Abstract: In order to improve the etching depth and/or the etching homogeneity at a substrate, a plasma source with one or more single electrodes or one or more magnets is proposed. The magnet generates a magnetic field in the vicinity of the electrodes, which may be rear-side or front-side.

Abstract: The present disclosure provides a shielding mechanism and a thin-film-deposition equipment using the same, wherein the shielding mechanism includes two shield members and a driver. The driver includes a motor and a shaft seal. The motor interconnects the two shield members via the shaft seal, and such that to drive the two shield members to sway in opposite directions and to switch between an open state and a shielding state. Furthermore, each of the two shield members is formed with at least one cavity, for reducing weights thereof and loading of the motor and the driver.

Abstract: A sputtering method and apparatus having at least one set of dual rotatable cylindrical sputtering targets mounted in a vacuum chamber. Magnet assemblies in hollow target cylinders provide erosion zones running long the parallel sides of a racetrack that act as target flux sources towards a substrate. These parallel erosion zones have a highly concentrated plasma density for rapid sputtering of the target and any reactive material. Features include the angular distance between normals to adjacent parallel erosion zones, the angle greater than 45° subtended at the center of the cylindrical target, placement of the substrate with respect to the targets, and pointing angles (orientation or tilt) of the racetracks toward the substrate and/or each other. These parameters form a relatively wide and efficient constant flux deposition region at the substrate, and allows for high deposition rates at constant reactive gas partial pressures with substantially uniform film stoichiometry and thickness.

Abstract: A tube target with an end block for supplying coolant to the tube target is provided. The end block comprises a rotatably mounted carrier shaft for holding and rotating the tube target; a connecting sleeve arranged in the carrier shaft; a sealing element for the tube target on its end facing the end block; a coolant inlet port in the interior of the tube target; and a coolant outlet port. The coolant outlet port is formed by at least one aperture in the sealing element. The aperture is located in the vicinity of the wall of the tube target, and eccentrically to the rotational axis of the tube target.

Abstract: A sputtering apparatus that includes at least a target presented as an inner surface of a confinement structure, the inner surface of the confinement structure is preferably an internal wall of a circular tube. A cathode is disposed adjacent the internal wall of the circular tube. The cathode preferably provides a hollow core, within which a magnetron is disposed. Preferably, an actuator is attached to the magnetron, wherein a position of the magnetron within the hollow core is altered upon activation of the actuator. Additionally, a carriage supporting the cathode and communicating with the target is preferably provided, and a cable bundle interacting with the cathode and linked to a cable bundle take up mechanism provided power and coolant to the cathode, magnetron, actuator and an anode of the sputtering apparatus.

Abstract: A magnetron sputtering apparatus (100) comprising: a magnetic array arranged to create a magnetic field (103) in the vicinity of a tubular target (2) which target at least partially surrounds the magnetic array and acts as a cathode (2a); an anode (2b); the magnetic array being arranged to create an asymmetric plasma distribution with respect to the normal angle of incidence to a substrate (3); and means (1b) for enhancing the magnetic field to produce a relatively low impedance path for electrons flowing from the cathode (2a) to the anode (2b).

Abstract: A rotary sputtering target bonded to a backing tube such that the bonding material is applied only proximate the ends of the rotary sputtering target and is also between the target and the backing tube to form a gap between the rotary sputtering target and the backing tube and a device for bonding a rotary sputtering target to a backing tube.

Abstract: The disclosure relates to a magnet arrangement for a sputtering system, wherein the magnet arrangement is adapted for a rotatable target of a sputtering system and includes: a first magnet element extending along a first axis; a second magnet element being disposed around the first magnet element symmetrically to a first plane; wherein the second magnet element includes at least one magnet section intersecting the first plane; and wherein a magnetic axis of the at least one magnet section is inclined with respect to a second plane being orthogonal to the first axis. Further, the disclosure relates to a target backing tube for a rotatable target of a sputtering system, a cylindrical rotatable target for a sputtering system, and a sputtering system.

Abstract: The present invention relates to a rotating magnetron sputtering target and a corresponding magnetron sputtering device. The rotating magnetron sputtering target comprises a cylindrical target, a pole shoe and a plurality of magnetrons. The magnetron comprises a first magnetic pole arranged on a central portion thereof and two second magnetic poles arranged on both sides thereof, and the first and the second magnetic poles have opposite polarities. The rotating magnetron sputtering target and the corresponding magnetron sputtering device of the present invention improve the plasma density within a coating region, so that it forms a film with better quality and better uniformity.

