JPH0248196A - Transfer equipment - Google Patents

Abstract

PURPOSE:To improve the reliability of a transfer equipment and improve the transfer efficiency by providing a circuit which detects the inductance of an electro-magnet and checking whether or not any substance to be transferred exists. CONSTITUTION:A detecting circuit 6 detects the movement of a hard H1 to the position B and according to this signal from the circuit 6, a control circuit 3 changes the position C of the switch of switch selectors 8 and 9 to the position (a) via a switch control circuit 7. As a result, an exciting power supply 10 is connected to the power supply of a bridge circuit to carry the current I1 across coil wound on the permanent magnet MG0 of a magnet chuck MG1. Variation in inductance at this time is detected and it is detected whether or not a mask M1 exists on a master holder MH1. From the result of this detection if the existence of the mask is detected, the hard H1 is moved to the position C and the mask M1 is released from the mask holder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transport device that determines the presence or absence of a mask when transporting a mask in a semiconductor exposure apparatus.

[Conventional technology]

When a semiconductor exposure apparatus forms a pattern on a wafer, a mask is positioned at a predetermined position on the exposure projection. The masks are mounted in a mask cassette or a mask holder, and a plurality of masks are stored in a mask carrier box, for example. When transporting a mask to position it on an exposure projection, a desired mask cassette or mask holder housed in a mask carrier box is moved to a mask take-out position. Then, a mask hand or the like serving as a transport unit mechanically holds the mask in the mask cassette or on the mask holder at the mask take-out position and transports it onto the exposure projection. However, the following problems arise in the above-described transport method. First, since the mask hand does not have a means to detect the presence or absence of a mask, it may detach from the mask it is holding during transportation by attempting to hold another mask while holding the mask.
There is a risk of damaging the mask. Furthermore, if the mask cassette or mask holder does not have a means for detecting the presence or absence of a mask, there is a possibility that the mask hand may carry the mask without holding it. A conveyance device without such a structure has the disadvantage of low reliability and poor conveyance efficiency.

[Means for Solving the Problems (and Effects)] In view of the problems in the conventional type described above, the purpose of the present invention is to install an electromagnet in the transport section to hold the mask (
In addition, an electromagnet is attached to the mask cassette or the mask holder to hold (attach and detach) the mask, and by detecting the inductance of the electromagnet, it is possible to determine whether the mask is present or not on the mask hand. This makes it possible to determine whether a mask is present or not inside a mask cassette or on a mask holder.

Next, as an example of the present invention, Example 1 is a method of detecting the presence or absence of a mask on a mask hand. In the second embodiment, a method for detecting whether or not a mask is present in a mask holder will be specifically described.

[Embodiments of the invention]

Embodiment 1 - Hereinafter, a specific embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a conveying means in one embodiment of the present invention, and FIG. 2 shows an enlarged view and electrical configuration of the same embodiment. In FIG. 1, Ml is an object to be transported, for example, a mask in this embodiment. Furthermore, the mask holder that holds the mask is assumed to be MHI. A plurality of permanent magnets (not shown) including degaussing coils are embedded in the mask holder MHI to attract and hold the mask or separate it, and the mask and mask holder are chucked (
In FIG. 1, the mask is placed vertically, but the mask may be placed horizontally. ). To separate the mask from the mask chuck, the magnetic field of the magnet is canceled by passing an exciting current through the coil wound around the permanent magnet, and the magnetic force of the permanent magnet is resolved (this makes separation possible).

Hl is a mask hand for transporting the mask. The shape of the mask hand is not particularly limited, as long as it can hold the mask reliably.

