Full-ceramic aluminum nitride electrostatic chuck and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor manufacturing equipment, and particularly relates to a full-ceramic aluminum nitride electrostatic chuck and a preparation method thereof. According to the invention, the aluminum nitride / metal ceramic composite material is adopted as the heating element and is combined with the aluminum nitride matrix to replace the traditional metal heating element; by accurately controlling oscillation pressure and temperature curves, rearrangement and densification of ceramic particles are promoted, co-sintering of a matrix and a heating element is achieved, and a high-density and high-strength interface is obtained. And finally, the high-performance full-ceramic aluminum nitride electrostatic chuck with long service life is obtained. According to the invention, the long-standing problem of a metal-ceramic interface is solved, and a key component with higher reliability, long service life and excellent temperature control performance is provided for semiconductor preparation.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing equipment technology, specifically relating to an all-ceramic aluminum nitride electrostatic chuck and its preparation method. Background Technology

[0002] Electrostatic chucks are key components in semiconductor manufacturing equipment (such as CVD, PVD, ALD, and etching equipment). They are used to electrostatically hold wafers in place and must possess characteristics such as precise temperature control, high thermal conductivity, high insulation, and resistance to plasma erosion. Traditional electrostatic chucks often use alumina or aluminum nitride ceramic substrates and achieve heating through embedded metal heating elements (such as molybdenum mesh or tungsten wire). However, metals and ceramics differ significantly in their coefficients of thermal expansion, chemical compatibility, and high-temperature stability. Problems often arise in actual production. For example, the large difference in thermal expansion coefficients between the metal heater and the ceramic substrate can easily generate interfacial stress during high-temperature cycling, leading to microcracks, delamination, or heating element breakage, resulting in chuck failure. Alternatively, the metal may oxidize or react with the ceramic during long-term high-temperature sintering, forming a weak interfacial layer, reducing thermal conductivity and heating uniformity, and affecting the accuracy of wafer temperature control. These problems severely impact the lifespan and reliability of traditional electrostatic chuck products and increase equipment maintenance costs.

[0003] In recent years, to improve the performance of electrostatic chucks, some studies have attempted to alleviate the aforementioned problems by optimizing ceramic materials or improving electrode structures. For example, patent CN111863693A proposes an electrostatic chuck in which an electrostatic electrode and a titanium-tungsten wire heating electrode are embedded in a ceramic matrix and sintered in one step. This aims to avoid material size differences and internal structure deterioration caused by multiple sintering processes, and to achieve zoned heating and temperature control. Patent CN107527851B further improves airtightness and adsorption uniformity through the design of metallization and nickel plating layers, but still uses metal electrodes as heating elements. Other solutions, such as CN105706351A, focus on surface pad design to reduce particle generation and wear, without addressing fundamental improvements to the heating element. While these existing technologies have partially improved chuck performance, they have not eliminated their dependence on metal heating elements and have failed to fundamentally solve the metal-ceramic interface mismatch problem. Furthermore, cermets have already begun to be used as heating elements in other fields, such as household appliances and metallurgy, due to their significant performance advantages, including high thermal efficiency, high temperature resistance, thermal shock resistance, and chemical stability. However, research on integrating them into electrostatic chucks and achieving one-piece sintering has not been reported. Therefore, developing an all-ceramic aluminum nitride electrostatic chuck, with its heating element made of pure ceramic materials (such as silicon nitride / cermet composites), and formed in one step through techniques such as oscillating hot pressing sintering, is of great significance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an all-ceramic aluminum nitride electrostatic chuck and its manufacturing method.

