CN115327236A - Reconfigurable frequency MEMS standing wave meter based on multi-port annular junction and preparation method - Google Patents

Reconfigurable frequency MEMS standing wave meter based on multi-port annular junction and preparation method Download PDF

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CN115327236A
CN115327236A CN202210985907.2A CN202210985907A CN115327236A CN 115327236 A CN115327236 A CN 115327236A CN 202210985907 A CN202210985907 A CN 202210985907A CN 115327236 A CN115327236 A CN 115327236A
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mems
port
photoresist
annular
coupling
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张志强
冯耀刚
李喆然
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Southeast University
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Southeast University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/04—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant in circuits having distributed constants, e.g. having very long conductors or involving high frequencies
    • G01R27/06—Measuring reflection coefficients; Measuring standing-wave ratio
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
    • B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
    • B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems

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Abstract

The invention discloses a reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction and a preparation method thereof. Two thermoelectric MEMS microwave power sensors positioned at a coupling port and an isolation port of the annular directional coupler respectively measure the output microwave power at the coupling port and the isolation port, so that the incident microwave power and the reflected microwave power can be obtained, and the size of the standing-wave ratio can be obtained; six same MEMS variable capacitors are respectively and equidistantly arranged on the annular directional coupler, different driving voltages are applied to the driving electrodes, and the height of the MEMS double-end fixed supporting beam can be changed, so that the electrical length between the ports of the annular directional coupler is changed, and the continuous tuning of the working frequency of the microwave standing wave meter is realized. The invention has the characteristics of miniaturization and tunability, is compatible with a silicon-based CMOS (complementary metal oxide semiconductor) process and is convenient to integrate.

Description

Reconfigurable frequency MEMS standing wave meter based on multi-port annular junction and preparation method
Technical Field
The invention belongs to the technical field of micro-electro-mechanical systems (MEMS), and particularly relates to a reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction and a preparation method thereof.
Background
The standing wave meter is a component for measuring standing wave ratio in a microwave system, plays a key role in self-detection application of a microwave system module, and has important research and application values in the microwave system. The MEMS standing wave meter mainly comprises a microwave signal extraction part and an extracted microwave signal detection part, wherein the microwave signal extraction part usually adopts structures such as a multi-port annular junction, a sampling transmission line, a directional coupler and the like; the microwave signal detection part is usually in the structure of diode, logic circuit and thermistor. Along with the improvement of the integration degree of the microwave system, the size of the microwave system becomes smaller and smaller, so that the system is difficult to measure and dismantle after being highly integrated, and the components of the system are easy to lose effectiveness due to environmental influence, so that the high-density microwave system needs to be subjected to on-line standing-wave ratio detection. However, the existing standing wave meter has the disadvantages of large volume and specific operating frequency, and cannot meet the requirement of passive detection. Therefore, there is a need to develop a passive standing wave meter with tunable operating frequency and easy integration to detect the standing wave ratio of the microwave system and determine whether the microwave system is operating normally. With the intensive research of the MEMS technology, a standing wave meter based on the MEMS technology to achieve the above functions is possible.
Disclosure of Invention
The invention aims to provide a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction and a preparation method thereof, and aims to solve the technical problems that the existing standing wave meter has the defects of large volume and specific working frequency and cannot meet the requirement of passive detection.
