A dynamic focal plane position compensation method and system

Abstract

The application discloses a dynamic focal plane position compensation method and system. A distance sensor is used to pre-scan the surface of a substrate, and a host computer generates a corresponding compensation array and sends it to a PLC. High-frequency pulses output by an encoder are processed by a synchronization board to reduce the frequency, and are converted into trigger pulses with fixed spatial intervals and suitable for high-speed counting of the PLC. The PLC calculates the installation offset of the sensor and the focusing assembly to determine the compensation starting position, accumulates the pulse count, and when the number of pulses corresponding to the fixed interval is reached, the focal plane target value of the compensation array is sequentially read in the hardware interrupt, the mover of the linear servo module is driven to move along the linear servo module axis, the thickness of the optical system is adjusted by moving the lower optical assembly to change the focal length, and dynamic compensation is realized. When the platform is backed up, the interrupt is shielded and the count is reset. The scheme realizes deterministic real-time focusing, automatically compensates for the installation offset, has a simple structure, fast response, and significantly improves the line width uniformity and product yield of long-stroke scanning exposure.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a dynamic focal plane position compensation method and system. Background Technology

[0002] In the field of precision laser direct writing exposure, substrates such as semiconductors, printed circuit boards, and flat panel displays often undergo slight deformations due to material stress, clamping, or thermal effects. If the focal plane cannot be adjusted in real time to adapt to the deformation during scanning exposure, it will lead to yield defects such as uneven linewidth and blurred patterns. Traditional focusing systems mostly perform static focusing or fixed-point sampling compensation before exposure, which is difficult to adapt to the dynamic changes in substrate height with position during long-stroke, multi-strip continuous scanning. Therefore, dynamic focal plane compensation technology needs to be introduced.

[0003] Existing dynamic focal plane compensation methods mainly employ displacement sensors for pre-scanning and establish a mapping relationship between the focal plane position and the exposure platform position. Such schemes achieve dynamic tracking to a certain extent by establishing a focal plane-position mapping or real-time position triggering.

[0004] However, existing solutions still have significant shortcomings. First, there is a fixed physical installation offset between the displacement sensor and the exposure lens, which current methods try to circumvent by alternating measurements and exposures, resulting in reduced scanning efficiency and inaccurate initial compensation positions. Second, focusing triggers directly use the original position signal of the exposure platform or pulses without spatial isometry conversion. The signal spacing is affected by fluctuations in movement speed, making it difficult to guarantee the determinism of compensation over long strokes. Furthermore, control units often employ dedicated controllers or complex processing modules, leading to high architectural costs and limited real-time response. In addition, during strip scanning retraction, there is a lack of a reliable shielding mechanism for the trigger signal, which easily causes false triggers and affects system stability. Therefore, how to simplify the system architecture while achieving spatial isometry triggering, automatic compensation for installation offset, and reliable management of the focusing process between strips has become an urgent problem to be solved. Summary of the Invention

[0005] In view of the above problems, a dynamic focal plane position compensation method and system are proposed to overcome or at least partially solve the above problems, specifically: A dynamic focal plane position compensation method includes: The host computer uses a distance sensor to scan the surface of the substrate, generates a compensation array based on the height data obtained from the scan, and sends the compensation array to the programmable logic controller. The encoder detects the displacement of the exposure platform and outputs position pulses. The synchronization board converts the position pulses into trigger pulses with fixed spatial intervals. The programmable logic controller calculates the installation offset between the distance sensor and the focusing optical assembly, determines the compensation starting position, and accumulates the number of trigger pulses. When the cumulative count reaches the count corresponding to the compensation start position, the programmable logic controller reads the focal plane target position value sequentially from the compensation array in the interrupt routine; The programmable logic controller controls the servo driver based on the read focal plane target position value, driving the focusing optical component to move along the axis of the linear servo module; When the exposure platform retracts, the programmable logic controller (PLC) blocks the interrupt response of the trigger pulse and resets the accumulated count before the next scan band is exposed.

[0006] Optionally, the trigger pulses with fixed spatial intervals output by the synchronization board are level-converted by the optocoupler module and then input to the programmable logic controller.

[0007] Optionally, the optocoupler module converts the trigger pulse level from 3.3V to 24V; the isolation voltage of the optocoupler module is not less than 1500V.

[0008] Optionally, the distance sensor communicates with the host computer via an Ethernet communication protocol; the host computer sends a scan start command to the distance sensor, and the distance sensor packages the height measurement values ​​of each sampling point and the corresponding encoder position information, and returns them to the host computer via data frames.

[0009] Optionally, the fixed spatial interval can be any one of 1mm, 2mm, 5mm or 10mm; the synchronization board down-frequency processes the position pulse to generate trigger pulses with a fixed spatial interval.

[0010] Optionally, the focusing optical component is driven by a linear servo module; the linear servo module includes a stator and a mover, the mover moves along the axial direction of the linear motor module, and the focusing optical component is mounted on the mover; the linear servo module is a voice coil motor module or a linear motor module.

[0011] Optionally, the linear servo module has a motion resolution of 1 micrometer and a repeatability of no more than ±2 micrometers; the linear servo module has a built-in optical or magnetic ruler as a position feedback element, and the servo driver performs closed-loop adjustment of the real-time position of the mover based on the position feedback.

[0012] Optionally, the programmable logic controller has a built-in high-speed counter that counts the rising edge of the trigger pulse; the accumulated count is the current count value of the high-speed counter.

[0013] Optionally, the host computer's processing of height data includes filtering and interpolation steps; the filtering step uses median filtering, mean filtering, or Gaussian filtering, and the interpolation step uses linear interpolation, cubic spline interpolation, or Lagrange interpolation, thereby generating a compensation array; each element in the compensation array uniquely corresponds to an exposure platform position with a fixed spatial interval.

