A method for reducing silicon residue on wafer surface

Abstract

The invention discloses a method for reducing silicon residue on the surface of a wafer, and belongs to the field of semiconductor technology. The method for reducing silicon residue on the surface of a wafer of the invention comprises the following steps: (1) dissolving a surfactant and a strong base and weak acid salt in deionized water to obtain a wafer cleaning solution; (2) treating the wafer with the wafer cleaning solution and then rinsing it with deionized water; (3) treating the wafer with an HF aqueous solution and then rinsing it with deionized water; (4) treating the wafer with an alkaline solution and then rinsing it with deionized water, and then drying the rinsed wafer; the invention first uses a surfactant and a strong base and weak acid salt to preliminarily clean the wafer, and then sequentially acid washes and alkaline washes. This cleaning method combination can effectively reduce the silicon concentration on the wafer surface, improve the cleaning quality of the wafer, and ensure the flatness of the wafer surface after cleaning with as little cleaning agent as possible. At the same time, the method provided by the technical solution of the invention is simple to operate, short in time, and can be applied in practice.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and in particular relates to a method for reducing silicon residue on a wafer surface. Background Art

[0002] Gallium arsenide and indium phosphide wafers are important compound semiconductor materials with superior properties such as high thermal conductivity, high electron saturation drift velocity, and high radiation impedance. They are used in the manufacture of high-frequency, high-speed microwave devices and optoelectronic integrated circuits. In the rapidly developing fields of optical fiber communications, lasers, millimeter-wave heterojunction bipolar transistors, high electron mobility transistors, etc., gallium arsenide and indium phosphide are the preferred substrate materials. To meet the production of the above devices, it is necessary to use molecular beam epitaxy or organometallic compound vapor phase epitaxy on the surface of a high-quality substrate to grow the epitaxial structure and design the device structure. The surface of gallium arsenide and indium phosphide single crystal wafers must have good surface flatness and the final cleaning must remove surface particles and metal ions.

[0003] At present, Chinese patent CN 102064090A discloses a method for cleaning gallium arsenide wafers; Chinese patent CN102456549A discloses a method for cleaning indium phosphide wafers, both of which can remove surface particles and metal ions to obtain better surface flatness. However, pollution from cleaning equipment, silicon impurities in clean room air, silicon impurities in deionized water during cleaning, and silicon dioxide in polishing liquid during chemical mechanical polishing may remain on the wafer surface. During the epitaxial growth of the device, Si as a shallow donor impurity will cause an N-type conductive layer to be generated at the interface between the substrate and the epitaxial layer, thereby affecting the performance of the epitaxial device. The above-disclosed patents do not have a good effect on reducing the surface silicon concentration. Therefore, it is necessary to develop a method to reduce the residual silicon concentration on the wafer surface and improve the epitaxial qualified rate of the device. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for reducing silicon residue on the surface of a wafer with high efficiency.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for reducing silicon residue on the surface of a wafer, comprising the following steps:

[0006] (1) dissolving a surfactant and a strong base and a weak acid salt in deionized water to obtain a wafer cleaning solution;

[0007] (2) treating the wafer with a wafer cleaning solution and then rinsing with deionized water;

[0008] (3) treating the wafer with HF aqueous solution and then rinsing with deionized water;

[0009] (4) After treating the wafer with an alkaline solution, the wafer is rinsed with deionized water and then dried.

[0010] The present invention first uses a surfactant and a strong base and weak acid salt to perform preliminary cleaning on the wafer, and then sequentially performs acid cleaning and alkali cleaning. This cleaning method combination can effectively reduce the concentration of residual silicon on the wafer surface with as little cleaning agent as possible, improve the cleaning quality of the wafer, and ensure the flatness of the wafer surface after cleaning, thereby avoiding damage to the wafer performance caused by the N-type conductive layer formed at the interface of the epitaxial layer formed by the wafer surface and the residual silicon.

[0011] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, the surfactant is a non-ionic surfactant.

[0012] Nonionic surfactants are preferred here because, on the one hand, they have good emulsifying, dispersing and solubilizing effects, and on the other hand, the entire molecule of nonionic surfactants is uncharged in the solvent, that is, its groups do not dissociate in the solvent, but instead form hydrogen bonds with water molecules in the form of polar functional groups, thereby avoiding the positive or negative charge carried by the dissociation from being adsorbed on the chip surface and having an adverse effect on the chip performance and subsequent cleaning process.

[0013] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, the surfactant is an alkylphenol polyoxyethylene ether type nonionic surfactant.

