A low cost method for distinguishing silicon carbide wafer silicon-carbon surface

Abstract

The present application relates to the field of silicon carbide wafer manufacturing, and particularly relates to a low-cost method for distinguishing silicon-carbon surfaces of silicon carbide wafers, comprising the following steps: (S.1) chamfering the edges of the silicon carbide crystal, so that a differentiated edge morphology is formed on the silicon surface and the carbon surface during material removal; (S.2) characterizing the morphology of the chamfered wafer edges by optical observation equipment, and determining the silicon surface when the chamfered edge region appears to be broken and chipped, and determining the carbon surface when the edge is smooth and uniform. The present application can distinguish the silicon-carbon surfaces of silicon carbide wafers at a low cost and with a high accuracy rate by simply chamfering the silicon carbide wafer. In addition, the technical solution in the present application has an essential difference compared to the etching method or polishing method used in the prior art, thereby successfully avoiding the limitations of traditional methods in terms of technical effects.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of silicon carbide wafer manufacturing, and in particular to a method for identifying the silicon-carbon surface of a silicon carbide wafer at low cost. BACKGROUND

[0002] At present, the mainstream method for industrial production of SiC crystals is the physical vapor transport method (PVT method). However, when growing 4H-SiC single crystals using the PVT method, the phenomenon of polymorphism coexistence is prone to occur, which causes the wafer yield to decrease and the performance of SiC-based devices to deteriorate. Therefore, ensuring the stable growth of a single 4H crystal type is extremely crucial for realizing the preparation of high-quality silicon carbide crystals, and during the crystal growth process, the growth parameters such as the gas phase Si / C, the doping type and concentration, the growth temperature, the supersaturation, the crystallization rate, and the 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 the appropriate off-axis angle, and the former is considered to be one of the most significant factors in determining the crystal type. Research has shown that the C face (000-1) with a lower free surface energy tends to generate 4H-SiC crystals, while the Si face (0001) with a higher surface energy is prone to form 6H-SiC crystals with lower enthalpy, and is independent of the seed crystal structure (4H, 6H, or 15R). Therefore, selecting the correct seed crystal growth surface plays a decisive role in the SiC crystal type. In addition, the Si face is generally selected for SiC epitaxial growth, and the Si face has better mechanical and electrical properties, and the S surface has smaller roughness than the C face, which can reduce the influence of the wafer surface on the device.

[0004] The C face and the Si face of the SiC wafer have their own advantages and limitations, and in actual applications, according to specific needs and device requirements, appropriate C faces and Si faces need to be selected for processing, and therefore, effectively identifying the silicon-carbon surface is of great significance for crystal growth, epitaxy, and the preparation of power devices.

[0005] However, the current methods for distinguishing the silicon carbide carbon silicon surface are: ① Positioning edge marking method, this method requires the crystal ingot to be positioned from the main and auxiliary flat edge during the forming process. With the expansion of the size of the crystal ingot, large size (such as 8 inches and 12 inches) crystal ingot / seed crystal / substrate has no main and auxiliary flat edge, so the crystal ingot output needs to be correctly distinguished from the crystal carbon silicon surface. Before wafer marking, the crystal ingot needs to be cut into wafers. In the cutting process, there is no special mark on the crystal, which can easily cause the carbon silicon surface to be marked incorrectly during wafer marking. ② Etching method, the surface free energy of the silicon surface is larger, and the silicon surface and the carbon surface of the SiC wafer are etched by potassium hydroxide. The etching speed of the silicon surface is greater than that of the carbon surface. The silicon surface is easy to form etching pits, while the carbon surface is not easy to form etching pits, and the etching pit morphology of the silicon surface and the carbon surface is different. However, this method will cause at least 40 μm damage to the wafer, and there is a risk of breaking. ③ Polishing rate, the polishing rates of the two sides of the SiC wafer are different. Due to the high hardness and oxidation resistance of the carbon surface, it can withstand high mechanical stress and chemical corrosion, so the carbon surface removal rate is small and the silicon surface removal rate is high through chemical mechanical polishing. The carbon surface removal rate is 0.05-0.1 μm / h, and the silicon surface removal rate is 0.3-0.4 μm / h. However, there are conflicting documents. The comparative study of CMP polishing of 6H-SiC (0001) surface and (000-1) surface indicates that the modified silicon sol polishing liquid with pH=1.11 is used for polishing, and the removal rate of the carbon surface is higher than that of the silicon surface. ④ Atomic force microscope (AFM) distinguishes the roughness of the carbon silicon surface. The roughness of the C and Si surfaces is measured by AFM, and the roughness value displayed is between 0.10-0.50 nm, then the tested surface is the silicon surface. If the roughness displayed is between 0.80-3.00 nm, then the tested surface is the carbon surface. The roughness of the C surface is larger, this method requires the wafer to be polished and cleaned, and atomic force microscope (AFM) is used for identification. The polishing cost and testing cost of each wafer is high, and the range of use is narrow.

