Multi-axis, non-contact vacuum seal for robotic applications in vacuum

Abstract

An apparatus provides a multi-axis, non-contact vacuum seal for robotic applications in vacuum. The apparatus includes one or more shafts located concentrically relative to one another and a cylindrical wall within a housing. A primary shaft is located concentrically within a secondary shaft with the first longitudinal axis and the second longitudinal axis co-located at a common longitudinal axis. The apparatus includes a first actuator system configured to move the primary shaft both rotationally about the common longitudinal axis and linearly along the common longitudinal axis and a second actuator system configured to move the secondary shaft in at least one of rotationally about the common longitudinal axis and linearly along the common longitudinal axis. A first set of passageways is formed in at least one of the primary shaft and the secondary shaft, and a second set of passageways is formed in at least one of the primary shaft.

Description

Multi- Axis, Non-Contact Vacuum Seal for Robotic Applications in VacuumBACKGROUND OF INVENTION

[0001] The present application relates generally to the use of vacuum seals to provide for the transfer of mechanical motion from an atmospheric motor system into a vacuum system where motion of components is needed. In general, when motion of components is needed in a vacuum system, there are two options: place a motor in vacuum; or keep a motor (partially) in atmosphere, but provide a mechanical feedthrough to transmit motion through the atmosphere / vacuum interface. In the former case, motors in vacuum suffer from several problems, such as outgassing of components, which can negatively impact vacuum quality and result in contamination of vacuum processes, and removal of waste heat generated in the motor windings, which is hard to implement in a vacuum system due to poor thermal conductance of heat in vacuum. Furthermore, motors often require shaft position encoders, which allow for precise determination and control of the motor, but implementation of such encoders often requires additional components to be put in the vacuum system, sometimes in combination with other switches and sensors for safety or motion hard stops. In the latter case, a suitable mechanical feedthrough or vacuum seal needs to be provided so that shafts in vacuum can be rotated properly.

[0002] While mechanical vacuum seals are known they generally only support one or two axes of motion. Many mechanical vacuum seals are friction-based seals: a sealing surface is contacted by a (usually compressible) material that is allowed to slide across such a surface, while maintaining an air-tight interface. Such a construction requires compressing the seal material which allows for a tight seal, but also increases friction between the shaft and the seal and hence requires significantly greater motor power for rotation of the shaft. Vacuum seals have also been implemented using permanentmagnets or electro-magnets. By using a thin barrier between the atmospheric environment and the vacuum, magnetic field lines can cross the barrier and provide motive force in the vacuum system. However, in such a system, at least some components (often permanent magnets) need to be situated inside the vacuum environment, which can lead to outgassing and result in vacuum system contamination. Furthermore, it is mechanically complicated to provide more than one or two axis of motion in such a fashion. Therefore, when three or four axes of motion are required, such structures are separated into two independent two-axis structures. This results in a morecomplicated mechanical coupling to support the required axes of motion. In particular, the mechanical coupling is increasingly complicated when other functions must also be accomplished such as providing a cooling fluid to a substrate, positioning a substrate, or gripping a substrate in the vacuum system. Furthermore, providing a rotation in a vacuum system, often requires a friction based seal technology, which results in a significantly larger motor being employed. Larger motors have known disadvantages including less positioning accuracy and a significantly larger heat load generated by the motor.

[0003] FIG. 1 illustrates a linear vacuum feedthrough as illustrated in U.S. Patent No. 4,726,689 (“the ‘689 patent”). Here, a cylindrical shaft (labeled 10 in the figure), is concentrically mounted in a housing (40). The housing 40 contains a series of grooves (labeled 41 , 10A, 10B, 10C and 10D). The shaft furthermore supports a substrate holder 20 and a substrate to be processed 30. A pressurized gas source 11 provides a centering gas layer around the shaft 10 and a small amount of air is vented out near where the shaft 10 exits the housing 40 as well as through groove 41. A series of pumps 60A, 60B, 60C and 60D provide incrementally lower levels of vacuum pressure, whilst the substrate 30 and substrate holder are in high vacuum (typically at a pressure of 10'4Pa (N / m2)). The cross section of the shaft 10 is chosen so that the weight of the shaft 10, substrate holder 20, and substrate 30 are counterbalanced by the vacuum force that attempts to pull the shaft assembly into the vacuum chamber (of which wall 50 is shown). The complete disclosure of U.S. Patent No. 4,726,689 is incorporated by reference herein.

[0004] The system described in the ‘689 patent allows all motors that drive the shaft to be kept at atmospheric pressure. This simplifies the cooling of the motors and their electrical wiring and connections. Other prior systems include motors, bearings and sensors that are (partially) placed in the vacuum system, for example, U.S. Patent Nos. 5,539,266 and 5,813,823 describe such an approach. However, these systems suffer from the problem that these components often outgas in vacuum, and cannot be easily cooled if needed. The complete disclosure of each of U.S. Patent No. 5,539,266 and U.S. Patent No. 5,813,823 are incorporated by reference herein, respectively.

[0005] Referring to FIG. 2, a cross sectional diagram of the concept illustrated in FIG. 1 of the ‘689 patent is provided. A vacuum- air-bearing system 200 consisting of a central shaft 201 is concentrically mounted in a housing 202 placed in atmosphere 218. The housing 202 is commonly fitted with a flange 203 and static O-ring seal 215 so that it can be mounted in the bottom of a vacuum vessel 216 of which a bottom portion is shown inthe figure. A number of grooves 212 provided in the housing 202 can be used to either provide pressurized air (for example groove 208), venting of excess air (for example grooves 207 and 209) or to provide differential pumping of air (for example grooves 210 and 211) as long as the desired level of high-vacuum in the area 217 above the shaft can be achieved (lower vacuum pressures can be achieved by - amongst other things - by increasing the distance between grooves, for example between grooves 210 and 211 and / or between groove 211 and the outlet 204 into the high vacuum area), increasing the number of grooves and pumps (adding a 3rdpump and groove for example), or increasing the pumping capacity in the high vacuum area or a combination thereof. The dimension of the gap 204 between the shaft 201 and the housing 202 is made to be very uniform and very small, usually in the 10 to 20 pm range with an accuracy of less than 1 pm, resulting in a very tight, non-contact region between the shaft 201 and the housing 202. With such a narrow gap any air flow along the shaft through the gap 204 is severely restricted, allowing one to apply successive grooves 210 and 211 with successively lower pressures until a high vacuum 217 can be obtained.

[0006] If the diameter of the shaft 201 is chosen so that the upward force FHV (205 a) counterbalances the gravitational force FG (205b), then the shaft (and any objects mounted thereto) can be moved vertically without having to overcome the force of gravity, or only a fraction of that force, depending on how well the balance is made. In this configuration, the primary motions (206) available to the shaft are a rotational movement and a vertical movement. Either one of these motions occurs without having to overcome friction forces. Mechanical vacuum seals such as O-rings, Lipseals, Ferrofluidic seals or bellows, suffer from the fact that the mechanical nature of the seal requires a fairly large force to overcome friction, in addition to potentially having to overcome gravitational forces. Furthermore, linear motion through a mechanical vacuum seal, typically leads to wear on the seal components and a small amount of air gets dragged through the seal as well. (It is worth noting that a vertical movement of shaft 201 also will drag a small amount of air along the shaft into the high vacuum area 217). Utilizing multiple O-rings or lip seals is feasible (and those can be differentially pumped between the seals), but each additional seal increases the force required to overcome the seal’s friction, and thus require significantly more motor force to overcome such friction.

[0007] In the system illustrated in FIG. 2, the shaft 201 can be moved by attaching two motors. Motor 1 (213) imparts a rotational movement to the shaft, whereas motor 2 (214) imparts a vertical, linear movement. It is possible to provide both motionssimultaneously. It is also worth noticing that, in principle, the rotational motion can be infinite: there is no fundamental limitation to the number of revolutions that shaft 201 can make, unless items are attached to the shaft that prevent such an infinite rotation, such as electrical wires or fluid connections and the like, that are not themselves equipped with a rotational coupling. Such a coupling, however, would also add friction and thus a resistance to motor 1 (213). In the vertical direction, motion is more limited by the length of the shaft 201 and the fact that shaft 201 cannot be allowed to move beyond the grooves 212.