[0014] A dynamic focal plane position compensation system, comprising: Distance sensor, used to collect height data of the substrate surface; The host computer is used to generate a compensation array based on the height data and then distribute it. A programmable logic controller (PLC) for storing a compensation array and equipped with an interrupt routine; The encoder, including a platform position feedback readout head, is used to detect the displacement of the exposure platform and output a position pulse; Synchronization board, used to convert position pulses into trigger pulses with fixed spatial intervals; The optocoupler module connects the synchronization board and the programmable logic controller (PLC) to convert the level of the trigger pulses output by the synchronization board and input them to the PLC. Servo driver, connected to a programmable logic controller; A linear servo module, including a focusing optical component, is driven by a servo driver to move along the axial direction of the linear servo module. The switch is used for communication and interaction between the host computer, the programmable logic controller, and the distance sensor. The programmable logic controller is also used to calculate the installation offset between the distance sensor and the focusing optical component to determine the compensation starting position, accumulate the number of trigger pulses, and when the accumulated number reaches the number corresponding to the compensation starting position, read the focal plane target position value sequentially from the compensation array in the interrupt program and drive the focusing optical component through the servo driver. The programmable logic controller is also used to shield the interrupt response of the trigger pulse when the exposure platform retracts and to reset the accumulated count.

[0015] This invention utilizes substrate surface height data acquired by a distance sensor during pre-scanning. This data is processed by a host computer to generate a compensation array, which is then downloaded to a programmable logic controller (PLC). The encoder position pulses are frequency-reduced via a synchronization board to generate trigger pulses with fixed spatial intervals, synchronizing the focusing action with the scanning displacement and eliminating the impact of exposure platform speed fluctuations on compensation position accuracy. The PLC determines the compensation starting position by calculating the installation offset between the distance sensor and the focusing optical component. When the cumulative number of trigger pulses reaches a certain value, a hardware interrupt is used to sequentially read the target focal plane position value from the compensation array, driving the focusing optical component to move axially along the linear servo module. This simplifies the system architecture while achieving real-time response and automatic compensation for installation errors. When the exposure platform retracts, the PLC disables the trigger pulse interrupt response and resets the cumulative count, effectively preventing false triggering during strip switching. The synergistic effect of these technologies ensures that the exposure focal plane remains in contact with the actual deformation of the substrate surface throughout the entire scanning stroke, significantly improving exposure linewidth uniformity and product yield. Furthermore, the system is compact, cost-effective, and suitable for high-speed scanning exposure production lines with substrates of various specifications. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a diagram illustrating the architecture of a dynamic focal plane position compensation system provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the position of the focusing optical component before it moves along the axial direction of the linear servo module, as provided in this embodiment of the invention. Figure 3 This is a schematic diagram of the position of the focusing optical component after it moves along the axial direction of the linear servo module, as provided in an embodiment of the present invention. Figure 4 This is a partially enlarged view of a dynamic focal plane position compensation system provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the working layout of a dynamic focal plane position compensation system provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Reference Figures 2 to 5 This invention provides a dynamic focal plane position compensation method, which may specifically include: A dynamic focal plane position compensation method includes: The distance sensor 1 scans the surface of the substrate, and the host computer 6 generates a compensation array based on the height data obtained from the scan, and sends the compensation array to the programmable logic controller 7. The encoder detects the displacement of the exposure platform 5 and outputs a position pulse. The synchronization board 11 converts the position pulse into trigger pulses with a fixed spatial interval. The programmable logic controller 7 calculates the installation offset between the distance sensor 1 and the focusing optical assembly 4, determines the compensation starting position, and accumulates the number of trigger pulses; When the cumulative count reaches the count corresponding to the compensation start position, the programmable logic controller 7 reads the focal plane target position value sequentially from the compensation array in the interrupt program; The programmable logic controller 7 controls the servo driver based on the read focal plane target position value, driving the focusing optical component 4 to move along the axial direction of the linear servo module; When exposure platform 5 retracts, programmable logic controller 7 disables the interrupt response of the trigger pulse and resets the accumulated count before the next scan band is exposed.

[0020] In the specific implementation process, the substrate is fixed on the exposure platform 5, which scans along the Y-axis. Distance sensor 1 is mounted at a fixed position above the exposure platform 5. When the exposure platform 5 moves the substrate at a constant speed through the measurement area of ​​distance sensor 1, distance sensor 1 continuously emits detection signals and receives reflected signals according to a set sampling interval, thereby acquiring the height data of each sampling point on the substrate surface along the scanning direction. Distance sensor 1 transmits the collected height data along with the corresponding exposure platform 5 position encoding information to the host computer 6. After receiving the complete scan data, the host computer 6 runs a data processing program to filter the original height data to eliminate random noise and performs interpolation processing based on the exposure platform 5 position to form a focal plane compensation curve that corresponds one-to-one with the exposure platform 5 position sequence. Then, discrete points at equal intervals on this curve are used to form a compensation array, where each element uniquely corresponds to a spatial position of the exposure platform 5. Subsequently, the host computer 6 sends the entire compensation array to the internal storage array of the programmable logic controller 7 for storage via a communication connection.

[0021] After the exposure platform 5 begins forward scanning exposure, the encoder mounted on the Y-axis drive structure of the exposure platform rotates as the exposure platform 5 moves, outputting position pulse signals reflecting the displacement increment of the exposure platform 5. The position pulses output by the encoder are received by the synchronization board 11. The synchronization board 11 down-clocks the input position pulses, converting the high-frequency position pulses into trigger pulses with a constant displacement of the exposure platform 5 between adjacent rising edges using internal configurable down-clocking logic. The distance the exposure platform 5 moves between adjacent rising edges of this trigger pulse is a predetermined fixed spatial interval, independent of changes in the speed of the exposure platform 5, ensuring the determinism of the spatial position at the trigger moment.

