A through-hole ground type phase change radio frequency switch and a preparation method thereof

Abstract

The application discloses a through-hole grounding type phase change radio frequency switch and a preparation method thereof, belongs to the technical field of microwave switch devices, and specifically comprises a two-terminal through-hole grounding type phase change radio frequency switch and a four-terminal through-hole grounding type phase change radio frequency switch; the application adopts a ground through-hole electrode to connect a back ground metal layer and a ground electrode; the through-hole electrode can be well equivalent to a metal wall, so that part of electromagnetic fields are confined between the through-hole electrodes, thereby reducing radiation loss and interference on adjacent transmission lines, improving an effective dielectric constant, and reducing characteristic impedance; based on this, the application can effectively improve on-conduction resistance and off-capacitance of the phase change radio frequency switch, and is suitable for a higher frequency band.

Description

Technical Field

[0001] This invention belongs to the field of microwave switching device technology, and more specifically, relates to a through-hole grounded phase-change radio frequency switch and its preparation method. Background Technology

[0002] Radio frequency (RF) switches control signal switching and communication channel transitions, finding wide application in phased array radar, satellite communications, electronic warfare systems, and mobile communication systems. Commonly used RF switches include PIN diode switches, FET (Field-Effect Transistor) switches, and RF-MEMS switches. However, all have drawbacks: FET switches are prone to distortion and voltage breakdown, while RF-MEMS switches suffer from complex manufacturing processes, high power consumption, and low yield. Compared to PIN and FET switches, phase-change RF switches have lower on-state resistance, relatively lower insertion loss, and are suitable for high-frequency circuits. Compared to RF-MEMS switches, phase-change RF switches offer advantages such as faster switching speed, smaller size, longer lifespan, simpler structure, easier integration with CMOS, and easier packaging.

[0003] With the development and progress of the times, wireless communication systems, radar, and satellites have placed higher demands on phase-change radio frequency switches. Existing phase-change radio frequency switches suffer more signal loss during transmission at high frequencies, leading to transmission failures or inaccuracies. Furthermore, as the frequency increases, the switches exhibit more pronounced nonlinear characteristics, resulting in instability and signal distortion, limiting their applicable frequency bands. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a through-hole grounded phase change radio frequency switch to solve the technical problem of the low applicable frequency band of the existing phase change radio frequency switch.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a two-terminal through-hole grounded phase-change radio frequency switch, comprising: a grounding electrode, a grounding through-hole electrode, and a back grounding metal layer, a substrate, a substrate isolation layer, a phase-change material layer and a radio frequency transmission electrode layer stacked sequentially from bottom to top;

[0006] The radio frequency transmission electrode layer includes two radio frequency transmission electrodes located on the same plane, and the tips of the two radio frequency transmission electrodes are connected by a phase change material layer.

[0007] The grounding electrodes are located on both sides of the center conductor band of the radio frequency transmission electrode layer;

[0008] The ground via electrode penetrates the substrate and the substrate isolation layer, and connects the back ground metal layer and the ground electrode.

[0009] More preferably, the grounding via electrode is located between the side of the grounding electrode near the center conductor of the RF transmission electrode layer and the central axis of the grounding electrode.

[0010] More preferably, the diameter of the grounding through-hole electrode is less than half the width of the grounding electrode.

[0011] More preferably, the substrate isolation layer is a substrate isolation layer with a thinned central region on the upper surface; the phase change material layer is embedded in the thinned region of the substrate isolation layer, and the phase change material layer is flush with the upper surface of the substrate isolation layer.

[0012] More preferably, the above-mentioned two-terminal through-hole grounded phase change radio frequency switch further includes a passivation layer located above the radio frequency transmission electrode layer; the passivation layer covers the tips of the two radio frequency transmission electrodes and the phase change material layer.

[0013] Secondly, the present invention provides a method for fabricating the above-mentioned two-terminal through-hole grounded phase-change radio frequency switch, comprising:

[0014] S11. Prepare a substrate isolation layer on the substrate;

[0015] S12. Prepare a phase change material layer on the substrate isolation layer;

[0016] S13. Prepare a radio frequency transmission electrode layer on the phase change material layer, and prepare ground electrodes on both sides of the central conductive band of the radio frequency transmission electrode layer.

[0017] S14. Prepare a grounding via electrode that penetrates the substrate and the substrate isolation layer, and prepare a back-side grounding metal layer on the back side of the substrate to obtain a phase-change radio frequency switch with two-end via grounding.

[0018] More preferably, step S12 includes:

[0019] S121. Thin the central region of the upper surface of the substrate isolation layer;

[0020] S122. Fill the thinned area with phase change material to obtain a phase change material layer, and use CMP process to make the phase change material layer flush with the upper surface of the substrate isolation layer.

[0021] Thirdly, the present invention provides a four-terminal through-hole grounded phase-change radio frequency switch, comprising: a grounding electrode, a grounding through-hole electrode, and a back grounding metal layer, a substrate, a substrate isolation layer, a heating layer, an electrical isolation layer, a phase-change material layer, and a radio frequency transmission electrode layer stacked from bottom to top.

[0022] The heating layer includes a micro heater and two heating electrodes connected to the micro heater; the micro heater is located directly below the phase change material layer and is completely covered by an electrical isolation layer.

