High-fluorine yttrium oxide ceramic and preparation method thereof

Abstract

The invention discloses a method for preparing high-density yttrium oxyfluoride ceramic by combining a hydrothermal method and hot pressed sintering. The method comprises the following steps: (1) respectively preparing a yttrium nitrate (Y (NO3) 3.6 H2O) solution and an ammonium fluoride (NH4F) solution; (2) mixing the raw materials, and stirring for 10 to 20 minutes; (3) adding a sodium hydroxide solution into the mixed solution to adjust the pH value of the system to 10-12, and continuously stirring for 10-20 minutes to obtain a premixed solution; (4) transferring the premixed solution into a hydrothermal kettle, and carrying out hydrothermal reaction under a high-temperature condition; (5) carrying out centrifugal separation and drying treatment on the hydrothermal reaction product to obtain a yttrium oxyfluoride precursor; (6) calcining the precursor in a muffle furnace in an air atmosphere; and (7) carrying out hot pressed sintering on the obtained powder under the conditions of 750-1000 DEG C and 20-40 MPa, and carrying out heat preservation for 30-90 minutes. The obtained ceramic has high compactness and excellent plasma etching resistance.

Description

Technical Field

[0001] This patent relates to the field of ceramic material preparation technology, and more specifically, to a yttrium fluoride ceramic and its preparation method. Background Technology

[0002] In recent years, the rapid development of the semiconductor and integrated circuit industries has driven the evolution of devices towards miniaturization and high integration. High-density plasma technology has become an indispensable part of wafer fabrication, and fluorine-containing plasma, due to its strong chemical reactivity, is widely used in silicon wafer etching processes. However, in this process, the aluminum and aluminum alloy materials inside the plasma chamber are often severely corroded, leading to particulate contamination, affecting the stability of the etching process, and even causing equipment damage and reduced yield. Therefore, improving the corrosion resistance of the plasma chamber wall materials has become a critical problem that urgently needs to be solved in the semiconductor manufacturing field.

[0003] Ceramic materials, with their high density and excellent chemical stability, have become ideal materials for plasma-resistant coatings. Y₂O₃ and YF₃ ceramic coatings, in particular, are widely used in etching equipment due to their superior resistance to fluorine-containing plasmas. High-purity Y₂O₃ coatings exhibit good chemical stability in both Cl-based and F-based plasma environments, while YF₃ coatings effectively reduce particulate contamination problems due to their excellent resistance to plasma erosion. However, both coatings still have certain limitations: firstly, coatings prepared by plasma spraying are relatively expensive; secondly, residual stress within the coating often leads to the formation of pores and microcracks, affecting its durability. Furthermore, before being put into production, Y₂O₃ coatings require a certain period of fluorine-containing plasma pretreatment to allow F element to penetrate into the coating and form a YxOyFz thin film. This process requirement increases the complexity and time cost of production, which is detrimental to the efficiency of semiconductor manufacturing.

[0004] Based on the aforementioned issues, yttrium oxyfluoride (YO) coatings have become a more promising solution due to their superior overall performance. Unlike Y₂O₃ and YF₃ coatings, YO₂ O₃ coatings have pre-introduced the element F into their structure, avoiding additional pretreatment steps, simplifying the production process, and improving resistance to plasma etching. Therefore, preparing high-purity, high-quality YO₂ O₃ powder is crucial for improving coating performance, extending equipment lifespan, and reducing particulate contamination.

[0005] Among numerous powder preparation technologies, the hydrothermal method is considered an ideal approach for preparing high-quality yttrium oxyfluoride (YOF) powder due to its unique advantages. Hydrothermal synthesis is carried out in a high-temperature, high-pressure environment, effectively preventing the escape of sulfur (F) and thus precisely controlling the elemental composition of the final product. Furthermore, YOF powder prepared by the hydrothermal method exhibits high purity, uniform particle size distribution, and good grain development, providing a high-quality raw material for subsequent ceramic coating preparation. Therefore, researching the hydrothermal preparation of YOF powder not only optimizes the corrosion resistance and stability of plasma chambers but also plays a significant role in improving the reliability and production efficiency of semiconductor manufacturing processes. Summary of the Invention

