JP2007279905A - Positioning control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive, safe and reliable means, as a run-away detection means for a positioning device, independently from software for controlling the drive of a mobile body. <P>SOLUTION: A sensor 1 for sensing passage of the mobile body is provided on the driving plane of the mobile body 7. A run-away determination means includes a state circuit 2, an oscillator 3, a pulse counter 4, a comparator 5, and a minimum allowable value storage memory 6 and is perfectly independent from a servo means of the mobile body. The passage time of the mobile body 7 on the sensor 1 is measured by the pulse counter 4. When the measurement is ended, the comparator 6 compares a run-away determination threshold stored in the minimum allowable value storage memory 5 with the pulse count value. Only when the measurement value is smaller than the threshold, a signal is transmitted to a brake circuit 13 to stop operation of a motor 8, a driving means of the mobile body. The mobile body 7 is thereby safely stopped to prevent breakage by run-away. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a positioning control device that positions a moving body that is driven at high speed such as a stage used in a semiconductor exposure apparatus or the like with high accuracy, and more particularly to a positioning device that takes measures against the runaway of the moving body.

Conventionally, as a countermeasure against the runaway of the moving body of the positioning control device, the runaway was stopped by a mechanical stopper. In addition, measures have been taken such as placing limit sensors on both ends of the drive stroke to detect runaway, or detecting and braking when the command value does not match the motor operation. Furthermore, a method of applying a brake when the speed is calculated from the differential value of the position of the moving body and the speed exceeds an allowable range assumed in normal driving has been taken as a similar measure (see Patent Document 1). ).
Japanese Patent Application Laid-Open No. 08-078506

However, such a conventional technique has the following problems.
(1) Stopping runaway with a mechanical stopper may cause large damage to a precision stage that is a moving body due to a large impact at that time, which may deteriorate positioning accuracy, and destroy the worst stage. End up. In order to suppress the impact by attaching an absorber to the mechanical stopper, it is necessary to lengthen the stroke, and a lot of space is required by configuring a plurality of absorbers.

  (2) Even when the runaway is stopped by the limit sensor, if the brake is applied suddenly, the moving body is greatly damaged for the same reason as in the case (1). Also, to avoid this, even if you try to slow down slowly after detecting with the limit sensor, the speed at the time of runaway cannot be predicted, so you must take a long stroke until the moving body stops after exceeding the limit sensor . Therefore, it cannot be easily realized.

  (3) In the runaway detection that detects that the command value and the motor operation do not match and applies the brake, the runaway cannot be detected if the command value itself is abnormal. Especially for software servos, this method is not sufficient because the command value itself may become abnormal due to a parameter input error or software malfunction.

  (4) The method of calculating the speed from the time differential value of the position of the moving body proposed in Patent Document 1 and applying the brake when driving at an abnormal speed is a differential operation for calculating the speed. Is required. Therefore, an arithmetic unit that operates by software such as a DSP (Digital Signal Processor) is required, leading to an increase in cost. Similarly to the method (3), if there is a defect in the software or if the operation of the software is stopped, the runaway cannot be detected. Therefore, it cannot be said that superiority is great not only in cost but also in reliability.

  In view of the above, an object of the present invention is to provide a safer runaway detection means having a simple configuration and independent of software that controls a moving body in a positioning control device. That is, when a runaway is detected, the moving body can be safely stopped at an acceleration that does not damage the moving body.

  In order to solve the above-described problem, in the present invention, as a runaway detection system, one or a plurality of sensors that detect the passage of a moving body such as a photo interrupter are provided in a driving section of the moving body at a predetermined interval. It is characterized by. In the present invention, from the signals of these sensors, the time and direction in which the moving body passes through the specific section are monitored, whether or not there is a runaway is determined, and the runaway is stopped. By providing such a series of runaway detection systems independently of the control system of the moving body, it becomes possible to determine runaway with higher reliability.

  According to the present invention, it is possible to detect a runaway of a moving object with a simple circuit configuration and to stop it safely, so that a runaway detection system with low cost and high reliability can be configured. Further, since the runaway is determined by monitoring the speed during driving, it is not necessary to increase the driving stroke or the like, and a runaway detection system with high feasibility can be constructed.

  The runaway detection system according to the present invention detects, for example, the current position of the moving body, and drives a command signal for positioning the moving body to the target position based on a deviation signal between the target position signal and the current position signal. The present invention is applied to an apparatus having servo means for outputting to the means. The device is also provided with brake means for emergency stop of the moving body.