Abstract: A magnetron sputtering electrode for use in a rotatable cylindrical magnetron sputtering device, the electrode including a cathode body defining a magnet receiving chamber and a cylindrical target surrounding the cathode body. The target is rotatable about the cathode body A magnet arrangement is received within the magnet receiving chamber, the magnet arrangement including a plurality of magnets. A shunt is secured to the cathode body and proximate to a side of the magnet arrangement, the shunt extending in a plane substantially parallel to the side of the magnet arrangement. A method of fine-tuning a magnetron sputtering electrode in a rotatable cylindrical magnetron sputtering device is also disclosed.

Abstract: A drive end block for a rotatable magnetron comprises a housing, which has a vacuum-tight rotary feedthrough extending through a wall of the housing, and a drive apparatus for generating a torque. An output end of the rotary feedthrough lies outside the housing for connection to the rotatable magnetron and a drive end of the rotary feedthrough lies inside the housing for introducing a torque. The drive apparatus is situated outside the housing of the drive end block and is connected using a torque transmission apparatus to the drive end of the rotary feedthrough so that the drive apparatus is electrically insulated from the housing and the rotary feedthrough of the drive end block.

Abstract: A magnetron unit moving apparatus for preventing magnetization and magnetron sputtering equipment having the same. The magnetron unit moving apparatus includes a magnetron unit disposed adjacent to a target, to generate a specific magnetic field, and a movement unit to space the magnetron unit and the target apart such that a strength of a magnetic field generated over the target is within a predetermined reference strength range. It is possible to space the target and the magnetron unit apart so as to prevent the target from being magnetized when a process is not performed.

Abstract: A seal and fixation assembly includes a cylindrical target having an inside surface with a shoulder that forms a stop within the target. A target retaining ring is disposed about the target. A seal plate is disposed within the target and engages the stop and the inside surface of the target. An end cap is disposed on the end of the target and includes a portion with a beveled surface within the target. A sealing element is disposed between the inside surface of the target, the seal plate, and the beveled surface of the end cap. A clamp is disposed over the end cap and the target retaining ring. Engagement of the end cap and the target retaining ring with the clamp causes the end cap to move within the target toward the stop to compress the sealing element between the target, the seal plate, and the beveled surface.

Abstract: A support device for a magnetron arrangement with a rotating target includes a housing with a drive shaft mounted to rotate in the housing. An end of the drive shaft accessible from outside of the housing connects to the rotating target and another end lies within the housing for introduction of a torque. An electric motor with a stator and a rotor is arranged within the housing to generate a torque.

Abstract: A sputtering apparatus that includes at least a target presented as an inner surface of a confinement structure, the inner surface of the confinement structure is preferably an internal wall of a circular tube. A cathode is disposed adjacent the internal wall of the circular tube. The cathode preferably provides a hollow core, within which a magnetron is disposed. Preferably, an actuator is attached to the magnetron, wherein a position of the magnetron within the hollow core is altered upon activation of the actuator. Additionally, a carriage supporting the cathode and communicating with the target is preferably provided, and a cable bundle interacting with the cathode and linked to a cable bundle take up mechanism provided power and coolant to the cathode, magnetron, actuator and an anode of the sputtering apparatus.

Abstract: A sputtering apparatus includes a susceptor for receiving a substrate, and a first target device disposed to be opposite to a center region of a substrate and at least second and third target devices disposed to be opposite to peripheral regions of the substrate, wherein the second and third target devices are rotatable.

Abstract: The invention provides devices and methods for depositing uniform coatings using cylindrical magnetron sputtering. The devices and methods of the invention are useful in depositing coatings on non-cylindrical workpiece surfaces. An assembly of electromagnets located within the bore of a hollow cylindrical emitter is used to form a magnetic field exterior to and near the exterior surface of the emitter. The magnet assembly configuration is selected to provide a magnetic field configuration compatible with the workpiece surface contour. The electromagnet assembly may be a plurality of magnet units, each unit having at least one electromagnet. The magnetic field strength from each magnet unit is separately and electrically adjustable. Each electromagnet in the assembly has a coil of electrically conducting material surrounding a specially shaped core of magnetic material.

