Method for improving perpendicularity of microgroove machined by femtosecond laser and machining system

Abstract

The invention belongs to the field of laser processing, and particularly relates to a method for improving the perpendicularity of a microgroove processed by femtosecond laser and a processing system. According to the method, the surface of a target to be processed is covered with a cover plate with a specific material and thickness and a buffer layer material, and then femtosecond laser processing is carried out, so that a microgroove array with higher processing quality, narrower microgroove width and higher perpendicularity is processed on the surfaces of a semiconductor material and a glass material. According to the scheme, a process database is constructed in combination with a large amount of real experimental data, then cutting or surface treatment is carried out on a machining target of any material, the optimal machining parameters can be rapidly determined in combination with working condition requirements, and then synchronous improvement of the machining efficiency and the machining quality is achieved. According to the scheme, the problems that a traditional femtosecond laser processing technology is insufficient in resolution and low in processing quality in some scenes can be effectively solved.

Description

Technical Field

[0001] The present invention belongs to the field of laser processing, and in particular relates to a method for improving the verticality of micro-grooves processed by femtosecond laser, a laser cutting method and a corresponding femtosecond laser processing system. Background Art

[0002] Femtosecond laser direct writing processing technology is an extremely high-precision micro-processing method that focuses light energy into a tiny area through optical path design and processes the material surface with a femtosecond pulse width. This technology has shown broad application prospects in the field of micro-processing with its advantages such as high precision and low heat-affected zone, and is widely used in the fields of microelectronic device manufacturing, biomedical device processing, and optical component manufacturing. In addition, femtosecond laser processing technology has been widely verified and is suitable for micro-nano processing of various materials, such as polymer animal vascular stents, metal micropore arrays, glass high aspect ratio micropores, and ceramic microstructures.

[0003] Patterned materials and molded structures have shown important value in many industrial applications at the micro-nano scale, making micro-nano processing technology a key research field. In particular, advanced technologies that can manufacture structures with resolutions beyond the optical diffraction limit not only reflect the potential for precision design and technological innovation, but also highlight their important role in promoting cutting-edge applications. With the rapid development of industries such as consumer electronics, integrated electronics, and photovoltaics, transparent, hard and brittle materials such as glass have been widely used in the manufacture of mobile phones, laptops, and other electronic devices. In the production process of these products, it is usually necessary to cut the glass substrate with high precision according to specific needs. Therefore, it is of great practical significance to study the high-quality and efficient cutting process of quartz glass.

[0004] Traditional cutting methods mainly rely on diamond cutting wheels, but their cutting quality is poor. Non-traditional cutting technologies include water jet and laser processing, among which crack control method is widely used in glass laser cutting. This method uses a laser beam to form scratches on the glass surface, and then guides the glass to break along a preset cutting path through subsequent mechanical stress or thermal stress. The crack control method has strict requirements on the process parameters of the scratch depth and the cracking process, the processing technology is complex, the yield is low, and additional processing is required after cutting.

[0005] Since the ablation threshold of quartz glass is high, when using picosecond laser cutting, its peak power is relatively low and the material removal rate of a single scan is small, so multiple repeated scans are required to complete the cutting. This significantly reduces the processing efficiency. In contrast, femtosecond lasers have received increasing attention due to their high precision, high efficiency and ease of implementation. Therefore, developing a low-cost and easy-to-operate method for cutting quartz glass will become an important breakthrough in this field. Summary of the invention

[0006] In order to solve the problem that it is difficult to process a groove structure meeting the verticality requirements on the surface of materials such as glass and semiconductors in the prior art, the present invention provides a method for improving the verticality of micro-grooves processed by femtosecond laser and a corresponding femtosecond laser processing system.

[0007] The technical solution provided by the present invention is:

[0008] A method for improving the verticality of microgrooves processed by femtosecond laser, comprising:

[0009] The material and target depth of the target to be processed are taken as the working condition requirements, and a process database is queried according to the working condition requirements to obtain several candidate process combinations that meet the processing requirements. Each process combination consists of a set of values ​​of cover material, cover thickness, laser power and number of scans.