[0022] Before the trigger pulse is used for focusing, the programmable logic controller (PLC) 7 needs to obtain the compensation start position. Due to the inherent physical installation offset between the distance sensor 1 and the focusing optical component 4 in the Y-axis direction, the PLC 7 reads the exposure start coordinates provided by the host computer 6 and, combined with the pre-stored installation offset value, calculates the threshold for the cumulative number of trigger pulses corresponding to the compensation start position. The PLC 7 integrates a high-speed counter, which continuously increments the rising edge of the trigger pulse from the moment the exposure platform 5 begins to move from the start point. When the cumulative count of the high-speed counter reaches the aforementioned threshold, it indicates that the exposure platform 5 has moved to the compensation start position, and the PLC 7 then enables the trigger pulse interrupt response.

[0023] Subsequently, when the rising edge of each trigger pulse reaches the high-speed input interface of the programmable logic controller 7, a hardware interrupt is triggered. The programmable logic controller 7 temporarily suspends the main program loop and enters the interrupt service routine. Within the interrupt service routine, the programmable logic controller 7 obtains the current cumulative count of the high-speed counter, subtracts the starting threshold, and obtains the array offset index corresponding to the current position. Using this index, the programmable logic controller 7 directly reads the focal plane target position value at the corresponding position from the internal memory array and encodes this value into a position command that the servo driver can parse. The servo driver outputs drive current to the linear servo module 9 according to the position command. The mover 3 of the linear servo module 9 moves along the axial direction of the linear servo module, and the focusing optical component 4 mounted on the mover 3 adjusts its height accordingly. When the substrate surface is concave relative to the reference plane, the focal plane target position value at the corresponding position in the compensation array decreases, and the focusing optical component 4 moves closer to the substrate; when the substrate surface is convex, the focal plane target position value increases, and the focusing optical component 4 moves away from the substrate. After the above adjustments, the movement of the focusing optical component changes the focal length of the optical system, and the deviation between the focal plane position of the exposure beam after passing through the focusing optical component and the actual height of the substrate surface is compensated, so that the image projection always remains clear.

[0024] As the exposure platform 5 continues to move, each trigger pulse triggers the aforementioned interrupt reading and driving process once, with the array index incrementing sequentially until the forward scan of the current scan band ends. Afterward, the exposure platform 5 enters a rollback phase, moving in the reverse direction along the Y-axis to return to the starting position of the next scan band. During rollback, the programmable logic controller 7 receives a rollback command from the host computer 6 and immediately disables the interrupt response channel for the trigger pulses. Even if trigger pulses continue to be generated, the programmable logic controller 7 will not enter the interrupt service routine, and the servo driver maintains its current state. Once the exposure platform 5 has completed rollback and stopped, the host computer 6 sends a start-up preparation command for the next scan band. The programmable logic controller 7 clears the accumulated count field of the high-speed counter and resets the array index to its initial state. The system enters the compensation-ready state for the next scan band, and the above process is repeated.

[0025] In one or more embodiments of the present invention, the trigger pulses with fixed spatial intervals output by the synchronization board 11 are input to the programmable logic controller 7 after level conversion by the optocoupler module 10. The optocoupler module 10 converts the trigger pulse level from 3.3V to 24V; the isolation voltage of the optocoupler module 10 is not less than 1500V.

[0026] After the synchronization board 11 completes the frequency reduction processing, it sends out trigger pulses with fixed spatial intervals from its pulse output port. These pulses are square wave signals with a high level of 3.3V and a low level of 0V. Since the high-speed counter input channel of the programmable logic controller 7 typically requires a 24V level, and interference is easily introduced through the ground wire when motor drivers, contactors, and other equipment operate in industrial environments, directly connecting the 3.3V pulse to the programmable logic controller 7 would lead to level mismatch and electromagnetic injection risks. Therefore, an optocoupler isolation module is added between the synchronization board 11 and the programmable logic controller 7. The input terminal of the optocoupler isolation module is connected to the pulse output terminal of the synchronization board 11, and the output terminal is connected to the high-speed counter input terminal of the programmable logic controller 7. The module internally uses an optocoupler as its core. The input LED is driven by the 3.3V pulse. When the level is high, the diode conducts and emits light, and the output-side photosensitive device conducts after receiving light, pulling the output level up to 24V; when the level is low, the diode is off, the output is turned off, and pulled down to 0V. Thus, the 3.3V pulse is converted to a 24V pulse, while the electrical isolation voltage between the input and output circuits is no less than 1500V, effectively blocking common-mode noise and surges in the power circuit and protecting the programmable logic controller 7. The optocoupler isolation module uses fast-response optocouplers to maintain the steepness of the pulse edges, enabling the programmable logic controller 7 to accurately capture the rising edge. The 24V fixed-space-interval trigger pulse, after level conversion and isolation, enters the high-speed counter interface of the programmable logic controller 7 and serves as the reference signal for subsequent counts and interrupt responses.

[0027] In one or more embodiments of the present invention, the distance sensor 1 communicates with the host computer 6 via the Ethernet communication protocol; the host computer 6 sends a scan start command to the distance sensor 1, and the distance sensor 1 packages the height measurement values ​​of each sampling point and the corresponding encoder position information, and returns them to the host computer 6 via data frames.

[0028] During the substrate scanning stage, distance sensor 1 establishes a communication connection with host computer 6 via an Ethernet interface. Both parties use the standard Ethernet communication protocol for data exchange, and the communication link is implemented based on the Gigabit Ethernet physical layer to ensure sufficient bandwidth and low transmission latency for height data and location information during transmission.

[0029] Before scanning begins, the host computer 6, acting as the communication master station, sends a scan start command frame to the distance sensor 1. This command frame contains the scan start position coordinates, sampling interval parameters, and scan direction flags. Upon receiving the start command, the distance sensor 1 immediately enters active acquisition mode and simultaneously begins listening for the position information of the exposure platform 5 transmitted from the encoder.

