JP2008168254A - Method and apparatus for applying coating liquid and method for manufacturing photomask blank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for applying a coating liquid, in each of which a liquid level can be managed reproducibly and correctly when the application of the coating liquid is started every time, the uniformity of the thickness of a coating film between substrates can be improved, and defective application due to foreign matter can be decreased drastically by efficiently removing suspended foreign matter carried in a liquid tank. <P>SOLUTION: The method for applying the coating liquid comprises the steps of: bringing the coating liquid, which is supplied from the coating liquid-filled liquid tank, passes through a nozzle and reaches an opening at the tip of the nozzle, into contact with the surface to be coated of a substrate; moving the substrate and the nozzle relatively to each other and in parallel to the surface to be coated; and applying the coating liquid to the surface to be coated to form the coating film. After first application is completed, the liquid tank is replenished with the coating liquid so that the liquid level is raised temporarily to the liquid level exceeding the liquid level desired when the application is started. Then, before next application is started, the coating liquid accumulated in the liquid tank to the liquid level, which exceeds the liquid level desired when the application is started, is overflowed to lower the liquid level to the liquid level desired when the application is started. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coating method and a coating apparatus for coating a coating liquid on a surface to be coated using a capillary phenomenon, and a photomask blank manufacturing method in which this coating method is applied to manufacturing a photomask blank.

  Conventionally, in pattern formation using a photolithography method, a step of forming a resist film by applying a coating solution such as a photoresist onto a substrate is required. As a coating apparatus (coater) for applying this coating solution, A so-called spin coater is known. This spin coater drops the coating solution on the center of the substrate (the surface to be coated) held horizontally, and then rotates the substrate at a high speed in a horizontal plane to extend the coating solution over the entire surface by the action of centrifugal force. The coating film is formed on the substrate surface.

  However, this spin coater has a problem in that resist swell called fringe occurs at the peripheral edge of the substrate. When such fringes occur, the film thickness of the resist film becomes non-uniform in the substrate surface, and CD in-plane variation occurs when a pattern is formed. In particular, the rise of the fringe promotes non-uniform film thickness when the shape of the substrate is not a rotation target (rectangular shape, etc.). Further, in the photomask for manufacturing a liquid crystal display device or a liquid crystal display device, the substrate However, there are problems such as difficulty in obtaining a rotation drive mechanism at a constant speed, necessity of a large rotation space (chamber), loss of coating liquid, and the like.

  On the other hand, as a coating apparatus suitable for a large substrate, a coating apparatus commonly referred to as “CAP coater” has been proposed (for example, Patent Document 1). In this CAP coater, a nozzle having a capillary gap inside is brought close to the surface to be coated of the substrate, the coating liquid passing through the nozzle from the liquid tank filled with the coating liquid, and reaching the nozzle tip opening is formed on the substrate. In this state, the substrate and the nozzle are moved relatively in parallel to the surface to be coated, thereby applying the coating liquid to the surface to be coated to form a coating film. To do.

  By the way, when a coating film such as a photoresist is formed on the substrate surface using such a CAP coater, the liquid discharge amount of the nozzle using the capillary phenomenon is the liquid level of the coating liquid stored in the liquid tank. Therefore, if the liquid surface height of the coating liquid in the liquid tank is not constant for each coating, the coating film thickness varies between the substrates. Therefore, Patent Document 1 describes a technique in which the liquid level at each application is monitored by a liquid level sensor and the liquid level in the liquid tank at the start of application is made constant. Patent Document 2 describes that an overflow pipe is arranged in the container in order to keep the level of the fluid (coating liquid) in the container (liquid tank) constant.

JP 2004-6762 A JP-A-8-224528

  In the technique disclosed in Patent Document 1, as described above, the liquid level at each application is monitored by the liquid level sensor, and the liquid level in the liquid tank at the start of application is kept constant. . This is advantageous in that the liquid level at the start of each application is made constant, the resistance of the application liquid rising the nozzle by capillary action is made constant with good reproducibility, and the film thickness of the application liquid is made constant. Because there is. However, even when the liquid level sensor disclosed in Patent Document 1 is used, it is not easy to make the liquid level of the coating liquid to be replenished for each coating with high reproducibility and precision. The reason for this will be described with reference to FIG. 7. First, a delay occurs in the detection of the liquid level sensor 204, and secondly, a communication pipe connected to the liquid tank 200 containing the coating liquid 21. The liquid level sensor 204 is attached to the 201 part to detect the liquid level, but since the diameter of the communication pipe 201 part is relatively small, the area of the liquid level is small, and the liquid level is detected by the influence of the surface tension of the coating liquid. For example, errors are likely to occur.

