JP2003277996A - Plating apparatus, and method for preparing composition of plating solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating apparatus capable of adjusting the composition of the plating solution to an adequate value irrespective of the total amount of the plating solution, and checking whether or not the composition of the plating solution is adequate after adjustment. <P>SOLUTION: This plating apparatus includes a plating solution storage tank 1 to store a large volume of plating solution, plating cups 2a-2d to perform the plating to works to be plated, a pure water feeder 21 to feed pure water to the plating solution storage tank 1, and a thinner solution feeder 31 to feed the thinner solution to the plating solution storage tank 1. A temperature sensor 15 to measure the temperature of the plating solution and an electromagnetic conductivity meter 16 to measure the conductivity of the plating solution are fitted to the plating solution storage tank 1. Solution feed branch pipes 4a-4d are provided between the plating solution storage tank 1 and the plating cups 2a-2d, and an absorbance meter 11 to measure the absorbance of the plating solution is interposed in the solution feed branch pipe 4a. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a plating apparatus capable of adjusting the composition of a plating solution, and a plating solution composition adjusting method for adjusting the composition of a plating solution.

[0002]

2. Description of the Related Art For example, in a semiconductor device manufacturing process, a copper thin film may be formed on a semiconductor wafer by electrolytic plating. In such a plating process, a plating solution containing copper salt, which is a target metal, a supporting electrolyte, and water as main components is generally used. It is known that the composition of the plating solution gradually deviates from the proper composition mainly due to evaporation of water. If a plating solution deviating from the proper composition is used, a good thin film cannot be formed.

A prior art for solving this problem is disclosed, for example, in Japanese Patent Laid-Open No. 6-33251. According to this prior art, the total amount of the plating liquid contained in the plating apparatus is set, and the amount of reduction of the plating liquid with respect to this total amount is regarded as the amount of reduction of water, and the total amount of plating liquid is kept constant. Is replenished.

[0004]

However, a plating apparatus generally includes a plating liquid storage tank (tank) for storing a large amount of plating liquid, a plating cup for plating an object to be processed, and a plating liquid storage tank for the plating liquid. And a plating cup for circulating the plating solution between the plating cup and the plating cup, and the plating solution is dispersed and present in each of these portions. In particular, a plurality of plating cups may be provided, and not all of these plurality of plating cups are used at the same time. That is,
The plating solution may be present in all the plating cups, or may be present in only some of the plating cups. Therefore, it is difficult to know the total amount of plating liquid.

Further, the reduction of the plating liquid in the plating apparatus is
Not all is caused by evaporation of water, and a part of the plating solution is taken out together with an object to be processed such as a semiconductor wafer. In this case, not only water but also the supporting electrolyte and the salt of the target metal (copper) are taken out from the plating apparatus. Therefore, if the amount of water corresponding to the reduction amount with respect to the total amount of the plating solution is replenished, the concentration of the supporting electrolyte and the concentration of the target metal become lower than the predetermined concentration of the supporting electrolyte and the predetermined concentration of the target metal.

Further, in the above-mentioned prior art, it was not possible to confirm whether or not the plating solution actually had an appropriate composition after replenishing water. Then, the objective of this invention is to provide the plating apparatus which can adjust a plating liquid to an appropriate composition, irrespective of the total amount of plating liquid. Another object of the present invention is to provide a plating apparatus capable of confirming whether or not the composition of the plating solution has become appropriate after adjusting the composition of the plating solution.

Still another object of the present invention is to provide a method for adjusting the composition of a plating solution which can adjust the plating solution to an appropriate composition regardless of the total amount of the plating solution. Still another object of the present invention is to provide a plating solution composition adjusting method capable of confirming whether or not the composition of the plating solution has become appropriate after the operation of adjusting the composition of the plating solution.

[0008]

Means for Solving the Problems and Effects of the Invention According to the first aspect of the invention for solving the above problems, an object to be treated using a plating solution containing a metal salt containing a target metal, a supporting electrolyte and water. A plating apparatus for plating an object with a target metal, the plating solution containing section (1, 3, 4a to 4d, 2a to 2d, 8a to 8d, 9,
10), a supporting electrolyte concentration measuring means (11, 15, 16) for measuring the concentration of the supporting electrolyte in the plating solution, and a water adding means (21) for adding water to the plating solution accommodated in the plating solution accommodating portion. ), And whether or not the supporting electrolyte concentration in the plating solution measured by the supporting electrolyte concentration measuring means is higher than a predetermined supporting electrolyte concentration, and the measured supporting electrolyte concentration is higher than the predetermined supporting electrolyte concentration. Based on the above determination, the plating apparatus is provided with a supporting electrolyte concentration control means (20) for controlling the water addition means to add water to the plating solution.

The alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies in this section below. According to the present invention, when the supporting electrolyte concentration control means determines that the supporting electrolyte concentration is higher than the predetermined concentration, the water adding means is controlled to add water to the plating liquid in the plating liquid accommodating portion. As a result, the supporting electrolyte concentration of the plating solution becomes low. After that, the supporting electrolyte concentration measuring means can measure the supporting electrolyte concentration of the plating solution to confirm whether or not the supporting electrolyte concentration is below a predetermined supporting electrolyte concentration.

When the supporting electrolyte concentration is controlled by the upper limit value and the lower limit value (when it is controlled by a predetermined control width), the supporting electrolyte concentration after the addition of water is between the upper limit value and the lower limit value. If there is, the supporting electrolyte concentration has been adjusted to an appropriate concentration. The amount of water added by the water addition means is preferably set so that the concentration of the supporting electrolyte after adding water will not be too low. When it can be considered that the composition of the plating solution is changed only by the decrease of water content due to evaporation or the like, the concentration of all components other than water is uniformly increased. Therefore, in this case, by adding water to reduce the concentration of the supporting electrolyte to an appropriate concentration, all the components have appropriate concentrations. That is, the plating solution is adjusted to have an appropriate composition.

