Light trapping structure laser processing method with high energy utilization rate and capable of reducing heat influence

Abstract

The invention discloses a light trapping structure laser processing method with high energy utilization rate and capable of reducing heat influence, and relates to the technical field of laser processing. The method comprises the following steps of: starting from analysis of an etching threshold value F of a processed material, firstly, setting the number of processing rows as N and the number of projection light spots processed in each row as M, and dividing a laser beam into M * N small light beams and the etching area as M * N by adopting a light splitting device; or an acousto-optic deflector is adopted to enable the light beam to deflect at a high speed, two processing points adjacent in position are staggered in time, and two pulses adjacent in time are separated in space. According to the invention, the energy utilization rate of the laser transmitter is maximized through the light splitting device and high-speed deflection of light instead of a pure mode of reducing the energy density or the pulse repetition rate, the heat affected zone is reduced, the processing efficiency and the light absorptivity are improved, and the processing and the manufacturing of the high-quality light trapping structure are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing, and particularly relates to a laser processing method for a light trapping structure with high energy utilization rate and reduced thermal influence. Background Art

[0002] A light trapping structure is a functional structure that significantly improves the light absorption rate. This structure can use surface roughening, porous or layered structures to force light to undergo multiple reflections or scattering inside, increasing the interaction time between light and matter, thereby greatly improving the light absorption rate.

[0003] In recent years, light trapping structures can be etched by ultra-short pulse (femtosecond or picosecond) laser processing, which can generate a very high energy density on the material surface and instantaneously vaporize the processed material when it exceeds the energy density threshold (etching threshold) required for processing the material.

[0004] Generally, the etching threshold of a material is determined by the material itself, laser wavelength, focal projection spot energy density, number of pulse trains, pulse frequency, and focal spot size. When the processed material, laser wavelength, focal spot size, etc. are determined, the etching threshold is mainly affected by the focal projection spot energy density and pulse frequency. Increasing the focal projection spot energy density or increasing the pulse repetition rate (PRR) will cause heat accumulation, resulting in an increase in the heat affected zone (HAZ), more sputtering, poor aesthetics and low light absorption rate of the processed product. Simply reducing the energy density or PRR to reduce heat accumulation can reduce the heat affected zone, but this also leads to insufficient energy utilization of the laser and slows down the processing efficiency. In addition, the GHz pulse train mode can effectively improve the energy utilization rate by dispersing the single pulse energy into high-frequency pulse packets. However, since the nanosecond-level pulse-to-pulse time interval is close to the thermal diffusion time after the material is excited by the pulse, heat accumulation continues. Therefore, a laser processing method for a light trapping structure with high energy utilization rate and reduced thermal influence is proposed to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems that when a light trapping structure is processed by ultra-short pulse laser, increasing the focal projection spot energy density or increasing the pulse repetition rate will cause heat accumulation, resulting in an increase in the heat affected zone, more sputtering, poor aesthetics and low light absorption rate of the processed product. Simply reducing the energy density or pulse repetition rate will also lead to insufficient energy utilization of the laser and slow down the processing efficiency. In addition, the GHz pulse train mode has continuous heat accumulation and affects the output quality due to the nanosecond-level pulse-to-pulse time interval being close to the thermal diffusion time after the material is excited by the pulse. The present invention provides a laser processing method for a light trapping structure with high energy utilization rate and reduced thermal influence.