[0010] The buffer layer material is coated on the processing area of ​​the cleaned target surface, and then a cover plate of corresponding specifications is covered on the buffer layer according to the selected process combination. Finally, the combination of the cover plate and the target to be processed is fixed, and a femtosecond laser is incident from one side of the cover plate according to the preset processing parameters to realize the processing of micro grooves of the specified structure on the target surface.

[0011] Among them, the process database is established in combination with real experimental data, which is used to characterize the maximum depth of micro-grooves that meet the verticality requirements when the femtosecond laser processing system uses any specified laser power and number of scans to process the target surface to be processed with a specified material covered with a cover plate of any material and thickness.

[0012] As a further improvement of the present invention, the buffer layer material is a substance whose heat resistance temperature, thermal expansion coefficient and light absorption performance meet preset thresholds and can be specifically removed by any chemical or physical means.

[0013] As a further improvement of the present invention, the buffer layer material adopts organic adhesive or polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyimide (PI), polyamide imide (PAI), polytetrafluoroethylene (PTEE) film coated with glue on the surface.

[0014] As a further improvement of the present invention, after the femtosecond laser processing is completed, the buffer layer material between the cover plate and the target to be processed is removed by a specified chemical or physical means, and the target to be processed is cleaned and dried to obtain a product with specified microgrooves.

[0015] The method for improving the verticality of microgrooves processed by femtosecond laser of the present invention is applicable to the materials of the target to be processed including glass, single crystal silicon, polycrystalline silicon or other semiconductor materials.

[0016] As a further improvement of the present invention, the material of the cover plate includes quartz glass, high-aluminum glass, high-borosilicate glass, sapphire glass, etc.

[0017] As a further improvement of the present invention, for any specified working condition requirement, all process combinations contained in the process database that are consistent with the target material to be processed and can produce a micro-groove with a maximum depth greater than the target depth can be used as candidate process parameters for the current working condition requirement.

[0018] As a further improvement of the present invention, the method for constructing a process database comprises the following steps:

[0019] S1: Preset several candidate values ​​of the material of the target to be processed and the cover plate, the thickness of the cover plate, the laser power and the number of scans as feasible domains of each parameter.

[0020] S2: Design an experimental plan that can cover all feasible domains of each parameter according to the orthogonal experimental method.

[0021] S3: Execute each experimental example in the experimental plan, cover the buffer layer and the cover plate on the target to be processed, and process the target to be processed covered with the cover plate through the femtosecond laser processing system according to the preset processing parameters. After the processing is completed, measure and record the maximum depth of the micro-groove formed on the target to be processed that meets the verticality requirement.

[0022] S4: Organize the experimental data, and use the material of the processing target, cover material, cover thickness, laser power, number of scans and micro-groove depth corresponding to each group of experiments as a process data, and then obtain a process database containing multiple process data.

[0023] The present invention also includes a laser cutting method, which includes taking the thickness of the workpiece to be cut as the target depth, and cutting the workpiece to be cut using the aforementioned method of improving the verticality of the micro-grooves processed by the femtosecond laser.

[0024] The present invention also includes a femtosecond laser processing system, which includes a device body and a host computer. The device body is composed of a femtosecond laser, a reflector, an attenuation plate, an optical gate, a scanning galvanometer and a three-dimensional moving stage. The three-dimensional moving stage is used to place the target to be processed; the device body is used to complete the processing task according to the received control instructions.

[0025] The host computer is electrically connected to the device body; the host computer has a built-in process database as in the aforementioned method for improving the verticality of microgrooves processed by femtosecond laser. The host computer is used to obtain the working condition requirements of each processing task, and then query the process database in conjunction with the industrial control computer to obtain candidate process combinations; the host computer automatically selects one of its process combinations through preset rules or selects a user-specified process combination through human-computer interaction, and then issues control instructions for the processing process to the device body according to the parameter values ​​contained in the selected process combination.

