Special grating photoetching method and its glue filling system

Abstract

This invention discloses a special grating photolithography method and its resist replenishment system. Based on laser direct writing technology, this invention utilizes the characteristic that the printed grating has different resolution requirements in different dimensions. The printed structure is rotated in coordinates to ensure that the system's high-resolution projection matches the high-resolution requirements of the printed structure, achieving high-quality printing. Furthermore, to enable long-term writing and printing, this invention also provides a device for continuous resist replenishment during extended writing processes. This device can also be used for in-situ development and optical imaging.

Description

Technical Field

[0001] This invention belongs to the field of optics, specifically relating to a special grating lithography method based on laser direct writing and coordinate rotation, and a photoresist application system for this lithography method. Background Technology

[0002] Special gratings, including blazed gratings and tilted gratings, are grating devices with special structures. Compared with conventional rectangular gratings, they have unique performance characteristics and extremely wide applications.

[0003] Specifically, a blazed grating is a special type of reflective grating. Its surface is coated with a layer of metal or other reflective material and precision-machined into a periodic structure. Unlike traditional transmission diffraction gratings, blazed gratings utilize surface reflection to disperse and select incident light. When incident light strikes the surface of a blazed grating, it is reflected at different angles, producing multiple secondary reflections. These secondary reflections can be further dispersed into components of different wavelengths, forming a dispersion pattern. Therefore, blazed gratings can be used as high-resolution, high-sensitivity wavelength selectors and scanners, among other applications. Compared to traditional diffraction gratings, blazed gratings offer higher efficiency and a wider range of applications. For example, blazed gratings can be used to separate and measure light of different wavelengths for spectral analysis; in laser interferometry, blazed gratings can be used as mirrors in laser interferometers to measure parameters such as object shape and surface roughness by comparing the phase differences reflected from the laser beam; in holographic imaging, blazed gratings can be used to prepare holograms, and their diffraction effects can be used to record and reproduce three-dimensional images; in optical communication, blazed gratings can be used to manufacture transmission media, such as fiber optic cables and waveguides, to achieve high-speed data transmission; in modern display technology, especially in the AR / VR field, blazed gratings can be used to manufacture reflective display devices, such as digital projectors and head-mounted displays, and are key optical components for 3D glasses; in addition, blazed gratings can also be used in astronomical observations for energy spectrum analysis of galaxies and planets.

[0004] The structure of a tilted grating is similar to that of a rectangular grating, but the difference lies in the angle between the sidewalls and the bottom surface of the grating structure in its cross-section. When this angle is 90°, it becomes a regular rectangular grating. When incident light passes through a tilted grating, diffraction occurs due to the difference in refractive index. This diffraction can separate the light beam into components of different wavelengths, causing them to deviate from their original direction at different angles. Therefore, tilted gratings can be used as dispersive elements, spectrometers, and wavelength selectors. Furthermore, tilted gratings can achieve more complex functions by adjusting the spacing and angle of their grooves or protrusions. Similar to blazed gratings, tilted gratings have wide applications in display technology, holographic imaging, and laser interferometry. In addition, tilted gratings can be used for surface texturing of solar panels to improve their conversion efficiency; in the biomedical field, they can also be applied to cell imaging and fluorescence detection.

[0005] It is evident that blazed gratings and tilted gratings, as two special types of grating devices, have broad application prospects and commercial value. Since blazed gratings and tilted gratings are three-dimensional nanostructures, their manufacturing methods can only rely on high-precision photolithography technology with three-dimensional manufacturing characteristics. Currently, the fabrication of high-precision blazed gratings and tilted gratings mainly relies on electron beam lithography, which boasts ultra-high resolution and precision. However, the limitations of electron beam lithography are also obvious, mainly including:

[0006] 1. High production costs: Electron beam lithography equipment is expensive and has a limited lifespan, requiring frequent maintenance and upkeep, which increases production costs.

[0007] 2. Long manufacturing cycle: Since electron beam lithography is a point-by-point exposure method, manufacturing a large-area sample requires a lot of time and effort, and the manufacturing cycle is relatively long.

[0008] 3. Poor mass production capacity: Due to the long manufacturing cycle and low integration of electron beam lithography, it cannot meet the needs of large-scale mass production.

[0009] 4. Susceptible to environmental interference: During electron beam bombardment, environmental factors such as static electricity and magnetic fields may affect the exposure results. To eliminate these effects, strict control and adjustment of the equipment and laboratory environment are required.

