JPH0812076A - Work sensing method and device of magnetic levitation conveying device - Google Patents

Abstract

PURPOSE:To sense a work certainly without equipping a moving element with any special apparatus, by sensing work holding of the moving element from change in the control voltage to be distributed to electric magnets on the basis of the sensing value given by a sensor of a magnetic levitation device. CONSTITUTION:Differential signals obtained by taking difference between signals given by levitation control sensors 7 mounted on an actuation controller 9 and the set value are subjected to PID control by a magnetic levitation device 3, and voltage is distributed to a plurality of electric magnets 6 of the actuation controller 9 so that they generate magnetism. Then a magnetic substance 5 of a moving element 4 is attracted so that the element 4 is levitated magnetically, and if the actuation controller 9 is moved in the desired direction, the element 4 restrained magnetically moves also in the same direction. Because the element 4 is levitated magnetically, its attitude is inclined from the level by movement of the center of gravity depending upon existence of any work (a), but the element 4 can be corrected to the levitating attitude approx. horizontally by analyzing the sensing values of the sensors 7 as classified by purposes and controlling the distributed values for the magnets 6 upon subjecting the values to the PID control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation transfer device for transferring a substrate or other work in a magnetic levitation state in a chamber of a vacuum processing apparatus such as a sputtering apparatus or an etching apparatus used in a semiconductor manufacturing process. The present invention relates to a method and apparatus for detecting the presence or absence of

[0002]

2. Description of the Related Art Conventionally, for example, in a semiconductor manufacturing process,
When a workpiece such as a silicon wafer is subjected to sputtering or etching, the workpiece a is transferred into a vacuum processing chamber c such as a sputtering chamber by a magnetically levitated moving element b as shown in FIG. The transfer device in which the moving element b is magnetically levitated can isolate the mechanical sliding part,
Since the dust generated from the sliding portion does not adhere to the work and the work transfer chamber d can be limited to the presence of only the magnetically levitated mover b, the amount of released gas is reduced and the work transfer chamber d is kept above the work transfer chamber d. It is possible to create a high-vacuum atmosphere, and since the atmosphere in the processing chamber c such as the sputtering chamber or the etching chamber is not impaired, the processing chamber can be maintained in an ultra-high vacuum and is suitable for manufacturing high-density semiconductors. ing. An operation controller e that operates in a contactless manner is provided for operation control of the mover, and a magnetic levitation device is provided on the mover b and the operation controller e. The magnetic levitation device is composed of, for example, a magnetic body f such as a permanent magnet provided on a moving element and an electromagnet g provided on the operation control element e, and the moving element b is magnetized by controlling the voltage of the electromagnet g. When the robot floats and the operation controller e is attached to, for example, a robot hand and is turned or reciprocated, the mover b turns or reciprocates following the movement. In order to control the posture of the mover b, a levitation control sensor h such as a magnetic sensor is provided on the operation controller e, and the voltage of the electromagnet g is controlled based on the detection value of the levitation control sensor h to move the mover e. Attitude is controlled.

In order to transfer the work a to the mover b, the transfer means i is transferred to the work transfer chamber d and the vacuum processing chamber c.
i is provided, and a wafer detection device j is provided to detect whether the work a is present at a predetermined position before being carried into the processing chamber c and after being carried out from the processing chamber c. The wafer detection device j is usually a pair of wafer presence / absence detection sensors 1, 1 provided in the atmosphere outside the work transfer chamber d.
And an observation window k, k through which a signal of this is passed.

[0004]

The optical wafer presence / absence detection sensor 1 cannot be incorporated in the vacuum work transfer chamber c, and the transfer sensor is provided in the atmosphere to detect the wafer presence / absence sensor 2 in the transfer chamber c. Although a peep window k is required at some place, the shape of the transfer chamber in recent semiconductor manufacturing apparatuses is complicated, and it is difficult to find a place to mount the wafer presence / absence detection sensor l, and the space shape inside the transfer chamber is complicated. There is an inconvenience that the sensor 1 is likely to malfunction. It is also conceivable to incorporate a contact type wafer presence / absence detection sensor, for example, at a portion of the mover b where the wafer is held, but this requires a special structure or wiring for preventing the released gas in a vacuum. And its production is not easy.

Further, since the position where the wafer is monitored is limited to the wafer presence / absence detection sensor mounting position, the state of the wafer cannot be known when the wafer holding position is displaced or dropped due to some trouble during the transportation. If the deviation of the wafer holding position is large, it is not preferable because the wafer may drop or be damaged during transfer, for example, by interfering with other mechanisms in the processing chamber.

