Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2001-03-30
2003-10-14
Rutledge, D (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S077000, C355S067000, C430S311000, C250S492200
Reexamination Certificate
active
06633364
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. More particularly, the present invention relates to an exposure apparatus and an exposure method used to manufacture a semiconductor device and the like in a lithographic process, and a device manufacturing method using the exposure apparatus.
2. Description of the Related Art
Conventionally, in the lithographic process to manufacture a semiconductor device and the like, various exposure apparatus have been used. In recent years, exposure apparatus such as the reduction projection exposure apparatus based on the step-and-repeat method (the so-called stepper), and the scanning type projection exposure apparatus based on the step-and-scan method (the so-called scanning stepper), are becoming mainstream. The stepper reduces and transfers a mask pattern formed on a mask (also called a reticle), which is proportionally magnified 4 to 5 times, onto a substrate subject to exposure. And, the scanning stepper is an improvement of the stepper.
With these exposure apparatus, in order to cope with finer integrated circuits and achieve higher resolution, the exposure wavelength has shifted toward shorter wavelength. Recently, the exposure wavelength in practical use is 193 nm of the ArF excimer laser, however, exposure apparatus using shorter wavelength such as the F
2
laser beam having a wavelength of 157 nm or the Ar
2
laser beam having a wavelength of 126 nm are also being developed.
Light in the wavelength region called vacuum ultraviolet which wavelength belongs to the bandwidth of 200 nm to 120 nm such as the ArF excimer laser beam, the F
2
laser beam, or the Ar
2
laser beam, has low transmittance to optical glass. Therefore, the glass material that can be used is limited to fluoride crystal such as fluorite, magnesium fluoride, and lithium fluoride. In addition, vacuum ultraviolet light is greatly absorbed by gas such as oxygen, water vapor, and hydrocarbon gas (hereinafter referred to as “adsorptive gas”) existing on the optical path. It is also greatly absorbed by contaminants in the case organic contaminants or water and the like adhere on the surface of the optical elements. Therefore, gas existing on the optical path needs to be replaced with a low absorptive gas, that is, inert gas such as nitrogen or helium (hereinafter referred to as “low absorptive gas”). When the gas is replaced, impurities concentration of organic contaminants, water, absorptive gas, and the like in the optical path where the exposure light passes through is lowered so as not to exceed several ppm.
The design concept of the ArF excimer laser exposure apparatus and the F
2
laser exposure apparatus is to exclude the absorptive gas as much as possible from the optical path from the light source to the wafer. Based on the concept, for example, there is an idea of covering the reticle stage and the wafer stage with casings as is with the optical elements making up the projection optical system, and structuring each casing as an independent room so that the gas in each room may be exchanged with a low absorptive gas with high purity, for example, such as helium.
In such a case, either idea had been employed; to supply low absorptive gas with high purity to each room, circulate the gas and then simply exhaust the gas outside (gas of which purity such as nitrogen has decreased due to the influence of impurities (such as absorptive gas or organic materials)), or to collect and store at least a part of the gas exhausted.
In addition, the idea was employed of supplying low absorptive gas with high purity to all the rooms in parallel.
With the method of exhausting outside the gas circulated in each room which purity has decreased or with the method of storing a part of the gas, as is described above, however, most of the gas was done away with without being recycled or just simply stored after being collected. Also, in the case of supplying low absorptive gas with high purity to a plurality of rooms respectively in parallel, a huge amount of gas is required.
For these reasons, the concept described above had to consume an enormous amount of expensive gas such as nitrogen gas, or helium gas, which is more costly. This increased the cost burden, and was likely to become the cause of increasing the production cost when manufacturing a semiconductor device.
Whereas, by simply reducing the amount of low absorptive gas consumed, that is, by reducing the amount of gas supplied into each room, the impurity concentration in the optical path will increase. And as a consequence, the transmittance of the exposure light will decrease, which becomes a cause of an exposure defect.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the circumstances described above, and has as its first object to provide an exposure apparatus and an exposure method capable of improving the usage of the low absorptive gas so that it is used effectively and wasteful consumption is suppressed, while maintaining the transmittance of the exposure light.
It is the second object of the present invention to provide a device manufacturing method that can improve the productivity when a device is manufactured.
According to the first aspect of this invention, there is provided an exposure apparatus that illuminates a mask with an energy beam from an energy beam source and transfers a pattern formed on the mask onto a substrate, the exposure apparatus comprising: at least one closed space which is located on an optical path of the energy beam between the energy beam source and the substrate; and a gas supply system which is connected to a first chamber being at least an arbitrary of the closed space and supplies a specific gas with a characteristic feature of having transmittance to the exposure beam to the first chamber, and supplies gas exhausted from the first chamber to the second chamber being at least an arbitrary of the closed space.
In this description, “closed space” includes the concept of closed space that is not completely in a sealed state in the strict sense of the word, other than space in a sealed state to the outside.
With this apparatus, the gas supply system supplies the specific gas which has a predetermined purity to the first chamber, and the gas exhausted from the first chamber is supplied to the second chamber. In this case, the specific gas which has circulated in the first chamber and the purity decreased to some extent due to degassing is supplied to the second chamber as the replacement gas. Therefore, for example, by supplying specific gas with high purity to the first chamber, and at least setting a chamber where the optical path of the energy beam is relatively short and is not seriously affected by the decrease in transmittance due to the absorption of the energy beam by impurities such as air in the optical path as the second chamber, the purity of the specific gas required in the first chamber and the second chamber can be sufficiently satisfied and the transmittance of the energy beam (exposure light) can be maintained. In addition, since the specific gas circulated in the first chamber is not exhausted outside and is used as the replacement gas of the second chamber, the usage efficiency of the specific gas can be improved, which leads to suppressing wasteful consumption of the specific gas (low absorptive gas).
In this case, the first chamber and the second chamber can be different chambers.
In this case, the exposure apparatus can further comprise: a movable optical member which is arranged between the energy beam source and the substrate; and a driving system which is connected to the optical member and drives the optical member, wherein a closed space formed in between a first optical element and a second optical element that are arranged in between the energy beam source and the substrate can structure the first chamber, and a closed space which houses at least a part of the optical member and the driving system can structu
Nikon Corporation
Rutledge D
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