[0010] Similar to electron beam lithography, two-photon laser direct writing is a direct-writing lithography technique that utilizes the nonlinear effects of laser light on matter. Unlike electron beam lithography, laser direct writing typically uses visible light lasers as its light source, with wavelengths much longer than electron beams. Therefore, the precision of laser direct writing cannot reach that of electron beam lithography. However, laser direct writing also has significant advantages. Compared to electron beam lithography, it does not require a demanding processing environment, its cost is much lower, and its processing efficiency under the same conditions is higher. More importantly, because the beam can penetrate transparent materials and be focused into the interior of the medium, laser direct writing is a true three-dimensional manufacturing technology with broad application prospects in the fabrication of micro- and nano-optical components. Therefore, two-photon laser direct writing lithography can also be considered a high-precision micro- and nano-3D printing technology. However, limited by the diffraction limit, the precision of laser direct writing is restricted to around 100 nm. Therefore, it is impossible to manufacture high-precision blazed gratings and tilted gratings, which greatly limits the technological advantages and application promotion of laser direct writing in other aspects.

[0011] like Figure 1 In traditional two-photon printing, the optical diffraction limit prevents the light beam from being focused into an ideal point. Instead, it is focused at the focal plane of the objective lens into an ellipsoid with a certain spatial size. Its two minor axes lie within the focal plane, while its major axis is perpendicular to the focal plane along the optical axis. During printing, this focused spot undergoes relative displacement with the photoresist, exciting photoresist polymerization wherever it is applied, forming a three-dimensional structure. Because the focused spot is ellipsoidal, the printing resolution exhibits spatial non-uniformity. Figure 2 It can be seen that the focused spot has a small projection in the xy plane, that is, in the plane parallel to the focal plane, thus enabling higher resolution printing. However, in the yz plane, as... Figure 3 As shown, or within the xz plane (not shown in the figure), i.e., the plane perpendicular to the focal plane, the projected feature size is larger, meaning the printing resolution is lower. Therefore, in conventional two-photon 3D printing, the axial (yz, xz) resolution is generally considered lower than the lateral (xy) resolution. Consequently, when manufacturing certain structures with high requirements for axial resolution, the desired results cannot be achieved.

[0012] like Figure 4 The tilted grating shown is a special type of grating whose three-dimensional structure has a high spatial frequency only in a single plane, such as... Figure 5 The xz shown and as Figure 6 The xy directions are shown. And as in... Figure 7 When manufacturing blazed and tilted gratings along the yz direction as shown, the low-resolution projection of the focused spot in the traditional method and the projection of the cross section of the grating requiring high-resolution printing (hereinafter referred to as the "high-resolution requirement surface") are in the same direction, resulting in a step effect. Figure 8 As shown, this results in insufficient printing resolution, making it impossible to effectively print the required raster structure.

[0013] Therefore, this invention proposes a special grating photolithography method and a resist replenishment system based on laser direct writing technology, providing a new technical approach for the manufacture of high-precision special gratings. Summary of the Invention

[0014] The purpose of this invention is to address the special grating printing method by rotating the special grating structure to be printed in coordinates so that its high-resolution required surface is aligned with the high-resolution projection direction of the focused spot. This allows the special grating with higher feature size requirements to be printed in the direction with higher resolution of the focused spot, thereby achieving better printing results.

[0015] To achieve the above objectives, the present invention adopts the following technical solution:

[0016] A special grating photolithography method includes the following steps:

[0017] (1) The femtosecond laser enters the first polarization beam splitter after its polarization direction is rotated by the half-wave plate, and the picosecond laser enters the first polarization beam splitter after passing through the phase plate.

[0018] (2) After the femtosecond laser and picosecond laser are combined by the first polarization beam splitter, they enter the scanning system and focusing components, so that the combined light is focused on the photoresist.

[0019] This invention employs a femtosecond laser edge light suppression technique for photolithography. Traditional femtosecond photolithography systems are limited by the diffraction limit, making it difficult to break through the 50nm feature size. The edge light suppression technique uses another beam that can be focused into a hollow spot, namely a picosecond laser, to suppress the area of ​​the beam that excites the photoresist polymerization reaction, thereby achieving a smaller feature size and improving the writing accuracy.

[0020] Preferably, in step (1), the femtosecond laser emitted by the laser first enters the second half-wave plate and the second polarization beam splitter. The beam transmitted through the second polarization beam splitter is the excitation light. The light reflected by the second polarization beam splitter, after passing through the dispersive device, has its suppression pulse width broadened to the picosecond laser, i.e., the suppression light, in step (2). The excitation light and the suppression light then sequentially pass through the beam shrinking module, the acousto-optic modulator, and the beam expanding module before entering the first polarization beam splitter for beam combining. The beam shrinking module is used to reduce the beam diameter to meet the requirements of the acousto-optic modulator. The acousto-optic modulator is used to achieve rapid beam switching and power control. The beam expanding module is used to expand the beam diameter.

