A design method for a driving device of a fast reflector

Abstract

A method for designing a driving device for a fast reflector includes the following steps: calculating motor parameters based on the target design parameters of the primary driving device driving the fast reflector; selecting a motor model based on the motor parameters; calculating the maximum tension of the first spring under different postures of the fast reflector based on the motor holding force, and designing the first spring based on the maximum tension of the first spring under different postures; calculating PZT parameters based on the target design parameters of the secondary driving device driving the fast reflector, and selecting a PZT model based on the PZT parameters; calculating the static holding force of the PZT, and designing a second spring based on the static holding force of the PZT. Considering that the PZT needs to meet the resolution, stroke, stiffness, etc. required by the fast reflector, a suitable PZT is selected and a reasonable spring size is designed; considering the resolution, stroke, thrust, etc. required by the motor for the fast reflector, a suitable motor is selected and a reasonable spring is designed to ensure that the static holding force on the motor is less than the motor thrust, and to ensure structural stability.

Description

Technical Field

[0001] This invention relates to the field of lithography machine technology, and more specifically to a design method for a driving device for a fast-reflecting mirror. Background Technology

[0002] The fast mirror (FSM) is a core component of the beam stabilization unit in a lithography machine's illumination system, enabling the deflection of the beam's position and direction. The beam stabilization unit in a lithography machine's illumination system requires the FSM to have a large stroke, high precision, fast dynamic response, and a relatively large mirror size. Therefore, the design of the fast mirror's driving mechanism is of paramount importance. Summary of the Invention

[0003] To address the question of how to design a driving device for a fast reflector that enables the device to drive the fast reflector with a large stroke and high precision, so that the fast reflector meets the requirements of the lithography machine's illumination system, this application provides a design method for a driving device for a fast reflector.

[0004] The technical solution provided by this invention is as follows:

[0005] A design method for a driving device of a fast reflector, the driving device comprising a primary driving device and a secondary driving device, the primary driving device comprising a motor, an elastic plate, and a first spring; the secondary driving device comprising a PZT, a steel ball fulcrum, a second spring, and a tripod; two PZTs and the steel ball fulcrum form a support point, the tripod is pressed onto the support point by the second spring, and the PZTs drive the tripod to rotate around the steel ball fulcrum through their own extension and retraction; the design method includes the following steps:

[0006] The motor parameters are calculated based on the target design parameters of the fast reflector driven by the primary drive unit. The motor parameters include motor stroke, motor step, motor holding force, and motor thrust. The motor model is then selected based on these motor parameters.

[0007] Calculate the maximum tension of the first spring under different postures of the fast reflector based on the motor holding force, and design the first spring based on the maximum tension of the first spring under different postures.

[0008] The PZT parameters are calculated based on the target design parameters of the fast reflector driven by the secondary drive device. The PZT parameters include PZT stroke and PZT resolution. The PZT model is selected based on the PZT parameters.

[0009] Calculate the static holding force of PZT and design the second spring based on the static holding force of PZT.

[0010] More preferably, before calculating the motor parameters, the method further includes the steps of: calculating the distance L1 between the motor spindle and the pivot point, and setting the distance l1 between the first spring and the pivot point.

[0011] More preferably, the step of calculating the motor parameters based on the target design parameters of the fast-reflecting mirror driven by the primary drive device specifically includes the following steps:

[0012] Calculate the motor travel: Motor travel = A1·L1, where A1 is the target travel of the motor controlling the fast reflector;

[0013] Calculate the motor stepping: Motor stepping = B1·L1, where B1 is the target resolution of the motor-controlled fast reflector;

[0014] Calculate the motor holding force: Calculate the equivalent stiffness K. K T Let K be the first spring stiffness. S The stiffness of the elastic plate is given; the motor holding force is calculated based on the equivalent stiffness: Motor holding force = C + d × K, where C is the force pressed on the motor main shaft at the lowest point, d is the adjustable range of the first-stage drive, and K is the equivalent stiffness;

[0015] Calculate the motor thrust: Among them, F D F1 is the thrust of the motor, F1 is the static holding force of the motor, k is the torsional stiffness, and J is the moment of inertia of the first-stage drive unit. This represents the rotation angle of the motor.

