Cyclic surface preparation and surface pretreatment methods for epitaxial material growth

Abstract

A method for surface preparation based on cyclic processing is disclosed. The method includes activating the surface, removing excess material from the surface, treating the surface with low-energy particles, and repeating the above steps until the surface has the desired smoothness. This method can be applied to a variety of surfaces, including semiconductor surfaces, metallic surfaces, dielectric surfaces, and 2D material surfaces, as well as patterned and unpatterned surfaces. The low-energy particle treatment can be etching or deposition, and this process can be combined with ion beam shaping techniques and oblique incidence particle beam etching for improved surface preparation. Methods for substrate surface pretreatment and epitaxial material growth are also disclosed.

Description

Technical Field

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

Background Art

[0002] Semiconductor devices and other microelectronic components require extremely smooth surfaces for optimal performance. Surface roughness can lead to various problems such as defects in lithography processes, degraded device performance, and even device failures. Therefore, achieving a high level of surface smoothness is extremely important for the proper fabrication of these components.

[0003] Current polishing technologies such as chemical mechanical polishing (CMP) are widely used to reduce surface roughness on semiconductor wafers and other substrates. CMP involves the use of chemical slurries and polishing pads to remove material from the surface and result in a smoother surface. However, CMP has limitations in achieving the optimal level of smoothness required in some lithography processes, leading to potential failures. In addition, CMP is not suitable for polishing surfaces with different heights or slopes as it can only polish one horizontal plane at a time.

[0004] Another approach for reducing surface roughness is atomic layer etching (ALE), which involves the removal of material from the surface at the atomic scale. ALE provides a smoother surface than CMP, but it is not self-terminating and may remove unnecessary material from different surfaces. Furthermore, the ALE process requires the user to define the time for smoothing, which can be difficult due to varying surface conditions.

[0005] The lithography process itself contributes to surface roughness, affecting both the original surface and new surfaces such as sidewalls that arise from it. Hills and valleys on the wafer surface have different surface energies, making it difficult to develop a process that selectively removes hills without affecting the valleys. A method is needed that can reduce surface roughness without damaging surfaces that did not react with the activating gas during cyclic etching. [Overview of the project] [Problems that the invention aims to solve]

[0006] In short, conventional techniques have several drawbacks, including limitations in achieving optimal surface smoothness, the inability to polish surfaces with different heights or slopes, and the lack of selective etching methods. These issues highlight the need for improved surface preparation methods that can overcome the limitations of current techniques and achieve smoother surfaces for lithography processes and other microelectronic applications. To improve the performance of semiconductor devices and structures, improved surface pretreatment methods are needed in grown materials, particularly for dissimilar materials, that can reduce defects and stresses. Ideally, such methods should be able to pretreatment both flat and patterned surfaces, minimize surface damage, and address the problem of strain formation resulting from lattice mismatch between dissimilar materials. [Means for solving the problem]

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

[0008] The method may include a combination of etching and deposition, or alternating etching and deposition. The steps may be repeated until the process no longer affects the different processed surfaces. The method may further include ion beam shaping techniques and oblique incidence particle beam etching.

[0009] The surface to be processed by the method can be a sidewall surface or a sloped 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 may include exposing the surface to a gas, exposing the surface to a chemical solution, heating the surface to a specific temperature, or irradiating the surface with a particle beam. Low-energy particle treatment may 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] Surfaces prepared by the method are also provided.

[0012] A second aspect of this disclosure provides a method for surface pretreatment of a substrate and epitaxial material growth. The method includes exposing the surface to a cyclic removal process to remove impurities and defects from the surface. This process involves modifying the top surface layer of the surface by introducing chemical species such as halogens in a process chamber volume surrounding the substrate to obtain a modified top surface layer. The method also includes draining excess chemical species from the process chamber volume, activating the top modified surface layer to form volatile products, and optionally removing etching products from the process chamber volume. The cyclic removal process is followed by epitaxial material growth, the grown material being different from the surface material. The method provides a clean and smooth surface for epitaxial material growth and gives a high-quality thin film.

[0013] In some cases, the modification of the top surface layer is selectively carried out in a gas phase containing only neutral species. This allows for a more controlled and gentle modification process, reducing the risk of surface damage.

[0014] Optionally, in some examples, the cyclic removal process has an etching rate per cycle, which approaches zero as the number of cycles increases. This self-limiting characteristic ensures that the process does not over-etch the surface and preserves the desired surface properties.

[0015] In some cases, optionally, the activation of the topmost modified surface layer is carried out in the gas phase without surface bombardment with ions. This can help maintain an undamaged surface, which is crucial for subsequent epitaxial material growth.

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

[0017] Optionally, in some examples, the deposition process steps precede the cyclic removal process, or the deposition process steps follow the cyclic removal process. This flexibility in the order of steps allows for process optimization depending on the specific substrate and growth material.

[0018] Optionally, in some examples, the chemical species for coating growth include gallium, nitrogen, and optionally aluminum. These elements can be used to form various compound semiconductor materials, such as Group III nitride materials, which have numerous applications in optoelectronics and power electronics.

[0019] Optionally, in some cases, the deposition process is cyclic. This can result in a more controlled and uniform deposition process, ensuring a high-quality covering growth layer.

[0020] In some cases, the deposition process has a deposition rate per cycle, which approaches zero as the number of cycles increases. This self-limiting characteristic ensures that the process does not overdeposit the material and maintains the desired surface properties.

[0021] Optionally, in some examples, at least one of the steps includes a self-limiting reaction that slows down or stops as a function of time, or equivalently as a function of the seed supply. This helps ensure a controlled and precise process and can avoid over-etching or over-depositing of the material.

[0022] Optionally, in some examples, the self-limiting reaction includes conversions such as chemisorption, deposition, extraction, and / or oxidation or nitridation. This type of reaction can achieve a controlled and gentle process and reduce the risk of damage to the surface.

[0023] Optionally, in some examples, the method includes an additional passivation step preceding the epitaxial material growth to avoid surface oxidation or contamination prior to material growth. This can further improve the surface quality and help 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 may provide additional control such as strain relaxation and defect reduction for the characteristics of epitaxial material growth.

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

[0026] According to a fourth aspect of the present disclosure, a method for epitaxial material growth on a surface of a substrate is provided, including a cyclic process including any of the steps according to the second aspect of the present disclosure and then any of the steps according to the third aspect of the present disclosure. The method includes repeating the sequence multiple times, including epitaxial material growth of a growth material on the surface, where the growth material is different from the material of the surface. The method can provide a highly controlled and optimized process for pretreating the surface and growing a high-quality epitaxial material.

[0027] Optionally, in some examples, the steps are repeated until at least one of the steps has no further impact on the surface. This can help ensure that the surface is sufficiently pre-treated and optimized for epitaxial material growth, resulting in high-quality thin films.

[0028] Examples are described in more detail below with reference to the accompanying drawings.

