Method for inhibiting ion beam induced chromium / lithium tantalate interface foaming based on thickening and annealing composite process

Abstract

The invention relates to a method for inhibiting ion beam induced chromium / lithium tantalate interface foaming based on a thickening and annealing composite process. Comprising the following steps: (1) cleaning a cut lithium tantalate film; (2) depositing a chromium mask on the lithium tantalate film through a magnetron sputtering method to obtain coated lithium tantalate; (3) carrying out annealing treatment on the coated lithium tantalate; (4) etching a micro-nano structure on the annealed lithium tantalate film by using a focused ion beam; and (5) the chromium mask is removed, and after cleaning, processing of the device is completed. According to the method provided by the invention, ions are effectively prevented from penetrating to the chromium / lithium tantalate interface through the thickening mask, decomposition of organic pollutants and bubble nucleation are inhibited, structural relaxation of the film is promoted by means of annealing treatment, intrinsic tensile stress is reduced, a communicated microporous structure is formed, an escape channel is provided for interface gas, and the performance of the film is improved. Therefore, generation and expansion of bubbles are thoroughly inhibited, and the interface stability is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application relates to a method for inhibiting ion beam-induced bubbling at a lithium tantalate / lithium chromate interface based on a thickening and annealing composite process and belongs to the technical field of micro-nano integrated devices. BACKGROUND

[0002] Lithium tantalate (LiTaO3, LT) has important application value in the field of nano-photonic devices due to its excellent pyroelectric effect and nonlinear optical properties. However, when a traditional dry etching technology (such as reactive ion etching) is used, lithium fluoride particles with high melting points are easily generated, resulting in an increase in surface roughness. In contrast, focused ion beam etching removes material through a physical bombardment mechanism, which can avoid chemical reaction byproducts, thereby obtaining a smooth sidewall morphology.

[0003] When lithium tantalate is processed by a focused ion beam, a protective mask layer needs to be prepared on the surface of the lithium tantalate. The mask layer needs to have both electrical conductivity and sputtering resistance: firstly, it provides an effective charge dissipation path to inhibit local charge accumulation and the processing deviation caused thereby; and secondly, it acts as a hard mask to resist etching damage of the Gaussian distribution ion beam and ensure the fidelity of pattern transfer. Among common mask materials such as metals, oxides and nitrides, chromium film is outstanding due to its high electrical conductivity and low sputtering yield.

[0004] However, under the condition of high-energy ion beam bombardment, the mask layer is prone to structural degradation, and interface stability becomes a key limiting factor in the process. Among them, mask debonding or delamination is the main failure mode, which is mainly regulated by the interfacial bonding force and the stress state of the thin film. In particular, if low molecular weight impurities (such as hydrogen atoms or hydrogen-containing molecules) are introduced during the film forming process, solid-state diffusion and segregation behavior may be accelerated in subsequent processing (such as annealing), inducing high-pressure bubble nucleation and growth, and leading to sudden rupture of the interface. This phenomenon has been fully confirmed in aluminum oxide, silicon nitride and titanium / gold thin film systems. Ion beam bombardment itself can cause strong vibration of lattice atoms, further promoting defect aggregation and atomic migration, which theoretically provides conditions for impurity aggregation and bubble formation. However, for this specific chromium / lithium tantalate interface system, relevant mechanisms lack quantitative research, which is a major bottleneck restricting the reliable application of chromium masks.

[0005] On the other hand, intrinsic stress generated during film growth also poses a threat to the interface stability. For instance, in the case of room-temperature magnetron sputtering, the limited atomic mobility will suppress defect recovery, resulting in a high density of point defects and usually leading to tensile stress in the film; while high-energy deposition processes may generate compressive stress due to gas trapping, atomic displacement cascades or grain boundary densification. Tensile stress is prone to induce brittle crack propagation, while compressive stress often leads to buckling, wrinkling or blistering. In the ion beam etching environment, the above failure mechanisms may be further exacerbated: the radiation-enhanced defect aggregation effect, coupled with the direct and reflected acoustic wave stress induced by ion energy loss, may lead to catastrophic failure of the interface. Therefore, the coupling mechanism of stress state and defect structure is another key issue that needs to be addressed for the reliable application of chromium masks. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a method for inhibiting ion beam-induced blistering of the chromium / lithium tantalate interface based on a thickening and annealing composite process.

