A high-temperature in-situ self-attached sensor and a manufacturing method thereof

Abstract

This invention relates to the field of sensor manufacturing technology, specifically to a high-temperature in-situ self-adhesive sensor and its manufacturing method. The method involves obtaining a self-supporting polycrystalline diamond substrate, performing double-sided polishing and surface activation treatment; depositing a piezoelectric layer on the first surface of the substrate, and fabricating electrodes and an antenna; pre-depositing a titanium getter film on the second surface of the substrate, then using a shadow mask to shield it, and constructing a support frame in situ through electroplating a nickel layer or evaporating a molybdenum layer to form a pressure-sensitive cavity; using selective atomic layer deposition (SLD) technology to encapsulate and protect the sensor surface except for the bottom surface to be welded on the support frame; subsequently depositing a Ni-B self-fusing active layer on the exposed bottom of the support frame, attaching it to the device under test, and heating to induce a transient liquid-phase diffusion reaction to achieve atomic-level glue-free fusion integration. During this process, residual gas in the cavity reacts chemically with the pre-placed titanium film at high temperature and is absorbed, thereby forming an absolute pressure cavity.

Description

Technical Field

[0001] This invention relates to the field of sensor manufacturing technology, specifically to a high-temperature in-situ self-adhesive sensor and its manufacturing method. Background Technology

[0002] Aero-engine turbine blades, combustion chamber walls, and core components of hypersonic vehicles are subjected to extreme conditions of ultra-high temperatures, strong airflow, and high-frequency vibrations for extended periods. Real-time monitoring of pressure loads on the surfaces of these irregularly shaped components is crucial for assessing the thermal efficiency, structural reliability, and health status of the power system. Traditional wired sensors, operating in high-temperature, high-speed rotating environments, not only involve complex wiring but also suffer from highly susceptible to physical breakage or thermoelectric noise interference, severely impacting test accuracy. Wireless passive sensors are a research hotspot in extreme environment monitoring. However, existing high-temperature resistant wireless sensors often utilize rigid and brittle piezoelectric single-crystal substrates, which are rigid and lack ductility, making it impossible to conform to the surfaces of irregularly shaped components with complex curvatures, thus hindering in-situ, conformal pressure measurement.

[0003] Furthermore, existing pressure sensors face multiple challenges in environments above 1000°C: First, there's the issue of cavity collapse. Conventional MEMS structures experience a sharp drop in material elastic modulus at ultra-high temperatures, making the pressure-sensing cavity prone to inward collapse and loss of sensitivity. Second, there's the interface integration problem. Existing high-temperature inorganic binders (such as silicate or aluminate adhesives) are prone to carbonization and embrittlement at 1000°C, easily cracking under centrifugal forces of tens of thousands of Gs, leading to sensor detachment and failing to maintain metallurgical-grade connection strength. Third, there are oxidation and frequency limitations. Ordinary metal electrodes are prone to electromigration and oxidation at high temperatures, and their low operating frequency results in poor anti-interference capabilities and slow dynamic response. Therefore, developing a pressure sensor that balances ultra-high-temperature mechanical rigidity, high-frequency wireless transmission capabilities, and atomic-level adhesive-free self-fusion integration technology has become a critical challenge urgently needing to be solved in the aerospace testing field. Summary of the Invention

[0004] The purpose of this invention is to address the challenge of directly manufacturing sensors from large and complex components that cannot be placed in conventional micro-nano fabrication equipment, by providing a method for manufacturing sensors that can withstand extreme high temperatures of 1000℃ in situ with self-attached attachment. This invention effectively overcomes the process barriers of cross-scale manufacturing by combining standardized fabrication of independent microdevices with high-temperature self-fusion integration technology, achieving a seamless transition from laboratory prefabrication to in-situ monitoring in extreme environments.

[0005] This invention proposes a high-temperature in-situ self-adhesive sensor, comprising: a diamond substrate, a piezoelectric layer, a sensing unit, a support frame, a titanium getter film, an encapsulation layer, and a connection layer; The diamond substrate is a single-layer self-supporting polycrystalline diamond film; The piezoelectric layer is a c-axis oriented thin film epitaxially grown on the diamond substrate; The sensing unit is disposed on the piezoelectric layer; The support frame is grown in situ in the central region of the second surface of the diamond substrate, and together with the diamond substrate, they enclose a pressure-sensitive cavity. The titanium getter film is disposed on the second surface of the diamond substrate and located in the pressure-sensing cavity, and is used to adsorb residual gas in the pressure-sensing cavity to form an absolute pressure environment. The encapsulation layer is applied to the sensor surface, excluding the bottom of the support frame, using selective atomic layer deposition (SALD) technology. The connecting layer is disposed at the bottom of the support frame and is used to undergo a transient liquid-phase diffusion reaction with the surface of the test piece, thereby forming an atomic-level metallurgical bond.