Brief Description of the Drawings

[0029] [Figure 1] FIG. [FIGURE NUMBER] shows an example of a surface conditioning method based on cyclic processing. [Figure 2] FIG. [FIGURE NUMBER] shows another example of a surface conditioning method based on cyclic processing. [Figure 3] FIG. [FIGURE NUMBER] shows another example of a surface conditioning method based on cyclic processing. [Figure 4] FIG. [FIGURE NUMBER] is a flowchart showing a method for surface conditioning based on cyclic processing according to an example of the present disclosure. [Figure 5] FIG. [FIGURE NUMBER] is an atomic force microscope (AFM) micrograph of an initial surface and a final surface after a cyclic process according to an example. [Figure 6] FIG. [FIGURE NUMBER] is a schematic diagram showing the effect of a cyclic removal process for pre-treating a substrate surface for improved material growth, comparing material growth on a typical surface with material growth after a cyclic removal process. [Figure 7] FIG. [FIGURE NUMBER] is a schematic diagram showing the effect of a deposition process followed by a cyclic removal process for pre-treating a substrate surface for improved material growth, comparing material growth on a typical surface with material growth after material deposition followed by a cyclic removal process. [Figure 8] FIG. [FIGURE NUMBER] is a schematic diagram showing the effect of a cyclic removal and deposition process for pre-treating a substrate surface for improved material growth, comparing material growth on a typical surface with material growth after a cyclic removal process and deposition. Please note that the figure numbers in the translated text are placeholders and should be replaced with the actual figure numbers in the original document. [Figure 9] This block diagram shows the execution process flow of a cyclic process method for pre-treating a substrate surface for improved material growth. [Figure 10] These figures show atomic force microscope (AFM) images and line scans of the Si surface before and after cyclic etching, illustrating the reduction in roughness after the cyclic etching process. [Figure 11] These are atomic force microscopy (AFM) images of the GaN surface before the cyclic deposition process and the subsequent reduction in roughness after the cyclic etching process. [Modes for carrying out the invention]

[0030] A. Cyclic surface preparation The detailed description below provides information and examples of the disclosed technology with sufficient detail to enable a person skilled in the art to put this disclosure into practice.

[0031] Figure 1 shows an example of a surface preparation method based on cyclic processing. Figure 1a illustrates a substrate 100 with an initial surface roughness 110. The substrate 100 can be made from various materials, such as semiconductor materials, metallic materials, dielectric materials, or 2D materials. The surface of the substrate 100 can be patterned or unpatterned.

[0032] Figure 1b shows the final surface, where the substrate 100 has the desired surface 111 with reduced surface roughness while maintaining the original thickness of the substrate 100. This reduction in surface roughness is achieved through a cyclic processing method, which includes activating the surface, removing excess material, treating with low-energy particles, and repeating these steps until the desired smoothness is achieved. This surface preparation is achieved through a cyclic processing method as described above and may include any cyclic process, including atomic layer etching (ALE) or atomic layer deposition (ALD).

[0033] Figure 2 shows another example of a surface preparation method based on cyclic processing. Figure 2a illustrates an initial structure 110 with rough surfaces 111, 112, and 122. In addition, the substrate 100 has another feature section 210 of a different height than 110. The feature section 210 has different rough surfaces 211, 212, and 222, as shown.

[0034] Figure 2b shows the final structure with feature portion 110 having the desired surfaces 311, 312, and 322, and with reduced surface roughness of feature portion 110 while retaining the original dimensions of feature portion 110. Furthermore, Figure 2b shows feature portion 210 with the desired surfaces 411, 412, and 422, and with reduced surface roughness of feature portion 210 while retaining the original critical dimensions of feature portion 210. This surface preparation is achieved through cyclic processing methods as described above and may include any cyclic process, including atomic layer etching (ALE) or atomic layer deposition (ALD).

[0035] Figure 3 shows another example of a surface preparation method based on cyclic processing. Figure 3a illustrates the initial structure 110 with rough surfaces 111, 112, and 122.

[0036] Figure 3b shows the final structure with the desired surfaces 222, 212, and 211, and reduced surface roughness of the feature portion 110 while retaining the original critical dimensions of the feature portion 110. This surface preparation is achieved through a cyclic processing method as described above and may include any cyclic process, including atomic layer etching (ALE) or atomic layer deposition (ALD).

[0037] Figure 4 is a flowchart illustrating a method for surface preparation based on cyclic processing according to an example of the present disclosure. The method includes activating the surface (step 401), removing excess material from the chamber (step 402), subjecting the surface to low-energy particle treatment (step 403), and repeating the above steps until the surface has 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 oblique incidence particle beam etching.

[0038] Figure 5 shows atomic force microscope (AFM) images of the initial and final surfaces after a cyclic process, as in one example. Figure 5a shows a micrograph with a scan area of ​​500, which is approximately 1 μm². 2 In the graph below, roughness values ​​501, 502, and 503 are measured at different locations in the scan area: the top, middle, and bottom, respectively. The roughness was measured to be approximately 0.11 nm.

[0039] Figure 5b shows the results from the AFM measurement of the final surface. The upper part 504 shows a micrograph of the scan area, which is approximately 1 μm². 2In the graph below, roughness values ​​505, 506, and 507 are measured at different locations in the scan area: the top, middle, and bottom, respectively. The roughness was measured to be approximately 0.021 nm. This reduction in surface roughness was achieved through cyclic processing methods as described above and can include any cyclic process, including atomic layer etching (ALE) or atomic layer deposition (ALD).

[0040] A1. Surface activation process The surface activation process is a step in surface preparation methods based on cyclic processing. In this process, the substrate surface is activated to facilitate subsequent low-energy particle processing, which can involve etching, deposition, or a combination of both. The activation process can be carried out using various techniques, including gas exposure, chemical solution exposure, temperature-based activation, and particle beam activation. Each of these techniques has its own advantages and can be adapted to meet the specific requirements of the substrate material and the desired surface smoothness.

[0041] A1.1. Gas exposure activation In some cases, the surface activation process may involve exposing the surface to a gas or a mixture of gases. Gas exposure can modify the surface chemistry, making it more susceptible to the effects of low-energy particle treatment. The selection of an appropriate gas is necessary to achieve the desired surface activation and ensure compatibility with the substrate material.

[0042] A1.2. Chemical solution activation In some cases, the surface activation process may involve exposing the surface to a chemical solution. The chemical solution interacts with the surface material, altering its properties and making it more responsive to low-energy particle treatment. The selection of an appropriate chemical solution is crucial for achieving the desired surface activation and ensuring compatibility with the substrate material.

[0043] A1.3. Temperature-based activation In some cases, the surface activation process may involve heating the surface to a specific temperature or a specific temperature range. Temperature-based activation can cause thermal expansion or contraction of the surface material, leading to changes in surface properties that can facilitate the processing of low-energy particles. Determining the optimal temperature range is essential to achieving the desired surface activation and ensuring compatibility with the substrate material.