In order to solve the technical problems, the specific technical scheme of the invention is as follows:
a reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction comprises a silicon substrate, a CPW (capacitive micro-electromechanical systems) consisting of an annular directional coupler and a coupling port, an input port, an output port and an isolation port thereof, an MEMS variable capacitor, a connecting wire, a pressure welding block, an air bridge and two thermoelectric MEMS microwave power sensors, wherein the CPW, the MEMS variable capacitor, the connecting wire, the pressure welding block, the air bridge and the two thermoelectric MEMS microwave power sensors are arranged on the silicon substrate;
the CPW composed of the annular directional coupler and the coupling port, the input port, the output port and the isolation port thereof is placed on a silicon substrate to form a main body structure of the coupler; the characteristic impedance of the coupling port, the input port, the output port and the isolation port is 50 omega, and the characteristic impedance of the annular junction of the annular directional coupler is 70.7 omega;
the tail ends of the coupling port, the input port, the output port and the isolation port are connected with the annular directional coupling annular junction; the output port and the coupling port are positioned on two sides of the input port, and the distances between the intersection point of the output port, the coupling port and the annular directional coupling annular junction and the intersection point of the input port and the annular directional coupling annular junction are all quarter wavelengths; the input port and the isolation port are positioned on two sides of the output port, and the distances between the intersection point of the input port, the isolation port and the annular directional coupling annular junction and the intersection point of the output port and the annular directional coupling annular junction are quarter wavelengths; the coupling port and the isolation port are respectively connected with a thermoelectric MEMS microwave power sensor, so that a miniature thermoelectric MEMS integrated microwave standing wave meter is formed;
placing six MEMS variable capacitors above an annular directional coupling annular junction at equal intervals, wherein three MEMS variable capacitors are positioned between an input port and a coupling port, between an output port and the input port and between an isolation port and the output port, an upper polar plate of each MEMS variable capacitor is an MEMS double-end clamped beam, a lower polar plate of each MEMS variable capacitor is a driving electrode, the MEMS double-end clamped beam stretches across above a CPW signal line, two ends of each MEMS variable capacitor are respectively fixed on CPW ground lines on two sides of the CPW signal line through anchor areas, two driving electrodes are symmetrically placed on two sides of the CPW signal line below the MEMS double-end clamped beam, and the driving electrodes are respectively led out through connecting lines and connected with a pressure welding block;
each air bridge spans the connecting wire and is used for realizing the electrical interconnection between the CPW ground wires without an off-chip bonding wire;
each thermoelectric MEMS microwave power sensor comprises a coupling port or an isolation port, two load resistors, a thermopile and an MEMS substrate membrane structure; the coupling port is connected with two load resistors in parallel, and the isolation port is connected with the other two load resistors in parallel; two identical thermopiles are respectively and closely placed near the load resistors at the coupling port and the isolation port, but are not in contact with the load resistors; etching and thinning the silicon substrate below the load resistor and the hot end of the thermopile by a bulk etching technology to form an MEMS substrate film structure; the thermopile is composed of a semiconductor arm taking N + polysilicon as the thermopile and a metal arm taking metal as the thermopile.
Furthermore, each thermopile is formed by connecting four pairs of thermocouples in series.
Further, the six MEMS variable capacitors are identical; the two thermoelectric MEMS microwave power sensors are identical.
The invention also discloses a preparation method of the reconfigurable frequency MEMS standing wave meter based on the multi-port annular junction, which comprises the following steps:
step 1, preparing a silicon substrate: selecting high-resistance silicon as a substrate;
step 2, thermal oxidation of SiO 2 Dielectric layer: growing a layer of SiO on a silicon substrate 2 ；
Step 3, depositing polysilicon and injecting N type: depositing a layer of polycrystalline silicon on a silicon substrate in a chemical vapor deposition mode, and performing N-type ion implantation to form an MEMS structure;
step 4, photoetching the polysilicon: coating photoresist on the surface of the MEMS structure formed in the step 3, removing the photoresist in the area outside the semiconductor arm of the thermopile, etching the polysilicon, and removing the photoresist in the area of the semiconductor arm after the etching is finished;
