Preparation method and application of active and passive integrated thin-film lithium niobate / lithium tantalate photonic device

Abstract

The invention discloses a preparation method and application of an active and passive integrated thin-film lithium niobate / lithium tantalate photonic device, and belongs to the technical field of integrated optics. The preparation method comprises the following steps: providing a lithium niobate / lithium tantalate substrate, and carrying out patterned injection of erbium ions on the surface layer of one side of the substrate to form an erbium-doped region; carrying out high-temperature annealing treatment on the substrate; and carrying out structure processing on the substrate subjected to high-temperature annealing treatment to form a waveguide structure on one side where the erbium-doped region is located, bonding the waveguide structure on the carrier substrate, and forming a lithium niobate / lithium tantalate film on the body substrate to obtain the active and passive integrated film lithium niobate / lithium tantalate photonic device. According to the invention, the scheme of first doping and then thinning is adopted, the subsequent high-temperature process is prevented from influencing the quality of a bonding interface and a thin film, the photonic integrated device with high erbium-doped quality and high luminous efficiency is realized, meanwhile, the process compatibility is realized, the yield and reliability are improved, and the production cost is reduced. And a technical route is provided for realizing a large-scale and multifunctional lithium niobate / lithium tantalate photon integrated chip.

Description

Technical Field

[0001] This application relates to a method for fabricating an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device and its application, belonging to the field of integrated optical technology. Background Technology

[0002] Thin-film lithium niobate / lithium tantalate integrated photonic platforms possess superior electro-optic and nonlinear optical properties, a wide optical passband, and ultra-low transmission loss, bringing revolutionary prospects to integrated photonics. However, they lack inherent optical gain and cannot compensate for transmission and splitting losses, limiting the development of large-scale multifunctional photonic integrated circuits. Therefore, combining lithium niobate / lithium tantalate with erbium ions can achieve full-function integration of signal amplification, high-speed modulation, and wavelength conversion, constructing a complete optoelectronic system.

[0003] Currently, mainstream erbium-doped thin-film lithium niobate / lithium tantalate photonic integrated devices are fabricated on single-crystal lithium niobate / lithium tantalate thin-film wafers using methods including ion implantation, crystal growth doping, and thermal diffusion. Among these, ion implantation is the most widely used method. This involves accelerating the implantation of erbium ions into the lithium niobate / lithium tantalate thin film, followed by high-temperature annealing to repair lattice damage and activate erbium ion luminescence. This method achieves precise region-selective doping and is compatible with standard micro / nano fabrication processes. However, performing ion implantation and high-temperature annealing again on lithium niobate / lithium tantalate thin films fabricated using Smart-Cut technology can generate thermal stress at the bonding interface, leading to film detachment, cracking, or irreversible damage. Conversely, limiting the annealing temperature can result in residual lattice damage and insufficient erbium ion activation, affecting the quality and performance of the lithium niobate / lithium tantalate thin film. The crystal growth doping method involves directly incorporating erbium ions during the pulling of lithium niobate / lithium tantalate crystals, which can achieve higher and more uniform doping concentrations. However, the process is complex, and erbium ions are prone to segregation and diffusion during subsequent high-temperature processing, making it difficult to precisely control their distribution. The thermal diffusion method is relatively mature, but it requires extremely high diffusion temperatures and excessively long times, which can easily damage the thin film structure, limiting its practicality. Summary of the Invention

[0004] To address the problems in existing technologies for erbium-doped thin-film lithium niobate / lithium tantalate photonic integrated devices, such as damage to the bonding interface of the lithium niobate / lithium tantalate thin film fabricated by Smart-Cut during secondary ion implantation and high-temperature annealing, and the impact of limiting the annealing temperature on the lattice quality of the lithium niobate / lithium tantalate thin film, this application provides a fabrication technology for an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device. The technical solution adopted in this application is as follows: According to a first aspect of this application, a method for fabricating an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device is provided, comprising: A bulk lithium niobate / lithium tantalate substrate is provided, and erbium ions are patterned and implanted into one side surface layer of the bulk lithium niobate / lithium tantalate substrate to form an erbium-doped region; The bulk lithium niobate / lithium tantalate substrate is subjected to high-temperature annealing treatment; The bulk lithium niobate / lithium tantalate substrate after high-temperature annealing is structurally processed to form a waveguide structure on the side where the erbium-doped region is located, to bond the waveguide structure to the carrier substrate, and to form a lithium niobate / lithium tantalate thin film on the bulk lithium niobate / lithium tantalate substrate, thereby obtaining the active-passive integrated thin-film lithium niobate / lithium tantalate photonic device.

[0005] Optionally, the structural processing of the bulk lithium niobate / lithium tantalate substrate after high-temperature annealing includes: The side of the bulk lithium niobate / lithium tantalate substrate with the erbium-doped region after high-temperature annealing is etched to form a waveguide structure on the side where the erbium-doped region is located; The side of the bulk lithium niobate / lithium tantalate substrate having the waveguide structure is bonded to the carrier substrate; The side of the bulk lithium niobate / lithium tantalate substrate facing away from the carrier substrate is thinned to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film.

[0006] Optionally, the structural processing of the bulk lithium niobate / lithium tantalate substrate after high-temperature annealing includes: The side of the lithium niobate / lithium tantalate substrate having the erbium-doped region after high-temperature annealing is bonded to the carrier substrate. The side of the bulk lithium niobate / lithium tantalate substrate facing away from the carrier substrate is thinned to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film; The surface of the lithium niobate / lithium tantalate film is etched to form a waveguide structure on the surface where the erbium-doped region is located.

[0007] Optionally, the bulk lithium niobate / lithium tantalate substrate includes at least one of Z-cut or X-cut bulk lithium niobate / lithium tantalate wafers.

[0008] Optionally, the patterned implantation of erbium ions into one side surface layer of the bulk lithium niobate / lithium tantalate substrate includes: An ion implantation mask is prepared on one side surface of the bulk lithium niobate / lithium tantalate substrate; Patterned etching is performed on the ion implantation mask to form a patterned window; Erbium ion implantation is performed on the exposed portion of the bulk lithium niobate / lithium tantalate substrate in the graphics window; Remove the ion implantation mask.

