Selective working Lamb wave filter based on temperature compensation and preparation method thereof

Abstract

The invention discloses a selective working Lamb wave filter based on temperature compensation and a preparation method thereof, relates to a semiconductor technology, and aims to solve the problem that a passive device controlled by a temperature switch is lacked in the prior art. Comprising a series resonator and a parallel resonator which are arranged on a piezoelectric layer; the series resonator is connected in series between the first signal end and the second signal end, and the parallel resonator is connected in parallel between the second signal end and the ground; the temperature compensation layer is deposited on the surface of the piezoelectric layer; the temperature compensation layer is located at a position corresponding to the series resonator or the parallel resonator; the temperature frequency coefficient value of the temperature compensation layer and the temperature frequency coefficient value of the piezoelectric layer are opposite in positive and negative, and the temperature compensation layer is used for increasing the sensitive degree of the filtering characteristic to the temperature. The passive device has the advantages that the technical prejudice in the technical field is overcome, the temperature parameters originally needing to be filtered out as noise are sensitively amplified and used for the switch attribute of the passive device, and the passive device based on the temperature parameters as switch control is prepared.

Description

Technical Field

[0001] The present invention relates to semiconductor technology, and in particular to a temperature-compensated selectively operating Lamb wave filter and a preparation method thereof. Background Art

[0002] With the rapid development of fields such as information security, the Internet of Things, cold-chain transportation, and intelligent control, more and more application scenarios have put forward clear requirements for "temperature activation" or "environmental triggering" functions. In encrypted communication equipment, in order to prevent the device from starting under unauthorized conditions, the temperature detection module is often used in conjunction with the control logic to determine whether the communication signal transmission is allowed. In identity authentication systems, some high-security access control or wearable devices achieve "contact activation" by detecting body temperature to determine the authenticity of the user. In IoT scenarios, especially sensor terminals used in environments such as fire warning and hazardous materials storage, it is necessary to automatically start the communication module when a high-temperature event occurs. In cold-chain transportation, it is necessary to record or identify whether the goods have been exposed to over-temperature for product safety tracking. In industrial control systems, some precision equipment must also be allowed to start only after reaching the set temperature to prevent performance damage caused by improper operation at low temperatures.

[0003] Currently, most of these applications rely on traditional temperature detection and control circuits, such as microcontroller units (MCUs) combined with thermistors, digital temperature sensors, thermal switches, or electronic temperature recording tags. Although these methods are mature, they generally have problems such as complex system structure, multiple response paths, strong dependence on power supply, and high power consumption. For example, in the fields of communications and access control, temperature signals need to be sensed, converted, and judged before controlling the signal path, which results in logical delays and security vulnerabilities. In IoT and cold chain applications, the sensor module and communication module need to operate in coordination, which increases hardware costs and power consumption. Some irreversible temperature-changing tags, although simple in structure, have only single information and cannot achieve linkage control and remote feedback.

[0004] To meet the growing demand for low power consumption, miniaturization, and high safety, some research has begun to focus on passive or semi-passive structured device solutions. Against this backdrop, devices based on Lamb waves have gradually attracted attention. Lamb waves are a type of elastic wave that propagates along thin plates. They are multimodal, multi-band, fast, and have concentrated waveguide energy, making them suitable for high-sensitivity sensing and micro-integrated systems. Lamb wave devices, particularly in the fields of tunable filtering, wireless sensing, and micro-resonators, show great potential due to their excellent frequency selectivity, high quality factor, and process scalability.

[0005] Currently, there are no publications on passive devices that use temperature parameters as switch controls. Summary of the Invention

[0006] Currently, research on Lamb wave devices primarily focuses on frequency stability and sensor sensitivity, with their temperature characteristics being treated as noise sources and compensated for. However, the modal distribution and frequency response of Lamb waves are also predictable to temperature changes. Through material design and structural control, temperature response characteristics of different modes can be achieved, thus creating the possibility of constructing a temperature-selective operating mechanism. The main purpose of this invention is to couple this structural response characteristic with temperature changes so that the device automatically enters the operating or shut-down state when the temperature reaches a specific threshold, especially in the context of applications that pursue extremely low power consumption, a simple structure, and a self-activating mechanism.

[0007] The present invention discloses a selectively operating Lamb wave filter based on temperature compensation, including a series resonator and a parallel resonator arranged on a piezoelectric layer; the series resonator is connected in series between a first signal terminal and a second signal terminal, and the parallel resonator is connected in parallel between the second signal terminal and the ground; a temperature compensation layer is provided on the surface of the piezoelectric layer; the temperature compensation layer is located at a position corresponding to the series resonator or the parallel resonator; the temperature frequency coefficient of the temperature compensation layer is opposite in sign to the temperature frequency coefficient of the piezoelectric layer, and is used to increase the sensitivity of the filtering characteristics to temperature.

