JP3202308B2 - Composite positioning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed and high-precision positioning device for a stage mounted on a surface plate supported by a vibration isolator, and more particularly to a reaction force applied to the surface plate when the stage itself is driven. The present invention relates to a composite positioning device configured to fit.

[0002]

2. Description of the Related Art In an LSI manufacturing apparatus such as an electron microscope or a stepper to which an electron beam is applied, a configuration in which a positioning device is mounted on a vibration isolator is adopted. Usually, an XY stage driven in two horizontal axes is generally used as a positioning device. Such an anti-vibration device has a function of attenuating the vibration by a vibration absorbing means such as an air spring, a coil spring, and an anti-vibration rubber. However, in the passive vibration isolator, there is a problem that even if the vibration transmitted from the floor can be attenuated to some extent, the vibration generated by the positioning device mounted thereon cannot be effectively attenuated. That is, the reaction force generated by the high-speed movement of the positioning device itself shakes the vibration isolator, and this vibration is a disturbance that hinders the high-speed and high-precision positioning of the positioning device.

For example, FIG. 4 shows a deviation signal in a position control system when a positioning device (stage) mounted on a surface plate provided with a vibration isolator is step-driven. As shown in the figure, a transient vibration of the natural frequency of the position control system occurs at an early stage of the waveform. However, it decayed relatively quickly, and the subsequent waveform has a long superimposition of the vibration of the natural frequency of the surface plate. Therefore, productivity was significantly impaired as a result of prolonging the position settling time.

[0004] This phenomenon is formulated as follows using a dynamic model when a stage is mounted on a surface plate.

FIG. 5 shows the X of the stage 1 mounted on the surface plate 2.
Alternatively, it is a dynamic model in one horizontal Y-axis direction. As shown, the dynamic model has two degrees of freedom including the surface plate 2 and the stage 1. Here, the equation of motion is represented by the following equation using the symbols shown.

[0006]

(Equation 1) However, the meaning of each symbol is as follows.

M ₁ : Stage mass [kg], m ₂ : Surface plate mass [kg], b ₁ : Viscous friction coefficient of stage [Ns /
m], b ₂ : viscous friction coefficient of the surface plate [Ns / m], k ₁ : spring constant of the stage [N / m], k ₂ : spring constant of the surface plate [N / m], x ₁ : Stage displacement [m], x ₂ : surface plate displacement [m], f ₁ : driving force [N].

When this is expressed in a block based on the above equation, a portion 3 surrounded by a broken line in FIG. 6 is obtained. That is, 3 indicates a control target. Parts other than the broken lines are blocks of the position control system. In the figure, reference numeral 4 denotes a position detecting and converting means, 5 a compensator for improving the characteristics of a position control system, 6 a power amplifier, and 7 an actuator. However, it is assumed that the position detection conversion means 4 includes, for example, a laser interferometer and a deviation counter as position detectors.

The operation of FIG. 1 will be described below. First, x ₀ is the deviation between the detected position (x ₁ -x ₂₎ the target position x ₀ -
(X ₁ −x ₂ ) is multiplied by the position gain k _p of the position detecting and converting means 4. Further, the power amplifier 6 is driven through the compensator 5 for improving the characteristics of the position control system. Finally, the thrust constant k _{t of} the actuator 7 that drives the positioning device
Through the transformation it is configured to generate a driving force f ₁ by.

Here, the feedback of the position is detected by (x
_The reason for ₁₋ x ₂ ) is that, for example, a laser interferometer, which is a position detecting means, is usually installed on the surface plate 2 in a normal case. In the case shown in the figure, the compensator for improving the characteristics of the position control system is a PID compensator, which means P: proportional operation, I: integral operation, and D: differential operation. Further, the meanings and dimensions of the illustrated symbols are as follows.

K _p : position gain [V / m], F _x : P operation gain [V / V], F _i : I operation gain [V / Vse
c], F _v: D operation gain [Vsec / V], K _i: Driver Gain [A / V], T _d: When the driver constant [s
ec], K _t : Thrust constant [N / A], s: Laplace operator [rad / sec].