[0006] Therefore, there is an urgent need for a low-cost method for distinguishing the silicon carbide carbon silicon surface. SUMMARY

[0007] The present application is to overcome the defects of the prior art method for distinguishing the silicon carbide carbon silicon surface, which usually has low recognition accuracy, is easy to cause the risk of breaking and has high testing cost, and provides a low-cost method for distinguishing the silicon carbide carbon silicon surface to overcome the above shortcomings.

[0008] To achieve the above-mentioned application purposes, the present application is realized by the following technical solutions:

[0009] In a first aspect, the present application first provides a low-cost method for distinguishing the silicon carbide carbon silicon surface, comprising the following steps:

[0010] (S.1) chamfering the edge of the silicon carbide crystal to form a differentiated edge morphology in the silicon surface and carbon surface during material removal;

[0011] (S.2) characterizing the morphology of the chamfered wafer edge by an optical observation device, and determining the silicon surface when the chamfered edge region appears to be chipped, and determining the carbon surface when the edge is smooth and uniform.

[0012] As described in the background, accurate discrimination of the silicon-carbon surface of the silicon carbide wafer is a fundamental problem of 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 crystal, the differences in physical and chemical properties of silicon surface and carbon surface directly affect the crystal growth quality, epitaxial layer structure and device performance. For a long time, the industry has generally used etching, polishing rate or atomic force microscope (AFM) to realize the discrimination of silicon-carbon surface. However, these methods not only rely on expensive equipment or special chemical treatment, but also may increase production costs due to damage to the wafer surface or introduction of errors. For example, the etching method needs to remove at least 40 μm of wafer thickness to distinguish the surface type by the difference in etching pit morphology, which not only greatly increases the material loss, but also may cause the wafer to be scrapped due to over-etching; the AFM method requires a precise optical system and a high-purity test environment, which is costly and cannot be used on a large scale in the production line; and the polishing rate method has questionable reliability due to different crystal types, doping conditions or contradictory literature data. These technical defects directly hinder the large-scale industrial application of silicon carbide technology. Under this background, how to develop a low-cost silicon-carbon surface discrimination technology that can avoid wafer damage and does not require complex instruments has become a real demand that needs to be addressed.

[0013] During the study of the processing of silicon carbide wafers, the technical team of the present application found a phenomenon different from the traditional understanding: when chamfering the silicon carbide wafer, the micro-morphology of the edge of the silicon surface and the carbon surface is significantly different, that is, by chamfering the wafer, the silicon surface will produce a large number of fine chipped edges, while the carbon surface edge will always maintain a smooth transition morphology. Further research revealed that this phenomenon is due to the essential difference in the bond strength of the carbon surface and the silicon surface in the silicon carbide crystal: the C-C bond formed during the growth of the carbon surface has higher bond energy, and the atomic layers are more tightly bound, making its hardness and mechanical stress resistance significantly higher than that of the silicon surface (the Si-Si bond length and bond angle distribution on the silicon surface is more prone to stress concentration and micro-crack propagation). Therefore, when using the same mechanical chamfering process, the silicon surface will form more chipped defects 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 of relying on chemical etching or complex equipment detection, providing a theoretical basis for a low-cost discrimination method.

[0014] The core innovation of the technical solution of the present application is to convert the conventional chamfering process into an active detection means for distinguishing silicon and carbon surfaces. In specific implementation, only the wafer to be tested needs to be placed in a standard chamfering machine to process the edge according to the set parameters, and then the chamfering area morphology is observed under an ordinary optical microscope (100-200 times magnification): the silicon surface will show a fine sawtooth-like broken edge, while the carbon surface will show a continuous smooth arc-shaped profile. The above-mentioned morphology difference can be identified by naked eye without complex image processing, and the interpretation accuracy can reach more than 95% after verification of multiple batches of wafers.

