Printing device of tunable micro-nano structure and printing method thereof

Abstract

According to the printing device and the printing method of the tunable micro-nano structure, the mode that a projection element directly loads a pattern to carry out micro-structure projection is utilized, an oxidation structure is prevented from being formed in the femtosecond laser micro-nano structure machining process through medium assistance, and the structure and components do not obviously change when the exposure time is prolonged; the liquid medium can reduce generation of bubbles and / or discharge the bubbles in time, the influence of the bubbles on light is reduced, and the precision of the micro-nano structure is improved.

Description

Technical Field

[0001] The invention relates to the field of material surface micro-nano structure processing, and in particular to a printing method for tunable micro-nano structure patterns using femtosecond laser processing. Background Art

[0002] With the continuous development of science and technology, the demand for micro-nano structures on the surface of materials is increasing. Among the many methods for making micro-nano structures, laser processing technology has attracted much attention due to its advantages such as high precision, high flexibility and non-contact.

[0003] Traditional laser processing methods often have some limitations when making micro-nano structures on the surface of materials. For example, the processing accuracy is limited, making it difficult to achieve complex micro-pattern structures; the pattern has poor tunability and is difficult to meet the needs of different application scenarios; and the processing may cause thermal damage to the material, affecting the performance and service life of the material.

[0004] As an ultrashort pulse laser, femtosecond laser has extremely high peak power and extremely short pulse width, which can achieve high-precision material processing. However, pure femtosecond laser processing also faces some challenges, such as low processing efficiency, high requirements for processing environment, and single processing method.

[0005] By utilizing the interaction between lasers and materials to form subwavelength surface stripes, it is possible to achieve accuracy that exceeds the diffraction limit. This has important applications in the manufacture of high-precision gratings, electromagnetic wave control devices, biosensors, hydrophilic and hydrophobic surfaces, and regulation of cell growth.

[0006] At present, laser-induced periodic surface structures (LIPSS) mainly include low-period LSFL (period>λ / 2) and high-period HSFL (period>λ / 2), among which HSFL can usually only be induced by ultrafast laser. At present, there are still great technical barriers to the formation of multi-level ordered and controllable micro-nano patterned structures for HSFL. On the one hand, the existing technology mainly uses galvanometer and field mirror scanning, and the flexibility of pattern formation is poor. On the other hand, when the laser enters the medium, it is limited by nonlinear effects, the spot cannot reach a tight focus state, and the precision of the formed pattern is low.

[0007] At present, although there have been some studies on femtosecond laser processing, there are relatively few studies on tunable micro-nanostructure pattern printing. Therefore, developing an efficient, precise, and tunable femtosecond laser projection-induced micro-nanostructure pattern printing method on the surface of materials has important practical significance and application value. Summary of the invention

[0008] The present invention provides a printing device and a printing method for a tunable micro-nano structure, which realizes the manufacture of a submicron-level controllable structure and a super-periodic surface structure.

[0009] The tunable micro-nanostructure printing device comprises an ultrafast laser, an optical switch, an energy regulating device, a beam shaping device, a lens group, a first reflector, a second reflector, a third reflector, a spatial light modulator, an imaging lens, a laser reflector, an imaging objective lens, a sample, a three-axis displacement stage, an illumination light source, a spectroscope, a second reflector, an imaging lens, a detector and a computer control system.

[0010] During processing, the ultrafast laser 1 emits a light beam which passes through the optical switch 2 and the energy adjustment device 3, enters the beam shaping device 4, and then passes through the lens group 5 to expand the beam and passes through the first reflector 6. Then, the angle of the incident spatial light modulator 9 is adjusted by the second reflector 7 and the third reflector 8. The spatial light modulator loads the pattern, and the light beam generates spatial chirp through the spatial light modulator 9, passes through the imaging lens 10, enters the laser reflector 11, and projects the pattern onto the sample 13 placed on the three-axis translation stage 14 through the imaging objective lens 12.

[0011] At the same time, the light emitted by the illumination light source 15 is reflected by the beam splitter 16, passes through the laser reflector 11 and the imaging objective lens 12, and irradiates the sample 13, so that the image information on the reflected sample 13 passes through the laser reflector 11, the beam splitter 16, the fourth reflector 17, and the imaging lens 18, and is collected by the detector 19 for monitoring the printed pattern on the sample surface.

[0012] The processed samples are not limited to metal-semiconductor composite films, but can be processed on silicon wafers, metals and other materials.

[0013] Furthermore, the beam shaping device 4 is used to homogenize the beam.

[0014] Furthermore, the spatial light modulator 9 is a DMD spatial light modulator.

