Patent Publication Number: US-2022216088-A1

Title: Motion device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the priority of the Chinese patent application No. 201910363238.3 filed on Apr. 30, 2019 and titled “Motion device”, and a Chinese patent application No. 201910628196.1 filed on Jul. 12, 2019 and titled “Motion device”, the full disclosure of the above applications are incorporated herein by reference. 
     TECHNICAL FIELD 
     This invention relates to integrated circuit equipment manufacturing, and in particular to a motion device which can provide high-precision vertical movement and rotation functions. 
     TECHNICAL BACKGROUND 
     In the art of semiconductor wafer film thickness detection, it is required that the workpiece stage can complete the transfer of the wafer with the wafer transfer system, and at the same time, the workpiece stage is required to rotate by 360° and move vertically when carrying a 12-inch or 8-inch wafer to complete the wafer film thickness detection. Therefore, for the workpiece stage device used in film thickness detection, the rotation/vertical movable stage is the core component. With the continuous improvement of the requirements for productivity and the continuous improvement of film thickness detection precision, the operating speed, acceleration and performance of the workpiece stage have also increased. This requires a more lightweight, flatter, and higher movement precision design for the workpiece stage. In the US patent US2004246012A1, a workpiece stage solution in this art is proposed. The vertical movable stage (support stage  112 ) of this invention is fixed on the vertical device, and the chuck unit is fixed on the vertical movable stage. And, the vertical device is driven to move vertically by a linear motor driving the wedge block and the reciprocating force provided by two 0.5 mm thick reeds. The structure of the invention is relatively simple, but the height dimension is relatively large and it is difficult to be made flat. 
     In the U.S. Pat. No. 6,779,278B1, a workpiece stage solution in this art is proposed. The vertical movable stage (Z stage) of this invention is fixed on the vertical device, and the chuck unit is fixed on the vertical movable stage. The vertical device is directly driven by the voice coil motor, and the gravity of the stage is offset by the spring, which reduces the load of the voice coil motor. The structure of the invention is relatively simple, the vertical dimension is relatively small and the low profile design is basically realized. However, since the voice coil motor uses a spring for gravity offsetting, it is difficult to achieve high precision in vertical movement. 
     Therefore, in the field of integrated circuit equipment manufacturing, there is a need for a precise motion device that can achieve a low profile and at the same time solve the problem of low vertical movement precision. 
     SUMMARY 
     The invention solves the problem of relatively large height size of the motion device in the prior art by providing a precise motion device with a low profile structure, realizes a low profile design, and solves the problem of low vertical movement precision. 
     In particular, this invention solves the above-mentioned problems by providing a motion device, which includes: 
     a tray; 
     a rotary stage, which is located below the tray, the upper surface of the rotary stage is provided with an annular upper cavity, the lower surface of the rotary stage is provided with a lower cavity, wherein the projections of the annular upper cavity and the lower cavity in the projection direction perpendicular to the upper surface of the rotary stage are not overlapped with each other; 
     a rotary motor, which is accommodated in the annular upper cavity, the rotary motor including a rotor of the rotary motor and a stator of the rotary motor, the stator of the rotary motor being fixed with respect to the rotary stage, and the rotor of the rotary motor being fixed with respect to the tray; 
     a vertical movable device, which is located in the lower cavity and configured to drive the rotary stage to move vertically; and 
     a magnetic levitation gravity offsetting device, which is located in the lower cavity and configured to offset the gravity of the rotary stage. 
     In an embodiment, the vertical movable device and the magnetic levitation gravity offsetting device are integrated with each other and are located in the lower cavity. 
     In an embodiment, the lower cavity includes a plurality of lower cavities, and the vertical movable device and the magnetic levitation gravity offsetting device are respectively located in different lower cavities. 
     In an embodiment, the plurality of lower cavities comprising a central cavity and peripheral cavities, the plane position of the central cavity is surrounded by the annular upper cavity and is used for accommodating the vertical movable device; the peripheral cavities are located on the outer periphery of the annular upper cavity and is used for accommodating the magnetic levitation gravity offsetting device. 
     In an embodiment, the motion device further comprising a wafer loading and unloading device configured to place a workpiece on the tray or remove the workpiece from the tray. 
     In an embodiment, the vertical motion device comprises a voice coil motor that is a hollow structure, and the tray is a vacuum chuck device. 
