Magnetic stops for rotary motion systems

Abstract

The present invention relates to a magnetic stopper (10) for a rotary motion system, comprising a base unit (102) and a rotary unit (104) rotatably mounted on the base unit (102). The magnetic stopper (10) comprises a static part (12) configured to be mounted on the base unit (102) and a rotary arm (30) configured to be mounted on the rotary unit (104). The static part (12) comprises a rotary arm stopper part (14) configured to receive a distal end part (32b) of the rotary arm (30), and a movable device comprising a magnet holder (26) and a movable magnet (28) mounted on the magnet holder (26) and adapted to be movable within the rotary arm stopper part (14). The swivel arm (30) includes a swivel arm magnet (36) configured to magnetically interact with the movable magnet (28) when the static portion (12) and the swivel portion (30) are mounted on the base unit (102) and the swivel unit (104), respectively, to prevent excessive movement of the swivel unit (104) when the swivel motion system is operating.

Description

Technical Field

[0001] The present invention relates to a magnetic stopper for a rotary unit of a rotary motion system. The present invention also relates to a high-precision positioning system, which comprises a rotary motion system equipped with a magnetic stopper and mounted on an XY motion system. Background Art

[0002] The rotary motion system of the wafer chuck type rotatably mounted on the base unit generally includes a vacuum tube connected to the wafer chuck (hereinafter referred to as the rotary wafer holding unit) and a vacuum source so as to hold the wafer in place by applying negative pressure to the back side of the wafer through vacuum holes or ring patterns arranged on the surface of the rotary wafer holding unit. Therefore, the wafer holding unit cannot withstand continuous rotary movement, otherwise the vacuum tube will be disconnected from the vacuum source and entangled around the wafer chuck, resulting in wear and tear of the tube, and possible damage to the rotary motion system.

[0003] Typically, the rotary wafer holding unit is configured to be driven to rotate both in a clockwise and counterclockwise direction from a reference position. Various mechanical stops have been provided to prevent continued rotation of the rotary wafer holding unit, thereby allowing the holding unit to rotate slightly more than 180° from the reference position when driven in a clockwise or counterclockwise direction.

[0004] FIG1 shows an example of a mechanical stopper as part of the prior art. The mechanical stopper comprises a static part A mounted on a base station B of a rotary motion system, while a pin C is mounted on and perpendicular to a radial extension D which forms an integral part with a rotating wafer holding unit E rotatably mounted on the base station B. The static part of the mechanical stopper comprises a shock absorber F connected to a pivot G and two hard stops H arranged on both sides of the pivot. The pin C of the rotating wafer holding unit E is configured to hit either side of the shock absorber F depending on the direction of rotation of the rotating wafer holding unit E. The impact between the pins C on either side of the shock absorber F causes the shock absorber F to rotate around the pivot G to gradually stop the rotating wafer holding unit.

[0005] In case the rotating wafer holding unit E enters an error mode and exceeds a predetermined rotation, the pin C of the holding unit strikes the shock absorber F, which then rotates about the pivot G until it contacts any hard stop H to stop the rotating wafer holding unit.

[0006] However, for precision positioning systems used in cleanroom environment applications, mechanical shocks should be avoided because these shocks may generate particles that can have significant negative effects on both front-end and back-end applications in semiconductor device manufacturing.

[0007] FIG2 shows a mechanical stop which is part of the prior art and which has been developed to prevent the shock absorber of FIG1 from swinging and hitting the two hard stops H when subjected to high accelerations. This is particularly true for high precision positioning applications when a rotary position system of the type shown in FIG1 is mounted on an XY motion system which is subject to high accelerations.

[0008] The stopper comprises an arm I having a proximal portion pivotably mounted on a pivot G and a distal portion arranged to be struck by a pin C of a rotating wafer holding unit E of FIG. 1 . A magnet K is mounted in the arm I, which is positioned in a bracket L made of ferromagnetic material. When the XY motion system is accelerated, the magnet K is pushed against either side of the bracket L, thereby locking the arm into a first or second locking position by magnetic attraction, depending on the direction of the acceleration. This mechanical stopper thus overcomes the problem of mechanical impact of the two hard stops H when subjected to high accelerations.

[0009] However, even with the mechanical stopper of FIG. 2 , particles may be generated not only by the impact between the pin C and the distal end portion of the arm I, but also by the friction occurring between the pivot G and the arm I when the arm I rotates.

[0010] It is therefore an object of the present invention to provide a particle-free stop for a rotary unit of a rotary motion system, or at least a stop which generates fewer particles.

[0011] Another object of the present invention is to provide a resilient and durable stopper for a rotary unit of a rotary motion system.