[0014] Alkylphenol polyoxyethylene ethers are preferred as components of the wafer cleaning solution of the present invention because they have good wetting, penetration and washing abilities, and also have good emulsification ability. At the same time, they have good chemical stability and are not easily destroyed by strong acids and strong bases. Therefore, they can be well combined with strong base and weak acid salts to form a wafer cleaning solution with excellent ability to remove impurities from the wafer surface in the early stage.

[0015] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, the surfactant includes nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, and dodecyl polyoxyethylene ether.

[0016] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, the mass ratio of the surfactant to the strong base and weak acid salt is (1.2-2.0):1.

[0017] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, the mass ratio of the surfactant to the strong base and weak acid salt is (1.2-1.6):1.

[0018] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer of the present invention, the ratio of the sum of the masses of the surfactant and the salt of the strong base and the weak acid to the volume of deionized water is (15-25) g:1L.

[0019] When the mass ratio of the surfactant to the strong base weak acid salt is within the range of (1.2-2.0):1, especially within the range of (1.2-1.6):1, and the ratio of the sum of the masses of the surfactant and the strong base weak acid salt to the volume of deionized water is within the range of (15-25) g:1L, the purpose of preliminary cleaning of the wafer can be more effectively achieved, so that when the same volume of HF aqueous solution and alkaline solution are used for cleaning in the later stage, more wafers can be cleaned. From a side view, it means that the wafer cleaning agent in the above range can effectively reduce the use of HF aqueous solution and alkaline solution in the later stage, thereby ensuring safe production to a certain extent, and having economic and environmental benefits.

[0020] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, the strong base and weak acid salt include at least one of sodium carbonate, potassium carbonate, sodium acetate, sodium phosphate, sodium silicate and potassium acetate.

[0021] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, in the step (2), the treatment time is 3-10 minutes and the treatment temperature is 40-45°C.

[0022] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer of the present invention, in the step (2), the treatment method includes static immersion or rotating the wafer in the wafer cleaning solution.

[0023] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, in the step (3), the mass concentration of HF in the HF aqueous solution is 5-40%, the treatment time is 10-60 seconds, and the treatment temperature is ≤25°C.

[0024] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, in the step (3), the mass concentration of HF in the HF aqueous solution is 10-20%, and the treatment temperature is 10-23°C.

[0025] The wafer is treated with an HF aqueous solution, wherein the silicon dioxide on the wafer reacts with HF to form soluble silicon fluoride, thereby reducing the silicon concentration on the wafer surface. In this step, the mass concentration of the HF aqueous solution is preferably 5-40%, especially 10-20%, which can avoid production hazards caused by excessively high concentrations of the HF aqueous solution, and can avoid corrosion of the wafer surface by the HF aqueous solution to cause loss of the wafer and possible unevenness of the wafer surface. On the other hand, it can also avoid excessively high silicon concentration on the wafer surface in the later stage due to incomplete reaction when the mass concentration of the HF aqueous solution is too low, thereby failing to achieve an effective cleaning effect. When the treatment temperature is preferably 10-23° C., on the one hand, it can avoid corrosion of the wafer surface by the solution due to excessively high temperature to reduce the flatness of the wafer surface as much as possible, and on the other hand, it can avoid the problems of increased energy consumption and decreased reaction rate due to increased reaction time and reduced efficiency caused by too low a temperature.

[0026] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer of the present invention, in the step (3), the treatment method includes static immersion or rotating the wafer in the wafer cleaning solution.

[0027] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, in the step (4), the pH value of the alkaline solution is 11-13.

[0028] The hydroxide ions in the alkaline solution can react with silicon compounds such as silicon dioxide on the surface of the wafer to generate soluble silicate ions, thereby reducing the silicon concentration on the wafer surface and improving the quality of the wafer. When the pH value of the alkaline solution is between 11 and 13, there are enough hydroxide ions in the alkaline solution to react with silicon compounds, and damage to the wafer surface caused by an overly alkaline environment can be avoided.

[0029] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer according to the present invention, in the step (4), the treatment time is 30-120 seconds and the treatment temperature is 0-15°C.

