An in-plane sliding parallel-capacitor RF switch based on the floating potential

Abstract

The present invention provides an in-plane sliding parallel capacitor radio frequency switch based on structural superlubricity, which includes a substrate, first to third driving components, an insulating layer, and a sliding component. When a driving voltage is applied between the first and second driving components, the sliding component slides above the first and second driving components under the action of a horizontal force. At this time, a large capacitance is formed between the first and second driving components and the sliding component, and the radio frequency signal is almost completely reflected, resulting in transmission cutoff. When a driving voltage is applied between the second and third driving components, the sliding component slides above the second and third driving components under the action of a horizontal force. At this time, there is no overlapping area in the vertical direction between the first driving electrode and the sliding component, and the capacitance is very small, enabling the radio frequency signal to achieve almost lossless transmission.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency microelectromechanical system switches (RF MEMS Switch), and particularly relates to a in-plane sliding parallel-capacitance radio frequency switch based on a floating potential. Background Art

[0002] With the development of radar and wireless communication technologies, radio frequency devices with small size, low power consumption, high performance, and multi-functionality have become the development trend in the radio field. Radio frequency devices are developing towards miniaturization and integration, and MEMS switches have emerged as the times require. RF MEMS switches have gradually replaced traditional GaAs FET switches and become the development direction of radio frequency switches (RF Switch). Compared with traditional switches, RF MEMS switches have the advantages of lower insertion loss, higher isolation, better linearity, lower power consumption, smaller size, etc., and can be easily integrated with IC circuits, having broad application prospects. Currently, the existing RF MEMS switches mainly have several driving methods such as electrostatic driving mechanism, thermal driving mechanism, electromagnetic driving mechanism, piezoelectric driving mechanism, etc.

[0003] As a basic electronic component, the RF MEMS electrostatic switch has the characteristics of low power consumption, low insertion loss, low crosstalk, high isolation, high linearity, etc. compared with traditional P-I-N diode switches and FET field effect thyristor switches, and is considered to be one of the most important MEMS devices. In particular, with the rapid development of 5G communication systems, radar systems, satellite communication systems, high-performance radio frequency chip systems in recent years, the industry has put forward higher requirements for the power consumption, reliability, isolation, linearity, power handling ability, etc. of underlying RF radio frequency switch devices. For example, the LTE-A antenna switch with carrier aggregation function in the 5G system must meet the requirement of IIP3 = 90 dBm, and the RF-MEMS radio frequency switch is the only switch that can achieve IIP3 > 90 dBm. Due to the fact that traditional solid-state semiconductor switches (P-I-N and FET) rely on doped carrier conduction and the existence of contact barriers, the switches exhibit poor quality factors (Ron×Coff) and there is leakage current in the off state, which seriously affects the insertion loss, isolation, and linearity of the switches, making such switches not suitable for high-frequency radio frequency signal switching. The RF MEMS electrostatic switch relies on mechanical contact to conduct radio frequency signals, and there is physical isolation between signal lines. Therefore, it has low power consumption (nj), low insertion loss, high isolation, and linearity, which can greatly reduce the energy consumption and cost of wireless communication systems, radar detection systems, and satellite systems, improve the fidelity of radio frequency signal transmission, and significantly enhance the comprehensive performance of the system. Its research and application have become the key technology for advanced electronic equipment such as wireless communication (5G) systems, radar systems, and satellite systems.

[0004] Compared with the widely used semiconductor RF switches, although RF MEMS electrostatic switches have many advantages, the mechanical contact-type on-off mode brings serious reliability problems. The contacts or insulation layers of RF MEMS electrostatic switches are easily damaged in high-speed collisions, resulting in increased on-resistance, which in turn causes a strong thermal effect and device failure. At the same time, the damage to the insulation layer will also aggravate the accumulation of surface charges. When the charge accumulation exceeds the critical value, the switch will fail due to self-electrostatic adsorption; the arc discharge that occurs at the moment of disconnection can cause the contact material to melt, causing a significant increase in contact resistance or even direct adhesion between the contact and the conductive line; when high-energy power passes through the switch, it will couple sufficient electrostatic force between the upper and lower contacts or plates, causing the switch to self-lock and close. Usually, the processing power of RF MEMS electrostatic switches is less than 1W, while semiconductor switches can reach 1-10W. The above is one of the main reasons affecting the reliability and application field of RF MEMS. Compared with traditional semiconductor switches, the service life of RF MEMS electrostatic switches is more than two orders of magnitude lower. In addition, the standard voltage used in IC integrated circuit systems is currently lower than 5V, while the driving voltage of RF MEMS electrostatic switches is generally between 10V and 80V, which is one of the reasons why RF-MEMS electrostatic switches are rarely used in mobile phone wireless communication systems. In summary, improving power handling capabilities, reducing driving voltage, and improving reliability are key issues that need to be addressed for the further development of RF-MEMS electrostatic switches.

