JP3857957B2 - Method for drying quartz substrate and quartz substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for drying a quartz substrate after cleaning, and relates to a method for drying a quartz substrate that can prevent the occurrence of stains 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 clean a quartz substrate at each stage such as a substrate, a photomask blank, or a photomask. As a method for drying the cleaned quartz substrate surface, a solvent using isopropyl alcohol (IPA) vapor is used. There are a method of drying by substitution, a method of blowing a liquid by centrifugal force and drying (spin drying), and the like.
[0003]
However, in the method using the IPA vapor, the drying time can be shortened, but since the IPA is heated and used, it is difficult to handle on fire prevention, and therefore the device needs to be a special device for safety. The cost of equipment is inevitable.
[0004]
Further, in the method of drying by spinning off the liquid with a centrifugal force (spin drying), if the drying time becomes long, dust is generated from the rotating mechanism and the quartz substrate is easily contaminated. In particular, when spin-drying a square quartz substrate, the turbulence of the airflow increases due to the wind, and the drying time is prolonged, which easily causes contamination. Furthermore, there is a problem that drying is incomplete and the watermark tends to remain.
[0005]
In addition, there is a problem that, during storage, the surface of the substrate is stained over time or particles are adhered. The problem of particle adhesion can be prevented by keeping the storage environment clean, but it has not been possible to prevent the occurrence of stains that appear over time on the substrate surface during storage. Therefore, in the past, the storage time after drying the quartz substrate has been shortened and sent to the next process, but it is impossible to completely eliminate the storage, and the cleaning process must be put in again 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. When a dried quartz substrate after cleaning is stored, the substrate surface is prevented from being stained and stored. An object of the present invention is to provide a quartz substrate drying method capable of reducing 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 to solve the above-described problems, and is a method for drying a quartz substrate after washing, and is a first method of performing spin drying on at least the washed quartz substrate after the step of washing the quartz substrate. And a second drying step in which the quartz substrate is dried after or simultaneously with the drying step .
[0008]
Thus, after the step of cleaning the quartz substrate, at least a first drying step of performing spin drying on the cleaned quartz substrate and a second drying step of heating the quartz substrate thereafter or simultaneously are performed. Sprinkle water on the substrate in a short time by drying, and by drying by heating, the water film remaining on the substrate surface, which is the cause of stains over time, can be evaporated more effectively, so store the dried quartz substrate in this way In this case, it is possible to prevent a stain from occurring over time on the substrate surface. Moreover, since the drying process is divided into two stages, a first drying process and a second drying process, each drying time can be shortened, thereby reducing the possibility of the substrate being contaminated in the drying process. In addition, the throughput of the drying process can be improved.
In the present specification, “stain” is generated with 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, and this is detected as atomic force. When observed with a microscope (AFM, Atomic Force Microscope), it is confirmed as a droplet.
[0009]
In this case, the second drying step for drying the quartz substrate is preferably performed by any one or more of drying with an infrared lamp, warm air drying, and substrate heating drying with a hot plate .
[0010]
In this way, the second drying step for drying the quartz substrate can be any one or more of drying with an infrared lamp, drying with hot air, or substrate heating with a hot plate. This method can be configured easily and inexpensively, and the water film remaining on the surface of the substrate, which is the cause of the stain over time, can be effectively evaporated by heating while maintaining the quartz substrate with high cleanliness. Can do.
[0011]
Further according to the present invention, the drying process the dried quartz substrate after cleaning is provided with, also, a quartz substrate and dried after washing, in the period of time of storage is within at least 7 days after drying of the quartz substrate There is provided a quartz substrate which does not generate a stain having a size of 0.2 μm or more on the surface .
