A chip-level micro-heating structure MEMS resonator and a temperature control method thereof

Abstract

The application provides a chip-level micro-heating structure MEMS resonator and a temperature control method thereof, and belongs to the technical field of temperature adjustment of resonators. The MEMS resonator comprises a package, a thermal isolation layer, a micro-heating layer, a heat-conducting metal, a resonant structure, a temperature sensor, an oxide layer, a connecting line and an ASIC chip; the oxide layer, the micro-heating layer, the oxide layer, the heat-conducting metal and the resonant structure are sequentially stacked above the thermal isolation layer; the temperature sensor is integrated at the edge of the resonant structure; the micro-heating layer contains a thermistor; the ASIC chip is integrated with a temperature comparator, a signal processing unit, a PID controller and a micro-heating circuit; the connecting line is used for connecting the ASIC chip with the temperature sensor and the thermistor; the package is used for wrapping all devices; and a temperature control method of the MEMS resonator is also disclosed. The frequency stability of the MENS resonator is improved, and the temperature drift can be controlled within 0.5ppm; and the application is suitable for high-precision clock sources, radio frequency filters and sensors and the like.

Description

Technical Field

[0001] This invention belongs to the field of temperature regulation technology for resonators, and particularly relates to a MEMS resonator with a chip-level micro-heating structure and its temperature control method. Background Technology

[0002] Clock references are widely used in fields such as electronic information and wireless communication, determining the performance of these systems. Quartz oscillators, with their low phase noise and high temperature stability, have dominated the clock market for decades. However, their large size, high power consumption, and poor shock resistance severely limit their application in miniaturized, low-power products. Compared to traditional quartz crystal resonators, MEMS resonators offer advantages such as small size, shock and vibration resistance, high sensitivity, ease of integration, low power consumption, low electromagnetic radiation, and rapid delivery, making them highly promising and in high demand.

[0003] Traditional MEMS resonators (such as SiTime's electrostatic MEMS or TDK's piezoelectric MEMS) exhibit poor frequency stability under temperature variations, with typical temperature drift of ±20-50ppm. This necessitates external temperature compensation circuitry, such as temperature-compensated crystal oscillators (TCXOs), leading to high system complexity and increased power consumption. While oven-controlled quartz crystal oscillators (OCXOs) offer high stability (±0.01ppm), they are bulky and expensive. Electrostatic MEMS rely on algorithmic compensation, but long-term aging affects accuracy. Optimization with piezoelectric MEMS still results in higher temperature drift than quartz crystals, and performance degrades in high-temperature environments. Traditional temperature-controlled technologies require external heating modules, making integration into chip-level packaging impossible. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a MEMS resonator with a chip-level micro-heating structure and its temperature control method, achieving constant temperature control to ensure the frequency stability of the resonator.

[0005] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0006] A chip-level micro-heating structure MEMS resonator, the MEMS resonator comprising a package, a thermal isolation layer, a micro-heating layer, a thermally conductive metal, a resonant structure, a temperature sensor, an oxide layer, interconnects, and an ASIC chip;

[0007] An oxide layer, a micro-heating layer, another oxide layer, a thermally conductive metal, and a resonant structure are stacked sequentially above the thermal isolation layer. A temperature sensor is integrated at the edge of the resonant structure. A thermistor is contained in the micro-heating layer. The ASIC chip integrates a temperature comparator, a signal processing unit, a PID controller, and a micro-heating circuit. Connecting wires are used to connect the ASIC chip to the temperature sensor and the thermistor. The package encapsulates the thermal isolation layer, the micro-heating layer, the thermally conductive metal, the resonant structure, the temperature sensor, the oxide layer, the connecting wires, and the ASIC chip.

[0008] Furthermore, the resonant structure is a cantilever beam resonator made of silicon; the resonant structure includes two anchor points 201, a beam 202, a driving electrode 203 and a detection electrode 204; an anchor point 201 is connected to each end of the beam 202, and the driving electrode 203 and the detection electrode 204 are located below the beam 202.

[0009] Furthermore, the resonant structure is a bulk acoustic resonator made of piezoelectric material; the resonant structure includes a top electrode 301, a piezoelectric layer 302 and a bottom electrode 303 stacked from top to bottom; the top electrode 301 is made of molybdenum or aluminum, and the electrode is a comb structure with staggered arrangement or a segmented fan-shaped, ring-shaped or strip-shaped structure; the piezoelectric layer 302 is made of AlScN.

[0010] Furthermore, the micro-heating circuit includes a thermistor Rt, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first capacitor C1, a second capacitor C2, a first transistor T1, a second transistor T2, and an operational amplifier OP, used to heat the resonant structure.

