JPH11293493A - Electroplating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the uniformity of film thickness of a plating layer formed on a surface to be film-formed by forming the surface of an anode facing the surface to be film-formed into a curved surface to almost uniformize current density on the surface to be film formed. SOLUTION: The curved surface is preferably formed so that the distance between the surface to be film-formed in the vicinity in contact with a cathode and the surface of the anode at the opposed position is longer than the distance between the surface to be film-formed apart from the vicinity of a position in contact with the cathode and the surface of the anode at the opposed position. Only the surface 33 to be film-formed is brought into contact with the surface of the plating solution 21 to be plated and the cathode 12 is brought into contact with a plurality of positions along the peripheral part of the surface 33 to be film-formed. The anode 13 of copper is disposed in the plating solution 21 and is formed into the convex-like curved surface to uniformize the current density in the surface 33 to be film-formed. The current density can be also uniformized by dividing the anode 13 to form a plurality of divided electrodes and changing the position or the impressed voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic plating apparatus, and more particularly, to an electrolytic plating apparatus for forming a plating layer on a surface on which a film is to be formed with high uniformity.

[0002]

2. Description of the Related Art Due to the high integration of LSIs, the internal wiring has been miniaturized and multilayered, and accordingly, flattening technology at the time of forming wiring, processing technology of fine wiring, and securing reliability of wiring have been achieved. Is important. Among them, embedded wiring technology has been attracting attention and is being studied. In particular, high-speed operation,
Attention has been focused on embedded copper wiring technology for low power consumption. For the copper embedded wiring technology, a method using a sputtering method and a reflow method, a CVD (Chemical Vapor Deposit) method.
ion) method, a method using electrolytic plating, and the like. Among these methods, a method of forming a buried wiring using an electrolytic plating method has attracted particular attention.

In the method of forming a buried wiring using the electrolytic plating method, a barrier metal layer is first formed in a groove or a connection hole, and then a copper film serving as an adhesion layer is formed by a normal sputtering method or a CVD method. A copper film is formed by an electrolytic plating method using a copper sulfate solution. In this electrolytic plating method,
At room temperature, copper can be buried in grooves and connection holes having a high aspect ratio.

First, the principle of electrolytic plating will be described with reference to the schematic diagram of FIG. As shown in FIG. 4, a copper sulfate solution is used as the plating solution 201, and an anode 221 made of copper and an adhesion layer of a conductive film on the surface (not shown) are used in the plating solution 201.
Is immersed in a state where the cathode 231 made of a wafer having the above-mentioned is opposed to the cathode 231. Then, a positive potential is applied to the anode 221, a negative potential is applied to the cathode 231, and copper is eluted from the anode 221 as copper ions (Cu ²⁺ ).
A copper plating layer (not shown) is formed by attaching u to the cathode 231 on the wafer surface. In addition, a laminated film of copper and barrier metal formed by sputtering is generally used for the adhesion layer.

Next, a conventional electrolytic plating apparatus will be described with reference to a schematic configuration diagram of FIG. As shown in FIG. 5, a plating bath 121 stores a plating solution 121. Wafer 131 to be plated has its surface (surface to be plated)
132, a cathode electrode 112 serving as a cathode is attached to the wafer 13
1 near the edge. In addition, the wafer 131 is arranged so that only the front surface 132 of the wafer 131 contacts the plating solution 121 in order to reduce the wraparound of the plating solution onto the back surface 133 of the wafer 131 and simplify the cleaning process. An anode electrode (anode) 11 made of a copper flat plate is provided at a position facing the surface 132 of the wafer 131.
3 are arranged. The electrode 112 serving as a cathode is connected to a negative electrode (−) of a power supply 114, and the anode electrode 123 serving as an anode is connected to a positive electrode (+) of the power supply 114.

