JP2011166006A - Etching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching method capable of maintaining an appropriate concentration of an indium ion, in particular, out of an indium ion and a tin ion included in an etchant. <P>SOLUTION: The etching method comprises an etching step of supplying and ejecting the etchant L stored in a storage vessel 11 storing the etchant L including an oxalic acid from nozzle members 16, 17 for etching a substrate K formed with an indium tin oxide film and collecting the etchant L ejected from the nozzle members 16, 17 into the storage vessel 11, and a metal removing step of making the etchant L stored in the storage vessel 11 pass through adsorption container 32, 33 filled with a chelating agent for adsorbing and removing the indium ion and the tin ion included in the etchant L by etching and returning them back into the storage vessel 11. The indium ion concentration of the etchant L stored in the storage vessel 11 is maintained at 260 ppm or lower. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an etching method for etching a substrate on which an indium tin oxide film is formed using an etching solution containing oxalic acid.

  In the process of manufacturing various substrates such as a semiconductor wafer, a liquid crystal glass substrate, a photomask glass substrate, and an optical disk substrate, there is a step of etching these substrates with an etching solution.

  Conventionally, as an etching apparatus for performing such a process, for example, an apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-96264 is known. The etching apparatus includes a storage tank that stores an etching solution, an etching mechanism that etches the substrate with the etching solution, and supplies the etching solution in the storage tank to the etching mechanism, and collects the supplied etching solution in the storage tank. And an etching circulation mechanism for circulating an etching solution between the storage tank and the etching mechanism.

  The etching mechanism includes a processing chamber, a plurality of transport rollers that are disposed in the processing chamber and transports the substrate, and a plurality of nozzle bodies that are disposed in the processing chamber and discharge an etching solution toward the upper surface of the substrate. The etching circulation mechanism includes a supply pipe that connects the storage tank and each nozzle body, a supply pump that supplies an etching solution to each nozzle body via the supply pipe, a bottom of the processing chamber, and the storage tank And a recovery pipe connecting the two.

  And in this etching apparatus, the etching liquid in the storage tank supplied to each nozzle body is discharged toward the upper surface of the board | substrate conveyed with a conveyance roller, and a board | substrate is etched with the discharged etching liquid. Moreover, the etching liquid discharged on the upper surface of the substrate is recovered in the storage tank by the recovery tube.

  By the way, when the board | substrate used as an etching object is a board | substrate with which the indium tin oxide film was formed in the upper surface, for example, when the said board | substrate is etched, the indium and tin which comprise this indium tin oxide film will melt | dissolve in etching liquid. For this reason, in the said etching apparatus which circulates and uses etching liquid, the density | concentration of the indium and tin (indium ion and tin ion) which are contained in the etching liquid in a storage tank rises gradually, and the etching rate falls In addition, there arises a problem that the substrate cannot be etched with high accuracy.

  Therefore, in the above etching apparatus, the etching solution in the storage tank must be periodically replaced, and the cost for the replacement of the etching solution (disposal cost of used etching solution and purchase cost of new etching solution). Increases the processing cost. Further, the etching apparatus cannot be operated during the exchanging operation of the etching solution, which also increases the processing cost.

  Therefore, the applicant of the present application has proposed an etching apparatus in which indium ions and tin ions are removed from the etching solution and the etching solution can be regenerated (see Japanese Patent Application Laid-Open No. 2008-252049). In addition to the above configuration, this etching apparatus has an adsorption tower filled with a chelating agent that adsorbs indium ions and tin ions, and an etching solution in a storage tank is passed through the adsorption tower, and etching after the passage is performed. A removal circulation mechanism is further provided for recirculating the liquid into the storage tank and circulating the etching liquid between the storage tank and the adsorption tower.

  In such an etching apparatus, when the etching solution circulates between the storage tank and the adsorption tower, indium ions and tin ions in the etching liquid are adsorbed and removed by the chelating agent of the adsorption tower. Since the increase in the concentration of indium ions and tin ions contained in the etching solution can be suppressed, the above-described problem can be prevented.

JP 2000-96264 A JP 2008-252049 A

  However, the inventors of the present application have made extensive studies, and even when the etching solution is circulated between the storage tank and the adsorption tower to adsorb and remove indium ions and tin ions contained in the etching solution, In particular, it has been found that the concentration of indium ions must be controlled to an appropriate concentration. This is because when the concentration of indium ions exceeds a certain level, indium in the etching solution and oxalic acid in the etching solution are combined and crystallized as indium oxalate.

