Method for removing impurities from wafer surface

Abstract

The present invention relates to the field of microelectronics technology, and discloses a method for removing impurities on the surface of a wafer, comprising: cleaning the wafer with an alkaline solution; cleaning the wafer with an ethanol solution; placing the wafer in a vacuum chamber, and heating the wafer. By adopting the embodiment of the present invention, the fluorine ion impurities remaining on the surface of the wafer can be effectively removed, thereby improving the yield of the wafer.

Description

Technical Field

[0001] The invention relates to the field of microelectronic technology, and in particular to a method for removing impurities from the surface of a wafer. Background Art

[0002] During the semiconductor processing, impurities are likely to remain on the surface of the wafer. Currently, the impurities remaining on the surface of the wafer are generally fluoride ions, which will affect the quality of the wafer and reduce the yield of the wafer. Therefore, a method is needed to remove the fluoride ion impurities remaining on the surface of the wafer. Summary of the invention

[0003] The purpose of the embodiment of the present invention is to provide a method for removing impurities on the surface of a wafer, which can effectively remove fluorine ion impurities remaining on the surface of the wafer, thereby improving the yield of the wafer.

[0004] In order to solve the above technical problems, an embodiment of the present invention provides a method for removing impurities from the surface of a wafer, comprising:

[0005] The wafer is cleaned using an alkaline solution;

[0006] Cleaning the wafer with an ethanol solution;

[0007] The wafer is placed in a vacuum chamber and heated.

[0008] As an improvement of the above solution, the wafer is cleaned with an alkaline solution, specifically:

[0009] The wafer is soaked and cleaned with an alkaline solution, wherein the soaking time is 5-10 minutes.

[0010] As an improvement of the above solution, the alkaline solution is a potassium hydroxide solution.

[0011] As an improvement of the above scheme, the pH value of the potassium hydroxide solution is 9.

[0012] As an improvement of the above scheme, the temperature of the ethanol solution is 23-25°C.

[0013] As an improvement of the above solution, the wafer is placed in a vacuum chamber and heated, specifically:

[0014] The wafer is placed in a vacuum chamber, heated, and simultaneously subjected to a vacuum treatment, so that the vacuum degree in the vacuum chamber fluctuates back and forth within a preset range.

[0015] As an improvement of the above solution, the preset range is 400-500 Pa.

[0016] As an improvement of the above solution, the method further includes:

[0017] Activated carbon is used to adsorb the gas exhausted from the vacuum chamber.

[0018] As an improvement of the above solution, the time for heating the wafer is 15-25 minutes, and the temperature for heating the wafer is 250-300°C.

[0019] Implementing the embodiments of the present invention has the following beneficial effects:

[0020] The embodiment of the present invention provides a method for removing impurities on the surface of a wafer, firstly using an alkaline solution to clean the wafer so that the fluoride ions on the surface of the wafer form salts and precipitate, thereby preliminarily removing the fluoride ions on the surface of the wafer; then using an ethanol solution to clean the wafer so that the fluoride ions on the surface of the wafer react with ethanol, thereby further removing the fluoride ions on the surface of the wafer; then placing the wafer in a vacuum chamber, heating the wafer so that the fluoride ions on the surface of the wafer volatilize, thereby further removing the fluoride ions on the surface of the wafer. Based on the above analysis, it can be seen that the method for removing impurities on the surface of a wafer provided by the embodiment of the present invention can effectively remove the fluoride ion impurities remaining on the surface of the wafer, thereby improving the yield of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of a method for removing impurities from the surface of a wafer in an embodiment provided by the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] See also Figure 1 As shown, it is a flow chart of a method for removing impurities from the surface of a wafer in an embodiment provided by the present invention. The method for removing impurities from the surface of a wafer comprises the following steps:

[0024] S10, cleaning the wafer with an alkaline solution;

[0025] S11, cleaning the wafer with an ethanol solution;

[0026] S12, placing the wafer in a vacuum chamber, and heating the wafer.

[0027] In this embodiment, the wafer is first cleaned with an alkaline solution so that the fluoride ions on the surface of the wafer form salts and precipitate, thereby preliminarily removing the fluoride ions on the surface of the wafer; then the wafer is cleaned with an ethanol solution so that the fluoride ions on the surface of the wafer react with the ethanol, thereby further removing the fluoride ions on the surface of the wafer; then the wafer is placed in a vacuum chamber and heated so that the fluoride ions on the surface of the wafer volatilize, thereby further removing the fluoride ions on the surface of the wafer. Based on the above analysis, it can be seen that the method for removing impurities on the surface of the wafer provided by the embodiment of the present invention can effectively remove the fluoride ion impurities remaining on the surface of the wafer, thereby improving the yield of the wafer.

