A method of cleaning a silicon carbide wafer

Abstract

The application discloses a cleaning method of a silicon carbide wafer, and the cleaning method comprises the following steps: S100, providing a spin rotating silicon carbide wafer to be cleaned; spraying and cleaning the silicon carbide wafer to be cleaned by using a water-air two-fluid, and obtaining a first wafer; S200, cleaning the first wafer by using a first cleaning solution, and obtaining a second wafer; the solute of the first cleaning solution comprises a polyoxyethylene ether surfactant, potassium pyrophosphate and a solubilizing agent; the solvent of the first cleaning solution is ultrapure water; S300, cleaning the second wafer by using an ammonia water solution, and obtaining a third wafer; S400, sequentially cleaning the third wafer by using an SC-2 cleaning solution and a hydrofluoric acid solution, and obtaining a fourth wafer; S500, spraying and cleaning the fourth wafer by using a water-air two-fluid, and obtaining a fifth wafer after drying. By using the first cleaning solution with the components of the polyoxyethylene ether surfactant, the potassium pyrophosphate and the solubilizing agent, the surface cleanliness of the silicon carbide wafer is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a method for cleaning silicon carbide wafers. Background Technology

[0002] Silicon carbide (SiC), as a typical third-generation semiconductor material, possesses superior characteristics compared to traditional semiconductor materials such as silicon (Si) and gallium arsenide (GaAs). These characteristics, including a wide bandgap, high electron mobility, high critical breakdown field strength, and high thermal conductivity, make it a promising candidate for applications in power electronics, high-frequency communications, high-temperature sensing, and high-power and high-temperature electronic devices. With the continuous expansion and deepening of these applications, the industry is placing increasingly stringent requirements on the quality and performance of silicon carbide wafers. Among these requirements, the cleanliness of the wafer surface is a key factor affecting subsequent device manufacturing processes and the final device performance. However, in the actual processing of large-size silicon carbide wafers, a series of necessary steps such as cutting, grinding, chemical mechanical polishing (CMP), and silicon film deposition inevitably introduce various types of contaminants, including organic residues, dust particles, and metal ions, onto the wafer surface. These contaminants not only significantly reduce the surface cleanliness of the silicon carbide wafer but may also interfere with subsequent device manufacturing processes, further reducing the device's performance and reliability.

[0003] Therefore, in order to increase the surface cleanliness of silicon carbide wafers, it is urgent to optimize a cleaning process that can produce silicon carbide wafers with high surface cleanliness and high cleaning efficiency. Summary of the Invention

[0004] One objective of this application is to provide a cleaning method for silicon carbide wafers, which is beneficial to improving the cleanliness of the silicon carbide wafer surface and enhancing cleaning efficiency and uniformity.

[0005] To achieve the above objectives, this application provides a method for cleaning silicon carbide wafers, comprising the following steps: S100, providing a self-rotating silicon carbide wafer to be cleaned, and using a water-air two-fluid jet cleaning method to obtain a first wafer; S200, cleaning the first wafer with a first cleaning solution to obtain a second wafer, wherein the solute of the first cleaning solution includes a polyoxyethylene ether surfactant, potassium pyrophosphate, and a solubilizer, and the solvent of the first cleaning solution is ultrapure water; S300, cleaning the second wafer with an ammonia solution to obtain a third wafer; S400, cleaning the third wafer sequentially with an SC-2 cleaning solution and a hydrofluoric acid solution to obtain a fourth wafer; S500, cleaning the fourth wafer by a water-air two-fluid jet cleaning method, and drying it to obtain a fifth wafer.

[0006] In some embodiments, the polyoxyethylene ether surfactant is an alkylphenol polyoxyethylene ether, and the solubilizer is sodium dimethylbenzenesulfonate.

[0007] In some embodiments, the preparation process of the first cleaning solution in step S200 includes the following steps: A100, preparing a cleaning stock solution with alkylphenol polyoxyethylene ether, potassium pyrophosphate and sodium dimethylbenzenesulfonate as solutes and ultrapure water as solvent, wherein the mass concentration of alkylphenol polyoxyethylene ether is 3wt.%~7wt.%, the mass concentration of potassium pyrophosphate is 3wt.%~7wt.%, and the mass concentration of sodium dimethylbenzenesulfonate is 3wt.%~7wt.%; A200, adding ultrapure water to the cleaning stock solution for dilution to obtain the first cleaning solution, wherein the volume ratio of the cleaning stock solution to ultrapure water is 1:(15~25).

[0008] In some embodiments, step S200 further includes: rotating the first wafer at a speed of 400 r / min to 800 r / min, cleaning the first wafer with the first cleaning solution for 10 s to 30 s, and obtaining the second wafer, wherein the flow rate of the first cleaning solution is 0.2 L / min to 0.5 L / min.