[0044] A1.3.1. Determine the optimal temperature range. The optimal temperature range for a temperature-based activation process depends on the substrate material and the desired surface properties. In some cases, the temperature range may be selected to induce thermal expansion or contraction of the surface material, leading to changes in surface roughness or other properties that can facilitate low-energy particle processing. In other cases, the temperature range may be selected to induce a phase transition or other structural change in the surface material, which can alter its properties and make it more responsive to 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, the desired surface properties, and the compatibility of the temperature range with the low-energy particle processing process.

[0045] A1.4. Particle Beam Activation In some examples, a surface activation process may involve irradiating a surface with a particle beam. The selection of a particle beam for a 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 can physically sputter the surface material or chemically react with it to modify its properties. In other examples, the particle beam may include photons or other electromagnetic radiation that can induce electronic or vibrational excitations in the surface material, leading to changes in surface properties that can facilitate low-energy particle processing. The selection of an appropriate particle beam may be 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.

[0046] A2. Excess material removal process For 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 surrounding environment after the surface activation process. Removal of 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 purging gas, pumping gas, or a combination of pumping and purging.

[0047] A2.1. Gas purging In some cases, the excess material removal process may include gas purging. Gas purging involves introducing an inert gas, such as nitrogen or argon, into the processing chamber to replace and remove any excess material, including reactive gases or by-products from surface activation processes. Gas purging can be introduced at controlled flow rates and pressures to ensure efficient removal of excess material without damaging the surface or altering its surface properties. In excess material removal processes, the use of gas purging offers the advantage of being a simple and cost-effective technique for removing unwanted material from the processing environment.

[0048] A2.2. Gas pump exhaust In other examples, the excess material removal process may include pumping gases. Pumping gases involves using a vacuum pump to evacuate the processing chamber, thereby removing any excess material, including reactive gases or by-products from the surface activation process. The vacuum pump can be operated at controlled pressure and flow rate to ensure efficient removal of excess material without damaging the surface or altering its surface properties. In the excess material removal process, the use of pumping gases offers the advantage of more thorough removal of unwanted material from the processing environment compared to purging gases alone.

[0049] A2.3. Combination of pump exhaust and purging In some cases, the excess material removal process may include a combination of pumping and purging. This technique involves using both a vacuum pump to evacuate the processing chamber and an inert gas to replace and remove any excess material, including reactive gases or by-products from the surface activation process. The combination of pumping and purging can be carried out sequentially or simultaneously, depending on the specific requirements of the surface conditioning process. In the excess material removal process, the use of a combination of pumping and purging offers the advantage of more comprehensive removal of unwanted material from the processing environment, ensuring that subsequent low-energy particle treatment can be effectively applied to the surface without interference from excess material.

[0050] The excess material removal process can be adapted to meet the specific requirements of the surface conditioning process, 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. By effectively removing excess material from the surface and surrounding environment, the excess material removal process plays a certain role in achieving the desired surface smoothness and ensuring the overall success of the surface conditioning method based on cyclic processing.

[0051] A3. Low-energy particle processing For example, a surface preparation method based on cyclic processing 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 a variety of materials, including semiconductor surfaces, metallic surfaces, dielectric surfaces, and 2D material surfaces. Low-energy particle treatment can be carried out using a low-energy particle beam with particle energy between 10 eV and 100 eV, or low-energy plasma treatment with plasma power between 1 W and 50 W.

[0052] A3.1. Low-energy particle etching In some cases, low-energy particle processing may include low-energy particle etching processes. This etching process is used to selectively remove material from a surface, thereby reducing surface roughness and improving overall surface quality. Low-energy particle etching processes can be carried out using various techniques such as ion beam etching, reactive ion etching, or plasma etching.

[0053] A3.1.1. Atomic layer etching with molecular activation (ALE) For example, low-energy particle etching processes can include atomic layer etching (ALE) with molecular activation. ALE with molecular activation is a highly controlled etching process that allows for the removal of material at the atomic level, resulting in a very smooth surface. This process involves surface activation using an appropriate activation method 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 with molecular activation can offer several advantages, including improved control over the etching process, reduced surface roughness, and minimal damage to the underlying material.

[0054] A3.2. Low-energy particle deposition In some cases, low-energy particle processing may include low-energy particle deposition processes. These deposition processes are used to selectively deposit material onto a surface, thereby filling any surface irregularities and improving overall surface quality. Low-energy particle deposition processes can be carried out using various techniques, such as atomic layer deposition (ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD).

[0055] A3.2.1. Atomic layer deposition (ALD) For example, low-energy particle deposition processes can include atomic layer deposition (ALD). ALD is a highly controlled deposition process that allows for the deposition of material at the atomic level, resulting in a very smooth surface. This process involves sequential exposure of the surface to various precursor gases that react with the surface to form a thin layer of the desired material. The use of ALD can offer several advantages, including improved control over the deposition process, reduced surface roughness, and the ability to deposit material with high conformability and uniformity.

[0056] A3.3. Combination of Etching and Deposition In some cases, low-energy particle processing may involve a combination of etching and deposition processes. This may 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 specific areas of a surface while depositing material in other areas, thereby reducing surface roughness and improving overall surface quality.

[0057] A3.3.1. Alternate between etching and deposition. In one example, low-energy particle processing may involve alternating etching and deposition steps. This may 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 the etching and deposition steps, surface roughness can be reduced while maintaining the overall thickness of the material. This technique can offer several advantages, including improved control over the surface preparation process, reduced surface roughness, and the ability to selectively modify the surface without affecting the underlying material.

[0058] A4. Cyclic Processing and Surface Smoothing In one example, the cyclic processing and surface smoothing section focuses on determining the desired surface smoothness, implementing a self-stopping cyclic process, and monitoring the reduction of surface roughness during the surface conditioning process. The cyclic processing method may include a variety of optional features to achieve the desired surface smoothness and effectively reduce surface roughness.

[0059] A4.1. Determine the desired surface smoothness. In some cases, the desired surface smoothness is determined based on the specific application or requirements of the processed substrate. Surface smoothness can be quantified using various surface roughness parameters, such as root mean square (RMS) roughness, mean roughness, or peak-to-valley roughness. The desired surface smoothness can be achieved by repeating the cyclic processing steps until the surface roughness parameter reaches a predetermined value or the specific requirements of the processed substrate are met.

[0060] A4.2. Self-Stopping Cyclic Processes For example, a cyclic processing method may include a self-stopping feature, in which case the process automatically stops when it has no further effect on the surface or when the surface roughness parameter reaches 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 feature. 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, ensuring that once the desired smoothness is achieved, the process has minimal or no effect on the surface.

[0061] A4.3. Monitoring of Surface Roughness Reduction In some cases, surface roughness reduction during cyclic processing can be monitored using various in-situ or ex-situ measurement techniques. In-situ measurement techniques may include optical monitoring, ellipsometry, or reflectometry, which can provide real-time feedback on surface roughness parameters during cyclic processing. Ex-situ measurement techniques may 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.

