Integrated multiplexing multi-physical field acousto-optic intermodulation waveguide and preparation method thereof

Abstract

The invention relates to an integrated multiplexing multi-physics field acousto-optic intermodulation waveguide and a preparation method thereof. The multi-physics field acousto-optic intermodulation waveguide comprises the following steps: providing a support substrate; the dielectric layer is positioned on the supporting substrate; the piezoelectric film is positioned on the dielectric layer; the patterned metal structure is positioned on the piezoelectric film; etching the piezoelectric film so as to form a waveguide above the dielectric layer; etching the piezoelectric film so as to form a first grating coupler and a second grating coupler on the supporting substrate; the patterned metal structure comprises a first piezoelectric transducer, a second piezoelectric transducer, a first modulation electrode and a second modulation electrode; the first modulation electrode and the second modulation electrode are located on the two sides of the waveguide and are parallel to the waveguide. The sound field and the light field are limited to one waveguide, two physical fields are propagated and modulated at the same time, the information propagation density can be increased, and the modulation efficiency can be improved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor devices, and in particular relates to an integrated multiplexed multi-physical field acousto-optic intermodulation waveguide and a preparation method thereof. Background Art

[0002] Lithium niobate is a powerful ferroelectric material. After polarization, lithium niobate crystals have multiple properties such as piezoelectricity, ferroelectricity, optoelectronics, nonlinear optics, thermoelectricity, and photorefractive effect. Lithium niobate crystal is one of the most widely used new inorganic materials. It is a good piezoelectric transducer material, ferroelectric material, electro-optical material. As an electro-optical material, lithium niobate plays a role in light modulation in optical communications. Its single crystal is an important material for optical waveguides, mobile phones, piezoelectric sensors, optical modulators and various other linear and nonlinear optical applications.

[0003] The electro-optic effect refers to the effect that the refractive index of a crystal changes when an electric field is applied to the crystal. Since lithium niobate has a strong Pockels effect, integrated optical waveguides based on lithium niobate show great potential in confining optical modes and optical modulation.

[0004] At the same time, lithium niobate performs well in piezoelectric transducers, and acoustic filters based on lithium niobate are already very mature. Lithium niobate waveguides also have many applications in delay lines and integrated acoustic circuits. Researchers generally apply the piezoelectric effect of lithium niobate to acoustic wave excitation and modulate the sound waves to directly modulate information.

[0005] However, the acoustic and optical applications of lithium niobate are often separated, so only one dimension of the physical field is used for modulation, and the modulation efficiency cannot be optimized to a maximum value. The shape of the lithium niobate waveguide allows it to confine both the light field and the acoustic field. If the acoustic field and the light field can be confined to one waveguide, and the two physical fields can be propagated and modulated at the same time, the density of information propagation can be increased, as well as the modulation efficiency. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide an integrated multiplexed multi-physical field acousto-optical cross-modulation waveguide and a preparation method thereof, wherein the waveguide confines the acoustic field and the optical field to one waveguide, propagates the two physical fields simultaneously and performs modulation, thereby increasing the density of information propagation and the efficiency of modulation.

[0007] The present invention provides an integrated multiplexed multi-physics field acousto-optic intermodulation waveguide, the multi-physics field acousto-optic intermodulation waveguide comprising:

[0008] providing a supporting substrate;

[0009] a dielectric layer located on the supporting substrate;

[0010] a piezoelectric film located on the dielectric layer;

[0011] a patterned metal structure on the piezoelectric film;

[0012] etching the piezoelectric film to form a waveguide above the dielectric layer;

[0013] The piezoelectric film is etched to form a first grating coupler and a second grating coupler on the supporting substrate; the patterned metal structure includes a first piezoelectric transducer, a second piezoelectric transducer, a first modulation electrode and a second modulation electrode; the first modulation electrode and the second modulation electrode are located on both sides of the waveguide and are parallel to the waveguide.

[0014] Preferably, the support substrate is made of silicon, and has a resistance greater than 10000Ω·cm.

[0015] Preferably, the material of the dielectric layer is silicon dioxide.

[0016] Preferably, the material of the piezoelectric film is selected from lithium niobate or lithium tantalate; the crystal cut of the piezoelectric film is a rotated Y-cut, X-cut or Z-cut film.

