Silicon-based constant-temperature surface acoustic wave filter and preparation method thereof

Abstract

The invention relates to the technical field of wireless communication, and provides a silicon-based constant-temperature surface acoustic wave filter and a preparation method thereof, and the preparation method comprises the following steps: carrying out monocrystalline silicon ion implantation on a silicon substrate to respectively form an n-type thermocouple pair and a p-type thermocouple pair; manufacturing a dielectric layer; a thermocouple pair interconnection layer is manufactured, so that the n-type thermocouple pair and the p-type thermocouple pair are connected to form a path; manufacturing a passivation adhesion layer on the surface, far away from the silicon substrate, of the dielectric layer; manufacturing an acoustic layer on the surface, far away from the silicon substrate, of the passivation adhesion layer; windowing the acoustic layer to form a first groove and a second groove, and exposing the n-type thermocouple pair and the p-type thermocouple pair respectively; a first electrical interconnection layer and a second electrical interconnection layer are manufactured in the first groove and the second groove respectively, an interdigital structure is manufactured on the surface, away from the silicon substrate, of the acoustic layer, and the silicon-based constant-temperature surface acoustic wave filter is obtained. According to the silicon-based constant-temperature surface acoustic wave filter, the temperature stability and the power tolerance performance can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communications, and in particular to a silicon-based constant temperature surface acoustic wave filter and a preparation method thereof. Background Art

[0002] The temperature drift problem of surface acoustic wave (SAW) filters refers to the phenomenon that its key performance parameters (such as center frequency, bandwidth, insertion loss and out-of-band rejection) shift with changes in ambient temperature. This phenomenon is essentially due to the basic physical properties of surface acoustic wave devices: when the temperature changes, the piezoelectric substrate material (such as or The lattice constant of the CMOS device undergoes thermal expansion, causing a change in the propagation velocity of surface acoustic waves (the speed of sound decreases by approximately 0.02% for every 1°C increase in temperature). Simultaneously, the thermal expansion of the metal electrodes of the interdigital transducer (IDT) also changes the electrode period. These two effects result in a typical negative temperature coefficient (approximately -30 to -45 ppm / °C) in the device's center frequency.

[0003] In high-frequency applications such as 5G communications, this temperature drift can cause serious system problems. For example, a 3.5GHz SAW filter can experience frequency drift of up to 3MHz within an operating temperature range of -40°C to +85°C. This can not only cause passband mismatch and adjacent channel leakage, but also degrade key performance indicators such as EVM (Error Vector Magnitude) and ACLR (Adjacent Channel Leakage Ratio). To address this challenge, various innovative solutions have been developed. For example, TC-SAW (temperature-compensated surface acoustic wave) filters utilize a SiO2 temperature compensation layer deposited on a conventional LiTaO3 substrate (its positive temperature coefficient partially offsets the substrate's negative temperature effect), reducing the temperature drift coefficient to -10 to -15ppm / °C. IHP-SAW (Incredible High Performance) technology reduces the temperature drift coefficient to -15 to -25ppm / °C by optimizing the electrode structure and material stack, achieving improved temperature stability while maintaining low insertion loss (<1.5dB).

[0004] However, these improvements often require a trade-off between performance, cost, and size, forcing system designers to select the appropriate filter solution based on different application scenarios (for example, base stations require better temperature stability, while mobile terminals are more concerned with size and cost). In the future, as 6G communications require higher frequency bands (such as terahertz) and wider temperature ranges, the temperature drift problem of SAW filters will continue to drive innovations in materials science, micro-nanofabrication, and thermal management technologies.

[0005] Therefore, although the related technologies TC-SAW and IHP-SAW improve the temperature drift problem of traditional SAW filters, their temperature drift coefficients are still inferior to BAW filters (bulk acoustic wave filters). They are prone to problems such as high design complexity, high material costs, and poor power tolerance. Summary of the Invention