  Moreover, if the application is repeated, it is completely unavoidable that the minute foreign matter 9 is mixed into the liquid tank 200 due to bringing in the substrate. Among such foreign substances 9, there are those having a specific gravity smaller than that of the coating liquid 21 and floating near the surface of the coating liquid (floating foreign substances). The same applies to the coating apparatus disclosed in Patent Document 1, but normally, the coating liquid is supplied from a liquid supply line 202 attached to the bottom wall of the liquid tank 200, and the coating liquid is discharged similarly. 200 is performed from a drainage line 203 attached to the bottom wall of 200 (see FIG. 7), and the coating liquid 21 in the liquid tank 200 is partially discharged and supplied repeatedly for each application. At this time, the coating liquid can be circulated and used, and foreign matters can be removed by a filter during the circulation process. However, since the above-described foreign matter 9 floats on the surface of the coating liquid stored up to the upper position of the liquid tank 200, there is almost no opportunity to be discharged from the drain line 203 on the bottom wall of the liquid tank 200. As a result, the liquid tank It stays inside and gradually accumulates in the liquid tank. If such foreign matter adheres to the nozzle and prevents the rise of the coating liquid in the nozzle, or further adheres to the substrate during application, the portion becomes an application defect. Furthermore, it cannot be used as a photomask. Further, when patterning is performed with foreign matters mixed in the resist film, for example, foreign matters may fall off at the development stage, and the portion may eventually become a white defect (pinhole defect).

  On the other hand, in the technique disclosed in Patent Document 2, there is a description that the overflow pipe is submerged in the liquid tank, and the fluid flows out as soon as the fluid level reaches the upper end of the overflow pipe. However, in such an apparatus, floating foreign substances brought into the fluid (coating liquid) by the substrate or the like can flow out only around the overflow pipe, but those around the nozzle continue to stay, There exists a problem that the coating defect by a foreign material cannot be reduced effectively.

Therefore, in view of the above-mentioned problems of the prior art, the present invention can accurately manage the liquid level at the start of each application with good reproducibility, and can improve the uniformity of the coating film thickness between the substrates, It is a first object of the present invention to provide a coating method and a coating apparatus capable of efficiently removing floating foreign substances brought into a liquid tank and greatly reducing coating defects due to the foreign substances.
In addition, by applying the coating method of the present invention to apply a photoresist on a substrate to form a photoresist film, a photomask with good coating film thickness uniformity between substrates and reduced coating defects A second object is to provide a blank manufacturing method.

In order to solve the above problems, the present invention has the following configuration.
(Configuration 1) The coating liquid that has passed through the nozzle from the liquid tank filled with the coating liquid and reached the nozzle tip opening is brought into contact with the coated surface of the substrate, and the substrate and the nozzle are relatively moved relative to the coated surface. In the coating method in which the coating liquid is applied to the surface to be coated to form a coating film, the coating liquid is replenished to the liquid tank after one application, The liquid level was temporarily raised to a liquid level exceeding the desired liquid level, and then, prior to the next application, the liquid level exceeding the desired liquid level at the start of application in the liquid tank was stored. In the coating method, the liquid level is lowered to a desired liquid level at the start of the coating by overflowing the coating liquid.

(Configuration 2) The liquid tank has an overflow plate of a predetermined height that regulates a desired liquid level at the start of application, and is stored up to a liquid level that exceeds the desired liquid level at the start of application. 2. The coating method according to Configuration 1, wherein the liquid level is brought to a desired liquid level at the start of coating by causing the liquid to overflow from the upper end of the overflow plate.
(Configuration 3) The liquid tank is divided into at least two parts including an application tank and an overflow tank by an overflow plate, and the application liquid flows from the application layer into the overflow tank at the time of the overflow. It is the coating method of the structure 1 or 2 characterized by these.

(Configuration 4) The coating method according to Configuration 3, wherein the overflow is performed by draining at least a part of the coating solution in the overflow tank.
(Structure 5) The coating method according to Structure 4, wherein the coating liquid drained from the overflow tank is supplied to the coating tank after foreign matters are removed by a filter member.

(Structure 6) The coating method according to any one of Structures 1 to 5, wherein the replenishment of the coating liquid is performed in a state where the nozzle is immersed in a coating liquid in a liquid tank.
(Arrangement 7) According to any one of Arrangements 4 to 6, wherein after replenishing the coating solution, at least a part of the nozzle is floated from the coating solution, and then the overflow tank is drained. Application method.

(Configuration 8) A gap communicating with the tip opening is provided, the nozzle for guiding the coating liquid to the tip opening through the gap, the coating liquid is accommodated, and at least a part of the nozzle is immersed in the coating liquid. A liquid tank for supplying the coating liquid to the nozzle, and the tip opening of the nozzle is brought close to the surface to be coated of the substrate, and the coating liquid guided to the tip opening is applied to the surface to be coated of the substrate. A nozzle contacting / separating means for contacting the liquid, and the substrate and the nozzle are applied to the substrate in a state where the tip opening of the nozzle is brought close to the application surface of the substrate by the nozzle contacting / separating means. A moving means for moving in parallel and relative to the surface, a control means for controlling the nozzle contacting / separating means and the moving means, and the liquid tank includes a liquid supply line for supplying a coating liquid therein. If the liquid level of the coating liquid is When exceeded, a coating apparatus characterized in that it comprises means for overflowing the coating solution.

(Configuration 9) The liquid tank has an overflow plate of a predetermined height that regulates a desired liquid level at the start of application, and is stored up to a liquid level that exceeds the desired liquid level at the start of application. The coating apparatus according to Configuration 8, wherein the liquid level is controlled to be constant depending on the height of the overflow plate by causing the liquid to overflow from the upper end of the overflow plate. .

