A MEMS probe laser etching method and device and a MEMS probe

Abstract

The application relates to the technical field of MEMS probes, and discloses a MEMS probe laser etching method and device and a MEMS probe, wherein the method comprises the following steps: performing single-pulse ablation test on a probe material, measuring a single-pulse safe ablation depth and corresponding first-path reference pulse energy, and establishing a path-by-path decreasing formula; modulating laser output energy to the first-path reference pulse energy, performing first-path femtosecond pulse scanning etching on the probe material, and calculating a second energy decreasing rate; calculating single-pulse energy of a second path to an Nth path based on the path-by-path decreasing formula and the second energy decreasing rate, and sequentially performing second-path to Nth-path scanning etching after inter-path cooling and waiting; when each i-path scanning is performed, the single-pulse energy is decreased according to the path-by-path decreasing formula, and the pulse repetition frequency is increased according to an increasing coefficient, and the scanning etching of the second path to the Nth path is sequentially completed; and the method solves the problems of tip overburning and root underburning caused by traditional single-energy scanning.

Description

Technical Field

[0001] This invention relates to the field of MEMS probe technology, and in particular to a MEMS probe laser etching method, apparatus and MEMS probe. Background Technology

[0002] MEMS probes are core devices in microelectronic testing and biomedical detection, and the precision of their tip microstructure fabrication directly determines the contact reliability and lifespan of the probes. Femtosecond lasers, with their ultrashort pulse width and cold ablation characteristics, have become an important method for precision machining of MEMS probes. However, traditional femtosecond laser multi-channel etching processes generally employ constant energy single-channel etching or equal-energy multi-channel etching strategies, which fail to fully consider the thermal accumulation effect during multi-channel scanning.

[0003] During multi-pass scanning, the residual heat generated by the previous pass raises the material surface temperature, and the resulting roughened surface significantly increases the laser absorption rate. These two factors together lower the effective ablation threshold of the material. If subsequent passes use the same pulse energy as the first pass, over-ablation will inevitably occur, causing the ablation depth in the probe tip area to become uncontrollable with each pass. The width of the heat-affected zone will exceed the design value by several times, and the thickness of the edge molten recast layer will increase significantly, severely affecting the probe's geometric accuracy and surface quality. Summary of the Invention

[0004] This invention provides a method, apparatus, and MEMS probe for laser etching. This invention solves the problems of tip overburning and root underburning caused by traditional single-energy scanning, overcomes the deficiency of the lack of heat accumulation compensation mechanism in the prior art, reduces the width of the heat-affected zone, accurately controls the tip curvature radius, improves surface quality, and increases the processing yield.

[0005] In a first aspect, the present invention provides a MEMS probe laser etching method, the MEMS probe laser etching method comprising:

[0006] A single-pulse ablation test was conducted on the probe material to determine the safe ablation depth of a single pulse and the corresponding first reference pulse energy. Based on the first reference pulse energy and the first energy decay rate, a progressive decrease formula was established.

[0007] The laser output energy is modulated to the first reference pulse energy, and the probe material is subjected to the first femtosecond pulse scanning etching. The actual ablation depth of the first pass is measured, and the second energy decay rate is calculated based on the actual ablation depth of the first pass and the single-pulse safe ablation depth.

[0008] Based on the aforementioned channel-by-channel reduction formula and the second energy reduction rate, the single pulse energy of channels 2 to N is calculated. After inter-channel cooling and waiting, the scanning etching of channels 2 to N is performed sequentially. When performing the i-th channel scan, the single pulse energy is reduced according to the aforementioned channel-by-channel reduction formula, and the pulse repetition frequency is increased according to the increment coefficient. The scanning etching of channels 2 to N is completed sequentially.

[0009] In conjunction with the first aspect, in a first implementation of the first aspect of the present invention, the step of performing a single-pulse ablation test on the probe material, determining the single-pulse safe ablation depth and the corresponding first reference pulse energy, and establishing a successive decreasing formula based on the first reference pulse energy and a first energy decay rate includes:

[0010] Single-pulse ablation tests with different energies were conducted on the probe material, and multiple sets of ablation depth data were measured.

[0011] A calibration curve of pulse energy versus ablation depth is established based on the multiple sets of ablation depth data, and the ablation threshold energy density of the probe material is determined through the calibration curve.

[0012] The single-pulse energy was gradually reduced to conduct a test burn experiment. The maximum depth that could be removed by a single pulse was determined under the condition that no observable heat-affected zone was generated in the ablation area. This value was taken as the safe ablation depth of a single pulse. The pulse energy value that made the ablation depth reach the safe ablation depth of a single pulse was found according to the calibration curve and used as the first reference pulse energy.

[0013] The number of scans is calculated based on the total probe removal depth and the single-pulse safe ablation depth. A formula is established to decrease the energy of the i-th single pulse by multiplying the energy of the first reference pulse by one minus i minus 1 multiplied by the first energy decay rate.

[0014] In conjunction with the first aspect, in a second implementation of the first aspect of the present invention, the step of calculating the number of scan channels based on the total probe removal depth and the single-pulse safe ablation depth, and establishing a channel-by-channel decreasing formula for the single-pulse energy of the i-th channel by multiplying the energy of the first channel reference pulse by one minus i minus 1 multiplied by the first energy decay rate, includes:

[0015] The theoretical number of passes is calculated by dividing the total probe removal depth by the single-pulse safe ablation depth.

[0016] Multiply the theoretical number of traces by a preset coefficient and round up to obtain the actual number of scan traces N;

[0017] When the thermal diffusivity of the probe material is the first thermal diffusivity, the first energy decay rate is selected within the first value range; when the thermal diffusivity of the probe material is the second thermal diffusivity, the first energy decay rate is selected within the second value range.

[0018] Establish a formula for decreasing the energy of the i-th single pulse, which is equal to the energy of the first reference pulse multiplied by one minus i minus 1 multiplied by the first energy decay rate.

[0019] In conjunction with the first aspect, in a third implementation of the first aspect of the present invention, the step of modulating the laser output energy to the first reference pulse energy, performing a first femtosecond pulse scanning etching on the probe material, measuring the first actual ablation depth, and calculating the second energy decay rate based on the first actual ablation depth and the single-pulse safe ablation depth includes:

[0020] The laser output energy is modulated to the first reference pulse energy, the pulse repetition frequency is set to the first frequency value, and the probe material is subjected to the first scanning etching according to the preset scanning path.

[0021] The ablation grooves formed by the first scan were measured to obtain the actual ablation depth of the first scan.

[0022] The depth deviation rate is calculated by subtracting the actual ablation depth of the first pass from the single-pulse safe ablation depth and dividing by the single-pulse safe ablation depth. When the absolute value of the depth deviation rate exceeds the preset deviation threshold, the depth deviation rate is multiplied by the preset correction coefficient to obtain the adjustment amount of the first energy decay rate.

[0023] The first energy decay rate is added to the adjustment amount to obtain the second energy decay rate.

[0024] In conjunction with the first aspect, in the fourth implementation of the first aspect of the present invention, the step of calculating the single-pulse energy of the second to Nth channels based on the pass-by-pass decreasing formula and the second energy decay rate, and sequentially performing scan etching of the second to Nth channels after inter-channel cooling and waiting, wherein the single-pulse energy is decreased according to the pass-by-pass decreasing formula and the pulse repetition frequency is increased according to the increasing coefficient during each i-th channel scan, thereby sequentially completing the scan etching of the second to Nth channels, includes:

[0025] Substitute the second energy decay rate into the channel-by-channel decay formula to calculate the single pulse energy of each channel from channel 2 to channel N, and obtain the energy sequence of each channel.

[0026] When the probe thickness is less than the first thickness threshold, the inter-channel cooling time is selected within the first time interval; when the probe thickness is greater than the first thickness threshold, the inter-channel cooling time is selected within the second time interval.

[0027] Before the start of the i-th scan, the inter-channel cooling time is waited for. The single pulse energy of the i-th channel is extracted from the energy sequence of each channel and modulated to the laser output terminal. At the same time, the pulse repetition frequency is increased from the first frequency value to the i-th channel frequency value by an increment factor. The scanning speed is adjusted synchronously by the same increment factor. The scanning etching of the 2nd to Nth channels is completed in sequence.