[0023] The radio frequency transmission electrode layer includes two radio frequency transmission electrodes located on the same plane, and the tips of the two radio frequency transmission electrodes are connected by a phase change material layer.

[0024] The grounding electrodes are located on both sides of the center conductor band of the radio frequency transmission electrode layer;

[0025] The ground via electrode penetrates the substrate and the substrate isolation layer, and connects the back ground metal layer and the ground electrode.

[0026] More preferably, the grounding via electrode is located between the side of the grounding electrode near the center conductor of the RF transmission electrode layer and the central axis of the grounding electrode; the diameter of the grounding via electrode is less than half the width of the grounding electrode.

[0027] More preferably, the substrate isolation layer is a substrate isolation layer with a thinned central region on the upper surface; the micro heater is embedded in the thinned region of the substrate isolation layer, and the micro heater is flush with the upper surface of the substrate isolation layer.

[0028] More preferably, the above-mentioned four-terminal through-hole grounded phase change radio frequency switch further includes a passivation layer located above the radio frequency transmission electrode layer; the passivation layer covers the tips of the two radio frequency transmission electrodes and the phase change material layer.

[0029] Fourthly, the present invention provides a method for fabricating the above-mentioned four-terminal through-hole grounded phase-change radio frequency switch, comprising:

[0030] S21. Prepare a substrate isolation layer on the substrate;

[0031] S22. A heating layer is fabricated on a substrate isolation layer; wherein the heating layer includes: a micro heater and two heating electrodes connected to the micro heater;

[0032] S23. Prepare an electrically insulating layer that completely covers the micro heater on the heating layer;

[0033] S24. Prepare a phase change material layer on the electrically insulating layer;

[0034] S25. Prepare a radio frequency transmission electrode layer on the phase change material layer, and prepare ground electrodes on both sides of the central conductive band of the radio frequency transmission electrode layer.

[0035] S26. Prepare a grounding via electrode that penetrates the substrate and the substrate isolation layer, and prepare a back grounding metal layer on the back side of the substrate. Connect the grounding via electrode to the back grounding metal layer and the grounding electrode to obtain a four-terminal via grounding phase-change radio frequency switch.

[0036] More preferably, step S22 includes:

[0037] S221. Thin the central region of the upper surface of the substrate isolation layer;

[0038] S222. Fill the thinned area with microheater material to obtain a microheater, and use CMP process to make the microheater flush with the upper surface of the substrate isolation layer. Then, prepare two heating electrodes connected to the microheater to obtain a heating layer.

[0039] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0040] 1. In the two-terminal through-hole grounded phase-change RF switch and the four-terminal through-hole grounded phase-change RF switch provided by the present invention, the grounding through-hole electrode is used to connect the back grounding metal layer and the grounding electrode. The through-hole electrode can be well equivalent to a metal wall, so that part of the electromagnetic field is confined between the through-hole electrodes, thereby reducing radiation loss and interference to adjacent transmission lines, while improving the effective dielectric constant and reducing the characteristic impedance. Based on this, the present invention can effectively improve the on-resistance and off-resistance of the phase-change RF switch and has a higher applicable frequency band.

[0041] 2. Furthermore, in the two-terminal through-hole grounded phase-change radio frequency switch and the four-terminal through-hole grounded phase-change radio frequency switch provided by the present invention, the grounding through-hole electrode is located between the side of the grounding electrode near the center conductor of the radio frequency transmission electrode layer and the central axis of the grounding electrode, so that the grounding through-hole electrode can be better equivalent to a metal wall.

[0042] 3. Furthermore, in the two-terminal through-hole grounded phase-change RF switch and the four-terminal through-hole grounded phase-change RF switch provided by this invention, the grounding through-hole electrode itself exhibits parasitic effects. The higher its operating frequency, the greater the impact of parasitic effects on its performance. Simultaneously, the smaller the aperture of the through-hole in the design, the smaller its parasitic effect, and the smaller its impact on product performance. Moreover, the larger the through-hole, the more it affects electrical parameters such as the equivalent dielectric constant. Therefore, the aperture of the grounding through-hole electrode in this invention is less than half the width of the grounding electrode to balance the contradiction between parasitic effects and manufacturing costs.

[0043] 4. Furthermore, the two-terminal through-hole grounded phase change radio frequency switch and the four-terminal through-hole grounded phase change radio frequency switch provided by the present invention also include a passivation layer located above the radio frequency transmission electrode layer to isolate the phase change material layer from contact with the external environment and improve the heating efficiency.

[0044] 5. Furthermore, in the two-end through-hole grounded phase change radio frequency switch provided by the present invention, the substrate isolation layer is a substrate isolation layer with a thinned central region on the upper surface; the phase change material layer is embedded in the thinned region of the substrate isolation layer, and the phase change material layer is flush with the upper surface of the substrate isolation layer, thereby reducing the step difference between the phase change material layer and the radio frequency electrode, thereby solving the cracking problem caused by stress changes in the existing phase change radio frequency switch and improving the reliability of the phase change switch.

