Manufacturing method of surface acoustic wave sensor and surface acoustic wave sensor

Abstract

The invention provides a manufacturing method of a surface acoustic wave sensor and the surface acoustic wave sensor, and belongs to the technical field of sensors. The method comprises the following steps: forming a plurality of groups of interdigital transducers and a plurality of groups of reflecting gratings on the upper surface of the same piezoelectric substrate; wherein the two groups of interdigital transducers, the two groups of reflecting gratings and the piezoelectric substrate form a temperature measurement area; the other group of interdigital transducers or the other two groups of interdigital transducers, the other two groups of reflecting gratings and the piezoelectric substrate form a vibration measurement area; forming an isolation groove in the piezoelectric substrate between the temperature measurement area and the vibration measurement area; a cantilever beam and a vibration mass block are formed on the lower surface of the piezoelectric substrate in the vibration measurement area; the vibration measurement area, the cantilever beam and the vibration mass block form a vibration sensing structure. According to the invention, synchronous detection of temperature and vibration on a single sensor chip is realized, and mutual interference between temperature measurement and vibration measurement is reduced through the isolation groove.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically to a method for manufacturing a surface acoustic wave (SAW) sensor and a SAW sensor itself. Background Technology

[0002] In many fields such as industry, medicine, and scientific research, accurate monitoring of temperature and vibration is crucial. Traditional solutions often rely on independent temperature and vibration sensors, such as thermocouples and thermistors for temperature sensors, and piezoelectric and capacitive vibration sensors. These sensors occupy a large space, are complex to install and maintain, and are difficult to synchronize with. They are also susceptible to interference in complex environments, affecting measurement accuracy and stability.

[0003] Surface acoustic wave (SAW) sensors, based on the piezoelectric effect of piezoelectric materials, convert physical quantities such as temperature and vibration into electrical signals. They offer advantages such as small size, high sensitivity, fast response, and wireless transmission capabilities, making them a focus of attention in the sensing field. However, existing SAW temperature and vibration sensors are mostly single-function designs. For example, one existing SAW temperature sensor uses interdigital transducers fabricated on a piezoelectric substrate to measure temperature by utilizing the effect of temperature changes on the propagation characteristics of surface acoustic waves, but it is insensitive to vibration. Some SAW vibration sensors employ a cantilever beam structure, using vibration to deform the cantilever beam and change the surface acoustic wave characteristics to measure vibration, but they struggle to simultaneously measure temperature.

[0004] In existing technologies, temperature and vibration detection typically require discrete sensors or multi-chip combinations, resulting in large size, high cost, and difficulties in signal synchronization. Although attempts have been made to integrate temperature and vibration sensing functions into a single chip, the measurement accuracy is reduced due to mutual interference between temperature and vibration measurements (e.g., thermal stress caused by temperature changes can interfere with vibration measurements). Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for manufacturing a surface acoustic wave (SAW) sensor and a SAW sensor.

[0006] The first aspect of this invention provides a method for manufacturing a surface acoustic wave sensor, comprising: Multiple sets of interdigital transducers and multiple sets of reflective gratings are formed on the upper surface of the same piezoelectric substrate; two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute a temperature measurement area; another set of interdigital transducers or two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute a vibration measurement area. An isolation groove is formed in the piezoelectric substrate between the temperature measurement area and the vibration measurement area; the isolation groove is used to block the propagation of surface acoustic waves generated by the interdigital transducer in the temperature measurement area to the vibration measurement area, and to block the influence of mechanical shocks generated by vibration in the vibration measurement area on the temperature measurement area. A cantilever beam and a vibrating mass block are formed on the lower surface of the piezoelectric substrate in the vibration measurement area; the interdigitated transducer and reflector grid in the vibration measurement area together with the cantilever beam and the vibrating mass block constitute a vibration sensing structure.

[0007] In this embodiment of the invention, the manufacturing method of the surface acoustic wave sensor further includes: forming a temperature-sensitive film on the surface of a piezoelectric substrate between two sets of interdigital transducers; The temperature measurement area is composed of two sets of reflective gratings, two sets of interdigital transducers, and a temperature-sensitive film and piezoelectric substrate between the two sets of interdigital transducers.

[0008] In this embodiment of the invention, the manufacturing method of the surface acoustic wave sensor further includes: The isolation groove is filled with insulating medium material.