  This crystallization is unlikely to occur in a portion that is constantly wet by the etching solution. For example, a chamber (adjacent chamber) adjacent to the processing chamber into which the etching solution is discharged and the inner space communicating with the inner space of the processing chamber. Indium oxalate is deposited by the inner wall of the substrate, the substrate transfer roller disposed in the adjacent chamber, the shutter for opening and closing the substrate carry-in port or the substrate carry-out port of the processing chamber, and the like. More specifically, when the shutter is opened when the substrate is loaded or unloaded, a mist-like etching solution flows from the processing chamber into the adjacent chamber via the substrate loading port or the substrate loading port, and the inner wall and the substrate are transferred. Moisture in the adhering etchant that adheres to the rollers and shutters is likely to evaporate in the adjacent chamber because the etchant is not discharged as in the processing chamber, and when the water evaporates, indium in the etchant The concentration of ions increases and supersaturated indium is precipitated as indium oxalate. Further, once indium oxalate is precipitated, crystals grow using this as a nucleus.

  When indium oxalate crystallizes in this manner, the substrate is damaged by the crystals adhering to the substrate transport roller, or the shutter malfunctions. In addition, when indium oxalate crystals fall into the etching solution collected in the storage tank, the crystals circulate together with the etching solution, which may cause clogging of a filter that removes impurities such as dust from the circulating etching solution. In order to prevent such a problem, it is sufficient to remove crystals attached to the inner wall, the substrate transfer roller and the shutter, or to replace the filter. However, such maintenance work should be performed periodically. Then, the operating efficiency of the etching apparatus decreases. Note that indium oxalate crystals, unlike simple oxalic acid crystals, are difficult to dissolve even when dropped into the etchant, and thus are included in the etchant as crystals.

  Thus, even when indium ions and tin ions are adsorbed and removed from the etching solution by the chelating agent, it is necessary to manage the concentration of indium ions at an appropriate concentration.

  The present invention has been made as a result of intensive studies by the inventors of the present invention, and an etching method capable of maintaining the concentration of indium ions and tin ions, particularly indium ions, contained in an etching solution at an appropriate concentration. The purpose is to provide

To achieve the above object, the present invention provides:
A substrate on which an indium tin oxide film is formed by supplying the etching liquid from a storage tank in which an etching liquid containing oxalic acid is stored to a nozzle body disposed in the processing chamber, and the etching liquid discharged from the nozzle body And etching step for recovering the discharged etching solution from the processing chamber into the storage tank,
The etching solution stored in the storage tank is passed through an adsorption vessel filled with a chelating agent that adsorbs indium ions and tin ions, and indium ions and tin ions that are included in the etching solution by etching. And a metal removal step of refluxing the etching solution in which the indium ions and tin ions are adsorbed and removed into the storage tank.
An etching method characterized in that in the metal removal step, indium ions and tin ions are adsorbed and removed so that the concentration of indium ions in the etching solution stored in the storage tank is maintained at 260 ppm or less. Related.

  According to this etching method, when etching the substrate on which the indium tin oxide film is formed with the etching solution containing oxalic acid, the etching step is performed by discharging the nozzle from the nozzle body while circulating the etching solution in the storage tank. And a metal removal step of adsorbing and removing indium ions and tin ions in the etching solution with a chelating agent in the adsorption vessel while circulating the etching solution in the storage vessel. In the metal removal step, Indium ions and tin ions are adsorbed and removed so that the concentration of indium ions contained in the etching solution is maintained at 260 ppm or less.

  As described above, in particular, in the case of indium ions, when the concentration exceeds a certain level, for example, a chamber (adjacent to the processing chamber in which the etching solution is discharged and adjacent to the internal space of the processing chamber). Indium oxalate is crystallized by the inner wall of the chamber), the substrate transport roller disposed in the adjacent chamber, the shutter for opening and closing the substrate carry-in port or the substrate carry-out port of the processing chamber, and the crystal adhering to the substrate transport roller. Impurities such as dust are circulated from the circulating etchant by the indium oxalate crystals that are damaged by the substrate, cause the shutter to malfunction, or fall into the etchant recovered in the storage tank. The problem of clogging the filter to be removed occurs, and in order to prevent such a problem, the inner wall, Or to remove the crystals adhered like a plate carrying roller and the shutter, when so as to replace the filter, the processing efficiency of the etching is reduced for such maintenance work.