[0006] Furthermore, the underlying thin film is an aluminum nitride piezoelectric layer, and the sensing unit includes a pressure sensing unit and an antenna. The pressure sensing unit has electrodes, and both the electrodes and the antenna are made of high-temperature resistant precious metal materials.

[0007] Furthermore, the support frame is a nickel support layer or a molybdenum support layer.

[0008] Furthermore, the pressure-sensing cavity is a square cavity.

[0009] Furthermore, the sensing unit is a single pressure sensing unit with its center operating frequency in the GHz band, and the antenna is electrically connected to the electrodes of the pressure sensing unit to achieve complex impedance matching.

[0010] This invention also proposes a method for manufacturing a high-temperature in-situ self-adhesive sensor, comprising the following steps: S1. Obtain a self-supporting polycrystalline diamond film, perform chemical mechanical polishing on its front and back sides, and perform surface cleaning and activation to prepare a diamond substrate. S2. Using pulsed laser deposition or magnetron sputtering technology, a piezoelectric layer is epitaxially grown on the first surface of the diamond substrate, and then an antenna and a pressure sensing unit are fabricated on the piezoelectric layer to form a sensing unit. S3. A titanium getter film is vapor-deposited on the second surface of the diamond substrate. A mask is placed at the center to reserve a pressure-sensing cavity. A support frame is constructed around the mask using additive manufacturing to form a physical cavity. Selective atomic layer deposition technology is used to encapsulate and protect the sensor surface except for the bottom of the support frame. Then, a self-fluxing active layer is deposited at the bottom of the support frame. Finally, the sensor is attached to the surface of the test piece and a transient liquid-phase diffusion reaction is initiated by heating to form an atomic-level metallurgical bond.

[0011] Furthermore, the deposition amount of the titanium getter film is matched with the encapsulation volume of the pressure-sensitive cavity and the expected gas outflow rate of the inner surface of the pressure-sensitive cavity, ensuring that the total number of titanium atoms participating in the reaction is greater than the total number of residual and released active gas molecules in the cavity within the expected lifespan.

[0012] Furthermore, the method for constructing the support frame around the mask using additive manufacturing processes is as follows: first, a titanium seed layer is sputtered around the mask, followed by electroplating to deposit a pure nickel layer; or, a chromium transition layer is sputtered around the mask, followed by ion-assisted electron beam evaporation to deposit a metallic molybdenum layer.

[0013] Furthermore, the selective atomic layer deposition technique employs a composite stack grown conformally using atomic layer deposition technology.

[0014] Furthermore, the titanium getter film utilizes the chemical reactivity of Ti at the activation temperature to react with the residual active gas molecules after the pressure-sensitive cavity is sealed through chemical adsorption, generating TiH. x : The process of titanium oxide formation: Ti + O₂ → TiO₂ The formation process of titanium nitride: 2Ti + N₂ → 2TiN The process of forming titanium oxide and releasing hydrogen gas: Ti + H₂O → TiO + H₂ H2 is adsorbed to form TiH x .

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves high linearity and zero collapse of the cavity at extremely high temperatures by combining a thin-film diaphragm with an in-situ framework through a rigid-flexible coupling structure. It abandons the traditional multi-layer substrate lamination process and innovatively grows a nickel or molybdenum support framework in situ on the back of a single-layer thin diamond layer. Utilizing the highest known elastic modulus of diamond and the rigid boundary constraints provided by the thick metal framework, it completely solves the cavity collapse failure problem caused by material modulus softening in conventional thin-film pressure sensors at 1000℃. By introducing a titanium or chromium nanoscale interlayer, not only is the chemical bonding between the metal framework and diamond enhanced, but it also acts as a mismatch buffer during thermal cycling, effectively alleviating interfacial shear stress concentration. Due to the stable thermodynamic properties of diamond and its extremely small elastic modulus shift, it ensures a very high linear relationship between the pressure-induced frequency shift and the external pressure, significantly reducing hysteresis errors caused by high-temperature creep. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a wireless in-situ self-adhesive pressure sensor that can withstand extremely high temperatures of 1000℃, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the diamond substrate after the piezoelectric layer and electrodes have been deposited on the front side, as provided in an embodiment of the present invention. Figure 3 This is a partial enlarged cross-sectional view of the pressure-sensing cavity region in an embodiment of the present invention; Figure 4 A schematic diagram illustrating the interface evolution of the sensor provided in this embodiment of the invention, which is integrated with the stainless steel device surface through transient liquid phase diffusion (TLP) fusion via a Ni-B active layer. Figure 5 This is a schematic diagram of the antenna structure provided in an embodiment of the present invention; Figure 6 This is a process flow diagram of an embodiment of the present invention.

