Patent Application
20070114127
The present invention relates to a plating apparatus, which conducts a plating treatment by using a diaphragm to separate an anode positioned in a plating tank from an object to be plated such as a wafer, a printed-wiring board, and the like.
Conventionally, various kinds of plating treatments have been conducted on objects to be plated such as a wafer for a semiconductor, a printed-wiring board, and the like. As an apparatus for conducting a plating treatment on such objects to be plated, jet-flow plating apparatuses are known.
A jet-flow plating apparatus is generally provided with: an opening on which an object to be plated can be placed; a solution-supply tube for supplying a plating solution toward the object to be plated; and an anode positioned in an opposed manner to the object to be plated, thereby a plating treatment is carried out while a plating solution is supplied through the solution-supply tube toward the object to be plated. Due to capability of conducting a uniform plating treatment on a surface to be plated of the object to be plated and conducting a plating treatment while objects to be plated that are to be placed on the opening are sequentially replaced, the jet-flow plating apparatuses are now widely used as a preferable one for small lot production and automation of a plating treatment.
Although the jet-flow plating apparatus has the above-described advantages, a film, for instance a black film or the like, to be formed onto a surface of an anode may be broken away into a solution and become impurities to flow in a plating solution supplied toward an objective to be plated, thereby possibly causing a negative effect on a plating treatment. Additionally, air mixed in a solution or bubbles generated from an anode sometimes reach a surface to be plated, thereby inhibiting a good plating treatment. In this jet-flow plating apparatus, therefore, a diaphragm for separating an object to be plated and an anode is arranged within a plating tank (see Patent Document 1: Japanese Patent Application Laid-Open No. 350185/1999).
The jet-flow plating apparatus having a diaphragm arranged within a plating tank as shown in Patent Document 1 resists a negative impact exerted by impurities generated from an anode, prevents wastage of plating additive agent which occurs when an insoluble anode is used, and furthermore surely overcome a negative impact exerted by air bubbles generated from an anode.
However, like the above described prior art document, it is not an easy operation to dispose a diaphragm within a plating tank to assure isolation of an anode from an object to be plated. Especially, when a diaphragm is arranged in a cone-shaped manner in a plating tank as seen in Patent Document 1, such herculean operations were entailed in producing or maintaining an apparatus because a special mounting jig should be prepared for avoiding some inconvenience including wrinkles from generating in the diaphragm, or cone-shaped diaphragms should be arranged in a divided manner.
The present invention was made against a backdrop of the above circumstances, and it is an object of the present invention to provide a technology, which enables a diaphragm to be arranged in a more facilitated manner in a plating tank of a jet-flow type plating apparatus provided with a diaphragm for isolating an object to be plated from an anode.
In order to solve the above problem, the present inventor improved both the plating tank and solution supply tube to reach the present invention, in which a diaphragm can be arranged in the plating tank in a more facilitated manner. The present invention is a plating apparatus having a plating tank, which plating tank comprises: an opening on which an object to be plated is placed; a solution-supply tube for supplying a plating solution toward the object to be plated; an anode positioned opposed to the object to be plated; and a diaphragm for isolating the object to be plated from the anode, wherein an inner wall of the plating tank is provided with a diaphragm-periphery fixing part for fixing a peripheral end of the diaphragm, and the solution-supply tube is composed of a dual tube consisting of an inner tube and an outer tube. The inner tube has an inner tube part allowed to pass through a through-hole formed at a center of the diaphragm and a diaphragm through-hole fixing part for fixing the through-hole, and the outer tube has an engaging part for accommodating and fixing inner tube and further has a tank-fixing part to be fixed in the plating tank.
In the present invention, the diaphragm to be arranged in the plating tank is preliminarily processed the periphery thereof so as to be fixed at an inner tube of the plating tank, and is also formed to have a through hole at a center of the diaphragm, through which the inner tube is passed. Then, the periphery of the diaphragm is fixed on the diaphragm-periphery fixing part provided on the inner wall of the present plating tank. Through the through hole provided at the center of the diaphragm, the inner tube of the solution-supply tube is allowed to pass. An outer tube part of the solution-supply tube of the present invention is separately fixed in the plating tank, an inner tube part passing through the through hole of the diaphragm is inserted into the outer tube, and the entire inner tube is allowed to shift until the inner tube engages with an engaging part of the outer tube part. When the outer tube and the inner tube are engaged with each other to become unified, the periphery of the diaphragm is fixed on the diaphragm-periphery fixing part provided on the inner wall of the present plating tank, and the through hole of the diaphragm is fixed to a diaphragm through-hole fixing part, thereby the diaphragm is arranged in the plating tank. Thus, in the present invention, since the diaphragm is formed with a periphery shaped in conformity with the internal shape of the plating tank and formed with a thorough hole, neither any special mounting jig nor any substantial design change of the apparatus itself is required, thereby a diaphragm can be arranged in a plating tank in an extremely easy manner. Especially, even a diaphragm which is very difficult to handle, for instance one formed by a soft material or small in thickness, the present invention makes it possible to arrange a diaphragm in a plating tank properly without causing damage or wrinkles to the diaphragm.
