JPH05250041A - Positioning device provided with multiple acceleration feedback - Google Patents

Abstract

PURPOSE:To make influences exerted by disturbance impressed to a surface plate upon a fine moving stage and a coarse moving stage none at all or minimum in the positioning device consisting of the coarse moving stage mounted on the surface plate and the fine moving stage provided on that coarse moving stage. CONSTITUTION:This positioning device consists of a fixed board 2 composed of an oscillation removing device, coarse moving stage 1 loaded on the fixed board 1, and fine moving stage 9 loaded on the coarse moving stage 1. The device is provided with a coarse moving stage acceleration feedback means 14 to detect the acceleration signal of the coarse moving stage 1 and to add it to the driving force of the fine moving stage 9, and a fixed board acceleration feedback means 18 to detect the acceleration of the fixed board 2 and to add it to the driving force of the coarse moving stage 1. Further, the coarse moving stage acceleration feedback amount performs optimum feedback to the variable amount of the fine moving stage 9, and the fixed board acceleration feedback amount performs optimum feedback to the variable amount both of the coarse moving stage 1 and the fine moving stage 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning device used in, for example, a semiconductor exposure device for printing a reticle or mask pattern on a substrate, a liquid crystal substrate manufacturing device, an electron microscope, etc. , A positioning device including a coarse movement stage mounted on the coarse movement stage and a fine movement stage further mounted on the coarse movement stage for improving high-speed and high-accuracy positioning by significantly suppressing response from disturbance It is about.

[0002]

2. Description of the Related Art In a LSI manufacturing apparatus such as an electron microscope or a stepper that applies an electron beam, a structure in which an XY stage, which is a coarse movement stage, is mounted on a vibration isolation device, and a fine movement stage is further mounted thereon is adopted. It The vibration isolator in this configuration has a function of damping vibration by vibration absorbing means such as an air spring, a coil spring, and a vibration isolating rubber. However, in the passive vibration isolator, there is a problem that the vibrations transmitted from the floor can be damped to some extent, but the vibrations generated by the coarse movement stage itself or the fine movement stage itself mounted therein cannot be effectively damped. That is, the reaction force generated by the high-speed movement of the coarse movement stage itself causes the vibration isolation device to swing, and this vibration becomes a disturbance that hinders the high-speed and high-precision positioning of the coarse movement stage. Further, the reaction force against the high-speed movement of the fine movement stage itself shakes the coarse movement stage, and this swing is also transmitted to the vibration isolation device, and this vibration becomes a disturbance factor that hinders high-speed and high-precision positioning of the fine movement stage.

First, a vibration isolation device (hereinafter abbreviated as a surface plate)
The related technical contents of the present invention will be described by the formulation of the dynamic model when only the coarse movement stage is mounted on the top.

FIG. 5 shows a coarse movement stage 1 mounted on a surface plate 2.
Is a mechanical model in the X or Y horizontal 1-axis direction. As shown in the figure, the mechanical model has two degrees of freedom including the surface plate 2 and the coarse movement stage 1. Here, the equation of motion is expressed as follows using the symbols shown.

[0005]

[Equation 1] However, the meaning of each symbol is as follows.

M ₁ : Mass of coarse stage [Kg] m ₂ : Mass of plate [Kg] b ₁ : Coefficient of viscous friction of coarse stage [Ns / m] b ₂ : Coefficient of viscous friction of plate [Ns / m ] K ₁ : Spring constant of coarse movement stage [N / m] k ₂ : Spring constant of surface plate [N / m] x ₁ : Coarse movement stage displacement [m] x ₂ : Surface plate displacement [m] f: Coarse Dynamic stage driving force [N] f _ext : Disturbance [N]

When the above equation is expressed as a block, the controlled object 3 shown by the broken line in FIG. 6 is obtained. Here, from f and f _ext , x ₁ and x
First, find the relationship up to ₂ . However, s is a Laplace operator.

[0008]

[Equation 2]

Therefore, from f and f _ext , the relative displacement (x ₁
The relationship up to −x ₂ ) is as follows. However, the reason why the position detection is relative displacement (x ₁ -x ₂ ) is that the laser interferometer of the position detection means with respect to the coarse movement stage 1 is the surface plate 2.
Because it will be installed in.

