Insulating layer for C / SiC composite material substrate film sensor and preparation method thereof

Abstract

The invention discloses an insulating layer for a C / SiC composite material substrate film sensor and a preparation method, and belongs to the technical field of film sensor design and production. The insulating layer comprises a Si3N4 buffer layer, an AlN transition layer, an Al2O3 barrier layer and an Al2O3 insulating layer which are sequentially arranged from bottom to top. Wherein the coefficient of thermal expansion of the Si3N4 buffer layer is similar to that of the C / SiC composite material substrate, the Si3N4 buffer layer and the C / SiC composite material substrate have the same Si element, and bond transition is formed at the interface of the film and the substrate, so that the insulating layer and the substrate have better adhesive force. The thermal expansion coefficient difference between the AlN transition layer and the Si3N4 buffer layer is small, and the AlN transition layer and the Si3N4 buffer layer are nitrides, so that good chemical bonding can be realized, and the binding force between the film layers can be enhanced. The Al2O3 thin film is compact in structure, and diffusion of external oxygen elements can be effectively blocked; chemical bonding of the transition layer is similar to chemical bonding of the lower AlN layer, interface bonding is good, and the transition layer can be effectively protected from being oxidized.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film sensor design and production, and particularly relates to an insulating layer for a C / SiC composite substrate thin film sensor and a preparation method thereof. Background Art

[0002] With the development of aerospace technology towards high efficiency, high reliability, etc., the gas temperature inside the engines of aerospace aircraft is continuously increasing, and the temperature that the thermal structure components need to withstand has gradually approached the critical working temperature of superalloy materials. Using high-temperature-resistant materials with better thermal stability to prepare thermal structure components can better ensure their structural integrity and functional stability in high-temperature environments. Among them, carbon fiber reinforced silicon carbide matrix composite material (C / SiC) has good wear resistance, impact resistance, heat resistance, ablation resistance and high-temperature oxidation resistance, and also has characteristics such as high strength and low density. It is considered to be one of the advanced materials for improving the high-temperature resistance of spacecraft components and reducing the overall mass of spacecraft, and is currently widely used in the preparation of key thermal structure components in various aerospace fields. However, thermal structure components working in extreme environments such as high temperature, high pressure, and high centrifugal force for a long time may experience ablation or fracture, which will seriously affect the service life of aerospace equipment. In order to improve the reliability and safety of aerospace aircraft, it is necessary to evaluate the health status of thermal structure components by monitoring thermal parameters such as temperature, strain, and heat flux.

[0003] Thin film sensors directly prepared on the measured components by processes such as vacuum evaporation, sputtering, and chemical vapor deposition can not only effectively avoid the high-temperature creep and signal hysteresis caused by the adhesion of traditional sensors, but also hardly affect the flow field characteristics on the surface of the component while not damaging the original structure of the measured component. In addition, since thin film sensors are usually only a few micrometers thick and their mass is negligible, they can minimally affect the vibration and working mode of the component and achieve accurate measurement of the state parameters of the component in harsh environments such as high temperature and high pressure.

[0004] Due to the good electrical conductivity of the C / SiC composite substrate, it is necessary to deposit an insulating film with a certain thickness between the thin film sensor and the substrate to ensure the normal operation of the thin film sensor. However, the surface flatness of the C / SiC composite material is poor, with a large number of depressions, holes and other defects. If an insulating film is directly prepared on the material surface, problems such as film layer peeling are likely to occur, ultimately leading to a decline in sensor performance or even the inability to output an effective signal. In the patent document with the publication number CN116949428A, "An Insulating Layer for a Thin Film Sensor on a C / SiC Composite Substrate and Its Preparation Method" is disclosed. In this invention patent, a SiO2 filling layer is first prepared on the surface of the C / SiC composite material by the sol-gel method, and then a Si3N4 buffer layer is deposited on it by PECVD or magnetron sputtering technology. Next, an Al2O3 barrier layer is prepared by PEALD deposition technology, and finally, a YSZ / Al2O3 insulating film is prepared by reactive sputtering and annealed. However, it is difficult to control the thickness uniformity of the SiO2 film prepared by the sol-gel method, and it is easy to crack in an environment with drastic temperature changes, resulting in discontinuous film layers; the bonding force between the Si3N4 buffer layer and the Al2O3 barrier layer is also poor, and it is easy to cause film layer peeling when the temperature changes sharply, thereby rendering the insulating film ineffective. Summary of the Invention

