Photocopying – Projection printing and copying cameras – With temperature or foreign particle control
Reexamination Certificate
2002-07-30
2004-04-13
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
With temperature or foreign particle control
C355S053000
Reexamination Certificate
active
06721032
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an exposure apparatus used for manufacturing, e.g., a semiconductor element, an image sensing element, a liquid crystal display element, a thin film magnetic head, and other microdevices.
BACKGROUND OF THE INVENTION
In a photolithography process for manufacturing a semiconductor element and the like, an exposure apparatus has been used which projects the pattern image of a mask (e.g., a reticle) onto a photosensitive substrate through a projection optical system and exposes it. In recent years, development of a micropatterned semiconductor integrated circuit has been progressing, and in the photolithography process, the wavelength of a photolithography light source is becoming short.
As the exposure light, when a vacuum ultraviolet ray, particularly, a light beam with a wavelength shorter than 250 nm, e.g., harmonics of a KrF excimer laser (with a wavelength of 248 nm), an ArF excimer laser (with a wavelength of 193 nm), an (F
2
laser (with a wavelength of 157 nm), or a YAG laser, or when X-rays are used, the intensity of the exposure light undesirably decreases because, e.g. the exposure light is absorbed by oxygen.
In view of this, conventionally, in an exposure apparatus having a light source such as an F
2
excimer laser, a hermetically sealed space that seals only the optical path portion is formed. The gas in the hermetically sealed space is substituted by a gas not containing oxygen, e.g., nitrogen, so a decrease in transmittance of the exposure light is prevented.
FIG. 15
is a view showing an exposure apparatus in which an inert gas is supplied to an optical path space between the final optical member of a projection optical system (lens barrel) and a photosensitive substrate (wafer) so as to form an inert gas atmosphere in the optical path space, and exposure is performed. In this exposure apparatus, a shielding member is formed around the optical path space in order to separate the optical path space above the exposure region and an atmosphere surrounding it, and the inert gas is supplied to this space from around the exposure region. Hence, the inert gas concentration of the atmosphere in the optical path space can be set high.
In the exposure apparatus shown in
FIG. 15
, a temperature control gas is supplied to around the exposure region in order to stabilize the temperature of the surrounding atmosphere. The pressure increases slightly at that end of the wafer stage to which the temperature control gas is blown directly. As the wafer stage moves, the pressure distribution around the optical path space changes. In this case, the pressure in the optical path space also changes in accordance with a pressure change accompanying the movement of the wafer stage, and the concentration of the inert gas in the optical path space changes undesirably in accordance with the change in pressure. Consequently, the inert gas concentration is not stable.
As shown in
FIGS. 16 and 17
, an atmosphere surrounding the optical path space may be entrained when the stage moves. When the surrounding atmosphere flows in the +X direction, as shown in
FIG. 16
, the stage moving in the +X direction entrains an atmosphere present below nozzle
1
(space A). To the contrary, the stage moving in the −X direction entrains an atmosphere present below nozzle
2
(space B). Due to the flow of the surrounding atmosphere, most of an inert gas leaked from the optical path space exists below nozzle
2
(space B). The inert gas concentration becomes different between spaces A and B, and is higher in space B. The concentration of the inert gas which enters the optical path space changes depending on the stage moving direction, thus changing the inert gas concentration in the optical path space.
The same problem occurs when the inert gas is supplied to around a mask (e.g., a reticle). With the reticle as well, the inert gas concentration in the optical path space surrounded by a shielding member also changes, and the inert gas concentration is not stable.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problem, and has as its object to provide an exposure apparatus in which an inert gas concentration in an optical path space including a space through which exposure light passes (exposure region), such as a space between a projection optical system and a substrate, a space between an illumination optical system for illuminating a mask (e.g., a reticle) and a mask stage for holding the mask, and a space between the mask stage and the projection optical system, can be stabilized at high precision, a control method for the same, and a device manufacturing method.
According to the present invention, the foregoing object is attained by providing an exposure apparatus comprising:
an illumination optical system which illuminates a pattern formed on a mask with light from a light source;
a movable mask stage for holding the mask;
a projection optical system which guides light from a pattern of the mask to a wafer;
a movable wafer stage for holding the wafer;
a shielding member which forms an optical path space including an optical path of exposure light and a space surrounding the optical path space at, of a space through which the exposure light passes, at least one portion between said illumination optical system and said mask stage, between said mask stage and said projection optical system, or between said projection optical system and said wafer stage;
first gas supply means for supplying an inert gas to the optical path space; and
reduction means for reducing a change in total light quantity of the exposure light reaching the wafer that is caused by movement of said mask stage and/or said wafer stage.
In a preferred embodiment, said reduction means includes means for adjusting a light quantity which reaches the pattern of the mask.
In a preferred embodiment, said reduction means includes means for adjusting a light quantity of the light source.
In a preferred embodiment, said reduction means includes means for inserting a filter into the optical path of the exposure light from the light source.
In a preferred embodiment, said reduction means includes means for adjusting a stop arranged in the optical path of the exposure light from the light source.
In a preferred embodiment, said reduction means includes means for adjusting a driving speed of said mask stage and/or said wafer stage.
In a preferred embodiment, said reduction means is controlled based on at least one of positional information of said mask stage and/or said wafer stage, information about a moving speed, and information about a moving direction.
In a preferred embodiment, said apparatus further comprises a pressure sensor which measures a pressure in the optical path space, and
said reduction means is controlled in accordance with an output from said sensor.
In a preferred embodiment, said apparatus further comprises a concentration sensor which measures an oxygen concentration and/or a wafer concentration in the optical path space.
said reduction means is controlled in accordance with an output from said sensor.
In a preferred embodiment, said apparatus further comprises a second gas supply means for supplying a gas to the surrounding space.
In a preferred embodiment, said gas supplied by said second gas supply means is an inert gas.
In a preferred embodiment, said apparatus further comprises:
said shielding member which shields from the surrounding space a first optical path space between said wafer stage and said projection optical system,
wherein said first gas supply means supplies said inert gas toward a predetermined direction.
In a preferred embodiment, said apparatus further comprises:
said shielding member which shields from the surrounding space a first optical path space between said wafer stage and said projection optical system,
said shielding member shielding from the surrounding space a second optical path space between said illumination optical system and said mask stage and/or between said mask stage and said projectio
Hasegawa Noriyasu
Terashima Shigeru
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Henry Hung
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