CN119310808A

CN119310808A - A special grating lithography method and its glue filling system

Info

Publication number: CN119310808A
Application number: CN202411699292.2A
Authority: CN
Inventors: 请求不公布姓名
Original assignee: Hangzhou Yuzhiquan Precision Instrument Co ltd
Current assignee: Hangzhou Yuzhiquan Precision Instrument Co ltd
Priority date: 2024-11-26
Filing date: 2024-11-26
Publication date: 2025-01-14

Abstract

The present invention discloses a special grating lithography method and a glue filling system thereof. The present invention is based on laser direct writing technology, and utilizes the characteristics that the printed grating has different resolution requirements in different dimensions to rotate the coordinates of the printed structure, so that the high-resolution projection of the system is consistent with the high-resolution requirement dimension of the printed structure, thereby achieving high-quality printing of the structure. At the same time, in order to achieve long-term engraving and printing, the present invention also provides a device for continuous glue filling for long-term engraving, and the device can also be used to achieve in-situ development and optical imaging.

Description

Special grating photoetching method and glue supplementing system thereof

Technical Field

The invention belongs to the field of optics, and particularly relates to a special grating photoetching method based on laser direct writing and coordinate rotation and a glue supplementing system for the photoetching method.

Background

The special grating comprises a blazed grating and an inclined grating, is a grating device with a special structure, has unique performance characteristics compared with the conventional rectangular grating, and has extremely wide application.

In particular, blazed gratings are a special type of reflective grating whose surface is coated with a metal or other reflective material and is fabricated into a periodic structure by precision machining. Unlike conventional transmissive diffraction gratings, blazed gratings utilize surface reflection to achieve dispersion and selection of incident light. When incident light impinges on the blazed grating surface, it is reflected to different angles and multiple secondary reflections are produced. These secondary reflections may be further dispersed into components of different wavelengths, forming a dispersion pattern. Therefore, blazed gratings can be used as wavelength selectors, scanners, etc. with high resolution and high sensitivity. Blazed gratings have a higher efficiency and a wider range of applications than conventional diffraction gratings. For example, blazed gratings can be used to separate and measure light of different wavelengths for spectral analysis, as mirrors for laser interferometry, to measure object shape, surface roughness, etc. by comparing phase differences reflected from laser beams, as holograms, to record and reproduce three-dimensional stereoscopic images using their diffraction effects, as optical communications, to manufacture transmission media such as fiber optic cables and waveguides for high-speed data transmission, as modern display technology, especially in the AR/VR field, as key optics for 3D glasses, as well as for astronomical observation, as in the AR/VR field.

The structure of the inclined grating is similar to that of a rectangular grating, except that the side wall and the bottom surface of the grating structure in the section of the inclined grating have a certain angle, and when the angle is 90 degrees, the inclined grating is a common rectangular grating. When incident light passes through the inclined grating, diffraction phenomenon occurs due to the difference of refractive indexes. Such diffraction can split the beam into components of different wavelengths and deviate them from the original direction at different angles. Thus, the tilted grating can be used as a dispersive element, a spectrometer, a wavelength selector, and the like. In addition, the inclined grating can realize more complex functions by adjusting the groove line or the convex spacing and angle. Similar to blazed gratings, tilted gratings have found wide application in display technology, holographic imaging, and laser interferometry. In addition, the inclined grating can be used for surface texture treatment of a solar cell panel to improve the conversion efficiency of the solar cell panel, and can be also applied to aspects of cell imaging, fluorescence detection and the like in the biomedical field.

It can be seen that the blazed grating and the inclined grating are used as two special grating devices, and have wide application prospects and commercial values. Because blazed gratings and inclined gratings belong to three-dimensional nano structures, the manufacturing method can only rely on high-precision photoetching technology with three-dimensional manufacturing characteristics. Currently, the fabrication of three-dimensional structures of high precision blazed and tilted gratings is largely dependent on electron beam lithography, which has ultra-high resolution and precision. However, the disadvantages of electron beam lithography are also evident, mainly including:

1. the production cost is high, the price of the electron beam lithography equipment is high, the service life is limited, and frequent maintenance is needed, which increases the production cost.