[0009] Optionally, the conditions for patterned implantation of erbium ions include: the implantation energy range in the ion implantation process is 200 keV to 2 MeV; And / or, the injection metering range is 1×10 14 ions / cm 2 ~ 1×10 20 ions / cm 2 ; And / or, the implantation depth is 100nm~2000nm.

[0010] Optionally, the conditions for the high-temperature annealing treatment include: an annealing temperature of 1000℃~1100℃ and an annealing time of 2h~10h; And / or, before annealing, the temperature is increased to the annealing temperature at a rate of 2°C / min to 5°C / min; And / or, after annealing, cool at a rate of 1℃ / min to 3℃ / min; And / or, the annealing atmosphere is flowing oxygen or wet oxygen.

[0011] Optionally, the waveguide structure has a thickness of 200nm to 2000nm.

[0012] Optionally, the step of thinning the side of the bulk lithium niobate / lithium tantalate substrate away from the carrier substrate to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film, includes: The bulk lithium niobate / lithium tantalate substrate is thinned stepwise as follows: Coarse grinding reduces the thickness to 20μm~50μm; Fine grinding reduces the thickness to 5μm~10μm; Polish to below 3μm; The ion beam is trimmed to expose the erbium-doped region.

[0013] Optionally, the uniformity of the lithium niobate / lithium tantalate film is made less than or equal to 5%.

[0014] According to a second aspect of this application, the aforementioned method for fabricating active and passive integrated thin-film lithium niobate / lithium tantalate photonic devices is provided for use in the fabrication of waveguide amplifiers, high-speed modulators, and active lasers.

[0015] The beneficial effects of this application include: The active-passive integrated thin-film lithium niobate / lithium tantalate photonic device fabrication method provided in this application achieves optimal erbium-doped lithium niobate / lithium tantalate thin film quality and luminous efficiency. By first doping with erbium and then fabricating the thin film, ion implantation and high-temperature annealing processes are performed on a robust bulk lithium niobate / lithium tantalate substrate, allowing for the use of optimal annealing temperatures, typically 1000℃~1100℃. This method can completely repair lattice damage caused by ion implantation while ensuring Erbium-doped luminous efficiency. 3+ Ions can effectively enter the correct positions in the lithium niobate / lithium tantalate lattice, maximizing luminescence efficiency. Compared with the current mainstream preparation methods, when ion implantation is performed again on the single-crystal lithium niobate / lithium tantalate film prepared by Smart-Cut, the bonding interface and silicon dioxide layer under the film cannot withstand the high-temperature annealing temperature, which is usually limited to <800℃, resulting in problems such as residual lattice damage and insufficient erbium ion activation.

[0016] The preparation method provided in this application offers higher process compatibility and higher yield. By pre-doping with erbium before film preparation, the high-temperature process steps that affect film quality and bonding interfaces are moved forward, avoiding high-temperature annealing in the film state. This also mitigates thermal stress, protects the film structure and bonding interfaces, and improves the preparation yield and reliability. Compared with current mainstream preparation methods, when ion-implanting single-crystal lithium niobate / lithium tantalate films prepared by Smart-Cut, high-temperature annealing may cause bonding interface failure, leading to film cracking and other problems, affecting film quality and bonding interface stability. Attached Figure Description

[0017] Figure 1 A flowchart of the fabrication method for an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device provided for this application; Figure 2 A schematic diagram of the fabrication method for the active-passive integrated thin-film lithium niobate / lithium tantalate photonic device provided in this application; Figure 3 for Figure 2 (a) and Figure 2 (b) Schematic diagram of the general steps S1 and S2; Figure 4 for Figure 2 (a) A schematic diagram of the specific process of step S3a; Figure 5 for Figure 2 (a) Schematic diagram of the specific process of steps S4a and S5a; Figure 6 for Figure 2 (b) A detailed flowchart of step S3b; Figure 7 for Figure 2(b) Schematic diagram of the specific process of steps S4b and S5b; Figure 8 This is a schematic diagram illustrating the photonic device fabrication method as a comparative example of this application.

[0018] Attached Figure Labels 1. Carrier substrate; 2. Photocurable resin adhesive layer; 30. Bulk lithium niobate / lithium tantalate substrate; 31. Lithium niobate / lithium tantalate thin film; 32. Lithium niobate / lithium tantalate waveguide; 41. Ion implantation mask; 42. Hard mask; 51. Coating layer; 52. Exposure mask. Detailed Implementation

[0019] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0020] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0021] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0022] This application provides a method for fabricating an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device. The method employs a doping-then-thinning approach to avoid the impact of subsequent high-temperature processes on the bonding interface and thin film quality, thereby achieving a photonic integrated device with high erbium doping quality and high luminous efficiency. At the same time, it achieves process compatibility, improves yield and reliability, and provides a technical route for realizing large-scale, multifunctional lithium niobate / lithium tantalate photonic integrated chips.

[0023] According to one embodiment of this application, a method for fabricating an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device includes: A bulk lithium niobate / lithium tantalate substrate is provided, and erbium ions are patterned and implanted into one side surface layer of the bulk lithium niobate / lithium tantalate substrate to form an erbium-doped region; The bulk lithium niobate / lithium tantalate substrate is subjected to high-temperature annealing treatment; The bulk lithium niobate / lithium tantalate substrate after high-temperature annealing is structurally processed to form a waveguide structure on the side where the erbium-doped region is located, to bond the waveguide structure to the carrier substrate, and to form a lithium niobate / lithium tantalate thin film on the bulk lithium niobate / lithium tantalate substrate, thereby obtaining the active-passive integrated thin-film lithium niobate / lithium tantalate photonic device.

[0024] In one embodiment, the structural processing of the bulk lithium niobate / lithium tantalate substrate after high-temperature annealing includes: The side of the bulk lithium niobate / lithium tantalate substrate with the erbium-doped region after high-temperature annealing is etched to form a waveguide structure on the side where the erbium-doped region is located; The side of the bulk lithium niobate / lithium tantalate substrate having the waveguide structure is bonded to the carrier substrate; The side of the bulk lithium niobate / lithium tantalate substrate facing away from the carrier substrate is thinned to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film.