[0008] FIG. 3 illustrates the vacuum seal of FIG. 2 (rotated in the figure to a horizontal aspect for illustration only), and identifies typical pressures experienced in the gap 204 along the shaft 201, and housing 202. Generally, air pressure is provided in one or more grooves at a pressure of 5* 105to 106Pa. This creates a collar of compressed air around shaft 201 in gap 204 and prevents the shaft from touching the housing 202, even when a radial force is applied to the shaft 201. Differentially pumped grooves 210 and 211 connected to vacuum pumps (not shown) provide a progressively lower pressure in the gap 204, which ultimately drops to the pressure of the high vacuum chamber, and can be in the 10"5Pa range. Graph 300 illustrates the pressure gradients in gap 204. Atmospheric pressure 301 is found at the bottom of shaft 201 and high vacuum 302 at the top of the shaft 201.

[0009] FIG. 4 illustrates another prior system described in U.S. Patent No. 6,172,372 (“the ‘372 patent”). This system utilizes two seal assemblies similar to those illustrated in FIGS. 1 and 2, herein. The ‘372 patent describes a system to overcome the requirement for the unit to be mounted vertically. Also, gravity is not a factor in moving the shaft 14. By locating the seals on opposite sides of the vacuum chamber 12a, a natural counterbalance is achieved and the shaft can still easily be moved rotationally and linearly / horizontally. However, since the seal assemblies are expensive to manufacture, due to their tight tolerances, using two seal assemblies is expensive and alignment between the two assemblies is critical. Further, because the vacuum forces tend to deform the chamber 12, it is hard to achieve positional accuracy the ‘372 patent describes a system that is an over-constrained mechanical system. The complete disclosure of U.S. Patent No. 6,172,372 is incorporated by reference herein.

[0010] FIG. 5 illustrates a different seal assembly of the prior art as described in U.S. Patent No. 7,210,246 (“the ‘246 patent”). The system of the ‘246 patent achieves a vertical motion through means of motor 39002 and lead screw 39010. The verticalmovement is made possible by using a bellows seal 39014. At the same time, the seal assembly in the ‘246 patent utilizes two direct drive rotational motors 39006 and 39004 to provide rotation to two concentrically located shafts (not labeled in the figure) which in turn are sealed by O-rings, Lipseals or Ferrofluidic seals 39016. The seal assembly in the ‘246 patent allows for all the mechanical components of the motors such as magnets 39020, bearings 39018 and shaft position encoders 39008 to remain outside of the vacuum environment 39000. However, the friction in the seals, particularly if Ferrofluidic seals are used, result in substantial non-linear motion behavior, since the seal friction is not linear with velocity and is also temperature dependent. Furthermore, the inner and outer seals 39016 result in a coupling force between the two shafts: when one attempts to move one shaft, the other shaft is dragged along, making precise motion control much more difficult. The complete disclosure of U.S. Patent No. 7,210,246 is incorporated by reference herein.

[0011] FIG. 6 illustrates a seal as described in the ‘266 patent in which two shafts (34 and 36) are outfitted with sets of magnets 30 and 32, that transmit motion through a vacuum wall (not labeled in the figure). In this arrangement, a dynamic seal is not required, however, the coupling between the magnets in air (30 and 32) and the magnets in vacuum (43 and 44) is not very rigid, particularly during high acceleration of the shafts 34 and 36. The result is that the motion through the vacuum separating wall is not very accurate and the actual position of the magnets 42 and 44 is not known, unless additional components such as limit switches or encoders are added inside the vacuum. This implementation requires the use of magnets, bearings (52 and 50) and other components in vacuum, which can also lead to outgassing and a lack of capability to operate at higher temperatures since magnets can have a limited operating temperature range. Other prior systems (for example, U.S. Patent No. 5,899,658) use a similar approach with a magnetic coupling and add a Z-axis through means of a bellows. However, these systems suffer from the same problems as Stevens with magnets, bearings, encoders and sensors present in vacuum, resulting in potential outgassing and contamination.

[0012] In addition, mechanical bearing systems such as ball bearings or roller bearings are traditionally employed in combination with rotating shafts in systems that operate at atmospheric pressure and often in systems that include a feed-through to a vacuum chamber. These conventional bearings suffer from drawbacks including wear that reduces a life of the bearings and friction that places greater demands on any motor used to rotate the shaft.SUMMARY OF INVENTION

[0013] There is a need for a system that provides a cost efficient, manufacturable, and mechanically efficient method to bring multiple axes of mechanical motion into a vacuum system in a way that allows for additional functions to be optionally added such as substrate cooling, positioning or gripping, whilst at the same time reducing the forces needed to provide such motion in the vacuum system. Various embodiments described herein provided apparatus, systems and methods that deliver mechanical motion in three or more axes of motion in a vacuum system via a single contactless bearing system. In some embodiments, the single contactless bearing system is employed with multiple shafts arranged concentrically about a common axis of location. In further embodiments, the concentric shafts are motor operated to provide each of the respective shafts with both a linear motion and a rotational motion.

[0014] According to some embodiments, an apparatus includes a housing having a first end configured to couple to a vacuum chamber and a second end located opposite the first end. The housing includes a hollow cylindrical tube extending axially from the first end to the second end, the hollow cylindrical tube defined by a cylindrical wall formed within the housing. A plurality of shafts are located concentrically relative to one another and the cylindrical wall within the housing. The primary shaft is located concentrically within the secondary shaft with the first longitudinal axis and the second longitudinal axis colocated at a common longitudinal axis of the plurality of shafts. The apparatus includes a first actuator system configured to move the primary shaft both rotationally about the common longitudinal axis and linearly along the common longitudinal axis and a second actuator system configured to move the secondary shaft in at least one of rotationally about the common longitudinal axis and linearly along the common longitudinal axis. A first set of passageways is formed in at least one of the primary shaft and the secondary shaft, and a second set of passageways is formed in at least one of the primary shaft. The first set of passageways are configured to couple to at least one of a source of pressurized fluid, at least one fluid relief line and at least one source of vacuum pumping, the first set of passageways fluidically coupled to a first cylindrical region separating the primary shaft from the secondary shaft. The second set of passageways configured to couple to at least one of a source of pressurized fluid, at least one fluid relief line and at least one source of vacuum pumping, the second set of passageways fluidically coupled to a second cylindrical region separating the secondary shaft from the cylindrical wall.

[0015] Provided herein are methods and systems used for providing motion into a vacuum system, from one or more motors that are located outside of the vacuum system. In accordance with one or more embodiments the methods and systems include providing a cylindrically symmetrical housing, a first, hollow shaft located co-axially withing such housing and a second shaft co-axially located within the first shaft. In embodiments, the housing is outfitted with a series of grooves, some of which provide a fluid to one or more of the grooves, some of which provides a pumping or vacuum function to one or more of the grooves. In embodiments, a first groove supplies a fluid such as compressed air, or a vacuum oil to one of the grooves. In embodiments, the second shaft is outfitted with a series of grooves, some of which provide a fluid to one or more of the grooves, some of which provides a pumping or vacuum function to one or more of the grooves. In embodiments, the fluid is compressed air, in embodiments the fluid is a vacuum oil or other suitable fluid with low outgassing characteristics in vacuum. In embodiments, the first shaft is connectively coupled to one or more motors. In embodiments, a first motor provides linear motion to such first shaft. In embodiments, a first motor provides rotational motion to such first shaft. In embodiments, two motors are provided wherein the first motor provides linear motion and a second motor provides rotational motion to such first shaft. In embodiments, the second shaft is connectively coupled to one or more motors. In embodiments, a first motor provides linear motion to such second shaft. In embodiments, a first motor provides rotational motion to such second shaft. In embodiments, two motors are provided wherein the first motor provides linear motion and a second motor provides rotational motion to such second shaft. In embodiments, the diameter of the first shaft is slightly smaller than the diameter of the co-axial opening in the housing. In embodiments, the diameter of the second shaft is slightly smaller than the diameter of the opening in the first shaft. In embodiments, the diameter of the second shaft is slightly smaller than the diameter of the opening in the fust shaft. In embodiments, the area exposed to the vacuum system of the first shaft is chosen such that the weight of the first shaft and mechanical systems connected to it is approximately the same as the vacuum force pulling on the first shaft. In embodiments, the area exposed to the vacuum system of the second shaft is chosen such that the weight of the second shaft and mechanical systems connected to it is approximately the same as the vacuum force pulling on the second shaft.

[0016] In embodiments, the housing is outfitted with one or more channels that provide fluids, pumping or vacuum to one or more of the grooves in the housing. Inembodiments, the second shaft is outfitted with one or more channels that provide fluids, pumping or vacuum to one of more of the grooves in the second shaft. In embodiments, the first and second shaft are outfitted with a mounting surface to accommodate a robotic arm structure or other devices that require motion.

