Special grating photoetching method and glue supplementing system thereof

Abstract

The invention discloses a special grating photoetching method and a glue supplementing system thereof. Based on the laser direct writing technology, the characteristic that the printed grating has different resolution requirements in different dimensions is utilized, coordinate rotation is conducted on the printed structure, the high-resolution projection of the system is made to be consistent with the high-resolution requirement dimension of the printed structure, and high-quality printing of the structure is achieved. Meanwhile, in order to achieve long-time inscribing and printing, the invention further provides a continuous glue supplementing device for long-time inscribing, and meanwhile the device can be used for achieving in-situ development and optical imaging.

Description

Technical Field

[0001] The invention belongs to the field of optics, and in particular relates to a special grating lithography method based on laser direct writing and coordinate rotation and a glue filling system used for the lithography method. Background Art

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

[0003] Specifically, a blazed grating is a special reflective grating whose surface is coated with a layer of metal or other reflective materials and is made into a periodic structure through precision machining. Unlike traditional transmission diffraction gratings, blazed gratings use surface reflection to disperse and select incident light. When incident light hits the surface of a blazed grating, it is reflected at different angles and produces multiple secondary reflections. These secondary reflections can be further dispersed into components of different wavelengths to form a dispersion pattern. Therefore, blazed gratings can be used as high-resolution, high-sensitivity wavelength selectors and scanners, etc. Compared with traditional diffraction gratings, blazed gratings have 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 reflectors of laser interferometers to measure parameters such as object shape and surface roughness by comparing the phase difference of the reflected laser beam. In holographic imaging, blazed gratings can be used to prepare holograms, and their diffraction effect can be used to record and reproduce three-dimensional images. In optical communications, 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 field of AR / VR, blazed gratings can be used to manufacture reflective display devices, such as digital projectors and head-mounted display devices, and are key optical devices 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 the tilted grating is similar to that of the rectangular grating, except that the sidewall and bottom surface of the grating structure in its cross section have a certain angle. When this angle is 90°, it is an ordinary rectangular grating. When the incident light passes through the tilted grating, diffraction occurs due to the different refractive indices. This diffraction can separate the light beam into components of different wavelengths and cause them to deviate from the original direction at different angles. Therefore, the tilted grating can be used as a dispersion element, spectrometer, and wavelength selector. In addition, the tilted grating can also achieve more complex functions by adjusting the spacing and angle of its grooves or protrusions. Similar to the blazed grating, the tilted grating is widely used in display technology, holographic imaging, and laser interferometry. In addition, the tilted grating can also be used for surface texture treatment of solar panels to improve their conversion efficiency; in the biomedical field, it can also be used for cell imaging and fluorescence detection.

[0005] It can be seen that blazed gratings and tilted gratings, as two special 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 lithography technology with three-dimensional manufacturing characteristics. At present, the manufacturing of three-dimensional structures of high-precision blazed gratings and tilted gratings mainly relies on electron beam lithography, which has ultra-high resolution and precision. However, the shortcomings of electron beam lithography are also obvious, mainly including: 1. High production cost: Electron beam lithography equipment is expensive and has a limited service life. It requires frequent maintenance and upkeep, which will increase production costs.

[0006] 2. Long manufacturing cycle: Since electron beam lithography is a point-by-point exposure method, it takes a lot of time and effort to manufacture a large-area sample, and the manufacturing cycle is relatively long.

[0007] 3. Poor mass production capability: Due to the long manufacturing cycle and low integration of electron beam lithography, it is unable to meet the needs of large-scale mass production.

[0008] 4. Susceptible to environmental interference: During the electron beam bombardment process, environmental factors such as static electricity and magnetic fields may affect the exposure results. In order to eliminate these influences, strict control and adjustment of the equipment and laboratory environment are required.