[0006] To address the technical problems mentioned in the background art, such as the easy escape of fluorine element and inaccurate composition control during the preparation of yttrium oxyfluoride powder, and the high production cost and complex process caused by the need for plasma pretreatment for Y2O3 coating, this invention provides a method for preparing yttrium oxyfluoride ceramics, comprising the following steps: (1) Prepare yttrium nitrate (Y(NO3)3·6H2O) solution and ammonium fluoride (NH4F) solution respectively; (2) Mix the ammonium fluoride solution with the yttrium nitrate solution and stir for 10-20 min; (3) Add sodium hydroxide solution to the mixed solution to adjust the pH of the system to 10-12, and continue stirring for 10-20 min to obtain a premixed solution; (4) Transfer the premixed solution to a hydrothermal reactor and carry out the hydrothermal reaction under high temperature conditions; (5) The hydrothermal reaction products were centrifuged and dried to obtain the yttrium fluoride precursor; (6) The yttrium fluoride precursor is pretreated and calcined in an air atmosphere in a muffle furnace, and then ground into YxOyFz powder, wherein 0 < (x + y): z < 2; (7) The obtained powder is hot-pressed and sintered at 750-1000℃ and 20-40 MPa for 30-90 min to obtain high-density yttrium fluoride ceramic.

[0007] This method effectively prevents the escape of fluorine (F) element through a hydrothermal reaction in a closed system, ensuring precise composition control. Simultaneously, the alkaline environment promotes the uniform formation of the yttrium fluoride oxyfluoride precursor, avoiding impurity generation. Finally, high-density ceramics are obtained through hot-pressing sintering. This invention features a simple synthesis procedure, uses safe and environmentally friendly raw materials, effectively suppresses F escape, improves the controllability of powder composition, and yields ceramics with high density and excellent resistance to plasma etching. This avoids the need for plasma pretreatment required for traditional Y₂O₃ coatings, thereby reducing preparation costs and extending the lifespan of semiconductor devices.

[0008] Optionally, the stirring time in step (2) is 10 to 20 minutes.

[0009] By controlling the stirring time, the reactants are thoroughly mixed, avoiding precursor quality fluctuations caused by uneven local concentrations, thereby improving the uniformity and consistency of the final ceramic.

[0010] Optionally, the sodium hydroxide solution used to adjust the pH in step (3) is added rapidly, and the adjusted pH value is 10 to 12.

[0011] By rapidly adjusting the pH to a suitable range, the uniform formation of precursors is promoted, the purity of powder and the quality of crystallization are improved, thereby improving the performance of the final ceramic.

[0012] Optionally, the hydrothermal reaction temperature in step (4) is 140–200 °C and the reaction time is 6–12 h.

[0013] By controlling the hydrothermal reaction conditions, a precursor with complete crystallization and uniform composition is obtained, providing high-quality raw materials for subsequent calcination and sintering, thereby improving the density and properties of the final ceramic.

[0014] Optionally, in step (5), the centrifugation speed is 3000-8000 r / min and the centrifugation time is 3-10 min.

[0015] By optimizing centrifugation conditions, the recovery rate and purity of precursors can be improved, ensuring the quality of subsequent calcined powders, thereby enhancing the performance and consistency of the final ceramics.

[0016] Optionally, in step (6), the calcination heating rate is 1 to 10 °C / min, the calcination temperature is 350 to 450 °C, and the holding time is 1 to 4 h.

[0017] By precisely controlling the calcination conditions, powder with uniform composition and appropriate particle size can be obtained, which is beneficial for densification during hot pressing and sintering, thereby improving the density and performance of ceramics.

[0018] Optionally, in step (1), the concentration ratio a:b of yttrium nitrate solution to ammonium fluoride solution is set to 1:1 according to the target product YOF; in step (1), the concentration ratio a:b of yttrium nitrate solution to ammonium fluoride solution is set to 5:7 according to the target product Y5O4F7.

[0019] By precisely controlling the raw material concentration ratio, yttrium fluoride powder with specific components can be obtained to meet the needs of different application scenarios and improve the applicability and performance of the product.

[0020] Optionally, the sintering heating rate in step (7) is 10 °C / min.