[0009] In some embodiments, step S300 further includes: rotating the second wafer at a speed of 400 r / min to 800 r / min, cleaning the second wafer with the ammonia solution for 10 s to 20 s, and then brushing the second wafer on both sides with a polyvinyl alcohol sponge brush to obtain the third wafer, wherein the molar concentration of the ammonia solution is 0.5 mol / L to 1.0 mol / L, and the flow rate of the ammonia solution is 0.2 L / min to 0.5 L / min.

[0010] In some embodiments, step S400 further includes: rotating the third wafer at a speed of 200 r / min to 400 r / min, cleaning the third wafer with the SC-2 cleaning solution for 10 s to 20 s, and then cleaning the third wafer with the hydrofluoric acid solution for 10 s to 20 s to obtain the fourth wafer, wherein the SC-2 cleaning solution is a mixed solution of hydrochloric acid, hydrogen peroxide and ultrapure water in a volume ratio of 1:(0.8~1.2):(20~40), the flow rate of the SC-2 cleaning solution is 0.2 L / min to 0.5 L / min, and the molar concentration of the hydrofluoric acid solution is 0.5 mol / L to 1.5 mol / L.

[0011] In some embodiments, in steps S100 and S500, the silicon carbide wafer to be cleaned and the fourth wafer rotate at a speed of 400 r / min to 800 r / min, and the water-air two-fluid cleaning time is 5 s to 30 s.

[0012] In some embodiments, step S500 further includes: after spray cleaning the fourth wafer with a water-air two-fluid system, rotating and drying the fourth wafer at a speed of 1800 r / min to 2500 r / min to obtain the fifth wafer.

[0013] In some embodiments, between step S200 and step S300, the following step is further included: S210, spraying the second wafer with ultrapure water, wherein the cleaning time of the ultrapure water is 15s~25s, and the rotation speed of the second wafer is 400r / min~800r / min; between step S300 and step S400, the following step is further included: S310, spraying the third wafer with ultrapure water, wherein the cleaning time of the ultrapure water is 5s~15s, and the rotation speed of the third wafer is 400r / min~800r / min.

[0014] Compared with the prior art, the beneficial effects of this application are as follows:

[0015] (1) This application enhances the cleaning effect on stubborn contaminants adhering to the surface of silicon carbide wafers by using a first cleaning solution composed of alkylphenol polyoxyethylene ether, potassium pyrophosphate, and sodium dimethylbenzenesulfonate. Alkylphenol polyoxyethylene ether, as a nonionic surfactant, possesses both hydrophilic polyoxyethylene chains and lipophilic alkylphenol groups, enhancing emulsification and dispersion, which is beneficial for removing oily contaminants from the surface of silicon carbide wafers. Potassium pyrophosphate, as an alkaline chelating agent, can complex metal ions to form stable soluble complexes and can also decompose residual inorganic matter. Furthermore, the solubilizer enhances the compatibility of the components in the first cleaning solution, increases the electrostatic repulsion between contaminant particles, and prevents salting out or re-aggregation or redeposition of contaminants onto the wafer surface. Through the synergistic effect of the components in the first cleaning solution, the cleaning effect on stubborn contaminants on the surface of silicon carbide wafers to be cleaned is further enhanced.

[0016] (2) Since the first cleaning solution used in this application can remove most of the contaminants attached to the surface of the silicon carbide wafer, a lower concentration of ammonia solution and hydrofluoric acid solution can be used for cleaning in the subsequent ammonia cleaning and hydrofluoric acid treatment steps. This helps to reduce the corrosive effect on the silicon carbide wafer, further reduce process cost consumption, and increase environmental friendliness. On the other hand, this application further improves the surface cleanliness of the silicon carbide wafer by using a multi-step cleaning process to progressively clean the silicon carbide wafer. Detailed Implementation

[0017] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0018] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variation thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements and may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0019] When a quantity, concentration, or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range is disclosed as “1 to 5”, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range includes its endpoints and all integers and fractions within that range.

[0020] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0021] The applicant found that most current industry practices for cleaning silicon carbide wafers employ RCA cleaning processes or methods with minor modifications. However, the market offers a limited variety of specialized cleaning agents for silicon carbide wafers, with inconsistent performance. Furthermore, as silicon carbide wafer sizes increase, ensuring cleaning uniformity becomes difficult. During the cleaning of large silicon carbide wafers, uneven cleaning fluid flow or contact with the carrier can hinder mass transfer at the edges, affecting the removal of contaminant particles and leading to incomplete or over-cleaning in certain areas. This, in turn, impacts the overall quality and consistency of the silicon carbide wafers. The introduction of two- or multi-step cleaning processes to further improve efficiency and effectiveness not only increases the complexity and cost of the cleaning process but also requires precise control of cleaning parameters at each step to ensure overall effectiveness.