[0018] In the figure: 100, high temperature pressure sensor; 101, self-supporting diamond substrate; 102, piezoelectric layer; 103, antenna; 104, Ti layer; 105, pressure sensing unit; 106, support frame; 107, pressure-sensing cavity; 108, encapsulation layer; 109, Ni-B self-fluxing active layer; 110, device under test. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a high-temperature in-situ self-adhesive sensor and its manufacturing method, the core structure and integrated logic of which are as follows: Figure 1 As shown, the high-temperature pressure sensor 100 adopts a rigid-flexible coupling system consisting of a single-layer self-supporting diamond substrate 101 and a support frame 106 grown in situ on the back side.

[0021] The self-supporting diamond substrate 101 and piezoelectric layer 102 are used to control the physical properties. The self-supporting diamond substrate 101 selected in this invention is a 20µm thick self-supporting polycrystalline diamond sheet. Diamond still has an extremely high Young's modulus at 1000℃, which can provide physical support for the pressure-sensitive diaphragm. Before fabrication, the substrate needs to be subjected to double-sided chemical mechanical polishing (CMP) to ensure ultra-low scattering loss of acoustic waves in the GHz band.

[0022] The piezoelectric layer 102 disposed on the first surface of the substrate is preferably an aluminum nitride (AlN) thin film, which is preferentially oriented and grown along the c-axis using PLD technology. This highly oriented piezoelectric structure does not depolarize at 1000°C and can maintain stable electromechanical coupling efficiency, providing a high-performance sensing source for the pressure sensing unit 105.

[0023] A pressure sensing unit 105 and an antenna 103 are machined on the first surface of a self-supporting diamond substrate 101. The electrode material is preferably a platinum-rhodium alloy (Pt-13Rh), and the antenna 103 is as follows: Figure 5 As shown, a planar folded dipole configuration is adopted, and its physical length is optimized to achieve complex impedance matching with the GHz resonant unit, ensuring the wireless backhaul signal-to-noise ratio in strong interference environments.

[0024] The structural logic of the in-situ grown support frame 106 is as follows: Figure 3 As shown, a support frame 106 is in situ constructed on the second surface of the self-supporting diamond substrate 101. The support frame 106 is preferably a pure nickel layer or a molybdenum layer, which, together with the self-supporting diamond substrate 101, encloses a pressure-sensitive cavity 107. The support frame 106 not only defines the mechanical boundary of the pressure-sensing area but also provides extremely high bending stiffness due to its thickness, solving the technical problem of the ultra-thin film sheet easily collapsing inward under ultra-high temperature and pressure conditions. The pressure-sensitive cavity 107 is filled with a carbon film thermally volatile material to provide temporary physical support during the fabrication process and prevent the substrate from collapsing under pressure.

[0025] The encapsulation layer 108 and interface connection logic are shown. The entire surface of the high-temperature pressure sensor 100 (including the front antenna 103, the sidewalls of the rear support frame 106, and the inner wall of the pressure-sensing cavity 107) is covered by an encapsulation layer 108 composed of a 40nm Al2O3 and 60nm HfO2 stack. This nanoscale protective skin prevents oxygen from contacting the substrate and electrodes. Figure 5As shown, the bottom of the support frame 106 has 108 removed by etching and a 3µm-5µm Ni-B self-fluxing active layer 109 deposited thereon. When the high-temperature pressure sensor 100 is attached to the surface of the device to be tested 110 (such as a stainless steel component) and heated to 1100°C, the Ni-B self-fluxing active layer 109 initiates a transient liquid phase diffusion (TLP) reaction, achieving atomic-level metallurgical bonding. At the same time, the thermally volatile material in the pressure-sensing cavity 107 completely evaporates, forming a vacuum pressure-free cavity.

[0026] Example 1 This embodiment provides a method for manufacturing a high-temperature in-situ self-adhesive sensor based on an electroplated pure nickel (Ni) support frame, comprising the following steps: Phase 1: Diamond substrate treatment and piezoelectric epitaxy (reference) Figure 2 ) A self-supporting polycrystalline diamond film was obtained through ultra-precision polishing of a self-supporting diamond substrate, which served as the self-supporting diamond substrate 101. Chemical mechanical polishing (CMP) was employed, using 50 nm diamond abrasive particles, and the substrate was double-sided polished under 8 psi pressure. This step aimed to eliminate grain spikes generated during CVD growth, improving the first surface roughness R01. a <1nm, to reduce surface scattering loss during high-frequency transmission.

[0027] The self-supporting polycrystalline diamond film used in this invention has a gradient grain structure prepared by CVD. The surface polished layer has a grain size of 50nm~500nm, the main body of the film is 200nm~2μm, and the core of the film is 1μm~5μm. The grain orientation is random, the grain boundaries are clean and free of impurities, and the thickness ranges from 15~30μm (preferably 20μm). This self-supporting polycrystalline diamond film has excellent flexibility. At room temperature, the minimum recoverable bending radii corresponding to film thicknesses of 15μm, 20μm, and 30μm are ≤3mm, ≤... For films with thicknesses of 5mm and ≤8mm, the minimum recoverable bending radius at 1000℃ is ≤10mm. After more than 1000 cyclic bending cycles around the corresponding radius, no plastic deformation or microcracks are observed. Quantitatively, at room temperature, the maximum recoverable elastic strain that films with thicknesses of 15μm, 20μm, and 30μm can withstand is ≤1.2%, ≤0.8%, and ≤0.5%, respectively; at 1000℃, the corresponding values ​​are ≤1.0%, ≤0.6%, and ≤0.4%. The room temperature strain rate for sensor mounting processes is 10. -3 ~10 -1 s -1 The strain rate of high-temperature laser fusion is 10. -4 ~10 -2 s -1 .