It is preferable to provide the plating apparatus according to the present invention with a diverging solution flow path formed between the inner wall of the outer tube and the outer wall of the inner tube when the inner tube has been fixed to the outer tube, for supplying a plating solution to the anode chamber, which is formed by separating by use of the diaphragm from the object to be plated. When the interior of the plating tank is separated via the diaphragm into the anode chamber and the cathode chamber where the object to be plated is present, it is necessary to secure a solution supply path for supplying a solution other than a plating solution to be supplied to the object to be plated, in order to exchange the solution present in the anode chamber. In such a case, if the diverging solution flow path for flowing the plating solution to thon the strength e anode chamber is formed on the solution supply tube having a dual tube structure according to the present invention, a part of the plating solution to be supplied will be supplied to the anode chamber side in a facilitated manner by diverging the plating solution to be supplied toward the object to be plated. The structure will eliminate a need to provide extra solution supply tube for supplying a plating solution to the anode chamber side, thereby making the plating apparatus structure itself simple. In this case, it is desirable to provide in the anode chamber a solution discharge path for discharging the plating solution to be supplied to the anode chamber side out of the anode chamber. The solution discharge path can be provided on any area, for example on the inner wall of the plating tank or the bottom of the plating tank so far as the area is within the plating tank. What matters is the plating solution should be supplied into, circulated within, and discharged out of the anode chamber appropriately.
It is also preferable if the diaphragm of the plating apparatus according to the present invention be arranged in the plating tank in a cone-shaped manner. For instance, if the diaphragm is arranged in a cone-shaped manner so that its periphery rises, air bubbles generating from the anode will move along the inclination of the diaphragm toward the periphery thereof, thereby effects of the air bubbles can be circumvented. In order to arrange the diaphragm in a cone-shaped manner, a position, where the diaphragm through hole should be fixed by use of the solution supply tube, only has to be determined lower than a horizontal position of a diaphragm-periphery fixing part provided on the inner wall of the plating tank.
It is further preferable that the plating apparatus according to the present invention is provided beneath the diaphragm-periphery fixing part with an anode-chamber solution discharge port for discharging a plating solution out of the anode chamber, and the anode-chamber solution discharge port is provided with a filter for removing impurities present in the plating solution. In the anode chamber formed by the arrangement of the diaphragm in the plating tank, such impurities for instance black films generating at the anode are highly likely to mix into the solution. If the solution discharged out of the anode chamber should be mixed as it is with the counterpart present in the cathode chamber side, namely the plating solution to be supplied toward the object to be plated, impurities will mix in the entire plating solution, and therefore it is feared a negative effect may be caused on a good plating treatment. In this respect, if the impurities contained in the plating solution discharged out of the anode chamber should be removed by means of the filter, the entire plating solution can be prevented from being contaminated by the impurities.
Further in the plating apparatus according to the present invention, it is preferable if the inner tube has a cap part which covers the periphery of the outer tube, and on a tip of the cap part, there is provided the diaphragm through-hole fixing part. It is also preferable if an upper end of the outer tube be provided with an anode-chamber solution supply port for supplying to the anode chamber the plating solution flowing through the diverging solution flow path, and the anode-chamber solution supply port be provided at a position higher than the horizontal position of the anode-chamber solution discharge port and the diaphragm through-hole fixing part be provided at a position lower than the horizontal position of the anode-chamber solution discharge port.
The interior of the plating tank where the diaphragm has been arranged is to be divided into two chambers consisting of the anode chamber in which an anode exists and the cathode chamber in which the object to be plated has been arranged. When an object to be plated should be replaced after a plating solution has been supplied to each chamber and a plating treatment has been completed, the plating solution is sometimes discharged. When the plating solution in the plating tank has been discharged and the diaphragm emerges from the plating solution and is exposed, the diaphragm itself will be in contact with the air. That is to say, the plating solution level is lower than the position of the diaphragm arranged, the diaphragm will be in contact with the air, which condition will allow air to enter the anode chamber. Under the condition, the diaphragm is likely to deteriorate in an advancing manner, although the deterioration will be dependent on a type or quality of the diaphragm to be used, thereby a weftability of the diaphragm with respect to the plating solution will be deteriorated. Further, if the air enters the anode chamber, an anode used itself will be oxidized if it is a soluble one, and it is feared subsequent plating treatments will be subject to an adverse affect.
