JP2004019993A - Drying method for quartz substrate, and quartz substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drying method for a quartz substrate capable of preventing generation of an aging stain on a substrate surface when storing the dried quartz substrate after the washing to reduce a frequency of execution of the rewashing before sending the stored quartz substrate to the following process. <P>SOLUTION: In this drying method for the quartz substrate after the washing, at least a first drying process for executing spin-drying to the washed quartz substrate and a second drying process for succeedingly or simultaneously heating and drying the quartz substrate after a process for washing the quartz substrate. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for drying a quartz substrate after cleaning, and more particularly to a method for drying a quartz substrate that can prevent generation of spots on the surface over time even if the quartz substrate is stored after drying.
[0002]
[Prior art]
In the semiconductor photomask manufacturing process, it is necessary to wash the quartz substrate at each stage such as a substrate, a photomask blank or a photomask. As a method for drying the washed quartz substrate surface, a solvent using isopropyl alcohol (IPA) vapor is used. A method of drying by replacement, a method of drying by blowing off a liquid by centrifugal force (spin drying), and the like are performed.
[0003]
However, in the method using IPA vapor, the drying time can be shortened. However, since the IPA is heated and used, it is difficult to handle on fire prevention. Therefore, it is necessary to use a special device for safety. Inevitably increases the cost of the device.
[0004]
In the method of drying by spinning off the liquid by centrifugal force (spin drying), if the drying time is long, dust is generated from the rotating mechanism, and the quartz substrate is easily contaminated. In particular, when a square quartz substrate is spin-dried, the turbulence of the air current becomes large due to the wind, and the drying time is prolonged, thereby easily causing contamination. Furthermore, there is a problem that drying is incomplete and a watermark is likely to remain.
[0005]
In addition, during storage, there is a problem that the substrate surface is stained with time and particles adhere. The problem of the adhesion of particles can be prevented by keeping the storage environment clean, but it has not been possible to prevent the appearance of stains that appear on the substrate surface over time during storage. For this reason, conventionally, the storage time after drying the quartz substrate is shortened and sent to the next process, but it is impossible to completely eliminate the storage, and it is necessary to repeat the washing process before sending to the next process I had to deal with it.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems, and when storing a dried quartz substrate after washing, it is possible to prevent the occurrence of blemishes on the substrate surface over time, and to store the quartz that has been stored. It is an object of the present invention to provide a method for drying a quartz substrate, which can reduce the frequency of re-cleaning before sending the substrate to the next step.
[0007]
[Means for Solving the Problems]
The present invention has been made in order to solve the above-mentioned problems, and is a method for drying a quartz substrate after washing, wherein after a step of washing the quartz substrate, at least a first step of spin-drying the washed quartz substrate is performed. And a second drying step in which the quartz substrate is dried by heating the quartz substrate thereafter or simultaneously (claim 1).
[0008]
Thus, after the step of cleaning the quartz substrate, at least a first drying step of spin-drying the washed quartz substrate and a second drying step of heating the quartz substrate thereafter or simultaneously are performed, so that the spinning is performed. The water on the substrate is shaken off in a short time by drying, and the water film remaining on the surface of the substrate, which is a cause of bleeding over time, can be more effectively evaporated by the drying by heating. Therefore, the quartz substrate thus dried is stored. In this case, it is possible to prevent the occurrence of bleeding over time on the substrate surface. In addition, since the drying step is performed in two stages, the first drying step and the second drying step, each drying time can be shortened, thereby reducing the possibility of contamination of the substrate in the drying step. Besides, it is possible to improve the throughput of the drying step.
In the present specification, “stain” is generated over time when a dried quartz substrate is stored, and is detected as a bright spot of 0.2 μm or more by a particle counter. When observed with a microscope (AFM, Atomic Force Microscope), it refers to what is confirmed as a droplet.
[0009]
In this case, the second drying step of drying the quartz substrate by heating is preferably performed by any one or more of drying with an infrared lamp, hot air drying, and substrate heating and drying using a hot plate. 2).
[0010]
In this manner, the second drying step of performing drying by heating the quartz substrate can be performed by drying with an infrared lamp, hot air drying, or any one or more of substrate heating and drying using a hot plate. With the method described above, it is possible to easily and inexpensively configure, and it is possible to effectively evaporate a water film remaining on the substrate surface, which is a cause of aging spots, by heating while maintaining the quartz substrate with high cleanliness. Can be.
[0011]
Further, according to the present invention, there is provided a quartz substrate dried after washing by the drying method (Claim 3), and the quartz substrate dried after washing, wherein the storage period of the quartz substrate is at least 7 after drying. A quartz substrate is provided that does not cause spots having a size of 0.2 μm or more on the surface within a period of less than one day (claim 4).