[0006]

However, in the above-described electroplating method, since the electrodes are brought into contact with the edges of the wafer, current concentrates near the electrodes, and the edges of the wafer are thicker than other portions. A copper film is formed, and the uniformity of the film thickness tends to deteriorate. FIG. 6 illustrates the distribution of sheet resistance in a wafer surface when a copper film is formed by an electrolytic plating method. As shown in FIG. 6, the contact portions of the electrodes with the wafer 131 are at six positions indicated by arrows, and the thickness of copper in those portions tends to be large, and the wafers separated from the contact positions of the electrodes The film thickness of copper near the central portion of 113 is thin. At this time, the uniformity of the sheet resistance in the wafer surface was about 7.5% (1σ). The in-plane uniformity of the sheet resistance when copper is formed by a normal sputtering method is about 1.5% (1σ). However, it can be seen that the film thickness uniformity in the wafer surface is poor.

If the uniformity of the film thickness on the wafer surface is not good as described above, it takes a long time to perform partial overpolishing during chemical mechanical polishing (hereinafter referred to as CMP) of excess copper in the embedded wiring process. Become. Therefore, dishing and thinning in grooved wiring
Is more likely to occur.

[0008]

The present invention is an electrolytic plating apparatus made to solve the above-mentioned problems. The first electrolytic plating apparatus includes an anode electrode in which an anode electrode surface facing a deposition surface on which a plating layer is formed is formed in a curved surface. The anode electrode surface has a curved surface shape on which the current density on the film formation surface is substantially uniform.

In the first electrolytic plating apparatus, since the anode electrode surface facing the film formation surface on which the plating layer is formed is provided with the anode electrode formed into a curved surface, the film formation surface and the anode are formed on the surface. The distance between the opposed anode electrode surface can be made different depending on the position of the film formation surface. Therefore, by providing an anode electrode having a curved anode electrode surface for making the current density on the film-forming surface almost uniform, the growth rate of the plating layer formed on the film-forming surface can be substantially increased over the entire film-forming surface. Be uniformed.

The second electrolytic plating apparatus has an anode electrode composed of a plurality of divided electrodes.

Since the second electrolytic plating apparatus has an anode electrode composed of a plurality of divided electrodes, a different desired voltage is applied to each of the divided electrodes so that the surface on which the film is to be formed is formed. Is almost uniform over the entire surface.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an embodiment relating to a first electrolytic plating apparatus of the present invention will be described with reference to a schematic configuration diagram of FIG.

As shown in FIG. 1, a plating tank 11 is provided.
The plating solution 21 is stored in the inside. The wafer 31 to be plated is made of a plating solution 2
In order to reduce the wraparound of 1 and simplify the cleaning process, only the film formation surface 33 on which plating is performed is arranged so as to be in contact with the surface of the plating solution 21. In addition, the deposition surface 3
Along the peripheral end portion 3, a cathode electrode 12 serving as a cathode is in contact with a plurality of locations. These cathode electrodes 12 are usually in point contact. It is more preferable to use one that linearly contacts the cathode electrode along the side circumference of the wafer 31.

The plating solution 2 facing the film-forming surface 33
An anode electrode (anode) 13 made of copper, which serves as an anode, is disposed in 1. This anode electrode 13
The anode electrode surface 14 facing the film formation surface 33 is formed in a curved shape so that the current density on the film formation surface 33 is substantially uniform. For example, the anode electrode surface 14
The distance from the anode electrode surface 14 at a position facing the deposition surface 33 in the vicinity of the contact with the cathode electrode 12 is farther from the vicinity of the position where the cathode electrode 12 is in contact (for example, Deposition surface near the center of wafer 31)
And a curved surface that is longer than the distance from the anode electrode surface 14 at a position facing the surface, for example, a convex surface toward the film-forming surface 33.

A power supply 15 is provided,
5, each of the cathode electrodes 12 is connected to the negative electrode (−) of
The anode electrode 13 is connected to the positive electrode (+) of the power supply 15.

