Method for distinguishing silicon-carbon surface of silicon carbide wafer at low cost

Abstract

The invention relates to the field of silicon carbide wafer manufacturing, in particular to a low-cost method for distinguishing a silicon carbide wafer silicon surface and a carbon surface, which comprises the following steps: (S.1) chamfering the edge of a silicon carbide crystal to form differentiated edge morphology on the silicon surface and the carbon surface in the material removal process; and (S.2) carrying out morphology characterization on the edge of the chamfered wafer through optical observation equipment, judging that the wafer is a silicon surface when the chamfered edge area has a broken edge phenomenon, and judging that the wafer is a carbon surface when the edge is smooth and uniform. According to the method, the silicon carbide wafer is simply chamfered, so that the carbon-silicon surface of the silicon carbide wafer can be distinguished with low cost and high accuracy. In addition, compared with a corrosion method or a polishing method used in the prior art, the principle of the technical scheme has essential difference, and therefore the limitation of a traditional method is successfully avoided on the technical effect.

Description

Technical Field

[0001] The present invention relates to the field of silicon carbide wafer manufacturing, and particularly to a method for low-cost identification of the silicon-carbon surface of a silicon carbide wafer. Background Art

[0002] At present, the mainstream method for industrial production of SiC crystals is the Physical Vapor Transport method (abbreviated as PVT method). However, when growing 4H-SiC single crystals using the PVT method, polytype co-growth phenomena are likely to occur, resulting in a reduction in wafer yield and deterioration of the performance of SiC-based devices. Therefore, ensuring the stable growth of a single 4H polytype is extremely crucial for achieving high-quality silicon carbide crystal preparation. During the crystal growth process, growth parameters such as gaseous Si / C, doping type and concentration, growth temperature, supersaturation, crystallization rate, and working pressure need to be precisely controlled.

[0003] At the same time, it is also very important to select the correct seed crystal growth surface and appropriate off-axis angle. The former is considered to be one of the most significant factors determining the polytype type. Research has confirmed that the C plane (000-1) with a lower free surface energy tends to generate the 4H-SiC polytype, while the Si plane (0001) with a higher surface energy is prone to form the 6H-SiC polytype with a lower enthalpy, and is independent of the seed crystal polytype structure (4H, 6H, or 15R). Therefore, choosing the correct seed crystal growth surface plays a decisive role in the SiC polytype. In addition, for SiC epitaxial growth, the Si plane is generally selected. The Si plane has better mechanical and electrical properties, and the S surface has a smaller roughness than the C surface, which can reduce the impact of the wafer surface on the device.

[0004] The C plane and Si plane of the SiC wafer have their respective advantages and limitations. In practical applications, according to specific requirements and device requirements, it is necessary to select the appropriate C plane and Si plane for processing. Therefore, effectively identifying the carbon-silicon surface is of great significance for crystal growth, epitaxy, and the preparation of power devices.

[0005] However, the current methods for identifying the SiC carbon-silicon plane are as follows: ① The positioning edge marking method. This method requires the main and secondary flat edges of the ingot to be positioned during the forming and processing. However, as the size of the ingot increases, large-sized (such as 8-inch and 12-inch) ingots / seeds / substrates do not have main and secondary flat edges. Therefore, it is necessary to correctly distinguish the carbon-silicon plane of the crystal during ingot production. Before wafer marking, the ingot needs to be cut into wafers. During the cutting process, without special crystal markings, it is easy to cause errors in marking the carbon-silicon plane during wafer marking. ② The etching method. The surface free energy of the silicon plane is relatively large. Potassium hydroxide is used to etch the silicon plane and carbon plane of the SiC wafer. The etching rate of the silicon plane is greater than that of the carbon plane. Etching pits are easily formed on the silicon plane, while etching pits are not easily formed on the carbon plane, and the morphologies of the etching pits on the silicon plane and carbon plane are different. However, this method will cause at least 40 μm of damage to the wafer and has a risk of producing broken wafers. ③ The polishing rate. The polishing rates of the two sides of the SiC wafer are different. Due to the large hardness and oxidation resistance of the carbon plane, it can withstand higher mechanical stress and chemical corrosion. Therefore, through chemical mechanical polishing, the removal rate of the carbon plane is small, and the removal rate of the silicon plane is relatively high. The removal rate of the carbon plane is 0.05 - 0.1 μm / h, and the removal rate of the silicon plane is 0.3 - 0.4 μm / h. However, there is a conflict in the literature. In the comparative study of CMP polishing of the 6H-SiC (0001) plane and (000-1) plane, it is pointed out that when using a modified silica sol polishing solution with pH = 1.11 for polishing, the removal rate of the carbon plane is higher than that of the silicon plane. ④ Atomic force microscope (AFM) to identify the roughness of the carbon-silicon plane. The roughness of the C and Si planes is measured by AFM. If the displayed roughness value is between 0.10 - 0.50 nm, the tested surface is the silicon plane; if the displayed roughness is between 0.80 - 3.00 nm, the tested surface is the carbon plane, and the surface with larger roughness is the C plane. The wafers used in this method need to be chemically mechanically polished and cleaned, and need to be identified by an atomic force microscope (AFM). The polishing cost and testing cost per wafer are relatively high, and the application range is narrow.