[0022] Therefore, according to the first aspect of this application, a method for cleaning silicon carbide wafers is provided, comprising the steps of:

[0023] S100: Provide a self-rotating silicon carbide wafer to be cleaned, and use a water-air two-fluid jet cleaning method to obtain a first wafer;

[0024] S200. The first wafer is cleaned using a first cleaning solution to obtain a second wafer. The solute in the first cleaning solution includes polyoxyethylene ether surfactants, potassium pyrophosphate, and a solubilizer. The solvent in the first cleaning solution is ultrapure water.

[0025] S300: Clean the second wafer with an ammonia solution to obtain the third wafer;

[0026] S400, the third wafer is cleaned sequentially with SC-2 cleaning solution and hydrofluoric acid solution to obtain the fourth wafer;

[0027] S500: The fourth wafer is sprayed and cleaned using a water-air two-fluid system, and then dried to obtain the fifth wafer.

[0028] It is worth mentioning that this application enhances the cleaning effect on stubborn contaminants adhering to the surface of silicon carbide wafers by using a first cleaning solution composed of alkylphenol polyoxyethylene ether, potassium pyrophosphate, and a solubilizer. Alkylphenol polyoxyethylene ether, as a nonionic surfactant, possesses both hydrophilic polyoxyethylene chains and lipophilic alkylphenol groups, which enhances emulsification and dispersion, effectively removing oily contaminants from the silicon carbide wafer surface. Potassium pyrophosphate, as an alkaline chelating agent, can complex metal ions to form stable soluble complexes and decompose residual inorganic substances. Furthermore, the solubilizer enhances the compatibility of the components in the first cleaning solution and increases the electrostatic repulsion between contaminant particles, preventing salting out or re-aggregation or redeposition of contaminants onto the wafer surface. Through the synergistic effect of the components in the first cleaning solution, the cleaning effect on stubborn contaminants on the surface of the silicon carbide wafer is further enhanced, thereby obtaining a silicon carbide wafer with good surface cleanliness.

[0029] It should be understood that in step S100, large, loose contaminants on the surface of the silicon carbide wafer to be cleaned are first removed using a water-air two-fluid process. The precision chemical cleaning with the first cleaning solution in step S200 helps remove organic contaminants and some metal ions. Further, the ammonia solution in step S300 removes some residual metal ions and residues from the first cleaning solution. In step S400, the SC-2 cleaning solution and hydrofluoric acid solution remove heavy metal ions and prevent their redeposition on the wafer surface. The hydrofluoric acid solution is used to remove any oxide layer that may form on the silicon carbide wafer surface. Finally, the silicon carbide wafer undergoes a final physical rinse with a water-air two-fluid process in step S500 to ensure no chemical residue remains.

[0030] In some embodiments, the polyoxyethylene ether surfactant is an alkylphenol polyoxyethylene ether, a fatty alcohol polyoxyethylene ether, or a fatty acid polyoxyethylene ether; more preferably, the polyoxyethylene ether surfactant is an alkylphenol polyoxyethylene ether. The solubilizer can be an alkylbenzene sulfonate, an alkyl sulfonate, or a fatty alcohol polyoxyethylene ether sulfate; more preferably, the solubilizer is sodium dimethylbenzene sulfonate. It is worth noting that potassium pyrophosphate acts as an alkaline complexing agent, and sodium dimethylbenzene sulfonate is very stable in the alkaline environment provided by potassium pyrophosphate, without hydrolysis or degradation. Using stable sodium dimethylbenzene sulfonate can improve the solubility of alkylphenol polyoxyethylene ether, ensuring its full detergency. Through the synergistic effect of the three components, the stability and cleaning performance of the first cleaning solvent are enhanced.

[0031] In some embodiments, the first cleaning solution removes contaminants such as stubborn polishing fluid from the processing. The solutes in the first cleaning solution are nonylphenol polyoxyethylene ether, potassium pyrophosphate, and sodium dimethylbenzenesulfonate, and the solvent is ultrapure water. It is understood that nonylphenol polyoxyethylene ether, as a nonionic surfactant, provides emulsifying and dispersing power, removing oily contaminants from the silicon carbide surface. Because the first cleaning solution contains potassium pyrophosphate as an alkaline chelating agent, it provides a weakly alkaline environment for the nonylphenol polyoxyethylene ether, enabling it to emulsify organic contaminants more efficiently. On one hand, potassium pyrophosphate begins to complex with metallic contaminants, causing the contaminants to loosen and decompose. At this point, sodium dimethylbenzenesulfonate rapidly adsorbs onto the loosened contaminant particles, carrying them away from the silicon carbide wafer surface through electrostatic repulsion and steric hindrance, preventing the contaminants from re-aggregating or redepositing on the wafer surface. On the other hand, compared to strong alkalis such as sodium hydroxide or potassium hydroxide, potassium pyrophosphate provides a relatively mild alkaline environment, resulting in less corrosiveness to the silicon carbide wafer. Furthermore, the alkalinity provided by potassium pyrophosphate can decompose organic pollutants such as oils and fats into water-soluble fatty acid salts, thereby removing them.