[0028] In conjunction with the first aspect, in a fifth implementation of the first aspect of the present invention, the step of performing the inter-channel cooling time before the start of the i-th channel scan, extracting the single-pulse energy of the i-th channel from the energy sequence of each channel and modulating it to the laser output terminal, simultaneously increasing the pulse repetition frequency from the first frequency value to the i-th channel frequency value by an increment factor, and synchronously adjusting the scanning speed by the same increment factor to complete the scanning etching of the 2nd to Nth channels sequentially, includes:

[0029] Before the start of the i-th scan, the inter-channel cooling time is performed to allow the probe material surface temperature to drop from the peak temperature of the previous scan to below a preset safe temperature threshold.

[0030] Extract the i-th single pulse energy from each energy sequence and modulate it to the laser output terminal using an acousto-optic modulator. Calculate 1 plus 0.2 multiplied by i minus 1 to obtain the increment coefficient. Multiply the first frequency value by the increment coefficient to obtain the i-th frequency value and set the pulse repetition frequency.

[0031] The scanning speed of the first scan is multiplied by the increment factor to calculate the scanning speed of the i-th scan. The i-th scan is then performed on the probe material according to the i-th scan speed and the preset scan path. The scanning etching of the second to the Nth scans is completed in sequence.

[0032] In conjunction with the first aspect, in a sixth implementation of the first aspect of the present invention, the MEMS probe laser etching method further includes:

[0033] The ablation trench formed by the i-th scan is measured to obtain the actual removal depth of the i-th scan. The actual removal depths of each scan from the 1st scan to the i-th scan are summed to obtain the cumulative removal depth.

[0034] Multiply the total probe removal depth by i and divide by the actual number of scans N to calculate the target progress depth. Calculate the depth deviation by subtracting the target progress depth from the cumulative removal depth.

[0035] When the absolute value of the depth deviation exceeds the preset depth deviation threshold, the depth deviation is multiplied by the energy of the first reference pulse and then divided by the product of the theoretical number of passes and the single-pulse safe ablation depth to calculate the energy compensation amount. The energy compensation amount is then added to the single-pulse energy corresponding to each pass from the i+1th to the Nth pass in the energy sequence of each pass.

[0036] In conjunction with the first aspect, in the seventh implementation of the first aspect of the present invention, the MEMS probe laser etching method further includes:

[0037] Energy spatial modulation rules are established based on the radial coordinate range of the tip cone region in the probe material. When the diameter corresponding to the radial coordinate of the scanning spot is less than the first diameter threshold, the energy coefficient takes the first coefficient value. When the corresponding diameter is between the first diameter threshold and the second diameter threshold, the energy coefficient takes the second coefficient value. When the corresponding diameter is greater than the second diameter threshold, the energy coefficient takes the third coefficient value.

[0038] Set the spiral scanning path parameters for the tip conical region, add the preset extension value to the probe tip design radius as the spiral starting radius, set the pitch as the first pitch value, and calculate the number of spiral turns by dividing the probe conical height by the first pitch value.

[0039] During the i-th scan, the radial coordinates of the scanning spot are obtained in real time through the scanning system. The energy of the i-th single pulse is multiplied by the energy coefficient corresponding to the radial coordinate to obtain the real-time modulation energy. The energy of the laser output end is modulated to the real-time modulation energy, and the first to Nth scan etchings are completed on the needle tip conical region according to the spiral scanning path parameters.

[0040] Secondly, the present invention provides a MEMS probe laser etching apparatus, the MEMS probe laser etching apparatus comprising:

[0041] A module is established to perform single-pulse ablation tests on probe materials, determine the safe ablation depth of a single pulse and the corresponding first reference pulse energy, and establish a step-by-step decreasing formula based on the first reference pulse energy and the first energy decay rate.

[0042] The calculation module is used to modulate the laser output energy to the first reference pulse energy, perform the first femtosecond pulse scanning etching on the probe material, measure the first actual ablation depth, and calculate the second energy decay rate based on the first actual ablation depth and the single-pulse safe ablation depth.

[0043] The etching module is used to calculate the single pulse energy of the second to the Nth channels based on the channel-by-channel reduction formula and the second energy reduction rate. After inter-channel cooling and waiting, the second to the Nth channels are sequentially scanned and etched. When the i-th channel is scanned, the single pulse energy is reduced according to the channel-by-channel reduction formula and the pulse repetition frequency is increased according to the increment coefficient, so as to complete the scanning etching of the second to the Nth channels sequentially.

[0044] A third aspect of the present invention provides a MEMS probe that performs the above-described MEMS probe laser etching method.

[0045] The technical solution provided by this invention establishes a personalized energy benchmark by measuring the material ablation threshold and determines a differentiated energy decay rate based on the material's thermal diffusivity, thus matching the energy modulation strategy with the material characteristics. Real-time verification feedback of the first ablation depth enables adaptive correction of the energy decay rate, avoiding ablation depth deviations caused by batch-to-batch material variations. An energy-frequency coordinated decay mechanism is established, progressively reducing single-pulse energy while increasing the pulse repetition frequency. This compensates for the ablation threshold drop caused by heat accumulation and maintains ablation efficiency by utilizing the enhanced light absorption of the rough surface, achieving dual optimization of peak heat load control and material removal rate. Real-time monitoring of cumulative removal depth and linear energy compensation construct a closed-loop precision control system, ensuring a high degree of consistency between the final processing depth and the design target. A dual spatial and pass-based decay modulation strategy is implemented for the probe tip conical region, adjusting the pulse energy in real-time based on the radial position coordinates. This solves the problems of tip overburning and root underburning caused by traditional single-energy scanning, overcomes the deficiency of existing technologies lacking a heat accumulation compensation mechanism, reduces the width of the heat-affected zone, precisely controls the tip curvature radius, improves surface quality, and increases the processing yield.

[0046] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of an embodiment of the MEMS probe laser etching method in this invention;

[0049] Figure 2 This is a schematic diagram of one embodiment of the MEMS probe laser etching device in this invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] The terms "comprising" and "having," and any variations thereof, used in the embodiments of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0052] To facilitate understanding of this embodiment, a detailed description of a MEMS probe laser etching method disclosed in this embodiment of the invention will be provided first. For example... Figure 1 As shown, this method includes the following steps:

[0053] Step 101: Perform a single-pulse ablation test on the probe material, determine the safe ablation depth of the single pulse and the corresponding first reference pulse energy, and establish a step-by-step reduction formula based on the first reference pulse energy and the first energy reduction rate.

[0054] Specifically, a series of single-pulse ablation experiments were performed on the selected materials of the target MEMS probe. These experiments utilized a femtosecond laser to output laser pulses with a pulse width of 400 to 500 femtoseconds and a wavelength of 1064 nanometers. While maintaining a focused spot diameter of 15 to 20 micrometers, the material surface was sequentially irradiated with single-point lasers of different energy levels by modulating the pulse energy. The depth of the ablation pits generated after each laser irradiation was obtained using a laser confocal microscope or scanning electron microscope, collecting data points containing multiple energy-depth correspondences. Based on these data points, a fitting curve or interpolation function between the femtosecond pulse energy and the corresponding ablation depth was constructed as the energy-depth calibration curve for the probe material. Furthermore, the energy density threshold corresponding to the appearance of a clear ablation initiation phenomenon was identified, yielding the material's ablation threshold energy density. Under the known calibration curve, the single-pulse energy was further reduced and the ablation experiment was repeated. After each ablation, heat-affected zone detection methods (such as microscopic thermal reflection observation or nanothermal analysis) were used to determine whether there were obvious signs of thermal diffusion. When the boundary of the ablation area was clear and no melting recasting or microcracks were observed, the ablation depth corresponding to this set of laser parameters was identified as the safe ablation depth for a single pulse. The pulse energy used could be determined by reverse verification from the calibration curve and used as the reference pulse energy for the first pass. Combining the total removal depth parameter required for MEMS probe design, the minimum number of scan passes theoretically required to meet the structural processing requirements was obtained by dividing the total depth by the safe ablation depth for a single pulse. A decreasing model for controlling the energy of each scan pass was established, i.e., the single-pulse energy E of the i-th pass. i It equals the first reference pulse energy E1 multiplied by [1 minus (i minus 1) multiplied by the first energy decay rate K], i.e., E i=E1×[1–(i–1)×K], constructing a pass-by-pass decreasing energy modulation strategy that adapts to different passes, ensures thermal balance, and controls the stability of ablation depth.

