Phase change radio frequency switch based on optical waveguide laser heating and preparation method thereof
Through the optical waveguide laser heating structure, the parasitic capacitance and heat loss problems caused by the microheater in the phase change RF switch are solved, the coupling efficiency is improved and the power consumption is reduced, meeting the needs of high-frequency millimeter wave applications.
Patent Information
- Application Number
- CN202510721536.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-30
- Publication Date
- 2025-09-12
AI Technical Summary
The microheaters in existing phase-change RF switches cause parasitic capacitance and heat dissipation problems, and the coupling efficiency of the optical waveguide laser heating method is low.
An optical waveguide laser heating structure is adopted, including a substrate, a substrate isolation layer, an optical waveguide lower cladding layer, an optical waveguide core layer, an optical waveguide upper cladding layer, a phase change layer and a radio frequency transmission layer. A grating coupler is used to achieve efficient coupling between the laser and the phase change layer, avoiding the use of a microheater.
It improves the laser coupling efficiency, reduces power consumption, and reduces heat loss, meeting the needs of high-frequency millimeter wave applications.
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Figure CN120640962A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of radio frequency switches, and in particular relates to a phase change radio frequency switch based on optical waveguide laser heating and a preparation method thereof. Background Art
[0002] In recent years, radio frequency switches based on phase change materials have attracted widespread attention due to their excellent radio frequency performance and non-volatile properties in the millimeter wave band. Phase change radio frequency switches use Joule heating to control the transition of phase change materials between crystalline and amorphous states, thereby controlling on and off. When the phase change material is in the crystalline state, it is in a low resistance state, and the switch is on; when it is in the amorphous state, it is in a high resistance state, and the switch is off. Phase change radio frequency switches include direct heating type and indirect heating type. Direct heating type switches control the state switching of the phase change material by applying voltage pulses to the radio frequency transmission electrode, using the Joule heating effect of the phase change material itself; indirect heating type switches use the Joule heating effect of the microheater to transfer the heat generated by the microheater to the phase change material by applying voltage pulses, thereby controlling the crystallization or amorphization of the phase change material.
[0003] The indirect heating type phase change RF switch consists of a substrate, an electrical isolation layer, a microheater, a microheater isolation layer, a phase change material, an RF transmission electrode, and a passivation layer. Its crystallization and amorphization processes occur relatively completely, with a large on-off ratio and high power capacity, showing excellent performance in the lower millimeter wave frequency band. However, the introduction of the microheater causes parasitic capacitance to be generated between the RF transmission electrode and the microheater, resulting in an increase in the on-state insertion loss of the switch, making it difficult to meet the application requirements of higher frequency millimeter waves. In addition, part of the heat generated by heating with a microheater is dissipated into the substrate and isolation layer, resulting in severe heat transfer losses and high power consumption. Therefore, how to optimize the device heating structure, use non-microheater heating methods to solve the parasitic capacitance problem, and further reduce the device power consumption is of great significance to the development of phase change RF switches.
[0004] Existing solutions rely on applying external laser drive to the phase-change RF switch, resulting in low device integration and difficult packaging. Another approach involves fabricating an optical waveguide structure on top of the switch device for laser drive. However, this approach presents some challenges in fabrication. Furthermore, optical waveguides made of single-crystal silicon or other dielectrics are difficult to fabricate effectively on-chip. Excessively high fabrication temperatures can cause volatilization or damage to the phase-change material. Furthermore, relying solely on the optical waveguide's own inclined surface for coupling can lead to unevenness, causing some laser light to pass through the inclined surface, resulting in low coupling efficiency. Therefore, designing an optical waveguide structure in the appropriate location to address these shortcomings is particularly necessary. Summary of the Invention
[0005] In response to the defects of the existing technology and the need for improvement, its purpose is to solve the parasitic capacitance and heat dissipation problems generated by the microheater when the traditional microheater drives the phase change RF switch, and secondly to solve the problem of low coupling efficiency caused by relying solely on the inclined structure of the optical waveguide itself when laser heating in the existing technology.
[0006] The present invention provides a phase-change radio frequency switch based on optical waveguide laser heating, comprising:
[0007] a substrate, located on a semiconductor substrate;
[0008] a substrate isolation layer, disposed on the substrate;
[0009] an optical waveguide lower cladding layer, arranged on the substrate isolation layer;
[0010] The optical waveguide core layer and the optical waveguide upper cladding layer are combined and arranged on the optical waveguide lower cladding layer, wherein the optical waveguide core layer is embedded in the optical waveguide upper cladding layer, and the optical waveguide core layer includes a grating coupler, and the laser is diffracted by the grating coupler;
[0011] A phase change layer is provided on the upper cladding layer of the optical waveguide, and the laser is diffracted by the grating coupler to heat the phase change layer, thereby changing the state of the phase change layer, including changing from a high resistance state to a low resistance state or from a low resistance state to a high resistance state;
[0012] The first RF transmission layer and the second RF transmission layer are on the same horizontal plane and are respectively arranged at both ends of the phase change layer without contact. When the phase change layer changes from a high-resistance state to a low-resistance state, the first RF transmission layer and the second RF transmission layer are connected through the phase change layer. When the phase change layer changes from a low-resistance state to a high-resistance state, the first RF transmission layer and the second RF transmission layer are disconnected. The first RF transmission layer is the input end of the phase change RF switch, and the second RF transmission layer is the output end of the phase change RF switch.
