Alkaline stripping liquid for silicon-based surface composite film and stripping method thereof

Abstract

The invention discloses alkaline stripping liquid for a silicon-based surface composite film and a stripping method of the alkaline stripping liquid. The alkaline stripping liquid is prepared from the following raw materials in percentage by mass: 12 to 17 percent of alkaline substance, 0.08 to 0.15 percent of oxidizing agent, 0.02 to 0.1 percent of composite complexing agent, 0.01 to 0.05 percent of interfacial agent and the balance of water, wherein the composite complexing agent is composed of an aluminum complexing agent and a molybdenum complexing agent according to the mass ratio of 1: 1. The method has the advantages of being good in stripping effect, small in silicon substrate damage, free of residues, high in universality, easy and convenient to operate and the like, and can be widely applied to the field of electronic chemicals, the technical field of semiconductors and the technical field of film stripping.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor and film stripping, and in particular relates to an alkaline stripping solution for a silicon-based surface composite film and a stripping method thereof. Background Art

[0002] In the fields of electronic chemicals, semiconductor technology and film stripping technology, silicon-based surface treatment and film preparation are important research directions. Silicon-based materials are widely used in electronics, optoelectronics and microelectronics due to their excellent physical and chemical properties. However, with the development of science and technology, the metal film layers on the silicon-based surface have become more and more complex. These film layers have evolved from single conventional metal film layers to multi-metal composite film layers, which may contain multiple elements, such as aluminum, molybdenum, scandium, etc. How to effectively strip these composite film layers has become an important technical challenge. Solutions of existing technologies: The existing technology still stays at stripping a single film layer, and an acidic stripping solution is usually used to strip a single film layer on the silicon-based surface. This acidic stripping solution usually contains strong acids such as hydrochloric acid and nitric acid, which can achieve the stripping of the film layer by chemically reacting with the metal elements in the film layer. However, this acidic stripping solution is highly corrosive and causes great damage to the silicon-based surface, which may reduce the performance of silicon-based reuse. At the same time, the preparation and use process of the acidic stripping solution is relatively complicated, requiring complex equipment and processes, which increases the difficulty and cost of operation.

[0003] Although the existing acidic stripping solution can achieve the stripping of a single component film layer on the surface of a silicon-based material, its strong corrosiveness causes great damage to the silicon-based material, which may lead to a decrease in material performance and cannot meet the requirements of silicon wafer recycling and removal of composite films that protect the silicon base. In addition, the existing technology is not effective in stripping composite film layers containing rare elements and cannot meet the needs of practical applications. Therefore, how to develop a new, efficient and simple stripping technology is an important problem facing the current technology. In addition, when a strong base is used alone to strip the scandium-doped aluminum nitride, aluminum nitride, and molybdenum composite film layer on the silicon base, it will not only corrode the silicon-based material, resulting in an increase in surface roughness, but also a large amount of difficult-to-remove residues will be produced on the silicon-based surface, which will make the silicon-based material difficult to reuse. Therefore, how to achieve the successful stripping of the scandium-doped aluminum nitride, aluminum nitride, and molybdenum composite film layer on the silicon base, while ensuring the smoothness of the silicon-based surface and avoiding residues on the surface, is an important problem facing the current technology. Summary of the invention

[0004] In view of the above technical problems, the present invention provides an alkaline stripping solution for silicon-based surface composite films and a stripping method thereof, which has the advantages of good stripping effect, little damage to the silicon base, no residue, strong versatility and easy operation, and can be widely used in the fields of electronic chemicals, semiconductor technology and film stripping technology.

[0005] In order to achieve the above object, the present invention provides an alkaline stripping solution for silicon-based surface composite membranes, which is composed of the following raw materials in percentage by mass: 12-17% alkaline substance, 0.08-0.15% oxidant, 0.02-0.1% composite complexing agent, 0.01-0.05% surfactant, and the balance is water.

[0006] Preferably, the composite complexing agent is composed of an aluminum complexing agent and a molybdenum complexing agent in a mass ratio of 1:1.

[0007] Further preferably, the aluminum complexing agent is one or more of ethylenediaminetetraacetic acid, ethylenediaminetetrapropionic acid, ethylenediaminetetraacetic acid potassium, ethylenediaminetetraacetic acid ammonium, ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraacetic acid dianhydride, diethylenetriaminepentaacetic acid, diethylenetriaminepentaacetic acid pentasodium, common chelating agent of sodium tripolyphosphate, and polyvinyl alcohol ammonium phosphate.