[0017] In embodiments, such a robotic arm structure consists of a Selectively Compliant Articulated Robot Arm (SCARA). In embodiments the SCARA arm is outfitted with an end effector designed to support a substrate. In embodiments the SCARA arm accommodates two or more linkages. In embodiments the SCARA arm supports two end effectors each capable of supporting a substrate. In embodiments, the robotic arm consists of a “frogleg” robotic arm. In embodiments, the robotic arm consists of two opposing “frogleg” arms. In embodiments, the robotic arm consists of dual “frogleg” arms positioned on an “X” shaped lower arm member structure.

[0018] In embodiments, a substrate holder is mounted to the first and second shafts. In embodiments, rotational motion of the first shaft results in rotational motion of the substrate holder. In embodiments, vertical motion of the first shaft results in aspect angle change of the substrate holder about a vertical axis. In embodiments, rotational motion of the second shaft results in an aspect angle change about a horizontal axis. In embodiments, vertical motion of the first and second shaft simultaneously results in vertical motion of the substrate holder. In embodiments, an ion, electron or laser beam is directed at the substrate holder. In embodiments, the various rotations and orientations of the substrate holder allow a workpiece to be exposed to such ion, electron or laser beams.

[0019] In embodiments, a first, movable shaft is located in a housing. In embodiments, the first shaft is hollow and accommodates a second shaft that is coaxially located within the first shaft. In embodiments, the housing is outfitted with a series of grooves. In embodiments, the second shaft is outfitted with a second set of grooves and a third set of grooves. In embodiments, one or more of the second set of grooves is fluidly connected to the third set of grooves. In embodiments, the third set of grooves in the second shaft is surrounded by a third shaft that is places co-axially to the first and second shafts, but is separated from the first and second shafts in such a way that the first and second shafts are allowed to independently move, whereas the third shaft can be moved independently from the first and second shafts or can be fixedly held. In embodiments the third shaft is fluidically connected to a fixed series of fluid or vacuum lines, which are connected to the grooves in the second shaft across a narrow gap between the second and third shafts. In embodiments, the first and second shafts are outfitted with auxiliary channels to transportliquids or electrical signals from the atmospheric side of said shafts to the vacuum side of said shafts.

[0020] In one or more embodiments, a cylindrically shaped housing is mounted in a vacuum vessel. In embodiments, the cylindrical housing has a cylindrical opening that is occupied by a first cylindrical shaft, and wherein there is a narrow gap between the housing and the first shaft. In embodiments, the first shaft has a co-axial cylindrical opening that accommodates a second cylindrical shaft wherein there is a narrow opening between the first and second shafts. In embodiments, the first shaft is outfitted with a first set of grooves and a second set of grooves. In embodiments, the first set of grooves is located on an interior surface of the first shaft and the second set of grooves is located on the opposite, exterior surface of the first shaft. In embodiments, one or more of the grooves in the first set of grooves are fluidically connected to the one or more of the grooves in the second set of grooves. In embodiments, the connected sets of grooves are fluidically connected to channels leading to the atmospheric side of the first shaft. In embodiments, the first or the second shafts are outfitted with additional channels to supply fluids, or electrical signals between the atmospheric side of said shafts and the vacuum side of said shafts. In embodiments, the first shaft is extended below the housing in such a way that a motor and encoder can be mounted on the second shaft, whilst at the same time, fluidic connections can be made on the extension of the first shaft. In embodiments, the extension of the first shaft is outfitted with a third set of grooves. In embodiments, the third one or more of the third set of grooves is fluidically connected to the first and second sets of grooves.

[0021] In one or more embodiments, a cylindrical housing is mounted in a vacuum chamber. In embodiments, the cylindrical is outfitted with a cylindrical opening in which a shaft is mounted. In embodiments, the housing is outfitted with a set of grooves that allow fluids to be directed toward, or removed from the narrow gap between the housing and the shaft. In embodiments, such a fluid is compressed air, or a vacuum compatible oil such as Fomblin vacuum oil or any other suitable fluid. In embodiments, one or more of the grooves is fluidically connected to a fluid supply system. In embodiments, one of more of the supply lines is outfitted with a flow limiting nozzle. In embodiments, the nozzle consists of a device that uses turbulent vortexes to automatically limit the fluid flow. In embodiments, some of the grooves are connected to a fluid supply and some of the grooves are connected to a fluid removal device. In embodiments, some of the supplyand removal channels are sized so that a narrow gap is maintained between the housing and the shaft.

[0022] In one or more embodiments, a cylindrical shaft is surrounded by a co-axial cylindrical housing, in which one or more fluid flow nozzles supply a fluid between the shaft and the housing. In embodiments, the nozzles are flow limiting nozzles. In embodiments, the nozzles contain features that cause vortexes to occur in the fluid when flow rates exceed a design value. In embodiments, the fluid is removed from the gap by a set of drains pipes which optionally can also be outfitted with nozzles. In embodiments, the drain nozzles are flow limiting nozzles. In embodiments, the drain nozzles contain features that cause vortexes to occur in the fluid when flow rates exceed a design value. In embodiments several alternating sets of supply and drain nozzles and pipes are arranged in a radial direction along the perimeter of the housing. In embodiments, there are several rows of nozzles spaced along layers in a vertical direction along the primary axis of the shaft and housing. In embodiments, the several rows and layers of nozzles are connected to the same or different fluids supplied to the gap between the housing and the shaft. In embodiments, the gap between the housing and the shaft is maintained very evenly by the offsetting forces between the nozzle supply and drain pipes resulting in a high resistance to the shaft contacting the housing while it is subjected to cantilevered loads.

[0023] In one or more embodiments, a first cylindrical shaft is surrounded by a co-axial cylindrical housing, in which one or more fluid flow nozzles supply a fluid between the shaft and the housing and a second cylindrical shaft is surrounded by the co-axially located first shaft. In embodiments, the nozzles are flow limiting nozzles. In embodiments, the nozzles contain features that cause vortexes to occur in the fluid when flow rates exceed a design value. In embodiments, the fluid is removed from the gap between the first and second shaft by a set of drains pipes which optionally can also be outfitted with nozzles. In embodiments, the drain nozzles are flow limiting nozzles. In embodiments, the drain nozzles contain features that cause vortexes to occur in the fluid when flow rates exceed a design value. In embodiments several alternating sets of supply and drain nozzles and pipes are arranged in a radial direction along the perimeter of the first or second shaft. In embodiments, there are several rows of nozzles spaced along layers in a vertical direction along the primary axis of the first or second shaft. In embodiments, the several rows and layers of nozzles are connected to the same or different fluids supplied to the gap between the first and the second shaft. Inembodiments, the gap between the first and the second shaft is maintained very evenly by the offsetting forces between the nozzle supply and drain pipes resulting in a high resistance to the second shaft contacting the first shaft while it is subjected to cantilevered loads.

[0024] According to another aspect, a system provides a non-contact bearing for a shaft, hi this aspect, the system includes a housing having a first end and a second end located opposite the first end. In various embodiments, the housing includes an outer surface extending axially between the first end and the second end, an inner surface defining an opening that extends axially between the first end and the second end, a wall extending axially between the first end and the second end, a first passageway formed in the wall and providing a first fluid path between the inner surface and the outer surface and a second passageway formed in the wall and providing a second fluid path between the inner surface and the outer surface. According to these embodiments, the opening has a first longitudinal axis, the wall is defined by a region located between the inner surface and the outer surface of the housing, the first passageway is configured to couple to a fluid supply line and the second passageway is configured to couple to a fluid return line. In some embodiments, the housing is configured to receive a motor-driven shaft having a second longitudinal axis where the motor-driven shaft has a shape and an outside diameter sized such that a gap exists between the inner surface and the motor-driven shaft for 360 degrees about the motor-driven shaft with the motor-driven shaft concentrically located within the opening. At least one of the first passageway and the second passageway includes a flow choke, and a concentric positioning of the motor-driven shaft within the opening is maintained during a dynamic operation of the shaft, the concentric positioning achieved via a balance of forces provided by a flow of fluid received by the first passageway and returned by the second passageway.

