Cyclic surface conditioning method and surface preparation method for epitaxial material growth

Abstract

Methods for surface conditioning based on cyclic processing are disclosed. The method includes activating the surface, removing excess material from the surface, applying a low energy particle treatment to the surface, and repeating the above steps until the surface has a desired smoothness. The method can be applied to various surfaces, including semiconductor surfaces, metal surfaces, dielectric surfaces, and 2D material surfaces, as well as patterned and non-patterned surfaces. The low energy particle treatment may be etch or deposition, and the process may be combined with ion beam shaping techniques and angled particle beam etch to improve surface conditioning. Methods of making substrates and epitaxial material grown surfaces are also provided.

Description

Technical Field

[0001] This technology relates to the field of surface conditioning and modification, specifically focusing on methods for improving the smoothness and uniformity of various surfaces, such as semiconductor surfaces, metal surfaces, dielectric surfaces, and 2D material surfaces. This field is particularly relevant in industries such as microelectronics, nanotechnology, and advanced materials, where precise control over surface properties is crucial for device performance and functionality. Background Technology

[0002] Semiconductor devices and other microelectronic components require extremely smooth surfaces to achieve optimal performance. Surface roughness can lead to a variety of problems, such as defects in the photolithography process, degraded device performance, and even device failure. Therefore, achieving a high level of surface smoothness is crucial for the successful manufacture of these components.

[0003] Current polishing techniques, such as chemical mechanical polishing (CMP), are widely used to reduce surface roughness on semiconductor wafers and other substrates. CMP involves using chemical slurries and polishing pads to remove material from the surface, resulting in a smoother surface. However, CMP has limitations in achieving the optimal level of smoothness required for certain photolithography processes, leading to potential defects. Additionally, CMP is unsuitable for polishing surfaces with varying heights or angles because it can only polish one horizontal plane at a time.

[0004] Another method to reduce surface roughness is atomic layer etching (ALE), which involves removing material from the surface at the atomic level. ALE can produce smoother surfaces than CMP, but it is not self-stopping and may unnecessarily remove material from different surfaces. Furthermore, the ALE process requires the user to limit the time used for smoothing, which can be challenging due to varying surface conditions.

[0005] The photolithography process itself contributes to surface roughness, thus affecting the original surface and any new surfaces created as a result, such as sidewalls. Peaks and valleys on a wafer surface have different surface energies, making it difficult to develop processes that selectively remove peaks without affecting valleys. A method is needed that can reduce surface roughness during cyclic etching without damaging surfaces that have not reacted with the activating gas.

[0006] In summary, existing technologies have several drawbacks, including limitations in achieving optimal surface smoothness, the inability to polish surfaces with varying heights or tilts, and a lack of selective etching methods. These issues highlight the need for improved surface conditioning methods that can overcome the limitations of current technologies and provide smoother surfaces for photolithography processes and other microelectronic applications. Improved surface fabrication methods are needed, particularly for different materials, to reduce defects and stresses in the grown materials, thereby enhancing the performance of semiconductor devices and structures. Ideally, such methods should be able to fabricate flat and patterned surfaces, thereby minimizing surface damage and addressing the problem of strain formation due to lattice mismatch between different materials. Summary of the Invention

[0007] According to a first aspect of this disclosure, a method for surface conditioning based on cyclic processing is provided. The method includes activating the surface, removing excess material from the surface and its surrounding environment, applying a low-energy particle treatment to the surface, and repeating the above steps until the surface achieves a desired smoothness. Optionally, the low-energy particle treatment uses ions and may be atomic layer etching (ALE) or atomic layer etching utilizing molecular activation. The cyclic processing may also include a deposition step, which may result in atomic layer deposition (ALD).

[0008] This method may include a combination of etching and deposition, and may involve alternating etching and deposition. These steps may be repeated until the process has no further effect on the different treated surfaces. The method may also include ion beam shaping techniques and angled particle beam etching.

[0009] The surface processed by this method can be a sidewall surface or an inclined surface, and can be selected from the group consisting of semiconductor surfaces, metal surfaces, dielectric surfaces, and 2D material surfaces. The surface can be a patterned surface or an unpatterned surface.

[0010] Surface activation can include applying gas exposure to the surface, exposing the surface to a chemical solution, heating the surface to a specific temperature, or applying a particle beam to the surface. Low-energy particle treatment can include low-energy particle beams with particle energies between 10 eV and 100 eV or low-energy plasma treatment with plasma power between 1 W and 50 W.

[0011] It also provides a surface that can be adjusted using this method.

[0012] According to a second aspect of this disclosure, a method for preparing a substrate and a surface for epitaxial material growth is provided. The method includes exposing the surface to a cyclic removal process to remove impurities and defects from the surface. The process involves modifying a topmost surface layer of the surface by introducing chemical species, such as halogens, into a processing chamber volume enclosing the substrate to obtain a topmost modified surface layer. The method further includes extracting excess chemical species from the processing chamber volume, activating the topmost modified surface layer to form volatile products, and optionally removing etching products from the processing chamber volume. Following the cyclic removal process is epitaxial material growth, wherein the growth material differs from the surface material. This method provides a clean and smooth surface for epitaxial material growth, resulting in a high-quality film.

[0013] Alternatively, in some examples, the modification of the topmost surface layer is performed in a gas phase containing only neutral species. This provides a more controlled and gentler modification process, thereby reducing the risk of surface damage.

[0014] Alternatively, in some examples, the cyclic removal process has an etch rate per cycle, wherein the etch rate approaches zero as the number of cycles increases. This self-limiting feature ensures that the process does not over-etch the surface, thus preserving the desired surface properties.

[0015] Alternatively, in some examples, the activation of the topmost modified surface layer is performed in the gas phase without involving surface bombardment with ions. This helps to maintain a damage-free surface, which is crucial for subsequent epitaxial material growth.

[0016] According to a third aspect of this disclosure, the method includes a deposition process step of overgrowing impurities and defects on a surface, said step comprising modifying the topmost surface layer by introducing chemical species for said overgrowth into the processing chamber volume. This additional step can help to further improve surface quality and ensure a smooth and defect-free surface for epitaxial material growth.

[0017] Alternatively, in some examples, the deposition process step is performed before or after the cyclic removal process. This flexibility in the step sequence allows for optimization of the process based on specific substrates and growth materials.

[0018] Optionally, in some examples, the chemical species used for the overgrowth include gallium, nitrogen, and optionally aluminum. These elements can be used to form a variety of compound semiconductor materials, such as group III nitride materials, which have many applications in optoelectronics and power electronics.

[0019] Optionally, in some examples, the deposition process is cyclic. This can provide a more controlled and uniform deposition process, thereby ensuring a high-quality overgrown layer.

[0020] Alternatively, in some examples, the deposition process has a deposition rate per cycle, where the deposition rate approaches zero as the number of cycles increases. This self-limiting feature ensures that the process does not over-deposit material, thus preserving the desired surface properties.

[0021] Optionally, in some examples, at least one step includes a self-limiting reaction that slows down or stops over time or equivalently based on species dosage. This can help ensure a controlled and precise process, thereby avoiding over-etching or over-deposition of material.

[0022] Alternatively, in some examples, self-limiting reactions include chemisorption, deposition, extraction, and / or transformation, such as oxidation or nitriding. These types of reactions can provide a controlled and gentle process, thereby reducing the risk of surface damage.

[0023] Optionally, in some examples, the method includes an additional passivation step prior to epitaxial material growth to prevent surface oxidation or contamination before material growth. This can help further improve surface quality and ensure a clean and defect-free surface for epitaxial material growth.

[0024] Optionally, in some examples, the surface includes patterns such as regularly arranged holes, lines, and / or pillars. This can provide additional control over the properties of epitaxial material growth, such as strain relaxation and defect reduction.