[0006] In view of the above deficiencies in the prior art, the present invention proposes a silicon-based constant temperature surface acoustic wave filter and a preparation method thereof, so as to solve the problems of poor temperature drift suppression and power tolerance of the prior surface acoustic wave filters.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: In a first aspect, an embodiment of the present invention provides a method for preparing a silicon-based temperature-controlled surface acoustic wave filter, the method comprising the following steps: Step S1, selecting a silicon substrate and implanting single crystal silicon ions into the silicon substrate to form an n-type thermocouple pair and a p-type thermocouple pair; Step S2, forming a dielectric layer on the upper surface of the silicon substrate, so that the dielectric layer completely covers the upper surfaces of the silicon substrate, the n-type thermocouple pair, and the p-type thermocouple pair; Step S3, performing a first windowing on the dielectric layer to expose the n-type thermocouple pair and the p-type thermocouple pair, and fabricating a thermocouple pair interconnection layer at the first windowing position to connect the n-type thermocouple pair and the p-type thermocouple pair to form a path; Step S4, forming a passivation adhesion layer on the surface of the dielectric layer away from the silicon substrate, and completely covering the dielectric layer and the thermocouple interconnection layer; Step S5, forming an acoustic layer on the surface of the passivation adhesion layer away from the silicon substrate, and completely covering the passivation adhesion layer; Step S6: performing a second windowing operation downward from the surface of the acoustic layer to form a first groove and a second groove for respectively exposing the n-type thermocouple pair and the p-type thermocouple pair; wherein the positions of the first windowing and the second windowing are different; Step S7: fabricate a first electrical interconnection layer and a second electrical interconnection layer in the first groove and the second groove, respectively, so that the first electrical interconnection layer extends in contact with the inner groove wall of the first groove and is electrically connected to the n-type thermocouple, and the second electrical interconnection layer extends in contact with the inner groove wall of the second groove and is electrically connected to the p-type thermocouple, and fabricate an interdigitated structure on the surface of the acoustic layer away from the silicon substrate to obtain a silicon-based constant temperature surface acoustic wave filter.

[0008] Preferably, in step S1, the doping concentration of the single crystal silicon ions used to make the n-type thermocouple pair and the p-type thermocouple pair is greater than or equal to 1×1019 cm -3 The thickness of the n-type thermocouple pair and the p-type thermocouple pair formed by implanting the single crystal silicon ions is 1um-4um.

[0009] Preferably, the thickness of the n-type thermocouple pair and the p-type thermocouple pair are both 2 μm.

[0010] Preferably, in step S2, the dielectric layer is made of SiN material or SiO2 material.

[0011] Preferably, in step S5, the process for manufacturing the acoustic layer is any one of a SiO2 hydrophilic low-temperature bonding process, a SiO2 hydrophilic BCB bonding process, or a deposition process.

[0012] Preferably, the material of the acoustic layer is a piezoelectric material, and the piezoelectric material is any one of lithium niobate, lithium tantalate, aluminum nitride and PZT.

[0013] Preferably, in the step S6, the acoustic layer is subjected to the second windowing process using a reactive ion etching process to form the first groove and the second groove.

[0014] Preferably, in step S7, the thickness of the first electrical interconnection layer and the second electrical interconnection layer is less than or equal to 0.5 um; and the thickness of the interdigital structure is greater than or equal to 1.0 um.

[0015] Preferably, in step S7, the materials of the interdigital structure, the first electrical interconnection layer and the second electrical interconnection layer are all made of aluminum, titanium-aluminum alloy, or any one of aluminum and titanium-aluminum alloy laminates.

[0016] In a second aspect, an embodiment of the present invention provides a silicon-based temperature-controlled surface acoustic wave filter, which is manufactured based on the above-mentioned method for manufacturing a silicon-based temperature-controlled surface acoustic wave filter.

[0017] Compared with the related art, in the embodiment of the present invention, through the above steps S1 to S7, single crystal silicon ions are implanted into the silicon substrate to form an n-type thermocouple pair and a p-type thermocouple pair respectively; when the ambient temperature changes, the voltage magnitude and direction at both ends of the thermocouple pair are controlled by the control circuit to heat or cool the resonator, thereby maintaining a constant temperature of the surface acoustic wave resonator, eliminating temperature drift of the surface acoustic wave resonator, and improving the temperature stability and power tolerance performance of the surface acoustic wave resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be described in detail below with reference to the accompanying drawings. The above and other aspects of the present invention will become clearer and easier to understand through the detailed description made with reference to the following drawings. In the accompanying drawings: Figure 1 Flowchart of a method for preparing a silicon-based constant temperature surface acoustic wave filter provided in Example 1 of the present invention; Figure 2 A specific process flow chart of the method for preparing a silicon-based constant temperature surface acoustic wave filter provided in Example 1 of the present invention; Figure 3 This is a schematic structural diagram of a silicon-based constant temperature surface acoustic wave filter provided in the second embodiment of the present invention.

