Wafer handling robot with rotary joint encoder

Abstract

A wafer handling robot is provided that is configured to provide high wafer placement accuracy.Such a robot utilizes a rotary drive transfer mechanism and a rotary encoder located at each rotary joint rather than just at the motor output.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Application No. 15 / 815,325, filed on November 16, 2017, entitled “WAFER HANDLING ROBOTS WITH ROTATIONAL JOINT ENCODERS,” which is incorporated herein by reference in its entirety and for all purposes. Background Art

[0003] Semiconductor wafer handling robots are a very specialized type of robot that typically includes one or two robotic arms terminating in an end effector that can be used to lift semiconductor wafers. These robots are used to transport semiconductor wafers between locations in semiconductor processing tools, and can operate in either a vacuum or atmospheric environment. These arms typically move primarily in the horizontal plane, however they may also be equipped with a Z-axis linear drive to allow the entire arm assembly to move vertically; they typically do not include the ability to rotate about an axis other than the vertical axis (no pitch / roll, only yaw). Summary of the invention

[0004] The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will be apparent from the description, drawings, and claims.

[0005] In some implementations, a wafer handling system is provided, which includes a robot arm. The robot arm may include: a base; a first movable connection member, wherein the first end of the first movable connection member is rotatably connected to the base via a first rotation joint; a second movable connection member, wherein the first end of the second movable connection member is rotatably connected to the second end of the first movable connection member via a second rotation joint; and a first rotation drive transmission mechanism, which includes a first pulley, a second pulley, and one or more first transmission belts spanning between the first pulley and the second pulley. In such an implementation, the second pulley can be fixedly connected to the second movable connection member, and the first rotation drive transmission mechanism can be configured so that: the rotation of the first pulley relative to the first movable connection member causes the second pulley and the second movable connection member to rotate relative to the first movable connection member around the central axis of the second rotation joint. Such an implementation may also include a first motor located in the base, the first motor having a rotation output connected to the first movable connection member and configured to drive the first movable connection member. Such an implementation also has a second motor located in the base, the second motor having a rotational output connected to the first pulley and configured to drive the first pulley. Such an implementation may also include a first rotary encoder having a first portion fixedly connected to the base and a second portion fixedly connected to the first movable connection; and a second rotary encoder having a first portion fixedly connected to the first movable connection and a second portion fixedly connected to the second movable connection.

[0006] In some additional implementations, the first rotary encoder and the second rotary encoder may each have a resolution selected from the group consisting of: 30 bits or more and 33 micro degrees or more.

[0007] In some additional implementations, the first rotational joint may include a first ferrofluid seal between the base and a portion of the first movable connection extending into the base, and the second rotational joint may include a second ferrofluid seal between the first movable connection and a portion of the second movable connection extending into the first movable connection.

[0008] In some other implementations, the robot arm may also include: a third movable connection, wherein the first end of the third movable connection is rotatably connected to the second end of the second movable connection via a third rotation joint; a second rotation drive transmission mechanism, which includes a third pulley, a fourth pulley, and one or more second transmission belts spanning between the third pulley and the fourth pulley; and a third rotation encoder, which has a first part fixedly connected to the second movable connection and a second part fixedly connected to the third movable connection. In such an implementation, the third pulley can be fixedly connected to the first movable connection, the fourth pulley can be fixedly connected to the third movable connection, and the second rotation drive transmission mechanism can be configured so that: the rotation of the third pulley relative to the second movable connection causes the fourth pulley and the third movable connection to rotate relative to the second movable connection around the central axis of the third rotation joint.

[0009] In some implementations, the robot arm may further include: a third motor; a third movable connection member, wherein the first end of the third movable connection member is rotatably connected to the second end of the second movable connection member via a third rotation joint; a second rotation drive transmission mechanism, which includes a third pulley, a fourth pulley, and one or more second transmission belts spanning between the third pulley and the fourth pulley; and a third rotary encoder, which has a first portion fixedly connected to the second movable connection member and a second portion fixedly connected to the third movable connection member. In such an implementation, the third motor may be configured to cause the third pulley to rotate around the rotation axis of the second rotation joint, the fourth pulley may be fixedly connected to the third movable connection member, and the second rotation drive transmission mechanism may be configured so that: the rotation of the third pulley around the central axis of the second rotation joint relative to the second movable connection member causes the fourth pulley and the third movable connection member to rotate relative to the second movable connection member around the central axis of the third rotation joint.

[0010] In some embodiments, the first rotational joint may include a first ferrofluid seal between the base and the portion of the first movable connection extending into the base, the second rotational joint may include a second ferrofluid seal between the first movable connection and the portion of the second movable connection extending into the first movable connection, and the third rotational joint may include a third ferrofluid seal between the second movable connection and the portion of the third movable connection extending into the second movable connection.

[0011] In some implementations, the first movable connection may include a third rotational drive transmission mechanism including a fifth pulley, a sixth pulley, and one or more third drive belts spanning between the fifth pulley and the sixth pulley.

[0012] In some implementations, the third motor can be located within the first movable connection.

[0013] In some implementations, the robot arm may further include: a fourth motor; a fourth movable connection member, wherein the first end of the fourth movable connection member is rotatably connected to the second end of the second movable connection member via the third rotation joint; a fourth rotation drive transmission mechanism, which includes a seventh pulley, an eighth pulley, and one or more fourth transmission belts spanning between the seventh pulley and the eighth pulley; and a fourth rotary encoder, which has a first portion fixedly connected to the second movable connection member and a second portion fixedly connected to the fourth movable connection member. In such an implementation, the fourth motor may be configured to cause the seventh pulley to rotate around the rotation axis of the second rotation joint, the eighth pulley may be fixedly connected to the fourth movable connection member, and the fourth rotation drive transmission mechanism may be configured so that: the rotation of the seventh pulley around the central axis of the second rotation joint relative to the second movable connection member causes the eighth pulley and the fourth movable connection member to rotate relative to the second movable connection member around the central axis of the third rotation joint.

[0014] In some implementations, the first movable connection may further include a fifth rotational drive transmission mechanism including a ninth pulley, a tenth pulley, and one or more fifth transmission belts spanning between the ninth pulley and the tenth pulley.

[0015] In some implementations, the fourth motor can be located within the first movable connection.

[0016] In some implementations, the one or more first transmission belts may be made of stainless steel and may include at least two first transmission belts, and each of the at least two first transmission belts may have a first end and a second end, the first end being fixedly attached to one of the first pulley of the first rotational drive transmission mechanism and the second pulley of the first rotational drive transmission mechanism, and the second end being fixedly attached to the other of the first pulley of the first rotational drive transmission mechanism and the second pulley of the first rotational drive transmission mechanism.