[0009] In this embodiment of the invention, multiple sets of interdigital transducers and multiple sets of reflective gratings are formed on the upper surface of the same piezoelectric substrate, including: Photoresist is coated onto the cleaned piezoelectric substrate surface. Through exposure and development processes, the patterns of interdigitated transducers and reflective gratings are formed on the photoresist on the piezoelectric substrate surface. Metal is sputtered onto the surface of a piezoelectric substrate to form a metal film of the pattern, which serves as an interdigital transducer and a reflective grating.

[0010] In this embodiment of the invention, an isolation groove is formed in the piezoelectric substrate between the temperature measurement area and the vibration measurement area, including: The surface of the piezoelectric substrate between the temperature measurement area and the vibration measurement area is ground and polished to remove part of the piezoelectric substrate material and form an isolation groove of a preset depth. Alternatively, dry or wet etching processes can be used to etch the piezoelectric substrate between the temperature measurement area and the vibration measurement area to form an isolation trench of a preset depth. The preset depth is greater than or equal to one-quarter of the wavelength of the surface acoustic wave.

[0011] In this embodiment of the invention, a cantilever beam and a vibrating mass block are formed on the lower surface of the piezoelectric substrate in the vibration measurement area, including: The lower surface of the piezoelectric substrate in the vibration measurement area is etched to form a cantilever beam; One end of the cantilever beam is etched to form a vibrating mass; or, a piezoelectric ceramic material is bonded, grown, or bonded to one end of the cantilever beam to form a vibrating mass.

[0012] In this embodiment of the invention, the piezoelectric substrate is a piezoelectric crystal or a piezoelectric substrate on an insulator; Piezoelectric crystals are made of quartz crystals, lithium niobate crystals, lithium tantalate crystals, lithium gallate crystals, bismuth germanate crystals, or polycrystalline piezoelectric ceramics. The piezoelectric substrate on an insulator comprises: a top piezoelectric single crystal layer, a middle silicon dioxide insulating layer, and a bottom high-resistivity silicon substrate.

[0013] A second aspect of the present invention provides a surface acoustic wave sensor, comprising: a piezoelectric substrate, multiple sets of interdigital transducers formed on the upper surface of the piezoelectric substrate, and multiple sets of reflective gratings; wherein two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute a temperature measurement region; and another set of interdigital transducers or two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute a vibration measurement region. The lower surface of the piezoelectric substrate in the vibration measurement area is provided with a cantilever beam and a vibrating mass block. The interdigital transducer and reflector grid in the vibration measurement area, together with the cantilever beam and the vibrating mass block, constitute a vibration sensing structure. An isolation groove is provided in the piezoelectric substrate between the temperature measurement area and the vibration measurement area. The isolation groove is used to block the propagation of surface acoustic waves generated by the interdigital transducer in the temperature measurement area to the vibration measurement area, and to block the influence of mechanical impact caused by vibration in the vibration measurement area on the temperature measurement area.

[0014] In this embodiment of the invention, the isolation groove is filled with an insulating medium material.

[0015] In this embodiment of the invention, a temperature-sensitive film is formed on the surface of the piezoelectric substrate between the two sets of interdigital transducers; The temperature measurement area is composed of two sets of reflective gratings, two sets of interdigital transducers, and a temperature-sensitive film and piezoelectric substrate between the two sets of interdigital transducers.

[0016] In this embodiment of the invention, the two sets of reflective gratings in the temperature measurement area are symmetrically distributed on both sides of the two sets of interdigital transducers; The two sets of reflective grids in the vibration measurement area are symmetrically distributed on both sides of one or two sets of interdigital transducers.

[0017] In this embodiment of the invention, the lengths of the interdigitated fingers in each group of interdigitated transducers are not equal; The length of each interdigit is determined by applying apodization weighting to interdigital transducers with equal-length interdigital fingers using a window function.

[0018] The above technical solution, through the partitioning and isolation of temperature measurement and vibration sensing, forms multiple sets of interdigital transducers and multiple sets of reflective gratings on the same piezoelectric substrate, constituting mutually independent temperature measurement and vibration measurement areas, thus achieving synchronous detection of temperature and vibration on a single sensor chip. Furthermore, an isolation groove is set in the piezoelectric substrate between the temperature measurement area and the vibration measurement area. This isolation groove blocks the propagation of surface acoustic waves from the detection channel to the reference channel and blocks the influence of mechanical impacts generated by vibration in the vibration measurement area on the temperature measurement area, reducing mutual interference between the temperature measurement area and the vibration measurement area (suppressing cross-interference between temperature and vibration measurements) and improving measurement accuracy.

