A low dielectric constant borosilicate glass suitable for TGV process and a method for preparing the same

Abstract

This invention discloses a low-dielectric-constant borosilicate glass suitable for TGV processes and its preparation method. By introducing a synergistic system of Ag₂O and Ce₂O₃, this glass exhibits a dielectric constant ≤4.5, dielectric loss ≤0.003 at 10GHz, a thermal expansion coefficient matching that of silicon, and a Young's modulus ≥70 GPa. The preparation method includes steps such as mixing, high-temperature melting, clarification and homogenization, and annealing. The resulting glass exhibits an etching selectivity of over 25:1 after laser irradiation, enabling the fabrication of high-quality, vertically smooth through-holes, making it suitable for 5G / 6G communication chip packaging and glass adapter boards.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor packaging materials technology, specifically relating to a low dielectric constant borosilicate glass suitable for glass through-hole processes, its preparation method, and its application in high-frequency chip packaging and glass adapters. Background Technology

[0002] With the rapid development of fifth-generation (5G) and future sixth-generation (6G) mobile communication technologies, high-frequency, high-speed, and low-latency signal transmission places more stringent performance requirements on semiconductor packaging materials. Through-glass via (TW) technology, due to its excellent high-frequency electrical performance, precisely adjustable coefficient of thermal expansion, good dimensional stability, and panel-level manufacturing cost advantages, is considered a key technology path for next-generation 3D integration and advanced packaging, and is widely used in RF front-end modules, high-performance computing chip adapter boards, and integrated passive devices.

[0003] However, existing glass materials suitable for TGV processes still face numerous technical bottlenecks. First, to achieve low dielectric constants, traditional glasses typically employ high silica and high boron oxide systems. While this reduces signal propagation delay, it often results in a loose glass network structure and low Young's modulus, making it difficult to meet the rigidity requirements of thin substrates. Second, the mismatch in thermal expansion coefficients between the glass material and the silicon chip or metal package shell is significant, easily generating thermal stress during temperature cycling, leading to warping or sealing failure. Furthermore, the core step of the TGV process—laser-induced deep etching—places specific requirements on the glass material: the glass must undergo significant physicochemical changes in the laser irradiation area, forming easily etchable micro-regions with a high etch selectivity compared to the unmodified areas. Existing commercial glasses perform poorly in this regard, often exhibiting low etch selectivity, conical via morphology, and rough sidewalls, severely hindering the realization of high-density interconnects.

[0004] Therefore, developing a special TGV glass material that combines excellent high-frequency dielectric properties, matched thermal expansion characteristics, high mechanical strength, and good adaptability to laser processing has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention discloses a low-dielectric-constant borosilicate glass specifically designed for TGV processes and its preparation method. By precisely controlling the glass network structure and introducing functional components, the problem of simultaneously achieving high-frequency dielectric properties and laser processing adaptability is solved. The preparation process involves mixing, high-temperature melting, clarification and homogenization, and annealing to obtain a glass material with uniform properties. The resulting glass exhibits excellent high-frequency dielectric properties, a coefficient of thermal expansion matching that of silicon, and high mechanical strength. Particularly valuable is its ability to form highly etch-selective regions after laser irradiation, easily obtaining high-quality, vertically smooth through-holes. This glass can be widely used in 5G / 6G communications and advanced packaging fields.

[0006] This invention provides a method for preparing low dielectric constant borosilicate glass suitable for TGV process, which is prepared from the following raw materials in the following molar percentages:

[0007]

[0008] Component description:

[0009] 1) SiO2, B2O3, and Al2O3 constitute the main network framework of the glass. The total content of SiO2 and B2O3 is controlled at over 70% to ensure that the glass has intrinsic low dielectric properties; Al2O3 enters the network in the form of [AlO4] tetrahedra, effectively improving the Young's modulus of the glass.

[0010] 2) The total amount of alkaline earth metal oxides (MgO, CaO, BaO, SrO) is controlled at 1%~5%. The melting temperature and thermal expansion coefficient of the glass are adjusted by the mixed alkali effect to achieve precise matching with the silicon substrate (CTE ~3-4 ppm / ℃).

