Aluminum nitride ceramic with adjustable volume resistivity and method for manufacturing the same

Abstract

This invention discloses an aluminum nitride ceramic with adjustable volume resistivity and its preparation method. Using high-purity aluminum nitride powder as the main raw material, and by adding specific types and amounts of resistivity modifiers, along with an optimized sintering aid system, a wide range of precise control over the volume resistivity of the aluminum nitride ceramic is achieved. The resistivity modifiers include electronically conductive phases and / or acceptor or donor dopants. By adjusting their doping ratio, the volume resistivity of the aluminum nitride ceramic can be adjusted to within 10... 6 ~10 12 The resistance is continuously adjustable within the Ω•cm range. This invention also provides a corresponding preparation method, including steps such as ingredient preparation, ball milling and mixing, granulation, molding, debinding, sintering, and subsequent processing. This method has a simple process flow and controllable cost. The resulting aluminum nitride ceramic, while maintaining high thermal conductivity, possesses flexibly designable volume resistivity characteristics, enabling it to adapt to different application requirements in electronic devices for heat dissipation and insulation / conductivity.

Description

Technical Field

[0001] This invention relates to the field of functional ceramic materials, and in particular to an aluminum nitride ceramic with adjustable volume resistivity and its preparation method. Background Technology

[0002] Aluminum nitride ceramics have broad application prospects in electronic packaging, substrate materials, and high-temperature structural components due to their excellent thermal conductivity, good insulation, thermal expansion coefficient matching that of silicon, and low dielectric constant. Traditional aluminum nitride ceramics typically require extremely high volume resistivity (>10⁻⁶). 12 Ω•cm) is used as an insulating component.

[0003] However, as microelectronics technology and power electronic devices develop towards higher frequencies and higher power densities, certain specific applications (such as electrostatic chucks, semiconductor process cavity components, resistance heating substrates, and packaging shells requiring electrostatic discharge) place new demands on materials: aluminum nitride needs both high thermal conductivity to ensure efficient heat dissipation and specific, tunable resistivity, rather than simply extremely high insulation. For example, in electrostatic chuck applications, the material needs a certain degree of conductivity to achieve electrostatic adsorption and desorption; in some power modules, the substrate may require a specific resistivity to equalize potential or prevent charge accumulation.

[0004] Currently, research on controlling the volume resistivity of aluminum nitride ceramics is still insufficient. Conventional methods often involve introducing a single second phase (such as carbon or metal) to reduce resistivity. However, this method often suffers from problems such as a narrow control range, poor repeatability, significant damage to thermal conductivity, or poor compatibility with the aluminum nitride matrix, making it difficult to achieve precise, wide-range, and predictable control of resistivity. Therefore, developing a formulation and preparation method that can flexibly and precisely adjust the volume resistivity of aluminum nitride ceramics over a wide range without significantly sacrificing other excellent properties has significant technological value and market potential. Summary of the Invention

[0005] In view of this, the present invention addresses the deficiencies of the prior art, and its main objective is to provide an aluminum nitride ceramic with adjustable volume resistivity and its preparation method, which can effectively solve the problem that existing aluminum nitride ceramics are difficult to control precisely, over a wide range, and predictably.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An aluminum nitride ceramic with adjustable volume resistivity comprises the following components by mass percentage: 45 wt.%–85 wt.% aluminum nitride powder, 0 wt.%–15.0 wt.% sintering aid, 0.1 wt.%–40 wt.% resistivity modifier, 1.0 wt.%–3.0 wt.% dispersant (based on the total mass of aluminum nitride powder, sintering aid, and resistivity modifier), and 1.0 wt.%–10.0 wt.% binder (based on the total mass of aluminum nitride powder, sintering aid, and resistivity modifier); wherein the resistivity modifier comprises an electronically conductive phase and / or an acceptor or donor dopant.

[0007] As a preferred embodiment, the electronically conductive phase is selected from one or more of TiN, TiB2, MoSi2, ZrB, and TiO2.

[0008] As a preferred embodiment, the acceptor or donor dopant is selected from one or more oxides or nitrides of Mg, Zn, Be, Si, and Zr.

[0009] As a preferred option, when the target volume resistivity is 10... 6 ~10 12 At Ω•cm, the resistivity modifier is mainly composed of acceptor or donor dopants, and its addition amount is 0.1 wt.% to 40 wt.%.

