JP2010091774A - Cleaning method and cleaning fluid supplying apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method with which generation of foreign matter can be extremely reduced when a substrate to be cleaned such as a transparent substrate for a photomask, a photomask blank, a photomask production intermediate, and a photomask, is cleaned, and to provide a cleaning fluid supplying apparatus that supplies a cleaning fluid to a cleaning apparatus. <P>SOLUTION: The method for cleaning a substrate to be cleaned by supplying a cleaning fluid to a cleaning apparatus includes filtering the cleaning fluid with a filter for removing foreign matter and supplying the filtered cleaning fluid to the cleaning apparatus through a supply pipe to the cleaning apparatus to clean the objective substrate, wherein at least prior to supplying the filtered cleaning fluid to the cleaning apparatus, the filtered cleaning fluid is discharged to the outside of a system through a discharge pipe and then the filtered cleaning fluid is supplied to the cleaning apparatus through the supply pipe. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a substrate cleaning method and a cleaning liquid supply apparatus, and in particular, a cleaning method for cleaning a substrate such as a transparent substrate for photomask used in lithography, a photomask blank, a photomask blank manufacturing intermediate, a photomask, and the like. The present invention relates to a cleaning liquid supply apparatus.

  Photomasks used in a wide range of applications including the manufacture of semiconductor integrated circuits such as IC, LSI, and VLSI are basically thin films containing a metal or metal compound on a light-transmitting substrate (photomask substrate). The light-shielding film of the photomask blank on which the light-shielding film is formed is processed into a predetermined light-shielding film pattern using an electron beam photolithography method or the like.

  In the lithography method used in the process for producing precision electronic materials such as LSIs, for example, a photomask on which a diagram of an electronic circuit is drawn is used as an original drawing, and the pattern is formed on the photosensitive material by light irradiation. In recent years, along with market demands such as higher integration of semiconductor integrated circuits, pattern miniaturization has rapidly progressed, and higher precision of masks used for exposure has been required, and there has been a demand for defects in photomask blanks. It has become expensive.

For this reason, it is required that the quartz, CaF _{2 and} other substrates for manufacturing the photomask blank and the photomask blank be cleaned very precisely. Therefore, usually, after cleaning with a surfactant, multi-stage cleaning with hydrogen water or ozone water is performed, and rinsing with ultrapure water is performed at each stage as required (for example, Patent Documents). 1 and Patent Document 2).

  On the other hand, even when the multi-stage cleaning as described above is performed, the obtained substrate is not unconditionally cleaned, and fine foreign matters may occur at a considerable frequency. For example, when the drying method is not appropriate, contamination (foreign matter) may occur when water droplets are dried (see Patent Document 3).

JP 2001-96241 A JP 2002-151453 A Japanese Patent Laid-Open No. 2004-19993

  The present invention has been made in view of such problems, and foreign matter is generated when a substrate to be cleaned, such as a transparent substrate for photomask, a photomask blank, a photomask blank manufacturing intermediate, a photomask, or the like is cleaned. It is an object of the present invention to provide a cleaning method capable of reducing the amount of the cleaning liquid and a cleaning liquid supply apparatus that supplies the cleaning liquid to the cleaning apparatus.

  In order to solve the above-mentioned problems, the present invention provides a cleaning method for supplying a cleaning liquid to a cleaning apparatus to clean a substrate to be cleaned, wherein the cleaning liquid is filtered with a filter for removing foreign matter, and the filtered cleaning liquid When the substrate to be cleaned is supplied to the cleaning apparatus through the supply pipe, at least prior to supplying the filtered cleaning liquid to the cleaning apparatus, the filtered cleaning liquid is discharged out of the system through the discharge pipe. The cleaning method is characterized in that the filtered cleaning liquid is supplied to the cleaning device through a supply pipe (Claim 1).

  In such a cleaning method, prior to supplying the filtered cleaning liquid to the cleaning device, the filtered cleaning solution is discharged out of the system through the discharge pipe, and then the filtered cleaning liquid is supplied to the cleaning device through the supply pipe. For example, even if fine bubbles are generated in the cleaning liquid staying after filtration while supply of the cleaning liquid to the cleaning device is stopped, the cleaning liquid containing the fine bubbles is discharged out of the system in advance. Can do. As a result, when supplying the cleaning liquid to the cleaning device, the amount of fine bubbles in the cleaning liquid can be suppressed more than before, and the generation of minute foreign matter defects caused by the fine bubbles originated from the cleaning of the substrate. It can be remarkably suppressed, and productivity and yield can be improved.

  In particular, when cleaning the substrate to be cleaned by supplying the filtered cleaning liquid to the cleaning device through a supply pipe, at least the filtered cleaning liquid is discharged out of the system through a discharge pipe, and then the filtered cleaning liquid is supplied. It is desirable that the cleaning liquid is continuously discharged from the discharge pipe until it starts to be supplied to the cleaning device through the pipe (claim 2).

  With such a cleaning method, the filtered cleaning liquid is discharged out of the system through the discharge pipe, and then the cleaning liquid continues to be discharged from the discharge pipe until the filtered cleaning liquid starts to be supplied to the cleaning device through the supply pipe. Even if fine bubbles are generated in the cleaning liquid staying later, the cleaning liquid containing the fine bubbles can be discharged out of the system. As a result, it is possible to prevent the cleaning liquid containing the fine bubbles from being sent to the cleaning device. Therefore, it is possible to further suppress the occurrence of minute foreign matter defects caused by the cleaning of the substrate and caused by the fine bubbles, and the productivity and the yield can be improved.

