Method for preparing fluorine-doped porous low-dielectric glass through normal-pressure drying and application of fluorine-doped porous low-dielectric glass
By introducing fluorinated silanes during the sol preparation stage and using atmospheric pressure drying to prepare fluorine-doped porous low-dielectric glass, the problems of hydrophobicity and moisture resistance of materials under atmospheric pressure drying are solved, achieving a balance between low dielectric constant and superhydrophobicity, making it suitable for high-frequency electronic device applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-18
- Publication Date
- 2026-03-13
AI Technical Summary
Existing technologies make it difficult to prepare porous SiO2 materials with low dielectric constants under normal pressure drying. Furthermore, conventional hydrophobic treatment processes are complex, costly, and have unstable hydrophobic properties, which cannot meet the reliability requirements of high-frequency electronic devices.
Fluorine-containing silanes were used as co-precursors to participate in the hydrolysis-condensation reaction. Fluorine-doped porous low-dielectric glass was prepared in one step by combining atmospheric pressure drying. Hydrophobic functional groups were bonded at the molecular level in the SiO2 network, avoiding high-pressure supercritical drying and subsequent hydrophobic treatment.
It achieves low dielectric constant (1.8-2.2), superhydrophobicity (water contact angle >150°) and excellent moisture resistance. The material has stable performance in humid and hot environments, is suitable for mass production, reduces manufacturing costs and improves the long-term reliability of devices.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of functional glass materials technology, and particularly to a low-k dielectric constant material for high-frequency electronic devices and its preparation method. Specifically, this invention provides a method for preparing fluorine-doped porous glass with both superhydrophobicity and high moisture resistance by atmospheric pressure drying, as well as the porous glass material prepared by this method and its application in electronic devices such as integrated circuits, high-frequency circuit boards, and microwave dielectric resonators. Background Technology
[0002] With the rapid development of 5G, AI, and HPC technologies, electronic devices are evolving towards higher frequencies, higher integration, and higher computing speeds. Against this backdrop, signal transmission delay and crosstalk have become increasingly prominent, representing key bottlenecks restricting breakthroughs in chip performance. According to the International Technology Roadmap for Semiconductors (ITRS), once chip process nodes reach the nanoscale, interconnect delay surpasses gate delay, becoming the dominant factor affecting circuit response speed. Interconnect delay is directly related to the dielectric constant (Dk value) of the dielectric layer material, a relationship described by the formula: the delay time constant is proportional to the square root of the dielectric constant. Therefore, developing dielectric materials with ultra-low dielectric constants (Dk < 2.5) is crucial for reducing signal transmission loss, improving signal integrity, and lowering power consumption.
[0003] Porous silica (SiO2) materials are widely recognized as the most promising next-generation low-dielectric materials due to their unique physicochemical properties. Their core advantage lies in the ability to significantly reduce the overall dielectric constant of the material (up to 1.0-2.0) by introducing nanoscale air pores (where Dk≈1 for air), while maintaining excellent thermal stability and electrical insulation. Ideally, porous SiO2 materials should possess mutually isolated nanoscale pores, a narrow pore size distribution, high porosity, and a stable framework structure to minimize polarization effects and leakage current risks.
[0004] Currently, the mainstream technology for preparing high-performance porous SiO2 materials in industry and academia is supercritical drying. This technology first forms a wet gel using the sol-gel method, and then raises the temperature and pressure of the system in a high-pressure reactor above the critical point of the solvent (usually ethanol or carbon dioxide). In this supercritical state, the gas-liquid interface disappears, and surface tension ceases to exist, thus allowing for the non-destructive removal of the solvent from the gel pores, resulting in a three-dimensional nanonetwork structure with a high specific surface area (up to 1000 m²). 2 / g) and silica aerogels with extremely low dielectric constants. Although this method can prepare materials with complete structures and excellent properties, its inherent defects greatly limit its commercialization prospects: First, the process needs to be carried out under harsh conditions of high temperature (>200℃) and high pressure (>7MPa), which places extremely high demands on equipment and results in huge investment costs; second, the supercritical reaction involves high-pressure operation, which poses significant safety risks and requires strict explosion-proof requirements for the production environment; third, the process has extremely high energy consumption, long drying cycle, and low production efficiency, making it difficult to meet the needs of large-scale, continuous production.
[0005] To overcome the drawbacks of supercritical drying, atmospheric pressure drying has been proposed as a promising alternative. This method involves slow drying at low temperatures under atmospheric pressure, using clever chemical modifications to control capillary forces and prevent the collapse of the gel network structure. However, porous SiO2 materials prepared by conventional atmospheric pressure drying have a large number of unreacted hydrophilic silanol groups (-Si-OH) on their framework surface. These polar groups have a strong physical adsorption effect on water molecules in the environment (Dk≈80), leading to water accumulation within the nanopores. This results in a significant increase in dielectric constant and a sharp deterioration in dielectric loss (Df), causing a drastic degradation in the material's performance stability under humid and hot environments, making it unable to meet the stringent reliability requirements of electronic devices.