(Configuration 10) The liquid tank is divided into at least two parts including an application tank and an overflow tank by an overflow plate, and the application liquid flows from the application layer into the overflow tank at the time of the overflow. 10. The coating apparatus according to Configuration 8 or 9, wherein
(Structure 11) The coating apparatus according to Structure 10, wherein the overflow is performed by draining at least part of the coating liquid in the overflow tank.

(Structure 12) The structure 11 has a filter means for removing foreign matter in the coating liquid drained from the overflow tank, and a circulating means for circulating the coating liquid after removing the foreign matter to the coating tank. It is a coating device of description.
(Structure 13) The coating liquid is a photoresist, and includes a step of forming a coating film by coating the coating liquid on a surface to be coated by the coating method according to any one of Structures 1 to 7. It is a manufacturing method of the photomask blank.

  According to the first aspect of the present invention, since the liquid level at the start of each application can be accurately managed with good reproducibility due to overflow, the uniformity of the coating film thickness between the substrates can be improved. In addition, after the completion of one application, the liquid tank is replenished with the application liquid, and the liquid level is temporarily raised to a liquid level that exceeds the desired liquid level at the start of application. Since the coating liquid stored up to the liquid level exceeding the desired liquid level at the start of application in the tank is overflowed, floating foreign substances brought into the liquid tank can be efficiently removed by overflow, Coating defects can be greatly reduced.

According to the invention of claim 2, the liquid tank has an overflow plate of a predetermined height that regulates a desired liquid level at the start of application, thereby exceeding the desired liquid level at the start of application. Since the coating liquid stored up to the level is allowed to overflow from the upper end of the overflow plate, the liquid level at the start of each application can be accurately managed with good reproducibility depending on the height of the overflow plate.
According to invention of Claim 3, since the said liquid tank is divided into at least two parts containing an application tank and an overflow tank by the overflow board, in the case of overflow, a coating liquid is the said overflow from the said application layer. It can be set as the structure which flows in into a tank.

According to the invention of claim 4, since overflow is performed by draining at least a part of the coating liquid in the overflow tank, the liquid level at the start of coating is controlled to be constant and simultaneously in the coating tank. Floating foreign matter flows into the overflow tank and is removed from the coating tank.
According to the invention of claim 5, since the coating liquid drained from the overflow tank is supplied to the coating tank after foreign matters are removed by the filter member, the coating liquid containing the floating foreign substances drained Since it is completely purified and recycled, coating defects can be greatly reduced.

According to the invention of claim 6, since the replenishment of the coating liquid is performed in a state where the nozzle is immersed in the coating liquid in the liquid tank, there is an advantage that drying of the nozzle can be prevented.
According to the invention of claim 7, after replenishing the coating liquid, at least a part of the nozzle is floated from the coating liquid, and then the overflow tank is drained, whereby the nozzle floats on the coating liquid surface. Since the liquid level can be controlled by overflow after the vibration of the liquid level becomes quiet, there is an advantage that the liquid level at the start of coating can be accurately controlled with high reproducibility.

According to invention of Claim 8, the coating device suitable for enforcing the coating method concerning this invention can be provided. That is, by forming a coating film on the substrate using the coating apparatus of the present invention, the liquid level at the start of each coating can be accurately managed with good reproducibility, and the uniformity of the coating film thickness between the substrates can be achieved. In addition to being able to improve, floating foreign substances brought into the liquid tank can be efficiently removed, and coating defects due to the foreign substances can be greatly reduced.
According to the ninth aspect of the present invention, the liquid tank has an overflow plate having a predetermined height that regulates a desired liquid level at the start of application, thereby exceeding the desired liquid level at the start of application. Since the coating liquid stored up to the level is allowed to overflow from the upper end of the overflow plate, the liquid level at the start of each application can be accurately managed with good reproducibility depending on the height of the overflow plate.

According to the invention of claim 10, since the liquid tank is partitioned into at least two parts including the application tank and the overflow tank by the overflow plate, the application liquid is discharged from the application layer in the overflow. It can be set as the structure which flows in into a tank.
According to the invention of claim 11, since at least a part of the coating liquid in the overflow tank is drained, the overflow is performed, so that the liquid level at the start of coating is controlled to be constant and simultaneously in the coating tank. The floating foreign matter flows into the overflow tank and can be removed from the coating tank.

According to the twelfth aspect of the invention, since the coating liquid drained from the overflow tank is circulated to the coating tank after the foreign matters are removed by the filter means, the coating liquid containing the floating foreign substances drained is once Since it is completely purified and recycled, coating defects can be greatly reduced.
According to the invention of claim 13, by applying the coating method of the present invention and applying a photoresist on a substrate to form a photoresist film, the coating film thickness uniformity between substrates is good, A photomask blank with reduced defects can be obtained.

