Terahertz memristor RF switch based on suspended nanoelectrodes and its fabrication method

Abstract

This invention discloses a terahertz memristor RF switch based on suspended nanoelectrodes on a high-resistivity silicon substrate and its fabrication method. The switch includes a substrate, a bonding layer on its upper surface, an inert electrode layer on its upper surface, a Nafion dielectric layer on its upper surface, an active electrode layer on its upper surface, and an inert metal layer on its upper surface. The RF switch in this design uses a Nafion ion exchange membrane as the main material and comprises, from bottom to top, a silicon substrate, a chromium bonding layer, an inert bottom electrode, a Nafion thin film intermediate layer, an active top electrode, and an inert metal protective layer. A protruding microstructure is fabricated on the silicon substrate using an etching process to suspend the inert electrode. The entire memristor RF switch is mainly composed of two electrodes and an intermediate layer stacked together. By connecting the active electrode to the positive terminal and the inert electrode to the negative terminal, non-volatility is exhibited when turn-on and turn-off voltages are applied.

Description

Technical Field

[0001] This invention belongs to the field of non-volatile electronic devices, specifically relating to a terahertz memristor radio frequency switch based on a suspended nanoelectrode and its fabrication method. Background Technology

[0002] An RF switch is a device used to control the transmission of radio frequency (RF) signals. It is commonly used in RF systems such as wireless communication systems, radar systems, and satellite communication systems. RF switches enable the switching, connection, or isolation of RF signals, making them an important component of RF systems.

[0003] Traditional radio frequency (RF) switches commonly employ mechanical, solid-state, and electromagnetic operating principles. Mechanical RF switches typically rely on mechanical mechanisms to switch signals on and off, offering high voltage and current withstand capabilities, but suffer from short lifespan and slow response. Solid-state RF switches use solid-state devices (such as MOSFETs and PIN diodes) as switching elements, offering advantages like fast response, long lifespan, and small size, but with higher power consumption and lower voltage withstand capabilities. Electromagnetic RF switches utilize electromagnetic principles to control signals, providing high voltage and current withstand capabilities, but are bulky and consume significant power.

[0004] Non-volatile devices are a class of devices that can retain stored information even when power is off, as opposed to volatile devices. They are commonly used in storage devices, such as computer memory and solid-state drives, as well as in some specialized applications, such as aerospace and military. Traditional non-volatile devices include flash memory and EEPROM (Electrically Erasable Programmable Read-Only Memory). These devices operate primarily based on principles of dielectrics, electrochemistry, and magnetism, storing and retrieving information by altering the physical state or charge distribution of the material. Summary of the Invention

[0005] To address the aforementioned issues, this invention discloses a novel RF switch based on suspended nanoelectrodes, which reduces power consumption, provides rapid response, and exhibits high isolation and low insertion loss, making it a non-volatile device. Furthermore, a method for fabricating this non-volatile device with good manufacturability and high processing precision is provided.

[0006] Technical Solution: The terahertz memristor RF switch based on suspended nanoelectrodes of this invention uses a high-resistivity silicon-based wafer as a carrier, comprising, from bottom to top, a silicon substrate layer, a chromium interconnect layer, an inert bottom electrode, a Nafion dielectric layer, an active top electrode, and an inert metal protective layer. A raised microstructure is fabricated on the silicon substrate layer using an etching process to achieve the suspension of the inert electrode. The entire non-volatile device is mainly composed of two electrodes and an intermediate layer stacked together. By connecting the active electrode to the positive terminal and the inert electrode to the negative terminal, non-volatility is exhibited when turn-on and turn-off voltages are applied.

[0007] Furthermore, in the terahertz memristor RF switch based on suspended nanoelectrodes of the present invention, the positive electrode is an active electrode (e.g., metallic copper) that applies a forward voltage in the MIM structure; and the negative electrode is an inert electrode (e.g., metallic gold) that applies a reverse voltage in the MIM structure.

[0008] Furthermore, in the terahertz memristor RF switch based on suspended nanoelectrodes of the present invention, the negative electrode metal covers the micro-convex structure, and the Nafion thin film covers both the negative electrode metal and the micro-convex structure.

[0009] Furthermore, in the terahertz memristor RF switch based on suspended nanoelectrodes of the present invention, the inert metal layer is to prevent the oxidation of the active metal of the positive electrode from affecting the device performance.

[0010] Furthermore, in the terahertz memristor RF switch based on suspended nanoelectrodes of the present invention, the negative electrode metal layer and the inert metal layer must not overlap with the edge of the positive electrode metal layer to avoid short circuit.

[0011] This invention utilizes optical lithography, spin coating, and electron beam evaporation to fabricate non-volatile devices. The design of rational process steps, including the shape of the photolithography template, obtains the desired silicon-based microstructure, reduces insertion loss in novel RF switches, and improves isolation.

