JP4342872B2 - Mask blank storage method, mask blank storage body, and mask blank manufacturing method - Google Patents

Description

  The present invention relates to a method for storing a mask blank with a resist film for manufacturing a photomask used for manufacturing an electronic device.

  In recent years, electronic devices, particularly color filters or TFT elements for semiconductor elements and liquid crystal monitors, are required to be further miniaturized with the rapid development of IT technology. 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 to be an original using a lithography technique on a mask blank in which a light-shielding film is formed on a translucent substrate. By the way, if there is foreign matter such as particles on the surface of the mask blank, it will cause defects in the pattern to be formed. Therefore, it is necessary to keep the surface of the mask blank clean so that the foreign matter does not adhere to the surface.

As a container for storing, storing, and transporting such mask blanks, a mask transport case as described in, for example, Patent Document 1 below has been conventionally known.
In other words, a conventional container for storing and storing mask blanks has an inner case called a carrier or the like that holds several to several tens of mask blanks and holds the inner case holding the mask blanks in an outer box (case body). ) And a cover on the outer box to accommodate the mask blanks. 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.
JP 2001-154341 A

  As electronic devices have become more sophisticated in recent years, patterns formed on transfer masks are required to be further miniaturized, and the mask blanks are extremely clean to form such miniaturized patterns. Otherwise it will be unacceptable. Accordingly, it is necessary to keep the mask blanks as clean as possible, particularly during storage of the mask blanks, by suppressing the adhesion of foreign substances or the like to the mask blanks as much as possible. Above all, in the case of mask blanks having a resist film on the surface, it is difficult to remove once the foreign matter adheres to the surface, and since cleaning cannot be performed at this stage, patterning is performed with the foreign matter attached, resulting in pattern defects. become.

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 energy rays such as an electron beam or an electromagnetic wave, the contained catalytic substance can be exposed to produce 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.
However, 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 mask blanks with a chemically amplified resist film, it is not necessary to simply remove foreign substances such as particles, and in order to eliminate the effects of contamination by basic chemical substances, store them in a particularly clean atmosphere. There is a need to.

However, according to the study by the present inventors, it has been found that even if contamination by the basic chemical substance is prevented, a stable resist performance cannot always be obtained, and a desired resist pattern cannot always be formed. In other words, in the manufacturing process of mask blanks with chemically amplified resist film, we thoroughly investigated the cause of the generation of basic substances such as amines, and paid sufficient attention to the storage packaging environment of mask blanks. Nevertheless, it has been found that there is a problem that the accuracy of the resist pattern to be formed varies.
Therefore, the present invention solves the above-mentioned conventional problems, and is particularly suitable for a mask blank formed with a chemically amplified resist film that needs to be stored in a clean atmosphere, and is stable for forming a desired mask pattern. An object of the present invention is to provide a mask blank storage method and the like that can maintain the resist performance.

As described above, the contaminants of the chemically amplified resist were conventionally considered to be basic chemical substances such as amines, but according to the study of the present inventors, such basic chemical substances are It has been found that even if mask blanks are stored in an excluded environment, stable resist performance may not be obtained, and a desired fine pattern may not be formed during mask manufacturing.
Accordingly, as a result of intensive studies to solve the above problems, the present inventors have unexpectedly found that mask blanks having chemically amplified resist films are contaminated not only by basic substances but also by adhesion of acidic substances, and are stable. It has been found that the fine pattern formation may be hindered. The acidic substance mainly affects the sensitivity of the chemically amplified resist, and has also been found to have an effect of enhancing the chemical amplification effect more than desired. The present invention has been completed based on a series of these findings.

