A phase grating-based static alignment system and alignment method

Abstract

This application provides a static alignment system and method based on a phase grating. Incident light emitted from a light source passes through a rotating plate and illuminates a diffraction beam filtering mirror group. The incident light then sequentially passes through the diffraction beam filtering mirror group and a first lens, illuminating alignment marks on the surface of the sample to be tested, generating diffraction beams of various orders. The diffraction beam filtering mirror group filters and selects each order of diffraction beam to obtain multiple sets of target order diffraction beams. These multiple sets of target order diffraction beams generate interference fringes of different orders on the surface of a reference grating. An alignment signal acquisition unit acquires the periodic sinusoidal light intensity signal formed by each order of interference fringes and transmits it to a host computer, which calculates the alignment position of the sample to be tested. This application uses a rotating plate to dynamically modulate the angle of the illumination beam, enabling the synchronous acquisition of the alignment mark's position diffraction information without requiring displacement of the alignment mark, thus achieving static scanning and improving alignment accuracy.

Description

Technical Field

[0001] This application relates to the field of photolithography technology, and in particular to a static alignment system and alignment method based on a phase grating. Background Technology

[0002] As integrated circuit manufacturing equipment develops towards higher precision and higher yield, higher requirements are placed on the manufacturing integration accuracy and process adaptability of the equipment. In particular, the alignment system is the core function to achieve accurate positioning of precision equipment and small manufacturing errors in repeated processing.

[0003] Traditional alignment technologies mainly include two methods: imaging alignment and phase grating scanning alignment. Imaging alignment is based on image recognition and photoelectric sensor detection, such as Canon's patent CN103309169B and Shanghai Microelectronics' patent CN106483777B. However, it is difficult to process, assemble, and manufacture, and it is difficult to meet the alignment requirements under complex working conditions due to strict aberration control. On the other hand, phase grating scanning alignment mainly achieves alignment by collecting higher-order diffraction signals, such as ASML's patent CN1506768B and Nikon's CN111045302A. However, this alignment method is complex to assemble and can only obtain the current position information by scanning. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide at least one static alignment system and alignment method based on a phase grating. This application uses a rotating plate to dynamically modulate the angle of the illumination beam, so that the position diffraction information of the alignment mark can be obtained synchronously without the displacement of the alignment mark, thereby realizing static scanning and improving alignment accuracy.

[0005] This application mainly includes the following aspects:

[0006] In a first aspect, embodiments of this application provide a static alignment system based on a phase grating. The static alignment system includes an alignment subsystem, a first lens, and a host computer. The alignment subsystem includes a light source, a rotating plate, a second lens, a reference grating, an alignment signal acquisition unit, and a diffraction beam filtering mirror group disposed between the first and second lenses. The rotating plate is mounted on a rotating motor, which is driven and controlled by the host computer to rotate the rotating plate. Incident light emitted from the light source is deflected by the rotating plate and then illuminates the diffraction beam filtering mirror group. The incident light sequentially passes through the diffraction beam filtering mirror group and the first lens, illuminating an alignment mark on the surface of the sample to be tested. The alignment mark is a phase grating structure in the horizontal XY direction. Under the action of the incident light, the alignment mark diffracts diffracted beams of various orders carrying position information in the XY direction. Each order of diffracted beam passes through the first lens and the second lens. A lens illuminates a diffraction beam filtering mirror group with parallel light. The diffraction beam filtering mirror group performs order filtering on the diffraction beams of each order, obtaining multiple sets of target order diffraction beams, which are then transmitted to a second lens. After passing through the second lens, the multiple sets of target order diffraction beams generate interference fringes of different orders on the surface of a reference grating. The surface of the reference grating is processed with grating marks of the same period as each order interference fringe. For each order interference fringe, the order interference fringe illuminates a reference grating with the same period as that order interference fringe. An alignment signal acquisition unit is attached to each reference grating to acquire the periodic sinusoidal light intensity signal formed by each order interference fringe at the corresponding reference grating, and transmits the periodic sinusoidal light intensity signal corresponding to each order interference fringe to a host computer. The host computer uses the periodic sinusoidal light intensity signal generated at each reference grating to calculate the static alignment position of the sample under test.

[0007] In one possible implementation, the static alignment system further includes an incident optical fiber, a collimating lens, and a focusing lens arranged sequentially between the light source and the rotating plate. Both the collimating lens and the focusing lens are lens groups with positive optical power. The incident optical fiber is a single-mode polarization-maintaining fiber. The light emitted from the light source passes through the incident optical fiber and emits a beam of outgoing light with a preset wavelength and preset polarization state. The outgoing light is converted into parallel light by the collimating lens and transmitted to the focusing lens. The parallel light passes through the focusing lens and the rotating plate in sequence and converges on the focal plane of the first lens and the second lens.