[0006] The present invention specifically adopts the following technical solutions to achieve the above purpose:

[0007] A method for laser processing of a light trapping structure with high energy utilization rate and reduced thermal influence, comprising the following steps: 1) Analyze the etching threshold F of the material to be processed; 2) Start the laser emitter and set the repetition rate of the laser emitted by the laser emitter to PRR, 20 kHz ≤ PRR ≤ 400 kHz or PRR ≤ 1.5 MHz; 3) Use a beam splitting device to split a beam of laser into M*N small beams, the number of processing rows is N, the number of projected light spots processed in each row is M, the etching area is M*N, or use an acousto-optic deflector AOD to deflect the beam at high speed, and the jumping coordinates after deflection are as follows:

[0008] 11, 13, 15, 12, 14

[0009] 21, 23, 25, 22, 24

[0010] 31, 33, 35, 32, 34

[0011] 41, 43, 45, 42, 44

[0012] 51, 53, 55, 52, 54; 4) Among them, the distance between adjacent projected light spots in M is dm, the moving speed of the projected light spot is Vs, the time interval is ΔT, ΔT = dm / Vs, 30 um ≤ dm ≤ 50 um, 50 mm / s ≤ Vs ≤ 2000 mm / s, the number of processing times for each processing point on the material is S times, 2 ≤ S ≤ 50; Among them, in the high-speed deflection of AOD, the processing time interval Δt between two adjacent processing points in position ≥ the thermal diffusion time τ, and the processing distance interval Δd between two adjacent pulses in time ≥ the thermal diffusion length L; 5) Perform laser processing with the energy density of the focused projected light spot being to cause the material to undergo a phase change and obtain the hole structure of the processed light trapping structure. The hole structure includes V-shaped, trapezoidal, and rectangular shapes.

[0013] Furthermore, F < the energy density of the focused projected light spot

[0014] Furthermore, N ≥ 1, 2 ≤ M = S ≤ 50.

[0015] Furthermore, Wz*N ≤ the total power W of the laser.

[0016] Furthermore, the beam splitting device includes a diffractive optical element DOE and a spatial light modulator SLM.

[0017] Furthermore, the scanning angle range Δθ of the AOD = (λ / Vs)*Δfs, where λ is the laser wavelength, Vs is the speed of sound, and Δfs is the scanning frequency bandwidth.

[0018] Furthermore, the thermal diffusion time τ = Lc2 / α, where α = k / (p*Cp), Lc is the characteristic length scale, α is the thermal diffusivity of the material, and the thermal diffusion length L is the characteristic distance for heat to diffuse in the material Tpulse is the width of the laser pulse.

[0019] Further, the main beam emitted by the laser emitter passes through the acousto-optic deflector AOD and reaches the galvanometer mirror, which is installed on an axial displacement device or a CNC machining platform.

[0020] Further, the material to be processed includes silicon, copper, aluminum, iron, and zinc.

[0021] Further, the etching threshold range is 0.01 J / cm 2 -10 J / cm 2 .

[0022] The beneficial effects of the present invention are as follows: By optimizing two methods in the laser processing light-trapping structure, instead of simply reducing the energy density or pulse repetition rate, through the form of DOE / SLM beam splitting and AOD high-speed deflection, the energy utilization rate of the laser emitter is maximized, and the thermal affected zone is reduced to a reasonable range, preventing sputtering and the generation of molten substances during the processing, improving the processing efficiency and the light absorption rate of the product, thereby realizing the processing and manufacturing of a high-quality light-trapping structure. Description of the Drawings

[0023] Figure 1 is a schematic diagram of laser processing using DOE / SLM in the present invention;

[0024] Figure 2 is a two-dimensional surface morphology diagram of the light-trapping structure after processing in the present invention;

[0025] Figure 3 is a three-dimensional morphology diagram of the light-trapping structure after processing in the present invention;

[0026] Figure 4 is a cross-sectional contour diagram of the light-trapping structure after processing in the present invention;

[0027] Figure 5 is a comparison diagram of the effects between the present invention and other processing methods;

[0028] Figure 6 is a schematic diagram of laser processing using AOD in the present invention;

[0029] Figure 7 is a schematic diagram of AOD jump processing in the present invention;

[0030] Figure 8 is a schematic diagram of the AOD laser pulse trigger direction distribution in the present invention;

[0031] Figure 9 It is a schematic diagram of the AOD hierarchical scanning strategy in the present invention;

