JPH10144590A - Stage control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To move a stage correctly regardless of the length of distance by switching the control method of the stage when the moving distance of the stage is long and short. SOLUTION: When a target moving distance is longer than a boundary moving distance, a switch 26 is connected with a terminal P1 and the output of a second comparator 21 is connected with the stop terminal of a pulse generator 14. The second comparator 21 determines the difference between the residual moving distance and the additional moving amount after receiving a stop instruction and stops generation of pulse from the pulse generator 14 when the difference is equalized. Consequently, a stage 11 is moved additionally to a target position correctly. When the target moving distance is shorter than a boundary moving distance, output from a first comparator 20 goes O and the switch 26 is turned to a terminal P2 . A divider circuit 22 determines the target moving distance and the moving amount of the stage per step of a motor 12 and turns the motor 12 by a number of steps thus determined to move the stage 11 to a target position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stage control system in an electron beam lithography system or the like, which can accurately move a stage on which a material to be drawn or a sample is placed.

[0002]

2. Description of the Related Art In an electron beam lithography apparatus, a wafer or a glass plate, which is a material to be irradiated with an electron beam, is placed on an XY stage. Then, a desired pattern is drawn by an electron beam while moving this stage.

FIG. 1 is a conceptual diagram of a stage driving method in such an electron beam drawing apparatus.
XY by the ball screw 3 rotated by the motor 2
Moved in the direction. A voltage corresponding to the count value of the up / down counter 4 is applied to the motor 2 by the DA converter 5 and the amplifier 6.
Is supplied via

A pulse is supplied from a control unit 7 to an up-count terminal of the counter 4, and a pulse from an encoder 8 connected to the motor 2 is supplied to a down-count terminal of the counter 4. The movement position of the stage 1 is monitored by the laser length measuring device 9.

In the above configuration, when the stage 1 is moved, a pulse is supplied from the control unit 7 to the counter 4, and the counter counts up the pulse. The count value of the counter 4 is converted by the DA converter 5 into a voltage signal corresponding to the count value. The output voltage of the DA converter 5 is amplified by the amplifier 6 and supplied to the motor 2, so that the motor 2 is driven and the ball screw 3 rotates. The stage 1 is moved straight by the rotation of the ball screw 3.

The amount of rotation of the motor 2 (corresponding to the amount of movement of the stage 1) is measured by the encoder 8, and a pulse corresponding to the amount of rotation from the encoder 8 is supplied to the down-count terminal of the up / down counter 4. As a result, the count value of the counter 4 is equal to the rotation of the motor 2, that is,
When the count is down-counted by the movement of the stage 1 and pulses are supplied from the encoder 8 by a predetermined number of pulses supplied from the control unit 7, the value of the counter 4 becomes 0 and the motor 2 stops.

When the position control type servo motor 2 is used for the movement of the stage 1, if the number of pulses of the motor corresponding to the distance to be moved is given, the motor 2 is rotated by the number of steps. Has become. However, even if the motor 2 rotates accurately, if the ball screw 3 or the like is used as a mechanical system for converting the rotation into a linear movement, the stage 1 does not stop at a target position due to an error of the ball screw 3. . This error increases mainly in proportion to the moving distance.

Therefore, the position of the stage 1 is detected by using a measuring device such as a laser length measuring device 9 and the motor 2 is controlled. As a general control method, from the viewpoint of shortening the positioning time, the rotational speed of the motor 2 is reduced near the target position and the moving speed of the stage 1 is switched to a low speed. This is performed by making the interval between pulses supplied from the control unit 7 to the counter 4 relatively long.

[0009]

When the laser length measuring device 9 detects that the stage 1 has moved to just before the target position, the supply of the pulse from the control section 7 is stopped and the rotation of the motor 2 is stopped. Stop. The reason for stopping immediately is that, even if the supply of the pulse is stopped, the movement amount corresponding to the count number remaining in the counter moves due to the structure shown in FIG.

FIG. 2 shows this state, and FIG.
Indicates the frequency of the pulse supplied to the motor 2, and FIG.
(B) shows the amount of movement of the stage 1. FIG.
In both (a) and (b), the horizontal axis is time. Here, when moving the stage 1 by a distance M _1, the pulse shown in FIG. 2 (a) is supplied to the motor 2.

The stage 1 is moved by this pulse. The ideal movement of the stage 1 by this pulse is shown in FIG.
This is indicated by the line A in (b). However, there is a time lag in the movement of the stage 1 with respect to the supply of the pulse, and as described above, even if the pulse is stopped, the stage is excessive. Therefore, the movement amount of the stage 1 is measured by the laser distance measuring device 9, when the stage 1 is moved to the position M ₂ slightly before the setting movement position M _1,
The control unit 7 stops supplying the pulse.