[0016] More preferably, before calculating the PZT parameters, the method further includes the steps of: calculating the distance L2 between PZT and the steel ball fulcrum, and setting the distance l2 between the second spring and the steel ball fulcrum.

[0017] More preferably, the calculation of PZT parameters based on the target design parameters of the fast-reflecting mirror driven by the secondary drive device specifically includes the following steps:

[0018] Calculate the PZT travel: PZT travel = A2·L2, where A2 is the target travel of the PZT control of the fast reflector;

[0019] Calculate PZT resolution: PZT resolution = B2·L2, where B2 is the target resolution of the PZT-controlled fast reflector.

[0020] More preferably, the calculation of the PZT static holding force specifically includes:

[0021] Where, m eff ΔL0 is the weight of the secondary drive unit, ΔL0 is the nominal displacement of PZT, f is the operating frequency, and t is the safety factor to prevent external vibration.

[0022] More preferably, the rotation fulcrums of the primary drive device and the secondary drive device are on the same side, and the rotation axis of the primary drive device is parallel to the rotation axis of the secondary drive device.

[0023] The drive device design method provided by this invention allows for the selection of appropriate PZT and the design of reasonable spring dimensions in the design of the secondary drive device, taking into account the required resolution, stroke, and stiffness of the fast reflector. In the design of the primary drive device, a suitable motor is selected based on the required resolution, stroke, and thrust of the motor for the fast reflector, and a reasonable spring is designed to ensure that the static holding force on the motor is less than the motor thrust and to guarantee structural stability. Attached Figure Description

[0024] Figure 1 Flowchart for the design of the drive mechanism for the fast reflector;

[0025] Figure 2 This is a schematic diagram of the primary drive unit.

[0026] Figure 3 This is a schematic diagram of the secondary drive unit. Detailed Implementation

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0028] Considering the motion state of the FSM in actual operation, the FSM structure adopts a two-stage transmission. The first-stage drive unit consists of two stepper motors, which, due to their large stroke, enable large-stroke rotation of the FSM. The second-stage drive unit mainly consists of two PZT (piezoelectric ceramic motors). PZT motors are characterized by fast response and high precision, enabling high-precision, rapid small-angle rotation of the FSM. This application designs the first-stage and second-stage drive units, selecting suitable PZT motors, appropriate motors, and designing reasonable spring dimensions. The design method provided in this application is described in detail below.

[0029] In this application, the driving device of the fast reflector includes a primary driving device and a secondary driving device. The primary driving device weighs 0.478 kg and the secondary driving device weighs 0.1752 kg. The rotation fulcrum of the primary driving device and the secondary driving device are on the same side, and the rotation axis of the primary driving device is parallel to the rotation axis of the secondary driving device, which can ensure that the primary and secondary drives have the same adjustment direction.

[0030] The primary drive unit mainly includes: a motor, an elastic plate, two first springs (tension springs), a base, a square platform, M5 pointed screws, a limit block (upper limit), a limit plate (lower limit), and a circuit board. Key components include the motor, elastic plate, two tension springs, and circuit board. The selection of the motor requires specific requirements for resolution, stroke, and thrust. The elastic plate flexibly connects the base and the square platform, increasing stiffness in non-working rotational directions while minimizing stiffness in the working rotational direction. A well-designed spring ensures that the static holding force on the motor is less than the motor thrust, guaranteeing structural stability. The upper limit block limits the maximum extension of the motor spindle, with a maximum displacement of 2mm. The lower limit plate is mounted on the motor spindle, with a maximum displacement of 2mm. The lower limit also serves as the stepper motor's zero-return mechanism; therefore, a magnet is mounted on the lower limit block, and an electromagnetic sensor is installed below it.