[0025] In one embodiment, the structural processing of the bulk lithium niobate / lithium tantalate substrate after high-temperature annealing includes: The side of the lithium niobate / lithium tantalate substrate having the erbium-doped region after high-temperature annealing is bonded to the carrier substrate. The side of the bulk lithium niobate / lithium tantalate substrate facing away from the carrier substrate is thinned to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film; The surface of the lithium niobate / lithium tantalate film is etched to form a waveguide structure on the surface of the erbium-doped region.

[0026] In one embodiment, the bulk lithium niobate / lithium tantalate substrate comprises at least one of Z-cut or X-cut bulk lithium niobate / lithium tantalate wafers.

[0027] In one embodiment, the patterned implantation of erbium ions on one side of the bulk lithium niobate / lithium tantalate substrate includes: preparing an ion implantation mask on one side of the bulk lithium niobate / lithium tantalate substrate. Patterned etching is performed on the ion implantation mask to form a patterned window; Erbium ion implantation is performed on the exposed portion of the bulk lithium niobate / lithium tantalate substrate in the graphics window; Remove the ion implantation mask.

[0028] Traditional doping (such as erbium diffusion) imparts gain to the entire substrate, which is often unnecessary and can even introduce unwanted background loss. Patterned ion implantation technology can precisely confine erbium ions to specific areas requiring optical amplification or laser generation, while maintaining the substrate's original low-loss characteristics in other areas (such as passive waveguides and modulator regions), thus achieving true "active / passive monolithic integration." Furthermore, patterned ion implantation technology is mature and its process is controllable, easily implemented on standard semiconductor fabrication lines, which is beneficial for future large-scale, low-cost production.

[0029] In one embodiment, the conditions for patterned implantation of erbium ions include: the implantation energy range in the ion implantation process is 200 keV to 2 MeV; And / or, the injection metering range is 1×10 14 ions / cm 2 ~ 1×10 20 ions / cm2 ; And / or, the implantation depth is 100nm~2000nm.

[0030] The injection energy directly determines the depth to which ions penetrate the crystal, and the injection dose directly determines the number of erbium ions incorporated per unit volume, i.e., the doping concentration. By precisely controlling the spatial distribution and concentration of erbium ions in lithium niobate / lithium tantalate crystals through these conditions, the size of the target region for the active distribution of erbium ions can be determined.

[0031] In one embodiment, the conditions for the high-temperature annealing treatment include: an annealing temperature of 1000℃~1100℃ and an annealing time of 2 h~10 h, during which internal recrystallization, point defect repair, and Er are achieved in the lithium niobate / lithium tantalate crystal are realized. 3+ Ion repositioning process; And / or, before annealing, the temperature is increased to the annealing temperature at a rate of 2℃ / min to 5℃ / min to avoid excessive thermal stress causing cracking or defects in the lithium niobate / lithium tantalate wafer; And / or, after annealing, cool down at a rate of 1℃ / min to 3℃ / min to avoid excessively rapid cooling that could cause a quenching effect, leading to wafer warping or internal dislocation problems; And / or, the annealing atmosphere is flowing oxygen or wet oxygen.

[0032] In one embodiment, the waveguide structure formed on the surface of the erbium-doped region has a thickness of 200 nm to 2000 nm. The thickness of the waveguide structure can be the same as or less than the thickness of the erbium-doped region.

[0033] In one embodiment, thinning the side of the bulk lithium niobate / lithium tantalate substrate away from the carrier substrate to expose the erbium-doped region to form a lithium niobate / lithium tantalate thin film includes: The bulk lithium niobate / lithium tantalate substrate is thinned stepwise as follows: Coarse grinding reduces the thickness to 20μm~50μm; Fine grinding reduces the thickness to 5μm~10μm; Polish to below 3μm; The ion beam is trimmed to expose the erbium-doped region. This trimming can be done by simply exposing the erbium-doped region, or by thinning away a certain thickness of the erbium-doped region. For example, thinning from the waveguide structure side can either just expose the waveguide structure end face or thin away a certain thickness of the waveguide structure. Alternatively, thinning from the side away from the waveguide structure can either just expose the side of the erbium-doped region away from the waveguide structure or thin away a certain thickness of the erbium-doped region away from the waveguide structure.

[0034] The thickness of lithium niobate / lithium tantalate is rapidly reduced by coarse grinding, and then reduced to less than ten micrometers by fine grinding; mechanically damaged layers are removed by chemical mechanical polishing; and the thickness non-uniformity of lithium niobate / lithium tantalate wafer films is improved by ion beam trimming.

[0035] In one embodiment, the uniformity of the lithium niobate / lithium tantalate film is made less than or equal to 5% to meet optical applications, and the damaged layer can then be removed again by fine polishing.

[0036] The technical solution of this application will be further described in detail below with reference to the accompanying drawings, such as... Figure 1 (a) and Figure 2 As shown in (a), according to one embodiment of this application, a method for fabricating an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device includes: S1. Er-induced patterning on a bulk lithium niobate / lithium tantalate substrate 3+ : A bulk lithium niobate / lithium tantalate substrate is provided, and erbium ions are patterned and implanted into one side surface layer of the bulk lithium niobate / lithium tantalate substrate to form an erbium-doped region; In one embodiment, Er is patterned and implanted onto a bulk lithium niobate / lithium tantalate substrate. 3+ The process includes: fabricating an ion implantation mask on a bulk lithium niobate / lithium tantalate substrate; fabricating a patterned window on the ion implantation mask; implanting Er3+ ions into the exposed lithium niobate / lithium tantalate through the patterned window; and removing the ion implantation mask.

[0037] In one embodiment, Er is patterned and implanted onto a bulk lithium niobate / lithium tantalate substrate. 3+ The process is as follows Figure 3 As shown, it includes: (1) An ion implantation mask 41 was fabricated on a bulk lithium niobate / lithium tantalate substrate 30. Figure 3 (a) Specifically, a silicon dioxide hard mask is deposited by plasma-enhanced chemical vapor deposition or thermal oxidation, with a thickness ranging from 1 μm to 2 μm.