[0010]

[Equation 3]

Conventionally, the disturbance fext has a relative displacement (x ₁ −
As a method of suppressing the influence on x ₂ ), there is a method of detecting the acceleration signal of the surface plate 2 and feeding it back to the power amplifier input section for driving the coarse movement stage 1. That is, there has been known a method of adding the surface plate acceleration signal to the driving force of the coarse movement stage 1. For example, the literature, the journal of Japan Society for Precision Engineering, “Prototype of high-speed air XY stage (JSPE-52-10, '8
6-10-1713) ”discloses a configuration in which the surface plate acceleration is detected and fed back to the control system.

The effect of this platen acceleration feedback will be considered based on the equation of motion.

First, the following equation of motion is established.

[0014]

[Equation 4]

In this case, the relational expression similar to the expression (3) is as follows.

[0016]

[Equation 5]

As is clear from the above equation, the influence from the disturbance f _ext to the relative displacement (x ₁ -x ₂ ) is the acceleration feedback gain A,

[0018]

[Equation 6] You can make it zero by choosing. The relation of the above equation (6) is
Although the discussion has been made in the case where the position control loop is not configured for the controlled object 3, for example, when the position control loop is configured, the relation of the expression (6) can be similarly derived. For confirmation, how to reduce the response from the disturbance f _ext to the relative displacement (x ₁ −x ₂ ) when the surface plate acceleration feedback is applied when the position control loop is configured will be described below.

FIG. 6 is a control block diagram when a position control system is constructed for the dynamic model shown in FIG. In the figure, 3 is a control target which is the block representation of FIG.
Is a position detection conversion means, 5 is a compensator for improving the characteristics of the position control system, 6 is a power amplifier, 7 is a thrust constant of the actuator, and 8 is a platen acceleration feedback circuit. However, the position detection conversion means 4 includes, for example, a laser interference system as a position detector and a deviation counter.

The operation of the figure will be described below. First, to detect the relative displacement _{(x 1 -x 2), x} 0 is the deviation between the target position x ₀ - position gain K _p of the position detecting transformation unit 4 is multiplied with respect to (x ₁ -x ₂₎ .. Further, the power amplifier 6 is driven through the compensator 5 for improving the characteristics of the position control system.
Finally, the driving force f is generated through conversion by the thrust constant K _t of the actuator that drives the coarse movement stage 1. In the illustrated case, 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: derivative operation, respectively. Further, the meanings and dimensions of the symbols shown in the figure are as follows.

K _p : Position gain [V
/ M] F _x : P operation gain [V / V] F _i : I operation gain [V / Vsec] F _v : D operation gain [Vsec / V] K _i : Power amplifier gain [A / V] T _d : time constant [sec] K _t of the power amplifier: thrust constant [N / a] a _a: plate acceleration feedback gain [V / m / sec
² ] T _a : Time constant of acceleration signal [sec]

In the position control system of FIG. 6, the target position x ₀
And the relation from the disturbance f _ext to the relative displacement (x ₁ −x ₂ ) are as follows. However, here, the surface plate acceleration feedback circuit 8 is not yet turned on.

[0023]

[Equation 7]

Next, the relational expression when the surface plate acceleration feedback circuit 8 is made to function is as follows.

[0025]

[Equation 8]

The above equations (8a) and (8b) indicate that the positioning time is the sum of the responses from the target position x ₀ and the disturbance fext. Therefore, the disturbance f _ext
Therefore, suppressing the influence on the relative displacement (x ₁ −x ₂ ) is important not only for shortening the positioning time but also for ensuring the positioning accuracy.

Now, consider only the response from the disturbance f _ext with x ₀ = 0 in the expression (8a). Extracting the expression in [] in the numerator polynomial of the disturbance term

[0028]

[Equation 9] Is. Therefore, if the surface plate acceleration feedback gain A _a is set as in the following equation, the response from the disturbance f _ext can be considerably reduced compared to the case of the equation (7a).

[0029]

[Equation 10]

This relational expression shows the same contents as the expression (6). That is, in the case of the expression (6), the surface plate acceleration feedback gain A is specified in the unit of mass, but in the case of the expression (10), the unit of the acceleration detection gain A _a is V / m / se.
and c ^2, and is the gain of the power amplifier Symbol 6 for generating a driving force and its time constant is taken into account. Therefore, there is no essential difference in discussion.

