Electricity: motive power systems – Positional servo systems – With particular 'error-detecting' means
Reexamination Certificate
2000-10-10
2002-10-29
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Positional servo systems
With particular 'error-detecting' means
C318S623000, C318S611000
Reexamination Certificate
active
06472840
ABSTRACT:
INCORPORATION BY REFERENCE
The present application is based upon the one identified below, and the contents thereof are incorporated herein by reference:
Japanese Patent Application Heisei 10 No. 97595 (filed upon April 9th, Heisei 10).
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibration cancellation apparatus and to an exposure apparatus, and more particularly relates to a vibration cancellation apparatus and to an exposure apparatus which, based upon vibration which is detected, reduce the above-described vibration by driving a weight in a direction to quell it.
2. Related Art
In accompaniment with enhancement of the accuracy of precision equipment such as step-and-repeat type and step-and-scan and-scan type exposure apparatus and the like, the requirement has arisen for isolating minute vibrations at the micro-G level which act upon a base table (a vibration cancellation table) from the surface of a foundation floor on which a precision equipment is set. For this reason, there have been many proposals to support the vibration cancellation table by vibration cancellation pads, so as to isolate vibrations from the surface of the foundation floor. Various types of vibration cancellation pads have been used to support the vibration cancellation tables of vibration cancellation apparatus, such as mechanical dampers containing compression coil springs in damping fluid and air type dampers or the like. In particular, air spring vibration cancellation apparatus equipped with air type dampers are widely used for supporting precision equipment, because it is possible to set the spring constant low so as to isolate vibrations above about 10 Hz. Further, active vibration cancellation apparatus have recently been proposed in order to defeat the limitations of prior art passive vibration cancellation apparatus (for example, refer to Japanese Patent Laying Open Publication Heisei 8-166043 filed by the same applicant as the present application). These are vibration cancellation apparatus which perform vibration control by detecting vibration of the vibration cancellation table by a sensor and by driving an actuator based upon the output of this sensor, and theoretically they are endowed with a vibration isolation efficacy which exhibits no resonant peaks in the low frequency control band.
The use of a reaction frame has been practiced as one means for yet further enhancement of the vibration cancellation performance of the above-described active vibration cancellation apparatus. Such a reaction frame will now be explained. A mask stage or a substrate stage is set up upon the vibration cancellation table of the above-explained exposure apparatus. During exposure action, in accompaniment with repeated acceleration and deceleration of the mask stage or the substrate stage (hereinafter termed the moving stage), vibration increasing forces act upon the vibration cancellation table due to reactions received from the moving stage. An element used for preventing this vibration increasing forces from acting upon the vibration cancellation table is a reaction frame.
That is, the reaction frame is fixedly provided upon the surface of the foundation floor on which the exposure apparatus is installed, and this reaction frame receives the reactions which accompany acceleration and deceleration of the moving stage. Accordingly, the above-described reactions which are transmitted to the reaction frame are not transmitted to the vibration cancellation table, but are transmitted to the surface of the foundation floor. By doing this, it is possible to prevent vibration of the vibration cancellation table in accompaniment with acceleration and deceleration of the moving stage.
Further, with the above described exposure apparatus, it has been proposed to set up the illumination optical system and the exposure apparatus main body as separate units (for example, in Japanese Patent Application Heisei 9-310438 filed by the same applicant as the present application). Such an arrangement is for preventing vibration generated during the scanning exposure action of a step-and-scan exposure apparatus when the reticle blind which intercepts light outside the exposure range upon the reticle pattern moves synchronously with scanning exposure from being transmitted to the exposure apparatus main body. With the above described step-and-scan exposure apparatus, the exposure apparatus main body and the illumination optical system are mutually separately provided and each of them is supported by an active vibration cancellation apparatus, and vibration cancellation action is performed independently for each of them while their relative position is maintained. By doing this, along with it being possible to prevent vibration generated as described above in the illumination optical system from being transmitted to the exposure apparatus main body, it is also possible to maintain the accuracy of relative position determination between the illumination optical system and the exposure apparatus main body, as is desirable.
However, along with the increase in accuracy of position determination of the moving stage which is being required, it has become impossible to ignore vibration set up in the reaction frame itself. That is to say, the reaction frame receives the reactions generated accompanying acceleration and deceleration of the moving stage. Vibration is set up in the reaction frame when it experiences these reactions. And vibration of the reaction frame is transmitted through the surface of the foundation floor on which the exposure apparatus is installed to the exposure apparatus main body.
As an accuracy of position determination of the moving stage becomes high, it has become impossible to ignore vibration transmitted to the exposure apparatus main body.
Further, with an apparatus in which the illumination optical system and the exposure apparatus main body are set up as separate units, there have been demands for further suppression of vibration generated within the illumination optical system, in order to enhance the performance of position determination of the illumination optical system and the exposure apparatus. The reason for this is that vibration generated within the illumination optical system is also transmitted to the exposure apparatus main body via the surface of the foundation floor as well.
Yet further, when a stage or the like operates within the exposure apparatus main body, it may happen that residual vibration which has not been eliminated by the reaction frame generates undesirable vibration in the projection optical system. When this happens, exposure action cannot be performed until the vibration of the projection optical system has been abated to a specified level, and sometimes this leads to deterioration of the throughput of the exposure apparatus.
The above problems due to vibration can occur not only with an exposure apparatus, but also with a precision tool machine or a precision measuring device or the like as well. That is to say, it can happen that vibration set up within a precision tool machine or a precision measuring device, or vibration transmitted from the outside, can deteriorate the processing accuracy in the case of a precision tool machine, or the measurement accuracy in the case of a precision measuring device.
SUMMARY OF THE INVENTION
A first objective of the present invention is to enhance the throughput of an exposure apparatus and the accuracy of positional determination for a moving stage thereof, by suppressing vibration set up in a reaction frame.
A second objective of the present invention is to enhance the accuracy of relative position determination between an exposure apparatus main body and an illumination optical system which are provided as mutually separate units, by suppressing vibration set up due to movement of a movable element housed in the illumination optical system.
A third objective of the present invention is to propose a vibration cancellation apparatus which can be provided to a device etc. for which reduction
Oliff & Berridg,e PLC
Ro Bentsu
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