Thin film structure, preparation method thereof and electronic device

Abstract

The invention provides a thin film structure, a preparation method thereof and an electronic device, and relates to the technical field of semiconductor elements. The thin film structure comprises a supporting structure and a thin film layer arranged on the supporting structure. The thin film layer comprises a lithium niobate thin film layer and a doped lithium niobate thin film layer which are arranged in parallel. The resistance of the lithium niobate crystal can be reduced, the electro-optical modulation efficiency of the electronic device can be ensured, and the performance of the electronic device is further improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device technology, and more particularly to a thin film structure and a method for preparing the same, and an electronic device. Background Art

[0002] Electro-optic modulators are the core components of optical communication systems. With the increasing demand for communication capacity and speed, the new generation of electro-optic modulators must meet the requirements of high integration density, low cost and high performance. Lithium niobate crystals have attracted much attention due to their good physical and chemical stability, wide low optical loss window and large linear electro-optic coefficient. However, in practical applications, electro-optic modulators are affected by external conditions such as changes in temperature and humidity, abnormal physical stress and external interference electric fields, which can cause phase drift and the DC bias operating point of the device to drift. This is the "DC drift" phenomenon. When the operating point of the modulator with DC drift falls in the nonlinear region, the modulated optical signal will be distorted, resulting in device failure and limiting the practical application of the device.

[0003] In order to suppress DC drift, the related technology usually reduces the resistance of the lithium niobate crystal; however, while reducing the resistance of the lithium niobate crystal, it will also cause the electro-optical modulation efficiency of the electro-optical modulator to decrease, thereby reducing the performance of the electro-optical modulator. Summary of the invention

[0004] In view of the above problems, the embodiments of the present application provide a thin film structure and a preparation method thereof, and an electronic device, which can reduce the resistance of the lithium niobate crystal while ensuring the electro-optical modulation efficiency of the electronic device, thereby improving the performance of the electronic device.

[0005] A first aspect of an embodiment of the present application provides a thin film structure, comprising:

[0006] A support structure and a film layer disposed on the support structure;

[0007] The thin film layer includes a lithium niobate thin film layer and a doped lithium niobate thin film layer arranged in parallel.

[0008] In a possible implementation, the thin film layer includes a waveguide structure, and the waveguide structure spans the lithium niobate thin film layer and the doped lithium niobate thin film layer.

[0009] In a possible implementation manner, the lithium niobate thin film layer and the doped lithium niobate thin film layer are arranged along a first direction.

[0010] In a possible implementation, the support structure is a strip structure; the first direction is the length direction of the support structure, and the dimensions of the lithium niobate thin film layer and the doped lithium niobate thin film layer in the second direction are equal to the width of the support structure;

[0011] Alternatively, the first direction is the width direction of the support structure, and the dimensions of the lithium niobate thin film layer and the doped lithium niobate thin film layer in the second direction are equal to the length of the support structure;

[0012] The first direction intersects with the second direction.

[0013] A second aspect of an embodiment of the present application provides a method for preparing a thin film structure, comprising:

[0014] Providing a lithium niobate wafer and a doped lithium niobate wafer arranged side by side along a first direction;

[0015] Bonding the lithium niobate wafer and the doped lithium niobate wafer in parallel to form a bonding structure; wherein the top surface of the lithium niobate wafer is flush with the top surface of the doped lithium niobate wafer;

[0016] Performing an ion implantation process on the bonding structure so that the bonding structure forms a thin film layer, an implantation layer and a residual layer which are stacked;

[0017] The thin film layer of the bonding structure after the ion implantation process is bonded to the support structure, and the implantation layer and the residual layer are removed to form a bonding body; wherein the thin film layer includes a lithium niobate thin film layer and a doped lithium niobate thin film layer arranged in parallel.

[0018] In a possible implementation, the method further includes patterning the thin film layer of the bonding body to form a waveguide structure in the thin film layer, wherein the waveguide structure spans the lithium niobate thin film layer and the doped lithium niobate thin film layer.

[0019] In a possible implementation, the lithium niobate wafer has a first bonding surface, and the doped lithium niobate wafer has a second bonding surface;

[0020] After the step of providing the lithium niobate wafer and the doped lithium niobate wafer arranged in parallel, and before the step of performing an ion implantation process on the bonding structure, the method further includes:

[0021] The first bonding surface and the second bonding surface are respectively activated to improve the activities of the first bonding surface and the second bonding surface.