[0045] 6. Furthermore, in the four-terminal through-hole grounded phase-change radio frequency switch provided by the present invention, the substrate isolation layer is a thinned substrate isolation layer in the central region of the upper surface; the micro heater is embedded in the thinned region of the substrate isolation layer and is flush with the upper surface of the substrate isolation layer, thereby reducing the step difference between the phase change material and the radio frequency electrode, solving the crack problem caused by stress changes in the existing phase-change radio frequency switch, and improving the reliability of the phase-change switch. Attached Figure Description

[0046] Figure 1 A schematic diagram of the longitudinal cross-sectional structure of a two-terminal phase-change radio frequency switch provided in an embodiment of the present invention;

[0047] Figure 2 A schematic diagram of the transverse cross-sectional structure of a two-terminal phase-change radio frequency switch provided in an embodiment of the present invention;

[0048] Figure 3 This is a simulation diagram of the insertion loss of the two-terminal phase-change radio frequency switch in the DC-110GHz range provided in the embodiment of the present invention;

[0049] Figure 4 This is a simulation diagram of the isolation of the two-terminal phase-change radio frequency switch in the DC-110GHz range provided in the embodiment of the present invention.

[0050] Figure 5 This is a schematic diagram of the longitudinal cross-sectional structure of a four-terminal phase-change radio frequency switch provided in an embodiment of the present invention;

[0051] Figure 6 A schematic diagram of the transverse cross-sectional structure of a four-terminal phase-change radio frequency switch provided in an embodiment of the present invention;

[0052] Figure 7 This is a simulation diagram of the insertion loss of the four-terminal phase-change radio frequency switch provided in the embodiment of the present invention in the DC-110GHz range;

[0053] Figure 8 This is a simulation diagram of the isolation of the four-terminal phase-change radio frequency switch provided in the embodiment of the present invention in the DC-110GHz range. Detailed Implementation

[0054] 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 accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0055] To achieve the above objectives, in a first aspect, the present invention provides a two-terminal through-hole grounded phase-change radio frequency switch, comprising: a grounding electrode, a grounding through-hole electrode, and a back grounding metal layer, a substrate, a substrate isolation layer, a phase-change material layer and a radio frequency transmission electrode layer stacked sequentially from bottom to top;

[0056] The radio frequency transmission electrode layer includes two radio frequency transmission electrodes located on the same plane, and the tips of the two radio frequency transmission electrodes are connected by a phase change material layer. It should be noted that the two radio frequency transmission electrodes of the present invention are located on the same plane, which can avoid parasitic capacitance of the electrodes in the spatial stacking direction.

[0057] The grounding electrodes are located on both sides of the center conductor band of the radio frequency transmission electrode layer;

[0058] The ground via electrode penetrates the substrate and the substrate isolation layer, and connects the back ground metal layer and the ground electrode.

[0059] It should be noted that the grounding via electrode of the present invention connects the back grounding metal layer and the grounding electrode. In higher operating frequency bands, the spacing between the grounding via electrodes is much smaller than the operating wavelength, allowing the via electrode to be effectively equivalent to a metal wall. The electromagnetic field consists of the field located in the gap and the field on the metal surface; therefore, part of the electromagnetic field is confined between the via electrodes, thereby reducing radiation loss and interference to adjacent transmission lines, while simultaneously increasing the effective dielectric constant and reducing the characteristic impedance. Thus, the present invention can effectively improve the on-resistance and off-resistance of the switch, and is applicable to higher frequency bands. Preferably, the grounding via electrode is located between the side of the grounding electrode near the center conductor of the RF transmission electrode layer and the central axis of the grounding electrode, thereby allowing the via electrode to be better equivalent to a metal wall.

[0060] Furthermore, due to the parasitic effect inherent in the grounding via electrode, the higher its operating frequency, the greater the impact of this parasitic effect on its performance. In design, a larger aperture of the grounding via electrode can affect electrical parameters such as the equivalent dielectric constant of the dielectric, while a smaller aperture results in a smaller parasitic effect and thus a smaller impact on product performance. Therefore, a comprehensive consideration is needed to balance the contradiction between parasitic effects and manufacturing costs during device fabrication. Preferably, the aperture of the grounding via electrode is less than half the width of the grounding electrode. It should be noted that the grounding via electrode has a columnar structure, specifically a cylinder, square prism, triangular prism, trapezoidal prism, or prismatic prism. The aperture of the grounding via electrode is the diameter, width, or side length of its contact surface with the grounding electrode, determined according to the specific shape.

[0061] To reduce the step difference between the phase change material layer and the radio frequency transmission electrode, preferably, the substrate isolation layer is a thinned substrate isolation layer with a reduced central region on its upper surface; the phase change material layer is embedded in the thinned region of the substrate isolation layer, and the phase change material layer is flush with the upper surface of the substrate isolation layer. It should be noted that this scheme is only a preferred scheme to reduce the step difference between the phase change material layer and the radio frequency transmission electrode. The substrate isolation layer can also be an unthinned substrate isolation layer, with the phase change material layer directly on top of the unthinned substrate isolation layer.

[0062] Preferably, the above-mentioned two-terminal through-hole grounded phase change radio frequency switch further includes a passivation layer located above the radio frequency transmission electrode layer; the passivation layer covers the tips of the two radio frequency transmission electrodes and the phase change material layer, and is used to isolate the phase change material layer from the external environment and improve the heating efficiency.

[0063] To further illustrate the two-terminal through-hole grounded phase-change radio frequency switch provided by the present invention, a specific embodiment is described in detail below, such as... Figure 1 and Figure 2 The figures shown are a cross-sectional view and a top view of the two-terminal through-hole grounded phase-change radio frequency switch provided in this embodiment.