[0038] (2) A patterned window is fabricated on the ion implantation mask 41, specifically: a pattern is defined on the ion implantation mask using a patterning process, and a patterned window is fabricated on the ion implantation mask using an etching process. Figure 3 (e) exposes the lithium niobate / lithium tantalate in the ion-implanted region. The patterning process includes coating ( Figure 3 (b) Soft baking, exposure ( Figure 3 (c) Developing ( Figure 3 (d) Hardening, desizing ( Figure 3(f)). The etching process is dry etching, including at least one of reactive ion etching and inductively coupled plasma etching.

[0039] (3) Ion implantation of Er onto lithium niobate / lithium tantalate exposed in the graphics window 3+ ( Figure 3 (g)), wherein the ion implantation energy range is 200 keV to 2 MeV, and the implantation quantitation range is 1×10 14 ions / cm 2 ~ 1×10 20 ions / cm 2 This achieves an injection depth of 100nm~2000nm.

[0040] (4) Removal of ion implantation mask 41 ( Figure 3 (h) Specifically, the silicon dioxide hard mask is removed by a selective wet etching process using a buffered hydrofluoric acid solvent.

[0041] S2, High-temperature annealing to repair the lithium niobate / lithium tantalate lattice: The bulk lithium niobate / lithium tantalate substrate is subjected to high-temperature annealing treatment; In one embodiment, the high-temperature annealing method includes: a first stage of slow heating; a second stage of high-temperature holding; a third stage of slow cooling; and removal for testing after cooling.

[0042] In one embodiment, the high-temperature annealing method is carried out in a high-purity quartz tube annealing furnace, and the annealing atmosphere is selected as flowing oxygen or wet oxygen.

[0043] In one embodiment, the method for repairing the crystal lattice by high-temperature annealing includes, as follows: Figure 3 As shown: The first stage involves a slow heating rate of 2°C / minute to 5°C / minute to avoid excessive thermal stress that could cause cracking or defects in the lithium niobate / lithium tantalate wafers. The second stage involves high-temperature insulation, specifically at a temperature range of 1000℃ to 1100℃ for a time range of 2 to 10 hours. During this stage, internal recrystallization of lithium niobate / lithium tantalate crystals, repair of point defects, and Er... 3+ Ion repositioning process; The third stage involves slow cooling, specifically at a rate of 1°C / minute to 3°C / minute, to avoid excessively rapid cooling that could cause a quenching effect, leading to wafer warping or internal dislocation problems. After high-temperature annealing, the lithium niobate / lithium tantalate lattice is repaired to complete the erbium doping ( Figure 3 (i)~ Figure 3 (j)).

[0044] S3a, Waveguide structure fabrication using semiconductor processes: The side of the lithium niobate / lithium tantalate substrate with the erbium-doped region after high-temperature annealing is etched to form a waveguide structure on the surface of the erbium-doped region. In one embodiment, the method for fabricating the waveguide structure includes: fabricating a hard mask on the erbium-doped side of a bulk lithium niobate / lithium tantalate substrate; fabricating a patterned window on the hard mask; etching the lithium niobate / lithium tantalate waveguide structure; and removing the hard mask.

[0045] In one embodiment, the method for fabricating the waveguide structure is as follows: Figure 4 As shown, it includes: (1) A hard mask 42 was prepared on the erbium-doped side of a bulk lithium niobate / lithium tantalate substrate. Figure 4 (a) Specifically, a hard mask is deposited by plasma-enhanced chemical vapor deposition or by sputtering, with a thickness ranging from 200 nm to 1 μm; for example, the hard mask material includes at least one of silicon dioxide, chromium, and amorphous silicon. (2) Fabricating a patterned window on the hard mask 42, specifically: defining a pattern on the hard mask 42 using a patterning process, and fabricating the patterned window on the hard mask 42 using an etching process. Figure 4 (e)). The patterning process includes applying adhesive ( Figure 4 (b) Soft baking, exposure ( Figure 4 (c) Developing ( Figure 4 (d) Hardening, desizing ( Figure 4 (f) The etching process is dry etching, including at least one of reactive ion etching and inductively coupled plasma etching; (3) Etching of lithium niobate / lithium tantalate waveguide structure 32 ( Figure 4 (g) Specifically, the lithium niobate / lithium tantalate substrate 30 is etched by at least one dry etching process, either reactive ion etching or inductively coupled plasma etching, with an etching depth ranging from 200 nm to 2000 nm. (4) Remove the hard mask 42 ( Figure 4 (h) Specifically, the hard mask is removed by a selective wet etching process, using at least one of a buffered hydrofluoric acid solution, a special chromium etching solution, or a potassium hydroxide solution.

[0046] S4a, Waveguide surface bonded to carrier substrate: The side of the bulk lithium niobate / lithium tantalate substrate having the waveguide structure is bonded to the carrier substrate; In one embodiment, the carrier substrate 1 includes at least one of a silicon substrate, a glass substrate, a lithium niobate substrate, a lithium tantalate substrate, and a sapphire substrate.

[0047] In one embodiment, the photocurable resin adhesive layer 2 is at least one of epoxy-negative adhesive, BrewerScience HD-3000, acrylate UV adhesive, etc.

[0048] In one embodiment, the bonding method in step S4a is resin bonding, which includes: using one side of the bulk lithium niobate / lithium tantalate substrate as the bonding surface, preparing a photocurable resin adhesive layer on the carrier substrate, aligning the bonding surface of the bulk lithium niobate / lithium tantalate substrate and the adhesive layer of the carrier substrate into contact, and then baking and curing.