[0032] Figure 10 It is a schematic diagram of the AOD thermal accumulation suppression effect in the present invention;

[0033] Figure 11 It is a schematic diagram of the etching threshold changes of copper, silicon, and colloid under different conditions in the present invention. Detailed implementation manners

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0036] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, the terms "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0037] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "inner", "outer", "upper", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0038] A laser processing method for a light trapping structure with high energy utilization rate and reduced thermal influence, comprising the following steps: 1) Analyze the etching threshold F of the material to be processed; 2) Start the laser emitter and set the repetition rate of the laser emitted by the laser emitter to PRR, 20 kHz ≤ PRR ≤ 400 kHz or PRR ≤ 1.5 MHz; 3) Use a beam splitting device to split a beam of laser into M * N small beams, the number of processing rows is N, the number of projected spots processed in each row is M, and the etching area is M * N, or use an acousto-optic deflector AOD to deflect the beam at high speed. The jumping coordinates after deflection are as follows:

[0039] 11, 13, 15, 12, 14

[0040] 21, 23, 25, 22, 24

[0041] 31, 33, 35, 32, 34

[0042] 41, 43, 45, 42, 44

[0043] 51, 53, 55, 52, 54; 4) Among them, the distance between adjacent projected spots in M is dm, the moving speed of the projected spot is Vs, and the time interval is ΔT, ΔT = dm / Vs, 30 μm ≤ dm ≤ 50 μm, 50 mm / s ≤ Vs ≤ 2000 mm / s, and the number of processing times for each processing point on the material is S times, 2 ≤ S ≤ 50; Among them, in the high-speed deflection of AOD, the processing time interval Δt between two adjacent processing points in position ≥ the thermal diffusion time τ, and the processing distance interval Δd between two adjacent pulses in time ≥ the thermal diffusion length L; 5) Perform laser processing with the energy density of the focused projected spot as to cause the material to undergo a phase change, and obtain the hole structure of the processed light trapping structure. The hole structure includes V-shaped, trapezoidal, and rectangular shapes.

[0044] As Figure 1 shown, DOE or SLM is used to split a beam of laser into multiple small beams M * N, and these small beams are arranged in a linear array along the processing direction; the distance between small beams is dm, and the range of dm is 30 μm - 1000 μm. Use a scanning galvanometer to scan the small beams along the arrangement direction, and the scanning speed Vs is (50 mm / s - 10000 mm / s);

[0045] This configuration simulates a process of performing M*N repeated scribing operations with low pulse energy and a time interval ΔT, where the time interval ΔT = dm / Vs. Taking dm = 50um and Vs = 2000mm / s as an example, the time interval is 25us, which is equivalent to processing a single machining point S times at intervals of 25us, with S = M = 50 times. Compared with the GHz pulse train mode where the landing point time interval is only 1ns, the time interval between pulse landings is greatly increased, enabling more effective control of the heat generated during processing.

[0046] At the same time, the laser beam of the laser emitter is split into small beams through DOE / SLM, improving the utilization rate of the laser energy of the laser. Assuming that the laser energy required for high-quality processing of the material is Q% (1% - 50%), and it takes M (2 - 100 times) times of processing to form the final processing morphology, then the utilization rate of the laser energy of the laser increases from Q% to M*N*Q% (M*Q% <= 100%, and at this time N = 1). In this way, the power energy of the laser emitter can be utilized at 80% - 90% and above.

[0047] If the laser energy M*Q% <= 50% used when scribing a single line, then it can be further considered to replicate and expand the linearly arranged small beams longitudinally to form a beam matrix array with N > 1, further improving the utilization rate of the laser energy of the laser. In this way, parallel processing of N > 1 lines can be achieved. At this time, the utilization rate of the laser energy of the laser increases from M*N*Q% (N = 1) to N*M*Q% (N*M*Q% <= 100%, N > 1). In this way, the power energy of the laser emitter can be utilized close to 100%.