[0064] Specifically, the two-end through-hole grounded phase change radio frequency switch in this embodiment includes: a back ground metal layer (1), a substrate (2), a ground through-hole electrode (3), a substrate isolation layer (4), a phase change material layer (5), a radio frequency transmission electrode layer (6), a ground electrode (8), and a passivation layer (7).

[0065] The central region of the upper surface of the substrate isolation layer (4) is thinned, and the phase change material layer (5) is embedded in the thinned region of the substrate isolation layer (4), and the phase change material layer (5) is flush with the upper surface of the substrate isolation layer (4).

[0066] The tips of the two radio frequency transmission electrodes (6-1, 6-2) are connected by a phase change material layer (5);

[0067] The ground electrode (8) is located on both sides of the center conductor band of the radio frequency transmission electrode layer (6).

[0068] The back-side ground metal layer (1) is a metal layer deposited on the back side of the substrate (2);

[0069] The grounding via electrode (3) penetrates the substrate (2) and the substrate isolation layer (4), and connects the back metal layer (1) and the grounding electrode (8);

[0070] The tip portions of the two radio frequency transmission electrodes (6-1, 6-2) and the entire portion of the phase change material layer (5) are covered by a passivation layer (7).

[0071] The upper and lower metal-clad surfaces of the substrate (2) are composed of a central conductive strip and ground planes on both sides of the substrate. There is a gap between the central conductive strip and the ground electrodes on both sides of the central conductive strip. The metal-clad surfaces on both sides of the substrate are connected by metallized vias (ground via electrodes).

[0072] In this embodiment, there are four grounding through-hole electrodes (3), namely... Figure 2 The positions of the four grounding via electrodes are 3-1, 3-2, 3-3, and 3-4. The position range of each grounding via electrode extends from the central axis of the grounding electrode (8) towards the center conduction band of the RF transmission electrode layer to the edge of the grounding electrode (8). The diameter of the grounding via electrode is less than half the width of the grounding electrode (i.e., the length of the grounding electrode in the lateral direction). It should be noted that a rectangular coordinate system is established on the lateral cross-section of the phase-change RF switches at both ends, with the center of the cross-section as the origin, the x-axis perpendicular to the center conduction band of the RF transmission electrode layer as the x-axis, and the y-axis parallel to the center conduction band of the RF transmission electrode layer as the y-axis. The positions of the four grounding via electrodes on the lateral cross-section of the phase-change RF switches at both ends are distributed in the four quadrants of the rectangular coordinate system.

[0073] In this embodiment, the material of the back grounding metal layer (1) can be gold, copper, chromium, aluminum, tungsten, tantalum, or nickel. The material of the substrate (2) includes, but is not limited to, one or more of SiC, Si, AlN, GaN, GaAs, InP, glass, sapphire, diamond, PC, PET, and PI. The material of the grounding via electrode (3) can be one or more of chromium, copper, gold, aluminum, tungsten, tantalum, or nickel grown by magnetron sputtering or electron beam evaporation. The material of the substrate isolation layer (4) includes, but is not limited to, one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide, and has a thickness greater than 10 nm. The material of the phase change layer (5) includes, but is not limited to, one or more of phase change materials such as GeTe, GeSbTe, SbTe, and VO2. The RF transmission electrode (6) can be a metal or multilayer metal structure that forms an ohmic contact with the phase change material, and its material can be one or more of chromium, copper, gold, aluminum, tungsten, tantalum, or nickel grown by magnetron sputtering or electron beam evaporation. The material of the passivation layer (7) mentioned above includes, but is not limited to, one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide, and its thickness is greater than 10 nm.

[0074] It should be noted that in the two-terminal phase-change RF switch provided by this invention, the two RF transmission electrodes are located on the same plane, effectively avoiding parasitic capacitance of the electrodes in the spatial stacking direction. During the phase change process, the phase change layer itself generates Joule heating by applying an electrical pulse, thereby solving the problem of low thermal conductivity and insufficient heat dissipation of the isolation layer, thus improving the switching speed of the phase-change RF switch.

[0075] The two-terminal phase-change RF switch structure proposed in this invention was simulated and verified from an electromagnetic perspective using HFSS simulation software, and the results are as follows: Figure 3 and Figure 4 The HFSS simulation results are shown below; where, Figure 3 This is a simulation diagram of the insertion loss of the two-terminal phase-change RF switch in the DC-110GHz range. Figure 4 This is a simulation diagram of the isolation of a two-terminal phase-change RF switch in the DC-110GHz range. From... Figure 3 and Figure 4 As can be seen, in the frequency range of 0GHz to 110GHz, the insertion loss is always better than 0.8dB and the off-state isolation is better than 17dB.

[0076] Secondly, the present invention provides a method for fabricating the above-mentioned two-terminal through-hole grounded phase-change radio frequency switch, comprising:

[0077] S11. Prepare a substrate isolation layer on the substrate;

[0078] S12. Prepare a phase change material layer on the substrate isolation layer;

[0079] S13. Prepare a radio frequency transmission electrode layer on the phase change material layer, and prepare ground electrodes on both sides of the central conductive band of the radio frequency transmission electrode layer.

[0080] S14. Prepare a grounding via electrode that penetrates the substrate and the substrate isolation layer, and prepare a back-side grounding metal layer on the back side of the substrate to obtain a phase-change radio frequency switch with two-end via grounding.

