Photocopying – Projection printing and copying cameras – Reflector between original and photo-sensitive paper
Reexamination Certificate
2001-08-13
2003-08-05
Font, Frank G. (Department: 2877)
Photocopying
Projection printing and copying cameras
Reflector between original and photo-sensitive paper
C355S067000, C355S053000, C355S069000, C355S070000, C355S077000, C356S399000, C356S400000, C356S138000, C348S745000, C348S746000, C348S747000
Reexamination Certificate
active
06603532
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an illuminance measurement apparatus, exposure apparatus, and exposure method, more particularly relates to an illuminance measurement apparatus used for measuring the illuminance of illumination light irradiated through a projection optical system provided in an exposure apparatus, illumination distribution in a region irradiated by the illumination light, etc., an exposure apparatus provided with such an illuminance measurement apparatus, and an exposure method using such an illuminance measurement apparatus.
2. Description of the Related Art
When producing a semiconductor device, a liquid crystal display device, or other device, use is made of an exposure apparatus for transfer of a pattern drawn on a mask or reticle (hereinafter also referred to all together as a “mask”) or other master on to a semiconductor wafer or glass plate coated with a resist or other photosensitive substrate. To form a fine pattern on a photosensitive substrate using an exposure apparatus, it is necessary to strictly manage the illuminance of the illumination light emitted from an excimer laser or mercury lamp or other light source. Therefore, the exposure apparatus is provided with an illuminance measurement apparatus on the stage carrying the photosensitive substrate.
An illuminance measurement apparatus is generally configured by a light receiving element arranged in a chassis. The chassis is a housing formed at its top surface with a light receiving aperture. The light receiving element is set at a position where its light receiving surface corresponds to the light receiving aperture of the chassis, receives the exposure light entering from the light receiving aperture, and outputs an electrical signal corresponding to the illuminance to the outside through a wire etc. Note that an electrical board (printed circuit board) is sometimes also provided inside the chassis. In this case, the light receiving element is mounted on the electrical board. The illuminance of the illumination light is measured before transferring the pattern formed on the mask to the photosensitive substrate. By moving the stage in the in-plane direction of the stage, the light receiving aperture is arranged inside the region illuminated by the exposure light for measurement.
Such an illuminance measurement apparatus is adjusted by a high accuracy so that the height position of the light receiving aperture is in register with the surface of the photosensitive substrate and arranged on the stage carrying the photosensitive substrate. Here, the height position of the light receiving aperture is brought into register with the surface of the photosensitive substrate by a high precision so as to accurately measure the actual amount of exposure when transferring an image of a pattern formed on the mask to the photosensitive substrate. An image of the pattern formed on the mask is transferred to the photosensitive substrate in a state with the height position of the surface of the photosensitive substrate in register with an image plane of the projection optical system.
A reference board having a surface formed with fiducial marks etc. in register with the surface of the photosensitive substrate is provided on the stage. Detection light is irradiated toward the reference board and the reflected light received to find the height position of the reference board and the position of the stage in the height direction is adjusted so that the height position of the reference board is in register with the image plane of the projection optical system, assuming that the height positions of the reference board and light receiving aperture are in register, so that the light receiving aperture is in register with the image plane of the projection optical system.
If the height position of the reference board and the height position of the light receiving aperture are offset from each other, however, the measurement is performed in a state with the light receiving aperture defocused relative to the image plane of the projection optical system and therefore the illuminance or illumination distribution cannot be measured accurately. Therefore, to prevent this inconvenience, it is necessary to set the machining precision high when producing the illuminance measurement apparatus or mounting surface of the stage and to precisely mechanically adjust the height position of the light receiving aperture to strictly be in register with the height position of the reference board.
To bring the height position of the surface of the photosensitive substrate (height position of reference board) and height position of the light receiving aperture formed in the illuminance measurement apparatus into strict register with each other in this way, it is necessary to produce the illuminance measurement apparatus and the mounting surface of the stage with a high processing precision, so a large number of steps were required for machining and assembling the components and the cost became high.
Further, the illuminance measurement apparatus is not placed on the stage at all times. It is attached to the stage when measuring the illuminance of the illumination light before transferring the image of the pattern formed on the mask to the photosensitive substrate. Therefore, fine mechanical adjustment becomes necessary so that the height position of the light receiving aperture becomes accurately in register with the height position of the reference board at the time of mounting. Careful attention is required in the work. Due to the structure of the apparatus, the work is difficult. Along with this, a long time is required for the work. This becomes one reason lowering the throughput. Further, if foreign matter adheres to the back surface of the illuminance measurement apparatus or the mounting surface of the stage, the reproducibility of mounting of the illuminance measurement apparatus deteriorates, the chassis surface where the light receiving aperture is formed becomes tilted, and the precision of setting of the height position falls. If it is not possible to bring the height positions of the light receiving aperture and reference board into accurate register, it is not possible to accurately measure the illuminance and not possible to transfer a pattern with a high precision.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to improve the accurately of measurement of the illuminance of exposure light irradiated on a substrate, facilitate processing and assembly, and speed up and facilitate mounting work and thereby reduce costs and improve throughput.
According to a first aspect of the present invention, there is provided an illuminance measurement apparatus having a chassis having a detection surface formed with an aperture and a light receiving element with a light receiving surface arranged at a position corresponding to the aperture in the chassis, wherein the chassis is provided with a reflection surface for detection light for detecting at least one of the position and posture of the detection surface.
According to the present invention, since the chassis having the detection surface formed with the aperture is provided with a reflection surface of the detection light, the relative positional relationship between the detection surface and the reflection surface is fixed unambiguously. Therefore, it becomes possible to adjust the position (and/or posture) of the detection surface based on the results of detection of the reflection surface obtained by irradiating detection light to the reflection surface. As a result, it becomes possible to detect the illuminance with a high precision. Further, since the relative positional relationship between the reflection surface and detection surface does not change, there is less of a need to produce or mount the illuminance measurement apparatus with a high precision than in the past and as a result it is possible to relax the requirement on manufacturing tolerance or mounting tolerance of the illuminance measureme
Kawada Keizaburo
Tsuji Toshihiko
Brown Khaled
Font Frank G.
Nikon Corporation
Oliff & Berridge
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