Phase shifter structure and preparation method thereof

Abstract

The invention discloses a phase shifter structure and a preparation method thereof, the phase shifter structure comprises a first dielectric layer and a functional layer which are sequentially arranged on a substrate, and the functional layer is provided with a waveguide structure and first dielectric isolation structures located at two axial sides of the waveguide structure; wherein the waveguide structure comprises a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding which are sequentially stacked from inside to outside, and the heating electrode layer is isolated from the waveguide core layer through the heat transfer layer. The modulation efficiency of the thermo-optic effect phase shifter can be improved, the modulation time can be optimized, loss can be reduced, thermal crosstalk between adjacent devices and channels can be reduced, the preparation method is compatible with a silicon-based CMOS process, large-scale production integration can be realized, and the production cost can be reduced. And the development of active devices such as filters, modulators and the like based on the thermo-optic effect in silicon-based optical chips is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of thermo-optical effect phase shifter, and in particular to a phase shifter structure capable of improving thermal modulation efficiency and reducing thermal crosstalk and a preparation method thereof. Background Art

[0002] In traditional microelectronic chips, due to the gradual reduction of transistor feature size, they are limited by physical limits such as quantum tunneling, and the electrical interconnection process (copper interconnection) will face problems such as transmission delay, power consumption and signal crosstalk. Silicon-based optoelectronic technology has the advantages of low cost, high photon transmission rate, strong anti-interference, and compatibility with traditional silicon-based CMOS processes, and is gradually replacing traditional electrical interconnection chips in short-distance communications. Among them, the electro-optic modulator, as one of the important active devices in silicon-based optoelectronic chips, realizes the function of electro-optical signal conversion by changing the phase, frequency, intensity and polarization of light waves.

[0003] The modulation structure of silicon-based electro-optic modulators based on the thermo-optic effect can be mainly divided into two basic structures, namely microring resonators and Mach-Zehnder interferometers. These two structures are currently also used in the wavelength division multiplexing technology of silicon-based optical chips to achieve high-bandwidth information transmission. Among them, the microring resonant cavity in the microring resonator is a very clever resonant structure. It is composed of a section of waveguide connected end to end to form a ring structure. The metal electrode is deposited on the waveguide signal arm of the microring resonator to form a phase shifter structure. The feedback is formed by the waveguide loop, and different periodic responses are made to light of different wavelengths to achieve phase control of light. The microring resonator has a simple structure. A microring resonant cavity plus a bus waveguide can realize simple functions. Many lasers, filters, modulators, and optical switches use this structure. The Mach-Zehnder interferometer divides a beam of light signal into two paths through a beam splitter, inputs them into two different optical waveguides, and then combines them into one path through a beam combiner. By depositing metal electrodes on the waveguide signal arm of the Mach-Zehnder interferometer modulator, a phase shifter structure can be formed, in which the optical signal is phase modulated by changing its phase through the phase shifter, and is converted into intensity modulation by interference at the beam combiner.

[0004] At present, the waveguide structure of the phase shifter in the above-mentioned microring resonator and Mach-Zehnder interferometer based on the thermo-optic effect usually adopts a layer of metal heating electrode or two-dimensional material deposited on the waveguide core layer as a microheater. Since the metal heating electrode will absorb the light in the waveguide, it will cause a large transmission loss, so it can only be placed at a distance from the waveguide or deposited on the silicon dioxide cladding of the silicon waveguide. However, due to the low thermal conductivity of silicon dioxide, the heat transfer efficiency into the silicon waveguide is extremely low, which will lead to higher power consumption and low modulation efficiency. Microheaters using two-dimensional materials cannot be integrated in large-scale production because the two-dimensional materials are incompatible with silicon-based CMOS processes during mechanical peeling and transfer.

[0005] Recently, the number and position of the heating electrodes have been optimized to reduce the absorption loss of light by the metal heating electrodes by placing multiple metal heating electrodes on the silica cladding above the waveguide. However, the arrangement of multiple heating electrodes will cause thermal crosstalk to adjacent devices and channels. Moreover, the refractive index change achieved by thermal conduction of low thermal conductivity silica always takes a certain amount of time, so this type of modulator generally has a low modulation rate (in microseconds) and is not suitable for high-speed devices.

