Processing method of high aspect ratio structure, sensor and verification method
By adjusting the path and parameters through laser direct writing and combining it with air jet assistance, rapid processing of high aspect ratio structures was achieved, solving the problem of complex processing flow in traditional MEMS accelerometers and enabling rapid design verification and cost reduction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTHEAST UNIV
- Filing Date
- 2026-01-16
- Publication Date
- 2026-04-21
AI Technical Summary
Traditional MEMS accelerometers have complex manufacturing processes, long cycles, and high costs, and their structural design iteration efficiency is low, lacking rapid manufacturing methods to verify design schemes.
High aspect ratio structures are processed using laser direct writing. By adjusting the laser direct writing path, scanning strategy, and processing parameters, and combined with compressed air jet assistance, rapid processing of high aspect ratio structures can be achieved.
It significantly shortens the processing cycle from weeks to hours, reduces costs, is suitable for rapid design verification of MEMS inertial devices, and improves the stability and consistency of structural fabrication.
Smart Images
Figure CN121894601A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a fabrication method, sensor, and verification method for a high aspect ratio structure, belonging to the field of microelectromechanical systems (MEMS) inertial device technology. Background Technology
[0002] MEMS accelerometers typically consist of a mass block, spring beams, and capacitive electrodes. Traditional MEMS manufacturing processes involve multiple steps, including photolithography, mask fabrication, etching, cleaning, and thin film deposition. These processes are complex, time-consuming, and costly. Furthermore, if the sensor structure design is adjusted, the mask needs to be remade and the photolithography-etching process repeated. Therefore, the efficiency is extremely low during the structural design iteration stage, hindering the development progress of MEMS accelerometers.
[0003] In the early stages of conceptual design, structural optimization, and topology design of MEMS accelerometers, researchers urgently need a rapid fabrication method that does not require photolithography and masks, which can complete the structural fabrication in minutes to hours, so that the design can be quickly verified, such as the intrinsic frequency, range, sensitivity, and shock resistance. However, there is currently no corresponding rapid fabrication method. Summary of the Invention
[0004] This invention provides a method for fabricating high aspect ratio structures, a sensor, and a verification method, which solves the problems disclosed in the background art.
[0005] According to one aspect of this application, a method for processing high aspect ratio structures is provided, wherein the high aspect ratio structure is processed using a laser direct writing method, the method comprising:
[0006] Based on the design drawings of the high aspect ratio structure, the laser direct writing path, laser scanning strategy, and laser processing parameters were determined. The laser direct writing path includes a boundary path and an intermediate path. The boundary path is distributed along the boundary of the material removal area and maintains a safe distance from the structural area to account for thermal effects. The intermediate path is located within the material removal area and divides the material removal area into multiple partitions. The laser scanning strategy involves performing thickness layering on the area corresponding to the laser direct writing path, and repeatedly scanning the area corresponding to the same laser direct writing path layer by layer. The laser processing parameters include deposition energy per unit length and spot radius. The deposition energy per unit length is used to control the layered processing, and the spot radius is used to ensure that the bottom of the trench remains in the effective focal zone during deep trench processing.
[0007] Based on the laser direct writing path, laser scanning strategy, and coordinated laser processing parameters, laser direct writing is performed to obtain a high aspect ratio structure. During the laser direct writing process, a compressed air jet is introduced into the laser action area to blow the ablation products away from the laser action area.
[0008] Furthermore, if the material removal area is the area between spring beams, the intermediate path is distributed along the width direction of the material removal area; if there are corners in the material removal area, intermediate paths distributed along the diagonal are set at the corners.
[0009] Furthermore, in the laser scanning strategy, if there is a symmetrical structure in the high aspect ratio structure, the laser direct writing path area corresponding to the symmetrical structure is scanned symmetrically or alternately in layers.
