Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2000-08-21
2002-08-06
Valentine, Donald R. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C273S279000
Reexamination Certificate
active
06428661
ABSTRACT:
TECHNICAL HELD OF THE INVENTION
The present invention relates to a plating apparatus, a plating system and a plating method using the plating apparatus or the plating system. More particularly the invention relates to a plating apparatus, which allows a metal to be piled up on a substrate, such as a wafer, a plating system having the above function and a plating method using the above plating apparatus or the above plating system.
BACKGROUND OF THE INVENTION
As for the packaging of semiconductor chips on a substrate to construct an electronic instrument, it has been risen to package a great number of tips in a fixed area as possible, namely, the increased requirement of high-density packaging. With this requirement of high density packaging, the wiring on the substrate also has a tendency of high densification and therefore, the refined wiring adopting various methods has been progressed.
As the method of building the refined wiring, there is employed a plating method of first forming fine underlying electrodes on the substrate by a film deposition method, such as a chemical vapor deposition (CVD) method, and secondly depositing a metal on the underlying electrodes. In this plating method, it is firstly executed to dip the electrodes in a solution containing metallic ions. Thereupon, an electricity is supplied into the solution in order to cause a deoxidization on the negative pole (underlying electrode) and an oxidization on the positive pole, so that the metal can be piled up on the underlying electrode owing to the deoxidization on the negative pole.
FIG. 9
shows a schematically sectional view of a plating apparatus used for the plating process.
As shown in
FIG. 9
, the plating apparatus
51
has a plating bath
52
filled up with a plating solution, an outer wall
53
arranged around the plating bath
52
, a tank
54
for storing the plating solution and a pump
55
for supplying the plating solution in the tank
54
into the plating bath
52
via the center of a bottom of the plating bath
52
.
The plating bath
52
is provided, on a top end thereof, with four inward projections
56
at intervals of 90 degrees on the inner peripheral face of the bath
52
. On the inward projections
56
, a copper ring
57
is mounted. On the copper ring
57
, a wafer
58
as the object being processed is set while arranging its plating surface downward. On the wafer
58
, an underlying electrode
59
is formed as the negative pole constituting the above plating surface and electrically connected to the copper ring
57
. The wafer
58
mounted on the copper ring
57
is fixed by a fixing jig
60
utilizing pressing means. That is, the shown plating apparatus is constructed so that the plating solution in the plating bath
52
does not flow round the backside (upper face) of the wafer
58
even when the plating solution comes in contact with the wafer
58
.
On the bottom of the plating bath
52
, an anode plate
61
as the positive pole is arranged in parallel with the wafer
58
. This anode plate
61
and the copper ring
57
are together connected to a power source
62
electrically.
In the plating apparatus
51
, when the plating solution supplied into the plating bath
52
flows in the direction from the center part of the wafer
58
toward the periphery uniformly and fills up the plating bath
52
, then the plating solution flows from the upper part of the bath
52
to the circumference. Then, the overflowing plating solution is stored into the tank
54
through a pipe
63
. In this way, the plating apparatus
51
has a circulating structure to circulate the plating solution therein.
The feeding of electricity is initiated after several seconds have passed since the plating solution supplied into the plating bath
52
came into contact with the wafer
58
, whereby a plating film is formed on the underlying electrode
59
.
Meanwhile, the underlying electrode
59
is formed with fine irregularities and therefore, there is a possibility that the plating solution does not infiltrates into dents of the irregularities completely. Further, there is a case that air bubbles generated in the plating bath
52
stick to the underlying electrode
59
, particularly, the above dents. In these cases, there would be generated an unevenness in a current distribution in the underlying electrode
59
thereby increasing a difference in thickness of a plating film formed on the underlying electrode
59
due to the current difference in the underlying electrode
59
. Therefore, the plating apparatus has a problem of impossibility to form a uniform plating film on the underlying electrode
59
.
Although the whole upper surface of copper ring
57
comes into contact with the wafer
58
, it is difficult to accomplish a uniform contact resistance in the upper surface. Thus, due to the difference in contact resistance in both contact surfaces of the ring
57
and the wafer
58
, there would be also generated the unevenness in the current distribution in the underlying electrode
59
. Such the unevenness in the current distribution would cause a great difference in thickness of the plating film formed on the underlying electrode
59
due to the current difference in the underlying electrode
59
. Also from this reason, there is a problem of impossibility to form the uniform plating film on the underlying electrode
59
.
While, in case of using electrode pins in place of the copper ring
57
, then it is possible to reduce the unevenness in the current distribution in the underlying electrode
59
in comparison with the previous case of using the copper ring
57
. However, this measure is accompanied with a limitation of the amount of current capable of flowing through the electrode pins. Thus, the thickness of the plating film on the underlying electrode
59
is so limited that the plating apparatus has a problem of reduced applicability.
In order to solve the above-mentioned problems, an object of the present invention is to provide a plating apparatus, a plating system and a plating method using them, all of which can form a plating film having an uniform thickness on an object to be processed.
DISCLOSURE OF THE INVENTION
In order to solve the above-mentioned problems, the plating apparatus of the present invention is characterized by comprising a plating bath filled up with a plating solution, a connecting member arranged on a top part of the plating bath, for electrical connection with a first electrode formed on a semiconductor wafer, a second electrode disposed in the plating bath and an ultrasonic oscillating member arranged in the plating bath. According to the plating apparatus of the invention, the object to be processed is arranged on the connecting member in a manner that the first electrode is electrically connected with the connecting member and the plating solution is charged into the plating bath. When the plating bath is filled up with the plating solution, electricity is supplied into the plating apparatus and the ultrasonic oscillating member continuously applies ultrasonic oscillations into the plating bath. Although the supply of electricity causes the plating solution to be chemically reacted thereby to generate bubbles, for example, hydrogen bubbles in the plating solution, they are prevented from adhering to the first electrode owing to the ultrasonic oscillations of the solution itself. Additionally, the circulation of the plating solution in the plating bath is promoted by the ultrasonic oscillations, so that the plating solution is supplied to the whole surface of the first electrode. Thus, the current distribution on the first electrode becomes uniformly, so that a plating film having a uniform thickness is formed on the first electrode.
Further, the plating apparatus of the present invention is characterized in that the semiconductor wafer is arranged so that the first electrode to be processed directs downward and furthermore, the semiconductor wafer is fixed on the plating bath.
As the other feature in the plating apparatus of the present invention, the ultrasonic oscillating membe
Finnegan Henderson Farabow Garrett & Dunner LLP
Tokyo Electron Ltd.
Valentine Donald R.
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