CN110859042A - Distance sensor for measuring a distance to a ferromagnetic element, magnetic levitation system and method for measuring a distance to a ferromagnetic element - Google Patents

Distance sensor for measuring a distance to a ferromagnetic element, magnetic levitation system and method for measuring a distance to a ferromagnetic element Download PDF

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CN110859042A
CN110859042A CN201880030816.5A CN201880030816A CN110859042A CN 110859042 A CN110859042 A CN 110859042A CN 201880030816 A CN201880030816 A CN 201880030816A CN 110859042 A CN110859042 A CN 110859042A
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distance sensor
distance
magnetic
hall element
magnetic field
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克里斯蒂安·沃尔夫冈·埃曼
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Applied Materials Inc
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Applied Materials Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67242—Apparatus for monitoring, sorting or marking
    • H01L21/67259—Position monitoring, e.g. misposition detection or presence detection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/003—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring position, not involving coordinate determination
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
    • G01B7/023—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring distance between sensor and object
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67242—Apparatus for monitoring, sorting or marking
    • H01L21/67253—Process monitoring, e.g. flow or thickness monitoring
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/677—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations
    • H01L21/67703—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations between different workstations
    • H01L21/67709—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations between different workstations using magnetic elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/677—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations
    • H01L21/67703—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations between different workstations
    • H01L21/67712—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations between different workstations the substrate being handled substantially vertically
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/677—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations
    • H01L21/67703—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations between different workstations
    • H01L21/6773—Conveying cassettes, containers or carriers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/677—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations
    • H01L21/67739—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations into and out of processing chamber
    • H01L21/67751—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for conveying, e.g. between different workstations into and out of processing chamber vertical transfer of a single workpiece
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G54/00—Non-mechanical conveyors not otherwise provided for
    • B65G54/02—Non-mechanical conveyors not otherwise provided for electrostatic, electric, or magnetic
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
    • G01D5/147—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Container, Conveyance, Adherence, Positioning, Of Wafer (AREA)

Abstract

The present disclosure relates to a distance sensor for measuring a distance to a ferromagnetic element, a magnetic levitation system for magnetically levitating a ferromagnetic element, and a method for compensating for stray magnetic fields in a distance sensor. According to a first aspect, a distance sensor for measuring a distance to a ferromagnetic element is proposed. According to a second aspect, a magnetic levitation system for magnetically levitating a ferromagnetic element is proposed, comprising at least one electromagnetic actuator and at least one distance sensor according to the first aspect, wherein the at least one distance sensor is configured to measure a distance to the ferromagnetic element. According to a third aspect, a method of measuring a distance to a ferromagnetic element is proposed, comprising providing a distance sensor comprising a first hall element and a second hall element; detecting a first signal of the first hall element and a second signal of the second hall element; and subtracting the second signal from the first signal. According to a fourth embodiment, the use of a distance sensor according to the first aspect is proposed, wherein the distance sensor is used in a magnetic levitation device, wherein the distance sensor is configured to measure a distance to a levitated body.

Description

Distance sensor for measuring a distance to a ferromagnetic element, magnetic levitation system and method for measuring a distance to a ferromagnetic element
Technical Field
Embodiments of the present disclosure relate to a distance sensor for measuring a distance to a ferromagnetic element. More particularly, embodiments of the present disclosure relate to, among other things, a magnetic levitation system for magnetically levitating a ferromagnetic element and a method for compensating for stray magnetic fields (stray magnetic fields) in a distance sensor.
Background
Known systems are used to perform various processes, such as coating a substrate in a processing chamber. Several methods are known for depositing materials on a substrate. As an example, the substrate may be coated using an evaporation process, a Physical Vapor Deposition (PVD) process, such as a sputtering process, a spraying process, or a Chemical Vapor Deposition (CVD) process. The process may be performed in a processing chamber of a deposition apparatus in which the coated substrate is located. A deposition material is provided in the processing chamber. A variety of materials, such as small molecules, metals, oxides, nitrides, and carbides, may be used to deposit on the substrate. In addition, other processes such as etching, structuring, annealing, or the like may be performed in the processing chamber.
For example, the coating process may be exemplified as a large area substrate considered for use in display manufacturing technology. The coated substrate can be used in several applications and in several technical fields. For example, one application may be an Organic Light Emitting Diode (OLED) panel. Other applications include insulating panels, microelectronics such as semiconductor devices, substrates with Thin Film Transistors (TFTs), color filters, or the like. OLEDs are solid-state devices composed of (organic) molecular thin films, which use electrical applications to generate light. As an example, OLED displays can provide bright displays on electronic devices and use less power than Liquid Crystal Displays (LCDs), for example. In the processing chamber, organic molecules are generated (e.g., evaporated, sputtered, or sprayed, etc.) and deposited as a layer on the substrate. The particles may be illustrated as passing through a mask having a boundary or a specific pattern to deposit material at a specific location on the substrate, as illustrated by the formation of an OLED pattern on the substrate.
The processing system may include a magnetic levitation system for example to guide the carrier in the processing chamber during the coating process. The magnetic levitation system may be adapted to provide a carrier in a processing location and/or to transport a carrier in a processing chamber. The magnetic levitation system can include one or more levitation units having electromagnetic actuators, sensors, signal processors, and power amplifiers to form a closed loop control such that the levitated carrier is maintained at a predetermined distance from the magnetic bearings.
