CN119225051A - A phase shifter structure and preparation method thereof - Google Patents

Abstract

The invention discloses a phase shifter structure and a preparation method thereof, wherein the phase shifter structure comprises a first dielectric layer and a functional layer which are sequentially arranged on a substrate, the functional layer is provided with a waveguide structure and first dielectric isolation structures positioned on two axial sides of the waveguide structure, the waveguide structure comprises a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer which are sequentially overlapped from inside to outside, and the heating electrode layer is isolated from the waveguide core layer through the heat transfer layer. The invention can improve the modulation efficiency of the thermo-optic effect phase shifter, optimize the modulation time, reduce the loss, reduce the thermal crosstalk between adjacent devices and channels, and the preparation method is compatible with the silicon-based CMOS process, can realize mass production integration, and has a pushing effect on the development of active devices such as filters, modulators and the like based on the thermo-optic effect in the silicon-based optical chip.

Description

Phase shifter structure and preparation method thereof

Technical Field

The invention relates to the technical field of thermo-optic effect phase shifters, in particular to a phase shifter structure capable of improving thermal modulation efficiency and reducing thermal crosstalk and a preparation method thereof.

Background

In a conventional microelectronic chip, due to the gradual reduction of the feature size of a transistor, the transistor is limited by physical limits such as quantum tunneling, and the electrical interconnection process (copper interconnection) is faced with problems such as transmission delay, power consumption, signal crosstalk and the like. The silicon-based photoelectronic technology has the advantages of low cost, high photon transmission rate, strong anti-interference performance, compatibility with the traditional silicon-based CMOS technology and the like, and gradually replaces the traditional electric interconnection chip in short-distance communication. The electro-optic modulator is used as one of important active devices in the silicon-based photoelectronic chip, and the function of electro-optic signal conversion is realized by changing the phase, frequency, intensity and polarization of light waves.

The modulation structure of the silicon-based electro-optic modulator based on the thermo-optic effect can be mainly divided into two basic structures, namely a micro-ring resonator and a Mach-Zehnder interferometer. The two structures are also applied to the wavelength division multiplexing technology of the silicon-based optical chip at present to realize the information transmission with large bandwidth. The micro-ring resonant cavity in the micro-ring resonator is a very ingenious resonant structure, and is formed by connecting a section of waveguide end to form a ring-shaped structure, and a metal electrode is deposited on a waveguide signal arm of the micro-ring resonator, so that a phase shifter structure can be formed. The feedback is formed by the loop of the waveguide, and the phase regulation and control of the light are realized by having different periodic responses to the light with different wavelengths. The micro-ring resonator has a simple structure, a bus waveguide is additionally arranged in a micro-ring resonant cavity, so that simple functions can be realized, and a plurality of lasers, filters, modulators and optical switches all use the structure. The Mach-Zehnder interferometer divides a beam of optical signals into two paths through a beam splitter, inputs the two paths of optical waveguides, and combines the two paths of optical signals into one path through a beam combiner. A phase shifter structure can be formed by depositing a metal electrode on a waveguide signal arm of a Mach-Zehnder interferometer modulator, wherein an optical signal changes phase through the phase shifter to carry out phase modulation of the signal, and interference conversion is carried out at a beam combiner to be intensity modulation.

Currently, the waveguide structure of the phase shifter in the two structures of the micro-ring resonator and the mach-zehnder interferometer based on the thermo-optical effect generally adopts a layer of metal heating electrode or two-dimensional material deposited above a waveguide core layer as a micro-heater. Since the metallic heater electrode absorbs light in the waveguide, it causes a large transmission loss, and therefore can only be placed at a distance from the waveguide or deposited on the silica cladding of the silicon waveguide. But the thermal transfer efficiency into the silicon waveguide is extremely low due to the lower thermal conductivity of silicon dioxide, which results in higher power consumption and low modulation efficiency. And the micro heater made of the two-dimensional material cannot realize large-scale production integration because the two-dimensional material is incompatible with a silicon-based CMOS (complementary metal oxide semiconductor) process in the mechanical stripping and transferring processes.

