Methods and systems for preventing collisions between coarse and fine stages of positioning systems

Abstract

The problem of preventing collisions between the coarse and fine stages of a stage positioning module is addressed by methods and systems that use a back EMF in one or more coarse stage motors coupled to the coarse stage to determine an acceleration, velocity, or position of the coarse stage. This information can then be used to apply a force to a fine stage motor coupled to the fine stage or to the same or another coarse stage motor couple to the coarse stage. The applied force can prevent collisions between the coarse and fine stages during braking. Such methods and systems may prevent costly repairs that would be required if the coarse and fine stages were to collide.

Description

METHODS AND SYSTEMS FOR PREVENTING COLLISIONS BETWEEN COARSE AND FINE STAGES OF POSITIONING SYSTEMSCROSS-REFERENCE

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 714,135, entitled “METHODS AND SYSTEMS FOR PREVENTING COLLISIONS BETWEEN COARSE AND FINE STAGES OF POSITIONING SYSTEMS,” filed October 31, 2024, which is incorporated herein by reference in its entirety for all purposes.BACKGROUND OF THE INVENTION

[0002] Numerous positioning systems (such as those used in semiconductor wafer processing) utilize coarse and fine stages to position a substrate (such as a semiconductor wafer). The coarse stage is capable of quickly making large movements that bring the substate near to a desired position. The fine stage then makes relatively minor positioning adjustments to bring the substate to the desired position. Using such positioning systems, the substrate can be quickly moved to a desired position with a positioning error of as small as a few nanometers (nm). The coarse and fine stages are often close to one another, sometimes being located less than 1 millimeter (mm) apart. As such, sensors (such as optical sensors or capacity sensors) are often used to measure the accelerations, velocities, or positions of the coarse and fine stages. These measurements can then be used as feedback in controlling the motions of the coarse and fine stages to ensure that the coarse and fine stages do not collide with one another. Unfortunately, such sensors sometimes suffer from errors that prevent them from making such measurements. In such cases, braking is often applied to the motors that control the coarse and fine stages in an attempt to reduce the chances of the coarse and fine stages colliding with one another. However, because of the sensor error, such braking is often performed without any information regarding the accelerations, velocities, or positions of the coarse and fine stages,and the risk of such collisions remains. Accordingly, presented herein are methods and systems for estimating coarse or fine stage accelerations, velocities, or positions following such sensor errors and for using such estimates to prevent collisions between the coarse and fine stages.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Various embodiments of the invention are disclosed in the following detailed description and the accompanying drawings.

[0004] FIG. 1 shows a flowchart depicting an exemplary method for estimating an acceleration, velocity, or position of a coarse stage based on a measured back electromagnetic force (EMF) in a coarse stage motor and using the estimate to apply a force to a fine stage motor in order to avoid collisions between the coarse stage and a fine stage of a stage positioning module.

[0005] FIG. 2 shows a schematic depicting an exemplary system for estimating an acceleration, velocity, or position of a coarse stage based on a measured back EMF in a coarse stage motor and using the estimate to apply a force to a fine stage motor in order to avoid collisions between the coarse stage and a fine stage of a stage positioning module.

[0006] FIG. 3 shows a flowchart depicting an exemplary method for estimating an acceleration, velocity, or position of a coarse stage based on a measured back EMF in a first coarse stage motor and using the estimate to apply a force to a second coarse stage motor to avoid collisions between the coarse stage and a fine stage of a stage positioning module.

[0007] FIG. 4 shows a schematic depicting an exemplary system for estimating an acceleration, velocity, or position of a coarse stage based on a measured back EMF in a first coarse stage motor and using the estimate to apply a force to a second coarse stage motor to avoid collisions between the coarse stage and a fine stage of a stage positioning module.

[0008] FIG. 5 shows a block diagram of a computer system for performing the method of FIG. 1 or FIG. 3 or for use with the system of FIG. 2 or FIG. 4.DETAILED DESCRIPTION

[0009] The invention can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer readable storage medium; and / or a processor, such as a processor configured to execute instructions stored on and / or provided by a memory coupled to the processor. In this specification, these implementations, or any other form that the invention may take, may be referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the scope of the invention. Unless stated otherwise, a component such as a processor or a memory described as being configured to perform a task may be implemented as a general component that is temporarily configured to perform the task at a given time or a specific component that is manufactured to perform the task. As used herein, the term “processor” refers to one or more devices, circuits, and / or processing cores configured to process data, such as computer program instructions.

[0010] A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications, and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.

[0011] As used herein, the term “or” shall convey both disjunctive and conjunctive meanings, unless otherwise indicated or impossible. For instance, the phrase “A or B” shall beinterpreted to include element A alone, element B alone, and the combination of elements A and B. As another example, the phrase “A, B, or C’ shall be interpreted to include element A alone, element B alone, element C alone, the combination of elements A and B but not C, the combination of elements A and C but not B, the combination of elements B and C but not A, and the combination of elements, A, B, and C.

[0012] Recent work in automated positioning systems has led to the ability to rapidly move a substrate to within a few nm of a desired position. Such positioning systems generally utilize coarse and fine stages to position the substrate. The coarse stage is capable of quickly making large movements that bring the substrate near to a desired position. The fine stage then makes relatively minor positioning adjustments to bring the substrate to the desired position. Such positioning systems are especially important in applications, such as semiconductor wafer processing, that require exquisite alignment of the substrate as it is moved from one processing operation to another. For instance, semiconductor wafer processing may require a series of processing operations (such as multiple rounds of metal deposition, lithography, etching, and so forth on). Each such operation requires the semiconductor wafer to be precisely positioned prior to the operation in order to ensure that all electrical components on the semiconductor wafer are properly fabricated.