[0031] The secondary drive unit mainly includes: two PZT (piezoelectric ceramic motors), two second springs (compression springs), a tripod, a flexible plate, a circular platform, a lens, countersunk bolts, and a frame. The ball heads and steel ball fulcrums of the two PZTs form a three-point support, which together form an isosceles right triangle. The tripod is pressed against these three points by two springs. The PZTs drive the tripod to rotate around the fulcrum through their own extension and retraction, thereby enabling the tripod to rotate in two directions.

[0032] The main components in the secondary drive unit are: PZT, spring, and circular platform. The PZT needs to meet the resolution, stroke, stiffness, etc. required by the FSM. At the same time, the stiffness of the PZT, the stiffness of the spring, and the rotational inertia of the structure determine the natural frequency of the system. Therefore, a comprehensive analysis is required to select a suitable PZT and design a reasonable spring size.

[0033] Based on the components of the first-stage and second-stage drive units described above, this application mainly designs the motor and spring in the first-stage drive unit, and the PZT and spring in the second-stage drive unit, so that the designed motor, PZT, and spring meet the driving requirements of the fast-reflecting mirror. The specific design method includes the following steps, the flowchart of which is shown below. Figure 1 As shown.

[0034] S100: Calculate the motor parameters based on the target design parameters of the fast reflector driven by the primary drive unit. The motor parameters include motor stroke, motor step, motor holding force, and motor thrust. Select the motor model based on the motor parameters.

[0035] S200: Calculate the maximum tension of the first spring under different postures of the fast reflector based on the holding force of the motor, and design the first spring based on the maximum tension of the first spring under different postures.

[0036] S300: Calculate the PZT parameters based on the target design parameters of the fast reflector driven by the secondary drive device. The PZT parameters include PZT stroke and PZT resolution. Select the PZT model based on the PZT parameters.

[0037] S400: Calculate the static holding force of PZT and design the second spring based on the static holding force of PZT.

[0038] Before step S100, the method further includes calculating the distance L1 between the motor spindle and the pivot point, and setting the distance l1 between the first spring and the pivot point. Specifically, this is based on the motor rotation angle. The distance L1 between the motor spindle and the pivot point is calculated based on the motor rotation displacement. The distance l1 between the first spring and the pivot point is set based on empirical values. The schematic diagram of the first-stage drive motion after the distance is determined is shown below. Figure 2 As shown.

[0039] In step S100, the motor parameters are calculated based on the target design parameters of the primary drive device driving the fast reflector, specifically including the following steps.

[0040] S101: Calculate motor stroke.

[0041] Motor stroke = A1·L1, where A1 is the target stroke of the motor controlling the fast reflector.

[0042] For example, if the target stroke of the motor-controlled FSM is 10 mrad, then the actual stroke of the motor is:

[0043] 10 mrad·L1≈10 -2 L1(mm)=10 -2 ×40mm=0.4mm.

[0044] S102: Calculate motor stepping.

[0045] Motor stepping = B1·L1, where B1 is the target resolution of the motor-controlled fast reflector.

[0046] For example, if the resolution of the motor-controlled FSM is 10 μrad, then according to geometric relationships, the motor's step size is: 10 μrad·L1 = 10. -5 L1(mm)=0.4μm.

[0047] S103: Calculate the motor holding force.

[0048] Calculate the equivalent stiffness K. K T Let K be the first spring stiffness. SThe stiffness of the elastic plate is given by the following formula: Motor holding force = C + d × K, where C is the force pressed on the motor spindle at the lowest point, d is the adjustable range of the first-stage drive, and K is the equivalent stiffness.