Recently, there has been a reduction in absorption loss of light by metal heating electrodes by optimizing the number and positions of the heating electrodes in such a manner that a plurality of metal heating electrodes are placed on a silica cladding above a waveguide. However, the arrangement of the plurality of heating electrodes may cause thermal crosstalk to adjacent devices and channels. Moreover, the refractive index change achieved by thermal conduction of low thermal conductivity silica always requires a certain time, and therefore such modulators generally have a low modulation rate (on the order of microseconds) and are not suitable for high-speed devices.

In summary, the thermal modulation efficiency of the silicon-based phase shifter is improved, the thermal crosstalk is reduced, and the development of the thermo-optical effect electro-optical modulator and the importance thereof have great influence on the development of devices such as lasers, filters, modulators, optical switches and the like in the silicon-based optical chip.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a phase shifter structure and a preparation method thereof.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

the present invention provides a phase shifter structure comprising:

The functional layer is provided with a waveguide structure and first medium isolation structures positioned on two axial sides of the waveguide structure;

The waveguide structure comprises a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer which are sequentially overlapped from inside to outside, and the heating electrode layer is isolated from the waveguide core layer through the heat transfer layer.

Further, the first dielectric isolation structure comprises a first air isolation wall.

Further, 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, which is opposite to the substrate, and the side surfaces of the two sides of the waveguide core layer.

Further, the heat transfer layer and the heating electrode layer also extend from the top surface of the waveguide core layer onto at least one of the side surfaces.

Further, a second dielectric isolation structure is further arranged in the first dielectric layer, the second dielectric isolation structure is connected with the first dielectric isolation structures at two sides, and the waveguide structure is isolated from the substrate through the second dielectric isolation structure.

Further, the first dielectric isolation structure comprises a first air isolation wall, the second dielectric isolation structure comprises a second air isolation wall serving as a second waveguide cladding, the second air isolation wall is communicated with the first air isolation walls on two sides, and the second air isolation wall is in direct contact with the bottom surface of the waveguide core layer.

Further, the heat transfer layer material comprises at least one of Al ₂O₃、AlN、Si₃N₄, siC, and/or the heated electrode layer material comprises at least one of Au, ag, pt, ti, W, al.

The invention also provides a preparation method of the phase shifter structure, which comprises the following steps:

providing a substrate, wherein a first dielectric layer and a functional layer are sequentially arranged on the substrate;

And forming a waveguide structure and first medium isolation structures positioned on two axial sides of the waveguide structure on the functional layer, so that the formed waveguide structure comprises a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer which are sequentially overlapped from inside to outside, and the heating electrode layer is isolated from the waveguide core layer through the heat transfer layer.

Further, the forming a waveguide structure and first medium isolation structures located at two axial sides of the waveguide structure 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 which are sequentially stacked from inside to outside, and the insulating layer isolates the heating electrode layer from the waveguide core layer through the heat transfer layer, specifically including:

Performing first patterning, and forming a waveguide core layer positioned in the functional layer and grooves positioned on two axial sides of the waveguide core layer downwards from the surface of the functional layer;

forming a heat transfer material layer on the surface of the functional layer, and covering the surface of the waveguide core layer;

performing a second patterning of the layer of heat transfer material, forming a heat transfer layer on at least a top surface of the waveguide core layer;

Forming a heating electrode material layer on the surface of the functional layer, and covering the surfaces of the waveguide core layer and the heat transfer layer;

Performing a third patterning on the heating electrode material layer, forming a heating electrode layer on the surface of the heat transfer layer, and isolating the heating electrode layer from the waveguide core layer by the heat transfer layer;

Forming a second dielectric layer on the surface of the functional layer, and covering the surfaces of the waveguide core layer, the heating electrode layer and the heat transfer layer;

And performing fourth patterning on the second medium layer to form a first waveguide cladding layer which is axially coated on the top surface of the waveguide core layer and the side surfaces of the two sides of the waveguide core layer, so as to form a waveguide structure comprising the waveguide core layer, the heat transfer layer, the heating electrode layer and the first waveguide cladding layer which are sequentially stacked from inside to outside, and forming a first air isolation wall serving as a first medium isolation structure by the grooves.