[0032] In some embodiments, the preparation process of the first cleaning solution in step S200 includes the following steps: A100, preparing a cleaning stock solution with alkylphenol polyoxyethylene ether, potassium pyrophosphate and sodium dimethylbenzenesulfonate as solutes and ultrapure water as solvent, wherein the mass concentration of alkylphenol polyoxyethylene ether is 3wt.%~7wt.%, the mass concentration of potassium pyrophosphate is 3wt.%~7wt.%, and the mass concentration of sodium dimethylbenzenesulfonate is 3wt.%~7wt.%; A200, adding ultrapure water to the above cleaning stock solution for dilution to obtain the first cleaning solution, wherein the volume ratio of the cleaning stock solution to ultrapure water is 1:(15~25).

[0033] It should be understood that in step A100, the mass concentration of alkylphenol polyoxyethylene ether can be, but is not limited to, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, or 7 wt.%. More preferably, the mass concentration of alkylphenol polyoxyethylene ether is 4.5 wt.% to 5.5 wt.%. The mass concentration of potassium pyrophosphate can be, but is not limited to, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, or 7 wt.%. More preferably, the mass concentration of potassium pyrophosphate is 4.5 wt.% to 5.5 wt.%. The mass concentration of alkylphenol polyoxyethylene ether can be, but is not limited to, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, or 7 wt.%. More preferably, the mass concentration of alkylphenol polyoxyethylene ether is 4.5 wt.%~5.5 wt.%. In step A200, the volume ratio of the cleaning stock solution to ultrapure water is 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, and more preferably, the volume ratio of the cleaning stock solution to ultrapure water is 1:(18~22). It is worth mentioning that by diluting the cleaning stock solution, it is beneficial to reduce the concentration of each component in the first cleaning solution, further reducing the cost consumption in the cleaning process, and each component can still maintain stable cleaning efficiency after being diluted nearly 20 times.

[0034] In some embodiments, step S200 further includes: rotating the first wafer at a speed of 400 r / min to 800 r / min, cleaning the first wafer with a first cleaning solution for 10 s to 30 s, to obtain a second wafer, wherein the flow rate of the first cleaning solution is 0.2 L / min to 0.5 L / min. It is understood that by rotating the first wafer, dynamic cleaning can be achieved, further improving the uniformity of cleaning. On the other hand, by setting an appropriate flow rate of the first cleaning solution, cleaning efficiency and effect can be improved while further reducing cleaning costs, which is beneficial to improving economic benefits.

[0035] In some embodiments, the rotational speed of the first wafer in step S200 can be 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, or 800 r / min. More preferably, the rotational speed of the first wafer is 600 r / min. The cleaning time of the first cleaning solution on the first wafer is 10 s, 15 s, 20 s, 25 s, or 30 s, and the flow rate of the first cleaning solution is 0.2 L / min, 0.25 L / min, 0.3 L / min, 0.35 L / min, 0.4 L / min, 0.45 L / min, or 0.5 L / min. More preferably, the flow rate of the first cleaning solution is 0.32 L / min. It should be understood that the radial distance between the spray position of the first cleaning solution and the center of the first wafer is 1 / 6 to 1 / 2 of the diameter. More preferably, the radial distance between the spray position of the first cleaning solution and the center of the first wafer is 1 / 6, 1 / 5, 1 / 4, 1 / 3, or 1 / 2 of the diameter.

[0036] In some embodiments, step S300 further includes: rotating the second wafer at a speed of 400 r / min to 800 r / min, cleaning the second wafer with an ammonia solution for 10 s to 20 s, and then brushing both sides of the second wafer with a polyvinyl alcohol sponge brush to obtain a third wafer. The ammonia solution has a molar concentration of 0.5 mol / L to 1.0 mol / L, a flow rate of 0.2 L / min to 0.5 L / min, and the radial distance from the spray position of the ammonia solution to the center of the second wafer is 1 / 6 to 1 / 2 of its diameter. It should be understood that by setting appropriate ammonia solution concentration and flow rate, cleaning efficiency and effectiveness can be improved while further reducing cleaning costs, thus improving economic benefits.

[0037] It is worth mentioning that the ammonia solution can promote the detachment of solid particles from the surface of the second wafer and react chemically with metal ions to form soluble complexes. At the same time, the polyvinyl alcohol sponge brush can work in conjunction with the spraying of the ammonia solution to effectively remove stubborn stains and tiny particles from the surface of the second wafer and dissolve and remove them from the surface of the second wafer.