At this time, after the filtered cleaning liquid is started to be supplied, the filtered cleaning liquid can be continuously supplied through the discharge pipe while being supplied through the supply pipe.
In this way, it is possible to more reliably prevent the cleaning liquid from staying, suppress the generation of bubbles, and supply the cleaning liquid containing no bubbles to the cleaning device.

Further, when the supply of the filtered cleaning liquid to the cleaning device is stopped, the filtered cleaning liquid can be continuously discharged through the discharge pipe (claim 4).
In this way, the cleaning liquid filtered by the filtration filter is discharged out of the system even when the supply to the cleaning device is stopped, so that the filtered cleaning liquid can be virtually eliminated. The generation of fine bubbles at the next supply can be suppressed.

Furthermore, the filtered cleaning liquid can be continuously discharged through the discharge pipe until the cleaning of all the substrates to be cleaned is completed.
In this way, the filtered cleaning liquid is not retained, and control for discharging the cleaning liquid out of the system is extremely easy, and the operation can be simplified.

Further, when the filtered cleaning liquid is supplied to the cleaning device, it is preferable that the height position of the inlet of the discharge pipe is higher than the height position of the inlet of the supply pipe.
By doing so, fine bubbles generated in the filtered cleaning liquid can be more efficiently guided to the discharge pipe, and the cleaning liquid containing bubbles can be further prevented from being supplied to the cleaning device. it can.

The substrate to be cleaned can be any one of a photomask transparent substrate, a photomask blank, a photomask blank manufacturing intermediate, and a photomask.
In this way, if the cleaning method of the present invention is applied to those requiring precise cleaning, it is possible to provide a product that generates less foreign matter than the prior art in response to market demands.

In these cleaning methods of the present invention, the cleaning liquid can be ultrapure water (claim 8).
Cleaning failure due to fine bubbles is particularly likely to occur during rinsing with ultrapure water, and by applying the present invention to cleaning with ultrapure water, it is possible to strongly suppress the generation of fine foreign matter that occurs during cleaning.

  The present invention is also a cleaning liquid supply apparatus that supplies a cleaning liquid to a cleaning apparatus that cleans a substrate to be cleaned, and supplies at least a filtration filter for removing foreign substances from the cleaning liquid and the cleaning liquid to the cleaning apparatus. A supply pipe, a discharge pipe for discharging the cleaning liquid out of the system, and a valve disposed in each of the supply pipe and the discharge pipe for controlling the amount of the cleaning liquid, from the filtration filter Further, the supply pipe and the discharge pipe are connected on the downstream side, and the cleaning liquid filtered by the filtration filter is supplied to the cleaning apparatus and / or the system by opening and closing valves of the supply pipe and the discharge pipe. Provided is a cleaning liquid supply device which can be discharged to the outside (claim 9).

  With such a cleaning liquid supply apparatus, it is possible not only to supply the cleaning liquid filtered by the filtration filter to the cleaning apparatus but also to discharge it out of the system. Therefore, for example, even if fine bubbles are generated in the cleaning liquid that has been filtered and stayed, the cleaning liquid containing the fine bubbles can be discharged out of the system, and the cleaning liquid containing the fine bubbles is included in the cleaning device. Can be prevented from being sent. Thereby, generation | occurrence | production of a micro foreign material defect can be suppressed remarkably in a board | substrate, and productivity and a yield can be improved.

At this time, it is preferable that the height position of the inlet of the discharge pipe is higher than the height position of the inlet of the supply pipe at the connection portion between the supply pipe and the discharge pipe.
If this is the case, the fine bubbles generated in the filtered cleaning liquid can be easily guided to the discharge pipe, and more effectively prevent the cleaning liquid containing bubbles from being supplied to the cleaning device. it can.

  And a filter housing having the filtration filter and a housing surrounding the filter housing, wherein the cleaning liquid flows from the housing through the filtration filter into the filter housing, and at least air bubbles in the cleaning liquid are contained in the housing. It is preferable that a bubble evacuation tube for removing the gas from the system is connected (claim 11).

  If it is such, the bubble in the washing | cleaning liquid in the housing surrounding a filter housing can be excluded out of the system. Therefore, it is possible to reduce the amount of bubbles in the cleaning liquid that is filtered by the filter and supplied to the cleaning device. Moreover, the fall of the filtration capability by a bubble and dust generation can be suppressed.

The substrate to be cleaned can be any one of a transparent substrate for photomask, a photomask blank, a photomask blank manufacturing intermediate, and a photomask.
If the substrate to be cleaned is like this, these are those for which extremely precise cleaning is desired, and in response to market demand, it is possible to provide a cleaned substrate with less generation of foreign matter than before. it can.

  Further, if the cleaning liquid is ultrapure water (claim 13), it is possible to strongly suppress the generation of fine foreign matters that are particularly likely to occur during cleaning with ultrapure water.

