JP2011195926A - Electrolytic deposition apparatus and electrolytic deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic deposition apparatus and an electrolytic deposition method in which the deposition rate of a substance by electrolytic deposition is improved, and the consumption of gas used as a material for electrolytic deposition can be reduced.SOLUTION: The electrolytic deposition apparatus 1 includes an electrolytic cell 2, a buffer tank 3, a liquid circulation line 4 for connecting the electrolytic cell 2 and the buffer tank 3, and a micro bubble generation and mixing part 6 and a micro bubble stirring part 7 which are provided in the liquid circulation line 4. In the electrolytic cell 2, a substrate W and a counter electrode 21 are oppositely placed and immersed in the electrolyte. Thus, the electrolyte flowing in the liquid circulation line 4 and the micro bubbles generated in the micro bubble generation and mixing part 6 are in a stirred state in the micro bubble stirring part 7. As a result, there is produced an electrolyte containing excess gas which has a saturated dissolved concentration and also has micro bubbles of gas. Electrolytic deposition is performed in a state where the liquid flow of the electrolyte containing excess gas is formed in the direction along an electrolytically deposited surface FS of the substrate W in the electrolytic cell 2.

Description

  The present invention relates to an electrolytic deposition apparatus and an electrolytic deposition method for electrochemically depositing a substance.

  The photoelectrode of the dye-sensitized solar cell must have a porous structure in order to adsorb many sensitizing dyes on the surface and improve the conversion efficiency. In order to obtain such a porous structure, a method of sintering nano-particles and producing them has heretofore been mainstream, but in recent years, a technique using an electrolytic deposition method has attracted attention.

  For example, when depositing zinc oxide using this electrolytic deposition method, electrons generated by applying a voltage to the electrode immersed in the electrolytic solution and the substrate that is the electrodeposited, and the electrolytic solution Oxygen and water in it react to produce hydroxide ions. As the hydroxide ions react with the zinc ions in the electrolytic solution, zinc oxide is deposited on the substrate surface. The hydroxide ion concentration produced | generated by dissolved oxygen concentration changes, and affects the reaction rate of the production | generation reaction of zinc oxide. That is, it can be said that the deposition rate is determined by the dissolved concentration of the gas, in this case, oxygen, which is the material for electrolytic deposition in the electrolytic solution. However, when the gas used as the material for electrolytic deposition is oxygen, since the partial pressure ratio of oxygen under atmospheric pressure (= oxygen partial pressure / atmospheric pressure) is approximately 0.2, the dissolved oxygen concentration in the electrolytic solution Is minute.

  As a method for forcibly increasing the dissolved oxygen concentration, for example, there is a method of bubbling oxygen gas in an electrolytic solution. However, bubbles generated by bubbling have a large diameter, and the surface of the material to be electrodeposited is covered with bubbles, so that the material is not uniformly deposited on the entire surface, and an electrolytic cell for storing the electrolyte is provided. If it is large, there is a problem that the amount of oxygen used becomes extremely large.

  As a method for increasing the dissolved oxygen concentration, there is also a method using a gas dissolution unit using a hollow fiber filter. Since bubbles are not generated, the problem of the bubbling method that the surface to be deposited is covered with bubbles and the uniformity of the deposited substance is impaired is solved. However, for example, when an electrolytic solution in which the dissolved oxygen concentration is saturated is supplied from the lower part of the electrolytic cell by the hollow fiber filter, the dissolved oxygen is consumed by the electrolytic deposition reaction below the electrolytic cell. Among them, the dissolved oxygen concentration decreases as the electrolyte solution is near the upper side. Therefore, when the electrodeposited surface of the substrate, which is the electrodeposited material, is held vertically, unevenness occurs in the film thickness above and below the electrodeposited surface. Furthermore, since the additive often contained in the electrolytic solution is often an organic polymer compound, it is easily adsorbed on the hollow fiber filter and clogs. For this reason, the hollow fiber filter must be periodically replaced, and the running cost increases.

  In order to solve these problems, Patent Document 1 discloses a bubbling technique using oxygen as a gas used as a material for electrolytic deposition and oxygen microbubbles. Since bubbling is performed using microbubbles, it is possible to prevent the bubbles from covering the electrodeposited surface of the substance. Moreover, since it is a microbubble, it is possible to reduce the usage-amount of oxygen, and the fall of a dissolved oxygen concentration can be suppressed by retaining a microbubble in electrolyte solution.

JP 2008-163396 A

  However, in the case of the bubbling method using microbubbles disclosed in Patent Document 1, the microbubbles are retained in the electrolyte solution for as long as possible, so that stirring cannot be forcibly performed in the electrolytic cell. The flow rate of the electrolyte on the surface cannot be controlled. Since the flow rate of the electrolytic solution on the substrate surface affects the reaction rate of the electrolytic deposition reaction, the deposition rate becomes an uncontrollable element and becomes ad hoc. Therefore, it cannot be desired to exceed the deposition rate disclosed in Patent Document 1. In particular, when the substrate is enlarged, a sufficient stirring effect cannot be obtained, so that the possibility of a decrease in the deposition rate is increased. Such a decrease in the deposition rate leads to a decrease in productivity, leading to a problem of an increase in manufacturing cost.

  The present invention has been made in view of the above problems, and is an electrolytic deposition apparatus and electrolytic deposition method capable of improving the deposition rate of a substance to be electrolytically deposited and reducing the consumption of gas as a material for electrolytic deposition. It is a first object to provide

  A second object of the present invention is to provide an electrolytic deposition apparatus and an electrolytic deposition method capable of changing the deposition rate of a substance to be electrolytically deposited while achieving the first object.

