BOE solution for TGV glass through hole etching and application thereof

Abstract

The invention discloses a BOE solution for etching a TGV glass through hole and application of the BOE solution. The BOE solution is prepared from the following components in percentage by mass: 10 to 30 weight percent of hydrofluoric acid, 5 to 40 weight percent of fluoride, 0.05 to 0.5 weight percent of organic corrosion inhibitor, 0.05 to 0.5 weight percent of complexing agent and the balance of deionized water; the fluoride is composed of tetramethylammonium fluoride and ammonium fluoride according to the mass ratio of 1: (0.2-1.0). The TMAF is introduced to replace part of NH4F, and the organic corrosion inhibitor and the complexing agent are combined, so that transverse etching is inhibited, and the perpendicularity of the structure is improved; the wettability of the solution is improved, and the roughness of the etched glass surface is reduced; the balance of active fluorine species is stabilized, and the etching rate is ensured to be stable and repeatable.

Description

Technical Field

[0001] This invention belongs to the field of microelectronic packaging and microstructure processing technology, specifically relating to a BOE solution for etching through-holes in TGV glass and its application. Background Technology

[0002] TGV (Through-Glass Vias) is a key technology for 3D integration and high-frequency device manufacturing. It creates vertical interconnect channels (similar to Through-Silicon Vias, TSVs) on glass substrates for chip packaging, RF devices, MEMS, and optoelectronics. TGV glass refers to this type of functional glass substrate with through-hole structures. With its low dielectric loss and excellent insulation, it has applications in RF chips, high-end MEMS sensors, and high-density system integration. It has become one of the preferred solutions in the 3D packaging of 5G and 6G high-frequency communication chips; and it is widely used in the packaging of large chips such as AI chips, CPUs, and GPUs due to its high-density interconnect capabilities. Furthermore, it can be used to mount inductors within glass and to achieve multi-chip module packaging with stacked glass substrates, solving the problem of thermal expansion coefficient mismatch in traditional packaging. Currently, commonly used TGV processes include laser drilling, wet / dry etching, and metallization (such as copper filling). However, the via diameter and spacing of sandblasting and electrochemical discharge methods are relatively large, making it difficult to meet the requirements of high-density packaging. Laser ablation has low batch drilling efficiency and the vias have a tapered shape. While the mainstream laser-induced etching method has better overall performance, it still requires precise control of laser parameters and chemical etching rhythm; otherwise, it can easily lead to uneven via dimensions. At the same time, in high aspect ratio scenarios, controlling the smoothness and perpendicularity of the via inner wall is extremely difficult, and excessive sidewall roughness and tapering will exacerbate signal loss in high-frequency applications. Therefore, how to improve the process system for the perpendicularity of TGV glass has become a key constraint for improving the quality of TGV glass.

[0003] Chinese patent CN111799169A discloses a process for processing TGV using femtosecond laser combined with HF wet etching. In this process, a femtosecond laser is used to scan the area around the hole on the glass surface, and HF etching is used to etch the hole in a ring. Then, the back side of the wafer is thinned and the components are engineered. Finally, a second pattern etching process is performed on the glass surface using HF etching to complete the perforation, thereby peeling off the glass in the isolated area in the middle and completing the overall TGV through-hole.

[0004] Chinese patent CN118812168A discloses a method for processing TGV through holes in high aluminosilicate glass. The method involves pre-treating the high aluminosilicate glass substrate to be processed; then irradiating the target area of ​​the high aluminosilicate glass substrate with a laser at a pressure of 0.5 to 10 kg / cm, repeating the process multiple times to obtain through holes with a small taper, smooth inner walls, and a diameter of 20 to 52 micrometers.

[0005] However, current etching solutions used for TGV glass etching cannot guarantee a high degree of vertical taper. Furthermore, laser-based TGV glass processing is complex, requires sophisticated equipment and advanced operation, and still necessitates the use of an etching solution. Therefore, it is necessary to develop an etching system with high verticality and a simple application method for preparing TGV glass. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a BOE solution for etching through-holes in TGV glass and its application, which significantly improves the perpendicularity, wettability, and surface roughness after etching, while maintaining a high etching rate.

[0007] To achieve the above objectives, the present invention provides a BOE solution for etching through-holes in TGV glass, comprising the following components by mass percentage: 10-30 wt% hydrofluoric acid, 5-40 wt% fluoride, 0.05-0.5 wt% organic corrosion inhibitor, 0.05-0.5 wt% complexing agent, and the balance being deionized water.