In applications where substrates are processed in high vacuum, the metallic shielding of actuators, sensors and other components prevents the application of several forms of distance sensors. In such applications, distance sensors based on magnetic effects, such as hall effect sensors (hall effect sensors), are used because they are capable of measuring distance through a non-ferrous metal shield.
One aspect of the magnetic levitation system is to position the electromagnetic actuator and the distance sensor close to each other in the levitation unit to achieve a minimum size of the magnetic levitation system and to improve control performance by the collocation of the actuator and the sensor.
In view of the above, an aspect of the present disclosure is to provide a distance sensor and a method for operating the same, while overcoming at least some of the problems in the art.
Disclosure of Invention
According to a first embodiment, a distance sensor for measuring a distance to a ferromagnetic element is proposed. The distance sensor comprises at least one first permanent magnet element; at least one first Hall element; and at least one second Hall element; wherein the first permanent magnet element generates a first magnetic field, and a direction of the first magnetic field at the position of the first hall element is substantially opposite to a direction of the first magnetic field at the position of the second hall element.
According to a second embodiment, a magnetic levitation system for magnetically levitating a ferromagnetic element is presented. The magnetic levitation system comprises at least one electromagnetic actuator and at least one distance sensor according to the first embodiment; wherein the at least one distance sensor is configured to measure a distance to the ferromagnetic element.
According to a third embodiment, a method for measuring a distance to a ferromagnetic element is proposed. The method includes providing a distance sensor including a first hall element and a second hall element; detecting a first signal of the first Hall element and a second signal of the second Hall element; and subtracting the second signal from the first signal.
According to a fourth embodiment, the use of a distance sensor according to the first embodiment is proposed. Distance sensors are used in magnetic levitation devices, wherein the distance sensor is configured to measure the distance to a levitated body.
Embodiments are also directed to apparatuses for performing the disclosed methods and including apparatus components for performing each of the described method steps. The method steps may be performed by hardware components, a computer programmed by suitable software, any combination of the two, or in any other manner. Furthermore, embodiments according to the present disclosure also relate to methods by which the devices operate. It comprises method steps for performing the functions of the device.
Drawings
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The attached drawings relate to embodiments of the disclosure and are illustrated below:
FIG. 1 shows a schematic front view of a magnetic levitation system according to embodiments described herein;
FIG. 2a shows a cross-sectional side view of a magnetic levitation system according to embodiments described herein;
FIG. 2b depicts a cross-sectional front view of a magnetic levitation system according to embodiments described herein;
FIGS. 3a, 3b show cross-sectional side views of a distance sensor according to embodiments described herein;
FIG. 4 depicts a flow diagram of a method for measuring distance to a ferromagnetic element according to embodiments described herein; and
FIG. 5 depicts a flow diagram of a method for further compensating for an erroneous component of a range signal according to embodiments described herein.
Detailed Description
Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. In the following description of the drawings, like reference numerals may refer to like parts. Generally, only the differences with respect to the individual embodiments will be described. Each example is provided by way of illustration of the present disclosure and is not meant as a limitation of the present disclosure. Furthermore, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present description include such modifications and variations.
Embodiments described herein include magnetic levitation and/or transport of a carrier, such as a substrate carrier. The magnetic suspension of the carrier can then be contactless. The term "non-contact" as used throughout this disclosure may be understood to mean that the weight of the carrier is not supported by mechanical contact or force, but by magnetic force. In particular, the carrier may be supported in a suspended or floating state using magnetic forces instead of mechanical forces. In some applications, there may not be any mechanical contact between the carrier and the rest of the apparatus during levitation in the system and, for example, movement of the carrier.
It is an advantage that the non-contact levitation does not suffer from frictional forces that affect the linearity and/or accuracy of the movement of the carrier, compared to mechanical means for guiding the carrier in the processing system. The non-contact transport of the carrier provides a frictionless movement of the carrier, wherein the position of the carrier, for example with respect to the mask, can be controlled and maintained with high accuracy in the deposition process. In addition, levitation provides rapid acceleration or deceleration of the carrier, and/or fine adjustment of the carrier velocity.
For example, during the deposition process, a non-contact suspension or transport of the carrier is advantageous, no particles being generated during transport of the carrier due to mechanical contact between the carrier and parts of the apparatus, such as a mechanical track. Thus, the non-contact magnetic levitation system provides improved purity and uniformity of the layers deposited on the substrate, particularly because particle generation is minimized when non-contact magnetic levitation is used.
The magnetic levitation system can be configured to operate in a vacuum environment. The processing system may include at least one vacuum chamber in which a deposition process is performed on a substrate. The at least one vacuum chamber may comprise one or more vacuum pumps connected to the vacuum chamber for generating a vacuum inside the vacuum chamber. The one or more vacuum pumps are, for example, turbo pumps and/or cryopumps (cryo-pumps). The magnetic levitation system can be configured to transfer the substrate into, out of, or through a vacuum chamber.
Magnetic levitation systems can be used to transport carriers. The carrier may be adapted to carry one substrate, a plurality of substrates and/or a mask. The carrier may be a substrate carrier, such as one suitable for carrying a large area substrate and/or a plurality of large area substrates. Alternatively, the carrier may be a mask carrier, for example, adapted to carry an edge exclusion mask (edge exclusion mask). The edge exclusion mask is used to avoid coating the edge of the substrate during the deposition process.
The carrier according to embodiments described herein need not be limited to a substrate carrier or a mask carrier. The methods described herein are also applicable to other types of carriers, i.e., carriers suitable for carrying objects or devices other than, for example, substrates or masks.
