JP2510874B2 - Precision movement table - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a precision moving table used in an apparatus that requires highly accurate position control, such as a precision processing machine, a semiconductor exposure apparatus, and a precision measuring machine.

[Prior Art] A conventional means for driving a precision moving table for a semiconductor exposure apparatus converts a rotary motion of a DC servo motor or the like into a linear motion by a feed screw or the like, and moves the table along a guide in the X and Y directions. It was a structure to move. On the other hand, in recent years, with the miniaturization of the minimum line width of printing and the increase in processing speed of the semiconductor exposure apparatus, extremely high precision is required for the movement accuracy and movement speed of the XY table. However, if a feed screw is used, non-linear components such as friction of the screw, play, and unevenness of feed will deteriorate the responsiveness, and speeding up will be hindered, and whirling of the feed screw will cause unnecessary swinging force.
The table movement accuracy was deteriorated. For this reason, it has been proposed to eliminate the non-linear element by using a linear motor as a driving means to achieve high speed and high accuracy.

[Problems to be Solved by the Invention] However, when a linear motor is used for the precision moving table, the table is locally heated by the heat generated by the linear motor. As a result, the table is deformed by thermal stress,
There is a problem that a member serving as an accuracy standard of the table is deformed and high-precision movement control cannot be performed.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems of the prior art, and eliminates the temperature distribution that causes deformation due to thermal stress and enables highly accurate position movement control with the entire table at a steady temperature. The purpose is to provide a precision moving table.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a cooling means for cooling the stage driving means (for example, a linear motor), which is a heating element, and serves as a reference member for table movement control. The cooling means is controlled so that the temperature difference between the base and the linear motor becomes zero.

[Operation] If there is no temperature difference, heat does not flow and heat is not transferred.
Therefore, the temperature distribution generated on the table base due to the heat generation of the linear motor is stabilized.

[Embodiment] FIG. 1 shows an embodiment of a precision moving table according to the present invention. This precision moving table includes a base 8, two parallel guides 7 arranged on the upper surface of the base 8 along both ends thereof, and a Y stage 2 mounted between these guides 7, 7. The X stage 1 mounted on the Y stage 2. The upper surface of the base 8 constitutes an accuracy reference surface 28. Therefore, the upper surface of the base 8 is finished to have a high flatness, for example, a mouth of 0.5 μm. The Y stage 2 is supported by the guide 7 in the horizontal direction via an air bearing, and is similarly supported on the base 8 in the vertical direction via an air bearing. The Y stage 2 is linearly slidable along the guide 7. The X stage 1 is horizontally supported by the Y stage 2 via an air bearing, and is vertically supported on the base 8 by an air bearing. The X stage 1 slides on the Y stage 2 in a direction perpendicular to the moving direction of the Y stage 2. 3 is a static pressure fluid bearing (air bearing) mounting plate for the X stage, and 4 is a static pressure fluid bearing mounting plate for the Y stage.

A linear motor 5 which is a driving means of the X stage 1 is mounted in the Y stage 2. A linear motor 6 which is a driving means of the Y stage 2 is mounted on the outside of each of the two guides 7. These linear motors 5 and 6 are composed of a stator 33 and a mover 32 that slides on the stator 33.
Two temperature sensors 9 are attached to each mover 32. A coolant passage for cooling is formed in the stator 33, and the flexible tube 22 for cooling inflow is connected to the stator 33. Base 8
A hole 29 is formed in the hole, and a temperature sensor 30 is installed inside.

FIG. 2 shows the configuration of the linear motor. The permanent magnets 37 are arranged so as to face each other, and are attached to the yoke 12, which is a magnetic flux passage. The upper and lower yokes 12 are connected to each other via a spacer 13 to form a box-shaped mover. The coil 11 is fixed between the two coil support members 10. Two coil support members
10 are connected by a connecting member 15 to form a stator.
Since the coil 11 of the stator is arranged in the magnetic field formed by the box-shaped mover, the thrust can be generated by energizing the coil 11. Coil support member
A coolant passage 16 through which a coolant for cooling is made is formed in 10 to remove the Joule heat generated in the coil by energization.

FIG. 3 shows a system diagram of the flow of the refrigerant. An appropriate amount of refrigerant is contained in the refrigerant tank 17, and is kept at a constant temperature by a temperature adjusting device (not shown). This refrigerant is a pump
18 circulates in the refrigerant system path including the flexible tube 22 via the four solenoid valves 19a, 19b, 19c and 19d. These solenoid valves are automatically controlled by a temperature control circuit described later to turn on / off the flow of the refrigerant.