[0022] In a possible implementation, the support structure is a strip structure;

[0023] The first direction is the length direction of the supporting structure; or, the first direction is the width direction of the supporting structure.

[0024] In a possible implementation, before the step of bonding the thin film layer of the bonding structure after ion treatment to the support structure, the following steps are further included:

[0025] providing a substrate;

[0026] A capture layer and an isolation layer are stacked on the substrate. The capture layer and the isolation layer are made of different materials, and the capture layer has a thickness of 300nm to 5000nm.

[0027] In a possible implementation manner, the step of bonding the thin film layer of the bonding structure after ion treatment to the support structure further includes:

[0028] The bonded bonding structure and the supporting structure are subjected to at least one heat treatment process to peel off the implantation layer and the residual layer of the bonding structure.

[0029] In a possible implementation, a first heat treatment process is performed on the bonded bonding structure and the supporting structure to peel off the injection layer and the residual layer; wherein the temperature of the first heat treatment process is 100° C. to 600° C., and the heat treatment time is 1 min to 48 hrs;

[0030] A second heat treatment process is performed on the peeled bonding structure and the supporting structure, wherein the temperature of the second heat treatment process is 300° C. to 600° C., and the heat treatment time is 1 min to 100 hrs.

[0031] A third aspect of the embodiments of the present application provides an electronic device, comprising the thin film structure described in the second aspect.

[0032] In the thin film structure and preparation method thereof, and the electronic device provided in the embodiment of the present application, a lithium niobate wafer and a doped lithium niobate wafer are bonded in parallel to form a bonding structure, and the top surface of the bonded lithium niobate wafer is flush with the top surface of the doped lithium niobate wafer. In this way, the material of the bonding structure includes both lithium niobate and doped lithium niobate, so that the advantages of the two materials can be combined, and the resistance value of the formed thin film structure can be reduced by using doped lithium niobate to better suppress the drift phenomenon; the higher linear electro-optic coefficient of lithium niobate can also be used to improve the electro-optic modulation efficiency of the thin film structure, so that the electronic device has better performance in the fields of photoelectric conversion and optical signal processing.

[0033] In addition to the technical problems solved by the embodiments of the present application described above, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions, the thin film structure and its preparation method, other technical problems that can be solved by the electronic device provided by the embodiments of the present application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 Equivalent circuit diagrams of electronic devices provided for related technologies;

[0036] Figure 2 A process flow chart of a method for preparing a thin film structure provided in an embodiment of the present application;

[0037] Figure 3 A structural diagram designed in the method for preparing the thin film structure provided in the embodiment of the present application;

[0038] Figure 4 Schematic diagram of the film structure provided in the embodiment of the present application Figure 1 ;

[0039] Figure 5 Schematic diagram of the film structure provided in the embodiment of the present application Figure 2 .

[0040] Reference numerals:

[0041] 100: bonding structure; 110: lithium niobate wafer; 111: first bonding surface; 120: doped lithium niobate wafer; 121: second bonding surface; 130: film layer; 131: lithium niobate film layer; 132: doped lithium niobate film layer; 140: injection layer; 150: residual layer; 160: waveguide structure; 171: positive electrode; 172: negative electrode; 173: ground electrode; 174: signal electrode;

[0042] 200: support structure; 210: substrate; 220: capture layer; 230: isolation layer;

[0043] 300: bonding body;

[0044] 400: Thin film structure. DETAILED DESCRIPTION

[0045] DC drift is a key factor that affects the performance stability of lithium niobate electro-optic modulators and limits their practical applications. In related technologies, the DC drift performance of electro-optic modulators is usually studied using an "equivalent circuit model". Figure 1The figure shows a schematic diagram of the cross-sectional structure of a lithium niobate thin film waveguide modulator, in which a modulation voltage signal is applied to the waveguide through an Au electrode, and the modulation electric field direction is parallel to the z-axis direction of the lithium niobate crystal to utilize its maximum linear electro-optic coefficient γ 33 .