[0010] As a preferred option, when the target volume resistivity is 10... 6 ~10 12 At Ω•cm, the resistivity regulator is mainly composed of an electronically conductive phase, and its addition amount is 0.1 wt.% to 40 wt.%.

[0011] As a preferred embodiment, the volume resistivity of the aluminum nitride ceramic is 10⁻⁶. 6 ~10 12 Adjustable within the range of Ω•cm.

[0012] A method for preparing aluminum nitride ceramics with tunable volume resistivity includes the following steps: a) Ingredients and mixing: Weigh all components except the binder according to the formula, and ball mill them to obtain a mixed slurry; at the same time, weigh the required binder powder according to the formula and stir it to dissolve it in anhydrous ethanol for later use; after stirring the ball-milled mixed slurry for a certain period of time, add the binder colloid and continue ball milling for a certain period of time. b) Granulation: The mixed slurry after the addition of binder is granulated; c) Cold isostatic pressing: The granulated powder is pressed into shape to obtain a green body; d) Debinding and sintering: After debinding the raw blank, it is sintered in a sintering furnace.

[0013] As a preferred embodiment, the sintering atmosphere is one of hydrogen, nitrogen, a mixture of nitrogen and hydrogen, or vacuum (≤10Pa), the sintering temperature is 1650~1900℃, and the sintering holding time is 2~8 hours.

[0014] An application of aluminum nitride ceramic with adjustable volume resistivity, which is used in the preparation of electronic packaging substrates, electrostatic chucks, semiconductor process cavity components or resistance heating elements.

[0015] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution: (1) Wide resistivity control range: By selecting different types of resistivity modifiers (such as electronically conductive phases and / or acceptor or donor dopants) and precisely controlling their addition amounts, the volume resistivity of aluminum nitride ceramics can be controlled within a range of 10. 6 ~10 12 Continuous and precise adjustment within the Ω•cm range allows for meeting the diverse electrical performance requirements of materials in various application scenarios.

[0016] (2) Excellent overall performance: While achieving effective control of resistivity, the aluminum nitride ceramics prepared based on the optimized sintering aid system and reasonable process still have excellent thermal conductivity. The thermal conductivity can usually be maintained above 100 W / (m•K), and the specific value depends on the composition of the formula, thus achieving a good synergy between high thermal conductivity and controllable resistivity.

[0017] (3) Good process compatibility: The preparation method of the present invention is based on the traditional aluminum nitride ceramic preparation process, which does not require special equipment, has a simple process, and the parameters are easy to control, which is conducive to industrial production and cost control.

[0018] (4) The formulation design is reasonable and scientific: By introducing resistivity regulators based on different mechanisms of action—the electronic conductive phase mainly reduces the resistance directly by constructing conductive pathways, while the acceptor dopant indirectly regulates the resistance by controlling the intrinsic defect chemical behavior of aluminum nitride. The two can be used alone or in synergy, thus providing a more flexible and precise design means for the microscopic conductive mechanism of materials.

[0019] (5) Fast response speed: By controlling the amount of resistivity regulator added, the volume resistivity of the ceramic can change rapidly, minimizing the time difference between the time it takes for the ceramic to reach the set temperature and the time it takes to reach the set volume resistivity, so that the electrostatic chuck can quickly reach the working state, thereby greatly improving the production efficiency of the equipment and the coordinated response speed of temperature and electrostatic force. Attached Figure Description

[0020] Figure 1 This is a scatter plot of the volume resistivity-time variation of the present invention. Detailed Implementation