[0015] Optionally, the sample is in a liquid medium, and the laser needs to pass through the liquid medium when projecting to the sample; the boiling point of the liquid medium is relatively high, so that it is not easy to generate too many bubbles during the laser ablation process, and secondly, the surface tension of the liquid medium should be small, so that small bubbles collide and are not easy to aggregate to form large bubbles during the laser ablation process. The liquid medium is water or isopropyl alcohol or propylene glycol methyl ether acetate (PGMEA).

[0016] Optionally, a liquid medium of set thickness is loaded through a container, which is a watch glass; manufacturing is performed in the watch glass to ensure the supply of the liquid medium and to ensure that there is enough liquid medium to regulate the bubbles generated during the manufacturing process, allowing the bubbles to flow away and reducing the impact of the bubbles on light.

[0017] Optionally, a cover glass is placed on the sample, the liquid medium is added between the cover glass and the sample, and the liquid medium loading is adjusted to a set thickness by a liquid surface thickness adjustment device; the liquid medium is covered by the cover glass to reduce the evaporation rate of the liquid medium, which can ensure the stability of the medium in the efficient large-area manufacturing process. The above-mentioned setting of the thickness of the liquid medium loading is to ensure the thickness of the liquid medium above the sample surface.

[0018] Optionally, the liquid medium is loaded into the space between the coverslip and the liquid through a peristaltic pump from one side, flows out from the other side and enters a waste liquid collection cycle, thereby realizing flow loading of a medium of fixed thickness; thus, a stable flow of medium is continuously provided, reducing the impact of bubbles and nanoparticles formed by ablation, and improving manufacturing efficiency.

[0019] Based on the above printing device, a printing method for tunable micro-nanostructures is proposed, comprising:

[0020] Step 1: placing the sample on the three-axis translation stage 14, with a cover glass covering the sample, and a liquid medium between the cover glass and the sample;

[0021] Step 2: The ultrafast laser 1 emits a light beam to the optical switch 2. After being adjusted by the energy adjustment device, the light beam enters the beam shaping device to be homogenized. The homogenized light beam is expanded by the lens group 5. After being expanded, the light beam is reflected by the first reflector 6 and passes through the second reflector 7 and the third reflector 8 before entering the spatial light modulator 9. The first reflector 6, the first reflector group 7 and the second reflector group 8 are used to adjust the incident angle of the light beam entering the spatial light modulator 9. After the spatial light modulator loads the pattern to be processed, it performs time conditioning on the incoming light beam so that it carries the pattern information. The light and matter inside the pattern spontaneously form nanoscale stripes, and then pass through the imaging lens 10, enter the laser reflector 11, and project the pattern onto the sample 13 through the imaging objective lens 12, and ablate the sample surface to form a micro-nano structure;

[0022] The direction of the spontaneously formed nanoscale stripes in the pattern changes with the polarization direction of the laser.

[0023] The beneficial effects of the present invention are:

[0024] 1. Most existing technologies form patterns by scanning point by point, which requires complex trajectory programming. However, this paper proposes a method of using a projection element to directly load patterns for microstructure projection, which can realize a complex pattern projection etching method without trajectory programming.

[0025] 2. The existing method of using a projection unit for projection faces the problem of uneven light spots and oxidation of the material surface in the air, which causes changes in not only the structure but also the composition of the sample. In the medium-assisted method proposed in this work, the liquid medium environment isolates the air to avoid the formation of an oxidized structure, and the nanostructure and components do not change significantly when the exposure time is increased. At the same time, the liquid medium can reduce the generation of bubbles and / or expel bubbles in time, reduce the impact of bubbles on light, and improve the accuracy of the micro-nano structure.

[0026] 3. In the device provided in this article, during the manufacturing process, the spatial light modulator will disperse the laser light, produce a spatiotemporal focusing effect, and reduce the peak power of other areas outside the focus, thereby realizing the formation of a HSFL structure inside a constrained high-precision structure. Ultimately, the formation of nanoscale stripes inside a submicron-scale structure can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of a tunable micro-nanostructure printing device provided by the present invention;

[0028] Figure 2 It is a carrying method for processing samples of the present invention;

[0029] Figure 3 It is the second loading method for processing samples of the present invention;

[0030] Figure 4 This is the third loading method for processing samples of the present invention;

[0031] Figure 5 It is a schematic diagram of the ablation results of processed samples in different medium environments. DETAILED DESCRIPTION

[0032] In order to better illustrate the purpose and advantages of the present invention, the following is a further description of the invention in conjunction with the accompanying drawings and examples. It should be noted that the implementation of the present invention is not limited to the following embodiments, and any form of modification or change made to the present invention will fall within the protection scope of the present invention.