[0013] The present invention also discloses a method for preparing the above-mentioned phase-change radio frequency switch based on optical waveguide laser heating, comprising:
[0014] S1: depositing a substrate isolation layer on a substrate, wherein the substrate isolation layer is deposited on a surface of a silicon substrate by a plasma enhanced chemical vapor deposition method, wherein the substrate comprises one or more of silicon, diamond, sapphire, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass; and the substrate isolation layer is one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide;
[0015] S2: depositing an optical waveguide lower cladding layer on the substrate isolation layer by PECVD or magnetron sputtering, wherein the optical waveguide lower cladding layer is one or more of silicon dioxide, silicon nitride, and lithium niobate;
[0016] S3: depositing an optical waveguide core layer on the optical waveguide lower cladding, wherein the optical waveguide core layer includes a grating coupler, selecting a pure silicon wafer, using plasma cleaning to perform surface activation treatment, bonding the pure silicon wafer to the wafer with the optical waveguide lower cladding by a bonding method, strengthening the bonding strength between the two wafers by annealing, thinning the pure silicon wafer by grinding and polishing to obtain a single crystal silicon layer on the optical waveguide lower cladding, fabricating a waveguide and grating pattern on the single crystal silicon layer by photolithography, forming a waveguide structure and a grating coupler by dry etching, and completing the preparation of the optical waveguide core layer after debonding;
[0017] S4: depositing an optical waveguide upper cladding layer on the optical waveguide core layer by using a PECVD method, treating the surface by chemical mechanical polishing, and flattening the surface to complete the preparation of the optical waveguide upper cladding layer;
[0018] S5: depositing a phase change layer on the upper cladding of the optical waveguide, using a magnetron sputtering method to deposit a phase change material as the phase change layer on the upper cladding of the optical waveguide, patterning the phase change material using a photolithography method, obtaining the phase change material directly above the grating coupler as a mask protection, etching away the phase change material outside the patterned area using an etching method, and completing the preparation of the phase change layer after debonding;
[0019] S6: depositing a first RF transmission layer and a second RF transmission layer on the phase change layer, patterning the first RF transmission layer and the second RF transmission layer on the wafer by photolithography, depositing a thin film of metal material on the wafer in sequence by electron beam evaporation coating, removing the photoresist and the metal material outside the pattern area by a wet stripping process, and completing the preparation of the first RF transmission layer and the second RF transmission layer.
[0020] S7: Deposit a passivation layer on the first RF transmission layer and the second RF transmission layer, deposit the passivation layer material on the wafer using the PECVD method, pattern the passivation layer material using the photolithography method to obtain the phase change material area and the RF transmission electrode area, expose the interface area of the first RF transmission layer and the second RF transmission layer, etch away the passivation layer material outside the pattern area by etching, and complete the preparation of the passivation layer after degumming.
[0021] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:
[0022] (1) The problem of the prior art coupling structure using the inclined surface of the optical waveguide itself, in which the uneven inclined surface causes part of the laser to pass through the inclined surface and the coupling efficiency is low, is solved, that is, the coupling efficiency of the laser is improved;
[0023] (2) The problem that optical waveguides made of single-crystal silicon or other media are difficult to effectively prepare on-chip and that excessively high preparation temperatures may cause volatilization or damage of phase change materials during the preparation process is solved, thereby improving the preparation yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 A schematic front cross-sectional view of a phase-change radio frequency switch based on optical waveguide laser heating provided by an embodiment of the present invention;
[0025] Figure 2 A schematic side view of the structure of a phase-change radio frequency switch based on optical waveguide laser heating provided by an embodiment of the present invention;
[0026] Figure 3 A top view of a grating coupler of a phase-change radio frequency switch based on optical waveguide laser heating provided by an embodiment of the present invention;
[0027] Figure 4 A top view of the RF transmission layer, phase change layer, and passivation layer of a phase change RF switch based on optical waveguide laser heating provided by an embodiment of the present invention;
[0028] Figure 5 The structure, size and position relationship of a grating coupler and a phase change layer provided in an embodiment of the present invention;
[0029] Figure 6 Schematic diagram of the front cross-sectional structure of a phase-change radio frequency switch based on optical waveguide laser heating and having a substrate reflective layer in an embodiment of the present invention;
[0030] In the figure, 1 is a substrate, 2 is a substrate isolation layer, 3 is an optical waveguide lower cladding, 31, 32, and 33 are combined to form an optical waveguide lower cladding, wherein 32 is a reflective layer, 31 is a first lower cladding, 33 is a second lower cladding, 4 is an optical waveguide core layer, 5 is an optical waveguide upper cladding, 6 is a phase change layer, 71-74 are radio frequency transmission layers, and 8 is a passivation layer;
[0031] Figure 7 This is the S parameter simulation curve of the phase change RF switch in the on-state of the traditional micro-heater indirect heating structure;
[0032] Figure 8 The on-state S-parameter simulation curve of a phase-change radio frequency switch based on optical waveguide laser heating provided by an embodiment of the present invention;
[0033] Figure 9 COMSOL thermal simulation curve of the Set process of a phase-change radio frequency switch based on optical waveguide laser heating provided by an embodiment of the present invention;
[0034] Figure 10COMSOL thermal simulation curve of the reset process of a phase-change radio frequency switch based on optical waveguide laser heating provided by an embodiment of the present invention. DETAILED DESCRIPTION
[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is 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 for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
[0036] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.