[0031]

[Equation 11] Is equivalent.

From the above analysis, the effect of acceleration feedback for reducing the influence from the disturbance f _ext to the relative position (x ₁ -x ₂ ) can be discussed even in a state in which a control loop such as a position control system is assembled. Although it is good, it can be easily understood that the discussion may be made on the configuration of only the control target that does not configure the control loop. In short, the base plate acceleration that reduces the influence from the disturbance f _ext to the relative displacement (x ₁ -x ₂ ) which is the position detection output of the coarse motion stage when positioning is performed when only the coarse motion stage is mounted on the base plate. The effect of feedback was shown.

[0033] In summary, the relative displacement from the disturbance f _ext in when optimally set as if the surface plate acceleration feedback and without the feedback gain (10) (x ₁ -
The transfer functions up to x ₂ ) are as follows.
(1) When there is no surface plate acceleration feedback

[0034]

[Equation 12] (2) When the platen acceleration feedback is optimally set

[0035]

[Equation 13]

Looking at the numerator polynomials of the equations (12) and (13), it is understood that the equation (12) has a lower order by one. Also, from the results of numerical analysis and actual measurement of frequency response, it is known that the main roots of the characteristic equation of the position control system hardly change with or without the platen acceleration feedback. Therefore, by comparing the orders of the numerator polynomials of the equations (12) and (13), the optimum setting of the surface plate acceleration feedback gain as shown in the equation (10) is performed.
The response of the low frequency component will be suppressed more than in the case without the same feedback.

The above formulation will be shown by experimental facts. That is, the actual measurement result of the step response waveform of the coarse movement stage is shown to compare with the presence or absence of the platen acceleration feedback. FIG. 7A shows the deviation output of the position control system when the coarse motion stage is step-responsive when there is no platen acceleration feedback. In this case, a phenomenon occurs in which transient vibration is generated at the natural frequency of the position control system, and then vibration is repeated at the natural frequency of the surface plate mechanism for a long time. However, in the case of FIG. 6B, the platen acceleration feedback is set almost optimally, and although transient vibration occurs at the natural frequency of the control system at the initial stage of the step response, the subsequent platen mechanism Vibration of natural frequency is suppressed.

[0038]

As described above, the conventional example relates to the positioning when only the coarse movement stage is mounted on the surface plate, and is intended to improve the positioning accuracy from the disturbance and the positioning time. It was However, in the positioning device including the surface plate, the coarse movement stage, and the fine movement stage, the performance of the uppermost fine movement stage plays a final important role. This circumstance is quite natural when the positioning device is a stepper. That is, no matter how much the positioning performance of the coarse movement stage with respect to the disturbance is improved, the accuracy of printing on the IC wafer cannot be expected unless the positioning performance of the fine movement stage mounted thereon is considered a problem. In other words, it is not possible to focus only on the performance improvement of the coarse movement stage located at the intermediate stage among the three movable mechanisms that constitute the positioning device. The final performance indicator of the positioning device is the printing accuracy,
It is not the positioning accuracy of the coarse movement stage itself. In order to improve the baking accuracy, it is necessary to improve the positioning accuracy of the fine movement stage which is located at the uppermost stage and directly positions the IC wafer. In the conventional technique, the technical content is to add the surface plate acceleration signal to the driving force of the coarse movement stage in the configuration in which only the coarse movement stage is mounted on the surface plate. Therefore, a method of reducing disturbance for a positioning device in which three types of movable mechanisms, that is, a surface plate, a coarse movement stage, and a fine movement stage are integrated in order from the floor has not been clearly shown.

The present invention has been made in view of the above points, and is a positioning device including a coarse movement stage mounted on a surface plate and a fine movement stage installed thereon.
The purpose is to reduce or significantly reduce the influence of disturbance applied to the surface plate on the positioning characteristics of both the fine movement stage and the coarse movement stage.

