JP2003037160A - Hand for conveying wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hand for conveying a wafer that can hold the wafer without dropping it even when the power source is cut off or the supply of a fluid pressure is terminated while the wafer is being conveyed owing to some reasons during the period of wafer manufacturing process. SOLUTION: The drive unit is composed of a cylinder 6, and a spring 15 is inserted into a pressure chamber formed by the cylinder 6 and a piston 8 so that the piston 8 is put into a state of being always pressed toward the top of the fork and the pressure chamber into which the spring 15 is inserted is changed to a pressure chamber for a negative pressure.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer transporting hand mounted on an industrial robot or the like, which is used to process a plurality of wafers stored in a wafer cassette in a silicon wafer manufacturing process. The present invention relates to a wafer transfer hand for supplying wafers one by one to a processing step and taking out wafers after processing is completed and inserting them into a cassette. 2. Description of the Related Art Hands mounted on an industrial robot or the like and used for transferring a wafer include those that transfer a wafer in a non-contact manner using Bernoulli's theorem, and those that suction and transfer a wafer by negative pressure. A variety of methods are used, such as a device that uses a fluid pressure cylinder, an electromagnet, or the like as a driving unit, and that operates a gripper to grip a wafer. In the case of the non-contact type holding device using the Bernoulli's theorem, the wafer is held in a state where it does not come in contact with anywhere, so that the wafer cannot be positioned. Since it cannot be used for supplying a wafer, a method of sucking a positionable wafer is used. In the case of a holding device that sucks a wafer by negative pressure, the main body can be made thin and lightweight because it has no moving parts, but the surface of the processed wafer must be sucked when the wafer is transferred. However, when adsorbed, there is a problem that dust adheres or scratches are caused, and as a method for solving the problem, a wafer described in JP-A-4-277647 or JP-A-7-22502 is used. 2. Description of the Related Art A wafer transfer hand of a type in which a plurality of gripping claws grip an outer periphery of a wafer is known. The wafer transfer hand of the above-described method is a wafer transfer hand of a method in which a gripper fixed to a hand body and a gripper attached to a movable portion that reciprocates by a driving mechanism grips the outer periphery of the wafer, and has a wafer surface. By gripping the wafer without touching the wafer, the problem of dust adhesion and scratches on the wafer surface is eliminated, and at the same time, gripping claws are arranged so that the number of contact points with the outer periphery of the wafer when gripping the wafer is three or more. With this, the drive unit that operates the gripping claw is a wafer transfer hand that enables the wafer center point to be held at a constant position regardless of the orientation flat provided on the wafer. Uses an electromagnet or a fluid pressure cylinder. In the case of an apparatus using an electromagnet or a fluid pressure cylinder as a drive unit, such as the wafer transfer hand, if the supply of power or fluid pressure is interrupted for some reason during the transfer, the wafer being transferred is simply dropped and damaged. However, there has been a problem that pieces of the dropped and damaged wafer are scattered, deteriorating the environment around the apparatus, and requiring a very large number of man-hours for recovery. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is intended for a case where power supply is cut off or supply of fluid pressure is interrupted for some reason during wafer transfer in a wafer manufacturing process. It is another object of the present invention to provide a wafer transfer hand capable of holding a wafer without falling down. SUMMARY OF THE INVENTION The present invention relates to a fork having a fixed claw attached to a tip thereof, a frame to which the fork is fixed, a drive unit fixed to the frame, and a movable unit slidable by the drive unit. As a means for solving the above-mentioned problems, in a wafer transfer hand composed of a part, a driving part is composed of a cylinder, and a spring is inserted into a pressure chamber formed by the cylinder and the piston, and the piston always operates by the spring. The pressure chamber is pressed toward the tip end of the fork, and the pressure chamber in which the spring is inserted is used as a negative pressure chamber. When the movable part and the gripping claw attached to the movable part are pushed toward the tip of the fork by the driving part, the piston of which is constantly pressed in the tip direction of the fork by the spring, the power supply is interrupted or the fluid is shut off for some reason. Even when the supply of pressure is cut off, the wafer can be gripped without dropping. Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, as shown in FIG. 1, a fork 1 having two fixed claws 2 attached to the tip, a frame 7 to which the fork 1 is fixed, a driving unit 5 and a frame 7 fixed to the frame 7 The drive fork 11 comprises a movable portion 4 slidably mounted. The fork 1 is made of a thin material in order to carry the silicon wafer 14 stored in the wafer cassette, and has two fixed claws 2 fixed to the tip side. The other end of the fork 1 is fixed to a frame, and the frame 7 is fixed to a robot. A movable portion 4 is provided on the fork side of the frame 7 in parallel with the fork, and the movable portion 4 is fixed to a tip of a driving fork 11 at a position where three gripping claws 3 circumscribe a silicon wafer 14. The other end is fixed by the drive unit 5 and the block 9. Further, the block 9 serves as a guide that slides in parallel with the fork 1 by the cover 10. Next, the drive unit 5 includes a cylinder 6, a piston 8 inserted into the cylinder 6, and a spring 15 for pushing the piston 8 toward the fork 1. Inside the cylinder, a pressure chamber is formed by the cylinder 6 and the piston 8, and a spring 15 is installed in the pressure chamber. The fixed claw 2 and the gripping claw 3 are concave at the center in order to grip the silicon wafer 14, and the pitch of each of the two fixed claw and the three gripping claw is longer than the length of the orientation flat of the silicon wafer. Set and fixed. Next, the operation will be described. The cylinder 6 of the drive unit 5 is provided with an air port communicating with the pressure chamber, and the pressure in the pressure chamber is reduced because a negative pressure device such as a vacuum pump is connected. Therefore, the piston 8 compresses the spring 15, so that the driving fork 11 of the movable portion is spread toward the frame. In this state, the robot enters the cassette and moves the robot to a position where the silicon wafer accommodated in the case enters between the fixed claw 2 and the holding claw 3. Here, by turning off a negative pressure device such as a vacuum pump, the pressure in the pressure chamber rises to the same pressure as the atmospheric pressure, and the spring 15 installed in the pressure chamber expands. The fork 11 is driven toward the silicon wafer, and is clamped by the fixed claws 2 and the grip claws 3. The clamped silicon wafer is transported by the robot from the cassette for processing in each process. When the conveyed silicon wafer reaches a predetermined location, the negative pressure device is driven, and the piston 8 compresses the spring 11 to drive the driving fork 11 fixed to the block 9 to the robot side to reduce the pressure in the pressure chamber. And fixed nail 2
Then, the silicon wafer clamped by the holding claws 3 is released to be placed at a predetermined position. The silicon wafer that has been processed in each step is transported again to the case. However, since the above operation is repeated, the description is omitted. The wafer transfer hand according to the present invention has a structure in which the driving fork is constantly pressed in the gripping direction by a spring inserted into the cylinder chamber, so that power supply or fluid pressure is cut off for some reason. However, the wafer can be gripped without falling. Further, when releasing the gripped wafer, the pressure in the pressure chamber into which the spring is inserted is reduced by a negative pressure device to compress the spring and slide the driving fork toward the robot side to release the wafer. Even if a problem occurs in a fluid passage such as a pipe, dust and the like are not released into the clean room, and the environment in the clean room can be maintained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a wafer transfer hand of the present invention. FIG. 2 is a rear view of the wafer transfer hand of the present invention. FIG. 3 is an enlarged view of a wafer transfer hand drive unit of the present invention. FIG. 4 is a schematic view showing a conventional wafer transfer hand (a) suction method (b) gripping method [Description of symbols] 1 fork 2 fixed claw 3 gripping claw 4 movable section 5 drive section 6 cylinder 7 frame 8 Piston 9 block 10 cover 11 drive fork 12 sensor 13 magnet 14 silicon wafer 15 spring 16 suction pad 17 drive cylinder

Claims (1)

Claims: 1. A movable part having two fixed claws fixed to a tip end of a fork, a movable part having three gripping claws guided by a guide part, and a driving part for operating the movable part. In the wafer transfer hand, the cylinder constituting the driving unit is a negative pressure cylinder that operates by negative pressure, and a spring is inserted into the pressure chamber, and the movable unit is constantly pressed in the direction of gripping the wafer by the spring. A wafer transfer hand characterized in that: