JP4371494B2 - Cup type plating equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for plating a semiconductor wafer, and particularly to a cup type plating apparatus.
[0002]
[Prior art]
Conventionally, a cup type plating apparatus is known as an apparatus for plating a semiconductor wafer. This cup-type plating apparatus has a wafer surface to be plated by bringing the peripheral edge of a wafer into contact with a ring-shaped cathode electrode disposed in an opening of a plating tank and polarizing with an anode electrode disposed in the plating tank. A plating current is supplied to the substrate to perform a plating process. Therefore, it is widely used as suitable for the production of small lots and the automation of the plating process because the plating process can be performed sequentially by exchanging the wafer to the plating tank opening.
[0003]
In recent years, in the surface treatment of wafers, this cup-type plating apparatus is used to further plate copper or the like on a wafer whose seed metal is previously coated on the surface to be plated by a sputtering method or a CVD method. Such a plating process on a wafer requires a plating process with high uniformity over the entire surface to be plated of the wafer, particularly a plating process in which the plating film thickness is constant over the entire surface to be plated. Therefore, in the conventional cup-type plating apparatus, in order to achieve this uniform plating process, in order to supply a uniform plating current to the wafer, from the non-plated surface side of the wafer (the surface side where the plating process is not performed) By applying an external force and pressing it against the cathode electrode, the peripheral edge of the wafer and the cathode electrode are uniformly contacted over the entire circumference.
[0004]
However, recently, the following new demands have arisen, and conventional cup-type plating apparatuses cannot sufficiently cope with them. First of all, there is a demand for a plating process having a uniform thickness over the entire surface of the wafer. Secondly, it is required to increase the area that can be used in the subsequent post-process by plating the wafer, that is, to increase the effective use area of the wafer. Furthermore, from the viewpoint of improving productivity, it is also required to further increase the plating processing speed.
[0005]
In response to such new requirements, it is necessary to increase the plating current supplied to the wafer and to reduce the area of the peripheral edge of the wafer in contact with the cathode electrode as much as possible. In order to uniformly supply the plating current to the entire surface to be plated of the wafer, it is necessary to have a uniform contact area at the contact portion of the entire periphery of the wafer and the cathode electrode. This means that in a conventional cup type plating apparatus, the alignment accuracy when placing the wafer is improved, and the pressing pressure applied to the wafer to ensure contact with the cathode electrode must be increased.
[0006]
However, there is a limit to improving the positioning accuracy when placing the wafer and increasing the pressing pressure of the wafer. In conventional cup-type plating equipment, the contact between the peripheral edge of the wafer and the cathode electrode is limited. When the plating process is performed by reducing the area of the part and increasing the plating current, the plating current flowing through the wafer tends to be non-uniform over the entire surface to be plated, and the plating film thickness over the entire surface to be plated is non-uniform. The phenomenon of becoming occurs.
[0007]
[Problems to be solved by the invention]
Therefore, in the present invention, the conventional cup type plating apparatus is improved so that it can easily and easily cope with an increase in plating area and an increase in plating current, and the plating film thickness is uniform over the entire surface to be plated of the wafer. An object is to provide a cup type plating apparatus that can supply a uniform plating current to a wafer.
[0008]
[Means for Solving the Problems]
For this purpose, in the present invention, the peripheral edge of the wafer is brought into contact with the ring-shaped cathode electrode disposed in the plating tank opening, the wafer and the anode electrode disposed in the plating tank are polarized, and the wafer In the cup type plating apparatus in which the plating process is performed by supplying a plating current to the ring, the ring-shaped cathode electrode is formed from a plurality of divided cathode electrodes and the divided cathode electrode and the anode electrode are used as a current. A mirror circuit is formed to uniformly supply the plating current flowing from each divided cathode to the wafer.
