JP2002131890A - Cleaning method and cleaning solvent for photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method and cleaning solvent for removing a silicon adhesion sticking to a photomask which is used to adhere a pellicle to the photomask. SOLUTION: As a cleaning solvent, a water solubility solvent 6 is used including condensation diammonium hydrogen phosphate as a main component, urea as an adjuvant or its transformation component and acid. The cleaning solvent 6 is put in a cleaning tank 5, the photomask 1 with adhesive residual spots 4 is dipped in the cleaning tank 5 and adhesive residual spots 4 are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a photomask and a cleaning solution used therefor, and more particularly to a method for cleaning a photomask for removing an adhesive material attached to a photomask for attaching a pellicle. And a cleaning liquid used for such cleaning.

[0002]

2. Description of the Related Art In a glass photomask (hereinafter, referred to as a "photomask"), a dustproof cover is attached in a photomechanical process in order to prevent foreign substances from adhering to the photomask. This dust cover is called a pellicle. The pellicle is composed of, for example, a pellicle film made of cellulose or the like, and a frame for attaching the pellicle film to a photomask in an expanded state. The pellicle film, the frame, and the photomask are respectively attached with an adhesive such as epoxy.

In the photoengraving process, photoengraving is performed by irradiating a photoresist applied on a semiconductor substrate with exposure light transmitted through a photomask. recent years,
In order to cope with miniaturization of semiconductor devices, miniaturization of patterns formed on photomasks and shortening of wavelength of exposure light have been attempted.

Since exposure light having a shorter wavelength has higher energy than exposure light having a longer wavelength, conventional adhesives such as epoxy may emit smoke due to continuous irradiation of the exposure light. Therefore, in order to prevent such smoking, as an adhesive for bonding the pellicle to the photomask,
Silicone adhesives have been applied.

[0005]

However, when a silicon-based adhesive is used as an adhesive for bonding a pellicle to a photomask, there are the following problems.

In the case of a pellicle, it is necessary to replace the pellicle because the pellicle film is broken or the pellicle film is deteriorated by using a photomask. When replacing the pellicle, the frame must be peeled from the photomask. However, the adhesive material that bonds the frame and the photomask is not completely removed from the photomask, but remains attached to the photomask.

[0007] In order to remove the adhesive adhered to the photomask, the photomask is cleaned with a cleaning liquid such as an organic solvent. At this time, in the case of washing using, for example, acetone as an organic solvent, the adhered adhesive material could not be completely removed only by weakening the adhesive force. In the case of washing with hexane, the adhered adhesive could be dissolved to some extent, but the adhesive could not be completely removed.

[0008] As shown in FIG.
Dissolves into the photomask 101 by dissolving
5 covers the light-shielding film 101a, and the photomask 10
In some cases, it could not be used as 1.

Further, when cleaning is performed using an acid containing sulfuric acid and hydrogen peroxide solution in addition to an organic solvent as a cleaning liquid, the silicon component in the silicon-based adhesive is oxidized and silicon dioxide (SiO 2) is removed. ₂ ) As a result, it was firmly attached to the photomask, and it was extremely difficult to remove it from the photomask. In addition, if the silicon dioxide was forcibly removed, the photomask was damaged, and a new photomask had to be created.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and one object of the present invention is to reliably remove an adhesive material attached to a photomask for attaching a pellicle to the photomask. Another object of the present invention is to provide a cleaning method, and another object of the present invention is to provide a cleaning liquid used in such a cleaning method.

[0011]

A method of cleaning a photomask according to the present invention is a method of cleaning a photomask for removing an adhesive material for attaching a pellicle attached to the photomask, the method comprising the steps of: And a pressure-sensitive adhesive removing step of removing the pressure-sensitive adhesive by using a cleaning liquid containing condensed ammonium phosphate to be used, urea or a transformation component thereof to be an auxiliary agent, and an acid.

According to this photomask cleaning method, the silicon-based adhesive material adhered to the photomask can be effectively removed without significantly damaging the light-shielding film formed on the photomask.

The degree of polymerization of the condensed ammonium phosphate contained in the cleaning solution is preferably 200 or less in order to sufficiently dissolve the condensed ammonium phosphate and enhance the cleaning effect.