[0030] As a preferred embodiment of the method for reducing silicon residue on the surface of a wafer of the present invention, in the step (4), the treatment method includes static immersion or rotating the wafer in the wafer cleaning solution.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] First, the technical solution provided by the present invention first uses a surfactant and a strong base and weak acid salt to preliminarily clean the wafer, and then sequentially performs acid cleaning and alkali cleaning. This cleaning method combination can effectively reduce the concentration of residual silicon on the wafer surface with as little cleaning agent as possible, improve the cleaning quality of the wafer, and ensure the flatness of the wafer surface after cleaning, thereby avoiding the damage to the wafer performance caused by the N-type conductive layer formed at the interface of the epitaxial layer formed by the wafer surface and the residual silicon;

[0033] Second: The preliminary cleaning of the wafer cleaning agent composed of a surfactant and a strong base and weak acid salt provided by the technical solution of the present invention can reduce impurities such as oil, metal, and metal compounds on the surface of the wafer to a certain extent, so that when the HF aqueous solution and the alkaline aqueous solution are used for subsequent cleaning, more wafers that have been preliminarily cleaned can be cleaned under the condition of the same amount of HF aqueous solution and alkaline aqueous solution, thereby reducing the amount of HF aqueous solution and alkaline aqueous solution, achieving the effect of safety, environmental protection, and economy;

[0034] Third: The method for reducing silicon residue on the wafer surface provided by the technical solution of the present invention is simple to operate and short in time, and therefore can be suitable for practical applications. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0036] Example 1

[0037] The method for reducing silicon residue on the surface of a wafer in this embodiment specifically comprises the following steps:

[0038] (1) Weigh 1.5 parts of nonylphenol polyoxyethylene ether and 1 part of sodium carbonate and dissolve them in 0.125 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the mass of nonylphenol polyoxyethylene ether and sodium carbonate to the deionized water is 20 g:1 L;

[0039] (2) maintaining the temperature of the wafer cleaning solution between 40° C. and 45° C., immersing the wafer in the wafer cleaning solution for 5 minutes, then removing the wafer and rinsing it with deionized water;

[0040] (3) immersing the wafer treated in step (2) in an HF aqueous solution having a mass concentration of 15% and a temperature of 15-18° C. for 20 seconds, then taking out the wafer and rinsing it with deionized water;

[0041] (4) soaking the wafer treated in step (3) in an alkaline aqueous solution having a pH value of 12 and a temperature of 5-10° C. for 80 seconds, then taking out the wafer and rinsing it with deionized water;

[0042] (5) Drying the wafer after being processed in step (4) to obtain a cleaned wafer.

[0043] Example 2

[0044] The method for reducing silicon residue on the surface of a wafer in this embodiment specifically comprises the following steps:

[0045] (1) Weigh 1.2 parts of nonylphenol polyoxyethylene ether and 1 part of sodium silicate and dissolve them in 0.15 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the mass of nonylphenol polyoxyethylene ether and sodium silicate to the deionized water is 15 g:1 L;

[0046] (2) maintaining the temperature of the wafer cleaning solution between 40° C. and 45° C., immersing the wafer in the wafer cleaning solution and rotating and maintaining for 10 minutes, then taking out the wafer and rinsing it with deionized water;

[0047] (3) immersing the wafer treated in step (2) in an HF aqueous solution having a mass concentration of 12% and a temperature of 10-15° C. and rotating and maintaining for 60 seconds, then taking out the wafer and rinsing it with deionized water;

[0048] (4) immersing the wafer treated in step (3) in an alkaline aqueous solution having a pH value of 11 and a temperature of 0-5° C., rotating and maintaining for 120 seconds, then taking out the wafer and rinsing it with deionized water;

[0049] (5) Drying the wafer after being processed in step (4) to obtain a cleaned wafer.

[0050] Example 3

[0051] The method for reducing silicon residue on the surface of a wafer in this embodiment specifically comprises the following steps:

[0052] (1) Weigh 1.5 parts of nonylphenol polyoxyethylene ether and 1 part of sodium carbonate and dissolve them in 0.1 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the mass of nonylphenol polyoxyethylene ether and sodium carbonate to the deionized water is 25 g:1 L;

[0053] (2) maintaining the temperature of the wafer cleaning solution between 40° C. and 45° C., immersing the wafer in the wafer cleaning solution for 3 minutes, then removing the wafer and rinsing it with deionized water;

[0054] (3) immersing the wafer treated in step (2) in an HF aqueous solution having a mass concentration of 19% and a temperature of 20-23° C. for 12 seconds, then taking out the wafer and rinsing it with deionized water;

[0055] (4) soaking the wafer treated in step (3) in an alkaline aqueous solution having a pH value of 13 and a temperature of 10-15° C. for 35 seconds, then taking out the wafer and rinsing it with deionized water;

[0056] (5) Drying the wafer after being processed in step (4) to obtain a cleaned wafer.

