Optics: measuring and testing – By light interference – Having polarization
Reexamination Certificate
1999-08-19
2001-04-03
Turner, Samuel A. (Department: 2877)
Optics: measuring and testing
By light interference
Having polarization
C356S487000, C356S500000, C356S509000
Reexamination Certificate
active
06211965
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser interferometer, a position measuring apparatus, and an exposure apparatus, and more particularly to a laser interferometer and a position measuring apparatus for superposing a measurement beam reflected from a moving mirror and a reference beam reflected from a reference mirror, and measuring the position of a moving object, and to an exposure apparatus in which this interferometer or position measuring apparatus is provided as a position measuring apparatus for at least one of a mask stage and a substrate stage. The present invention also relates to a position measuring method and to a method for manufacturing a laser interferometer, a position measuring apparatus, and an exposure apparatus. The laser interferometer and position measuring apparatus pertaining to the present invention are particularly suitable for use as scanning exposure apparatus in the manufacture of liquid-crystal display panels, plasma display panels, and other display elements.
2. Description of the Related Art
Scanning exposure apparatus capable of exposing large surface areas in a single sweep are currently used on a comparatively large scale to accommodate increased dimensions of liquid-crystal substrates used in lithographic processes for manufacturing liquid-crystal display panels or the like. As disclosed, for example, in U.S. Pat. No. 5,729,331 corresponding to Japanese Patent laid-open No. 07-57986, known scanning exposure apparatus for such liquid crystal applications are configured such that a projection optical system is constructed using a plurality of same-size, erect projection optical units composed of two partial optical systems each of which contains a refraction system and a concave reflecting mirror, and a mask and a plate (substrate) are moved as a unitary structure relative to the projection optical system to achieve single-scan exposure.
An increase in the size of a liquid-crystal substrate makes it necessary to increase the scanning distance for the mask stages and substrate stages in a scanning exposure apparatus used in liquid crystal applications. Consequently, reflecting mirrors in which the length of the reflecting surfaces in the scanning direction exceeds the length of the stages in the scanning direction must be provided as moving mirrors or fixed mirrors in order to achieve high accuracy when measuring the positions of mask and substrate stages in a non-scanning direction by a laser interferometer. A scanning exposure apparatus equipped with a fixed mirror that extends a considerable distance in the scanning direction is disclosed, for example, in Japanese Patent Laid-open No. 10-74692. Disclosed in this publication is a double-pass laser interferometer for measuring the position of a stage in a non-scanning direction, wherein a beam splitter (for dividing laser light into a reference beam and a measurement beam), a mirror, a corner cube, and the like are fixed to a stage, and a fixed mirror consisting of a plane mirror that is longer than the stage is used as a reference mirror.
Recently, however, liquid-crystal substrates have grown in size even further, gradually making it more difficult to use the technique described in Japanese Patent Laid-open No. 10-74692 without further modifications and to measure the position of a stage in a non-scanning direction with high accuracy. This is attributed to the fact that stages have recently grown in size to match the increased size of substrates, so the aforementioned fixed mirrors have become longer, making it more difficult to process and polish reflecting surfaces thereof with sufficient accuracy.
Liquid-crystal substrates and the like will undoubtedly continue to increase in size in the future, and an urgent need therefore exists to develop a novel technique capable of accommodating this trend.
SUMMARY OF THE INVENTION
The first object of the present invention, which was achieved in order to overcome the drawbacks of prior art, is to provide a laser interferometer and a position measuring apparatus capable of measuring the position of a moving object in a direction orthogonal to the long stroke direction across the entire region of a movement stroke in excess of the total length of the moving object, using a reflecting mirror that is shorter than the total length of the moving object; and to provide a method for manufacturing these.
It is a second object of the present invention to provide an exposure apparatus capable of controlling the position of a mask stage or a substrate stage with high accuracy even when the substrate is bulky, and to provide a method for manufacturing this apparatus.
It is a third object of the present invention to provide a position measuring method capable of measuring the position of a moving object in a direction orthogonal to the long stroke direction across the entire region of a movement stroke in excess of the total length of the moving object, using a reflecting mirror that is shorter than the total length of the moving object.
According to a first aspect of the present invention, there is provided a laser interferometer for measuring by means of a laser beam a position of a moving object in a first direction (Y-axis direction) orthogonal to a second direction (X-axis direction) when the object moves in the second direction, this laser interferometer comprising:
a separating optical system (
21
or
21
′) for separating the laser beam into a measurement beam and a reference beam;
a moving mirror (
22
or
22
′) which is attached to the moving object (
4
or
5
) and reflects the measurement beam;
a reference mirror (
26
or
26
′) which is provided independently from the moving object and reflects the reference beam;
a moving device (
6
or
6
′) for moving the separating optical system in the second direction at a speed different from the speed of the moving object; and
a detector for detecting the measurement beam reflected from the moving mirror and the reference beam reflected from the reference mirror, and determining the position of the moving object in the first direction on the basis of the interference effect of these beams.
The laser beam emitted by a light source is thus separated into a reference beam and a measurement beam by a separating optical system. The measurement beam is reflected from the reflecting surface of a moving mirror provided to the moving object, and the reference beam is reflected from the reference mirror. The position of the moving object with respect to the first direction is measured based on a photoelectric conversion signal of interference light, which is composed of the light of the measurement beam reflected from the moving mirror and the light of the reference beam reflected from the reference mirror.
The above-described measurements are performed during the movement of a moving object, but because the separating optical system moves in the second direction with a different speed than does the moving object, the measurement beam separated by the separating optical system continuously strikes a different position on the reflecting surface of the moving mirror, and the position of the moving object in the first direction can be measured as long as the following expression is satisfied: S=|V1/(V1−V2)|L1>L1, or 0<V2<2V1 (V1≠V2), where L1 is the length of the moving mirror in a second direction (long stroke direction) orthogonal to the first direction, which is the measuring direction of the object; V1 is the speed of the moving object in the second direction; V2 is the speed of the separating optical system in the second direction; and S is the movement stroke of the moving object in the second direction. It is therefore possible to measure the position of a moving object (measurement object) in a direction orthogonal to the long stroke direction across the entire region of a movement stroke in excess of the total length of the moving object, using a reflecting mirror that is shorter than the total le
Hazama Junji
Tsuchiya Makoto
Nikon Corporation
Oliff & Berridg,e PLC
Turner Samuel A.
LandOfFree
Photolithographic position measuring laser interferometer... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photolithographic position measuring laser interferometer..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photolithographic position measuring laser interferometer... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2468602