A compact novel RF MEMS series capacitance switch

Abstract

The application discloses a compact novel RF MEMS series capacitance switch and belongs to the technical field of radio frequency micro electro mechanical system.The switch comprises back metal, a substrate, a negative electrode nonmetal DC bias line, an artificial air bridge, a DC port, a positive electrode nonmetal DC bias line, a right lower layer anchor point, a defect coplanar waveguide ground, a coplanar waveguide signal line, an electrode dielectric layer, a right upper layer anchor point, a metal cantilever beam, a silicon dioxide skirt beam, a left anchor point, a positive electrode metal bias line, a metal beam and a signal bridge.The switch integrates the upper electrode into the signal bridge to form a series capacitance switch structure, and the switch size can be reduced; the metal cantilever beam uses single-end DC power supply, the power supply structure is simple, the composite structure of the cantilever metal beam and the fixed support silicon dioxide beam is adopted, the switch warping caused by the cantilever beam is avoided, and the restoring force is provided; the switch has a large working bandwidth, a large switch isolation degree and a small insertion loss; the defect coplanar waveguide ground and the DC port isolation structure are designed, the switch can be prevented from exploding after breakdown or short circuit under high voltage, and radio frequency probes and other adjacent devices can be prevented from being damaged.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency microelectromechanical systems (MEMS) technology, and specifically relates to a compact novel RF MEMS series capacitor switch. Background Technology

[0002] RF MEMS switches are classified according to their mechanical structure into cantilever beam switches and fixed beam switches; according to their connection method in RF circuits into series and parallel types; and according to their contact method into capacitively coupled switches and ohmic contact switches. Based on their driving mechanism, they can be classified into electrostatically driven, electromagnetically driven, thermally driven, piezoelectrically driven, and shape memory alloy driven switches, among others. The most common type is the electrostatically actuated switch, which is also the most mature RF MEMS switch. Compared with traditional solid-state switches, RF MEMS switches feature low loss, high linearity, and low power consumption, and are widely used in communication system networks, satellite systems, broadband spectrum analysis, instrumentation, and radar systems.

[0003] Currently, RF MEMS series capacitor cantilever beam switches have warping issues, while double-ended fixed support composite beams have problems such as large size, stress concentration in folded beam structures, and complex DC electrode power supply structures.

[0004] To address the aforementioned technical issues, the existing technology "Novel Beam Design for Compact RFMEMS Series Switches" discloses adding a set of dimples to a metal cantilever beam to locally and directionally reduce the stress sensitivity of the metal cantilever beam, thereby reducing cantilever switch warpage and increasing MEMS switch yield. Results show that the cantilever beam switch achieves an insertion loss better than 0.35dB at a driving voltage of 60V, a return loss of up to 24dB at 40GHz, and a switch isolation better than 22dB. However, the dimple structure design has a significant impact on manufacturing processes and can only suppress switch warpage to a limited extent. The existing technology "A High-Reliability High-Linearity High-Power RF MEMS Metal-Contact Switch for DC–40-GHz Applications" discloses a fixed-beam switch with an inverted crab topology to reduce the impact of residual stress and temperature on the switch and improve switch reliability. The switch has a drive voltage of 80-90V, an on-state capacitance of 8fF, and isolation levels of 46, 31, and 14dB at 1GHz, 6GHz, and 40GHz, respectively. It can operate from 0-40GHz and has a cycle life exceeding 100 million cycles. However, this switch uses a pure metal beam, making it impossible to implement a switch-capacitor series structure. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a compact novel RF MEMS series capacitor switch.

[0006] The technical problem addressed by this invention is solved as follows:

[0007] A novel compact RF MEMS series capacitive switch includes a backing metal 1, a substrate 2, a negative non-metallic DC bias line 3, a simulated air bridge 4, a DC port 5, a positive non-metallic DC bias line 6, a lower right anchor point 7, a defective coplanar waveguide ground 8, a coplanar waveguide signal line 9, an electrode dielectric layer 10, an upper right anchor point 11, a metal cantilever beam 12, a silicon dioxide skirt beam 13, a left anchor point 14, a positive metal bias line 15, a metal beam 16, and a signal bridge 17.

[0008] The backing metal 1 is located on the lower surface of the substrate 2;

[0009] The coplanar waveguide signal line 9 is located on the upper surface of the substrate 2, and has a symmetrical stepped structure with a break in the middle, parallel to the edge of the substrate 2.

