Titanium sapphire film preparation method based on ion implantation stripping and homogeneous bonding and gain device thereof

Abstract

The invention relates to a titanium sapphire film preparation method based on ion implantation stripping and homogeneous bonding and a gain device thereof, a film is activated and bonded with the surface of a sapphire substrate through ion implantation, thickness-controllable heterogeneous integration is realized through high-temperature annealing, and thermal mismatch stress and interface defects are remarkably reduced; in combination with a silicon nitride waveguide structure design, through optimizing a light field limiting factor and mode distribution, interaction between light and a gain medium is enhanced, a broadband light amplification function is realized, and peak gain reaches 1.2 dB / cm. The method does not need a complex dry etching or heterogeneous bonding process, is compatible with a CMOS (Complementary Metal-Oxide-Semiconductor Transistor) integration platform, supports the repeated utilization of the titanium sapphire substrate, and reduces the preparation cost; the obtained titanium sapphire thin film has few surface defects and good doping uniformity, can be flexibly adapted to different supporting substrates, and expands the application of the titanium sapphire thin film in integrated photonic devices. According to the invention, through the high-precision film transfer and waveguide integration technology, a solution for large-scale production is provided for high-performance and miniaturized Ti sapphire lasers and amplifiers.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of integrated optics and optoelectronic devices, and particularly relates to a preparation method of a titanium sapphire (Ti:Al2O3) film based on ion implantation stripping and homogenous bonding and a gain device thereof. BACKGROUND

[0002] With the continuous progress of integrated optics technology, the miniaturization and energy efficiency ratio of optoelectronic devices have become the core development direction. Especially in the frontier fields of quantum technology, atomic clock and precision measurement, higher requirements are put forward for the reliability, compactness and power consumption performance of visible light photon integrated systems. As a key component, the high integration of optical amplifiers with on-chip devices can realize low loss and high stability transmission. The breakthrough of silicon nitride waveguide technology (such as the low-loss photon integrated chip proposed by N. Chauhan et al., which realizes an ultra-high resonant cavity quality factor of 6x10 7 of the visible light waveguide amplifier, which significantly improves the signal quality and system stability by extending the interaction distance of light and gain medium and compressing the laser linewidth, especially providing a new path for the integration of quantum devices. Visible light waveguide amplifiers are therefore considered as a core technology to break through the loss bottleneck of short-wavelength signals and promote the research and development of the next generation of quantum devices.

[0003] However, the practical application of current visible light waveguide amplifiers still faces many challenges. Although semiconductor waveguide amplifiers dominate due to their high efficiency and high integration, their inherent defects such as limited gain bandwidth, polarization sensitivity and performance degradation caused by thermal loss greatly limit their applicability in high-density integration scenarios. Nonlinear waveguide amplifiers show potential in visible light signal modulation and data processing through nonlinear effects, but still need to solve key problems such as nonlinear loss management and material coefficient stability. On the contrary, titanium sapphire waveguide amplifiers have become a new direction for high-performance laser sources due to their wide spectral coverage (730-830 nm), tunability and high beam quality. The team of H. X. Tang at Yale University realized milliwatt-level low-threshold laser emission through titanium sapphire and SiN hetero-integration technology, while J. Yang et al. at Stanford University further reduced the threshold to sub-milliwatt level through wafer bonding and dry etching process, marking a key step towards practical application of the technology.

[0004] However, the large-scale application of titanium sapphire waveguide amplifiers is still restricted by the material hetero-integration bottleneck. Due to the mismatch of the thermal expansion coefficient between titanium sapphire and silicon nitride substrates, the interface mechanical stress accumulates, which easily leads to the decline of long-term stability of the device; in addition, the existing bonding and polishing technology is only suitable for small-size integration, and large-size preparation process is complex and costly. These problems interact with each other, seriously restricting the actual performance and integration potential of the technology. SUMMARY

[0005] The present application is directed to the above-mentioned deficiencies in the prior art, proposes a method for preparing titanium sapphire thin film by ion implantation and stripping, to solve the problem of the prior art that the thickness of the prepared thin film is thin, the bonding substrate is needed for support, and the thin film material is easy to crack, and the whole stripping preparation process is complex.

[0006] By improving the LPCVD film coating process, optimizing the hetero-interface bonding strength, and combining the doping regulation technology to improve the gain medium material performance, Si3N4 waveguide structure on titanium sapphire thin film is realized. Through the synergistic optimization of the above key technologies, the physical limitations of the existing hetero-integrated material system are broken through, and finally the low threshold, high performance and large-scale application of visible light band titanium sapphire solid waveguide laser are promoted.