[0010] Furthermore, the formula for deposition energy per unit length is:
[0011] ;
[0012] In the formula, E l E represents the energy deposited per unit length. p For single-pulse energy, A is the effective area of the laser at the focal point, and F is... th Let f be the ablation threshold of the material, f be the laser repetition frequency, and v be the scanning speed. f and v are synergistically adjusted, and their relationship is as follows: , Where is the pulse coverage ratio, and D is the effective laser spot diameter.
[0013] Furthermore, the formula for the spot radius is:
[0014] ;
[0015] In the formula, Where is the radius of the light spot. Let z be the laser beam waist radius, and z be the axial offset distance along the laser propagation direction relative to the ideal focal point. R It is the Rayleigh length.
[0016] Furthermore, laser processing parameters also include thermal diffusion length, which is used to control the heat-affected zone and the recast layer;
[0017] ;
[0018] In the formula, L th denoted as the thermal diffusion length, a as the thermal diffusion coefficient of the material, and f as the laser repetition frequency.
[0019] According to another aspect of this application, a sensor is provided, wherein the high aspect ratio structure of the sensor is fabricated using the aforementioned high aspect ratio structure fabrication method.
[0020] According to another aspect of this application, a verification method is provided, comprising:
[0021] The high aspect ratio structure of the sensor is fabricated using the above-mentioned high aspect ratio structure fabrication method;
[0022] The intrinsic frequency, range, sensitivity, and shock resistance of the processed sensor are tested.
[0023] Based on the test results, an analysis of sensor structural defects was conducted.
[0024] The beneficial effects achieved by this invention are as follows: This invention adjusts the laser direct writing path, laser scanning strategy and laser processing parameters of the traditional laser direct writing method, so that the laser direct writing method can be applied to the processing of high aspect ratio structures, overcomes the defects of the traditional MEMS process flow, and can realize the rapid processing of sensors. Attached Figure Description
[0025] Figure 1 A flowchart of the fabrication method for high aspect ratio structures;
[0026] Figure 2 This is a schematic diagram of a laser direct writing system;
[0027] Figure 3 A schematic diagram of laser direct writing processing for the spring suspension structure of a MEMS accelerometer;
[0028] Figure 4 A partial SEM image showing the laser direct writing process results of the spring suspension structure of a MEMS accelerometer.
[0029] Figure 5 A flowchart for verifying the method;
[0030] Figure 6 A schematic diagram of path planning for processing corners and large areas. Detailed Implementation
[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps described in these embodiments do not limit the scope of this application.
[0033] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.
[0034] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.
[0035] In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.
[0036] It should be noted that similar symbols and letters in the accompanying drawings represent similar items; therefore, once an item is defined in one accompanying drawing, it does not need to be discussed further in subsequent accompanying drawings.
[0037] See Figure 1 , Figure 1 This is a flowchart of a high aspect ratio structure processing method provided in an embodiment of this application. Specifically, the method uses a laser direct writing method to process the high aspect ratio structure.
[0038] It should be noted that the laser direct writing method is mainly implemented using a laser direct writing system, the structure of which can be found in [reference needed]. Figure 2 It includes a laser 1, an optical path system (including an optical path 2, a beam expander 3, and a reflector 4), a galvanometer 5, a displacement stage 7, a control connection line 8, and a control computer 9.
[0039] The control computer 9 contains laser control software and galvanometer software, used to import processing patterns, laser direct writing paths 10, laser scanning strategies, and laser processing parameters, and to control the entire system to work together. The pulsed laser emitted by the laser 1 is collimated and expanded by the beam expander 3 and redirected by the reflector 4. The galvanometer 5 controls the deflection and focusing of the laser beam onto the surface of the processing substrate 6 placed on the displacement stage 7, so as to remove material from the processing substrate 6 according to the preset laser direct writing path 10, forming the corresponding structure, such as a MEMS accelerometer sensor structure.
[0040] It should be noted that laser 1 can be a nanosecond pulsed laser, specifically a diode-pumped solid-state Q-switched (DPSS) nanosecond laser with a pulse width of 10 ns at a frequency of 50 kHz. The displacement stage 7 can achieve precise movement, processing structures exceeding the scanning field of view of the galvanometer, and realizing three-dimensional processing of the structure. The substrate 6 can be made of single-crystal silicon, semiconductor materials, quartz, fused silica, or composite materials.
