JP3264175B2 - Electroplating apparatus and electroplating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroplating apparatus and an electroplating method, and more particularly to high-quality and high-speed electroplating particularly suitable for applications such as forming electrode bumps on a semiconductor wafer. The present invention relates to a jet type electroplating apparatus and an electroplating method.

[0002]

2. Description of the Related Art Conventionally, electroplating is generally performed as a method of forming electrode bumps having a size of about several tens to several hundreds of micrometers on a semiconductor wafer, for example, when manufacturing a flip chip IC. In this method, for example, FIG.
As shown in FIG. 1, a metal thin film 2 is formed on a silicon wafer 10 by vapor deposition or the like, and a resist layer 3 having an opening 4 is formed on the metal thin film 2 by applying, exposing, and developing a resist.
To form Next, electroplating is performed using the metal thin film 2 as a cathode, and a bump electrode 5 is formed on the metal thin film 2 exposed in the resist layer opening 4 as shown in FIG.

The electroplating used to form the bump electrode 5 is roughly classified into three types: (1) immersion type, (2) overflow type, and (3) jet type.
The immersion method is the most classical electroplating method. As shown in FIG. 7, several semiconductor wafers 10 are mounted on a hanger 7 and immersed in a plating bath 13 in an arrangement facing a copper anode 16. This is a method of performing electroplating.

In the immersion method, the semiconductor wafer 1 facing the copper anode 16 has a large throughput per batch.
Inevitably, the current distribution becomes inhomogeneous in the 0-plated surface, and therefore, there is a disadvantage that the dimensions of the bump electrodes 5 vary. The overflow method is shown in FIG.
As shown in the figure, a copper anode 16 is placed in a cylindrical plating cell P.
Are placed horizontally, and a semiconductor wafer 10 is placed on the upper end of a plurality of current-carrying pins 9 arranged at intervals along the upper edge of the plating cell P with the surface to be plated facing downward.
Thereby, the surface to be plated of the semiconductor wafer 10 is pressed against the upper ends of the pins 9 and fixed. The plating solution 13 is supplied from below into the plating cell P, and the used plating solution overflows from the gap corresponding to the height of the pins 9 between the upper edge of the plating cell P and the wafer 10 while the plating solution is used. It is a method of performing.

In the case of the overflow method, although the drawback of the immersion method is eliminated, as shown in FIG. 5, bubbles 6 of hydrogen gas generated at the time of plating adhere to the surface to be plated of the semiconductor wafer 10 and have a shape. This causes the formation of the defective bump electrode 5A. The jet method is disclosed by the present inventors in Japanese Patent Application Laid-Open No. 2-61089, and prevents the above-mentioned variation in bump electrode dimensions and defective shape,
This is a new method that can form bump electrodes with high speed and high accuracy.

[0006] As shown in FIG. 9, the electroplating apparatus of the jet flow type has an object 10 to be plated such as a semiconductor wafer.
Is fixed on a pallet 12 of a plating apparatus with a holding jig 11 to form a nozzle group 15 for supplying a plating solution 13 as a jet 14 to a surface 10A to be plated, and a nozzle head 17 having an anode 16 therein is connected to a nozzle group. A front surface 17A having an opening 15 is arranged so as to face the surface 10A to be plated and to have an area covering the surface 10A to be plated.
A mechanism for relatively two-dimensional swinging in parallel with A is provided.

[0007] The plating solution acting on the surface 10A to be plated is:
In FIG. 9, the nozzle head 17 returns to the nozzle head 17 as indicated by an arrow 19 and is discharged from the peripheral portion of the nozzle head 17 as indicated by an arrow 20. The jet method is very effective for forming bump electrodes on wafers up to 4 inches in diameter.
By optimizing the nozzle diameter and pitch, a desired bump electrode can be formed in a short time.

However, it has been found that when applied to a wafer having a larger diameter in order to improve the throughput of the wafer processing step, a shape defect occurs in the bump electrode.
That is, as shown in FIG. 5 described above, a bump electrode 5A having a poor shape is formed due to the influence of bubbles 6 generated during plating. This is because when the diameter of the wafer becomes larger, the liquid returns to the center of the front surface of the nozzle head, especially in the central portion, and the liquid tends to stay there. This is because the gas cannot be completely removed.