[0013] In such positioning systems, the coarse and fine stages are often close to one another, sometimes being located less than 1 mm apart. As such, sensors (such as optical sensors or Hall effect sensors) are often used to measure the accelerations, velocities, or positions of the coarse and fine stages. These measurements can then be used as feedback in controlling the motions of the coarse and fine stages to ensure that the coarse and fine stages do not collide with one another. Unfortunately, such sensors sometimes suffer from errors that prevent them from making such measurements. For instance, the sensors or associated electronics (such as amplifiers) may fail or experience sensor drift. In such cases, braking isoften applied to the motors that control the coarse and fine stages in an attempt to reduce the chances of the coarse and fine stages colliding with one another. However, because of the sensor error, such braking is often performed without any information regarding the accelerations, velocities, or positions of the coarse and fine stages, and the risk of such collisions remains.

[0014] As such, there is a need for methods and systems for estimating coarse or fine stage accelerations, velocities, or positions following such sensor errors and for using such estimates to prevent collisions between the coarse and fine stages.

[0015] Accordingly, the problem of estimating coarse or fine stage accelerations, velocities, or positions following such sensor errors and for using such estimates to prevent collisions between the coarse and fine stages is addressed by the methods and systems described herein. The methods and systems generally use a back EMF in one or more coarse stage motors coupled to the coarse stage to determine an acceleration, velocity, or position of the coarse stage. This information can then be used to apply a force to one or more fine stage motors coupled to the fine stage or to one or more coarse stage motors coupled to the coarse stage. The applied force can prevent collisions between the coarse and fine stages during braking. Such methods and systems may prevent costly repairs that would be required if the coarse and fine stages were to collide.

[0016] FIG. 1 shows a flowchart depicting an exemplary method 100 for estimating an acceleration, velocity, or position of a coarse stage based on a measured back EMF in a coarse stage motor and using the estimate to apply a force to a fine stage motor in order to avoid collisions between the coarse stage and a fine stage of a stage positioning module. In the example shown, a back EMF induced in one or more coarse stage motors is measured at 110. In some embodiments, the one or more coarse stage motors comprise linear motors. In some embodiments, the one or more coarse stage motors comprise three-phase linear motors. In someembodiments, the one or more coarse stage motors are coupled to (e.g., mounted to, on, in, above, below, or to a side of) a coarse stage of a stage positioning module. In some embodiments, the back EMF is measured by measuring an electric current or voltage across a sense resistor. In some embodiments, the sense resistor is coupled to (e.g., electrically coupled to) the one or more coarse stage motors. In some embodiments, the sense resistor is placed in series with the one or more coarse stage motors.

[0017] At 120, an acceleration, a velocity, or a position of the coarse stage is determined based on the measured back EMF. In some embodiments, the acceleration, velocity, or position is determined using any one or more of Equations (l)-(22) presented herein.

[0018] The back EMF Vb pof a coil p in the one or more coarse stage motors depends on the velocity of the coarse stage y, the back EMF constant kbof the coarse stage motor, and the magnetic flux phase 9pin the coil pVb.p = kby sin 0p (1)

[0019] Thus, the electric current Ipor voltage Vcs pmeasured by a sense resistor placed in series with a coil p of the one or more coarse stage motors is given by:

[0020] In Equation (2), 7?sis the resistance of the sense resistor, Lcis the inductance of the one or more coarse stage motors, s is the differential operator or Laplace variable, and Rcis the resistance of the one or more coarse stage motors. In Equation (2), it is assumed that the measurement is performed on an inactive coarse stage motor that is not being actively driven by an amplifier. For a three-phase motor with phases u, v, and w, sin29„ + sin20V+ sin20W= 3 / 2 and thus:

[0021] The norm of the three-phase current Inis given by:

[0022] In Equation (4), yQis the initial velocity of the coarse stage. For each coil phase p, the force Fpgenerated by the back EMF current Ipis given by:p= k1fsin 0„p p= k Jfk °hsin20np- Lcs+R - -c+RsJy (v5)7

[0023] In Equation (5), kj is the force constant of each individual phase. Thus, the overall braking force Fmotoron a coarse stage motor is:

[0024] Since the motor force constant kF= 3 / 2kf, the braking force on the coarse stage induced by the back EMF in a coarse stage motor is:Fmotor pln (7)

[0025] Acceleration of the coarse stage may be estimated with the braking forces from N coarse stage motors, the reaction force of the fine stage FFS. and the mass of the coarse stage Mcs'.a =77 (—FFS+ ^k=l Fmotor, k) (8)

[0026] Thus, in some embodiments, the acceleration of the coarse stage may be determined by: (i) determining, based on the measured back EMF, a braking force imparted on the coarse stage by the measured back EMF (i.e., using any one or more of Equations (l)-(7)); and (ii) determining, based on the braking force and a mass of the coarse stage, an acceleration imparted on the coarse stage by the braking force (i.e., using Equation (8)). Of course, a velocity' v and position y of the coarse stage may be calculated by integrating the acceleration, if the initial velocity and position of the coarse stage are known:v = JO a dt' (9)y = fn fnadt' dt‘ (10)

[0027] Alternatively, or in combination, the velocity of the coarse stage may be estimated directly from the back EMF of a coarse stage motor which is being actively driven by an amplifier. The electric current Ipor voltage Vcspmeasured by a sense resistor placed in series with a coil phase p of the one or more coarse stage motors is given by:

[0028] The back EMF is related to the voltage Vvspacross the input and output of an amplifier powering the coil p and the voltage Vcspmeasured by the sense resistor according to:

[0029] The back EMF may thus be directly determined from Vvspand Vcsp. Returning to Equation (1), the back EMF voltages from each phase of the coarse stage motor may be written as:vb,u=kt>ysin 0u (13) ycos 0u) (14)ycos 0u) (15)