[0012] Another object of the present invention is to provide a high precision positioning system that complies with stringent clean room classifications and standards. Summary of the invention

[0013] These objects are achieved by a magnetic stopper for a rotary motion system, which includes a base unit and a rotary unit rotatably mounted on the base unit. The magnetic stopper includes a static part configured to be mounted on the base unit and a rotary arm configured to be mounted on the rotary unit. The static part includes a rotary arm stopper configured to receive a distal end portion of the rotary arm and a movable device, the movable device including a magnet holder and a movable magnet mounted on the magnet holder and movable within the rotary arm stopper. The rotary arm includes a rotary arm magnet, which is configured to magnetically interact with the movable magnet when the static part and the rotary part are respectively mounted on the base unit and the rotary unit, so as to prevent excessive movement of the rotary unit when the rotary motion system is operating.

[0014] In one embodiment, the magnet holder is shaped to hold the movable magnet such that the poles NS of the magnet are aligned with a tangent to the circular trajectory of the swivel arm magnet when the swivel arm moves within the swivel arm stop portion of the static portion.

[0015] In one embodiment, the movable magnet and the swivel arm magnet are positioned so that when the swivel arm moves within the swivel arm stop portion, the same poles of the movable magnet and the swivel arm magnet face each other, thereby repelling each other without any contact.

[0016] In one embodiment, the circular trajectory of the swivel arm magnet within the swivel arm stop portion extends between 10° and 20°, and preferably between 10° and 15°.

[0017] In one embodiment, the distal end portion of the swivel arm comprises a magnet receiving portion in which the swivel arm magnet is mounted, wherein the opposite magnetic poles NS of the swivel arm magnet are aligned with a tangent to a circular trajectory of the swivel arm magnet when the swivel unit rotates relative to the base unit.

[0018] In one embodiment, the movable device further comprises a blade comprising a proximal portion connected to the static portion and a distal portion connected to the magnet holder. The blade is configured to bend when the rotating arm magnet magnetically interacts with the movable magnet.

[0019] In one embodiment, the static part comprises a housing.When the blade is in the static configuration, the blade is positioned within the housing along an axis equidistant from lateral sides of the housing.

[0020] In one embodiment, the rotating arm stop portion includes two inclined opposite side portions relative to the axis. In the case where the rotating unit exceeds a predetermined rotation, the magnet holder contacts against any one of the opposite side portions.

[0021] In one embodiment, the static portion of the magnetic stopper further comprises a static magnet mounted on the housing to prevent the magnet holder from contacting against either of the two opposing sides of the rotating arm stop portion if the rotating unit enters an error mode and exceeds a predetermined rotation.

[0022] In one embodiment, the movable magnet has a rectangular parallelepiped shape, and the rotating arm magnet has a cylindrical shape.

[0023] Another aspect of the invention relates to a rotary motion system, comprising a rotary unit rotatably mounted on a base unit. The rotary motion system further comprises a magnetic stopper as described above. The rotary arm of the magnetic stopper is mounted on the rotary unit, while the static part of the magnetic stopper is mounted on the base unit.

[0024] In one embodiment, the swivel arm is mounted on a lateral side portion of the swivel unit and extends radially outwards from an outer edge of said lateral portion.

[0025] Another aspect of the present invention relates to a high-precision positioning system, which includes an XY motion system and a rotational motion system as described above mounted on an XY motion system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention will be better understood with the aid of the description of several embodiments given by way of example and illustrated by the accompanying drawings, in which:

[0027] FIG1 shows a top view of a wafer holding unit rotatably mounted on a base unit and including a stopper according to the prior art;

[0028] FIG2 shows a perspective view of an improved stopper according to the prior art;

[0029] Figure 3 A perspective view showing a magnetic stopper according to an embodiment of the present invention;

[0030] Figure 4 Shows from Figure 3 A partial perspective view of the magnetic stopper viewed from another angle;

[0031] Figure 5 A rotatably mounted on a base unit and comprising Figure 3 and 4 A partial perspective view of a wafer holding unit of a magnetic stopper;

[0032] Figure 6 Shows Figure 5 A top view of

[0033] Figure 7 yes Figure 3 and 4 A top view of a magnetic retainer of the embodiment of the present invention, wherein the rotating arm is about to magnetically interact with the static portion of the magnetic retainer;

[0034] Figure 8 yes Figure 7 , whereby the swivel arm has reached a stop position corresponding to a state of repulsive equilibrium between the swivel arm magnet and the movable magnet;

[0035] Fig. 9 According to another embodiment Figure 8 A similar view of

[0036] Fig.10 When the rotation unit exceeds the predetermined rotation and enters the error mode Figure 8 Similar view of . DETAILED DESCRIPTION

[0037] refer to Figure 5 and 6 , the rotary motion system 100 includes a base unit 102 and a rotating unit, such as a rotating wafer holding unit 104, which is rotatably mounted on the base unit 102. The rotating unit is configured to be driven to rotate both clockwise and counterclockwise from a reference position within a predetermined range of ±182.5 degrees.

