Atomistic Removal Mechanisms of SiC in Hydrogen Peroxide Solution

To elucidate the atomic mechanisms of the chemical mechanical polishing (CMP) of silicon carbide (SiC), molecular dynamics simulations based on a reactive force field were used to study the sliding process of silica (SiO2) abrasive particles on SiC substrates in an aqueous H2O2 solution. During the CMP process, the formation of Si-O-Si interfacial bridge bonds and the insertion of O atoms at the surface can lead to the breakage of Si-C bonds and even the complete removal of SiC atoms. Furthermore, the removal of C atoms is more difficult than the removal of Si atoms. It is found that the removal of Si atoms largely influences the removal of C atoms. The removal of Si atoms can destroy the lattice structure of the substrate surface, leading the neighboring C atoms to be bumped or even completely removed. Our research shows that the material removal during SiC CMP is a comprehensive result of different atomic-level removal mechanisms, where the formation of Si-O-Si interfacial bridge bonds is widespread throughout the SiC polishing process. The Si-O-Si interfacial bridge bonds are the main removal mechanisms for SiC atoms. This study provides a new idea for improving the SiC removal process and studying the mechanism during CMP.


Introduction
Silicon carbide (SiC) has excellent thermal conductivity, high electron drift rate, large lattice mismatch tolerance, and high breakdown field strength, and it is an excellent material for manufacturing high-power electronic devices and optoelectronic devices, like silicon carbon-based MOSFET and PiN [1].In these electronic devices, it is critical to ensure that the SiC surface achieves an atomic-level, high-precision, damage-free surface, as the surface flatness and surface accuracy directly affect the quality of the SiC epitaxial layer, ultimately determining the performance of the device [2,3].Therefore, the flattening of SiC surfaces has received extensive attention.
Chemical mechanical polishing (CMP) is widely recognized as a global flattening technique to achieve high-quality wafer surfaces.It has been applied to hard and brittle materials, such as silicon, copper, and glass [4][5][6][7].Several researchers have deduced the material removal mechanism of SiC by examining the composition of the chemical components on the SiC surface before and after polishing.For example, Qi et al., using a scanning electron microscope and an energy dispersive spectrograph, measured the percentage of oxygen on the surface of SiC samples before and after dry CMP using five different solid-phase oxidants [8].They deduced that the solid-phase oxidants facilitate the friction chemical reaction on the SiC surface under the effect of frictional heat, which generates an oxidation reaction film, promoting the oxidation of the silicon carbide surface.Consequently, it is inferred that under the impact of CMP, the solid-phase oxidizer can either oxidize the SiC surface with oxygen or engage in a chemical reaction with the SiC surface.
Micromachines 2024, 15, 754 2 of 13 Furthermore, some researchers have experimentally investigated the effects of factors such as ultrasonic waves [9], abrasive concentration [10], abrasive particle size [11], temperature [12], pressure [13], and others in removing SiC materials.Shen et al. utilized XPS to infer the types of surface products and the potential chemical reactions occurring on SiC surfaces post-CMP based on spectral characteristics [14].Although these macro-scale experiments effectively determine the process parameters affecting the CMP process, they do not clearly describe the mechanism of CMP for SiC due to the difficulty in observing the details of the SiC chemical reactions in real time.While XPS inspection can provide atomic details of the SiC CMP process, it cannot provide a dynamic view of atomic removal and thus fails to describe the mechanism of the process fully.However, understanding the removal mechanism is essential to improve the CMP process.
Molecular Dynamics (MD) simulation is a reliable tool for studying molecular motion from a microscopic perspective [15][16][17][18].It has evolved into various theoretical systems to accommodate complex reactions in different environments.The commonly used MD is a simulation system based on Newtonian mechanics, which is suitable for analyzing intermolecular mechanical interactions.However, it fails to capture the state of intermolecular chemical reactions accurately.On the other hand, first-principle atomic dynamics can accurately describe the chemical reactions between atoms in computational systems [19][20][21].However, the extensive computational cost associated with first-principal MD simulations, which involve many molecules, limits their application in CMP.In recent years, a new reactive force field (ReaxFF) MD simulation method was introduced to reflect the relationship between molecular movements based on changes at the bond level [22][23][24].ReaxFF-MD simulations have been widely applied in various fields, such as physics, biology, and so on [25][26][27].Ashish et al. reoptimized the ReaxFF parameters of the Si/O/C/H/N system to effectively address the stress analysis and temperature effect evaluation of SiC ceramic fibers [28].These studies facilitate the development of the ReaxFF potential functions, expanding their application domains.Chen et al. employed the ReaxFF-MD method to investigate the oxidation behavior of different polar surfaces of 3C-SiC in aqueous solution and oxygen environments [29].They accurately understood the system reaction activity and rate of SiC under various experimental conditions in the reaction and also clearly observed the formation mechanism of surface product SiO 2 .He et al. utilized the ReaxFF-MD simulation method to investigate the atomic oxidation, removal, and damage characteristics of nanoscale polished SiC substrates under the influence of chemical solution and abrasive vibrations [30].They found that the vibration behavior of abrasives in vibration-assisted CMP enhanced the mechanical action, the atomic hybridization of SiC substrates, and the atomic activity, promoting the penetration of oxygen and hydrogen atoms.Meanwhile, this further promotes the adsorption of the chemical reaction between the solution and the substrate.According to Wu et al. [31], in their study of the mechanical properties of the oxide layer, the oxidation surface dramatically reduces the mechanical properties of the SiC surface.Yang et al. revealed that the H 2 O 2 solution forms oxidation bonds on the 6H-SiC surface during the polishing process, thereby promoting the removal of Si and C atoms [32].Thus, the oxidation of the SiC surface promotes the removal of atoms from the SiC surface.In this study, we will delve into how the oxidation of the SiC surface works during SiC CMP as well as the individual contributions of each removal mechanism to the total amount of substrate removal.
In this study, we utilized a previously developed transferable ReaxFF parameter set for carbon-and silicon-based solid materials.This parameter set was trained using a multi-objective simulated annealing algorithm and encompasses parameters for the elements H, C, O, and Si, covering a wide range of carbon/silicon-based solid materials.We employed ReaxFF-MD to investigate the atomic removal mechanism of SiC substrates by SiO 2 abrasive polishing in CMP in hydrogen peroxide solution.During the CMP of SiC, the ionization and decomposition of H 2 O and H 2 O 2 in the polishing solution will change the chemical properties of the SiC surface, resulting in a large number of H and O atoms on the SiC surface [33].We explained the effect of the surface oxide layer on the removal of SiC from the surface material.Subsequently, we observed various SiC removal mechanisms and quantified their respective contributions to the overall removal process.The insights gained from this study enhance our understanding of the material removal process and mechanisms involved in SiC CMP, providing valuable guidance for optimizing CMP techniques in semiconductor fabrication.