2. The manufacturing cycle is long, and because electron beam lithography is a point-by-point exposure mode, a large amount of time and effort are required to manufacture a large-area sample, and the manufacturing cycle is relatively long.

3. Poor mass productivity, and can not meet the requirement of large-scale mass production due to the factors of long manufacturing period, low integration level and the like of electron beam lithography.

4. Is easy to be disturbed by environment, and in the electron beam bombardment process, the exposure result can be influenced by static electricity, magnetic field and other environmental factors. To eliminate these effects, strict control and adjustment of the equipment and laboratory environment is required.

Similar to electron beam direct writing lithography, two-photon laser direct writing is a direct writing lithography technique that utilizes the nonlinear effects of laser and substances. Unlike electron beams, laser direct writing techniques often use laser light in the visible band as a light source, which is at a wavelength much higher than that of the electron beam. Therefore, the precision of the laser direct writing technique cannot reach the precision of the electron beam writing. But the advantage of laser direct writing is also obvious, compared with the electron beam lithography, the laser direct writing technology does not need a harsh processing environment, the cost is far less than that of the electron beam lithography equipment, the processing efficiency under the same condition is higher than that of the electron beam lithography equipment, and more importantly, the laser direct writing technology is a real space three-dimensional manufacturing technology because light beams can pass through transparent materials to be focused into a medium, and the laser direct writing technology has wide application prospect in the aspect of manufacturing micro-nano optical elements. Therefore, two-photon laser direct-write lithography can also be considered as a high-precision micro-nano three-dimensional printing technique. However, due to diffraction limit, the precision of laser direct writing is limited to about 100nm, so that high-precision blazed gratings and inclined gratings cannot be manufactured, and the technical advantages and application popularization of laser direct writing in other aspects are greatly limited.

In the conventional two-photon printing technique as shown in fig. 1, the light beam is not focused to an ideal point due to the limitation of the optical diffraction limit, but is focused to an ellipsoid having a certain spatial dimension at the focal plane of the objective lens, two short axes of the ellipsoid are in the focal plane, and the long axis is perpendicular to the focal plane along the optical axis direction. During printing, the focusing light spot generates relative displacement with the photoresist in the photoresist, and the photoresist is stimulated to polymerize to form a three-dimensional structure. Since the focused spot is ellipsoidal, the resolution of the print is spatially non-uniform. As can be seen from fig. 2, the focused spot has a smaller projection in the x-y plane, i.e. the plane parallel to the focal plane, i.e. a higher resolution printing can be achieved. Whereas in the y-z plane, as shown in fig. 3, or in the x-z plane (not shown), i.e. in the plane perpendicular to the focal plane, the projected feature size is larger, i.e. the resolution at printing is lower. Thus, in conventional two-photon three-dimensional printing, the axial (y-z, x-z) resolution is generally considered to be lower than the lateral (x-y) resolution. Furthermore, it is not desirable to manufacture structures that have high requirements for axial resolution.

The tilted grating shown in fig. 4 acts as a special grating whose three-dimensional structure has a high spatial frequency in only a single plane, the x-z direction shown in fig. 5 and the x-y direction shown in fig. 6. In the case of manufacturing blazed gratings and inclined gratings in the y-z direction as shown in fig. 7, the low resolution projection of the focused light spot and the projection of the cross section of the grating requiring high resolution printing (hereinafter referred to as "high resolution required surface") are projected in one direction by the conventional method, so that the step effect is generated as shown in fig. 8, and the printing resolution is insufficient, and the required grating structure cannot be printed effectively.

Therefore, the invention provides a special grating photoetching method and a glue supplementing system based on a laser direct writing technology, and provides a new technical approach for manufacturing high-precision special gratings.