Further, when the first patterning is performed, the bottom surface of the waveguide core layer and the bottom surface of the trench are contacted with the top surface of the first dielectric layer, and after the fourth patterning is performed, the method further comprises:

forming a protective layer on the surface of the functional layer, and covering the surface of the first waveguide cladding layer;

And removing part of the first dielectric layer below the waveguide structure through a release process, forming a cavity which is communicated with the groove below the waveguide structure, and forming a second air isolation wall which is used as a second dielectric isolation structure and is in direct contact with the bottom surface of the waveguide core layer by using the cavity.

According to the technical scheme, the heating electrode layer is arranged between the waveguide cladding layer (the first waveguide cladding layer) and the waveguide core layer in the phase shifter waveguide structure, the heat transfer layer with high heat conductivity and low refractive index is arranged between the heating electrode layer and the waveguide core layer, so that the total reflection transmission of light in the phase shifter waveguide core layer is met, the heat modulation efficiency is improved, the modulation time is optimized, meanwhile, the medium isolation structures (the first air isolation wall/the first medium isolation structure and the second air isolation wall/the second medium isolation structure) in the form of air isolation walls are arranged on two sides of the waveguide structure or below the waveguide structure, the heat energy can be limited to the maximum extent on the waveguide structure in the central area, the modulation loss and the transmission loss can be effectively reduced, the heat crosstalk between adjacent devices and channels can be reduced, and the contact area in the heat conduction process can be increased by enabling the heating electrode layer (comprising the heat transfer layer) to extend from the top surface of the waveguide core layer to the side, and the heat utilization rate can be further improved. The invention can effectively solve the problems of larger light transmission loss and lower heat transfer efficiency caused by the prior arrangement of the heating electrode layer on the waveguide cladding, is beneficial to reducing the power consumption of devices and is suitable for high-speed devices.

Drawings

FIG. 1 is a schematic diagram of a phase shifter structure according to a first preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of a phase shifter according to a second preferred embodiment of the present invention;

FIGS. 3-14 are process flow diagrams illustrating a method for fabricating a phase shifter structure according to a first preferred embodiment of the present invention;

fig. 15-17 are process flow diagrams illustrating a method for fabricating a phase shifter structure according to a second preferred embodiment of the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Unless otherwise defined, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. As used herein, the word "comprising" and the like means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof without precluding other elements or items.

In order to solve the problems of low heat utilization rate, low modulation efficiency, high power consumption and the like caused by the fact that a metal heating electrode positioned outside a waveguide cladding has larger absorption loss to light and a silicon dioxide waveguide cladding has lower heat conductivity in a phase shifter based on a thermo-optical effect in the prior art, the invention provides a phase shifter structure.

The invention can improve the thermal modulation efficiency and optimize the modulation time while meeting the total reflection and transmission of light in the waveguide core layer of the phase shifter by changing the arrangement structure of the heating electrode on the waveguide structure, arranging the heating electrode layer between the first waveguide cladding layer and the waveguide core layer in the waveguide structure of the phase shifter and arranging the heat transfer layer with high heat conductivity and low refractive index between the heating electrode layer and the waveguide core layer, and simultaneously, can limit the heat energy to the maximum extent on the waveguide structure in the central area by arranging the first medium isolation structures on two sides of the waveguide structure and arranging the first medium layer below the waveguide structure, thereby effectively reducing the modulation loss and the transmission loss and reducing the thermal crosstalk between adjacent devices and channels.

Therefore, the invention effectively solves the problems of larger optical transmission loss and lower heat transfer efficiency in the prior art, can not only improve the heat modulation efficiency and optimize the modulation time, but also is beneficial to reducing the power consumption of devices, thereby being applicable to high-speed devices.

The following describes the embodiments of the present invention in further detail with reference to the accompanying drawings.

