JPH04101795A - Holding device for wafer - Google Patents

Abstract

PURPOSE:To eliminate the rubging of a wafer with its pushing, and to damage no wafer, nor dusting, even in case of there being the misregistrations of wafer and gripper, in the wafer holding, by providing a piezoelectric element for opening and closing a claw and a detection means which detects the holding force of the wafer and claw. CONSTITUTION:The displacements of piezoelectric elements 12-15 are transmitted to claws 17, 18, the contact force with two claws 17, 18 and a wafer 1 is detected simultaneously, the contact force is increased in the range that the wafer 1 is not moved, with the claw of a weaker contact force being displaced further, the contact force is increased with this being performed alternately, and the wafer 1 is held. Consequently, the wafer 1 can be held, without moving the wafer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wafer gripping and handling device in a semiconductor manufacturing process.

[Conventional technology]

In the semiconductor manufacturing process, as devices become more highly integrated, fine dust particles increasingly affect the quality of the devices. Therefore, in the field, it is increasingly necessary to improve the cleanliness of the clean room, to prevent dust generation in the clean room, and to prevent dust from adhering to wafers.

Grippers for gripping wafers also require measures to prevent dust generation, and one such method is a method using a piezoelectric element described in Japanese Patent Application Laid-open No. 111440/1983. This method uses a displacement amplification mechanism to magnify the displacement of the piezoelectric element and transmits it to the claws to open and close the claws.Since there is no mechanical sliding surface, this method is characterized by the fact that no dust is generated.

[Problem to be solved by the invention]

The above-mentioned conventional example does not take into consideration dust generation due to contact between the wafer and the nail. In other words, at the moment when the claws come into contact with the wafer, one of the two claws comes into contact first, pushing the wafer, and then the other one comes into contact. In this case, the surface of the wafer will rub against the table, causing dust to be generated.

An object of the present invention is to provide a wafer gripping device that grips a wafer without moving the wafer and eliminates the generation of dust.

[Means to solve the problem]

In order to achieve the above object, the present invention is a wafer gripping device that is attached to the tip of a robot and used for handling wafers, which includes one or two pairs of claws for gripping the wafer and a drive source for opening and closing the claws. It is characterized in that it includes a piezoelectric element, a force detection means for detecting the contact force between the wafer and the claw, and an arithmetic processing means for processing the force detection data.

[Effect]

The displacement of the piezoelectric element is transmitted to the claws, and at the same time the contact force between the wafer and the two claws is detected, and the claw with the weaker contact force is further displaced to increase the contact force without moving the wafer. Do this alternately to increase the contact force and grip the wafer.

Therefore, the wafer can be gripped without moving the wafer.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 schematically shows an embodiment of the wafer gripping device of the present invention. The wafer gripping device of the present invention is used by being attached to the tip 11 of a robot body (not shown).

The main components of the gripping device of the present invention include four bimorph piezoelectric elements (hereinafter referred to as piezoelectric elements) 12 to 15, a base 16 that fixes the piezoelectric elements, and a pair of claws 17 that grip the wafer 1.・Consists of 18.

The wafer 1 is gripped by claws 17 and 18 from two opposing locations, and the claws 17 and 18 are attached to piezoelectric elements 13 and 15. Piezoelectric element 13.15 further includes piezoelectric element 1
Attach to 2.14 and form an L-shape.

When a voltage is applied to the piezoelectric elements 13 to 18 from the outside, depending on the polarity of the voltage, the piezoelectric elements 13 to 18 take on an arcuate shape (shape indicated by a broken line) as shown in FIG.
When two sheets of 22 are placed one on top of the other, ten electrodes are connected to one electrode, and one electrode is connected to the other, and a voltage is applied, the electrode is displaced to the side to which the + electrode is connected. Therefore, with the configuration shown in FIG.
18 can be opened and closed.

Next, the configuration of a control circuit for driving the gripping device of the present invention will be explained with reference to FIG. A force detection sensor 21 is attached to the claw 17 and detects the gripping force of the wafer 1. 23 is an adder, which passes from the force detection sensor 21 to the force detection circuit;
The obtained data and the force target value f1 sent from the computer via the D/A (digital/analog) converter
The difference is calculated and sent to the drive control circuit. In the drive control circuit, based on the data sent from the adder 24, a predetermined drive command for the claw 17 is sent to the drive circuit for the piezoelectric element 12 and the piezoelectric element 13, and the piezoelectric element 12 and the piezoelectric element 13. The drive control circuit also uses the force detection sensor 21 based on the data sent from the adder 24.
If it is determined that the data has reached the force target value f, the data is sent to the computer to notify that the driving of the claw 17 has been completed. The computer then sends commands to the pawl 18 drive control circuit to drive the pawl 18. The claw 18 drive control circuit sends a predetermined drive command to the piezoelectric element 14 drive circuit and the piezoelectric element 15 drive circuit to drive the piezoelectric elements 14 and 15. Thereafter, the force detection sensor 22 detects the gripping force of the wafer 1. The subsequent steps are the same as the control circuits described above, and will therefore be omitted.

