JPH09155772A - Work carrying mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a work carrying mechanism with sufficient strokes while keeping a minimum turning radius small and make it light weight and a high speed in operation by symmetrically rotating two driving shafts to give elastic deformation to plate springs connecting work supporting tables to turning parts for straight movement. SOLUTION: Arms are formed in symmetry on two driving shafts 2 coaxially coming out of a drive mechanism 1 and turning parts 3 are mounted on the respective driving shafts 2. When the driving shafts 2 are symmetrically rotated, rotating shafts 4 arranged on the outer peripheries of the turning parts 3 are moved so as to draw a circle. The rotating shafts 4 in a bearing structure have springs 5 mounted on the free rotation side, on which work supporting tables are mounted. The plate springs 5 are displaced with elastic deformation in accordance with a difference between a distance between the rotating shafts 4 placed in symmetry and a distance between two positions where the work supporting tables 6 are jointed to the plate springs 5, thus to move the work supporting tables 6 straight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work transfer device for transferring a work, and more particularly to a work transfer technique for transferring a thin and lightweight work such as a semiconductor wafer or a glass substrate.

[0002]

2. Description of the Related Art In a wafer processing process for forming a circuit on a semiconductor wafer, there are many processes such as a resist coating process for coating a semiconductor wafer with a resist solution. In order to convey the semiconductor wafer to each process, Robots are used.

As a transfer mechanism used in this robot, as shown in FIG. 4, a transfer mechanism (hereinafter referred to as "two-step rotation type transfer mechanism") in which a two-stage arm that horizontally turns is used to perform a straight-moving operation. 5), and a frog leg type transport mechanism that moves straight with an arm intersecting in a rhombus as shown in FIG. 5, and a deformation of a leaf spring as shown in JP-A-5-318345 and FIG. There is a spring arm type transfer mechanism.

[0004]

The two-stage swivel type transport mechanism is the most widely used mechanism, but it requires a timing belt, a timing pulley, etc. for transmitting rotation in the two-stage arm. Actually it has a complicated internal structure,
The shape of parts is complicated, the number of parts is large, and it is difficult to reduce the cost. Also, due to the complicated internal structure, the weight becomes heavy, the moment of inertia increases, and it is difficult to perform high-speed operation.

Further, during the linear movement, the inertial force of the arm also acts in a direction (θ direction) perpendicular to the moving direction with respect to the moving direction, so that vibration occurs in the θ direction during movement, so that the wafer cassette is moved. Lateral rubbing is likely to occur during wafer loading and unloading, and vibration continues after stopping, requiring a waiting time for delivery. Moreover, since it is necessary to use a timing belt or the like for transmission, the influence of backlash cannot be ignored, and it is difficult to improve the stopping accuracy.

The frog leg type transport mechanism requires a gear for maintaining a symmetrical operation at the terminal end portion of the mechanism in order to carry out a straight movement operation, and it is necessary to dispose a sliding portion near a work piece where foreign matter does not adhere. It tends to be a problem of adhesion. Further, in order to realize the mechanism in a small space, it is necessary to form a multi-step rhombus, and if this is done, the rigidity is reduced, and it becomes difficult to maintain the straightness accuracy in the vertical direction when going straight.

The spring arm type transfer mechanism has excellent characteristics for ultra-high vacuum and the like, but since the spring is used for a long distance, the rigidity is low and the vibration becomes large when operating at high speed. Moreover, the minimum turning radius is large, which is not suitable for downsizing.

An object of the present invention is to realize a sufficient stroke of a mechanism for conveying a work while keeping the minimum turning radius small.

Another object of the present invention is to reduce the weight of the mechanism for conveying a work with a simple structure to speed up the operation.

Still another object of the present invention is to reduce the number of parts and the cost for a mechanism for conveying a work with a simple structure.

Still another object of the present invention is to reduce vibration during operation of a mechanism for conveying a work.

Still another object of the present invention is to improve the stopping accuracy and the straight traveling accuracy of a mechanism for conveying a work while maintaining a required rigidity.

Still another object of the present invention is to reduce foreign matter generation in a mechanism for conveying a work.

