A high-temperature, high-insulation 96 alumina ceramic and its preparation method

Abstract

This invention belongs to the field of ceramic materials technology and discloses a high-temperature, high-insulation 96 alumina ceramic and its preparation method. The material is made by mixing α-Al₂O₃ powder with a dopant, wherein the dopant is composed of TiO₂ and CaO mixed in a mass ratio of (1-3):(3-1). Its average volume resistivity at room temperature is higher than 10 Ω·cm. 15 The optimal component insulation resistivity can reach 1.75 × 10⁻⁶ Ω·cm at a high temperature of 500°C. 12 The preparation method involves mixing α-Al₂O₃ powder with dopants TiO₂ and CaO according to their doping content; mixing the raw material powder with anhydrous ethanol and then ball-milling; drying and sieving the ball-milled slurry; adding a binder to the obtained powder, sieving it again, granulating it, and pressing it into a green body; firing the green body after debinding to obtain the final ceramic sample. This invention utilizes Ca... 2+ Ti 4+ By doping and modifying the material, 96 alumina ceramics that meet the properties of coulombic electrostatic chucks were prepared. While reducing the sintering temperature, the resistivity was maintained, thus better meeting the practical application requirements.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, specifically, it relates to a 96 alumina ceramic and its preparation method. Background Technology

[0002] In chip manufacturing, electrostatic chucks (ESCs) serve as wafer carriers in vacuum and plasma environments. Their core mechanism involves applying a high-voltage direct current between the electrodes and the wafer, inducing polarization in the dielectric layer and generating Coulomb forces, thereby achieving flat clamping of the wafer. These chucks require the volume resistivity of the dielectric material to remain at 10 ohms at room temperature. 14 Above Ω·cm. At this level, current cannot flow through the dielectric layer, charge does not move macroscopically, and the adsorption force comes entirely from the Coulomb force generated by the polarization of the dielectric layer.

[0003] To ensure electrical reliability in advanced semiconductor processes, ESC materials require comprehensive optimization of their dielectric constant, dielectric loss, and Q·f value. These dielectric parameters directly affect the material's charge-carrying capacity and determine its dielectric heating suppression level in radio frequency environments, ensuring the system's thermal stability and energy transfer efficiency under complex electromagnetic fields. Furthermore, high dielectric strength is crucial to preventing breakdown failure of the dielectric layer under continuous high-voltage electric fields, directly supporting the long-term operational stability of the entire system.

[0004] In physical vapor deposition (PVD) processes, magnetron sputtering cavities are typically equipped with high-temperature electrostatic chucks (HESCs) to hold GaN and other wafers in process environments up to 300°C. Alumina ceramics are the preferred choice for such applications due to their superior electrical insulation properties: their volume resistivity is approximately 10 times higher than that of ordinary ceramics, and unlike polymer materials, they do not exhibit aging and embrittlement at high temperatures, demonstrating excellent long-term stability.

[0005] However, the electrical insulation properties of alumina materials are highly dependent on their purity and microstructure. Industrially used 96% alumina ceramics, due to the presence of fluxes such as SiO2 and MgO, tend to segregate at grain boundaries, forming a glassy phase. These glassy phases induce ion migration and conductivity, leading to drastic thermal response characteristics in the material's resistivity. This thermally induced effect can cause resistivity to range from >10... 14 Ω·cm drops sharply to 10 10 Below Ω·cm, the adsorption mechanism is forced to shift from "pure Coulomb force" to "Johnson-Labec (JR) force". The resulting charge trapping effect generates significant residual charge, ultimately leading to de-chucking failure of the wafer, which seriously affects production efficiency. Summary of the Invention

[0006] This invention aims to solve related technical problems of Al2O3 ceramic materials, and provides a high-temperature, high-insulation 96 alumina ceramic and its preparation method, through Ca... 2+ Ti 4+ By doping and modifying the material, 96 alumina ceramics that meet the properties of coulombic electrostatic chucks were prepared. While reducing the sintering temperature, the resistivity was maintained, thus better meeting the practical application requirements.

[0007] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution:

[0008] According to one aspect of the present invention, a high-temperature, high-insulation 96% alumina ceramic is provided, which is composed of α-Al₂O₃ powder and a dopant, wherein the mass ratio of α-Al₂O₃ powder to dopant is 96:4; the dopant is composed of CaO and TiO₂ mixed in a mass ratio of (1-3):(3-1); its average volume resistivity at room temperature is higher than 10 Ω·cm. 15 Ω·cm.

[0009] Preferably, the mass ratio of CaO to TiO2 is 2.5:1.5, and its average volume resistivity at room temperature is higher than 10. 16 Its insulation resistivity at 500℃ is higher than 10 Ω·cm. 12 Ω·cm.