[0012] The present invention provides a method for fabricating a terahertz memristor radio frequency switch based on a suspended nanoelectrode, comprising the following steps:

[0013] Step 1: Spin-coat photoresist onto the surface of a silicon wafer, and then use optical lithography to define the desired pattern on the spin-coated photoresist layer;

[0014] Step 2: Using a dry etching process, the pattern of the micro-bump structure is etched onto silicon to obtain a silicon pillar of a predetermined size;

[0015] Step 3: Using a wet etching process, anisotropic etching is used to etch the silicon pillar into a cone shape;

[0016] Step 4: Spin-coat photoresist onto the surface of the silicon wafer, and then use optical lithography to define the desired pattern on the spin-coated photoresist layer;

[0017] Step 5: Electron beam evaporation is used to deposit the connecting layer and inert electrode layer on the pattern, and finally the residual photoresist and excess material are removed.

[0018] Step 6: Spin-coat Nafion solution onto the surface of the inert electrode layer to form a film using a process;

[0019] Step 7: Spin-coat photoresist onto the upper surface of the device, and then use optical lithography to spin-coat the photoresist to define the required pattern on the upper layer;

[0020] Step 8: Use argon ion etching to etch away the photoresist and Nafion thin film outside the desired pattern to prepare the Nafion dielectric layer;

[0021] Step 9: Spin-coat photoresist onto the upper surface of the device, and then use optical lithography to define the required pattern on the spin-coated photoresist.

[0022] Step 10: Electron beam evaporation is used to deposit the active electrode layer and the inert metal layer on the pattern. Finally, the residual photoresist and excess material are removed. The inert electrode layer must not overlap with the edges of the active electrode layer and the inert metal layer to avoid short circuits. The inert metal layer is to prevent oxidation of the active metal layer from affecting the device performance.

[0023] Furthermore, in the method of the present invention, the positive electrode is an active metal deposited by vapor deposition, such as Cu or Ag; the negative electrode is an inert metal deposited by vapor deposition, such as Au or Pt.

[0024] Considering the small size, simple fabrication, and strong cycling characteristics of the terahertz memristor RF switch based on suspended nanoelectrodes, the applicant designed and fabricated this memristor RF switch using advanced micro-nano fabrication technology.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0026] 1. The non-volatility of memristor RF switches enables them to remain stable during switching states without continuously consuming energy, thus achieving low-power RF switches; and they also have good electrochemical activity, enabling fast switching response speeds to meet the high-speed signal switching requirements of RF systems.

[0027] 2. By precisely inducing the formation direction of the potential barrier of the conductive filament through a tip discharge effect, the generation of the conductive filament is theoretically controllable, which significantly improves the stability of switch switching and effectively overcomes the inherent defects of switches based on this mechanism, laying a solid foundation for the practical application of this type of switch.

[0028] 3. The nanoscale design of the RF switch significantly improves its performance under high-frequency conditions, breaking through the technical bottleneck of traditional switches in the high-frequency field.

[0029] 4. While achieving nanoscale performance, the process utilizes the processing precision requirements of tens of micrometers to enable mass production, which is cost-effective and provides technical support for the industrial application of radio frequency switches. Attached Figure Description

[0030] Figure 1 Side view of a terahertz memristor RF switch based on suspended nanoelectrodes;

[0031] Figure 2 Top view of a terahertz memristor RF switch based on suspended nanoelectrodes;

[0032] Figure 3 Process flow diagram of terahertz memristor RF switch based on suspended nanoelectrodes;

[0033] Figure 4 Example of a levitated electrode for a terahertz memristor RF switch based on levitated nanoelectrodes;

[0034] Figure 5 Response time of terahertz memristor RF switches based on suspended nanoelectrodes.

[0035] List of reference numerals in the attached diagram: 1. Silicon substrate layer; 2. Connector layer; 3. Inert electrode layer; 4. Nafion layer; 5. Active electrode layer; 6. Inert metal protective layer. Detailed Implementation

[0036] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0037] Example: This example is a terahertz memristor RF switch based on suspended nanoelectrodes:

[0038] Example 1: This invention relates to a terahertz memristor RF switch based on suspended nanoelectrodes. Using a high-resistivity silicon-based wafer as a carrier, the switch comprises, from bottom to top, a silicon substrate layer 1, a connecting layer 2, an inert electrode layer 3, a Nafion dielectric layer 4, an active electrode layer 5, and an inert metal protective layer 6. A raised microstructure is fabricated on the silicon substrate layer using an etching process, enabling the inert positive electrode to be suspended. The entire non-volatile device is mainly composed of two electrodes and an intermediate layer stacked together. Non-volatility is exhibited by connecting the active electrode to the positive electrode and the inert electrode to the negative electrode, and applying turn-on and turn-off voltages. This memristor RF switch covers the inert electrode on the high-resistivity silicon-based wafer, with an electrode thickness of 500 nm. The active electrode on top also has a thickness of 500 nm.

[0039] The present invention provides a method for fabricating non-volatile devices based on MIM structures to prepare terahertz memristor RF switches based on suspended nanoelectrodes. Taking an inert electrode thickness of 500 nm, a dielectric layer thickness of 500 nm, and an active electrode thickness of 500 nm as an example, the fabrication process is as follows:

[0040] Step 1: Spin-coat photoresist onto the upper surface of substrate layer 1 of the silicon wafer, and then use optical lithography to define the required pattern on the spin-coated photoresist layer, as shown in Figure 3(a);

[0041] Step 2: Using a dry etching process, the pattern of the micro-bump structure is etched onto silicon to obtain a silicon pillar of a predetermined size, as shown in Figure 3(c).