[0005] To address the above problems, this invention provides a method for preparing an all-ceramic aluminum nitride electrostatic chuck, comprising the following steps: 1) Raw material preparation: First, prepare the matrix powder (aluminum nitride matrix powder) and the conductive composite powder (aluminum nitride / metal-ceramic composite powder) separately: The matrix powder (aluminum nitride matrix powder) is composed of the following components by weight: 93.5~95.5 wt% aluminum nitride (AlN), 4~6 wt% sintering aid and 0.4~0.6 wt% dispersant; The conductive composite powder (aluminum nitride / metal-ceramic composite powder) is composed of the following components by weight: 44.5~84.5wt% aluminum nitride, 10~50 wt% metal-ceramic (preferably 35%), 4.5~5.5wt% sintering aid, and 0.4~0.6 wt% dispersant; The matrix powder and the conductive composite powder are respectively subjected to wet ball milling to obtain the matrix slurry and the conductive composite slurry respectively. Note: The content of metal ceramics can be adjusted according to different AC / DC voltages; 2) Preparation of granulated powder: The matrix slurry and the conductive composite slurry are spray-granulated to obtain matrix granulated powder and conductive composite granulated powder (aluminum nitride / metal ceramic composite granulated powder). 3) Raw blank processing: First, the granulated matrix powder is laid and pressed to serve as the lower matrix layer. A matrix granulated powder is laid on the lower substrate as an intermediate layer. A groove is dug in the intermediate layer to support the conductive composite granulated powder. The conductive composite granulated powder is filled into the groove (the conductive composite granulated powder fills the entire groove and is flush with the upper surface of the intermediate layer). Then it is pressed, and the result is named the intermediate layer with heating element. The matrix granulated powder is covered on the intermediate layer with heating element and pressed to form the upper sealing layer. This forms a green blank with an embedded heating element (a green blank with a three-dimensional structure). That is, in this invention: the matrix is ​​composed of aluminum nitride powder, and the heating element is composed of aluminum nitride powder doped with cermet; 4) Vibratory hot pressing sintering and annealing: The green body obtained in step 3) is first subjected to oscillating hot pressing sintering, and then annealed; to obtain a full ceramic aluminum nitride electrostatic chuck blank.

[0006] As an improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention, it further includes the following step 5): The all-ceramic aluminum nitride electrostatic chuck blank is precision machined, including surface treatment, to obtain the all-ceramic aluminum nitride electrostatic chuck.

[0007] Generally, the sintered blank is subjected to planar grinding, electrode area finishing and surface treatment to obtain an electrostatic chuck with specified dimensions and surface characteristics.

[0008] As a further improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention: the cermet is molybdenum dioxide or tungsten carbide.

[0009] As a further improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention: the sintering aid is a rare earth oxide, wherein the rare earth oxide is yttrium oxide and magnesium oxide; The dispersant is polyethylene glycol (PEG, average molecular weight 1000).

[0010] As a further improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention: step 3) is performed by molding or cold isostatic pressing.

[0011] As a further improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention: the oscillating hot pressing sintering in step 4) is as follows: The green body obtained in step 3) is placed in a sintering furnace with oscillating pressure function. Under an inert atmosphere or vacuum atmosphere, the temperature is first raised to remove the binder (heating at a rate of 6~10℃ / min to 600±50℃ and holding for 1±0.2h to remove the binder). Then the temperature is raised to 1750~1850℃ and oscillating pressure (oscillating uniaxial pressure) is applied. The oscillating pressure range is 5~40 MPa (with a variation range of 5MPa) and the frequency is 0.1~5 Hz. Sintering and densification are carried out at 1750~1850℃ (holding and pressure sintering) for 1~4h.

[0012] As a preferred option, the sintering temperature is 1800℃, the pressure is 30 MPa with a variation range of 5 MPa, the frequency is 1 Hz, and the sintering time is 2 h, so as to achieve the integrated and dense molding of the substrate and the heating element as much as possible.

[0013] As a further improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention: the annealing in step 4) is: annealing treatment is carried out in a vacuum or inert atmosphere, the annealing temperature is 100~300℃ lower than the sintering temperature, and the annealing time is 2~6h.

[0014] Note: After the annealing process is completed, the furnace is cooled to obtain a dense all-ceramic aluminum nitride electrostatic chuck blank.

[0015] As a further improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention: in step 1): Deionized water was added to the matrix powder and wet ball milled to obtain a matrix slurry with a solid content of 40±5%. The conductive composite powder was added to deionized water and wet ball milled to obtain a conductive composite slurry with a solid content of 40±5%.

[0016] Note: The wet ball milling speed is 250~350 rpm, and the time is 4~8 h.

[0017] As a further improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention: the cross-sectional size of the lower substrate layer, the middle layer (the middle layer with a heating element) and the upper sealing layer are the same, with a diameter of 240~340 mm; The thickness of the lower substrate layer is 5~20 mm; the thickness of the middle layer is 3~10 mm; and the thickness of the upper sealing layer is 0.5~2 mm. The grooves of the granulated powder loaded with conductive composite have a width of 0.3~7 mm and a depth of 0.01~5 mm.

