Glass substrate tgv flat bottom blind via fabrication method and glass substrate

Abstract

The application provides a glass substrate TGV flat-bottom blind hole preparation method and a glass substrate. The method comprises the following steps: obtaining a scanning track, the scanning track comprises coaxially nested dot matrix tracks and a ring cutting track, the dot matrix tracks comprise a plurality of interval arranged track points, and the ring cutting track comprises a continuous annular track line; laser point-by-point scanning is performed along each track point in the dot matrix tracks to form a dot matrix modification area located in a center area of a target blind hole; continuous scanning is performed along the ring cutting track to form an annular modification area located outside the dot matrix modification area; and the glass substrate after laser-induced processing is placed in an etching solution for wet etching, the annular modification area is expanded by etching to form a side wall of the target blind hole, and the dot matrix modification area is connected by etching to form a bottom of the target blind hole. The above blind hole preparation method effectively overcomes the blind hole bottom tapering defect caused by the Gaussian distribution of laser energy by adopting coaxially nested dot matrix tracks and a ring cutting track for laser induction.

Description

Technical Field

[0001] This invention relates to the field of TGV hole fabrication technology, and in particular to a method for preparing TGV flat-bottom blind holes on a glass substrate and the glass substrate thereof. Background Technology

[0002] Through-Glass Via (TGV) technology, as an advanced microelectronic packaging interconnect technology, is widely used in high-density system-in-package, microelectromechanical systems (MEMS), radio frequency devices, and optoelectronic systems due to the excellent high-frequency electrical properties, adjustable coefficient of thermal expansion, and good mechanical stability of glass materials. In the fabrication process of TGV blind vias, the "laser-induced wet etching" technique has become the mainstream choice for mass production in the industry due to its advantages such as low processing cost, high etching selectivity, minimal damage to the glass substrate, and adaptability to micro- and nano-scale aperture fabrication.

[0003] The core principle of existing laser-induced wet etching processes is to use laser energy to act on a glass substrate, causing chemical bond breakage or structural rearrangement in the irradiated area to form a modified layer. Subsequently, a hydrofluoric acid-based etching solution is used to selectively etch the modified layer at a high rate to form blind holes. In conventional process practice, laser-induced etching typically employs a single scanning trajectory, such as a continuous circular scan along the edge of the target aperture, or a spiral scan progressing from the center to the edge.

[0004] However, existing technologies face a significant technical bottleneck in the fabrication of TGV blind vias: limited by the inherent Gaussian distribution of laser beam energy (i.e., high energy density at the center and low energy density at the edges), the modified layer formed when the laser acts on the glass substrate inevitably exhibits a gradient distribution with a "deep center and shallow edges" in the depth direction. This non-uniform modification depth directly results in the inability to form a flat surface at the bottom of the blind via during subsequent wet etching, instead generally exhibiting a conical (V-shaped) structure.

[0005] This tapered bottom structure has several adverse effects on the subsequent application of TGV blind vias: First, the tapered bottom limits the effective planar area of ​​the blind via bottom, resulting in uneven metal layer deposition during subsequent metallization processes, reducing the interconnect contact area, and thus increasing the interconnect resistance; Second, the sharp bottom structure is prone to stress concentration under thermal cycling or mechanical loads, reducing the reliability of the package structure; In addition, the tapered space utilization is low, making it difficult to adapt to the packaging requirements of micro sensors or high-frequency devices with special requirements for internal space morphology.

[0006] While existing technologies have attempted to optimize the modification effect by adjusting parameters such as laser pulse width, frequency, or focal length, these methods have failed to fundamentally alter the decisive influence of the energy Gaussian distribution on the hole bottom morphology under a single-track scan. Other non-laser-induced processes, such as laser direct drilling, suffer from problems like rough hole walls and excessive debris residue; while deep reactive ion etching (DRIE) faces the challenges of extremely high equipment costs, complex processes, and difficulty in mass production.

[0007] Therefore, how to prepare TGV flat-bottom blind holes with flat bottoms and controllable morphology is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing TGV flat-bottom blind holes on a glass substrate, based on the mature laser-induced wet etching process architecture, overcoming the limitations caused by the Gaussian distribution of laser energy, so as to prepare TGV flat-bottom blind holes with flat bottoms and controllable morphology.