[0030] Since Vu+ Vb v+ Vb w=the velocity may thus be estimated from the three-phase back EMF voltages as follows:

[0031] The sign of the velocity sign(y) may be determined from the initial velocity yQbefore the braking or deceleration begins. The position of the coarse stage may be determined by integrating the velocity:

[0032] Moreover, the position of the coarse stage may be estimated directly from the phase of the back EMF. Returning to Equations (13)-(15):Vb.u ~ Vb.v ~ Vb.w =by (sin 0u- sin (0u+ y) - sin (0u- y)) = 2 / cbysin 0u(18)Vb,v + Vb, w = kby (sin (0U+ y) + sin (0U- y)) = -kby sin 0U(19)Vb,v ~vb,w =kby (sin

[0033] Dividing Equation (18) by Equation (20), Equation (19) by Equation (20), and Equation (13) by Equation (20), and solving each of the resulting equations for 0U, we obtain:0

[0034] From the magnetic phase of the u-phase coil, the wrapped motor position y wrapped may be obtained as follows:

[0035] Here, Lpitchis the magnetic pitch (i.e., the distance between two consecutive north poles of the motor). Since the output of the arctangent functions in Equations (21)-(23)[ TC Tri— -, - I, an unwrapping treatment may be used to obtain the motor position estimate y beyond the magnetic pitch range:yUnwrap y wrapped)' (25)

[0036] Thus, in some embodiments, the velocity of the coarse stage may be determined based on the acceleration (i.e., using Equation (9) or Equation (16)) and the position of the coarse stage may be determined based on the velocity (i.e., using Equation (10), Equation (17), or the procedure outlined in Equations (21)-(25)).

[0037] At 130, a force is applied to one or more fine stage motors coupled to a fine stage of the stage positioning module based on the acceleration, velocity, or position of the coarse stage. In some embodiments, the force applied to the one or more fine stage motors prevents, mitigates, or reduces (e.g., by decreasing the relative speed between the coarse stage and the fine stage at a point of collision, if such a collision cannot be completely avoided) the impact of a collision between the coarse stage and the fine stage. In some embodiments, the force is determined using Equation (26) presented herein.

[0038] Since the force on a body may be simply approximated as its mass times its acceleration, two bodies (e.g., the coarse stage and the fine stage) may be accelerated or decelerated at the same rate by setting the quotient of each body’s force and its mass equal to one another. Decelerating the coarse stage and the fine stage at the same rate will avoid a collision. Since the deceleration of the coarse stage (of mass Mcs) is due to the braking force Fcson the coarse stage, a force FFSmay be applied to the fine stage (of mass MFS) to decelerate the fine stage at the same rate as the coarse stage:

[0039] In some embodiments, the force FFSis imparted using the one or more fine stage motors, which may comprise linear motors or single-phase linear motors.

[0040] In some embodiments, operations 110, 120, and 130 of the method 100 are implemented in response detecting a fault in one or more sensors (such as optical or capacity sensors) that are configured to determine one or more accelerations, velocities, or positions of the coarse stage or the fine stage. Thus, in some embodiments, the method 100 further comprises, prior to operation 110, detecting a fault condition in one or more of the sensors.

[0041] FIG. 2 shows a schematic depicting an exemplary system 200 for estimating an acceleration, velocity, or position of a coarse stage based on a measured back EMF in a coarse stage motor and using the estimate to apply a force to a fine stage motor in order to avoidcollisions between the coarse stage and a fine stage of a stage positioning module. In the example shown, the system 200 comprises a coarse stage 210. In some embodiments, the coarse stage 210 comprises or is coupled to one or more coarse stage motors 212. Although only one coarse stage motor 212 is depicted in FIG. 2, in some embodiments, the coarse stage 210 comprises or is coupled to at least about 1, 2, 3, 4, or more coarse stage motors, at most about 4, 3, 2, or 1 coarse stage motors, or a number of coarse stage motors that is within a range defined by any two of the preceding values. In some embodiments, the one or more coarse stage motors 212 comprise linear motors. In some embodiments, the one or more coarse stage motors 212 comprise three-phase linear motors.

[0042] In the example shown, the system 200 comprises a fine stage 220. In some embodiments, the fine stage 220 comprises or is coupled to one or more fine stage motors 222. Although only one fine stage motor 222 is depicted in FIG. 2, in some embodiments, the fine stage 220 comprises or is coupled to at least about 1, 2, 3, 4, or more fine stage motors, at most about 4, 3, 2, or 1 fine stage motors, or a number of fine stage motors that is within a range defined by any two of the preceding values. In some embodiments, the one or more fine stage motors 222 comprise linear motors. In some embodiments, the one or more fine stage motors 222 comprise single-phase linear motors.

[0043] In the example shown, the system 200 comprises one or more back EMF sensors 230. In some embodiments, the one or more back EMF sensors 230 are configured to measure a back EMF induced in the one or more coarse stage motors 212. In some embodiments, the one or more back EMF sensors 230 are configured to measure the back EMF by measuring an electric current or voltage across a sense resistor (not shown in FIG. 2) coupled to the one or more coarse stage motors 212. In some embodiments, the sense resistor is placed in series with the one or more coarse stage motors 212. as described herein with respect to method 100 of FIG. 1.