  The runaway detection system according to the present invention includes a runaway determination unit that constantly monitors the time during which a moving body passes a certain section and determines the runaway. As for the passing time of the moving body, it is desirable to provide two sensors for detecting the passing of the moving body and measure the time for the moving body to pass between the sensors with a pulse counter operating at a certain clock frequency. Also, by monitoring the order of fluctuation of the two sensor output signals determined by the moving direction of the moving body, not only the passing time but also the driving direction of the moving body is detected, and the moving body is driven in a certain direction. It is desirable to add a function that can detect runaway only during

  The runaway determination means stores in advance a minimum allowable time until the two bodies pass between the two sensors when the moving body is normally driven. Then, the minimum allowable time and the passing time of the moving body are compared one by one, and it is determined that the runaway occurs only when the passing time is smaller than the allowable minimum time. When the runaway determination means determines that the runaway occurs, the moving body is safely stopped by the brake circuit. The runaway determination means is provided separately from the servo means for the moving body.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an outline when a runaway detection system according to an embodiment of the present invention is mounted on a positioning control device. This positioning control device is used, for example, as a mask stage or wafer stage of a semiconductor exposure apparatus.
A configuration example of the runaway determination unit according to the present invention will be described with reference to FIG. The motor 8 which is a driving means for the moving body 7 is controlled by a control system provided separately from the runaway detection system. The runaway detection system includes a sensor 1 that detects the passage of the moving body 7 provided in the driving path of the moving body 7, and a runaway determination unit 11 that is connected to the sensor 1 and indicated by a dotted line block in FIG. Have.

  The runaway determination unit 11 includes a state circuit 2, an oscillator 3, a pulse counter 4, a comparator 5, and a minimum allowable value storage memory 6. The state circuit 2 is a circuit that controls the operation of the pulse counter 4 and the comparator 5. The runaway determination unit is connected to the brake circuit 13, and a brake is applied to the motor 8 which is a driving unit of the moving body by the signal from the runaway determination unit to stop the moving body. The runaway detection system according to the present embodiment is a highly reliable runaway detection system because it is completely independent from the control system for the driving means of the moving body.

Next, a method for determining the runaway of a moving object will be described.
While the moving body 7 passes over the sensor 1, the runaway determination unit 11 transmits a Control signal to the pulse counter 4 configured in the unit 20. While the control signal is being transmitted, the pulse counter 4 increases the count value in a cycle corresponding to the frequency of the oscillator 3. Since the count value is the number of pulses while the moving body 7 passes over the sensor 1, measuring the count value is equivalent to measuring the passing time of the moving body 7. When the passage of the moving body 7 is completed, the state circuit 2 transmits a Comp signal to the comparator 5 and latches the count value at that time in the comparator 5 and simultaneously outputs a Clear signal for clearing the count value of the pulse counter 4. Send to pulse counter. The comparator 5 compares the measured count value with the minimum allowable value of the passage time stored in the minimum allowable value storage memory 6 constituted by an EEPROM or the like, and only when the count value is smaller than the minimum allowable value, A signal is transmitted to the brake circuit 13 to operate the emergency stop brake means. Thereby, the runaway of the moving body 7 is detected, and even in that case, the moving body 7 can be safely stopped.

The minimum allowable value sets a count value when the moving body 7 passes over the sensor 1 by normal driving. If the count value when the moving body 7 passes over the sensor 1 is less than or equal to the minimum allowable count value, it means that the moving body 7 has been driven at a speed higher than the speed allowed for normal driving. Therefore, in this case, the runaway determination unit 11 determines that the moving body 7 has runaway and transmits a signal to the brake circuit 13. Thereby, the moving mobile body 7 is braked, and the mobile body 7 can be safely stopped.
Since the moving object runaway determination means 11 is independent of the normal servo means (not shown), even if the servo means does not function, it is possible to detect the moving object runaway.

Hereinafter, four different embodiments when the runaway detection system according to the present invention is applied to a driving device (positioning control device) for the moving body 7 will be described.
[Example 1]
FIG. 2 shows a moving body driving apparatus according to Embodiment 1 of the present invention.
In FIG. 2, the moving body is 7, the motor that drives the moving body 7 is 8, and the surface plate whose upper part is the guide surface of the moving body 7 is 9. The sensor 1 that detects the passage of the moving body 7 includes a photo interrupter 10 a and a light shielding plate 12. The runaway detection means of the moving body 7 is 11a, and the circuit for transmitting a brake signal to the motor 8 is 13.