Computational Details
In this study, we use a previously developed MD simulator (Laskyo) to perform the CMP process [34].Moreover, ReaxFF is based on a bond-order reactive force field that can precisely represent bond formation and breakage.Thus, in this study, we employed the ReaxFF parameters developed in our previous study.These parameters effectively capture the interactions within the SiO 2 /water/SiC system [35].All snapshots in this paper were generated by OVITO [36].
Figure 1 shows the simulation model for polishing the SiC slab with a single cluster of SiO 2 , which is widely employed as an abrasive grain [37,38].In this study, we chose the 4H-SiC structure for constructing the SiC slab, because it has high electron mobility anisotropy, low mobility, and lower growth rate, making it more suitable for applying electronic components.Meanwhile, the SiC(1-100) surface (m-face) is employed as the polished surface because the (1-100) surface is the most stable crystalline surface compared to the SiC (0001) surface and the (000-1) surface.This stability plays an important role in manufacturing lateral SiC power devices [39].The m-face of SiC crystals, comprising 1344 SiC atoms, is prepared using NVP simulation with the temperature set at 300 K. Temperature control is achieved using a Berendsen heat bath with a damping constant of 0.25 ps to minimize surface atomic energy [40].We employed an aqueous solution containing 100 H 2 O molecules and 60 H 2 O 2 molecules equilibrated by NVT simulation to accelerate the chemical reaction rate during the CMP process.To reduce the computational cost, we used a sine function to isolate an amorphous SiO 2 structure using a sinusoidal function with a maximum value of 16 Å and retaining the 8 Å thickness of the flat plate above, which contains 513 Si atoms and 1026 O atoms.Next, the surface of the SiO 2 particles was annealed using the Nose-Hoover thermostat to eliminate edge effects.This was achieved by subjecting the particle to NVT simulation, raising its temperature to 8000 K and then lowering it to 300 K to minimize potential energy through the rearrangement of surface atoms, a method similar to that used by Russo et al. [41].Then, the SiC substrate, aqueous H 2 O 2 , and SiO 2 were combined along the z-axis to generate the final simulation model, resulting in total system dimensions of 30.2 Å × 40.6 Å × 100 Å.
on the SiC surface [33].We explained the effect of the surface oxide layer on the rem of SiC from the surface material.Subsequently, we observed various SiC removal me nisms and quantified their respective contributions to the overall removal process.insights gained from this study enhance our understanding of the material removal cess and mechanisms involved in SiC CMP, providing valuable guidance for optimi CMP techniques in semiconductor fabrication.

Computational Details
In this study, we use a previously developed MD simulator (Laskyo) to perform CMP process [34].Moreover, ReaxFF is based on a bond-order reactive force field that precisely represent bond formation and breakage.Thus, in this study, we employed ReaxFF parameters developed in our previous study.These parameters effectively ture the interactions within the SiO2/water/SiC system [35].All snapshots in this p were generated by OVITO [36].
Figure 1 shows the simulation model for polishing the SiC slab with a single clu of SiO2, which is widely employed as an abrasive grain [37,38].In this study, we chose 4H-SiC structure for constructing the SiC slab, because it has high electron mobility sotropy, low mobility, and lower growth rate, making it more suitable for applying e tronic components.Meanwhile, the SiC(1-100) surface (m-face) is employed as the ished surface because the (1-100) surface is the most stable crystalline surface comp to the SiC (0001) surface and the (000-1) surface.This stability plays an important ro manufacturing lateral SiC power devices [39].The m-face of SiC crystals, comprising SiC atoms, is prepared using NVP simulation with the temperature set at 300 K. Tem ature control is achieved using a Berendsen heat bath with a damping constant of 0.2 to minimize surface atomic energy [40].We employed an aqueous solution containing H2O molecules and 60 H2O2 molecules equilibrated by NVT simulation to accelerate chemical reaction rate during the CMP process.To reduce the computational cost, we u a sine function to isolate an amorphous SiO2 structure using a sinusoidal function w maximum value of 16 Å and retaining the 8 Å thickness of the flat plate above, w contains 513 Si atoms and 1026 O atoms.Next, the surface of the SiO2 particles was nealed using the Nose-Hoover thermostat to eliminate edge effects.This was achieved subjecting the particle to NVT simulation, raising its temperature to 8000 K and then l ering it to 300 K to minimize potential energy through the rearrangement of surface ato a method similar to that used by Russo et al. [41].Then, the SiC substrate, aqueous H and SiO2 were combined along the z-axis to generate the final simulation model, resul in total system dimensions of 30.2 Å × 40.6 Å × 100 Å.In Figure 1, the SiC surface model contains seven layers: (1) the fixed layer of the bottom SiC substrate atoms, which is constrained to be stationary over the entire simulation; (2) the thermostat layer of the SiC substrate, which is used to control the system temperature as constant; (3) the free SiC substrate layer; (4) aqueous H 2 O 2 at the interface between the SiC substrate and SiO 2 abrasive grain surfaces; (5) the free SiO 2 abrasive grain layer, with atoms allowed to move dynamically in the simulations; (6) the thermostat layer of SiO 2 abrasive grains; and (7) the rigid layer of the amorphous structure, which is laterally movable.The parameters set in this MD simulation are based on a metastable ReaxFF reaction model for carbon-and silicon-based solid materials.This model was previously developed and successfully applied in our previous aqueous H 2 O 2 study.
All simulations are performed in the NVT ensemble with a time step of 0.25 fs.The Nose-Hoover temperature control method is employed to maintain the temperature at 300 K.The following five steps in the polishing process are conducted to simulate the sliding removal process: (1) To simulate the natural polishing environment more accurately, we initiate the α-SiO 2 /polishing solution/SiC system at a temperature of 300 k for 50 ps, allowing sufficient interaction between the system abrasive grains, the polishing solution, and the SiC substrate.(2) The normal load is uniformly applied to the top rigid layer of SiO 2 along the z-axis.(3) The SiO 2 moves vertically towards the surface of the SiC substrate, compressing the hydrogen peroxide solution at the interface until the target normal force matches the predetermined load to be applied to the SiO 2 .(4) The CMP simulation model is equilibrated for 50 ps.(5) SiO 2 is slid laterally for 500 ps along the y-axis at a constant velocity of 100 m/s.In this study, a pressure of 2, 4, and 6 GPa is employed to investigate the effect of pressure on the CMP process.The specific simulation parameters are shown in Table 1.