According to the present invention, a uniform plating current can be supplied to the wafer by each divided cathode electrode without being affected by the contact resistance at the contact portion between the cathode electrode and the peripheral portion of the wafer. Therefore, the burden on the structure of the apparatus necessary for increasing the pressure of pressing the wafer against the cathode electrode becomes unnecessary. In addition, in order to obtain the cup type plating apparatus of the present invention, a split cathode that comes into contact with the peripheral edge of the wafer, for example, a conventional ring-shaped cathode electrode is appropriately divided in the circumferential direction to prepare a split cathode electrode. Since a current mirror circuit may be formed by combining a transistor corresponding to the number of divisions and a constant current power source that has been conventionally used, only an inexpensive and easy improvement over a conventional cup-type plating apparatus Thus, a uniform plating process can be performed on the wafer.
[0010]
In addition, when the plating current is increased in order to increase the plating processing speed, the conventional cup-type plating apparatus has a tendency that the plating film thickness on the entire surface to be plated tends to be extremely uneven. Since the same value of current is supplied from each split cathode electrode in the plating system, a uniform plating current can be constantly supplied over the entire surface to be plated, and a plating process with a uniform film thickness is possible over the entire surface to be plated. It becomes.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described. FIG. 1 shows an outline of a cross section of a plating tank of a cup type plating apparatus according to the present embodiment. As shown in FIG. 1, the cup-type plating apparatus 1 according to the present embodiment is configured so that the wafer 3 can be placed along the upper opening of the plating tank 2 so as to come into contact with the peripheral edge 4 of the wafer 3. As shown in FIG. 2, the cathode electrode C formed in a ring shape by the divided cathode electrodes (C1 to C6) is disposed. Under the cathode electrode C, a seal packing 5 for preventing leakage of the plating solution is disposed.
[0012]
In the plating tank 2, the plating solution supplied from the plating solution supply port 6 can flow out of the plating solution 2 in an upward flow toward the plating solution supply port 6 at the center of the bottom and the wafer 3 placed thereon. A plating solution outlet 7 is provided. Furthermore, an anode electrode 8 is installed at the bottom of the plating tank 2 so as to face the wafer 3 to be placed.
[0013]
In the cup type plating apparatus in this embodiment, the current mirror circuit is formed as follows. As shown in FIG. 2, the cathode electrode C is a composite material in which a Ti base material is coated with TiN, and is formed in a ring shape by six divided cathode electrodes (C1 to C6). A current mirror circuit as shown in FIG. 3 is formed by the divided cathode electrodes (C1 to C6), the anode electrode 8, and a constant current power source (not shown).
[0014]
Here, the current mirror circuit will be described. When the electrical characteristics of Tr0 and Tr1 in FIG. 3 are the same, the collector current Ic0 of Tr0 and the collector current Ic1 of Tr1 depend on the value of the load resistance (C1 to C6). The same value. Then, by setting the value of R, Ic0 is determined, and the value is reflected on each of Ic1 to Ic6 like a mirror, and becomes the same collector current value.
[0015]
By forming such a current mirror circuit, the plating current supplied to the wafer 3 is different even if the area of the contact portion between the peripheral edge 4 of the wafer 3 and the cathode electrode C differs in the circumferential direction. 3, even if there is a difference in contact resistance value between the peripheral edge 4 of each of the three and each of the divided cathode electrodes (C1 to C6), a constant current is supplied from each of the divided cathode electrodes (C1 to C6). Therefore, a uniform plating current is supplied over the entire surface to be plated of the wafer 3.
[0016]
【The invention's effect】
According to the cup-type plating apparatus of the present invention, when plating a wafer, it becomes possible to increase the plating area and the plating current easily and inexpensively, and uniform plating over the entire surface to be plated of the wafer. Since an electric current can be supplied, a highly uniform plating film thickness can be realized over the entire surface to be plated of the wafer.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a plating tank of a cup-type plating apparatus in the present embodiment.
FIG. 2 is a schematic plan view of a cathode electrode. FIG. 3 is a circuit diagram of a current mirror.
DESCRIPTION OF SYMBOLS 1 Cup type plating apparatus 2 Plating tank 3 Wafer 4 Peripheral part 5 Seal packing 6 Plating solution supply port 7 Plating solution outlet 8 Anode electrode C Cathode electrodes C1 to C6 Split cathode electrode

Claims (1)

The peripheral edge of the wafer is brought into contact with the ring-shaped cathode electrode disposed in the plating tank opening, the wafer and the anode electrode disposed in the plating tank are polarized, and the plating current is supplied to the wafer to perform the plating process. In the cup-type plating equipment that was designed to be applied,
The ring-shaped cathode electrode is formed from a plurality of divided cathode electrodes and a current mirror circuit is formed by each divided cathode electrode and anode electrode so as to uniformly supply a plating current flowing from each divided cathode to the wafer. A cup-type plating apparatus characterized by that.

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