[0006] Therefore, there is an urgent need for a method with low cost to identify the carbon-silicon plane of silicon carbide. Summary of the Invention

[0007] The present invention aims to overcome the deficiencies in the prior art methods for identifying the carbon-silicon plane of silicon carbide, which usually have low recognition accuracy, high risk of producing broken wafers, and high testing costs. A method with low cost for identifying the silicon-carbon plane of silicon carbide wafers is provided to overcome the above deficiencies.

[0008] To achieve the above invention objective, the present invention is realized through the following technical solutions: In the first aspect, the present invention first provides a method with low cost for identifying the silicon-carbon plane of silicon carbide wafers, including the following steps: (S.1) Chamfer the edge of the silicon carbide crystal so that a differential edge morphology is formed on the silicon plane and carbon plane during the material removal process; (S.2) The edge of the chamfered wafer is characterized by optical observation equipment. When the chamfered edge area shows broken edges, it is determined to be a silicon surface. When the edge is smooth and uniform, it is determined to be a carbon surface.

[0009] As described in the background technology, accurate identification of the silicon-carbon surface of silicon carbide wafers is an important but long-standing technical challenge in semiconductor manufacturing and device preparation. In the growth, cutting, polishing and epitaxial process of silicon carbide single crystals, the difference in physical and chemical properties between the silicon surface and the carbon surface directly affects the crystal growth quality, epitaxial layer structure and device performance. For a long time, the industry has generally adopted means such as etching, polishing rate or atomic force microscopy (AFM) to achieve the distinction between silicon and carbon surfaces. However, these methods not only rely on expensive equipment or special chemical treatments, but may also increase production costs by damaging the wafer surface or introducing errors. For example, the etching method requires the removal of at least 40 μm of wafer thickness to identify the surface type through the difference in the morphology of the etching pits, which not only greatly increases material loss, but may also cause the wafer to be scrapped due to over-etching; the AFM method requires a precision optical system and a high-cleanliness test environment, which is expensive and cannot be applied on a large scale on the production line; and the polishing rate method is questionable in reliability due to different crystal forms, doping conditions or contradictions in literature data. These technical defects directly hinder the large-scale industrial application of silicon carbide technology. In this context, how to develop a low-cost silicon-carbon surface identification technology that can avoid chip damage and does not require complex instruments has become a practical need that needs to be urgently addressed.

[0010] When studying the processing of silicon carbide wafers, the technical team of this application discovered a phenomenon that is different from traditional cognition: when the silicon carbide wafer is chamfered, there is a significant difference in the microscopic morphology of the edge of the silicon surface and the carbon surface, that is, by chamfering the wafer, a large number of fine broken edges will be produced on the silicon surface, while the edge of the carbon surface always maintains a relatively smooth transition morphology. After in-depth research, it was revealed that this phenomenon originated from the essential difference in the atomic bonding strength between the carbon surface and the silicon surface in the silicon carbide crystal: the CC bond energy formed on the carbon surface during the crystal growth process is higher, and the atomic layers are more tightly bonded, making its hardness and resistance to mechanical stress significantly higher than that of the silicon surface (the bond length and bond angle distribution of the Si-Si bond on the silicon surface are easier to propagate microcracks during stress concentration). Therefore, when the mechanical chamfering process with the same parameters is used, the silicon surface will form more broken defects during the processing due to its relatively low mechanical stability, while the carbon surface will present a smooth edge due to its stronger resistance to plastic deformation. This discovery breaks through the traditional technical path that relies on chemical corrosion or complex equipment detection, and provides a theoretical basis for low-cost discrimination methods.