  In order to solve the above-mentioned problem, the invention of claim 1 is an electrolytic deposition apparatus for depositing a predetermined substance on the surface of an electrodeposit by utilizing an electrochemical reaction, and an electrolysis containing the electrodeposit. An electrolytic solution supply means for supplying an electrolytic solution into the tank, an electrode disposed in the electrolytic tank, and the electrodeposited material are immersed in the electrolytic solution, and the electrodeposited material and the electrode A voltage application means for applying a voltage between the electrolyte solution supply means, the electrolyte solution supplied to the electrolytic cell, as a solution for the electrolytic deposition, gas dissolved in a saturated state, and A gas excess electrolyte generating means for generating a gas excess electrolyte having the gas microbubbles;

  Invention of Claim 2 is the electrolytic deposition apparatus of Claim 1, Comprising: The said gas excess electrolyte production | generation means mixes a gas-liquid mixture by mixing the said gas microbubble to electrolyte solution. The contact area between the gas and the electrolytic solution is increased by interposing between the mixed part to be generated, and between the mixed part and the electrolytic cell, thereby causing a stirring state of the gas-liquid mixture. A stirring section for generating the gas excess electrolyte.

  Invention of Claim 3 is the electrolytic deposition apparatus of Claim 2, Comprising: While the said stirring part passes the said gas-liquid mixture over predetermined length, the flow of the said gas-liquid mixture itself A conduit for agitating the gas-liquid mixture by pressure and thereby producing the gas-excess electrolyte.

  Invention of Claim 4 is the electrolytic deposition apparatus in any one of Claim 1 thru | or 3, Comprising: In the said electrolytic cell, from the supply part of the said gas excess electrolyte solution to the said electrolytic cell, and the said electrolytic cell In the steady flow of the excess gas electrolyte formed between the discharge portion of the excess gas electrolyte, electrolytic deposition on the deposition object is performed.

  A fifth aspect of the present invention is the electrolytic deposition apparatus according to the fourth aspect, wherein the steady flow is formed in a direction along the deposition surface of the deposition object held in the electrolytic cell. .

  Invention of Claim 6 is the electrolytic deposition apparatus of Claim 4 or 5, Comprising: The said supply part introduces the said gas excess electrolyte solution supplied from the said electrolyte solution supply means to the said electrolytic vessel And a diffusion member for spatially diffusing a jet of the gas excess electrolyte ejected from the inlet and leveling the flow velocity distribution of the gas excess electrolyte on the electrodeposition surface.

  A seventh aspect of the present invention is the electrolytic deposition apparatus according to any one of the fourth to sixth aspects, further comprising a flow rate changing means for changing a flow rate of the steady flow.

  The invention according to claim 8 is the electrolytic deposition apparatus according to claim 7, further comprising a return path for returning the used electrolyte discharged from the electrolytic cell to the electrolyte supply means, The flow rate changing means includes operating speed changing means for changing the operating speed of a pump inserted in the return path.

  The invention according to claim 9 is an electrolytic deposition method in which a predetermined substance is deposited on an electrodeposit by utilizing an electrochemical reaction in an electrolytic solution, and a dissolved concentration of a gas serving as a material for electrolytic deposition is The substance is deposited by applying a voltage between an electrodeposition electrode and an electrodeposit that is saturated and is immersed in a gas-excess electrolyte containing fine gas bubbles.

  A tenth aspect of the invention is an electrolytic deposition method according to the ninth aspect of the invention, in which an electrolytic deposition is performed while generating a liquid flow of the gas-excess electrolyte along the surface of the electrodeposited electrodeposition. I do.

  The eleventh aspect of the present invention is the electrolytic deposition method according to the tenth aspect, wherein the flow rate of the liquid excess electrolyte solution depends on a desired deposition rate of the substance deposited on the electrodeposit. To change.

  According to the first to eighth aspects of the present invention, the gas as the material for electrolytic deposition dissolves in a saturated state, and a gas excess electrolyte solution having gas microbubbles is generated. The decrease in the dissolved concentration of the gas that is the material for analysis is suppressed. For this reason, the reaction rate of the electrolytic deposition reaction is improved, and the deposition rate of the substance is improved. Furthermore, since microbubbles are used, the contact area with the electrolytic solution is increased, and the microbubbles are efficiently dissolved in the electrolytic solution. For this reason, the consumption of the gas used as the material of electrolytic deposition can be reduced.

  According to the invention of claim 2, since the gas excess electrolyte generation means includes the mixing part and the stirring part, the dissolved concentration of the gas used as the material for electrolytic deposition is saturated in the stirring part. Can do. Therefore, since the electrolytic solution having a saturated dissolved concentration can be supplied into the electrolytic cell, the reaction rate of the electrolytic deposition reaction is improved and the deposition rate of the substance is improved. In addition, since the gas is efficiently dissolved in the electrolytic solution in the stirring section, the consumption of gas that is a material for electrolytic deposition can be reduced.

  According to the invention of claim 3, since the agitating part has the pipe line, the gas-liquid mixture is stirred at the flow pressure of the gas-liquid mixture itself when passing through the pipe line. For this reason, microbubbles and an electrolyte solution can contact efficiently and the dissolved concentration of the gas used as the material of electrolytic deposition can be saturated in a stirring part.

