Cleaning method for removing post-polish wafer surface residue marks and micro-particles

Abstract

This invention discloses a cleaning method for removing residual marks and microparticles on the surface of a polished wafer, comprising: performing a primary cleaning of the wafer with pure water; wiping and cleaning the wafer surface with ethanol; immersing the wafer in pure water to remove the ethanol after cleaning; immersing the wafer in a first cleaning solution, followed by immersion in pure water; immersing the wafer in a second cleaning solution, followed by immersion in pure water; immersing the wafer in a third cleaning solution, followed by immersion in pure water; immersing the wafer in the first cleaning solution again, followed by immersion in pure water; finally immersing the wafer in pure water for mega-sound cleaning while simultaneously introducing carbon dioxide gas, and then spin-drying the wafer after cleaning.

Description

Technical Field

[0001] This application belongs to the field of semiconductor material cleaning processes, and particularly relates to a cleaning method for removing residual marks and microparticles on the surface of a wafer after polishing. Background Technology

[0002] In semiconductor device manufacturing, polishing residues remain on the surface of wafers after polishing, especially due to human-caused contamination, such as fingerprints, particles, and other organic and inorganic impurities. These impurities exist on the wafer surface in atomic or ionic states, or in thin film or particle form, leading to various defects in semiconductor devices. Therefore, wafers must be rigorously cleaned to remove surface contaminants including fingerprints, organic matter, static ions, heavy metal ions, and particulate matter.

[0003] In existing technologies, the cleaning method for solving the problem of wafer surface contamination is usually as follows: performing primary cleaning on the wafer; cleaning the wafer after primary cleaning with HF solution; placing the wafer after cleaning with HF solution into pure water at a certain temperature for a period of time; removing the wafer from the pure water, cleaning the wafer with DHF (diluted hydrogen fluoride) solution, and placing the wafer after cleaning with DHF solution into pure water at a certain temperature for a period of time.

[0004] However, both existing cleaning methods require an additional hydrofluoric acid immersion step to remove the oxide layer on the wafer surface. This cleaning process introduces fluorine into the wafer surface, which is neither economical nor environmentally friendly. Moreover, the particulate matter residue measured after cleaning is between 1000-2000, which will have a significant impact on the performance of semiconductor devices. Summary of the Invention

[0005] This application provides a cleaning method for removing residual marks and microparticles on the surface of a wafer after polishing, in order to solve the problems in the prior art where the wafer surface cleaning process introduces fluorine elements into the wafer surface, causing environmental pollution, and the residual particulate matter after cleaning is between 1000-2000, which reduces the performance of semiconductor devices.

[0006] This application provides a cleaning method for removing residual marks and microparticles on the surface of a polished wafer. The method includes: performing a primary cleaning of the polished wafer with pure water; wiping the surface of the wafer after the primary cleaning with ethanol, and then immersing the wafer in pure water for the first time after cleaning; immersing the wafer after the first immersion in pure water with a first cleaning solution, and then immersing the wafer in pure water a second time; immersing the wafer after the second immersion in pure water with a second cleaning solution, and then immersing the wafer in pure water a third time; immersing the wafer after the third immersion in pure water with a third cleaning solution, and then immersing the wafer in pure water a fourth time; immersing the wafer after the fourth immersion in pure water with the first cleaning solution, and then immersing the wafer in pure water a fifth time; and then, for the wafer immersed in pure water five times, passing carbon dioxide gas through it for megasonic cleaning, and then spin-drying the cleaned wafer.

[0007] In one implementation, the concentration of the ethanol is 98%.

[0008] In one implementation, the composition ratio of the first cleaning solution is: ammonia: hydrogen peroxide: water = 1:1:5-15.

[0009] In one implementation, the composition ratio of the second cleaning solution is: hydrochloric acid: hydrogen peroxide: water = 1:1:5-15.

[0010] In one implementation, the composition ratio of the third cleaning solution is: sulfuric acid: hydrogen peroxide = 5-9:1.

[0011] In one implementation, the temperature of the third cleaning solution is controlled at 100-120 degrees Celsius.