[0017] In some implementations, the interior spaces of the base, the first movable connection, and the second movable connection may be in fluid communication with each other; and both the first rotational joint and the second rotational joint are equipped with vacuum-grade seals.

[0018] In some implementations, each of the one or more first drive belts can be a continuous drive belt.

[0019] In some implementations, each of the one or more first transmission belts may be selected from the group consisting of: a V-shaped transmission belt, a flat transmission belt, a toothed transmission belt, or a round transmission belt; and each of the one or more first transmission belts may be made of a material such as rubber and rubber combined with a braided material.

[0020] In some implementations, the wafer handling system may further include a chamber having a nominal width, length, and height. The chamber may have a plurality of wafer stations disposed along opposing walls, each wafer station having a wafer center point. In such an implementation, the width may define a nominal distance between the opposing walls; and the base may be positioned such that a center axis of the first revolute joint is located within 10% to 30% of the width from one of the opposing walls.

[0021] In some implementations, the wafer handling system may further include: an end effector configured to support a semiconductor wafer and connected to the robotic arm such that the end effector is supported by the first movable connection and the second movable connection. In some implementations, the wafer handling system may further include: a controller having a memory and one or more processors, the memory and the one or more processors being communicatively connected. The memory may store computer executable instructions for controlling the one or more processors to: receive rotational position data from the first rotary encoder; receive rotational position data from the second rotary encoder; and determine a horizontal position relative to a point fixed in space by the end effector based at least in part on the rotational position data from the first rotary encoder and the second rotary encoder.

[0022] In some implementations, the memory may also store computer executable instructions for further controlling the one or more processors to perform the following operations: controlling the first motor, the second motor, or the first motor and the second motor to start and last for one or more time periods to move the point fixed in space relative to the end effector from a first position to a second position.

[0023] Details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. Note that the relative dimensions of the following drawings may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various embodiments disclosed herein are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like reference numerals refer to similar elements.

[0025] Figure 1 An exemplary steel belt drive system is depicted.

[0026] Figure 2 An exemplary radially configured delivery system is depicted.

[0027] Figure 3 An exemplary rectangular conveyor system with a centrally located robotic arm is depicted.

[0028] Figure 4 An exemplary rectangular conveyor system with an offset robotic arm is depicted.

[0029] Figure 5 Depicted Figure 4 Front view of the conveyor system.

[0030] Figure 6 An exemplary wafer handling robot is depicted.

[0031] Figure 7 Depicting another example of a wafer handling robot DETAILED DESCRIPTION

[0032] Importantly, the concepts discussed herein are not limited to any single aspect or embodiment discussed herein, nor to any combination and / or permutation of such aspects and / or embodiments. Additionally, each aspect of the invention and / or its embodiments may be employed alone or in combination with one or more of the other aspects and / or its embodiments. For the sake of brevity, many of these permutations and combinations will not be discussed and / or described separately herein.

[0033] Semiconductor wafer handling robots are expected to move quickly, precisely, and with little potential for noise, vibration, or particle generation. Therefore, these robots are typically designed so that the drive components (motors) of the robot arm or arms are located in the base (thereby reducing the weight in the moving parts and increasing the rate at which the robot can operate), and then use some form of mechanical drive (such as a steel belt) to transmit the motive force provided by those motors through the arm links to the driven links.

[0034] Such a steel belt drive mechanism is preferred in semiconductor processing equipment for a number of reasons. First, stainless steel belts may be less susceptible to chemical attack than timing belts (which are typically made of a combination of polymeric and textile materials; these materials are more likely to be damaged by chemicals that may be encountered in a semiconductor processing equipment environment). Stainless steel belts are significantly less likely to generate particles during operation, whereas timing belts may both generate particles (due to their lower strength) and outgas (due to the polymeric materials used) - both of which are potentially problematic in a semiconductor processing environment because they may affect wafer handling and cleanliness. Timing belts also tend to become thermally stressed in a vacuum environment because they lose the ability to dissipate heat by convection (due to the lack of atmosphere). As timing belts heat up, they become substantially more susceptible to thermal damage and may exhibit higher failure rates and particle generation.

[0035] Steel belt drive mechanisms typically feature two non-continuous steel belts attached to two sets of pulleys operating in parallel, for example, with each set of pulleys connected to a common shaft. Each belt will be rigidly connected to one of the pulleys in the set, with each belt sitting on the opposite side of the pulley from the other belt. This is conceptually illustrated in Figure 1 In. Figure 1 , a two-pulley drive mechanism is shown, wherein the first pulley 152 and the second pulley 154 are connected by two first transmission belts 172 (172A and 172B). Figure 1 The upper figure in FIG. 1 shows the first pulley 152, the second pulley 154 and the separate first drive belt 172A; as can be seen, the first drive belt 172A is discontinuous and, in this example, is fixed to the first pulley 152 and the second pulley 154 by pins. In actual operation, this attachment may be more complex and may provide, for example, the ability to adjust the tension of the first drive belt 172A between the two pulleys.

[0036] As will be apparent, rotating the first pulley 152 counterclockwise approximately 160 degrees will also cause the second pulley 154 to rotate counterclockwise. In this case, since the first pulley 152 is approximately twice as large as the second pulley 154, the second pulley 154 will rotate at twice the rate of the first pulley 152 - such a drive belt system can also be used with pulley systems of different ratios, such as a 1:1 ratio pulley.

[0037] However, clockwise rotation of the first pulley 152 does not result in a corresponding clockwise movement in the second pulley 154 because the first drive belt 172A is not under tension in this rotation mode. To allow this clockwise movement, the first drive belt 172B (see FIG. 14 ) may be rotated in substantially the same manner as the first drive belt 172A. Figure 1The first belt 172B is fixed to the first pulley 152 and the second pulley 154, but the first belt 172B is connected to these pulleys at a substantially different position than the first belt 172A. The resulting rotary drive transmission mechanism can provide precise rotational positioning that is quiet and lightweight. However, a key limitation of this system is that the amount of rotational movement that can be provided by such a steel belt system is less than 360° because such a belt is typically not allowed to overlap the connection points between the belts and the pulleys. Therefore, there is typically at least 10° to 20° of dead zone (in Figure 1 The dead zone is shown in the bottom portion of the figure (shown with a cross-hatched pie segment showing both drive belts on the pulleys at the same time). The pulleys cannot rotate through this dead zone. This limits the range of rotational motion of a robot using this steel belt rotation drive transmission mechanism, however in most typical embodiments this is not a problem because the available space within the environment in which the robot arm operates is typically large enough to avoid having to undergo rotations that would conflict with such a limited range of motion.

