Electrochemically assisted diamond wire sawing process, silicon carbide wafer, and semiconductor device

Abstract

This invention discloses an electrochemically assisted diamond wire cutting process, silicon carbide wafers, and semiconductor devices, relating to the field of semiconductor technology. It innovatively introduces an electrochemical-assisted mechanism, applying current to the silicon carbide ingot being cut in an alkaline electrolyte environment, utilizing an electrochemical reaction to generate an easily removable softened silicon dioxide layer in situ at the cutting tip. Diamond wire cutting transforms the process from "grinding" the hard silicon carbide ingot body to "scraping away" the softened oxide layer, significantly reducing the mechanical cutting stress and damage to the wafer. This process brings the dual benefits of a leap in silicon carbide wafer quality and a significant reduction in production costs, representing a key technological breakthrough driving the silicon carbide power semiconductor industry towards higher performance and lower costs. Its "soft-to-hard" chemical-mechanical synergy provides a novel path to solving the precision machining challenges of ultra-hard and brittle materials.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to electrochemically assisted diamond wire cutting processes, silicon carbide wafers, and semiconductor devices. Background Technology

[0002] Silicon carbide (SiC), as a representative of third-generation semiconductor materials, exhibits great application potential in power electronics, radio frequency devices, and other fields due to its excellent properties such as wide bandgap, high breakdown field strength, and high thermal conductivity. SiC single crystals are typically grown into cylindrical ingots using the physical vapor transport (PVT) method, which then require subsequent processes such as cutting, grinding, polishing, and cleaning to prepare thin wafers to meet device manufacturing requirements. In the ingot cutting stage, the current mainstream process in the industry is diamond wire cutting technology, which relies on the mechanical grinding action of diamond abrasive grains to divide the ingots. However, this technology has the following drawbacks: (1) Due to the extremely high hardness and brittleness of SiC, diamond abrasive grains need to apply extremely high normal pressure during the cutting process to generate effective cutting, which leads to the formation of micron-level crack networks and residual stress fields inside the wafer; (2) The surface / subsurface damage is severe, resulting in microcracks, broken layers, etc., which need to be removed by subsequent grinding and polishing, increasing processing time and material consumption, and reducing wafer yield; (3) The release of residual stress causes wafer warping and deformation, which seriously affects the depth of focus control of the photolithography process; (4) In order to balance the cutting efficiency and the risk of wire breakage, the diameter of diamond wire is set to >120μm, but it is very easy to cause a wide cutting kerf, serious material waste and a significant reduction in the number of wafers produced from the ingot; (5) In terms of processing economy, the limited cutting speed and high wire consumption of SiC have become one of the key bottlenecks restricting the cost reduction of SiC devices.

[0003] Therefore, how to achieve low damage, low warpage, and low material loss in silicon carbide ingot cutting while improving wafer quality has become one of the technical challenges that urgently need to be solved in this field.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide an electrochemically assisted diamond wire cutting process, silicon carbide wafers, and semiconductor devices to solve or improve the aforementioned technical problems.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides an electrochemically assisted diamond wire cutting process, comprising the following steps: The silicon carbide crystal rod is detachably installed on the cutting system and connected to the positive terminal of the power supply; the diamond wire is connected to the negative terminal of the power supply; the electrolyte is an alkaline solution with a mass concentration of 15wt%-25wt%. The cutting system is started, current is applied, and the diamond wire cuts the fed silicon carbide crystal rod.

[0007] It should be noted that the present invention does not impose a particular limitation on the diameter of the silicon carbide crystal rod, which can be selected according to actual needs, such as 150mm, 200mm, etc. The diameter of the silicon carbide crystal rod used in the embodiments of the present invention is 200mm.

[0008] In an optional implementation, during the silicon carbide ingot cutting process, the cutting system has at least one of the following features: Feature one: The applied current density is 0.3 A / cm². 2 -0.7 A / cm 2 ; Feature 2: The applied voltage is 5V-12V; Feature 3: It adopts either DC mode or pulse mode; wherein, the frequency of pulse mode is 100Hz-500Hz and the duty cycle is 50%-70%; Feature 4: The cutting time for silicon carbide crystal rods is 30-36 hours; Feature 5: The feed rate of the silicon carbide crystal rod is 0.5 mm / min - 0.8 mm / min; Feature 6: The cutting system outputs 410-450 silicon carbide wafers per hour.