Thus, the present inventor studied a structure, which achieves, in replacing objects to be plated in a jet-flow plating apparatus, a condition where the diaphragm is not in contact with the air by positively maintaining the plating solution level higher than the position of the diaphragm placed even after the plating solution in the plating tank is discharged. As a result, it was found that the plating solution level after the plating solution in the plating tank has been discharged should be maintained higher than the position that diaphragm was arranged in the plating tank, namely the diaphragm should be present in the plating solution. Therefore, the apparatus was adapted to have a structure, where the inner tube has a cap part which covers the periphery of the outer tube, and on a tip of the cap part, there is provided the diaphragm through-hole fixing part, the anode-chamber solution supply port provided on the upper end of the outer tube is provided higher than the horizontal position of the anode-chamber solution discharge port, and the diaphragm through-hole fixing part is arranged lower than the horizontal position of the anode-chamber solution discharge port.
In addition, as described above, in adopting a structure for achieving a condition where the diaphragm is not in contact with the air after the plating solution in the plating tank is discharged, it is preferable if a back-flow prevention device is provided so that the plating solution in the anode chamber will not flow out, when the plating solution is discharged, into a diverging solution flow path which is formed between the inner tube and the outer tube in the solution-supply tube having a dual tube structure. With such a back-flow prevention device provided, a condition is securely achievable where a diaphragm is immersed in a plating tank even when the plating solution in a plating tank has been discharged.
Further in addition, in the plating apparatus of the present invention, it is preferable to provide the inner tube with a solution flow diverting means for diverting a plating solution to be supplied toward an object to be plated. In a plating treatment of an object to be plated, it is sometimes severely required a uniformity of a plating thickness, and especially in an alloy plating, a homogeneity of a plating composition. Specifically, depending on the type of a plating solution being used and the conditions of a plating treatment such as an electric current density, the uniformity in both plating thickness and plating composition may sometimes be realized across the plated surface of the object to be plated due to greatly affected by a flowing condition of the plating solution supplied toward the object to be plated. Especially, when the plating solution supplied toward the object to be plated flows in a manner that it spreads from an essential center of the object to be plated to a peripheral direction thereof, the plating thickness in the central area of the object to be plated may sometimes become greater than that of the peripheral area. Further, for instance, when an alloy plating treatment including a Ag—Sn alloy plating is carried out, the alloy plating compositions in the central area and in the peripheral area of the object to be plated are liable to differ from each other. In such a case, it is preferable to provide the inner tube in the plating apparatus of the present invention with a solution flow diverting means for diverting a plating solution to be supplied toward an object to be plated so that the plating solution will not be supplied intensively to a specific area of the object to be plated, thereby conducting a plating treatment providing a uniform plating thickness across the plated surface of the object to be plated and a homogeneous plating composition.
The solution flow diverting means provided in the inner tube is not so limited in terms of its structure insofar as the supplying direction of the plating solution to be supplied from the inner tube toward the object to be plated does not disperse. Specifically, a disk-shaped damper body provided on an upper part in the inner tube at a plating solution supplying side can disperse the flowing condition of the plating solution being supplied, into the plating tank. It is also acceptable to adopt a structure in which a flow-dividing channel is formed within the inner tube in order to disperse the supplying direction of the plating solution into the plating tank.
As described above, the present invention makes it possible to arrange a diaphragm within a plating tank in a very facilitated manner in a plating apparatus having a diaphragm for separating an object to be plated and an anode. The present invention further improves efficiency in a manufacture or maintenance work of a plating apparatus without causing wrinkles in a diaphragm even when the diaphragm is arranged in a cone-shaped manner.
Preferred embodiments of a plating apparatus related to the present invention are described below with reference to drawings.
A schematic cross-sectional view of a plating apparatus according to First Embodiment of the present invention is shown in
The opening 10 of the plating tank B is formed of a top ring 101, an annular cathode electrode 102 coming into contact with a periphery of the object to be plated W, a seal packing 103, and an annual support 104. There is formed beneath the opening 10 in the plating tank B a solution discharge path 40 for a plating solution supplied toward the object to be plated W. The plating solution discharged through the solution discharge path 40 passes through a wall of the plating tank B and is sent to a not-shown plating-solution storage tank.
As
As
Next, procedures for installing the diaphragm in the plating apparatus of the present embodiment are described.