[0062] Monitoring surface roughness reduction can be advantageous in determining the progress of the surface preparation process and ensuring that the desired surface smoothness is achieved. In addition, monitoring can provide valuable information for optimizing process parameters and improving the efficiency of cyclic processing methods.

[0063] A5. Integration with ion beam shaping technology For example, surface preparation methods based on cyclic processing can be integrated with ion beam shaping technology to further enhance the surface smoothing process. Ion beam shaping technology can be used to modify surface topography by controlling ion beam parameters such as ion energy, ion species, ion incidence angle, and ion flux. This integration can provide additional control over the surface preparation process, enabling more precise and efficient surface smoothing.

[0064] A5.1. Obliquely incident particle beam etching In some cases, the integration of ion beam shaping techniques with surface preparation methods can include oblique incidence particle beam etching. Oblique incidence particle beam etching can be used to selectively remove material from specific areas of a surface, such as peaks in surface roughness features, while preserving valleys. This can result in more uniform surface topography and reduced surface roughness.

[0065] For example, oblique incidence particle beam etching can be performed by directing an ion beam at a certain angle to the surface perpendicular line. 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 species, ion incidence angle, and ion flux, the etching process can be adapted to achieve a desired surface smoothing effect.

[0066] A5.2. Optimization of ion beam parameters In some cases, ion beam parameters can be optimized to achieve the desired surface conditioning effect. Ion beam parameters can include ion energy, ion species, ion incidence angle, and ion flux. By adjusting these parameters, ion beam shaping techniques can be adapted to specific surface features and material properties, resulting in more efficient and precise surface smoothing.

[0067] For example, ion energy can be adjusted to control the penetration depth of ions into the surface material. Higher ion energy results in deeper penetration and more corrosive etching, while lower ion energy results in shallower penetration and milder etching. The optimal ion energy may depend on the specific surface features and material properties, as well as the desired surface smoothing effect.

[0068] In another example, ionic species can be selected based on their chemical reactivity with the surface material. Some ionic species may be effective in etching certain materials, while others may be less effective or even cause undesirable side effects such as surface damage or contamination. The optimal ionic species may depend on the specific surface features and material properties, as well as the desired surface smoothing effect.

[0069] In yet another example, the ion incidence angle can be adjusted to control the directionality of the etching process. By directing the ion beam at a certain angle to the surface perpendicularity, the etching process can be made more selective, allowing for preferential removal of material from specific areas of the surface, such as peaks in surface roughness features. The optimal ion incidence angle may depend on the specific surface features and material properties, as well as the desired surface smoothing effect.

[0070] In yet another example, ion flux can be adjusted to control etching rate and uniformity. Higher ion flux results in faster etching and more corrosive surface smoothing, while lower ion flux results in slower etching and milder surface smoothing. The optimal ion flux may depend on the specific surface features and material properties, as well as the desired surface smoothing effect.

[0071] By optimizing ion beam parameters, integrating ion beam shaping technology with cyclic processing-based surface preparation methods can achieve more precise and efficient surface smoothing, resulting in improved surface quality and reduced surface roughness. This integration can be particularly advantageous for applications requiring high-quality surfaces, such as semiconductor devices, optical components, and other advanced technologies.

[0072] A6. Surface preparation for various surface types Surface preparation methods based on cyclic processing can be applied to a variety of surface types, including not only surfaces made from different materials such as semiconductor materials, metallic materials, dielectric materials, and 2D materials, but also patterned and unpatterned surfaces. The methods can be adapted to address the specific requirements of each surface type and material, providing a versatile and efficient approach to surface preparation.

[0073] A6.1. Patterned Surfaces In some cases, surface conditioning methods can be applied to patterned surfaces that may contain features such as lines, dots, columns, vias, grids, and other patterns. The methods can be adapted to address specific challenges associated with conditioning patterned surfaces, such as reducing surface roughness while preserving the original dimensions of the feature areas.

[0074] A6.1.1. Side wall surface For example, a surface conditioning method can be applied to the sidewall surface of a patterned feature. The method can be adapted to address specific challenges associated with conditioning the sidewall surface, such as maintaining the original dimensions of the feature while reducing surface roughness. Cyclic processing methods, including activation, excess material removal, and low-energy particle treatment, can be optimized to achieve the desired surface smoothness of the sidewall surface without affecting the overall dimensions of the patterned feature.

[0075] A6.1.2. Inclined surfaces In some cases, surface conditioning methods can be applied to the inclined surfaces of patterned features. The methods can be adapted to address specific challenges associated with conditioning inclined surfaces, such as maintaining the original dimensions of the features while reducing surface roughness. Cyclic processing methods, including activation, excess material removal, and low-energy particle treatment, can be optimized to achieve desired surface smoothness on inclined surfaces without affecting the overall dimensions of the patterned features.

[0076] A6.2. Unpatterned surfaces For example, a surface conditioning method can be applied to an unpatterned surface, such as the surface of a substrate 100. The method can be adapted to address specific challenges associated with conditioning an unpatterned surface, such as reducing surface roughness without affecting the overall thickness of the substrate. Cyclic processing methods, including activation, excess material removal, and low-energy particle treatment, can be optimized to achieve desired surface smoothness on an unpatterned surface while preserving the original thickness of the substrate.

[0077] A6.3. Material-Specific Surface Preparation Surface preparation methods based on cyclic processing can be adapted to address the specific requirements of various materials, including semiconductor materials, metallic materials, dielectric materials, and 2D materials. In some cases, activation processes, excess material removal, and low-energy particle treatments can be adapted to specific material properties and requirements to ensure optimal surface preparation results.

[0078] 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 and deposition processes, can be adapted to specific material properties and requirements.

[0079] By adapting surface conditioning methods to specific material properties and requirements, the methods can provide efficient and effective surface conditioning results for various surface types and materials, ensuring optimal performance and reliability of the conditioned surface.

[0080] B. Surface pretreatment methods for epitaxial material growth Figure 6 shows a schematic diagram illustrating the effect of a cyclic removal process for pre-treating a substrate surface (Si, sapphire, SiC, GaN, or any substrate) for improved material growth. The left side shows material growth on a typical surface 2200 of substrate 2100. The right side shows material growth after the cyclic removal process, resulting in a pre-treated substrate surface 2201. The grown material 2301 is improved by reducing defects compared to the grown material 2300.

[0081] Figure 7 shows a schematic diagram illustrating the effect of a deposition process and subsequent cyclic removal process for pre-treating 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 material deposition 2400 and the subsequent cyclic removal process is shown, resulting in a pre-treated substrate surface 2202. The grown material 2302 is improved by reducing defects compared to the grown material 2300.

