A method and device for preparing a micro-nano structure on a sapphire surface

Abstract

The application provides a sapphire surface micro-nano structure preparation method and a preparation device, and comprises the following steps: applying a preset load to a silicon-based material or a sapphire, and making the silicon-based material and the sapphire move relative to each other, so that continuous friction occurs between the silicon-based material and a friction surface, and pure water is introduced to continuously flush the friction surface; under the continuous friction of the silicon-based material and the friction surface, hydroxyl groups on the surface of the silicon-based material combine with hydroxyl groups on the surface of the sapphire to generate chemical bonds; under the condition of continuous friction, the pulling action of the chemical bonds provides the required shear stress for dislocation slip of atoms on the friction surface, induces the atoms on the friction surface to slip along a specific crystal surface direction, causes plastic deformation, and there is a certain mis-cut angle between the surface of the sapphire and the crystal surface of the sapphire, the plastic deformation is generated along the specific crystal surface direction, and then the micro-nano step structure is formed. The process flow of the application is simple, and the sapphire surface is not easy to be damaged, the operation is simple, low in cost and pollution-free.

Description

Technical Field

[0001] This application relates to the field of micro-nano structure fabrication technology, and in particular to a method and apparatus for fabricating micro-nano structures on sapphire surfaces. Background Technology

[0002] Sapphire is widely used in precision optics, epitaxial growth, and defense industries due to its extremely high hardness, stable physicochemical properties, and excellent optical and thermal properties. In the manufacturing process of light-emitting diodes (LEDs), the epitaxial growth of GaN (Gallium Nitride) is a crucial step, and sapphire is the most important substrate material for GaN epitaxial growth.

[0003] However, due to the lattice mismatch and thermal expansion coefficient mismatch between the sapphire substrate and the GaN epitaxial material, the GaN epitaxial material grown on the planar sapphire substrate always has a dislocation density, which in turn causes a decrease in the performance of LED devices.

[0004] In existing technologies, patterned sapphire substrates are used to fabricate micro- and nano-structures with a certain periodicity on the surface of sapphire, which can effectively improve the luminous efficiency of light-emitting diodes. Common fabrication methods include laser engraving and chemical etching. However, these existing methods still have problems such as complex fabrication processes, high costs, and difficulties in subsequent process routes.

[0005] Therefore, a solution is needed to address at least one of the aforementioned problems. Summary of the Invention

[0006] In response to at least one of the defects in the prior art, this application proposes a method and apparatus for preparing micro / nano structures on the surface of sapphire.

[0007] The technical solution adopted by this application to solve at least one of the above-mentioned technical problems is as follows:

[0008] A method for preparing micro / nano structures on the surface of sapphire includes:

[0009] A preset load is applied to a silicon-based material or sapphire to make the friction surfaces of the silicon-based material and the sapphire fit tightly together;

[0010] The silicon-based material and the sapphire are moved relative to each other to cause continuous friction between the silicon-based material and the friction surface, while pure water is introduced to continuously rinse the friction surface.

[0011] Under the continuous friction between the silicon-based material and the friction surface, the silicon-based material and the sapphire adsorb hydroxide ions from pure water to form hydroxyl groups, and the hydroxyl groups on the surface of the silicon-based material combine with the hydroxyl groups on the surface of the sapphire to form chemical bonds.

[0012] Under continuous friction, the attraction of the chemical bonds provides the necessary shear stress for dislocation slip of the atoms on the friction surface, inducing the atoms on the friction surface to slip along a specific crystal plane direction, triggering plastic deformation. Furthermore, there is a certain shear angle between the sapphire surface and the sapphire crystal plane, and the plastic deformation is generated along the specific crystal plane direction, thereby forming a micro / nano step structure. As friction continues, the plastic deformation accumulates along the crystal plane direction, ultimately achieving the fabrication of micro / nano structures on the sapphire surface.

[0013] In one specific embodiment, the load includes a constant load, the value of which is determined based on the contact area between the silicon-based material and the sapphire friction surface, and a preset feasible pressure range for the fabrication of micro-nano structures.

[0014] The feasible pressure range is 300 MPa to 600 MPa.

[0015] In one specific embodiment, the method further includes: determining the friction surface and friction direction of the sapphire;

[0016] The process of determining the friction surface of the sapphire includes: orienting the sapphire, identifying the C-face, A-face, and M-face of the sapphire, and using any one of the three surfaces as the friction surface;

[0017] When surface C is defined as the friction surface, the friction direction is perpendicular to surface A or surface M.

[0018] In one specific embodiment, after determining the friction surface and friction direction of the sapphire, the method further includes: setting preparation parameters;

[0019] The preparation parameters set include any one or more of the following: load value, pure water flow rate, flow velocity and flow direction, relative friction speed, friction direction, friction distance and friction time.

[0020] In one specific embodiment, the preparation parameters are determined based on a combination of multiple influencing factors;

[0021] The influencing factors include one or more of the following: the target micro / nano structure morphology, the type and area of ​​silicon-based materials, and the area of ​​the friction surface.

[0022] In one specific embodiment, after the fabrication of the micro / nano structure on the sapphire surface is completed, the method further includes: cleaning the sapphire with a cleaning agent and drying the cleaned sapphire by blowing nitrogen gas.

[0023] In one specific embodiment, the method further includes determining whether the morphology of the micro / nano structure on the sapphire surface conforms to a preset target;

[0024] If the preset target is not met, the fabrication of the micro / nano structure will be repeated.

[0025] The preset targets include: whether a layered step structure appears on the friction surface, the length, width and thickness of the layered step structure, and the trend and periodicity of the layered step structure.