The plating tank 11 may be a so-called overflow type tank. For example, plating tank 1
In this method, the plating solution 21 is supplied from the bottom of the plating tank 1 and the plating solution 21 flows out from the upper end of the plating tank. The flowing out plating solution 21 may be supplied to the plating tank 11 again through, for example, a filter (not shown). That is,
A plating tank of a circulation filtration system may be used.

In the first electrolytic plating apparatus 1, the anode electrode 13 having a curved surface is formed on the anode electrode surface 14 facing the film formation surface 33 on which the plating layer is formed. Surface 14 is the cathode electrode 12
The deposition surface 33 and the deposition surface 3 near the
The distance from the anode electrode surface 12 at the position facing the cathode electrode 3 is different from the vicinity of the position where the cathode electrode 12 is in contact, and the anode electrode surface 14 at the position facing the film formation surface 33 Is formed on the convex curved surface so as to be longer than the distance between the cathode electrode 12 and the current density that is to be increased by the contact of the cathode electrode 12 is reduced. Is controlled so that As a result, the current density on the film formation surface 33 is made substantially uniform, so that the growth rate of the plating layer (not shown) formed on the film formation surface 33 becomes substantially uniform, and the thickness of the formed plating layer is also reduced. It becomes almost uniform.

Even if the current density on the film formation surface 33 may have a distribution, the current density on the film formation surface 33 is stepwise because the anode electrode surface 14 is formed in a curved shape. The current density distribution difference is smaller than that of the conventional electrolytic plating using a flat plate type anode electrode, and a smooth current density distribution is obtained.

The anode electrode 13 has a power source 1
5, the concentration of the plating solution 21, etc.
A material having an anode electrode surface having an optimum radius of curvature is appropriately selected and used. The power source 15 has a plating solution 21.
A power source that can vary the applied voltage in accordance with the concentration of the liquid crystal may be used. In this case, although not shown, the plating solution 21
And a voltage controller that determines an applied voltage based on the concentration of the plating solution 21 detected by the detector and instructs the power supply 15 of the determined voltage value. .

Next, an example of forming a groove wiring using the above-described electrolytic plating apparatus 1 will be described with reference to a manufacturing process diagram of FIG.

As shown in FIG. 2A, a normal LSI
After an element (not shown) is formed on the silicon substrate 51 by a process, an interlayer insulating film 52 is formed. Next, the groove 53 in which the groove wiring is buried in the interlayer insulating film 52 is formed by usual resist coating, lithography technology and etching technology (for example, reactive ion etching).
To form Here, the width of the groove 53 is 0.4 μm and the depth thereof is 0.5 μm.

Next, as shown in FIG. 2B, titanium (T) is formed on the inner wall of the groove 53 and the interlayer insulating film 52 by magnetron sputtering under an industrial high vacuum atmosphere.
i) A film and a titanium nitride (TiN) film are sequentially formed to form a base barrier metal layer 54.

An example of the conditions for forming the Ti film will be described below. Argon (Ar): 100 sc for the process gas
cm [hereinafter, sccm is the volume flow rate (c
m ³ / min), a DC power of 5 kW, a pressure of a film forming atmosphere of 0.4 Pa, and a substrate temperature of 150 ° C., to form a Ti film with a thickness of 20 nm.

An example of the conditions for forming the TiN film will be described below. Argon (Ar): 30 as the process gas
Using a sccm and nitrogen (N ₂ ) of 80 sccm, a DC power = 5 kW, a pressure of a film forming atmosphere = 0.4 Pa, a substrate temperature = 150 ° C., and a TiN film was formed to a thickness of 50 nm.

Subsequently, an adhesion layer 55 is formed by forming a copper (Cu) film by a magnetron sputtering method in an industrial high vacuum atmosphere.

