Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement
Reexamination Certificate
2001-05-25
2003-10-28
Pert, Evan (Department: 2829)
Radiation imagery chemistry: process, composition, or product th
Including control feature responsive to a test or measurement
C430S494000, C438S005000, C414S805000
Reexamination Certificate
active
06638672
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus for exposing a wafer so as to transfer a reticle pattern onto the wafer, a coating/developing apparatus for coating a resist on a wafer and developing the resist-coated wafer, a method of transferring a substrate (e.g., a reticle, a wafer), a method of producing a device, a semiconductor production factory, and a method of maintaining an exposure apparatus.
2. Description of the Related Art
A recent trend in the exposure apparatus industry has been to reduce the wavelength of exposure light to enhance resolution, thereby allowing exposure of an even finer pattern. A fluorine (F
2
) excimer laser is an example of a light source capable of emitting light with a short wavelength. If an exposure apparatus employs a fluorine excimer laser, however, it is necessary to purge oxygen (O
2
) from the optical path of the exposure light to prevent a reduction in transmission of the exposure light. More specifically, it is desirable that the oxygen concentration in the path of the exposure light be less than about 1 ppm.
When a substrate such as a wafer or a reticle is transferred from a coating/developing apparatus (CD apparatus), having an ambient of atmospheric air, into an exposure apparatus, having a low-oxygen-concentration ambient such as an inert gas, the transfer is effected through a load lock chamber (LL chamber) to prevent intrusion of oxygen from the atmospheric air into the exposure apparatus. More specifically, the wafer or the reticle first is transferred from the CD apparatus into the LL chamber, which initially is filled with atmospheric air. The atmospheric air in the LL chamber then is replaced with an inert gas. After that, the wafer or the reticle is transferred into the exposure apparatus having an ambient of the inert gas.
A problem with the foregoing process is that it takes a long time to replace the atmospheric air in the LL chamber with the inert gas. Thus, the wafer or the reticle must remain in the LL chamber until the atmospheric air has been replaced. This limits throughput.
SUMMARY OF THE INVENTION
The present invention provides a technique for suppressing intrusion or leakage of an ambient gas which can occur when a substrate is carried between apparatuses such as an exposure apparatus, a coating/developing apparatus, and a load lock chamber, thereby achieving an improvement in throughput and a reduction in operating cost.
According to one aspect of the present invention, there is provided an exposure apparatus comprising an enclosure having a controllable internal ambient; a gate valve through which a substrate is transferred into or out of the enclosure; and gas ejection means for ejecting a gas into a region in close proximity to the gate valve, and in a direction substantially perpendicular to the direction of movement of the substrate as it is transferred into or out of the enclosure, wherein a gas curtain is formed by the gas ejected by the gas ejection means, such that an opening of the gate valve is shielded by the gas curtain. A stage on which a substrate such as a wafer or a reticle is placed during an exposure process may be provided within the enclosure.
According to another aspect of the present invention, there is provided a coating/developing apparatus comprising a resist coating unit for coating a resist on a wafer and a developing unit for developing the wafer. The coating/developing apparatus further comprises an enclosure in which the resist coating unit and the developing unit are disposed, the enclosure having a controllable internal environment; a gate valve through which a substrate is transferred into or out of the enclosure; and gas ejection means for ejecting a gas into a region in close proximity to the gate valve, and in a direction substantially perpendicular to the direction of movement of the substrate as it is transferred into or out of the enclosure, wherein a gas curtain is formed by the gas ejected by the gas ejection means, such that an opening of the gate valve is shielded by the gas curtain.
Preferably, the gas is ejected in a direction substantially parallel to a face of the substrate so that the substrate does not disturb the flow of the gas curtain as it passes therethrough.
Although the ejected gas may have the same composition as that of the atmospheric air, it is desirable to employ a gas having the same composition as that of the ambient gas in each chamber. More specifically, a gas having the same composition as that of a purge gas used to purge oxygen or moisture may be employed. An example is a pure inert gas such as pure nitrogen gas or pure helium gas. Use of such a gas makes it possible to create a gas curtain without causing an increase in the oxygen concentration of the ambient of the apparatus in which the gas curtain is created.
A guide may be disposed near a gas ejection unit for the gas curtain and also at the opposite end of the gas curtain to regulate the flow of the gas. This prevents mixing between the gas of the gas curtain and the ambient gas. Thus it is possible to form the gas curtain using a low-cost gas such as atmospheric air (or a gas having a higher oxygen content than the ambient gas). Even when an inert gas is used for the gas curtain, use of the guide prevents turbulent flow from occurring in the gas curtain, further enhancing the sealing capability.
In the present invention, although the gas of the gas curtain may be ejected at a constant flow rate throughout the process, it is preferable that, in order to reduce operating costs, the gas curtain be created only when necessary or that the flow rate of the gas curtain be changed as required.
In a specific example, a concentration detection means (such as a sensor, or a F
2
light transmission meter) is disposed to detect the concentration of oxygen or moisture in the internal ambient of an enclosure enclosing an exposure apparatus, a coating/developing apparatus, or a load lock chamber disposed between the exposure apparatus and the coating/developing apparatus. A means is disposed for turning on or off the gas curtain or continuously varying the flow rate of the gas curtain in accordance with the concentration detected by the concentration detection means.
In another specific example, a substrate detection means (such as a sensor, or means for detection by means of a sequence) is disposed to detect the presence or absence of a substrate in a region close to the gate valve, and a means is disposed for turning on or off the gas curtain or continuously varying the flow rate of the gas curtain, in response to the detection of the presence or absence of the substrate.
In the system according to the present invention, when the gate valve is opened to transfer a substrate, if a sensor detects that the substrate is being passed through the gate valve, a control signal is sent to the flow rate control means to increase the flow rate of the gas curtain, thereby preventing the intrusion of oxygen. When wafers are continuously transferred, the opening in the gate valve is sealed with the gas curtain. Otherwise, the gate valve closes when transferring is not performed for a while. This allows the gas of the gas curtain to be saved.
In the system according to the present invention described above, it is possible to transfer a wafer or a reticle into the exposure apparatus even when the environment outside the exposure apparatus includes a relatively high oxygen concentration. This reduces the time needed to replace the gas in the load lock chamber with an inert gas.
According to still another aspect of the present invention, there is provided a method of transferring a reticle or a wafer into or out of an exposure apparatus, the method comprising the steps of controlling an ambient in an enclosure; opening and closing a gate valve disposed in the enclosure; transferring the reticle or the wafer into or out of the enclosure through the gate valve; and ejecting a gas into a region in close proximity to the gate valve and in a direction substa
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Pert Evan
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