[0030] As the exposure platform 5 moves along the scanning direction, the distance sensor 1 continuously emits a probe beam towards the substrate surface and receives reflected signals according to a preset sampling interval. After each height measurement of a sampling point is completed, the distance sensor 1 synchronously latches the position count value of the exposure platform 5 provided by the encoder at the current moment, as the position information of that sampling point. The distance sensor 1 encapsulates the measurement data of each sampling point into a data frame unit, which includes a frame header, sampling point number, height measurement value, and corresponding exposure platform 5 position count field. Among them, the height measurement value field records the relative height of the surface with the reference plane as the zero point, and the exposure platform 5 position count field records the cumulative pulse value of the encoder at that sampling moment, ensuring that each height data point corresponds precisely to the spatial position of the exposure platform 5.

[0031] When the number of acquired data frame units reaches the preset value of the internal buffer, distance sensor 1 assembles multiple data frame units into a single Ethernet data frame and sends it to host computer 6 via the Ethernet interface. The receiving program on host computer 6 continuously monitors the network port, captures arriving data frames, and then disassembles and verifies them. The verification process includes comparing the frame header identifier, checking the data length field, and verifying the cyclic redundancy check code to ensure that no data loss or bit errors occur during transmission. After successful verification, host computer 6 sequentially stores the height measurement values ​​of each sampling point and the corresponding exposure platform 5 position count values ​​into the raw data area in memory for subsequent filtering, interpolation, and compensation array generation.

[0032] If the host computer 6 detects a data frame verification failure or a discontinuous sequence number during the reception process, it sends a retransmission request to the distance sensor 1. The distance sensor 1 then repackages and retransmits the corresponding data frame unit until the data is received completely. After completing the acquisition of the entire scanning area, the host computer 6 sends a scan stop command to the distance sensor 1. The distance sensor 1 exits the active acquisition state and clears its internal buffer, preparing to enter the next scanning cycle.

[0033] In one or more embodiments of the present invention, the fixed spatial interval is any one of 1mm, 2mm, 5mm or 10mm; the synchronization board performs frequency reduction processing on the position pulse to generate trigger pulses with a fixed spatial interval.

[0034] The synchronization board 11 has a programmable frequency reduction logic. This frequency reduction logic is implemented through an accumulator counter, and the preset value of the counter is the frequency reduction coefficient. The frequency reduction coefficient is calculated by the host computer 6 based on the displacement equivalent of the encoder's original position pulse and the target fixed spatial interval. The calculation formula is that the frequency reduction coefficient equals the target spatial interval divided by the displacement corresponding to a single position pulse. For example, if the displacement corresponding to a single encoder position pulse is 0.1 μm and the target spatial interval is 1 mm, then the frequency reduction coefficient is 10000. Each time the synchronization board 11 receives a position pulse, the internal counter increments by one. When the count value reaches the frequency reduction coefficient, the synchronization board 11 outputs a pulse, and the counter is reset to zero to start the next round of counting. The resulting trigger pulse has a platform displacement between adjacent rising edges that is equal to the frequency reduction coefficient multiplied by the original pulse displacement equivalent, which is the set fixed spatial interval. Furthermore, the trigger pulse frequency is equal to the original position pulse frequency divided by the frequency reduction coefficient, thus achieving the frequency reduction effect.

[0035] After frequency reduction processing, the trigger pulse frequency is significantly lower than the original position pulse frequency, so that the pulse frequency entering the input terminal of the high-speed counter of the programmable logic controller is within the frequency band that the high-speed counter can stably capture, thus meeting the programmable logic controller's requirements for receiving input pulse frequency.

[0036] The choice of fixed spatial interval depends on the feature size of the exposure pattern and the spatial frequency of the substrate surface undulations. For substrates with abrupt changes in surface topography, an interval of 1 mm or 2 mm can provide denser compensation sampling points; for substrates with relatively flat surfaces, an interval of 5 mm or 10 mm can reduce the frequency of interrupt processing by the programmable logic controller 7 while ensuring the compensation effect. The fixed spatial interval trigger pulse output by the synchronization board 11 is then sent to the optocoupler isolation module for level conversion.

[0037] In one or more embodiments of the present invention, the focusing optical component 4 is driven by a linear servo module 9; the linear servo module 9 includes a stator 2 and a mover 3, the mover 3 moves along the axial direction of the linear servo module, and the focusing optical component 4 is mounted on the mover 3; the linear servo module 9 is a voice coil motor module or a linear motor module.

[0038] The focusing optical assembly 4 is driven by a linear servo module 9. The linear servo module 9 consists of a stator 2 and a mover 3. The stator 2 is fixedly mounted on the frame structure of the exposure machine and mechanically secured by bolts and locating pins. The mover 3 moves along the axial direction of the linear servo module, and the focusing optical assembly 4 is rigidly mounted on the moving exposure platform 5 of the mover 3 via mechanical connectors, moving synchronously with the movement of the mover 3.

[0039] The linear servo module 9 can be a voice coil motor module. The voice coil motor module operates based on the Lorentz force. When the servo driver supplies current to the coil windings of the voice coil motor, the energized coil experiences axial thrust in the air gap magnetic field generated by the permanent magnet of the stator 2, driving the mover 3 to move axially along the linear servo module. Because the voice coil motor module lacks a cog and core, the thrust is linearly related to the current, and the mover 3 exhibits no significant torque fluctuation during movement, making it suitable for focusing applications requiring smooth motion. The mover 3 and stator 2 are connected via rolling guides or crossed roller guides. These guide pairs provide linear guidance while bearing radial and torque loads.