[0037] Example 1
[0038] like Figure 1-5 FIG. 1 is a structural diagram of a phase change radio frequency switch based on optical waveguide laser heating provided by an embodiment of the present invention. Figure 1 The structure shown includes a substrate 1, a substrate isolation layer 2, an optical waveguide lower cladding layer 3, an optical waveguide core layer 4, an optical waveguide upper cladding layer 5, a phase change layer 6, radio frequency transmission layers 71 and 72, and radio frequency transmission layers 73 and 74, wherein the radio frequency transmission layers 73 and 74 are ground electrodes and a passivation layer 8. The substrate isolation layer 2 is located on the substrate 1, the optical waveguide lower cladding layer 3 is located on the substrate isolation layer 2, and the optical waveguide core layer 4 is located on the optical waveguide lower cladding layer 3, wherein the optical waveguide lower cladding layer 3 provides a refractive index difference with the optical waveguide core layer 4 to achieve confinement and transmission of optical signals. The optical waveguide core layer 4 includes a grating coupler. In an optional manner, the grating coupler is formed by processes such as grating patterning, etching, debonding, and cleaning. The grating coupler has a periodic structure (grating), which changes the propagation direction of light through the periodic structure to achieve efficient coupling between the waveguide and free space. Reference Figure 1 and Figure 2As shown, the optical waveguide upper cladding 5 is located above the optical waveguide core 4, and the optical waveguide core 4 is embedded within the optical waveguide upper cladding 5. In other words, the optical waveguide upper cladding 5 is larger than the optical waveguide core 4. The upper cladding 5 and the optical waveguide core 4 are combined and located above the optical waveguide lower cladding 3. The upper cladding 5 and the optical waveguide lower cladding 3 are made of the same material. The upper cladding 5 and the lower cladding 3 form a refractive index difference with the optical waveguide core 4 to confine the light field and prevent light leakage to the external environment. The phase change layer 6 is located on the optical waveguide upper cladding 5. After patterning, the phase change layer region is located directly above the grating coupler. When light waves pass through the grating coupler, they diffract into the phase change layer 6, changing its state, for example, from an amorphous state to a crystalline state or vice versa. The amorphous state corresponds to the high-resistance state of the phase change layer, while the crystalline state corresponds to the low-resistance state of the phase change layer. RF transmission layers 71 and 72, as well as RF transmission layers 73 and 74, are located on the same horizontal plane. RF transmission layers 71 and 72 are respectively disposed at opposite ends of the phase change layer and above the phase change layer. An opening structure is included between RF transmission layers 71 and 72, and the two layers do not contact each other. For example, the distance between RF transmission layers 71 and 72 is 200nm-1000nm. RF transmission layers 71 and 72 are connected via phase change layer 6. RF transmission layer 71, phase change layer 6, and RF transmission layer 72 constitute an RF transmission channel. When phase change layer 6 changes from a high-impedance state to a low-impedance state, the RF signal is transmitted from RF transmission layer 71 to RF transmission layer 72 via phase change layer 6, indicating that the phase change RF switch is in the on state. Specifically, one end of the RF transmission layer 71 includes a first electrode, which is the portion of the RF transmission layer 71 not covered by the passivation layer 8 (please refer to the following description for a detailed description). The first electrode further serves as the input end of the phase change RF switch for receiving RF signals, and the other end of the RF transmission layer 71 is connected to the phase change layer 6. Similarly, one end of the RF transmission layer 72 includes a second electrode, which serves as the output end of the phase change RF switch for outputting RF signals. The second electrode is the portion of the RF transmission layer 72 not covered by the passivation layer 8, and the other end of the RF transmission layer 72 is connected to the phase change layer 6. When the input end receives the RF signal, the phase change RF switch is turned on, and the RF signal is transmitted from the input end to the output end. The passivation layer 8 is located above the RF transmission layers 71, 72 and the phase change layer 6, covering the phase change layer 6, and is used to protect the device and prevent the phase change material from being oxidized. The size of the passivation layer 8 is adjustable. The passivation layer 8 at least needs to cover the phase change material area in the phase change layer 6 that is not covered by the RF transmission layer 71 and the RF transmission layer 72. The positional relationship between the above-mentioned components is as follows: Figure 1 and Figure 2 As shown, the connection relationship between the phase change layer 6 and the radio frequency transmission layers 71 and 72, as well as the size relationship between the phase change layer 6 and the passivation layer 8 are shown in FIG. Figure 4 shown.