[0021] By controlling the sintering heating rate, the sintering process is ensured to proceed uniformly, resulting in high-density ceramics with uniform structure and improved resistance to plasma etching.

[0022] Optionally, in step (6), the average particle size of the powder obtained by grinding after calcination is 0.2 to 13 μm.

[0023] By controlling the powder particle size within a suitable range, the densification efficiency during the hot pressing sintering process can be improved, resulting in high-density yttrium oxyfluoride ceramics with excellent performance.

[0024] Another aspect of the present invention provides a yttrium fluoride ceramic, characterized in that it is prepared by any one of the methods of claims 1 to 9.

[0025] This yttrium oxyfluoride ceramic has high density and excellent resistance to plasma etching, which avoids the problem of plasma pretreatment required for traditional Y2O3 coatings, reduces production costs and extends the service life of semiconductor devices.

[0026] In summary, this invention systematically solves the technical challenges of easy fluorine (F) escape and inaccurate composition control during the preparation of yttrium fluoride oxychloride powder by combining a hydrothermal method with hot-pressing sintering. This method conducts the hydrothermal reaction in a closed system, effectively preventing F escape and ensuring precise composition control. By precisely controlling the pH value, hydrothermal reaction conditions, calcination parameters, and hot-pressing sintering process, YxOyFz powder with uniform composition and suitable particle size is obtained, ultimately producing high-density yttrium fluoride oxychloride ceramics. This invention not only avoids the plasma pretreatment step required for traditional Y2O3 coatings, simplifying the production process, but also significantly improves the plasma etching resistance of the ceramics, thereby reducing the maintenance costs of semiconductor equipment, extending equipment lifespan, and providing a high-performance, low-cost solution for the semiconductor manufacturing field. Attached Figure Description

[0027] To more clearly illustrate the embodiments of this patent, a brief description of the relevant drawings will be provided below. It should be understood that the drawings described below are only for illustrating some embodiments of this patent, and those skilled in the art can obtain many other technical features and connections not mentioned herein based on these drawings.

[0028] Figure 1 The image shows the XRD pattern of YOF powder obtained in Example 1 using a yttrium nitrate:ammonium fluoride ratio of 1:1. Figure 2 The image shows the XRD pattern of Y5O4F7 powder obtained in Example 2 with a yttrium nitrate:ammonium fluoride ratio of 5:7. Figure 3 The calcination temperature curves for step 3 in Examples 1 and 2 are shown. Figure 4 The hot pressing sintering temperature curves are shown in step 4 of Examples 1 and 2. Figure 5 The image shows a cross-sectional scanning electron microscope (SEM) image of the dense YOF ceramic prepared by hot pressing and sintering of powder in Example 2. Figure 6 The surface morphology (SEM) of the dense YOF ceramic prepared by hot pressing and sintering of powder in Example 2 before and after 1.5 h of SF6 / Ar mixed plasma etching is shown in the following figures: (a) before etching; (b) after etching. Table 1 shows the test results for Example 2; Figure 7 The refined XRD pattern of the dense cubic YOF ceramic prepared by hot pressing and sintering of powder in Example 2; Table 1 shows the test results for Example 2. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0030] In the semiconductor manufacturing field, fluorine-containing plasma etching is a core step in wafer fabrication, placing stringent requirements on the corrosion resistance of the materials inside the plasma chamber. These chambers typically use aluminum and aluminum alloys as their basic structural materials, but they are highly susceptible to chemical corrosion in fluorine-containing plasma environments, leading to frequent particulate contamination issues. This not only affects the stability of the etching process but can also cause equipment damage and reduced product yield. To address this problem, ceramic coating materials are widely used for chamber wall protection due to their excellent chemical stability and high density. Among them, Y2O3 and YF3 coatings, with their resistance to fluorine-containing plasma corrosion, have become the mainstream solution in the industry.