The present invention provides a method for constantly monitoring the presence or absence of a work held by a magnetically levitated moving element during the transportation of the moving element without providing any special equipment on the moving element, and detecting a deviation or a drop of the workpiece. The object is to provide a possible work detection method.

[0007]

According to the present invention, a moving element for holding a work and an operation control element provided opposite to the moving element are provided.
A magnetic levitation device capable of magnetically levitating the mover by a plurality of electromagnets and controlling a magnetic levitation posture of the mover by a levitation control sensor is provided, and the mover magnetically levitated by the magnetic levitation device operates. In a magnetic levitation transfer device that moves following the movement of a control element, the movement of a work piece of the movement element is controlled by a change in a control voltage distributed to the electromagnet based on a detection value of a levitation control sensor of the magnetic levitation apparatus. The above object was achieved by detecting the presence or absence. The magnetic levitation device is composed of a plurality of magnetic bodies provided on the moving element, a plurality of electromagnets provided on the operation controller, and a plurality of levitation control sensors, and a signal detected by the sensor and setting The signal of the difference between the sensor signal and the set value is controlled by PID controlling the signal of the difference between the sensor signal and the set value by controlling the distribution value of the voltage to each electromagnet. By comparing the change in the P value of the PID control value with the setting value for detecting the presence / absence of the work holding to detect the presence / absence of the work holding of the mover, the above object can be achieved more appropriately.

[0008]

[Operation] In the magnetic levitation device, the signal of the difference between the levitation control sensor signal and the set value is PID-controlled, and the voltage is distributed to a plurality of electromagnets of the operation controller to generate magnetism, which causes movement. When the magnetic body of the child is attracted and the mover magnetically levitates, and the operation controller is moved in a desired direction, the magnetically restrained mover also moves in the same direction. The mover holds, for example, a work such as a silicon wafer received from the transfer means at its tip and carries it into the inside of a processing chamber such as a sputtering chamber, and transfers the work to the transfer means inside the processing chamber. Since the mover is magnetically levitated, the posture will be tilted from the horizontal state due to the movement of the center of gravity depending on the presence or absence of the work,
The posture is corrected by analyzing the detection values of a plurality of levitation control sensors provided in the operation controller according to the purpose and controlling the distribution value of the voltage of each electromagnet by PID control. By correcting the voltage of the electromagnet facing the magnetic body of the tilted side mover to a higher level than the voltage of the electromagnet facing the magnetic body of the mover tilted up, the mover is corrected to a substantially horizontal levitation posture. To be done.

Whether the work piece is held by the mover is judged by comparing the distribution value of the voltage of the electromagnet, which shows the largest inclination depending on the presence of the work piece, with the set value. When the difference is large, the judgment that there is no work piece is output. As a result, an alarm is issued and the operation controller is deactivated, and the inconvenience that the mover operates without a workpiece is prevented. Since the distribution value of the voltage of the electromagnet is proportional to the change of the P value when the signal of the difference between the output of the levitation control sensor and the set value is PID controlled, for example, the pitching detection circuit uses the pitching from the output of the levitation control sensor. The angle signal is detected and the difference signal is set to PI to eliminate the difference from the set value.
By comparing the P output value obtained when the D control is performed with the set value, the presence or absence of the work on the mover can be detected.

Further, when the work held by the mover is displaced and the mover tilts, for example, left and right with respect to the traveling direction, the voltage distribution value of one of the left and right electromagnets is adjusted to correct this tilt. However, it is possible to know the degree of deviation of the work by detecting this change, and if there is a large deviation, it may interfere with other mechanisms during conveyance. In order to prevent this, an alarm is issued and the operation of the operation controller is stopped to correct the work deviation.