[0082] Figure 8 presents a schematic diagram illustrating the effect of a cyclic removal and deposition process for pre-treating a substrate surface (Si, sapphire, SiC, GaN, or any substrate) for improved material growth. On the left, material growth is shown on a typical surface 2200 of substrate 2100. On the right, the cyclic removal and deposition process gives the substrate surface 2204 for material growth. The intermediate planar surface 2203 of the substrate and the material deposit 2401 are also shown. The grown material 2303 is improved by reducing defects compared to the grown material 2300.

[0083] Figure 9 is a block diagram showing the execution process flow of a cyclic process method for pre-treating a substrate surface for improved material growth.

[0084] Figure 10 shows atomic force microscope (AFM) images and line scans of the initial Si surface (left) and the surface after cyclic etching (right). The upper sections 2500 and 2504 show micrographs of the scan area, which has an area of ​​approximately 1 μm². The lower graphs 2501, 2502, 2503, 2505, 2506, and 2507 are line scans at different locations, upper, middle, and lower, corresponding to scan areas 2500 and 2504, respectively. After the cyclic etching process, roughness is significantly reduced.

[0085] Figure 11 shows atomic force microscopy (AFM) images of the GaN surface before deposition (left) and the surface after cyclic deposition and subsequent cyclic etching (right). Roughness is significantly reduced after the cyclic deposition and subsequent cyclic etching processes.

[0086] Further discussion of surface pretreatment for epitaxial material growth related to Figures 6-11 is provided in sections 6-8 below.

[0087] B2. Substrate material In some examples, the surface material can be silicon (Si), sapphire, silicon carbide (SiC), gallium nitride (GaN), or other suitable substrate material. The choice of surface material can significantly affect the quality of the grown material and the effectiveness of the cyclic removal process. Surfaces can have a variety of materials and patterns, which can affect material growth. In some examples, the surface of a substrate may contain patterns such as regularly arranged holes, lines, and / or columns. The disclosed method can be applied to these patterned surfaces, enabling substrate pretreatment with various geometries and topographies. The method is adapted to accommodate various surface patterns to ensure optimal material growth.

[0088] B3. Surface preparation methods B3.1. Cyclic Removal Process For example, a cyclic removal process involves exposing the substrate surface to a series of steps that remove impurities and defects from the surface. This process can be repeated multiple times to obtain the desired surface quality.

[0089] B3.1.1. Modify the top surface layer. The top surface layer of a substrate is modified by introducing chemical species, such as halogens, within a process chamber volume surrounding the substrate. The process chamber volume is an enclosed space where the substrate is exposed to the chemical species and a cyclic removal process occurs. The halogens can be chlorine, bromine, or iodine. The chemical species chemiadsorb to the surface. This results in the formation of a modified top surface layer on the substrate. The modification step forms a thin, reactive surface layer of a clearly defined thickness, which is subsequently removed more easily than the unmodified material. The modified layer is characterized by a steep gradient of chemical composition. The rate of chemiadsorption can be increased, for example, by activating the chemical species using plasma. The modification of the top surface layer may be a self-limiting process that slows down or stops as a function of time, or equivalently as a function of the species supply.

[0090] In some cases, after modifying the top surface layer, excess chemical species may be discharged from the process chamber volume. This discharge can be performed using an inert gas, which ensures that undesirable chemical species that may interfere with the cyclic removal process are removed from the process chamber volume.

[0091] B3.1.2. Activating the uppermost modified surface layer. The topmost modified surface layer is activated to form volatile products. Activation removes the thin reactive surface layer obtained in the preceding surface modification step. This activation can be carried out in the gas phase without ions or surface bombardment, such as by temperature cycling, light pulse exposure, and / or chemical reactions. By preventing surface bombardment by high-energy particles during the cyclic removal process, the formation of an undamaged surface is ensured, providing an optimal surface for epitaxial material growth. The activation of the topmost modified surface layer may be a self-limiting process that slows down or stops as a function of time, or equivalently as a function of seed supply.

[0092] In some cases, activating the top modified surface layer may involve plasma pulse steps using low ion energies, such as ion energies below 60 eV in the plasma pulse. Ion energies around 20 eV yield particularly favorable results in some cases. The use of low ion energies ensures low-damage etching of the surface, resulting in a damage-free surface ideal for epitaxial material growth.

[0093] In some cases, after activating the top modified surface layer, etching products can be removed from the process chamber volume. This removal ensures that etching products that could interfere with subsequent steps of the method, such as epitaxial material growth, are removed from the process chamber volume.

[0094] The surface modification and activation steps provide an atomic layer etching process. The atomic layer etching process may further 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, providing optimized results in surface pretreatment before material growth.

[0095] The substrate surface pretreatment and epitaxial material growth methods may include a variety of optional features and steps, such as deposition processes to cover and grow impurities and defects on the surface, passivation steps preceding epitaxial material growth, and the use of self-limiting reactions in cyclic removal processes. 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.

[0096] B3.1.3. Number of cycles and etching rate per cycle The number of cycles in a cyclic removal process can be optimized based on the surface roughness. For example, the number of cycles can range from 5 to 200. For instance, 20 cycles may provide a particularly optimal surface for material growth.

[0097] In some examples, cyclic removal processes have an etching rate per cycle, which approaches zero as the number of cycles increases, indicating that the process becomes self-limiting as a function of time or seed supply. This allows for a process that is easily made to control the amount of material removed from the surface, ensuring a smooth and defect-free surface for subsequent material growth.

[0098] The cyclic removal process can be combined with the ion beam forming process to smooth and clean different surfaces of structured surfaces, such as surfaces with regularly spaced patterns of holes, lines, and / or columns. This can further enhance the quality of the grown material and expand the potential applications of the method.

[0099] B3.2. Sedimentation Process In some examples, the method may involve a deposition process to cover and grow impurities and defects on the surface. This process involves modifying the top surface layer by introducing chemical species into the process chamber volume for coating growth. Chemical species for coating growth may include gallium, nitrogen, and optionally aluminum. The deposition process may include a quasi-atomic layer deposition process that may involve quasi-self-limiting and non-self-limiting reactions.

[0100] B3.2.1. Growing by covering impurities and defects In some cases, the deposition process creates an interfacial layer by depositing a thin film material onto the surface. This interfacial layer relieves stress caused by lattice mismatch between dissimilar materials in contact with each other, and mitigates lattice mismatch problems with the material subsequently grown by epitaxy. The deposition process can also fill valleys on the surface, ensuring that the surface remains smooth even during the subsequent epitaxial growth of very thin films.

[0101] The deposition process may precede or follow the cyclic removal process, depending on the desired surface quality and material growth requirements. In some cases, an additional passivation step may be performed before epitaxial material growth to avoid surface oxidation or contamination before material growth. This can further improve the quality of the grown material.

[0102] B3.2.2. Chemical species for cover growth In some examples, the chemical species used for coating growth 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.