[0031] In existing technologies, Y₂O₃ coatings are typically prepared using plasma spraying, a method that involves melting Y₂O₃ powder at high temperatures and spraying it onto the inner wall of a cavity to form a protective layer. YF₃ coatings employ a similar process, obtaining a corrosion-resistant surface by spraying YF₃ powder. Both types of coatings must structurally meet the requirement of being dense and non-porous to prevent plasma penetration and subsequent substrate corrosion. However, before practical application, Y₂O₃ coatings must undergo a fluorine-containing plasma pretreatment process to allow fluorine (F) to diffuse from the plasma into the coating interior, forming a YxOyFz thin film, thus maximizing their corrosion resistance. This pretreatment step not only prolongs the equipment preparation cycle but also increases process complexity and production costs.

[0032] Existing technologies have significant limitations in principle: plasma spraying is performed at high temperatures, causing phosphorus (F) to easily escape during coating formation, making it difficult to precisely control the elemental composition of the final product. This limitation directly leads to microscopic defects such as pores and microcracks within the coating. These defects originate from residual stress generated during spraying, severely affecting the coating's density and structural integrity. The presence of these microscopic defects not only reduces the coating's corrosion resistance but also provides penetration channels for the plasma, accelerating the corrosion process of the substrate material.

[0033] Further analysis reveals that the aforementioned surface defects can trigger more serious systemic problems: the Y₂O₃ coating requires an additional plasma pretreatment step to allow the fluorine element to penetrate into the coating and form a stable YxOyFz structure. However, the pretreatment process itself presents challenges in parameter control; the penetration depth and uniformity of the fluorine element are difficult to precisely regulate, leading to significant fluctuations in coating performance between different batches. More critically, the pretreatment process consumes additional equipment operating time, reducing the overall efficiency of the semiconductor production line and fundamentally contradicting the industry's pursuit of high capacity and low cost.

[0034] To address the aforementioned issues, those skilled in the art may attempt to improve coating quality by extending the pretreatment time or optimizing spraying parameters. However, while extending the pretreatment time can promote fluorine (F) penetration, it fails to solve the fundamental problem of F escape during spraying, instead increasing production cycle time and energy consumption. Optimizing spraying parameters often leads to decreased coating thickness uniformity and may even introduce new interfacial bonding problems. These improvement approaches fail to address the core contradiction in F control and cannot simplify the process while ensuring coating quality.

[0035] In view of this, the embodiments of the present invention aim to provide a yttrium oxyfluoride ceramic and its preparation method. Yttrium oxyfluoride powder is prepared by hydrothermal method using yttrium nitrate and ammonium fluoride as raw materials, and the prepared yttrium oxyfluoride ceramic is a cubic phase. The method of the present invention can eliminate the time required for the transformation from Y₂O₃ to YxOyF₂, saving costs, enhancing plasma etching resistance, and improving the service life of semiconductor equipment, thereby solving the problems of easy escape of F element and inaccurate composition control in the preparation process of yttrium oxyfluoride powder in the prior art.

[0036] Example 1 In the preparation of protective materials for semiconductor manufacturing equipment chambers, a method for preparing yttrium fluoride ceramics can employ a process combining hydrothermal synthesis and hot-pressing sintering. First, yttrium nitrate and ammonium fluoride solutions are prepared separately, then mixed and stirred. The yttrium nitrate and ammonium fluoride solutions can be thoroughly mixed using a mechanical stirrer, with the mixing time controlled within 10 to 20 minutes to ensure uniform dispersion of the reactants. Next, sodium hydroxide solution is rapidly added to the mixture to adjust the pH value, maintaining it within the alkaline range of 10 to 12. This adjustment can be performed by titration. After adjustment, stirring continues for 10 to 20 minutes to promote the uniform formation of the precursor. Subsequently, the premixed solution is transferred to a pressure-resistant reactor for a hydrothermal reaction under sealed conditions. The reaction temperature can be set between 140 and 200°C, and the reaction time can be controlled within 6 to 12 hours. After the reaction, the product can be centrifuged. The centrifugation speed can be set to 3000 to 8000 rpm, and the centrifugation time can be 3 to 10 minutes. The separated precipitate can be washed sequentially with deionized water and ethanol. The washed material can be dried at 80 to 105°C for more than 12 hours to obtain the yttrium fluoride oxyfluoride precursor. To further optimize the powder properties, the precursor can be calcined in a muffle furnace under air atmosphere. The calcination heating rate can be controlled at 1 to 10°C / min, the calcination temperature can be set at 350 to 450°C, and the holding time can be 1 to 4 hours. The average particle size of the powder obtained after calcination and grinding can be controlled within the range of 0.2 to 13 micrometers. Finally, the obtained powder can be placed in a hot-pressing sintering device and sintered at a temperature of 750 to 1000℃ and a pressure of 20 to 40 MPa for a holding time of 30 to 90 minutes. The sintering heating rate can be controlled at 10℃ / min, thereby obtaining a high-density yttrium fluoride oxyceramic material. The ingenuity of this preparation method lies in the effective suppression of fluorine escape by utilizing a closed hydrothermal system, ensuring the precise controllability of the product composition.