[0011]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 2 shows an embodiment in which a workpiece a is transported by a mover 4 which is magnetically levitated by a magnetic levitation device 3 between a vacuum processing chamber 1 such as a sputtering chamber or an etching chamber and a transfer chamber 2. The magnetic levitation device 3 Is an operation control in which a mover 4 provided with a plurality of magnetic bodies 5 such as permanent magnets and iron pieces, a plurality of electromagnets 6 and a levitation control sensor 7 are provided to perform a predetermined operation by a robot or a guide rod 8. And child 9. The details of the mover 4 are as shown in FIG. 3, which has a work holding portion 4a branched at the tip, and a mounting plate 4 for mounting the magnetic body 5 on the rear side.
The movable member 4 and the mounting plate 4b are made of a non-magnetic material. The mounting plate 4b has four magnetic bodies 5 such as four permanent magnets symmetrically in the front-rear direction and the left-right direction.
a, 5b, 5c, 5d are arranged, and four electromagnets 6a, 6b, 6c, 6d and four levitation control sensors 7a, 7b, 7c, 7d are arranged in the operation controller 9 so as to face each magnetic body 5. It is arranged as shown in FIG. In the illustrated example, the transfer chamber 2 is partitioned by the airtight partition wall 2a into a lower chamber 2b in which the moving element 4 is housed and an upper chamber 2c in which the operation controller 9 is housed. The levitation control sensor 7 must detect the position of the mover 4 through the partition wall 2a, and therefore detects the magnetic flux of the levitation permanent magnet 5 arranged on the mounting plate 4b of the mover 4, for example, a Hall element. A magnetic transformer or an inductor-type sensor whose inductance changes due to a change in magnetic flux density is used, and the distance between the sensor 7 and the permanent magnet 5 can be detected by the change in magnetic flux density. Incidentally, a sensor magnet may be provided separately from the levitation permanent magnet 5.

Each levitation control sensor 7 includes a levitation state control circuit 15 having a conversion circuit 10, a levitation error detection circuit 11, a pitching detection circuit 12, a rolling detection circuit 13, and a distribution circuit 14, as shown in FIG. Through each electromagnet 6
Connected to the coil 6e of each of the detection circuits 11, 12, 13
The detected value in the PID calculation circuit 16a, 16b, 16
In c, PID control (proportional / integral / derivative control) is performed, and the voltage value of each coil 6a is distributed by the distribution circuit 14 according to the output value, whereby the magnetic levitation of the mover 4 is made in a desired state. The state is controlled. The floating error detection circuit 1
The reference numeral 1 compares the detection value of the levitation control sensor 7 with the levitation set value, and controls the voltage to the electromagnet 6 so as to maintain the levitation distance of the mover 4 at the set value. The voltages of the front and rear electromagnets 6 are adjusted by comparing the detection values of the levitation control sensor 7 before and after the moving element 4 so as to eliminate the difference between the front and rear inclination of the moving element 4, that is, the angle in the pitching direction and the set value. The rolling detection circuit 13 compares the detection values of the left and right levitation control sensors 7 of the moving element 4 to prevent the workpiece a held by the moving element 4 from falling in the front-back direction. The voltage between the electromagnets 6 is adjusted to eliminate the horizontal inclination of the moving element 4, that is, the difference between the angle in the rolling direction and the set value, to prevent the work a held by the moving element 4 from falling in the horizontal direction. Carry out the action.

The magnetically levitated state of the moving element 4 changes depending on whether or not the work a is held, and has a long moving element 4 as shown in the figure.
When the work a is held at the tip of the pitching state, it greatly appears in the change of the pitching state, and especially in the change of the P value when PID control is performed.
The value is compared with the set value in the comparison circuit 17, and when the value exceeds a certain range, a signal indicating the presence or absence of the work a is output. The alarm signal can be activated or the drive circuit 9a of the activation controller 9 can be deactivated by the presence / absence signal, and when the work a is not conveyed, the apparatus is meaningless or the work a is unloaded. If this is not done, the operation of the device that damages the work a can be prevented.

The set value of the comparison circuit 17 is set by the voltage, and this set value is changed by the switching circuit 18 according to the weight of the work a which changes with the size of the work a. Also, the
The output from the PID calculation circuit 16 is introduced into the comparison circuit 17 via a low-pass three-wave circuit (LPF) 19 in order to prevent malfunction due to the influence of noise or the like.