[0025] Optionally, in some examples, the method includes retrieving process control information, such as information from optical emission and residual gas analysis, wherein process parameters of the method are adjusted based on the process control information. This can help optimize the process in real time, thereby ensuring the best possible surface quality and epitaxial material growth.

[0026] According to a fourth aspect of this disclosure, a method for growing epitaxial material on a surface of a substrate is provided. The method includes a cyclic process comprising a sequence of any step according to a second aspect of this disclosure followed by any step according to a third aspect of this disclosure. The method involves repeatedly performing this sequence to grow epitaxial material on the surface, wherein the grown material differs from the surface material. This method provides a highly controllable and optimized process for preparing surfaces and growing high-quality epitaxial materials.

[0027] Optionally, in some examples, the steps are repeated until at least one of the steps has no further effect on the surface. This can help ensure that the surface is adequately prepared and optimized for epitaxial material growth, resulting in a high-quality film. Attached Figure Description

[0028] The example is described in more detail below with reference to the accompanying drawings.

[0029] Figure 1 An example of a surface conditioning method based on cyclic processing is shown.

[0030] Figure 2 Another example of a surface conditioning method based on cyclic processing is shown.

[0031] Figure 3 Another example of a surface conditioning method based on cyclic processing is shown.

[0032] Figure 4 This is a flowchart illustrating an example of a method for surface conditioning based on cyclic processing, according to the present disclosure.

[0033] Figure 5 These are atomic force micrographs (AFM) of the initial surface and the final surface after the cycle process, based on the example.

[0034] Figure 6 This is a schematic diagram illustrating the effect of a cyclic removal process used to prepare a substrate surface for improved material growth, comparing material growth on a typical surface with material growth after the cyclic removal process.

[0035] Figure 7 This is a schematic diagram illustrating the effect of a deposition process followed by a cyclic removal process for preparing a substrate surface for improved material growth, comparing material growth on a typical surface with material growth after material deposition and subsequent cyclic removal.

[0036] Figure 8 This is a schematic diagram illustrating the effect of a cyclic removal and deposition process for preparing a substrate surface for improved material growth, comparing material growth on a typical surface with material growth after the cyclic removal and deposition process.

[0037] Figure 9 This is a block diagram illustrating the execution process flow of a method for preparing a cyclic process for improving the surface of a substrate for material growth.

[0038] Figure 10 Atomic force microscopy (AFM) images and line scans of the initial Si surface and the surface after cyclic etching are shown, demonstrating the reduction in roughness after the cyclic etching process.

[0039] Figure 11 Atomic force microscopy (AFM) images of the initial GaN surface and the surface after cyclic deposition followed by cyclic etching are shown, demonstrating the reduction in roughness after the cyclic deposition process followed by the cyclic etching process. Detailed Implementation

[0040] A. Circulating surface conditioning

[0041] The detailed description set forth below provides information and examples of the disclosed technology in sufficient detail to enable those skilled in the art to practice the contents of this disclosure.

[0042] Figure 1 An example of a surface conditioning method based on cyclic processing is shown. Figure 1 Figure a shows a substrate 100 having an initial surface roughness 110. The substrate 100 can be made of various materials such as semiconductor materials, metallic materials, dielectric materials, or 2D materials. The surface of the substrate 100 can be patterned or unpatterned.

[0043] exist Figure 1 Figure b illustrates the final surface, where substrate 100 has a desired surface 111 with reduced surface roughness while retaining the original thickness of substrate 100. This reduction in surface roughness is achieved through a cyclic processing method, which includes activating the surface, removing excess material, applying low-energy particle treatment, and repeating these steps until the desired smoothness is achieved. This surface conditioning is achieved through a cyclic processing method as described above, which can involve any cyclic process, including atomic layer etching (ALE) or atomic layer deposition (ALD).

[0044] Figure 2 Another example of a surface conditioning method based on cyclic processing is shown. Figure 2 Figure a shows an initial structure 110 having surfaces 111, 112, and 122, which have roughness. Additionally, the substrate 100 has another feature 210, which has a different height than 110. Feature 210 has different surfaces 211, 212, and 222, which have roughness, as shown.

[0045] exist Figure 2 Figure b shows the final structure, which has feature 110 with the desired surfaces 311, 312, and 322, and a reduced surface roughness of feature 110, while retaining the original dimensions of feature 110. Furthermore, Figure 2 b illustrates feature 210 with desired surfaces 411, 412, and 422, and the reduced surface roughness of feature 210 while preserving its original critical dimensions. This surface conditioning is achieved through a cyclic processing method as described above, which can involve any cyclic process, including atomic layer etching (ALE) or atomic layer deposition (ALD).

[0046] Figure 3 Another example of a surface conditioning method based on cyclic processing is shown. Figure 3 Figure a shows an initial structure 110 having surfaces 111, 112 and 122, which have roughness.

[0047] exist Figure 3 Figure b shows the final structure, which has the desired surfaces 222, 212, and 211 of feature 110 and reduced surface roughness, while retaining the original critical dimensions of feature 110. This surface conditioning is achieved through a cyclic processing method as described above, which can involve any cyclic process, including atomic layer etching (ALE) or atomic layer deposition (ALD).

[0048] Figure 4 This is a flowchart illustrating an example of a method for surface conditioning based on a cyclic process, according to the present disclosure. The method includes activating the surface (step 401), removing excess material from the chamber (step 402), applying a low-energy particle treatment to the surface (step 403), and repeating the above steps until the surface achieves the desired smoothness (step 404). The low-energy particle treatment can be etching, deposition, or a combination of both. The method may also include ion beam shaping techniques and angled particle beam etching.

[0049] Figure 5 Atomic force microscopy (AFM) images of the initial surface and the final surface after the cycling process, based on an example, are shown. Figure 5 Figure a shows a photomicrograph of the scanned area 500, which has an area of ​​approximately 1 μm. 2 In the bottom image, roughness values ​​501, 502, and 503 were measured at different locations (top, middle, and bottom) of the scanned area. The roughness was measured to be approximately 0.11 nm.

[0050] exist Figure 5 Figure b shows the results of the AFM measurements on the final surface. Top section 504 shows a micrograph of the scanned area, with an area of ​​approximately 1 μm. 2 In the bottom image, roughness values ​​505, 506, and 507 were measured at different locations (top, middle, and bottom) of the scanned area. The roughness was measured to be approximately 0.021 nm. This reduction in surface roughness was achieved through a cyclic processing method as described above, which can involve any cyclic process, including atomic layer etching (ALE) or atomic layer deposition (ALD).

[0051] A1. Surface activation process

[0052] Surface activation is a step in a cyclic processing-based surface conditioning method. In this process, the surface of the substrate is activated to facilitate subsequent low-energy particle treatment, which can be etching, deposition, or a combination of both. The activation process can be performed using various techniques such as gas exposure, chemical solution exposure, temperature-based activation, and particle beam activation. Each of these techniques has its advantages and can be tailored to suit the specific requirements of the substrate material and the desired surface smoothness.

[0053] A1.1. Gas Exposure Activation

[0054] In some examples, the surface activation process may include exposing the surface to a gas or a mixture of gases. Gas exposure can alter the surface chemistry, making it more susceptible to the effects of low-energy particle treatment. The appropriate gas selection is crucial to achieving the desired surface activation and ensuring compatibility with the substrate material.

[0055] A1.2. Chemical solution activation

[0056] In some examples, the surface activation process may include exposing the surface to a chemical solution. The chemical solution can interact with the surface material, altering its properties and making it more suitable for low-energy particle processing. The selection of a suitable chemical solution is crucial for achieving the desired surface activation and ensuring compatibility with the substrate material.

[0057] A1.3. Temperature-based activation

[0058] In some examples, the surface activation process may include heating the surface to a specific temperature or a specific temperature range. Temperature-based activation causes thermal expansion or contraction of the surface material, resulting in changes in surface properties that can facilitate the processing of low-energy particles. Determining the optimal temperature range is crucial for achieving the desired surface activation and ensuring compatibility with the substrate material.