[0046] In order to study the effect of the buffer layer in the LNOI film on the DC drift phenomenon and exclude other influencing factors, no buffer layer is set between the modulation electrode and the lithium niobate film layer. The corresponding equivalent circuit model is as follows: Figure 1 As shown, where E0 is the voltage across the electrodes, V t is the voltage across the optical waveguide region, R LN1 (C LN1 ) and R LN2 (C LN2 ) are the lateral and longitudinal resistances (capacitances) of the lithium niobate film waveguide region, R SIO1 (C SIO1 ) and R SIO2 (C SIO2 ) are the lateral and longitudinal resistance (capacitance) of the buffer layer, R Sub (C Sub ) is the resistance (capacitance) of the substrate region. Similar to the equivalent circuit model of the titanium diffused waveguide modulator, the effective voltage actually applied to the optical waveguide is not constant, but varies with time. This phenomenon is called DC drift. When t→∞, V t It will tend to a stable value:

[0047]

[0048] Among them, R a is the total effective lateral resistance:

[0049]

[0050] R b is the effective lateral resistance of the buffer layer and substrate region:

[0051]

[0052] According to the equivalent circuit model and formula (1), in order to suppress the DC drift phenomenon, the simplest method is to reduce the longitudinal resistance R of the lithium niobate crystal. LN2 , so that R LN2 < <R a , thus achieving V ∞ Approaching E0.

[0053] Based on the above theory, in the related art, metal elements (Mg) are usually doped into lithium niobate crystals to significantly reduce the resistivity of lithium niobate crystals. For example, the resistivity of pure CLN crystals is 10 18-19 Ω·cm, the resistivity of MgO-doped CLN crystal is 10 12 Ω·cm, and the resistivity of lithium niobate crystal can be reduced by 6-7 orders of magnitude by doping MgO with a threshold concentration. However, compared with pure CLN crystal, the linear electro-optic coefficient γ of CLN crystal doped with MgO is 33 It drops by 20-30%, resulting in a decrease in the efficiency of electro-optical modulation.

[0054] In view of the above technical problems, the embodiments of the present application provide a thin film structure and a preparation method thereof, and an electronic device, wherein a lithium niobate wafer and a doped lithium niobate wafer are bonded in parallel to form a bonding structure, and the top surface of the bonded lithium niobate wafer is flush with the top surface of the doped lithium niobate wafer. In this way, the material of the bonding structure includes both lithium niobate and doped lithium niobate, so that the advantages of the two materials can be combined, and the resistance value of the formed thin film structure can be reduced by using doped lithium niobate to better suppress the drift phenomenon; the higher linear electro-optic coefficient of lithium niobate can also be used to improve the electro-optic modulation efficiency of the thin film structure, so that the electronic device has better performance in the fields of photoelectric conversion and optical signal processing.

[0055] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of this application.

[0056] Please refer to the attached Figure 1 and attached Figure 2 , a method for preparing a thin film structure provided in an embodiment of the present application comprises the following steps:

[0057] Step S100: providing a lithium niobate wafer and a doped lithium niobate wafer arranged in parallel along a first direction.

[0058] In this embodiment, the lithium niobate wafer 110 is a pure lithium niobate wafer and does not contain doping elements. Exemplarily, the thickness of the lithium niobate wafer 110 is 0.5 mm, and the surface of the lithium niobate wafer 110 is relatively smooth. The lithium niobate single crystal thin film material not only has the excellent properties of bulk materials, but also has a higher refractive index and contrast, thereby achieving dense integration, reducing the size of electronic devices, reducing the power consumption of electronic devices, and improving the performance of electronic devices. It is an important direction of material research and has important application value and prospects in fields such as optical fiber communications and data centers.

[0059] The doping element in the doped lithium niobate wafer 120 (Congruent Lithium Niobate, referred to as CLN) can be a metal element with high conductivity, for example, the doping element is magnesium, zinc or other metal elements. As a possible embodiment, the doping element in the doped lithium niobate wafer 120 is magnesium, and the magnesium exists in the form of oxide. Specifically, the material of the doped lithium niobate wafer 120 includes a mixture of magnesium oxide and lithium niobate, and the molar percentage concentration of the magnesium element in the doped lithium niobate wafer 120 is 5%; that is, the ratio of the molar mass of the magnesium element to the molar mass of the niobium element in the doped lithium niobate wafer 120.

[0060] In the embodiment of the present application, the lithium niobate wafer 110 and the doped lithium niobate wafer 120 are arranged side by side along a first direction. The first direction can be understood as a direction parallel to the horizontal plane, or the first direction can be any direction in the horizontal plane. For example, the first direction can be the X direction in the horizontal plane, or the Y direction in the horizontal plane, or it can be a certain angle with the X direction or the Y direction of the horizontal plane.

[0061] Step S200: bonding a lithium niobate wafer and a doped lithium niobate wafer in parallel to form a bonding structure; wherein the top surface of the lithium niobate wafer is flush with the top surface of the doped lithium niobate wafer.