Hereinafter, the best mode for carrying out a coating method and a coating apparatus according to the present invention and a photomask blank manufacturing method to which the coating method of the present invention is applied will be described in detail with reference to the drawings.
In the present invention, the coating liquid that has passed through the nozzle from the liquid tank filled with the coating liquid and reached the nozzle tip opening is brought into contact with the coated surface of the substrate, and the substrate and the nozzle are relatively moved relative to the coated surface. In the coating method in which the coating liquid is applied to the surface to be coated to form a coating film, the coating liquid is replenished to the liquid tank after one application, The liquid level was temporarily raised to a liquid level exceeding the desired liquid level, and then, prior to the next application, the liquid level exceeding the desired liquid level at the start of application in the liquid tank was stored. In the coating method, the liquid level is lowered to a desired liquid level at the start of the coating by overflowing the coating liquid.

  According to the coating method of the present invention, since the liquid level at the start of each coating can be accurately managed by overflow, the uniformity of the coating film thickness between the substrates can be improved. In addition, after the completion of one application, the liquid tank is replenished with the application liquid, and the liquid level is temporarily raised to a liquid level that exceeds the desired liquid level at the start of application. Since the coating liquid stored up to the liquid level exceeding the desired liquid level at the start of application in the tank is overflowed, floating foreign substances brought into the liquid tank can be efficiently removed by overflow, Coating defects can be greatly reduced.

Here, the said liquid tank can be set as the structure which has an overflow board of the predetermined height which regulates the desired liquid level at the time of a coating start. In such a configuration, the liquid level is increased from the upper end of the overflow plate to the liquid level that exceeds the desired liquid level at the start of application, thereby causing the liquid level to reach the desired liquid level at the start of application. To level. In other words, since the coating liquid stored up to the liquid level exceeding the desired liquid level at the start of application overflows from the upper end of the overflow plate, the liquid level at the start of application every time depends on the height of the overflow plate. It can be managed accurately with good reproducibility.
In particular, when the coating liquid overflows, a flow near the surface of the coating liquid is generated toward the overflow plate, so that the foreign matter is easily moved by this flow.

The liquid tank is divided into at least two parts including the coating tank and the overflow tank by the overflow plate, and the coating liquid flows into the overflow tank from the coating layer when the overflow occurs. be able to.
In this case, since the overflow is performed by draining at least a part of the coating liquid in the overflow tank, the liquid level at the start of coating is controlled to be constant, and at the same time, floating foreign substances in the coating tank overflow. Since it flows into the tank, floating foreign substances are efficiently removed from the coating tank.

Next, an embodiment of a coating apparatus that can be preferably used in carrying out the coating method of the present invention will be described.
FIG. 1 is a schematic side view of the coating apparatus according to the present invention, and FIG. 2 is a schematic front view thereof.
As shown in FIG. 1, the coating apparatus 1 is configured to move the coating unit 2 provided on the base frame 11, the suction unit 3 provided on the moving frame 12, and the moving frame 12 in the horizontal direction on the base frame 11. The moving unit 4, the holding unit 5 that holds the substrate 10 detachably, and a control unit (not shown) are provided.

  The application unit 2 applies the application liquid to the substrate 10 with the surface to be applied facing downward. The coating means 2 is provided at the approximate center of a rectangular box-shaped base frame 11. The configuration of the coating unit 2 will be described in more detail later.

  The moving frame 12 is formed by integrally forming a pair of opposing side plates and a top plate for connecting the side plates, so that the positional accuracy between the substrate 10 and the coating means 2 is not deviated. Strength. The moving frame 12 is connected to the base frame 11 via the linear way 41 so as to be movable in the horizontal direction. In the moving frame 12, suction means 3 is provided. The suction means 3 is composed of, for example, a suction plate in which a plurality of suction holes (not shown) are formed in a substantially central portion of the top plate. Further, one side plate of the moving frame 12 protrudes from a moving portion 13 formed with a nut into which a ball screw 42 described later is screwed.

  The moving means 4 includes a linear way 41 that moves while guiding the side plate of the moving frame 12, a ball screw 42 that is screwed into a nut of the moving unit 13, and a motor 43 that rotates the ball screw 42. . When the motor 43 is rotated by an instruction from a control unit (not shown), the ball screw 42 rotates, and the moving unit 13 can be moved horizontally by a predetermined distance in a direction corresponding to the rotation direction of the ball screw 42.

  The holding means 5 includes a holding means frame 51 formed integrally with the base frame 11, a linear way 53 provided on the holding means frame 51, and a guide guided by the linear way 53 on the holding means frame 51. , A linear motor 54 for moving the base plate 52 in the horizontal direction, and an air cylinder (or electromagnetic solenoid) 56 provided with a holding member 55 at the tip of the rod. The air cylinder 56 is detachably attached to an arbitrary attachment position of the base plate 52 so as to be compatible with various substrate sizes. The holding member 55 includes a placement surface on which the peripheral edge of the substrate 10 is placed and a locking step for positioning the substrate 10. For example, for the rectangular substrate 10, the holding members 55 are disposed at the four corners of the base plate 52 so as to hold the four corners of the substrate 10. Of course, the arrangement position of the holding member 55 can be appropriately changed in consideration of the shape of the substrate, the positional accuracy, and the like.

