JP2000252233A - Method and system for fabricating semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make uniform the plating thickness over the entire surface of a matter to be processed while protecting element in a region close to a conduction electrode against damage by performing electroplating while varying the position where the conduction electrode touches the matter to be processed having a region to be plated over the entire surface. SOLUTION: Electroplating is performed while varying the position where a conduction electrode touches a matter 1 to be processed having a region to be plated over the entire surface in a plating liquid 4 through a drive means 5. The contact position is varied by fixing the conduction electrode 2 and moving the matter 1 to be processed continuously or intermittently. Alternatively, the matter 1 to be processed is fixed and the conduction electrode 2 is moved continuously or intermittently. According to the method, a plating film can be formed at a constant thickness on the surface of the matter 1 to be processed while suppressing the problem of electroplating system, i.e., uneven film thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device and an apparatus for manufacturing the same, and more particularly, to a technique for forming copper wiring of a semiconductor device. Higher device reliability
In order to realize multi-function, it is very important to increase the number of wiring layers and increase the speed.

With the miniaturization of elements, there are concerns about problems such as an increase in resistance value due to a decrease in wiring cross-sectional area and deterioration in electromigration (EM) resistance due to an increase in current density.

[0003] Copper wiring is a conventional Al-C
In addition to having a resistance value that is 40 to 50% lower than that of the u-alloy wiring, as well as having an EM resistance that is two orders of magnitude higher, attention has been paid to measures against the limitations of conventional Al-Cu alloy wiring.

[0004] However, the wiring technique using copper has a different problem from that of aluminum. That is, dry etching for processing a thin film into a predetermined fine wiring shape is difficult for copper, and the fine processing characteristics of the copper thin film are poor.

Therefore, a method called a damascene method has been reported as a method for forming a fine pattern on a wiring material which is difficult to dry-etch, and is being put to practical use.

That is, an insulating film (mainly a silicon oxide film)
A groove-shaped concave portion having a predetermined wiring shape is formed in advance, and a metal film is deposited so as to be embedded by electroplating or CVD over the entire surface including the inside of the groove. Is a method of forming a metal film into a predetermined fine wiring shape by performing chemical mechanical polishing (hereinafter, referred to as CMP processing) up to the surface of the metal film.

As a method of embedding the copper wiring, a sputter reflow method, a CVD-Cu method, a plating-Cu method, and the like are known. Among these, the method of forming a copper film by plating has attracted attention in recent years because it is lower in cost than other methods and can be embedded in a groove pattern having a high aspect ratio.

[0008]

2. Description of the Related Art There are an electroplating method and an electroless plating method as a method of forming a copper film by plating. Currently, the electroplating method is used due to a high film forming speed and easy handling of a plating solution. Is the mainstream.

The following is an example of an electroplating method currently used as a copper wiring forming technique in semiconductor manufacturing.

That is, a copper thin film serving as a seed is formed on the entire surface of the wafer by sputtering, and this film is used as a cathode. When this wafer is placed in a plating bath and a potential is applied between the cathode and the anode provided in the plating solution, an electric current flows, and copper ions in the plating solution reach the surface of the wafer serving as the cathode, and the copper film is formed. Accumulates.

[0011]

It is known that when a plating film is formed by an electroplating method, the thickness of the plating varies depending on the measurement site.

It is often experienced that there is a difference between a place where a current is strong and a place where a current is weak in each object to be processed.
There may be areas where the plating is only thin or not at all.

Therefore, in order to minimize variations in plating thickness, the current distribution on the object to be processed must be considered first.

The literature (for example, “Practical plating 2 for field engineers” edited by the Japan Plating Association) describes the throwing power as follows.

The throwing power indicates the ability of the electroplating film to deposit a uniform thickness on each part. In order for each part to have a uniform thickness, each point on the effective surface of the cathode deposits metal. It is necessary that the decomposition voltage required for the operation has been reached, and that the current density at each point be uniform.

Therefore, a material having a high ability to provide a uniform current density provides a high throwing power.

That is, the throwing power is a macroscopic view of the properties relating to variations in plating thickness, and it is important that the current density distribution on the surface is uniform.

Factors that affect the throwing power include the shape of the object to be processed, the relative size, position, shape, and other geometrical differences between the cathode and the anode. The distribution is called a primary current distribution.

If the primary current distribution is different, the current density of each part will be different. This causes a different polarization, and a new polarization resistance is added to generate a new secondary current distribution. Also, the distribution of the plating thickness differs depending on the working conditions (current density, temperature, presence or absence of stirring, solution composition, etc.).

Therefore, it can be said that the ability of the primary current distribution due to the geometrical arrangement to generate and average the secondary current distribution by polarization is uniform electrodeposition.

As a feature of the electroplating, a current is supplied from a current-carrying electrode to an object to be treated as a cathode, so that the deposition rate of copper near the current-carrying electrode increases, and as the distance from the current-carrying electrode increases, the rate of copper deposition increases. The rate of deposition remains slow.