[0037] (1) When the target product is YOF, the concentration ratio of yttrium nitrate solution to ammonium fluoride solution can be set to 1:1, preparing a mixed solution of 0.5 mol / L yttrium nitrate solution and 0.5 mol / L ammonium fluoride solution. This ratio can precisely control the elemental proportions to obtain the target product YOF. Stirring for 15 min ensures that yttrium nitrate and ammonium fluoride are fully in contact and react, avoiding precursor mass fluctuations caused by local concentration differences. This reasonable control of stirring time can promote effective collisions between reactant molecules, improve reaction efficiency, and avoid energy waste that may result from excessive stirring.

[0038] (2) In the pH adjustment step, sodium hydroxide solution can be added rapidly. For example, the pre-prepared sodium hydroxide solution can be injected into the mixed system within 1 minute, or multiple points can be injected simultaneously to accelerate the pH adjustment process. Adjusting the pH of the mixed solution to 11 can balance the reaction rate and product purity, ensuring the effective formation of yttrium fluoride and avoiding side reactions that may occur under excessively alkaline conditions.

[0039] (3) Continue stirring the reaction at room temperature for 10 minutes to promote uniform crystallization of the precursor and avoid uneven composition caused by pH gradient. Transfer it into a reactor and hydrothermally react for 12 hours. After the hydrothermal reaction is completed, centrifuge and dry to obtain the precursor.

[0040] (4) The centrifugation steps described above require controlling the rotation speed at 8000 r / min and centrifuging for 5 min. This parameter combination can effectively separate the precursor precipitate while avoiding particle breakage that may occur due to excessively high rotation speed. The precipitate obtained by centrifugation is washed three times with deionized water and ethanol, respectively. The centrifugation parameters for each wash can be kept consistent with those for the initial separation to thoroughly remove impurity ions adsorbed on the surface and improve the purity of the precursor. The slurry after centrifugation and washing is dried at 105℃ for 24 h and then ground to obtain the precursor.

[0041] (5) The precursor was placed in a muffle furnace and heated to 400°C at a heating rate of 3°C / min for 2 hours and then cooled in the furnace to obtain YOF powder. This condition can ensure the full decomposition of organic matter and the stable transformation of crystal phase.

[0042] (6) Place 4.0g of YOF powder in a graphite mold and sinter by hot pressing. The heating rate is 10℃ / min to 950℃. Heating at a rate of 10℃ / min can avoid stress concentration caused by excessive temperature gradient and reduce the formation of internal defects in the ceramic. After holding at the temperature for 60min, the temperature is lowered with the furnace. Highly dense YOF ceramics are prepared.

[0043] Example 2 (1) When the target product is Y5O4F7, the concentration ratio can be set to 5:7, preparing a mixed solution of 0.5 mol / L yttrium nitrate and 0.7 mol / L ammonium fluoride. This ratio can meet the stoichiometric requirements of Y5O4F7. This flexible adjustment of the concentration ratio can adapt to the preparation needs of yttrium fluoride materials with different compositions, providing customized protective materials for semiconductor devices. From the perspective of chemical reaction mechanism analysis, the precise ratio of raw materials can ensure the stoichiometric balance of the reaction system, avoid the formation of impurity phases, and thus improve the purity and performance consistency of the product.