[0021] To make the technical problem to be solved by the present invention, the technical solution, and the beneficial effects clearer, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0022] This invention discloses an aluminum nitride ceramic with adjustable volume resistivity, comprising the following components by mass percentage: 45 wt.%–85 wt.% aluminum nitride powder, 0 wt.%–15.0 wt.% sintering aid, 0.1 wt.%–40 wt.% resistivity modifier, 1.0 wt.%–3.0 wt.% dispersant (based on the total mass of aluminum nitride powder, sintering aid, and resistivity modifier), and 1.0 wt.%–10.0 wt.% binder (based on the total mass of aluminum nitride powder, sintering aid, and resistivity modifier); the resistivity modifier comprises an electronically conductive phase and / or an acceptor or donor dopant. The purity of the aluminum nitride powder is not less than 99.5%, and the average particle size is 0.5–2.0 μm. The sintering aid is a composite of one or more rare earth oxides and alkaline earth metal oxides; preferably one or more of Y₂O₃, Al₂O₃, CaO, Sm₂O₃, and Dy₂O₃. The electronically conductive phase is used to reduce the volume resistivity. This phase is selected from one or more of TiN, TiB2, MoSi2, ZrB, and TiO2. By forming a conductive network or providing free electrons, it significantly improves the conductivity of the material. The acceptor or donor dopant is used to introduce acceptor / donor energy levels into the aluminum nitride lattice. Under certain conditions, the resistivity is adjusted through hole conduction or free electron conduction mechanisms. This dopant is selected from one or more oxides or nitrides of Mg, Zn, Be, Si, and Zr. When the target volume resistivity is 10... 6 ~10 12 At a resistivity of Ω•cm, the resistivity adjuster is mainly composed of acceptor or donor dopants, with an addition amount of 0.1 wt.% to 40 wt.%. When the target volume resistivity is 10 Ω•cm, the resistivity adjuster is mainly composed of acceptor or donor dopants, with an addition amount of 0.1 wt.% to 40 wt.%. 6 ~10 12 At a resistivity of Ω•cm, the resistivity adjuster is mainly of electronically conductive phase, and its addition amount is 0.1 wt.% to 40 wt.%. The volume resistivity of the aluminum nitride ceramic is at 10 Ω•cm. 6 ~10 12 Adjustable within the Ω•cm range. When a specific resistivity curve or intermediate value is required, a combination of electronically conductive phase and acceptor / donor dopant can be used.

[0023] This invention also discloses a method for preparing aluminum nitride ceramics with adjustable volume resistivity, comprising the following steps: a) Ingredients and Mixing: Weigh the aluminum nitride powder, sintering aid, resistivity regulator, and dispersant according to the above formula, place them in a ball mill jar, and ball mill and mix for 6-20 hours using anhydrous ethanol as the medium. Then add the binder and ball mill and mix for another 6-20 hours to ensure uniform mixing. By adjusting the amount of resistivity regulator added, the rate of change of ceramic volume resistivity during the heating process can be controlled, thus controlling the time to reach the target volume resistivity. The amount of resistivity regulator added is set according to the rate of change of the electrostatic chuck temperature. The rate of change of volume resistivity of conventional aluminum nitride electrostatic chucks is slower than the rate of change of temperature, resulting in insufficient adsorption force when the working temperature reaches the set value before it can be put into operation, which takes a long time. By adopting this preferred solution, the time difference between the time for the ceramic to reach the set temperature and the time to reach the set volume resistivity can be shortened as much as possible, allowing the electrostatic chuck to quickly reach the working state, and the response time can be effectively shortened by 30% to 70%. Furthermore, the preferred embodiment includes: 1. Adjusting the amount of resistance regulator added near the percolation threshold according to its temperature change rate, so that the volume resistivity drops rapidly to the required value; 2. Changing the resistivity by adjusting the amount of resistance regulator added to regulate the phase composition and continuity at the grain boundary.

[0024] b) Granulation: After filtering the above uniformly mixed slurry, place it in the feed tank of a centrifugal granulation spray dryer and granulate it at the set inlet air temperature and outlet air speed. During granulation, the slurry is continuously stirred to prevent sedimentation.

[0025] c) Cold isostatic pressing: The granulated powder is placed into a customized mold, the mold is sealed, and then placed into a cold isostatic pressing chamber. The powder is pressed in a three-stage pressure range of 30-140 MPa to obtain a green blank.

[0026] d) Debinding and sintering: The green body is heated to 400-600℃ in an air atmosphere furnace and held for 10-20 hours to remove the binder. Then, the debinded green body is hot-pressed in a flowing nitrogen atmosphere according to the sintering curve, and held at 1650-1900℃ and 170-230 tons of pressure for 2-6 hours. It is then cooled to room temperature in the furnace. e) Post-processing: As needed, the sintered ceramic sheets can be cut, ground, and polished.

[0027] This invention also discloses an application of aluminum nitride ceramic with adjustable volume resistivity, which is used in the preparation of electronic packaging substrates, electrostatic chucks, semiconductor process cavity components or resistance heating elements.

