Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
1996-12-27
2001-09-25
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S053000, C355S030000
Reexamination Certificate
active
06295121
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to an exposure apparatus and, more particularly, to a projection exposure apparatus using an excimer laser, for example, and being suitable for the manufacture of various devices such as semiconductor devices, for example.
In order to meet the miniaturization of microdevices such as semiconductor devices (ICs, LSIs) or liquid crystal panels, those light sources (exposure light sources) which provide light of a shorter wavelength have been used in exposure apparatuses. More specifically, in exposure apparatuses for semiconductor device manufacture, for example, g-line light of a super high pressure Hg lamp has been replaced by i-line light, for reduced wavelength. Currently, the wavelength of KrF excimer laser light (248 nm) or ArF excimer laser light (193 nm), which is deep ultraviolet light of a shorter wavelength, is used.
Since light of a KrF excimer laser or an ArF excimer laser in the deep ultraviolet region has a high photon energy, there is a possibility that, due to the action of the energy, minute dust along the path of the light reacts with oxygen in air along the path, with a result of adhesion of impurities to the optical system (lens surface or mirror surface), or that the lens coating material of the optical system reacts with oxygen in the air, with a result of contamination of the optical system. In order to avoid adhesion of impurities to the optical system or contamination of the optical system, conventionally, an inert or inactive gas is charged to flow along the path of deep ultraviolet light to thereby prevent reaction of dust or the lens coating material with oxygen. To this end, a serviceman or operator is required to do the following work in relation to the portion of the optical system which is filled with an inert gas: that is, in order to avoid suffocation with the inert gas, first, the serviceman or operator closes the main tap of the inert gas, which is usually located at the back of the exposure apparatus, and then checks stoppage of the flow of inert gas into the portion of the apparatus, filled with the inert gas. After an elapse of a certain time period, the serviceman or operator opens the cover of the portion filled with the inert gas.
When the apparatus is to be re-started after completion of the above-described work, the serviceman or operator closes the cover of the portion to be filled with inert gas, and opens the main tap of the inert gas at the back of the apparatus. The serviceman or operator has to wait there for an elapse of a certain time period, until the portion to be filled with inert gas is filled with the inert gas.
This procedure needs many and time-consuming steps: to close the main tap of the inert gas at the back of the apparatus; to check stoppage of flow of inert gas into the portion filled with inert gas; to leave the apparatus for a certain time period; and to open the cover of the portion filled with inert gas. If the operator makes an error and opens the cover of the portion filled with inert gas, without shutting off the main tap, for example, there is a danger to the life of the operator since the operator may be exposed to the inert gas. Even if the main tap is closed, if the cover is opened before the density of inert gas is decreased sufficiently, the operator may similarly be exposed to the inert gas, which is very dangerous to the life of the operator.
Also, in relation to a re-start of the apparatus after completion of the above-described work, the procedure needs many and time-consuming steps: thereafter, to close the cover of the portion to be filled with inert gas; to open the main tap of inert gas at the back of the apparatus; and thereafter, to leave the apparatus for a certain time period until that portion is filled with the inert gas. If the operator makes an error to miss opening the main tap after closing the cover of the portion to be filled with inert gas, there is a possibility that the excimer laser is oscillated before inert gas charging. Laser emission in the state in which the inert gas charging is not started or completed causes adhesion of impurities to the optical system or contamination of the lens coating material of the optical system, as described hereinbefore, and it results in decreased optical performance. If such impurity adhesion of or contamination occurs, the optical element (or elements) damaged has to be demounted from the optical system. Thus, an enormous volume of work is necessary to recover adequate optical performance of the optical system. This directly decreases the operation efficiency of the apparatus.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved exposure apparatus which assures a smaller decrease in optical performance and enables enhanced safety.
In accordance with an aspect of the present invention, there is provided an exposure apparatus, comprising: an optical system for directing exposure light to a substrate to be exposed; a cover for a predetermined portion of said optical system; gas supplying means for supplying an inert or inactive gas to the inside of said cover; detecting means for detecting a quantity of inert gas inside said cover; and notifying means for notifying information related to the quantity of inert gas, on the basis of an output of said detecting means.
Said detecting means may detect a density of the inert gas.
Said detecting means may detect a flow rate of the inert gas.
Said cover may have one of a door and a lid, and said apparatus may further comprise fixing means for fixing said door to said cover as said door or said lid is being closed.
Said apparatus may further comprise a sensor for detecting closure/opening of said door or said lid.
Said apparatus may further comprise an excimer laser for providing the exposure light.
Said notifying means may include display means for displaying the information.
Said optical system may include an illumination optical system for illuminating a mask, and the predetermined portion to be covered by said cover may be a portion of or the whole of said illumination optical system.
Said optical system may further include a projection optical system for projecting a pattern of the mask, illuminated by said illumination optical system, onto the substrate to be exposed.
Said apparatus may further comprise an excimer laser for providing the exposure light.
Said detecting means may detect a density of the inert gas.
Said detecting means may detect a flow rate of the inert gas.
Said cover may have one of a door and a lid, and said apparatus may further comprise fixing means for fixing said door to said cover as said door or said lid is being closed.
Said notifying means may include first display means for displaying the information.
Said cover may have one of a door and a lid, and said apparatus may further comprise a sensor for detecting closure/opening of said door or said lid.
Said supplying means may include an electromagnetically openable/closable valve for adjusting flow of the inert gas.
Said electromagnetically openable/closable valve may be controlled on the basis of an output of said sensor.
Said notifying means may further include second display means for displaying closure/opening of said electromagnetically openable/closable valve.
Said apparatus may further comprise control means wherein, when an output of said sensor represents a change of said door or said lid from a closed state to an open state, said control means is serviceable to close said electromagnetically openable/closable valve, is serviceable to cause said second display means to display closure of said electromagnetically openable/closable valve, and is serviceable to cause said first display means to display whether a detected value, detected by said detecting means, exceeds a predetermined value.
When an output of said sensor represents a change of said door or said lid from the closed state to the open state, said control means may be serviceable to produce a signal to stop light emission of said excimer laser.
Said apparatus
Adams Russell
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Hung Henry
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