JP2889086B2 - Scanning exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning type exposure apparatus which is a semiconductor manufacturing apparatus, and more particularly to a scanning type exposure apparatus which performs a division exposure, while performing a scanning exposure while maintaining a synchronous relationship between two axes of a reticle and a wafer. The present invention relates to a scanning type exposure apparatus including a control device that performs high-precision exposure by controlling the deviation of a synchronization relationship due to disturbance, parameter variation, or the like when performing the exposure.

[0002]

2. Description of the Related Art FIG. 10 is a diagram showing a configuration of a scanning type exposure apparatus which is a conventional example and to which the present invention is applied. FIG.
Is a driving means 30 for moving the reticle 32b.
b and position detecting means 80 for detecting a reticle position
b and driving means 30a for moving the wafer 32a
And position detecting means 80a for detecting a wafer position
And the image information recorded on the reticle 32b
a projection means 20 for projecting the reticle target position, a reticle target position generating means 1b and a wafer target position generating means 1a, and a control means 2 for determining control input signals to the reticle driving means 30b and the wafer driving means 30a. .

FIG. 11 shows an example of a conventional control method for such an exposure apparatus. Here, the first axis is on the wafer side, and the second axis is on the reticle side. The first axis of the control target 3 in FIG. 11 is a secondary system shown as 3a in the figure, and the second axis is a secondary system shown as 3b in the figure. The controlled object 3a is the wafer driving means 3 in FIG.
0a and the wafer 32a, and the controlled object 3b corresponds to the reticle driving means 30b and the reticle 32b in FIG. Also, the position signals 8a and 8b in FIG. 11 correspond to the output signals 8a and 8b of the wafer position detecting means 80a and the reticle position detecting means 80b in FIG. 10, respectively.
The speed signals 18a and 18b in FIG. 11 do not show the elements corresponding to FIG. 10, but assume that the speed information is measured by adding a speed detector similarly to the position detectors 80a and 80b. The position target value signals 6a and 6b in FIG. 11 are output signals of the wafer position target value generating means 1a and the reticle position target value generating means 1b in FIG.
The control means 2 in FIG. 11 corresponds to the control means 2 in FIG.

In the control system shown in FIG. 11, the two-axis control system is a position control system having the same configuration and having a speed control system for stabilization as a minor loop. As described above, in the conventional control method, the control input 7a to the first axis is obtained from the target position command value 6a of the first axis, the position 8a of the first axis, and the speed information 18a, and the control input 7b to the second axis is obtained. Is obtained from the target position command value 6b of the second axis, the position 8b of the second axis, and the speed information 18b, and the two axes are controlled independently of each other. The moving speed of the reticle and the moving speed of the wafer are determined so that desired accuracy is realized. The target value generating means 1a, 1b generates position target values 6a, 6b so as to achieve this speed ratio and instructs the reticle and wafer position control systems 2a, 2b. Usually, the moving speed ratio between the reticle and the wafer is set faster than the moving speed of the reticle. In this example, since the control system constitutes a position control system, in order to move at a constant speed, the position target value is a ramp signal. At this time, the target value signal is instructed so that the synchronous relationship between the two axes is always maintained.

The synchronous relationship between the two axes can be known by considering a plane having the first axis as the horizontal axis and the second axis as the vertical axis, and drawing the movement trajectory on this plane. When the two axes are in a synchronous relationship, the following trajectory moves on a straight line of the angle of the speed ratio of the two axes. The deviation from this straight line indicates that the synchronization relationship is broken. It is relatively easy to set the control characteristics of the two axes to be the same and to maintain the synchronous relationship of the two axes in the absence of disturbance.

[0006]

In the conventional method, since each axis is independently controlled, disturbance on the reticle side is suppressed by using only information on the reticle side, and disturbance on the wafer side is suppressed on the wafer side. The disturbance suppression was performed using only the information of. In such a method, there is no other way to reduce the deviation of the synchronization relationship due to disturbance except for increasing the servo rigidity of each axis. However, in order to increase the servo rigidity, the band of the control system must be set wide, which is difficult to realize. Further, the fluctuation of the constant of the control target of each axis also impairs the synchronous relationship between the two axes, similarly to the disturbance. In the conventional method, such a change in the constant is suppressed by setting the band of the control system wide, but it is also difficult to realize this. As described above, the conventional method has a drawback that when a disturbance is applied, or when a constant of a control object fluctuates, the synchronous relationship between the two axes is easily lost, and a good projected image cannot be obtained.