[0038] For example, in a vacuum environment, it is common to position the base of a wafer handling robot near / at the center of the vacuum environment so that semiconductor processing chambers, load lock chambers, and other workstations / locations (where wafers can be placed or retrieved) are equidistant from the robot base, which reduces the length of the robot, allows for easier control of settings (because the robot motions are essentially identical for interacting with each workstation), and allows the robot to operate without large joint rotations. Figure 2 An example of a radially configured transfer chamber is described, which is a chamber that is typically maintained in a vacuum and has multiple wafer processing chambers that are connected to the multiple wafer processing chambers at a number of locations around its circumference or perimeter. In this example, the transfer chamber 201 (which can also be considered a wafer handling system 200) has four wafer processing chambers 203 arranged along four different sides and two load lock chambers 205, which act as air locks to allow wafers to enter and leave the vacuum environment of the transfer chambers arranged along the other two sides without disturbing it. As can be seen, the robot arm can easily enter and exit any processing chamber or load lock chamber from its central mounting position.

[0039] Even in non-radially configured transfer chambers, the base of the wafer handling robot is typically mounted approximately in the center of the chamber. Figure 3 An example rectangular transfer chamber is depicted, with two sets of three processing chambers 303 arranged along opposite sides of the transfer chamber 301. A centrally located robot arm 302 is able to reach all processing stations 303 without any rotation of the robot arm 302 exceeding 180°.

[0040] The inventors have attempted to create a new type of transfer chamber in which, for example, a robot arm similar to the belt-driven robot arm discussed previously, or a variation thereof discussed in more detail below, is mounted in an off-center position. Since the drive motor and other electronics of such a robot arm (including any vertical lift capability) are typically located in the robot arm base, the base of such a robot arm can be very large, such as 1 foot in diameter and 2 feet in length or more. For a vacuum transfer chamber, the robot arm base is typically mounted in the transfer chamber so that the base protrudes beyond the bottom of the transfer chamber so that the chamber volume does not need to include headroom for the base. This reduces the volume of the transfer chamber, making it less expensive to manufacture, easier to seal, and reducing the amount of time required to pump the transfer chamber to a vacuum. However, when the base of the robot arm extends through the floor of the transfer chamber, it may intrude on, for example, a walkway or other personnel access passageway under the transfer chamber. Such a walkway or passageway may allow personnel to repair or access components of the processing station that may be located below the processing chamber itself. The inventors appreciated that this configuration made it difficult for personnel to perform such maintenance or otherwise access such components, and decided to move the robot so that the base of the robot was positioned closer to one side or the other of the transfer room, resulting in a less cramped configuration beneath the transfer room. Instead of having the robot base bisect any walkways or passages extending beneath the transfer room, the base is offset to one side, leaving a single open path through it that is twice as wide as the path through the base would be if the base were in a central position.

[0041] Figure 4 An example of this new type of transfer chamber is described. Figure 4 , the transfer chamber 301 is similar to Figure 3 301, except that the base of the robot 302 has been shifted to one side and is disposed adjacent to one side of the transfer chamber 301. In practice, it may be desirable to place the base of the robot 302 as close to one side or the other as possible, although allowances may be made for tolerances, safety gaps, moving parts clearances, and the like. More generally, the base may be centered within 25% of one of the walls defining the width of the transfer chamber. For example, if the width of the transfer chamber ( Figure 4 The left and right dimensions in the figure are 40 inches, and the base of the robot arm 302 can be centered on the left or right side of the transfer chamber 301 (depending on the Figure 4303) within 10 inches of one of the robot bases, e.g., about 7 inches from the side. For a typical robot base having a diameter of about 12 inches in this exemplary embodiment, this leaves about a 28 inch gap between the base and the opposite side of the transfer chamber 301. Thus, even if the equipment below the processing chamber 303 extends to the side of the transfer chamber, there will still be at least a two foot wide passageway between the robot base and the equipment under the transfer chamber, thereby making it easier for personnel to enter and exit.

[0042] Figure 5 describe Figure 3 and 4 A front view of the transfer chamber 301. Figure 5 , the transfer chamber 301 is raised off the floor. Each process chamber 303 has chamber support equipment 303A below it, such as a vertical riser for moving a wafer stage up and down within the process chamber 303, a cooling system, a power supply, etc., which may extend down to the floor (or at least halfway to the floor). As can be seen, the pedestal 304 is positioned to one side of the transfer chamber 301, leaving a gap "X" for personnel to enter and exit through the pedestal 304. The dashed outline to the right of the pedestal 304 depicts the pedestal in a centered position, as would typically be done with an existing transfer chamber. As can be seen, this centered position greatly reduces access below the transfer chamber 301.

[0043] However, the inventors also understand that if a conventional belt-driven wafer handling robot were used in this off-center position, the robot might need to undergo rotations greater than the normal range of some of its attachments in order to enter and exit some processing chambers; these rotations would cause the robot to exceed the maximum allowable rotation permitted by such a belt system.

[0044] The inventors were able to overcome this problem by designing a new type of wafer handling robot that utilizes techniques and methods not typically found in wafer handling robots. Generally speaking, such a wafer handling robot replaces the steel belt system that is typically used with a continuous belt system (e.g., using a polymer-based or polymer and fabric-based timing belt). This allows a full 360° rotation without being limited by the rotary drive transmission mechanism used. At the same time, the inventors determined that rather than using a rotary encoder located at the output of the drive motor (as is typically done in such robots), it would be preferable to install a rotary encoder at each rotary joint in the robot, even when no motor is located at that rotary joint. In conventional wafer handling robot systems, the rotary encoder is juxtaposed with the motor (or even built into the motor as an integrated unit, such as a servo motor) because this allows the wiring of the rotary encoder and the motor to be laid out together. For many robot arm joints, this also avoids the need to route encoder wiring through the revolute joints (or at least avoids the need to route encoder wiring through any revolute joints that do not already have electrical feedthroughs or cabling for controlling any motors that may potentially be located, for example, in a robot arm attachment segment adjacent to the base), thereby simplifying the robot arm design. In contrast, the new wafer handling robot arm of the subject matter of the present disclosure can route wiring to the rotary encoder via many of the robot arm's kinematic joints that are inserted between the robot arm's base and the location of the rotary encoder. Thus, the revolute joints can be hollow along their midlines to allow the cabling to pass through them without being exposed to the environment outside the arm and to reduce the amount of movement such cables experience during movement of the robot arm. In some alternative such designs, the cable itself may not be continuous or may not even be a cable. For example, a flexible or non-flexible printed circuit substrate may be used to provide a conductive path for signals to and from the rotary encoder, and a slip ring or other similar mechanism for providing electrical continuity across the rotary interface may be used to electrically connect the rotary encoder to the controller. Such a slip ring or similar mechanism may be located within a sealed portion of, for example, a revolute joint in order to protect the conductive paths and also prevent any particles generated by such a mechanism from escaping the robot arm (other than through the base).

