Method for modifying a glass substrate aperture and method for fabricating an integrated waveguide
By employing a combination of laser ring scanning and dot matrix scanning on the glass substrate, the problems of non-vertical sidewalls and uneven bottoms of blind holes were solved, achieving high-precision and low-cost hole-making and improving the performance and reliability of millimeter-wave slow-wave passive devices.
Patent Information
- Application Number
- CN202610937883.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-26
- Publication Date
- 2026-07-28
AI Technical Summary
In the existing technology, the blind holes processed on the glass substrate have non-vertical sidewalls and uneven bottoms, which leads to the deterioration of the performance of millimeter-wave slow-wave passive devices and cannot meet the requirements of high precision and high integration.
A closed modified ring is formed by scanning along the outer contour of a pre-set opening using a laser focus. A dot matrix scan is then performed within the modified ring, and combined with differential control of laser energy density and wet etching, through holes and blind holes with vertical sidewalls and flat bottoms are prepared.
It enables high-precision, low-cost hole processing on glass substrates, improving the performance and reliability of slow-wave substrate integrated waveguides and meeting the depth-to-diameter ratio requirements of high-frequency devices.
Smart Images
Figure CN122474860A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microwave and millimeter-wave passive device manufacturing technology, and more particularly to a method for modifying glass substrate openings and a method for fabricating integrated waveguides. Background Technology
[0002] As wireless communication systems evolve towards millimeter-wave and even terahertz bands, higher demands are placed on the miniaturization, high performance, and integration of passive devices. Slow-wave structures, by introducing periodic loading along the electromagnetic wave propagation path, effectively reduce phase velocity, thereby significantly shrinking the physical size of devices with the same electrical length. This has become an important technological path for realizing miniaturized passive devices. Substrate integrated waveguides (SIWs), due to their advantages such as planar integration, low loss, and high Q value, are often used as a platform for realizing slow-wave structures, forming slow-wave substrate integrated waveguides (SW-SIWs). Among various glass materials, glass, due to its stable physicochemical properties, is widely used in the fundamental research of through-glass via (TGV) technology.
[0003] Currently, microstructure fabrication based on through-glass via (TGV) technology primarily employs laser-induced wet etching. However, in existing technologies, blind via fabrication typically involves modifying the glass using single-point laser scanning or a single-trajectory scanning method. Due to the material properties of glass and the physical mechanism of laser-matter interaction, this conventional processing method results in anisotropy of the laser-modified region along the depth direction. During subsequent wet etching, the etching rate of the etchant along the modified region is uneven, ultimately resulting in a distinctly tapered sidewall (wider at the top and narrower at the bottom) and an uneven bottom. This tapered blind via structure cannot meet the precise capacitance and inductance requirements of SW-SIW, leading to device performance degradation or even failure, thus severely limiting the practical application of glass in millimeter-wave SW-SIW.
[0004] Therefore, how to fabricate a vertical sidewall and flat bottom opening structure on a glass substrate with high precision and high consistency, so as to give full play to its material advantages and realize a high-performance miniaturized SW-SIW, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] The purpose of this invention is to provide a method for modifying the opening of glass substrates, which can assist in the high-precision fabrication of through holes and blind holes with vertical sidewalls and flat bottoms on glass substrates at low cost.
[0006] Another objective of this invention is to provide a method for fabricating integrated waveguides, which can precisely fabricate through-holes and blind holes with vertical sidewalls and flat bottoms on glass substrates, while being low in cost and effectively improving the performance of millimeter-wave slow-wave passive devices.
[0007] To achieve the above objectives, the present invention provides a method for modifying an opening in a glass substrate, comprising the following steps: focusing a laser on the side of the glass substrate near its bottom surface; controlling the laser focus to perform a circular scan along the outer contour of a preset opening to form a closed modification ring; controlling the laser focus to perform a point-by-point scan at a preset dot matrix spacing within the inner region enclosed by the modification ring to form an array of modified dots; and ensuring that the laser energy density in the circumferential region of the modification ring is lower than the laser energy density in the filled region of the modified dots.
[0008] Compared with existing technologies, this invention uses a glass substrate as the glass base. By controlling the laser focus to perform a circular scan along the outer contour of a preset opening to form a closed modification ring, and then scanning the modified ring with the laser to form an array of modified dots, the invention utilizes the method of combining outer ring cutting and inner dot matrix laser scanning to create a trajectory. In addition, by focusing the laser focus at the bottom of the glass substrate and partitioning the laser energy density into different regions, namely the ring cutting region and the dot matrix filling region, the problem of anisotropy in the depth direction of traditional single-point or single-trajectory laser modification is solved. This ensures that the opening with vertical sidewalls and a flat bottom is obtained after subsequent wet etching, thereby improving the performance of the slow-wave substrate integrated waveguide.