[0055] Step 102: Modulate the laser output energy to the first reference pulse energy, perform the first femtosecond pulse scanning etching on the probe material, measure the actual ablation depth of the first pass, and calculate the second energy decay rate based on the actual ablation depth of the first pass and the single-pulse safe ablation depth.

[0056] Specifically, the output pulse energy of the femtosecond laser is modulated to the first reference pulse energy value obtained through pre-experimentation. This first reference pulse energy is the energy corresponding to the ablation depth that precisely reaches the safe ablation depth per pulse, ensuring effective removal while avoiding the expansion of the heat-affected zone. Simultaneously, the laser pulse repetition frequency is set to a first frequency value, such as 200 to 300 kHz, to match the requirements of processing efficiency and pulse overlap rate. An appropriate scanning path is selected based on the probe type; for example, a unidirectional grating scanning path perpendicular to the long axis of the beam is used for cantilever beam probes, while a spiral progressive scanning path is used for tapered probe tips, thus completing the first etching task. After the first etching is completed, a high-precision non-contact measuring device such as a laser displacement sensor or laser confocal microscope is used to perform three-dimensional measurement of the etched trench, obtaining the actual ablation depth d1 corresponding to the first etching. The difference between the actual ablation depth and the single-pulse safe ablation depth d0 determined in the previous experiment is calculated to obtain the depth deviation value (d1–d0). The depth deviation value is then divided by d0 to obtain the standardized depth deviation rate δ1, i.e., δ1=(d1–d0) / d0, which quantifies the deviation between the first etching effect and the theoretical expectation. If the absolute value of the depth deviation rate exceeds the preset deviation threshold (e.g., ±15%), it indicates that the first energy decay rate K has not fully compensated for the heat conduction or heat accumulation effect of the material after energy absorption. K is adjusted to improve the accuracy of subsequent etching passes. The depth deviation rate δ1 is multiplied by a preset correction coefficient η, for example, 0.01, to obtain the decay rate adjustment amount ΔK used for correction, i.e., ΔK=η×δ1. The decay rate adjustment amount is then added to the original first energy decay rate K to obtain a new second energy decay rate K′=K+ΔK, which is used to update the energy decay formula in the subsequent etching process, forming an adaptive energy control strategy.

[0057] Step 103: Calculate the single pulse energy of channels 2 to N based on the channel-by-channel reduction formula and the second energy reduction rate. After cooling and waiting between channels, perform scanning etching of channels 2 to N in sequence. When performing scanning of channel i, reduce the single pulse energy according to the channel-by-channel reduction formula and increase the pulse repetition frequency according to the increment coefficient. Complete scanning etching of channels 2 to N in sequence.

[0058] Specifically, after determining the first etching pass and the second energy decay rate, the modified energy decay rate K′ is substituted into the pass-by-pass decay formula E. i = E1 × [1 – (i–1) × K′], calculate the single-pulse energy required for each channel from channel 2 to channel N, and obtain the multi-channel energy sequence {E2, E3, ..., E n After the first etching pass is completed, to prevent heat accumulation from interfering with the etching effect of subsequent passes, an inter-pass cooling management mechanism is introduced. Specifically, the required cooling time interval is determined based on the thickness characteristics of the probe structure. When the probe thickness is less than a first thickness threshold (e.g., 30 μm), the cooling time Δt is selected within a first time interval (e.g., 80–120 ms). When the probe thickness is greater than the first thickness threshold, the cooling time is selected within a second time interval (e.g., 150–200 ms) to ensure that residual heat from the previous pass is fully dissipated and the material surface temperature drops below a set safe value. After each inter-pass cooling wait, the i-th etching preparation stage begins, and the single-pulse target energy E of the i-th pass is extracted based on the energy sequence. i The single-pulse target energy is modulated to the laser output via an acousto-optic modulator or an electro-optic modulator, achieving quantitative control of the laser power. Simultaneously, in conjunction with an energy reduction mechanism, the laser pulse repetition frequency is sequentially increased from the initial first frequency value f1 to the i-th frequency value f1 by an increment factor r (e.g., 1.2). i That is, f i = f1× r^(i–1), to increase the number of pulses per unit time, thereby compensating for the decrease in total energy density caused by the reduction in single pulse energy; to maintain a stable pulse overlap rate, the scanning speed v i Maintain the same incremental ratio as the frequency adjustment, i.e., v i = v1×r^(i–1), which ensures the continuity of the processing trajectory while maintaining the uniformity of energy coverage in the processing area. By completing energy extraction, frequency modulation, and cooling before the i-th scan, and continuing this process from the 2nd to the Nth scan, a femtosecond laser multi-channel scanning etching process with coordinated control of energy decrease and frequency increase, controllable heat distribution, and continuous trajectory optimization is formed.

[0059] In one specific embodiment, the process of performing step 101 may specifically include the following steps:

[0060] Single-pulse ablation tests with different energies were conducted on the probe material, and multiple sets of ablation depth data were measured.

[0061] A calibration curve of pulse energy versus ablation depth was established based on multiple sets of ablation depth data, and the ablation threshold energy density of the probe material was determined through the calibration curve.

[0062] The single-pulse energy was gradually reduced to conduct a test burn experiment. The maximum depth that a single pulse could remove was determined under the condition that no observable heat-affected zone was generated in the ablation area. This value was taken as the safe ablation depth of a single pulse. The pulse energy value that made the ablation depth reach the safe ablation depth of a single pulse was found according to the calibration curve and used as the first reference pulse energy.

[0063] The number of scans is calculated based on the total probe removal depth and the single-pulse safe ablation depth. A formula is established to decrease the single-pulse energy of the i-th track by multiplying the energy of the first track reference pulse by one minus i minus 1 multiplied by the first energy decay rate.

[0064] Specifically, a systematic single-pulse ablation experiment was conducted on the target probe material using a femtosecond laser system. The single-pulse ablation experiment employed laser pulses with a pulse width of 400 to 500 femtoseconds and a wavelength of 1064 nanometers. A high-precision energy controller progressively adjusted the single-pulse energy output within a certain range, for example, continuously varying it in a set step size from 0.5 microjoules to 3 microjoules. Single-point laser irradiation was applied to each set energy point, and the focused spot diameter was maintained between 15 and 20 micrometers in a highly stable environment. After each single-pulse irradiation, the nanometer-scale depth of the ablation pit was measured using a laser confocal microscope, scanning electron microscope, or atomic force microscope to obtain the ablation depth data at the corresponding energy. After processing and organizing the obtained pulse energy and ablation depth data, a nonlinear regression model, such as an exponential or logarithmic curve, was used to fit the data and construct a calibration function relationship between pulse energy and ablation depth. From this calibration function, the minimum energy density required for the laser pulse to just produce ablation signs on the material surface was derived; this is the material's ablation threshold energy density, defined as the minimum effective energy flux per unit area, for example, 0.8 to 1.2 joules per square centimeter for nickel-cobalt alloys. Single-pulse ablation experiments were then conducted again under gradually decreasing energy conditions, focusing on observing the thermal effects of the ablation region at different energies. Microstructural images were used to determine whether obvious melting zones, hot recasting zones, or microcracks appeared, until the maximum removal depth achievable without any observable thermally affected area at the edge of the ablation region was determined. This depth is defined as the single-pulse safe ablation depth, such as 0.8 micrometers or 1.0 micrometers. Combined with the established energy-depth calibration curve, the pulse energy value corresponding to this single-pulse safe ablation depth was found and set as the first reference pulse energy, serving as the starting point for multi-pass etching energy control. Based on the total removal depth required by the MEMS probe microstructure design, such as 20 to 50 micrometers, the minimum number of scan passes (N=D / d0) is calculated by dividing the total depth by the safe ablation depth, thus yielding the minimum number of energy applications required. To effectively mitigate heat accumulation and precisely control the ablation depth differences between passes, an energy decay control mechanism is introduced. This involves defining a first energy decay rate K and establishing a formula for calculating the pulse energy E that decreases sequentially across each pass. i= E1× [1 – (i –1) × K], where E1 is the reference pulse energy of the first pass, i is the current pass number, and the single pulse energy gradually decreases during each etching pass. At the same time, the enhanced light absorption rate of the material surface and the reduced thermal threshold effect during the previous processing are considered. The thermal compensation and depth accuracy of the subsequent ablation behavior are achieved by the decreasing energy configuration.