[0045] For purposes of this disclosure, the phrases "directly driven," "direct drive," "directly driven," and variations thereof, mean a relationship between a rotating part and a motor providing a rotational input to the rotating part, wherein the motor has a center of rotation that is substantially coaxial with the axis of rotation of the rotating part (there may be some slight deviation due to manufacturing tolerances, and some systems may use a rotary flexible coupling to adjust for this deviation, but the motor axis of rotation and the rotating part axis of rotation will still be understood to be "substantially coaxial with each other."). Rotating parts that are directly driven by their respective motors also rotate at the same rate as the rotational outputs of these motors; there is no intermediate gear reduction or other speed reducer / intensifier interposed between the motor and the rotating part.

[0046] Similarly, the phrases "indirectly driven", "indirectly driven", "indirectly driven" and variations thereof refer to the relationship between a rotating part and a motor that provides a rotational input to the rotating part, wherein the motor has a center of rotation that is offset (some design amount, as opposed to an offset due to assembly or manufacturing tolerances) from the rotational axis of the rotating part in a direction perpendicular to the rotational axis of the rotating part. In the context of the present application, the mechanism that implements this indirect drive is referred to as a "rotational drive transmission mechanism". Such a rotational drive transmission mechanism generally includes two pulleys, each of which is attached to a driving rotating part (which may be the output of the motor or may be driven by some other rotational input such as the rotational output of another rotational drive transmission mechanism) or a driven rotating part. In practice, each rotating part may have a single pulley or may have multiple pulleys connected to the same shaft or other shared part of the rotating part. In such a multi-pulley case, the term pulley may be understood to apply to the pulley individually or to a plurality of pulleys that rotate together around the same axis in general.

[0047] Thus, the wafer handling robot described below (which is merely an example of a robot arm embodying the concepts presented herein and is not intended to limit the application of these concepts to other robots) can be generally described as having at least one rotary drive transmission mechanism and at least one revolute joint between the movable connecting members of these robots, the at least one revolute joint being driven by the rotary drive transmission mechanism and having a rotary encoder associated with the revolute joint. Such a robot arm may also include additional rotary drive mechanisms and revolute joints, and additional rotary encoders at these additional revolute joints.

[0048] The wafer handling robot described below and other robots embodying similar concepts are also capable of achieving positioning accuracy currently unheard of in the robot arm industry. For example, for a typical robot arm having a maximum extension length (measured from the center of rotation of the arm to the center of a wafer being transported by the arm) of about 1.7 meters, the concepts discussed herein, including the placement of rotary encoders at each rotary joint, may allow the robot arm to have a wafer positioning accuracy or repeatability as low as ±25 μm, which is nearly two-thirds lower than many prior art wafer handling robots (which may have a wafer positioning accuracy or repeatability of ±70 μm). This improved wafer positioning accuracy may allow a wafer to be placed or centered with greater accuracy on a wafer receiving stage or chuck in a semiconductor processing chamber, thereby allowing smaller feature sizes to be processed on the wafer.

[0049] A further benefit of the wafer handling robot discussed below is that the placement of the encoder at the revolute joint as opposed to at the rotary input (motor) allows any added inaccuracies that may result from the use of a timing belt or other non-steel belt to be captured and removed by the closed loop control system. For example, if the timing belt stretches slightly when in use, this stretch will cause the driven pulley to rotate in a slightly different orientation than the drive pulley (assuming a 1:1 pulley diameter ratio), which, if the drive pulley is where the rotary encoder is located, will result in added inaccuracies as to where the movable link is located in the robot arm.

[0050] Figure 6 A diagram depicting an exemplary wafer handling robot. Figure 6, an exemplary robot arm 602 is depicted. In this example, the robot arm 602 has a base 604, a first movable connection 606, a second movable connection 608, and a third movable connection 610. The third movable connection 610 terminates in a first end effector 614, which can be a blade-type end effector that can be arranged under a semiconductor wafer like a spatula to lift the semiconductor wafer from below. The first end 606A of the first movable connection 606 can be rotatably connected to the base 604 via a first rotation joint 618, and the first rotation joint 618 can include one or more sets of rotation bearings 694. Similarly, the first end 608A of the second movable connection 608 can be rotatably connected to the second end 606B of the first movable connection 606 through a second rotation joint 620, and the first end 610A of the third movable connection 610 can be rotatably connected to the second end 608B of the second movable connection 608 through a third rotation joint 622. The first revolute joint 618 can be configured to allow the first movable connection 606 to rotate relative to the base 604 about a first rotational axis 624 in response to a rotational input received by a first motor 630 located in the base 604. Similarly, the second revolute joint 620 can be configured to allow the second movable connection 608 to rotate relative to the first movable connection 606 about a second rotational axis 626, and the third revolute joint 622 can be configured to allow the third movable connection 610 to rotate relative to the second movable connection 608 about a third rotational axis 628. The revolute joints discussed herein may also be referred to herein as revolute interfaces.

[0051] The exemplary robotic arm 602 depicted has only two degrees of freedom - extension and retraction of the first end effector 614 along an axis intersecting and perpendicular to the first rotational axis 624. Thus, only two motors are shown, namely a first motor 630 and a second motor 632. Both motors are housed within the base to avoid having the weight of the motors sitting in the movable connection.

[0052] In this exemplary robot arm, the first motor 630 directly drives the first movable connection 606 as shown by extending downwardly into the tubular shaft of the first motor 630. However, the second motor 632 indirectly drives the second movable connection 608 through the first rotational drive transmission mechanism 642, which includes a first pulley 652, a second pulley 654, and a first drive belt 672. In this example, the first drive belt 672 is a timing belt or other continuous endless belt. The first pulley 652 is directly driven by the second motor 632, and the second pulley 654 is fixedly connected to the second movable connection 608, so that the second movable connection 608 and the second pulley 654 move together. When the first pulley 652 rotates around the first rotation axis 624 relative to the first movable connection 606, for example by actuating the second motor 632 without actuating the first motor 630 (or by actuating the two motors at different rates and / or directions), the relative rotational motion can be transmitted to the second pulley 654 through the first transmission belt 672, thereby causing the second pulley 654 and the second movable connection 608 connected thereto to rotate relative to the first movable connection 606.