Surface Oxidation of SiC in the Hydrogen Peroxide Solution
Figure 2 illustrates the state of the polishing model at the end of relaxation and after loading, as well as the surface of the SiC after fully reacting with the aqueous H 2 O 2 .Figure 2 shows that the surface exhibits termination with Si-OH, Si-H 2 O, C-H, Si-O, and C-O-Si group structures.This is consistent with a previous study reported by Shen et al. [14].H 2 O and H 2 O 2 molecules undergo decomposition and ionization, generating numerous -H, -OH, -O, and other groups.These groups are adsorbed onto the surface of SiC, forming bonds such as Si-O-(O-) and C-O.This indicates that the SiC surface is oxidized after interaction with the aqueous H 2 O 2 , leading to surface softening, and the result is consistent with the literature [42].To understand the effect of loading and hydrogen peroxide molecules on the oxida tion of the SiC surface, we monitored the formation process of the surface structure and quantified the number of H2O2 molecules and main bonds (including Si-O and C-O) ove the simulation time.As shown in Figure 3, during the first 50 ps, the substrate and abra sive grains remain stationary.The H2O2 solution at the interface (Figure 3a) reacts suffi ciently with the abrasive grains and substrate to oxidize the substrate surface.Then, from 50-100 ps, we load the abrasive grains and performed relaxation calculations to construc the CMP model.Meanwhile, we find a further increase of the number of Si-O and C-O bonds (Figure 3b) on the substrate surface at this stage, and the SiC substrate forms a smal number of Si-O and C-O bonds with SiO2 abrasive grains.Figure 2 shows that when th abrasive grain loading is complete, the bottom of the SiO2 surface undergoes plastic de formation due to extrusion.Figure 4 is a snapshot of the beginning of the loading phas for SiO2.We observe that during the loading process, O 1 atoms from SiO2 are compressed to the SiC surface to form the O 1 -C 1 bond with the C 1 atom and attach to the substrat surface, facilitating the softening of the SiC surface.From Figure 3, it can be observed tha the number of Si-O bonds formed on the surface of SiC after sufficient reaction with aque ous H2O2 is obviously higher than that of C-O bonds, indicating that the oxidation of S atoms is the main form of SiC surface oxidation during the softening process of the SiC substrate.To understand the effect of loading and hydrogen peroxide molecules on the oxidation of the SiC surface, we monitored the formation process of the surface structure and quantified the number of H 2 O 2 molecules and main bonds (including Si-O and C-O) over the simulation time.As shown in Figure 3, during the first 50 ps, the substrate and abrasive grains remain stationary.The H 2 O 2 solution at the interface (Figure 3a) reacts sufficiently with the abrasive grains and substrate to oxidize the substrate surface.Then, from 50-100 ps, we load the abrasive grains and performed relaxation calculations to construct the CMP model.Meanwhile, we find a further increase of the number of Si-O and C-O bonds (Figure 3b) on the substrate surface at this stage, and the SiC substrate forms a small number of Si-O and C-O bonds with SiO 2 abrasive grains.Figure 2 shows that when the abrasive grain loading is complete, the bottom of the SiO 2 surface undergoes plastic deformation due to extrusion.Figure 4 is a snapshot of the beginning of the loading phase for SiO 2 .We observe that during the loading process, O 1 atoms from SiO 2 are compressed to the SiC surface to form the O 1 -C 1 bond with the C 1 atom and attach to the substrate surface, facilitating the softening of the SiC surface.From Figure 3, it can be observed that the number of Si-O bonds formed on the surface of SiC after sufficient reaction with aqueous H 2 O 2 is obviously higher than that of C-O bonds, indicating that the oxidation of Si atoms is the main form of SiC surface oxidation during the softening process of the SiC substrate.To understand the effect of loading and hydrogen peroxide molecules on the ox tion of the SiC surface, we monitored the formation process of the surface structure quantified the number of H2O2 molecules and main bonds (including Si-O and C-O) the simulation time.As shown in Figure 3, during the first 50 ps, the substrate and a sive grains remain stationary.The H2O2 solution at the interface (Figure 3a) reacts s ciently with the abrasive grains and substrate to oxidize the substrate surface.Then, f 50-100 ps, we load the abrasive grains and performed relaxation calculations to cons the CMP model.Meanwhile, we find a further increase of the number of Si-O and bonds (Figure 3b) on the substrate surface at this stage, and the SiC substrate forms a s number of Si-O and C-O bonds with SiO2 abrasive grains.Figure 2 shows that when abrasive grain loading is complete, the bottom of the SiO2 surface undergoes plastic formation due to extrusion.Figure 4 is a snapshot of the beginning of the loading p for SiO2.We observe that during the loading process, O 1 atoms from SiO2 are compre to the SiC surface to form the O 1 -C 1 bond with the C 1 atom and attach to the subs surface, facilitating the softening of the SiC surface.From Figure 3, it can be observed the number of Si-O bonds formed on the surface of SiC after sufficient reaction with a ous H2O2 is obviously higher than that of C-O bonds, indicating that the oxidation atoms is the main form of SiC surface oxidation during the softening process of the substrate.

Mechanisms for the Removal of SiC Material
To reveal the removal mechanism of the SiC surface, we tracked the breakage and formation process of their surface bonds and interfacial covalent bonds during the CMP process.It was found that the formation of Si-O-Si interfacial bridge bonds and the insertion of O atoms into the SiC surface can lead to the breakage of surface Si-C bonds, achieving atomic removal.Figure 5 presents some snapshots of the polishing process, from which we can observe deformation and even abrasion of the substrate as the abrasive grains continuously slide along the SiC surface.This is due to the fact that the hardness of SiO2 is much lower than that of SiC, and also because the SiO2 polishing process only removes the oxide layer of the substrate without causing subsurface damage (SSD) to the SiC surface.The detailed process is discussed in the following section using the example of a pressure of 6 GPa. Figure 6 shows the process of removal of the Si atom from the SiC surface through an interfacial bridge bond.Before the sliding removal process, the Si 1 atom belongs to the substrate and is bonded with three C atoms (C 1 , C 2 , and C 3 ) and -O 1 H 1 (Figure 6a).During the sliding process, the proton of H 1 diffuses, and Si 2 and O 1 atoms form bridge bonds at the Si 1 -O 1 -Si 2 interface, thus binding the abrasive grains to the substrate surface (Figure 6b).As the abrasive grains move, the Si 1 atom is pulled up from the substrate surface because of the bridge bonding (Figure 6c).At 25 ps, the bonds of Si 1 -C 1 and Si 1 -C 2 are broken due to the tension generated by the continuous sliding of the abrasive grain, leading to the complete removal of the Si 1 atom.