[0005] Structural super-slip technology studies the frictionless and wear-free sliding phenomenon between two or the same materials. Initial research was limited to super-slip phenomena at the nanoscale, such as super-slip between multi-arm coaxial carbon nanotubes, super-slip between nanoprobes and two-dimensional materials, etc. In 2013, Professor Zheng Quanshui discovered the super-slip phenomenon between HOPG (Highly Oriented Pyrolytic Graphite) sheet materials at the micrometer scale for the first time, marking the transition of super-slip from basic research to applied technical research. Based on the principle of structural super-slip, the present invention proposes an in-plane sliding parallel capacitor RF switch, which can reduce the driving voltage and greatly improve the service life and power handling capacity of the switch. SUMMARY OF THE INVENTION

[0007] Technical issues

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an in-plane sliding parallel capacitor RF switch based on structural super-slippery according to the low-friction, wear-free in-plane sliding motion between the super-slippery structure and a flat heterogeneous substrate.

[0009] Solution to the problem

[0010] Technical Solutions

[0011] To achieve the above-mentioned invention objectives, the technical solution provided by the present invention is: an in-plane sliding parallel capacitor radio frequency switch based on structural superlubricity. It includes a substrate, a driving component, an insulating layer, and a sliding component. When a driving voltage is applied between the driving components, the sliding component slides above the driving components under the action of a horizontal force. At this time, a large capacitance is formed between the driving component and the sliding component, and the radio frequency signal is almost completely reflected, and the transmission is cut off; when a driving voltage is applied between other driving components, the sliding component slides above another driving component under the action of a horizontal force. At this time, there is no facing area between the previous driving electrode and the sliding component in the vertical direction, the capacitance is very small, and the radio frequency signal can achieve almost lossless transmission.

[0012] Specifically, the in-plane sliding parallel capacitor radio frequency switch provided by the present invention is realized through the following scheme:

[0013] An in-plane sliding parallel capacitor radio frequency switch based on structural superlubricity, including a substrate, a driving component, an insulating layer, and a sliding component, characterized in that: the driving component is placed in the substrate, the insulating layer is placed on the surface of the substrate, the sliding component is placed above the insulating layer, the sliding component has a superlubricating surface and contacts the insulating layer through the superlubricating surface; the driving component at least includes a first driving component, a second driving component, and a third driving component, and the sliding component can be driven by the driving component and change the position of the sliding component relative to the driving component.

[0014] Further, the sliding component can be driven to slide horizontally in the plane, and the switch is realized by adjusting the overlap and separation of the driving component and the sliding component in the vertical plane.

[0015] Further, the driving component includes at least 3 driving electrodes.

[0016] Further, the sliding component is a superlubricating sheet, preferably selected from graphite, preferably HOPG.

[0017] Further, the substrate is selected from insulating materials or semiconductor materials.

[0018] Further, the semiconductor material is preferably high-group silicon; the insulating material is preferably selected from SiO2, SiC, sapphire, mica, etc.

[0019] Further, the insulating layer is preferably selected from silicon oxide layers.

[0020] Further, the thickness of the insulating layer is nanoscale.

[0021] Further, the thickness of the insulating layer is preferably 2-50 nanometers.

[0022] Further, the driving manner in which the driving component drives the sliding component to slide horizontally in the plane is electrostatic driving.