[0007] To achieve the above-mentioned purposes and other related purposes, the present application provides a method for preparing titanium sapphire thin film by ion implantation and stripping, which at least comprises the following steps:

[0008] A substrate is provided, ion implantation is carried out in the substrate, the energy of ion implantation is sufficient to make the implanted ions reach a preset depth in the substrate, and a defect layer is formed at the preset depth; part of the substrate is stripped along the defect layer to obtain a thin film with a thickness sufficient to be self-supporting.

[0009] As a preferred scheme of the method for preparing titanium sapphire thin film by ion implantation and stripping of the present application, the ions implanted in the substrate are H ions or He ions.

[0010] As a preferred scheme of the method for preparing titanium sapphire thin film by ion implantation and stripping of the present application, the dose of ion implantation is 1E16cm -2 ~ 6E17cm -2 .

[0011] As a preferred scheme of the method for preparing titanium sapphire thin film by ion implantation and stripping of the present application, the ions implanted in the substrate are H ions and He ions.

[0012] As a preferred scheme of the method for preparing titanium sapphire thin film by ion implantation and stripping of the present application, the H ions and the He ions are implanted simultaneously.

[0013] As a preferred scheme of the method for preparing titanium sapphire thin film by ion implantation and stripping of the present application, the implantation dose of the H ions and the He ions is 1E16cm -2 ~ 6E17cm -2 .

[0014] As a preferred scheme of the method for preparing a titanium sapphire thin film by ion implantation and exfoliation, the energy of the implanted H ions is greater than or equal to 100 keV, and the energy of the implanted He ions is greater than or equal to 200 keV during the ion implantation in the substrate.

[0015] As a preferred scheme of the method for preparing a titanium sapphire thin film by ion implantation and exfoliation, the thickness of the thick film is greater than or equal to 100 nm and less than or equal to 1 μm.

[0016] As a preferred scheme of the method for preparing a titanium sapphire thin film by ion implantation and exfoliation, the material of the substrate is single crystal silicon, thermal oxide, silicon carbide, or diamond.

[0017] As a preferred scheme of the method for preparing a titanium sapphire thin film by ion implantation and exfoliation, the specific method for exfoliating part of the substrate along the defect layer is to perform annealing treatment on the substrate with the defect layer formed thereon.

[0018] As a preferred scheme of the method for preparing a titanium sapphire thin film by ion implantation and exfoliation, the annealing process is performed in a vacuum environment or in a protective atmosphere formed by at least one of nitrogen and inert gas, the annealing temperature is 300-1200 °C, and the annealing time is 1 minute-10 hours.

[0019] As a preferred scheme of the method for preparing a titanium sapphire thin film by ion implantation and exfoliation, the specific method for exfoliating part of the substrate along the defect layer further includes the step of applying a transverse mechanical force to the defect layer after the annealing treatment on the substrate.

[0020] As a preferred scheme of the method for preparing a titanium sapphire thin film by ion implantation and exfoliation, the specific method for exfoliating part of the substrate along the defect layer further includes the step of exfoliating the defect layer by performing phosphoric acid bath etching on the substrate.

[0021] As a preferred scheme of the method for preparing a titanium sapphire thin film by ion implantation and exfoliation, the specific method for exfoliating part of the substrate along the defect layer further includes the step of maintaining the annealing temperature and rapidly cooling the substrate after depositing an auxiliary material layer on the implanted surface of the substrate after the annealing treatment on the substrate; wherein the auxiliary material layer has a different thermal expansion coefficient from the substrate.

[0022] As a preferred scheme of the method for preparing a titanium sapphire thin film gain device, the Si3N4 layer with a thickness of 100-500 nm is obtained by using an LPCVD film plating process.

[0023] As a preferred scheme of the preparation method of the titanium sapphire thin film gain device, the Si3N4 waveguide is microprocessed by using electron beam exposure, femtosecond laser direct writing or inductively coupled plasma etching.

[0024] As a preferred scheme of the preparation method of the titanium sapphire thin film gain device, the Si3N4 waveguide is microprocessed by using electron beam exposure, femtosecond laser direct writing or inductively coupled plasma etching.

[0025] The titanium sapphire thin film prepared by the ion implantation stripping method has the advantages that multiple films can be separated from a titanium sapphire and repeatedly used in a film transfer process, the recycling rate is greater than or equal to 90%, and the production cost is reduced; the composite structure of the Si3N4 waveguide and the SiO2 cladding layer obtained after film plating and microprocessing supports 650-900 nm broadband optical amplification, the peak gain is greater than or equal to 1.2 dB / cm, and the device size is small enough, less than 5 mm. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 FIG. 1 is a schematic diagram of the ion implantation stripping method for preparing a titanium sapphire thin film according to the present application.