[0026] As a further improvement of the present invention, the strategy of the host computer to automatically select the process combination is:

[0027] First, the cover material and cover thickness corresponding to the cover with the largest surplus in the spare parts library are screened out from the candidate process combinations; then, the process combination with the best power consumption among the remaining candidate process combinations is selected based on the laser power and the number of scans.

[0028] The technical solution provided by the present invention has the following beneficial effects:

[0029] The method provided by the present invention of first bonding a glass cover plate and a buffer layer material to the processing target surface and then performing femtosecond laser processing can significantly improve the processing resolution and processing quality of femtosecond laser at a very low cost. This method can not only process a micro-groove structure with a narrower width and higher straightness, but also provides a good foundation for subsequent cutting of high-precision glass devices with neat edges of higher verticality.

[0030] Since glass devices are widely used in the fields of optics, electronics and micromechanics, such as optical lenses, beam splitters and waveguides, this technology has broad application prospects and huge commercial potential. And through further process optimization and expansion, this method is expected to play a greater role in the field of high-precision glass processing and provide a reliable solution for the manufacture of complex structures. For example, it can be used in the preparation of optical components, microfluidic chips, micro-optical structures and complex micromechanical components to improve the functional performance and reliability of the corresponding devices.

[0031] The scheme of the present invention can further effectively improve the processing quality by optimizing the material coverage strategy, laying a technical foundation for the precision manufacturing of complex structures. At the same time, the improved scheme of this process has strong scalability and can be applied to the processing needs of various materials and various structures, expanding the application potential of femtosecond laser in the field of advanced manufacturing.

[0032] In addition, the research results of the present invention also provide a new reference direction for the optimization of femtosecond laser processing parameters. By reasonably adjusting the number of scans, laser power, processing speed, and the thickness and type of the covering material, more efficient and high-quality processing solutions can be further explored. This not only provides the possibility of reducing processing costs and improving processing efficiency, but also opens up new possibilities for achieving precise control of complex morphologies and functionalized structures. Therefore, this result has important scientific value and practical application prospects in the field of micro-nano processing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of a femtosecond laser processing solution for adding a glass cover plate and a buffer layer in Example 1 of the present invention.

[0034] Figure 2 This is a flow chart of the steps of the method for improving the verticality of microgrooves processed by femtosecond laser provided in Example 1 of the present invention.

[0035] Figure 3 This is a flowchart of the steps of the method for constructing a process database in Example 1 of the present invention.

[0036] Figure 4 This is a schematic diagram of the femtosecond laser processing system provided in Example 1 of the present invention.

[0037] Figure 5 To verify the variation curve of micro-groove width with scanning times produced by the two schemes in the experiment.

[0038] Figure 6 To verify the variation curve of micro-groove depth with scanning times produced by the two schemes in the experiment.

[0039] Figure 7 To verify the variation curve of verticality of micro-grooves processed by two schemes in the experiment with the number of scans.

[0040] Figure 8 The schematic diagram shows the principle of optimizing the quality of micro grooves during the processing of the present invention.

[0041] Fig. 9 To verify the microscopic morphology of the glass samples in four different schemes after multiple repeated scanning. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] Example 1

[0044] Femtosecond laser processing is one of the most common processing technologies for surface morphology processing or material cutting of semiconductor and glass materials. However, in some precision processing scenarios, the grooves generated by traditional femtosecond laser processing often have a V-shaped structure that is wide at the top and narrow at the bottom. In addition, the flying slag phenomenon and the influence on the thermal stress distribution of the material during femtosecond laser processing may also form structural defects caused by contamination and cracks on the target surface after cutting or processing. These phenomena will limit the application of femtosecond laser processing technology in related fields.

[0045] In order to solve the problem that the femtosecond laser processing system is difficult to adapt to such processing scenarios, the technicians of this embodiment found in their research that: Figure 1As shown in the figure, when a high melting point glass material is superimposed on the target material to be processed as a cover plate, the femtosecond laser will first melt through the upper cover plate, and then process the target material below. The laser modulation effect generated by the melted cover plate enables the femtosecond laser to form a groove with a higher verticality on the surface of the target material, improve the slope of the cutting mouth, and thus significantly improve the processing effect. Among them, the cover plate material is usually preferably a material with a higher melting point and higher light transmittance, such as quartz glass, high aluminum glass, high borosilicate glass, sapphire glass, etc.