Disclosure of Invention

The invention aims at carrying out coordinate rotation on a printed special grating structure aiming at a special grating printing method, so that a high-resolution requirement surface of the printed special grating structure is consistent with a high-resolution projection direction of a focusing light spot, and a direction with higher focusing light spot resolution is printed in a direction with higher special grating feature size requirement, thereby obtaining a better printing effect.

In order to achieve the above purpose, the invention adopts the following technical scheme:

A special grating photoetching method comprises the following steps:

(1) The femtosecond laser enters the first polarization beam splitter prism after rotating the polarization direction of the femtosecond laser through the half-wave plate, and the picosecond laser enters the first polarization beam splitter prism after passing through the phase plate;

(2) The femtosecond laser and the picosecond laser enter a scanning system and a focusing assembly after being combined by the first polarization beam splitting prism, so that the combined beam light is focused on the photoresist.

The invention adopts the edge light inhibition technique photoetching method of the femtosecond laser, the traditional femtosecond photoetching system is limited by diffraction limit, the characteristic size is difficult to break through 50nm, the edge light inhibition technique adopts another beam which can be focused into a hollow facula, namely picosecond laser, to inhibit the action area of the beam for exciting the polymerization reaction of the photoresist, thereby having smaller characteristic size and improving the inscription precision.

Preferably, in the step (1), the femtosecond laser emitted by the laser enters the second half-wave plate and the second polarization beam splitter prism first, the light beam transmitted by the second polarization beam splitter prism is excitation light, the suppression light pulse width of the light reflected by the second polarization beam splitter prism after passing through the dispersion device is widened to the picosecond laser in the step (2), namely the suppression light, and the excitation light and the suppression light enter the first polarization beam splitter prism to be combined after passing through the beam shrinking module, the acousto-optic modulator and the beam expanding module in sequence. The beam shrinking module is used for shrinking the beam diameter to enable the beam diameter to meet the use requirement of the acousto-optic modulator. The acousto-optic modulator is used for realizing quick on-off and power regulation of the light beam. The beam expanding module is used for expanding the beam diameter.

Femtosecond lasers are used to achieve photoresist polymerization, and the beam is called excitation light. Picosecond lasers are used to achieve an edge-quench effect, and the beam is called quench light. The suppressing light may be continuous light. In order to reduce the cost, the invention adopts a single laser to divide the laser into excitation light and inhibition light through the second polarization beam splitter prism, thereby realizing edge light laser direct writing.

Preferably, in the step (1), the beam shrinking module is composed of two lenses, the beam shrinking module shrinks the transmitted beam transmitted by the second polarization splitting prism to below a first set value to become excitation light, the beam shrinking module shrinks the reflected beam reflected by the second polarization splitting prism to the first set value, and then the polarization direction is rotated through the half-wave plate. The first set point may be 2-3mm.

Preferably, in the step (1), the excitation light after beam shrinkage and the reflected light after beam shrinkage are respectively reflected by a reflecting mirror and enter two acousto-optic modulators, after exiting, the beam diameters of the excitation light and the reflected light are respectively expanded to a second set value through a beam expanding module, the second set value is generally 4-5mm, the purpose of the second set value is that enough pixels can be covered when the light beam is incident on a subsequent spatial light modulator, the beam expanding module comprises a reflecting mirror, a diaphragm, a lens and a beam expanding aperture, the beam expanding Shu Xiaokong is placed on focal planes of the two lenses, the emergent light beam makes the light beam enter the center of the vertical diaphragm through the reflecting mirror, and the excitation light and the reflected light sequentially pass through the lens, the beam expanding aperture and the lens and then enter the first polarization splitting prism for beam combination.