[0005] The purpose of the present invention is to propose an insulating layer for a thin film sensor on a C / SiC composite substrate and a preparation method in view of the problems existing in the background technology. The insulating layer film continuously deposited on the surface of the C / SiC composite material in the present invention helps to improve the performance stability of the thin film sensor in extreme environments.

[0006] To achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0007] An insulating layer for a thin film sensor on a C / SiC composite substrate includes a Si3N4 buffer layer, an AlN transition layer, an Al2O3 barrier layer and an Al2O3 insulating layer arranged in sequence from bottom to top; wherein the thickness of the Si3N4 buffer layer is 0.1 - 4μm, the thickness of the AlN transition layer is 0.1 - 2μm, the thickness of the Al2O3 barrier layer is 10 - 200nm, and the thickness of the Al2O3 insulating layer is 0.1 - 3μm.

[0008] Furthermore, the Si3N4 buffer layer is prepared by magnetron sputtering, the AlN transition layer is prepared by magnetron sputtering, the Al2O3 barrier layer is prepared by PEALD, and the Al2O3 insulating layer is prepared by magnetron sputtering.

[0009] A preparation method for an insulating layer for a thin film sensor on a C / SiC composite substrate includes the following steps:

[0010] Step 1. Surface pretreatment of C / SiC composite substrate;

[0011] The C / SiC composite material was successively immersed in acetone, absolute ethanol and deionized water for ultrasonic cleaning. After cleaning, the residual moisture was removed by air drying or baking.

[0012] Step 2. Preparation of Si3N4 buffer layer on the C / SiC composite substrate by magnetron sputtering;

[0013] The vacuum in the sputtering equipment cavity was pumped to a vacuum degree of below 8×10 -4 Pa. Using a Si target as the sputtering target and a mixed gas of N2 and Ar as the sputtering gas, where the flow ratio of N2 to Ar is 5:25 - 6:30, the sputtering pressure is 0.4 - 0.8 Pa, and the substrate temperature is 100℃ - 200℃. A Si3N4 thin film was deposited by reactive sputtering to obtain a Si3N4 buffer layer with a thickness of 0.1 - 4μm.

[0014] Step 3. Preparation of AlN thin film on the Si3N4 buffer layer prepared in Step 2;

[0015] The vacuum in the sputtering equipment cavity was pumped to below 8×10 -4 Pa. Using an Al target as the sputtering target and N2 as the sputtering gas, the N2 gas flow rate is 100 - 200 sccm, the sputtering pressure is 0.4 - 1.2 Pa, and the substrate temperature is 250℃ - 350℃. An AlN thin film was deposited by reactive sputtering to obtain an AlN transition layer with a thickness of 0.1 - 2μm.

[0016] Step 4. Preparation of Al2O3 thin film on the AlN transition layer prepared in Step 3;

[0017] The vacuum in the PEALD (plasma enhanced atomic layer deposition) equipment cavity was pumped to a vacuum degree of below 0.15 torr, the temperature in the reaction cavity was set to 100 - 200℃, trimethylaluminum (TMA) and water vapor (H2O) were used as reaction gases, and N2 was used as the cleaning gas. An Al2O3 thin film was formed through chemical reactions to obtain an Al2O3 barrier layer with a thickness of 10 - 200 nm.