[0049] For example, if the FSM primary drive has an adjustable range of ±2mm, the elastic plate stiffness is 2.5N / mm, and the tension spring stiffness is 5.27N / mm, then the equivalent stiffness is:

[0050] It must be ensured that there is a certain pressure acting on the motor spindle within the adjustable range of ±2mm. Taking the force of 10N pressing on the motor spindle at the lowest point as the calculation, the motor holding force in the leveling state is 10N + 2mm × 5.66N / mm = 21.32N.

[0051] At the highest point, the static holding force acting on the motor spindle is 10N + 4mm × 5.66N / mm = 32.64N, which meets the motor thrust requirement.

[0052] S104: Calculate the motor thrust.

[0053] Among them, F D F1 is the thrust of the motor, F1 is the static holding force of the motor, k is the torsional stiffness, and J is the moment of inertia of the first-stage drive unit. This represents the rotation angle of the motor.

[0054] Specifically, based on the corresponding time index of 10–30 ms @ 100 μrad, the angular acceleration of the motor is calculated according to the principle of uniform acceleration followed by uniform deceleration. Based on the index "10–30 ms @ 100 μrad", the calculation is performed as 100 μrad rotation every 10 ms, resulting in the following angular acceleration: The maximum angular velocity is: The maximum speed of the motor is:

[0055] Moment of inertia: J = 3.01 × 10⁻⁶ -4 kg·m 2 , With k T = 5.26 N / mm, k s =2.5 N / mm gives the torsional stiffness Substituting the above parameters into F D In the middle, the thrust F of the motor is obtained. D .

[0056] Furthermore, the natural frequency of the first-stage drive unit can be calculated. The specific calculation process is as follows:

[0057] The differential equation is as follows:

[0058]

[0059] Where F1 is the static holding force; F D k is the thrust of the motor; k is the torsional stiffness, k = k T l 2 +k s L 2 k T For spring stiffness, k s For the rigidity of the steel plate; L1 is the rotation angle, and J = 301 kg·mm is the distance between the motor drive point and the rotating support point. 2 The moment of inertia of the primary drive unit.

[0060] Solving this differential equation yields the angular frequency:

[0061]

[0062] The natural frequency of the first-stage drive unit is:

[0063]

[0064] Based on the motor parameters calculated above, the 28H47-05-A51 model motor from Hayden Linear Motor Co., Ltd. was selected. The parameter list of this motor is shown in Table 1 below.

[0065] Table 1

[0066] Motor parameters Step length journey motor thrust Calculated value 0.4μm 0.4mm 26.8N Motor parameters 0.18μm 12.7mm 70N

[0067] In step S200, the maximum tension of the first spring under different postures of the fast-reflecting mirror is calculated based on the motor holding force, and the first spring is designed based on the maximum tension of the first spring under different postures. The specific design method is as follows:

[0068] If we neglect gravity and calculate the static holding force of the motor as 21N, the spring forces under different installation configurations are listed in Table 2 below.

[0069] Table 2

[0070]

[0071] The design parameters of the first spring are shown in Table 3 below. The spring force is 38N and the stiffness is 5.67N / mm.

[0072] Table 3

[0073]

[0074] Before step S300, the method further includes calculating the distance L2 between PZT and the steel ball fulcrum, and setting the distance l2 between the second spring and the steel ball fulcrum. Specifically, this is based on the rotation angle of PZT. The distance L2 between PZT and the steel ball fulcrum is calculated based on the rotational displacement S of PZT. The distance l2 between the second spring and the steel ball fulcrum is set according to empirical values. The schematic diagram of the secondary drive motion after the distance is determined is shown below. Figure 3 As shown.

[0075] In step S300, the PZT parameters are calculated based on the target design parameters of the fast reflector driven by the secondary drive device. Specifically, the following steps are included, wherein the target design parameters of the fast reflector controlled by PZT are shown in Table 4 below.