[0009] In an optional embodiment, during the silicon carbide ingot cutting process, the electrolyte has at least one of the following characteristics: Feature 1: The electrolyte flow rate is 30L / min-50L / min; Feature 2: The electrolyte temperature is 40℃-50℃; Feature 3: The pH of the electrolyte is 13.5-14.0.

[0010] In an optional embodiment, during the silicon carbide ingot cutting process, the diamond wire has at least one of the following characteristics: Feature 1: The diameter of the diamond wire is 78μm-87μm; Feature 2: The tension of the diamond wire is 18N-22N; Feature three: the linear velocity of the diamond wire is 10m / s-14m / s.

[0011] In an optional implementation, the diameter of the diamond wire is 70μm-75μm; The material of the diamond wire is selected from at least one of high carbon steel and tungsten alloy wire; The material of the coating on the diamond wire surface is selected from at least one of Ni and nickel-cobalt alloy; The average particle size of the diamond abrasive grains on the surface of the diamond wire is 8μm-12μm.

[0012] In an optional embodiment, the mass concentration of the electrolyte is 18wt%-22wt%; And / or, the solute in the electrolyte is selected from sodium hydroxide and / or potassium hydroxide, and the solvent is selected from at least one of deionized water, purified water, mineral water and ultrapure water.

[0013] In an optional implementation, when cutting silicon carbide crystal rods, the cutting system is powered on for 1-2 minutes before cutting the silicon carbide crystal rods; 8-12 seconds before the end of the cutting, the power is turned off and the cutting of the diamond wire is stopped. And / or, the process also includes cleaning the silicon carbide wafers obtained after dicing.

[0014] In a second aspect, the present invention provides a silicon carbide wafer, which is manufactured using an electrochemically assisted diamond wire cutting process as described in any of the foregoing embodiments.

[0015] In an optional embodiment, the silicon carbide wafer has at least one of the following characteristics: Feature 1: The thickness of the subsurface damage layer of the silicon carbide wafer is <1μm; Feature 2: The warpage of the silicon carbide wafer is 30μm-45μm.

[0016] Thirdly, the present invention provides a semiconductor device fabricated using a silicon carbide wafer as described in any of the foregoing embodiments.

[0017] The present invention has the following beneficial effects: This invention innovatively introduces an electrochemically assisted (ECM) mechanism into the electrochemically assisted diamond wire cutting process. By applying a precise microcurrent to the silicon carbide ingot (anode) being cut in a specially formulated alkaline electrolyte environment, an easily removable softened silicon dioxide layer is generated in situ at the cutting tip via an electrochemical reaction. The primary role of the diamond abrasive grains shifts from "grinding" the hard silicon carbide ingot body to "scraping away" the softened oxide layer, thereby significantly reducing the mechanical cutting stress and damage to the ingot. Specifically, the cutting stress reduction is >60%, wafer warpage is controlled to <50μm, and the diamond wire diameter is successfully reduced to 80μm.

[0018] This invention's electrochemical-assisted diamond wire cutting process brings the dual benefits of a leap in wafer quality (low damage, high flatness) and a significant reduction in production costs (high yield, low wire loss, reduced post-processing). It represents a key technological breakthrough driving the silicon carbide power semiconductor industry towards higher performance and lower costs. Its "soft-to-hard" chemical-mechanical synergy provides a novel approach to solving the precision machining challenges of ultra-hard and brittle materials. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The image shows the morphology of the silicon carbide wafer obtained in Example 1. Figure 2 This is a morphological image of the silicon carbide wafer prepared in Comparative Example 1. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] In a first aspect, the present invention provides an electrochemically assisted diamond wire cutting process, comprising the following steps: The silicon carbide (SiC) crystal rod is detachably installed on the cutting system and connected to the positive terminal of the power supply; the diamond wire is connected to the negative terminal of the power supply; the electrolyte is an alkaline solution with a mass concentration of 15wt%-25wt%. The cutting system is started, current is applied, and the diamond wire cuts the fed silicon carbide crystal rod.

[0023] This invention employs a chemical-mechanical synergistic cutting process to cut silicon carbide ingots. During diamond wire cutting, a controllable electrochemical action (ECM) is simultaneously applied, utilizing the electrolyte and microcurrent to promote the oxidation and softening of the silicon carbide ingot surface, significantly reducing the difficulty and damage of diamond wire mechanical cutting (WS). The cutting process of this invention is abbreviated as ECM-WS process.