In order for the tracking position signal to maintain a synchronous relationship,
The characteristics of the two-axis control systems must match. It is relatively easy to match the characteristics of the position control system, but it is difficult to match the characteristics of the speed control system. 3 and 4 are trajectories when two axes are controlled so that the reticle side and the wafer side move at the same speed. C0 in the figure
Indicates a target trajectory, and C1 indicates a conventional trajectory.
FIG. 3 is a trajectory when the speed control gains of the two axes are different due to a change in the constant of the control target. FIG. 4 shows a trajectory when the disturbance is applied to the first axis at point D while the control gains of the two axes are the same. As described above, in the conventional method, each axis independently performs the operation of suppressing the parameter fluctuation and the disturbance with respect to the fluctuation of the constant or the disturbance of the controlled object.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has been made in consideration of the two-axis synchronous relationship even when disturbance is applied to the controlled object or when the constant of the controlled object fluctuates. It is an object of the present invention to provide a scanning type exposure apparatus capable of obtaining a good projection image without breaking.

[0009]

In order to achieve the above object, according to the present invention, instead of forming a control loop independently for each axis to be controlled as in the conventional system, the present invention is not limited to a state quantity or a target value. This is characterized in that a control loop is formed by using not only the axis of this axis but also the state quantities and target values of other axes.

That is, when a disturbance is applied to the wafer, the reticle also performs the disturbance suppressing operation at the same time. Conversely, when a disturbance is applied to the reticle side, the wafer side simultaneously performs the disturbance suppression operation. By configuring such a control system, it is possible to perform control so that a synchronous relationship during movement between the wafer side and the reticle side is not broken.

In a preferred embodiment of the present invention, a desired path control is performed by defining an evaluation function unique to the present invention and constructing a control system that optimizes the evaluation function. This control system includes, for example, an equation (1) including an evaluation term of the equation (2) or (3).

[0012]

(Equation 3)

[0013]

(Equation 4) Such an evaluation function is determined, and an optimal control input that minimizes this function is sequentially obtained from a state quantity and a target value of the controlled object by a computer or the like, and is realized by sequentially instructing the controlled object to this control input. . That is, configuring the control system involves calculating an optimal control input that minimizes the evaluation function of Expression (1). The configuration diagram at this time is shown in FIG.
Shown in Note that an optimal control input that minimizes the evaluation function as in Expression (1) is, for example, DP (Dinamic).
(Programming) method or the like.

[0014]

Embodiment 1 FIG. 1 shows an embodiment of the present invention. The correspondence with FIG. 10 is the same as the correspondence shown in the description of the conventional method, except for the configuration of the control means 2. In the figure, the state quantities 8a and 8b representing information such as position and speed are one line, but this is a vector quantity and is a state vector indicating a plurality of pieces of information. Other lines are also vector quantities. The characteristics of the controlled object are represented by a state equation. Equation (5) is obtained by converting this state equation into a discrete-time equation.

[0015]

(Equation 5) Further, the evaluation function is represented by Expression (1). Here, the evaluation function includes an evaluation term such as Expression (2) or Expression (3). This evaluation term indicates the area of a closed region formed by two curves of the target position command value and the follow-up value as shown by S1 _k and S2 _k in FIG. 2 and is called an area evaluation term. The evaluation term is S1 _{k in} FIG.
Using either or both of the S2 _k. In this embodiment, both are used.

Therefore, the weighting function of the equation (1) is given by the following equation (6)
It is represented as

[0017]

(Equation 6)

By introducing the area evaluation term, the control system that minimizes the evaluation function of the equation (1) is a control system in which independent control objects interfere with each other. The optimum control input for minimizing this evaluation function is obtained as in the following equation (7). Therefore, the controller 4 in FIG. 1 can be realized by calculating the following equation (7) using a microcomputer or the like.

[0019]

(Equation 7) By transforming equation (7), equation (8) is obtained as follows.

[0020]

(Equation 8) In equation (8), the control inputs 7a and 7b correspond to U1 and U2. The state quantities 8a and 8b correspond to X1 and X2, and the target value inputs 6a and 6b correspond to R1 and R2. Therefore, from equation (8), the control inputs 7a and 7b are obtained by combining the target value inputs 6a and 6b with the state quantities 8a and 8b. Here, the state quantity X is a vector including the position information and the speed information.

When the control system is configured as described above, the control input to the first axis is based on the target position command values for the first and second axes and the position and speed information of the first and second axes. Desired. Similarly, the control input to the second axis is obtained from the target position command value to the first and second axes, and the position and speed information of the first and second axes. As described above, in the control system of the present embodiment, the first axis and the second axis interfere with each other and control is performed. That is, by configuring a control system that optimizes the evaluation function of Expression (1) including the evaluation terms expressed by Expressions (2) to (4), the target value and the state quantity interfere with each other as described above. A suitable control means 2 can be made.