step 5, coating photoresist on the surface of the MEMS structure obtained in the step 4 and removing the photoresist at the position where the load resistor is to be manufactured;
step 6, depositing TaN: depositing TaN, stripping the photoresist left in the step 5, and removing the TaN on the photoresist to form a load resistor;
and 7, sputtering and photoetching a Cr/Au layer: coating photoresist on the surface of the MEMS structure formed in the step 6, removing the photoresist on the positions of metal arms and pressure welding blocks for preparing the CPW, the driving electrode, the connecting wire, the thermopile, sputtering Cr/Au, and then removing the photoresist to form the CPW, the connecting wire, the thermoelectric MEMS microwave power sensor, the pressure welding block structure and the driving electrode;
and 8, depositing and photoetching a polyimide sacrificial layer: coating a polyimide sacrificial layer on the MEMS structure obtained in the step (7), photoetching the polyimide sacrificial layer, and only reserving the polyimide sacrificial layer below the air bridge and the MEMS double-end clamped beam;
step 9, evaporating the seed layer: growing a seed layer for electroplating on the surface of the MEMS structure obtained in the step 8 in an evaporation mode, and evaporating titanium/gold/titanium to serve as the seed layer;
step 10, coating photoresist on the surface of the MEMS structure obtained in the step 9, and removing the photoresist at the positions of the MEMS double-end clamped beam and the air bridge to be manufactured;
step 11, gold electroplating: electroplating a layer of gold on the surface of the seed layer, wherein a seed layer is evaporated on the surface of the obtained MEMS structure in the step 9, but because the seed layer except the MEMS double-ended clamped beam and the air bridge is covered by the photoresist in the step 10, the electroplating only carries out metal growth on the exposed seed layer, namely the gold electroplating is only carried out on the surfaces of the seed layer at the MEMS double-ended clamped beam and the air bridge, and the residual photoresist is removed;
step 12, reversely etching titanium/gold/titanium: corroding the titanium/gold/titanium seed layer to completely form the MEMS double-end clamped beam and the air bridge;
step 13, coating photoresist on the back surface of the silicon substrate, and removing the photoresist for forming the MEMS substrate film structure on the back surface of the silicon substrate;
step 14, reverse dry etching of the substrate: etching a silicon substrate at the hot end of the thermopile and below the load resistor, and reserving the silicon substrate with the thickness of 10 mu m to form an MEMS substrate membrane structure;
step 15, releasing the polyimide sacrificial layer: and soaking in a developing solution, removing the polyimide sacrificial layer below the MEMS double-end clamped beam and the air bridge, slightly soaking in deionized water, dehydrating with absolute ethyl alcohol, volatilizing at normal temperature, and drying.
The reconfigurable frequency MEMS standing wave meter based on the multi-port annular junction and the preparation method have the following advantages that:
1. the MEMS standing wave meter adopts the annular directional coupler based on the CPW to replace the traditional microstrip line structure, realizes the function of extracting the incident microwave power and the reflected microwave power, can ensure that the standing wave meter has lower microwave loss in higher frequency band, and is convenient for connecting other devices in series and in parallel because the signal line and the ground line are on the same plane.
2. In the structural design, six identical MEMS variable capacitors are respectively connected in parallel on the annular directional coupler, and the electrical length of the annular junction is changed by increasing the capacitance to be equivalent to the corresponding physical length of the annular junction, so that the structural dimension area is reduced, and the miniaturization of the MEMS integrated microwave standing wave meter is realized.
3. In the structure of the invention, two identical thermoelectric MEMS microwave power sensors are used for respectively converting the extracted incident microwave power and the reflected microwave power into direct current thermal voltages, and the thermoelectric MEMS microwave power sensors have zero direct current power consumption, high power, high sensitivity and good linearity.
4. The invention realizes the continuous tuning of the working frequency of the standing wave meter by controlling the magnitude of the driving voltage on the driving electrode in the MEMS variable capacitor to change the magnitude of the capacitance, solves the problem of measuring a single frequency band of the traditional standing wave meter, and further realizes the standing wave ratio measurement of the reconfigurable microwave micro-system.
