JP2007072402A - Mask blank housing case, method for housing mask blank, and mask blank housing body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mask blank housing case suitable for a mask blank having resist film that requires to be stored in a clean atmosphere, and capable of maintaining stable resist performance for forming a desired mask pattern, and to provide a method for housing a mask blank and a mask blank housing body. <P>SOLUTION: The mask blank housing case to house a mask blank exhibits properties, such that when an extracted solution, obtained by hot water extraction of the mask blank housing case, is measured by ion chromatography under anion measurement conditions, the number of peaks in a retention period of 2.8 minutes to 15 minutes is fewer than 13, and the ratio of the peak areas in the retention period of 2.8 minutes to 15 minutes to a peak area of sulfuric acid ion standard solution is smaller than 15. The mask blank housing case is made of a material that essentially comprises acrylic resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mask blank storage case or the like for manufacturing a photomask used for manufacturing an electronic device.

  With recent rapid development of IT, electronic devices such as semiconductor devices, color filters for liquid crystal monitors, or thin film transistor (TFT) devices are required to be further miniaturized. One of the technologies that support such a fine processing technology is a lithography technology using a photomask called a transfer mask. In this lithography technique, a fine pattern is formed on a silicon wafer by exposing an electromagnetic wave of an exposure light source to a silicon wafer with a resist film through a transfer mask. This transfer mask is usually manufactured by forming a pattern serving as an original plate using a lithography technique on a mask blank in which a light-shielding film is formed on a light-transmitting substrate. By the way, if there is a foreign substance such as a particle on the surface of the mask blank, it will cause a defect in the pattern to be formed.

As a container for storing, transporting and transporting such a mask blank, a mask transport case as described in, for example, the following Patent Document 1 is conventionally known.
That is, a conventional container for storing and storing a mask blank has an inner case called a carrier or the like in which several to several tens of mask blanks are arranged and held, and the inner case holding the mask blank is placed in an outer box (case main body). ) And a cover on the outer box to accommodate the mask blank. And by sticking an adhesive tape on the junction part of an outer box and a lid | cover, while sealing a case, it was trying to prevent entrance of external air, a foreign material, etc. Conventionally, most of these containers are made of resin.
JP 2001-154341 A

  As the performance of electronic devices in recent years has increased, the pattern formed on the transfer mask is also required to be further miniaturized. In order to form such a miniaturized pattern, the cleanness of the mask blank is extremely high. Otherwise it will be unacceptable. Therefore, it is necessary to maintain the cleanliness as high as possible, particularly during storage of the mask blank, by suppressing as much as possible foreign matter from adhering to the mask blank. In particular, in the case of a mask blank having a resist film on the surface, it is difficult to remove once foreign matter adheres to the surface, and sufficient cleaning cannot be performed at this stage. Will occur.

  In addition, the resist for the photomask may be affected by chemical contamination. If affected by chemical contamination, the desired performance may not be obtained. However, many types of resist materials are known, and it is difficult to specifically identify which chemical substances each resist material is susceptible to. Further, it is considered that most of these chemical substances are released as outgas components by impurities contained in the material of the storage case. Most of the material of the storage case is made of resin, but it is difficult to completely remove impurities contained in this resin material. Even if a material containing almost no impurities is used, the main material of the storage case is used. There is a possibility that components derived from components, by-products in the molding process, deposits after molding, and the like are released as outgas components.

  Recently, a chemically amplified resist has attracted attention as a resist for photomasks. This chemically amplified resist is described in, for example, Japanese Patent Application Laid-Open No. 2000-66380. Since this chemically amplified resist is superior in characteristics such as sensitivity and contrast to conventional photoresists, it is advantageous for forming a miniaturized pattern. The chemically amplified resist contains a high molecular compound having a resist action (positive type), or a low molecular compound (negative type) that generates a high molecular compound by a crosslinking reaction or the like and a catalytic substance. By irradiating the chemically amplified resist with an energy beam such as an electron beam or an electromagnetic wave, the contained catalytic substance can be exposed to form an acidic catalyst substance in the resist. This acidic catalyst substance has a catalytic action for a chemical reaction (chemical amplification reaction) that solubilizes the polymer compound in the developer or generates a polymer compound and insolubilizes it in the developer.