Abstract: The invention relates to a target arrangement comprising a tubular-shaped carrier element and a hollow-cylindrical target having at least one target material, said target comprising at least one one-piece tube segment which at least partially surrounds the carrier element. Said carrier element and the tube segment are partially interconnected in a material fit by at least two plastically deformable compensating means. The invention also relates to a method for producing said type of target arrangement and a tubular segment.

Abstract: A cylindrical magnetron sputtering apparatus includes a rotating cylindrical sputtering target, a non-rotating magnet structure within the cylindrical sputtering target and at least one non-rotating trim magnet adjacent an end of the magnet structure. The trim magnets are manipulated during operation of the apparatus to alter a magnetic field produced by the magnet structure within the cylindrical sputtering cathode. As a result the shape of a racetrack discharge plasma formed at an end of the sputtering target is altered such that the formation of an erosion groove is avoided.

Abstract: A magnetron sputtering system generates a high density plasma on a target by applying magnetic fields intersecting an electric field by using a plurality of magnets that are rotatably supported. The respective magnets are revolved and rotated so that the time variation of regions where a magnetic field (line of magnetic force) generated by the each magnet is orthogonal to an electric field is prevented from becoming monotonous. Further, the respective magnets are arranged to make the distances between the center of rotation and the center of revolution of the respective magnets different from each other, so that the regions where the magnetic field (line of magnetic force) generated by the each magnet is orthogonal to the electric field are dispersed in the radial direction of a target.

Abstract: A method of sputtering with sputtering apparatus is for depositing a layer upon a substrate. The apparatus includes a sputter target with a face exposed to the substrate and a magnetron providing a magnetic field that moves relative to the target face. The speed of movement of the field is controlled such that the uniformity of the deposition on the substrate is enhanced. A particular method includes monitoring uniformity verses speed, selecting the speed that gives the preferred uniformity and controlling the field to the selected speed. The selected speed may vary over the life of the target, with increased speeds becoming desirable as the target thins.

Abstract: Provided is a magnetron sputtering apparatus that increases an instantaneous plasma density on a target to improve a film forming rate. The magnetron sputtering apparatus includes a substrate to be processed, a target installed to face the substrate and a rotary magnet installed at a side opposite to the substrate across the target. In the magnetron sputtering apparatus, plasma loops are formed on a target surface. The plasma loops are generated, move and disappear in an axis direction of the rotary magnet according to a rotation of the rotary magnet.

Abstract: A physical vapor deposition reactor includes a metal sputter target, a D.C. sputter power source coupled to the metal sputter target and a wafer support pedestal facing the metal sputter target. A movable magnet array is adjacent a side of the metal sputter target opposite the wafer support pedestal. A solid metal RF feed rod engages the metal sputter target and extends from a surface of the target on a side opposite the wafer support pedestal. A VHF impedance match circuit is coupled to an end of the RF feed rod opposite the metal sputter target and a VHF RF power generator coupled to said VHF impedance match circuit. Preferably, the reactor of further includes a center axle about which the movable magnet array is rotatable, the center axle having an axially extending hollow passageway, the RF feed rod extending through the passageway.

Abstract: A new and useful rotatable sputter magnetron assembly is provided, that addresses the issue of uneven wear of the target electrode tube. According to the principles of the present invention, a rotatable sputter magnetron assembly for use in magnetron sputtering target material onto a substrate comprises a. a longitudinally extending tubular shaped target electrode tube having a longitudinal central axis, b. the target electrode tube extending about a magnet bar that is configured to generate a plasma confining magnetic field adjacent the target electrode tube, c. the magnet bar being held substantially stationary within the target electrode tube, and d. the target electrode tube supported for rotation about its longitudinal central axis and for axial movement along its longitudinal central axis, so that wear of the target electrode tube can be controlled by moving the target electrode tube axially during magnetron sputtering of the target material.

Abstract: Rotatable magnetron sputtering apparatuses are described for depositing material from a target while reducing premature burn through issues. The rotatable magnetron sputtering apparatus includes electric coils wound on pole pieces to modulate the magnetic fields at the ends of the magnetron magnetic assembly. Changing the direction of electric current moves the sputtering region alternately around its normal central position to decrease the rate of erosion depth at the ends of the target material.