[0041] The laser direct writing system described above is an existing system and will not be described in detail here.
[0042] It should be noted that traditional laser direct writing is mainly used for surface microstructure or marking processing, and it cannot be applied to processing high aspect ratio structures, such as MEMS accelerometer structures. Therefore, this application improves the traditional laser direct writing method by adjusting the laser direct writing path 10, laser scanning strategy and laser processing parameters, so that laser direct writing can achieve structure processing with an aspect ratio ≥ 15:1.
[0043] The above-mentioned high aspect ratio structure processing method may include at least the following steps:
[0044] Step 1: Based on the design drawing of the high aspect ratio structure, determine the laser direct writing path 10, the laser scanning strategy, and the laser processing parameters. The laser direct writing path 10 includes a boundary path and an intermediate path. The boundary path is distributed along the boundary of the material removal area 11 and maintains a safe distance from the structural area to account for thermal effects. The intermediate path is located within the material removal area 11 and divides the material removal area 11 into multiple partitions. The laser scanning strategy involves performing thickness layering on the area corresponding to the laser direct writing path 10, and repeatedly scanning the same area corresponding to the laser direct writing path 10 layer by layer. The laser processing parameters include the deposition energy per unit length and the spot radius. The deposition energy per unit length is used to control the layered processing, and the spot radius is used to ensure that the bottom of the trench remains in the effective focal zone during deep trench processing.
[0045] It should be noted that, based on the design drawing of the high aspect ratio structure, the material removal area 11 and the structural area can be determined; among them, the material removal area 11 is the area that needs to be removed by laser ablation, and the structural area is the structure that needs to be retained. Taking the MEMS accelerometer structure as an example, the structural area includes spring beams, mass blocks, electrodes, etc.
[0046] To make laser direct writing applicable to high aspect ratio structures, it is necessary to design the laser direct writing path 10, laser scanning strategy, and laser processing parameters for key structures that have strict requirements for high aspect ratio, low heat-affected zone, and consistency of structural mechanical properties.
[0047] It should be noted that removing the material removal area 11 mainly involves separating its boundary from the processing substrate 6. Taking structures such as spring beams and mass blocks in MEMS accelerometers as examples, these structures are highly sensitive to cross-sectional dimensions, edge morphology, and symmetry due to their small size and large aspect ratio. Even minor structural differences can directly cause intrinsic frequency shifts, inconsistencies in sensitivity, and increased zero-bias and nonlinear errors. Therefore, laser direct writing cannot be equated with ordinary two-dimensional contour cutting. Instead, it is necessary to plan a reasonable laser direct writing path 10 to ensure the spatial consistency and controllability of the material removal process.
[0048] During laser direct writing, material removal is not a continuous process, but rather is completed point-by-point by discrete pulses along the scanning laser direct writing path 10. If the laser direct writing path 10 is not planned properly, it will lead to abnormal local pulse overlap rates, excessively high or low energy deposition per unit length in some areas, causing uneven ablation, sidewall tilting, or local overburning. Therefore, the planning of the laser direct writing path 10 is a spatial realization method for achieving coordinated parameter control.
[0049] To remove the material removal area 11, the laser direct writing path 10 may include a boundary path and an intermediate path; wherein, the boundary path is distributed along the boundary of the material removal area 11 and leaves a safe distance from the structural area to take into account the thermal effect, and the intermediate path is located within the material removal area 11 and divides the material removal area 11 into multiple partitions.
[0050] In some embodiments, if the material removal area is the area between spring beams, the intermediate path is distributed along the width direction of the material removal area; if there is a corner in the material removal area, an intermediate path distributed along the diagonal is provided at the corner.