With the cleaning method of the present invention, it is possible to extremely strongly suppress the generation of minute foreign matters due to bubbles in the cleaning liquid after filtration, so that it is possible to obtain a substrate with less contamination by particles after cleaning. And yield can be improved.
In addition, with the cleaning liquid supply apparatus of the present invention, the filtered cleaning liquid can be supplied to the cleaning apparatus, or can be discharged out of the system, and the cleaning liquid containing fine bubbles is supplied to the cleaning apparatus. Can be prevented. Therefore, it is possible to suppress the generation of minute foreign matters during the cleaning of the substrate and perform a precise cleaning.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
Currently, cleaning of transparent substrates for photomasks, photomask blanks, photomask blank manufacturing intermediates, photomasks, etc., related to lithographic processing of products with extremely fine patterns such as semiconductors, also causes contamination by foreign particles due to extremely fine particles. It is desired to be eliminated, and various proposals have been made including improvements in cleaning liquids and improvements in drying methods as mentioned in the prior art.

However, although any method has found a certain effect, the problem of fine foreign matters has still occurred suddenly.
In addition, the present inventor has also inspected the substrate after cleaning for defects due to extremely fine foreign matter of about 0.08 μm. Even when the substrate is cleaned with great care, the problem of fine foreign matter is still considerable. It has been found that it may occur suddenly with frequency.

  When such defects due to fine foreign matter occur on a transparent substrate or a film-forming intermediate film, they may cause peeling of the laminated film or abnormal behavior during etching processing, and mask blanks. In the case of the above, there is a possibility of giving an abnormal behavior at the time of etching, peeling of the resist film, and an abnormal shape of the resist pattern. Therefore, in order to manufacture a photomask having a fine pattern with high reliability, it is necessary to solve such a problem of fine foreign matters.

  Therefore, in order to solve this problem, the present inventor has eagerly studied fine foreign matters on the substrate after cleaning. Specifically, by assuming various causes of the occurrence of foreign substances and adding an operation to eliminate the cause, the cause of the problem and how to solve it are examined using the method of how the pollution occurrence status changes. went.

  Usually, the cleaning liquid is provided with a cleaning liquid supply device upstream of the cleaning device in order to prevent entry of fine foreign matters, and is filtered using a filter just before use. In addition, in order to control the flow of cleaning liquid around the filtration filter, an opening / closing mechanism is placed upstream of the filtration filter in case particles are generated from the opening / closing control mechanism such as a valve. In this case, the system can be removed with a filter.

  However, the present inventor has repeatedly studied such an apparatus, and when this conventional apparatus is used, the cleaning liquid staying in the cleaning liquid supply apparatus while the liquid feeding to the cleaning apparatus is interrupted, in particular, It was thought that bubbles are likely to be generated from the cleaning liquid that stays in a relatively large amount in the space downstream of the filter in the filter filter housing, and this is sent to the use point without being eliminated midway. The bubbles may adhere to the substrate to be cleaned during cleaning, which may cause fine foreign matter.

  Therefore, as described above, the present inventor actually uses the fine bubbles generated in the filter housing having the filtration filter of the cleaning liquid supply device during the cleaning operation, particularly while the supply of the cleaning liquid is stopped. Assuming that the contamination of the cleaning liquid supplied to the liquid is the cause of the generation of foreign matter, we tried to eliminate such bubbles and cleaning liquid containing bubbles from the cleaning liquid supplied to the point of use. It has been found that the occurrence of contamination due to sudden fine foreign matters can be strongly suppressed.

  That is, the present inventor has discovered that the cause of the generation of foreign matter is derived from bubbles, and in particular, the fine bubbles generated from the cleaning liquid staying after filtration flow to the cleaning liquid supplied to the cleaning device. As a result, the inventors have found that the above-described foreign matter problem can be solved, and have reached the present invention.

Below, although the washing | cleaning liquid supply apparatus and washing | cleaning method of this invention are demonstrated in detail, referring drawings, this invention is not limited to this.
First, the cleaning liquid supply apparatus of the present invention will be described.
(First embodiment)
FIG. 1 shows an outline of an example of the cleaning liquid supply apparatus of the present invention. A cleaning apparatus 10 disposed downstream of the cleaning liquid supply apparatus 1 and a substrate 12 to be cleaned to be cleaned with a cleaning liquid sprayed from a nozzle 11 (use point) of the cleaning apparatus are also shown.

The substrate to be cleaned 12 can be, for example, a photomask transparent substrate, photomask blank, photomask blank manufacturing intermediate, and photomask that require precise cleaning. Of course, the present invention can be applied to other than these cleanings.
In addition, when the cleaning liquid is, for example, ultrapure water, an apparatus for producing ultrapure water is generally equipped with a device that excludes gas that may be generated by processing such as UV sterilization out of the system. Such degassed pure water can also be used. The cleaning liquid to which the effect can be particularly usefully applied in the present invention is a cleaning liquid generally used for a cleaning operation without applying a process using a scrub after applying the cleaning liquid to the substrate to be cleaned. Examples include pure water, ultrapure water whose conductivity is adjusted by introducing gas, hydrogen water, ozone water, dilute hydrofluoric acid water, and the like.

  As shown in FIG. 1, the cleaning liquid supply apparatus 1 has a housing 2, and the housing 2 is provided with a cleaning liquid inlet 3 through which the cleaning liquid sent after passing through a heating process or the like enters the housing 2. It has been. A filter housing 5 having a filtration filter 4 is provided in the housing 2, and the cleaning liquid that has entered the housing 2 is filtered by the filtration filter 4 and flows into the filter housing 5.