     In an embodiment, the lower cavity comprises four peripheral cavities each accommodating a magnetic levitation gravity offsetting device. 
     In an embodiment, the structure in which the vertical motion device and the magnetic levitation gravity offsetting device are integrated with each other comprising: 
     a voice coil motor stator, the outer surface of the voice coil motor stator is surrounded with an inner magnetic ring; and 
     a voice coil motor mover, the outer surface of the voice coil motor mover is surrounded with an outer magnetic ring. 
     In one embodiment, the rotary stage includes: a rotation grating scale located in the annular upper cavity. 
     In one embodiment, the rotary stage includes: only one bearing is provided between the rotor of the rotary motor and the inner peripheral wall of the annular upper cavity. 
     In the prior motion device capable of realizing multi-dimensional motion, the parts for realizing the rotational movement and the vertical movement are usually superimposed on each other, so that the vertical size of the motion device is too large. Compared with the prior art, the vertical size of the motion device of the present invention is significantly reduced, and with the application of the magnetic levitation gravity offsetting device, the vertical movement precision of the motion device is significantly improved. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a motion device according to the present invention. 
         FIG. 2  is a cross-sectional view of the motion device according to the present invention. 
         FIG. 3  is a top view of the motion device according to the present invention with the tray removed. 
         FIG. 4  is a perspective view of the magnetic levitation gravity offsetting device according to the present invention. 
         FIG. 5  is a cross-sectional view of the magnetic levitation gravity offsetting device according to the present invention. 
         FIG. 6  is a top perspective view of the base of the rotary stage according to the present invention. 
         FIG. 7  is a bottom perspective view of the base of the rotary stage according to the present invention. 
         FIG. 8  is a cross-sectional view of the voice coil motor of a precise motion device according to the present invention. 
         FIG. 9  is another embodiment of the layout of a magnetic levitation gravity offsetting device according to the present invention. 
         FIG. 10  is yet another embodiment of a magnetic levitation gravity offsetting device according to the present invention. 
     
    
    
     EMBODIMENTS 
     The preferred embodiment of this invention will be described in detail with reference to the accompanying drawings, so that the purposes, the characteristics and the advantages of the invention can be more clearly understood. It should be understood that the embodiments shown in the figures are not intended to limit the scope of this invention, but illustrate the essential spirit of the technical solution of this invention. 
     In the following description, certain specific details are set forth for purposes of illustrating the various disclosed embodiments to provide a thorough understanding of the various disclosed embodiments. However, those skilled in this art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known devices, structures, and techniques associated with the present application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. 
     Unless otherwise desired by context, throughout the specification and claims, the terms “comprising” and variations thereof, such as “containing” and “having”, are to be construed as non-exclusive, i.e., to be construed as “comprising, but not limited to” 
     Throughout the specification “one embodiment” or “one embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the presence of “in one embodiment” or “in one embodiment” at various locations throughout the specification need not all refer to the same embodiment. Additionally, particular features, structures, or features may be combined in any manner in one or more embodiments. 
     The singular forms “a” and “said” as used in the specification and appended claims include plural references unless the context clearly dictates otherwise. The term “or” be used in its usual sense including “and/or” unless the context clearly dictates otherwise. 
     In the following description, for clarity of illustration of the structure and mode of operation of the present invention, various directional terms will be used to describe the present invention, but words such as “front”, “rear”, “left”, “right”, “outer”, “inner”, “outward”, “inward”, “upper”, “lower”, and the like, should be understood as convenient terms and should not be construed as limiting terms. 
     The motion device  100  according to the present invention will now be described with reference to the accompanying drawings. As shown in  FIGS. 1-8 , this embodiment discloses a motion device  100  including a wafer loading and unloading device, a tray  102 , a rotary stage  103 , a vertical movable device  104 , a magnetic levitation gravity offsetting device  105 , a horizontal movable device  106 , a bracket  108 , a horizontal base  1062 , and a vertical base  1045 . 
     The wafer loading and unloading device is fixed on a bracket  108  of the motion device. The wafer loading and unloading device is used to complete the transfer of silicon wafers together with an external robot (not shown) and the tray  102 . As shown in  FIG. 1 , the wafer loading and unloading device includes four wafer transferring chucks  101   a ,  101   b ,  101   c , and  101   d . The wafer loading and unloading device receives and transfers the silicon wafers to be measured from the external robot to the tray  102  through the four wafer transferring chucks  101   a ,  101   b ,  101   c , and  101   d , and transfers the measured wafers from the tray  102  to the external robot. 