  It has been pointed out that this chemically amplified resist is easily affected by contamination of basic chemical substances due to its reaction mechanism. In other words, the presence of certain types of basic chemical substances, such as ammonia and amines, inhibits the generation of acidic catalyst substances that serve as catalysts for chemical amplification reactions and suppresses the function of the generated acidic catalyst substances. Inhibition (for example, deactivation) may occur, and desired performance may not be obtained. For this reason, in the case of a mask blank on which a resist film such as a chemically amplified resist is formed, it is not necessary to simply remove foreign substances such as particles, and it is particularly clean because it eliminates the influence of chemical contamination. Must be stored in an atmosphere.

However, in order to eliminate the influence of chemical contamination, even if the mask blank with resist film is stored and packed in an atmosphere cleaned using a chemical filter, it is stored during subsequent storage as described above. Chemical substances may be released from the container as outgas and contaminate the stored mask blank. In particular, the release of outgas components may be accelerated depending on the temperature change or pressure change of the outside air during storage. In this case, even if a material that emits less outgas components over time is used, contamination over time cannot be completely eliminated, and the material of the storage container is restricted.
Therefore, the present invention solves the above-mentioned conventional problems and is suitable for a mask blank on which a resist film that needs to be stored in a clean atmosphere is formed, and has stable resist performance for forming a desired mask pattern. An object is to provide a mask blank storage case that can be maintained.

  As described above, for example, the contaminants of the chemically amplified resist have been conventionally considered to be basic chemical substances such as amines, but according to the study of the present inventors, such basic chemical substances are considered. It has been found that even if a mask blank is stored in an environment where the above is excluded, stable resist performance may not be obtained, and a desired fine pattern may not be formed during mask manufacturing. Further, as a result of further studies, the present inventors have found that a mask blank having a chemically amplified resist film is contaminated not only by basic substances but also by adhesion of acidic substances, and stable fine pattern formation may be inhibited. I found something.

As described above, in particular, in the case of a chemically amplified resist, chemical substances are likely to be contaminated in general. However, in the case of a resist other than a chemically amplified resist, there is a possibility that the chemical substance may be contaminated. As a result of diligent research, the present inventor has paid attention to the anion component among components extracted from the mask blank storage case, and the number of peaks detected when analyzed under anion measurement conditions by ion chromatography, It was found that there is a causal relationship between the influence of the outgas component on the resist film in the mask blank with the resist film stored in the storage case.
The present invention has been completed based on the obtained knowledge.

That is, the present invention has the following configuration.
(Configuration 1) A mask blank storage case for storing a mask blank having a thin film for forming a mask pattern on a substrate, wherein a solution extracted by hot water extraction of the mask blank storage case is obtained by ion chromatography. The mask blank storage case is characterized in that the number of peaks at a retention time of 2.8 minutes to 15 minutes detected when measured under anion measurement conditions is less than 13.
(Configuration 2) Sulfuric acid having a peak area at a retention time of 2.8 minutes to 15 minutes, which is detected when the solution extracted by hot water extraction of the mask blank storage case is measured under anion measurement conditions by ion chromatography. The mask blank storage case according to Configuration 1, wherein the ratio of the ion standard solution to the peak area is less than 15.
(Configuration 3) The mask blank storage case according to Configuration 1 or 2, wherein the mask blank storage case is formed of a material mainly composed of an acrylic resin.
(Configuration 4) A mask blank storage method, wherein at least one mask blank is stored in the mask blank storage case according to any one of configurations 1 to 3.
(Structure 5) The mask blank storing method according to Structure 4, wherein the mask blank is a mask blank having a resist film.

(Structure 6) The mask blank storing method according to Structure 5, wherein the resist is a chemically amplified positive resist.
(Structure 7) A mask blank storage body comprising the mask blank storage case according to any one of structures 1 to 3 and at least one mask blank stored in the storage case. .
(Structure 8) The mask blank container according to Structure 7, wherein the mask blank is a mask blank having a resist film.
(Structure 9) The mask blank container according to Structure 8, wherein the resist is a chemically amplified positive resist.