[0011] 3) Ag₂O and Ce₂O₃ constitute a core functional synergistic system. Under ultrafast laser irradiation, they undergo a photochemical reduction reaction, inducing structural relaxation in the modified region and forming easily etchable micro-regions, significantly improving the selectivity of laser-induced etching. The mass ratio of Ag₂O to Ce₂O₃ is preferably controlled within the range of 0.2 to 0.8.

[0012] 4) Clarifying agents are used to promote the removal of bubbles during the high-temperature melting process of glass molten glass, ensuring the internal quality and optical uniformity of the glass substrate. They are at least one of SnO2, CeO2, NaCl or sulfate.

[0013] This invention also provides a method for preparing low-melting-point sealing glass powder for MEMS, characterized by comprising the following steps:

[0014] 1) Accurately weigh the quartz sand, alumina, boric acid, carbonate, silver nitrate, cerium oxide and clarifying agent according to the molar percentage, and dry at 120℃ for 2 hours to remove moisture.

[0015] 2) Put the dried raw materials into a V-type mixer and mix at 250 rpm for 3 hours. Then pass the mixture through a 40-mesh sieve to obtain a uniform batch.

[0016] 3) The batch material is loaded into a platinum crucible and heated to 1600℃ at a rate of 5℃ / min. The temperature is maintained for 5 hours, and the mixture is stirred once every hour during the process to promote homogenization.

[0017] 4) After melting, let it stand at 1600℃ for 1.5 hours to allow the bubbles to rise and escape, thus obtaining a clear and transparent glass melt.

[0018] 5) Pour the molten glass into a preheated 400°C mold to form the glass, then immediately transfer it to a muffle furnace and hold it at 620°C for 3 hours. Cool it to room temperature at a rate of 1°C / min.

[0019] 6) Cut, grind, and polish the glass block to prepare a 50 mm × 50 mm × 0.5 mm substrate with a surface roughness Ra < 1 nm.

[0020] 7) The device is modified by scanning with a picosecond laser according to a preset pattern, placed in 10% hydrofluoric acid at 30°C for ultrasonic etching for 30 minutes, and then cleaned and dried to obtain a through hole.

[0021] 8) Test the dielectric constant and loss, thermal expansion coefficient, Young's modulus, and etching selectivity at 10 GHz, and observe the via morphology using SEM.

[0022] This glass combines excellent high-frequency dielectric properties with good TGV process adaptability. Not only does it have a dielectric constant ≤4.5 and dielectric loss ≤0.003 at 10GHz, but its thermal expansion coefficient is precisely matched with that of the silicon substrate and its Young's modulus ≥70 GPa. At the same time, the etching selectivity after laser irradiation is above 25:1, which can obtain high-quality through holes with vertical smoothness.

[0023] This invention is the first to synergistically introduce Ag2O and Ce2O3 into the TGV glass system, utilizing the redox reaction of the two under laser irradiation to induce structural relaxation in the modified region, thereby significantly improving etching selectivity; at the same time, through the optimization of the SiO2-Al2O3-B2O3 network structure and the multi-component compounding of alkaline earth metals, the dielectric properties, mechanical strength and thermal compatibility are synergistically improved. Attached Figure Description

[0024] A low dielectric constant borosilicate glass suitable for TGV process and its preparation method are described below: Detailed Implementation

[0025] The glass compositions of three specific embodiments of a low dielectric constant borosilicate glass suitable for the TGV process are shown in Table 1:

[0026] Table 1: Glass Formulations for Three Specific Examples

[0027]

[0028] Example 1

[0029] The composition is shown in Table 1, #1, and the specific preparation process is as follows:

[0030] 1) Accurately weigh SiO2, Al2O3, B2O3, MgO, CaO, BaO, Ag2O, Ce2O3, and SnO2 according to the formula, and place the raw materials in a 120℃ oven to dry for 2 hours to remove moisture.