FIG. 3 is a trajectory when two axes are controlled so that the reticle side and the wafer side move at the same speed. In the figure, C0 indicates a target trajectory, C1 indicates a following trajectory of the conventional method, and C1 indicates a trajectory.
Reference numeral 2 denotes a tracking locus of the control system. FIG. 3 is a trajectory when the control gains of the two axes are different. As described above, in the present control method, a control system with a small deviation in synchronization relation with respect to parameter fluctuations and the like can be realized as compared with the conventional method.

[0023]

[Other Embodiment] (Embodiment 2) Disturbance Estimation The control method of Embodiment 1 cannot sufficiently suppress the influence of disturbance when applied. In the present embodiment, disturbance is estimated by a disturbance estimator, and the disturbance is suppressed by using this value W1 in equation (9). Here, W1 is the output of the disturbance estimator.

[0024]

(Equation 9) Although there are various types of disturbance estimators, a Kalman filter as shown in FIG. 5 is used here. The model of the actual control target is a secondary inertial system as shown in FIG. 6, and the disturbance generation model is a primary system and constitutes a disturbance estimator. A control system for minimizing an evaluation function similar to that of the first embodiment is configured using the disturbance estimated value W1 output from the disturbance estimator. That is, the state vector X is obtained by the equation (9), and the state vector X is used in the equation (1). In FIG. 5, 3 is a control target model, 7 is a control input, 8 is a measurement state quantity signal, 10
Is an estimated disturbance signal (W1), 21 is a disturbance signal generation model,
22 is a Kalman gain and 23 is an estimated state quantity signal. In FIG. 6, 3 is a control target, 7 is a control input, 8 is a state quantity signal (position signal), 9 is a disturbance signal, 10
Is an estimated disturbance signal, 12 is a measured disturbance signal, and 21 is a disturbance signal generation model.

FIG. 7 is a diagram collectively showing the configurations of the second embodiment and the following third and fourth embodiments. This embodiment is configured by removing the virtual control target and the disturbance measuring means from FIG.

FIG. 4 is a trajectory when two axes are controlled so that the reticle side and the wafer side move at the same speed. In the figure, C0 indicates a target trajectory, C1 indicates a following trajectory of the conventional method, and C1 indicates a trajectory.
Reference numeral 2 denotes a tracking locus of the control system. FIG. 4 shows the trajectory when the disturbance is applied to the first axis at point D, while the control gains of the axes are the same. As described above, the present control method can realize a control system with a small deviation of the synchronous relationship with respect to disturbance as compared with the conventional method.

(Embodiment 3) Virtual axis In Embodiments 1 and 2, a large overshoot occurs at the end of the trajectory. In this embodiment, a virtual axis is introduced to suppress the overshoot to a small value. As the virtual axis, a virtual control axis is considered in addition to the actual control target axis, and a control system is configured in the same manner as in the first embodiment by including this axis as a control target. FIG. 7 shows a configuration of a control system when a virtual axis is used. The characteristics of the first axis and the second axis to be controlled and the target position value are the same as in the first embodiment. Here, it is assumed that the characteristics of the virtual axis are the same as those of the first axis, and that the position target value signal for the virtual axis moves at a constant speed from when the movement of the two axes stops. C3 in FIG. 8 shows the response of this system. C2 indicates the response of the control system according to the first embodiment having no virtual axis. From the figure, it can be seen that in the control system using the virtual axis, the overshoot at the terminal end is small.

(Embodiment 4) Disturbance Prediction In the second embodiment, the configuration in the case where the disturbance cannot be known in advance is shown. However, in the case where a torque disturbance or the like corresponding to the target position is known in advance, better control can be performed by performing control using this information. In this case, the characteristics of the control target are expressed as in equation (10) to form a control system. Here, W1 is the value of Example 2.
Is an estimated value of the disturbance estimator used in the above, and W2 is a known disturbance that is known in advance. The configuration of this system is also shown in FIG.

[0029]

(Equation 10) A position target value and a disturbance similar to those in the second embodiment are given to the control system configured as described above. If the disturbance is given at the same value and at the same timing as a known value, the influence of the disturbance hardly appears in the response of the control system, and good control is possible. The response when the known value of the disturbance is half the value of the actual disturbance is shown at C3 in FIG. here,
C0 is a target trajectory, and C2 is a follow trajectory when disturbance is not known in advance. Comparing C2 and C3, it can be seen that the variation due to the disturbance is smaller in C3 when the disturbance is known in advance.

(Embodiment 5) Others The above embodiment may be further modified and implemented as follows.

(1) Speed information can be calculated from position information, and the value can be used as speed information to form a control system.

(2) In the third embodiment, the characteristics of the virtual axis are set to be the same as those of the first axis, but this characteristic may be any convenient one.

