A global high-dynamic exposure interference field locking device and method

Abstract

A global, high-dynamic exposure interference field locking device and method includes first and second beam paths providing coherent light beams, a reference grating arranged coplanarly with a grating substrate to be exposed, an optical path difference adjustment device disposed on the first beam path, an incident angle adjustment device disposed on the second beam path, and a moiré fringe detection sensor. The exposure interference field generates moiré fringes via the reference grating, and the moiré fringe detection sensor detects the overall translational and overall telescopic changes of the moiré fringes. A controller controls the optical path difference adjustment device to adjust the optical path difference between the first and second beams based on the overall translational changes of the moiré fringes to achieve phase locking of the exposure interference field, and controls the incident angle adjustment device to adjust the relative incident angle between the first and second beams based on the overall telescopic changes of the moiré fringes to achieve period locking of the exposure interference field. This invention effectively improves the stability of the exposure interference field during grating holographic processing exposure.

Description

Technical Field

[0001] The present invention relates to holographic lithography processing technology, and in particular to a global high-dynamic exposure interference field locking device and method. Background Art

[0002] Holographic lithography is an important grating fabrication method. This method uses the exposure interference field generated by a coherent light beam to expose a photosensitive substrate coated with a photosensitive material, thereby forming a periodic microstructure on its surface. However, due to environmental disturbances such as changes in temperature and humidity, and vibrations of optical devices, the exposure interference field can drift during the exposure process. This drift manifests as a phase drift (the overall translation of the exposure interference image) and a periodic drift (the overall expansion and contraction of the exposure interference image). These two types of drift accumulate over the exposure process, resulting in a decrease in the contrast of the exposure interference fringes and ultimately affecting the quality of the finished grating. The effects of such disturbances are difficult to completely eliminate through passive control methods such as creating a constant temperature and humidity environment and improving optical platform vibration isolation. Therefore, a locking technique is required to actively control the exposure interference field to maintain its stability during the exposure process.

[0003] Existing fringe locking methods can be divided into two types, depending on the type of holographic lithography system they are applied to: those for narrow-beam scanning interferometry exposure and those for wide-beam interferometry exposure. Fringe locking methods for narrow-beam scanning exposure, such as those described in Patent No. 2013106933281, utilize heterodyne interferometry to measure fringe phase drift and employ an acousto-optic modulator to frequency-shift the exposure interference field for phase compensation. This method offers high control bandwidth and high response speed, but its monitoring method limits it to controlling only the phase drift of the exposure interference field, failing to meet the global locking requirements for both phase and period drift. Furthermore, it requires the introduction of additional measurement and control elements in the interferometry optical path, hindering the full utilization of laser exposure energy. Fringe locking methods for wide-beam interferometry exposure, such as those described in Patent No. 2023101336610, utilize moiré fringes on a measuring grating and a photodetector to monitor fringe phase drift. Phase compensation is achieved using piezoelectric ceramics to drive a rectangular prism within the exposure beam. This method has high phase compensation accuracy and a relatively simple system layout, but it also only utilizes the phase information of the moiré fringes and cannot achieve global locking of the exposure interference field including periodic drift. Zhang Dong, Zhao Chengqiang, Xu Wendong, et al. Locking of fringe translation and period in large-scale holographic grating exposure [J]. Acta Photonica Sinica, 2018. The moiré fringes of the measuring grating are used with a CCD camera to monitor the drift of the fringe phase and period, and a piezoelectric ceramic driver is used to drive the reflector and spatial light filter to achieve synchronous locking of the two. However, this monitoring and locking system has a sampling frequency of only 20Hz, which cannot effectively suppress mechanical vibrations in the medium and high frequency bands. In addition, the method of moving the spatial light filter affects the collimation of the exposure light field after beam expansion.