Since the supporting electrolyte concentration can be measured regardless of the total amount of the plating liquid, this plating apparatus can adjust the plating liquid to an appropriate composition regardless of the total amount of the plating liquid. The plating liquid storage unit is, for example, a plating liquid storage tank that stores a large amount of plating liquid, a plating cup that performs a plating process on an object to be processed, and a pipe for circulating the plating liquid between the plating liquid storage tank and the plating cup. Etc. may be included. Even if the plating solution is dispersed and present in the plating solution storage tank, the plating cup, the pipe, etc., the adjustment operation of the plating solution can be performed.

The invention according to claim 2 is further provided with a plating liquid stirring means (P1 to P4) for stirring the plating liquid stored in the plating liquid storage portion. Is. After adding water to the plating solution, the plating solution can be made uniform by agitating the plating solution in the plating solution accommodating portion by the plating solution stirring means. This makes it possible to measure the average supporting electrolyte concentration of the entire plating solution in the plating solution storage section. Therefore, it is possible to accurately determine whether or not the supporting electrolyte concentration of the plating liquid in the plating liquid accommodating portion is higher than a predetermined supporting electrolyte concentration.

When the plating apparatus can circulate the plating solution between the plating solution storage tank and the plating cup, the plating solution stirring means is, for example, a pump for circulating the plating solution. be able to. The water adding means includes a water supply pipe for flowing water, an on-off valve which is interposed in the water supply pipe and opens and closes a flow path of the water flowing through the water supply pipe, and a flow rate of the water flowing through the water supply pipe to a predetermined flow rate. A flow rate adjusting mechanism for adjusting may be provided. In this case, the supporting electrolyte concentration control means controls the water addition means to add water to the plating solution, and by controlling the on-off valve to open for a predetermined time, the predetermined amount of water is added to the plating solution. It may be added.

According to a third aspect of the present invention, the supporting electrolyte concentration control means uses the water adding means until the supporting electrolyte concentration measured by the supporting electrolyte concentration measuring means is determined to be equal to or lower than the predetermined supporting electrolyte concentration. The plating apparatus according to claim 1 or 2, wherein addition of a predetermined amount of water to the plating solution and control of the measurement of the supporting electrolyte concentration by the supporting electrolyte concentration measuring means are repeated. According to this invention, even when the supporting electrolyte concentration after adding water is not lower than the predetermined supporting electrolyte concentration,
By further adding water, the concentration of the supporting electrolyte can be made equal to or lower than the predetermined concentration of the supporting electrolyte, or can be brought close to the predetermined concentration of the supporting electrolyte. By repeating the addition of water and the measurement of the supporting electrolyte concentration, the plating solution can be made to have an appropriate composition.

When this plating apparatus is equipped with a plating solution stirring means, the plating solution may be stirred to make it uniform when water is added. The plating apparatus may further include a liquid level sensor (level meter) that detects the liquid level of the plating liquid in the plating liquid storage portion. In this case, even if the total amount of the plating solution increases due to the addition of water, it is possible to control (for example, stop adding the water) so that the plating solution does not overflow from the plating solution container based on the detection result of the liquid level sensor. it can.

According to a fourth aspect of the invention, the supporting electrolyte concentration measuring means has an absorptiometer (11) for measuring the absorbance of the plating solution with respect to light of a specific wavelength, and a temperature for measuring the temperature of the plating solution. 4. The plating apparatus according to claim 1, further comprising a sensor (15) and a conductivity measuring means (16) for measuring the conductivity of the plating solution. The concentration of the target metal in the plating solution can be determined from the absorbance of the plating solution with respect to light of a specific wavelength. If the concentration of the target metal, the liquid temperature, and the conductivity of the plating liquid are known, the concentration of the supporting electrolyte can be known. Therefore, the supporting electrolyte concentration of the plating solution can be measured by the supporting electrolyte concentration measuring means equipped with the absorbance meter, the temperature sensor, and the conductivity measuring means.

The absorptiometer may include, for example, a transparent cell through which a plating solution can flow, and a light emitting portion and a light receiving portion which are arranged to face each other with the cell sandwiched therebetween. In this case, the absorbance can be measured by measuring the intensity of the light emitted from the light emitting unit, transmitted through the plating liquid in the cell and received by the light receiving unit. Such an absorbance meter can measure the absorbance regardless of the total amount of the plating solution.
Also, the temperature and conductivity of the plating solution can be measured independently of the total amount of plating solution.

The supporting electrolyte may be sulfuric acid, for example as described in claim 5. The target metal may be copper, for example as described in claim 6. In this case, the metal salt of the target metal may be copper sulfate as described in claim 7. With such a plating solution, for example, the surface of a semiconductor wafer can be suitably plated with copper. The plating solution may have a composition other than these, for example, when the target metal is copper, the supporting electrolyte may be potassium pyrophosphate (K ₂ P ₂ O ₇ ), or a metal containing the target metal. The salt may be copper pyrophosphate (Cu ₂ P ₂ O ₇ ). Furthermore, the target metal may be gold, in which case
The supporting electrolyte may be potassium cyanide (KCN), and the metal salt containing the target metal is potassium cyanide (KA).
u (CN) ₂ ) may be used.

According to an eighth aspect of the present invention, a metal concentration measuring means (11) for measuring the concentration of the target metal in the plating solution, and the plating solution contained in the plating solution container is supported with water and a predetermined concentration. It is determined whether or not the concentration of the target metal measured by the metal concentration measuring unit is higher than a predetermined target metal concentration, and the concentration of the target metal is determined by determining whether the concentration of the target metal measured by the metal concentration measuring unit is higher than a predetermined target metal concentration It is characterized by further comprising a metal concentration control means (20) for controlling the thinning solution addition means to add the thinning solution to the plating solution based on the determination that the concentration is higher than the predetermined target metal concentration. Claim 1
The plating apparatus according to any one of 1 to 7.