[0040] The linear servo module 9 can also be a linear motor module. The stator 2 of the linear motor module can be composed of a permanent magnet array, and the mover 3 has multi-phase windings embedded inside. The servo driver sequentially supplies alternating phase currents to the windings of the mover 3, generating a traveling wave magnetic field around the windings. This magnetic field interacts with the magnetic field of the permanent magnets in the stator 2, generating thrust along the axial direction of the linear servo module. The linear motor module can control the magnitude and direction of the thrust by adjusting the amplitude and phase of the phase current, achieving acceleration, constant speed, and deceleration of the mover 3. The stator 2 and mover 3 of the linear motor module are connected via an air-bearing guide or a rolling guide. The air-bearing guide utilizes compressed air to form an air film between the mating surfaces, eliminating mechanical contact wear during movement.

[0041] The linear servo module 9 integrates a position feedback element to measure the actual position of the mover 3 along the axial direction of the linear servo module in real time and provide feedback signals to the servo driver. The position feedback element can be a linear encoder, with its reading head mounted on the mover 3 and the scale grating fixed to the stator 2. The reading head detects the scale lines on the scale grating through photoelectric scanning and outputs an electrical signal proportional to the displacement. Alternatively, a magnetic encoder can be used, with its magnetic head mounted on the mover 3 and the magnetic scale fixed to the stator 2. The magnetic head measures displacement by detecting changes in the magnetic poles on the magnetic scale. After receiving the position feedback signal, the servo driver compares it in real time with the target position value output by the programmable logic controller 7 and adjusts the drive current output to the linear servo module 9 according to the position deviation, thus forming a closed-loop position control.

[0042] When the target focal plane position value read by the programmable logic controller 7 in the interrupt program changes relative to the current value, the servo driver drives the mover 3 to move a corresponding displacement along the axial direction of the linear servo module. If the target focal plane position value indicates that the substrate surface is concave relative to the reference surface, the mover 3 drives the focusing optical component 4 to move closer to the substrate to shorten the focal length and lower the focal plane position accordingly; if the target focal plane position value indicates that the substrate surface is convex, the mover 3 drives the focusing optical component 4 to move away from the substrate to increase the focal length and raise the focal plane position accordingly. Through the combination of the above mechanical transmission and closed-loop control, the actual position of the focusing optical component 4 is continuously adjusted to a height that matches the surface topography of the substrate, thereby realizing dynamic compensation of the focal plane during the scanning exposure process.

[0043] In one or more embodiments of the present invention, the motion resolution of the linear servo module 9 reaches 1 micrometer and the repeatability positioning accuracy does not exceed ±2 micrometers; the linear servo module 9 has a built-in optical or magnetic ruler as a position feedback element, and the servo driver performs closed-loop adjustment of the real-time position of the mover 3 based on the position feedback.

[0044] When the linear servo module 9 integrates a grating ruler as the position feedback element, the grating ruler has periodically arranged lines engraved on its scale. When the reading head moves relative to the grating, the photodetector inside the reading head captures the light intensity signal of the changing brightness and converts it into two analog voltage signals with a 90-degree phase difference. These two sinusoidal signals enter the front-end processing circuit of the servo driver, are discretely sampled by an analog-to-digital converter at a sampling rate higher than the highest frequency of the signal, and the digital signal processor performs real-time calculation on the sampled data. The calculation process uses a coordinate rotation digital computer algorithm to subdivide the two signals into phases. By calculating the electrical angle corresponding to the signal in each sampling period, the basic grating line spacing is further divided into hundreds or even thousands of equal parts, so that the length corresponding to the single measurement step is much smaller than the basic grating line spacing. When the grating ruler line spacing is 20μm and the subdivision factor is 20 times, the minimum displacement step of the position feedback is 1μm. When a magnetic scale is selected, multiple Hall elements are integrated inside the magnetic head to sense the spatial magnetic field distribution generated by the magnetic poles arranged at a certain distance periodically on the magnetic scale, and output two orthogonal analog signals. After the same subdivision processing flow in the servo driver, a displacement feedback resolution of 1μm can also be obtained.

[0045] In each control cycle, the servo driver reads the absolute coordinates or relative displacement increments of the mover 3 provided by the position feedback element and calculates the difference between these values ​​and the target position value sent by the programmable logic controller 7 to obtain the current position following deviation. The digital signal processor inside the servo driver runs a proportional-integral-derivative (PID) control algorithm or a proportional-plus-integral (PII) control algorithm based on this deviation to calculate the current amplitude and direction to be output to the linear servo module 9. After adjustment by the pulse width modulation circuit, this current is applied to the windings of the mover 3 through a power stage amplifier. The proportional gain setting causes the mover 3 to generate a recovery thrust proportional to the magnitude of the deviation, while the integral stage accumulates the persistent small deviations and outputs a compensation amount, gradually adjusting the steady-state position deviation to near zero. Through gain parameter tuning during the debugging process, under the premise of stable guide rail pair guiding accuracy and motion resistance, and no change in load, when the mover 3 is positioned multiple times from any direction to the same target position, the difference between the actual reached position and the target position can be limited to within ±2μm, meeting the technical requirement of repeatability positioning accuracy not exceeding 2μm. To mitigate the effects of mechanical resonance during motion, the servo driver can incorporate a band-stop filter within the control loop to attenuate gain in a specific frequency range. Simultaneously, when a step change occurs in the target position, a feedforward compensation component can be introduced into the control loop to output a drive current that matches the rate of change of the target trajectory in advance, thereby reducing position overshoot and adjustment time during dynamic tracking.

[0046] In one or more embodiments of the present invention, the programmable logic controller 7 has a built-in high-speed counter that counts the rising edge of the trigger pulse; the accumulated count is the current count value of the high-speed counter.