[0007] The technical solution of the present application is as follows:

[0008] A method for inhibiting ion beam-induced blistering of the chromium / lithium tantalate interface based on a thickening and annealing composite process, comprising the following steps:

[0009] (1) Cleaning the cut lithium tantalate film;

[0010] (2) Depositing a chromium mask on the lithium tantalate film by magnetron sputtering to obtain a plated lithium tantalate film;

[0011] (3) Annealing the plated lithium tantalate film;

[0012] (4) Etching micro-nano structures on the annealed lithium tantalate film using a focused ion beam (FIB);

[0013] (5) Removing the chromium mask and cleaning to complete the processing of the device.

[0014] According to the present application, preferably in step (1), the lithium tantalate film is z-cut or x-cut, and the thickness is 300-900 nm.

[0015] According to the present application, preferably in step (1), the cleaning is specifically as follows: first, ultrasonic cleaning the lithium tantalate film with acetone solution for 1-3 min; then, sequentially rinsing with isopropyl alcohol solution and deionized water; and finally, drying with a nitrogen gun.

[0016] According to the present application, preferably in step (2), the magnetron sputtering is performed in an Ar gas environment with a pressure of 2-3 Pa and at a power of 15-20 W to deposit a chromium mask with a thickness of 30-60 nm.

[0017] Further preferably, the magnetron sputtering method is performed in an Ar gas environment with a pressure of 2.5 Pa and at a power of 18 W to deposit a chromium mask with a thickness of 60 nm.

[0018] According to the application, preferably, in step (3), the annealing treatment is performed under the conditions of N2 atmosphere and 180-220℃ for 9 hours or more.

[0019] According to the application, preferably, in step (4), the focused ion beam is Ga + The ion beam has an acceleration voltage of 30 kV, an ion beam current of 0.2-0.3 nA, and a dwell time of 8-12 μs.

[0020] According to the application, preferably, in step (4), the etching time of the micro-nano structure is 1-3 min.

[0021] According to the application, preferably, in step (5), the specific process of removing the chromium mask and cleaning is as follows: the lithium tantalate film with the micro-nano structure etched is immersed in a mixed solution of nitric acid and cerium ammonium nitrate, soaked at room temperature for 3-5 min, and then cleaned with acetone, isopropyl alcohol and deionized water in sequence.

[0022] Further preferably, in the mixed solution of nitric acid and cerium ammonium nitrate, the concentration of nitric acid is 5-15%, and the concentration of cerium ammonium nitrate is 10-20%.

[0023] Technical features of the application:

[0024] The application further discloses a method for preparing a lithium tantalate film with a micro-nano structure.

[0025] Beneficial effects are as follows:

[0026] 1. The application provides a composite processing scheme for inhibiting interface blistering of a chromium mask on a lithium tantalate substrate under ion beam etching, which significantly improves the interface stability by increasing the chromium film thickness to more than 60 nm and combining a low-temperature annealing process of not less than 9 hours at 200 DEG C. The method not only effectively blocks the penetration of ions to the chromium / lithium tantalate interface by thickening the mask to inhibit the decomposition of organic contaminants and the nucleation of bubbles, but also promotes the structural relaxation of the film by annealing treatment to reduce the intrinsic tensile stress and form a connected microporous structure, thereby providing an escape channel for the interface gas, thereby completely inhibiting the formation and expansion of the blister.

[0027] 2. The method provided by the application based on the thickening and annealing composite process for inhibiting ion beam-induced chromium / lithium tantalate interface blistering significantly improves the etching resistance and structural integrity of the chromium mask in the ion beam processing environment, realizes effective inhibition of the interface blistering phenomenon without significantly modifying the existing process, guarantees the precision and reliability of the pattern transfer in the preparation process of the nano-optical device, and has the characteristics of strong process compatibility, clear parameters and wide applicability. The method is not only suitable for the chromium / lithium tantalate system, but also can provide technical reference for the interface stability control of other metal / ceramic film systems in ion beam processing. The method provides an economical and effective solution for the interface quality control of thin films and substrates in high-precision nanofabrication. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Ion-induced secondary electron (iSE) imaging results of the lithium tantalate micro-nano structure prepared in Examples 1-2;

[0029] In the figure, a is Example 1, and b is Example 2.

