JPH01246546A - Pellicle protected by conductive film - Google Patents

Abstract

PURPOSE:To effectively prevent the adhesion of dust to a mask by covering the aperture in the lower part of a supporting frame and an adhesive agent surface with a conductive film having specific volumetric resistance. CONSTITUTION:The aperture in the lower part of the supporting frame and the adhesive agent surface are covered by the conductive film. The conductive film is a high-polymer film having the volumetric resistance ranging 10<-2>-10<10>OMEGA.cm and is more preferably a high-polymer film having the electrical conductivity ranging 10<0>-10<8>OMEGA.cm. The more particularly preferable film as the high-polymer film having such electrical conductivity is the film formed by kneading conductive fillers therein and above all, the film formed by using a carbon black as a filler is inexpensive and is capable of providing the sufficient electrical conductivity. The electrification of the pellicle is thereby minimized and the adhesion of the dust thereon is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a protective dust-proof body for photomasks and reticles (hereinafter abbreviated as masks) used in lithography steps in the manufacture of semiconductor integrated circuits.

[Prior Art] In the manufacture of semiconductor integrated circuits, the step of patterning a semiconductor wafer coated with a resist material by light exposure is an important step that affects the yield of integrated circuits.

At this time, if there are scratches or dust on the mask, which is the original pattern, the scratches or foreign matter will be printed on the wafer along with the pattern, causing short circuits and disconnections in the produced circuits. For this reason, mask protection and dustproofing are extremely important issues in improving productivity. In particular, in the stepper type, which uses the same reticle to repeatedly form patterns on a single wafer, if there are scratches or dust on the reticle, the defects that occur will affect all the circuits on the wafer. Also, the adhesion of dust must be avoided as much as possible.

Recently, it has been proposed and implemented to cover one or both sides of a mask with a transparent plastic thin film, that is, a pellicle, for the purpose of protecting the mask and preventing dust. At this time, by keeping a sufficiently large distance between the mask and the plastic thin film, even if dust adheres to the plastic thin film, the focus of the optical system of the exposure device is shifted, so that the dust will not form an image on the wafer. Not done. Furthermore,
Since the conventional process of cleaning and removing dust adhering to the mask is no longer necessary, it also simplifies the production process, and its usefulness is becoming clear.

Needless to say, the pellicle used to protect the mask and prevent dust must not contain dust large enough to cause problems during exposure. In particular, if there is dust attached to the inside of the pellicle, that is, the surface of the thin film facing the mask surface, the inner surface of the support frame, and the adhesive surface, there is a risk that the dust will fall onto the mask when or after the pellicle is attached to the mask. Therefore, even stricter waste management is required.

A proposed method to protect the inside of the pellicle from contamination by dust during the period from pellicle fabrication to attachment of the pellicle to the mask is to cover the opening with a flat cover sheet coated with a contact adhesive (published). Patent 1986-
No. 502121).

However, with this method, cover sea!・Difficulties in cleaning the pellicle make it difficult to obtain sufficient cleanliness, such as during handling when making the pellicle, while storing the pellicle in a case and transporting it, and especially when peeling the cover sheet from the support frame. However, since the cover sheet and plastic thin film are charged with static electricity, they tend to attract dust.

[Problems to be Solved by the Invention] ゛The present invention solves the problems of the conventional pellicle dust prevention method described above, thereby preventing dust from forming on the pellicle from the time the pellicle is manufactured to the time it is attached to the mask. This provides an effective method for preventing pellicle adhesion and obtaining an extremely clean pellicle.

[Means for Solving the Problems] The present inventors conducted intensive studies to obtain an excellent pellicle free from defects due to adhesion of dust, and arrived at the present invention.

That is, the present invention provides a photomask or reticle for manufacturing semiconductor integrated circuits, in which a transparent thin film is stretched over the upper part of a ring-shaped support frame having a constant height, and an adhesive is applied to the lower end surface for attachment to a substrate. It is a dustproof body that protects the surface of the substrate, and the opening at the bottom of the support frame and the adhesive surface have a volume resistance of 10.
The present invention provides a pellicle protected by a conductive film, characterized in that it is covered with a conductive film of ~1010 Ω·cIll.

In general, polymer films are insulators with a volume resistance of 1011 Ω・cm or more, so if they are used to cover the lower part of the pellicle support frame, contact and friction during handling or transportation of the pellicle may cause the pellicle to become a mask. When a polymer film is peeled off from an adhesive surface for pasting, it is easily charged with static electricity, and the static electricity stored in the film is not released, making it unavoidable that dust tends to collect.

Therefore, not only is it not possible to protect the pellicle from contamination by dust, but the dust also adheres to the pellicle.

