A kind of acoustic-optical coupling substrate, device and device preparation method

Abstract

The present application discloses an acousto-optic coupling substrate, a device and a method for preparing the device, wherein an acousto-optic coupling substrate comprises a substrate layer, a dielectric layer, an acoustic layer and an optical layer stacked in sequence: the material of the substrate layer comprises silicon; the material of the dielectric layer comprises silicon dioxide; the material of the acoustic layer comprises high-quality aluminum nitride, where high quality means that the crystal half-width is less than 150 arc seconds in an X-ray diffraction test; and the material of the optical layer comprises silicon carbide. The acousto-optic coupling substrate and device are formed by direct bonding, which improves the problem of ion damage in the current preparation of silicon-based silicon carbide films using ion beam technology, and at the same time realizes wafer-level heterogeneous integration of silicon-based high-single-crystal quality acoustic device layers and optical device layers.

Description

Technical Field

[0001] The present application relates to the field of information functional material preparation, and in particular to an acousto-optic coupling substrate, a device and a device preparation method. Background Art

[0002] Silicon carbide has become an ideal material for integrated optical, nonlinear and optomechanical devices due to its wide band gap (2.4-3.2 electron volts), high physical strength (Mohs hardness 9.5, Knoop hardness 2480 kg / mm2), and high thermal conductivity (480 W / m·K).

[0003] Surface acoustic waves can be electromechanically excited, and the sound frequency in piezoelectric materials reaches tens of gigahertz. Aluminum nitride is the current mainstream piezoelectric material, but aluminum nitride materials are usually grown on sapphire or silicon carbide substrates. Due to chemical inertness, the feasibility of micro-nano processing is poor; on the other hand, aluminum nitride is not suitable for optical applications. Summary of the invention

[0004] The present application provides an acousto-optic coupling substrate, a device and a method for preparing the device, which can at least improve the problem of ion damage in the current preparation of silicon-based silicon carbide films using ion beam technology.

[0005] An embodiment of the present invention provides an acousto-optic coupling substrate, comprising:

[0006] The substrate layer, dielectric layer, acoustic layer and optical layer are stacked in sequence:

[0007] The material of the substrate layer includes silicon;

[0008] The material of the dielectric layer includes silicon dioxide;

[0009] The material of the acoustic layer includes high-quality aluminum nitride, where high quality means that the half-width at half maximum of the crystal direction is less than 150 arc seconds in the X-ray diffraction test;

[0010] The material of the optical layer includes silicon carbide.

[0011] Optionally, the thickness of the acoustic layer is 0-3 microns; the thickness of the optical layer is 100 nanometers-5 microns.

[0012] An embodiment of the present invention provides a method for preparing an acousto-optic coupling device, comprising:

[0013] Obtaining the above-mentioned acousto-optic coupling substrate;

[0014] etching the optical layer of the acousto-optic coupling substrate into waveguides and resonant cavities;

[0015] A plurality of through holes penetrating the acoustic layer are opened on the acoustic layer of the acoustic-optic coupling substrate, and the plurality of through holes are arranged in a preset shape;

[0016] Wet etching the dielectric layer of the acousto-optic coupling substrate through a plurality of through holes so that the acoustic layer in a preset shape is suspended;

[0017] An interdigital electrode is prepared on the side of the suspended acoustic layer away from the dielectric layer to obtain an acousto-optic coupling device; wherein the waveguide and the resonant cavity constitute the optical device part of the acousto-optic coupling device, and the suspended acoustic layer and the interdigital electrode constitute the acoustic device part of the acousto-optic coupling device.

[0018] Optionally, an acousto-optic coupling substrate is obtained, including: growing an acoustic layer on a silicon carbide wafer based on high-quality aluminum nitride to obtain a first wafer; high quality means that in an X-ray diffraction test, the crystal half-width is less than 150 arc seconds; growing a first dielectric layer on the acoustic layer based on silicon dioxide to obtain a second wafer; bonding the first dielectric layer to a second dielectric layer in a silicon substrate at a first temperature to obtain a first bonding structure; the silicon substrate includes a stacked substrate layer and a second dielectric layer, the material of the substrate layer includes silicon, and the material of the second dielectric layer includes silicon dioxide; the first dielectric layer and the second dielectric layer constitute a dielectric layer; thinning the thickness of the silicon carbide wafer in the first bonding structure to a specified thickness to obtain an acousto-optic coupling substrate; wherein the silicon carbide wafer of the specified thickness constitutes the optical layer of the acousto-optic coupling substrate.

