Global high-dynamic exposure interference field locking device and method

Abstract

The invention relates to a global high-dynamic exposure interference field locking device and a global high-dynamic exposure interference field locking method. Comprising a first light beam path, a second light beam path, a reference grating, an optical path difference adjusting device, an incident angle adjusting device and a moire fringe detection sensor, wherein the first light beam path and the second light beam path provide coherent light beams; the reference grating and a grating substrate to be subjected to exposure processing are arranged in a coplanar manner; the exposure interference field generates moire fringes through the reference grating, the moire fringe detection sensor detects the overall translation change and overall telescopic change of the moire fringes, and the controller controls the optical path difference adjusting device to adjust the optical path difference between the first light beam and the second light beam according to the overall translation change of the moire fringes so as to achieve phase locking of the exposure interference field. And the incident angle adjusting device is controlled to adjust the relative incident angle between the first light beam and the second light beam according to the overall telescopic change of the moire fringes so as to realize periodic locking of the exposure interference field. The stability of the exposure interference field in the grating holographic processing exposure process is effectively improved.

Description

Technical Field

[0001] The 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 processing method. This method uses the exposure interference field generated by a coherent light beam to expose the photosensitive material coated on the lithography substrate, thereby forming a periodic microstructure on its surface. However, due to the influence of environmental disturbances such as temperature and humidity changes, vibration of optical devices, etc., the exposure interference field will drift during the exposure process, which is manifested as the phase drift of the overall translation of the exposure interference image and the periodic drift of the overall expansion and contraction of the exposure interference image. These two types of drifts are accumulated during 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 impact caused by such disturbances is difficult to completely eliminate through passive control methods such as creating a constant temperature and humidity environment and improving the vibration isolation of the optical platform. For this reason, locking technology 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 fringe locking methods for fine beam scanning interference exposure and fringe locking methods for wide beam interference exposure according to the type of holographic lithography system to which they are applied. The fringe locking method for fine beam scanning exposure, such as the invention patent with patent number 2013106933281, uses heterodyne interferometry to measure fringe phase drift, and uses an acousto-optic modulator to perform frequency shift control on the exposure interference field to achieve phase compensation. This method has a high control bandwidth and response speed, but its monitoring method limits it to only controlling the phase drift of the exposure interference field, which cannot meet the global locking requirements of phase drift and period drift, and requires the introduction of additional measurement and control elements in the interference optical path, which cannot fully utilize the laser exposure energy. The fringe locking method for wide beam interference exposure, such as the invention patent with patent number 2023101336610, uses the moiré fringes of the measuring grating and the photodetector to monitor the fringe phase drift, and uses piezoelectric ceramics to drive the right-angle prism located in an exposure beam to achieve phase compensation. This method has high phase compensation accuracy and a relatively simple system layout, but it also only uses the phase information of the moiré fringes and cannot achieve global locking of the exposure interference field containing periodic drift. 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 moiré fringes of the measuring grating and the CCD camera are used to monitor the drift of the fringe phase and period, and the piezoelectric ceramic driver is used to drive the reflector and the spatial light filter to achieve synchronous locking of the two. However, the monitoring and locking system has a sampling frequency of only 20Hz, which cannot effectively suppress the mechanical vibration in the medium and high frequency bands, and the way of moving the spatial light filter will affect 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 for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the 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 comprises 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, wherein the first beam and the second beam are irradiated onto the grating substrate to form an exposure interference field, and moiré fringes are generated through the reference grating, wherein the moiré fringe detection sensor detects the overall translation change (phase change) and overall expansion change (periodic change) of the moiré fringes, and the controller controls the optical path difference adjustment device to adjust the optical path difference between the first beam and the second beam according to 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 beam and the second beam according to 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 comprises a plane reflector and a piezoelectric ceramic actuating rod or a piezoelectric nano displacement stage for driving the plane reflector to move.

[0010] The incident angle adjustment device comprises a plane reflector and a piezoelectric nano-rotating table 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 moire fringe detection sensor is a camera for capturing moire fringe images, and the controller determines the overall translation change and overall expansion change of the moire fringe by analyzing the moire fringe images captured by the camera.

[0013] The moire fringe detection sensor is a plurality of photoelectric detectors arranged at a position capable of detecting the moire fringe light intensity distribution, and the controller determines the overall translation change and overall telescopic change of the moire 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, wherein the sampling line spans a plurality of moiré fringes periods, for monitoring phase and period changes of the moiré fringes;

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

[0019] During the exposure process, a light intensity distribution curve on the sampling line is obtained in real time, and compared 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 fringes;

[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, 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 according to the pixel drift value multiplied 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] Receiving as input a pixel drift value of a periodic sampling line;

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

[0031] Applying a feedback control voltage to the incident angle adjustment device to achieve overall telescopic motion locking 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] Wherein, the proportional-integral-derivative (PID) control algorithm includes:

[0035] Proportional link, calculates the control amount according to 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 view of the problem of exposure interference field drift during grating holographic processing exposure, the present invention proposes a global high-dynamic exposure interference field locking device and method, which effectively improves the stability of the exposure interference field during grating holographic processing exposure by synchronously locking the phase and period of the exposure interference field.