Drawings
FIG. 1 is a schematic diagram of a multi-port ring junction based reconfigurable frequency MEMS standing wave meter of the present invention;
FIG. 2 isbase:Sub>A cross-sectional view A-A of the reconfigurable frequency MEMS standing wave meter based on the multi-port ring junction of the present invention;
FIG. 3 is a B-B cross section of the reconfigurable frequency MEMS standing wave meter based on the multi-port ring junction of the present invention;
the notation in the figure is: 1. CPW; 2. a MEMS variable capacitor; 3. fixing and supporting the beam at the two ends of the MEMS; 4. a lower polar plate; 5. an air bridge; 6. a connecting wire; 7. a thermoelectric MEMS microwave power sensor; 8. a semiconductor arm; 9. a metal arm; 10. a load resistance; 11. a ring-shaped directional coupler; 12. pressing a welding block; 13. a silicon substrate; 14. SiO 2 2 A dielectric layer; 15. a MEMS substrate film; 16-1, a coupling port; 16-2, input port; 16-3, an output port;16-4, isolating the port.
Detailed Description
In order to better understand the purpose, structure and function of the present invention, a reconfigurable frequency MEMS standing wave meter based on a multi-port ring junction and a manufacturing method thereof are described in further detail below with reference to the accompanying drawings.
The specific implementation scheme of the reconfigurable frequency MEMS standing wave meter based on the multi-port annular junction is as follows:
a reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction adopts high-resistance silicon as a substrate, and a CPW1, six MEMS variable capacitors 2, a connecting wire 6, a pressure welding block 12, an air bridge 5 and two thermoelectric MEMS microwave power sensors 7 which are composed of an annular directional coupler 11 and a coupling port 16-1, an input port 16-2, an output port 16-3 and an isolation port 16-4 thereof are arranged on a silicon substrate 13; a CPW1 consisting of the annular directional coupler 11, a coupling port 16-1, an input port 16-2, an output port 16-3 and an isolation port 16-4 is arranged on a silicon substrate 13 to form a main body structure of the coupler; the characteristic impedance of the coupling port 16-1, the input port 16-2, the output port 16-3 and the isolation port 16-4 is 50 omega, and the characteristic impedance of the annular junction of the annular directional coupler 11 is 70.7 omega; the tail ends of the coupling port 16-1, the input port 16-2, the output port 16-3 and the isolation port 16-4 are connected with the annular junction; the output port 16-3 and the coupling port 16-1 are positioned on two sides of the input port 16-2, and the distances between the intersection point of the output port 16-3, the coupling port 16-1 and the annular junction and the intersection point of the input port 16-2 and the annular junction are quarter wavelengths; the input port 16-2 and the isolation port 16-4 are positioned at two sides of the output port 16-3, and the distance between the intersection point of the input port 16-2, the isolation port 16-4 and the annular junction and the intersection point of the output port 16-3 and the annular junction is a quarter wavelength;
six MEMS variable capacitors 2 are equidistantly arranged above the annular junction, three MEMS variable capacitors 2 are positioned between an input port 16-2 and a coupling port 16-1, between an output port 16-3 and the input port 16-2 and between an isolation port 16-4 and an output port 16-3, an upper polar plate and a lower polar plate of each MEMS variable capacitor 2 are respectively an MEMS double-end clamped beam 3 and a driving electrode 4, the MEMS double-end clamped beam 3 spans above a CPW1 signal line, two ends of the MEMS double-end clamped beam are respectively fixed on CPW1 ground lines at two sides of the CPW1 signal line through anchor areas, two driving electrodes 4 are symmetrically arranged at two sides of the CPW1 signal line below the double-end MEMS clamped beam 3, and the driving electrodes 4 are respectively led out through lead wires 6 and connected with pressure welding blocks 12; by applying a driving voltage to the bonding pad 12, based on the electrostatic principle, the distance between the MEMS two-terminal clamped beam 3 and the CPW1 signal line can be continuously changed, so that different capacitance values can be achieved under different driving voltages, that is, the electrical length of the ring junction can be continuously changed, thereby tuning the frequency.