  Therefore, as a result of repeating various experiments, the present inventors have found that if the concentration (mass concentration) of indium ions is 260 ppm or less, indium oxalate does not precipitate on the inner wall, the substrate transfer roller, the shutter, and the like. Obtained.

  Therefore, in the present invention, indium ions and tin ions are removed so that the concentration of indium ions contained in the etching solution in the storage tank is maintained at 260 ppm or less. Thereby, precipitation of indium oxalate can be reliably prevented. For this reason, indium oxalate crystals that are damaged by the crystals attached to the substrate transport roller, cause malfunction of the shutter, or fall into the etching solution collected in the storage tank. This eliminates the problem of clogging the filter that removes impurities such as dust from the circulating etching solution, and eliminates the need for maintenance such as removal of crystals adhering to the inner wall, substrate transfer roller and shutter, and filter replacement. .

  In order to maintain the indium ion concentration at 260 ppm or less, the etching solution in the storage tank may be constantly passed through the adsorption container, or the etching solution in the storage tank may be passed through the adsorption container. When the indium ion concentration decreases, the liquid flow into the adsorption container may be temporarily stopped, and the liquid flow method into the adsorption container is not limited at all.

  In addition, chelating agents generally have the property that the higher the equilibrium concentration, the greater the amount of equilibrium adsorption. If the equilibrium concentration and the equilibrium adsorption amount are described in terms of adsorption of indium ions, the equilibrium concentration is the adsorption vessel. It corresponds to the concentration of indium ions in the etching solution to be passed through, and the equilibrium adsorption amount corresponds to the maximum amount of indium adsorbed by the chelating agent per unit weight.

  Therefore, the higher the indium ion concentration of the etching solution that is passed through the adsorption vessel, the more indium ions can be adsorbed to the chelating agent than when the etching solution is low, and the indium ions adsorbed to the chelating agent reach a saturated state. The number of processed substrates can be increased. From such a point of view, it is preferable that the concentration of indium ions contained in the etching solution in the storage tank be as high as possible within a range of 260 ppm or less in which no crystal is generated. However, if the concentration of indium ions is 100 ppm or more, the number of substrates processed until the indium ions adsorbed by the chelating agent reach a saturated state can be secured at a certain level or more, and the economic efficiency is not impaired.

  Further, in the metal removal step, at least two of the adsorption containers are used, an etching solution is selectively passed through any one of these adsorption vessels, and the etching solution after passing is stored in the reservoir. You may make it reflux in a tank. In this case, the adsorption capacity of the chelating agent is kept constant by switching the adsorption container to which the etching solution is supplied, for example, when it is determined that the indium ions and / or tin ions adsorbed to the chelating agent have reached a substantially saturated state. Can be maintained. Note that the chelating agent in the adsorption container whose supply of the etching liquid is switched by switching the adsorption container to which the etching liquid is supplied is appropriately regenerated using an eluent that elutes the indium and tin adsorbed thereto. .

  As described above, crystallization of indium oxalate is unlikely to occur in a portion that is constantly wet by the etching solution. The inner wall of the chamber adjacent to the processing chamber and communicating with the inner space of the processing chamber, and the chamber Moisture in the etching solution adhering to the inner structure is evaporated and the concentration of indium ions is increased, so that supersaturated indium is precipitated as indium oxalate. Therefore, if the etching solution or pure water is applied to at least one of the inner wall of the chamber adjacent to the processing chamber and the structure disposed in the chamber, the attached etching solution It is possible to prevent the water content from evaporating and the concentration of indium ions from increasing to a saturation concentration or higher. Thereby, it can prevent more reliably that indium oxalate precipitates. The etching solution or pure water may be applied periodically, irregularly, or constantly.

  As described above, according to the etching method of the present invention, among indium and tin (indium ions and tin ions) dissolved in the etching solution by etching the substrate, particularly indium ions can be maintained at an appropriate concentration. , The formation of precipitates can be prevented.

It is the block diagram which showed schematic structure of the etching apparatus for enforcing the etching method which concerns on one Embodiment of this invention. It is a graph (adsorption isotherm) showing the relationship between the equilibrium concentration and the equilibrium adsorption amount. It is the graph which showed the relationship between the indium ion density | concentration of the etching liquid stored in the storage tank, and the number of etching of a board | substrate when maintaining an indium ion density | concentration at 250 ppm, 200 ppm, 150 ppm, and 100 ppm.

  Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. In this embodiment, an etching apparatus 1 as shown in FIG. 1 is used to etch the substrate K on which the indium tin oxide film is formed on the upper surface with an etching solution L having an oxalic acid concentration (weight concentration) of 3.4%. The case of doing this will be described as an example.

  First, the etching apparatus 1 will be described. As shown in FIG. 1, the etching apparatus 1 performs etching between a storage tank 11 that stores an etching solution L, an etching mechanism 12 that etches a substrate K with the etching solution L, and a storage tank 11 and an etching mechanism 12. An etching circulation mechanism 20 for circulating the liquid L, an adsorption mechanism 31 for adsorbing and removing indium and tin dissolved in the etching liquid L, and a removal mechanism for circulating the etching liquid L between the storage tank 11 and the adsorption mechanism 31 It comprises a circulation mechanism 34, a control device 28 that controls the operation of the etching mechanism 12, the etching circulation mechanism 20, and the removal circulation mechanism 34.

  The etching mechanism 12 includes a processing chamber 13 having a closed space, a plurality of transport rollers 14 disposed in the processing chamber 13 for horizontally supporting the substrate K and transporting the substrate K in a predetermined direction (arrow direction), The upper surface of the substrate K disposed in the upper portion of the processing chamber 13 and through which the etching solution L supplied by the etching circulation mechanism 20 flows, and the substrate K fixed to the flow tube 15 and transported by the transport roller 14. A plurality of spray nozzle bodies 16 that discharge the etching solution L toward the surface, and disposed on the upper surface of the substrate K in the processing chamber 13 upstream of the spray nozzle body 16 in the substrate transport direction and transported by the transport rollers 14. A slit nozzle body 17 that discharges the etching solution L toward the surface, a pendulum type substrate detection sensor 18 disposed in the processing chamber 13, and the like.

  A substrate carry-in port 13 a and a substrate carry-out port 13 b are formed in the processing chamber 13, and the substrate carry-in port 13 a is opened and closed by a shutter 19. A discharge port 13c is formed on the bottom surface of the processing chamber 13, and the etching solution L in the processing chamber 13 is discharged to the outside from the discharge port 13c.

  The etching mechanism 12 includes chambers 50 and 55 disposed adjacent to the processing chamber 13 on the upstream side and the downstream side in the substrate transport direction. The internal space of the chamber 50 is connected to the substrate carry-in port 13 a and communicates with the internal space of the processing chamber 13, and the transport roller 14 is provided in the chamber 50.

  The internal space of the chamber 55 is connected to the internal space of the processing chamber 13 by connecting to the substrate carry-out port 13b. In the chamber 55, the transport roller 14 and the substrate K transported by the transport roller 14 are connected. Two slit nozzle bodies 56 that discharge air toward the upper surface are provided. The chamber 55 is formed with a substrate carry-out port 55a that is opened and closed by a shutter 57, and a discharge port 55b for discharging the etching solution L in the chamber 55 to the outside. Note that either air or pure water is switched and supplied to the slit nozzle body 56 from the supply section 58 via the supply pipe 59.

  Further, pure water supplied from a supply source (not shown) is supplied to each of the chambers 13, 50, and 55, with some transport rollers 14, shutters 19 and 57, inner walls of the chambers 50 and 55, and slit nozzle bodies 17 and 56. There is provided a nozzle body 60 that discharges toward the outer surface. Further, the etching solution L is always supplied to the movable portion of the substrate detection sensor 18 via a supply pipe (not shown).

  The etching circulation mechanism 20 has one end connected to the storage tank 11, the other end branched and connected to the flow pipe 15 and the slit nozzle body 17, and the supply pipe 21 passes through the flow pipe 15. A supply pump 22 for supplying the etching solution L to the slit nozzle body 17, a recovery pipe having one end branched and connected to the discharge port 13 c of the processing chamber 13 and the discharge port 55 b of the chamber 55, and the other end connected to the storage tank 11. 23 or the like.

  The adsorption mechanism 31 is a chelating agent (not shown) that adsorbs indium and tin (indium ions and tin ions) dissolved in the etching liquid L by the etching process in the etching mechanism 12 and included in the etching liquid L. ) Is provided with at least two adsorption containers (first adsorption container 32 and second adsorption container 33) filled therein. The chelating agent has a property of adsorbing metal ions such as indium ions and tin ions and eluting the adsorbed metal by a specific solution. The chelating agent is not particularly limited as long as it can adsorb at least indium ions and tin ions.