[0011] The core innovation of the technical solution of this application lies in transforming the conventional chamfering process into an active detection method for silicon-carbon surface discrimination. During specific implementation, just place the wafer to be tested into a standard chamfering machine to process the edge according to the set parameters, and then observe the morphology of the chamfered area under an ordinary optical microscope (with a magnification of 100 - 200): the silicon surface will present a fine serrated broken edge, while the carbon surface will show a continuous and smooth arc contour. The above-mentioned morphological differences can be visually identified by the naked eye without complex image processing, and the reading accuracy rate has been verified to be over 95% through multiple batches of wafers.

[0012] It should be noted that the applicability of this method not only covers the polished finished wafers, but can also be directly applied to the cutting wafers, grinding wafers and even the ingot stage, achieving full process coverage. For the confirmation of the carbon-silicon surface of the initial wafer after the large-size ingot is cut, at this time, the wafer has not formed geometric features that can be used for flat edge marking, and the traditional positioning edge method completely fails. However, the chamfering method can quickly complete the surface type determination through small-range edge processing, effectively avoiding incorrect operations in subsequent processing. From the economic perspective, the chamfering machine and microscope required by this method are both standard equipment in the semiconductor production line, without the need to purchase additional special instruments. The single detection cost is reduced by more than 80% compared with the etching method, and the problem of chemical waste liquid treatment is completely avoided. In addition, since the chamfering process only acts on the non-functional area of the wafer periphery, the wafer can directly enter the subsequent process without further treatment after detection, further improving the production efficiency.

[0013] Although there are individual methods in the prior art that use mechanical processing to discriminate material properties, their technical paths are essentially different from this solution. For example, a patent has proposed to discriminate the wafer material type through the difference in grinding pressure. However, its core is to indirectly infer the crystal plane properties by measuring the load parameters during the grinding process, which essentially still belongs to the physical parameter detection method, and there are significant differences from the morphological feature reading directly relying on the mechanical response of the material itself in this solution.

[0014] More critically, the prior art has never revealed the hardness-topography correlation law between the silicon surface and the carbon surface in chamfering processing, nor has it been able to amplify the characteristic differences to an optically directly observable level through parameter optimization. By creatively combining the intrinsic properties of silicon carbide crystals with the mechanical processing dynamics characteristics, this method realizes highly reliable discrimination of carbon and silicon surfaces in conventional process steps, and its technical path has prominent non-obviousness compared with existing solutions. In addition, there are essential physical differences between the chip breakage edge formation mechanism utilized by the chamfering method and the material removal principles of the etching method or the polishing method (mechanical stress concentration inducing brittle fracture vs. chemical etching or abrasive shearing action). Therefore, in terms of technical effects, the limitations of traditional methods are successfully avoided - even in the case of the presence of an oxide layer or processing residues on the wafer surface, the chamfering method can still truly reflect the crystal plane properties through the edge mechanical response, while the etching method may lead to misjudgment due to surface contamination. From the perspective of technical upgrade potential, this solution can also be adapted to silicon carbide wafers with different crystal forms or doping concentrations by adjusting the chamfering parameters, showing good process ductility. This universal solution developed based on the basic physical properties of materials provides a high-efficiency, reliable and low-cost crystal plane discrimination technology benchmark for the semiconductor manufacturing field.

[0015] Finally, from the ingot to the polished wafer, it needs to go through multiple process flows such as shaping (rounding, surface grinding), wire cutting, marking, annealing, chamfering, grinding, polishing, cleaning, etc. The processes are complex, there are many operators, and it is easy to confuse the carbon and silicon surfaces of the wafers. By using this method to distinguish the carbon and silicon surfaces of silicon carbide wafers, the cost is low, it is simple and feasible, and the application range is wide. The ingot, cutting wafer, grinding wafer, polished wafer, etc. can all be chamfered. The carbon and silicon surfaces of the silicon carbide crystal are judged by whether chip breakage edges are generated at the ingot / wafers edge. At the same time, the detection instrument used in this process is a microscope with a magnification of 100-200 times, which does not belong to precision instruments. The detection cost of this method is much lower than that of existing methods.

[0016] Preferably, the silicon carbide crystal includes any one of a silicon carbide ingot, a silicon carbide cutting wafer, a silicon carbide grinding wafer, and a silicon carbide polished wafer.

[0017] Preferably, the crystal form of the silicon carbide crystal is any one of 4H-SiC, 6H-SiC, and 15R-SiC.

[0018] Preferably, in the step (S.1), the grinding particle size of the grinding head used in the chamfering process is 1000-2500 mesh, the feed speed is 0.005-0.05 mm / cut, and the rotation speed is 5000-12000 rpm.

