JP2009293083A - Method for manufacturing semiconductor device, method for detecting concentration of decomposition product, plating solution and plating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which can easily measure a concentration of a decomposition product in a plating solution without requiring expensive facilities. <P>SOLUTION: A plating apparatus includes: plating parts 1 and 2 which immerse an article to be treated in the plating solution and form a thin film of a metal on the article to be treated by using the plating solution to which an additive necessary for forming the thin film and an analysis sample including metal ions having a lower standard electrode potential than the metal that forms the thin film have been added; an additive concentration detecting part 6 for detecting the concentration of the additive in the plating solution; an analysis sample concentration detecting part 7 for detecting the concentration of the analysis sample in the plating solution; and a decomposition product concentration calculating part 8 which recognizes a change of a concentration balance of the additive and the analysis sample with respect to the balance at the time when the plating solution has been supplied, on the basis of each detection result obtained in the additive concentration detecting part 6 and the analysis sample concentration detecting part 7, and calculates the concentration of the decomposition product of the additive in the plating solution. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device for forming a semiconductor multilayer wiring or a printed wiring board using electrolytic plating, a decomposition product concentration detection method used when performing the electrolytic plating, a plating solution, and a plating treatment. Relates to the device.

  In the manufacturing process of a semiconductor device, electrolytic copper plating is used for forming a semiconductor multilayer wiring, a printed wiring board, and the like. And in an electrolytic copper plating process, in order to control the physical property of the copper thin film formed by the said process, it is common that various additives are mixed in a plating solution. Specifically, for example, in the case of copper sulfate-based electrolytic copper plating treatment, sulfuric acid is mixed in the copper sulfate aqueous solution for the purpose of increasing the conductivity of the plating solution, and the mirror finish and the fine unevenness on the surface of the plating film are eliminated. Various additives are mixed in order to perform a plating process for increasing the growth rate of the recesses as in the semiconductor copper wiring process. Examples of the additive include an accelerator (SPS) that promotes plating, a suppressor (polyethylene glycol or the like) or leveler that suppresses plating, and chlorine ions as an inorganic additive.

The concentration of the additive in such a plating solution has a great influence on the plating process. Therefore, various analysis methods have been developed and used for the additive concentration.
As an example, utilizing the fact that the accumulated current amount required to peel the copper plated on the electrode differs depending on the plating additive concentration, create a calibration curve of the plating additive concentration and the accumulated current required for peeling, Based on this, a CVS (cyclic voltammetric stripping) method for calculating the actual additive concentration of the plating solution has been proposed (see, for example, Patent Document 1).
Further, as a method for directly measuring plating solution additives and decomposition products, HPLC (high performance liquid chromatography) method, ESI-TOF MS (electrospray ionization time-of-flight mass spectrometry) method and the like are also known. (For example, refer to Patent Document 2).
Furthermore, there is also a hull cell method in which the state of the plating solution is investigated by observing the state of the electrode surface at various current densities using a specially shaped electrolytic cell in which the electrode is installed obliquely with respect to the anode (for example, , See Patent Document 3).
Then, by grasping the state of the plating solution using these analytical methods, the concentration of the effective additive in the plating solution is managed, and a deficiency is newly added or a certain amount of the plating solution is periodically added. It is also proposed that the performance of the plating process can be maintained by exchanging the material (bleed and feed) (see, for example, Patent Document 4).

US Pat. No. 4,132,605 JP 2005-520131 A Japanese Patent Laid-Open No. 5-72167 US Pat. No. 6,527,920

However, the above-described conventional techniques have the following problems.
For example, in the electrochemical additive concentration calculation method represented by the CVS method disclosed in Patent Document 1, decomposition products (by-products) generated by the reaction of the additive during the plating process are described. It is difficult to measure the absolute amount in the plating solution. The same applies to the Halcell method disclosed in Patent Document 3.
On the other hand, if it is the HPLC method disclosed by the said patent document 2, it is possible to measure the density | concentration of the organic additive and decomposition product in a plating solution. However, since a dedicated column is required for the measurement, it is difficult to measure a plurality of additives at the same time, and it is impossible to measure continuously in a closed loop as in the case of using the CVS method. is there. The ESI-TOF MS method overcomes the weaknesses of the HPLC method and can continuously measure various additives without maintenance, and can measure with high accuracy including degradation products, but the equipment cost is very high. As a result, the process cost increases.

Thus, measuring the absolute amount of the decomposition product in the plating solution is generally not widespread because the measurement is difficult or requires expensive equipment.
Therefore, as disclosed in Patent Document 4, even if the plating solution is bleed-and-feeded while maintaining the effective additive concentration in the plating solution constant, every time the plating process is performed. Since the decomposition product is generated, the concentration of the decomposition product in the plating solution increases. As a result, for example, in the electroplating process used for semiconductor copper wiring formation, the bottom-up and the initial stage after mixing the plating solution and after using it for a certain period (for example, several months) while adjusting the additive concentration There may be a difference in the characteristics of the plating treatment using the plating solution such that the characteristics of the fill deteriorate. Such a difference in plating characteristics may hinder the performance of embedding copper in fine wiring, and so its occurrence should be prevented.