[0010] Furthermore, the resistivity can be controlled by adjusting the doping content of CaO.

[0011] According to another aspect of the present invention, a method for preparing the above-mentioned high-temperature, high-insulation 96 alumina ceramic is provided, comprising:

[0012] (1) Prepare α-Al2O3 powder and dopants TiO2 and CaO according to the doping content; mix the raw material powder with anhydrous ethanol and then ball mill it;

[0013] (2) Dry and sieve the slurry after ball milling in step (1) to obtain powder;

[0014] (3) Add a binder to the powder obtained in step (2), sieve it again, granulate it, and press it into a green body;

[0015] (4) Remove the glue from the green body obtained in step (3);

[0016] (5) The blank after removing the binder is sintered at a temperature of 1550-1600℃ to obtain the final ceramic sample.

[0017] Preferably, in step (1), the ball milling is carried out in the form of 400 rpm clockwise for 40-50 minutes, resting for 10-20 minutes, 400 rpm counterclockwise for 40-50 minutes, and resting for 10-20 minutes, for a total of six sets of ball milling.

[0018] Preferably, the drying in step (2) is infrared drying, and the drying temperature is 110-130℃.

[0019] Preferably, the sieving in step (2) is to pass through a 40-mesh sieve 1-2 times.

[0020] Preferably, the binder in step (3) is paraffin wax with a mass percentage of 7-10%.

[0021] Preferably, the sieving in step (3) is to pass through an 80-mesh sieve 1-2 times.

[0022] Preferably, the temperature for degreasing in step (3) is 600-700℃ and the time is 4-6h.

[0023] The beneficial effects of this invention are:

[0024] This invention uses Al2O3, TiO2, and CaO as raw materials to prepare 96% alumina ceramic that meets the coulomb requirements of electrostatic chucks. By precisely controlling the CaO / TiO2 doping mass ratio, grain refinement was achieved while ensuring high material density (suppressing porosity). The reduction in grain size significantly increased grain boundary density, effectively enhancing the barrier effect and scattering of charge carriers, thereby suppressing leakage current and significantly improving volume resistivity. Simultaneously, this modified material exhibits excellent thermal stability: its resistivity remains at 10⁻⁶ even at a high temperature of 500℃. 12 The above represents a significant improvement over traditional formulations. Furthermore, by introducing TiO2 as a low-temperature sintering aid, the high-temperature sintering environment of 1750℃ required for pure alumina was successfully reduced to 1500–1600℃, significantly lowering process energy consumption while optimizing performance. Attached Figure Description

[0025] Figure 1 The image shows a SEM image of the sample prepared in Example 1.

[0026] Figure 2 This is a particle size distribution diagram of the sample prepared in Example 1;

[0027] Figure 3 The image shows the SEM image of the sample prepared in Example 2.

[0028] Figure 4 This is a particle size distribution diagram of the sample prepared in Example 2;

[0029] Figure 5The image shows a SEM image of the sample prepared in Example 3.

[0030] Figure 6 This is a particle size distribution diagram of the sample prepared in Example 3;

[0031] Figure 7 The image shows the SEM image of the sample prepared in Example 4.

[0032] Figure 8 This is a particle size distribution diagram of the sample prepared in Example 4;

[0033] Figure 9 The image shows a SEM image of the sample prepared in Example 5.

[0034] Figure 10 This is a SEM image of the sample prepared in Example 6. Detailed Implementation

[0035] The specific implementation of the present invention will be described in more detail below with reference to the accompanying drawings and embodiments, so as to better understand the solution of the present invention and the advantages of its various aspects. It should be noted that the specific implementation methods and embodiments described below are for illustrative purposes only and are not intended to limit the present invention.

[0036] Example 1

[0037] Step 1. Prepare Al2O3 and dopants CaO and TiO2 according to the proportions; put the raw material powders in the proportions in Table 1 into a ball mill jar, add about 100ml of anhydrous ethanol, and then ball mill six groups for a total of 10 hours in the form of 400 rpm forward rotation for 40 minutes, rest for 10 minutes, then reverse rotation for 40 minutes, and rest for 40 minutes.

[0038] Table 1 Composition of ceramic samples

[0039] Element <![CDATA[Al2O3]]> CaO <![CDATA[TiO2]]> Content (wt%) 96 1 3

[0040] Step 2. Place the ball-milled slurry from Step 1 in an infrared oven and dry it at 118°C, then pass it through a 40-mesh sieve once.

[0041] Step 3. After sieving in Step 2, add 7% by mass of paraffin powder as a binder to granulate the powder, pass it through an 80-mesh sieve, and then use a powder tablet press to press it into a green body at a pressure of 2MPa.