[0012] The actual movement amount of the stage 1 by such control is shown by line B in FIG. 2 (b), the stage 1 at time t ₁ is moved up slightly before the target position, when the , The supply of the pulse is stopped. Then, the stage 1 is moved up to the time t _2, the stops at the position M ₁ of the target. In this way, if a command to stop the motor 2 is issued in anticipation of the overshoot of the stage 1, there is no need to return after the stage 1 is overshoot, so that there is an effect that the time for moving the stage can be saved.

Here, a problem arises in the case of movement of a very short distance. That is, there is a slight delay before the motor 2 starts operating at the time of starting. If the command is continued until the stage moves just before the target value, a pulse will be sent beyond the moving distance, and the stage will stop when it has gone too far.

FIG. 3 shows this state. FIG. 3A shows the frequency of the pulse supplied to the motor 2, and FIG. 3B shows the amount of movement of the stage 1. The pulse 1 is supplied to the stage 1 by the target moving amount M _3. Stopping only when moved to the M ₄ is a front pulse (time t ₁₎ of the stage 1 on the basis of the pulse until it ends up moving to the position M ₅ (time t _2). In FIG. 3B, a line A indicates the movement of the stage in an ideal state by supplying a pulse, and a line B
Indicates the actual stage movement.

The present invention has been made in view of the above points, and an object of the present invention is to realize a stage control method capable of accurately moving a stage even at a relatively long distance or a short distance. .

[0016]

According to a first aspect of the present invention, there is provided a stage control system for an electron beam drawing apparatus or the like in which a stage is moved by a motor rotating according to the number of pulses. Compare the distance to a preset distance, if the distance is long, generate a pulse to rotate the motor, monitor the movement of the stage, stop the generation of pulses according to the position of the stage, When the distance is short, the stage is moved by rotating the motor with a pulse corresponding to the distance.

According to the first aspect of the present invention, the distance to the target position of the stage is compared with a predetermined distance, and the control of the stage is switched between when the distance is long and when the distance is short. That is, when the distance is long, a pulse for rotating the motor is generated, and the movement of the stage is monitored.
The generation of the pulse is stopped according to the position of the stage, and when the distance is short, the stage is moved by rotating the motor with the pulse corresponding to the distance.

According to a second aspect of the present invention, there is provided a stage control system comprising: a stage; a motor for moving the stage; a measuring device for measuring an amount of movement of the stage; and a distance to a target movement position of the stage. Comparing means for comparing with the boundary distance, and if the distance to the target position is longer than the boundary distance according to the comparison result of the comparing means, the first control system is selected, and the distance to the target position is larger than the boundary distance. If the stage is short, there is provided a selecting means for selecting the second control system, and the first control system stops the supply of the pulse for rotating the motor when the stage moves to a position short of the target position. The second control system is characterized in that pulses for rotating the motor are generated in a number corresponding to the distance to the target position.

According to the second aspect of the present invention, the amount of movement of the stage is measured, and the distance to the target movement position of the stage is compared with a preset boundary distance, and the distance to the target position is determined according to the comparison result. If the distance is longer than the boundary distance, the first control system is selected. If the distance to the target position is shorter than the boundary distance, the second control system is selected. And the first
The control system stops the supply of the pulse for rotating the motor when the stage moves to a position just before the target position, and the second control system sets the pulse for rotating the motor to the distance to the target position. Generate as many as you want.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 shows an example of a circuit for implementing the stage control method according to the present invention. In the drawing, although not shown, a material to be drawn such as a wafer or a glass dry plate is placed on the stage 11, and the stage 11 is placed in a drawing chamber of the electron beam drawing apparatus which is evacuated to a vacuum. Has been put in.

The stage 11 is moved in the X and Y directions by a ball screw 13 rotated by the rotation of a motor 12. The motor 12 is supplied with a pulse from a pulse generator 14 via a position control type servo amplifier 15. The stage 11 is moved by the rotation of the motor 12, and the movement amount is measured by the laser length measuring device 16.

Reference numeral 17 denotes a register.
Is set to a target movement amount m _{1 of the} stage 11 from the terminal T ₁ . The target movement amount m ₁ set in the register 17 is
The signal is supplied to one terminal of the subtractor 18. The movement amount of the stage 11 measured by the laser length measuring device 16 is supplied to the other terminal of the subtractor 18. The output of the subtractor 18 is supplied to an absolute value calculation circuit 19, and the absolute value of the output of the subtracter 18 is obtained.