[0062] Exemplarily, a bonding process is used to bond the lithium niobate wafer 110 and the doped lithium niobate wafer 120 to form a bonding structure 100. It should be understood that before bonding, the lithium niobate wafer 110 and the doped lithium niobate wafer 120 are cleaned to remove pollutants that the wafers are exposed to during production, transportation or other processes, wherein the pollutants may be dust or grease, which helps to form good chemical bonding or physical adsorption, thereby improving the strength and stability of the bonding structure.

[0063] It should be noted that the cleaning process in this embodiment may include organic solvent cleaning, ultrasonic cleaning or deionized water washing, etc. In addition, parallel bonding can be understood as the lithium niobate wafer 110 and the doped lithium niobate wafer 120 being arranged horizontally, not stacked.

[0064] In order to further improve the bonding strength between the lithium niobate wafer 110 and the doped lithium niobate wafer 120 , the embodiment of the present application further processes the bonding surfaces of the lithium niobate wafer 110 and the doped lithium niobate wafer 120 .

[0065] Exemplarily, the lithium niobate wafer 110 has a first bonding surface 111, and the doped lithium niobate wafer 120 has a second bonding surface 121. The first bonding surface 111 and the second bonding surface 121 are respectively activated to improve the activity of the first bonding surface 111 and the second bonding surface 121, so as to facilitate bonding of the first bonding surface 111 and the second bonding surface 121.

[0066] For example, oxygen plasma can be used to perform plasma activation treatment on the first bonding surface 111 and the second bonding surface 121; high-energy particles (such as oxygen atoms and oxygen ions) in the oxygen plasma bombard the surfaces of the first bonding surface 111 and the second bonding surface 121, breaking the original chemical bonds and forming new, more active chemical bonds (such as hydroxyl groups, carboxyl groups, etc.), thereby improving the bonding strength of the first bonding surface 111 and the second bonding surface 121. At the same time, the plasma can also remove trace amounts of organic matter and oxides on the surface, further cleaning the surfaces of the first bonding surface 111 and the second bonding surface 121.

[0067] Step S300: performing an ion implantation process on the bonding structure, so that the bonding structure forms a stacked thin film layer, an implantation layer and a residual layer.

[0068] The ion implantation process may be a conventional process, for example, the ion implantation process may be a plasma implantation process. The implanted ions may be ions that can generate gas through heat treatment, for example, the implanted ions may be hydrogen ions, helium ions, nitrogen ions, oxygen ions or argon ions.

[0069] It should be understood that the layer where the ions are located is the implantation layer 140, or the implantation layer 140 is the area where the implanted ions stop in the bonding structure 100. The implantation layer 140 divides the bonding structure 100 into a thin film layer 130 and a residual layer 150, wherein the residual layer 150 refers to the area that the implanted ions fail to reach during the ion implantation process, and this layer usually maintains the properties of the original material because it is not directly affected by the ions. The thin film layer 130 usually refers to the area below the implantation layer 140, which may be formed due to energy deposition and subsequent treatment (such as heat treatment) during the implantation process.

[0070] In the embodiment of the present application, the diffusion width of the injection layer 140 can be adjusted by adjusting the ion injection dose. Specifically, the larger the ion injection dose, the wider the diffusion width of the injection layer 140. On the contrary, the smaller the ion injection dose, the narrower the diffusion width of the injection layer.

[0071] In addition, the thickness of the thin film layer 130 can also be adjusted by adjusting the ion implantation depth. Specifically, the greater the depth of the ion implantation, the greater the thickness of the prepared thin film layer 130; conversely, the smaller the depth of the ion implantation, the smaller the thickness of the prepared thin film layer 130.

[0072] It should be understood that the ion implantation dose and / or implantation energy needs to be adaptively adjusted according to the type of implanted ions.

[0073] In one example, the implanted ions are hydrogen ions, and the implantation dose may be 3×10 16 ions / cm 2 ~8×10 16 ions / cm 2 , the implantation energy may be 100 keV to 400 keV. In another example, the implanted ions are helium ions, and the implantation dose may be 1×10 16 ions / cm 2 ~1×10 17 ions / cm 2 , the implantation energy can be 50keV to 1000keV. In another example, the implanted ions are argon ions. At this time, the implantation dose of the argon ions is controlled. For example, the implantation dose of the argon ions is 4×10 16 ions / cm 2 The implantation energy is such that the implantation depths of the argon ions in the lithium niobate wafer 110 and the doped lithium niobate wafer 120 are consistent.