[0011] One end of the thermistor Rt is connected to one end of the first resistor R1, the positive terminal of the operational amplifier OP, one end of the second resistor R2, one end of the third resistor R3, and one end of the fourth resistor R4. The other ends of the thermistor Rt and the third resistor R3 are connected to ground. The other ends of the first resistor R1 and the second resistor R2 are connected to the power supply voltage VCC. The other end of the fourth resistor R4 is connected to the negative terminal of the operational amplifier OP, one end of the fifth resistor R5, and one end of the first capacitor C1. The other end of the fifth resistor R5 is connected to one end of the second capacitor C2. One end of the sixth resistor R6 is connected to the output terminal of the operational amplifier OP, the other end of the first capacitor C1, and the other end of the second capacitor C2. The other end of the sixth resistor R6 is connected to the base of the first transistor T1 and the collector of the second transistor T2. One end of the seventh resistor R7 is connected to the emitter of the first transistor T1 and the base of the second transistor T2. The other end of the seventh resistor R7 and the emitter of the second transistor T2 are connected to ground. The collector of the first transistor T1 is connected to the power supply voltage VCC.

[0012] Furthermore, the first resistor R1, the second resistor R2, the third resistor R3, the thermistor Rt and the operational amplifier form a Wheatstone bridge; the fourth resistor R4, the fifth resistor R5, the first capacitor C1 and the second capacitor C2 form a feedback network to adjust the micro-heating circuit; the first transistor T1 is the heating tube, the first transistor T2 is the current-limiting transistor, and the seventh resistor R7 determines the total current of the micro-heating circuit.

[0013] Furthermore, the temperature sensor is a PN junction or resistor R temperature sensor integrated into the edge of the resonant structure; the temperature sensor is used to detect the real-time temperature of the resonant structure.

[0014] Furthermore, the micro-heating layer is a Pt or polycrystalline silicon thin film with a thickness of 50-200 nm, and is isolated by a SiO2 / Si3N4 insulating layer, making it compatible with CMOS technology. The micro-heating layer is used to heat the resonant structure according to the real-time temperature of the resonant structure collected by the temperature sensor, so that the operating temperature of the resonant structure is constant.

[0015] Furthermore, the packaging is a wafer-level vacuum package with a vacuum level of less than 1 Pa.

[0016] Furthermore, the oxide layer is made of silicon dioxide.

[0017] This invention also proposes a temperature control method for a MEMS resonator with a chip-level micro-heating structure, the method comprising the following steps:

[0018] Step S1: The temperature sensor acquires the real-time temperature of the resonant structure and sends the acquired real-time temperature to the temperature comparator;

[0019] Step S2: The temperature comparator compares the real-time temperature with the temperature threshold and sends the comparison result to the signal processing unit;

[0020] Step S3: The signal processing unit obtains a control signal as to whether the temperature needs to be increased based on the comparison result, and sends the control signal to the PID controller;

[0021] Step S4: The PID controller controls the micro-heating circuit according to the obtained control signal. When the signal indicates that heating is required, the circuit continuously generates heat under the action of current, and the temperature of the resonant structure rises. When the signal indicates that heating is not required, the circuit is turned off, the heat dissipates, and the temperature of the resonant structure decreases.

[0022] Step S5l: Repeat steps S1 to S4 until the temperature of the resonant structure remains constant.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] 1) The frequency stability of the MENS resonator of the present invention is improved, and the temperature drift can be controlled within ±0.5ppm (close to the 0CX0 level).

[0025] 2) This invention uses vacuum packaging and micro-heating technology, and the overall power consumption is less than 10mW, while the power consumption of traditional OCXO reaches 500mW.

[0026] 3) The overall package size of this invention is ≤22mm, which is a chip-level size, suitable for wearable devices and 5G modules; this invention is applicable to applications such as high-precision clock sources, RF filters, and sensors. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a MEMS resonator and temperature control provided for an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of an electrostatic MEMS resonator provided for an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of a piezoelectric MEMS resonator provided for an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the micro-heating circuit according to an embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention proposes a MEMS resonator with a chip-level micro-heating structure, such as... Figure 1 As shown, it includes a package 101, a thermal isolation layer 102, a micro heating layer 103, a thermally conductive metal 104, a resonant structure 105, a temperature sensor 106, an oxide layer 107, a connecting line 108, and an ASIC chip 109.