[0038] The rotary motion system 100 can be mounted on an XY motion system to provide a high precision positioning system. High precision positioning systems are particularly useful in front-end and back-end applications in the semiconductor industry where precise alignment between process or control tools and wafers or semiconductor chips is critical.

[0039] In an advantageous embodiment, the rotary motion system 100 comprises a magnetic stopper which is not subject to any friction nor to any impact under operating conditions. The magnetic stopper 10 comprises a static part 12 mounted on a base unit 102 and a rotary arm 30 mounted on a rotary unit 104. Figure 5 As shown, the proximal end portion 32a of the rotating arm 30 is fixedly mounted on the rotating unit 104, for example, in a cavity arranged on a lateral side portion of the rotating unit 104. The rotating arm 30 extends radially and protrudes outwardly in a horizontal plane from the outer edge of the lateral side portion of the rotating unit 104. The static portion 12 of the magnetic stopper 10 is fixed to the mounting base portion 103 of the base unit 102, so that the distal end portion 32b of the rotating arm 30 can interact magnetically with a portion of the static portion 12.

[0040] More specifically, if Figure 3 and Figure 4 As shown, the static part 12 of the magnetic stopper 10 includes a housing 13, and a blade 24 is mounted in the housing 13. The blade 24 includes a proximal portion 24a connected to the housing 13, for example, by a clamping device 25. A magnet holder 26 is connected to the distal portion 24b of the blade 24 ( Figure 7 ). The magnet holder 26 includes a first magnet holder fixing portion 26a disposed against one side of the distal end portion of the blade 24 and a second magnet holder fixing portion 26b disposed against the opposite side of the distal end portion of the blade 24 and connected to the first fixing portion 26a so as to press the distal end portion 24b therebetween. Figure 3 and 4 As shown, the second magnet holder fixing part 26b can be screwed into the first magnet holder fixing part 26a, for example. Figure 7As shown, the blade 24 is positioned in the housing 13 along an axis equidistant from the lateral sides 13a, 13b of the housing when the blade is in the non-operating configuration. The swivel arm stop portion 14 comprises two opposite sides 18a, 18b inclined relative to said axis.

[0041] The distal end portion 32b of the swivel arm 30 comprises a magnet receiving portion 34, for example in the form of a cavity, inside which a polarized swivel arm magnet 36 having a preferably cylindrical shape is mounted. The swivel arm magnet 36 is oriented in the magnet receiving portion 34 so that when the swivel unit 104 rotates relative to the base unit 102 of the rotary motion system 100, the opposite magnetic poles NS of the magnet 36 are aligned with the tangent of the circular trajectory of the swivel arm magnet 36.

[0042] The magnet holder 26 of the static part 12 is shaped to hold a movable magnet 28, preferably having a shape such as Figure 3 The rectangular parallelepiped shape shown in FIG. 2 makes it possible for the blade 24 to be in a Figure 7 In the non-operating configuration shown, the magnetic poles NS of the magnets are also aligned with the tangent of the circular trajectory of the rotating arm magnet 36. The movable magnet 28 and the rotating arm magnet 36 are positioned so that when the rotating arm 36 of the rotating unit 104 engages the rotating arm stopper portion 14 of the magnetic stopper 10, the same magnetic poles of each magnet 28, 36 face each other, thereby repelling each other without any contact. The rectangular parallelepiped shape of the movable magnet 28 and the cylindrical shape of the rotating arm magnet 36 have been preferably taken into account the relative position change between the magnets 28, 36 when the magnets 28, 36 interact with each other.

[0043] Figure 7 The magnetic stopper 10 is shown about to be switched from the non-operating configuration to the operating configuration. The rotation holding unit 104 has been driven to rotate so that the rotating arm magnet 36 has traveled along an arc of 174° from the reference position to engage the rotating arm stop portion 14 without reaching a position close enough to magnetically interact with the movable magnet 28.