[0018] Step 5. Preparation of Al2O3 thin film on the Al2O3 barrier layer prepared in Step 4;

[0019] The vacuum in the sputtering equipment cavity was pumped to 8×10 -4Below Pa, using an Al target as the sputtering target and a mixed gas of Ar and O2 as the sputtering gas, where the flow ratio of Ar to O2 is 48:3 to 51:4, the sputtering pressure is 0.4 to 1.2 Pa, the substrate temperature is 100 °C to 200 °C, and the Al2O3 film is deposited by reactive sputtering to obtain an Al2O3 insulating layer with a thickness of 0.1 to 3 μm; the preparation of the insulating layer for the C / SiC composite substrate thin film sensor is completed.

[0020] Further, the preparation process of the Al2O3 insulating layer in step 5 can also be:

[0021] Pump the background vacuum of the sputtering equipment to 8×10 -5 Pa, using an Al2O3 target as the sputtering target and Ar as the sputtering gas, the Ar gas flow rate is 10 to 20 sccm, the sputtering pressure is 0.7 to 1 Pa, the substrate heating temperature is set to 300 °C to 350 °C, and the Al2O3 film is deposited by magnetron sputtering to obtain an Al2O3 insulating layer with a thickness of 0.1 to 3 μm.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. An insulating layer for a C / SiC composite substrate thin film sensor provided by the present invention includes a Si3N4 buffer layer, an AlN transition layer, an Al2O3 barrier layer, and an Al2O3 insulating layer from bottom to top. The Si3N4 buffer layer has advantages such as thermal shock resistance and high temperature resistance, and also has good chemical stability and is not prone to cracking in a high temperature environment; at the same time, the Si3N4 buffer layer has a similar thermal expansion coefficient to the C / SiC composite substrate, and both contain the same Si element, so a bonding transition can be formed at the interface between the film and the substrate, resulting in good adhesion between the insulating layer and the substrate. AlN is not only a good high temperature and heat shock resistant material, but also the thermal expansion coefficient of the AlN transition layer is not much different from that of the Si3N4 buffer layer, and both the AlN transition layer and the Si3N4 buffer layer are nitrides, enabling good chemical bonding and helping to enhance the bonding force between the film layers. The Al2O3 barrier layer is deposited by the PEALD process, and the Al2O3 film prepared by PEALD has a dense structure, which can effectively block the diffusion of external oxygen elements; moreover, it has a similar chemical bonding to the lower layer AlN and a good interface bonding, which can effectively protect the transition layer from oxidation.

[0024] 2. An insulating layer for a C / SiC composite substrate thin film sensor provided by the present invention uses a Si3N4 buffer layer, an AlN transition layer, and an Al2O3 barrier layer. The thermal expansion coefficients of these three films gradually increase, realizing a gradual transition from a low expansion coefficient substrate to a high expansion coefficient film, effectively avoiding the problem of film layer peeling caused by thermal stress concentration at high temperatures, and thus preventing the failure of the insulating layer.

[0025] 3. The preparation method of the insulating layer for the C / SiC composite substrate thin film sensor provided by the present invention prepares the Al2O3 insulating layer by magnetron sputtering. It has the same chemical composition as the Al2O3 barrier layer and has good chemical bonding between them, which can improve the adhesion between the film layers. In addition, the thickness of the Al2O3 insulating layer prepared by sputtering is much larger than that of the Al2O3 barrier layer, which can provide antioxidant protection for the transition layer, improve the high-temperature stability of the insulating film layer, and achieve good electrical insulation at the same time. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the insulating layer for the C / SiC composite substrate thin film sensor provided in the embodiment.

[0027] Figure 2 It is the test result of the high-temperature insulation performance of the insulating layer in the embodiment. Detailed Embodiments

[0028] The present invention will be further described below with reference to the drawings and embodiments.

[0029] Embodiment

[0030] As Figure 1 shown, it is a schematic structural diagram of the insulating layer for the C / SiC composite substrate thin film sensor provided in the embodiment; it includes a Si3N4 buffer layer, an AlN transition layer, an Al2O3 barrier layer, and an Al2O3 insulating layer arranged in sequence from bottom to top.