That is, the present invention has the following configuration.
(Configuration 1) A method of storing mask blanks having a chemically amplified resist film in a storage container, wherein the mask blanks are stored in a storage container together with an atmosphere from which at least an acidic substance has been removed. How to store blanks.
(Configuration 2) A method of storing mask blanks having a chemically amplified resist film in a storage container, wherein the mask blanks are stored in a storage container in an atmosphere from which at least an acidic substance has been removed. How to store mask blanks.
(Configuration 3) The mask blank storage method according to Configuration 1 or 2, wherein the storage container has means for absorbing or adsorbing an acidic substance.
(Configuration 4) A mask blank storage body in which mask blanks having a chemically amplified resist film are stored in a storage container having an atmosphere not containing at least an acidic substance.
(Structure 5) A mask characterized in that after a thin film for forming a mask pattern is formed on a substrate, a chemically amplified resist film is formed on the thin film in an atmosphere from which at least an acidic substance has been removed. Blanks manufacturing method.
(Configuration 6) A step of forming a chemically amplified resist film on a mask blank obtained by forming a thin film for forming a mask pattern on a substrate, a post-processing step to be performed as necessary, and A mask blank manufacturing method comprising: a step of inspecting the mask blank with resist film, and a step of storing and packing the mask blank with resist film in a storage container, wherein at least one of the above steps is performed. One process is implemented in the atmosphere from which the acidic substance was removed at least, The manufacturing method of the mask blanks characterized by the above-mentioned.

In the present invention, the acidic substance to be removed particularly includes an acidic contaminant that adheres to the chemically amplified resist film and affects the chemical amplification effect of the chemically amplified resist. Examples of such an acidic substance include a substance containing chlorine ions, a substance containing sulfate ions, a substance containing phosphate ions, and a substance containing nitrate ions. These acidic substances mainly affect the sensitivity of chemically amplified resists, have the effect of increasing the chemical amplification effect more than desired, and stable resist performance cannot be obtained, resulting in stable Formation of the resist pattern is hindered, and a desired fine pattern may not be formed during mask manufacturing.
The degree of removal of these acidic substances is not necessarily 100%, as long as they are removed to the extent that they do not contaminate the chemically amplified resist film even if they exist in the atmosphere. Of course, the higher the degree of removal of acidic substances, the better the quality because the cleanliness will be better. However, the production cost may be reduced, so the acidic substances are within the profit line and do not cause product failure. May be removed from the atmosphere. As a specific example, for example, in the case of a substance containing chlorine ion, 0.05 μg or less of chlorine ion per 1 cubic meter of atmosphere, and 0.1 μg of sulfate ion in the case of a substance containing sulfate ion. Hereinafter, in the case of a substance containing nitrate ions, the nitrate ions are preferably 0.7 μg or less.

As a method for removing an acidic substance from the atmosphere, a filter that adsorbs a chemical substance (chemical filter) can be used. As a chemical filter for removing an acidic substance, it is preferable to use a chemical filter in which an acid neutralizing substance is mixed. Preferred examples of the acid neutralizing substance include carbonate substances. As such a carbonate substance, potassium carbonate can be preferably mentioned. As such a chemical filter, an activated carbon filter containing an adsorbent such as activated carbon can be preferably used, and a filter containing the adsorbent such as activated carbon containing the acid neutralizing substance can be preferably used. .
In the present invention, as in Configuration 1, the mask blank having a chemically amplified resist film is stored in a storage container together with an atmosphere from which at least an acidic substance has been removed. That is, when storing the mask blanks in the storage container, the mask blanks are stored and stored together with the atmosphere by supplying an atmosphere from which at least the acidic substance is removed. Thereby, the adhesion of acidic contaminants to the mask blanks can be most preferably prevented in practice.

As a method for supplying an atmosphere from which acidic substances have been removed, a method for supplying the atmosphere from which acidic substances have been removed using the above-described chemical filter to the environment for storing mask blanks, or supplying the atmosphere to a storage container for storage. Examples include a method of replacing the inside of the container, or a method of purging the storage container in the above atmosphere.
For example, as in Configuration 2, it is preferable to store the mask blank having the chemically amplified resist film in the storage container in an atmosphere from which at least the acidic substance has been removed. This is because the mask blank storage operation is normally performed in a clean room or the like, and therefore it is easy to supply an atmosphere from which acidic substances have been removed using a chemical filter or the like to the mask blank storage operation environment.
In addition to the acidic substance, it is also preferable to remove basic chemical substances that inhibit the desired chemical amplification effect of the chemically amplified resist, such as ammonia and amines. As a method for removing such a basic chemical substance, a method using a chemical filter in which an alkali neutralizing substance such as phosphoric acid is mixed may be used. As the chemical filter, an activated carbon filter containing an adsorbent such as activated carbon can be preferably used, and a filter containing the alkali neutralizing substance in an adsorbent such as activated carbon can be preferably used.