[0074] Step S400: bonding the thin film layer of the bonding structure after the ion implantation process to the support structure, and removing the implantation layer and the residual layer to form a bonding body; wherein the thin film layer includes a lithium niobate thin film layer and a doped lithium niobate thin film layer arranged in parallel.

[0075] In this embodiment, the support structure 200 may be a single-layer support structure, such as a silicon substrate; other structures may also be used.

[0076] Exemplarily, a substrate is provided. The substrate 210 may be a silicon (Si) substrate, an epitaxial silicon (epi-Si) substrate, a silicon germanium (SiGe) substrate, a silicon carbide (SiC) substrate, or a silicon-on-insulator (SOI) substrate. Preferably, the substrate 210 may be pure single crystal silicon.

[0077] The thickness of the substrate 210 is 0.5 mm. It should be understood that the substrate 210 may be cleaned in this step to improve the cleanliness of the surface of the substrate 210 .

[0078] After that, please refer to the attached Figure 3A capture layer 220 and an isolation layer 230 are stacked on a substrate 210. The capture layer 220 and the isolation layer 230 are made of different materials, and the capture layer 220 has a thickness of 300 nm to 5000 nm.

[0079] The capture layer 220 can be prepared by a deposition process or by other processes. For example, the capture layer 220 and the substrate 210 are separate film layers. In this case, the capture layer 220 with a certain thickness can be formed on the substrate 210 by a deposition process. The capture layer 220 is made of at least one of polycrystalline silicon, amorphous silicon or polycrystalline germanium.

[0080] For another example, the capture layer 220 may be formed from a partial region of the substrate 210. In this case, the capture layer 220 is formed in the substrate 210. For example, the capture layer 220 may be formed by etching the substrate 210 or by implanting the substrate 210 to generate implantation damage.

[0081] Afterwards, an isolation layer 230 is formed on the capture layer 220. The material of the isolation layer 230 is different from the material of the capture layer 220. For example, the material of the isolation layer 230 includes at least one of silicon dioxide, silicon oxynitride, or silicon nitride.

[0082] The preparation process of the isolation layer 230 may be a deposition process or an oxidation process. The deposition process may include chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD). The oxidation process may include an in-situ generation process or a thermal oxidation process.

[0083] Specifically, when the isolation layer 230 is prepared by an oxidation process, the material of the capture layer 220 is polysilicon. At this time, the capture layer 220 is oxidized. Among them, the side of the capture layer 220 away from the substrate 210 is oxidized to form a silicon dioxide layer, forming the isolation layer 230, and the side of the capture layer 220 close to the substrate 210 is not oxidized; the oxidation temperature when the isolation layer is prepared by the oxidation method can be 900°C to 1000°C.

[0084] In this example, there is a certain density of lattice defects in the capture layer 220, which can capture carriers between the isolation layer 230 and the substrate 210, preventing these carriers from causing carrier aggregation at the interface between the isolation layer 230 and the substrate 210, thereby reducing the loss of the thin film structure.

[0085] Furthermore, the thickness of the capture layer 220 can be 300nm to 5000nm. For example, the thickness of the capture layer 220 is 300nm, 400nm, 500nm, 550nm, 600nm, 1000nm, 1300nm, 1500nm, 2000nm, 3500nm, 4000nm, 4500nm, 5000nm or a range between any two values. By precisely controlling the thickness of the capture layer 220, its effect of capturing carriers can be further optimized, while avoiding the waste of materials caused by being too thick or the problem of insufficient capture capacity caused by being too thin. This thickness adjustability enables the capture layer 220 to be suitable for different application scenarios and performance requirements.

[0086] In a possible implementation, please refer to the attached Figure 4 and attached Figure 5 , the support structure 200 is a strip structure; illustratively, the strip structure can be a rectangle or a square. Preferably, the support structure 200 is a rectangle.

[0087] This embodiment will define and explain the first direction based on the shape of the support structure 200. In one example, the first direction is the length direction of the support structure 200, and the lithium niobate wafer 110 and the doped lithium niobate wafer 120 are arranged along the length direction of the support structure 200. Figure 3 As an example, the first direction is the direction of Figure 3 Middle X direction.

[0088] In another example, the first direction is the width direction of the support structure 200, and the lithium niobate wafer 110 and the doped lithium niobate wafer 120 are arranged along the width direction of the support structure 200. Figure 3 As an example, the first direction is the direction of Figure 3 Center Y direction.