  According to the invention of claim 4, since electrolytic deposition is performed in the steady flow of the gas excess electrolyte, the inside of the electrolytic cell is stirred, and the deposition rate of the substance can be improved.

  Further, according to the invention of claim 5, since a steady flow is formed in the direction along the electrodeposition surface of the electrodeposit, the gas excess electrolyte near the surface of the electrodeposition surface is stirred, The deposition rate of the substance can be improved.

  Further, according to the invention of claim 6, since the flow velocity distribution of the gas excess electrolyte on the electrodeposition surface can be leveled by diffusing the jet of the gas excess electrolyte from the inlet, the film thickness on the electrodeposition surface. Can be prevented from becoming non-uniform.

  According to the invention of claim 7, since the flow rate of the steady flow can be changed, the substance deposition rate can be changed by affecting the stirring of the gas excess electrolyte on the surface of the electrodeposit.

  Further, according to the invention of claim 8, the pump is provided in the return path, and the flow rate of the steady flow is changed by changing the operating speed of the pump. The deposition rate of can be changed.

  According to the ninth to eleventh aspects of the present invention, electrolytic deposition is performed in a gas-excess electrolytic solution in which a gas that is a material for electrolytic deposition is dissolved in a saturated state and also has gas microbubbles. For this reason, the fall of the dissolved concentration of the gas used as the material of the electrolytic deposition in an electrolytic vessel is suppressed. Therefore, since the reaction rate of the electrolytic deposition reaction is improved, the deposition rate of the substance is improved. Furthermore, since microbubbles are used, the contact area with the electrolytic solution is increased, and the microbubbles are efficiently dissolved in the electrolytic solution. For this reason, the consumption of the gas used as the material of electrolytic deposition can be reduced.

  According to the invention of claim 10, since electrolytic deposition is performed in the liquid flow of the gas excess electrolyte, the gas excess electrolyte can be agitated to improve the deposition rate of the substance.

  According to the eleventh aspect of the present invention, the desired deposition rate of the substance deposited on the deposition object can be realized by changing the flow rate of the liquid flow of the gas excess electrolyte. For this reason, the film thickness of the substance can be changed to a desired value.

It is XZ sectional drawing showing the schematic structure of the electrolytic deposition apparatus which concerns on this invention. It is a schematic block diagram showing the microbubble production | generation mixing part and microbubble stirring part of the electrolytic deposition apparatus concerning this invention. It is a schematic block diagram showing an example of the diffusion nozzle used for the electrolytic deposition apparatus which concerns on this invention. It is a schematic block diagram showing an example of the diffusion nozzle used for the electrolytic deposition apparatus which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the following description, XYZ orthogonal coordinates shown in the drawings are used as appropriate when indicating directions and orientations. Here, the X-axis and Y-axis directions indicate the horizontal direction, and the Z-axis direction indicates the vertical direction (the + Z side is the upper side and the -Z side is the lower side). For convenience, the X-axis direction is the left-right direction, and the Y-axis direction is the depth direction.

  FIG. 1 is a schematic diagram showing a schematic configuration of an electrolytic deposition apparatus 1 according to an embodiment of the present invention. The electrolytic deposition apparatus 1 is an apparatus that deposits a substance using an electrolytic deposition reaction. This electrolytic deposition apparatus 1 is suitably used for a process of forming an oxide film on a substrate surface of a photoelectrode used for a photoelectric conversion element such as a dye-sensitized solar cell. As such an oxide film of the photoelectrode, it is preferable to use zinc oxide having a porous structure in order to adsorb the sensitizing dye on the surface.

  The electrolytic deposition apparatus 1 includes an electrolytic tank 2 that causes an electrolytic deposition reaction, a buffer tank 3 that receives an electrolytic solution overflowing from the electrolytic tank 2, a liquid circulation line 4 that connects the electrolytic tank 2 and the buffer tank 3, and a liquid circulation A pump 5 inserted in the line 4, a microbubble generation / mixing unit 6, and a microbubble stirring unit 7 are provided. In the electrolytic cell 2, a substrate W on which deposition is performed by an electrolytic deposition reaction, an electrode 21 functioning as a counter electrode (hereinafter referred to as counter electrode 21), and an electrode 22 functioning as a reference electrode (hereinafter referred to as reference electrode 22). Is installed.

  The electrolytic tank 2 is a tank in which electrolytic deposition is performed, and an electrolytic solution is stored therein. This electrolytic solution is a medium that conducts ions during the electrolytic deposition reaction, and is composed of a solution in which an electrolyte is dissolved in a solvent. For example, when electrolytically depositing zinc oxide, an aqueous solution in which a zinc salt is dissolved in water is employed as the electrolytic solution. Examples of zinc salts that can be used include zinc halides such as zinc chloride, zinc bromide, and zinc iodide, zinc nitrate, and zinc perchlorate. In addition, potassium hydroxide may be included for pH adjustment in order to optimize the electrolytic deposition reaction conditions, and a pH buffer solution may be included to maintain the pH.

  The substrate W placed in the electrolytic cell 2 functions as a cathode in the electrolytic deposition reaction, and is connected to the power supply device 9. The power supply device 9 mainly functions as a power supply for applying a voltage, but also has a current measurement function, a voltage measurement function, and the like. As the substrate W, for example, a glass substrate or a film substrate is used. Indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or the like is uniformly applied as a transparent conductive film on the surface FS of these substrates W (hereinafter also referred to as “deposited surface FS”). On the other hand, no transparent conductive film is formed on the back surface RS of the substrate W.