Conventionally, as a method of suppressing the influence of the reaction force due to the driving of the stage 1 on the position (x ₁ -x ₂ ), an input of a power amplifier 6 for driving the stage 1 by detecting an acceleration signal of the base 2 is provided. A method of feeding back to the department was known. For example, in the literature, the Journal of Precision Engineering, "Air-floating high-speed XY
Stage prototype (JSPE-52-10, '86 -10)
-1713) ”discloses a configuration in which a surface plate acceleration is detected and fed back to a control system.

[0013]

However, the above-mentioned prior art has the following problems.

First, in order to prevent the vibration of the floor from being transmitted to the stage, the vibration isolator must be soft. By doing so, the effect of floor vibration can be reduced. However, with such a soft configuration, the vibration generated by the stage mounted on the vibration isolator cannot be effectively attenuated. Conversely, if the surface plate is made hard, the rigid surface plate will not move even if there is a driving reaction force of the stage. However, in this case, since the floor vibration is transmitted directly, the vibration isolation performance against the floor vibration is sacrificed. That is, vibration isolation and vibration suppression have a trade-off relationship with each other. Conventionally, a balance between vibration isolation and vibration suppression has to be taken for each installation location of a surface plate on which a stage is mounted. Therefore, the adjustment work is complicated, and there is a problem that the start-up period of the apparatus is significantly prolonged.

Secondly, as a method of avoiding the above-mentioned trade-off by control means, there is known a surface plate acceleration feedback method of detecting an acceleration signal of an anti-vibration device and feeding it back to a driver input terminal of a stage. Journal of the Japan Society of Precision Engineering, “Prototype of an Air Levitated High Speed XY Stage (JSPE
-52-10, '86 -10-1713) "). However, for detecting the surface plate acceleration signal, for example, a servo type acceleration sensor having high detection sensitivity at a low frequency must be used. This servo acceleration sensor is expensive,
Also destroyed by a small mechanical shock. Also, the installation of such an acceleration sensor and the optimal adjustment thereof have been very troublesome.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and does not use a servo-type acceleration sensor that is expensive, fragile, and has troublesome detection setting adjustment. It is an object of the present invention to provide a composite positioning device that achieves the vibration damping action of the above, thereby maximizing the vibration damping action of vibration from the floor.

[0017]

In order to achieve the above object, according to the present invention, at least two stages are mounted on a platen supported by a vibration isolator, and the reaction forces against the platen are mutually canceled. Thus, the composite positioning apparatus is characterized in that the stage is driven synchronously. In other words, in the conventional positioning device, the driving force of the stage was directly applied as a reaction force to the surface plate supported by the vibration isolator, but the stage was supported by the vibration isolator and mounted on the surface plate. At least two or more positioning devices, a speed / position control device that drives stages of each positioning device, and an impulse that is a product of acceleration / deceleration start time and acceleration / deceleration time and driving force in driving each stage. And a synchronizing controller for performing a synchronous operation in which the signs of the impulse of the two are opposite to each other, the reaction force of the stage drive is canceled each other.

The above operation will be described using mathematical formulas based on a dynamic model. Now, the dynamic model of the stage mounted on the surface plate is as shown in FIG. As shown in the figure, two stages 1a and 1b are mounted on the surface plate 2. This equation of motion is as follows.

[0019]

(Equation 2) Therefore, the block diagram of the above equation is shown in FIG. here,
The total reaction force on the surface plate 2 caused by the driving of the stages 1a and 1b is obtained by adding the respective reaction forces with a minus sign as shown in the right side of the equation (2C). This acted on the surface plate as a forcing force, and the surface plate was being moved. However, the following equation (3)

[0020]

(3) If driven so as to satisfy the relationship of f _1a = −f _1b (3), the right side of the expression (2c) becomes zero. That is, there is no force for driving the surface plate. The condition of equation (3) is, that is, stage 1
a and 1b are driven in opposite directions.