[0019] Other features and advantages of the technical solution of the present invention will be described in detail in the following detailed embodiments section. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram (top view) of the structure of the surface acoustic wave sensor provided in an embodiment of the present invention. Figure 2 This is a structural schematic diagram (cross-section) of the temperature sensing unit of the surface acoustic wave sensor provided in an embodiment of the present invention. Figure 3 This is a structural schematic diagram (cross-section) of the vibration sensing unit of the surface acoustic wave sensor provided in an embodiment of the present invention. Figure 4 This is a schematic diagram (top view) of the structure of a surface acoustic wave sensor provided in another embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures 1-Piezoelectric substrate, 2-Temperature measurement area, 3-Vibration measurement area, 4-Isolation groove 11-Interdigital transducer, 12-Reflective grating, 13-Temperature-sensitive film, 14-Cantilever beam 15-Vibrating mass block. Detailed Implementation

[0022] To make the technical solutions and advantages of the embodiments of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "interlocked" should be interpreted broadly, referring to mechanical connections, electrical connections, or connections that allow for mutual communication; direct connections or indirect connections via an intermediate medium; and connections within two components or interactions between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0025] In existing technologies, temperature and vibration detection typically require discrete sensors or multi-chip combinations, resulting in bulky size, high cost, and difficulties in signal synchronization. Although attempts have been made to integrate temperature and vibration sensing functions into a single chip, interference between temperature and vibration measurements leads to reduced measurement accuracy. For example, in some integrated designs, thermal stress caused by temperature changes can interfere with vibration measurements, and mechanical shocks from vibrations can also affect the accuracy of temperature measurements, severely limiting sensor performance.

[0026] To address the problems of existing technologies, this invention provides a single-chip integrated surface acoustic wave (SAW) sensor for temperature and vibration detection, along with its manufacturing method. This invention achieves simultaneous detection of temperature and vibration on a single sensor chip by partitioning and isolating temperature measurement and vibration sensing areas. Multiple sets of interdigital transducers and multiple sets of reflective gratings are formed on the same piezoelectric substrate, creating independent temperature and vibration measurement areas. Furthermore, an isolation groove is provided in the piezoelectric substrate between the temperature and vibration measurement areas. This groove blocks the propagation of SAW from the detection channel to the reference channel and also blocks the mechanical impact of vibration in the vibration measurement area on the temperature measurement area, reducing mutual interference between the two areas (suppressing cross-interference between temperature and vibration measurements) and improving measurement accuracy.

[0027] like Figure 1 , Figure 2 , Figure 3As shown, this embodiment of the invention provides a single-chip integrated surface acoustic wave (SAW) sensor for temperature and vibration detection. The SAW sensor includes: a piezoelectric substrate 1, multiple sets of interdigital transducers 11 formed on the upper surface of the piezoelectric substrate 1, and multiple sets of reflective gratings 12. Two sets of interdigital transducers and two sets of reflective gratings, together with the piezoelectric substrate 1, constitute a temperature measurement region, which forms a temperature sensing unit. Another set of interdigital transducers or two sets of interdigital transducers and two sets of reflective gratings, together with the piezoelectric substrate 1, constitute a vibration measurement region 3; or, two sets of interdigital transducers and two sets of reflective gratings, together with the piezoelectric substrate 1, constitute a vibration measurement region 3. Figure 1 The diagram only shows the case where one set of interdigital transducers and two sets of reflective gratings constitute the vibration measurement area. A cantilever beam 14 and a vibrating mass block 15 are provided on the lower surface of the piezoelectric substrate in vibration measurement area 3. The interdigital transducers 11 and reflective gratings 12 in vibration measurement area 3, together with the cantilever beam 14 and vibrating mass block 15, constitute a vibration sensing structure (i.e., a vibration sensing unit). An isolation groove 4 is provided in the piezoelectric substrate 1 between temperature measurement area 2 and vibration measurement area 3. The isolation groove 4 is used to block the propagation of surface acoustic waves generated by the interdigital transducers in temperature measurement area 2 to vibration measurement area 3, and to block the influence of mechanical impacts generated by vibration in vibration measurement area 3 on temperature measurement area 2.