[0103] B3.2.3. Cyclic Deposition Process In some cases, the deposition process can be cyclic, with the deposition rate approaching zero as the number of cycles increases. This allows for easy control over the thickness of the deposited material, ensuring a smooth, defect-free surface for subsequent material growth. The deposition process can also be a self-limiting process as a function of time or seed supply, as will be further detailed below.

[0104] The number of cycles in the deposition process can be optimized based on the surface roughness. For example, the number of cycles can range from 5 to 200. For instance, 20 cycles may provide a particularly optimal surface for material growth.

[0105] B4. Cyclic processes and subsequent epitaxial material growth In some examples, the method may involve a series of steps in a cyclic process, including one of the steps described in sections 3.1 and 3.2. The entire sequence can be repeated multiple times to achieve optimized surface quality and pre-treat the surface for epitaxial material growth. High-quality thin film growth of various materials is achieved on the pre-treated substrate surface.

[0106] In some cases, all steps in a cyclic process can be repeated multiple times to achieve optimized surface quality. The number of cycles can be optimized based on the surface roughness, ranging from 5 to 200 cycles. For example, 20 cycles may provide a particularly optimal surface for material growth.

[0107] Therefore, following the cyclic process, epitaxial material growth is performed on the pre-treated surface of the substrate. This involves forming a high-quality thin film of the growth material on the substrate surface. Unlike the surface material, the growth material may, in some examples, be a group III nitride material grown on a silicon substrate.

[0108] The cyclic process can be integrated with growth techniques such as molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), allowing surface pretreatment to be performed within the same chamber or adjacent chambers without exposure to ambient air between the surface pretreatment and the growth process, further improving the quality of the grown thin film. The method can also be combined with other processes such as atomic layer cleaning, rapid surface temperature cycling, and self-assembly, which can further enhance the quality of the grown material.

[0109] The method may include extracting process control information, such as information from emission and residual gas analysis, and adjusting the process parameters of the method based on the process control information. This can help optimize the process for different substrates and surface patterns, resulting in improved material growth. In other words, monitoring and control of the cyclic process is used to adjust the process parameters required for the desired results. In situ control is preferred and typically involves monitoring parameters such as emission and residual gas analysis, and monitoring thin film properties in various ways, such as using optical interferometry. By monitoring these parameters, the process endpoint and intermediate process points can be determined, and the process time and process parameters can be adjusted as needed to obtain an improved and pre-treated surface for material growth.

[0110] B5. Self-limiting reaction In some examples, the method may include at least one self-limiting reaction that slows down or stops as a function of time, or equivalently as a function of seed supply. These self-limiting reactions can provide a controlled and precise process for modifying the surface layer and activating the topmost modified surface layer, and similarly in some examples, provide a controlled and precise deposition process to ensure consistent, high-quality surface pretreatment for epitaxial material growth.

[0111] Processes in prior art such as GB2601404A do not stop after removing the non-uniform damaged surface layer, etching the original, undamaged layer beneath. This can be a major drawback when smoothing very thin films and structures where the removal of further material by a few nanometers may be fatal and undesirable. Chemical mechanical polishing or planarization (CMP) processes also do not stop after removing the non-uniform damaged surface layer, removing several underlying, original, undamaged layers.

[0112] In one example, a self-limiting reaction may involve chemiadsorption, in which case chemical species are chemiadsorbed onto a surface. In some examples, a self-limiting reaction may involve deposition, in which case chemical species are introduced into the process chamber volume to cover and grow impurities and defects on the surface. In one example, a self-limiting reaction may involve extraction. In the case of extraction, the original material is a multi-element compound, and a surface modification step preferentially removes one element from the surface, while different elements are removed in subsequent activation / removal steps. This extraction process can be self-limiting and may slow down or stop as a function of time or seed supply. A controlled extraction process can achieve consistent, damage-free removal of the topmost modified surface layer, giving a clean, smooth surface for epitaxial material growth. In some examples, a self-limiting reaction may involve transformation, such as oxidation or nitriding, in which case chemical species introduced into the process chamber volume react with the surface to form a modified surface layer. This transformation process is self-limiting and may slow down or stop as a function of time or seed supply. The controlled transformation process enables consistent and precise modification of the surface layer, providing an optimal surface for epitaxial material growth.

[0113] B6. Examples of process steps in different orders This section describes various examples of disclosed methods for pre-treating substrate surfaces for improved material growth. These examples illustrate various configurations and sequences of method steps, which can be adapted to specific applications and requirements.

[0114] B6.1. Sedimentation process preceding the cyclic removal process 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 interfacial layer by depositing a thin film material on the substrate surface before the cyclic removal process. The interfacial layer can help alleviate stress caused by lattice mismatch between dissimilar materials in contact with each other, and mitigate the problem of lattice mismatch with the material subsequently grown by epitaxy. This embodiment is shown in Figure 7, in which the cyclic removal process follows the material deposition 2400, resulting in a pre-treated substrate surface 2202.

[0115] B6.2. Deposition process following the cyclic removal process In another example, the deposition process follows a cyclic removal process. This configuration may be advantageous in certain situations because it allows for the growth of coatings of impurities and defects on the surface after the cyclic removal process. The deposition process can fill valleys on the surface and ensure that the surface remains smooth even during the subsequent epitaxial growth of very thin films. This embodiment is shown in Figure 8, in which a material deposition 2401 follows a cyclic removal process, resulting in a pre-treated substrate surface 2204.

[0116] B6.3. Passivation Steps Preceding Epitaxial Material Growth In some cases, the method may include an additional passivation step preceding epitaxial material growth. This can further enhance the quality of the grown material by protecting the pre-treated surface from undesirable reactions with ambient gases or contaminants. For example, a passivation step may be advantageous in avoiding surface oxidation or contamination prior to material growth, ensuring a high-quality thin film of the grown material on the pre-treated substrate surface. The passivation step can be carried out using various techniques, such as chemical passivation, plasma passivation, or thermal passivation.

[0117] B7. Examples of surface pretreatment for epitaxial material growth B7.1 The process of the first example relates to Figures 6 and 9: The surface of the Si is smoothed using a cyclic removal process, and then the GaN material is grown on top of this surface.