[0012] In one implementation, the temperatures of the first cleaning solution and the second cleaning solution are controlled at 50-70 degrees Celsius.

[0013] In one implementation, the temperature of the pure water immersion is controlled at 50-70 degrees Celsius.

[0014] In one implementation, the spin-drying step specifically involves: placing the cleaned wafer on a vacuum suction cup, and then starting a drying device to rotate the wafer adsorbed on the vacuum suction cup at high speed to spin-dry the wafer.

[0015] In one implementation, the pure water is placed in a hot water bath suitable for wafers with a thickness of 0.19-0.75 mm.

[0016] As can be seen from the above scheme, the cleaning method for removing residual marks and microparticles on the wafer surface after polishing provided in this application can remove residues on the wafer surface without introducing fluorine. Specifically, ethanol is used to wipe and remove fingerprints and residual pure water from the wafer surface; the first cleaning solution removes organic matter and static ions; the second cleaning solution removes heavy metal ions; the third cleaning solution removes organic impurities; and a second cleaning with the first cleaning solution removes the static electricity generated by washing the wafer surface with water. Simultaneously, the introduction of carbon dioxide for megasonic cleaning removes static electricity, reduces the resistivity of pure water, and removes micron-sized particles, thus controlling the particle residue to below 100 particles or even less than 10 particles, thereby obtaining a higher performance wafer. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart illustrating a cleaning method for removing residual marks and microparticles from the surface of a polished wafer, as provided in this application. Detailed Implementation

[0019] The embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described below do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application as detailed in the claims.

[0020] It should be noted that the simplified explanations of terms used in this application are merely for the purpose of facilitating understanding of the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meanings.

[0021] The terms "first," "second," "third," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar or related objects or entities and do not necessarily imply a specific order or sequence, unless otherwise specified. It should be understood that such terms are interchangeable where appropriate. The terms "comprising" and "having," and any variations thereof, are intended to cover but not exclude other inclusions; for example, a product or device comprising a series of components is not necessarily limited to all components explicitly listed, but may include other components not explicitly listed or inherent to such product or device.

[0022] Currently, after wafers are etched with dilute hydrofluoric acid, the etched wafer surface needs to be cleaned. However, after drying, liquid marks or particulate contaminants remain on the wafer surface. This is because the wafer surface has been etched with dilute hydrofluoric acid, and the common cleaning method is to directly rinse the wafer surface with a cleaning solution to wash away the etching residue. However, the etched wafer surface is then exposed to air, making it prone to reacting with impurities in the air to generate particles, or air pollutants may settle on the wafer surface. Since the etched wafer surface is hydrophobic, these impurities are not easily washed away during cleaning, leaving liquid marks or particulate defects on the wafer surface even after drying.

[0023] Existing wafer surface cleaning processes introduce fluorine into the wafer surface, which is neither economical nor environmentally friendly. Furthermore, significant amounts of particulate matter remain after cleaning, greatly impacting the performance of semiconductor devices. Highly integrated devices require wafer cleaning to minimize contamination of the wafer surface caused by the solution itself or the process itself. Simultaneously, more economical and less polluting processes are needed to obtain higher-performance wafers.

[0024] This application discloses a cleaning method for removing residual marks and microparticles from the surface of a wafer after polishing. See [link to relevant documentation]. Figure 1 The method includes the following steps:

[0025] S1, perform a primary cleaning of the polished wafer using pure water; S2, wipe the surface of the wafer after the primary cleaning using ethanol, and then immerse the wafer in pure water for the first time after cleaning; S3, immerse the wafer in a first cleaning solution (i.e., SC1 solution) and then immerse it in pure water for a second cleaning; S4, immerse the wafer in a second cleaning solution (i.e., SC2 solution) and then immerse it in pure water for the second cleaning. S5. The wafer immersed in the liquid is immersed three times with pure water; S6. The wafer after being immersed three times with pure water is immersed and cleaned with a third cleaning solution (i.e., SC3 solution), and the wafer after being immersed in the SC3 solution is immersed four times with pure water; S7. The wafer after being immersed four times with pure water is immersed and cleaned with SC1 solution, and the wafer after being immersed in the SC1 solution is immersed five times with pure water; S8. The wafer after being immersed five times in pure water is subjected to megasonic cleaning by passing carbon dioxide gas through it, and the cleaned wafer is then spun dry.