[0059] A1.3.1. Determine the optimal temperature range

[0060] The optimal temperature range for temperature-based activation processes depends on the substrate material and desired surface properties. In some examples, the temperature range can be selected to induce thermal expansion or contraction of the surface material, resulting in changes in surface roughness or other properties that can facilitate low-energy particle processing. In other examples, the temperature range can be selected to induce phase transitions or other structural changes in the surface material, which can alter the properties of the surface material and make it more suitable for low-energy particle processing. The determination of the optimal temperature range can be based on factors such as the thermal properties of the substrate material, desired surface properties, and the compatibility of the temperature range with the low-energy particle processing process.

[0061] A1.4. Particle Beam Activation

[0062] In some examples, the surface activation process may include applying a particle beam to a surface. The choice of particle beam for the particle beam activation process depends on the substrate material and the desired surface properties. In some examples, the particle beam may include ions, electrons, or neutral particles that may be physically sputtered or chemically react with the surface material to alter its properties. In other examples, the particle beam may include photons or other electromagnetic radiation that may induce electronic or vibrational excitation in the surface material, resulting in changes in surface properties that can facilitate low-energy particle processing. A suitable particle beam may be selected based on factors such as the reactivity of the particles with the substrate material, the desired surface properties, and the compatibility of the particle beam with the low-energy particle processing process.

[0063] A2. Excess Material Removal Process

[0064] In one example, the excess material removal process is a step in a surface conditioning method based on cyclic processing. This process aims to remove any excess material from the surface and its surrounding environment after the surface activation process. Removing excess material ensures that subsequent low-energy particle treatment can be effectively applied to the surface without interference from unwanted material. The excess material removal process can include various techniques, such as purge gases, pumped gases, or a combination of pumping and purging.

[0065] A2.1. Purge gas

[0066] In some examples, the excess material removal process may include a purge gas. Purge gas involves introducing an inert gas, such as nitrogen or argon, into the processing chamber to replace and remove any excess material, including reaction gases or byproducts from surface activation processes. The purge gas can be introduced at a controlled flow rate and pressure to ensure efficient removal of excess material without damaging or altering the surface properties. Using purge gas in excess material removal processes offers the advantage of a simple and cost-effective technique for removing unwanted material from the processing environment.

[0067] A2.2. Pumped out gas

[0068] In other examples, the excess material removal process may include pumping out gas. Pumping out gas involves evacuating the processing chamber using a vacuum pump to remove any excess material, including reaction gases or byproducts from the surface activation process. The vacuum pump can operate at controlled pressures and flow rates to ensure efficient removal of excess material without damaging or altering the surface properties. Using pumped out gas in the excess material removal process offers the advantage of more thorough removal of unwanted material from the processing environment compared to purge gas alone.

[0069] A2.3. Combination of pumping and purging

[0070] In some examples, the excess material removal process may include a combination of pumping and purging. This approach involves evacuating the processing chamber using a vacuum pump and replacing and removing any excess material, including reactant gases or byproducts from the surface activation process, using an inert gas. Depending on the specific requirements of the surface conditioning process, the combination of pumping and purging can be performed sequentially or simultaneously. Using a combination of pumping and purging in the excess material removal process offers the advantage of more comprehensive removal of unwanted material from the processing environment, thereby ensuring that subsequent low-energy particle treatment can be effectively applied to the surface without interference from excess material.

[0071] Taking into account factors such as the type of surface being treated, the materials involved in the surface activation process, and the desired surface smoothness, the excess material removal process can be tailored to the specific requirements of the surface conditioning process. By effectively removing excess material from the surface and its surrounding environment, the excess material removal process plays a role in achieving the desired surface smoothness and ensuring the overall success of cyclic processing-based surface conditioning methods.

[0072] A3. Low-energy particle treatment

[0073] In one example, the cyclic processing-based surface conditioning method includes a low-energy particle treatment step. This low-energy particle treatment can be applied to various types of surfaces, such as patterned and unpatterned surfaces, and can be used on different materials, including semiconductor surfaces, metallic surfaces, dielectric surfaces, and 2D material surfaces. The low-energy particle treatment can be performed using a low-energy particle beam with particle energies between 10 eV and 100 eV, or a low-energy plasma treatment with plasma power between 1 W and 50 W.

[0074] A3.1. Low-energy particle etching

[0075] In some examples, low-energy particle treatment may include a low-energy particle etching process. This etching process can be used to selectively remove material from a surface, thereby reducing surface roughness and improving overall surface quality. Low-energy particle etching processes can be performed using various techniques such as ion beam etching, reactive ion etching, or plasma etching.

[0076] A3.1.1. Atomic Layer Etching (ALE) Utilizing Molecular Activation

[0077] In one example, a low-energy particle etching process may include atomic layer etching (ALE) utilizing molecular activation. ALE using molecular activation is a highly controlled etching process that allows material removal at the atomic level, resulting in a very smooth surface. The process involves activating the surface using suitable activation methods such as gas exposure, chemical solution exposure, heating, or particle beam exposure, followed by the application of a low-energy particle beam or plasma treatment to selectively remove material from the surface. The use of ALE utilizing molecular activation can offer several advantages, such as improved control over the etching process, reduced surface roughness, and minimized damage to the underlying material.

[0078] A3.2. Low-energy particle deposition

[0079] In some examples, low-energy particle processing can include a low-energy particle deposition process. This deposition process can be used to selectively deposit material onto a surface, thereby filling any surface irregularities and improving the overall surface quality. Low-energy particle deposition processes can be performed using various techniques such as atomic layer deposition (ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD).

[0080] A3.2.1. Atomic Layer Deposition (ALD)

[0081] In one example, low-energy particle deposition processes can include atomic layer deposition (ALD). ALD is a highly controlled deposition process that allows material to be deposited at the atomic level to produce very smooth surfaces. The process involves sequentially exposing the surface to different precursor gases, which react with the surface to form thin layers of the desired material. The use of ALD can offer several advantages, such as improved control over the deposition process, reduced surface roughness, and the ability to deposit materials with high conformality and uniformity.

[0082] A3.3. Combination of Etching and Deposition

[0083] In some examples, low-energy particle treatment may include a combination of etching and deposition processes. This can involve alternating etching and deposition steps, or performing both etching and deposition simultaneously. The combination of etching and deposition can be used to selectively remove material from certain areas of a surface while depositing material in other areas, thereby reducing surface roughness and improving overall surface quality.

[0084] A3.3.1. Alternate etching and deposition.

[0085] In one example, low-energy particle processing may include alternating etching and deposition steps. This could involve performing an etching step to selectively remove material from the surface, followed by a deposition step to selectively deposit material onto the surface. By alternating between etching and deposition steps, surface roughness can be reduced while maintaining the overall thickness of the material. This approach offers several advantages, such as improved control over the surface conditioning process, reduced surface roughness, and the ability to selectively modify the surface without affecting the underlying material.

[0086] A4. Cyclic processing and surface smoothness

[0087] In one example, the cyclic processing and surface smoothing sections focus on determining the desired surface smoothness, implementing a self-stopping cyclic process, and monitoring the reduction in surface roughness during the surface conditioning process. The cyclic processing method can include various optional features to achieve the desired surface smoothness and effectively reduce surface roughness.

[0088] A4.1. Determine the desired surface smoothness

[0089] In some examples, the desired surface smoothness is determined based on the specific application or requirements of the treated substrate. Surface smoothness can be quantified using various surface roughness parameters such as root mean square (RMS) roughness, average roughness, or peak-valley roughness. The desired surface smoothness can be achieved by repeating cyclic processing steps until the surface roughness parameter reaches a predetermined value or meets the specific requirements for the treated substrate.