[0076] Table 4

[0077] Indicator Item Indicator parameters Lens size 75mm x 50mm x 10mm journey 1000 μrad (PZT) Response time (motion time) 5–10 ms @ 100 μrad (PZT) resolution 1 μrad (PZT); accuracy ±2μrad@100μrad (PZT closed loop); Coupling error 5μrad@100μrad Short-term stability 2μrad@1s

[0078] S301: Calculate the PZT travel.

[0079] PZT stroke = A2·L2, where A2 is the target stroke of the PZT-controlled fast reflector; specifically, the stroke of the PZT-controlled FSM is 1000 μrad, and according to geometric relationships, the PZT stroke d2 is:

[0080] d² = 1000 μrad·L² = 1 × 10 -3 ×19.8mm=19.8μm.

[0081] S302: Calculate PZT resolution.

[0082] PZT resolution = B²·L², where B² is the target resolution of the fast reflector controlled by PZT; specifically, if the resolution of the FSM controlled by PZT is 1 μrad, then the PZT resolution is:

[0083] 1 μrad·L2=10 -6 ×19.8mm=19.8nm;

[0084] Therefore, the minimum resolution of PZT is 19.8nm.

[0085] Based on the travel and resolution of the PZT, the selected model is PSt150 / 5×5 / 20H, and its parameters are shown in Table 5.

[0086] Table 5

[0087]

[0088] In step S400, the static holding force of PZT is calculated, and the specific calculation method is as follows:

[0089] The preload should not impair the displacement of the piezoelectric ceramic, and the preload stiffness should be relatively low, a few percent of the ceramic's stiffness. The preload should be high enough to accelerate the load's rapid rebound, thus preventing the ceramic from being subjected to tensile forces. During dynamic operation, the dynamic force must be controlled to be less than the preload. Based on a 5ms cycle (corresponding to a frequency of 200Hz), a safety factor of 2, and an operating frequency of 400Hz, the dynamic force can be calculated using the following formula:

[0090]

[0091] In addition to considering dynamic forces, to prevent potential external vibrations, a safety factor of 3 is taken, resulting in a static holding force of 34N. Therefore, when designing the compression spring, it is necessary to ensure that the static holding force borne by PZT is 34N.

[0092] Based on the PZT static holding force of 34N, and neglecting the mass of the lens, frame, and tripod, the spring force is 62.3N. The mass of the secondary moving parts (lens, frame, and tripod, etc.) is 0.114kg. The forces acting on the second spring under different postures are shown in Table 6.

[0093] Table 6

[0094]

[0095] As shown in Table 6, the spring force changes under different FSM postures. The second spring is designed with a spring tension of 63N as the standard. The parameters of the second spring are shown in Table 7.

[0096] Table 7

[0097] Spring wire diameter Spring middle diameter Working load unfolded length Material Valid number of laps Total laps Free length 1.2mm 4.8mm 75N 91.1mm 65SiMnWA 4 6 9mm

[0098] Furthermore, it also includes calculating the PZT vibration frequency, the specific calculation process of which is as follows:

[0099] like Figure 3 As shown, the simplified kinematic diagram of PZT includes: a spring, PZT, and a pressure plate that can rotate around a center (dashed line in the diagram). The distance between the spring and the center is l2 = 10.8 mm, and the distance between PZT and the center is L2 = 19.8 mm. Using 3D software, the moment of inertia of PZT about the two rotation axes is calculated to be J1 = 51 kg·mm². 2 J2 = 76.78 kg·mm 2 .

[0100] like Figure 3 As shown, for any displacement S of PZT during its motion, the torque acting on the pressure plate is:

[0101]

[0102] Spring stiffness C T = 46.2 N / mm. From Table 5, we can see that the stiffness C of PZT is... F =60N / μm

[0103] Then the following differential equation exists:

[0104]

[0105] in, For the corner of the pressure plate, It is angular acceleration, and it exists.