[0030] Figure 2 During the preparation of the lithium tantalate micro-nano structure in Comparative Example 1, the chromium mask was subjected to Ga + Blistering process evolution under ion beam etching;

[0031] In the figure, a-d are representative surface morphologies by ion-induced secondary electron (iSE) imaging after etching for 0, 1, 2 and 3 minutes, respectively; e is an iSE image after etching into a periodic array; all scales in the figure represent 2 microns.

[0032] Figure 3 FIB etching process simulation results of the depth distribution of Ga + Ion incident into Cr.

[0033] Figure 4 Schematic diagram of the inhibition mechanism of the annealing process on the blister formation process in Example 1;

[0034] In the figure, a is Ga +The schematic diagram of the formation process of the interface blister under ion etching; b is the schematic diagram of the mechanism of the annealing-induced formation of the gas escape channel and the realization of the blister suppression.

[0035] Figure 5 The anti-bubbling performance characterization results of the chromium films with different thicknesses and after different annealing time treatments;

[0036] In the figure, a is the iSE image of the Cr-60 mask after ion beam etching for 0, 3, 6 min; b is the iSE image of the Cr-30 film after annealing at 200℃ for 1, 4, 9 h, and then ion beam etching for 2 min; the scale in the figure represents 2 μm.

[0037] Figure 6 The nanoindentation analysis results of the residual stress evolution of the lithium tantalate micro-nano structure prepared in Example 3 during annealing;

[0038] In the figure, a is the schematic diagram of the indentation morphology corresponding to different residual stress types in the theoretical model; b is the load-displacement curve of the Cr-30 mask after annealing at 200℃ for 0, 9, 36 h.

[0039] Figure 7 The microstructure characterization results of the Cr-30 mask of the plated lithium tantalate before and after annealing in Example 1;

[0040] In the figure, a and b are the bright field image and Z-contrast image of the transmission electron microscope (TEM) of the plated film before annealing, showing a typical columnar crystal structure; c and d are the bright field image and Z-contrast image of the TEM of the plated film after annealing at 200℃ for 9 h; e and f are the energy spectrum area distribution maps of the chromium element and the carbon element in the region b; g and h are the energy spectrum area distribution maps of the chromium element and the carbon element in the region f; all the scales in the figure represent 20 nm. Figure 7 b is the energy spectrum area distribution map of the chromium element and the carbon element in the region; e and f are the bright field image and Z-contrast image of the TEM of the plated lithium tantalate after annealing at 200℃ for 9 h; g and h are the energy spectrum area distribution maps of the chromium element and the carbon element in the region f; all the scales in the figure represent 20 nm. Figure 7 f is the energy spectrum area distribution map of the chromium element and the carbon element in the region; e and f are the bright field image and Z-contrast image of the TEM of the plated lithium tantalate after annealing at 200℃ for 9 h; g and h are the energy spectrum area distribution maps of the chromium element and the carbon element in the region f; all the scales in the figure represent 20 nm.

[0041] Specific experimental methods

[0042] The present application is further described below in conjunction with specific examples, but is not limited thereto. The raw materials used in the examples are all conventional raw materials, which are commercially available, unless otherwise specified; the methods are all prior art, unless otherwise specified.

[0043] In the examples, the lithium tantalate thin film used is commercially available from Jinzheng Electronics Technology Co., Ltd. in Jinan. The tangent can be z tangent or x tangent, the thickness is 300-900 nm, the lower layer of the thin film has a 2-5 μm thick SiO2 layer, and the further lower layer is a 250-300 μm thick lithium tantalate or silicon substrate. Any combination of the parameters of the tangent, the pad layer and the substrate is applicable to the processing method proposed in the present application.

[0044] The tangential direction is z-cut or x-cut, the thickness is 300-900 nm, the lower layer of the thin film is a 2-5 μm thick SiO2 layer, and the lower layer is a 300 μm thick lithium tantalate or silicon substrate. Any combination of the above parameters related to the tangential direction, the pad layer and the substrate is suitable for the processing method proposed in the present application.