  The counter electrode 21 functions as an anode in the electrolytic deposition reaction, and is connected to the power supply device 9 similarly to the substrate W. A platinum electrode or the like is used for the counter electrode 21.

  The substrate W and the counter electrode 21 are placed in the electrolytic cell 2 such that the surfaces of the substrate W and the counter electrode 21 are substantially along the vertical direction, and the surface FS of the substrate W on which the transparent conductive film is formed and the surface of the counter electrode 21 face each other. ing. The substrate W can be held in the vertical position in the electrolytic cell 2 using a predetermined substrate holding member (not shown). For example, the substrate holding member may be formed so as to detachably hold two side portions opposed to each other in the vertically oriented substrate W with a groove. The illustrated example is a single-wafer type apparatus that processes the substrates W one by one. However, in the case of a batch-type apparatus that simultaneously processes a plurality of substrates, a plurality of vertical substrates are spaced apart from each other. It is also possible to use a frame-like member that is aligned and held at a distance. In any case, electrolytic deposition occurs only on the conductive surface (surface FS on which the transparent conductive film is formed). When a voltage is applied from the power supply device 9, an oxidation-reduction reaction of a substance in the electrolytic solution occurs between the substrate W and the counter electrode 21. The current generated at this time can be measured by the current measurement function of the power supply device 9. The substrate W functions as a working electrode, and a metal oxide (for example, zinc oxide ZnO) present in the electrolytic solution is deposited on the surface FS of the substrate W on which the transparent conductive film is formed by the electrolytic deposition reaction.

  As the reference electrode 22, a silver / silver chloride electrode or the like is used. The reference electrode 22 is installed above the counter electrode 21 with the surface in a direction substantially along the vertical direction, and the reference electrode 22 is connected to the power supply device 9. That is, the power supply device 9 measures the potential between the substrate W as the working electrode and the reference electrode 22 with the potential of the reference electrode 22 as a reference, and sets the potential between the substrate W and the counter electrode 21 so that the potential falls within a predetermined range. A voltage is applied between them.

  A buffer tank 3 is installed next to the electrolytic tank 2, and the electrolytic solution overflowing and overflowing from the electrolytic tank 2 flows into the buffer tank 3. The lower surface of the buffer tank 3 and the lower surface of the electrolytic cell 2 are connected by a liquid circulation line 4 (return path). Since the liquid circulation line 4 is provided with a pump 5, the electrolyte flowing into the buffer tank 3 from the electrolytic tank 2 due to overflow is driven by the pump 5 so that the liquid P 4, the pipe P 2, and the pipe of the liquid circulation line 4 are driven. It is supplied again to the electrolytic cell 2 through P3. Thus, the electrolytic solution circulates in the electrolytic deposition apparatus 1 from the electrolytic cell 2 to the electrolytic cell 2 again via the buffer tank 3 and the liquid circulation line 4. Therefore, at the start of the electrolytic deposition process, the buffer tank 3 is supplied from a supply nozzle 99 connected to an electrolyte supply source (not shown) such as an electrolyte storage tank provided above the buffer tank 3. By supplying the stock solution of the electrolytic solution, the electrolytic solution can be supplied into the electrolytic deposition apparatus 1.

  The pump 5 is connected to the control unit 8, and the control unit 8 includes a speed switch 81. The controller 8 sets the flow rate in the liquid circulation line 4 with respect to the number of rotations of the pump 5 and the thickness of the film deposited on the surface FS of the substrate W after a predetermined time has elapsed with respect to the flow rate in the liquid circulation line 4. Has been. Therefore, by changing the speed switch 81 and changing the rotational speed of the pump 5 to a predetermined value, not only the flow rate of the electrolytic solution flowing in the liquid circulation line 4 but also the flow rate of the electrolytic solution flowing in the electrolytic cell 2 is changed. be able to. For this reason, it is possible to change the deposition rate of the substance to a desired value, whereby the thickness of the substance deposited on the surface FS of the substrate W per unit time can be changed according to the situation.

  The liquid circulation line 4 is further provided with a microbubble generation / mixing unit 6. The microbubble generation / mixing unit 6 and the pump 5 are connected by a pipe P <b> 2, and the microbubble generation / mixing unit 6 is provided on the downstream side of the pump 5. The electrolytic cell 2 and the microbubble generation / mixing unit 6 are connected by a microbubble stirring unit 7 which is a pipe P3 having a predetermined length. The length of the pipe P3 depends on the liquid flow and the inner diameter of the pipe P3, but is, for example, 50% to 200% of the length of the substrate W (the length in the Z-axis direction that is the direction of the liquid flow in the electrolytic cell 2). %. As a specific numerical example, for example, about 30 to 50 cm is an example of the range of the length of the pipe P3.

  FIG. 2 is a schematic cross-sectional view of the microbubble generation / mixing unit 6 and the microbubble stirring unit 7. As shown in FIG. 2, the microbubble generation / mixing unit 6 has a channel cross-sectional area perpendicular to the traveling direction ((+ Z) direction) of the electrolyte flow (solid arrow in FIG. 2) in the liquid circulation line 4. The throttle part 61 smaller than the flow path cross-sectional area, the throttle part 61 and the microbubble agitation part 7 are connected, the mixing part 62 in which the microbubbles SB are mixed in the electrolyte, and the side surface of the throttle part 61. The gas supply line 63 supplies gas to the throttle unit 61. The gas supply line 63 is provided with a valve and a flow meter (not shown). The gas (dotted arrow in FIG. 2) supplied into the throttle part 61 from the gas supply line 63 is introduced by using a gas supply source 100 such as a gas cylinder or a compressor. By adjusting the gas supply pressure from the gas supply source 100 using a valve or a flow meter, the gas-liquid ratio in the throttle unit 61 can be arbitrarily set.