[0025] According to another aspect, a system provides a non-contact bearing for a shaft, where the cross-sectional profile of the shaft has a triangular shape. According to various embodiments, one or more fluid flow nozzles supply fluid between the shaft and the housing. In some embodiments, a second triangular shaft is located co-axially within and surrounded by the first shaft. According to some embodiments, the fluid flow nozzles are flow limiting nozzles. In various embodiments, the nozzles include features that cause vortexes to occur in the fluid when flow rates exceed a design value. In some embodiments, the fluid is removed from the gap between the first and second shaft by a set of drains pipes which may optionally also include fluid flow nozzles. In furtherembodiments, the drain nozzles are flow limiting nozzles that can include features that cause vortexes to occur in the fluid when flow rates exceed a design value.

[0026] According to some embodiments several alternating sets of supply and drain nozzles and pipes are arranged in a radial direction along the perimeter of the first shaft or the second shaft. In embodiments, there are several rows of nozzles spaced along layers in a vertical direction along the primary axis of the first or second shaft. In various embodiments, the several rows and layers of nozzles are connected to the same or different fluids supplied to the gap between the first and the second shaft. In operation, these embodiments can maintain the gap between the first shaft and the second shaft very evenly. According to these embodiments, an offsetting force is established between the nozzle supply and the drain pipes resulting in a force that provides a high resistance to the second shaft contacting the first shaft when subject to cantilevered loads. In some further embodiments, the first shaft includes a plurality of magnets and an electrical coil that is in proximity to the second shaft. In these embodiments, the electrical coil can be energized with electrical power such that an electro-motive force acts on the plurality of magnets coupled to the first shaft. This provides a linear motor that can rapidly displace the first shaft in a controlled manner.

[0027] As used herein the term “fluid” refers to either compressed, dry air, or dry nitrogen, or any other suitable gas, or to a liquid such as Fomblin vacuum oil, or any other suitable oil or liquid.

[0028] In no way is the description of the applications intended to limit the disclosure to these applications. Many construction variations can be envisioned to combine the various elements mentioned above each with its own advantages and disadvantages. The present disclosure in no way is limited to a particular set or combination of such elements.BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figuresis represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

[0030] FIG. 1 illustrates a linear vacuum feedthrough using an air bearing technology according to the prior art.

[0031] FIG. 2 illustrates a linear and rotary vacuum feedthrough using an air bearing according to the prior art.

[0032] FIG. 3 depicts the pressure drop along the shaft of the linear and rotary vacuum feedthrough of FIG. 2 using an air bearing technology.

[0033] FIG. 4 illustrates a two-axis linear and rotary vacuum feedthrough according to the prior art.

[0034] FIG. 5 illustrates a three-axis vacuum feedthrough according to the prior art.

[0035] FIG. 6 illustrates a two-axis vacuum coupling according to the prior art.

[0036] FIG. 7 illustrates a four-axis vacuum feedthrough in accordance with an embodiment of the invention.

[0037] FIG. 8 illustrates a cross sectional view of the system of FIG. 7 in accordance with one embodiment.

[0038] FIG. 9 illustrates the system of FIG. 8 employed with a robotic arm in accordance with one embodiment.

[0039] FIGS. 10A-10F illustrates other robotic arms that can be mounted to the system of FIG. 8 in accordance with various embodiments.

[0040] FIGS. 11 A- 1 ID illustrate an embodiment of a substrate processing disk positioned in different orientations using a four-axis vacuum feed through system in accordance with one embodiment.

[0041] FIG. 12A illustrates the substrate processing disk of FIG. 11 with cooling fluid supplied to the processing disk in accordance with one embodiment.

[0042] FIG. 12B illustrates the substrate processing disk of FIG. 11 with cooling fluid supplied to the processing disk in accordance with an alternate embodiment.

[0043] FIG. 13 illustrates a four-axis vacuum feedthrough in an alternate embodiment including a secondary air-bearing.

[0044] FIG. 14 illustrates a four-axis vacuum feedthrough in an alternate embodiment in which connections to the air-bearing grooves are made through the secondary shaft.

[0045] FIG. 15 illustrates a four- axis vacuum feedthrough in an alternate embodiment including a separate air bearing section connected to the secondary shaft.

[0046] FIG. 16 illustrates a linear and rotary vacuum feedthrough system including a fluid flow limiting choke in accordance with one embodiment.

[0047] FIG. 17 illustrates a set of flow limiting nozzles according to one embodiment.

[0048] FIG. 18 illustrates a cross sectional view of the system of FIG. 16 showing one embodiment of a non-contact bearing.

[0049] FIGS. 19A and 19B illustrate operation of a non-contact bearing in accordance with one embodiment.

[0050] FIG. 20 illustrates a linear and rotary vacuum feedthrough system including a fluid flow limiting choke in accordance with another embodiment.

[0051] FIGS. 21 A and 2 IB illustrate operation of a non-contact bearing in accordance with one embodiment.

[0052] FIG. 22 illustrates a non-contact bearing in accordance with an embodiment having a triangular cross-sectional shape.

[0053] FIG. 23 illustrates a view of a non-contact bearing in accordance with an embodiment having a triangular cross-sectional shape in combination with a linear motor.DETAILED DESCRIPTION

[0054] Referring now to FIG. 7, a system 700 is illustrated including a non-contact vacuum seal in a rotary vacuum feedthrough configuration in accordance with various embodiments. In general, the system 700 operates to provide a vacuum seal for a plurality of shafts located concentrically relative to one another. Embodiments of the system 700 are configured to operate the shafts to deliver three or more axes of motion to a robotic arm located in a vacuum chamber. According to the illustrated embodiment, a primary (central) shaft 701 is outfitted with a number of grooves (labeled 71 IB through 715B). The central shaft 701 is located concentrically inside a secondary shaft 702. The gap 722 between the primary shaft 701 and secondary shaft 702 is very tightly controlled and ranges from 10 to 20 pm with an accuracy of less than 1 pm. Applying a pressurized fluid for example compressed air in one or more of the grooves 721 (for example in groove 712B) results in a very tight, non-contact fluid layer between the primary shaft 701 and the secondary shaft 702. Vent grooves can be provided such as grooves 71 IB and 713B. Additional grooves 714B and 715B can provide for differential pumping of the gap between the primary shaft 701 and secondary shaft 702 allowing high vacuum724 to be maintained in the region above the shafts separate from the atmospheric region725 below the assembly 700.

[0055] The secondary shaft 702 is in turn concentrically located in a housing 703. The housing 703 is outfitted with a set of grooves 720, labeled 711 A through 715 A in the figure). By applying a pressurized fluid, for example compressed air in one or more of the grooves (for example in groove 712A) again results in a very tight, non-contact fluid layer between the shaft 702 and the housing 703. The gap 723 between the shaft 702 and housing 703 is very tightly controlled and ranges from 10 to 20 pm with an accuracy of less than 1 pm. Vent grooves can be provided such as grooves 711A and 713A. Additional grooves 714A and 715 A can provide for differentia] pumping of the gap between the central shaft 702 and the housing 703 allowing high vacuum 724 to be maintained in the region above the shaft separate from the atmospheric region 725 below the assembly 700.

[0056] Housing 703 is in turn mounted in the bottom of a vacuum chamber 710, of which only a small portion is shown and is sealed to the chamber 710 by means of a static seal 726. The central shaft 701 will typically have a mounting surface 708 in the vacuum area 724, where fasteners can be located to mount a mechanical system such as a robotic arm segment. Similarly, the secondary shaft 702 will have a mounting surface 706 in vacuum 724, where fasteners can be located to mount a different mechanical system. By selecting the diameter of the shafts 701 and 702, and the weight of the mechanical systems connected to these shafts appropriately, the forces from gravity and the vacuum system can be approximately balanced as indicated in the figure in 705 and 707. This structure will allow for almost frictionless motion in four independent directions as indicated by 709 in the figure. By connecting shaft 701 to a linear motor 719 and a rotational motor 718, and connecting shaft 702 to a linear motor 717 and a rotational motor 716, 4 independent axis of motion can be delivered into the vacuum system. Motors are not shown in the figure. According to other embodiments, an actuator system for imparting motion to the shafts 701 and 702 does not include motors. For example, such a system can include other electrically operated elements (for example, solenoids), pneumatic or hydraulic elements. According to a further embodiment, an actuator system for imparting motion to the shafts 701 and 702 includes motors with different actuator elements such as different electrically operated elements, hydraulic elements or other elements.