[0023] The present invention utilizes a sandwich structure with a driving component, an insulating layer, and a sliding component from bottom to top, to achieve in-plane extremely low-friction and wear-free sliding of the sliding component on the surface of the flat insulating layer; when in the off state, the capacitance between the sliding component and the driving component is extremely small, such that the radio frequency signal has almost no loss; when in the on state, due to the insulating layer with a nanoscale thickness, the sliding component and the driving component form a relatively large capacitance, and the radio frequency signal is completely reflected. The on / off of the radio frequency switch is controlled by setting a voltage control timing sequence.

[0024] Advantages of the Invention

[0025] Advantages

[0026] Due to the extremely low friction and no wear of the present invention, it can achieve a low driving voltage, an extremely high service life, and a high power handling capacity, is expected to break through a major obstacle restricting the life of RF MEMS electrostatic switches, promote their practical application process, and facilitate the leapfrog development of related electronic equipment research such as wireless communication systems (5G), high-performance phased array radars, and satellite communication systems.

[0027] Brief Description of the Drawings Description of the Drawings

[0028] Figure 1 Schematic diagram of the on state of the shunt capacitor radio frequency switch of the present invention;

[0029] Figure 2 Top view of the on state of the shunt capacitor radio frequency switch of the present invention;

[0030] Figure 3 Schematic diagram of the blocking state of the shunt capacitor radio frequency switch of the present invention;

[0031] Figure 4 Top view of the blocking state of the shunt capacitor radio frequency switch of the present invention;

[0032] Figure 5 Cross-sectional view of the substrate with the embedded driving electrode of the shunt capacitor radio frequency switch of the present invention;

[0033] Reference numerals: 1. HOPG super slider, 2. insulating layer, 3. substrate, 4. first driving electrode, 5. second driving electrode, 6. third driving electrode.

[0034] Best Embodiment for Implementing the Invention

[0035] Best Embodiment of the Present Invention

[0036] The super slider described in the present invention is a part of the super sliding pair in the prior art. Between the two contacting surfaces of the existing super sliding pair, the frictional force is almost zero during relative sliding, the friction coefficient is less than one-thousandth, and the wear is zero.

[0037] For example, the specific preparation method of the existing super slider based on HOPG graphite is as follows:

[0038] Step 1: Cover photoresist on HOPG in sequence. The photoresist can be covered by spin coating.

[0039] Step 2: Pattern the photoresist to retain multiple photoresist islands. The step of patterning the photoresist determines the layout of the island-like structures formed in the subsequent steps. For example, the photoresist can be patterned by electron beam lithography. The formed photoresist islands can be, for example, with an average diameter of 1 μm to 30 μm, and the average interval between the photoresist islands is 1 μm to 100 μm. Thus, the etched island-like structures also have corresponding average diameters and average intervals.

[0040] Step 3: Etch the substrate to remove the part of the substrate not protected by the photoresist, thereby forming multiple island-like structures. The etching can be, for example, reactive ion etching.

[0041] Step 4: Use a robotic arm to push each of the island-like structures one by one to detect whether it has a super-slipping shear plane. Among the island-like structures with self-recovery performance, the HOPG sheet structure with a super-slipping shear plane on the lower surface is the super slider.

[0042] Embodiment of the Invention

[0043] Embodiment Modes of the Present Invention

[0044] The following further describes the embodiments of the present invention with reference to the accompanying drawings:

[0045] As Figure 1As shown in the figure, the in-plane sliding parallel capacitor RF switch is composed of a high-resistance silicon substrate 3, a first driving electrode 4, a second driving electrode 5, a third driving electrode 6, an insulating layer 2, and a HOPG ultra-sliding sheet 1. The first driving electrode 4, the second driving electrode 5, and the third driving electrode 6 are embedded in the substrate 3; the surfaces of the substrate 3, the first driving electrode 4, the second driving electrode 5, and the third driving electrode 6 are flush and maintain atomic-level flatness; the insulating layer 2 covers the first driving electrode 4, the second driving electrode 5, and the third driving electrode 6 for insulation between the HOPG ultra-sliding sheet and the first driving electrode 4, the second driving electrode 5, and the third driving electrode 6. The thickness of the insulating layer 2 is controlled between 2 nm and 50 nm, so that the gap between the first driving electrode 4, the second driving electrode 5, and the third driving electrode 6 and the ultra-sliding sheet 1 is small enough to ensure a small excitation voltage. The HOPG ultra-sliding sheet 1 is placed on the insulating layer to form an ultra-smooth contact pair with the insulating layer 2. Its initial position is directly opposite to the first driving electrode 4. Due to the atomic-level flat and ultra-smooth surface of the HOPG ultra-sliding sheet 1, it can slide on the surface of the insulating layer 2 with extremely low friction and no wear. At the same time, it will not suffer from adhesion failure due to charge accumulation on the electrode and can achieve an extremely long service life.