[0021]

FIG. 1 is a block diagram of a composite positioning apparatus according to an embodiment of the present invention. In the figure, reference numeral 8a denotes a stage to be positioned, on which a mirror 9a is mounted, and the position is measured by a laser interferometer 10a. Then, the rotational movement of the DC motor 11a with the tacho generator 14a is transmitted to the ball screw 12a, and the movement is converted via the nut 13a to drive the stage 8a in a linear direction.

Accordingly, the movement mechanism including the DC motor 11a, the tach generator 14a, the ball screw 12a, the nut 13a, and the stage 8a constitutes a positioning device mounted on the stage base 15a. Further, the positioning device is mounted on a surface plate 16 of a main body supported by a vibration isolator 17 for blocking floor vibration.

Next, a control device for driving the stage 8a will be described. First, reference numeral 18a denotes a digital-to-analog converter (hereinafter abbreviated as DAC) that operates with a deviation between the laser interferometer 10a and a target value. This output is output to the position controller 19
a and the amplifier 20a. The output of the amplifier 20a is output when operating in the speed mode, and the position controller 1 is output when operating in the position mode.
9a is selected by the electronic switch 25a, and the speed controller 2 connected after the electronic switch 25a is selected.
1a and the current controller 22a are sequentially excited. That is, the DAC 18a, the position controller 19a, the amplifier 20a,
Electronic switch 25a, speed controller 21a, current controller 2
2a constitutes the speed position control device 23a.

Note that, as shown in FIG. 1, the meaning of the reference numeral b is the same as the description of the reference numeral a.

In the above-described configuration, the synchronous controller 24 manages both the speed position controller 23a for driving the stage 8a and the speed position controller 23b for driving the stage 8b. Here, the stages 8a and 8b
Are controlled in such a manner that the motors are driven in opposite directions. Specifically, the stages 8a and 8b are both operated in the speed mode for most of the stroke, and are switched to the position mode when entering the vicinity of the target position, and are finally positioned at the target position. Among these operation modes, the speed mode includes three sections of acceleration-constant speed-deceleration, and the section in which the reaction force of the stage drive is generated is mainly the acceleration and deceleration section. Therefore, the stages 8a and 8b are driven with the start time of acceleration / deceleration being matched, and the absolute value of the impulse which is the product of the duration of acceleration / deceleration and the driving force generated by the current controllers 22a and 22b is calculated. The function of the synchronous controller 24 is to make the synchronous operation such that they coincide with each other and the signs of the impulse are opposite to each other.

In the above embodiment, two positioning devices having substantially the same characteristics are mounted on the surface plate 16, and these are driven under the control of the synchronous controller 24. That is, the masses of the stages 8a and 8b, the models of the DC motors 11a and 11b,
Viscous friction, static friction, spring constant of a motion mechanism composed of ball screws 12a, 12b and nuts 13a, 13b,
The driving device is a positioning device having almost the same driving pitch.

However, as shown in the equation (3), another configuration may be adopted as long as the reaction force generated by the stage drive cancels each other and the base plate 16 is not shaken. That is, it is not always necessary that the positioning device has almost uniform characteristics. The positioning devices having different masses of the stages 8a and 8b may be used. In short, synchronous operation is performed in which the start times of acceleration and deceleration are matched to drive the two stages, the absolute values of the impulse during acceleration and deceleration are matched, and the signs of the impulse are opposite to each other. It just has to be done.

Further, in the two positioning devices shown in FIG. 1, both of the DC motors 11a and 11b, the tachogenerators 14a and 14b, the ball screws 12a and 12b,
Although the exercise mechanism includes the nuts 13a and 13b and the stages 8a and 8b, it is needless to say that the present invention is not limited to this. For example, one positioning device may be a positioning device having a ball screw and a nut in a motion conversion mechanism, and the other positioning device may be a positioning device having no motion conversion mechanism using a linear motor as an actuator.