In addition, there are many fluctuation factors such as the difficulty in making the contact resistance of the current-carrying electrode uniform, and the distribution of plating solution composition, circulation conditions, temperature, ion concentration, etc.
The method of obtaining uniform electrodeposition cannot be described in a single word, but the resulting uneven plating thickness results in a nonuniform copper film having a uniform thickness by chemical mechanical polishing. It is easy to understand what is difficult to do.

Furthermore, since a plating film is not formed at a contact portion between the current-carrying electrode and the object to be processed, an element near the current-carrying electrode is likely to be defective.

FIG. 4 is a configuration diagram showing a part of a cross section of a face-down type plating apparatus used in the prior art.

Generally, a plating apparatus which has been used conventionally has a plurality of energizing electrodes for supplying power to the object to be processed, for example, six points. Current is supplied.

FIG. 5 shows the position of the current-carrying electrode as viewed from the object to be processed at that time. The thickness distribution of the plating film is affected by the number and position of the current-carrying electrodes, and is particularly affected around the current-carrying electrodes of the object to be processed.

Further, in the plating apparatus used in the prior art, the position where the current-carrying electrode is in contact is kept fixed, so that the object to be processed in contact with the current-carrying electrode is not plated. After completion, the contact portion will remain as a hole.

As described above, the variation in the thickness of the plating film in the vicinity of the current-carrying electrode is one of the causes of in-plane variation of the entire object to be processed.

FIGS. 6 and 7 show examples of the distribution of the plating thickness in the radial direction of the object to be processed, and show that the thickness increases near the current-carrying electrode, and conversely, decreases.
It can be seen that the film thickness stabilizes toward the center, but the film thickness varies more near the current-carrying electrode.

This is also apparent from FIG. That is, this figure shows an example of the in-plane distribution of the sheet resistance value of the object to be processed, and an apparatus for measuring the sheet resistance that is inversely proportional to the in-plane film thickness distribution of the object (KLA Tencor) 4 in the plane with the device name prometrix)
It is a contour map (omunimap) when 9 points are measured. Therefore, it is apparent that the distribution has a distribution derived from the current-carrying electrode.

In FIG. 8, the thick line indicates the average resistance value at 49 points, and the negative values indicate the sheet resistance values (thicker film thickness) lower than the average and the positive values. The area shown has a sheet resistance value (thin film thickness) higher than the average.

Further, as described above, the distribution of the plating thickness is affected not only by the position of the current-carrying electrode but also by factors such as the composition of the plating solution, the circulation conditions, the temperature, and the distribution of the ion concentration. It is clear only that the plating thickness tends to change greatly near the current-carrying electrode.

An object of the present invention is to provide a method of manufacturing a semiconductor device in which elements in a region close to a current-carrying electrode do not become defective and the plating thickness over the entire surface of an object to be processed is made uniform.

[0034]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the above-mentioned problems have been solved by energizing an object to be processed having a whole area to be plated in a plating bath. The problem is solved by a method for manufacturing a semiconductor device including a step of applying an electroplating while changing the contact position of the current-carrying electrode with respect to the object to be processed while bringing the electrode for contact into contact.

That is, according to the manufacturing method of the present invention, uniform plating thickness can be ensured.

In a plating bath, a current-carrying electrode is brought into contact with an object to be treated having an area to be plated on the entire surface,
As a driving means for changing the contact position of the current-carrying electrode with respect to the object to be processed, there is the following method.

That is, one is a method in which the current-carrying electrode is fixed and the object to be processed is continuously or intermittently moved. According to the manufacturing method of the present invention, uniform plating thickness can be ensured.

The other is a method in which the object to be processed is fixed, and the current-carrying electrode is moved continuously or intermittently. According to the manufacturing method of the present invention, uniform plating thickness can be ensured.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

FIG. 1 is a configuration diagram showing a part of a cross section of a face-down type electroplating apparatus according to the present invention.

FIG. 2 is a partially enlarged view of a structure in which the object to be processed is moved while fixing the current-carrying electrode, and FIG. 3 is a partially enlarged view of a structure in which the object to be processed is moved while fixing the object to be processed. ing.

In the drawing, reference numeral 1 denotes an object to be processed, 2 denotes a current-carrying electrode, 3 denotes an anode, 4 denotes a plating solution, and 5 denotes a driving means.

In this embodiment, a silicon wafer of a semiconductor device was used as the object 1 to be processed. Clamp 2mm from the outer circumference of this 8-inch silicon wafer,
A copper film serving as a seed was formed to a thickness of 150 nm over the entire area to be plated by sputtering.

[Example 1] Six current-carrying electrodes 2 used in the prior art are employed as they are, and a silicon wafer as an object to be processed 1 is rotated at a constant speed of 5 times / minute by a driving means 5. The electroplating process was performed under the following conditions.

