A method for laser-induced etching of quartz glass steps using blind via arrays

Abstract

The present application relates to the technical fields of micro-electro-mechanical system manufacturing, and particularly relates to a preparation method of laser-induced etching quartz glass step by blind hole array, comprising: focusing a Bessel beam inside the quartz glass, discretizing the step removal volume boundary into a modified blind hole array by calibrating the effective modified beam length, precisely controlling the depth of the modified unit by using the defocus amount, and writing the modified track; through wet etching, making the modified area through and separating the block to be removed, and forming the step. For non-edge steps, a full-coverage blind hole array is used, and a high flatness step bottom surface is obtained through the coplanar bottom surfaces of the blind holes; for edge steps, an L-shaped slit composed of vertical and horizontal modified tracks is used, and two rows of modified tracks are used to separate the block. The present application does not need a mask, the etching depth is controlled by the geometric defocus open loop, reaches the sub-micron precision, and can be combined with the surface roughness to optimize the verticality of the step, and can be applied to the manufacturing of complex quartz glass structures.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical systems (MEMS) manufacturing technology, and specifically to a method for laser-induced etching of quartz glass steps using a blind-hole array. Background Technology

[0002] A micro-hemispherical resonator gyroscope is a miniature angular rate / angle sensor based on the Coriolis effect. Its core is typically a three-dimensional rotationally symmetric thin-walled resonator with a diameter on the order of millimeters, generally in a hemispherical shape. It maintains four-antinode standing wave vibration through electrostatic excitation. When an external angular velocity is input, the Coriolis force causes the mode shape to precess circumferentially. In full-angle mode, the precession angle of the standing wave is strictly proportional to the input angle; directly detecting this angle provides information about the carrier's rotation, thus achieving high-precision angle or angular rate measurement. Unlike traditional hemispherical resonator gyroscopes, micro-hemispherical resonators are typically manufactured using micromachining processes such as glass thermoforming, laser-induced etching, and chemical mechanical polishing, allowing for mass production and significantly reducing manufacturing costs. The micro-hemispherical resonator has an extremely high mechanical quality factor, its rotationally symmetric structure provides high environmental robustness, and it has no internal rotating wear parts, resulting in high reliability and theoretical accuracy ranging from tactical to navigation-grade.

[0003] High-purity quartz glass, due to its excellent optical transmittance, thermal stability, chemical inertness, and high hardness, has become the primary material for manufacturing micro-hemispherical resonators. To achieve rapid mass production while avoiding structural damage from precision machining, micro-hemispherical resonators are currently mainly manufactured using a thermoforming process. The basic principle of this process is to utilize a heat source, a mold, and a vacuum pump to achieve rapid thermal deformation of the quartz glass. The process includes: heating the quartz glass placed in the mold chamber with a heat source until it reaches its softening point temperature, while simultaneously evacuating the chamber using a vacuum pump. Under the combined influence of the heat source temperature, pressure difference, and mold structural constraints, the softened quartz glass undergoes bending deformation to form the predetermined structure.

[0004] When manufacturing resonators with diameters in the millimeter range using thermoforming processes, flat sheets of quartz glass with a thickness of about several hundred micrometers are typically used. After the flat sheet softens upon heating, the thickness decreases in areas of greater deformation, potentially leading to poor environmental robustness in the finished resonator. Using thicker flat sheets, however, could increase the resonator's stiffness and affect its mechanical sensitivity. A better solution is to use variable-thickness quartz glass sheets instead of flat sheets. These sheets have a stepped thickness distribution, meaning they are thicker in areas of greater deformation and thinner in areas of less deformation during the forming process. Resonators manufactured using these variable-thickness quartz glass sheets exhibit high robustness and high mechanical sensitivity. These variable-thickness quartz glass sheets are typically manufactured using a mask-based wet etching method. However, due to the large etching depth (step height) (typically several hundred micrometers), this method presents the following technical challenges:

[0005] 1. Isotropic etching. The corrosion rate of SiO2 by hydrofluoric acid is almost equal in all spatial directions. To obtain a step with a depth of h, the lateral etching depth below the mask is also approximately h, and the step cross-section must be arc-shaped or funnel-shaped. Vertical sidewalls are physically impossible to achieve.