[0017] Preferably, the material of the patterned metal structure is one or an alloy of aluminum, copper, gold, titanium, nickel, molybdenum and platinum.

[0018] Preferably, the first piezoelectric transducer and the second piezoelectric transducer comprise interdigital electrodes, a first bus bar and a second bus bar; wherein the first bus bar and the second bus bar form a rectangular structure for an electrical port for electroacoustic excitation.

[0019] The acoustic mode excited in the piezoelectric transducer is consistent with the acoustic mode transmitted in the waveguide, which can be a zero-order horizontal shear wave mode, a Rayleigh mode, or a longitudinal leakage mode; the optical mode transmitted in the waveguide includes but is not limited to TE00, TE10, and TM00. The optical mode must satisfy the maximum value of the overlapping action volume integral with the acoustic mode.

[0020] Preferably, the first grating coupler and the second grating coupler are composed of a plurality of rectangular periodic waveguides located on a piezoelectric film.

[0021] Preferably, voltages of opposite potentials or opposite phases are applied to the first modulation electrode and the second modulation electrode.

[0022] Furthermore, the patterned metal structure also includes a third modulation electrode and a fourth modulation electrode. Optionally, the third modulation electrode and the fourth modulation electrode need to apply voltages of opposite potential or opposite phase. The voltage is a DC or AC sinusoidal signal with a frequency less than 1kHz. Signals are added to the first grating coupler and the first piezoelectric transducer respectively, and after the voltage is applied, the phases of the signals in the second grating coupler and the second piezoelectric transducer change. If the signal is applied only to the first piezoelectric transducer, the waves propagating in the waveguide are only mechanical waves; if the signal is applied only to the first grating coupler, the waves propagating in the waveguide are only electromagnetic waves. If the signal is applied to the first grating coupler and the first piezoelectric transducer at the same time, mechanical waves and electromagnetic waves are propagated in the waveguide at the same time, and stimulated Brillouin scattering will occur under appropriate conditions.

[0023] The present invention also provides a method for preparing an integrated multiplexed multi-physical field acousto-optic intermodulation waveguide, comprising the following steps:

[0024] (1) Preparing a piezoelectric film and a supporting substrate;

[0025] (2) performing ion implantation on the piezoelectric film; forming a dielectric layer on the supporting substrate;

[0026] (3) bonding the piezoelectric film to the supporting substrate;

[0027] (4) annealing to form a piezoelectric film-dielectric layer-support substrate structure; then thinning the piezoelectric film;

[0028] (5) defining a waveguide pattern and etching the piezoelectric film to form a waveguide structure;

[0029] (6) Patterning metal electrodes and depositing metal to form a patterned metal structure to obtain the integrated multiplexed multi-physical field acousto-optic intermodulation waveguide.

[0030] Preferably, the ion implantation type in step (2) is hydrogen ions or helium ions.

[0031] Preferably, the dielectric layer is formed in step (2) by chemical vapor deposition, physical vapor deposition or thermal evaporation.

[0032] Preferably, the bonding in step (3) is specifically as follows: plasma activation is required before bonding, the gas includes at least one of argon, oxygen, and nitrogen, the energy range is 500eV to 2000eV, and after activation, at least one of an argon-rich layer, an oxygen-rich layer, and a nitrogen-rich layer can be formed on the surface of the film; the activated film surface is directly bonded, and the bonding environment conditions include but are not limited to a vacuum environment, normal temperature and pressure; the bonding temperature is 20-700°C.

[0033] Preferably, the annealing in step (4) is specifically as follows: the annealing atmosphere is nitrogen, the annealing temperature is 500° C. to 1400° C., and the annealing time is 1 min to 24 h.

[0034] Preferably, the thinning in step (4) is specifically as follows: firstly mechanically grinding to 5 μm to 8 μm, then chemically mechanical polishing to 200 nm to 1000 nm, and ensuring that the surface roughness of the film is less than 0.3 nm.