The output of the absolute value calculation circuit 19 is supplied to a first comparator 20 and compared with a first set moving distance m ₂ supplied from a terminal T ₂ . Also, the absolute value calculation circuit 19
Is also supplied to a second comparator 21 and a division circuit 22. The second comparator 21 compares the output with the second set moving distance m ₃ supplied from the terminal T ₃ .

Further, the dividing circuit 22 outputs the output and the motor 12
Is divided by the amount of movement of the stage 11 per step, and the result of the division is supplied to the third comparator 23. Third
The other terminal of the comparator 23 is supplied with a count value from a counter 24 that counts output pulses of the pulse generator 14.

The count value of the counter 24 is cleared by the start signal supplied from a terminal T _4. Incidentally, the start signal from the terminal T _4, the pulse generator 14
, And the pulse generator 14 generates a pulse according to the start signal.

Further, although the start signal is also supplied to the register 25, the register 25 based on the comparison result and a start signal of the first comparator 20 switches the switch circuit 26 to the terminal P ₁ or P _2. The terminal P ₁ is supplied with a signal from the second comparator 21, and the terminal P ₂ is supplied with a signal from the third comparator 23. The signal from the switch circuit 26 is supplied to the stop terminal of the pulse generator 14. The operation of such a configuration will now be described.

[0027] In the above configuration, stage 1 to the terminal T ₁
One target movement position m ₁ is supplied, and as a result, the target movement position m ₁ is set in the register 17. In addition, terminal T
_{In 2} , a moving distance m ₂ of a boundary when two control methods to be described later are selected is set. The set value of the register 17 is supplied to the subtractor 18, but when the stage 11 has not moved yet, the output of the subtractor 18 corresponds to the movement distance to the target movement position.

The absolute value of the output of the subtractor 18 is calculated by an absolute value calculating circuit 19, and the calculated output is the first comparator 2
0 is supplied. The first comparator 20 compares the target moving distance m ₁ with the boundary moving distance m _2, and outputs 1 when m ₁ > m ₂ . When m ₁ ≦ m ₂ , 0
Is output. The output of this first comparator 20 is
5 is supplied.

Here, when a start signal for stage movement is supplied from the terminal T _4, the start signal is supplied to the pulse generator 14 and also to the register 25. The pulse generator 14 generates a pulse by supplying a start signal, and the pulse is supplied to the motor 12 via the servo amplifier 15. The motor 12 starts rotating by the supplied pulse, and the ball screw 1
3 also rotates. The stage 11 moves by the rotation of the ball screw 13. The servo amplifier 15 is supplied with a motor rotation direction command signal, and the direction of movement of the stage can be changed based on the command signal.

At the same time as the stage 11 moves, the register 25 switches the switch 26 according to the start signal. When the output of the register 25 is 1, that is, when the target moving distance m ₁ is longer than the boundary moving distance m ₂ , the switch 26 is connected to the terminal P ₁ and the output of the second comparator 21 is Connected to stop terminal.

As described above, the stage 11 starts moving in response to the start signal. The amount of movement of the stage 11 is measured by the laser length measuring device 16, and the measured amount of movement is supplied to the subtractor 18. The subtractor 18 is a register 1
The difference between the actual movement amount of the stage 11 from the target movement distance m ₁ from 7 is always calculated. The signal of this difference is supplied to the second comparator 21 after the absolute value calculation.

In the second comparator 21, the target moving distance m ₁
, The difference between the remaining travel distance and the travel distance m ₃ (M ₁ −M ₂ in FIG. ₂ ) that moves extra after issuing the stop command supplied from the terminal T ₃ . Seeking. When this difference is equal, i.e., when the stage 11 has reached the position of the M ₂ in FIG. 2, the second
The comparator 21 generates a signal of 1 and this signal is supplied to the stop terminal of the pulse generator 14 via the switch circuit 26, so that the pulse generator 14 stops generating pulses.

Even if the pulse from the pulse generator 14 stops, the stage 11 moves slightly due to an error in the ball screw 13. As a result, the stage 11 includes the pulse generator 1
Even if the pulse from 4 stops, the stage 11 moves extra by the distance m ₃ , and as a result, the stage 11 moves exactly by the target moving distance m ₁ .

Next, the target moving distance m ₁ of the stage 11
Is shorter than the boundary movement distance m ₂ (m ₁ ≦ m ₂ ), that is, when the stage 11 is moved by a very short distance,
The output of the first comparator 20 becomes 0, switch 26 is switched to the terminal P _2. As a result, the third comparator 24
Is supplied to the stop terminal of the pulse generator 14.