[0008] In one possible implementation, the diffraction beam filtering lens group includes a reflecting prism and an order aperture. The reflecting prism is disposed at the pupil surface of the focusing lens, and the order aperture is pre-set with multiple light-transmitting holes for filtering diffraction beams of a preset order. Incident light emitted from the light source passes through a rotating plate and converges at the reflecting prism, forming a light spot on the surface of the reflecting prism that rotates and moves in a circle with the beam. The light spot moving in a circle is reflected by the reflecting prism to form an illumination beam that is incident on the first lens. After passing through the first lens, the incident light illuminates the alignment mark on the surface of the sample to be tested in a parallel light orientation.

[0009] In one possible implementation, when the diffracted beams of each order passing through the first lens pass through the order aperture, the multiple light-passing holes on the order aperture filter and select the diffracted beams of each order to obtain multiple sets of target order diffracted beams, which then illuminate the second lens.

[0010] In one possible implementation, the diffraction beam filtering mirror group further includes an order separation component disposed between the second lens and the reflecting prism. The order separation component is composed of multiple wedge angle combinations bonded together. Multiple sets of target order diffraction beams are deflected and separated in different directions by the order separation component to obtain multiple sets of target order diffraction beams propagating in different directions in space. Each set of target order diffraction beams after deflection and separation carries the propagation angle information corresponding to the target order diffraction beam and is incident on the second lens. The propagation angle information indicates the deflection angle of the target order diffraction beam propagating into space by the order separation component.

[0011] In one possible implementation, positive and negative diffracted beams of the same order are deflected at the same angle after passing through the order separation component. The order separation component is located at the focal plane of the first and second lenses. After passing through the second lens, multiple sets of target order diffracted beams, for positive and negative diffracted beams of the same order, coherently superimpose and interfere on the reference grating, generating interference fringes of different orders on the surface of the reference grating.

[0012] In one possible implementation, the static alignment system of the phase grating further includes another alignment subsystem with the same structure as the alignment subsystem. The alignment system also includes a polarizing beam splitter group disposed between the order stop and the first lens. The two alignment subsystems are located on opposite sides of the polarizing beam splitter surface corresponding to the polarizing beam splitter group. The incident light beams emitted by the two alignment subsystems correspond to different wavelengths. Specifically, for each alignment subsystem: the incident light beam passing through the order stop is incident on the polarizing beam splitter group; the polarizing beam splitter group combines the two incident light beams of different wavelengths and linearly polarized states from the two alignment subsystems at the alignment mark according to the polarization states corresponding to the two alignment subsystems; the combined polarized light is reflected to the first lens, and then incident on the polarizing beam splitter group through the first lens. The polarizing beam splitter group splits the beams, and the resulting two incident light beams are respectively incident on the corresponding alignment system to achieve static alignment of the dual-wavelength phase grating through subsequent optical paths.

[0013] In one possible implementation, the rotation axis of the rotating plate and the surface of the rotating plate are at a preset angle.

[0014] In one possible implementation, the alignment signal acquisition unit includes a signal optical fiber and a signal acquisition board attached to each reference grating. For each reference grating: the signal optical fiber attached to the grating acquires a periodic sinusoidal light intensity signal formed at that grating; the signal optical fiber transmits the acquired periodic sinusoidal light intensity signal to the signal acquisition board; the signal acquisition board performs signal conversion, demodulation, and amplification on the received periodic sinusoidal light intensity signal acquired through the reference grating, and transmits the processed periodic sinusoidal light intensity signal to a host computer; the host computer uses a preset algorithm to complete the static position alignment of the sample under test based on the processed periodic sinusoidal light intensity signal corresponding to each reference grating.

[0015] Secondly, this application also provides an alignment method applied to the static alignment system based on a phase grating according to any one of claims 1-9. The method includes: a host computer driving a rotating plate to rotate via a rotary motor; incident light emitted from a light source passing through the rotating plate, a diffraction beam filtering mirror group, and a first lens at a varying incident angle illuminating an alignment mark on the surface of the sample to be tested. The alignment mark is a phase grating structure mark in the horizontal XY direction. Under the action of the incident light with a continuously changing incident angle, the alignment mark diffracts diffracted beams of various orders carrying position information in the XY direction. Each order of diffraction beam passes through the first lens and illuminates the diffraction beam filtering mirror group in a parallel light orientation. The diffraction beam filtering mirror group filters and selects each order of diffraction beam to obtain multiple sets of target order diffraction beams. The beams are transmitted to the second lens; after passing through the second lens, multiple sets of target order diffracted beams generate different order interference fringes on the surface of the reference grating under the action of the second lens. The surface of the reference grating is processed with grating marks with the same period as each order interference fringe formed. For each order interference fringe, the order interference fringe illuminates the reference grating with the same period as the order interference fringe. The alignment signal acquisition unit is close to each reference grating to acquire the periodic sinusoidal light intensity signal formed by each order interference fringe at the corresponding reference grating under the action of the rotating plate, and transmits the periodic sinusoidal light intensity signal corresponding to each order interference fringe to the host computer. The host computer uses the periodic sinusoidal light intensity signal generated at each reference grating to calculate the static alignment position of the sample under test.