[0035] Beneficial Effects

[0036] The present invention uses an optimized waveguide design to simultaneously propagate localized mechanical waves and optical waves in the waveguide, and integrates an on-chip electroacoustic transducer and a grating coupler into a monolithic chip, so that mechanical waves and optical waves can be introduced onto the chip at the same time; the acoustic field and the optical field are confined to one waveguide, and the two physical fields are propagated and modulated at the same time, which can increase the density of information propagation and the efficiency of modulation, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a front view of the integrated multiplexed multi-physical field acousto-optic intermodulation waveguide of the present invention;

[0038] Figure 2 A top view of the integrated multiplexed multi-physics field acousto-optic cross-modulation waveguide of the present invention;

[0039] Figure 3 A schematic diagram of the structure of the first bus bar and the second bus bar used in the present invention;

[0040] Figure 4 This is a schematic diagram of the structure of the interdigital electrode used in the present invention;

[0041] Figure 5 A top view of the modulation metal electrode and waveguide used in the present invention;

[0042] Figure 6 A front view of the modulation metal electrode and waveguide used in the present invention;

[0043] Figure 7 A schematic diagram of the structure of the grating coupler used in the present invention;

[0044] Figure 8 A schematic diagram of a waveguide used in the present invention;

[0045] Fig. 9 It is a schematic diagram of the principle of the integrated multiplexed multi-physical field acousto-optic intermodulation waveguide of the present invention;

[0046] Fig.10 The present invention is a flow chart of the preparation process of the integrated multiplexed multi-physical field acousto-optic intermodulation waveguide;

[0047] Fig.11 It is the zero-order horizontal shear wave mode of the multi-physical field acousto-optic intermodulation waveguide integrated and multiplexed by the present invention;

[0048] Fig.12 The Rayleigh mode of the multi-physics field acousto-optic cross-modulation waveguide integrated and multiplexed by the present invention;

[0049] Fig.13 The longitudinal leakage mode of the multi-physics field acousto-optic cross-modulation waveguide integrated and multiplexed by the present invention;

[0050] Fig.14 The TE00 mode of the multi-physical field acousto-optic intermodulation waveguide integrated and multiplexed by the present invention;

[0051] Fig.15 The TE10 mode of the multi-physical field acousto-optic intermodulation waveguide integrated and multiplexed by the present invention;

[0052] Fig.16 It is the TM00 mode of the multi-physical field acousto-optic intermodulation waveguide integrated and multiplexed by the present invention. DETAILED DESCRIPTION

[0053] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0054] Example 1

[0055] This embodiment proposes an integrated multiplexed multi-physics field acousto-optic cross-modulation waveguide (such as Figure 1 , Figure 2 As shown), the structure includes: a supporting substrate;

[0056] providing a supporting substrate;

[0057] a dielectric layer located on the supporting substrate;

[0058] a piezoelectric film located on the dielectric layer;

[0059] a patterned metal structure on the piezoelectric film;

[0060] etching the piezoelectric film to form a waveguide above the dielectric layer;

[0061] The piezoelectric film is etched to form a first grating coupler and a second grating coupler on the supporting substrate; the patterned metal structure includes a first piezoelectric transducer, a second piezoelectric transducer, a first modulation electrode and a second modulation electrode; the first modulation electrode and the second modulation electrode are located on both sides of the waveguide and are parallel to the waveguide.

[0062] The piezoelectric transducer (including the first piezoelectric transducer and the second piezoelectric transducer) can realize the conversion of signals from electrical signals to mechanical waves, and can also realize the conversion of signals from mechanical waves to electrical signals. It includes interdigitated electrodes, a first bus bar and a second bus bar; wherein the first bus bar and the second bus bar form a rectangular structure for an electrical port (such as Figure 3 As shown); the interdigitated electrodes are formed by periodically arranging electrodes that are alternately connected to voltage and ground. Define twice the center distance between adjacent electrodes as λ, λ ranges from 500nm to 5um, define the distance between two bus bars as Wa, ranges from 5μm to 50μm (as shown Figure 4 shown).

[0063] The waveguide width W is in the range of 200nm to 5um, the metal modulation electrode of the waveguide is parallel to the waveguide, the distance D between the modulation electrode and the waveguide is in the range of 500nm to 2um, the waveguide height H is in the range of 100nm to 600nm, the height of the modulation metal electrode is in the range of 200nm to 2um (such as Figure 5 , Figure 6 shown).

[0064] The material of the patterned metal structure may include a metal material selected from aluminum, copper, gold, titanium, nickel, molybdenum, and platinum, or an alloy material or a multilayer electrode composed of two of the above materials.