Next, the operating procedure of the gripping device of the present invention will be explained.

When the value sent from the force detection sensor 21 to the adder 23 is calculated, the adder 23 outputs the force target value f1 and the detection data f! The difference between The force target value f1 is within a range in which the wafer 1 on the wafer stand 31 does not move even if the claw 17 pushes it, and
The value is determined to be larger than the data f3 of the force detection sensor 22. That is, the relationship f s < f t≦f4 holds true. Here, f4 is the value of the force detection sensor 21 at the moment when frictional resistance is generated between the wafer support stand 31 and the wafer 1 when the wafer 1 is supported by the wafer stand 31, and the static frictional resistance changes from the dynamic frictional resistance. It is.

The claw 17 drive control circuit determines from the values of f and -f whether or not to further drive the piezoelectric element, although the force has reached the target value. The subsequent steps are the same as described for the control circuit, so they will be omitted.

Next, hold the wafer 1 to the target gripping force in the fourth state.
This will be explained using figures. FIG. 4 shows time on the horizontal axis and gripping force on the vertical axis, and the gripping force of the claws 21 is increased within a range where the output of the sensor 21 does not shift the wafer 1. Next, the gripping force of the claws 22 is increased while being detected by the sensor 22 within a range where the wafer l does not move. In this way, the gripping force is increased alternately, and when the target gripping force is reached, the gripping operation is completed.

In this way, the wafer can be gripped without moving.
It does not damage the wafer or generate dust.

In the gripping device of the present invention, the same procedure is used to release the wafer from the gripped state, so that the wafer is not damaged or dust is generated.

In addition, a force detection sensor is installed on the wafer table, and the piezoelectric element is displaced to detect data from the force detection sensor.
By placing the wafer on a wafer stand, it is possible to eliminate the shock when placing the wafer, and a similar effect can be obtained.

〔Effect of the invention〕

According to the present invention, even if there is a misalignment between the wafer and the gripper when gripping the wafer, the wafer will not be pushed and rubbed, so the wafer will not be damaged or any dust will be emitted.

Moreover, even when releasing, the wafer is not pushed and rubbed due to the timing of the claw opening being shifted, so the wafer is not damaged or dust is generated.

Further, when placing the wafer, no impact is applied to the wafer, so the same effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a control block diagram of the gripping device of the present invention, FIG. 2 is a perspective view of the present invention, and FIG. 3 shows the state before displacement (solid line) and the state after displacement (broken line) of the pimol type piezoelectric element. Explanatory diagram,
FIG. 4 is an explanatory diagram showing the steps to reach the target gripping force when gripping with the gripping device of the present invention. 1...Wafer 12,
13.14.15...Bimorph type piezoelectric element 17.1
8・・・・・・・・・Claw 21.22・・・・・・
...Force detection sensor! if'i1 diagram

Claims (1)

[Claims] 1. A wafer gripping device for handling a wafer, comprising: a pair or two pairs of claws for gripping the wafer; a piezoelectric element for opening and closing the claws; A wafer gripping device characterized by being provided with a detection means for detecting a gripping force with a claw. 2. The wafer gripping device according to claim 1, wherein bimorph piezoelectric elements are connected in an L shape to open and close the claws, and the wafer is gripped from above. 3. In claim 1, the wafer gripping device using a pair of said claws has a configuration of two independently movable first and second claws, and the gripping force acting on said first claw is detected; a drive control circuit that displaces the piezoelectric element so that the force reaches a predetermined target force value; and a drive control circuit that detects the gripping force acting on the second claw and displaces the piezoelectric element so that the grip force reaches a predetermined force target value. Wafer gripping device equipped with a control circuit. 4. The wafer gripping device according to claim 1, further comprising a force detecting means on the wafer table and a drive control circuit for displacing the piezoelectric element so that the force detecting means reaches a predetermined force target value.