JP2002131889A - Cleaning method and cleaning device of quartz substrate for photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe and inexpensive cleaning technology which can easily purify a quartz substrate from foreign particles, etc., sticking to the substrate surface when the quartz substrate is cleaned in photomask manufacturing process. SOLUTION: This cleaning method of a quartz substrate for photomask has a characteristic using a low-concentration hydrofluoric acid as a cleaning solvent in a cleaning method of the quartz substrate for photomask by cleaning solvent. Desirably, the concentration of the low-concentration hydrofluoric acid is in the range between 0.005% and 5% range and the cleaning time is in the range between 10 seconds and 180 seconds. Concretely, the quartz substrate for photomask is soaked in the low-concentration hydrofluoric acid or the low- density hydrofluoric acid is sprayed to the quartz substrate from a spray nozzle. And the cleaning effect can be much more improved by the cleaning using the low-concentration hydrofluoric acid after carrying out a scrub cleaning beforehand.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a substrate,
The present invention relates to a technique for cleaning a quartz substrate for a photomask such as a mask blank or a photomask, which removes foreign substances such as fine particles, stains, and dirt on the surface of a quartz substrate in a semiconductor photomask manufacturing process in a semiconductor photomask manufacturing process and improves a yield in a subsequent process.

[0002]

2. Description of the Related Art In manufacturing a photomask used for forming an integrated circuit, a quartz glass substrate is subjected to various processes such as polishing, film formation, resist coating, exposure, development, and etching to form a pattern image. A mask is manufactured.

In the manufacture of such a photomask, the substrate is contaminated by various causes, for example, an abrasive adheres in a polishing step, and is contaminated from the atmosphere in other steps. In order to remove such contamination, a cleaning process is performed between steps to clean the substrate. However, the degree of achievement of this cleaning greatly affects the yield of products finally obtained. In particular, it is difficult to remove the abrasive after polishing.In general, scrub cleaning with a sponge brush, or immersion of the substrate in hot concentrated sulfuric acid or a mixed solution of sulfuric acid and hydrogen peroxide, etc., is performed for cleaning. I have.

In recent years, as semiconductor devices have become more highly integrated,
Although very fine particles adhering to the quartz substrate surface have been regarded as a problem, on the other hand, in order to obtain a substrate with higher flatness, the particle size of the abrasive is also particularly small, Many things cannot be removed by the current scrub cleaning.

[0005] In addition, although cleaning using hot concentrated sulfuric acid exhibits a high effect of removing dirt, it is not easy to handle because heating equipment is expensive and corrosiveness is extremely high. In addition, since the concentration of sulfuric acid is high, there is also a problem that a high treatment cost is required for waste liquid treatment, which leads to an increase in cost. Furthermore, regarding the mixture of sulfuric acid and hydrogen peroxide,
Since the liquid life is short and deteriorates immediately, it is difficult to obtain stable quality and the running cost increases.
In addition, since it has a strong corrosive property like the hot concentrated sulfuric acid, there is a problem that the equipment cost is also high.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to easily remove dirt such as foreign particles adhering to a substrate surface in cleaning a quartz substrate in a photomask manufacturing process. It is an object of the present invention to provide a safe, inexpensive cleaning technique.

[0007]

Means for Solving the Problems As a result of diligent studies to achieve the above object, the present inventor has found that in a method of cleaning a quartz substrate in a photomask manufacturing process, the substrate is cleaned with a low concentration of hydrofluoric acid. By doing so, it is possible to easily obtain a highly purified quartz substrate for photomasks without corrosion on the substrate and removing foreign substances such as fine particles, stains, and dirt on the substrate, and wastewater treatment equipment costs and wastewater treatment. The inventors have found that the reduction of costs such as costs can be achieved, and have completed the present invention.

That is, according to the present invention, there is provided a method for cleaning a quartz substrate for a photomask, wherein a low-concentration hydrofluoric acid is used as the cleaning solution in the method for cleaning a quartz substrate for a photomask with a cleaning solution. (Claim 1).