[0012]
As described above, according to the present invention, after the quartz substrate is washed, the first drying step for performing spin drying and the second drying step for performing heating drying are performed, so that even when stored after drying, It is possible to provide a quartz substrate that can prevent the occurrence of spotting. Such a quartz substrate is placed in a polypropylene box, for example, in a clean room of class 10 or lower, and stored in an ABS resin outer box. No stain of 0.2 μm or more is generated. Therefore, even if it is stored for a longer time than a quartz substrate in which the drying process is only spin drying, the quartz substrate can be used without being re-cleaned before being sent to the next process. Further, when such a quartz substrate is used in a photomask manufacturing process, a device manufacturing process, such as a substrate, a photomask blank, or a photomask, the frequency with which re-cleaning is required is reduced, and productivity is increased. And yield can be improved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although embodiment of this invention is described, this invention is not limited to these.
When the washed quartz substrate is dried and stored, the cause of the stain over time is that the synthetic quartz has a hydrophilic surface and good wettability, so that the water film remaining on the substrate surface I found out that Accordingly, the quartz substrate after cleaning is spin-dried to sprinkle water on the substrate surface in a short time, and thereafter or simultaneously, the quartz substrate is heated to vaporize the residual water film on the substrate surface. The present invention has been completed by conceiving that it is possible to suppress the occurrence of.
[0014]
In the method for drying a quartz substrate according to the present invention, after the step of cleaning the quartz substrate, at least a first drying step of performing spin drying on the cleaned quartz substrate and a second of performing drying by heating the quartz substrate thereafter or simultaneously. The drying step is performed. In this case, when the drying process is only drying by heating, it takes a very long time to dry the quartz substrate, and it is predicted that stains frequently occur on the substrate surface. Therefore, the water on the substrate surface was shaken off in a short time by performing spin drying before or at the same time as drying to heat. By shortening the spin drying time, dust generation and substrate contamination due to the long spin drying time as described above are not caused. In addition, when the drying process is only spin drying, if the quartz substrate is stored after drying, stains with time will occur on the substrate surface. However, by performing heating drying after or simultaneously with spin drying, It is possible to completely evaporate the water film remaining on the substrate surface, which is the cause of the stain. From the above, in the present invention, the washed quartz substrate is dried in two stages.
[0015]
First, 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 hydrofluoric acid aqueous solution, potassium hydroxide aqueous solution or ultrapure water. To do. In addition, in the present invention, the quartz substrate cleaning step is not particularly limited, and any of the methods conventionally used may be used.
[0016]
Next, spin drying is performed as a first drying step. In spin drying, water on the substrate is spun off by centrifugal force to dry the quartz substrate. Thereby, while being able to shorten the drying time of a 2nd drying process, since there is a 2nd drying process, the time of spin drying can also be shortened. Therefore, the possibility that the substrate is contaminated in the drying process can be reduced, and the throughput of the drying process can be improved as a whole, and the productivity can be improved.
[0017]
After the spin drying or at the same time, as the second drying step, drying is performed by heating the substrate. As the drying to be heated, for example, at least one of drying with an infrared lamp, warm air drying, substrate heating drying with a hot plate, or the like is preferably performed. By these methods, heating the quartz substrate from which water has been spun off by spin drying can effectively vaporize the residual water film on the substrate surface. It is possible to prevent the occurrence of natural spots.
[0018]
The quartz substrate after drying is placed in a polypropylene box in a clean room of class 10 or lower, for example, and stored in an outer box made of ABS resin. In this way, if the storage environment is made clean, contamination due to the adhesion of particles during storage can be prevented, and in the present invention, in particular, stains due to residual water film occur during storage. Can be prevented. When storing the quartz substrate of the present invention, the method for storing the quartz substrate itself is not particularly limited, and may be any conventionally used method 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 cleaning step and the drying step. By heating the quartz substrate with warm water, the substrate is warmed, and in the subsequent drying step, evaporation of water is promoted, and the drying time can be further shortened.