[0004] It should be noted that the information disclosed in the above background technology section is only used to understand the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0005] The main purpose of the present invention is to solve the problems existing in the above-mentioned background technology and to provide a global high-dynamic exposure interference field locking device and method to improve the global stability of the exposure interference field in grating holographic processing.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A global high-dynamic exposure interference field locking device includes a first beam path and a second beam path providing coherent light beams, a grating substrate to be exposed, a reference grating arranged coplanarly with the grating substrate to be exposed, an optical path difference adjustment device arranged on the first beam path, an incident angle adjustment device arranged on the second beam path, a moiré fringe detection sensor, and a controller. The first and second light beams are irradiated onto the grating substrate to form an exposure interference field, and moiré fringes are generated through the reference grating. The moiré fringe detection sensor detects the overall translation change (phase change) and overall expansion change (period change) of the moiré fringes. The controller controls the optical path difference adjustment device to adjust the optical path difference between the first and second light beams based on the overall translation change of the moiré fringes to achieve phase locking of the exposure interference field, and controls the incident angle adjustment device to adjust the relative incident angle between the first and second light beams based on the overall expansion change of the moiré fringes to achieve period locking of the exposure interference field.

[0008] Further:

[0009] The optical path difference adjustment device includes a plane reflector and a piezoelectric ceramic actuator rod or a piezoelectric nano-displacement stage for driving the plane reflector to move.

[0010] The incident angle adjustment device includes a plane reflector and a piezoelectric nano-rotation stage or a piezoelectric screw mirror frame for driving the plane reflector to rotate.

[0011] A spatial light filter and a collimating lens are sequentially arranged after the optical path difference adjusting device and the incident angle adjusting device.

[0012] The moiré fringe detection sensor is a camera for capturing moiré fringe images, and the controller determines the overall translation change and overall expansion change of the moiré fringe by analyzing the moiré fringe images captured by the camera.

[0013] The moiré fringe detection sensor is a plurality of photoelectric detectors arranged at a position capable of detecting the moiré fringe light intensity distribution. The controller determines the overall translation change and overall expansion change of the moiré fringe according to the light intensity distribution detected by the plurality of photoelectric detectors.

[0014] The light beam emitted by the laser is split by a beam splitter prism to obtain the first light beam and the second light beam.

[0015] An exposure interference field locking method using the global high-dynamic exposure interference field locking device comprises:

[0016] Detecting the moiré fringes produced by the interaction of two exposure light beams and a reference grating;

[0017] Selecting at least one sampling line on the detected moiré fringes, where the sampling line spans multiple moiré fringes periods, for monitoring phase and period changes of the moiré fringes;

[0018] Before exposure begins, recording the initial light intensity distribution curve on the sampling line as a reference state of the interference field;

[0019] During the exposure process, obtaining the light intensity distribution curve on the sampling line in real time and comparing it with the initial light intensity distribution curve;

[0020] By cross-correlation operation, the difference between the real-time light intensity distribution curve and the initial light intensity distribution curve is calculated to determine the phase and period drift of the moiré fringe;

[0021] executing a control algorithm to calculate a desired feedback control signal based on the result of the cross-correlation operation;

[0022] The exposure interference field is dynamically adjusted, and the feedback control signal controls the optical path difference adjustment device to adjust the optical path difference between the first light beam and the second light beam to achieve phase locking of the exposure interference field, and controls the incident angle adjustment device to adjust the relative incident angle between the first light beam and the second light beam to achieve period locking of the exposure interference field.

[0023] Preferably, before the start of exposure, two sampling lines are selected from the detected Moiré fringes, which are 10 fringe periods apart and each spans 2 to 3 fringe periods in length. They are used as the exposure interference field phase reference sampling line and the period reference sampling line, respectively. The sinusoidal initial light intensity distribution curves on the two sampling lines are recorded and low-pass filtered.

[0024] Optionally, the control algorithm is a proportional control algorithm, a constant step size control algorithm or a proportional-integral-derivative (PID) control algorithm;

[0025] Wherein, the proportional control algorithm includes:

[0026] receiving as input a pixel shift value of a phase sampling line;

[0027] The corresponding feedback control voltage is calculated by multiplying the pixel drift value by the set proportional coefficient;

[0028] Applying a feedback control voltage to the optical path difference adjustment device to achieve overall translational motion locking of the moiré fringes;

[0029] Receives pixel drift values ​​of periodic sampling lines as input;

[0030] The corresponding feedback control voltage is calculated by multiplying the pixel drift value by the set proportional coefficient;