[0038] In some embodiments, in step S300, the rotational speed of the second wafer can be 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, or 800 r / min, and the cleaning time of the ammonia solution on the second wafer is 10 s, 15 s, or 20 s, respectively. The rotation direction of the polyvinyl alcohol sponge brush head is the same as the rotation of the second wafer, and the brush head rotation speed is 1000 r / min to 1500 r / min, preferably 1200 r / min. The diameter of the brush head is 20 mm to 30 mm, preferably 25 mm. During brushing, the sponge brush performs at least one reciprocating motion along the diameter direction of the second wafer, further improving the cleaning uniformity and cleaning effect. The flow rates of the ammonia solution are 0.2 L / min, 0.25 L / min, 0.3 L / min, 0.35 L / min, 0.4 L / min, 0.45 L / min, and 0.5 L / min. The molar concentration of the ammonia solution can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, and 1.0 mol / L. The ammonia solution is a mixed solution of concentrated ammonia and ultrapure water with a volume ratio of 1:(15~25), wherein the volume ratio of concentrated ammonia to ultrapure water can be 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, and 1:25. More preferably, the volume ratio of concentrated ammonia to ultrapure water is 1:(18~22). The radial distances from the spray position of the ammonia solution to the center of the second wafer are 1 / 6, 1 / 5, 1 / 4, 1 / 3, and 1 / 2 of the diameter.

[0039] In some embodiments, step S400 further includes: rotating the third wafer at a speed of 200 r / min to 400 r / min, cleaning the third wafer with SC-2 cleaning solution for 10 s to 20 s, and then cleaning the third wafer with hydrofluoric acid solution for 10 s to 20 s to obtain a fourth wafer. The SC-2 cleaning solution is a mixed solution of hydrochloric acid, hydrogen peroxide, and ultrapure water with a volume ratio of 1:(0.8~1.2):(20~40), the flow rate of the SC-2 cleaning solution is 0.2 L / min to 0.5 L / min, the molar concentration of the hydrofluoric acid solution is 0.5 mol / L to 1.5 mol / L, and the radial distance between the spray positions of the SC-2 cleaning solution and the hydrofluoric acid solution and the center of the third wafer is 1 / 6 to 1 / 2 of the diameter. It should be understood that the hydrochloric acid in the SC-2 cleaning solution can dissolve various metal impurities, and the hydrogen peroxide has strong oxidizing properties, which can prevent metal ions from being reduced and then re-deposited onto the wafer surface, thus improving cleaning efficiency. Therefore, the synergistic effect of the two solutes in the SC-2 cleaning solution can chemically react with various metals, oxidizing and dissolving various metal impurities to form water-soluble metal ions or metal complexes, thereby removing metal impurities from the surface of the third wafer. Furthermore, cleaning with hydrofluoric acid solution can remove the oxide layer on the surface of the third wafer while etching away metal impurities oxidized by ozone and embedded in the oxide layer, ensuring that even difficult-to-remove metal impurities are thoroughly washed away.

[0040] Understandably, because the preceding ammonia solution treatment step uses an ammonia solution with a lower concentration, the thickness of the oxide layer grown on the silicon carbide wafer surface due to the alkaline environment provided by the ammonia solution can be reduced. As the oxide layer thickness decreases, the concentration of the hydrofluoric acid solution can be reduced, thereby minimizing the corrosive effect on the silicon carbide wafer.

[0041] Furthermore, the SC-2 cleaning solution can more completely remove metallic impurities from the surface of the third wafer, which is beneficial for the subsequent hydrofluoric acid cleaning step. This is because when metallic impurities such as aluminum, calcium, and magnesium remain on the surface of the third wafer, they will immediately react with hydrofluoric acid to form water-insoluble fluorides that adhere to the surface of the third wafer, thus increasing the difficulty of post-processing.

[0042] In some embodiments, in step S400, the rotational speed of the third wafer can be 200 r / min, 250 r / min, 300 r / min, 350 r / min, or 400 r / min; the cleaning time of the SC-2 cleaning solution and hydrofluoric acid solution on the second wafer is 10 s, 15 s, or 20 s; and the flow rates of the SC-2 cleaning solution and hydrofluoric acid solution are 0.2 L / min, 0.25 L / min, 0.3 L / min, 0.35 L / min, 0.4 L / min, 0.45 L / min, or 0.5 L / min. More preferably, the flow rate of the SC-2 cleaning solution and hydrofluoric acid solution is 0.32 L / min. The molar concentration of the hydrofluoric acid solution can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, or 1.5 mol / L. The hydrofluoric acid solution is a mixed solution of hydrofluoric acid and ultrapure water with a volume ratio of 1:(20~40).

[0043] In some embodiments, in steps S100 and S500, the silicon carbide wafer to be cleaned and the fourth wafer rotate at a speed of 400 r / min to 800 r / min, and the water-air two-fluid cleaning time is 5 s to 30 s. It should be understood that the rotation speed of the silicon carbide wafer to be cleaned and the fourth wafer can be 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, or 800 r / min, and the water-air two-fluid cleaning time can be 5 s, 10 s, 15 s, 20 s, 25 s, or 30 s. Suitable water-air two-fluid cleaning conditions enhance the cleaning effect on the silicon carbide wafer and the fourth wafer. Furthermore, using water-air two-fluid jet cleaning of the silicon carbide wafer utilizes the impact force of high-speed water and air flow to quickly peel off and remove loose metal ions and impurity particles from the surface of the silicon carbide wafer.

