JP2005203652A - Positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanism system, its positioning control technology, and their initializing technology capable of realizing a high bandwidth control system in an X and Qz direction with regard to a positioning device of a semiconductor aligner. <P>SOLUTION: A control device of a moving body moving within a XY plane comprises a twin-fuselage linear motor in a Y direction, at least two reference planes in the X direction provided to a fixed part outside the moving body, at least two electromagnets arranged to the moving body in facing to the two X-directional reference planes and generating a force in an X direction between the moving body and the reference plane, and a position measuring means for measuring a position of at least XYQz three degrees of freedom of the moving body. The position control of the moving body in the X direction is conducted by at least two electromagnets. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a positioning stage device in a semiconductor exposure apparatus, and is particularly suitable for a reticle stage positioning device.

  Recent rapid development of semiconductor devices has led to a dramatic improvement in the performance of various information devices equipped with these devices, and is changing our lives dramatically. Supporting this development is semiconductor manufacturing technology, and a wafer exposure apparatus, usually called a stepper or scanner, is the core apparatus. The stepper moves the semiconductor wafer on the stage device stepwise under the projection lens, and reduces and projects the pattern image formed on the reticle onto the wafer with the projection lens, and sequentially exposes to multiple locations on a single wafer. It is something to do. The scanner moves the semiconductor wafer on the wafer stage and the reticle on the reticle stage relative to the projection lens, irradiates the exposure light on the slit during the scanning movement, and projects the reticle pattern onto the wafer. The scanner is regarded as the mainstream of the exposure apparatus in terms of performance of resolution and overlay accuracy.

  FIG. 2 shows an overview of a reticle stage conventionally used in a scanner. The reticle stage main body is provided with a static pressure guide by a static pressure pad between XL and XR reference planes which are the upper and side surfaces of the surface plate 1, and is supported freely in the Y direction. In the Qz direction, there is spring rigidity due to the lateral hydrostatic pad, but it can rotate within a small movable range in the Qz direction defined by the gap. A reticle is mounted on the reticle stage 2 body by a reticle chuck (not shown). Two corner cubes 10 and 11 are provided on the reticle stage 2, and the measurement light from the laser interferometers 7 and 8 is reflected to measure the Y-direction displacement of the reticle stage 2 at two points. The positions of the center of gravity in the Y direction and the Qz direction are calculated.

  Further, movers 3 and 4 made of magnets are provided on both sides of the reticle stage 2, and Lorentz force is obtained by stators 5 and 6 made of coils attached to the same structure as the stage surface plate. A linear motor using is configured. By these two left and right linear motors, the reticle stage 2 is given a driving force in the Y direction along the reference plane and in the minute Qz direction around the reference plane. The reticle stage 2 is positioned and controlled with high accuracy in the Y direction along the reference plane and in the minute Qz direction around the reference plane by a position control system (not shown).

  One index of apparatus performance is the throughput expressed by the number of wafers processed per hour. In order to achieve high throughput, the stage is required to move at high speed, and acceleration / deceleration during movement is increasing. In the conventional linear motor using the air-core type Lorentz force of FIG. 2, if a large thrust is generated during acceleration / deceleration, heat generation in the coil portion becomes very large. When this heat generation is transmitted to the stage structure, the stage and the reticle itself undergo thermal expansion, which deteriorates the exposure overlay accuracy. In addition, the burden on the electrical equipment for passing a large current also increases.

  As a configuration of a linear motor capable of generating a large thrust with low heat generation, an iron core type linear motor as shown in FIG. 3 has been proposed. In the stator 50 of this linear motor, a coil 52 is wound around an iron core 51 formed by laminating comb-like silicon steel thin plates. The mover 53 is configured by arranging permanent magnets 54 so that their polarities are alternately arranged. Since an attractive force is generated between the permanent magnet 54 and the iron core 51, the stator is arranged in such a manner that the movable magnet 54 is sandwiched from above and below in order to offset this. In this type of linear motor, the calorific value can be reduced to several tenths or less compared to a Lorentz type linear motor of the same size.

  The acceleration / deceleration linear motor of the exposure apparatus is often a movable magnet type. In such a configuration, the driving wire may be on the stator (stator) side, so there is no stress on the wire part and there is no fear of disconnection, and heat generation is also on the stator side, so cooling with refrigerant is easy. It is suitable for various fields including a semiconductor manufacturing apparatus that requires high reliability and accuracy.