[0019] Optionally, thinning the thickness of the silicon carbide wafer in the first bonding structure to a specified thickness includes: heat treating the first bonding structure at a second temperature to obtain a second bonding structure; the second temperature is higher than the first temperature; and thinning the thickness of the silicon carbide wafer in the second bonding structure to a specified thickness.

[0020] An embodiment of the present invention provides an acousto-optic coupling device, comprising:

[0021] A substrate layer, a dielectric layer, an acoustic layer and an optical device part are stacked in sequence;

[0022] The optical device part includes a waveguide and a resonant cavity;

[0023] The acoustic layer is provided with a plurality of through holes, and the plurality of through holes are arranged in a preset shape; the acoustic layer in the preset shape is suspended; a side of the suspended acoustic layer away from the dielectric layer is provided with a forked electrode; wherein the suspended acoustic layer and the forked electrode constitute the acoustic device part of the acousto-optic coupling device.

[0024] Optionally, the width of the waveguide and the resonant cavity is a first width; the first width is 400-2000 nanometers.

[0025] Optionally, the waveguide is a grating waveguide.

[0026] Optionally, the sum of the comb width and the comb spacing of the interdigitated electrodes is twice the first width.

[0027] Optionally, the distance between the interdigital electrodes and the through-holes is 5-100 microns.

[0028] The beneficial effects of the present invention are as follows: transferring high-purity silicon carbide films and high-quality aluminum nitride films to silicon substrates through heterogeneous integration technology can effectively overcome the problem of ion damage in the current preparation of silicon-based silicon carbide films using ion beam technology, while achieving wafer-level heterogeneous integration of silicon-based high-single-crystal quality acoustic device layers and optical device layers, and is expected to provide important technical support and solutions in the fields of large-scale integrated photonics, radio frequency filters and hybrid integrated devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 is a schematic structural diagram of an acousto-optic coupling substrate provided by an embodiment of the present invention;

[0031] Figure 2 It is a schematic flow chart of a method for preparing an acousto-optic coupling device provided by an embodiment of the present invention;

[0032] Figure 3 It is a schematic flow chart of a method for preparing an acousto-optic coupling substrate provided by an embodiment of the present invention;

[0033] Figure 4 is a structural schematic diagram of an acousto-optic coupling device provided by an embodiment of the present invention;

[0034] Figure 5 is a schematic structural diagram of an optical device provided by an embodiment of the present invention;

[0035] Figure 6 It is a schematic diagram of the structure of an acoustic device provided by an embodiment of the present invention.

[0036] The reference numerals in the figure correspond to: 1-substrate layer; 2-dielectric layer; 3-acoustic layer; 4-optical layer; 5-; 21-first dielectric layer; second dielectric layer 22; 31-through hole; 32-interdigitated electrode; 40-silicon carbide wafer; 41-waveguide; 42-resonant cavity; 321-tooth comb width; 322-tooth comb spacing; 411-first width; 2011-first wafer; 2012-second wafer; 2013-first bonding structure. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0038] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] Embodiment 1

[0040] See also Figure 1 , Figure 1 It is a schematic diagram of the structure of an acousto-optic coupling substrate provided in an embodiment of the present invention. The acousto-optic coupling substrate includes a substrate layer 1, a dielectric layer 2, an acoustic layer 3 and an optical layer 4 which are stacked in sequence. The material of the substrate layer 1 includes silicon, and the material of the dielectric layer 2 includes silicon dioxide. The material of the acoustic layer 3 includes high-quality aluminum nitride, wherein high quality means that in an X-ray diffraction test, the half-width at half maximum of the crystal direction is less than 150 arc seconds; optionally, the thickness of the acoustic layer 3 is 0-3 microns. The material of the optical layer 4 includes silicon carbide, such as a combination of one or more of polycrystalline silicon carbide, α-silicon carbide, and β-silicon carbide; optionally, the thickness of the optical layer 4 is 100 nanometers to 5 microns.