  The mask blank storage case according to the present invention has a retention time 2 detected when the solution extracted by hot water extraction of the mask blank storage case is measured under anion measurement conditions by ion chromatography, as in Configuration 1. A mask blank storage case having a peak number of less than 13 at 8 minutes to 15 minutes. In this way, when a mask blank with a resist film is stored and stored by having specific characteristics detected when the extracted components from the mask blank storage case are analyzed by ion chromatography, contamination of the resist film during storage Stable resist performance can be obtained after storing and storing the mask blank. As a result, a stable resist pattern is formed at the time of mask manufacture, and a high-quality transfer mask on which a desired mask pattern is formed can be obtained. For example, when a mask blank with a positive resist film is stored and stored in a storage case in which the detection peak is 13 or more, when the mask blank taken out after storage is developed with a developer, it is unexposed, The ratio of the resist film thickness after development to the resist film thickness before development (film thickness after development / film thickness before development) (that is, the remaining film ratio) is greatly reduced, and the film thickness is reduced with respect to a mask blank having a positive resist film. May cause. In addition, not only a positive resist film but also a mask blank having a negative resist film may cause a film reduction.

When analyzing the storage case using the ion chromatography method, the sample solution can be extracted by, for example, putting ultrapure water inside the cover of the storage case, putting it in a bag for extraction analysis, and sealing it. And extraction at 60 ° C. for 4 hours. The sample solution extracted by this method is analyzed by ion chromatography under anion measurement conditions. The anion measurement conditions are conditions for detecting components such as Cl ⁻ , NO ₃ ⁻ , SO ₄ ^2−, etc. contained in the sample solution. As an eluent in this case, for example, a mixed solution of 2.7 mM Na ₂ CO ₃ and 0.3 mM NaHCO ₃ is used. In addition, the sample injection amount, the type of separation column, and the like are appropriately selected.

An example of anion measurement conditions (anion measurement conditions in the examples described later) is as follows.
Equipment: DX-500 manufactured by Dionex
Sample injection amount: 0.5 cm ³
Eluent: 2.7 mM-Na ₂ CO ₃ /0.3 mM-NaHCO ₃
Separation column: 4mmφ Ion Pac AS12A
Detector: Electric conductivity meter

  For example, an ion chromatogram as shown in FIG. 5 is obtained by such an ion chromatography measurement. FIG. 5 is an ion chromatogram in the case of Example 1 described later. In the present invention, for example, in the ion chromatogram as shown in FIG. 5, a peak with a peak area of 300 (au) or more is detected. And

In the present invention, as in Configuration 2, the retention time 2.8 detected when the solution extracted by hot water extraction of the mask blank storage case is measured under anion measurement conditions by ion chromatography. More preferably, the ratio of the peak area in minutes to 15 minutes to the peak area of the sulfate ion standard solution is less than 15.
In the present invention, the sulfate ion standard solution is a sulfate ion (SO ₄ ²⁻ ) standard solution having a concentration of 30 ppb.

  In the present invention, when the analysis by the ion chromatography method is performed, it is preferable to carry out a cleaning process for the mask blank storage case in advance. This is because the influence of chemical substances or foreign substances adhering to the surface of the storage case may be reflected in the analysis result. In this case, it is preferable to use pure water as the cleaning liquid. Preferred examples of the pure water include reverse osmotic membrane water (hereinafter referred to as “RO water”) and ultrafiltration membrane water (hereinafter referred to as “UF water”). I can do it. At this time, ion exchange treatment (also referred to as de-ionized water, hereinafter referred to as “DI water”) may be performed by performing ion exchange treatment together.

The mask blank storage case in the present invention includes a member for storing and holding the mask blank (for example, a middle case in the storage case).
The material of the mask blank storage case in the present invention is not particularly limited as long as it has specific characteristics detected when analyzed by the ion chromatography method described above, but it is a lightweight and easy-to-handle resin. Preferred materials can be mentioned. Examples of such resin materials include polypropylene resins, acrylic resins, polyethylene resins, polybutylene resins, and polycarbonate resins. Among these, acrylic resins, especially polymethylmethacrylate (PMMA) resins, are materials with relatively low outgas. Therefore, when the molded case has specific characteristics according to the present invention, it can be stored and stored in a mask blank. The performance of the formed resist film can be maintained satisfactorily. In the case of a storage case molded of ABS resin (acrylonitrile, butadiene and styrene copolymer resin), the positive resist film formed on the mask blank does not cause film thickness reduction. This may cause film thickness reduction for the type resist film.