     In the embodiment shown in  FIG. 2 , the tray  102  includes a suction chuck  1021  and a suction chuck base  1022  and is used to fix silicon wafers. In this embodiment, the tray  102  is a vacuum suction chuck, a disc-shaped suction chuck  1021  is provided with vent holes communicated with a vacuum supply below it, so the silicon wafer can be fixed on the suction chuck  1021  by vacuum suction. However, it should be understood that the tray  102  can also fix the silicon wafers on the suction chuck  1021  in other ways, for example, the silicon wafer can be fixed by clamping the periphery of the silicon wafer by clamping claws. 
     As shown in  FIG. 2 , the rotary stage  103  is arranged under the tray  102  and can drive the tray  102  to rotate around the central axis. The motion device  100  further includes a rotary motor which comprising a stator  1031  of the rotary motor and a rotor  1032  of the rotary motor. The rotary stage  103  includes: a bearing  1033 , a rotary stage base  1034 , and a rotation grating scale  1035 . 
       FIG. 6  and  FIG. 7  show the specific structure of the rotary stage base  1034 . As shown in  FIG. 6 , the rotary stage base  1034  has a substantially rectangular parallelepiped shape, specifically a rectangular parallelepiped with a substantially square horizontal cross-section. However, it should be understood that the shape of the rotary stage base  1034  is not limited to the above-mentioned shape, but can be set as required. An upper annular cavity  1034   a  is provided on the upper surface of the rotary stage base  1034 , and a lower cavity (as described below) is provided on the lower surface. The projections of the above-mentioned upper annular cavity  1034   a  and the lower cavity in the direction perpendicular to the upper surface of the rotary stage base  1034  are not overlapped with each other, so that the upper annular cavity  1034   a  and the lower cavity can be arranged at the same vertical height, which can significantly reduce the vertical size of the rotary stage base  1034 . This structure of the rotary stage base  1034  effectively reduces the vertical height of the entire motion device. 
     Specifically, the inner and outer peripheral walls of the upper annular cavity  1034   a  are cylindrical. A circular surface  1034   c  is formed around the top of the inner peripheral wall. In the case where the tray  102  is used to fix the silicon wafer by vacuum suction, a tray air supply hole  1034   b  is formed on the circular surface. 
     As shown in  FIG. 7 , a lower cavity is provided on the lower surface of the rotary stage base  1034 . The lower cavity includes a magnetic levitation gravity offsetting device cavity  1034   d  and a vertical voice coil motor cavity  1034   e . In particular, in this embodiment, the four corner positions between the outer peripheral contour of the rotary stage base  1034  and the aforementioned upper annular cavity  1034   a  are respectively provided with magnetic levitation gravity offsetting device cavities  1034   d  for accommodating the magnetic levitation gravity offsetting devices  105 . A vertical voice coil motor cavity  1034   e  is provided in the center of the lower surface of the rotary stage base  1034  corresponding to the area surrounded by the inner peripheral wall of the upper annular cavity  1034   a.    