[0028] Surface stress relief and chemical activation were performed by placing the polished self-supporting diamond substrate 101 in a vacuum annealing furnace and annealing it at 800°C for 2 hours to eliminate internal stress. Subsequently, the first surface was cleaned using oxygen plasma with a power of 300W to remove the non-diamond phase and introduce oxygen-containing functional groups, thereby improving the chemical activity and wettability of the substrate surface.

[0029] In this step, the evaluation of oxygen plasma chemical activation is based on a comprehensive assessment of multiple indicators. The core criterion is that the physicochemical properties of the substrate surface meet the standards and are suitable for subsequent epitaxial growth of the AlN piezoelectric layer. Specifically, the surface is tested by Raman spectroscopy and XPS, and there are no obvious graphite phases, amorphous carbon phases, or other non-diamond phases. The surface coverage of oxygen-containing functional groups such as hydroxyl and carbonyl groups is ≥30%, and the carbon purity is ≥99.9%. The contact angle of deionized water is ≤30° and the contact angle deviation of different areas of the surface is ≤5°, indicating a uniform improvement in wettability. The surface is tested by AFM and SEM, and there are no defects such as pinholes or pits caused by plasma etching. The roughness still maintains a polishing level of Ra<1nm. At the same time, the bonding force between the subsequently epitaxially grown AlN piezoelectric layer and the substrate interface is ≥20N / mm. The film grows along the c-axis with preferred orientation, and the full width at half maximum (FWHM) of its c-axis crystal plane rocking curve is <2.0°. The film surface has no island growth, high density, and a thickness deviation of ≤5%. Based on these criteria, the activation effect of the substrate surface is comprehensively judged to be up to standard.

[0030] The aluminum nitride piezoelectric layer was epitaxially grown using pulsed laser deposition (PLD) technology. A 1.2 µm thick aluminum nitride piezoelectric layer was grown on the first surface of the substrate under conditions of a substrate temperature of 750 °C and a nitrogen pressure of 0.8 Pa. The laser energy density was controlled to be 2.5 J / cm². 2 This induces AlN molecules to preferentially grow along the c-axis, resulting in a highly oriented piezoelectric structure with a full width at half maximum (FWHM) of less than 2.0° on the c-axis rocking curve.

[0031] Phase Two: Graphicalization of Sensing Units and Antenna Structures (Reference) Figure 2 ) The patterning of the micro / nano electrode structure was defined by coating an electron beam photoresist layer 102 and using an electron beam lithography system to define high-frequency interdigitated electrodes. The interdigitated linewidth and spacing were set to 600 nm to match operating frequencies above GHz. This step determined the core location of the pressure sensing unit 105.

[0032] Deposition of platinum-rhodium alloy electrodes with antennas A platinum-rhodium alloy (Pt-13Rh) was deposited using electron beam evaporation. The addition of 13% rhodium was intended to pin platinum dislocations and prevent recrystallization at 1000°C. A complete electrode was then formed using a lift-off process, and the antenna 103 was integrated synchronously with it.

[0033] Phase 3: In-situ additive construction of the rear support frame (reference) Figure 3 , Figure 4 ) Backside titanium getter pre-positioning and mask arrangement: On the second surface (backside) of the self-supporting diamond substrate 101, a titanium (Ti) thin film is first deposited using electron beam evaporation or magnetron sputtering. This titanium layer has a dual function in subsequent processes: serving as a getter in the central region and as a seed layer for electroplating in the edge region. Subsequently, a square hard mask with a side length of 1.3 mm is placed directly below the corresponding pressure sensing unit 105 using a high-precision alignment system to protect the titanium getter and reserve a pressure-sensing cavity.

[0034] In-situ growth of the support frame 106: The exposed titanium (Ti) layer outside the mask is directly used as a conductive seed layer. The substrate is placed in a nickel sulfamate electroplating bath, and the current density is controlled at 1.5 A / dm². Under a constant temperature environment of 55°C, a pure nickel layer with a thickness of 40 µm is grown in situ on the Ti layer to form the support frame 106. This frame, together with the self-supporting diamond substrate 101, forms a pressure-sensitive cavity 107. Due to the combination of the high temperature modulus of nickel and the ultra-high rigidity of diamond, the problem of cavity collapse at 1000°C is solved.

