JP3940648B2 - Wafer plating equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plating apparatus for electrolytically plating a wafer to be plated, and particularly to a cup-type plating apparatus.
[0002]
[Prior art]
There is a so-called cup-type plating apparatus as a plating apparatus that performs electrolytic plating on a surface to be plated of a wafer (see FIG. 1). As shown in FIG. 7, the wafer support portion of the conventional cup type plating apparatus 100 includes an annular end surface portion 111 extending along the upper end opening of the plating solution tank, and an annular end surface portion installed on the end surface portion 111. The seal packing 121 includes an annular cathode electrode 122 installed on the upper surface of the seal packing 121. The seal packing 121 and the cathode electrode are fixed to the plating solution tank (on the end surface portion 111) by a top ring 123. The annular seal packing 121 includes an annular convex portion 121a protruding upward at the inner peripheral edge thereof.
[0003]
When performing the plating process with such a plating apparatus 100, first, the wafer W to be plated is placed on the support portion, and then the outer periphery of the wafer W is pressed against the support portion 120 side by the press ring 124. In addition to preventing the plating solution from leaking, the energized state between the outer peripheral portion of the wafer W and the cathode electrode 122 is ensured, and then energized to perform plating.
[0004]
By the way, even by fixing the wafer in this way, it is difficult to apply plating with a uniform film thickness to the plating target surface of the wafer, even if leakage of the plating solution can be prevented. In addition, a thin-film seed is provided on the contact surface with the cathode electrode on the outer peripheral portion of the wafer for the purpose of obtaining a good energized state, etc. When the resistance of this seed is high or the thickness is thin In particular, it is difficult to bring the outer peripheral portion of the wafer into uniform contact with the cathode electrode over the entire circumference. Simply pressing the outer periphery of the wafer all the way to the support side (cathode electrode) makes it impossible to bring the entire periphery of the wafer into contact with the cathode electrode (that is, the contact state is biased). ) As a result, it is considered that an even energized state cannot be secured. If the pressing force is increased, a wider contact area can be secured. However, there is a limit to increasing the pressing force because there is a restriction on the strength of the plating bath.
[0005]
In addition, there is another plating solution tank 101 having a wafer support as shown in FIG. In the support portion of the plating apparatus 101, a cathode electrode 122 having a plurality of protrusions 122 a at a position facing the wafer W is used. If the protrusion 122a is formed in this manner, the wafer W and the cathode electrode 122 can be reliably brought into contact with each other at the position of the protrusion. However, in this case, it takes time to form the protrusion 122a on the cathode electrode 122. The material of the cathode electrode 122 is limited to a material having workability sufficient to form the protrusion 122a, such as gold. When the material of the cathode electrode 122 is inferior in workability (e.g., easily cracked) such as titanium, the protrusion 122a cannot be formed or the yield is low even if it can be done, which is extremely troublesome. Further, the cathode electrode 122 is in contact with the wafer W only at the portion of the protrusion 122a, and it is difficult to ensure as wide a current-carrying area as possible by bringing the surface of the cathode electrode 122 into contact as much as possible.
[0006]
[Problems to be solved by the invention]
The present invention has been made under the background as described above, and it is possible to form a plating with a uniform film thickness on a wafer, and in that case, it is necessary to perform a process for providing a projection on the cathode electrode. It is an object of the present invention to provide a plating apparatus with a simple structure of the support portion.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the inventor investigated the contact state between the wafer and the outer peripheral portion of the wafer pressed against the cathode electrode. As a result, the contact area was about 80% to 90% of the whole. Then, it was found that the non-contact area is biased to a limited place, for example, about one place or about two places, and this prevents uniform energization over the entire circumference of the outer peripheral portion of the wafer. Moreover, even if the pressing force was increased, the contact area was only improved by about several percent, and an even energized state could not be obtained. For this reason, it has been found that when a conventional cathode electrode having no protrusion is used, it is extremely difficult to bring the cathode electrode into contact with the wafer entirely. Therefore, it was decided to investigate a structure capable of evenly contacting the cathode electrode having no protrusions without contacting the wafer entirely. As a result, it has been found that if the non-contact portion can be scattered all around the cathode electrode (or the outer peripheral portion of the wafer), an even energized state can be ensured over the entire circumference, and as a result of further studies, the present invention I came to the idea.
[0008]
The present invention includes a plating solution tank in which an anode electrode is installed in a tank, an annular end surface extending along an opening edge of the plating solution tank, and a seal packing installed on the end surface; In a wafer plating apparatus having a wafer support portion composed of a cathode electrode installed on the seal packing, a protrusion is formed at a position facing the cathode electrode of the seal packing so as to surround the opening of the plating solution tank. It is characterized by doing.