[0034] An oxide layer 107, a micro-heating layer 103, another oxide layer 107, a thermally conductive metal 104, and a resonant structure 105 are stacked sequentially above the thermal isolation layer 102. A temperature sensor 106 is integrated at the edge of the resonant structure 105. A thermistor is contained in the micro-heating layer 103. An ASIC chip 109 integrates a temperature comparator, a signal processing unit, a PID controller, and a micro-heating circuit. A connecting line 108 is used to connect the ASIC chip 109 to the temperature sensor 106 and the thermistor. A package 101 encapsulates the thermal isolation layer 102, the micro-heating layer 103, the thermally conductive metal 104, the resonant structure 105, the temperature sensor 106, the oxide layer 107, the connecting line 108, and the ASIC chip 109.

[0035] The packaging is a wafer-level vacuum package (WLCSP) with a vacuum level of less than 1 Pa.

[0036] The thermal insulation layer is formed of thermal insulation material and is used to prevent heat diffusion.

[0037] The micro-heating layer is a Pt (platinum) or polycrystalline silicon thin film with a thickness of 50-200 nm. It is isolated by a SiO2 / Si3N4 insulating layer and is compatible with CMOS processes.

[0038] The thermally conductive metal is a material such as gold, used to transfer heat.

[0039] The temperature sensor is a PN junction or resistor R temperature sensor integrated into the edge of the resonant structure; the temperature sensor is used to detect the real-time temperature of the resonant structure.

[0040] The micro-heating layer is used to heat the resonant structure based on the real-time temperature of the resonant structure collected by the temperature sensor, so that the operating temperature of the resonant structure remains constant.

[0041] The oxide layer is made of silicon dioxide and is generally used for isolation.

[0042] The connecting wire is made of gold and is used for connections between circuits.

[0043] The resonant structure is a cantilever beam resonator or a bulk acoustic resonator made of silicon or piezoelectric material.

[0044] Further piezoelectric materials include AlN (aluminum nitride) or AlScN (scandium-doped aluminum nitride).

[0045] This invention proposes a resonant structure as follows: Figure 2 As shown, the resonant structure is a cantilever beam resonator made of silicon; the resonant structure includes two anchor points 201, a beam 202, a driving electrode 203, and a detection electrode 204. An anchor point 201 is connected to each end of the beam 202, and the driving electrode 203 and the detection electrode 204 are located below the beam 202.

[0046] This invention also proposes another resonant structure, such as Figure 3 As shown, the resonant structure is a bulk acoustic resonator made of piezoelectric material; the resonant structure includes a top electrode 301, a piezoelectric layer 302, and a bottom electrode 303 stacked sequentially from top to bottom. The top electrode 301 is made of molybdenum (Mo) or aluminum (Al), and the electrodes are arranged in a staggered comb structure or a segmented fan-shaped, ring-shaped, or strip-shaped structure; the piezoelectric layer 302 is made of AlScN.

[0047] The ASIC chip is used to dynamically adjust the heating power.

[0048] The temperature comparator is used to compare the real-time temperature of the resonant structure detected by the temperature sensor with the temperature threshold; the signal processing unit generates the control signal for the micro-heating circuit based on the signal obtained from the temperature comparator; the PID controller is used to control the micro-heating circuit according to the control signal.

[0049] like Figure 4 As shown, the micro-heating circuit includes a thermistor Rt, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first capacitor C1, a second capacitor C2, a first transistor T1, a second transistor T2, and an operational amplifier OP, used to heat the resonant structure.

[0050] One end of the thermistor Rt is connected to one end of the first resistor R1, the positive terminal of the operational amplifier OP, one end of the second resistor R2, one end of the third resistor R3, and one end of the fourth resistor R4. The other ends of the thermistor Rt and the third resistor R3 are connected to ground. The other ends of the first resistor R1 and the second resistor R2 are connected to the power supply voltage VCC. The other end of the fourth resistor R4 is connected to the negative terminal of the operational amplifier OP, one end of the fifth resistor R5, and one end of the first capacitor C1. The other end of the fifth resistor R5 is connected to one end of the second capacitor C2. One end of the sixth resistor R6 is connected to the output terminal of the operational amplifier OP, the other end of the first capacitor C1, and the other end of the second capacitor C2. The other end of the sixth resistor R6 is connected to the base of the first transistor T1 and the collector of the second transistor T2. One end of the seventh resistor R7 is connected to the emitter of the first transistor T1 and the base of the second transistor T2. The other end of the seventh resistor R7 and the emitter of the second transistor T2 are connected to ground. The collector of the first transistor T1 is connected to the power supply voltage VCC.