[0009] Preferably, the radius of the outer circle of the modified ring is 5 μm larger than the filling radius of the modified lattice.
[0010] Preferably, the laser emission point spacing of the modified ring is in the range of 1-3 μm.
[0011] Preferably, the spacing between the points in the modified lattice is 5-7 μm.
[0012] A method for fabricating a slow-wave substrate integrated waveguide includes the following steps: selecting a glass wafer as a glass substrate; modifying the preset through-holes and preset blind holes of the glass substrate using a glass substrate aperture modification method; immersing the laser-modified glass substrate in an etching solution for wet etching to obtain through-holes and blind holes at preset positions on the glass substrate; forming a conductive layer on the inner walls of the through-holes and blind holes, as well as on the surface and bottom of the glass substrate, using a combined metallization process; and fabricating the circuit pattern required for the slow-wave passive device on the metallized glass substrate surface using photolithography and etching processes.
[0013] Preferably, after selecting the glass substrate and before modification, the glass substrate is cleaned to remove surface contaminants.
[0014] Preferably, a hydrofluoric acid (HF) solution is used, the water bath temperature is controlled at 15-50℃, and ultrasonic oscillation at 35-45kHz is used, with an etching time of 0.2h-4h.
[0015] Preferably, a potassium hydroxide (KOH) solution is used, the water bath temperature is controlled at 70-180℃, and the etching time is 1h-20h.
[0016] Preferably, in the step of forming the conductive layer, a seed layer is deposited on all surfaces, including the vias and the blind vias, using physical vapor deposition (PCD), atomic layer deposition (ALD), or chemical plating.
[0017] Specifically, an electroplating process is used to thicken or completely fill the through holes and blind holes with metal. Attached Figure Description
[0018] Figure 1 This is a flowchart of the modification method for opening holes in the glass substrate according to the present invention.
[0019] Figure 2 This is a flowchart of the fabrication method of the slow-wave substrate integrated waveguide of the present invention.
[0020] Figure 3 This is a cross-sectional structural diagram of the slow-wave substrate integrated waveguide of the present invention.
[0021] Figure 4 This is an array diagram of through holes and blind holes in the slow-wave substrate integrated waveguide of the present invention.
[0022] Figure 5 This is a diagram showing the arrangement of the modified ring and modified dot matrix of one of the blind holes in the slow-wave substrate integrated waveguide of the present invention before etching.
[0023] Figure 6 This is a structural diagram of the glass substrate of the present invention after through holes and blind holes are formed. Detailed Implementation
[0024] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.
[0025] like Figure 1 As shown, this invention discloses a method for modifying openings in a glass substrate, comprising the following steps: Step S11: Focus the laser on the side of the glass substrate closest to its bottom surface.
[0026] Step S12: Control the laser focus to perform a circular scan along the outer contour of the preset opening to form a closed modified ring.
[0027] Step S13: In the inner region enclosed by the modified ring, the focus of the laser is controlled to scan point by point with a preset dot matrix spacing to form an array of modified dots; and the laser energy density of the circumferential region of the modified ring is lower than the laser energy density of the filling region of the modified dots.
[0028] like Figure 2 As shown, this invention discloses a method for fabricating a slow-wave substrate integrated waveguide, comprising the following steps: Step S21: Select a glass wafer as the glass substrate.
[0029] Step S22: Modify the preset through holes and preset blind holes of the glass substrate using a glass substrate opening modification method.
[0030] Step S23: Immerse the laser-modified glass substrate in an etching solution for wet etching to obtain through holes and blind holes at preset positions on the glass substrate.
[0031] Step S24: A conductive layer is formed on the inner walls of the through holes and the blind holes, as well as on the surface and bottom of the glass substrate, using a combined metallization process.
[0032] Step S25: The circuit pattern required for the slow-wave passive device is fabricated on the metallized glass substrate surface through photolithography and etching processes.