The thermoelectric MEMS microwave power sensors 7 are positioned at the tail ends of the coupling port 16-1 and the isolation port 16-4, and each thermoelectric MEMS microwave power sensor 7 comprises 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 with two load resistors 10 in parallel, and the isolation port 16-4 is connected with the other two load resistors 10 in parallel. The resistance value of each load resistor 10 is 100 Ω. Two identical thermopiles are placed close to the load resistance at the coupled port 16-1 and the isolated port 16-4, respectively, but not in contact with the load resistance 10. Wherein, each thermopile is formed by connecting four pairs of thermocouples in series. When the load resistor 10 absorbs the microwave power, heat is generated, the temperature of the end of the thermopile near the load resistor 10, which is called the hot end of the thermopile, increases, while the temperature of the other end of the thermopile far from the load resistor 10 remains almost constant, which is the ambient temperature, called the cold end of the thermopile. When the load resistor 10 absorbs microwave power, heat is generated, the temperature of the hot end and the cold end of the thermopile is caused to be different, and the thermopile generates output hot voltage based on the Seebeck effect. In order to improve the transmission efficiency of heat from the load resistor 10 to the hot end of the thermopile and further improve the temperature difference between the hot and cold ends of the thermopile, a silicon substrate is etched and thinned below the load resistor and the hot end of the thermopile by a bulk etching technology to form an MEMS substrate film 15 structure. The thermopile is composed of a semiconductor arm 8 which takes N + polysilicon as the thermopile and a metal arm 9 which takes metal as the thermopile.
The invention also discloses a preparation method of the reconfigurable frequency MEMS standing wave meter based on the multi-port annular junction, which comprises the following steps:
(1) Preparation of the silicon substrate 13: selecting high-resistance silicon as a substrate;
(2) Thermal oxidation of SiO 2 Dielectric layer 14: growing a layer of SiO on the silicon substrate 13 2 ；
(3) Depositing polysilicon and N-type injection: depositing a layer of polycrystalline silicon on the silicon substrate 13 by a chemical vapor deposition mode, and performing N-type ion implantation;
(4) And (3) photoetching the polysilicon: coating photoresist on the surface of the MEMS structure obtained in the step 3, removing the photoresist in the region except the semiconductor arm 8 of the thermopile, etching the polysilicon, and then removing the photoresist;
(5) Coating photoresist on the surface of the MEMS structure obtained in the step 4 and removing the photoresist on the position where the load resistor 10 is prepared to be manufactured;
(6) Depositing TaN: depositing TaN, stripping the photoresist left in the step 5, and removing the TaN on the photoresist to form a load resistor 10;
(7) Sputtering and photo-etching a Cr/Au layer: coating photoresist, removing the photoresist at the positions of preparing the CPW1, the driving electrode 4, the connecting wire 6, the metal arm 9 of the thermopile and the pressure welding block 12, sputtering Cr/Au, and then removing the photoresist to form the CPW1, the connecting wire 6, the thermoelectric MEMS microwave power sensor 7, the pressure welding block 12 structure and the driving electrode 4;
(8) Depositing and photoetching a polyimide sacrificial layer: coating a polyimide sacrificial layer on the surface of the MEMS structure obtained in the step (7), photoetching the polyimide sacrificial layer, and only reserving the polyimide sacrificial layer below the air bridge 5 and the MEMS double-end clamped beam 3;
(9) Seed layer evaporation: growing a seed layer for electroplating in an evaporation mode, and evaporating titanium/gold/titanium to be used as the seed layer;
(10) Coating photoresist, and removing the photoresist on the MEMS double-end clamped beam 3 and the air bridge 5 to be manufactured;
(11) Gold electroplating: electroplating a layer of gold, and removing the residual photoresist;
(12) Reverse etching titanium/gold/titanium: corroding the titanium/gold/titanium seed layer to completely form the MEMS double-end clamped beam 3 and the air bridge 5;
(13) Coating photoresist on the back surface of the silicon substrate 13, and removing the photoresist for preparing the structure of the MEMS substrate film 15 formed on the back surface of the silicon substrate 13;
(14) And (3) reverse dry etching of the substrate: etching a silicon substrate 13 at the hot end of the thermopile and below the load resistor 10, and reserving the silicon substrate 13 with the thickness of 10 microns to form an MEMS substrate film 15 structure;
(15) Releasing the polyimide sacrificial layer: and (3) soaking in a developing solution, removing the polyimide sacrificial layer below the MEMS double-end clamped beam 3 and the air bridge 5, slightly soaking in deionized water, dehydrating with absolute ethyl alcohol, volatilizing at normal temperature, and airing.