[0044] In the example shown, the system comprises a controller 240. In some embodiments, the controller comprises the computer system 500 described herein with respect to FIG. 5. In some embodiments, the controller 240 is configured to: (a) based on the measured back EMF, determine an acceleration, a velocity, or a position of the coarse stage 210; and (b) based on the acceleration, velocity,, or position of the coarse stage 210, direct the one or more fine stage motors 222 to apply a force to the fine stage 220 to thereby prevent a collision between the coarse stage 210 and the fine stage 220. In some embodiments, (a) comprises: (i) determining, based on the measured back EMF, a braking force imparted on the coarse stage 210 by the measured back EMF; and (ii) determining, based on the braking force and a mass of the coarse stage 210, an acceleration imparted on the coarse stage 210 by the braking force. In some embodiments, (a) further comprises: (iii) determining, based on the acceleration, a velocity of the coarse stage 210. In some embodiments, (a) further comprises: (iv) determining, based on the velocity, a position of the coarse stage 210. In some embodiments, the controller 240 performs (a)(i), (a)(ii), (a)(iii), (a)(iv), or (b) using the principles described herein with respect to operations 120 and 130 of method 100 of FIG. 1 and with respect to Equations (1)-(25).

[0045] In some embodiments, the system 200 further comprises one or more sensors (such as optical or capacity sensors, not shown in FIG. 2). In some embodiments, the one or more sensors are configured to determine one or more accelerations, velocities, or positions of the coarse stage 210 or the fine stage 220, as described herein with respect to method 100 of FIG. 1. In some embodiments, the controller 240 is configured to perform (a)(i), (a)(ii), (a)(iii), (a)(iv), or (b) in response to a detecting a fault condition in the one or more sensors.

[0046] FIG. 3 shows a flowchart depicting an exemplary method 300 for estimating an acceleration, velocity, or position of a coarse stage based on a measured back EMF in a first coarse stage motor and using the estimate to apply a force to a second coarse stage motor inorder to avoid collisions between the coarse stage and a fine stage of a stage positioning module. In the example shown, a back EMF induced in a first coarse stage motor is measured at 310. In some embodiments, the first coarse stage motor comprises a linear motor. In some embodiments, the first coarse stage motor comprises a three-phase linear motor. In some embodiments, the first coarse stage motor is coupled to (e.g., mounted to, on, in, above, below, or to a side of) a coarse stage of a stage positioning module. In some embodiments, the back EMF is measured by measuring an electric current or voltage across a sense resistor. In some embodiments, the sense resistor is coupled to (e.g., electrically coupled to) the first coarse stage motor. In some embodiments, the sense resistor is placed in series with the first coarse stage motor.

[0047] At 320, an acceleration, a velocity, or a position of the coarse stage is determined based on the measured back EMF. In some embodiments, the acceleration, velocity, or position is determined using any one or more of Equations (l)-(25) presented herein.

[0048] Thus, in some embodiments, the acceleration of the coarse stage may be determined by: (i) determining, based on the measured back EMF, a braking force imparted on the coarse stage by the measured back EMF (i.e., using any one or more of Equations (l)-(7)); and (ii) determining, based on the braking force and a mass of the coarse stage, an acceleration imparted on the coarse stage by the braking force (i.e., using Equation (8)). Further, in some embodiments, the velocity of the coarse stage may be determined based on the acceleration (i.e., using Equation (9) or Equation (16)) and the position of the coarse stage may be determined based on the velocity (i.e., using Equation (10), Equation (17), or the procedure outlined in Equations (21)-(25)).

[0049] At 330. a force is applied to a second coarse stage motor coupled to the coarse stage based on the acceleration, velocity, or position of the coarse stage. In some embodiments,the second coarse stage motor comprises a linear motor. In some embodiments, the second coarse stage motor comprises a three-phase linear motor. In some embodiments, the force applied to the second coarse stage motor prevents, mitigates, or reduces (e.g., by decreasing the relative speed between the coarse stage and a fine stage of the stage positioning module at a point of collision, if such a collision cannot be completely avoided) the impact of a collision between the coarse stage and the fine stage. In some embodiments, the force is determined using Equation (27):

[0050] Here, ydis an intended position for the coarse stage at time t, y is the actual (measured) position of the coarse stage at time t, ydis an intended velocity for the coarse stage at time t, and y is the actual (measured) velocity of the coarse stage at time t. Thus, the intended and measured positions and velocities of the coarse stage can be used for feedback to control the force applied to the coarse stage in order to direct the coarse stage to slow along a well-defined, predictable trajectory..

[0051] In some embodiments, the fine stage comprises or is coupled to one or more fine stage motors. In some embodiments, the one or more fine stage motors comprise linear motors. In some embodiments, the one or more fine stage motors comprise single-phase linear motors.

[0052] In some embodiments, operations 310, 320, and 330 of the method 300 are implemented in response detecting a fault in one or more sensors (such as optical or Hall effect sensors) that are configured to determine one or more accelerations, velocities, or positions of the coarse stage or the fine stage. Thus, in some embodiments, the method 300 further comprises, prior to operation 310, detecting a fault condition in one or more of the sensors.

[0053] Although FIG. 3 depicts an embodiment in which the acceleration, velocity, or position of the coarse stage is determined based on a measured back EMF in the first coarsestage motor, and the force is applied to the second coarse stage motor to thereby prevent a collision between the coarse stage and the fine stage, the disclosure is not intended to be so limiting. For instance, the acceleration, velocity, or position of the coarse stage may be determined based on a measured back EMF in the second coarse stage motor, and the force may be applied to the first coarse stage motor. As another example, the acceleration, velocity, or position of the coarse stage may be determined based on a measured back EMF in the first coarse stage motor, and the force may be applied to the first coarse stage motor. As another example, the acceleration, velocity, or position of the coarse stage may be determined based on a measured back EMF in the second coarse stage motor, and the force may be applied to the second coarse stage motor. As yet another example, the acceleration, velocity, or position of the coarse stage may be determined based on a measured back EMF in both the first and second coarse stage motors, and the force may be applied to both the first and second coarse stage motors. Thus, in some embodiments, the first and second coarse stage motors are the same. In some embodiments, the first and second coarse stage motors are different.