[0006] To address this moisture absorption problem, current solutions involve additional surface hydrophobication post-treatment of porous materials after atmospheric pressure drying. This can be achieved by applying low surface energy substances such as fluorinated silanes to the material surface using chemical vapor deposition (CVD) or liquid-phase impregnation. However, these post-treatment processes have several inherent limitations: First, they increase production steps and cycles, raising process complexity and production costs. Second, modifiers typically only adhere to the material surface, failing to penetrate evenly into the deep pores, resulting in uneven modification effects. Third, and most importantly, the surface-modified layer formed through physical adsorption or weak chemical bonding exhibits poor mechanical strength and weak adhesion, making it prone to detachment or degradation during subsequent chip processing (such as chemical mechanical polishing, CMP), thermal cycling, or minor wear. This leads to hydrophobic performance failure, insufficient durability, and ultimately affects the long-term reliability of the device.
[0007] Therefore, developing a material that combines low dielectric constant, excellent hydrophobicity (especially bulk hydrophobicity), high mechanical strength, and outstanding environmental stability, and preparing it through a simple, low-cost, easily scalable, and compatible method with existing integrated circuit processes, has become an urgent and highly challenging technical problem in the field of low dielectric materials, and is also a research focus of common concern in academia and industry. Summary of the Invention
[0008] The primary objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing porous glass with low dielectric constant, superhydrophobicity and excellent moisture resistance in one step without supercritical drying or post-hydrophobic treatment.
[0009] The specific technical solution adopted by this invention is as follows:
[0010] To achieve the above objectives, the present invention adopts the following technical solution:
[0011] In a first aspect, the present invention provides a method for preparing fluorine-doped porous low-dielectric glass by atmospheric pressure drying, comprising the following steps:
[0012] S1. Sol preparation: A silicon source, solvent, acid catalyst and water are mixed and subjected to a hydrolysis reaction to obtain a hydrolysate; then a fluorinated silane and a network modifier are added to the hydrolysate and mixed to obtain a mixed sol;
[0013] S2. Gelation: An alkaline catalyst is added to the mixed sol, the pH is adjusted to induce a gelation reaction, and then the mixture is allowed to stand until it is completely gelled to obtain a wet gel.
[0014] S3. Aging: The wet gel is sealed and aged in an aging solution to strengthen its network structure;
[0015] S4. Drying at ambient pressure: Place the aged wet gel in a drying device and dry it at ambient pressure using a gradient temperature program.
[0016] The fluorine-doped porous low-dielectric glass is finally obtained;
[0017] Preferably, the fluorinated silane in step S1 is at least one of heptadecafluorodecyltrimethoxysilane and tridecafluorooctyltriethoxysilane; the molar ratio of the fluorinated silane to the silicon source is (5%-20%):1.
[0018] Preferably, the network modifier in step S1 is methyltrimethoxysilane (MTMS); the molar ratio of the network modifier to the silicon source is (10%-40%):1.
[0019] Preferably, the temperature of the hydrolysis reaction in step S1 is 40-70°C;
[0020] Preferably, the pH adjustment range in step S2 is 7-10;
[0021] Preferably, the temperature in step S3 is 30-60℃; the sealing aging time is 24-72 hours.
[0022] Preferably, the gradient temperature program in step S4 is as follows: drying at 40-50℃ for 20-28 hours; drying at 60-70℃.
[0023] 20-28 hours
[0024] Dry at 80-90℃ for 20-28 hours; or at 100-120℃ for 4-8 hours.
[0025] Secondly, the present invention provides a fluorine-doped porous low-dielectric glass prepared by the above method, characterized in that:
[0026] The glass material has a nanoporous structure with fluorocarbon chains bonded to the surface of its pore walls; the dielectric constant of the glass material is 1.8-2.2 at 1MHz, the water contact angle is greater than 150°, and the roll-off angle is less than 10°; after being treated at 85℃ / 85%RH for 72 hours, the change rate of its dielectric constant is less than 5%.
[0027] Thirdly, the present invention provides the application of the above-mentioned fluorine-doped porous low-dielectric glass in high-frequency electronic devices, including but not limited to: dielectric layers in integrated circuits, high-frequency circuit boards, antenna substrates, and microwave dielectric resonators.