Next, the overall operation of the coating apparatus 1 having the above configuration will be described.
First, in the initial state of the coating apparatus 1, the base plate 52 is at the substrate setting position, the moving frame 12 is at the suction position, and the rods of the air cylinders 56 at the four corners on the base plate 52 are lowered. State.
Next, the operator (or robot) places the substrate 10 on the placement surface of the holding member 55 with the coated surface facing downward. Since the holding member 55 is provided with the locking step, the substrate 10 can be easily positioned. Further, the step 10 for locking allows the substrate 10 to be locked when the base plate 52 moves from the set position to the suction position and stops (described later).

When the substrate 10 is placed on the holding member 55 as described above, the following operation is performed in accordance with an instruction from the control unit.
First, the base plate 52 is moved to the suction position by the linear motor 54 and stopped. When the holding means 5 is positioned at the suction position in this way, the rods of the four air cylinders 56 at the four corners are simultaneously lifted to bring the substrate 10 into contact with or close to the suction means 3. Here, the substrate 10 is adsorbed by the adsorbing means 3 by suction by the adsorbing means 3. When the rod of each air cylinder 56 is lowered, the moving frame 12 moves toward the processing position. While the moving frame 12 passes the processing position, the coating liquid is applied from below to the coating surface of the substrate 10 with the coating surface facing downward.

  When the application by the application means 2 is completed, the motor 43 (ball screw 42) is rotated in the reverse direction, and the moving frame 12 returns from the processing position to the suction position. At that time, the rod of each air cylinder 56 rises, and the mounting surface of the holding member 55 and the substrate 10 are brought into contact with each other. At this time, the substrate 10 is positioned by the locking step of the holding member 55. Then, after the suction by the suction means 3 is stopped, the rods of the air cylinders 56 are simultaneously lowered, and the coated substrate 10 is placed on the holding member 55. Next, the base plate 52 is moved from the suction position to the set position by the linear motor 54, and the operator (or robot) takes out the coated substrate 10 from the holding member 55. The moving frame 12 may be moved by using a ball screw or other means such as a linear motor.

  As described above, one application operation is completed. In the above-described configuration, the moving frame 12 (the suction unit 3) moves in the direction of the processing position, and the coating liquid is applied to the surface to be coated of the substrate 10 from below by the coating unit 2 while passing the processing position. However, for example, the application unit 2 may be applied by moving in the horizontal direction without moving the moving frame 12 (that is, with the substrate 10 fixed at a predetermined position). Furthermore, it is good also as a structure which moves both the moving frame 12 and the application | coating means 2. FIG.

Next, the configuration of the coating unit 2 will be described in more detail.
FIG. 3 is a cross-sectional view showing the configuration of the coating means 2 in this coating apparatus.
As shown in FIG. 3, the coating means 2 raises the coating liquid (for example, liquid photoresist liquid) 21 stored in the liquid tank 20 by capillary action in the capillary gap 23 of the nozzle 22 and is directed downward. The tip (upper end) of the nozzle 22 is brought close to the surface to be coated of the substrate 10 and the coating liquid rising to the nozzle tip is brought into contact with the surface to be coated of the substrate 10 through the nozzle tip. It is configured.

Here, the liquid tank 20 has a length of one side in the horizontal direction of the substrate 10, that is, a direction orthogonal to the vertical direction moved by the moving frame 12 (in FIG. 3, the direction orthogonal to the paper surface). ) Has a width that is longer than the length of one side (see FIG. 6 described later). The liquid tank 20 is attached to and supported by the upper end side of the support plate 24 so as to be movable in the vertical direction with respect to the support plate 24 by a drive mechanism (not shown).
And this support plate 24 is supported on the bottom frame 14 of the base frame 11 via the linear ways 25 and 26 arrange | positioned mutually orthogonally in the lower end side. That is, the position of the support plate 24 can be adjusted in two orthogonal directions on the bottom frame 14. In addition, a support rod 28 that supports the nozzle 22 accommodated in the liquid tank 20 is attached to the support plate 24 via a slide mechanism 27. The slide mechanism 27 moves the support rod 28 in the vertical direction with respect to the support plate 24 by a drive mechanism (not shown) (nozzle contact / separation means). That is, the liquid tank 20 and the nozzle 22 can be moved up and down with respect to the support plate 24 independently of each other.

FIG. 4 is a cross-sectional view showing the configuration of the main part of the coating means 2. As shown in FIG. 4, the upper end side of the support rod 28 enters the liquid tank 20 through a through hole 20 b provided in the bottom surface of the liquid tank 20. The nozzle 22 is attached to the upper end of the support rod 28. That is, the nozzle 22 is supported by the support rod 28 and stored in the liquid tank 20. The nozzle 22 has a length (horizontal width) corresponding to at least the length of the substrate 10 in the horizontal direction (the direction perpendicular to the paper surface in FIG. 4). A slit-like capillary gap 23 is provided along the direction). The nozzle 22 has a sharp cross-sectional shape with a narrow width on the tip side across the capillary gap 23. The upper end portion of the capillary gap 23 is opened at the tip end portion of the nozzle 22 in a slit shape that extends over substantially the entire length (lateral width) of the nozzle 22. The capillary gap 23 is also open toward the lower side of the nozzle 22.
Further, the upper surface of the liquid tank 20 is provided with a through hole 20a for the tip of the nozzle 22 to protrude above the liquid tank 20, and the coating liquid in the liquid tank 20 is provided. In order to prevent the liquid from being exposed to the atmosphere as much as possible, the upper surface portion of the liquid tank 20 has a cross-sectional shape in which the width on the upper end side is narrowed. The periphery of the through hole 20b on the bottom surface of the liquid tank 20 and the bottom surface of the nozzle 22 are connected by a bellows 29 to prevent the coating liquid 21 in the liquid tank 20 from leaking from the through hole 20b.