Depending on the characteristics of the plating solution, the concentration of the target metal in the plating solution may increase with time regardless of the decrease in water content. In this case, even if water is added to adjust the supporting electrolyte to an appropriate concentration, the concentration of the target metal is not adjusted to an appropriate concentration. Therefore, it is necessary to adjust the concentration of the target metal separately from the concentration of the supporting electrolyte. According to the present invention, when the metal concentration control means determines that the concentration of the target metal is higher than the predetermined target metal concentration, the diluting solution adding means is controlled to dilute the plating solution in the plating solution accommodating portion by a predetermined amount. The liquid is added. As a result, the concentration of the target metal becomes low. When the concentration of the target metal is controlled by the upper limit value and the lower limit value, if the metal concentration after adding the thinning solution falls between the upper limit value and the lower limit value, it means that the concentration has been adjusted to an appropriate value.

The composition of the diluting solution may be, for example, a mixture of a supporting electrolyte and water at a ratio substantially equal to that in a plating solution having an appropriate composition. As a result, the concentration of the target metal can be reduced without keeping the ratio of water to the supporting electrolyte in the plating solution from a predetermined ratio. Since the concentration of the target metal can be obtained without depending on the total amount of the plating liquid, this plating apparatus can properly adjust the concentration of the target metal without depending on the total amount of the plating liquid.

The metal concentration measuring means may be, for example, an automatic titrator that automatically samples and titrates the plating liquid contained in the plating liquid container. When the plating apparatus is equipped with a stirring means, the concentration of the target metal can be confirmed after stirring the plating solution to make the composition of the plating solution uniform when the thinning solution is added. As described above, the concentration of the target metal can be adjusted by the metal concentration control means by the same method as that for adjusting the support electrolyte concentration by the support electrolyte concentration control means. When the concentration of the target metal does not fall below the predetermined target metal concentration by the addition of the diluting solution, the addition of the diluting liquid may be repeated until the concentration of the target metal falls below the predetermined target metal concentration.

According to a ninth aspect of the present invention, there is provided the plating apparatus according to the eighth aspect, wherein the plating solution contains a redox agent. If the plating solution contains a redox agent,
Dispose a lump of metal that is the source of the target metal in the plating solution,
By oxidizing with a redox agent, the ions of the target metal can be generated from the mass of the target metal. By the ions of the target metal thus generated, it is possible to supplement the target metal deposited on the object to be treated and lost, and to keep the concentration of the target metal in the plating solution substantially constant.

In such a plating method, when the redox agent is oxidized by the oxygen dissolved in the plating solution,
Due to the action of this oxidized redox agent, excess target metal ions are generated from the mass of the target metal, and the concentration of the target metal in the plating solution increases with time. In such a case, the concentration of the target metal can be properly adjusted by adding a thinning solution to the plating solution as described above. The redox agent may be iron, for example as described in claim 10.

The eleventh aspect of the present invention is a plating solution composition adjusting method for adjusting the composition of a plating solution containing a metal salt containing a target metal, a supporting electrolyte, and water, wherein the supporting electrolyte concentration of the plating solution is measured. Supporting electrolyte concentration measuring step, a supporting electrolyte concentration determining step of determining whether the supporting electrolyte concentration measured in the supporting electrolyte concentration measuring step is higher than a predetermined supporting electrolyte concentration, and the supporting electrolyte concentration determining step, the measurement And a water adding step of adding water to the plating solution based on the determination that the supported electrolyte concentration is higher than the predetermined supporting electrolyte concentration.

By this method of adjusting the composition of the plating solution, the same effect as the plating apparatus according to the first aspect can be obtained. The invention according to claim 12 determines whether the concentration of the target metal in the plating solution is measured, and whether the concentration of the target metal measured in the metal concentration measuring step is higher than a predetermined target metal concentration. In the metal concentration determination step of determining and in the metal concentration determination step, it is determined that the measured concentration of the target metal is higher than the predetermined target metal concentration. The plating solution composition adjusting method according to claim 11, further comprising a step of adding a diluting solution to the plating solution.

By this method of adjusting the composition of the plating solution, the same effect as that of the plating apparatus according to the eighth aspect can be obtained. In the invention according to claim 13, after the water addition step,
13. The metal concentration measuring step, the metal concentration determining step, and the thinning solution adding step are performed.
It is the method for adjusting the composition of the plating solution described above. According to the present invention, the concentration of the target metal can be adjusted by adjusting the supporting electrolyte concentration to a predetermined concentration in the water adding step, and then performing the metal concentration measuring step, the metal concentration determining step, and the diluting solution adding step. If the supporting electrolyte concentration of the diluting solution is almost the same as the supporting electrolyte concentration in the plating solution with the proper composition, the supporting electrolyte concentration will change even if the diluting solution is added to the plating solution whose supporting electrolyte concentration has already been adjusted to the prescribed composition. Absent. Therefore, with such a plating solution composition adjusting method, the concentration of the supporting electrolyte and the concentration of the target metal can be easily adjusted to predetermined concentrations.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, referring to the accompanying drawings,
Embodiments of the present invention will be described in detail. Figure 1
It is a schematic sectional view showing a configuration of a plating apparatus according to an embodiment of the present invention. This plating apparatus includes a plating liquid storage tank 1 capable of storing a large amount of plating liquid, and a plurality of plating liquids (4 in this embodiment) for performing a plating process on an object to be processed.
3) plating cups 2a to 2d. The plating solution used in this plating apparatus contains sulfuric acid as a supporting electrolyte, copper sulfate as a metal salt of a target metal, iron as a redox agent, and water as main components.