[0040]

In order to achieve the above object, the present invention detects the acceleration of a surface plate and adds it to the driving force of the coarse movement stage, and detects the acceleration of the coarse movement stage to detect the fine movement stage. Provided is a positioning control device having multiple acceleration feedback that is added to the driving force of.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a control block showing the structure of a position control system provided with multiple acceleration feedback for a positioning device comprising a surface plate, a coarse movement stage and a fine movement stage according to an embodiment of the present invention. It is a figure. Prior to the explanation of the figure, the related technical contents will be explained by using a horizontal uniaxial dynamic model of a positioning device comprising a surface plate, a coarse movement stage and a fine movement stage shown in FIG.

FIG. 2 shows a mechanical model in which the coarse movement stage 1 is mounted on the surface plate 2 and the fine movement stage 9 is present on the coarse movement stage 1. Here, the equation of motion is expressed as the following equation using the symbols shown.

[0043]

[Equation 14]

However, the meaning of each symbol is the same as in the explanation of the equation (1), and the new symbols not explained there are as follows.

M _B : Fine movement stage mass [Kg] b _B : Fine movement stage viscous friction coefficient [Ns / m] k _B : Fine movement stage spring constant [N / m] x _B : Fine movement stage displacement [m] f _B : Fine movement stage driving force [N]

When the contents of the expressions (14a) to (14c) are expressed in blocks, the controlled object 10 shown by the broken line in FIG. 1 is obtained. In FIG. 1, 11 is a power amplifier for driving the fine movement stage 9, 12 is a compensation circuit for improving the characteristics of the position control system for the fine movement stage 9, and 13 is a position detection conversion means. Further, 15 is a power amplifier for driving the coarse movement stage 1, 16 is a compensation circuit for improving the characteristics of the position control system for the coarse movement stage 1, and 17 is a position conversion means. In the above position control system configuration, further, the acceleration of the coarse movement stage 1

[0047]

[Equation 15] To the coarse feedback stage acceleration feedback circuit 14 and add it to the input part of the power amplifier 11, and

[0048]

[Equation 16] Is provided to the surface plate acceleration feedback circuit 18 and added to the input portion of the power amplifier 15. The effect of multiple acceleration feedback will be shown below.

Here, based on the background explaining the equivalence of the equations (6) and (10), the surface plate acceleration feedback and the coarse movement are performed with respect to the controlled object 10 including the surface plate, the coarse movement stage and the fine movement stage. Formulate when multiplying the stage acceleration feedback at the same time. That is, the position and velocity control loops for the coarse and fine movement stages are not configured.

First, referring to the dynamic model of FIG. 2, the equation of motion when multiple acceleration feedback is applied is as follows, and its block expression is shown in FIG.

[0051]

[Equation 17]

From a simple calculation, the transfer function from the disturbance f _ext to the relative displacement and (x _B -x ₁ ) and (x ₁ -x ₂ ) is as follows.

[0053]

[Equation 18]

Therefore, from the equation (16a), the coarse stage acceleration feedback gain B is

[0055]

[Formula 19] Relative displacement from the disturbance f _ext by choosing the (x _B -
It is possible to reduce the influence up to x ₁ ) to zero.

Further, the surface plate acceleration feedback gain A is calculated from the equation (16b).

[0057]

[Equation 20] By choosing the relative displacement from the disturbance f _ext (x ₁ -x
It is possible to reduce the effects up to ₂ ).

That is, the optimum value of the coarse movement stage acceleration feedback gain B is an amount equivalent to the mass of the movable portion of the fine movement stage 9 mounted on the coarse movement stage 1, and the optimum value of the surface plate acceleration feedback gain A is. This is an amount corresponding to the total mass of the coarse movement stage 1 and the fine movement stage 9 mounted on the surface plate. By optimally performing these multi-acceleration feedbacks in the above-mentioned sense, it is possible to simultaneously eliminate or reduce the influence of the disturbance applied to the surface plate on the coarse movement stage and the fine movement stage.

The effects of the equations (17) and (18) hold even when a control system is configured for the fine movement stage 9 and the coarse movement stage 1. This fact has already been solved in equations (6) and (10).
It was shown in the process of deriving the formula. Therefore, as shown in FIG. 1, even when a position control system is configured for both the fine movement stage 9 and the coarse movement stage 1, the effect of suppressing the disturbance due to the multiple acceleration feedback functions effectively.

