Patent Publication Number: US-2023140269-A1

Title: Substrate holding device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. JP 2021-178555, filed Nov. 1, 2021 in the Japanese Patent Office, the entire contents of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a substrate holding device that holds a substrate irradiated with an ion beam. 
     2. Description of Related Art 
     The ion beam irradiation device incorporates a substrate holding device that holds a substrate irradiated with an ion beam. Some of the substrate holding device include a holder that holds a substrate irradiated with an ion beam, and a driving device that rotates the holder to change the inclination of the substrate held by the holder with respect to the ion beam. 
     Such driving device is configured for capable of precisely controlling the inclination of the substrate by controlling, for example, a direct drive motor directly connected to the holder. 
     However, in this configuration, an attempt to output a high torque in order to rotate the holder causes an increase in size and cost of the direct motor. On the other hand, when a reduction gear is used to reduce the size of a motor, it would be difficult to precisely control the inclination of a substrate due to wear of a gear, backlash, or the like. 
     SUMMARY 
     One embodiment of the substrate holding device comprises a holder that holds a substrate irradiated with an ion beam, and a driving device that rotates the holder about a predetermined axis to change an inclination of the held substrate with respect to the ion beam. In this substrate holding device, the driving device comprises a power source that outputs power to rotates the holder, a reduction gear provided in the middle of a power transmission path from the power source to the holder, a first shaft member that rotates together with the holder by the power outputted from the reduction gear, a first detector that detects a rotational motion of the first shaft member, and a power control device that controls the power source based on a detection value of the first detector. 
     Here, “detects a rotational motion of the first shaft member ” is a concept including not only the meaning of directly detecting the rotational motion of the first shaft member, but also the meaning of detecting the rotational motion of the member rotating in synchronization with the first shaft member as the rotational motion of the first shaft member. 
     In addition, in the present specification, “rotating in synchronization” means rotating at the same angular velocity. 
     One embodiment of the substrate holding device further includes a plurality of transmission gears interposed between the power source and the first shaft member. 
     One embodiment of the substrate holding device may further include a second detector that detects a rotational motion of the output shaft of the power source, and a monitoring device that compares a detection value of the first detector and a detection value of the second detector to determine whether an abnormality has occurred in the driving device. 
     Here, “detects a rotational motion of the output shaft ” is a concept including not only the meaning of directly detecting the rotational motion of the output shaft, but also the meaning of detecting the rotational motion of a member rotating in synchronization with the output shaft as the rotational motion of the output shaft. 
     By comparing such detection values, it is possible to detect or judge an abnormality based on a difference in rotational motion between the output shaft of the power source and the first shaft member, and it is possible to allow the monitoring device to monitor, for example, a gear damage, a gear replacement timing due to an amount of wear exceeding a specified value, and the like. 
     In one embodiment of the substrate holding device, the first detector detects a change in a magnetic field caused by a rotating operation of the first shaft member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will become apparent and more readily appreciated from the following description of example embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG.  1    is a schematic diagram showing an overall configuration of an ion beam irradiation device according to an embodiment. 
         FIG.  2    is a perspective view showing a configuration of the substrate holding device according to an embodiment. 
         FIG.  3    is a schematic view showing a configuration of a substrate holding device according to the embodiment. 
         FIG.  4    is a schematic view showing a configuration of a transmission gear and a housing according to the embodiment. 
         FIG.  5    is a functional block diagram showing functions of a control unit according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of a substrate holding device according to the present disclosure is described with reference to the drawings. 
     As shown in  FIG.  1   , the substrate holding device  100  of the present embodiment is incorporated in an ion beam irradiation device  200 . 
     First, the ion beam irradiation device  200  is briefly described. 
     The ion beam irradiation device  200  is an ion implantation device for irradiating a surface of a substrate W such as a semiconductor wafer with an ion beam IB, injecting ions into the substrate W, and imparting the desired characteristics to the substrate W. The ion beam irradiation device  200  is not limited to the ion implantation device, and may be, for example, an ion beam etching device or the like. 