Although hydrofluoric acid is effective in removing foreign substances, it has a high etching property with respect to a quartz substrate. Therefore, if high concentration hydrofluoric acid is used for cleaning the quartz substrate for photomask,
There is a problem that the substrate itself is corroded even in a short time. Therefore, in the present invention, by cleaning the quartz substrate for a photomask using low-concentration hydrofluoric acid as described above, the quartz substrate itself is not corroded, and fine particles such as abrasives adhered to the substrate are removed. And foreign substances such as stains and other stains can be effectively removed.

Therefore, by applying the above-mentioned cleaning method to the cleaning process in the photomask manufacturing, the influence of the fine particles and the like does not remain in the post-process, and the productivity and the yield of the photomask can be improved and the quality can be improved. it can. Furthermore, according to the present invention, equipment costs are reduced because a heating facility is not required as in the case of using hot concentrated sulfuric acid, and since the concentration of hydrofluoric acid used is low, it is possible to handle chemicals safely. The used washing liquid (drained liquid) can be easily treated.

In the present invention, the concentration of the low-concentration hydrofluoric acid is:
The cleaning time is preferably in the range of 0.005% to 5% (claim 2), and the cleaning time is preferably in the range of 10 seconds to 180 seconds (claim 3). If the quartz substrate is cleaned with the above-described concentration or cleaning time, foreign substances on the surface can be sufficiently removed without causing corrosion or the like of the substrate with a small amount of a chemical solution.

A specific method of cleaning the quartz substrate for a photomask with the low-concentration hydrofluoric acid is to immerse the quartz substrate for a photomask in the low-concentration hydrofluoric acid. It can be carried out by applying hydrofluoric acid to the quartz substrate for photomask (Claim 5) As described above, the quartz substrate for photomask is immersed in hydrofluoric acid of low concentration, or the hydrofluoric acid is coated on the quartz substrate for photomask. , The entire surface of the substrate can be reliably brought into contact with low-concentration hydrofluoric acid, and contaminants such as foreign substances can be reliably removed.

Further, in the cleaning of the quartz substrate for a photomask according to the present invention, scrub cleaning can be performed in addition to the cleaning with the low concentration hydrofluoric acid. If the cleaning with the low concentration hydrofluoric acid and the scrub cleaning are used in this manner, the cleaning effect can be further enhanced.

According to the present invention, there is provided a cleaning apparatus for cleaning a quartz substrate for a photomask, wherein at least a cleaning tank containing low-concentration hydrofluoric acid and a quartz substrate for a photomask are automatically conveyed. A cleaning device for a quartz substrate for a photomask, comprising: a carrier for immersing the substrate in hydrofluoric acid in a tank. further,
At least, a processing tank in which a quartz substrate for a photomask is stored during cleaning, a transfer device for automatically transferring the quartz substrate into the processing tank, and a low-concentration hydrofluoric acid applied to the quartz substrate transferred into the processing tank. There is also provided an apparatus for cleaning a quartz substrate for a photomask, comprising: an ejector for ejecting the quartz substrate.

By using a cleaning apparatus for automatically transporting a quartz substrate and immersing it in low-concentration hydrofluoric acid or a cleaning apparatus for spraying low-concentration hydrofluoric acid on a quartz substrate, a photomask made of low-concentration hydrofluoric acid is used. The quartz substrate for cleaning can be safely and easily cleaned. In addition, since the automatic conveyance is used, contamination from the outside can be prevented, and extremely advanced cleaning can be performed.

[0016]

Embodiments of the present invention will be specifically described below with reference to the drawings, but the present invention is not limited to these embodiments. The “quartz substrate for a photomask” referred to in the present invention includes not only the first quartz glass substrate itself (so-called substrate) in the photomask manufacturing process, but also a mask blank in which a light-shielding thin film is formed on the glass substrate. Further, it includes any type of substrate in the photomask manufacturing process, such as a photomask having a pattern image formed on the mask blank, and may be referred to as a “quartz substrate” or simply as a “substrate”.

The concentration of the low-concentration hydrofluoric acid used in the present invention may be determined in consideration of the degree of contamination of the quartz substrate and the influence on the substrate. Is preferably 0.005% to 5%, more preferably 0.2% to 2.0%. If the concentration of hydrofluoric acid is in this range, a high cleaning effect can be obtained with a small amount. Further, if the low-concentration hydrofluoric acid as described above is used, waste liquid treatment such as neutralization after use becomes easy, and the influence on the environment can be extremely suppressed.