[0028] In another embodiment, a different single-chip integrated surface acoustic wave sensor for temperature and vibration detection is provided. For example... Figure 4 As shown, the surface acoustic wave sensor includes: a piezoelectric substrate 1, multiple sets of interdigital transducers 11 formed on the upper surface of the piezoelectric substrate 1, and multiple sets of reflective gratings 12. A temperature-sensitive film 13 is formed on the surface of the piezoelectric substrate between two sets of interdigital transducers. The two sets of reflective gratings, the two sets of interdigital transducers, and the temperature-sensitive film 13 between the two sets of interdigital transducers, together with the piezoelectric substrate 1, constitute a temperature measurement region 2, which forms a temperature sensing unit. Another set of interdigital transducers, or two sets of interdigital transducers and two sets of reflective gratings, together with the piezoelectric substrate 1, constitute a vibration measurement region 3. A cantilever beam 14 and a vibrating mass block 15 are provided on the lower surface of the piezoelectric substrate in the vibration measurement region 3. The interdigital transducers 11 and reflective gratings 12 in the vibration measurement region 3, together with the cantilever beam 14 and the vibrating mass block 15, constitute a vibration sensing structure (i.e., a vibration sensing unit). An isolation groove 4 is provided in the piezoelectric substrate 1 between the temperature measurement area 2 and the vibration measurement area 3. The isolation groove 4 is used to block the propagation of surface acoustic waves generated by the interdigital transducer in the temperature measurement area 2 to the vibration measurement area 3, and to block the influence of mechanical impacts caused by vibration in the vibration measurement area 3 on the temperature measurement area 2. The surface acoustic wave sensor provided in this embodiment has a temperature-sensitive membrane in the temperature measurement area, which can achieve more accurate temperature measurement.

[0029] In the above embodiments, the isolation groove is filled with an insulating dielectric material. In other embodiments, the isolation groove may not be filled with any material.

[0030] In this embodiment, one end of the cantilever beam is fixed to the piezoelectric substrate, and the other end is a free end. A vibrating mass block is provided at the free end of the cantilever beam, and the vibrating mass block is connected to the free end of the cantilever beam as a whole. The vibrating mass block can be formed in the following two ways: (1) etching one end of the cantilever beam to form the vibrating mass block; (2) bonding, growing or bonding piezoelectric ceramic material to one end of the cantilever beam to form the vibrating mass block.

[0031] In a preferred embodiment, the two sets of reflective gratings in the temperature measurement area 2 are symmetrically distributed on both sides of the two sets of interdigital transducers. Similarly, the two sets of reflective gratings in the vibration measurement area 3 are symmetrically distributed on both sides of one or both sets of interdigital transducers.

[0032] In this embodiment, the lengths of all interdigital fingers in the interdigital transducer (IDT) are equal. In other embodiments, the lengths of all interdigital fingers in each group of interdigital transducers (IDTs) are unequal (non-equal-length interdigital fingers). The length of each interdigital finger can be determined by applying an apodization weighting process to interdigital transducers with equal-length interdigital fingers using a window function. The window function can be at least one of the following: Blackman window, rectangular window, Bartlett window, triangular window, Hanning window, Hamming window, Taylor window, and Kaiser window.

[0033] In this embodiment, the piezoelectric substrate 1 is a piezoelectric crystal, or a POI substrate (piezoelectric substrate on insulator). The crystal is a quartz crystal, lithium niobate crystal, lithium tantalate crystal, lithium gallium oxide crystal, bismuth germanate crystal, or polycrystalline piezoelectric ceramic. The piezoelectric substrate on insulator includes: a top piezoelectric single crystal layer, a middle silicon dioxide insulating layer, and a bottom high-resistivity silicon substrate.

[0034] In this embodiment, the temperature sensing unit and the vibration sensing unit share a piezoelectric substrate, and the temperature sensing unit and the vibration sensing unit are isolated from each other by an isolation groove.

[0035] In this embodiment, the temperature sensing unit is a delayed linear SAW structure. The delayed linear SAW structure mainly consists of a piezoelectric substrate, an input interdigital transducer (IDT), and an output interdigital transducer (IDT). The piezoelectric substrate acts as the "carrier" of the entire device, allowing surface acoustic waves to propagate stably on its surface. The input interdigital transducer (IDT), acting as the signal "transmitter," consists of two sets of alternating metal electrodes (such as aluminum or gold), converting externally input electrical signals into surface acoustic waves via the piezoelectric effect, which then propagate along the substrate surface. The output interdigital transducer (IDT), acting as the signal "receiver," converts the surface acoustic waves propagating there back into electrical signals via the piezoelectric effect, outputting them to subsequent circuits.