Next, an example of a storage case for storing a mask blank to which the present invention is applied will be described. 1 to 4 show an example of a mask blank storage case. FIG. 1 is a perspective view showing a cover of the storage case, FIG. 2 is a perspective view showing a state in which the mask blank is stored in an inner case, and FIG. FIG. 4 is a perspective view showing the main body (outer case) of the storage case, and FIG. 4 is a longitudinal sectional view of the storage case in which the mask blank is stored.
In the storage case of this example, a mask blank 1 in which a light-shielding thin film such as a chrome film is formed on one main surface of a glass substrate having a square main surface, and the above-described chemically amplified resist film is formed thereon. The structure is housed in the middle case 2, the middle case 2 is housed in the main body 3, and the lid 4 is put on the opening side of the main body 3 (FIG. 4).
In addition, it is also possible to adopt a form in which the mask blank 1 is housed in the main body 3 by providing a groove or the like without using the middle case 2. However, if the middle case 2 is used as in this example, it is convenient because several to several tens of mask blanks can be handled together in the middle case 2.

  The middle case 2 is formed by forming a plurality of grooves 21 and 22 from the opening side (upper side) to the bottom side (lower side) at a predetermined interval on one inner surface facing each other. Opening windows 23 and 24 and an opening 27 are provided on the bottom of the bottom surface side of the 21 and 22 and the bottom of the middle case, respectively, and a substrate support 26 is formed on the bottom of the middle case. The lower end face of the blank 1 is supported (FIGS. 2 and 4). Then, concave portions 28 and 29 for housing and fixing the middle case 2 in the main body 3 are formed on the other opposite outer surfaces of the middle case from the bottom surface side to the middle of the opening portion side (see FIG. 2). Note that the height dimension from the upper end surface 25 on the opening side of the middle case 2 to the substrate support portion 26 corresponds to the main part of the height dimension of the mask blank 1 to be accommodated. When stored, the upper part of the mask blank 1 protrudes from the upper end surface 25 of the middle case 2 (FIG. 4). When several mask blanks 1 are inserted along the pair of grooves 21 and 22 of the middle case 2, these mask blanks stand in parallel with each other at a predetermined interval. In the form of this example, forests are formed in the vertical direction, but they may be inclined.

The main body 3 is formed with projecting portions 31 and 32 adapted to abut against the concave surface portions 28 and 29 of the above-described middle case 2 on inner surfaces facing each other, and the bottom of the projecting portions 31 and 32 is the bottom surface of the main body 3. They are also joined together (FIG. 3). In addition, convex portions 33 and 34 are formed on the opening side of one opposing outer surface. The outer peripheral surface 36 following the position slightly below the opening edge 35 of the main body 3 and the convex surfaces of the convex portions 33 and 34 are formed on substantially the same plane.
The lid 4 has recesses 43, 44 in engagement pieces 41, 42 extending from one opposing lower edge (the edge on the opening side to be inserted into the container body and facing upward in FIG. 1) 47. Is forming. Thus, when the lid 4 is put on the main body 3, the concave portions 43 and 44 engage with the convex portions 33 and 34 of the main body 3, respectively, so that the lid 4 and the main body 3 are fixed (FIG. 4). ). Further, stoppers 45 and 46 that contact the upper end surface 25 on the opening side of the middle case 2 and support and fix the middle case 2 in the vertical direction are formed on one inner surface so as to face each other (FIG. 1).

The material of the above-mentioned middle case 2, the main body 3 and the lid 4 is preferably a resin material as described above, and is preferably a PMMA resin. In addition, if a charge accumulates during storage of the mask blank, it may cause a discharge breakdown in the mask manufacturing process, resulting in a pattern defect. For example, carbon or the like is mixed into the constituent resin of the main body 3 to provide conductivity. Can do.
When the lid 4 is put on the main body 3 and the concave portions 43, 44 of the lid 4 are engaged with the convex portions 33, 34 of the main body 3 to fix the lid 4 and the main body 3, the outer periphery following the lower edge of the lid 4 The surface 48 and the outer peripheral surface 36 following the opening edge of the main body 3 are overlapped and joined in the front-rear direction.

Moreover, as it exists in the structures 7-9, the mask blank storage body of this invention has the mask blank stored in the storage case of this invention, and is especially suitable as a mask blank storage body which has a resist film. Furthermore, it is suitable as a mask blank housing body having a positive chemically amplified resist film.
The mask blank to which the present invention is applied is not particularly limited, and is a mask blank in which a light shielding film such as Cr is formed on a light-transmitting substrate such as a glass substrate, and a phase shift type in which a phase shift film is formed on the substrate. Examples include a mask blank for a mask, a mask blank for a reflective mask in which, for example, a Mo / Si multilayer reflective film that reflects exposure light and a Ta-based absorber film that absorbs exposure light are formed on the substrate.