[0009] To achieve the above objectives, the present invention provides a method for fabricating TGV flat-bottom blind vias on a glass substrate, comprising: A scanning trajectory is obtained to indicate the movement of a laser for laser-induced processing of the glass substrate. The scanning trajectory includes a coaxially nested dot matrix trajectory and a circumferential trajectory. The circumferential trajectory is located outside the dot matrix trajectory. The dot matrix trajectory includes a plurality of trajectory points arranged at intervals. The circumferential trajectory includes a continuous circular trajectory line. Laser scanning is performed point by point along each trajectory point in the dot matrix to form a dot matrix modification area located in the center region of the target blind hole; Continuous scanning is performed along the circumferential trajectory to form an annular modification region located outside the lattice modification region; The glass substrate, after laser-induced processing, is placed in an etching solution for wet etching. The annular modified region is etched and expanded to form the sidewall of the target blind hole, and the lattice modified region is etched and connected to form the bottom of the target blind hole.

[0010] Preferably, scanning is performed first along the dot matrix trajectory, and then scanning is performed along the circumferential trajectory.

[0011] Preferably, the laser focal depth when scanning along the dot matrix trajectory is greater than the laser focal depth when scanning along the circumferential trajectory.

[0012] Preferably, the method for determining the size parameters of the scanning trajectory includes: Based on the aperture and depth of the target blind hole, the laser parameters and etching time of the laser output by the laser are confirmed; Based on the etching time, the radial width of the etching solution expanding outward from the annular modified region during the etching process is confirmed. The diameter of the circumferential trajectory is equal to the difference between the aperture and the radial width; The diameter of the dot matrix trajectory is equal to the difference between the diameter of the circumferential trajectory and a preset constant.

[0013] Preferably, the laser parameters, etching time, and radial width are confirmed by gradient experiments.

[0014] Preferably, before performing the laser-induced operation, the method further includes a pretreatment method for the glass substrate: using a mixture of anhydrous ethanol and deionized water as a cleaning solution to ultrasonically clean the glass substrate; and placing the cleaned glass substrate in an oven for drying.

[0015] Preferably, the etching solution is magnetically stirred during the etching process.

[0016] Preferably, after etching is completed, a post-processing step is also included: removing the glass substrate from the etching solution and cleaning it sequentially with deionized water and anhydrous ethanol; and drying the cleaned glass substrate.

[0017] The present invention also provides a glass substrate, comprising a substrate body having blind holes formed based on the above-described glass substrate TGV flat-bottom blind hole preparation method.

[0018] Compared with existing technologies, the blind via fabrication method provided by the above technical solution effectively overcomes the tapered defect at the bottom of the blind via caused by the Gaussian distribution of laser energy by using coaxial nested lattice trajectories and circumferential trajectories for laser induction. Specifically, the lattice trajectories form a uniform lattice modification region at the center, which interconnects during wet etching to form a flat bottom, significantly increasing the effective interconnect area at the bottom of the blind via, ensuring the uniformity of subsequent metallization deposition, and reducing the risk of interconnect resistance and stress concentration. At the same time, the circumferential trajectories precisely define the sidewall shaping, achieving high-precision flat-bottom fabrication of TGV blind vias, improving packaging reliability and internal space utilization, and offering strong process compatibility without requiring additional complex equipment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram showing the distribution of the laser scanning trajectory corresponding to a blind hole in an embodiment of the present invention.

[0020] Figure 2 This is a longitudinal cross-sectional view of a glass substrate with blind holes processed in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram illustrating the principle of obtaining parameters for the scanning trajectory in an embodiment of the present invention.

[0022] Figure 4 This is a flowchart of the blind hole preparation method in an embodiment of the present invention. Detailed Implementation

[0023] 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.

[0024] This embodiment provides a method for fabricating flat-bottom blind vias on glass substrates using TGV etching. This method aims to solve the problem in existing laser-induced wet etching processes where the Gaussian distribution of laser energy causes a tapered structure at the bottom of the blind via.

[0025] like Figure 1 and Figure 4 As shown, the preparation method mainly includes the following steps: S1: Obtain the scan trajectory.

[0026] First, a scanning trajectory is acquired to guide the movement of the laser for laser-induced processing of the glass substrate. Unlike the single spiral or concentric circle trajectory in the prior art, the scanning trajectory in this embodiment is a composite trajectory, specifically including a coaxial nested dot matrix trajectory 10 and a circumferential trajectory 11.