[0021] Femtosecond lasers are used to achieve photoresist polymerization, and the beam is called the excitation beam. Picosecond lasers are used to achieve edge suppression effects, and the beam is called the suppression beam. The suppression beam can also be continuous. To reduce costs, this invention uses a single laser to split into excitation and suppression beams via a second polarizing beam splitter, achieving direct laser writing of edge light.

[0022] Preferably, in step (1), the beam-shrinking module consists of two lenses. The beam-shrinking module shrinks the transmitted beam from the second polarizing beam splitter to below a first set value to become the excitation light. The beam-shrinking module also shrinks the reflected beam from the second polarizing beam splitter to the first set value, and then rotates the polarization direction through a half-wave plate. The first set value can be 2-3 mm.

[0023] Preferably, in step (1), the excitation light and the reflected light after beam contraction are reflected by the mirrors and enter the two acousto-optic modulators respectively. After exiting, they pass through the beam expansion module to expand the beam diameter to a second set value. The second set value is generally 4-5mm. The purpose is to ensure that the beam can cover a sufficient number of pixels when it is incident on the subsequent spatial light modulator. The beam expansion module includes a mirror, an aperture, a lens and a beam expansion aperture. The beam expansion aperture is placed on the focal plane of the two lenses. After exiting, the beam passes through the mirror so that the beam is incident perpendicularly to the center of the aperture. The excitation light and the reflected light pass through the lens, the beam expansion aperture and the lens in sequence, and then pass through the mirror and the half-wave plate to enter the first polarizing beam splitter for beam combining.

[0024] Preferably, in step (2), the combined beam is incident on the left half-screen of the spatial light modulator through a reflector. At this time, the polarization states of the excitation light and the suppression light are both linearly polarized and perpendicular to each other. By rotating the angle of the spatial light modulator so that its response polarization state is the same as that of the suppression light, the corresponding phase of the suppression focal spot can be generated by loading the left half-screen to control the suppression light. At this time, the excitation light is not affected. After the combined beam exits from the left half-screen of the spatial light modulator, it is reflected by a quarter-wave plate and a reflector and incident on the right half-screen of the spatial light modulator. At this time, the excitation light is controlled by the phase mask on the right half-screen of the spatial light modulator, while the suppression light is not affected. The combined beam exiting from the spatial light modulator is then converted into circularly polarized light by a quarter-wave plate. In this way, while ensuring that the excitation light and the suppression light are coaxial, the required phase control can be achieved, and thus focused into solid and hollow light spots.

[0025] Preferably, in step (1), after the beam enters the half-wave plate and the second polarizing beam splitter, the beam transmitted through the second polarizing beam splitter becomes the excitation beam, and after passing through the coupler, it enters the excitation fiber, the fiber acousto-optic modulator, and the collimator before entering the half-wave plate and the first polarizing beam splitter for beam combining. The beam reflected by the second polarizing beam splitter also passes through the coupler, enters the suppression fiber, the fiber acousto-optic modulator, and the collimator before entering the half-wave plate and the first polarizing beam splitter for beam combining. Using fiber optic devices can reduce the wavefront aberration caused by the spatial optical path and improve the beam quality. At the same time, it can reduce the system volume and increase the system's compactness. Using fiber optic devices can also reduce the system's calibration difficulty to a certain extent and make it easier to maintain. The suppression fiber can be a special mode fiber used to generate a hollow spot. Alternatively, it can be a fiber with a special end face structure.

[0026] Preferably, in step (2), the focusing components include a scanning module, a scanning lens, a field lens, a dichroic mirror, a beam splitter and an objective lens. The combined beam passes through the scanning module, the scanning lens, the field lens, the dichroic mirror, the beam splitter and the objective lens in sequence, and is finally focused onto the sample on the stage by the objective lens.

[0027] Preferably, it also includes step (3), the specific method of which is as follows:

[0028] (3) The light beam emitted by the LED is reflected by the dichroic mirror and then enters the objective lens through the beam splitter to illuminate the sample surface. The light signal from the sample surface is received by the charge-coupled device (CCD) after it returns. The light beams reflected back by the focused spot of the excitation light and the suppression light on the sample surface are partially reflected by the beam splitter and enter the PMT detector.