[0051] The first resistor R1, the second resistor R2, the third resistor R3, the thermistor Rt and the operational amplifier form a Wheatstone bridge; the fourth resistor R4, the fifth resistor R5, the first capacitor C1 and the second capacitor C2 form a feedback network to adjust the micro-heating circuit; the first transistor T1 is the heating tube, the first transistor T2 is the current-limiting transistor, and the seventh resistor R7 determines the total current of the micro-heating circuit.

[0052] The micro-heating circuit operates as follows:

[0053] The thermistor Rt is a negative temperature coefficient thermistor. When the circuit starts, the thermistor Rt has a high resistance, and the voltage at the positive terminal of the operational amplifier OP is greater than the voltage at the negative terminal. At this time, the operational amplifier OP operates in a non-linear state, outputting a high level. This high level, through the sixth resistor R6, turns on the first transistor T1, initiating heating. As the current in the first transistor T1 increases, a voltage drop occurs across the seventh resistor R7, causing the emitter voltage of the first transistor T1 to increase as the current increases. When the emitter voltage of the first transistor T1 exceeds 0.7V, the second resistor R2 turns on, causing the base voltage of the first transistor T1 to become low. At this point, the first transistor T1 is cut off, and heating stops. Through this feedback control, the current of the micro-heating circuit stabilizes at 0.7V / R7 amperes. By adjusting the value of the seventh resistor R7, the stable heating current of the micro-heating circuit can be controlled.

[0054] After the heating current stabilizes, the resonant structure continues to heat up. The resistance of the thermistor Rt decreases as the temperature rises. Once the set temperature is exceeded (determined by the ratio of the second resistor R2 to the third resistor R3), the voltage at the positive terminal of the operational amplifier OP becomes less than the voltage at the negative terminal, the op-amp outputs a low level, the first transistor T1 is cut off, and the circuit stops heating. As the heat dissipates and the temperature decreases, the resistance of the thermistor Rt increases, and the voltage at the positive terminal of the operational amplifier OP increases, forming a closed-loop control. After reaching the set temperature, the voltage at the positive terminal of the operational amplifier OP is approximately equal to the voltage at the negative terminal, and the operational amplifier OP enters a linear operating state. The output voltage is proportional to the voltage difference between the positive and negative terminals, and this ratio is determined by the value of the fifth resistor R5 / the fourth resistor R4.

[0055] Preferably, the temperature of the resonant structure can be monitored in real time.

[0056] Preferably, the heating power of the micro-heating circuit is dynamically adjusted by a PID algorithm (a closed-loop feedback control algorithm), and the temperature fluctuation of the resonant structure is ≤ ±0.1℃.

[0057] Based on the above-mentioned chip-level micro-heating structure of MEMS resonators, this invention proposes a temperature control method for MEMS resonators with chip-level micro-heating structures, the method comprising the following steps:

[0058] Step S1: The temperature sensor acquires the real-time temperature of the resonant structure and sends the acquired real-time temperature to the temperature comparator.

[0059] Step S2: The temperature comparator compares the real-time temperature with the temperature threshold and sends the comparison result to the signal processing unit.

[0060] Step S3: The signal processing unit obtains a control signal as to whether the temperature needs to be increased based on the comparison result, and sends the control signal to the PID controller.

[0061] Step S4: The PID controller controls the micro-heating circuit according to the obtained control signal. When the signal indicates that heating is required, the circuit continuously generates heat under the action of current, and the temperature of the resonant structure rises. When the signal indicates that heating is not required, the circuit is turned off, the heat dissipates, and the temperature of the resonant structure decreases.

[0062] Step S5l: Repeat steps S1 to S4 until the temperature of the resonant structure remains constant.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A MEMS resonator with a chip-level micro-heating structure, characterized in that, The MEMS resonator includes a package, a thermal isolation layer, a micro-heating layer, a thermally conductive metal, a resonant structure, a temperature sensor, an oxide layer, connecting wires, and an ASIC chip. An oxide layer, a micro-heating layer, another oxide layer, a thermally conductive metal, and a resonant structure are stacked sequentially above the thermal isolation layer. A temperature sensor is integrated at the edge of the resonant structure. A thermistor is contained in the micro-heating layer. The ASIC chip integrates a temperature comparator, a signal processing unit, a PID controller, and a micro-heating circuit. Connecting wires are used to connect the ASIC chip to the temperature sensor and the thermistor. The package encapsulates the thermal isolation layer, the micro-heating layer, the thermally conductive metal, the resonant structure, the temperature sensor, the oxide layer, the connecting wires, and the ASIC chip.

2. The MEMS resonator with a chip-level micro-heating structure according to claim 1, characterized in that, The resonant structure is a cantilever beam resonator made of silicon; the resonant structure includes two anchor points 201, a beam 202, a driving electrode 203 and a detection electrode 204; an anchor point 201 is connected to each end of the beam 202, and the driving electrode 203 and the detection electrode 204 are located below the beam 202.