The term "substrate" as used herein may include both non-flexible substrates, such as glass substrates, wafers, transparent crystal sheets such as sapphire or the like, and flexible substrates, such as webs or foils. According to embodiments, which can be combined with other embodiments described herein, embodiments described herein can be used for display PVD, i.e., sputter deposition, on large area substrates for the display market.
According to embodiments, the large-area substrate or the individual carrier may have a thickness of at least 0.67m2The size of (c). The size may be from about 0.67m2(0.73m x 0.92 m-4.5 th generation) to about 8m2More particularly from about 2m2To about 9m2Or even up to 12m2. For example, the large area substrate or carrier may be of generation 4.5, generation 5, generation 7.5, generation 8.5, or even generation 10, generation 4.5 corresponding to about 0.67m2Substrate (0.73m x 0.92.92 m), generation 5 corresponds to about 1.4m2Substrate (1.1m x 1.3.3 m), generation 7.5 corresponds to about 4.29m2Substrate (1.95m x 2.2.2 m), generation 8.5 corresponds to about 5.7m2Base plate (2.2m x2.5m), generation 10 corresponding to about 8.7m2The substrate (2.85 m.times.3.05 m). Even higher generations, such as 11 th and 12 th generations, and corresponding substrate areas may be applied in a similar manner.
The figure depicts the carrier oriented vertically. As exemplarily shown in fig. 1, the carrier 110 supporting the substrate 120 is oriented in a plane defined by a first direction 192 and a second direction 194, wherein the first direction 192 is substantially oriented in the carrier transport direction and the second direction 194 is oriented substantially parallel to the direction of gravity. The first direction 192 is oriented substantially perpendicular to the second direction 194. However, the embodiments described herein are not limited to vertically oriented carriers. Other orientations of the carrier, such as a horizontal orientation, may also be provided.
In the present disclosure, the term "substantially parallel" direction may include directions that form a small angle of up to 10 degrees, or even up to 15 degrees, with respect to each other. The term "substantially perpendicular" direction may include directions that form an angle of less than 90 degrees with respect to each other, such as at least 80 degrees or at least 75 degrees. Similar considerations apply to the concept of substantially parallel or perpendicular axes, planes, areas, orientations, or the like.
Some embodiments described herein incorporate the concept of "vertical orientation". The vertical direction is considered to be a direction parallel or substantially parallel to the direction extending along the gravity. The vertical direction may deviate from exactly vertical (the latter being defined by gravity) by an angle of, for example, 15 degrees.
Embodiments described herein may further include the concept of "horizontal orientation". The horizontal direction is understood to be distinguished from the vertical direction. The horizontal direction may be vertical or substantially vertical to the exact vertical direction defined by gravity.
Embodiments described herein relate to a distance sensor for measuring a distance to a ferromagnetic element, and a magnetic levitation system for magnetically levitating a ferromagnetic element. Referring initially to FIG. 1, FIG. 1 depicts a schematic diagram of an example of a magnetic levitation system 100 according to embodiments described herein.
The magnetic levitation system 100 shown in fig. 1 includes a carrier 110. The carrier 110 supports the substrate 120. The carrier 110 includes a ferromagnetic element 150, the ferromagnetic element 150 being illustrated as a bar of ferromagnetic material. The magnetic levitation system 100 includes a plurality of levitation units 170, the levitation units 170 including, for example, active magnetic units such as electromagnets, solenoids, coils, or superconducting magnets. Individual ones of the plurality of suspension units 170 are designated by reference numeral 175. The plurality of suspension units 170 extend in a first direction 192. The carrier 110 is movable along the plurality of suspension units 170. The ferromagnetic element 150 and the plurality of suspension units 170 are configured to provide a magnetic levitation force to levitate the carrier 110. The magnetic levitation force extends in the second direction 194.
The magnetic levitation system 100 shown in fig. 1 may include a plurality of distance sensors (not shown) disposed on the plurality of levitation units 170. A distance sensor may be provided to each of the levitation units 175. Alternatively, a distance sensor may be provided in each of the levitation units 175. The distance sensor may be configured for measuring the distance between the plurality of levitation units 170 and the carrier 110 during non-contact levitation of the carrier 110.
Magnetic levitation system 100 shown in fig. 1 includes a magnetic drive structure 180. The magnetic drive structure 180 includes a plurality of magnetic drive units. The individual magnetic drive units of the magnetic drive structure 180 are designated with reference numeral 185. The carrier 110 may include a second ferromagnetic element 160 to interact with the magnetic drive unit 185 of the magnetic drive structure 180. The magnetic drive unit 185 of the magnetic drive structure 180 is illustrated as driving a carrier in the processing system along a first direction 192. For example, the second ferromagnetic element 160 may include a plurality of permanent magnets arranged in alternating polarities. The generated magnetic field of the second ferromagnetic element 160 may interact with the plurality of magnetic drive units 185 of the magnetic drive structure 180 to move the carrier 110 in the first direction 192 while levitated.
Magnetic levitation system 100 includes a control unit 130. The control unit 130 may be connected to the plurality of levitation units 170 and/or the distance sensor. The control unit 130 may be configured for controlling the magnetic levitation of the carrier 110. The control unit 130 may be configured for controlling the distance between the carrier 110 and the plurality of suspension units 170 during the suspension of the carrier 110, based on, for example, the distance measured by a distance sensor supplied to the control unit 130. The magnetic driving structure 180 may drive the carrier 110 under the control of the control unit 130.