[0029] Preferably, in step (1), the femtosecond laser enters the adjustment system before entering the half-wave plate. The adjustment system includes a half-wave plate, a third polarizing beam splitter, a mirror, a grating pair, a roof prism, and an anti-drift module. The femtosecond laser first passes through the half-wave plate and the third polarizing beam splitter to adjust the beam energy of the subsequent system, then is reflected by the mirror into the grating pair, then reflected by the roof prism, passes through the grating pair again, and then passes through the mirror into the anti-drift module. The two mirrors before the anti-drift module are used to adjust the position and angle of the beam entering the anti-drift module over a wide range. The anti-drift module is used to achieve beam stabilization.

[0030] Because the subsequent beam passes through numerous optical devices during its propagation in space, the pulse width of the femtosecond beam will broaden. Therefore, a grating is used in conjunction with a roof prism to compensate for the pulse broadening of the beam. Typically, since the laser emits a polarized beam, the combination of a half-wave plate and a third polarizing beam splitter can adjust the beam energy entering the subsequent system; excess beam energy is reflected by the P-type beam into a beam deflector to avoid safety hazards.

[0031] A photoresist replenishment system for a special grating lithography method includes a photoresist tank and an in-situ developing device. The photoresist tank includes a photoresist inflow channel attached to the outside of the objective lens, with the bottom of the channel inclined towards the center of the objective lens. The in-situ developing device includes a sample cell with a sample stage. Photoresist flows to the sample stage through the photoresist inflow channel. A developer inflow channel is located on one side of the sample stage, and a developer and photoresist outflow channel is located on the other side of the sample stage.

[0032] Normally, the tilting gratings and blazed gratings targeted by this invention are flat in shape. However, due to the use of coordinate rotation, this invention requires a larger space in the axial direction. This photoresist replenishment system allows liquid photoresist to be added to the sample cell through two photoresist inflow channels close to the objective lens, enabling automatic replenishment. The developer flows in from inside the sample stage and, after development, flows out through a unified developer and photoresist outflow channel.

[0033] By adopting the above technical solution, the present invention has the following beneficial effects:

[0034] 1. This invention employs a femtosecond laser edge light suppression technique for photolithography. Traditional femtosecond photolithography systems are limited by the diffraction limit, making it difficult to break through 50nm in feature size. The edge light suppression technique uses another beam that can be focused into a hollow spot, namely a picosecond laser, to suppress the area of ​​action of the beam that excites the photoresist polymerization reaction, thereby reducing the feature size and improving the writing accuracy to 40nm.

[0035] 2. In order to reduce costs, this invention uses a single laser to split the excitation light and the suppression light through a second polarization beam splitter to achieve edge laser direct writing.

[0036] 3. The photoresist replenishment system occupies a small space, allowing liquid photoresist to be automatically replenished into the sample cell through two photoresist inflow channels closely attached to the objective lens. The developer flows in from the sample stage and flows out through a unified outflow channel after development. This method allows for continuous photoresist replenishment based on the printing progress, avoiding objective lens contamination and material waste caused by injecting too much at once. Furthermore, this device enables in-situ development, allowing for in-situ imaging observation after printing. Attached Figure Description

[0037] The invention will now be further described with reference to the accompanying drawings.

[0038] Figure 1 This is a schematic diagram illustrating how, in traditional two-photon printing technology, the light beam is focused at the focal plane of the objective lens to form an ellipsoid with a certain spatial size.

[0039] Figure 2 This is a schematic diagram of the focused light spot in the xy plane.

[0040] Figure 3This is a schematic diagram of the focused light spot in the yz plane.

[0041] Figure 4 This is a schematic diagram of the tilted grating.

[0042] Figure 5 This is a low-resolution projection of the focused light spot onto the xz plane.

[0043] Figure 6 To project the focused light spot onto the xy plane in a high resolution.

[0044] Figure 7 To project the focused light spot onto the yz plane at low resolution.

[0045] Figure 8 This is a schematic diagram of the actual printed structure.

[0046] Figure 9 This is a schematic diagram of the apparatus for a special grating lithography method in Example 1.

[0047] Figure 10 This is a schematic diagram of an apparatus for a special grating lithography method in Example 2.

[0048] Figure 11 This is the suppressed light spot formed in Example 2.

[0049] Figure 12 This is a schematic diagram of an apparatus for a special grating lithography method in Comparative Example 1.

[0050] Figure 13 This is a cross-sectional view of the glue application system.

[0051] Figure 14 This is a 3D view of the adhesive filling system.

[0052] Figure 15 This is a schematic diagram of the structure of the blazed grating printed in Example 1.

[0053] Figure 16 This is a schematic diagram of the structure of the blazed grating actually printed in Example 1 in the xy plane.