[0036] Specifically, the temperature sensing unit adopts a dual-port delay line structure, including: an input interdigital transducer, a corresponding reflective grating near the input interdigital transducer, an output interdigital transducer, and a corresponding reflective grating near the output interdigital transducer. The core principle of the dual-port delay line SAW temperature sensor is that temperature changes alter the thermal expansion of the piezoelectric substrate and the propagation speed of surface acoustic waves, causing a change in the propagation delay time of the SAW. The temperature value can be deduced by measuring the minute changes in the delay time. The dual-port delay line SAW sensor utilizes the correlation between "delay time" and temperature. By measuring the time difference (i.e., delay time τ) between the "transmitted electrical signal" and the "received electrical signal," the propagation characteristics of the SAW can be reflected. Temperature changes cause changes in the propagation speed or propagation path length of the SAW, thus causing changes in the delay time τ. By calibrating the correspondence between τ and temperature, the measured temperature can be deduced by measuring τ.

[0037] In this embodiment, the vibration sensing unit is a resonant SAW structure, which mainly consists of a piezoelectric substrate, an interdigital transducer (IDT), and reflection gratings. The piezoelectric substrate, acting as the "carrier" and "sound wave propagation medium" of the device, is made of a material with a stable piezoelectric effect; its characteristics directly determine the propagation speed of the surface acoustic wave, the stability of the resonant frequency, and the device loss. The interdigital transducer (IDT) is the core of the "electro-acoustic" and "acoustic-electro-" conversion, and its structure is similar to that of the IDT in a delay-line SAW, consisting of alternating metal electrodes (such as aluminum or gold). In the resonant structure, the IDT is typically located between two reflection gratings, responsible for converting the input electrical signal into a surface acoustic wave, and also for converting the resonant surface acoustic wave into an output electrical signal. The reflection gratings are a key component distinguishing the resonant SAW from the delay-line type, consisting of two groups: an input reflection grating and an output reflection grating, symmetrically distributed on both sides of the IDT. Each set of reflective gratings consists of multiple rows of parallel metal strips. Their function is to reflect surface acoustic waves, so that an "acoustic resonant cavity" is formed between the IDT and the two reflective gratings, allowing the surface acoustic waves to reflect back and forth in the cavity, eventually forming a stable resonance.

[0038] In this embodiment, the vibration sensing unit adopts a "cantilever beam-SAW resonator" structure, including a cantilever beam assembly and a SAW resonator. The cantilever beam assembly includes a cantilever beam and a vibrating mass block located below the free end of the cantilever beam. One end of the cantilever beam is fixed to a piezoelectric substrate, while the other end is free. The entire cantilever beam assembly is hollowed out at the bottom by etching the piezoelectric substrate. The vibrating mass block is achieved by etching the piezoelectric substrate to a certain depth (partial etching). The SAW resonator can be a single-ended structure (one set of interdigital transducers (IDTs) + two sets of reflective grids) or a double-ended structure (two sets of IDTs + two sets of reflective grids). The difference is that a single-ended pair has only one IDT that simultaneously handles both transmitting and receiving signals, while a double-ended pair has two IDTs, one for transmitting signals and the other for receiving signals. The principle of measuring vibration using a cantilever beam-SAW resonator structure is as follows: external vibration is converted into strain through the cantilever beam. This strain is transmitted to the SAW resonator, changing the propagation speed of its surface acoustic waves, ultimately manifesting as a shift in the resonant frequency. By measuring the frequency shift, the intensity of the vibration (such as acceleration) can be deduced. Key logic: vibration intensity (such as acceleration). α → Cantilever beam strain ε → SAW substrate stress → SAW velocity ν change → Resonant frequency f0 shift. By measuring the frequency shift Δf = f - f0 (where f is the measured frequency and f0 is the reference frequency without vibration), the intensity of the vibration can be deduced.

[0039] Specifically, the piezoelectric substrate can be a piezoelectric crystal, such as quartz crystal, lithium niobate crystal, lithium tantalate crystal, polycrystalline piezoelectric ceramics (barium titanate, lead zirconate titanate, lead magnesium niobate (PMN) and related ternary ceramics), and other piezoelectric crystals (lithium gallate, bismuth germanate), etc. The piezoelectric substrate can also be a POI (Piezoelectric on Insulator) substrate structure. A POI substrate mainly has a three-layer structure, including a top piezoelectric single-crystal layer, a middle silicon dioxide insulating layer, and a bottom high-resistivity silicon substrate. The top piezoelectric single-crystal layer typically uses piezoelectric thin film materials such as lithium tantalate, lithium niobate, ZnO, AlN, ScAlN, and PZT, which have uniform thickness and stable performance; the middle silicon dioxide insulating layer is used to isolate the piezoelectric layer from the substrate, reducing signal interference; and the bottom high-resistivity silicon substrate provides mechanical support and reduces parasitic capacitance. The SAW sensor with integrated temperature and vibration detection on a single chip in this application is a collaborative design that integrates temperature detection and vibration detection structures on the same piezoelectric substrate or the same POI substrate.