[0045] The magnetic control sputtering instrument used is a B22-068 type high vacuum three-chamber magnetic control sputtering thin film deposition system produced by Shenyang Scientific Instrument Co., Ltd., Chinese Academy of Sciences.

[0046] The model of the focused ion beam instrument used is Thermo-Fisher Helios 5.

[0047] Example 1

[0048] A method for inhibiting ion beam-induced bubbling at the chromium / lithium tantalate interface based on a thickening and annealing composite process, comprising the following steps:

[0049] (1) The cut lithium tantalate film is first cleaned with an acetone solution for 2 min, then rinsed with isopropanol solution and deionized water, and finally dried with a nitrogen gun;

[0050] (2) A chromium mask (Cr-30 mask) with a thickness of 30 nm is deposited on the lithium tantalate film by magnetic control sputtering at a power of 18 W in an Ar gas environment with a pressure of 2.5 Pa, to obtain a plated lithium tantalate film;

[0051] (3) The plated lithium tantalate film is annealed at 200°C for 9h in a N2 atmosphere;

[0052] (4) A focused ion beam (FIB) is used to etch micro-nano structures on the annealed lithium tantalate film;

[0053] The focused ion beam is Ga + , the acceleration voltage is 30 kV, the ion beam current is 0.23 nA, the dwell time is 10 μs, and the etching time is 2 min;

[0054] (5) At room temperature, the sample is soaked in a mixed solution of nitric acid and cerium ammonium nitrate for 3 min, and then cleaned with acetone, isopropanol and deionized water in sequence to complete the structure preparation;

[0055] The concentration of nitric acid in the mixed solution of nitric acid and cerium ammonium nitrate is 10%, and the concentration of cerium ammonium nitrate is 15%.

[0056] Example 2

[0057] A method for inhibiting ion beam-induced bubbling at the chromium / lithium tantalate interface based on a thickening and annealing composite process, comprising the following steps:

[0058] (1) The cut lithium tantalate film is first cleaned with an acetone solution for 2 min by ultrasonic cleaning; then it is rinsed with isopropanol solution and deionized water in sequence, and finally dried by nitrogen gun;

[0059] (2) A chromium mask (Cr-60 mask) with a thickness of 60 nm is deposited on the lithium tantalate film by magnetron sputtering method under the conditions of an Ar gas environment with a pressure of 2.5 Pa and a power of 18 W, to obtain a coated lithium tantalate film;

[0060] (3) The coated lithium tantalate film is annealed at 200℃ for 9 h in a N2 atmosphere;

[0061] (4) A focused ion beam (FIB) is used to etch a micro-nano structure on the annealed lithium tantalate film;

[0062] The focused ion beam is Ga + , the acceleration voltage is 30 kV, the ion beam current is 0.23 nA, and the dwell time is 10 μs; the etching time is 2 min;

[0063] (5) The sample is soaked in a mixed solution of nitric acid and cerium ammonium nitrate at room temperature for 5 min, and then cleaned with acetone, isopropanol and deionized water in sequence to complete the structure preparation;

[0064] The concentration of nitric acid in the mixed solution of nitric acid and cerium ammonium nitrate is 10%, and the concentration of cerium ammonium nitrate is 15%.

[0065] Example 3

[0066] A method for inhibiting ion beam-induced bubbling at the chromium / lithium tantalate interface based on a thickening and annealing combined process, the specific steps are as in Example 1, except that in step (3), the annealing time of the coated lithium tantalate film is 36 h.

[0067] Comparative Example 1

[0068] A method for preparing a lithium tantalate micro-nano structure, comprising the following steps:

[0069] (1) The cut lithium tantalate film is first cleaned with an acetone solution for 2 min by ultrasonic cleaning; then it is rinsed with isopropanol solution and deionized water in sequence, and finally dried by nitrogen gun;

[0070] (2) A chromium mask (Cr) with a thickness of 30 nm is deposited on the lithium tantalate film by magnetron sputtering method under the conditions of an Ar gas environment with a pressure of 2.5 Pa and a power of 18 W, to obtain a coated lithium tantalate film;

[0071] (3) A focused ion beam (FIB) is used to etch a micro-nano structure on the lithium tantalate film;

[0072] The focused ion beam is Ga + The acceleration voltage is 30 kV, the ion beam current is 0.23 nA, and the dwell time is 10 s; the etching time is 2 min.