[0027] The circumferential trajectory 11 is located outside the dot matrix trajectory 10, with their centers coinciding. The dot matrix trajectory 10 is not a continuous line, but rather consists of several spaced-apart trajectory points evenly distributed in the central region of the target blind hole. The circumferential trajectory 11 is a continuous closed loop trajectory line used to define the sidewall boundary of the blind hole.

[0028] S2: Laser-induced processing.

[0029] The scanning trajectory described above is imported into the laser processing system, and the laser is controlled to expose the glass substrate.

[0030] Specifically, laser scanning is performed point-by-point along each trajectory point in the dot matrix trajectory 10. The laser beam stays at each trajectory point for a predetermined time or emits a predetermined number of pulses, causing modification inside the glass substrate (such as chemical bond breaking or structural rearrangement), thereby forming a dot matrix modification region located in the central region of the target blind hole. Due to the use of a dot matrix, the problem of excessively high energy at the center of the Gaussian beam can be overcome by controlling the dot spacing and single-point energy, thus achieving a uniform energy distribution in the central region.

[0031] A continuous scan is performed along the circumferential trajectory 11. The laser beam moves continuously along the annular path, forming an annular modification region located outside the lattice modification region within the glass substrate.

[0032] S3: Wet etching.

[0033] The laser-induced processed glass substrate was placed in an etching solution for wet etching. Because the modified glass exhibits a significantly higher etching rate (higher selectivity) in the specific etching solution than the unmodified glass, the etching process is as follows: The annular modified area is first contacted and dissolved by the etching solution. As the etching time progresses, the etching solution expands outward and downward, thereby forming the sidewall of the target blind hole.

[0034] Simultaneously, the etching solution penetrates into the central lattice-modified region. Because the modified points within the lattice-modified region are uniformly distributed and have a consistent degree of modification, during the etching process, each modified point is rapidly etched and interconnected. This interconnection allows the bottom material to be uniformly removed, thereby forming a flat bottom for the target blind hole, such as... Figure 2 Instead of the conical bottom found in traditional processes.

[0035] Therefore, it can be seen that the above-mentioned blind hole preparation method effectively overcomes the tapered defect at the bottom of the blind hole caused by the Gaussian distribution of laser energy by using coaxial nested lattice trajectory 10 and circumferential trajectory 11 for laser induction.

[0036] Specifically, the lattice trajectory 10 forms a uniform lattice modification area at the center, which is interconnected during wet etching to form a flat bottom, significantly increasing the effective interconnect area at the bottom of the blind hole, ensuring the uniformity of subsequent metallization deposition, and reducing the risk of interconnect resistance and stress concentration.

[0037] Meanwhile, the circumferential cutting trajectory 11 precisely defines the sidewall forming, enabling high-precision flat-bottom fabrication of TGV blind holes, improving packaging reliability and internal space utilization, and providing strong process compatibility without the need for additional complex equipment.

[0038] In another embodiment, before actual processing, it is necessary to deduce the laser trajectory parameters based on the specifications of the target product. For example... Figure 3 The specific steps are as follows: A: Parameters confirmed.

[0039] Based on the design requirements of the target blind hole, namely the target aperture (e) and the target depth (d), the process parameters need to be confirmed first.

[0040] Specifically, by using gradient experiments (e.g., testing different parameters on glass of the same material), the laser parameters (f, including power, pulse energy, etc.) of the laser output laser required to reach the target depth (d) and the corresponding etching time (g) are determined.

[0041] B: Determine the radial width.

[0042] In wet etching, the etching solution not only etches along the depth direction, but also expands laterally in an isotropic or anisotropic manner. Based on the etching time (g) confirmed above, the radial width (b, i.e., ring width) of the etching solution expanding outward from the laser-modified area during the etching process is confirmed through experimental data recording or simulation calculation.

[0043] C: Calculate the trajectory radius.

[0044] Based on the above data, calculate the geometric dimensions of the scan trajectory: Radius (a) of the circumferential tangent trajectory 11: To ensure that the final aperture equals the target aperture (e), the radius of the circumferential tangent trajectory 11 should be equal to the difference between the target aperture and the radial width. That is: a = e b.