[0047] Within the internal hardware resources of the programmable logic controller 7, a set of high-speed counter logic units is configured. This high-speed counter is directly associated with the high-speed input interface of the programmable logic controller 7. The physical terminals of the high-speed input interface receive fixed-space-interval trigger pulses from the synchronization board 11 via an optocoupler isolation module. During the hardware configuration phase, the operating mode of the high-speed counter is set to external pulse counting mode, the trigger edge is set to rising edge trigger, and the count value reset mode is set to software-controllable reset using a programming tool.

[0048] Once the exposure platform 5 begins its forward scanning motion, the fixed-interval trigger pulses output by the synchronization board 11 undergo level conversion via an optocoupler isolation module, arriving at the high-speed input terminal of the programmable logic controller 7 as a 24V square wave. Upon the rising edge of each trigger pulse, the internal hardware logic of the high-speed counter detects the transition of the input voltage from low to high, and increments the current value of the counter by one in the next internal clock cycle. This counting process is autonomously completed by the hardware circuitry and does not occupy any instruction cycles of the programmable logic controller 7's central processing unit. The counting response delay is limited only by the maximum input frequency parameter of the high-speed counter unit. The current count value of the high-speed counter can be read in real-time by the main program or interrupt program via the internal bus; this count value represents the cumulative number of trigger pulses.

[0049] After the compensation start position is determined, the programmable logic controller 7 stores the cumulative count threshold corresponding to the compensation start position into a comparison register. Each trigger pulse updates the high-speed counter value, and the hardware comparison logic automatically compares the updated count value with the threshold in the comparison register. When the cumulative count is less than the threshold, it indicates that the exposure platform 5 has not yet reached the compensation start position, and the programmable logic controller 7 does not trigger an interrupt service. When the cumulative count reaches the threshold, the comparison output signal is set, triggering the execution condition of the interrupt service routine. Each subsequent rising edge of a trigger pulse will continue to increment the cumulative count and trigger an interrupt service. The interrupt service routine calculates the array index based on the difference between the current cumulative count and the threshold, and reads the corresponding focal plane target position value from the compensation array.

[0050] When the high-speed counter reaches the preset maximum count value, the hardware automatically flips to zero and continues to increment. During the flipping process, the interrupt triggering logic and index calculation logic are unaffected. After the exposure of a single scan band is completed, the accumulated count field of the high-speed counter is cleared by the programmable logic controller 7 in response to the instruction from the host computer 6. After clearing, the current count value of the high-speed counter is zero, preparing for the trigger counting of the next scan band.

[0051] In one or more embodiments of the present invention, the processing of height data by the host computer 6 includes a filtering step and an interpolation step; the filtering step uses median filtering, mean filtering or Gaussian filtering, and the interpolation step uses linear interpolation, cubic spline interpolation or Lagrange interpolation, thereby generating a compensation array; each element in the compensation array uniquely corresponds to the position of an exposure platform 5 with a fixed spatial interval.

[0052] During the compensation array generation stage, after receiving the raw scanning data transmitted by the distance sensor 1 via the Ethernet communication protocol, the host computer 6 first performs a filtering step. The raw scanning data contains the height measurement values ​​of each sampling point in the scanning direction and the corresponding position information of the exposure platform 5. Due to factors such as the possible presence of local foreign objects on the substrate surface, slight fluctuations in the thickness of the photoresist coating, and internal electronic noise of the sensor, random noise components are inevitably superimposed on the raw height data. If it is directly used to generate the compensation array, it will cause unnecessary frequent micro-movements of the focusing optical component 4 during the scanning process, affecting the quality of the exposure pattern.

[0053] When median filtering is used in the filtering step, the host computer sets a sliding window for the original height data sequence. The window width is an odd number of sampling points. The height values ​​of all sampling points within the window are sorted by numerical value, and the value in the middle position after sorting is selected as the filtered height value of the window center point. Then, the window slides along the data sequence by one sampling point interval, and the above sorting and value selection process is repeated until all sampling points are traversed. Median filtering has a better removal effect on isolated impulse noise. At abnormal height jumps caused by foreign particles or transient electrical interference, it can effectively preserve the true surface contour while eliminating noise spikes.

[0054] When mean filtering is used in the filtering step, the host computer sums up the height values ​​within the sliding window and divides them by the window width, then assigns the arithmetic mean to the center point of the window. The calculation process of mean filtering is simple and suitable for processing substrate surface data with gentle amplitude changes and uniform random noise distribution, effectively smoothing small-amplitude high-frequency fluctuations.

[0055] When Gaussian filtering is used in the filtering step, the host computer 6 generates a set of weighting coefficients based on the Gaussian function. The scale parameter of the Gaussian function is selected according to the spatial frequency characteristics of the substrate surface undulations, and the window width is taken as an integer multiple of the scale parameter. The height value of each sampling point within the sliding window is multiplied by the corresponding Gaussian weighting coefficient and then summed to obtain the filtered value at the center point of the window. Gaussian filtering smooths noise while preserving the edge features of the surface contour well, making it suitable for processing substrates with both large undulations and fine textures in their surface morphology.

[0056] After the filtering step is completed, the host computer 6 performs the interpolation step. Because the actual sampling interval of the distance sensor 1 may not perfectly match the preset fixed spatial interval due to factors such as fluctuations in movement speed and trigger signal jitter, the positions of the exposure platform 5 corresponding to the filtered height data points are not strictly equidistant. To ensure that each element in the compensation array corresponds one-to-one with the position of the exposure platform 5 corresponding to the fixed spatial interval trigger pulse output by the synchronization board 11, the height values ​​at these equidistant positions need to be calculated through interpolation.

[0057] When linear interpolation is used in the interpolation step, the host computer 6, for the position of the exposure platform 5 corresponding to the k-th element in the compensation array, finds the two closest measured data points in the filtered data point sequence. Based on the proportional relationship between the distances from this position to the two points, it calculates the height value corresponding to this position using a linear function. Linear interpolation has a relatively small computational load and is suitable for use in situations with relatively high data point density.