[0020]
FIG. 2 shows a schematic configuration example of a spin dryer equipped with an infrared lamp that can be used when the drying method of the present invention is carried out. This spin dryer 1 has a drying chamber 2 and a partition 3 inside thereof, and a spindle 4 that can rotate and move up and down. At the upper end of the spindle 4 is a support base 5 for holding a quartz substrate. Above the support base 5, an IR lamp 6 for irradiating infrared light to the quartz substrate held by the support base 5 can be moved up and down. Is attached. The inside of the drying chamber 2 and the partition wall 3 has a function of exhausting and draining through the exhaust ports 8 and 9, respectively.
[0021]
In this apparatus, first, a quartz substrate is set on the support base 5 and the spindle 4 is rotated at a high speed while exhausting from the exhaust ports 8 and 9, whereby moisture (cleaning liquid) adhering to the quartz substrate on the support base 5. ) Can be spin dried. At this time, desired drying can be performed by adjusting the rotation speed of the spindle, the exhaust pressure, and the drying time. The splashed water hits the partition wall 3 and floats in the drying chamber 2 to prevent reattachment to the substrate. When the spin drying is completed, the IR lamp 6 is lowered, and the IR lamp 6 is disposed immediately above the quartz substrate on the support base 5, and the quartz substrate can be dried by an infrared lamp by turning on the lamp. In this apparatus, since the IR lamp is provided during spin drying, the IR lamp 6 can be turned on while the spindle 4 is rotated, and drying can be performed simultaneously. By doing so, the drying time can be further shortened. 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, the occurrence of stains over time is suppressed during storage after drying. When such a quartz substrate is placed in a polypropylene box in a clean room of class 10 or less and stored in an outer box made of ABS resin, the quartz substrate is stored within at least 7 days or even 14 days. Since it is possible to prevent a stain with a size of 0.2 μm or more appearing on the substrate surface over time, it can be shipped as it is once packed in a box, and the quartz substrate is re-cleaned before being used in the next process. It is also possible to use it as it is out of the box. Therefore, 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.
[0023]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to the following Example etc.
Example 1
A 200 cm ² square quartz substrate (a substrate without film formation) was prepared. First, as a cleaning process, the prepared square quartz substrate is shower-washed with a 0.5 wt% hydrofluoric acid aqueous solution, showered with ultrapure water, then shower-washed with a pH 11 potassium hydroxide aqueous solution, and subsequently ultrapure water. Washed with shower. Next, the square quartz substrate cleaned in the washing step was rinsed by pouring with warm 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, it was dried by heating with an infrared lamp for 180 seconds. After drying, the quartz substrate was placed in a polypropylene box in a clean room of class 10 or lower and stored in an outer box made of ABS resin. The number of spots on the surface of the substrate was counted by first confirming a bright spot having a size of 0.2 μm or more with a particle counter, and confirming whether or not the spot was spotted with an atomic force microscope (AFM, Atomic Force Microscope). As a result, the occurrence of stains over time on the 0th, 2nd, 5th, 7th, 10th, and 14th days after storage was 0 in the size of 0.2 μm or more, and 1 on the 18th, 20th, 21st 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 process, the prepared square quartz substrate is shower-washed with a 0.5 wt% hydrofluoric acid aqueous solution, showered with ultrapure water, then shower-washed with a pH 11 potassium hydroxide aqueous solution, and subsequently ultrapure water. Washed with shower. Next, the rectangular quartz substrate cleaned in the washing step was rinsed by pouring into warm 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 by heating with a hot plate at 120 ° C. for 120 seconds. After drying, the quartz substrate was placed in a polypropylene box in a clean room of class 10 or lower and stored in an outer box made of ABS resin. The number of stains on the surface of the substrate was counted by first confirming a bright spot of 0.2 μm or more with a particle counter and confirming whether it was a stain with AFM. As a result, the occurrence of blots over time after storage for 7 days was zero with 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 process, the prepared square quartz substrate is shower-washed with a 0.5 wt% hydrofluoric acid aqueous solution, showered with ultrapure water, then shower-washed with a pH 11 potassium hydroxide aqueous solution, and subsequently ultrapure water. Washed with shower. Next, the rectangular quartz substrate cleaned in the washing step was rinsed by pouring into warm 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 polypropylene box in a clean room of class 10 or lower and stored in an outer box made of ABS resin. The number of stains on the surface of the substrate was counted by first confirming a bright spot of 0.2 μm or more with a particle counter and confirming whether it was a stain with AFM. As a result, the occurrence of blots over time after storage for 7 days was zero with a size of 0.2 μm or more.
