Compact novel RF MEMS series capacitor switch

Abstract

The invention discloses a compact novel RF MEMS series capacitor switch, and belongs to the technical field of RF MEMS. The switch comprises back coating metal, a substrate, a negative electrode nonmetal direct current bias line, a simulation air bridge, a direct current port, a positive electrode nonmetal direct current 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 edge beam, a left anchor point and a positive electrode metal bias line. A metal beam and a signal bridge. According to the switch, the upper electrode is integrated to the signal bridge to form a series capacitor switch structure, so that the size of the switch can be reduced; the metal cantilever beam supplies direct current through a single end, the power supply structure is simple, a composite structure of the cantilever metal beam and the fixed supporting silicon dioxide beam is adopted, switch warping generated by the cantilever beam is avoided, and restoring force is provided; the switch is large in working bandwidth, large in switch isolation degree and small in insertion loss; the designed defect coplanar waveguide ground and direct current port isolation structure can prevent the switch from being broken down under high voltage or exploded after short circuit, and damage to a radio frequency probe and other adjacent devices is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of radio frequency micro electro mechanical systems, and in particular relates to a compact novel RF MEMS series capacitor switch. Background Art

[0002] RF MEMS switches are divided into cantilever beam switches and fixed beam switches according to the mechanical structure; they are divided into series and parallel types according to the connection method of the switch in the RF circuit; and they can be divided into capacitive coupling switches and ohmic contact switches according to the switch contact method. According to the driving mechanism, they can be divided into electrostatic drive, electromagnetic drive, thermal drive, piezoelectric drive, shape memory alloy drive, etc. The most common is the electrostatic actuator switch, which is also the most mature RF MEMS switch. Compared with traditional solid-state switches, RE MEMS switches have the characteristics of low loss, high linearity and low power consumption. They 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 a warping problem, while the double-ended fixed support composite beam has large size, stress concentration in the folded structure beam, and a complex DC electrode power supply structure.

[0004] In order to solve the above-mentioned technical problems, the prior art "Novel Beam Design for Compact RFMEMS Series Switches" discloses adding a group of dimples in the metal cantilever beam to locally and directionally reduce the stress sensitivity of the metal cantilever beam, reduce the warpage of the cantilever switch, and increase the yield of the MEMS switch. The results show that the driving voltage of the cantilever beam switch is 60V, the insertion loss is better than 0.35dB, the return loss is 24dB up to 40GHz, and the switch isolation is better than 22dB. However, the design process of the dimple structure has a great influence, and the switch warpage can only be suppressed to a limited extent. The prior art "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 structure to reduce the influence of residual stress and temperature on the switch and improve the reliability of the switch. The switch has a driving voltage of 80-90V, an upper state capacitance of 8fF, an isolation of 46, 31 and 14dB at 1GHz, 6GHz and 40GHz respectively, and can operate at 0-40GHz. The number of cycles is greater than 100 million times. However, the switch uses a pure metal beam and cannot realize a switch series capacitor structure. Summary of the invention

[0005] The object of the present invention is to overcome the above-mentioned defects of the prior art and provide a compact novel RF MEMS series capacitor switch.

[0006] The technical problem proposed by the present invention is solved in this way:

[0007] A compact novel RF MEMS series capacitor switch comprises a back 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 right lower layer anchor point 7, a defective coplanar waveguide ground 8, a coplanar waveguide signal line 9, an electrode dielectric layer 10, a right upper layer 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 back 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 is in a symmetrical stepped structure, disconnected in the middle and 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, has a step-type defect structure on the right side of the coplanar waveguide signal line 9, and has an air bridge on the right side of the step-type defect structure;

[0011] The right lower layer anchor point 7 is located on the upper surface of the substrate 2, in the step-type defect structure of the defective coplanar waveguide ground 8, and is isolated from the defective coplanar waveguide ground 8 by a gap;

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

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

[0014] Two simulated air bridges 4 are respectively located at two ends of the coplanar waveguide signal line 9 and cross the defective coplanar waveguide ground 8; the simulated air bridge 4 is connected to the end 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, and one end of each of the two positive metal bias lines 15 is connected to the DC port 5 on the left side;

