JP2006089810A - Wafer plating apparatus and method using auxiliary cathode - Google Patents

Abstract

【Task】
When partial plating is performed on the wafer, the auxiliary cathode, which has the same polarity as the object to be plated and can control the current ratio, is arranged between the anode and the cathode in the form of a grid or mesh on the entire anode side of the object to be plated. A method of reducing plating uneven distribution and, as a result, plating with little variation in thickness.
When plating an unevenly distributed product in the plating area, the plating thickness variation becomes large.
Large variations can adversely affect productivity, cost, and quality.
[Solution]
A grid-like auxiliary cathode is arranged in front of the object to be plated, and the plating area is unevenly distributed in the object and the auxiliary cathode in total. Further, the current flowing through the auxiliary cathode is minimized by managing the current flowing through the substrate and the auxiliary cathode separately. Further, the relative position is changed during the plating operation so that the auxiliary cathode arranged on the front surface does not affect a specific part of the object to be plated.

[Selection] Figure 3

Description

The present invention relates to a method for suppressing thickness variation when performing partial plating on a wafer.

  Conventionally, in general plating, a shielding plate and an auxiliary electrode are used in order to suppress plating thickness variation. In addition, there is means for changing the current density as a method for suppressing plating thickness variation. Further, copper sulfate plating generally used is mainly composed of copper sulfate and sulfuric acid. However, as the copper sulfate concentration is higher, the supply of copper ions is more advantageous and a larger amount of current per unit time can flow. As a result, the plating speed increases, but as the copper sulfate concentration increases, the plating thickness variation increases. Therefore, in order to reduce the plating thickness variation, it is generally necessary to reduce the copper concentration and perform plating at a low current. There is a problem with productivity.

The shielding plate is a method in which a baffle plate for controlling electricity is inserted between the anode and the cathode to be plated to make the plating thickness uniform. For example, in the case where plating is performed with a square object having the same size arranged in parallel with respect to a square anode, the thickness of the periphery, particularly the corner portion, is increased. As a countermeasure, a shielding plate that masks the periphery, particularly the corner, is used for the object to be plated.
Japanese Patent Application No. 6-236458 Japanese Patent Application No. 8-285682

Auxiliary electrodes include a dummy arranged to reduce the thickness variation around the thickness of the wafer where the thickness of the wafer is increased, using the electrode as a cathode. For example, if the auxiliary cathode is disposed around the square plated portion, even if the plating thickness variation in the auxiliary cathode portion is large, the plating thickness variation in the square plated portion can be suppressed. It is commonly known as escape and is electrically connected to the object to be plated with the same polarity.
Japanese Patent Application No. 7-335647

If the shape of the object to be plated is limited for both the shielding plate and the auxiliary cathode as a dummy, it can be dealt with using a jig according to the shape, but like the partial plating of the wafer, the shape of the wafer itself However, when the patterns of the parts to be plated are all different and are unevenly arranged inside, it is practically difficult to cope with the shielding plate and the auxiliary cathode as a dummy.
Therefore, in reality, a shielding plate is disposed in the peripheral portion, and plating is performed over time at a low current density within a range where variation is allowed.

  An object of the present invention is to reduce plating thickness variations caused by uneven plating areas in an object to be plated.

The means for solving the problem will be described below.

Between the anode and the object to be plated, an auxiliary cathode (hereinafter referred to as the present auxiliary cathode) having a structure for allowing a plating solution made of a metal plate having a lattice shape or a mesh shape to pass is disposed on the entire surface. Even if the plating area of the object to be plated is uneven, the variation of the plating area combined with the auxiliary cathode is reduced, and as a result, the dispersion due to the unevenness of the plating area of the object to be plated is reduced.

In addition, the current value flowing through the object to be plated and the auxiliary cathode can be controlled so that it can be used effectively depending on the degree of variation in the plating area of the object to be plated. The relative position of the object to be plated and the auxiliary cathode was changed so that the influence of the arrangement of the auxiliary cathode did not appear at a specific location. As a method for changing the relative position, the object to be plated or the auxiliary cathode was rotated or reciprocated left and right or up and down.