In order to solve this problem, the present inventors have proposed in Japanese Patent Application No. 7-57450 an apparatus provided with a return flow path for efficiently discharging a return liquid from a surface to be plated from a nozzle head. did. The device of the above proposal is different from the device of FIG. 9 in that the return liquid 19 is provided by a return flow path 30 provided between the nozzles of the nozzle group 15 as shown in FIG.
It is designed to discharge efficiently through

If the return flow path 30 is provided so as to penetrate the anode 16 in the nozzle head 17 as shown in FIG. 9, the return liquid discharge efficiency will be extremely improved. Decreases by an amount corresponding to the return passage 30 corresponding to the penetrating portion. As a result, the plating current per unit area of the anode 16 increases, and the anode 16 wears out quickly, which makes maintenance and management complicated. The auxiliary electrode 3 is used to compensate for a reduction in the power supply area of the anode 16.
5 can be provided, but this not only complicates the device structure and increases the cost, but also requires extra maintenance and management.

[0011]

SUMMARY OF THE INVENTION According to the present invention, when performing electroplating by the jet flow method, the return liquid can be efficiently discharged from the front surface of the nozzle head without reducing the anode area in the nozzle head, and the surface to be plated is reduced. An object of the present invention is to provide a high-speed and high-precision electroplating apparatus and an electroplating method capable of forming a bump having a good shape and dimensions even with a large diameter.

[0012]

According to the present invention, the structure of a nozzle head for forming a nozzle group for jetting a plating solution and having an anode therein is improved. A tapered surface extending from the ridge line crossing the central part to the periphery of the nozzle head on both sides is provided, and using this tapered surface as a return flow path, the return liquid from the surface to be plated is efficiently discharged from the front surface of the nozzle head. I do.

According to the present invention, since the return flow path is provided as a tapered portion on the outer surface of the nozzle head and does not penetrate the anode in the nozzle head, the power supply area of the anode does not decrease.
This return flow path is formed as a tapered surface extending from the ridge line portion traversing the central portion of the nozzle head to the peripheral portion of the nozzle head on both sides thereof at a portion between the nozzles on the front surface of the nozzle head. The nozzle head is smoothly guided along the surface, and the front surface of the nozzle head is efficiently discharged from its central portion to its peripheral portion.

Thus, even on a surface to be plated having a large diameter, bumps having a predetermined shape and size can be formed at high speed and with high accuracy without requiring complicated maintenance and management of the anode.

[0015]

FIG. 1 is a sectional view of a cell part of a jet electroplating apparatus according to the present invention, and FIG. 2 is a perspective view of a nozzle head according to the present invention. The basic configuration of the plating cell P of the plating apparatus according to the present invention shown in FIG. 1 is the same as that of the conventional plating apparatus shown in FIG. That is, the object to be plated 10 such as a semiconductor wafer is fixed on the pallet 12 of the plating apparatus with the holding jig 11 with the surface to be plated 10A facing downward. The nozzle head 17 supplies the plating solution 13 as a jet 14 from the nozzle group 15 to the surface 10A to be plated.
Further, an anode 16 is provided inside. Nozzle head 17
Is the surface 10 to be plated by a crank mechanism (not shown) or the like.
It swings two-dimensionally in the X-Y direction as indicated by an arrow 18 in parallel with A.

FIG. 2 shows a front surface 17A of the nozzle head 17.
As shown in (1), it has a plurality of nozzle rows 15A including a plurality of nozzles 15, and a plurality of tapered surfaces 31 provided between the nozzle rows 15A. The outline of the opening end of the nozzle 15 is illustrated, and the opening ends of all the nozzles 15 are formed so as to be aligned on the same plane. That is, the upper surfaces of the nozzle rows 15A are aligned on the same plane. Tapered surface 3
1 is a ridge line portion 3 crossing the center of the nozzle head 17
2 to both sides thereof to a nozzle head peripheral portion 33. The ridge portion 32 is substantially at the same height as the upper surface of the nozzle row 15A.
5A is a slope continuously descending to the nozzle head peripheral portion 33 between the 5A. That is, each tapered surface 31 is constituted by a pair of slopes continuous at the ridge line portion 32, and forms a roof shape having the ridge line 32 as a top.

By providing the tapered surface 31 on the front surface 17A of the nozzle head 17 as described above, the return liquid 19 (FIG. 1) from the surface to be plated can be tapered on both sides from the ridge 32 at the center of the front surface of the nozzle head 17. Arrow 22 on surface 31
As shown in FIGS. 1 and 2, the fluid flows down toward the peripheral edge 33 of the nozzle head 17. Thereby, the return liquid 1
9 can be discharged very efficiently from the center of the nozzle head 17. Therefore, the anode 16 having a large power supply area can be disposed in the nozzle head 17 without requiring a return flow path penetrating through the anode in the nozzle head 17 unlike the related art.