[0016] 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, and include mutually connected straight line segments and multiple folded line segments; the straight line segments are isolated from the defective coplanar waveguide ground 8 and connected to the adjacent simulated air bridge 4, and the multiple folded line segments are connected to the adjacent positive metal bias line 15;

[0017] Two electrode dielectric layers 10 are both rectangular in structure, covering both ends of the disconnected portion of the coplanar waveguide signal line 9, with a width covering a step of the coplanar waveguide signal line 9 and not contacting 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 has a smaller area than 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 a multi-folded metal line and a metal patch. The metal patch is located on the upper surface of the right upper 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 disconnected portion of the coplanar waveguide signal line 9. A gap is formed between the signal bridge 17 and the electrode dielectric layer 10 through the right upper anchor point 11.

[0020] The left anchor point 14 is located on the upper surface of the defective coplanar waveguide ground 8, including two layers stacked up and down and having the same shape; the lower layer and the right upper layer anchor point 11 are located at the same height, and the center line is parallel to the edge of the substrate 2 and passes through the center position of the disconnected part of the coplanar waveguide signal line 9; the upper layer and the metal cantilever beam 12 are located at the same height;

[0021] The silicon dioxide skirt beam 13 is located on the upper surfaces of the left anchor point 14 and the metal cantilever beam 12 , and covers both of them; the silicon dioxide skirt beam 13 spans across the middle disconnected portion of the coplanar waveguide signal line 9 .

[0022] Furthermore, the silica skirt beam 13 is hollowed out at positions corresponding to the left anchor point 14 and the middle part of the signal bridge 17, and at positions corresponding to the multiple folded metal wires, to form a left-middle-right end ring arm connected structure, the ring arm path is a spline curve, the connection between the two ends of the ring arm is an arc transition, and the length of the ring arm close to the left anchor point 14 is shorter than the other ring arm.

[0023] Furthermore, the signal bridge 17 and the silica skirt beam 13 are both provided with release holes at corresponding positions of the signal bridge 17 , and the diameter of the release hole is four times the gap.

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

[0025] Furthermore, the coplanar waveguide signal line 9, defective coplanar waveguide ground 8, lower right anchor point 7, positive metal bias line 15, DC port 5 and 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 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 non-metallic DC bias line 3 is made of TaN with a thickness of 0.2 μm;

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

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

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

[0030] The working principle of the switch of the present invention is:

[0031] A DC driving voltage is applied to the signal bridge 17 and the coplanar waveguide signal line 9. Due to the electrostatic force, the signal bridge 17 drives the silicon dioxide skirt beam 13 to be pressed down together, and 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 contacts the electrode dielectric layer 10, the coplanar waveguide signal line 9 is turned on, and the RF signal is transmitted from one end to the other end 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 pole of the RF MEMS switch; the lower right anchor point 7 is used to support the RF MEME switch and connect the DC port 5; the two DC ports 5 are used to provide a DC driving voltage to the RF MEME switch; the simulated air bridge 4 is used to simulate the actual situation that the DC bias line is connected to the coplanar waveguide signal line 9; the positive metal bias line 15 is used to transmit direct current, and the use of metal materials can reduce the voltage division caused by non-metallic materials; the negative non-metallic DC bias line 3 is used to transmit the DC driving voltage; the electrode dielectric layer 10 is used for the coplanar waveguide signal line 9 and the signal bridge 17 to form a capacitor structure and prevent direct current short circuit; the metal cantilever beam 12 is used to switch on and off the radio frequency signal; the silicon dioxide skirt beam 13 is used to connect the left anchor point 14 and the metal cantilever beam 12 and provide a 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 the present invention are:

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

[0035] (2) Compared with the composite fixed beam with double-end power supply, the metal cantilever beam 12 in the switch of the present invention uses a single-end DC power supply, has a simple power supply structure, and adopts a composite structure of a cantilever metal beam and a fixed supporting silicon dioxide beam to avoid the switch warping caused by the cantilever beam and provide a larger restoring force;

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

[0037] (4) The defective coplanar waveguide ground and the 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, causing the switch to break down or explode after a short circuit under high voltage, thereby damaging the RF probe and other adjacent devices.