Abstract: A plasma-enhanced physical vapor deposition method in which VHF power is applied to the sputter target in addition to a D.C. voltage that is also applied to the target, the VHF power level being 3.5 kW or greater, so that the D.C. target power may be reduced to less than 500 W while still attaining a very high ion fraction (in excess of 50%), permitting a very small workpiece-to-target spacing not exceeding a fraction (7/30) of the workpiece diameter to enhance the ionization fraction throughout the process region.

Abstract: A drive end block for a magnetron arrangement with a rotating target, comprises an end block housing having a rotatably mounted drive shaft. The drive shaft is arranged in the end block housing, accessible at an end from outside of the end block housing for connection to the rotating target, and adapted at its end inside the end block housing for introduction of a torque. An electric motor with a stator and a rotor for creating the torque is arranged inside the end block housing.

Abstract: A sputtering magnetron (300) insertable in a rotatable target is described. The magnetron is designed around a single piece, multiwalled tube (102, 202) with compartments (316, 316?, 318, 318?) extending over the length of the tube. The multiwalled tube gives a much stiffer magnetron carrier structure compared to prior art magnetrons. As a result, the magnetic field generator can be mounted inside a compartment and the distance between magnets and target surface is easily adjustable as the tube is much stiffer than the generator. Additionally, the coolant channels can be incorporated inside the tube and close to the outer wall of the tube so that coolant can be supplied in the vicinity of the magnetic field generator. The increased stiffness of the magnetron allows the target tube to be carried by the magnetron—not the other way around—at least during part of the useful life of the target.

Abstract: Rotatable magnetron sputtering apparatuses are described for depositing material from a target while reducing premature burn through issues. The rotatable magnetron sputtering apparatus includes electric coils wound on pole pieces to modulate the magnetic fields at the ends of the magnetron magnetic assembly. Changing the direction of electric current moves the sputtering region alternately around its normal central position to decrease the rate of erosion depth at the ends of the target material.

Abstract: A coating apparatus includes a deposition case, a reaction assembly, two precursors, a target, and a driving assembly. The deposition case includes a housing defining a cavity for receiving workpieces. The reaction assembly receives in the cavity and includes an outer barrel, an inner barrel, a plurality of nozzles, and a plurality of pipes. The outer barrel includes a main body and two protruding bodies. The main body and the inner barrel cooperatively define a first room therebetween. Each protruding body defines a second room communicating with the first room. The inner barrel defines a third room. The nozzles extend from the main body and communicate with the first room. The pipes extend from the inner barrel and communicate with the third room. The precursors receive in the second rooms. The target receives in the third room. The driving assembly drives the housing to rotate relative to the reaction assembly.

Abstract: Disclosed invention uses a coaxial microwave antenna to enhance ionization in PVD or IPVD. The coaxial microwave antenna increases plasma density homogeneously adjacent to a sputtering cathode or target that is subjected to a power supply. The coaxial microwave source generates electromagnetic waves in a transverse electromagnetic (TEM) mode. The invention also uses a magnetron proximate the sputtering cathode or target to further enhance the sputtering. Furthermore, for high utilization of expensive target materials, a target can rotate to improve the utilization efficiency. The target comprises dielectric materials, metals, or semiconductors. The target also has a cross section being substantially symmetric about a central axis that the target rotates around. The target may have a substantially circular or annular a cross section.

Abstract: To achieve an improved end block, in which heating by induction eddy currents, which may occur during AC sputtering, for example, is significantly reduced relative to known end blocks, an end block for a magnetron configuration having a rotating target comprises an end block housing having an attachment surface for attaching the end block on a support apparatus, a pivot bearing for rotatable mounting of the rotating target, and at least one current conduction apparatus which conducts current through the end block housing in operation of the end block. The end block housing is implemented so that each current path in the end block housing which encloses the current conduction apparatus has an interruption at least one point.

Abstract: A coating apparatus (100) for batch coating of substrates is presented. In the batch coater layers of a stack can be deposited by means of physical vapor deposition, by means of chemical vapor deposition or by a mixture of both processes. When compared to previous apparatus, the mixed mode process is particularly stable. This is achieved by using a rotatable magnetron (112) rather than the prior-art planar magnetrons. The apparatus is further equipped with a rotatable shutter that allows for concurrent or alternating process steps.

Abstract: An end block for a magnetron device having a rotatable target comprises an end block housing having a pivot bearing. The end block housing is adapted on its outer side for attachment on a support unit, and the pivot bearing is adapted on an end that is accessible from outside the end block housing, for connection to the rotatable target. The end block housing is movably attached on the support unit. A vacuum coating apparatus has a vacuum chamber, a magnetron device situated in the vacuum chamber, and a rotatable target rotatably mounted on at least one such end block.