  The principle that the microbubbles SB are generated in the microbubble generation / mixing unit 6 will be described. The microbubble SB here means a bubble having a diameter of 1 mm or less and existing in the electrolytic solution. As described above, the flow path cross-sectional area from the inlet 611 to the outlet 612 of the throttle part 61 is smaller than the flow path cross-sectional area in the pipe P2 of the liquid circulation line 4 through which the electrolytic solution has flowed. For this reason, the flow rate of the electrolytic solution flowing in the inlet side pipe P <b> 2 is higher in the throttle portion 61 than in the pipe P <b> 2. The air current from the gas supply source 100 is supplied into the electrolyte flowing in the throttle unit 61 via the gas supply line 63, so that the air flow is divided and into the electrolyte in the throttle unit 61. A relatively large bubble NB is generated. When the electrolytic solution having the bubbles NB flows from the restricting portion 61 into the mixing portion 62 having a larger flow path cross-sectional area than the restricting portion 61, a swirling flow whose axis is the flow direction is generated. By such a swirl flow, the bubbles NB are sheared, and microbubbles SB are generated in the swirl flow.

  The generated electrolytic solution having the microbubbles SB is sent to the microbubble stirring unit 7. The microbubble agitation unit 7 is a pipe P3 constituting the liquid circulation line 4 and is provided between the microbubble generation and mixing unit 6 and the electrolytic cell 2, and connects the mixing unit 62 to the electrolytic cell 2. Have a predetermined length.

  The microbubbles SB and the electrolyte are mixed more positively and stirred by the flow pressure of the swirling flow that flows in the pipe P3 that is the microbubble stirring section 7. In addition, since the total surface area of the bubbles occupying per unit volume increases as the size of the bubbles decreases, the gas supplied into the electrolyte solution has a contact area with the electrolyte solution by using the microbubbles SB. Can be larger. Therefore, in the microbubble stirring unit 7, the microbubble SB is dissolved in the electrolytic solution, and the dissolved concentration is increased to a saturated state. In this way, a gas-excess electrolytic solution in which the gas used as the material for electrolytic deposition is saturated in the microbubble stirring unit 7 and also has the gas microbubbles SB is generated and sent to the electrolytic cell 2. . Note that the saturated state here means that the partial pressure ratio (= partial pressure of the gas / total pressure of the mixed gas) of the gas used as the material for electrolytic deposition is 1 or higher than the solubility determined at a predetermined temperature. Is defined as a state in which the gas is dissolved in the liquid. Therefore, the term “saturation” in this specification means not only a state in which an amount of gas corresponding to the solubility is dissolved in the liquid (narrowly “saturation” or “pure saturation”), but also generally “supersaturation”. In other words, a state where the gas is dissolved in the liquid in excess of the solubility is also included. The electrolyte in the present invention is not only saturated and dissolved in the gas in the solution, but also has gas phase microbubbles, so the gas dissolves beyond the theoretical solubility. In order to distinguish it from the “supersaturated” state, it is called “excess gas (electrolyte)”.

  The excess gas electrolyte fed toward the electrolytic cell 2 is supplied into the electrolytic cell 2 from the lower surface of the electrolytic cell 2 through the supply port 78 as shown in FIG. At this time, the supply port 78 is located between the substrate W and the counter electrode 21 along the X-axis direction. Therefore, the jet of the gas excess electrolyte supplied into the electrolytic cell 2 is longitudinally ((+ Z) direction), that is, on the surface FS on which the transparent conductive film of the substrate W placed in the electrolytic cell 2 is formed. It flows in the direction along. The excess gas electrolyte supplied to the electrolytic cell 2 eventually overflows from the upper end of the electrolytic cell 2 to the buffer tank 3. Accordingly, a steady flow of excess gas electrolyte is formed in the electrolytic cell 2 from the bottom to the top.

  In the supply port 78, a diffusion portion 70 (FIG. 1) that makes the gas excess electrolyte flow rate distribution along the surface FS of the substrate W substantially uniform by diffusing the gas excess electrolyte into the electrolytic cell 2. In the figure, a diffusion nozzle 72 is provided. 3 and 4 are schematic cross-sectional views showing examples of the diffusion nozzle 72, respectively. The diffusion nozzle 72a shown in FIG. 3 has a slit-like shape in which the discharge port 73 of the diffusion nozzle 72a is thin in the X-axis direction (the direction perpendicular to the surface of the substrate W) and elongated in the Y-axis direction (the lateral width direction of the substrate W). The longitudinal direction of the slit opening is substantially parallel to the surface FS of the substrate W placed in the electrolytic cell 2. Accordingly, the diffusion nozzle 72 a has a divergent shape in which the supply port 78 and the discharge port 73 having a slit shape are connected and the diameter is increased toward the discharge port 73. In this diffusion nozzle 72a, a baffle plate 721 is provided at a position for directly receiving the excess gas electrolyte from the microbubble stirring section 7, and the baffle plate 722 is symmetrically positioned on both sides with the baffle plate 721 as a center. is set up. In FIG. 3, rectifying plates 722 provided in order from the inside around the baffle plate 721 are referred to as rectifying plates 722a to 722c, and the arrangement intervals of the rectifying plates 722a to 722c, that is, the intervals of the flow paths of the gas excess electrolyte solution are T1 to T4. And At this time, T1 is the minimum, T4 is the maximum, and the rectifying plates 722a to 722c are installed so that the interval gradually increases from T1 to T4. The liquid flow of the gas excess electrolyte supplied from the microbubble stirring unit 7 collides with the baffle plate 721, so that the pressure flowing in the straight direction is weakened and the flow toward the outside in the diffusion nozzle 72a is generated. Although the pressure of the liquid flow tends to be weakened toward the outer side of the diffusion nozzle 72a, since the rectifying plates 722a to 722c are installed so that the intervals become wider toward the outer side, the pressure loss becomes smaller and finally from the discharge port 73. The electrolytic solution discharged into the electrolytic cell 2 forms a flow along the deposition surface FS of the substrate W with a substantially constant flow velocity distribution. Such a diffusion nozzle 72a is preferably used in a single wafer processing system in which only one substrate W is held in the electrolytic cell 2 because the discharge port 73 has a slit shape.