[0024] The working principle of the cutting system is analyzed as follows: During the silicon carbide ingot cutting process, after applying current, in an alkaline electrolyte environment, the silicon carbide ingot is connected to the positive terminal of the power supply, which acts as the anode and undergoes an electrochemical oxidation reaction. The specific reaction equations for the anode and cathode are as follows: Anode reaction equation: SiC + 6OH - → SiO3 2- + CO2 + 3H2O + 4e - ; Cathode reaction equation: 2H₂O + 2e⁻ - → H2 + 2OH- .

[0025] Under current-driven conditions, the surface of a silicon carbide crystal rod is oxidized to form a relatively soft silicon dioxide layer or silicate layer. The reaction equation for the formation of silicon dioxide is SiC + 8OH⁻. - → SiO2 + CO2 + 4H2O + 8e - In this process, the hardness of SiO2 is much lower than that of the silicon carbide crystal rod body. The abrasive grains carried by the diamond wire no longer primarily cut the hard silicon carbide crystal rod body, but rather scrape / grind the softened oxide layer and expose a new silicon carbide surface for further oxidation and softening. The mechanical cutting force is mainly used to remove the softened layer, rather than directly acting on the high-hardness silicon carbide crystal rod body, thereby achieving continuous softening of the silicon carbide crystal rod.

[0026] The cutting process continuously softens the front end of the silicon carbide ingot, significantly reducing its "effective hardness." The continuous mechanical force provided by the diamond wire scrapes away the softened layer while renewing the reaction surface of the silicon carbide ingot, ensuring the orderly progress of the cutting process. The alkaline electrolyte continuously provides the reaction medium (OH-). - (Ions), which enable the electrochemical reaction to continue.

[0027] The characteristics of electrochemically assisted diamond wire cutting technology are analyzed as follows: (1) In-situ softening mechanism: The softening layer (SiO2) is generated and removed in real time and in situ at the cutting front end by electrochemical reaction, which greatly reduces the "effective hardness" of the material; (2) Precise current control: The current density is <1 A / cm 2 The microcurrent system ensures that the cutting process is controllable and uniform, avoids excessive etching or thermal damage to silicon carbide crystal rods, and improves the yield of silicon carbide wafers; (3) Alkaline electrolyte: A special composite electrolyte with good conductivity (solute is KOH and / or NaOH), dispersion stability (suspending abrasive particles), lubricity and controllable reactivity (dissolving SiO2) has been developed; (4) Application of fine diameter (~80μm) diamond wire: thanks to the significant reduction in cutting force, a breakthrough in significantly reducing the diameter of diamond wire has been achieved.

[0028] For ease of comparison, the traditional diamond wire cutting process (hereinafter referred to as the "traditional process") and the electrochemical assisted diamond wire cutting process of the present invention (hereinafter referred to as the "ECM-WS process") are compared and analyzed, and the relevant results are summarized in Table 1.

[0029] Table 1 Comparison Results of Different Processes

[0030] In an optional implementation, during the silicon carbide ingot cutting process, the cutting system has at least one of the following features: Feature one: The applied current density is 0.3 A / cm². 2 -0.7 A / cm 2 The current is a microcurrent and must be strictly controlled during use to ensure a controllable and uniform reaction, avoiding excessive etching or thermal damage to the SiC ingot or the cut SiC wafer during the cutting process. If the current is too low, the softening effect on the SiC ingot surface will be insufficient; if the current is too high, it may lead to excessive etching of the SiC ingot or uneven reaction.

[0031] Furthermore, the applied current density is 0.4 A / cm². 2 -0.6 A / cm 2 The current is adjusted appropriately according to actual needs, and is generally obtained by controlling the voltage. For example, the applied current density can be selected from 0.4 A / cm². 2 0.45 A / cm 2 0.5A / cm 2 and 0.6 A / cm 2 Any one of them, or 0.4 A / cm 2 -0.6 A / cm 2 Other values ​​within the range.

[0032] Feature 2: The applied voltage is 5V-12V; the voltage design depends on the distance between the positive and negative electrodes and the concentration of the electrolyte.

[0033] It should be noted that the cutting system monitors the voltage and current in real time, and can automatically adjust if fluctuations occur.