  Therefore, the present invention provides a semiconductor that can easily measure the concentration of decomposition products in the plating solution without requiring expensive equipment in order to prevent the plating characteristics from changing over time. An object of the present invention is to provide an apparatus manufacturing method, a decomposition product concentration detection method, a plating solution, and a plating processing apparatus.

  The present invention provides a method for manufacturing a semiconductor device devised to achieve the above object, wherein a constituent substrate of a semiconductor device is immersed in a plating solution to form a metal thin film on the constituent substrate, and the plating solution includes A plating process using an additive necessary for forming a thin film and an analysis sample made of metal ions having a standard electrode potential lower than that of the metal, and an addition for detecting the concentration of the additive in the plating solution Supply of the plating solution from each detection result in the agent concentration detection step, the analysis sample concentration detection step for detecting the concentration of the analysis sample in the plating solution, and the additive concentration detection step and the analysis sample concentration detection step Recognizing a change in concentration balance between the additive and the analysis sample with respect to time, a decomposition product for calculating the concentration of the additive decomposition product in the plating solution And a degree calculating step.

  In the semiconductor device manufacturing method of the above procedure, a plating solution to which an analysis sample is added in addition to the additive is used. Since the analysis sample has a standard electrode potential lower than that of the metal thin film formed by the plating process, no reduction reaction (or oxidation reaction) is involved in the plating process. That is, unlike the additive, it does not affect the plating process. Therefore, for example, through the plating process, the additive reacts to become a decomposition product (by-product), and even if the amount of the additive in the plating solution decreases, the analysis sample in the plating solution The amount will not change. This means, for example, to maintain a constant effective additive concentration in the plating solution after the plating process (concentration of additive acting on the plating process) based on the results of the additive concentration measurement. This means that the concentration of the analytical sample in the plating solution increases as the concentration of the decomposition product in the plating solution increases when the concentration adjustment operation added to the plating solution is performed. Thus, when the additive in the plating solution becomes a decomposition product through the plating treatment, the concentration balance between the additive and the analysis sample changes in the plating solution. Therefore, if the concentration of the analytical sample in the plating solution is detected, the concentration of the decomposition product in the plating solution can be calculated based on the recognition result of the change in the concentration balance between the additive in the plating solution and the analytical sample. Can do. That is, the concentration of the decomposition product can be indirectly measured from the detection result of the concentration of the analysis sample.

According to the present invention, since the plating solution to which the analysis sample is added in addition to the additive is used, the concentration of the decomposition product in the plating solution can be indirectly measured from the detection result of the concentration of the analysis sample. . Therefore, it becomes possible to recognize the absolute amount of the decomposition product in the plating solution based on the result of measuring the concentration of the decomposition product, and as a result, the plating characteristics due to the plating solution may change over time. It is possible to prevent this.
Moreover, in the present invention, an analysis sample mixed in the plating solution is used for measuring the concentration of the decomposition product. Since this analysis sample is made of metal ions, its concentration can be detected using a known method such as atomic absorption analysis or inductively coupled plasma emission spectroscopy. Therefore, unlike the case of using, for example, the ESI-TOF MS method, expensive equipment is not required for measuring the concentration of decomposition products.

  Hereinafter, a semiconductor device manufacturing method, decomposition product concentration detection method, plating solution, and plating apparatus according to the present invention will be described with reference to the drawings. Here, electrolytic copper plating in a semiconductor copper wiring process, that is, electrolytic copper plating for forming a copper thin film on a constituent substrate (wafer substrate) of a semiconductor device is taken as an example.

[Description of plating solution]
First, a specific example of the electrolytic copper plating solution used for the electrolytic copper plating treatment, that is, the plating solution according to the present invention will be described.
The electrolytic copper plating solution exemplified here is obtained by adding an additive necessary for forming a copper thin film and an analysis sample made of metal ions having a standard electrode potential lower than that of copper. Specifically, it is conceivable to use an electrolytic copper plating solution configured as described below.

  For example, the water-soluble copper salt constituting the electrolytic copper plating solution is preferably 10 to 200 g / L, particularly 20 to 150 g / L (excluding hydrate) using copper sulfate (pentahydrate). . Further, sulfuric acid is used as an acid for improving the conductivity of the electrolytic copper plating solution, and the blending amount is preferably 5 to 200 g / L, particularly 10 to 160 g / L. Moreover, it is possible to add water-soluble chloride (for example, NaCl) and hydrochloric acid as chlorine ions. Such a constituent liquid is called VMS (Virgin Make-up Solution).