[0026] For example, this application provides a cleaning method for removing residual marks and microparticles on the surface of a polished wafer. First, the polished wafer surface is initially cleaned with pure water. Then, the wafer surface is wiped with ethanol. Next, the wiped wafer is soaked in pure water again. Then, the wafer is soaked and cleaned in SC1 solution, SC2 solution, and SC3 solution in sequence. After soaking and cleaning with SC1 solution, SC2 solution, and SC3 solution, it is necessary to soak it in pure water for a period of time. Then, the wafer is soaked and cleaned again with SC1 solution and pure water. Finally, the wafer is soaked in pure water for mega-sound cleaning while CO2 (carbon dioxide) gas is introduced. After cleaning, the wafer is spun dry.

[0027] In some embodiments, the concentration of the ethanol is 98%.

[0028] For example, this application provides a cleaning method for removing residual marks and microparticles from the surface of a polished wafer, using 98% ethanol. Furthermore, in this application, the ethanol is applied by wiping, which removes fingerprints and water from the wafer surface. Specifically, fingerprints are aggregated organic impurities that can separate into layers, and ethanol can dissolve them, achieving a better cleaning effect.

[0029] In some embodiments, the composition ratio of the first cleaning solution is: ammonia: hydrogen peroxide: water = 1:1:5-15.

[0030] For example, the composition ratio of the first cleaning solution (i.e., SC1 solution) in this application is: ammonia: hydrogen peroxide: water = 1:1:5-15. Specifically, the water ratio in the SC1 solution can be selected from 5 to 15. Furthermore, immersing and cleaning the wafer with the SC1 solution can remove organic matter and electrostatic ions from the wafer surface.

[0031] In some embodiments, the composition ratio of the second cleaning solution is: hydrochloric acid: hydrogen peroxide: water = 1:1:5-15.

[0032] For example, the composition ratio of the second cleaning solution (i.e., SC2 solution) in this application is: hydrochloric acid: hydrogen peroxide: water = 1:1:5-15. Specifically, the water ratio in the SC2 solution can be selected from 5 to 15. Furthermore, using the SC2 solution to soak and clean the wafer can remove heavy metal ions from the wafer surface.

[0033] In some embodiments, the composition ratio of the third cleaning solution is: sulfuric acid: hydrogen peroxide = 5-9:1.

[0034] For example, the composition ratio of the third cleaning solution (i.e., SC3 solution) in this application is: sulfuric acid: hydrogen peroxide = 5-9:1. Specifically, the sulfuric acid ratio in the SC3 solution can be selected from 5-9. Furthermore, using the SC3 solution to soak and clean the wafer can remove organic impurities from the wafer surface.

[0035] In some embodiments, the temperature of the SC3 solution is controlled at 100-120 degrees Celsius.

[0036] In some embodiments, the temperature of the SC1 solution and the SC2 solution is controlled at 50-70 degrees Celsius.

[0037] In some embodiments, the temperature of the pure water immersion is controlled at 50-70 degrees Celsius.

[0038] In some embodiments, the spin-drying step specifically involves: placing the cleaned wafer on a vacuum suction cup, and then starting a drying device to rotate the wafer adsorbed on the vacuum suction cup at high speed to spin-dry the wafer.

[0039] For example, this application concludes with megasonic cleaning using carbon dioxide to remove static electricity, reduce water resistivity, and remove micron-sized particles. Specifically, the number of particles remaining can be controlled to be below 100, and preferably below 10. Furthermore, after cleaning, the wafer is placed on a vacuum chuck. Once the spin-drying equipment is activated, the wafer is adsorbed onto the vacuum chuck and rotated at high speed, utilizing centrifugal force for drying.

[0040] It should be noted that this application uses SC1 solution to perform a second immersion cleaning of the wafer, which can remove the surface static electricity generated by water washing.