If the concentration of hydrofluoric acid is less than 0.005%, the processing time is prolonged, so that efficient cleaning may not be performed. On the other hand, if the hydrofluoric acid concentration exceeds 5%, corrosion on the substrate proceeds quickly, so that it is difficult to control the cleaning time, and the yield may be reduced.

The time for cleaning the substrate with low-concentration hydrofluoric acid may be appropriately selected in consideration of the hydrofluoric acid concentration, the degree of contamination on the substrate surface, the influence on the quartz substrate, and the like. More preferably, from 20 seconds to 6
0 seconds. If the cleaning is performed within this range, foreign substances on the substrate surface can be effectively removed, and the substrate is hardly corroded. If the contact time of the substrate surface with hydrofluoric acid is less than 10 seconds, a sufficient cleaning effect may not be obtained. On the other hand, if it exceeds 180 seconds, the substrate surface may be corroded.

The specific cleaning of the substrate surface with low-concentration hydrofluoric acid is sufficient if low-concentration hydrofluoric acid can efficiently contact the entire surface of the substrate. For example, the cleaning is performed by immersing a quartz substrate for a photomask in low-concentration hydrofluoric acid. Alternatively, it can be performed by spraying low-concentration hydrofluoric acid on the substrate through a nozzle or the like, or by spraying the substrate with a shower. If low-concentration hydrofluoric acid is brought into contact with the substrate in such a manner, it is possible to reliably remove stains on the entire surface of the substrate. Further, by automating such a cleaning process, productivity and safety can be further improved.

Further, in the present invention, the effect of removing foreign substances can be further enhanced by performing scrub cleaning in addition to cleaning with low-concentration hydrofluoric acid. For example, after polishing a quartz substrate, removing relatively large foreign substances by scrub cleaning, and then performing cleaning with low-concentration hydrofluoric acid, a higher cleaning effect is exhibited, and extremely minute foreign substances such as abrasives can be surely obtained. Can be removed.

Since the surface of the thus-cleaned quartz substrate is very cleaned, the adverse effects of fine deposits are greatly reduced in the post-cleaning process, and the yield of the photomask is improved. Can be done.

Hereinafter, the cleaning apparatus according to the present invention will be described more specifically while showing the same. FIG. 1 shows the configuration of an example of a cleaning apparatus for cleaning a quartz substrate for a photomask with low-concentration hydrofluoric acid. The cleaning apparatus 1 includes a cleaning tank 6 containing low-concentration hydrofluoric acid, and a transporter (transport robot) 2 for automatically transporting a quartz substrate for a photomask and immersing it in hydrofluoric acid in the cleaning tank 6. In addition, scrub tank 4,
Rinsing tanks 5, 7 and a drying tank 8 are provided.

When a quartz substrate for a photomask is cleaned by the apparatus 1, first, a quartz substrate is taken out from a cassette (not shown) placed on a loader 3 by a transfer robot 2 and sent to a surface scrub tank 4. In the surface scrub tank 4, the surface of the substrate is rubbed (scrubbed) with a rotating brush material or the like while applying water or an appropriate cleaning liquid, and the attached matter is removed. The scrub cleaning as described above is particularly effective for removing relatively large abrasive particles attached to the polished substrate.

After the scrub-cleaned quartz substrate is rinsed with ultrapure water in a rinsing bath 5, it is immersed in a low-concentration hydrofluoric acid contained in a cleaning bath (immersion bath) 6. When the quartz substrate is immersed in the low-concentration hydrofluoric acid as described above, the stains on both surfaces of the substrate are simultaneously removed, and the processing can be performed in a short time.
In this case, the low-concentration hydrofluoric acid may be stirred, or the quartz substrate may be rocked. After immersing the substrate for a predetermined time, it is sent to the next rinsing tank 7 and rinsed with ultrapure water. The rinsed substrate is placed in an ultrapure water rinsing tank 7
Is sent to the drying tank 8 to perform, for example, isopropyl alcohol vapor drying (IPA-Vap drying). After drying, the substrate is placed on the unloader 9.