Preferably, in the step (2), the combined light beam is incident to the left half screen of the spatial light modulator through the reflecting mirror, at this time, the polarization states of the excitation light and the suppression light are both linearly polarized and mutually perpendicular, the angle of the spatial light modulator is rotated to enable the response polarization state to be the same as the polarization state of the suppression light, the corresponding phase of the suppression focal spot can be generated when the left half screen is loaded, the suppression light is regulated and controlled, at this time, the excitation light is not affected, after the combined light beam exits from the left half screen of the spatial light modulator, the combined light beam is reflected through the quarter wave plate and the reflecting mirror, and is incident to the right half screen of the spatial light modulator, at this time, the excitation light is regulated and controlled by the phase mask on the right half screen of the spatial light modulator, the suppression light is not affected, and the combined light after exiting from the spatial light modulator is converted into circular polarized light by the quarter wave plate. Thus, under the condition that excitation light and inhibition light are coaxial, the respective required phase regulation and control can be realized, and then the solid light spots and the hollow light spots are focused.

Preferably, in the step (1), after the light beam enters the half-wave plate and the second polarization beam splitter prism, the light beam transmitted by the second polarization beam splitter prism becomes excitation light, and enters the excitation light fiber, the optical fiber acousto-optic modulator and the collimator through the coupler, and then enters the half-wave plate and the first polarization beam splitter prism to combine, and the light beam reflected by the second polarization beam splitter prism also enters the light suppression fiber, the optical fiber acousto-optic modulator and the collimator through the coupler, and then enters the half-wave plate and the first polarization beam splitter prism to combine. The optical fiber device can reduce wavefront difference brought by a space optical path and improve the quality of light beams. At the same time, the system volume is reduced, and the compactness of the system is increased. The optical fiber device can also reduce the adjustment difficulty of the system to a certain extent, and is easy to maintain. The suppression optical fiber may employ a special mode fiber for producing hollow spots. Optical fibers having a special structure on the end face may also be used.

Preferably, in the step (2), the focusing assembly includes a scanning module, a scanning lens, a field lens, a dichroic mirror, a spectroscope and an objective lens, and the beam after beam combination sequentially passes through the scanning module, the scanning lens, the field lens, the dichroic mirror, the spectroscope and the objective lens, and is finally focused on the sample on the objective table by the objective lens.

Preferably, the method further comprises a step (3), and the specific method of the step (3) is as follows:

(3) After the light beam emitted by the LED is reflected by the dichroic mirror, the light beam enters the objective lens through the spectroscope to illuminate the sample surface, the light signal of the sample surface is received by the charge coupled device CCD after being returned, and the excitation light and the light beam reflected by the focusing light spot of the light on the sample surface are reflected by the spectroscope part and enter the PMT detector.

Preferably, in the step (1), the femtosecond laser enters the adjusting system before entering the half wave plate, wherein the adjusting system comprises a half wave plate, a third polarization beam splitting prism, a reflecting mirror, a grating pair, a roof prism and an anti-drift module, the femtosecond laser is used for adjusting the beam energy of the subsequent system through the half wave plate and the third polarization beam splitting prism, is reflected by the reflecting mirror to enter the grating pair, is reflected by the roof prism, is again reflected by the grating pair, and enters the anti-drift module through the reflecting mirror. The two reflectors in front of the anti-drift module are used for adjusting the position and the angle of the light beam entering the anti-drift module in a large range. The anti-drifting module is used for achieving the light beam stabilizing effect.

The pulse width of the femtosecond beam is widened due to the fact that the subsequent beam passes through a plurality of optical devices when propagating in space. The grating pair is used to compensate for the pulse spread of the beam in conjunction with the roof prism. Generally, as the laser emits polarized light beams, the combination of the half-wave plate and the third polarization splitting prism can adjust the energy of the light beams entering the subsequent system, and the redundant energy of the light beams is reflected by P to enter the light barrier so as to avoid potential safety hazards.