Mechanisms for the Removal of SiC Material
To reveal the removal mechanism of the SiC surface, we tracked the breakage and formation process of their surface bonds and interfacial covalent bonds during the CMP process.It was found that the formation of Si-O-Si interfacial bridge bonds and the insertion of O atoms into the SiC surface can lead to the breakage of surface Si-C bonds, achieving atomic removal.Figure 5 presents some snapshots of the polishing process, from which we can observe deformation and even abrasion of the substrate as the abrasive grains continuously slide along the SiC surface.This is due to the fact that the hardness of SiO 2 is much lower than that of SiC, and also because the SiO 2 polishing process only removes the oxide layer of the substrate without causing subsurface damage (SSD) to the SiC surface.The detailed process is discussed in the following section using the example of a pressure of 6 GPa.

Mechanisms for the Removal of SiC Material
To reveal the removal mechanism of the SiC surface, we tracked the breakage and formation process of their surface bonds and interfacial covalent bonds during the CMP process.It was found that the formation of Si-O-Si interfacial bridge bonds and the insertion of O atoms into the SiC surface can lead to the breakage of surface Si-C bonds, achieving atomic removal.Figure 5 presents some snapshots of the polishing process, from which we can observe deformation and even abrasion of the substrate as the abrasive grains continuously slide along the SiC surface.This is due to the fact that the hardness of SiO2 is much lower than that of SiC, and also because the SiO2 polishing process only removes the oxide layer of the substrate without causing subsurface damage (SSD) to the SiC surface.The detailed process is discussed in the following section using the example of a pressure of 6 GPa. Figure 6 shows the process of removal of the Si atom from the SiC surface through an interfacial bridge bond.Before the sliding removal process, the Si 1 atom belongs to the substrate and is bonded with three C atoms (C 1 , C 2 , and C 3 ) and -O 1 H 1 (Figure 6a).During the sliding process, the proton of H 1 diffuses, and Si 2 and O 1 atoms form bridge bonds at the Si 1 -O 1 -Si 2 interface, thus binding the abrasive grains to the substrate surface (Figure 6b).As the abrasive grains move, the Si 1 atom is pulled up from the substrate surface because of the bridge bonding (Figure 6c).At 25 ps, the bonds of Si 1 -C 1 and Si 1 -C 2 are broken due to the tension generated by the continuous sliding of the abrasive grain, leading to the complete removal of the Si 1 atom.Figure 6 shows the process of removal of the Si atom from the SiC surface through an interfacial bridge bond.Before the sliding removal process, the Si 1 atom belongs to the substrate and is bonded with three C atoms (C 1 , C 2 , and C 3 ) and -O 1 H 1 (Figure 6a).During the sliding process, the proton of H 1 diffuses, and Si 2 and O 1 atoms form bridge bonds at the Si 1 -O 1 -Si 2 interface, thus binding the abrasive grains to the substrate surface (Figure 6b).As the abrasive grains move, the Si 1 atom is pulled up from the substrate surface because of the bridge bonding (Figure 6c).At 25 ps, the bonds of Si 1 -C 1 and Si 1 -C 2 are broken due to the tension generated by the continuous sliding of the abrasive grain, leading to the complete removal of the Si 1 atom.
The formation of Si-O-Si interfacial bridge bonds is also observed during the loading process.However, there is no observed breakage of Si-C bonds in the region of the Si atoms forming the interfacial bridge bonds.Whereas, as the abrasive grains slide along the surface of the substrate when the Si-O-Si bonds are stretched to a certain extent, the breakage of the Si-C bonds is more likely to occur than for the Si-O bonds.This is because the previous experimental observations using angle-resolved X-ray photoelectron spectroscopy under water vapor plasma irradiation reveal that the bonding energy of the Si-C bond is lower than that of the Si-O [43], and thus, the activation energy for the breakage of the Si-C bond is much lower than the activation energy of the Si-O bond.The formation of Si-O-Si interfacial bridge bonds is also observed during the loading process.However, there is no observed breakage of Si-C bonds in the region of the Si atoms forming the interfacial bridge bonds.Whereas, as the abrasive grains slide along the surface of the substrate when the Si-O-Si bonds are stretched to a certain extent, the breakage of the Si-C bonds is more likely to occur than for the Si-O bonds.This is because the previous experimental observations using angle-resolved X-ray photoelectron spectroscopy under water vapor plasma irradiation reveal that the bonding energy of the Si-C bond is lower than that of the Si-O [43], and thus, the activation energy for the breakage of the Si-C bond is much lower than the activation energy of the Si-O bond.
Besides breaking the Si-C bonds due to the interfacial bridge bonds, which leads to the removal of Si atoms, the insertion of oxygen atoms also leads to the removal of Si atoms from the substrate.Figure 2 illustrates various oxygenated species on the SiC surface, such as Si-OH, Si-H2O, Si-O, and C-O-Si groups, resulting from interaction with an H2O2 solution.During the polishing process, O atoms from these species appear to insert into the surface, forming Si-O-C bonds (Figure 7).At 94 ps, the O 2 H 1 is observed to adsorb on the Si 1 atom of the SiC substrate.Meanwhile, the bond of Si 1 -O 1 -C 1 is formed (Figure 7a).Then, the O 1 atom inserts into the SiC surface under the pressure and sliding of the abrasive grains, and the lattice structure where the Si 1 atom located is obviously deformed.At 107.5 ps, the O 1 atom is entirely inserted into the substrate interior, while the Si 1 atom is extruded.Additionally, this facilitates the easier removal of the Si 1 atom protruding from the surface.As the sliding continues, the Si 1 -C 2 , Si 1 -O 1 , and Si 1 -C 3 bonds break sequentially, completely separating the Si 1 atom from the SiC surface (Figure 7c).Besides breaking the Si-C bonds due to the interfacial bridge bonds, which leads to the removal of Si atoms, the insertion of oxygen atoms also leads to the removal of Si atoms from the substrate.Figure 2 illustrates various oxygenated species on the SiC surface, such as Si-OH, Si-H 2 O, Si-O, and C-O-Si groups, resulting from interaction with an H 2 O 2 solution.During the polishing process, O atoms from these species appear to insert into the surface, forming Si-O-C bonds (Figure 7).At 94 ps, the O 2 H 1 is observed to adsorb on the Si 1 atom of the SiC substrate.Meanwhile, the bond of Si 1 -O 1 -C 1 is formed (Figure 7a).Then, the O 1 atom inserts into the