Stage system for exposure apparatus

Details Stage system for exposure apparatus Stage system for exposure apparatus

1999-02-01

2001-11-20

Adams, Russell (Department: 2851)

Photocopying

Projection printing and copying cameras

Detailed holder for photosensitive paper

C355S076000, C355S075000

Reexamination Certificate

active

06320649

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART
This invention relates to a stage system suitably usable in an exposure apparatus for the manufacture of semiconductor devices, for example. In another aspect, the invention is concerned with an exposure apparatus having such a stage system, or with a device manufacturing method using the same.
FIG. 17
shows a typical structure of a stage system used in an exposure apparatus. Denoted at
101
in the drawing is a wafer having a resist applied to the surface of a monocrystal silicon substrate. A reticle pattern formed on a reticle substrate is to be projected and transferred to the wafer through a reduction exposure system. Denoted at
102
is a fine-motion stage for fine adjustment of the wafer with respect to an optical axis direction of the reduction exposure system and to a rotational direction about the optical axis direction. Denoted at
103
is an X linear motion for moving the fine-motion stage in an X-axis direction. Denoted at
105
is a Y guide for guiding the fine-motion stage
102
and the X linear motor
103
in a Y-axis direction and a Z-axis direction. Denoted at
104
a
and
104
b
are Y sliders for moving the X linear motor
103
and Y linear motors
106
a
and
106
b
in the Y direction. Denoted at
107
(
108
,
110
) is a stage base for supporting the fine-motion stage and the Y guide.
In
FIG. 18
, at the back of the fine-motion stage
102
where there is a scanning surface of the stage base
107
, air pads
102
a
and preloading magnets
102
b
for applying preload to the stage are juxtaposed. As regards the air pads
102
a
, pressurized air is supplied through a pressurized air line
102
c
so that an air spring is formed uniformly at the pad surface of the air pads
102
a
. By this, the fine-motion stage
102
is floated, and without contact, it is supported movably in the X and Y directions. Also, at the back of the Y sliders
104
a
and
104
b
, there are air pads
104
c
and preloading magnets
104
d
for applying a preload to the Y sliders, juxtaposed with each other. They function to float the Y sliders
104
a
and
104
b
, such that without contact the sliders are supported movably in the X and Y directions.
The preloading magnets
102
b
comprise magnetic preloading magnets which serve to produce an attraction force for attracting the fine-motion stage
102
, being floated by the air pads
102
c
, in a direction toward the stage base
107
. Due to the floating force provided by the air pads
102
c
and the attraction force provided by the preloading magnets
102
d
, the floating gap is maintained substantially constant while motion in the X and Y directions is enabled. Similarly, the preloading magnets
104
d
comprise magnets for producing an attraction force for attracting the Y guides
104
a
and
104
b
, floated by the air pads
104
c
, in a direction toward the stage base
107
. Due to the floating force provided by the air pads
104
c
and the attraction force provided by the preloading magnets
104
d
, the floating gap is maintained substantially constant, while motion in the X and Y directions is enabled.
The preloading magnets
102
d
and preloading magnets
104
d
produce a magnetically attracting force, for attraction toward the stage base
107
, and perform magnetic preloading. If the product of a holding force Hc of the stage base
107
and saturation magnetic flux density B is large, the magnetic hysteresis becomes large and, as a result, during movement of the preloading magnets, a force is produced in a direction opposite to the movement direction, acting against the movement. If a movement load resulting from this magnetic hysteresis is large, there occurs a large loss of thrust of the X and Y linear motors. This leads to enlargement in size of the linear motor and, in addition thereto, enlargement of electric current to be applied to the linear motor. It causes a problem of large heat generation.
Japanese Laid-Open Patent Application, Laid-Open No. 5463/1997 shows a stage base made of alumina ceramics material. Since the alumina ceramics is a non-magnetic material, so that magnetic preloading is not attainable, vacuum preloading is used. However, as compared with the structure wherein preloading magnets are used, the structure using preloading pads comprising vacuum pads involves inconveniences such as follows. In order to produce an attraction force similar to that produced by the preloading magnets, it requires a large pad area as compared with the preloading magnet areas. Also, in addition to the pressurized air line, a vacuum line is necessary. As a result, the assembling at the bottom of the fine-motion stage where pads are to be mounted as well as the assembling of piping within the whole stage system are complicated. Moreover, use of a vacuum air of a high vacuum is necessary to obtain an attraction force similar to the preloading magnet. An air line of a high vacuum must be provided in the exposure apparatus.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved stage system by which, through improvement of the material or structure of a stage base, low cost as well as light weight and high rigidity are assured.
It is another object of the present invention to provide an exposure apparatus and/or a device manufacturing method using such a stage system.
In accordance with an aspect of the present invention, there is provided a stage system, comprising: a movable stage; and a base having a guiding surface for guiding said stage, wherein said base has an accumulated structure of different material layers.
In a preferred form of this aspect of the present invention, said movable stage may be guided by said guiding surface and through a static bearing and a magnet preloading mechanism.
The different material layers may include a first layer of a magnetic material provided at the guiding surface side, and a second layer of a non-magnetic material.
The different material layers may include a first layer of a magnetic material provided at the guiding surface side, and a second layer of a material having a smaller specific gravity as compared with the magnetic material.
The different material layers may include a first layer of a magnetic material provided at the guiding surface side, and a second layer of a material having a higher Young's modulus as compared with the magnetic material.
The material of the first layer may be permalloy or silicon steel.
The material of the second layer may be ceramics.
The different material layers may include a first layer of a permalloy or silicon steel material provided at the guiding surface side, and a second layer of ceramics material.
The ceramics material may include one of alumina ceramics, silicon nitride ceramics, zirconia, and silicon carbide.
The stage system may further comprise means for bonding the first and second layers to each other on the basis of vacuum attraction or electromagnetic attraction.
The bonding between the first and second layers may be releasable.
The bonding may be performed when an ambient temperature becomes substantially constant, when said stage system is placed movable, or in response to a signal from a stage control system.
The stage system may further comprise a third layer, below the second layer, of a material having substantially the same thermal expansion coefficient as that of the first layer.
The layers may be bonded to each other on the basis of one of a high melting point metal bonding method, an activated metal bonding method, an oxidization bonding method and an adhesion bonding method.
The second layer may have one of a bored rib structure and a hollow structure.
In accordance with another aspect of the present invention, there is provided an exposure apparatus, comprising: a base having a guiding surface; and a movable stage guided by said guiding surface, wherein said base has an accumulated structure having a first layer of a magnetic material provided at the guiding surface side, and a second layer of a non-magnetic material.
The movable stage may be guided by s

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