[0044] When the rotation holding unit 104 rotates further, the rotating arm magnet 36 reaches a position, and then the magnetic repulsion between the movable magnet 38 and the same magnetic pole (e.g., the north pole) of the rotating arm magnet 36 begins to occur, thereby starting to bend the blade 24 until the magnetic interaction between the two magnets 36, 38 reaches a repulsive equilibrium state, such as Figure 8 In this exemplary embodiment, the repulsive equilibrium state is reached when the rotation holding unit 104 has been driven to rotate so that the rotating arm magnet 36 has traveled along an arc of approximately 182.5° from the reference position.

[0045] When the rotation holding unit 104 is driven in the opposite direction through its predetermined range (i.e., 182.5°), the blade 24 returns to its non-operating configuration until the rotating arm magnet 36 engages the other side of the rotating arm stop portion 14, whereupon magnetic repulsion between the movable magnet 38 and the same magnetic pole (i.e., the south pole in this exemplary embodiment) of the rotating arm magnet 36 begins to occur, thereby beginning to bend the blade 24 in the opposite direction until the magnetic interaction between the two magnets 36, 38 reaches a repulsive equilibrium.

[0046] like Fig.10 As shown, when the rotation holding unit enters the error mode and exceeds its predetermined range of ±182.5 degrees, the distal end portion 32b of the rotation arm 30 contacts the magnetic retainer 26, and the magnetic retainer 26 abuts against the inclined opposite side portions 18a, 18b of the rotation arm stop portion. The two inclined opposite side portions 18a, 18b can withstand the peak torque of the motor of the rotation motion system.

[0047] exist Fig. 9 In the illustrated embodiment, the static portion 12 of the magnetic stopper 10 comprises two static magnets 22a, 22b mounted on the housing 13, preferably close to two inclined opposite side portions 18a, 18b, to prevent the magnet holder 26 from contacting either of the opposite side portions 18a, 18b when the rotating unit exceeds its predetermined range (such as any oscillation caused by disturbances or accelerations of the rotating motion system) or is limited by a pair of repulsive forces: i) a repulsive force occurs between the movable magnet 28 and the rotating arm magnet 36, and ii) a repulsive force occurs between the movable magnet 28 and either of the static magnets 22a, 22b.

[0048] The configuration of the magnetic stop as described above has the advantage of not generating any particles when in operation, since there are no impacts between the different parts of the magnetic stop, nor any friction occurs. The magnetic stop is also more resilient and more durable than conventional mechanical stops. This is mainly due to different factors, in particular:

[0049] - Contrary to conventional stops with pivoting parts, the blades are not subject to wear and tear caused by the friction generated at the pivoting level;

[0050] - the maximum occurring stress amplitude to which the blades are subjected remains below their fatigue strength during normal operating conditions and even when the rotary unit enters an error mode and exceeds a predetermined rotation angle, and

[0051] - Contrary to conventional brakes with hard stops, the magnetic interaction between the movable magnet and the rotating arm magnet avoids any contact that would cause wear and tear.

[0052] Although the magnetic stopper is particularly suitable for a high-precision positioning system including an XY motion system and a rotary motion system mounted thereon for clean room environment applications, the magnetic stopper may be used in any other application where a rotary unit is rotatably mounted on a base unit.

[0053] Furthermore, although according to the advantageous embodiment described above, the movable magnet of the static part is connected to the blade via a magnet holder, any other means for guiding the movable magnet without friction or with reduced friction may be implemented within the scope of the appended claims. For example, according to an embodiment not shown, instead of using a blade for supporting the movable magnet 28, according to an advantageous embodiment as described above, the movable magnet may be mounted on the distal part of another rotating arm, the proximal part of which is mounted around the pivot on the static part of the magnetic actuator, so that the movable magnet is mounted on the distal part of the rotating arm, suitable for following the same circular trajectory within the stop part of the rotating arm as the movable magnet when connected to the distal part of the blade. The further rotating arm is preferably mounted around the pivot via a ceramic bearing, which is known to have significantly lower friction properties than conventional stainless steel bearings.

[0054] Reference numerals list

[0055] Rotary motion system 100

[0056] Base unit 102

[0057] Mounting base part 103

[0058] Rotating unit 104

[0059] Rotating wafer holding unit

[0060] Magnetic stopper 10

[0061] Static part 12

[0062] Housing 13

[0063] Lateral side portions 13a, 13b

[0064] Rotating arm stop portion 14

[0065] Inclined opposite side portions 18a, 18b

[0066] Static magnets 22a, 22b (one embodiment)

[0067] Mobile device

[0068] Movable magnet support

[0069] Blade 24

[0070] Proximal portion 24a

[0071] Distal portion 24b

[0072] Blade connection device 25

[0073] Clamping device

[0074] Magnet holder 26

[0075] First magnet holder fixing portion 26a

[0076] Second magnet holder fixing portion 26b

[0077] Movable magnet 28

[0078] Rotating arm 30

[0079] Proximal portion 32a

[0080] Distal portion 32b

[0081] Magnet receiving portion 34

[0082] Rotating arm magnet 36.