  The removal circulation mechanism 34 has one end side connected to the storage tank 11, the other end side branched and connected to each adsorption container 32, 33, and each adsorption container 32, 33 via the supply pipe 35. A supply pump 36 for supplying the etching solution L therein, one end side connected to the storage tank 11, the other end side branched and connected to each adsorption vessel 32, 33, and the other end side of the supply pipe 35 From the first supply side switching valve 38 and the second supply side switching valve 39 provided respectively, and the first discharge side switching valve 40 and the second discharge side switching valve 41 provided on the other end side of the recovery pipe 37, respectively. Become.

  In the removal circulation mechanism 34, when the first supply side switching valve 38 and the first discharge side switching valve 40 are open, and the second supply side switching valve 39 and the second discharge side switching valve 41 are closed, the first adsorption container. 32, when the first supply-side switching valve 38 and the first discharge-side switching valve 40 are closed and the second supply-side switching valve 39 and the second discharge-side switching valve 41 are open, the etching liquid L is added to the second adsorption container 33. In this way, the etching solution L in the storage tank 11 is selectively supplied to one of the adsorption containers 32 and 33 via the supply pipe 35. Then, the etching solution L flowing through the adsorption containers 32 and 33 is collected in the storage tank 11 by the collection pipe 37.

  The control device 28 controls the supply pump 22 to circulate the etching solution L between the storage tank 11 and the etching mechanism 12, and controls the supply pump 36 and the switching valves 38, 39, 40, and 41. Then, the process of circulating the etching solution L between the storage tank 11 and any one of the adsorption containers 32 and 33 and the supply unit 58 are controlled so that either the air or pure water is passed through the slit nozzle body 56. The processing to be supplied to is executed.

  Next, a method for continuously etching a plurality of substrates K using the etching apparatus 1 configured as described above will be described. It is assumed that a new etching solution L that does not contain indium ions and tin ions is stored in the storage tank 11.

  First, an etching process is performed. In this etching process, the substrate K supplied from the previous process sequentially passes through the chamber 50, the processing chamber 13 and the chamber 55 and is discharged to the subsequent process by the transport roller 14. K is conveyed in a predetermined direction. In addition, the etching liquid L stored in the storage tank 11 is supplied to each spray nozzle body 16 and the slit nozzle body 17 by the supply pump 22 and discharged from the nozzle bodies 16 and 17 toward the upper surface of the substrate K. Then, the etchant L discharged toward the upper surface of the substrate K is circulated through the collection pipe 23 from the discharge port 13 c of the processing chamber 13 and collected in the storage tank 11. Further, air is supplied from the supply unit 58 to the slit nozzle body 56 and discharged.

  Then, the substrate K is etched by the etching liquid L (succinic acid in the etching liquid L) discharged from each spray nozzle body 16 and the slit nozzle body 17 when passing through the processing chamber 13, and this etching causes the substrate K to be etched. The indium tin oxide film is dissolved in the etching solution L, so that the circulating etching solution L contains indium ions and tin ions. Further, when the substrate K passes through the chamber 55, the etching solution L is removed from the substrate K by the air discharged from the slit nozzle body 56, and the removed etching solution L is discharged from the discharge port 55 b of the chamber 55. It is refluxed into the storage tank 11 through the recovery pipe 23.

  Thereafter, when the indium tin oxide film is dissolved and the concentrations of indium ions and tin ions in the circulating etching solution L increase and reach a certain concentration, the metal removal step is started.

  In this metal removal step, the etching liquid L stored in the storage tank 11 is supplied to either one of the adsorption containers 32 and 33 via the supply pipe 35 by the supply pump 36 and circulated in the adsorption containers 32 and 33. The etching solution L is collected in the storage tank 11 through the collection pipe 37. In this way, indium ions and tin ions contained in the etching solution L are adsorbed and removed by the chelating agent in the adsorption vessels 32 and 33, and the concentrations of indium ions and tin ions contained in the etching solution L in the storage tank 11 are constant. Keep it below the concentration.

  Whether or not the concentrations of indium ions and tin ions in the etching solution L have reached a certain level is determined by, for example, the number of substrates K that have passed through the processing chamber 13 based on an output signal obtained from the substrate detection sensor 18. That is, the number of substrates K etched by the etching mechanism 12 is counted, and whether or not the counted number reaches a preset number (the number of indium ions and tin ions estimated to reach the predetermined concentration). Can be judged. Moreover, the said fixed density | concentration can be arbitrarily set by the density | concentration (mass concentration) of 100 ppm or more and 260 ppm or less about an indium ion.