[0046] In addition, the technicians of this embodiment also found during the research process that when a buffer layer composed of organic materials is added between the cover plate and the target material, the buffer layer material can effectively fill the gap between the target material and the cover plate, forming a protective layer covering the upper surface of the target material, thereby preventing the flying slag from the processing process from contaminating the surface of the target material. On the other hand, the buffer layer material can also absorb the mutual stress between the target material and the cover plate caused by thermal expansion during the processing, and improve the cracks on the surface and inside of the target material caused by stress.

[0047] Based on the above success, the technicians of this embodiment further systematically analyzed several factors that affect the verticality and processing depth of the grooves on the target material, and then designed a new processing technology that can be applied to different processing conditions and can process microgroove arrays with higher processing quality, narrower microgroove widths, and higher verticality on the surface of semiconductor materials and glass materials. Specifically, this embodiment first provides a method for improving the verticality of microgrooves processed by femtosecond laser, such as Figure 2 As shown, the method includes:

[0048] 1. Query and determine processing parameters

[0049] The material α and target depth h of the target to be processed are used as working condition requirements, and a process database is queried according to the working condition requirements to obtain several candidate process combinations that meet the processing requirements. Each process combination consists of a set of values ​​of cover material β, cover thickness d, laser power W, and number of scans N.

[0050] In the scheme of this embodiment, the processing target is the material that needs to be grooved, cut or surface morphology processed. The scheme of this embodiment can be applied to improve the femtosecond laser processing effect of processing targets of various different high-melting-point materials, such as glass, single crystal silicon, polycrystalline silicon, gallium nitride and other semiconductor materials, etc. The target depth refers to the depth of the groove that meets the required verticality during the processing. Of course, when used to cut the processing target, the target depth here is actually equal to the thickness of the target material. It should be emphasized that the maximum target depth that can be achieved during the processing of each type of material has an upper limit, and the user should select the process within the range supported by the system processing capabilities.

[0051] This embodiment scheme queries the process database through the information of the working condition requirements, and then obtains the processing parameters that can meet the requirements. Among them, the process database is established in combination with real experimental data, and is used to characterize the maximum depth of the micro-groove that meets the verticality requirements when the femtosecond laser processing system uses any specified laser power and scanning times to process the target surface to be processed with a specified material covered with a cover plate of any material and thickness.

[0052] Specifically, the process database of this embodiment is a data set composed of a large number of six-element arrays as basic elements. The data format of each six-element array is {α, β, d, W, N, h}, which is used to represent: when the user covers a cover plate with a material of β and a thickness of d on a processing target of α material, and sets the laser power to W, after repeatedly scanning the specified area N times, the depth h of the groove that meets the verticality requirement can be obtained on the processing target.

[0053] It should be further explained that for any working condition requirement where the values ​​of α and h are clear, there may be more than one combination of processing parameters of β, d, W, and N that can achieve the corresponding processing effect. Therefore, the query results are usually presented in the form of multiple candidate process combinations, and technicians can select a more appropriate process combination according to the actual situation.

[0054] In addition, in a process database with limited data samples, there may not be a candidate process combination (i.e., a six-tuple) that is exactly the same as the expected target depth h. In this case, for any specified working condition requirement; all process combinations contained in the process database that are consistent with the target material to be processed and can produce microgrooves with a maximum depth greater than the target depth can be used as candidate process parameters for the current working condition requirement. For example, the target depth to be achieved in a certain actual working condition requirement is 0.03mm, and in the process combination with the material matching in the process data set, there is no data of d=0.03mm. At this time, if there is any process combination with a material matching and d>0.03mm, this process combination can be used as a candidate process combination. The inherent mechanism of the process selection strategy adopted in this embodiment is that for each process parameter, it reflects the maximum depth of the microgrooves that can be processed under the current processing conditions to meet the verticality requirements. When the number of repeated scans N in the process parameter is reduced, the depth of the corresponding microgrooves that meet the verticality requirements will also be reduced, so each process parameter can adapt to the working condition requirements with a smaller actual d value.