Abstract: A sputter target for sputtering a silicon-containing film is provided. The target includes a silicon-containing sputter material layer, and a carrier for carrying the sputter material layer, wherein the sputter material layer contains less than 200 ppm iron.

Abstract: A magnetron sputtering device includes a main body and a magnet mounting system for receiving magnets. The magnet mounting system comprises a first annular member, a second annular member coaxially encasing the first member, a third annular member coaxially encasing the second member, a first driving device connected to the first annular member, a second driving device connected to the second annular member, and a third driving device connected to the third annular member. The first driving device, the second driving device, and the third driving device are respectively configured for driving the first annular member, the second annular member, and the third annular member to move along an axis of the first annular member.

Abstract: This invention relates to a coater for the coating, in particular, of large-area substrates by means of cathode sputtering, the coater having a coating chamber and, provided therein, a cathode assembly (2) where the material to be sputtered is located on a target (4) with a curved surface, the material to be sputtered being located, in particular, on the lateral surface of a cylinder, there being in a single coating chamber for a coherent coating zone at least three, preferably more, cathode assemblies (2) with rotatable, curved targets (4) positioned one beside the other.

Abstract: A cylindrical magnetron sputtering cathode comprises a rotatable cylindrical sputtering target, a magnet assembly that includes a plurality of Halbach magnet arrays disposed within the rotatable cylindrical sputtering target and a magnetic magnet support and field shaper disposed within the sputtering target and to which the magnet assembly is attached.

Abstract: Certain example embodiments of this invention relate to a rotatable magnetron sputtering target(s) for use in sputtering material(s) onto a substrate. In certain example embodiments, the target includes a cathode tube with a target material applied thereto via plasma spraying or the like. A bonding layer is provided on the tube, between the cathode tube and the target material. The bonding layer is thicker proximate at least one end portion of the target than at a central portion of the target in order to reduce the likelihood of burn-through to or of the cathode tube during sputtering.

Abstract: A vacuum pumping system and method in conjunction with a sputter reactor having a vacuum-pumped magnetron chamber sealed to the target backing plate. A main sputter chamber is vacuum sealed to the target front and cryo pumped. A bypass conduit and valve connect the magnetron and main chambers. A mechanical roughing pump connected to the magnetron chamber pumps the main chamber through the bypass conduit to less than 1 Torr before the bypass valve is closed and the cryo pump is opened and thereafter continues to pump the magnetron chamber to reduce the pressure differential across the target. A pressure differential switch connected across the bypass valve immediately open it whenever the pressure differential exceeds a limit, such as 20 Torr, for example when there is a leak or an electrical failure. The bypass conduit is also used in a venting procedure.

Abstract: A module to carry targets in a sputter deposition installation for coating two-sided substrates is described. The module is mountable to the installation through an interface flange that carries at least two targets with their associated magnet systems. When the module is mounted, the targets take positions at opposite sides of the two-sided substrate, while the magnet systems orient the sputter deposition towards the substrate. The module enables coating of both sides of the substrate in one single pass. Different configurations are described with gas distribution systems and additional substrate supports. An enclosure with adjustable blinds in order to reduce gas spreading is also included.

Abstract: The present invention is a device for controlling sputter coating deposition to at least one surface of at least one substrate. The device includes a magnetic structure having a plurality of electrically isolated and magnetically coupled magnetic pole piece structures. A plurality of magnetic concentric rings is mounted behind at least one target surface. A central upright common magnetic core connects the plurality of magnetic pole piece structures. A plurality of upright pole pieces arranged parallel to each other is attached to each of the magnetic pole piece structures and arranged at midpoints of the plurality of magnetic concentric rings. The magnetic structure includes a plurality of electromagnetic coils wound over the plurality of magnetic pole piece structures arranged to form sets of coils. The sets of coils can be energized in forward or reverse mode thereby impacting the target at a greater angle resulting in higher angle particle ejection.