[0026] In one specific embodiment, the silicon-based material includes one or more of monocrystalline silicon, silicon dioxide, silicon nitride, or silicon carbide.

[0027] An apparatus for fabricating micro / nano structures on the surface of sapphire, employing any one of the methods for fabricating micro / nano structures on the surface of sapphire described in Part One, includes at least:

[0028] A loading device is used to apply a preset load to a silicon-based material or sapphire so that the silicon-based material and the friction surface of the sapphire are in close contact.

[0029] The loading device is provided with a first clamping device, which is used to clamp the silicon-based material or the sapphire.

[0030] A receiving groove, wherein a second clamping device is provided on the receiving groove, the second clamping device being used to clamp the silicon-based material or the sapphire;

[0031] The receiving tank is equipped with a flow guiding device. The flow guiding device is used to continuously introduce pure water to continuously rinse the friction surface when the silicon-based material and the friction surface are in continuous relative friction. Under the continuous friction between the silicon-based material and the friction surface, the silicon-based material and the sapphire respectively adsorb hydroxide ions in the pure water to form hydroxyl groups. The hydroxyl groups on the surface of the silicon-based material and the hydroxyl groups on the surface of the sapphire combine to form chemical bonds.

[0032] A movable platform is provided at the bottom of the receiving groove. The movable platform is used to make the silicon-based material and the sapphire move relative to each other, so that the silicon-based material and the friction surface continuously rub against each other.

[0033] Under continuous friction, the chemical bonds provide the necessary shear stress for dislocation slip of atoms on the friction surface, inducing the atoms on the friction surface to slip along a specific crystal plane direction, triggering plastic deformation. Furthermore, there is a certain shear angle between the sapphire surface and the sapphire crystal plane, and the plastic deformation occurs along the specific crystal plane direction, thereby forming a micro / nano step structure. As friction continues, the plastic deformation accumulates along the crystal plane direction, ultimately achieving the fabrication of micro / nano structures on the sapphire surface.

[0034] In one specific embodiment, the diversion device is provided with a water outlet, and the receiving tank is provided with a drain outlet;

[0035] The water outlet faces the friction surface of the sapphire, the water outlet is not lower than the friction surface, and the drain outlet is not higher than the friction surface.

[0036] Beneficial effects:

[0037] This application provides a method and apparatus for preparing micro-nano structures on the surface of sapphire. The process is simple and does not easily damage the sapphire surface. It is easy to operate, low in cost, and pollution-free. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the sapphire surface micro / nano structure fabrication method in this embodiment;

[0040] Figure 2 This is a schematic diagram illustrating the fabrication principle of the sapphire surface micro / nano structure preparation method in this embodiment.

[0041] Figure 3 This is a simplified process flow diagram of the sapphire surface micro / nano structure fabrication method in this embodiment;

[0042] Figure 4 This is a diagram of the sapphire crystal structure in this embodiment;

[0043] Figure 5 This is a schematic diagram of the sapphire processing direction in this embodiment;

[0044] Figure 6 This example compares the fabrication effects of sapphire surface micro / nano structures. Figure 1 ;

[0045] Figure 7 This example compares the fabrication effects of sapphire surface micro / nano structures. Figure 2 ;

[0046] Figure 8 This is a surface topography diagram of the epitaxial layer on the sapphire substrate in this embodiment;

[0047] Figure 9 This is a rocking curve diagram of the epitaxial layer on the sapphire substrate in this embodiment;

[0048] Figure 10 This is a structural diagram of the sapphire surface micro / nano structure fabrication device in this embodiment;

[0049] Figure 11 This is a schematic diagram showing the relationship between the sapphire surface and crystal plane morphology before preparation in this embodiment.

[0050] Figure label:

[0051] 1-Loading device; 11-First clamping device; 2-Receiving groove; 21-Second clamping device; 3-Drainage device; 31-Outlet; 32-Drain outlet; 4-Moving platform; 5-Silicon-based material; 6-Sapphire; 61-Friction surface. Detailed Implementation

[0052] Various embodiments of this disclosure will be described more fully below. This disclosure may have various embodiments, and adjustments and changes may be made therein. However, it should be understood that there is no intention to limit the various embodiments of this disclosure to the specific embodiments disclosed herein, but rather this disclosure should be understood to cover all adjustments, equivalents, and / or alternatives falling within the spirit and scope of the various embodiments of this disclosure.

[0053] The expressions used in the various embodiments of this disclosure (such as "first," "second," etc.) may modify various components in the various embodiments, but do not limit the corresponding components. For example, the above expressions do not limit the order and / or importance of the components. The above expressions are only used for the purpose of distinguishing one component from other components.

[0054] The terminology used in the various embodiments of this disclosure is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of this disclosure. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this disclosure pertain. The terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning unless clearly defined in the various embodiments of this disclosure.

[0055] Example 1

[0056] This application provides a method for preparing micro / nano structures on the surface of sapphire, such as... Figures 1 to 3 As shown, it includes:

[0057] S100, apply a preset load to silicon-based materials or sapphire to make the friction surfaces of silicon-based materials and sapphire fit tightly together;

[0058] Specifically, in some embodiments of this application, the preset load is a constant load, which is an ideal state; slight changes in the load are inevitable in the actual preparation process, and the existence of changes is allowed, as long as the uniformity, periodicity, and trend consistency of the sapphire micro-nano structure are not affected.

[0059] Alternatively, a constant load can be applied to either silicon-based materials or sapphire; of course, there is no restriction on whether the specific object to which the load is applied is silicon-based material or sapphire.