[0055] 2. Process preparation and implementation

[0056] The buffer layer material is coated on the processing area of ​​the cleaned target surface, and then a cover plate of corresponding specifications is covered on the buffer layer according to the selected process combination. Finally, the combination of the cover plate and the target to be processed is fixed, and a femtosecond laser is incident from one side of the cover plate according to the preset processing parameters to realize the processing of micro grooves of the specified structure on the target surface.

[0057] In the scheme of this embodiment, the buffer layer material mainly plays a role in the femtosecond laser processing process. When the processing is completed, the buffer layer material should be peeled off from the processing target surface. Therefore, based on the above analysis of the role of the buffer material, it can be seen that the buffer layer material is preferably a material whose heat resistance temperature, thermal expansion coefficient and light absorption performance meet the preset threshold and can be specifically removed by any chemical or physical means. Such as organic adhesives or polyphenylene sulfide, polyphenylene ether, polyimide, polyamide, polytetrafluoroethylene film with glue on the surface.

[0058] This embodiment selects a material with certain specificity as the buffer layer, mainly to better select a specified chemical or physical means after the processing is completed to remove the buffer layer material between the cover plate and the target to be processed, and avoid damaging the target to be processed. For example, when both the target to be processed and the cover plate are glass, an organic adhesive can be used as the buffer layer material. At this time, after the femtosecond laser processing is completed, the buffer layer material between the target to be processed and the cover plate can be dissolved by an organic solvent, and finally the target to be processed is cleaned and dried to obtain a product with specified microgrooves.

[0059] In the method for improving the verticality of micro-grooves processed by femtosecond laser provided in this embodiment, the process database is a key tool for realizing accurate process parameter selection, and is also one of the core advantages of the solution of this embodiment. Specifically, Figure 3 As shown, the method for constructing the process database includes the following steps:

[0060] S1: Preset several candidate values ​​of the material of the target to be processed and the cover plate, the thickness of the cover plate, the laser power and the number of scans as feasible domains of each parameter.

[0061] S2: Design an experimental plan that can cover all feasible domains of each parameter according to the orthogonal experimental method.

[0062] S3: Execute each experimental example in the experimental plan, cover the buffer layer and the cover plate on the target to be processed, and process the target to be processed covered with the cover plate through the femtosecond laser processing system according to the preset processing parameters. After the processing is completed, measure and record the maximum depth of the micro-groove formed on the target to be processed that meets the verticality requirement.

[0063] S4: Organize the experimental data, and use the material of the processing target, cover material, cover thickness, laser power, number of scans and micro-groove depth corresponding to each group of experiments as a process data, and then obtain a process database containing multiple process data.

[0064] Finally, in combination with the method for improving the verticality of microgrooves processed by femtosecond laser provided above, this embodiment further provides a laser cutting method, which includes taking the thickness of the workpiece to be cut as the target depth, and using the method for improving the verticality of microgrooves processed by femtosecond laser as mentioned above to cut the workpiece to be cut.

[0065] In summary, the technology provided in this embodiment provides a good foundation for the cutting and fine processing of micro devices. After preliminary processing, the edges of the quartz glass are smoother and the surface is smoother, which greatly optimizes the overall quality of the micro devices. This innovative processing method not only reduces the processing difficulty, but also improves production efficiency and product consistency, providing important technical support for further applications in the fields of high-precision optical devices, microfluidic chips, etc.