Referring now to fig. 2a and 2b, fig. 2a and 2b illustrate a cross-sectional view of the suspension unit 175. Fig. 2a shows a cross-sectional view in a first direction 192 or in a carrier transport direction, and fig. 2b a cross-sectional view in a third direction 196 or in a direction transverse to the carrier transport direction, the third direction 196 being perpendicular to the first direction 192 and the second direction 194.
According to embodiments of the present disclosure, which can be combined with other embodiments described herein, the levitation unit 175 includes at least one electromagnetic actuator 178. The electromagnetic actuator 178 may include at least one coil 178a and at least one ferromagnetic core 178b, and generate a magnetic field based on a current applied to the coil 178 a. The magnetic field generated by the electromagnetic actuator 178 provides a magnetic levitation force to the ferromagnetic element 150 in the second direction 194 causing the carrier 110 to which the ferromagnetic element 150 is attached to levitate.
According to embodiments of the present disclosure, which may be combined with other embodiments described herein, the at least one electromagnetic actuator, the at least one distance sensor and the controller may be contained in a gas-tight housing. Because magnetic levitation system 100 is operated in high or ultra-high vacuum applications, various components of levitation unit 175 are isolated from the surrounding vacuum environment. For this purpose, the levitation unit 175 may further include a housing 176 that encloses the components of the levitation unit 175 while isolating the components of the levitation unit 175 from the surrounding vacuum environment. The housing 176 may be an airtight enclosure that encloses the interior space 177 such that the interior space 177 is separated from the surrounding vacuum environment. Separating the interior space 177 from the ambient vacuum environment avoids contamination of the ambient vacuum environment.
The housing 176 may include a non-ferromagnetic material and at least one distance sensor 200 positioned in the housing 176 is provided to detect a magnetic field through the housing 176. For example, the housing 176 may comprise a metal, particularly an aluminum alloy or a non-ferromagnetic stainless steel.
The interior space 177 may be maintained at the same pressure as the ambient vacuum environment, or at a different pressure than the ambient vacuum environment. For example, the interior space 177 may be maintained at a pressure higher than an ambient vacuum environment. This feature allows the components of the levitation unit 175 contained in the housing 176 to be cooled by convection or adjusts the mean free path (mean free path) of the internal space 177 so that arcing of the electrical or electronic components contained in the housing 176 is avoided. In addition, the interior space 177 may include a gas composition that is the same as the ambient vacuum environment, or a gas composition that is different from the ambient vacuum environment.
According to embodiments of the present disclosure, which can be combined with other embodiments described herein, the levitation unit 175 can further include a controller 179. The controller 179 is electrically attached to at least one distance sensor 200 and at least one electromagnetic actuator 178. The controller 179 can obtain a distance signal from the at least one distance sensor 200, which corresponds to the distance X between the distance sensor 200 and the ferromagnetic element 150. Based on the derived distance signal, the controller 179 outputs an actuation signal corresponding to the target actuation force provided by the electromagnetic actuator 178.
According to embodiments of the present disclosure, which can be combined with other embodiments described herein, the controller 179 can be configured for closed loop control of the at least one electromagnetic actuator to control the distance to the ferromagnetic element 150. For example, the controller 179 may apply a closed-loop control mechanism to maintain the target distance. The closed-loop control mechanism may include a proportional-integral (PI) controller, a proportional-integral-derivative (PID) controller, or any other closed-loop controller known in the art. The closed-loop control mechanism may have as an input at least one distance signal and may generate as an output a control signal for at least one electromagnetic actuator. The closed loop control mechanism may be configured to receive other input signals. For example, the estimated current signal of the at least one electromagnetic actuator may be used as an additional input signal.
As exemplarily shown in fig. 2a and 2b, the controller 179 may be a component of the levitation unit 175. In this case, each levitation unit 175 of the plurality of levitation units 170 may each have a separate controller 179, which may independently control each levitation unit 175. Separate controllers 179 provided in the levitation units 175 may optionally be electrically attached to the control unit 130, as exemplarily shown in fig. 1. Alternatively, the controller 179 may be a component of the control unit 130, wherein each controller 179 for each levitation unit 175 of the plurality of levitation units 170 is integrated into a single control unit 130.
According to embodiments of the present disclosure, which can be combined with other embodiments described herein, the levitation unit 175 further includes at least one distance sensor 200. As exemplarily shown in fig. 2a, the levitation unit 175 may include two distance sensors 200 disposed on both sides of the electromagnetic actuator 178. The number of distance sensors 200 may apply at least one distance sensor for each electromagnetic actuator 178, in particular two distance sensors for each electromagnetic actuator 178.
The distance sensor 200 may include at least one transducer that varies its output voltage in response to a magnetic field. For example, the distance sensor 200 may include a hall effect sensor or a Giant Magnetoresistive (GMR) sensor. The distance sensor 200 is configured for detecting the magnetic field of the ferromagnetic element 150 such that the distance X between the distance sensor 200 and the ferromagnetic element 150 can be determined. The distance sensor 200 can thus be used to contactlessly determine the distance between the levitation unit 175 and the carrier 110 to which the ferromagnetic element 150 is attached 110. Further, because the magnetic field of the ferromagnetic element 150 is detected, the presence of a non-ferromagnetic element between the distance sensor 200 and the ferromagnetic element 150 does not interfere with the operation of the distance sensor 200.
The distance sensor 200 may be located in a position to reliably measure the distance X to the ferromagnetic element 150. The distance sensor 200 may be mounted to the levitation unit 175, or may be located in the levitation unit 175. As exemplarily shown in fig. 2a and 2b, the distance sensor 200 may be connected in series with the electromagnetic actuator 178. The arrangement of sensors and actuators in a sensor/actuator pair is preferred to achieve reliable and high performance control of the suspension unit 175. Therefore, it is preferable that the distance sensor 200 be positioned close to the electromagnetic actuator 178. Furthermore, positioning the distance sensor 200 close to the electromagnetic actuator 178 has the additional benefit of providing a closer spacing of the suspension elements 175.