[0057] Example 4

[0058] The method for reducing silicon residue on the surface of a wafer in this embodiment specifically comprises the following steps:

[0059] (1) Weigh 2.0 parts of dodecyl polyoxyethylene ether and 1 part of sodium carbonate and dissolve them in 0.105 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the mass of nonylphenol polyoxyethylene ether and sodium carbonate to the deionized water is 20 g:1 L;

[0060] (2) maintaining the temperature of the wafer cleaning solution between 40° C. and 45° C., immersing the wafer in the wafer cleaning solution for 5 minutes, then removing the wafer and rinsing it with deionized water;

[0061] (3) immersing the wafer treated in step (2) in an HF aqueous solution having a mass concentration of 15% and a temperature of 15-18° C. for 20 seconds, then taking out the wafer and rinsing it with deionized water;

[0062] (4) soaking the wafer treated in step (3) in an alkaline aqueous solution having a pH value of 12 and a temperature of 5-10° C. for 80 seconds, then taking out the wafer and rinsing it with deionized water;

[0063] (5) Drying the wafer after being processed in step (4) to obtain a cleaned wafer.

[0064] Example 5

[0065] The method for reducing silicon residue on the surface of a wafer in this embodiment specifically comprises the following steps:

[0066] (1) Weigh 1.5 parts of nonylphenol polyoxyethylene ether and 1 part of sodium carbonate and dissolve them in 0.125 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the mass of nonylphenol polyoxyethylene ether and sodium carbonate to the deionized water is 20 g:1 L;

[0067] (2) maintaining the temperature of the wafer cleaning solution between 40° C. and 45° C., immersing the wafer in the wafer cleaning solution for 5 minutes, then removing the wafer and rinsing it with deionized water;

[0068] (3) immersing the wafer treated in step (2) in an HF aqueous solution having a mass concentration of 5% and a temperature of 15-18° C. for 60 seconds, then taking out the wafer and rinsing it with deionized water;

[0069] (4) soaking the wafer treated in step (3) in an alkaline aqueous solution having a pH value of 12 and a temperature of 5-10° C. for 80 seconds, then taking out the wafer and rinsing it with deionized water;

[0070] (5) Drying the wafer after being processed in step (4) to obtain a cleaned wafer.

[0071] Example 6

[0072] The method for reducing silicon residue on the surface of a wafer in this embodiment specifically comprises the following steps:

[0073] (1) Weigh 1.5 parts of nonylphenol polyoxyethylene ether and 1 part of sodium carbonate and dissolve them in 0.125 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the mass of nonylphenol polyoxyethylene ether and sodium carbonate to the deionized water is 20 g:1 L;

[0074] (2) maintaining the temperature of the wafer cleaning solution between 40° C. and 45° C., immersing the wafer in the wafer cleaning solution for 5 minutes, then removing the wafer and rinsing it with deionized water;

[0075] (3) immersing the wafer treated in step (2) in an HF aqueous solution having a mass concentration of 40% and a temperature of 15-18° C. for 10 seconds, then taking out the wafer and rinsing it with deionized water;

[0076] (4) soaking the wafer treated in step (3) in an alkaline aqueous solution having a pH value of 12 and a temperature of 5-10° C. for 80 seconds, then taking out the wafer and rinsing it with deionized water;

[0077] (5) Drying the wafer after being processed in step (4) to obtain a cleaned wafer.

[0078] Comparative Example 1

[0079] The method for reducing silicon residue on the surface of a wafer in this comparative example specifically comprises the following steps:

[0080] (1) Immerse the wafer in an HF aqueous solution with a mass concentration of 15% and a temperature of 15-18° C. for 20 seconds, then take out the wafer and rinse it with deionized water;

[0081] (2) immersing the wafer treated in step (1) in an alkaline aqueous solution having a pH value of 12 and a temperature of 5-10° C. for 80 seconds, then taking out the wafer and rinsing it with deionized water;

[0082] (3) Drying the wafer after being processed in step (2) to obtain a cleaned wafer.