[0006] In summary, improving the thermal modulation efficiency of silicon-based phase shifters and reducing thermal crosstalk are extremely important for the development of thermo-optical electro-optic modulators, and will have a great impact on the development of lasers, filters, modulators, optical switches and other devices in silicon-based optical chips. Summary of the invention

[0007] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and to provide a phase shifter structure and a preparation method thereof.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] The present invention provides a phase shifter structure, comprising:

[0010] A first dielectric layer and a functional layer are sequentially arranged on the substrate, wherein the functional layer is provided with a waveguide structure and a first dielectric isolation structure located on both sides of the waveguide structure in an axial direction;

[0011] The waveguide structure includes a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer stacked in sequence from the inside to the outside, and the heating electrode layer is isolated from the waveguide core layer by the heat transfer layer.

[0012] Furthermore, the first medium isolation structure includes a first air isolation wall.

[0013] Furthermore, the heat transfer layer and the heating electrode layer are arranged on the top surface of the waveguide core layer, and the first waveguide cladding layer is axially coated on the top surface of the waveguide core layer facing away from the substrate and on both side surfaces thereof.

[0014] Furthermore, the heat transfer layer and the heating electrode layer also extend from the top surface of the waveguide core layer to at least one of the side surfaces.

[0015] Furthermore, a second dielectric isolation structure is provided in the first dielectric layer, the second dielectric isolation structure is connected to the first dielectric isolation structure on both sides, and the waveguide structure is isolated from the substrate by the second dielectric isolation structure.

[0016] Furthermore, the first dielectric isolation structure includes a first air isolation wall, and the second dielectric isolation structure includes a second air isolation wall serving as a second waveguide cladding, the second air isolation wall is connected to the first air isolation walls on both sides, and the second air isolation wall is in direct contact with the bottom surface of the waveguide core layer.

[0017] Furthermore, the heat transfer layer material includes at least one of Al2O3, AlN, Si3N4, and SiC, and / or the heating electrode layer material includes at least one of Au, Ag, Pt, Ti, W, and Al.

[0018] The present invention also provides a method for preparing a phase shifter structure, comprising:

[0019] Providing a substrate, on which a first dielectric layer and a functional layer are sequentially arranged;

[0020] A waveguide structure and a first dielectric isolation structure located on both axial sides of the waveguide structure are formed on the functional layer, so that the formed waveguide structure includes a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer stacked in sequence from the inside to the outside, and the heating electrode layer is isolated from the waveguide core layer by the heat transfer layer.

[0021] Further, the waveguide structure and the first dielectric isolation structure located on both sides of the waveguide structure in the axial direction are formed on the functional layer, so that the formed waveguide structure includes a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer stacked in sequence from the inside to the outside, and the heating electrode layer is isolated from the waveguide core layer by the heat transfer layer, specifically including:

[0022] Performing a first patterning to form a waveguide core layer located in the functional layer and grooves located on both sides of the waveguide core layer in an axial direction from the surface of the functional layer downward;

[0023] forming a heat transfer material layer on the surface of the functional layer to cover the surface of the waveguide core layer;

[0024] performing a second patterning on the heat transfer material layer to form a heat transfer layer on at least the top surface of the waveguide core layer;

[0025] forming a heating electrode material layer on the surface of the functional layer to cover the surfaces of the waveguide core layer and the heat transfer layer;

[0026] Performing a third patterning on the heating electrode material layer to form a heating electrode layer on the surface of the heat transfer layer, and isolating the heating electrode layer from the waveguide core layer through the heat transfer layer;

[0027] forming a second dielectric layer on the surface of the functional layer to cover the surfaces of the waveguide core layer, the heating electrode layer and the heat transfer layer;

[0028] The second dielectric layer is subjected to a fourth patterning to form a first waveguide cladding axially covering the top surface of the waveguide core layer and the side surfaces on both sides thereof, thereby forming a waveguide structure including the waveguide core layer, the heat transfer layer, the heating electrode layer and the first waveguide cladding stacked in sequence from the inside to the outside, and the groove is used to form a first air isolation wall as a first dielectric isolation structure.

[0029] Furthermore, when performing the first patterning, the bottom surface of the formed waveguide core layer and the bottom surface of the groove are in contact with the top surface of the first dielectric layer; after performing the fourth patterning, the method further includes:

[0030] forming a protective layer on the surface of the functional layer to cover the surface of the first waveguide cladding layer;

[0031] Through a release process, part of the first dielectric layer below the waveguide structure is removed to form a cavity communicating with the groove below the waveguide structure, and the cavity is used to form a second air isolation wall serving as a second dielectric isolation structure and directly contacting the bottom surface of the waveguide core layer.