[0054] Figure 17 This is a schematic diagram of the structure of the blazed grating printed in Comparative Example 1.

[0055] Figure 18 This is a schematic diagram of the actual printed blazed grating in the yz plane in Comparative Example 1.

[0056] Figure 19 This is a projection diagram of the focused light spot in Example 1.

[0057] Figure 20 This is a projection of the focused spot in Comparative Example 1.

[0058] Figure 21 The blazed grating pattern is shown in Example 1.

[0059] Figure 22 The image shows a blazed grating pattern depicted by the focused light spot in Comparative Example 1. Detailed Implementation

[0060] Example 1:

[0061] like Figure 9 The special grating photolithography method shown includes the following steps:

[0062] (1) The beam emitted by laser 1 passes through the third half-wave plate 2 and the third polarization beam splitter 3. Laser 1 uses a beam with a wavelength of around 532nm and the pulse width of laser 1 is less than 200 femtoseconds.

[0063] (2) The beam reflected by the third polarizing beam splitter 3 enters the light blocker 4. The beam passing through the third polarizing beam splitter 3 is reflected by the mirror 5 and enters the grating pair 6. After being reflected by the roof prism 7, it passes through the grating pair 6 again and then through the two mirrors 5 to enter the anti-drift module 8. The anti-drift module 8 can use a direct-write anti-drift system as described in patent CN 113189846 A to achieve beam stabilization.

[0064] (3) After the beam exits from the anti-drift module 8, it passes through the second half-wave plate 9 and is split by the second polarizing beam splitter 10. The beam transmitted from the second polarizing beam splitter 10 enters a beam-shrinking module composed of two lenses 11 and is shrunken to less than 2 mm to become the excitation light. The beam reflected by the second polarizing beam splitter 10 passes through a dispersing device 12, which broadens the pulse width of the beam to the level of hundreds of picoseconds to become the suppression light. Then it passes through the beam-shrinking module composed of two lenses 11 to be shrunken to less than 2 mm. Then it passes through the fourth half-wave plate 13 to rotate the polarization direction to meet the requirements of the acousto-optic modulator 14.

[0065] (4) The excitation light is reflected by two mirrors 5 and enters the acousto-optic modulator 14. The angle and position of the beam entering the acousto-optic modulator 14 can be controlled by adjusting the two mirrors 5. A power detector (not shown in the figure) is placed after the acousto-optic modulator 14 to receive the first-order diffracted light after the acousto-optic modulator 14, while preventing the zero-order light of the acousto-optic modulator 14 from entering the power detector. The power detector is used to calibrate the energy efficiency of the acousto-optic modulator. By adjusting the two mirrors 5 in front of the acousto-optic modulator 14 and applying the maximum bias voltage to the acousto-optic modulator 14, the diffraction efficiency of the first-order light is maximized, usually reaching more than 95%. Two mirrors 5 are placed after the first-order light is emitted. The beam emitted from the acousto-optic modulator 14 passes through the aperture 15, lens 11, beam expander aperture 16, and lens 11 in sequence. By adjusting the two mirrors 5, the beam is made to be incident perpendicularly to the center of the aperture 15. The zero-order light emitted from the acousto-optic modulator 14 is blocked by reducing the size of the aperture 15. A beam-expanding aperture 16 is placed at the focal plane of the two lenses 11. To filter out stray light around the Gaussian spot, the aperture 16 is selected to be 0.9 times the size of an Airy disk. The beam-expanding module expands the beam diameter by 5 mm. The expanded excitation light passes through a mirror 5 and a first half-wave plate 17 before entering the first polarizing beam splitter 18 for beam combining. The first half-wave plate 17 is used to further adjust the beam polarization state, allowing it to pass through the first polarizing beam splitter 18 with maximum efficiency. The suppression light also undergoes the same steps before entering the first polarizing beam splitter 18 for beam combining.

[0066] (5) The combined beam passes through mirror 5 and enters the left half-screen of the spatial light modulator 19. At this time, the polarization states of the excitation light and the suppression light are both linearly polarized and perpendicular to each other. The angle of the spatial light modulator 19 is rotated so that its response polarization state is the same as that of the suppression light. The response phase that can generate the suppression focal spot is loaded on the left half-screen to modulate the suppression light. At this time, the excitation light is not affected. After the combined beam exits from the left half-screen of the spatial light modulator 19, it is reflected by the quarter-wave plate 20 and mirror 5 and enters the right half-screen of the spatial light modulator 19. Because it passes through the quarter-wave plate 20 twice, the polarization state of the beam rotates by 90°. At this time, the excitation light can be modulated by the phase mask on the right half-screen of the spatial light modulator 19, while the suppression light is not affected. The combined beam exiting from the spatial light modulator 19 is then converted into circularly polarized light by the quarter-wave plate 20.