[0028] It should be noted that, after in-depth research by the inventors, the inventors found that: step S10 mainly removes fluorine ion dust with a diameter of 10-15 nanometers, step S11 mainly removes fluorine ion dust with a diameter of 5-10 nanometers, and step S12 mainly removes fluorine ion dust with a diameter of 0.5-5 nanometers. Therefore, the method for removing impurities on the wafer surface provided in this embodiment can specifically remove fluorine ion dust of different diameters, thereby achieving good removal effect.

[0029] Wherein, the alkaline solution can be a sodium hydroxide solution or a potassium hydroxide solution.

[0030] As an optional embodiment, the concentration of the ethanol solution is 99%.

[0031] As an optional embodiment, the step S10 is specifically as follows:

[0032] The wafer is soaked and cleaned with an alkaline solution, wherein the soaking time is 5-10 minutes.

[0033] In this embodiment, the wafer is cleaned by immersion cleaning, which can improve the cleaning effect and thus improve the effect of removing impurities on the wafer surface.

[0034] Furthermore, the alkaline solution is a potassium hydroxide solution.

[0035] Furthermore, the pH of the potassium hydroxide solution is 9.

[0036] After the inventors conducted in-depth research on the pH of the potassium hydroxide solution, the inventors found that: when the pH of the selected potassium hydroxide solution is 8, the reaction rate of the potassium hydroxide solution with the fluoride ions on the wafer surface is slow, which is not beneficial to production; when the pH of the selected potassium hydroxide solution is above 9, not only the cost is high, but also the reaction rate of the potassium hydroxide solution with the fluoride ions on the wafer surface is too fast, which is not conducive to process control; when the pH of the selected potassium hydroxide solution is 9, the reaction rate of the potassium hydroxide solution with the fluoride ions on the wafer surface is relatively moderate, which can achieve a good wafer surface impurity removal effect, and the cost is moderate.

[0037] As an optional embodiment, the temperature of the ethanol solution is 23-25°C.

[0038] After in-depth research on the temperature of the ethanol solution by the inventors, the inventors found that when the temperature of the ethanol solution is 23-25° C., a good impurity removal effect on the wafer surface can be achieved in a shorter time.

[0039] As one of the optional embodiments, the step of placing the wafer in a vacuum chamber and heating the wafer is specifically as follows:

[0040] The wafer is placed in a vacuum chamber, heated, and simultaneously subjected to a vacuum treatment, so that the vacuum degree in the vacuum chamber fluctuates back and forth within a preset range.

[0041] In this embodiment, the change in vacuum degree can make the fluorine ions volatilize more fully, thereby further improving the removal effect of impurities on the wafer surface.

[0042] Preferably, the preset range is 400-500 Pa.

[0043] Furthermore, the method further comprises:

[0044] Activated carbon is used to adsorb the gas exhausted from the vacuum chamber.

[0045] In this embodiment, the gas exhausted from the vacuum chamber is treated by activated carbon so that the fluoride ions are adsorbed, thereby preventing them from being directly discharged into the air and causing environmental pollution.

[0046] In a specific embodiment, activated carbon with a surface area of ​​more than 1500 m2 / g may be installed at the end of the vacuum tube of the vacuum chamber, so as to achieve adsorption treatment of the gas exhausted from the vacuum chamber.

[0047] As one of the optional embodiments, the time for heating the wafer is 15-25 minutes.

[0048] After the inventors conducted in-depth research on the heating temperature of the wafer, the inventors found that when the wafer is heated for 15-25 minutes, a good effect of removing impurities from the wafer surface can be achieved.

[0049] The implementation process of this scheme is described below through the first specific embodiment, including: first, potassium hydroxide is added to deionized water to make the pH value 9, thereby preparing a potassium hydroxide solution, then the wafer is immersed in the potassium hydroxide solution for 5 minutes, so that the fluorine on its surface forms salt, thereby precipitating, so as to remove the fluorine ion dust with a diameter of 10-15 nanometers; then the wafer is taken out and immersed in an ethanol solvent for cleaning, and the ethanol cleaning temperature is 23°C to remove the fluorine ion dust with a diameter of 5-10 nanometers; then the wafer is taken out and placed in a vacuum chamber, the wafer is heated to keep the temperature at 250°C, and the vacuum is evacuated at the same time, and the vacuum degree fluctuates back and forth between 400-500 Pa, and the processing time of the vacuum chamber is 25 minutes. By heating, the fluorine ions on the surface of the wafer can be volatilized, and the change in vacuum degree can make the fluorine ions volatilize more fully, so as to remove the fluorine ion dust with a diameter of 0.5-5 nanometers. Then, by observing the processed wafer, it is found that there is no fluorine ion residue on the wafer surface, so a good effect of removing impurities on the wafer surface is achieved.