[0039] In an optional embodiment of the present invention, the substrate 1 includes but is not limited to one or more of silicon, diamond, sapphire, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass; the substrate isolation layer 2 includes but is not limited to one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide; the optical waveguide core layer 4 includes but is not limited to one or more of single crystal silicon, silicon nitride, and aluminum oxide; the optical waveguide lower cladding 3 and the optical waveguide upper cladding 5 include but are not limited to one of silicon dioxide, silicon nitride, and SU-8, and the lower cladding and the upper cladding are preferably selected from the group consisting of silicon dioxide, silicon nitride, and SU-8. A symmetrical design is adopted with the same refractive index; the phase change layer 6 is a chalcogenide compound, or a chalcogenide compound doped with one or more of the elements such as indium, hafnium, yttrium, scandium, gallium, titanium, etc. as a phase change material, wherein the chalcogenide compounds include but are not limited to germanium telluride, antimony telluride, germanium antimony telluride, etc.; the radio frequency transmission layers 71-74 include but are not limited to gold, copper, silver, aluminum, platinum, etc., which are one or more metal materials with high electrical conductivity; the passivation layer 8 includes but is not limited to one or more of silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, and aluminum nitride.
[0040] Figure 3 A top view of a grating coupler of a phase-change radio frequency switch based on optical waveguide laser heating provided by an embodiment of the present invention; as shown in the figure, the grating coupler has a grating structure with periodic arrangement of gratings.
[0041] Figure 4 A top view of the RF transmission layer, phase change layer, and passivation layer of a phase change RF switch based on optical waveguide laser heating provided in an embodiment of the present invention; the relationship between the phase change layer 6 and the RF transmission layers 71 and 72 is shown in FIG. Figure 4 As shown, the phase change layer 6 is connected to one end of the RF transmission layer 71 and the RF transmission layer 72 respectively. The ends of the RF transmission layer 71 and the RF transmission layer 72 connected to the phase change layer 6 can be pointed, rectangular or arc-shaped, and are not limited to a specific shape. They can keep in contact with the phase change layer 6. Preferably, when they are pointed, the size of the phase change layer 6 can be reduced. The other ends of the RF transmission layer 71 and the RF transmission layer 72 are respectively provided with a first electrode and a second electrode, which serve as the input and output ends of the phase change RF switch. The first electrode and the second electrode are exposed outside the passivation layer 8, and the RF transmission layer 73 and the RF transmission layer 74 are provided as ground electrodes. The passivation layer 8 at least covers the phase change material area not covered by the RF transmission layer 71 and the RF transmission layer 72. The size of the passivation layer 8 is adjustable. Figure 4 As shown, the red dotted line indicates an adjustable range of the passivation layer 8. Those skilled in the art should understand that the shape of the passivation layer 8 is not limited to Figure 4 As shown, any other shape that can cover the phase change layer is included.
[0042] Furthermore, in order to better understand the position and size relationship between the structure of the grating coupler and the phase change layer, Figure 5A schematic diagram of the relationship between the structure, size and position of a grating coupler and a phase change layer provided by an embodiment of the present invention. Figure 5 As shown, the thickness of the lower cladding of the optical waveguide is h1, the period of the grating coupler is p, the sawtooth width is w, the sawtooth depth is h2, the thickness of the upper cladding of the optical waveguide is h3, the length of the grating coupler in the x direction is x1, the length of the phase change layer in the x direction is x2, the distance between the leftmost end of the phase change layer material and the leftmost end of the grating coupler is x, the angle between the diffracted light and the normal of the grating coupler is θ, the laser wavelength is λ, the refractive index of the optical waveguide core layer is n0, and the refractive index of the upper cladding of the optical waveguide is n1. Among them, the period p of the grating coupler satisfies p=λ / (n eff -n1sinθ), the equivalent refractive index of the grating is n eff =n0(w / p)+n1((pw) / p), the distance between the leftmost end of the phase change layer 6 and the leftmost end of the grating coupler is x=(h2+h3)tanθ. Figure 5 As shown, in an optional embodiment of the present invention, the length x1 of the grating coupler in the x direction is greater than or equal to the length x2 of the phase change layer in the x direction, and the length in the direction perpendicular to the cross section of the device is greater than or equal to the length of the phase change layer 6; the ratio w / p of the period of the grating coupler to the sawtooth width is 0.4 to 0.6; the angle θ between the diffracted light and the normal of the grating coupler is in the range of 0 to 15°; the laser wavelength λ is 1550 nm, the period p of the grating coupler is 585 to 824 nm; and the sawtooth depth h2 is 80 to 100 nm. Preferably, when the thickness of the lower cladding of the optical