[0009]
The cathode electrode is a thin member and can be deformed according to the uneven shape of the seal packing. Therefore, when the protrusion is provided on the seal packing as in the present invention, when the wafer is pressed against the support portion, the cathode electrode is pressed to the wafer side by the protrusion, and the pressed portion (hereinafter referred to as preferential contact). Preferentially comes into contact with the wafer. In the present invention, examples of the protrusion formed on the seal packing so as to surround the opening of the plating solution tank include a protrusion extending in a ring shape over the entire circumference. As the shape of the annular end surface extending along the opening edge of the plating bath, various shapes such as a circle and a polygon such as a quadrangle are conceivable, and the shape of the protrusion formed on the seal packing is also the shape of the end surface. Various shapes such as a circle and a quadrangle are conceivable depending on the case. If such a protrusion is formed and the cathode electrode and the wafer are brought into contact with each other, the total contact area may be reduced as compared with the case where the protrusion is not provided, but it is limited to the preferential contact portion pushed by the protrusion. For example, the contact ratio of this portion is remarkably improved. And it is thought that there is almost no non-contact area. As a result, the wafer comes into contact with the cathode electrode evenly over the entire circumference of the outer peripheral portion, and it is considered that an even energized state is ensured over the entire circumference. If a uniform energization state is ensured, plating with a uniform film thickness can be obtained on the plating target surface of the wafer.
[0010]
Moreover, as a protrusion formed on the seal packing so as to surround the opening of the plating solution tank, in addition to a ring-shaped protrusion over the entire circumference, a protrusion formed at equal intervals along the circumferential direction of the opening There is. When this protrusion is formed, the preferential contact portion is formed at almost equal intervals around the entire circumference of the outer peripheral portion of the wafer. If non-contact parts occur, they will occur in areas not pressed by the protrusions, that is, in areas between the preferential contact parts, but preferential contact parts occur at equal intervals around the entire circumference. Therefore, the non-contact portions are scattered all around the outer peripheral portion of the wafer.
[0011]
Thus, if the non-contact part, which has been unevenly distributed in the past, can be scattered all around the outer periphery of the wafer, the cathode electrode cannot be brought into full contact with the wafer, and the outer periphery of the wafer An even energized state is ensured over the entire circumference. For example, if the cathode electrode is an annular shape made of a flat plate, the outer periphery of the wafer can be brought into close contact with the outer periphery of the wafer and the cathode electrode by expelling a non-contact portion (gap) between them. It is difficult to bring the entire portion into contact with the cathode electrode, and the non-contact portion tends to be unevenly distributed. However, the present invention for ensuring uniform energization by scattering the non-contact portion is the case of the cathode electrode having such a shape. Also effective. If a uniform energization state is ensured, plating with a uniform film thickness can be obtained on the plating target surface of the wafer.
[0012]
Further, according to the present invention, it has been found that the contact area between the wafer and the cathode electrode can be ensured as usual or comparable to the contact area. This is considered to be the following reason. Since the seal packing is made of a flexible material such as rubber, when the wafer is pressed against the support portion, the protrusions are deformed and crushed (in other words, embedded in the seal packing body). In this state, the shape of the cathode electrode is apparently the same as that of the conventional cathode electrode having no protrusion, and the conventional contact area is secured. In addition, since a contact part exists as a breadth centering on a priority contact part, the state where a non-contact part is scattered is maintained. As described above, according to the present invention, even if a uniform energization state is ensured, the contact area does not decrease or the decrease is suppressed to the minimum. In addition, when the case where the protrusion extending in the ring shape is provided and the case where the protrusion is provided at equal intervals along the circumferential direction are compared, it is easier to secure a wider contact area in the latter case. This is probably because the latter case is easier to crush the protrusion. On the other hand, as described in the prior art, when the projection is provided on the cathode electrode, the cathode electrode can be reliably brought into contact with the wafer at the position of the projection, but the cathode electrode is flexible like a seal packing. Therefore, even if the wafer is pressed against the cathode electrode, the cathode electrode and the wafer cannot be brought into contact with each other other than the protrusions, and it is difficult to ensure a wide contact area.
[0013]
As described above, according to the present invention, the cathode electrode does not need to be processed at all, and a conventional cathode electrode having no protrusion can be used. That is, the material of the cathode electrode is not limited. Further, since only a protrusion needs to be added to the surface of the seal packing, the support portion of the wafer has a very simple structure. Therefore, it can be easily manufactured as before. However, in terms of securing a wider contact area, the cathode electrode is more preferably flexible, and in this respect, the cathode electrode is preferably made of gold or platinum.