[0026]
(Comparative Example 1)
A 200 cm ² square quartz substrate was prepared. First, as a cleaning process, the prepared square quartz substrate is shower-washed with a 0.5 wt% hydrofluoric acid aqueous solution, showered with ultrapure water, then shower-washed with a pH 11 potassium hydroxide aqueous solution, and subsequently ultrapure water. Washed with shower. Next, the square quartz substrate cleaned in the washing step was rinsed by pouring with warm pure water at 60 ° C. for 60 seconds. Next, as a drying process, the square quartz substrate was spin-dried at a rotational speed of 1500 rpm for 60 seconds. After drying, the quartz substrate was placed in a polypropylene box in a clean room of class 10 or lower and stored in an outer box made of ABS resin. The number of stains on the surface of the substrate was counted by first confirming a bright spot of 0.2 μm or more with a particle counter and confirming whether it was a stain with AFM. As a result, the occurrence of stains over time on the 0th and 2nd days after storage was 0 in the size of 0.2 μm or more, but 2 on the 5th day, 3 on the 7th day, 10th day It was confirmed that there were 6 on the 14th, 14th, 18th, 20th and 21st day.
[0027]
FIG. 1 is a graph showing the occurrence of stains over time in Example 1 and a comparative example. In Example 1, it can be seen that no stain with a size of 0.2 μm or more was generated on the surface of the substrate on the 7th day and the 14th day after storage. On the other hand, in the comparative example, no stain with time has occurred on the substrate surface until the second day after storage, but the stain has occurred early after the fifth day.
[0028]
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0029]
For example, in the above embodiment, a square synthetic quartz substrate is used to dry the quartz substrate after cleaning, but the method of the present invention is not limited to the quartz substrate having such a shape and form. It can also be applied to a photomask blank or a photomask provided with a patterning film.
[0030]
【The invention's effect】
According to the present invention, when the quartz substrate cleaned by the cleaning process is dried, the substrate is subjected to spin drying as the first drying process, and thereafter or simultaneously heated to be heated as the second drying process, It is possible to prevent the stain on the substrate surface from occurring over time. Therefore, since the frequency of re-cleaning the quartz substrate before using it in the next process can be reduced, it can be shipped as it is once packed in a box, and it can also be used as it is out of the box. Further, 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 a stain over time in the conventional case and the present invention.
FIG. 2 is a schematic configuration diagram of a spin dryer provided with an infrared lamp used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Spin dryer, 2 ... Drying chamber, 3 ... Bulkhead, 4 ... Spindle, 5 ... Support stand, 6 ... IR lamp, 7 ... Support arm, 8, 9 ... Exhaust port.

Claims (3)

A drying method of a quartz substrate after cleaning, after the step of cleaning the quartz substrate, at least, first carried out a first drying step of performing spin drying the washed quartz substrate, after which the dry heating the quartz substrate A method for drying a quartz substrate, comprising performing a second drying step. 2. The method for drying a quartz substrate according to claim 1, wherein a step of heating the quartz substrate with warm water is performed between the cleaning step and the drying step. 2. The second drying step of performing drying by heating the quartz substrate is performed by any one or more of drying with an infrared lamp, warm air drying, and substrate heating drying with a hot plate. Alternatively, the method for drying a quartz substrate according to claim 2 .

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