Still another object of the present invention is to improve the reliability of holding a work during movement of a mechanism for transferring the work.

Still another object of the present invention is to achieve the above object even when a mechanism for transferring a work is carried out in vacuum.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0017]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the work transfer mechanism of the present invention has two
It has a pair of symmetrically-moving arms that connect two drive shafts and a table that supports the workpiece, and each arm has a pair of arms.
The swivel part that rotates around the drive shaft, the rotary shaft that is provided in the arc motion part of the swivel part in parallel with the drive shaft, and the swivel part and the swivel part that are connected via the rotary shaft to connect the work support table and the swivel part. By having two leaf springs that rotate symmetrically, the leaf springs are elastically deformed and the work moves straight. The entire pair of arms is swung to move the R axis,
The polar coordinate operation of the θ axis may be performed. By arranging the symmetrically arranged swivel parts coaxially and rotating both shafts in the same rotation direction by the same angle, the swivel motion in the θ direction is performed, and the polar coordinate motions of the R axis and the θ axis are performed. May be. The drive shaft of this arm may be sealed with magnetic fluid or the like, or the rotary shaft may be sealed with magnetic fluid or the like. The rotating shaft may be slightly tilted with respect to the turning shaft in order to further reduce a slight change in the amount of bending when performing a straight movement operation. In order to suppress vibration during operation of the work transfer mechanism, the table supporting the work and the magnet attached to the revolving part or rotating shaft come close to each other at the revolving position or the end point of the rectilinear motion, and repulsive force or attractive force is generated. You may arrange a magnet in. In order to prevent the work from falling when it is conveyed, keep holding the end face of the work, and in the most extended state of the linear motion, the table supporting the work and the magnet attached to the swivel part or the rotary shaft approach, A magnet may be arranged so as to generate a repulsive force or an attractive force so that the state in which the work is grasped can be released only in the most extended position by the straight-ahead movement.

The position where the center of the work is aligned with the center of the θ-direction turning axis of the work transfer mechanism is considered to be almost the same as the minimum turning radius of this mechanism. At this time, the leaf spring, the support for the work, and the work are inside the arc of the trajectory drawn by the rotation axis, and the minimum turning radius is approximately the distance between the drive axis and the rotation axis.
For example, for a wafer with a diameter of 200 mm, about 160 m
Keeping the minimum turning radius of m, the straight distance is about 300m
It can be m.

Since the arm does not need to transmit the rotation through the inside of the arm to the table for supporting the work in order to carry out the rectilinear movement, the arm can be constructed with a simple and lightweight structure including only the revolving part, the rotating shaft and the leaf spring. It can be configured, the moment of inertia becomes small, and the operation can be speeded up. Further, since the number of parts is small, the cost can be reduced.

When the arm moves straight, since the arm operates symmetrically in the θ direction, the inertial force is canceled out, and the vibration in the θ direction is unlikely to occur.

The portion using the leaf spring is close to the weighted point,
Since the leaf spring does not need to be so long, there is no fear that the rigidity will be significantly reduced. Further, since the straightness is maintained by the symmetrical deformation of the leaf spring, the stop position error factor due to the backlash due to the timing belt, the gear, etc. is eliminated.

The sliding parts of the mechanism for performing the straight movement are only the drive shaft and the rotary shaft, and this position can be moved away from the work. Further, by sealing these shafts with a magnetic fluid or the like, sufficient countermeasures against foreign matter can be taken. Further, since the arm has a simple structure, the arm is formed of a flat surface, so that cleaning is easy and foreign matter does not easily accumulate.
Furthermore, since the leaf spring is oriented almost parallel to the circular arc during turning, vortex flow due to turning is less likely to occur and foreign matter is less likely to adhere.

There are two positions where the arm is apt to vibrate during operation: the minimum turning radius when turning, and the stop position when the arm is fully extended. At these two locations, the table supporting the work and the magnets attached to the swivel part or the rotary shaft are brought close to each other, and vibration can be suppressed by exerting repulsive force or attractive force.