[0027] Figure 2 FIG. 3 is a schematic diagram of a waveguide amplifier based on the Si3N4 thin film grown on the prepared titanium sapphire thin film.

[0028] Figure 3 FIG. 5 is an SEM image of the substrate after ion implantation in the ion implantation stripping method for preparing a titanium sapphire thin film according to the present application.

[0029] Figure 4 FIG. 7 is a test diagram of the titanium sapphire-SiN waveguide amplifier under 532 nm pump light excitation.

[0030] Figure 5 FIG. 8 is a titanium sapphire thin film obtained by using the ion implantation stripping method for preparing a titanium sapphire thin film according to the present application.

[0031] Figure 6 FIG. 10 is a gain test diagram of a bare chip device.

[0032] FIG. 11 is a diagram of internal components.

[0033] 10: titanium sapphire single crystal wafer

[0034] 11: stripped film layer

[0035] 12: implantation damage layer

[0036] 13: substrate

[0037] 14: recyclable remaining titanium sapphire single crystal wafer

[0038] 15: polished titanium-sapphire thin film

[0039] 16: deposition of SiN waveguide layer

[0040] 17: deposition of SiO2 cladding layer

[0041] 18: device structure DETAILED DESCRIPTION

[0042] The technical solutions of the present application will be further described below in conjunction with examples and drawings, but the protection scope of the present application should not be limited thereby.

[0043] Example 1

[0044] 1) Sample preparation: titanium-sapphire single crystal wafer is provided, polished using CMP to make the surface roughness Ra < 0.5 nm;

[0045] 2) Ion implantation: the surface treated in step 1) is the implantation surface, ion implantation is performed in the titanium-sapphire wafer, the energy of ion implantation is sufficient to make the implanted ions reach a preset depth, and a defect layer 12 is formed at the preset depth;

[0046] 3) Bonding: the implantation surface of the titanium-sapphire single crystal in step 2) is bonded to the provided sapphire single crystal wafer after surface activation;

[0047] High-temperature annealing treatment is performed, the titanium-sapphire thin film is peeled off along the defect layer and transferred to the sapphire substrate, and the thickness of the thin film is controlled to be less than 1 μm;

[0048] 4) Si3N4 film plating: the titanium-sapphire thin film in step 3) is selected for LPCVD film plating in the complete and flat area, a silicon nitride (Si3N4) waveguide layer is deposited on the surface of the titanium-sapphire thin film, and a waveguide structure is formed through a photoetching or etching process;

[0049] The geometric parameters of the Si3N4 waveguide are optimized, including width (W = 1000 nm) and height (H = 150 nm);

[0050] 5) Deposition of cladding layer: a silicon dioxide (SiO2) cladding layer is deposited on the Si3N4 waveguide in step 4), and the integration of the gain device is completed;

[0051] Figure 5 is the titanium-sapphire thin film obtained in example 1 of the present application, the surface roughness Ra of the subsequent test is ~ 2 nm, the areas with high local integrity are selected for steps 4) and 5), the titanium-sapphire thin film gain device with Si3N4 as the waveguide is completed, and the parameters of the waveguide are continuously optimized to enhance the light field restriction factor (Γ≥75%), and the Ti 3+Ion energy level transition, realizing 650-900 nm broadband optical amplification, peak gain up to 1.2 dB / cm.

[0052] Example 2

[0053] According to He injection dose of 5E16cm -2 , the annealing temperature after bonding is 600℃, the geometric parameters of Si3N4 waveguide are optimized, including width (W=1000nm) and height (H=150nm), and other conditions are the same as in Example 1, titanium-sapphire thin film gain device can be obtained.

[0054] Example 3

[0055] According to He injection dose of 2E17cm -2 , the annealing temperature after bonding is 600℃, the geometric parameters of Si3N4 waveguide are optimized, including width (W=1000nm) and height (H=150nm), and other conditions are the same as in Example 1, titanium-sapphire thin film gain device can be obtained.

[0056] Example 4

[0057] According to He injection dose of 3E17cm -2 , the annealing temperature after bonding is 600℃, the geometric parameters of Si3N4 waveguide are optimized, including width (W=1000nm) and height (H=150nm), and other conditions are the same as in Example 1, titanium-sapphire thin film gain device can be obtained.

[0058] Example 5

[0059] According to H / He co-injection dose of 1E17cm -2 , the annealing temperature after bonding is 600℃, the geometric parameters of Si3N4 waveguide are optimized, including width (W=1000nm) and height (H=150nm), and other conditions are the same as in Example 1, titanium-sapphire thin film gain device can be obtained.

[0060] Example 6

[0061] According to He injection dose of 2E17cm -2 , the annealing temperature after bonding is 600℃, the geometric parameters of Si3N4 waveguide are optimized, including width (W=600nm) and height (H=100nm), and other conditions are the same as in Example 1, titanium-sapphire thin film gain device can be obtained.