[0040] An isolation groove is an isolation structure of a certain depth set on the edge of the temperature sensing unit on the piezoelectric substrate to block the lateral propagation of sound waves from the temperature sensing unit to the vibration sensing unit. The isolation groove can be filled with an insulating medium material, such as silicone rubber.

[0041] This invention also provides a method for manufacturing the above-described surface acoustic wave sensor, the method comprising the following steps: Step 1, as follows Figure 1 As shown, multiple sets of interdigital transducers 11 and multiple sets of reflective gratings 12 are formed on the upper surface of the same piezoelectric substrate 1; two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute the temperature measurement area 2; another set of interdigital transducers (or two sets of interdigital transducers) and another two sets of reflective gratings together with the piezoelectric substrate constitute the vibration measurement area 3.

[0042] Or, such as Figure 4 As shown, multiple sets of interdigital transducers 11 and multiple sets of reflective gratings 12 are formed on the upper surface of the same piezoelectric substrate 1, and a temperature-sensitive film 12 is formed on the surface of the piezoelectric substrate between two sets of interdigital transducers. The two sets of reflective gratings, the two sets of interdigital transducers, and the temperature-sensitive film between the two sets of interdigital transducers together with the piezoelectric substrate constitute a temperature measurement area 2 (i.e., a temperature sensing unit).

[0043] Step 2: Form a piezoelectric substrate 1 between temperature measurement area 2 and vibration measurement area 3, as shown in the figure. Figure 1 The isolation groove 4 is shown. The isolation groove 4 is used to block the propagation of surface acoustic waves generated by the interdigital transducer in the temperature measurement area 2 to the vibration measurement area 3, and to block the influence of mechanical impact caused by vibration in the vibration measurement area 3 on the temperature measurement area 2.

[0044] Step 3, as Figure 3 As shown, a cantilever beam 14 and a vibrating mass block 15 are formed on the lower surface of the piezoelectric substrate 1 in the vibration measurement area 3; the interdigital transducer 11 and the reflector grating 12 in the vibration measurement area 3 together with the cantilever beam 14 and the vibrating mass block 15 constitute a vibration sensing structure (i.e., a vibration sensing unit).

[0045] In step one above, the specific method for forming the interdigital transducer and the reflective grating is as follows: photoresist is coated on the surface of the cleaned piezoelectric substrate, and the patterns of the interdigital transducer and the reflective grating are formed on the photoresist on the surface of the piezoelectric substrate through exposure and development. Then, metal is sputtered on the surface of the piezoelectric substrate to form a metal film of the pattern, which serves as the interdigital transducer and the reflective grating.

[0046] Piezoelectric substrates can be made of piezoelectric crystals or POI (Piezoelectric on Insulator) substrates. Piezoelectric crystals are at least one of the following: quartz crystals, lithium niobate crystals, lithium tantalate crystals, polycrystalline piezoelectric ceramics (barium titanate, lead zirconate titanate, lead magnesium niobate (PMN) and related ternary ceramics), and other piezoelectric crystals (lithium gallium oxide, bismuth germanate). POI substrates mainly have a three-layer structure: a top piezoelectric single-crystal layer, a middle silicon dioxide insulating layer, and a bottom high-resistivity silicon substrate. The top piezoelectric single-crystal layer typically uses piezoelectric thin film materials such as lithium tantalate, lithium niobate, ZnO, AlN, ScAlN, and PZT, which have uniform thickness and stable performance. The middle silicon dioxide insulating layer isolates the piezoelectric layer from the substrate, reducing signal interference. The bottom high-resistivity silicon substrate provides mechanical support and reduces parasitic capacitance.

[0047] In step two above, there are two specific methods for forming the isolation groove: 1. Grinding and polishing the surface of the piezoelectric substrate between the temperature measurement area and the vibration measurement area using grinding tools and polishing materials to remove some of the piezoelectric substrate material and form an isolation groove of a predetermined depth; 2. Etching the piezoelectric substrate between the temperature measurement area and the vibration measurement area using dry etching or wet etching processes to form an isolation groove of a predetermined depth. The predetermined depth is greater than or equal to one-quarter of the wavelength of the surface acoustic wave, i.e., the depth of the isolation groove is ≥λ / 4, where λ is the wavelength of the surface acoustic wave.

