JP2002115096A - Plating apparatus - Google Patents

Abstract

(57) [Problem] To provide a plating apparatus for forming a metal film such as a copper film, which can further improve in-plane uniformity of film thickness and embedding performance. SOLUTION: A plating apparatus 10 according to the present invention comprises a liquid tank 12 in which a plating solution 22 is stored and a plating solution is circulated in a predetermined direction, and a copper plate 14 arranged in the liquid tank.
A wafer holder 16 for holding the semiconductor wafer W so as to be disposed in the liquid tank so as to face the film-forming material source, a power supply 34 having a copper plate as an anode and a film-forming surface of the semiconductor wafer as a cathode, And a stirring means arranged to stir the flow of the plating solution flowing through the tank toward the semiconductor wafer. By providing stirring means,
The replacement of the plating solution in the vicinity of the film formation surface of the wafer can be efficiently performed, and the effect of the additive can be particularly promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing technique, and more particularly to an electrolytic plating apparatus used for forming a metal film such as copper.

[0002]

2. Description of the Related Art In recent years, high integration and miniaturization of semiconductor devices have been rapidly progressing, and there is a steady transition from the present sub-half micron to sub-quarter micron. In response to such demands for higher integration and miniaturization of semiconductor devices, copper, which has low resistance and excellent electromigration resistance, has attracted attention as a wiring material, and has been practically put into practical use.

There are various methods for forming a copper wiring film, such as a sputter reflow method and a CVD method, and an electrolytic plating method has been widely adopted because a relatively good embedding property can be obtained at a low cost and a high throughput. I have.

[0004] Conventional general copper electroplating apparatuses include:
A face-down type as shown in FIG. 5 is known. In this plating apparatus, a semiconductor wafer W is immersed in a plating solution 2 in a liquid tank 1 with its surface on which a film is to be formed facing downward, and the semiconductor wafer W is placed between the copper plate 3 disposed below the liquid tank 1 and the semiconductor wafer W. By applying a voltage, copper is deposited on the semiconductor wafer W.

[0005]

However, when a copper film is formed by a conventional electrolytic plating apparatus, a portion having a locally different film thickness or a portion having a poor embedding property in a wiring groove or a contact hole is generated. Or you may.

In order to solve this problem, conventionally, means for rotating the semiconductor wafer W at a low speed and means 4 for circulating the plating solution 2 through an automatic chemical solution control system outside the solution tank 1 in order to keep the composition of the plating solution 2 constant have been known. It is considered.

[0007] However, even if such improvement measures are taken, the film thickness and the in-plane uniformity of burying have not been sufficiently satisfactory.

Accordingly, an object of the present invention is to provide a plating apparatus capable of further improving the in-plane uniformity of the film thickness and embedding performance of copper or the like.

[0009]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies and found that there is a difference in the film thickness and the embedding performance between the center part (range of about 1 cm in diameter) of the wafer and its periphery. We focused on what is happening. That is, in the conventional plating apparatus shown in FIG. 5, the plating solution 2 rises in the gap between the solution tank 1 and the copper plate 3 and overflows from the periphery of the semiconductor wafer W to the outside of the tank. It has been found that the plating solution easily stays in the part and the replacement of the plating solution is less than in the outer peripheral part. Further, even with the configuration in which the semiconductor wafer W is rotated, the flow velocity at the center of the semiconductor wafer W is close to zero, and it is considered that the plating solution is rather retained.

Here, the plating solution will be briefly described. Copper sulfate is a main component of the plating solution. In order to improve the embedding property in a groove or a hole by utilizing the so-called “leveling effect of electrolytic plating”, an additive is used. Has also been added.
There are various types of additives, for example, those containing a component such as a nonionic surfactant or a sulfur compound which is easily adsorbed selectively on the convex portion and has an action of suppressing the reduction of copper ions. Is common. When an additive containing such a component is added, the reduction reaction rate of copper ions at the projections is suppressed, and the reaction rate of the depressions is relatively increased, so that the embedding property is improved.

However, when the plating solution is not replaced as described above, the effect of the additive is impaired, and the film thickness and the embedding property are affected.

The present invention has been made based on such knowledge, and includes a liquid tank in which a plating solution is stored and a plating solution is circulated in a predetermined direction, and a copper or the like disposed in the liquid tank. A holding means for holding the object to be disposed in the liquid tank so as to face the film material source, and an object to be processed held by the holding means using the film material source as an anode. The plating apparatus is characterized by comprising a power supply unit having a film-forming surface of the body as a cathode and a stirring unit arranged to stir the flow of the plating solution flowing through the liquid tank toward the object to be processed.

By providing the stirring means, it is possible to efficiently exchange the plating solution in the vicinity of the film-forming surface of the object to be processed, and particularly to promote the effect of the additive.