[0042] Step 3: Using a wet etching process, anisotropic etching is used to etch the silicon pillar into a cone shape, as shown in Figure 3(d);

[0043] Step 4: Spin-coat photoresist onto the surface of the silicon wafer, and then use optical lithography to define the desired pattern on the spin-coated photoresist layer, as shown in Figure 3(e);

[0044] Step 5: Electron beam evaporation is used to deposit the connecting layer 2 and the inert electrode layer 3 on the pattern. Finally, the residual photoresist and excess material are removed. The result is shown in Figure 3(g).

[0045] Step 6: Spin-coat Nafion solution onto the surface of the inert electrode layer 3 and form a film using the process. The result is shown in Figure 3(h).

[0046] Step 7: Spin-coat photoresist onto the upper surface of the device, and then use optical lithography to define the required pattern on the spin-coated photoresist, as shown in Figure 3(i);

[0047] Step 8: The photoresist and Nafion film outside the desired pattern are etched away by argon ion etching to prepare Nafion dielectric layer 4, as shown in Figure 3(k);

[0048] Step 9: Spin-coat photoresist onto the upper surface of the device, and then use optical lithography to define the required pattern on the spin-coated photoresist, as shown in Figure 3(l);

[0049] Step 10: Electron beam evaporation is used to deposit the active electrode layer 5 and the inert metal layer 6 on the pattern. Finally, the residual photoresist and excess material are removed, as shown in Figure 3(n). The inert electrode layer 3 must not overlap with the edges of the active electrode layer 5 and the inert metal layer 6 to avoid short circuits. The inert metal layer 6 is to prevent oxidation of the active metal layer 5 from affecting device performance. The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

[0050] Example 2: This invention relates to a terahertz memristor RF switch based on suspended nanoelectrodes. Using deep silicon anisotropic etching, a tapered silicon pillar, as shown in Figure 4, is fabricated on a silicon substrate. The top of the pillar is nanoscale, thus suspending the inert electrode layer. As shown in Figure 5, actual testing achieved an on-state response time of 45 ns and an off-state response time of 120 ns. Based on these data, the on-state power consumption is calculated to be approximately 0.174 nJ, and the off-state power consumption is approximately 8.619 nJ.

[0051] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A terahertz memristor radio frequency switch based on suspended nanoelectrodes, characterized in that, The substrate (1) includes a connecting layer (2) on the upper surface of the substrate (1), an inert electrode layer (3) on the upper surface of the connecting layer (2), a Nafion dielectric layer (4) on the upper surface of the inert electrode layer (3), an active electrode layer (5) on the upper surface of the Nafion dielectric layer, and an inert metal layer (6) on the upper surface of the active electrode layer (5). The substrate silicon layer (1) is prepared with a protruding microstructure by an etching process; The inert electrode layer (3) covers the protruding microstructure portion in the substrate silicon layer (1); The inert electrode layer (3) shall not overlap with the edges of the active electrode layer (5) and the inert metal layer (6).

2. The method for fabricating a terahertz memristor radio frequency switch based on a suspended nanoelectrode according to claim 1, characterized in that, The fabrication of this memristor RF switch includes the following steps: Step 1: Spin-coat photoresist onto the surface of a silicon wafer, and then use optical lithography to define the desired pattern on the spin-coated photoresist layer; Step 2: Using a dry etching process, the pattern of the raised microstructure is etched onto silicon to obtain a silicon pillar of a predetermined size; Step 3: Using a wet etching process, anisotropic etching is used to etch the silicon pillar into a cone shape; Step 4: Spin-coat photoresist onto the surface of the silicon wafer, and then use optical lithography to define the desired pattern on the spin-coated photoresist layer; Step 5: Electron beam evaporation is used to deposit a connecting layer (2) and an inert electrode layer (3) on the pattern, and finally the residual photoresist and excess material are removed; Step 6: Spin-coat Nafion solution onto the surface of the inert electrode layer (3) to form a film through the process; Step 7: Spin-coat photoresist onto the upper surface of the device, and then use optical lithography to define the required pattern on the spin-coated photoresist. Step 8: The photoresist and Nafion film outside the desired pattern are etched away by argon ion etching to prepare the Nafion dielectric layer (4). Step 9: Repeat step 7 to spin-coat photoresist onto the upper surface of the device, and then use optical lithography to define the required pattern on the spin-coated photoresist. Step 10: Electron beam evaporation is used to deposit the active electrode layer (5) and the inert metal layer (6) on the pattern. Finally, the residual photoresist and excess material are removed. The inert electrode layer (3) must not overlap with the edge of the active electrode layer (5) and the inert metal layer (6).

3. The method for fabricating a terahertz memristor radio frequency switch based on a suspended nanoelectrode according to claim 2, characterized in that, The positive electrode is an active electrode deposited by vapor deposition, the negative electrode is an inert electrode deposited by vapor deposition, and the connecting layer is a metal with stronger adhesion.

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