Additives include accelerators (Acc.), Suppressors (Sup.) And levelers (Lev.).
Accelerators are NaO3SC3H3S-SC3H3SO3Na “bis (3-sulfopropyl) disulfide (disodium salt)”, bis (2-sulfopropyl) disulfide (disodium salt), bis (3-sulfo-2-hydroxypropyl) ) Organic thio compounds such as thiourea and its derivatives such as disulfide (disodium salt).
The suppressor is an oxyalkylene polymer such as polyvinyl alcohol, ethylene oxide such as polyethylene glycol and derivatives thereof, propylene oxide and a copolymer or block copolymer thereof, and the like.
Levelers are acetamide, N, N-dimethylmethacrylamide, polyacrylic acid amide, organic amides and the like.
The electrolytic copper plating solution is mixed with these accelerator / suppressor / leveler aqueous solutions. And it adjusts so that the density | concentration in an electrolytic copper plating solution may be 0.001-5 g / L by adding 1-20 ml / L of these.
The pH of the electrolytic copper plating solution is 1 or less, the plating temperature is 20 to 30 ° C., and the current density is 1 to 8 A / dm 2.

In addition, a certain amount of analysis sample is added to each additive aqueous solution. The analysis sample is made of a metal ion having a standard electrode potential lower than that of copper. More specifically, the standard electrode potential is 2.0 V or more lower than that of copper or hydrogen, and does not form oxide ions or complex ions in an aqueous solution. Atomic absorption spectrometry, inductively coupled plasma emission spectroscopy, ion chromatography, It is conceivable to use metal ions (for example, alkali metal ions such as potassium ion, sodium ion, rubidium ion, and cesium ion) that can be measured by a known method such as capillary electrophoresis. Note that “the standard electrode potential is 2.0 V or lower” is derived from an empirical rule through experiments and the like in order to ensure that oxide ions and complex ions are not formed. .
FIG. 1 is an explanatory diagram showing a specific example of the standard electrode potential. For example, if the metal to be formed is copper (Cu) (see the broken line in the figure), any metal ion that is 2.0 V or more lower than the standard electrode potential “0.34 V” ( (See the arrow area in the figure.), Used as an analysis sample.
About the addition density | concentration of such an analytical sample, it is possible to adjust so that it may be 2 times more than the measurement limit of each metal ion measuring method after throwing into an electrolytic copper plating solution. The measurement limit is, for example, about several ppb for atomic absorption spectrometry, about several ppb to several tens of ppb for inductively coupled plasma emission spectrometry, and about several tens of ppb for ion chromatography.
In any case, it is necessary to mix any of the above-described metal ions with an accuracy of, for example, 50 mg / L or more and ± 0.1 mg / L as the analysis sample. As the raw material, the metal ion hydroxide (for example, NaOH, KOH, CsOH), or the metal ion sulfate (for example, Na2SO4, K2SO4) can be used.
Specifically, since the sodium salt is generally used for the accelerator, after adjusting the accelerator concentration, adjustment is performed using a NaOH aqueous solution or a sodium sulfate aqueous solution so as to obtain a target concentration. In that case, the target concentration may be set to 500 mg / L, for example. Alternatively, an alkali metal (for example, potassium) that is not used in the accelerator raw material may be additionally prepared by the same method. In that case, the target concentration may be set to 100 mg / L, for example.
Moreover, about a suppressor / leveler, the metal ion which is not used for an accelerator is introduce | transduced 100 mg / L, respectively. For example, when sodium ions are used for the accelerator, potassium can be applied to a suppressor or a leveler. And it is possible to set each alkali metal ion concentration to 100 mg / L, for example.

[Description of plating equipment]
Next, a specific example of a plating apparatus that performs electrolytic copper plating using the above-described electrolytic copper plating solution, that is, a plating apparatus according to the present invention will be described.
FIG. 2 is a functional block diagram showing a schematic configuration example of the plating apparatus according to the present invention.

  The plating apparatus shown in the figure includes a plating solution tank 1 for storing an electrolytic copper plating solution having the above-described configuration, and a plating cell unit 2 for performing an electrolytic copper plating process using the electrolytic copper plating solution in the plating solution tank 1. And. These function as a plating processing section in the present invention. The plating bath 1 is provided with a liquid level detection sensor 3 for detecting the upper limit position and the lower limit position of the electrolytic copper plating solution. In addition, about the plating solution tank 1, the plating cell part 2, and the liquid level detection sensor 3, since it is the same as that of a conventional structure, the detailed description is abbreviate | omitted here.