The plating liquid can be supplied from the plating liquid supply source into the plating liquid storage tank 1 through the plating liquid supply pipe 17. An air valve 18 and a flow meter 19 with a flow rate adjusting valve are provided in the plating liquid supply pipe 17. The flow meter with flow rate adjusting valve 19 is used for the plating liquid supply pipe 1
The flow rate of the plating liquid flowing in 7 can be set to a predetermined flow rate. The air valve 18 can be opened and closed under the control of the control unit 20, and the amount of the plating solution supplied to the plating solution storage tank 1 can be controlled by controlling the time for which the air valve 18 is opened.

A drain pipe 26 is connected in communication with the lower portion of the side surface of the plating liquid storage tank 1. An on-off valve 27 is interposed in the drainage pipe 26, and by opening the on-off valve 27,
The plating liquid in the plating liquid storage tank 1 can be drained. The plating cups 2a to 2d are the plating liquid storage tank 1
It is located higher. This plating apparatus includes an anode electrode and a cathode electrode (not shown) corresponding to each of the plating cups 2a to 2d. The anode electrode is arranged in the plating cups 2a to 2d. A liquid delivery pipe 3 extends from a lower portion of a side surface of the plating liquid storage tank 1, and the liquid delivery pipe 3 includes four liquid delivery branch pipes 4a to 4a.
It branches to d. The liquid delivery branch pipes 4a to 4d extend upward and are connected to the central portions of the lower surfaces of the plating cups 2a to 2d, respectively.

Pumps P1 to P4 and filters 7a to 7d are provided in the liquid delivery branch pipes 4a to 4d in this order from the bottom to the top. Pumps P1 to P4
Are the plating cups 2a to
The plating solution can be sent to 2d. The operation of the pumps P1 to P4 is controlled by the control unit 20. Filter 7a-
7d can remove particles (foreign matter) and bubbles in the plating solution. The plating cups 2a to 2d include plating tanks 5a to 5d arranged inward, and recovery tanks 6a to 6d arranged around the plating tanks 5a to 5d. The liquid supply branch pipes 4a to 4d are connected to the plating tanks 5a to 5d, respectively, and are connected to the recovery tanks 6a to 6d.
Return branch pipes 8a to 8d respectively extend from the lower portions of the. The return branch pipes 8 a to 8 d are connected to the return pipe 9 so as to communicate with each other, and the return pipe 9 is extended into the plating liquid storage tank 1.

With the above-described structure, for example, by operating the pump P1, the plating solution is sent from the plating solution storage tank 1 to the plating tank 5a through the solution sending pipe 3 and the solution sending branch pipe 4a. It Plating liquid is plating tank 5
It overflows from a and is returned to the plating liquid storage tank 1 from the recovery tank 6a through the return branch pipe 8a and the return pipe 9 by the action of gravity. That is, the plating solution is circulated between the plating solution storage tank 1 and the plating cup 2a. Similarly, by activating pumps P2 to P4,
The plating solution can be circulated between the plating solution storage tank 1 and the plating cups 2b to 2d. Part of the circulation path through which the plating solution circulates (for example, in the plating solution storage tank 1)
A copper supply source (not shown) made of metallic copper is arranged in the.

One end of a bypass pipe 10 is connected in communication between the pump P1 and the filter 7a in the liquid supply branch pipe 4a. The other end of the bypass pipe 10 is open to the plating liquid storage tank 1. The bypass pipe 10 is provided with an absorptiometer 11 that measures the absorbance of the plating solution for light of a specific wavelength. The absorptiometer 11 includes a cell 12 made of a transparent material, and a light emitting portion 13 and a light receiving portion 14 which are arranged to face each other with the cell 12 interposed therebetween. The light emitting section 13 can emit light of a specific wavelength (for example, 780 nm), and the light receiving section 14 can measure the intensity of light emitted from the light emitting section 13 and transmitted through the plating liquid in the cell 12. The absorbance of the plating solution can be obtained from the intensity of this light.
The signal indicating the absorbance is input to the control unit 20.

A temperature sensor 15 and an electromagnetic conductivity meter 16 are attached to the side surface of the plating liquid storage tank 1. The temperature sensor 15 and the electromagnetic conductivity meter 16 are mounted at a position lower than the liquid level of the plating liquid when the plating liquid is stored in the plating liquid storage tank 1. Temperature sensor 15
Also, the detection part of the electromagnetic conductivity meter 16 is the plating liquid storage tank 1
It projects inside and can measure the liquid temperature and conductivity of the plating liquid respectively. Output signals of the temperature sensor 15 and the electromagnetic conductivity meter 16 are input to the control unit 20.

If the absorbance of the plating solution is known, the copper concentration can be known. Regarding the plating solution, copper concentration, solution temperature,
And if the conductivity is known, the sulfuric acid concentration can be known. Hereinafter, a method for obtaining the copper concentration from the absorbance of the plating solution and a method for obtaining the sulfuric acid concentration from the copper concentration, the solution temperature, and the conductivity of the plating solution will be described. In order to obtain the copper concentration of the plating solution, the relationship between the copper concentration and the absorbance is investigated in advance. First, a plurality of sample plating solutions having different copper concentrations are prepared and prepared. When preparing the sample plating solution, copper is added as copper sulfate. The components other than copper of each sample plating solution are the same as those of the predetermined composition used in actual plating. The absorbance of such a sample plating solution is measured by the absorptiometer 11. As a result, FIG.
As shown in, the relationship between the copper concentration of the sample plating solution and the measured absorbance (first calibration curve) is obtained.

When determining the copper concentration of the plating solution having an unknown copper concentration, the absorbance is measured by the absorptiometer 11. The copper concentration is obtained from the measured absorbance and the first calibration curve. Next, in order to obtain the sulfuric acid concentration of the plating solution, the relationship between the sulfuric acid concentration and the conductivity at a plurality of copper concentrations is investigated in advance. Sample plating solutions having different copper concentrations (for example, R1, R2, R3) and sulfuric acid concentrations are prepared and prepared. Components of each plating solution other than copper and sulfuric acid are equivalent to those of the plating solution having a predetermined composition actually used during plating. With respect to such a sample plating solution, the temperature is measured by the temperature sensor 15 and the conductivity is measured by the electromagnetic conductivity meter 16. The conductivity changes depending on the solution temperature even if the composition of the sample plating solution is the same, so the conductivity measured based on the measured solution temperature is converted into the conductivity at the standard temperature. As a result, as shown in FIG. 3, the relationship (second calibration curve) between the sulfuric acid concentration and the conductivity at each copper concentration (R1, R2, R3) is obtained.