  Further, a supply pipe 6 for supplying the filtered cleaning liquid to the cleaning apparatus 10 and a discharge pipe 7 for discharging the filtered cleaning liquid to the outside of the system are disposed on the downstream side of the filter 4. In the case of FIG. 1, one pipe connected to the filter housing 5 is branched and connected to the supply pipe 6 and the discharge pipe 7.

In this case, the shape of the branch may take any shape according to the apparatus. However, in order to guide the bubbles in the cleaning liquid to the discharge pipe 7 and to easily escape to the outside of the system, the branch portion has a gravity direction. The tube located on the upper side of the tube is referred to as a discharge tube 7. That is, it is preferable that the connection is made such that the height position of the inlet 8 b of the discharge pipe 7 is higher than the height position of the inlet 8 a of the supply pipe 6.
Typically, the branch is T-shaped, and the supply pipe 6 protrudes downward such that the pipe coming from the filter housing 5 side and the discharge pipe 7 are in a straight line.
The arrangement of the supply pipe 6 and the discharge pipe 7 described above stays even if the vertical relationship in the height direction is reversed due to the flow path design in the housing 2 and the setting of the discharge amount from the discharge pipe 7. It is possible to make it possible to almost completely discharge the cleaning liquid from the inlet 8 b of the discharge pipe 7.

The supply pipe 6 is provided with a valve 9a. The amount of the cleaning liquid supplied to the cleaning device 10 can be controlled by opening and closing the valve 9a. The discharge pipe 7 is provided with a valve 9b, and the amount of the cleaning liquid discharged outside the system can be controlled by opening and closing.
These valves 9a and 9b are not particularly limited, and various types such as a drive type on-off valve such as air drive and electromagnetic drive, and a needle valve can be used. Any device that can control the amount of the cleaning solution can be used, and any device that can be automatically controlled by a program or the like is preferable. Furthermore, it is more convenient if valves 9a and 9b are controlled in conjunction with each other. What is necessary is just to be able to flow the cleaning liquid through the supply pipe 6 and the discharge pipe 7 at a desired timing and amount. Further, the quantity to be arranged is not particularly limited.

  Further, when the distance from the branch portion of the supply pipe 6 and the discharge pipe 7 (or the connection portion of the supply pipe to the filter housing in the case of FIGS. 2 and 3 described later) to the use point is too long, for example. When the supply of the cleaning liquid is stopped, bubbles may be generated in the pipe, and the effect of the present invention is reduced. For this reason, the distance of the piping from the filter 4 to a use point should be short, Preferably it is less than 5m, More preferably, it is less than 2m.

Further, as shown in FIG. 1, the bubble exclusion tube 13 can be connected to the housing 2 as necessary. The connection position of the bubble evacuation tube 13 is not particularly limited, but the upper portion of the housing 2 is preferable because bubbles can be more efficiently eliminated. In FIG. 1, the bubble exclusion pipe 13 is connected to the side surface of the housing 2 on the same side as the cleaning liquid inlet 3. The bubble evacuation tube 13 is provided with, for example, a gas-liquid separator 14 or an intermittent valve, and by these, bubbles existing in the cleaning liquid in the housing 2 can be excluded from the system through the bubble evacuation tube 13. it can.
As a result, bubbles contained in the cleaning liquid in the housing 2 can be eliminated, and finally, it is possible to more effectively prevent the cleaning liquid containing bubbles from being supplied to the cleaning device 10. In addition, it is possible to suppress the reduction of the filtration capability and the dust generation from the filtration filter 4 due to bubbles, thereby improving the efficiency of cleaning and further suppressing the generation of particles on the substrate after cleaning. Is possible.

Many gas-liquid separators 14 are already known, and gas-liquid separation membranes that allow only gas molecules to pass through are used to remove gas with a negative pressure on the outside. Although what is used is known, any can be used as long as bubbles are efficiently eliminated.
On the other hand, it is not equipped with a type that completely separates the cleaning liquid and bubbles and excludes only the bubbles out of the system, but also has a type that eliminates the cleaning liquid and bubbles together with the cleaning liquid and bubbles. it can.
For example, in the case of the gas-liquid separator type using the above-described specific gravity difference, not only bubbles are excluded, but bubbles can be excluded from the system together with a certain amount of cleaning liquid. Therefore, the size of the apparatus for complete separation is unnecessary, and the gas-liquid separator can be miniaturized.

  In the conventional cleaning liquid supply apparatus, since the discharge pipe 7 in the cleaning liquid supply apparatus 1 of the present invention is not connected downstream of the filter, the filtered cleaning liquid is supplied to the cleaning apparatus as it is to be cleaned. Had been sprayed.

  However, with the cleaning liquid supply device 1 of the present invention as described above, in addition to the supply pipe 6 that supplies the cleaning liquid to the cleaning apparatus 10 on the downstream side of the filtration filter, a discharge pipe for discharging out of the system. 7 is connected, for example, it is possible to discharge the cleaning liquid after filtration that stays in the filter housing 5 due to the stop of the cleaning operation and has generated fine bubbles to the outside through the discharge pipe 7. is there. That is, it is possible to prevent the cleaning liquid containing fine bubbles after filtration from being supplied to the cleaning apparatus 10 and sprayed onto the substrate 12 to be cleaned.

In addition to the control of the valves 9a and 9b, the cleaning liquid after filtration with little generation of fine bubbles without staying in the filter housing 5 is supplied to the cleaning device 10 through the supply pipe 6 to clean the substrate to be cleaned. Can be injected.
Therefore, with the cleaning liquid supply apparatus of the present invention, it is possible to suppress the occurrence of minute foreign matter defects found on the substrate after cleaning, and it is possible to clean the substrate with high productivity and yield.