[0031] 2) After drying, the raw materials are fed into a V-type mixer, zirconia grinding balls are added, and the mixture is stirred at 250 rpm for 3 hours. The mixture is then passed through a 40-mesh sieve to obtain a uniform batch. The batch is then placed in a platinum crucible and placed in a silicon molybdenum rod high-temperature furnace. The temperature is increased to 1000℃ at 5℃ / min and held for 1 hour to decompose the carbonates. The temperature is then increased to 1600℃ at 5℃ / min and held for 5 hours. During this period, the mixture is stirred once an hour to promote homogenization.

[0032] 3) After melting, let it stand at 1600℃ for 1.5 hours to clarify, allowing the bubbles to rise and escape, and obtain a clear and transparent glass melt. Quickly pour the glass melt into a preheated 400℃ cast iron mold to form it, and immediately transfer it to a muffle furnace to anneal at 620℃ for 3 hours, and cool it to room temperature at 1℃ / min.

[0033] 4) The annealed glass block was cut, ground, and polished to prepare a 50 mm × 50 mm × 0.5 mm substrate with a surface roughness Ra < 1 nm. A picosecond laser (wavelength 1030 nm, pulse energy 8 μJ, repetition frequency 200 kHz) was used to scan and modify the substrate according to a preset pattern. The substrate was then ultrasonically etched in 10% hydrofluoric acid at 30°C for 30 minutes, followed by cleaning and drying to obtain through-holes.

[0034] 5) Tested at 10GHz: dielectric constant 4.3, dielectric loss 0.0025, coefficient of thermal expansion 4.2 ppm / ℃, Young's modulus 72 GPa, bending strength 95 MPa, etching selectivity 32:1, and SEM observation showed that the vias were vertical and smooth.

[0035] Example 2

[0036] The composition is shown in Table 1, #2, and the specific preparation process is as follows:

[0037] 1) Accurately weigh SiO2, Al2O, B2O3, MgO, CaO, BaO, Ag2O, Ce2O3, and NaCl according to the formula. Place the raw materials in a 120℃ oven and dry for 2 hours to remove moisture.

[0038] 2) After drying, the raw materials are fed into a V-type mixer, zirconia grinding balls are added, and the mixture is stirred at 250 rpm for 3 hours. The mixture is then passed through a 40-mesh sieve to obtain a uniform batch. The batch is then placed in a platinum crucible and placed in a silicon molybdenum rod high-temperature furnace. The temperature is increased to 1000℃ at 5℃ / min and held for 1 hour to decompose the carbonates. The temperature is then increased to 1600℃ at 5℃ / min and held for 5 hours. During this period, the mixture is stirred once an hour to promote homogenization.

[0039] 3) After melting, allow the glass to stand at 1600℃ for 1.5 hours to clarify, allowing bubbles to rise and escape, resulting in a clear and transparent glass melt. Quickly pour the glass melt into a preheated 400℃ cast iron mold, immediately transfer it to a muffle furnace, and anneal at 620℃ for 3 hours, cooling to room temperature at a rate of 1℃ / min. Cut, grind, and polish the annealed glass block to prepare a 50 mm × 50 mm × 0.5 mm substrate with a surface roughness Ra < 1 nm.

[0040] 4) The modification is performed by scanning the pre-set pattern using a picosecond laser (wavelength 1030 nm, pulse energy 10 μJ, repetition frequency 200 kHz), followed by ultrasonic etching in 10% hydrofluoric acid at 30°C for 30 minutes, and then cleaning and drying to obtain through holes.

[0041] 5) Tested at 10GHz: dielectric constant 4.2, dielectric loss 0.0022, coefficient of thermal expansion 4.0 ppm / ℃, Young's modulus 74 GPa, bending strength 98 MPa, etching selectivity 38:1, and SEM observation showed that the vias were vertical and smooth.

[0042] Example 3

[0043] The composition is shown in Table 1, #3, and the specific preparation process is as follows:

[0044] 1) Accurately weigh SiO2, Al2O3, B2O3, MgO, CaO, SrO, Ag2O, Ce2O3, and SnO2 according to the formula. Place the raw materials in a 120℃ oven and dry for 2 hours to remove moisture.