[0014]
Incidentally, as described above, according to the present invention, it is easy to ensure a contact area between the wafer and the cathode electrode. However, when a projection having a high height is provided, the seal packing and the cathode electrode are contacted at a portion other than the projection. The required contact area may not be secured even if the wafer is pressed with a strong force. Therefore, the height was examined. As a result, it was found that the height of the protrusion is preferably equal to or less than the height of the convex portion formed for preventing plating solution leakage, and specifically, 0.3 mm or less is preferable. On the other hand, it was found that 0.1 mm or more is preferable. If it is lower than this, a part of the cathode electrode cannot be preferentially brought into contact with the wafer, and the non-contact part may not be dispersed. As the shape of the protrusion, various shapes such as a protrusion having a spherical surface such as a hemisphere or a conical protrusion such as a cone may be employed.
[0015]
When the cathode electrode has a ring shape, the plurality of protrusions formed on the seal packing connect the respective protrusions to the center of the ring-shaped cathode electrode placed on the seal packing to obtain a line segment. It is preferable that the adjacent line segments are formed at intervals of 4 ° to 20 °. This is because the non-contact portion may not be evenly distributed over the entire circumference of the outer peripheral portion of the wafer at an interval where the angle is 20 ° or more or an interval where the angle is less than 4 °. And in the point which can ensure a uniform electricity supply state within the said range easily, as for the space | interval of protrusion, 5 degrees or more is more preferable as a lower limit. Moreover, as an upper limit, 10 degrees or less are more preferable. In addition, if the seal packing is an annular shape concentric with the cathode electrode, for example, a disc shape, the interval between the protrusions can be specified with reference to the center of the packing. Also, in the case of a ring shape other than a circle, for example, an ellipse is the intersection of the major and minor axes, a quadrangle is a diagonal intersection, and a pentagon is a circle drawn through each vertex. The positions of the projections can be specified using the line segments obtained by extending the centers of the projections from the centers to the projections.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of a cup-type plating apparatus according to the present invention will be described with reference to the drawings.
[0017]
As shown in FIG. 1, the cup type plating apparatus 1 includes a plating solution tank 10 for containing a plating solution, and a circular opening at the upper end of the plating solution tank 10 is an object to be plated. A support unit 20 on which the wafer W is placed is provided. As shown in FIG. 2, the support portion 20 includes an end surface portion 11 having an annular upper end surface 11 a (see FIG. 2) extending along the opening edge, and a seal packing installed on the end surface portion 11. 21 and a gold cathode electrode 22 installed on the seal packing 21. An annular top ring 24 that covers the outer peripheral region of the support portion 20 is placed on the cathode electrode 22 via the packing 23. The seal packing 21 and the cathode electrode 22 are connected to the top ring 24 and the end surface portion. 11 is fixed to the plating bath 10 while being sandwiched between the two.
[0018]
Of the members constituting the support portion 20, the seal packing 21 has an annular shape as shown in FIG. 3, and is formed on the inner peripheral edge thereof over the entire circumference as shown in FIG. 4 (a). Convex portion 21a. The convex portion 21a is a portion that comes into close contact with the wafer W placed on the support portion 20. When the wafer W and the convex portion 21a are brought into close contact with each other, the plating solution leaks from the plating solution tank 10. Is prevented. A plurality of protrusions 21b are formed at equal intervals along the circumferential direction at a position on the upper surface of the seal packing 21 facing the cathode electrode 22. When the protrusions 21b are present, the cathode electrode 22 preferentially contacts the wafer at a position corresponding to each protrusion 21b. The interval between the projections 21b is an interval at which the angle formed by the line segment L (see FIG. 4A) obtained by connecting the center of the annular cathode electrode 22 and each projection 21b becomes 10 °. As shown in FIG. 4B, it was hemispherical and had a height of 0.2 mm.
[0019]
The cathode electrode 22 on the seal packing 21 is made of an annular thin plate material. The cathode electrode 22 had a thickness of 0.1 mm and could be easily bent and deformed.
[0020]
As shown in FIG. 1, the plating solution tank 10 includes a plating solution supply port 12 on the bottom surface, and a plating solution discharge port 13 on the peripheral wall surface 10 a immediately below the end surface portion 11. ing. At the bottom of the plating bath 10, an annular anode electrode 25, which is a counter electrode of the cathode electrode 22, is installed so as to surround the supply port. Reference numeral “26” denotes a pressing ring that presses the wafer W placed on the support unit 20 against the support unit 20.
[0021]
When plating is performed on the wafer W using such a plating apparatus 1, first, the seed is formed in a state where the plating target surface of the wafer W is directed into the plating solution tank 10 filled with the plating solution. The outer peripheral portion of the wafer W is placed on the support portion 20. Then, as shown in FIG. 5, the outer peripheral portion of the wafer W is pressed against the support portion 20 by the press ring 26. Then, the convex portion 21a of the seal packing 21 comes into close contact with the wafer W, and the plating solution in the plating solution tank 10 is prevented from leaking.