[0032] It can be seen from the above technical scheme that the present invention arranges the heating electrode layer between the waveguide cladding (first waveguide cladding) and the waveguide core layer in the phase shifter waveguide structure, and arranges a heat transfer layer with high thermal conductivity and low refractive index between the heating electrode layer and the waveguide core layer, so as to improve the thermal modulation efficiency and optimize the modulation time while satisfying the total reflection transmission of light in the phase shifter waveguide core layer; at the same time, by arranging a dielectric isolation structure (first air isolation wall / first dielectric isolation structure, second air isolation wall / second dielectric isolation structure) such as an air isolation wall on both sides of the waveguide structure or even below the waveguide structure, the heat energy can be limited to the waveguide structure in the central area to the maximum extent, thereby effectively reducing the modulation loss and transmission loss, and reducing the thermal crosstalk between adjacent devices and channels; and by extending the heating electrode layer (including the heat transfer layer) from the top surface of the waveguide core layer to the side surface, the contact area in the heat conduction process can be increased, thereby further improving the thermal utilization rate. The present invention can effectively solve the problems of large light transmission loss and low heat transfer efficiency caused by arranging the heating electrode layer on the waveguide cladding, is beneficial to reducing the power consumption of the device, and is suitable for high-speed devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of a phase shifter structure according to a preferred embodiment of the present invention;

[0034] Figure 2 A schematic diagram of a phase shifter structure according to a preferred embodiment 2 of the present invention;

[0035] Figure 3-Figure 14 It is a process flow chart of a method for preparing a phase shifter structure according to a preferred embodiment 1 of the present invention;

[0036] Figure 15-17 The figure is a process flow chart of a method for preparing a phase shifter structure according to a preferred embodiment 2 of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0038] In order to solve the problems of low thermal utilization rate, low modulation efficiency, high power consumption, etc. caused by large light absorption loss of the metal heating electrode located outside the waveguide cladding and low thermal conductivity of the silicon dioxide waveguide cladding in the phase shifter based on the thermo-optic effect in the prior art, the present invention provides a phase shifter structure, comprising: a first dielectric layer and a functional layer sequentially arranged on a substrate, the functional layer being provided with a waveguide structure and a first dielectric isolation structure located on both axial sides of the waveguide structure; wherein the waveguide structure comprises a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding sequentially stacked from the inside to the outside, and the heating electrode layer is isolated from the waveguide core layer by the heat transfer layer.

[0039] The present invention changes the arrangement structure of the heating electrode on the waveguide structure, arranges the heating electrode layer between the first waveguide cladding and the waveguide core layer in the phase shifter waveguide structure, and arranges a heat transfer layer with high thermal conductivity and low refractive index between the heating electrode layer and the waveguide core layer, thereby improving the thermal modulation efficiency and optimizing the modulation time while satisfying the total reflection transmission of light in the phase shifter waveguide core layer; at the same time, by arranging the first dielectric isolation structure on both sides of the waveguide structure and arranging the first dielectric layer under the waveguide structure, the thermal energy can be limited to the waveguide structure in the central area to the maximum extent, thereby effectively reducing the modulation loss and transmission loss, and reducing the thermal crosstalk between adjacent devices and channels.

[0040] Therefore, the present invention effectively solves the problems of large optical transmission loss and low heat transfer efficiency in the prior art. It can not only improve the thermal modulation efficiency and optimize the modulation time, but also help to reduce the power consumption of the device, so that it can be suitable for high-speed devices.

[0041] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0042] refer to Figure 1 , Figure 1 FIG. 1 is a schematic diagram of a phase shifter structure according to a preferred embodiment of the present invention. Figure 1 As shown, a phase shifter structure of the present invention includes: a first dielectric layer 12 arranged on the surface of a substrate 11, a functional layer 13 arranged on the surface of the first dielectric layer 12, a waveguide structure 15 arranged on the functional layer 13, and a first dielectric isolation structure 14 located on both sides of the waveguide structure 15 in the axial direction (i.e., in the direction perpendicular to the drawing).

[0043] The bottom surfaces of the two first dielectric isolation structures 14 are located above the bottom surface of the functional layer 13 and maintain a certain longitudinal distance from the first dielectric layer 12. The bottom of the waveguide structure 15 is connected to the functional layer 13 as a whole, thereby forming a ridge waveguide structure 15 located on the functional layer 13.