[0018] All pressing processes were performed using cold isostatic pressing at a pressure of 150±20 MPa and a holding pressure of 10±2 min.

[0019] The shape of the groove can be the same as that of a conventional metal heating electrode.

[0020] As a further improvement to the preparation method of the all-ceramic aluminum nitride electrostatic chuck of the present invention: in step 2, the slurry feed rate is controlled at 40~60 mL / min, the hot air inlet temperature is 250~300℃, the outlet temperature is 70~90℃, and the centrifugal atomizer frequency is 40~70 Hz to ensure good flowability of the granulated powder.

[0021] The present invention also provides an all-ceramic aluminum nitride electrostatic chuck prepared using any of the above methods.

[0022] This electrostatic chuck is made entirely of ceramic, and its internal heating element is an aluminum nitride / metal-ceramic composite material with a volume resistivity of 10. -5 ~10 -2 The thermal conductivity of the heating element at room temperature is ≥ 100 W / (m·K), which varies widely depending on the amount of metal ceramic added.

[0023] The all-ceramic aluminum nitride electrostatic chuck of the present invention can be used in any field of semiconductor manufacturing, such as PVD (physical vapor deposition), CVD (chemical vapor deposition) and ALD (atomic layer deposition), etching and other advanced fabrication processes. It has excellent performance in wafer adsorption, temperature control and transport in semiconductor manufacturing processes.

[0024] The existing technology suffers from the following technical problems: traditional electrostatic chucks, due to the use of metal heating elements (such as molybdenum mesh), suffer from metal-ceramic thermal expansion mismatch, microcracks and delamination caused by interface stress, easy breakage of heating elements, and poor reliability and short lifespan under long-term high temperatures. To address these problems, this invention provides an all-ceramic aluminum nitride electrostatic chuck and its preparation method. This invention aims to resolve the aforementioned conflicts through the following technical points: by using an aluminum nitride / metal-ceramic composite material as the heating element, combined with an aluminum nitride matrix, replacing the traditional metal heating element; by precisely controlling the oscillation pressure and temperature curves, promoting ceramic particle rearrangement and densification, achieving co-sintering of the matrix and heating element, obtaining a high-density, high-strength interface. Ultimately, a high-performance all-ceramic aluminum nitride electrostatic chuck with a long service life is obtained. This invention fills the gap in the application of pure ceramic heaters in electrostatic chucks, solves the long-standing metal-ceramic interface problem, and provides a key component with higher reliability, longer lifespan, and excellent temperature control performance for semiconductor fabrication.

[0025] In summary, this invention relates to an integrated sintering technology that replaces traditional metal heaters (such as molybdenum and tungsten materials) with pure ceramic heating elements, mainly solving the problems of poor reliability and short lifespan caused by the thermal expansion mismatch between metal and ceramic in existing electrostatic chucks that use metal wires as heating devices.

[0026] The preparation method of this invention was obtained by the inventors through in-depth research and numerous experimental optimizations; the technical advantages of this invention are: (1) By using aluminum nitride-metal ceramic composite material as the built-in heating element to replace the traditional metal heater, and combining it with the oscillating hot pressing sintering process, the problem of thermal expansion mismatch between metal-ceramic heterogeneous materials is effectively solved, the rearrangement of ceramic particles and the densification of the interface are promoted, and a high-density and high-strength integrated structure is realized.

[0027] (2) By controlling the arrangement of the heating elements and adjusting the amount of metal ceramics added during the blank forming process, the electrothermal efficiency, thermal conductivity and electrical conductivity of the electrostatic chuck can be adjusted in a highly controllable manner, which is suitable for meeting the various needs in semiconductor manufacturing processes.

[0028] (3) The process of the present invention significantly improves the service life, temperature control accuracy and reliability of the electrostatic chuck under high temperature conditions, while having excellent insulation, thermal conductivity and mechanical strength. It is suitable for semiconductor manufacturing equipment (such as etching, CVD, PVD and ALD equipment) with extremely demanding requirements for cleanliness, thermal management performance and long-term reliability, and has good prospects for industrial promotion. Attached Figure Description

[0029] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of the structure of the electrostatic chuck product of the present invention; Figure 1 The image below is a cross-sectional view of the image above. Figure 2 A photograph of the internal heater of the electrostatic chuck prepared in Example 1 of this invention; Figure 3 This is a scanning electron microscope image of the internal heater of the electrostatic chuck prepared in Example 1 of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto: Aluminum nitride has a particle size of 10-20 micrometers, while cermets (including molybdenum dioxide) have a particle size of 5-10 micrometers.