(Second embodiment)
FIG. 2 shows a cleaning liquid supply apparatus 201 according to another embodiment of the present invention. In the case of FIG. 2, the supply pipe 206 and the discharge pipe 207 are directly connected to the upper surface of the filter housing 205.
At this time, as shown in FIG. 2A, for example, the housing 202 and the filter housing 205 of the cleaning liquid supply apparatus 201 are installed horizontally, and the height position of the inlet 208a of the supply pipe 206 and the height of the inlet 208b of the discharge pipe 207 are set. The supply pipe 206 and the discharge pipe 207 may be connected so that the positions are the same.

  On the other hand, as shown in FIG. 2B, for example, the housing 202 and the filter housing 205 of the cleaning liquid supply apparatus 201 are installed obliquely. As a result, the height position of the inlet 208b of the discharge pipe 207 is set to the supply pipe 206. The supply pipe 206 and the discharge pipe 207 may be connected so as to be higher than the height position of the inlet 208a. If the connecting portion between the supply pipe 206 and the discharge pipe 207 is in such a positional relationship, it is more preferable because the bubbles in the cleaning liquid after filtration can be easily discharged out of the system through the discharge pipe 207 as described above.

  Further, although FIG. 1 illustrates the housing 2 provided with the bubble evacuation tube 13, the bubble evacuation tube may not be provided as shown in FIG. 2. In particular, in the case of the form of FIG. 2, bubbles in the cleaning liquid in the housing 202 are likely to move to the upper end of the housing 202, and it is considered that the bubbles are less likely to move from the filtration filter 204 into the filter housing 205 than in the form of FIG. . However, as a matter of course, even in the form as shown in FIG.

(Third embodiment)
FIG. 3 shows a cleaning liquid supply apparatus 301 according to another embodiment of the present invention.
In the case of FIG. 3, the supply pipe 306 and the discharge pipe 307 are directly connected to the side surface of the filter housing 305. In this case, it is also preferable that the outlet pipe 307 is connected so that the height position of the inlet 308b is higher than the height position of the inlet 308a of the supply pipe 306.
The bubble exclusion pipe 313 is connected to the side surface of the housing 302 opposite to the cleaning liquid inlet 303.

As described above, the embodiments of the cleaning liquid supply apparatus of the present invention have been described by way of examples. However, the present invention is not limited to these embodiments. At least a supply pipe and a discharge pipe each provided with a valve are provided on the downstream side of the filter, and the cleaning liquid filtered by the filter is supplied to the cleaning device and / or outside the system by controlling the opening and closing of the valve. Any material that can be discharged to the surface is acceptable.
Moreover, it does not specifically limit about the component of other apparatuses, For example, it can be set as the same thing as a conventional product.

Next, the cleaning method of the present invention will be described.
Here, a cleaning method using the cleaning liquid supply apparatus 1 of FIG. 1 will be described, but the cleaning liquid supply apparatus to be used is not limited to this. In the cleaning method of the present invention, the cleaning liquid is filtered through a filtration filter to remove foreign matters, and when the substrate to be cleaned is cleaned by supplying the cleaning liquid after filtration to the cleaning device through the supply pipe, at least the filtered cleaning liquid Prior to supply to the cleaning device, it is sufficient if the filtered cleaning solution is discharged out of the system through the discharge pipe, and then the filtered cleaning solution can be supplied to the cleaning device through the supply tube. And then do it.

  That is, in the cleaning method of the present invention, before supplying the cleaning liquid to the cleaning apparatus 10 and cleaning the substrate 12 to be cleaned, the cleaning liquid filtered by the filter 4 is first opened by opening the valve 9b. Discharge from the discharge pipe 7 to the outside of the system. Thereby, it is possible to discharge the cleaning liquid mainly staying in the filter housing 5 together with the fine bubbles generated in the cleaning liquid.

Then, as described above, the cleaning liquid is once discharged out of the system and, for example, after the valve 9b is closed, the valve 9a is opened to supply the cleaning liquid by actually injecting the cleaning liquid from the nozzle 11 and supplying the valve 9a. A cleaning solution is supplied from the tube 6.
More preferably, when supplying the cleaning liquid to the cleaning apparatus 10, the cleaning liquid is continuously discharged out of the system through the discharge pipe 7 until the valve 9 a is opened and the filtered cleaning liquid is supplied from the supply pipe 6. Therefore, the generation of fine bubbles can be suppressed without causing the cleaning liquid to stay inside the filter housing 5 and the like, and the cleaning liquid in which the generation of bubbles is suppressed can be supplied to the cleaning device 10.
Thereby, the to-be-cleaned substrate 12 can be cleaned with a cleaning liquid in which fine bubbles are extremely suppressed, and it is possible to prevent generation of minute defects and foreign matters due to the fine bubbles.

In this case, the discharge of the cleaning liquid from the discharge pipe 7 may be performed until the filtered cleaning liquid starts to be supplied to the cleaning device 10 through the supply pipe 6 as described above, and the subsequent operation is not particularly limited.
Therefore, for example, the cleaning liquid may be continuously discharged from the discharge pipe 7 even after the valve 9a is opened and the cleaning liquid 10 is started to be supplied to the cleaning device 10 through the supply pipe 6. Then, after continuing to discharge for a predetermined time, the discharge of the cleaning liquid can be stopped by closing the valve 9b, and the supply of the cleaning liquid to the cleaning apparatus 10 is stopped after the cleaning of one substrate to be cleaned. When cleaning the substrate to be cleaned, the valve 9b is opened before the cleaning liquid is discharged from the discharge pipe 7 in advance.