[0019] Among them, 100, silicon-based constant temperature surface acoustic wave filter, 1, silicon substrate, 2, n-type thermocouple pair, 3, p-type thermocouple pair, 4, dielectric layer, 5, thermocouple pair interconnection layer, 6, passivation adhesion layer, 7, acoustic layer, 8, first groove, 9, second groove, 10, first electrical interconnection layer, 11, second electrical interconnection layer, 12, interdigital structure. DETAILED DESCRIPTION

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of the application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0021] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Example 1 See also Figure 1-Figure 2 As shown, an embodiment of the present invention provides a method for preparing a silicon-based constant temperature surface acoustic wave filter 100, the preparation method comprising the following steps: Step S1: Select a silicon substrate 1 and perform single crystal silicon ion implantation on the silicon substrate 1 to form an n-type thermocouple pair 2 and a p-type thermocouple pair 3. The positions of the n-type thermocouple pair 2 and the p-type thermocouple pair 3 on the silicon substrate 1 are not limited, and the positions of the n-type thermocouple pair 2 and the p-type thermocouple pair 3 can be interchanged.

[0024] Specifically, an n-type thermocouple pair 2 and a p-type thermocouple pair 3 are formed by directly injecting single-crystal silicon ions into the silicon substrate 1, and a thermoelectric stack constant temperature structure of a semiconductor thermocouple pair based on the Peltier effect and the Seebeck effect is provided under the filter. This can ensure that the device is continuously cooled by the thermopile under high-power working conditions, which not only reduces the temperature drift, but also improves the power tolerance of the device.

[0025] The Peltier effect is based on the physical principle that charge carriers moving from higher energy levels to lower energy levels in different materials release excess heat, while the reverse direction requires heat absorption from the outside world. When current flows through a loop composed of n-type and p-type semiconductors, one junction absorbs heat while the other releases it. This effect is reversible; reversing the direction of the current also changes the junction that absorbs and releases heat.

[0026] The Seebeck effect, also known as the first thermoelectric effect, refers to the thermoelectric phenomenon in which a voltage difference between two different conductors or semiconductors is caused by a temperature difference. The direction of the thermoelectric potential is generally defined as electrons flowing from negative to positive at the hot end. In a circuit consisting of two metals A and B, if the temperatures of the two contact points are different, a current will flow in the circuit, called a thermoelectric current. The corresponding electromotive force is called the thermoelectric potential, and its direction depends on the direction of the temperature gradient.

[0027] Step S2: Forming a dielectric layer 4 on the upper surface of the silicon substrate 1. The dielectric layer 4 completely covers the silicon substrate 1, the n-type thermocouple pair 2, and the p-type thermocouple pair 3. The dielectric layer 4 can provide passivation, protection, and insulation for the upper surfaces of the silicon substrate 1, the n-type thermocouple pair 2, and the p-type thermocouple pair 3.

[0028] Step S3: perform a first windowing on the dielectric layer 4 to expose the n-type thermocouple pair 2 and the p-type thermocouple pair 3, and fabricate a thermocouple pair interconnection layer 5 at the first windowing position to connect the n-type thermocouple pair 2 and the p-type thermocouple pair 3 to form a path.

[0029] Step S4: Form a passivation adhesion layer 6 on the surface of the dielectric layer 4 away from the silicon substrate 1, completely covering the dielectric layer 4 and the thermocouple interconnect layer 5. Forming the passivation adhesion layer 6 can isolate the underlying electrical signal and increase the bonding and adhesion strength of the piezoelectric layer.

[0030] Step S5 : forming an acoustic layer 7 on a surface of the passivation adhesion layer 6 away from the silicon substrate 1 , and completely covering the passivation adhesion layer 6 .

[0031] The acoustic waveguide circuit is formed by directly depositing the acoustic layer 7 on the surface of the silicon substrate 1 or cooperating with structures such as an interdigital transducer (IDT) and a reflection grating.