[0010] The defective coplanar waveguide ground 8 is located on the upper surface of the substrate 2, surrounds the coplanar waveguide signal line 9 and leaves a gap in the middle, and has a stepped defect structure on the right side of the coplanar waveguide signal line 9, and an air bridge is provided on the right side of the stepped defect structure.

[0011] The lower right anchor point 7 is located on the upper surface of the substrate 2, within the stepped defect structure of the defect coplanar waveguide ground 8, and is separated from the defect coplanar waveguide ground 8 by a gap.

[0012] Two DC ports 5 are located on the upper surface of substrate 2, on the left and right sides of defect coplanar waveguide ground 8, respectively;

[0013] The positive non-metallic DC bias line 6 is located on the upper surface of the substrate 2, passes through the air bridge of the defect coplanar waveguide ground 8, and is used to connect the lower right anchor point 7 and the DC port 5 on the right.

[0014] Two simulated air bridges 4 are located at the two ends of the coplanar waveguide signal line 9, respectively, and span the defective coplanar waveguide ground 8; the simulated air bridges 4 are connected to the ends of the adjacent coplanar waveguide signal line 9.

[0015] Two positive metal bias lines 15 are located on the upper surface of the substrate 2, with one end connected to the DC port 5 on the left side respectively.

[0016] Two negative non-metallic DC bias lines 3 are located on the upper surface of substrate 2, at the two ends of coplanar waveguide signal line 9 respectively, including a straight section and a multi-folded section connected to each other; the straight section is isolated from the defective coplanar waveguide ground 8 and connected to the adjacent simulated air bridge 4, and the multi-folded section is connected to the adjacent positive metallic bias line 15.

[0017] The two electrode dielectric layers 10 are both rectangular in structure, covering the two ends of the broken part in the middle of the coplanar waveguide signal line 9. The width covers one step of the coplanar waveguide signal line 9 and does not contact the defective coplanar waveguide ground 8.

[0018] The upper right anchor point 11 is located on the upper surface of the lower right anchor point 7, and its area is smaller than that of the lower right anchor point 7.

[0019] The metal cantilever beam 12 includes a connected metal beam 16 and a signal bridge 17. The metal beam 16 includes multiple folded metal wires and metal patches. The metal patches are located on the upper surface of the upper right anchor point 11. The frame of the signal bridge 17 does not exceed the frame of the electrode dielectric layer 10 and spans the middle break of the coplanar waveguide signal line 9. A gap is formed between the signal bridge 17 and the electrode dielectric layer 10 through the upper right anchor point 11.

[0020] The left anchor point 14 is located on the upper surface of the defective coplanar waveguide ground 8, and includes two layers of the same shape stacked one above the other; the lower layer and the upper right layer anchor point 11 are at the same height, and the center line connecting them is parallel to the edge of the substrate 2 and passes through the center of the broken part of the coplanar waveguide signal line 9; the upper layer is at the same height as the metal cantilever beam 12.

[0021] The silica skirt beam 13 is located on the upper surface of the left anchor point 14 and the metal cantilever beam 12, and covers both of them; the silica skirt beam 13 spans the middle break of the coplanar waveguide signal line 9.

[0022] Furthermore, the silica skirt beam 13 has a hollowed-out section at the corresponding position between the left anchor point 14 and the signal bridge 17, and a hollowed-out section at the corresponding position of the folded metal wire, forming a ring arm connected structure from the left end to the middle and right end. The ring arm path is a spline curve, and the connection between the two ends of the ring arm is a circular arc transition. The length of the ring arm closer to the left anchor point 14 is less than that of the other ring arm.

[0023] Furthermore, both the signal bridge 17 and the silica skirt beam 13 have release holes at corresponding positions on the signal bridge 17, with the diameter of the release hole being four times the clearance.

[0024] Furthermore, the substrate 2 is made of quartz glass with a relative permittivity of 3.78 and a dielectric loss tangent of 0.0008.

[0025] Furthermore, the coplanar waveguide signal line 9, the defective coplanar waveguide ground 8, the lower right anchor point 7, the positive metal bias line 15, the DC port 5, and the metal cantilever beam 12 are made of gold with a thickness of 0.5 μm; the upper right anchor point 11 and the left anchor point 14 are made of gold with a thickness of 1 μm.

[0026] Furthermore, the positive electrode non-metallic DC bias line 6 is made of TaN material, with a thickness of 0.2 μm and a width of 5 μm; the negative electrode non-metallic DC bias line 3 is made of TaN material, with a thickness of 0.2 μm.