[0016] This application provides a static alignment system and method based on a phase grating. Incident light emitted from a light source passes through a rotating plate and illuminates a diffraction beam filtering mirror group. The incident light sequentially passes through the diffraction beam filtering mirror group and a first lens, illuminating alignment marks on the surface of the sample to be tested, generating diffraction beams of various orders. The diffraction beam filtering mirror group filters and selects each order of diffraction beam to obtain multiple sets of target order diffraction beams. These multiple sets of target order diffraction beams generate interference fringes of different orders on the surface of a reference grating. An alignment signal acquisition unit acquires the periodic sinusoidal light intensity signal formed by each order interference fringe passing through the reference grating and transmits it to a host computer, which calculates the alignment position of the sample to be tested. This application uses a rotating plate to dynamically modulate the angle of the illumination beam, enabling the synchronous acquisition of the alignment mark's position diffraction information without requiring displacement of the alignment mark, achieving static scanning alignment and improving alignment accuracy.

[0017] The advantages of this application are:

[0018] 1. The alignment system of the present invention adopts a phase grating alignment system. Unlike the traditional dynamic scanning phase grating alignment system, the present invention adds a rotating plate to dynamically modulate the illumination beam at an angle, so that the position diffraction information of the alignment mark can be obtained synchronously without the displacement of the alignment mark, thus achieving the function of static scanning.

[0019] 2. The grating alignment mark introduced in this invention can be flexibly adapted to the mainstream phase grating alignment marks currently available on the market, such as PM, XPA, SPM and other alignment marks.

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This illustration shows one of the structural schematic diagrams of a static alignment system provided in an embodiment of this application;

[0023] Figure 2 A second schematic diagram of a static alignment system provided in an embodiment of this application is shown;

[0024] Figure 3 The third schematic diagram shows the structure of a static alignment system provided in an embodiment of this application;

[0025] Figure 4 The fourth schematic diagram shows a static alignment system provided in an embodiment of this application;

[0026] Figure 5a This illustration shows an incident schematic diagram of two beams with different polarization states provided in an embodiment of this application;

[0027] Figure 5b This illustration shows a schematic diagram of the emission of two beams with different polarization states according to an embodiment of this application;

[0028] Figure 6a This illustration shows one of the incident schematic diagrams of two beams with the same polarization state provided in an embodiment of this application;

[0029] Figure 6b This is shown as a second incident schematic diagram of two beams with the same polarization state provided in an embodiment of this application;

[0030] Figure 6c This illustration shows a schematic diagram of the emission of two beams with the same polarization state provided in an embodiment of this application. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0032] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0033] Traditional alignment technologies mainly include two methods: imaging alignment and phase grating scanning alignment. Imaging alignment is based on image recognition and photoelectric sensor detection, as exemplified by Canon's patent CN103309169B and Shanghai Microelectronics' patent CN106483777B. However, it is difficult to manufacture and assemble, requires strict aberration control, and struggles to meet alignment requirements under complex working conditions. Phase grating scanning alignment, on the other hand, primarily achieves alignment by collecting higher-order diffraction signals, as exemplified by ASML's patent CN1506768B and Nikon's CN111045302A. This alignment method involves complex assembly and can only acquire current position information through scanning.

[0034] Based on this, embodiments of this application provide a static alignment system and method based on a phase grating, as detailed below:

[0035] Please see Figure 1 , Figure 1 This illustration shows one of the structural schematic diagrams of a static alignment system provided in an embodiment of this application. For example... Figure 1 As shown, the static alignment system provided in this application embodiment includes at least one alignment subsystem, a first lens 31, and a host computer 6. The alignment subsystem includes a light source 1, a rotating plate 2, a second lens 32, a reference grating 4, an alignment signal acquisition unit 5, a host computer 6, and a diffraction beam filtering mirror group 7 disposed between the first lens 31 and the second lens 32. In each alignment subsystem, the second lens 32 and the first lens 31 form a 4F optical structure.

[0036] The rotating plate 2 is mounted on a rotating motor (not shown in the figure). The rotating motor is driven and controlled by the host computer 6 so that the host computer 6 drives the rotating plate 2 to rotate through the rotating motor.

[0037] The incident light emitted from the light source 1 is deflected by the rotating plate 2 and then illuminates the diffraction beam filtering mirror group 7. The incident light passes through the diffraction beam filtering mirror group 7 and the first lens 31 in sequence and illuminates the alignment mark on the surface of the sample 8 to be tested. The alignment mark is a phase grating structure mark in the horizontal XY direction.

[0038] Under the action of the incident light, the alignment mark diffracts in the XY direction, and each order of diffracted beam carries position information. Each order of diffracted beam passes through the first lens 31 and illuminates the diffracted beam filtering mirror group 7 in a parallel light attitude. The diffracted beam filtering mirror group 7 performs order filtering on each order of diffracted beam to obtain multiple sets of target order diffracted beams and transmits them to the second lens 32.

[0039] After passing through the second lens 32, multiple sets of target order diffracted beams generate different order interference fringes on the surface of the reference grating 4. The surface of the reference grating 4 is processed with grating marks with the same period as each order interference fringe formed. For each order interference fringe, the order interference fringe illuminates the reference grating with the same period as the order interference fringe.