waveguide is 2 μm, the downward diffraction of the laser can be effectively reduced; the thickness of the core layer of the optical waveguide is 220 nm, and the thickness of the upper cladding of the optical waveguide is between 1 and 2 μm; the distance x between the leftmost end of the phase change layer 6 and the leftmost end of the grating coupler is between 0 and 860 nm; the laser wavelength λ is 1550 nm, the refractive index of the core layer of the optical waveguide is 3.42, the refractive index of the upper cladding of the optical waveguide is 1.5, and the period p of the grating coupler is 630 nm, the sawtooth width is 315 nm, the sawtooth depth is 90 nm, the angle θ between the diffracted light and the normal of the grating coupler is close to 0°, and the grating is close to vertical coupling. The close to 0° here means that the angle θ between the diffracted light and the normal of the grating coupler is a single-digit difference from 0°, or lower, and the loss is lowest when the light is diffracted, and the light is directly diffracted to the phase change layer 6. In an optional embodiment, the phase change layer has a length of 5-10 μm in the x-direction, a length of 10-25 μm in the direction perpendicular to the device cross-section, and a thickness of 100-150 nm. The above is merely intended to illustrate or better understand the relationship between the structure of the grating coupler and the structural dimensions of the phase change layer. Those skilled in the art should understand that the above dimensions and positional relationships are not exclusive and should not be construed as limitations of the present invention. Embodiments employing other dimensions or positions disclosed herein, in which the state of the phase change layer 6 is changed by the grating coupler, are all encompassed within the design concepts of the present invention.
[0043] Furthermore, Figure 6 FIG. 1 is a front structural diagram of a phase-change radio frequency switch based on optical waveguide laser heating and having a substrate reflective layer 32 in an embodiment of the present invention. Figure 6 and Figure 1 In comparison, Figure 5 The optical waveguide lower cladding 3 is replaced by Figure 6 As shown in FIG, the structure of the first lower cladding layer 31, the reflective layer 32 and the second lower cladding layer 33, wherein 31 and 33 are Figure 5 The optical waveguide lower cladding 3 is made of the same material as the optical waveguide. A reflective layer 32 is provided between 31 and 33. Here, reflective layer 32 acts as a reflector for substrate 2. When the laser passes through the grating coupler, reflective layer 32 reflects light scattered from the substrate back to the grating coupler, thereby improving the coupling efficiency of the grating coupler, enhancing laser heating efficiency, and reducing power consumption. In an optional embodiment of the present invention, reflective layer 32 is made of a metal material such as gold, silver, or aluminum, but is not limited thereto.
[0044] It should be noted that in order to achieve better RF performance, the phase change RF switch usually transmits in the horizontal direction, and the longitudinal dimension is much smaller than the lateral dimension. When the laser drives the phase change layer in the vertical direction, the driven area of the phase change layer is the largest. The grating coupling structure provided in Example 1 of the present invention realizes the vertical coupling of the horizontally transmitted laser on the chip. Specifically, by setting the size of the grating coupler and the relative position with the phase change layer, the laser coupling efficiency is improved, and the laser is transmitted in a direction to the phase change layer. By using lasers of different powers, the phase change layer is driven, that is, the phase change layer is changed from a high resistance state to a low resistance state or from a low resistance state to a high resistance state. The phase change RF switch based on optical waveguide laser heating disclosed by the present invention improves the optical coupling efficiency, the driving capability of the phase change layer and reduces the power consumption of the phase change RF switch.
[0045] Example 2
[0046] The present invention discloses a method for preparing a phase-change radio frequency switch based on optical waveguide laser heating, which specifically comprises the following steps:
[0047] S1: depositing a substrate isolation layer 2 on the substrate 1; in an optional embodiment, high-resistance silicon is selected as the substrate 1. After cleaning the substrate 1, a SiN layer is deposited on the surface of the silicon substrate by plasma enhanced chemical vapor deposition (PECVD) as the substrate isolation layer 2. The substrate isolation layer 2 is used to avoid the influence of device performance caused by leakage and heat conduction problems of the substrate when the device is working. The above-selected materials are only a specific embodiment, wherein the substrate includes one or more of silicon, diamond, sapphire, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass; the substrate isolation layer is one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide.
[0048] S2: depositing an optical waveguide lower cladding layer 3 on the substrate isolation layer 2. Specifically, in an optional embodiment, SiO2 is deposited on the substrate isolation layer 2 by PECVD or magnetron sputtering as the optical waveguide lower cladding layer 3, wherein the optical waveguide lower cladding layer 3 includes but is not limited to one of silicon dioxide, silicon nitride, and SU-8.