[0009] Similar to electron beam direct writing lithography, two-photon laser direct writing is a direct writing lithography technology that utilizes the nonlinear effect of laser and matter. Unlike electron beam, laser direct writing technology often uses laser in the visible light band as the light source, and its wavelength is much higher than that of electron beam. Therefore, the accuracy of laser direct writing technology cannot reach the accuracy of electron beam writing. However, the advantages of laser direct writing are also obvious. Compared with electron beam lithography technology, laser direct writing technology does not require a harsh processing environment, and the cost is much lower than that of electron beam lithography equipment. The processing efficiency under the same conditions is higher than that of electron beam lithography. More importantly, since the light beam can pass through transparent materials and focus on the inside of the medium, laser direct writing technology is a true spatial three-dimensional manufacturing technology, which has broad application prospects in the manufacture of micro-nano optical components. Therefore, two-photon laser direct writing lithography can also be considered as a high-precision micro-nano three-dimensional printing technology. However, due to the diffraction limit, the accuracy of laser direct writing is limited to about 100nm. Therefore, it is impossible to manufacture high-precision blazed gratings and tilted gratings, which greatly limits the technical advantages and application promotion of laser direct writing in other aspects.

[0010] like Figure 1 In the traditional two-photon printing technology shown in the figure, due to the limitation of optical diffraction limit, the light beam cannot be focused to an ideal point, but is focused at the focal plane of the objective lens to form an ellipsoid with a certain spatial size, with its two short axes in the focal plane and its long axis perpendicular to the focal plane along the optical axis. During printing, the focused light spot produces relative displacement with the photoresist in the photoresist, and stimulates the polymerization of the photoresist wherever it reaches, forming a three-dimensional structure. Since the focused light spot is ellipsoidal, the resolution of the printing is spatially non-uniform. Figure 2 It can be seen that the focused spot has a smaller projection in the xy plane, that is, in the plane parallel to the focal plane, which means that higher resolution printing can be achieved. Figure 3 As shown, or in the xz plane (not shown in the figure), that is, in the plane perpendicular to the focal plane, the projected feature size is larger, that is, the resolution during printing is lower. Therefore, in conventional two-photon 3D printing, it is generally believed that the axial (yz, xz) resolution is lower than the lateral (xy) resolution. As a result, when manufacturing certain structures with high requirements for axial resolution, it cannot meet expectations.

[0011] like Figure 4 The tilted grating shown is a special grating whose three-dimensional structure has a high spatial frequency only in a single plane, such as Figure 5 The xz shown and Figure 6 The xy direction shown. Figure 7 When manufacturing blazed gratings and tilted gratings in the yz direction shown in the figure, the low-resolution projection of the focused light spot in the traditional method and the cross-section of the grating that needs to be printed with high resolution (hereinafter referred to as the "high-resolution required surface") are projected in one direction, producing a step effect such as Figure 8 As shown, the printing resolution is insufficient and the required raster structure cannot be effectively printed.

[0012] To this end, the present invention proposes a special grating lithography method and a glue filling system based on laser direct writing technology, which provides a new technical approach for the manufacture of high-precision special gratings. Summary of the invention

[0013] The purpose of the present invention is to perform coordinate rotation on the special grating structure to be printed in a special grating printing method so that its high-resolution required surface is consistent with the high-resolution projection direction of the focused light spot, so that the direction with higher resolution of the focused light spot can print the direction with higher characteristic size requirement of the special grating, thereby obtaining a better printing effect.

[0014] In order to achieve the above object, the present invention adopts the following technical solution: A special grating lithography method comprises the following steps: (1) The femtosecond laser enters the first polarization splitter prism after its polarization direction is rotated by a half-wave plate, and the picosecond laser enters the first polarization splitter prism after passing through a phase plate; (2) After being combined by the first polarization beam splitter, the femtosecond laser and the picosecond laser enter the scanning system and focusing component, so that the combined beam is focused on the photoresist.

[0015] The present invention adopts the edge light suppression technology lithography method of femtosecond laser. The traditional femtosecond lithography system is limited by the diffraction limit, and the feature size is difficult to exceed 50nm. The edge light suppression technology uses another light beam that can be focused into a hollow spot, namely a picosecond laser, to suppress the action area of ​​the light beam that excites the polymerization reaction of the photoresist, thereby having a smaller feature size and improving the writing accuracy.