[0032] In addition, the material density, elastic modulus and other parameters of the acoustic layer 7 determine the propagation velocity of the surface acoustic wave to satisfy the following relationship: v = ρC ,in C is the elastic constant, ρ By designing the acoustic layer 7 with different materials or thicknesses, the speed of the sound wave can be adjusted, thereby controlling the center frequency and bandwidth of the filter.

[0033] The design of the acoustic layer 7 directly determines the core indicators of the SAW filter, such as the frequency range, bandwidth, and insertion loss. By precisely controlling the propagation path and characteristics of the sound waves, frequency-selective filtering of electrical signals is achieved. This is a key technical link in fields such as RF front-ends and sensors.

[0034] Step S6: Perform a second windowing downward from the surface of the acoustic layer 7 to form a first groove 8 and a second groove 9 for respectively exposing the n-type thermocouple pair 2 and the p-type thermocouple pair 3. The positions of the first windowing and the second windowing are different.

[0035] Step S7: Form a first electrical interconnection layer 10 and a second electrical interconnection layer 11 in the first groove 8 and the second groove 9, respectively, so that the first electrical interconnection layer 10 extends along the inner groove wall of the first groove 8 and is electrically connected to the n-type thermocouple pair 2, and the second electrical interconnection layer 11 extends along the inner groove wall of the second groove 9 and is electrically connected to the p-type thermocouple pair 3. Furthermore, an interdigitated structure 12 is formed on the surface of the acoustic layer 7 away from the silicon substrate 1, thereby obtaining a silicon-based constant-temperature surface acoustic wave filter 100. The first electrical interconnection layer 10 and the second electrical interconnection layer 11 are formed by depositing them in the first groove 8 and the second groove 9, respectively. The first electrical interconnection layer 10 and the second electrical interconnection layer 11 are used to connect to external electrical equipment, thereby facilitating the provision of electrical signals, etc., to the surface acoustic wave filter.

[0036] Optionally, the first electrical interconnection layer 10 and the second electrical interconnection layer 11 completely cover the first groove 8 and the second groove 9 respectively, and the first electrical interconnection layer 10 and the second electrical interconnection layer 11 also extend to the surface of the acoustic layer 7 away from the silicon substrate 1, making conduction more convenient.

[0037] In a specific implementation, a silicon substrate 1 is selected and single crystal silicon ion implantation is performed on the silicon substrate 1 to form an n-type thermocouple pair 2 and a p-type thermocouple pair 3 respectively; a dielectric layer 4 is formed on the upper surfaces of the silicon substrate 1, the n-type thermocouple pair 2 and the p-type thermocouple pair 3; a window is opened on the dielectric layer 4 to expose the n-type thermocouple pair 2 and the p-type thermocouple pair 3, and a thermocouple pair interconnection layer 5 is formed to connect the n-type thermocouple pair 2 and the p-type thermocouple pair 3 to form a path; a dielectric layer 4 is formed away from the silicon substrate 1 A passivation adhesion layer 6 is formed on the surface of the passivation adhesion layer 6 away from the silicon substrate 1; an acoustic layer 7 is formed on the surface of the passivation adhesion layer 6 away from the silicon substrate 1; a first groove 8 and a second groove 9 are opened in the acoustic layer 7 to expose the n-type thermocouple pair 2 and the p-type thermocouple pair 3, respectively; a first electrical interconnection layer 10 and a second electrical interconnection layer 11 are formed in the first groove 8 and the second groove 9, respectively; and an interdigital structure 12 is formed on the surface of the acoustic layer 7 away from the silicon substrate 1, thereby obtaining a silicon-based constant-temperature surface acoustic wave filter 100. The silicon-based constant-temperature surface acoustic wave filter 100 is formed by implanting single-crystal silicon ions into the silicon substrate 1 to form the n-type thermocouple pair 2 and the p-type thermocouple pair 3, respectively. When the ambient temperature changes, the voltage across the thermocouple pair is controlled by a control circuit to heat or cool the resonator, thereby maintaining a constant temperature of the surface acoustic wave resonator, eliminating temperature drift of the surface acoustic wave resonator, and improving the temperature stability and power tolerance of the surface acoustic wave resonator.

[0038] In this embodiment, in step S1, the doping concentration of the single crystal silicon ions used to make the n-type thermocouple pair 2 and the p-type thermocouple pair 3 is greater than or equal to 1×10 19 cm -3 The thickness of the n-type thermocouple pair 2 and the p-type thermocouple pair 3 formed by implanting the single crystal silicon ions are both 1um-4um.