The moving element 4 is magnetically levitated and its posture,
In order to control the position, it is necessary to control six degrees of freedom, but the degrees of freedom related to the purpose of the work detection of the present invention are the degrees of freedom in the gravity direction, the pitching direction, and the rolling direction, and other degrees. The degrees of freedom are omitted and explained. In the illustrated embodiment, when the electromagnets 6 of the operation controller 9 are excited, the magnetic body 5 of the mover 4 is attracted in the transfer chamber 2, and the mover 4 is cantilevered by the electromagnet 6. The operation controller 9 moves forward along the guide rod 8 so as to float in the shape of a beam and move the mover 4 up to a table-like delivery mechanism 20 that can be moved up and down provided in the transfer chamber 2. The mover 4
A work a such as a silicon wafer is placed on the work holder 4a by lowering the delivery mechanism 20. When the operation control element 9 is further advanced along the guide rod 8, the magnetically restrained movement element 4 is also advanced, and the work a
When the wafer is loaded into the vacuum processing chamber 1, the vacuum processing chamber 1
The delivery mechanism 21 inside rises, and the work a is delivered to the delivery mechanism 21. Then, the operation controller 9 moves backward along the guide rod 8 and the conveying process ends. In such an operation, if the center of gravity of the mover 4 is at the center of the four levitation control sensors 7 and the four electromagnets 6 as shown in FIG. 4,
Sum (A + B + C +) of the outputs of the four levitation control sensors 7
D) is an output proportional to the flying distance of the moving element 4 at the center of gravity, and the pitching angle of the moving element 4 is {(A + B).
-(C + D)} / L, and the rolling angle is
It is calculated by {(B + D)-(A + C)} / W. Here, L is the distance between the levitation control sensors 7a (or 7b) and 7c (or 7d), and W is 7a (or 7c) and 7b (or 7).
It is the interval of d). The signals of these three degrees of freedom are compared with the respective set values of the levitation distance, pitching angle and rolling angle in each of the detection circuits 11, 12 and 13, and the output of the error is compared in each PID arithmetic circuit 16. PID control is performed, and the control voltage is distributed to the coils of the electromagnets 6 via the distribution circuit 14, and the moving element 4 is maintained at a predetermined levitation distance, pitching angle, and rolling angle.

When the workpiece a is placed on the mover 4, a moment change in the pitching direction occurs. The change is detected by the four sensors 7 and a control voltage that cancels the moment change by PID control is 4%. It is distributed to the individual electromagnets 6 and output. The change in the moment at this time causes the output of the pitching detection circuit 13 to be most prominent in the control voltage of the P value (proportional) of the PID calculation circuit 16, so this P value is compared with a certain set value in the comparison circuit 17. By doing so, the presence or absence of the work a can be detected. This set value is set to the work a on the mover 4.
It is preferable to set the voltage value corresponding to the limit value of the change of the P value due to the fact that the work a is not placed on the mover 4 when the P value is small as a result of the comparison in the comparison circuit 17. It can be seen that the work is displaced from the normal position, and the work a is also displaced when the P value is larger than the set value. This work detection method does not require any special equipment or structure to be provided in the transfer chamber 2 and can be performed by using the levitation control circuit of the mover 4, and the work a can be reliably transferred even in a transfer chamber having a complicated structure. Presence can be detected.

Further, in order to detect only the positional deviation of the work a, the P value (proportional) of the PID calculation circuit 16 connected to the rolling detection circuit 13 is set as a set value in a comparison circuit similar to the comparison circuit 15. This can be done by comparison, and in this case, it is possible to eliminate the inconvenience that the workpiece a interferes with other equipment or the like and is dropped or damaged during transportation due to a large positional deviation.

In the above embodiments, the case where the work a is conveyed by the tip of the moving element 4 has been described, but the moving element 4 is attached to the mounting plate 4.
When the carriage 4 is carried on the position a, there is no change in the moment of the mover 4 depending on the presence or absence of the work a. In this case, the magnetic levitation distance of the mover 4 changes depending on the presence or absence of the work a.
The PID value of the PID calculation circuit 16 of the levitation error detection circuit 11 is connected so as to be introduced into the comparison circuit 17, and the P value is a set value corresponding to the control voltage when the work a is placed in the comparison circuit 15. The presence or absence of the work a can be detected by comparing with. Further, when the change in the rolling direction of the mover 4 is remarkable depending on the presence or absence of the work a, the PID calculation circuit 1 of the rolling detection circuit 13 is included in the comparison circuit 15 as in the case described above.
The presence or absence of the work a on the mover 4 can be detected by connecting so as to introduce the P value of 6 and comparing the P value with a set value corresponding to the change of the control voltage depending on the presence or absence of the work a.

[0019]

As described above, according to the present invention, whether or not the work piece is held by the moving element is held by the change of the control voltage distributed to the electromagnet of the magnetic levitation device based on the detection value of the levitation control sensor of the magnetic levitation device. It is possible to detect the presence or absence of work without the need to install a special sensor or viewing window in the transfer path of the moving element, and it is possible to interfere with other devices and structures even in a transfer room with a complicated structure. The presence / absence of a work can be reliably detected without doing so, the detection can be continuously performed from the start to the end of conveyance, and the shift of the work can be detected if necessary, which is advantageous.

