Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
2000-07-05
2003-04-08
Kim, Robert H. (Department: 2882)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C250S548000, C250S559290, C250S559370, C356S399000, C356S401000, C355S053000
Reexamination Certificate
active
06545284
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a face position detection method and a face position detection apparatus, and an exposure method and an exposure apparatus, a production method for an exposure apparatus and a production method for a semiconductor device, used in an exposure step in, for example, thin-film magnetic head production.
2. Description of the Related Art
Heretofore, various exposure apparatus have been used when manufacturing thin-film magnetic heads, semiconductor devices or liquid crystal display devices by a photolithography process. Presently however, exposure apparatus are typically being used, which transfer a pattern image formed on a photo mask or a reticle (hereinafter, referred to as a “mask”) onto a substrate, on the surface of which a photosensitive material such as a photoresist or the like is applied, via a projection optical system.
Recently, with a pattern projected onto an exposure area (shot area) on the substrate being made minute, the numerical aperture NA of the projection optical system of the exposure apparatus is set large, and as a result, the depth of focus of the projection optical system becomes shallow. Therefore, such an exposure apparatus is provided with an auto focus mechanism for adjusting the position of the substrate projection optical system in the direction of the optical axis, and a leveling mechanism for adjusting the inclination of the substrate with respect to the optical axis, in order to accommodate the exposure area on the substrate within the depth of focus of an imaging plane (focal position) of the projection optical system.
The auto focus leveling mechanism comprises, as an example, a beam irradiation system for irradiating beams onto a plurality of measurement points on the exposure area on the substrate, from an inclined direction with respect to the optical axis of the projection optical system for projecting, for example, an image of a slit pattern serving as a probe pattern, and a beam photodetecting system for receiving reflected light of the image on the plurality of probe patterns and re-imaging the image on the photodetector. Then, after the position of the exposure area on the substrate with respect to the focal position of the projection optical system, and the inclination of the exposure area on the substrate with respect to the optical axis have been detected, based on the detection signals of the beam photodetecting system corresponding to the plurality of measurement points, the exposure area on the substrate is subjected to positional adjustment in the direction of the optical axis (focal position adjustment) and inclination adjustment with respect to the optical axis (leveling adjustment) of the projection optical system.
The focal position adjustment and the leveling adjustment are performed by comparing a position of the probe pattern image on the photodetector which changes when the exposure area on the substrate is moved in the direction of the optical axis of the projection optical system or the exposure area on the substrate is inclined with respect to the optical axis, and a position of the probe pattern image pre-determined at the time of arranging the exposure area on the substrate at a focal position of the projection optical system, and moving a table on which the substrate is mounted in the direction of the optical axis of the projection optical system or inclining the table with respect to the optical axis thereof, so that the amount of discrepancy between these images is within a predetermined range. In this case, the focal position adjustment is performed based on, for example, the average value of respective detection signals corresponding to all the measurement points, and the leveling adjustment is performed so as to match the substrate with the least squares approximation plane for the respective detection signals. That is to say, the focal point adjustment and the leveling adjustment are performed with respect to all the plurality of measurement points on the substrate. Then, a pattern image of the mask is projected onto the substrate having been subjected to the focal point adjustment and the leveling adjustment via the projection optical system, to thereby form a pattern on the surface.
The pattern to be formed on the substrate in this manner is formed by repeating lithography steps such as exposure, development and the like, while changing a plurality of masks, and is in a rectangular shape having a stepped portion comprising a plurality of layers. In this case, particularly in a production process for thin-film magnetic heads for a magnetic disk apparatus, there may be a case where the difference of elevation (of the stepped portion comprising the plurality of layers) between the substrate surface and the thin-film magnetic head is relatively large, for example, 10 to 20 &mgr;m. When a beam for detecting the face position is irradiated onto the substrate having a pattern with low flatness, the beam may be irradiated at a time so as to span over the concave and convex portions in the stepped portion. Since the reflected light of the beam at that time is not stable, then in particular, the position of the exposure area on the substrate with respect to the focal position of the projection optical system cannot be detected with high precision.
Moreover, the focal position adjustment is performed based on the average value of the detection signals corresponding to all the plurality of measurement points. Hence, the precision of the focal position adjustment in a certain area on the substrate decreases. That is to say, if the focal position adjustment is performed with respect to a pattern having, for example, a large stepped portion, the focal position of the projection optical system does not coincide with the concave portion or convex portion in the stepped portion. Therefore, when a focus is to be adjusted only on the concave portion or the convex portion, focal position adjustment cannot be performed with high precision. Moreover, since the focal position adjustment and the leveling adjustment is performed using detection signals corresponding to all the plurality of measurement points, the processing time for calculating the optimum position of the substrate in the direction of the optical axis and the optimum inclination angle with respect to the optical axis becomes long.
On the other hand, such a pattern is formed by overlapping a plurality of layers by means of a multiplicity of exposures using a plurality of masks. However in this case, the substrate thermally expands due to heating from the exposure light. Hence there may be a case where the layers cannot be overlapped with high precision.
SUMMARY OF THE INVENTION
In view of the above situation, it is an object of the present invention to provide a face position detection method and a face position detection apparatus which can perform detection of the face position of a substrate with high precision, even when a pattern having a large stepped portion is formed by means of a plurality of layers on the surface of the substrate, and an exposure method and an exposure apparatus, a production method for the exposure apparatus and a production method for a semiconductor device.
To solve the above described problems, the present invention adopts the following constructions associated with
FIG. 1
to
FIG. 6
showing an the embodiment.
A face positional information detection method of the present invention is a method for detecting face positional information for the surface of an object (W), comprising steps for: irradiating measurement beams (S
1
to S
9
) onto a plurality of places on the surface of an object; detecting the plurality of measurement beams from the surface of the object; and determining face positional information for the surface of the object based on the detection results for the plurality of measurement beams, and is characterized in that, in the step for irradiating the measurement beams, at least either one of the shape and size of at least one (S
9
)
Ho Allen C.
Kim Robert H.
Oliff & Berridg,e PLC
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