate in the filled conductor 5 was evaluated. . Table 1 shows the experimental conditions, and Table 2 shows the experimental results.

In general, when the aspect ratio is high, voids are generated. However, at a current density of 2 A / dm ² , the short side 4c of the opening 4 is 20 μm, the depth 3a is 49 μm, and the aspect ratio is 2.45. It is possible to form and fill the conductor 5 without voids even under conditions where voids are generated, and it is possible to expand the application range of via fill plating.

  By using the electroplating apparatus 6 described above, the short side 4c of the opening 4 is 20 to 40 [mu] m, the depth 3a is 0 to 67 [mu] m, and the aspect ratio (depth / external shape of the opening) is 2 without reducing the current density. .45 or less via holes and openings 4 for forming wirings 2 can be filled with conductors 5 without generating voids, and can be plated on both sides at the same time. A plating apparatus 6 can be provided.

  In the electroplating apparatus according to the present invention, a cathode electrode and an anode electrode are immersed substantially vertically in a plating tank in which a plating solution is stored, and the cathode electrode is electrically connected to the main surface of the cathode electrode. After fixing a to-be-plated body, it is an electroplating apparatus which forms and fills a plating film in the wiring and via hole which were formed in the said to-be-plated body by supplying with electricity between these cathode electrodes and anode electrodes. The plating tank includes a convection nozzle that convects the plating solution in the plating tank by spraying upward the excess plating solution stored in the reserve tank at the bottom, and from the main surface of the cathode electrode, that is, from the object to be plated. Stirring means that can swing and reciprocate vertically and horizontally at a certain distance is provided, so that the plating solution that convects along the surface of the object to be plated from the bottom is stirred by disturbing the flow. Can do. Therefore, even for via holes with a small diameter and a large aspect ratio, a new plating solution can be infiltrated and supplied as needed. As a result, openings such as wiring and via holes can be formed with dense plating that does not generate voids. Since it has an effect of being able to fill the portion with a conductor, it is useful for an electroplating apparatus for filling the inside of an opening such as a wiring or a via hole formed on a printed wiring board or a semiconductor wafer by plating.

(A) Front view for explaining an example in which a conductor layer is filled in an opening formed on an object to be plated using the electroplating apparatus in the present embodiment, (b) AA-AA cross section in FIG. 1 (a) Figure Sectional drawing for demonstrating the electroplating apparatus in one embodiment of this invention (A) Front view of cathode electrode viewed from C-CC direction in FIG. 2, (b) D-DD cross-sectional view in FIG. It is an example of a stirring means, and the front view seen from the E-EE direction of FIG. Front view explaining another example of stirring means Diagram explaining the results of examination of plating solution composition and void generation rate The figure explaining the examination result of the motor rotation speed and void generation rate of the stirring means

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 To-be-plated body 2 Wiring 6 Electroplating apparatus 7 Plating solution 8 Plating tank 9 Cathode electrode 10 Stirring means 11 Current shielding plate 12 Anode electrode 13 Convection nozzle 15 Reserve tank 17 Through-hole 18 Feeding ring 19 First crosspiece 20 Stirring paddle 21 Motor 22 Second crosspiece

Claims (7)

A plating tank that stores a plating solution, a cathode electrode that is immersed in the plating tank and includes a power supply ring that fixes the object to be plated on the main surface and is electrically connected to the wiring formed on the object to be plated; An anode electrode that is provided opposite to the cathode electrode and energizes the plating solution, a current shielding plate that has a through hole and is provided between the anode electrode and the cathode electrode, and an excess from the plating tank. A reserve tank for storing a plating solution, and an electroplating apparatus provided with a convection nozzle for convection of the plating solution in the plating tank by supplying the plating solution in the reserve tank from the bottom, wherein the current shielding plate An electroplating apparatus provided with stirring means for further stirring the convected plating solution between the cathode electrode and the cathode electrode. The electroplating apparatus according to claim 1, wherein the distance between the object to be plated and the current shielding plate is set to 20 to 30 mm, and the outer shape of the through hole is smaller than that of the object to be plated. The stirring means comprises a stirring paddle composed of a plurality of first bars provided substantially vertically at equal intervals, and a motor for reciprocating the stirring paddle horizontally and vertically at a fixed length. Electroplating equipment. The electroplating apparatus according to claim 3, wherein the stirring paddle is provided with a plurality of second bars at equal intervals perpendicular to the first bars. The electroplating apparatus according to claim 4, wherein a cross-sectional shape of the second crosspiece is a quadrangle. The electroplating apparatus according to claim 1, wherein power supply means are provided on both principal surfaces of the cathode electrode, and two anode electrodes are provided with the cathode electrode as a substantially center. The plating solution is a copper plating solution containing a copper sulfate concentration of 220 to 260 g / L, a sulfuric acid concentration of 25 to 100 g / L, a chloride ion of 25 mg / L, an accelerator, an inhibitor, and a smoothing agent. Item 4. The electroplating apparatus according to Item 1.

Images