[0016] Preferably, in step (1), the femtosecond laser emitted by the laser first enters the second half-wave plate and the second polarization beam splitter prism, the light beam transmitted through the second polarization beam splitter prism is the excitation light, the light reflected by the second polarization beam splitter prism passes through the dispersion device and the pulse width of the suppression light is widened to the picosecond laser in step (2), i.e. the suppression light, and the excitation light and the suppression light respectively 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 prism for beam combination. The beam shrinking module is used to reduce the beam diameter to meet the use requirements of the acousto-optic modulator. The acousto-optic modulator is used to achieve rapid on-off and power regulation of the beam. The beam expanding module is used to expand the beam diameter.

[0017] Femtosecond laser is used to achieve photoresist polymerization, and the light beam is called excitation light. Picosecond laser is used to achieve edge suppression effect, and the light beam is called suppression light. The suppression light can also be continuous light. In order to reduce costs, the present invention uses a single laser to be divided into excitation light and suppression light through a second polarization beam splitter prism to achieve edge light laser direct writing.

[0018] Preferably, in step (1), the beam reduction module is composed of two lenses, and the beam reduction module reduces the transmitted light beam transmitted through the second polarization beam splitter prism to below a first set value to become the excitation light; the beam reduction module reduces the reflected light beam reflected by the second polarization beam splitter prism to a first set value, and then rotates the polarization direction through a half-wave plate. The first set value can be 2-3 mm.

[0019] Preferably, in step (1), the excitation light after being beam-contracted and the reflected light after being beam-contracted are respectively reflected by a reflector and enter two acousto-optic modulators. After being emitted, they are respectively expanded through a beam expansion module to expand the beam diameter to a second set value. The second set value is generally 4-5 mm. The purpose is to allow the light beam to cover enough pixels when it is incident on a subsequent spatial light modulator. The beam expansion module includes a reflector, an aperture, a lens and a beam expansion hole. The beam expansion hole is placed on the focal plane of the two lenses. The emitted light beam passes through a reflector to make the light beam incident perpendicular to the center of the aperture. The excitation light and the reflected light pass through the lens, the beam expansion hole, the lens in turn, and then pass through a reflector and a half-wave plate to enter the first polarization beam splitter prism for beam combination.

[0020] Preferably, in step (2), the combined light beam passes through a reflector and is incident on the left half screen of the spatial light modulator. 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 the polarization state of the suppression light. The corresponding phase of the suppression focal spot can be generated by loading on the left half screen to regulate the suppression light. At this time, the excitation light is not affected. After the combined light beam is emitted from the left half screen of the spatial light modulator, it is reflected by a quarter wave plate and a reflector and is incident on the right half screen of the spatial light modulator. At this time, the excitation light is regulated by the phase mask on the right half screen of the spatial light modulator, while the suppression light is not affected. The combined light beam emitted from the spatial light modulator is then converted into circularly polarized light by a quarter wave plate. In this way, the required phase regulation of each can be achieved while ensuring that the excitation light and the suppression light are coaxial, and then they can be focused into a solid light spot and a hollow light spot.

[0021] Preferably, in step (1), after the light beam enters the half-wave plate and the second polarization beam splitter prism, the light beam transmitted through the second polarization beam splitter prism becomes the excitation light, and passes through the coupler to enter the excitation light fiber, the fiber acousto-optic modulator, and the collimator, and then enters the half-wave plate and the first polarization beam splitter prism for beam combination. The light beam reflected by the second polarization beam splitter prism also passes through the coupler to enter the suppression light fiber, the fiber acousto-optic modulator, and the collimator, and then enters the half-wave plate and the first polarization beam splitter prism for beam combination. The use of optical fiber devices can reduce the wavefront difference caused by the spatial light path and improve the beam quality. At the same time, it can reduce the system volume and increase the compactness of the system. The use of optical fiber devices can also reduce the difficulty of system adjustment to a certain extent and facilitate maintenance. The suppression light fiber can use a special mode fiber to produce a hollow light spot. An optical fiber with a special structure on the end face can also be used.