[0048] In the actual processing process, examples of using a beam splitting device to split a laser beam into M*N small beams include: when processing silicon materials, the total power of the laser emitter used is W = 100W, and the repetition rate PRR is 400kHz, then the maximum pulse energy Ep_max = W / PRR = 250uJ. The projected spot diameter D of the laser beam after being focused by a galvanometer is 20um, and the etching threshold F for processing silicon with a single pulse is approximately 0.5J / cm 2 We choose an energy density of 1.2F to process silicon. The etching threshold F refers to the minimum energy density (unit: J / cm2) required for the material to be removed (ablated) by a laser pulse. When the energy density of the focal projected spot is greater than F, the material undergoes a phase change (melting / vaporization), thereby achieving the effect of removing the material. Then the energy density of the pulse is The corresponding laser power

[0049] Taking When performing path processing on silicon materials with an energy density, it is necessary to process 20 times to reach the required geometric depth. Correspondingly, we set the number of sub-focus spots M in the processing direction to 20, S = M. The size of each sub-focus spot is 20um, and the energy density formed by each sub-focus is 0.6J / cm 2 . Then correspondingly, the laser power Wz corresponding to these sub-foci is Wz = 20 * 0.75W(S * Wx) = 15W.

[0050] The spacing dm of the sub-foci in the M direction needs to be selected according to the process test results. Let the laser perform multi-pulse punching on the same position with different repetition rates PRR. Different repetition rates mean different time intervals for multi-pulse punching. Gradually reducing the PRR can improve the heat-affected zone at the punching edge. When the appropriate PRR = 20kHz is found, the corresponding time interval is 50us. If the desired galvanometer scanning speed is 1m / s, then the spacing dm between the sub-foci is dm = 1m / s * 50us = 50um. Since the total power of the laser is 100W, that is, the laser power corresponding to a row of sub-focus spots in the M direction is 15W. Therefore, the sub-focus spots in the M direction can be replicated in the N direction to form a 20 * 6 sub-focus spot matrix. In this way, the energy utilization rate of the laser is increased from 15W to 90W. At the same time, due to the expansion of the sub-focus spots in the N direction, 6 paths can be processed simultaneously, improving the processing efficiency.

[0051] As Figure 2 , 3 and shown in Figure 4, the actual microscopic processing effect of the prepared micro-light-trapping structure. Among them, the upper left picture presents the surface morphology of the light-trapping structure after processing; the upper right picture shows the three-dimensional morphology of the light-trapping structure; the bottom picture gives the cross-sectional contour diagram of the structure. It can be clearly seen from these pictures that the light-trapping structure processed based on this scheme has uniform and complete periodic characteristics. The spacing and depth of the microstructures are precisely controlled and remain within a consistent range. The depth and width are both about 28um. From the processed microstructures, the morphology of the microstructures is uniform and clear, the cross-sectional morphology of the microstructures is flat and smooth, and there are no abnormal phenomena such as local protrusions or depressions at the edges and bottoms. This reflects that during the entire processing process, heat transfer and material reactions are precisely controlled within a reasonable range, thus ensuring the consistency of the processing effect.

[0052] As Figure 5As shown, the effects of ordinary infrared femtosecond processing, infrared picosecond GHz pulse train processing, and infrared picosecond DOE beam splitting processing involved in this patent are respectively shown from left to right. The first row in the picture shows the surface effect of the material under an optical microscope after micro-nano scribing processing. The second row shows the 3D surface profile roughness effect. The third row shows the contour map of the scribing cross-section. The required contour cross-section should be V-shaped. By comparing the processing effects and processing parameters, it can be seen that although conventional femtosecond processing can achieve the processing effect to a certain extent, the energy utilization rate and processing efficiency are very low, and the appearance effects of the surface microscope view and the surface contour map are not as good as those after infrared picosecond DOE beam splitting processing. Although infrared GHz picosecond processing can improve the energy utilization rate, due to the too-close pulse time intervals, a large amount of heat is generated during processing, even resulting in the generation of molten matter, making the processed shape uncontrollable. It can be seen from the figure that sputtering is relatively serious, which greatly affects the appearance and quality. Finally, using a similar sub-pulse energy for DOE beam splitting processing, the processed shape is clean, the surface heat-affected zone HAZ is controlled within a very small area, and both the laser energy utilization rate and the processing efficiency can be maintained at a relatively high level.