[0040] The alignment signal acquisition unit 5 is placed close to each reference grating to acquire the periodic sinusoidal light intensity signal formed by each order interference fringe at the corresponding reference grating, and transmits the periodic sinusoidal light intensity signal generated at each reference grating to the host computer 6.

[0041] The host computer 6 calculates the static alignment position of the sample under test by receiving the periodic sinusoidal light intensity signals generated at each reference grating.

[0042] In specific implementation, the light source 1 in this application can generate lasers with wavelengths such as 532nm or 632.8nm.

[0043] In another preferred embodiment, please refer to Figure 2 , Figure 2This is a second schematic diagram of a static alignment system provided in an embodiment of this application. Figure 2 As shown, the alignment system also includes an incident optical fiber 9, a collimating lens 10, and a focusing lens 11 arranged sequentially between the light source 1 and the rotating plate 2.

[0044] Among them, the incident fiber 9 can be a single-mode polarization-maintaining fiber, and the wavelength of the incident fiber 9 can be 532nm or 632.8nm. The collimating lens 10 and the focusing lens 11 are both lens groups with positive optical power. Specifically, the collimating lens 10 or the focusing lens 11 can be an aspherical lens with good spherical aberration correction, or it can be a spherical lens group with good spherical aberration and chromatic aberration correction.

[0045] In one example, light emitted from light source 1 passes through incident fiber 9 and emits a beam of light with a preset wavelength and preset polarization state. The emitted light is converted into parallel light by collimating lens 10 and transmitted to focusing lens 11. The parallel light passes through focusing lens 11 and rotating plate 2 and converges on the focal plane of first lens 31 and second lens 32. The rotation axis of rotating plate 2 has a preset angle with the surface of rotating plate 2.

[0046] In order to reduce the impact of interference between the lens group and the surface of the sample under test in the static alignment system on the alignment accuracy, in this application, the incident laser generated by the light source 1 can be phase modulated before entering the incident fiber 9 to reduce the stray light effect caused by unnecessary beam interference.

[0047] The collimating lens 10 is mainly used to collect energy from the outgoing light rays of the incident fiber 9 and to propagate them in parallel. The focusing lens 11 is mainly used to converge the incident parallel light rays.

[0048] In another preferred embodiment, such as Figure 2 As shown, the diffraction beam filtering lens group 7 includes a reflecting prism 71 and an order aperture 72. The reflecting prism 71 is located at the pupil surface of the focusing lens. The order aperture is pre-set with multiple light-transmitting holes for filtering diffraction beams of a preset order. The position of the reflecting prism 71 is also the central common focal point of the 4F optical system. The reflecting prism 71 is a reflecting prism with the light incident angle perpendicular to the surface.

[0049] Preferably, the incident light emitted from the light source 1 passes through the rotating plate 2 and converges at the reflecting prism 71, forming a light spot on the surface of the reflecting prism 71 that rotates and moves in a circle. The light spot that moves in a circle is reflected by the reflecting prism 71 to form an illumination beam that is incident on the first lens 31. After passing through the first lens 31, the incident light shines on the alignment mark on the surface of the sample 8 under test in a parallel light posture.

[0050] Specifically, for any rotation angle of the rotating plate 2, the light spot formed by the incident light at the reflecting prism 71 is converged by the reflecting prism 71 and the first lens 31 after passing through the reflecting prism 71 and the first aperture 72. The light beam emitted from the first lens 31 then illuminates the alignment mark on the surface of the sample 8 under test in a parallel light posture approximately perpendicular to the first lens 31.

[0051] In this application, the sample to be tested 8 can be a planar sample with preset alignment marks, such as a silicon wafer or silicon carbide wafer. The position and size of each light-transmitting hole on the order aperture 72 are preset in order to select the preset order diffraction beam for subsequent alignment calculations.

[0052] In one example, since the alignment mark on the surface of the sample 8 is a phase grating structure in the horizontal XY direction, the incident light illuminating the surface of the alignment mark will produce diffraction beams of different orders under the influence of the phase grating structure. The diffraction beam order produced by the alignment mark under the illumination of the incident light is from ±1st to ±7th order. Specifically, the diffraction order corresponding to the diffraction beam can be determined by the following formula:

[0053] P sin(θ-θ0)=kλ

[0054] In this formula, P represents the alignment mark period, θ is the exit angle of the diffracted beam, θ0 is the incident angle of the incident light illuminating the alignment mark, k is the diffraction order of the diffracted beam, and λ is the wavelength of the incident light illuminating the alignment mark. As can be seen from this formula, when the alignment mark period and the wavelength λ of the incident light are fixed, θ and θ0 together determine the diffraction order of the diffracted beam.

[0055] Therefore, in this application, due to the continuous rotation of the rotating plate, the intensity and angle of the incident light rays incident on the surface of the sample to be tested are also constantly changing, so different diffracted beams can be obtained. This design of the present application is to get rid of the traditional phase grating scanning alignment method and to identify the position information of the alignment mark in a static way.