Abstract: Disclosed is an invention that uses a coaxial microwave antenna as a primary plasma source in PVD. The coaxial microwave antenna is positioned inside a sputtering target. Instead of using a cathode assist in sputtering, microwaves generated from the coaxial microwave antenna may leak through the sputtering target that comprises a dielectric material to form microwave plasma outside the sputtering target. To further enhance plasma density, a magnetron or a plurality of magnetrons may be added inside the target to help confine secondary electrons. An electric potential may be formed between adjacent magnetrons and may further enhance ionization. To achieve directional control of the generated microwaves, a shield that comprises a dielectric material or dielectric material coated metal may be added proximate the coaxial microwave antenna. Furthermore, for high utilization of expensive target materials, a target can rotate to improve the utilization efficiency.

Abstract: The invention relates to a rotatable sputter target and to a method to manufacture such a sputter target. The sputter target comprises a target material and a magnet array located at the interior of the target material. The magnet array defines a central zone extending along the major part of the length of the target material and defines an end zone at each end of the central zone. The target material comprises a first material and a second material. The target material comprises the first material at least on the central zone and comprises the second material at least on the end zones. The second material has a lower sputter deposition rate than the first material. The second material is preferably applied by thermal spraying. The first material comprises a first element and the second material comprises a compound of the first element of the first material.

Abstract: A magnetron actuator for moving a magnetron in a nearly arbitrary radial and azimuthal path in the back of a target in a plasma sputter reactor. The magnetron includes two coaxial rotary shafts extending along the chamber central axis and coupled to two independently controllable rotary actuators. An epicyclic gear mechanism or a frog-leg structure mechanically couple the shafts to the magnetron to control its radial and azimuthal position. A vertical actuator moves the shafts vertically in tandem to vary the magnetron's separation from the target's back surface and compensate for erosion of the front surface. The rotary actuators may be separately coupled to the shafts or a rotatable ring gear may be coupled to the shafts through respectively fixed and orbiting idler gears. Two radially spaced sensors detect reflectors attached to the inner and outer arms of the epicyclic gear mechanism for homing of the controller.

Abstract: In some embodiments, the invention includes a cylindrical cathode target assembly for use in sputtering target material onto a substrate that comprises a generally cylindrical target, means for rotating the target about its axis during a sputtering operation, an elongated magnet carried within the target for generation of a plasma-containing magnetic field exterior to but adjacent the target, a framework for supporting the magnet against rotation within the target, and a power train for causing the magnet to oscillate within and axially of the target in a substantially asynchronous manner to promote generally uniform target utilization along its length, as well as its method of use. In some embodiments, the magnet is oscillated in response to rotation of the target.

Abstract: A support device for a magnetron arrangement with a rotating target includes a housing with a drive shaft mounted to rotate in the housing. An end of the drive shaft accessible from outside of the housing connects to the rotating target and another end lies within the housing for introduction of a torque. An electric motor with a stator and a rotor is arranged within the housing to generate a torque.

Abstract: A supply end block to supply a sputter cathode with a coolant and electrical voltage, includes a housing with a coolant connection and a current connection as well as a support shaft mounted to rotate, on which a target tube is fastened. The coolant connection and current connection are brought together directly at a feed site so that the coolant is brought to the potential of the applied electric voltage on entering the housing of the end block. Optimal cooling of the current feed is achieved, and optimal potential equalization of the coolant simultaneously occurs.

Abstract: To provide a sputtering apparatus and method, and a sputtering control program which are configured simply and can secure the uniformity of the film thickness from the beginning to the end of the use of a target. There are provided: a target 15 disposed so as to face an object to be treated 19; a permanent magnet unit M which generates a high-density plasma by means of a magnetic field and deposits a material of the target 15 on the object to be treated, in the form of a film; a rotational mechanism 9 which rotates the permanent magnet unit M; and a rotation number control apparatus 7 which gradually changes the number of rotations of the permanent magnet unit M rotated by the rotational mechanism 9.

Abstract: In one embodiment, a magnetron assembly comprises a plurality of magnets and a yoke configured to hold the plurality of magnets in at least four independent linear arrays. The plurality of magnets is arranged in the yoke so as to form a pattern comprising an outer portion and an inner portion. The outer portion substantially surrounds the perimeter of the inner portion. The magnets used to form the outer portion have a first polarity and the magnets used to form the inner portion having a second polarity. The outer portion of the pattern comprises a pair of elongated sections that are substantially parallel to one another. The outer portion of the pattern comprises a pair of turnaround sections, wherein each turnaround section substantially spans respective ends of the pair of elongated sections and wherein each turnaround section comprises a plurality of magnets having the first polarity. Other embodiments are described.