To obtain the sulfuric acid concentration of a plating solution having an unknown sulfuric acid concentration, the absorbance is measured by the absorbance meter 11, the temperature of the solution is measured by the temperature sensor 15, and the conductivity is measured by the electromagnetic conductivity meter 16. From the measured absorbance and the first calibration curve,
The copper concentration is obtained. The conductivity at the standard temperature can be obtained from the measured conductivity and the liquid temperature. The sulfuric acid concentration is obtained from the obtained copper concentration, the electric conductivity at the standard temperature, and the second calibration curve. The control unit 20 includes a ROM in which the data of the first calibration curve and the data of the second calibration curve are stored. Control unit 2
0 can determine the copper concentration from the output signal of the absorptiometer 11 and the data of the first calibration curve, and the output signals of the absorptiometer 11, the temperature sensor 15, and the electromagnetic conductivity meter 16 and the first and second calibration curves. The sulfuric acid concentration of the plating solution can be calculated based on the data of 1.

An ultrasonic level meter 28 is attached to the upper portion of the plating liquid storage tank 1. Ultrasonic level meter 2
8 can detect the liquid level of the plating liquid in the plating liquid storage tank 1. The output signal of the ultrasonic level meter 28 is input to the control unit 20. In the plating liquid storage tank 1,
Pure water can be supplied by the pure water supply device 21. The pure water supply device 21 includes a pure water supply pipe 22 for supplying pure water. One end of the pure water supply pipe 22 is connected to a pure water supply source, and the other end of the pure water supply pipe 22 is open in the plating liquid storage tank 1. In the pure water supply pipe 22, from the pure water supply source side toward the plating solution storage tank 1 side,
A regulator 23, an air valve 24, and a flowmeter 25 with a flow rate adjusting valve are provided in this order.

The pressure applied to the pure water in the pure water supply pipe 22 is adjusted to an appropriate pressure lower than the pressure in the pure water supply source by the regulator 23. Flowmeter with flow adjustment valve 25
Can set the flow rate of the pure water flowing through the pure water supply pipe 22 to a predetermined flow rate. The control unit 20 can control the opening and closing of the air valve 24, and by opening the air valve 24, pure water can be supplied to the plating solution storage tank 1. Further, the thinning liquid supply device 31 can supply the thinning liquid to the plating liquid storage tank 1. The thinning solution is mainly composed of dilute sulfuric acid, and the ratio of sulfuric acid to water is almost the same as that in the plating solution having a predetermined composition. The diluting liquid supply device 31 includes a diluting liquid supply pipe 32 for flowing the diluting liquid. One end of the diluting liquid supply pipe 32 is connected to the diluting liquid supply source, and the other end of the diluting liquid supply pipe 32 is open to the plating liquid storage tank 1. A regulator 33, an air valve 34, and a flow meter with a flow rate adjusting valve 35 are sequentially provided in the dilution liquid supply pipe 32 from the dilution liquid supply source side toward the plating liquid storage tank 1 side.

The pressure applied to the diluting liquid in the diluting liquid supply pipe 32 is adjusted by the regulator 33 to a predetermined pressure lower than the pressure in the diluting liquid supply source. The flow meter 35 with a flow rate adjusting valve can set the flow rate of the diluting solution flowing in the diluting solution supply pipe 32 to a predetermined flow rate. The control unit 20 can control the opening and closing of the air valve 34, and by opening the air valve 34, the dilution liquid can be supplied to the plating liquid storage tank 1. When performing plating with this plating apparatus, for example, the pump P1 is operated to circulate the plating solution between the plating solution storage tank 1 and the plating cup 2a while
In a, a plating liquid is brought into contact with a processing object (for example, a semiconductor wafer). At this time, the object to be treated is brought into contact with the cathode electrode. When electricity is applied between the cathode electrode and the anode electrode in the plating cup 2a, copper ions in the plating solution are deposited on the object to be treated to form a copper thin film.

The plating treatment may be carried out simultaneously by operating the four pumps P1 to P4 at the same time by the plating cups 2a to 2d, or by operating only a part of the pumps P1 to P4 and corresponding plating cups 2a to 2d. You can go by. Iron as a redox agent is present as divalent and trivalent ions in the plating solution. During plating, the divalent iron ions in the plating solution donate electrons to the anode electrode to become trivalent iron ions. Correspondingly, electrons are given to copper ions in the plating solution on the cathode electrode side, that is, on the side of the object to be treated, and copper atoms are deposited on the surface of the object to be treated. The trivalent iron ion robs an electron from the metal copper of the copper source to generate a copper ion, and becomes a divalent iron ion. In the above reaction, the amount of copper ions generated from metallic copper is equal to the amount of copper ions deposited on the object to be treated and lost. Therefore, the copper concentration in the plating solution is kept substantially constant.

However, since the upper portions of the plating cups 2a to 2d are open, the water in the plating solution is gradually lost due to evaporation. Therefore, the sulfuric acid concentration and the copper concentration in the plating solution increase. Furthermore, since the plating solution is exposed to the air, oxygen is present in the plating solution. Oxygen in the plating solution acts to oxidize divalent iron ions into trivalent iron ions. The trivalent iron ions generated in this way also deprive electrons of metallic copper to generate copper ions. The copper ion thus generated causes the copper concentration in the plating solution to gradually increase.