An example of the conditions for forming the above-mentioned Cu film is as follows. As a process gas, argon (Ar): 100 sccm is used.
With a C power of 5 kW, a pressure of a film formation atmosphere of 0.4 Pa, and a substrate temperature of 150 ° C., a Cu film was formed to a thickness of 20 nm.

Next, as shown in FIG. 1C, a copper (Cu) film is formed on the adhesion layer 55 by using the electrolytic plating apparatus 1 described with reference to FIG. 56 is formed.

An example of the conditions for the electrolytic plating of Cu will be described below. Copper sulfate (CuSO ₄ ): 67 for the plating solution
g / dm ³ , sulfuric acid (H ₂ SO ₄ ): 170 g / dm ³ , hydrochloric acid (HCl): 70 ppm as an additive, plating solution temperature = 20 ° C., applied current = 9 A (8 inch wafer) , And a Cu plating layer.

Next, the Cu film 56, the adhesion layer 55, and the underlying barrier metal layer 54 are polished by ordinary CMP while leaving the Cu film 56, the adhesion layer 55, and the underlying barrier metal layer 54 inside the groove 52. To remove. As a result, as shown in FIG. 1D, a wiring 57 made of a Cu film 56 is formed in the groove 52.

An example of the above CMP conditions will be described below. Alumina slurry to which hydrogen peroxide (H ₂ O ₂ ) was added was used as the polishing slurry, and a polishing pad was prepared by bonding a polyurethane independent foam to a nonwoven fabric of polyester fiber. Polishing pressure = 100 g / cm ² , Slurry addition amount = 100 cm ³ / min, polishing atmosphere temperature = 2
As a 5 ° C. solution at 30 ° C., CMP was performed.

In the above example, the case where copper is used as the wiring material has been described. However, noble metals such as gold (Au) and platinum (Pt), silver (Ag), aluminum (Al), and alloys containing them are used for wiring. It is also possible to use it as a material.

In general, in electrolytic plating, when the distance between the cathode electrode and the anode electrode is short, the current density on the surface on which the film is to be formed increases, and when the distance between the cathode electrode and the anode electrode is long, the current density on the surface on which the film is to be formed is low. Lower. Therefore,
By using the anode electrode 13 having the convexly curved anode electrode surface 14 as described with reference to FIG. 1, the central portion of the wafer 31 distant from the vicinity of the position where the cathode electrode 12 is in contact with the anode electrode 13 Becomes shorter, and the distance from the anode electrode 12 becomes longer in the peripheral portion of the wafer 31 where the cathode electrode 12 is in contact. For example, when the distance between the electrodes at the central portion of the wafer is substantially equal to the case where the flat-plate anode electrode is used, the flat-plate anode electrode 13 is used even when the convex-curved anode electrode 13 is used. Even when the type anode electrode is used, the current density at the center of the wafer is almost equal. On the other hand, at the peripheral portion of the wafer where the current density was high when the flat anode electrode was used, when the curved anode electrode 13 was used, the distance between the electrodes was longer than when the flat anode electrode was used. , The current density decreases. In this way, the current density is made uniform over the entire surface of the wafer.
Therefore, the thickness of the Cu film 56 generated by the electrolytic plating is substantially uniform.

Next, an embodiment of the second electrolytic plating apparatus according to the present invention will be described with reference to FIG. The electrolytic plating apparatus described here differs from the electrolytic plating apparatus 1 described with reference to FIG. 1 only in the shape of the anode electrode, and other components are the same as the electrolytic plating apparatus 1. Therefore, here, the anode electrode will be described in detail, and other components will be described briefly. In FIG. 3, (1) shows a schematic configuration diagram, and (2) shows a plan view of the anode electrode. The same components as those described with reference to FIG. 1 are denoted by the same reference numerals.

As shown in FIG. 3, a plating tank 11 is provided.
The plating solution 21 is stored in the inside. The wafer 31 to be plated is arranged such that only the film formation surface 33 to be plated contacts the surface of the plating solution 21. In addition, the cathode electrode 12 serving as a cathode is in contact with a plurality of locations at the peripheral end of the film formation surface 33.