[0027] Furthermore, the electrode dielectric layer 10 is made of Si3N4 material with a relative permittivity of 7.6.

[0028] Furthermore, the silicon dioxide skirt beam 13 is made of SiO2 with a thickness of 1μm.

[0029] Furthermore, the gap distance between the defective coplanar waveguide ground 8 and the coplanar waveguide signal line 9 is 5μm.

[0030] The working principle of the switch described in this invention is as follows:

[0031] When a DC driving voltage is applied to the signal bridge 17 and the coplanar waveguide signal line 9, the signal bridge 17 drives the silicon dioxide skirt beam 13 to press down together due to the electrostatic force. The metal cantilever beam 12 and the coplanar waveguide signal line 9 form a switching gap through the upper right anchor point 11. When the signal bridge 17 and the electrode dielectric layer 10 come into contact, the coplanar waveguide signal line 9 is turned on. The radio frequency signal is transmitted from one end to the other through the coplanar waveguide structure formed by the coplanar waveguide signal line 9 and the defective coplanar waveguide ground 8.

[0032] The coplanar waveguide signal line 9 is used to transmit radio frequency signals and serves as the DC negative terminal of the RF MEMS switch; the lower right anchor point 7 is used to support the RF MEMS switch and connect the DC port 5; the two DC ports 5 are used to provide DC drive voltage to the RF MEMS switch; the simulated air bridge 4 is used to simulate the connection between the DC bias line and the coplanar waveguide signal line 9 in actual conditions; the positive metal bias line 15 is used to transmit DC current, and the use of metal material can reduce the voltage division caused by non-metallic materials; the negative non-metallic DC bias line 3 is used to transmit DC drive voltage; the electrode dielectric layer 10 is used to form a capacitor structure between the coplanar waveguide signal line 9 and the signal bridge 17 and to prevent DC short circuits; the metal cantilever beam 12 is used to switch the radio frequency signal on and off; the silicon dioxide skirt beam 13 is used to connect the left anchor point 14 and the metal cantilever beam 12 and provide restoring force to prevent the metal cantilever beam 12 from causing excessive warping; the release holes of the signal bridge 17 and the silicon dioxide skirt beam 13 are used to accelerate the release of the sacrificial layer and can reduce the downward air damping.

[0033] The beneficial effects of this invention are:

[0034] (1) The switch described in this invention is a series switch structure in which electrodes and signal bridge are integrated into one unit, which can reduce the size of the switch;

[0035] (2) Compared with the composite fixed beam with dual-end power supply, the metal cantilever beam 12 in the switch of the present invention uses single-end DC power supply, the power supply structure is simple, and the composite structure of cantilever metal beam and fixed support silicon dioxide beam is adopted to avoid switch warping caused by cantilever beam and provide greater restoring force.

[0036] (3) The switch described in this invention has a large operating bandwidth. In the range of 12GHz-78GHz, the switch isolation is greater than 10dB and the insertion loss is less than 1dB. In the range of 12GHz-48GHz, the switch isolation is greater than 15dB and the insertion loss is less than 1dB.

[0037] (4) The defective coplanar waveguide ground and DC electrode in the switch of the present invention are isolated to prevent the DC electrode from being applied to the defective coplanar waveguide ground. If the switch breaks down or short-circuits under high voltage, it will explode and damage the radio frequency probe and other adjacent devices.

[0038] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and will also become apparent in part to those skilled in the art upon studying the description, or may be learned by practice of the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures specifically pointed out in the description and drawings.

[0039] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0040] Figure 1 This is a three-dimensional structural schematic diagram of the series capacitor switch described in this invention;

[0041] Figure 2 This is a cross-sectional view of the series capacitor switch described in this invention;

[0042] Figure 3 This is an exploded view of the series capacitor switch described in this invention;

[0043] Figure 4 This is a schematic diagram showing the dimensions of the series capacitor switch described in this invention;

[0044] Figure 5 This is a schematic diagram showing the dimensions of the horizontal and vertical metal cantilever beams of the series capacitor switch described in this invention;

[0045] Figure 6 This is a schematic diagram showing the dimensions of the silicon dioxide skirt beam of the series capacitor switch described in this invention;

[0046] Figure 7 This is a simulation diagram of a modified series capacitor switch as described in the embodiment;

[0047] Figure 8 The surface von Mises stress simulation diagram of the series capacitor switch described in the embodiment;

[0048] Figure 9 This is a simulation diagram of the driving voltage of the series capacitor switch described in the embodiment;

[0049] Figure 10 The following is a simulation diagram of the insertion loss and isolation of the series capacitor switch described in the embodiment;

[0050] Figure 11 This is a SEM image of the actual fabricated part of the series capacitor switch described in the embodiment.