[0056] In a preferred embodiment, when the diffracted beams of each order passing through the first lens 31 pass through the order aperture 72, the multiple light-passing holes on the order aperture 72 filter and select the diffracted beams of each order to obtain multiple sets of target order diffracted beams, and the multiple sets of target order diffracted beams are incident on the second lens 32.

[0057] In this application, multiple sets of diffracted beams change their original beam propagation direction under the action of the first lens 31 and propagate towards the order stop 72 in an approximately parallel manner. When the multiple sets of diffracted beams pass through the order stop 72, each order of diffracted beam is affected by multiple light-transmitting holes on the order stop 72, which selectively intercepts higher-order beams that are not needed in subsequent alignment calculations, and only retains the multiple sets of target order diffracted beams in the XY direction that are needed to propagate into the subsequent optical path. In other words, the multiple light-transmitting holes pre-set on the order stop 72 in this application determine the diffraction order that is allowed to pass.

[0058] In another preferred embodiment, the diffraction beam filtering mirror group 7 further includes an order separation component 73 disposed between the second lens 32 and the reflecting prism 71. The order separation component 73 is composed of a combination of various wedges bonded together. The order separation component 73 can achieve spatial propagation direction modulation of multiple sets of target order diffraction beams. After passing through the order separation component 73, the propagation directions of multiple sets of target order diffraction beams are different. For example, a two-layer wedge plate can achieve 2^2 = 4 diffraction orders of deflection, and a complex wedge layer can achieve more complex diffraction orders and more deflection directions.

[0059] Preferably, multiple sets of target order diffracted beams are deflected and separated in different directions by the order separation component 73 to obtain multiple sets of target order diffracted beams that propagate in different directions in space. Each set of target order diffracted beams after deflection and separation carries the propagation angle information corresponding to the target order diffracted beam and is incident on the second lens 32. The propagation angle information indicates the deflection angle of the target order diffracted beam propagating into space by the order separation component 73.

[0060] Positive and negative diffracted beams of the same order have the same deflection angle after passing through the order separation component 73. The order separation component is set at the focal plane of the first lens 31 and the second lens 32. After passing through the second lens 32, multiple sets of target order diffracted beams, for positive and negative diffracted beams of the same order, coherently superimpose and interfere on the reference grating, producing interference fringes of different orders on the surface of the reference grating.

[0061] In this application, since the positive and negative diffraction beams of the same order have the same deflection angle, after passing through the second lens 32, the two positive and negative diffraction beams of the same order coherently superimpose and interfere at the focal plane of the second lens 32 to form interference fringes. The periods of the interference fringes of different orders are not exactly the same.

[0062] The alignment signal acquisition unit 5 includes a signal fiber (not shown in the figure) and a signal acquisition board (not shown in the figure) attached to each reference grating.

[0063] For each reference grating:

[0064] The periodic sinusoidal light intensity signal formed at the reference grating is acquired using a signal fiber attached to the reference grating. The signal fiber transmits the acquired periodic sinusoidal light intensity signal to the signal acquisition board (OADB). The signal acquisition board (OADB) performs signal conversion, demodulation, and amplification on the received periodic sinusoidal light intensity signal acquired by the reference grating, and transmits the processed periodic sinusoidal light intensity signal to the host computer. The host computer uses a preset algorithm to complete the static position alignment of the sample under test based on the processed periodic sinusoidal light intensity signal corresponding to each reference grating.

[0065] Signal conversion can involve first converting an optical signal into an analog signal, and then into a digital signal.

[0066] In this application, the surface of the reference grating 4 is processed with a reference grating having the same period as each order of interference fringes formed. As the rotating plate 2 rotates continuously, each order of interference fringes will move along the original fringe direction. After passing through the reference grating with the same period, a corresponding periodic sinusoidal light intensity signal is formed. This periodic sinusoidal light intensity signal is collected by the subsequent signal fiber close to the reference grating. The collected periodic sinusoidal light intensity signal is transmitted to the rear signal acquisition board, processed by the signal acquisition board, and then transmitted to the host computer 6. The host computer 6 uses a preset algorithm integrated inside to calculate the processed periodic sinusoidal light intensity signal corresponding to each reference grating, thereby obtaining the position information of the current alignment mark and realizing the alignment of the mark position.

[0067] In another preferred embodiment of this application, please refer to Figure 3 , Figure 3 This is shown as a third schematic diagram of a static alignment system provided in an embodiment of this application. Figure 3 As shown, the static alignment system also includes a polarizing beam splitter group 13 disposed between the secondary aperture 72 and the first lens 31.

[0068] Please see Figure 4 , Figure 4 The fourth schematic diagram shows a static alignment system provided in an embodiment of this application. Figure 4 As shown, the static alignment system also includes another alignment subsystem B with the same structure as alignment subsystem A, such as... Figure 4 As shown, alignment subsystem A and alignment subsystem B are located on opposite sides of the polarization beam splitter surface corresponding to the polarization beam splitter group, and the incident light beams emitted by the two alignment subsystems have different wavelengths.