[0044] The waveguide structure 15 is provided with a waveguide core layer 19 at the core; a heat transfer layer 18, a heating electrode layer (heating electrode) 17 and a first waveguide cladding layer 16 are sequentially stacked on the surface of the waveguide core layer 19. In addition, the heating electrode layer 17 is isolated from the waveguide core layer 19 by the heat transfer layer 18.

[0045] In some embodiments, the heat transfer layer 18 is axially attached to the top surface of the waveguide core layer 19 (the upper surface facing away from the substrate 11 in the figure); the heating electrode layer 17 is attached to the surface of the heat transfer layer 18, and the boundary of the heating electrode layer 17 is located within the boundary of the heat transfer layer 18. The first waveguide cladding layer 16 is axially coated on the top surface of the waveguide core layer 19 and the side surfaces on both sides of the top surface, and covers the heating electrode layer 17 and the heat transfer layer 18.

[0046] In some embodiments, the heat transfer layer 18 and the heating electrode layer 17 are attached to the top surface of the waveguide core layer 19 in the axial direction, and extend from the top surface of the waveguide core layer 19 to at least one side surface of the waveguide core layer 19. For example, the heat transfer layer 18 and the heating electrode layer 17 are continuously distributed on the top surface and both side surfaces of the waveguide core layer 19, and are covered by the first waveguide cladding layer 16 together with the waveguide core layer 19, as shown in FIG. Figure 1 That is, the setting area and size of the heating electrode layer 17 on the surface of the waveguide core layer 19 can be adjusted, so that the contact area in the heat conduction process can be increased by optimizing the structure of the heating electrode layer 17 and expanding the coverage area of ​​the heating electrode layer 17. Therefore, while satisfying the total reflection transmission of light in the phase shifter waveguide, the heat utilization rate can be further improved, the heat modulation efficiency can be increased, and the modulation time can be optimized.

[0047] refer to Figure 1 . The first dielectric isolation structure 14 includes a first air isolation wall. In some embodiments, grooves are provided on both axial sides of the waveguide structure 15, and the grooves are filled with air, thereby forming a first air isolation wall as the first dielectric isolation structure 14. By utilizing the combined structure of the first air isolation wall and the first dielectric layer 12 under the waveguide structure 15, thermal energy can be limited to the central area of ​​the waveguide structure 15 as much as possible, which can effectively reduce modulation loss and transmission loss, improve thermal modulation efficiency, and reduce thermal crosstalk between adjacent devices and channels.

[0048] In some embodiments, the substrate 11 may be a conventional semiconductor substrate, for example, a silicon substrate 11 .

[0049] The material of the first dielectric layer 12 may be a conventional dielectric material, for example, silicon dioxide.

[0050] The material of the functional layer 13 may be a conventional material used to prepare a waveguide, for example, the material of the functional layer 13 may be silicon.

[0051] In some embodiments, the material of the heat transfer layer 18 may be at least one of Al2O3, AlN, Si3N4, and SiC having high thermal conductivity and low refractive index characteristics.

[0052] The material of the heating electrode layer 17 can be at least one of Au, Ag, Pt, Ti, W, and Al.

[0053] The first waveguide cladding 16 material may be a conventional cladding material. For example, the first waveguide cladding 16 material may be silicon dioxide.

[0054] In some embodiments, a phase shifter structure can be formed on an SOI silicon wafer 100, which has a bottom silicon layer 101, an intermediate buried oxide layer 102 and a top silicon layer 103 from bottom to top. The bottom silicon layer 101 can be used as a substrate 11, the intermediate buried oxide layer 102 is a first dielectric layer 12, and the top silicon layer 103 is a functional layer 13. A phase shifter structure having a waveguide structure 15 with a silicon waveguide core layer 19 and a first air isolation wall structure located on both axial sides of the waveguide structure 15 is formed on the top silicon layer 103 of the SOI silicon wafer 100.