[0008] Further preferably, the molybdenum complexing agent is one or more of citric acid, sodium citrate, ammonium citrate, potassium citrate, choline citrate, quinoline-4-amine, 5-quinolinic acid, isoquinoline, 7-quinolinecarboxylic acid, 4-quinolineacetic acid, and 6-quinolineacetic acid.

[0009] Preferably, the alkaline substance is one or more of potassium hydroxide, sodium hydroxide, ammonia water, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

[0010] Preferably, the oxidant is one or more of hydrogen peroxide, ammonium persulfate, potassium persulfate, potassium permanganate, sodium hypochlorite, potassium iodide, catechol, potassium iodate, sodium iodate, potassium dichromate, and sodium dichromate.

[0011] Preferably, the surfactant is one or more of lauryl amide propyl betaine, dodecyl dimethyl hydroxypropyl sulfobetaine, octyl sulfobetaine, lauryl dimethyl sulfobetaine, and cocamidopropyl betaine.

[0012] The present invention also provides a stripping method for a silicon-based surface composite film, wherein the stripping method comprises stripping the silicon-based surface composite film using an alkaline stripping solution.

[0013] Preferably, the stripping method is to use isopropanol to clean the silicon-based surface composite film for 1 minute, blow it dry with nitrogen, place it in an alkaline stripping solution, react at room temperature for 0.5-2 hours, then take it out, clean it with deionized water, and complete the stripping.

[0014] Further preferably, the silicon-based surface composite film is one or more of scandium-doped aluminum nitride, aluminum nitride and molybdenum.

[0015] The beneficial effects of the present invention are: 1. Good stripping effect: The alkaline stripping solution of the present invention contains an oxidant, a composite complexing agent and a surfactant. The main function of the oxidant is to accelerate the chemical reaction rate of each component in the film layer. First, it can accelerate the reaction speed of scandium-doped aluminum nitride to ensure that scandium is completely stripped off the silicon-based surface without residue. At the same time, the solubility of molybdenum when oxidized into different oxides is quite different, and the solubility is different. Molybdate is formed under alkaline conditions, which can be quickly dispersed in the stripping solution away from the silicon-based surface by a molybdenum complexing agent. However, when a certain amount of oxidant is present in the system, aluminum ions that accumulate on the surface of the test piece will be oxidized to generate solids attached to the silicon-based surface, thereby causing the roughness of the silicon-based surface to increase. Therefore, the aluminum ions on the surface are complexed by adding an aluminum complexing agent to ensure that the aluminum ions are away from the silicon-based surface faster. The addition of surfactants can also further ensure the smoothness of the silicon-based surface. Under the joint action of these various components, the successful stripping of the scandium-doped aluminum nitride, aluminum nitride, and molybdenum composite film layers on the silicon-based substrate is achieved, while ensuring the smoothness of the silicon-based surface and avoiding residues on the surface, thus overcoming the problem of poor stripping effect of existing technologies for composite film layers containing rare elements.

[0016] 2. Little damage to the silicon base and no residue: Alkaline stripping fluid is less corrosive and causes less damage to the silicon base than existing acidic stripping fluids. The formulated stripping fluid can ensure the smoothness of the silicon base surface, which helps maintain the original performance and service life of the silicon base.

[0017] 3. Strong versatility: The alkaline stripping solution of the present invention can be widely used in the film stripping of various silicon-based materials and has strong versatility.

[0018] 4. Easy operation: The preparation and use process of the alkaline stripping solution of the present invention is relatively simple, does not require complicated equipment and processes, is easy to operate and control, and can be widely used in the fields of electronic chemicals, semiconductor technology, and film stripping technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is an ultra-depth-of-field microscope image of the surface of the test piece after being stripped by the alkaline stripping solution prepared in Example 1.

[0020] Figure 2 This is an ultra-depth-of-field microscope image of the surface of the test piece after being stripped by the alkaline stripping solution prepared in Example 2.

[0021] Figure 3 This is an ultra-depth-of-field microscope image of the surface of the test piece after being stripped by the stripping solution prepared in Comparative Example 1.

[0022] Figure 4 This is an ultra-depth-of-field microscope image of the surface of the test piece after being stripped by the stripping liquid prepared in Comparative Example 2.

[0023] Figure 5This is an ultra-depth-of-field microscope image of the surface of the test piece after stripping with the stripping liquid prepared in Comparative Example 3.