Claims

1. A magnetic stopper (10) for a rotary motion system (100), the rotary motion system (100) comprising a base unit (102) and a rotary unit (104) rotatably mounted on the base unit (102), the magnetic stopper (10) comprising a static part (12) configured to be mounted on the base unit (102) and a rotary arm (30) configured to be mounted on the rotary unit (104), the static part (12) comprising a swivel arm stop portion (14) configured to receive a distal end portion (32b) of the swivel arm (30), and a movable device, It is characterized in that The movable device comprises a magnet holder (26) and a movable magnet (28) mounted on the magnet holder (26) and adapted to be movable within the rotating arm stop portion (14), wherein the rotating arm (30) includes a rotating arm magnet (36) configured to magnetically interact with the movable magnet (28) when the static part (12) and the rotating arm (30) are mounted on the base unit (102) and the rotating unit (104), respectively, so as to prevent excessive movement of the rotating unit (104) when the rotating motion system (100) is operating, wherein the movable magnet (28) and the rotating arm magnet (36) are positioned so that when the rotating arm (30) moves within the rotating arm stop portion (14), the same magnetic poles of the movable magnet (28) and the rotating arm magnet (36) face each other, thereby repelling each other without any contact.

2. The magnetic stopper (10) according to claim 1, wherein: The magnet holder (26) is shaped to hold the movable magnet (28) so that the poles of the swivel arm magnet are aligned with a tangent to a circular trajectory of the swivel arm magnet (36) when the swivel arm (30) moves within the swivel arm stop portion (14) of the static portion (12).

3. The magnetic stopper (10) according to claim 1 or 2, wherein: The circular trajectory of the swivel arm magnet (36) within the swivel arm stop portion (14) extends between 10° and 20°.

4. The magnetic stopper (10) according to claim 1 or 2, wherein: The circular trajectory of the swivel arm magnet (36) within the swivel arm stop portion (14) extends between 10° and 15°.

5. The magnetic stopper (10) according to claim 1 or 2, wherein: The distal end portion (32b) of the rotating arm (30) includes a magnet receiving portion (34), in which the rotating arm magnet (36) is installed, wherein when the rotating unit (104) rotates relative to the base unit (102), the relative magnetic pole NS of the rotating arm magnet is aligned with a tangent of a circular trajectory of the rotating arm magnet (36).

6. The magnetic stopper (10) according to claim 1 or 2, the movable device further comprising a blade (24), the blade comprising a proximal portion (24a) connected to the static portion (12) and a distal portion (24b) connected to the magnet holder (26), wherein The blade (24) is configured to flex when the rotating arm magnet (36) magnetically interacts with the movable magnet (28).

7. The magnetic stopper (10) according to claim 6, the static part (12) comprising a housing (13), wherein: When the blade (24) is in a rest configuration, the blade (24) is positioned within the housing (13) along an axis equidistant from the lateral sides (13a, 13b) of the housing.

8. The magnetic stopper (10) according to claim 7, the rotating arm stop portion (14) comprising two inclined opposite side portions (18a, 18b) relative to the axis, wherein In a case where the rotating unit (104) exceeds a predetermined rotation, the magnet holder (26) comes into contact against any one of the opposing side portions (18a, 18b).

9. The magnetic stopper (10) according to claim 1 or 2, wherein: The static portion (12) of the magnetic stopper also includes static magnets (22a, 22b) to prevent the magnet holder (26) from contacting against either of the two opposing sides (18a, 18b) of the rotating arm stop portion (14) when the rotating unit (104) exceeds a predetermined rotation.

10. The magnetic stopper (10) according to claim 1 or 2, wherein: The movable magnet (28) has a rectangular parallelepiped shape, and the rotating arm magnet (36) has a cylindrical shape.

11. A rotary motion system, comprising a rotary unit (104) rotatably mounted on a base unit (102), the rotary motion system further comprising a magnetic stopper (10) according to any one of claims 1 to 10, wherein: The rotating arm (30) of the magnetic stopper is mounted on the rotating unit (104), while the static part (12) of the magnetic stopper is mounted on the base unit (102).

12. The rotary motion system according to claim 11, wherein: The rotating arm (30) is mounted on a lateral side portion of the rotating unit (104) and extends radially outward from an outer edge of the lateral side portion.

13. A high-precision positioning system, comprising an XY motion system and a rotational motion system according to claim 11 or 12.

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