[0060] Preferably, the direction in which the preset load is applied to the silicon-based material or sapphire is the normal direction.

[0061] Applying a constant load helps maintain the relative stability between the silicon-based material and the sapphire friction surface, thereby helping to keep the force on the friction surface stable during the friction process.

[0062] Furthermore, during the fabrication of micro- and nano-structures on the surface of sapphire, silicon-based materials and sapphire need to maintain reciprocating friction for a long time and multiple times. The constant applied load is equivalent to reducing the variables between each friction, which helps to achieve consistency in frictional motion, so that the micro- and nano-structures as a whole exhibit a consistent trend and obvious periodicity.

[0063] S200 causes relative movement between the silicon-based material and the sapphire, so that continuous friction occurs between the silicon-based material and the friction surface, while pure water is introduced to continuously rinse the friction surface.

[0064] Optionally, the relative motion between the silicon-based material and the sapphire can be achieved by fixing one of the two materials and allowing it to move relative to the other material while maintaining a constant speed; or by having both materials move simultaneously to provide stable thermal and mechanical energy conditions for the subsequent chemical friction reaction.

[0065] Understandably, sapphire is generally harder than silicon-based materials. Therefore, silicon-based materials will wear down during friction, producing debris. This debris can easily fall onto the friction surface of sapphire. The presence of debris can damage the fabricated micro / nano structures, disrupting the uniformity and periodicity of their surfaces. Furthermore, the presence of debris can affect the fabrication process, causing the silicon-based material and sapphire to collide with each other, leading to misalignment or displacement and affecting the consistency of the orientation and trend of the micro / nano structures.

[0066] However, in addition to removing material debris generated during processing from the friction surface in a timely manner, which helps to optimize the final micro-nano structure preparation effect, the introduction of pure water to continuously rinse the friction surface can also provide hydroxyl groups required for the formation of tribochemical reactions by hydroxide ions.

[0067] S300, under the continuous friction between the silicon-based material and the friction surface, the silicon-based material and the sapphire adsorb hydroxide ions from pure water to form hydroxyl groups. The hydroxyl groups on the surface of the silicon-based material and the hydroxyl groups on the surface of the sapphire combine to form chemical bonds.

[0068] Specifically, such as Figure 2 As shown, flowing pure water continuously washes the interface between the silicon-based material and the sapphire. Both the sapphire and silicon-based materials adsorb hydroxide ions from the pure water to form hydroxyl groups. During the friction process, due to factors such as localized thermal effects, the hydroxyl groups on the surfaces of the sapphire and silicon-based materials combine to form chemical bonds.

[0069] The specific process is as follows: Al-OH + Si-OH → Al-O-Si + H2O.

[0070] Understandably, the generated Al-O-Si chemical bonds are located between the silicon-based material and the friction surface of sapphire. The silicon atoms are provided by the silicon-based material, and the aluminum atoms are provided by the sapphire. The aluminum, oxygen, and silicon atoms in the Al-O-Si chemical bonds are connected by covalent bonds and have a certain connection strength. When the silicon-based material moves relative to the friction surface, it can generate shear stress, which can cause dislocation slip of the atoms on the surface of the sapphire material, thereby promoting the shedding or deformation of the sapphire surface material and helping to prepare the micro-nano structure on the sapphire surface.

[0071] Under continuous friction between silicon-based materials and sapphire surfaces, chemical bonds are constantly generated. The Al-O-Si chemical bonds may also be affected by mechanical stress, leading to their breakage. The breakage of chemical bonds also affects the movement of atoms, thereby influencing the rearrangement of atoms on the sapphire surface and changes in local structure. Through the continuous generation and breakage of chemical bonds, the transfer of sapphire friction surface materials is effectively promoted.

[0072] In S400, under continuous friction, the traction of chemical bonds provides the necessary shear stress for dislocation slip of atoms on the friction surface, inducing atoms on the friction surface to slip along a specific crystal plane direction, triggering plastic deformation. Furthermore, there is a certain shear angle between the surface of sapphire and the crystal plane of sapphire, and plastic deformation is generated along the specific crystal plane direction, thereby forming a micro-nano step structure.

[0073] The misalignment angle refers to the angle between the atomic arrangement of the sapphire crystal facets and the actual atomic arrangement of the surface. Sapphire manufacturing requires cutting. Ideally, the cut sapphire surface should coincide with the crystal facets. However, in actual processing, the cut surface rarely perfectly aligns with the crystal facets, resulting in a certain misalignment angle. Specifically, as shown... Figure 11 As shown;

[0074] It is worth noting that, generally speaking, the surface of sapphire does not show a step structure. When the surface atoms are subjected to shear stress provided by Al-O-Si chemical bonds, dislocation slip will occur along a specific crystal plane direction, which will lead to plastic deformation. Due to the existence of the shear angle, the resulting plastic deformation will exhibit a step structure morphology.

[0075] S500, as friction continues, plastic deformation accumulates along the crystal plane, ultimately achieving the fabrication of micro-nano structures on the sapphire surface.

[0076] Specifically, as friction continues, atoms on the friction surface continuously undergo dislocation slip along specific crystal planes and exhibit step-like plastic deformation, ultimately achieving the fabrication of micro / nano structures on the sapphire surface.

[0077] Furthermore, the load includes a constant load, the value of which is determined based on the contact area between the silicon-based material and the sapphire friction surface, and a preset feasible pressure range for the fabrication of micro-nano structures.