[0038] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention may be achieved and obtained by the structures specifically indicated in the specification and the accompanying drawings.

[0039] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the three-dimensional structure of the series capacitor switch of the present invention;

[0041] Figure 2 is a cross-sectional view of the series capacitor switch of the present invention;

[0042] Figure 3 An exploded view of the series capacitor switch of the present invention;

[0043] Figure 4 A schematic diagram of the dimensions of the series capacitor switch of the present invention;

[0044] Figure 5 A schematic diagram of the dimensions of the horizontal and vertical metal cantilever beams of the series capacitor switch of the present invention;

[0045] Figure 6 A schematic diagram of the dimensions of the silicon dioxide skirt beam of the series capacitor switch of the present invention;

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

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

[0048] Fig. 9 A driving voltage simulation diagram of the series capacitor switch described in the embodiment;

[0049] Fig.10 The insertion loss and isolation simulation diagram of the series capacitor switch described in the embodiment;

[0050] Fig.11 This is a SEM image of the actual processed series capacitor switch described in the embodiment.

[0051] The figure marks involved in the accompanying drawings are: back metal 1, substrate 2, negative non-metallic DC bias line 3, simulated air bridge 4, DC port 5, positive non-metallic DC bias line 6, lower right anchor point 7, defect coplanar waveguide ground 8, coplanar waveguide signal line 9, electrode dielectric layer 10, upper right anchor point 11, metal cantilever beam 12, silicon dioxide skirt beam 13, left anchor point 14, positive metal bias line 15, metal beam 16 and signal bridge 17. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

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

[0054] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, elements, steps or components, 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” herein may refer not only to a direct connection but also to an indirect connection involving an intermediate.

[0056] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or similar components.

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

[0058] The back 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 is in a symmetrical stepped structure, disconnected in the middle and 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, has a step-type defect structure on the right side of the coplanar waveguide signal line 9, and has an air bridge on the right side of the step-type defect structure;

[0061] The right lower layer anchor point 7 is located on the upper surface of the substrate 2, in the step-type defect structure of the defective coplanar waveguide ground 8, and is isolated from the defective coplanar waveguide ground 8 by a gap;

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

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

[0064] Two simulated air bridges 4 are respectively located at two ends of the coplanar waveguide signal line 9 and cross the defective coplanar waveguide ground 8; the simulated air bridge 4 is connected to the end 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, and one end of each of the two positive metal bias lines 15 is connected to the DC port 5 on the left side;

[0066] 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, and include mutually connected straight line segments and multiple folded line segments; the straight line segments are isolated from the defective coplanar waveguide ground 8 and connected to the adjacent simulated air bridge 4, and the multiple folded line segments are connected to the adjacent positive metal bias line 15;

[0067] Two electrode dielectric layers 10 are both rectangular in structure, covering both ends of the disconnected portion of the coplanar waveguide signal line 9, with a width covering a step of the coplanar waveguide signal line 9 and not contacting 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 has a smaller area than 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 a multi-folded metal line and a metal patch. The metal patch is located on the upper surface of the right upper 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 disconnected portion of the coplanar waveguide signal line 9. A gap is formed between the signal bridge 17 and the electrode dielectric layer 10 through the right upper anchor point 11.

[0070] The left anchor point 14 is located on the upper surface of the defective coplanar waveguide ground 8, including two layers stacked up and down and having the same shape; the lower layer and the right upper layer anchor point 11 are located at the same height, and the center line is parallel to the edge of the substrate 2 and passes through the center position of the disconnected part of the coplanar waveguide signal line 9; the upper layer and the metal cantilever beam 12 are located at the same height;

[0071] The silicon dioxide skirt beam 13 is located on the upper surfaces of the left anchor point 14 and the metal cantilever beam 12 , and covers both of them; the silicon dioxide skirt beam 13 spans across the middle disconnected portion of the coplanar waveguide signal line 9 .

