JPS63179355A - Reticle protective case - Google Patents

Abstract

PURPOSE:To prevent adsorption of microparticles to a case, etc., by using a synthetic resin into which carbon fibers are incorporated as an external case and using a material which decreases the surface resistance thereof to suppress the static electricity to be electrified on the surface of the protective case. CONSTITUTION:The case 11 of the reticle protective case 13 which is mounted on a metallic bottom plate 12 and puts the external case on the plate 12 consists of the synthetic resin contg. the carbon fibers. The surface resistance value decreases sharply when the carbon fiber content in the synthetic resin such as polyacetal exceeds prescribed %. The static electricity to be electrified on the surface of the protective case is thereby suppressed in the case of using the carbon fiber-contg. synthetic resin as the external case. Adsorption of the microparticles of the case is eventually suppressed and the removal of the microparticles is facilitated. Redropping of the microparticles onto the reticle surface and the sticking thereof to the surface are thereby prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a protective case for a reticle used when reducing and transferring a circuit pattern onto a semiconductor substrate in a reduction projection exposure step in semiconductor manufacturing. .

[Conventional technology]

Conventionally, a diagonal reticle is used to transfer the necessary circuit pattern onto a wafer in such a reduced projection exposure process, but storage and transportation of the reticle is difficult.

A clean synthetic resin protective case was used when installing the device.

FIG. 6 is a partially exploded perspective view of a conventional reticle protective case.1 This protective case has a reticle 13 mounted on a metal bottom plate 12, and is covered with a synthetic resin outer case 21 and a synthetic resin front cover 22. It was something like that.

[Problem that the invention seeks to solve]

Generally, in the semiconductor manufacturing process, there are several exposure steps, and a mask shaped like a part of the circuit pattern is used to transfer the necessary circuit pattern onto the semiconductor substrate using a reticle. In the exposure method, a pattern on a single reticle is repeatedly transferred onto a wafer. Therefore, if minute dust adheres to the reticle, if the shape of the fine dust is repeatedly transferred onto the wafer, all of these wafers will become defective.
It was necessary to pay sufficient attention to the adhesion of minute dust.

For example, in the most common example, there should not be a single piece of dust with a size of 11/1000 in an area of 225III112.

For this reason, after pasting a protective film called a pellicle on the reticle surface and repeatedly cleaning the reticle protective case, the reticle was attached very gently and used.

However, pellicles are expensive and have short usable lifespans, and since the reticle protective case is made of synthetic resin, cleaning it with ultrapure water creates static electricity that attracts minute particles to the surface. However, when the reticle is attached, the fine particles fall onto the reticle again and cause circuit pattern defects.

The purpose of the present invention is to eliminate these drawbacks, improve the conductivity of the surface of the case, suppress resistance, and prevent the generation of static electricity on the surface, and provide a reticle protective case that can be used without adsorbing minute particles. It's about doing.

[Means for solving problems]

The present invention provides a reticle protection case in which a reticle used in a reduction projection exposure process of semiconductor devices is mounted on a metal bottom plate and an outer case is placed over the metal bottom plate, and the outer case contains carbon fiber in a synthetic resin. The material is characterized by the use of a material with reduced surface resistance.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

In the figure, 11 is an exterior case made of carbon fiber-containing synthetic resin, 12 is a metal bottom plate, and 13 is a reticle. The potential can be lowered, so it does not generate static electricity or attract particles, making it much more useful than conventional protective cases.

FIG. 2 is a graph showing the relationship between the carbon fiber content of the carbon fiber-containing synthetic resin used in this example and its surface resistance.

In this case, the content rate is 0 for the conventional product, and in this case, the surface resistance is very high at about 1014Ω, but when the content rate exceeds 5%, the resistance value rapidly decreases to 108Ω or less. When used in the exterior case of this embodiment, a range of 5% to 20% is appropriate from the viewpoint of resin hardness. Further, the original resin containing the carbon fibers may be polyacetal, vinyl chloride, ABS resin, etc., but polyacetal was used in this example. Further, carbon particles can be included in order to provide electrical conductivity, but this is unsuitable because it lowers the strength and causes the formation of fine particles.

FIG. 3 is a graph showing the relationship between surface resistivity and electrostatic charge, and it can be seen that charging can be prevented by lowering the surface resistivity.

FIG. 4 is a graph showing the relationship between the electrostatic charge and the number of attached fine particles obtained from the experimental results of this example, and it is clear that the higher the charging voltage is, the more particles are attached. In other words, it is clear that in order to reduce the number of microparticles adhering to the surface of the exterior case, it is sufficient to lower the surface resistance by incorporating carbon fibers.

FIG. 5 is a sectional view showing a second embodiment of the invention. This embodiment shows a case in which a reticle 13 is housed using a flat carbon fiber-containing conductive synthetic resin case 11' and a metal bottom plate and blackboard 12'.

〔Effect of the invention〕

As explained above, the present invention has a surface resistivity of 1010
By using carbon fiber-containing synthetic resin with a resistance of 102Ω for the exterior case, the static electricity that builds up on the surface of the protective case can be reduced.
It has the effect of suppressing electricity, thereby suppressing the adsorption of minute particles to the case, making it easier to remove minute particles, and preventing minute particles from falling again or adhering to the reticle surface. .

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a reticle protection case according to an embodiment of the present invention, Fig. 2I21 is a characteristic diagram showing the carbon fiber content and surface resistance of the synthetic resin used in the reticle protection case of this embodiment, and Fig. 3 is a characteristic diagram showing the surface resistance and the amount of static electricity, FIG. 4 is a characteristic diagram showing the amount of static electricity and the number of particles attached to the surface, FIG. 5 is a cross-sectional view of the second embodiment of the present invention, and FIG. 6 is a conventional reticle. FIG. 2 is a partially exploded perspective view of an example of a protective case. 11...Exterior case made of conductive synthetic resin containing carbon fiber. 12.12'...Metal bottom plate, 13...Reticle, 21...Synthetic resin case, 22...Synthetic resin front cover.

Claims (1)

[Claims] In a reticle protection case in which a reticle used in the reduction projection exposure process of semiconductor devices is mounted on a metal bottom plate and an outer case is placed over the metal bottom plate, carbon fiber is contained in a synthetic resin as the outer case to reduce its surface resistance. A reticle protection case characterized by using a lowered material.