[0006] 2. Mask protection failure. Hydrofluoric acid is an extremely penetrating acid that can penetrate along the interface between the mask and the quartz glass, forming interfacial corrosion channels. Although metal masks are insoluble in hydrofluoric acid, pinhole defects in the film layer allow the acid to penetrate and etch the underlying substrate. Especially during long-term etching processes, the mask is prone to peeling off, leading to localized etching of the substrate. The adhesion of photoresist decreases sharply in hydrofluoric acid, making it difficult to protect the substrate from etching for extended periods.

[0007] While femtosecond laser ablation of quartz glass enables maskless processing, the extremely short depth of field of the Gaussian beam necessitates repeated layer-by-layer scanning to process structures hundreds of micrometers deep, resulting in significant time consumption. Furthermore, this process essentially involves material vaporization or plasmaization, which can easily generate microcracks. Additionally, laser beam refraction within transparent materials can damage non-processed surfaces, impacting processing quality. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a method for laser-induced etching of quartz glass steps using a blind-hole array, specifically including the following steps:

[0009] The Bessel beam is focused inside the quartz glass substrate, so that the effective modification length of the beam is L. eff ;

[0010] The boundary of the target step removal volume is discretized into a set of modified trajectories consisting of a set of blind holes, and the set of modified trajectories at least partially encloses the volume to be removed;

[0011] For each modified unit in the modified trajectory set, the relative position of the quartz glass incident surface and the Bessel beam is adjusted by a precision motion stage to make the defocusing amount Δz = L eff - D, where D is the required modification depth or length of the modification unit, triggering laser writing into the modification region;

[0012] The glass substrate is treated with an etchant that selectively etches the modified areas, so that the modified tracks are preferentially etched and interconnected, causing the enclosed blocks to separate from the substrate and form steps.

[0013] Compared with the prior art, the advantages of the present invention are as follows:

[0014] 1. Completely eliminate lateral etching and achieve vertical sidewalls. Etching is confined within the laser-written modified layer, and the sidewall verticality is determined by the vertical orientation of the Bessel beam, no longer affected by isotropic etching.

[0015] 2. No physical mask required. The laser-induced modified region itself serves as a virtual mask, and since it is made of the same quartz glass as the substrate, there are no heterogeneous interfaces or adhesion issues, fundamentally avoiding mask penetration and pinhole corrosion.

[0016] 3. Precise depth control. Depth is determined by the defocus amount Δz = L eff – Independent D control, decoupled from pulse energy and etching time, accuracy depends only on the positioning accuracy of the displacement stage.

[0017] 4. Balancing precision and efficiency. Offers two processing methods: full-coverage blind hole array and edge L-shaped kerf. The former is suitable for step processing at any location on a quartz glass substrate, while the latter utilizes edge freedom to significantly reduce the number of processing points, improving efficiency by up to tens of times. Attached Figure Description

[0018] Figure 1 A flowchart of a method for laser-induced etching of quartz glass steps using a blind-hole array is provided for this invention;

[0019] Figure 2 The present invention provides a trajectory diagram for laser processing when the step is not located at the edge of the glass substrate;

[0020] Figure 3 A trajectory diagram of laser processing when a step is located at the edge of a glass substrate, provided by the present invention;

[0021] Figure 4 This invention provides a laser processing trajectory diagram for a step with an inclined plane bottom and a linearly varying depth. Detailed Implementation

[0022] The technical solutions of the embodiments 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, and 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.