[0028] Beneficial effects
[0029] Compared with existing technologies, this invention exhibits significant comprehensive advantages. By introducing fluorosilanes (FAS) as co-precursors during the sol preparation stage to directly participate in the hydrolysis-condensation reaction, this invention achieves molecular-level bonding and uniform distribution of hydrophobic functional groups in the SiO2 network. This one-step in-situ modification technology fundamentally solves the hydrophobicity problem of materials, not only eliminating cumbersome and unstable post-processing steps but also ensuring the material's inherent hydrophobic properties. Simultaneously, the entire process employs atmospheric pressure drying technology, completely avoiding expensive, dangerous, and energy-intensive supercritical drying equipment. This simplifies the process, provides mild conditions, and is highly suitable for large-scale production, significantly reducing manufacturing costs. In terms of performance, the prepared porous glass not only possesses excellent low dielectric constant (~1.9) and superhydrophobicity (water contact angle >150°), but more importantly, it exhibits outstanding moisture resistance, with almost no performance degradation after humid heat aging. This effectively solves the core problem of performance failure caused by moisture absorption in atmospheric pressure-dried Low-k materials. Furthermore, the introduction of network modifiers (MTMS) significantly enhances the flexibility of the network, effectively suppresses the tendency to crack during the drying process, ensures the integrity of the material, and since the hydrophobic function originates from the material itself, it can still maintain superhydrophobicity even with slight surface wear, and its durability far exceeds that of surface coating modified materials. Detailed Implementation
[0030] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.
[0031] Example 1
[0032] 1. Sol preparation: In a 250mL Erlenmeyer flask, mix n(TEOS):n(EtOH):n(H2O):n(HCl) = 1:8:
[0033] In a molar ratio of 4:0.0005, tetraethyl orthosilicate (TEOS), anhydrous ethanol, deionized water, and 0.1M HCl solution were added sequentially. The mixture was placed in a 60°C water bath and stirred at 300 rpm for 1 hour to obtain a clear hydrolysate. Subsequently, methyltrimethoxysilane (MTMS) and heptadecafluorodecyltrimethoxysilane (FAS) were added to the hydrolysate at molar ratios of 20% and 10%, respectively, and stirring was continued for 1 hour to obtain a mixed sol.
[0034] 2. Gelation: Cool the mixed sol to room temperature, and add 0.1M ammonia water dropwise while stirring to adjust the pH to 8.5. Then pour the sol into a polytetrafluoroethylene mold, seal it, and let it stand for 12 hours to completely gel, obtaining a wet gel.
[0035] 3. Aging: Add a mixture of ethanol and FAS (volume ratio 95:5) to the mold to completely immerse the wet gel, seal it and place it in a 40℃ oven for aging for 48 hours.
[0036] 4. Drying under normal pressure: Remove the aged wet gel, blot the surface liquid with filter paper, and place it in a forced-air drying oven. Perform a gradient drying process according to the following procedure: 40℃ / 24h -> 60℃ / 24h -> 80℃ / 24h -> 120℃ / 6h. After natural cooling,
[0037] A complete fluorine-doped porous low-dielectric glass sample was obtained.
[0038] Comparative Example 1
[0039] The steps are the same as in Example 1, but FAS is not added during the sol preparation stage, and the aging solution is also pure ethanol.
[0040] 1. Sol Preparation: In a 250 mL Erlenmeyer flask, tetraethyl orthosilicate (TEOS), anhydrous ethanol, deionized water, and 0.1 M HCl solution were added sequentially in a molar ratio of n(TEOS):n(EtOH):n(H2O):n(HCl) = 1:8:4:0.0005. The mixture was placed in a 60 °C water bath and stirred at 300 rpm for 1 hour to obtain a clear hydrolysate. Subsequently, methyltrimethoxysilane (MTMS) was added to the hydrolysate at molar ratios of 20% and 10%, and stirring was continued for 1 hour to obtain a mixed sol.
[0041] 2. Gelation: Cool the mixed sol to room temperature, and add 0.1M ammonia water dropwise while stirring to adjust the pH to 8.5. Then pour the sol into a polytetrafluoroethylene mold, seal it, and let it stand for 12 hours to completely gel, obtaining a wet gel.
[0042] 3. Aging: Add pure ethanol to the mold to completely submerge the wet gel, seal it, and place it in a 40°C oven for 48 hours to age.
[0043] 4. Drying under normal pressure: Remove the aged wet gel, blot the surface liquid with filter paper, place it in a forced-air drying oven, and dry under normal pressure.
[0044] The glass was dried using a gradient temperature increase procedure: 40℃ / 24h -> 60℃ / 24h -> 80℃ / 24h -> 120℃ / 6h. After natural cooling, a complete fluorine-doped porous low-dielectric glass sample was obtained.
