Photocopying – Projection printing and copying cameras – With temperature or foreign particle control
Reexamination Certificate
2000-10-18
2003-11-25
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
With temperature or foreign particle control
C355S053000, C355S055000, C355S067000, C250S492200, C250S492220, C430S311000, C430S312000
Reexamination Certificate
active
06654095
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus, a making method of the exposure apparatus, and a device manufacturing method. More particularly, the present invention relates to an exposure apparatus and the method of making the apparatus used in lithographic process, to transfer a pattern formed on a mask onto a substrate when manufacturing devices such as a semiconductor device, a pick up device (such as a CCD), a liquid crystal display device, and a thin-film magnetic head device. The present invention shows a superb effect, when applied to an exposure apparatus using vacuum ultraviolet light as an illumination light for exposure.
2. Description of the Related Art
In the case of manufacturing devices such as semiconductors, as an exposure apparatus to transfer a pattern formed on a reticle as a mask onto each shot area of a wafer being coated with a photoresist, conventionally, a step-and repeat-type (a static exposure type) reduction projection type exposure apparatus (a stepper) was often used. Whereas, in recent years, to cope with the demand of a larger transfer pattern subject to exposure without imposing a heavy burden on the projection optical system, a projection exposure apparatus based on a step-and-scan method, that is, a scanning stepper is gathering attention. The scanning stepper sequentially transfers a reduced image on the reticle, by synchronously scanning the reticle and the wafer in respect to the projection optical system in a state where the pattern formed on the reticle is partially projected on the wafer via the projection optical system as a reduced image. This scanning stepper is an exposure apparatus developed by combining the advantage of a transfer method (the slit-scan method) of an aligner, which transfers the entire pattern formed on the reticle by equal magnification on one scanning exposure, and the advantage of the transfer method of the stepper.
Also, with the projection exposure apparatus in general, higher resolution is required. A method of increasing the resolution is to use an illumination light for exposure, which has a shorter wavelength. With the conventional exposure apparatus, an emission line (g line or i line) in the ultraviolet range emitted by an ultra-high pressure mercury lamp has been used. However, recently, light in the deep ultraviolet light region or the vacuum ultraviolet light region such as the KrF excimer laser beam (wavelength: 248 nm) or the ArF excimer laser beam (wavelength: 193 nm) is being used. In addition, the use of a metal vapor laser beam or a harmonic of a YAG laser beam is being considered.
Meanwhile, in the case of using an ultraviolet light such as an excimer light as the illumination light for exposure, the necessity of circulating nitrogen (N
2
) gas or a gas with ozone removed (such as air) was pointed out. This was due to the fact that the ultraviolet light is absorbed by ozone, as well as in consideration of the properties of the photoresist. However, simply replacing the entire gas within the chamber where the projection optical system is arranged to gas such as nitrogen gas, may cause nitrogen gas with high concentration to leak out, when a worker opens the door of the chamber during maintenance operation by accident.
In order to improve such inconvenience, details of a projection exposure apparatus is disclosed in Japanese Patent Laid Open No. 09-246140, that uses a laser light source emitting a beam having a wavelength range equal to or shorter than the ultraviolet region; houses the illumination optical system, projection optical system, the reticle stage, and the substrate stage separately in a plurality of independent casings; and has a gas supplying means to at least one of the plurality of casings to supply multiple types of gases in the cases with a switching operation. With this projection exposure apparatus, a low absorptive gas to the illumination light for exposure is supplied in the selected casing when usual exposure is performed, whereas in cases when pilot exposure is performed during maintenance gas such as air, which is safe for the worker, is supplied. This allows prevention of the leakage of nitrogen with high concentration almost without fail, and provided the advantage of simplifying the maintenance operation.
As the degree of integration for semiconductor devices become more and more demanding each year, a requirement for improving the resolution of the exposure apparatus have surfaced. For this reason, the KrF excimer laser beam or the ArF excimer laser beam is no longer sufficient enough as the illumination light for exposure. Therefore, possibilities of using a light with a shorter wavelength such as the F
2
laser beam (wavelength: 157 nm) or a vacuum ultraviolet light with a shorter wavelength as the illumination light for exposure are being seriously explored. Thus, it is safely said that the F
2
laser exposure apparatus is a prime possibility of the exposure apparatus of the next generation.
With the projection exposure apparatus referred to the disclosure above, however, as a premise, the KrF excimer laser beam or the ArF excimer laser beam is used as the illumination light for exposure. Accordingly, two types out of three gases being nitrogen, ozone-depleted air, and air, are used by switching operation.
Also, with the projection exposure apparatus referred to the disclosure above, nitrogen with a low purity level is exhausted to the external atmosphere.
Meanwhile, in the case of using the F
2
laser beam or the vacuum ultraviolet light having a wavelength shorter than the F
2
laser beam, vacuum ultraviolet light is absorbed by gases such as oxygen, vapor, and hydrocarbon gas on the optical path. And this makes it difficult to secure the sufficient transmittance to the laser beam. Therefore, a possibility can be considered to remove the gases above from the optical path of the laser beam by replacing it with helium gas.
Helium gas, however, is costly, compared with nitrogen gas, therefore; simply replacing nitrogen with helium gas in the disclosure above only increases the cost of the apparatus. Also, when using the F
2
laser beam, the degree of chemical cleanliness of the optical path needs to be maintained at a tighter level compared with the case of using ArF excimer laser beam. So, from this point as well, it is not sufficient enough to employ the disclosure above without any modification.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the inconvenience of the prior art, and has as its first object to provide a new exposure method and an exposure apparatus that exhibits high performance in the aspects of the degree of chemical cleanliness and the transmittance to the illumination light for exposure.
It is the second object of the present invent ion to provide a device manufacturing method that can improve the productivity when producing highly integrated microdevices.
According to the first aspect of the present invention, there is provided an exposure apparatus which performs exposure on a substrate with an illumination light from a light source, the exposure apparatus comprising: at least a first type air conditioning room arranged on an optical path between the light source and the substrate, the first type air conditioning room having a short optical path of the illumination light passing through and a predetermined level of chemical cleanliness degree; at least a second type air conditioning room arranged on the optical path, the second type air conditioning room having a longer optical path of the illumination light passing through and a higher degree of chemical cleanliness compared with the first type air conditioning room; a first air conditioning control unit which supplies a first gas to air condition the first type air conditioning room; and a second air conditioning control unit which supplies a second gas to air condition the second type air conditioning room.
Air conditioning, here, means in general, conditioning the air, that is automatically a
Adams Russell
Brown Khaled
Nikon Corporation
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