Referring to fig. 1, fig. 1 is a schematic diagram of a phase shifter structure according to a first preferred embodiment of the present invention. As shown in fig. 1, a phase shifter structure of the present invention includes a first dielectric layer 12 provided on a surface of a substrate 11, a functional layer 13 provided on the surface of the first dielectric layer 12, a waveguide structure 15 provided on the functional layer 13, and first dielectric isolation structures 14 located on both sides of the waveguide structure 15 in an axial direction (i.e., a direction perpendicular to the drawing plane).

The bottom surfaces of the two first dielectric isolation structures 14 are located above the bottom surface of the functional layer 13 and are kept at 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.

The waveguide structure 15 is provided with a waveguide core layer 19 positioned at the core, and 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. And the heating electrode layer 17 is isolated from the waveguide core layer 19 by the heat transfer layer 18.

In some embodiments, the heat transfer layer 18 is attached axially to the top surface of the waveguide core layer 19 (shown as the upper surface facing away from the substrate 11), 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 16 is coated on the top surface of the waveguide core layer 19 and the side surfaces on both sides of the top surface in the axial direction, and covers the heating electrode layer 17 and the heat transfer layer 18.

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 formed in a continuous distribution on the top surface and both side surfaces of the waveguide core layer 19, and are covered with the first waveguide clad layer 16 together with the waveguide core layer 19, as shown in fig. 1. Namely, the arrangement area and the 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, thereby further improving the heat utilization rate, increasing the heat modulation efficiency and optimizing the modulation time while meeting the requirement that light is totally reflected and conveyed in the phase shifter waveguide.

Reference is made to fig. 1. The first dielectric isolation structure 14 includes a first air isolation wall. In some embodiments, the waveguide structure 15 is provided with grooves on both axial sides, which are filled with air, thereby forming a first air partition 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 below the waveguide structure 15, the heat energy can be limited to the central area of the waveguide structure 15 as much as possible, the modulation loss and the transmission loss can be effectively reduced, the thermal modulation efficiency can be improved, and the thermal crosstalk between adjacent devices and channels can be reduced.

In some embodiments, substrate 11 may be a conventional semiconductor substrate. For example, the substrate 11 may be a silicon substrate 11.

The first dielectric layer 12 material may be a conventional dielectric material. For example, the first dielectric layer 12 material may be silicon dioxide.

The functional layer 13 material may be a conventional material used to prepare waveguides. For example, the functional layer 13 material may be silicon.

In some embodiments, the heat transfer layer 18 material may be at least one of Al ₂O₃、AlN、Si₃N₄, siC having high thermal conductivity, low refractive index properties.

The heating electrode layer 17 material may be at least one of Au, ag, pt, ti, W, al.

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

In some embodiments, the phase shifter structure may be formed on an SOI silicon wafer 100, where 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 may be utilized as a substrate 11, the middle buried oxide layer 102 is a first dielectric layer 12, the top silicon layer 103 is a functional layer 13, and the phase shifter structure is formed on the top silicon layer 103 of the SOI silicon wafer 100 with a waveguide structure 15 having a silicon waveguide core layer 19, and first air isolation wall structures located on both axial sides of the waveguide structure 15.

Referring to fig. 2, fig. 2 is a schematic diagram of a phase shifter structure according to a second preferred embodiment of the present invention. As shown in fig. 2, the difference from the above embodiment of fig. 1 is that in the phase shifter structure of the present invention, the trench bottom surfaces 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, i.e. the bottom surface of the waveguide core layer 19 is also located on the surface of the first dielectric layer 12, thereby forming the strip waveguide structure 15. The first dielectric layer 12 is also provided with a second dielectric isolation structure 20, and the second dielectric isolation structure 20 is positioned in the first dielectric layer 12 below the waveguide structure 15 and is connected with the first dielectric isolation structures 14 positioned above two sides of the second dielectric isolation structure 20. The waveguide structure 15 is isolated from the substrate 11 by a second dielectric isolation structure 20.