[0054] FIG. 4 shows a schematic depicting an exemplary system 400 for estimating an acceleration, velocity, or position of a coarse stage based on a measured back EMF in a first coarse stage motor and using the estimate to apply a force to a second coarse stage motor in order to avoid collisions between the coarse stage and a fine stage of a stage positioning, module.

[0055] In the example shown, the system 400 comprises a coarse stage 410. In some embodiments, the coarse stage 410 comprises or is coupled to a first coarse stage motor 412 and a second coarse stage motor 414. Although only two coarse stage motors 412 and 414 are depicted in FIG. 4, in some embodiments, the coarse stage 410 comprises or is coupled to at least about 2, 3, 4. or more coarse stage motors, at most about 4. 3, or 2 coarse stage motors, or a number of coarse stage motors that is within a range defined by any two of the precedingvalues. In some embodiments, the first coarse stage motor 412 or the second coarse stage motor 414 comprises a linear motor. In some embodiments, the first coarse stage motor 412 or the second coarse stage motor 414 comprises a three-phase linear motor.

[0056] In the example shown, the system 400 comprises a fine stage 420. In some embodiments, the fine stage 420 comprises or is coupled to one or more fine stage motors 422. Although only one fine stage motor 422 is depicted in FIG. 4, in some embodiments, the fine stage 420 comprises or is coupled to at least about 1, 2, 3, 4, or more fine stage motors, at most about 4, 3, 2, or 1 fine stage motors, or a number of fine stage motors that is within a range defined by any two of the preceding values. In some embodiments, the one or more fine stage motors 422 comprise linear motors. In some embodiments, the one or more fine stage motors 422 comprise single-phase linear motors.

[0057] In the example shown, the system 400 comprises one or more back EMF sensors 430. In some embodiments, the one or more back EMF sensors 430 are configured to measure a back EMF induced in the one or more coarse stage motors 412. In some embodiments, the one or more back EMF sensors 430 are configured to measure the back EMF by measuring an electric current or voltage across a sense resistor (not shown in FIG. 4) coupled to the first coarse stage motor 412. In some embodiments, the sense resistor is placed in series with the first coarse stage motor 412, as described herein with respect to method 300 of FIG. 3.

[0058] In the example shown, the system comprises a controller 440. In some embodiments, the controller comprises the computer system 500 described herein with respect to FIG. 5. In some embodiments, the controller 440 is configured to: (a) based on the measured back EMF, determine an acceleration, a velocity, or a position of the coarse stage 410; and (b) based on the acceleration, velocity, or position of the coarse stage 410, direct the second coarse stage motor 414 to apply a force to the coarse stage 420 to thereby prevent a collision between the coarse stage 410 and the fine stage 420. In some embodiments, (a) comprises: (i)determining, based on the measured back EMF, a braking force imparted on the coarse stage 410 by the measured back EMF; and (ii) determining, based on the braking force and a mass of the coarse stage 410, an acceleration imparted on the coarse stage 410 by the braking force. In some embodiments, (a) further comprises: (iii) determining, based on the acceleration, a velocity, of the coarse stage 410. In some embodiments, (a) further comprises: (iv) determining, based on the velocity, a position of the coarse stage 410. In some embodiments, the controller 440 performs (a)(i), (a)(ii), (a)(iii), (a)(iv), or (b) using the principles described herein with respect to operations 320 and 330 of method 300 of FIG. 3 and with respect to Equations (1)-(25).

[0059] In some embodiments, the system 400 further comprises one or more sensors (such as optical or Hall effect sensors, not shown in FIG. 4). In some embodiments, the one or more sensors are configured to determine one or more accelerations, velocities, or positions of the coarse stage 410 or the fine stage 420, as described herein with respect to method 300 of FIG. 3. In some embodiments, the controller 440 is configured to perform (a)(i), (a)(ii), (a)(iii), (a)(iv), or (b) in response to a detecting a fault condition in the one or more sensors.

[0060] Although FIG. 4 depicts an embodiment in which the acceleration, velocity, or position of the coarse stage is determined based on a measured back EMF in the first coarse stage motor, and the force is applied to the second coarse stage motor to thereby prevent a collision between the coarse stage and the fine stage, the disclosure is not intended to be so limiting. For instance, the acceleration, velocity, or position of the coarse stage may be determined based on a measured back EMF in the second coarse stage motor, and the force may be applied to the first coarse stage motor. As another example, the acceleration, velocity, or position of the coarse stage may be determined based on a measured back EMF in the first coarse stage motor, and the force may be applied to the first coarse stage motor. As another example, the acceleration, velocity, or position of the coarse stage may be determined basedon a measured back EMF in the second coarse stage motor, and the force may be applied to the second coarse stage motor. As yet another example, the acceleration, velocity, or position of the coarse stage may be determined based on a measured back EMF in both the first and second coarse stage motors, and the force may be applied to both the first and second coarse stage motors.

[0061] Additionally, systems are disclosed that can be used to perform any of the methods 100 and 300, respectively, of FIGs. 1 and 3, or any of operations 120, 130, 320, and 330 described herein. In some embodiments, the systems comprise one or more processors and memory coupled to the one or more processors. In some embodiments, the one or more processors are configured to implement one or more operations of method 100 or 300, such as any of operations 120, 130, 320, and 330. In some embodiments, the memory is configured to provide the one or more processors with instructions corresponding to the operations. In some embodiments, the instructions are embodied in a tangible computer readable storage medium.

