Reconfigurable frequency MEMS standing wave meter based on multi-port ring junction and its preparation method

Abstract

The present invention discloses a reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction and a preparation method thereof, which is mainly composed of an annular directional coupler, a MEMS thermoelectric microwave power sensor and a MEMS variable capacitor. Two thermoelectric MEMS microwave power sensors located at the coupling port and the isolation port of the annular directional coupler respectively measure the output microwave power at the coupling port and the isolation port, thereby obtaining the magnitude of the incident microwave power and the reflected microwave power, and thus obtaining the magnitude of the standing wave ratio; six identical MEMS variable capacitors are equidistantly placed on the annular directional coupler, and different driving voltages are applied to the driving electrodes to change the height of the MEMS double-ended fixed beam, thereby changing the electrical length between the ports of the annular directional coupler, and realizing continuous tuning of the working frequency of the microwave standing wave meter. The present invention has the characteristics of miniaturization and tunability, is compatible with silicon-based CMOS technology, and is easy to integrate.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-electromechanical systems (MEMS), and in particular relates to a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction and a preparation method thereof. Background Art

[0002] The standing wave meter is a component for measuring the standing wave ratio in the microwave system. It plays a key role in the self-detection application of the microwave system module. The reconfigurable frequency MEMS standing wave meter has important research and application value in the microwave system. The MEMS standing wave meter mainly includes a microwave signal extraction part and an extracted microwave signal detection part. The microwave signal extraction part usually adopts structures such as multi-port ring junction, sampling transmission line and directional coupler; and the extracted microwave signal detection part usually adopts structures such as diode, logic circuit and thermistor. With the improvement of the integration degree of microwave systems, the size of microwave systems has become smaller and smaller, which makes it difficult to measure and dismantle the highly integrated system, and its components are easily affected by the environment and fail. Therefore, it is necessary to perform online standing wave ratio detection on high-density microwave systems. However, the existing standing wave meters have the disadvantages of large size and specific operating frequency, and cannot meet the needs of passive detection. Therefore, it is necessary to develop a passive, frequency-tunable and easy-to-integrate standing wave meter to detect the standing wave ratio of the microwave system and determine whether the microwave system is working properly. With the in-depth research of MEMS technology, it is possible to realize the standing wave meter based on MEMS technology. Summary of the invention

[0003] The purpose of the present invention is to provide a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction and a preparation method thereof, so as to solve the technical problems that the existing standing wave meters have the disadvantages of large size, specific operating frequency, and cannot meet the requirements of passive detection.

[0004] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0005] A reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction, comprising a silicon substrate and a CPW composed of an annular directional coupler and its coupling port, input port, output port and isolation port, a MEMS variable capacitor, a connecting line, a bonding block, an air bridge and two thermoelectric MEMS microwave power sensors arranged on the silicon substrate;

[0006] The CPW composed of the ring directional coupler and its coupling port, input port, output port and isolation port is placed on the silicon substrate to form the main structure of the coupler; the characteristic impedance of the coupling port, input port, output port and isolation port is 50Ω, and the characteristic impedance of the ring junction of the ring directional coupler is 70.7Ω;

[0007] The ends of the coupling port, input port, output port and isolation port are all connected to the annular directional coupling ring junction; wherein the output port and the coupling port are located on both sides of the input port, and the distance between the intersection of the output port, the coupling port and the annular directional coupling ring junction and the intersection of the input port and the annular directional coupling ring junction is a quarter wavelength; the input port and the isolation port are located on both sides of the output port, and the distance between the intersection of the input port, the isolation port and the annular directional coupling ring junction and the intersection of the output port and the annular directional coupling ring junction is a quarter wavelength; by connecting a thermoelectric MEMS microwave power sensor to the coupling port and the isolation port respectively, a micro thermoelectric MEMS integrated microwave standing wave meter is formed together;

[0008] Six MEMS variable capacitors are placed equidistantly above the annular directional coupling annular junction, and three of the MEMS variable capacitors are located between the input port and the coupling port, between the output port and the input port, and between the isolation port and the output port. The upper electrode plate of each of the MEMS variable capacitors is a MEMS double-ended clamped beam, and the lower electrode plate is a driving electrode. The MEMS double-ended clamped beam spans above the CPW signal line, and both ends are fixed to the CPW ground wires on both sides of the CPW signal line through anchor areas. Two driving electrodes are symmetrically placed on both sides of the CPW signal line below the MEMS double-ended clamped beam, and the driving electrodes are respectively led out through connecting wires and connected to the pressure welding block;