[0053] In addition to the first rotary drive transmission mechanism 642 located in the first movable connection 606, the robot arm 602 may also have a second rotary drive transmission mechanism 644 located in the second movable connection 608. The second rotary drive transmission mechanism 644 may include a third pulley 656 (in this case, it is just the outside of the tubular shaft extending through the second rotation joint 620), a fourth pulley 658, and a second drive belt 674. In this particular embodiment, the third pulley 656 is fixedly connected to the first movable connection 606. As a result, relative rotational movement between the first movable connection 606 and the second movable connection 608 around the second rotation axis 626 (such as can be caused by the operation of the first rotary drive transmission mechanism 642) can thereby cause the second rotary drive transmission mechanism 644 to operate. This relative rotational movement can therefore be transmitted to the third movable connection 610 via the fourth pulley 658 that can be connected to the third movable connection 610, and thus directly drive the third movable connection 610.

[0054] In this example, the first pulley 652 and the second pulley 654 have a 2:1 diameter ratio, which will cause the second pulley 654 to rotate at twice the rate and amount of the first pulley 652; this ratio can be used to cause the first movable link 606 and the second movable link 608 to "scissor" outwardly and inwardly while the third rotational axis 628 translates along a radius extending away from the first rotational axis 624. Correspondingly, the third pulley 656 and the fourth pulley 658 have a 1:2 diameter ratio, which causes the third movable link 610 and the first end effector 614 to rotate about the third rotational axis 628 at half the rate at which the first movable link 606 and the second movable link 608 rotate relative to each other about the second rotational axis 626. This causes the first end effector 614 to remain aligned with the previously mentioned radius during extension and retraction of the robotic arm 602.

[0055] As mentioned above, the robotic arm 602 also includes a rotary encoder located at each rotary joint. For example, the first rotary encoder 682 may be located at the first rotary joint 618, the second rotary encoder 684 may be located at the second rotary joint 620, and the third rotary encoder may be located at the third rotary joint 622. A rotary encoder (as that term is used herein) means a sensor device configured to measure a rotational displacement about an axis between two components. The device includes two parts, each of which is fixed to a different one of the two components. Of course, the two parts are free to rotate relative to each other, and in some cases, may be coupled together into a single integrated unit (much like a ball bearing may have an inner race and an outer race, each of which is connected to a different one of the two parts between which the ball bearing is mounted). In other cases, the two parts may be physically separate from each other, for example, one part may be mounted on one rotatable component and the other part mounted on another rotatable component - the two rotatable components are then mated together and the two parts of the rotary encoder may be aligned with each other to enable rotational position measurement, but the two parts may never actually contact each other during operation. Figure 6 , the first rotary encoder 682 may have a first portion 682a fixedly connected to the first movable connection 606 and a second portion 682b fixedly connected to the base 604. Similarly, the second rotary encoder 684 may have a first portion 684a fixedly connected to the second movable connection 608 and a second portion 684b fixedly connected to the first movable connection 606, and the third rotary encoder 686 may have a first portion 686a fixedly connected to the third movable connection 610 and a second portion 686b fixedly connected to the second movable connection 608.

[0056] Encoders suitable for use with the wafer handling robot discussed herein may generally be of the optically based variety, such as an encoder in which one portion includes a set of high precision fiducial marks that can be optically read by a sensor located in a second portion. Other types of encoders, such as mechanical, magnetic or capacitive encoders are generally not suitable for use with such robots due to poor accuracy, friction or other factors. Examples of rotary encoders that may be used with the embodiments discussed herein include, for example, the RESOLUTE 1000 supplied by Renishaw Plc of New Mills, Wotton-under-Edge, Gloucestershire, England. TM The present inventors have determined that the accuracy provided by the optical rotary encoder outweighs this potential disadvantage.

[0057] The rotary encoders in the robot arm 602 may be connected to a controller 696, which may include one or more processors 699 and memory 698, via one or more cables that feed through various rotary joints of the robot arm that separate each rotary encoder from the base 604. For example, the memory 698 may store instructions for executing a PID (proportional-integral-derivative) control loop that uses data from the rotary encoders to determine the rotational rate for the motors (the controller 696 may also be in communication with the motors and provide control signals to the motors for controlling the motors).

[0058] Figure 6 The robot arm 602 shown in FIG. 6 is suitable for use under atmospheric conditions and, as shown, does not include seals or other features that would make it suitable for use in a vacuum environment. However, it should be understood that the robot arm can be easily modified to operate in a vacuum by replacing or enhancing some or all of the existing rotary bearings with vacuum-grade / sealed bearings, as will be discussed in more detail with reference to the following embodiments. In addition, while the rotary encoder is shown as being mounted on the exterior of the robot arm, other embodiments may feature the rotary encoder being located within the movable connector and / or base 604 to better protect the rotary encoder from damage and dirt.

[0059] Figure 7 Describes the Figure 6Another more complex exemplary robotic arm is shown in FIG; the example depicted not only includes two end effectors, but each end effector is also capable of independent rotation relative to the movable connection that supports them. The example depicted also includes z-axis motion capability (it should be understood that this can also be used with Figure 6 ) and is configured to operate in a vacuum environment.

[0060] exist Figure 7 , an exemplary robotic arm 702 is depicted. In this example, the robotic arm 702 has a base 704, a first movable connection 706, a second movable connection 708, a third movable connection 710, and a fourth movable connection 712. The third movable connection 710 and the fourth movable connection 712 terminate in a first end effector 714 and a second end effector 716, respectively. The first end effector 714 and the second end effector 716 can be blade-type end effectors, which can be arranged under a semiconductor wafer like a spatula to lift the semiconductor wafer from below. The first end 706A of the first movable connection 706 can be rotatably connected to the base 704 via a first rotation joint 718, and the first rotation joint 718 can include one or more sets of rotation bearings 794. Similarly, the first end 708A of the second movable link 708 may be rotatably connected to the second end 706B of the first movable link 706 via a second rotational joint 720, and the first end 710A of the third movable link 710 may be rotatably connected to the second end 708B of the second movable link 708 via a third rotational joint 722. The first rotational joint 718 may be configured to allow the first movable link 706 to rotate relative to the base 704 about a first rotational axis 724 in response to a rotational input received by a first motor 730 located in the base 704. Similarly, the second rotational joint 720 may be configured to allow the second movable link 708 to rotate relative to the first movable link 706 about a second rotational axis 726, and the third rotational joint 722 may be configured to allow the third movable link 710 and the fourth movable link 712 to independently rotate relative to the second movable link 708 about a third rotational axis 728.