The solution tank has a plating solution supply port at the bottom,
A type in which an upward flow is formed inside and overflows from the upper end is preferable. In such a liquid tank, a film-forming material film source, for example, a copper plate, is horizontally arranged at a lower portion in the liquid tank. Further, when the object to be processed is a semiconductor wafer, the holding means is a wafer holder that holds the semiconductor wafer downward so that the film formation surface of the semiconductor wafer faces the copper plate. In such a configuration, it is effective that the stirring means is at least one stirring plate disposed between the copper plate and the wafer holder.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

FIG. 1 is a schematic sectional view showing an embodiment of an electrolytic plating apparatus according to the present invention. This plating apparatus 10
Is for depositing copper on a semiconductor wafer W as an object to be processed.
And a disk-shaped copper plate 14 serving as a film forming material source disposed below the liquid tank 12, and a wafer holder (holding unit) 16 for holding the semiconductor wafer W downward.

A plating solution supply port 18 is provided at the bottom of the solution tank 12. An external pump 20 is connected to the plating solution supply port 18, whereby the plating solution 22 is supplied from the bottom into the solution tank 12 and flows upward. Further, the periphery of the liquid tank 12 is surrounded by an outer tank 24, so that the plating liquid 22 overflowing from the liquid tank 12 can be received, and the plating liquid 22 can be collected in an external tank 26. . Since the tank 26 is connected to the suction port of the pump 20, the plating solution 22 is circulated. Although not shown, the tank 26 preferably forms an automatic chemical liquid control system. That is, tank 2
6, a supply source of each component of the plating solution 22 and a component concentration detector are connected, and the supply amount from the supply source is controlled according to a signal from the concentration detector, and the composition of the plating solution 22 sent to the solution tank 12 is controlled. Is always constant.

The copper plate 14 is disposed substantially coaxially at the bottom of the substantially cylindrical liquid tank 12, and an annular gap is formed between the inner wall surface of the liquid tank 12 and the copper plate 14. Therefore,
Plating solution 2 supplied from supply port 18 at the bottom of solution tank 12
2 rises in the liquid tank 12 through this gap.

Above the copper plate 14, a wafer holder 16 for holding the semiconductor wafer W and immersing it in the plating solution 22 stored in the liquid tank 12 is arranged. Wafer holder 1
6, the wafer holding surface 28 is oriented horizontally and downward, and the film formation surface of the semiconductor wafer W held by the holding surface 28 also faces downward. The wafer holder 16 is connected to a rotation drive source 30 so as to be driven to rotate about a vertical center axis of the liquid tank 12. Further, the wafer holder 16 is positioned such that the center point of the semiconductor wafer W is on the rotation axis of the wafer holder 16 in a state where the semiconductor wafer W is arranged and held at a predetermined position on the wafer holding surface 28. Note that the wafer holder 16 is provided with a vertical mechanism (not shown) so that the semiconductor wafer W can be moved above the liquid tank 12 for wafer replacement or the like.

The wafer holder 16 has a wafer holding surface 28
An electric terminal 32 is provided in contact with an edge portion of the semiconductor wafer W held by the above-mentioned. The electric terminal 32 is connected to a cathode of a power supply 34. A thin copper seed layer (conductive film) is previously formed on the film formation surface of the semiconductor wafer W to be copper-plated by a PDV method or the like, and this copper seed layer functions as a cathode. In addition, copper plate 1
The anode of the power supply 34 is connected so that 4 functions as an anode.

Further, in the illustrated embodiment, a stirring plate 36 is arranged between the wafer holder 16 and the copper plate 14 and is fixed to the inner wall surface of the liquid tank 12. The stirring plate 36 has a function of deflecting the flow of the plating solution 22 ascending from below the liquid tank 12 and stirring it (turbulent flow). Although various shapes of the stirring plate 36 for performing this function can be considered, FIG.
Double rings 38, 39 concentrically arranged as shown in FIG.
Are connected by a plurality of arms 40 extending in the radial direction. The stirring plate 36 is made of an insulating material in order to minimize the influence on the electric field between the semiconductor wafer W (copper seed layer) on the wafer holder 16 and the copper plate 14 as much as possible.

A method for forming a copper film on a semiconductor wafer W using the electroplating apparatus 10 having such a configuration will be described.

First, the pump 20 is driven to supply the plating solution 22 containing copper sulfate as a main component to the solution tank 12 and circulate through the outer tank 24 and the tank 26. Then, the semiconductor wafer W is immersed in the plating solution 22 in the liquid tank 12 with the semiconductor wafer W set on the wafer holder 16, and the rotation drive source 30 is driven to rotate the semiconductor wafer W at a low speed. When the power supply 34 is turned on in this state, the copper ions in the liquid tank 12 are reduced on the film formation surface (copper seed layer) of the semiconductor wafer W as a cathode and grow as a copper film.