SiC surface under the pressure and sliding of the abrasive grains, and the lattice structure where the Si 1 atom located is obviously deformed.At 107.5 ps, the O 1 atom is entirely inserted into the substrate interior, while the Si 1 atom is extruded.Additionally, this facilitates the easier removal of the Si 1 atom protruding from the surface.As the sliding continues, the Si 1 -C 2 , Si 1 -O 1 , and Si 1 -C 3 bonds break sequentially, completely separating the Si 1 atom from the SiC surface (Figure 7c).The formation of Si-O-Si interfacial bridge bonds is also observed during the loa process.However, there is no observed breakage of Si-C bonds in the region of t atoms forming the interfacial bridge bonds.Whereas, as the abrasive grains slide a the surface of the substrate when the Si-O-Si bonds are stretched to a certain exten breakage of the Si-C bonds is more likely to occur than for the Si-O bonds.This is bec the previous experimental observations using angle-resolved X-ray photoelectron troscopy under water vapor plasma irradiation reveal that the bonding energy of th C bond is lower than that of the Si-O [43], and thus, the activation energy for the brea of the Si-C bond is much lower than the activation energy of the Si-O bond.
Besides breaking the Si-C bonds due to the interfacial bridge bonds, which lea the removal of Si atoms, the insertion of oxygen atoms also leads to the removal atoms from the substrate.Figure 2 illustrates various oxygenated species on the SiC face, such as Si-OH, Si-H2O, Si-O, and C-O-Si groups, resulting from interaction wi H2O2 solution.During the polishing process, O atoms from these species appear to i into the surface, forming Si-O-C bonds (Figure 7).At 94 ps, the O 2 H 1 is observed to ad on the Si 1 atom of the SiC substrate.Meanwhile, the bond of Si 1 -O 1 -C 1 is formed (Fi 7a).Then, the O 1 atom inserts into the SiC surface under the pressure and sliding o abrasive grains, and the lattice structure where the Si 1 atom located is obviously defor At 107.5 ps, the O 1 atom is entirely inserted into the substrate interior, while the Si 1 is extruded.Additionally, this facilitates the easier removal of the Si 1 atom protru from the surface.As the sliding continues, the Si 1 -C 2 , Si 1 -O 1 , and Si 1 -C 3 bonds brea quentially, completely separating the Si 1 atom from the SiC surface (Figure 7c).As depicted in Figure 7, inserting an O atom into the SiC surface leads to breaking the Si-C bond due to internal stresses.This causes local lattice deformation at the O atom's location and protrusion of Si atoms from the surface.However, the Si-O-C bonds did not break during oxidation and pressure loading.This demonstrates that the removal of surface atoms due to the insertion of oxygen atoms demands the co-action of interfacial shear.This removal mechanism of SiC is similar to the removal mechanism of Cu surface materials.The previous studies for the removal mechanism of Cu atoms suggest that some copper atoms in the surface layer will oxidize and protrude from the surface after a certain reaction time and are then removed by the mechanical shear continuously generated by the sliding process of the abrasive grains [43,44].
Next, we tracked the removal process of the C atoms.During the CMP process, it was observed that the chemical reactivity of C atoms is not as active as that of Si atoms.This makes it more difficult to remove C atoms than Si atoms during the processing of SiC surfaces.Figure 8 shows the removal process of the C atoms.Simulation results indicate that the removal of Si atoms in SiC changes the structural stability of the neighboring C atoms, reducing their strength and leading to subsequent removal (Figure 8).
break during oxidation and pressure loading.This demonstrates that the removal of surface atoms due to the insertion of oxygen atoms demands the co-action of interfacial shear.This removal mechanism of SiC is similar to the removal mechanism of Cu surface materials.The previous studies for the removal mechanism of Cu atoms suggest that some copper atoms in the surface layer will oxidize and protrude from the surface after a certain reaction time and are then removed by the mechanical shear continuously generated by the sliding process of the abrasive grains [43,44].
Next, we tracked the removal process of the C atoms.During the CMP process, it was observed that the chemical reactivity of C atoms is not as active as that of Si atoms.This makes it more difficult to remove C atoms than Si atoms during the processing of SiC surfaces.Figure 8 shows the removal process of the C atoms.Simulation results indicate that the removal of Si atoms in SiC changes the structural stability of the neighboring C atoms, reducing their strength and leading to subsequent removal (Figure 8).Before the sliding removal process, the C 1 atom belongs to the substrate and forms Si-C bonds with each of the three Si atoms (Si 1 , Si 2 , and Si 3 ); the H 1 atom is adsorbed on the surface of C 1 to form a C 1 -H 1 bond.At 3.5 ps, Si 5 from the abrasive grain and O 1 atom form a Si 5 -O 1 -Si 1 bond under the combined effects of pressure and sliding of the abrasive grains.During the polishing process from 3.5 to 50.5 ps, the Si 1 atom is pulled out of the SiC surface by the horizontal movement of the SiO 2 abrasive grains due to the Si-O-Si interfacial bridge bond, making the surrounding structure of the original Si 1 atom unstable.At 51.5 ps, the dissociation of the water molecule (H-O 3 -H 3 ) generated O 3 H, which attached to the surface of the C 1 atom to form a C 1 -O 3 H 3 bond.During 51.5-127.5 ps, the O 3 atom is inserted into the surface of the SiC substrate and combined with the Si 3 atom to form the Si 3 -O 3 -C 1 bond under the influence of the sliding motion of the abrasive grains.The originally stable tetrahedral lattice structure is apparently deformed after removal of the Si 1 atom and the insertion of the O 3 atom into the SiC surface.This also causes the C 1 atom to protrude significantly from the SiC, making it much easier to remove.At 192.5 ps, the abrasive grains' bond with C 1 to form the Si 6 -O 4 -C 1 interfacial bridge bonds, and with the continuous sliding of the abrasive grains to the right, the C 1 -O 3 bond and the C 1 -Si 2 bond are sequentially broken, resulting in the complete removal of the C 1 atom from the SiC surface, as depicted in Figure 8f.
It can be seen from Figure 8 that the removal of Si atoms can lead to the removal of the C atoms next to them.Additionally, removing all other C atoms requires the removal of Si atoms first.Thus, it is concluded that C atoms are harder to remove than Si atoms.The Si atoms can be removed directly, whereas C atoms need to be structurally destabilized by the removal of Si atoms before they can be removed.