[0019] Based on the physical mechanism that when using the mechanical chamfering process with the same parameters, the silicon surface forms more chipping defects during processing due to its relatively low mechanical stability, while the carbon surface shows smooth edges due to its stronger resistance to plastic deformation, the technical team of this application systematically studied the influence law of chamfering parameters (number of grinding head meshes, feed rate, spindle speed) on the edge morphology of the wafer: when the number of grinding head meshes exceeds 1000 meshes, the micro-cutting effect of the abrasive grains on the silicon surface is more likely to trigger local stress concentration, resulting in the removal of materials in a chipping manner, while the carbon surface inhibits the formation of chipping edges due to its high hardness under the same conditions; when the feed rate is lower than 0.05 mm per cut, the silicon surface will form visible chipping edges under the cumulative stress of multiple rounds of cutting, while the carbon surface still maintains continuous removal. Through repeated experiments, it was finally confirmed that when the number of grinding head meshes is 2000 meshes, the feed rate is 0.01 mm per cut, and the spindle speed is 10000 rpm, the difference in chipping edge morphology between the silicon surface and the carbon surface reaches the best observable state, establishing a scientific basis for parameter selection in actual production.

[0020] Preferably, the chamfering process in the step (S.1) includes two stages: rough chamfering and fine chamfering. The grinding head grinding particle size in the rough chamfering stage is 1000 - 2000, the feed rate is 0.02 - 0.05 mm per cut, and the rotation speed is 5000 - 8000 rpm. The grinding head grinding particle size in the fine chamfering stage is 2000 - 2500 meshes, the feed rate is 0.005 - 0.01 mm per cut, and the spindle speed is 10000 - 12000 rpm.

[0021] The hardness difference between the silicon surface and the carbon surface of the silicon carbide wafer is the basis for its discrimination and detection. However, the contradiction to be solved in actual processing is that it is necessary to quickly trigger the brittle chipping of the silicon surface while ensuring the complete processing of the carbon surface to maintain the contrast of the criterion. In the rough chamfering stage, a medium grinding particle size of 1000 - 2000 meshes is used, combined with a relatively high feed rate (0.02 - 0.05 mm per cut) and a relatively low rotation speed. The core is to trigger the brittle fracture of the silicon surface through high-stress impact. Since the atomic binding energy of the silicon surface is relatively low (the average bond energy of the Si - Si bond is about 2.3 eV, and the C - C bond is about 3.6 eV), microcracks are more likely to rapidly expand under the high load in the rough grinding stage. The carbon surface can withstand higher stress without chipping due to its stronger bond force, but will form a preliminary smooth profile in the rough chamfering (because the carbon surface has higher toughness and the material is removed mainly by plastic deformation). Therefore, the rough chamfering quickly strips the surface layer material and amplifies the brittle characteristics of the silicon surface (the prototype of the chipping edge), providing a reference morphology for subsequent finishing.

[0022] In the fine chamfering stage, higher grit size (2000 - 2500 mesh), lower feed rate (0.005 - 0.01 mm / cut) and higher rotational speed (10000 - 12000 rpm) are adopted to precisely control the edge quality through low-stress multi-frequency micro-cutting. Among them, for the silicon surface, the high rotational speed and small feed rate in the fine grinding stage significantly reduce the single-cut depth. At this time, the fragmented chipping edges left by the rough chamfering will be further regularized (reducing the interference of random cracks) during the finish machining, forming a stable serrated edge. On the carbon surface, the high rotational speed of the fine chamfering can suppress the scratching effect of large abrasive grains (the particle distribution of the small-grit grinding head is more uniform), and combined with slow feeding, atomic-level continuous removal is formed, making the smoothness of the carbon surface edge tend to be consistent. Therefore, the introduction of fine chamfering eliminates the random defects introduced by the rough machining and strengthens the contrast of the edge characteristics between the silicon surface and the carbon surface.

[0023] Finally, in the silicon carbide ingot slicing process, the wafer edge chamfering was originally only a conventional step (not a detection means) to reduce the risk of chipping. The creativity of this application lies in endowing the conventional processing step with a new technical mission and making it an efficient discrimination tool for the carbon and silicon surfaces through parameter reconstruction. This design concept of seamlessly integrating the processing and detection functions significantly surpasses the traditional understanding of the chamfering process.

[0024] Existing chamfering processes usually take "deburring" or "improving mechanical strength" as the single goal, and their parameter selection does not distinguish the processing stages, nor is it related to the mechanical response characteristics of the silicon carbide crystal plane differences. The proposed phased parameter range in this application (especially the specific combination of low rotational speed / high feed in the rough chamfering stage and high rotational speed / low feed in the fine chamfering stage) belongs to the first engineering verification scheme for the discrimination of silicon carbide crystal planes.