[0022] Preferably, in step (2), the focusing assembly includes a scanning module, a scanning lens, a field lens, a dichroic mirror, a beam splitter and an objective lens. The combined light 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 by the objective lens onto the sample on the stage.

[0023] Preferably, the method further comprises step (3), wherein the specific method of step (3) is as follows: (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 returned and received by the charge-coupled device (CCD). The light beam reflected back from the focused spot on the sample surface by the excitation light and the suppression light is partially reflected by the beam splitter and enters the PMT detector.

[0024] Preferably, in step (1), before the femtosecond laser enters the half-wave plate, it first enters the adjustment system, and the adjustment system includes a half-wave plate, a third polarization beam splitter prism, a reflector, a grating pair, a roof prism and an anti-drift module. The femtosecond laser first passes through the half-wave plate and the third polarization beam splitter prism to adjust the beam energy of the subsequent system, and then is reflected by the reflector to enter the grating pair, and then passes through the grating pair again after being reflected by the roof prism, and then passes through the reflector to enter the anti-drift module. The two reflectors in front of the anti-drift module are used to adjust the position and angle of the light beam entering the anti-drift module over a large range. The anti-drift module is used to achieve beam stabilization.

[0025] Since the subsequent light beam passes through many optical devices during spatial propagation, the pulse width of the femtosecond light beam will be broadened. Therefore, a grating pair is used in conjunction with a roof prism to compensate for the pulse broadening of the light beam. Usually, since the laser emits a polarized light beam, the combination of a half-wave plate and a third polarization beam splitter can adjust the energy of the light beam entering the subsequent system, and the excess light beam energy is reflected by P into the light blocker to avoid safety hazards.

[0026] A glue filling system for a special grating lithography method includes a liquid tank device and an in-situ developing device, wherein the liquid tank device includes a photoresist inflow channel closely attached to the outer side of an objective lens, and the bottom of the photoresist inflow channel is inclined toward the center of the objective lens. The in-situ developing device includes a sample pool, and the sample pool is provided with a sample stage. The photoresist flows to the sample stage through the photoresist inflow channel, a developer inflow channel is provided on one side of the sample stage, and developer and photoresist outflow channels are provided on the other side of the sample stage.

[0027] Under normal circumstances, the tilted grating and blazed grating targeted by the present invention are flat in appearance. Since the present invention adopts coordinate rotation, a larger space is required in the axial direction. The glue replenishment system allows liquid photoresist to be replenished into the sample pool through two photoresist inflow channels close to the objective lens, and automatic glue replenishment can be achieved. The developer flows into the sample stage, and after the development is completed, it flows out through the unified developer and photoresist outflow channel.

[0028] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: 1. The present invention adopts the edge light suppression technology lithography method of femtosecond laser. The traditional femtosecond lithography system is limited by the diffraction limit, and the feature size is difficult to exceed 50nm. The edge light suppression technology uses another beam that can be focused into a hollow spot, namely picosecond laser, to suppress the action area of ​​the beam that excites the polymerization reaction of the photoresist, thereby reducing the feature size and improving the writing accuracy to 40nm.

[0029] 2. In order to reduce costs, the present invention uses a single laser to be divided into excitation light and suppression light through a second polarization beam splitter prism to achieve edge light laser direct writing.

[0030] 3. The glue replenishment system takes up little space, and the liquid photoresist is replenished into the sample pool through two photoresist inflow channels close to the objective lens, which can realize automatic glue replenishment. The developer flows in from the sample stage, and after the development is completed, it flows out from the unified outflow channel. This method can continuously replenish the photoresist according to the printing process, avoiding the contamination of the objective lens and waste of materials caused by injecting too much at one time. At the same time, the device can realize in-situ development, and can realize in-situ imaging observation after printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below with reference to the accompanying drawings.

[0032] Figure 1 This is a schematic diagram of the traditional two-photon printing technology, in which the light beam is focused at the focal plane of the objective lens to form an ellipsoid with a certain spatial size.

[0033] Figure 2 Schematic diagram of the focused light spot in the xy plane.

[0034] Figure 3 Schematic diagram of the focused spot in the yz plane.

[0035] Figure 4 Schematic diagram of the structure of the tilted grating.