[0034] Feature 3: It adopts either DC mode or pulse mode; wherein, the frequency of pulse mode is 100Hz-500Hz and the duty cycle is 50%-70%; Employing a pulsed current mode can reduce bubble accumulation and improve the uniformity of softening the silicon carbide ingot. Furthermore, the duty cycle of the pulsed mode is 55%-65%.

[0035] Feature 4: The time for cutting silicon carbide crystal rods is 30-36 hours; the traditional diamond wire cutting process takes about 50 hours, saving as much as 28%-40%.

[0036] Feature 5: The feed rate of the silicon carbide crystal rod is 0.5 mm / min-0.8 mm / min; this feed rate is significantly improved compared with the traditional diamond wire cutting process (feed rate ≤ 0.3 mm / min).

[0037] The feed rate can be adjusted reasonably according to actual needs. For example, the feed rate can be selected from any one of 0.5 mm / min, 0.6 mm / min, 0.7 mm / min and 0.8 mm / min, or other values ​​in the range of 0.5 mm / min to 0.8 mm / min.

[0038] Feature six: The cutting system outputs 410-450 silicon carbide wafers per hour. Traditional diamond wire cutting processes only output about 350 silicon carbide wafers per hour, representing a 17%-28.5% increase in silicon carbide wafer production efficiency.

[0039] The output quantity of silicon carbide wafers is a comprehensive result of various parameters of the cutting system, and the specific quantity is subject to actual conditions.

[0040] In an optional embodiment, during the silicon carbide ingot cutting process, the electrolyte has at least one of the following characteristics: Feature one: The electrolyte flow rate is 30L / min-50L / min; electrolyte circulation is initiated, allowing current to flow through the electrolyte to form a circuit between the anode (silicon carbide crystal rod) and the cathode (diamond wire), achieving continuous softening and cutting of the silicon carbide crystal rod. Furthermore, electrolyte circulation also facilitates the renewal of reactants and heat dissipation of the electrolyte system.

[0041] Furthermore, the electrolyte flow rate is 35 L / min-45 L / min; the electrolyte flow rate is adjusted appropriately according to actual needs to ensure that the cutting area is fully wetted in the electrolyte. For example, the electrolyte flow rate can be adjusted appropriately according to actual needs; for example, the electrolyte flow rate can be selected from any one of 35 L / min, 38 L / min, 40 L / min, 42 L / min, 43 L / min, and 45 L / min, or other values ​​within the range of 35 L / min-45 L / min.

[0042] Feature 2: The electrolyte temperature is 40℃-50℃; if the temperature is >50℃, the electrolyte volatilization is accelerated; if the temperature is <40℃, the reaction rate is reduced.

[0043] Feature three: The electrolyte pH is 13.5-14.0. During the cutting process, the pH of the electrolyte is monitored in real time using a pH meter. If the pH drops, solute is added promptly.

[0044] In an optional embodiment, during the silicon carbide ingot cutting process, the diamond wire has at least one of the following characteristics: Feature 1: The diameter of the diamond wire is 78μm-87μm. The reduction in the diameter of the diamond wire can significantly reduce the kerf loss width (Kerf Loss refers to the material loss width caused by the physical width of the diamond wire and the offset of the cutting vibration during the cutting process), and improve the yield of single wafers by 15%-20%.

[0045] Feature 2: The wire tension of the diamond wire is 18N-22N, which is lower than the wire tension of 25N-30N required in traditional processes. The reduction in tension not only reduces the probability of wire breakage and wire consumption costs, but also improves cutting accuracy.

[0046] The third feature is that the diamond wire has a linear speed of 10m / s-14m / s. This linear speed is lower than that of traditional processes, allowing sufficient time for the electrochemical reaction.

[0047] In an optional implementation, the diameter of the diamond wire is 70μm-75μm; The material of the diamond wire is selected from at least one of high carbon steel and tungsten alloy wire; The material of the coating on the diamond wire surface is selected from at least one of Ni and nickel-cobalt alloy; The average particle size of the diamond abrasive grains on the surface of the diamond wire is 8μm-12μm.

[0048] In an optional implementation, the mass concentration of the electrolyte is 18wt%-22wt%. If the concentration is too low, the reaction rate is slow and the effect is poor. If the concentration is too high, the corrosiveness and viscosity will increase, which may affect the fluidity of the electrolyte and the life of the equipment, and may also cause corrosion to the diamond wire or equipment components.