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, so as to form a second air isolation wall serving as the second dielectric isolation structure 20, so that communication is formed between the second dielectric isolation structure 20 and 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 walls surrounding the side surfaces and the bottom surface of the waveguide structure 15 are utilized to form the waveguide structure 15 in an overhead form, so that not only can the total reflection condition of light in waveguide transmission be met, but also the transmission loss of light in the waveguide transmission process can be reduced to the greatest extent (because the refractive index of air is about 1, compared with the refractive index difference between Si-air structures is smaller, and the Si-SiO ₂ structure), heat is concentrated at the center position of the strip waveguide to the greatest extent, and the thermal modulation efficiency is improved.

The following describes a method for manufacturing a phase shifter structure according to the present invention in further detail by means of the detailed description and the accompanying drawings.

Referring to fig. 3-14, fig. 3-14 are process flow diagrams of a method for fabricating a phase shifter structure according to a first preferred embodiment of the present invention. As shown in fig. 3-14, a phase shifter structure manufacturing method of the present invention may be used to manufacture a phase shifter structure such as that shown in fig. 1, and may include the steps of:

Step S1, providing a substrate 11, and sequentially arranging a first dielectric layer 12 and a functional layer 13 on the substrate 11.

As shown in fig. 3, an SOI silicon wafer 100 may be used, where 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.

The SOI wafer 100 may be first subjected to a cleaning process to remove particles, organic matter, and the like from the surface of the substrate 11 and to blow off residual liquid from the surface of the substrate 11.

Step S2, forming a waveguide structure 15 and first medium isolation structures 14 positioned on two axial sides of the waveguide structure 15 on the functional layer 13, wherein the formed waveguide structure 15 comprises a waveguide core layer 19, a heat transfer layer 18, a heating electrode layer 17 and a first waveguide cladding layer 16 which are sequentially stacked from inside to outside, and the heating electrode layer 17 is isolated from the waveguide core layer 19 through the heat transfer layer 18.

The functional layer 13 (the top silicon layer 103) may be first patterned using photolithography and etching processes, and the waveguide core layer 19 located in the functional layer 13 and the trenches 141 located on both axial sides of the waveguide core layer 19 are formed downward from the surface of the functional layer 13.

As shown in fig. 4, in the present embodiment, the SOI wafer 100 after cleaning is placed in a resist homogenizer, and the first photoresist 21 is spin-coated on the surface of the functional layer 13. The first photoresist 21 is subjected to an exposure process using a first photolithography process to form a pattern of the first photoresist 21 for etching the waveguide core layer 19 and the trench 141.

Then, the waveguide core layer 19 and the trenches 141 located at both axial sides of the waveguide core layer 19 may be formed on the surface of the functional layer 13 using the first photoresist 21 pattern as a mask by an Inductively Coupled Plasma (ICP) etching process. By utilizing the ICP etching technology with high selectivity and directionality, the patterns of the waveguide core layer 19 with high-definition side walls, uniform and smooth width can be prepared, so that not only can the better etching directionality be obtained, but also the etching speed can be greatly improved.

As shown in fig. 5, after etching, the residual first photoresist 21 and residual particles on the SOI wafer 100 may be removed by using an acetone/alcohol alternative soaking and cleaning method, and a device structure having a ridge waveguide core layer 19 and a trench 141 is formed on the surface of the functional layer 13.

As shown in fig. 6, a heat transfer material layer 181 is then deposited on the surface of the functional layer 13 by means of electron beam evaporation, radio frequency sputtering, reactive dc sputtering, or the like. The heat transfer material layer 181 may be selected to have a high thermal conductivity and a low refractive index, such as Al ₂O₃、AlN、Si₃N₄, siC, or the like.

The deposited layer 181 of heat transfer material covers the surface of the waveguide core layer 19 and the inner walls of the trenches 141. Further, chemical Mechanical Polishing (CMP) may be employed to remove the overgrown heat transfer material layer 181 on the top surface of the waveguide core layer 19 to obtain a surface of the heat transfer material layer 181 on the top surface of the waveguide core layer 19 having a certain thickness and being flat.