[0009] Each of the air bridges spans across the connection line, and is used to achieve electrical interconnection between CPW ground wires without the need for off-chip bonding wires;

[0010] Each of the thermoelectric MEMS microwave power sensors comprises one of the coupling port and the isolation port, two load resistors, a thermopile and a MEMS substrate membrane structure; wherein the coupling port is connected in parallel to the two load resistors, and the isolation port is connected in parallel to the other two load resistors; two identical thermopiles are respectively placed close to the load resistors at the coupling port and the isolation port, but are not in contact with the load resistors; through body etching technology, a silicon substrate is etched and thinned below the load resistors and the hot end of the thermopile to form a MEMS substrate membrane structure; the thermopile is composed of N+ polysilicon as the semiconductor arm of the thermopile and metal as the metal arm of the thermopile.

[0011] Furthermore, each thermopile is formed by four pairs of thermocouples connected in series.

[0012] Further, the six MEMS variable capacitors are identical; and the two thermoelectric MEMS microwave power sensors are identical.

[0013] The present invention also discloses a method for preparing a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction, the preparation method comprising:

[0014] Step 1, prepare silicon substrate: select high-resistance silicon as substrate;

[0015] Step 2, thermal oxidation of SiO2 dielectric layer: growing a layer of SiO2 on a silicon substrate;

[0016] Step 3, depositing polysilicon and performing N-type ion implantation: depositing a layer of polysilicon on a silicon substrate by chemical vapor deposition, and performing N-type ion implantation to form a MEMS structure;

[0017] Step 4, photolithography of polysilicon: coating the surface of the MEMS structure formed in step 3 with photoresist, removing the photoresist in the area other than the semiconductor arm of the thermopile, etching the polysilicon, and removing the photoresist in the semiconductor arm area after etching;

[0018] Step 5, coating the surface of the MEMS structure obtained in step 4 with photoresist and removing the photoresist at the location where the load resistor is to be fabricated;

[0019] Step 6, depositing TaN: depositing TaN, stripping the photoresist left in step 5, and removing the TaN on the photoresist to form a load resistor;

[0020] Step 7, sputtering and photolithography of Cr / Au layer: coating the surface of the MEMS structure formed in step 6 with photoresist, removing the photoresist where the CPW, driving electrode, connecting wire, metal arm of the thermopile and the pad are prepared, sputtering Cr / Au, and then removing the photoresist to form the CPW, connecting wire, thermoelectric MEMS microwave power sensor, pad structure and driving electrode;

[0021] Step 8, depositing and photolithography a polyimide sacrificial layer: coating a polyimide sacrificial layer on the MEMS structure obtained in step 7, photolithography the polyimide sacrificial layer, and only retaining the polyimide sacrificial layer below the air bridge and the MEMS double-end clamped beam;

[0022] Step 9, evaporating a seed layer: growing a seed layer for electroplating on the surface of the MEMS structure obtained in step 8 by evaporation, evaporating titanium / gold / titanium as the seed layer;

[0023] Step 10, coating the surface of the MEMS structure obtained in step 9 with photoresist, and removing the photoresist at the MEMS double-end clamped beam and air bridge to be prepared;

[0024] Step 11, gold electroplating: electroplating a layer of gold is performed on the surface of the seed layer. In step 9, a seed layer is evaporated on the surface of the obtained MEMS structure. However, in step 10, the seed layers except the MEMS double-ended clamped beam and the air bridge are covered with photoresist. Therefore, the electroplating here will only perform metal growth on the exposed seed layer, that is, the gold electroplating will only be performed on the surface of the seed layer at the MEMS double-ended clamped beam and the air bridge, and the residual photoresist will be removed.

[0025] Step 12, reverse etching titanium / gold / titanium: corroding the titanium / gold / titanium seed layer to completely form the MEMS double-ended clamped beam and air bridge;

[0026] Step 13, coating the back side of the silicon substrate with photoresist, and removing the photoresist prepared to form the MEMS substrate film structure on the back side of the silicon substrate;

[0027] Step 14, substrate reverse dry etching: etching the silicon substrate below the hot end of the thermopile and the load resistor, leaving a 10 μm thick silicon substrate to form a MEMS substrate membrane structure;

[0028] Step 15, release the polyimide sacrificial layer: soak in developer to remove the polyimide sacrificial layer under the MEMS double-ended clamped beam and the air bridge, soak in deionized water for a while, dehydrate with anhydrous ethanol, evaporate at room temperature, and dry.