In the cleaning apparatus 1 shown in FIG. 1, the substrate is sequentially transferred to each tank, and the above-described series of steps automatically proceed, whereby the cleaning process can be performed safely and easily, and contamination from outside can be prevented. . Further, if a method of automatically preparing a cleaning liquid (low-concentration hydrofluoric acid) and supplying it to the cleaning tank 6 is employed, safety, easiness, stability, productivity, and the like can be further improved, which is desirable. .

The configuration of each tank is not limited to this. For example, the scrub tank 4 may not be provided, and substantial dirt may be removed only by the hydrofluoric acid cleaning tank 6. Further, the number of transfer robots is not limited to one.

FIG. 2 shows another example of the structure of the cleaning apparatus according to the present invention. The cleaning apparatus 11 includes a processing tank 14 in which a quartz substrate for a photomask is stored during cleaning, a transfer device (transfer robot) 12 for automatically transferring the quartz substrate into the processing tank 14, Is provided with an injector 15 for injecting low-concentration hydrofluoric acid onto the quartz substrate transported to the substrate.

In the cleaning device 11, first, the quartz substrate is taken out of the cassette of the loader 13 by the transfer robot 12 and transferred into the processing tank 14. Next, processing tank 1
In 4, low-concentration hydrofluoric acid is injected from the injector 15 onto the quartz substrate to clean the surface. After removing foreign matters and the like by applying low-concentration hydrofluoric acid to the substrate, rinsing is performed by injecting ultrapure water from another injector 16. In this case, more uniform cleaning can be performed by rotating the substrate during cleaning and rinsing. Further, in order to clean both front and back surfaces of the substrate, a substrate reversing mechanism may be provided. The substrate cleaned by the above method is dried by spin drying or the like, and is transferred to the unloader 18 by another transfer robot 17.

Although two transfer robots are provided in the apparatus shown in FIG. 2, one transfer robot may be used, and one loader 13 and one unloader 18 may be used. Further, two or more processing tanks may be provided.

FIG. 3 shows an example of the injector 15 and the processing tank 14 used in the cleaning apparatus 11 of FIG. The injector 15 has a mechanism for injecting the cleaning liquid (low-concentration hydrofluoric acid) in the chemical liquid tank 20 onto the quartz substrate 30 on the support base 22 according to a signal from the control box 21. The signal to the control box 21 is supplied when each of the cleaning conditions is programmed and executed, and a necessary chemical solution (low concentration hydrofluoric acid, ultrapure water, etc.) is selected. Injector 15 shown
, The pump 19 always operates to circulate the chemical
5 and only when necessary, valve 23
The nozzles a and 23b are opened to the process side so that the chemical liquid can be ejected from the ejection nozzle 24 onto the substrate 30.

The chemical solution is not limited to being sprayed from the nozzle 24 at a predetermined pressure. For example, a low-concentration hydrofluoric acid is showered on the substrate using a shower head having a large number of holes in place of the nozzle 24 and showering. Is also good. Also, a filter can be provided in the middle of the line as needed. Further, without providing the circulation line 25, the pump 19 may be operated to inject the chemical liquid only when necessary.

According to the method of applying the cleaning liquid to the substrate,
Since the substrate is always cleaned with a new cleaning liquid, there is an advantage that the substrate is not re-contaminated by the cleaning liquid. On the other hand, the immersion method has an advantage that a plurality of substrates can be processed at one time.

The cleaning apparatus of the present invention as shown in FIGS. 1 to 3 exhibits a high cleaning ability for cleaning a quartz substrate, and is more safe if the hydrofluoric acid is automatically diluted and prepared. Can handle chemicals. Therefore, if the cleaning apparatus of the present invention is used to clean the quartz substrate for a photomask, it is very effective in removing foreign substances such as fine particles, stains, and dirt on the substrate surface, and is used for a highly purified photomask. A quartz substrate can be obtained safely and efficiently.

Further, in the cleaning method and the cleaning apparatus of the present invention, since low concentration hydrofluoric acid is used, the equipment cost can be kept low, and the wastewater treatment can be easily performed. There is also the advantage that the impact on the environment can be reduced.

[0036]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. (Embodiment 1) Using a cleaning apparatus configured as shown in FIG.
After showering 0.5% hydrofluoric acid on the square quartz substrate, showering with ultrapure water is performed, and then spin drying (15%).
(00 rpm) to clean the substrate. The processing time in each of the above steps is as shown in Table 1, and 10 substrates were cleaned by such a cleaning process. The cleaned substrate is 6025 size (6 inches x 6 inches x
0.25 inch) synthetic quartz substrate with an average particle size of 1
Immediately after polishing using a 20 nm abrasive.