[0053] As Figure 6 shown, using an acousto-optic deflector AOD to deflect the beam at high speed is to perform processing with only one beam. After the processing beam passes through the AOD, its emission direction will be controlled by the AOD to perform high-speed deflection. Therefore, the processing position and processing timing of the focal projection spot corresponding to this beam within a local area (within the AOD scanning range) can be defined independently without being affected by the galvanometer processing direction. However, since the AOD scanning range is generally small, it is necessary to cooperate with a scanning galvanometer for large-area processing. The main function of this scheme is that after the beam is deflected at high frequency through the AOD, two pulses adjacent in time can be separated in terms of spatial distance (distance interval Δd ≥ thermal diffusion length L) within a local area (within the AOD scanning range), and two processing points adjacent in position can also be staggered in terms of processing time (time interval Δt ≥ thermal diffusion time τ). In this way, more effective thermal management can be carried out during the processing.

[0054] It should be noted that after the laser beam emitted by the laser emitter passes through the AOD, according to the different acoustic wave frequencies applied to the AOD, its outgoing direction will be quickly deflected. This deflection will ultimately cause the rapid movement of the position of the projected light spot on the processing plane. This movement range is within the scanning range of the AOD. The scanning angle range Δθ of the AOD = (λ / Vs) * Δfs, where λ is the laser wavelength, Vs is the speed of the acoustic wave, and Δfs is the scanning frequency bandwidth. Since the scanning range of the AOD is usually small, the laser beam deflected by the AOD will ultimately enter the galvanometer. Relying on the mirror driven by the motor in the galvanometer, a larger area processing can be achieved. Simply put, it is to perform processing along the processing path in the macro direction through the galvanometer, and during processing, the high-speed jump of the position of the laser pulse light spot is locally achieved through the AOD.

[0055] The acousto-optic deflector AOD is used to deflect the light beam at high speed. During the actual processing process, there are processing examples as follows: When processing silicon materials, after absorbing the laser pulse, L = 40um, τ = 2us, the repetition rate PRR of the laser is 1MHz, the pulse time interval, T_pulse = 1 / PRR = 1us, the scanning speed Vs of the galvanometer is 1m / s, the deflection rate V_AOD of the AOD is 200ns / mm, the scanning range of the AOD can cover 5x5 processing points within 100um * 100um, the spacing between processing points is 20um, and the deflection time is 20ns. This means that within the 1us pulse time interval, the AOD can perform high-speed local adjustment on the processing position of the next pulse in 20ns. And because the spacing of 20um between adjacent processing points is less than L = 40um, the AOD can control the pulse to perform jump processing at an interval of one processing point, as Figure 7 shown, and the jump coordinates are as follows:

[0056] 11, 13, 15, 12, 14

[0057] 21, 23, 25, 22, 24

[0058] 31, 33, 35, 32, 34

[0059] 41, 43, 45, 42, 44

[0060] 51, 53, 55, 52, 54

[0061] Through the above jump, the processing time interval between adjacent processing points is also extended. Before using AOD, each adjacent point needs to be processed according to the strict time interval of the laser pulse, and the pulse time interval T_pulse = 1us < thermal diffusion time τ = 2us, which will lead to the problem of local heat accumulation. After using AOD, the processing time interval T_pulse between any two adjacent processing points is greater than or equal to 2us. In this way, the local heat accumulation generated during processing can be greatly improved.