[0057] FIG. 8 illustrates a cross sectional view of the shaft system of FIG. 7 wherein the cross section also shows how the vacuum and fluid supplies for grooves 720 and 721 are routed through the shafts and how rotational motors can be mounted to the shafts. For example, fluid supply port 712A is cross drilled and closed by plugs 805 to the fluidsupply line 809. Similarly, there are connections for the inner shaft 701 through line 806 for venting, and for lines 807 and 808 for pumping into for example groove 813. Line 811 included in the housing 703 provides vacuum to the groove 812. Groove 810 provides a location for a static seal 726 as was shown in FIG. 7.

[0058] Also shown in the figure are motors 803 and 804, which can impart rotational motion for the shafts 701 and 702 respectively. Motors 803 and 804 are also outfitted with high resolution position encoders 801 and 802. As can be seen in the figure, all motor, bearing and encoder components can be mounted outside of the vacuum environment.

[0059] FIG. 9 illustrates the cross-sectional drive system of FIG. 8, coupled to a Selectively Compliant Articulated Robot Arm (SCARA) 900, in this example, a single end effector 907 for supporting a substrate is connectively coupled to the SCARA arm which is able to move radially, tangentially and vertically. Underarm 901 is mechanically affixed to flange 706 from FIG. 7, and pully 902 is mechanically affixed to shaft 701. Belt 903, which can be a flat, metal belt or a timing belt with teeth, or a wire, or any convenient, flexible connection, transmits motion to double pully 905, which in turn connects to belt 906 located inside upper arm 904. The distal end 908 of upper arm 904 also contains a pully (not shown) and is connected to end effector 907. There are many other arrangements of pulleys and linkages known in the art and many of these can be made to work with the present vacuum seal drive system from FIG. 7. Motor 804 is fixedly connected to shaft 702, and will extend the SCARA arm radially when motor 803, which is fixedly connected to shaft 701, is counter-rotated at the same time. When both motor 803 and 804 are rotated in the same direction, the SCARA arm will rotate about the central axis in its entirety. By adding a vertical, linear axis (not shown) as discussed earlier, the entirety of the SCARA arm and shaft assembly can be moved up or down in the vertical direction thereby allowing the SCARA arm to move up or down as the case may be.

[0060] FIG. 10 illustrates various embodiments of planar SCARA style arms as are known in the art. FIG 10A illustrates the SCARA arm from FIG. 900 for comparison. FIG. 10B illustrates a SCARA arm with an additional linkage 1004. Motor 1 is coupled to a linkage 1001, and motor 2 is coupled to a pully 1002, and belt 1003. The belt 1003 transmits motion to a double pulley 1005 which has a second belt 1006 connected to it. Belt 1006 resides in a linkage 1004, and connects to another double pulley 1009, which in turn connects to a third belt 1010, located in a third linkage 1008. Belt 1010 connects to afinal pully 1011, which is fixedly connected to double end effector 1007, which is meant to support one or two substrates simultaneously, such as by way of example, semiconductor wafers and the like.

[0061] FIG. 10C has a similar structure as FIG. 10 A and 10B, however the motor connection of motor 1 is made in the middle of linkage 1021. Pulley 1020 is connected to motor 2 and contains belts 1022 and 1028, which can also be a single belt. Belt 1022 connects to double pulley 1025 which is also connected to a belt 1024 in linkage 1023. Belt 1024 connects to pulley 1027, which in turn connects to end effector 1026. Similarly belt 1028 connects to double pulley 1031, which also connects to belt 1030 in linkage 1029. Belt 1030 connects to pulley 1032, which is fixedly connected to end effector 1033. By rotating motor 1 and 2 in opposite directions, end effector 1033 will extend radially and end effector 1026 will retract radially. This allows a substrate on end effector 1033 to be extended into, for example, a processing station.

[0062] FIG. 10D illustrates an alternative embodiment known in the art as a “frogleg” robotic arm. Linkage 1040 is fixedly connected to shaft 702 and motor 1 (not shown), whereas linkage 1041 is fixedly connected to shaft 701 and motor 2 (not shown). Secondary linkages 1044 and 1045 are connected through a double bearing pivot 1042 and 1043, respectively. Linkages 1044 and 1045 are respectively also connected to pivots 1047 and 1048. Pivots 1047 and 1048 are fixedly connected to end effector 1046, and are also coupled through a small belt 1049 as described by Hendrickson (US 5,180,276), which can also be a pair of meshing gears, as described for example by Hardegen et. al (US 4,909,701).

[0063] FIG. 10E shows a “dual frogleg” arm as known in the art as described by Hendrickson (US 5,180,276), essentially by adding a second “frogleg” arm on the pivot points 1042 and 1043 from FIG. 10D. Linkages 1050 and 1051 are connected to motors 1 and 2 respectively. Pivot points 1052 and 1053 connect additional linkages 1054, 1056, 1055 and 1057. As in FIG. 10D, the distal ends of these linkages are connected to pivot points 1058, 1059, 1062 and 1063 respectively. Small belts 1064, which can also be gears as in FIG. 10D, ensure that the pivot points 1058, 1059, 1062 and 1063 are connected and ensure that end effectors 1060 and 1061 stay fixed in a radial orientation.

[0064] FIG. 10F shows an alternative concept for a “same side dual frogleg” arm wherein the lower members of the first arm are extended beyond the center, thereby forming an “X” pattern and the second arm is flipped over so that both end effectors 1082 and 1083 face in the same direction (a “same side” arm, for example, Hosek et. al. US 7,245,989).Lower arm members 1070 and 1071 are connected to motor 2 and motor 1 respectively (motors are not shown). Pivot points 1074 and 1075 connect to a first set of upper arms 1072 and 1073, whereas pivot points 1076 and 1077 connect to a second set of upper arms 1078 and 1079. Arm members 1072 and 1073 connect to pivot points 1084 and 1085, which are fixedly connected to end effector 1083, and to each other by means of a small belt or gear 1086. Likewise, arm members 1078 and 1079 are connected to end effector 1082 through pivot points 1080 and 1081, and to each other by means of a small belt or gear 1086.

[0065] FIGS. 11A - 1 ID illustrate an application of another embodiment of a 4-axis vacuum seal for providing motion to a substrate holder, such as during processing of substrates in a vacuum system, e.g. during Ion Implantation of semiconductor wafers, a process common in Semiconductor Manufacturing. FIG. HA shows in a simplified way, how rotation of shaft 1101 (which corresponds with shaft 701 in FIG. 7), can impart rotational motion 1105 to substrate holder 1103, and substrates 1104. Secondary shaft 1102 (which corresponds to shaft 702 in FIG. 700) is kept stationary with regards to the housing 1109 (which corresponds to housing 703 in FIG. 7). FIG. 1 IB illustrates how movement of shaft 1101 in a vertical direction 1106, can be used to tilt the substrate holder 1103 and substrates 1104 backwards about a horizontal axis, thereby changing the incident angle of substrate processing, such as for example is used during Ion Implantation, a common process step in Semiconductor Manufacturing. FIG. 11C, illustrates how simultaneous rotation 1107 of both shaft 1 101 and shaft 1102 results in exposure of the substrate holder 1103 and substrates 1104 about a vertical angle. FIG.1 ID shows how simultaneous movement in a vertical direction 1108 results in a vertical movement of substate holder 1103 and substrates 1104.

[0066] In Ion Implantation, a process commonly used in Semiconductor Manufacturing, the energy from the impacting Ions onto the substrate holder 1103 and substrates 1104, often is high, resulting in undesirably high substrate temperatures. FIGS. 12A and 12B illustrate two means of providing a cooling fluid to the substrate holder 1104. In FIG. 12A, shaft 1101 (which is similar to shaft 701 in FIG. 7) and secondary shaft 1102 (similar to 702 in FIG. 7) are located in the housing 1109 (which is similar to 703 in FIG. 7). Shaft 1101 is outfitted with liquid coolant supply channel 1201 and coolant drain channel 1202. Ion beam 1204 impacts on the substrate support 1103 and substrates 1104 and the heat energy thus generated is removed by the liquid coolant, while still allowing for 4 axes rotational and vertical motion 1203 about horizontal and vertical axis. FIG.12B illustrates an embodiment, in which the coolant supply channel 1205 is provided in the secondary shaft 1102, rather than in the primary shaft 1101. Likewise, the coolant removal channel 1206 is also provided in the secondary shaft 1102. As before, this arrangement will also still allow for 4 axes of motion 1203 in the vacuum system.