[0061] Unlike the robot arm 602, the exemplary robot arm 702 described has five degrees of freedom. To provide such degrees of freedom, the robot arm 702 includes a total of four motors and a linear actuator 738. The first motor 730 and the second motor 732 and the linear actuator 738 are housed in the base, while the third motor 734 and the fourth motor 736 are located in the first movable connection 706. It should be understood that, alternatively, the third motor 734 and / or the fourth motor 736 are also housed in the base 704, and their rotational output is transmitted through the first revolute joint 718 using a concentric drive shaft (as has been done for the output of the second motor 732). The linear actuator 738 can be used to drive the sub-portion of the base that houses the first motor 730 and the second motor 732, and supports the first revolute joint 718 and the movable connection upward and downward in the vertical dimension to facilitate z-axis motion. The guide rail 740 can guide this action and provide stable motion along the z-axis. The bellows 790 may be configured to seal a movable subsection of the base 704 relative to the remainder of the base 704, thereby enabling the subsection to move vertically relative to the remainder of the base 704 without providing a leakage path for gas to enter the base 704. In practice, the upper surface of the base 704 may be connected, for example, in a gas-tight manner to an interface to a transfer module to prevent leakage through the upper surface of the base 704, thereby maintaining a vacuum environment around the movable connection of the robot arm 702.

[0062] In this exemplary robotic arm, the first motor 730 directly drives the first movable connection 706 as shown by extending downwardly into the tubular shaft of the first motor 730. However, the second motor 732 indirectly drives the second movable connection 708 through the first rotational drive transmission mechanism 742, which includes a first pulley 752, a second pulley 754, and a first drive belt 772. In this example, the first drive belt 772 is a timing drive belt or other continuous loop drive belt. The first pulley 752 is directly driven by the second motor 732. However, unlike the second pulley 654, the second pulley 754 is fixedly connected to the second movable connection 708, so that the second movable connection 708 and the second pulley 754 move together. When the first pulley 752 is rotated about the first rotation axis 724 relative to the first movable connection member 706, for example by actuating the second motor 732 without actuating the first motor 730 (or by actuating the two motors at different speeds and / or directions), the relative rotational action between them can be transmitted to the second pulley 754 via the first transmission belt 772, thereby causing the second pulley 754 and the second movable connection member 708 connected thereto to rotate relative to the first movable connection member 706.

[0063] In addition to the first rotational drive transmission mechanism 742 located in the first movable connection 706, the robot arm 702 may also have a second rotational drive transmission mechanism 744 located in the second movable connection 708. The second rotational drive transmission mechanism 744 may include a third pulley 756, a fourth pulley 758, and a second transmission belt 774. Compared with the third pulley 656 fixedly connected to the first movable connection 606, in this example, the third pulley 756 is rotatably connected to the first movable connection 706, so that the first movable connection 706 and the third pulley 756 can rotate independently around the second rotation axis 726. In this example, the third pulley 756 is driven by the third rotational drive transmission mechanism 746, which may include a fifth pulley 760, a sixth pulley 762, and a third transmission belt 776. The output of the third motor 734 can drive the fifth pulley 760, which in turn drives the third drive belt 776, thereby causing the sixth pulley 762 and the third pulley 756 to which it is fixedly connected to rotate - which causes the fourth pulley 758 and the third movable connection 710 to which it is fixedly connected to rotate relative to the second movable connection 708. It should be understood that other embodiments can have the third motor 734 directly drive the sixth pulley 762 / third pulley 756 or can have the third motor 734 located in the base, with an additional drive transmission mechanism used to transmit the motive force from the third motor 734 to the sixth pulley 762 (and thus to the third pulley 756). It should be understood that in some cases, the third pulley 756 and the sixth pulley 762 can be the same diameter, and even just different parts of the same cylindrical outer surface of the tube (this is also true for the seventh pulley 764 and the tenth pulley 770, which are discussed below). Since each revolute joint in the exemplary robotic arm is independently driven by a separate motor, the size of the various pulleys used can be modified if necessary, with any modifications accommodated by control of the motor speed / displacement.

[0064] In the dual end effector embodiment, a fourth rotational drive transmission mechanism 748 may be provided, which includes a seventh pulley 764, an eighth pulley 766, and a fourth drive belt 778. The eighth pulley 766 may be fixedly connected to the fourth movable connection 712, such that rotation of the eighth pulley 766 about the third rotation axis 728 relative to the second movable connection 708 causes the fourth movable connection 712 and the second end effector 716 to also rotate about the third rotation axis 728 relative to the second movable connection 708. Similar to the third pulley 756, the seventh pulley 764 may be rotatably connected to the first movable connection 706 and the second movable connection 708, such that the seventh pulley 764 may rotate independently of the first movable connection 706 and the second movable connection 708. Therefore, when the seventh pulley 764 rotates around the second rotation axis 726 relative to the second movable connection member 708, the corresponding movement of the fourth transmission belt 778 can also cause the eighth pulley 766 to rotate, thereby causing the fourth movable connection member 712 to rotate around the third rotation axis 728 relative to the second movable connection member 708.

[0065] In this example, the seventh pulley 764 is driven by the fifth rotary drive transmission mechanism 750, which may include a ninth pulley 768, a tenth pulley 770, and a fifth drive belt 780. The output of the fourth motor 736 may drive the ninth pulley 768, which in turn drives the fifth drive belt 780, thereby causing the tenth pulley 770 and the seventh pulley 764 fixedly connected thereto to rotate - which causes the eighth pulley 766 and the fourth movable connection 712 fixedly connected thereto to rotate relative to the second movable connection 708. It should be understood that other embodiments may have the fourth motor 736 directly drive the seventh pulley 764 / tenth pulley 770, or may have the fourth motor 736 located in the base 704, with an additional drive transmission mechanism used to deliver the motive force from the fourth motor 736 to the tenth pulley 770 (and thus to the seventh pulley 764).

[0066] This configuration allows the second motor 732 and the third motor 734 to independently control the relative rotational position of the second movable connection member 708 and the third movable connection member 710, respectively.

[0067] As discussed above, the robotic arm 702 also includes a rotary encoder located at each rotary joint. For example, the first rotary encoder 782 may be located near the first rotary joint 718 (in this case, it is located adjacent to the first motor 730 and is located within the base 704, but it is still centered on the first rotation axis 724 of the first rotary joint 718), the second rotary encoder 784A may be located at the second rotary joint 720, and the third rotary encoder 786 and the fourth rotary encoder 788 may be located at the third rotary joint 722.

[0068] exist Figure 7 , the first rotary encoder 782 may have a first portion 782a fixedly connected to the first movable connection 706 and a second portion 782b fixedly connected to the base 704. Similarly, the second rotary encoder 784A may have a first portion 784Aa fixedly connected to the second movable connection 708 and a second portion 784Ab fixedly connected to the first movable connection 706, the third rotary encoder 786 may have a first portion 786a fixedly connected to the third movable connection 710 and a second portion 786b fixedly connected to the second movable connection 708, and the fourth rotary encoder 788 may have a first portion 788a fixedly connected to the fourth movable connection 712 and a second portion 788b fixedly connected to the second movable connection 708. Additionally, in some embodiments, additional rotary encoders (also referred to herein as rotary encoders) may be provided at other locations to provide the potential for even greater accuracy. For example, an additional second rotary encoder 784B (with a first portion 784Ba fixedly connected to the first pulley 752 and a second portion 784Bb fixedly connected to the vertically translatable portion of the base 704) may be provided at the second motor 632; in this case, the output of the second rotary encoder 784A located at the second rotary joint 720 may be used to provide position data to the control loop, while another second rotary encoder 784B located at the second motor 732 may be used to provide speed data to the control loop. This approach may be used to grasp any compliance in the first drive belt 772; similar approaches may be used for other rotary encoders used if desired.