Although not shown in FIG. 1, the mask hand is driven by an actuator, such as a DC motor, and further includes a potentiometer that detects the position of the hand in an absolute manner. The MCI is a magnetic chuck, and a permanent magnet MGO is embedded therein. The mask hand has the function of chucking the mask to the mask hand when removing the mask from the mask holder and transporting it, the function of releasing the mask at the transported position, and the function of the mask hand to determine whether there is a mask on the mask holder or the mask hand. It has a detection function using the magnetic chuck MCI. Therefore, the first
In the figure, the method of transporting the mask by the mask hand H1 is to confirm by MCI that the mask hand H1 is not holding a mask at position A, and then move the mask holder in one direction by the actuator of the mask hand. When the mask hand further moves to position B, M
The CI can determine whether there is a mask in the mask holder or not, and if there is a mask, the actuator moves the mask hand to position C, the MCI attaches the mask to the mask hand H1, and the mask is removed. If not, the mask hand returns to position A. Further, a detailed explanation will be given using FIG. 2. FIG. 2 shows an enlarged view of the MG1 portion attached to the mask hand H1 and the outer peripheral portion of the mask within the broken line area. Furthermore, as an electrical configuration, 1
2 is an amplifier that amplifies the output signal from the bridge circuit; 4 is an actuator for moving the mask hand, such as a DC
5 is a motor, a potentiometer that detects the position of the mask hand H1 in an absolute manner, and 6 is a circuit that converts a signal from the potentiometer into a position detection signal.

Reference numeral 10.11 is a power source for passing current for excitation and reverse excitation of the coil wound around the MCI, and reference numerals 8 and 9 are a selector switch for selecting the power source of 10.11, and a control circuit for controlling the selector switch. 3 is a control circuit that controls these circuits. In the enlarged view within the broken line area, there is a permanent magnet M in the magnetic chuck MCI.
A GO is embedded, and a coil is wound around the permanent magnet.

A, B, and C on Figure 2 are A on Figure 1.

This shows the same positional relationship as B and C. The distance between the outer circumference of the mask and the MCI at position B is 62, δ1 is the distance of the magnetic path length in the air of the magnetic chuck MCI, and δ3 is the distance within the mask. The distance from the outer periphery of the mask to the magnetic path length when the magnetic path length is 1/2 of the radial thickness of the mask. In this embodiment, the material of the frame on the outer periphery of the mask is not particularly limited as long as it is magnetic, but it is preferably one with relatively high magnetic permeability. For example, in this embodiment, the frame of the mask is made of pure iron. Next 12. is the average total magnetic path length of the magnetic chuck MCI, and I! 2 is the length of the gap in the U-shaped MGI.

Now, the mask hand is P, M5 and A by the position detection circuit 6.
, the mask hand H1 detects that it is not holding a mask. First, from the control circuit 3 through the switch control circuit 7, selector switch 1
By switching 0.11 from position C to position b, it is connected to the reverse excitation power source, and a current I2 in the direction of reverse excitation of the coil flows through the bridge circuit.

Since the current I2 is in a direction that generates magnetic flux in the same direction as the magnetic flux direction of the permanent magnet MGO, it does not cancel out the magnetic field of the permanent magnet. Furthermore, a half-wave rectified waveform is used as the voltage waveform for reverse excitation. -The inductance that occurs when a current is passed through a coil wound around a magnetic material when fishing on a boat is given as follows.

Here, I is the current flowing through the coil, n is the number of turns in the coil, Φ is the magnetic flux generated in the coil, S is the cross-sectional area of the magnetic material, l is the average magnetic path length of the magnetic material, and μ0 is the permeability in vacuum. Magnetism.

Therefore, in this embodiment, the inductance can be measured using the above equation (1).

When the mask hand H1 has a mask, in this embodiment, the length of the magnetic chuck A is 12+ = 7 mm.
, 12=6mm, and N (number of turns) of the coil is N=140.
, the cross-sectional area S of the magnetic chuck is 2.3 mm2, and if there is a mask, the position is C in FIG.

Therefore, since the magnetic path length on the mask frame is almost in close contact with the MCI, it becomes β2+263, and δ3 becomes δ3=2.5 mm when the mask frame width is 5 mm. Also 1,
The magnetic permeability of the mask frame is the initial magnetic permeability (μFe)μ
If Fe#250 is used, and similarly when the mask hand H1 does not have a mask, the magnetic path length is considered to be the magnetic path length in air. In Figure 2, the magnetic path length in air is 2δ1+12
Assume that δ1 is twice as long as δ3. Therefore, the inductance when the mask is held is Ll, and the inductance when the mask is not held is Ll. Then,
L, Tori. By detecting each signal output from the bridge circuit in the mask hand H1, for example, by setting a certain threshold level and comparing the output signal (detection signal) with that level, it is possible to determine whether there is a mask in the mask hand H1. Can be distinguished.