  Further, in a semiconductor exposure apparatus, in order to improve throughput, an increase in wafer size, which is a substrate to which an original is transferred, and an improvement in acceleration force and maximum speed required for a linear motor are required. From such a background, a long stroke is required compared to the size of the mover, and thus a plurality of coil pairs are required. At that time, if all the coil pairs are connected to the same current driver, it becomes possible to generate a thrust, but a coil that does not reach the magnetic field of the mover does not generate a thrust and only a loss (heat generation) due to the electrical resistance of the coil. Therefore, the efficiency of the motor becomes extremely low. In order to prevent this, a current driver is connected to each coil pair so that the current command value of the current driver connected to each coil can be given individually, so that no current flows through the coil that does not reach the magnetic field of the mover. A method is conceivable. This method requires current drivers and command value generation units as many as the number of coil pairs, and the cost increases in proportion to the stroke. Therefore, this method cannot be employed in the case of a long stroke. Therefore, this problem is solved by using a technique in which a current driver is connected to each coil via a relay or the like so that only a coil in the range of the magnetic field of the mover selectively flows (Patent Document 1, Patent). Reference 2).

  In this case, there is a problem with the initialization method of the position measuring means. As a high-precision, long-stroke position measuring unit such as an exposure apparatus, a control system is configured using an incremental type position measuring unit with high resolution such as a laser interferometer or an encoder. In this case, in the initial state or the state immediately after resetting, the change amount of the stage position can be detected by the position detecting means, but the absolute position of the stage cannot be known. If the system does not require electrifying coil selection, the stage can be driven with relative displacement information and initialization can be performed. However, in a system that involves electrifying coil selection, the absolute position is measured and energized. It is necessary to select a coil to be used. That is, the stage cannot be driven in a state where the coil to be selected / energized cannot be determined.

As means for solving such a problem, methods such as Patent Document 3 and Patent Document 4 are disclosed. With these techniques, the absolute position of the stage can be detected and the coil can be selected to initialize the stage.
JP-A-6-284785 Japanese Patent Laid-Open No. 8-1111998 JP-A-5-64487 JP-A-11-316607

  However, in the above-described conventional stage positioning apparatus, since the positioning control in the Qz direction is realized by a configuration that is restrained by the static pressure guide in the X direction, the dynamic rigidity of the position control system in the Qz direction is static pressure. It is greatly affected by the natural vibration determined by the rigidity of the guide and the weight of the stage. The natural frequency tends to decrease with the increase in the size of the stage as the reticle size increases. For this reason, the conventional technique has a problem that high-precision positioning control cannot be performed in the Qz direction. In addition, in the case of such a mechanism configuration using a static pressure pad, positioning control in the X direction is impossible, and it cannot be used for a positioning device that requires positioning in the X direction.

  In order to solve the above-mentioned conventional problems, a method of eliminating the static pressure guide in the X direction and providing a linear motor in the X direction instead to perform positioning control in the X direction is also conceivable. However, in this method, it is necessary to dispose a fixed coil or a fixed magnet that covers the entire movable range in the Y direction in order to cope with an increase in the movable range in the Y direction of the stage as the reticle size increases. For this reason, a long stator coil or a stator coil is required. Therefore, it is difficult to arrange in the stage space in a compact manner as in the static pressure pad method, and there is a problem that the control band is reduced due to the increase in the stage size and the decrease in the natural frequency of the stage.

  Further, the iron core linear motor used for realizing the high thrust generates a cogging force depending on the stage position, which may cause deterioration in positioning characteristics. For this, the influence of cogging can be effectively removed by table correction. However, as the exposure apparatus is required to have higher accuracy, it is difficult to obtain sufficient accuracy only by such a feedforward method using table correction. A more effective feedback mechanism / control system is constructed in combination with the feedforward method, and further suppression of cogging force is required.

  In addition, for a shaft that performs long stroke movement, such as the Y-direction linear motor in the reticle stage described in the prior art, a magnet actuator type linear motor that switches stator coils is often used. In such a case, it is difficult to initialize the stage because absolute position information is required as compared with the method that does not perform coil switching as described above. For this reason, in the case of a stage including a control axis for switching coils, it is important to establish an initialization technique for the entire stage.

  As described above, compared with the conventional stage, there has been a demand for establishment of a mechanism system that can realize a higher-band control system in the X direction and the Qz direction, a positioning control technique thereof, and an initialization technique for the mechanism system. .

  In view of such a problem in the prior art, the following means are used in the present invention.

  1) Between at least two X-direction reference planes provided in a fixed portion outside the movable body and the movable body and the reference plane disposed on the movable body facing the two X-direction reference planes. Is provided with at least two sets of electromagnets that generate force in the X direction, and control of the position of the movable body in the X direction is performed by the at least two sets of electromagnets, thereby realizing a control system free from restrictions on mechanical resonance in the Qz direction. To do.