[0048] An isolation groove is a narrow, elongated etched area between the temperature measurement area and the vibration measurement area. The isolation groove can be hollow or filled with an insulating medium, such as silicone rubber.

[0049] In an optional embodiment, after step two above, an insulating medium material can be filled into the isolation groove. For example, silicone rubber insulating material can be filled into the isolation groove to block the lateral propagation of sound waves between the temperature measurement area and the vibration measurement area, reducing coupling interference. The method of filling the isolation groove with silicone rubber insulating material is as follows: according to the size and insulation performance requirements of the isolation groove, silicone rubber substrate and filler are mixed in proportion, and the silicone rubber and filler are thoroughly mixed. The mixture is then processed into a specified shape by compression molding, extrusion molding, or casting molding, and filled into the isolation groove, ensuring that the filler material fits tightly with the isolation groove. The filled isolation groove is then deburred and leveled to ensure a smooth surface of the filler layer and improve insulation performance.

[0050] In step three above, the lower surface of the piezoelectric substrate in the vibration measurement area is etched to form a cantilever beam. Then, one end of the cantilever beam is etched to form a vibrating mass block; alternatively, piezoelectric ceramic material is bonded, grown, or bonded to one end of the cantilever beam to form a vibrating mass block. The lower surface of the piezoelectric substrate corresponding to the temperature measurement area is not etched; only the lower surface of the piezoelectric substrate corresponding to the vibration measurement area is etched. The cantilever beam formed on the lower surface of the piezoelectric substrate has one end fixed to the piezoelectric substrate and the other end free. Alternatively, the other end (free end) of the cantilever beam can be etched to form a vibrating mass block at the free end of the cantilever beam, thus connecting the vibrating mass block to the free end of the cantilever beam as a single unit.

[0051] In an interdigital transducer (IDT), the lengths of the individual interdigitals can be unequal. The length of each interdigital ...

[0052] The single-chip integrated surface acoustic wave sensor for temperature and vibration detection and its manufacturing method provided in this invention have the following advantages: (1) In the prior art, temperature and vibration detection usually need to be achieved through discrete sensors or multi-chip combinations, resulting in large size, high cost and difficulty in signal synchronization. The present invention integrates temperature measurement unit and vibration measurement unit on piezoelectric substrate through partitioned isolation and collaborative working architecture of temperature detection area and vibration detection area, so as to realize single-chip synchronous detection of temperature and vibration; (2) An isolation groove of a certain depth is formed on the piezoelectric substrate between the temperature measurement area and the vibration measurement area to block the lateral propagation of sound waves to the vibration measurement unit and improve the cross-interference suppression ratio; (3) The single-chip integrated temperature and vibration SAW sensor chip structure of the present invention is manufactured using micromachining technology. Compared with traditional complex assembly structures, it can be integrated and mass-produced, reducing production costs. The present invention can meet the needs of various scenarios such as industrial equipment condition monitoring, aerospace environmental detection, automotive electronic system monitoring, and precision instrument operation and maintenance.

[0053] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. As long as such combination does not violate the spirit of the embodiments of the present invention, it should also be considered as the content disclosed in the embodiments of the present invention.

Claims

1. A method for manufacturing a surface acoustic wave sensor, characterized in that, include: Multiple sets of interdigital transducers and multiple sets of reflective gratings are formed on the upper surface of the same piezoelectric substrate; two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute a temperature measurement area; another set of interdigital transducers or two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute a vibration measurement area. An isolation groove is formed in the piezoelectric substrate between the temperature measurement area and the vibration measurement area; the isolation groove is used to block the propagation of surface acoustic waves generated by the interdigital transducer in the temperature measurement area to the vibration measurement area, and to block the influence of mechanical shocks generated by vibration in the vibration measurement area on the temperature measurement area. A cantilever beam and a vibrating mass block are formed on the lower surface of the piezoelectric substrate in the vibration measurement area; the interdigitated transducer and reflector grid in the vibration measurement area together with the cantilever beam and the vibrating mass block constitute a vibration sensing structure.

2. The method for manufacturing a surface acoustic wave sensor according to claim 1, characterized in that, The method further includes: A temperature-sensitive film is formed on the surface of the piezoelectric substrate between two sets of interdigital transducers; The temperature measurement area is composed of two sets of reflective gratings, two sets of interdigital transducers, and a temperature-sensitive film and piezoelectric substrate between the two sets of interdigital transducers.