[0062] FIG. 5 is a block diagram of a computer system 500 used in some embodiments to perform portions of the methods for avoiding collisions between a coarse stage and a fine stage of a stage positioning module described herein. In some embodiments, the computer system 500 may be utilized as a component in systems for avoiding collisions between a coarse stage and a fine stage of a stage positioning module described herein. FIG. 5 illustrates one embodiment of a general-purpose computer system. Other computer system architectures are possible. System 500, made up of various subsystems described below, includes at least one microprocessor subsystem 501. In some embodiments, the microprocessor subsystem comprises at least one central processing unit (CPU) or graphical processing unit (GPU). The microprocessor subsystem can be implemented by a single-chip processor or by multiple processors. In some embodiments, the microprocessor subsystem is a general-purpose digital processor which controls the operation of the computer system 500. Using instructionsretrieved from memory 504, the microprocessor subsystem controls the reception and manipulation of input data, and the output and display of data on output devices.

[0063] The microprocessor subsy stem 501 is coupled bi-directionally with memory 504, which can include a first primary storage, typically a random- access memory (RAM), and a second primary' storage area, typically a read-only memory (ROM). As is well known in the art, primary' storage can be used as a general storage area and as scratch-pad memory', and can also be used to store input data and processed data. It can also store programming instructions and data, in the form of data objects and text objects, in addition to other data and instructions for processes operating on microprocessor subsystem. Also, as well known in the art, primary storage typically includes basic operating instructions, program code, data and objects used by the microprocessor subsystem to perform its functions. Primary storage devices 504 may include any suitable computer-readable storage media, described below, depending on whether, for example, data access needs to be bi-directional or uni-directional. The microprocessor subsystem 501 can also directly and very rapidly retrieve and store frequently needed data in a cache memory (not shown).

[0064] A removable mass storage device 505 provides additional data storage capacity for the computer system 500, and is coupled either bi-directionally (read / write) or unidirectionally (read only) to microprocessor subsystem 501. Storage 505 may also include computer-readable media such as magnetic tape, flash memory, signals embodied on a carrier wave, PC-CARDS, portable mass storage devices, holographic storage devices, and other storage devices. A fixed mass storage 509 can also provide additional data storage capacity. The most common example of mass storage 509 is a hard disk drive. Mass storage 505 and 509 generally store additional programming instructions, data, and the like that typically are not in active use by the processing subsystem. It will be appreciated that the information retained within mass storage 505 and 509 may be incorporated, if needed, in standard fashion as part ofprimary storage 504 (e.g., RAM) as virtual memory.

[0065] In addition to providing processing subsystem 501 access to storage subsystems, bus 506 can be used to provide access other subsystems and devices as well. In the described embodiment, these can include a display monitor 508, a network interface 507, a keyboard 502, and a pointing device 503, as well as an auxiliary input / output device interface, a sound card, speakers, and other subsystems as needed. The pointing device 503 may be a mouse, stylus, track ball, or tablet, and is useful for interacting with a graphical user interface.

[0066] The network interface 507 allows the processing subsystem 501 to be coupled to another computer, computer network, or telecommunications network using a network connection as shown. Through the network interface 507, it is contemplated that the processing subsystem 501 might receive information, e.g., data objects or program instructions, from another network, or might output information to another network in the course of performing the above-described method steps. Information, often represented as a sequence of instructions to be executed on a processing subsystem, may be received from and outputted to another network, for example, in the form of a computer data signal embodied in a carrier wave. An interface card or similar device and appropriate software implemented by processing subsystem 501 can be used to connect the computer system 500 to an external network and transfer data according to standard protocols. That is, method embodiments of the present invention may execute solely upon processing subsystem 501, or may be performed across a network such as the Internet, intranet networks, or local area networks, in conjunction with a remote processing subsystem that shares a portion of the processing. Additional mass storage devices (not shown) may also be connected to processing subsystem 501 through network interface 507.

[0067] An auxiliary I / O device interface (not shown) can be used in conjunction with computer system 500 and can include general and customized interfaces that allow the processing subsystem 501 to send and receive data from other devices such as microphones,touch-sensitive displays, transducer card readers, tape readers, voice or handwriting recognizers, biometrics readers, cameras, portable mass storage devices, and other computers.

[0068] Embodiments of the present invention further relate to computer storage products with a computer readable medium that contains program code for performing various computer-implemented operations. The computer-readable medium is any data storage device that can store data which can thereafter be read by a computer system. The media and program code may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well known to those of ordinary skill in the computer software arts. Examples of computer-readable media include, but are not limited to, all the media mentioned above: magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROM disks; magneto-optical media such as floptical disks; and specially configured hardware devices such as application-specific integrated circuits (ASICs), programmable logic devices (PLDs), and ROM and RAM devices. The computer-readable medium can also be distributed as a data signal embodied in a carrier wave over a network of coupled computer systems so that the computer-readable code is stored and executed in a distributed fashion. Examples of program code include both machine code, as produced, for example, by a compiler, or files containing higher level code that may be executed using an interpreter. The computer system shown in FIG. 5 is but an example of a computer system suitable for use with the invention. Other computer systems suitable for use with the invention may include additional or fewer subsystems. In addition, bus 506 is illustrative of any interconnection scheme serving to link the subsystems. Other computer architectures having different configurations of subsystems may also be utilized.RECITATION OF EMBODIMENTS

[0069] Embodiment 1. A method comprising:a. measuring a back electromagnetic force (EMF) induced in one or more coarse stage motors coupled to a coarse stage of a stage positioning module;b. based on the measured back EMF, determining an acceleration, a velocity,, or a position of the coarse stage;c. based on the acceleration, velocity,, or position of the coarse stage, applying a force to one or more fine stage motors coupled to a fine stage of the stage positioning module to thereby prevent a collision between the coarse stage and the fine stage.

[0070] Embodiment 2. The method of Embodiment 1, wherein (a) comprises measuring an electric current or voltage across a sense resistor coupled to the one or more coarse stage motors.