[0049] For example, the mass concentration of the electrolyte can be selected from any one of 18wt%, 19wt%, 20wt%, 21wt%, and 22wt%, or other values ​​in the range of 18wt% to 22wt%.

[0050] And / or, the solute in the electrolyte is selected from sodium hydroxide and / or potassium hydroxide, and the solvent is selected from at least one of deionized water, purified water, mineral water and ultrapure water.

[0051] In an optional implementation, during silicon carbide ingot cutting, the cutting system is powered on for 1-2 minutes before cutting the silicon carbide ingot; 8-12 seconds before the end of cutting, the power is turned off first, followed by the diamond wire cutting. Powering on first helps establish a stable electrochemical environment, achieving oxidation and softening of the silicon carbide ingot, facilitating the subsequent diamond wire cutting process. At the end of cutting, the power is turned off first, followed by the mechanical cutting of the diamond wire. The reason for using mechanical diamond wire cutting to finish is that when cutting is near completion, the wafer is about to separate from the ingot. If the electrochemical reaction is still ongoing at this time, the bottom edge of the wafer will lose support and be excessively etched by the electrolyte, forming micron-level depressions. Etching may also cause local thinning of the edges, reducing mechanical strength and making subsequent processing prone to edge chipping.

[0052] And / or, the process also includes cleaning the silicon carbide wafers obtained after dicing.

[0053] The purpose of cleaning is mainly to remove the alkaline electrolyte remaining on the surface of the silicon carbide wafer.

[0054] After cleaning, the silicon carbide wafers need to be inspected for damage. The inspection method is not particularly limited and can be reasonably selected according to the actual situation. For example, XRD or etching method can be used to inspect the subsurface damage layer of the silicon carbide wafers.

[0055] In an optional embodiment, the electrochemically assisted diamond wire cutting process further includes a pretreatment, wherein the electrode connection is as follows: The SiC crystal rod is bonded to the upper surface of the anode substrate (such as ceramic or metal carrier plate). To ensure the conductivity of the bonding surface, conductive adhesive is used for bonding. The bonded anode substrate and SiC crystal rod are cured. After curing, they are installed on the cutting machine worktable and connected to the positive terminal of the power supply.

[0056] The diamond wire serves as the cathode and is connected to the negative terminal of the power supply.

[0057] The pretreatment of the electrolyte circulation system includes: cleaning the storage tank and then injecting the prepared alkaline electrolyte in the appropriate amount.

[0058] Power settings: Select DC mode or pulse mode.

[0059] In summary, the electrochemical-assisted diamond wire cutting process provided by this invention includes the following steps: (1) Pretreatment The SiC crystal rod is bonded to the upper surface of the anode substrate (such as ceramic or metal carrier plate). To ensure the conductivity of the bonding surface, conductive adhesive is used for bonding. The bonded anode substrate and SiC crystal rod are cured. After curing, they are installed on the cutting machine worktable and connected to the positive terminal of the power supply.

[0060] The diamond wire serves as the cathode and is connected to the negative terminal of the power supply.

[0061] Electrolyte circulation system: After cleaning the storage tank, inject the prepared alkaline electrolyte in the appropriate amount.

[0062] (2) Electrochemical Assisted Diamond Wire Cutting Process The cutting fluid circulation is started, current is applied, and the diamond wire is started to cut the fed silicon carbide crystal rod. The parameters (voltage, current and electrolyte pH value) are monitored and adjusted in real time. The cutting is completed.

[0063] The parameters of the cutting system are set as follows: the applied current density is 0.4 A / cm². 2 -0.6 A / cm 2 The applied voltage is 5V-12V; DC mode or pulse mode is used; the frequency of pulse mode is 100Hz-500Hz, and the duty cycle is 50%-70%; the cutting time of silicon carbide ingot is 30h-36h; the feed speed of silicon carbide ingot is 0.5mm / min-0.8mm / min.

[0064] The electrolyte parameters are set as follows: the electrolyte flow rate is 35L / min-45L / min; the electrolyte temperature is 40℃-50℃; the electrolyte pH is 13.5-14.0; the electrolyte mass concentration is 18wt%-22wt%; the solute in the electrolyte is selected from sodium hydroxide and / or potassium hydroxide, and the solvent is selected from at least one of deionized water, purified water, mineral water and ultrapure water.