[0069] In this application, the optical path and light transmission method of the alignment subsystem B are exactly the same as those of the alignment subsystem A, and will not be repeated here. However, the wavelengths of the incident light beams transmitted by the two alignment subsystems are different according to actual needs.

[0070] Specifically, for each alignment subsystem: the incident beam passing through the cascade stop 72 is incident on the polarizing beam splitter group 13. The polarizing beam splitter group 13 combines the two incident beams of different wavelengths with linear polarization states from the two alignment subsystems at the alignment mark according to the polarization states corresponding to the two alignment subsystems. The combined polarized light is reflected to the first lens 31 and then incident on the polarizing beam splitter group 13 through the first lens 31. The polarizing beam splitter group 13 splits the beam, and the two incident beams are respectively incident on the corresponding alignment system to achieve static alignment of the dual-wavelength phase grating through the subsequent optical path.

[0071] The subsequent optical path transmission process is the same for each alignment system, as explained above, and will not be repeated here.

[0072] In one possible implementation, please refer to Figure 5a , Figure 5a This diagram illustrates the incident projection of two beams with different polarization states, as provided in an embodiment of this application. Figure 5a As shown, the polarizing beam splitter group 13 includes a polarizing beam splitter 131.

[0073] When the polarization states of the incident beams corresponding to the two alignment systems are not the same:

[0074] like Figure 5a As shown, assuming the incident light corresponding to alignment system A is P-polarized light and the incident light corresponding to alignment system B is S-polarized light, the incident light of alignment system A passes through the polarizing beam splitter 131 and directly enters the first lens 31. The incident light S2 of alignment system B cannot pass through the polarizing beam splitter 131, so it is reflected by the polarizing beam splitter 131 and enters the first lens 31. The first lens 31 combines the light beams from alignment system A and alignment system B and then enters the sample 8 to be tested.

[0075] Please see Figure 5b , Figure 5b This diagram illustrates the emission of two beams with different polarization states, as provided in an embodiment of this application. Figure 5b As shown, the combined polarized light is reflected to the first lens 31, and then incident on the polarization beam splitter prism 131 through the first lens 31. The polarization beam splitter prism 131 then splits the beam, returning the P-polarized light to the alignment system A and the S-polarized light to the alignment system B. Then, for each alignment system, static alignment of the dual-wavelength phase grating is achieved through the subsequent optical path.

[0076] The polarizing beam splitter assembly 13 also includes a quarter-wave plate 132 and a reflecting mirror 133.

[0077] In one possible implementation, please refer to Figure 6a , Figure 6a This illustration shows one of the incident schematic diagrams of two beams with the same polarization state provided in an embodiment of this application. When the polarization states of the incident beams corresponding to the two alignment systems are the same:

[0078] like Figure 6a As shown, assuming that the incident rays corresponding to alignment system A and alignment system B are both S-polarized light, the incident ray of alignment system A passes through polarizing beam splitter 131, is reflected by polarizing beam splitter 131, and is incident on mirror 133 through quarter wave plate 132.

[0079] Please see Figure 6b , Figure 6b This is shown as a second incident schematic diagram of two beams of light with the same polarization state, provided in an embodiment of this application. For example... Figure 6b As shown, the reflector 133 reflects the incident beam to the quarter-wave plate 132. The quarter-wave plate 132 converts the S-polarized light into P-polarized light, which is then incident on the polarization incident surface of the polarization beam splitter 131 and directly passes through the polarization incident surface to reach the first lens 31. The incident light from the alignment system B cannot pass through the polarization surface of the polarization beam splitter 131, so it is reflected at the polarization incident surface and incident on the first lens 31. The first lens 31 combines the beams from the alignment system A and the alignment system B and then incident them on the sample 8 to be tested.

[0080] like Figure 6b As shown, the combined polarized light is reflected to the first lens 31, and then incident on the polarization beam splitter prism 131 through the first lens 31. The polarization beam splitter prism 131 then splits the beam, returning the P-polarized light to the alignment system A and the S-polarized light to the alignment system B. Then, for each alignment system, static alignment of the dual-wavelength phase grating is achieved through the subsequent optical path.

[0081] Please see Figure 6c , Figure 6c This diagram illustrates the emission of two beams with the same polarization state, according to an embodiment of this application. Figure 6cAs shown, the combined polarized light is reflected to the first lens 31, and then incident on the polarization incident surface of the polarization beam splitter prism 131. The polarization beam splitter prism 131 then splits the beam. The P-polarized light is incident on the quarter-wave plate 132 through the polarization beam splitter prism 131, and then on the reflecting mirror 133. The reflecting mirror 133 then reflects the beam back to the quarter-wave plate 132. The quarter-wave plate 132 converts the P-polarized light into S-polarized light, which is then incident on the polarization reflecting surface of the polarization beam splitter prism 131. After refraction by the polarization reflecting surface, the light returns to the alignment system A.