This controlled refrigerant flow is removable connector 20a, 20
They are connected to the flexible tubes 22 via b and 20c, respectively, and are led to the cooling pipes 21a, 21b and 21c (refrigerant passage 16) of the linear motors. With such a configuration, the amount of heat removed from the linear motor can be controlled by turning the refrigerant on and off. The pipes exiting the cooling pipe of the linear motor are combined into one, pass through the flexible tube 22 and the detachable connector 20 again, merge with the outlet of the bypass solenoid valve 19d, and then return to the refrigerant tank 17. Here, since the flexible tube 22 is used, when the table moves, it does not hinder the movement of the table, and if the removable connectors 20, 20a to 20c are removed, the table is assembled, maintained,
Inspection and the like can be easily performed.

FIG. 4 shows a circuit for temperature detection. Resistances r _A1 , r in the figure
_A2 , r _B1 , and r _B2 are resistance temperature detectors that are temperature sensors, for example, platinum resistors, and their resistance values change according to the temperature change of the measured object. These four temperature sensors are connected in a bridge shape and are connected to a constant voltage source V via a variable resistor r for fine adjustment.

Further, the pair of temperature sensors r _A1 and r _A2 is fixed to a part of the linear motor, for example, in a temperature sensor mounting pit 14 provided on the yoke 12 of the linear motor shown in FIG. The other pair, r _B1 and r _B2, is provided separately with a temperature control reference member, for example, a surface plate on which the table is mounted, or a temperature sensor mounting pit similarly provided on the base 8 shown in FIG. . The resistance value of the platinum resistance thermometer is r = R + α ・ ΔT
Changes linearly. Here, r is the resistance value of the platinum resistance temperature detector, R · α is a constant, and ΔT is the temperature change. The temperature change of the four sensors r _A1 , r _A2 , r _B1 , r _B2 is ΔT
_{Assuming A1} , ΔT _A2 , ΔT _B1 , and ΔT _B2 , the output voltage e is shown as follows assuming that the variable resistance r for fine adjustment is small.

From the above equation, it can be seen that the output e is a voltage proportional to the difference between the average temperature of the pair of temperature sensors r _A1 and r _{A2 and} the average temperature of the other pair of temperature sensors r _B1 and r _B2 . With such a configuration, there are the following advantages as compared with the circuit (FIG. 10) conventionally used. That is, in order to measure the temperature stably without drift error, in the case of the conventional example, normally, the accuracy of the reference resistor r ₃ must be high and the temperature coefficient must be very low. If the sensor has a bridge structure, no reference resistor is required. Also, an output proportional to the temperature difference from the reference temperature can be taken out.

FIG. 5 shows a temperature control circuit. Each output e ₁ ~ of the above-mentioned temperature sensor bridge circuit corresponding to three linear motors
The e ₃ is amplified by the amplifiers 23a to 23c. The amplification factor of each amplifier is 100 dB, for example. The noise amplified by each amplifier 23a-23c is guided to the low-pass filters 24a-24c and attenuated. Since the temperature changes relatively slowly, the cutoff frequency of this low pass filter may be low, for example 1 Hz.
The signals that have passed through the low-pass filters 24a to 24c are guided to the hysteresis circuits 25a to 25c and shaped into ON-OFF signals for opening and closing the solenoid valves. This ON-OFF signal is the power amplifier 26a-26
The solenoid valves 19a to 19c are turned on and off via c. FIG. 6 shows _three such temperature control circuits for three inputs e ₁ , e ₂ , and e ₃ , which correspond to the three linear motors of the table device described in FIG. It is a thing. In addition, the solenoid valve 19d for bypass has the NOR circuit 27, that is, the ON / OFF logic of the three solenoid valves 19a to 19c corresponding to the linear motor.
A circuit that is turned on when these three solenoid valves are closed at the same time as A, B, and C Controlled by.