  Thereafter, the adsorption capacity of the chelating agent in the adsorption vessels 32 and 33 to which the etching solution L is supplied is reduced, and the concentration of indium ions and tin ions contained in the etching solution L in the storage tank 11 can be suppressed to a predetermined concentration or less. When it becomes difficult, that is, based on the output signal obtained from the substrate detection sensor 18, the number of substrates K etched by the etching mechanism 12 is counted, and the counted number becomes a preset number. When the number of indium ions and / or tin ions adsorbed on the surface is estimated to have reached a nearly saturated state, the etching liquid L is circulated by switching the adsorption containers 32 and 33 to which the etching liquid L is supplied.

  Thereafter, every time the number of substrates K etched by the etching mechanism 12 reaches a preset number (the number of indium ions and / or tin ions adsorbed on the chelating agent is estimated to be substantially saturated). The etching solution L stored in the storage tank 11 is supplied to one of the adsorption containers 32 and 33 while alternately switching the adsorption containers 32 and 33.

  Thus, in the metal removal step, the adsorption vessels 32 and 33 are alternately switched to circulate the etching solution L while maintaining the adsorption capacity of the chelating agent to be constant, thereby being included in the etching solution L in the storage tank 11. Indium ions and tin ions are maintained at a certain concentration or less (indium ions are 100 ppm or more and 260 ppm or less).

  Note that the adsorption containers 32 and 33 whose supply of the etching liquid L has been stopped by switching the adsorption containers 32 and 33, that is, the used adsorption containers 32 and 33 are unused (regenerated) (indium in the chelating agent). And the adsorption vessels 32 and 33 in which tin is not adsorbed). Alternatively, an eluent for eluting indium and tin adsorbed by the chelating agent is passed through the used adsorption vessels 32 and 33, and after eluting indium and tin into the eluent, the inside A washing liquid for washing is passed to wash away the eluent remaining in the adsorption containers 32 and 33, and thus the adsorption containers 32 and 33 can be reused (regenerated).

  Further, the movable portion of the substrate detection sensor 18 is always supplied with the etching solution L in the storage tank 11 via a supply pipe (not shown), and a part of the substrate detection sensor 18 is regularly, irregularly, or always transferred. Pure water is discharged from the nozzle body 60 toward the rollers 14, the shutters 19 and 57, the inner walls of the chambers 50 and 55, and the outer surfaces of the slit nozzle bodies 17 and 56, and pure water is supplied from the supply unit 58 to the slit nozzle body 56. To do. The reason for this is to prevent indium in the etching solution L and oxalic acid in the etching solution L from being combined and crystallized as indium oxalate. In addition, when supplying pure water to the slit nozzle body 56, a valve (not shown) provided in the recovery pipe 23 is switched and appropriately recovered in the recovery unit so that the pure water does not flow into the storage tank 11. .

  By the way, in particular, when the concentration of indium ions exceeds a certain level, indium in the etching solution L and oxalic acid in the etching solution L are combined and crystallized as indium oxalate. This crystallization is unlikely to occur in a portion that is always wet by the etching solution L, but is a mist-like etching that flows into the chamber 50 from the processing chamber 13 through the substrate carry-in port 13a when the shutter 19 is opened. The inner wall of the chambers 50 and 55 to which the liquid L and the mist-like etching liquid L that has flowed into the chamber 55 from the processing chamber 13 through the substrate carry-out port 13b adhere, and some of the chambers 50 and 55 disposed therein. On the outer surfaces of the transport roller 14, the shutters 19 and 57, the slit nozzle body 56, and the like, moisture in the attached etching solution L evaporates and the concentration of indium ions increases, so that supersaturated indium is precipitated as indium oxalate. . In addition, since the mist-like etching solution L adheres to the outer surface of the slit nozzle body 17 as well, indium oxalate is deposited in the same manner as described above. Further, the movable portion of the substrate detection sensor 18 is also disposed on the lower side of the substrate K, and since the etching liquid L is not so much applied, it is easy to dry and indium oxalate is likely to deposit. Once indium oxalate is deposited, crystals grow using this as a nucleus.