[0049] S3: Depositing an optical waveguide core layer 4 on the optical waveguide lower cladding layer 3, wherein the optical waveguide core layer 4 includes a grating coupler. In an optional manner, the grating coupler is formed by processes such as grating patterning, etching, degumming, and cleaning. The grating coupler has a periodic structure (grating), which changes the propagation direction of light through the periodic structure to achieve efficient coupling between the waveguide and free space. Specifically, in an optional embodiment, a pure silicon wafer is prepared, the surface is cleaned with plasma for surface activation treatment, and the pure silicon wafer is bonded to a wafer having an optical waveguide lower cladding 3 by a bonding method at room temperature. The bonding strength between the two wafers is enhanced by annealing. The pure silicon wafer is thinned by grinding and polishing to a certain thickness to obtain a single crystal silicon layer on the optical waveguide lower cladding 3. Waveguide and grating patterns are produced on the single crystal silicon layer by photolithography technology, and waveguide structures and grating coupler structures are formed by dry etching. After debonding, the preparation of the optical waveguide core layer 4 is completed, wherein the optical waveguide core layer includes one or more of single crystal silicon, silicon nitride, and aluminum oxide.
[0050] S4: depositing an optical waveguide upper cladding 5 on the optical waveguide core layer 4; specifically, in an optional embodiment, SiO2 is deposited on the optical waveguide core layer 4 as the optical waveguide upper cladding 5 by a PECVD method, and the surface is treated by chemical mechanical polishing (CMP) to flatten the surface to complete the preparation of the optical waveguide upper cladding 5. When the laser is transmitted, total reflection occurs at the interface between the optical waveguide core layer 4 and the lower cladding 3 and the upper cladding 5. The optical waveguide upper cladding 5 limits the transmission of the laser in the optical waveguide core layer 4, wherein the optical waveguide upper cladding includes one of silicon dioxide, silicon nitride, and SU-8.
[0051] S5: Depositing a phase change layer 6 on the upper cladding layer 5 of the optical waveguide, wherein the light wave is diffracted by the grating coupler to the phase change layer 6 and heats the phase change layer 6, thereby changing the resistance state of the phase change layer 6. Specifically, in an optional embodiment, a phase change material GeTe is deposited on the upper cladding layer 5 of the optical waveguide by magnetron sputtering as the phase change layer 6, and the phase change material is patterned by photolithography to achieve mask protection of the phase change material directly above the grating coupler, and the phase change material outside the patterned area is etched away by etching. After de-resistance, the preparation of the phase change layer 6 is completed, wherein the phase change layer 6 is a chalcogenide compound, or a chalcogenide compound doped with one or more elements selected from the group consisting of indium, hafnium, yttrium, scandium, gallium, and titanium, wherein the chalcogenide compound includes germanium telluride, antimony telluride, and germanium antimony telluride.
[0052] S6: Depositing radio frequency transmission layers 71 and 72 on the phase change layer 6. Specifically, in an optional embodiment, the radio frequency transmission electrodes are patterned on the wafer by photolithography, and chromium and gold films are sequentially deposited on the wafer by electron beam evaporation coating. The photoresist and metal materials outside the pattern area are removed by a wet stripping process. The wet stripping process specifically uses acetone, stripping solution, isopropyl alcohol and ultrapure water for cleaning in sequence to complete the preparation of the radio frequency transmission layers 71 and 72, wherein the radio frequency transmission layers 71 and 72 are metal materials, including but not limited to gold, copper, silver, aluminum, platinum, etc., which are one or more metal materials with high electrical conductivity.
[0053] S7: Depositing a passivation layer 8 on the RF transmission layers 71 and 72. Specifically, in an optional embodiment, SiO2 is deposited on the wafer as the passivation layer material by a PECVD method, and the passivation layer material is patterned by a photolithography method to protect the phase change material area and part of the RF transmission electrode area, exposing the pad area of the RF transmission electrode, and etching away the passivation layer material outside the patterned area by an etching method. After de-bonding, the preparation of the passivation layer 8 is completed. Figure 1 A phase change radio frequency switch based on optical waveguide laser heating is prepared as shown in the figure, wherein the passivation layer 8 includes one or more of silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, and aluminum nitride.
[0054] In another optional embodiment of the present invention, the deposition of the optical waveguide lower cladding layer 3 in step S2 can be replaced by Figure 6The lower cladding layer composed of 31, 32, and 33 is the optical waveguide lower cladding including the reflective layer 32. Specifically, SiO2 is deposited on the substrate isolation layer 2 by PECVD or magnetron sputtering as the first lower cladding layer 31, followed by the reflective layer 32, for example, made of a metal such as gold, silver, or aluminum. Finally, SiO2 is deposited as the second lower cladding layer 33. Compared to the above-described embodiment 2, the optical waveguide lower cladding including the reflective layer reflects light scattered from the substrate when the laser passes through the grating coupler back to the grating coupler, thereby improving the coupling efficiency of the grating coupler, enhancing laser heating efficiency, and reducing power consumption.