[0067] (6) The combined beam passes sequentially through scanning module 21, scanning lens 22, field lens 23, dichroic mirror 24, beam splitter 25, and objective lens 26, and is finally focused by objective lens 26 onto the sample on stage 27. Scanning module 21 preferably uses a three-mirror scanning system. The dichroic mirror transmits at 532 Hz and reflects at 640 Hz.

[0068] (7) The 640 nm light beam emitted by LED39 is reflected by beam splitter 25 and dichroic mirror 24, and then enters objective lens 26 through beam splitter 25 to illuminate the sample surface. The light signal from the sample surface is received by charge-coupled device CCD 28 after it returns.

[0069] (8) The beams of excitation light and suppression light reflected back from the focused spot on the sample surface are partially reflected by the beam splitter 25 and enter the PMT detector 29, which can realize the detection of the system point spread function (PSF).

[0070] (9) Place a 532-band autocorrelation instrument on the sample surface to test the pulse width of the excitation and suppression light. By adjusting the spacing of grating pair 6, suppress the pulse width of the 532 femtosecond laser to below 200 fs. Adjust the parameters of dispersive device 12 to make the pulse width of the suppression light around 500 ps.

[0071] Example 2

[0072] like Figure 10 The special grating photolithography method shown includes the following steps:

[0073] (1) The beam emitted by laser 1 passes through the third half-wave plate 2 and the third polarization beam splitter 3. Laser 1 uses a beam with a wavelength of around 532nm and the pulse width of laser 1 is less than 200 femtoseconds.

[0074] (2) The beam reflected by the third polarizing beam splitter 3 enters the beam blocker 4. The beam passing through the third polarizing beam splitter 3 is reflected by the mirror 5 and enters the grating pair 6. After being reflected by the roof prism 7, it passes through the grating pair 6 again and then through the two mirrors 5 to enter the anti-drift module 8. The anti-drift module 8 can use a direct-write anti-drift system as described in patent CN 113189846 A to achieve beam stabilization.

[0075] (3) After exiting the anti-drift module 8, the light beam passes through the second half-wave plate 9 and is split by the second polarizing beam splitter 10. The transmitted light beam is called the excitation light and enters the excitation light fiber 30 through the coupler 31 and then enters the fiber acousto-optic modulator 141. The reflected light beam also passes through the coupler 31 and enters the suppression light fiber 32 and then enters the fiber acousto-optic modulator 141. Among them, the excitation light fiber 30 is a photonic crystal fiber with low dispersion, and the suppression light fiber 32 is a common single-mode fiber with high dispersion. In addition, the suppression light fiber 32 is a fiber that can generate a high-order vortex light field mode to generate the required hollow light spot.

[0076] (4) After the two beams of light emerge from the optical fiber, they are collimated by their respective collimators 33 and the first half-wave plate 17, and then combined by the first polarizing beam splitter 18. The combined beam passes sequentially through the scanning module 21, scanning lens 22, field lens 23, dichroic mirror 24, beam splitter 25, and objective lens 26, and is finally focused by objective lens 26 onto the sample on stage 27. The scanning module 21 preferably uses a three-mirror scanning system. The dichroic mirror transmits light in the 532 Hz band and reflects light in the 640 Hz band.

[0077] (5) The system also includes an illumination monitoring system. The light beam with a wavelength of 640 nm emitted by LED39 is reflected by dichroic mirror 24 and then enters objective lens 26 through beam splitter 25 to illuminate the sample surface. The light signal from the sample surface is received by charge-coupled device CCD 28 after it returns.

[0078] (6) The beams of excitation light and suppression light reflected back from the focused spot on the sample surface are partially reflected by the beam splitter 25 and enter the PMT detector 29, which can realize the detection of the system PSF.

[0079] (7) Place a 532-band autocorrelation instrument on the sample surface to test the pulse width of the excitation and suppression light. By adjusting the spacing of grating pair 6, suppress the pulse width of the 532 femtosecond laser to below 200 fs. Adjust the length of the suppression light fiber 32 to make the suppression light pulse width around 500 ps.

[0080] If special-mode fibers are not used for suppression, fibers with special micro / nano structures at the end faces can also be selected. The resulting suppression light spot is as follows: Figure 11 As shown.