[0049] In one embodiment, the method of bonding the waveguide surface to the carrier substrate, such as Figure 5 As shown, it includes: (1) Using the side of the lithium niobate / lithium tantalate substrate 30 waveguide structure as the bonding surface, a photocurable resin adhesive layer 2 is prepared on the carrier substrate 1. Specifically, the photocurable resin adhesive layer 2 is spin-coated on the bonding surface of the carrier substrate 1, with a spin-coating thickness ranging from 5 μm to 20 μm; and then soft-baked on a hot plate at a temperature of 95 °C for a baking time ranging from 1 minute to 5 minutes.

[0050] (2) Align and cure the bonding surfaces of the bulk lithium niobate / lithium tantalate substrate 30 and the carrier substrate 1. Specifically, place the carrier substrate 1 coated with the photocurable resin adhesive layer 2 with the bonding surface facing up, and place the bulk lithium niobate / lithium tantalate substrate 30 with the waveguide structure facing down into the bonding machine. Align it under a microscope and slowly lower the upper bulk lithium niobate / lithium tantalate substrate 30 to make soft contact with the lower adhesive layer 2. Figure 5 (a)); Vacuum is drawn inside the bonding machine cavity, with a range of 1×10⁻⁶. -2 Apply a uniform and controllable mechanical pressure of mbar or lower, ranging from 0.1 MPa to 0.5 MPa, to ensure close bonding between the two wafers; then use an ultraviolet lithography machine to expose the wafers from the substrate side. Figure 5 (b)), the exposure energy range is 100 mJ / cm 2 ~ 500 mj / cm 2 After bonding the wafers, place them on a hot plate and bake. Figure 5 (c) Bake at 120℃~150℃ for 5 to 15 minutes; check the bonding interface and clean up any excess adhesive.

[0051] S5a, Thinning of the lithium niobate / lithium tantalate back substrate to form a thin film: The side of the bulk lithium niobate / lithium tantalate substrate facing away from the carrier substrate is thinned to expose the erbium-doped region.

[0052] In one embodiment, the thinning method in step S5a includes: using the side of the bulk lithium niobate / lithium tantalate substrate away from the substrate as the thinning surface; rapidly thinning the lithium niobate / lithium tantalate by coarse grinding; reducing the thickness of the lithium niobate / lithium tantalate to less than ten micrometers by fine grinding; removing the mechanically damaged layer by chemical mechanical polishing; and improving the thickness non-uniformity of the lithium niobate / lithium tantalate wafer thin film by ion beam trimming.

[0053] In one embodiment, the method for thinning the lithium niobate / lithium tantalate back substrate to form a thin film is as follows: Figure 6 As shown, it includes: (1) The side of the lithium niobate / lithium tantalate substrate 30 away from the substrate is used as the thinning surface; using a diamond grinding disc or diamond polishing slurry with a larger particle size of 30 μm, the thickness of lithium niobate / lithium tantalate is rapidly reduced from 500 μm to 20 μm~50 μm by coarse grinding. Figure 5 (d)).

[0054] (2) Using finer 9μm or 3μm diamond abrasives, the thickness of lithium niobate / lithium tantalate is reduced to 5μm~10μm through fine grinding. Figure 5 (e)).

[0055] (3) Remove the mechanically damaged layer by chemical mechanical polishing process and polish the thickness to below 3 μm, including at least one of coarse polishing and fine polishing.

[0056] (4) The thickness non-uniformity of lithium niobate / lithium tantalate wafer thin films is improved by ion beam trimming, reducing the thickness to below 2 μm and the uniformity to <5%, which meets the requirements for optical applications. Subsequently, fine polishing can be used to remove the damaged layer again. Figure 5 (f)).

[0057] like Figure 1 (b) and Figure 2 As shown in (b), according to one embodiment of this application, a method for fabricating an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device includes: S1. Er-induced patterning on a bulk lithium niobate / lithium tantalate substrate 3+ ,and Figure 1 (a) Figure 2 (a) Same.

[0058] S2, High-temperature annealing to repair the lithium niobate / lithium tantalate lattice: The bulk lithium niobate / lithium tantalate substrate is subjected to high-temperature annealing treatment, and with Figure 1 (a) Figure 2 (a) Same.

[0059] S3b, Er 3+ Injection surface bonding to carrier substrate: The side of the lithium niobate / lithium tantalate substrate having the erbium-doped region after high-temperature annealing is bonded to the carrier substrate. In one embodiment, the carrier substrate 1 includes at least one of a silicon substrate, a glass substrate, a lithium niobate substrate, a lithium tantalate substrate, and a sapphire substrate.

[0060] In one embodiment, the photocurable resin adhesive layer 2 is at least one of epoxy-negative adhesive, BrewerScience HD-3000, acrylate UV adhesive, etc.

[0061] In one embodiment, the bonding method in step S3 is at least one of direct bonding or resin bonding, including: using the erbium-doped side of the bulk lithium niobate / lithium tantalate substrate as the bonding surface, and aligning and bonding the bonding surface of the bulk lithium niobate / lithium tantalate substrate with the bonding surface of the carrier substrate.

[0062] In one embodiment, the bonding in step S3 employs a direct bonding method, such as... Figure 6 As shown, it includes: (1) Using the 30% erbium-doped side of the bulk lithium niobate / lithium tantalate substrate as the bonding surface, the bonding surface of the bulk lithium niobate / lithium tantalate substrate and the bonding surface of the carrier substrate are treated by plasma activation process, using at least one of argon or nitrogen plasma. Figure 6 (a)).

[0063] (2) In a cleanroom environment, the two activated bonding surfaces are aligned and brought into close contact at room temperature to form a pre-bonded body. Figure 6 (b)).

[0064] (3) The pre-bonded sample is placed in an annealing furnace and hardened by low-temperature annealing in the range of 200℃ to 400℃, during which strong chemical bonds are formed at the interface. Figure 6 (c) S4b, Thinning of the lithium niobate / lithium tantalate back substrate to form a thin film: The side of the bulk lithium niobate / lithium tantalate substrate facing away from the carrier substrate is thinned to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film; In one embodiment, the method for thinning the back substrate of lithium niobate / lithium tantalate to form a thin film is as follows: Figure 6 As shown, it includes: (1) The side of the lithium niobate / lithium tantalate substrate 30 away from the substrate is used as the thinning surface; using a diamond grinding disc or diamond polishing slurry with a larger particle size of 30 μm, the thickness of lithium niobate / lithium tantalate is rapidly reduced from 500 μm to 20 μm~50 μm by coarse grinding. Figure 6 (d)).