[0065] In one specific embodiment, the process of calculating the number of scan tracks based on the total probe removal depth and the single-pulse safe ablation depth, and establishing a track-by-track decreasing formula for the single-pulse energy of the i-th track by multiplying the energy of the first track reference pulse by one minus i minus 1 multiplied by the first energy decay rate, can specifically include the following steps:

[0066] The theoretical number of passes is calculated by dividing the total probe removal depth by the single-pulse safe ablation depth.

[0067] Multiply the theoretical number of traces by a preset coefficient and round up to obtain the actual number of traces N;

[0068] When the thermal diffusivity of the probe material is the first thermal diffusivity, the first energy decay rate is selected within the first value range; when the thermal diffusivity of the probe material is the second thermal diffusivity, the first energy decay rate is selected within the second value range.

[0069] Establish a formula for the decreasing energy of the i-th single pulse, which is equal to the energy of the first reference pulse multiplied by one minus i minus 1 multiplied by the first energy decrease rate.

[0070] Specifically, the total probe removal depth D is extracted based on the known dimensions of the target structure. Combined with the single-pulse safe ablation depth d0 determined in previous single-pulse ablation experiments, D is divided by d0 to obtain the minimum number of passes N0 theoretically required to meet the target total depth, i.e., N0 = D / d0. The minimum number of passes represents the ideal number of passes without considering the effects of heat accumulation. Considering the interference of residual heat from previous passes on the ablation efficiency of subsequent passes during femtosecond laser etching, and to provide sufficient control margin for introducing energy decay modulation, the theoretical number of passes is extended and corrected by multiplying N0 by a preset pass redundancy coefficient η, for example, set to 1.5, and rounding the product up to obtain the actual number of scan passes N required for processing, i.e., N = ceil(η × N0). Based on the thermal diffusivity parameters of different probe materials, an appropriate energy decay rate range is selected for parameter configuration: when the target material is a metal with a low thermal diffusivity, such as a nickel-cobalt alloy, the thermal diffusivity α is the first thermal diffusivity, approximately 20 mm. 2 When the value is / s, the first energy decay rate K1 should be selected within the first value range, which is 0.06 to 0.08; while when the probe material is a tungsten-based material with a high thermal diffusivity, α is approximately 60mm. 2If the value is / s, then a first energy decay rate K2 is selected within the lower second value range, approximately 0.04 to 0.05, to match its strong thermal diffusion capability and laser ablation response behavior. After determining the first reference pulse energy E1 and the material-adapted energy decay rate K, a pass-by-pass decay control model for the single pulse energy of each pass is established. The pulse energy E1 used for the i-th etching pass is... i Calculated according to a unified formula, i.e., E i = E1×[1 – (i – 1) × K], where i is the pass number and K is the selected energy decay rate. The energy control strategy combines material properties to adjust the energy decay rate, so that the single pulse energy continuously decreases as the pass progresses, adapting to the heat accumulation effect caused by the previous etching and the increasing trend of surface absorbance, and effectively controlling the expansion of the heat-affected zone and the linear controllability of the etching depth.

[0071] In one specific embodiment, the process of performing step 102 may specifically include the following steps:

[0072] The laser output energy is modulated to the first reference pulse energy, the pulse repetition frequency is set to the first frequency value, and the first scanning etching is performed on the probe material according to the preset scanning path.

[0073] The ablation grooves formed by the first scan were measured to obtain the actual ablation depth of the first scan.

[0074] The depth deviation rate is calculated by subtracting the actual ablation depth from the single-pulse safe ablation depth and dividing by the single-pulse safe ablation depth. When the absolute value of the depth deviation rate exceeds the preset deviation threshold, the depth deviation rate is multiplied by the preset correction coefficient to obtain the adjustment amount of the first energy decay rate.

[0075] Add the first energy decay rate to the adjustment amount to obtain the second energy decay rate.

[0076] Specifically, control the output energy of the femtosecond laser to the first benchmark pulse energy E1 determined in the preliminary test. This energy value is obtained by looking up the calibration curve in the single-pulse test burn and is exactly the optimal energy level corresponding to the maximum safe ablation depth without thermal influence. Set the pulse repetition frequency of the laser to the first frequency value f1, and select a value within the range of 200 kHz to 300 kHz to apply an appropriate amount of energy per unit time and satisfy the matching relationship between the scanning speed and the pulse overlap rate. Select a suitable scanning path according to the probe structure characteristics. For the cantilever beam structure, use a linear grating scanning method perpendicular to the beam long axis. For the conical tip region, a spiral progressive scanning path is more suitable to ensure a high adaptability of the scanning trajectory to the microstructure topography. Start the first etching scanning process with this parameter configuration. Immediately after completion, use a non-contact three-dimensional topography measurement device such as a laser confocal microscope, a white light interferometer, or a scanning electron microscope to perform high-resolution measurement on the etched groove, extract the groove depth d1 actually formed in the first scan, and compare it with the single-pulse safe ablation depth d0 known from the preliminary test. Calculate the relative deviation value between the two, that is, the depth deviation rate δ1 = (d1 – d0) / d0, to quantify the relative offset degree between the actual etching behavior and the ideal etching behavior. If the absolute value of the depth deviation rate exceeds the preset deviation threshold ε, set to ±15%, it means that the current used energy reduction rate K per channel has deficiencies or redundancies in predicting the subsequent multi-channel etching behavior, and perform adaptive correction based on the feedback. The correction operation is to multiply the depth deviation rate δ1 by a preset correction coefficient λ, and the value range of the correction coefficient is set between 0.005 and 0.02 to balance the adjustment amplitude and the stability of the system response, and obtain the adjustment amount ΔK of the first energy reduction rate, that is, ΔK = λ × δ1. Add the adjustment amount ΔK to the originally set first energy reduction rate K to obtain the updated second energy reduction rate K′ = K + ΔK, and re-import the K′ value as the core energy control parameter for the second to the Nth etching processes into the step-by-step reduction formula E i = E1× [1 – (i–1) × K′].

[0077] In a specific embodiment, the process of executing step 103 may specifically include the following steps:

[0078] Substitute the second energy reduction rate into the step-by-step reduction formula to calculate the single-pulse energy of each pass from the second to the Nth pass, and obtain the energy sequence of each pass;

[0079] When the probe thickness is less than the first thickness threshold, select the inter-pass cooling time within the first time interval. When the probe thickness is greater than the first thickness threshold, select the inter-pass cooling time within the second time interval;

[0080] Before the start of the i-th scan, an inter-channel cooling time is performed. The single pulse energy of the i-th channel is extracted from the energy sequence of each channel and modulated to the laser output terminal. At the same time, the pulse repetition frequency is increased from the first frequency value to the i-th channel frequency value by an increment factor. The scanning speed is adjusted synchronously by the same increment factor. The scanning etching of the 2nd to Nth channels is completed in sequence.