[0028] Based on the percolation theory, this invention states that when the amount of resistivity regulator added is below the critical threshold, the conductive phase particles are dispersed in the ceramic matrix and cannot form a continuous conductive network, resulting in a slow decrease in resistivity. When the amount added is above the critical threshold, the conductive phase quickly connects to form a continuous network, and the resistivity decreases sharply. Based on this principle, the amount of resistivity regulator added can be adjusted according to the time it takes for the ceramic to reach the set temperature, thereby accurately controlling the time to reach the target resistivity.

[0029] The present invention will be further described in detail below with reference to several embodiments and comparative examples: Example 1: This embodiment provides an aluminum nitride ceramic formulation with adjustable volume resistivity. By mass percentage, it contains 45 wt.%–85 wt.% aluminum nitride powder, 0 wt.%–15.0 wt.% sintering aid, 0 wt.%–40 wt.% resistivity modifier, 1.0 wt.%–3.0 wt.% dispersant (based on the total mass of aluminum nitride powder, sintering aid, and resistivity modifier), and 1.0 wt.%–10.0 wt.% binder (based on the total mass of aluminum nitride powder, sintering aid, and resistivity modifier).

[0030] Furthermore, the sintering aid is Y2O3, and contains one or more of Al2O3, CaO, and Sm2O3, expressed as a percentage by mass: 0-15% Al2O3, 0-5% CaO, 0-5% Sm2O3, with the remainder being Y2O3.

[0031] Further, the resistivity regulator is an electronically conductive phase comprising one or more of TiN, TiB2, MoSi2, ZrB, and TiO2, wherein, by mass percentage, it contains 20%–20% TiB, 20%–40% MoSi, 0%–30% ZrB, 20%–10% TiO2, and the remainder is TiN. Further, the amount of the resistivity regulator added is 0.1 wt.%–40 wt.%, resulting in a product with a volume resistivity of 10⁻⁶. 9 ~10 11 The time required to reach the product's volume resistivity is 40 min to 60 min (Ω•cm).

[0032] Furthermore, the ceramic preparation method includes the following steps: 1. Ingredients and mixing: Weigh the aluminum nitride powder, sintering aid, resistivity regulator and dispersant according to the above formula, place them in a ball mill jar, use anhydrous ethanol as medium and ball mill with alumina balls for 6 to 20 hours, add the binder (such as an ethanol solution of acrylic acid and polyvinyl butyral), and ball mill for another 6 to 20 hours to ensure that the materials are mixed evenly.

[0033] 2. Granulation: After filtering the above-mentioned uniformly mixed slurry, place it in the feed tank of the centrifugal granulation spray dryer. The inlet air temperature of the centrifugal granulation spray dryer is set to 60-150℃, and the outlet air speed is kept stable at about 40-60℃. During granulation, the slurry is continuously stirred to prevent sedimentation.

[0034] 3. Cold Isostatic Pressing: The granulated powder is placed into a customized mold, the mold is sealed, and then placed into a cold isostatic pressing chamber for pressing using a three-stage pressurization method. First, the pressure is increased to 30-60 MPa and held for 60-120 seconds, then the pressure is increased to 60-100 MPa and held for 60-120 seconds, and finally the pressure is increased to 100-140 MPa and held for 150-450 seconds to obtain the green body.

[0035] 4. Debinding and sintering: The green body is heated to 400-600℃ in an air atmosphere furnace at a heating rate of 0.5-3℃ / min, and then held at that temperature for 10-20 hours to remove the binder. The debinded green body is then hot-pressed in a flowing nitrogen atmosphere according to the sintering curve, and held at 1650-1900℃ and 170-230 tons of pressure for 2-6 hours. It is then cooled to room temperature in the furnace. 5. Post-processing: As needed, the sintered ceramic sheets can be cut, ground, and polished.

[0036] Example 2 Compared with Example 1, the difference in Example 2 is that the resistivity regulator used in Example 2 is an acceptor or donor dopant. As a preferred embodiment, it contains one or more oxides or nitrides of Mg, Zn, Si, and Zr. By mass percentage, it contains 40-50% ZnO, 35-45% ZrO2, and 15-30% Si3N4 / SiO2. Furthermore, the amount of resistivity regulator added is 0.1 wt.% to 40 wt.%, resulting in a product with a volume resistivity of 10⁻⁶. 9 ~10 11 The time required to reach the product's volume resistivity is 40 min to 60 min (Ω•cm).

