Wafer cleaning method

Abstract

The application provides a wafer cleaning method, comprising the steps of: performing first cleaning on the wafer by using diluted SC-1 cleaning solution; performing first rinsing on the wafer; performing second cleaning on the wafer by using SC-2 cleaning solution; performing second rinsing on the wafer; wherein the first rinsing and the second rinsing are both performed by using hydrogen water generated by electrolytic ionized water. The wafer cleaning method provided by the application can effectively prevent re-adsorption caused by the wafer and the contaminant particles being charged with the same electric charge, and the chemical force of the hydrogen water can fully remove the particles adsorbed on the wafer surface, so that in the case of using the diluted SC-1 cleaning solution for the first cleaning, the subsequent rinsing by using the hydrogen water generated by electrolysis can still effectively remove the particle pollution on the wafer surface, which helps to reduce the cleaning cost while ensuring the wafer cleaning quality.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a wafer cleaning method. Background Technology

[0002] With increasing demands for environmental protection and cost reduction in semiconductor manufacturing, reducing the use of chemicals has become a crucial issue in the semiconductor industry. For wet cleaning processes, researchers are conducting extensive research on reducing chemical concentrations and deionized water (DIW) usage while maintaining contaminant removal capabilities, as well as developing new cleaning solvents. However, currently, there is no new method to replace existing RCA cleaning methods, and the increased use of chemicals and the resulting higher environmental costs remain a reality in the industry.

[0003] Although methods such as DIW cleaning, diluted hydrofluoric acid cleaning, and ozone cleaning, which are alternatives to RCA cleaning, have entered the evaluation stage, they have not yet shown significant effects. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a wafer cleaning method to solve the problems of large chemical usage, increased cleaning costs, and environmental pollution caused by the existing wafer cleaning methods.

[0005] To achieve the above and other related objectives, the present invention provides a wafer cleaning method, comprising the steps of:

[0006] The wafer was first cleaned using diluted SC-1 cleaning solution;

[0007] The wafer undergoes its first rinse;

[0008] The wafer was cleaned a second time using SC-2 cleaning solution;

[0009] The wafer undergoes a second rinse;

[0010] The first and second rinses were both carried out using hydrogen water generated during the electrolysis of ionized water.

[0011] Optionally, both the first and second rinses are performed in the anode chamber of the electrolytic cell, and water electrolysis continues during the rinsing process.

[0012] Optionally, during the water electrolysis process, the electrolyte added to the electrolytic cell includes sodium hydroxide.

[0013] Optionally, the concentration of the added electrolyte during water electrolysis is 10ppm-100ppm.

[0014] Optionally, after the second cleaning is completed, a step of drying the wafer is also included.

[0015] Alternatively, the method for drying the wafer includes the Marangoni drying process.

[0016] Optionally, the first and second rinses can be completed in 2-30 minutes.

[0017] Optionally, the concentration of SC-1 cleaning solution is diluted to half of the reference concentration, wherein the reference concentration is the volume ratio of ammonia water: hydrogen peroxide: deionized water = 1:1:5-1:2.

[0018] Optionally, in the SC-2 cleaning solution, the volume ratio of hydrochloric acid:hydrogen peroxide:deionized water is 1:1:6-1:2:8, wherein the concentration of hydrogen chloride is 37% and the concentration of hydrogen peroxide is 30%, and the operating temperature of the SC-1 and SC-2 cleaning solutions is 75-85℃.

[0019] Optionally, the hydrogen water has a pH of 1.7 and a redox potential of 1.3V.

[0020] As described above, the wafer cleaning method of the present invention has the following beneficial effects: In the wafer cleaning method provided by the present invention, both the first and second rinsing are performed using hydrogen water generated during the electrolysis of ionized water. This can effectively prevent the re-adsorption caused by the wafer and contaminant particles being charged with the same charge. Furthermore, the chemical force of hydrogen water can fully remove particles adsorbed on the wafer surface. Therefore, even when a diluted SC-1 cleaning solution is used in the first cleaning, the subsequent rinsing with hydrogen water generated by electrolysis can still effectively remove particulate contamination from the wafer surface. Thus, while ensuring the quality of wafer cleaning, the amount of chemicals used can be effectively reduced, which helps to reduce cleaning costs and reduce environmental pollution caused by chemical emissions. Attached Figure Description

[0021] Figure 1 The diagram shows the structure of a water electrolysis device.