However, because the electromagnetic actuator 178 generates an electromagnetic field to levitate the carrier 110, positioning the distance sensor 200 proximate to the electromagnetic actuator 178 becomes problematic. The distance sensor 200 may detect stray magnetic fields generated by the electromagnetic actuators 178 such that unwanted cross-coupling between the electromagnetic actuators 178 occurs. This cross-coupling due to stray magnetic fields affects a reliable determination of the distance X between the distance sensor 200 and the ferromagnetic element 150 and thus the distance between the carrier and the magnetic levitation system.
Referring now to fig. 3a and 3b, fig. 3a and 3b illustrate side cross-sectional views of a distance sensor 200 according to an embodiment of the present disclosure. Therein, a distance sensor 200 for measuring a distance X to the ferromagnetic element 150 is provided. The distance sensor 200 comprises at least one first permanent magnet element 201, at least one first hall element 203 and at least one second hall element 204, wherein the first permanent magnet element 201 generates a first magnetic field 205. The first hall element 203 and the second hall element 204 are oriented such that the direction of the first magnetic field 205 at the location of the first hall element 203 is substantially opposite to the direction of the first magnetic field 205 at the location of the second hall element 204.
The second magnetic field 206 may be generated by the electromagnetic actuator 178 as an unwanted effect of the levitating carrier 110. The second magnetic field 206 may include stray magnetic fields. Because the magnitude of the second magnetic field 206 depends on the levitation force supplied to the carrier 110, the effect of the second magnetic field 206 on the distance sensor 200 creates an undesirable cross-coupling between the electromagnetic actuator 178 and the distance sensor 200. By providing a distance sensor 200 according to the present disclosure, this unwanted coupling can be compensated for.
Providing the distance sensor 200 with at least a first permanent magnet element 201 and first and second hall elements 203,204 allows the distance X between the ferromagnetic element 150 and the distance sensor 200 to be determined by detecting the first magnetic field 205, while also compensating for the second magnetic field 206. The first magnetic field 205 generates a positive voltage component passing through the first hall element 203 and a negative voltage component passing through the second hall element 204. At the same time, the second magnetic field 206 generates a positive voltage component that passes through the first hall element 203 and the second hall element 204. By subtracting the voltage generated by the second hall element 204 from the voltage generated by the first hall element 203, the voltage component generated by the second magnetic field 206 of the first hall element 203 and the second hall element 204 is cancelled, and the voltage component generated by the first magnetic field 205 of the first hall element 203 and the second hall element 204 remains.
The first hall element 203 and the second hall element 204 generate voltages based on the magnetic field supplied thereto. The first hall element 203 and the second hall element 204 are positioned such that the first magnetic field 205 induces a voltage in the first hall element 203 and the second hall element 204. The strength of the first magnetic field 205 is affected by the presence of the ferromagnetic element 150 such that a difference in the first magnetic field 205 is produced when the ferromagnetic element 150 is close to or far from the distance sensor 200. By positioning the first hall element 203 and the second hall element 204 such that the first magnetic field 205 generates a voltage therein, the distance between the distance sensor 200 and the ferromagnetic element 150 can be measured.
The first magnetic field 205 is generated by at least one first permanent magnet element 201. Referring first to the embodiment exemplarily shown in fig. 3a, the distance sensor 200 comprises a first permanent magnet element 201. The first permanent magnet element 201 is positioned such that a magnetic field loop is generated with the flux direction on one side of the distance sensor 200 in a first flux direction away from the ferromagnetic element 150 and the flux direction on the other side of the distance sensor 200 in a second flux direction towards the ferromagnetic element 150. The distance sensor 200 may further include a core element 202 positioned to direct the first magnetic field 205. The first hall element 203 and the second hall element 204 are positioned in the first magnetic field 205 such that the first hall element 203 is located in a magnetic flux region in the first magnetic flux direction and the second hall element 204 is located in a magnetic flux region in the second magnetic flux direction.
An alternative arrangement is exemplarily shown in fig. 3 b. In this embodiment, a first permanent magnet element 201a and a second permanent magnet element 201b are provided. The polarities of the first and second permanent magnet elements 201a,201b are arranged opposite to each other so that a magnetic field loop is generated with the flux direction on one side of the distance sensor 200 in a first flux direction away from the ferromagnetic element 150 and the flux direction on the other side of the distance sensor 200 in a second flux direction towards the ferromagnetic element 150. The distance sensor 200 may further include a core element 202 positioned to direct the first magnetic field 205. The first hall element 203 and the second hall element 204 are positioned in the first magnetic field 205 such that the first hall element 203 is located in a magnetic flux region in the first magnetic flux direction and the second hall element 204 is located in a magnetic flux region in the second magnetic flux direction.
The at least one first permanent magnet element 201 may be included in a plurality of permanent magnet elements. For example, the distance sensor 200 may include at least two first permanent magnet elements, or may include at least two first permanent magnet elements and at least two second permanent magnet elements. The plurality of permanent magnet elements may be oriented such that they form a Halbach array (Halbach array) with the magnetic field generated by the plurality of permanent magnet elements being stronger on the side facing the ferromagnetic element 150 and weaker on the side opposite the ferromagnetic element 150. The halbach array has the advantage that it does not generate a magnetic field on its rear surface, so that other components located in the levitation unit, which may be sensitive to magnetic interference, are less affected by the first magnetic field than conventional magnet elements.