[0065] (2) Using finer 9μm or 3μm diamond abrasives, the thickness of lithium niobate / lithium tantalate is reduced to 5μm~10μm through fine grinding. Figure 6 (e)).

[0066] (3) Remove the mechanically damaged layer by chemical mechanical polishing process and polish the thickness to below 3 μm, including at least one of coarse polishing and fine polishing.

[0067] (4) The thickness non-uniformity of lithium niobate / lithium tantalate wafer thin films is improved by ion beam trimming, reducing the thickness to below 2 μm and the uniformity to <5%, which meets the requirements for optical applications. Subsequently, fine polishing can be used to remove the damaged layer again. Figure 6 (f) S5b, Waveguide structure fabrication using semiconductor technology: The surface of the lithium niobate / lithium tantalate film is etched to form a waveguide structure on the surface of the erbium-doped region.

[0068] In one embodiment, the etching method in step S5b includes: preparing a hard mask on the side of the erbium-doped lithium niobate / lithium tantalate thin film away from the substrate; preparing a patterned window on the hard mask; etching the lithium niobate / lithium tantalate waveguide structure; and removing the hard mask.

[0069] In one embodiment, the hard mask material in step S5b includes at least one of silicon dioxide, chromium, and amorphous silicon.

[0070] In one embodiment, the method for fabricating the waveguide structure using semiconductor technology is as follows: Figure 7 As shown, it includes: (1) A hard mask 42 is prepared on the side of the erbium-doped lithium niobate / lithium tantalate film 31 away from the substrate 1. Figure 7 (a) Specifically, a silicon dioxide hard mask is deposited by plasma-enhanced chemical vapor deposition, or a chromium or amorphous silicon hard mask is deposited by sputtering, with a thickness ranging from 200 nm to 1 μm.

[0071] (2) Fabricating a patterned window on the hard mask 42, specifically: defining a pattern on the hard mask 42 using a patterning process, and fabricating the patterned window on the hard mask 42 using an etching process. Figure 7 (e)). The patterning process includes applying adhesive ( Figure 7 (b) Soft baking, exposure ( Figure 7 (c) Developing ( Figure 7 (d) Hardening, desizing ( Figure 7 (f)). The etching process is dry etching, including at least one of reactive ion etching and inductively coupled plasma etching.

[0072] (3) Etching of lithium niobate / lithium tantalate waveguide structure 32 ( Figure 7 (g) Specifically, the erbium-doped lithium niobate / lithium tantalate film 31 is etched by at least one dry etching process, namely reactive ion etching or inductively coupled plasma etching, with an etching depth ranging from 200 nm to 2000 nm.

[0073] (4) Remove the hard mask 42 ( Figure 7 (h) includes removing the hard mask by a selective wet etching process, using at least one of a buffered hydrofluoric acid solution, a special chromium etching solution, or a potassium hydroxide solution.

[0074] According to another embodiment of this application, the aforementioned method for fabricating active and passive integrated thin-film lithium niobate / lithium tantalate photonic devices is applied to the fabrication of waveguide amplifiers, high-speed modulators, and active lasers.

[0075] Example 1 The fabrication method of active and passive integrated thin-film lithium niobate / lithium tantalate photonic devices employs methods such as Figure 1 (a) and Figure 2 The process shown in (a), based on the aforementioned preparation method, includes the following specific steps and parameter information: Step 1: Perform standard cleaning on the X-section lithium niobate substrate. Deposit a silicon dioxide hard mask with a thickness of 1 μm on the bulk lithium niobate substrate using plasma-enhanced chemical vapor deposition. Coat the hard mask with photoresist uniformly. Bake the sample at low temperature on a hot plate to cure the photoresist. Use a UV lithography machine to expose the photoresist through a mask with ion implantation patterns. Dissolve the unexposed photoresist with a developer to expose the hard mask in the ion implantation area. Use inductively coupled plasma etching to etch the silicon dioxide hard mask to expose the lithium niobate in the ion implantation area. Remove the photoresist with solvents such as acetone. Use an ion implanter to implant Er3+ ions multiple times into the exposed lithium niobate area, achieving an erbium-doped layer with an effective optical thickness of at least 600 nm. Remove the silicon dioxide hard mask with buffered hydrofluoric acid solvent.

[0076] Step 2: Place the ion-implanted sample into a tubular annealing furnace, introduce flowing high-purity oxygen, slowly heat to 1000℃ at a rate of 3℃ / min, hold at high temperature for 5 hours, and slowly cool to room temperature at a rate of 3℃ / min to repair the lithium niobate lattice.

[0077] Step 3: Deposit a silicon dioxide hard mask on the surface of the erbium-doped film, spin-coat photoresist, transfer the waveguide pattern onto the photoresist using ultraviolet lithography, transfer the pattern from the photoresist to the hard mask layer using reactive ion etching, etch the erbium-doped lithium niobate using inductively coupled plasma etching to a depth of 300 nm, and remove the silicon dioxide hard mask using buffered hydrofluoric acid solvent to complete the fabrication of the waveguide structure.

[0078] Step 4: Perform standard cleaning on the silicon substrate. Fix the silicon substrate on a spin coater and drop in UV-curable resin SU8. First, spread the resin at a low speed, then spin it at a high speed for 30 seconds, controlling the resin layer thickness to 20μm. Bake the sample on a hot plate at 95℃ for 3 minutes. Using a bonding machine, align the side of the bulk lithium niobate substrate with the adhesive layer on the silicon substrate, with the front structure facing down. Slowly lower the upper bulk lithium niobate substrate to make soft contact with the lower adhesive layer. Apply a uniform pressure of 0.5Mpa and evacuate the vacuum to ensure tight contact and no air bubbles at the bonding interface. Expose the sample to UV light from one side of the silicon substrate. Place the sample on a hot plate and bake at 150℃ for 10 minutes to cure the adhesive layer. Inspect the bonding interface and clean up any excess resin.