  In this embodiment, a photo interrupter is used as the sensor 1 for detecting the passage of the moving body 7. The moving body 7 includes a means such as a light shielding plate 12 that can shield light from the photo interrupter 10a. By passing through the moving body 7, the light from the photo interrupter 10 a is blocked by the light blocking plate 12 for a time corresponding to the driving speed of the moving body 7. The runaway determination unit 11a measures the time for the moving body 7 to pass over the photo interrupter 10a using the pulse counter according to the method described above.

  For example, the width of the light shielding plate is 15 mm, and the oscillation frequency of the oscillator of the runaway determination unit is 50 kHz. In normal driving, assuming that the moving body 7 passes through the photo interrupter 10a at 500 mm / s, the count value of the pulse counter at this time is (15/500) * (1/50000) = 1500. If the moving body does not pass the above section at 500 mm / s or more in normal driving, the minimum allowable value stored in the minimum allowable value storage memory in the runaway determination means at this time is 1500. In other words, at this time, the runaway discrimination means 11a sets the threshold for runaway discrimination to 500 mm / s, and the minimum allowable value is equivalent to the threshold for runaway discrimination. Any value can be set as the minimum allowable value. The runaway determination means holds this value using a storage element such as an EEPROM.

  The runaway determination unit 11a monitors the time required for the moving body 7 to pass over the photo interrupter 10a. When the time is smaller than the minimum allowable value, that is, when the moving body 7 is driven at a speed higher than a normally assumed speed, it is determined that the moving body 7 has runaway and a signal is sent to the brake circuit 13. . Thereafter, the brake circuit 13 stops the motor 8 and stops the moving body 7 safely. The minimum allowable value is a threshold for the runaway determination speed, and also varies depending on the maximum acceleration, maximum speed, and movement stroke of the moving body 7. Therefore, in order to improve versatility, it is possible to have means for switching the minimum allowable time according to the driving condition of the moving body.

  FIG. 6 shows a process flowchart of the runaway determination means in the first embodiment. Briefly, the counter is raised while the photo interrupter 10a is shielded from light. The pulse counter 4 is stopped at the moment when light is transmitted from the light shielding, and the measured value at that time is compared with a threshold value. When the measured value is smaller than the threshold value, the brake is applied, and when the measured value is larger, the process returns to the Wait state.

[Example 2]
A second embodiment is shown in FIG. FIG. 3 shows an embodiment when the two photo interrupters 10a and 10b are used for detecting the passage of the moving body 7. FIG. In this case, two runaway detection means are also provided corresponding to each of the photo interrupters 10a and 10b. Therefore, this is an example of construction of a system capable of detecting runaway in two sections. The runaway determination means 11a and 11b measure the time for passing through 10a and 10b during normal driving. Since different runaway discrimination thresholds can be set for 10a and 10b, runaway detection can be performed in two sections. That is, according to the present method, by providing a photo interrupter and the same number of runaway determination means as those, it becomes possible to detect runaway in a plurality of sections, and a safer system can be constructed.
The processing flow of the runaway determination unit at this time is the same as that in the first embodiment, and the counter is controlled by light shielding and light transmission of the photo interrupter.

[Example 3]
A third embodiment is shown in FIG. FIG. 4 shows an embodiment when two pairs of photo interrupters are used for detecting the passage of a moving object. In this case, the runaway determination unit 11a measures a count value from passing through the photo interrupter 10b to passing through the photo interrupter 10a. The advantage of using a pair of photo interrupters is that the runaway is monitored only when the passing order of the sensors is changed from 10b to 10a, that is, when the moving body 7 is driven in a certain direction. Can also prevent false detection of runaway. Further, unlike the first and second embodiments, since the count value does not depend on the width of the light shielding plate 12, the system can be easily mounted. The minimum allowable value in this case is also the count value of the pulse counter when the moving body 7 passes between the sensors at the maximum speed during normal driving. The runaway detection means 11a makes a runaway determination and urgently stops the mobile body 7 when the count value due to the passage of the mobile body 7 is smaller than this value.
A processing flowchart of the runaway determination means at this time is shown in FIG. The difference from the first and second embodiments is that the counter is raised by shielding the photo interrupter 10b and stopped by shielding the photo interrupter 10a.

[Example 4]
A fourth embodiment is shown in FIG. FIG. 5 shows an embodiment when three photo interrupters are used. In this case, the runaway determination unit measures the time from passing through the photo interrupter 10c to passing through the photo interrupter 10b and the time from passing through the photo interrupter 10b to passing through the photo interrupter 10a. The minimum allowable time for passing between the photo interrupters 10c and 10b and the minimum allowable time for passing between the photo interrupters 10b and 10a may be different values. Further, as in the second embodiment, the runaway of the moving body can be detected in two sections. Similarly to the third embodiment, the runaway is possible only when the moving body is driven in a specific direction. Furthermore, since the runaway determination threshold does not depend on the width of the light shielding plate, there is an advantage that the superiority is high in terms of mounting.
The processing flow of the runaway determination means at this time is as shown in FIG. 7 as in the case of the third embodiment. The counter starts to rise when one photointerrupter is shielded, and the counter is counted when the other photointerrupter is shielded. Stop.