     The ion beam irradiation device  200  performs mass analysis of the ion beam IB extracted from the ion source  101  by the mass analyzer  102 , and then irradiates the substrate W held by the substrate holding device  100  with the ion beam IB to inject a desired ion species into the substrate W. The path of the ion beam from the ion source  101  to the substrate holding device  100  is surrounded by a vacuum vessel (not shown), and is maintained in a vacuum during ion implantation. 
     The ion beam irradiation device  200  includes a PFG (plasma flood gun)  103  that supplies electrons to the ion beam IB or the surface of the substrate W in order to suppress charging of the surface of the substrate W. 
     The ion beam IB in the present embodiment is a ribbon beam or a sheet beam. That is, the ion beam IB in this embodiment has a band shape that is long in one direction and has a thickness in a direction orthogonal to the length direction. In the present embodiment, the traveling direction of the ion beam IB is defined as a Z direction, and two directions substantially orthogonal to each other in a plane substantially orthogonal to the Z direction are defined as an X direction and a Y direction. For example, the X direction is the thickness direction of the ion beam IB, the Y direction is the length direction of the ion beam IB, the X direction and the Z direction are the horizontal direction, and the Y direction is the vertical direction. The Y direction is a fixed direction, but the X direction and the Z direction are not absolute directions but change along the traveling direction of the ion beam IB. However, the ion beam IB is not limited to a ribbon beam, and may be a spot beam. 
     The substrate W held by the substrate holding device  100  is scanned in the X direction in a manner to cross the ion beam IB along the thickness direction. Thus, the ion beam IB is irradiated on the entire surface of the substrate W. The scanning direction of the substrate W may also be the Y direction. 
     Next, the substrate holding device  100  will be described. 
     As shown in  FIG.  2   , the substrate holding device  100  includes a holder  10  for holding a substrate W and a driving device  20  for driving the holder  10 . 
     The holder  10  is configured to be rotatable, and is switched from the fallen state to the upright state or switched from the upright state to the fallen state by rotating. First, when the holder  10  is in the fallen state, the substrate W is placed on the holder  10 . Thereafter, the holder  10  is rotated while holding the mounted substrate W, thereby the holder  10  is brought into an upright posture. When the holder  10  is in an upright state, the substrate W held by the holder  10  is irradiated with the ion beam IB.  FIG.  2    shows the holder  10  in an upright state. 
     The driving device  20  can change the inclination of the substrate W held by the holder  10  with respect to the ion beam IB by rotating the holder  10  around a predetermined rotation axis L. 
     The “inclination of the substrate W with respect to the ion beam IB” is an angle formed by a normal line of the surface of the substrate W and a traveling direction of the ion beam IB, and is also referred to as a tilt angle. 
     The rotation axis L of the holder  10  is set parallel to the substrate mounting surface  11  of the holder  10 , and is set in the X direction in  FIG.  2   , that is, set along the thickness direction of the ion beam IB immediately before irradiating on the substrate W. However, the rotation axis L of the holder  10  may also be set along the Y direction. 
     In the present embodiment, as shown in  FIG.  2   , a first casing C 1  and a second casing C 2  are provided at positions sandwiching the holder  10 , and a third casing C 3  is provided on the rear surface side of the holder  10  opposite to the substrate mounting surface  11 . 
     In the present embodiment, as shown in  FIG.  3   , the components of the driving device  20  are mainly accommodated in the first casing C 1 . Further, the second casing C 2  accommodates a power supply cable used for rotating the holder  10  around an axis along a normal line direction of the substrate mounting surface  11 , various wires and pipes such as a pipe member through which cooling water flows, and the like, and the third casing C 3  accommodates a twist motor M and the like for rotating the holder  10  around an axis along a normal line direction of the substrate mounting surface  11 . 
     The present invention is characterized by the driving device  20  and is described in detail below. 
     As shown in  FIG.  3   , the driving device  20  includes a power source  21  for rotating the holder  10 , and a power transmission unit  22  for transmitting power from the power source  21  to the holder  10 . 
     The power source  21  in the present embodiment is an electric motor, and a servomotor capable of controlling a rotation angle (rotational position) is used here. However, the present invention is not necessarily limited to this, and various types of power sources may be used. 