In order to securely fix the work being conveyed, a holding force is usually exerted so that the end face of the work is grasped, and only at the position where the arm is fully extended, the base for supporting the work and the revolving part or the rotary shaft respectively. The holding of the work can be released by making the magnet attached to the approach and exerting repulsive force or attractive force.

The above-mentioned seal made of magnetic fluid or the like is effective for operation in a vacuum and can be easily applied to a vacuum atmosphere.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIGS. 1 to 3 are views showing a work transfer mechanism according to an embodiment of the present invention. The work transfer mechanism is, for example, a surface of a semiconductor wafer (hereinafter, simply referred to as a wafer) W. It is used to transfer the wafer W to a spin coater that rotates the wafer in a horizontal state in order to drop the resist solution onto the wafer.

The two drive shafts 2 which are coaxially output from the drive mechanism section 1 are symmetrically arranged with arms, and the swivel portions 3 are attached to the respective drive shafts 2. The drive shafts 2 are shown symmetrically. When it is rotated so as to change from the state of 1 to the state of FIG. 2, the rotary shaft 4 arranged on the outer periphery of the revolving unit 3 moves in an arc. The rotating shaft 4 has a bearing structure, and a plate spring 5 is attached to the shaft on the side that can freely rotate. This plate spring 5 is also attached to a table 6 for supporting the work, and the distance between the rotating shafts 4 at symmetrical positions and the distance between the two positions where the table 6 for supporting the work and the plate spring 5 are connected. Depending on the difference, the leaf spring 5 is displaced due to elastic deformation. As a result, the linear movement of the table 6 that supports the work becomes possible. The force and bending moment generated in this leaf spring are expressed in a dynamic model as shown in FIG. 7, and can be easily solved by using a cantilever calculation formula, and the curve drawn by the leaf spring can be obtained.

Here, δ: displacement, P: force acting on the rotary shaft 4, L: distance from the work support 6 to the rotary shaft 4,
E: longitudinal elastic modulus of the leaf spring material, I: second moment of area of the leaf spring, P = (3 × E × I × δ) / L3
(Equation 1), and from P obtained here, the moment M at the distance x from the work support base 6 can be expressed by M = P · x (Equation 2). If the leaf spring 5 has the same cross-sectional shape, the moment of the portion connected to the work support base 6 becomes maximum, so that the secondary moment of area from the rotary shaft 4 to the work support base 6 is reduced so that the difference between the moments is minimized. It is better to change it to increase. When the moment at each position is obtained, the curvature 1 / ρ at each position becomes 1 / ρ = M / EI (Equation 3), which is calculated for each position and tabulated to obtain a curve.

If the above curve is calculated for each position of the rotary shaft 4, the moving position of the table 6 supporting the work corresponding to the angle of the drive shaft 2 can be obtained.

During the movement from the state of FIG. 1 to the state of FIG.
Since the revolving unit 3, the rotary shaft 4, and the leaf spring 5 perform symmetrical operations with respect to the traveling direction, there is no acceleration force in the direction perpendicular to the traveling direction and vibration in the θ direction is unlikely to occur.

In the case of a wafer having a diameter of 200 mm, the distance from the center position of the wafer to the rotating shaft 4 is 120 mm to 2
It is possible to operate in the range of 00 mm, and the weight of the base 6 supporting the wafer W and the work is about 300 g. Therefore, if the length of the leaf spring is up to about 100 mm, the sectional shape of the leaf spring is If the size is about 0.3 mm × 30 mm, the bending in the direction of gravity is about 0.4 mm, so the rigidity does not matter.

Regarding the durability by repeated bending, the bending stress (σ) is 7.8 × 10 8 N / m 2 or less. The relationship among the plate thickness (t), the bending stress (σ), the radius of curvature (r), and the longitudinal elastic modulus (E) is represented by t = 2rσ / E (Equation 4), and in the case of stainless steel, E = 2 x 1011 N / m
2, σ = 7.8 × 108 N / m 2, and t = 0.3 m
When m, r = 38 mm, and it was confirmed that the curvature was practically no problem.