[0072] The silica skirt beam 13 is hollowed out at positions corresponding to the left anchor point 14 and the middle part of the signal bridge 17, and is hollowed out at positions corresponding to the multiple folded metal wires, forming a left-middle-right end ring arm connected structure, the ring arm path is a spline curve, the connection between the two ends of the ring arm is an arc transition, and the length of the ring arm close to the left anchor point 14 is shorter than the other ring arm.

[0073] The signal bridge 17 and the silicon dioxide skirt beam 13 are both provided with release holes at corresponding positions of the signal bridge 17 , and the diameter of the release hole is four times the gap.

[0074] Aiming at the warping problem of the RF MEMS series capacitor cantilever beam switch in the prior art, and the technical problems that the double-ended fixed support composite beam has a large size, the folded structure beam has stress concentration, and the DC electrode power supply structure is complex, the present invention provides a compact novel RF MEMS series capacitor switch, designs a series capacitor switch structure in which the switch upper electrode and the signal bridge are integrated into one, thereby reducing the switch size; designs a metal cantilever beam single-end DC power supply structure, which is simple to power supply; designs a composite structure of a cantilever metal beam and a fixed support silicon dioxide beam, avoids the switch warping caused by the cantilever beam and provides a large restoring force; designs a defective coplanar waveguide ground and a DC port isolation structure, prevents the switch from breaking down or exploding after a short circuit under high voltage, thereby damaging the RF probe and other adjacent devices; the switch has high isolation and low insertion loss at 12GHz-48GHz.

[0075] Isolation is defined as the ratio of the power of the RF signal leaking to other ports to the input power, and the unit can be decibel (dB); isolation is an indicator to measure the quality of the switch. When the switch is qualified, the isolation between the ports is good and the signal leakage is minimal.

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

[0077] Stress refers to the internal force generated by the interaction between the various parts per unit area of ​​an object when it is deformed due to external factors such as force and temperature.

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

[0079] The drive voltage refers to the minimum operating voltage of the switch from the up state to the down state.

[0080] The coplanar waveguide is composed of a central conductor strip made on one surface of a dielectric substrate and conductor planes made on both sides of the central conductor strip. The coplanar waveguide propagates TEM waves and has no cutoff frequency.

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

[0082] The material used for the coplanar waveguide signal line 9 is 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. There are gradient structures on both sides for impedance matching. The length of each stage at both ends is 112 μm. The gradient structure is stepped, and the width of the end stage is slightly larger than the width of the signal bridge. Simulation shows that the larger the width of the former is than the latter, the worse the RF performance. The width of one side of each step of the step is 5 μm, which is used to transmit RF signals and serve as the DC negative pole of the RF MEMS switch.

[0083] The gap distance between the defective coplanar waveguide ground 8 and the coplanar waveguide signal line 9 is 5μm. It and the coplanar waveguide signal line form a coplanar waveguide structure, and its two ends are connected, which is convenient for using lumped port simulation in electromagnetic simulation software. In actual processing, its two ends are not connected, but the negative non-metallic DC bias line is directly connected to the coplanar waveguide signal line. The selected material is gold with a thickness of 0.5μm. There is a defective structure and an air bridge on the side of the lower right anchor point. The purpose is to isolate the lower right anchor point from the defective coplanar waveguide ground by DC, and connect the bias line to the DC port through the air bridge to prevent the DC electrode from being applied to the defective coplanar waveguide ground. The switch will explode after breakdown or short circuit under high voltage, damaging the RF probe and other adjacent devices.

[0084] The material of the right lower layer anchor point 7 is gold, with a thickness of 0.5 μm, and is isolated from the defective coplanar waveguide ground gap, and is used to support the RFMEME switch and connect the DC electrode. Its width a20 is greater than the width of the right first layer anchor point 10 μm, 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 with a thickness of 0.2 μm and a width of 5 μm. It passes through the air bridge of the defective coplanar waveguide ground, and the two sides are separated by 5 μm from the defective coplanar waveguide ground. Its function is to connect the lower right anchor point and the DC port. The use of 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 0.2 μm. It is located at both ends of the coplanar waveguide signal line and has multiple folds near one end of the coplanar waveguide signal line. The folds are used to increase the bias line inductance and reduce the impact on the RF performance. One end is spaced from the defective coplanar waveguide and connected to the simulated air bridge, and the other end is connected to the positive metal bias line for transmitting a DC drive voltage.