[0051] See also Figure 6 In order to reduce processing time and thermal damage, the area between the spring beams is partially ablated only along the boundary path (i.e., some boundary paths are not ablated). The material cannot be dropped directly in the middle of the material removal area. In order to facilitate the dropping of the unprocessed material in the middle, an ablation path is added in the middle of the material removal area. Specifically, the middle of the area is divided into blocks along the width direction. This allows the unprocessed material in the middle of the material removal area to drop without damaging the spring beams.
[0052] See also Figure 6 For the material removal areas corresponding to the four corners of the mass block, there are corners. In order to reduce processing time and reduce thermal damage, only partial ablation is performed along the boundary path (i.e., some boundary paths are not ablated). Material cannot be dropped directly in the middle of the material removal area, especially in the corners. In addition to adding intermediate paths along the width direction, intermediate paths are also added at the corners. By dividing the middle of the area into blocks and decomposing the corner areas, the material in the unprocessed part of the middle of the area can be dropped without damaging the side connecting beams, springs and the mass block. This improves the removal efficiency and keeps the boundaries clear.
[0053] In the processing of high aspect ratio structures, material removal is a process that accumulates layer by layer and depth by depth. By planning the laser direct writing path, the laser energy can be transmitted downwards evenly and stably in the depth direction, which is a prerequisite for the realization of high aspect ratio processing.
[0054] Similarly, in the processing of high aspect ratio structures, laser scanning also involves repeatedly scanning the same laser direct writing path 10. This requires layering the area corresponding to the laser direct writing path 10 into different thicknesses and repeatedly scanning the area corresponding to the same laser direct writing path 10 layer by layer. That is, scanning layer by layer according to a predetermined layer thickness. This way, the amount removed in each scan is small and stable, avoiding the collapse of the sidewall caused by a single large energy, which is beneficial to maintaining the verticality of the groove wall.
[0055] In some embodiments, if a symmetrical structure (such as a differential spring or a symmetrical mass block) exists within the high aspect ratio structure, the laser direct writing path 10 region corresponding to the symmetrical structure is subjected to symmetrical or alternating layered scanning, such as... Figure 3 The processing area example shown is processed twice according to the processing path 10 of the upper left corner, lower right corner, upper right corner, lower left corner and middle area respectively. The processing is carried out in a cycle according to the above processing order, and symmetrical or alternating layer scanning is performed. Heat dissipation time is reserved for each processing area. This can avoid thermal stress concentration and structural warping caused by processing one side first.
[0056] It should be noted that although the effects of single-pulse energy, pulse repetition frequency, and scanning speed on laser processing effects are well known in the field of laser processing, existing technologies only remain at the level of qualitative understanding of the influence of a single parameter, without establishing a synergistic mapping relationship between multiple parameters, and without applying this mapping relationship to the stable realization of high aspect ratio structures.
[0057] Existing laser direct writing technology generally suffers from problems such as enhanced plasma shielding effect and significant decrease in energy density at the bottom of the tank due to focus deviation as the processing depth increases. This results in a rapid decline in longitudinal removal capability and makes it difficult to achieve high aspect ratio structures. Therefore, this application proposes a technical solution based on the relationship between focus position, pulse overlap rate and deposition energy per unit length, which dynamically adjusts the focus position and controls parameters in coordination with the processing depth to maintain stable ablation conditions at the bottom of the tank.
[0058] The laser processing parameters set here mainly include the deposition energy per unit length and the spot radius; among them, the deposition energy per unit length is used to control the realization of layered processing, and the spot radius is used to control the bottom of the trench to always be in the effective focal zone during deep trench processing.
[0059] The ablation energy of a material can be expressed as:
[0060] ;
[0061] In the formula, F is the energy of material ablation, and E p Let A be the single pulse energy, A be the effective area of the laser at the focal point, and F be the laser pulse energy. th This is the ablation threshold of the material, which is related to both the material and the laser pulse width.
[0062] Ep Whether ablation can occur depends on several factors: too low a temperature prevents vertical accumulation, while too high a temperature allows melting to become the dominant process, leading to sidewall collapse and thickening of the recast layer. It can be limited to a stable ablation range slightly above the ablation threshold.