[0025] When the parameters of the rough chamfering and the fine chamfering are mismatched (such as only performing rough chamfering), the fragmented chipping edges generated on the silicon surface show irregular distribution (there are no criterion features in some areas); when only fine chamfering is performed, incomplete triggering of the silicon surface criterion will occur due to insufficient initial processing load (only slight edge burrs). Only through the coordination of the two-stage parameters (the rough chamfering generates the basic morphology + the fine chamfering strengthens the criterion) can a stable and measurable morphological difference be formed.

[0026] Preferably, before the chamfering process in the step (S.1), a wafer pretreatment step is further included, and the pretreatment includes plasma cleaning of the wafer surface to remove the surface oxide layer and attachments.

[0027] An oxide layer (SiO2 and SiO x C y complex) and adsorbed pollutants (such as organic residues, metal particles) will naturally form on the surface of the silicon carbide wafer during storage or transportation. The interference manifestations of such surface heterogeneous layers on the chamfering process are as follows: (1) After the oxide layer (hardness ~8 GPa) covers the silicon surface body (hardness of about 18 GPa), the load at the initial stage of chamfering needs to first break through the oxide layer (causing the grinding head to slip or load fluctuations), resulting in a decrease in the effective stress actually borne by the silicon surface (the stress is absorbed by the oxide), and the triggering of chipping edges is delayed or random fractures are aggravated. (2) At the same time, the oxide layer on the carbon surface is thinner (due to its better oxidation resistance), but there is still a nanoscale disordered carbon-oxygen layer (hardness ~12 GPa), which weakens the hardness contrast between the carbon surface and the silicon surface.

[0028] This application uses a hydrogen-argon mixed plasma to completely strip the surface heterogeneous layer through two paths: physical sputtering (Ar + ion bombardment) and chemical reduction (reaction of H radicals with oxides). The original hardness of the silicon surface is restored (Ar + sputtering removes SiO2), and high-energy H radicals reduce silicon suboxides (such as SiO) to volatile SiH4. Due to the chemical inertness of the C-C bonds on the carbon surface, only physical sputtering is needed to remove the adsorbed substances, leaving a small amount of surface carbon dangling bonds (which is beneficial to suppressing subsequent oxidation), so that the chamfering load directly acts on the intrinsic substrates of the silicon and carbon surfaces.

[0029] When the oxide layer is removed, the frictional force between the abrasive grains and the wafer surface changes from "elastic deformation dominated" (viscoelastic buffering of the oxide) to "plastic shear dominated" (direct contact of the substrate). Due to the higher friction coefficient of the silicon surface (clean surface), microcrack nucleation is accelerated, causing the formation of chipping edges to advance to the initial stage of chamfering. The low friction characteristic of the carbon surface (more significant after cleaning) enables it to maintain a stable shear removal mode.

[0030] Preferably, the power of the plasma cleaning is 300 - 500 W, the gas environment is a mixed gas of argon and hydrogen, and the mixing ratio is 3:1 - 5:1.

[0031] Preferably, the pretreatment further includes plasma irradiation pretreatment of the silicon carbide crystal. The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0032] Plasma irradiation creatively utilizes the difference in chemical reaction activity between the silicon and carbon surfaces to generate a silicon nitride layer (SiN x ) on the silicon surface and an amorphous carbon layer on the carbon surface. The hardness of silicon nitride (~17 GPa) is significantly lower than that of the silicon surface of the silicon carbide body (~26 GPa). In subsequent chamfering, the brittleness of the silicon surface material is further aggravated, making the chipping edge phenomenon easier to trigger and the morphology regularized (reducing the interference of disordered cracks), while the amorphous carbon layer on the carbon surface inhibits the expansion of abrasive scratches due to its self-lubricating effect, forming a more uniform and smooth edge. This pretreatment actively modifies the surface properties to make up for the possible problem of fuzzy edge criteria that only rely on the difference in bulk hardness.

[0033] Preferably, the plasma irradiation pretreatment specifically includes: Place the wafer in a vacuum chamber, introduce a mixed gas of argon and nitrogen, and control the pressure at 10 - 50 Pa, where the volume ratio of argon is 80 - 95%; Use a radio frequency power supply to excite plasma on the wafer surface, with a radio frequency power of 200 - 400 W and an irradiation time of 30 - 120 seconds; After the plasma irradiation ends, purge the chamber with helium to atmospheric pressure; The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0034] Preferably, the optical observation device in step (S.2) is an optical microscope with a magnification of 100 - 200 times.