[0041] Embodiment 2

[0042] The embodiment of the present invention provides a method for preparing an acousto-optic coupling device. Figure 2 The preparation method shown includes:

[0043] S201: Obtain an acousto-optic coupling substrate.

[0044] The acousto-optic coupling substrate is the acousto-optic coupling substrate in the first embodiment, that is, the composition structure is a substrate layer 1, a dielectric layer 2, an acoustic layer 3 and an optical layer 4 stacked in sequence. Figure 3 As shown, S201 obtains the acousto-optic coupling substrate including:

[0045] S2011 : Based on high-quality aluminum nitride, an acoustic layer 3 is grown on the silicon carbide wafer 40 to obtain a first wafer 2011 .

[0046] The silicon carbide wafer 40 includes a combination of one or more of polycrystalline silicon carbide, α-silicon carbide, and β-silicon carbide, with a thickness of 300-500 microns. High-quality aluminum nitride refers to aluminum nitride with a crystal half-width of less than 150 arc seconds in an X-ray diffraction test, and the high-quality aluminum nitride layer, i.e., the acoustic layer 3, has a thickness of 0-3 microns.

[0047] Specifically, the growth method includes plasma enhanced chemical vapor deposition or low pressure chemical vapor deposition, the growth temperature is 800-1700 degrees Celsius, and the growth time is 0-24 hours.

[0048] S2012: Based on silicon dioxide, a first dielectric layer 21 is grown on the acoustic layer 3 to obtain a second wafer 2012 .

[0049] Specifically, the growth method includes thermal oxidation or vapor phase chemical deposition, and the thickness of the first dielectric layer 21 is 0-5 microns. After the growth of the first dielectric layer 21 is completed, the second wafer 2012 can be subjected to chemical mechanical polishing to facilitate subsequent bonding.

[0050] S2013 : at a first temperature, bonding the first dielectric layer 21 to the second dielectric layer 22 in the silicon substrate to obtain a first bonding structure 2013 .

[0051] The first temperature is 0-800 degrees Celsius, the bonding method is direct bonding, and the bonding environment includes any one of vacuum, atmosphere, and nitrogen. The silicon substrate includes a stacked substrate layer 1 and a second dielectric layer 22, the material of the substrate layer 1 includes silicon, and the material of the second dielectric layer 22 includes silicon dioxide. After bonding is completed, the first dielectric layer 21 and the second dielectric layer 22 constitute a dielectric layer 2.

[0052] Optionally, before the second wafer 2012 and the silicon substrate are bonded, the two bonding surfaces are processed by plasma activation, and the gas used for plasma activation includes a combination of one or more of nitrogen, oxygen, and argon.

[0053] S2014: thinning the thickness of the silicon carbide wafer 40 in the first bonding structure 2013 to a specified thickness to obtain an acousto-optic coupling substrate.

[0054] The silicon carbide wafer 40 of a specified thickness constitutes the optical layer 4 of the acousto-optic coupling substrate.

[0055] Specifically, thinning the thickness of the silicon carbide wafer 40 in the first bonding structure 2013 to a specified thickness includes:

[0056] The first bonding structure 2013 is heat treated at a second temperature to obtain a second bonding structure. The second temperature is higher than the first temperature and is 500-1100 degrees Celsius. The heat treatment atmosphere includes any one of nitrogen, argon, hydrogen, and vacuum, and the heat treatment time is 1 minute to 24 hours.

[0057] The thickness of the silicon carbide wafer 40 in the second bonding structure is thinned to a specified thickness. The thinning method includes a combination of one or more of mechanical grinding, chemical mechanical polishing, and precision polishing. As an optional implementation, in the first step, the thickness of the silicon carbide wafer 40 is reduced from 300-500 microns to 5-10 microns by mechanical grinding; in the second step, the silicon carbide wafer 40 is precisely controlled by chemical mechanical polishing, and the thickness is reduced to 500-1200 nanometers; in the third step, the uniformity of the silicon carbide wafer 40 is controlled by precision polishing, and the thickness of the silicon carbide wafer 40 is reduced to a specified thickness: 100 nanometers-5 microns.

[0058] S202 : etching the optical layer 4 of the acousto-optic coupling substrate into a waveguide 41 and a resonant cavity 42 .