According to an embodiment of the present disclosure, the first and second hall elements 203,204 are oriented opposite to each other such that the first magnetic field 205 generates a positive voltage in the first and second hall elements 203, 204. This means that the first hall element 203 and the second hall element 204 are oriented such that the first hall element 203 located in a magnetic flux area in the first magnetic flux direction is oriented in the first magnetic flux direction and the second hall element 204 located in a magnetic flux area in the second magnetic flux direction is oriented in the second magnetic flux direction. In the sectional side views shown in fig. 3a and 3b, it follows that the first hall element 203 is oriented upward and the second hall element 204 is oriented downward.
In the case where the first and second hall elements 203 and 204 are oriented opposite to each other, the first magnetic field 205 generates a positive voltage in both the first and second hall elements 203 and 204, so that the magnitudes of the voltages are substantially equal to each other. However, the second magnetic field 206 generates a positive voltage in one of the first hall element 203 and the second hall element 204 and a negative voltage in the other of the first hall element 203 and the second hall element 204, so that the magnitudes of the voltages are substantially equal to each other. It follows that the voltages generated by each of the first hall element 203 and the second hall element 204 can be added such that the voltage generated by the first magnetic field 205 is maintained and the voltage generated by the second magnetic field 206 is cancelled, while compensating for the measured voltage for any effect of the second magnetic field 206 on the output voltage of the distance sensor 200.
As an alternative embodiment, the first hall element 203 and the second hall element 204 may be oriented in the same direction as each other such that the first magnetic field 205 generates a positive voltage in one hall element and a negative voltage in the other hall element. In the sectional side views shown in fig. 3a and 3b, this follows that in this case both the first hall element 203 and the second hall element 204 are oriented upwards or both downwards.
In the case where the first hall element 203 and the second hall element 204 can be oriented in the same direction as each other, the first magnetic field 205 generates a positive voltage in the first hall element 203 and a negative voltage in the second hall element 204 so that the magnitudes of the respective voltages are substantially the same as each other. However, the second magnetic field 206 generates a positive voltage in both the first hall element 203 and the second hall element 204, so that the magnitudes of the voltages are substantially the same as each other. It follows that the voltages generated by each of the first and second hall elements 203,204 can be subtracted such that the voltage generated by the first magnetic field 205 is maintained and the voltage generated by the second magnetic field 206 is cancelled, while compensating for the measured voltage for any effect of the second magnetic field 206 on the output voltage of the distance sensor 200.
By configuring the distance sensor 200 according to the present disclosure, stray magnetic fields may be compensated. The stray magnetic field may for example be generated by an electromagnetic actuator, a magnetic element on the substrate carrier, or a cathode target. Compensating for stray magnetic fields provides for positioning closer to the electromagnetic actuator from the sensor 200 so that improved performance of the magnetic levitation system can be achieved by the sensor and actuator combination. In addition, by compensating for stray magnetic fields, distance sensor 200 may produce more reliable and accurate distance measurements so that the distance between the carrier and the magnetic levitation system may be more reliably and accurately maintained.
According to embodiments of the present disclosure, which may be combined with other embodiments described herein, the controller 179 shown in fig. 2a and 2b may be configured for compensating for stray magnetic fields generated by the at least one electromagnetic actuator and acting on the at least one distance sensor. The controller 179 may be electrically attached to the at least one distance sensor 200 such that the controller 179 may receive the first and second signals from the first and second hall elements, respectively. The controller 179 may be configured to subtract the first signal and the second signal from each other such that a signal contribution due to a stray magnetic field generated by the at least one electromagnetic actuator is compensated.
According to a third embodiment of the present disclosure, a method for measuring a distance to a ferromagnetic element is presented. The method comprises providing a distance sensor, wherein the distance sensor comprises a first Hall element and a second Hall element; detecting a first signal of the first Hall element and a second signal of the second Hall element; and subtracting the second signal from the first signal.
Referring now to fig. 5, fig. 5 depicts a flow diagram of a method 500 for measuring distance to a ferromagnetic element, according to an embodiment of the present disclosure. Method 500 begins at start point 510.
At block 511, a distance sensor is provided, the distance sensor including a first hall element and a second hall element. The distance sensor may be a distance sensor according to embodiments described herein, wherein the distance sensor is capable of measuring a distance to the ferromagnetic element. A distance sensor may for example be provided adjacent to the electromagnetic actuator. Unwanted stray magnetic fields generated by the electromagnetic actuator may affect the distance sensor such that cross-coupling between the electromagnetic actuator and the distance sensor occurs.
At block 512, a first signal of the first hall element is detected, and at block 513, a second signal of the second hall element is detected. The first and second signals of the first and second hall elements may each comprise components of a distance measurement signal and a stray magnetic field signal, respectively. The distance measurement signal components of each of the first and second signals may be substantially equal in magnitude but opposite in polarity, while the stray magnetic field signal components of each of the first and second signals may be substantially the same in magnitude and may have the same polarity.
At block 514, the first signal of the first hall element and the second signal of the second hall element are subtracted from each other. Because the stray magnetic field signal components of each of the first and second signals are substantially the same in magnitude and have the same polarity, the first and second signals are subtracted from each other to cancel each of the stray magnetic field signal components of the first and second signals. The stray field signal contribution is thus compensated so that a distance signal can be generated which remains unaffected by unwanted stray magnetic fields. Finally, the method 500 ends at end 520.