[0090] A4.2. Self-stopping loop process

[0091] In one example, the cyclic processing method may include a self-stopping feature, where the process automatically stops when it has no further impact on the surface or when the surface roughness parameters reach a plateau. This self-stopping feature can be advantageous in preventing over-processing of the surface and preserving the original dimensions of the substrate or patterned features. A self-stopping cyclic process can be achieved by optimizing process parameters such as activation conditions, excess material removal methods, and low-energy particle treatment conditions to ensure that the process has minimal or no impact on the surface once the desired smoothness is achieved.

[0092] A4.3. Monitoring the reduction in surface roughness

[0093] In some examples, various in-situ or ex-situ metrology techniques can be used to monitor the reduction in surface roughness during cyclic processing. In-situ metrology techniques can include optical monitoring, ellipsography, or reflectometry, which can provide real-time feedback on surface roughness parameters during cyclic processing. Ex-situ metrology techniques can include atomic force microscopy (AFM), scanning electron microscopy (SEM), or transmission electron microscopy (TEM), which can provide high-resolution images and quantitative measurements of surface roughness parameters after cyclic processing.

[0094] Monitoring the reduction in surface roughness can be beneficial in determining the progress of the surface conditioning process and ensuring the achievement of the desired surface smoothness. Furthermore, monitoring can provide valuable information for optimizing process parameters and improving the efficiency of cyclic processing methods.

[0095] A5. Integration with ion beam shaping technology

[0096] In one example, a cyclic processing-based surface conditioning method can be integrated with ion beam shaping technology to further enhance the surface smoothing process. Ion beam shaping can be used to modify surface morphology by controlling ion beam parameters such as ion energy, ion species, ion incident angle, and ion flux. This integration provides additional control over the surface conditioning process, resulting in more precise and efficient surface smoothing.

[0097] A5.1. Angled Particle Beam Etching

[0098] In some examples, the integration of ion beam shaping techniques with surface conditioning methods can include angled particle beam etching. Angled particle beam etching can be used to selectively remove material from specific regions of a surface, such as peaks of surface roughness characteristics, while preserving valleys. This can result in a more uniform surface morphology and reduced surface roughness.

[0099] In one example, angled particle beam etching can be performed by guiding an ion beam at an angle relative to the surface normal. The angle can be adjusted to optimize the etching process for specific surface features and material properties. By controlling ion beam parameters such as ion energy, ion type, ion incident angle, and ion flux, the etching process can be tailored to achieve the desired surface smoothing effect.

[0100] A5.2. Optimization of Ion Beam Parameters

[0101] In some examples, ion beam parameters can be optimized to achieve the desired surface shaping effect. Ion beam parameters can include ion energy, ion species, ion incident angle, and ion flux. By adjusting these parameters, ion beam shaping techniques can be tailored to specific surface features and material properties, resulting in more efficient and precise surface smoothing.

[0102] In one example, the ion energy can be adjusted to control the depth of ion penetration into the surface material. Higher ion energies produce deeper penetration and stronger etching, while lower ion energies produce shallower penetration and gentler etching. The optimal ion energy can depend on specific surface features and material properties, as well as the desired surface smoothing effect.

[0103] In another example, the type of ion can be selected based on its chemical reactivity with the surface material. Some ion types may be more effective at etching certain materials, while others may be less effective or even cause unwanted side effects such as surface damage or contamination. The optimal ion type can depend on the specific surface features and material properties, as well as the desired surface smoothness.

[0104] In yet another example, the ion incident angle can be adjusted to control the directionality of the etching process. By guiding the ion beam at an angle relative to the surface normal, the etching process can be made more selective, preferentially removing material from specific regions of the surface (e.g., peaks of surface roughness features). The optimal ion incident angle can depend on specific surface features and material properties, as well as the desired surface smoothing effect.

[0105] In another example, the ion flux can be adjusted to control the etching rate and uniformity. A higher ion flux produces faster etching and a stronger surface smoothing, while a lower ion flux produces slower etching and a milder surface smoothing. The optimal ion flux can depend on specific surface features and material properties, as well as the desired surface smoothing effect.

[0106] By optimizing ion beam parameters, the integration of ion beam shaping technology with cyclic processing-based surface conditioning methods can provide more precise and efficient surface smoothing, resulting in improved surface quality and reduced surface roughness. This integration is particularly advantageous for applications requiring high-quality surfaces, such as semiconductor devices, optical components, and other advanced technologies.

[0107] A6. Surface conditioning for various surface types

[0108] Circular processing-based surface conditioning methods can be applied to various surface types, including patterned and unpatterned surfaces, as well as surfaces made of different materials such as semiconductors, metals, dielectrics, and 2D materials. This method can be tailored to address the specific requirements of each surface type and material, thus providing a general and efficient approach to surface conditioning.

[0109] A6.1. Patterned Surface

[0110] In some examples, surface conditioning methods can be applied to patterned surfaces, which may include features such as lines, dots, pillars, through-holes, grids, and other patterns. This method can be adapted to address specific challenges associated with conditioning patterned surfaces, such as preserving the original dimensions of features while reducing surface roughness.

[0111] A6.1.1. Sidewall Surface

[0112] In one example, a surface conditioning method can be applied to the sidewall surfaces of a patterned feature. This method can be tailored to address specific challenges associated with conditioning the sidewall surfaces, such as maintaining the original dimensions of the feature while reducing surface roughness. A cyclical processing approach, including activation, removal of excess material, and low-energy particle treatment, can be optimized to achieve the desired surface smoothness on the sidewall surfaces without affecting the overall dimensions of the patterned feature.

[0113] A6.1.2. Inclined Surface

[0114] In some examples, surface conditioning methods can be applied to the tilted surfaces of patterned features. These methods can be adapted to address specific challenges associated with conditioning tilted surfaces, such as maintaining the original dimensions of the feature while reducing surface roughness. A cyclical processing approach, including activation, removal of excess material, and low-energy particle treatment, can be optimized to achieve the desired surface smoothness on the tilted surface without affecting the overall dimensions of the patterned feature.

[0115] A6.2. Unpatterned surfaces

[0116] In one example, the surface conditioning method can be applied to an unpatterned surface, such as the surface of substrate 100. The method can be tailored to address specific challenges associated with conditioning unpatterned surfaces, such as reducing surface roughness without affecting the overall thickness of the substrate. A cyclical processing approach, including activation, removal of excess material, and low-energy particle treatment, can be optimized to achieve the desired surface smoothness on the unpatterned surface while preserving the original thickness of the substrate.

[0117] A6.3. Material-Specific Surface Conditioning

[0118] Surface conditioning methods based on cyclic processing can be adapted to address the specific requirements of various materials, such as semiconductors, metals, dielectrics, and 2D materials. In some examples, activation processes, removal of excess material, and low-energy particle treatments can be tailored to specific material properties and requirements to ensure optimal surface conditioning results.

[0119] For example, the selection of appropriate gases, chemical solutions, temperature ranges, and particle beams for activation processes can be based on specific material properties and requirements. Similarly, the selection of appropriate low-energy particle treatments (such as etching or deposition processes) can be tailored to specific material properties and requirements.

[0120] By adapting the surface conditioning method to specific material properties and requirements, this method can provide efficient and effective surface conditioning results for various surface types and materials, thereby ensuring the optimal performance and reliability of the conditioned surface.

[0121] B. Surface preparation methods for epitaxial material growth

[0122] Figure 6 This diagram illustrates the effect of a cyclic removal process used to prepare a substrate surface (Si, sapphire, SiC, GaN, or any substrate) for improved material growth. On the left, material growth on a typical surface 2200 of substrate 2100 is shown. On the right, material growth after the cyclic removal process is shown, resulting in the prepared substrate surface 2201. Compared to the grown material 2300, the grown material 2301 is improved by reducing defects.