[0055] refer to Figure 2 , Figure 2 FIG. 1 is a schematic diagram of a phase shifter structure of a preferred embodiment 2 of the present invention. Figure 2 As shown, Figure 1 The difference from the above-mentioned embodiments is that in this embodiment, in a phase shifter structure of the present invention, the bottom surfaces of the grooves of the two first dielectric isolation structures 14 pass through the functional layer 13 and are located on the surface of the first dielectric layer 12, and the bottom surface of the waveguide core layer 19 is flush with the bottom surface of the functional layer 13, that is, the bottom surface of the waveguide core layer 19 is also located on the surface of the first dielectric layer 12, thereby forming a strip waveguide structure 15. In addition, a second dielectric isolation structure 20 is also provided in the first dielectric layer 12; the second dielectric isolation structure 20 is located in the first dielectric layer 12 below the waveguide structure 15, and is connected to the first dielectric isolation structure 14 located above both sides of the second dielectric isolation structure 20. The waveguide structure 15 is isolated from the substrate 11 by the second dielectric isolation structure 20.

[0056] In some embodiments, a cavity is provided in the first dielectric layer 12 below the waveguide structure 15, and the cavity is filled with air, thereby forming a second air isolation wall as the second dielectric isolation structure 20, so that the second dielectric isolation structure 20 is connected to the first dielectric isolation structure 14 in the form of an air isolation wall, and the second air isolation wall is in direct contact with the bottom surface of the waveguide core layer 19. In this way, the air isolation wall surrounding the side and bottom of the waveguide structure 15 is used to form an overhead waveguide structure 15, which can not only meet the total reflection condition of light in waveguide transmission, but also minimize the transmission loss of light in the waveguide transmission process (since the refractive index of air is about 1, the refractive index difference between Si-air structures is smaller than that of Si-SiO2 structure), and the heat is concentrated to the maximum extent at the center of the strip waveguide, thereby improving the thermal modulation efficiency.

[0057] A method for preparing a phase shifter structure of the present invention is further described in detail below through specific implementations and in conjunction with the accompanying drawings.

[0058] refer to Figure 3-Figure 14 , Figure 3-Figure 14 FIG. 1 is a process flow chart of a method for preparing a phase shifter structure according to a preferred embodiment of the present invention. Figure 3-Figure 14 As shown, a method for preparing a phase shifter structure of the present invention can be used to prepare, for example Figure 1 A phase shifter structure is shown, and may include the following steps:

[0059] Step S1: providing a substrate 11, on which a first dielectric layer 12 and a functional layer 13 are sequentially arranged.

[0060] like Figure 3 As shown, a SOI silicon wafer 100 can be used. The SOI silicon wafer 100 has a bottom silicon layer 101, a middle buried oxide layer 102 and a top silicon layer 103 from bottom to top. The bottom silicon layer 101 is used as a substrate 11, the middle buried oxide layer 102 is used as a first dielectric layer 12, and the top silicon layer 103 is used as a functional layer 13.

[0061] The SOI silicon wafer 100 may be cleaned first to remove particles, organic matter and other contaminants on the surface of the substrate 11 , and to blow away residual liquid on the surface of the substrate 11 .

[0062] Step S2: forming a waveguide structure 15 and a first dielectric isolation structure 14 located on both axial sides of the waveguide structure 15 on the functional layer 13, so that the formed waveguide structure 15 includes a waveguide core layer 19, a heat transfer layer 18, a heating electrode layer 17 and a first waveguide cladding 16 stacked in sequence from the inside to the outside, and the heating electrode layer 17 is isolated from the waveguide core layer 19 by the heat transfer layer 18.

[0063] The functional layer 13 (top silicon layer 103) can be first patterned by photolithography and etching processes to form a waveguide core layer 19 in the functional layer 13 and grooves 141 on both axial sides of the waveguide core layer 19 from the surface of the functional layer 13 downward.

[0064] like Figure 4 As shown, in this embodiment, the cleaned SOI silicon wafer 100 is placed in a photoresist, and the first photoresist 21 is spin-coated on the surface of the functional layer 13. The first photoresist 21 is exposed by a first photolithography to form a first photoresist 21 pattern for etching the waveguide core layer 19 and the groove 141.

[0065] Then, an inductively coupled plasma (ICP) etching process can be used to form the waveguide core layer 19 and the grooves 141 located on both sides of the axial direction of the waveguide core layer 19 on the surface of the functional layer 13 using the first photoresist 21 pattern as a mask. By using the ICP etching technology with high selectivity and directionality, a waveguide core layer 19 pattern with a high steep sidewall and uniform width and smoothness can be prepared, which can not only obtain better etching directionality, but also greatly improve the etching speed.