As the condensed ammonium phosphate contained in the cleaning solution, from the viewpoint of selectively attacking and removing the silicon component of the adhesive adhered to the photomask,
It is preferably a monomer of condensed ammonium phosphate.

In order to easily clean the photomask, the step of removing the adhesive preferably includes a step of immersing the photomask in a cleaning solution.

Further, in order to clean the photomask with higher cleanliness, it is more preferable that the step of removing the adhesive material includes a step of spraying a cleaning liquid onto the photomask.

Furthermore, in order to enhance the effect of removing the adhesive adhered to the photomask, the step of removing the adhesive includes a step of applying ultrasonic waves to the cleaning liquid, and the temperature of the cleaning liquid is set to 80 ° C. or more and 100 ° C. or less. And preferably contains a surfactant.

The cleaning liquid according to the present invention is a cleaning liquid for removing an adhesive material for attaching a pellicle, which has adhered to a photomask, and is composed of condensed ammonium phosphate as a main component and urea or an urea as an auxiliary agent. Contains transformation components and acids.

According to this cleaning solution, the silicon-based adhesive material adhered to the photomask can be effectively removed without significantly damaging the light-shielding film formed on the photomask.

The acid is preferably phosphoric acid or orthophosphoric acid from the viewpoint of enhancing the effect of removing the adhesive adhered to the photomask and suppressing damage to the light shielding film.

As described above, the degree of polymerization of the condensed ammonium phosphate is preferably 200 or less in order to sufficiently dissolve the condensed ammonium phosphate and enhance the washing effect.

Further, the condensed ammonium phosphate is preferably a monomer of condensed ammonium phosphate from the viewpoint of selectively attacking and removing the silicon component of the adhesive adhered to the photomask.

Further, in order to effectively remove the adhesive material attached to the photomask, the cleaning liquid preferably contains a surfactant.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 A photomask cleaning method according to Embodiment 1 of the present invention and a cleaning solution used for the same will be described.

First, as shown in FIG. 1, in order to prevent foreign matter from adhering to the photomask 1 in the photolithography process, the pellicle 2 attached to the photomask 1
As shown in FIG. 2, a pellicle film 2a made of, for example, cellulose or the like, and a frame 2b for attaching the pellicle film 2a to a photomask in a state where the pellicle film 2a is expanded. The pellicle film 2a, the frame 2b, and the photomask 1 are respectively attached with a silicon-based adhesive.

When the pellicle 2 is replaced, the frame 2b is separated from the photomask 1. At this time, as shown in FIG. 3, the adhesive material for bonding the frame 2 b and the photomask 1 is not peeled off, and the adhesive material residual trace 4 remains so as to surround the light shielding film 1 a formed on the photomask 1. .

Next, a description will be given of a cleaning liquid for cleaning the photomask 1 in which the adhesive material residue trace 4 remains.

First, the washing solution is a water-soluble washing solution containing condensed ammonium phosphate as a main component, urea or its modified component as an auxiliary agent, and an acid. The condensed ammonium phosphate is desirably a condensed ammonium phosphate having a degree of polymerization of 200 or less. This is because, when the degree of polymerization of the condensed ammonium phosphate exceeds 200, the condensed ammonium phosphate is not sufficiently dissolved and the washing effect is reduced.

In particular, in order to selectively attack the silicon component of the adhesive residue traces 4 and to remove the adhesive residue traces 4 more effectively, the condensed ammonium phosphate is as follows:
Experiments have shown that a monomer of condensed ammonium phosphate is desirable.

The acid is preferably phosphoric acid or orthophosphoric acid from the viewpoint of the effect of removing the residual traces of the adhesive and the solubility in the light-shielding film. Furthermore, it is also desirable to add a surfactant to the cleaning solution in order to enhance the effect of removing the residual adhesive.

Next, a cleaning method using the above-described cleaning liquid will be described. First, as shown in FIG. 4, the cleaning liquid 6 is put into the cleaning tank 5. Next, the photomask 1 with the remaining adhesive material traces 4 is immersed in the cleaning liquid 6.

At this time, the temperature of the cleaning solution 6 is set to 80 ° C. or higher and 1
It is desirable to set the temperature to 00 ° C or lower. This is because the adhesive residue trace 4 could not be removed when the temperature of the cleaning liquid was lower than 80 ° C. On the other hand, if the temperature of the cleaning liquid exceeds 100 ° C., the evaporation of water becomes remarkable, and it becomes difficult to control the concentration of the cleaning liquid.