  The diffusion nozzle 72 may have a shape as shown in FIG. The diffusion nozzle 72 b shown in FIG. 4 is hemispherical and is installed in the electrolytic cell 2. A plurality of ejection holes 725 are distributed and distributed in the hemispherical portion of the diffusion nozzle 72b, and the excess gas electrolyte fed from the microbubble stirring unit 7 is contained in the electrolytic cell 2 from the plurality of ejection holes 725. It is ejected in the shape of a shower. The gas excess electrolyte solution ejected from each ejection hole 725 is supplied in all directions without being biased to the entire electrolytic cell 2 because the ejection pressure is equal. As a result, a flow of excess gas electrolyte along the deposition surface FS of the substrate W is formed in the electrolytic cell 2 with a substantially constant flow velocity distribution. Such a diffusion nozzle 72b is particularly effective in a batch processing method in which a plurality of substrates W are held in the electrolytic cell 2.

  As described above, the gas excess electrolytic solution fed from the microbubble stirring unit 7 is supplied into the electrolytic cell 2 through the diffusion nozzle 72, so that the flow velocity distribution is substantially constant and the electrodeposited surface FS of the substrate W. Is formed in the electrolytic cell 2 in the Z-axis direction of the gas excess electrolyte along The excess gas electrolyte overflowed from the electrolytic cell 2 flows into and is stored in the buffer tank 3 and is supplied again from the liquid circulation line 4 to the electrolytic cell 2.

  Subsequently, the case where zinc oxide is deposited on the electrodeposited surface FS of the substrate W in the electrolytic deposition apparatus 1 according to the present embodiment will be described more specifically.

  The electrolytic solution in which zinc salt is dissolved, which is pumped by driving the pump 5 in the liquid circulation line 4, and the oxygen supplied from the air compressor as the gas supply source 100 through the gas supply line 63 generate microbubbles. It is sent to the mixing part 6. The swirl flow generated in the microbubble generation / mixing unit 6 shears the oxygen bubbles NB and generates microbubbles SB. The generated microbubbles SB and the electrolytic solution are mixed by the swirling flow pressure in the microbubble stirring unit 7 which is the pipe P3, and the microbubbles SB are dissolved in the electrolytic solution. In this way, an oxygen-excess electrolyte in which the dissolved oxygen concentration is saturated and the oxygen microbubbles SB are present in the liquid is generated in the microbubble stirring unit 7 and supplied into the electrolytic cell 2. Since the oxygen-excess electrolytic solution is supplied from the lower surface of the electrolytic cell 2 into the electrolytic cell 2 through the diffusion nozzle 72, a liquid flow having a substantially uniform flow velocity distribution is formed in the electrolytic cell 2 from below to above. Is done. As described above, after a liquid flow is formed in the electrolytic cell 2, a voltage is applied between the substrate W as the electrodeposited material and the counter electrode 21.

When a voltage is applied, the reduction reaction shown in (1) occurs near the surface FS of the substrate W in the oxygen-excess electrolyte, and oxygen is reduced to generate hydroxide ions. Due to the presence of the hydroxide ions, the pH in the vicinity of the surface FS of the substrate W increases. As a result, as shown in (2) in the vicinity of the substrate W, zinc hydroxide (Zn (OH) ₂ ) is generated by zinc ions and hydroxide ions, and finally by the reaction shown in (3). Then, zinc oxide (ZnO) is deposited on the transparent conductive film formed on the surface FS of the substrate W.
O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (1)
Zn ²⁺ + 2OH ⁻ → Zn (OH) ₂ (2)
Zn (OH) ₂ → ZnO + H ₂ O (3)

  Such electrolytic deposition reaction is performed in an oxygen-excess electrolytic solution in which the dissolved oxygen concentration is saturated in the electrolytic cell 2 and also has oxygen microbubbles SB. Since the dissolved oxygen concentration is in a saturated state, the above-described zinc oxide formation reaction is likely to proceed, and the reaction rate is increased. Moreover, even if the dissolved oxygen in the oxygen-excess electrolyte is consumed by the zinc oxide formation reaction, the dissolved oxygen concentration can always be kept saturated because the oxygen microbubbles SB are dissolved in the solution. Accordingly, since the dissolved oxygen concentration can be kept saturated from the upper layer to the lower layer of the electrolytic cell 2, the film thickness of the zinc oxide deposited on the surface of the substrate W is formed uniformly.