[0041] In some embodiments, the pure water is placed in a hot water bath suitable for wafers with a thickness of 0.19-0.75 mm.

[0042] Specifically, the solution provided in this application can eliminate residual marks and microparticles on the surface of a wafer after polishing. The specific implementation steps are as follows.

[0043] Example 1:

[0044] (1) Perform primary cleaning of the wafer with pure water;

[0045] (2) Wipe the wafer surface with 98% ethanol; after cleaning, soak it in pure water at 50 degrees Celsius until the ethanol is removed;

[0046] (3) The wafer was soaked and cleaned with SC1 solution at 50 degrees Celsius. After being soaked in SC1 solution, the wafer was soaked in pure water at 50 degrees Celsius until the SC1 solution was removed. The composition ratio of SC1 solution is: ammonia water: hydrogen peroxide: water = 1:1:5.

[0047] (4) The wafer was soaked and cleaned with SC2 solution at 50 degrees Celsius. After being soaked in SC2 solution, the wafer was soaked in pure water at 50 degrees Celsius until the SC2 solution was removed. The composition ratio of SC2 solution is: hydrochloric acid: hydrogen peroxide: water = 1:1:5.

[0048] (5) The wafer was soaked and cleaned with SC3 solution at 100 degrees Celsius. After soaking in SC3 solution, the wafer was soaked in pure water at 50 degrees Celsius until the SC3 solution was removed. The composition ratio of SC3 solution was: sulfuric acid: hydrogen peroxide = 5:1.

[0049] (6) The wafer is soaked and cleaned again with SC1 solution at 50 degrees Celsius. The wafer soaked in SC1 solution is then soaked in pure water at 50 degrees Celsius until the SC1 solution is removed.

[0050] (7) Finally, the wafer is immersed in pure water and CO2 gas is introduced while performing megason cleaning. After cleaning, the wafer is placed on a vacuum suction cup. After the equipment is started, the wafer is adsorbed on the vacuum suction cup and rotated at high speed, and dried by centrifugal force.

[0051] As can be seen from the above technical solutions, in this embodiment, pure water at 50 degrees Celsius, SC1 solution, SC2 solution, and SC3 solution at 100 degrees Celsius are specifically used. Further, in this embodiment, the composition ratio of SC1 solution is: ammonia: hydrogen peroxide: water = 1:1:5; the composition ratio of SC2 solution is: hydrochloric acid: hydrogen peroxide: water = 1:1:5; and the composition ratio of SC3 solution is: sulfuric acid: hydrogen peroxide = 5:1.

[0052] Example 2:

[0053] (1) Perform primary cleaning of the wafer with pure water;

[0054] (2) Wipe the wafer surface with 98% ethanol; after cleaning, soak it in pure water at 50-70 degrees Celsius until the ethanol is removed;

[0055] (3) The wafer was soaked and cleaned with SC1 solution at 60 degrees Celsius. After being soaked in SC1 solution, the wafer was soaked in pure water at 60 degrees Celsius until the SC1 solution was removed. The composition ratio of SC1 solution was: ammonia: hydrogen peroxide: water = 1:1:10.

[0056] (4) The wafer is soaked and cleaned with SC2 solution at 60 degrees Celsius. After soaking in SC2 solution, the wafer is soaked in pure water at 60 degrees Celsius until the SC2 solution is removed. The composition ratio of SC2 solution is: hydrochloric acid: hydrogen peroxide: water = 1:1:10.

[0057] (5) The wafer was soaked and cleaned with SC3 solution at 110 degrees Celsius. After soaking in SC3 solution, the wafer was soaked in pure water at 60 degrees Celsius until the SC3 solution was removed. The composition ratio of SC3 solution was: sulfuric acid: hydrogen peroxide = 7:1.

[0058] (6) The wafer is soaked and cleaned again with SC1 solution at 60 degrees Celsius. The wafer soaked in SC1 solution is then soaked in pure water at 60 degrees Celsius until the SC1 solution is removed.