[0059] The waveguide 41 and the resonant cavity 42 obtained by etching constitute the optical device part of the acousto-optic coupling device, wherein the waveguide 41 is in the form of a grating waveguide; the etching methods include electron beam exposure and dry etching.

[0060] S203: a plurality of through holes 31 penetrating the acoustic layer 3 are opened on the acoustic layer 3 of the acousto-optic coupling substrate, and the plurality of through holes 31 are arranged in a preset shape.

[0061] Figure 2 A schematic diagram of a three-dimensional diagram (left) and a schematic diagram of a cross-sectional diagram (right) are also presented, wherein the method of opening the through hole 31 includes a combination of one or more of electron beam lithography, femtosecond laser, and deep ultraviolet lithography.

[0062] S204: wet-etching the dielectric layer 2 of the acousto-optic coupling substrate through the plurality of through holes 31, so that the acoustic layer 3 in the preset shape is suspended.

[0063] Figure 2 A schematic perspective view (left) and a schematic cross-sectional view (right) are presented simultaneously, wherein the wet etching includes wet etching using hydrogen fluoride.

[0064] S205: preparing interdigital electrodes 32 on the side of the suspended acoustic layer 3 away from the dielectric layer 2 to obtain an acoustic-optical coupling device.

[0065] Figure 2A three-dimensional schematic diagram (left) and a cross-sectional schematic diagram (right) are presented at the same time. The suspended acoustic layer 3 and the interdigitated electrode 32 constitute the acoustic device part of the acoustic-optic coupling device, wherein the material of the interdigitated electrode 32 includes aluminum or gold; and the method of preparing the interdigitated electrode 32 includes electron beam evaporation or magnetron sputtering.

[0066] Embodiment 3

[0067] The embodiment of the present invention provides an acousto-optic coupling device, such as Figure 4 As shown, the acousto-optic coupling device comprises a substrate layer 1, a dielectric layer 2, an acoustic layer 3 and an optical device part which are stacked in sequence.

[0068] The material of the substrate layer 1 includes silicon; the material of the dielectric layer 2 includes silicon dioxide; and the material of the acoustic layer 3 includes aluminum nitride having a crystal half-width of less than 150 arc seconds in an X-ray diffraction test.

[0069] The optical device part includes a waveguide 41 and a resonant cavity 42, and the material includes a combination of one or more of polycrystalline silicon carbide, α-silicon carbide, and β-silicon carbide. Optionally, the waveguide 41 is in the form of a grating waveguide, and the resonant cavity 42 is in the shape of a racetrack. Figure 5 As shown, the widths of the waveguide 41 and the resonant cavity 42 are consistent, both being a first width 411: 400-2000 nanometers.

[0070] A plurality of through holes 31 are provided on the side of the acoustic layer 3 away from the optical device part, and the plurality of through holes 31 are arranged in a preset shape. Optionally, the preset shape is three-quarters open, and the through holes 31 in three directions can prevent the acoustic layer 3 on the lower side of the optical device part from being excessively corroded.

[0071] The acoustic layer 3 in the preset shape is suspended, and a forked electrode 32 (made of aluminum or gold) is provided on the side of the suspended acoustic layer 3 away from the dielectric layer 2. The suspended acoustic layer 3 and the forked electrode 32 together constitute the acoustic device part of the acoustic-optic coupling device. In principle, the closer the forked electrode 32 and the through hole 31 are, the better. Optionally, the distance between the forked electrode 32 and the through hole 31 is 5-100 microns. The enlarged schematic diagram of the forked electrode is shown in FIG. Figure 6 As shown, the sum of the comb width 321 and the comb spacing 322 of the interdigital electrode 32 is twice the first width 411, ie, 800-4000 nanometers, wherein the comb width 321 is 500-2000 nanometers.

[0072] It can be seen from the embodiments provided by the present invention that the present invention utilizes heterogeneous integration technology to transfer high-purity silicon carbide films and high-quality aluminum nitride films to a silicon substrate, effectively overcoming the problem of ion damage in the current preparation of silicon-based silicon carbide films using ion beam technology, while achieving wafer-level heterogeneous integration of silicon-based high-single-crystal quality acoustic device layers and optical device layers.