[0033] A tunable micro-nanostructure printing device includes an ultrafast laser, an optical switch, an energy regulating device, a beam shaping device, a lens group, a first reflector, a second reflector, a third reflector, a spatial light modulator, an imaging lens, a laser reflector, an imaging objective lens, a sample, a three-axis displacement stage, an illumination light source, a spectroscope, a second reflector, an imaging lens, a detector and a computer control system.

[0034] The processed samples are not limited to metal-semiconductor composite films, but can be processed on silicon wafers, metals and other materials.

[0035] The sample is in a liquid medium, and the light beam needs to pass through the liquid medium when projected to the sample; the liquid medium is water or propylene glycol methyl ether acetate (PGMEA); a quantitative amount of liquid medium can be loaded through a container, such as a watch glass, so as to regulate the bubbles generated during the manufacturing process, let the bubbles flow away, and reduce the impact of the bubbles on the light.

[0036] Optionally, the sample is covered with a coverslip, and the liquid medium is loaded between the coverslip and the sample. The coverslip covers the liquid medium, which reduces the evaporation rate of the liquid medium, thereby ensuring the stability of the medium during efficient and large-area manufacturing. The liquid surface thickness adjustment device can be used to load the liquid medium between the coverslip and the sample with a fixed thickness. The peristaltic pump can also be used to load the liquid medium from one side between the coverslip and the liquid, and the liquid medium flows out from the other side and enters a waste liquid collection cycle, thereby realizing flow loading of a medium with a fixed thickness. In this way, a stable flowing medium is continuously provided, reducing the impact of bubbles and nanoparticles formed by ablation, thereby improving manufacturing efficiency.

[0037] The optical path during processing is as follows: the light beam emitted by the ultrafast laser 1 passes through the optical switch 2 and the energy adjustment device 3, enters the beam shaping device 4 (for beam homogenization), expands the beam through the lens group 5, passes through the first reflector 6, and then adjusts the angle of the incident spatial light modulator 9 through the second reflector 7 and the third reflector 8. The light beam is modulated in time and space by the DMD spatial light modulator 9, passes through the imaging lens 10, enters the laser reflector 11, and projects the pattern onto the sample 13 placed on the three-axis translation stage 14 through the imaging objective lens 12;

[0038] At the same time, the light emitted by the illumination light source 15 is reflected by the beam splitter 16 , passes through the laser reflector 11 and the imaging objective lens 12 , and irradiates the sample 13 .

[0039] The reflected image information is collected by the detector 19 through the laser reflector 11 , the beam splitter 16 , the fourth reflector 17 , and the imaging lens 18 .

[0040] Based on the above printing device, a printing method for tunable micro-nanostructures is proposed, comprising:

[0041] Step 1: placing the sample on the three-axis translation stage 14, with a cover glass covering the sample, and a liquid medium between the cover glass and the sample;

[0042] Step 2: The ultrafast laser 1 emits a light beam to the optical switch 2. After passing through the energy adjustment device, it enters the beam shaping device to homogenize the light beam. The homogenized light beam is expanded by the lens group 5. After the expansion, it is reflected by the first reflector 6, passes through the second reflector 7 and the third reflector 8, and then enters the spatial light modulator 9. The first reflector 6, the first reflector group 7 and the second reflector group 8 are used to adjust the incident angle of the light beam entering the spatial light modulator 9. The light beam is spatiotemporally modulated by the spatial light modulator 9 to form a micron-level pattern (the spatial light modulator loads the pattern to be processed and then spatiotemporally modulates the incoming light beam to form a micron-level pattern). Nanoscale stripes are spontaneously formed inside the pattern by light and matter, and then pass through the imaging lens 10, enter the laser reflector 11, and project the pattern onto the sample 13 through the imaging objective lens 12, and ablate the sample surface to form a micro-nano structure; the direction of the spontaneously formed nanoscale stripes in the pattern changes with the polarization direction of the laser.