[0081] Preferably, step S12 includes:

[0082] S121. Thin the central region of the upper surface of the substrate isolation layer;

[0083] S122. Fill the thinned area with phase change material to obtain a phase change material layer, and use CMP process to make the phase change material layer flush with the upper surface of the substrate isolation layer.

[0084] Preferably, the above preparation method further includes step S15 performed between steps S13 and S14; wherein step S15 includes: preparing a passivation layer above the radio frequency transmission electrode layer, and making the passivation layer cover the tips of the two radio frequency transmission electrodes and the phase change material layer.

[0085] To further illustrate the above preparation method, a specific embodiment is described in detail below:

[0086] In this embodiment, the fabrication method of the above-mentioned two-terminal through-hole grounded phase-change radio frequency switch includes:

[0087] A1. Preparation of substrate isolation layer on substrate: A substrate isolation layer of one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide with a thickness of 1 μm is grown on the substrate by magnetron sputtering or vapor deposition to obtain the first sample.

[0088] A2. Prepare a phase change material layer on the substrate isolation layer;

[0089] Specifically, the phase change material layer is one or more of GeTe, Ge2Se2Te5, and Sb2Te3 with a thickness of 200nm. As one embodiment, the specific steps are as follows: the morphology of the phase change material layer is photolithographically patterned on the surface of the isolation layer of the first sample substrate; the isolation layer is thinned by 200nm in the phase change material layer region by etching; the phase change material layer is then grown by magnetron sputtering or evaporation; a lift-off process is then performed; and a CMP process is used to make the phase change material layer and the upper surface of the RF electrode flush, achieving stepless contact and obtaining a complete phase change material layer, thus obtaining the second sample.

[0090] A3. Prepare a radio frequency transmission electrode layer on the phase change material layer, and prepare ground electrodes on both sides of the central conductive band of the radio frequency transmission electrode layer.

[0091] Specifically, the RF transmission electrode layer and the ground electrode are made of gold with a thickness of 200 nm. As one embodiment, the specific steps are as follows: the morphology of the RF transmission electrode and the ground electrode is photolithographically etched on the surface of the isolation layer of the second sample substrate; the electrodes are grown by magnetron sputtering or evaporation; and then a lift-off process is performed to obtain the complete electrodes, thus obtaining the third sample.

[0092] A4. Based on the third sample, the designed phase change passivation layer pattern is photolithographically etched, and the passivation layer material is generated by sputtering or vapor deposition. Then, the area where the passivation layer is exposed is peeled off to obtain the fourth sample.

[0093] Specifically, the passivation layer is any one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide with a thickness of 100nm. Its specific function is to isolate the phase change material layer from the external environment and improve the heating efficiency.

[0094] A5. Prepare a grounding via electrode that penetrates the substrate and the substrate isolation layer, and prepare a back-side grounding metal layer on the back side of the substrate;

[0095] Specifically, in this embodiment, the back grounding metal layer and the via grounding material are gold. As an optional implementation, the specific steps are as follows: the bottom of the fourth sample is thinned, and a substrate via is prepared by dry etching. Electrodes are grown by magnetron sputtering or evaporation to establish a grounding via electrode on the front side of the wafer, thereby obtaining the fifth sample, which is the two-terminal phase-change RF switch device designed in this invention.

[0096] Thirdly, the present invention provides a four-terminal through-hole grounded phase-change radio frequency switch, comprising: a grounding electrode, a grounding through-hole electrode, and a back grounding metal layer, a substrate, a substrate isolation layer, a heating layer, an electrical isolation layer, a phase-change material layer, and a radio frequency transmission electrode layer stacked from bottom to top.

[0097] The heating layer includes a micro heater and two heating electrodes connected to the micro heater; the micro heater is located directly below the phase change material layer and is completely covered by an electrical isolation layer.

[0098] The radio frequency transmission electrode layer includes two radio frequency transmission electrodes located on the same plane, and the tips of the two radio frequency transmission electrodes are connected by a phase change material layer.

[0099] The grounding electrodes are located on both sides of the center conductor band of the radio frequency transmission electrode layer;

[0100] The ground via electrode penetrates the substrate and the substrate isolation layer, and connects the back ground metal layer and the ground electrode.

[0101] It should be noted that the grounding via electrode of the present invention connects the back grounding metal layer and the grounding electrode. In higher operating frequency bands, the spacing between the grounding via electrodes is much smaller than the operating wavelength, allowing the via electrode to be effectively equivalent to a metal wall. The electromagnetic field consists of the field located in the gap and the field on the metal surface; therefore, part of the electromagnetic field is confined between the via electrodes, thereby reducing radiation loss and interference to adjacent transmission lines, while simultaneously increasing the effective dielectric constant and reducing the characteristic impedance. Thus, the present invention can effectively improve the on-resistance and off-resistance of the switch, and is applicable to higher frequency bands. Preferably, the grounding via electrode is located between the side of the grounding electrode near the center conductor of the RF transmission electrode layer and the central axis of the grounding electrode, thereby allowing the via electrode to be better equivalent to a metal wall.