[0035] Phase 4: Full Surface Encapsulation Protection and Integration Preparation (Reference) Figure 5 , Figure 6 ) Construction of Selective Atomic Layer Deposition (SALD) Encapsulation Layer 108: SALD technology was employed, using masking or selective growth processes to protect areas other than the bottom of the support frame (the surface to be soldered). Trimethylaluminum (TMA) and water vapor were alternately introduced to grow a 40nm layer. Al2O3 capping was performed at a deposition temperature of 150-200℃. This temperature range ensures sufficient adsorption and reaction of the precursor while preventing thermal damage to the sensor substrate and the fabricated structure. The TMA precursor pulse duration was set to 0.1-0.3s, and the water vapor pulse duration to 0.2-0.5s. This selection was made to ensure that the precursor forms a monolayer adsorption saturation on the surface to be deposited, avoiding insufficient deposition due to excessively short pulses or waste and cross-contamination due to excessively long pulses. The number of cycles was calculated based on the target Al2O3 thickness of 40nm and the single-cycle deposition rate (0.1-0.2nm / cycle) and set to 200-400 cycles to ensure precise control of the capping thickness. Subsequently, a hafnium precursor (such as tetrahydrocannabinol) was introduced. (Ethylmethylamine)hafnium) was used to grow an HfO2 capping layer, with the deposition temperature maintained at the same level as the Al2O3 capping layer (150-200℃). This was done to ensure tight bonding at the layer interface and avoid interfacial stress caused by sudden temperature changes. The hafnium precursor pulse time was set to 0.3-0.5s, and the water vapor pulse time was set to 0.2-0.5s. This was chosen because the hafnium precursor molecule volume is larger than TMA, requiring a longer pulse time to achieve monolayer saturation adsorption. The number of cycles was calculated based on the target HfO2 thickness (preferably 20-40nm) and the single-cycle deposition rate (0.05-0.1nm / cycle), and set to 200-800 cycles to ensure the overall density and oxidation resistance of the stacked encapsulation layer, forming the stacked encapsulation layer 108. This layer can conformally cover the inner wall of the back pressure-sensitive cavity 107 and the sidewall of the frame, while retaining the exposed nickel metal body at the bottom of the supporting frame.

[0036] Preparation of Ni-B self-fluxing active layer 109: A 4µm thick Ni-B self-fluxing active layer 109 was directly prepared at the bottom of the retained bare metal frame using an electrodeposition process. The electrodeposition temperature was selected as 40-60℃. This temperature range balances the deposition rate and coating uniformity. Too low a temperature leads to a slow deposition rate and a loose coating, while too high a temperature easily results in coarse coating grains and uneven boron content distribution. The pulse time for the nickel salt precursor (e.g., nickel sulfate) was set to 1-3s, and the pulse time for the boron source precursor (e.g., sodium borohydride) was set to 0.5-1.5s. The selection was based on controlling the Ni²⁺ content through pulse time. + With B³ +The co-deposition rate was carefully controlled to ensure that the boron (B) atom content in the coating was maintained at 3-8 at.% (this range is crucial for reducing the instantaneous melting point of the interface and forming atomic-level metallurgical bonding). The number of electrodeposition cycles was calculated based on the target Ni-B active layer thickness of 4 µm and the single-cycle deposition rate (0.01-0.02 µm / cycle), and set to 200-400 cycles to ensure precise control of the active layer thickness, providing a uniform and stable active interface for the direct diffusion of metal atoms during the subsequent TLP fusion process. The presence of B atoms will significantly reduce the instantaneous melting point of the interface to 850-950℃, providing an active interface for subsequent metallurgical reactions.

[0037] Phase 5: Atomic-level connectivity and system decoupling (Reference) Figure 6 ) Transient liquid phase diffusion (TLP) integration and in-situ absolute pressure cavity formation: A high-temperature pressure sensor 100 is attached to the surface of the device under test 110 (such as a stainless steel blade). A laser high-temperature gun is used to momentarily heat the local area to 1100°C. At this point, the Ni-B layer melts and diffuses with the matrix elements, forming an atomic-level metallurgical interface. During this process, residual gases (nitrogen, oxygen, etc.) sealed within the cavity are activated by the high temperature, undergoing an irreversible chemical reaction with a pre-placed titanium getter film and being completely absorbed, thereby forming a high-vacuum pressure-sensing cavity 107 in situ inside the sensor, eliminating interference from gas thermal expansion.

[0038] Application of temperature and pressure compensation algorithm based on data fusion: In actual monitoring at 1000℃, the system receives the frequency signal transmitted back by antenna 103. To address the issue of pressure sensing unit 105 being susceptible to high-temperature interference, synchronous temperature acquisition parameters are introduced. By constructing a decoupling compensation matrix and a temperature and pressure fusion algorithm, parameter thermal drift interference caused by the high-temperature environment is effectively suppressed, temperature coupling errors are accurately isolated, and ultimately, stable and accurate extraction of pressure signals under high-temperature conditions is achieved.