[0083] Comparative Example 2

[0084] The method for reducing silicon residue on the surface of a wafer in this comparative example specifically comprises the following steps:

[0085] (1) Weigh 1.5 parts of nonylphenol polyoxyethylene ether and 1 part of sodium carbonate and dissolve them in 0.125 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the mass of nonylphenol polyoxyethylene ether and sodium carbonate to the deionized water is 20 g:1 L;

[0086] (2) maintaining the temperature of the wafer cleaning solution between 40° C. and 45° C., immersing the wafer in the wafer cleaning solution for 5 minutes, then removing the wafer and rinsing it with deionized water;

[0087] (3) immersing the wafer treated in step (2) in an alkaline aqueous solution having a pH value of 12 and a temperature of 5-10° C. for 80 seconds, then taking out the wafer and rinsing it with deionized water;

[0088] (4) immersing the wafer treated in step (3) in an HF aqueous solution having a mass concentration of 15% and a temperature of 15-18° C. for 20 seconds, then taking out the wafer and rinsing it with deionized water;

[0089] (5) Drying the wafer after being processed in step (4) to obtain a cleaned wafer.

[0090] Comparative Example 3

[0091] The method for reducing silicon residue on the surface of a wafer in this comparative example specifically comprises the following steps:

[0092] (1) Weigh 1 part of nonylphenol polyoxyethylene ether and dissolve it in 0.05 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of nonylphenol polyoxyethylene ether to deionized water is 20 g:1 L;

[0093] (2) maintaining the temperature of the wafer cleaning solution between 40° C. and 45° C., immersing the wafer in the wafer cleaning solution for 5 minutes, then removing the wafer and rinsing it with deionized water;

[0094] (3) immersing the wafer treated in step (2) in an HF aqueous solution having a mass concentration of 15% and a temperature of 15-18° C. for 20 seconds, then taking out the wafer and rinsing it with deionized water;

[0095] (4) soaking the wafer treated in step (3) in an alkaline aqueous solution having a pH value of 12 and a temperature of 5-10° C. for 80 seconds, then taking out the wafer and rinsing it with deionized water;

[0096] (5) Drying the wafer after being processed in step (4) to obtain a cleaned wafer.

[0097] Comparative Example 4

[0098] The only difference between this comparative example and Example 1 is that in step (1) of this comparative example, 1.5 parts of hexadecyltrimethylammonium bromide and 1 part of sodium carbonate are weighed and dissolved in 0.125 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the masses of nonylphenol polyoxyethylene ether and sodium carbonate to deionized water is 20g:1L.

[0099] Comparative Example 5

[0100] The only difference between this comparative example and Example 1 is that in step (1) of this comparative example, 2 parts of nonylphenol polyoxyethylene ether and 0.5 parts of sodium carbonate are weighed and dissolved in 0.125 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the masses of nonylphenol polyoxyethylene ether and sodium carbonate to deionized water is 20g:1L.

[0101] Comparative Example 6

[0102] The only difference between this comparative example and Example 1 is that in step (1) of this comparative example, 0.5 parts of nonylphenol polyoxyethylene ether and 2 parts of sodium carbonate are weighed and dissolved in 0.125 parts of deionized water to obtain a wafer cleaning solution; wherein the volume ratio of the sum of the masses of nonylphenol polyoxyethylene ether and sodium carbonate to deionized water is 20g:1L.

[0103] Comparative Example 7

[0104] The only difference between this comparative example and Example 1 is that the mass concentration of the HF aqueous solution in step (3) of this comparative example is 55%.

[0105] Comparative Example 8

[0106] The only difference between this comparative example and Example 1 is that the temperature in step (3) of this comparative example is 35°C.

[0107] Comparative Example 9

[0108] The only difference between this comparative example and Example 1 is that the pH value in step (4) of this comparative example is 14.

[0109] Effect example

[0110] The surface flatness and surface silicon concentration of the cleaned wafers prepared in Examples 1-6 and Comparative Examples 1-9 were tested, wherein the surface flatness was tested according to the national standard "Measurement Method for Surface Flatness of Silicon Wafers", and the surface silicon concentration was tested according to TXRF. The specific test results are shown in Table 1;

[0111] Table 1: Test data of cleaned wafers prepared in Examples 1-6 and Comparative Examples 1-9

[0112]

[0113] It can be seen from Table 1 that when the technical solution of the present invention is adopted, the surface flatness of the prepared crystal is high and the silicon concentration is low. Among them, the silicon concentration of Examples 1-6 is 84E10 atoms / cm 2 The surface flatness is below 7.8 μm, especially in Examples 1-3, where the silicon concentration is 48E10 atoms / cm 2 Below, the surface flatness is below 6.5 μm, indicating that the technical solution provided by the present invention can achieve excellent cleaning effect;