[0031] The preparation method of the insulating layer for the C / SiC composite substrate thin film sensor provided in the embodiment specifically includes the following steps:

[0032] Step 1. Surface pretreatment of the C / SiC composite substrate;

[0033] The C / SiC composite substrate is successively placed in acetone, absolute ethanol, and deionized water for ultrasonic cleaning for 10 minutes each. The purpose is to remove organic pollutants, dust, and other impurities that may exist on the surface of the substrate, and then use equipment such as a nitrogen gun and a heating table to remove the residual deionized water on the surface of the sample;

[0034] Step 2. Prepare the Si3N4 buffer layer on the C / SiC composite substrate by magnetron sputtering;

[0035] The C / SiC composite substrate sample processed in Step 1 is placed in a magnetron sputtering device, and the vacuum in the sputtering device cavity is pumped to a vacuum degree of 8×10 -4Below Pa, using a Si target as the sputtering target and a mixed gas of N2 and Ar as the sputtering gas, where the flow ratio of N2 to Ar is 5:25, the sputtering pressure is 0.4 Pa, the substrate temperature is 150 °C, the RF radio frequency power is 120 W, and a Si3N4 thin film is deposited by reactive sputtering to obtain a Si3N4 buffer layer with a thickness of 1 μm;

[0036] Step 3. Prepare an AlN thin film on the Si3N4 buffer layer prepared in Step 2;

[0037] Put the composite substrate obtained in Step 2 into a magnetron sputtering device, and evacuate the sputtering device cavity to 8×10 -4 Below Pa, using an Al target as the sputtering target and N2 as the sputtering gas, the N2 gas flow rate is 100 sccm, the sputtering pressure is 0.8 Pa, the substrate temperature is 300 °C, the medium frequency power supply power is 2000 W, and an AlN thin film is deposited by reactive sputtering to obtain an AlN transition layer with a thickness of 1 μm;

[0038] Step 4. Prepare an Al2O3 thin film on the AlN transition layer prepared in Step 3;

[0039] Put the composite substrate obtained in Step 3 into the reaction chamber of PEALD (plasma enhanced atomic layer deposition), evacuate the vacuum in the PEALD device chamber to below 0.15 torr, set the temperature in the reaction chamber to 150 °C, use trimethylaluminum (TMA) and water vapor (H2O) as the reaction gases, alternately introduce TMA and H2O, set the cycle parameter to 1000 cycles, and use N2 as the cleaning gas. Through chemical reactions, an Al2O3 thin film is formed to obtain an Al2O3 barrier layer with a thickness of 100 nm;

[0040] Step 5. Prepare an Al2O3 thin film on the Al2O3 barrier layer prepared in Step 4;

[0041] Put the composite substrate obtained in Step 4 into a magnetron sputtering device, and evacuate the sputtering device cavity to 8×10 -4 Below Pa, using an Al target as the sputtering target and a mixed gas of Ar and O2 as the sputtering gas, where the flow ratio of Ar to O2 is 48:3, the sputtering pressure is 0.4 Pa, the substrate temperature is 150 °C, the DC direct current power is 100 W, and an Al2O3 thin film is deposited by reactive sputtering to obtain an Al2O3 insulating layer with a thickness of 1 μm; Successfully prepare the insulating layer structure of the C / SiC composite substrate thin film sensor.

[0042] The test results of the high-temperature insulation performance of the insulating layer prepared in the embodiment are as Figure 2As shown, when the temperature is lower than 440 °C, the longitudinal insulation resistance of the insulating layer exceeds the test range of the resistance meter (200 MΩ). As the temperature further rises, the longitudinal insulation resistance gradually decreases and is still greater than 100 kΩ at 850 °C.