[0039] Example 2 This embodiment provides a method for fabricating a high-temperature, high-frequency wireless pressure sensor resistant to 1000℃ based on a vapor-deposited molybdenum (Mo) support frame, comprising the following steps: This embodiment provides a method for fabricating a high-temperature pressure sensor using molybdenum as a support frame. The core of this method lies in utilizing the extremely high recrystallization temperature (approximately 1100°C) and excellent high-temperature creep resistance of molybdenum, combined with a single-layer diamond substrate, to ensure the geometric stability of the pressure-sensing cavity under extreme working conditions.

[0040] Phase 1: Nanoscale surface treatment of the diamond substrate Substrate Selection and Polishing: A 20 μm thick self-supporting polycrystalline diamond film was selected as the self-supporting diamond substrate 101. Chemical mechanical polishing (CMP) was used to thin and planarize the film on both sides. A chemically active component containing hydroxide ions was added to the polishing slurry to assist mechanical wear. After 6 hours of cyclic polishing, the roughness of both the first and second surfaces of the self-supporting diamond substrate 101 was reduced to 0.7 nm, providing an atomically smooth propagation path for high-frequency acoustic waves.

[0041] Interface cleaning and annealing: The substrate was ultrasonically cleaned in acetone and anhydrous ethanol, followed by thermal annealing at 800°C for 3 hours in a vacuum environment to eliminate microscopic residual stress accumulated during growth and polishing. Finally, the first surface was activated by high-energy impact with oxygen plasma for 5 minutes to enhance the adhesion of the subsequent piezoelectric layer.

[0042] Phase Two: In-situ Construction of High-Frequency Sensing Layer and Electrode System Epitaxial growth of c-axis oriented piezoelectric layer 102: A 1.5 μm thick aluminum nitride piezoelectric layer was epitaxially grown on the first surface using pulsed laser deposition (PLD) technology. The laser frequency was set to 5 Hz, and high-purity nitrogen gas at 0.5 Pa was introduced into the cavity. The substrate temperature was controlled at 780 °C. XRD rocking curve testing showed that the full width at half maximum (FWHM) of the c-axis crystal plane peak of the AlN thin film was 1.7°, exhibiting excellent piezoelectric properties and high-velocity acoustic propagation characteristics.

[0043] Patterning of High-Temperature Platinum-Rhodium Electrodes and Antennas: A high-frequency interdigitated electrode array was defined on the piezoelectric layer 102 using electron beam lithography. Subsequently, a platinum-rhodium alloy (Pt-13Rh) was deposited by electron beam evaporation. This alloy exhibits extremely strong resistance to grain growth and electromigration at 1000℃. The resulting pattern resembles... Figure 2 The pressure sensing unit 105 shown and as follows Figure 5 Antenna 103 is shown.

[0044] Phase 3: In-situ growth of a molybdenum (Mo) support framework Backside titanium getter pre-positioning and mask alignment: On the second surface of the self-supporting diamond substrate 101, a titanium (Ti) getter film is first deposited using evaporation or sputtering technology. Subsequently, a square mask with a side length of 1.3 mm is placed in the center of the pressure-sensitive area to protect the titanium getter and reserve a pressure-sensitive cavity. A 50 nm thick chromium (Cr) layer is deposited as a transition layer in the outer region of the mask using magnetron sputtering technology to enhance the bonding force between molybdenum and diamond and alleviate shear stress caused by the difference in thermal expansion coefficients.

[0045] Ion-Assisted Electron Beam Evaporation (IAD-EB) Support Framework: A molybdenum support framework 106 is deposited on the Cr transition layer using IAD-EB technology in the masked area. Momentum transfer of molybdenum atoms during the evaporation process is achieved through an ion source, improving the density of the metal film. The resulting support framework 106, together with the self-supporting diamond substrate 101, forms a structure resembling... Figure 3 The pressure-sensing cavity 107 is shown.

[0046] Phase 4: Full Surface Encapsulation and Atomic-Level Integration The conformal encapsulation layer 108: Using selective atomic layer deposition (ALD) technology, a composite layer of Al2O3+HfO2 is grown in the sensor area except for the bottom of the support frame (the surface to be soldered) through masking or selective growth processes. This nanoscale protective layer completely encapsulates the front IDT electrode, the back support frame, and the inner wall of the cavity, blocking the high-temperature oxidation path while retaining the metallic activity at the bottom of the molybdenum frame.

[0047] Interface self-fusion and in-situ absolute pressure cavity formation: A Ni-B self-fusing active layer 109 is directly deposited at the bottom of the exposed molybdenum framework retained in step S41. After attaching the sensor to the device under test 110, a transient liquid-phase diffusion (TLP) reaction is initiated by in-situ laser heating to 1100°C. Figure 5 As shown, B atoms diffuse into the matrix and form a metallurgical bond; at the same time, the residual gas sealed in the pressure-sensitive cavity 107 is activated by high temperature, undergoes an irreversible chemical reaction with the pre-placed titanium getter film and is completely absorbed, thereby forming a high-vacuum absolute pressure cavity in situ inside the sensor.