[0118] Process steps: 1. Pre-cleaning: Before starting the cyclic process, it is desirable that the silicon substrate is free from contaminants and native oxides. This can be achieved through a pre-cleaning step, which often involves a short exposure to plasma or chemical treatment to remove impurities. For removing native oxides from the Si surface, buffered oxide etching (BOE) 10:1 is favored, and this etching can be carried out by immersing the substrate in buffered HF for 30 seconds, then rinsing with deionized water for 30 seconds, and drying with N2 for 15 seconds. 2. Initial gas exposure for modifying the top surface layer: In the cyclic removal process, the Si surface is first exposed to chlorine gas for chemiadsorption. This step is self-limiting and slows down or stops as a function of time, or equivalently as a function of the seed supply. For faster chemiadsorption, it may be advantageous to activate the Cl2 gas with a plasma, for example. Exemplary process parameters for this step: Chlorine (Cl2) flow rate: in the range of 1 to 40 sccm (standard cubic centimeters per minute). • Pressure: Between 1 mTorr and 60 mTorr, preferably set to 3 mTorr. • Time: Between 15 milliseconds and 2 minutes. For inactivated Cl2 gas at room temperature, the preferred time is between 5 and 60 seconds, determined based on the process pressure. At a process pressure of 20 mTorr at room temperature, the optimal exposure time was determined to be 20 seconds. Specific optimal parameters may depend on other process details such as gas flow rate. The optimal gas flow rate is determined based on the process chamber volume and the exposed sample surface. In one example, a Cl2 gas flow rate greater than 20 sccm was determined to be optimal for the process results. At room temperature, if the gas is not activated, spontaneous Si etching by Cl2 gas was not observed. 3. Purge - Removal of excess chemical species: After chemical adsorption of surface chlorine, the reactor is purged with an inert gas (such as argon) to remove any excess chlorine gas from the chamber volume. Exemplary process parameters for this step: Argon (Ar) flow rate: between 3 and 80 sccm. • Purge time: Between 15 milliseconds and 120 seconds, preferably set to 40 seconds. • Pressure: Maintained between 1 and 60 mTorr, preferably set to 3 mTorr. 4. The topmost modified surface layer is activated to form volatile products, using a plasma pulse step in this example. During this step, a plasma is generated using an inert gas (such as argon (Ar) gas). Ions from the plasma are used to remove the topmost activated layer by chemiadsorption of chlorine. Exemplary process parameters for this step: • Argon (Ar) flow rate: Controlled between 1 and 40 sccm, preferably set to 20 sccm. • Ion energy: Below 60 eV. An ion energy of around 20 eV was determined to yield the best results. • Time: Between 3 and 60 seconds, preferably set to 10 seconds in a good example. • Pressure: Between 1 mTorr and 60 mTorr, preferably set to 3 mTorr. 5. Optional second purging step – removal of etching products: Its primary purpose is to remove any residual etching gases, reaction by-products, or other contaminants from the reaction chamber before proceeding to the next cycle of the cyclic removal process. Exemplary process parameters for this step: • Argon (Ar) flow rate: between 3 and 80 sccm. A flow rate of 20 sccm was determined to yield the best results. • Purge time: Between 2 and 20 seconds. A purge time of 2 seconds was determined to yield the best results. • Pressure: Maintained between 1 and 60 mTorr. A pressure of 3 mTorr was determined to yield the best results. 6. Repeat the cycle: Steps 2 through 5 are repeated a specific number of times. The optimal number of repetitions is determined to be between 5 and 200, based on the original roughness of the Si surface. For a typical Si surface after a chemical mechanical polishing (CMP) process, the optimal number of repetitions was determined to be 20. These precise parameters are particularly advantageous for smoothing the Si surface to the extent necessary for growing the improved GaN material on top of this surface; see Figure 10.

[0119] B7.2. The process of the second example relates to Figures 8 and 9: In this example, the process outlined in the first example is followed by a deposition process to cover and grow impurities and defects on the surface. Particularly favorable results are achieved when the deposition process is carried out in the same chamber as the cyclic removal process presented in the first example. This allows for minimal oxidation of the upper surface after the previous processing.

[0120] Process steps: B1. Purge: This step removes excess gas. Exemplary process parameters for this step: • Inert gas purging: Argon (Ar) is set to 20 sccm in preferred examples. • Purge time: Between 30 and 60 seconds, preferably set to 30 seconds. • Purge pressure: Between 1 and 10 mTorr. A pressure of 10 mTorr was determined to yield the best results. 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 monolayer of gallium atoms. Exemplary process parameters for this step: • TMG flow rate: Between 10 and 50 sccm, preferably set to 20 sccm. • Pulse duration: Between 0.1 and 2 seconds, preferably set to 1 second in a preferred example. Chamber pressure: Between 1 and 100 mTorr, preferably set to 50 mTorr in a preferred example. • TMG vaporizer temperature: set between 60 and 100°C, preferably at 80°C. 3. Purge - Inert Gas: Removes excess TMG and reaction byproducts from the previous step, ensuring that only a monolayer of gallium atoms remains on the substrate surface. Exemplary process parameters for this step: • Ar flow rate: Between 50 and 200 sccm, preferably set to 100 sccm. • Purge time: Between 10 and 30 seconds, preferably set to 20 seconds. • Purge pressure: Between 1 and 10 mTorr, preferably set to 10 mTorr. 4. Deposition Process - Nitrogen (N) Precursor Pulse: Ammonia (NH3) is introduced and reacts with gallium atoms exposed on the surface to form a monolayer of GaN. This completes the deposition of one atomic layer of GaN. Exemplary process parameters for this step: • H3 flow rate: Between 10 and 50 sccm, preferably set to 20 sccm. • Pulse duration: Between 0.1 and 2 seconds, preferably set to 1 second in a preferred example. • ALD chamber pressure: between 1 and 100 mTorr. A pressure of 50 mTorr was determined to yield the best results. 5. Purge - Inert Gas: As with the previous purging step, argon gas is used to remove excess NH3 and reaction byproducts and to pre-treat the surface for the next cycle. Exemplary process parameters for this step: Argon flow rate: Between 50 and 200 sccm • Purge time: Between 10 and 30 seconds • Purge pressure: Between 1 and 10 mTorr 6. Repeat the cycle: Steps 2 through 5 are repeated a specific number of times. It was determined that the favorable number of repetitions is between 5 and 200. It was determined that the optimal number of repetitions to accumulate the initial GaN nucleation layer is 20.

[0121] The process is preferably continuously monitored, and process parameter data are analyzed. For example, in situ characterization techniques such as optical emission spectroscopy (OES) and optical reflectivity can be used for this process monitoring. A preferred method for this process monitoring is to verify the actual process parameters and compare them to reference values. Specifically, it has been found that the process is best monitored by in-line tracking of the applied and reflected radio frequency (RF) signal, maintaining the plasma and the corresponding matching parameters for the RF line. This monitoring allows for precise adjustment of the number of cycles required to pre-treat the surface for subsequent growth of GaN material onto the top. Depending on the results of the process monitoring, it may be advantageous to repeat the process steps outlined in the first example. In some cases, it is necessary to adjust the plasma pulse step (step 3) by increasing the ion energy, typically keeping it below 90 eV. In some examples, an ion energy of around 30 eV was found to yield the best results. In some examples, it may be necessary to repeat the steps of the first and second examples above multiple times. It was determined that five iterations yielded the optimal results. The number of these iterations can be optimized and determined based on situ monitoring and process tracking.

[0122] B8. Experimental Results This section provides a detailed description of experimental results obtained using the disclosed method for pre-treating the substrate surface for improved material growth. These results demonstrate the effectiveness of the method in reducing surface roughness and improving the quality of the grown material.