[0023] This invention provides a method for laser-induced etching of quartz glass steps using a blind-hole array, such as... Figure 1 Specifically, it includes the following steps:

[0024] The Bessel beam is focused inside the quartz glass substrate, so that the effective modification length of the beam is L. eff ;

[0025] The boundary of the target step removal volume is discretized into a set of modified trajectories consisting of a set of blind holes, and the set of modified trajectories at least partially encloses the volume to be removed;

[0026] For each modified unit in the modified trajectory set, the relative position of the quartz glass incident surface and the Bessel beam is adjusted by a precision motion stage to make the defocusing amount Δz = L eff - D, where D is the required modification depth or length of the modification unit, triggering laser writing into the modification region;

[0027] The glass substrate is treated with an etchant that selectively etches the modified areas, so that the modified tracks are preferentially etched and interconnected, causing the enclosed blocks to separate from the substrate and form steps.

[0028] Implementation Case 1

[0029] This embodiment provides a method for laser-induced etching of quartz glass steps using a blind hole array. A full-coverage blind hole array is used to process high-precision non-edge steps on a quartz glass sheet. Specifically, the method includes the following steps:

[0030] (a) A Bessel beam is focused inside a quartz glass substrate to form a nearly diffraction-free beam in the focal region. Before formal processing, single-pulse modified beams with different defocusing amounts are written onto quartz glass from the same batch as the sample to be processed. After etching with a 5% (w / w) hydrofluoric acid solution, the effective length of each modified beam is measured using a scanning electron microscope. A "defocusing amount - effective modification length" curve is plotted to determine the effective modification length as L. eff ;

[0031] (b) Calculate the defocusing amount Δz = L based on the target height D of the step. eff – D. Discretize the step width horizontally with a spacing Δx, generating a total of N processing points. The spacing Δx is designed based on parameters such as etching time and laser processing power to ensure a smooth connection of the sidewalls after etching;

[0032] (c) Mount the quartz glass plate on an XYZ three-axis displacement stage. Use the objective lens to locate the upper surface of the glass plate and set it as the zero point of the Z-axis. Raise the Z-axis upward by Δz so that only the portion of the Bessel beam of length D is inside the glass plate. The displacement stage carries the glass plate to each preset point in sequence and triggers the laser to complete the writing of the modified beam at that point. After completing all N points, a row of modified blind holes of depth D and vertically equidistant are formed inside the quartz glass, with the processing trajectory as shown in the figure. Figure 2 As shown;

[0033] (d) The laser-processed quartz glass slide is completely immersed in a 5% (w / w) hydrofluoric acid solution and ultrasonic waves are applied. The modified blind hole array is preferentially etched and interconnected, and the block enveloped by the blind hole array is completely separated from the substrate. The glass slide is removed, rinsed with deionized water, and then immersed in a 1% (w / w) hydrofluoric acid solution for a short-term smooth etching at room temperature for 30 seconds. It is then rinsed with deionized water and dried with nitrogen.

[0034] This invention utilizes a Bessel beam incident on the interior of quartz glass. The quartz glass irradiated by the Bessel beam undergoes modification within the beam's spot diameter and effective incident depth range (this range can be obtained in advance through testing with different glass materials and different defocusing amounts). The modified areas are etched away by the etching solution at a much higher rate than the unmodified areas, thus forming blind holes after etching. Those skilled in the art can adjust the depth or length of the blind holes based on the effective modification length of the beam and the distance between the glass material and the beam emission position.