A photoresist supplementing system for special grating photoetching method is composed of a liquid tank unit consisting of photoresist flowing channel, and an in-situ developing unit. The in-situ developing device comprises a sample tank, wherein the sample tank is provided with a sample stage, photoresist flows to the sample stage through a photoresist inflow channel, one side of the sample stage is provided with a developer inflow channel, and the other side of the sample stage is provided with a developer and photoresist outflow channel.

Conventionally, the inclined grating and blazed grating to which the present invention is directed are flat in shape, and the present invention requires a large space in the axial direction due to the use of the coordinate rotation. The photoresist supplementing system enables the liquid photoresist to be supplemented into the sample pool through the two photoresist inflow channels which are tightly attached to the objective lens, and can realize automatic photoresist supplementing. The developing solution flows in from the sample stage, and after the development is finished, the developing solution flows out from the unified developing solution and photoresist outflow channel.

By adopting the technical scheme, the invention has the following beneficial effects:

1. The invention adopts the edge light inhibition technique photoetching method of a femtosecond laser, the traditional femtosecond photoetching system is limited by diffraction limit, the characteristic size is difficult to break through 50nm, the edge light inhibition technique adopts another beam which can be focused into a hollow facula, namely picosecond laser, to inhibit the action area of the beam for exciting the polymerization reaction of photoresist, thereby reducing the side of a characteristic ruler and improving the inscription precision to 40nm.

2. In order to reduce the cost, the invention adopts a single laser to divide the laser into excitation light and inhibition light through the second polarization beam splitter prism, thereby realizing edge light laser direct writing.

3. The glue supplementing system occupies small space, so that the liquid photoresist is supplemented into the sample pool through the two photoresist inflow channels which are tightly attached to the objective lens, and automatic glue supplementing can be realized. The developing solution flows in from the sample stage, and after the development is finished, the developing solution flows out from the unified outflow channel. The method can continuously supplement the photoresist according to the printing process, and avoids the pollution of the objective lens and the waste of materials caused by too much injection at one time. Meanwhile, the device can realize in-situ development and in-situ imaging observation after printing is finished.

Drawings

The invention is further described below with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of a conventional two-photon printing technology in which a focal plane of a beam objective lens is focused into an ellipsoid having a certain spatial dimension.

Fig. 2 is a schematic view of a focused spot in the x-y plane.

FIG. 3 is a schematic view of a focused spot in the y-z plane.

Fig. 4 is a schematic diagram of the structure of the tilted grating.

Fig. 5 is a low resolution projection of a focused spot onto the x-z plane.

Fig. 6 is a high resolution projection of a focused spot on an x-y plane.

Fig. 7 is a low resolution projection of a focused spot on the y-z plane.

Fig. 8 is a schematic diagram of the outline of an actual printing structure.

Fig. 9 is a schematic diagram of an apparatus for a special grating lithography method in embodiment 1.

Fig. 10 is a schematic diagram of an apparatus for a special grating lithography method in embodiment 2.

Fig. 11 is a suppressed flare formed in example 2.

FIG. 12 is a schematic diagram of an apparatus for a special grating lithography method according to comparative example 1.

Fig. 13 is a cross-sectional view of the glue system.

Fig. 14 is a perspective view of the glue dispensing system.

Fig. 15 is a schematic structural view of the blazed grating printed in embodiment 1.

Fig. 16 is a schematic view showing the structure of the blazed grating actually printed in the x-y plane in example 1.

Fig. 17 is a schematic diagram of the structure of the blazed grating printed in comparative example 1.

Fig. 18 is a schematic view showing the structure of the blazed grating actually printed in comparative example 1 in the y-z plane.

Fig. 19 is a projection view of the focused spot in example 1.

Fig. 20 is a projection view of the focused spot in comparative example 1.

Fig. 21 is a blazed grating pattern written in example 1.

Fig. 22 is a blazed grating pattern of the focus spot of comparative example 1.