3. The method for manufacturing a surface acoustic wave sensor according to claim 1, characterized in that, The method further includes: The isolation groove is filled with insulating medium material.

4. The method for manufacturing a surface acoustic wave sensor according to claim 1, characterized in that, Multiple sets of interdigital transducers and multiple sets of reflective gratings are formed on the upper surface of the same piezoelectric substrate, including: Photoresist is coated onto the cleaned piezoelectric substrate surface. Through exposure and development processes, the patterns of interdigitated transducers and reflective gratings are formed on the photoresist on the piezoelectric substrate surface. Metal is sputtered onto the surface of a piezoelectric substrate to form a metal film of the pattern, which serves as an interdigital transducer and a reflective grating.

5. The method for manufacturing a surface acoustic wave sensor according to claim 1, characterized in that, An isolation groove is formed in the piezoelectric substrate between the temperature measurement area and the vibration measurement area, including: The surface of the piezoelectric substrate between the temperature measurement area and the vibration measurement area is ground and polished to remove part of the piezoelectric substrate material and form an isolation groove of a preset depth. Alternatively, dry or wet etching processes can be used to etch the piezoelectric substrate between the temperature measurement area and the vibration measurement area to form an isolation trench of a preset depth. The preset depth is greater than or equal to one-quarter of the wavelength of the surface acoustic wave.

6. The method for manufacturing a surface acoustic wave sensor according to claim 1, characterized in that, A cantilever beam and a vibrating mass block are formed on the lower surface of the piezoelectric substrate in the vibration measurement area, including: The lower surface of the piezoelectric substrate in the vibration measurement area is etched to form a cantilever beam; One end of the cantilever beam is etched to form a vibrating mass; or, a piezoelectric ceramic material is bonded, grown, or bonded to one end of the cantilever beam to form a vibrating mass.

7. A surface acoustic wave sensor, characterized in that, include: The piezoelectric substrate, multiple sets of interdigital transducers formed on the upper surface of the piezoelectric substrate, and multiple sets of reflective gratings; wherein two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute a temperature measurement area; and another set of interdigital transducers or two sets of interdigital transducers and two sets of reflective gratings together with the piezoelectric substrate constitute a vibration measurement area. The lower surface of the piezoelectric substrate in the vibration measurement area is provided with a cantilever beam and a vibrating mass block. The interdigital transducer and reflector grid in the vibration measurement area, together with the cantilever beam and the vibrating mass block, constitute a vibration sensing structure. An isolation groove is provided in the piezoelectric substrate between the temperature measurement area and the vibration measurement area. The isolation groove is used to block the propagation of surface acoustic waves generated by the interdigital transducer in the temperature measurement area to the vibration measurement area, and to block the influence of mechanical impact caused by vibration in the vibration measurement area on the temperature measurement area.

8. The surface acoustic wave sensor according to claim 7, characterized in that, The isolation groove is filled with insulating medium material.

9. The surface acoustic wave sensor according to claim 7, characterized in that, A temperature-sensitive film is formed on the surface of the piezoelectric substrate between the two sets of interdigital transducers; The temperature measurement area is composed of two sets of reflective gratings, two sets of interdigital transducers, and a temperature-sensitive film and piezoelectric substrate between the two sets of interdigital transducers.

10. The surface acoustic wave sensor according to claim 7, characterized in that, The two sets of reflective gratings in the temperature measurement area are symmetrically distributed on both sides of the two sets of interdigital transducers. The two sets of reflective grids in the vibration measurement area are symmetrically distributed on both sides of one or two sets of interdigital transducers.

11. The surface acoustic wave sensor according to claim 7, characterized in that, The lengths of the interdigitated fingers in each group of interdigitated transducers are not equal. The length of each interdigit is determined by applying apodization weighting to interdigital transducers with equal-length interdigital fingers using a window function.

12. The surface acoustic wave sensor according to claim 7, characterized in that, The piezoelectric substrate is a piezoelectric crystal or a piezoelectric substrate on an insulator; The piezoelectric crystal is a quartz crystal, lithium niobate crystal, lithium tantalate crystal, lithium gallate crystal, bismuth germanate crystal, or polycrystalline piezoelectric ceramic. The piezoelectric substrate on the insulator includes: a top piezoelectric single crystal layer, a middle silicon dioxide insulating layer, and a bottom high-resistivity silicon substrate.

Images