[0082] The S-polarized light incident on the polarizing beam splitter 131 through the first lens 31 is directly refracted back to the alignment system B by the polarizing reflector.

[0083] In this application, different alignment subsystems generate incident light rays with different wavelengths and polarization states. After adding the polarization beam splitter 13, static alignment of the dual-wavelength phase grating can be achieved.

[0084] The static alignment system of this application adopts a phase grating static alignment system, which is different from the traditional dynamic scanning phase grating static alignment system. By adding a rotating plate, the illumination beam is dynamically modulated at an angle, so that the present invention can obtain the position diffraction information of the alignment mark synchronously without the displacement of the alignment mark, thereby achieving the effect of static scanning and improving alignment accuracy and efficiency.

[0085] Based on the same concept, this application also provides an alignment method corresponding to the static alignment system based on a phase grating provided in the above embodiments, the method including:

[0086] The host computer drives the rotating plate to rotate via a rotary motor. The incident light emitted by the light source passes through the rotating plate, the diffraction beam filtering lens group, and the first lens, and illuminates the alignment mark on the surface of the sample under test at a changing incident angle.

[0087] Under the action of incident light with constantly changing incident angle, the alignment mark diffracts outwards diffracted beams of various orders with varying brightness. Each order of diffracted beam passes through the first lens and illuminates the diffracted beam filtering mirror group in a parallel light posture. The diffracted beam filtering mirror group filters and filters each order of diffracted beam to obtain multiple sets of target order diffracted beams and transmits them to the second lens.

[0088] After multiple sets of target order diffracted beams pass through the second lens, different order interference fringes are generated on the surface of the reference grating under the action of the second lens. The surface of the reference grating is processed with grating marks with the same period as each order interference fringe formed. For each order interference fringe, the order interference fringe illuminates the reference grating with the same period as the order interference fringe.

[0089] The alignment signal acquisition unit is attached to each reference grating to acquire the periodic sinusoidal light intensity signal formed by each order of interference fringes at the corresponding reference grating under the action of the rotating plate. The periodic sinusoidal light intensity signal corresponding to each order of interference fringes is transmitted to the host computer, which calculates the alignment position of the sample under test.

[0090] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and devices described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division; in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Another point is that the displayed or discussed mutual coupling or direct coupling or communication connection may be through some communication interfaces; the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.

[0091] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0092] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0093] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0094] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A phase grating based static alignment system, characterized in that, The static alignment system includes an alignment subsystem, a first lens, and a host computer. The alignment subsystem includes a light source, a rotating plate, a second lens, a reference grating, an alignment signal acquisition unit, and a diffraction beam filtering mirror group disposed between the first and second lenses. The rotating plate is mounted on a rotary motor, which is driven and controlled by the host computer, so that the host computer drives the rotating plate to rotate. In this process, the incident light emitted from the light source is deflected by the rotating plate and then illuminates the diffraction beam filtering mirror group. The incident light then passes sequentially through the diffraction beam filtering mirror group and the first lens, illuminating alignment marks on the surface of the sample to be tested. The alignment marks are phase grating structures in the horizontal XY direction. The alignment mark diffracts diffracted beams of various orders carrying position information in the XY direction under the action of the incident light. Each order diffracted beam passes through the first lens and illuminates the diffracted beam filtering mirror group in a parallel light attitude. The diffracted beam filtering mirror group performs order filtering on each order diffracted beam to obtain multiple sets of target order diffracted beams and transmits them to the second lens. After passing through the second lens, the multiple sets of target order diffraction beams generate different order interference fringes on the surface of the reference grating. The surface of the reference grating is processed with grating marks with the same period as each order interference fringe formed. For each order interference fringe, the order interference fringe illuminates the reference grating with the same period as the order interference fringe. The alignment signal acquisition unit is attached to each reference grating to acquire the periodic sinusoidal light intensity signal formed by each order of interference fringes at the corresponding reference grating, and transmits the periodic sinusoidal light intensity signal corresponding to each order of interference fringes to the host computer. The host computer uses the periodic sinusoidal light intensity signals generated at each reference grating to calculate the static alignment position of the sample under test.

2. The static alignment system of claim 1, wherein, The alignment system further includes an incident optical fiber, a collimating lens, and a focusing lens sequentially disposed between the light source and the rotating plate. Both the collimating lens and the focusing lens are lens groups with positive optical power. The incident optical fiber is a single-mode polarization-maintaining fiber. Wherein, the light emitted from the light source passes through the incident optical fiber and emits a beam of outgoing light with a preset wavelength and preset polarization state; The outgoing light rays are converted into parallel light rays by the collimating lens and then transmitted to the focusing lens; The parallel light rays pass sequentially through the focusing lens and the rotating plate, converging on the focal plane of the first lens and the second lens.