  Here, the configuration of the liquid tank 20 in the present embodiment will be described in more detail with reference to FIG. FIG. 6 is a cross-sectional view of the liquid tank 20 in the longitudinal direction (horizontal width direction when viewed from the front side). The liquid tank 20 has an entire length in the width direction when viewed from the side surface side. The overflow tank 6 has a predetermined height (h1), and the liquid tank 20 is partitioned by the overflow board 6 into two parts (regions), an application tank 20A and an overflow tank 20B. The overflow plate 6 regulates a desired liquid level at the start of application to a predetermined height (h1). Moreover, since the nozzle 22 is accommodated in the coating tank 20A in the liquid tank 20, the lateral width of the coating tank 20A has a length that does not hinder at least the entire nozzle 22 being accommodated. Yes. Further, the lateral width of the overflow tank 20B is not particularly limited and is arbitrary, but if it is too long, the lateral width of the entire liquid tank 20 becomes longer than necessary, so that the lateral width is as short as possible so that the effects of the present invention can be sufficiently exhibited. Is appropriate. Moreover, the coating liquid 21 is supplied to the coating tank 20A through the liquid supply line 7 provided on the bottom surface of the coating tank 20A (arrow A in the figure). Then, the coating liquid 21 in the overflow tank 20B is drained through the drain line 8 provided on the bottom surface of the overflow tank 20B (arrow B in the figure). In the present embodiment, the communication pipe 100 connected to the side wall of the coating tank 20A is provided, but a liquid level sensor (not shown) for controlling the supply amount when supplying the coating liquid 21 to the coating tank 20A. Can be attached.

FIG. 5 is a cross-sectional view showing a state where the coating means 2 is coating.
That is, as shown in FIG. 5, the coating liquid 21 stored in the liquid tank 20 is raised by the capillary phenomenon in the slit-like capillary gap 23 (gap gap T) of the nozzle 22, and the substrate 10 directed downward is formed. The tip portion (upper end portion) of the nozzle 22 is brought close to the coating surface 10a through a predetermined coating gap G, and the coating liquid rising to the nozzle tip portion is applied to the coating surface 10a of the substrate 10 through the nozzle tip portion. Then, the substrate 10 and the nozzle 22 are moved relative to each other and parallel to the coated surface 10a, and the coating liquid 21 is coated on the coated surface 10a of the substrate 10 to form a coated film. The relative movement direction of the substrate 10 and the nozzle 22 at this time is a direction orthogonal to the slit-shaped opening formed by the capillary gap 23 at the tip of the nozzle 22 as indicated by an arrow V in FIG. .

Next, the operation of the coating means 2 of the coating apparatus will be described in more detail, and the coating method of the present invention implemented using this coating apparatus will also be described in detail.
(1) After one application is completed, the liquid tank 20 is lowered to a predetermined position, and the nozzle 22 is immersed in the coating liquid 21 in the liquid tank 20 (application tank 20A) (in the state shown in FIG. 4). This is the so-called initial state of the positions of the liquid tank 20 and the nozzle 22).
At this time, the liquid level of the coating liquid 21 in the coating tank 20A is lower than the height (h1) of the overflow plate 6 (because it is consumed in the previous coating). The coating liquid in the overflow tank 20B is drained from the drain line 8.

(2) Next, with the drainage line 8 closed, the coating liquid is supplied (supplemented) from the liquid supply line 7 to the coating tank 20A. The liquid level of the coating liquid in the coating tank 20A first reaches the height (h1) of the overflow plate 6, and when the supply of the coating liquid is continued, it overflows from the upper end of the overflow plate 6 and flows into the overflow tank 20B. . Since the drain line 8 is closed, the liquid level of the coating liquid in the overflow tank 20B rises and reaches the height (h1) of the overflow plate 6. Further, when the liquid level of the entire coating liquid 21 in the liquid tank 20 reaches a predetermined height (h2) (h2> h1), the supply of the coating liquid is stopped (in FIG. 6A). Status). The supply amount of the coating liquid at this time may be controlled by installing a liquid level sensor in the communication pipe 100 described above and monitoring the liquid level.