Detailed Description

Example 1

The special grating photoetching method as shown in fig. 9 comprises the following steps:

(1) The light beam emitted by the laser 1 passes through the third half wave plate 2 and the third polarization splitting prism 3, the laser 1 selects the light beam with the wavelength of 532nm, and the pulse width of the laser 1 is below 200 femtoseconds.

(2) The light beam reflected by the third polarization splitting prism 3 enters the light barrier 4, the light beam transmitted through the third polarization splitting prism 3 is reflected by the reflecting mirror 5 and enters the grating pair 6, then passes through the grating pair 6 again after being reflected by the roof prism 7, and then enters the anti-drifting module 8 through the two reflecting mirrors 5. The anti-drift module 8 may employ a direct write-path anti-drift system as described in patent CN 113189846A for beam stabilization.

(3) The light beam is emitted from the drift prevention module 8 and then is split by the second polarization splitting prism 10 through the second half wave plate 9, the light beam transmitted by the second polarization splitting prism 10 enters a group of beam shrinking modules consisting of two lenses 11 to shrink to below 2mm to become excitation light, the light beam reflected by the second polarization splitting prism 10 is stretched to the hundred picoseconds level to become inhibition light through a dispersion device 12, then is condensed to below 2mm through a beam shrinking module consisting of two lenses 11, and the polarization direction is rotated through a fourth half wave plate 13 to meet the incident requirement of the acousto-optic modulator 14.

(4) The excitation light is reflected by the two mirrors 5 into the acousto-optic modulator 14, and the angle and position of the light beam entering the acousto-optic modulator 14 can be controlled by adjusting the two mirrors 5. A power detector (not shown) is placed behind the acousto-optic modulator 14 to receive the diffracted light of the next order of the acousto-optic modulator 14 without allowing the zero order light of the acousto-optic modulator 14 to enter the power detector. The power detector is used to tune 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 can be maximized, and can be generally above 95%. After the primary light is emitted, two reflectors 5 are arranged, and the light beam emitted from the acousto-optic modulator 14 sequentially passes through a diaphragm 15, a lens 11, a beam expansion aperture 16 and the lens 11. The beam is made to enter perpendicularly to the center of the diaphragm 15 by adjusting the two reflecting mirrors 5, and zero-order light emitted from the acousto-optic modulator 14 is blocked by the size of the diaphragm 15. The beam expanding small holes 16 are arranged on the focal surfaces of the two lenses 11, and the size of the beam expanding small holes 16 is 0.9 Airy spot for filtering stray light around Gaussian light spots. The beam expanding module expands the beam diameter by 5 mm a. The excitation light after beam expansion enters a first polarization splitting prism 18 to be combined through a reflecting mirror 5 and a first half wave plate 17. 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 splitting prism 18 with the highest efficiency. The suppressed light also enters the first polarization splitting prism 18 to be combined through the same procedure as described above.

(5) The combined light beam is incident to the left half screen of the spatial light modulator 19 through the mirror 5, and the polarization states of the excitation light and the inhibition light are linear polarized light and are perpendicular to each other. The spatial light modulator 19 is rotated so that its response polarization is the same as the suppressed light polarization. The response phase of the suppressed focal spot can be generated by loading on the left half screen, the suppressed light is regulated and controlled, and the excitation light is not affected at the moment. The combined beam is emitted from the left half screen of the spatial light modulator 19, reflected by the quarter wave plate 20 and the reflecting mirror 5, and then enters the right half screen of the spatial light modulator 19. Because the polarization state of the light beam is rotated by 90 ° by passing through the quarter wave plate 20 twice, 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 after exiting the spatial light modulator 19 is converted into circular polarized light by the quarter wave plate 20.

(6) The combined 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 this order, and is finally focused by the objective lens 26 onto the sample on the stage 27. The scanning module 21 preferably uses a triple-galvanometer scanning system. The dichroic mirror transmits 532 and reflects 640.