[0044] In some embodiments, step S500 further includes: after spray cleaning the fourth wafer with a water-air two-fluid system, rotating and drying the fourth wafer at a speed of 1800 r / min to 2500 r / min to obtain a fifth wafer. The rotation speed of the fourth wafer can be 1800 r / min, 1900 r / min, 2000 r / min, 2100 r / min, 2200 r / min, 2300 r / min, 2400 r / min, or 2500 r / min; preferably, the rotation speed is 2000 r / min. By rotating the fourth wafer at high speed, moisture on the wafer surface can be removed from the wafer surface at an extremely fast rate without introducing any new chemical substances, resulting in a fifth wafer with high cleanliness uniformity and good cleanliness.

[0045] In some embodiments, between steps S200 and S300, the following step is further included: S210, spraying and cleaning the second wafer with ultrapure water, wherein the cleaning time of the ultrapure water is 15s~25s, the rotation speed of the second wafer is 400r / min~800r / min, and the radial distance from the spray position of the ultrapure water to the center of the second wafer is 1 / 6~1 / 2 of the diameter; between steps S300 and S400, the following step is further included: S310, spraying and cleaning the third wafer with ultrapure water, wherein the cleaning time of the ultrapure water is 5s~15s, the rotation speed of the third wafer is 400r / min~800r / min, and the radial distance from the spray position of the ultrapure water to the center of the second wafer is 1 / 6~1 / 2 of the diameter. By setting suitable ultrapure water cleaning conditions, not only can impurities removed in each step be removed in a timely manner, reducing the risk of impurities re-adhering to the surface of the silicon carbide wafer, but also the solution remaining on the surface of the silicon carbide wafer in the previous step can be removed. Furthermore, the impact force of the water flow can strip away and remove the metal ions and impurity particles removed from the surface of the silicon carbide wafer, keeping the surface of the silicon carbide wafer in a moist state and providing stable reaction conditions for subsequent steps.

[0046] In some embodiments, the silicon carbide wafers in each step remain in a self-rotating state. By superimposing the physical impact force brought about by the fluid and the self-rotation, it is easier to remove the tiny particles while preventing the impurity particles from being deposited again, thereby facilitating the thorough removal of the metal impurities encapsulated in the impurity particles.

[0047] According to a second aspect of this application, a silicon carbide wafer is provided, prepared by any of the cleaning methods described above. Through the multi-step cleaning process provided in this application, the silicon carbide wafer is cleaned layer by layer, further improving the surface cleanliness of the silicon carbide wafer.

[0048] Example 1

[0049] A method for cleaning silicon carbide wafers, comprising the following steps:

[0050] (1) Randomly select 15 8-inch silicon carbide wafers and put them on a single-wafer double-sided cleaning machine. Use water and air two-fluids to spray and clean the silicon carbide wafers. The wafer rotation speed is 600r / min and the cleaning time of the fluid is 20s. During the cleaning process, the wafers always maintain their own rotation.

[0051] (2) The cleaning stock solution (the main components of the cleaning stock solution are nonylphenol polyoxyethylene ether, potassium pyrophosphate and sodium dimethylbenzenesulfonate, each with a mass concentration of 5%) is diluted with ultrapure water at a dilution ratio of 1:20 to prepare the first cleaning solution. The silicon carbide wafer is then subjected to fluid cleaning. The flow rate of the first cleaning solution is 320 mL / min, the cleaning time is 20 s, the wafer rotation speed is 600 r / min, and the wafer is always rotating during the cleaning process. The radial distance between the spray position of the specific cleaning agent solution and the center of the wafer is 1 / 4 of the diameter.

[0052] (3) The silicon carbide wafer was sprayed with ultrapure water. The wafer rotation speed was 600 r / min and the ultrapure water cleaning time was 20 s. The wafer was always rotating during the cleaning process. The radial distance between the solution spray position and the center of the wafer was 1 / 4 of the diameter.

[0053] (4) Ammonia solution was used to clean the silicon carbide wafer. The ammonia solution was a mixture of concentrated ammonia and ultrapure water with a volume ratio of 1:30. The flow rate of the ammonia solution was 400 mL / min, the cleaning time was 15 s, the wafer rotation speed was 600 r / min, and the wafer was kept rotating during the cleaning process. The radial distance between the ammonia solution spray position and the center of the wafer was 1 / 4 of the diameter. Then, a PVA sponge brush was used to brush both sides of the silicon carbide wafer. The wafer and the brush head rotated in the same direction. The brush head rotated 1200 r / min and the diameter of the brush head was 25 mm. The brush head moved back and forth once along the diameter of the wafer.