[0051] The reference numerals in the attached figures are as follows: 1. Backing metal; 2. Substrate; 3. Negative electrode non-metallic DC bias line; 4. Simulated air bridge; 5. DC port; 6. Positive electrode non-metallic DC bias line; 7. Lower right anchor point; 8. Defect coplanar waveguide ground; 9. Coplanar waveguide signal line; 10. Electrode dielectric layer; 11. Upper right anchor point; 12. Metal cantilever beam; 13. Silicon dioxide skirt beam; 14. Left anchor point; 15. Positive electrode metal bias line; 16. Metal beam; and 17. Signal bridge. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0053] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only structures closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0054] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0055] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0056] In the following description, embodiments of the invention will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar parts.

[0057] This embodiment provides a compact novel RF MEMS series capacitor switch, the overall structure of which is shown in the schematic diagram below. Figure 1 As shown, the cross-sectional view is as follows Figure 2 As shown, the exploded view is as follows Figure 3As shown in the figure, the dimensions are as follows: Figure 4 As shown, it includes a backing metal 1, a substrate 2, a negative non-metallic DC bias line 3, a simulated air bridge 4, a DC port 5, a positive non-metallic DC bias line 6, a lower right anchor point 7, a defect coplanar waveguide ground 8, a coplanar waveguide signal line 9, an electrode dielectric layer 10, an upper right anchor point 11, a metal cantilever beam 12, a silicon dioxide skirt beam 13, a left anchor point 14, a positive metal bias line 15, a metal beam 16, and a signal bridge 17.

[0058] The backing metal 1 is located on the lower surface of the substrate 2;

[0059] The coplanar waveguide signal line 9 is located on the upper surface of the substrate 2, and has a symmetrical stepped structure with a break in the middle, parallel to the edge of the substrate 2.

[0060] The defective coplanar waveguide ground 8 is located on the upper surface of the substrate 2, surrounds the coplanar waveguide signal line 9 and leaves a gap in the middle, and has a stepped defect structure on the right side of the coplanar waveguide signal line 9, and an air bridge is provided on the right side of the stepped defect structure.

[0061] The lower right anchor point 7 is located on the upper surface of the substrate 2, within the stepped defect structure of the defect coplanar waveguide ground 8, and is separated from the defect coplanar waveguide ground 8 by a gap.

[0062] Two DC ports 5 are located on the upper surface of substrate 2, on the left and right sides of defect coplanar waveguide ground 8, respectively;

[0063] The positive non-metallic DC bias line 6 is located on the upper surface of the substrate 2, passes through the air bridge of the defect coplanar waveguide ground 8, and is used to connect the lower right anchor point 7 and the DC port 5 on the right.

[0064] Two simulated air bridges 4 are located at the two ends of the coplanar waveguide signal line 9, respectively, and span the defective coplanar waveguide ground 8; the simulated air bridges 4 are connected to the ends of the adjacent coplanar waveguide signal line 9.

[0065] Two positive metal bias lines 15 are located on the upper surface of the substrate 2, with one end connected to the DC port 5 on the left side respectively.

[0066] Two negative non-metallic DC bias lines 3 are located on the upper surface of substrate 2, at the two ends of coplanar waveguide signal line 9 respectively, including a straight section and a multi-folded section connected to each other; the straight section is isolated from the defective coplanar waveguide ground 8 and connected to the adjacent simulated air bridge 4, and the multi-folded section is connected to the adjacent positive metallic bias line 15.

[0067] The two electrode dielectric layers 10 are both rectangular in structure, covering the two ends of the broken part in the middle of the coplanar waveguide signal line 9. The width covers one step of the coplanar waveguide signal line 9 and does not contact the defective coplanar waveguide ground 8.

[0068] The upper right anchor point 11 is located on the upper surface of the lower right anchor point 7, and its area is smaller than that of the lower right anchor point 7.

