Electricity: motive power systems – Positional servo systems – With particular 'error-detecting' means
Reexamination Certificate
2000-11-27
2004-12-28
Fletcher, Marlon (Department: 2837)
Electricity: motive power systems
Positional servo systems
With particular 'error-detecting' means
C318S568160, C074S4710XY, C074S479010, C248S638000
Reexamination Certificate
active
06836093
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure method and an exposure apparatus to be used, for example, when a mask pattern is transferred onto a substrate in the lithography step for producing, for example, semiconductor elements, liquid crystal display elements, plasma display elements, and thin film magnetic heads. In particular, the present invention relates to an exposure apparatus in which a vibration-preventive control is adopted.
2. Description of the Related Art
A high exposure accuracy is required for the exposure apparatus of the full field exposure type (stepper type) or the scanning exposure type (for example, those based on the step-and-scan system) to be used when the semiconductor element or the like is produced. Therefore, in the exposure apparatus, an arrangement, which makes it possible to perform highly accurate positioning or highly accurate scanning, is adopted for a reticle stage on which a reticle as a mask is placed and positioned and for a wafer stage on which a wafer as a substrate is placed and two-dimensionally moved respectively.
That is, the reticle stage for the conventional exposure apparatus of the scanning exposure type is arranged, for example, such that a frame-shaped coarsely movable stage, which is movable at an approximately constant velocity in the scanning direction, is placed on a reticle base, and a finely movable stage, on which the reticle is placed, is connected into the coarsely movable stage by the aid of an actuator which is used to performing positioning in a minute amount two-dimensionally. In this arrangement, the coarsely movable stage and the finely movable stage are slidably placed on the common reticle base by the aid of air bearings respectively.
Also in the case of the reticle stage for the conventional exposure apparatus of the full field exposure type, a driving unit such as a linear motor, which is used to drive a movable stage on which the reticle is placed, is installed on the reticle stage.
On the other hand, in recent years, in order to enhance the throughput, a so-called double-wafer stage, which is provided with two movable stages, has been suggested as a wafer stage for the exposure apparatus. When the double-wafer stage is used, the throughput can be improved by performing exchange and alignment for a wafer on the second movable stage during a period in which exposure is performed for a wafer on the first movable stage. The conventional double-wafer stage has been constructed as follows in order to simplify the arrangement. That is, a guide for one axis of two orthogonal driving axes is commonly used by the two movable stages, or the two movable stages are independently driven by using plane motors.
Further, a system, which is based on the mechanical contact such that upward and downward movement is performed, for example, with a cam mechanism, is adopted for the driving system for a sample base (Z leveling stage) for performing leveling and focusing in the conventional wafer stage.
The conventional exposure apparatus has been assembled on a base plate which is installed by the aid of a plurality of (for example, four) vibration-preventive pedestals including air dampers in order to mitigate the influence of vibration from the floor. However, when an excimer laser light source is used as an exposure light source, some of members of the exposure light source and the illumination optical system are supported by support members different from the base plate. Recently, in order to allow other stage sections and other components to be not affected by the vibration generated in respective stage sections of the exposure apparatus, a system has been also suggested, in which a wafer base for supporting a wafer stage and a reticle base for supporting a reticle stage are supported mutually independently by a plurality of active type vibration-preventive units including air dampers and electromagnetic control units respectively.
Among the double-wafer stages of the conventional exposure apparatuses as described above, as for the arrangement in which the guide for one axis of the orthogonal axes is used for both of the two movable stages, an inconvenience arises such that the influence of vibration of the second movable stage tends to be transmitted to the first movable stage. For this reason, for example, it is necessary to provide certain restriction for the control sequence, for example, such that the high speed movement operation of the second movable stage is avoided during the transfer operation of the first movable stage. It has been impossible to increase the throughput so much.
Further, the conventional sample base (Z leveling stage) has been driven in accordance with the system based on the mechanical contact. Therefore, the following inconvenience arises. That is, it is impossible to increase the response speed so much, and the vibration from the bottom surface side of the movable stage tends to be transmitted to the wafer.
Taking the foregoing viewpoints into consideration, a first object of the present invention is to provide an exposure method and an exposure apparatus in which the influence of vibration is hardly transmitted among a plurality of movable stages to one another, and the exposure accuracy can be maintained to be high, when the plurality of movable stages for substrates (for example, wafers) as exposure objectives are provided.
A second object of the present invention is to provide an exposure method and an exposure apparatus in which the external vibration is hardly transmitted to a movable stage for a substrate as an exposure objective, and a high exposure accuracy can be obtained.
A third object of the present invention is to provide an exposure method and an exposure apparatus which make it possible to perform the leveling or the focusing for a substrate as an exposure objective at a high speed, in which the influence of vibration is scarcely exerted on the substrate.
Another object of the present invention is to provide a production method which makes it possible to efficiently produce the exposure apparatus as mentioned above, and a method for producing highly accurate devices, based on the use of the exposure method as mentioned above.
SUMMARY OF THE INVENTION
A first exposure method according to the present invention lies in an exposure method for exposing a second object with an exposure light beam via a first object (R
1
); the exposure method comprising preparing a first movable stage (
14
A) on which a first substrate (W
1
) as the second object is placed, and a second movable stage (
14
B) on which a second substrate (W
2
) as the second object is placed; two-dimensionally driving the first and second movable stages on a predetermined guide surface respectively; and dealing with reaction forces, which are generated when the first and second movable stages are driven, independently from each other.
According to the present invention as described above, the influence of vibration is scarcely transmitted mutually between the two movable stages. Therefore, the exposure accuracy is maintained to be high.
When this invention is applied to a scanning exposure type exposure method, the first object and the second object are relatively moved in a predetermined direction during the process in which a pattern on the first object is transferred to the second object. For this purpose, it is desirable that the first and second movable stages are driven while substantially satisfying law of conservation of momentum respectively when the first and second movable stages are driven in the predetermined direction. Accordingly, it is possible to perform the scanning exposure more stably.
A first exposure apparatus according to the present invention lies in an exposure apparatus for exposing a second object with an exposure light beam via a first object (R
1
); the exposure apparatus comprising a first movable stage (
14
A) on which a first substrate (W
1
) as the second object is placed; a second movable stage (
14
B) on which a second substrate (W
Fletcher Marlon
Nikon Corporation
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