[0066] like Figure 5 As shown, after etching, the residual first photoresist 21 and residual particles on the SOI silicon wafer 100 can be removed by alternately immersing and cleaning with acetone and alcohol, and a device structure having a ridge-shaped waveguide core layer 19 and a groove 141 is formed on the surface of the functional layer 13 .

[0067] like Figure 6 As shown, then, a heat transfer material layer 181 is deposited on the surface of the functional layer 13 by electron beam evaporation, radio frequency sputtering or reactive DC sputtering. The heat transfer material layer 181 can be made of a material with high thermal conductivity and low refractive index, such as Al2O3, AlN, Si3N4, SiC, etc.

[0068] The deposited heat transfer material layer 181 covers the surface of the waveguide core layer 19 and the inner wall of the groove 141. Furthermore, chemical mechanical polishing (CMP) can be used to remove the overgrown heat transfer material layer 181 on the top surface of the waveguide core layer 19, so as to obtain a flat surface of the heat transfer material layer 181 with a certain thickness on the top surface of the waveguide core layer 19.

[0069] Next, a second patterning process may be performed on the heat transfer material layer 181 by using a photolithography and etching process to form a heat transfer layer 18 on at least the top surface of the waveguide core layer 19 .

[0070] like Figure 7As shown, in this embodiment, the second photoresist 22 is spin-coated on the surface of the functional layer 13 to completely cover the heat transfer material layer 181, and the second photoresist 22 is soft-baked. Then, the second photoresist 22 is exposed by a second photolithography to form a second photoresist 22 pattern for etching the heat transfer material layer 181.

[0071] like Figure 8 As shown, then, an ICP etching process can be used to form a heat transfer layer 18 on the top surface and side surface of the waveguide core layer 19 using the second photoresist 22 pattern as a mask, and the heat transfer material layer 181 at positions other than the heat transfer layer 18 is removed by etching in this step (i.e., only the heat transfer material layer 181 at the top surface and side surface of the corresponding waveguide core layer 19 is retained). After etching, the remaining second photoresist 22 and residual particles can be removed by cleaning.

[0072] like Fig. 9 As shown, physical vapor deposition (PVD) can be used to deposit a heating electrode material layer 171 on the surface of the functional layer 13 having the heat transfer layer 18, so as to cover the surface of the waveguide core layer 19, the heat transfer layer 18 and the inner wall of the groove 141. The heating electrode material layer 171 can be made of at least one of Au, Ag, Pt, Ti, W, and Al, or can be a conductive alloy.

[0073] Next, the heater electrode material layer 171 is subjected to third patterning to form the heater electrode layer 17 on the surface of the heat transfer layer 18 , and the heater electrode layer 17 is isolated from the waveguide core layer 19 by the heat transfer layer 18 .

[0074] like Fig.10 As shown, in this embodiment, the third photoresist 23 is spin-coated on the surface of the functional layer 13 to completely cover the heating electrode material layer 171, and the third photoresist 23 is soft-baked. Then, the third photoresist 23 is exposed by a third photolithography to form a third photoresist 23 pattern for etching the heating electrode material layer 171.

[0075] like Fig.11 As shown, then, an ICP etching process can be used to form a heating electrode layer 17 on the top and side surfaces of the waveguide core layer 19 (heat transfer layer 18) using the third photoresist 23 pattern as a mask, and the heating electrode material layer 171 at positions other than the heating electrode layer 17 is removed by etching in this step (i.e., only the heating electrode material layer 171 at the top and side surfaces of the corresponding heat transfer layer 18 is retained). After etching, the residual third photoresist 23 and residual particles can be removed by cleaning.

[0076] like Fig.12As shown, plasma enhanced chemical vapor deposition (PECVD) can be used to deposit a second dielectric layer 161 such as silicon dioxide on the surface of the functional layer 13 having the heating electrode layer 17 and the heat transfer layer 18, covering the surface of the waveguide core layer 19, the heating electrode layer 17, the heat transfer layer 18 and the inner wall of the groove 141, and performing high temperature annealing.

[0077] Furthermore, chemical mechanical polishing (CMP) can be used to remove the overgrown second dielectric layer 161 on the top surface of the waveguide core layer 19 (heating electrode layer 17 ) to obtain a second dielectric layer 161 with a certain thickness and a smooth surface on the top surface of the waveguide core layer 19 .

[0078] Then, the second dielectric layer 161 is subjected to a fourth patterning process to form a first waveguide cladding layer 16 axially covering the top surface of the waveguide core layer 19 and the side surfaces on both sides thereof.