[0008] The preparation method of the present invention is used to prepare the temperature-compensated selective Lamb wave filter, comprising the following steps:

[0009] S1. growing the piezoelectric layer on the substrate;

[0010] S2. Preparing a series resonator and a parallel resonator on the piezoelectric layer;

[0011] S3. The substrate is etched to expose the piezoelectric layer to form a suspended membrane-type Lamb resonator structure;

[0012] S4. Depositing the temperature compensation layer on the surface of the piezoelectric layer.

[0013] The advantage of the temperature-compensated selectively working Lamb wave filter and its preparation method described in the present invention is that they overcome the technical bias in this technical field, amplify the sensitivity of the temperature parameter that was originally to be filtered out as noise, and use it for the switching properties of passive devices to prepare a passive device based on temperature parameters as switching control. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural diagram of the selectively working Lamb wave filter described in the present invention.

[0015] Figure 2 It is a schematic diagram of the circuit principle of the selective working Lamb wave filter described in the present invention.

[0016] Figure 3 It is a schematic diagram of the cross-sectional structure of the selectively operating Lamb wave filter described in the present invention.

[0017] Figure 4 It is a schematic diagram of the response curve of the selective working Lamb wave filter in the present invention when the filtering state is turned on within the working temperature range.

[0018] Figure 5 It is a schematic diagram of the response curve of the selective working Lamb wave filter in the present invention when the filtering state is closed outside the working temperature range.

[0019] Reference numerals:

[0020] 101 - substrate, 102 - piezoelectric layer, 103 - series resonator, 104 - parallel resonator, 105 - temperature compensation layer. DETAILED DESCRIPTION

[0021] like Figures 1 to 3 As shown, the temperature-compensated selectively operating Lamb wave filter described in the present invention includes a series resonator 103 and a parallel resonator 104 disposed on a piezoelectric layer 102. The series resonator 103 is connected in series between a first signal terminal and a second signal terminal, and the parallel resonator 104 is connected in parallel between the second signal terminal and ground. The first signal terminal can serve as a signal input or output terminal, and accordingly, the second signal terminal serves as an output or input terminal adapted to the first signal terminal.

[0022] A temperature compensation layer 105 is deposited on the surface of the piezoelectric layer 102. The temperature compensation layer 105 is located at a position corresponding to the series resonator 103 or the parallel resonator 104. The temperature-frequency coefficient of the temperature compensation layer 105 has a sign opposite to that of the piezoelectric layer 102, thereby increasing the sensitivity of the filter characteristics to temperature.

[0023] The working principle of the temperature-compensated selective Lamb wave filter described in the present invention is as follows: when the series resonant frequency f s1 The parallel resonant frequency f of the parallel resonator p2 When aligned, a filter can be formed. At this time, f p2 At the point where the impedance of the parallel resonator is reduced, the signal is grounded through the parallel resonator, resulting in signal loss. Here, S21 has an obvious drop peak. At f p2 and f s1 When it is near, the impedance of the parallel resonator increases and the impedance of the series resonator decreases, so the signal can be transmitted well to the ports on both sides. Here, S21 has a bandpass region. p1At , the impedance of the series resonator increases, the signal cannot be transmitted to the ports on both sides, and S21 has an obvious decreasing peak. The above frequency response characteristics constitute the bandpass characteristics of the filter.

[0024] When a temperature compensation layer is not provided, the series resonator and the parallel resonator utilize the same materials and structural processes, and their frequency drift trends with temperature have a consistent temperature coefficient of frequency (TCF). The positive or negative value of this coefficient depends on the piezoelectric layer. Materials with negative TCF values ​​have a resonant frequency that decreases with increasing temperature; conversely, materials with negative TCF values ​​have a resonant frequency that increases with decreasing temperature. To make the filter's frequency response highly sensitive to temperature changes and achieve automatic mismatch control, the present invention introduces a temperature compensation structure into one of the resonators, causing its TCF to be opposite to that of the uncompensated state.

[0025] In this embodiment, the temperature compensation layer is positioned at the corresponding location of the series resonator, so that the frequency response of the region to temperature is opposite to that of the piezoelectric layer. Based on the same operating principle, those skilled in the art will appreciate that the temperature compensation layer can achieve the same effect when positioned at the corresponding location of the parallel resonator.