[0029] The reconfigurable frequency MEMS standing wave meter based on multi-port annular junction and the preparation method of the present invention have the following advantages:

[0030] 1. The MEMS standing wave meter of the present invention adopts a CPW-based annular directional coupler to replace the traditional microstrip line structure, realizing the function of extracting the incident microwave power and the reflected microwave power, so that the standing wave meter has lower microwave loss in a higher frequency band, and because the signal line and the ground line are on the same plane, it is convenient to connect other devices in series and parallel.

[0031] 2. In the structural design of the present invention, six identical MEMS variable capacitors are connected in parallel on the annular directional coupler, and the electrical length of the annular junction is changed by increasing the size of these capacitors to be equivalent to its corresponding physical length, so that the structural size area becomes smaller, thereby realizing the miniaturization of the MEMS integrated microwave standing wave meter.

[0032] 3. In the structure of the present invention, two identical thermoelectric MEMS microwave power sensors are used to convert the extracted incident microwave power and reflected microwave power into DC thermovoltages respectively, which have zero DC power consumption, high power, high sensitivity and good linearity.

[0033] 4. The present invention controls the driving voltage on the driving electrode in the MEMS variable capacitor to change the capacitance, thereby achieving continuous tuning of the operating frequency of the standing wave meter, solving the measurement problem of a single frequency band of the traditional standing wave meter, thereby realizing the standing wave ratio measurement of the reconfigurable microwave microsystem. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic diagram of a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction of the present invention;

[0035] Figure 2 It is an AA cross-sectional view of the reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction of the present invention;

[0036] Figure 3 It is a BB cross-sectional view of the reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction of the present invention;

[0037] Explanation of the marks in the figure: 1. CPW; 2. MEMS variable capacitor; 3. MEMS double-ended clamped beam; 4. Lower plate; 5. Air bridge; 6. Connecting wire; 7. Thermoelectric MEMS microwave power sensor; 8. Semiconductor arm; 9. Metal arm; 10. Load resistor; 11. Ring directional coupler; 12. Bonding block; 13. Silicon substrate; 14. SiO2 dielectric layer; 15. MEMS substrate membrane; 16-1. Coupling port; 16-2. Input port; 16-3. Output port; 16-4. Isolation port. DETAILED DESCRIPTION

[0038] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction and a preparation method of the present invention in conjunction with the accompanying drawings.

[0039] The specific implementation scheme of the reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction of the present invention is as follows:

[0040] The reconfigurable frequency MEMS standing wave meter based on multi-port annular junction adopts high-resistance silicon as substrate, and a CPW 1 composed of an annular directional coupler 11 and its coupling port 16-1, input port 16-2, output port 16-3 and isolation port 16-4, six MEMS variable capacitors 2, connecting wires 6, bonding blocks 12, air bridges 5 and two thermoelectric MEMS microwave power sensors 7 are arranged on the silicon substrate 13; a CPW composed of an annular directional coupler 11 and its coupling port 16-1, input port 16-2, output port 16-3 and isolation port 16-4 1 is placed on the silicon substrate 13 to form the main structure of the coupler; wherein the characteristic impedances of the coupling port 16-1, the input port 16-2, the output port 16-3 and the isolation port 16-4 are all 50Ω, and the characteristic impedance of the ring junction of the ring directional coupler 11 is 70.7Ω; the ends of the coupling port 16-1, the input port 16-2, the output port 16-3 and the isolation port 16-4 are all connected to the ring junction; wherein the output port 16-3 and the coupling port 16-1 are located on both sides of the input port 16-2, and the distance between the intersection of the output port 16-3 and the coupling port 16-1 and the ring junction and the intersection of the input port 16-2 and the ring junction is a quarter wavelength; the input port 16-2 and the isolation port 16-4 are located on both sides of the output port 16-3, and the distance between the intersection of the input port 16-2 and the isolation port 16-4 and the ring junction and the intersection of the output port 16-3 and the ring junction is a quarter wavelength;