[0008] Preferably, the BOE solution comprises the following components by mass percentage: 10-22 wt% hydrofluoric acid, 12-28 wt% fluoride, 0.1-0.3 wt% corrosion inhibitor, 0.05-0.2 wt% deionized water.

[0009] Preferably, the organic corrosion inhibitor is one or more of 4,4,4-trifluorobutyric acid, trifluoropropionic acid, 2-(difluoromethoxy)acetic acid, or tetrafluorosuccinic acid.

[0010] Preferably, the complexing agent is one or more of ethylenediaminetetramethylenephosphonate sodium (EDTMPS), diethylenetriaminepentamethylenephosphonate (DTPMPA), or EDTA.

[0011] Preferably, the fluoride is composed of tetramethylammonium fluoride and ammonium fluoride in a mass ratio of 1:0.2-1.0.

[0012] More preferably, the tetramethylammonium fluoride is a solid with a mass percentage ≥ 99 wt%.

[0013] More preferably, the ammonium fluoride is an aqueous solution with a mass percentage of 30-50%.

[0014] Preferably, the hydrofluoric acid has a mass percentage of 40-55%.

[0015] Preferably, the deionized water is ultrapure water with a conductivity of 18.2 MΩ.

[0016] The present invention also provides an application of BOE solution for etching through-holes in TGV glass, the application comprising the following steps: (1) Add the slow-release agent and complexing agent to deionized water, mix well, add fluoride, mix well, add hydrofluoric acid, and mix well to obtain BOE solution. (2) Etch the TGV glass after heating the BOE solution to form a vertical through hole.

[0017] Preferably, the etching conditions in step (2) are etching at 20-30°C for 100-300 min.

[0018] Preferably, the TGV glass in step (2) is silicate glass with a thickness of 500 μm.

[0019] The beneficial effects of this invention are as follows: 1. This invention adds ammonium fluoride and tetramethylammonium fluoride to hydrofluoric acid, and optimizes the selection and concentration of organic corrosion inhibitors and complexing agents to achieve the following objectives: inhibiting lateral etching and improving the verticality of the structure; tetramethylammonium fluoride and organic corrosion inhibitors have surface activity, which can reduce the surface tension of the solution, thereby improving the wettability of the solution; stabilizing the balance of active fluorine species ensures a stable and repeatable etching rate. Simultaneously, while maintaining a high etching rate, process stability and long-term solution lifespan are extended; the complexing agent can promote product dissolution and reduce the roughness of the glass surface after etching.

[0020] 2. Tetramethylammonium fluoride and ammonium fluoride are used as fluorides. The TMA⁺ cations ionized from tetramethylammonium fluoride are adsorbed at the gas-liquid interface and solid-liquid interface, reducing surface tension and improving microporous wettability.

[0021] 3. Using 4,4,4-trifluorobutyric acid, trifluoropropionic acid, 2-(difluoromethoxy)acetic acid or tetrafluorosuccinic acid as organic corrosion inhibitors, the side etching of glass is selectively slowed down through weak adsorption or film formation, thereby reducing side etching and improving the verticality of the etched via.

[0022] 4. Using EDTMPS, EDTA, etc. as complexing agents, through interaction with SiF6 2- Ca 2+ Mg 2+ Plasma complexation reaction regulates the dissolution and diffusion of etching byproducts, avoiding localized high concentrations of SiF6. 2- This causes over-etching, preventing the precipitation of Ca and Mg metals and reducing the roughness of the glass surface after etching.

[0023] 5. The BOE etching solution prepared by this invention can be reused to etch multiple batches of TGV glass. After etching 20 batches, the etching rate can still be maintained at 930 Å / min. It can still perform high-speed, high-perpendicularity, and low-roughness etching on TGV glass. Therefore, it has the advantages of long etching life and stable etching rate during long-term use. Attached Figure Description

[0024] Figure 1 The surface morphology of the borosilicate glass sheet before etching (n=0.210nm).

[0025] Figure 2 The surface morphology of the borosilicate glass sheet after etching with the BOE solution prepared in Example 11 (n=0.228nm).

[0026] Figure 3 The surface morphology of the borosilicate glass sheet after etching with the BOE solution prepared in Comparative Example 2 is shown (n=0.758nm). Detailed Implementation

[0027] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0028] In the following examples and comparative examples: hydrofluoric acid is an aqueous solution of hydrofluoric acid with a mass percentage of 49%; Ammonium fluoride is a 40% (w / w) aqueous solution of ammonium fluoride; Tetramethylammonium fluoride is a solid with a purity of 99 wt%.