[0079] like Fig.13 As shown, in this embodiment, the fourth photoresist 24 is spin-coated on the surface of the functional layer 13 to completely cover the second dielectric layer 161, and the fourth photoresist 24 is soft-baked. Then, the fourth photoresist 24 is exposed by a fourth photolithography to form a fourth photoresist 24 pattern for etching the second dielectric layer 161.

[0080] like Fig.14 As shown, then, an ICP etching process can be used, with the fourth photoresist 24 pattern as a mask, to form a first waveguide cladding 16 on the top and side surfaces of the waveguide core layer 19 (heating electrode layer 17), and by etching in this step, the second dielectric layer 161 at positions other than the first waveguide cladding 16 is removed (i.e., only the second dielectric layer 161 at the top and side positions corresponding to the waveguide core layer 19 is retained). After etching, the remaining fourth photoresist 24 and residual particles can be removed by cleaning. Thus, a waveguide structure 15 including a waveguide core layer 19, a heat transfer layer 18, a heating electrode layer 17 and a first waveguide cladding 16 stacked in sequence from the inside to the outside is formed; and by filling the remaining space of the groove 141 with air, i.e., forming a first air isolation wall as the first dielectric isolation structure 14, a phase shifter structure with a ridge waveguide morphology of the present invention is prepared.

[0081] refer to Figure 15-17 , Figure 15-17 FIG. 1 is a process flow chart of a method for preparing a phase shifter structure according to a preferred embodiment 2 of the present invention. Figure 15-17 As shown, a method for preparing a phase shifter structure of the present invention can be used to prepare, for example Figure 2 A phase shifter structure shown in FIG. Figure 3-Figure 14The difference between the above-mentioned embodiments is that, in this embodiment, when the top silicon layer 103 (functional layer 13) of the SOI silicon wafer 100 is first patterned, it is necessary to make the bottom surface of the formed waveguide core layer 19 and the bottom surface of the groove 141 contact with the top surface of the first dielectric layer 12.

[0082] like Fig.15 As shown, after forming a first photoresist 21 pattern for etching the waveguide core layer 19 and the groove 141 on the surface of the functional layer 13, an ICP etching process is adopted to etch through the functional layer 13 using the first photoresist 21 pattern as a mask, so that the etching bottom surface is located on the surface (top surface) of the first dielectric layer 12, so as to form a waveguide core layer 19 and a groove 141 on the surface of the functional layer 13 whose bottom surface contacts the top surface of the first dielectric layer 12.

[0083] like Fig.16 As shown, after the heat transfer layer 18, the heating electrode layer 17 and the first waveguide cladding 16 covering the waveguide core layer 19 are sequentially formed on the top surface and the side surface of the waveguide core layer 19, the method further includes:

[0084] A protective material layer is formed on the surface of the functional layer 13 by plasma enhanced chemical vapor deposition process to cover the surface of the waveguide structure 15 and the inner wall of the groove 141. The material of the protective material layer needs to be different from that of the first dielectric layer 12, for example, it can be Si3N4.

[0085] The protective material layer is patterned fifthly by using photolithography and etching processes to form a protective layer 25 on the top surface and side surfaces of the waveguide structure 15 , completely covering the surface of the first waveguide cladding layer 16 .

[0086] like Fig.17 As shown, a portion of the first dielectric layer 12 below the waveguide structure 15 is removed through a release process, and a cavity 201 communicating with the groove 141 is formed below the waveguide structure 15, so that air is filled into the cavity 201, and a second air isolation wall is formed in the cavity 201 as a second dielectric isolation structure 20 and in direct contact with the bottom surface of the waveguide core layer 19, thereby preparing a phase shifter structure with a strip waveguide morphology according to the present invention.

[0087] The groove 141 can be used as a release hole in the release process. For example, a Bosch process can be used to form a through hole (not shown) with the bottom reaching the middle buried oxide layer 102 (first dielectric layer 12) on the back of the bottom silicon layer 101 (substrate 11) of the SOI silicon wafer 100 as a release hole in the release process.

[0088] In summary, the present invention can improve the modulation efficiency of the thermo-optical effect phase shifter, optimize the modulation time, and reduce the loss. The preparation method is compatible with the silicon-based CMOS process and can realize large-scale production integration. It has a driving effect on the development of active devices such as filters and modulators based on thermo-optical effects in silicon-based optical chips.