[0048] Example 3 The implementation of a high-temperature, high-frequency wireless dual-parameter integrated sensor resistant to 1000℃ and its temperature and pressure decoupling compensation algorithm includes the following steps: This embodiment provides a wireless high-frequency pressure sensor. Under extreme operating conditions (such as the combustion chamber of an aircraft engine), drastic fluctuations in ambient temperature can cause significant drift in propagation velocity, and the resulting frequency shift is often much greater than the shift caused by pressure load. To achieve high-precision pressure monitoring, this embodiment uses a pressure sensing unit 105 integrated on a single 10mm×10mm diamond chip, introduces synchronous temperature monitoring parameters, and effectively suppresses temperature coupling interference under ultra-high temperature environments through high-frequency wireless telemetry and a back-end decoupling compensation algorithm, thus achieving accurate extraction of pressure signals.

[0049] (I) Structural layout and precision fabrication of dual-parameter integrated sensors Differential layout design of the chip: This embodiment uses a self-supporting diamond substrate 101 with a thickness of 20µm. For example... Figure 2As shown, two sets of units with different mechanical response characteristics are fabricated on the piezoelectric layer 102 on the first surface (front side). Pressure sensing unit 105: arranged at the geometric center of the self-supporting diamond substrate 101, with the pressure-sensing cavity 107 grown in situ on the back side directly below it. When external pressure is applied to the diaphragm, the diamond film produces a slight deflection, causing a change in the speed of sound.

[0050] It should be noted that the cavity height, i.e. the height of the deposited Ni, is preferably 40 micrometers, and the ratio of cavity diameter to film thickness is preferably 2:1.

[0051] Fabrication of the GHz-level high-frequency unit: Platinum-rhodium alloy (Pt-13Rh) interdigitated electrodes were fabricated using nanoimprint lithography. Thanks to the extremely high acoustic velocity characteristics of the diamond substrate, the sensor's center frequency was increased to over GHz. This GHz-level high-frequency operation not only significantly reduced the physical size of the antenna 103, allowing it to be attached to irregularly shaped blades like a sticker, but also enabled real-time capture of high-frequency pressure pulsations within the combustion chamber through extremely short acoustic cycles (nanoseconds), thus improving the dynamic response bandwidth.

[0052] Example 4 This embodiment provides an ALD nano-full-shell encapsulation process that can withstand extreme environments up to 1000℃ and its antioxidant and corrosion-resistant protection mechanism, including the following steps: In the combustion chamber of an aircraft engine or the turbine section of a gas turbine, sensors not only face… The above-mentioned high temperatures must also withstand the severe scouring caused by high flow rates, sulfur, oxygen, and complex water vapor compositions. This embodiment focuses on how the encapsulation layer 108 constructed using atomic layer deposition (ALD) technology in step S41 locks the failure paths of the diamond, AlN, and platinum-rhodium electrodes through conformal coating and chemical inertness.

[0053] (a) Precision construction process of nanoscale composite encapsulation layer 108 Growth of the first sealed Al2O3 layer: TMA (trimethylaluminum) and high-purity water vapor were used as precursors. Alternating current is introduced into the vacuum chamber to form a 40nm thick amorphous aluminum oxide film on the entire surface of the high-temperature pressure sensor 100 (including the sensing unit on the front and the sidewalls of the support frame 106 on the back). This layer utilizes the excellent step coverage capability of ALD technology to achieve atomic-level conformal coating of the edge gaps of the high-frequency interdigitated electrodes, initially establishing a dense physical barrier against oxygen atoms.

[0054] Second floor Growth of a stable sealing layer: Based on the first sealing layer, tetra(ethylmethylamino)hafnium (TEMAH) and water vapor are immediately alternately introduced to grow a hafnium oxide film with a thickness of 60 nm.

[0055] Hafnium oxide, as a refractory oxide with high dielectric constant and high melting point, possesses excellent thermal stability and chemical inertness. The bilayer composite structure aims to utilize... density and The high temperature resistance and stability form a synergistic effect, constructing a nanoscale composite armor encapsulation layer 108.

[0056] (II) Analysis of Physicochemical Protection Mechanisms under Extreme Environments 1. Anti-oxidation protection for self-supporting diamond substrate 101: Diamond in air for more than This would result in severe oxidation and ablation. In this embodiment, the encapsulation layer 108 completely blocks the contact path between external oxygen molecules and the diamond surface. Even... In a highly oxidizing gas, the encapsulation layer 108 can still maintain its physical integrity, preventing the self-supporting diamond substrate 101 from carbonizing and disappearing or losing mass, thus ensuring the structural strength of the sensor.