[0069] Like robot 602, robot 702 may also include a controller 796 having a memory 798 and one or more processors 799; the memory 798 may similarly store computer executable instructions for controlling robot 702, such as instructions for executing a PID subroutine to use input from a rotary encoder to control a motor to cause the robot to move to a desired position.

[0070] Another difference between robot arm 602 and robot arm 702 is that robot arm 702 includes a vacuum-tight rotary seal 792 at each rotary joint, or at least at each rotary joint that has a pulley attached to it. An example of such a vacuum-tight seal is a ferrofluid seal that provides a strong, low-friction vacuum seal that produces little, if any, particulate contamination (any metal particles that wear off during operation are immediately captured by the seal's magnetic field, thereby preventing such particles from migrating to, for example, wafers being transported by a wafer handling robot). The vacuum-tight seal may be integrated into a bearing assembly or used in conjunction with a rotary bearing that allows smooth rotary motion through the vacuum-tight seal. This allows the interior of the movable connections sealed with the vacuum-tight seal to be maintained at atmospheric pressure, while the environment surrounding these movable connections is maintained at a vacuum. Generally speaking, only the outermost seal of each movable connection that is maintained at atmospheric pressure may be provided by a vacuum-tight seal; other rotary bearings may not be equipped with such seals. By sealing the belt drive system to the atmospheric portion of such a movable connection, any particulates generated by the drive belt will remain isolated from the vacuum environment, thereby maintaining its cleanliness.

[0071] It should be understood that the concepts of eccentric robot arm mounting, the use of timing belts instead of steel belts, and the use of rotary encoders at each rotary joint of the robot arm may each represent independent ideas and may be implemented separately or as interdependent combinations or sub-combinations. Thus, for example, a robot arm with a timing belt and joint-mounted rotary encoders may be used in a non-eccentric mounting position, etc.

[0072] It should be understood that, unless further limited, the term "group" means a group of one or more items - unless there is further language suggesting the presence of multiple items, there need not be multiple items. For example, "a group of two or more items" will be understood to have at least two items. Conversely, "a group of one or more items" will be understood to have possibly only one item. Likewise, it should be understood that the term "each" may be used herein to mean each member of a group, even if the group includes only one member. The term "each" may also be used in the same manner as an implied group, for example, where the term "group" is not used but other language suggests the presence of a group. For example, "each item in one or more items" should be understood to be equivalent to "each item in the group of one or more items."

[0073] As discussed above, in some implementations, the controller may be part of the wafer handling system discussed herein. The wafer handling system may also be considered as a semiconductor processing tool, for example, it may also include a semiconductor processing device, which includes a processing chamber or multiple processing chambers, a platform or multiple platforms for processing, and / or specific processing components (wafer stage, gas flow system, etc.). These systems (including robotic arms) can be integrated with electronic devices for controlling their operations before, during, and after the processing of semiconductor wafers or substrates. The electronic device may be referred to as a "controller", which can control various components or subcomponents of one or more systems. Depending on the processing requirements and / or system type, the controller may be programmed to control any process disclosed herein (such as a process for controlling a wafer handling robot), as well as other processes or parameters not discussed herein, the delivery of process gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operation settings, wafer transfer in and out of the chamber and other transfer tools and / or load locks connected to or connected to a specific system through an interface.

[0074] In general, a controller can be defined as an electronic device having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, etc. The integrated circuit can include a chip in the form of firmware that stores program instructions, a digital signal processor (DSP), a chip defined as an application specific integrated circuit (ASIC), and / or one or more microprocessors, or a microcontroller that executes program instructions (e.g., software). The program instructions can be instructions sent to the controller in the form of various individual settings (or program files) that define operating parameters for performing a specific process on or for a semiconductor wafer or system. In some embodiments, the operating parameters can be part of a recipe defined by a process engineer to complete one or more processing steps during the manufacture of one or more (kinds of) layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0075] In some implementations, the controller may be part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the "cloud" or all or part of a wafer fab host system that may allow remote access to wafer processing. The computer may enable remote access to the system to monitor the current progress of a manufacturing operation, check the history of past manufacturing operations, check trends or performance criteria for multiple manufacturing operations, change parameters of a current process, set processing steps to follow the current process, or start a new process. In some examples, a remote computer (e.g., a server) may provide a process recipe to the system via a network (which may include a local network or the Internet). The remote computer may include a user interface that enables input or programming of parameters and / or settings, which are then sent from the remote computer to the system. In some examples, the controller receives instructions in the form of data that specify parameters for each processing step to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller may be distributed, for example, by including one or more discrete controllers networked together and working toward a common purpose (e.g., the process and control described herein). An example of a distributed controller for such a purpose is one or more integrated circuits on a chamber communicating with one or more integrated circuits remotely (e.g., at a platform level or as part of a remote computer), which combine to control the process on the chamber.

[0076] Exemplary wafer handling systems may include (having attached thereto) but are not limited to plasma etching chambers or modules, deposition chambers or modules, spin rinse chambers or modules, metal plating chambers or modules, cleaning chambers or modules, chamfer edge etching chambers or modules, physical vapor deposition (PVD) chambers or modules, chemical vapor deposition (CVD) chambers or modules, atomic layer deposition (ALD) chambers or modules, atomic layer etching (ALE) chambers or modules, ion implantation chambers or modules, track chambers or modules, and any other semiconductor processing system that may be associated with or used in the manufacture and / or preparation of semiconductor wafers.

[0077] As described above, depending on one or more processing steps to be performed by the tool, the controller can communicate with one or more other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout the factory, a host computer, another controller, or tools used in material transport to transport wafer containers to and from tool locations and / or load ports in a semiconductor manufacturing facility.

[0078] It should be understood that the above disclosure, while focused on a particular example embodiment or embodiments, is not limited to only the examples discussed, but is also applicable to similar variations and mechanisms, and such similar variations and mechanisms are also considered to be within the scope of the present disclosure.