  2) Further, using the redundancy of positioning control in the Qz direction in the above configuration (because positioning control may be performed by either the linear motor or the electromagnet), one is used for positioning control, and the other is used in the Qz direction. By configuring the control system to perform the speed control, a positioning control system in the Qz direction with higher stability and control accuracy is realized.

  3) Further, initialization of the position measuring means in the X direction with respect to the movable body is performed in a state of being attracted to the X direction reference plane by at least one of the electromagnets, and then the X direction servo is applied by the electromagnet. After functioning as a direction guide, the Y-direction position measuring means is initialized.

  According to the present invention, a higher-band control system than a two-axis or three-axis type stage mechanism including a control axis that performs a long stroke movement in one direction generally used in the related art and its control mechanism. It is possible to realize a mechanism system capable of realizing the above, a positioning control technique thereof, and a stable initialization technique.

(First embodiment)
FIG. 1 is a plan view of a reticle stage according to an embodiment of the present invention. In this figure, 1 is a surface plate, 2 is a stage, 3 and 4 are YL and YR linear motor movers, and 5 and 6 are YL and YR. Linear motor stator, 7-9 are YL, YR, X interferometers, 10, 11 are YL, YR corner cubes, 12, 13 are XL, XR reference planes, 14-17 are XL1, XR1, XL2, XR2 electromagnets, Reference numeral 18 denotes a bar mirror, and the same reference numerals are given to the same ones as in the prior art.

  Next, in this embodiment, the reticle stage main body is provided with a static pressure guide by a static pressure pad (not shown) between the upper surface of the surface plate 1 and the reticle stage supports the XY plane freely without restriction. Has been. A reticle is mounted on the reticle stage body by a reticle chuck (not shown). Two corner cubes 10 and 11 are provided on the reticle stage, and the measurement light from the laser interferometers 7 and 8 is reflected to measure the Y-direction displacement at two points of the reticle stage 2. Measurement in the X direction is performed by a bar mirror mounted on the stage and a laser interferometer in the X direction. These measurement means calculate the positions of the center of gravity of the stage in the X, Y and Qz directions.

  Movers 3 and 4 made of magnets are provided on both sides of the reticle stage, and Lorentz force is used by stators 5 and 6 made of coils attached to the same structure as the stage surface plate. A linear motor is configured. With these two left and right linear motors, the reticle stage can apply a driving force in the Y direction along the reference plane and in the Qz direction centered on the reference plane. As a result, the Y and Qz directions of the reticle stage can be controlled using control means (not shown).

  Further, the reticle stage is provided with electromagnets 14 to 17 that generate an attracting force in the X direction so as to face the two X direction reference side surfaces of the stage surface plate.

  Since the electromagnet itself generates only a simple unidirectional attracting force, in order to use it as an actuator, it is used as a set of actuators by two opposing electromagnets provided on two reference surfaces. In this embodiment, two sets of such electromagnets are provided and function as two X-direction actuators. The two sets of electromagnets enable control of the reticle stage in the X and Qz directions using a control means (not shown).

  In a mechanical system using such an electromagnet, mechanical resonance due to the rigidity of the mechanical system does not occur unlike a conventional guide mechanism using a static pressure pad. Therefore, the servo band in the Qz direction can be set higher than that of the conventional mechanism system, and positioning with high accuracy is possible.

  Further, when realizing a servo mechanism in the X direction using a linear motor, it is difficult to realize the servo mechanism in the Qz direction with a linear motor in the X direction because of the reticle stage mechanism that moves in a long stroke in the Y direction. It was. On the other hand, according to the present invention, the servo mechanism in the Qz direction can be easily realized by an electromagnet in the X direction in addition to being realized by a twin-barrel type Y linear motor. By utilizing this redundancy, in the present invention, it is possible to apply the position in the Qz direction while applying one of the Y-direction linear motor or the X-direction electromagnet and at the same time apply the speed control in the Qz direction. . As a result, a position servo mechanism with speed feedback can be realized as the Qz servo mechanism. As a result, the cogging force, which is one of the problems in the conventional method, can be further reduced, and a higher-accuracy positioning mechanism can be realized, and at the same time, the servo system can be increased in bandwidth.

  Furthermore, since the mechanism system can be realized with a more compact size than when the X-direction servo is realized by an X-direction linear motor, the mechanism system can be made highly rigid.