[0045] 2) After drying, the raw materials are fed into a V-type mixer, zirconia grinding balls are added, and the mixture is stirred at 250 rpm for 3 hours. The mixture is then passed through a 40-mesh sieve to obtain a uniform batch. The batch is then placed in a platinum crucible and placed in a silicon molybdenum rod high-temperature furnace. The temperature is increased to 1000℃ at 5℃ / min and held for 1 hour to decompose the carbonates. The temperature is then increased to 1600℃ at 5℃ / min and held for 5 hours. During this period, the mixture is stirred once an hour to promote homogenization.

[0046] 3) After melting, let it stand at 1600℃ for 1.5 hours to clarify, allowing the bubbles to rise and escape, and obtain a clear and transparent glass melt. Quickly pour the glass melt into a preheated 400℃ cast iron mold to form it, and immediately transfer it to a muffle furnace to anneal at 620℃ for 3 hours, and cool it to room temperature at 1℃ / min.

[0047] 4) The annealed glass block was cut, ground, and polished to prepare a 50 mm × 50 mm × 0.5 mm substrate with a surface roughness Ra < 1 nm. A picosecond laser (wavelength 1030 nm, pulse energy 6 μJ, repetition frequency 200 kHz) was used to scan and modify the substrate according to a preset pattern. The substrate was then ultrasonically etched in 10% hydrofluoric acid at 30°C for 30 minutes, followed by cleaning and drying to obtain through-holes.

[0048] 5) Tested at 10GHz: dielectric constant 4.4, dielectric loss 0.0028, coefficient of thermal expansion 3.8 ppm / ℃, Young's modulus 70 GPa, bending strength 88 MPa, etching selectivity 28:1, and SEM observation showed that the vias were vertical and smooth.

Claims

1. A low dielectric constant borosilicate glass suitable for TGV process, characterized in that, It consists of the following components by mass percentage:

2. The borosilicate glass according to claim 1, characterized in that, The glass has a dielectric constant of less than or equal to 4.5 and a dielectric loss of less than or equal to 0.003 at a frequency of 10 GHz.

3. The borosilicate glass according to claim 1, characterized in that, The coefficient of thermal expansion (CTE) of the glass is 3.0~5.0 ppm / ℃, which is compatible with silicon substrates or Kovar alloy materials.

4. The borosilicate glass according to claim 1, characterized in that, The glass has a Young's modulus greater than or equal to 70 GPa.

5. The borosilicate glass according to claim 1, characterized in that, The laser-induced etching selectivity of the glass is greater than or equal to 25:

1.

6. The borosilicate glass according to claim 1, characterized in that, The clarifying agent includes at least one of SnO2, CeO2, NaCl, or sulfate.

7. The borosilicate glass according to claim 1, characterized in that, The mass ratio of Ag2O to Ce2O3 in the glass satisfies: 0.2 ≤ Ag2O / Ce2O3 ≤ 0.

8.

8. A method for preparing low dielectric constant borosilicate glass suitable for TGV process as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Weigh the raw materials according to the proportions, mix them evenly to obtain the batch material; S2. The batch material is fed into the melting furnace and melted and clarified at a high temperature of 1580~1620℃ to obtain a uniform glass melt. S3. The molten glass is shaped and annealed at a temperature of 600~650℃ for 2~6 hours, and then cooled to room temperature in the furnace to obtain a glass substrate.

9. The preparation method according to claim 8, characterized in that, In step S2, a platinum or quartz crucible is used for melting, and the melting time is 4 to 8 hours.

10. A method for processing TGV through holes in glass according to any one of claims 1-7, characterized in that, include: Ultrafast pulsed lasers are used to irradiate a predetermined area of ​​a glass substrate to induce modification; The glass substrate irradiated by laser is immersed in a hydrofluoric acid-based etching solution for etching to form through holes; In this process, Ag2O and Ce2O3 in the glass substrate undergo a redox reaction under laser irradiation, which promotes the relaxation of the structure in the laser-modified region and increases the etching rate of this region in the etching solution.

11. The method according to claim 10, characterized in that, The etching solution is a hydrofluoric acid solution with a mass fraction of 5% to 15%, and the etching temperature is 25 to 35°C.

12. A glass transition plate, characterized in that, It comprises the glass according to any one of claims 1-7, or is prepared by the method according to any one of claims 8-11.

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