  In addition, the plating apparatus of the illustrated example includes a plating solution supply unit 4 that supplies an electrolytic copper plating solution to the plating solution tank 1 as necessary, and an electrolytic copper plating solution from the plating solution tank 1 as necessary. And a waste water valve section 5 for discharging. Among these, in the plating solution supply unit 4, a certain amount of analysis sample corresponding to the VMS is added to the accelerator by the accelerator as the first additive, and a suppressor as the second additive. A plating solution tank in which a certain amount of an analysis sample corresponding to the above is added and a sample in which a certain amount of an analysis sample corresponding to the third additive is added by a leveler as a third additive 1 is supplied. In addition, although accelerator / suppressor / leveler is mentioned here as an example as an additive, the kind, number, etc. are not specifically limited.

Furthermore, the plating apparatus of the illustrated example includes an additive concentration detector 6 that detects the concentration of the additive in the electrolytic copper plating solution in the plating solution tank 1 and the concentration of the analysis sample in the plating solution in the plating solution tank 1. And an analytical sample concentration detection unit 7 for detecting.
The additive concentration detection unit 6 obtains the additive concentration detection result by performing detection using a known method such as the CVS method or the Hull cell method.
The analytical sample concentration detection unit 7 detects the concentration detection result of the analytical sample using any one of techniques such as atomic absorption spectrometry, inductively coupled plasma emission spectrometry, ion chromatography, capillary electrophoresis, etc. Get by. In atomic absorption spectrometry, a sample is atomized at a high temperature, light is transmitted through the sample, and an absorption spectrum is measured to identify and quantify elements in the sample. Inductively coupled plasma optical emission spectrometry is a method in which a liquid sample is sprayed into a high-temperature plasma, and the emission wavelength of atoms in the decomposed sample is examined with a spectrometer to identify the types of elements contained in the sample. In addition, the concentration of the element is quantified from the intensity of light emission. Ion chromatography is a type of ion exchange chromatography in which the strong electrolyte used in the eluent is replaced with water or one with low conductivity, and only the target ion species is detected with high sensitivity using an electrical conductivity detector. It is. In capillary electrophoresis, a sample solution is injected into a hollow capillary, a high voltage is applied, the target component is electrophoresed, and the target component is analyzed with a UV detector. Since these methods are all known, a detailed description thereof will be omitted here.

  Furthermore, the plating apparatus shown in the figure includes an arithmetic control unit 8 that gives an operation instruction to the plating solution supply unit 4 based on the detection results of the additive concentration detection unit 6 and the analysis sample concentration detection unit 7. Yes. As will be described in detail later, in this calculation control unit 8, electrolytic copper plating from the plating solution supply unit 4 into the plating solution tank 1 is performed based on the detection results of the additive concentration detection unit 6 and the analysis sample concentration detection unit 7. Recognizing a change in the concentration balance between the additive and the analysis sample with respect to the supply of the solution, the concentration of the additive decomposition product in the electrolytic copper plating solution is calculated. Further, as will be described in detail later, the arithmetic control unit 8 performs electrolysis in the plating bath 1 based on the detection result of the additive concentration detection unit 6 and the concentration calculation result of the additive decomposition product described above. Concentration management processing for the copper plating solution is performed. That is, the arithmetic control unit 8 functions as a decomposition product concentration calculation unit and a concentration management processing unit in the present invention.

[Description of processing operation in plating equipment]
Next, an example of processing operation in the plating apparatus having the above-described configuration will be described. The processing operation performed by the plating apparatus includes a basic processing operation for keeping the additive concentration in the electrolytic copper plating solution in the plating solution tank 1 constant, and an additive decomposition product in the electrolytic copper plating solution. There is a decomposition product concentration detection operation for calculating the concentration of the additive and a concentration management processing operation for setting the additive decomposition product in the electrolytic copper plating solution to a concentration equal to or less than a predetermined amount.

[Description of basic processing operations]
In the plating processing apparatus having the above-described configuration, as a basic processing operation, in order to keep the additive concentration in the electrolytic copper plating solution in the plating solution tank 1 constant, based on the detection result in the additive concentration detector 6, Additives that are lacking in the electrolytic copper plating solution are introduced.

FIG. 3 is a flowchart showing a specific example of the additive concentration measurement processing operation which is one of the basic processing operations in the plating apparatus.
As shown in the figure, in the plating apparatus, the additive concentration detector 6 detects and measures the concentration of the additive in the electrolytic copper plating solution in the plating solution tank 1 at a preset periodic timing (step). 11. The following steps are abbreviated as “S”.)
When the additive concentration detection unit 6 detects and measures the concentration of the additive, the arithmetic control unit 8 receives the concentration detection result, compares it with a preset reference value, and there is a difference between them. Whether or not there is a deviation in the concentration of the additive in the electrolytic copper plating solution in the plating solution tank 1 is determined (S12). As a result, if a concentration deviation occurs, the arithmetic control unit 8 determines to introduce the additive into the plating solution tank 1 in order to eliminate the concentration deviation, and the plating solution supply unit 4 and the waste water valve. An operation instruction is given to the unit 5 (S13).
And when measuring an additive concentration continuously (S14), the additive concentration detection part 6 and the calculation control part 8 repeat the above processing operation (S11-S14).