By immersing the photomask 1 in the cleaning solution for an appropriate time, it was confirmed that the adhesive residue traces 4 were easily and completely removed from the photomask 1 as shown in FIG.

In this embodiment, the case where the adhesive residue traces 4 are removed by using only the main cleaning liquid has been described. In addition to this, the conventional cleaning with acetone or hexane and the conventional cleaning with sulfuric acid and hydrogen peroxide solution are used. After washing,
The photomask 1 may be cleaned with the main cleaning liquid.

In this case as well, silicon dioxide formed by oxidizing the silicon component in the adhesive residue traces 4 with sulfuric acid and aqueous hydrogen peroxide can be effectively removed as particles by the main cleaning liquid.

Second Embodiment Next, damage to a light-shielding film formed on a photomask when the photomask is cleaned with the main cleaning liquid will be described.

Among the photomasks, there is a halftone type phase shift mask for improving the resolution by utilizing the phase change of light. In a halftone phase shift mask, exposure light can pass through a light-shielding film having a predetermined transmittance, and the phase difference between the exposure light transmitted through the light-shielding film and the exposure light transmitted through portions other than the light-shielding film is 180. ° is set.

In this halftone type phase shift mask, a MoSi film is used as a light shielding film. Therefore, the etching rate of the MoSi film with the main cleaning liquid was evaluated as damage to the light-shielding film.

First, the temperature of the cleaning liquid was maintained at 80 ° C., and a halftone type phase shift mask was immersed in the cleaning liquid for 1 hour. MoS eluted in the cleaning solution from the difference in mass of the halftone phase shift mask before and after immersion
The mass of i was determined. Then, the etching rate of the MoSi film was estimated from the mass of the eluted MoSi.

At this time, Mo and Si in the MoSi film
Since the ratio is unknown, the range of the etching rate was estimated based on the following assumption.

First, the light shielding film is made of only Mo (Mo: 100).
%), The etching rate of the light-shielding film was estimated to be about 0.03 nm (0.3 °) / min. On the other hand, the light shielding film is made of only Si (Si: 100%)
, The etching rate of the light-shielding film was estimated to be about 0.17 nm (1.7 °) / min. From this, the etching rate of the MoSi film containing Mo and Si at a certain ratio is about 0.03 n
It is estimated to be not less than m / min and not more than 0.17 nm / min.

From these results, it is assumed that the average etching rate of the MoSi film is 0.1 nm / min, and in the case of a halftone type phase shift mask for an i-line light source, the allowable phase angle change is 5 ° and the MoSi film thickness is About 160 nm
(1600 °), it was estimated that the halftone phase shift mask could be used without any problem up to the cumulative cleaning time of about 45 minutes.

In the case of a halftone type phase shift mask for a KrF excimer light source, the allowable phase angle change is 5 °.
Assuming that the MoSi film thickness is about 135 nm (1350 °), it has been estimated that the halftone phase shift mask can be used without any problem until the cumulative cleaning time is about 40 minutes.

On the other hand, in a normal photomask, a Cr film is used as a light shielding film. When the same evaluation was performed on this Cr film, it was found that the etching rate of the Cr film was 0.01 nm (0.1 °) / min or less. In consideration of the value of the etching rate of the Cr film and the thickness of the Cr film (underlying film: about 80 nm, antireflection film: 20 nm), it is estimated that there is no problem in practical use up to a cumulative cleaning time of about 200 minutes. Was.

Third Embodiment In the first and second embodiments, the method of removing the adhesive residual traces 4 by immersing the photomask 1 with the adhesive residual traces 4 in the cleaning liquid has been described. In the third embodiment, a method for cleaning by spraying the cleaning liquid described in the first embodiment onto a photomask will be described.

That is, as shown in FIG. 6, the cleaning liquid is sprayed from the nozzle 7 toward the photomask 1 on which the adhesive material residual marks 4 remain. At this time, the cleaning liquid 6 is evenly sprayed on the entire surface of the photomask 1 while being intensively jetted toward the adhesive residue traces 4 remaining on the photomask 1, as shown in FIG. 4 can be completely removed.

In this case, the temperature of the cleaning liquid is not particularly limited. However, as described in the first embodiment, by setting the temperature of the cleaning liquid to 80 ° C. or higher and 100 ° C. or lower, the adhesive residue trace 4 Can be more effectively removed.