[0029] Examples 1-16, Comparative Examples 1-7 The preparation method is as follows: (1) Dissolve the sustained-release agent and the complexing agent in deionized water to prepare sustained-release agent solution and complexing agent solution with a mass percentage of 2.5% and 2.5%, respectively; (2) Add tetramethylammonium fluoride to the ammonium fluoride solution, mix and dissolve to obtain a fluoride solution; (3) Add the slow-release agent solution and complexing agent solution to the deionized water in sequence, mix well, and then add the fluoride solution and mix well. (4) Place the mixed solution obtained in step (3) in a ventilated environment, add HF solution, and mix well to obtain BOE solution; The specific formula is shown in Table 1: Table 1 Formulations of Examples and Comparative Examples

[0030] Note: The table only lists the usage of the main raw materials; the remainder is supplemented by deionized water.

[0031] Example 17 The BOE etching solution prepared in the above examples and comparative examples was used to etch a laser-induced borosilicate glass sheet (thickness 500 μm, diameter 25 mm, induced area diameter 50 μm) at 25°C. The etching included immersion etching for 2 min and batch deep hole etching to the target depth (50 μm). After etching, the perpendicularity of the etched cross-section was detected by SEM scanning, the thickness difference before and after etching was detected by ultra-depth-of-field microscopy, the etching rate was calculated, and the roughness of the glass surface after etching was detected by AFM. The test results are shown in Table 2. Table 2 Etching Results

[0032] The results are shown in Table 1-2. Figure 1-3 As shown, in Examples 1-15, tetramethylammonium fluoride and ammonium fluoride were combined as fluorides, and a slow-release agent and a complexing agent were added to prepare the BOE etching solution. This still maintained an etching rate of over 800 Å / min, and the perpendicularity of the etched glass was ≥77°, making it suitable for etching TGV glass. In Comparative Example 1, the BOE solution prepared using hydrofluoric acid, ammonium fluoride, a slow-release agent, and a complexing agent produced good surface roughness, but the perpendicularity was only 69°, indicating a relatively high amount of lateral etching. In Comparative Example 2, only hydrofluoric acid and ammonium fluoride were used to prepare the BOE solution for etching the glass, resulting in a perpendicularity of only 65° and a high amount of lateral etching.

Claims

1. A BOE solution for etching through-holes in TGV glass, characterized in that: The composition by mass percentage is as follows: hydrofluoric acid 10-30 wt%, fluoride 5-40 wt%, organic corrosion inhibitor 0.05-0.5 wt%, complexing agent 0.05-0.5 wt%, and the balance is deionized water.

2. The BOE solution for etching through-holes in TGV glass according to claim 1, characterized in that: The organic corrosion inhibitor is one or more of 4,4,4-trifluorobutyric acid, trifluoropropionic acid, 2-(difluoromethoxy)acetic acid, or tetrafluorosuccinic acid.

3. The BOE solution for etching through-holes in TGV glass according to claim 1, characterized in that: The complexing agent is one or more of ethylenediaminetetramethylene phosphate sodium, diethylenetriaminepentamethylene phosphonate, or EDTA.

4. The BOE solution for etching through-holes in TGV glass according to claim 1, characterized in that: The fluoride is composed of tetramethylammonium fluoride and ammonium fluoride in a mass ratio of 1:0.2-1.

0.

5. The BOE solution for etching through-holes in TGV glass according to claim 4, characterized in that: The tetramethylammonium fluoride is a solid with a mass percentage ≥ 99 wt%.

6. The BOE solution for etching through-holes in TGV glass according to claim 4, characterized in that: The ammonium fluoride is an aqueous solution with a mass percentage of 30-50%.

7. The BOE solution for etching TGV glass through-holes according to claim 1, characterized in that: The hydrofluoric acid has a mass percentage of 40-55%.

8. The application of a BOE solution for etching TGV glass through-holes as described in any one of claims 1-7, characterized in that: The application includes the following steps: (1) Add the slow-release agent and complexing agent to deionized water, mix well, add fluoride, mix well, add hydrofluoric acid, and mix well to obtain BOE solution. (2) Etch the TGV glass after heating the BOE solution to form a vertical through hole.

9. The application according to claim 8, characterized in that: The etching conditions described in step (2) are etching at 20-30℃ for 100-300 min.

10. The application according to claim 8, characterized in that: The TGV glass mentioned in step (2) is silicate-based glass with a thickness of 500 μm.

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