[0039] To ensure ohmic contact (which would become a normal resistor) and subsequent connection between the metal and silicon substrate 1, the thermocouple pair must be connected to the external circuit via electrode leads. Heavy doping can form a low-barrier ohmic contact between the semiconductor and the metal electrode (avoiding the rectification effect caused by the Schottky barrier), reducing contact resistance. If the doping concentration is insufficient, a high-resistance barrier may form at the contact interface, resulting in an increase in the series resistance of the entire thermocouple pair and increased power loss.

[0040] in, The above doping concentration and depth of 1~4 μm are the balance points for optimizing the performance of the thermocouple in the three aspects of "electricity, heat and structure". It not only ensures high carrier transport efficiency, but also achieves the unity of temperature difference maintenance and process feasibility through thickness control. It is a key design parameter for improving thermoelectric power generation efficiency and device reliability.

[0041] In this embodiment, the thickness of the n-type thermocouple pair 2 and the p-type thermocouple pair 3 are both 2 μm. When the depth of the n-type thermocouple pair 2 and the p-type thermocouple pair 3 are both 2 μm, the constant temperature structure of the thermopile formed by the n-type thermocouple pair 2 and the p-type thermocouple pair 3 can ensure that the device is continuously cooled by the thermopile under high-power operating conditions, which not only reduces temperature drift but also improves the power tolerance of the device.

[0042] In this embodiment, in step S2, the dielectric layer 4 is made of SiN (silicon nitride) or SiO2 (silicon dioxide). Silicon nitride and silicon dioxide dielectric layers 4 in surface acoustic wave filters achieve comprehensive optimization of filter frequency response, loss, and reliability through three core functions: acoustic property regulation, structural protection, and process compatibility. Material selection requires careful consideration of the application frequency band (low / high frequency), environmental requirements (temperature, humidity), and cost targets, taking into account properties such as acoustic velocity, impedance, and mechanical strength.

[0043] In this embodiment, in step S5, the acoustic layer 7 is manufactured by any one of a SiO2 hydrophilic low-temperature bonding process, a SiO2 hydrophilic BCB bonding process, and a deposition process.

[0044] Among them, the SiO2 hydrophilic low-temperature bonding interface has no intermediate layer and high bonding strength (>20MPa). SiO2 itself has good chemical stability and can be used as an acoustic insulation layer. In the low temperature range of 110-150℃, the dehydration condensation rate of hydroxyl groups is moderate, which can form sufficient covalent bonds while avoiding thermal stress cracking of the substrate due to excessive temperature. First, the two silicon wafers to be bonded are immersed in water for hydrophilic treatment. The water adsorbed on the wafer surface destroys the Si-O-Si bond on the silicon wafer surface and forms OH bonds with water. Then, at 110-150℃, the two wafers with OH bonds after hydrophilic treatment can undergo a polymerization reaction to produce water and Si-O bonds, achieving bonding.

[0045] The hydrophilic SiO2 BCB bonding process has low acoustic velocity and density. As acoustic layer 7, it provides "acoustic impedance buffering," reducing surface acoustic wave reflections, making it particularly suitable for low-frequency surface acoustic wave filters. The BCB bonding process typically involves a staged temperature increase: first, from room temperature to 100-150°C over 30 minutes, then holding for 10-15 minutes. The temperature is then raised to a curing temperature of 200-275°C, held for 30-60 minutes, and then naturally cooled to room temperature.

[0046] The density and elastic constants of SiO2 films produced by the deposition process are stable. Stress can be controlled by adjusting deposition parameters (such as temperature and pressure), minimizing interference with surface acoustic wave filter propagation. The deposition process typically uses plasma-enhanced chemical vapor deposition, with temperatures typically controlled between 80 and 200°C. By controlling conditions such as the supply rates of the silicon and oxygen sources, high-quality, stable SiO2 films can be formed at relatively low temperatures.

[0047] In this embodiment, the acoustic layer 7 is made of a piezoelectric material layer, and the piezoelectric material layer is any one of lithium niobate, lithium tantalate, aluminum nitride, and PZT.

[0048] Among them, lithium niobate ( ) has high piezoelectric coefficient, high acoustic velocity, wide-band adaptability and high thermal stability; by rationally utilizing the anisotropy and physical properties of lithium niobate, SAW filters can achieve high-performance signal processing in fields such as communications and sensing.