[0045] Radius (c) of lattice trajectory 10: To ensure a flat bottom and without damaging the sidewall structure, the radius of the filling area of ​​lattice trajectory 10 should be slightly smaller than that of the circumferential trajectory 11. Specifically, the radius of lattice trajectory 10 is equal to the difference between the radius (a) of the circumferential trajectory 11 and a preset constant (k). That is: c = a k. In this embodiment, the preset constant k is preferably 5μm to ensure a proper transition between the lattice region and the ring-cut region, and to prevent edge breakage caused by excess energy.

[0046] Therefore, to ensure structural stability, the preferred scanning sequence is: first, scan along the lattice trajectory 10 to complete the modification of the central region; then scan along the circumferential cutting trajectory 11 to form the outer contour. This inside-out processing sequence can avoid affecting the processing accuracy of the central lattice due to stress release or microcrack propagation after processing the outer circumferential cutting area first.

[0047] Furthermore, in some embodiments with high aspect ratios or extremely high requirements for bottom flatness, the laser focal depth when scanning along the dot matrix trajectory 10 is greater than the laser focal depth when scanning along the circumferential trajectory 11. That is, when processing the center dot matrix, the laser focus is concentrated deeper into the glass substrate. This differentiated focal setting helps compensate for energy attenuation during laser transmission, ensuring sufficient modification depth at the bottom, thereby obtaining a more perfect flat bottom structure after etching.

[0048] In another embodiment, the cleanliness of the substrate surface must be ensured before laser-induced operation. Specifically, a mixture of anhydrous ethanol and deionized water is used as the cleaning solution. The glass substrate is immersed in the cleaning solution for ultrasonic cleaning to remove oil and particles. After cleaning, the glass substrate is placed in an oven for drying to remove surface moisture and prevent water film from interfering with laser focusing.

[0049] Furthermore, the etching solution is a mixture of hydrofluoric acid (HF) and nitric acid (HNO₃). HF forms the main component for etching the glass, while HNO₃ is used to regulate the reaction rate and improve surface quality. During the etching process, the etching solution is magnetically stirred. Magnetic stirring accelerates the diffusion of reaction products and the supply of fresh etching solution, ensuring that the etching rate inside the blind hole (especially at the bottom) is consistent with that at the hole opening, further improving the flatness of the hole bottom.

[0050] In addition, the reaction must be stopped and the substrate cleaned immediately after etching. The glass substrate is removed from the etching solution and cleaned sequentially with deionized water (to remove acid residue) and anhydrous ethanol (to remove water stains and organic residue). Finally, the cleaned glass substrate is dried to obtain the finished product.

[0051] In summary, this invention discloses a method for preparing a TGV flat-bottom blind via on a glass substrate. The following is a detailed description using a TGV flat-bottom blind via with a diameter of 50 μm and a depth of 200 μm as an example.

[0052] 1. Preparation: A borosilicate glass substrate with a thickness of 0.5 mm was selected. It was ultrasonically cleaned with a mixture of anhydrous ethanol and deionized water for 10 minutes and then dried in an oven at 100°C for 30 minutes.

[0053] 2. Trajectory Planning and Parameter Calculation: Target parameters: target aperture (radius) e=50μm, target depth d=200μm.

[0054] Experimental determination: Preliminary experiments confirmed that the etching time required to reach a depth of 200 μm under the selected pulsed ultraviolet laser parameters is T. At this etching time T, the total radial expansion (radial width) b caused by the etching solution is approximately 30 μm.

[0055] Trajectory calculation: Circular trajectory 11 Radius a=e b=50μm 30μm = 20μm.

[0056] 10-dot matrix trajectory with radius c=a 5μm=20μm 5μm = 15μm.

[0057] Trajectory generation: Generate a circle with a radius of 20μm as the circumferential trajectory 11, and coaxially generate a circular region with a radius of 15μm inside it. This region is filled with a uniformly distributed array of laser spot patterns (the spot spacing is set according to the size of the laser spot, for example, 2-3μm).

[0058] 3. Laser-induced: The substrate was fixed on the worktable. Using a pulsed ultraviolet laser, the dot matrix within a 15μm radius area was first scanned point by point to form a central uniform modification region; then, a ring path with a 20μm radius was continuously scanned to form a ring modification region.