[0058] When cubic spline interpolation is used in the interpolation step, the host computer 6 constructs a piecewise cubic polynomial function passing through all nodes, using each filtered data point as a node, and requires that the first and second derivatives be continuous at the nodes. Substituting the position of the exposure platform 5 corresponding to each element in the compensation array into the cubic polynomial expression of the corresponding interval yields the corresponding focal plane target position value. The compensation curve generated by cubic spline interpolation is smooth and even overall, suitable for application on substrates with continuous surface topography.

[0059] When Lagrange interpolation is used in the interpolation step, the host computer 6 constructs a Lagrange interpolation polynomial based on several filtered data points near the location to be interpolated. The height value is then obtained by substituting the location to be interpolated into this polynomial. The order of the interpolation polynomial is determined according to the number of selected neighboring points, which can adapt to data distributions with different densities.

[0060] After filtering and interpolation, the host computer 6 obtains a sequence of focal plane target position values ​​equidistantly arranged along the scanning direction of the exposure platform 5. The spatial interval between adjacent values ​​in the sequence is the same as the fixed spatial interval output by the synchronization board 11. The host computer 6 encapsulates this sequence into a compensation array. The zeroth element in the compensation array corresponds to the focal plane target position value at the compensation starting position, and subsequent elements correspond to the focal plane target position values ​​at each fixed spatial interval as the exposure platform 5 advances. The host computer 6 transmits the entire compensation array to the data storage area of ​​the programmable logic controller 7 through the communication interface, completing the preparation and distribution of the compensation data.

[0061] Reference Figure 1 This invention also provides a dynamic focal plane position compensation system, comprising: Distance sensor 1 is used to collect data on the height of the substrate surface. The host computer 6 is used to generate and distribute a compensation array based on the height data. Programmable logic controller 7 is used to store the compensation array and is equipped with an interrupt program; The encoder includes a platform position feedback reading head 12, which is used to detect the displacement of the exposure platform 5 and output position pulses; Synchronization board 11 is used to convert position pulses into trigger pulses with fixed spatial intervals; Optical coupler module 10 is connected between synchronization board 11 and programmable logic controller 7, and is used to convert the level of the trigger pulse output by synchronization board 11 and input it to programmable logic controller 7. Servo driver 8 is connected to programmable logic controller 7; The linear servo module 9 includes a focusing optical component 4, which is driven by a servo driver to move along the axial direction of the linear servo module. Switch 13 is used for communication and interaction between the host computer 6, the programmable logic controller 7 and the distance sensor 1; The programmable logic controller 7 is also used to calculate the installation offset between the distance sensor 1 and the focusing optical component 4 to determine the compensation starting position, accumulate the number of trigger pulses, and when the accumulated number reaches the number corresponding to the compensation starting position, read the focal plane target position value sequentially from the compensation array in the interrupt program and drive the focusing optical component 4 through the servo driver. The programmable logic controller 7 is also used to shield the interrupt response of the trigger pulse and reset the accumulated count when the exposure platform 5 retracts.

[0062] In this system, distance sensor 1 can be connected to host computer 6 via gigabit Ethernet. Host computer 6 runs data processing software, and programmable logic controller 7 receives the compensation array sent by host computer 6 via Ethernet and stores it in its internal data storage area. The encoder includes two platform position feedback reading heads 12, which are respectively installed on both sides of the Y-axis moving part of the exposure platform 5. They simultaneously read the displacement of the same scale grating line and output two differential signals with orthogonal phases to synchronization board 11. Synchronization board 11 merges the two signals into a single position pulse sequence, and then reduces the frequency of the pulse through internal down-frequency logic, outputting trigger pulses with fixed spatial intervals according to a preset down-frequency coefficient. The pulse output terminal of synchronization board 11 is connected to the high-speed counter input channel of programmable logic controller 7 via optocoupler module 10. Optocoupler module 10 completes the 3.3V to 24V level conversion and provides isolation of not less than 1500V between the input and output terminals. Servo driver 8 is connected to programmable logic controller 7 via pulse direction interface or industrial Ethernet bus. The output terminal of servo driver 8 is connected to the winding of mover 3 of linear servo module 9. The stator 2 of the linear servo module 9 is fixed to the optical base, the mover 3 moves along the axial direction of the linear servo module, the focusing optical component 4 is installed on the mover 3, and the side of the mover 3 is provided with a grating ruler reading head, which forms a closed-loop position feedback with the scale grating on the stator 2.

[0063] During system operation, the host computer 6 first sends a scan start command to the distance sensor 1. The distance sensor 1 moves with the exposure platform 5, collecting substrate surface height data and corresponding encoder position count values, and returns them to the host computer 6 via Ethernet data frames. The host computer 6 filters and interpolates the raw height data to generate a compensation array, which is then sent to the data storage area of ​​the programmable logic controller 7 via Ethernet. The host computer 6 then sets the exposure start coordinates and sends them to the programmable logic controller 7. The programmable logic controller 7 calculates the threshold number of trigger pulses corresponding to the compensation start position based on the preset installation offset and stores it in the comparison register. After the forward scanning of the exposure platform 5 begins, the position pulses output by the two encoder reading heads are down-frequency converted by the synchronization board 11 and the optocoupler module 10, forming trigger pulses with fixed spatial intervals that enter the high-speed counter. The high-speed counter accumulates the number of trigger pulses on the rising edge. When the accumulated number reaches the threshold, the programmable logic controller 7 enables interrupt response, and thereafter, each rising edge of the trigger pulse triggers an interrupt service routine. The interrupt service routine uses the difference between the accumulated count and the threshold as an array index to read the corresponding focal plane target position value from the compensation array, sends a position command to the servo driver 8, and drives the actuator 3 to move the focusing optical component 4 along the axial direction of the linear servo module to the target position. After the forward scan is completed, the host computer 6 sends a rollback command, and the programmable logic controller 7 clears the interrupt enable bit to mask the interrupt response of the trigger pulse. After the exposure platform 5 rolls back to its position and receives the next exposure start command, the programmable logic controller 7 clears and resets the high-speed counter count value and array index, and the system enters the next cycle.