As shown in FIG. 1, from a DC power supply 25 for supplying a plating current, a negative lead 25A is connected to the surface 10A to be plated of the wafer 10, and a positive lead 25B is connected to the anode 16 in the nozzle head 17. , Are connected respectively. FIG. 6 shows an example of the overall configuration of a plating apparatus incorporating the plating cell P of FIG. The plating cell P and the plating solution storage tank 52 are connected by a plating solution supply system 56 and a plating solution return system 58. The plating solution storage tank 52 includes a cooler 52A and a heater 52B for maintaining the plating solution 13 stored therein at a predetermined temperature. The plating solution supply system 56 includes a plating solution circulation pump 56B, a filter 56C, and a flow meter 56D in the middle of the pipe 56A. The plating solution return system 58 is substantially constituted by piping. The plating solution storage tank 52 has a filter 54 for removing sludge generated during plating and mixed in the plating solution.
Comes with. The filter 54 includes, for example, a plating solution suction pump 54A, an activated carbon filter 54B, and a fine particle filter 54C.

The plating solution 13 is supplied from the plating solution storage tank 52 to the plating cell P by the supply system 56, and is used in the cell P, and then passes from the cell P through the return system 58 to the storage tank 52.
Return to [Embodiment] Using the plating apparatus according to the present invention described with reference to FIGS. 1, 2, and 6, copper sulfate was plated to form a copper bump electrode on a silicon wafer.

The front portion 17A of the nozzle head 17 is made of acrylic resin having a diameter of 155 mm and a thickness of 17 mm. As shown in FIG. 2, seven rows of four nozzles 15 and seven rows of nozzles 15 are provided. Is a tapered surface 31 having a taper angle of 8 °. Nozzle head 17 using copper plate anode electrode 16
Is oscillated two-dimensionally in the X and Y directions parallel to the surface 10A to be plated of the silicon wafer 10, and the flow rate is 10 m /
In seconds, the plating solution 13 was jetted onto the surface 10A to be plated of the wafer 10, and plating was performed at a plating current density of 25A / dm. The composition of the plating solution was 100 g of sulfuric acid (H ₂ SO ₄ ) /
L, copper sulfate (CuSO ₄ .5H ₂ O) 100 g / L.

Under the above conditions, a diameter of 4 inches and a diameter of 5
Copper bump electrodes were formed on an inch silicon wafer.
FIG. 11 shows the shape defect rate and dimensional variation of the obtained copper bump electrodes. For comparison, FIG.
-61089 (Conventional method A: No return channel)
The results of forming copper bumps under the same conditions as above by the method of Japanese Patent Application No. 7-57450 (conventional method B: with an anode through return flow path) are also shown.

As shown in FIG. 11, in the case of the conventional method A in which the return flow path of the plating solution was not provided, in the case of a 4-inch wafer, good bumps were formed without any bump shape defect and dimensional variation. However, in the case of a 5-inch wafer having a large diameter, a defective bump shape occurred. In the conventional method B in which a return flow path was provided through the anode, good bumps were formed on a 5-inch wafer without any shape defects or dimensional variations.

In the case of the method of the present invention, as in the case of the conventional method B, good bumps were formed on a 5-inch wafer without any shape defects or dimensional variations. As a result, the present invention can form a bump having a good shape and dimensions without having to provide a return flow path penetrating through the anode as in the conventional method B, so that the anode shape can be simplified. Since the power supply area of the anode can be sufficiently secured, the consumption of the anode is reduced, and the maintenance and management can be simplified.

Next, the taper angle of the tapered surface 31 of the nozzle head front surface portion 17A is set to 0 ° (no taper), 3 °,
Using four types of nozzle heads 17 changed to 6 ° and 8 °, copper electroplating was performed under the same conditions as above to form copper bump electrodes. FIG. 12 shows the obtained results. As shown in FIG. 12, when the taper angle was 6 ° or more, a good copper bump electrode having no shape defect and little dimensional variation was obtained.

As described above, according to the present invention, the return liquid is formed along the tapered surface by providing the tapered surface on the front surface of the nozzle head as the return flow path for the return liquid from the surface to be plated. The bump electrode can be guided and smoothly discharged from the front surface of the nozzle head, and a bump electrode having no shape defect and small dimensional variation can be formed even on a large-diameter plating surface such as a 5-inch wafer. As a result, since a return flow path that penetrates the anode in the nozzle head is not required unlike the conventional case, the anode shape can be simplified,
There is no decrease in the anode power supply area due to the return channel penetration, the consumption of the anode can be reduced, and the maintenance and management can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a cell portion of a jet type electroplating apparatus according to the present invention.

FIG. 2 is a perspective view showing an example of a front part of a nozzle head of the electroplating apparatus according to the present invention.

FIG. 3 is a cross-sectional view showing a step of sequentially forming a metal thin film and a resist layer having an opening thereon to form a bump electrode on a semiconductor wafer.