     The power transmission unit  22  forms a power transmission path from the power source  21  to the holder  10 , and specifically, includes at least a reduction gear  23  provided in the middle of the power transmission path and a first shaft member  24  connected to the holder  10 . 
     The reduction gear  23  reduces the rotational speed by using a plurality of gears, amplifies the input torque to a torque proportional to the speed reduction ratio, and outputs the amplified torque. Specifically, the reduction gear  23  may be, for example, a harmonic drive (registered trademark). However, the reduction gear  23  is not necessarily limited to this, and various types may be used. 
     The first shaft member  24  rotates by the power (torque) outputted from the reduction gear  23  and rotates the holder  10 . The first shaft member  24  is formed by the output shaft of the reduction gear  23  in the present embodiment. The first shaft member  24  may be the output shaft itself of the reduction gear  23  as in the present embodiment, or may be a shaft member different from the reduction gear  23  interposed between the reduction gear  23  and the holder  10 . 
     More specifically, when the first shaft member  24  rotates, the holder  10  rotates around the rotation axis L in synchronization with the rotation. In other words, the first shaft member  24  rotates the holder  10  during adjustment of the tilt angle. 
     The first shaft member  24  of the present embodiment may be a member which is separate from the output shaft of the reduction gear  23  and rotates in synchronization with the output shaft of the reduction gear  23  to rotate the holder  10 . When the first shaft member  24  is a shaft member different from the output shaft of the reduction gear  23 , the first shaft member  24  need not always rotate in synchronization with the output shaft of the reduction gear  23  depending on the configuration of the power transmission path, for example, a configuration in which a gear is interposed between the reduction gear  23  and the holder  10 . In this case, the first shaft member  24  may be any member that rotates at least the holder  10  in synchronization. 
     The first shaft member  24  integrally rotates the holder  10  and the twist motor M, and passes through the first casing C 1  and the third casing C 3 . 
     In the present embodiment, an annular seal member (not shown) such as a lip seal is provided around the first shaft member  24 , and a space between the first casing C 1  and the third casing C 3  is sealed by the seal member. 
     Thus, during ion implantation into the substrate W, the inside of the first casing C 1  communicates with the atmosphere, and the inside of the third casing C 3  maintains in the vacuum atmosphere. The second casing C 2  maintains in a vacuum atmosphere during ion implantation into the substrate W. 
     In this configuration, the first casing C 1  accommodates the reduction gear  23  constituting the power transmission unit  22 , other various components and the power source  21 . 
     As shown in  FIGS.  2  and  3   , the power transmission unit  22  of the present embodiment further includes a plurality of transmission gears  25  provided in the middle of the power transmission path. 
     More specifically, a plurality of (three in this case) transmission gears  25  are provided between the power source  21  and the reduction gear  23 . As shown in  FIGS.  2  and  4   , these transmission gears  25  are accommodated in the housing  30 . 
     The plurality of transmission gears  25  are arranged in a posture in which respective rotation shafts intersect with the vertical direction, and in this embodiment, the plurality of transmission gears  25  are arranged in a posture in which the rotation shafts extend along the horizontal direction. However, the transmission gear  25  may be arranged in a posture in which the rotation shaft is inclined with respect to both the vertical direction and the horizontal direction. 
     The plurality of transmission gears  25  are arranged in a direction intersecting the vertical direction when the holder  10  is in the upright posture. Specifically, in a state where the holder  10  is in the upright posture, an imaginary line J connecting the centers of the transmission gears  25  adjacent to each other intersects the vertical direction, and in here is inclined with respect to both the vertical direction and the horizontal direction. Although the centers of the plurality of transmission gears  25  are arranged on a straight line in this embodiment, they may be arranged on a curved line. 
     As shown in  FIG.  2   , the housing  30  is attached to the first casing C 1 , and specifically, as shown in  FIG.  4   , the housing  30  has a housing main body  31  formed with a plurality of recesses G in which each transmission gear  25  is accommodated, and an outer cover  32  for closing the recesses G. Although the housing  30  in  FIG.  2    is illustrated in a state in which the inside is visible for easy understanding, the inside of the housing  30  does not necessarily have to be visible from the outside. 