[0040] Compared with the prior art, the present invention makes full use of the reflection of the reference grating moiré fringes on the phase and period information of the exposure interference field, realizes the synchronous monitoring and locking of two degrees of freedom, and ensures 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 need to introduce additional components in the interference optical path. It has the advantages of high laser energy utilization and little effect 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, thereby ensuring 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, which has high dynamic control performance, can effectively suppress the drift of the exposure interference field caused by environmental disturbances, and improves 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 It 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 Schematic diagram of the fringe locking process in the global high dynamic exposure interference field locking method according to an embodiment of the present invention, wherein the upper part of the figure represents the real-time moiré fringe image during the exposure process, and the lower part represents the initial moiré fringe image before the exposure starts;

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

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

[0048] Figure 5 It is a principle diagram of a fringe drift algorithm in a global high dynamic exposure interference 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 interference 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 and application of the present invention.

[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 fixing as well as for coupling or communication.

[0053] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0054] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0055] In some embodiments, reference Figure 1 The structure of the global high dynamic exposure interference field locking system is shown, and the exposure interference field locking system includes a laser 1, a first half-wave plate 3, a second half-wave plate 5, a beam splitter 4, a first plane reflector 2, a second plane reflector 7, a third plane reflector 12, a fourth plane reflector 14, a fifth plane reflector 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 rod 6, a piezoelectric nano-rotating stage 15, and a controller 10. Among them, the moiré fringes generated by the reference grating 16 are used as the locking basis of the exposure interference field, and the plane reflector 7 is driven by the piezoelectric ceramic actuator rod 6 to move to achieve phase locking control by modifying the optical path difference of the two exposure beams, and the piezoelectric nano-rotating stage 15 is used to drive the fourth plane reflector 14 to modify the incident angle of the two exposure beams to achieve periodic locking control.

[0056] In some embodiments, reference Figure 2The components of the controller in 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 realize high-speed monitoring of Moire 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 on the two sampling lines and the initial light intensity curve 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 and controlled, 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 light intensity distribution of the interference fringes formed by the two exposure beams on the grating substrate to be processed,

[0061]

[0062] Where c0 and c1 are constants representing the background light intensity and light intensity amplitude of the exposure fringes, g is the period of the exposure interference fringes, 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 twice the 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 light intensity distribution The change causes the moiré fringe pattern to shift as a whole; when the exposure interference field period drifts, the period g of the exposure interference fringe changes, causing the moiré fringe pattern to expand and contract as a whole. Therefore, the moiré fringe can be used as a basis for monitoring and locking the 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 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 sinusoidal initial light intensity distribution curve on the two sampling lines with I p,0 [x], such as Figure 2 The leftmost and rightmost stripes of the first sub-image. 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 the stripe movement at the 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 locking As the phase-locked feedback, it is transmitted to the proportional control algorithm of the control program to calculate and apply 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-figure are aligned. At this time, the stripes remaining at the periodic sampling line move by 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 , realize 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 The stripes at both ends of the third sub-image in 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 shoots the moiré fringe pattern generated by the reference grating during the exposure process, and transmits the image data to the host computer through the CameraLink high-speed camera acquisition card; the host computer uses the algorithm implemented by the control software to calculate the phase and period change of the exposure interference field according to the change of the moiré fringe pattern, and 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 and the piezoelectric power amplifier, and the piezoelectric nano-rotation stage digital controller and generate corresponding movements, thereby realizing the locking control of the phase and period of the exposure interference field by changing the optical path difference and the angle between the two exposure light 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 given 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. The overall translational motion of the exposure interference field and the moiré fringes is realized. 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, the large reflector is driven to rotate slightly. By changing the incident angle θ of the exposure interference beam, the period g of the exposure interference field is changed, and the overall scaling motion of the exposure interference field and the moiré fringes is realized.

[0080] A global high dynamic exposure interference 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 and arrange it 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 light beams after passing through the reference grating, and fine-tune the angle of the large reflector at the rear end of the exposure optical path to make the two spots overlap and generate moiré fringes with a suitable width of 0.5 to 1 mm, and adjust the position of the CCD camera 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 steps on the host computer: Figure 4 The fringe locking host computer control program shown in the figure configures the camera acquisition card, the 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 to 3 stripes at one end of the reference fringe image collected, and select a period reference sampling line spanning 2 to 3 stripes at the other end of the reference image with an interval of 10 stripe cycles. Adjust the low-pass filter parameters according to the light intensity distribution curve on the sampling line to make it have better sinusoidality, 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 stripe locking system: start the phase locking function alone to observe the locking effect, and repeatedly adjust the proportional coefficient of the movement of the piezoelectric ceramic actuator in the stripe locking system until the locking performance is optimal; after the phase locking proportional coefficient is adjusted, start the periodic locking system while starting the phase locking to observe the periodic locking effect, and repeatedly adjust the proportional coefficient of the movement of the piezoelectric nano-rotation stage in the stripe locking system until the performance is optimal, and complete the debugging of the stripe locking system parameters;