[0089] Please continue to refer to the attached Figure 3 In this embodiment, the isolation layer 230 of the support structure 200 is bonded to the film layer 130 of the bonding structure 100 by a bonding process, so that the support structure 200 and the bonding structure 100 are fixedly connected. In this way, the support structure 200 can provide support for the bonding structure 100.

[0090] Afterwards, the implantation layer 140 and the residual layer 150 of the bonding structure 100 need to be removed to form a bonding body 300. That is, the bonding body 300 includes the support structure 200 and the film layer 130, so that the film layer 130 is exposed.

[0091] Exemplarily, at least one heat treatment process is performed on the bonded bonding structure and the supporting structure to peel off the injection layer and the residual layer of the bonding structure. It should be understood that the number of heat treatment processes in this embodiment can be one, two, three or even more. The following will take the number of heat treatment processes as two times as an example to explain in detail the peeling process of the injection layer 140 and the residual layer 150.

[0092] The first heat treatment process is performed on the bonded bonding structure 100 and the supporting structure 200. The temperature of the first heat treatment process is 100°C to 600°C, and the heat treatment time is 1min to 48hrs. For example, at a heat treatment temperature of 180°C to 300°C, the first heat treatment process is performed on the bonded bonding structure 100 and the supporting structure 200 to peel off the injection layer 140 and the residual layer 150 from the above-mentioned product. In this process, H ions form hydrogen, He ions form helium, etc. As the heat treatment progresses, the bubbles in the injection layer 140 are connected together, and finally the injection layer 140 is cracked, and the residual layer 150 is separated from the film layer 130, so that the residual layer 150 is peeled off from the bonding body 300.

[0093] Afterwards, the peeled bonding structure and the supporting structure are subjected to a second heat treatment process, the temperature of the second heat treatment process is 300°C to 600°C, and the heat treatment time is 1 min to 100 hrs. Exemplarily, the heat treatment is carried out in a vacuum environment or in a protective atmosphere formed by at least one of nitrogen and inert gas, the heat treatment temperature is 400°C, and the holding time is 3 hrs. This step can enhance the bonding force (greater than 10 MPa), and can restore the damage to the thin film layer 130 caused by ion implantation, so that the obtained lithium niobate (or) thin film layer is close to the properties of pure lithium niobate or doped lithium niobate single crystal.

[0094] In a possible implementation, after bonding is completed, the bonded body needs to be processed. Exemplarily, the method for preparing the thin film structure also includes: patterning the thin film layer of the bonded body to form a waveguide structure in the thin film layer, wherein the waveguide structure spans the lithium niobate thin film layer and the doped lithium niobate thin film layer.

[0095] Exemplarily, a mask layer (not shown) is formed on the thin film layer 130 of the bonding body 300, and then the mask layer is patterned to form a mask pattern on the mask layer, and the mask pattern is used to define the waveguide structure 160. The mask layer can be a photoresist or a hard mask layer. For example, a photoresist layer of a certain thickness is spin-coated on the thin film layer 130 by a coating process, and then the waveguide structure 160 is defined in the photoresist layer by an electron beam exposure (EBL) technology. The structure can be referred to in the attached Figure 4 and attached Figure 5 .

[0096] Afterwards, the mask layer is used as a mask to etch the mask layer, and an etching process is performed to etch the thin film layer 130, so as to transfer the mask pattern in the mask layer to the thin film layer 130, so as to form the waveguide structure 160. The etching process may be dry etching or wet etching. Exemplarily, the waveguide structure 160 is transferred from the photoresist to the surface of the thin film layer 130 by inductively coupled plasma dry etching (ICP) technology.

[0097] During the plasma dry etching process, the thin film layer 130 protected by the photoresist is not etched, while the thin film layer 130 exposed outside is etched to a certain depth, thereby forming a waveguide structure 160 .

[0098] It should be noted that in the step of forming the waveguide structure, metal electrodes can also be prepared on both sides of the ridge-type waveguide structure by the lift-off process. The electrode material is Au, which is prepared by electron beam evaporation. The electrode thickness is 600nm (usually a 15nm Cr electrode needs to be deposited under the Au electrode as an adhesion layer). The incident end and the output end of the electro-optic modulator also need to be polished and coated to improve the end coupling efficiency of the optical signal.

[0099] The electrodes may include a positive electrode 171, a negative electrode 172, a ground electrode 173, and a signal electrode 174. The positive electrode 171 and the negative electrode 172 are disposed in the lithium niobate film layer 131, and are respectively located on both sides of the waveguide structure 160 of the lithium niobate film layer 131; the ground electrode 173 and the signal electrode 174 are respectively located in the doped lithium niobate film layer 132, and are respectively located on both sides of the waveguide structure 160 of the doped lithium niobate film layer 132. It should be understood that the performance of each electrode can be referred to in the relevant technology, and this embodiment will not be repeated here.