[0036] Figure 5 It is a low-resolution projection of the focused spot on the xz plane.

[0037] Figure 6 It is a high-resolution projection of the focused light spot on the xy plane.

[0038] Figure 7 It is a low-resolution projection of the focused light spot on the yz plane.

[0039] Figure 8 This is a schematic diagram of the actual printed structure.

[0040] Fig. 9Schematic diagram of a device for a special grating lithography method in Example 1.

[0041] Fig.10 Schematic diagram of a device for a special grating lithography method in Example 2.

[0042] Fig.11 This is the suppression light spot formed in Example 2.

[0043] Fig.12 This is a schematic diagram of a device for a special grating lithography method in comparative example 1.

[0044] Fig.13 A cross-sectional view of the glue filling system.

[0045] Fig.14 This is a three-dimensional diagram of the glue filling system.

[0046] Fig.15 Schematic diagram of the structure of the blazed grating printed in Example 1.

[0047] Fig.16 Schematic diagram of the structure of the blazed grating actually printed in Example 1 in the xy plane.

[0048] Fig.17 Schematic diagram of the structure of the blazed grating printed in Comparative Example 1.

[0049] Fig.18 Schematic diagram of the structure of the blazed grating actually printed in Comparative Example 1 in the yz plane.

[0050] Fig.19 This is a projection diagram of the focused light spot in Example 1.

[0051] Fig. 20 This is the projection diagram of the focused light spot in Comparative Example 1.

[0052] Fig.21 This is the blazed grating pattern engraved in Example 1.

[0053] Fig. 22 This is the blazed grating pattern engraved by the focused light spot in Comparative Example 1. DETAILED DESCRIPTION Example 1

[0054] like Fig. 9 A special grating lithography method is shown, comprising the following steps: (1) The light beam emitted by laser 1 passes through the third half-wave plate 2 and the third polarization beam splitter prism 3. Laser 1 selects a light beam with a wavelength of about 532 nm, and the pulse width of laser 1 is less than 200 femtoseconds.

[0055] (2) The light beam reflected by the third polarization beam splitter prism 3 enters the light blocker 4, and the light beam passing through the third polarization beam splitter prism 3 is reflected by the reflector 5 and enters the grating pair 6, and then passes through the roof prism 7 and passes through the grating pair 6 again, and then passes through the two reflectors 5 and enters the anti-drift module 8. The anti-drift module 8 can adopt the direct writing path anti-drift system described in patent CN 113189846 A to achieve the beam stabilization effect.

[0056] (3) After being emitted from the anti-drift module 8, the light beam passes through the second half-wave plate 9 and is split by the second polarization beam splitter prism 10. The light beam transmitted from the second polarization beam splitter prism 10 enters a beam reduction module composed of two lenses 11 and is reduced to less than 2 mm, becoming the excitation light. The light beam reflected by the second polarization beam splitter prism 10 passes through a dispersion device 12, and the pulse width of the light beam is widened to hundreds of picoseconds to become the suppression light. Then, the light beam passes through the beam reduction module also composed of two lenses 11 and is reduced to less than 2 mm. Then, the polarization direction is rotated by the fourth half-wave plate 13 to meet the requirements of the incident acousto-optic modulator 14.

[0057] (4) The excitation light is reflected by two reflectors 5 and enters the AOM 14. The angle and position of the light beam entering the AOM 14 can be controlled by adjusting the two reflectors 5. A power detector (not shown) is placed after the AOM 14 to receive the first-order diffracted light after the AOM 14, and to prevent the zero-order light of the AOM 14 from entering the power detector. The power detector is used to adjust the energy efficiency of the AOM. By adjusting the two reflectors 5 in front of the AOM 14 and applying a maximum bias voltage to the AOM 14, the diffraction efficiency of the first-order light is maximized, which can usually reach more than 95%. Two reflectors 5 are placed after the first-order light is emitted. The light beam emitted from the AOM 14 passes through the aperture 15, the lens 11, the beam expansion aperture 16 and the lens 11 in sequence. The two reflectors 5 are adjusted to make the light beam incident perpendicular to the center of the aperture 15, and the zero-order light emitted by the AOM 14 is blocked by reducing the size of the aperture 15. The beam expansion aperture 16 is placed on the focal plane of the two lenses 11. To filter out stray light around the Gaussian spot, the beam expansion aperture 16 uses a size of 0.9 Airy disk. The beam expansion module expands the beam diameter by 5 mm. The expanded excitation light passes through a reflector 5 and the first half-wave plate 17 to enter the first polarization beam splitter prism 18 for beam combination. The first half-wave plate 17 is used to further adjust the polarization state of the light beam so that it passes through the first polarization beam splitter prism 18 with the highest efficiency. The suppressed light also goes through the same steps as above and enters the first polarization beam splitter prism 18 for beam combination.