  According to the present invention, by having specific characteristics detected when the extracted components from the mask blank storage case are analyzed by ion chromatography, stable resist performance is obtained after storing and storing the mask blank with a resist film, As a result, a stable resist pattern is formed at the time of mask manufacture, and a high-quality transfer mask on which a desired mask pattern is formed can be obtained. The present invention is suitable for housing a mask blank with a resist film, and particularly suitable for housing a mask blank with a chemically amplified resist film that is particularly susceptible to contamination by chemical substances.

Hereinafter, the present invention will be described with reference to specific examples.
Example 1
A storage case having the form shown in FIGS. 1 to 4 was produced. In this embodiment, the material of the lid, main body, and middle case of the storage case is PMMA resin, and after the PMMA resin is molded into the above form, the storage case is washed with ultrapure water having a water temperature of 40 ° C. . The storage case after the washing was heated in a clean oven. The heat treatment condition was 50 ° C. for 3 hours. In addition, the said washing | cleaning process and heat processing process were implemented in the clean room cleaned using the activated carbon filter containing potassium carbonate, the activated carbon filter containing phosphoric acid, and the air filter together. The storage case thus obtained is referred to as a storage case of Example 1.

The storage case of Example 1 was analyzed using an ion chromatography method.
That is, 100 ml of ultrapure water was placed inside the lid of the storage case of Example 1, and this was placed in a bag for extraction analysis and sealed, and then extracted at 60 ° C. for 4 hours. The sample solution extracted by this method was measured by ion chromatography under the following anion measurement conditions.
(Anion measurement conditions)
Equipment: DX-500 manufactured by Dionex
Sample injection amount: 0.5 cm ³
Eluent: 2.7 mM-Na ₂ CO ₃ /0.3 mM-NaHCO ₃
Separation column: 4mmφ Ion Pac AS12A
Detector: Electric conductivity meter

The obtained ion chromatogram is shown in FIG. In the ion chromatogram shown in FIG. 5, a peak having a peak area of 300 (au) or more was taken as a detection peak. As a result, the number of detected peaks in the storage case of Example 1 was 8 at a retention time of 2.8 minutes to 15 minutes. In addition, the total peak area of the detection peaks in the retention time of 2.8 minutes to 15 minutes is 284327 (au), and the ratio to the peak area (36769 (au)) of the sulfate ion (SO ₄ ²⁻ ) standard solution with a concentration of 30 ppb. Was 8.

Next, a halftone film was formed on a quartz substrate (size: 6 inches × 6 inches) by a sputtering method, and a resist film was formed thereon by a spin coating method to manufacture a mask blank with a resist film. At this time, a MoSi-based metal film was used as the halftone film, and a positive chemically amplified resist FEP171 (manufactured by Fuji Film Arch) was used as the resist. The resist film was formed in a clean room that was cleaned using an activated carbon filter containing potassium carbonate, an activated carbon filter containing phosphoric acid, and an air filter.
The ten mask blanks with resist films produced in this way were stored in the storage case of the above-described Example 1 (the one subjected to the above-described cleaning and heat treatment). The mask blank was stored in a clean room cleaned with the activated carbon filter and air filter.

This storage case was further packed in a packing bag and carried by aircraft. Then, after storing the transported storage container in a packaged state (not a clean room) for about one month, the container is opened in a clean room similar to the above, and the resist-dedicated developer is used for the removed mask blank. Then, development (development temperature: 20 ° C.) was performed, and the film thickness reduction of the resist film thickness after development relative to the resist film thickness before development was measured. The results are shown in FIG. In FIG. 9, the results indicated by ● are the results of Example 1. The horizontal axis of FIG. 9 is a coordinate in which the position of the end in the direction close to the case on the mask blank surface is 0. The vertical axis in FIG. 9 indicates the amount of film reduction of the resist film at each coordinate position.
In this example, the amount of film reduction is 10 nm or less, and it can be seen that no particularly problematic film reduction action occurs. In addition, since the distribution of the film thickness reduction on the mask blank surface is uniform, there is no practical problem. In the case of the storage case of Example 1, it was found that during storage and storage of the mask blank with resist film, chemical substances that contaminate the positive chemically amplified resist film were hardly released from the storage case. It was.