The control unit 20 controls the absorbance meter 1 at regular intervals.
Based on the output signal of 1, the copper concentration in the plating solution is obtained.
Further, the control unit 20 obtains the sulfuric acid concentration in the plating solution based on the output signals of the absorbance meter 11, the temperature sensor 15, and the electromagnetic conductivity meter 16 at regular intervals. The time interval for determining the copper concentration and the time interval for determining the sulfuric acid concentration do not have to be the same, for example, when the increase in copper concentration due to air oxidation of iron ions is slower than the increase in sulfuric acid concentration and copper concentration due to water evaporation. The time interval for obtaining the sulfuric acid concentration may be shorter than the time interval for obtaining the copper concentration.

When the copper concentration or the sulfuric acid concentration becomes higher than the predetermined copper concentration or the predetermined sulfuric acid concentration, the control section 20 performs the operation of adjusting the composition of the plating solution. Copper concentration and sulfuric acid concentration are controlled by upper limit value and lower limit value (control width),
By the adjusting operation, the copper concentration and the sulfuric acid concentration are made to fall between the predetermined upper limit value and the predetermined lower limit value, respectively. less than,
The operation of adjusting the plating solution composition by the control unit 20 will be described. First, the pumps P1 to P4 are operated by the control unit 20 so that the plating liquid contains the plating liquid storage tank 1 and the plating cup 2.
It is circulated between a and 2d. At that time, part of the plating liquid flowing through the liquid supply branch pipe 4a flows into the bypass pipe 10 due to the pressure loss due to the filter 7a. That is, the plating liquid can be flown through the bypass pipe 10 without providing a dedicated pump in the bypass pipe 10. In this way, the control unit 20 can obtain the absorbance (copper concentration) of the plating solution flowing through the bypass pipe 10 based on the output signal of the absorbance meter 11.

When the sulfuric acid concentration is obtained, the control unit 20 determines whether the obtained sulfuric acid concentration is higher than a predetermined sulfuric acid concentration. When the obtained sulfuric acid concentration is determined to be equal to or lower than the predetermined sulfuric acid concentration, the control unit 20 does not perform any particular control and after a certain period of time elapses, obtains the sulfuric acid concentration again. When it is determined that the obtained sulfuric acid concentration is higher than the predetermined sulfuric acid concentration,
The air valve 24 is opened under the control of the control unit 20, and pure water is supplied to the plating solution storage tank 1 from the pure water supply pipe 22.
Since the flow rate of pure water flowing through the pure water supply pipe 22 is set to a predetermined flow rate by the flow meter 25 with a flow rate adjusting valve, the supply amount of pure water is controlled by the time the air valve 24 is open.
A predetermined amount of pure water can be added to the plating solution. For example, when the capacity of the plating liquid storage tank 1 is about 100 liters, the amount of pure water to be added can be 100 milliliters. With this amount of addition, the sulfuric acid concentration of the plating solution after the addition of pure water does not become lower than the appropriate concentration (lower limit of control width).

Since the pumps P1 to P4 are operated,
The plating liquid is contained in the plating liquid storage tank 1 and the plating cups 2a to 2d.
It is agitated while being circulated between and. At this time, since there is no part where the plating solution is accumulated in the plating device,
When the plating solution is circulated for an appropriate time, the total amount of the plating solution to which pure water is added has a uniform composition. After the homogenization time for the composition of the plating solution to become sufficiently uniform, the control unit 20
Again determines the sulfuric acid concentration in the plating solution based on the output signals of the absorbance meter 11, the temperature sensor 15, and the electromagnetic conductivity meter 16, and determines whether the sulfuric acid concentration is higher than a predetermined sulfuric acid concentration. The homogenization time may be a predetermined constant time or a time until the change in the absorbance monitored by the absorptiometer 11 becomes equal to or less than a predetermined amplitude.

When it is determined that the sulfuric acid concentration is higher than the predetermined sulfuric acid concentration, the control unit 20 again controls the air valve 24 to open for a predetermined time to add a predetermined amount of pure water to the plating solution, After the homogenization time has elapsed, it is determined whether the sulfuric acid concentration is higher than a predetermined sulfuric acid concentration. Hereinafter, the same operation is repeated until the sulfuric acid concentration becomes equal to or lower than a predetermined sulfuric acid concentration.
During this time, the pumps P1 to P4 are continuously operated to maintain the circulation of the plating solution.

During the above adjustment operation, the ultrasonic level meter 2
The liquid level of the plating liquid in the plating liquid storage tank 1 is monitored by 8 and the control unit 20 stops adding water to the plating liquid when the liquid level becomes higher than a predetermined level. To control. As a result, the plating liquid storage tank 1
It is possible to avoid the situation where the plating solution overflows from the inside. Absorber 1
It is effective to perform such control in the case where the temperature sensor 15, the electromagnetic conductivity meter 16 and the like fail and the correct sulfuric acid concentration cannot be obtained.

Next, the operation for adjusting the copper concentration will be described. First, the pumps P1 to P4 are operated by the control unit 20 so that the plating liquid contains the plating liquid storage tank 1 and the plating cup 2a.
Circulated between ~ 2d. When the copper concentration is obtained, the control unit 20 determines whether the obtained copper concentration is higher than a predetermined copper concentration. When it is determined that the obtained copper concentration is less than or equal to the predetermined copper concentration, the control unit 20 does not perform any particular control and after a certain period of time elapses, obtains the copper concentration again.

When it is judged that the obtained copper concentration is higher than the predetermined copper concentration, the air valve 34 is opened for a predetermined time by the control of the control unit 20, and a predetermined amount of the thinning liquid is plated from the thinning liquid supply pipe 32. It is supplied to the liquid storage tank 1. The flow rate of the diluting liquid flowing through the diluting liquid supply pipe 32 is a flow meter with a flow rate adjusting valve
Since the flow rate is set to a predetermined value, the supply amount of the diluting liquid can be controlled by the time the air valve 34 is open. The supply amount of the diluting liquid is set so that the copper concentration does not become lower than an appropriate concentration (lower limit of control range) by adding the diluting liquid.