During this time, the plating solution 22 rises from the bottom of the solution bath 12 through the space between the inner wall surface of the bath and the copper plate 14, but the upflow is disturbed by the presence of the stirring plate 36. More specifically, the outer ring 39 of the stirring plate 36 deflects a part of the flow of the plating solution 22 rising along the inner wall surface of the tank toward the center of the tank. Also, the plating solution 22 rising in the center of the tank
Is branched by the inner ring 38 of the stirring plate 36,
It merges with the flow deflected by the outer ring 39. As a result, the upflow of the plating solution 22 is disturbed, causing a stirring action, and the plating solution 22 in the solution tank 12 exhibits an irregular flow. Therefore, in the related art, the plating solution 22 tends to stay near the center of the rotating semiconductor wafer W, but such stay is greatly reduced by the stirring plate 36, The replacement of the plating solution 22 is efficiently performed in the entire vicinity of the film formation surface. By ensuring that the plating solution 22 is replaced,
The effect of the additive contained in the plating solution 22 is also exerted uniformly on the entire surface of the semiconductor wafer W, and the embedding property into the contact hole and the wiring groove and the in-plane uniformity of the film thickness are improved.

Although the preferred embodiments of the present invention have been described in detail, it goes without saying that the present invention is not limited to the above embodiments.

For example, in the above embodiment, the stirring plate 36 has the structure of the flat double rings 38 and 39, but the shape thereof can be appropriately changed from the state of the flow of the plating solution 22 in the solution tank 12. And may have a deflection fin.

Further, two or more stirring plates 36 may be arranged as shown in FIG. In such a case, in order to further improve the stirring effect, the inner and outer rings 38 and 39 of the stirring plates 36a and 36b are eccentric as shown in FIGS. 4A and 4B, and the axes of the inner rings 38 do not match. Up and down 2
It is effective to arrange the stirring plates 36a and 36b.

Further, the stirring plate 36 is rotated,
Stirring means for increasing the stirring effect by rotating the wafer 2 with respect to the wafer holder 16 may be considered.

Further, the plating apparatus 10 of the above embodiment is
The semiconductor wafer W is of a face-down type in which the surface on which the film is to be formed faces downward, but the present invention is also applicable to a face-up type and other plating apparatuses, and the film forming material may be a metal other than copper. .

[0030]

As described above, according to the present invention, a metal film such as a copper film can be formed with a uniform film thickness on the entire surface of an object to be processed, for example, a semiconductor wafer. The in-plane uniformity of the embedding and the embedding itself are also improved. Therefore, according to the present invention, it is possible to satisfactorily embed holes and the like having a high aspect ratio, thereby contributing to higher speed, higher performance and miniaturization of semiconductor devices, and to improvement in yield. it can.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a copper plating apparatus according to the present invention.

FIG. 2 is a plan view showing a shape of a stirring plate in the plating apparatus of FIG.

FIG. 3 is an explanatory view schematically showing another embodiment of the plating apparatus according to the present invention.

FIGS. 4 (a) and (b) are plan views showing the shape of the stirring plate as viewed along the lines IVa-IVa and IVb-IVb in FIG. 3, respectively.

FIG. 5 is an explanatory view schematically showing a conventional plating apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Plating apparatus, 12 ... Liquid tank, 14 ... Copper plate (film forming material source), 16 ... Wafer holder (holding means), 18 ... Plating solution supply port, 20 ... Pump, 22 ... Plating solution, 28 ... Wafer holding surface, 34 ... power supply, 36, 36a, 36b ... stirring plate (stirring means), 38 ... inner ring, 39 ... outer ring,
40: arm, W: semiconductor wafer (workpiece)

Continued on the front page (72) Inventor Ryoho Ito 14-3, Shinzumi, Narita-shi, Chiba Pref. In the Nogedaira Industrial Park F-term (reference) 4K024 AA09 BB12 CB02 CB06 CB15 CB26 GA16 4M104 BB04 DD52 HH20

Claims (3)

[Claims] A liquid tank in which a plating solution is stored and in which a plating solution is circulated in a predetermined direction; a film-forming material source disposed in the liquid tank; Holding means for holding the object to be disposed in the liquid tank; power supply means for using the film-forming material source as an anode and using a film-forming surface of the object to be processed held by the holding means as a cathode; And a stirring means arranged to stir the flow of the plating solution flowing through the liquid tank toward the object to be processed. 2. The plating apparatus according to claim 1, wherein the film forming material source is made of copper, and the object to be processed is a semiconductor wafer. 3. The liquid tank is provided with a plating solution supply port at the bottom, the film forming material film source is a disk-shaped copper plate horizontally disposed at a lower part in the liquid tank, and the holding means is A wafer holder for holding the semiconductor wafer downward so that a film-forming surface of the semiconductor wafer faces the copper plate, wherein the stirring means comprises at least one stirring member disposed between the copper plate and the wafer holder. The plating apparatus according to claim 2, which is a plate.