[0012]
As described above, according to the present invention, after the quartz substrate is washed, the first drying step of performing spin drying and the second drying step of performing drying by heating are performed. A quartz substrate that can prevent occurrence of stains can be provided. Such a quartz substrate is placed in a box made of polypropylene, for example, in a clean room of class 10 or less, and is stored in an outer box made of ABS resin. In which no spots having a size of 0.2 μm or more are generated. Therefore, even if the quartz substrate is stored for a longer time than a quartz substrate in which the drying process is performed only by spin drying, the quartz substrate can be used without being washed again before being sent to the next process. Further, when such a quartz substrate is used in a photomask manufacturing process such as a substrate, a photomask blank, or a photomask, a device manufacturing process, etc., the frequency at which recleaning is required is reduced, and productivity is reduced. And the yield can be improved.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
The inventors of the present invention have found that, after drying and storing the washed quartz substrate, the cause of aging is caused by the water film remaining on the substrate surface due to the high hydrophilicity and high wettability of the synthetic quartz surface. It was found to be due to. Therefore, the water on the substrate surface is shaken off in a short time by spin-drying the washed quartz substrate, and thereafter or simultaneously, the residual water film on the substrate surface is vaporized by heating the quartz substrate, thereby causing a stain over time. The present invention has been completed in view of the fact that generation of the above can be suppressed.
[0014]
The method for drying a quartz substrate of the present invention comprises, after the step of washing the quartz substrate, at least a first drying step of spin-drying the washed quartz substrate, and a second drying step of heating the quartz substrate thereafter or simultaneously. Is performed. This is because, if the drying process is only drying by heating, it takes much time to dry the quartz substrate, and moreover, it is expected that stains frequently occur on the substrate surface. Therefore, spin drying is performed before or at the same time as drying by heating, so that water on the substrate surface is shaken off in a short time. By shortening the spin drying time, dust generation and contamination of the substrate due to the long spin drying time as described above are not caused. Further, when the drying step is only spin drying, when the quartz substrate is stored after drying, the surface of the substrate is stained with time. It is possible to completely evaporate the water film remaining on the substrate surface, which is a cause of the generation of stains. As described above, in the present invention, the dried quartz substrate is dried in two stages of the drying process.
[0015]
First, in the step of cleaning the quartz substrate, the quartz substrate is cleaned by a general method such as immersion cleaning with hot sulfuric acid, scrub cleaning with a surfactant, shower cleaning with a hydrofluoric acid aqueous solution, a potassium hydroxide aqueous solution and ultrapure water. I do. In addition, in the present invention, the step of cleaning the quartz substrate is not particularly limited, and may be any of conventionally used methods.
[0016]
Next, spin drying is performed as a first drying step. In spin drying, water on the substrate is shaken off by centrifugal force to dry the quartz substrate. Thus, the drying time in the second drying step can be reduced, and the spin drying time can be also reduced because of the second drying step. Therefore, the possibility that the substrate is contaminated in the drying step can be reduced, and the throughput of the drying step can be improved as a whole, and the productivity can be improved.
[0017]
After or simultaneously with the spin drying, the substrate is dried by heating as a second drying step. As the drying by heating, for example, it is preferable to perform any one or more of drying with an infrared lamp, drying with hot air, and heating and drying the substrate with a hot plate. By heating the quartz substrate to which water has been shaken off by spin drying by these drying methods, the residual water film on the substrate surface can be effectively vaporized, and even if the quartz substrate is stored after drying, It is possible to prevent the occurrence of stains.
[0018]
The dried quartz substrate is placed in a polypropylene box in a clean room of class 10 or less, for example, and stored in an outer box made of ABS resin. As described above, if the storage environment is clean, contamination due to adhesion of particles during storage can be prevented.In particular, in the present invention, it is possible to prevent the occurrence of spots due to the residual water film during storage. Can be prevented. When the quartz substrate of the present invention is stored, the method of storing the quartz substrate itself is not particularly limited, and may be any of conventionally used methods capable of preventing adhesion of particles during storage.
[0019]
Note that a step of heating the quartz substrate with warm water may be performed between the washing step and the drying step. By heating the quartz substrate with warm water, the substrate is heated, and in the subsequent drying step, evaporation of water is promoted, and the drying time can be further reduced.