[0069] The metal cantilever beam 12 includes a connected metal beam 16 and a signal bridge 17. The metal beam 16 includes multiple folded metal wires and metal patches. The metal patches are located on the upper surface of the upper right anchor point 11. The frame of the signal bridge 17 does not exceed the frame of the electrode dielectric layer 10 and spans the middle break of the coplanar waveguide signal line 9. A gap is formed between the signal bridge 17 and the electrode dielectric layer 10 through the upper right anchor point 11.

[0070] The left anchor point 14 is located on the upper surface of the defective coplanar waveguide ground 8, and includes two layers of the same shape stacked one above the other; the lower layer and the upper right layer anchor point 11 are at the same height, and the center line connecting them is parallel to the edge of the substrate 2 and passes through the center of the broken part of the coplanar waveguide signal line 9; the upper layer is at the same height as the metal cantilever beam 12.

[0071] The silica skirt beam 13 is located on the upper surface of the left anchor point 14 and the metal cantilever beam 12, and covers both of them; the silica skirt beam 13 spans the middle break of the coplanar waveguide signal line 9.

[0072] The silica skirt beam 13 has a hollowed-out section at the corresponding position between the left anchor point 14 and the signal bridge 17, and a hollowed-out section at the corresponding position of the folded metal line, forming a ring arm connected structure from the left end to the middle and right end. The ring arm path is a spline curve, and the connection between the two ends of the ring arm is a circular arc transition. The length of the ring arm closer to the left anchor point 14 is smaller than that of the other ring arm.

[0073] Both the signal bridge 17 and the silica skirt beam 13 have release holes at corresponding positions on the signal bridge 17, and the diameter of the release hole is four times the clearance.

[0074] To address the warping issues inherent in existing RF MEMS series capacitor cantilever beam switches, and the problems of large size, stress concentration in folded beam structures, and complex DC electrode power supply structures in double-ended fixed-support composite beams, this invention provides a compact novel RF MEMS series capacitor switch. The design integrates the switch's upper electrode and signal bridge into a single series capacitor switch structure, reducing switch size. A single-ended DC power supply structure using a metal cantilever beam simplifies power supply. A composite structure combining the cantilever metal beam and the fixed-support silica beam prevents switch warping caused by the cantilever beam and provides greater restoring force. An isolation structure for the defective coplanar waveguide ground and DC port is designed to prevent the switch from exploding after breakdown or short circuit under high voltage, thus protecting the RF probe and other adjacent devices. The switch exhibits high isolation and low insertion loss in the 12GHz-48GHz range.

[0075] Isolation is defined as the ratio of the power of the radio frequency signal leaking to other ports to the input power, and the unit can be decibels (dB). Isolation is an indicator of switch quality. When the switch is qualified, the ports are well isolated and the signal leakage is minimal.

[0076] Insertion loss is the loss of load power caused by inserting components or devices into a transmission system. It is expressed as the ratio of input power to power transmitted to the load, and the unit can be decibels (dB).

[0077] Stress refers to the internal force generated between different parts of an object per unit area when the object deforms due to external factors such as force and temperature.

[0078] Stress concentration refers to the phenomenon of localized increases in stress within an object, which generally occurs where the shape of the object changes drastically.

[0079] The driving voltage refers to the minimum operating voltage required for a switch to switch from the up state to the down state.

[0080] A coplanar waveguide is formed by creating a central conductor strip on one side of a dielectric substrate and creating conductor planes on both sides of the central conductor strip. Coplanar waveguides propagate TEM waves and have no cutoff frequency.

[0081] In this embodiment, the substrate material is quartz glass with a relative permittivity of 3.78 and a dielectric loss tangent of 0.0008. This material has the advantages of low cost and mature technology.

[0082] The coplanar waveguide signal line 9 is made of gold with a thickness of 0.5 μm. It is formed on the substrate and is disconnected in the middle to form a series structure with the signal bridge. It has a gradient structure on both sides for impedance matching. The length of each stage at both ends is 112 μm. The gradient structure is stepped. The width of the last stage is slightly larger than the width of the signal bridge. Simulation shows that the larger the width of the former is than the width of the latter, the worse the RF performance. The width of one side of each step is 5 μm, which is used to transmit RF signals and serve as the DC negative terminal of the RF MEMS switch.