[0066] Example 2

[0067] Based on the solution of Example 1, this embodiment further provides a femtosecond laser processing system, which includes a device body and a host computer. Figure 4As shown, the device body is composed of a femtosecond laser, a reflector, an attenuation plate, an optical gate, a scanning galvanometer and a three-dimensional moving stage. Among them, the pulsed laser is emitted from the amplifier stage outlet of the femtosecond laser and decomposed into several laser beams with uniform energy by a laser beam splitter. The split laser is reflected to the attenuation plate by a reflector, and the attenuation plate is used to adjust the energy of the incident light beam. The adjusted laser beam enters the reflector through the optical gate and is finally focused on the surface of the sample to be processed through the scanning galvanometer. The on and off of the entire optical path is controlled by the optical gate, and the user can manually operate the controller to realize the switch adjustment of the optical path. The three-dimensional moving stage is used to place the target to be processed; in the system of this embodiment, the focusing operation can be realized through manual and program control, and the processing target can be moved in three dimensions. In actual work, the device body of this embodiment is used to complete the processing task according to the received control instructions.

[0068] The host computer is electrically connected to the device body; the host computer has a built-in process database as described in the aforementioned method for improving the verticality of microgrooves processed by femtosecond laser. The host computer is used to obtain the working condition requirements of each processing task, and then query the process database in conjunction with the industrial control computer to obtain candidate process combinations; the host computer automatically selects one of its process combinations through preset rules or selects a user-specified process combination through human-computer interaction, and then issues control instructions for the processing process to the device body based on the parameter values ​​contained in the selected process combination. Specifically, the strategy for the host computer to automatically select the process combination is:

[0069] First, the cover material and cover thickness corresponding to the cover with the largest surplus in the spare parts library are screened out from the candidate process combinations; then, the process combination with the best power consumption among the remaining candidate process combinations is selected based on the laser power and the number of scans.

[0070] Verification experiment

[0071] In order to further verify the feasibility of the technical solutions provided in the above embodiments and test the processing effect of the femtosecond laser processing system improved by the above solutions, the technicians carried out the following test experiments.

[0072] 1. The influence of cover plate on the structural characteristics of machined micro-grooves

[0073] This experiment first compares the parameters of the microgrooves processed by the improved scheme of pasting the cover plate provided by the present invention and the two conventional schemes of directly processing without pasting the cover plate, in order to verify the influence of the two schemes on the morphology of the microgrooves finally processed by the femtosecond laser processing system.

[0074] The experimental process specifically includes: First, the quartz glass is thoroughly cleaned with alcohol to remove contaminants on its surface. Then, the cleaned quartz glass is placed in a vacuum drying oven for drying to ensure that there is no moisture residue on the glass surface. After drying, a 60μm thick transparent tape is pasted on the surface of the quartz glass, and then a 160μm thick thin glass is pasted on the transparent tape. This stacked structure provides a stable substrate support for femtosecond laser microgroove processing.

[0075] At the same time, the CSmark processing software on the femtosecond laser control computer was opened to draw a straight line segment with a length of 5 mm, and the scanning interval was set to 0.1 mm. This graph provides a reference for the processing path for subsequent microgroove processing. Then the laser scanning speed of the femtosecond laser processing system was set to 5 mm / s, and the scanning power was set to 200 mW. In order to study the effect of the number of scans on the depth and width of the microgroove, four sets of scanning number parameters were designed in this experiment: 150 times, 200 times, 250 times, and 300 times.

[0076] After completing the parameter setting, click the preview button in the software. The drawn preview straight line segment appears on the glass surface. By adjusting the three-dimensional mobile platform, the laser focus is accurately located on the glass surface. After the focus is aligned, click the "marking" button to start automatic micro-groove processing on the glass. After the processing is completed, use a microscope to measure the depth and width of the micro-groove, and record the measurement data under each set of parameter conditions. And draw the following according to the measurement results. Figure 5 The curves showing the variation of micro-groove width with the number of scans produced by the two schemes are shown in FIG. Figure 6 The curves showing the change of micro-groove depth with the number of scans produced by the two schemes are shown in FIG. Figure 7 The curves shown are those that characterize the change in the verticality of the microgrooves processed by the two schemes with the number of scans.

[0077] First, combine Figure 5 and Figure 6 The data in Figure 2 show that as the number of femtosecond laser scans increases, the width and depth of the microgrooves on the quartz glass surface increase. This phenomenon can be attributed to the cumulative removal effect of the laser after repeated action on the material. However, when a thin layer of glass is attached to the surface of the quartz glass, the rate and amount of change of the depth and width of the microgrooves processed at different scan times are significantly reduced; theoretically, this should significantly improve the verticality of the processed microgrooves.