[0100] The embodiment of the present application further provides a thin film structure 400 , which is manufactured by the manufacturing method described in any of the above embodiments. The thin film structure 400 includes a support structure 200 and a thin film layer 130 disposed on the support structure 200 .

[0101] The film layer 130 includes a lithium niobate film layer 131 and a doped lithium niobate film layer 132 arranged in parallel, and the film layer includes a waveguide structure 160, and the waveguide structure 160 spans the lithium niobate film layer 131 and the doped lithium niobate film layer 132. In other words, one end of the waveguide structure 160 is located in the lithium niobate film layer 131, and the other end is located in the doped lithium niobate film layer 132. With such a configuration, the DC bias region of the film structure can be located in the doped lithium niobate film layer 132, and the high-frequency modulation region is located in the lithium niobate film layer 131. In this way, the resistance value of the formed film structure can be reduced by doping lithium niobate to better suppress the drift phenomenon; the higher linear electro-optic coefficient of lithium niobate can also be used to improve the electro-optic modulation efficiency of the film structure, so that the electronic device has better performance in the fields of photoelectric conversion and optical signal processing.

[0102] In the embodiment of the present application, the lithium niobate thin film layer 131 and the doped lithium niobate thin film layer 132 are arranged along a first direction. The first direction can be understood as a direction parallel to the horizontal plane, or the first direction can be any direction in the horizontal plane. For example, the first direction can be the X direction in the horizontal plane, or the Y direction in the horizontal plane, or it can be at a certain angle to the X direction or the Y direction of the horizontal plane.

[0103] In this way, the arrangement direction of the lithium niobate film layer 131 and the doped lithium niobate film layer 132 can be reasonably set according to the performance requirements of the film structure, thereby improving the design flexibility of the film structure. This embodiment will define and explain the first direction based on the shape of the support structure 200.

[0104] As a possible implementation, the first direction is the length direction of the support structure 200, and the lithium niobate wafer 110 and the doped lithium niobate wafer 120 are arranged along the length direction of the support structure 200; and the size of the lithium niobate film layer 131 and the doped lithium niobate film layer 132 in the second direction is equal to the width of the support structure 200, and the first direction and the second direction intersect. Figure 3 As an example, the first direction is the direction of Figure 3 The middle X direction, the second direction is the Figure 3 Center Y direction.

[0105] The width of the lithium niobate wafer 110 is equal to the width of the doped lithium niobate wafer 120 , and is also equal to the width of the support structure 200 .

[0106] In this way, the size of the bonding surface between the lithium niobate wafer 110 and the doped lithium niobate wafer 120 depends on the width of the support structure 200, the aspect ratio of the bonding interface is relatively small, and the bonding difficulty is low, which can improve the bonding quality of the lithium niobate wafer 110 and the doped lithium niobate wafer 120, thereby improving the quality of the prepared thin film structure.

[0107] As another possible implementation, the first direction is the width direction of the support structure 200, the lithium niobate wafer 110 and the doped lithium niobate wafer 120 are arranged along the width direction of the support structure 200, and the dimensions of the lithium niobate film layer 131 and the doped lithium niobate film layer 132 in the second direction are equal to the length of the support structure 200; the first direction and the second direction intersect. Figure 4 As an example, the first direction is the direction of Figure 4 The middle Y direction, the second direction is the Figure 4 Middle X direction.

[0108] The length of the lithium niobate wafer 110 and the length of the doped lithium niobate wafer 120 are equal to the length of the support structure 200 , and the sum of the width of the lithium niobate wafer 110 and the width of the doped lithium niobate wafer 120 is equal to the width of the support structure 200 .

[0109] The length of the DC bias region can be very long, even comparable to the total length of the device. In this case, the DC bias voltage required to introduce a phase delay of π / 2 can be very low, thereby further suppressing DC drift.

[0110] One end of the waveguide structure of the thin film structure extends from one end of the doped lithium niobate wafer 120 to the other end of the doped lithium niobate wafer 120, then bends and extends to one end of the doped lithium niobate wafer 120, and finally extends along the length direction of the lithium niobate wafer 110 to the other end of the lithium niobate wafer 110. In this way, the waveguide structure of the thin film structure can present an S-shape or even a serpentine structure. In this way, the incident end and the output end of the optical signal can be designed on both sides of the electro-optical modulation chip, reducing the difficulty of device packaging.