[0073] (4) At room temperature, the sample is soaked in a mixed solution of nitric acid and cerium ammonium nitrate for 5 min, and then cleaned with acetone, isopropanol and deionized water in sequence to complete the structure preparation.

[0074] In the mixed solution of nitric acid and cerium ammonium nitrate, the concentration of nitric acid is 10%, and the concentration of cerium ammonium nitrate is 15%.

[0075] Compared with Example 1, Comparative Example 1 does not undergo annealing treatment, which is equivalent to an annealing time of 0 h; compared with Example 2, the Cr film thickness of Comparative Example 1 is thinner.

[0076] Test Example

[0077] 1. The lithium tantalate micro-nano structure prepared in Examples 1-2 is subjected to ion-induced secondary electron (iSE) imaging, and the results are shown in Figure 1 .

[0078] During the preparation of the lithium tantalate micro-nano structure in Comparative Example 1, the representative surface morphology of the lithium tantalate micro-nano structure ion-induced secondary electron (iSE) imaging after etching for 0, 1, 2 and 3 minutes is recorded in sequence, and the chromium mask is under Ga + ion beam etching.The evolution of the blistering process under Ga Figure 2 ion beam etching is shown in a-d, and the iSE image after etching into a periodic array is shown in e. Figure 2

[0079] As can be seen from Figures 1-2 , the annealing or thickening Cr film treatment introduced in the present application can significantly inhibit mask blistering, solve the blistering and rupture problem of the chromium mask on the lithium tantalate substrate caused by interface organic gasification and stress accumulation during ion beam etching, and effectively guarantee the structural integrity and processing precision of the nano device through a composite process.

[0080] This is because: the blistering phenomenon at the chromium / lithium tantalate interface is mainly caused by the inevitable residual organic contaminants on the surface of the lithium tantalate substrate during the production of the thin film. Annealing treatment can significantly inhibit interface blistering, which is accompanied by a decrease in tensile stress in the thin film and the formation of a microporous structure.

[0081] 2、In the process of thin film deposition, the damage mechanism is usually closely related to the residual stress, so it is necessary to analyze the influence of stress on the blistering behavior first. In the process of magnetron sputtering, atoms undergo a transition from disorder to order, which can spontaneously introduce vacancy defects. The present application is deposited at room temperature far below the melting point of chromium (1907℃), and the self-diffusion process is inhibited, and vacancies cannot be fully annihilated, thereby leading to the formation of tensile stress. According to the elastic deformation volume invariable assumption, the in-plane tensile strain will lead to out-of-plane shrinkage, and this mechanical mechanism is more inclined to promote the formation of cracks or holes, rather than the development of wrinkles or blisters. Therefore, from the mechanical mechanism, the residual stress is not the dominant factor of the interface blistering in this case.

[0082] Combined with the preparation process, there are two kinds of impurities that can be introduced into the sample: one is argon gas that can be embedded in the film during the sputtering process, but the SIMS composition analysis has confirmed that the sample does not contain Ar; even if there is trace Ar (below the ppm level detection limit), such low concentration is difficult to induce macroscopic blistering. The second is organic contaminants such as ethanol and acetone remaining during the cleaning process of the lithium tantalate substrate. Because the surface of lithium tantalate is covered with O 2 -ions are easy to form hydroxyl groups, which can adsorb organic molecules. Therefore, the present application simulates the depth distribution of Ga + ions incident on Cr by SRIM simulation software, and the results are shown in Figure 3 .

[0083] According to the theoretical calculation of Figure 3 , the penetration depth of 30keV Ga + ions in chromium is about 33nm, which is comparable to the thickness of the chromium mask (30nm). Ion etching can induce the decomposition of organic matter at the interface into low molecular weight hydrocarbons, and then induce blistering. At the same time, the tensile stress state and high vacancy density structure together enhance the atomic diffusion behavior, promote gas aggregation and subsequent blister evolution. Increasing the thickness of the chromium mask to more than 30nm (such as 60nm) can effectively block the damage of the ion beam to the interface organic matter, thereby avoiding blistering.