[0042] Step 4. Remove the glue from the green body obtained in step 3 at 650℃ and keep it at that temperature for 4 hours;

[0043] Step 5. Place the blank after debinding in step 4 into a high-temperature furnace for sintering. Raise the temperature to 1550℃ and hold for 4 hours to produce alumina ceramic.

[0044] Step 6. Coat both sides of the prepared alumina ceramic with silver electrodes and test the resistivity in a resistance box.

[0045] Example 2

[0046] Alumina ceramics were prepared according to the preparation method of Example 1, with the only difference being that the mass percentage of each dopant is shown in Table 2.

[0047] Table 2 Composition of ceramic samples

[0048] Element <![CDATA[Al2O3]]> CaO <![CDATA[TiO2]]> Content (wt%) 96 1.5 2.5

[0049] Example 3

[0050] Alumina ceramics were prepared according to the preparation method of Example 1, with the only difference being that the mass percentage of each dopant is shown in Table 3.

[0051] Table 3 Composition of ceramic samples

[0052] Element <![CDATA[Al2O3]]> CaO <![CDATA[TiO2]]> Content (wt%) 96 2 2

[0053] Example 4

[0054] Alumina ceramics were prepared according to the preparation method of Example 1, with the only difference being that the mass percentage of each dopant is shown in Table 4.

[0055] Table 4 Composition of ceramic samples

[0056] Element <![CDATA[Al2O3]]> CaO <![CDATA[TiO2]]> Content (wt%) 96 2.5 1.5

[0057] Example 5

[0058] Alumina ceramics were prepared according to the preparation method of Example 1, with the only difference being that the mass percentage of each dopant is shown in Table 5.

[0059] Table 5 Composition of ceramic samples

[0060] Element <![CDATA[Al2O3]]> CaO <![CDATA[TiO2]]> Content (wt%) 96 3 1

[0061] Example 6

[0062] Alumina ceramics were prepared according to the preparation method of Example 1, with the only difference being that the mass percentage of each dopant is shown in Table 6.

[0063] Table 6 Composition of ceramic samples

[0064] Element <![CDATA[Al2O3]]> CaO <![CDATA[TiO2]]> Content (wt%) 96 3.5 0.5

[0065] Example 7

[0066] Alumina dielectric ceramics were prepared according to the preparation method of Example 1, with the heating temperature in step 5 being 1500℃.

[0067] Example 8

[0068] Alumina dielectric ceramics were prepared according to the preparation method of Example 1, with the heating temperature in step 5 being 1525°C.

[0069] Example 9

[0070] Alumina dielectric ceramics were prepared according to the preparation method of Example 1, with the heating temperature in step 5 being 1575°C.

[0071] Example 10

[0072] Alumina dielectric ceramics were prepared according to the preparation method of Example 1, with the heating temperature in step 5 being 1600℃.

[0073] The samples obtained in the above examples were tested using scanning electron microscopy (SEM), and the particle size distribution of the samples prepared in Examples 1, 2, 3, and 4 was statistically analyzed. The electrical properties of the examples at room temperature are shown in Tables 7 and 8, and the resistivity of the examples at varying temperatures is shown in Table 9.

[0074] Table 7. Room temperature electrical performance test results of ceramic samples prepared in Examples 1-6

[0075]

[0076] Table 8. Room temperature electrical performance test results of ceramic samples prepared in Examples 7-10

[0077]

[0078] Table 9. Temperature-dependent resistivity (Ω·cm) test results of ceramic samples prepared in each embodiment.

[0079] For Examples 1-6, the doping content of Ca and Ti elements was varied while other experimental conditions remained constant to examine the density of the prepared alumina. Generally, the sintering temperature of pure alumina ceramics must be higher than 1700℃ to obtain samples with good density. However, alumina with different titanium dioxide contents exhibited relatively good bulk density (>3.82 g / cm³) at a sintering temperature of 1550℃. 3This is because α-Al₂O₃ and TiO₂ have similar crystal structures, with aluminum and titanium ions having radii of 0.053 nm and 0.068 nm, respectively, enabling them to form limited substitution solid solutions. The substitution of aluminum ions by titanium ions leads to lattice distortion and cation vacancies, increasing the diffusion rate of aluminum ions and thus lowering the sintering temperature of alumina, which contributes to the densification of the ceramic. The ceramic sample prepared exhibits the highest insulation resistivity when the mass ratio of CaO to TiO₂ is 2.5:1.5.