[0026] In this embodiment, the piezoelectric layer is made of LiNbO3, AlN, Al 1-x Sc x N or ε-Ga2O3; accordingly, the temperature compensation layer is selected from one of SiO2, Cr, or borosilicate glass with a positive value. Under the guidance of the present invention, those skilled in the art may select one of ST-cut quartz or lead magnesium niobate-lead titanate with a positive value for the piezoelectric layer; accordingly, the temperature compensation layer is selected from one of AlN, ZnO, and Si with a negative value when the opposite positive and negative values ​​are required.

[0027] When the temperature is within the preset range T0±ΔT, the series resonant frequency of the series resonator and the parallel resonant frequency of the parallel resonator are aligned on the frequency axis, that is, the two are at the critical points of their respective frequency responses, thereby forming a stable and matched filter passband at the set center frequency, such as Figure 4 As shown. This alignment relationship is the basis for the normal operation of the filter. It ensures that the signal can pass through the device smoothly within the target frequency range and suppresses other frequency components. When the temperature exceeds the preset range T0±ΔT, since the frequency temperature coefficients of the series resonator and the parallel resonator are in opposite directions, their operating frequencies will shift in opposite directions, resulting in the center frequency no longer matching, thereby destroying the conditions for the formation of the filter passband, changing the on-off state of the filter, and the filtering function will fail. Figure 5 shown.

[0028] To avoid electrical performance degradation, such as increased insertion loss, increased resistance, and parasitic modal interference, as well as interface delamination or cracking caused by material thermal expansion coefficient mismatch, and the combined high-temperature process stress that may cause metal electrode deformation or even fracture, directly affecting device accuracy and long-term stability, the temperature compensation layer 105 is preferably disposed on the surface of the piezoelectric layer 102 away from the resonator.

[0029] The preparation method of the present invention is used to prepare the temperature-compensated selective Lamb wave filter, comprising the following steps:

[0030] S1. Growing the piezoelectric layer 102 on the substrate 101 .

[0031] S2 . Fabricate a series resonator 103 and a parallel resonator 104 on the piezoelectric layer 102 .

[0032] S3. Etching the substrate 101 to expose the piezoelectric layer 102 and form a suspended membrane Lamb resonator structure.

[0033] S4. Depositing the temperature compensation layer 105 on the surface of the piezoelectric layer 102 .

[0034] In this embodiment, the growth process, etching process, and deposition process all adopt conventional processes in the prior art. The technical improvement is that the piezoelectric layer 102 and the temperature compensation layer 105 TCF are made of inverted positive and negative materials.

[0035] Those skilled in the art can make various other corresponding changes and deformations based on the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A temperature-compensated selectively operating Lamb wave filter, comprising a series resonator (103) and a parallel resonator (104) arranged on a piezoelectric layer (102); the series resonator (103) is connected in series between a first signal terminal and a second signal terminal, and the parallel resonator (104) is connected in parallel between the second signal terminal and ground; It is characterized in that A temperature compensation layer (105) is deposited on the surface of the piezoelectric layer (102); The temperature compensation layer (105) is located at a position corresponding to the series resonator (103) or the parallel resonator (104); The temperature frequency coefficient of the temperature compensation layer (105) has a value that is opposite in sign to the temperature frequency coefficient of the piezoelectric layer (102), and is used to increase the sensitivity of the filtering characteristics to temperature.

2. The temperature-compensated selective Lamb wave filter according to claim 1, characterized in that: The temperature compensation layer (105) is arranged on a surface of the piezoelectric layer (102) away from the resonator.

3. The temperature-compensated selective Lamb wave filter according to claim 1, characterized in that: The temperature frequency coefficient of the piezoelectric layer (102) is a negative value; the temperature frequency coefficient of the temperature compensation layer (105) is a positive value.

4. The temperature-compensated selective Lamb wave filter according to claim 3, characterized in that: The material of the piezoelectric layer (102) is LiNbO3, AlN, Al 1-x Sc x One of N or ε-Ga2O3.

5. The temperature-compensated selective Lamb wave filter according to claim 3, characterized in that: The material of the temperature compensation layer (105) is one of SiO2, Cr or borosilicate glass.

6. A method for preparing a temperature-compensated selective Lamb wave filter according to any one of claims 1 to 5, comprising the following steps: S1. growing the piezoelectric layer (102) on the substrate (101); S2. Preparing a series resonator (103) and a parallel resonator (104) on the piezoelectric layer (102); S3. Etching the substrate (101) to expose the piezoelectric layer (102) to form a suspended membrane Lamb resonator structure; It is characterized in that S4. Depositing the temperature compensation layer (105) on the surface of the piezoelectric layer (102).

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