3. The MEMS resonator with a chip-level micro-heating structure according to claim 1, characterized in that, The resonant structure is a bulk acoustic resonator made of piezoelectric material; the resonant structure includes a top electrode 301, a piezoelectric layer 302 and a bottom electrode 303 stacked from top to bottom; the top electrode 301 is made of molybdenum or aluminum, and the electrode is a comb structure with staggered arrangement or a segmented fan-shaped, ring-shaped or strip-shaped structure; the piezoelectric layer 302 is made of AlScN.

4. The MEMS resonator with a chip-level micro-heating structure according to claim 1, characterized in that, The micro-heating circuit includes a thermistor Rt, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first capacitor C1, a second capacitor C2, a first transistor T1, a second transistor T2, and an operational amplifier OP, used to heat the resonant structure. One end of the thermistor Rt is connected to one end of the first resistor R1, the positive terminal of the operational amplifier OP, one end of the second resistor R2, one end of the third resistor R3, and one end of the fourth resistor R4. The other ends of the thermistor Rt and the third resistor R3 are connected to ground. The other ends of the first resistor R1 and the second resistor R2 are connected to the power supply voltage VCC. The other end of the fourth resistor R4 is connected to the negative terminal of the operational amplifier OP, one end of the fifth resistor R5, and one end of the first capacitor C1. The other end of the fifth resistor R5 is connected to one end of the second capacitor C2. One end of the sixth resistor R6 is connected to the output terminal of the operational amplifier OP, the other end of the first capacitor C1, and the other end of the second capacitor C2. The other end of the sixth resistor R6 is connected to the base of the first transistor T1 and the collector of the second transistor T2. One end of the seventh resistor R7 is connected to the emitter of the first transistor T1 and the base of the second transistor T2. The other end of the seventh resistor R7 and the emitter of the second transistor T2 are connected to ground. The collector of the first transistor T1 is connected to the power supply voltage VCC.

5. The MEMS resonator with a chip-level micro-heating structure according to claim 1, characterized in that, The first resistor R1, the second resistor R2, the third resistor R3, the thermistor Rt and the operational amplifier form a Wheatstone bridge; the fourth resistor R4, the fifth resistor R5, the first capacitor C1 and the second capacitor C2 form a feedback network to adjust the micro-heating circuit; the first transistor T1 is the heating tube, the first transistor T2 is the current-limiting transistor, and the seventh resistor R7 determines the total current of the micro-heating circuit.

6. The MEMS resonator with a chip-level micro-heating structure according to claim 1, characterized in that, The temperature sensor is a PN junction or resistor R temperature sensor integrated into the edge of the resonant structure; the temperature sensor is used to detect the real-time temperature of the resonant structure.

7. The MEMS resonator with a chip-level micro-heating structure according to claim 1, characterized in that, The micro-heating layer is a Pt or polycrystalline silicon thin film with a thickness of 50-200 nm. It is isolated by a SiO2 / Si3N4 insulating layer and is compatible with CMOS technology. The micro-heating layer is used to heat the resonant structure according to the real-time temperature of the resonant structure collected by the temperature sensor, so that the operating temperature of the resonant structure is constant.

8. The MEMS resonator with a chip-level micro-heating structure according to claim 1, characterized in that, The packaging is a wafer-level vacuum package with a vacuum level of less than 1 Pa.

9. The MEMS resonator with a chip-level micro-heating structure according to claim 1, characterized in that, The oxide layer is made of silicon dioxide.

10. A temperature control method for a MEMS resonator with a chip-level micro-heating structure, characterized in that, The method for controlling the temperature of the MEMS resonator according to any one of claims 1-9 comprises the following steps: Step S1: The temperature sensor acquires the real-time temperature of the resonant structure and sends the acquired real-time temperature to the temperature comparator; Step S2: The temperature comparator compares the real-time temperature with the temperature threshold and sends the comparison result to the signal processing unit; Step S3: The signal processing unit obtains a control signal as to whether the temperature needs to be increased based on the comparison result, and sends the control signal to the PID controller; Step S4: The PID controller controls the micro-heating circuit according to the obtained control signal. When the signal indicates that heating is required, the circuit continuously generates heat under the action of current, and the temperature of the resonant structure rises. When the signal indicates that heating is not required, the circuit is turned off, the heat dissipates, and the temperature of the resonant structure decreases. Step S5l: Repeat steps S1 to S4 until the temperature of the resonant structure remains constant.

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