[0062] like Figure 8 , 9 As shown in Figure 10, the schematic diagram of the coordinated control of the scanning galvanometer and the AOD high-frequency deflection is shown. Figure 8 The layered scanning strategy of this processing method is to control the movement in the main direction (macro direction) through the galvanometer, and the AOD controls the deflection of the laser beam incident to the galvanometer when the galvanometer is processing along the main direction, so as to achieve high-speed jump of the focal projection spot in the secondary direction (local area) of the processing plane. Figure 9 The principle of pulse distribution is specifically demonstrated. After each laser pulse emitted by the laser transmitter passes through the AOD, its emission direction will be rearranged, and finally the positions of the projection spots of these pulses at the focal point will be changed. For example, after deflection by the AOD, the projection spot position of the nth laser pulse is (x1, y1), the projection spot position of the n+1th laser pulse is (x2, y2), and the projection spot position of the n+3th laser pulse is (x3, y3). Within the scanning range of the AOD, the projection spot positions of these three pulses can be placed arbitrarily without being restricted by the main direction of the galvanometer processing. At the same time, with the movement of the galvanometer, the entire processing trajectory can be finally processed. Figure 10 The benefits of this processing method in suppressing heat accumulation during processing are demonstrated, that is, through the high-speed movement of the projection spot, the temporally adjacent pulses are separated from the pulse projection spot in space (distance interval ≥ heat-affected zone length), and the spatially adjacent pulse projection spots are separated from the pulse in time (time interval ≥ heat diffusion time).

[0063] It should be noted that the thermal diffusion time τ = Lc 2 / α,α=k / (p*Cp), Lc is the characteristic length scale, α is the thermal diffusivity of the material, and the thermal diffusion length L is the characteristic distance that heat diffuses in the material T_pulse is the width of the laser pulse, the thermal diffusion time τ is the characteristic time for the material to diffuse the absorbed laser energy to the surrounding area through heat conduction, which determines the duration of heat in the local area, Lc is the characteristic length scale (such as the thickness of the material or the focal projection spot diameter), It directly affects the size of the heat affected zone (HAZ). From the formula, we can see that the greater the energy density of the focal spot, the larger the heat affected zone generated during processing.

[0064] It should be noted that the processing area range that can be processed by the galvanometer in cooperation with the AOD processing scheme is limited by the area of the galvanometer. When the area of the product to be processed is larger than the area of the galvanometer, this set of systems can be installed on the shaft-type displacement device or the CNC processing platform to increase the processing range. The shaft-type displacement device includes a linear movement shaft, a rotary compensation shaft, and a flexible coupling.

[0065] As Figure 11 shown, the etching threshold of the material is usually determined by the material itself, the laser wavelength, the energy density of the focal projection spot, the single pulse width of the laser, the number of pulse trains, and the size of the focused spot. When the processed material, the laser wavelength, and the size of the focused spot are determined, the etching threshold is mainly affected by the energy density of the focal projection spot and the pulse frequency, and is also affected by the single pulse width and the number of pulse trains (that is, the pulse frequency). This figure respectively shows the changes in the etching threshold of copper, silicon, and colloid under different single pulse widths and numbers of pulse trains, showing that in the case of a single pulse, the etching threshold of different materials changes with the pulse width. The longer the pulse width, the higher the etching threshold, which means that a higher single pulse energy is required. Generally speaking, the more pulses in the pulse train, the lower the etching threshold of the material, which means that the energy of the sub-pulses required is lower, and the energy density of the laser pulses required to reach the etching threshold of the material is relatively low. Taking silicon material as an example, in the case of single pulse processing and a single pulse width of 550 fs, the etching threshold is F = 0.52 J / cm 2 , to process a 30-μm microstructure, it is necessary to use a focused spot with a diameter of d = 30 μm for calculation. The required single pulse energy is Ep = F*(d / 2)² = 3.68 μJ. Assuming that the repetition rate of the laser is PRR = 1 MHz, the required laser power is = Ep*PRR = 3.68 W. The power of 3.68 W is far lower than the maximum power that industrial lasers on the current market can provide.