[0029]

As described above, the present invention provides a composite positioning apparatus having at least two stages mounted on a surface plate and operating synchronously so that their driving reaction forces cancel each other. I have. Therefore, there is an effect that the platen is not shaken. That is, since the vibration of the surface plate mechanism is no longer excited, there is an effect that the positioning time can be shortened by not superimposing the vibration on the positioning waveform of the stage. Further, since the two stages are mounted on the same surface plate, productivity is improved. In addition, since it is not necessary to arrange a plurality of devices each having a stage mounted on the surface plate as one unit, the floor space occupied by the devices can be reduced. In addition, conventionally, a transport device for handling objects mounted on the stage was required for each unit,
Since one transfer device may be installed for the composite positioning device on which at least two stages are mounted, the cost is reduced and the installation area is not increased.

Further, in the conventional positioning apparatus, since there is a trade-off relationship between vibration isolation and vibration suppression, it is necessary to balance the two. That is, neither the anti-vibration performance nor the vibration suppression performance could be set optimally. However, according to the present invention, it is no longer necessary to consider the problem of vibration suppression due to the stage drive, and therefore, the surface plate may be designed only in consideration of the vibration isolation performance. Therefore, unlike the conventional case, a situation in which the vibration isolation performance is sacrificed to some extent is avoided, and a high-performance vibration isolation device pursuing only the vibration isolation performance can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a composite positioning device according to an embodiment of the present invention.

FIG. 2 is a mechanical model diagram of two stages mounted on a surface plate in one horizontal axis direction.

FIG. 3 is a block diagram in a horizontal I-axis direction of two stages mounted on a surface plate.

FIG. 4 is a step response waveform diagram of a stage mounted on a surface plate.

FIG. 5 is a mechanical model diagram of a stage mounted on a surface plate in one horizontal axis direction.

FIG. 6 is a control block diagram of an I control system for a stage mounted on a surface plate.

[Explanation of symbols]

Reference Signs List 1; Stage 2, Surface plate 3, Control target 4, Position detection conversion means 5, Compensator 6, Power amplifier 7, Actuator, 8a, 8b, Stage, 9a, 9b, Mirror, 10a, 10b A laser interferometer, 11a, 11b;
DC motors, 12a, 12b; ball screws, 13a, 1
3b; nut, 14a, 14b; tachogenator, 15
a, 15b; stage surface plate, 16; surface plate, 17; anti-vibration device, 18a, 18b; digital / analog converter,
19a, 19b; position controller, 20a, 20b; amplifier, 21a, 21b; speed controller, 22a, 22b; current controller, 23a, 23b; speed position controller, 24;
Synchronous controller, 25a, 25b; electronic switch.

Continuation of the front page (56) References JP-A-62-108185 (JP, A) JP-A-5-82579 (JP, A) JP-A-62-26555 (JP, U) (58) Fields investigated (Int .Cl. ⁷ , DB name) H01L 21/027 H01L 21/68

Claims (3)

(57) [Claims] 1. A surface plate supported by a vibration isolating means, a plurality of stages mounted on the surface plate, each of which can be independently driven and controlled, and a speed and a position controlled by driving each stage. Synchronous control for synchronizing the speed position control device and each stage so that the sum of the impulse, which is the product of the acceleration / deceleration time and the driving force, becomes equal to the start of acceleration / deceleration when driving each stage. A composite positioning device comprising means. 2. The apparatus according to claim 2, wherein the two stages are mounted, and the synchronous control unit matches the impulse, which is the product of the start of acceleration / deceleration and the acceleration / deceleration time, with the driving when driving each stage.
2. The composite positioning apparatus according to claim 1, wherein each stage is operated synchronously so that the signs of the impulse of the two are opposite to each other. 3. A laser interferometer for measuring the position of each stage, and a D / A converter operating with a deviation between the output of the laser interferometer and a target value, wherein the output side of the D / A converter is selectively switched by an electronic switch. An output side of the position controller and the amplifier is connected to a speed controller via an adder / subtractor together with an output of a tacho generator of a stage driving DC motor, and the speed controller is connected to a switchable position controller and an amplifier. The speed position control device is further connected to a current controller, and comprises the DA converter, a position controller, an amplifier, an electronic switch, a speed controller, and a current controller. 1. Composite positioning device.