[0022]
Further, when the outer peripheral portion of the wafer W is pressed against the support portion 20, the cathode electrode 22 is pushed toward the wafer W by the projection 21 b at a position in contact with each projection 21 b on the back side (lower side in the drawing). To touch. Since each protrusion 21b is formed at equal intervals, as shown in FIG. 6, the contact portion (preferential contact portion) S by the protrusion 21b is evenly formed on the entire outer periphery of the wafer W. A non-contact portion T is generated between the contact portions S. As described above, according to the plating apparatus 1 of the present embodiment, the contact portion S between the wafer W and the cathode electrode 22 is evenly formed on the entire circumference of the outer peripheral portion of the wafer W, and the non-contact portion T between them is the wafer W. Scattered all around the outer periphery. In FIG. 6, the contact area between the seal packing 21 or the cathode electrode 22 and the wafer W is schematically shown by hatching. In addition, a belt-like contact region existing on the inner peripheral side of the contact portion S is a contact region between the wafer W and the seal packing 21.
[0023]
In this state, the plating solution is supplied from the supply port 12, and the plating solution is discharged from the discharge port 13, and the plating process is performed by energizing the wafer W and the anode electrode 25 via the plating solution. When plating was actually performed, plating with a uniform film thickness was obtained on the plating target surface of the wafer W. This is considered to be because an even energized state is ensured over the entire circumference of the outer peripheral portion of the wafer W.
[0024]
In some cases, the cathode electrode is bonded to the seal packing using an adhesive. If both are bonded, the advantage that the cathode electrode positioning work to the seal packing is unnecessary and the handling is easy, and the invasion of the plating solution between the seal packing and the cathode electrode is prevented. When a new wafer is placed on the cathode electrode and pressed, the plating solution is prevented from oozing out between the cathode electrode and the seal packing, and the leached plating solution dissolves the thin-film seed on the wafer surface. This is because there is an advantage that it is prevented. Accordingly, a plating treatment test was also performed with a plating apparatus that adhered the seal packing 21 and the cathode electrode 22. As a result, plating with a uniform film thickness was obtained on the plating target surface of the wafer W. Even when both are bonded, it is considered that if the seal packing 21 is provided with a protrusion, the non-contact portion between the cathode electrode 22 and the wafer W can be scattered all around the outer periphery of the wafer W. It is done.
[0025]
【The invention's effect】
As can be seen from the above description, according to the present invention, the entire circumference of the outer peripheral portion of the wafer can be energized uniformly, and plating with a uniform film thickness can be obtained on the plating target surface of the wafer.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a plating solution tank of a plating apparatus according to an embodiment.
FIG. 2 is a cross-sectional view showing a support portion of a wafer.
FIG. 3 is a plan view showing a seal packing. FIG. 4 is an enlarged plan view and cross-sectional view showing a main part (region A in FIG. 3) of the seal packing.
FIG. 5 is a cross-sectional view showing a state in which a wafer is fixed on a support portion.
6 is a plan view showing a CC plane of FIG. 5. FIG.
FIG. 7 is a cross-sectional view showing a support portion of a conventional plating apparatus.
FIG. 8 is a cross-sectional view showing a support portion of another conventional plating apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plating apparatus 10 Plating solution tank 10a Perimeter wall surface 11 End surface part 11a Upper end surface (end surface)
12 Supply Port 13 Discharge Port 20 Support Portion 21 Seal Packing 21a Protruding Portion 21b Protrusion 22 Cathode Electrode 23 Packing 24 Top Ring 25 Anode Electrode 26 Holding Ring W Wafer

Claims (4)

It has a plating bath with an anode electrode installed in the bath,
A seal packing having an end face portion of the annular extending along the opening edge of the plating solution tank, is placed on the said end face portion, a convex portion formed over the entire circumference inner periphery, the seal Wafer plating having a wafer support portion comprising a cathode electrode placed on the packing , and securing the energized state by bringing the outer peripheral portion of the wafer placed on the support portion into contact with the cathode electrode In the device
The seal packing, an upper surface of the cathode electrode is placed, the plating apparatus of the wafer, characterized by forming the protrusions so as to surround the opening of the plating solution tank. The wafer plating apparatus according to claim 1 , wherein the protrusions are formed at equal intervals along a circumferential direction of the opening.   The wafer plating apparatus according to claim 1, wherein the protrusion has a height of 0.1 mm to 0.3 mm.   The cathode electrode has a ring shape, and the plurality of protrusions formed on the seal packing are adjacent to each other when the center of the ring-shaped cathode electrode placed on the seal packing and each protrusion are connected to obtain a line segment. The wafer apparatus according to any one of claims 1 to 3, wherein the angle formed by the line segments to be formed is 4 ° to 20 °.

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