[0123] Figure 7 This diagram illustrates the effect of a deposition process followed by a cyclic removal process for preparing a substrate surface (Si, sapphire, SiC, GaN, or any substrate) to improve material growth. On the left, material growth on a typical surface 2200 of substrate 2100 is shown. On the right, material growth after material deposition 2400 and the subsequent cyclic removal process is shown, resulting in the prepared substrate surface 2202. Compared to the grown material 2300, the grown material 2302 is improved by reducing defects.

[0124] Figure 8 A schematic diagram illustrating the effect of a cyclic removal and deposition process used to prepare a substrate surface (Si, sapphire, SiC, GaN, or any substrate) for improved material growth is presented. On the left, material growth on a typical surface 2200 of substrate 2100 is shown. On the right, the cyclic removal and deposition process provides a substrate surface 2204 for material growth. A centrally flat surface 2203 of the substrate and material deposition 2401 are also shown. Compared to the grown material 2300, the grown material 2303 is improved by reducing defects.

[0125] Figure 9 This is a block diagram illustrating the execution process flow of a method for preparing a cyclic process for improving the surface of a substrate for material growth.

[0126] Figure 10Atomic force microscopy (AFM) images and line scans of the initial Si surface (left) and the surface after cyclic etching (right) are shown. Top portions 2500 and 2504 show microscopy images of the scanned areas, with an area of ​​1 μm². Bottom images 2501, 2502, 2503, 2505, 2506, and 2507 show line scans at different locations (top, middle, and bottom) of the corresponding scanned areas 2500 and 2504, respectively. The roughness is significantly reduced after the cyclic etching process.

[0127] Figure 11 The image presents atomic force micrographs (AFM) of the initial GaN surface (left) and the surface after cyclic deposition followed by cyclic etching (right). The roughness is significantly reduced after the cyclic deposition process followed by the cyclic etching process.

[0128] about Figures 6 to 11 Further discussion of the surface preparation of epitaxial materials is provided in Sections 6 through 8 below.

[0129] B2. Substrate Material

[0130] In some examples, the surface material can be silicon (Si), sapphire, silicon carbide (SiC), gallium nitride (GaN), or any other suitable substrate material. The choice of surface material can significantly affect the quality of the grown material and the effectiveness of the cycle removal process. The surface can have a variety of materials and patterns, which will affect the material growth. In some examples, the substrate surface can include patterns such as regularly arranged holes, lines, and / or pillars. The disclosed method can be applied to these patterned surfaces, thereby allowing the fabrication of substrate surfaces with a variety of geometries and morphologies. The method can be adapted to accommodate a variety of surface patterns to ensure optimal material growth.

[0131] B3. Surface preparation method

[0132] B3.1. Cyclic Removal Process

[0133] In one example, the cyclic removal process involves a series of steps that expose the surface of the substrate to remove impurities and defects from the surface. This process can be repeated multiple times to achieve the desired surface quality.

[0134] B3.1.1. Modify the top surface layer

[0135] The top surface layer of a substrate is modified by introducing a chemical species, such as a halogen, into a processing chamber volume enclosing the substrate. The processing chamber volume is an enclosed space in which the substrate is exposed to the chemical species and a cyclic removal process occurs. The halogen can be chlorine, bromine, or iodine. The chemical species is chemisorbed onto the surface. This results in the formation of a top modified surface layer on the substrate. The modification step forms a thin reactive surface layer of well-defined thickness, which is subsequently easier to remove than the unmodified material. This modified layer is characterized by a steep gradient of chemical composition. The rate of chemisorption can be increased, for example, by activating the chemical species with plasma. The modification of the top surface layer can be a self-limiting process, which slows down or stops over time or equivalently based on the species dosage.

[0136] In some examples, after modifying the topmost surface layer, excessive chemical species can be extracted from the processing chamber volume. This evacuation can be accomplished using an inert gas, thus ensuring that the processing chamber volume is free of unwanted chemical species that could interfere with the cyclic removal process.

[0137] B3.1.2. Activate the top modified surface layer

[0138] The topmost modified surface layer is activated to form volatile products. Activation removes the thin reactive surface layer produced by the previous surface modification steps. This activation can be performed in the gas phase without involving surface bombardment with ions, for example, by temperature cycling, light pulse exposure, and / or chemical reactions. By eliminating surface bombardment from high-energy particles during the cyclic removal process, a damage-free surface is ensured, providing an optimal surface for epitaxial material growth. The activation of the topmost modified surface layer can be a self-limiting process, which slows down or stops over time or equivalently based on species dosage.

[0139] In some examples, activation of the topmost modified surface layer may include a plasma pulse step with low ion energies for the plasma pulse, such as below 60 eV. In some examples, ion energies of around 20 eV provide particularly favorable results. The use of low ion energies ensures low-damage etching of the surface, resulting in a damage-free surface optimal for epitaxial material growth.

[0140] In some examples, after activating the topmost modified surface layer, etch products can be removed from the processing chamber volume. This removal ensures that the processing chamber volume is free of etch products that could interfere with subsequent steps of the method, such as epitaxial material growth.

[0141] Surface modification and activation steps provide an atomic layer etching process. The atomic layer etching process can also include a quasi-atomic layer etching process, which may include quasi-self-limiting and non-self-limiting reactions. Isotropic atomic layer etching processes using thermal desorption and chemical reactions are particularly advantageous in some examples and provide optimized results for surface preparation prior to material growth.

[0142] Methods for preparing substrates and surfaces for epitaxial material growth can include various optional features and steps, such as deposition processes for overgrowing impurities and defects on the surface, passivation steps prior to epitaxial material growth, and the use of self-limiting reactions during cyclic removal. These optional features can further enhance the effectiveness of the method and improve the quality of the grown material, and are described in more detail below.

[0143] B3.1.3. Number of cycles and etch rate per cycle

[0144] The number of cycles in the cyclic removal process can be optimized based on the surface roughness. In one example, the number of cycles ranges from 5 to 200. For instance, 20 cycles may provide a particularly optimal surface for material growth.

[0145] In some examples, the cyclic removal process has an etch rate per cycle, where the etch rate approaches zero with increasing cycle number, indicating that the process becomes self-limiting over time or with varying species dosage. This enables processes that facilitate control over the amount of material removed from the surface, thereby ensuring a smooth and defect-free surface for subsequent material growth.

[0146] The cyclic removal process can be combined with an ion beam shaping process to smooth and clean different surfaces of structured surfaces, such as surfaces with patterns like regularly arranged holes, lines, and / or pillars. This can further enhance the quality of the grown material and expand the potential applications of the method.

[0147] B3.2. Deposition process

[0148] In some examples, the method may include a deposition process that overgrows impurities and defects on the surface. This process involves modifying the topmost surface layer by introducing chemical species for overgrowth into the processing chamber volume. The chemical species for overgrowth may include gallium, nitrogen, and optionally aluminum. The deposition process may include a quasi-atomic layer deposition process, which may include quasi-self-limiting and non-self-limiting reactions.

[0149] B3.2.1. Overgrowth impurities and defects

[0150] In some examples, the deposition process provides an interface layer by depositing a thin film of material on the surface. This interface layer can alleviate strain relaxation caused by lattice mismatch between different materials in contact with each other, thereby mitigating lattice mismatch problems with materials subsequently grown epitaxially. The deposition process can also fill valleys on the surface, ensuring that the surface remains smooth even during subsequent epitaxial growth of very thin films.

[0151] Depending on the desired surface quality and material growth requirements, the deposition process can be performed before or after the cyclic removal process. In some cases, an additional passivation step can be performed before epitaxial material growth to prevent surface oxidation or contamination prior to material growth. This can further improve the quality of the grown material.