[0058] (5) The combined light beam passes through the reflector 5 and is incident on 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 the polarization state of the suppression light. Loading the left half screen can produce a response phase that suppresses the focal spot and regulates the suppression light. At this time, the excitation light is not affected. After the combined light beam is emitted from the left half screen of the spatial light modulator 19, it is reflected by the quarter wave plate 20 and the reflector 5 and is incident on 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 light beam is rotated by 90°. At this time, the excitation light can be regulated by the phase mask on the right half screen of the spatial light modulator 19, while the suppression light is not affected. The combined light beam emitted from the spatial light modulator 19 is then converted into circularly polarized light by the quarter wave plate 20.

[0059] (6) The combined light beam passes through the scanning module 21, scanning lens 22, field lens 23, dichroic mirror 24, beam splitter 25 and objective lens 26 in sequence, 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 the 532 band and reflects the 640 band.

[0060] (7) The light beam with a wavelength of 640 nm emitted by LED 39 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 returned and received by charge coupled device CCD 28.

[0061] (8) The light beams reflected from the focused spots of the excitation light and the suppression light on the sample surface are partially reflected by the beam splitter 25 and enter the PMT detector 29, thereby realizing the detection of the system point spread function PSF.

[0062] (9) Place a 532-band autocorrelator on the sample surface to test the pulse width of the excitation light and the suppression light. By adjusting the spacing of the grating pair 6, the pulse width of the 532 femtosecond laser is suppressed to below 200 fs. Adjust the parameters of the dispersion device 12 to make the suppression light pulse width around 500 ps. Example 2

[0063] like Fig.10 A special grating lithography method shown includes the following steps: (1) The light beam emitted by laser 1 passes through the third half-wave plate 2 and the third polarization beam splitter prism 3. Laser 1 selects a light beam with a wavelength of about 532 nm, and the pulse width of laser 1 is less than 200 femtoseconds.

[0064] (2) The light beam reflected by the third polarization beam splitter prism 3 enters the light blocker 4, and the light beam passing through the third polarization beam splitter prism 3 is reflected by the reflector 5 and enters the grating pair 6, and then passes through the roof prism 7 and passes through the grating pair 6 again, and then passes through the two reflectors 5 and enters the anti-drift module 8. The anti-drift module 8 can adopt the direct writing path anti-drift system described in patent CN 113189846 A to achieve the beam stabilization effect.

[0065] (3) After the light beam is emitted from the anti-drift module 8, it passes through the second half-wave plate 9 and is split by the second polarization beam splitter prism 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 uses a photonic crystal fiber with a smaller dispersion, and the suppression light fiber 32 uses an ordinary single-mode fiber with a larger dispersion. In addition, the suppression light fiber 32 uses an optical fiber that can generate a high-order vortex light field mode to generate the required hollow light spot.

[0066] (4) After the two beams of light are emitted 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 polarization beam splitter prism 18. The combined light beam passes through the scanning module 21, the scanning lens 22, the field lens 23, the dichroic mirror 24, the beam splitter 25 and the objective lens 26 in sequence, and is finally 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 the 532 band and reflects the 640 band.

[0067] (5) The system also includes an illumination monitoring system. The light beam with a wavelength of 640 emitted by LED 39 is reflected by the dichroic mirror 24, and then passes through the beam splitter 25 and enters the objective lens 26 to illuminate the sample surface. The light signal from the sample surface is returned and received by the charge coupled device CCD 28.