[0041] Six MEMS variable capacitors 2 are equidistantly placed above the annular junction, and three of the MEMS variable capacitors 2 are located between the input port 16-2 and the coupling port 16-1, between the output port 16-3 and the input port 16-2, and between the isolation port 16-4 and the output port 16-3. The upper plate and the lower plate of each of the MEMS variable capacitors 2 are respectively a MEMS double-ended clamped beam 3 and a driving electrode 4. The MEMS double-ended clamped beam 3 spans above the CPW 1 signal line and its two ends are respectively fixed to the CPW 1 ground wire on both sides of the CPW 1 signal line through anchor areas. Two driving electrodes 4 are symmetrically placed on both sides of the CPW 1 signal line below the MEMS double-ended clamped beam 3. The driving electrodes 4 are respectively led out through leads 6 and connected to the pressure welding block 12. By applying a driving voltage to the pressure welding block 12, based on the principle of electrostatics, the spacing between the MEMS double-ended clamped beam 3 and the CPW 1 signal line will change continuously, thereby achieving different capacitance values ​​under different driving voltages, that is, the electrical length of the annular junction can be continuously changed, thereby tuning the frequency.

[0042] The thermoelectric MEMS microwave power sensor 7 is located at the end of the coupling port 16-1 and the isolation port 16-4. Each of the thermoelectric MEMS microwave power sensors 7 includes one of the coupling port 16-1 or the isolation port 16-4, two load resistors 10, a thermopile and a MEMS substrate film 15 structure; wherein the coupling port 16-1 is connected in parallel to the two load resistors 10, and the isolation port 16-4 is connected in parallel to the other two load resistors 10. The resistance value of each load resistor 10 is 100Ω. Two identical thermopiles are placed close to the load resistors at the coupling port 16-1 and the isolation port 16-4, respectively, but not in contact with the load resistor 10. wherein each thermopile is composed of four pairs of thermocouples connected in series. when the load resistor 10 absorbs microwave power, heat is generated, and the temperature of the end of the thermopile close to the load resistor 10 rises, and this end is called the hot end of the thermopile, while the temperature of the other end of the thermopile away from the load resistor 10 remains almost unchanged, which is the ambient temperature, and is called the cold end of the thermopile. When the load resistor 10 absorbs microwave power, it generates heat, causing the temperature of the hot and cold ends of the thermopile to be different. Based on the Seebeck effect, the thermopile generates an output thermovoltage. In order to improve the efficiency of heat transmission from the load resistor 10 to the hot end of the thermopile, and thus increase the temperature difference between the hot and cold ends of the thermopile, the silicon substrate is etched and thinned under the load resistor and the hot end of the thermopile by body etching technology to form a MEMS substrate film 15 structure. The thermopile is composed of N+ polysilicon as the semiconductor arm 8 of the thermopile and metal as the metal arm 9 of the thermopile.

[0043] The present invention also discloses a method for preparing a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction, the method comprising:

[0044] (1) Preparing a silicon substrate 13: Selecting high-resistance silicon as the substrate;

[0045] (2) Thermal oxidation of SiO2 dielectric layer 14: growing a layer of SiO2 on silicon substrate 13;

[0046] (3) Depositing polysilicon and performing N-type ion implantation: depositing a layer of polysilicon on the silicon substrate 13 by chemical vapor deposition, and performing N-type ion implantation;

[0047] (4) Photolithography of polysilicon: coating the surface of the MEMS structure obtained in step 3 with photoresist, removing the photoresist from the area other than the semiconductor arm 8 of the thermopile, etching the polysilicon, and then removing the photoresist;

[0048] (5) coating the surface of the MEMS structure obtained in step 4 with photoresist and removing the photoresist at the location where the load resistor 10 is to be fabricated;

[0049] (6) Depositing TaN: Depositing TaN, stripping the photoresist left in step 5, and removing the TaN on the photoresist, to form a load resistor 10;

[0050] (7) Sputtering and photolithography of Cr / Au layer: applying photoresist, removing the photoresist where CPW 1, driving electrode 4, connecting wire 6, metal arm 9 of thermopile and pad 12 are prepared, sputtering Cr / Au, and then removing the photoresist to form CPW 1, connecting wire 6, thermoelectric MEMS microwave power sensor 7, pad 12 structure and driving electrode 4;