Alternatively, the valve 9a can be opened to start supplying the cleaning liquid to the cleaning device 10 through the supply pipe 6, and at the same time, the discharge of the cleaning liquid from the discharge pipe 7 can be stopped by closing the valve 9b. That is, the cleaning liquid is discharged only immediately before the start of supply, and only the cleaning liquid staying in the filter housing 5 is discharged. By using this method, the consumption of the cleaning liquid can be most suppressed.
In this case, in the cleaning process, it is necessary to take time for the discharge operation to be performed immediately before the start of use of the cleaning liquid, and in order to prevent the supply timing from being delayed with respect to the discharge timing, a standard cycle of supply during cleaning is created. And it is preferable to operate each valve etc. according to the program. By automatically controlling the opening and closing of the valves 9a and 9b, the cleaning liquid can be supplied and discharged more reliably at a desired timing. Of course, such valves 9a and 9b can be automated also in other cycles.

  When creating the program as described above, the time for performing only the discharge from the start of the operation of discharging the retained cleaning liquid with the valve 9b opened to the start of supply with the valve 9a opened is the filter housing 5 By adjusting the amount of discharged liquid according to the size of the liquid, it is preferable that sufficient discharge is performed in a short time, but it is preferable to adjust so that it can be performed in about 0.2 to 5 seconds.

Such control can be performed by a sequencer, for example. That is, when a signal for using the cleaning liquid is input, first, the valve 9b is opened, and after a predetermined time for sufficient discharge, a device capable of a cooperative operation such that the valve 9a is opened and the valve 9b is closed. Just assemble.
Of course, it is also possible to control these valves 9a, 9b and the like manually without using a program.

Further, for example, for the purpose of cleaning a plurality of substrates to be cleaned, after the supply to the cleaning apparatus 10 for cleaning the first substrate to be cleaned is started, the cleaning of the last substrate to be cleaned is completed. (In other words, from the start to the end of the cleaning process) The valve 9b is opened and the remaining cleaning liquid after filtration is discharged just before the valve 9a is opened from the closed state as described above. In order to reduce the likelihood of occurrence, the valve 9b may always be opened when the valve 9a is closed.
By this operation, the cleaning liquid does not stay in the filter housing 5, so that bubbles are hardly generated. Further, when this method is adopted, when it is desired to start the supply to the cleaning apparatus 10 as described above, a problem related to the supply timing such as a time lag corresponding to the time for discharging is not caused. Therefore, particularly when the cleaning operation is performed manually, this method can be performed with a simpler apparatus and the operability is good.

  In addition, for the purpose of cleaning one or more substrates to be cleaned, after the supply to the cleaning apparatus 10 is started, until the cleaning process is completed (that is, until all the substrates to be cleaned are cleaned), The valve 9b may be always open. When this method is adopted, the cleaning liquid is somewhat wasted, but it is not necessary to open and close the valve 9b in conjunction with the opening and closing of the valve 9a, and the apparatus can be controlled with a very simple one. become.

  By the way, when the valve 9b is opened even when the valve 9a is opened, the amount of the cleaning liquid discharged through the discharge pipe 7 is 1/20 to 3 times as a standard with respect to the amount of the cleaning liquid supplied from the supply pipe 6. Preferably, the amount is set to 1/10 to 2 times the amount. Since the optimum value of the discharge amount at this time depends on the shape of the housing 2 and the arrangement of the supply pipe 6 and the discharge pipe 7, etc., it is necessary to adjust to the actual apparatus. Can give more effective results. Moreover, since discharging more than the necessary amount means not only wasting of the cleaning liquid but also an increase in filtration pressure, depending on the selection of the filtration filter 4, depending on the case, the foreign matter removal ability of the filtration filter 4 may be reduced. Therefore, it is preferable to avoid discharging more than three times the supply amount.

Further, when supplying the cleaning liquid to the cleaning device 10 and discharging it out of the system, it is preferable that the height position of the inlet of the discharge pipe is higher than the height position of the inlet of the supply pipe. As described above, the above condition can be achieved by using a T-shaped branch as described above.
On the other hand, if a device in which the supply pipe and the discharge pipe are directly connected to the filter housing is used, the filter housing is installed obliquely as shown in FIG. It is preferable to install it so that it is higher than the inlet of the tube.

If it is difficult to install the device in such a way, when opening the valve on the discharge pipe side from closed to open, the orientation of the filter housing can be adjusted so that the discharge pipe is above the supply pipe. It is preferable to keep it.
In particular, when taking a method in which the valve on the discharge pipe side is always open during the above-described cleaning process, the discharge pipe is adjusted so that the discharge pipe is above the supply pipe at the start of use. Then, even if the inlet of the supply pipe becomes higher than the inlet of the discharge pipe, the effect of the present invention can be sufficiently obtained.