[0049] In this embodiment, in step S6, the acoustic layer 7 is subjected to the second windowing using a reactive ion etching process to form the first groove 8 and the second groove 9. Windowing is performed by using a reactive ion etching process (RIE), which can achieve a synergistic effect of physics and chemistry; ions bombard the surface vertically under electric field constraints to form grooves with steep sidewalls, thus avoiding lateral drilling by wet etching; and precise control capabilities. In addition, by defining the size, shape, and position of the grooves, the geometric design requirements of the device are met. Selective etching is used to avoid damage to the underlying material and ensure the compatibility of the multi-layer structure. By regulating the etching parameters, the electrical, acoustic, or mechanical properties of the device are improved. Its advantage lies in balancing mass production efficiency and precision control, and it is an indispensable key process in semiconductor devices.

[0050] In this embodiment, in step S7, the thickness of the first electrical interconnect layer 10 and the second electrical interconnect layer 11 is less than or equal to 0.5 μm; the thickness of the interdigital structure 12 is greater than or equal to 1.0 μm. By setting different thicknesses, costs can be effectively reduced. The interconnect layer is thinned to accommodate high-frequency signals and multi-layer integration; the interdigital structure 12 is thickened to reduce resistive losses and enhance acoustic-electrical coupling. The thickness difference between the two complements each other, jointly supporting the high-performance operation of micro-nanosystems such as SAW filters and thermoelectric devices.

[0051] In this embodiment, in step S7, the interdigital structure 12, the first electrical interconnect layer 10, and the second electrical interconnect layer 11 are all made of aluminum, titanium-aluminum alloy, or a laminate of aluminum and titanium-aluminum alloy. This further compensates for the shortcomings of pure aluminum in adhesion and mechanical strength, making it a preferred electrode material for micro-nano devices such as SAW filters. This allows the interdigital structure 12 to exhibit high acoustic-electrical coupling and low resistance. The first electrical interconnect layer 10 and the second electrical interconnect layer 11 exhibit high adhesion and compatibility with multi-layer wiring.

[0052] Example 2 See also Figure 3 As shown, an embodiment of the present invention provides a silicon-based temperature-controlled surface acoustic wave filter 100 , which is manufactured based on the above-mentioned method for manufacturing the silicon-based temperature-controlled surface acoustic wave filter 100 .

[0053] Specifically, the silicon-based constant-temperature surface acoustic wave filter 100 includes a silicon substrate 1, an n-type thermocouple pair 2 and a p-type thermocouple pair 3 formed on the silicon substrate 1 at intervals, a dielectric layer 4 stacked on the upper surface of the silicon substrate 1, a window formed in the dielectric layer 4 and a thermocouple pair interconnection layer 5 mounted thereon, a passivation adhesion layer 6 stacked on the upper surface of the dielectric layer 4, an acoustic layer 7 stacked on the passivation adhesion layer 6, a first groove 8 and a second groove 9 formed through the acoustic layer 7, a first electrical interconnection layer 10 and a second electrical interconnection layer 11 mounted within the first groove 8 and the second groove 9, respectively, and an interdigital structure 12 stacked and fixed to the surface of the acoustic layer 7 away from the silicon substrate 1. The first groove 8 and the second groove 9 are formed through the acoustic layer 7, the passivation adhesion layer 6, and the dielectric layer 4 in sequence, and are connected to the n-type thermocouple pair 2 and the p-type thermocouple pair 3, respectively. In this way, by implanting single crystal silicon ions into the silicon substrate 1, an n-type thermocouple pair 2 and a p-type thermocouple pair 3 are formed respectively; when the ambient temperature changes, the voltage magnitude and direction at both ends of the thermocouple pair are controlled by the control circuit to heat or cool the resonator, thereby maintaining a constant temperature of the surface acoustic wave resonator, eliminating temperature drift of the surface acoustic wave resonator, and improving the temperature stability and power tolerance performance of the surface acoustic wave resonator.

[0054] It should be noted that the various embodiments described above with reference to the accompanying drawings are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Those skilled in the art should understand that any modifications or equivalent substitutions to the present invention that do not depart from the spirit and scope of the present invention are intended to be encompassed within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include the plural form, and vice versa. Furthermore, unless otherwise specified, all or part of any embodiment may be used in combination with all or part of any other embodiment.

