Photocopying – Projection printing and copying cameras – With temperature or foreign particle control
Reexamination Certificate
2001-03-29
2003-09-02
Mathews, Alan A. (Department: 2851)
Photocopying
Projection printing and copying cameras
With temperature or foreign particle control
C355S053000, C430S005000
Reexamination Certificate
active
06614504
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus, an exposure method, and a device manufacturing method for manufacturing electronic devices such as semiconductor devices, liquid crystal displays, image-capturing devices (such as a CCD), thin-film magnetic heads or the like.
2. Description of the Related Art
Projection exposure apparatuses are used in manufacturing electronic devices such as semiconductor devices and liquid crystal displays by using photolithography. This type of projection exposure apparatus projects the image of a pattern formed on a mask or reticle (hereinafter called “reticle”) on projection (shot) areas on a substrate whose surface is coated with a photosensitive agent (resist) via a projection optical system. The circuit of the electronic device is formed by transferring circuit pattern on the substrate by using the projection exposure apparatus, and by post-processing. An integrated circuit comprises, for example, approximately twenty layers of such circuit interconnections provided repeatedly.
Due to recent high-intensity integration of integrated circuits (i.e. miniaturization of circuit patterns), the wavelengths of illumination light for exposure (hereinafter called “exposure light”) in the projection exposure apparatus are becoming shorter. In other words, exposure apparatuses that use a KrF excimer laser (wavelength: 248 nm) and an ArF excimer laser (193 nm) are nearing the final stage of practical use. In the quest for even higher-intensity integration, research is being made into an F
2
laser (157 nm) and an Ar
2
laser (126 nm).
Light (energy beam) having a wavelength of approximately 120 nm to 200 nm belongs in the vacuum ultraviolet region, and such light (hereinafter called “vacuum ultraviolet rays”) does not pass through air. This is due to the act that substances such as oxygen molecules, water molecules, and carbon dioxide molecules (hereinafter called “light-absorptive substance”) in the air absorb the energy of the light.
For this reason, when the vacuum ultraviolet rays are used as the exposure light, the light-absorptive substance in the space on the path of the exposure light must be reduced in order to enable the exposure light to attain a sufficient level of illumination on the substrate. Therefore, in conventional exposure apparatuses, the light-absorptive substance in the light path space is reduced by maintaining the space in a state of reduced pressure, and replacing the gas in the space with a supply of a gas (low absorptive gas) which has low absorption of energy of exposure light after reducing the pressure of the space.
For instance, in an exposure apparatus using the F
2
laser, the entire space on the path of the exposure light beam must be purged with a high-purity inert gas. In this case, when the total light wavelength is for example 1000 nm, the density of the light-absorptive substance on the optical path should for practical purposes be less than approximately 1 ppm.
However, a reticle generally has a protection member called a pellicle in order to prevent unwanted substances from adhering to the pattern formation areas, and the pellicle is usually fixed to the reticle via a frame (metal frame). Consequently, when the vacuum ultraviolet rays are used as the exposure light as described above, it is also necessary to reduce a light-absorptive substance in the space (space inside pellicle) created by the pellicle and the metal frame.
The frame usually comprises an opening (ventilation hole) for preventing the pellicle from breaking when the atmospheric pressure changes. The opening prevents the pellicle being broken without creating any difference between the pressure in the space in the pellicle and the atmospheric pressure, even when the atmospheric pressure changes as a result of, for example, transportation by aircraft, a change in weather or the like.
The pellicle is an extremely thin transparent film having a thickness of approximately several hundred nanometers to several micrometers, and has an organic compound such as nitrocellulose as its essential component. Therefore, in the aforementioned method for reducing pressure in the space, there is a danger that the pellicle will deform and break as a result of changes in the pressure in the space, making it difficult to stably reduce the light-absorptive substance.
SUMMARY OF THE INVENTION
The present invention has been achieved in order to solve the above problems. It is an object of the present invention to provide an exposure method and apparatus, and a device manufacturing method, which can stably and efficiently reduce a light-absorptive substance from the space formed by a pellicle in a reticle, and increase the precision of the exposure light.
In order to achieve the above objects, a first aspect of the present invention provides an exposure apparatus comprising a mask having a first space formed by a protection member, which protects a pattern formation area on a mask substrate, and a frame, which supports the protection member, inside a second space, the pattern of the mask provided in the second space being transferred onto a substrate by using an energy beam from a light source. The exposure apparatus has a gas replacement chamber which replaces gas in the first space with a predetermined gas, which the energy beam passes through, while maintaining a predetermined pressure in the first space.
In this exposure apparatus, the gas replacement chamber replaces the gas in the first space, formed by the protection member and the frame, with the predetermined gas while maintaining a predetermined pressure in the first space. Deforming of the protection member due to pressure change is thereby reduced, and breakage of the protection member is prevented. Therefore, the light-absorptive substance is stably reduced from the first space.
In this case, a gas supply device which supplies the predetermined gas to the gas replacement chamber may be provided, and the frame may have a supply opening, which supplies the predetermined gas in the gas replacement chamber to the space, and an exhaust opening, which exhausts the gas in the space into the gas replacement chamber. The gas supply device supplies the predetermined gas to the gas replacement chamber, and the flow of gas in the gas replacement chamber at this time causes the predetermined gas to be supplied via the supply opening in the frame to the first space, and causes the gas in the first space to be exhausted via the exhaust opening.
An exhaust device may be provided in order to exhaust the gas, exhausted from the first space to the gas replacement chamber, thereby shortening the time taken to replace the gas.
The supply opening of the frame and the supply opening of the gas supply device may be provided opposite each other. Furthermore, the exhaust opening of the frame and the exhaust opening of the gas exhaust device may be provided opposite each other. In this case, the predetermined gas, which has flowed through the supply opening of the gas supply device, maintains an approximately steady fluidity as it flows from the supply opening of the frame to the first space, and gas flows out from the exhaust opening in the first space.
The gas replacement chamber may comprise a gas supply device having a supply nozzle connected to the supply opening in the frame, and a gas exhaust device having an exhaust nozzle connected to the exhaust opening in the frame. In this case, the gas supply nozzle leads the predetermined gas, supplied from the gas supply device, via the supply opening in the frame directly to the first space. In addition, the gas exhaust nozzle leads the gas in the first space via the exhaust opening in the frame directly to the gas replacement mechanism. Consequently, little of the predetermined gas is wasted when replacing gas in the first space.
The gas replacement chamber may be equipped with a detection device which detects pressure change in the first space, and a control device which maintains the pressure in the first space at a pre
Aoki Takashi
Owa Soichi
Mathews Alan A.
Nikon Corporation
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