[0067] FIG. 13 illustrates another embodiment of the multi-axes non-contact vacuum seal in a rotary vacuum feedthrough configuration. Because it is often desirable to provide an infinite rotation of the primary shaft 701 and the secondary shaft 702, the vacuum ports 714A and 715A have no problem accommodating such infinite rotation. However, vacuum ports 714B and 715B need to be connected to pump 1 and pump 2, through some means of a rotational coupling. Conventional rotational couplings such as those made with O-rings or lip seals, could be employed, but they exhibit significant friction, resulting in the need to employ larger motors. By adding an additional collar 1301 on the shaft 701 , which can be fixedly located, and by adding an additional set of elongated grooves 1302, and by connecting pumping grooves 714B and 715B, and pressurized fluid groove 712B to the elongated grooves 1302, pressurized fluid port 1303, and pump ports 1304 and 1305 can be connected, thereby allowing for infinite, frictionless rotation of shaft 701 . Vertical travel of shaft 701 will be limited to the height of the elongated grooves 1302. A provision for liquid coolant can still be provided through the center of the primary shaft 701 (not shown) or on the secondary shaft 702 as shown in the figure by pipe 1306. As before in figure 700, motors 1 and 2 (1307) can be connected to shaft 702, and motors 3 and 4 (1308) can be connected to shaft 701. Lastly, the fluid such as air coming from the vent groove 721, can simply be vented in a location 1309 along the shaft 701.

[0068] FIG. 14 illustrates another embodiment of the multi-axes non-contact vacuum seal in a rotary vacuum feedthrough configuration. According to this embodiment, the groove sets 1408, 1409, 1410, 1411 and 1412, are located on secondary shaft 1402, thereby eliminating the need for grooves on housing 1403 or primary shaft 1401. In some embodiments, motors 1 and 2 (1406) are used for rotational and translational motion of shaft 1402 and motors 3 and 4 (1407) are used for rotational and translational motion of shaft 1401. Optional liquid coolant pipes 1404 and 1405 can also be provided if needed. Ports 1413 can be drilled to connect the sets of grooves to the atmospheric side of the seal assembly.

[0069] FIG. 15 illustrates still another embodiment of the multi-axes non-contact vacuum seal in a rotary vacuum feedthrough configuration. By adding an extension 1501 to theshaft 1402 and a second collar 1502, outfitted with wider grooves 1503, the rotational limitation caused by the pump connections, can again be circumvented. Extending pump lines 1504 as shown in the figure allows for an infinite rotation, whilst the vertical motion is limited by the height of the grooves 1503. Motors 1 and 2 (1506) on shaft 701 provide for rotation and translation, while motors 3 and 4 (1505) provide for rotation and translation of shaft 1402.

[0070] FIG. 16 illustrates a system 1600 including a non-contact vacuum seal with a plurality of flow chokes 1606, 1607, 1608 in a rotary vacuum feedthrough configuration in accordance with one embodiment. According to the illustrated embodiment, the system 1600 corresponds to the system illustrated in FIG. 2 but with the addition of the flow chokes to provide previously unrealized advantages identified by the Applicant. In general, the addition of the flow chokes 1606, 1607 and 1608 to the supplied fluid or to the removed fluid, provides for an accurate control the flow of the fluid. According to some embodiments, the flow chokes 1607, 1608 are optional and only a single flow choke1606 is required. The flow chokes 1606, 1607 and 1608 operate at low flow rates to provide a flow of the fluid that is primarily laminar and increases linearly with fluid pressure. However, at higher fluid pressures the flow chokes 1606, 1607 and 1608 automatically limit the fluid flow rate by creating vortexes in the respective fluid channel that limit the flow.

[0071] In FIG. 2, the fluid was indicated to be compressed air and the like but previously unrealized advantages are found where the fluid is a high vacuum oil (i.e. an oil with a low vapor pressure in a vacuum environment such as Fomblin® PFPE Eubricants manufactured by Solvay S.A.). With appropriate sizing of the shaft 201 diameter, the grooves and the flow choke 1606, and optional flow chokes and grooves 1607 and 1608, it is possible to widen the gap between the shaft 201 and the housing 202, making the manufacturing of such shafts less critical. For example, according to some embodiments, the gap 204 between the shaft 201 and the bezel housing 202 may be increased above 30pm. Furthermore, where compressed air is replaced, for example, by a high vacuum oil, the viscosity of the oil will also play a role in determining: a) the dimensions of the gap 204; b) the diameter of the grooves; and c) the dimensions of the flow chokes (1606,1607 and 1608). In these embodiments, an oil film 1608 will be created which provides radial support for shaft 201. The oil that is returned though the oil return grooves and chokes assembly can be recovered and resupplied (indicated by lines 1604 and 1605) to the oil supply groove and choke 1606.

[0072] Increasing a dimension of the gap 204, results in significantly reduced manufacturing costs, since tolerances can be reduced as well. However, if the supply fluid is air, uneven pressures and hence leakage may occur if the gap 204 becomes uneven. By adding flow chokes 1606 and optional chokes 1607 and 1608, and by switching to a higher viscosity fluid such as Fomblin oil, and dimensioning the shaft and grooves properly, an even flow of the fluid is assured. The flow choke 1606 limits the amount of fluid that is delivered to the gap 204. The flow choke 1606 can be designed to handle any fluid by properly dimensioning the size and shape of the nozzle. It is also possible to implement a flow choke 1607 or 1608 on the return channel of the fluid. For example, if the fluid is compressed air, the nozzles 1607 or 1608 can be connected to a vacuum pump. As discussed earlier, when the shaft is moved in a vertical direction, some of the fluid will be dragged along the shaft 201, and excess fluid is removed in the upper groove 1603 or lower groove 1607. Pumping grooves 210 and 211 allow for differential pressure drop in gap 204 along the shaft 201. However, switching to a fluid like Fomblin oil, reduces or eliminates the necessity for grooves 210 and 211, thereby reducing the complexity of the seal 1600 even further. In such a system where grooves 210 and 211 are eliminated, the vertical speed of motion of the shaft 201, should be controlled to limit the vertical speed so that is the oil or fluid that is dragged along the shaft can be removed by the grooves 1607 and 1608 in a timely fashion.

[0073] FIG. 17 illustrates how a set of flow channels 1788 can be implemented, for example, with a first flow channel 1708 of the pair receiving a fluid 1701 that can be a compressed air or other convenient fluid. The second flow channel 1709 is pumped, for example, by a vacuum pump where any remaining fluid 1711 is removed by the pump (not shown). In the supply channel 1708, the entering fluid 1701 is forced over a series of structures 1702, that alter the direction of the flow 1703. These can be referred to as fluid chokes. Some of the features 1702 divert the flow in such a way that the flow creates vortexes 1704 and 1705, which pinch-off the fluid flow, thereby reducing the flow rate 1706 at the exit of the flow channel. Any increase in the supply pressure of the entering fluid 1701, will not result in an increase in the flow 1706 at the exit of the channel.

[0074] In the illustrated embodiment, a substrate or other surface 1707 diverts some of the fluid flow in such a way that the fluid is partially directed towards an exit channel 1710, which can be a straight channel 1708 or can exhibit similar structures 1702 as the supply channel. If the distance between the substrate 1707 and the exit 1706 of the supply channel increases, the flow exiting the supply channel 1706 will not increasebecause the flow is limited by the vortexes, however, the flow 1711 through the exit channel will increase because the exit flow is not limited by vortexes. This increase in flow will reduce in a pressure drop between the substrate 1707 and the exit channel 1710, forcing the substrate back towards the exit channel 1710. As a result, the force moving the substrate 1707 away from the flow exit 1706 is counteracted by the increase pulling force at the exit channel 1710 resulting in a balance of forces if flow rates and dimensions of the features 1702 and channel diameters are sized properly.

[0075] FIG. 18 illustrates a cross-sectional view of an embodiment having multiple sets of flow channels 1888 located at an axial location along a longitudinal axis 1891 of a housing 1889 for 360 degrees about the axis 1891. The flow channels 1888 are similar in construction to, for example, flow channels 1788 as illustrated in FIG. 17. According to the illustrated embodiment, they are presented as a cross sectional view of the flow channels 1606 shown in FIG. 16. According to some embodiments, this configuration provides a system in which the shaft 201 is automatically centered within a hollow central region 1890 of the housing 1889. That is, the shaft 201 self-centers to maintain a substantially uniform gap 204 between the shaft 201 and the housing 1889 even during the dynamic operation of the shaft (for example, rotation of the shaft 201 within the housing 1889). Each pair of channels 1888 provides a force balancing feature, and by placing multiple sets of flow channels 1888 around the perimeter of the shaft 201, the shaft is kept centered within the gap 204. This dynamic adjustment is achieved with a push-pull of counteracting forces that is balanced for 360 degrees about the longitudinal axis of the hollow cylindrical tube formed within the housing 1889 and within which the shaft 201 is located. According to these embodiments, by including flow chokes the force moving the shaft 201 away any of the flow exits is counteracted by the increase pulling force at the exit channel resulting in a balance of forces if flow rates and dimensions of the choke features and channel diameters are sized properly.