[0068] (6) The light beams reflected from the focused spots of the excitation light and the suppression light on the sample surface are partially reflected by the beam splitter 25 and enter the PMT detector 29, thereby realizing the detection of the system PSF.

[0069] (7) Place a 532-wavelength autocorrelator on the sample surface to test the pulse width of the excitation light and the suppression light. By adjusting the spacing of the grating pair 6, the pulse width of the 532 femtosecond laser is suppressed to below 200 fs. Adjust the length of the suppression light fiber 32 to make the suppression light pulse width around 500 ps.

[0070] If the suppression optical fiber does not use special mode optical fiber, it can also use optical fiber with special micro-nano structure on the end face. Fig.11 shown.

[0071] Comparative Example 1 like Fig.12 A special grating lithography method shown includes the following steps: (1) The femtosecond laser emitted by laser 1 passes through half-wave plate 2 and polarization beam splitter prism 3. Laser 1 uses a beam with a wavelength of about 532nm, and the pulse width of laser 1 is less than 200 femtoseconds.

[0072] (2) The light beam reflected by the third polarization beam splitter prism 3 enters the light blocker 4. The light beam passing through the third polarization beam splitter prism 3 passes through the acousto-optic modulator 14 and is reflected by the reflector 5 to enter the aperture 15, the lens 11, the beam expansion aperture 16 and the lens 11. Then, by adjusting the two reflectors 5, the light beam passes through the scanning module 21, the scanning lens 22, the field lens 23, the dichroic mirror 24, the beam splitter 25 and the objective lens 26 in sequence, and is finally 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 the 532 band and reflects the 640 band.

[0073] (4) The light beam with a wavelength of 640 nm emitted by LED 39 is reflected by beam splitter 25 and dichroic mirror 24, and then enters objective lens 26 to illuminate the sample surface. The light signal from the sample surface is then received by charge coupled device CCD 28.

[0074] like Fig.13 and Fig.14 A photoresist filling system for a special grating lithography method is shown, comprising a liquid tank device and an in-situ developing device, wherein the liquid tank device comprises a photoresist inflow channel 34 close to the outside of the objective lens 26, and the bottom of the photoresist inflow channel 34 is inclined toward the center of the objective lens 26. The in-situ developing device comprises a sample pool 35, wherein the sample pool 35 is provided with a sample stage 36, and the photoresist 40 flows to the sample stage 36 through the photoresist inflow channel 34, wherein 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.

[0075] Under normal circumstances, the tilted grating and blazed grating targeted by the present invention are flat in appearance. Since the present invention adopts coordinate rotation, a larger space is required in the axial direction. The glue replenishment system allows the liquid photoresist 40 to be replenished into the sample pool 35 through two photoresist inflow channels 34 close to the objective lens 26, so that automatic glue replenishment can be achieved. The developer flows into the developer inflow channel 37, and after the development is completed, it flows out through the unified developer and photoresist outflow channel 38.

[0076] Take the blazed gratings printed in Example 1 and Comparative Example 1 as examples.

[0077] Fig.15 is a schematic diagram of the structure of the blazed grating printed in Example 1, Fig.16Schematic diagram of the structure of the blazed grating actually printed in Example 1 in the xy plane. Fig.15 The middle surface A is parallel to the xy plane.

[0078] Fig.17 is a schematic diagram of the structure of the blazed grating printed in Comparative Example 1, Fig.18 Schematic diagram of the structure of the blazed grating actually printed in Comparative Example 1 in the yz plane. Fig.17 The A surface in is parallel to the yz plane.

[0079] Fig.15 The A side and Fig.17 Side A in the figure is the same side on which the blazed grating structure is printed.

[0080] Fig.19 is a projection diagram of the focused light spot in Example 1, Fig. 20 It is a projection diagram of the focused light spot in comparative example 1. By comparison, it can be seen that the focused light spot in embodiment 1 is a high-resolution projection, while the focused light spot in comparative example 1 is a low-resolution projection.