In the above-described embodiment, the coarse movement stage acceleration feedback and the platen acceleration feedback are simultaneously applied to the fine movement stage 9 and the apparatus movement stage 1, respectively. However, as shown in FIG.
Only coarse movement stage acceleration feedback may be applied to only. In this case, the disturbance f _ext applied to the surface plate
To the relative displacement (x _B −x ₁ ) is as follows.

[0061]

[Equation 21]

The meaning of the above equation is the same as that of equation (6) or (16a). That is, the acceleration feedback gain B of the coarse movement stage is set to the mass m of the fine movement stage.
If it is set to exactly the same amount as _B , the disturbance f applied to the surface plate f
The influence from _ext disappears.

The above-mentioned conventional technique is intended for the case where the coarse movement stage which is one movable mechanism is mounted on the surface plate, whereas the present invention is intended for the positioning device having three movable mechanisms. There is. Moreover, in the present invention, the influence of the disturbance f _ext applied to the surface plate on the fine movement stage existing in the uppermost stage is improved by adding the acceleration of the coarse movement stage existing in the intermediate stage to the driving force of the fine movement stage. It Such technical contents are not disclosed in the related art. Furthermore, it has not been known at all in the prior art that there is an optimum value for the acceleration feedback amount.

In the present invention, the surface plate which is the vibration isolation device is passive, but it may be an active vibration isolation device. In other words, even when the coarse vibration stage is mounted on the active vibration isolator, and the fine motion stage is present on the coarse vibration stage, even when multiple acceleration feedback is provided, it is applied to the active vibration isolator. The effect of multi-acceleration feedback is effective to reduce the effect from external disturbances.

[0065]

As described above, according to the present invention,
In a positioning device consisting of three types of movable mechanisms, the influence on the positioning characteristics of the fine movement stage existing in the uppermost stage from the disturbance applied to the surface plate and the influence on the positioning characteristics of the coarse movement stage in the intermediate stage are simultaneously reduced. There is an effect that you can. Therefore, when the positioning device is, for example, a stepper, the accuracy of printing on the IC wafer is increased, and the productivity and the yield are improved, and thereby the cost of the IC chip is reduced.

[Brief description of drawings]

FIG. 1 is a control block diagram showing a configuration of a position control system including multiple acceleration feedback in a positioning device including a surface plate, a coarse movement stage, and a fine movement stage according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a horizontal uniaxial dynamic model of a positioning device including a surface plate, a coarse movement stage, and a fine movement stage.

FIG. 3 is a block diagram when multiple acceleration feedback is applied to a positioning device including a surface plate, a coarse movement stage, and a fine movement stage.

FIG. 4 is a block diagram in which coarse movement stage acceleration feedback is applied to a positioning device including a surface plate, a coarse movement stage, and a fine movement stage.

FIG. 5 is an explanatory diagram showing a dynamic model of a coarse movement stage mounted on a surface plate in a horizontal uniaxial direction.

FIG. 6 is a control block diagram when a position control system is configured.

FIG. 7 is a step response waveform diagram of the coarse movement stage depending on the presence or absence of the platen acceleration feedback.

[Explanation of symbols]

1; coarse movement stage, 2; surface plate, 3; control target, 4; position detection conversion means, 5; compensator, 6; power amplifier, 7; thrust constant, 8; surface plate acceleration feedback circuit, 9; fine movement stage Control object, 11; Power amplifier, 12; Compensator, 13; Position detection conversion means, 14; Coarse stage acceleration feedback circuit, 15; Power amplifier, 16; Compensator, 17; Position detection conversion means, 18 A surface plate acceleration feedback circuit.

Claims (1)

[Claims] 1. A positioning device comprising a surface plate composed of a vibration isolation device, a coarse movement stage mounted on the surface plate, and a fine movement stage mounted on the coarse movement stage. The coarse movement stage acceleration feedback means for detecting and adding the coarse movement stage acceleration feedback means for detecting and adding to the fine movement stage driving force and the coarse movement stage acceleration feedback means for detecting the addition of the coarse movement stage acceleration feedback to the coarse movement stage acceleration feedback Positioning with multi-acceleration feedback characterized by optimal feedback for the movable mass of the fine movement stage, and optimal feedback for the surface plate acceleration feedback amount for the movable mass of both the coarse and fine movement stages. apparatus.