When rotating the work transfer mechanism,
It is necessary to reduce the minimum turning radius in the state of FIG. Under the above conditions, the turning radius can be reduced to about 160 mm. At this time, since the leaf spring 5 is deformed in a direction close to the arc drawn by the turning, the disturbance of the atmosphere due to the turning operation can be reduced.

(Embodiment 2) In the work transfer mechanism of Embodiment 1, when the two drive shafts 2 are arranged coaxially,
Drive shaft 2 to rotate the two in the same direction by the same angle
By controlling, it becomes possible to operate in the θ direction.
R-axis and θ-axis polar coordinate operations become possible.

(Embodiment 3) FIGS. 9 to 11 are views showing a work transfer mechanism according to an embodiment of the present invention, which is used for the same purpose of transfer as in the first embodiment.

Arms are symmetrically formed on the two drive shafts 2 output from the drive mechanism unit 1 to different shafts, and a swivel unit 3 is attached to each of the drive shafts 2. The drive shafts 2 are symmetrical. When the state of FIG. 10 is rotated so as to change from the state of FIG. 10 to the state of FIG. 9, the rotary shaft 4 arranged on the outer periphery of the turning portion 3 moves in an arc. The rotating shaft 4 has a bearing structure, and a plate spring 5 is attached to the shaft on the side that can freely rotate. This plate spring 5 is also attached to a table 6 for supporting the work, and the difference between the distance between the rotating shafts 4 at symmetrical positions and the distance between the two positions where the table 6 for supporting the work and the plate spring 5 are connected. Accordingly, the elastic deformation of the leaf spring 5 causes a displacement. As a result, the linear movement of the table 6 that supports the work becomes possible.

In order to rotate the work transfer mechanism in the θ direction, the θ rotation mechanism 16 is installed between the drive mechanism section 1 and the base surface of the apparatus. The θ rotation mechanism 16 can rotate the drive mechanism unit 1 placed on it in the θ direction. This enables polar coordinate operations of the R axis and the θ axis.

(Fourth Embodiment) In the work transfer mechanism of the first embodiment, it is only the bearings used for the drive shaft 2 and the rotary shaft 4 that are considered to be the sliding portions, and the bearing faces the atmosphere as shown in FIG. By installing a magnetic fluid seal on the side, the generation of foreign matter can be prevented.

(Fifth Embodiment) In the work transfer mechanism of the first embodiment, when it is installed in a vacuum and used, what is considered to be a rotating portion is the bearing 1 used for the drive shaft 2 and the rotating shaft 4.
As shown in FIG. 8, by installing the magnetic fluid seal 13 on the side facing the vacuum atmosphere, a bearing of atmospheric specifications can be used, and the drive mechanism unit 1 can be sealed against the vacuum. You can do it. With this structure, 1
It is possible to seal against a vacuum up to about 10-4 Pa.

(Sixth Embodiment) In the work transfer mechanism of the second embodiment, when the work transfer mechanism is operated at a high speed, particularly in the turning operation, the θ direction acts in the direction in which the rigidity of the leaf spring 5 is weak.
As shown in FIG. 12, the table 6 for supporting the workpiece and the magnet 17 attached to the revolving unit 3 are installed so as to come close to each other in the state of the minimum revolving radius which is the position where the θ operation is performed, and the repulsive force or attractive force of the magnet is set. It is possible to generate and suppress the vibration during the turning operation.

Further, as shown in FIG. 13, the magnet mounted on the table 6 for supporting the work both in the minimum turning radius state in which the θ operation is performed and in the position farthest from the axis of the turning operation in the R operation. 17 and a magnet 17 attached via a fixed part 18 to the shaft of the rotating shaft 4 that rotates at the same time as the leaf spring 5 are installed so as to come close to each other.
The repulsive force or the attractive force of No. 7 can be generated to suppress the vibration during the turning operation or when the vehicle is stopped straight ahead.

In the above use, when the magnet cannot be used, vibration can be suppressed by contacting parts instead of the magnet with the same arrangement.