  When indium oxalate is crystallized in this way, the substrate K is damaged by the crystals adhering to the transport roller 14, the malfunction of the shutters 19 and 57, the erroneous detection of the substrate detection sensor 18, or the slit nozzle body. The opening of 56 is blocked and air is not discharged uniformly, resulting in unevenness in the liquid draining process. In addition, when the crystals of indium oxalate fall into the etching solution L collected in the storage tank 11, the filter that removes impurities such as dust from the circulating etching solution L becomes clogged. On the other hand, in order to prevent such a problem, the inner walls of the chambers 50 and 55, a part of the conveyance rollers 14 disposed in the chambers 50 and 55, the shutters 19 and 57, the outer surfaces of the slit nozzle bodies 17 and 56, and If the crystal adhering to the movable part of the substrate detection sensor 18 is removed or the filter is replaced, the operation efficiency of the etching apparatus 1 decreases due to such maintenance work. Note that indium oxalate crystals, unlike simple oxalic acid crystals, are difficult to dissolve even when dropped into the etchant L, and thus are included in the etchant as crystals.

  Therefore, as a result of repeating various experiments, the inventors of the present application have determined that if the concentration of indium ions is 260 ppm or less, the inner walls of the chambers 50 and 55, a part of the transport rollers 14 disposed in the chambers 50 and 55, It was found that indium oxalate does not precipitate on the shutters 19 and 57, the outer surfaces of the slit nozzle bodies 17 and 56, the movable part of the substrate detection sensor 18, and the like.

  Therefore, in the etching method of this example, indium ions and tin ions in the etching solution L are adsorbed in the metal removal step so that the concentration of indium ions contained in the etching solution L in the storage tank 11 is maintained at 260 ppm or less. It was made to remove. Thereby, precipitation of indium oxalate can be reliably prevented. For this reason, the substrate K is damaged by the crystals adhering to the transport roller 14, the malfunction of the shutters 19 and 57, the erroneous detection of the substrate detection sensor 18, or impurities such as dust are removed from the circulating etching solution L. There is no problem that the filter is clogged or the opening of the slit nozzle body 56 is blocked to cause unevenness in the liquid draining process, and the inner wall of the chambers 50 and 55 and the chambers 50 and 55 are disposed. There is no need to perform maintenance such as removal of crystals attached to some transport rollers 14, shutters 19 and 57, outer surfaces of the slit nozzle bodies 17 and 56, movable portions of the substrate detection sensor 18, and filter replacement.

  Further, in this example, the etching solution L is supplied to the movable portion of the substrate detection sensor 18, and is directed toward some of the transport rollers 14, the shutters 19 and 57, the inner walls of the chambers 50 and 55, and the outer surfaces of the slit nozzle bodies 17 and 56. Since pure water is discharged, it is possible to prevent these from drying and more reliably prevent indium oxalate from precipitating. Further, by supplying pure water into the slit nozzle body 56, indium oxalate adhering to the opening can be washed away and removed.

  Note that chelating agents are generally known to have adsorption characteristics as shown in FIG. FIG. 2 is a graph (adsorption isotherm) showing the relationship between the equilibrium concentration (mg / L) and the equilibrium adsorption amount (mg / L). The equilibrium concentration and the equilibrium adsorption amount are explained with respect to the adsorption of indium ions. For example, the equilibrium concentration indicates the concentration of indium ions of the etching solution L that is passed through the adsorption vessels 32 and 33, and the equilibrium adsorption amount is the maximum amount of indium adsorbed by the chelating agent per unit weight (mg / g). ).

  As can be seen from FIG. 2, the higher the indium ion concentration of the etching solution L passed through the adsorption vessels 32 and 33, the more indium ions can be adsorbed to the chelating agent than when the etching solution L is low. Therefore, the concentration of indium ions in the etching solution L in the storage tank 11 is preferably as high as possible within a range of 260 ppm or less. By doing so, until the indium ions adsorbed on the chelating agent reach a saturated state. It is economical because the number of etching can be increased and the switching cycle of the adsorption containers 32 and 33 can be lengthened.

  On the other hand, FIG. 3 shows the indium ion concentration of the etching solution L stored in the storage tank 11 and the number of etched substrates K when the indium ion concentration is maintained at, for example, 250 ppm, 200 ppm, 150 ppm, and 100 ppm. It is the graph which calculated | required the relationship. In this illustrated example, after the etching process is started, the metal removal process is started when the indium ion concentration in the storage tank 11 becomes 250 ppm, 200 ppm, 150 ppm, and 100 ppm, and the etching solution is switched while the adsorption vessels 32 and 33 are switched. L was circulated to maintain the indium ion concentration in the storage tank 11 at about 250 ppm, 200 ppm, 150 ppm and 100 ppm. Further, when the indium ion concentration in the storage tank 11 is maintained at 250 ppm, 200 ppm, 150 ppm and 100 ppm, the switching cycles of the adsorption containers 32 and 33 are about 9000 sheets, 7950 sheets, 6800 sheets and 5450 sheets, respectively. When maintained at 100 ppm, it was about 40% less than when maintained at 250 ppm.