[0015] Notably, the applicability of this method not only covers polished finished wafers, but also can be directly applied to cutting pieces, grinding pieces, and even ingot stages, achieving coverage of the entire process flow. For the initial wafer carbon-silicon surface confirmation after cutting of large-size ingots, the wafer has not yet formed geometric features that can be used for edge marking at this time, and the traditional positioning edge method is completely ineffective, while the chamfering method can quickly complete the surface type determination through small-range edge processing, effectively avoiding errors in subsequent processing. From the economic point of view, the chamfering machine and microscope required by this method are standard equipment for semiconductor production lines, without the need for additional purchase of special instruments, the cost of single detection is reduced by more than 80% compared with the corrosion method, and the problem of chemical waste liquid treatment is completely avoided. In addition, since chamfering processing only acts on the periphery of the wafer non-functional area, the wafer after detection can directly enter the subsequent process without further processing, further improving the production efficiency.

[0016] Although there are individual methods in the prior art that use mechanical processing to distinguish material characteristics, there are essential differences between their technical paths and the present solution. For example, an existing patent proposes to distinguish wafer material types by grinding pressure difference, but its core is to indirectly infer the properties of the wafer surface by measuring the load parameters during grinding, which is essentially still a physical parameter detection method, and there is a significant difference from the present solution which directly relies on the morphology features of the mechanical response of the material itself.

[0017] More importantly, the prior art has never disclosed the hardness-morphology correlation rule of the silicon surface and the carbon surface in the chamfering process, and has failed to optimize the parameters to amplify the feature difference to the extent that can be optically distinguished. The method creatively combines the intrinsic properties of silicon carbide crystals and the mechanical processing dynamics to achieve a high-reliability carbon-silicon surface discrimination in the conventional process link, and the technical path has outstanding non-obviousness compared with the existing solutions. In addition, the chamfering method uses the chipping edge formation mechanism, which is essentially different from the material removal principle of the etching method or the polishing method (mechanical stress concentration induced brittle fracture vs. chemical etching or abrasive shear action), thereby successfully avoiding the limitations of traditional methods in terms of technical effects. Even in the presence of an oxide layer or processing residues on the wafer surface, the chamfering method can still reflect the crystal surface properties through the edge mechanical response, while the etching method may be misjudged due to surface contamination. In terms of technical upgrading potential, the present solution can also be adapted to silicon carbide wafers of different crystal forms or doping concentrations by adjusting the chamfering parameters, showing good process extensibility. This universal solution based on material basic physical properties provides a high-efficiency, reliable and low-cost crystal surface discrimination technology benchmark for the semiconductor manufacturing field.

[0018] Finally, from the crystal ingot to the polished wafer, it needs to go through multiple processes such as shaping (rounding, flat grinding), wire cutting, marking, annealing, chamfering, grinding, polishing, and cleaning. The process is complex, there are many operators, and it is easy to confuse the carbon-silicon surface of the wafer. This method can distinguish the carbon-silicon surface of the silicon carbide wafer at low cost, is simple and feasible, and has a wide range of applications. Crystal ingots, cutting wafers, grinding wafers, and polished wafers can all be chamfered, and the carbon and silicon surfaces of the silicon carbide crystal can be determined by whether the edge of the ingot / wafer produces a chipping edge. At the same time, the detection instrument used in this process is a microscope with a magnification of 100-200 times, which is not a precision instrument. The detection cost of this method is much lower than that of existing methods.

[0019] As a preferred embodiment, 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 polishing wafer.

[0020] As a preferred embodiment, the crystal form of the silicon carbide crystal is any one of 4H-SiC, 6H-SiC, and 15R-SiC.

[0021] As a preferred embodiment, the grinding particle size of the grinding head used in the chamfering process in step (S.1) is 1000-2500 mesh, the feed speed is 0.005-0.05 mm / blade, and the rotation speed is 5000-12000 rpm.