[0080] like Figure 1 , 3 As shown in Figures 5 and 7, SEM tests were performed on each embodiment. Comparing the SEM images of Examples 1-4, it can be observed that the ceramic samples prepared in Examples 1-4 are more densely sintered with clearer grain boundaries. During the preparation of Al2O3 ceramics, the addition of CaO reacts with Al2O3 to form the CA6 phase, which hinders the growth of Al2O3 grains. With the increase of Ca doping, the grain size decreases, and the area of ​​grain boundaries increases. The increase in grain boundary area hinders carrier migration, reduces carrier mobility, and leads to an increase in volume resistivity.

[0081] like Figure 2 , 4 As shown in Figures 6 and 8, the particle size distribution of the samples prepared in Examples 1-4 was statistically analyzed, and the ceramic sample prepared in Example 4 had the smallest average grain size, which was 5.21 μm. Figure 9 As shown in Figure 10, SEM tests were performed on Examples 5-6. Comparing Examples 5-6 with Examples 1-4, a significant increase in pores on the ceramic surface was observed. This is because when the mass ratio of CaO to TiO2 continues to increase to 3:1, the amount of CA6 phase gradually increases with the increase of the added amount. CA6 is distributed in a plate-like, interwoven manner in the alumina ceramic matrix, forming many fine pores. With the increase of CaO addition, the porosity of Al2O3 ceramic gradually increases, and the bulk density gradually decreases, resulting in a decrease in the density of the ceramic sample and thus a decrease in resistivity.

[0082] As can be seen from Table 8, the resistance first increases with increasing temperature and then tends to remain constant, with 1550℃ being the optimal sintering temperature.

[0083] As shown in Table 9, the resistivity of the doped component in Example 4 is higher than that of other components. Although its resistivity decreases when the temperature is raised to 300°C, it can still be stably maintained at 10 Ω·cm. 14 The Ω·cm level meets the insulation performance requirements of Coulomb force adsorption.

[0084] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit of the invention and the scope of protection of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. A high-temperature, high-insulation 96% alumina ceramic, characterized in that, It is composed of α-Al₂O₃ powder and dopant, with a mass ratio of α-Al₂O₃ powder to dopant of 96:4; the dopant is composed of CaO and TiO₂ mixed in a mass ratio of (1-3):(3-1); its average volume resistivity at room temperature is higher than 10 Ω·cm. 15 Ω·cm.

2. The high-temperature, high-insulation 96 alumina ceramic according to claim 1, characterized in that, The mass ratio of CaO to TiO2 is 2.5:1.5, and its average volume resistivity at room temperature is higher than 10. 16 Its insulation resistivity at 500℃ is higher than 10 Ω·cm. 12 Ω·cm.

3. The high-temperature, high-insulation 96 alumina ceramic according to claim 1, characterized in that, The resistivity can be controlled by adjusting the doping content of CaO.

4. A method for preparing high-temperature, high-insulation 96 alumina ceramic as described in any one of claims 1-3, characterized in that, include: (1) Prepare α-Al2O3 powder and dopants TiO2 and CaO according to the doping content; mix the raw material powder with anhydrous ethanol and then ball mill it; (2) Dry and sieve the slurry after ball milling in step (1) to obtain powder; (3) Add a binder to the powder obtained in step (2), sieve it again, granulate it, and press it into a green body; (4) Remove the glue from the green body obtained in step (3); (5) The blank after removing the binder is sintered at a temperature of 1550-1600℃ to obtain the final ceramic sample.

5. The method for preparing a high-temperature, high-insulation 96 alumina ceramic according to claim 4, characterized in that, In step (1), the ball milling process is carried out in the form of 400 rpm clockwise for 40-50 minutes, resting for 10-20 minutes, 400 rpm counterclockwise for 40-50 minutes, and resting for 10-20 minutes, for a total of six sets.

6. The method for preparing a high-temperature, high-insulation 96 alumina ceramic according to claim 4, characterized in that, The drying in step (2) is infrared drying, and the drying temperature is 110-130℃.

7. The method for preparing a high-temperature, high-insulation 96 alumina ceramic according to claim 4, characterized in that, In step (2), the sieving process involves passing the material through a 40-mesh sieve 1-2 times.

8. The method for preparing a high-temperature, high-insulation 96 alumina ceramic according to claim 4, characterized in that, The binder in step (3) is paraffin wax with a mass percentage of 7-10%.

9. The method for preparing a high-temperature, high-insulation 96 alumina ceramic according to claim 4, characterized in that, The sieving in step (3) involves passing the material through an 80-mesh sieve 1-2 times.

10. The method for preparing a high-temperature, high-insulation 96 alumina ceramic according to claim 4, characterized in that, The temperature for degreasing in step (3) is 600-700℃ and the time is 4-6h.

Images