According to a further embodiment, which can be combined with other embodiments described herein, the distance sensor provided in block 511 may further comprise at least one first permanent magnet element for generating a first magnetic field, wherein the direction of the first magnetic field at the location of the first hall element is substantially opposite to the direction of the first magnetic field at the location of the second hall element. Alternatively, the distance sensor provided at block 511 may further comprise at least one first permanent magnet element and at least one second permanent magnet element for generating a first magnetic field, wherein a direction of the first magnetic field at the location of the first hall element is substantially opposite to a direction of the first magnetic field at the location of the second hall element. The first magnetic field thus causes the first hall element to generate a first distance-measuring signal component and the second hall element to generate a second distance-measuring signal component, wherein the polarity of the first distance-measuring signal component is opposite to the polarity of the second distance-measuring signal component. For example, the first magnetic field may cause the first hall element to generate a positive voltage component and the second hall element to generate a negative voltage component. The first and second distance-measuring signal components generated by the first and second hall elements, respectively, may be substantially the same in magnitude, such that when the first and second signals of the first and second hall elements, respectively, are subtracted from each other in block 514, the first and second distance-measuring signal components do not cancel each other, and the first and second stray magnetic field components compensate. Thus, a distance signal can be generated that remains unaffected by the effects of stray magnetic fields.
The method 500 may be performed using a controller. For example, referring again to fig. 2a and 2b, the method 500 may be performed by the controller 179, which controller 179 may be a component of the levitation unit 175. The controller 179 may be electrically attached to the at least one distance sensor 200 such that the controller 179 receives as inputs the first signal and the second signal.
As described above, an aspect of the magnetic levitation system is to position the electromagnetic actuator and the distance sensor close to each other in the levitation unit to achieve a minimum size of the magnetic levitation system and to improve control performance by the collocation of the actuator and the sensor. One unwanted effect of the close proximity between the electromagnetic actuator and the distance sensor is that stray magnetic fields generated by the electromagnetic actuator induce cross-coupling effects with the distance sensor. The embodiments described herein are illustrated as using the first and second hall elements to subtract the signals of the first and second hall elements to compensate for stray magnetic fields.
However, when the distance sensor is positioned even closer to the electromagnetic actuator, other unwanted effects are induced, as stray magnetic fields may affect the first and second hall elements in the distance sensor unequally. For example, the curvature of the stray magnetic field may be high in the area where the distance sensor is located, or the magnitude of the stray magnetic field may be non-uniform. These effects create problems in particular for distance sensors which may be exemplified by being located between several electromagnetic actuators. In such a case, the first and second magnetic field signal components may not be sufficiently identical in magnitude to allow the second magnetic field signal to be fully compensated by subtraction. Therefore, additional compensation of these effects may be advantageous.
Referring now to fig. 6, fig. 6 depicts a flow chart of a method 501 for measuring distance to a ferromagnetic element. According to an embodiment of the present disclosure, which can be combined with other embodiments described herein, the method 501 further comprises an additional step of detecting a coil current of the at least one electromagnetic actuator using the coil current to estimate a magnetic flux generated by the at least one electromagnetic actuator, and an additional step of compensating for an erroneous component of the distance signal measured by the distance sensor. The method 501 begins at a start point 510.
The method 501, including blocks 511, 512, 513, and 514 according to the method 500 described above, further includes detecting a coil current of at least one electromagnetic actuator in block 515. The coil current in an electromagnetic actuator is proportional to the magnetic flux generated by the electromagnetic actuator. The coil current may be detected from a current signal delivered to the electromagnetic actuator, or by using a current sensor configured to measure the current in the coil of the electromagnetic actuator.
In addition, at block 516, the magnetic flux generated by the at least one electromagnetic actuator is estimated. The estimation of the generated magnetic flux is based on the coil current of the at least one electromagnetic actuator detected in block 515. Estimating the magnetic flux includes generating a flux compensation signal. The flux compensation signal may be used to compensate for an erroneous component of the distance signal generated by the distance sensor.
Finally, in block 517, the erroneous component of the distance signal measured by the distance sensor is compensated. Compensation is performed by subtracting the flux compensation signal generated in block 516 from the distance signal detected by the distance sensor such that other effects of cross-coupling between the electromagnetic actuator and the distance sensor that have not been compensated for by block 514 are compensated.
Performing the method 501 as described above provides other compensation for stray magnetic fields, such as non-uniform or high curvature stray magnetic fields, or stray magnetic fields from adjacent electromagnetic actuators, so that the distance sensor can be positioned even closer to the electromagnetic actuators, altering the performance of the magnetic levitation system.
According to embodiments of the present disclosure that may be combined with other embodiments described herein, estimating magnetic flux in block 516 includes calculating a model of magnetic flux based on the magnitude and/or frequency of the coil current. The coil current may, for example, induce eddy currents (eddy currents) in the housing 176, or may produce a magnitude of the provided magnetic flux that is frequency dependent. Further, the ferromagnetic element 150 may be a non-laminated element that can direct frequency dependence (frequency dependence). The model may comprise a predetermined or pre-calculated model of the magnetic flux generated by the electromagnetic actuator for the magnitude and/or frequency of the coil current provided. For example, the model may comprise a look-up table of pre-calculated values. Alternatively, the model may be calculated in real time based on a mathematical approximation of the magnetic flux generated by the electromagnetic actuator for the magnitude and/or frequency of the coil current provided.