[0079] Step 5: Using the side of the lithium niobate substrate furthest from the substrate as the thinning surface, the lithium niobate thickness is rapidly reduced from 500μm to 50μm using a diamond abrasive with a particle size of 30μm. Then, the lithium niobate thickness is reduced to 5μm using a diamond abrasive with a particle size of 9μm. The mechanically damaged layer is removed by chemical mechanical polishing, and the lithium niobate thickness is polished to 1μm. The thickness non-uniformity of the lithium niobate wafer film is improved by ion beam trimming, reducing the thickness to 300nm with a uniformity of <5%. The thinned surface is then inspected and cleaned.

[0080] Example 2 The fabrication method of active and passive integrated thin-film lithium niobate / lithium tantalate photonic devices employs methods such as Figure 1 (b) and Figure 2 The process shown in (b), based on the aforementioned preparation method, includes the following specific steps and parameter information: Step 1: Perform standard cleaning on the X-section bulk lithium tantalate substrate. Deposit a silicon dioxide hard mask with a thickness of 1 μm on the bulk lithium tantalate substrate using plasma-enhanced chemical vapor deposition. Coat the hard mask with photoresist uniformly. Bake the sample at low temperature on a hot plate to cure the photoresist. Use a UV lithography machine to expose the photoresist through a mask with ion implantation patterns. Dissolve the unexposed photoresist with a developer to expose the hard mask in the ion implantation area. Etch the silicon dioxide hard mask using inductively coupled plasma etching to expose the lithium tantalate in the ion implantation area. Remove the photoresist using solvents such as acetone. Use an ion implanter to implant the lithium tantalate in the ion implantation area. 3+ Multiple ion implantations exposed the lithium tantalate region, with an erbium-doped layer having an effective optical thickness of at least 600 nm. The silicon dioxide hard mask was removed using a buffered hydrofluoric acid solvent.

[0081] Step 2: Place the ion-implanted sample into a tubular annealing furnace, introduce flowing high-purity oxygen, slowly heat to 1000℃ at a rate of 3℃ / min, hold at high temperature for 5 hours, and slowly cool to room temperature at a rate of 3℃ / min to repair the lithium tantalate lattice.

[0082] Step 3: The bonding surfaces of the erbium-doped lithium tantalate side and the silicon substrate are subjected to ultra-precision polishing to achieve atomic-level smoothness, ensuring bonding quality. The two surfaces to be bonded are then subjected to plasma spark testing using nitrogen plasma. The plasma bombardment of the crystal surface generates dangling bonds, forming hydrophilicity and adsorbing a thin layer of water molecules. When the two surfaces come into contact, initial pre-bonding occurs through strong hydrogen bonding. In a cleanroom environment, the two activated surfaces are aligned and brought into close contact at room temperature to form a pre-bonded structure with a certain mechanical strength. The pre-bonded structure is then placed in an annealing furnace and annealed under controlled atmosphere with gradual temperature increases. At a low temperature of 300°C, water molecules at the interface diffuse away, forming strong covalent bonds.

[0083] Step 4: Using the side of the bulk lithium tantalate substrate furthest from the substrate as the thinning surface, the lithium tantalate thickness is rapidly reduced from 500μm to 50μm using a diamond abrasive with a particle size of 30μm. Then, the lithium tantalate thickness is further reduced to 5μm using a diamond abrasive with a particle size of 9μm. The mechanically damaged layer is removed by chemical mechanical polishing, and the lithium tantalate thickness is polished to 3μm. The thickness non-uniformity of the lithium tantalate wafer film is improved by ion beam trimming, reducing the thickness to 600nm with a uniformity of <5%. The thinned surface is then inspected and cleaned.

[0084] Step 5: Deposit a silicon dioxide hard mask on the thinned film surface, spin-coat photoresist, use ultraviolet lithography to transfer the waveguide pattern onto the photoresist, transfer the pattern from the photoresist to the hard mask layer by reactive ion etching, etch the erbium-doped lithium tantalate film using inductively coupled plasma etching process to an etching depth of 300 nm, and remove the silicon dioxide hard mask using buffered hydrofluoric acid solvent.

[0085] Comparative Example 1 like Figure 8 The diagram shows the preparation method of the comparative example. The comparative example provided in this application uses a method of preparing single-crystal lithium niobate thin films with erbium doping using Smart-Cut.

[0086] Step 1: Perform standard cleaning on the bulk lithium niobate substrate, and then use an ion implanter to implant high-energy He into the surface of the bulk lithium niobate substrate. + Ions, implantation depth 800nm.

[0087] Step 2: Select a thermally oxidized silicon wafer as the carrier substrate and the silicon dioxide layer on the surface as the lower cladding layer. Perform oxygen plasma treatment on the carrier substrate and the surface of the helium-ion implanted bulk lithium niobate substrate. Align and contact the two activated bonding surfaces at room temperature for pre-bonding. Anneal the pre-bonded wafer pair at 300℃ to form strong Si-O-Ln covalent bonds at the interface.

[0088] Step 3: The bonded wafers are heat-treated at 500°C. At this time, the helium ion bubbles in the implanted area will generate huge pressure, causing the bulk lithium niobate substrate to split neatly along the implanted helium ion layer. The lithium niobate film is bonded to the substrate. In an oxygen atmosphere, the stripped lithium niobate film is annealed at a high temperature above 1000°C to repair the surface damage.

[0089] Step 4: Perform chemical mechanical polishing on the surface of the lithium niobate film to remove the surface damage layer, achieving a film thickness of 600nm, and thoroughly clean the lithium niobate film.

[0090] Step 5: Spin-coat photoresist onto a single-crystal lithium niobate thin film wafer, define the erbium-doped region using photolithography, and perform multiple ion implantations of Erbium onto the surface of the lithium niobate thin film. 3+ Ions, erbium-doped layer with an effective optical thickness of at least 600 nm, and removal of photoresist.

[0091] Step Six: Anneal at 800°C for several hours in a flowing oxygen atmosphere to repair the lithium niobate lattice and activate erbium ions.