[0114] It can be seen from the data of Example 1 and Comparative Example 1 that when the wafer cleaning agent composed of a surfactant, a strong base and a weak acid salt and deionized water is not used for preliminary cleaning, the surface silicon concentration of the treated wafer increases by 411.90% compared with the preliminary cleaning, and the surface flatness does not change significantly, indicating that the preliminary treatment can effectively reduce the silicon concentration on the wafer surface; it can be seen from the data of Example 1 and Comparative Example 2 that when the order of acid cleaning and alkali cleaning is changed, if the alkali cleaning is performed first and then the acid cleaning in Comparative Example 2, the silicon concentration of the treated product increases by 119.05% compared with the preliminary cleaning, and the surface flatness value is 10.64% higher than that of the preliminary cleaning. The washing increased by 48.39%, indicating that the acid washing followed by alkali washing of the present invention can effectively reduce the silicon concentration on the wafer surface and effectively improve the surface flatness of the wafer. This may be because the acid washing followed by alkali washing can first remove the metal and metal compounds on the crystal surface. If alkali washing is used first, some metals and metal compounds may react with the alkali solution to form water-insoluble precipitation and then deposit on the wafer surface, which is difficult to remove later. In addition, some silicon ions may be deposited in the deposition process, thereby reducing the surface flatness of the wafer and the effect of reducing the silicon concentration is not obvious. From the data of Example 1 and Comparative Example 3, it can be seen that It can be seen that if only the surfactant is dissolved in deionized water in the early wafer cleaning agent without strengthening the weak alkali acid salt, the silicon concentration on the surface of the treated product is not significantly reduced; from the data of Example 1 and Comparative Example 4, it can be seen that when the surfactant is changed to an ionic surfactant, the silicon concentration of the treated product is higher and the surface flatness value is also higher. This is because the ionic surfactant will dissociate to form positive and negative ions during the treatment process, which may exist and combine with the metal, metal compound and its substance on the original wafer surface, which is reflected in the result that the surface silicon concentration is increased and the wafer surface is uneven; from the data of Example 1 and Comparative Example 4, it can be seen that when the surfactant is changed to an ionic surfactant, the silicon concentration of the treated product is higher and the surface flatness value is also higher. It can be seen from the data of Example 1 and Comparative Examples 5-6 that when the amount of surfactant is too much or too little, it will have a greater impact on the silicon concentration; it can be seen from the data of Example 1 and Comparative Examples 7-9 that when the mass concentration in the HF aqueous solution is too high, or the temperature during pickling is too high, or the pH of the alkaline washing is too high, the treated product has a significant effect on reducing the silicon concentration on the wafer surface, but all three will cause the flatness of the treated wafer surface to be significantly reduced, among which, when the HF concentration is too high, the change in flatness is the greatest. Compared with the flatness in Example 1, the flatness value of Comparative Example 7 is increased by 117.74% compared with that of Example 1.

[0115] Finally, it should be noted that the above embodiments are intended to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for reducing silicon residue on a wafer surface, characterized in that: The following steps are involved: (1) Dissolve the surfactant and the strong base and weak acid salt in deionized water to obtain a wafer cleaning solution; (2) Treat the wafer with a wafer cleaning solution and then rinse with deionized water; (3) Treat the wafer with HF aqueous solution and then rinse with deionized water; (4) treating the wafer with an alkaline solution and rinsing it with deionized water, and then drying the rinsed wafer; The surfactant is an alkylphenol polyoxyethylene ether nonionic surfactant; The strong base and weak acid salt is at least one of sodium carbonate, potassium carbonate, sodium acetate, sodium phosphate, sodium silicate and potassium acetate; The mass ratio of the surfactant to the strong base and weak acid salt is (1.2-2.0): 1; The ratio of the sum of the mass of the surfactant and the strong base and weak acid salt to the volume of deionized water is (15-25) g: 1 L; In the step (3), the mass concentration of HF in the HF aqueous solution is 5-40%, the treatment time is 10-60 seconds, and the treatment temperature is ≤25°C; In the step (4), the pH value of the alkaline solution is 11-13.

2. The method for reducing silicon residue on the wafer surface according to claim 1, characterized in that: In the step (2), the treatment time is 3-10 minutes and the treatment temperature is 40-45°C.

3. The method for reducing silicon residue on the wafer surface according to claim 1, characterized in that: In the step (3), the mass concentration of HF in the HF aqueous solution is 10-20%, and the treatment temperature is 10-23°C.

4. The method for reducing silicon residue on the wafer surface according to claim 1, characterized in that: In the step (4), the treatment time is 30-120 seconds and the treatment temperature is 0-15°C.

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