Moreover, it is preferable to use an air filter in combination with a chemical filter for removing the acidic substance and the basic substance. Preferred examples of such an air filter include a HEPA filter (high efficiency particulate air filter) and a ULPA filter (ultra low penetration particulate air filter). The HEPA filter is a highly efficient air filter, and the material is mainly made of glass fiber. The ULPA filter is an ultra-high performance filter mainly made of glass fiber or fluorine resin. The filter is preferably a filter that can capture particles of 0.05 μm or more. The selection of an air filter such as a HEPA filter or ULPA filter can be appropriately selected in consideration of cost effectiveness.

Moreover, there is no restriction | limiting in particular in the storage container for accommodating the mask blanks used by this invention. 1 to 4 show an example of a mask blank storage container, FIG. 1 is a perspective view showing a cover of the storage container, 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 container main body (outer case) of the storage container, and FIG. 4 is a longitudinal sectional view of the storage container with mask blanks stored therein.
The storage container of this example has 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-mentioned chemically amplified resist film is formed thereon. The container is housed in the middle case 2, the middle case 2 is housed in the container body 3, and the lid 4 is put on the opening side of the container body 3 (FIG. 4).
Note that the mask blanks 1 may be stored in the container main body 3 directly with 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 blanks 1 is supported (FIGS. 2 and 4). Then, concave surface portions 28 and 29 for accommodating and fixing the middle case 2 in the container 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 ( Figure 2). 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 blanks 1 to be accommodated. When stored, the upper portion 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 container body 3 is formed with protrusions 31 and 32 adapted to abut against the concave surfaces 28 and 29 of the above-described middle case 2 on inner surfaces facing each other, and the bottoms of the protrusions 31 and 32 are container bodies. The three bottom surfaces are also joined (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 container 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. Accordingly, when the lid 4 is put on the container body 3, the concave portions 43 and 44 are engaged with the convex portions 33 and 34 of the container main body 3, so that the lid 4 and the container 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). In addition, it is good also as a structure which can cover the lid | cover 4 as it is, without providing the recessed parts 43 and 44 of the lid | cover 4, and the convex parts 33 and 34 of the container main body 3. FIG. Further, even when the concave portion of the lid 4 and the convex portion of the container main body 3 are engaged, such engaging means may be formed not only on one side facing each other but also on each of the four sides.

The material of the above middle case 2, the container main body 3, and the lid | cover 4 is suitably selected from resin, such as a polypropylene, an acryl, polyethylene, a polycarbonate, polyester, polyamide, a polyimide, a polyethyl sulfite, for example. Among these, polycarbonate or polyester is preferable. The material of the container body 3 and the lid 4 is preferably polycarbonate, and the material of the middle case 2 is preferably polyester. As this polyester, polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and the like are preferable. In addition, if charges are accumulated during storage of mask blanks, discharge breakdown may occur in the mask manufacturing process, resulting in pattern defects. For example, carbon or the like is mixed into the constituent resin of the container body 3 to provide conductivity. It is preferable.
When the lid 4 is put on the container body 3 and the recesses 43 and 44 of the lid 4 are engaged with the projections 33 and 34 of the container body 3 to fix the lid 4 and the container body 3, the lower edge of the lid 4 The outer peripheral surface 48 that follows and the outer peripheral surface 36 that follows the opening edge of the container main body 3 are overlapped and joined in the front-rear direction.