[0057] 2. Maintaining the high-temperature stability of platinum-rhodium alloy electrodes: Unencapsulated platinum electrodes are prone to "agglomeration" at high temperatures, leading to narrowing of the interdigitated electrode linewidth or even open circuits. The encapsulation layer 108 effectively suppresses surface diffusion and thermoelectric migration of metal atoms through mechanical clamping and surface energy modification of the electrode surface, ensuring that the frequency shift of the high-frequency signal of the pressure sensing unit 105 is minimized after long-term operation.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-temperature in-situ self-adhesive sensor, characterized in that, include: Diamond substrate, piezoelectric layer, sensing unit, support frame, titanium getter film, encapsulation layer and bonding layer; The diamond substrate is a single-layer self-supporting polycrystalline diamond film; The piezoelectric layer is a c-axis oriented bottom film grown epitaxially on the diamond substrate, and the bottom film is an aluminum nitride piezoelectric layer. The sensing unit is disposed on the piezoelectric layer; The support frame is grown in situ in the central region of the second surface of the diamond substrate, and together with the diamond substrate, they enclose a pressure-sensitive cavity. The titanium getter film is disposed on the second surface of the diamond substrate and located in the pressure-sensing cavity, and is used to adsorb residual gas in the pressure-sensing cavity to form an absolute pressure environment. The encapsulation layer is applied to the sensor surface, excluding the bottom of the support frame, using selective atomic layer deposition (SALD) technology. The connecting layer is disposed at the bottom of the support frame and is used to undergo a transient liquid-phase diffusion reaction with the surface of the test piece, thereby forming an atomic-level metallurgical bond.

2. The high-temperature in-situ self-adhesive sensor according to claim 1, characterized in that, The sensing unit includes a pressure sensing unit and an antenna. The pressure sensing unit has electrodes, and both the electrodes and the antenna are made of high-temperature resistant precious metal materials.

3. The high-temperature in-situ self-adhesive sensor according to claim 1, characterized in that, The support frame is a nickel support layer or a molybdenum support layer.

4. The high-temperature in-situ self-adhesive sensor according to claim 1, characterized in that, The pressure-sensitive cavity is a square cavity.

5. The high-temperature in-situ self-adhesive sensor according to claim 2, characterized in that, The sensing unit is a single pressure sensing unit with a center operating frequency in the GHz band, and the antenna is electrically connected to the electrodes of the pressure sensing unit to achieve complex impedance matching.

6. A method for manufacturing a high-temperature in-situ self-adhesive sensor according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Obtain a self-supporting polycrystalline diamond film, perform chemical mechanical polishing on its front and back sides, and perform surface cleaning and activation to prepare a diamond substrate. S2. Using pulsed laser deposition or magnetron sputtering technology, a piezoelectric layer is epitaxially grown on the first surface of the diamond substrate, and then an antenna and a pressure sensing unit are fabricated on the piezoelectric layer to form a sensing unit. S3. A titanium getter film is deposited on the second surface of the diamond substrate by vapor deposition. A mask plate is placed at the center to reserve a pressure-sensitive cavity. A support frame is constructed around the mask by additive manufacturing process to form a physical cavity. Selective atomic layer deposition (SLD) is used to encapsulate and protect the sensor surface except for the bottom of the support frame. Then, a self-fusing active layer is deposited at the bottom of the support frame. Finally, the sensor is attached to the surface of the test piece and a transient liquid-phase diffusion reaction is initiated by heating to form an atomic-level metallurgical bond.

7. The method for manufacturing a high-temperature in-situ self-adhesive sensor according to claim 6, characterized in that, The deposition amount of the titanium getter film is matched with the encapsulation volume of the pressure-sensitive cavity and the expected gas outflow rate of the inner surface of the pressure-sensitive cavity, ensuring that the total number of titanium atoms participating in the reaction is greater than the total number of active gas molecules remaining and released in the cavity within the expected lifespan.

8. The method for manufacturing a high-temperature in-situ self-adhesive sensor according to claim 6, characterized in that, The method for constructing a support frame around a mask using additive manufacturing is as follows: first, a titanium seed layer is sputtered around the mask, followed by electroplating to deposit a pure nickel layer; or, a chromium transition layer is sputtered around the mask, followed by ion-assisted electron beam evaporation to deposit a molybdenum layer.

9. The method for manufacturing a high-temperature in-situ self-adhesive sensor according to claim 6, characterized in that, The selective atomic layer deposition technique employs a composite stack grown conformally using atomic layer deposition technology.

10. The method for manufacturing a high-temperature in-situ self-adhesive sensor according to claim 6, characterized in that, The titanium getter film utilizes the chemical reactivity of Ti at the activation temperature to react with residual active gas molecules after the pressure-sensitive cavity is sealed via chemical adsorption, generating TiH. x : The process of titanium oxide formation: Ti + O₂ → TiO₂ The formation process of titanium nitride: 2Ti + N₂ → 2TiN The process of forming titanium oxide and releasing hydrogen gas: Ti + H₂O → TiO + H₂ H2 is adsorbed to form TiH x .

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