[0022] Based on the same parameters of mechanical chamfering process, the silicon surface will form more chipping defects in the processing process due to its relatively low mechanical stability, while the carbon surface will present a smooth edge due to its stronger resistance to plastic deformation. The technical team of the present application systematically studied the influence of chamfering parameters (grinding head mesh, feed speed, spindle speed) on the edge morphology of the wafer: when the mesh of the grinding head exceeds 1000 mesh, the micro-cutting effect of the abrasive particles on the silicon surface is more likely to trigger local stress concentration, leading to material removal in the form of chipping, while the carbon surface is inhibited from forming a chipping edge under the same conditions due to its high hardness. When the feed speed is less than 0.05 mm / cutter, the silicon surface will form visible chipping edges under the cumulative stress of multiple cutting, while the carbon surface remains continuous removal. Through repeated experiments, it is finally confirmed that when the mesh of the grinding head is 2000, the feed speed is 0.01 mm / cutter, 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, providing a scientific basis for parameter selection in actual production.

[0023] As a preferred, the chamfering process in step (S.1) comprises two stages of rough chamfering and fine chamfering:

[0024] The grinding head grit size of the rough chamfering stage is 1000-2000, the feed speed is 0.02-0.05 mm / cutter, and the rotation speed is 5000-8000 rpm;

[0025] The grinding head grit size of the fine chamfering stage is 2000-2500 mesh, the feed speed is 0.005-0.01 mm / cutter, and the spindle speed is 10000-12000 rpm.

[0026] The hardness difference between the silicon surface and the carbon surface of the silicon carbide wafer is the basis for its discrimination and detection, but the contradiction that needs to be solved in actual processing is that both the brittle chipping of the silicon surface and the complete processing of the carbon surface need to be ensured to maintain the contrast of the criterion. The core of the rough chamfering stage with medium grit size of 1000-2000 mesh, higher feed speed (0.02-0.05 mm / cutter) and lower rotation speed is to trigger the brittle fracture of the silicon surface by high stress impact. Since the atomic binding energy of the silicon surface is lower (the average bond energy of Si-Si bond is about 2.3 eV, and the average bond energy of C-C bond is about 3.6 eV), the rapid expansion of micro-cracks is more likely to be triggered under high load in the rough grinding stage, and the carbon surface can withstand higher stress without chipping due to its stronger bonding force, but a preliminary smooth profile will be formed in the rough chamfering (because the carbon surface is more ductile, the material is removed mainly in the form of plastic deformation). Therefore, the rough chamfering quickly removes the surface layer material and enlarges the brittle characteristics of the silicon surface (chipping edge prototype), providing a reference morphology for subsequent fine processing.

[0027] And the fine chamfering stage adopts higher granularity (2000-2500 mesh), lower feed speed (0.005-0.01 mm / blade) and high rotation speed (10000-12000 rpm), aiming to accurately regulate the edge quality through low-stress multi-frequency micro-cutting. Among them, for the silicon surface, the high rotation speed and small feed amount of the fine grinding stage significantly reduce the single cutting depth, and at this time the broken edge left by the rough chamfering will be further regularized (reduce random crack interference) in the fine machining, forming a stable sawtooth edge. While on the carbon surface, the high rotation speed of the fine chamfering can inhibit the scratching effect of large particles (small granularity of abrasive head particles is more uniform), combined with slow feeding to form atomic-level continuous removal, so that the smoothness of the carbon surface edge tends to be consistent. Therefore, the introduction of fine chamfering eliminates the random defects introduced by rough machining, and strengthens the contrast of the edge characteristics of the silicon and carbon surfaces.

[0028] Finally, in the slicing process of silicon carbide ingots, the edge chamfering of the wafer was originally only a conventional step (non-detection means) to reduce the risk of edge collapse. The innovation of the present application is to give the conventional processing step a new technical mission, and make it become an efficient discrimination tool for carbon and silicon surfaces through parameter reconstruction. This seamless integration of processing and detection functions significantly surpasses the traditional understanding of chamfering process.

[0029] The existing chamfering process usually takes "deburring" or "improving mechanical strength" as a single target, and the parameter selection does not distinguish between processing stages, nor does it correlate the mechanical response characteristics of the differences between the silicon carbide crystal surfaces. The staged parameter interval proposed in the present application (especially the specific combination of low rotation speed / high feed of the rough chamfering stage and high rotation speed / low feed of the fine chamfering stage) is the first engineering verification scheme for discriminating silicon carbide crystal surfaces.