In addition, like the structure 3, it is preferable that the said storage container has a means to absorb or adsorb | suck an acidic substance. Even if the mask blanks are stored in a storage container together with the atmosphere from which the acidic substances have been removed, during transport and storage of the mask blanks storage body, for example, the acidic substances are present together with the outside air from the joint between the storage container lid and the container body. Even in such a case, the storage container has a means for absorbing or adsorbing the acidic substance, thereby removing the acidic substance contained in the outside air and making the inside of the storage container a clean atmosphere. Because it can be kept. As a means for absorbing or adsorbing an acidic substance, for example, a simple method is to install a material that absorbs or adsorbs an acidic substance (absorption or adsorbent of an acidic substance) in a storage container. As a material that absorbs or adsorbs an acidic substance, for example, a material containing a carbonate substance such as potassium carbonate can be used. Further, the material constituting the storage container may contain a material that absorbs or adsorbs the acidic substance. Further, an adsorbent such as activated carbon may be used in combination.
Further, as in Configuration 4, the mask blank storage body according to the present invention stores the mask blank having a chemically amplified resist film in a storage container having an atmosphere that does not contain at least an acidic substance. Note that not containing an acidic substance is not necessarily limited to the case where it does not exist at all in the atmosphere, and may be contained in the atmosphere slightly as long as it does not contaminate the chemically amplified resist film. A specific allowable value in the case where an acidic substance is contained in the atmosphere is the same as the above-described degree of removal of the acidic substance.

As described above, an atmosphere from which an acidic substance has been removed may be used when storing the mask blanks, but it is preferable to use the above atmosphere also in the mask blank manufacturing process. That is, as in Configuration 5, after a thin film for forming a mask pattern is formed on a substrate such as a glass substrate, a chemically amplified resist film is formed on the thin film in an atmosphere from which at least an acidic substance has been removed. By forming the film, it is possible to prevent adhesion of an acidic substance or the like at the manufacturing stage of the mask blank with a resist film.
Moreover, it is suitable to use the said atmosphere in a series of processes from manufacture of mask blanks to storage packaging. That is, as in Configuration 6, a step of forming a chemically amplified resist film on a mask blank obtained by forming a thin film for forming a mask pattern on a substrate, and post-processing to be performed as necessary In a series of steps including a step, a step of inspecting the mask blanks with resist film performed as necessary, and a step of storing and packing the mask blanks with resist film in a storage container, at least one of the steps This step is preferably performed in an atmosphere from which at least an acidic substance has been removed. Examples of the post-processing step performed as necessary include a heating (baking) step for improving the adhesion of the resist film and a dry cleaning step.
In particular, it is preferable to carry out in an atmosphere from which at least an acidic substance has been removed, from the step of forming a chemically amplified resist film on the mask blank to the step of storing and packing the mask blank with resist film.
The mask blank to which the present invention is applied 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 in which a halftone (semi-transparent) film is formed on the substrate. Includes mask blanks for shift masks, and mask blanks for reflective masks 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, when mask blanks having a chemically amplified resist film are stored in a storage container, an atmosphere from which at least an acidic substance has been removed is used to achieve a desired chemical amplification effect of the chemically amplified resist film. It is possible to prevent contamination due to the adhesion of acidic substances that have an influence and increase the chemical amplification effect more than desired. Therefore, stable resist performance can be obtained after storing the mask blanks. As a result, a stable resist pattern is formed during mask manufacturing, and a high-quality transfer mask having a desired mask pattern can be obtained.
In addition, according to the present invention, even if a mask blank containing a mask blank having a chemically amplified resist film is stored in a storage container, the mask blank stored in the storage container is transported to a remote place or the like using a transportation means. Since contamination of the resist film can be suppressed, high reliability for transporting the mask blanks to a remote place or the like can be ensured.
In addition, according to the present invention, a thin film for forming a mask pattern on a substrate is formed, and then a chemically amplified resist film is formed in an atmosphere from which at least an acidic substance has been removed. It is possible to prevent adhesion of an acidic substance or the like in the mask blank manufacturing stage.
Further, in the series of steps from the manufacture of mask blanks to the storage packaging, contamination by acidic substances can be suitably prevented by using the atmosphere from which the acidic substances have been removed.