[0085] Step 5: officially 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] When the exposure interference field is not locked, the phase is locked, and the phase cycle is synchronously locked, the fringe drift values ​​on the two monitoring sampling lines are as follows: Figure 6When the fringe lock is not turned on, the exposure interference field drifts with a large amplitude due to the influence of external disturbances. After the phase lock is started, the overall translation of the exposure interference field is effectively suppressed, but there is still a certain amplitude drift on the periodic monitoring sampling line. After the phase cycle is synchronously locked, the drift value on the periodic monitoring sampling line is further reduced, thereby achieving global locking of the exposure interference field.

[0087] Alternative embodiment:

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

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

[0090] The sensor (high-speed CCD camera 13) receiving the reference grating moiré fringes can be replaced with two sets of photodetectors, which are respectively arranged at the intervals of several fringes of the reference grating moiré fringes, and the voltage indication of one of them is used as the exposure interference field phase locking reference, and the voltage indication of the other is used as the exposure interference field period locking reference. The advantages of using photodetectors include using only single-point light intensity information, small data volume, and the ability to achieve higher frequency monitoring.

[0091] exist Figure 2 In the controller configuration shown, the high-speed CCD camera and the 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 of phase and cycle locking control can be replaced by a constant step control algorithm and a proportional-integral-differential (PID) algorithm. The constant step control algorithm means that when the drift of the stripes in a certain direction is detected, the piezoelectric ceramic actuator rod / piezoelectric nano-rotation stage is controlled to move in another direction with a constant step length, and the cycle is repeated until the drift is zero and stops.

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

[0095] To sum up, the present invention aims at 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, the technology needs to arrange an acousto-optic modulator in the two interference light beams and use the frequency shift effect of the diffracted light to perform phase modulation of the exposure interference light beam, which requires the introduction of additional elements and the use of only the first order of the diffracted light leads to low energy utilization rate of laser exposure; compared with the technology of the present invention, the optical system is simple to set up, and no additional elements need to be introduced in the interference light path, and the energy utilization rate of the laser is high;

[0097] Compared with the technology of CN2023101336610, which only uses the phase information of the moiré fringes for locking, the present invention makes full use of 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, thus 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-size holographic grating exposure [J]. Journal of Photonics, 2018., the present invention only modulates the incident angle of the interference beam after beam 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 of the grating;

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

[0100] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. 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 can 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 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, wherein 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, wherein the moiré fringe detection sensor detects the overall translation change and overall expansion change of the moiré fringes, and the controller controls the optical path difference adjustment device to adjust the optical path difference between the first light beam and the second light beam according to the overall translation change of the moiré fringes so as 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 according to the overall expansion change of the moiré fringes so as to achieve period locking of the exposure interference field.

2. The global high dynamic exposure interference field locking device according to claim 1, characterized in that: The optical path difference adjustment device comprises a plane reflector and a piezoelectric ceramic actuating 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 comprises a plane reflector and a piezoelectric nano-rotating table 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 4, characterized in that: The moire fringe detection sensor is a camera for capturing moire fringe images, and the controller determines the overall translation change and overall expansion change of the moire fringe by analyzing the moire fringe images captured by the camera.

6. The global high dynamic exposure interference field locking device according to any one of claims 1 to 4, characterized in that: The moire fringe detection sensor is a plurality of photoelectric detectors arranged at a position capable of detecting the moire fringe light intensity distribution, and the controller determines the overall translation change and overall telescopic change of the moire 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 6, 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, wherein the sampling line spans a plurality of moiré fringes periods, for monitoring phase and period changes of the moiré fringes; Before exposure begins, an initial light intensity distribution curve on the sampling line is recorded as a reference state of the interference field; During the exposure process, a light intensity distribution curve on the sampling line is obtained in real time, and compared 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 fringes; executing a control algorithm to calculate a desired feedback control signal based on the result of the cross-correlation operation; 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.

9. The exposure interference field locking method according to claim 8, characterized in that: 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 the period reference sampling line, respectively. The sinusoidal initial light intensity distribution curves on the two sampling lines are recorded and low-pass filtered.

10. The exposure interference field locking method according to claim 8, characterized in that: 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 according to the pixel drift value multiplied 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; Receiving as input a pixel drift value of a periodic sampling line; The corresponding feedback control voltage is calculated according to the pixel drift value multiplied by the set proportional coefficient; Applying a feedback control voltage to the incident angle adjustment device to achieve overall telescopic motion locking 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; Wherein, the proportional-integral-derivative (PID) control algorithm includes: Proportional link, calculates the control amount according to 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.

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