Next, the operation of the embodiment of the present invention having the above configuration will be described.
When driving the table, the coil of the linear motor 11
Energize (Fig. 2). As a result, the mover including the yoke 12 linearly moves and Joule heat is generated in the coil. This value is 12.5 at maximum in the table in this embodiment.
W. When this heat reaches the base 8 (FIG. 1) through each part, a temperature distribution is generated in the base 8. If the base is deformed due to this temperature distribution, the precision of the base in the table of the present configuration serves as the accuracy reference, and the movement accuracy of the table deteriorates. However, in this embodiment, when the temperature of the coil 11 rises due to the heat generated by the coil 11 of the linear motor, the temperature of the yoke 12 and the spacer 13 surrounding the coil also rises and is attached to the temperature sensor attachment pit 14 (FIG. 2). The resistance values of the temperature sensors r _A1 and r _A2 are increased. On the other hand, the temperature rise of the base is slower than the temperature rise of the yoke of the linear motor, so the resistance values of the reference temperature sensors r _B1 and r _B2 attached to the base do not change. Therefore, the temperature difference detecting bridge circuit shown in FIG. 4 is out of balance and the output voltage e is generated. The voltage e proportional to the temperature difference between the linear motor and the base is led to the circuit shown in FIG. 6, amplified by the amplifier 23, the low-pass filter 24, the hysteresis circuit.
Solenoid valve 19 by power amplifier 26 after shaping through 25
open. 3, when the solenoid valves 19a to 19C are opened, the refrigerant pumped by the pump 18 is guided through the flexible tube 22 to the linear motor cooling pipes 21a to 21c (refrigerant passage 16 in FIG. 2). The heat generated by the heat is removed. Therefore, this control circuit can bring the temperature difference between the linear motor and the base close to zero. If the temperature difference approaches zero, the heat flow will be suppressed, and the base temperature will be stable. Since the flatness of the upper surface of the base is the accuracy standard in the table of this embodiment, if the temperature of the base is stable, there is no deformation due to the temperature of the base, and high movement accuracy can be maintained. In this case, the mounting position of the temperature sensor r _A is important. Although the coil portion where heat is generated is hot and the vicinity of the cooling pipe becomes cold, it is difficult to remove the amount of heat generated without excess or deficiency unless the average temperature of both is detected and controlled. For example, according to experiments, when the temperature sensor is attached to the side surface of the coil 11, the temperature of the yoke 12 rises by 0.5 ° C. in 1.5 hours, and the temperature of the Y stage 2 also rises by 0.6 ° C. along with it.

On the other hand, when this temperature sensor was attached to the yoke 12, the temperature fluctuation of the yoke 12 was suppressed to -0.6 to + 0.2 ° C and the temperature of the Y stage 2 did not rise.

FIG. 6 shows a second embodiment of the present invention. In this embodiment, a plurality of (three in this example) temperature reference measuring sensors 30a to 30c are installed on the base 8. Since the base 8 of the semiconductor exposure apparatus generally occupies a large area of about 400 mm × 400 mm, it is difficult to eliminate the temperature distribution of the base 8 and make it completely uniform. Therefore, consider a case where the base 8 is in equilibrium with a certain temperature distribution. In the above-described first embodiment, only one temperature sensor is provided in the base and that temperature is used as the reference temperature. Therefore, a temperature difference may occur between the linear motor and the base near the linear motor. If there is a temperature difference, heat flows, so the heat of the linear motor is transferred to the base.

Therefore, in the second embodiment, the reference temperature measurement points are expanded, the base average temperatures near the linear motors are measured for each linear motor, and these are set as the reference temperatures. That is, in FIG. 6, for temperature control of the linear motor 6a, the output of the sensor 30a in the hole 29a provided at a position close to the linear motor 6a is used as a reference temperature, and the temperature difference between the linear motor 6a and the temperature sensor 30a is set to zero. Is controlled by the temperature control circuit. Similarly, for the linear motor 5 for the X stage, the temperature sensor 30b in the hole 29b is used, and for the other linear motor 6b for the Y stage, the temperature sensor 30c in the hole 29c is used, and the output of each temperature sensor is used as a reference. The temperature is controlled as the temperature. By providing a plurality of reference temperature measurement points in this way, the temperature difference between the linear motor and the base in the vicinity of the linear motor can be reduced to zero, so that heat is not transferred between the two. Therefore, even if the base has a temperature distribution, it is possible to prevent heat from flowing in and out between the linear motor and the base, and to keep the temperature of the base steady.

Other configurations and operational effects are similar to those of the first embodiment described above.

FIG. 7 shows a third embodiment of the present invention. In the second embodiment, the configuration in which the inflow and outflow of heat can be suppressed even if the base (surface plate) has a certain temperature distribution has been described, but the third embodiment is relatively close to the linear motor and other than the base. A configuration for coping with the case where the temperature of a member such as the X stage or the Y stage and the temperature of the base are different is shown. In such a case, a temperature difference occurs between the linear motor, which is a heating element, and the members in the vicinity thereof, and heat flows. Therefore, if the reference temperature measurement point is brought closer to the linear motor, such local temperature distribution is further alleviated. FIG. 7 is a cross-sectional view of the XY stage taken along a plane perpendicular to the traveling direction of the X stage. Insulation
34 is provided so that the heat generated by the linear motor does not diffuse to the surroundings. The reference temperature measuring sensor 9a is attached to the X stage 1
Alternatively, it is attached to the Y stage as shown at 9b. By installing the sensor in such a position and controlling the temperature in the same manner as described above, the average temperature difference between the linear motor and the X stage or the Y stage can be made zero, and the inflow and outflow of heat can be suppressed. it can.