  In addition, since the microbubbles SB are used, the total surface area where the gas supplied in the electrolyte solution comes into contact with the electrolyte solution is increased, and the microbubbles SB and the electrolyte solution are generated by the swirling flow pressure in the microbubble stirring unit 7. Are positively mixed and stirred, so that the microbubbles SB are efficiently dissolved in the electrolytic solution and become saturated. Therefore, since the amount of oxygen released into the atmosphere without dissolving in the liquid is reduced, the amount of oxygen used can be reduced.

  In addition, the liquid flow of the oxygen-excess electrolyte formed in the electrolytic cell 2 flows along the surface FS of the substrate W on which the transparent conductive film is formed, and always overflows after passing through the surface of the substrate W. It flows into the tank 3. Accordingly, since the vicinity of the surface FS of the substrate W is stirred by the liquid flow, the deposition rate is improved. Further, the output of the pump 5 provided in the liquid circulation line 4 can be changed by switching the speed switch 81. Accordingly, not only the flow rate of the electrolyte flowing in the liquid circulation line 4 but also the flow rate of the liquid flow in the electrolytic cell 2 can be changed. That is, the deposition rate of zinc oxide can be changed. For this reason, when it is desired to reduce the film thickness of zinc oxide deposited per unit time, the output of the pump 5 is lowered to slow the flow rate, and when it is desired to increase the film thickness, the output of the pump 5 is increased to increase the flow rate. For example, the film thickness can be freely changed by variably controlling the flow rate. Further, the substrate W may be cracked or the transparent conductive film may be peeled off from the substrate W due to stress generated when the substance is deposited. In order to prevent such cracking of the substrate W and peeling of the transparent conductive film, the deposition rate can be changed, and the deposition rate can be set to a desired value without being excessively increased.

  Further, since the liquid flow in the electrolytic cell 2 is formed by the jet of the oxygen-excess electrolytic solution supplied to the electrolytic cell 2, it is not necessary to install a special device for forming the liquid flow, and the liquid circulation Since the flow rate of the liquid flow can be changed by changing the output of the pump 5 provided in the line 4, it is not necessary to provide a separate device for changing the liquid flow in the electrolytic cell 2. That is, the device configuration can be simplified.

  Further, since the diffusion nozzle 72 is installed at the supply port 78 to the electrolytic cell 2, an uneven liquid flow is prevented in the electrolytic cell 2, and the oxygen-excess electrolytic solution on the electrodeposited surface FS of the substrate W is prevented. The flow velocity distribution can be leveled. Therefore, the uniformity of the zinc oxide deposited on the surface FS of the substrate W is greatly improved, and the color unevenness when the zinc oxide is peeled off or the sensitizing dye is applied can be suppressed.

  Then, the modification of the electrolytic deposition apparatus 1 which concerns on embodiment of this invention is demonstrated.

  In the said embodiment, although the zinc oxide was taken out as an example and demonstrated as a substance deposited by an electrolytic deposition reaction, it is not restricted to this. The type of substance to be electrodeposited is not limited as long as it is porous and can be deposited by an electrolytic deposition reaction.

  Moreover, in the said embodiment, gas excess electrolyte solution is supplied into the electrolytic cell 2 from the lower surface of the electrolytic cell 2 via the supply port 78, and the board | substrate W of the board | substrate W goes upwards from the downward direction of the electrolytic cell 2. Although the liquid flow is formed in the direction along the surface FS, it is not limited to such a form. The liquid flow of the excess gas electrolyte may be supplied from the side of the substrate W as long as it is in the direction along the surface FS of the substrate W. That is, the form in which the supply port 78 of the gas excess electrolyte solution to the electrolytic cell 2 is provided on the side surface of the electrolytic cell 2 may be used. Further, if the liquid flow of the gas excess electrolyte flows in the direction along the surface FS of the substrate W, the supply port 78 may be provided on both the lower surface and the side surface of the electrolytic cell 2. That is, the flow path of the gas excess electrolyte after passing through the microbubble stirring unit 7 is branched, one at the lower surface supply port provided on the lower surface of the electrolytic cell 2 and the other at the side surface of the electrolytic cell 2. It may be in a form connected to the side supply port. Even when the size of the substrate W is increased by such a combination, the liquid flow of the excess gas electrolyte flows along the surface FS of the substrate W without being biased, so that the vicinity of the surface FS of the substrate W is substantially uniform. The film thickness can be uniformly formed.

  Moreover, in the said embodiment, although the microbubble production | generation mixing part 6 produced the microbubble SB by shearing the bubble NB in a swirl flow, it is not restricted to such a form. Any mechanism may be adopted as long as microbubbles SB having a size according to the definition in the present specification are generated.

  Moreover, in the said embodiment, although the board | substrate W becomes the attitude | position in which the to-be-deposited surface FS follows a perpendicular direction, it is not restricted to this. As for the mounting posture of the substrate W in the electrolytic cell 2, for example, the electrodeposition surface FS may be installed in a substantially horizontal direction or an oblique direction. As long as the liquid flow flows along the deposition surface FS of the substrate W, the mounting posture of the substrate W in the electrolytic cell 2 may be any posture.