[0033] Please combine again Figures 3 to 5 As shown, specific embodiments of the present invention are as follows: This embodiment describes the fabrication process of a slow-wave integrated waveguide based on a borosilicate (BF33) glass substrate operating in the Ka band. The slow-wave integrated waveguide 100 includes a glass substrate 1, with a row of through holes 11 on each side of the glass substrate 1, and blind holes 12 arrayed between the two rows of through holes 11. A metal filling layer 2 is disposed on the upper and lower surfaces of the glass substrate 1 and on the walls of the through holes 11 and blind holes 12. The core fabrication process satisfies the following requirements: the target aperture of both the blind holes 12 and the through holes 11 is 100 μm; the process logic is "laser circumferential cutting 70 μm modification + wet etching 30 μm"; the circumferential cutting produces a light spot spacing of 2 μm; the spacing between each point in the lattice filling is 5 μm; and the circumferential cutting radius is 5 μm larger than the filling radius of the modified lattice. The specific steps are as follows: Step 1: Substrate preparation.
[0034] A 6-inch, 500μm thick, double-sided polished borosilicate (BF33) glass wafer was selected as the glass substrate 1. It was ultrasonically cleaned sequentially with acetone, isopropanol, and deionized water for 10 minutes each, and then dried with nitrogen gas to ensure the surface of the glass substrate 1 was free of oil, dust, and other contaminants, thus avoiding any impact on subsequent laser modification and etching effects. Of course, quartz glass, high borosilicate glass, or high-alumina glass can also be used as the glass substrate; this is not a limitation.
[0035] Step 2: Laser modification.
[0036] An ultrafast laser processing system with a wavelength of 1030 nm and a pulse width of less than 3000 fs is used. This system features a precision Z-axis displacement stage, enabling accurate control of the focal position. The core of this step is to create a modified region of a predetermined size through laser modification, laying the foundation for subsequent etching to achieve the target aperture of 100 μm. All parameters strictly adhere to design requirements without any alterations. Focus control: The laser focus is always controlled below the surface of the glass substrate 1 (i.e., near the bottom surface) by a precision Z-axis displacement stage to ensure effective energy deposition inside the glass substrate 1, avoid surface energy overload that could cause microcracks, and ensure the uniformity of the modified area in the depth direction.
[0037] Through-hole 11 modification: According to the design layout, at the predetermined location for forming through-hole 11 (design target aperture 100μm), the laser scans from the upper surface to the lower surface of the glass substrate 1 in a circular trajectory with a radius of 35μm (i.e., circumferential diameter 70μm) along the vertical direction (Z-axis) to form a through-hole modified through-hole 11 line; the laser emission point spacing L on the circumferential trajectory of the modified ring 121 is controlled to be 2μm to ensure the continuity and uniformity of the through-hole 11 modification area.
[0038] Blind via 12 modification: At the predetermined locations where blind vias 12 are to be formed, three arrays of blind vias 12 with depths of 100 μm, 200 μm, and 300 μm are fabricated, respectively. The target aperture for all blind vias 12 is 100 μm. The specific processing parameters for blind vias 12 (through holes 11) are as follows: Outer ring cut (e.g.) Figure 5 The laser focus scans in a circular pattern with a radius of 35 μm (i.e., a circumferential diameter of 70 μm) to form a modified ring 121. In this embodiment, the filling radius of the modified dot matrix 122 is 30 μm (i.e., a dot matrix filling diameter of 60 μm). The circumferential radius R (35 μm) of the modified ring 121 is 5 μm larger than the filling radius r (30 μm) of the modified dot matrix 122, which meets the design requirements. The scanning speed and scanning spacing are set so that the laser emission point spacing is 2 μm. By controlling the laser power (set to P1, P1 = 80% relative power), the modification intensity of the modified region of the modified ring 121 is moderate, mainly used to form sidewalls, avoiding excessive modification of the sidewalls due to excessive energy.
[0039] Internal dot matrix filling (e.g.) Figure 5Within a circle with a radius of 30 μm (i.e., a dot matrix filling diameter of 60 μm), the dot matrix spacing N is set to 5 μm, with adjacent points in both the horizontal and vertical directions also having a spacing of 5 μm. The laser focal point dot matrix is scanned reciprocally to form a uniformly distributed modified dot matrix 122. Furthermore, in the modification of the blind via 12, by controlling the laser power (set to P2, P2 = 100% relative power, P2 > P1), the modification intensity in this area is made slightly higher than that in the circumferential cutting area, ensuring that the bottom of the blind via 12 is sufficiently modified to achieve a smooth etching.