[0076] In addition, multiple sets of nozzles can be placed at different locations along the longitudinal axis of the housing 1889. That is, the sets are located co-planar to crosssection 18-18. With multiple sets of flow channels, these embodiments can increase the stiffness of the support for the shaft 201, thereby better supporting cantilevered loads such as the various robotic arms illustrated in FIG. 10.

[0077] While the flow channels 1888 as illustrated in FIG. 18 only include a flow choke on the fluid supply flow channel, the flow chokes can be distributed differently in other embodiments to achieve the same automatic self-centering of the shaft 201 within thehollow central region 1890. In one embodiment, flow chokes are included in both the fluid supply channels and the fluid return channels. According to another embodiment, flow chokes are included in the fluid return channels and are not included in the fluid supply channels.

[0078] Referring now to FIGS. 19A and 19B, operation of a system 1900 including a self-centering non-contact bearing for a shaft 1901 including flow chokes is illustrated in accordance with one embodiment. The illustration includes an inner surface 1992 formed by a wall defined within a housing. The complete outer wall of the housing is not shown in FIGS. 19A and 19B. Applicant notes that the shape and overall profile of the outer surface of the wall of the housing in any of the embodiments described herein can vary and need not be curved, round or cylindrical. The shaft 1901 is positioned longitudinally within the opening. A gap 1904 exists between the shaft 1901 and the inner surface 1992. The system 1900 includes two pairs of fluid connections including a first fluid supply 1994A and an associated first fluid return 1995 A, and a second fluid supply 1994B and an associated second fluid return 1995B. According to the illustrated embodiment, fluid choke A is included in the first fluid supply line and fluid choke B is included in the second fluid supply line. Fluid pump A is connected to the first fluid return line and fluid pump B is connected to the second fluid return line. FIG. 19B includes a pair of arrows showing the relative direction and amount of force found in Region A and Region B. The solid left facing arrow illustrates a relative direction and amount of force found in Region A. The solid right facing arrow illustrates a relative direction and amount of force found in Region B. The resulting relative direction and amount of net force is illustrated by the arrow drawn in phantom, facing to the right.

[0079] In FIG. 19 A, the gap 1904 is even all the way around the shaft 1901. A typical gap design is around 30um (and generally within a 10-100um range). The dimensions of the gap 1901 can be the same for air as for oils. However, the choke and pump line diameters are sized differently depending on the pressures and viscosities of the fluids involved. In addition, the dimensions of the undulating features and / or irregular surface shapes in the flow choke will be different depending on the pressure and viscosity of the selected fluid. As illustrated in FIG. 19B, the gap 1904 is un-even because the shaft 1901 is not centered within the opening in the housing defined by the inner surface 1992. In region A, there is a high flow-resistance from Choke A to Pump A where the gap is narrow. In region B there is a low flow-resistance from Choke B to Pump B where the gap is wider. Pump A does not remove a lot of fluid from the narrow gap. In contrast,Pump B removes more fluid because Choke B does not allow an increase in fluid flow into the gap. As a result, Region B has a lower pressure, which creates a net force on the shaft towards region B. The net force acts as a self-centering force that re-positions the shaft concentrically within the opening as illustrated in FIG. 19B should other dynamic forces temporarily move the shaft from a central location in the opening.

[0080] Referring to FIG. 20, a system 2000 including a non-contact vacuum seal with a plurality of flow chokes in a rotary vacuum feedthrough configuration is illustrated in accordance with one embodiment. According to the illustrated embodiment, the system 2000 corresponds to the system illustrated in FIG. 16 but with the addition of a second oil supply line and the use of the flow chokes in both oil supply lines. According to this embodiment, the system 2000 includes a first oil supply line 2096A and a first oil return line 2097 A. The system also includes a second oil supply line 2096B and a second oil return line 2097B. A first choke 2098 A is included in the first oil supply line 2096A and a second choke 2098B is included in the second oil supply line 2096B. In general, this embodiment demonstrates a system that operates to automatically vertically -plumb a shaft should dynamic forces during operation temporarily move the shaft out of plumb.

[0081] Referring now to FIGS. 21 A and 2 IB, a simplified view of a system such as the system 2000 illustrated in FIG. 20 is shown in a vertical cross-sectional view. In FIG. 21A the shaft is vertically balanced (i.e., “plumb”). In this vertical cross-section, the gap 2104 is un-even between the two rings of choke / pump line features. In region A, the left to right gap is about the same, resulting in little to no force, but in region B the gap on the left is much larger, resulting in a force that is causing the shaft to righten itself. This configuration is effective to maintain a shaft that is vertically plumb even when the shaft must support cantilevered loads in dynamic operations for example those that can occur with the robot arm configurations illustrated in FIG. 9 and 10. That is, using two pump / choke rings, not only centers the shaft but also prevents the shaft from tilting under cantilevered loads. In addition, these embodiments also maintain a shaft in a vertically plumb orientation even when the shaft is supporting a cantilevered load that is static. In these embodiments, the righting force provides resistance to keep the shaft plumb under static loads that remain off center for an extended period. Applicant notes that this differs from prior systems because prior systems do not provide resistance to being off-center under a static cantilevered load. The system of FIG. 1 illustrates one example that does not provide a righting force for a static cantilevered load in a manner that is typical of prior systems.

[0082] While the embodiments including flow chokes illustrated and described with reference to FIGS. 16 and 20, include a vacuum feedthrough, the construction and arrangement of the flow chokes illustrated and described with reference to any of FIGS. 16-21 can be employed in operating environments that solely include atmospheric pressure. In these embodiments, the shaft 201 is employed to provide motion to systems that operate at atmospheric pressure.

[0083] Further, while the embodiments including flow chokes of FIGS. 16 — 21 are illustrated and described with reference to a housing that receives a cylindrical shaft in cylindrical opening these embodiments are not limited to use with shafts having a cross- sectional profile that is round. Instead, in various embodiments, the shaft can include a cross-sectional profile with a different shape including an elliptical cross-sectional shape and a quadrangle cross-sectional shape as two examples. It will be apparent to those of ordinary skill in the art based on the disclosure herein that these alternate embodiments can operate in a self-centering manner during dynamic operation of the shaft in applications where the shaft moves axially but does not rotate.

[0084] Referring now to FIG. 22, a shaft having a cross-sectional profile that is a triangular shape is illustrated in combination with flow chokes. These embodiments provide a triangular seal. FIG. 22 illustrates a triangular shaft 2201, a triangular housing 2202 and a combination flow chokes and pump channels 2203. A gap 2204 exists in the space between the shaft 2201 and the housing 2202. According to the illustrated embodiment, the flow chokes and fluid pump channels 2203 are fluidly coupled to a fluid pump and operate similarly to flow choke 1606 and pump channel 210 in FIG. 16. For example, the triangular cross section seal can support linear motion like the embodiment illustrated in FIG. 16. However, unlike the embodiment of FIG. 16, the triangular shaft 2201 is rotationally fixed. This can be advantageous in applications where only a linear motion is needed, and shaft rotation is undesirable. By employing fluid flow chokes and pump channels 2203, like flow choke 1606 and pump channel 210 in FIG. 16, a centering action can be obtained that counteracts any rotation, while allowing for smooth linear motion.

[0085] Referring now to FIG. 23, the triangular shaft 2201 is outfitted with a drive coil 2205 and a plurality of magnets 2206 that provide a linear motor. According to the illustrated embodiment, the plurality of magnets 2206 are located centrally within the triangular shaft 2201. The magnets are arranged such that an orientation of the north and south poles of any one magnet are positioned opposite an orientation of the poles of theimmediately adjacent magnet(s). This locates the north poles adjacent south poles in the plurality of magnets 2206. In operation, the drive coil 2205 is energized with a source of electrical power to move the shaft 2301 in an axial direction via electromagnetic action. In the illustrated embodiment, the seal and centering action provide with use of a fluid pump supports the shaft in a contactless bearing arrangement while the motor provides the drive force for axial motion. A light shaft in this linear-motor arrangement can operate very quickly when driven by the motor. This very rapid linear shaft motion (displacement) can be advantageous in applications where a high-speed operation is desired. According to various embodiments, other different types of motor- arrangements can be employed, for example, any of voice-coil motors, piezo motors, pneumatic actuators can be employed in some embodiments.

