JP2001219390A - Carrying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrying device capable of efficiently carrying an article to carry such as a wafer W, etc., by properly selecting and controlling carrying characteristics such as carrying speed(s), etc., even in the case when holding force(f) to hold the object to be carried such as the wafer W, etc., is lowered. SOLUTION: This carrying device has a holding part H to hold the object W to be carried, a detection part SNS, 5 to detect holding force by the holding part H, a selection part 6 to select a specified carrier characteristic S in correspondence with the holding force and a control part 7 to control the selected carrying characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transfer device, and more particularly to a transfer device suitable for transferring a photosensitive substrate such as a wafer.

[0002]

2. Description of the Related Art Conventionally, when a wafer is transferred using a transfer device, for example, a predetermined threshold value for the holding force is used as a reference, and when the holding force is equal to or larger than the threshold value, a transfer at a constant speed is performed. Alternatively, when the holding force is equal to or less than the threshold, the conveyance is stopped as an error state.

[0003]

In the prior art, when the holding force on the wafer is equal to or higher than a predetermined threshold,
Regardless of the magnitude of the wafer holding force, the transfer was performed at a constant speed. Therefore, when a wafer is transported in a state where the holding force is reduced while being larger than the predetermined threshold, the position of the transferred wafer is shifted from the predetermined position, or in the worst case, the wafer is moved. There was a problem that it would be shaken off. Here, as a case where the holding force decreases when the holding force is the vacuum suction force,
For example, when the original pressure in the factory decreases due to some external factor, when the vacuum value of the transfer device is temporarily reduced by drawing a vacuum in another device other than the transfer device, and further depending on weather conditions When the low pressure arrives, the pressure difference from the atmosphere becomes small, and the holding force is reduced.

On the other hand, when the holding force of the wafer is less than a predetermined threshold value, the transfer operation is not performed as an error state, so that the reliability of the transfer device such as a low operation rate has been a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to appropriately select and control transfer characteristics such as transfer speed even when a holding force for holding a transferred object such as a wafer is reduced. Accordingly, it is an object of the present invention to provide a transport device capable of transporting efficiently.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a holding unit for holding an object to be transported, a detecting unit for detecting a holding force by the holding unit, and a holding unit corresponding to the holding force. Provided is a transport device, comprising: a selection unit that selects a predetermined transport characteristic; and a control unit that controls the selected transport characteristic.

In the present invention, the holding force is preferably a vacuum suction force. Here, the holding force refers to a magnetic force, an adhesive force, and the like in addition to the vacuum suction force. The holding force is not limited to a physical force, and is a concept that encompasses all aspects suitable for holding a transferred object. For example, it is wrapped in a net.

In the present invention, it is preferable that the transport characteristic is a speed at which the transported object is transported. At this time, if the holding force is equal to or less than the threshold, it is desirable to reduce the speed of transport. FIG. 1 is a diagram showing a typical pattern for changing the transport speed (the horizontal axis is time t, and the vertical axis is speed s). For example, a trapezoidal pattern (a) and an S-shaped pattern (b) as shown in the figure are given.

Further, in the present invention, it is preferable that the transport characteristic is an acceleration at which the transported object is transported. Further, when the wafer held by the transfer arm is transferred while controlling the transfer acceleration (FIG. 2), it is desirable that the following expression (A) is satisfied. (A) m · α <μ (S × P + m × G) where α: acceleration during wafer transfer, S: area of wafer suction surface, Ps: pressure of suction unit (negative pressure), P0: wafer transfer , P = P0−Ps m: weight of wafer G: gravity μ: coefficient of static friction.

If the operation pattern is controlled so as to satisfy the conditional expression (A), no positional deviation of the wafer occurs. Therefore, it is possible to select an efficient operation pattern that does not generate a position shift.

In the present invention, it is preferable that the transport characteristic is a predetermined pattern including at least one of an acceleration and a speed at which the transported object is transported.

For example, the following cases can be cited as examples of selecting the transport characteristics. (1) When the holding force is measured before the start of the transfer and the transfer route (course) is switched in advance (2) When the holding force is reduced during the transfer and the holding pattern is detected to change the transfer pattern Further, even if the pattern is changed during the conveyance, the object can be conveyed to a predetermined target position by using a pulse control technique, a feedback technique, a position control technique, or the like.

In the above-described configuration, it is possible to control the transfer characteristics to be optimum according to the holding force of the transferred object (for example, a wafer). For this reason, even if the holding force changes due to aging of the wafer holding mechanism or a change in vacuum pressure, the position of the wafer does not shift during transfer. Also, there is no error due to vacuum pressure drop,
A transport operation can be performed.