[0063] The pulse coverage ratio (overlap rate) can be expressed as:
[0064] ;
[0065] In the formula, Where is the pulse coverage ratio, D is the effective laser spot diameter, f is the laser repetition frequency, and v is the scanning speed.
[0066] Too low a pulse coverage ratio will lead to discontinuous processing and limited longitudinal depth, while too high a pulse coverage ratio will lead to severe heat accumulation and expansion of the heat-affected zone. This can be addressed by adjusting f and v in a coordinated manner, so that the pulse coverage ratio is in the range of continuous ablation without significant heat accumulation.
[0067] Along the scan path, the deposition energy per unit length can be expressed as:
[0068] ;
[0069] In the formula, E l Energy deposited per unit length.
[0070] This formula links single-pulse energy, laser repetition frequency, and scanning speed together. This determines the removal depth per scan and whether vertical accumulation is possible. High aspect ratio machining requirements. It is sufficient to drive longitudinal removal, but cannot cause large-area melting. This can be addressed by controlling... Layered processing is achieved within a stable longitudinal ablation window.
[0071] It should be noted that during the processing of high aspect ratio structures, focal spot offset has a decisive impact on longitudinal energy deposition. Therefore, it is necessary to establish a mapping relationship between the focal spot position and the energy density at the bottom of the trench, and propose a dynamic focusing strategy to fundamentally solve the problem of longitudinal removal failure in deep trench processing. Specifically, this can be achieved by controlling the spot radius to ensure that the bottom of the trench is always in the effective focal zone during deep trench processing. The formula can be expressed as:
[0072] ;
[0073] In the formula, Where is the radius of the light spot. Let z be the laser beam waist radius, and z be the axial offset distance along the laser propagation direction relative to the ideal focal position (the ideal state is z=0, no deviation). RRayleigh length (representing the distance at which the beam remains approximately non-divergent near the focal point).
[0074] Focus shift causes the laser spot to enlarge, reducing the laser energy density. This results in insufficient energy at the bottom of the groove during the processing of high aspect ratio structures, halting longitudinal removal and preventing the achievement of a high aspect ratio. To address this, a dynamic focusing strategy is employed where the focus shifts synchronously with the depth. During deep groove processing, the path layer is matched to the amount of focus shift, ensuring that the bottom of the groove remains within the effective focal zone during each scan. This maintains stable ablation conditions, preventing processing failure as depth increases, and thus allows for continuous longitudinal removal, significantly improving the aspect ratio.
[0075] In some embodiments, the laser processing parameters further include a thermal diffusion length, which is used to control the heat-affected zone and the recast layer, and can be expressed by the formula:
[0076] ;
[0077] In the formula, L th Let f be the thermal diffusion length and a be the thermal diffusivity of the material. An excessively high f will lead to insufficient thermal diffusion, resulting in heat accumulation and affecting the processing morphology. Here, f is controlled in conjunction with the scanning speed to control L. th Smaller than the structural feature size, thus achieving a small heat-affected zone and a controllable recast layer.
[0078] By coordinating and controlling the above parameters, and combining the strategy of dynamically adjusting the focal position with the processing depth, the bottom of the tank is always kept in a stable ablation range, thereby achieving high aspect ratio structure processing and effectively reducing the heat-affected zone and recast layer.
[0079] It should be noted that the coupling effect between single-pulse energy, pulse repetition frequency, scanning speed, and focal position exhibits significant nonlinear characteristics, and its combined influence on aspect ratio and heat-affected zone is not a linear superposition. The high aspect ratio microstructure and low heat-affected zone effect achieved in this application through parameter synergistic control is a comprehensive technical effect resulting from the synergistic effect of multiple parameters.
[0080] Step 2: Based on the laser direct writing path 10, the laser scanning strategy, and the coordinated laser processing parameters, laser direct writing is performed to obtain a high aspect ratio structure. During the laser direct writing process, a compressed air jet is introduced into the laser action area to blow the ablation products away from the laser action area.