In addition, although it does not specifically limit as a washing | cleaning liquid, For example, an ultrapure water can be used. If ultrapure water is used, the present invention is particularly effective. The type of the cleaning liquid can be appropriately determined as necessary.
Moreover, it does not specifically limit about the to-be-cleaned substrate 12, For example, the cleaning method of this invention is applicable with respect to the transparent substrate for photomasks, a photomask blank, a photomask blank manufacturing intermediate body, and a photomask.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this.
Example 1
A cleaning liquid is supplied to a spin cleaning / drying machine, a photomask substrate is cleaned, and a spin drying apparatus (cleaning apparatus) is used, and a cleaning liquid supply line for supplying the cleaning liquid to this apparatus is disposed 30 cm before the apparatus in FIG. The cleaning liquid supply apparatus 201 of the present invention was installed. At this time, a fluororesin-processed air operated valve (manufactured by Advance Co., Ltd.) for sending the cleaning liquid in conjunction with the cleaning process of the cleaning device was installed downstream of the supply pipe, and two stop valves were installed downstream of the discharge pipe.

  Next, when the air operated valve downstream of the supply pipe is opened, the amount of cleaning liquid supplied from the supply pipe is 1 L per minute, and the amount of cleaning liquid discharged from the discharge pipe is 1 L downstream of the discharge pipe. The amount of discharge was adjusted using the remaining stop valves while one of the stop valves was opened. In addition, when the cleaning liquid is not used, the stop valve opened above is closed so that the discharge can be shut off.

  Next, as a substrate to be cleaned, a light shielding film 26 nm made of CrN (Cr: N = 9: 1 (atomic ratio)) and CrON (Cr: N: O = 4: 5: 1 (atomic ratio)) on the main surface are used. 20 quartz substrates each having an antireflection film 20 nm formed by sputtering are prepared, and defects on each substrate are analyzed using MAGICS manufactured by Lasertec Corporation. 0.08 μm or more and less than 0.1 μm, 0.1 μm or more The positions of defects of less than 0.2 μm and 0.2 μm or more were specified.

Next, as shown in FIG. 2 (B), the direction of the cleaning liquid supply device is held such that the height position of the inlet of the discharge pipe is higher than the height position of the inlet of the supply pipe. The discharge of the cleaning liquid was started by opening the stop valve that had shut off the discharge from the tank. Then, the substrate on which the defect position is specified is placed on a spin cleaning / drying machine, and after 5 seconds from the discharge of the cleaning liquid, 1 L of ultrapure water that has passed through the cleaning liquid supply apparatus is supplied for 10 minutes per minute. After washing, spin drying was performed at 1000 rpm for 30 seconds after washing.
That is, the cleaning method of the present invention was performed.
After performing the above-described cleaning operation on each of the 20 substrates prepared, the defect inspection was performed again, and the defects generated at new positions were measured.

The total number of defects newly observed for all the 20 substrates is 7 (0.35 pieces / piece), 0.08 μm or more and less than 0.1 μm, and 0.1 μm or more and less than 0.2 μm. There were two (0.1 / sheet) and two (0.1 / sheet) 0.2 μm or more.
These are less compared to Comparative Example 1 described later. In particular, Example 1 is much less than Comparative Example 1 for 0.08 μm or more and less than 0.1 μm. This is considered to be because the substrate can be prevented from being cleaned by the cleaning liquid containing fine bubbles according to the present invention.

(Comparative Example 1)
The position of the defect is specified in exactly the same manner as in Example 1 except that a device having no discharge pipe is used as compared with the device used in Example 1 and no cleaning liquid is discharged from the discharge pipe. 20 substrates on which a chromium film was formed were washed with ultrapure water. That is, cleaning was performed by a conventional cleaning method. Thereafter, spin drying was performed, and defects generated at new positions were measured.

The total number of defects newly observed for all 20 substrates is 28 (1.4 / sheet) of 0.08 μm or more and less than 0.1 μm, and 0.1 μm or more and less than 0.2 μm. There were 3 (0.15 / sheet) and 6 (0.3 / sheet) 0.2 μm or more.
Compared with Example 1, those having a value of 0.08 μm or more and less than 0.1 μm were particularly increased.

(Example 2)
A cleaning liquid is supplied to a spin cleaning / drying machine, a photomask substrate is cleaned and a spin drying apparatus is used, and a cleaning liquid supply line for supplying the cleaning liquid to this apparatus is disposed 30 cm in front of the apparatus as shown in FIG. A cleaning liquid supply device 301 having a cleaning liquid inlet and a bubble exclusion pipe, a supply pipe for sending the cleaning liquid to the use point downstream of the filtration filter, and a discharge pipe for discharging the cleaning liquid staying in the filter housing was attached.

  An air operated valve is installed downstream of the supply pipe to send the cleaning liquid in conjunction with the cleaning process, and the air of the supply pipe for sending the cleaning liquid to the point of use is located downstream of the discharge pipe and bubble exclusion pipe. An air operated valve that can be operated in conjunction with the operated valve was installed, and a stop valve was provided at each outlet to adjust the discharge amount.

Furthermore, at the same time as the supply of the cleaning liquid was started, the air operated valve downstream of the discharge pipe and the bubble exclusion pipe was closed, and the supply to the use point was adjusted to 1 L / min. Further, at the same time as the air operated valve downstream of the supply pipe is closed, the air operated valve downstream of the discharge pipe and the bubble exclusion pipe is opened, and the cleaning liquid is discharged by 0.5 L from both the discharge pipe and the bubble exclusion pipe. When the device was not used, all the solenoid valves were closed.
That is, cleaning is performed by the cleaning method of the present invention.