FIG. 4 is a flowchart showing a specific example of a bleed-and-feed operation, which is another basic processing operation in the plating apparatus.
As shown in the figure, in the plating processing apparatus, the plating solution supply unit 4 and the waste water valve unit 5 bleed and feed the electrolytic copper plating solution in the plating solution tank 1 in accordance with an operation instruction from the arithmetic control unit 8. I do.
That is, when there is an operation instruction from the calculation control unit 8, the plating solution supply unit 4 mixes each additive (a sample in which a certain amount of analysis sample is added) at a predetermined rate set for the VMS. The electrolytic copper plating solution is supplied (feeded) into the plating solution tank 1 (S21). Then, the electrolytic copper plating solution is continuously supplied into the plating solution tank 1 until the liquid level detection sensor 3 detects that the level of the electrolytic copper plating solution has reached the upper limit position (S22).
When the level of the electrolytic copper plating solution reaches the upper limit position, the wastewater valve unit 5 then opens the drain valve of the plating solution tank 1 to discharge (bleed) the electrolytic copper plating solution from the plating solution tank 1. Perform (S23). The electrolytic copper plating solution is continuously discharged from the plating solution tank 1 until the liquid level detection sensor 3 detects that the liquid level of the electrolytic copper plating solution has reached the lower limit position (S24).
When the liquid level of the electrolytic copper plating solution reaches the lower limit position, the waste water valve unit 5 closes the drain valve of the plating solution tank 1 and finishes discharging the electrolytic copper plating solution from the plating solution tank 1 (S25). . When the bleed-and-feed operation is continuously performed (S26), the plating solution supply unit 4 and the waste water valve unit 5 repeatedly perform the above processing operations (S21 to S26).

FIG. 5 is an explanatory diagram showing an outline of the operation result of the basic processing operation.
In general, when an electrolytic copper plating process is performed using an electrolytic copper plating solution in the plating solution tank 1, the additive in the electrolytic copper plating solution does not function as an additive due to oxidative decomposition, and decomposed and generated. It remains in the electrolytic copper plating solution as a product.
On the other hand, when the additive is introduced based on the detection result in the additive concentration detector 6 as described above, in the plating solution tank 1, as shown in FIG. The concentration of each additive in (see Acc., Sup., Lev. In the figure), and more specifically, the effective additive concentration acting on the electrolytic copper plating treatment is controlled to be kept constant. However, the concentration of the decomposition product of the additive that has stopped functioning as an additive increases according to the amount of additive introduced (see the broken line in the figure). Therefore, as shown in FIG. 5B, when a bleed-and-feed operation is performed, a certain amount of old electrolytic copper plating solution is discarded at a periodic timing, and new electrolytic copper plating solution is introduced. As a result, as shown in FIG. 5 (c), the concentration rise speed of the decomposition product can be slowed down and further saturated in a certain concentration region (see the broken line in the figure). .)
Therefore, even after the electrolytic copper plating treatment is performed, the concentration of each additive in the electrolytic copper plating solution as shown in FIG. (See Acc., Sup., Lev. In the figure.) More specifically, the concentration of the effective additive acting on the electrolytic copper plating process is controlled to be kept constant, and the concentration of decomposition products is increased. By keeping the speed low (see the broken line in the figure), the performance of the electrolytic copper plating process is maintained.

[Explanation of decomposition product concentration detection operation]
Subsequently, a decomposition product concentration detection operation as one of characteristic processing operations in the plating apparatus having the above-described configuration, that is, a decomposition product concentration detection method according to the present invention will be described.

In the plating processing equipment, as one of the basic processing operations, a technique for controlling the concentration of the effective additive constant and a bleed-and-feed of the electrolytic copper plating solution that keeps the concentration of the decomposition product of the additive low are performed. Yes.
Even if it is possible to keep the effective additive concentration in the electrolytic copper plating solution constant, the amount of decomposition products generated each time the electrolytic copper plating process is performed increases or decreases depending on the amount of plating process. . Even if bleed-and-feed is performed, if the ratio is small or the amount of plating treatment is temporarily increased, the amount of decomposition products in the electrolytic copper plating solution will increase, and the concentration will increase. There is a fear. The decomposition product has an adverse effect on the plating characteristics during the electrolytic copper plating treatment, and therefore it is desirable that the concentration can be easily and accurately grasped.
For this reason, the plating processing apparatus performs a decomposition product concentration detection operation according to the procedure described below.