[0031] Applying a feedback control voltage to the incident angle adjustment device to achieve locking of the overall telescopic motion of the moiré fringes;

[0032] Wherein, the constant step size control algorithm includes:

[0033] When it is detected that the fringes drift in a certain direction, the optical path difference adjustment device or the incident angle adjustment device is controlled to move in the opposite direction with a constant step length, and the cycle is performed until the drift is zero;

[0034] The proportional-integral-derivative (PID) control algorithm includes:

[0035] The proportional link calculates the control amount based on the monitored drift amplitude;

[0036] Integral link, the drift amplitude is integrated over time to enhance the control effect;

[0037] The differential link predicts the future trend of drift to speed up the response of the control system.

[0038] The present invention has the following beneficial effects:

[0039] In response to the problem of exposure interference field drift during grating holographic processing, the present invention proposes a global high-dynamic exposure interference field locking device and method. By synchronously locking the phase and period of the exposure interference field, the stability of the exposure interference field during grating holographic processing is effectively improved.

[0040] Compared with the prior art, the present invention fully utilizes the reflection of the phase and period information of the exposure interference field by the reference grating moiré fringes to achieve synchronous monitoring and locking of two degrees of freedom, ensuring good globality during grating exposure processing. At the same time, the optical path system of the present invention is simple to set up and does not require the introduction of additional components in the interference optical path. It has the advantages of high laser energy utilization and little impact on the collimation of the exposure beam.

[0041] The embodiment of the present invention only modulates the incident angle of the collimated interference beam during period locking, which has little effect on the collimation of the wide beam interference exposure field and ensures the global consistency of the interference fringes during large-area exposure processing of the grating.

[0042] The present invention proposes a highly efficient monitoring and control method with high dynamic control performance, which can effectively suppress the exposure interference field drift caused by environmental disturbances and improve the surface groove quality of the processed grid.

[0043] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the system structure of a global high dynamic exposure interference field locking device according to an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the fringe locking process in the global high dynamic exposure interferometer field locking method according to an embodiment of the present invention. The upper portion of the figure shows the real-time moiré fringe image during the exposure process, and the lower portion shows the initial moiré fringe image before the start of exposure.

[0046] Figure 3 Schematic diagram of a controller in a global high dynamic exposure interferometer field locking method according to an embodiment of the present invention;

[0047] Figure 4 Flow chart of a control program in a global high dynamic exposure interferometer field locking method according to an embodiment of the present invention;

[0048] Figure 5 This is a principle diagram of a fringe drift algorithm in a global high dynamic exposure interferometric field locking method according to an embodiment of the present invention;

[0049] Figure 6 This is an experimental drift curve diagram of the global high dynamic exposure interferometric field locking method according to an embodiment of the present invention.

[0050] Figure numerals: 1-laser, 2-first plane mirror, 3-first half-wave plate, 4-beam splitter, 5-second half-wave plate, 6-piezoelectric ceramic actuator rod, 7-second plane mirror, 8-first spatial light filter, 9-first collimating lens, 10-controller, 11-grating substrate to be exposed, 12-third plane mirror, 13-high-speed CCD camera, 14-fourth plane mirror, 15-piezoelectric nano-rotation stage, 16-reference grating, 17-second collimating lens, 18-second spatial light filter, 19-fifth plane mirror. DETAILED DESCRIPTION

[0051] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present invention and its application.

[0052] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and coupling or communication.

[0053] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0054] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0055] In some embodiments, reference Figure 1 The structure of the global high-dynamic exposure interference field locking system is shown, which includes a laser 1, a first half-wave plate 3, a second half-wave plate 5, a beam splitter 4, a first plane mirror 2, a second plane mirror 7, a third plane mirror 12, a fourth plane mirror 14, a fifth plane mirror 19, a first spatial light filter 8, a second spatial light filter 18, a first collimating lens 9, a second collimating lens 17, a grating substrate 11 to be exposed, a reference grating 16, a high-speed CCD camera 13, a piezoelectric ceramic actuator 6, a piezoelectric nano-rotation stage 15, and a controller 10. The moiré fringes generated by the reference grating 16 are used as the basis for locking the exposure interference field, and the piezoelectric ceramic actuator 6 drives the plane mirror 7 to move to achieve phase locking control by modifying the optical path difference between the two exposure beams. The piezoelectric nano-rotation stage 15 drives the fourth plane mirror 14 to modify the incident angle between the two exposure beams to achieve periodic locking control.