[0065] The material of the piezoelectric film can be selected from lithium niobate or lithium tantalate; the crystal cut of the piezoelectric film is a rotated Y-cut, and the corresponding Euler angle is (0, -β, 0), or it can be an X-cut, and the corresponding Euler angle is (α, -90, -90), where α is an arbitrary angle; it can also be a Z-cut film, and the corresponding Euler angle is (α, 0, 0).

[0066] The material of the dielectric film is silicon dioxide;

[0067] The support substrate is made of silicon, and its resistance is greater than 10000Ω·cm.

[0068] The thickness of the patterned metal structure is between 50nm and 300nm, the thickness of the piezoelectric film is between 200nm and 800nm, and the thickness of the dielectric layer is between 0 and 5um.

[0069] The acoustic mode excited in the piezoelectric transducer is consistent with the acoustic mode transmitted in the waveguide and can be a zero-order horizontal shear wave mode, a Rayleigh mode, or a longitudinal leakage mode, e.g. Figure 11-13 As shown; the optical modes transmitted in the waveguide include but are not limited to TE00, TE10 or TM00, such as Figure 14-16 As shown in Figure 2, the optical mode must satisfy the overlap with the acoustic mode and the volume integral must be the maximum.

[0070] like Figure 7 As shown, the grating coupler (including the first grating coupler and the second grating coupler) is composed of a plurality of rectangular periodic waveguides located on the piezoelectric film, the waveguide width Wg ranges from 500nm to 1200nm, the waveguide repetition period Pg ranges from 1um to 3um, the waveguide height Hg ranges from 300nm to 700nm, and the number of unit repetitions is 10 to 20.

[0071] In the acousto-optic intermodulation waveguide, the first modulation electrode and the second modulation electrode need to apply voltages of opposite potential or opposite phase, and optionally, the third modulation electrode and the fourth modulation electrode need to apply voltages of opposite potential or opposite phase. The voltage is a direct current or alternating current sinusoidal signal with a frequency less than 1kHz. Signals are added to the first grating coupler and the first piezoelectric transducer respectively, and after the voltage is applied, the phases of the signals in the second grating coupler and the second piezoelectric transducer change. If the signal is applied only to the first piezoelectric transducer, the waves propagating in the waveguide are only mechanical waves; if the signal is applied only to the first grating coupler, the waves propagating in the waveguide are only electromagnetic waves. If the signal is applied simultaneously to the first grating coupler and the first piezoelectric transducer, mechanical waves and electromagnetic waves are propagated simultaneously in the waveguide, and stimulated Brillouin scattering will occur under appropriate conditions.

[0072] like Figure 8 As shown, the top view of the waveguide structure can be a rectangle or an arc, as well as a section intercepted from the arc; the radius R of the arc ranges from 50um to 1000um; the connection of the waveguide is a "Y"-shaped structure, and its angle range θ is from 20° to 70°.

[0073] like Fig. 9 As shown, the acoustic signal of the present invention is transmitted and received through a piezoelectric transducer, and the optical signal is transmitted and received through a grating coupler, wherein the acoustic signal path and the optical signal path intersect and overlap, and the acoustic signal and the optical signal propagate in the waveguide at the same time.

[0074] like Fig.10 As shown, the process steps for manufacturing the acousto-optic intermodulation waveguide include:

[0075] ①Prepare piezoelectric film materials and supporting substrate materials;

[0076] ②Implant the piezoelectric film with ions of hydrogen or helium; chemically vapor deposit, physically vapor deposit, or thermally evaporate a dielectric layer on the supporting substrate;

[0077] ③ Bonding two materials: Plasma activation is required before bonding, and the gas includes at least one of argon, oxygen, and nitrogen, with an energy range of 500eV to 2000eV. After activation, at least one of an argon-rich layer, an oxygen-rich layer, and a nitrogen-rich layer can be formed on the surface of the film; the activated film surface is directly bonded, and the bonding environment conditions include but are not limited to a vacuum environment, normal temperature and pressure; further, as described, the bonding temperature is 20-700°C;

[0078] ④ Annealing, peeling off the piezoelectric material to form a piezoelectric film-dielectric layer-support substrate material. The annealing atmosphere is nitrogen, the annealing temperature is 500℃~1400℃, and the annealing time is 1min~24h; then thin the film, first use mechanical grinding to 5μm~8μm, use chemical mechanical polishing to grind to 200nm~1000nm, and ensure that the surface roughness of the film is less than 0.3nm; form the target material structure;

[0079] ⑤Define the waveguide pattern and etch it to form an etched waveguide structure;

[0080] ⑥ Patterning the metal electrode pattern and depositing a layer of metal to form a metal structure, forming a patterned metal structure, and obtaining the integrated multiplexed multi-physical field acousto-optic intermodulation waveguide.