FIG. 4 is a cross-sectional view showing a step of forming a bump electrode on the metal thin film exposed in the opening of the resist layer by performing electroplating using the metal thin film as a cathode, following the process of FIG.

FIG. 5 is a cross-sectional view showing a bump electrode having a poor shape formed by bubbles such as hydrogen gas generated at the time of plating adhering to a surface to be plated of a semiconductor wafer.

FIG. 6 is a layout diagram showing an overall layout example of an electroplating apparatus according to the present invention.

FIG. 7 is a sectional view showing an immersion type electroplating apparatus.

FIG. 8 is a sectional view showing an overflow type electroplating apparatus.

FIG. 9 is a cross-sectional view showing a cell portion of a conventional jet-type electroplating apparatus having no return flow path.

FIG. 10 is a cross-sectional view showing a cell portion of a conventional jet-type electroplating apparatus provided with a return flow path penetrating an anode in a nozzle head.

FIG. 11 is a graph showing the shape defect rate and dimensional variation of a copper bump electrode formed by electroplating according to the present invention in comparison with a copper bump electrode formed by a conventional method under the same conditions.

FIG. 12 is a graph showing the relationship between the taper angle of a tapered surface provided on the front surface of a nozzle head as a return channel according to the present invention, and the shape defect rate and dimensional variation of a formed copper bump electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Plate object 10A ... Plate surface 13 ... Plating solution 14 ... Jet 15 ... Nozzle (group) 16 ... Anode 17 ... Nozzle head 17A ... Nozzle head front surface 18 ... Two-dimensional swinging direction 19 ... Return liquid 31 ... Taper Surface 32: ridgeline 33: Peripheral edge of nozzle head

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-61089 (JP, A) JP-A-3-260085 (JP, A) JP-A-56-151291 (JP, A) JP-A-7- 321115 (JP, A) Japanese Utility Model Showa 60-143776 (JP, U) JP-B 62-14235 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25D 5/08 C25D 7 / 12 H01L 21/288

Claims (8)

(57) [Claims] 1. A nozzle head having an anode a plating solution therein and constitutes a nozzle group to be spouted into the plated surface of the object to be plated, placed so as to face the front of the nozzle groups is open to the surface to be plated In the electroplating apparatus provided with a mechanism that relatively two-dimensionally swings the surface to be plated and the nozzle head in parallel with the surface to be plated, the nozzle group includes a plurality of nozzles each including a plurality of nozzles.
The nozzle rows are arranged in parallel, and a portion between the adjacent nozzle rows on the front face of the nozzle head is provided with a tapered surface extending from the ridge line portion traversing the central portion of the nozzle head to the peripheral portion of the nozzle head on both sides thereof, An electroplating apparatus, wherein a return flow path for discharging a return liquid from a surface to be plated from a front surface of a nozzle head is constituted by the tapered surface. 2. The electroplating apparatus according to claim 1, wherein a taper angle of the tapered surface is 6 ° or more. 3. The method according to claim 2, wherein the nozzle row and the return channel are
4. The method according to claim 1, wherein the ridge is perpendicular to the ridge.
Is an electroplating apparatus according to 2. 4. The method according to claim 1, wherein the nozzle head has a cylindrical shape.
The nozzle row is formed on the upper surface of the cylinder, and the ridge line
2. The method according to claim 1, wherein the portion passes through the center of the upper surface.
The electroplating apparatus according to any one of claims 1 to 3. 5. The nozzle head having an anode a plating solution therein and constitutes a nozzle group to be spouted into the plated surface of the object to be plated, place the front of the nozzle groups is open to face the surface to be plated In the method of performing electroplating by relatively two-dimensionally swinging the surface to be plated and the nozzle head in parallel with the surface to be plated, the nozzle group includes a plurality of nozzles each including a plurality of nozzles.
The nozzle rows are arranged in parallel, and a portion between the adjacent nozzle rows on the front face of the nozzle head is provided with a tapered surface extending from the ridge line portion traversing the central portion of the nozzle head to the peripheral portion of the nozzle head on both sides thereof, An electroplating method, wherein a return liquid from a surface to be plated is discharged from a front surface of a nozzle head through a return flow path constituted by the tapered surface. 6. The electroplating method according to claim 5, wherein a taper angle of the tapered surface is 6 ° or more. 7. The method according to claim 7, wherein the nozzle row and the return flow path are
6. The structure according to claim 5, wherein the ridge is perpendicular to the ridge.
Is an electroplating method according to 6. 8. The method according to claim 8, wherein the nozzle head has a cylindrical shape.
The nozzle row is formed on the upper surface of the cylinder, and the ridge line
6. The method according to claim 5, wherein the portion passes through the center of the upper surface.
An electroplating method according to any one of claims 1 to 7.