     Referring again to  FIG. 2 , the stator  1031  of the rotary motor is cylindrical in shape with a certain wall thickness and is accommodated and fixed in the upper annular cavity  1034   a  of the rotary stage base  1034 . The rotary stage base  1034  is located below the tray  102 , and the circular surface  1034   c  surrounded by the top of the inner peripheral wall of the upper annular cavity  1034   a  is used to bear the tray  102 . The rotor  1032  of the rotary motor is also accommodated in the upper annular cavity  1034   a  and located inside the inner periphery of the stator  1031  of the rotary motor. The rotor  1032  of the rotary motor is fixedly connected to the suction chuck base  1022 . The rotor  1032  of the rotary motor can rotate with respect to the stator  1031  of the rotary motor to drive the suction chuck base  1022  which in turn drives the tray  102  to rotate, and the rotation grating scale  1035  provides a rotation position signal. The rotation grating scale  1035  is arranged in the upper annular cavity  1034   a  of the rotary stage base  1034 , and is located at the lower end of the rotor  1032  of the rotary motor, so that the rotation position of the rotor of the rotary motor can be detected by reading the position data of the rotation grating scale  1035 , therefore the rotation position of the tray  102  can also be detected. Since the rotation grating scale  1035  is arranged in the upper annular cavity  1034   a , there is no need to install the grating scale on the upper surface of the stage, thereby the structure of the motion device can be made more compact. The bearing  1033  is arranged between the rotor  1032  of the rotary motor and the rotary stage base  1034  to provide rotation guidance for the rotary stage. In the present invention, since the rotary stage base  1034  can be made lowered and the height of the upper annular cavity  1034   a  can be reduced, only one bearing  1033  is enough to realize the rotation between the rotor  1032  of the rotary motor and the stator  1031  of the rotary motor. The reduction in the number of bearings further renders the structure of the entire motion device more compact. As shown in  FIG. 2 , the vertical movable device  104  is located in the vertical voice coil motor cavity  1034   e  on the lower surface of the rotary stage base  1034 , and bears the rotary stage base  1034 . In this embodiment, the vertical movable device  104  includes: a voice coil motor mover  1041 , a voice coil motor stator  1042 , a vertical guider  1043 , a vertical grating scale  1044 , and a vertical base  1045  (see  FIG. 3 ). The voice coil motor stator  1042  is fixed on the vertical base  1045 , the voice coil motor mover  1041  is provided around the voice coil motor stator  1042  and can move vertically with respect to the voice coil motor stator  1042 , the voice coil motor mover  1041  and the rotary stage base  1034  is fixedly connected to drive the rotary stage  103  to move vertically, and the vertical grating scale  1044  provides a vertical position signal. In the illustrated embodiment, the vertical grating scale  1044  is arranged around the rotary stage base  1034  and placed vertically, so as to determine the vertical position of the rotary stage base  1034  and the born tray  102 . 
       FIG. 8  specifically shows the structure of the voice coil motor. The voice coil motor stator  1042  has a cylindrical hollow structure. The voice coil motor mover  1041  is cylindrical in shape, and its lower surface is provided with a central through hole  10411  and a ring cavity, the ring cavity is used to accommodate the cylindrical wall of the voice coil motor stator  1042 . When the tray  102  is a vacuum suction tray, the central through hole  10411  provides installation space for the vacuum pipeline. It should be understood that the vertical movable device  104  may alternatively be provided as other linear movable devices such as hydraulic movable devices without departing from the scope of the present invention. 
     A vertical guider  1043  is provided between the rotary stage base  1034  and the horizontal base  1062 . In the embodiment shown in  FIG. 3 , a total of two vertical guiders  1043   a ,  1043   b  are provided between the rotary stage base  1034  and the vertical base  1045  that are substantially rectangular parallelepiped. Each vertical guider includes a guiding rail and a slider, which are respectively fixed on the rotary stage base  1034  and the vertical base  1045  to provide a guiding function for vertical movement, so that the rotary stage base  1034  and the tray  102  born by the rotary stage base can be moved vertically with respect to the vertical base  1045 . 
     In this embodiment, four groups of magnetic levitation gravity offsetting devices  105  are respectively arranged in the magnetic levitation gravity offsetting device cavities  1034   d  in the four corners of the rotary stage base  1034  to provide gravity offsetting for the vertical voice coil motor and improve vertical movement precision. As shown in  FIGS. 4 and 5 , the magnetic levitation gravity offsetting device  105  includes: an inner magnetic ring support  1051 , an inner magnetic ring  1052 , an outer magnetic ring  1053 , and an outer magnetic ring seat  1054 . The inner magnetic ring support  1051  includes a cylindrical rod portion  1051   a  and a disc-shaped head  1051   b  on the top of the rod portion. The inner magnetic ring  1052  is fitted over the outer peripheral surface of the cylindrical rod portion  1051   a  of the inner magnetic ring support  1051 . And the disc-shaped head  1051   b  is in contact with the top of the magnetic levitation gravity offsetting device cavity  1034   d , and bears the rotary stage base  1034 . The outer magnetic ring seat  1054  is cylindrical, and the outer magnetic ring  1053  is embedded in the inner surface of the outer magnetic ring seat  1054 . An annular gap is formed between the inner magnetic ring  1052  and the outer magnetic ring  1053 . The magnetic pole direction of the inner magnetic ring  1052  is upward in the axial direction (Z direction), while the magnetic pole direction of the outer magnetic ring  1053  is radially outward. However, it should be understood that the magnetic pole direction of the inner magnetic ring  1052  can be axially downward, while the magnetic pole direction of the outer magnetic ring  1052  can be radially inward. Through the magnetic force between the inner magnetic ring  1052  and the outer magnetic ring  1053 , the inner magnetic ring bracket  1051  can be pushed up, thereby exerting an upward lifting force on the top surface of the magnetic levitation gravity offsetting device cavity  1034   d , making the lifting force approximately equal to the gravity of the rotary stage base  1034  and other devices born by the rotary stage base  1034 , such as the driving motor of the rotary stage and the tray. 