[0065] The parameters of the diamond wire are set as follows: the wire diameter is 78μm-87μm; the wire tension is 18N-22N; the wire speed is 10m / s-14m / s; the wire diameter of the diamond wire is 70μm-75μm; the material of the diamond wire is selected from at least one of high carbon steel and tungsten alloy wire; the material of the diamond wire surface coating is selected from at least one of Ni and nickel-cobalt alloy; the average particle size of the diamond abrasive grains on the diamond wire surface is 8μm-12μm.

[0066] It should be noted that when cutting silicon carbide crystal rods, the cutting system should be powered on for 1-2 minutes before starting the cutting of the silicon carbide crystal rods; 8-12 seconds before the end of the cutting, the power should be turned off first and then the cutting of the diamond wire should be stopped.

[0067] (3) Post-processing The process after cutting also includes cleaning the silicon carbide wafers obtained from the cutting.

[0068] In a second aspect, the present invention provides a silicon carbide wafer, which is manufactured using an electrochemically assisted diamond wire cutting process as described in any of the foregoing embodiments.

[0069] In an optional embodiment, the silicon carbide wafer has at least one of the following characteristics: Feature 1: The thickness of the subsurface damage layer of the silicon carbide wafer is <1μm; Feature 2: The warpage of the silicon carbide wafer is 30μm-45μm.

[0070] Thirdly, the present invention provides a semiconductor device fabricated using a silicon carbide wafer as described in any of the foregoing embodiments.

[0071] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0072] Example 1 This embodiment provides a silicon carbide wafer fabricated using an electrochemically assisted diamond wire cutting process, specifically including the following steps: (1) Pretreatment The SiC crystal rod (200mm in diameter) is bonded to the upper surface of the anode base (such as ceramic or metal substrate). To ensure the conductivity of the bonding surface, conductive adhesive is used for bonding. The bonded anode base and SiC crystal rod are cured. After curing, they are installed on the cutting machine worktable and connected to the positive terminal of the power supply.

[0073] The diamond wire serves as the cathode and is connected to the negative terminal of the power supply.

[0074] Electrolyte circulation system: After cleaning the storage tank, inject the prepared alkaline electrolyte in the appropriate amount.

[0075] (2) Electrochemical Assisted Diamond Wire Cutting Process The cutting fluid circulation is started, current is applied, and the diamond wire is started to cut the fed silicon carbide crystal rod. The parameters (voltage, current and electrolyte pH value) are monitored and adjusted in real time. The cutting is completed.

[0076] The parameters of the cutting system are set as follows: the applied current density is 0.5 A / cm². 2 The applied voltage is 8V; DC mode or pulse mode is used; the frequency of pulse mode is 260Hz and the duty cycle is 60%; the cutting time of silicon carbide ingot is 34h; the feed speed of silicon carbide ingot is 0.65mm / min.

[0077] The electrolyte parameters are set as follows: electrolyte flow rate is 42 L / min; electrolyte temperature is 45℃; electrolyte pH is 13.5; electrolyte mass concentration is 20 wt%; the solute in the electrolyte is potassium hydroxide and the solvent is deionized water.

[0078] The parameters of the diamond wire are set as follows: the wire diameter is 80μm; the wire tension is 20N; the wire speed is 12m / s; the wire diameter of the main wire is 72μm; the main wire material is high carbon steel; the coating material on the surface of the diamond wire is Ni; and the average particle size of the diamond abrasive grains on the surface of the diamond wire is 8μm.

[0079] It should be noted that when cutting silicon carbide crystal rods, the cutting system should be powered on for 2 minutes before starting the cutting of the silicon carbide crystal rods; 10 seconds before the end of the cutting, the power should be turned off first and then the cutting of the diamond wire should be stopped.

[0080] (3) Post-processing The process after cutting also includes cleaning the silicon carbide wafers obtained from the cutting.

[0081] Comparative Example 1 This comparative example provides a silicon carbide wafer, which is prepared using a traditional diamond wire cutting process, specifically including the following steps: Pure mechanical cutting: The material is continuously cut by friction using a high-speed moving diamond wire (diamond abrasive grains fixed on the surface of the steel wire), and the SiC crystal structure is broken by the micro-cutting action of the abrasive grains.

[0082] The SiC crystal rod (200mm in diameter) is bonded to a glass or ceramic substrate using epoxy resin. After curing, it is loaded onto the cutting machine table.