[0081] The process of defining the waveguide pattern includes:

[0082] ① Spinning: depositing a layer of photoresist on the material;

[0083] ② Use electron beam lithography (EBL), laser direct writing lithography, or ultraviolet lithography to pattern the developing electrode;

[0084] ③ Use inductively coupled plasma etching (ICP) or ion beam etching (IBE) to etch the material surface;

[0085] ④ Soak in acetone or NMP solution to remove excess photoresist.

[0086] The processes that define patterned metal include:

[0087] ① Spinning: depositing a layer of photoresist on the material;

[0088] ② Use electron beam lithography (EBL), laser direct writing lithography, or ultraviolet lithography to pattern the developing electrode;

[0089] ③Use electron beam evaporation metal coating process to deposit a layer of metal;

[0090] ④ Soak in acetone or NMP solution to remove excess metal and photoresist.

Claims

1. An integrated multiplexed multi-physics field acousto-optic intermodulation waveguide, characterized in that: The multi-physics field acousto-optic intermodulation waveguide comprises: providing a supporting substrate; a dielectric layer located on the supporting substrate; a piezoelectric film located on the dielectric layer; a patterned metal structure on the piezoelectric film; etching the piezoelectric film to form a waveguide above the dielectric layer; Etching the piezoelectric film to form a first grating coupler and a second grating coupler on the supporting substrate; The patterned metal structure includes a first piezoelectric transducer, a second piezoelectric transducer, a first modulation electrode and a second modulation electrode; the first modulation electrode and the second modulation electrode are located at both sides of the waveguide and are parallel to the waveguide.

2. The multi-physics field acousto-optic intermodulation waveguide according to claim 1, characterized in that: The support substrate is made of silicon, and its resistance is greater than 10000Ω·cm.

3. The multi-physics field acousto-optic intermodulation waveguide according to claim 1, characterized in that: The material of the dielectric layer is silicon dioxide.

4. The multi-physics field acousto-optic intermodulation waveguide according to claim 1, characterized in that: The material of the piezoelectric film is selected from lithium niobate or lithium tantalate; the crystal cut of the piezoelectric film is a rotating Y-cut, X-cut or Z-cut film.

5. The multi-physics field acousto-optic intermodulation waveguide according to claim 1, characterized in that: The material of the patterned metal structure is one or an alloy of aluminum, copper, gold, titanium, nickel, molybdenum, and platinum.

6. The multi-physics field acousto-optic intermodulation waveguide according to claim 1, characterized in that: The first piezoelectric transducer and the second piezoelectric transducer include interdigital electrodes, a first bus bar and a second bus bar; wherein the first bus bar and the second bus bar form a rectangular structure for an electrical port for electroacoustic excitation.

7. The multi-physics field acousto-optic intermodulation waveguide according to claim 1, characterized in that: The first grating coupler and the second grating coupler are composed of a plurality of rectangular periodic waveguides located on a piezoelectric film.

8. The multi-physics field acousto-optic intermodulation waveguide according to claim 1, characterized in that: Voltages of opposite potentials or opposite phases are applied to the first modulation electrode and the second modulation electrode.

9. The multi-physics field acousto-optic intermodulation waveguide according to claim 1, characterized in that: The patterned metal structure also includes a third modulation electrode and a fourth modulation electrode.

10. A method for preparing an integrated multiplexed multi-physics field acousto-optic intermodulation waveguide, comprising the following steps: (1) Preparing a piezoelectric film and a supporting substrate; (2) performing ion implantation on the piezoelectric film; forming a dielectric layer on the supporting substrate; (3) bonding the piezoelectric film to the supporting substrate; (4) annealing to form a piezoelectric film-dielectric layer-support substrate structure; The piezoelectric film is then thinned; (5) defining a waveguide pattern and etching the piezoelectric film to form a waveguide structure; (6) Patterning metal electrodes and depositing metal to form a patterned metal structure to obtain the integrated multiplexed multi-physical field acousto-optic intermodulation waveguide.

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