Claims

1. A method for preparing a silicon-based constant temperature surface acoustic wave filter, characterized in that: The preparation method comprises the following steps: Step S1, selecting a silicon substrate and implanting single crystal silicon ions into the silicon substrate to form an n-type thermocouple pair and a p-type thermocouple pair; Step S2, forming a dielectric layer on the upper surface of the silicon substrate, so that the dielectric layer completely covers the upper surfaces of the silicon substrate, the n-type thermocouple pair, and the p-type thermocouple pair; Step S3, performing a first windowing on the dielectric layer to expose the n-type thermocouple pair and the p-type thermocouple pair, and fabricating a thermocouple pair interconnection layer at the first windowing position to connect the n-type thermocouple pair and the p-type thermocouple pair to form a path; Step S4, forming a passivation adhesion layer on the surface of the dielectric layer away from the silicon substrate, and completely covering the dielectric layer and the thermocouple interconnection layer; Step S5, forming an acoustic layer on the surface of the passivation adhesion layer away from the silicon substrate, and completely covering the passivation adhesion layer; Step S6: performing a second windowing operation downward from the surface of the acoustic layer to form a first groove and a second groove for respectively exposing the n-type thermocouple pair and the p-type thermocouple pair; wherein the positions of the first windowing and the second windowing are different; Step S7: fabricate a first electrical interconnection layer and a second electrical interconnection layer in the first groove and the second groove, respectively, so that the first electrical interconnection layer extends in contact with the inner groove wall of the first groove and is electrically connected to the n-type thermocouple, and the second electrical interconnection layer extends in contact with the inner groove wall of the second groove and is electrically connected to the p-type thermocouple, and fabricate an interdigitated structure on the surface of the acoustic layer away from the silicon substrate to obtain a silicon-based constant temperature surface acoustic wave filter.

2. The method for preparing a silicon-based temperature-controlled surface acoustic wave filter according to claim 1, wherein: In step S1, the doping concentration of the single crystal silicon ions used to make the n-type thermocouple pair and the p-type thermocouple pair is greater than or equal to 1×10 19 cm -3 The thickness of the n-type thermocouple pair and the p-type thermocouple pair formed by implanting the single crystal silicon ions is 1um-4um.

3. The method for preparing a silicon-based temperature-controlled surface acoustic wave filter according to claim 2, wherein: The thickness of the n-type thermocouple pair and the p-type thermocouple pair are both 2 μm.

4. The method for preparing a silicon-based constant temperature surface acoustic wave filter according to claim 1, wherein: In step S2, the dielectric layer is made of SiN material or SiO2 material.

5. The method for preparing a silicon-based temperature-controlled surface acoustic wave filter according to claim 1, wherein: In the step S5, the process for manufacturing the acoustic layer is any one of a SiO2 hydrophilic low-temperature bonding process, a SiO2 hydrophilic BCB bonding process, or a deposition process.

6. The method for preparing a silicon-based constant temperature surface acoustic wave filter according to claim 5, wherein: The acoustic layer is made of a piezoelectric material, which is any one of lithium niobate, lithium tantalate, aluminum nitride and PZT.

7. The method for preparing a silicon-based constant temperature surface acoustic wave filter according to claim 1, wherein: In the step S6, the acoustic layer is subjected to the second windowing process using a reactive ion etching process to form the first groove and the second groove.

8. The method for preparing a silicon-based temperature-controlled surface acoustic wave filter according to claim 1, wherein: In step S7, the thickness of the first electrical interconnection layer and the second electrical interconnection layer is less than or equal to 0.5 um; and the thickness of the interdigital structure is greater than or equal to 1.0 um.

9. The method for preparing a silicon-based constant temperature surface acoustic wave filter according to claim 1, wherein: In step S7, the materials of the interdigital structure, the first electrical interconnection layer, and the second electrical interconnection layer are all made of aluminum, titanium-aluminum alloy, or any one of aluminum and titanium-aluminum alloy laminates.

10. A silicon-based constant temperature surface acoustic wave filter, characterized in that: The silicon-based constant temperature surface acoustic wave filter is manufactured based on the method for preparing a silicon-based constant temperature surface acoustic wave filter according to any one of claims 1 to 9.

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