     Each of the recesses G is a cylindrical recess having an outer diameter slightly larger than that of the transmission gear  25 , and an area of an inner side surface of the recesses G including a meshing portion of the transmission gear  25  is cut out, and the recesses G communicates with each other via the cut-out. 
     In the above-described configuration, the transmission gear  25  of the present embodiment is coated with grease or the like as a lubricant in order to reduce wear. The lubricant splashes around the transmission gear  25  by the rotation of the transmission gear  25 , and adheres to the inner peripheral surface of the recesses G. When the transmission gear  25  is stopped, the lubricant travels along the inner peripheral surface of the recesses G and is accumulated in the bottom portion  33  of the recesses G. 
     That is, in the housing  30  of the present embodiment, the bottom portion  33  of the recesses G functions as a reservoir portion in which lubricant such as grease is accumulated. 
     With this configuration, when the transmission gear  25  is rotated again, the lubricant accumulated in the accumulation portion circulates again in the housing  30 , and the effect of reducing wear of the transmission gear  25  is exhibited. 
     Referring back to  FIG.  3   , a shaft member connected to one transmission gear  25 ( a ) of the plurality of transmission gears  25  described above and interposed between the one transmission gear  25 ( a ) and the holder  10 , and a shaft member connected to another transmission gear  25 ( b ) different from the one transmission gear  25 ( a ) and interposed between the another transmission gear  25 ( b ) and the power source  21 , are provided on the same side with respect to the one transmission gear  25 ( a ) and the another transmission gear  25 ( b ). 
     More specifically, one transmission gear  25 ( a ) is closest to the holder  10  among the transmission gears  25  constituting the above-described power transmission path, and the input shaft IA of the reduction gear  23  is connected to the transmission gear  25 ( a ). 
     The another transmission gear  25 ( b ) is closest to the power source  21  among the transmission gears  25  constituting the power transmission path, and the output shaft OA of the power source  21  is connected to the transmission gear  25 ( b ). 
     Although the input shaft IA of the reduction gear  23  is directly connected to one transmission gear  25 ( a ) in the present embodiment, the output shaft OA may be indirectly connected to the transmission gear  25 ( a ) via another shaft member. 
     Although the output shaft OA of the power source  21  is directly connected to another transmission gear  25 ( b ), the input shaft IA may be indirectly connected to the transmission gear  25 ( b ) via another shaft member. 
     The input shaft IA connected to one transmission gear  25 ( a ) and the output shaft OA connected to another transmission gear  25 ( b ) are provided on the same side with respect to one transmission gear  25 ( a ) and another transmission gear  25 ( b ). In other words, the holder  10  and the power source  21  are provided on the same side with respect to the transmission gears  25 . 
     However, in the present embodiment, as shown in  FIG.  3   , the driving device  20  further includes a first detector  26  for detecting the rotational motion of the first shaft member  24 , and a control unit P for controlling the power source  21 . 
     Here, “detecting the rotational motion of the first shaft member  24 ” is a concept including not only the meaning of directly detecting the rotational motion of the first shaft member  24 , but also the meaning of detecting the rotational motion of a member rotating in synchronization with the first shaft member  24  as the rotational motion of the first shaft member  24 . 
     The first detector  26  detects a rotation angle or a rotation position of the first shaft member  24  as a rotation motion, and is accommodated in the first casing C 1 . The first detector  26  of the present embodiment detects a change in the magnetic field caused by the rotational motion of the first shaft member  24 , and is specifically a magnetic encoder, but is not necessarily limited thereto, and may be an optical, mechanical, or electromagnetic induction encoder or the like. 
     The control unit P is a computer including a CPU, a memory, and the like, and is accommodated in the first casing C 1  described above. The control unit P is not necessarily to be accommodated in the first casing C 1 , and may be connected to the first detector  26  via a signal line and disposed under atmospheric pressure outside the first casing C 1 . 
     The control unit P functions at least as a power control device P 1  as shown in  FIG.  5    by the cooperation of the CPU and its peripheral devices in accordance with a program stored in the memory. 
     The power control device P 1  acquires a detection value detected by the first detector  26 , and controls the power source  21  based on the detection value. 