[0030] When the parameters of rough chamfering and fine chamfering are mismatched (such as only rough chamfering is performed), the broken edge of the silicon surface presents irregular distribution (part of the area has no criterion characteristics); only fine chamfering is performed, and the initial processing load is insufficient, which will lead to incomplete triggering of the silicon surface criterion (only slight edge burr). Only through the cooperation of two-stage parameters (rough chamfering generates basic morphology + fine chamfering strengthens criterion), can stable and measurable morphology difference be formed.

[0031] As a preferred, the step (S.1) further comprises a wafer pretreatment step before chamfering processing, and the pretreatment comprises plasma cleaning of the wafer surface to remove surface oxide layer and attachments.

[0032] The surface of the silicon carbide wafer will naturally form an oxide layer (SiO2 and SiO x C y complexes) and adsorb contaminants (such as organic residues, metal particles) during storage or transportation, and such surface heterostructures have the following interference performances on chamfering processing:

[0033] (1) Oxide layer (hardness ~8 GPa) covers the silicon surface body (hardness ~18 GPa), the load at the initial chamfering stage needs to break through the oxide layer (causing the grinding head to slip or load fluctuation), resulting in the effective stress actually borne by the silicon surface being reduced (stress is absorbed by the oxide), and the delay of the broken edge triggering or the intensification of random fracture is caused.(2) Meanwhile, the oxide layer of the carbon surface is thinner (because the carbon surface is more resistant to oxidation), but there is still a nanoscale disordered carbon oxide layer (hardness ~12 GPa), which weakens the hardness contrast between the carbon surface and the silicon surface.

[0034] The present application uses a hydrogen-argon mixed plasma to remove the surface hetero-layer by physical sputtering (Ar + ion bombardment) and chemical reduction (H free radicals react with oxides) through two paths, wherein the silicon surface restores the original hardness (Ar + sputtering removes SiO2), and high-energy H free radicals reduce silicon suboxides (such as SiO) to volatile SiH4, and the carbon surface only needs to be physically sputtered to remove adsorbates due to the chemical inertness of C-C bonds, and a small amount of surface carbon dangling bonds are retained (which is beneficial to inhibit subsequent oxidation), so that the chamfering load directly acts on the intrinsic matrix of the silicon and carbon surfaces.

[0035] When the oxide layer is removed, the friction between the abrasive particles and the wafer surface changes from "elastic deformation dominated" (oxide viscoelastic buffer) to "plastic shear dominated" (matrix direct contact). Because the silicon surface has a higher coefficient of friction (clean surface), it accelerates the nucleation of microcracks, so that the broken edge is formed in advance to the initial stage of chamfering. The low-friction property of the carbon surface (more pronounced after cleaning) allows it to maintain a stable shear removal mode.

[0036] As a preferred, the power of the plasma cleaning is 300-500 W, and the gas environment is a mixed gas of argon and hydrogen, and the mixing ratio is 3:1-5:1.

[0037] As a preferred, the pretreatment further includes plasma irradiation pretreatment of the silicon carbide crystal, and the plasma pretreatment forms a silicon nitride transition layer on the surface of the silicon surface and generates an amorphous carbon layer on the surface of the carbon surface.

[0038] The plasma irradiation creatively utilizes the difference in chemical reactivity of 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), which further intensifies the brittleness of the silicon surface material in subsequent chamfering, making the broken edge phenomenon more likely to trigger and regularize the morphology (reducing the interference of disordered cracks), while the amorphous carbon layer of the carbon surface will inhibit the abrasive scratch propagation due to the self-lubricating effect, forming a more uniform smooth edge. This pretreatment actively modifies the surface properties, making up for the possible edge criterion ambiguity problem that only relies on the difference in bulk hardness.

[0039] As preferred, the plasma irradiation pretreatment specifically comprises:

[0040] The wafer is placed in a vacuum chamber, and a mixed gas of argon and nitrogen is introduced, with the pressure controlled at 10-50 Pa, wherein the volume ratio of argon is 80-95%;

[0041] A radio frequency power source is used to excite plasma on the wafer surface, with the radio frequency power being 200-400 W, and the irradiation time being 30-120 seconds;

[0042] After the plasma irradiation, the chamber is purged with helium to normal pressure;

[0043] The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0044] As preferred, the optical observation device in step (S.2) is an optical microscope with a magnification of 100-200 times.

[0045] As preferred, the angle between the incident angle of the observation light source and the normal direction of the wafer surface is 20°-45°.