[0062] Example 7

[0063] According to He injection dose of 2E17cm -2, the annealing temperature after bonding is 600℃, the geometry parameters of Si3N4 waveguide are optimized, including width (W=600nm) and height (H=150nm), and other conditions are the same as those in Embodiment 1, and a titanium-sapphire thin film gain device can be obtained.

[0064] Embodiment 8

[0065] According to the He injection dose of 2E17cm -2 , the annealing temperature after bonding is 500℃, the geometry parameters of Si3N4 waveguide are optimized, including width (W=600nm) and height (H=200nm), and other conditions are the same as those in Embodiment 1, and a titanium-sapphire thin film gain device can be obtained.

[0066] Embodiment 9

[0067] According to the He injection dose of 2E17cm -2 , the annealing temperature after bonding is 500℃, the geometry parameters of Si3N4 waveguide are optimized, including width (W=1000nm) and height (H=150nm), and other conditions are the same as those in Embodiment 1, and a titanium-sapphire thin film gain device can be obtained.

[0068] According to other conditions stated in the claims of the present application, titanium-sapphire thin films and wideband gain devices with Si3N4 waveguide of different qualities can also be obtained, which are not listed here, but do not affect the protection scope of the claims of the present application.

Claims

1. A method for preparing a titanium-sapphire thin film based on ion implantation exfoliation and homo-bonding, characterized in that, The method comprises the following steps: Step 1. providing a titanium sapphire (Ti:Al2O3) single crystal wafer; Step 2. ion implantation is performed on the polished surface of the titanium sapphire single crystal wafer to form an implantation damage layer at a preset depth; Step 3. providing a sapphire single crystal wafer which is surface-activated and then bonded to the implantation damage layer of the titanium sapphire single crystal wafer obtained in step 2; Step 4. annealing the bonded composite structure at high temperature to cause the implantation damage layer to peel off, thereby obtaining a titanium sapphire thin film with a thickness of less than 1 μm.

2. The method of claim 1, wherein the titanium-based thin film is prepared by ion implantation and epitaxial growth. The ion implantation in step (2) employs He + ions or H + ions, when He + ions are employed, the implantation energy is > 100 keV, when H + ions are employed, the implantation energy is > 200 keV.

3. The method of claim 1, wherein the ion implantation is performed by using a titanium target. In step (3), the plasma activation treatment uses one of Ar, N2 or O2 as the activation gas, the activation time is 1-10 minutes, and the activation power is 50-200 W.

4. The method of claim 1, wherein the titanium-based thin film is formed by ion implantation and epitaxial growth. In step (4), the high-temperature annealing treatment further comprises applying a pressure of 0.01-1 MPa during annealing to enhance the bonding strength of the bonding interface.

5. The method of claim 1, wherein the titanium-based thin film is formed by ion implantation and epitaxial growth. The Si3N4 waveguide layer is deposited by low-pressure chemical vapor deposition (LPCVD), has a thickness of 100-200 nm, and a refractive index of ≥1.

9.

6. The method of claim 1, wherein: The optical field confinement factor (Γ) is optimized by finite element method simulation to ensure that the overlap rate of the mode fields of the pump light and the signal light in the titanium sapphire active layer is ≥40%.

7. The method of claim 1, wherein the titanium-sapphire thin film is prepared by ion implantation and epitaxial growth. The remaining titanium sapphire single crystal wafer obtained in step 4 can be repeatedly used for thin film preparation in steps 1-4.

8. The method according to any one of claims 1 to 7, wherein the titanium thin film is formed by ion implantation and epitaxial growth. The method comprises the following steps: Step 5. depositing a silicon nitride (Si3N4) waveguide layer on the surface of the titanium sapphire thin film, and forming a waveguide structure by photolithography and etching process; Step 6. depositing a silicon dioxide (SiO2) cladding layer on the surface of the waveguide structure to complete device packaging.

9. A titanium sapphire gain device prepared by the method of claim 8, wherein, The method comprises the following steps: a sapphire substrate; A titanium sapphire thin film with a thickness less than 1 μm is arranged on a sapphire substrate, Ti 3+ The doping concentration is 1×10 24 ~1×10 25 m -3 The crystal defect density is ≤10 6 cm -2 ; a Si3N4 waveguide structure disposed on the titanium sapphire thin film, having a width of 600-1000 nm and a height of 100-200 nm; a SiO2 cladding layer covering the waveguide structure.

10. The titanium sapphire gain device of claim 9, wherein, The device supports 650-900 nm broadband optical amplification, has a peak gain of ≥1.2 dB / cm, and a size of ≤1 cm×1 cm.

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