[0078] Further observation Figure 7The data in the figure can verify that when thin glass is attached, the verticality of the micro grooves is indeed significantly improved. This shows that the method provided by the present invention can significantly improve the slope, offset, jitter or irregularity that may occur during the processing, thereby obtaining a higher quality processing effect. This improvement is of great significance, especially for optical components with extremely high edge accuracy requirements.

[0079] Based on the above results, we can combine Figure 8 Analyze the internal principle of the present invention to achieve the above technical effects:

[0080] After the thin glass is pasted as the cover plate in this embodiment, the action range of the laser is more concentrated, thereby improving the processing resolution. And under the influence of this concentration effect, under the same scanning conditions of the femtosecond laser processing system, the system can process a narrower microgroove structure. In addition, the introduction of the cover plate and buffer layer materials in the scheme of the present invention optimizes the transmission and action mode of the laser energy. The thin glass may play a role in stabilizing the laser optical path, reducing scattering and improving the heat-affected zone, thereby making the edges of the microgroove more neat and smooth.

[0081] 2. The influence of buffer layer on the structural characteristics of machined microgrooves

[0082] This experiment further studies the effect of the use of a buffer layer on the morphology of the microgrooves ultimately processed by the femtosecond laser processing system. Four control groups were set up in this experiment, in which control group 1 did not adhere any material to the surface of the glass to be processed, control group 2 coated a layer of 40μm thick organic adhesive on the surface of the glass to be processed; control group 3 adhered a 160μm thick glass cover plate on the surface of the glass to be processed; control group 4 first coated the surface of the glass to be processed with an organic adhesive, and then covered it with a glass cover plate, with an overall thickness of 160μm; finally, the samples of the four control groups were scanned repeatedly 200, 300, and 400 times at a power of 300mW and a speed of 10mm / s. The final processing effect is as follows: Fig. 9 shown. Fig. 9 The four horizontal columns in the figure reflect the processing effects of samples in different control groups, and the three vertical rows in each column reflect the processing effects of the same sample under different scanning times.

[0083] analyze Fig. 9From the data in, it can be found that: under the condition of the same number of scans, the microgroove structure morphology formed by femtosecond laser processing can be different by covering different materials on the surface of quartz glass; and the selection of different covering materials has a significant effect on the thermal impact and surface quality of the processing area. Among them, compared with the other three samples, under the combined condition of setting a glass cover plate and a buffer layer on the surface of the quartz glass at the same time, the surface morphology processed shows significant advantages, the thermal damage and processing residues in the microgroove area are significantly reduced, the edges are clearer and the surface quality is higher. Analysis of the reasons for its ability to produce such technical effects may be: on the one hand, the joint covering strategy of thin glass and buffer layer significantly improves the quality of the processed surface by reducing the thermal effect of the direct interaction between the laser and the material, on the other hand, compared with the directly exposed quartz glass surface or the treatment method of a single covering material, the joint covering of the glass cover plate and the buffer layer material can provide a more stable processing environment, reduce the spatter, heat accumulation and possible micro cracks or debris generated during the laser action. Therefore, the improvement proposed in the present invention not only significantly improves the quality of the processed surface, but also provides a new path for high-precision and low-pollution microstructure processing.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the verticality of microgrooves processed by femtosecond laser, characterized in that: It includes: The material and target depth of the target to be processed are taken as working condition requirements, and a process database is queried according to the working condition requirements to obtain several candidate process combinations that meet the processing requirements; each process combination is composed of a set of values ​​of cover material, cover thickness, laser power and number of scans; A buffer layer material is coated on the processing area of ​​the cleaned target surface, and then a cover plate of corresponding specifications is covered on the buffer layer according to the selected process combination; finally, the combination of the cover plate and the target to be processed is fixed, and a femtosecond laser is irradiated from one side of the cover plate according to the preset processing parameters to realize the processing of micro grooves of a specified structure on the target surface; The process database is established in combination with real experimental data, and is used to characterize the maximum depth of microgrooves that meet the verticality requirements when a femtosecond laser processing system uses any specified laser power and scanning times to process a target surface to be processed of a specified material covered with a cover plate of any material and thickness.