[0083] Cutting fluid system: Inject non-conductive cutting fluid (PEG-based or mineral oil-based, containing dispersants and lubricants).

[0084] Diamond wire installation: The diamond wire is wound around the guide wheel system to form a mesh cutting surface. After the preparation is completed, the cutting fluid spray is started, the diamond wire runs at high speed, the crystal rod is fed at low speed, and the grinding and cutting are carried out continuously until the cutting is completed.

[0085] The linear velocity is 18 m / s, the tension is 28 N, and the ingot feed rate is 0.25 mm / min.

[0086] Test Example 1 This test case performs performance tests on the silicon carbide wafers prepared in Example 1 and Comparative Example 1, and compares and analyzes the process parameters and performance during the cutting process. The relevant results are summarized in Table 2.

[0087] Warpage was measured using a white light interferometer.

[0088] The thickness of the subsurface damage layer was measured using photoluminescence spectroscopy (PL).

[0089] Table 2 Comparative analysis results of process parameters and performance of Example 1 and Comparative Example 1

[0090] Test Example 2 This test example performs morphology analysis on the silicon carbide wafers prepared in Example 1 and Comparative Example 1, respectively. The relevant results are shown in [link to relevant data]. Figures 1-2 ;in, Figure 1 The image shows the morphology of the silicon carbide wafer obtained in Example 1. Figure 2 This is a morphological image of the silicon carbide wafer prepared in Comparative Example 1.

[0091] Combination Figure 1 and Figure 2 It can be seen that the surface of the silicon carbide wafer prepared in Example 1 is relatively flat and smooth, and there are no obvious cutting marks. The damage to the surface of the silicon carbide wafer is small, which is beneficial to simplifying the subsequent processing. The surface of the silicon carbide wafer in Comparative Example 1 has obvious mechanical cutting marks, and subsequent grinding and polishing are required to remove the cutting marks, which causes great damage to the surface of the silicon carbide wafer.

[0092] Experimental Example 1 This experiment investigated the effect of KOH concentration on silicon carbide cutting. All other process parameters were the same as in Example 1. The relevant results are summarized in Table 3. The current density was fixed at 0.5 A / cm². 2 The linear velocity is 12 m / s and the wire diameter is 80 μm.

[0093] Table 3. Effects of KOH concentration on cutting process

[0094] Conclusion: The optimal mass concentration of KOH is 20 wt%, which balances reaction efficiency, silicon carbide quality, and process stability.

[0095] Experimental Example 2 This experiment was used to investigate the effect of current density on silicon carbide cutting. The other process parameters were the same as in Example 1. The relevant results are summarized in Table 4. The following parameters were fixed: KOH mass concentration of 20wt%, line speed of 12 m / s, and line diameter of 80μm.

[0096] Table 4. Investigating the effect of current density on cutting process

[0097] Conclusion: The current density is 0.5 A / cm². 2 The optimal current density is >0.7 A / cm². 2 This could lead to over-etching and chipping at the chip edges.

[0098] Experimental Example 3 This experiment investigated the effect of linear velocity on silicon carbide cutting. All other process parameters were the same as in Example 1. The relevant results are summarized in Table 5. The following parameters were fixed: KOH mass concentration of 20 wt% and current density of 0.5 A / cm². 2 The wire diameter is 80μm.

[0099] Table 5. Investigating the effect of linear speed on cutting process

[0100] Conclusion: A line speed of 12m / s yields the best results; a line speed greater than 15m / s leads to a surge in line loss and increased damage.

[0101] Test Example 4 This experiment investigated the effect of diamond wire diameter on silicon carbide cutting. All other process parameters were the same as in Example 1. The relevant results are summarized in Table 6. The following parameters were fixed: KOH mass concentration of 20 wt% and current density of 0.5 A / cm². 2 The linear velocity is 12 m / s.

[0102] Table 6. Investigating the effect of diamond wire diameter on cutting process

[0103] Conclusion: With controllable wire breakage, 80μm wire diameter maximizes the film yield.

[0104] In summary, the electrochemically assisted diamond wire cutting process provided by this invention innovatively introduces an electrochemically assisted (ECM) mechanism. By applying a precise microcurrent to the silicon carbide ingot (anode) being cut in a specially formulated alkaline electrolyte environment, an easily removable softened silicon dioxide layer is formed at the cutting tip through an electrochemical reaction. The main role of the diamond abrasive grains changes from "hard grinding" the hard silicon carbide ingot body to "scraping away" the softened oxide layer, thereby significantly reducing the stress and damage caused by mechanical cutting of the ingot. Specifically, the cutting stress reduction is >60%, wafer warpage is controlled to <50μm, and the diamond wire diameter is successfully reduced to 80μm.