[0081] It should be noted that during laser ablation, high-temperature plasma clouds, evaporated gases, and ablation particles are instantaneously generated on the material surface. If these substances remain in the processing area, they will shield and scatter subsequent laser pulses. Furthermore, the molten droplets and tiny particles formed during the ablation process are prone to redeposition on the sidewalls or bottom of the structure, forming a recast layer.
[0082] To address the aforementioned issues, this application introduces a compressed air jet into the laser-affected area. Specific methods include, but are not limited to: directing compressed air into the laser processing area through coaxially or laterally positioned nozzles; ensuring the jet direction is parallel to or at an angle to the laser incident direction; and positioning the nozzle outlet close to the processing surface or the inlet of a deep groove. The compressed air pressure is adjusted according to the processing depth, material type, and laser parameters to ensure stable airflow into the processing area without causing structural vibration or processing trajectory deviation.
[0083] Compressed air acts synchronously or continuously with the laser pulse during laser ablation, specifically including: continuous jetting during laser scanning; or maintaining a stable airflow environment during multiple scans; ensuring that the processing area is always under controlled gas-assisted conditions.
[0084] For deep groove structures, such as the spring beam gap and mass block release groove in MEMS accelerometers, compressed air enters the groove along the groove opening. As the processing depth increases, it can still generate effective gas disturbance in the bottom area of the groove, thereby ensuring the consistency of processing conditions inside the deep groove.
[0085] After the introduction of compressed air, plasma and evaporation products are quickly blown away from the laser-affected area, allowing laser energy to be transferred more effectively to the material surface or the bottom of the tank, significantly improving laser energy utilization, especially in deep tank processing. The introduction of compressed air promotes the discharge of ablation products along the tank, reducing energy dissipation within the tank and maintaining stable ablation conditions at the bottom, thereby delaying longitudinal removal failure and increasing the maximum achievable processing depth and aspect ratio. The introduction of compressed air can also promptly remove molten and evaporation products, reducing their adhesion probability on the sidewalls and bottom, effectively reducing the thickness and inhomogeneity of the recast layer. The compressed air flow can also provide some convective heat dissipation to the processing area, reducing local temperature rise. Although not the primary cooling method, it helps to slow down heat accumulation and reduce the size of the heat-affected zone in high-repetition-frequency processing.
[0086] By introducing compressed air assistance during laser direct writing, the plasma shielding effect can be effectively suppressed, ablation products can be promptly discharged, longitudinal material removal capability can be enhanced, and molten material re-deposition can be reduced, thereby improving the processing morphology, reducing the heat-affected zone, and improving the stability and consistency of high aspect ratio structure processing.
[0087] The above method adjusts the laser direct writing path 10, laser scanning strategy, and laser processing parameters of the traditional laser direct writing method, enabling the laser direct writing method to be applied to the processing of high aspect ratio structures (processing examples can be found in [reference needed]). Figure 4This method overcomes the shortcomings of traditional MEMS processes and enables rapid processing of sensors. It is particularly suitable for the rapid processing of various microstructures such as MEMS inertial sensors (e.g., gyroscopes), MEMS pressure sensors, MEMS micro-spring structures, micro-cantilever beams, and micro-optomechanical structures.
[0088] The above method avoids the complex processes of traditional photolithography, etching, and mask making, and realizes direct writing processing from "digital model" to "physical structure", shortening the processing cycle from weeks or even months to hours; it eliminates the need to make expensive masks and reduces the use of multiple process equipment, greatly reducing economic costs; by designing the processing pattern and adjusting the processing parameters, and combining with auxiliary gas, it can realize the processing of microstructures with high aspect ratio.
[0089] This application also discloses a sensor, such as a MEMS accelerometer, whose high aspect ratio structure can be fabricated using the above method, namely, by laser direct writing.
[0090] See Figure 5 , Figure 5 This is a flowchart of a verification method provided in an embodiment of this application. The method may include at least the following steps:
[0091] 1) A high aspect ratio structure fabrication method is used to fabricate the high aspect ratio structure of the sensor.