Hereinafter, the present invention will be described with reference to specific examples.
(Example)
A halftone film was formed on a quartz substrate (6 inches × 6 inches) by a sputtering method, and a resist film was formed thereon by a spin coating method to produce 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 film was used as the resist film. The resist film was formed in a clean room cleaned with an activated carbon filter and a ULPA filter containing potassium carbonate.
The 100 mask blanks manufactured in this way were stored separately in 10 storage containers of the form shown in FIGS. The lid and container body were made of polycarbonate, and the middle case was made of polybutylene terephthalate. The storing operation was performed in a clean room cleaned with an activated carbon filter and a ULPA filter. As the activated carbon filter, an activated carbon filter containing potassium carbonate and an activated carbon filter containing phosphoric acid were used in combination.
This storage container was further packed in a packing bag, and cargo was transported by aircraft. Then, the transported storage container was opened in a clean room similar to the above, and a predetermined electron beam was drawn on the taken-out mask blanks, followed by predetermined development and etching to produce a phase shift type transfer mask. . When the quality of the manufactured phase shift mask was examined in detail with a scanning electron microscope, no particularly problematic defect was found from any of the 100 sheets.

(Comparative example)
In the above-mentioned Example, except that the activated carbon filter containing potassium carbonate in a clean room was not used, mask blanks were produced, stored and transported in the same manner as in the Example.
When the quality of the phase shift mask manufactured using the mask blanks after transport in the same manner as in the example was inspected in detail with a scanning electron microscope, the line width of the pattern was disturbed from any of the 100 sheets. It was discovered that This is because some acidic substances exist in the atmosphere of the clean room and are packed in the storage container, and the mask blanks chemically amplified resist film is chemically contaminated by these acidic substances during transportation. It is thought to be caused by

It is a perspective view which shows the cover of a storage container. It is a perspective view which shows the state which accommodates mask blanks 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 blanks in the storage container.

Explanation of symbols

1 Mask Blanks 2 Middle Case 3 Container Body 4 Lid

Claims (6)

A method for storing a mask blank having a chemically amplified resist film in a storage container, wherein an atmosphere from which at least an acidic substance is removed is supplied to an environment for storing mask blanks, and at least an atmosphere in which the acidic substance is removed A method for storing mask blanks, comprising storing the mask blanks in a storage container. Supplying an atmosphere from which at least acidic substances have been removed to the mask blank storage environment, and storing mask blanks having chemically amplified resist films in a storage container in an atmosphere from which at least acidic substances have been removed Characteristic mask blanks container.   The mask blank storage body according to claim 2, wherein the storage container has means for absorbing or adsorbing an acidic substance.   When the atmosphere from which the acidic substance is removed contains at least one of chlorine ion, sulfate ion or nitrate ion, 0.05 μg or less of chlorine ion, 0.1 μg or less of sulfate ion or nitrate ion per cubic meter of atmosphere It is 0.7 microgram or less, The mask blanks storage body of Claim 2 or 3 characterized by the above-mentioned. After forming a thin film for forming a mask pattern on the substrate, an atmosphere from which at least an acidic substance has been removed is supplied to the environment of the resist film forming process, and at least an atmosphere in which the acidic substance has been removed is applied on the thin film. A method for producing a mask blank, comprising: forming a chemically amplified resist film on the substrate. A process of forming a chemically amplified resist film on a mask blank obtained by forming a thin film for forming a mask pattern on a substrate, a post-processing process to be performed as necessary, and a process to be performed as necessary A mask blank manufacturing method including an inspection process of the mask blanks with resist film and a process of storing and packing the mask blanks with resist film in a storage container, wherein at least one of the processes is A method for producing a mask blank, characterized in that an atmosphere from which at least an acidic substance is removed is supplied to the environment of the step, and the process is performed in an atmosphere from which at least an acidic substance has been removed.

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