[0046] The working process of the in-plane sliding parallel capacitor RF switch is as follows: Figure 1 、 Figure 2 When the RF switch is in the on state, a driving voltage V is applied between the first driving electrode 4 and the second driving electrode 5. At this time, charges will be induced at the left and right ends of the HOPG ultra-sliding sheet 1, generating a floating potential. The HOPG ultra-sliding sheet 1 will move to the position with the minimum electric potential energy, that is, the center-symmetric position relative to the first driving electrode 4 and the second driving electrode 5. At this time, since there is no overlapping area in the vertical direction between the HOPG ultra-sliding sheet 1 and the third driving electrode 6, the capacitance is close to zero, and the RF signal can pass through completely without reflection loss.

[0047] When a driving voltage V is applied between the second driving electrode 5 and the third driving electrode 6, as Figure 3 、 Figure 4 shown, the HOPG ultra-sliding sheet 1 is subjected to a leftward acting force and is pulled to the center-symmetric position of the second driving electrode 5 and the third driving electrode 6. Since the thickness of the insulating layer 2 is at the nanometer level, a relatively large capacitance is formed between the HOPG ultra-sliding sheet 1 and the third driving electrode 6, and the RF signal is completely reflected and the transmission is cut off.

[0048] By adjusting the number, arrangement, timing control of the driving electrodes and the size of the HOPG ultra-sliding sheet, in-plane continuous sliding of the HOPG ultra-sliding sheet can be achieved.

[0049] Industrial Applicability

[0050] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. An in-plane sliding parallel-capacitance RF switch, comprising a substrate, a driving component, an insulating layer, and a sliding component, characterized in that: The driving component is placed inside the substrate, the insulating layer is placed on the surface of the substrate, the sliding component is placed on top of the insulating layer, the sliding component has a super-slippery surface, the insulating layer is atomically smooth, and contacts the insulating layer through the super-slippery surface; the driving component at least includes a first driving component, a second driving component, and a third driving component. The sliding component can be driven by the driving component and change its position relative to the driving component. The sliding component can be driven to slide horizontally in the plane, and the switch is realized by adjusting the overlap and separation of the driving component and the sliding component in the vertical plane of the surface.

2. The in-plane sliding parallel-capacitance RF switch according to claim 1, characterized in that: The driving component is a driving electrode.

3. The in-plane sliding parallel-capacitance RF switch according to claim 1, characterized in that: The sliding component is a super-sliding piece with a super-slippery surface.

4. The in-plane sliding parallel-capacitance RF switch according to claim 3, characterized in that: The insulating layer is a HOPG super-sliding piece.

5. The in-plane sliding parallel-capacitance RF switch according to any one of claims 1-4, characterized in that: The substrate is selected from insulating materials or semiconductor materials.

6. The in-plane sliding parallel-capacitance RF switch according to claim 5, characterized in that: The semiconductor material is high-resistance silicon; the insulating material is any one or more of SiO2, SiC, sapphire, and mica.

7. The in-plane sliding parallel-capacitance RF switch according to any one of claims 1-4, characterized in that: The insulating layer is a silicon oxide layer.

8. The in-plane sliding parallel-capacitance RF switch according to any one of claims 1-4, characterized in that: The thickness of the insulating layer is 1 - 100 nanometers.

9. The in-plane sliding parallel-capacitance RF switch according to any one of claims 1-4, characterized in that: The thickness of the insulating layer is 2 - 50 nanometers.

10. The in-plane sliding parallel-capacitance RF switch according to any one of claims 1-4, characterized in that: The driving method of the sliding component is electrostatic driving.

Images