[0056] In some embodiments, reference Figure 2The controller components of the global high-dynamic exposure interference field locking system shown include a high-speed camera acquisition card, a piezoelectric ceramic voltage amplifier, a digital / analog conversion card, a piezoelectric nano-rotation stage digital controller, a host computer, and a control program. A high-speed CCD camera and a host computer control program are used to achieve high-speed monitoring of moiré fringe drift.

[0057] In some embodiments, the global high dynamic exposure interference field locking method includes: line sampling: selecting two sampling lines on the collected moiré fringe image as reference sampling lines for phase and period locking; cross-correlation drift calculation: using the real-time light intensity curve and the initial light intensity curve on the two sampling lines to calculate the peak position of the cross-correlation function as the drift amount; proportional control algorithm: multiplying the calculated fringe drift amount by the proportional coefficient as the driving voltage of the actuator.

[0058] In some embodiments, when the exposure interference field is locked, the piezoelectric ceramic actuator rod 6 is first activated to achieve phase locking of the exposure interference field, and then the piezoelectric nano-rotation stage 15 is synchronously activated to achieve synchronous locking of the exposure interference field period and phase.

[0059] Working principle of global high dynamic exposure interference field locking device:

[0060] For the intensity distribution of interference fringes formed by the two exposure beams on the grating substrate to be processed, we have

[0061]

[0062] Where c0 and c1 are constants representing the background light intensity and light intensity amplitude of the exposure fringe, g is the period of the exposure interference fringe, which depends on the laser wavelength λ and the angle θ between the two exposure beams, that is,

[0063]

[0064] is the phase difference between the two exposure interference beams, which depends on the optical path difference Δl of the two exposure beams, that is,

[0065]

[0066] When a reflective grating with a period d twice the period g of the exposure interference field is placed in the same plane as the grating substrate surface to be exposed in the exposure interference field as a reference grating, the positive and negative first-order diffraction lights generated by the two exposure beams irradiating the reference grating interfere again to form a moiré fringe pattern. The light intensity distribution of the moiré fringe can be expressed as

[0067]

[0068] Where k0 and k1 are constants representing the background light intensity and light intensity amplitude, is the phase difference between the exposure interference field fringes and the reference grating fringes. The period of the moiré fringes is

[0069]

[0070] When the reference grating period d is close enough to the double exposure interference field period 2g, a moiré fringe with a width large enough to be captured by a CCD camera is generated. When the exposure interference field phase drifts due to environmental disturbances, the phase difference of the moiré fringe intensity distribution is The change causes the overall moiré pattern to shift. When the exposure interference field period drifts, the period g of the exposure interference fringes changes, causing the overall moiré pattern to expand and contract. Therefore, the moiré fringes can be used as a basis for monitoring and locking exposure interference field drift.

[0071] Figure 2 The fringe locking process in the global high dynamic exposure interference field locking method is shown. Before the exposure starts, two sampling lines with a distance of L = 10p and a length of each spanning 2 to 3 fringe periods are selected from the moiré fringe image collected by the CCD camera as the exposure interference field phase reference sampling lines. With periodic reference sampling line l p Record and use low-pass filtering to obtain the initial sinusoidal light intensity distribution curve on the two sampling lines with I p,0 [x], such as Figure 2 The leftmost and rightmost stripes in the first sub-graph. The real-time light intensity distribution curves on the two sampling lines are obtained in the same way during the exposure process. And perform cross-correlation operation with the recorded initial light intensity distribution curve:

[0072]

[0073]

[0074] The number of pixels of stripe movement between two sampling lines can be calculated based on the shift of the peak position of the cross-correlation function. With τ p ,Right now

[0075]

[0076]