Japanese Patent Application No. Hei 11-99460 discloses a method of disposing a conductive auxiliary electrode having a current-controlled hole between a cathode and an anode as a prior patent relating to a method for controlling the plating thickness. However, at first glance, although the structure is similar to the present application, in Japanese Patent Application No. 11-99460, the auxiliary electrode is an anode, and in this patent, the auxiliary electrode is a cathode. This difference is completely different from the viewpoint of plating characteristics. That is, the point of the present application is to reduce the unevenness of the plating thickness by reducing the unevenness of the plating area of the cathode, that is, the object to be plated, for the purpose of suppressing the plating thickness variation. Basically, the components are different from those described.
Japanese Patent Application No.11-99460

When plating an object to be plated in which the plating area is unevenly distributed without using this auxiliary cathode, as a method of reducing the variation in plating thickness, the plating solution composition is changed, or the current density is reduced to a certain extent. Although the variation can be improved, the current density in the portion where the plating area density is low is higher than that in the area where the plating area density is high, and it is difficult to suppress the plating thickness variation, and the quality is also lowered.
However, when the auxiliary cathode of the present invention is used, the plating area density becomes substantially uniform, and as a result, the plating thickness variation is suppressed.

  This not only improves the uniformity, but also improves productivity because plating can be performed at a relatively high current density.

  If the plating area distribution is uniform and this auxiliary cathode is not necessary, or if it is necessary but not very effective, adjust the current flowing to the object to be plated and the current flowing to this auxiliary cathode. This makes it possible to work without replacing the installed jig.

  In FIG. 1, a plating mask 3 is formed on a wafer in order to plate an opening via an underlying conductive layer 2. Many actual wafers 1 have a shape in which a land portion of 50 to 300 μmφ or □, or the land portion is connected in a pattern having a width of 10 to 100 μm, but will be described in FIG.

  In FIG. 1, the plating area is biased to the right half of the wafer. If plating is performed as it is, current concentrates on the left plating area portion, and the plating thickness of that portion becomes abnormally high.

  FIG. 2 shows an example of the auxiliary cathode. The conductive material 5 is formed in a substantially uniform lattice shape or mesh shape 5 or a combination thereof. As a lattice when an object to be plated is an 8-inch wafer, a 5 mm square to 20 mm square vicinity is preferable. The best wire diameter is a round wire around 10% of the lattice spacing. If it is a square bar, the corner will grow faster and its life will be shorter.

  As shown in FIG. 3, the auxiliary cathode 5 is disposed between the anode 4 and the workpiece 6. The current flowing through the auxiliary cathode and the current flowing through the object to be plated can be controlled by inserting a variable resistor 7 between the circuit of the rectifier 10 and the object 6 to be plated. Of course, an ammeter 9 is installed on the object to be plated or the auxiliary cathode in addition to the ammeter 8 of the rectifier, and the ratio of the current flowing between the cathode and the auxiliary cathode and the current value flowing through the object to be plated are controlled.

The ratio between the current value flowing through the auxiliary cathode and the current value flowing through the object to be plated is determined from the degree of unevenness of the plating area distribution and the required uniformity of the plating thickness. When there is almost no uneven distribution, the auxiliary cathode according to the contents of the application is unnecessary, and when the auxiliary cathode is installed, it is not necessary to pass a current to the auxiliary cathode side. A shield plate installed in the periphery or a general auxiliary cathode can be used. When there is an extreme bias as shown in FIG. 1, a current of about 10 times is supplied to the auxiliary cathode side. Increasing the number does not reduce the effect, but the amount of improvement in variation decreases for the increase in cost.
The current passed through the object to be plated is determined from the plating solution, the shape of the object to be plated, the apparatus, etc. that are generally performed.
(Comparative Example 1)

FIG. 4 shows a plating thickness distribution when plating is performed by a conventional apparatus in which a shielding plate or an auxiliary cathode is disposed in the peripheral portion. Although there is relatively little variation in the plating thickness within the uniformly arranged part, the unevenly distributed part becomes extremely thick.

  FIG. 5 shows an installation example of a shielding plate. In order to cut off the flow of current from the periphery, the shielding plate 12 is generally disposed on the object 6 to be plated. Uniformity can be ensured when performing full-surface plating, but partial plating with uneven plating areas cannot be handled as in the previous section.