(3) Next, the drainage line 8 is opened, and the coating liquid in the overflow tank 20B is discharged. At this time, at least a part of the coating liquid in the coating tank 20A overflows from the overflow plate 6 and flows into the overflow tank 20B (state shown in FIG. 6B). At this time, the flow (movement) of the coating liquid in one direction occurs toward the overflow tank at least in the vicinity of the surface of the coating liquid, and this overflow brings it into the coating tank 20A and floats on the surface of the coating liquid. Since the foreign material 9 also efficiently flows into the overflow tank 20B, the foreign material 9 is removed from the coating solution in the coating tank 20.
The liquid level in the coating tank 20A is the same as the height (h1) of the overflow plate 6, that is, it is constantly managed at the desired liquid level at the start of coating (state shown in FIG. 6C).
As described above, in the present invention, after one application is completed, the application liquid is replenished to the application tank 20A, and the liquid level is temporarily increased to a liquid level exceeding the desired liquid level at the start of application, Prior to the next application, the liquid level in the application tank 20A is started by allowing the application liquid stored up to the liquid level exceeding the desired liquid level at the start of application to overflow from the upper end of the overflow plate 6. The liquid level is set to a desired level at the time.

  Even if the coating solution in the overflow tank 20B is not completely discharged, the liquid level according to the present invention can be obtained with good reproducibility. However, floating foreign substances brought into the coating solution are removed. In order to exhibit the effect of doing more, it is desirable that the coating liquid in the overflow tank 20B described above is completely discharged and purified in the steps described later. For this reason, it is preferable that the drainage line 8 is installed on the bottom surface of the overflow tank 20B as in the present embodiment. Further, the liquid level is temporarily raised to a liquid level exceeding the desired liquid level at the start of coating. In this case, the liquid level exceeding the desired liquid level at the start of coating (that is, h2) It is preferable to set so that the effect of removing floating foreign substances brought into 20A by overflow can be obtained satisfactorily. For example, the height (liquid level) is preferably such that the foreign matter 9 brought into the coating tank 20A and floating mainly on the surface of the coating liquid comes above the height (h1) of the overflow plate 6.

(4) When the liquid level of the coating tank 20A becomes constant as described above, the nozzle 22 and the liquid tank 20 are raised to a predetermined position while the nozzle 22 is immersed in the coating liquid of the coating tank 20A. Only the nozzle 22 is projected, and the coating liquid at the tip of the nozzle 22 is in contact with the surface to be coated. Then, in a state where the liquid contact is maintained, the nozzle 22 (and / or the liquid tank 20) is lowered by a predetermined amount according to a desired coating film thickness, so that the coating gap G between the nozzle 22 and the surface to be coated is appropriately set. adjust. Then, the coating is started by relatively moving the substrate (surface to be coated) and the nozzle 22 (in this embodiment, only the substrate is moved).
(5) When one application is completed in this way, the above-described step (1) is performed again.

  In addition, the coating liquid recovered from the drainage line 8 in the above-described step (3) removes foreign matters through the filter means in the middle, and then is supplied again from the liquid supply line 7 to the coating tank 20A. Since the coating solution containing the drained floating foreign matter is once completely purified and recycled, coating defects can be greatly reduced.

  In the step (3) described above, the control of the liquid level due to overflow may be performed in a state where the nozzle 22 is immersed in the coating liquid in the coating tank 20A as described above. After the replenishment of the liquid, it may be performed after the tip of the nozzle 22 is lifted from the coating liquid for the next coating process. According to the former, since the replenishment of the coating liquid is performed in a state where the nozzle 22 is immersed in the coating liquid in the coating tank 20A, there is an advantage that the drying of the nozzle 22 can be prevented. Further, according to the latter, since the nozzle 22 floats on the coating liquid surface and the liquid surface vibration becomes quiet, the liquid surface level can be controlled by overflow, so that the liquid surface level at the start of coating is more reproducible. There is an advantage that it can be controlled well and accurately.

  As described above, by performing the coating film formation on the substrate using the coating apparatus of the present invention, the liquid level at the start of each coating can be accurately managed with good reproducibility due to overflow, so that between the substrates The uniformity of the coating film thickness can be improved. Moreover, after one application is completed, the application liquid is replenished to the liquid tank (coating tank), the liquid level is temporarily raised to a liquid level exceeding the desired liquid level at the start of application, and then the next application is performed. Prior to this, the coating liquid stored up to the liquid level exceeding the desired liquid level at the start of application in the liquid tank is overflowed, so that floating foreign substances brought into the coating tank can be efficiently removed by overflow. It is possible to greatly reduce coating defects due to foreign matters. In addition, by having an overflow plate of a predetermined height that regulates a desired liquid level at the start of application, the coating liquid stored up to a liquid level exceeding the desired liquid level at the start of application Since the overflow is performed from the upper end, the liquid level at the start of each application can be accurately managed with high reproducibility depending on the height of the overflow plate.

  The overflow means is not limited to the above-described means. For example, the liquid tank may have a double structure of an inner tank (coating tank) and an outer tank (overflow tank), and the overflow liquid from the inner tank may flow out to the outer tank. Also, the overflow plate that can be moved up and down by mechanical means or the like is raised to a predetermined site that exceeds a desired liquid level at the start of application, and after the application liquid is supplied to the liquid tank to the predetermined site, the overflow plate May be lowered to a predetermined height (a desired liquid level at the start of application).