[0081] Specifically, the second energy decay rate K′ obtained from the first feedback correction will be substituted into the successive decay control formula E. i = E1 × [1 – (i – 1) × K′], where E1 is the first reference pulse energy, i is the current track number, and the single pulse energy of each track from track 2 to track N is calculated continuously to construct the track energy sequence {E2, E3, ..., E n To effectively suppress excessive thermal diffusion and ablation threshold fluctuations caused by surface temperature rise under continuous laser irradiation, an inter-channel cooling time Δt needs to be allocated between each scan. The parameter is selected based on the thickness characteristics of the probe structure to be processed. When the probe thickness is less than the first thickness threshold h0, for example, 30 micrometers, Δt is selected within the first cooling time interval, typically ranging from 80 to 120 milliseconds, to meet the requirements of a fast scanning rhythm and adequate thermal buffering. When the probe thickness is greater than h0, Δt is selected within the second cooling time interval, for example, 150 to 200 milliseconds, to provide a more sufficient heat dissipation process for thicker materials, avoiding microcracks or overheating caused by localized heat accumulation. Before entering each etching pass, a cooling time waiting operation is performed to ensure that the material surface temperature drops to a safe range. Then, the single-pulse energy Ei corresponding to the i-th pass is extracted from the generated energy sequence and modulated to the laser output end through a high-speed response acousto-optic modulator or electro-optic modulation module to achieve high-fidelity power application. Simultaneously, to enhance etching efficiency and maintain pulse coverage uniformity, the laser pulse repetition frequency and scanning speed are synchronously adjusted. The reference frequency value f1 used in the first pass is iteratively superimposed according to a preset increment coefficient r, that is, the frequency of the i-th pass is set to f1. i = f1 × [1 + (i – 1) × r], where r is selected as a scaling factor between 0.2 and 0.3 to match the increase in pulse density per unit time due to frequency increase with the enhanced etching capability. To maintain a fixed pulse overlap rate and spatial energy deposition uniformity, the scan speed v i With frequency f i Maintain the same increment coefficient, i.e., v i= v1× [1 + (i – 1) × r], where v1 is the scanning speed set for the first pass. By linking and controlling the laser energy, pulse frequency and scanning speed, and cooperating with the inter-pass cooling strategy, the etching operations of the second to Nth passes are completed sequentially. This effectively achieves dynamic compensation for thermal diffusion effects during multi-pass femtosecond laser etching, feedforward adjustment of ablation depth error, and adaptive control of the material microstructure response characteristics.

[0082] In one specific embodiment, the execution steps include waiting for inter-channel cooling time before the start of the i-th scan, extracting the single-pulse energy of the i-th channel from the energy sequence of each channel and modulating it to the laser output terminal, simultaneously increasing the pulse repetition frequency from a first frequency value to the i-th channel frequency value by an increment factor, and synchronously adjusting the scan speed by the same increment factor to complete the scanning etching process of the 2nd to Nth channels in sequence. The specific steps include the following:

[0083] Before the start of the i-th scan, an inter-channel cooling time is performed to allow the probe material surface temperature to drop from the peak temperature of the previous scan to below a preset safe temperature threshold.

[0084] Extract the i-th single pulse energy from each energy sequence and modulate it to the laser output terminal using an acousto-optic modulator. Calculate 1 plus 0.2 multiplied by i minus 1 to obtain the increment coefficient. Multiply the first frequency value by the increment coefficient to obtain the i-th frequency value and set the pulse repetition frequency.

[0085] The scanning speed of the first pass is multiplied by an increment factor to calculate the scanning speed of the i-th pass. The i-th scan etching is performed on the probe material according to the i-th scan speed and the preset scan path. The scanning etching of the second to the Nth passes is completed in sequence.

[0086] Specifically, before each i-th etching pass, the probe material surface undergoes thermal recovery processing, i.e., an inter-pass cooling time waiting operation is performed. Based on the peak surface temperature of the material after the previous scan, the material is allowed to cool naturally at a set time interval Δt, gradually reducing its surface temperature to below a preset safe temperature threshold, such as below 350K. This effectively avoids localized thermal damage or structural distortion caused by heat accumulation due to continuous pulse action. After cooling, the single-pulse energy E corresponding to the i-th pass is extracted from the pass energy sequence established in advance based on the second energy decay rate K′. iThe single-pulse energy value is loaded into the laser output system via an acousto-optic modulator to ensure that the laser incident energy is highly consistent with the target pass design parameters. A synchronization increment factor R1 for frequency and speed is calculated based on the current pass number i, specifically R1 = 1 + 0.2 × (i – 1). This increment factor is used to synchronously control the laser pulse repetition frequency and scanning displacement speed, enabling dynamic improvement in processing efficiency while maintaining the same pulse overlap rate and heat input uniformity. Based on the increment factor, the pulse repetition frequency f1 used in the first pass is multiplied by R1 to obtain the required frequency value f for the i-th pass. i = f1 × R1, and immediately load the frequency value into the laser control system to adjust the pulse trigger rate; at the same time, in order to maintain a constant pulse density per unit length, multiply the scanning speed v1 used in the first pass by the same increment coefficient R1 to obtain the scanning speed v of the i-th pass. i = v1×R1, and update the displacement command of the motion control module accordingly. After completing the bidirectional update of frequency and speed, the probe material surface is etched by femtosecond laser scanning under the control parameters of the i-th channel according to the preset scanning path in the system, until the etching of that channel is completed. The entire process continues from the 2nd channel to the Nth channel, and each channel follows the control chain of "thermal recovery - energy extraction - frequency adjustment - speed synchronization - trajectory execution".

[0087] In one specific embodiment, the MEMS probe laser etching method further includes the following steps:

[0088] The ablation trench formed by the i-th scan is measured to obtain the actual removal depth of the i-th scan. The actual removal depths of each scan from the 1st scan to the i-th scan are summed to obtain the cumulative removal depth.

[0089] Multiply the total probe removal depth by i and divide by the actual number of scans N to calculate the target progress depth. Subtract the target progress depth from the cumulative removal depth to calculate the depth deviation.

[0090] When the absolute value of the depth deviation exceeds the preset depth deviation threshold, the depth deviation is multiplied by the energy of the first reference pulse and then divided by the product of the theoretical number of passes and the safe ablation depth of a single pulse to calculate the energy compensation amount. The energy compensation amount is then added to the single pulse energy corresponding to each pass from the i+1th to the Nth pass in the energy sequence of each pass.

[0091] Specifically, after the i-th laser scanning etching is completed, the ablation trench formed by the i-th layer is measured. The longitudinal depth information of the etched area is extracted using non-contact high-resolution measurement equipment such as a laser confocal microscope, a three-dimensional white light interferometer, or a laser displacement sensor, to obtain the actual removal depth d of the i-th layer. iThe actual removal depth is recorded in the system as the true processing depth parameter for the current pass. From pass 1 to pass i, the actual removal depth of each pass is accumulated sequentially to calculate the cumulative removal depth, which represents the actual processing progress under the current etching condition. Based on the total probe removal depth Dtotal and the actual number of scan passes N given in the design requirements, the target progress depth Dtarget that should theoretically be achieved when performing the i-th scan is calculated. The formula is Dtarget = Dtotal × i / N. By comparing this target progress depth with the currently measured cumulative removal depth, the current processing depth deviation is calculated, reflecting the deviation of the actual etching progress from the theoretical progress. When the absolute value of the deviation exceeds the set depth deviation tolerance threshold ε, for example, 2 micrometers, it indicates that there is a significant under-etching or over-etching problem under the existing etching path. Therefore, a feedforward correction is performed on the subsequent energy allocation. Multiply the depth deviation ΔD by the initial reference pulse energy E1 and divide by the product of the theoretical number of passes N0 and the single-pulse safe ablation depth d0, i.e., ΔE = ΔD × E1 / (N0 × d0), to calculate an energy compensation amount ΔE, which is used to uniformly increase or decrease the single-pulse energy of each pass from the (i+1)th pass to the Nth pass. In actual implementation, ΔE is directly superimposed on the single-pulse energy E corresponding to each pass starting from the (i+1)th pass in the pass energy sequence. i ′, that is, execute E i ′ = E i + ΔE ensures that the energy applied in each subsequent etching process has the ability to compensate.

[0092] In one specific embodiment, the MEMS probe laser etching method further includes the following steps:

[0093] Energy spatial modulation rules are established based on the radial coordinate range of the tip cone region in the probe material. When the diameter corresponding to the radial coordinate of the scanning spot is less than the first diameter threshold, the energy coefficient takes the first coefficient value. When the corresponding diameter is between the first diameter threshold and the second diameter threshold, the energy coefficient takes the second coefficient value. When the corresponding diameter is greater than the second diameter threshold, the energy coefficient takes the third coefficient value.

[0094] Set the spiral scanning path parameters for the tip conical region, add the preset extension value to the probe tip design radius as the spiral starting radius, set the pitch as the first pitch value, and calculate the number of spiral turns by dividing the probe conical height by the first pitch value.