In this cleaning method, a fresh cleaning solution 6 is always sprayed on the photomask 1, and foreign substances in the cleaning solution can be removed from the photomask 1 as compared with the case where the photomask is cleaned by dipping in the cleaning solution. Will not re-adhere to the surface.

As a result, the cleanliness of the photomask 1 can be further increased. Fourth Embodiment In the present embodiment, a method of applying ultrasonic waves to the cleaning liquid described in the first embodiment to remove the adhesive residual traces 4 will be described.

As shown in FIG. 8, for example, a cleaning tank 5 having an ultrasonic vibrator 8 attached to the bottom is used as a cleaning tank.
The cleaning solution described in the first embodiment is put into the cleaning tank 5, and the photomask 1 on which the adhesive material residual trace 4 remains is immersed. Then, the cleaning liquid 6 is vibrated by the ultrasonic vibrator 8. When the cleaning liquid 6 vibrates, as shown in FIG.
The adhesive material residual trace 4 can be completely removed.

In this case, the temperature of the cleaning liquid is not particularly limited. However, as described in the first embodiment, by setting the temperature of the cleaning machine to 80 ° C. or more and 100 ° C. or less, it is possible to apply ultrasonic waves. At the same time, the adhesive residue traces 4 can be effectively removed.

Fifth Embodiment In this embodiment, another method for applying the ultrasonic wave to the cleaning liquid described in the first embodiment to remove the adhesive residual trace 4 will be described.

As shown in FIG. 10, a nozzle 7 having an ultrasonic vibrator 9 attached to the tip is used as the nozzle.
The cleaning liquid is sprayed from the nozzle 7 toward the photomask 1 on which the adhesive material residual trace 4 remains. Ultrasonic waves are applied to the cleaning liquid ejected from the nozzle 7.

While the cleaning liquid to which the ultrasonic wave was applied was mainly sprayed onto the adhesive material residual marks 4 remaining on the photomask 1,
By spraying the entire surface of the photomask 1 evenly, the residual traces 4 of the adhesive can be completely removed as shown in FIG.

In this cleaning method, since the cleaning liquid vibrates in addition to the fact that the cleaning liquid 6 is always sprayed on the photomask 1, the removed foreign substances are allowed to adhere to the surface of the photomask 1 again. Therefore, the adhesive residue trace 4 can be removed more reliably.

It should be understood that the embodiment shown this time is illustrative in all aspects and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0057]

According to the photomask cleaning method of the present invention, the silicon-based adhesive material adhered to the photomask can be effectively removed without significantly damaging the light-shielding film formed on the photomask. be able to.

The degree of polymerization of the condensed ammonium phosphate contained in the cleaning solution is preferably 200 or less in order to sufficiently dissolve the condensed ammonium phosphate and enhance the cleaning effect.

As the condensed ammonium phosphate contained in the cleaning solution, from the viewpoint of selectively attacking and removing the silicon component of the adhesive material adhered to the photomask,
It is preferably a monomer of condensed ammonium phosphate.

In order to easily clean the photomask, the step of removing the adhesive preferably includes a step of immersing the photomask in a cleaning solution.

Further, in order to clean the photomask with higher cleanliness, it is more preferable that the step of removing the adhesive material includes a step of spraying a cleaning liquid onto the photomask.

Further, in order to enhance the effect of removing the adhesive material adhered to the photomask, the adhesive material removing step includes a step of applying ultrasonic waves to the cleaning liquid, and the temperature of the cleaning liquid is set to 80 ° C. or more and 100 ° C. or less And preferably contains a surfactant.

According to the cleaning liquid of the present invention, the silicon-based adhesive material adhered to the photomask can be effectively removed without significantly damaging the light-shielding film formed on the photomask.

The acid is preferably phosphoric acid or orthophosphoric acid from the viewpoint of enhancing the effect of removing the adhesive adhered to the photomask and suppressing damage to the light shielding film.

As described above, the degree of polymerization of the condensed ammonium phosphate is preferably 200 or less in order to sufficiently dissolve the condensed ammonium phosphate and enhance the washing effect.

Further, the condensed ammonium phosphate is preferably a monomer of condensed ammonium phosphate, from the viewpoint of selectively attacking and removing the silicon component of the adhesive adhered to the photomask.