[0051] (8) Depositing and photolithography a polyimide sacrificial layer: coating a polyimide sacrificial layer on the surface of the MEMS structure obtained in step 7, and photolithography the polyimide sacrificial layer, leaving only the polyimide sacrificial layer below the air bridge 5 and the MEMS double-end clamped beam 3;

[0052] (9) Evaporation of seed layer: growing a seed layer for electroplating by evaporation, evaporating titanium / gold / titanium as a seed layer;

[0053] (10) coating photoresist and removing the photoresist on the MEMS double-ended clamped beam 3 and the air bridge 5 to be manufactured;

[0054] (11) Gold electroplating: electroplating a layer of gold and removing the residual photoresist;

[0055] (12) Reverse etching of titanium / gold / titanium: etching the titanium / gold / titanium seed layer to completely form the MEMS double-ended clamped beam 3 and the air bridge 5;

[0056] (13) coating a photoresist on the back side of the silicon substrate 13, and removing the photoresist prepared to form the MEMS substrate film 15 structure on the back side of the silicon substrate 13;

[0057] (14) Substrate reverse dry etching: etching the silicon substrate 13 below the hot end of the thermopile and the load resistor 10, leaving a 10 μm thick silicon substrate 13 to form a MEMS substrate membrane 15 structure;

[0058] (15) Releasing the polyimide sacrificial layer: Soak in developer to remove the polyimide sacrificial layer below the MEMS double-ended clamped beam 3 and the air bridge 5, soak in deionized water for a while, dehydrate with anhydrous ethanol, evaporate at room temperature, and dry.

[0059] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction, characterized in that: It comprises a silicon substrate (13), and a CPW (1) arranged on the silicon substrate (13) and consisting of a ring-shaped directional coupler (11) and its coupling port (16-1), an input port (16-2), an output port (16-3) and an isolation port (16-4), a MEMS variable capacitor (2), a connecting line (6), a bonding block (12), an air bridge (5), and two thermoelectric MEMS microwave power sensors (7); A CPW (1) consisting of a ring directional coupler (11) and its coupling port (16-1), input port (16-2), output port (16-3) and isolation port (16-4) is placed on a silicon substrate (13) to form a main structure of the coupler; wherein the characteristic impedances of the coupling port (16-1), input port (16-2), output port (16-3) and isolation port (16-4) are all 50Ω, and the characteristic impedance of the ring junction of the ring directional coupler (11) is 70.7Ω; The ends of the coupling port (16-1), the input port (16-2), the output port (16-3) and the isolation port (16-4) are all connected to the annular junction of the annular directional coupler (11); wherein the output port (16-3) and the coupling port (16-1) are located on both sides of the input port (16-2), and the distance between the intersection of the output port (16-3) and the coupling port (16-1) and the annular junction of the annular directional coupler (11) and the intersection of the input port (16-2) and the annular junction of the annular directional coupler (11) is one quarter wavelength; The input port (16-2) and the isolation port (16-4) are located on both sides of the output port (16-3), and the distance between the intersection of the input port (16-2) and the isolation port (16-4) and the annular directional coupling (11) ring junction and the intersection of the output port (16-3) and the annular directional coupling (11) ring junction is a quarter wavelength; by connecting a thermoelectric MEMS microwave power sensor (7) to the coupling port (16-1) and the isolation port (16-4), a micro thermoelectric MEMS integrated microwave standing wave meter is formed together; Six MEMS variable capacitors (2) are equidistantly placed above the annular junction of the annular directional coupling (11), and three of the MEMS variable capacitors (2) are located between the input port (16-2) and the coupling port (16-1), between the output port (16-3) and the input port (16-2), and between the isolation port (16-4) and the output port (16-3). The upper electrode plate of each of the MEMS variable capacitors (2) is a MEMS double-ended fixed beam (3), and the lower electrode plate is a driving electrode (4). The MEMS double-ended fixed beam (3) spans above the CPW (1) signal line and its two ends are fixed to the CPW (1) ground line on both sides of the CPW (1) signal line through anchor areas. Two driving electrodes (4) are symmetrically placed on both sides of the CPW (1) signal line below the MEMS double-ended fixed beam (3). The driving electrodes (4) are respectively led out through connecting wires (6) and connected to the pressure welding block (12); Each of the air bridges (5) spans over the connection wire (6) to achieve electrical interconnection between the ground wires of the CPW (1) without the need for off-chip bonding wires; Each of the thermoelectric MEMS microwave power sensors (7) comprises one of a coupling port (16-1) or an isolation port (16-4), two load resistors (10), a thermopile and a MEMS substrate film (15) structure; wherein the coupling port (16-1) is connected in parallel to the two load resistors (10), and the isolation port (16-4) is connected in parallel to the other two load resistors (10); two identical thermopiles are respectively placed close to the load resistors (10) at the coupling port (16-1) and the isolation port (16-4), but are not in contact with the load resistors (10); a silicon substrate is etched and thinned below the load resistors (10) and the hot end of the thermopile by body etching technology to form a MEMS substrate film (15) structure; the thermopile is composed of a semiconductor arm (8) of the thermopile made of N+ polycrystalline silicon and a metal arm (9) of the thermopile made of metal.