(7) The light beam with the wavelength 640 emitted from the LED39 is reflected by the beam splitter 25 and the dichroic mirror 24, and then enters the objective lens 26 through the beam splitter 25, thereby illuminating the sample surface. The optical signal of the sample surface is received by the charge coupled device CCD28 after being returned.

(8) The excitation light and the light beam reflected by the focusing light spot of the suppression light on the sample surface are partially reflected by the beam splitter 25 into the PMT detector 29, so that the detection of the system point spread function PSF can be realized.

(9) And placing an autocorrelation instrument of 532 wave bands on the sample surface, testing pulse widths of excitation light and suppression light, and pressing the pulse width of 532 femtosecond laser below 200fs by adjusting the interval of the grating pair 6. The dispersion device 12 parameters are adjusted to suppress the light pulse width to about 500 ps.

Example 2

The special grating photoetching method as shown in fig. 10 comprises the following steps:

(3) The light beam is split by the second polarization splitting prism 10 through the second half-wave plate 9 after exiting from the anti-drifting module 8, and the transmitted light beam is converted into excitation light and enters the excitation light fiber 30 through the coupler 31 and then enters the fiber acousto-optic modulator 141. The reflected beam also passes through the coupler 31 and enters the optical fiber acousto-optic modulator 141 after entering the optical fiber 32. Wherein, the exciting optical fiber 30 is a photonic crystal fiber with smaller chromatic dispersion, and the suppressing optical fiber 32 is a common single-mode fiber with larger chromatic dispersion. In addition, the optical fiber 32 is selected to generate the high-order vortex optical field mode to generate the required hollow light spot.

(4) After the two beams of light are emitted from the optical fibers, the two beams of light are collimated by the respective collimators 33 and pass through the first half-wave plate 17, and then are combined by the first polarization splitting prism 18. The combined 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 this order, and is finally focused by the objective lens 26 onto the sample on the stage 27. The scanning module 21 preferably uses a triple-galvanometer scanning system. The dichroic mirror transmits 532 and reflects 640.

(5) The system also comprises an illumination monitoring system, and the light beam with the wavelength of 640 emitted by the LED39 enters the objective lens 26 through the spectroscope 25 after being reflected by the dichroic mirror 24, so as to illuminate the sample surface. The optical signal of the sample surface is received by the charge coupled device CCD28 after being returned.

(6) The excitation light and the light beam reflected by the focusing light spot of the suppression light on the sample surface are partially reflected by the beam splitter 25 and enter the PMT detector 29, so that the PSF of the system can be detected.

(7) And placing an autocorrelation instrument of 532 wave bands on the sample surface, testing pulse widths of excitation light and suppression light, and pressing the pulse width of 532 femtosecond laser below 200fs by adjusting the interval of the grating pair 6. The length of the optical fiber 32 is adjusted so that the optical pulse width is about 500 ps.

If the inhibiting optical fiber does not adopt the special mode optical fiber, the inhibiting optical fiber can also adopt the optical fiber with the special micro-nano structure on the end face. The suppressed light spots formed are shown in fig. 11.

Comparative example 1

A special grating lithography method as shown in fig. 12, comprising the steps of:

(1) The femtosecond laser emitted by the laser 1 passes through the half-wave plate 2 and the polarization beam splitter prism 3, the laser 1 selects light beams with wavelength of 532nm, and the pulse width of the laser 1 is below 200 femtoseconds.

(2) The light beam reflected by the third polarization splitting prism 3 enters the light blocker 4, the light beam transmitted through the third polarization splitting prism 3 passes through the acousto-optic modulator 14 and then is reflected by the reflecting mirror 5 to enter the diaphragm 15, the lens 11, the beam expanding small hole 16 and the lens 11, the light beam passes through the scanning module 21, the scanning lens 22, the field lens 23, the dichroic mirror 24, the spectroscope 25 and the objective lens 26 sequentially by adjusting the two reflecting mirrors 5, and finally is focused on the sample on the objective table 27 by the objective lens 26. The scanning module 21 preferably uses a triple-galvanometer scanning system. The dichroic mirror transmits 532 and reflects 640.

