JPH01195389A - Precise moving table - Google Patents

Abstract

PURPOSE:To control movement with a high precision by providing a cooling means which cools a stage driving means as a heating body and controlling the cooling means so that the temperature difference between a base and a linear motor is zero. CONSTITUTION:When the temperature of a coil rises by the heat generated by a coil 11 of the linear motor, temperatures of a yoke 12 and a spacer 13 surrounding this coil rise, and resistance values of temperature sensors 9 and 9 attached to a temperature sensor attaching pit 14 are increased. Meanwhile, resistance values of reference temperature sensors 30 and 30 attached to the base are not changed because the rise of temperature of the base is slower than that of the yoke of the linear motor. Consequently, the balance of a temperature difference detecting bridge circuit is lost to generate an output voltage. This voltage is amplified to open a solenoid valve. Since the solenoid valve is opened, a refrigerant sent with a pressure by a pump is led to a linear motor cooling duct (refrigerant path 16) through a flexible tube 22 to remove the heat. Thus, the temperature difference between the linear motor and the base is approximated to zero by this control circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] The present invention relates to a precision moving table used in precision processing machines, semiconductor exposure equipment, precision measuring machines, and other devices that require highly accurate position control.

[Prior Art] Conventional means for driving a precision movement table for semiconductor exposure equipment converts the rotational motion of a DC servo motor or the like into linear motion using a feed screw or the like, and moves the table along a guide in the X and Y directions. It was configured to be moved. On the other hand, in recent years, with the miniaturization of the minimum printed line width and the increase in the processing speed of semiconductor exposure apparatuses, extremely high accuracy in both the movement accuracy and movement speed of the XY child table is required. however,
When a feed screw is used, non-linear components such as screw friction, backlash, and uneven feed deteriorate responsiveness and prevent higher speeds.Additionally, the whirling of the feed screw generates unnecessary rocking force, which may hinder table movement. It was deteriorating the accuracy. For this reason, a linear motor is used as the drive means to eliminate nonlinear elements,
Proposals have been made to improve speed and accuracy.

E Problems to be Solved by the Invention] However, when a linear motor is used in the wI compact moving block, the table is locally heated due to the heat generated by the linear motor. As a result, the table deforms due to thermal stress,
There has been a problem in that the member that serves as the accuracy standard for the table is deformed and highly accurate movement control cannot be performed.

[Purpose of the invention]

The present invention has been made in view of the problems of the prior art, and provides a precision moving table that eliminates the temperature distribution that causes deformation due to thermal stress and maintains the entire table at a steady temperature to enable highly accurate positional movement control. The purpose is to provide.

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

[Operation] If there is no temperature difference, no heat will flow and no heat transfer will occur. Therefore, the temperature distribution generated at the base of the table due to the heat generated by the linear motor is stabilized.

[Embodiment] Fig. 1 shows an embodiment of a precision movement table according to the present invention. 7, a Y stage 2 mounted between these guides 7 and 7, and an X stage 1 mounted on this Y stage 2. The upper surface of the base 8 constitutes an accuracy reference surface 28. Therefore, the upper surface of this base 8 is finished with a high flatness, for example, 0.5 μm.

The Y stage 2 is supported horizontally by a guide 7 via an air bearing, and vertically supported by a base 8 via an air bearing. This Y stage 2 is linearly slidable along a guide 7. X
Stage 1 is horizontally connected to Y via an air bearing.
It is supported on the stage 2 and vertically on the base 8 via 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 serving as a drive means for the X stage 1 is mounted inside the Y stage 2. A linear motor 6, which is a driving means for the Y stage 2, is mounted on the outside of two guides 7, respectively. These linear motors 5 and 6 are composed of a stator 33 and a movable element 32 that slides on the stator 33. Two temperature sensors 9 are attached to each movable element 32. A refrigerant passage for cooling is formed in the stator 33, and a flexible tube 22 for cooling inflow is connected to the stator 33. A hole 29 is bored in the base 8, and a temperature sensor 30 is installed inside.

FIG. 2 shows the configuration of a linear motor. Permanent magnets 37 are placed facing each other and attached to the yoke 12, which is a path for magnetic flux. 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 two coil support members 10. The two coil supporting members 10 are connected by a connecting member 15 to constitute a stator. Since the stator coil 11 is disposed in the magnetic field formed by the box-shaped mover, thrust can be generated by energizing the coil 11. A refrigerant passage 16 through which a cooling refrigerant flows is formed in the coil support member 10 to remove Joule heat generated in the coil by energization.