2. The method for improving the verticality of microgrooves processed by femtosecond laser according to claim 1, characterized in that: The buffer layer material is a substance whose heat resistance temperature, thermal expansion coefficient and light absorption performance meet preset thresholds and can be specifically removed by any chemical or physical means.

3. The method for improving the verticality of microgrooves processed by femtosecond laser according to claim 2, characterized in that: The buffer layer material is made of organic adhesive or polyphenylene sulfide, polyphenylene ether, polyimide, polyamide-imide, or polytetrafluoroethylene film with glue coated on the surface.

4. The method for improving the verticality of microgrooves processed by femtosecond laser according to claim 2, characterized in that: After the femtosecond laser processing is completed, the buffer layer material between the cover plate and the target to be processed is removed by specified chemical or physical means, and the target to be processed is cleaned and dried to obtain a product with specified microgrooves.

5. The method for improving the verticality of microgrooves processed by femtosecond laser according to claim 1, characterized in that: The applicable materials of the target to be processed include glass, single crystal silicon, polycrystalline silicon or other semiconductor materials; and / or The material of the cover plate includes quartz glass, high aluminum glass, high borosilicate glass, and sapphire glass.

6. The method for improving the verticality of microgrooves processed by femtosecond laser according to claim 1, characterized in that: For any specified working condition requirement, all process combinations contained in the process database that are consistent with the target material to be processed and can produce a micro-groove with a maximum depth greater than the target depth can be used as candidate process parameters for the current working condition requirement.

7. The method for improving the verticality of microgrooves processed by femtosecond laser according to claim 1, characterized in that: The method for constructing the process database comprises the following steps: S1: Preset several candidate values ​​of the material of the target to be processed and the cover plate, the thickness of the cover plate, the laser power and the number of scans as the feasible domain of each parameter; S2: Design an experimental plan that can cover all feasible regions of each parameter according to the orthogonal experimental method; S3: Execute each experimental example in the experimental plan, cover the buffer layer and the cover plate on the target to be processed, and process the target to be processed covered with the cover plate by the femtosecond laser processing system according to the preset processing parameters, and measure and record the maximum depth of the micro-groove formed on the target to be processed that meets the verticality requirement after the processing is completed; S4: Organize the experimental data, and use the material of the processing target, cover material, cover thickness, laser power, number of scans and micro-groove depth corresponding to each group of experiments as a process data, and then obtain a process database containing multiple process data.

8. A laser cutting method, characterized in that: It includes: The thickness of the workpiece to be cut is taken as the target depth, and the workpiece to be cut is cut using the method for improving the verticality of micro-grooves processed by femtosecond laser as described in any one of claims 1 to 7.

9. A femtosecond laser processing system, characterized in that: It includes: The device body is composed of a femtosecond laser, a reflector, an attenuation plate, an optical shutter, a scanning galvanometer and a three-dimensional moving stage; the three-dimensional moving stage is used to place the target to be processed; the device body is used to complete the processing task according to the received control instructions; A host computer is electrically connected to the device body; the host computer has a built-in process database for the method for improving the verticality of microgrooves processed by femtosecond laser as described in any one of claims 1 to 7; the host computer is used to obtain the working condition requirements of each processing task, and then query the process database in conjunction with the industrial computer to obtain candidate process combinations; the host computer automatically selects one of its process combinations through preset rules or selects a user-specified process combination through human-computer interaction, and then the device body issues control instructions for the processing process based on the parameter values ​​contained in the selected process combination.

10. The femtosecond laser processing system according to claim 9, characterized in that: The strategy of the host computer to automatically select the process combination is: First, the cover material and cover thickness corresponding to the cover with the largest surplus in the spare parts library are screened out from the candidate process combinations; then, the process combination with the best power consumption among the remaining candidate process combinations is selected based on the laser power and the number of scans.

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