  As can be seen from FIG. 3, the higher the indium ion concentration of the etching solution L in the storage tank 11 is, the more the number of etching is performed until the indium ions adsorbed on the chelating agent reach the saturation state. The switching cycle is long. However, even when the concentration of indium ions in the storage tank 11 is maintained at 100 ppm, a switching cycle of about 60% when the concentration is maintained at 250 ppm can be secured, which is at an acceptable level. Therefore, from an economic viewpoint, it is preferable to maintain the indium ion concentration of the etching solution L in the storage tank 11 as high as possible. However, if the indium ion concentration is 100 ppm or more, the switching cycle of the adsorption vessels 32 and 33 is performed. Can be made longer than a certain level to reduce the cost required to regenerate the chelating agent.

  As mentioned above, although one Embodiment of this invention was described, the specific aspect which this invention can take is not limited to this at all.

  In the above example, the switching between the adsorption containers 32 and 33 to which the etching liquid L is supplied is controlled by the number of etchings of the substrate K, but is not limited to this, and the adsorption containers 32 and 33 to which the etching liquid L is supplied. May be switched at a predetermined time interval, that is, at a time interval in which indium ions and / or tin ions adsorbed on the chelating agent are estimated to reach a substantially saturated state, or the etching liquid L stored in the storage tank 11 may be switched. The indium ion concentration and / or tin ion concentration may be measured, and the adsorption containers 32 and 33 may be switched based on the measured concentration.

  In addition, the mode in which the etching solution L is passed through the adsorption containers 32 and 33 is not limited to the above-described mode, and any mode may be used. For example, in the above example, the etching solution L in the storage tank 11 is always passed through the adsorption vessels 32 and 33 after the start of the metal removal step. However, when the indium ion concentration and the tin ion tin concentration decrease, the indium ions are again introduced. The liquid flow into the adsorption vessels 32 and 33 may be temporarily stopped until the concentration and the tin ion tin concentration reach a certain concentration.

DESCRIPTION OF SYMBOLS 1 Etching apparatus 11 Reservoir 12 Etching mechanism 13 Processing chamber 14 Transfer roller 16 Spray nozzle body 17 Slit nozzle body 20 Etching circulation mechanism 21 Supply pipe 22 Supply pump 23 Recovery pipe 31 Adsorption mechanism 32 First adsorption container 33 Second adsorption container 34 Removal circulation mechanism 35 Supply pipe 36 Supply pump 37 Recovery pipe 50 Chamber 55 Chamber 56 Slit nozzle body K Substrate L Etching solution

Claims (4)

A substrate on which an indium tin oxide film is formed by supplying the etching liquid from a storage tank in which an etching liquid containing oxalic acid is stored to a nozzle body disposed in the processing chamber, and the etching liquid discharged from the nozzle body And etching step for recovering the discharged etching solution from the processing chamber into the storage tank,
The etching solution stored in the storage tank is passed through an adsorption vessel filled with a chelating agent that adsorbs indium ions and tin ions, and indium ions and tin ions that are included in the etching solution by etching. And a metal removal step of refluxing the etching solution in which the indium ions and tin ions are adsorbed and removed into the storage tank.
In the metal removing step, indium ions and tin ions are adsorbed and removed so that the concentration of indium ions in the etching solution stored in the storage tank is maintained at 260 ppm or less.   2. In the metal removal step, indium ions and tin ions are adsorbed and removed so that the concentration of indium ions in the etching solution stored in the storage tank is maintained at 100 ppm or more. The etching method as described.   In the metal removal step, at least two of the adsorption containers are used, and an etching solution is selectively passed through any one of these adsorption vessels, and the etched solution after the solution is passed into the storage tank. 3. The etching method according to claim 1, wherein the etching method is refluxed.   At least one of an inner wall of the chamber adjacent to the processing chamber and having an inner space communicating with the inner space of the processing chamber and a structure disposed inside the chamber includes the etching solution or pure water. The etching method according to claim 1, wherein the etching method is applied.

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