[0077] The pixel drift value of the phase sampling line is used first in the lock As the phase-locked feedback, it is transmitted to the proportional control algorithm of the control program to calculate and apply the feedback control voltage to the piezoelectric ceramic actuator rod. To achieve the locking of the overall translational motion of the moiré fringe, such as Figure 2The leftmost stripes in the second sub-graph are aligned. At this time, the stripes remaining at the periodic sampling line move τ p It is caused by the overall expansion and contraction of the stripes, and compared with the periodic drift value Δp=p'-p of a single stripe, it has been amplified by L / p times, which improves the monitoring accuracy of the periodic drift. p The feedback control voltage ΔU of the piezoelectric nano-rotation stage is calculated by the proportional control algorithm of the control program as the periodic locking feedback quantity. p =K p τ p , realizing the locking of the overall telescopic motion of the moiré fringe, thereby completing the global synchronous locking of the exposure interference field, such as Figure 2 In the third figure, the stripes at both ends are aligned.

[0078] Figure 3 The components of the controller in the global high-dynamic exposure interference field locking method are shown, including a high-speed camera acquisition card, a piezoelectric ceramic voltage amplifier, a digital / analog conversion card, a piezoelectric nano-rotation stage digital controller, a host computer, and a control program. The high-speed CCD camera captures the moiré fringe pattern generated by the reference grating during the exposure process and transmits the image data to the host computer via the CameraLink high-speed camera acquisition card. The host computer uses an algorithm implemented by control software to calculate the phase and period changes of the exposure interference field based on the changes in the moiré fringe pattern, and thus calculates the feedback movement of the piezoelectric ceramic actuator rod and the piezoelectric nano-rotation stage, and sends instructions to the digital / analog conversion card and the piezoelectric nano-rotation stage digital controller. The piezoelectric ceramic actuator rod and the piezoelectric nano-rotation stage are respectively controlled by the digital / analog conversion card, the piezoelectric power amplifier, and the piezoelectric nano-rotation stage digital controller and generate corresponding movements, thereby achieving locking control of the phase and period of the exposure interference field by changing the optical path difference and angle between the two exposure beams.

[0079] A piezoelectric ceramic actuator rod is fixed behind a reflector of one of the beams in the exposure interference optical path. When a control voltage is applied to the piezoelectric ceramic actuator rod, it pushes the reflector to move along the surface normal direction, changing the phase of the exposure interference field by changing the optical path difference Δl between the two exposure beams. This achieves the overall translational motion of the exposure interference field and the moiré fringes. A piezoelectric nano-rotation stage is installed under the large reflector in the other beam of the exposure interference light path. When a control voltage is applied, this stage causes the large reflector to rotate slightly. By varying the incident angle θ of the exposure interference beam, the period g of the exposure interference field is changed, achieving the overall scaling motion of the exposure interference field and the moiré fringes.

[0080] A global high dynamic exposure interferometer field locking method comprises the following steps:

[0081] Step 1: Adjust the optical path to obtain moiré fringes: After adjusting the holographic grating exposure processing optical path, shield the grating substrate to be processed and fix the reference grating in the exposure interference field, arranged coplanar with the grating substrate to be exposed. Observe the positions of the positive and negative first-order diffraction light spots of the two processing beams after passing through the reference grating. By fine-tuning the angle of the large reflector at the rear end of the exposure optical path, the two spots are overlapped to produce moiré fringes with an appropriate width of 0.5-1mm. The position of the CCD camera is adjusted so that the moiré fringes can be projected onto the CCD camera.

[0082] Step 2: Start and configure the stripe locking system: Start the controller and start the following on the host computer: Figure 4 The fringe locking host computer control program shown in the figure configures the camera acquisition card, digital / analog conversion card, and the port number of the piezoelectric nano-rotation stage digital controller, starts the reference fringe image acquisition, and the CCD camera acquisition frame rate is 280fps. According to the acquired reference fringe image, the camera acquisition parameters such as exposure time and acquisition area are adjusted until a reference fringe image with appropriate brightness and high resolution is obtained;

[0083] Step 3: Select sampling lines and record the initial state of the exposure interference field: Select a phase reference sampling line spanning 2-3 fringes at one end of the acquired reference fringe image, and select a period reference sampling line spanning 2-3 fringes at the other end of the reference image separated by 10 fringe periods. Adjust the low-pass filter parameters based on the light intensity distribution curve on the sampling line to ensure good sinusoidal properties, and then record the light intensity distribution curves on the two reference sampling lines at this time as the initial light intensity distribution curve;