Next, a second patterning of the thermally conductive material layer 181 may be performed using photolithography and etching processes, forming a thermally conductive layer 18 on at least the top surface of the waveguide core layer 19.

As shown in fig. 7, in the present embodiment, the second photoresist 22 is spin-coated on the surface of the functional layer 13, the heat transfer material layer 181 is completely covered, and soft baking is performed on the second photoresist 22. Then, the second photoresist 22 is subjected to an exposure process using a second photolithography to form a second photoresist 22 pattern for etching the heat transfer material layer 181.

As shown in fig. 8, next, an ICP etching process may be used to form the heat transfer layer 18 on the top and side surfaces of the waveguide core layer 19 using the second photoresist 22 pattern as a mask, and the heat transfer material layer 181 on the positions other than the heat transfer layer 18 is removed (i.e., only the heat transfer material layer 181 on the positions corresponding to the top and side surfaces of the waveguide core layer 19 is left) by the present etching. The residual second photoresist 22 and residual particles may be removed by cleaning after etching.

As shown in fig. 9, a heating electrode material layer 171 may be deposited on the surface of the functional layer 13 having the heat transfer layer 18 by Physical Vapor Deposition (PVD), covering the surfaces of the waveguide core layer 19, the heat transfer layer 18, and the inner walls of the trenches 141. The heating electrode material layer 171 material may be at least one of Au, ag, pt, ti, W, al or may be a conductive alloy.

Next, the heating electrode material layer 171 is subjected to third patterning, the heating electrode layer 17 is formed on the surface of the heat transfer layer 18, and the heating electrode layer 17 is isolated from the waveguide core layer 19 by the heat transfer layer 18.

As shown in fig. 10, in the present embodiment, the third photoresist 23 is spin-coated on the surface of the functional layer 13, the heating electrode material layer 171 is completely covered, and soft baking is performed on the third photoresist 23. Then, the third photoresist 23 is subjected to an exposure process using a third photolithography to form a third photoresist 23 pattern for etching the heating electrode material layer 171.

As shown in fig. 11, next, the heating electrode layer 17 may be formed on the top and side surfaces of the waveguide core layer 19 (the heat transfer layer 18) using the third photoresist 23 pattern as a mask by an ICP etching process, and the heating electrode material layer 171 on the positions other than the heating electrode layer 17 may be removed (i.e., only the heating electrode material layer 171 on the positions corresponding to the top and side surfaces of the heat transfer layer 18 may be left) by the present step of etching. The residual third photoresist 23 and residual particles may be removed by cleaning after etching.

As shown in fig. 12, a second dielectric layer 161 of, for example, silicon dioxide is deposited on the surface of the functional layer 13 having the heating electrode layer 17 and the heat transfer layer 18 by Plasma Enhanced Chemical Vapor Deposition (PECVD), and the surfaces of the waveguide core layer 19, the heating electrode layer 17, the heat transfer layer 18 and the inner walls of the trenches 141 are covered and subjected to a high temperature annealing treatment.

Further, chemical Mechanical Polishing (CMP) may be used to remove the overgrown second dielectric layer 161 on the top surface of the waveguide core layer 19 (the heating electrode layer 17) to obtain a planar surface of the second dielectric layer 161 with a certain thickness on the top surface of the waveguide core layer 19.

Then, fourth patterning is performed on the second dielectric layer 161, forming the first waveguide cladding layer 16 axially clad on the top surface of the waveguide core layer 19 and both side surfaces thereof.

As shown in fig. 13, in this embodiment, a fourth photoresist 24 is spin-coated on the surface of the functional layer 13, the second dielectric layer 161 is completely covered, and soft baking is performed on the fourth photoresist 24. Then, the fourth photoresist 24 is subjected to an exposure process using fourth photolithography to form a fourth photoresist 24 pattern for etching the second dielectric layer 161.