[0087] The simulated air bridge 4 is located on both sides of the coplanar waveguide signal line, spans the connection between the two ends of the defective coplanar waveguide, and is connected to the coplanar waveguide signal line and the negative non-metallic DC bias line. An impedance boundary of 50 ohms square resistance is set on the surface to simulate the actual situation that the DC bias line is connected to the coplanar waveguide signal line. In actual processing, there is no such structure, but the negative non-metallic DC bias line and the coplanar waveguide signal line are directly connected;

[0088] The positive metal bias line 15 is made of Au with a thickness of 0.5 μm and is located on both sides of the DC port. Both ends are connected to the DC port and the negative non-metal DC bias line for transmitting DC power. The use of metal material can reduce the voltage division caused by non-metal material.

[0089] The DC port 5 is made of Au with a thickness of 0.5 μm and is located on both sides of the defective coplanar waveguide to provide a DC driving voltage to the RF MEME switch.

[0090] The electrode dielectric layer 10 is formed on the coplanar waveguide signal line and is located below the metal cantilever beam. It is used to form a capacitor structure between the first two layers to isolate the DC short circuit. The material used is Si3N4 with a relative dielectric constant of 7.6. The shape is rectangular and the width is larger 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, resulting in a short circuit.

[0091] The upper right anchor point 11 is made of Au with a thickness of 1 μm, formed on the lower right anchor point, and has an area 10 μm smaller than the former, and is used to form an RF MEMS switch gap, and has arc chamfers near the periphery 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 close to the coplanar waveguide signal line is an arc chamfer 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 size of the metal cantilever beam in this embodiment. The metal cantilever beam is made of Au and has a thickness of 0.5μm. It is formed on the upper right anchor point and includes a metal beam and a signal bridge. The metal beam has multiple folds to reduce the driving voltage and increase the inductance. There is a release hole on the signal bridge. The diameter of the release hole is four times the gap to speed up 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 of electrostatic attraction and are used to switch on and off radio frequency signals. The signal bridge structure integrates the upper electrode and radio frequency switch functions into one, which can reduce the size of the switch.

[0094] Figure 6 The figure is a schematic diagram of the dimensions of the silica skirt beam in this embodiment. The silica 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 to connect the left anchor point and the metal cantilever beam and provide a restoring force to prevent the metal cantilever beam from causing excessive warping. The material is SiO2 with a thickness of 1 μm. The two ends and the middle are connected by ring arms. The path of the ring arm is a spline curve. The junction of the two ends of the ring arm is an arc transition. The length of the ring arm near the left anchor point is shorter than 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 deformation simulation diagram of the compact novel RF MEMS series capacitor switch described in this embodiment, Figure 8 This is a simulation diagram of the von Mises stress on the surface of the compact novel RF MEMS series capacitor switch described in this embodiment. Fig. 9 This is a simulation diagram of the driving voltage of the compact new RF MEMS series capacitor switch described in this embodiment. The electromechanical coupling simulation was performed using COMSOL Multiphysics. The Si3N4 electrode dielectric layer was not added during the simulation process. The solid mechanics part includes the silicon dioxide skirt beam, the metal cantilever beam, the lower right anchor point, the upper right anchor point, the left anchor point, and the coplanar waveguide signal line. Figure 7 The deformation of the switch when it is pressed down 0.9 μm by electrostatic force is shown; Figure 8The figure shows the von Mises stress distribution of the switch after it is pressed down by electrostatic force by 0.9μm. It can be seen that the stress distribution on the switch beam is uniform, and the maximum stress of 53.5MPa occurs at the middle edge of the silica skirt beam, which is less than the yield strength of Au 201MPa and the fatigue failure strength of Au 63MPa (data from the paper).