FIG. 8 shows a fourth embodiment of the present invention. In the first embodiment, the solenoid valve is used to control the flow rate of the refrigerant. Therefore, the speed of the refrigerant changes rapidly when the solenoid valve turns on and off. Therefore, a shocking vibration is generated, and the linear motor and the flexible tube 22 communicating with the cooling pipeline are swung. Such vibration is extremely harmful to a table that requires precise movement control. Therefore, as shown in FIG. 8, instead of the solenoid valve, the flow rate control valve 38a capable of adjusting the flow rate is used.
Use ~ 38d to prevent shocking flow rate changes. The valve control circuit in this case is shown in FIG. FIG. 9 shows a circuit that controls the flow rate control valves 38a to 38c by the output e of the temperature sensor described in FIG. 4 via a general PID controller 40 and a power amplifier 41 for driving the flow rate control valves. Further, the valve 38d of the bypass circle has three valves 38a to 38a as in the above embodiment.
Open when c is closed. With this configuration, the flow rate can be changed comparatively gently, and the generation of harmful vibration due to a sudden change in flow rate can be prevented.

[Effects of the Invention] By providing the temperature control device according to the present invention as described above, the temperature difference between the average temperature of the base or surface plate, which is the accuracy reference member of the table, and the average temperature of the motor part, which is the heating element, can be reduced. Because it can approach zero,
Heat entering and exiting the table accuracy reference member is suppressed, and the temperature distribution of the table accuracy reference member is steadily stabilized. Therefore, the shape stability of the table accuracy reference member is guaranteed, and the movement accuracy of the table can be maintained high.

The present invention is particularly effective when the heating element is arranged at a position relatively close to the accuracy reference member as in the table having the structure shown in the embodiment.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of a precision moving table according to the present invention, FIG. 2 is a perspective view of a linear motor constituting the present invention, and FIG. 3 is a refrigerant system of a temperature control device according to the present invention. FIG. 4 is a temperature detection circuit diagram according to the present invention, FIG. 5 is a temperature control circuit diagram according to the present invention, FIG. 6 is a perspective view of a second embodiment of the present invention, and FIG. FIG. 8 is a perspective view of a third embodiment of the invention, FIG. 8 is an explanatory view of another example of the temperature control device according to the present invention, and FIG. 9 is a control circuit diagram of the temperature control device of FIG.
The figure is a conventional temperature detection circuit diagram. 1: X stage, 2: Y stage, 5, 6: Linear motor, 7: Guide, 8: Base, 9,30: Temperature sensor, 11: Coil, 12: Yoke, 16: Refrigerant passage, 22: Flexible tube.

Claims (9)

(57) [Claims] 1. A base, a stage which moves on the base, a drive means for moving the stage, a cooling means for cooling the drive means, and a first means for detecting the temperature of the base. No. 1 temperature detecting means, second temperature detecting means for detecting the temperature of the driving means, and control means for controlling the cooling means so that the output difference from the first and second temperature detecting means becomes zero. A precision moving table comprising: 2. The stage is provided on the base 2
Book parallel guides, a first stage mounted between the guides and sliding linearly along the guides, and a slide of the first stage mounted on the first stage A second stage that slides in a direction perpendicular to the direction;
Stage air bearing means for slidably supporting the stage with respect to the base and the guide, and second stage air for slidably supporting the second stage with respect to the base and the first stage. The precision moving table according to claim 1, comprising a bearing means. 3. A linear motor, wherein the driving means comprises a stator having one of a coil and a magnet, and a mover having another one of a coil and a magnet that linearly moves along the stator. The precision moving table according to claim 1 or 2, wherein: 4. The cooling means includes a refrigerant tank, a refrigerant passage provided in a stator of the linear motor, a refrigerant circulation system passage connecting the refrigerant tank and the refrigerant passage, and the refrigerant passage connected to the refrigerant passage. 4. The precision moving table according to claim 3, comprising a flexible tube forming a circulation system path and a refrigerant control valve means provided on the refrigerant circulation system path. 5. The precision moving table according to any one of claims 1 to 4, wherein the first and second temperature detecting means are resistance temperature detectors. 6. A bridge circuit for obtaining an output according to a difference in resistance values of the resistance temperature detectors constituting the first and second temperature detecting means is formed by using the resistance temperature detectors. The precision moving table according to claim 5. 7. The resistance temperature detector is provided at a plurality of different positions in the base, as set forth in claim 5.
The precision moving table according to item 6 or 6. 8. The precision moving table according to any one of claims 1 to 7, wherein the first temperature detecting means is provided on the stage. 9. The cooling means includes first and second cooling systems for respectively cooling the linear motors mounted on both guides for the first stage, and a linear drive for driving the second stage. A third cooling system path for cooling the motor is provided, and the valve means is provided on each cooling system path so that each valve means can be controlled according to the temperature difference between each of the three linear motors and the base. The precision moving table according to any one of claims 4 to 8 characterized by the above.