Effect of the Pressure on the SiC CMP Process
Pressure plays an important role in the material removal rate during the macro-scale CMP of various semiconductor materials.To further investigate the influence of pressure on the material removal, different pressures of 2, 4, and 6 GPa are set in our simulations.To quantify the degree of removal during the CMP process, we calculated the displacement of each atom in SiC during the sliding process, In the CMP process, (x 0 , y 0 , z 0 ) are the initial coordinates of the Si and C atoms, and (x 1 , y 1 , z 1 ) are the position of the Si and C atoms.Previous studies have shown, through the analysis of the radial distribution function, that Si-C in SiC is no longer bonded when the distance is greater than 2.6 Å [15].Thus, in this study, the amount of removal is defined by the number of SiCatoms with a displacement, d, greater than 2.6 Å during CMP.
As depicted in Figure 9, the total removal of Si and C atoms during the CMP process of SiC gradually increases with polishing pressure.At 500 ps, the number of atoms removed at loads of 2, 4, and 6 GPa are 7, 10, and 14, respectively, with a linear growth trend.It is well known that the polished removal versus pressure and velocity, etc., can be expressed by Preston's equation [45]: where k is the system parameter, p is the pressure, v is the velocity between the polishing disc and the wafer, and t is the polishing time.The removal is linearly related to the pressure when the velocity is constant.Our results are consistent with this trend of change.
Moreover, this result aligns with the experimental findings of Zhou et al. [46] and Pan et al. [47] regarding the effect of polishing pressure on the removal of SiC materials, which demonstrated a positive correlation.
The Si atoms can be removed directly, whereas C atoms need to be structurally destabilized by the removal of Si atoms before they can be removed.

Effect of the Pressure on the SiC CMP Process
Pressure plays an important role in the material removal rate during the macro-scale CMP of various semiconductor materials.To further investigate the influence of pressure on the material removal, different pressures of 2, 4, and 6 GPa are set in our simulations.To quantify the degree of removal during the CMP process, we calculated the displacement of each atom in SiC during the sliding process, In the CMP process, (x0, y0, z0) are the initial coordinates of the Si and C atoms, and (x1, y1, z1) are the position of the Si and C atoms.Previous studies have shown, through the analysis of the radial distribution function, that Si-C in SiC is no longer bonded when the distance is greater than 2.6 Å [15].Thus, in this study, the amount of removal is defined by the number of SiCatoms with a displacement, d, greater than 2.6 Å during CMP.
As depicted in Figure 9, the total removal of Si and C atoms during the CMP process of SiC gradually increases with polishing pressure.At 500 ps, the number of atoms removed at loads of 2, 4, and 6 GPa are 7, 10, and 14, respectively, with a linear growth trend.It is well known that the polished removal versus pressure and velocity, etc., can be expressed by Preston's equation [45]: where k is the system parameter, p is the pressure, v is the velocity between the polishing disc and the wafer, and t is the polishing time.The removal is linearly related to the pressure when the velocity is constant.Our results are consistent with this trend of change.Moreover, this result aligns with the experimental findings of Zhou et al. [46] and Pan et al. [47] regarding the effect of polishing pressure on the removal of SiC materials, which demonstrated a positive correlation.We investigated the effect of pressure on the chemical modification of the SiC surface during polishing by monitoring the variation of oxidation bonds and H2O2 molecules on the SiC surface at different pressures (Figure 10).The results indicate that with higher We investigated the effect of pressure on the chemical modification of the SiC surface during polishing by monitoring the variation of oxidation bonds and H 2 O 2 molecules on the SiC surface at different pressures (Figure 10).The results indicate that with higher pressure, the total number of oxidation bonds on the SiC surface is higher (indicating a higher degree of oxidation on the SiC surface), which is more conducive to the removal of SiC atoms.In other words, pressure can promote the occurrence of chemical reactions on the polished surface.
pressure, the total number of oxidation bonds on the SiC surface is higher (indicatin higher degree of oxidation on the SiC surface), which is more conducive to the remova SiC atoms.In other words, pressure can promote the occurrence of chemical reactions the polished surface.Furthermore, we distinguished the removal mechanisms leading to the remova SiC atoms and quantified the number of atoms removed by different mechanisms to vestigate the effect of pressure on the removal mechanisms (Figure 11).For the remo of Si atoms, it is observed that the removal of Si atoms is mainly caused by Si-O-Si in facial bridge bonds and O insertion at each pressure.Under normal pressure, the con bution of different removal mechanisms to the removal of Si atoms from SiC surface slightly higher for the Si-O-Si interfacial bridge bonds than for the type of removal me anism of O insertion.Furthermore, the same trend exists under different loads.Ther the same trend at different loads, which is more pronounced at higher loads.In addit for the removal of the C atoms, it is found that when the pressure is less than 6 GPa, C atoms are not completely removed during the simulation time, although Si atoms removed.When the pressure level is 6 GPa, three C atoms are removed, and all of th are removed in such a way that the surrounding Si atoms are removed first, which le to structural instability, thus making the C atoms easy to remove, as shown in Figur These structures indicate that Si atoms can be removed directly during the CMP proc while carbon atoms are not easily removed.Meanwhile, increasing the pressure can p mote the removal of C atoms.From Figures 10 and 11, it is evident that the removal of atoms results from both chemical reactions and mechanical loading, although chem reactions play a critical and dominant role.Furthermore, we distinguished the removal mechanisms leading to the removal of SiC atoms and quantified the number of atoms removed by different mechanisms to investigate the effect of pressure on the removal mechanisms (Figure 11).For the removal of Si atoms, it is observed that the removal of Si atoms is mainly caused by Si-O-Si interfacial bridge bonds and O insertion at each pressure.Under normal pressure, the contribution of different removal mechanisms to the removal of Si atoms from SiC surfaces is slightly higher for the Si-O-Si interfacial bridge bonds than for the type of removal mechanism of O insertion.Furthermore, the same trend exists under different loads.There is the same trend at different loads, which is more pronounced at higher loads.In addition, for the removal of the C atoms, it is found that when the pressure is less than 6 GPa, the C atoms are not completely removed during the simulation time, although Si atoms are removed.When the pressure level is 6 GPa, three C atoms are removed, and all of them are removed in such a way that the surrounding Si atoms are removed first, which leads to structural instability, thus making the C atoms easy to remove, as shown in Figure 8.These structures indicate that Si atoms can be removed directly during the CMP process, while carbon atoms are not easily removed.Meanwhile, increasing the pressure can promote the removal of C atoms.From Figures 10 and 11, it is evident that the removal of SiC atoms results from both chemical reactions and mechanical loading, although chemical reactions play a critical and dominant role.Furthermore, we distinguished the removal mechanisms leading to the removal of SiC atoms and quantified the number of atoms removed by different mechanisms to investigate the effect of pressure on the removal mechanisms (Figure 11).For the removal of Si atoms, it is observed that the removal of Si atoms is mainly caused by Si-O-Si interfacial bridge bonds and O insertion at each pressure.Under normal pressure, the contribution of different removal mechanisms to the removal of Si atoms from SiC surfaces is slightly higher for the Si-O-Si interfacial bridge bonds than for the type of removal mechanism of O insertion.Furthermore, the same trend exists under different loads.There is the same trend at different loads, which is more pronounced at higher loads.In addition, for the removal of the C atoms, it is found that when the pressure is less than 6 GPa, the C atoms are not completely removed during the simulation time, although Si atoms are removed.When the pressure level is 6 GPa, three C atoms are removed, and all of them are removed in such a way that the surrounding Si atoms are removed first, which leads to structural instability, thus making the C atoms easy to remove, as shown in Figure 8.These structures indicate that Si atoms can be removed directly during the CMP process, while carbon atoms are not easily removed.Meanwhile, increasing the pressure can promote the removal of C atoms.From Figures 10 and 11, it is evident that the removal of SiC atoms results from both chemical reactions and mechanical loading, although chemical reactions play a critical and dominant role.In addition, the structure of the substrate surface after the CMP process is important, as it is often used to evaluate the effectiveness of the overall CMP process.We further analyzed the original positions of the removed atoms.Figure 12a-c shows that the removal behavior of SiC atoms only affects atoms in the first two layers of the substrate.As the pressure increases, an apparent local lattice distortion occurs on the polished surface, causing some atoms to protrude.To quantify the removal of atoms from each layer of the SiC surface, the initial origin of each removed atom is traced and statistically counted (Figure 12d).It can be observed that seven atoms are removed at 2 GPa pressure.In comparison, 10 and 14 SiC atoms are removed at 4 and 6 GPa pressure, respectively, belonging to the first layer.This result significantly impacts the realization of single-layer atom removal in ultra-precision machining.
In addition, the structure of the substrate surface after the CMP process is impo as it is often used to evaluate the effectiveness of the overall CMP process.We fu analyzed the original positions of the removed atoms.Figure 12a-c shows that th moval behavior of SiC atoms only affects atoms in the first two layers of the substra the pressure increases, an apparent local lattice distortion occurs on the polished su causing some atoms to protrude.To quantify the removal of atoms from each layer SiC surface, the initial origin of each removed atom is traced and statistically cou (Figure 12d).It can be observed that seven atoms are removed at 2 GPa pressure.In parison, 10 and 14 SiC atoms are removed at 4 and 6 GPa pressure, respectively, belo to the first layer.This result significantly impacts the realization of single-layer ato moval in ultra-precision machining.