[0097] Fig.10 This is a simulation diagram of the insertion loss and isolation of the compact novel RF MEMS series capacitor switch described in this embodiment. It can be seen that at 12GHz-78GHz, the switch isolation is greater than 10db and the insertion loss is less than 1db; at 12GHz-48GHz, the switch isolation is greater than 15db and the insertion loss is less than 1db, and the switch has a large operating bandwidth.

[0098] Fig.11 This is a SEM image of the actual switch processing described in this embodiment. Figure 5 The signal bridge of the metal cantilever beam is different, and the rest of the dimensions and structures are the same Figure 1 Similarly, it can be seen that the beams and signal bridges of the SEM switch have no serious warping.

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

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[0102]

Claims

1. A new compact RF MEMS series capacitor switch, characterized in that: It includes a back-coated 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 right lower layer anchor point (7), a defective coplanar waveguide ground (8), a coplanar waveguide signal line (9), an electrode dielectric layer (10), a right upper layer 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 back 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), presenting a symmetrical stepped structure, disconnected in the middle, and 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, has a step-type defect structure on the right side of the coplanar waveguide signal line (9), and has an air bridge on the right side of the step-type defect structure; The right lower layer anchor point (7) is located on the upper surface of the substrate (2), in the step-type defect structure of the defective coplanar waveguide ground (8), and is isolated from the defective coplanar waveguide ground (8) by a gap; Two DC ports (5) are located on the upper surface of the substrate (2), respectively located on the left and right sides of the defect coplanar waveguide ground (8); A positive non-metallic DC bias line (6) is located on the upper surface of the substrate (2), passes through the air bridge of the defective coplanar waveguide ground (8), and is used to connect the right lower layer anchor point (7) and the DC port (5) on the right side; Two simulated air bridges (4) are respectively located at two ends of the coplanar waveguide signal line (9) and span the defective coplanar waveguide ground (8); the simulated air bridge (4) is connected to the end of the adjacent coplanar waveguide signal line (9); Two positive metal bias lines (15) are located on the upper surface of the substrate (2), and one end of each of the two positive metal bias lines is connected to the DC port (5) on the left side; 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), and include mutually connected straight line segments and multiple folded line segments; the straight line segments are isolated from the defective coplanar waveguide ground (8) and connected to the adjacent simulated air bridge (4), and the multiple folded line segments are connected to the adjacent positive metal bias line (15); Two electrode dielectric layers (10) are both rectangular in structure, covering the two ends of the disconnected portion in the middle of the coplanar waveguide signal line (9), with a width covering a step of the coplanar waveguide signal line (9) and not contacting 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 has a smaller area than the lower right anchor point (7); The metal cantilever beam (12) includes a connected metal beam (16) and a signal bridge (17), the metal beam (16) includes a multi-folded metal wire and a metal patch, and the metal patch is located on the upper surface of the right upper 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 disconnected portion of the coplanar waveguide signal line (9); a gap is formed between the signal bridge (17) and the electrode dielectric layer (10) through the right upper anchor point (11); The left anchor point (14) is located on the upper surface of the defective coplanar waveguide ground (8), and includes two layers stacked up and down and having the same shape; the lower layer and the right upper layer anchor point (11) are located at the same height, and the center line is parallel to the edge of the substrate (2) and passes through the center position of the disconnected part in the middle of the coplanar waveguide signal line (9); the upper layer and the metal cantilever beam (12) are located at the same height; The silicon dioxide 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 silicon dioxide skirt beam (13) spans the middle disconnected portion of the coplanar waveguide signal line (9).

2. The novel compact RF MEMS series capacitor switch according to claim 1, characterized in that: The silicon dioxide skirt beam (13) is hollowed out at positions corresponding to the left anchor point (14) and the middle part of the signal bridge (17), and at positions corresponding to the multiple folded metal wires, to form a ring arm connected structure of the left end, the middle end, and the right end. The path of the ring arm is a spline curve, and the connection between the two ends of the ring arm is an arc transition. The length of the ring arm close to the left anchor point (14) is shorter than that of the other ring arm.

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

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

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

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

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

6.

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

9. The novel compact 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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