  FIG. 6 shows an installation example of the auxiliary cathode. A dummy object 13 is arranged around the object to be plated so that the peripheral portion where the current is concentrated and the plating thickness is increased does not enter the product. As in the previous section, partial plating with uneven plating areas cannot be used.

  FIG. 7 is an apparatus diagram when plating is performed while a wafer is horizontally disposed and rotated. The periphery uses a shielding plate 12 opened to a general size of φ140 mm, the auxiliary cathode 5 is fixed, the object 6 is rotated, and the relative position of both is changed.

  The auxiliary cathode 5 made of a circular net knitted with a 1 mm diameter copper wire with a 10 mm grid is disposed on an object to be plated on an 8-inch wafer. A current of 0.5 A is applied to the object to be plated for a plating area of 10 square centimeters (0.1 deci) of the object 6 to be plated, and the current is adjusted so that a total current of approximately 5.5 A flows through the rectifier. The object 6 was plated at 60 rpm for 60 minutes.

  FIG. 8 is an apparatus diagram in the case where the wafer is arranged vertically and plating is performed. A shield plate 12 having a general diameter of 140 mm is used for the periphery, the auxiliary cathode 5 is fixed, the object to be plated 6 is swung, and the relative position of both is changed.

  This auxiliary cathode made of a circular net knitted with a 0.8 mm diameter copper wire in a 15 mm pitch hexagonal mesh lattice is placed on an object to be plated on an 8-inch wafer. A current of 0.5 A is applied to the object to be plated with respect to a plating area of 0.1 decici of the object to be plated, and the current is adjusted so that a total current of approximately 5.5 A flows through the rectifier. The object to be plated was plated at a speed of 3 m / min with a width of 50 mm for 60 minutes.

  FIG. 9 shows the auxiliary cathode divided into three parts, the outer periphery, the middle and the center. Each auxiliary cathode can adjust each current value, and has a structure that can adjust the plating thickness of the object to be plated. The number of divisions can be adjusted as appropriate depending on the object to be plated.

  FIG. 10 shows the auxiliary cathode divided into nine parts. Each auxiliary cathode can adjust each current value, and has a structure that can adjust the plating thickness of the object to be plated. The number of divisions can be adjusted as appropriate depending on the object to be plated.

Structure example of the plating object before plating Structure example of this auxiliary cathode Connection example of this auxiliary cathode Example of uneven plating area and plating thickness General shielding plate layout example General auxiliary cathode arrangement example Horizontal type shielding plate and this auxiliary cathode embodiment Vertical type shielding plate and this auxiliary cathode embodiment Example of structure of split type auxiliary cathode Example of structure of split type auxiliary cathode

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer 2 Conductive layer 3 Plating resist 4 Anode 5 This auxiliary cathode 6 To-be-plated object 7 Variable resistance 8 To-be-plated ammeter 9 This auxiliary cathode ammeter 10 Rectifier
11 Plating area
12 Shield plate
13 Auxiliary cathode

Claims (7)

  When a plating mask is formed on a wafer and plating is performed, an auxiliary cathode having a structure capable of passing a plating solution is placed between the anode and an object to be plated to perform plating, and the method The manufactured product.   A plating method in which a plating mask is formed on a wafer and an auxiliary cathode having a structure in which a plating solution can be passed between the anode and the object to be plated is made of a metal such as a lattice or a mesh. , Equipment, and products manufactured by the method.   3. A plating method, apparatus, and a product manufactured by the method, wherein the amount of current flowing through the auxiliary cathode in claim 1 or 2 is controlled separately from the amount of current flowing through the object to be plated.   3. A plating method, an apparatus, and a product manufactured by the method, wherein the relative position of the auxiliary cathode and the object to be plated is changed by swinging or rotating at least one of them in claim 1 or 2.   3. The plating method and apparatus according to claim 1 or 2, wherein the auxiliary cathode is arranged in the vicinity of the object to be plated at the same interval, and a product manufactured by the method.   The auxiliary cathode made of copper or stainless steel   The divided auxiliary cathode is an apparatus in which each divided portion can be adjusted individually.

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