[0078] The preset feasible pressure range for micro-nano structure fabrication is 300MPa to 600MPa, that is, the pressure between the silicon-based material and the friction surface is between 300MPa and 600MPa.

[0079] The pressure between the silicon-based material and sapphire can be adjusted by adjusting the load value. Specifically, in some embodiments of this application, it was found through multiple experiments that the fabrication of micro-nano structures on the sapphire surface can only be successfully achieved when the pressure value is in the range of 300-600 MPa. In the actual fabrication process, the specific applied load value needs to be calculated based on the size and shape of the silicon-based material and the contact area with the friction surface, and then the constant load value is derived from the required pressure.

[0080] In summary, the main factors influencing the constant load value are: the contact area between the silicon-based material and the sapphire friction surface, and the preset pressure range that is feasible for the fabrication of micro-nano structures.

[0081] Furthermore, under otherwise unchanged conditions, within the pressure range where micro-nano structure fabrication is feasible, the larger the load value, the larger the size of the micro-nano structure on the sapphire surface; the smaller the load value, the smaller the size of the micro-nano structure on the sapphire surface.

[0082] Furthermore, the method also includes: determining the friction surface and friction direction of the sapphire;

[0083] like Figure 5 As shown, to orient a sapphire, it is necessary to identify the C-face, A-face, and M-face of the sapphire and use any one of the three faces as the friction surface.

[0084] Specifically, such as Figure 4 As shown, sapphire (α-Al₂O₃) is a hexagonal crystal. Crystallography has unified rules for defining the crystal faces of hexagonal crystals; all crystal faces are defined based on the C-plane (0001). The C-plane of sapphire is a specific crystal face, that is, a face perpendicular to the C-axis. The A-plane (11-20) and the M-plane (10-10) are both perpendicular to the C-plane, and the A-plane and M-plane are also perpendicular to each other.

[0085] When surface C is defined as the friction surface, the friction direction is either towards or away from surface A, or towards or away from surface M.

[0086] Preferably, the friction direction is perpendicular to surface A or surface M.

[0087] Alternatively, the orientation of the sapphire crystal facets can be determined by X-ray diffraction, transmission electron microscopy, or electron backscatter diffraction; of course, there are no restrictions on the orientation of the sapphire crystal facets.

[0088] It should be noted that sapphire is an anisotropic single-crystal material, and the morphology of the micro-nano structures obtained by processing along different directions will be different. Different morphologies of micro-nano structures may have different properties. Therefore, before preparing micro-nano structures, it is necessary to determine the processing direction according to the usage and requirements of the sapphire substrate in order to obtain the expected micro-nano structure morphology in order to better meet the actual use requirements.

[0089] Among them, the C-plane has a relatively compact and stable lattice structure, which helps gallium nitride form better crystal quality and achieve a smaller dislocation density. The C-plane is also the most widely used surface of sapphire as a substrate.

[0090] The A-plane is also a commonly used sapphire crystal facet. Its lattice structure is more loose than that of the C-plane. In some cases, choosing the A-plane can optimize the growth process of GaN to meet the requirements of high orientation applications.

[0091] Preferably, in some embodiments of this application, a square prism-shaped sapphire is selected, and the processed crystal face is set as the C-face. The square prism-shaped sapphire has obvious geometric features, a flat surface and clear edges, which facilitates the polishing process and reduces the difficulty of preparation.

[0092] Of course, other surfaces of sapphire, such as the R-side and N-side, can also be used as substrates, and the friction direction can be set according to the friction surfaces.

[0093] Furthermore, after determining the friction surface and friction direction of the sapphire, the method also includes: setting preparation parameters;

[0094] The set preparation parameters include: load value, pure water flow rate, flow velocity and flow direction, relative friction speed, friction distance and friction time, any one or more of these parameters.

[0095] The size of the micro-nano structures on the sapphire surface can be adjusted. Specifically, by changing the fabrication process parameters such as the load during the friction process, the relative speed of movement between the sapphire and the silicon-based material, and the friction time, micro-nano structures of different sizes can be obtained.

[0096] Understandably, changes in parameters such as load value, pure water flow rate, flow velocity and direction, relative friction speed, friction distance and friction time can affect the final appearance of micro and nano structures.

[0097] For example, different friction directions can also produce micro / nano structures with different effects. For instance, when the C-plane is determined as the friction surface, the width of the micro / nano structure is larger and has better continuity when the fabrication direction is perpendicular to the M-plane; while the width of the micro / nano structure is smaller and has better dispersion when the fabrication direction is perpendicular to the A-plane.

[0098] In addition to the influence of individual parameter adjustments on the fabrication of micro and nano structures, it is also necessary to pay attention to the interaction between parameters. For example, when the relative friction speed increases, the pure water flow rate needs to be appropriately increased. Understandably, when the relative friction speed increases, the material debris generation rate increases. If the pure water flow rate is not matched, debris is easily retained on the friction surface, which can damage the micro and nano structures.

[0099] Preferably, in some embodiments of this application, the load is between 300MPa and 600MPa, the pure water flow rate is between 1200mL / min and 2000mL / min, the relative friction speed is between 20mm / min and 200mm / min, and the pure water flow direction is parallel to the friction direction.

[0100] Furthermore, the preparation parameters were determined based on a combination of various influencing factors;

[0101] Influencing factors include one or more of the following: the target micro / nano structure morphology, the type and area of ​​silicon-based materials, and the area of ​​the friction surface.

[0102] Among them, the type and area of ​​silicon-based materials, and the area of ​​the friction surface can be determined based on the preset target of the micro-nano structure morphology.