  Further, instead of the positive chemically amplified resist film, 10 mask blanks on which a negative resist film was formed were similarly stored and stored in the storage case of Example 1, and then opened and taken out. When exposure (entire surface) and development were performed, no particularly problematic film reduction occurred as in the case of the positive resist. In the storage case of Example 1, it was found that during storage and storage of the mask blank with a resist film, chemical substances that contaminate the negative resist film were hardly released from the storage case. It was.

(Example 2)
After molding in the same manner except that a PMMA resin different from that in Example 1 was used, the storage case was washed and heated in the same manner as in Example 1. The storage case thus obtained is referred to as a storage case of Example 2.
The storage case of Example 2 was analyzed by ion chromatography in the same manner as in Example 1.
The obtained ion chromatogram is shown in FIG. In the ion chromatogram shown in FIG. 6, a peak having a peak area of 300 (au) or more was taken as a detection peak. As a result, in the storage case of Example 2, the number of detected peaks was 9 in the retention time of 2.8 minutes to 15 minutes. In addition, the total peak area of the detected peaks in the retention time of 2.8 minutes to 15 minutes is 514766 (au), and the ratio to the peak area (36769 (au)) of the sulfate ion (SO ₄ ²⁻ ) standard solution having a concentration of 30 ppb. Was 14.

Next, 10 mask blanks with a resist film on which the same positive chemically amplified resist film as in Example 1 is formed are stored in the storage case of Example 2 described above (which has been subjected to the above-described cleaning and heat treatment). , Transported and stored.
After storage, the extracted mask blank was developed in the same manner as in Example 1, and the amount of film thickness reduction of the resist film after development relative to the resist film thickness before development was measured. The results are shown in FIG. 9 together with the results of Example 1. In FIG. 9, the results indicated by Δ are the results of Example 2.
In this example, the amount of film reduction is 10 nm or less, and it can be seen that no particularly problematic film reduction action occurs. In addition, since the distribution of the film thickness reduction on the mask blank surface is uniform, there is no practical problem. In the case of the storage case of Example 2, it was found that chemical substances that contaminate the positive chemically amplified resist film during storage were hardly released from the storage case.
Further, when the same test was performed on the mask blank on which the same negative resist film as in Example 1 was formed, no particularly problematic film reduction occurred as in the case of the positive resist. In the case of Example 2, it was found that even in the case of a negative resist film, chemical substances that contaminate the storage case during storage were hardly released from the case.

(Example 3)
After molding in the same manner as in Example 1 except that an ABS resin, which is a copolymer resin of acrylonitrile, butadiene, and styrene, was used, the storage case was washed and heated in the same manner as in Example 1. However, the heat treatment time was 30 minutes. The storage case thus obtained is referred to as a storage case of Example 3.
The storage case of Example 3 was analyzed by ion chromatography in exactly the same manner as in Example 1.
The obtained ion chromatogram is shown in FIG. In the ion chromatogram shown in FIG. 7, a peak having a peak area of 300 (au) or more was taken as a detection peak. As a result, the number of detected peaks in the storage case of Example 3 was 8 at a retention time of 2.8 minutes to 15 minutes. In addition, the total peak area of the detection peaks in the retention time of 2.8 minutes to 15 minutes is 46550 (au), and the ratio to the peak area (36769 (au)) of the sulfate ion (SO ₄ ²⁻ ) standard solution having a concentration of 30 ppb. Was 1.2.

Next, 10 mask blanks with a resist film on which the same positive chemically amplified resist film as in Example 1 is formed are stored in the storage case of the above-described Example 3 (which has been subjected to the above-described cleaning and heat treatment). , Transported and stored.
After storage, the removed mask blank was developed in the same manner as in Example 1, and the amount of reduction in the resist film thickness after development relative to the resist film thickness before development was measured. The same result as in Example 1 was obtained. It was. In other words, in the case of the storage case of Example 3, it was found that chemical substances that contaminate the positive chemically amplified resist film during storage were hardly released from the storage case.
Furthermore, when a similar test was performed on a mask blank on which the same negative resist film as in Example 1 was formed, the same result as in Example 1 was obtained.