The model of the magnetic flux may be determined by measuring the magnetic flux behavior of the electromagnetic actuator in response to the supplied coil current, and determining its effect on the distance signal. The ferromagnetic element is fixed at a known distance from the distance sensor, and a coil current is supplied to the electromagnetic actuator, which generates a distance signal from the distance sensor. Changing the coil current supplied to the electromagnetic actuator produces a change in magnetic flux, which under the influence of the magnetic flux changes the distance signal from the distance sensor. By measuring the change in the distance signal based on the coil current, the model can be calculated for estimating the effect the magnetic flux of the electromagnetic actuator has on the distance signal based on the coil current.
The model may estimate the magnetic flux generated by the at least one electromagnetic actuator taking into account other parameters. For example, the model may comprise parameters relating to coil currents of at least one neighboring electromagnetic actuator. Stray magnetic flux generated by an adjacent electromagnetic actuator may also cross-couple with an adjacent distance sensor if the electromagnetic actuator is positioned close to its neighbors. The erroneous contribution of the distance signal generated by the distance sensor due to stray magnetic flux acting on the distance sensor can thus be further compensated.
According to embodiments of the present disclosure, which can be combined with other embodiments described herein, estimating magnetic flux is performed on a digital signal processor. Digital signal processors typically include analog-to-digital converters (ADCs), digital signal processing units, and digital-to-analog converters (DACs) to provide real-time manipulation of analog signals. The digital signal processor may be a separate component provided in the levitation unit or may be integrated in the controller for the levitation unit. Performing the estimation of the magnetic flux on the digital signal processor provides a real-time estimation of the magnetic flux, provides faster acquisition of the distance signal, and provides better performance of the suspension system in maintaining the target distance between the carrier and the suspension system.
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims (16)

1. A distance sensor (200) for measuring a distance to a ferromagnetic element (150), the distance sensor comprising:
at least one first permanent magnet element (201,201 a);
at least one first hall element (203); and
at least one second Hall element (204);
wherein the first permanent magnet (201,201a) element generates a first magnetic field (205) and the direction of the first magnetic field (205) at the location of the first hall element (203) is substantially opposite to the direction of the first magnetic field (205) at the location of the second hall element (204).
2. A distance sensor (200) according to claim 1, further comprising at least a second permanent magnet element (201b) arranged parallel to the first permanent magnet element (201a) and having a polarity opposite to the first permanent magnet element (201a), wherein the first and second permanent magnet elements (201a,201b) generate the first magnetic field (205).
3. The distance sensor (200) of any of claims 1 and 2, wherein the first and second hall elements (203,204) are oriented opposite to each other such that the first magnetic field (205) generates a positive voltage in the first and second hall elements (203, 204).
4. A magnetic levitation system (100) for magnetically levitating a ferromagnetic element (150), the magnetic levitation system comprising:
at least one electromagnetic actuator (178); and
at least one distance sensor (200) according to any of claims 1 to 3;
wherein the at least one distance sensor (200) is configured to measure a distance (X) to the ferromagnetic element (150).
5. The magnetic levitation system (100) as recited in claim 4, further comprising a controller (130,179) configured for closed loop control of the at least one electromagnetic actuator (178) to control the distance (X) to the ferromagnetic element (150).
6. The magnetic levitation system as recited in claim 5, wherein the controller (130,179) is configured for compensating a magnetic field generated by the at least one electromagnetic actuator (178) and acting on the at least one distance sensor (200).
7. The magnetic levitation system (100) as recited in any one of claims 4-6, wherein the at least one electromagnetic actuator (178) is configured for transporting the ferromagnetic element (150) in a transport direction (192).
8. The magnetic levitation system (100) as recited in any of claims 4-7, wherein the ferromagnetic element is a substrate carrier (110).
9. The magnetic levitation system (100) as recited in any one of claims 5-8, wherein the at least one electromagnetic actuator (178), the at least one distance sensor (200), and the controller (179) are contained in a gas-tight enclosure (176).
10. The magnetic levitation system (100) as recited in any of claims 4-9, wherein the magnetic levitation system (100) is configured for operation in a vacuum.
11. A method for measuring a distance (X) to a ferromagnetic element (150), the method comprising:
providing a distance sensor (200) comprising a first hall element (203) and a second hall element (204);
detecting a first signal of the first hall element (203) and a second signal of the second hall element (204); and
subtracting the second signal from the first signal.
12. The method of claim 11, wherein the distance sensor (200) further comprises at least a first permanent magnet element (201,201a) for generating a first magnetic field (205), wherein the direction of the first magnetic field (205) at the position of the first hall element (203) is substantially opposite to the direction of the first magnetic field (205) at the position of the second hall element (204).
13. The method of any of claims 11 and 12, further comprising:
detecting a coil current of at least one electromagnetic actuator (178);
estimating a magnetic flux generated by the at least one electromagnetic actuator (178) using the coil current; and
-compensating for erroneous components of the distance signal measured by the distance sensor (200).
14. The method of claim 13, wherein estimating the magnetic flux comprises calculating a model of the magnetic flux based on a magnitude and/or frequency of the coil current.
15. The method of any one of claims 13 or 14, wherein estimating the stray magnetic flux is performed on a digital signal processor.
16. Use of a distance sensor (200) according to any of claims 1 to 3 in a magnetic levitation device (100), wherein the distance sensor (200) is configured to measure a distance (X) to a levitated body.
CN201880030816.5A 2018-06-26 2018-06-26 Distance sensor for measuring a distance to a ferromagnetic element, magnetic levitation system and method for measuring a distance to a ferromagnetic element Pending CN110859042A (en)

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