After the diaphragm F is positioned in the plating tank B by following the procedures shown in
In the plating apparatus as shown in First Embodiment, a plating treatment is carried out in a manner as follows. First, the diaphragm F is installed in the plating tank B by following the above-described procedures, and a wafer as being an object to be plated is positioned on the opening 10 of the plating tank B. The object to be plated W is depressed onto and fixed to the annular support 104 by means of a not-shown depressing means present above the object to be plated W. The periphery of the object to be plated W contacts the annular cathode electrode 102 installed on the opening 10, thereby plating current is supplied.
After the object to be plated W is positioned, a plating solution is sent to the solution-supply tube 20, the plating solution is supplied toward the object to be plated W through the main plating-solution supply path S1, and some of the plating solution passes the diverging solution flow path S2 of the solution-supply tube 20 and is supplied to the anode chamber A through the solution supply port 211.
A plating solution supplied through the main plating-solution supply path S1 flows to spread from around the center of a surface being plated of the object to be plated W toward periphery of the object to be plated W, and then is discharged out of the discharge path 40. A plating solution supplied to the anode chamber A is discharged out of the anode-chamber solution discharge port 502 provided in the diaphragm-periphery fixing part 50. Impurities present in the plating solution to be discharged out of the anode chamber is removed by means of the filter 503.
In the plating apparatus according to the above-described embodiment, operations during a manufacture of the apparatus, especially an operation where the diaphragm was installed in a cone-shaped manner was carried out extremely easily. Removal of the diaphragm required for operations including replacement of an anode were also carried out easily and a subsequent installation of a diaphragm was also carried out easily, so that efficiency in a maintenance work improved spectacularly.
In Second Embodiment, description is being made with respect to a plating apparatus having a different solution-supply tube in structure from the counterpart in present First Embodiment.
The plating apparatus according to Second Embodiment and shown in
In the plating apparatus according to Second Embodiment, the anode-chamber solution supply port 211 formed in the outer tube 21 of the solution-supply tube 20 is provided at a position slightly higher than a horizontal position of the anode-chamber solution discharge port 502 provided below the diaphragm-periphery fixing part 50. Consequently, in the plating apparatus according to Second Embodiment, even when a plating solution has been discharged out of the plating tank for the purpose of replacing an object to be plated W, a plating solution can be stored within the plating tank so that a condition where the diaphragm F can be maintained immersed in the plating solution, as seen from a wavy line, i.e. solution level in
Further, description is made with reference to
Since the solution supply tube 20′ shown in
In Third Embodiment, description is being made with respect to a plating apparatus of a structure having a solution flow diverting means provided in the inner tube of the solution supply tube according to Second Embodiment.
In the plating apparatus according to Third Embodiment, a solution flow diverting means 60 is provided in an inner tube 22 of a solution supply tube 20. The solution flow diverting means 60 is of a structure, which comprises a strut 61, and two funnel-shaped diversion plates having different size from each other disposed concentrically on the strut 61. The solution flow diverting means 60 is fixed through mounting the strut 61 onto a meshed stationary plate 63. Due to the solution flow diverting means 60, a plating solution supplied from the solution supply tube passes through the meshed stationary plate 63, advances along a solution flow diverting path formed with the two funnel-shaped diversion plates 62 having different size from each other, and will be supplied into a plating tank. Consequently, as indicated by bold line arrows in
Next, description is made with respect to a result of investigation conducted on advantage of the solution flow diverting means of Third Embodiment. The investigation of advantage of the solution flow diverting means was conducted by employing a Sn—Ag alloy plating solution, carrying out a Sn—Ag alloy plating with a targeted thickness of 7 μm on a wafer having a size of 300 mm in diameter, and measuring the thickness. A diameter of the inner tube was 30 mm, and the solution flow diverting path formed with the funnel-shaped diversion plates was about 1 mm in width. An electrolyte membrane was adopted as the diaphragm, and an insoluble electrode was adopted as the anode electrode. As the Sn—Ag alloy plating solution, a commercially available plating solution having a Sn concentration of 50 g/L and a Ag concentration of 0.5 g/L was employed, and a plating treatment was carried out under the conditions of: liquid temperature of 20° C.; a current density of 2.5 A/dm2; and a flow volume of the plating solution from the solution supply tube being 20 L/min.
In the measurements, both the plating apparatus according to Third Embodiment shown in
(Uniformity = (Maximal value − Minimum value)/(2 × Average value) × 100)
As Table 1 indicates, it was confirmed that a plating treatment by use of the plating apparatus provided with the solution flow diverting means of Example 1 has fewer fluctuation in plating thickness than the counterpart not provided with the solution flow diverting means (Comparative Example 1). With respect to uniformity value indicating a degree of evenness in thickness, Example 1 shows values less than half of in terms of Comparative Example 1, which proved high uniformity in plating thickness.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2005-336916 | Nov 2005 | JP | national |
| P2006-025673 | Feb 2006 | JP | national |