Moreover, this invention is a photomask blank manufacturing method including the process of apply | coating the said coating liquid to the to-be-coated surface of a board | substrate by the coating method of this invention, and forming a coating film, wherein a coating liquid is a photoresist.
That is, by applying the coating method of the present invention and applying a photoresist on a substrate to form a photoresist film, the photomask has a uniform coating film thickness between the substrates and reduced coating defects. A blank can be obtained. In particular, in a liquid crystal display device or a photomask for manufacturing a liquid crystal display device, for example, a large substrate having a side of 300 mm or more is used, and according to the present invention, there is no uniform film thickness variation over the entire surface of such a large substrate. Since the photomask blank in which the resist film is formed can be obtained, the present invention is particularly suitable.

It is the side schematic diagram of the coating device which enforces the coating method concerning the present invention. It is the front schematic of the said coating device. It is sectional drawing which shows the structure of the application means in the said coating device. It is sectional drawing which shows the structure of the principal part of the application means in the said coating device. It is sectional drawing which shows the state which the application | coating means in the said coating device is performing application | coating. It is front sectional drawing which shows the structure of the liquid tank in the said application means for demonstrating the coating method of this invention. It is front sectional drawing which shows the structure of the liquid tank in the conventional coating device for demonstrating a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Application | coating apparatus 2 Application | coating means 3 Adsorption means 4 Moving means 5 Holding means 6 Overflow board 10 Substrate 20 Liquid tank 21 Application liquid 22 Nozzle 23 Capillary gap

Claims (13)

The coating liquid that passes through the nozzle from the liquid tank filled with the coating liquid and reaches the nozzle tip opening is brought into contact with the surface to be coated of the substrate, and the substrate and the nozzle are moved relatively in parallel to the surface to be coated. In the coating method of forming a coating film by applying a coating liquid to the surface to be coated,
After the completion of one application, the liquid tank is replenished with the application liquid, the liquid level is temporarily raised to a liquid level exceeding the desired liquid level at the start of application, and then the liquid is applied prior to the next application. The liquid level is lowered to the desired liquid level at the start of coating by overflowing the coating liquid stored up to the liquid level exceeding the desired liquid level at the start of coating in the tank. How to apply.   The liquid tank has an overflow plate of a predetermined height that regulates a desired liquid level at the start of coating, and the coating liquid stored up to a liquid level exceeding the desired liquid level at the start of coating, 2. The coating method according to claim 1, wherein the liquid level is set to a desired liquid level at the start of coating by overflowing from the upper end of the overflow plate.   The liquid tank is divided into at least two parts including an application tank and an overflow tank by an overflow plate, and the application liquid flows from the application layer into the overflow tank at the time of the overflow. The coating method according to claim 1 or 2.   The coating method according to claim 3, wherein the overflow is performed by draining at least a part of the coating liquid in the overflow tank.   5. The coating method according to claim 4, wherein the coating liquid drained from the overflow tank is supplied to the coating tank after foreign matters are removed by a filter member.   The coating method according to claim 1, wherein the replenishment of the coating liquid is performed in a state where the nozzle is immersed in a coating liquid in a liquid tank.   The coating method according to claim 4, wherein after replenishing the coating solution, at least a part of the nozzle is floated from the coating solution, and then the overflow tank is drained. A nozzle having a gap communicating with the tip opening, and leading the coating liquid to the tip opening through the gap;
A liquid tank for containing the coating liquid and supplying the coating liquid to the nozzle by immersing at least a part of the nozzle in the coating liquid;
Nozzle contacting / separating means for bringing the tip opening of the nozzle closer to the surface to be coated of the substrate and bringing the coating liquid guided to the tip opening into contact with the surface to be coated of the substrate;
The substrate and the nozzle are moved in parallel with and relative to the coated surface of the substrate in a state where the tip opening portion of the nozzle is brought close to the coated surface of the substrate by the nozzle contact / separation means. Moving means to cause
Control means for controlling the nozzle contacting / separating means and the moving means;
Have
The liquid tank has a liquid supply line for supplying a coating liquid therein, and means for overflowing the coating liquid when the liquid level of the coating liquid exceeds a predetermined liquid level. Coating device.   The liquid tank has an overflow plate of a predetermined height that regulates a desired liquid level at the start of coating, and the coating liquid stored up to a liquid level exceeding the desired liquid level at the start of coating, The coating apparatus according to claim 8, wherein the liquid level of the coating liquid is controlled to be constant depending on the height of the overflow plate by overflowing from the upper end of the overflow plate.   The liquid tank is divided into at least two parts including an application tank and an overflow tank by an overflow plate, and the application liquid flows from the application layer into the overflow tank at the time of the overflow. The coating device according to claim 8 or 9.   The coating apparatus according to claim 10, wherein the overflow is performed by draining at least a part of the coating liquid in the overflow tank.   12. The coating according to claim 11, further comprising: a filter unit that removes foreign matter in the coating liquid drained from the overflow tank; and a circulation unit that circulates the coating liquid after removing the foreign matter to the coating tank. apparatus. A coating liquid is a photoresist, and includes a step of forming a coating film by coating the coating liquid on a coated surface of a substrate by the coating method according to claim 1. Mask blank manufacturing method.

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