In contrast, the present invention uses a conductive IQ molecule film, which prevents the generation and adhesion of dust when handling and transporting the pellicle, and especially when peeling the film from the adhesive surface. It becomes possible to effectively prevent the occurrence of defects due to dust not only inside but also on the outside surface of the pellicle.

The conductive film used in the present invention has a volume resistivity of 1
It is a polymer film having conductivity in the range of 0 to 10 10 Ω·(7), more preferably in the range of 100 to 10 8 Ω·cm. Examples of such conductive polymer films include those in which a conductive filler or an organic electrolyte is kneaded into the film, and those in which a layer of an organic electrolyte, metal 5, or metal oxide is formed on the surface of the film. It will be done. Films using organic electrolytes are difficult to obtain sufficient conductivity, and the electrolyte on the surface or the electrolyte that bleeds onto the surface may contaminate the pellicle, or a conductive layer of metal or metal oxide may form on the film surface. Care must be taken when using a conductive layer mixed with conductive filler, as there is a risk that the conductive layer may peel off from the film, or the peeled conductive layer may peel off in the form of flakes. Therefore, particularly preferable films are those mixed with conductive fillers, especially carbon black. A film using this as a filler is particularly recommended because it is inexpensive and provides sufficient conductivity.

On the other hand, the matrix polymer film must have sufficient strength and flexibility, and must have excellent releasability from the adhesive at the bottom of the support frame. Examples of such film materials include polyethylene, polypropylene, polyethylene terephthalate, and the like.

The thickness of the conductive polymer film is 20 μm or more and 500 μm
It is preferable that it is below. If the film is thinner than this, it lacks strength, and if it is thicker than this, it lacks flexibility, both of which become obstacles when peeling the film from the adhesive at the bottom of the support frame.

The conductive film of the present invention makes it possible to prevent the pellicle from being contaminated by dust during transportation or storage.
The effects of the invention can be achieved by making a case for storing the pellicle during transportation or storage from a similar conductive material and by providing at least one point of contact between the case and the conductive film of the pellicle. You can make it even more effective. That is, as a result, the pellicle and its case have continuous conductivity, which suppresses the electrification of the pellicle during transportation and storage as much as possible, and prevents the adhesion of dust.

The effects of the present invention are not dependent on the material of the transparent plastic thin film of the pellicle. That is, it can be used for widely known and well-known pellicles such as cellulose derivatives, polyethylene terephthalate, polypropylene, parylene, polymethyl methacrylate, and polyvinyl acetal.

[Effects of the Invention] As described above, the pellicle protected by the conductive film of the present invention is free from electrical charge during handling, transportation, and attachment to a mask, and is free from contamination by dust.
This effectively prevents dust from accumulating on the mask and is useful for improving the productivity of semiconductor integrated circuits.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 92 A transparent uniform thin film of polyvinyl propional with a thickness of 1.88 μm was stretched over a ring-shaped aluminum support frame with a width of 2.5 cm and a height of 5.5 cm, and a thin film of transparent uniform polyvinyl propional was applied to the lower end surface of the support frame. Acrylic double-sided adhesive tape was installed to create a polyvinylpropional pellicle. Next, a conductive polyethylene film containing carbon black and having a diameter of 92 mm, a thickness of 100 μm, and a volume resistance of 4×10 2 Ω·cm was pasted along the outer periphery of the support frame over the double-sided adhesive tape. The pellicle with the conductive film thus obtained was placed in a pellicle case made of conductive polyvinyl chloride containing carbon black and having a thickness of 600 g and a volume resistance of 6 x 103 Ω'' cm, and was transported.The pellicle after transportation was carried out. The pellicle was removed from its case and the conductive polyethylene film was peeled off from the double-sided adhesive tape on the supporting frame in order to attach it to the mask.When the pellicle was visually inspected under a halogen lamp just before being attached to the mask, no dust was observed. There wasn't.

Comparative Example The pellicle was handled, transported, and the support frame for the polyethylene film was carried out in exactly the same manner as in the example except that a regular polyethylene film measuring 92 mm square, 100 μm thick, and having a volume resistance of I x 1017 Ω' Cm was used instead of the conductive polyethylene film. When the pellicle was peeled off from the pellicle and visually inspected using a halogen lamp at each step, significant dust was observed adhering to the pellicle at each step.

Claims (1)

[Claims] Protection of the substrate surface of a photomask or reticle for manufacturing semiconductor integrated circuits, in which a transparent thin film is stretched over the upper part of a ring-shaped support frame having a certain height, and an adhesive is applied to the lower end surface for attachment to the substrate; It is a dustproof body, and the opening at the bottom of the support frame and the adhesive surface have a volume resistance of 10^-^2~10^
A pellicle protected by a conductive film characterized by being covered with a conductive film of 1^0Ω·cm.