[0084] Step 4: Debug the control parameters of the fringe locking system: Start the phase locking function alone to observe the locking effect, and repeatedly adjust the proportional coefficient of the fringe locking system that controls the movement of the piezoelectric ceramic actuator until the locking performance is optimized; after the phase locking proportional coefficient is adjusted, start the periodic locking system at the same time as the phase locking function to observe the periodic locking effect, and repeatedly adjust the proportional coefficient of the fringe locking system that controls the movement of the piezoelectric nano-rotation stage until the performance is optimized, completing the debugging of the fringe locking system parameters;

[0085] Step 5: formally start the exposure and stripe locking process. The workflow is as follows: Figure 4 As shown, the grating substrate to be processed is removed from the shielding, the shutter is started, and the phase and period synchronization locking function of the fringe locking system is started at the same time to achieve the synchronous locking of the phase and period drift of the exposure interference field during the exposure process.

[0086] The fringe drift values ​​on the two monitoring sampling lines when the exposure interference field is not locked, phase locked, and phase cycle synchronously locked are as follows: Figure 6When fringe locking is not enabled, the exposure interference field drifts with a large amplitude due to external disturbances. After phase locking is enabled, the overall translation of the exposure interference field is effectively suppressed, but a certain amplitude drift still exists on the periodic monitoring sampling line. After phase period synchronization is locked, the drift value on the periodic monitoring sampling line is further reduced, thus achieving global locking of the exposure interference field.

[0087] Alternative embodiment:

[0088] The actuator (piezoelectric ceramic actuator rod 6 ) that drives the second plane reflector 7 can be replaced with a uniaxial piezoelectric nano-displacement stage.

[0089] The actuator (piezoelectric nano-rotation stage 15) that drives the fourth plane mirror 14 can be replaced with a piezoelectric screw mirror frame. By adjusting the deflection screw on the piezoelectric screw mirror frame, the deflection angle of the mirror is changed, thereby changing the incident angle of the exposure beam and achieving locking of the exposure interference field period.

[0090] The sensor (high-speed CCD camera 13) that receives the reference grating moiré fringes can be replaced with two sets of photodetectors, one placed several fringes apart from the reference grating moiré fringes. The voltage reading from one set serves as a reference for phase locking of the exposure interference field, while the voltage reading from the other set serves as a reference for period locking of the exposure interference field. The advantages of using photodetectors include using only single-point light intensity information, resulting in a small amount of data and the ability to achieve higher-frequency monitoring.

[0091] exist Figure 2 In the controller configuration shown, the high-speed CCD camera and high-speed camera acquisition card can be replaced with a common industrial CCD / CMOS camera and connected to the host computer using a USB interface.

[0092] The sampling algorithm and drift calculation method for the reference grating moiré fringes can be replaced by selecting a sampling point at each end of the moiré fringes, and directly using the light intensity value at the sampling point as a reference for phase locking and period locking.

[0093] The proportional control algorithm for phase and cycle lock control can be replaced with a constant step-size control algorithm and a proportional-integral-derivative (PID) algorithm. The constant step-size control algorithm controls the piezoelectric ceramic actuator rod / piezoelectric nano-rotation stage to move in the other direction at a constant step size when drift in one direction is detected, and the cycle continues until the drift reaches zero.

[0094] The reflective grating (reference grating 16) used to generate reference moiré fringes can be replaced with a transmissive grating. In this case, the diffracted light formed by the exposure interference light passing through it and the projection direction of the moiré fringes pattern are opposite to those in the current implementation scheme, and become the same as the propagation direction of the exposure interference light.

[0095] In summary, the present invention addresses the problem of exposure interference field drift during grating holographic processing exposure, and proposes a global high-dynamic exposure interference field locking device and method. By synchronously locking the phase and period of the exposure interference field, the stability of the exposure interference field during grating holographic processing exposure is effectively improved.