  Next, the spin cleaning / cleaning apparatus in which the cleaning liquid supply device and the control system for supply and discharge of the cleaning liquid are installed on the 50 substrates on which the chromium film having the same defect positions as those in the first embodiment is specified are provided. Using a dryer, after cleaning with ultrapure water and spin drying, defects generated at new positions were measured.

  The total number of defects newly observed for all 50 substrates is 16 (0.32 pieces / piece) of 0.08 μm or more and less than 0.1 μm, 0.1 μm or more and less than 0.2 μm. 1 (0.02 / sheet), 0.2 μm or more (0.04 / sheet), and as in Example 1, the increase is very small compared to the comparative example. Met.

  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.

It is the schematic which shows the outline of an example of a washing | cleaning apparatus and the washing | cleaning-liquid supply apparatus of this invention. It is the schematic which shows the outline of an example of another embodiment of the washing | cleaning liquid supply apparatus of this invention. It is the schematic which shows the outline of an example of another embodiment of the washing | cleaning liquid supply apparatus of this invention.

Explanation of symbols

1, 201, 301 ... Cleaning liquid supply device of the present invention,
2, 202, 302 ... housing,
3, 303 ... Cleaning liquid inlet, 4, 204 ... Filtration filter,
5, 205, 305 ... Filter housing,
6, 206, 306 ... supply pipe, 7, 207, 307 ... discharge pipe,
8a, 208a, 308a ... inlet of supply pipe,
8b, 208b, 308b ... the inlet of the discharge pipe,
9a: a valve disposed in the supply pipe, 9b: a valve disposed in the discharge pipe,
10 ... Cleaning device, 11 ... Nozzle, 12 ... Substrate to be cleaned,
13, 313 ... Bubble exclusion tube, 14 ... Gas-liquid separator.

Claims (13)

A cleaning method for cleaning a substrate to be cleaned by supplying a cleaning liquid to a cleaning device,
When the substrate to be cleaned is cleaned by filtering the cleaning solution with a filter for removing foreign matter and supplying the filtered cleaning solution to the cleaning device through a supply pipe.
Prior to supplying at least the filtered cleaning liquid to the cleaning apparatus, the filtered cleaning liquid is discharged out of the system through a discharge pipe, and then the filtered cleaning liquid is supplied to the cleaning apparatus through a supply pipe. How to wash. When cleaning the substrate to be cleaned by supplying the filtered cleaning liquid to the cleaning device through a supply pipe,
At least the filtered cleaning liquid is discharged out of the system through a discharge pipe, and then the cleaning liquid is continuously discharged from the discharge pipe until the filtered cleaning liquid starts to be supplied to the cleaning device through a supply pipe. Item 2. The cleaning method according to Item 1.   The cleaning method according to claim 1 or 2, wherein after the supply of the filtered cleaning liquid is started, the filtered cleaning liquid is continuously supplied through the discharge pipe while being supplied through the supply pipe.   The cleaning method according to any one of claims 1 to 3, wherein when the supply of the filtered cleaning liquid to the cleaning device is stopped, the filtered cleaning liquid is continuously discharged through the discharge pipe. .   The cleaning method according to any one of claims 1 to 4, wherein the filtered cleaning liquid is continuously discharged through the discharge pipe until the cleaning of all of the substrates to be cleaned is completed.   The height position of the inlet of the discharge pipe is set higher than the height position of the inlet of the supply pipe when the filtered cleaning liquid is supplied to the cleaning device. The cleaning method according to claim 5.   The cleaning substrate according to any one of claims 1 to 6, wherein the substrate to be cleaned is any one of a transparent substrate for photomask, a photomask blank, a photomask blank production intermediate, and a photomask. Method.   The cleaning method according to any one of claims 1 to 7, wherein the cleaning liquid is ultrapure water. A cleaning liquid supply apparatus for supplying a cleaning liquid to a cleaning apparatus for cleaning a substrate to be cleaned,
At least a filtration filter for removing foreign substances from the cleaning liquid, a supply pipe for supplying the cleaning liquid to the cleaning device, a discharge pipe for discharging the cleaning liquid out of the system, and the supply pipe and the discharge pipe Each of which is provided with a valve for controlling the amount of the cleaning liquid,
The supply pipe and the discharge pipe are connected downstream of the filtration filter, and the cleaning liquid filtered by the filtration filter is supplied to the washing device by opening and closing each valve of the supply pipe and the discharge pipe. And / or a cleaning liquid supply device capable of being discharged out of the system. In the connection between the supply pipe and the discharge pipe,
The cleaning liquid supply apparatus according to claim 9, wherein the height position of the inlet of the discharge pipe is higher than the height position of the inlet of the supply pipe. A filter housing having the filtration filter and a housing surrounding the filter housing, wherein a cleaning liquid flows from the housing through the filtration filter and into the filter housing;
The cleaning liquid supply apparatus according to claim 9 or 10, wherein a bubble removal pipe for removing at least bubbles in the cleaning liquid from the system is connected to the housing.   The said to-be-cleaned board | substrate is any one of the transparent substrate for photomasks, a photomask blank, a photomask blank manufacturing intermediate body, and a photomask, It is any one of Claims 9-11 characterized by the above-mentioned. Cleaning liquid supply device.   The cleaning liquid supply apparatus according to any one of claims 9 to 12, wherein the cleaning liquid is ultrapure water.

Images