[0046] Therefore, the present application has the following beneficial effects:

[0047] The present application innovatively utilizes the gradient of the mechanical properties of silicon carbide crystal surfaces, precisely controls the edge morphology difference through chamfering, and optimizes optical detection, thereby realizing three major breakthrough advantages:

[0048] ① The cost is extremely low, only conventional chamfering equipment and ordinary microscopes are needed, and the single detection cost is reduced by more than 80% compared with the etching method;

[0049] ② Non-destructive and efficient, without damaging the main structure of the wafer, the discrimination is completed within 3 minutes and the accuracy is >97%;

[0050] ③ The process is universal, compatible with polished wafers, cut wafers and ingot processing stages, solves the industrialization bottleneck of the dependence on equipment and environment of traditional methods, and provides a cost-effective detection scheme for large-scale manufacturing of silicon carbide devices. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 The enlarged view of the chamfered wafer edge of the 4H-SiC polished wafer in Example 1.

[0052] Figure 2 The enlarged view of the chamfered wafer edge of the 6H-SiC polished wafer in Example 2. DETAILED DESCRIPTION

[0053] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below generally represent only a portion of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0054] Example 1

[0055] A low-cost method for identifying the silicon-carbon surface of a silicon carbide wafer comprises the following steps:

[0056] (S.1) A 4H-SiC cutting blade was placed in a chamfering machine for chamfering. The grinding head had a mesh size of 2000, the feed rate was 0.01 mm / blade, and the rotation speed was 10,000 rpm. This resulted in differentiated edge morphologies on the silicon and carbon surfaces of the silicon carbide cutting blade during chamfering.

[0057] (S.2) The wafer is then placed under a microscope at 100-200x magnification for observation. If the chamfered edge 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.

[0058] 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 appears to be broken and chipped. Figure 1 The C surface is on the middle right side, and its edges are smooth and even without any broken edges. After a large number of tests, the recognition accuracy rate is greater than 97%.

[0059] Example 2

[0060] A low-cost method for identifying the silicon-carbon surface of a silicon carbide wafer comprises the following steps:

[0061] (S.1) A 6H-SiC polishing wafer was placed in a chamfering machine for chamfering. The grinding head had a mesh size of 1500, a feed rate of 0.02 mm / cut, and a rotation speed of 11,000 rpm. This resulted in differentiated edge morphologies on the silicon and carbon surfaces of the silicon carbide cutting blade during chamfering.

[0062] (S.2) The wafer is then placed under a microscope at 100-200x magnification for observation. If the chamfered edge 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.

[0063] like Figure 2 As shown, Figure 2The middle left side is a Si surface, and the chipped edge phenomenon occurs at the chamfered edge thereof Figure 2 The middle right side is a C surface, and the edge thereof is smooth and uniform, and the recognition accuracy is greater than 97% after a large number of tests.

[0064] Example 3

[0065] A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer, comprising the following steps:

[0066] (S.1) The 4H-SiC wafer is placed in a plasma cleaner for plasma cleaning, the power of the plasma cleaning is 300W, the gas environment is a mixed gas of argon and hydrogen, and the mixing ratio is 5:1, so as to remove the surface oxide layer and the attached matter.

[0067] (S.2) The 4H-SiC wafer after plasma cleaning is placed in a chamfering machine for chamfering processing, so that the silicon carbide wafer forms a differential edge morphology in the chamfering process on the silicon surface and the carbon surface. The chamfering process includes two stages of rough chamfering and fine chamfering:

[0068] Rough chamfering stage: the grinding head has a grinding granularity of 1000, the feed speed is 0.05mm / sword, and the rotation speed is 8000rpm;

[0069] Fine chamfering stage: the grinding head has a grinding granularity of 2500 mesh, the feed speed is 0.005mm / sword, and the spindle speed is 12000rpm.

[0070] (S.3) Then the wafer is placed in a 100-200 times microscope for observation, when the chamfering edge region appears a chipped edge phenomenon, it is determined as a silicon surface, and when the edge is smooth and uniform, it is determined as a carbon surface, and the recognition accuracy is greater than 99% after a large number of tests.

[0071] Example 3

[0072] A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer, comprising the following steps:

[0073] (S.1) The 4H-SiC wafer is placed in a plasma cleaner for plasma cleaning, the power of the plasma cleaning is 300W, the gas environment is a mixed gas of argon and hydrogen, and the mixing ratio is 5:1, so as to remove the surface oxide layer and the attached matter.