[0035] Implementation Case 2

[0036] This invention provides a method for laser-induced etching of quartz glass steps using a blind-hole array, which efficiently processes edge steps on a quartz glass sheet using an L-shaped kerf. Specifically, it includes the following steps:

[0037] (a) A Bessel beam is focused inside a quartz glass substrate to form a nearly diffraction-free beam in the focal region. Before formal processing, single-pulse modified beams with different defocusing amounts are written onto quartz glass from the same batch as the sample to be processed. After etching with a 5% (w / w) hydrofluoric acid solution, the effective length of each modified beam is measured using a scanning electron microscope. A "defocusing amount - effective modified length" curve is plotted to determine the effective modified length as L. eff ;

[0038] (b) Clamp the quartz glass plate onto the XYZ three-axis displacement stage, with the edge to be removed facing upwards. Along the horizontal direction (X direction) of the step edge, set processing points at equal intervals, with a spacing of Δx, for a total of N1 points. Based on the target step height D... V Calculate the defocus amount Δz1 = L eff – D V After raising the Z-axis upwards by Δz1, lasers are triggered point by point to write a column of data with a depth of D. V Vertical modified blind holes. This column of blind holes forms a vertical modified slit, and the spacing Δx is designed according to parameters such as etching time and laser processing power to ensure a smooth surface of the structure after etching;

[0039] (c) Rotate the quartz glass slide 90° around the horizontal axis so that the side to be removed is facing upwards. Re-clamp the slide and use the objective lens to locate the substrate side surface, setting it as the zero point of the Z-axis. At this point, the original thickness direction of the glass slide becomes the horizontal direction. Set the processing points at equal intervals, with a spacing of Δx, for a total of N2 points. Based on the target depth D... H Calculate the defocusing amount Δz2 = L eff – D H After raising the Z-axis upwards by Δz2, lasers are triggered point by point to write a column of data with a depth of D. H Vertical modified blind holes. This row of blind holes forms a horizontal modified slit, with the spacing Δx designed according to parameters such as etching time and laser processing power to ensure a smooth surface after etching. The lower end of the vertical slit and the inner end of the horizontal slit are designed to intersect each other in space, and the processing trajectory is as follows: Figure 3 As shown;

[0040] (d) The laser-processed quartz glass slide is completely immersed in a 5% (w / w) hydrofluoric acid solution and ultrasonic waves are applied. The etching solution preferentially corrodes the vertical and horizontal modified blind holes, expanding them into continuous slits that penetrate at their intersection. The edge strips to be removed are completely separated along the L-shaped cut, forming edge steps. The glass slide is removed, rinsed with deionized water, and then immersed in a 1% (w / w) hydrofluoric acid solution for a short-term smooth etching at room temperature for 30 seconds. It is then rinsed with deionized water and dried with nitrogen.

[0041] Compared to Implementation Case 1, this embodiment shows that for edge steps, only two rows of modified blind holes are needed to remove them, which significantly shortens the processing time compared to a full-coverage array scheme of the same width.

[0042] Implementation Case 3

[0043] This invention provides a method for laser-induced etching of a step in quartz glass using a blind-hole array, which processes a step on a quartz glass sheet with a sloping bottom surface and a linearly varying depth. Specifically, it includes the following steps:

[0044] (a) A Bessel beam is focused inside a quartz glass substrate to form a nearly diffraction-free beam in the focal region. Before formal processing, single-pulse modified beams with different defocusing amounts are written onto quartz glass from the same batch as the sample to be processed. After etching with a 5% hydrofluoric acid solution, the effective length of each modified beam is measured using a scanning electron microscope, and a "defocusing amount - effective modified length" curve is plotted to determine the effective modified length as L. eff ;

[0045] (b) Discretize the step processing area into a point array. Discretize the horizontal direction into N sampling positions at intervals Δx. For the i-th point (i=0,1,…,N) in the horizontal direction, its horizontal coordinate is x. i The target depth D at this pointi Press D i = (D max Calculate using (× i / N), where D max Let be the maximum height of the inclined plane. For the i-th processing point in the horizontal direction, the required defocusing amount Δz i According to the formula Δz i = L eff – D i calculate.