From the above, Lo becomes as follows.

From equations (2) and (3), when we measure Lo, L,=
0.77 mH L, = 0.0024 mH, and the inductance showed a change of approximately 300 times depending on whether the mask was held in the mask hand H1 or not. Ll take. Since the value of can be obtained as an electrical output signal by the bridge circuit 1 and the amplifier 2, the mask M
It is easy to determine whether or not 1 is held. In this embodiment, the configuration of the bridge circuit 1 to be detected is a resistance ratio bridge configuration in which a potential difference in an unbalanced state can be detected, but other circuit configurations may be used as long as inductance can be measured.

The ratio of the inductances L, , L is expressed by equations (2) and (3), and is influenced by the magnetic permeability and magnetic path length of the frame of the mask M1.

If it is detected that a mask is being held on the mask hand, the control circuit 3 switches the selector switch from position b to position C through the switch control circuit 7, and continues to hold the mask with the magnetic force of the permanent magnet MGO. . Next, a method for determining the presence or absence of a mask will be described in the case where, after determining that there is no mask M1 in the mask hand H1, the actuator 1 of the mask hand H1 detects whether there is a mask in the mask holder MHI.

After detecting that there is no mask on the mask hand H1, the mask hand H1 moves to position B, and the position detection circuit 6 detects that the mask hand H1 has moved to the position B on the mask holder side by the actuator 1 of the mask hand H1. When the position signal is transmitted to the control circuit 3, the control circuit 3 selects the switch of the switch selector 8.9 from the position C to the position a through the switch control circuit 7. Therefore, the excitation power source 10 is connected to the power source of the bridge circuit. A current 11 flows from the excitation power source 10 in a direction illustrating the coil. Since the current I generates a magnetic flux in the opposite direction to the magnetic flux direction of the permanent magnet MGO, it has the effect of canceling the magnetic field of the permanent magnet. This prevents the magnetic force of the MGO from acting on the mask on the mask holder. At this time, the waveform of the excitation power source is a half-wave rectified waveform having the same frequency as the reverse excitation power source, and the voltage polarity is opposite to that of the reverse excitation.

When the mask hand H1 moves to position B, it is possible to detect the presence or absence of a mask by the magnetic chuck MCI based on the change in inductance described above. (2)
Calculating the inductance at position B from the formula, the inductance when there is a mask on the mask holder is L2, and the average magnetic path length at that time is δ2 is 1 of δ3 at position B.
Assuming that the magnetic path length is 5 times longer, L2-n2 ・μ.

μFe-8/[7,+2 (δ2+63)-11!
21, and L2=0.68mH. Also, from equation (4), the change ratio of L2/Lo #280 and inductance is sufficiently large, so even at position B, the mask holder M
The mask hand H determines the presence or absence of the mask M1 on the HI.
1 can be detected.

Therefore, if it can be determined that the mask M1 is present on the mask holder MHI at the position B, the mask hand H
1 moves to position C, and switches the switches of switch selectors 8 and 9 from position a to position C through control circuit 3 and switch control circuit 7. After the mask M1 is attached to the mask hand H1 by the magnetic force of the permanent magnet, the magnetic field of the permanent magnet embedded in the mask holder MHI is released to separate the mask holder MHI and the mask M1. From the above, the mask hand H1 is the mask M1
can be held and transported. Also, mask holder M
If it is detected that the mask M1 is not present at HI, the mask hand H1 returns to the position A. At that time, the switch selector 8.9 selects the switch to C by the switch control circuit 7.
Select the position. As above, mask hand H
The magnetic chuck MCI of No. 1 detects the presence or absence of the mask M1 on the mask holder MHI and further determines whether the hand H1 is holding the mask M1 by detecting changes in inductance. Example 2 is shown.