FIG. 3 shows a flow diagram of the refrigerant. An appropriate amount of refrigerant is contained in the refrigerant tank 17, and is maintained at a constant temperature by a temperature control device (not shown). This refrigerant is pumped through four electromagnetic valves 19a, 19b, 19c, 19 by a pump 18.
The refrigerant is circulated through a refrigerant system including the flexible tube 22 via d. These electromagnetic valves are automatically controlled by a temperature control circuit, which will be described later, to turn on and off the flow of refrigerant.

This controlled refrigerant flow includes a removable connector 20a,
The flexible tubes 22 are connected via 20b and 20c, respectively.
a cooling pipe line 21a for each of the linear motors,
21b, 21c (refrigerant passage 16). With this configuration, the amount of heat removed from the linear motor can be controlled by turning the refrigerant on and off. The pipes exiting the linear motor cooling pipe are combined into one, pass through the flexible tube 22 and the detachable connector 20 again, join the outlet of the bypass electromagnetic valve 19d, and then return to the refrigerant tank 17. Here, flexible tube 2
2, it does not impede the movement of the table when it moves, and the removable connector 20.2 is used.
By removing 0a to 20c, assembly, maintenance, inspection, etc. of the table itself can be easily performed.

Figure 4 shows the temperature detection circuit.
l r A21 r BI+ r A2 is a temperature sensing resistor, such as a platinum resistor, which is a temperature sensor, and its resistance value changes depending on the temperature change of the object to be measured. These 4
The two temperature sensors are connected in a bridge configuration and connected to a constant voltage source V via a variable resistor r for fine adjustment.

Further, the pair of temperature sensors rAIorA2 is fixed in a temperature sensor mounting pit 14 provided on a part of the linear motor, for example, the yoke 12 of the linear motor shown in FIG. The other vs. r! 11+rl12 is a temperature control reference member provided separately, such as a surface plate on which the main table is placed, or a temperature sensor mounting bit is similarly provided on the base 8 shown in FIG. 1 and is fixed there. The resistance value of the platinum side temperature resistor changes linearly with respect to temperature as shown by rwR+α·ΔT. Here, r is the resistance value of the platinum resistance temperature sensor, R2α is a constant, and ΔT is a temperature change. 4 sensors r^1゜r
Ah r B1+ r A2 temperature change ΔTA
,,ΔTA,.

ΔTB1. When ΔT0 is assumed, the output voltage e is expressed as follows assuming that the variable resistor r for fine adjustment is small.

e middle・1−i−((ΔTAI”ΔTA2)/2−(Δ
T1111"ΔT!12)/2) From the above equation, it can be seen that the output e is a voltage proportional to the difference between the average temperature of a pair of temperature sensors rAl+rA2 and the average temperature of another pair of temperature sensors ruler!12. This configuration has the following advantages over the conventionally used circuit (Fig. 10): In order to stably measure temperature without drift errors, in the conventional case, the reference resistance r,
It is necessary to have high accuracy and a very low temperature coefficient, but if the sensor is configured as a bridge as in the present invention, there is no need for a reference resistor, and an output proportional to the temperature difference from the reference temperature can be obtained. .

Figure 5 shows the temperature control circuit, each output e, ~ of the bridge circuit of the temperature sensor mentioned above corresponding to the three linear motors.
e3 is amplified by amplifiers 23a to 23c. The amplification factor of each amplifier is, for example, 100 dB. Each amplifier 23a-23
The noise amplified by c is passed through the low-pass filters 24a to 24.
c and is attenuated. Since the temperature changes relatively slowly, the cut-off frequency of this low-pass filter may be low, for example IHz. Low pass filter 24a~
The signal passing through 24c is sent to hysteresis circuits 25a to 25.
c and is shaped into an ON-OFF signal for opening and closing a solenoid valve. This 0N-OFF signal is the power amplifier 26a~2
The solenoid valves 19a to 19c are turned on and off via the solenoid valve 6c. Figure 6 shows such a temperature control circuit 81 * 62
+ Three systems are shown for the three inputs of A3, which correspond to the three linear motors of the table device explained in FIG. Also, a solenoid valve 19 for bypass
d is the ON/OFF logic of the NOR circuit 2F, that is, the three solenoid valves 19a to 19c corresponding to the linear motor.
, B, and C are controlled by a circuit (AnBnC=AUBUC) that turns ON when these three solenoid valves are closed simultaneously.

Next, the operation of the embodiment of the present invention having the above configuration will be explained. When driving the table, the coil 11 of the linear motor
(Figure 2) is energized. As a result, the movable element consisting of the yoke 12 moves linearly, and Joule heat is generated in the coil. This value is at most 1 in the table in this example.
It is 2.5W.