[0022] Figure 2 The diagram shown is a schematic flowchart of the wafer cleaning method provided by the present invention. Detailed Implementation

[0023] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. For ease of explanation, when detailing the embodiments of the present invention, the cross-sectional views showing the device structure are partially enlarged, not according to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0024] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0025] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0026] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show components related to the present invention and are not drawn according to the actual number, shape, and size of the components in the actual implementation. In the actual implementation, the form, quantity, and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex. To keep the illustrations as concise as possible, not all structures are shown in the figures.

[0027] RCA cleaning is a common method for cleaning wafers in the semiconductor industry, but it requires a large number of chemicals, leading to increased cleaning costs and significant environmental impact due to the large amount of chemical emissions. To address this, this patent proposes a method for cleaning wafers using electrolyzed ionized water, which can replace existing standard RCA cleaning.

[0028] Generally, when water containing ions is electrolyzed, the ions move due to electrostatic attraction, causing the anode side to become acidic and the cathode side to become alkaline. Furthermore, due to the movement of electrons on the electrode surface, oxidizing substances are generated near the anode and reducing substances are generated near the cathode, thus producing acidic oxidized water on the anode side and alkaline reduced water on the cathode side. Based on this, the wafer cleaning method proposed in this invention uses electrolysis, which allows adjustment of the liquid's pH value and / or redox properties, as a means of preparing the cleaning solution.

[0029] For the production of electrolyzed ionized water, refer to Figure 1 As shown, the water electrolysis equipment consists of an anode chamber 1, a cathode chamber 3, and an intermediate chamber 2. An anode electrode 11 is provided on the side of the anode chamber 1, a cathode electrode 31 is provided on the side of the cathode chamber 3, and ion exchange membranes 21 are provided on both sides of the intermediate chamber 2. The flow rate of each chamber can be adjusted. Electrolyte is added to adjust the pH value and oxidation-reduction potential (ORP) to prepare a cleaning solution with a cleaning effect.

[0030] The reaction formula for water electrolysis is shown below:

[0031] 1) Anode: 2H₂O → O₂ + 4H⁺ + 4e⁻ Electrode potential Eo = 1.23V

[0032] 3H₂O → O₃ + 6H⁺ + 6e⁻ Electrode potential Eo = 1.51V

[0033] 2) Cathode: 4H+ + 4e- → 2H2 Electrode potential Eo = 0.00V

[0034] Thus, acidic anolyte water, i.e. hydrogen-containing water (hereinafter referred to as hydrogen water), is obtained on the anode side, while alkaline catholyte water is obtained on the cathode side. Because the anolyte water (i.e., hydrogen water) is acidic, it has an oxidizing effect and can therefore be used to remove metals / organic substances. Because the catholyte water is alkaline, it has a reducing effect and can therefore be used to remove particulate matter and prevent natural oxidation. In this invention, anolyte water will be used primarily.

[0035] Specifically, such as Figure 2 As shown, the present invention provides a wafer cleaning method, including the following steps:

[0036] S01: The wafer is first cleaned using diluted SC-1 cleaning solution. That is, the SC-1 cleaning in this invention is carried out at a concentration of SC-1 cleaning solution that is lower than the industry standard, which helps to reduce the amount of chemicals used. SC-1 cleaning is mainly to remove particulate impurities and polymers on the wafer. However, after this cleaning, there may still be particulate impurities and polymer residues on the wafer, so subsequent processes are required.

[0037] S02: First rinse of the wafer;

[0038] S03: The wafer is cleaned a second time using SC-2 cleaning solution. The first and second cleaning can be carried out in a vacuum environment or in an inert gas atmosphere, such as a nitrogen atmosphere. SC-2 cleaning mainly removes metal ions from the wafer surface.