[0105] This invention's electrochemical-assisted diamond wire cutting process brings the dual benefits of a leap in wafer quality (low damage, high flatness) and a significant reduction in production costs (high yield, low wire loss, reduced post-processing). It represents a key technological breakthrough driving the silicon carbide power semiconductor industry towards higher performance and lower costs. Its "soft-to-hard" chemical-mechanical synergy provides a novel approach to solving the precision machining challenges of ultra-hard and brittle materials.

[0106] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrochemically assisted diamond wire cutting process, characterized in that, Includes the following steps: The silicon carbide crystal rod is detachably installed on the cutting system and connected to the positive terminal of the power supply; the diamond wire is connected to the negative terminal of the power supply; the electrolyte is an alkaline solution with a mass concentration of 15wt%-25wt%. The cutting system is started, current is applied, and the diamond wire cuts the fed silicon carbide crystal rod.

2. The electrochemically assisted diamond wire cutting process according to claim 1, characterized in that, During the silicon carbide ingot cutting process, the cutting system has at least one of the following characteristics: Feature one: The applied current density is 0.3 A / cm². 2 -0.7 A / cm 2 ; Feature 2: The applied voltage is 5V-12V; Feature 3: It adopts either DC mode or pulse mode; wherein, the frequency of pulse mode is 100Hz-500Hz and the duty cycle is 50%-70%; Feature 4: The cutting time for silicon carbide crystal rods is 30-36 hours; Feature 5: The feed rate of the silicon carbide crystal rod is 0.5 mm / min - 0.8 mm / min; Feature 6: The cutting system outputs 410-450 silicon carbide wafers per hour.

3. The electrochemically assisted diamond wire cutting process according to claim 1, characterized in that, During the silicon carbide ingot cutting process, the electrolyte has at least one of the following characteristics: Feature 1: The electrolyte flow rate is 30L / min-50L / min; Feature 2: The electrolyte temperature is 40℃-50℃; Feature 3: The pH of the electrolyte is 13.5-14.

0.

4. The electrochemically assisted diamond wire cutting process according to claim 1, characterized in that, During the silicon carbide ingot cutting process, the diamond wire has at least one of the following characteristics: Feature 1: The diameter of the diamond wire is 78μm-87μm; Feature 2: The tension of the diamond wire is 18N-22N; Feature three: the linear velocity of the diamond wire is 10m / s-14m / s.

5. The electrochemically assisted diamond wire cutting process according to claim 1, characterized in that, The diameter of the diamond wire is 70μm-75μm; The material of the diamond wire is selected from at least one of high carbon steel and tungsten alloy wire; The material of the coating on the diamond wire surface is selected from at least one of Ni and nickel-cobalt alloy; The average particle size of the diamond abrasive grains on the surface of the diamond wire is 8μm-12μm.

6. The electrochemically assisted diamond wire cutting process according to claim 1, characterized in that, The electrolyte concentration is 18wt%-22wt%; And / or, the solute in the electrolyte is selected from sodium hydroxide and / or potassium hydroxide, and the solvent is selected from at least one of deionized water, purified water, mineral water and ultrapure water.

7. The electrochemically assisted diamond wire cutting process according to claim 1, characterized in that, When cutting silicon carbide crystal rods, the cutting system is powered on for 1-2 minutes before cutting the silicon carbide crystal rods; 8-12 seconds before the end of the cutting, the power is turned off first and then the diamond wire cutting is stopped. And / or, the process may include cleaning the silicon carbide wafers obtained after dicing.

8. A silicon carbide wafer, characterized in that, It is prepared by the electrochemical-assisted diamond wire cutting process as described in any one of claims 1-7.

9. The silicon carbide wafer according to claim 8, characterized in that, The silicon carbide wafer has at least one of the following characteristics: Feature 1: The thickness of the subsurface damage layer of the silicon carbide wafer is <1μm; Feature 2: The warpage of the silicon carbide wafer is 30μm-45μm.

10. A semiconductor device, characterized in that, It is prepared using a silicon carbide wafer as described in any one of claims 8-9.

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