[0055] It should be noted that the materials of the substrate 1, substrate isolation layer 2, optical waveguide lower cladding 3 or first lower cladding 31, reflective layer 32 and second lower cladding 33, optical waveguide core layer 4, optical waveguide upper cladding 5, phase change layer 6, RF transmission layers 71 and 72, and passivation layer 8 in Example 2 are referred to the description in Example 1 and will not be repeated here to avoid redundancy. The specific schemes listed in the above preparation process are only used to explain the present invention and are not limited to the materials described above.
[0056] Furthermore, in order to verify the excellent performance of the phase-change RF switch in the present invention, HFSS simulation software was used to establish a phase-change RF switch based on optical waveguide laser heating and a phase-change RF switch based on indirect heating using a traditional microheater, and the performance of the two phase-change RF switches was compared. S-parameter simulations were performed on the two models in the frequency range of 0 to 110 GHz. The simulation results are shown in Figure 2. Figure 7 and Figure 8 As shown in the figure, when the frequency is greater than 60GHz, the insertion loss of the phase change RF switch indirectly heated by the traditional microheater increases rapidly. When the frequency is 100GHz, the insertion loss is greater than 0.6dB, while the insertion loss of the phase change RF switch based on optical waveguide laser heating is less than 0.4dB at 100GHz. The simulation results show that after removing the metal microheater, the RF signal transmission loss is significantly reduced and the on-state parasitic capacitance is reduced. Secondly, the COMSOL simulation software is used to establish a simulation model of the phase change RF switch based on optical waveguide laser heating, and the thermal conductivity performance based on optical waveguide laser heating is verified, as shown in the figure. Figure 9 As shown in Figure 3, the temperature change curve of the phase change layer during the phase change RF switch Set process. The applied laser power is 50mW. The phase change layer temperature can reach 580K at 300ns, reaching the crystallization temperature of GeTe phase change material (453K). The time to reach the crystallization temperature is much shorter than the crystallization time of the traditional microheater heating structure phase change RF switch. Figure 10Figure 3 is the temperature change curve of the phase change layer during the reset process. When the applied laser power is 250 mW, the phase change layer temperature can reach 1050 K after 100 ns, which is higher than the amorphous temperature of GeTe phase change material (998 K), and can reach below the crystallization temperature within 200 ns. It has a fast quenching speed and can complete the amorphous process.
[0057] In summary, the phase change RF switch based on optical waveguide laser heating disclosed in the present invention solves the problem of partial heat loss to the substrate and isolation layer during heating by a microheater, reduces heat transfer loss, and reduces power consumption.
[0058] It will be easily understood by those skilled in the art 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 in the scope of protection of the present invention.
Claims
1. A phase change radio frequency switch based on optical waveguide laser heating, characterized in that: include: a substrate, located on a semiconductor substrate; a substrate isolation layer, disposed on the substrate; an optical waveguide lower cladding layer, arranged on the substrate isolation layer; The optical waveguide core layer and the optical waveguide upper cladding layer are combined and arranged on the optical waveguide lower cladding layer, wherein the optical waveguide core layer is embedded in the optical waveguide upper cladding layer, and the optical waveguide core layer includes a grating coupler, and the laser is diffracted by the grating coupler; A phase change layer is provided on the upper cladding layer of the optical waveguide, and the laser is diffracted by the grating coupler to heat the phase change layer, thereby changing the state of the phase change layer, including changing from a high resistance state to a low resistance state or from a low resistance state to a high resistance state; The first RF transmission layer and the second RF transmission layer are on the same horizontal plane and are respectively arranged at both ends of the phase change layer without contact. When the phase change layer changes from a high-resistance state to a low-resistance state, the first RF transmission layer and the second RF transmission layer are connected through the phase change layer. When the phase change layer changes from a low-resistance state to a high-resistance state, the first RF transmission layer and the second RF transmission layer are disconnected. The first electrode on the first RF transmission layer is the input end of the phase change RF switch, and the second electrode on the second RF transmission layer is the output end of the phase change RF switch.
2. The phase change radio frequency switch based on optical waveguide laser heating according to claim 1, characterized in that: The phase change layer is arranged directly above the grating coupler, wherein the ratio w / p of the period of the grating coupler to the sawtooth width is 0.4 to 0.6; and the angle θ between the diffracted light and the normal of the grating coupler is in the range of 0 to 15°.
3. The phase change radio frequency switch based on optical waveguide laser heating according to claim 1, characterized in that: The optical waveguide lower cladding and the optical waveguide upper cladding are used to confine the light field generated by the laser, so that the laser passing through the optical waveguide core layer is totally reflected between the optical waveguide lower cladding and the optical waveguide upper cladding, wherein the optical waveguide lower cladding and the optical waveguide upper cladding are one or more of silicon dioxide, silicon nitride, and SU-8, and the optical waveguide core layer is one or more of single crystal silicon, silicon nitride, and aluminum oxide.