[0035] Preferably, the angle between the incident angle of the observation light source and the normal direction of the wafer surface in step (S.2) is 20° - 45°.

[0036] Therefore, the present invention has the following beneficial effects: This application innovatively utilizes the mechanical property gradient of the SiC crystal plane, precisely regulates the edge morphology difference through chamfering, and combines optical detection optimization to achieve three major breakthrough advantages: ① The cost is extremely low, only requiring conventional chamfering equipment and an ordinary microscope, and the single - detection cost is reduced by more than 80% compared with the etching method; ② It is non - destructive and efficient, without damaging the main structure of the wafer, and can complete the discrimination within 3 minutes with an accuracy rate > 97%; ③ The process is universal, compatible with polished wafers, cut wafers and ingots at each processing stage, solves the industrialization bottleneck of the traditional method's dependence on equipment and environment, and provides a cost - effective detection solution for large - scale manufacturing of SiC devices. Description of the Drawings

[0037] Figure 1 It is an enlarged view of the edge of a 4H - SiC polished wafer through chamfering in Example 1.

[0038] Figure 2 It is an enlarged view of the edge of a 6H - SiC polished wafer through chamfering in Example 2. Detailed Embodiments

[0039] The present invention is further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0040] Example 1 A low-cost method for identifying the silicon-carbon surface of a silicon carbide wafer comprises the following steps: (S.1) The 4H-SiC cutting blade is placed in a chamfering machine for chamfering, with a grinding head mesh of 2000, a feed speed of 0.01 mm / blade, and a rotation speed of 10000 rpm, so that the silicon carbide cutting blade forms differentiated edge morphologies on the silicon surface and the carbon surface during the chamfering process; (S.2) The wafer is then placed under a microscope at 100-200 times magnification for observation. If the chamfered edge area shows signs of chipping, it is identified as a silicon surface. If the edge is smooth and uniform, it is identified as a carbon surface.

[0041] like Figure 1 As shown, Figure 1 The left side of the middle is the Si surface. When the angle between the incident light source and the normal direction of the wafer surface is within the range of 20°-45°, the observer observes that the chamfered edge is broken and chipped. Figure 1 The C surface is on the middle right side, and its edge is smooth and even without any broken edges. After a large number of tests, the recognition accuracy rate is greater than 97%.

[0042] Example 2 A low-cost method for identifying the silicon-carbon surface of a silicon carbide wafer comprises the following steps: (S.1) The 6H-SiC polishing sheet was placed in a chamfering machine for chamfering, with the grinding head mesh number of 1500, the feed speed of 0.02 mm / knife, and the rotation speed of 11000 rpm, so that the silicon carbide cutting sheet formed differentiated edge morphologies on the silicon surface and the carbon surface during the chamfering process; (S.2) The wafer is then placed under a microscope at 100-200 times magnification for observation. If the chamfered edge area shows signs of chipping, it is identified as a silicon surface. If the edge is smooth and uniform, it is identified as a carbon surface.

[0043] like Figure 2 As shown, Figure 2 The left side of the middle is the Si surface, and the chamfered edge is broken. Figure 2 The C surface is on the middle right side, and its edges are smooth and uniform. After a large number of tests, the recognition accuracy rate is greater than 97%.

[0044] Example 3 A low-cost method for identifying the silicon-carbon plane of a silicon carbide wafer, comprising the following steps: (S.1) Place the 4H-SiC cutting wafer in a plasma cleaner for plasma cleaning. The power of the plasma cleaning is 300 W, and the gas environment is a mixed gas of argon and hydrogen with a mixing ratio of 5:1, so as to remove the surface oxide layer and attachments.

[0045] (S.2) Place the plasma-cleaned 4H-SiC cutting wafer in a chamfering machine for chamfering, so that different edge morphologies are formed on the silicon plane and the carbon plane during the chamfering process of the silicon carbide cutting wafer. Among them, the chamfering process includes two stages: rough chamfering and fine chamfering: Rough chamfering stage: The grinding head has a grinding grit size of 1000, the feed rate is 0.05 mm / cut, and the rotation speed is 8000 rpm; Fine chamfering stage: The grinding head has a grinding grit size of 2500 mesh, the feed rate is 0.005 mm / cut, and the spindle speed is 12000 rpm.