Then, the plating solution 2 facing the film formation surface 33
An anode electrode (anode) 16 made of copper, which serves as an anode, is arranged in 1. This anode electrode 16
Is composed of two divided electrodes 17 and 18 divided concentrically. The two divided electrodes 17 and 18 are separated from the vicinity of the deposition surface 33, which is distant from the vicinity of the position where the cathode electrode 12 is in contact, and from the vicinity of the deposition electrode 33 where the cathode electrode 12 is in contact. The film forming surface 33 and the divided electrode 18 at a position facing the surface are formed separately.

Also, power supplies 19 and 20 are provided,
The negative electrode (−) of the power supplies 19 and 20 is connected to the cathode electrode 12.
Is connected to the positive electrode (+) of the power source 19,
Is connected to the positive electrode (+) of the power
Is connected. Then, a voltage is applied to the divided electrodes 17 and 18 from the power supplies 19 and 20 so that the current density on the film formation surface 33 of the wafer 31 is substantially uniform.

The plating tank 11 may be a so-called overflow tank. For example, plating tank 1
In this method, the plating solution 21 is supplied from the bottom of the plating tank 1 and the plating solution 21 flows out from the upper end of the plating tank 11. The flowing out plating solution 21 is, for example, a filter (not shown).
May be supplied to the plating tank 11 again. That is, a plating tank of a circulation filtration system may be used.

In the second electrolytic plating apparatus 2, the anode electrode 1 composed of the divided electrodes 17 and 18 divided into a plurality
Because of the provision of 6, a desired voltage can be applied to each of the divided electrodes 17 and 18 to make the current density on the film formation surface 33 substantially uniform. Power sources 19, 2 to which a desired voltage for making the current density on the film formation surface 33 uniform are applied to the divided electrodes 17, 18, respectively.
Since 0 is provided, a desired voltage can be supplied to each of the divided electrodes 17 and 18. Further, the cathode electrode 12 is provided in contact with the film formation surface 33, and the divided electrode 17 at a position facing the film formation surface 33 in the vicinity where the cathode electrode 12 is in contact with the cathode electrode 12, Since the divided electrode 18 at a position facing the film forming surface 33 is formed separately, the voltage applied to the divided electrodes 17 and 18 is controlled to efficiently control the current density of the film forming surface 33. It becomes possible to do.

For example, the voltage V1 applied to the inner divided electrode 17 is set higher than the voltage V2 applied to the outer divided electrode 18. As a result, the current density in the central portion of the wafer 31 that is located at a distance from the contact portion of the cathode electrode 12 is increased, the film forming rate in this portion is increased, and the in-plane distribution of the film thickness is improved.

In the second electrolytic plating apparatus 2, the anode electrode 13 is constituted by the two divided electrodes 17 and 18. However, the number of the divided electrodes is not limited to the above-described divided form and the number of the divided electrodes. As long as the current density on the film forming surface 33 is made uniform, it is also possible to use three or more divided electrodes. The configuration is not limited to the concentric shape of the division form, and any configuration in which the current density on the film formation surface 33 is made uniform may be a matrix form, a concentric form, a radial form, or a division method combining them. Is also possible. For example, in order to further improve the current density distribution in the circumferential direction of the film formation surface 33, the outer divided electrode 18 may be further divided into a plurality of pieces corresponding to the contact position of the cathode electrode 12.

The above-described electrolytic plating apparatuses 1 and 2
By performing Cu plating on the film formation surface of the wafer by using the method described above, a Cu film having good uniformity in film thickness over the wafer surface is formed. Therefore, by forming the Cu film in forming the trench wiring using the above-described electrolytic plating apparatus 1 or 2, it is possible to form a Cu film having good film thickness uniformity. As a result, during the CMP of the excess copper in the embedded wiring process, the overpolishing time does not partially increase, and the occurrence of defects such as digging and thinning in the CMP of the trench wiring process is suppressed.