[0059] (7) Finally, the wafer is immersed in pure water and CO2 gas is introduced while performing megason cleaning. After cleaning, the wafer is placed on a vacuum suction cup. After the equipment is started, the wafer is adsorbed on the vacuum suction cup and rotated at high speed, and dried by centrifugal force.

[0060] As can be seen from the above technical solutions, in this embodiment, pure water at 50-70 degrees Celsius, SC1 solution and SC2 solution at 60 degrees Celsius, and SC3 solution at 110 degrees Celsius are specifically used. Further, in this embodiment, the composition ratio of SC1 solution is: ammonia: hydrogen peroxide: water = 1:1:10; the composition ratio of SC2 solution is: hydrochloric acid: hydrogen peroxide: water = 1:1:10; and the composition ratio of SC3 solution is: sulfuric acid: hydrogen peroxide = 7:1.

[0061] Example 3:

[0062] (1) Perform primary cleaning of the wafer with pure water;

[0063] (2) Wipe the wafer surface with 98% ethanol; after cleaning, soak it in pure water at 70 degrees Celsius until the ethanol is removed;

[0064] (3) The wafer was soaked and cleaned with SC1 solution at 70 degrees Celsius. After being soaked in SC1 solution, the wafer was soaked in pure water at 70 degrees Celsius until the SC1 solution was removed. The composition ratio of SC1 solution is: ammonia: hydrogen peroxide: water = 1:1:15.

[0065] (4) The wafer was soaked and cleaned with SC2 solution at 70 degrees Celsius. After soaking in SC2 solution, the wafer was soaked in pure water at 70 degrees Celsius until the SC2 solution was removed. The composition ratio of SC2 solution is: hydrochloric acid: hydrogen peroxide: water = 1:1:15.

[0066] (5) The wafer was soaked and cleaned with SC3 solution at 120 degrees Celsius. After soaking in SC3 solution, the wafer was soaked in pure water at 70 degrees Celsius until the SC3 solution was removed. The composition ratio of SC3 solution was: sulfuric acid: hydrogen peroxide = 9:1.

[0067] (6) The wafer is soaked and cleaned again with SC1 solution at 70 degrees Celsius. The wafer soaked in SC1 solution is then soaked in pure water at 70 degrees Celsius until the SC1 solution is removed.

[0068] (7) Finally, the wafer is immersed in pure water and CO2 gas is introduced while performing mega-sound cleaning. After cleaning, the wafer is placed on a vacuum suction cup. After the equipment is started, the wafer is adsorbed on the vacuum suction cup and rotated at high speed, and dried by centrifugal force.

[0069] As can be seen from the above technical solutions, in this embodiment, pure water at 70 degrees Celsius, SC1 solution, SC2 solution, and SC3 solution at 120 degrees Celsius are specifically used. Further, in this embodiment, the composition ratio of SC1 solution is: ammonia: hydrogen peroxide: water = 1:1:15; the composition ratio of SC2 solution is: hydrochloric acid: hydrogen peroxide: water = 1:1:15; and the composition ratio of SC3 solution is: sulfuric acid: hydrogen peroxide = 9:1.

[0070] As can be seen from the above specific embodiments, the cleaning steps adopted in this application are: pure water - ethanol - pure water - SC1 solution - pure water - SC2 solution - pure water - SC3 solution - pure water - SC1 solution - pure water - CO2 mega-acoustic cleaning and drying. The cleaning of this application can remove residues on the wafer surface without introducing fluorine. The alcohol is used to wipe, on the one hand removing fingerprints remaining on the wafer surface, and on the other hand removing water. Fingerprints are aggregated organic impurities that will be layered, and alcohol can dissolve the fingerprints. The role of SC1 solution is to remove organic matter and static ions; the role of SC2 solution is to remove heavy metal ions; the role of SC3 solution is to remove organic impurities. The role of cleaning with SC1 solution again is to remove the surface static force generated by water washing. The role of CO2 mega-acoustic cleaning is to remove static electricity, reduce the resistivity of water, and remove fine particles smaller than micrometers. It can control the particle residue to less than 100 particles, and further, it can control the residue to less than 10 particles. After each cleaning solution treatment, it is soaked in pure water for a period of time.