[0096] Compared with the technology of CN2013106933281, which requires arranging an acousto-optic modulator in the two interfering beams and utilizing the frequency shift effect of the diffracted light to perform phase modulation of the exposure interfering beam, this technology requires the introduction of additional components and, because only the first order of the diffracted light is used, results in low laser exposure energy utilization. In contrast, the optical system of the present invention is simple to set up, does not require the introduction of additional components in the interfering light path, and has high laser energy utilization.

[0097] Compared with the technology in CN2023101336610, which only uses the phase information of the moiré fringes for locking, the present invention fully utilizes the reflection of the reference grating moiré fringes on the phase and period information of the exposure interference field to achieve synchronous monitoring and locking of two degrees of freedom, ensuring good globality during grating exposure processing;

[0098] Compared with literature such as Zhang Dong, Zhao Chengqiang, Xu Wendong, et al. Locking of fringe translation and period in large-scale holographic grating exposure [J]. Acta Photonica Sinica, 2018, etc., the present invention only modulates the incident angle of the interference beam after expansion and collimation during period locking, which has little effect on the collimation of the wide beam interference exposure field, ensuring the global consistency of the interference fringes during large-area exposure processing.

[0099] Compared with Zhang Dong, Zhao Chengqiang, Xu Wendong, et al. Locking of fringe translation and period in large-size holographic grating exposure [J]. Acta Photonica Sinica, 2018., the present invention has higher dynamic control performance through high-efficiency monitoring and control algorithms, can effectively suppress the exposure interference field drift caused by environmental disturbances, and improve the groove quality of the processed grating surface.

[0100] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Persons skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features of different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of protection of the patent application.

Claims

1. A global high-dynamic exposure interference field locking device, characterized in that: The invention comprises a first beam path and a second beam path for providing coherent light beams, a grating substrate to be exposed, a reference grating arranged coplanar with the grating substrate to be exposed, an optical path difference adjustment device arranged on the first beam path, an incident angle adjustment device arranged on the second beam path, a moiré fringe detection sensor, and a controller. The first light beam and the second light beam are irradiated onto the grating substrate to form an exposure interference field, and moiré fringes are generated through the reference grating. The moiré fringe detection sensor detects the overall translation change and overall expansion change of the moiré fringes, and the controller calculates a feedback control signal and controls the overall translation change of the moiré fringes according to the overall translation change of the moiré fringes. The optical path difference adjustment device is controlled to adjust the optical path difference between the first light beam and the second light beam to achieve phase locking of the exposure interference field, and the incident angle adjustment device is controlled to adjust the relative incident angle between the first light beam and the second light beam according to the overall expansion and contraction change of the moiré fringes to achieve period locking of the exposure interference field; wherein the controller is configured to perform the following operations: calculate the difference between the real-time light intensity distribution curve and the initial light intensity distribution curve of the sampled line on the detected moiré fringes through a cross-correlation operation to determine the phase and period drift of the moiré fringes; and execute a control algorithm to calculate the required feedback control signal based on the result of the cross-correlation operation; The control algorithm is a proportional control algorithm, a constant step size control algorithm or a proportional-integral-derivative (PID) control algorithm; Wherein, the proportional control algorithm includes: receiving as input a pixel shift value of a phase sampling line; The corresponding feedback control voltage is calculated by multiplying the pixel drift value by the set proportional coefficient; Applying a feedback control voltage to the optical path difference adjustment device to achieve overall translational motion locking of the moiré fringes; Receives pixel drift values ​​of periodic sampling lines as input; The corresponding feedback control voltage is calculated by multiplying the pixel drift value by the set proportional coefficient; Applying a feedback control voltage to the incident angle adjustment device to achieve locking of the overall telescopic motion of the moiré fringes; Wherein, the constant step size control algorithm includes: When it is detected that the fringes drift in a certain direction, the optical path difference adjustment device or the incident angle adjustment device is controlled to move in the opposite direction with a constant step length, and the cycle is performed until the drift is zero; The proportional-integral-derivative (PID) control algorithm includes: The proportional link calculates the control amount based on the monitored drift amplitude; Integral link, the drift amplitude is integrated over time to enhance the control effect; The differential link predicts the future trend of drift to speed up the response of the control system.

2. The global high-dynamic exposure interference field locking device according to claim 1, characterized in that: The optical path difference adjustment device includes a plane reflector and a piezoelectric ceramic actuator rod or a piezoelectric nano-displacement stage for driving the plane reflector to move.