[0040] Energy Differentiation Control: Because the light-emitting point spacing (2μm) on the modified ring 121 is denser than the point spacing (5μm) of the modified dot matrix 122, the line energy accumulation in the circumferential region is higher under the same laser power. In this embodiment, by reducing the laser power of the modified ring 121 region to 80% of that of the modified dot matrix 122 region, the total energy input of the modified ring 121 region is lower than that of the modified dot matrix 122 region, thereby avoiding defects such as outer ring pits and hole bottom protrusions caused by excessive external energy after etching.
[0041] Depth control is based on focus setting: For blind holes 12 of different depths, a strategy of controlling the processing focal length is adopted; the focal depth of laser scanning is below the center of the glass. As the depth becomes shallower, the focal depth is lowered to be closer to the bottom surface, thus achieving the target depth (100μm, 200μm or 300μm); the same circumferential scanning trajectory and energy control strategy are executed to ensure uniform modification in the depth direction of blind holes 12 and avoid anisotropy in the depth direction.
[0042] Step 3: Wet etching.
[0043] The laser-treated glass substrate 1 wafer is immersed in an etching solution for wet etching. This embodiment uses two etching schemes for comparison and verification to broaden the adaptability of the process route. Specifically, there are two wet etching methods, and either of the following can be selected: Option A (Acid Etching): Use hydrofluoric acid (HF) solution, control the water bath temperature at 30℃, and supplement with 40kHz ultrasonic oscillation to improve etching uniformity, promote the exchange of etching solution in the hole, and avoid insufficient etching at the bottom of the high aspect ratio blind hole 12; the etching time is 45 minutes.
[0044] Option B (Alkaline Etching): Use potassium hydroxide (KOH) solution, control the water bath temperature at 80℃, and etch for 60 minutes.
[0045] During the etching process, the glass material in the laser-modified area is selectively removed. Due to the extremely high selectivity of the etching between the modified and unmodified areas, the etching solution mainly proceeds along the modification path. Measurements show that regardless of whether acid or alkaline etching is used, approximately 30 μm of thickness is uniformly removed from the surface of the glass substrate 1. Through the combination of "70 μm laser circumferential cutting modification + 30 μm etching removal," the apertures of through-hole 11 and blind hole 12 ultimately reach the preset target value of 100 μm, consistent with the design goal (e.g., ...). Figure 6 ).
[0046] Etching results show that, due to the optimized focal position, the combined trajectory of ring cutting and lattice (the radius of modified ring 121 is 5 μm larger than the filling radius of modified lattice 122), and the energy differentiation control strategy, the blind hole 12 has good sidewall verticality and small tilt, meeting the requirements of SW-SIW structure; the bottom of blind hole 12 is nearly flat, ensuring the uniformity of metallization filling within blind hole 12; there are no laser-induced microcracks on the glass surface and hole walls, improving the mechanical strength of the glass substrate and the reliability of the device.
[0047] Step 4: Metallization filling.
[0048] A Ti / Cu seed layer (Ti thickness 100 nm, Cu thickness 200 nm) is sputtered onto the surface and inside the holes of the glass substrate 1 using magnetron sputtering technology. The Ti layer is used to improve the adhesion between the Cu layer and the glass substrate 1, preventing the metal layer from detaching. Subsequently, copper electroplating is performed for filling. For blind holes 12, the electroplating time needs to be precisely controlled to ensure metallization without overfilling, avoiding affecting subsequent circuit pattern fabrication. For through holes 11, electroplating continues until the holes are completely filled with copper, increasing the surface copper layer thickness to 5 μm to ensure the conductivity and structural stability of through holes 11. In this embodiment, in addition to physical vapor deposition (PCD) for seed layer deposition, atomic layer deposition (ALD) or electroless plating can also be used.
[0049] Step 5: Circuit diagram creation.
[0050] Photoresist is spin-coated onto the surface of a metallized glass substrate 1. The substrate is exposed and developed using a pre-designed mask to define the top-level circuit pattern of the SW-SIW (including the resonant cavity, coupling window, and coplanar waveguide feed line). Then, excess copper layer is removed by wet etching, and finally, the photoresist is removed to obtain a clear and regular circuit.
[0051] Step 6: Obtain the finished product.
[0052] The glass substrate 1 is cut to obtain an independent BF33 glass-based slow-wave chip.
[0053] The method for modifying the opening of the glass substrate in this invention is not limited to open holes or blind holes, but can also be any other editable structure, such as square blind grooves, triangular blind grooves, etc.