As already described, the plating apparatus uses an electrolytic copper plating solution to which an analysis sample is added in addition to the additive.
Since the analytical sample has a lower standard electrode potential than the copper thin film formed by the electrolytic copper plating treatment, it does not involve an oxidation reaction or a reduction reaction during the electrolytic copper plating treatment. That is, unlike the additive, it does not affect the electrolytic copper plating process. Therefore, for example, the electrolytic copper plating solution undergoes an electrolytic copper plating treatment even if the additive reacts to become a decomposition product (byproduct) and the amount of the additive in the electrolytic copper plating solution decreases. The amount of the analysis sample in the inside does not change. This is because, for example, when the additive concentration adjustment for newly adding the shortage is performed in order to keep the effective additive concentration in the electrolytic copper plating solution constant after the electrolytic copper plating treatment, It means that the concentration of the analysis sample in the electrolytic copper plating solution also increases as the concentration of the decomposition product in the plating solution increases.
Thus, when the additive in the electrolytic copper plating solution becomes a decomposition product through the electrolytic copper plating treatment, a change occurs in the concentration balance between the additive and the analysis sample in the electrolytic copper plating solution. Therefore, if the concentration of the analytical sample in the electrolytic copper plating solution is detected, the decomposition product in the electrolytic copper plating solution is determined based on the recognition result of the change in concentration balance between the additive in the electrolytic copper plating solution and the analytical sample. Concentration can be calculated. That is, the concentration of the decomposition product can be indirectly measured from the detection result of the concentration of the analysis sample.

Specifically, when the plating solution supply unit 4 introduces the electrolytic copper plating solution into the plating solution tank 1, an appropriate amount of an additive mixed with an analysis sample is added to the VMS, and the electrolytic copper plating solution Adjust the density.
For example, the accelerator (Na +, 500 mg / L) is 4 to 20 ml / L with respect to the inorganic plating solution. More preferably, it may be 10 ml / L and the initial concentration of Na ions in the plating solution may be 5 mg / L.
Further, for example, the suppressor (K +, 100 mg / L) is 1 to 5 ml / L with respect to the inorganic plating solution. More preferably, it is considered to be 2 ml / L and the initial K ion concentration in the plating solution is 0.2 mg / L.
Further, for example, the leveler (Mg ++, 100 mg / L) is 1 to 5 ml / L with respect to the inorganic plating solution. More preferably, the concentration is 2 ml / L, and the initial Mg ion concentration in the plating solution is 0.2 mg / L.

When the electrolytic copper plating solution whose concentration has been adjusted in this way is additionally charged into the plating solution tank 1, the analytical sample is also additionally charged, and the concentration will increase. That is, the electrolytic copper plating function by the additive remains maintained, but the concentrations of the decomposition product and the analysis sample increase in relation to each other.
Therefore, in the plating apparatus, the analysis sample concentration detection unit 7 detects and measures the concentration of the analysis sample in the electrolytic copper plating solution in the plating solution tank 1 at a preset periodic timing. More specifically, the concentration of metal ions constituting the analysis sample is detected and measured using any of the methods such as atomic absorption spectrometry, inductively coupled plasma emission spectrometry, ion chromatography, capillary electrophoresis, etc. .
Then, when the analysis sample concentration detection unit 7 detects and measures the concentration of the analysis sample, the calculation control unit 8 receives the concentration detection result, and uses each concentration detection result in the procedure described below. Calculate the decomposition product concentration.

Here, taking the accelerator as an example, the calculation procedure of the decomposition product concentration by the arithmetic control unit 8 will be described.
For example, the accelerator decomposition product concentration Cab in the plating solution tank 1 when bleed-and-feed is not performed is the accelerator concentration of the electrolytic copper plating solution before the electrolytic copper plating treatment as shown in the following equation (1). The difference between Cta and the effective accelerator concentration (concentration of accelerator acting on electrolytic copper plating treatment) Ca specified from the detection result in additive concentration detection section 6 after electrolytic copper plating treatment is formed from one accelerator molecule. It can be calculated by multiplying by a predetermined coefficient a (constant) representing the number of decomposition product molecules.

  Cab = a (Cta−Ca) (1)

  Here, if the bleed-and-feed is not performed, the accelerator concentration Cta can be used as it is supplied from the plating solution supply unit 4, and the accelerator is charged as shown in the following equation (2). It can be calculated by dividing the total amount by the amount of electrolytic copper plating solution.

  Cta = (Accelerator input total amount / plating solution amount) (2)

  On the other hand, with respect to the accelerator concentration Cta when performing bleed-and-feed, the remaining amount in the electrolytic copper plating solution is determined using the concentration Mm of metal ions (for example, Na ions) serving as an analysis sample corresponding to the accelerator. It is necessary to calculate. Specifically, the ratio between the Na ion concentration Mm and the initial introduction amount M0 detected and measured by the analytical sample concentration detection unit 7 is the same as the ratio between the accelerator concentration Ca and the accelerator amount Cta remaining in the electrolytic copper plating solution. It is conceivable to calculate using the following equation (3) using this fact.