[Brief description of drawings]

FIG. 1 is a cutaway side view of a conventional example.

FIG. 2 is a cutaway side view of an embodiment of the present invention.

FIG. 3 is a plan view of the mover shown in FIG.

FIG. 4 is a perspective view of a main part of the operation controller of FIG.

FIG. 5 is a diagram of a floating state control circuit.

[Explanation of symbols]

a Work 2 Transport chamber 3 Magnetic levitation device 4 Moving element 5, 5a, 5b, 5c, 5d Magnetic body 6, 6a, 6b, 6c, 6d, Electromagnet 7, 7a, 7b, 7c, 7d Levitation control sensor 9 Operation control Child 9a Drive circuit 10 Conversion circuit 11 Levitation error detection circuit 12 Pitching detection circuit 13 Rolling detection circuit 14 Distribution circuit 15 Levitation state control circuit 16, 16a, 16b, 16c, 16d PID arithmetic circuit 17 Comparison circuit 18 Switching circuit 19 Low range 3 Wave circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location // H01L 21/203 S 9545-4M 21/3065

Claims (5)

[Claims] 1. A magnetic levitation posture of a moving element holding a work piece and an operation control element provided opposite to the moving element by magnetically levitating the moving element with a plurality of electromagnets and a levitation control sensor. A controllable magnetic levitation device, wherein the magnetic levitation device magnetically levitates the moving element so as to follow the movement of the operation control element. The method of detecting a work in a magnetic levitation transfer apparatus, wherein the presence or absence of holding of the work by the mover is detected based on a change in a control voltage distributed to the electromagnet based on the detection value of. 2. A moving element holding a work and an operation control element provided opposite to the moving element are magnetically levitated by a plurality of electromagnets, and the moving element is levitated by a levitation control sensor. PID the signal of the difference between the status signal and the set value
A magnetic levitation device for controlling the magnetic levitation posture of the moving element by controlling and distributing a control voltage to a plurality of electromagnets is provided, and the moving element magnetically levitated by the magnetic levitation apparatus is used to move the operation control element. In a magnetic levitation transport device that follows and moves, by comparing the output (P output) of a proportional control circuit for controlling the pitching direction with a set value according to the weight of the work, A method for detecting a work in a magnetic levitation transfer device, characterized by detecting the presence or absence of the work. 3. A mover holding a work is provided with a plurality of magnetic bodies such as permanent magnets constituting a magnetic levitation device, and an operation controller provided facing the mover cooperates with each magnetic body. An electromagnet of a magnetic levitation device that magnetically levitates the mover is provided, and a plurality of levitation control sensors of the magnetic levitation device that detect the levitation state of the mover are provided on the operation controller, and the signal detected by the sensor and the set value The magnetic levitation transfer is designed to control the magnetic levitation posture of the moving element that follows the movement of the operation controller by controlling the voltage distribution value of each electromagnet by PID controlling the signal of the difference between In the device, detecting the presence / absence of work holding of the mover by comparing the change in the P value of the PID control value of the signal of the difference between the sensor signal and the set value with the preset value for detecting the presence / absence of work holding Detection method in magnetic levitation transfer device characterized by . 4. The comparison circuit for comparing the P value and the set value can change the set value according to the size of the work,
4. The method for detecting a work in a magnetic levitation transfer apparatus according to claim 3, wherein the P value signal is input to the comparison circuit via a low-frequency three-wave circuit. 5. A moving body for holding a work is provided with a plurality of magnetic bodies such as permanent magnets constituting a magnetic levitation device, and an operation controller provided facing the moving body cooperates with each magnetic body. An electromagnet of a magnetic levitation device that magnetically levitates the mover is provided, and a plurality of levitation control sensors of the magnetic levitation device that detect the levitation state of the mover are provided on the operation controller, and the signal detected by the sensor and the set value The magnetic levitation transfer is designed to control the magnetic levitation posture of the moving element that follows the movement of the operation controller by controlling the voltage distribution value of each electromagnet by PID controlling the signal of the difference between The apparatus is provided with a comparison circuit for comparing a change in the P value of the PID control value of the signal of the difference between the sensor signal and the set value with the set value for detecting the presence / absence of work holding, and the comparison circuit is provided with the operation controller. Magnetic levitation transport device characterized by being connected to the drive circuit of Work detection device in storage.