[0071] Embodiment 3. The method of Embodiment 1 or 2, wherein (b) comprises:i) determining, based on the measured back EMF, a braking force imparted on the coarse stage by the measured back EMF; and ii) determining, based on the braking force and a mass of the coarse stage, an acceleration imparted on the coarse stage by the braking force.

[0072] Embodiment 4. The method of Embodiment 3, wherein (b) further comprises:iii) determining, based on the acceleration, a velocity of the coarse stage.

[0073] Embodiment 5. The method of Embodiment 4, wherein (b) further comprises:iv) determining, based on the velocity, a position of the coarse stage.

[0074] Embodiment 6. The method of any one of Embodiments 1-5. wherein the one or more coarse stage motors comprise linear motors.

[0075] Embodiment 7. The method of Embodiment 6, wherein the one or more coarsestage motors comprise three-phase linear motors.

[0076] Embodiment 8. The method of any one of Embodiments 1-7, wherein the one or more fine stage motors comprise linear motors.

[0077] Embodiment 9. The method of Embodiment 8, wherein the one or more fine stage motors comprise single-phase linear motors.

[0078] Embodiment 10. The method of any one of Embodiments 1-9, further comprising, prior to (a), detecting a fault condition in one or more sensors, wherein the one or more sensors are configured to determine one or more accelerations, velocities, or positions of the coarse stage or the fine stage.

[0079] Embodiment 11. A system comprising:a coarse stage comprising one or more coarse stage motors;a fine stage comprising one or more fine stage motors;one or more back EMF sensors configured to measure a back EMF induced in the one or more coarse stage motors; anda controller configured to:a. based on the measured back EMF, determine an acceleration, a velocity, or a position of the coarse stage; andb. based on the acceleration, velocity, or position of the coarse stage, direct the one or more fine stage motors to apply a force to the fine stage to thereby prevent a collision between the coarse stage and the fine stage.

[0080] Embodiment 12. The system of Embodiment 11. wherein the one or more back EMF sensors measure the back EMF by measuring an electric current or voltage across a sense resistor coupled to the one or more coarse stage motors.

[0081] Embodiment 13. The system of Embodiment 11 or 12, wherein (a) comprises:i) determining, based on the measured back EMF. a braking force impartedon the coarse stage by the measured back EMF; and ii) determining, based on the braking force and a mass of the coarse stage, an acceleration imparted on the coarse stage by the braking force.

[0082] Embodiment 14. The system of Embodiment 13, wherein (a) further comprises:iii) determining, based on the acceleration, a velocity of the coarse stage.

[0083] Embodiment 15. The system of Embodiment 14, wherein (a) further comprises:iv) determining, based on the velocity, a position of the coarse stage.

[0084] Embodiment 16. The system of any one of Embodiments 11-15, wherein the one or more coarse stage motors comprise linear motors.

[0085] Embodiment 17. The system of Embodiment 16, wherein the one or more coarse stage motors comprise three-phase linear motors.

[0086] Embodiment 18. The system of any one of Embodiments 11-17, wherein the one or more fine stage motors comprise linear motors.

[0087] Embodiment 19. The system of Embodiment 18, wherein the one or more fine stage motors comprise single-phase linear motors.

[0088] Embodiment 20. The system of any one of Embodiments 11-19, further comprising one or more sensors configured to determine one or more accelerations, velocities, or positions of the coarse stage or the fine stage; wherein the controller is configured to perform (a)-(b) in response to detecting a fault condition in the one or more sensors.

[0089] Embodiment 21. A method comprising:a. measuring a back electromagnetic force (EMF) induced in a first coarse stage motor coupled to a coarse stage of a stage positioning module;b. based on the measured back EMF, determining an acceleration, a velocity, or a position of the coarse stage;c. based on the acceleration, velocity, or position of the coarse stage, applying aforce to a second coarse stage motor coupled to the coarse stage to thereby prevent a collision between the coarse stage and a fine stage of the stage positioning module.

[0090] Embodiment 22. The method of Embodiment 21, wherein (a) comprises measuring an electric current or voltage across a sense resistor coupled to the first coarse stage motor.

[0091] Embodiment 23. The method of Embodiment 21 or 22, wherein (b) comprises:i) determining, based on the measured back EMF, a braking force imparted on the coarse stage by the measured back EMF; and ii) determining, based on the braking force and a mass of the coarse stage, an acceleration imparted on the coarse stage by the braking force.

[0092] Embodiment 24. The method of Embodiment 23, wherein (b) further comprises:iii) determining, based on the acceleration, a velocity of the coarse stage.

[0093] Embodiment 25. The method of Embodiment 24, wherein (b) further comprises:iv) determining, based on the velocity, a position of the coarse stage.

[0094] Embodiment 26. The method of any one of Embodiments 21-25, wherein the first or second coarse stage motor comprises a linear motor.

[0095] Embodiment 27. The method of Embodiment 26, wherein the first or second coarse stage motor comprises a three-phase linear motor.

[0096] Embodiment 28. The method of any one of Embodiments 21-27, wherein the fine stage comprises one or more fine stage motors and wherein the one or more fine stage motors comprise linear motors.

[0097] Embodiment 29. The method of Embodiment 28, wherein the one or more fine stage motors comprise single-phase linear motors.

[0098] Embodiment 30. The method of any one of Embodiments 21-29, furthercomprising, prior to (a), detecting a fault condition in one or more sensors, wherein the one or more sensors are configured to determine one or more accelerations, velocities, or positions of the coarse stage or the fine stage.

[0099] Embodiment 31. The method of any one of Embodiments 21-30, wherein the first and second coarse stage motors are the same.

[0100] Embodiment 32. The method of any one of Embodiments 21-30, wherein the first and second coarse stage motors are different.