(4) The light beam with the wavelength 640 emitted from the LED39 is reflected by the beam splitter 25 and the dichroic mirror 24, and enters the objective lens 26 to illuminate the sample surface. The optical signal of the sample surface is received by the charge coupled device CCD28 after being returned.

A resist replenishment system for a special grating lithography method as shown in fig. 13 and 14 comprises a liquid bath device and an in-situ developing device, wherein the liquid bath device comprises a resist inflow channel 34 closely attached to the outer side of an objective lens 26, and the bottom of the resist inflow channel 34 is inclined toward the center of the objective lens 26. The in-situ developing device comprises a sample tank 35, wherein the sample tank 35 is provided with a sample stage 36, photoresist 40 flows to the sample stage 36 through a photoresist inflow channel 34, one side of the sample stage 36 is provided with a developing solution inflow channel 37, and the other side of the sample stage 36 is provided with a developing solution and photoresist outflow channel 38.

Conventionally, the inclined grating and blazed grating to which the present invention is directed are flat in shape, and the present invention requires a large space in the axial direction due to the use of the coordinate rotation. The glue replenishing system can make the liquid photoresist 40 be replenished into the sample cell 35 through two photoresist inflow channels 34 which are closely attached to the objective lens 26, so that automatic glue replenishing can be realized. The developer flows into the developer inflow channel 37, and after the development is completed, the developer flows out through the unified developer and photoresist outflow channel 38.

Taking blazed gratings printed in example 1 and comparative example 1 as examples.

Fig. 15 is a schematic structural view of the blazed grating printed in example 1, and fig. 16 is a schematic structural view of the blazed grating actually printed in example 1 in the x-y plane. The a-plane is parallel to the x-y plane in fig. 15.

Fig. 17 is a schematic diagram of the structure of the blazed grating printed in comparative example 1, and fig. 18 is a schematic diagram of the structure of the blazed grating actually printed in comparative example 1 in the y-z plane. The a-plane in fig. 17 is parallel to the y-z plane.

The a-plane in fig. 15 is the same plane as the a-plane in fig. 17 as the printed blazed grating structure.

Fig. 19 is a projection view of the focused spot in example 1, fig. 20 is a projection view of the focused spot in comparative example 1, and it is understood that the focused spot in example 1 is a high-resolution projection, and the focused spot in comparative example 1 is a low-resolution projection.

Fig. 21 is an electron microscopic view of a blazed grating of a limited size printed in example 1, and fig. 22 is an electron microscopic view of a blazed grating of the same size printed in comparative example 1. In contrast, the triangular profile in fig. 21 is more obvious, and the triangular profile in fig. 22 is more rounded, so that the photolithography method in embodiment 1 results in higher printing accuracy of the blazed grating.

The above is only a specific embodiment of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions or modifications made on the basis of the present invention to solve the substantially same technical problems and achieve the substantially same technical effects are encompassed within the scope of the present invention.

Claims

1. A special grating lithography method, characterized in that it comprises the following steps:

(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 suppression light pulse width 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. According to claim 2, a special grating lithography method is 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 by 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 shrinkage and the reflected light after beam shrinkage are respectively reflected by a reflector and enter two acousto-optic modulators, and after emission, they are respectively expanded to a second set value through a beam expansion module, the beam expansion module comprises 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. The corresponding phase of the suppression focus can be generated 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 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, and 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 component includes a scanning module, a scanning lens, a field lens, a dichroic mirror, a beam splitter and an objective lens, and 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 it also includes step (3), and 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. After the light signal of the sample surface is returned, it is 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 the femtosecond laser enters the second half-wave plate, it first enters the adjustment system, and 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 passes through 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 as described in any one of claims 1 to 9, characterized in that it comprises a liquid tank device and an in-situ developing device, 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.