(Embodiment 7) In the work transfer mechanism of Embodiment 1, since the spring constant in the vertical direction differs depending on the bending operation state of the leaf spring 5, the bending in the vertical direction slightly varies depending on the position in the straight traveling direction. Especially when loading and unloading a wafer from a cassette for wafers, the clearance between adjacent wafers is around 1 mm.
It is important to reduce vertical deflection in units of m. Even in the calculation example of the first embodiment, a maximum bending of about 0.4 mm is expected, and in order to reduce the bending, as shown in FIG. 14, the axial direction of the drive shaft 2 of the arm, the turning portion 3, and the leaf spring 5 are changed. By slightly tilting the axial direction of the rotary shaft 4 that connects the two, it is possible to reduce the vertical fluctuation of the wafer W due to the operating position of the arm.

(Embodiment 8) In the work transfer mechanism of Embodiment 2, as shown in FIGS. 15 and 16, the table 6 for supporting the work and the revolving part 3 or the rotary shaft are provided only when the arm is extended most. The attached magnets 17 are installed so as to approach each other, and an attractive force of the magnets 17 is generated to release the force for grasping the wafer W generated between the work holding component 20 and the movable work holding component 21 by the work pressing spring 19. . At other positions, the pressing force of the work pressing spring 19 always acts on the end surface of the wafer W between the work holding component 20 and the movable work holding component 21, so that the reliability during transportation can be improved.

In the above operation, when the magnet 17 cannot be used, vibration can be suppressed by contacting parts instead of the magnet 17 with the same arrangement.

[0048]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1) The weight can be reduced and the operation can be speeded up with a simple structure.

(2) With a simple structure, the number of parts can be reduced and the cost can be reduced.

(3) Vibration can be reduced during operation,
Transport reliability is improved.

(4) It is possible to improve stopping accuracy and straightness accuracy while maintaining the required rigidity. (5) It is possible to prevent the generation of foreign matter.

(6) The reliability of holding the work during transportation can be improved.

(7) Conveying in vacuum is possible with a simple structure.

[Brief description of the drawings]

FIG. 1 is a plan view of a work transfer mechanism according to an embodiment of the present invention in a contracted state.

FIG. 2 is a plan view of the work transfer mechanism of FIG. 1 in an extended state.

FIG. 3 is a side view of FIG. 2;

FIG. 4 is an example of a conventional two-stage swivel transfer mechanism.

FIG. 5 is an example of a conventional frog leg type transport mechanism.

FIG. 6 is an example of a conventional spring arm type transfer mechanism.

[FIG. 7] Bending state explanatory diagram

FIG. 8 is an explanatory diagram of a sealing method

FIG. 9 is a plan view of an extended state of a mechanism for separately driving θ rotation.

FIG. 10 is a plan view of a mechanism for separately driving θ rotation in a contracted state.

FIG. 11 is a side view of a mechanism for separately driving θ rotation.

FIG. 12 is a plan view of a mechanism that prevents vibration during θ rotation.

FIG. 13 is a plan view of a mechanism that prevents vibration during θ rotation and vibration at the R-axis tip position.

FIG. 14 is a plan view of a mechanism that reduces vertical displacement during R-direction operation.

FIG. 15 is a plan view of a mechanism for holding a work during conveyance of the work.

FIG. 16 is a detailed view of a mechanism for holding a work during conveyance of the work.

[Explanation of symbols]

 1 Drive mechanism part 2 Drive shaft 3 Revolving part 4 Rotating shaft 5 Leaf spring 6 Platform for supporting the work 7 Minimum turning radius 8 Stroke 9 Rhombic arm 10 Node 11 Gear 12 Bearing 13 Magnetic fluid seal 14 Inner shaft 15 Outer shaft 16 θ Transfer Mechanism 17 Magnet 18 Fixed part 19 Work pressing spring 20 Work holding part 21 Movable work holding part W Wafer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Hayami, 3-3, Fujibashi, Tokyo, Ome City, Tokyo, 2-3 Hitachi Tokyo Electronics Co., Ltd. (72) Inventor, Shinichiro Watase, 3-chome, 3rd, Fujihashi, Ome, Tokyo Hitachi Tokyo Electronics Co., Ltd. (72) Inventor Takehito Mochizuki 3-3, Fujibashi, Ome-shi, Tokyo 2 Hitachi Tokyo Electronics Co., Ltd. (72) Masafumi Kaneto 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. (72) Inventor Hideo Kashima, 1-280, Higashi-Kengokubo, Kokubunji, Tokyo Metropolitan Institute of Hitachi, Ltd. (72) Katsuhiro Kuroda, 1-280, Higashi-Kengokubo, Kokubunji, Tokyo Hitachi, Ltd.