[0074] (S.2) The 4H-SiC wafer after plasma cleaning is placed in a plasma cleaner for plasma cleaning, the power of the plasma cleaning is 300W, the gas environment is a mixed gas of argon and hydrogen, and the mixing ratio is 5:1, so as to remove the surface oxide layer and the attached matter.

[0075] The plasma irradiation pretreatment is specifically as follows: the 4H-SiC wafer after plasma cleaning is placed in a vacuum chamber, a mixed gas of argon and nitrogen is introduced, the pressure is controlled at 30 Pa, and the volume ratio of argon is 85%.

[0076] A radio frequency power source is used to excite plasma on the wafer surface, the radio frequency power is 300 W, and the irradiation time is 60 seconds.

[0077] After the plasma irradiation is completed, the chamber is purged with helium to normal pressure.

[0078] The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0079] (S.3) The 4H-SiC wafer after irradiation pretreatment is placed in a chamfering machine for chamfering processing, so that the silicon carbide wafer forms a differential edge morphology on the silicon surface and the carbon surface during chamfering. The chamfering process includes two stages of rough chamfering and fine chamfering:

[0080] Rough chamfering stage: the grinding head has a grinding particle size of 2000, the feed speed is 0.02 mm / blade, and the rotation speed is 5000 rpm.

[0081] Fine chamfering stage: the grinding head has a grinding particle size of 2000 mesh, the feed speed is 0.01 mm / blade, and the spindle speed is 10000 rpm.

[0082] (S.4) Then the wafer is placed in a microscope of 100-200 times for observation, when the chamfering edge region appears a broken edge phenomenon, it is determined as a silicon surface, and when the edge is smooth and uniform, it is determined as a carbon surface. After a large number of tests, the recognition accuracy is greater than 99.9%.

[0083] Example 4

[0084] A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer includes the following steps:

[0085] (S.1) The 4H-SiC wafer is placed in a plasma cleaning chamber 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 the attached matter.

[0086] (S.2) The 4H-SiC wafer after plasma cleaning is subjected to plasma irradiation pretreatment, and the plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0087] The plasma irradiation pretreatment is specifically as follows: the wafer is placed in a vacuum chamber, a mixed gas of argon and nitrogen is introduced, the pressure is controlled at 10 Pa, and the volume ratio of argon is 95%.

[0088] The plasma is excited on the wafer surface by a radio frequency power source, the radio frequency power is 400 W, and the irradiation time is 30 seconds;

[0089] After the plasma irradiation is completed, the chamber is purged to normal pressure by helium;

[0090] The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0091] (S.3) The 4H-SiC wafer after plasma irradiation pretreatment is placed in a chamfering machine for chamfering processing, so that the silicon carbide wafer forms a differentiated edge morphology on the silicon surface and the carbon surface during chamfering. The chamfering process includes two stages of rough chamfering and fine chamfering:

[0092] Rough chamfering stage: the grinding head has a grinding particle size of 1500, the feed speed is 0.05 mm / blade, and the rotation speed is 8000 rpm;

[0093] Fine chamfering stage: the grinding head has a grinding particle size of 2200 mesh, the feed speed is 0.005 mm / blade, and the spindle speed is 10000 rpm.

[0094] (S.4) Then the wafer is placed in a microscope of 100-200 times to observe, when the edge region appears a broken edge phenomenon, it is determined as a silicon surface, and when the edge is smooth and uniform, it is determined as a carbon surface. After a large number of tests, the recognition accuracy is greater than 99.9%.

[0095] Example 5

[0096] A low-cost method for distinguishing the silicon-carbon surface of a silicon carbide wafer, comprising the following steps:

[0097] (S.1) The 4H-SiC wafer is placed in a plasma cleaning machine for plasma cleaning, the plasma cleaning power is 300 W, the gas environment is a mixture of argon and hydrogen, and the mixing ratio is 5:1, so as to remove the surface oxide layer and the attached matter.

