Optics: measuring and testing – By light interference – For dimensional measurement
Reexamination Certificate
1999-07-20
2002-10-08
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By light interference
For dimensional measurement
C356S450000
Reexamination Certificate
active
06462828
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus and, more particularly, to an exposure apparatus which executes exposure while controlling a substrate stage and master stage on the basis of outputs from interferometers. The present invention can be applied to, e.g., a scanning exposure apparatus.
2. Description of the Related Art
As typical exposure apparatuses used to manufacture semiconductor devices or the like, there are step-and-repeat exposure apparatuses (also referred to as steppers) which sequentially transfer the pattern of a master (reticle or mask) onto a plurality of exposure regions on a substrate (wafer or glass substrate) through a projection optical system by exposure while moving the substrate stepwise, or step-and-scan exposure apparatuses (also referred to as scanners or scanning exposure apparatuses) which repeat step movement and scanning exposure to repeatedly transfer a pattern onto a plurality of regions on a substrate by exposure. Especially, the step-and-scan exposure apparatuses are expected to be a mainstream in the future because they limit light through a slit and use only rays relatively close to the optical axis of the projection optical system, and therefore, allow exposure using a precise and wide-angled fine pattern.
For a step-and-scan exposure apparatus which synchronously moves the reticle stage and wafer stage for scanning during exposure, it is very important to improve the accuracy of synchronization between the reticle stage and wafer stage, unlike a step-and-repeat exposure apparatus in which the reticle and wafer are at rest during exposure. Since a reticle and wafer are moved for scanning during exposure, the synchronization accuracy and movement accuracy of stages are directly reflected on the exposure transfer accuracy.
To measure the stage position, laser interferometers capable of highly accurate distance measurement are normally used. Especially, in a scanning exposure apparatus, since not only the wafer stage but also the reticle stage moves for scanning, the number of axes, i.e., the number of axes of laser beams to be position-measured largely increases. However, improvement of the light amount output from one laser head is limited. In a method of dividing one laser beam into a desired number of axes to prepare measurement light beams, as the number of measurement axes increases, the light amount per measurement light beam decreases to lower the distance measurement accuracy.
In addition, when the number of measurement light beams increases, the number of optical elements for dividing or guiding the laser beams also increases. This complicates the space layout in which the optical elements are disposed and laser beams travel, and therefore, increases limitations on design.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to solve the problem of a decrease in light amount in use of a plurality of interferometers and to reduce limitations on layout of interferometers and associated elements.
According to the first aspect of the present invention, there is provided an exposure apparatus which has a substrate stage, a master stage, a projection optical system projecting an image of a master held by the master stage onto a substrate on the substrate stage, a first interferometer measuring a position of the substrate stage, and a second interferometer measuring a position of the master stage, and projects the image of the master onto the substrate by exposure while driving the substrate stage and the master stage on the basis of measurement results by the first and second interferometers, comprising a first light generation section providing first light to the first interferometer, a second light generation section providing second light to the second interferometer, and synchronization means for synchronizing the first light generation section and the second light generation section with each other.
In the exposure apparatus according to the first aspect of the present invention, preferably, for example, the synchronization means comprises a reference signal generation circuit generating a reference signal, and the first and second light generation sections are synchronized with each other by supplying the reference signal from the reference signal generation circuit to the first and second light generation sections.
In the exposure apparatus according to the first aspect of the present invention, the reference signal is preferably, e.g., an excitation signal.
In the exposure apparatus according to the first aspect of the present invention, for example, each of the first and second light generation sections preferably comprises an amplifier amplifying the excitation signal supplied from the reference signal generation circuit, and a laser tube generating a laser beam as the light in accordance with an output signal from the amplifier.
In the exposure apparatus according to the first aspect of the present invention, preferably, for example, the first interferometer is adapted to measure the position of the substrate stage in the horizontal direction, the apparatus further comprises a third interferometer measuring the position of the substrate stage in the vertical direction, and a third light generation section providing third light to the third interferometer, and the synchronization means is adapted to synchronize the first light generation section, the second light generation section, and the third light generation section with each other.
The exposure apparatus according to the first aspect of the present invention preferably further comprises, e.g., a lens-barrel platen supporting the projection optical system, the lens-barrel platen being elastically supported by a mount.
In the exposure apparatus according to the first aspect of the present invention, for example, the substrate stage and the lens-barrel platen are preferably insulated from each other in association with vibration.
In the exposure apparatus according to the first aspect of the present invention, for example, the first and second interferometers are preferably fixed with reference to the lens-barrel platen.
In the exposure apparatus according to the first aspect of the present invention, for example, the master stage is preferably fixed to a master stage platen fixed to the lens-barrel platen through a support frame.
In the exposure apparatus according to the first aspect of the present invention, for example, the first and second light generation sections are preferably fixed with reference to the lens-barrel platen.
In the exposure apparatus according to the first aspect of the present invention, for example, the first and second interferometers and the first and second light generation sections are preferably fixed with reference to the lens-barrel platen.
The exposure apparatus according to the first aspect of the present invention preferably further comprises, e.g., a reaction force reception structure receiving a reaction force generated upon driving the substrate stage.
The exposure apparatus according to the first aspect of the present invention preferably further comprises, e.g., a reaction force reception structure receiving a reaction force generated upon driving the master stage.
The exposure apparatus according to the first aspect of the present invention preferably further comprises, e.g., a first reaction force reception structure receiving a reaction force generated upon driving the substrate stage, and a second reaction force reception structure receiving a reaction force generated upon driving the master stage.
In the exposure apparatus according to the first aspect of the present invention, preferably, for example, the apparatus further comprises a stage base member supporting the substrate stage, and the reaction force reception structure receives a reaction force generated upon driving the substrate stage from the stage base member.
The exposure apparatus according to the first aspect of the present in
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Font Frank G.
Natividad Phil
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