(Comparative Example 1)
After molding in the same manner except that a PMMA resin different from that in Example 1 was used, the storage case was washed and heated in the same manner as in Example 1. However, the heat treatment time was 30 minutes. The storage case thus obtained is used as a storage case of a comparative example.
The storage case of this comparative example was analyzed by ion chromatography in the same manner as in Example 1.
The obtained ion chromatogram is shown in FIG. In the ion chromatogram shown in FIG. 8, a peak having a peak area of 300 (au) or more was taken as a detection peak. As a result, the storage case of this comparative example had a detection peak number of 13 at a retention time of 2.8 minutes to 15 minutes. Further, the total peak area of the detection peaks in the retention time of 2.8 minutes to 15 minutes is 551004 (au), and the ratio to the peak area (36769 (au)) of the sulfate ion (SO ₄ ²⁻ ) standard solution having a concentration of 30 ppb. Was 15.

Next, 10 mask blanks with a resist film in which the same positive chemically amplified resist film as in Example 1 is formed are stored in the storage case of the above-described comparative example (the one subjected to the above-described cleaning and heat treatment). Transported and stored.
After storage, the extracted mask blank was developed in the same manner as in Example 1, and the amount of film thickness reduction of the resist film after development relative to the resist film thickness before development was measured. The results are shown in FIG. 9 together with the results of Examples 1 and 2 described above. In FIG. 9, the results indicated by ◯ are the results of Comparative Example 1.
In this comparative example, the amount of film reduction was 33 nm at the maximum especially on the side close to the case, and the film thickness was more than three times that of Examples 1 and 2. In addition, since the distribution of the film thickness reduction on the mask blank surface is not uniform, uniform patterning cannot be performed in the process of manufacturing the transfer mask. That is, in the storage case of this comparative example, it was found that chemical substances that contaminate the positive chemically amplified resist film were released from the storage case during storage.
Further, when the same test was performed on the mask blank on which the same negative resist film as that in Example 1 was formed, as in the case of using the above positive resist, a large film thickness was reduced and the side closer to the case There was a large difference in resist film thickness between the mask blank and the center of the mask blank. For this reason, uniform patterning cannot be performed when a transfer mask is manufactured. That is, in the storage case of this comparative example, it was found that even in the case of a negative resist film, chemical substances that contaminate the storage case were released from the storage case during storage.

It is a perspective view which shows the cover of a storage container. It is a perspective view which shows the state which accommodates a mask blank in a middle case. It is a perspective view which shows the container main body (outer case) of a storage container. It is sectional drawing of the vertical direction of the state which accommodated the mask blank in the storage container. It is the ion chromatogram obtained when the storage case of Example 1 was analyzed by the ion chromatography method. It is the ion chromatogram obtained when the storage case of Example 2 was analyzed by the ion chromatography method. It is the ion chromatogram obtained when the storage case of Example 3 was analyzed by the ion chromatography method. It is the ion chromatogram obtained when the storage case of a comparative example was analyzed by the ion chromatography method. 6 is a graph showing a distribution of a reduction amount of a resist film thickness due to development after storing and storing a mask blank in a storage case in Examples 1 and 2 and Comparative Example 1. FIG.

Explanation of symbols

1 Mask blank 2 Middle case 3 Body 4 Lid

Claims (9)

A mask blank storage case for storing a mask blank having a thin film for forming a mask pattern on a substrate,
The number of peaks at a retention time of 2.8 to 15 minutes, which is detected when the solution extracted by hot water extraction of the mask blank storage case is measured under anion measurement conditions by ion chromatography, is less than 13. Characteristic mask blank storage case.   The sulfate ion standard solution having a peak area at a retention time of 2.8 minutes to 15 minutes, which is detected when the solution extracted by hot water extraction of the mask blank storage case is measured under anion measurement conditions by ion chromatography. 2. The mask blank storage case according to claim 1, wherein the ratio to the peak area is less than 15.   The mask blank storage case according to claim 1 or 2, wherein the mask blank storage case is formed of a material mainly composed of an acrylic resin.   A method for storing a mask blank, comprising storing at least one mask blank in the mask blank storage case according to any one of claims 1 to 3.   The mask blank storing method according to claim 4, wherein the mask blank is a mask blank having a resist film.   6. The mask blank storing method according to claim 5, wherein the resist is a chemically amplified positive resist.   A mask blank storage body comprising the mask blank storage case according to any one of claims 1 to 3 and at least one mask blank stored in the storage case.   The mask blank storage body according to claim 7, wherein the mask blank is a mask blank having a resist film.   The mask blank container according to claim 8, wherein the resist is a chemically amplified positive resist.

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