Further, in order to effectively remove the adhesive material adhered to the photomask, the cleaning liquid preferably contains a surfactant.

[Brief description of the drawings]

FIG. 1 is a plan view of a photomask to which a pellicle to be cleaned is attached in a cleaning method according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the photomask shown in FIG. 1 taken along the line II-II in the embodiment.

FIG. 3 is a plan view showing a photomask after a pellicle is peeled off in the embodiment.

FIG. 4 is a side view showing one step of a cleaning method in the embodiment.

FIG. 5 is a side view showing a state after cleaning in the embodiment.

FIG. 6 is a side view showing one step of a cleaning method according to a third embodiment of the present invention.

FIG. 7 is a side view showing a state after cleaning in the embodiment.

FIG. 8 is a side view showing one step of a cleaning method according to a fourth embodiment of the present invention.

FIG. 9 is a side view showing a state after cleaning in the embodiment.

FIG. 10 is a side view showing one step of a cleaning method according to Embodiment 5 of the present invention.

FIG. 11 is a side view showing a state after cleaning in the embodiment.

FIG. 12 is a plan view showing a state of a conventional photomask after cleaning.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass photomask, 1a light shielding film, 2 pellicle, 2a frame, 2b pellicle film, 4 residual traces of adhesive, 5 cleaning tank, 6 cleaning liquid, 7 nozzle, 8, 9
Ultrasonic transducer.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/027 H01L 21/30 502P (71) Applicant 397020283 FINE POLYMERS CO., LTD. Chome 11-2 (72) Inventor Shinichiro Tanaka 4-1-1, Mizuhara, Itami-shi, Hyogo Ryoden Semiconductor System Engineering Co., Ltd. (72) Inventor Satoshi Muranaka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Rishi Electric Co., Ltd. (72) Inventor Itaru Kanno 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Hiromasa Yamamoto 3-73 Fushimicho, Chuo-ku, Osaka-shi, Osaka Kishimoto Sangyo Co., Ltd. F term (reference) 2H095 BB20 BB30 3B201 AA02 AB01 BB02 BB21 BB82 BB92 BB94 BB96 CB01

Claims (13)

[Claims] 1. A method of cleaning a photomask for removing an adhesive for attaching a pellicle, which is attached to the photomask, comprising: a condensed ammonium phosphate as a main component; and urea or an urea as an auxiliary agent. A method for cleaning a photomask, comprising: an adhesive removing step of removing the adhesive using a cleaning liquid containing a transformation component and an acid. 2. The photomask cleaning method according to claim 1, wherein the degree of polymerization of the condensed ammonium phosphate contained in the cleaning liquid is 200 or less. 3. The method for cleaning a photomask according to claim 1, wherein the condensed ammonium phosphate contained in the cleaning liquid is a monomer of condensed ammonium phosphate. 4. The method for cleaning a photomask according to claim 1, wherein the step of removing the adhesive includes a step of immersing the photomask in the cleaning solution. 5. The method according to claim 1, wherein the step of removing the adhesive includes a step of spraying the cleaning liquid onto the photomask.
The method for cleaning a photomask according to any one of the above. 6. The method for cleaning a photomask according to claim 1, wherein the step of removing the adhesive includes a step of applying an ultrasonic wave to the cleaning liquid. 7. The temperature of the cleaning solution is 80 ° C. or higher and 100 ° C.
The method for cleaning a photomask according to any one of claims 1 to 6, which is as follows. 8. The method for cleaning a photomask according to claim 1, wherein said cleaning liquid contains a surfactant. 9. A cleaning solution for removing an adhesive for attaching a pellicle, which is attached to a photomask, comprising: a condensed ammonium phosphate as a main component; urea as an auxiliary agent, or a transformation component thereof; A cleaning solution containing an acid. 10. The cleaning solution according to claim 9, wherein the acid is phosphoric acid or orthophosphoric acid. 11. The cleaning solution according to claim 9, wherein the degree of polymerization of the condensed ammonium phosphate is 200 or less. 12. The cleaning solution according to claim 9, wherein the condensed ammonium phosphate is a monomer of the condensed ammonium phosphate. 13. The method according to claim 9, further comprising a surfactant.
13. The cleaning liquid according to any of the above items 12.