  Due to the above-described effects, the present invention enables more accurate and robust positioning control.

  Next, initialization of the reticle stage will be described.

  As described in the previous chapter, a magnet actuating linear motor by switching a stator coil is often used for an axis that performs long stroke movement, such as a Y-direction linear motor of a reticle stage. In such a case, it is difficult to initialize the stage as compared with the method that does not perform coil switching as described above. For this reason, in the case of a stage including a control axis for switching coils, it is important to establish an initialization technique for the entire stage.

  In the present embodiment, this is realized by the following procedure.

  (1) The X-direction position measuring unit of the movable body is initialized in a state where it is attracted to the X-direction reference plane by at least one of the electromagnets.

  (2) After the initialization of the position measuring means of the movable body in the X direction, the movable body is positioned in the X direction with two sets of electromagnets.

  (3) Further, the position measuring means in the Y direction is initialized.

  FIG. 4 shows a state in which the operation (1) is completed. That is, the reticle stage is attracted to the XR reference plane by two electromagnets XR1 and XR2. In this state, initialization of the X-direction interferometer is completed by setting the measurement position data by the X laser interferometer to an appropriate initial value.

  Thereafter, the attracted state is released, and the gap between the reticle stage and the XR and XL reference planes is kept constant by the two sets of electromagnetic actuators XR1 and XL1 and XR2 and XL2 that face each other according to the procedure (2). The servo system is configured as follows.

  In this state, the reticle stage is freely movable in the Y direction by an electromagnet guide mechanism. At this stage, as shown in (3), the position measuring means in the Y direction is initialized. As an initialization method of the position measuring means in the Y direction, it can be easily realized by using a known method.

  In addition, since the attractive force of the electromagnet has nonlinearity depending on a strong gap, the stroke range that can be stably used as a servo system is narrower than that of a normal linear motor. Therefore, the gap value at each electromagnet position can be calculated to correct the gap-dependent nonlinearity.

  However, in order to calculate the gap value, the absolute position information of the XYQz of the stage is required. Therefore, in the state where the initialization of the interferometer of the Y interferometer is not completed, the non-linearity correction cannot be performed and the initialization is performed. It becomes possible after operation.

(Other examples)
In the first embodiment, the laser interferometer is used as the position measuring means in the X direction of the reticle stage. However, the present invention can be realized in exactly the same manner by using a gap sensor such as a capacitance sensor. is there.

  In this case, since the gap calculation described in the first embodiment is unnecessary, the nonlinearity depending on the gap of the electromagnet is corrected from the step (2) in the stage initialization, and a more robust control system is realized. It is possible to perform the initialization operation while configuring.

It is a top view of the Example of the reticle stage apparatus based on the 1st Example of this invention. It is a top view of the Example of the reticle stage apparatus based on a prior art. It is a figure which shows an iron core type linear motor. It is a figure which shows the adsorption | suction state in stage initialization.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface plate 2 Stage 3 YL linear motor mover 4 YR linear motor mover 5 YL linear motor stator 6 YR linear motor stator 7 YL interferometer 8 YR interferometer 9 X interferometer interferometer 10 YL corner cube 11 YR corner Cube 12 XL reference plane 13 XR reference plane 14 XL1 electromagnet 15 XR1 electromagnet 16 XL2 electromagnet 17 XR2 electromagnet 18 Bar mirror

Claims (5)

A control device for a movable body that moves in an XY plane,
A Y-coordinated linear motor, at least two X-direction reference planes provided on a fixed portion outside the movable body, and disposed on the movable body facing the two X-direction reference planes, And at least two sets of electromagnets that generate a force in the X direction between the movable body and the reference surface, and a position measuring unit that measures a position of at least XYQz3 degrees of freedom of the movable body, and the X direction of the movable body The position control is performed by the at least two sets of electromagnets.   2. The control device according to claim 1, wherein position control in the Qz direction with respect to the movable body is performed by the at least two sets of electromagnets.   2. The control device according to claim 1, wherein speed control in the Qz direction with respect to the movable body is performed by either the Y-direction double-bore type linear motor or the at least two sets of electromagnets.   2. The control device according to claim 1, wherein initialization of the position measuring means in the X direction of the movable body is performed in a state where the movable body is attracted to the reference plane in the X direction by at least one of the electromagnets.   After initializing the position measuring means in the X direction of the movable body, positioning the movable body with at least two sets of electromagnets in the X direction at least in the X direction, and allowing the electromagnet to function as at least a guide in the X direction, 5. The control device according to claim 4, wherein the Y-direction position measuring means is initialized.

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