After cleaning, the number of bright spots (fine particles of 0.3 μm or more) on the substrate surface was counted using a defect inspection apparatus (GM-1000 manufactured by Hitachi Engineering). The number of bright spots on the surface of each of the ten washed substrates was measured as described above, and the average value is shown in Table 1.

[0038]

[Table 1]

(Comparative Example 1) The same rectangular quartz substrate as in Example 1 was subjected to surface scrubbing on each side, followed by showering with ultrapure water and spin drying in that order to wash the quartz substrate. After washing 10 substrates, the number of bright spots (fine particles of 0.3 μm or more) on the surface of each substrate was counted in the same manner as described above, and the average value is shown in Table 1.

As is clear from Table 1, the number of luminescent spots on the quartz substrate surface after cleaning was less than half in Example 1 as compared with that in Comparative Example 1, and a high cleaning effect was obtained. Also,
Comparing the cleaning times, the hydrofluoric acid shower in Example 1 was 4 times.
0 seconds, which is very short compared to the scrub cleaning in Comparative Example 1 (240 seconds). That is, it can be seen that the cleaning method of Example 1 based on the present invention has a high cleaning effect and can shorten the cleaning time.

(Example 2) Using a cleaning apparatus configured as shown in FIG. 1, a surface scrub was performed on each side of a polished square quartz substrate, and then a shower of ultrapure water, 0.3%
Immersion in concentrated hydrofluoric acid, immersion in ultrapure water, IPA-Va
The substrate was washed by sequentially performing p drying. The processing time in each of the above steps is as shown in Table 2, and 10 substrates were cleaned by such a cleaning process. The cleaned substrate is a 6025-size synthetic quartz substrate, which has just been polished using an abrasive having an average particle size of 80 nm.

After cleaning, the number of luminescent spots on the substrate surface was measured in the same manner as in Example 1, and the average value was shown in Table 2.

[0043]

[Table 2]

(Comparative Example 2) Hot concentrated sulfuric acid (concentration: 98) was used in place of the 0.3% hydrofluoric acid used in the cleaning treatment of Example 2.
%, Temperature 80 ° C.), except that the quartz substrate was cleaned in the same manner as in the cleaning treatment of Example 2. After washing 10 substrates, the number of bright spots (fine particles of 0.3 μm or more) on the surface of each substrate was counted in the same manner as described above, and the average value is shown in Table 2.

As shown in Table 2, the cleaning time in Example 2 and Comparative Example 2 was the same, but the number of substrate surfaces after cleaning was less than 1/3 of Comparative Example 2 in Example 2. Thus, there was a remarkable difference in the cleaning effect even with the same cleaning time. Further, as for the waste liquid treatment after the washing, in Comparative Example 2, it took considerable cost and time to neutralize the concentrated sulfuric acid waste liquid, but in Example 2, the concentration of hydrofluoric acid was low, so that the treatment could be easily performed. Was.

As is clear from the above Examples and Comparative Examples, the method of cleaning a quartz substrate with hydrofluoric acid of a low concentration according to the present invention has a higher cleaning effect as compared with a case of simply performing scrub cleaning or cleaning with sulfuric acid. In addition, the time required for cleaning and the labor required for waste liquid treatment can be significantly reduced. Also, it can be seen that a very high removal effect can be obtained by using scrub cleaning together before treatment with low concentration hydrofluoric acid.

The present invention is not limited to the above embodiment. The above embodiment is merely an example, and has substantially the same configuration as the technical idea described in the claims of the present invention, and has the same function and effect,
Anything is included in the technical scope of the present invention.

For example, in the above embodiment, the cleaning was performed using the square synthetic quartz substrate immediately after polishing. However, the cleaning method and the cleaning apparatus of the present invention are not limited to the quartz substrate having such a shape and form. It can be applied to a photomask blank or a photomask.

[0049]

By cleaning the quartz substrate for photomask using low-concentration hydrofluoric acid, it is possible to obtain an extremely clean quartz substrate surface for photomask in a short washing time without causing corrosion of the substrate. it can. Therefore, if the present invention is applied to the cleaning process in the manufacture of a photomask, it is possible to remove minute foreign matters that cannot be removed only by scrub cleaning, and to improve productivity and yield.