It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (4)

1. A reconfigurable frequency MEMS standing wave meter based on a multi-port annular junction is characterized by comprising a silicon substrate (13), a CPW (1), an MEMS variable capacitor (2), a connecting wire (6), a pressure welding block (12), an air bridge (5) and two thermoelectric MEMS microwave power sensors (7), wherein the CPW (1), the MEMS variable capacitor (2), the connecting wire (6), the pressure welding block (12), the air bridge (5) and the two thermoelectric MEMS microwave power sensors are arranged on the silicon substrate (13) and are composed of an annular directional coupler (11) and a coupling port (16-1) thereof, an input port (16-2), an output port (16-3) and an isolation port (16-4);
a CPW (1) consisting of a ring-shaped directional coupler (11) and a coupling port (16-1), an input port (16-2), an output port (16-3) and an isolation port (16-4) thereof is placed on a silicon substrate (13) to form a main body structure of the coupler; the characteristic impedance of the coupling port (16-1), the input port (16-2), the output port (16-3) and the isolation port (16-4) is 50 omega, and the characteristic impedance of the annular junction of the annular directional coupler (11) is 70.7 omega;
the tail ends of the coupling port (16-1), the input port (16-2), the output port (16-3) and the isolation port (16-4) are connected with the annular directional coupling (11) annular junction; the output port (16-3) and the coupling port (16-1) are positioned on two sides of the input port (16-2), and the distances between the intersection point of the output port (16-3), the coupling port (16-1) and the annular directional coupling (11) and the intersection point of the input port (16-2) and the annular directional coupling (11) are quarter wavelengths; the input port (16-2) and the isolation port (16-4) are positioned at two sides of the output port (16-3), and the distance between the intersection point of the input port (16-2), the isolation port (16-4) and the annular junction of the annular directional coupling (11) and the intersection point of the output port (16-3) and the annular junction of the annular directional coupling (11) are quarter wavelengths; the coupling port (16-1) and the isolation port (16-4) are respectively connected with a thermoelectric MEMS microwave power sensor (7), so that a micro thermoelectric MEMS integrated microwave standing wave meter is formed;
placing six MEMS variable capacitors (2) above an annular junction of an annular directional coupling (11) at equal intervals, wherein three MEMS variable capacitors (2) are positioned between an input port (16-2) and a coupling port (16-1), between an output port (16-3) and the input port (16-2), and between an isolation port (16-4) and an output port (16-3), an upper polar plate of each MEMS variable capacitor (2) is an MEMS double-end clamped beam (3), a lower polar plate is a driving electrode (4), the MEMS double-end clamped beam (3) spans above a signal line of the CPW (1), two ends of the MEMS double-end clamped beam are respectively fixed on ground lines of the CPW (1) at two sides of the signal line of the CPW (1) through anchor areas, two driving electrodes (4) are symmetrically placed at two sides of the signal line of the CPW (1) below the MEMS double-end clamped beam (3), and the driving electrodes (4) are respectively led out through connecting wires (6) and connected with a pressure welding block (12);
each air bridge (5) crosses over a connecting wire (6) and is used for realizing the electric interconnection between the CPW (1) and the ground wires without off-chip bonding wires;
each thermoelectric MEMS microwave power sensor (7) comprises 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 with two load resistors (10) in parallel, and the isolation port (16-4) is connected with the other two load resistors (10) in parallel; two identical thermopiles are respectively placed close to the load resistor (10) at the coupling port (16-1) and the isolation port (16-4), but are not in contact with the load resistor (10); through a body etching technology, etching and thinning a silicon substrate below a load resistor (10) and a hot end of a thermopile to form an MEMS substrate film (15) structure; the thermopile is composed of a semiconductor arm (8) which takes N + polysilicon as the thermopile and a metal arm (9) which takes metal as the thermopile.