[0111] The embodiment of the present application further provides an electronic device, which includes the thin film structure described in any of the above embodiments. The electronic device may be an electro-optic modulator.

[0112] In view of the fact that the embodiments of the present application include the thin film structure of any of the above embodiments, the structure and beneficial effects of the electronic device including the thin film structure will not be further elaborated in this embodiment.

[0113] The various embodiments or implementation methods in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referenced to each other.

[0114] In the description of this specification, reference to terms such as "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application.

[0115] In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A thin film structure, characterized in that: include: A support structure and a film layer disposed on the support structure; The thin film layer includes a lithium niobate thin film layer and a doped lithium niobate thin film layer arranged in parallel.

2. The thin film structure according to claim 1, characterized in that: The thin film layer includes a waveguide structure, and the waveguide structure spans the lithium niobate thin film layer and the doped lithium niobate thin film layer.

3. The thin film structure according to claim 1, characterized in that: The lithium niobate thin film layer and the doped lithium niobate thin film layer are arranged along a first direction.

4. The thin film structure according to claim 3, characterized in that: The support structure is a strip structure; the first direction is the length direction of the support structure, and the dimensions of the lithium niobate thin film layer and the doped lithium niobate thin film layer in the second direction are equal to the width of the support structure; Alternatively, the first direction is the width direction of the support structure, and the dimensions of the lithium niobate thin film layer and the doped lithium niobate thin film layer in the second direction are equal to the length of the support structure; The first direction intersects with the second direction.

5. A method for preparing a thin film structure, characterized in that: include: Providing a lithium niobate wafer and a doped lithium niobate wafer arranged side by side along a first direction; Bonding the lithium niobate wafer and the doped lithium niobate wafer in parallel to form a bonding structure; wherein the top surface of the lithium niobate wafer is flush with the top surface of the doped lithium niobate wafer; Performing an ion implantation process on the bonding structure so that the bonding structure forms a thin film layer, an implantation layer and a residual layer which are stacked; The thin film layer of the bonding structure after the ion implantation process is bonded to the support structure, and the implantation layer and the residual layer are removed to form a bonding body; wherein the thin film layer includes a lithium niobate thin film layer and a doped lithium niobate thin film layer arranged in parallel.

6. The method for preparing a thin film structure according to claim 5, characterized in that: The method further includes patterning the thin film layer of the bonding body to form a waveguide structure in the thin film layer, wherein the waveguide structure spans the lithium niobate thin film layer and the doped lithium niobate thin film layer.

7. The method for preparing a thin film structure according to claim 5, characterized in that: The lithium niobate wafer has a first bonding surface, and the doped lithium niobate wafer has a second bonding surface; After the step of providing the lithium niobate wafer and the doped lithium niobate wafer arranged in parallel, and before the step of performing an ion implantation process on the bonding structure, the method further includes: The first bonding surface and the second bonding surface are respectively activated to improve the activities of the first bonding surface and the second bonding surface.

8. The method for preparing a thin film structure according to claim 5, characterized in that: The supporting structure is a strip structure; The first direction is the length direction of the supporting structure; or, the first direction is the width direction of the supporting structure.

9. The method for preparing a thin film structure according to any one of claims 5 to 8, characterized in that: Before the step of bonding the thin film layer of the bonding structure after ion treatment to the support structure, the method further comprises: providing a substrate; A capture layer and an isolation layer are stacked on the substrate. The capture layer and the isolation layer are made of different materials, and the capture layer has a thickness of 300nm to 5000nm.

10. The method for preparing a thin film structure according to claim 9, characterized in that: The step of bonding the thin film layer of the bonding structure after ion treatment to the support structure also includes: The bonded bonding structure and the supporting structure are subjected to at least one heat treatment process to peel off the implantation layer and the residual layer of the bonding structure.

11. The method for preparing a thin film structure according to claim 10, characterized in that: Performing a first heat treatment process on the bonded bonding structure and the supporting structure to peel off the injection layer and the residual layer; wherein the temperature of the first heat treatment process is 100° C. to 600° C., and the heat treatment time is 1 min to 48 hrs; A second heat treatment process is performed on the peeled bonding structure and the supporting structure, wherein the temperature of the second heat treatment process is 300° C. to 600° C., and the heat treatment time is 1 min to 100 hrs.

12. An electronic device, characterized in that: The invention comprises the film structure according to any one of claims 1 to 4.

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