[0045] Comparative Example 2
[0046] The sample was prepared according to the method of Comparative Example 1. After obtaining hydrophilic porous glass, it was immersed in an ethanol solution of 1 wt% FAS for 24 hours, and then dried at 120°C for 2 hours for subsequent hydrophobic treatment.
[0047] 1. Sol Preparation: In a 250 mL Erlenmeyer flask, tetraethyl orthosilicate (TEOS), anhydrous ethanol, deionized water, and 0.1 M HCl solution were added sequentially in a molar ratio of n(TEOS):n(EtOH):n(H2O):n(HCl) = 1:8:4:0.0005. The mixture was placed in a 60 °C water bath and stirred at 300 rpm for 1 hour to obtain a clear hydrolysate. Subsequently, methyltrimethoxysilane (MTMS) was added to the hydrolysate at molar ratios of 20% and 10%, and stirring was continued for 1 hour to obtain a mixed sol.
[0048] 2. Gelation: Cool the mixed sol to room temperature, and add 0.1M ammonia water dropwise while stirring to adjust the pH to 8.5. Then pour the sol into a polytetrafluoroethylene mold, seal it, and let it stand for 12 hours to completely gel, obtaining a wet gel.
[0049] 3. Aging: Immerse it in an ethanol solution of 1 wt% FAS for 24 hours.
[0050] 4. Drying under normal pressure: Remove the aged wet gel, blot the surface liquid with filter paper, place it in a forced-air drying oven, and dry at 120℃ for 2 hours; after natural cooling, a complete fluorine-doped porous low-dielectric glass sample is obtained.
[0051] Performance testing:
[0052] The performance of samples from Example 1, Comparative Example 1, and Comparative Example 2 was tested, and the results are recorded in the table below:
[0053]
[0054] As shown in the table above, the sample prepared in Example 1 of this invention exhibits the best overall performance, successfully achieving a balance between low dielectric strength, superhydrophobicity, and ultra-high moisture resistance. Comparative Example 1, lacking hydrophobic modification, is completely ineffective; while Comparative Example 2, although its hydrophobicity was improved through post-treatment, still exhibits significantly inferior moisture resistance and dielectric properties compared to the one-step in-situ modification method of this invention. This fully demonstrates the non-obviousness and significant advancement of the technical solution of this invention.
[0055] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.
Claims
1. A method for preparing fluorine-doped porous low-dielectric glass by atmospheric pressure drying, characterized in that, Includes the following steps: S1. Sol preparation: A silicon source, solvent, acid catalyst and water are mixed and subjected to a hydrolysis reaction to obtain a hydrolysate; then a fluorinated silane and a network modifier are added to the hydrolysate and mixed to obtain a mixed sol; S2. Gelation: An alkaline catalyst is added to the mixed sol, the pH is adjusted to induce a gelation reaction, and then the mixture is allowed to stand until it is completely gelled to obtain a wet gel. S3. Aging: The wet gel is sealed and aged in an aging solution to strengthen its network structure; S4. Drying at atmospheric pressure: The aged wet gel is placed in a drying device and dried at atmospheric pressure using a gradient temperature program to finally obtain the fluorine-doped porous low-dielectric glass.
2. The method according to claim 1, characterized in that, The fluorinated silane is at least one of heptadecafluorodecyltrimethoxysilane and tridecaocyltriethoxysilane.
3. The method according to claim 1 or 2, characterized in that, The molar ratio of the fluorinated silane to the silicon source is (5%-20%):
1.
4. The method according to claim 1, characterized in that, The network modifier is methyltrimethoxysilane; the molar ratio of the network modifier to the silicon source is (10%-40%):
1.
5. The method according to claim 1, characterized in that, The gradient temperature program is as follows: drying at 40-50℃ for 20-28 hours; drying at 60-70℃ for 20-28 hours; drying at 80-90℃ for 20-28 hours; and drying at 100-120℃ for 4-8 hours.
6. A fluorine-doped porous low-dielectric glass prepared by the method according to any one of claims 1-5, characterized in that, The glass material has a nanoporous structure with fluorocarbon chains bonded to the surface of its pore walls; the dielectric constant of the glass material is 1.8-2.2 at 1MHz, and the water contact angle is greater than 150°.
7. The fluorine-doped porous low-dielectric glass according to claim 6, characterized in that, After being treated at 85℃ / 85%RH for 72 hours, the change rate of its dielectric constant is less than 5%.
8. The application of the fluorine-doped porous low-dielectric glass according to claim 6 or 7 in high-frequency electronic devices.
9. The application according to claim 8, characterized in that, The high-frequency electronic device is a dielectric layer in an integrated circuit, a high-frequency circuit board, or an antenna substrate.