[0123] B8.1. Microscopic images taken with an atomic force microscope (AFM) In one example, atomic force microscopy (AFM) images were used to analyze the surface roughness of a substrate before and after a cyclic removal process. AFM images provide a visual representation of the surface topography and allow for a direct comparison of surface roughness before and after the process. The reduction in surface roughness observed in the AFM images was also quantitatively analyzed, demonstrating the effectiveness of the method.

[0124] B8.1.1. Initial Si surface and surface after cyclic etching In one example, the initial Si surface (Figure 10 left) was compared to the surface after a cyclic removal process, i.e., cyclic etching (Figure 10 right). The AFM micrograph shows a significant reduction in surface roughness after the cyclic removal process. Two sections of the micrograph, 2500 and 2504, show a 1 μm² scan area. Graphs 2501, 2502, 2503, 2505, 2506, and 2507 below are line scans at different locations, top, middle, and bottom, corresponding to scan areas 2500 and 2504, respectively. The reduction in surface roughness after the cyclic removal process demonstrates the effectiveness of the method in substrate surface pretreatment for improved material growth.

[0125] B8.1.2. Initial GaN surface and surface after cyclic deposition and etching. In another example, the initial GaN surface (Figure 11 left) was compared to the surface after a cyclic deposition and subsequent cyclic removal process, i.e., after cyclic etching (Figure 11 right). AFM micrographs show a significant reduction in surface roughness after the combined cyclic deposition and removal processes. This result demonstrates that any chosen deposition process can further enhance surface pretreatment for improved material growth.

[0126] The reduction in surface roughness observed in these examples demonstrates the advantages of the disclosed method in substrate surface pretreatment for improved material growth. By reducing surface roughness, the method can significantly reduce the number of defects in the material grown on the surface, resulting in high-quality thin films. Furthermore, the method can be combined with ion beam forming processes to further enhance surface pretreatment and improve material growth on a variety of substrates.

[0127] The terms used herein are for the sole purpose of describing specific aspects and are not intended to limit the disclosure. Where used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. Where used herein, the term “and / or” includes all combinations of one or more of the enumerated items relating to it. Where used herein, the terms “comprises,” “comprising,” “includes,” and / or “including” indicate the presence of the described features, integers, actions, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components, and / or groups thereof.

[0128] In this specification, terms such as "first," "second," etc., may be used to describe various elements, but it will be understood that these elements should not be limited by these terms. These terms are used solely to distinguish one element from another. For example, the first element may be called the second element, and similarly, the second element may be called the first element without departing from the scope of this disclosure.

[0129] In this specification, relative terms such as “down,” “up,” “up,” “down,” “horizontal,” or “vertical” may be used to describe the relationship between one element and another, as shown in the diagrams. It will be understood that these terms, and the terms mentioned above, are intended to encompass different orientations of the device, in addition to the orientation depicted in the diagrams. When an element is said to be “connected” or “joined” to another element, it will be understood that the element may be directly connected or joined to the other element, or there may be an intervening element. In contrast, when an element is said to be “directly connected” or “directly joined” to another element, there is no intervening element.

[0130] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as those generally understood by those skilled in the art in which this disclosure pertains. Furthermore, terms used herein should be interpreted as having meanings consistent with their meanings in the context of this specification and related art, and should not be interpreted as idealized or overly formal unless expressly defined herein.

[0131] This disclosure is not limited to the embodiments described above and illustrated in the drawings, and rather, those skilled in the art will understand that many changes and modifications can be made within the scope of this disclosure and the attached claims. The drawings and specification disclose embodiments for illustrative purposes only and not limiting purposes, and the scope of the disclosure is set forth in the following claims.

Claims

1. A method for surface preparation based on cyclic processing, Activating the surface, Removing excess material from the aforementioned surface and surrounding environment, The surface is treated with low-energy particles, Repeat the above steps until the surface has the desired smoothness. Methods that include...

2. The method according to claim 1, wherein the low-energy particle processing 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 is atomic layer etching (ALE) with molecular activation.

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 the repetition of the step is carried out until the process no longer affects different processed surfaces.

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

11. The method according to claim 10, further comprising oblique incidence particle beam etching.

12. The method according to any one of claims 1 to 11, wherein the surface is a side wall surface.

13. The method according to any one of claims 1 to 12, wherein the aforementioned 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 a semiconductor surface, a metal surface, a dielectric surface, and a 2D material surface.

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 exposing the surface to a gas.

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 the activation of the surface includes 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 irradiating the surface with a particle beam.

21. The method according to any one of claims 1 to 20, wherein the low-energy particle treatment includes a low-energy particle beam having a particle energy 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 a plasma power between 1 W and 50 W.

23. A surface prepared by the method described in any one of claims 1 to 22.

24. A method for surface pretreatment of a substrate and epitaxial material growth, wherein the method is: A step of exposing the surface to a cyclic removal process to remove impurities and defects from the surface, To obtain the modified uppermost surface layer of the said surface, the uppermost surface layer of the said surface is modified by introducing chemical species such as halogens within the process chamber volume surrounding the substrate. The steps include: discharging excess chemical species from the process chamber volume; A step of activating the uppermost modified surface layer to form volatile products, The steps include optionally removing etching products from the process chamber volume and Steps including The cyclic removal process includes the continuation of epitaxial material growth. The growth material is different from the surface material, by a method.

25. The method according to claim 24, wherein the step of modifying the uppermost surface layer is performed in a gas phase containing only neutral species.

26. The method according to claim 24 or 25, wherein the cyclic removal process has an etching rate for each cycle, and the etching 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 uppermost modified surface layer is carried out in a gas phase without surface bombardment with ions.

28. The method according to any one of claims 24 to 27, comprising the step of a deposition process for covering and growing impurities and defects on the surface, wherein the step includes modifying the top surface layer by introducing chemical species into the process chamber volume for the covering growth.

29. The method according to claim 28, wherein the chemical species for covering growth comprises gallium, nitrogen, and optionally aluminum.

30. The method according to 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 for each cycle, and 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 reaction that slows down or stops as a function of time, or equivalently as a function of the seed supply.

33. The method according to claim 32, wherein the self-limiting reaction includes transformations such as chemiadsorption, deposition, extraction, and / or oxidation or nitriding.

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

35. The method according to any one of claims 24 to 34, wherein the surface includes a pattern of regularly arranged holes, lines, and / or columns.

36. The method according to any one of claims 24 to 35, comprising extracting process control information, such as information from luminescence and residual gas analysis, and adjusting the process parameters of the method based on the process control information.

37. A method for epitaxial material growth on the surface of a substrate, Any step according to any of claims 24 to 27, followed by any step according to any of claims 28 to 34. The method includes a cyclic process including a sequence, and the method is Repeating the above sequence multiple times, Epitaxial material growth of the growth material on the aforementioned surface and A method comprising the growth material being different from the material on the surface.

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

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