[0089] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A phase shifter structure, characterized in that: include: A first dielectric layer and a functional layer are sequentially arranged on the substrate, wherein the functional layer is provided with a waveguide structure and a first dielectric isolation structure located on both sides of the waveguide structure in an axial direction; The waveguide structure includes a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer stacked in sequence from the inside to the outside, and the heating electrode layer is isolated from the waveguide core layer by the heat transfer layer.

2. The phase shifter structure according to claim 1, characterized in that: The first medium isolation structure includes a first air isolation wall.

3. The phase shifter structure according to claim 1, characterized in that: The heat transfer layer and the heating electrode layer are arranged on the top surface of the waveguide core layer, and the first waveguide cladding layer is axially coated on the top surface of the waveguide core layer facing away from the substrate and on both side surfaces thereof.

4. The phase shifter structure according to claim 3, characterized in that: The heat transfer layer and the heating electrode layer further extend from the top surface of the waveguide core layer to at least one of the side surfaces.

5. The phase shifter structure according to claim 3, characterized in that: A second dielectric isolation structure is also provided in the first dielectric layer. The second dielectric isolation structure is connected to the first dielectric isolation structure on both sides. The waveguide structure is isolated from the substrate by the second dielectric isolation structure.

6. The phase shifter structure according to claim 5, characterized in that: The first dielectric isolation structure includes a first air isolation wall, and the second dielectric isolation structure includes a second air isolation wall serving as a second waveguide cladding. The second air isolation wall is connected to the first air isolation walls on both sides, and the second air isolation wall is in direct contact with the bottom surface of the waveguide core layer.

7. The phase shifter structure according to claim 1, characterized in that: The heat transfer layer material includes at least one of Al2O3, AlN, Si3N4, and SiC, and / or the heating electrode layer material includes at least one of Au, Ag, Pt, Ti, W, and Al.

8. A method for preparing a phase shifter structure, characterized in that: include: Providing a substrate, on which a first dielectric layer and a functional layer are sequentially arranged; A waveguide structure and a first dielectric isolation structure located on both axial sides of the waveguide structure are formed on the functional layer, so that the formed waveguide structure includes a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer stacked in sequence from the inside to the outside, and the heating electrode layer is isolated from the waveguide core layer by the heat transfer layer.

9. The method for preparing a phase shifter structure according to claim 8, characterized in that: The waveguide structure and the first dielectric isolation structure located on both sides of the waveguide structure in the axial direction are formed on the functional layer, so that the formed waveguide structure includes a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer stacked in sequence from the inside to the outside, and the heating electrode layer is isolated from the waveguide core layer by the heat transfer layer, specifically comprising: Performing a first patterning to form a waveguide core layer located in the functional layer and grooves located on both sides of the waveguide core layer in an axial direction from the surface of the functional layer downward; forming a heat transfer material layer on the surface of the functional layer to cover the surface of the waveguide core layer; performing a second patterning on the heat transfer material layer to form a heat transfer layer on at least the top surface of the waveguide core layer; forming a heating electrode material layer on the surface of the functional layer to cover the surfaces of the waveguide core layer and the heat transfer layer; Performing a third patterning on the heating electrode material layer to form a heating electrode layer on the surface of the heat transfer layer, and isolating the heating electrode layer from the waveguide core layer through the heat transfer layer; forming a second dielectric layer on the surface of the functional layer to cover the surfaces of the waveguide core layer, the heating electrode layer and the heat transfer layer; The second dielectric layer is subjected to a fourth patterning to form a first waveguide cladding axially covering the top surface of the waveguide core layer and the side surfaces on both sides thereof, thereby forming a waveguide structure including the waveguide core layer, the heat transfer layer, the heating electrode layer and the first waveguide cladding stacked in sequence from the inside to the outside, and the groove is used to form a first air isolation wall as a first dielectric isolation structure.

10. The method for preparing a phase shifter structure according to claim 9, characterized in that: When performing the first patterning, the bottom surface of the formed waveguide core layer and the bottom surface of the groove are in contact with the top surface of the first dielectric layer; After executing the fourth graphicization, the method further includes: forming a protective layer on the surface of the functional layer to cover the surface of the first waveguide cladding layer; Through a release process, part of the first dielectric layer below the waveguide structure is removed to form a cavity communicating with the groove below the waveguide structure, and the cavity is used to form a second air isolation wall serving as a second dielectric isolation structure and directly contacting the bottom surface of the waveguide core layer.

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