[0086] Having thus described several illustrative embodiments, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to form a part of this disclosure, and are intended to be within the spirit and scope of this disclosure.While some examples presented herein involve specific combinations of functions or structural elements, it should be understood that those functions and elements may be combined in other ways according to the present disclosure to accomplish the same or different objectives. In particular, acts, elements, and features discussed in connection with one embodiment are not intended to be excluded from similar or other roles in other embodiments. Additionally, elements and components described herein may be further divided into additional components or joined together to form fewer components for performing the same functions. Accordingly, the foregoing description and attached drawings are by way of example only and are not intended to be limiting.

Claims

WHAT IS CLAIMED IS:

1. An apparatus comprising: a housing having a first end configured to couple to a vacuum chamber and a second end located opposite the first end, the housing including a hollow cylindrical tube extending axially from the first end to the second end, the hollow cylindrical tube defined by a cylindrical wall formed within the housing; a plurality of shafts located concentrically relative to one another and the cylindrical wall within the housing, the plurality of shafts including at least a primary shaft having a first longitudinal axis and a secondary shaft having a second longitudinal axis, the primary shaft located concentrically within the secondary shaft with the first longitudinal axis and the second longitudinal axis co-located at a common longitudinal axis of the plurality of shafts; a first actuator system coupled to the primary shaft, the first actuator system configured to move the primary shaft both rotationally about the common longitudinal axis and linearly along the common longitudinal axis; a second actuator system coupled to the secondary shaft, the second actuator system configured to move the secondary shaft in at least one of rotationally about the common longitudinal axis and linearly along the common longitudinal axis; a first set of passageways formed in at least one of the primary shaft and the secondary shaft, the first set of passageways configured to couple to at least one of a source of pressurized fluid, at least one fluid relief line and at least one source of vacuum pumping, the first set of passageways fluidically coupled to a first cylindrical region separating the primary shaft from the secondary shaft with the primary shaft located concentrically within the secondary shaft; and a second set of passageways formed in at least one of the primary shaft, the secondary shaft and the housing, the second set of passageways configured to couple to at least one of a source of pressurized fluid, at least one fluid relief line and at least one source of vacuum pumping, the second set of passageways fluidically coupled to a second cylindrical region separating the secondary shaft from the cylindrical wall with the secondary shaft located within the hollow cylindrical tube.

2. The apparatus of claim 1 , wherein the primary shaft includes a solid outer surface,wherein the first set of passageways includes a first set of grooves formed in the solid outer surface, and wherein the second set of passageways includes a second set of grooves formed in the cylindrical wall of the housing.

3. The apparatus of claim 1, wherein the secondary shaft includes a hollow central tube in which the primary shaft is located, the hollow central tube defined by a first solid outer surface extending axially for 360 degrees about the second longitudinal axis within the secondary shaft, wherein the secondary shaft includes a second solid outer surface that defines a radially outward exterior surface of the secondary shaft, the second solid outer surface extending axially for 360 degrees about the second longitudinal axis, wherein the first set of passageways includes a first set of grooves formed in the first solid outer surface, and wherein the second set of passageways includes a second set of grooves formed in the second solid outer surface.

4. The apparatus of claim 1, wherein the primary shaft includes a first solid outer surface extending axially for 360 degrees about the first longitudinal axis, wherein the secondary shaft includes a second solid outer surface that defines a radially outward exterior surface of the secondary shaft, the second solid outer surface extending axially for 360 degrees about the second longitudinal axis, wherein the first set of passageways includes a first set of grooves formed in the first solid outer surface, and wherein the second set of passageways includes a second set of grooves formed in the second solid outer surface.

5. The apparatus of claim 3, wherein the central hollow tube includes a first end and a second end, and wherein with the housing coupled to the vacuum chamber and the secondary shaft positioned within the housing, the first end of the central hollow tube is positioned at a first location that is under vacuum and the second end of the central hollow tube is positioned at a second location that is at atmospheric pressure.

6. The apparatus of claim 1 , wherein the first actuator system includes a first motor coupled to the primary shaft, the first motor configured to move the primary shaft rotationally about the common longitudinal axis, wherein the first actuator system includes a second motor coupled to the primary shaft , the second motor configured to move the primary shaft linearly along the common longitudinal axis; wherein the second actuator system includes a third motor coupled to the secondary shaft, the third motor configured to move the secondary shaft rotationally about the common longitudinal axis, and wherein the second actuator system includes a fourth motor coupled to the secondary shaft, the fourth motor configured to move the secondary shaft linearly along the common longitudinal axis.

7. The apparatus of claim 1, wherein the primary shaft includes a hollow central region configured to receive a plurality of lines including at least one of a line configured to couple to a source of pressurized fluid, a fluid relief line and a line coupled to a source of vacuum pumping.

8. The apparatus of claim 1, further comprising a collar having an upper end and a lower end, the collar including fluid passages configured to couple to the at least one source of pressurized fluid and the source of vacuum pumping, wherein the hollow cylindrical tube is a first hollow cylindrical tube, wherein the collar includes a second hollow cylindrical tube extending axially from the upper end to the lower end, the second hollow cylindrical tube defined by a cylindrical wall formed within the collar, a third set of passageways formed within the cylindrical wall formed within the collar, and wherein the collar is configured to fluidly couple the at least one source of pressurized fluid and the source of vacuum pumping to corresponding process lines located within the hollow central region of the primary shaft via the third set of passageways.

9. The apparatus of claim 1 , wherein a first gap exists between the primary shaft and the secondary shaft, the first gap having a first width,wherein a second gap exists between the secondary shaft and the cylindrical wall, the second gap having a second width, wherein a dimension of the first width is in a range of no less than five micrometers and no greater than 100 micrometers, and wherein a dimension of the second width is in a range of no less than five micrometers and no greater than 100 micrometers.

10. A system providing a non-contact bearing for a shaft, the system comprising: a housing having a first end and a second end located opposite the first end, the housing including, an outer surface extending axially between the first end and the second end; an inner surface defining an opening that extends axially between the first end and the second end, the opening having a first longitudinal axis; a wall extending axially between the first end and the second end, the wall defined by a region located between the inner surface and the outer surface of the housing; a first passageway formed in the wall and providing a first fluid path between the inner surface and the outer surface, the first passageway configured to couple to a fluid supply line; and a second passageway formed in the wall and providing a second fluid path between the inner surface and the outer surface, the second passageway configured to couple to a fluid return line, wherein the housing is configured to receive a motor-driven shaft having a second longitudinal axis, the motor-driven shaft having a shape and an outside diameter sized such that a gap exists between the inner surface and the motor-driven shaft for 360 degrees about the motor-driven shaft with the motor-driven shaft concentrically located within the opening, wherein at least one of the first passageway and the second passageway includes a flow choke, and wherein a concentric positioning of the motor-driven shaft within the opening is maintained during a dynamic operation of the motor-driven shaft, the concentric positioning achieved via a balance of forces provided by a flow of fluid received by the first passageway and returned by the second passageway.

11. The system of claim 10, wherein the opening is a cylindrical shaped opening that extends axially between the first end of the housing and the second end of the housing, the cylindrical shaped opening configured to receive the motor-driven shaft having a round cross-sectional profile.

12. The system of claim 10, wherein the first end of the housing is configured to couple to a vacuum chamber, and wherein the housing includes a third passageway formed in the wall, the third passageway providing a third fluid path between the inner surface and the outer surface, the third passageway configured to couple to a source of vacuum pumping.

13. The system of claim 12, wherein the housing includes a first set of grooves formed in the inner surface for 360 degrees about the first longitudinal axis, the first set of grooves coupled to the third passageway.

14. The system of claim 10, wherein an axial distance separating the second passageway from the third passageway is greater than a maximum axial travel of the motor-driven shaft during the dynamic operation.

15. The system of claim 10, further comprising a linear motor configured to displace the motor-driven shaft, the linear motor including an electrical coil and a plurality of magnets, wherein the electrical coil is located proximate the housing, and wherein the plurality of magnets are positioned within the motor-driven shaft.

16. The system of claim 15, wherein the opening is a triangle shaped opening that extends axially between the first end of the housing and the second end of the housing, the triangular shaped opening configured to receive the motor-driven shaft having a triangular cross-sectional profile

Images