[0054] (5) The silicon carbide wafer was sprayed with ultrapure water. The wafer rotation speed was 600 r / min and the ultrapure water cleaning time was 10 s. The wafer was always rotating during the cleaning process. The radial distance between the solution spray position and the center of the wafer was 1 / 4 of the diameter.

[0055] (6) The silicon carbide wafer was cleaned by fluid using SC-2 cleaning solution. The SC-2 cleaning solution was a mixed solution of hydrochloric acid / hydrogen peroxide / ultrapure water with a volume ratio of 1:1:30. The flow rate of the SC-2 cleaning solution was 320 mL / min, the cleaning time was 15 s, the wafer rotation speed was 250 r / min, and the wafer was kept rotating during the cleaning process. The radial distance between the spray position of the SC-2 cleaning solution and the center of the wafer was 1 / 4 of the diameter.

[0056] (7) The silicon carbide wafer is cleaned by hydrofluoric acid solution. The hydrofluoric acid solution is a mixture of hydrofluoric acid and ultrapure water with a volume ratio of 1:30. The flow rate of the hydrofluoric acid solution is 320 mL / min, the cleaning time is 15 s, the wafer rotation speed is 250 r / min, the wafer is always rotating during the cleaning process, and the radial distance between the hydrofluoric acid solution spray position and the center of the wafer is 1 / 4 of the diameter.

[0057] (8) The silicon carbide wafer was sprayed with ultrapure water. The wafer rotation speed was 600 r / min and the ultrapure water cleaning time was 20 s. The wafer was always rotating during the cleaning process. The radial distance between the solution spray position and the center of the wafer was 1 / 4 of the diameter.

[0058] (9) A water-air two-fluid jet cleaning was performed on the silicon carbide wafer. The wafer rotation speed was 500 r / min and the cleaning time of the fluid was 10 s. During the cleaning process, the wafer always maintained its own rotation. The radial distance between the solution spray position and the center of the wafer was 1 / 4 of the diameter.

[0059] (10) The silicon carbide wafer is dried by high-speed rotation at a speed of 2000 r / min to obtain a clean silicon carbide wafer.

[0060] Example 2

[0061] The difference between Example 2 and Comparative Example 1 is that in step (2), the cleaning solution contains fatty alcohol polyoxyethylene ether (replacing nonylphenol polyoxyethylene ether), sodium citrate (replacing potassium pyrophosphate), and sodium isopropylbenzenesulfonate (replacing sodium dimethylbenzenesulfonate).

[0062] Example 3

[0063] The difference between Example 3 and Comparative Example 1 is that the cleaning solution in step (2) contains nonylphenol polyoxyethylene ether, sodium hydroxide (replacing potassium pyrophosphate), and sodium dimethylbenzenesulfonate.

[0064] Comparative Example 1

[0065] The difference between Comparative Example 1 and Example 1 is that step (2) was not performed.

[0066] Comparative Example 2

[0067] The difference between Comparative Example 2 and Example 1 is that the cleaning solution in step (2) is mainly composed of nonylphenol polyoxyethylene ether and potassium pyrophosphate, each with a mass concentration of 7.5%.

[0068] Comparative Example 3

[0069] The difference between Comparative Example 3 and Example 1 is that the cleaning solution in step (2) is mainly composed of nonylphenol polyoxyethylene ether and sodium dimethylbenzenesulfonate, each with a mass concentration of 7.5%.

[0070] Comparative Example 4

[0071] The difference between Comparative Example 4 and Example 1 is that the cleaning solution in step (2) is mainly composed of potassium pyrophosphate and sodium dimethylbenzenesulfonate, each with a mass concentration of 7.5%.

[0072] Performance testing

[0073] The number of impurity particles on the surface of 15 cleaned silicon carbide wafers in Examples 1-3 and each comparative example was statistically analyzed. Particles larger than 0.5 μm were designated as large particles, particles larger than 0.3 μm but smaller than 0.5 μm were designated as baseline particles, and particles larger than 0.2 μm but smaller than 0.3 μm were designated as small particles. For ease of comparison between Example 1 and the comparative examples, Table 3 uses the average values ​​of impurity particles from the surface of the 15 sample groups for comparison.

[0074] Table 1: Surface testing of silicon carbide wafers in Example 1

[0075]

[0076] Table 2: Surface testing of silicon carbide wafers in Example 2

[0077]

[0078] Table 3: Surface testing of silicon carbide wafers in Example 3

[0079]

[0080] Table 4: Surface testing of silicon carbide wafers in Comparative Example 1

[0081]

[0082] Table 5: Surface testing of silicon carbide wafers in Comparative Example 2

[0083]

[0084] Table 6: Surface testing of silicon carbide wafers in Comparative Example 3

[0085]

[0086] Table 7: Surface testing of silicon carbide wafers in Comparative Example 4

[0087]

[0088] Table 8: Surface testing of silicon carbide wafers in Examples 1-3 and Comparative Examples 1-4

[0089]

[0090] As shown in Tables 1 to 8, the cleaning method provided in this application can reduce the number of small particulate contaminants on the surface of silicon carbide wafers by more than 90% and the number of large particulate contaminants by more than 67%, which significantly improves the cleanliness and performance of silicon carbide wafers and increases the yield accordingly. This further meets the demand for high-quality silicon carbide wafers in the semiconductor manufacturing field and has good economic benefits and application prospects.