[0101] Embodiment 33. A system comprising:a coarse stage comprising a first coarse stage motor and a second coarse stage motor;a fine stage comprising one or more fine stage motors;one or more back EMF sensors configured to measure a back EMF induced in the first coarse stage motor; anda controller configured to:a. based on the measured back EMF, determine an acceleration, a velocity, or a position of the coarse stage; andb. based on the acceleration, velocity, or position of the coarse stage, direct the second coarse stage motor to apply a force to the course stage to thereby prevent a collision between the coarse stage and a fine stage of the stage positioning module.

[0102] Embodiment 34. The system of claim 33, wherein the one or more back EMF sensors measure the back EMF by measuring an electric current or voltage across a sense resistor coupled to the first coarse stage motor.

[0103] Embodiment 35. The system of Embodiment 33 or 34, wherein (b) comprises:i) determining, based on the measured back EMF. a braking force impartedon the coarse stage by the measured back EMF; and ii) determining, based on the braking force and a mass of the coarse stage, an acceleration imparted on the coarse stage by the braking force.

[0104] Embodiment 36. The system of Embodiment 35, wherein (b) further comprises:iii) determining, based on the acceleration, a velocity of the coarse stage.

[0105] Embodiment 37. The system of Embodiment 36, wherein (b) further comprises:iv) determining, based on the velocity, a position of the coarse stage.

[0106] Embodiment 38. The system of any one of Embodiments 33-37, wherein the first or second coarse stage motor comprises a linear motor.

[0107] Embodiment 39. The system of Embodiment 38, wherein the first or second coarse stage motor comprise a three-phase linear motors.

[0108] Embodiment 40. The system of any one of Embodiments 33-39, wherein the one or more fine stage motors comprise linear motors.

[0109] Embodiment 41. The system of Embodiment 40, wherein the one or more fine stage motors comprise single-phase linear motors.

[0110] Embodiment 42. The system of any one of Embodiments 33-41, further comprising, prior to (a), detecting a fault condition in one or more sensors, wherein the one or more sensors are configured to determine one or more accelerations, velocities, or positions of the coarse stage or the fine stage.

[0111] Embodiment 43. The system of any one of Embodiments 33-42, wherein the first and second coarse stage motors are the same.

[0112] Embodiment 44. The system of any one of Embodiments 33-42, wherein the first and second coarse stage motors are different.

Claims

CLAIMS1. A method comprising:a) measuring a back electromagnetic force (EMF) induced in one or more coarse stage motors coupled to a coarse stage of a stage positioning module; b) based on the measured back EMF, determining an acceleration, a velocity,, or a position of the coarse stage;c) based on the acceleration, velocity,, or position of the coarse stage, applying a force to one or more fine stage motors coupled to a fine stage of the stage positioning module to thereby prevent a collision between the coarse stage and the fine stage.

2. The method of claim 1, wherein (a) comprises measuring an electric current or voltage across a sense resistor coupled to the one or more coarse stage motors.

3. The method of claim 1 or 2, wherein (b) comprises:i) determining, based on the measured back EMF, a braking force imparted on the coarse stage by the measured back EMF; and ii) determining, based on the braking force and a mass of the coarse stage, an acceleration imparted on the coarse stage by the braking force.

4. The method of claim 3, wherein (b) further comprises:iii) determining, based on the acceleration, a velocity of the coarse stage.

5. The method of claim 4, wherein (b) further comprises:iv) determining, based on the velocity, a position of the coarse stage.

6. The method of any one of claims 1-5, wherein the one or more coarse stage motors comprise linear motors.

7. The method of claim 6, wherein the one or more coarse stage motors comprise three- phase linear motors.

8. The method of any one of claims 1-7, wherein the one or more fine stage motors comprise linear motors.

9. The method of claim 8, wherein the one or more fine stage motors comprise singlephase linear motors.

10. The method of any one of claims 1-9, further comprising, prior to (a), detecting a fault condition in one or more sensors, wherein the one or more sensors are configured to determine one or more accelerations, velocities, or positions of the coarse stage or the fine stage.

11. A system comprising:a coarse stage comprising one or more coarse stage motors;a fine stage comprising one or more fine stage motors;one or more back EMF sensors configured to measure a back EMF induced in the one or more coarse stage motors; anda controller configured to:a) based on the measured back EMF, determine an acceleration, a velocity, or a position of the coarse stage; andb) based on the acceleration, velocity, or position of the coarse stage, direct the one or more fine stage motors to apply a force to the fine stage to thereby prevent a collision between the coarse stage and the fine stage.

12. The system of claim 11, wherein the one or more back EMF sensors measure the back EMF by measuring an electric current or voltage across a sense resistor coupled to the one or more coarse stage motors.

13. The system of claim 11 or 12, wherein (a) comprises:i) determining, based on the measured back EMF. a braking force impartedon the coarse stage by the measured back EMF; andii) determining, based on the braking force and a mass of the coarse stage, an acceleration imparted on the coarse stage by the braking force.

14. The system of claim 13, wherein (a) further comprises:iii) determining, based on the acceleration, a velocity of the coarse stage.

15. The system of claim 14, wherein (a) further comprises:iv) determining, based on the velocity, a position of the coarse stage.

16. The system of any one of claims 11-15, wherein the one or more coarse stage motors comprise linear motors.

17. The system of claim 16, wherein the one or more coarse stage motors comprise three- phase linear motors.

18. The system of any one of claims 11-17, wherein the one or more fine stage motors comprise linear motors.

19. The system of claim 18, wherein the one or more fine stage motors comprise singlephase linear motors.

20. The system of any one of claims 11-19, further comprising one or more sensors configured to determine one or more accelerations, velocities, or positions of the coarse stage or the fine stage; wherein the controller is configured to perform (a)-(b) in response to detecting a fault condition in the one or more sensors.

Images