The plating solution is agitated while being circulated between the plating solution storage tank 1 and the plating cups 2a to 2d. When the plating solution is circulated for an appropriate time, the composition of the plating solution added with the thinning solution becomes uniform. After the homogenization time has elapsed, the control unit 20 obtains the copper concentration in the plating solution based on the output signal of the absorptiometer 11 and determines whether this copper concentration is higher than a predetermined copper concentration. If the copper concentration is higher than the predetermined copper concentration, the control unit 20 again controls the air valve 34 to open for a predetermined time to add a predetermined amount of the thinning solution to the plating solution,
After the homogenization period has elapsed, it is determined whether the copper concentration is higher than a predetermined copper concentration. Hereinafter, the same operation is repeated until the copper concentration becomes equal to or lower than a predetermined copper concentration.

Similar to the sulfuric acid concentration adjusting operation, the ultrasonic level meter 28 monitors the level of the plating liquid in the plating liquid accommodating tank 1 during the copper concentration adjusting operation. When the liquid surface level of the plating liquid becomes higher than a predetermined level, the addition of the thinning liquid is stopped and the situation where the plating liquid overflows from the plating liquid storage tank 1 is avoided. In this plating apparatus, the plating liquid is dispersed and present in the plating liquid storage tank 1, the plating cups 2a to 2d, the liquid feeding pipe 3, the liquid feeding branch pipes 4a to 4d, the return branch pipes 8a to 8d, the return pipe 9 and the like. However, it is difficult to know the total amount of the plating liquid because the plating process is not necessarily performed on all of the plating cups 2a to 2d. However, this plating apparatus can adjust the sulfuric acid concentration and the copper concentration to proper concentrations as described above regardless of the total amount of the plating solution.

When the composition of the plating solution changes mainly due to the evaporation of water, and the amount of the plating solution decreases mainly due to the evaporation of water and the removal of the plating solution by the object to be treated, all components other than water are uniformly distributed. Higher concentration. This is because when the semiconductor wafer is taken out, the plating solution is usually taken out at each concentration for all components, and the composition of the plating solution does not change. Therefore, in this case, by adding pure water to reduce the sulfuric acid concentration to an appropriate concentration, all components can be reduced to an appropriate concentration. Further, the plating apparatus can also adjust the copper concentration that changes independently of the supporting electrolyte concentration. That is, this plating apparatus can adjust the plating solution to a proper composition.

Further, in this plating apparatus, after the sulfuric acid concentration adjusting operation and the copper concentration adjusting operation are performed, it can be confirmed whether or not the sulfuric acid concentration and the copper concentration actually become appropriate concentrations (within the control range). Furthermore, even if the sulfuric acid concentration or the copper concentration does not fall below the predetermined sulfuric acid concentration or the predetermined copper concentration by one adjustment operation, the sulfuric acid concentration or the copper concentration can be adjusted to the proper concentration ( Within the control range).
The present invention is not limited to the above embodiment,
For example, the number of plating cups may be one, four
There may be a plurality other than one. Also, one pump P1
In (P3), a plurality of plating cups 2a, 2b (2c, 2)
The liquid delivery branch pipes 4a (4c) may be arranged so as to share d). That is, the liquid delivery branch pipe 4a (4c) is
It may be branched on the downstream side of the pump P1 (P3) and communicated with the plating cups 2a, 2b (2c, 2d).

When pure water or a thinning solution is added a plurality of times, it is not necessary to add the same amount each time. For example, the addition amount of the first time may be increased and the addition amount of the second time and thereafter may be decreased. . Further, the addition amount of pure water or the diluting solution may be determined based on the sulfuric acid concentration or the copper concentration before the concentration adjusting operation. Further, when adding pure water or a diluting solution for the second time and thereafter, the addition amount of the pure water or the diluting solution is determined in consideration of the sulfuric acid concentration or the copper concentration after the addition of the first time from the first addition. It may be that.

The predetermined sulfuric acid concentration and the predetermined copper concentration for discriminating the magnitude relationship between the measured sulfuric acid concentration and the copper concentration do not have to be the upper limit value of the control width. It can be a slightly lower value. in this case,
It is possible to avoid the situation where the sulfuric acid concentration and the copper concentration deviate from the control range in advance, instead of adjusting the concentration after the sulfuric acid concentration and the copper concentration deviate from the control range. The copper concentration measurement (copper concentration adjustment operation) is preferably performed after (immediately after) the sulfuric acid concentration adjustment operation. In this case, if the ratio of sulfuric acid to water in the diluting solution is almost the same as that in the plating solution having the predetermined composition, the sulfuric acid concentration of the plating solution whose sulfuric acid concentration has already been adjusted to the predetermined concentration will be Never change,
Only the copper concentration is reduced. By such a plating solution composition adjusting method, the sulfuric acid concentration and the copper concentration can be easily adjusted to predetermined compositions. In this case, whether or not to add the thinning solution may be determined based on the ratio between the sulfuric acid concentration and the copper concentration. That is, the diluting solution can be added when the ratio of the copper concentration to the sulfuric acid concentration is higher than a predetermined value.

An integrated flow meter is used instead of the flow meters 25 and 35 with flow rate adjusting valves, and a signal indicating the integrated flow rate is sent to the control unit 20.
It is also possible to configure to input to. In this case, the control unit 20 supplies the pure water or the diluting liquid to the plating liquid storage tank 1, and when a predetermined amount of the pure water or the diluting liquid passes through the pure water supply pipe 22 or the diluting liquid supply pipe 32, the air valve 24. Alternatively, the air valve 34 may be controlled to be closed. Thereby, a predetermined amount of pure water or a diluting solution can be added to the plating solution.