[0103] Understandably, different types of silicon-based materials have different structural features and lattice parameters, and also differ in physical and chemical properties.

[0104] For example, silicon nitride and silicon carbide are harder than single-crystal silicon and silicon dioxide. When using silicon nitride or silicon carbide to prepare micro and nano structures, they are not easily damaged under rapid friction, so the friction time can be appropriately shortened and the friction speed increased.

[0105] Furthermore, the hardness of silicon-based materials also affects the morphology of micro- and nano-structures; for example, the greater the hardness of silicon-based materials, the higher the height of the micro- and nano-structures.

[0106] More specifically, the friction distance and friction time also depend on the morphological target of the micro-nano structure.

[0107] As can be seen from the above, the applied load is closely related to the contact area of ​​the silicon-based material. It is calculated based on the size of the silicon-based material and the contact area of ​​the friction surface, and then the value of the constant load is derived from the required pressure. Therefore, the type and area of ​​the silicon-based material and the area of ​​the friction surface are also factors affecting the preparation parameters.

[0108] In some embodiments of this application, relative friction speed and relative motion speed have the same meaning.

[0109] Furthermore, it is necessary to determine the target micro / nano structure morphology based on application requirements. Based on the target micro / nano structure morphology, the fabrication surface of the sapphire micro / nano structure, the size and shape of the silicon-based material, and the contact area with the friction surface should be determined first. Then, the load value should be calculated and adjusted based on the size and shape of the silicon-based material and the contact area with the friction surface.

[0110] Based on the trend characteristics of the micro / nano structure morphology target, the friction direction is determined or adjusted, and then the pure water flow direction is adjusted according to the friction direction; based on the size characteristics of the micro / nano structure morphology target, the relative friction velocity is adjusted, and then the pure water flow rate and direction are adjusted according to the relative friction velocity; the influencing factors such as friction direction, constant load value, pure water flow rate and direction, and friction velocity are interconnected, interact, and influence each other, and are essential for achieving the expected morphology target of the micro / nano structure.

[0111] Furthermore, after completing the preparation of the micro-nano structure on the sapphire surface, the method also includes: cleaning the sapphire with a cleaning agent and drying the cleaned sapphire by blowing with nitrogen gas.

[0112] Specifically, in some embodiments of this application, the cleaning agent is pure water;

[0113] Sapphire substrates are one of the important base materials used to manufacture semiconductor devices and optical components. Contaminants or residues on the surface may affect the performance and stability of the devices.

[0114] Using nitrogen gas to blow through the sapphire surface can accelerate the evaporation of pure water, speed up the drying process, help reduce water spots and stains, and maintain the cleanliness of the micro-nano structure surface to meet the high-precision application requirements of semiconductor devices.

[0115] Furthermore, the method also includes determining whether the morphology of the micro / nano structure on the sapphire surface meets the preset target;

[0116] If the preset target is not met, the fabrication of the micro / nano structure will be repeated.

[0117] The preset targets include: whether a layered step structure appears on the friction surface, the length, width and thickness of the layered step structure, and the trend and periodicity of the layered step structure.

[0118] Specifically, in some embodiments of this application, whether the micro-nano structure morphology on the sapphire surface meets the preset target can be determined by using AFM, i.e., atomic force microscopy, to characterize and detect the micro-nano structure of the friction surface, which facilitates further judgment.

[0119] Understandably, the micro- and nanostructures of sapphire substrates need to have good periodicity and orientation consistency, that is, the entire substrate surface exhibits repeating shapes and sizes, which in turn affects the crystal quality of the epitaxial growth layer in order to solve problems such as lattice mismatch, thermal expansion coefficient mismatch, and misalignment of the grown epitaxial material, thereby optimizing optical and electronic performance and improving the luminous efficiency of optical components.

[0120] Whether the size and shape of the micro- and nano-structures on the sapphire substrate meet the preset requirements or the expected micro- and nano-structure morphology targets. The size of the micro- and nano-structures is usually one of the key parameters for sapphire patterning. For example, nanoscale structure substrates are more effective in improving LED luminous efficiency than micrometer-scale structure substrates, but the crystal quality of GaN epitaxial layers will decrease compared to micrometer-scale structure substrates.

[0121] Specifically, in some embodiments of this application, the surface micro / nano structures prepared by this method are layered step structures or conical structures, which match the crystal plane morphology and have larger patterned slopes, which are beneficial for the lateral growth of GaN epitaxial layers and reduce dislocation density.

[0122] Among them, the presence of a layered step structure on the sapphire friction surface / surface, and the consistent orientation and periodicity of the layered step structure are essential conditions. If these conditions are not met, it indicates that the micro-nano structure has not been successfully fabricated.

[0123] As another example, the uniformity of the substrate surface can also affect the repeatability and stability of the device.

[0124] Specifically, the length, width, and thickness of the layered step structure, the specific trend direction of the layered step structure, and the length and degree of periodicity are the factors for judging whether the preset goal has been achieved.

[0125] For example, the micro-nano structure morphology can be set to a width of approximately 100-300 nm and a height of approximately 7-10 nm, with the layered step structure generally exhibiting a trend parallel to plane A;

[0126] If a layered step structure with a width of 400 nm is found, it does not conform to the preset micro / nano structure morphology target; then the processing parameters need to be adjusted, such as increasing the relative friction speed, in order to re-prepare the micro / nano structure. The processing parameters can be adjusted according to the characteristics of the already processed structure.

[0127] Furthermore, silicon-based materials include one or more of monocrystalline silicon, silicon dioxide, silicon nitride, or silicon carbide.