Conclusions
The atomic mechanism of the CMP process on SiC surfaces polished by the abr grain of α-SiO2 is investigated by ReaxFF-MD simulations, and the following conclu can be drawn: ( (3) C atoms are more difficult to remove than Si atoms.The removal of Si atom stroys the lattice structure of the substrate surface, resulting in a bump or even com removal of the adjacent C atoms.
(4) Comparing the CMP process at different pressures, more SiC atoms are rem as the polishing pressure increases.We quantified the contribution of each removal m anism to the removal of Si atoms from the SiC surface at different pressures and sh that the contribution of Si-O-Si bridge bonds at the interface between SiO2 and SiC largest, followed by O insertion.Moreover, this phenomenon is more pronounc

Conclusions
The atomic mechanism of the CMP process on SiC surfaces polished by the abrasive grain of α-SiO 2 is investigated by ReaxFF-MD simulations, and the following conclusions can be drawn: ( (2) Throughout the CMP process, the removal of SiC atoms is primarily governed by chemical reactions.Two fundamental mechanisms, namely the Si-O-Si interfacial bridge and O insertion, contribute to breaking surface bonds and completely removing SiC atoms.Additionally, because of the Si-O-Si interfacial bridge bonds and the sliding of SiO 2 abrasive grains, mechanical shear plays a crucial supplementary role in facilitating the atom removal process.As a result, the removal of SiC atoms is a combined outcome of the synergistic effects of chemical reactions and mechanical loading.
(3) C atoms are more difficult to remove than Si atoms.The removal of Si atoms destroys the lattice structure of the substrate surface, resulting in a bump or even complete removal of the adjacent C atoms.
(4) Comparing the CMP process at different pressures, more SiC atoms are removed as the polishing pressure increases.We quantified the contribution of each removal mechanism to the removal of Si atoms from the SiC surface at different pressures and showed that the contribution of Si-O-Si bridge bonds at the interface between SiO 2 and SiC is the largest, followed by O insertion.Moreover, this phenomenon is more pronounced at higher pressure.However, the mechanical action promoted the removal of atoms throughout the polishing process.

Figure 2 .
Figure 2. Atomic adsorption on the surface of SiC after sufficient reaction with the hydrogen perox ide solution.The red box shows the surface of the substrate after sufficient reaction, and the arrow points to a localized magnified view of the area of the red box.

Figure 3 .
Figure 3. Variation in (a) the number of H2O2 molecules and (b) the number of oxidation bonds o the SiC surface during relaxation and loading.

Figure 2 .
Figure 2. Atomic adsorption on the surface of SiC after sufficient reaction with the hydrogen peroxide solution.The red box shows the surface of the substrate after sufficient reaction, and the arrow points to a localized magnified view of the area of the red box.

Figure 2 .
Figure 2. Atomic adsorption on the surface of SiC after sufficient reaction with the hydrogen p ide solution.The red box shows the surface of the substrate after sufficient reaction, and the a points to a localized magnified view of the area of the red box.