2. The reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction according to claim 1 is characterized in that: Each thermopile is composed of four pairs of thermocouples connected in series.

3. The reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction according to claim 1 is characterized in that: The six MEMS variable capacitors (2) are identical; the two thermoelectric MEMS microwave power sensors (7) are identical.

4. A method for preparing a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction according to any one of claims 1 to 3, characterized in that: The preparation method is: Step 1, preparing a silicon substrate (13): selecting high-resistance silicon as the substrate; Step 2, thermally oxidizing the SiO2 dielectric layer (14): growing a layer of SiO2 on the silicon substrate (13); Step 3, depositing polysilicon and performing N-type ion implantation: depositing a layer of polysilicon on the silicon substrate (13) by chemical vapor deposition, and performing N-type ion implantation to form a MEMS structure; Step 4, photolithography of polysilicon: coating the surface of the MEMS structure formed in step 3 with photoresist, removing the photoresist in the area other than the semiconductor arm (8) of the thermopile, etching the polysilicon, and removing the photoresist in the semiconductor arm (8) area after etching; Step 5, coating the surface of the MEMS structure obtained in step 4 with photoresist and removing the photoresist at the location where the load resistor (10) is to be fabricated; Step 6, depositing TaN: depositing TaN, stripping the photoresist left in step 5, and removing the TaN on the photoresist, to form a load resistor (10); Step 7, sputtering and photolithography of Cr / Au layer: coating the surface of the MEMS structure formed in step 6 with photoresist, removing the photoresist where the CPW (1), driving electrode (4), connecting wire (6), metal arm (9) of the thermopile and pad (12) are prepared, sputtering Cr / Au, and then removing the photoresist to form the CPW (1), connecting wire (6), thermoelectric MEMS microwave power sensor (7), pad (12) structure and driving electrode (4); Step 8, depositing and photolithography a polyimide sacrificial layer: coating a polyimide sacrificial layer on the MEMS structure obtained in step 7, photolithography of the polyimide sacrificial layer, and only retaining the polyimide sacrificial layer below the air bridge (5) and the MEMS double-end clamped beam (3); Step 9, evaporating a seed layer: growing a seed layer for electroplating on the surface of the MEMS structure obtained in step 8 by evaporation, evaporating titanium / gold / titanium as the seed layer; Step 10, coating the surface of the MEMS structure obtained in step 9 with photoresist, and removing the photoresist at the MEMS double-end clamped beam (3) and the air bridge (5) to be prepared; Step 11, electroplating gold: electroplating a layer of gold on the surface of the seed layer at the MEMS double-ended clamped beam (3) and the air bridge (5), and removing the residual photoresist; Step 12, reverse etching titanium / gold / titanium: etching the titanium / gold / titanium seed layer to completely form the MEMS double-ended clamped beam (3) and the air bridge (5); Step 13, coating a photoresist on the back side of the silicon substrate (13), and removing the photoresist prepared to form a MEMS substrate film (15) structure on the back side of the silicon substrate (13); Step 14, substrate reverse dry etching: etching the silicon substrate (13) below the hot end of the thermopile and the load resistor (10), leaving a 10 μm thick silicon substrate (13) to form a MEMS substrate membrane (15) structure; Step 15, releasing the polyimide sacrificial layer: soaking in developer to remove the polyimide sacrificial layer below the MEMS double-end clamped beam (3) and the air bridge (5), soaking in deionized water for a while, dehydrating with anhydrous ethanol, volatilizing at room temperature, and drying.

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