When stirring the plating solution to make it uniform, the pumps P1 to P4 may be operated simultaneously with the addition of pure water or a diluting solution, or may be operated after the addition of pure water or a diluting solution. When the target metal is copper, the supporting electrolyte may be potassium pyrophosphate in addition to sulfuric acid. In this case, the metal salt of the target metal may be copper pyrophosphate, and the copper concentration is analyzed by, for example, automatically sampling the plating solution from the plating solution storage tank 1 and determining the copper concentration by titration. You may go by.

The target metal may be gold instead of copper. In this case, the supporting electrolyte may be potassium cyanide. In this case, the metal salt of the target metal may be potassium gold cyanide, and the gold concentration is analyzed by, for example, automatically sampling the plating solution from the plating solution storage tank 1 and determining the gold concentration by titration. It may be performed by a device. The plating solution is a brightener, a promoter, which is usually added as a trace component, in addition to the supporting electrolyte and the metal salt containing the target metal.
It may contain a suppressor or the like.

The object to be plated (work) is not limited to the semiconductor wafer, and various members and parts to be plated can be used. In addition, various changes can be made within the scope of the matters described in the claims.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a configuration of a plating apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the copper concentration of a sample plating solution and the measured absorbance.

FIG. 3 is a diagram showing a relationship between sulfuric acid concentration and electrical conductivity at each copper concentration.

[Explanation of symbols]

1 Plating liquid storage tank 2a-2d plated cup 3 Liquid supply piping 4a-4d Liquid supply branch pipe 8a-8d Return branch piping 9 Return piping 10 Bypass piping 11 Absorbance meter 15 Temperature sensor 16 Electromagnetic conductivity meter 18, 24, 34 Air valve 20 Control unit 21 Pure water supply device 22 Pure water supply pipe 25,35 Flowmeter with flow adjustment valve 31 Diluting liquid supply device 32 Diluting liquid supply pipe

Claims (13)

[Claims] Claim: What is claimed is: 1. A plating apparatus for plating a target metal with a target metal using a plating solution containing a metal salt containing a target metal, a supporting electrolyte, and water, the plating solution containing section containing a plating solution. A supporting electrolyte concentration measuring means for measuring the concentration of the supporting electrolyte in the plating solution, a water adding means for adding water to the plating solution contained in the plating solution containing part, and a supporting electrolyte concentration measuring means for measuring the supporting electrolyte concentration. It is determined whether the supporting electrolyte concentration in the plating solution is higher than a predetermined supporting electrolyte concentration, and based on the measured supporting electrolyte concentration being determined to be higher than the predetermined supporting electrolyte concentration,
And a supporting electrolyte concentration control means for controlling the water addition means to add water to the plating solution. 2. The plating apparatus according to claim 1, further comprising plating liquid stirring means for stirring the plating liquid stored in the plating liquid storage portion. 3. The method for controlling the concentration of supporting electrolyte by the water adding means until the supporting electrolyte concentration controlling means determines that the supporting electrolyte concentration measured by the supporting electrolyte concentration measuring means is less than or equal to the predetermined supporting electrolyte concentration. The control is performed such that the addition of a fixed amount of water and the measurement of the supporting electrolyte concentration by the supporting electrolyte concentration measuring means are repeated.
Alternatively, the plating apparatus described in 2. 4. The supporting electrolyte concentration measuring means, an absorptiometer for measuring the absorbance of the plating solution with respect to light of a specific wavelength, a temperature sensor for measuring the temperature of the plating solution, and a conductivity of the plating solution. 4. The plating apparatus according to claim 1, further comprising a conductivity measuring unit for measuring the electric conductivity. 5. The plating apparatus according to claim 1, wherein the supporting electrolyte is sulfuric acid. 6. The plating apparatus according to claim 1, wherein the target metal is copper. 7. The plating apparatus according to claim 6, wherein the metal salt containing the target metal is copper sulfate. 8. A metal concentration measuring means for measuring the concentration of a target metal in a plating solution, and a diluting solution containing water and a predetermined concentration of a supporting electrolyte in the plating solution contained in the plating solution container. It is determined whether or not the concentration of the target metal measured by the liquid adding means and the metal concentration measuring means is higher than a predetermined target metal concentration, and it is determined that the concentration of the target metal is higher than the predetermined target metal concentration. 8. The plating apparatus according to claim 1, further comprising metal concentration control means for controlling the thinning solution addition means to add the thinning solution to the plating solution. 9. The plating apparatus according to claim 8, wherein the plating solution contains a redox agent. 10. The plating apparatus according to claim 9, wherein the redox agent is iron. 11. A plating solution composition adjusting method for adjusting the composition of a plating solution containing a metal salt containing a target metal, a supporting electrolyte, and water, which comprises a supporting electrolyte concentration measuring step of measuring the supporting electrolyte concentration of the plating solution. The supporting electrolyte concentration determination step of determining whether or not the supporting electrolyte concentration measured in the supporting electrolyte concentration measuring step is higher than a predetermined supporting electrolyte concentration, and the supporting electrolyte concentration determination step in the supporting electrolyte concentration determining step is And a water adding step of adding water to the plating liquid based on the determination that the concentration is higher than the predetermined supporting electrolyte concentration. 12. A metal concentration measuring step for measuring the concentration of a target metal in a plating solution, and a metal for determining whether or not the concentration of the target metal measured in the metal concentration measuring step is higher than a predetermined target metal concentration. In the concentration determination step and the metal concentration determination step, it is determined that the measured concentration of the target metal is higher than the predetermined target metal concentration, and then a thinning solution containing water and a predetermined concentration of the supporting electrolyte is plated. The plating solution composition adjusting method according to claim 11, further comprising a step of adding a diluting solution to the solution. 13. The plating solution composition adjusting method according to claim 12, wherein the metal concentration measuring step, the metal concentration determining step, and the diluting solution adding step are performed after the water adding step.