[0128] Different silicon-based materials have certain differences in their specific physical and chemical properties. Selecting them based on the morphological goals of micro- and nano-structures can help meet the practical needs of diverse micro- and nano-structure fabrication. Of course, there are no restrictions on the specific selection of silicon-based materials.

[0129] The applicant also used the sapphire surface micro / nano structure preparation method provided in this application to prepare sapphire surface micro / nano structures and verified the preparation effect. The experimental content and results are as follows:

[0130] The following examples demonstrate the micro / nano structure morphology of sapphire surfaces obtained by the method proposed in this invention.

[0131] Specifically, in one embodiment, the constant load value was adjusted to 400 MPa, the relative friction speed was 100 mm / min, the friction distance was 5 mm, the friction time was 2 h, the processed sapphire crystal surface was the C-plane, the processing direction was perpendicular to the M-plane, and the silicon-based material was spherical silicon dioxide; the sapphire after friction was characterized by AFM, and the results are shown in Figure 6.

[0132] At two measurement scales, 10×10μm and 1×1μm, the sapphire surface had no obvious morphology before rubbing. After the rubbing test, a layered step structure appeared on the sapphire surface. The width of the layered step structure was about 300-800nm ​​and the height was about 13-16nm. The layered step structure generally showed a tendency to be parallel to the M plane and had obvious periodicity.

[0133] This demonstrates that the processing method proposed in this invention has the capability to process layered, stepped micro / nano structures with periodic arrangements.

[0134] In another embodiment, the morphology of the micro / nano structure is controlled by changing the processing direction and adjusting the preparation process parameters. The following implementation example is another micro / nano structure obtained by changing the processing direction and adjusting the relative friction speed and friction time.

[0135] The load was adjusted to 400 MPa, the relative friction speed to 100 mm / min, the friction distance to 5 mm, and the friction time to 30 min. The sapphire crystal surface to be processed was the C-plane, and the processing direction was perpendicular to the M-plane. Spherical silicon dioxide was selected as the silicon-based material. The surface morphology of the rubbed sapphire was characterized by AFM, and the experimental results are shown in Figure 7.

[0136] After changing the relative motion speed and friction time of the sapphire, the micro-nano structure morphology of the sapphire surface changed at both the 10×10μm and 1×1μm measurement scales. Under the current fabrication process parameters, the width of the layered step structure on the sapphire surface obtained by friction is approximately 100nm-300nm, and the height is approximately 7-10nm. The layered step structure generally exhibits a tendency to be parallel to the M-plane and still has obvious periodicity.

[0137] Therefore, this method can adjust the fabrication size of sapphire surface micro-nano structures by adjusting the fabrication process parameters and coordinating the interrelated fabrication process parameters. With appropriate fabrication process parameters, layered stepped micro-nano structures with the required width and height can be obtained.

[0138] The applicant also conducted epitaxial growth performance tests on sapphire substrates, the details of which are as follows: To test the epitaxial growth performance of sapphire substrates with micro / nano structures, AlN epitaxial growth was simultaneously performed on both unstructured and rubbed substrates via thermal atomic layer deposition. Trimethylaluminum and nitrogen were used as Al and N precursors, respectively, and the reaction temperature was 400℃. After growth, the AlN film thickness was measured using ellipsometry, and the test results showed that the AlN thickness on both substrates was 41 nm.

[0139] The surface morphology of AlN epitaxial layers grown on two substrates was characterized by AFM, and the results are as follows: Figure 8 As shown.

[0140] Both AlN epitaxial layers on both substrates exhibited island-like growth. However, the number and height of island structures on the unstructured substrate were significantly greater than those on the micro / nanostructured substrate. This indicates that the lattice mismatch and wettability between the unstructured substrate and the epitaxial material were greater, making it more difficult for the epitaxial material to bond with the substrate.

[0141] In contrast, the epitaxial layer material on the micro / nano structure substrate exhibits a layered growth pattern, which is beneficial for the bonding between the epitaxial material and the substrate. AFM testing shows that the surface roughness of the AlN epitaxial layer on the unstructured substrate and the micro / nano structure substrate are RMS 8.91 nm and RMS 4.49 nm, respectively, with the surface roughness of the AlN epitaxial layer grown on the micro / nano structure substrate being approximately half that of the unstructured substrate.

[0142] The crystallinity of AlN epitaxial layers grown on two substrates was characterized using high-resolution thin-film X-ray diffraction (HRXRD). The rocking curve measurement mode of HRXRD allows for quantitative analysis of the crystallinity of the epitaxial film; a narrower full width at half maximum (FWHM) of the rocking curve indicates higher crystallinity of the epitaxial film.

[0143] The rocking curves of AlN epitaxial layers on two substrates are as follows: Figure 9 As shown, the full width at half maximum (FWHM) of the rocking curve of the AlN epitaxial layer grown on the unstructured substrate is 34.54 arcsec, while the FWHM of the rocking curve of the AlN epitaxial layer grown on the micro / nanostructured substrate is 12.24 arcsec, which is about one-third of the former. This indicates that the crystal quality of the AlN epitaxial layer grown on the micro / nanostructured substrate is significantly higher than that on the unstructured substrate.

[0144] The above results demonstrate that the sapphire substrate with micro-nano structure fabricated using the method proposed in this invention can significantly improve the quality of epitaxial growth, resulting in AlN epitaxial layer materials with fewer island structures, lower surface roughness, and higher crystal quality, which are expected to be applied in LED manufacturing, electronic devices, integrated circuits and other fields.