[0066] It should be pointed out that the processing area range that can be processed by the galvanometer in cooperation with the AOD processing scheme is limited by the area of the galvanometer. When the area of the product to be processed is larger than the area of the galvanometer, this set of systems can be installed on the CNC processing platform to increase the processing range.

[0067] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser processing method for a light trapping structure with high energy utilization and reduced thermal effects, characterized in that: The following steps are involved: 1) Analyze the etching threshold F of the processed material; 2) Start the laser transmitter and set the repetition frequency of the laser transmitter to PRR, 20kHz≤PRR≤400kHz or PRR≤1.5MHz; 3) Use a beam splitter to split a laser beam into M*N small beams, the number of processing rows is N, the number of projection spots processed in each row is M, and the etching area is M*N. Or use an acousto-optic deflector AOD to deflect the beam at high speed. The jump coordinates after deflection are as follows: 11，13，15，12，14 21，23，25，22，24 31，33，35，32，34 41，43，45，42，44 51，53，55，52，54； 4) Wherein, the spacing between adjacent projection spots in M ​​is dm, the moving speed of the projection spot is Vs, the time interval is ΔT, ΔT=dm / Vs, 30um≤dm≤50um, 50mm / s≤Vs≤2000mm / s, and the number of processing times for each processing point on the material is S times, 2≤S≤50; Among them, during the high-speed deflection of AOD, the processing time interval Δt between two adjacent processing points in position is ≥ the thermal diffusion time τ, and the processing distance interval Δd between two adjacent pulses in time is ≥ the thermal diffusion length L; 5) The energy density of the focal projection spot is Laser processing causes the material to undergo a phase change, resulting in a hole structure with a light-trapping structure after processing. The hole structures include V-shaped, trapezoidal and rectangular.

2. The laser processing method for a light trapping structure with high energy utilization and reduced thermal influence according to claim 1 is characterized in that: F <Focal projection spot energy density 3. The laser processing method for a light trapping structure with high energy utilization and reduced thermal influence according to claim 1, characterized in that: N≥1,2≤M=S≤50.

4. The laser processing method for a light trapping structure with high energy utilization and reduced thermal influence according to claim 1, characterized in that: Wz*N≤total laser power W.

5. The laser processing method for light trapping structure with high energy utilization and reduced thermal influence according to claim 1, characterized in that: The light splitting device includes a diffractive optical element DOE and a spatial light modulator SLM.

6. The laser processing method for a light trapping structure with high energy utilization and reduced thermal influence according to claim 1, characterized in that: The scanning angle range of AOD is Δθ=(λ / Vs)*Δfs, where λ is the laser wavelength, Vs is the speed of the sound wave, and Δfs is the scanning frequency bandwidth.

7. The laser processing method for a light trapping structure with high energy utilization and reduced thermal influence according to claim 1, characterized in that: Thermal diffusion time τ = Lc 2 / α,α=k / (p*Cp), Lc is the characteristic length scale, α is the thermal diffusivity of the material, and the thermal diffusion length L is the characteristic distance that heat diffuses in the material T_pulse is the width of the laser pulse.

8. The laser processing method for a light trapping structure with high energy utilization and reduced thermal influence according to claim 1, characterized in that: The laser transmitter emits a main beam through an acousto-optic deflector AOD to reach a galvanometer, and the galvanometer is mounted on an axis displacement device or a CNC processing platform.

9. The laser processing method for a light trapping structure with high energy utilization and reduced thermal effects according to claim 1, characterized in that: The materials processed include silicon, copper, aluminum, iron and zinc.

10. The laser processing method for light trapping structure with high energy utilization and reduced heat influence according to claim 1, characterized in that: The etching threshold range is 0.01J / cm 2 -10J / cm 2 .

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