[0083] The gap between the defective coplanar waveguide ground 8 and the coplanar waveguide signal line 9 is 5μm. It forms a coplanar waveguide structure with the coplanar waveguide signal line. The two ends are connected to facilitate the use of lumped port simulation in electromagnetic simulation software. In actual manufacturing, the two ends are not connected. Instead, the negative non-metallic DC bias line is directly connected to the coplanar waveguide signal line. The material used is gold with a thickness of 0.5μm. There is a defective structure and an air bridge on the right lower anchor point side. The purpose is to isolate the right lower anchor point from the defective coplanar waveguide ground by DC and to connect the bias line through the air bridge to the DC port. This prevents the DC electrode from being applied to the defective coplanar waveguide ground. If the switch breaks down or short-circuits under high voltage, it will explode and damage the RF probe and other adjacent devices.

[0084] The lower right anchor point 7 is made of gold with a thickness of 0.5μm. It is isolated from the defect coplanar waveguide ground gap and is used to support the RFMEME switch and connect the DC electrode. Its width a20 is 10μm greater than the width of the first right anchor point and is used to connect the latter to the positive non-metallic DC bias line.

[0085] The positive non-metallic DC bias line 6 is made of TaN material, with a thickness of 0.2μm and a width of 5μm. It passes through the air bridge of the defect coplanar waveguide ground and is 5μm apart from the defect coplanar waveguide ground on both sides. Its function is to connect the lower right anchor point and the DC port. Using non-metallic materials can reduce interference with electromagnetic waves.

[0086] The negative non-metallic DC bias line 3 is made of TaN with a thickness of 0.2μm. It is located at both ends of the coplanar waveguide signal line. There are multiple folds near the coplanar waveguide signal line. The folds are used to increase the inductance of the bias line and reduce the impact on the radio frequency performance. One end of it is separated from the defective coplanar waveguide ground and connected to the simulated air bridge. The other end is connected to the positive metal bias line for transmitting DC drive voltage.

[0087] Simulated air bridge 4 is located on both sides of the coplanar waveguide signal line, spanning the connection points of the two ends of the defective coplanar waveguide ground, and is connected to the coplanar waveguide signal line and the negative non-metallic DC bias line. The surface is set with an impedance boundary of 50 ohms sheet resistance to simulate the actual connection between the DC bias line and the coplanar waveguide signal line. In actual processing, this structure is not used, and the negative non-metallic DC bias line and the coplanar waveguide signal line are directly connected.

[0088] The positive electrode metal bias line 15 is made of Au material with a thickness of 0.5μm. It is located on both sides of the DC port and connected at both ends to the DC port and the negative electrode non-metallic DC bias line. It is used to transmit DC power. Using metal material can reduce the voltage drop caused by non-metallic material.

[0089] DC port 5 is made of Au material with a thickness of 0.5μm and is located on both sides of the defect coplanar waveguide ground to provide DC drive voltage for the RF MEME switch.

[0090] Electrode dielectric layer 10 is formed on the coplanar waveguide signal line and located below the metal cantilever beam. It is used to form a capacitor structure between the former two and to isolate DC short circuit. The material selected is Si3N4 with a relative permittivity of 7.6. It is rectangular in shape and its width is greater than the width of the coplanar waveguide signal line. At the same time, it cannot be connected to the defective coplanar waveguide ground to avoid direct contact between the coplanar waveguide signal line and the signal bridge after voltage is applied, which would cause a short circuit.

[0091] The upper right anchor point 11 is made of Au material with a thickness of 1μm. It is formed on the lower right anchor point and its area is 10μm smaller than the former. It is used to form the RF MEMS switch gap. Its perimeter is rounded to avoid stress concentration after the switch is pressed down.

[0092] The left anchor point 14 is made of Au and is formed on the defective coplanar waveguide ground. The side of it near the coplanar waveguide signal line is rounded to avoid stress concentration after the switch is pressed down. It is located on the side of the negative non-metallic DC bias line and is divided into two layers. The lower layer and the upper right anchor point are on the same layer with a thickness of 1μm, which is used to form the RF MEMS switch gap. The upper layer and the metal cantilever beam are on the same layer with a thickness of 0.5μm, which is used to support the silicon dioxide skirt beam.

[0093] Figure 5 This is a schematic diagram of the dimensions of the metal cantilever beam in this embodiment. The metal cantilever beam is made of Au material with a thickness of 0.5 μm and is formed on the upper right anchor point. It includes a metal beam and a signal bridge. The metal beam has multiple folds to reduce the driving voltage and increase the inductance. The signal bridge has a release hole with a diameter four times the gap to accelerate the release of the sacrificial layer and reduce the downward air damping. The signal bridge and the coplanar waveguide signal line together serve as an electrode plate for electrostatic attraction and are used to switch the radio frequency signal on and off. This signal bridge structure integrates the upper electrode and radio frequency switch functions into one unit, which can reduce the switch size.