[0145] The embodiments of this application have at least the following beneficial effects:

[0146] This application provides a method for fabricating micro / nano structures on sapphire surfaces, which differs from previous methods for fabricating micro / nano-scale structures on sapphire surfaces. Common methods for fabricating nanostructures include wet or dry etching and femtosecond laser combined with plasma-assisted ablation. Wet or dry etching requires photolithography, pattern transfer, and other processes, making the fabrication process complex and costly. Femtosecond laser combined with plasma-assisted ablation creates a heat-affected zone on the processed surface, which is detrimental to subsequent epitaxial growth. In contrast, this method is simple in steps, easy to operate, and has low fabrication costs. Furthermore, this method does not create a heat-affected zone on the processed surface, which is beneficial for subsequent process routes. This solution also does not limit the shape and size of the sapphire substrate, and can meet the diverse needs of sapphire substrate fabrication. It does not require violent chemical reactions, the process is simple, and it does not damage the sapphire surface, offering advantages such as simple operation, low cost, no damage, and no pollution.

[0147] Furthermore, using sapphire with micro-nano structures prepared by this method as a substrate can significantly improve the quality of epitaxial growth, achieving the effects of fewer island structures, lower surface roughness, and higher crystal quality, thus solving problems such as lattice mismatch, thermal expansion coefficient mismatch, and misalignment of epitaxial materials generated by sapphire substrates.

[0148] Example 2

[0149] This application provides an apparatus for fabricating micro / nano structures on the surface of sapphire, such as... Figure 10 As shown, it includes:

[0150] The loading device 1 is used to apply a preset load to the silicon-based material 5 or the sapphire 6 so that the friction surface 61 of the silicon-based material 5 and the sapphire 6 are tightly attached.

[0151] Specifically, in some embodiments of this application, the loading device 1 can apply a constant load to the first clamping device 11, and due to the force transmission, a constant load will exist between the silicon-based material 5 and the sapphire 6.

[0152] The loading device 1 is provided with a first clamping device 11, which is used to clamp the silicon-based material 5 or sapphire 6.

[0153] The receiving groove 2 is provided with a second clamping device 21, which is used to clamp the silicon-based material 5 or sapphire 6.

[0154] Specifically, in some embodiments of this application, the first clamping device 11 clamps the silicon-based material 5, so that the positional relationship between the silicon-based material 5 and the sapphire 6 is relatively fixed and it contacts the surface of the sapphire 6; the second clamping device 21 clamps the sapphire 6, so that the positional relationship between the sapphire 6 and the receiving groove 2 is relatively fixed and it is fixed at the bottom of the receiving groove 2.

[0155] Regarding the friction surface 61 of the sapphire 6 used to fabricate micro-nano structures and the direction of frictional movement, the posture of the sapphire 6 on the second clamping device 21 and / or receiving groove 2 can be adjusted.

[0156] A flow-guiding device 3 is provided on the receiving tank 2. When the silicon-based material 5 and the sapphire 6 are in continuous relative friction, pure water is introduced to continuously rinse the friction surface 61. Under the continuous friction between the silicon-based material 5 and the sapphire 6, the silicon-based material 5 and the sapphire 6 respectively adsorb hydroxide ions in the pure water to form hydroxyl groups. The hydroxyl groups on the surface of the silicon-based material 5 and the hydroxyl groups on the surface of the sapphire 6 combine to form chemical bonds.

[0157] Specifically, in some embodiments of this application, the flowing pure water is provided by the drainage device 3, which is placed above the sapphire 6. After flowing out of the drainage device 3, the pure water falls onto the surface of the sapphire 6, then spreads out and continuously washes the contact interface between the sapphire 6 and the silicon-based material 5. While providing hydroxyl ions to form the hydroxyl groups required for the tribochemical reaction, it also carries away the material debris generated by wear, thus avoiding damage to the processed micro-nano structure during subsequent friction.

[0158] A moving platform 4 is provided at the bottom of the receiving tank 2. The moving platform 4 is used to make the silicon-based material 5 and the sapphire 6 move relative to each other, so that the silicon-based material 5 and the friction surface 61 continuously rub against each other. Under the condition of continuous friction, the chemical bond pull provides shear stress, which induces the atoms of the friction surface 61 to produce dislocation slip. There is a certain shear angle between the surface of the sapphire 6 and the crystal plane of the sapphire 6. The dislocation slip will occur along a specific crystal plane direction and produce plastic deformation. As the friction continues, the atoms of the friction surface 61 continuously produce plastic deformation in the crystal plane direction, exhibiting a stepped structure morphology, and finally realizing the preparation of the micro-nano structure on the sapphire surface.

[0159] Specifically, in some embodiments of this application, the receiving groove 2 is fixed on the moving platform 4. The horizontal movement of the moving platform 4 drives the receiving groove 2 to move, which is equivalent to indirectly applying a force to the sapphire 6, causing the sapphire 6 to reciprocate linearly under the action of the force and rub against the silicon-based material 5. When the moving platform 4 drives the sapphire 6 to move, friction will be generated between the sapphire 6 and the silicon-based material 5, inducing a tribochemical reaction.

[0160] Furthermore, the diversion device 3 is provided with a water outlet 31, and the receiving tank 2 is provided with a drain outlet 32; the water outlet 31 faces the friction surface 61 of the sapphire 6, the water outlet 31 is not lower than the friction surface 61, and the drain outlet 32 ​​is not higher than the friction surface 61.