[0044] (2) After stirring for 15 minutes, the pH of the mixed solution was quickly adjusted to 11 using sodium hydroxide solution. This value balances the reaction rate and product purity, ensuring the effective formation of yttrium fluoride while avoiding potential side reactions under excessively alkaline conditions. This rapid pH adjustment technique effectively controls reaction kinetics, allowing the precursor to form uniformly in a suitable chemical environment, thereby improving the crystallinity and purity of the powder. The reaction was continued with stirring at room temperature for 10 minutes. The mixture was then transferred to a reactor and subjected to hydrothermal reaction for 6 hours. After the hydrothermal reaction was completed, the precursor was obtained by centrifugation and drying.

[0045] (3) The centrifugation steps described above require controlling the rotation speed at 8000 r / min and centrifuging for 5 min. The precipitate obtained by centrifugation is washed three times with deionized water and ethanol respectively, with the same centrifugation parameters as above. The centrifuged and washed slurry is dried at 105℃ for 24 h, and then ground to obtain the precursor.

[0046] (4) The precursor was placed in a muffle furnace and calcined at 400℃ for 2 hours at a heating rate of 3℃ / min, followed by furnace cooling to obtain Y5O4F7 powder. Appropriate calcination conditions can optimize the specific surface area and particle morphology of the powder, providing good sintering activity for subsequent hot pressing sintering. The average particle size of the calcined powder can be controlled within the range of 0.2 to 13 micrometers, and this particle size distribution can optimize the densification process of hot pressing sintering.

[0047] (5) 4.0 g of Y5O4F7 powder was placed in a graphite mold and sintered by hot pressing. The heating rate was 10 °C / min to 800 °C. From the perspective of sintering kinetics, a suitable heating rate can balance the grain growth and densification process, avoiding abnormal grain growth caused by excessively rapid heating or low production efficiency caused by excessively slow heating. After holding at the temperature for 60 min, the temperature was lowered with the furnace. Highly dense cubic YOF ceramics were prepared.

[0048] Table 1 Test results.

Claims

1. A method for preparing yttrium oxyfluoride ceramic, comprising the following steps: (1) preparing yttrium nitrate (Y(NO3)3.6H2O) solution and ammonium fluoride (NH4F) solution respectively; (2) mixing the ammonium fluoride solution with the yttrium nitrate solution and stirring for 10-20 min; (3) adding sodium hydroxide solution to the mixed solution to adjust the pH of the system to 10-12 and continuing to stir for 10-20 min to obtain a premixed solution; (4) transferring the premixed solution to an autoclave and performing hydrothermal reaction under high temperature conditions; (5) performing centrifugal separation and drying treatment on the hydrothermal reaction product to obtain yttrium oxyfluoride precursor; (6) performing pretreatment calcination on the yttrium oxyfluoride precursor in a muffle furnace under air atmosphere, and grinding the YxOyFz powder after calcination, wherein 0<(x+y):z<2; (7) performing hot-press sintering on the obtained powder at 750-1000℃ and 20-40 MPa for 30-90 min to obtain high-density yttrium oxyfluoride ceramic.

2. The method according to claim 1, wherein the stirring time in step (2) is 10-20 min.

3. The method according to claim 1, wherein the sodium hydroxide solution used for adjusting the pH in step (3) is added quickly, and the adjusted pH value is 10-12.

4. The method according to claim 1, wherein the hydrothermal reaction temperature in step (4) is 140-200℃, and the reaction time is 6-12 h.

5. The method according to claim 1, wherein the centrifugal speed in step (5) is 3000-8000 r / min, and the centrifugal time is 3-10 min.

6. The method according to claim 1, wherein the calcination heating rate in step (6) is 1-10℃ / min, the calcination temperature is 350-450℃, and the holding time is 1-4 h.

7. The method according to claim 1, wherein the concentration ratio a:b of the yttrium nitrate solution to the ammonium fluoride solution in step (1) is set to 1:1 according to the target product YOF, and the concentration ratio a:b of the yttrium nitrate solution to the ammonium fluoride solution in step (1) is set to 5:7 according to the target product Y5O4F7.

8. The method according to claim 1, wherein the sintering heating rate in step (7) is 10℃ / min.

9. The method according to claim 1, wherein in step (6), the average particle size of the powder obtained after calcination and grinding is 0.2-13 μm. Prepared by any one of the methods in claims 1-9. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 10. A yttrium oxyfluoride ceramic, characterized by, ​

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