JPH05304068A - Dust-proof housing case - Google Patents

Abstract

PURPOSE:To obtain an light exposure mask substrate dust-proof housing case which effectively prevents dust from attaching to a pellicle in stock. CONSTITUTION:The inner surface of a housing case is formed of material whose volume resistance is smaller than 10<10>OMEGA.cm and contact angle to water is smaller than 60 deg.. Surrounding dust is hardly attracted to the housing case, so that dust attached to the housing case can be lessened in amount. Even if dust attaches to the housing case, it is prevented from being fixed to the surface of the case. Dust can be easily removed from the housing case with air blow or pure water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust-proof storage case for an exposure mask substrate for preventing deposition of airborne dust which interferes with a lithography process.

[0002]

2. Description of the Related Art In recent years, integration has progressed in a lithographic process during the manufacture of large scale integrated circuits. Even a small amount of dust attached to the pattern of the exposure mask substrate leads to a defective product of the integrated circuit. Therefore, a thin film called a pellicle to prevent dust may be used on the mask substrate. After mounting the pellicle, even if dust adheres to the surface of the pellicle, the dust is out of focus during exposure due to the thickness of the pellicle and does not form an image on the photosensitive resin surface of the integrated circuit. by this,
Defective integrated circuit patterns due to dust are prevented.

The mask substrate is housed in a storage case, and is used by taking it out from the integrated circuit photosensitive resin surface each time it is exposed. If the pellicle on the mask substrate has dust in the storage case and the dust falls on the photosensitive surface of the integrated circuit during a lithography process or the like, the integrated circuit causes a product defect.

To prevent this, Japanese Patent Publication No. 63-777 proposes a method of providing an adhesive layer on the inside of the frame of a mask substrate on which a pellicle is mounted. JP-A-1-120555 discloses an adhesive on the surface of the pellicle. Have been proposed. Furthermore, in U.S. Pat.No. 4,470,508, the inner surface of the storage and storage case of the mask substrate on which the pellicle is mounted is made to have viscosity so that dust once attached to the surface of the pellicle or dust present in the vicinity of the pellicle is naturally removed. Methods have also been proposed.

[0005]

In the case of the above measures against dust, it is not possible to directly prevent dust from adhering to the surface of the pellicle even during storage of the mask substrate. It simply prevents the dust once attached from separating again and transferring to the photosensitive surface of the integrated circuit. It was insufficient as a method for preventing product defects in integrated circuits.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a dust-proof storage case for an exposure mask substrate which can effectively prevent dust from adhering to the pellicle during storage.

[0007]

The dustproof storage case of the present invention made to achieve the above object has a volume resistance of 10 ¹⁰ Ω · cm or less and a contact angle with water of 60 degrees or less at least on the surface in the storage section. It is formed of the material.

[0008]

In the dustproof storage case of the present invention, since the volume resistance of the surface inside the storage portion is 10 ¹⁰ Ω · cm or less, the generation of static electricity on the surface is prevented, and it is difficult to suck the surrounding dust. This reduces the amount of dust attached to the storage case. Even if dust adheres to it, it can be easily removed by air blowing or washing with pure water because the force of attracting dust is weak. Virtually less dust is attached. If the volume resistance of the surface exceeds 10 ¹⁰ Ω · cm, the generation of static electricity cannot be sufficiently prevented and the suction and adhesion of dust cannot be prevented, which is not preferable.

Further, in the present invention, the contact angle of water is 60 degrees or less. As a result, the fixing force of dust is reduced. From this point as well, even if dust adheres, it can be easily removed. When the contact angle to water is 60 degrees or more, the fixing force becomes strong, which is not preferable.

As a material having a size of an ordinary dustproof storage case and a volume resistance of 10 ¹⁰ Ω · cm or less on the surface thereof, in addition to general metals, those obtained by coating the surface of an insulator with a conductive substance can be cited. . As a method for coating the surface of a general plastic with a conductive substance, for example, a metal vapor deposition method, a sputtering method, or the like can be mentioned. A conductive material such as metal powder or carbon powder may be kneaded into ordinary plastics to be molded. Also by these methods, the volume resistance can be made 10 ¹⁰ Ω · cm or less.

As a substance having a contact angle of water of 60 degrees or less,
Examples include aluminum. In addition to these, for example, the contact angle can be set to 60 degrees or less by adding a surfactant to any resin. A surface treatment such as oxygen plasma treatment may be performed.

When the mask substrate on which the pellicle is mounted is stored in such a storage case, adhesion of dust during storage can be effectively prevented.

[0013]

EXAMPLES Examples of the present invention will be described below.

Examples 1 to 4 The materials shown in Table 1 were used, and the length and width 120 as shown in FIG.
mm, a depth of 10 mm, and a wall thickness of 0.5 mm, and a storage case including a storage unit 1 and a lid 2 thereof was produced. Table 2 shows the volume resistance of the surface and the contact angle with water.

[0015]

[Table 1]

[0016]

[Table 2]

Next, a pellicle was attached with nitrocellulose to the surface of a simulated mask substrate formed of an aluminum frame having a size of 110 squares and a thickness of 5 mm, and the pellicle was stored in the storage case in a class 10 clean bench. After 10 minutes, remove the simulated mask substrate from the storage case, 1
After 0 minutes, it was stored again in the storage case.

After the operation of putting in and out of the storage case was repeated 10 times, the number of dust particles attached to the pellicle was counted using a condenser lamp to obtain the number of dust particles.
The results are shown in Table 2. It was found that there was little attachment of dust.

Comparative Examples 1 to 3 The materials shown in Table 1 having a surface volume resistance of 10 ¹⁰ Ω · cm or more and a water contact angle of 60 ° or more were used. Others were the same as in Examples 1-3. The results are shown in Table 2. It turned out that a lot of dust adhered.

[0020]

As described above in detail, the dustproof storage case of the present invention is difficult to suck dust around it and does not fix it even if it adheres. It is also easy to remove by washing with air blow or pure water. Therefore, if the exposure mask substrate is stored as much as possible except when necessary, it is possible to effectively prevent dust from adhering to the surface of the pellicle.

[Brief description of drawings]

FIG. 1 is an embodiment of a dustproof storage case to which the present invention is applied.

[Explanation of symbols]

 1 is a storage part, 2 is a lid.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/68 T 8418-4M

Claims (1)

[Claims] 1. A dust-proof storage case for a mask substrate for exposure, characterized in that at least the surface inside the storage section is formed of a material having a volume resistance of 10 ¹⁰ Ω · cm or less and a contact angle with water of 60 degrees or less.