When this heat is transmitted through each part and reaches the base 8 (FIG. 1), it causes a temperature distribution in the base 8. If the base is deformed due to this temperature distribution, the table movement accuracy will deteriorate because the base is the accuracy standard for the table of this configuration. However, in this embodiment, the When the temperature of the coil rises due to heat, the temperature of the yoke 12 and spacer 13 that surround this coil also rises, and the resistance value of the temperature sensor r Al + r A2 attached to the temperature sensor mounting bit 14 (Fig. 2) increases. . On the other hand, since the temperature rise of the base is slower than the temperature rise of the yoke of the linear motor, a reference temperature sensor r! 11+'! The resistance value of 12 remains unchanged. Therefore, the balance of the temperature difference detection bridge circuit shown in FIG. 4 is lost, and an 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. open. In FIG. 3, when the solenoid valves 19a to 19C are opened, the refrigerant pumped by the pump 18 flows through the flexible tube 22 to the near motor cooling pipes 21a to 21c (refrigerant passage 16 in FIG. 2). The heat generated by the Joule heat is removed.

Therefore, this control circuit can bring the temperature difference between the linear motor and the base close to zero. When the temperature difference approaches zero, heat flow is suppressed, and the base temperature becomes stable. In the table of this embodiment, the flatness of the top surface of the base is the accuracy criterion, so if the temperature of the base is stable, there will be 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 rA is important. The part of the coil that generates heat is hot and the area around the cooling pipe is cold, but unless the average temperature of both is detected and controlled, it is difficult to remove the amount of heat generated in just the right amount.

For example, according to experiments, when a temperature sensor is attached to the side of the coil 11, the temperature of the yoke 12 reaches zero in 1.5 hours.
．． The temperature of X stage 2 increased by 5℃ and the temperature of X stage 2 also increased by 0.6℃.
℃ rose.

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.S to +0.2°C, and the temperature of the X 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 measurement sensors 30a to 30c are installed on a base 8. Since the base 8 of a semiconductor exposure device generally occupies a large area of about 400 mm x 400 ms, it is difficult to eliminate the temperature distribution of the base 8 and make it completely uniform.Therefore, the base 8 is balanced by having a certain temperature distribution. Consider the case. The first mentioned above
In the embodiment, only one temperature sensor was provided in the base, and that temperature was 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 will flow, and the heat from the linear motor will be transferred to the base.

Therefore, in this second embodiment, the reference temperature measurement points are increased,
Measure the base average temperature near the linear motor for each linear motor, and use these as the reference temperature. That is, in the temperature control of the linear motor 6a in FIG.
The temperature control circuit controls the temperature difference between temperature sensor 30a and temperature sensor 30a to zero. 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 X stage, the temperature sensor 30c in the hole 29c is used, and the output of each temperature sensor is referenced. Temperature control as temperature. By providing a plurality of reference temperature measurement points in this manner, the temperature difference between the linear motor and the base near the linear motor can be reduced to zero, so that no heat is transferred between the two. therefore,
Even if there is a temperature distribution in the base, it is possible to suppress the flow of heat between the linear motor and the base, and the temperature of the base can be kept constant.

The other configurations and effects are the same as those of the first embodiment described above.

FIG. 7 shows a third embodiment of the present invention. In the second embodiment, a configuration was described in which heat flow can be suppressed even if the base (surface plate) has a certain temperature distribution. Embodiment 3 shows a configuration that deals with a case where the temperature of a member other than the base that is relatively close to the linear motor, such as the X stage or the X stage, is different from the temperature of the base. A temperature difference is created between the material and nearby components, and heat flows. Therefore, if the reference temperature measurement point is moved closer to the linear motor, such local temperature distribution will be further relaxed. FIG. 7 is a cross-sectional view of the XX stage taken along a plane perpendicular to the direction of movement of the X stage. The heat insulating material 34 is provided to prevent the heat generated by the linear motor from diffusing to the surroundings. The reference temperature measurement sensor 9a is attached to the X stage as shown by X stage 1 or 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 X stage can be reduced to zero, and heat flow can be suppressed. can.