4. The phase change radio frequency switch based on optical waveguide laser heating according to claim 3, characterized in that: The optical waveguide lower cladding further includes a reflective layer, which is used to reflect the laser light scattered on the substrate back to the grating coupler, wherein the reflective layer is made of metal material.
5. The phase change radio frequency switch based on optical waveguide laser heating according to claim 1, characterized in that: The substrate includes one or more of silicon, diamond, sapphire, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass.
6. The phase change radio frequency switch based on optical waveguide laser heating according to claim 1, characterized in that: The substrate isolation layer is one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide.
7. The phase change radio frequency switch based on optical waveguide laser heating according to claim 1, characterized in that: The phase change layer is a chalcogenide compound or a chalcogenide compound doped with one or more of indium, hafnium, yttrium, scandium, gallium, and titanium, wherein the chalcogenide compound includes one or more of germanium telluride, antimony telluride, and germanium antimony telluride.
8. The phase change radio frequency switch based on optical waveguide laser heating according to claim 1, characterized in that: The first radio frequency transmission layer and the second radio frequency transmission layer are made of metal materials with conductive function.
9. The phase change radio frequency switch based on optical waveguide laser heating according to claim 1, characterized in that: It also includes a passivation layer, which is arranged on the first radio frequency transmission layer and the second radio frequency transmission layer and is used to isolate the phase change layer. The passivation layer is one or more of silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, and aluminum nitride.
10. A method for preparing a phase-change radio frequency switch based on optical waveguide laser heating according to any one of claims 1 to 9, characterized in that: include: S1: depositing a substrate isolation layer on a substrate, wherein the substrate isolation layer is deposited on a surface of a silicon substrate by a plasma enhanced chemical vapor deposition method, wherein the substrate comprises one or more of silicon, diamond, sapphire, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass; and the substrate isolation layer is one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide; S2: depositing an optical waveguide lower cladding layer on the substrate isolation layer by PECVD or magnetron sputtering, wherein the optical waveguide lower cladding layer is one or more of silicon dioxide, silicon nitride, and lithium niobate; S3: depositing an optical waveguide core layer on the optical waveguide lower cladding, wherein the optical waveguide core layer includes a grating coupler, selecting a pure silicon wafer, plasma cleaning the surface for surface activation, bonding the pure silicon wafer to the wafer with the optical waveguide lower cladding by a bonding method, strengthening the bonding strength between the two wafers by annealing, thinning the pure silicon wafer by grinding and polishing to obtain a single crystal silicon layer on the optical waveguide lower cladding, fabricating a waveguide and grating pattern on the single crystal silicon layer by photolithography, forming a waveguide structure and a grating coupler by dry etching, and completing the preparation of the optical waveguide core layer after debonding, wherein the optical waveguide core layer includes one or more of single crystal silicon, silicon nitride, and aluminum oxide; S4: depositing an optical waveguide upper cladding layer on the optical waveguide core layer, depositing an optical waveguide upper cladding layer material on the optical waveguide core layer by a PECVD method, treating the surface by chemical mechanical polishing to flatten the surface to complete the preparation of the optical waveguide upper cladding layer, wherein the optical waveguide upper cladding layer includes one of silicon dioxide, silicon nitride, and SU-8; S5: depositing a phase change layer on the upper cladding of the optical waveguide, depositing a phase change material as the phase change layer on the upper cladding of the optical waveguide by magnetron sputtering, patterning the phase change material by photolithography, obtaining the phase change material directly above the grating coupler as a mask protection, etching away the phase change material outside the patterned area by etching, and completing the preparation of the phase change layer after de-resistance, wherein the phase change layer is a chalcogenide compound, or a chalcogenide compound doped with one or more elements selected from the group consisting of indium, hafnium, yttrium, scandium, gallium, and titanium, wherein the chalcogenide compound includes germanium telluride, antimony telluride, and germanium antimony telluride; S6: depositing a first radio frequency transmission layer and a second radio frequency transmission layer on the phase change layer, patterning the first radio frequency transmission layer and the second radio frequency transmission layer on the wafer using a photolithography method, sequentially depositing a metal material thin film on the wafer using an electron beam evaporation coating method, and removing the photoresist and the metal material outside the patterned area using a wet stripping process to complete the preparation of the first radio frequency transmission layer and the second radio frequency transmission layer, wherein the first radio frequency transmission layer and the second radio frequency transmission layer are metal materials; S7: Deposit a passivation layer on the first RF transmission layer and the second RF transmission layer, deposit the passivation layer material on the wafer by using the PECVD method, pattern the passivation layer material by using the photolithography method to obtain the phase change material area and the RF transmission electrode area, expose the interface area of the first RF transmission layer and the second RF transmission layer, etch away the passivation layer material outside the pattern area by the etching method, and complete the preparation of the passivation layer after degumming. The passivation layer includes one or more of silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, and aluminum nitride.