Figure 3 .
Figure 3. Variation in (a) the number of H2O2 molecules and (b) the number of oxidation bond the SiC surface during relaxation and loading.

Figure 3 .
Figure 3. Variation in (a) the number of H 2 O 2 molecules and (b) the number of oxidation bonds on the SiC surface during relaxation and loading.

Figure 4 .
Figure 4. Bonding of O from SiO2 abrasive grains with SiC surface during loading.

Figure 5 .
Figure 5. Snapshots for the shape variations of SiO2 during the polishing process.

Figure 4 .
Figure 4. Bonding of O from SiO 2 abrasive grains with SiC surface during loading.

Figure 4 .
Figure 4. Bonding of O from SiO2 abrasive grains with SiC surface during loading.

Figure 5 .
Figure 5. Snapshots for the shape variations of SiO2 during the polishing process.

Figure 5 .
Figure 5. Snapshots for the shape variations of SiO 2 during the polishing process.

Figure 6 .
Figure 6.Snapshots for the breakage of the bonds on the SiC surface caused by the formation of Si-O-Si interfacial bridge bonds.The bond pointed to by the arrow is the one that is about to break, and the dotted line connects to the one that is already broken.

Figure 7 .
Figure 7.The snapshots of breakage of the bonds on the SiC surface arising from the insertion of oxygen atoms into the SiC surface.The bond pointed to by the arrow is the one that is about to break, and the dotted line connects to the one that is already broken.

Figure 6 .
Figure 6.Snapshots for the breakage of the bonds on the SiC surface caused by the formation of Si-O-Si interfacial bridge bonds.The bond pointed to by the arrow is the one that is about to break, and the dotted line connects to the one that is already broken.

Figure 6 .
Figure 6.Snapshots for the breakage of the bonds on the SiC surface caused by the formation O-Si interfacial bridge bonds.The bond pointed to by the arrow is the one that is about to b and the dotted line connects to the one that is already broken.

Figure 7 .
Figure 7.The snapshots of breakage of the bonds on the SiC surface arising from the inserti oxygen atoms into the SiC surface.The bond pointed to by the arrow is the one that is abo break, and the dotted line connects to the one that is already broken.

Figure 7 .
Figure 7.The snapshots of breakage of the bonds on the SiC surface arising from the insertion of oxygen atoms into the SiC surface.The bond pointed to by the arrow is the one that is about to break, and the dotted line connects to the one that is already broken.

Figure 8 .
Figure 8.The snapshots of the removal of Si atoms destroying the stable structure of C atoms and inducing the removal of C atoms.The bond pointed to by the arrow is the one that is about to break, and the dotted line connects to the one that is already broken.

Figure 8 .
Figure 8.The snapshots of the removal of Si atoms destroying the stable structure of C atoms and inducing the removal of C atoms.The bond pointed to by the arrow is the one that is about to break, and the dotted line connects to the one that is already broken.

Figure 9 .
Figure 9. Variation of atom removal on the surface of SiC with polishing time under different pressures during the polishing process.

Figure 9 .
Figure 9. Variation of atom removal on the surface of SiC with polishing time under different pressures during the polishing process.

Figure 10 .
Figure 10.Variation of the amount of (a) H2O2 molecules and (b) oxidation bonds on the surfac SiC with polishing time under different pressures during the polishing process.

Figure 11 .
Figure 11.A number of silicon atoms were removed from the SiC surface due to different rem mechanisms after 500 ps of sliding at the pressures of 2, 4, and 6 GPa.

Figure 10 .
Figure 10.Variation of the amount of (a) H 2 O 2 molecules and (b) oxidation bonds on the surface of SiC with polishing time under different pressures during the polishing process.

Figure 10 .
Figure 10.Variation of the amount of (a) H2O2 molecules and (b) oxidation bonds on the surface of SiC with polishing time under different pressures during the polishing process.

Figure 11 .
Figure 11.A number of silicon atoms were removed from the SiC surface due to different removal mechanisms after 500 ps of sliding at the pressures of 2, 4, and 6 GPa.

Figure 11 .
Figure 11.A number of silicon atoms were removed from the SiC surface due to different removal mechanisms after 500 ps of sliding at the pressures of 2, 4, and 6 GPa.

Figure 12 .
Figure 12.The snapshots of the atom removal from the first two layers of the silicon carbide s at (a) 2 GPa, (b) 4 GPa, and (c) 6 GPa.The first two layers of atoms are shown normally.The the atoms are transparent, showing only the chemical bonds.(d) The number of SiC atoms rem from the first and second layers.

1 )
During the reaction, Si-OH, Si-H2O, C-H, Si-O, and C-O-Si groups are those m present on the substrate surface.There are two sources of -H2O, -O, and -OH in the a products: one from H2O molecules and one from H2O2 molecules.During the loading cess, O atoms from the SiO2 abrasive grains combine with the SiC surface atoms under sure, resulting in the formation of C-O and Si-O bonds that attach to the surface.This pr further contributes to the softening of the substrate.Additionally, Si atoms on the sub surface are more easily oxidized than C atoms throughout the process.(2) Throughout the CMP process, the removal of SiC atoms is primarily govern chemical reactions.Two fundamental mechanisms, namely the Si-O-Si interfacial b and O insertion, contribute to breaking surface bonds and completely removing S oms.Additionally, because of the Si-O-Si interfacial bridge bonds and the sliding o abrasive grains, mechanical shear plays a crucial supplementary role in facilitatin atom removal process.As a result, the removal of SiC atoms is a combined outcome synergistic effects of chemical reactions and mechanical loading.

Figure 12 .
Figure 12.The snapshots of the atom removal from the first two layers of the silicon carbide surface at (a) 2 GPa, (b) 4 GPa, and (c) 6 GPa.The first two layers of atoms are shown normally.The rest of the atoms are transparent, showing only the chemical bonds.(d) The number of SiC atoms removed from the first and second layers.

1 )
During the reaction, Si-OH, Si-H 2 O, C-H, Si-O, and C-O-Si groups are those mainly present on the substrate surface.There are two sources of -H 2 O, -O, and -OH in the above products: one from H 2 O molecules and one from H 2 O 2 molecules.During the loading process, O atoms from the SiO 2 abrasive grains combine with the SiC surface atoms under pressure, resulting in the formation of C-O and Si-O bonds that attach to the surface.This process further contributes to the softening of the substrate.Additionally, Si atoms on the substrate surface are more easily oxidized than C atoms throughout the process.

Table 1 .
The specific simulation parameters.