[0014]

FIG. 3 is a diagram showing a schematic configuration of a transport device according to an embodiment of the present invention. The present apparatus is an apparatus for transferring a wafer W to a predetermined stage 4 position. First, the wafer holding unit H of the feeder arm 1 holds the wafer 2 with a predetermined holding force. Here, the holding force of the wafer 2 refers to a force obtained by adding a vacuum suction force and a static friction force due to gravity. Next, the wafer 2 is transferred to a wafer holding portion H ′ provided at the tip of one arm of a rotating arm 3 having two arms. The wafer holding unit H ′ holds the wafer 2 with a vacuum suction force similarly to the wafer holding unit H. Here, a vacuum sensor SNS for detecting a vacuum value is attached to the wafer holding unit H and the wafer holding unit H ′. The output from the sensor SNS is sent to the wafer holding force detection mechanism 5. The computer 6 has a correspondence table between a vacuum value and an optimum transport speed according to the vacuum value. FIG. 4 shows the vacuum value -Pa (horizontal axis) and the holding force f.
It is a figure which shows the relationship with (vertical axis). As is clear from the figure, the holding force uniquely corresponds to the measured vacuum value. It is sufficient that the transport speeds S1, S2,... Appropriate for the holding forces f1, f2,. In addition,
The table is not limited to one correspondence table, and preferably has a plurality of tables such as a correspondence table between a vacuum value and a transfer acceleration, and a correspondence table between a vacuum value and a transfer pattern. Further, instead of the table, the operator may determine the optimum transfer speed corresponding to the measured vacuum value and input an appropriate transfer speed from the keyboard KB.

Next, a signal from the computer 6 is sent to the wafer transfer speed control mechanism 7. Then, the feeder arm 1 or the rotating arm 3 is controlled by the control mechanism unit 7 so that the transport speed is optimal for the detected vacuum value. And it is conveyed on the stage 4 provided in the predetermined position.

Although the above embodiment has been described with reference to a wafer transfer apparatus, the present invention is not limited to this. For example, an apparatus having a mechanism for transferring an object to be transferred with an appropriate holding force, for example, a semiconductor projection exposure apparatus, The present invention can be applied to all devices such as a microscope observation device.

[0017]

As described above, according to the present invention,
For example, by changing the transfer speed by the holding force of the wafer, the wafer can always be properly transferred. Therefore, there is an effect that the wafer can be transported safely and accurately. Further, since it is possible to cope with a decrease in holding force due to aging and a decrease in holding force due to a change in vacuum pressure or the like, there is an effect that it is possible to easily cope with a change in an external environment. In addition, an efficient transfer characteristic can always be selected even when the holding force changes due to the state of the suction surface of the wafer. Further, even when the holding force is lower than the set threshold value, the transfer is not stopped as an error, so that a transfer device with improved reliability and excellent operation rate can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control pattern of a transport speed.

FIG. 2 is a diagram illustrating a cross section when a wafer is transferred.

FIG. 3 is a diagram illustrating a schematic configuration of a transport device according to the embodiment;

FIG. 4 is a diagram showing a relationship between a vacuum value, a holding force, and a transport speed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Feeder arm 2 Wafer 3 Rotating arm 4 Stage 5 Wafer holding force detection mechanism 6 Computer 7 Wafer transfer speed control mechanism SNS Vacuum sensor KB Keyboard

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3C007 DS01 FS01 FS06 FU01 FU04 GU03 KS30 LV10 NS09 3F059 AA01 BA09 DC04 FC02 3F061 AA01 CA01 CA06 CC01 CC13 DB04 DC03 DD02 DD03 5F031 CA02 FA01 GA07 GA08 GA09 JA45 PA10

Claims (5)

[Claims] 1. A holding unit for holding an object to be transferred, a detecting unit for detecting a holding force of the holding unit, a selecting unit for selecting a predetermined transfer characteristic corresponding to the holding force, and the selected transfer A transport device comprising: a control unit configured to control characteristics. 2. The transfer device according to claim 1, wherein the holding force is a vacuum suction force. 3. The transport device according to claim 1, wherein the transport characteristic is a speed at which the transported object is transported. 4. The transport apparatus according to claim 1, wherein the transport characteristic is an acceleration for transporting the transported object. 5. The transport device according to claim 1, wherein the transport characteristic is a predetermined pattern including at least one of an acceleration and a speed at which the transported object is transported.