     More specifically, the power control device P 1  acquires the rotation angle of the first shaft member  24 , that is, the rotation angle of the holder  10 , as the detection value of the first detector  26 , acquires the inclination of the substrate W held by the holder  10  with respect to the ion beam IB, that is, the target value of the tilt angle, and controls the servo motor as the power source  21  so that the detection value approaches the target value. The target value may be input via the input means, or may be previously stored in the memory. 
     As shown in  FIG.  3   , the driving device  20  of the present embodiment further includes a second detector  27  for detecting the rotational motion of the output shaft OA of the power source  21 , and the control unit P is configured to further exert a function as a monitoring device P 2  for monitoring the state of the driving device  20  as shown in  FIG.  5   . 
     Here, “detecting the rotational motion of the output shaft OA” is a concept including not only the meaning of directly detecting the rotational motion of the output shaft OA, but also the meaning of detecting the rotational motion of a member rotating in synchronization with the output shaft OA as the rotational motion of the output shaft OA. 
     The second detector  27  detects a rotation angle or a rotation position of the output shaft OA as a rotation motion, and is accommodated in the first casing C 1 . 
     The second detector  27  of the present embodiment detects a change in the magnetic field caused by the rotational motion of the output shaft OA, and specifically, is a magnetic encoder, and in this embodiment, a servomotor serving as the power source  21  is used. However, the second detector  27  is not necessarily limited to this, and may be an optical, mechanical, or electromagnetic induction encoder or the like, and may be provided separately from the servomotor serving as the power source  21 . 
     The monitoring device P 2  acquires the detection value of the first detector  26  and the detection value of the second detector  27 , and compares them to determine whether an abnormality has occurred in the driving device  20 . 
     Note that the “abnormality” as used herein means a state in which replacement of components of the driving device  20  or maintenance of the driving device  20  is necessary, and specifically, a state in which the gear constituting the driving device  20  is damaged, a state in which the wear amount of the gear exceeds a predetermined prescribed value, and/or the like. 
     The monitoring device P 2  compares the detection value of the first detector  26  with the detection value of the second detector  27 , calculates a difference or a ratio between the detection values, and determines that an abnormality has occurred in the driving device  20  when the calculated difference or ratio exceeds a preset threshold. 
     It should be noted that the monitoring device P 2  may be configured such that, when it is determined that an abnormality has occurred in the driving device  20 , the monitoring device P 2  gives notice of such situation by displaying the abnormality on a display, or by emitting sound, light, or the like. 
     According to the substrate holding device  100  configured as described above, since the power from the power source  21  is transmitted to the holder  10  via the reduction gear  23 , a high torque can be outputted to the holder  10  while using the small power source  21 . 
     In addition, since the rotational motion of the first shaft member  24  rotating together with the holder  10  is detected and the power source  21  is controlled based on the detection value, the rotational motion of the first shaft member  24  can be controlled by absorbing the influence of wear of the gear provided in the power transmission path on the control and the influence of backlash on the control. 
     Accordingly, it is possible to reduce the influence on the control of the above-described gear wear, backlash, and the like while achieving miniaturization of the motor, and it is possible to precisely control the inclination of the substrate W with respect to the ion beam IB. 
     Further, since the plurality of transmission gears  25  interposed between the power source  21  and the first shaft member  24  are interposed, for example, by changing the number or arrangement of the transmission gears  25 , the arrangement of the power source  21  can be changed, and the degree of freedom in arrangement can be improved. As a result, for example, by arranging the power source  21  away from the holder  10 , the influence of the magnetic field generated by the motor serving as the power source  21  on the electrons from the PFG  103  can be reduced. Moreover, as described above, the influence of wear of the transmission gear  25  on the control, the influence of backlash on the control, and the like can be absorbed, so that the operation and effect of the present invention can be more significantly exhibited. 
     When electrons supplied from the PFG  103  are influenced by a magnetic field generated from the power source  21 , the effect of suppressing charge-up on the surface of the substrate is reduced, thereby affecting neutralization of the surface of the substrate W. 