3. The static alignment system of claim 2, wherein, The diffraction beam filtering lens group includes a reflecting prism and an order aperture. The reflecting prism is disposed at the pupil plane of the focusing lens, and the order aperture is pre-set with multiple light-passing holes for filtering diffraction beams of a preset order. The incident light emitted from the light source passes through the rotating plate and converges on the reflecting prism, forming a light spot on the surface of the reflecting prism that rotates and modulates with the light beam to move in a circular motion. The light spot moving in a circular motion is reflected by the reflecting prism to form an illumination beam that enters the first lens; After passing through the first lens, the incident light rays illuminate the alignment marks on the surface of the sample under test in a parallel light orientation.

4. The static alignment system of claim 3, wherein, When the diffracted beams of each order passing through the first lens pass through the order aperture, the multiple light-passing holes on the order aperture filter and select the diffracted beams of each order to obtain multiple sets of target order diffracted beams, which then illuminate the second lens.

5. The static alignment system of claim 4, wherein, The diffraction beam filtering lens assembly also includes a sequence separation component disposed between the second lens and the reflecting prism, the sequence separation component being composed of a combination of various wedge angles bonded together. Among them, multiple sets of target order diffraction beams are deflected and separated in different directions by the order separation component to obtain multiple sets of target order diffraction beams that propagate in different directions in space. Each target order diffracted beam, after being deflected and separated, carries the propagation angle information corresponding to that target order diffracted beam and is incident on the second lens. The propagation angle information indicates the deflection angle of the target order diffracted beam as it propagates into space from the order separation component.

6. The static alignment system according to claim 5, characterized in that, Positive and negative order diffracted beams of the same order will have the same deflection angle after passing through the order separation component, which is positioned at the focal plane of the first and second lenses. Multiple target-order diffracted beams passing through the second lens, for positive and negative diffracted beams of the same order, coherently superimposed and interfered on the reference grating, producing interference fringes of different orders on the surface of the reference grating.

7. The static alignment system according to claim 3, characterized in that, The static alignment system of the phase grating also includes another alignment subsystem with the same structure as the alignment subsystem. The alignment system also includes a polarizing beam splitter group disposed between the order stop and the first lens. The two alignment subsystems are located on opposite sides of the polarizing beam splitter plane corresponding to the polarizing beam splitter group, and the incident light beams emitted by the two alignment subsystems correspond to different wavelengths. Specifically, for each alignment subsystem: the incident beam passing through the order aperture is incident on the polarizing beam splitter group; The polarizing beam splitter group combines two incident beams of different wavelengths with linear polarization states from the two alignment subsystems at the polarizing beam splitter according to the polarization states corresponding to the two alignment subsystems. The combined polarized light is incident on the first lens, and after being diffracted and split by the alignment mark, it is again incident on the polarization beam splitter group through the first lens. The polarization beam splitter group splits the beam, and the two incident beams are respectively incident on the corresponding alignment system to achieve static alignment of the dual-wavelength phase grating through the subsequent optical path.

8. The static alignment system according to claim 7, characterized in that, The rotation axis of the rotating plate has a preset angle with the surface of the rotating plate.

9. The static alignment system according to claim 1, characterized in that, The alignment signal acquisition unit includes a signal optical fiber and a signal acquisition board that are attached to each reference grating. For each reference grating: The periodic sinusoidal light intensity signal formed at the reference grating is acquired using a signal optical fiber that is closely attached to the reference grating, and the acquired periodic sinusoidal light intensity signal is sent to the signal acquisition board. The signal acquisition board performs signal conversion, demodulation, and amplification on the periodic sinusoidal light intensity signal acquired by the reference grating, and transmits the processed periodic sinusoidal light intensity signal to the host computer. The host computer uses a preset algorithm to complete the static position alignment of the sample under test based on the processed periodic sinusoidal light intensity signal corresponding to each reference grating.

10. An alignment method, said alignment method being applied to the static alignment system based on a phase grating as described in any one of claims 1-9, characterized in that, The method includes: The host computer drives the rotating plate to rotate via a rotary motor; The incident light emitted by the light source passes through the rotating plate, the diffraction beam filtering mirror group, and the first lens, and illuminates the alignment marks on the surface of the sample under test at a varying incident angle. The alignment marks are phase grating structure marks in the horizontal XY direction. The alignment mark diffracts outwards under the action of the incident light with the constantly changing incident angle, and diffracts beams of various orders carrying position information. Each order of diffracted beam passes through the first lens and illuminates the diffracted beam filtering mirror group in a parallel light attitude. The diffracted beam filtering mirror group filters and selects each order of diffracted beam to obtain multiple sets of target order diffracted beams and transmits them to the second lens. After the multiple sets of target order diffracted beams pass through the second lens, different order interference fringes are generated on the surface of the reference grating under the action of the second lens. The surface of the reference grating is processed with grating marks with the same period as each order interference fringe formed. For each order interference fringe, the order interference fringe illuminates the reference grating with the same period as the order interference fringe. The alignment signal acquisition unit is attached to each reference grating to acquire the periodic sinusoidal light intensity signal formed by the transmission of each order interference fringe at the corresponding reference grating under the action of the rotating plate. The periodic sinusoidal light intensity signal corresponding to each order interference fringe is transmitted to the host computer so that the host computer can calculate the static alignment position of the sample to be tested.

Images