[0102] Furthermore, due to the parasitic effect inherent in the grounding via electrode, the higher its operating frequency, the greater the impact of this parasitic effect on its performance. In design, a larger aperture of the grounding via electrode can affect electrical parameters such as the equivalent dielectric constant of the dielectric, while a smaller aperture results in a smaller parasitic effect and thus a smaller impact on product performance. Therefore, a comprehensive consideration is needed to balance the contradiction between parasitic effects and manufacturing costs during device fabrication. Preferably, the aperture of the grounding via electrode is less than half the width of the grounding electrode. It should be noted that the grounding via electrode has a columnar structure, specifically a cylinder, square prism, triangular prism, trapezoidal prism, or prismatic prism. The aperture of the grounding via electrode is the diameter, width, or side length of its contact surface with the grounding electrode, determined according to the specific shape.

[0103] To reduce the step difference between the phase change material layer and the radio frequency transmission electrode, preferably, the substrate isolation layer is a thinned substrate isolation layer with a reduced central region on its upper surface; the microheater is embedded in the thinned region of the substrate isolation layer, and the microheater is flush with the upper surface of the substrate isolation layer. It should be noted that this scheme is only a preferred scheme to reduce the step difference between the phase change material layer and the radio frequency transmission electrode. The substrate isolation layer can also be an unthinned substrate isolation layer, with the microheater located directly on the unthinned substrate isolation layer.

[0104] Preferably, the above-mentioned four-terminal through-hole grounded phase change radio frequency switch further includes a passivation layer located above the radio frequency transmission electrode layer; the passivation layer covers the tips of the two radio frequency transmission electrodes and the phase change material layer, and is used to isolate the phase change material layer from the external environment and improve the heating efficiency.

[0105] To further illustrate the four-terminal through-hole grounded phase-change radio frequency switch provided by the present invention, a detailed description is provided below with reference to a specific embodiment, such as... Figure 5 and Figure 6 The figures shown are a cross-sectional view and a top view of the four-terminal through-hole grounded phase-change radio frequency switch provided in this embodiment.

[0106] Specifically, the four-terminal through-hole grounded phase change radio frequency switch in this embodiment includes: a back grounding metal layer (1), a substrate (2), a grounding through-hole electrode (3), a substrate isolation layer (4), a heating layer, an electrical isolation layer (10), a phase change material layer (5), a radio frequency transmission electrode layer (6), a grounding electrode (8), and a passivation layer (7).

[0107] The heating layer includes a micro heater (9) and two heating electrodes (11-1, 11-2) connected to the micro heater (9); the micro heater (9) is located directly below the phase change material layer (5) and is completely covered by the electrical isolation layer (10);

[0108] The central region of the upper surface of the substrate isolation layer (4) is thinned, and the micro heater (9) is embedded in the thinned region of the substrate isolation layer (4). The micro heater (9) is flush with the upper surface of the substrate isolation layer (4) to achieve stepless contact.

[0109] An electrical isolation layer (10) covers the entire portion of the micro heater (9) and heats the tip portions of the electrodes (11-1, 11-2);

[0110] The phase change material layer (5) is located directly above the micro heater (9);

[0111] The tips of the two radio frequency transmission electrodes (6-1, 6-2) are connected by a phase change material layer (5);

[0112] The ground electrode (8) is located on both sides of the center conductor band of the radio frequency transmission electrode layer (6).

[0113] The back-side ground metal layer (1) is a metal layer deposited on the back side of the substrate (2);

[0114] The grounding via electrode (3) penetrates the substrate (2) and the substrate isolation layer (4), and connects the back metal layer (1) and the grounding electrode (8);

[0115] The tip portions of the two radio frequency transmission electrodes (6-1, 6-2) and the entire portion of the phase change material layer (5) are covered by a passivation layer (7).

[0116] The upper and lower metal-clad surfaces of the substrate (2) are composed of a central conductive strip and ground planes on both sides of the substrate. There is a gap between the central conductive strip and the ground electrodes on both sides of the central conductive strip. The metal-clad surfaces on both sides of the substrate are connected by metallized vias (ground via electrodes).

[0117] In this embodiment, there are four grounding through-hole electrodes (3), namely... Figure 6 The positions of the four grounding vias are 3-1, 3-2, 3-3, and 3-4. The position range of each grounding via extends from the central axis of the grounding electrode (8) towards the center conduction band of the RF transmission electrode layer to the edge of the grounding electrode (8). The diameter of the grounding via electrode is less than half the width of the grounding electrode (i.e., the length of the grounding electrode in the lateral direction). It should be noted that on the lateral cross-section of the four-terminal phase-change RF switch, a rectangular coordinate system is established with the center of the cross-section as the origin, the x-axis perpendicular to the center conduction band of the RF transmission electrode layer as the x-axis, and the y-axis parallel to the center conduction band of the RF transmission electrode layer as the y-axis. The positions of the four grounding via electrodes on the lateral cross-section of the four-terminal phase-change RF switch are distributed in the four quadrants of the rectangular coordinate system.