FIG. 8 shows a fourth embodiment of the invention. In the first embodiment, a solenoid valve was used to control the flow rate of the refrigerant. Therefore, the speed of the refrigerant also changes rapidly when the solenoid valve is turned on and off. For this reason, ffI shock vibrations occur, causing the linear motor and flexible tube 22 connected to the cooling pipe line to
oscillate. Such vibrations are extremely harmful to tables that require precise movement control. Therefore, as shown in FIG. 8, instead of the electromagnetic valves, flow rate control valves 38a to 38d, which can adjust the flow rate, are used to prevent sudden changes in the flow rate. The valve control circuit in this case is shown in FIG. 9. FIG. 9 shows the general P
This shows a circuit for controlling the flow rate control valves 38a to 38c via an ID controller 40 and a power amplifier 41 for driving the flow rate control valves.The bypass circular valve 38d also has three valves 38a to 38c as in the previous embodiment. Opens when closed.

With this configuration, the flow rate can be changed relatively gently, and harmful vibrations caused by sudden changes in the flow rate can be prevented.

[Effects of the Invention] As explained above, by providing the temperature control device according to the present invention, the temperature difference between the average temperature of the base or surface plate, which is the precision reference member of the table, and the average temperature of the motor part, which is the heating element, can be reduced. Since the temperature can be brought close to zero, the heat flowing in and out of the accuracy reference member of the table is suppressed, and the temperature distribution of the table accuracy reference member becomes steady and stable. Therefore, the shape stability of the table accuracy reference member is guaranteed,
High table movement accuracy can be maintained.

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 case of the table having the structure shown in the embodiment.

[Brief explanation of the drawing]

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 train constituting the present invention, and FIG. 3 is a perspective view of a temperature control device according to the present invention. Refrigerant system diagram, 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 the second embodiment of the present invention, and FIG. 7 is a perspective view of a third embodiment of the present invention,
FIG. 8 is an explanatory diagram of another example of the temperature control device according to the present invention,
FIG. 9 is a control circuit diagram of the temperature control device shown in FIG. 8, and FIG. 10 is a conventional temperature detection circuit diagram. 1: x stage, 2: Y stage, 5.6: linear motor, F: guide, 8: base, 9.30: temperature sensor, 11: coil, 12: yoke, 16: refrigerant passage, 22: flexible tube. Patent Applicant Canon Co., Ltd. Agent Patent Attorney Tetsuya Ito Agent Patent Attorney Tatsuo Ito Figure 3 ■ Figure 4 Figure 5 Section 7 Figure 8 Figure 9 ■ Figure 10

Claims (9)

[Claims] (1) A base, a stage that moves on the base, a driving means for moving the stage, a cooling means for cooling the driving means, and a first temperature for detecting the temperature of the base. a detection means, a second temperature detection means for detecting the temperature of the drive means, and a control means for controlling the cooling means so that the difference in output from the first and second temperature detection means becomes zero. A precision moving table characterized by: (2) The stage includes two parallel guides provided on the base, a first stage mounted between the two guides and sliding linearly along the guides, and a second stage that is mounted on the stage and slides in a direction perpendicular to the sliding direction of the first stage, and a first stage that supports the first stage slidably with respect to the base and the guide. and a second stage air bearing means for slidably supporting the second stage with respect to the base and the first stage. precision moving table. (3) The driving means is a linear motor comprising a stator equipped with one of a coil or a magnet, and a mover equipped with the other one of the coil or magnet that moves linearly along the stator. Claim 1 characterized in that
2. Precision movement table according to item 2 or item 2. (4) The cooling means includes a refrigerant tank, a refrigerant passage provided in the stator of the linear motor, a refrigerant circulation path connecting the refrigerant tank and the refrigerant passage, and a refrigerant circulation system connected to the refrigerant passage. 4. A precision moving table according to claim 3, comprising a flexible tube constituting a passage, and a refrigerant control valve means provided on said refrigerant circulation system passage. (5) Claims 1 to 4, characterized in that the first and second temperature sensing means are comprised of temperature-measuring resistors.
Precision moving table described in any one of the preceding paragraphs. (6) A bridge circuit for obtaining an output according to the difference in resistance value of the resistance temperature detectors constituting the first and second temperature sensing means is constructed using the resistance temperature detectors. A precision movement table according to claim 5. (7) A precision moving table according to claim 5 or 6, characterized in that the temperature measuring resistor is provided at a plurality of different positions within the base. (8) The precision movement table according to any one of claims 1 to 7, wherein the first temperature detection means is provided on the stage. (9) The cooling means includes first and second cooling systems for respectively cooling linear motors attached to both guides for the first stage, and a linear motor for driving the second stage. and a third cooling system path for cooling, the valve means are provided on each cooling system path, and each valve means is configured to be controllable according to the temperature difference between each of the three linear motors and the base. A precision movement table according to any one of claims 4 to 8.