[0152] B3.2.2. Chemical species used for overgrowth

[0153] In some examples, the chemical species used for overgrowth may include gallium, nitrogen, and optionally aluminum. The deposition process may involve forming a monolayer of gallium atoms, followed by the formation of an atomic layer of gallium nitride on the surface.

[0154] B3.2.3. Cyclic Deposition Process

[0155] In some examples, the deposition process can be cyclic, with the deposition rate approaching zero as the number of cycles increases. This allows for better control over the thickness of the deposited material and ensures a smooth, defect-free surface for subsequent material growth. The deposition process can be a self-limiting process based on time or species dosage, as described in further detail below.

[0156] The number of cycles in the deposition process can be optimized based on surface roughness. In one example, the number of cycles ranges from 5 to 200. For instance, 20 cycles may provide a particularly optimal surface for material growth.

[0157] B4. Cyclic Process and Subsequent Epitaxial Material Growth

[0158] In some examples, the method may involve a sequence of steps in a cyclic process (including any of the steps described in Sections 3.1 and 3.2). The overall sequence may be repeated multiple times to achieve optimized surface quality and prepare a surface for epitaxial material growth. High-quality films of various materials are provided for growth on prepared substrate surfaces.

[0159] In some examples, the total sequence of steps in the cyclic process can be repeated multiple times to achieve optimized surface quality. The number of cycles can be optimized based on the surface roughness, with a range of 5 to 200 cycles possible. For example, 20 cycles may provide a particularly optimal surface for material growth.

[0160] Therefore, after the cycling process, epitaxial material growth is performed on the prepared substrate surface. This involves forming a high-quality film of the growth material on the substrate surface. The growth material differs from the surface material, and in some examples, the growth material can be a group III nitride material grown on a silicon substrate.

[0161] The cyclic process can be integrated with growth techniques such as molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD) to provide surface preparation in the same chamber or in an adjacent chamber where the surface preparation process is not exposed to ambient air between the surface preparation and growth processes, which further improves the quality of the grown film. This method can also be combined with other processes such as atomic layer cleaning, rapid surface temperature cycling, and self-organization to further enhance the quality of the grown material.

[0162] The method may include retrieving process control information, such as information from optical emission and residual gas analysis, and adjusting process parameters based on this information. This can help optimize the process for different substrates and surface patterns, resulting in improved material growth. Specifically, monitoring and control of the cyclic process are used to adjust process parameters as needed to achieve the desired results. In-situ control is preferred and typically includes monitoring parameters such as optical emission and residual gas analysis, as well as monitoring thin film properties in various ways, such as using optical interferometry. By monitoring these parameters, process endpoints and intermediate process points can be determined, and process time and parameters can be adjusted as needed to achieve improved and prepared surfaces for material growth.

[0163] B5. Self-limiting reaction

[0164] In some examples, the method may include at least one self-limiting reaction that slows down or stops over time or equivalently based on species dosage. These self-limiting reactions can provide a controlled and precise process for modifying and activating the topmost modified surface layer, and in some examples, a controlled and precise deposition process, thereby ensuring consistent and high-quality surface preparation for epitaxial material growth.

[0165] Existing processes, such as those in GB2601404A, do not stop after removing the uneven, damaged surface layer and will etch away the underlying original, undamaged layer. This can be a significant drawback for smoothing very thin films and structures where removing an additional few nanometers of material may be crucial and unnecessary. Chemical mechanical polishing or planarization (CMP) processes also do not stop after removing the uneven, damaged surface layer and will remove some of the underlying original, undamaged layer.

[0166] In one example, a self-limiting reaction may include chemisorption, where chemical species are chemisorbed onto the surface. In some examples, a self-limiting reaction may include deposition, where chemical species are introduced into the processing chamber volume to overgrow impurities and defects on the surface. In one example, a self-limiting reaction may include extraction. In the case of extraction, the original material is a compound of elements, and the surface modification step preferentially removes one element from the surface, while different elements are removed in subsequent activation / removal steps. The extraction process may be self-limiting, slowed down or stopped depending on time or species dosage. Controlled extraction processes can provide consistent and non-destructive removal of the topmost modified surface layer, thus providing a clean and smooth surface for epitaxial material growth. In some examples, a self-limiting reaction may include conversion, such as oxidation or nitriding, where chemical species introduced into the processing chamber volume react with the surface to form a modified surface layer. The conversion process may be self-limiting, slowed down or stopped depending on time or species dosage. Controlled conversion processes can provide consistent and precise modification of the surface layer, thus providing an optimal surface for epitaxial material growth.

[0167] B6. Examples of process steps in different sequences

[0168] This section describes various examples of the disclosed methods for preparing substrate surfaces for improving material growth. These examples illustrate different configurations and sequences of method steps that can be tailored to specific applications and requirements.

[0169] B6.1. Deposition process prior to the cyclic removal process

[0170] In one example, the deposition process precedes the cyclic removal process. This configuration can be advantageous in certain situations because it allows for the formation of an interface layer by depositing a thin film material on the substrate surface prior to the cyclic removal process. This interface layer can help alleviate strain relaxation caused by lattice mismatch between different materials in contact with each other, thereby mitigating lattice mismatch problems with the material subsequently grown epitaxially. This implementation in... Figure 7 As shown, the material deposition 2400 is followed by a cyclic removal process, thereby producing the prepared substrate surface 2202.

[0171] B6.2. Deposition process following the cyclic removal process

[0172] In another example, the deposition process follows the cyclic removal process. This configuration can be advantageous in some cases because it allows for the overgrowth of impurities and defects on the surface after the cyclic removal process. The deposition process can fill in valleys on the surface, thus ensuring that the surface remains smooth even during subsequent epitaxial growth of very thin films. This implementation... Figure 8As shown, the cyclic removal process is followed by material deposition 2401, thereby producing the prepared substrate surface 2204.

[0173] B6.3. Passivation step before epitaxial material growth

[0174] In some examples, the method may include an additional passivation step prior to epitaxial material growth. This can further enhance the quality of the grown material by protecting the prepared surface from unwanted reactions with ambient gases or contaminants. For example, a passivation step can help prevent surface oxidation or contamination before material growth, thereby ensuring a high-quality grown material film on the prepared substrate surface. The passivation step can be performed using various techniques, such as chemical passivation, plasma passivation, or thermal passivation.

[0175] B7. Examples of surface preparation for epitaxial material growth

[0176] B7.1 First Example Procedure Involves Figure 6 and Figure 9 :

[0177] The surface of Si is smoothed using a cyclic removal process, and then GaN material is grown on top of that surface.

[0178] Process steps:

[0179] 1. Pre-cleaning: Preferably, the silicon substrate is free of contaminants and native oxides before starting the cycle process. This can be achieved through a pre-cleaning step, which typically involves brief exposure to plasma or chemical treatment to remove impurities. Buffered oxide etching (BOE) 10:1 is advantageous for removing native oxides from the Si surface and can be performed by immersing the substrate in buffered HF for 30 seconds, followed by rinsing in deionized water for 30 seconds and dry blowing with N2 for 15 seconds.

[0180] 2. Initial gas exposure for modifying the topmost surface layer: During the cyclic removal process, the Si surface is first exposed to chlorine gas, which is chemisorbed onto the surface. This step is self-limiting and slows down or stops over time or equivalently based on the species dosage. For faster chemisorption, activating the Cl2 gas with, for example, plasma may be advantageous. Example process parameters for this step:

[0181] • Chlorine (Cl2) flow rate: ranging from 1 sccm to 40 sccm (standard cubic centimeters per minute).

[0182] • Pressure: Between 1 mTorr and 60 mTorr, and in the preferred example it is set to 3 mTorr.