[0118] In this embodiment, the material of the back grounding metal layer (1) can be gold, copper, aluminum, tungsten, tantalum, nickel, or chromium. The material of the substrate (2) includes, but is not limited to, one or more of SiC, Si, AlN, GaN, GaAs, InP, glass, sapphire, diamond, PC, PET, and PI. The material of the grounding via electrode (3) can be one or more of chromium, copper, gold, aluminum, tungsten, tantalum, and nickel grown by magnetron sputtering or electron beam evaporation. The material of the substrate isolation layer (4) includes, but is not limited to, one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide, and has a thickness greater than 10 nm. The material of the phase change layer (5) includes, but is not limited to, one or more of phase change materials such as GeTe, GeSbTe, SbTe, and VO2. The RF transmission electrode (6) can be a metal or multilayer metal structure that forms an ohmic contact with the phase change material, and its material can be one or more of chromium, copper, gold, aluminum, tungsten, tantalum, and nickel grown by magnetron sputtering or electron beam evaporation. The passivation layer (7) is made of one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide, and its thickness is greater than 10 nm. The microheater (9) can be an element such as tungsten, chromium, nickel, or tandium, or a nitride of any one of the elements such as tungsten, chromium, nickel, or tandium, or an alloy composed of any combination of the elements such as tungsten, chromium, nickel, and tandium. The heating electrode (11) is made of silver, chromium, copper, gold, aluminum, tungsten, tantalum, or nickel. The electrical isolation layer (10) is made of one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide.

[0119] It should be noted that in the four-terminal through-hole grounded phase-change radio frequency switch provided by the present invention, the two radio frequency transmission electrodes are located on the same plane, and the two heating electrodes are located on the same plane, which effectively avoids the parasitic capacitance of the electrodes in the spatial stacking direction.

[0120] The four-terminal phase-change RF switch structure proposed in this invention was simulated and verified from an electromagnetic perspective using HFSS simulation software, and the results are as follows: Figure 7 and Figure 8 The HFSS simulation results are shown below; where, Figure 7 This is a simulation diagram of the insertion loss of a four-terminal phase-change RF switch in the DC-110GHz range. Figure 8 This is a simulation diagram of the isolation of a four-terminal phase-change RF switch in the DC-110GHz range. From... Figure 7 and Figure 8 As can be seen, in the frequency range of 0GHz to 110GHz, the insertion loss is always better than 2dB and the off-state isolation is better than 15dB.

[0121] Fourthly, the present invention provides a method for fabricating the above-mentioned four-terminal through-hole grounded phase-change radio frequency switch, comprising:

[0122] S21. Prepare a substrate isolation layer on the substrate;

[0123] S22. A heating layer is fabricated on a substrate isolation layer; wherein the heating layer includes: a micro heater and two heating electrodes connected to the micro heater;

[0124] S23. Prepare an electrically insulating layer that completely covers the micro heater on the heating layer;

[0125] S24. Prepare a phase change material layer on the electrically insulating layer;

[0126] S25. Prepare a radio frequency transmission electrode layer on the phase change material layer, and prepare ground electrodes on both sides of the central conductive band of the radio frequency transmission electrode layer.

[0127] S26. Prepare a grounding via electrode that penetrates the substrate and the substrate isolation layer, and prepare a back grounding metal layer on the back side of the substrate. Connect the grounding via electrode to the back grounding metal layer and the grounding electrode to obtain a four-terminal via grounding phase-change radio frequency switch.

[0128] Preferably, step S22 includes:

[0129] S221. Thin the central region of the upper surface of the substrate isolation layer;

[0130] S222. Fill the thinned area with microheater material to obtain a microheater, and use CMP process to make the microheater flush with the upper surface of the substrate isolation layer. Then, prepare two heating electrodes connected to the microheater to obtain a heating layer.

[0131] Preferably, the above preparation method further includes step S27 performed between steps S25 and S26; wherein step S27 includes: preparing a passivation layer above the radio frequency transmission electrode layer, and making the passivation layer cover the tips of the two radio frequency transmission electrodes and the phase change material layer.

[0132] To further illustrate the above preparation method, a specific embodiment is described in detail below:

[0133] In this embodiment, the fabrication method of the above-mentioned two-terminal through-hole grounded phase-change radio frequency switch includes:

[0134] B1. Preparation of substrate isolation layer on substrate: A substrate isolation layer of one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide with a thickness of 1 μm is grown on the substrate by magnetron sputtering or vapor deposition to obtain the first sample.

[0135] B2. A heating layer is fabricated on a substrate isolation layer; wherein the heating layer includes: a microheater and two heating electrodes connected to the microheater;

[0136] Specifically, the aforementioned microheater is any one of tungsten, chromium, nickel, tan, or their nitrides and alloys, with a thickness of 100 nm. As one embodiment, the specific steps are as follows: the morphology of the microheater is photolithographically patterned on the surface of the isolation layer of the first sample substrate; the isolation layer is thinned by 100 nm in the microheater region by etching; then the microheater material is grown by magnetron sputtering or evaporation; finally, a lift-off process is performed using CMP to obtain a complete microheater, thus obtaining the second sample.

[0137] The aforementioned heating electrode is made of silver with a thickness of 200 nm. As one embodiment, the specific steps are as follows: based on the second sample, the morphology of the designed heating electrode is photolithographically patterned, and then the heating electrode is grown by magnetron sputtering or evaporation. Afterward, the third sample is obtained by peeling off the area exposing the heating electrode.

[0138] B3. Prepare an electrically insulating layer that completely covers the microheater on the heating layer;

[0139] Specifically, the aforementioned electrical isolation layer is any one or more of silicon nitride, silicon dioxide, gallium oxide, tantalum oxide, titanium oxide, and aluminum oxide with a thickness of 40 nm. Its specific function is to ensure good electrical isolation between the microheater and the phase change material while also ensuring good thermal coupling between them. As one embodiment, the specific steps are as follows: based on the third sample, the designed phase change electrical isolation layer pattern is photolithographically etched; the electrical isolation layer material is generated by sputtering or vapor deposition; and then the area exposing the electrical isolation layer is peeled off to obtain the fourth sample.