[0037] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 did not contain a resistivity modifier.

[0038] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the resistivity regulator added in Comparative Example 2 is 40% to 55%, and its component content is the same as that in Example 1.

[0039] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that the resistivity regulator added in Comparative Example 3 is 40% to 55%, and its component content is the same as that in Example 2.

[0040] The ceramics prepared with different resistivity modifier formulations in Examples 1-2 and Comparative Examples 1-3 were subjected to performance tests, and the test results are shown in the table below:

[0041] Performance tests of aluminum nitride ceramics prepared with different resistivity modifier formulations show that adding volume resistivity modifiers can accelerate the rate of change in volume resistivity, shortening the time to reach the target volume resistivity. This allows the electrostatic chuck to quickly reach its working state, thereby greatly improving the equipment's coordinated response speed. Conversely, excessive addition of volume resistivity modifiers can lead to a decrease in the ceramic's volume resistivity, causing the electrostatic chuck to experience weakened adhesion, arcing, and breakdown.

[0042] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An aluminum nitride ceramic having an adjustable volume resistivity, characterized by: The composition comprises the following components by weight percentage: 45 wt.% to 85 wt.% aluminum nitride powder, 0 wt.% to 15.0 wt.% sintering aid, 0.1 wt.% to 40 wt.% resistivity modifier, 1.0 wt.% to 3.0 wt.% dispersant (based on the total mass of aluminum nitride powder, sintering aid, and resistivity modifier), and 1.0 wt.% to 10.0 wt.% binder (based on the total mass of aluminum nitride powder, sintering aid, and resistivity modifier); wherein the resistivity modifier comprises an electronically conductive phase and / or an acceptor or donor dopant.

2. The aluminum nitride ceramic of claim 1, wherein: The electronically conductive phase is selected from one or more of TiN, TiB2, MoSi2, ZrB, and TiO2.

3. The aluminum nitride ceramic of claim 1, wherein: The acceptor or donor dopant is selected from one or more oxides or nitrides of Mg, Zn, Be, Si, and Zr.

4. The aluminum nitride ceramic with adjustable volume resistivity according to any one of claims 1-3, characterized in that: When the target volume resistivity is 10 6 ~10 12 At Ω•cm, the resistivity modifier is mainly composed of acceptor or donor dopants, and its addition amount is 0.1 wt.% to 40 wt.t.

5. The aluminum nitride ceramic with adjustable volume resistivity according to any one of claims 1-3, characterized in that: When the target volume resistivity is 10 6 ~10 12 At Ω•cm, the resistivity regulator is mainly composed of an electronically conductive phase, and its addition amount is 0.1 wt.% to 40 wt.%.

6. The aluminum nitride ceramic with adjustable volume resistivity according to claim 1, characterized in that: The volume resistivity of the aluminum nitride ceramic is adjustable in the range of 10 6 ~ 10 12 Ω•cm.

7. A method of producing an aluminum nitride ceramic with adjustable volume resistivity according to any one of claims 1 to 6, characterized in that: Includes the following steps: a) Ingredients and mixing: Weigh all components except the binder according to the formula, and ball mill them to obtain a mixed slurry; at the same time, weigh the required binder powder according to the formula and stir it to dissolve it in anhydrous ethanol for later use; after stirring the ball-milled mixed slurry for a certain period of time, add the binder colloid and continue ball milling for a certain period of time. b) Granulation: The mixed slurry after the addition of binder is granulated; c) Cold isostatic pressing: The granulated powder is pressed into shape to obtain a green body; d) Debinding and sintering: After debinding the raw blank, it is sintered in a sintering furnace.

8. The method of claim 7, wherein the method further comprises: The sintering atmosphere is one of hydrogen, nitrogen, a mixture of nitrogen and hydrogen, or vacuum. The sintering temperature is 1650–1900℃, and the sintering holding time is 2–8 hours. ​ 9. Use of an aluminum nitride ceramic with adjustable volume resistivity according to any one of claims 1 to 6, characterized in that: It is used in the preparation of electronic packaging substrates, electrostatic chucks, semiconductor process cavity components or resistance heating elements.

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