[0039] S04: Perform a second rinse on the wafer;

[0040] The first and second rinsing processes both utilize hydrogen water generated during the electrolysis of ionized water. The reason for using hydrogen water generated by the electrolysis system for rinsing is that it can effectively prevent the re-adsorption of wafers and contaminant particles caused by the same charge. Furthermore, the chemical force of hydrogen water can effectively remove particles adsorbed on the wafer surface. Therefore, even when diluted SC-1 cleaning solution is used in the first cleaning, subsequent rinsing with hydrogen water generated by electrolysis can still effectively remove particulate contamination (such as organic particles) from the wafer surface. This approach effectively reduces the amount of chemicals used while ensuring wafer cleaning quality, thus helping to lower cleaning costs and reduce environmental pollution caused by chemical emissions.

[0041] The first and second rinsing processes can be carried out in a conventional rinsing tank. It is sufficient to promptly transfer the hydrogen-water produced during electrolysis to the rinsing tank. To ensure good cleaning quality and avoid a decrease in hydrogen concentration in the hydrogen-water due to excessive transport and / or storage time, it is preferable that the hydrogen-water is prepared and used immediately, and that the rinsing tank and the electrolytic cell are located as close as possible. In another example, the first and second rinsing can also be carried out in the anode chamber of the electrolytic cell, with continuous water electrolysis during the rinsing process to ensure the hydrogen-water has good oxidizing properties and ensures effective removal of contaminant particles.

[0042] To promote electrolysis, an electrolyte, such as sodium hydroxide, is typically added to the electrolytic cell during water electrolysis, but other salt electrolytes can also be used. In this embodiment, the concentration of the added electrolyte is required to be very low, for example, 10ppm-100ppm (including endpoint values; unless otherwise specified, all numerical ranges in this specification include endpoint values), and preferably 30-50ppm. In a preferred example, it is necessary to ensure that the pH of the hydrogen water produced after electrolysis is 1.7 or below, and the redox potential is 1.3V.

[0043] Preferably, after the second cleaning, the process includes a wafer drying step. In a preferred example, the wafer is dried using the Marangoni drying method, which utilizes the gradient change in surface tension of the wafer to achieve drying. Specifically, the Marangoni drying process involves first creating a thin water film on the outer surface of the wafer with flowing deionized water, followed by introducing a large amount of isopropanol gas to remove the water film, thus drying the wafer. This drying method has advantages such as being pollution-free and highly efficient. Because isopropanol (IPA) does not require heating and its vaporization is minimal, it poses no danger and offers relatively good safety, ensuring a good and safe drying effect. Of course, in other examples, a centrifugal isopropanol (IPA) vapor dryer or an inert gas air dryer can also be used; there are no strict limitations on this.

[0044] Preferably, the first and second rinses should last for 2-30 minutes, more preferably 5-10 minutes.

[0045] In this embodiment, it is preferable to dilute the concentration of SC-1 cleaning solution to half of the reference concentration. The reference concentration is a volume ratio of ammonia:hydrogen peroxide:deionized water of 1:1:5-1:2, wherein the concentration of ammonia is 27% and the concentration of hydrogen peroxide is 30%. The half-concentration standard is the optimal critical point determined by the inventors through extensive experiments. If the concentration of SC-1 is diluted to less than half of the reference concentration, the cleaning effect may be affected. Therefore, using half as the critical value can minimize the amount of chemicals used while ensuring the cleaning quality.

[0046] In this embodiment, the volume ratio of hydrochloric acid:hydrogen peroxide:deionized water in the SC-2 cleaning solution is 1:1:6-1:2:8, wherein the concentration of hydrogen chloride is 37% and the concentration of hydrogen peroxide is 30%, and the operating temperature of the SC-1 and SC-2 cleaning solutions is 75-85°C.

[0047] To evaluate the ability of the wafer cleaning method provided by this invention to clean organic particles, the inventors conducted an experiment. The experiment used multiple samples with a large number of polystyrene particles with a diameter of 0.3 μm attached to the contact holes for evaluation. The cleaning solutions included pure water, electrolyzed anolyte water (i.e., hydrogen water with a pH of 1.7 and a redox potential of 1.3 V), and APM cleaning solution (NH4OH / H2O2 / H2O).