[0092] Step 7: Deposit a silicon dioxide hard mask on the annealed wafer, spin-coat photoresist, transfer the waveguide pattern onto the photoresist using photolithography, transfer the pattern from the photoresist onto the hard mask using inductively coupled plasma etching, etch the exposed lithium niobate using inductively coupled plasma etching to fabricate the waveguide structure, and finally use wet etching to selectively remove the hard mask and thoroughly clean it.

[0093] The above comparative examples are typical cases of existing technologies for fabricating active and passive integrated thin-film lithium niobate photonic devices based on single-crystal lithium niobate thin-film wafers. Figure 8 (a)~ Figure 8 (e) The process flow for preparing single-crystal lithium niobate thin films using the Smart-Cut process, such as... Figure 8 As shown in (f), Er is implanted with ions again. 3+ During ionization, the bonding interface between the thin film and the silicon dioxide layer cannot withstand high-temperature processes. The annealing temperature is limited to <800℃, which will cause problems such as residual lattice damage and insufficient erbium ion activation, affecting the erbium doping quality. At the same time, the high-temperature process may cause problems such as film cracking, affecting the film quality and the stability of the bonding interface. This is a test of the thermal stability of single-crystal lithium niobate thin films and seriously affects the yield.

[0094] Compared to the comparative examples, the ion implantation and high-temperature annealing processes in Examples 1 and 2 were performed on robust bulk lithium tantalate substrates, allowing for the use of optimal annealing temperatures, typically 1000°C to 1100°C. This enabled the complete repair of lattice damage caused by ion implantation while ensuring Er 3+Ions can effectively enter the correct positions in the lithium tantalate lattice, maximizing luminescence efficiency. Simultaneously, high-temperature annealing in the thin film state is avoided, mitigating thermal stress, protecting the film structure and bonding interfaces, and improving the yield and reliability of the fabrication.

[0095] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for fabricating an active-passive integrated thin-film lithium niobate / lithium tantalate photonic device, characterized in that, include: A bulk lithium niobate / lithium tantalate substrate is provided, and erbium ions are patterned and implanted into one side surface layer of the bulk lithium niobate / lithium tantalate substrate to form an erbium-doped region; The bulk lithium niobate / lithium tantalate substrate is subjected to high-temperature annealing treatment; The bulk lithium niobate / lithium tantalate substrate after high-temperature annealing is structurally processed to form a waveguide structure on the side where the erbium-doped region is located, to bond the waveguide structure to the carrier substrate, and to form a lithium niobate / lithium tantalate thin film on the bulk lithium niobate / lithium tantalate substrate, thereby obtaining the active-passive integrated thin-film lithium niobate / lithium tantalate photonic device.

2. The preparation method according to claim 1, characterized in that, The structural processing of the bulk lithium niobate / lithium tantalate substrate after high-temperature annealing includes: The side of the bulk lithium niobate / lithium tantalate substrate with the erbium-doped region after high-temperature annealing is etched to form a waveguide structure on the side where the erbium-doped region is located; The side of the bulk lithium niobate / lithium tantalate substrate having the waveguide structure is bonded to the carrier substrate; The side of the bulk lithium niobate / lithium tantalate substrate facing away from the carrier substrate is thinned to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film.

3. The preparation method according to claim 1, characterized in that, The structural processing of the bulk lithium niobate / lithium tantalate substrate after high-temperature annealing includes: The side of the lithium niobate / lithium tantalate substrate having the erbium-doped region after high-temperature annealing is bonded to the carrier substrate. The side of the bulk lithium niobate / lithium tantalate substrate facing away from the carrier substrate is thinned to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film; The surface of the lithium niobate / lithium tantalate film is etched to form a waveguide structure on the surface where the erbium-doped region is located.

4. The preparation method according to claim 1, characterized in that, The bulk lithium niobate / lithium tantalate substrate includes at least one of Z-cut or X-cut bulk lithium niobate / lithium tantalate wafers.

5. The preparation method according to claim 1, characterized in that, The step of patterning erbium ion implantation on one side of the surface layer of the bulk lithium niobate / lithium tantalate substrate includes: An ion implantation mask is prepared on one side surface of the bulk lithium niobate / lithium tantalate substrate; Patterned etching is performed on the ion implantation mask to form a patterned window; Erbium ion implantation is performed on the exposed portion of the bulk lithium niobate / lithium tantalate substrate in the graphics window; Remove the ion implantation mask.

6. The preparation method according to claim 1, characterized in that, The conditions for patterned implantation of erbium ions include: The implantation energy range in the ion implantation process is 200 keV to 2 MeV; And / or, the injection metering range is 1×10 14 ions / cm 2 ~ 1×10 20 ions / cm 2 ; And / or, the implantation depth is 100nm~2000nm.

7. The preparation method according to claim 1, characterized in that, The conditions for the high-temperature annealing treatment include: The annealing temperature is 1000℃~1100℃, and the annealing time is 2 h~10 h; And / or, before annealing, the temperature is increased to the annealing temperature at a rate of 2°C / min to 5°C / min; And / or, after annealing, cool at a rate of 1℃ / min to 3℃ / min; And / or, the annealing atmosphere is flowing oxygen or wet oxygen.

8. The preparation method according to claim 1, characterized in that, The waveguide structure has a thickness of 200nm to 2000nm.

9. The preparation method according to claim 2 or 3, characterized in that, The step of thinning the side of the bulk lithium niobate / lithium tantalate substrate away from the carrier substrate to expose the erbium-doped region, forming a lithium niobate / lithium tantalate thin film, includes: The bulk lithium niobate / lithium tantalate substrate is thinned stepwise as follows: Coarse grinding reduces the thickness to 20μm~50μm; Fine grinding reduces the thickness to 5μm~10μm; Polish to below 3μm; The ion beam is trimmed to expose the erbium-doped region.

10. The application of the active-passive integrated thin-film lithium niobate / lithium tantalate photonic device fabrication method according to any one of claims 1 to 9 in the fabrication of waveguide amplifiers, high-speed modulators, and active lasers.

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