(3) In the fourth embodiment, the control system when the disturbance signal is known is shown. The known disturbance signal may be determined by a target position command value, or may be obtained by providing a disturbance signal detection unit.

[0034]

According to the present invention, a control system of a plurality of axes having better controllability can be constructed as compared with a conventional system in which a control system is constructed independently for each axis.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of a configuration of an embodiment of the present invention;

FIG. 2 is a diagram illustrating an area term;

FIG. 3 shows a follow-up characteristic with respect to a target linear path when a step disturbance is applied to a first axis at a time point D.

FIG. 4 shows a follow-up characteristic with respect to a target linear path when the constant of the first axis to be controlled is half the nominal value.

FIG. 5 is a block diagram showing a configuration of a disturbance observer;

FIG. 6 is a block diagram showing a configuration of a control target and a disturbance generation model;

FIG. 7 is a block diagram showing an outline of a configuration of another embodiment of the present invention;

FIG. 8 is a diagram illustrating an effect of a virtual axis;

FIG. 9 is a diagram illustrating an effect when a disturbance is known,

FIG. 10 is a block diagram illustrating an outline of a configuration of a scanning exposure apparatus;

FIG. 11 is a block diagram showing an outline of a configuration of a conventional system.

[Explanation of symbols]

1: Position command value generating means, 1a: First axis position target command value generating means, 1b: Second axis position target command value generating means, 1
c: virtual axis position target command value generating means 2: control means 2,
a: first axis control means, 2b: second axis control means, 3: control target (control target model), 3a: first axis control target, 3
b: second axis control target, 3c: virtual axis control target, 4: controller, 5a: first axis disturbance estimation means, 5b: second axis disturbance estimation means, 6a: first axis target value signal, 6b: No. 2-axis target value signal, 6c: virtual axis target value signal, 7: control input, 7a: first axis control input, 7b: second axis control input, 7c: virtual axis control input, 8: state quantity signal (position signal ), 8a: first axis state quantity signal, 8b: second axis state quantity signal, 8c: virtual axis state quantity signal, 9: disturbance signal, 9a: first axis disturbance signal, 9b:
Second axis disturbance signal, 10: estimated disturbance signal, 10a: first axis estimated disturbance signal, 10b: second axis estimated disturbance signal, 11a:
First axis disturbance measuring means, 11b: second axis disturbance measuring means, 1
2: measurement disturbance signal, 12a: first axis measurement disturbance signal, 12
b: second axis measurement disturbance signal, 18a: first axis speed signal, 1
8b: second axis speed signal, 20: projection means, 21: disturbance signal generation model, 22: Kalman gain, 23: estimated state quantity signal, 30a: wafer driving means, 30b: reticle driving means, 80a: wafer position detection Means, 80b: reticle position detecting means.

Claims (7)

(57) [Claims] 1. A reticle driving means for moving a reticle, a reticle position detecting means for detecting the reticle position, a wafer driving means for moving a wafer, and a wafer for detecting the wafer position Position detection means, projection means for projecting image information recorded on the reticle onto the wafer, reticle target position generation means,
In a scanning exposure apparatus having a wafer target position generating unit, and a control unit for determining a control input signal to the reticle driving unit and the wafer driving unit, the control unit outputs the control input to the reticle driving unit. The control input for outputting to the wafer driving means using the output signals of the wafer position detecting means and the wafer target position generating means in addition to the output signals of the reticle position detecting means and the reticle target position generating means when determining the signal. A scanning exposure apparatus, wherein when determining a signal, an output signal of the reticle position detecting means and a reticle target position generating means is used in addition to an output signal of the wafer position detecting means and a wafer target position generating means. 2. The apparatus according to claim 1, further comprising speed detecting means for detecting a reticle speed, and speed detecting means for detecting a wafer speed, wherein said control means further determines a control input signal using the speed information. The scanning type exposure apparatus according to claim 1, wherein 3. The control means converts the control input signal to be output to the following evaluation function: 3. The scanning exposure apparatus according to claim 1, further comprising a control system that determines so as to minimize. 3. 4. The following area evaluation term in the evaluation function: The scanning exposure apparatus according to claim 3, further comprising: 5. The control unit according to claim 3, further comprising a disturbance estimating unit for estimating a disturbance applied to a control target, and configuring the control system using the estimated disturbance information. 5. The scanning exposure apparatus according to 4. 6. The control system according to claim 3, wherein a virtual axis that does not physically exist as a control target and a target position command value for the virtual axis are newly added to configure the control system. The scanning exposure apparatus according to any one of the preceding claims. 7. The scanning system according to claim 3, wherein the control system is configured by using known disturbance information when a disturbance applied to a control target is known in advance. Exposure equipment.