[0048] Multiple samples were placed in cleaning tanks containing the three cleaning solutions mentioned above, and the structures of each cleaning tank were completely identical.

[0049] After the same cleaning time, the sample is taken out for testing, such as scanning electron microscopy analysis.

[0050] The test results showed that after washing with pure water, the number of polystyrene particles on the sample surface decreased slightly (approximately 5%), while after APM cleaning and then washing with electrolytic anolyte water, the polystyrene particles were completely removed. This indicates that electrolytic anolyte water has the same oxidizing power as APM cleaning, capable of oxidizing and decomposing the polystyrene particles. This sufficiently proves that electrolytic ionized water can achieve excellent cleaning capabilities with only very low concentrations of chemicals. Therefore, using electrolytic ionized water in wet cleaning processes can significantly reduce the amount of chemicals used.

[0051] Of course, the above evaluation process is only a summary of a large number of experiments. The inventors have confirmed through experiments that it shows basically similar results when used to evaluate other types of organic particles, which will not be elaborated on one by one.

[0052] The wafer cleaning method of this invention is applicable to wafer cleaning at various process stages, such as cleaning wafers after grinding and cleaning wafers after photolithography. In addition to semiconductor wafers, it is also suitable for cleaning solar panels.

[0053] In summary, this invention provides a wafer cleaning method, comprising the steps of: performing a first cleaning of the wafer using diluted SC-1 cleaning solution; performing a first rinsing of the wafer; performing a second cleaning of the wafer using SC-2 cleaning solution; and performing a second rinsing of the wafer; wherein both the first and second rinsing are performed using hydrogen water generated during the electrolysis of deionized water. The wafer cleaning method provided by this invention, by using hydrogen water generated during the first and second rinsing, can effectively prevent the re-adsorption of contaminant particles caused by the wafer and contaminant particles carrying the same charge. Furthermore, the chemical force of hydrogen water can effectively remove particles adsorbed on the wafer surface. Therefore, even when using diluted SC-1 cleaning solution in the first cleaning, the subsequent rinsing with hydrogen water generated by electrolysis can still effectively remove particulate contamination from the wafer surface. Thus, while ensuring wafer cleaning quality, it can effectively reduce the amount of chemicals used, helping to reduce cleaning costs and environmental pollution caused by chemical emissions. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0054] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A wafer cleaning method, characterized in that, Including steps, The wafer was first cleaned using diluted SC-1 cleaning solution, with the concentration of SC-1 cleaning solution diluted to half of the reference concentration; the reference concentration was ammonia water: hydrogen peroxide: deionized water with a volume ratio ranging from 1:1:5 to 1:

2. The wafer undergoes its first rinse; The wafer was cleaned a second time using SC-2 cleaning solution; The wafer undergoes a second rinse; The first and second rinsing processes both use hydrogen water generated during the electrolysis of deionized water, and both are carried out in the anode chamber of the electrolytic cell. Electrolysis of water continues during the rinsing process. During the electrolysis of water, the electrolyte added to the electrolytic cell includes sodium hydroxide, and the concentration of the added electrolyte is 30ppm-50ppm. The pH value of the hydrogen water is 1.7, and the oxidation-reduction potential is 1.3V.

2. The wafer cleaning method according to claim 1, characterized in that, After the second cleaning is completed, the wafer is also dried.

3. The wafer cleaning method according to claim 2, characterized in that, Methods for drying wafers include the Marangoni drying process.

4. The wafer cleaning method according to claim 1, characterized in that, The first and second rinses should last for 2-30 minutes.

5. The wafer cleaning method according to claim 1, characterized in that, In SC-2 cleaning solution, the volume ratio of hydrochloric acid: hydrogen peroxide: deionized water ranges from 1:1:6 to 1:2:8, with a hydrogen chloride concentration of 37% and a hydrogen peroxide concentration of 30%. The operating temperature for both SC-1 and SC-2 cleaning solutions is 75-85℃.

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