[0098] (S.2) The 4H-SiC wafer after plasma cleaning is subjected to plasma irradiation pretreatment, which forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0099] The plasma irradiation pretreatment is as follows: the wafer is placed in a vacuum chamber, a mixture of argon and nitrogen is introduced, and the pressure is controlled at 50 Pa, wherein the argon volume ratio is 80%;

[0100] The plasma is excited on the wafer surface by a radio frequency power source, the radio frequency power is 200 W, and the irradiation time is 120 seconds;

[0101] After the end of the plasma irradiation, the chamber is purged to normal pressure with helium gas;

[0102] The plasma pretreatment forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

[0103] (S.3) The 4H-SiC wafer after the plasma cleaning is placed in a chamfering machine for chamfering processing, so that the silicon carbide wafer forms a differential edge morphology on the silicon surface and the carbon surface during the chamfering process. The chamfering process includes two stages of rough chamfering and fine chamfering.

[0104] Rough chamfering stage: the grinding head has a grinding granularity of 1600, the feed speed is 0.04 mm / blade, and the rotation speed is 6000 rpm.

[0105] Fine chamfering stage: the grinding head has a grinding granularity of 2000 mesh, the feed speed is 0.008 mm / blade, and the spindle speed is 12000 rpm.

[0106] (S.4) Then the wafer is placed in a 100-200 times microscope for observation. When the chamfering edge region appears a broken edge phenomenon, it is determined as a silicon surface, and when the edge is smooth and uniform, it is determined as a carbon surface. After a large number of tests, the recognition accuracy is greater than 99.9%.

[0107] In summary, the present application can distinguish the silicon carbide wafer carbon silicon surface at low cost and high accuracy by simple chamfering processing of the silicon carbide wafer. The technical solution in the present application has essential differences compared with the etching method or polishing method used in the prior art, thereby successfully avoiding the limitations of traditional methods in technical effect.

[0108] The specific embodiments described herein are merely illustrative of the present application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, but will not deviate from the spirit of the present application or exceed the scope defined by the appended claims.

Claims

1. A low cost method of distinguishing the silicon-carbon face of a silicon carbide wafer, characterized by, The method comprises the following steps: (S.1) chamfering the edge of the silicon carbide crystal, so that the material removal process forms a differentiated edge morphology on the silicon surface and the carbon surface; The grinding head used in the chamfering process in step (S.1) has a grit size of 1000-2500 mesh, an infeed speed of 0.005-0.05 mm / blade, and a rotation speed of 5000-12000 rpm; The chamfering process includes two stages of rough chamfering and fine chamfering: The grinding head used in the rough chamfering stage has a grit size of 1000-2000 mesh, an infeed speed of 0.02-0.05 mm / blade, and a rotation speed of 5000-8000 rpm; The grinding head used in the fine chamfering stage has a grit size of 2000-2500 mesh, an infeed speed of 0.005-0.01 mm / blade, and a spindle rotation speed of 10000-12000 rpm; (S.2) observing the morphology of the chamfered wafer edge under a 100-200x optical microscope, and determining the silicon surface when the chamfered edge region appears to be broken and determining the carbon surface when the edge is smooth and uniform.

2. The method for distinguishing the silicon and carbon surfaces of a silicon carbide wafer at low cost according to claim 1, wherein the silicon carbide crystal is any one of a silicon carbide ingot, a silicon carbide cutting disc, a silicon carbide grinding disc, and a silicon carbide polishing disc.

3. The method for distinguishing the silicon and carbon surfaces of a silicon carbide wafer at low cost according to claim 1 or 2, wherein the silicon carbide crystal is any one of a 4H-SiC, 6H-SiC, and 15R-SiC crystal.

4. The method for distinguishing the silicon and carbon surfaces of a silicon carbide wafer at low cost according to claim 1, wherein the step (S.1) further comprises a wafer pretreatment step before chamfering, and the pretreatment comprises plasma cleaning the wafer surface to remove the surface oxide layer and attachments.

5. The method for distinguishing the silicon and carbon surfaces of a silicon carbide wafer at low cost according to claim 4, wherein the power of the plasma cleaning is 300-500 W, and the gas environment is a mixture of argon and hydrogen gas with a mixing ratio of 3:1-5:

1.

6. The method for distinguishing the silicon and carbon surfaces of a silicon carbide wafer at low cost according to claim 4 or 5, wherein the pretreatment further comprises plasma irradiation pretreatment of the silicon carbide crystal, which forms a silicon nitride transition layer on the silicon surface and an amorphous carbon layer on the carbon surface.

7. The method for distinguishing the silicon and carbon surfaces of a silicon carbide wafer at low cost according to claim 1, wherein 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°. ​ ​ ​ ​ ​ ​

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