[0081] Comparative Example 1

[0082] like Figure 12 The special grating photolithography method shown includes the following steps:

[0083] (1) The femtosecond laser emitted by laser 1 passes through half-wave plate 2 and polarizing beam splitter 3. Laser 1 uses a beam with a wavelength of around 532nm and the pulse width of laser 1 is less than 200 femtoseconds.

[0084] (2) The beam reflected by the third polarizing beam splitter 3 enters the light blocker 4. After passing through the third polarizing beam splitter 3 and the acousto-optic modulator 14, the beam is reflected by the reflector 5 and enters the aperture 15, lens 11, beam expander aperture 16, and then the beam is adjusted by the two reflectors 5 to pass through the scanning module 21, scanning lens 22, field lens 23, dichroic mirror 24, beam splitter 25, and objective lens 26 in sequence. Finally, the beam is focused by the objective lens 26 onto the sample on the stage 27. The scanning module 21 preferably uses a three-mirror scanning system. The dichroic mirror transmits at the 532 Hz band and reflects at the 640 Hz band.

[0085] (4) The 640 nm light beam emitted by LED39 is reflected by beam splitter 25 and dichroic mirror 24, and then enters objective lens 26 through beam splitter 25 to illuminate the sample surface. The light signal from the sample surface is received by charge-coupled device CCD 28 after it returns.

[0086] like Figure 13 and Figure 14 The illustrated photoresist replenishment system for a special grating lithography method includes a photoresist tank device and an in-situ developing device. The photoresist tank device includes a photoresist inflow channel 34 located close to the outside of the objective lens 26, with the bottom of the photoresist inflow channel 34 inclined towards the center of the objective lens 26. The in-situ developing device includes a sample cell 35, with a sample stage 36 provided in the sample cell 35. Photoresist 40 flows to the sample stage 36 through the photoresist inflow channel 34. A developer inflow channel 37 is provided on one side of the sample stage 36, and a developer and photoresist outflow channel 38 is provided on the other side of the sample stage 36.

[0087] Normally, the tilting gratings and blazed gratings targeted by this invention are flat in shape. However, due to the use of coordinate rotation, this invention requires a larger space in the axial direction. This photoresist replenishment system allows liquid photoresist 40 to be replenished into the sample cell 35 through two photoresist inflow channels 34 adjacent to the objective lens 26, enabling automatic photoresist replenishment. The developer flows in from the developer inflow channel 37 and, after development, flows out through the unified developer and photoresist outflow channel 38.

[0088] Take the blazed gratings printed in Example 1 and Comparative Example 1 as examples.

[0089] Figure 15 This is a schematic diagram of the structure of the blazed grating printed in Example 1. Figure 16 This is a schematic diagram of the structure of the blazed grating actually printed in Example 1 in the xy plane. Figure 15 The A plane is parallel to the xy plane.

[0090] Figure 17 This is a schematic diagram of the structure of the blazed grating printed in Comparative Example 1. Figure 18 This is a schematic diagram of the actual printed blazed grating in the yz plane in Comparative Example 1. Figure 17 Surface A in the diagram is parallel to the yz plane.

[0091] Figure 15 Side A in Figure 17 Surface A in the diagram is the same surface as the printed blazed grating structure.

[0092] Figure 19 This is a projection image of the focused light spot in Example 1. Figure 20 The image shown is a projection of the focused spot in Comparative Example 1. By comparison, it can be seen that the focused spot in Example 1 is a high-resolution projection, while the focused spot in Comparative Example 1 is a low-resolution projection.

[0093] Figure 21 An electron microscope image of the extreme-size blazed grating printed in Example 1. Figure 22 This is an electron microscope image of a blazed grating of the same size printed in Comparative Example 1. The comparison shows that... Figure 21 The middle triangle outline is more obvious, while Figure 22 The central triangle has a more rounded profile, so the blazed grating printing accuracy obtained by the photolithography method in Example 1 is higher.

[0094] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A special grating photolithography method, characterized in that, Includes the following steps: (1) The femtosecond laser rotates its polarization direction through the first half-wave plate and then enters the first polarization beam splitter, while the picosecond laser enters the first polarization beam splitter after passing through the phase plate. (2) After the femtosecond laser and picosecond laser are combined by the first polarization beam splitter, they enter the scanning system and focusing components, so that the combined light is focused on the photoresist.

2. The special grating photolithography method according to claim 1, characterized in that: In step (1), the femtosecond laser emitted by the laser first enters the second half-wave plate and the second polarization beam splitter. The beam transmitted through the second polarization beam splitter is the excitation light. The pulse width of the suppression light after the light reflected by the second polarization beam splitter passes through the dispersive device is broadened to the picosecond laser in step (2), which is the suppression light. The excitation light and the suppression light pass through the beam shrinking module, the acousto-optic modulator, and the beam expanding module in sequence, and then enter the first polarization beam splitter for beam combining.