Plating solution: Copper sulfate plating solution Metallic copper 18 g / L Sulfuric acid 180 g / L Chloride ion 50 ppm Parameter: Plating temperature 25 ° C. Plating solution flow rate 5.5 gal / min Current value 8.6 A Energizing time 2 minutes As a result, average In FIG. 9, (c) shows a distribution of the plating thickness in the circumferential direction at the position of the current-carrying electrode, and 1σ is 0.02.
%Met. Note that 1σ of the plating thickness distribution in the conventional technique shown in FIG. 9A is 5%.

When 49 points were measured by prometrix using the in-plane distribution of the wafer as the sheet resistance value.
The average value was 2.1 × 10 e ⁻² Ω / cm ² , and 1σ was 4.3%.

Example 2 A silicon wafer was fixed,
While the electroplating was continued, the electroplating process was performed while rotating the holding lid of the workpiece 1 on which the energizing electrode 2 was mounted at a constant speed of 5 rotations / minute by the driving means 5. Other conditions are the same as in the first embodiment.

As a result, although not shown, the average is 1
A μm-thick copper plating film was formed, and 1σ of the distribution of the plating thickness in the circumferential direction at the position of the conducting electrode at that time was 0.05%.

[Embodiment 3] Electroplating is performed for 10 seconds while the electroplating is continued without rotating the silicon wafer, and then the silicon wafer is rotated by the driving means 5 at a speed of 9 revolutions / minute for 1 second. The operation was repeated for 2 minutes. Other conditions are the same as in the first embodiment.

As a result, a copper plating having a thickness of 1 μm was formed on average, and the distribution of the plating thickness in the circumferential direction at the position of the energizing electrode at that time is as shown in FIG. 1σ was 1%. Example 4 A silicon wafer was fixed, electroplating was performed for 10 seconds while the electroplating was continued, and the energizing electrode 2 was also fixed, and then the energizing electrode 2 was driven by the driving means 5 at 9 revolutions / minute. The operation of rotating at a speed of 1 second for 1 second was repeated for 2 minutes. Other conditions are the same as in the first embodiment.

As a result, although not shown, the average is 1
A μm-thick copper plating film was formed, and 1σ of the distribution of the plating thickness in the circumferential direction at the position of the conducting electrode at that time was 1.5%.

In FIG. 9, the distribution of the plating thickness of the conventional example which does not move relative to each other is also shown for reference as (a).

As is clear from the above Examples 1-4,
According to the manufacturing method of the first aspect, a more stable and uniform plating thickness can be obtained as compared with the manufacturing method according to the related art.

In this embodiment, the case where a face-down type electroplating apparatus is used has been described, but the same applies to the case where a face-up type electroplating apparatus and a vertical type electroplating apparatus are used. can do.

[0055]

As described above, according to the present invention, plating with a constant thickness on the surface of the object to be processed can be achieved while reducing the nonuniformity of the film thickness distribution, which is a problem when using an electroplating apparatus. By facilitating the formation of the film and improving the uniformity, it can greatly affect the reduction of the global step in the subsequent CMP processing. It greatly contributes to the improvement of the yield in the process.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a cross section of a face-down type electroplating apparatus according to the present invention.

FIG. 2 is a partially enlarged view of a configuration in which an object to be processed is moved while fixing a current-carrying electrode according to the present invention.

FIG. 3 is a partially enlarged view of a configuration in which an object to be processed is fixed and an energizing electrode is moved according to the present invention.

FIG. 4 is a configuration diagram showing a part of a cross section of a face-down type plating apparatus used in the prior art.

FIG. 5 is a diagram showing a position of a current-carrying electrode.

FIG. 6 is an example (1) showing a distribution of plating thickness in a radial direction of an object to be processed;

FIG. 7 is an example (2) showing a distribution of a plating thickness in a radial direction of an object to be processed;

FIG. 8 is a diagram showing a contour map of sheet resistance values in the surface of the object after plating.

FIG. 9 is a diagram showing a plating thickness distribution in a circumferential direction near a position of a current-carrying electrode of a target object when the target electrode is moved while the target electrode is fixed.

[Description of Signs] 1 Workpiece 2 Electrode for conduction 3 Anode 4 Plating solution 5 Driving means

Claims (4)

[Claims] In a plating bath, a current-carrying electrode is brought into contact with an object to be treated having an area to be plated on the entire surface, and electroplating is performed while changing the contact position of the current-carrying electrode with respect to the object to be treated. A method for manufacturing a semiconductor device including steps. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the current-carrying electrode is fixed, and the object is moved continuously or intermittently. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the object to be processed is fixed, and the current-carrying electrode is moved continuously or intermittently. 4. An apparatus for manufacturing a semiconductor device, comprising: driving means for changing a contact position of the current-carrying electrode with respect to an object when electroplating the object.