[0084] 3、The present application further simulates the inhibition mechanism of the annealing treatment in Example 1 on the blistering formation process by image, as shown in Figure 4 .

[0085] According to the theoretical calculation of Figure 4It can be seen that the annealing process not only inhibits the solid-state diffusion of gas molecules, but also establishes a percolation channel for gas escape. There are a large number of vacancy-type defects in the chromium mask deposited at room temperature, which gradually annihilate during the annealing process. Since atomic diffusion in a solid is mainly achieved through a vacancy exchange mechanism, vacancy annihilation reduces the probability of gas molecule aggregation. It is particularly worth noting that when vacancies annihilate through a coalescence mechanism, they will produce a considerable free volume, which explains the formation of a surface-connected porous structure in the chromium mask after annealing. Such connected channels provide an effective escape path for the gas, avoiding its accumulation at the interface, thereby effectively inhibiting the disorderly expansion of blistering.

[0086] 4、To illustrate the formation mechanism of blistering at the interface of the chromium mask, the etching time in step (4) of Example 2 is adjusted to 0, 3, and 6 minutes, respectively, and then ion beam imaging is performed on the surface of the etched lithium tantalate at different time points to investigate the anti-bubbling performance of chromium films of different thicknesses, as shown in Figure 5 a.

[0087] As can be seen from Figure 5 a, even if the etching time is extended to 3 minutes, no blistering morphology appears on the surface of the plated lithium tantalate; further extending the etching time to 6 minutes still does not observe the nucleation of blistering, which fully proves that when the thickness of the chromium mask is not less than 60 nm, the interface blistering can be completely inhibited.

[0088] The above thickness-dependent inhibition effect clearly rules out the blistering mechanism dominated by bulk materials (which is expected to occur uniformly under different film thicknesses), indicating that the blistering phenomenon is essentially related to the physical and chemical processes at the chromium / lithium tantalate interface. Since blistering behavior usually involves diffusion and other kinetic processes, it is reasonable to speculate that annealing can further inhibit blistering by affecting the diffusion of atoms or gas molecules.

[0089] To verify this speculation, the annealing time in step (3) of Example 1 is adjusted to 1, 4, and 9 hours, respectively, and then ion beam imaging is performed on the surface of the etched lithium tantalate at different annealing times to investigate the anti-bubbling performance of different annealing time treatments, as shown in Figure 5 a.

[0090] As can be seen from Figure 5 b, the blistering density monotonically decreases with increasing annealing time. After 1 hour and 4 hours of annealing, the blistering gradually decreases, and after 9 hours, the blistering can be completely inhibited. This shows that even at a relatively low annealing temperature (about 0.22 times the melting point of chromium), this process can still effectively avoid the blistering problem in the chromium / lithium tantalate system.

[0091] 5. This invention uses nanoindentation technology to quantitatively characterize the residual stress evolution of the chromium mask during the annealing process in step (3) of Example 3. The maximum indentation depth was controlled at approximately 20 nm during the test. Although this depth exceeds the critical threshold for avoiding substrate interference (usually required to be less than 1 / 10 of the film thickness), making accurate stress calculation based on theoretical models such as Suresh-Giannakopoulos impossible, effective qualitative evaluation can still be performed based on the stress-deformation coupling principle. The results are as follows: Figure 6 As shown.

[0092] Depend on Figure 6 It is known that, under the same indentation load conditions, the tensile stress state significantly reduces the material's resistance to indenter penetration, specifically manifested as a larger indentation displacement (ht>hc, see [reference]). Figure 6 a) As the annealing time increased from 0 hours to 9 hours and then to 36 hours, the load-displacement curves showed a systematic leftward shift. Under a standard load of 150 μN, the indentation displacement increased by 14.5 nm, 12.4 nm, and 10.8 nm, respectively, indicating that the tensile residual stress in the film continued to relax during the annealing process and approached a stress-free stable state after 36 hours of treatment (ht>hc, see [reference]). Figure 6 b).

[0093] The stress evolution behavior is consistent with the predictions of the Thornton region model: sputtered films deposited under high argon pressure (>0.5 Pa) exhibit a microporous structure with tensile properties due to the atomic shadowing effect, and thermal annealing can effectively promote stress release and structural relaxation. This finding provides a key theoretical basis for the annealing process used in this invention.