As shown in fig. 14, next, an ICP etching process may be used to form the first waveguide clad layer 16 on the top and side surfaces of the waveguide core layer 19 (the heating electrode layer 17) using the fourth photoresist 24 pattern as a mask, and the second dielectric layer 161 on the position other than the first waveguide clad layer 16 is removed (i.e., only the second dielectric layer 161 on the top and side surfaces of the corresponding waveguide core layer 19 remains) by this step of etching. The remaining fourth photoresist 24 and the remaining particles may be removed by cleaning after etching. The phase shifter structure with the ridge waveguide morphology is prepared by forming the waveguide structure 15 comprising the waveguide core layer 19, the heat transfer layer 18, the heating electrode layer 17 and the first waveguide cladding layer 16 which are sequentially stacked from inside to outside, and filling air into the remaining space of the trench 141 to form the first air isolation wall serving as the first dielectric isolation structure 14.

Referring to fig. 15-17, fig. 15-17 are process flow diagrams of a method for fabricating a phase shifter structure according to a second preferred embodiment of the present invention. As shown in fig. 15-17, a phase shifter structure manufacturing method according to the present invention can be used to manufacture a phase shifter structure such as that shown in fig. 2, and is different from the above-described embodiments of fig. 3-14 in that in this embodiment, when the top silicon layer 103 (the functional layer 13) of the SOI silicon wafer 100 is subjected to the first patterning, the bottom surface of the waveguide core layer 19 and the bottom surface of the trench 141 need to be formed to be in contact with the top surface of the first dielectric layer 12.

As shown in fig. 15, after forming a first photoresist 21 pattern for etching the waveguide core layer 19 and the trench 141 on the surface of the functional layer 13, the functional layer 13 is etched through using the first photoresist 21 pattern as a mask by an ICP etching process so that the etched bottom surface is located on the surface (top surface) of the first dielectric layer 12 to form the waveguide core layer 19 and the trench 141 on the surface of the functional layer 13, the bottom surface of which is in contact with the top surface of the first dielectric layer 12.

As shown in fig. 16, after forming the heat transfer layer 18, the heating electrode layer 17, and the first waveguide clad layer 16, which cover the waveguide core layer 19, in this order on the top surface and the side surface of the waveguide core layer 19, further includes:

A protective material layer is formed on the surface of the functional layer 13 by a plasma enhanced chemical vapor deposition process to cover the surfaces of the waveguide structure 15 and the inner walls of the trenches 141. The material of the protective material layer needs to be different from that of the first dielectric layer 12, and may be Si ₃N₄, for example.

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

As shown in fig. 17, a portion of the first dielectric layer 12 under the waveguide structure 15 is removed by a release process, a cavity 201 communicating with the trench 141 is formed under the waveguide structure 15, air is filled into the cavity 201, and a second air partition wall as the second dielectric partition structure 20 and in direct contact with the bottom surface of the waveguide core layer 19 is formed in the cavity 201, thereby preparing the phase shifter structure having the stripe waveguide form of the present invention.

Wherein the grooves 141 may be utilized as release holes in a release process. A via (not shown) with its bottom reaching the intermediate buried oxide layer 102 (first dielectric layer 12) may also be formed on the back side of the underlying silicon layer 101 (substrate 11) of the SOI wafer 100, for example by Bosch process, as a release hole in a release process.

In summary, the invention can improve the modulation efficiency of the thermo-optic effect phase shifter, optimize the modulation time and reduce the loss, and the preparation method is compatible with the silicon-based CMOS process, can realize large-scale production integration, and has a pushing effect on the development of active devices such as filters, modulators and the like based on the thermo-optic effect in the silicon-based optical chip.

While embodiments of the present invention have been described in detail hereinabove, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. It is to be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the following claims. Moreover, the invention described herein is capable of other embodiments and of being practiced or of being carried out in various ways.

Claims (10)

1. A phase shifter structure, comprising:

The functional layer is provided with a waveguide structure and first medium isolation structures positioned on two axial sides of the waveguide structure;

The waveguide structure comprises a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer which are sequentially overlapped from inside to outside, and the heating electrode layer is isolated from the waveguide core layer through the heat transfer layer.

2. The phase shifter structure of claim 1, wherein the first dielectric isolation structure comprises a first air isolation wall.

3. The phase shifter structure of claim 1, wherein the heat transfer layer and the heating electrode layer are disposed 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. A phase shifter structure as set forth in claim 3 wherein said heat transfer layer and said heating electrode layer further extend from said top surface of said waveguide core layer onto at least one of said side surfaces.

5. The phase shifter structure of claim 3, wherein a second dielectric isolation structure is further disposed in the first dielectric layer, the second dielectric isolation structure is connected to the first dielectric isolation structures on both sides, and the waveguide structure is isolated from the substrate by the second dielectric isolation structure.

6. The phase shifter structure of claim 5, wherein the first dielectric isolation structure comprises a first air isolation wall, the second dielectric isolation structure comprises a second air isolation wall as a second waveguide cladding, the second air isolation wall communicates with the first air isolation wall on both sides, and the second air isolation wall is in direct contact with the bottom surface of the waveguide core.

7. The phase shifter structure of claim 1, wherein the heat transfer layer material comprises at least one of Al ₂O₃、AlN、Si₃N₄, siC, and/or the heating electrode layer material comprises at least one of Au, ag, pt, ti, W, al.

8. A method of fabricating a phase shifter structure, comprising:

providing a substrate, wherein a first dielectric layer and a functional layer are sequentially arranged on the substrate;

And forming a waveguide structure and first medium isolation structures positioned on two axial sides of the waveguide structure on the functional layer, so that the formed waveguide structure comprises a waveguide core layer, a heat transfer layer, a heating electrode layer and a first waveguide cladding layer which are sequentially overlapped from inside to outside, and the heating electrode layer is isolated from the waveguide core layer through the heat transfer layer.

9. The method for manufacturing a phase shifter structure according to claim 8, wherein a waveguide structure and first dielectric isolation structures located at two 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 inside to outside, and the heating electrode layer is isolated from the waveguide core layer by the heat transfer layer, specifically comprising:

Performing first patterning, and forming a waveguide core layer positioned in the functional layer and grooves positioned on two axial sides of the waveguide core layer downwards from the surface of the functional layer;

forming a heat transfer material layer on the surface of the functional layer, and covering the surface of the waveguide core layer;

performing a second patterning of the layer of heat transfer material, forming a heat transfer layer on at least a top surface of the waveguide core layer;

Forming a heating electrode material layer on the surface of the functional layer, and covering the surfaces of the waveguide core layer and the heat transfer layer;

Performing a third patterning on the heating electrode material layer, forming a heating electrode layer on the surface of the heat transfer layer, and isolating the heating electrode layer from the waveguide core layer by the heat transfer layer;

Forming a second dielectric layer on the surface of the functional layer, and covering the surfaces of the waveguide core layer, the heating electrode layer and the heat transfer layer;

And performing fourth patterning on the second medium layer to form a first waveguide cladding layer which is axially coated on the top surface of the waveguide core layer and the side surfaces of the two sides of the waveguide core layer, so as to form a waveguide structure comprising the waveguide core layer, the heat transfer layer, the heating electrode layer and the first waveguide cladding layer which are sequentially stacked from inside to outside, and forming a first air isolation wall serving as a first medium isolation structure by the grooves.

10. The method of manufacturing a phase shifter structure according to claim 9, wherein the first patterning is performed such that a bottom surface of the waveguide core layer and a bottom surface of the trench are formed in contact with a top surface of the first dielectric layer, and the fourth patterning is performed such that the method further comprises:

forming a protective layer on the surface of the functional layer, and covering the surface of the first waveguide cladding layer;

And removing part of the first dielectric layer below the waveguide structure through a release process, forming a cavity which is communicated with the groove below the waveguide structure, and forming a second air isolation wall which is used as a second dielectric isolation structure and is in direct contact with the bottom surface of the waveguide core layer by using the cavity.