In FIG. 3, although not shown, a mask M2, which is an object to be transported, is the same as M1 in the first embodiment. MH2 is a mask holder that holds the mask M2. MH2
The mask is held vertically above, and the mask M2 and mask holder MH2 are in contact with each other at the shaded area. Magnetic chucks MG2 to MG5 are for attaching and detaching the mask M2 to and from the mask hold MH2, and are embedded evenly within the shaded portion of the mask hold MH2. In this embodiment, the number is four, but the number is not limited as long as the mask M2 can be held. Magnetic chuck M02~MG5
The shape of the MCI is the same as that of the MCI shown in FIG. 2 of the first embodiment. Figure 4 shows the magnetic chucks MG2 to MG5 in Figure 3.
FIG. MG2~MG5
are connected in series. 12 to 19 in FIG. 4 are constructed of the same circuits as 1 to 11 (excluding 4, 5, and 6) in FIG. 2 of the first embodiment.

In Example 2, the magnetic chucks MG2 to MG5 in the mask holder MH2 are
The mask holder MH2 of the present invention has a function of holding a mask, and a function of determining whether or not there is a mask.

Next, the mask presence/absence determination function will be described. When M2 is held in MH2, it is based on the magnetic force of the permanent magnets provided in MG2 to MG5. At that time, no current is flowing through the coil wound around the permanent magnet, and the switch 16.17 is selected to GND (ground). The presence or absence of a mask can be determined by extracting the change in the inductance L of the coil as an electrical signal, as described in the first embodiment. This can be considered to be the same as the case at position C in FIG. 2, where Ml and Hl are in contact.

Therefore, according to the first embodiment, the change in inductance is determined by the magnetic permeability of the mask M2 and the length of the magnetic path. or,
If the mask frame MH2 does not have the mask M2, it corresponds to the position A in FIG. 2 of the first embodiment. Mask M2
Since the method for detecting can be performed by the same detection method as described in the first embodiment, it will not be described in the second embodiment. Furthermore, by using these methods, it is also possible to combine, for example, with the configuration of Embodiment 1, and the mask frame MH
It is also possible to give a movement signal to the actuator of the hand H1 so that the hand H1 holds the mask Ml (M2) only when the mask M1 (M2) is chucked on the I (MH2).

Further, when the mask M2 is separated from the mask frame MH2 (for example, when it is about to be carried by the hand H1), a current I is applied that cancels the magnetic field of the permanent magnets attached to the magnetic chucks MG2 to MG5 in FIG.
The hold is released by playing 2. These removal methods are also the same as in Example 1. The first and second embodiments of the present invention have been described above.

〔Effect of the invention〕

As explained above, according to the present invention, the conveyance mechanism and the mechanism for holding the conveyed object are each equipped with a magnetic chuck, so that the conveyed object is conveyed and held (attached and detached), and the coil wound on the magnetic chuck is We were able to add a function to detect changes in inductance by passing a current through and determine the presence or absence of an object to be transported, making the transport function reliable and highly reliable.

[Brief explanation of the drawing]

FIG. 1 is a transport mechanism diagram for explaining Embodiment 1 of the present invention. FIG. 2 is an enlarged view of the conveying hand portion and an electrical configuration diagram. FIG. 3 shows a mask frame and a mask chucking section for explaining the second embodiment. FIG. 4 is an electrical configuration diagram of a magnet for chucking. Ml, M2...Mask MHI, MH2...Mask frame H1...Hand MGI to MG5...Magnetic chuck MG
O...Permanent magnet 1.12...Bridge circuit 2.13
...Amplifier 3.14 ...Control circuit 4
...DCMOTOR5...Potentiometer 6...Position detection circuit 7, 15 8. 9. 16゜10.18 11.19 ... Switch control circuit ... Selector switch ... Excitation power supply ... Reverse excitation power supply

Claims (1)

[Claims] 1) A transport unit, a drive system for transporting the transported object, and a holder for holding the transported object, and the transporting section and the holder are capable of attaching and detaching the transported object to and from the holder by magnetic force. What is claimed is: 1. A conveyance device, wherein the presence or absence of a conveyance object on a conveyance section and a holder is determined by detecting the inductance of the electromagnet in the conveyance device equipped with an electromagnet. 2) The conveying device is configured to operate a presence/absence alarm device when detecting the inductance of an electromagnet and determining the presence/absence of the conveyed object. Conveyance device. 3) The conveyance device according to claim 1, wherein the conveyance device performs a self-check by detecting the presence or absence of an object to be conveyed before operating the device.