3. The special grating photolithography method according to claim 2, characterized in that: In step (1), the beam-shrinking module consists of two lenses. The beam-shrinking module shrinks the transmitted beam from the second polarizing beam splitter to below a first set value to become the excitation light. The beam-shrinking module shrinks the reflected beam from the second polarizing beam splitter to the first set value, and then rotates the polarization direction through a half-wave plate.

4. The special grating photolithography method according to claim 2, characterized in that: In step (1), the excitation light and the reflected light after beam contraction are reflected by the mirrors and enter the two acousto-optic modulators respectively. After exiting, they pass through the beam expansion module to expand the beam diameter to the second set value. The beam expansion module includes a mirror, an aperture, a lens and a beam expansion aperture. The beam expansion aperture is placed on the focal plane of the two lenses. After exiting, the beam passes through the mirror so that the beam is perpendicular to the center of the aperture. The excitation light and the reflected light pass through the lens, the beam expansion aperture and the lens in sequence, and then pass through the mirror and the half-wave plate to enter the first polarizing beam splitter for beam combining.

5. The special grating photolithography method according to claim 2, characterized in that: In step (2), the combined beam is incident on the left half screen of the spatial light modulator through the reflector. At this time, the polarization states of the excitation light and the suppression light are both linearly polarized and perpendicular to each other. The angle of the spatial light modulator is rotated so that its response polarization state is the same as that of the suppression light. The corresponding phase of the suppression focal spot can be generated by loading on the left half screen to control the suppression light. At this time, the excitation light is not affected. After the combined beam exits from the left half screen of the spatial light modulator, it is reflected by the quarter-wave plate and the reflector and incident on the right half screen of the spatial light modulator. At this time, the excitation light is controlled by the phase mask on the right half screen of the spatial light modulator, while the suppression light is not affected. The combined beam exiting from the spatial light modulator is then converted into circularly polarized light by the quarter-wave plate.

6. The special grating photolithography method according to claim 2, characterized in that: In step (1), after the beam enters the second half-wave plate and the second polarizing beam splitter, the beam transmitted through the second polarizing beam splitter becomes the excitation beam, and after passing through the coupler, it enters the excitation fiber, the fiber acousto-optic modulator, the collimator, and then enters the first half-wave plate and the first polarizing beam splitter for beam combining. The beam reflected by the second polarizing beam splitter also passes through the coupler, enters the suppression fiber, the fiber acousto-optic modulator, the collimator, and then enters the first half-wave plate and the first polarizing beam splitter for beam combining.

7. The special grating photolithography method according to claim 2, characterized in that: In step (2), the focusing components include a scanning module, a scanning lens, a field lens, a dichroic mirror, a beam splitter, and an objective lens. The combined beam passes through the scanning module, scanning lens, field lens, dichroic mirror, beam splitter, and objective lens in sequence, and is finally focused onto the sample on the stage by the objective lens.

8. The special grating photolithography method according to claim 7, characterized in that, It also includes step (3), the specific method of which is as follows: (3) The light beam emitted by the LED is reflected by the beam splitter and the dichroic mirror, and then enters the objective lens through the beam splitter to illuminate the sample surface. The light signal from the sample surface is received by the charge-coupled device CCD after it returns. The light beams reflected back by the focused spot of the excitation light and the suppression light on the sample surface are partially reflected by the beam splitter and enter the PMT detector.

9. The special grating photolithography method according to claim 2, characterized in that: In step (1), the femtosecond laser enters the adjustment system before entering the second half-wave plate. The adjustment system includes a third half-wave plate, a third polarization beam splitter, a mirror, a grating pair, a roof prism, and an anti-drift module. The femtosecond laser first passes through the third half-wave plate and the third polarization beam splitter to adjust the beam energy of the subsequent system, then is reflected by the mirror into the grating pair, then reflected by the roof prism and passes through the grating pair again, and then passes through the mirror into the anti-drift module.

10. A resist-repairing system for the special grating lithography method as described in any one of claims 1-9, characterized in that: The device includes a liquid tank assembly and an in-situ developing device. The liquid tank assembly includes a photoresist inflow channel that is closely attached to the outside of the objective lens. The bottom of the photoresist inflow channel is inclined towards the center of the objective lens. The in-situ developing device includes a sample pool with a sample stage. The photoresist flows to the sample stage through the photoresist inflow channel. One side of the sample stage has a developer inflow channel, and the other side of the sample stage has a developer and photoresist outflow channel.

Images