[0071] This application provides a cleaning method for removing residual marks and microparticles from the surface of polished wafers. It solves the problem in existing technologies that involve adding a hydrofluoric acid immersion step to remove the oxide layer on the wafer surface, thereby introducing fluorine. The introduction of fluorine is neither economical nor environmentally friendly, and the residual particulate matter after cleaning is measured to be between 1000-2000 particles, which can significantly impact the performance of semiconductor devices. Currently, the development of highly integrated devices requires wafer cleaning to minimize contamination on the wafer surface caused by the solution itself or the process. Simultaneously, it also demands the use of more economical and less polluting processes to obtain higher-performance wafers. Therefore, this application uses a first cleaning solution, a second cleaning solution, a third cleaning solution with different ratios and temperatures, and pure water for immersion cleaning to more efficiently and environmentally remove various residues on the wafer surface, remove fine particles smaller than micrometers, and control the particle residue to less than 100 particles, more preferably to less than 10 particles, greatly improving the cleaning effect and making the wafer surface cleaning process more efficient, environmentally friendly and economical, thereby obtaining high-performance wafers for production manufacturing.

[0072] Throughout this specification, references to "multiple embodiments," "some embodiments," "one embodiment," or simply "embodiment" indicate that a specific feature, component, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, phrases such as "in multiple embodiments," "in some embodiments," "in at least another embodiment," or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, specific features, components, or characteristics can be combined in any suitable manner. Therefore, without limitation, a specific feature, component, or characteristic shown or described in connection with one embodiment may be combined, in whole or in part, with features, components, or characteristics of one or more other embodiments. Such modifications and variations are intended to be included within the scope of this application.

[0073] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A cleaning method for removing residual marks and microparticles from the surface of a polished wafer, characterized in that, include: The polished wafer was initially cleaned using pure water. The wafer surface was wiped clean with ethanol after the initial cleaning, and then the wafer was soaked in pure water for the first time after cleaning. The wafers that have been initially soaked in the pure water are then soaked in the first cleaning solution and then soaked in the pure water a second time. The wafers after being soaked twice in pure water were soaked and cleaned with a second cleaning solution, and the wafers soaked in the second cleaning solution were soaked three times in pure water. The wafers that had been soaked three times in the pure water were then soaked in a third cleaning solution and then soaked in pure water four times. The wafers that had been soaked in the first cleaning solution four times with the pure water were then soaked in the first cleaning solution five times with pure water. The wafers that have been immersed in pure water five times are then subjected to mega-sonic cleaning by passing carbon dioxide gas through them, and the wafers are then spun dry after cleaning. The first cleaning solution comprises ammonia, hydrogen peroxide, and water; the second cleaning solution comprises hydrochloric acid, hydrogen peroxide, and water; and the third cleaning solution comprises sulfuric acid and hydrogen peroxide. The ratio of sulfuric acid to hydrogen peroxide is 5-9:

1. Specifically, the composition ratio of the first cleaning solution is 1:1:5 (ammonia:hydrogen peroxide:water), and the composition ratio of the second cleaning solution is 1:1:5 (hydrochloric acid:hydrogen peroxide:water).

2. The method according to claim 1, characterized in that, The concentration of the ethanol is 98%.

3. The method according to claim 1, characterized in that, The temperature of the third cleaning solution is controlled at 100-120 degrees Celsius.

4. The method according to claim 1, characterized in that, The temperature of the first cleaning solution and the second cleaning solution is controlled at 50-70 degrees Celsius.

5. The method according to claim 1, characterized in that, The temperature of the pure water immersion is controlled between 50 and 70 degrees Celsius.

6. The method according to claim 1, characterized in that, The spin-drying step specifically involves placing the cleaned wafer on a vacuum suction cup, and then starting the drying equipment to rotate the wafer adsorbed on the vacuum suction cup at high speed to spin-dry the wafer.

7. The method according to claim 1, characterized in that, The pure water is placed in a hot water tank, which is suitable for wafers with a thickness of 0.19-0.75 mm.

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