[0020]
FIG. 2 shows a schematic configuration example of a spin dryer having an infrared lamp that can be used when the drying method of the present invention is performed. The spin dryer 1 has a drying chamber 2 and a partition 3 inside the drying chamber 2, and a spindle 4 that can rotate and move up and down therein. At the upper end of the spindle 4, there is a support table 5 for holding a quartz substrate. Above the support table 5, an IR lamp 6 for irradiating the quartz substrate held by the support table 5 with infrared rays is vertically movable. Attached to. The inside of the drying chamber 2 and the inside of the partition 3 are also evacuated and exhausted by exhaust ports 8 and 9, respectively.
[0021]
In this apparatus, first, the quartz substrate is set on the support table 5 and the spindle 4 is rotated at a high speed while exhausting air from the exhaust ports 8 and 9, so that the water (cleaning liquid) adhering to the quartz substrate on the support table 5 is removed. ) Can be spin dried by shaking. At this time, desired drying can be performed by adjusting the rotation speed of the spindle, the exhaust pressure, and the drying time. The shaken water hits the partition wall 3 to prevent the water from floating in the drying chamber 2 and re-adhering to the substrate. When the spin drying is completed, the IR lamp 6 is lowered, and is placed immediately above the quartz substrate on the support base 5, and by turning on the lamp, the quartz substrate can be dried by the infrared lamp. In this apparatus, since the IR lamp is provided during the spin drying, the IR lamp 6 can be turned on while rotating the spindle 4, and the drying can be performed at the same time. By doing so, the drying time can be further reduced. However, it goes without saying that spin drying and drying for heating the quartz substrate may be performed by different apparatuses.
[0022]
In the quartz substrate obtained by the drying method of the present invention as described above, generation of spots over time is suppressed during storage after drying. For example, when such a quartz substrate is put in a polypropylene box in a clean room of class 10 or less and stored in an outer box made of an ABS resin, at least within 7 days, and even within 14 days. During this period, it is possible to prevent spots with a size of 0.2 μm or more from appearing on the surface of the substrate over time. Therefore, once packed in a box, the substrate can be shipped as it is. It is also possible to use it as it is without taking it out of the box. Therefore, when such a quartz substrate is used in, for example, a substrate, a photomask blank, or a photomask manufacturing process or a device manufacturing process, productivity and yield can be improved.
[0023]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples and the like.
(Example 1)
A 200 cm ² square quartz substrate (substrate without a film) was prepared. First, as a cleaning step, the prepared square quartz substrate is shower-washed with a 0.5% by weight aqueous hydrofluoric acid solution, showered with ultrapure water, and then showered with an aqueous solution of potassium hydroxide having a pH of 11 and subsequently ultrapure water. Was washed in the shower. Next, the square quartz substrate cleaned in the above-mentioned washing step was rinsed by flowing it in hot pure water at 60 ° C. for 60 seconds. Next, as a first drying step, the square quartz substrate was spin-dried at 1500 rpm for 20 seconds, and then, as a second drying step, dried by heating with an infrared lamp for 180 seconds. After drying, the quartz substrate was placed in a box made of polypropylene in a clean room of class 10 or less and stored in an outer box made of ABS resin. The number of stains on the substrate surface was determined by first confirming a bright spot having a size of 0.2 μm or more with a particle counter, and confirming whether the spot was a stain with an atomic force microscope (AFM, Atomic Force Microscope). As a result, the occurrence of spots with time on days 0, 2, 5, 7, 10, and 14 after storage was 0 for a size of 0.2 μm or more, and one for days 18, 20, and 21. It was confirmed that there was.
[0024]
(Example 2)
As in Example 1, a 200 cm ² square quartz substrate was prepared. First, as a cleaning step, the prepared square quartz substrate is shower-washed with a 0.5% by weight aqueous hydrofluoric acid solution, showered with ultrapure water, and then showered with an aqueous solution of potassium hydroxide having a pH of 11 and subsequently ultrapure water. Was washed in the shower. Next, the square quartz substrate cleaned in the washing step was rinsed by pouring it into hot pure water at 60 ° C. for 60 seconds. Next, as a first drying step, the square quartz substrate was spin-dried at 1500 rpm for 20 seconds, and then, as a second drying step, the square quartz substrate was dried by heating on a hot plate at 120 ° C. for 120 seconds. After drying, the quartz substrate was placed in a box made of polypropylene in a clean room of class 10 or less and stored in an outer box made of ABS resin. The number of spots on the surface of the substrate was determined by first checking the bright spots of 0.2 μm or more with a particle counter, and checking whether the spots were spots by AFM. As a result, the number of spots with time after storage for 7 days was 0 at a size of 0.2 μm or more.