[0059] 4. Wet etching: Prepare a mixed etching solution of hydrofluoric acid and nitric acid. Immerse the laser-treated substrate in the etching solution, turn on magnetic stirring, and maintain a constant temperature. During etching, the outer annular modified region is etched and expanded to form sidewalls, while the central lattice modified region is etched and connected to form the bottom. It should be noted that when the central lattice modified region is etched, the area between the lattice modified region and the annular modified region (radial width of 5 μm) is also etched together. It should also be noted that an alkaline solution can be used as the etching solution.

[0060] 5. Results and Post-processing: The substrate was removed when the etching depth reached 200 μm. It was then washed with deionized water and anhydrous ethanol and dried.

[0061] The final TGV blind vias were tested and found to have a diameter of 50 μm, a depth of 200 μm, and a flat bottom region radius exceeding 35 μm (corresponding to the expanded lattice region). Furthermore, the bottom surface was smooth and flat, without any obvious tapered tip. This significantly increased the effective interconnect area at the bottom of the blind via, which is beneficial for subsequent metallization processes.

[0062] In another preferred embodiment of the present invention, a glass substrate is also disclosed, which includes a substrate body having blind holes formed based on the glass substrate TGV flat-bottom blind hole preparation method in the above embodiments.

[0063] 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 claims of the present invention are still within the scope of the present invention.

Claims

1. A method for fabricating TGV flat-bottom blind vias on a glass substrate, characterized in that, include: A scanning trajectory is obtained to indicate the movement of a laser for laser-induced processing of the glass substrate. The scanning trajectory includes a coaxially nested dot matrix trajectory and a circumferential trajectory. The circumferential trajectory is located outside the dot matrix trajectory. The dot matrix trajectory includes a plurality of trajectory points arranged at intervals. The circumferential trajectory includes a continuous circular trajectory line. Laser scanning is performed point by point along each trajectory point in the dot matrix to form a dot matrix modification area located in the center region of the target blind hole; Continuous scanning is performed along the circumferential trajectory to form an annular modification region located outside the lattice modification region; The glass substrate, after laser-induced processing, is placed in an etching solution for wet etching. The annular modified region is etched and expanded to form the sidewall of the target blind hole, and the lattice modified region is etched and connected to form the bottom of the target blind hole.

2. The method for preparing TGV flat-bottom blind vias on a glass substrate according to claim 1, characterized in that, First, scan along the dot matrix trajectory, then scan along the circumferential trajectory.

3. The method for preparing TGV flat-bottom blind vias on a glass substrate according to claim 1, characterized in that, The laser focal depth when scanning along the dot matrix trajectory is greater than the laser focal depth when scanning along the circumferential trajectory.

4. The method for preparing TGV flat-bottom blind vias on a glass substrate according to claim 1, characterized in that, The method for determining the size parameters of the scanning trajectory includes: Based on the aperture and depth of the target blind hole, the laser parameters and etching time of the laser output by the laser are confirmed; Based on the etching time, the radial width of the etching solution expanding outward from the annular modified region during the etching process is confirmed. The diameter of the circumferential trajectory is equal to the difference between the aperture and the radial width; The diameter of the dot matrix trajectory is equal to the difference between the diameter of the circumferential trajectory and a preset constant.

5. The method for preparing TGV flat-bottom blind vias on a glass substrate according to claim 4, characterized in that, The laser parameters, etching time, and radial width were confirmed based on gradient experiments.

6. The method for preparing TGV flat-bottom blind vias on a glass substrate according to claim 1, characterized in that, Before performing the laser-induced operation, a method for pre-treating the glass substrate is also included: using a mixture of anhydrous ethanol and deionized water as a cleaning solution to ultrasonically clean the glass substrate; and placing the cleaned glass substrate in an oven for drying.

7. The method for preparing TGV flat-bottom blind vias on a glass substrate according to claim 1, characterized in that, During the etching process, the etching solution is magnetically stirred.

8. The method for preparing TGV flat-bottom blind vias on a glass substrate according to claim 1, characterized in that, After etching is completed, a post-processing step is also included: the glass substrate is removed from the etching solution and cleaned sequentially with deionized water and anhydrous ethanol; and the cleaned glass substrate is dried.

9. A glass substrate, characterized in that, It includes a substrate body having blind holes formed based on the glass substrate TGV flat-bottom blind hole preparation method according to any one of claims 1 to 8.

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