The patent's assignee is Canon Kabushiki Kaisha.
News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to a positioning apparatus, a lithography apparatus, and an article manufacturing method.
"A pattern is formed on a substrate by a lithography apparatus such as an exposure apparatus or the like in a lithography step included in manufacturing steps for a semiconductor device, a liquid crystal display device, and the like. For example, the exposure apparatus transfers a pattern of an original (reticle or mask) onto a photosensitive substrate (e.g., wafer, glass plate, and the like, where the surface thereof is coated with a resist layer) via a projection optical system. A lithography apparatus such as the exposure apparatus performs positioning of a stage (holder) for holding a substrate to thereby form a pattern on the substrate. A positioning apparatus that positions the stage to a desired position includes an interferometer that typically measures the position and the attitude of the stage. When the interferometer measures displacement of an object to be measured, the interferometer used for determining the origin of measurement needs to be initialized in order to specify the (absolute) position of the object to be measured.
"Japanese Patent Laid-Open No. 11-195584 discloses an exposure apparatus including two TTL (Through The Lens) mark detecting systems, which simultaneously detect the reference mark provided on a mask stage and the reference mark provided on a wafer stage, provided on the upper side of the mask stage. In the exposure apparatus, the reference mark provided on the wafer stage is detected by the TTL mark detecting system via the projection optical system. The position of the wafer stage can be initialized in the direction of the optical axis (Z-axis) of the projection optical system using a contrast of signals from the reference mark provided on the wafer stage obtained by the TTL mark detecting system. In addition, the tilt attitude (inclination relative to the X-Y plane) of the wafer stage can be initialized by using a contrast of signals from two reference marks provided on the wafer stage obtained by two TTL mark detecting systems. Then, the interferometer can be initialized with the position and the attitude of the wafer stage being initialized. WO 2011/080311 discloses an exposure method (drawing method) that measures the surface height of a wafer 101 placed on a wafer stage 102 using a plurality of capacitance sensors 103 as shown in FIG. 4. These capacitance sensors 103 are arranged around an electron beam irradiating unit in order to measure a local inclination on the wafer 101 to be exposed (drawn).
"Here, in the drawing apparatus that performs drawing on a substrate using an electron beam (charged particle beam), the mask stage and the TTL mark detecting system as disclosed in Japanese Patent Laid-Open No. 11-195584 are not included, and thus, the interferometer cannot be initialized by the method disclosed in Japanese Patent Laid-Open No. 11-195584.
"On the other hand, even when the interferometer is initialized by using the capacitance sensor disclosed in WO 2011/080311 that measures a local inclination on a wafer, such initialization is adversely affected by span limitations between a plurality of capacitance sensors and the distortion of the wafer surface, resulting in the disadvantage of reproducibility in initialization of the wafer stage."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventor's summary information for this patent application: "The present invention provides, for example, a positioning apparatus that is advantageous to initialization of an interferometer.
"According to an aspect of the present invention, a positioning apparatus including a holder configured to hold an original or a substrate and to be movable, and an interferometer for measuring a position of the holder, and positioning the holder based on an output from the interferometer is provided that comprises a reference member provided with the holder and including a reference plane; and a plurality of measuring devices respectively configured to face the reference plane, and to respectively measure positions of a plurality of measurement points on the reference plane in a measurement direction intersecting the reference plane.
"Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 is a side view illustrating a configuration of a drawing apparatus according to a first embodiment of the present invention.
"FIG. 2 is a plan view illustrating a configuration of a drawing apparatus as viewed from the A-A' plane shown in FIG. 1.
"FIG. 3 is a plan view illustrating a configuration of a drawing apparatus according to a second embodiment corresponding to that shown in FIG. 2.
"FIG. 4 is a cross-sectional view illustrating a configuration of a drawing apparatus using a conventional capacitance sensor."
For additional information on this patent application, see: ITO, Atsushi. Positioning Apparatus, Lithography Apparatus, and Article Manufacturing Method. Filed
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