[0035] The third comparator 24, the output signal of the output signal and the counter 24 of the dividing circuit 22 is supplied to the dividing circuit 22, a signal corresponding to the target movement distance m ₁ is supplied You. The division circuit 22 divides the target movement distance m _{1 by} the movement amount of the stage 11 per one step of the motor 12, and supplies the result of the division to the third comparator 23.
That is, if there is no error in the ball screw 13, if the motor 12 rotates by this number of steps, the stage 11 reaches the target position.

On the other hand, the other terminal of the third comparator 23 is supplied with the count value of the counter 24. The counter 24 is cleared by the start signal and counts the pulses from the pulse generator 24. When the pulse corresponding to the moving distance is output from the pulse generator 24, the value from the dividing circuit 22 and the value of the counter 24 become equal, and the signal 1 is generated from the third comparator 23.

Since the signal from the third comparator 23 is supplied to the stop terminal of the pulse generator 14, the supply of the pulse from the pulse generator 14 is stopped at this stage.
The motor 12 stops. As a result, the motor 12 rotates accurately by the commanded step with a delay. In this case, although the stage 11 moves due to the error of the ball screw 13, the error of the bolt screw accumulates mainly in proportion to the moving distance.

As described above, when the boundary moving distance is set and the stage is moved by a distance longer than the boundary moving distance,
As in the past, the motor rotation was stopped in anticipation of the extra travel distance of the stage due to the error of the ball screw, and in the case of a travel distance shorter than the boundary travel distance, the motor was driven by the required number of pulses. The stage can be accurately moved regardless of whether the distance is relatively long or short.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, the stages are controlled by hardware when the distance is longer and shorter than the boundary movement distance, but the same processing may be performed by a combination of a microprocessor and software. Also,
The stage control method of the present invention can be applied to not only an electron beam lithography apparatus but also an apparatus which requires precise movement of a stage.

[0040]

As described above, the stage control method according to the first aspect of the present invention compares the distance to the target position of the stage with a predetermined distance, and determines whether the distance is long or short. Is switched. That is,
When the distance is long, a pulse for rotating the motor is generated, the movement of the stage is monitored, and the generation of the pulse is stopped according to the position of the stage. When the distance is short, a pulse corresponding to the distance is generated. The motor is rotated to move the stage. As a result, the stage can be moved by a precisely set moving distance regardless of whether the moving distance is long or short.

The stage control method according to the second aspect of the present invention measures the amount of movement of the stage and compares the distance to the target movement position of the stage with a preset boundary distance. When the distance to the position is longer than the boundary distance, the first control system is selected, and when the distance to the target position is shorter than the boundary distance, the second control system is selected. Then, the supply of the pulse for rotating the motor is stopped by the first control system when the stage moves to a position just before the target position, and the pulse for rotating the motor is supplied to the target position by the second control system. It is generated by the number corresponding to the distance up to. As a result, the stage can be moved by a precisely set moving distance regardless of whether the moving distance is long or short.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a circuit for implementing a conventional stage control method.

FIG. 2 is a diagram showing a state of stage movement in the circuit of FIG.

FIG. 3 is a diagram showing a state of stage movement in the circuit of FIG. 1;

FIG. 4 is a diagram illustrating an example of a circuit that implements a stage control method according to the present invention.

[Explanation of symbols]

 Reference Signs List 11 stage 12 motor 13 ball screw 14 pulse generator 15 servo amplifier 16 laser length measuring device 17 register 18 subtracter 19 absolute value operation circuit 20, 21, 23 comparator 22 division circuit 24 counter 25 register 26 switch circuit

Claims (2)

[Claims] 1. A stage control method in which a stage is moved by a motor that rotates according to the number of pulses,
Compares the distance to the target position of the stage with a preset distance.If the distance is long, generates a pulse for rotating the motor, monitors the movement of the stage, and generates a pulse according to the position of the stage. A stage control method in which the motor is rotated by a pulse corresponding to the distance and the stage is moved when the distance is short. 2. A stage, a motor for moving the stage, a measuring device for measuring an amount of movement of the stage, a comparing means for comparing a distance to a target movement position of the stage with a preset boundary distance, If the distance to the target position is longer than the boundary distance according to the comparison result of the comparing means, the first control system is selected. If the distance to the target position is shorter than the boundary distance, the second control system is selected. A first control system configured to stop supply of a pulse for rotating the motor when the stage moves to a position short of a target position. Is a stage control system configured to generate pulses for rotating the motor in a number corresponding to the distance to the target position.