Claims (9)

[Claims] 1. A work transfer mechanism for linear movement, comprising a pair of symmetrically-moving arms for connecting two drive shafts and a table for supporting the work, each arm being driven by a drive mechanism. A swivel part that rotates around an axis, a rotary shaft that is provided parallel to the drive shaft in the arc motion part of the swivel part, and a swivel part that is connected via the rotary shaft. A work transfer mechanism that has a leaf spring that moves, and linearly moves by elastically deforming the leaf spring by rotating two drive shafts symmetrically. 2. A work transfer mechanism which moves by polar coordinate motions of the R axis and the θ axis, and performs a symmetrical operation by connecting two R drive shafts coaxially arranged with a table for supporting the work. Has a pair of arms,
Each arm is connected to the revolving part that rotates around the R drive shaft, the rotating shaft that is provided in the arc motion part of the revolving part in parallel with the R drive shaft, and the revolving part and the revolving shaft. It has a leaf spring that connects the supporting base and the turning part. By rotating the two R drive shafts symmetrically, the leaf springs are elastically deformed to move the R axis, and the two R drive shafts move in the same direction. A work transfer mechanism characterized by moving the θ axis by rotating it at the same angle. 3. A work transfer mechanism that moves in polar coordinate motions of the R axis and the θ axis, and performs a symmetrical operation by connecting two R drive shafts arranged side by side and a table that supports the work. Has a pair of arms,
Each arm is connected to the revolving part that rotates around the R drive shaft, the rotating shaft that is provided in the arc motion part of the revolving part in parallel with the R drive shaft, and the revolving part and the revolving shaft. It has a plate spring that connects the supporting base and the turning part, and elastically deforms the plate spring by rotating the two R drive shafts symmetrically to move the R shaft and hold the two R drive shafts. The work transfer mechanism is characterized by moving the θ axis by rotating the entire mechanism. 4. The work transfer device according to claim 1, wherein
A work transfer device that prevents foreign matter from occurring by sealing the drive shaft or rotating shaft with magnetic fluid. 5. The work transfer device according to claim 1, wherein
A work transfer device that can be used in vacuum by sealing the drive shaft or rotary shaft with magnetic fluid bearings. 6. The work transfer device according to claim 1, wherein
A magnet is installed on the platform that supports the work and the revolving part, and at the position where it rotates with the minimum revolving radius, the repulsive force or attractive force is generated by the approach of the magnet to suppress the vibration during the revolving operation. mechanism. 7. The work transfer device according to claim 1, wherein:
A magnet attached via a fixed part is installed on the shaft that rotates at the same time as the table that supports the work and the leaf spring of the rotary shaft, and the position that rotates with the minimum turning radius and the linear position that is farthest from the center position of the turning At, the repulsive force or attractive force is generated by the approach of the magnet,
A work transfer mechanism that suppresses vibrations when turning or stopping when moving straight. 8. The work transfer device according to claim 1, wherein
By slightly tilting the axial direction of the drive shaft of the arm and the axial direction of the rotary shaft that connects the rotating part and the leaf spring, it is possible to reduce the amount of bending due to the bending motion of the leaf spring. Work transfer mechanism characterized by correcting misalignment. 9. The work transfer device according to claim 1, wherein
The table that supports the work has a mechanism for gripping the end surface of the work. Normally, the force that continues to be gripped is applied to the table that supports the work and the magnet attached to the swivel part at the straight position that is farthest from the center position of the turning. Work transfer device characterized by having a mechanism for releasing the work by the repulsive force or attractive force due to the approach of the.