[0073] It should be noted that the above-mentioned sequence of the embodiments of the present application is for description only and does not represent the advantages and disadvantages of the embodiments. The above-mentioned specific embodiments of this specification are described. Other embodiments are within the scope of the attached claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0074] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0075] A person skilled in the art will understand that all or part of the steps to implement the above embodiments may be accomplished by hardware or by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a disk or an optical disk, etc.

[0076] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing an acousto-optic coupling device, characterized in that: include: Obtaining an acousto-optic coupling substrate; the acousto-optic coupling substrate comprises a substrate layer (1), a dielectric layer (2), an acoustic layer (3) and an optical layer (4) which are stacked in sequence; Etching the optical layer (4) into a waveguide (41) and a resonant cavity (42); A plurality of through holes (31) penetrating the acoustic layer (3) are provided on the acoustic layer (3), wherein the plurality of through holes (31) are arranged in a preset shape; Wet etching the dielectric layer (2) through the plurality of through holes (31) so that the acoustic layer (3) in the preset shape is suspended; An interdigitated electrode (32) is prepared on the side of the suspended acoustic layer (3) away from the dielectric layer (2) to obtain an acousto-optic coupling device; wherein the waveguide (41) and the resonant cavity (42) constitute the optical device part of the acousto-optic coupling device, and the suspended acoustic layer (3) and the interdigitated electrode (32) constitute the acoustic device part of the acousto-optic coupling device.

2. The method for preparing an acousto-optic coupling device according to claim 1, characterized in that: The method of obtaining the acousto-optic coupling substrate comprises: Based on high-quality aluminum nitride, an acoustic layer (3) is grown on a silicon carbide wafer (40) to obtain a first wafer (2011); the high quality means that in an X-ray diffraction test, the half-width at half maximum of the crystal direction is less than 150 arc seconds; Based on silicon dioxide, a first dielectric layer (21) is grown on the acoustic layer (3) to obtain a second wafer (2012); At a first temperature, the first dielectric layer (21) is bonded to the second dielectric layer (22) in a silicon substrate to obtain a first bonding structure (2013); the silicon substrate comprises the substrate layer (1) and the second dielectric layer (22) which are stacked, the material of the substrate layer (1) comprises silicon, and the material of the second dielectric layer (22) comprises silicon dioxide; the first dielectric layer (21) and the second dielectric layer (22) constitute a dielectric layer (2); The thickness of the silicon carbide wafer (40) in the first bonding structure (2013) is thinned to a specified thickness to obtain the acousto-optic coupling substrate; wherein the silicon carbide wafer (40) of the specified thickness constitutes an optical layer (4) of the acousto-optic coupling substrate.

3. The method for preparing an acousto-optic coupling device according to claim 2, characterized in that: The step of thinning the thickness of the silicon carbide wafer (40) in the first bonding structure (2013) to a specified thickness comprises: heat-treating the first bonding structure (2013) at a second temperature to obtain a second bonding structure; the second temperature is higher than the first temperature; The thickness of the silicon carbide wafer (40) in the second bonding structure is thinned to a specified thickness.

4. An acousto-optic coupling device, characterized in that: It comprises a substrate layer (1), a dielectric layer (2), an acoustic layer (3) and an optical device part which are stacked in sequence; The optical device part includes a waveguide (41) and a resonant cavity (42); The acoustic layer (3) is provided with a plurality of through holes (31) extending therethrough, and the plurality of through holes (31) are arranged in a preset shape; the acoustic layer (3) in the preset shape is suspended; a side of the suspended acoustic layer (3) away from the dielectric layer (2) is provided with an interdigitated electrode (32); wherein the suspended acoustic layer (3) and the interdigitated electrode (32) constitute an acoustic device portion of the acousto-optic coupling device.

5. The acousto-optic coupling device according to claim 4, characterized in that: The width of the waveguide (41) and the resonant cavity (42) is a first width (411); The first width (411) is 400-2000 nanometers.

6. The acousto-optic coupling device according to claim 4, characterized in that: The waveguide (41) is a grating waveguide.

7. The acousto-optic coupling device according to claim 5, characterized in that: The sum of the comb width (321) and the comb spacing (322) of the interdigitated electrode (32) is twice the first width (411).

8. The acousto-optic coupling device according to claim 5, characterized in that: The distance between the interdigital electrodes (32) and the through holes (31) is 5-100 micrometers.

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