     The air levitation gravity offsetting device is not shown in the figures. The device uses pressurized air to exert an upward lifting force on the top surface of the levitation gravity offsetting device cavity  1034   d , so that the lifting force is approximately equal to the gravity of the rotary stage base  1034  and other devices born by the rotary stage base  1034 , such as the driving motor for the rotary stage and the tray. 
     As shown in  FIGS. 1 and 2 , the horizontal movable device  106  includes: two horizontal guiders  1061   a  and  1061   b , a horizontal base  1062 , a horizontal linear motor  1063  and a horizontal grating scale  1064 . The mover and stator of the horizontal linear motor  1063  are respectively fixed on the horizontal base  1062  and the vertical base  1045  to provide horizontal movement for the vertical base  1045 . The horizontal base  1062  is fixedly connected to the bracket  108 . The horizontal grating scale  1064  provides a horizontal position signal for horizontal movement. In the illustrated embodiment, the horizontal grating scale  1064  is arranged on the lower side of the vertical base  1045 , but it should be understood that the horizontal grating scale  1064  can be arranged at any position as long as the horizontal movement signal of the vertical base  1045  can be obtained. The voice coil motor stator  1042  of the vertical movable device  104  is fixed on the vertical base  1045  to provide support for the rotary stage  103 . Two horizontal guiders  1061   a  and  1061   b  are fixed on both sides of the bracket  108  and are located between the bracket  108  and the horizontal base  1062  to provide guidance for horizontal movement. The horizontal guiders  1061   a  and  1061   b  include a guiding rail and a slider sliding on the guiding rail. The guiding rail and the slider are respectively arranged on the bracket  108  and the horizontal base  1062 . 
     In the above embodiment, four magnetic levitation gravity offsetting devices  105  are used to be arranged at the four corners of the rotary stage base  1034 . However, a triangular layout may also be adopted as in the embodiment shown in  FIG. 9 , preferably a 120° equiangular layout. That is, the rotary stage base  1034  is provided with three magnetic levitation gravity offsetting device cavities  1034   d , which are used to accommodate the magnetic levitation gravity offsetting devices  105   a ,  105   b ,  105   c , respectively. 
       FIG. 10  shows another modified embodiment of the present invention. In the foregoing two embodiments, the voice coil motor and the magnetic levitation gravity offsetting device  105  are two separate devices. The voice coil motor is arranged in the center of the rotary stage base  1034  and pushes the rotary stage and the tray  102  along the Z axis direction. The magnetic levitation gravity offsetting devices  105  (four-corner arrangement or triangular arrangement) arranged on the outer periphery provide gravity offsetting for the voice coil motor. However, this embodiment adopts an integrated structure in which a voice coil motor and a magnetic levitation gravity offsetting device  105  are combined, and is arranged in the center of the rotary stage base  1034 . As shown in  FIG. 10 , an inner magnetic ring  1052  is fitted over the outer surface of the voice coil motor stator  1042 , and an outer magnetic ring  1053  is fitted over the outer circumference of the motor coil  1055 . Therefore, the voice coil motor stator  1042  also functions as an inner magnetic ring support, and the motor coil  1055  also functions as an outer magnetic ring support. Therefore, on one hand, the integrated structure can generate levitation force through the magnetic force between the inner magnetic ring  1052  and the outer magnetic ring  1053  to offset the gravity born by the voice coil motor, and on the other hand, it can generate the Lorentz force through the coil cutting magnetic field to provide the vertical movement driving force for the rotary stage and the tray  102  moving in the Z direction. 
     The preferred embodiments of the present invention have been described in detail above, but it should be understood that, if necessary, aspects of the embodiments can be modified to adopt aspects, features, and concepts of various patents, applications, and publications to provide additional embodiments. 
     Considering the detailed description above, these and other variations can be made to the embodiments. Generally, in the claims, the terms used should not be construed as limiting the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments together with all equivalents to which these claims entitled.