[0046] (S.3) Then place the wafer in a microscope with a magnification of 100-200 times. When chipping and edge breakage occur in the chamfered edge area, it is determined as the silicon plane, and when the edge is smooth and uniform, it is determined as the carbon plane. After a large number of tests, the recognition accuracy is greater than 99%.

[0047] Example 3 A low-cost method for identifying the silicon-carbon plane of a silicon carbide wafer, comprising the following steps: (S.1) Place the 4H-SiC cutting wafer in a plasma cleaner for plasma cleaning. The power of the plasma cleaning is 500 W, and the gas environment is a mixed gas of argon and hydrogen with a mixing ratio of 3:1, so as to remove the surface oxide layer and attachments.

[0048] (S.2) Perform plasma irradiation pretreatment on the plasma-cleaned 4H-SiC cutting wafer. The plasma pretreatment forms a silicon nitride transition layer on the surface of the silicon plane and an amorphous carbon layer on the surface of the carbon plane.

[0049] The plasma irradiation pretreatment is specifically as follows: Place the plasma-cleaned 4H-SiC cutting wafer in a vacuum chamber, introduce a mixed gas of argon and nitrogen, control the pressure at 30 Pa, and the volume ratio of argon is 85%; Use a radio frequency power supply to excite plasma on the wafer surface. The radio frequency power is 300 W, and the irradiation time is 60 seconds; After the plasma irradiation is completed, purge the chamber with helium to normal pressure; The plasma pretreatment forms a silicon nitride transition layer on the surface of the silicon plane and an amorphous carbon layer on the surface of the carbon plane.

[0050] (S.3) Place the irradiated and pre-treated 4H-SiC cutting wafer in a chamfering machine for chamfering, so that the silicon carbide cutting wafer forms a differentiated edge morphology on the silicon surface and the carbon surface during the chamfering process. Among them, the chamfering process includes two stages: rough chamfering and fine chamfering: Rough chamfering stage: The grinding head has a grinding grain size of 2000, a feed rate of 0.02 mm per cut, and a rotational speed of 5000 rpm; Fine chamfering stage: The grinding head has a grinding grain size of 2000 mesh, a feed rate of 0.01 mm per cut, and a spindle speed of 10000 rpm.

[0051] (S.4) Then place the wafer in a microscope with a magnification of 100 - 200 times. When there is a phenomenon of chipping and edge breakage in the chamfered edge area, it is determined as the silicon surface, and when the edge is smooth and uniform, it is determined as the carbon surface. After a large number of tests, the recognition accuracy rate is greater than 99.9%.

[0052] Example 4 A method for low-cost identification of the silicon and carbon surfaces of silicon carbide wafers, comprising the following steps: (S.1) Place the 4H-SiC cutting wafer in a plasma cleaner for plasma cleaning. The power of the plasma cleaning is 400 W, the gas environment is a mixed gas of argon and hydrogen, and the mixing ratio is 4:1, so as to remove the surface oxide layer and attachments.

[0053] (S.2) Perform plasma irradiation pretreatment on the plasma-cleaned 4H-SiC cutting wafer. The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0054] The plasma irradiation pretreatment is specifically as follows: Place the wafer in a vacuum chamber, introduce a mixed gas of argon and nitrogen, control the pressure at 10 Pa, and the volume ratio of argon is 95%; Use a radio frequency power supply to excite plasma on the wafer surface. The radio frequency power is 400 W, and the irradiation time is 30 seconds; After the plasma irradiation is completed, purge the chamber with helium to normal pressure; The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0055] (S.3) Place the plasma-irradiated and pre-treated 4H-SiC cutting wafer in a chamfering machine for chamfering, so that the silicon carbide cutting wafer forms a differentiated edge morphology on the silicon surface and the carbon surface during the chamfering process. Among them, the chamfering process includes two stages: rough chamfering and fine chamfering: Rough chamfering stage: The grinding head has a grinding grain size of 1500, a feed rate of 0.05 mm per cut, and a rotational speed of 8000 rpm; Fine chamfering stage: the grinding head grinding particle size is 2200 mesh, the feed speed is 0.005mm / knife, and the spindle speed is 10000rpm.

[0056] (S.4) The wafer is then placed under a microscope with a magnification of 100-200 times for observation. When the chamfered edge area shows signs of chipping, it is identified as a silicon surface. When the edge is smooth and uniform, it is identified as a carbon surface. After a large number of tests, the recognition accuracy rate is greater than 99.9%.

[0057] Example 5 A low-cost method for identifying the silicon-carbon surface of a silicon carbide wafer comprises the following steps: (S.1) The 4H-SiC cutting blade is placed in a plasma cleaning chamber for plasma cleaning. The power of the plasma cleaning is 300 W. The gas environment is a mixture of argon and hydrogen with a mixing ratio of 5:1, so as to remove the surface oxide layer and attachments.