  In any of the embodiments, since the position for detecting the runaway of the moving body can be arbitrarily set, it is not necessary to extend the driving stroke of the moving body. Therefore, there is a great merit in terms of feasibility. It is a low-cost runaway detection means that is safe, reliable, and highly feasible.

[Example of device manufacturing]
Next, with reference to FIGS. 8 and 9, an embodiment of a device manufacturing method using an exposure apparatus using the above positioning control apparatus as a mask stage or a wafer stage will be described. FIG. 8 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). Here, a semiconductor chip manufacturing method will be described as an example.
In step S1 (circuit design), a semiconductor device circuit is designed. In step S2 (mask production), a mask is produced based on the designed circuit pattern. In step S3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step S4 (wafer process) is referred to as a pre-process, and an actual circuit is formed on the wafer using the mask and the wafer by the above exposure apparatus using the lithography technique. Step S5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer manufactured in step S4. Step S5 includes assembly processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In step S6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device manufactured in step S5 are performed. Through these steps, the semiconductor device is completed and shipped (step S7).

  FIG. 9 is a detailed flowchart of the wafer process in Step 4. In step S11 (oxidation), the surface of the wafer is oxidized. In step S12 (CVD), an insulating film is formed on the surface of the wafer. In step S13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step S14 (ion implantation), ions are implanted into the wafer. In step S15 (resist process), a photosensitive agent is applied to the wafer. In step S16 (exposure), the circuit pattern of the mask is exposed on the wafer by the exposure apparatus. In step S17 (development), the exposed wafer is developed. In step S18 (etching), portions other than the developed resist image are removed. In step S19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.

It is a block diagram which shows the concept at the time of applying the runaway discrimination | determination means based on one Example of this invention to the drive device of a moving body. It is a figure which shows one Example at the time of providing one runaway detection area. It is a figure which shows one Example at the time of providing two runaway detection areas. It is a figure which shows one Example when a runaway detection is performed only when a moving body drives to a specific direction. This is an embodiment in which runaway detection is performed only when a moving body is driven in a specific direction and two sections for detecting runaway are provided. It is a flowchart of the process of the runaway discrimination | determination means in the Example at the time of providing one runaway detection area. It is a flowchart of the process of a runaway discrimination | determination means in the Example in the case of performing a runaway detection only when a mobile body drives to a specific direction. It is a flowchart for demonstrating the Example of the device manufacture using an exposure apparatus. It is a detailed flowchart of the wafer process of step 4 of the flowchart shown in FIG.

Explanation of symbols

  1: sensor, 10a, 10b, 10c: photo interrupter, 2: state circuit, 3: oscillator, 4: pulse counter, 5: comparator, 6: minimum allowable value storage memory, 7: moving body, 8: motor, 9: Surface plate, 11a, 11b: runaway change means, 12: light shielding plate, 13: brake circuit.

Claims (7)

In a positioning control device that positions a moving body at a target position,
One or more sensors for detecting the passage of the moving body;
Means for measuring the time required for the moving body to pass between one sensor or two sensors;
Runaway determination means for determining the runaway of the moving object from the measurement time,
A positioning control apparatus comprising: an emergency stop unit that makes an emergency stop of the moving body when the runaway determination unit determines that the runaway has occurred.   2. The runaway determination unit compares the measurement time with a preset threshold for determination of runaway, and determines that the runaway occurs when the measurement time is smaller than the threshold. The positioning control device described in 1.   The positioning control device according to claim 2, wherein the threshold value can be set to a unique value for each sensor or between sensors, and is variable depending on a driving condition of the moving body.   The positioning control device according to claim 3, wherein the driving condition is at least one of a maximum speed, a maximum acceleration, and a driving stroke of the moving body.   There are two or more sensors that detect the passage of the moving body, the runaway determination means calculates a driving direction from the order in which the moving body passes the sensor, and only when the driving direction is a specific direction, The positioning apparatus according to claim 1, wherein the runaway is determined.   An exposure apparatus comprising the positioning control device according to claim 1.   A device manufacturing method comprising: exposing a substrate using the exposure apparatus according to claim 6; and developing the exposed substrate.

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