[0095] During the i-th scan, the radial coordinates of the scanning spot are obtained in real time through the scanning system. The energy of the i-th single pulse is multiplied by the energy coefficient corresponding to the radial coordinate to obtain the real-time modulation energy. The energy of the laser output end is modulated to the real-time modulation energy, and the scanning etching of the first to Nth channels is completed on the needle tip conical region according to the spiral scanning path parameters.

[0096] Specifically, an energy spatial modulation rule based on the radial position of the scanning spot is established. The rule divides the conical region into multiple energy adjustment segments based on different radial ranges. The entire tip cross-section is divided into segments using two levels of radial thresholds D1 and D2. When the diameter corresponding to the radial coordinate of the scanning spot is less than the first diameter threshold D1, it indicates that the spot is in the region near the tip. This region is the most concentrated in terms of heat and has the most sensitive structure, so a lower energy coefficient C1 (e.g., 0.7) is used to avoid excessive ablation or melting collapse of the tip. When the diameter corresponding to the radial coordinate is between the first diameter threshold D1 and the second diameter threshold D2, it indicates that the spot is in the middle transition zone, where the material structure is gradually stabilizing, and the energy coefficient is set to a medium value C2 (e.g., 0.85). When the diameter corresponding to the radial coordinate is greater than the second diameter threshold D2, it indicates that the spot is in the root connection region of the tip cone, which can withstand higher laser power. Therefore, the energy coefficient is set to C3 (e.g., 1.0). Through the multi-segment energy factor division strategy, the energy exhibits a spatially progressive change along the radial direction. The spiral scanning path parameters for the conical region are set by adding a certain extrapolation value ΔR (e.g., 10 μm) to the theoretical radius R0 of the probe tip as the starting radius of the spiral path, causing the scan to gradually converge from the periphery of the conical region towards the center. Simultaneously, a first pitch value P (e.g., 8–12 μm) is set as the radial spacing between each spiral path turn, and the entire conical height H is divided by P to calculate the number of spiral turns required, thus completing the definition of the scanning path structure. During the actual execution of the i-th scanning etching process, the radial coordinate r of the current laser focus is obtained in real time through the integrated spot control and feedback module. This radial coordinate is then mapped to the corresponding diameter value d = 2r, and the energy coefficient C(d) corresponding to the current radial position is matched according to the energy modulation rules described above. The energy coefficient is then compared with the predetermined single-pulse reference energy E for the i-th etching pass. i Multiply by each other to calculate the real-time modulation energy E′=E at the current spot position. i ×C(d), and then the energy at the laser output end is dynamically modulated to E′ by a high-speed acousto-optic modulator to ensure that the actual energy applied at each pulse matches the local structural sensitivity and thermal load-bearing capacity of the material. The laser spot is gradually advanced radially in the conical region according to the preset spiral path, and in conjunction with the energy modulation process, scanning and etching operations are performed cyclically from the first to the Nth pass to achieve full radial hierarchical processing control of the conical region structure of the probe tip, so that the tip curvature is maintained within the ideal range, the surface roughness is uniformly reduced, and the heat-affected zone is controlled within a minimum range.

[0097] The MEMS probe laser etching method further includes: during the i-th scan etching process, a photodetector is used to collect the plasma light emission signal generated in the ablation region, and the plasma light emission signal is analyzed in real time to obtain the plasma emission intensity sequence of the current channel; the plasma emission intensity sequence of the current channel is compared point by point with the pre-established plasma intensity baseline value under normal ablation conditions, and when the intensity value of any sampling point in the plasma emission intensity sequence of the current channel exceeds a preset multiple threshold of the plasma intensity baseline value, it is determined that excessive ablation or local phase transition of the material has occurred at that location, and the coordinate information of that location is recorded; the spatial range of the abnormal ablation region is determined according to the coordinate information, and the single pulse energy of the subsequent scan path of the abnormal ablation region is immediately reduced to a preset energy reduction ratio of the current channel set energy through an acousto-optic modulator, and the inter-channel cooling time after the end of the current channel scan is extended to a preset time extension multiple of the original set cooling time; in the next scan, the reduced single pulse energy is used to continue scanning for the abnormal ablation region, and the normal energy value calculated according to the step-by-step reduction formula is restored for the non-abnormal region, so as to realize the differentiated energy distribution of the ablation region.

[0098] The scanning speed of the i-th channel is calculated by multiplying the scanning speed of the first channel by an increment factor. This includes: calculating the unit energy removal efficiency of the i-th channel based on the actual removal depth and single pulse energy of that channel; comparing the unit energy removal efficiency with a preset standard removal efficiency to obtain a removal efficiency deviation coefficient; and correcting the target pulse overlap rate of the i-th channel when the absolute value of the removal efficiency deviation coefficient exceeds a preset efficiency threshold by multiplying the preset overlap rate by a correction factor equal to the removal efficiency deviation coefficient to obtain the corrected overlap rate of the i-th channel. The scanning speed of the i-th channel is calculated based on the frequency value of the i-th channel, the diameter of the focused spot, and the corrected overlap ratio of the i-th channel. The calculation formula is: the scanning speed of the i-th channel equals the frequency value of the i-th channel multiplied by the diameter of the focused spot multiplied by one minus the corrected overlap ratio of the i-th channel. The i-th channel scanning etching is performed using the i-th channel scanning speed, so that the pulse overlap density is dynamically adjusted according to the actual ablation efficiency. When the ablation efficiency is higher than the standard value, the overlap ratio is reduced and the scanning speed is increased. When the ablation efficiency is lower than the standard value, the overlap ratio is increased and the scanning speed is reduced, so as to ensure the stability of the cumulative energy deposition per unit area.

[0099] After completing the first to Nth scanning etching passes of the tip-conical region according to the helical scanning path parameters, the process also includes: performing three-dimensional morphological measurements of the probe tip after the Nth scan using a scanning electron microscope, extracting the measured values ​​of the tip curvature radius and surface roughness, comparing the measured value of the tip curvature radius with the designed target curvature radius to obtain the curvature radius deviation, and comparing the measured value of the surface roughness with the designed target roughness to obtain the roughness deviation; when the curvature radius deviation exceeds the preset curvature radius tolerance, the tip geometry refinement mode is activated, reducing the femtosecond laser pulse energy to the refinement energy value and increasing the pulse repetition frequency to the refinement frequency value, identifying areas where the measured value of the tip curvature radius is greater than the designed target curvature radius. In this domain, only large areas undergo a polishing scan with a fine-tuning scanning path. This process corrects the curvature radius deviation by cumulatively removing trace amounts of surface layer. When the roughness deviation exceeds the preset roughness tolerance, a surface polishing mode is activated. The femtosecond laser pulse energy is reduced to the polishing energy value, and the pulse repetition frequency is increased to the polishing frequency value. An ultra-low energy scan is performed on the entire surface of the probe tip. The cold ablation effect of the femtosecond laser selectively evaporates the surface protrusions and microstructures without melting and recasting, reducing the measured surface roughness value to within the design target roughness range. The morphology of the finely tuned or polished probe tip is measured again to verify that the measured values ​​of the tip curvature radius and surface roughness meet the design tolerance requirements, thus completing the closed-loop verification of the probe's quality.

[0100] During the i-th scan etching process, the procedure also includes plasma light emission monitoring and emergency energy control steps: A photodetector is used to collect the plasma light emission signal generated in the ablation region during the i-th scan, obtaining the real-time value of the plasma emission intensity at the current scan position; based on the plasma emission intensity data of the previous normal ablation passes, a plasma intensity baseline value is calculated, which is the average value of the plasma emission intensity of the previous normal ablation passes; the real-time plasma emission intensity value is compared with the plasma intensity baseline value. When the real-time plasma emission intensity value exceeds the plasma intensity baseline value multiplied by a preset intensity multiple, it is determined that excessive ablation or local phase transition of the material has occurred in the ablation region; immediately, the single-pulse energy of the subsequent region at the current scan position of the i-th pass is reduced to the original set energy of the i-th pass multiplied by an emergency reduction coefficient, with the emergency reduction coefficient ranging from 0.7 to 0.85; simultaneously, the inter-pass cooling time after the i-th scan is extended to the original cooling time multiplied by an extension factor, with the extension factor ranging from 1.3 to 1.6, thus completing the emergency suppression of excessive ablation.