     Further, since the shaft member connected to one transmission gear  25 ( a ) and interposed between the one transmission gear  25 ( a ) and the holder  10  and the shaft member connected to another transmission gear  25 ( b ) and interposed between the another transmission gear  25 ( b ) and the power source  21  are provided on the same side with respect to the one transmission gear  25 ( a ) and the another transmission gear  25 ( b ) by utilizing the improvement of the degree of freedom of arrangement, the holder  10  and the power source  21  can be arranged on the same side with respect to the transmission gears  25 . 
     As a result, compared with the configuration in which the power source  21  is arranged on the opposite side of the holder  10  with respect to the transmission gears  25 , the device can be kept compact, and the number of portions to be cleaned can be reduced, thereby improving maintainability. 
     Since the plurality of transmission gears  25  are accommodated in the housing  30 , it is possible to prevent lubricant such as grease used for the transmission gears  25  from scattering out of the housing  30 , and it is possible to reduce contamination of, for example, the first detector  26  and the second detector  27  due to the lubricant. 
     Further, since the plurality of transmission gears  25  are arranged in a direction intersecting with the vertical direction, the rotation axes of the transmission gears  25  intersect with the vertical direction, and each of the transmission gears  25  is accommodated in the recesses G formed in the housing  30 , the lubricant splashed around the transmission gears  25  due to the rotation of the transmission gears  25  adheres to the inner peripheral surface of the recesses G, and after the transmission gears  25  stop, the lubricant travels through the inner peripheral surface of the recesses G and be accumulated in the bottom portion  33  of the recesses G. When the transmission gears  25  rotate again, the lubricant accumulated in the bottom portion  33  of the recesses G circulates again in the housing  30 , so that the effect of reducing wear of the transmission gears  25  is exhibited. 
     Since the monitoring device P 2  for determining whether or not an abnormality has occurred in the driving device  20  is provided, for example, it is possible to monitor the timing of replacement of the gear due to damage of the gear or wear amount exceeding a prescribed value. 
     Since the first detector  26  and the second detector  27  are magnetic encoders, detection accuracy can be ensured even if grease adheres to these detectors, for example, as compared with the case where an optical detector is used. 
     Since the first casing C 1  is partitioned from the third casing C 3  by the seal member provided around the first shaft member  24 , and the inside of the first casing C 1  is communicated with the atmosphere, it is not necessary to use special devices for vacuum as the first detector  26 , the second detector  27 , and the power source  21 , and a general-purpose device can be used. 
     The present invention is not limited to the above embodiments. 
     For example, although a plurality of transmission gears  25  are interposed between the power source  21  and the first shaft member  24  in the above embodiment, an endless belt or the like may be interposed instead of or in addition to the transmission gears  25 . 
     Although the power source  21  is disposed on the holder  10  side with respect to the transmission gears  25  in the above embodiment, the power source  21  may be disposed on the side opposite to the holder  10  with respect to the transmission gears  25 . 
     The power control device P 1  of the above-described embodiment is configured to compare the detection value of the first detector  26  with the target value and control the power source  21  so that the detection value approaches the target value, and in such a configuration, the tilt angle as the rotation angle of the holder  10  can be accurately controlled, while the control time may be long. 
     Therefore, the power control device P 1  may be configured to compare the detection value of the first detector  26  with a predetermined target range to determine whether the detection value is within the target range. When the detection value does not fall within the target range, the power control device P 1  may be configured to control the power source  21  based on the detection value. Specifically, an example may be that the power control device P 1  controls the power source  21  based on the difference between the detection value and the upper or lower limit of the target range. 
     Even though the control accuracy of the tilt angle of the holder  10  is slightly inferior, such configuration is still advantageous in terms of throughput as the control time is shortened. 
     Further, the power control device P 1  may be configured to be switchable between a first mode in which the detection value and the target value are compared with emphasis on the control accuracy of the tilt angle, and a second mode in which the detection value and the target range are compared with emphasis on the throughput. 
     Further, although the monitoring device P 2  compares the detection value of the first detector  26  with the detection value of the second detector  27  in the above-described embodiment, the monitoring device P 2  may be configured to determine whether an abnormality has occurred in the driving device  20  based on the detection value of the first detector  26  and, for example, the amount of power supplied to the power source  21 . 
     The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the present invention.