[0050] The implementation process of this scheme is described below through the second specific embodiment, including: first, potassium hydroxide is added to deionized water to make the pH value 9, thereby preparing a potassium hydroxide solution, then the wafer is immersed in the potassium hydroxide solution for 7.5 minutes, so that the fluorine on its surface forms salt, thereby precipitating, so as to remove the fluorine ion dust with a diameter of 10-15 nanometers; then the wafer is taken out and immersed in an ethanol solvent for cleaning, and the ethanol cleaning temperature is 24°C to remove the fluorine ion dust with a diameter of 5-10 nanometers; then the wafer is taken out and placed in a vacuum chamber, the wafer is heated to keep the temperature at 275°C, and the vacuum is evacuated at the same time, and the vacuum degree fluctuates back and forth between 400-500 Pa, and the processing time of the vacuum chamber is 20 minutes. By heating, the fluorine ions on the surface of the wafer can be volatilized, and the change in vacuum degree can make the fluorine ions volatilize more fully, so as to remove the fluorine ion dust with a diameter of 0.5-5 nanometers. Then, by observing the processed wafer, it is found that there is no fluorine ion residue on the surface of the wafer, so that a good removal effect of impurities on the surface of the wafer is achieved.

[0051] The implementation process of this scheme is described below through the third specific embodiment, including: first, potassium hydroxide is added to deionized water to make the pH value 9, thereby preparing a potassium hydroxide solution, then the wafer is immersed in the potassium hydroxide solution for 10 minutes, so that the fluorine on its surface forms salt, thereby precipitating, so as to remove the fluorine ion dust with a diameter of 10-15 nanometers; then the wafer is taken out and immersed in an ethanol solvent for cleaning, and the ethanol cleaning temperature is 25°C to remove the fluorine ion dust with a diameter of 5-10 nanometers; then the wafer is taken out and placed in a vacuum chamber, the wafer is heated to keep the temperature at 300°C, and the vacuum is evacuated at the same time, and the vacuum degree fluctuates back and forth between 400-500 Pa, and the processing time of the vacuum chamber is 15 minutes. By heating, the fluorine ions on the surface of the wafer can be volatilized, and the change in vacuum degree can make the fluorine ions volatilize more fully, so as to remove the fluorine ion dust with a diameter of 0.5-5 nanometers. Then, by observing the processed wafer, it is found that there is no fluorine ion residue on the surface of the wafer, so a good effect of removing impurities on the surface of the wafer is achieved.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for removing impurities from a wafer surface, characterized in that: include: The wafer is cleaned with an alkaline solution to remove fluoride ion dust with a diameter of 10-15 nanometers; The wafer is cleaned with an ethanol solution to remove fluorine ion dust with a diameter of 5-10 nanometers; The wafer is placed in a vacuum chamber and heated to remove 0.5-5 nanometer fluorine ion dust.

2. The method for removing impurities from the surface of a wafer according to claim 1, characterized in that: The alkaline solution is used to clean the wafer, specifically: The wafer is soaked and cleaned with an alkaline solution, wherein the soaking time is 5-10 minutes.

3. The method for removing impurities from the surface of a wafer according to claim 2, characterized in that: The alkaline solution is a potassium hydroxide solution.

4. The method for removing impurities from the surface of a wafer according to claim 3, characterized in that: The pH of the potassium hydroxide solution is 9.

5. The method for removing impurities from the surface of a wafer according to claim 1, characterized in that: The temperature of the ethanol solution is 23-25°C.

6. The method for removing impurities from the surface of a wafer according to claim 1, characterized in that: Placing the wafer in a vacuum chamber and heating the wafer is specifically performed as follows: The wafer is placed in a vacuum chamber, heated, and simultaneously subjected to a vacuum treatment, so that the vacuum degree in the vacuum chamber fluctuates back and forth within a preset range.

7. The method for removing impurities from the surface of a wafer according to claim 6, characterized in that: The preset range is 400-500 Pa.

8. The method for removing impurities from the surface of a wafer according to claim 6, characterized in that: The method further comprises: Activated carbon is used to adsorb the gas exhausted from the vacuum chamber.

9. The method for removing impurities from the surface of a wafer according to claim 1, characterized in that: The time for heating the wafer is 15-25 minutes, and the temperature for heating the wafer is 250-300°C.

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