[0101] Before performing the first scanning etching on the probe material according to the preset scanning path, the process includes an adaptive selection of the scanning path and precise matching of the scanning speed: The scanning path mode is determined based on the probe structure type. When the probe is a cantilever beam structure, a unidirectional grating scanning path is selected; when the probe is a tapered tip structure, a spiral progressive scanning path is selected. The scanning direction of the unidirectional grating scanning path is perpendicular to the long axis of the cantilever beam. For the unidirectional grating scanning path, the scanning line spacing is set to the focused spot diameter multiplied by the line spacing coefficient, with the coefficient ranging from 0.3 to 0.5. The total number of scanning lines is calculated as the cantilever beam width divided by the scanning line spacing. For the spiral progressive scanning path… The spiral starting radius is set to the outer contour radius of the needle tip plus the spiral extension distance. The spiral pitch is set to the diameter of the focused spot multiplied by the pitch coefficient, with the pitch coefficient ranging from 0.4 to 0.6. The first scan speed is calculated based on the first frequency value, the diameter of the focused spot, and the preset pulse overlap rate. The first scan speed is equal to the first frequency value multiplied by the diameter of the focused spot multiplied by one minus the preset pulse overlap rate, with the preset pulse overlap rate ranging from 0.5 to 0.7. The scan path mode, path parameters, and the first scan speed are input into the scan control system to generate the first complete scan trajectory file. The first scan etching is performed according to the complete scan trajectory file.

[0102] After completing the first to Nth scanning etching passes, the process includes a closed-loop verification and fine-tuning compensation step: The probe tip after the Nth scan is measured in three dimensions using a scanning electron microscope to obtain the actual radius of curvature and surface roughness. The actual radius of curvature is compared with the designed target radius of curvature to calculate the deviation. When the deviation exceeds the preset curvature tolerance, the tip radius fine-tuning mode is activated. In this mode, the pulse energy is set to the fine-tuning energy value, which is 0.2 to 0.35 times the reference pulse energy of the first pass. The pulse repetition frequency is set to the fine-tuning frequency value, which is 2.5 to 3.5 times the first frequency value, maintaining precision... With the repair energy and fine-tuning frequency values ​​kept constant, only the tip deviation area corresponding to the curvature radius deviation value is subjected to 2 to 4 polishing scans, and the cumulative removal depth of each polishing scan is controlled within the range of 50 to 200 nanometers. After the tip radius fine-tuning mode is completed, the surface roughness is measured again. When the measured surface roughness is greater than the preset roughness threshold, the pulse energy is further reduced to 0.1 to 0.15 times the energy of the first reference pulse, and the pulse repetition frequency is increased to 4 to 5 times the first frequency value. An ultra-low energy polishing scan is performed on the probe surface, and the surface protrusions are selectively removed by the femtosecond laser cold ablation effect, reducing the measured surface roughness to below the preset roughness threshold, thus completing the probe quality closed-loop verification and fine-tuning compensation.

[0103] Before substituting the second energy decay rate into the pass-by-pass decay formula to calculate the single-pulse energy of each pass from the 2nd to the Nth pass, a multi-pass parameter co-optimization step based on thermal accumulation dynamic prediction is also included: establishing a multi-pass scanning thermal accumulation dynamic prediction model, calculating the predicted residual temperature of the probe material surface at the end of the i-th pass scan based on the actual ablation depth of the first pass scan and the thermal diffusivity of the probe material, the predicted residual temperature is equal to the ambient temperature plus the peak temperature rise of the first pass multiplied by the thermal accumulation decay coefficient raised to the power of i minus 1, the thermal accumulation decay coefficient being determined based on the inter-pass cooling time and the thermal diffusivity of the probe material, when... When the thermal diffusivity is the first thermal diffusivity, the thermal accumulation attenuation coefficient is selected within the first attenuation interval; when the thermal diffusivity is the second thermal diffusivity, the thermal accumulation attenuation coefficient is selected within the second attenuation interval. The multi-pass scanning parameter optimization problem is decomposed into an energy allocation sub-problem within each pass and a cooling scheduling sub-problem between passes. The energy allocation sub-problem within each pass aims to minimize the width of the heat-affected zone in a single pass, with the constraint that the ablation depth in a single pass must reach the target depth. The cooling scheduling sub-problem between passes aims to minimize the total processing time, with the constraint that the residual temperature between passes does not exceed the material's safe temperature. Threshold; Based on the predicted residual temperature and dynamic prediction model of heat accumulation, the optimal configuration relationship of single-pulse energy, pulse repetition frequency, and inter-track cooling time in the i-th track is derived. The optimal configuration relationship satisfies that the single-pulse energy of the i-th track is negatively correlated with the predicted residual temperature, the pulse repetition frequency is negatively correlated with the single-pulse energy of the i-th track, and the inter-track cooling time is positively correlated with the predicted residual temperature of the previous track. The second energy decay rate, the preset frequency increment coefficient, and the preset inter-track cooling time are used as initial iteration parameters. The alternating optimization algorithm is used to iteratively solve the energy allocation sub-problem within the track and the cooling scheduling sub-problem between tracks. In the k-th iteration, the optimal energy decay rate and frequency increment coefficient are solved by fixing the inter-pass cooling time. In the k+1-th iteration, the optimal inter-pass cooling time sequence is solved by fixing the energy decay rate and frequency increment coefficient. The iteration is terminated when the change in the objective function value of two consecutive iterations is less than the convergence threshold. The optimized energy decay rate, frequency increment coefficient, and cooling time sequence of each pass are output. The optimized energy decay rate is used as the corrected second energy decay rate and substituted into the pass-by-pass decay formula. The optimized frequency increment coefficient and cooling time sequence are used for the scanning etching parameter settings of the 2nd to Nth passes.

[0104] The above describes the MEMS probe laser etching method in the embodiments of the present invention. The following describes the MEMS probe laser etching apparatus in the embodiments of the present invention. Please refer to [link / reference]. Figure 2 One embodiment of the MEMS probe laser etching device in this invention includes:

[0105] A module is established to perform single-pulse ablation tests on probe materials, determine the safe ablation depth of a single pulse and the corresponding first reference pulse energy, and establish a step-by-step decreasing formula based on the first reference pulse energy and the first energy decay rate.

[0106] The calculation module is used to modulate the laser output energy to the first reference pulse energy, perform the first femtosecond pulse scanning etching on the probe material, measure the first actual ablation depth, and calculate the second energy decay rate based on the first actual ablation depth and the single-pulse safe ablation depth.

[0107] The etching module is used to calculate the single pulse energy of the second to Nth channels based on the pass-by-pass reduction formula and the second energy reduction rate. After inter-channel cooling and waiting, the second to Nth channels are sequentially scanned and etched. When the i-th channel is scanned, the single pulse energy is reduced according to the pass-by-pass reduction formula and the pulse repetition frequency is increased according to the increment coefficient, so as to complete the scan etching of the second to Nth channels sequentially.

[0108] above Figure 2 The laser etching device for MEMS probes in this embodiment of the invention will be described in detail from the perspective of modular functional entities. The MEMS probe in this embodiment of the invention will be described in detail from the perspective of hardware processing.

[0109] This invention provides a MEMS probe for implementing the steps of the above-described MEMS probe laser etching method.