Claims

1. A wafer handling system, comprising: The robotic arm include: Pedestal; a first movable connection member, a first end of the first movable connection member being rotatably connected to the base via a first revolute joint; a second movable connection member, a first end of the second movable connection member being rotatably connected to a second end of the first movable connection member via a second revolute joint; A first rotary drive transmission mechanism includes a first pulley, a second pulley, and one or more first transmission belts spanning between the first pulley and the second pulley, wherein: The second pulley is fixedly connected to the second movable connection member, and The first rotational drive transmission mechanism is configured such that: rotation of the first pulley relative to the first movable connection causes the second pulley and the second movable connection to rotate relative to the first movable connection about a central axis of the second revolute joint; a first motor seated in the base and having a rotational output connected to the first movable connection and configured to drive the first movable connection; a second motor seated in the base and having a rotational output connected to the first pulley and configured to drive the first pulley; a first rotary encoder having a first portion fixedly connected to the base and a second portion fixedly connected to the first movable connection; and a second rotary encoder having a first portion fixedly connected to the first movable connection and a second portion fixedly connected to the second movable connection, in: The inner spaces of the base, the first movable connection member, and the second movable connection member are fluidically connected to each other in the robot arm, The first revolute joint and the second revolute joint are both equipped with vacuum seals, The first rotary joint is hollow along its center line, and a portion of the wiring connected to the rotary second encoder is disposed in the hollow of the first rotary joint, Each of the one or more first drive belts is a V-belt, a flat belt, a toothed belt or a round belt, and Each of the one or more first drive belts is made of a material including a polymer material or a polymer material combined with a fabric.

2. The wafer handling system of claim 1, wherein the first rotary encoder and the second rotary encoder each have a resolution selected from the group consisting of: 30 bits or more and 33 micro degrees or more.

3. The wafer handling system according to claim 1, in: The first revolute joint includes a first ferrofluid seal between the base and a portion of the first movable connection extending into the base, and The second revolute joint includes a second ferrofluid seal between the first movable connection and a portion of the second movable connection extending into the first movable connection.

4. The wafer handling system according to claim 1, wherein the robot arm further include: a third movable connecting member, a first end of the third movable connecting member being rotatably connected to a second end of the second movable connecting member via a third revolute joint; A second rotational drive transmission mechanism, comprising a third pulley, a fourth pulley, and one or more second transmission belts spanning between the third pulley and the fourth pulley; as well as a third rotary encoder having a first portion fixedly connected to the second movable connection and a second portion fixedly connected to the third movable connection, wherein: The third pulley is fixedly connected to the first movable connecting member, The fourth pulley is fixedly connected to the third movable connecting member, and The second rotational drive transmission mechanism is configured such that rotation of the third pulley relative to the second movable connection causes the fourth pulley and the third movable connection to rotate relative to the second movable connection about a central axis of the third revolute joint.

5. The wafer handling system according to claim 1, wherein the robot arm further include: The third motor; a third movable connecting member, a first end of the third movable connecting member being rotatably connected to a second end of the second movable connecting member via a third revolute joint; A second rotational drive transmission mechanism, comprising a third pulley, a fourth pulley, and one or more second transmission belts spanning between the third pulley and the fourth pulley; as well as a third rotary encoder having a first portion fixedly connected to the second movable connection and a second portion fixedly connected to the third movable connection, wherein: The third motor is configured to cause the third pulley to rotate about the rotation axis of the second revolute joint, The fourth pulley is fixedly connected to the third movable connecting member, and The second rotary drive transmission mechanism is configured such that rotation of the third pulley relative to the second movable connection about the center axis of the second rotary joint causes the fourth pulley and the third movable connection to rotate relative to the second movable connection about the center axis of the third rotary joint.

6. The wafer handling system according to claim 5, in: The first revolute joint comprises a first ferrofluid seal between the base and a portion of the first movable connection extending into the base, The second revolute joint includes a second ferrofluid seal between the first movable connection and a portion of the second movable connection extending into the first movable connection, and The third revolute joint includes a third ferrofluid seal between the second movable connection and a portion of the third movable connection extending into the second movable connection.

7. The wafer handling system according to claim 5, wherein the first movable connection member comprises a third rotational drive transmission mechanism, and the third rotational drive transmission mechanism comprises a fifth pulley, a sixth pulley and one or more third transmission belts spanning between the fifth pulley and the sixth pulley.

8. The wafer handling system of claim 7, wherein the third motor is located within the first movable link.

9. The wafer handling system according to claim 7, wherein the robot arm further include: Fourth motor; a fourth movable connecting member, a first end of the fourth movable connecting member being rotatably connected to the second end of the second movable connecting member via the third revolute joint; a fourth rotational drive transmission mechanism comprising a seventh pulley, an eighth pulley, and one or more fourth transmission belts spanning between the seventh pulley and the eighth pulley; as well as a fourth rotary encoder having a first portion fixedly connected to the second movable connection and a second portion fixedly connected to the fourth movable connection, wherein: The fourth motor is configured to cause the seventh pulley to rotate about the rotation axis of the second revolute joint, The eighth pulley is fixedly connected to the fourth movable connecting member, and The fourth rotary drive transmission mechanism is configured such that rotation of the seventh pulley relative to the second movable connection about the center axis of the second rotary joint causes the eighth pulley and the fourth movable connection to rotate relative to the second movable connection about the center axis of the third rotary joint.

10. The wafer handling system according to claim 9, wherein the first movable connection member further comprises a fifth rotational drive transmission mechanism, the fifth rotational drive transmission mechanism comprising a ninth pulley, a tenth pulley and one or more fifth transmission belts spanning between the ninth pulley and the tenth pulley.

11. The wafer handling system of claim 10, wherein the fourth motor is located within the first movable link.

12. The wafer handling system of claim 1, wherein each of the one or more first belts is a continuous belt.

13. The wafer handling system of claim 1 further comprising a chamber having a nominal width, length, and height, in: The chamber has a plurality of wafer stations disposed along opposing walls, each wafer station having a wafer center point; The nominal width defines a nominal distance between the opposing walls; The base is positioned so that a central axis of the first revolute joint is located within 10% to 30% of the nominal width from one of the opposing walls.

14. The wafer handling system of claim 1, further comprising: an end effector configured to support a semiconductor wafer and connected to the robot arm such that the end effector is supported by the first movable connection and the second movable connection, and a controller having a memory and one or more processors, in: The memory is communicatively coupled to the one or more processors, The memory stores computer executable instructions for controlling the one or more processors to: receiving rotational position data from the first rotary encoder; receiving rotational position data from the second rotary encoder; and Based at least in part on the rotational position data from the first and second rotational encoders, a horizontal position relative to a point fixed in space by the end effector is determined.

15. A wafer handling system according to claim 14, wherein the memory also stores computer executable instructions for further controlling the one or more processors to perform the following operations: controlling the first motor, the second motor, or the first motor and the second motor to start for one or more time periods to move the point fixed in space relative to the end effector from a first position to a second position.

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