[0043] The laser parameters are 1kHz, 120fs, and the central wavelength is 798nm. Under the same power, the ablation results in air, water, and PGMEA materials are as follows: Figure 5 As shown. Through experiments, it is found that:

[0044] There are two main problems in pattern manufacturing in the air. On the one hand, the uniformity of the light spot will significantly lead to structural unevenness. By increasing the exposure time, the whole can be in an ablated state to a certain extent. However, if the exposure time in the air is too long, the strong ablation area will change from nano-scale LIPSS to micron-scale disordered structure. The weak ablation structure will form LIPSS, resulting in overall uneven texture. On the other hand, when the exposure time is too long, EDS imaging of the local structure shows that oxygen elements will be added to the formation of the structure, causing the composition of the structure to change;

[0045] When in a liquid environment, on the one hand, it can reduce the damage threshold, increase the direct writing window, and promote the improvement of uniformity. On the other hand, it can improve the isolation of oxygen in the air and inhibit the formation of oxidized structures. When FPL is performed in water, although the reduction of the damage threshold is controlled, the laser will induce the formation of viscous bubbles. These bubbles are adsorbed on the surface of the structure and are difficult to break. During the manufacturing process, aggregation will occur, so that when high energy is applied, bubbles will be formed locally, resulting in the superposition of LSFL on the basis of HSFL, producing hybrid micro-nano structures. In PGMEA, although bubbles will also form, because the bubbles are more fluid and the bubble state is unstable, the new bubbles will break or push away the previous bubbles after they are formed, thereby ensuring the overall uniformity. It can be seen that the uniformity formed by PGMEA in the process is stronger than the results in air and water. The microstructure is also more uniform.

[0046] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A tunable micro-nanostructure printing device, characterized in that: The invention comprises an ultrafast laser, an optical switch, an energy regulating device, a beam shaping device, a lens group, a first reflector, a second reflector, a third reflector, a spatial light modulator, an imaging lens, a laser reflector, an imaging objective lens, a sample, a three-axis displacement stage and a computer control system for controlling the above-mentioned components. During processing, the ultrafast laser emits a light beam which passes through the optical switch and the energy regulating device, and then passes through the first reflector after being expanded by the lens group 5, and then adjusts the angle of the incident spatial light modulator through the second reflector and the third reflector, the spatial light modulator loads a pattern, and the light beam generates spatial chirp through the spatial light modulator, passes through the imaging lens, enters the laser reflector, and projects the pattern onto the sample placed on the three-axis displacement stage through the imaging objective lens. The sample is surrounded by a liquid medium.

2. The printing device according to claim 1, characterized in that: A beam shaping device is also provided between the energy regulating device and the lens group for homogenizing the beam.

3. The printing device according to claim 1, characterized in that: It also includes an illumination light source, a beam splitter, a second reflector, an imaging lens and a detector; the light emitted by the illumination light source passes through the beam splitter, the laser reflector and the imaging objective lens to irradiate the sample, thereby reflecting the image information on the sample and then passing through the laser reflector, the beam splitter, the fourth reflector and the imaging lens to be collected by the detector.

4. The printing device according to claim 1, characterized in that: The spatial light modulator is a DMD spatial light modulator.

5. The printing device according to claim 4, characterized in that: The liquid medium is water or isopropyl alcohol or propylene glycol methyl ether acetate (PGMEA).

6. The printing device according to claim 1, characterized in that: The liquid medium of set thickness is loaded through the container.

7. The printing device according to claim 1, characterized in that: A cover glass is placed on the sample, and the liquid medium is added between the cover glass and the sample. The liquid medium is loaded with a set thickness by adjusting the liquid surface thickness adjusting device.

8. The printing device according to claim 1, characterized in that: The liquid medium is loaded into the space between the coverslip and the liquid through a peristaltic pump, and flows out from the other side into the waste liquid collection cycle, thus realizing the flow loading of the medium with a fixed thickness.

9. A method for printing a tunable micro-nanostructure, comprising: Step 1: Place the sample on a three-axis translation stage, with a cover glass on top of the sample and a liquid medium between the cover glass and the sample; Step 2: The ultrafast laser emits a light beam to the optical switch. After being adjusted by the energy adjustment device, it enters the beam shaping device to homogenize the light beam. The homogenized light beam is expanded by the lens group. After being expanded, it is reflected by the first reflector, passes through the second reflector and the third reflector, and then enters the spatial light modulator. The first reflector, the first reflector group, and the second reflector group are used to adjust the incident angle of the light beam entering the spatial light modulator. After the spatial light modulator loads the pattern to be processed, it performs time conditioning on the incoming light beam so that it carries the pattern information. The light and matter inside the pattern spontaneously form nanoscale stripes, and then pass through the imaging lens, enter the laser reflector, and project the pattern onto the sample through the imaging objective lens, and ablate the sample surface to form a micro-nano structure.

10. The printing method according to claim 9, characterized in that: The selection of the liquid medium should satisfy the following requirements: the liquid medium has a high boiling point, thereby reducing the generation of bubbles during laser ablation, and / or the liquid medium has a low surface tension, so that small bubbles collide and are not easily aggregated to form large bubbles during laser ablation.

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