2. The reconfigurable frequency MEMS standing wave meter based on the multi-port ring junction as claimed in claim 1, wherein each thermopile is formed by four pairs of thermocouples connected in series.
3. The multi-port ring junction based reconfigurable frequency MEMS standing wave meter according to claim 1, characterized in that six MEMS variable capacitors (2) are identical; the two thermoelectric MEMS microwave power sensors (7) are identical.
4. The preparation method of the reconfigurable frequency MEMS standing wave meter based on the multi-port annular junction according to any one of claims 1 to 3 is characterized by comprising the following steps:
step 1, preparing a silicon substrate (13): selecting high-resistance silicon as a substrate;
step 2, thermal oxidation of SiO 2 Dielectric layer (14): growing a layer of SiO on a silicon substrate (13) 2 ；
Step 3, depositing polysilicon and injecting N type: depositing a layer of polycrystalline silicon on a silicon substrate (13) in a chemical vapor deposition mode, and performing N-type ion implantation to form an MEMS structure;
step 4, photoetching the polysilicon: coating photoresist on the surface of the MEMS structure formed in the step 3, removing the photoresist in the region except the semiconductor arm (8) of the thermopile, etching polycrystalline silicon, and removing the photoresist in the region of the semiconductor arm (8) after etching is finished;
step 5, coating photoresist on the surface of the MEMS structure obtained in the step 4 and removing the photoresist at the position where the load resistor (10) is prepared to be manufactured;
step 6, depositing TaN: depositing TaN, stripping the photoresist left in the step 5, and removing the TaN on the photoresist to form a load resistor (10);
and 7, sputtering and photoetching a Cr/Au layer: coating photoresist on the surface of the MEMS structure formed in the step 6, removing the photoresist at the positions of preparing the CPW (1), the driving electrode (4), the connecting wire (6), the metal arm (9) of the thermopile and the pressure welding block (12), sputtering Cr/Au, and then removing the photoresist to form the CPW (1), the connecting wire (6), the thermoelectric MEMS microwave power sensor (7), the pressure welding block (12) structure and the driving electrode (4);
and 8, depositing and photoetching a polyimide sacrificial layer: coating a polyimide sacrificial layer on the MEMS structure obtained in the step (7), photoetching the polyimide sacrificial layer, and only reserving the polyimide sacrificial layer below the air bridge (5) and the MEMS double-end clamped beam (3);
step 9, evaporating the seed layer: growing a seed layer for electroplating on the surface of the MEMS structure obtained in the step 8 in an evaporation mode, and evaporating titanium/gold/titanium to serve as the seed layer;
step 10, coating photoresist on the surface of the MEMS structure obtained in the step 9, and removing the photoresist at the positions of the MEMS double-end clamped beam (3) and the air bridge (5) to be manufactured;
step 11, gold electroplating: electroplating a layer of gold on the surfaces of the seed layers at the MEMS double-end clamped beam (3) and the air bridge (5), and removing the residual photoresist;
step 12, reversely etching titanium/gold/titanium: corroding the titanium/gold/titanium seed layer to completely form the MEMS double-end clamped beam (3) and the air bridge (5);
step 13, coating photoresist on the back surface of the silicon substrate (13), and removing the photoresist for preparing the structure of the MEMS substrate film (15) formed on the back surface of the silicon substrate (13);
step 14, reverse dry etching of the substrate: etching a silicon substrate (13) at the hot end of the thermopile and below the load resistor (10), and reserving the silicon substrate (13) with the thickness of 10 mu m to form an MEMS substrate film (15) structure;
step 15, releasing the polyimide sacrificial layer: and (3) soaking in a developing solution, removing the polyimide sacrificial layer below the MEMS double-end clamped beam (3) and the air bridge (5), slightly soaking in deionized water, dehydrating with absolute ethyl alcohol, volatilizing at normal temperature, and airing.
CN202210985907.2A 2022-08-16 2022-08-16 Reconfigurable frequency MEMS standing wave meter based on multi-port annular junction and preparation method Pending CN115327236A (en)

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