  Cta = (Ca) × (Mm) / (M0) (3)

  By substituting the accelerator concentration Cta obtained by the equation (3) into the equation (1), it is possible to calculate the accelerator decomposition product concentration Cab when performing bleed-and-feed.

  Here, the accelerator is described as an example, but the decomposition product concentration can be calculated in exactly the same procedure for other additives, that is, suppressors and levelers.

According to the decomposition product concentration detection operation of the procedure as described above, by using the electrolytic copper plating solution to which the analysis sample is added in addition to the additive, the detection result of the concentration of the analysis sample can be used in the electrolytic copper plating solution. The decomposition product concentration of can be calculated. That is, it becomes possible to indirectly measure the concentration of the decomposition product in the electrolytic copper plating solution. Therefore, it becomes possible to recognize the absolute amount of the decomposition product in the electrolytic copper plating solution based on the concentration measurement result of the decomposition product, and as a result, the plating characteristics of the electrolytic copper plating solution differ over time. It becomes feasible to prevent this from occurring.
In addition, in the decomposition product concentration detection operation of the above-described procedure, an analysis sample mixed in the electrolytic copper plating solution is used to measure the decomposition product concentration. Since this analysis sample is made of metal ions, its concentration can be detected using a known method such as atomic absorption analysis or inductively coupled plasma emission spectroscopy. Therefore, unlike the case of using, for example, the ESI-TOF MS method, expensive equipment is not required for measuring the concentration of decomposition products.

[Explanation of concentration management processing operation]
Next, a concentration management processing operation as another characteristic processing operation in the plating apparatus having the above-described configuration will be described.

The additive in the electrolytic copper plating solution is consumed in proportion to the number of wafer substrates subjected to the electrolytic copper plating treatment (electrolytic copper plating treatment coulomb amount). Therefore, when the processing amount varies, the generation rate of decomposition products also varies.
On the other hand, if the absolute amount of the decomposition product in the electrolytic copper plating solution increases too much, the plating characteristics during the electrolytic copper plating process will be adversely affected.
For this reason, in the plating apparatus, the concentration management processing operation of the procedure described below is performed in order to bring the decomposition product in the electrolytic copper plating solution to a concentration equal to or less than a predetermined amount.

FIG. 6 is a flowchart showing a specific example of the density management processing operation.
As shown in the figure, in the concentration management processing operation, first, the above-described decomposition product concentration detection operation is performed. That is, in the plating apparatus, the analysis sample concentration detector 7 detects and measures the concentration of the analysis sample in the electrolytic copper plating solution in the plating solution tank 1 at a preset periodic timing (S31). When the analysis sample concentration detection unit 7 detects and measures the concentration of the analysis sample, the arithmetic control unit 8 receives the concentration detection result, and uses the concentration detection result while performing the decomposition product of each additive in the above-described procedure. Calculate the concentration.

  After calculating the decomposition product concentration of each additive, the calculation control unit 8 thereafter determines whether or not the decomposition product concentration in the electrolytic copper plating solution is appropriate based on the calculation result (S32). . Specifically, the calculation result of the decomposition product concentration is compared with a preset threshold value, and whether or not the calculation result exceeds the threshold value, that is, the decomposition product in the electrolytic copper plating solution has a predetermined amount. It is determined whether or not the concentration is the following (or absolute amount).

As a result, when it is determined that the decomposition product concentration is inappropriate, the arithmetic control unit 8 operates on the plating solution supply unit 4 and the waste water valve unit 5 in order to optimize the decomposition product concentration. An instruction is given (S33). Specifically, if the decomposition product concentration exceeds the threshold value, the plating during the bleed-and-feed operation is performed to dilute the concentration in the electrolytic copper plating solution of S21 shown in FIG. For example, the liquid introduction rate is increased (the slope of the hatched portion shown in FIG. 5A is steep).
When the concentration management processing operation is continuously performed (S34), the analysis sample concentration detection unit 7 and the calculation control unit 8 repeatedly perform the above processing operations (S31 to S34).

  By performing such a concentration management processing operation, the plating processing apparatus can control the amount of the decomposition product of the additive in the electrolytic copper plating solution in the plating solution tank 1 to be within a predetermined range. More specifically, based on the decomposition product concentration of the additive obtained in the above-described decomposition product concentration detection operation, for example, when the decomposition product concentration exceeds a first threshold (for example, 10 ppm), The introduction rate of a new electrolytic copper plating solution by the plating solution supply unit 4 is increased by a predetermined amount (for example, 10%). On the other hand, when the decomposition product concentration falls below the second threshold (for example, 5 ppm), the introduction rate of new electrolytic copper plating solution by the plating solution supply unit 4 is decreased by a predetermined amount (for example, 10%). . Thereby, the amount of decomposition products can be controlled within a predetermined range (for example, 5 to 10 ppm).