[0094] Figure 6 This is a schematic diagram of the dimensions of the silicon dioxide skirt beam in this embodiment. The silicon dioxide skirt beam is formed on the left anchor point and the metal cantilever beam and covers both of them. It spans the coplanar waveguide signal line and serves to connect the left anchor point and the metal cantilever beam and provide restoring force to prevent the metal cantilever beam from warping excessively. The material used is SiO2 with a thickness of 1μm. Its two ends and the middle are connected by ring arms. The path of the ring arm is a spline curve. The connection between the two ends of the ring arm is a circular arc transition. The length of the ring arm near the left anchor point is smaller than that of the ring arm at the other end.

[0095] The dimensions of the switch described in this embodiment are shown in Table 1.

[0096] Figure 7 This is a simulation diagram of a modified compact novel RF MEMS series capacitor switch described in this embodiment. Figure 8 This is a simulation diagram of von Mises stress on the surface of the compact novel RF MEMS series capacitor switch described in this embodiment. Figure 9 This is a simulation diagram of the driving voltage of the compact novel RF MEMS series capacitor switch described in this embodiment. The electrical coupling simulation was performed using COMSOL Multiphysics. The Si3N4 electrode dielectric layer was not included in the simulation. The solid-state mechanics part includes the silicon dioxide skirt beam, metal cantilever beam, lower right anchor point, upper right anchor point, left anchor point, and coplanar waveguide signal line. Figure 7 The deformation of the switch is shown when it is pressed down by an electrostatic force of 0.9 μm. Figure 8The von Mises stress distribution is shown after the switch is pressed down by electrostatic force for 0.9 μm. It can be seen that the stress distribution on the switch beam is uniform. The maximum stress of 53.5 MPa occurs at the middle edge of the silica skirt beam and is less than the yield strength of Au of 201 MPa and the fatigue failure strength of Au of 63 MPa (data from the paper).

[0097] Figure 10 The simulation diagrams for the insertion loss and isolation of the compact novel RF MEMS series capacitor switch described in this embodiment show that the switch has an isolation greater than 10dB and an insertion loss less than 1dB in the 12GHz-78GHz range; and an isolation greater than 15dB and an insertion loss less than 1dB in the 12GHz-48GHz range, indicating that the switch has a large operating bandwidth.

[0098] Figure 11 This is a SEM image of the actual switch fabricated in this embodiment. The switch in this SEM image is related to... Figure 5 Unlike the signal bridge with a metal cantilever beam, the other dimensions and structure are the same. Figure 1 Similarly, it can be seen that the beam and signal bridge of the SEM switch do not have severe warping.

[0099] Table 1. Dimensions of the switch described in this embodiment.

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[0102]