[0043] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An insulating layer for a C / SiC composite substrate thin film sensor, characterized in that, It includes a Si3N4 buffer layer, an AlN transition layer, an Al2O3 barrier layer, and an Al2O3 insulating layer that are sequentially arranged from bottom to top; wherein the thickness of the Si3N4 buffer layer is 0.1 - 4 μm, the thickness of the AlN transition layer is 0.1 - 2 μm, the thickness of the Al2O3 barrier layer is 10 - 200 nm, and the thickness of the Al2O3 insulating layer is 0.1 - 3 μm.

2. The insulating layer for the C / SiC composite substrate thin film sensor according to claim 1, characterized in that, The Si3N4 buffer layer is prepared by magnetron sputtering, the AlN transition layer is prepared by magnetron sputtering, the Al2O3 barrier layer is prepared by PEALD, and the Al2O3 insulating layer is prepared by magnetron sputtering.

3. A preparation method of an insulating layer for a C / SiC composite substrate thin film sensor, characterized in that, It includes the following steps: Step 1. Surface pretreatment of the C / SiC composite substrate; The C / SiC composite material is sequentially soaked in acetone, absolute ethanol, and deionized water for ultrasonic cleaning and then dried for standby; Step 2. Prepare the Si3N4 buffer layer on the C / SiC composite substrate by magnetron sputtering; The vacuum in the sputtering equipment cavity is pumped to a vacuum degree of 8×10 -4 Pa or less. Using a Si target as the sputtering target and a mixed gas of N2 and Ar as the sputtering gas, where the flow ratio of N2 to Ar is 5:25 to 6:30, the sputtering pressure is 0.4 to 0.8 Pa, the substrate temperature is 100°C to 200°C, and a Si3N4 thin film is deposited by reactive sputtering to obtain a Si3N4 buffer layer with a thickness of 0.1 to 4 μm; Step 3. Prepare an AlN thin film on the Si3N4 buffer layer prepared in Step 2; The sputtering equipment chamber is evacuated to below 8×10 -4 Pa. Using an Al target as the sputtering target, N2 as the sputtering gas, with the N2 gas flow rate being 100 - 200 sccm, the sputtering gas pressure being 0.4 - 1.2 Pa, and the substrate temperature being 250°C - 350°C, an AlN thin film is deposited by reactive sputtering to obtain an AlN transition layer with a thickness of 0.1 - 2 μm; Step 4. Prepare an Al2O3 thin film on the AlN transition layer prepared in Step 3; The vacuum in the PEALD equipment cavity is pumped to below 0.15 torr, the temperature in the reaction cavity is set to 100 - 200 °C, trimethylaluminum and water vapor are used as reaction gases, and N2 is used as a cleaning gas. Through chemical reactions, an Al2O3 thin film is generated to obtain an Al2O3 barrier layer with a thickness of 10 - 200 nm; Step 5. Prepare an Al2O3 thin film on the Al2O3 barrier layer prepared in Step 4; The sputtering equipment cavity is evacuated to below 8×10 -4 Pa, using an Al target as the sputtering target and a mixed gas of Ar and O2 as the sputtering gas, where the flow ratio of Ar to O2 is 48:3 to 51:4, the sputtering gas pressure is 0.4 to 1.2 Pa, the substrate temperature is 100°C to 200°C, and the Al2O3 thin film is deposited by reactive sputtering method to obtain an Al2O3 insulating layer with a thickness of 0.1 to 3 μm; the preparation of the insulating layer for the C / SiC composite substrate thin film sensor is completed.

4. The preparation method of the insulating layer for the C / SiC composite substrate thin film sensor according to claim 3, characterized in that, The preparation process of the Al2O3 insulating layer in Step 5 is replaced by: The background vacuum of the sputtering equipment was pumped to 8×10 -5 Pa. Using an Al2O3 target as the sputtering target, Ar as the sputtering gas, with the Ar gas flow rate being 10 - 20 sccm, the sputtering pressure being 0.7 - 1 Pa, the substrate heating temperature was set to 300°C - 350°C, and the Al2O3 thin film was deposited by magnetron sputtering to obtain an Al2O3 insulating layer with a thickness of 0.1 - 3 μm.

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