[0032] The performance testing method involved in this invention is as follows: 1. Referring to "GB / T 5594.5-1985 Test Methods for Performance of Structural Ceramic Materials for Electronic Components - Test Method for Volume Resistivity" and "GB / T 39862-2021 Test of Thermal Conductivity of High Thermal Conductivity Ceramics", the resistivity and thermal conductivity data of the composite ceramics were measured.

[0033] 2. Density data of aluminum nitride ceramic matrix and composite ceramic (conductive composite) were measured by Archimedes' displacement method.

[0034] 3. Referring to GB / T 10066.1 General Test Methods for Industrial Electric Heating Devices, the maximum power per unit area, the electrothermal efficiency, and the fastest time to heat up to 1000℃ of the finished electrostatic chuck heating layer were measured.

[0035] 4. Measure and record the time when the electrothermal efficiency abnormally decreases (to below 80% of the initial value) at 1000℃ without power interruption, i.e., the time when the internal heater fails. This time is taken as the product's uninterrupted service life and used to measure the product's stability.

[0036] Example 1: A method for preparing an all-ceramic aluminum nitride electrostatic chuck, comprising the following steps: 1) Raw material preparation: First, prepare the matrix powder (aluminum nitride matrix powder) and the conductive composite powder (aluminum nitride / metal-ceramic composite powder) separately. The formulation of the matrix powder (aluminum nitride matrix powder) is: 94.5 wt% aluminum nitride (AlN), 5 wt% sintering aid and 0.5 wt% dispersant; The formulation of the conductive composite powder (aluminum nitride / metal ceramic composite powder) is: 59.5 wt% aluminum nitride, 35 wt% metal ceramic, 5 wt% sintering aid and 0.5 wt% dispersant; The cermet is molybdenum dioxide, the sintering aid is magnesium oxide, and the dispersant is polyethylene glycol (PEG, with an average molecular weight of approximately 1000).

[0037] The matrix powder and deionized water were mixed at a mass ratio of 4:6, placed in a ball mill, and wet-milled at 300 rpm for 6 hours to obtain a matrix slurry with a solid content of 40%.

[0038] The conductive composite powder was mixed with deionized water at a mass ratio of 4:6, placed in a ball mill, and wet-milled at 300 rpm for 6 hours to obtain a conductive composite slurry with a solid content of 40%.

[0039] Note: The above-mentioned matrix slurry and conductive composite slurry are homogeneous slurries obtained by ball milling with water as the medium.

[0040] 2) Preparation of granulated powder: The matrix slurry and the conductive composite slurry are each processed by a conventional spray granulation tower: the hot air inlet temperature is controlled at 270℃, the outlet temperature at 80℃, the centrifugal atomizer frequency at 50 Hz, and the feed flow rate at 45 mL / min, thereby obtaining two types of spherical granulated powders with good flowability, namely matrix granulated powder (aluminum nitride ceramic granulated powder) and conductive composite granulated powder (aluminum nitride / metal ceramic composite granulated powder).

[0041] 3) First, spread the granulated matrix powder and press it. The resulting layer is called the lower matrix layer. A matrix granulated powder is laid on a lower substrate as an intermediate layer. Grooves are carved into the intermediate layer to support the conductive composite granulated powder. The conductive composite granulated powder is then filled into the grooves, filling them completely and flush with the upper surface of the intermediate layer. The resulting layer is named the intermediate layer with a heating element (composite ceramic heating element) (i.e., the intermediate layer using aluminum nitride / metal ceramic composite granulated powder as the heating element). The shape of the groove can be set with reference to the shape of a conventional metal heating electrode.

[0042] The matrix granulated powder is covered on the middle layer and pressed to serve as the upper sealing layer.

[0043] The lower substrate layer, intermediate layer, and upper sealing layer have the same cross-sectional size, with a diameter of 240~340 mm (320 mm in this case). The thickness of the lower substrate layer is generally 5~20 mm (10 mm in this case); the thickness of the intermediate layer is generally 3~10 mm (6 mm in this case); and the thickness of the upper sealing layer is generally 0.5~2 mm (preferably 1 mm).

[0044] The specific dimensions of the groove for the granulated powder of the conductive composite load are: width 0.3~7 mm (set to 2 mm in this case) and depth 0.01~5 mm (set to 3 mm in this case).