[0081] Fig.21 This is an electron microscope image of the extreme size blazed grating printed in Example 1. Fig. 22 This is an electron microscope image of the blazed grating of the same size printed in Comparative Example 1. By comparison, Fig.21 The middle triangle is more obvious, Fig. 22 The contour of the middle triangle is more rounded, so the blazed grating obtained by the photolithography method in Example 1 has higher printing accuracy.

[0082] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A special grating lithography method, characterized in that: The steps include: (1) The femtosecond laser enters the first polarization splitter prism after its polarization direction is rotated by the first half-wave plate, and the picosecond laser enters the first polarization splitter prism after passing through the phase plate; (2) After being combined by the first polarization beam splitter, the femtosecond laser and the picosecond laser enter the scanning system and focusing component, so that the combined beam is focused on the photoresist.

2. A special grating lithography 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 prism, the light beam transmitted through the second polarization beam splitter prism is the excitation light, the light reflected by the second polarization beam splitter prism passes through the dispersion device and the pulse width of the suppression light is widened to the picosecond laser in step (2) as the suppression light, and the excitation light and the suppression light respectively 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 prism for beam combination.

3. A special grating lithography method according to claim 2, characterized in that: In step (1), the beam reduction module is composed of two lenses. The beam reduction module reduces the transmitted light beam transmitted through the second polarization beam splitter prism to below the first set value to become the excitation light. The beam reduction module reduces the reflected light beam reflected by the second polarization beam splitter prism to the first set value, and then rotates the polarization direction through a half-wave plate.

4. A special grating lithography method according to claim 2, characterized in that: In step (1), the excitation light after beam contraction and the reflected light after beam contraction are respectively reflected by the reflector and enter the two acousto-optic modulators. After emission, they are respectively passed through the beam expansion module to expand the beam diameter to the second set value. The beam expansion module includes a reflector, an aperture, a lens and a beam expansion hole. The beam expansion hole is placed on the focal plane of the two lenses. The emitted light beam passes through the reflector to make the light beam incident perpendicular to the center of the aperture. The excitation light and the reflected light pass through the lens, the beam expansion hole, the lens in turn, and then pass through the reflector and the half-wave plate to enter the first polarization beam splitter prism for beam combination.

5. A special grating lithography method according to claim 2, characterized in that: In step (2), the combined light beam passes through a reflector and is incident on the left half screen of the spatial light modulator. 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 the polarization state of the suppression light. Loading the left half screen can produce a corresponding phase for suppressing the focal spot, and the suppression light is regulated. At this time, the excitation light is not affected. After the combined light beam is emitted from the left half screen of the spatial light modulator, it is reflected by a quarter wave plate and a reflector and is incident on the right half screen of the spatial light modulator. At this time, the excitation light is regulated by the phase mask on the right half screen of the spatial light modulator, while the suppression light is not affected. The combined light emitted from the spatial light modulator is then converted into circularly polarized light by the quarter wave plate.

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

7. A special grating lithography method according to claim 2, characterized in that: In step (2), the focusing assembly includes a scanning module, a scanning lens, a field lens, a dichroic mirror, a beam splitter and an objective lens. The combined light 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 by the objective lens onto the sample on the stage.

8. A special grating lithography method according to claim 7, characterized in that: The method further includes step (3), wherein the specific method of step (3) 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 returned and received by the charge coupled device (CCD). The light beam reflected back by the focused spot of the excitation light and the suppression light on the sample surface is partially reflected by the beam splitter and enters the PMT detector.

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

10. A glue filling system for the special grating lithography method according to any one of claims 1 to 9, characterized in that: The invention comprises a liquid tank device and an in-situ developing device, wherein the liquid tank device comprises a photoresist inflow channel closely attached to the outer side of the objective lens, the bottom of the photoresist inflow channel is inclined toward the center of the objective lens, the in-situ developing device comprises a sample pool, the sample pool is provided with a sample stage, the photoresist flows to the sample stage through the photoresist inflow channel, a developer inflow channel is provided on one side of the sample stage, and developer and photoresist outflow channels are provided on the other side of the sample stage.

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