  As described above, if the decomposition product amount is measured by the decomposition product concentration detection operation and the concentration management processing operation is performed based on the result to control the decomposition product amount within a predetermined range, the electrolytic copper plating solution It is possible to prevent the plating characteristics from changing with time. In addition, the plating process can be stabilized, for example, by suppressing the occurrence of imbedding defects during the electrolytic copper plating process.

In the present embodiment, the preferred specific examples of the present invention have been described. However, the present invention is not limited to the contents, and can be appropriately changed without departing from the gist thereof.
For example, in the present embodiment, the electrolytic copper plating process in the semiconductor copper wiring process has been described as an example of the plating process. However, the plating is performed by immersing the workpiece in a plating solution to form a metal thin film on the workpiece. If it is a process, it can be applied to other plating processes in exactly the same manner.

It is explanatory drawing which shows the specific example of a standard electrode potential. It is a functional block diagram which shows the schematic structural example of the plating processing apparatus which concerns on this invention. It is a flowchart which shows the specific example of the measurement processing operation | movement of an additive density | concentration which is one of the basic processing operations in a plating processing apparatus. It is a flowchart which shows the specific example of the bleed-and-feed operation | movement which is another basic processing operation | movement in a plating processing apparatus. It is explanatory drawing which shows the outline | summary of the operation result by the basic processing operation in a plating processing apparatus. It is a flowchart which shows the specific example of the density | concentration management processing operation in the plating processing apparatus which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Plating solution tank, 2 ... Plating cell part, 3 ... Liquid level detection sensor, 4 ... Plating solution supply part, 5 ... Waste water valve part, 6 ... Additive concentration detection part, 7 ... Analytical sample concentration detection part, 8 ... Arithmetic control unit

Claims (6)

A component substrate of a semiconductor device is immersed in a plating solution to form a metal thin film on the component substrate, and an additive necessary for forming the thin film as the plating solution and metal ions having a lower standard electrode potential than the metal A plating process using a sample to which an analysis sample is added;
An additive concentration detection step of detecting the concentration of the additive in the plating solution;
An analytical sample concentration detection step for detecting the concentration of the analytical sample in the plating solution;
From each measurement result in the additive concentration detection step and the analysis sample concentration detection step, the change in concentration balance between the additive and the analysis sample with respect to the supply time of the plating solution is recognized, and the addition in the plating solution A decomposition product concentration calculating step for calculating a concentration of the agent decomposition product. Based on the calculation result in the decomposition product concentration calculation step, a concentration management processing step for performing concentration management processing on the plating solution so that the additive decomposition product in the plating solution has a concentration of a predetermined amount or less. A method for manufacturing a semiconductor device according to claim 1, comprising: An object to be processed is immersed in a plating solution to form a metal thin film on the object to be processed, and the plating solution includes additives necessary for forming the thin film and metal ions having a standard electrode potential lower than that of the metal. A plating process using an analysis sample added; and
An additive concentration detection step of detecting the concentration of the additive in the plating solution;
An analytical sample concentration detection step for detecting the concentration of the analytical sample in the plating solution;
From the detection results in the additive concentration detection step and the analysis sample concentration detection step, the change in the concentration balance between the additive and the analysis sample with respect to the supply time of the plating solution is recognized, and the addition in the plating solution A decomposition product concentration detection method comprising: a decomposition product concentration calculation step of calculating a concentration of the agent decomposition product. An additive necessary for forming the thin film when performing a plating process to form a thin film of metal on the workpiece;
And an analysis sample made of a metal ion having a standard electrode potential lower than that of the metal,
A plating solution configured to be capable of calculating a concentration of an additive decomposition product generated through the plating treatment based on a change in a concentration balance between the additive and the analysis sample. An object to be processed is immersed in a plating solution to form a metal thin film on the object to be processed, and the plating solution includes additives necessary for forming the thin film and metal ions having a standard electrode potential lower than that of the metal. A plating treatment unit using an analysis sample added, and
An additive concentration detector for detecting the concentration of the additive in the plating solution;
An analytical sample concentration detector for detecting the concentration of the analytical sample in the plating solution;
From the detection results at the additive concentration detection unit and the analysis sample concentration detection unit, the change in the concentration balance between the additive and the analysis sample with respect to the supply time of the plating solution is recognized and added to the plating solution. A plating apparatus comprising: a decomposition product concentration calculation unit that calculates the concentration of the agent decomposition product. Based on the calculation result in the decomposition product concentration calculation unit, the concentration management process for the plating solution so that the additive decomposition product in the plating solution used by the plating unit has a concentration of a predetermined amount or less. The plating processing apparatus of Claim 5 provided with the density | concentration management processing part which performs.

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