[0042]

As described above, according to the first electrolytic plating apparatus of the present invention, the anode electrode in which the anode electrode surface facing the film formation surface on which the plating layer is formed is formed in a curved surface is formed. Is provided, the distance between the film formation surface and the anode electrode surface facing the film formation surface can be changed depending on the position of the film formation surface. Therefore, by providing an anode electrode having a curved anode electrode surface that makes the current density on the film formation surface almost uniform, the growth rate of the plating layer formed on the film formation surface can be substantially increased over the entire film formation surface. It can be made uniform. Therefore, the uniformity of the film thickness of the plating layer formed on the deposition surface can be improved.

According to the second electrolytic plating apparatus, since the anode electrode is composed of a plurality of divided electrodes, each of the divided electrodes cannot be applied to a single electrode which could not be conventionally applied with a single voltage. It is possible to apply a different desired voltage for each. Therefore, by adjusting the voltage applied to each of the divided electrodes constituting the anode electrode, the current density on the surface on which the film is to be formed can be made substantially uniform over the entire surface. Therefore, the uniformity of the thickness of the plating layer formed on the deposition surface can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment according to a first electrolytic plating apparatus of the present invention.

FIG. 2 is a manufacturing process diagram of an example of forming a trench wiring using the electrolytic plating apparatus 1;

FIG. 3 is an explanatory diagram of an embodiment relating to a second electrolytic plating apparatus of the present invention.

FIG. 4 is a schematic diagram illustrating the principle of electrolytic plating.

FIG. 5 is a schematic configuration diagram of a conventional electrolytic plating apparatus.

FIG. 6 is a distribution diagram of a sheet resistance of a copper film formed by an electrolytic plating method in a wafer surface.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electroplating apparatus, 13 ... Anode electrode, 14 ... Anode electrode surface, 33 ... Deposition surface

Claims (8)

[Claims] 1. An electroplating apparatus for forming a plating layer on a surface on which a film is to be formed by an electrolytic plating method, comprising an anode electrode having a curved anode surface facing the surface on which the film is to be formed. Electroplating equipment. 2. The electroplating apparatus according to claim 1, wherein the anode electrode surface has a curved surface shape for making current density on the surface on which the film is formed substantially uniform. 3. The electroplating apparatus according to claim 2, wherein the anode electrode surface is in the vicinity of the film formation surface in contact with a cathode electrode and the anode electrode surface in a position facing the film formation surface. Is formed on a curved surface that is longer than the distance between the film-forming surface separated from the vicinity of the position where the cathode electrode is in contact and the anode electrode surface at a position facing the film-forming surface. An electroplating apparatus characterized in that: 4. The electrolytic plating apparatus according to claim 3, wherein said anode electrode surface is formed in a convex curved surface. 5. An electrolytic plating apparatus for forming a plating layer on a surface on which a film is formed by an electrolytic plating method, wherein an anode electrode of the electrolytic plating apparatus comprises a plurality of divided electrodes. 6. The electroplating apparatus according to claim 5, further comprising a cathode electrode in contact with the surface on which the film is to be formed, wherein the division at a position facing the surface on which the film is to be formed near the cathode electrode. An electroplating apparatus, wherein an electrode and the split electrode at a position facing the film-forming surface that is separated from the vicinity of the position where the cathode electrode is in contact are formed separately. 7. The electroplating apparatus according to claim 5, wherein a power supply to which a voltage for making a current density on the surface on which the film is formed substantially uniform is applied is connected to each of the divided electrodes. Electroplating equipment. 8. The electroplating apparatus according to claim 6, wherein a power supply is connected to each of the divided electrodes, to which a voltage for making the current density on the surface on which the film is to be formed substantially uniform is applied. Electroplating equipment.