[0091] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A method for cleaning silicon carbide wafers, characterized in that, Including the following steps: S100: Provide a self-rotating silicon carbide wafer to be cleaned, and use a water-air two-fluid jet cleaning method to obtain a first wafer; S200. The first wafer is cleaned using a first cleaning solution to obtain a second wafer. The solute in the first cleaning solution includes polyoxyethylene ether surfactants, potassium pyrophosphate, and a solubilizer. The solvent in the first cleaning solution is ultrapure water. S300: Clean the second wafer with an ammonia solution to obtain the third wafer; S400: The third wafer is cleaned sequentially with SC-2 cleaning solution and hydrofluoric acid solution to obtain the fourth wafer; S500: The fourth wafer is sprayed and cleaned by a water-air dual-fluid system, and then dried to obtain the fifth wafer.

2. The cleaning method according to claim 1, characterized in that, The polyoxyethylene ether surfactant is an alkylphenol polyoxyethylene ether, and the solubilizer is sodium dimethylbenzenesulfonate.

3. The cleaning method according to claim 2, characterized in that, The preparation process of the first cleaning solution in step S200 includes the following steps: A100, prepare a cleaning stock solution using alkylphenol polyoxyethylene ether, potassium pyrophosphate, and sodium dimethylbenzenesulfonate as solutes and ultrapure water as solvent, wherein the mass concentration of alkylphenol polyoxyethylene ether is 3wt.%~7wt.%, the mass concentration of potassium pyrophosphate is 3wt.%~7wt.%, and the mass concentration of sodium dimethylbenzenesulfonate is 3wt.%~7wt.%. A200. Dilute the cleaning stock solution with ultrapure water to obtain the first cleaning solution, wherein the volume ratio of the cleaning stock solution to ultrapure water is 1:(15~25).

4. The cleaning method according to claim 3, characterized in that, Step S200 further includes: rotating the first wafer at a speed of 400 r / min to 800 r / min, cleaning the first wafer with the first cleaning solution for 10 s to 30 s, and obtaining the second wafer, wherein the flow rate of the first cleaning solution is 0.2 L / min to 0.5 L / min.

5. The cleaning method according to claim 1, characterized in that, Step S300 further includes: rotating the second wafer at a speed of 400 r / min to 800 r / min, cleaning the second wafer with the ammonia solution for 10 s to 20 s, and then brushing the second wafer on both sides with a polyvinyl alcohol sponge brush to obtain the third wafer, wherein the molar concentration of the ammonia solution is 0.5 mol / L to 1.0 mol / L, and the flow rate of the ammonia solution is 0.2 L / min to 0.5 L / min.

6. The cleaning method according to claim 1, characterized in that, Step S400 further includes: rotating the third wafer at a speed of 200 r / min to 400 r / min, cleaning the third wafer with the SC-2 cleaning solution for 10 s to 20 s, and then cleaning the third wafer with the hydrofluoric acid solution for 10 s to 20 s to obtain the fourth wafer. The SC-2 cleaning solution is a mixed solution of hydrochloric acid, hydrogen peroxide and ultrapure water with a volume ratio of 1:(0.8~1.2):(20~40), the flow rate of the SC-2 cleaning solution is 0.2 L / min to 0.5 L / min, and the molar concentration of the hydrofluoric acid solution is 0.5 mol / L to 1.5 mol / L.

7. The cleaning method according to claim 1, characterized in that, In steps S100 and S500, the silicon carbide wafer to be cleaned and the fourth wafer rotate at a speed of 400 r / min to 800 r / min, and the cleaning time of the water and air two fluids is 5 s to 30 s.

8. The cleaning method according to claim 1, characterized in that, Step S500 further includes: after spray cleaning the fourth wafer with a water-air two-fluid system, the fourth wafer is rotated and dried at a speed of 1800 r / min to 2500 r / min to obtain the fifth wafer.

9. The cleaning method according to any one of claims 1-8, characterized in that, The step between step S200 and step S300 further includes: S210. The second wafer is sprayed with ultrapure water for cleaning, wherein the cleaning time of the ultrapure water is 15s~25s, and the self-rotation speed of the second wafer is 400r / min~800r / min. The step between step S300 and step S400 further includes: S310. The third wafer is sprayed with ultrapure water for cleaning, wherein the cleaning time of the ultrapure water is 5s to 15s, and the self-rotation speed of the third wafer is 400r / min to 800r / min.

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