[0054] This invention uses a borosilicate glass substrate as the glass base. By controlling the laser focus to perform a circular scan along the outer contour of a preset opening, a closed modified ring 121 is formed. Then, laser scanning within the modified ring 121 forms an array of modified dots 122. By using a combination of outer ring cutting and internal dot matrix laser scanning to create a trajectory, and by focusing the laser focus at the bottom of the glass substrate 1 and differentiating the laser energy density between the cut area and the dot matrix filling area, the anisotropy problem in the depth direction of traditional single-point or single-trajectory laser modification is solved. After wet etching, through holes 11 with vertical sidewalls and flat bottoms and blind holes 12 are obtained. The vertical sidewalls and flat bottom blind holes 12 provide precise geometric boundaries, allowing for accurate calculation of the equivalent capacitance of the slow-wave structure. The actual device performance highly matches the electromagnetic simulation results, thus significantly shortening the design iteration cycle and reducing costs. Furthermore, the via modification method of the present invention can optimize metallization quality and reliability. By optimizing physical vapor deposition parameters, the quality of the seed layer is ensured, and the advantages of the flat-bottomed blind via 12 in the subsequent electroplating filling stage are fully utilized to obtain high-quality metal interconnects with no voids and low stress, significantly improving the long-term reliability and power handling capability of the device. The present invention can also extend the aspect ratio limit. The vertical sidewall structure can be used to process blind vias 12 with higher aspect ratios (>3:1), thereby meeting the requirements of higher frequency slow-wave devices for deep blind vias 12.
[0055] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the scope of the present invention are still within the scope of the present invention.
Claims
1. A method for modifying the openings in a glass substrate, characterized in that, Includes the following steps: The laser is focused on the side of the glass substrate closest to its bottom surface; The laser's focus is controlled to perform a circular scan along the outer contour of a preset opening to form a closed modified ring; In the inner region enclosed by the modified ring, the laser focus is controlled to scan point by point at a preset dot spacing to form an array of modified dots; and the laser energy density of the circumferential region of the modified ring is lower than the laser energy density of the filled region of the modified dots.
2. The method for modifying the opening of a glass substrate according to claim 1, characterized in that: The radius of the outer circle of the modified ring is 5 μm larger than the filling radius of the modified lattice.
3. The method for modifying the opening of a glass substrate according to claim 1, characterized in that: The laser emission point spacing of the modified ring ranges from 1 to 3 μm.
4. The method for modifying the opening of a glass substrate according to claim 1, characterized in that: The spacing between the points in the modified lattice is 5-7 μm.
5. A method for fabricating a slow-wave substrate integrated waveguide, characterized in that, Includes the following steps: Glass wafers were selected as the glass substrate; The pre-set through holes and pre-set blind holes of the glass substrate are modified using the glass substrate opening modification method according to any one of claims 1 to 4. The glass substrate, after laser modification, is immersed in an etching solution for wet etching to obtain through holes and blind holes at predetermined positions on the glass substrate. A conductive layer is formed on the inner walls of the through holes and the blind holes, as well as on the surface and bottom of the glass substrate, using a combined metallization process; The circuit patterns required for slow-wave passive devices are fabricated on the metallized glass substrate surface using photolithography and etching processes.
6. The method for fabricating a slow-wave substrate integrated waveguide according to claim 5, characterized in that: After selecting the glass substrate and before modification, the glass substrate is cleaned to remove surface contaminants.
7. The method for fabricating a slow-wave substrate integrated waveguide according to claim 5, characterized in that: Hydrofluoric acid (HF) solution is used, the water bath temperature is controlled at 15-50℃, and ultrasonic oscillation at 35-45kHz is used simultaneously, with an etching time of 0.2h-4h.
8. The method for fabricating a slow-wave substrate integrated waveguide according to claim 5, characterized in that: Using potassium hydroxide (KOH) solution, the water bath temperature is controlled at 70-180℃, and the etching time is 1h-20h.
9. The method for fabricating a slow-wave substrate integrated waveguide according to claim 5, characterized in that: In the step of forming the conductive layer, a seed layer is deposited on all surfaces, including the vias and the blind vias, using physical vapor deposition (PCD), atomic layer deposition (ALD), or chemical plating.
10. The method for fabricating a slow-wave substrate integrated waveguide according to claim 9, characterized in that: Electroplating is used to thicken or completely fill the through holes and blind holes with metal.