3. The global high-dynamic exposure interference field locking device according to claim 1, characterized in that: The incident angle adjustment device includes a plane reflector and a piezoelectric nano-rotation stage or a piezoelectric screw mirror frame for driving the plane reflector to rotate.

4. The global high-dynamic exposure interference field locking device according to any one of claims 1 to 3, characterized in that: A spatial light filter and a collimating lens are sequentially arranged after the optical path difference adjusting device and the incident angle adjusting device.

5. The global high-dynamic exposure interference field locking device according to any one of claims 1 to 3, characterized in that: The moiré fringe detection sensor is a camera for capturing moiré fringe images, and the controller determines the overall translation change and overall expansion change of the moiré fringe by analyzing the moiré fringe images captured by the camera.

6. The global high-dynamic exposure interference field locking device according to any one of claims 1 to 3, characterized in that: The moiré fringe detection sensor is a plurality of photoelectric detectors arranged at a position capable of detecting the moiré fringe light intensity distribution. The controller determines the overall translation change and overall expansion change of the moiré fringe according to the light intensity distribution detected by the plurality of photoelectric detectors.

7. The global high-dynamic exposure interference field locking device according to any one of claims 1 to 3, characterized in that: The light beam emitted by the laser is split by a beam splitter prism to obtain the first light beam and the second light beam.

8. An exposure interference field locking method using the global high-dynamic exposure interference field locking device according to any one of claims 1 to 7, characterized in that: include: Detecting the moiré fringes produced by the interaction of two exposure light beams and a reference grating; Selecting at least one sampling line on the detected moiré fringes, where the sampling line spans multiple moiré fringes periods, for monitoring phase and period changes of the moiré fringes; Before exposure begins, recording the initial light intensity distribution curve on the sampling line as a reference state of the interference field; During the exposure process, obtaining the light intensity distribution curve on the sampling line in real time and comparing it with the initial light intensity distribution curve; By cross-correlation operation, the difference between the real-time light intensity distribution curve and the initial light intensity distribution curve is calculated to determine the phase and period drift of the moiré fringe; executing a control algorithm to calculate a desired feedback control signal based on the result of the cross-correlation operation; Dynamically adjusting the exposure interference field, controlling the optical path difference adjustment device to adjust the optical path difference between the first light beam and the second light beam by a feedback control signal to achieve phase locking of the exposure interference field, and controlling the incident angle adjustment device to adjust the relative incident angle between the first light beam and the second light beam to achieve period locking of the exposure interference field; The control algorithm is a proportional control algorithm, a constant step size control algorithm or a proportional-integral-derivative (PID) control algorithm; Wherein, the proportional control algorithm includes: receiving as input a pixel shift value of a phase sampling line; The corresponding feedback control voltage is calculated by multiplying the pixel drift value by the set proportional coefficient; Applying a feedback control voltage to the optical path difference adjustment device to achieve overall translational motion locking of the moiré fringes; Receives pixel drift values ​​of periodic sampling lines as input; The corresponding feedback control voltage is calculated by multiplying the pixel drift value by the set proportional coefficient; Applying a feedback control voltage to the incident angle adjustment device to achieve locking of the overall telescopic motion of the moiré fringes; Wherein, the constant step size control algorithm includes: When it is detected that the fringes drift in a certain direction, the optical path difference adjustment device or the incident angle adjustment device is controlled to move in the opposite direction with a constant step length, and the cycle is performed until the drift is zero; The proportional-integral-derivative (PID) control algorithm includes: The proportional link calculates the control amount based on the monitored drift amplitude; Integral link, the drift amplitude is integrated over time to enhance the control effect; The differential link predicts the future trend of drift to speed up the response of the control system.

9. The exposure interference field locking method according to claim 8, wherein: Before the start of exposure, two sampling lines with a distance of 10 fringe periods and a length of 2 to 3 fringe periods are selected from the detected Moiré fringes as the exposure interference field phase reference sampling line and period reference sampling line, respectively. The sinusoidal initial light intensity distribution curves on the two sampling lines are recorded and low-pass filtered.

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