[0161] Specifically, in some embodiments of this application, the side of the receiving tank 2 has a drain outlet 32, the height of which is lower than the surface of the friction surface 61. When the water level in the receiving tank 2 reaches the height of the drain outlet 32, the water is automatically discharged from the drain outlet 32, thus preventing the water from submerging the surface of the friction surface 61 and causing material debris to be unable to be discharged in time.

[0162] The rest is the same as in Example 1, and will not be repeated here.

[0163] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application.

[0164] Those skilled in the art will understand that the modules in the apparatus of the implementation scenario can be distributed within the apparatus of the implementation scenario as described, or they can be located in one or more apparatuses different from this implementation scenario, with corresponding changes. The modules of the above-described implementation scenario can be combined into one module, or they can be further divided into multiple sub-modules.

[0165] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of the implementation scenario.

[0166] The above disclosures are only a few specific implementation scenarios of this application. However, this application is not limited to these. Any variations that can be conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A method for preparing a micro-nano structure on a sapphire surface, characterized in that, The method comprises the following steps: applying a preset load to the silicon-based material or sapphire so that the silicon-based material is tightly attached to the friction surface of the sapphire; moving the silicon-based material relative to the sapphire so that continuous friction occurs between the silicon-based material and the friction surface, and pure water is introduced to continuously flush the friction surface; under the continuous friction of the silicon-based material and the friction surface, the silicon-based material and the sapphire respectively adsorb hydroxyl ions in the pure water to form hydroxyl groups, and the hydroxyl groups on the surface of the silicon-based material combine with the hydroxyl groups on the surface of the sapphire to form chemical bonds; under the condition of continuous friction, the existence of the chemical bonds provides the required shear stress for the dislocation slip of the atoms of the friction surface, induces the atoms of the friction surface to slip along a specific crystal plane direction, causes plastic deformation, and there is a certain mis-cut angle between the surface of the sapphire and the crystal plane of the sapphire, the plastic deformation occurs along a specific crystal plane direction, and then a micro-nano step structure is formed; with the continuous friction, the plastic deformation continuously accumulates in the crystal plane direction, and finally the micro-nano structure of the sapphire surface is prepared.

2. The method according to claim 1, wherein The load comprises a constant load, and the value of the load is determined according to the contact area of the silicon-based material and the friction surface of the sapphire and a preset feasible pressure interval for micro-nano structure preparation. The feasible pressure interval is 300 MPa to 600 MPa.

3. The method according to claim 1, wherein the method further comprises the step of: The method further comprises determining the friction surface and the friction direction of the sapphire. ​ The determination of the friction surface of the sapphire comprises orienting the sapphire, identifying the C surface, the A surface and the M surface of the sapphire, and taking any one of the C surface, the A surface or the M surface of the sapphire as the friction surface. When the C surface is determined as the friction surface, the friction direction is perpendicular to the A surface or the M surface.

4. The method according to claim 3, wherein the method further comprises the step of: After the friction surface and the friction direction of the sapphire are determined, the method further comprises setting preparation parameters. The set preparation parameters comprise any one or more of the load value, the pure water flow, the flow rate and the flow direction, the relative friction speed, the friction direction, the friction distance and the friction time.

5. The method according to claim 4, wherein the method further comprises the step of: The set preparation parameters are determined according to a plurality of influencing factors. ​ The influencing factors comprise one or more of the micro-nano structure morphology target, the type and area of the silicon-based material, and the area of the friction surface.

6. The method according to claim 1, wherein After the micro-nano structure of the sapphire surface is prepared, the method further comprises cleaning the sapphire using a cleaning agent, and drying the cleaned sapphire by nitrogen blowing.

7. The method according to claim 1, wherein the method is characterized by, The method further comprises judging whether the micro-nano structure morphology of the sapphire surface meets a preset target. If the preset target is not met, the micro-nano structure is prepared again. The preset target comprises whether the friction surface appears a layered step structure, the length, width and thickness of the layered step structure, and the trend and periodicity of the layered step structure.

8. The method according to claim 1, wherein The silicon-based material comprises one or more of monocrystalline silicon, silicon dioxide, silicon nitride or silicon carbide.

9. A device for preparing a micro-nano structure on a sapphire surface, characterized in that, The method for preparing a micro-nano structure on a sapphire surface comprises at least the following steps: a loading device for applying a preset load to a silicon-based material or sapphire so that the silicon-based material is tightly attached to the friction surface of the sapphire; The loading device is provided with a first clamping device for clamping the silicon-based material or the sapphire; The accommodating groove is provided with a second clamping device for clamping the silicon-based material or the sapphire; The accommodating groove is provided with a drainage device for continuously introducing pure water to flush the friction surface while the relative friction between the silicon-based material and the friction surface continuously occurs; The bottom of the accommodating groove is provided with a moving platform for relative movement of the silicon-based material and the sapphire to continuously generate friction between the silicon-based material and the friction surface; Under the condition of continuous friction, the chemical bond provides the required shear stress for the dislocation slip of the atoms of the friction surface, induces the atoms of the friction surface to slip along a specific crystal plane direction, causes plastic deformation, and there is a certain mis-cut angle between the surface of the sapphire and the crystal plane of the sapphire. The plastic deformation occurs along a specific crystal plane direction, thereby forming a micro-nano step structure. With the continuous friction, the plastic deformation continuously accumulates in the crystal plane direction, and finally the micro-nano structure of the sapphire surface is prepared. 10.The device for preparing a micro-nano structure on a sapphire surface according to claim 9, wherein, The drainage device is provided with a water outlet, and the accommodating groove is provided with a drain; The water outlet faces the friction surface of the sapphire, the water outlet is not lower than the friction surface, and the drain is not higher than the friction surface.

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