Photocopying – Projection printing and copying cameras – Detailed holder for photosensitive paper
Reexamination Certificate
2000-02-28
2002-07-30
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Detailed holder for photosensitive paper
C355S053000
Reexamination Certificate
active
06426790
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a holder for holding a substrate such as a mask or a wafer, such substrates, a stage apparatus for holding and moving the holder, and an exposure apparatus for performing exposure processing using a mask and a substrate held by the stage apparatus. Moreover, the invention relates to a scanning exposure apparatus for performing exposure while moving the stage.
2. Description of the Related Art
Heretofore, various exposure apparatus have been used when manufacturing semiconductor devices or liquid crystal display devices by a lithography process. Presently however, projection exposure apparatus are typically being used, which transfer a pattern image of a photo mask or a reticle (hereinafter, generally referred to as “reticle”) onto a substrate such as a wafer or a glass plate, on the surface of which a photosensitive material such as a photoresist or the like is applied, via a projection optical system. Recently, as such projection exposure apparatus, a so-called step and repeat type reduced size projection exposure apparatus (a so-called stepper) is becoming predominant. With this apparatus a substrate is mounted on a two-dimensionally moveable substrate stage, and the substrate is stepped by the substrate stage, to thereby repeat an operation for exposing a pattern image of the reticle onto each shot area on the substrate in sequence.
Recently a step and scan type projection exposure apparatus (a scanning exposure apparatus as described for example in Japanese Unexamined Patent Application, First Publication No. 7-176468) which is an improvement on a static type exposure apparatus such as the stepper, is being used to a considerable degree. The step and scan type projection exposure apparatus (scanning stepper) can expose a larger field with a smaller optical system, compared to the stepper. Hence there are merits in that production of the projection optical system is facilitated, that high throughput can be expected due to a decrease in the number of shots by using the large field exposure, that a balancing effect is obtained by scanning the reticle and the wafer relative to the projection optical system, and that improvement of the distortion and the depth of focus can be expected. Moreover, it is being said that as the degree of integration of the semiconductor device is increased from a DRAM of 16 MB (megabyte) to a DRAM of 64 MB, and further in the future, will be increased to 256 MB, and even to 1 GB (gigabyte) with time, a large field will become essential. Hence the scanning projection exposure apparatus will become predominant instead of the stepper.
In such a stepper or scanning stepper, a table which can be moved in the direction of the optical axis for adjustment of the focal position and is capable of leveling adjustment is installed on a stage. Then, a holder for attracting and holding a substrate, and a mobile mirror for reflecting the detection light are provided on the stage in a predetermined positional relationship. Detection light is then irradiated from a position detection device, such as a laser interferometer or the like arranged opposite to the mobile mirror, and a distance from the stage is measured based on the reflected light from the mobile mirror, to thereby detect the position of the substrate to a high precision. As for the reticle, in a similar manner, a mobile mirror is provided on a reticle stage that attracts and holds the reticle. Detection light is then irradiated from the position detection device, and a distance from the reticle stage is measured, to thereby detect the position of the reticle to a high precision.
As described above, with the integration of semiconductor devices, the circuits are being made finer, and the line width thereof is becoming highly precise in the order of sub-microns. Therefore, the precision required for such exposure apparatus for forming a circuit pattern as described above is increasing year after year, and positioning precision of for example 5 to 10 nm or less is required. Consequently, in the stage portion of the exposure apparatus, positioning precision of about 1 nm is required.
Conventionally, as one means for realizing such high-precision positioning, attempts have been made where the exposure apparatus is installed in a chamber, the temperature of which is strictly controlled, and the stages are separately installed in housings, the temperature of which is more strictly controlled. As a result, expansion and contraction of the stages due to the change in temperature is suppressed, and positioning error resulting from the temperature change is eliminated.
Moreover, as for the holder, in a condition with the substrate supported by a multiplicity of fine protrusions with tips lying in a single plane, an approximately closed off space between the holder and the substrate is reduced in pressure for attachment, thereby reducing the contact area between the holder and the substrate. As a result, a situation where the flatness of the substrate is deteriorated due to dust and dirt caught between the substrate and the holder can be prevented, thereby eliminating positioning error resulting from deterioration of flatness.
However, with the above described conventional stage apparatus and holder, and scanning exposure apparatus and exposure apparatus, problems as described below exist.
The diameter of substrates is being increased in order to improve production efficiency, and wafers having an outer diameter of about 300 mm have recently been developed and put to practical use. In this case, the distance between the center of the wafer and the mobile mirror becomes about 200 mm, and even if ceramics having a relatively small thermal expansion, such as alumina, silicon nitride or the like are used for the holder and the mobile mirror, as in the conventional case, it is necessary to control the atmosphere temperature at the stage portion to the order of 0.001° C. in order to ensure positioning precision of 1 nm. Hence, there are such problems that cost relating to temperature control is significantly increased, and if the temperature control is out of order due to unforeseen circumstances, the possibility of the positioning precision not being satisfied increases.
In particular, in the case of an exposure apparatus that performs double exposure by using a plurality of reticles for high resolution exposure, two reticles for example are provided in a row and held on the reticle stage. However, there is a problem in that with the position measurement for the reticle on the far side from the mobile mirror in the row direction, the distance between the reticle and the mobile mirror is further increased. Hence higher precision temperature control is required.
Moreover, even if the atmosphere temperature is controlled within a predetermined range, and the contact area between the holder and the substrate is very small, the heat accompanying the exposure processing is applied to the holder via the substrate, resulting in thermal expansion. Therefore, if the substrate is subjected to exposure processing over a plurality of shot areas, the holder undergoes thermal expansion with the progress of the exposure processing. Hence, the expansion length becomes different between shot areas on the substrate, causing a problem in that high-precision superposition onto this layer becomes difficult for each shot area.
SUMMARY OF THE INVENTION
In view of the above situation, it is an object of the present invention to provide a stage apparatus and holder, and a scanning exposure apparatus and an exposure apparatus which can maintain positioning precision relative to the substrate, without excessively relying on the precision of temperature control.
To achieve the above described object, the present invention adopts the following construction.
The stage apparatus of the present invention comprises: a holder for holding a substrate, and a position detection device for detecting a position of the substrate, based on reflected light from a mobile mirr
Adams Russell
Fuller R.
Nikon Corporation
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