[0183] • Time: Between 15 milliseconds and 2 minutes. For Cl2 gas deactivated at room temperature, the preferred time is between 5 and 60 s, determined based on the process pressure. For a process pressure of 20 mTorr at room temperature, the optimal exposure time was determined to be 20 s. Specific optimal parameters may depend on other process details, such as gas flow rate. The optimal gas flow rate is determined based on the processing chamber volume and the exposed sample surface. In the example, a Cl2 gas flow rate above 20 sccm was determined to be optimal for the process results. It has been determined that spontaneous Si etching utilizing the gas does not exist at room temperature if the Cl2 gas is not activated.

[0184] 3. Purging - Removal of Excess Chemicals: After chlorine chemisorption on the surface, the reactor is purged with an inert gas (e.g., argon) to remove any excess chlorine from the chamber volume. Example process parameters used for this step:

[0185] Argon (Ar) flow rate: between 3 sccm and 80 sccm.

[0186] • Purge time: Between 15 ms and 120 seconds, and is set to 40 seconds in the preferred example.

[0187] • Pressure: Maintained between 1 mTorr and 60 mTorr, and set to 3 mTorr in the preferred example.

[0188] 4. In this example, a plasma pulse step is used to activate the top modified surface layer to form volatile products. During this step, an inert gas (e.g., argon (Ar)) is used to generate plasma. Ions from the plasma are used to remove the top activated layer by chlorination. Example process parameters used for this step:

[0189] Argon (Ar) flow rate: controlled between 1 sccm and 40 sccm, and set to 20 sccm in the preferred example.

[0190] • Ion energy: Below 60 eV. Ion energies of approximately 20 eV have been determined to provide optimal results.

[0191] • Time: Between 3 and 60 seconds, and in the preferred example it is set to 10 seconds.

[0192] • Pressure: Between 1 mTorr and 60 mTorr, and in the preferred example it is set to 3 mTorr.

[0193] 5. Optional Second Purging Step – Removal of Etching Products: Its main purpose is to remove any remaining etchant gases, reaction byproducts, or other contaminants from the reaction chamber before the next cycle of the cyclic removal process. Example process parameters for this step:

[0194] • Argon (Ar) flow rate: between 3 sccm and 80 sccm. A flow rate of 20 sccm was determined to provide the best results.

[0195] • Purge time: Between 2 and 20 seconds. A 2-second purge time has been determined to provide the best results.

[0196] • Pressure: Maintained between 1 mTorr and 60 mTorr. A pressure of 3 mTorr was determined to provide optimal results.

[0197] 6. Repeated loop:

[0198] Steps 2 through 5 are repeated for a specific number of cycles. A favorable number of repetitions is determined to be between 5 and 200, based on the initial roughness of the Si surface. For a typical Si surface after a chemical mechanical polishing (CMP) process, the optimal number of cycles is determined to be 20.

[0199] These precise parameters are particularly advantageous for smoothing the Si surface to the degree required for growing improved GaN material on top of that surface, see [link to relevant documentation]. Figure 10 .

[0200] B7.2. The second example process involves Figure 8 and Figure 9 :

[0201] In this example, the process outlined in the first example is followed by a deposition process to overgrow impurities and defects on the surface. Particularly advantageous results were achieved when the deposition process was completed in the same chamber as the cyclic removal process presented in the first example. This allows for minimization of top surface oxidation following the previous treatment.

[0202] Process steps:

[0203] B1. Purging: This step removes excess gas. Example process parameters used for this step:

[0204] • Inert gas purging: Argon (Ar), in a preferred example set to 20 sccm.

[0205] • Purging time: between 30 s and 60 s, set to 30 s in the preferred example.

[0206] • Purge pressure: Between 1 mTorr and 10 mTorr. A pressure below 10 mTorr was determined to provide optimal results.

[0207] 2. Deposition Process - Gallium (Ga) Precursor Pulse: A controlled pulse of trimethylgallium (TMG) is introduced into the reaction chamber. TMG reacts with the GaN surface to form a gallium atomic monolayer. Example process parameters used for this step:

[0208] • TMG flow rate: between 10 sccm and 50 sccm, set to 20 sccm in the preferred example.

[0209] • Pulse duration: between 0.1 seconds and 2 seconds, set to 1 second in the preferred example.

[0210] • Chamber pressure: between 1 mTorr and 100 mTorr, set to 50 mTorr in the preferred example.

[0211] • TMG vaporizer temperature: between 60°C and 100°C, set to 80°C in a preferred example.

[0212] 3. Purging with inert gas: This step removes excess TMG and reaction byproducts from previous steps, ensuring that only a single gallium atom monolayer remains on the substrate surface. Example process parameters for this step:

[0213] • Ar flow rate: between 50 sccm and 200 sccm, set to 100 sccm in the preferred example.

[0214] • Purge time: Between 10 and 30 seconds, set to 20 seconds in the preferred example.

[0215] • Purge pressure: Between 1 mTorr and 10 mTorr, set to 10 mTorr in the preferred example.

[0216] 4. Deposition Process - Nitrogen (N) Precursor Pulse: Ammonia (NH3) is introduced to react with the exposed gallium atoms on the surface, thereby forming a GaN monolayer. This completes the deposition of one atomic layer of GaN. Example process parameters used for this step:

[0217] • H3 flow rate: between 10 sccm and 50 sccm, set to 20 sccm in the preferred example.

[0218] • Pulse duration: between 0.1 seconds and 2 seconds, set to 1 second in the preferred example.

[0219] • ALD chamber pressure: Between 1 mTorr and 100 mTorr. A pressure of 50 mTorr was determined to provide optimal results.

[0220] 5. Purge - Inert Gas: Similar to the previous purging step, argon gas is used to remove excess NH3 and reaction byproducts to prepare the surface for the next cycle. Example process parameters used for this step:

[0221] Ar flow rate: between 50 sccm and 200 sccm

[0222] • Purging time: between 10 and 30 seconds

[0223] • Purging pressure: between 1 mTorr and 10 mTorr

[0224] 6. Repeat the cycle: Repeat steps 2 through 5 for a specific number of cycles. A favorable number of repetitions was determined to be between 5 and 200. The optimal number of cycles was determined to be 20 cycles to establish the initial nucleation layer of GaN.

[0225] Preferably, the process is continuously monitored, and process parameter data are analyzed. In-situ characterization techniques, such as optical emission spectroscopy (OES) and optical reflectance measurements, can be used for process monitoring. A preferred method for process monitoring is to verify the actual process parameters and compare them with reference values. Specifically, it has been found that monitoring the process is best done by tracking the applied and reflected radio frequency (RF) signals online to maintain corresponding matching parameters between the plasma and the RF lines. This monitoring allows for precise adjustment of the number of cycles required to prepare the surface for subsequent GaN material growth on top. Based on the process monitoring results, repeating the process steps outlined in the first example may be advantageous. In some cases, the plasma pulse step (step 3) needs to be adjusted, typically by increasing the ion energy while keeping it below 90 eV. In some examples, an ion energy of approximately 30 eV has been found to provide optimal results. In some examples, the steps in the first and second examples above may need to be repeated multiple times. Five repetitions have been found to provide optimal results. The number of these repetitions can be optimized and determined based on in-situ monitoring and process tracking.

[0226] B8. Experimental Results

[0227] This section provides a detailed description of experimental results obtained using the disclosed method for preparing substrate surfaces for improved material growth. The results demonstrate the effectiveness of the method in reducing surface roughness and improving the quality of the grown material.

[0228] B8.1. Atomic force microscope (AFM) photomicrographs

[0229] In one example, atomic force microscopy (AFM) images were used to analyze the surface roughness of the substrate before and after the cyclic removal process. AFM images provide a visual representation of the surface morphology, allowing for direct comparison of surface roughness before and after the process. The reduction in surface roughness observed in the AFM images was also quantitatively analyzed to demonstrate the effectiveness of the method.