[0045] All three pressing processes were: cold isostatic pressing, with a pressure of 150 MPa and a holding time of 10 min, to form a green blank with a three-dimensional structure and an embedded heating element.

[0046] Figure 1 The bolded ring line represents a groove (containing a conductive composite ceramic heating element prepared from granulated conductive composite powder), the shape of which can be the same as that of a conventional metal heating electrode. As a specific example, Figure 1 The diameter of the annular groove can be set sequentially from the inside to the outside, for example, to 120mm, 160mm, 240mm, and 260mm.

[0047] 4) Place the green body obtained in step 3) into a graphite mold and put it into a vibrating hot pressing sintering furnace. Evacuate to 10... -2 Pa, the temperature is increased to 600℃ at 8℃ / min for debinding, and held at that temperature for 1 h; then the temperature is increased to 1800℃ at 10℃ / min for sintering, and oscillation pressure is applied at the same time as sintering, with a pressure of 30 MPa, a frequency of 1 Hz, and a variation amplitude of 5 MPa. The holding and pressure sintering time at the above-set sintering temperature and oscillation pressure is 2 h.

[0048] 5) After sintering, at 10 -2 Annealing is performed at Pa, with an annealing temperature of 1500~1700℃ (preferably 1600~1650℃), and the annealing is held at this temperature for 6 hours. After that, the furnace is cooled to room temperature before the product is removed from the furnace.

[0049] 6) Perform conventional double-sided planar grinding on the sintered blank to achieve a surface flatness of ≤8 μm; use diamond tools to machine electrode grooves and adsorption areas on the blank surface; polish the surface to a roughness Ra<0.02 μm. The final product is a fully ceramic heater that meets specifications.

[0050] The performance of the all-ceramic aluminum nitride electrostatic chuck obtained in Example 1 was tested, and the results are as follows: The electrostatic chuck has a high overall density, with the AlN ceramic matrix formed from granulated matrix powder having a density of 3.376 g / cm³. 3 The density of the composite ceramic heating element formed from conductive composite granulated powder (aluminum nitride / metal-ceramic composite granulated powder) is 5.102 g / cm³. 3 The composite ceramic heating element and the AlN ceramic matrix have no cracks or delamination in their internal structure, and are densely bonded without defects, such as... Figure 3 As shown, the volume resistivity of the composite ceramic heating element is 8.36 × 10⁻⁶. -5 Ω·cm, and the room temperature thermal conductivity is 187.3 W / (m·K).

[0051] The all-ceramic aluminum nitride electrostatic chuck obtained in Example 1 has good stability and thermoelectric properties.

[0052] Example 2: A method for preparing an all-ceramic aluminum nitride electrostatic chuck: Compared to Example 1, in Example 2, the formulation of the conductive composite powder in step 1) is changed to: 44.5 wt% aluminum nitride, 50 wt% cermet powder, 5 wt% sintering aid, and 0.5 wt% dispersant.

[0053] The remaining steps are the same as in Example 1.

[0054] The all-ceramic aluminum nitride electrostatic chuck obtained in Example 2 also exhibits good performance and structural strength, with an AlN ceramic matrix density of 3.341 g / cm³. 3 The density of the composite ceramic heating element is 6.256 g / cm³. 3 The volume resistivity of the composite ceramic heating element is 3.48 × 10⁻⁶. -5 The thermal conductivity at room temperature is 143.3 W / (m·K). With increasing metal ceramic content, the density of the composite ceramic heating element increases, while both the volume resistivity and room temperature thermal conductivity decrease significantly, demonstrating that the performance of the composite ceramic can be controlled by adjusting the amount of metal ceramic added.

[0055] Example 3: A method for preparing an all-ceramic aluminum nitride electrostatic chuck: Compared to Example 1, in Example 3 the formulation of the conductive composite powder in step 1) is changed to: 84.5 wt% aluminum nitride, 10 wt% cermet powder, 5 wt% sintering aid, and 0.5 wt% dispersant.

[0056] The remaining steps are the same as in Example 1.

[0057] The all-ceramic aluminum nitride electrostatic chuck obtained in Example 3 has an AlN ceramic matrix with a density of 3.349 g / cm³.3 The density of the composite ceramic heating element is 3.871 g / cm³. 3 The volume resistivity of the composite ceramic heating element is 7.38 × 10⁻⁶. -2 The thermal conductivity at room temperature is 277.6 W / (m·K). As the amount of cermet added decreases, the density of the composite ceramic decreases, and the volume resistivity and room temperature thermal conductivity of the heating element both increase to some extent.