[0092] 2) Test the intrinsic frequency, range, sensitivity and shock resistance of the processed sensor.
[0093] It should be noted that, taking a MEMS accelerometer as an example, the intrinsic frequency is used to verify the structural stiffness and mass design; the range (maximum displacement) is used to verify the flexibility of the spring beam; the sensitivity (displacement under acceleration excitation) is used to verify the actual dynamic response capability; and the impact resistance is used to verify the stability of the structure under transient loads.
[0094] 3) Based on the test results, analyze the structural defects of the sensor.
[0095] The test results can be used to analyze whether the structure meets the design requirements, identify structural defects, and complete rapid verification.
[0096] This invention enables laser direct writing to achieve structure processing and performance verification with an aspect ratio ≥ 15:1 without the need for photolithography and etching processes, through multi-parameter collaborative optimization and gas-assisted processing. This significantly shortens the R&D cycle and reduces R&D costs, making it suitable for the rapid verification stage of MEMS sensor structure design. It can significantly save R&D time and economic costs, and has universality and promotional value.
[0097] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.
Claims
1. A method for processing a high aspect ratio structure, characterized in that, High aspect ratio structures are fabricated using a laser direct writing method, the method comprising: Based on the design drawings of the high aspect ratio structure, the laser direct writing path, laser scanning strategy, and laser processing parameters were determined. The laser direct writing path includes a boundary path and an intermediate path. The boundary path is distributed along the boundary of the material removal area and maintains a safe distance from the structural area to account for thermal effects. The intermediate path is located within the material removal area and divides the material removal area into multiple partitions. The laser scanning strategy involves performing thickness layering on the area corresponding to the laser direct writing path, and repeatedly scanning the area corresponding to the same laser direct writing path layer by layer. The laser processing parameters include deposition energy per unit length and spot radius. The deposition energy per unit length is used to control the layered processing, and the spot radius is used to ensure that the bottom of the trench remains in the effective focal zone during deep trench processing. Based on the laser direct writing path, laser scanning strategy, and coordinated laser processing parameters, laser direct writing is performed to obtain a high aspect ratio structure. During the laser direct writing process, a compressed air jet is introduced into the laser action area to blow the ablation products away from the laser action area.
2. The method according to claim 1, characterized in that, If the material removal area is the area between spring beams, the intermediate paths are distributed along the width of the material removal area; if there are corners in the material removal area, intermediate paths are set at the corners and distributed along the diagonal.
3. The method according to claim 1, characterized in that, In laser scanning strategies, if a symmetrical structure exists within a high aspect ratio structure, the laser direct writing path region corresponding to the symmetrical structure is scanned symmetrically or alternately in layers.
4. The method according to claim 1, characterized in that, The formula for deposition energy per unit length is: ； In the formula, E l E represents the energy deposited per unit length. p For single-pulse energy, A is the effective area of the laser at the focal point, and F is... th Let f be the ablation threshold of the material, f be the laser repetition frequency, and v be the scanning speed. f and v are synergistically adjusted, and their relationship is as follows: , Where is the pulse coverage ratio, and D is the effective laser spot diameter.
5. The method according to claim 1, characterized in that, The formula for the light spot radius is: ； In the formula, The radius of the light spot is... Let z be the laser beam waist radius, and z be the axial offset distance along the laser propagation direction relative to the ideal focal point. R It is the Rayleigh length.
6. The method according to claim 1, characterized in that, Laser processing parameters also include thermal diffusion length, which is used to control the heat-affected zone and the recast layer; ； In the formula, L th denoted as the thermal diffusion length, a as the thermal diffusion coefficient of the material, and f as the laser repetition frequency.
7. A sensor, characterized in that, The high aspect ratio structure of the sensor is fabricated using the method described in any one of claims 1 to 6.
8. A verification method, characterized in that, include: The high aspect ratio structure of the sensor is fabricated using the method described in any one of claims 1 to 6; The intrinsic frequency, range, sensitivity, and shock resistance of the processed sensor are tested. Based on the test results, an analysis of sensor structural defects was conducted.