[0064] This invention utilizes substrate surface height data acquired by a distance sensor during pre-scanning. This data is processed by a host computer to generate a compensation array, which is then downloaded to a programmable logic controller (PLC). The encoder position pulses are frequency-reduced via a synchronization board to generate trigger pulses with fixed spatial intervals, synchronizing the focusing action with the scanning displacement and eliminating the impact of exposure platform speed fluctuations on compensation position accuracy. The PLC determines the compensation starting position by calculating the installation offset between the distance sensor and the focusing optical component. When the cumulative number of trigger pulses reaches a certain value, a hardware interrupt is used to sequentially read the target focal plane position value from the compensation array, driving the focusing optical component to move axially along the linear servo module. This simplifies the system architecture while achieving real-time response and automatic compensation for installation errors. When the exposure platform retracts, the PLC disables the trigger pulse interrupt response and resets the cumulative count, effectively preventing false triggering during strip switching. The synergistic effect of these technologies ensures that the exposure focal plane remains in contact with the actual deformation of the substrate surface throughout the entire scanning stroke, significantly improving exposure linewidth uniformity and product yield. Furthermore, the system is compact, cost-effective, and suitable for high-speed scanning exposure production lines with substrates of various specifications.

[0065] The above provides a detailed description of the dynamic focal plane position compensation method and system. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method of dynamic focal plane position compensation, characterized in that, The method includes: The host computer scans the substrate surface using a distance sensor, generates a compensation array based on the height data obtained from the scan, and sends the compensation array to the programmable logic controller. The encoder detects the displacement of the exposure platform and outputs a position pulse, and the synchronization board converts the position pulse into trigger pulses with a fixed spatial interval; The programmable logic controller calculates the installation offset between the distance sensor and the focusing optical component, determines the compensation starting position, and accumulates the number of trigger pulses; When the cumulative number of times reaches the number corresponding to the compensation start position, the programmable logic controller reads the focal plane target position value sequentially from the compensation array in the interrupt routine; The programmable logic controller controls the servo driver based on the read focal plane target position value, driving the focusing optical component to move along the axial direction of the linear servo module; When the exposure platform retracts, the programmable logic controller blocks the interrupt response of the trigger pulse and resets the accumulated count before the next scan band is exposed.

2. The method of claim 1, wherein, The trigger pulses with fixed spatial intervals output by the synchronization board are level-converted by the optocoupler module and then input to the programmable logic controller.

3. The method of claim 2, wherein, The optocoupler module converts the trigger pulse level from 3.3V to 24V; the isolation voltage of the optocoupler module is not less than 1500V.

4. The method according to claim 3, characterized in that, The distance sensor communicates with the host computer via Ethernet communication protocol; the host computer sends a scan start command to the distance sensor, and the distance sensor packages the height measurement value of each sampling point and the corresponding encoder position information, and returns it to the host computer through a data frame.

5. The method according to claim 4, characterized in that, The fixed spatial interval is any one of 1mm, 2mm, 5mm or 10mm; the synchronization board down-frequency processes the position pulse to generate the trigger pulse of the fixed spatial interval.

6. The method according to claim 5, characterized in that, The focusing optical component is driven by a linear servo module; the linear servo module includes a stator and a mover, the mover moves along the axial direction of the linear servo module, and the focusing optical component is mounted on the mover; the linear servo module is a voice coil motor module or a linear motor module.

7. The method according to claim 6, characterized in that, The linear servo module has a motion resolution of 1 micrometer and a repeatability of no more than ±2 micrometers. The linear servo module has a built-in optical or magnetic ruler as a position feedback element, and the servo driver performs closed-loop adjustment of the real-time position of the mover based on the position feedback.

8. The method according to claim 7, characterized in that, The programmable logic controller has a built-in high-speed counter that counts the rising edge of the trigger pulse; the accumulated count is the current count value of the high-speed counter.

9. The method according to claim 8, characterized in that, The host computer's processing of the height data includes a filtering step and an interpolation step; the filtering step uses median filtering, mean filtering, or Gaussian filtering, and the interpolation step uses linear interpolation, cubic spline interpolation, or Lagrange interpolation, thereby generating the compensation array; each element in the compensation array uniquely corresponds to an exposure platform position at a fixed spatial interval.

10. A dynamic focal plane position compensation system, characterized in that, The system includes: Distance sensor, used to collect height data of the substrate surface; The host computer is used to generate a compensation array based on the height data and then distribute it. A programmable logic controller, used to store the compensation array and equipped with an interrupt routine; The encoder, including a platform position feedback readout head, is used to detect the displacement of the exposure platform and output a position pulse; A synchronization board is used to convert the position pulses into trigger pulses with fixed spatial intervals; An optocoupler module is connected between the synchronization board and the programmable logic controller (PLC) to convert the level of the trigger pulse output by the synchronization board and input it to the PLC. A servo driver, connected to the programmable logic controller; A linear servo module, including a focusing optical component, is driven by the servo driver to move along the axial direction of the linear servo module; The switch is used for communication and interaction between the host computer, the programmable logic controller, and the distance sensor. The programmable logic controller is also used to calculate the installation offset between the distance sensor and the focusing optical component to determine the compensation starting position, accumulate the number of trigger pulses, and when the accumulated number reaches the number corresponding to the compensation starting position, read the focal plane target position value sequentially from the compensation array in the interrupt program, and drive the focusing optical component through the servo driver. The programmable logic controller is also used to shield the interrupt response of the trigger pulse when the exposure platform retracts, and to reset the accumulated count.

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