[0230] B8.1.1. Initial Si surface and surface after cyclic etching

[0231] In one example, the initial Si surface ( Figure 10 (left) and the surface after the cyclic removal process (i.e., cyclic etching). Figure 10 The images (right side) are compared. AFM micrographs show a significant reduction in surface roughness after the cyclic removal process. The top portions of micrographs 2500 and 2504 show a 1 µm² scan area. Bottom images 2501, 2502, 2503, 2505, 2506, and 2507 show line scans at different locations (top, middle, and bottom) of the corresponding scan areas 2500 and 2504, respectively. The reduction in surface roughness after the cyclic removal process demonstrates the effectiveness of this method in preparing substrate surfaces for improving material growth.

[0232] B8.1.2. Initial GaN surface and surface after cycle deposition and etching

[0233] In another example, the initial GaN surface ( Figure 11 (Left) and the surface after cyclic deposition followed by a cyclic removal process (i.e., cyclic etching). Figure 11 The images (right side) are compared. AFM micrographs show a significant reduction in surface roughness after the combined cyclic deposition and removal process. This result demonstrates that optional deposition processes can further enhance surface preparation for improved material growth.

[0234] The observed reduction in surface roughness in these examples demonstrates the advantages of the disclosed method in preparing substrate surfaces for improved material growth. By reducing surface roughness, this method can significantly reduce the number of defects in the material grown on the surface, resulting in higher quality films. Furthermore, this method can be combined with ion beam shaping processes to further enhance surface preparation and improve material growth on a variety of substrates.

[0235] The terminology used herein is for descriptive purposes only and is not intended to limit the scope of this disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to also include the plural forms. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprise,” “comprising,” “include,” and / or “including” as used herein specify the presence of the stated feature, integer, action, step, operation, element, and / or component, but do not preclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components, and / or groups thereof.

[0236] It will be understood that although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited to these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0237] As shown in the figures, relative terms such as “below,” “above,” “upper,” “lower,” “horizontal,” or “vertical” may be used in this document to describe the relationship between one element and another. It will be understood that these terms, and those discussed above, are intended to cover different orientations of the device other than those depicted in the figures. It will be understood that when an element is referred to as “connected” or “coupled” to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements present. In contrast, when an element is referred to as “directly connected” or “directly coupled” to another element, there are no intermediate elements present.

[0238] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that the terms used herein shall be interpreted as having the same meaning as they have in the context of this specification and the relevant field, and shall not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0239] It should be understood that this disclosure is not limited to the aspects shown above and in the accompanying drawings; rather, those skilled in the art will recognize that many changes and modifications can be made within the scope of this disclosure and the appended claims. Aspects disclosed in the drawings and specification are for illustrative purposes only and not for limiting purposes, and the scope of this disclosure is set forth in the appended claims.

Claims

1. A method for surface conditioning based on cyclic processing, the method comprising: Activate the surface; Remove excess material from the surface and surrounding environment; The surface is treated with low-energy particles; as well as Repeat the above steps until the surface has the desired smoothness.

2. The method according to claim 1, wherein, The low-energy particle treatment uses ions.

3. The method according to claim 2, wherein, The low-energy particle treatment is atomic layer etching (ALE).

4. The method according to claim 3, wherein, The low-energy particle treatment utilizes molecularly activated atomic layer etching (ALE).

5. The method according to claim 1, wherein, The cyclic processing includes a deposition step.

6. The method according to claim 5, wherein, The deposition step results in atomic layer deposition (ALD).

7. The method according to any one of claims 2 to 6, comprising a combination of etching and deposition.

8. The method according to any one of claims 2 to 7, comprising alternating etching and deposition.

9. The method according to any one of claims 1 to 8, wherein, Repeat the steps until the process has no further effect on the different treated surfaces.

10. The method according to any one of claims 1 to 9 further includes ion beam shaping technology.

11. The method of claim 10, further comprising angled particle beam etching.

12. The method according to any one of claims 1 to 11, wherein, The surface in question is the sidewall surface.

13. The method according to any one of claims 1 to 12, wherein, The surface is an inclined surface.

14. The method according to any one of claims 1 to 13, wherein, The surface is selected from the group consisting of semiconductor surfaces, metal surfaces, dielectric surfaces, and 2D material surfaces.

15. The method according to any one of claims 1 to 14, wherein, The surface is a patterned surface.

16. The method according to any one of claims 1 to 15, wherein, The surface is a non-patterned surface.

17. The method according to any one of claims 1 to 16, wherein, The activation of the surface includes applying gas exposure to the surface.

18. The method according to any one of claims 1 to 17, wherein, The activation of the surface includes exposing the surface to a chemical solution.

19. The method according to any one of claims 1 to 18, wherein, Activating the surface involves heating the surface to a specific temperature.

20. The method according to any one of claims 1 to 19, wherein, The activation of the surface includes applying a particle beam to the surface.

21. The method according to any of the preceding claims, wherein, The low-energy particle processing includes low-energy particle beams with particle energies between 10 eV and 100 eV.

22. The method according to any one of claims 1 to 20, wherein, The low-energy particle treatment includes low-energy plasma treatment with plasma power between 1 W and 50 W.

23. A surface adjusted by the method according to any one of claims 1 to 22.

24. A method for preparing a substrate and a surface on which an epitaxial material is grown, the method comprising the following steps: Exposing the surface to a cyclic removal process to remove impurities and defects from the surface includes: The topmost surface layer of the surface is modified by introducing chemical species such as halogens into the processing chamber volume surrounding the substrate, thereby obtaining a modified topmost surface layer of the surface. Excessive chemical species are extracted from the processing chamber volume. Activate the topmost modified surface layer to form volatile products. Optionally, the etching products are removed from the processing chamber volume. The cyclic removal process is followed by epitaxial material growth, and The growth material is different from the material of the surface.

25. The method according to claim 24, wherein, The modification of the topmost surface layer was carried out in a gas phase containing only neutral species.

26. The method according to any one of claims 24 to 25, wherein, The cyclic removal process has an etch rate per cycle, wherein the etch rate approaches zero as the number of cycles increases.

27. The method according to any one of claims 24 to 26, wherein, The activation of the topmost modified surface layer is completed in the gas phase without involving surface bombardment with ions.

28. The method according to any one of claims 24 to 27, comprising a deposition process step of overgrowing impurities and defects on the surface, including: The topmost surface layer is modified by introducing chemical species for the overgrowth into the volume of the processing chamber.

29. The method according to claim 28, wherein, The chemical species used for the overgrowth include gallium, nitrogen, and optionally aluminum.

30. The method of claim 28 or 29, wherein the deposition process is cyclic.

31. The method according to any one of claims 28 to 30, wherein, The deposition process has a deposition rate per cycle, wherein the deposition rate approaches zero as the number of cycles increases.

32. The method according to any one of claims 24 to 31, wherein, At least one of the steps includes a self-limiting response that is slowed down or stopped based on time or, equivalently, based on species dosage.

33. The method according to claim 32, wherein, The self-limiting reactions include chemisorption, deposition, extraction and / or transformation, such as oxidation or nitridation.

34. The method according to any one of claims 24 to 33, comprising an additional passivation step prior to the growth of the epitaxial material to avoid surface oxidation or contamination prior to the growth of the material.

35. The method according to any one of claims 24 to 34, wherein, The surface includes patterns, such as regularly arranged holes, lines, and / or pillars.

36. The method according to any one of claims 24 to 35, comprising retrieving process control information, such as information from optical emission and residual gas analysis, wherein, The process parameters of the method are adjusted based on the process control information.

37. A method for growing an epitaxial material on the surface of a substrate, the method comprising a cyclic process, the cyclic process comprising the following sequence: The method comprises any step of any one of claims 24 to 27, and then any step of any one of claims 28 to 34, wherein the method includes: Repeat the sequence multiple times. The epitaxial material grows on the surface, and The growth material is different from the surface material.

38. The method of claim 37, wherein the steps are repeated until at least one of the steps has no further effect on the surface.

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