  In the above embodiment, the flow rate of the steady flow in the electrolytic cell 2 as well as the flow rate of the electrolyte flowing in the liquid circulation line 4 is changed by changing the operating speed of the pump 5 provided in the liquid circulation line 4. However, the present invention is not limited to such a form. For example, a pump for forming a steady flow of the gas excess electrolyte in the electrolytic cell 2 may be provided, and the flow rate of the steady flow may be changed by changing the operating speed of the pump. . Moreover, the valve which can be opened and closed is provided in the supply port 78, and the form which adjusts the opening degree of a valve and changes the flow velocity of a steady flow may be sufficient. Thus, as long as the flow rate of the steady flow of the excess gas electrolyte in the electrolytic cell 2 can be changed, the position and form in which the flow rate changing means is provided are not limited.

  Moreover, in the said embodiment, although the board | substrate W was the single wafer processing system processed one by one in the electrolytic cell 2, it is not restricted to such a form. A batch processing method in which a plurality of substrates W are placed in the electrolytic cell 2 to cause an electrolytic deposition reaction may be employed.

  Moreover, in the said embodiment, although the mechanism by which the undiluted | stock solution of electrolyte solution is supplied in the buffer tank 3 from the supply nozzle 99 from the electrolyte supply source which is not illustrated is described, it is not restricted to such a form. . For example, a mechanism for supplying an undiluted electrolyte solution may be provided in the pipe P <b> 1 of the liquid circulation line 4 inserted between the buffer tank 3 and the pump 5. By using the electrolytic solution supply mechanism provided in the pipe P1, the electrolytic solution stock solution may be additionally supplied during the electrolytic deposition process.

DESCRIPTION OF SYMBOLS 1 Electrolytic deposition apparatus 2 Electrolytic tank 3 Buffer tank 4 Liquid circulation line 5 Pump 6 Microbubble production | generation mixing part 7 Microbubble stirring part 61 Restriction part 62 Mixing part 72 Diffusion nozzle W Substrate SB Microbubble

Claims (11)

An electrolytic deposition apparatus that deposits a predetermined substance on the surface of an electrodeposit using an electrochemical reaction,
An electrolytic solution supply means for supplying an electrolytic solution into the electrolytic cell containing the deposition object;
A voltage applying means for applying a voltage between the electrodeposition and the electrode, with the electrode disposed in the electrolytic cell and the electrodeposition being immersed in the electrolytic solution;
With
The electrolytic solution supply means is a gas that generates a gas-excess electrolytic solution in which a gas that is a material for electrolytic deposition dissolves in a saturated state and also has micro bubbles of the gas, as the electrolytic solution supplied to the electrolytic cell. Excess electrolyte generation means,
An electrolytic deposition apparatus comprising: The electrolytic deposition apparatus according to claim 1,
The gas excess electrolyte production means is
A mixing unit for generating a gas-liquid mixture by mixing the gas microbubbles in the electrolyte; and
By interposing between the mixing part and the electrolytic cell, and causing the gas-liquid mixture to be stirred, the contact area between the gas and the electrolytic solution is increased, and the gas excess electrolytic solution is A stirring unit to be generated;
An electrolytic deposition apparatus comprising: The electrolytic deposition apparatus according to claim 2,
The stirring unit is
A line for stirring the gas-liquid mixture by the flow pressure of the gas-liquid mixture itself while passing the gas-liquid mixture over a predetermined length, thereby generating the gas excess electrolyte,
The electrolytic deposition apparatus characterized by having. The electrolytic deposition apparatus according to any one of claims 1 to 3,
In the electrolytic cell, a steady flow of the excess gas electrolyte formed between the supply portion of the excess gas electrolyte to the electrolyte cell and the discharge portion of the excess electrolyte solution from the electrolyte bath. The electrolytic deposition apparatus is characterized in that electrolytic deposition is performed on the electrodeposits. The electrolytic deposition apparatus according to claim 4,
The electrolytic deposition apparatus characterized in that the steady flow is formed in a direction along an electrodeposited surface of the electrodeposited material held in the electrolytic cell. The electrolytic deposition apparatus according to claim 4 or 5,
The supply unit
An inlet for introducing the gas excess electrolyte supplied from the electrolyte supply means into the electrolytic cell;
A diffusion member for spatially diffusing a jet of the gas excess electrolyte ejected from the inlet and leveling a flow velocity distribution of the gas excess electrolyte on the electrodeposition surface;
An electrolytic deposition apparatus comprising: The electrolytic deposition apparatus according to any one of claims 4 to 6,
A flow rate changing means for changing the flow rate of the steady flow;
An electrolytic deposition apparatus further comprising: The electrolytic deposition apparatus according to claim 7,
A return path for returning the used electrolyte discharged from the electrolytic cell to the electrolyte supply means;
Further comprising
The flow rate changing means is
Operating speed changing means for changing the operating speed of the pump inserted in the return path;
An electrolytic deposition apparatus comprising: An electrolytic deposition method in which a predetermined substance is deposited on an electrodeposit using an electrochemical reaction in an electrolyte solution,
The substance is obtained by applying a voltage between an electrodeposition electrode and an electrodeposited electrode that is immersed in a gas-excess electrolytic solution having a saturated gas concentration as a material for electrolytic deposition and having gas microbubbles. An electrolytic deposition method characterized by depositing a metal. The electrolytic deposition method according to claim 9, comprising:
An electrolytic deposition method comprising performing electrolytic deposition while generating a liquid flow of the gas-excess electrolyte along the surface of the electrodeposit. The electrolytic deposition method according to claim 10, comprising:
An electrolytic deposition method characterized by changing a flow rate of the flow of the gas-excess electrolyte according to a desired deposition rate of the substance deposited on the electrodeposit.

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