[0110] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0111] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0112] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for laser etching of MEMS probes, characterized in that, include: A single-pulse ablation test is performed on the probe material to determine the safe ablation depth and the corresponding first reference pulse energy. A progressive reduction formula is established based on the first reference pulse energy and a first energy decay rate. Specifically, this includes: conducting single-pulse ablation tests on the probe material with different energies and measuring multiple sets of ablation depth data; establishing a calibration curve of pulse energy versus ablation depth based on the multiple sets of ablation depth data, and determining the ablation threshold energy density of the probe material through the calibration curve; gradually reducing the single-pulse energy to conduct a test burn, and determining the maximum depth that can be removed by a single pulse as the safe ablation depth under the condition that no observable heat-affected zone is generated in the ablation area; finding the pulse energy value that allows the ablation depth to reach the safe ablation depth based on the calibration curve, and using it as the first reference pulse energy; calculating the number of scans based on the total probe removal depth and the safe ablation depth, and establishing a progressive reduction formula for the i-th single-pulse energy by multiplying the first reference pulse energy by one minus i minus 1 multiplied by the first energy decay rate. The laser output energy is modulated to the first reference pulse energy, and a first femtosecond pulse scanning etching is performed on the probe material. The actual ablation depth of the first pass is measured, and a second energy decay rate is calculated based on the actual ablation depth of the first pass and the single-pulse safe ablation depth. Specifically, this includes: modulating the laser output energy to the first reference pulse energy, setting the pulse repetition frequency to a first frequency value, and performing a first scanning etching on the probe material according to a preset scanning path; measuring the ablation trench formed by the first scan to obtain the actual ablation depth of the first pass; calculating the depth deviation rate by dividing the difference between the actual ablation depth of the first pass and the single-pulse safe ablation depth by the single-pulse safe ablation depth; when the absolute value of the depth deviation rate exceeds a preset deviation threshold, multiplying the depth deviation rate by a preset correction coefficient to obtain the adjustment amount of the first energy decay rate; and adding the first energy decay rate and the adjustment amount to obtain the second energy decay rate. Based on the aforementioned channel-by-channel reduction formula and the second energy reduction rate, the single pulse energy of channels 2 to N is calculated. After inter-channel cooling and waiting, the scanning etching of channels 2 to N is performed sequentially. When performing the i-th channel scan, the single pulse energy is reduced according to the aforementioned channel-by-channel reduction formula, and the pulse repetition frequency is increased according to the increment coefficient. The scanning etching of channels 2 to N is completed sequentially.

2. The MEMS probe laser etching method according to claim 1, characterized in that, The calculation of the number of scan channels based on the total probe removal depth and the single-pulse safe ablation depth, and the establishment of a channel-by-channel decreasing formula for the single-pulse energy of the i-th channel by multiplying the energy of the first channel reference pulse by one minus i minus 1 multiplied by the first energy decay rate, includes: The theoretical number of passes is calculated by dividing the total probe removal depth by the single-pulse safe ablation depth. Multiply the theoretical number of traces by a preset coefficient and round up to obtain the actual number of scan traces N; When the thermal diffusivity of the probe material is the first thermal diffusivity, the first energy decay rate is selected within the first value range; when the thermal diffusivity of the probe material is the second thermal diffusivity, the first energy decay rate is selected within the second value range. Establish a formula for decreasing the energy of the i-th single pulse, which is equal to the energy of the first reference pulse multiplied by one minus i minus 1 multiplied by the first energy decay rate.

3. The MEMS probe laser etching method according to claim 1, characterized in that, The process involves calculating the single-pulse energy of channels 2 to N based on the pass-by-pass decreasing formula and the second energy decay rate. After inter-channel cooling and waiting, the scan etching of channels 2 to N is performed sequentially. During each i-th scan, the single-pulse energy is decreased according to the pass-by-pass decreasing formula, and the pulse repetition frequency is increased by an increment factor. This sequential process completes the scan etching of channels 2 to N, including: Substitute the second energy decay rate into the channel-by-channel decay formula to calculate the single pulse energy of each channel from channel 2 to channel N, and obtain the energy sequence of each channel. When the probe thickness is less than the first thickness threshold, the inter-channel cooling time is selected within the first time interval; when the probe thickness is greater than the first thickness threshold, the inter-channel cooling time is selected within the second time interval. Before the start of the i-th scan, the inter-channel cooling time is waited for. The single pulse energy of the i-th channel is extracted from the energy sequence of each channel and modulated to the laser output terminal. At the same time, the pulse repetition frequency is increased from the first frequency value to the i-th channel frequency value by an increment factor. The scanning speed is adjusted synchronously by the same increment factor. The scanning etching of the 2nd to Nth channels is completed in sequence.

4. The MEMS probe laser etching method according to claim 3, characterized in that, Before the start of the i-th scan, the inter-channel cooling time is performed, the single-pulse energy of the i-th channel is extracted from the energy sequence of each channel and modulated to the laser output terminal, and the pulse repetition frequency is increased from the first frequency value to the i-th channel frequency value by an increment factor. The scanning speed is adjusted synchronously by the same increment factor, and the scanning etching of the 2nd to Nth channels is completed sequentially, including: Before the start of the i-th scan, the inter-channel cooling time is performed to allow the probe material surface temperature to drop from the peak temperature of the previous scan to below a preset safe temperature threshold. Extract the i-th single pulse energy from each energy sequence and modulate it to the laser output terminal using an acousto-optic modulator. Calculate 1 plus 0.2 multiplied by i minus 1 to obtain the increment coefficient. Multiply the first frequency value by the increment coefficient to obtain the i-th frequency value and set the pulse repetition frequency. The scanning speed of the first scan is multiplied by the increment factor to calculate the scanning speed of the i-th scan. The i-th scan is then performed on the probe material according to the i-th scan speed and the preset scan path. The scanning etching of the second to the Nth scans is completed in sequence.

5. The MEMS probe laser etching method according to claim 4, characterized in that, The MEMS probe laser etching method further includes: The ablation trench formed by the i-th scan is measured to obtain the actual removal depth of the i-th scan. The actual removal depths of each scan from the 1st scan to the i-th scan are summed to obtain the cumulative removal depth. Multiply the total probe removal depth by i and divide by the actual number of scans N to calculate the target progress depth. Calculate the depth deviation by subtracting the target progress depth from the cumulative removal depth. When the absolute value of the depth deviation exceeds the preset depth deviation threshold, the depth deviation is multiplied by the energy of the first reference pulse and then divided by the product of the theoretical number of passes and the single-pulse safe ablation depth to calculate the energy compensation amount. The energy compensation amount is then added to the single-pulse energy corresponding to each pass from the i+1th to the Nth pass in the energy sequence of each pass.

6. The MEMS probe laser etching method according to claim 5, characterized in that, The MEMS probe laser etching method further includes: Energy spatial modulation rules are established based on the radial coordinate range of the tip cone region in the probe material. When the diameter corresponding to the radial coordinate of the scanning spot is less than the first diameter threshold, the energy coefficient takes the first coefficient value. When the corresponding diameter is between the first diameter threshold and the second diameter threshold, the energy coefficient takes the second coefficient value. When the corresponding diameter is greater than the second diameter threshold, the energy coefficient takes the third coefficient value. Set the spiral scanning path parameters for the tip conical region, add the preset extension value to the probe tip design radius as the spiral starting radius, set the pitch as the first pitch value, and calculate the number of spiral turns by dividing the probe conical height by the first pitch value. During the i-th scan, the radial coordinates of the scanning spot are obtained in real time through the scanning system. The energy of the i-th single pulse is multiplied by the energy coefficient corresponding to the radial coordinate to obtain the real-time modulation energy. The energy of the laser output end is modulated to the real-time modulation energy, and the first to Nth scan etchings are completed on the needle tip conical region according to the spiral scanning path parameters.

7. A MEMS probe laser etching apparatus, characterized in that, A method for performing MEMS probe laser etching as described in any one of claims 1-6, comprising: A module is established to perform single-pulse ablation tests on probe materials, determine the safe ablation depth of a single pulse and the corresponding first reference pulse energy, and establish a step-by-step decreasing formula based on the first reference pulse energy and the first energy decay rate. The calculation module is used to modulate the laser output energy to the first reference pulse energy, perform the first femtosecond pulse scanning etching on the probe material, measure the first actual ablation depth, and calculate the second energy decay rate based on the first actual ablation depth and the single-pulse safe ablation depth. The etching module is used to calculate the single pulse energy of the second to the Nth channels based on the channel-by-channel reduction formula and the second energy reduction rate. After inter-channel cooling and waiting, the second to the Nth channels are sequentially scanned and etched. When the i-th channel is scanned, the single pulse energy is reduced according to the channel-by-channel reduction formula and the pulse repetition frequency is increased according to the increment coefficient, so as to complete the scanning etching of the second to the Nth channels sequentially.

8. A MEMS probe, characterized in that, The MEMS probe is used to perform the MEMS probe laser etching method as described in any one of claims 1-6.

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