[0025]
(Example 3)
As in Example 1, a 200 cm ² square quartz substrate was prepared. First, as a cleaning step, the prepared square quartz substrate is shower-washed with a 0.5% by weight aqueous hydrofluoric acid solution, showered with ultrapure water, and then showered with an aqueous solution of potassium hydroxide having a pH of 11 and subsequently ultrapure water. Was washed in the shower. Next, the square quartz substrate cleaned in the washing step was rinsed by pouring it into hot pure water at 60 ° C. for 60 seconds. Next, as a first drying step, the square quartz substrate was spin-dried at a rotation speed of 1500 rpm for 20 seconds, and then, as a second drying step, the square quartz substrate was dried with hot air at 60 ° C. for 120 seconds. After drying, the quartz substrate was placed in a box made of polypropylene in a clean room of class 10 or less and stored in an outer box made of ABS resin. The number of spots on the surface of the substrate was determined by first checking the bright spots of 0.2 μm or more with a particle counter, and checking whether the spots were spots by AFM. As a result, the number of spots with time after storage for 7 days was 0 at a size of 0.2 μm or more.
[0026]
(Comparative Example 1)
A square quartz substrate of 200 cm ² was prepared. First, as a cleaning step, the prepared square quartz substrate is shower-washed with a 0.5% by weight aqueous hydrofluoric acid solution, showered with ultrapure water, and then showered with an aqueous solution of potassium hydroxide having a pH of 11 and subsequently ultrapure water. Was washed in the shower. Next, the square quartz substrate cleaned in the above-mentioned washing step was rinsed by flowing it in hot pure water at 60 ° C. for 60 seconds. Next, as a drying step, the square quartz substrate was spin-dried at a rotation speed of 1500 rpm for 60 seconds. After drying, the quartz substrate was placed in a box made of polypropylene in a clean room of class 10 or less and stored in an outer box made of ABS resin. The number of spots on the surface of the substrate was determined by first checking the bright spots of 0.2 μm or more with a particle counter, and checking whether the spots were spots by AFM. As a result, the occurrence of spots with time on days 0 and 2 after storage was 0 for a size of 0.2 μm or more, but 2 on day 5, 3 on day 7, and 10 on day 7. It was confirmed that the number was 6, and the number was 8 on the days 14, 18, 20, and 21.
[0027]
FIG. 1 is a graph showing the occurrence of spots over time in Example 1 and Comparative Example. In Example 1, it can be seen that no staining with a size of 0.2 μm or more over time occurred on the substrate surface until the 7th day and further the 14th day after storage. On the other hand, in the comparative example, no bleeding over time occurred on the substrate surface until the second day after storage, but the bleeding occurred as early as the fifth day.
[0028]
Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same operation and effect can be realized by the present invention. It is included in the technical scope of the invention.
[0029]
For example, in the above embodiment, the quartz substrate after cleaning was dried using a square synthetic quartz substrate, but the method of the present invention can be applied without being limited to a quartz substrate having such a shape and form. In addition, the present invention can be applied to a photomask blank or a photomask provided with a pattern film.
[0030]
【The invention's effect】
According to the present invention, when drying the quartz substrate cleaned by the cleaning step, spin drying is performed on the substrate as a first drying step, and thereafter, drying is performed by heating as a second drying step. It is possible to prevent the occurrence of aging spots on the substrate surface. Therefore, the frequency of re-cleaning the quartz substrate before using it in the next step can be reduced, so that once it is packed in a box, it can be shipped as it is, and it is also possible to use it out of the box. Furthermore, when such a quartz substrate is used in, for example, a substrate, a photomask blank, a photomask manufacturing process, or a device manufacturing process, productivity and yield can be improved.
[Brief description of the drawings]
FIG. 1 is a graph showing the occurrence of spots over time in the conventional case and the present invention.
FIG. 2 is a schematic structural example diagram of a spin dryer having an infrared lamp used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Spin dryer, 2 ... Drying room, 3 ... Partition wall, 4 ... Spindle, 5 ... Support stand, 6 ... IR lamp, 7 ... Support arm, 8, 9 ... Exhaust port.

Claims (4)

A method for drying a quartz substrate after washing, wherein after the step of washing the quartz substrate, at least a first drying step of spin-drying the washed quartz substrate and thereafter or simultaneously performing drying to heat the quartz substrate. A method for drying a quartz substrate, comprising performing a second drying step. The second drying step of performing drying by heating the quartz substrate includes performing at least one of drying with an infrared lamp, drying with hot air, and substrate heating and drying with a hot plate. 3. The method for drying a quartz substrate according to item 1. A quartz substrate dried after being washed by the method according to claim 1. A quartz substrate that has been dried after cleaning, wherein the surface of the quartz substrate is free from spots having a size of 0.2 μm or more when stored for at least 7 days after drying. Quartz substrate.

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