Photocopying – Projection printing and copying cameras – Detailed holder for photosensitive paper
Reexamination Certificate
2001-03-13
2004-03-23
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
Detailed holder for photosensitive paper
C355S075000
Reexamination Certificate
active
06710857
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate holding apparatus and an exposure apparatus including the substrate holding apparatus, and more particularly, to a substrate holding apparatus, which is used for holding a substrate when transferring a mask pattern onto the substrate in a lithography process for manufacturing devices such as a semiconductor device, a liquid crystal display device, a plasma display device and a thin film magnetic head, and to an exposure apparatus including the substrate holding apparatus.
2. Description of the Related Art
In the case of manufacturing a semiconductor device or the like, in order to transfer a reticule pattern image used as a mask to each shot area on a wafer (or a glass plate, etc.) which is used as a substrate onto which a resist is applied, a full field exposure type, such as a step-and-repeat type, exposure apparatus, and a scanning exposure type, such as a step-and-scan type, exposure apparatus are used. In the aforesaid exposure apparatuses, a wafer is held on a wafer holder by vacuum chucking, electrostatic chucking or/the like, and the wafer holder is fixed on a coarsely and finely movable wafer stage.
A conventional wafer holder includes, as disclosed, for example, in Japanese Unexamined Patent Application Publication No.1-129438, a large number of pins arranged like a square lattice, and a suction portion for sucking the gas from a suction hole between these pins. In a state in which the wafer is placed on the large number of pins, the gas between the wafer and the wafer holder is exhausted by the suction portion, and thereby, the wafer has been chucked and held. Moreover, in order to prevent the wafer from being electrically charged, the entire surface of the wafer holder is coated with a conductive material, and further, earth connection is carried out with respect to the back side of the wafer holder.
As described above, in the conventional wafer holder, the wafer is placed on the plurality of pins arranged, for example, like a square lattice, and the wafer is held by vacuum chucking or the like. However, a deformation (warp, etc.) is locally generated in the wafer by the vacuum chucking or the like. When the deformation is increased to a range of the depth of focus of a projection optical system, a resolution at that portion is lowered; for this reason, preferable exposure cannot be made locally in some shot areas on the wafer.
In order to suppress the above wafer deformation due to vacuum chucking or the like, there is a need of making fine intervals between pins arranged for supporting the wafer or weakening a suction force. However, when the suction force is simply weakened, there is a possibility such that a shift occurs in wafer alignment during acceleration period and deceleration period of step movement. On the other hand, when the intervals between the arranged pins are made fine, a contact rate of the wafer with the wafer holder increases, and there is a high possibility such that foreign matters are held between the back side of wafer and the wafer holder. For this reason, a problem arises such that a flatness of wafer is reduced.
Moreover, in the case where the wafer holder is formed of a material having a low coefficient of thermal expansion, when the surface of the wafer holder is coated with an anti-electrical charging material, an internal stress is generated due to a difference in the coefficients of thermal expansion between the anti-electrical charging material and the material forming the wafer holder. As a result, there is a possibility such that the anti-electrical charging material cracks and peels off. For this reason, it is difficult to thick coat the anti-charging material to the surface of the wafer holder. Therefore, after the surface of the wafer holder is coated with an anti-electronic charging material, in order to improve a flatness of the contact surface of the wafer holder with the wafer, it is difficult to carry out polishing and the like with respect to the contact surface (coating surface). As a result, a problem arises such that micro unevenness remains in the contact surface.
In addition, in a manufacture of semiconductor device or the like, an improvement of throughput has been demanded. However, in a conventional exposure apparatus, a wafer is first placed on a wafer bolder, and thereafter, the exhaust (suction) of the gas is started by a vacuum pump for chucking and holding the wafer. For this reason, it takes a long time until a force required for holding the wafer is increased up to a desired value. Further, in the case of carrying out the wafer from the wafer holder for wafer exchange, conventionally, a valve communicating with a gas having an atmospheric pressure is simply opened in the case of stopping the suction by the vacuum pump. For this reason, it takes a long time until the suction force of wafer is lost. Therefore, in the conventional wafer holder, it takes a time to load and unload the wafer; for this reason, this is a factor of faults in improvement of throughput of exposure process.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems in the prior art. It is, therefore, a first object of the present invention to provide a substrate holding apparatus, which can reduce a deformation in the case of chucking a substrate such as a wafer with respect to a contact area of the substrate with the wafer holder.
Further, a second object of the present invention is to provide a substrate holding apparatus, which is constructed in a manner that an area including a contact surface with the substrate is coated with, for example, an anti-electronic charging material, and can prevent a crack and the like of the anti-electronic charging material.
Further, a third object of the present invention is to provide a substrate holding apparatus, which can carry out a substrate chucking start operation or substrate chucking release operation at a high speed so that throughput is improved.
Further, another object of the present invention is to provide an exposure apparatus including the aforesaid substrate holding apparatus.
According to a first aspect of the present invention, there is provided a substrate holding apparatus which holds a flat-like substrate, comprising:
a base member; and
a plurality of projecting support members disposed on said base member such that the supporting members are arranged like a triangular lattice and distal end portions thereof are positioned on substantially the same plane, wherein
the substrate is to be placed on the plurality of support members.
Like the substrate holding apparatus according to the first aspect of the present invention, in a case where the plurality of support members which are to contact the substrate are arranged like a triangular lattice, the following effect is obtained. More specifically, as compared with the case where these plural support members are arranged like a rectangular lattice, an interval between the plural support members and the position of the center of gravity is shortened with respect to a density of the support members (area contacting with the substrate), and a deformation of the substrate is reduced. Therefore, according to the first aspect of the present invention, the following effect is obtained. More specifically, when a probability that foreign/matters are held between the substrate and the plurality of support members is the same as the conventional case, it is possible to reduce a deformation of the substrate in the case where the substrate is chucked by electrostatic chucking or vacuum chucking, and thus, to prevent a flatness of the substrate from becoming worse. As a result, in a case where the substrate holding apparatus is applied to an exposure apparatus, a mask pattern can be transferred on the entire surface of the substrate at a high resolution.
In this case, it is preferable to provide a suction mechanism which sucks the substrate placed on the plurality of support members toward the base member side. By t
Nguyen Henry Hung
Nikon Corporation
Oliff & Berridg,e PLC
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