JPH022104A - Mask holder - Google Patents

Abstract

PURPOSE:To prevent damages to masks due to the collision of a mask with a mask chuck by a method wherein a means for detecting the positions of a mask and a mask holder carried is provided, and an attraction force is exerted or not according to the result of the detection by the means and a carry means is controlled. CONSTITUTION:After a mask 8 is grasped by a hand 11 at a lower position, the motor 13 of an up-and-down movement apparatus 14 is driven and the mask 8 is moved toward the bottom surface of a mask chuck 9. At this juncture, a current for demagnetization flows through a coil 3 and the attraction force of a permanent is 0 or substantially negligible seemingly. While the mask 8 is rising, a light sensor detects the position of the mask. When the mask contacts the chuck, a circuit 19 generates a contact signal. The demagnetization current is cut out by this signal and a mask frame is attracted by the permanent magnet. The mask is held by the permanent magnet in this manner after the fact that the mask and the mask chuck are very close to each other or in contact with each other is confirmed. Therefore, strong impacts due to collision are not given to the mask at chucking.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for preventing damage to the mask due to collisions, etc. when holding the mask in a mask holding means in a semiconductor exposure apparatus.
This invention relates to a mask holding means that allows the mask to be held safely.

[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. 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. Then, the transported mask is passed to a mask holder and held by suction.However, in conventional devices like this, there were the following problems when passing the mask to the mask holder. . Conventional devices do not have a means for detecting contact between the mask holder and the mask, and the mask hand is controlled by a control means according to the amount of movement of the mask, and usually the mask is brought close to the mask chuck or Although it is set to stop at the contact position, the amount of movement is determined in advance, so if the thickness of the mask changes, the mask may collide with the mask chuck, causing damage to the mask. There were other problems.

[Means to solve the problem]

In order to solve the above-mentioned conventional problems, the present invention provides a means for detecting the position of the transported mask and the mask holder, and turns on the suction force according to the detection result of the means.
, OFF and control of the transport means, problems such as collision between the mask and the mask holder are solved. Details will be described in the following examples.

〔Example〕

FIG. 1 shows the configuration of a conventional magnetic chuck attraction unit, where 5 is a mask chuck and 1 is an attraction magnetic unit. The detailed configuration of the unit will be described later.

The magnetic units 1 are arranged on the lower surface of the mask chuck 5 at intervals of 90° in the circumferential direction.

3 is a demagnetizing coil, 4 is a permanent magnet that attracts and holds the mask, and 6 is a terminal of the coil, to which a demagnetizing current is applied when the mask is removed.

FIG. 2 is a configuration diagram of the magnetic unit.

Components with the same numbers as in FIG. 1 above refer to the same components. 2 is a yoke. The yoke is U-shaped and holds a permanent magnet in between. The permanent magnet has a sufficient attracting force to hold the mask, and is of a size that does not require a large amount of current during demagnetization.

The above is the configuration of a conventional mask chuck. When holding a mask on such a mask chuck, there are problems as described above.

The structure of the mask chuck according to the present invention will be explained, and the operation of attracting and detaching a mask using the mask chuck will be explained with reference to FIG.

11 is a hand that grasps the mask. This hand 11 is a driving device that moves the hand in the left-right direction in the drawing, causes the hand to grasp the mask frame 7 when moving to the right, and releases the mask when moving to the left. Further, this hand 11 is moved up and down by a vertical moving device 14 having a motor 13 to bring the top surface of the mask 8 close to or in contact with the bottom surface of the chuck 5, or to move it away from the bottom surface of the chuck 5. Reference numeral 1 denotes a magnetic unit, and its arrangement and configuration on the lower surface of the mask chuck are not particularly different from the conventional example described above. 2 is a yoke, 3 is a demagnetizing coil, and 4 is a permanent magnet. A light source 21 is provided on the mask chuck 9 and projects light onto the upper surface of the mask frame 6. The amount of light reflected from the mask frame is received by the optical sensor 20. The output of this optical sensor is input to the signal processing circuit 19 and compared with a light amount reference signal that would be obtained when the upper surface of the mask 8 and the lower surface of the mask chuck 9 come into contact.

When the output of the optical sensor and the reference signal match, the circuit 19 outputs a signal indicating that the mask and the chuck have contacted each other.

Note that a contact signal may be obtained based on the position of the light spot reflected from the mask frame by using the optical sensor as a light spot position detector.

Also, an air sensor or a capacitance sensor may be used instead of the optical sensor. Further, the detection can be performed using a magnetic unit in the mask chuck without providing a special position detection sensor as described above.

In other words, this is also possible by detecting the change in inductance that occurs when current is passed through the coil in the magnetic unit.

More specifically, the inductance generated when a current is passed through a coil wound around a magnetic material during boat fishing is given as follows.

Here, ■ is the current flowing through the coil, n is the number of turns of the coil, and 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 μ. is the magnetic permeability in vacuum.