Further, equipment for raising the temperature as in the case of washing with hot concentrated sulfuric acid is not required, and the treatment of waste liquid becomes easy, so that the environmental load can be greatly reduced. As a result, the cost of equipment and the cost of cleaning treatment can be improved, which leads to the inexpensive provision of high-quality photomasks.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of an apparatus for cleaning a quartz substrate for a photomask according to the present invention.

FIG. 2 is a configuration diagram showing another example of the apparatus for cleaning a quartz substrate for a photomask according to the present invention.

FIG. 3 is a schematic view showing an example of an injector and a processing tank used in the cleaning apparatus according to the present invention.

[Explanation of symbols]

1. Cleaning device 2. Transporter (transport robot) 3.
Loader, 4 ... Surface scrub tank, 5 ... Rinse tank,
6 ... Hydrofluoric acid cleaning tank (immersion tank), 7 ... Rinse tank, 8 ...
Drying tank, 9 ... Unloader, 11 ... Cleaning device, 1
2 ... Conveyer (transport robot) 13 ... Loader, 1
4 ... Treatment tank, 15, 16 ... Injector, 17 ... Conveyer (transport robot), 18 ... Unloader, 19 ... Pump, 20 ... Chemical liquid tank, 21 ... Control box, 2
2 ... Support, 23a, 23b ... Valve, 24 ... Injection nozzle, 25 ... Circulation line, 30 ... Quartz substrate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaki Takeuchi 28, Nishifukushima, Oaza, Kushiro-mura, Nakakushiro-gun, Niigata Pref. Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratories Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Laboratory, 28-1, Nishi-Fukushima, Gunku-jo Castle Village, Japan (72) Inventor Satoshi Okazaki 28, Nishi-Fukushima, Oku-ku, Niigata Pref., Shin-Etsu Chemical Industry Co., Ltd. In-house (72) Inventor Masayuki Suzuki 28-28 Nishifukushima, Nishi-Juku-mura, Nakakushiro-gun, Niigata Pref. Shin-Etsu Chemical Co., Ltd.Precision Functional Materials Laboratory CC05 3B201 AA02 BA02 BA13 BB21 BB93 BB96 CB15 CC01 CC11 CC13 CC21

Claims (8)

[Claims] 1. A method of cleaning a quartz substrate for a photomask using a cleaning solution, wherein low-concentration hydrofluoric acid is used as the cleaning solution. 2. The method according to claim 1, wherein the concentration of the low concentration hydrofluoric acid is 0.005.
The method for cleaning a quartz substrate for a photomask according to claim 1, wherein the ratio is in the range of 5% to 5%. 3. The cleaning time with said low concentration hydrofluoric acid is 10
2. The method according to claim 1, wherein the time is within a range of seconds to 180 seconds.
Alternatively, the method for cleaning a quartz substrate for a photomask according to claim 2. 4. The photomask quartz substrate is washed with the low-concentration hydrofluoric acid by immersing the photomask quartz substrate in the low-concentration hydrofluoric acid. The method for cleaning a quartz substrate for a photomask according to any one of the preceding claims. 5. The photomask quartz substrate is washed with the low-concentration hydrofluoric acid by applying the low-concentration hydrofluoric acid to the photomask quartz substrate. The method for cleaning a quartz substrate for a photomask according to claim 1. 6. The method for cleaning a quartz substrate for a photomask according to claim 1, wherein scrub cleaning is performed in addition to the cleaning with the low concentration hydrofluoric acid. 7. A cleaning apparatus for cleaning a quartz substrate for a photomask, comprising: a cleaning tank containing at least a low-concentration hydrofluoric acid; An apparatus for cleaning a quartz substrate for a photomask, comprising: a carrier that is immersed in an acid. 8. A cleaning apparatus for cleaning a quartz substrate for a photomask, comprising: at least a processing tank for accommodating the quartz substrate for a photomask at the time of cleaning; and automatically transporting the quartz substrate into the processing tank. And a jetting machine for jetting low-concentration hydrofluoric acid onto the quartz substrate conveyed into the processing tank.