[0058] Example 4: A method for preparing an all-ceramic aluminum nitride electrostatic chuck: Compared to Example 1, in Example 4, the sintering in step 4) is changed to: vacuuming to 10 -2 Pa, the temperature is increased to 600℃ at 8℃ / min for debinding, and held for 1 h; the temperature is then increased to 1850℃ at 10℃ / min for holding and sintering, while oscillation pressure of 40 MPa, frequency of 5 Hz, and variation amplitude of 5 MPa is applied. The holding and pressure sintering time at the above-set sintering temperature and oscillation pressure is 4 h.

[0059] The remaining steps are the same as in Example 1.

[0060] The all-ceramic aluminum nitride electrostatic chuck obtained in Example 4, due to the change in sintering parameters, showed that although the density of the AlN ceramic matrix increased to 3.402 g / cm³. 3 However, the density of the composite ceramic heating element decreased to 4.927 g / cm³. 3 The volume resistivity of the composite ceramic heating element also increased slightly to 9.63 × 10⁻⁶. -5 The thermal conductivity is Ω·cm, while the room temperature thermal conductivity is 193.2 W / (m·K).

[0061] Example 5: A method for preparing an all-ceramic aluminum nitride electrostatic chuck: Compared to Example 1, in Example 5, the sintering in step 4) is replaced with: vacuuming to 10... -2 Pa, the temperature is increased to 600℃ at 8℃ / min for debinding, and held for 1 h; the temperature is then increased to 1750℃ at 10℃ / min for holding and sintering, while oscillation pressure of 5 MPa, frequency of 5 Hz, and variation amplitude of 5 MPa is applied. The holding and pressure sintering time at the above-set sintering temperature and oscillation pressure is 1 h.

[0062] The remaining steps are the same as in Example 1.

[0063] The all-ceramic aluminum nitride electrostatic chuck obtained in Example 5 exhibits a significantly reduced density due to the overall decrease in sintering temperature, holding time, and pressure; the density of the AlN ceramic matrix is ​​2.810 g / cm³. 3The density of the composite ceramic heating element is 4.726 g / cm³. 3 Furthermore, it affected the thermoelectric performance; the volume resistivity of the composite ceramic heating element was 1.92 × 10⁻⁶. -3 Ω·cm, and the room temperature thermal conductivity is 161.0 W / (m·K).

[0064] Comparative Example 1: A method for preparing an aluminum nitride electrostatic chuck: Compared to Example 1, Comparative Example 1 no longer uses conductive composite granulated powder (aluminum nitride / metal ceramic composite granulated powder) as the heating element, but instead uses traditional metal molybdenum wire as the heater. That is, according to the structure of the intermediate layer in Example 1, the metal molybdenum wire is embedded in the groove (i.e., the metal molybdenum wire is embedded in the aluminum nitride ceramic matrix), thereby ensuring the consistency of the heating layer structure of the two electrostatic chucks, and other sintering and processing steps are the same as in Example 1.

[0065] The electrostatic chuck obtained in Comparative Example 1 has a heating wire with a volume resistivity of 5.53 × 10⁻⁶. -8 The thermal conductivity at room temperature is 142.6 W / (m·K), which is close to the performance of the composite ceramic heating element obtained in Example 1. However, the metal wire is prone to deformation and other problems during long-term use, and the electrothermal efficiency and other properties will decrease linearly, resulting in a shorter service life.

[0066] To further evaluate the thermoelectric performance and service life of the products, the relevant performance parameters of the products obtained in the above embodiments and comparative examples were tested, and the results are shown in Table 1 below.

[0067] Table 1. Thermoelectric properties of various products at 1000℃

[0068] Note: " / " indicates that no test was performed.

[0069] Compared to the molybdenum wire heater of Comparative Example 1, the composite ceramic heater of Example 1 of the present invention has significantly improved electrothermal efficiency, heating speed and maximum heating power. Especially in terms of performance, under the condition of maintaining 1000°C without interruption of power, Example 1 can maintain its performance without significant decline for about 380 hours, which proves the performance advantage of the composite ceramic heating layer in Example 1.