Using the inductance value when the mask and the chuck are in contact as a reference signal, the relationship between the detected inductance value when there is no contact and the distance between the mask and the mask chuck is determined in advance and inputted to the signal circuit 18. It can detect the position and whether the mask is in contact or not.

Reference numeral 15 denotes a power source that supplies a demagnetizing current to the coil 3 via a current adjustment circuit 16. Then, the current adjustment circuit 16 turns off the flow of the demagnetizing current based on the output of the circuit 19.

116 and 117 are motor control circuits.

Next, the operation of the device shown in FIG. 3 will be explained according to the flowchart shown in FIG. 4. After gripping the mask 8 in the lower position with the hand 11, the motor 13 of the vertical movement device 14 is driven, and the mask 8 is moved into the mask chuck 9. Move toward the bottom of the screen. At this time, a demagnetizing current flows through the coil 3, and the permanent magnet apparently has zero or almost no force to attract the mask. While the mask 8 is being raised, the optical sensor is detecting the position of the mask. When the mask comes into contact with the chuck,
Circuit 19 generates a touch signal. In response to this signal, the demagnetizing current is turned off, and the mask frame is attracted by the permanent magnet. At the same time, the motor 13 stops.

As a result, the mask is firmly attracted to the chuck. Next, the hand 11 moves to the left, and the chucking operation ends.

In addition, in the above explanation, when the mask contacts the chuck,
The degaussing current may be turned off, or the degaussing current may be caused to flow when the mask and chuck are spaced at a very narrow and constant interval. After confirming that the mask and mask chuck are in close proximity or in contact with each other in this way, the mask is held by a permanent magnet, so that the mask is not subjected to strong impact due to collision during chucking.

Particularly in the case of an X-ray exposure mask in which the mask is formed of a thin film, the mask may be damaged by this impact, but this method eliminates this damage.

Next, using FIG. 5 to explain how to remove the mask, the moving device 12 is activated and the hand 11 is moved to the right. A grip completion signal for gripping the mask frame 7 is obtained by a sensor (not shown). This signal is input to the processing circuit 19. A current is applied to the coil 3 by a signal from the circuit 19, and the magnetic unit 1 loses its attraction force. Next, the vertical movement device 14 is activated to move the mask downward.

In the above explanation, the magnetic force of a permanent magnet is used as the attraction force, but this may be an electrostatic chuck or vacuum attraction using air.

In addition, in the case of the magnetic chuck described in the above embodiment, demagnetization is performed by applying an attractive force, that is, magnetic force, to the coil until the mask is held, but this causes problems such as heat generation, so the mask is not held in the mask chuck. When the mask is near the mask chuck, it is necessary to demagnetize the mask so that the sudden attraction force does not act on the mask, but if the mask is completely below the mask chuck, it is better to not energize the coil so that the mask will attract the mask. Since no force is applied, it is better to consider the issue of heat generation. In other words, when the mask is being transported by the mask hand, the coil is not energized to demagnetize until the mask chuck reaches a position where the mask does not have any attraction force, and the mask is demagnetized within the range where the attraction force is applied to the mask. When the position of is reached,
Energize the coil to demagnetize it. Since the range of the adsorption force is known in advance, if the detected value at that position is stored in memory, then depending on the output of the position detection, it is possible to turn on the current to the coil other than when holding, as described above. O
FF can also be controlled.

〔Effect of the invention〕

As explained above, according to the present invention, when a mask is conveyed to a mask chuck by a conveyance mechanism such as a mask hand, a means for detecting contact or non-contact between the mask and the mask chuck is provided. Damage to the mask due to collision with the mask chuck can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional mask holding device (mask chuck). FIG. 2 is a configuration diagram of a magnetic unit in the mask holding device of FIG. 1. FIG. 3 is a diagram of a mask holding device and a mask transport mechanism for explaining Embodiment 1 of the present invention. FIG. 4 is a flowchart showing a mask holding operation for explaining Embodiment 1 of the present invention. FIG. 5 is a flowchart showing the mask removal operation for explaining the first embodiment of the present invention.

Claims (1)

[Claims] 1. A mask holding device of a transfer device that irradiates irradiation energy onto a sensitive body through a mask and transfers a pattern formed on the mask onto the sensitive body includes the following: . means for holding the mask on a holding surface by suction means; means for moving the mask in the direction of the holding surface; when the mask and the holding surface of the mask come into contact or are in a certain close distance; a position detection means for emitting a signal to that effect; and a control means for generating an adsorption force of the adsorption means in response to the signal from the position detection means. 2. Claim 1, wherein the moving means stops moving in the direction of the holding surface in response to the signal.
Mask holding device as described in section. 3. The mask holding device according to claim 1, wherein the attraction means is a combination of a permanent magnet that generates a holding force and a canceling coil that releases the magnetic force of the permanent magnet. 4. The mask holding device according to claim 1, wherein a plurality of said suction means are installed. 5. The mask holding device according to claim 1, wherein the position detection means is an optical sensor. 6. The mask holding device according to claim 3, wherein the position detection means detects the inductance of the cancellation coil.