[0058] (S.2) Pre-treating the plasma-cleaned 4H-SiC cutting blade by plasma irradiation, wherein the plasma pre-treatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0059] The plasma irradiation pretreatment is as follows: the wafer is placed in a vacuum chamber, and a mixed gas of argon and nitrogen is introduced, with the pressure controlled at 50 Pa, of which the volume of argon accounts for 80%; A radio frequency power source was used to excite plasma on the wafer surface, the radio frequency power was 200 W, and the irradiation time was 120 seconds; After the plasma irradiation, the chamber was purged with helium to normal pressure; The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0060] (S.3) Placing the plasma cleaned 4H-SiC cutting blade in a chamfering machine for chamfering, so that the silicon carbide cutting blade forms differentiated edge morphologies on the silicon surface and the carbon surface during the chamfering process. The chamfering process includes two stages: rough chamfering and fine chamfering: Rough chamfering stage: the grinding head grinding size is 1600, the feed speed is 0.04mm / knife, and the rotation speed is 6000 rpm; Fine chamfering stage: the grinding head grinding particle size is 2000 mesh, the feed speed is 0.008mm / knife, and the spindle speed is 12000rpm.

[0061] (S.4) The wafer is then placed under a microscope with a magnification of 100-200 times for observation. When the chamfered edge area shows signs of chipping, it is identified as a silicon surface. When the edge is smooth and uniform, it is identified as a carbon surface. After a large number of tests, the recognition accuracy rate is greater than 99.9%.

[0062] In summary, by simply chamfering the silicon carbide wafer, the present application can identify the carbon-silicon surface of the silicon carbide wafer with low cost and high accuracy. The principle of the technical solution in the present application is essentially different from the etching method or polishing method used in the prior art, thus successfully avoiding the limitations of the traditional methods in terms of technical effects.

[0063] The specific embodiments described herein are merely illustrative of the present invention. Those skilled in the art to which the present invention pertains may make various modifications or supplements to the described specific embodiments or use similar means for substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A method for low-cost identification of the silicon-carbon surface of a silicon carbide wafer, characterized in that, The following steps are involved: (S.1) Chamfering the edge of the silicon carbide crystal so that differentiated edge morphologies are formed on the silicon side and the carbon side during the material removal process; (S.2) The edge of the chamfered wafer is characterized by optical observation equipment. When the chamfered edge area shows broken edges, it is determined to be a silicon surface. When the edge is smooth and uniform, it is determined to be a carbon surface.

2. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 1, characterized in that: The silicon carbide crystal includes any one of a silicon carbide ingot, a silicon carbide cutting sheet, a silicon carbide grinding sheet, and a silicon carbide polishing sheet.

3. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 1 or 2, characterized in that: The crystal form of the silicon carbide crystal is any one of 4H-SiC, 6H-SiC and 15R-SiC.

4. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 1, characterized in that: The grinding head used in the chamfering process in the step (S.1) has a grinding particle size of 1000-2500 mesh, a feed speed of 0.005-0.05 mm / knife, and a rotation speed of 5000-12000 rpm.

5. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 4, characterized in that: The chamfering process in step (S.1) includes two stages: rough chamfering and fine chamfering: The grinding head grinding grit size in the rough chamfering stage is 1000-2000, the feed speed is 0.02-0.05mm / knife, and the rotation speed is 5000-8000 rpm; The grinding head grinding particle size in the fine chamfering stage is 2000-2500 mesh, the feed speed is 0.005-0.01mm / knife, and the spindle speed is 10000-12000rpm.

6. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 1, characterized in that: The step (S.1) also includes a wafer pretreatment step before the chamfering process, and the pretreatment includes plasma cleaning the wafer surface to remove the surface oxide layer and attachments.

7. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 6, characterized in that: The power of the plasma cleaning is 300-500W, and the gas environment is a mixed gas of argon and hydrogen with a mixing ratio of 3:1-5:

1.

8. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 6 or 7, characterized in that: The pretreatment also includes plasma irradiation pretreatment of the silicon carbide crystal, wherein the ion irradiation pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

9. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 1, characterized in that: The optical observation device in the step (S.2) is an optical microscope with a magnification of 100 to 200.

10. A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer according to claim 9, characterized in that: In the step (S.2), the included angle between the incident angle of the observation light source and the normal direction of the wafer surface is 20°-45°.

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