[0046] (c) Mount the quartz glass plate onto the XYZ three-axis translation stage. Use the objective lens to locate the upper surface of the glass plate and set it as the zero point of the Z-axis. The control system preloads the coordinates of all points and the corresponding defocusing amounts. The machining path adopts a line-by-line scanning method: move the translation stage to the target point i, and raise the Z-axis upward by Δz. i After the Z-axis is in place, the laser writing depth is triggered to D. i The modified beam is then moved to the next point. This creates a blind aperture array inside the quartz glass sheet, with the bottom envelope of the array precisely fitting the designed inclined plane, and the processing trajectory is as follows: Figure 4 As shown.

[0047] (d) The laser-processed quartz glass slide is completely immersed in a 5% (w / w) hydrofluoric acid solution and ultrasonic waves are applied. The etching solution preferentially corrodes the vertical and horizontal modified blind holes, expanding them into continuous slits that penetrate at their intersection. The edge strips to be removed are completely separated along the L-shaped cut, forming edge steps. The glass slide is removed, rinsed with deionized water, and then immersed in a 1% (w / w) hydrofluoric acid solution for a short-term smooth etching at room temperature for 30 seconds. It is then rinsed with deionized water and dried with nitrogen.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for laser-induced etching of quartz glass steps using a blind-hole array, characterized in that, Specifically, the following steps are included: The Bessel beam is focused inside the quartz glass substrate, so that the effective modification length of the beam is L. eff ; The boundary of the target step removal volume is discretized into a set of modified trajectories consisting of a set of blind holes, and the set of modified trajectories at least partially encloses the volume to be removed; For each modified unit in the modified trajectory set, the relative position of the quartz glass incident surface and the Bessel beam is adjusted by a precision motion stage to make the defocusing amount Δz = L eff - D, where D is the required modification depth or length of the modification unit, triggering laser writing into the modification region; The glass substrate is treated with an etchant that selectively etches the modified areas, so that the modified tracks are preferentially etched and interconnected, causing the enclosed blocks to separate from the substrate and form steps.

2. The method for laser-induced etching of quartz glass steps using a blind-hole array according to claim 1, characterized in that, When the step is not located at the edge of the glass substrate, the modified trajectory set includes one or more rows of blind holes arranged at intervals Δx along the step height or horizontal direction, and the bottoms of the blind holes together form the bottom surface or sidewall of the step.

3. The method for laser-induced etching of quartz glass steps using a blind-hole array according to claim 2, characterized in that, The distance Δx between adjacent blind apertures is greater than or equal to the spot diameter d of the Bessel beam.

4. The method for laser-induced etching of quartz glass steps using a blind-hole array according to claim 1, characterized in that, When the step is located at the edge of the glass substrate, the set of modified trajectories includes a series of vertical blind holes along the height direction of the step sidewall and a series of horizontal blind holes along the bottom surface of the step; the vertical blind holes and the horizontal blind holes intersect in the root space to form an L-shaped modified trajectory.

5. The method for laser-induced etching of quartz glass steps using a blind-hole array according to claim 4, characterized in that, The process for creating a horizontal blind hole is as follows: the quartz glass substrate is rotated around a horizontal axis so that the height direction is perpendicular to the Bessel beam. By controlling the defocusing amount, a blind hole with a writing depth equal to the width of the bottom surface of the step is formed.

6. The method for laser-induced etching of quartz glass steps using a blind-hole array according to claim 1, characterized in that, Effective beam modification length L eff The calibration method is as follows: under different defocusing amounts, a single-pulse modified beam is written into the quartz glass substrate. After wet etching, the actual length of the filament is measured, the "defocusing amount - effective modified length" curve is plotted, and the length of the flat top range of the curve is extracted.

7. The method for laser-induced etching of quartz glass steps using a blind-hole array according to claim 1, characterized in that, The corrosive solution is a 5%-10% hydrofluoric acid solution or a 10%-20% potassium hydroxide solution.

8. The method for laser-induced etching of quartz glass steps using a blind-hole array according to claim 1, characterized in that, The surface roughness of the steps is optimized by immersing them in a hydrofluoric acid solution with a mass fraction of ≤1% for 20 to 60 seconds after separation.

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