Claims

1. A novel compact RF MEMS series capacitor switch, characterized in that, It includes a backing metal (1), a substrate (2), a negative non-metallic DC bias line (3), a simulated air bridge (4), a DC port (5), a positive non-metallic DC bias line (6), a lower right anchor point (7), a defect coplanar waveguide ground (8), a coplanar waveguide signal line (9), an electrode dielectric layer (10), a upper right anchor point (11), a metal cantilever beam (12), a silicon dioxide skirt beam (13), a left anchor point (14), a positive metal bias line (15), a metal beam (16), and a signal bridge (17); The backing metal (1) is located on the lower surface of the substrate (2); The coplanar waveguide signal line (9) is located on the upper surface of the substrate (2), and has a symmetrical stepped structure with a break in the middle, parallel to the edge of the substrate (2). The defective coplanar waveguide ground (8) is located on the upper surface of the substrate (2), surrounds the coplanar waveguide signal line (9) and leaves a gap in the middle, and has a stepped defect structure on the right side of the coplanar waveguide signal line (9), and an air bridge is provided on the right side of the stepped defect structure. The lower right anchor point (7) is located on the upper surface of the substrate (2), within the stepped defect structure of the defect coplanar waveguide ground (8), and is separated from the defect coplanar waveguide ground (8) by a gap; Two DC ports (5) are located on the upper surface of the substrate (2), on the left and right sides of the defect coplanar waveguide ground (8), respectively; The positive non-metallic DC bias line (6) is located on the upper surface of the substrate (2), passes through the air bridge of the defect coplanar waveguide ground (8), and is used to connect the lower right anchor point (7) and the DC port (5) on the right side. Two simulated air bridges (4) are located at the two ends of the coplanar waveguide signal line (9) and span the defective coplanar waveguide ground (8); the simulated air bridges (4) are connected to the ends of the adjacent coplanar waveguide signal lines (9); Two positive metal bias lines (15) are located on the upper surface of the substrate (2), and one end is connected to the DC port (5) on the left side respectively. Two negative non-metallic DC bias lines (3) are located on the upper surface of the substrate (2), respectively at the two ends of the coplanar waveguide signal line (9), including a straight line segment and a multiple folded line segment; the straight line segment is isolated from the defect coplanar waveguide ground (8) and connected to the adjacent simulated air bridge (4), and the multiple folded line segment is connected to the adjacent positive metal bias line (15); The two electrode dielectric layers (10) are rectangular in structure and cover the two ends of the broken part in the middle of the coplanar waveguide signal line (9). The width covers a step of the coplanar waveguide signal line (9) and does not contact the defective coplanar waveguide ground (8). The upper right anchor point (11) is located on the upper surface of the lower right anchor point (7), and its area is smaller than that of the lower right anchor point (7). The metal cantilever beam (12) includes a connecting metal beam (16) and a signal bridge (17). The metal beam (16) includes multiple folded metal wires and metal patches. The metal patches are located on the upper surface of the upper right anchor point (11). The frame of the signal bridge (17) does not exceed the frame of the electrode dielectric layer (10) and spans the middle break of the coplanar waveguide signal line (9). A gap is formed between the signal bridge (17) and the electrode dielectric layer (10) through the upper right anchor point (11). The left anchor point (14) is located on the upper surface of the defective coplanar waveguide ground (8), comprising two layers of the same shape stacked one above the other; the lower layer and the upper right layer anchor point (11) are at the same height, and the center line connecting them is parallel to the edge of the substrate (2) and passes through the center of the broken part of the coplanar waveguide signal line (9); the upper layer is at the same height as the metal cantilever beam (12); The silica skirt beam (13) is located on the upper surface of the left anchor point (14) and the metal cantilever beam (12) and covers both; the silica skirt beam (13) spans the middle break of the coplanar waveguide signal line (9).

2. The compact novel RF MEMS series capacitor switch according to claim 1, characterized in that, The silica skirt beam (13) has a hollowed-out section at the corresponding position between the left anchor point (14) and the signal bridge (17), and a hollowed-out section at the corresponding position of the folded metal wire, forming a ring arm connected structure with the left end, middle and right end. The ring arm path is a spline curve, and the connection between the two ends of the ring arm is a circular arc transition. The length of the ring arm closer to the left anchor point (14) is less than that of the other ring arm.

3. The compact novel RF MEMS series capacitor switch according to claim 1, characterized in that, The signal bridge (17) and the silica skirt beam (13) both have release holes at the corresponding positions of the signal bridge (17), and the diameter of the release hole is four times the gap.

4. The compact novel RF MEMS series capacitor switch according to claim 1, characterized in that, The substrate (2) is made of quartz glass with a relative permittivity of 3.78 and a dielectric loss tangent of 0.0008.

5. The compact novel RF MEMS series capacitor switch according to claim 1, characterized in that, The coplanar waveguide signal line (9), the defective coplanar waveguide ground (8), the lower right anchor point (7), the positive metal bias line (15), the DC port (5) and the metal cantilever beam (12) are made of gold with a thickness of 0.5 μm; the upper right anchor point (11) and the left anchor point (14) are made of gold with a thickness of 1 μm.

6. The compact novel RF MEMS series capacitor switch according to claim 1, characterized in that, The positive electrode non-metallic DC bias line (6) is made of TaN with a thickness of 0.2 μm and a width of 5 μm; the negative electrode non-metallic DC bias line (3) is made of TaN with a thickness of 0.2 μm.

7. The compact novel RF MEMS series capacitor switch according to claim 1, characterized in that, The electrode dielectric layer (10) is made of Si3N4 material with a relative permittivity of 7.

6.

8. The compact novel RF MEMS series capacitor switch according to claim 1, characterized in that, The silicon dioxide skirt beam (13) is made of SiO2 with a thickness of 1μm.

9. The compact novel RF MEMS series capacitor switch according to claim 1, characterized in that, The gap distance between the defective coplanar waveguide ground (8) and the coplanar waveguide signal line (9) is 5 μm.

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