[0070] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for preparing an all-ceramic aluminum nitride electrostatic chuck, characterized in that... Includes the following steps: 1) Raw material preparation: First, prepare the matrix powder and conductive composite powder separately: The matrix powder consists of the following components by weight: 93.5~95.5 wt% aluminum nitride, 4~6 wt% sintering aid and 0.4~0.6 wt% dispersant; The conductive composite powder is composed of the following components by weight: 44.5~84.5wt% aluminum nitride, 10~50 wt% cermet, 4.5~5.5wt% sintering aid, and 0.4~0.6 wt% dispersant; The matrix powder and the conductive composite powder are respectively subjected to wet ball milling to obtain the matrix slurry and the conductive composite slurry respectively. 2) Preparation of granulated powder: The matrix slurry and the conductive composite slurry are spray-granulated separately to obtain matrix granulated powder and conductive composite granulated powder respectively. 3) Raw blank processing: First, the granulated matrix powder is laid and pressed to serve as the lower matrix layer. A matrix granulated powder is laid on the lower substrate as an intermediate layer. A groove is dug in the intermediate layer to support the conductive composite granulated powder. The groove is filled with conductive composite granulated powder and then pressed. The resulting intermediate layer is named the intermediate layer with a heating element. The matrix granulated powder is covered on the intermediate layer with the heating element and pressed to form the upper sealing layer. This forms a green blank with an embedded heating element; 4) Vibratory hot pressing sintering and annealing: The green body obtained in step 3) is first subjected to oscillating hot pressing sintering, and then annealed; to obtain a full ceramic aluminum nitride electrostatic chuck blank.

2. The method for preparing the all-ceramic aluminum nitride electrostatic chuck according to claim 1, characterized in that... It also includes the following step 5): The all-ceramic aluminum nitride electrostatic chuck blank is precision machined, including surface treatment, to obtain the all-ceramic aluminum nitride electrostatic chuck.

3. The method for preparing an all-ceramic aluminum nitride electrostatic chuck according to claim 1 or 2, characterized in that: The cermet is made of molybdenum dioxide and tungsten carbide.

4. The method for preparing the all-ceramic aluminum nitride electrostatic chuck according to claim 3, characterized in that: The sintering aid is a rare earth oxide, specifically yttrium oxide and magnesium oxide. The dispersant is polyethylene glycol.

5. The method for preparing the all-ceramic aluminum nitride electrostatic chuck according to claim 4, characterized in that: In step 3), molding or cold isostatic pressing is used.

6. The method for preparing the all-ceramic aluminum nitride electrostatic chuck according to claim 5, characterized in that... The oscillating hot pressing sintering in step 4) is as follows: The green body obtained in step 3) is placed in a sintering furnace with oscillation pressure function. Under an inert atmosphere or vacuum atmosphere, the temperature is first raised to remove the binder, and then the temperature is raised to 1750~1850℃ and oscillation pressure is applied. The oscillation pressure range is 5~40 MPa and the frequency is 0.1~5 Hz. Sintering and densification are carried out at 1750~1850℃ for 1~4 h.

7. The method for preparing the all-ceramic aluminum nitride electrostatic chuck according to claim 6, characterized in that... The annealing in step 4) is performed in a vacuum or inert atmosphere, with the annealing temperature 100~300℃ lower than the sintering temperature and the annealing time 2~6 h.

8. The method for preparing the all-ceramic aluminum nitride electrostatic chuck according to claim 7, characterized in that... In step 1): Deionized water was added to the matrix powder and wet ball milled to obtain a matrix slurry with a solid content of 40±5%. The conductive composite powder was added to deionized water and wet ball milled to obtain a conductive composite slurry with a solid content of 40±5%.

9. The method for preparing an all-ceramic aluminum nitride electrostatic chuck according to any one of claims 1 to 8, characterized in that: The lower substrate layer, the middle layer, and the upper sealing layer have the same cross-sectional size, with a diameter of 240~340 mm; The thickness of the lower substrate layer is 5~20 mm; the thickness of the middle layer is 3~10 mm; and the thickness of the upper sealing layer is 0.5~2 mm. The grooves of the granulated powder containing the conductive composite load have a width of 0.3~7 mm and a depth of 0.01~5 mm. All pressing processes were performed using cold isostatic pressing at a pressure of 150±20 MPa and a holding pressure of 10±2 min.

10. An all-ceramic aluminum nitride electrostatic chuck prepared by any one of claims 1 to 9.

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