Electric lamp and discharge devices – Electrode and shield structures – Indirectly heated cathodes
Reexamination Certificate
1998-09-14
2001-01-30
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Electrode and shield structures
Indirectly heated cathodes
C313S446000, C313S449000, C204S280000
Reexamination Certificate
active
06181057
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrode assembly, a cathode device and a plating apparatus that may be employed in an ideal manner when plating substrates for various types of electronic components, IC wafers or the like.
2. Discussion of Background
During a plating process for substrates for various types of electronic components and IC wafers and the like, plating must be implemented within a limited planar area on the object that is being plated, i.e., the substrate or wafer. In order to implement a plating process, a plating base film is formed in advance on a surface of the object to be plated and then plating is implemented by placing a cathode device in surface contact with the plating base film in such a manner that the cathode device surrounds the plating area. Publications that disclose this prior art technology include Japanese Unexamined Patent Publication No. 66698/1992 and Japanese Unexamined Patent Publication No. 125596/1993. In the cathode devices of the known art disclosed in these publications, a cathode is placed in surface contact with the object being plated.
Methods that may be adopted to plate an object to be plated such as a wafer include the frame plating method and the pattern plating method. In the frame plating method, a resist frame is formed in advance on the wafer by employing a high-precision pattern forming technology such as photolithography and the required plate is electro-deposited within an area that is not covered by the resist frame.
In the pattern plating method, almost the entire surface of the plate forming surface of the object to be plated is covered with a resist film, a pattern of perforations for plating is opened in the resist film and the plate is electro-deposited at the area where the pattern of perforations is present.
Cathode devices employed in the frame plating method and the pattern plating method bear similarity in that they are provided with a cathode member that comes in contact with the plating base film deposited at a front surface of the object to be plated, although their structural characteristics are somewhat different otherwise. The cathode member is provided with a frame portion that comes in contact with the object to be plated and a hole through which the plating bath solution enters. The internal circumferential edge of the frame portion that defines the hole is exposed.
One of the problems of the cathode device in the prior art described above is caused by the exposure of the internal circumferential edge of the cathode member that comes into contact with the plating base film. When the internal circumferential edge of the cathode member is exposed, the plating film becomes deposited in a continuous manner between the plating base film and the internal circumferential edge of the cathode member. If the plating film becomes deposited in this manner, the plating film and the plating base film deposited on the object to be plated will peel off at the contact area where they are in contact with the cathode member when the object to be plated is removed from the cathode device after the plating process is completed in the frame plating method.
In the pattern plating method, the plating film will become adhered to the internal circumferential edge of the cathode member, causing a change in the diameter of the hole at the cathode member, and thus, when continuous plating is implemented using a single cathode device to plate different wafers, the film formation rate of the plating film among the individual wafers becomes unstable, which results in poor repeating reproducibility among the wafers.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electrode assembly, a cathode device and a plating apparatus with which it is possible to prevent a plating film formed on an object to be plated from becoming peeled off when the frame plating method is employed.
It is a further object of the present invention to provide an electrode assembly, a cathode device and a plating apparatus with which the repeating reproducibility among wafers can be improved when the pattern plating method is adopted.
In order to achieve the objects described above, the electrode assembly according to the present invention includes a cathode member, and an insulating member. The cathode member is provided with a hole enclosed by a frame portion and a contact surface that comes into contact with an object to be plated at one surface of the frame portion. The insulating member is provided with a hole enclosed by a frame portion, with one surface of the frame portion lying adjacent to another surface of the frame portion of the cathode member, its hole being concentric with the hole of the cathode member and the internal circumferential edge of the frame portion covering the internal circumferential edge of the cathode member. The cathode device according to the present invention includes the electrode assembly described above.
The general structure of the plating apparatus according to the present invention includes a plating tank, a cathode device and an anode device. The cathode device and the anode device constitute an electric circuit for performing plating via a plating bath solution implemented inside the plating tank.
In the plating apparatus described above, when a DC voltage using the anode as a positive electrode and the cathode as a negative electrode is applied, required plating is implemented on a plate forming surface (conductive surface) of the object to be plated whose potential is maintained equal to the potential of the cathode member in conformance to the line of electrical force flowing from the anode to the cathode via the plating bath solution. The plate forming surface is constituted of a plating base film.
In the plating apparatus according to the present invention, the cathode device according to the present invention described earlier is employed as its cathode device. Since the cathode member is provided with a hole enclosed by a frame portion and a contact surface that comes into contact with the object to be plated at one surface of the frame portion in the cathode device according to the present invention, the plate forming surface (conductive surface) of the object to be plated can be placed in contact with the frame portion of the cathode member.
The cathode device according to the present invention further includes the insulating member which is provided with a hole enclosed by a frame portion with one surface of the frame portion lying adjacent to another surface of the frame portion of the cathode member and its hole concentric with the hole of the cathode member. Consequently, the plating bath solution can be placed in contact with the plate forming surface (conductive surface) of the object to be plated through the hole at the insulating member and the hole at the cathode member.
The present invention is characterized in that the internal circumferential edge of the frame portion of the insulating member covers the internal circumferential edge of the cathode member in the electrode assembly or the cathode device structured as described above. This structure allows the insulating member with no plate deposited to be present between the plate forming surface of the object to be plated and the internal circumferential edge of the cathode member. Thus, when the frame plating method is employed, the plating film and the plating base film that have been deposited on the object to be plated can be prevented from becoming peeled off when removing the object to be plated from the cathode device after the plating process is completed. In the prior art, since the internal circumferential edge of the cathode member is exposed, the plating film is formed continuously from the plate forming surface of the object to be plated to the internal circumferential edge of the cathode member to cause the plating film deposited on the object to be plated to become peeled off when removing the object to be plated from the cathode device after t
Inoue Satoshi
Tanaka Toyoaki
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Nimeshkumar D.
TDK Corporation
Williams Joseph
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