[0106] Simplified, we get:

[0107]

[0108] The angular frequency is:

[0109] The inherent frequency of the PZT secondary drive is:

[0110]

[0111] Based on the design methods of the primary and secondary drive devices provided in this application, in the design of the secondary drive device, a suitable PZT is selected and a reasonable spring size is designed, taking into account the resolution, stroke, stiffness, etc. required by the fast reflector. In the design of the primary drive device, a suitable motor is selected and a reasonable spring is designed, taking into account the resolution, stroke, thrust, etc. required by the motor for the fast reflector. This ensures that the static holding force on the motor is less than the motor thrust and guarantees structural stability.

[0112] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A design method for a driving device of a fast-reflecting mirror, characterized in that, The driving device includes a primary driving device and a secondary driving device. The primary driving device includes a motor, an elastic plate, and a first spring. The secondary driving device includes a PZT, a steel ball fulcrum, a second spring, and a tripod. Two PZTs and the steel ball fulcrum form a support point. The tripod is pressed against the support point by the second spring. The PZTs drive the tripod to rotate around the steel ball fulcrum through their own extension and retraction. The design method includes the following steps: The motor parameters are calculated based on the target design parameters of the fast reflector driven by the primary drive unit. The motor parameters include motor stroke, motor step, motor holding force, and motor thrust. The motor model is then selected based on the motor parameters. Calculate the maximum tension of the first spring under different postures of the fast reflector based on the motor holding force, and design the first spring based on the maximum tension of the first spring under different postures. The formula for calculating the motor holding force is: Motor holding force = C + d × K, where C is the force pressed on the motor main shaft at the lowest point, d is the adjustable range of the first-stage drive, and K is the equivalent stiffness of the elastic plate and the first spring. The formula for calculating the motor thrust is as follows: Among them, F D F1 is the thrust of the motor, F1 is the static holding force of the motor, k is the torsional stiffness, and J is the moment of inertia of the first-stage drive unit. The rotation angle of the motor. Angular acceleration; The PZT parameters are calculated based on the target design parameters of the fast reflector driven by the secondary drive device. The PZT parameters include PZT stroke and PZT resolution. The PZT model is selected based on the PZT parameters. Calculate the static holding force of PZT, and design the second spring based on the static holding force of PZT. The specific calculation formula is as follows: Where, m eff ΔL0 is the weight of the secondary drive unit, ΔL0 is the nominal displacement of PZT, f is the operating frequency, and t is the safety factor to prevent external vibration.

2. The drive device design method as described in claim 1, characterized in that, Before calculating the motor parameters, the steps include: calculating the distance L1 between the motor spindle and the pivot point, and setting the distance l1 between the first spring and the pivot point.

3. The drive device design method as described in claim 2, characterized in that, The calculation of motor parameters based on the target design parameters of the fast-reflecting mirror driven by the primary drive unit includes the following steps: Calculate the motor travel: Motor travel = A1·L1, where A1 is the target travel of the motor controlling the fast reflector; Calculate the motor stepping: Motor stepping = B1·L1, where B1 is the target resolution of the motor-controlled fast reflector. Calculate the equivalent stiffness K. K T Let K be the first spring stiffness. S For the stiffness of the elastic plate; 4. The drive device design method as described in claim 1, characterized in that, Before calculating the PZT parameters, the steps include: calculating the distance L2 between PZT and the steel ball fulcrum, and setting the distance l2 between the second spring and the steel ball fulcrum.

5. The drive device design method as described in claim 4, characterized in that, The calculation of PZT parameters based on the target design parameters of the fast reflector driven by the secondary drive device specifically includes the following steps: Calculate the PZT travel: PZT travel = A2·L2, where A2 is the target travel of the PZT control of the fast reflector; Calculate PZT resolution: PZT resolution = B2·L2, where B2 is the target resolution of the PZT-controlled fast reflector.

6. The drive device design method as described in claim 1, characterized in that, The rotation fulcrums of the primary drive device and the secondary drive device are on the same side, and the rotation axis of the primary drive device is parallel to the rotation axis of the secondary drive device.

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