[0140] B4. Prepare a phase change material layer on the electrically insulating layer;

[0141] Specifically, the aforementioned phase change material layer is one or more of GeTe, Ge2Se2Te5, and Sb2Te3 with a thickness of 200 nm. As one embodiment, the specific steps are as follows: the morphology of the phase change layer is photolithographically patterned on the surface of the electrical isolation layer of the fourth sample; then, the phase change layer is grown by magnetron sputtering or evaporation; finally, a lift-off process is performed to obtain a complete phase change layer, thus obtaining the fifth sample.

[0142] B5. Prepare a radio frequency transmission electrode layer on the phase change material layer, and prepare ground electrodes on both sides of the central conductive band of the radio frequency transmission electrode layer;

[0143] Specifically, the aforementioned radio frequency transmission electrode and ground electrode are made of gold with a thickness of 200 nm. As one embodiment, the specific steps are as follows: the morphology of the radio frequency transmission electrode and ground electrode is photolithographically patterned on the surface of the isolation layer of the fifth sample substrate; the electrodes are grown by magnetron sputtering or evaporation; and then a lift-off process is performed to obtain the complete electrodes, thus obtaining the sixth sample.

[0144] B6. Prepare a grounding via electrode that penetrates the substrate and the substrate isolation layer, and prepare a back grounding metal layer on the back side of the substrate. Connect the grounding via electrode to the back grounding metal layer and the grounding electrode to obtain a four-terminal via grounding phase-change radio frequency switch.

[0145] Specifically, the back grounding metal layer and the via grounding electrode material mentioned above are made of gold. As one embodiment, the specific steps are as follows: the bottom of the sixth sample is thinned, and a substrate via is prepared by dry etching. Electrodes are grown by magnetron sputtering or evaporation to establish a grounding via electrode on the front side of the wafer, thereby obtaining the seventh sample, which is the four-terminal phase-change radio frequency switch device designed in this invention.

[0146] In summary, this invention relates to a via-grounded phase-change radio frequency (RF) switch, applicable to both two-terminal direct-type and four-terminal indirect-type RF switch structures. In the two-terminal RF switch, RF transmission and phase-change operation share a common electrode, while in the four-terminal RF switch, RF transmission and phase-change operation follow independent paths. Microheaters or phase-change layers are fabricated using etching and CMP processes to reduce the step difference between the phase-change layer and the RF electrodes. The grounding via is etched, and after etching the substrate isolation layer and the substrate, grounding metal is filled and deposited on the back side of the substrate, confining most of the propagating electromagnetic energy within the dielectric, thus reducing radiation loss and surface wave leakage. This invention effectively improves the switch's on-resistance and off-resistance, expanding the application frequency band of the phase-change RF switch.

[0147] Compared to four-terminal phase-change RF switches, two-terminal phase-change RF switches avoid the problem of insufficient heat dissipation caused by the low thermal conductivity of the electrical isolation layer in four-terminal phase-change RF switches, and the switching speed of phase-change RF switches is faster. Compared to two-terminal phase-change RF switches, four-terminal phase-change RF switches have higher RF performance, such as RF power capacity.

[0148] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-terminal through-hole grounded phase-change radio frequency switch, characterized in that, include: Grounding electrode, grounding via electrode, and a back grounding metal layer, substrate, substrate isolation layer, phase change material layer and radio frequency transmission electrode layer stacked from bottom to top; The radio frequency transmission electrode layer includes two radio frequency transmission electrodes located on the same plane, and the tips of the two radio frequency transmission electrodes are connected through the phase change material layer. The grounding electrode is located on both sides of the center conductor band of the radio frequency transmission electrode layer; The grounding via electrode penetrates the substrate and the substrate isolation layer, and connects the back grounding metal layer and the grounding electrode; The substrate isolation layer is a thinned substrate isolation layer in the central region of the upper surface; The phase change material layer is embedded in the thinned region of the substrate isolation layer, and the phase change material layer is flush with the upper surface of the substrate isolation layer.

2. The two-terminal through-hole grounded phase-change radio frequency switch according to claim 1, characterized in that, The grounding via electrode is located between the central conductor of the grounding electrode and the central axis of the grounding electrode, near the center conductor of the radio frequency transmission electrode layer; the diameter of the grounding via electrode is less than half the width of the grounding electrode.

3. The two-terminal through-hole grounded phase-change radio frequency switch according to any one of claims 1-2, characterized in that, It also includes a passivation layer located above the radio frequency transmission electrode layer; the passivation layer covers the tips of the two radio frequency transmission electrodes and the phase change material layer.

4. The method for fabricating the two-terminal through-hole grounded phase-change radio frequency switch as described in claim 1, characterized in that, include: S11. Prepare a substrate isolation layer on the substrate; S12. Prepare a phase change material layer on the substrate isolation layer; S13. A radio frequency transmission electrode layer is prepared on the phase change material layer, and ground electrodes are prepared on both sides of the central conductive band of the radio frequency transmission electrode layer. S14. Prepare a grounding via electrode that penetrates the substrate and the substrate isolation layer, and prepare a back-side grounding metal layer on the back side of the substrate, thereby obtaining the two-end via grounded phase-change radio frequency switch.

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