[0094] 6. To elucidate the interfacial bubbling mechanism, this invention used transmission electron microscopy (TEM) to characterize the microstructure of the Cr-30 mask before and after annealing in Example 1. The results are as follows: Figure 7 As shown.

[0095] Depend on Figure 7 As can be seen from a to c, both the bright-field image and the Z-contrast image of the deposited chromium mask exhibit a typical columnar crystal structure. Figure 7 (a, 7b) have grain boundaries perpendicular to the substrate interface. The corresponding chromium element distribution shows the presence of linear chromium-deficient regions along the columnar grain boundaries. Figure 7 c) indicates that the region is a structurally weak area.

[0096] Depend on Figure 7 From a to g, it can be seen that there is a significant low-contrast region at the chromium / lithium tantalate interface. Figure 7 b) Energy dispersive spectroscopy analysis confirmed the presence of carbon enrichment at this location. Figure 7d), consistent with the characteristics of organic contaminants adsorbed on the original substrate surface. After annealing at 200 °C for 9 h, the columnar crystal morphology was maintained, but a tubular nanopore structure was formed along the grain boundaries Figure 7 e, 7f). Elemental mapping of chromium showed that these regions were in a near- complete chromium-depleted state Figure 7 g), confirming the formation of a porous channel network throughout the film thickness. In addition, the interfacial organic residues were present, although their morphology had changed.

[0097] The above results clearly reveal that the vacancy-mediated grain boundary diffusion is the dominant mechanism: vacancies condense through the grain boundaries to form a connected pore structure during annealing, not only providing an escape channel for organic decomposition gas, but also effectively relaxing the tensile stress in the film through vacancy annihilation, thereby inhibiting the generation and development of interfacial blistering. This microscopic mechanism provides an important structural theoretical basis for the annealing process used in the present application.

Claims

1. A method for suppressing ion beam induced blistering at a lithium tantalate / chromium interface based on a thickening and annealing composite process, characterized in that, The method comprises the following steps: (1) cleaning the cut lithium tantalate film; (2) depositing a chromium mask on the lithium tantalate film by a magnetron sputtering method to obtain a plated lithium tantalate film; (3) annealing the plated lithium tantalate film; (4) etching a micro-nano structure on the annealed lithium tantalate film using a focused ion beam (FIB); (5) removing the chromium mask and cleaning to complete the processing of the device.

2. The method of claim 1, wherein, In step (1), the lithium tantalate film is z-cut or x-cut, and the thickness is 300-900 nm.

3. The method of claim 1, wherein, In step (1), the cleaning is specifically as follows: first, ultrasonic cleaning the lithium tantalate film with an acetone solution for 1-3 min; then, sequentially rinsing with an isopropanol solution and deionized water; and finally, drying with a nitrogen gun.

4. The method of claim 1, wherein, In step (2), the magnetron sputtering method is performed in an Ar gas environment with a pressure of 2-3 Pa and at a power of 15-20 W to deposit a chromium mask with a thickness of 30-60 nm.

5. The method of claim 4, wherein, The magnetron sputtering method is performed in an Ar gas environment with a pressure of 2.5 Pa and at a power of 18 W to deposit a chromium mask with a thickness of 60 nm.

6. The method of claim 1, wherein, In step (3), the annealing treatment is performed at 180-220 ℃ in a N2 atmosphere for 9 h or more.

7. The method of claim 1, wherein, In step (4), the focused ion beam is Ga + The ion beam has an acceleration voltage of 30 kV, an ion beam current of 0.2-0.3 nA, and a dwell time of 8-12 μs.

8. The method of claim 1, wherein, In step (4), the etching time of the micro-nano structure is 1-3 min.

9. The method of claim 1, wherein, In step (5), the specific process of removing the chromium mask and cleaning is as follows: immersing the lithium tantalate film etched with the micro-nano structure in a mixed solution of nitric acid and cerium ammonium nitrate, soaking at room temperature for 3-5 min, and then sequentially cleaning with acetone, isopropanol, and deionized water.

10. The method of claim 9, wherein, In the mixed solution of nitric acid and cerium ammonium nitrate, the concentration of nitric acid is 5-15%, and the concentration of cerium ammonium nitrate is 10-20%.

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