[0024] Figure 6 This is an ultra-depth-of-field microscope image of the surface of the test piece after being stripped by the stripping liquid prepared in Comparative Example 4. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be understood as limiting the present invention. The protection scope of the present invention shall be based on the contents recorded in the claims. Any modification or replacement made by those skilled in the art to the technical solution of the present invention without creative work shall fall within the protection scope of the present invention.

[0026] Example 1 An alkaline stripping solution for silicon-based surface composite films, the formula of which is 16% potassium hydroxide (alkaline substance), 0.1% hydrogen peroxide (oxidant), 0.1% composite complexing agent, 0.01% lauramide propyl betaine (surfactant), and the balance is deionized water; wherein the composite complexing agent is composed of ethylenediaminetetraacetic acid (aluminum complexing agent) and potassium citrate (molybdenum complexing agent) in a mass ratio of 1:1; Preparation method: (1) mixing an aluminum complexing agent and a molybdenum complexing agent at room temperature to obtain a composite complexing agent; (2) Add an alkaline substance, an oxidant, a complexing agent and a surfactant to deionized water in sequence at room temperature and mix them to obtain an alkaline stripping solution.

[0027] Example 2 An alkaline stripping solution for a silicon-based surface composite film has the same formula and preparation method as Example 1, except that the aluminum complexing agent is replaced by potassium ethylenediaminetetraacetate from ethylenediaminetetraacetic acid.

[0028] Example 3 An alkaline stripping solution for a silicon-based surface composite film has the same formula and preparation method as Example 1, except that the aluminum complexing agent is replaced by sodium tripolyphosphate from ethylenediaminetetraacetic acid.

[0029] Example 4 An alkaline stripping solution for a silicon-based surface composite film, the formula and preparation method are the same as those in Example 1, only the molybdenum complexing agent is replaced by quinoline-4-amine from potassium citrate.

[0030] Example 5 An alkaline stripping solution for silicon-based surface composite films, the formula and preparation method are the same as those in Example 1, only the molybdenum complexing agent is replaced by 4-quinolineacetic acid from potassium citrate.

[0031] Example 6 An alkaline stripping solution for a silicon-based surface composite film has the same formula and preparation method as Example 1, except that the surfactant is replaced by octyl sulfobetaine from lauryl amide propyl betaine.

[0032] Example 7 An alkaline stripping solution for a silicon-based surface composite film has the same formulation and preparation method as Example 1, except that the oxidant is replaced by potassium persulfate from hydrogen peroxide.

[0033] Example 8 An alkaline stripping solution for silicon-based surface composite films, the formula and preparation method are the same as those in Example 1, only the oxidant is replaced by sodium hypochlorite instead of hydrogen peroxide.

[0034] Example 9 An alkaline stripping solution for silicon-based surface composite films has the same formula and preparation method as Example 1, except that the oxidant is replaced by sodium hypochlorite instead of hydrogen peroxide, and the surfactant is replaced by octyl sulfobetaine instead of lauryl amide propyl betaine.

[0035] Example 10 An alkaline stripping solution for silicon-based surface composite films, comprising 17% tetraethylammonium hydroxide (alkaline substance), 0.08% catechol (oxidant), 0.02% composite chelating agent, 0.05% surfactant, and the balance being deionized water; wherein the composite chelating agent is composed of ethylenediaminetetramethylenephosphonic acid (aluminum chelating agent) and 7-quinolinecarboxylic acid (molybdenum chelating agent) in a mass ratio of 1:1; and the surfactant is composed of cocamidopropyl betaine and lauryl dimethyl sulfonobetaine in a mass ratio of 1:1.

[0036] Embodiment 11 An alkaline stripping solution for silicon-based surface composite films, the formula is 17% tetraethylammonium hydroxide (alkaline substance), 0.1% sodium dichromate (oxidant), 0.04% composite complexing agent, 0.03% dodecyl dimethyl hydroxypropyl sulfobetaine (surfactant), and the balance is deionized water; wherein the composite complexing agent is composed of an aluminum complexing agent and a molybdenum complexing agent in a mass ratio of 1:1, wherein the aluminum complexing agent is composed of ammonium ethylenediaminetetraacetate and polyvinyl ammonium phosphate in a mass ratio of 1:1, and the molybdenum complexing agent is composed of choline citrate and 6-quinolineacetic acid in a mass ratio of 1:1.

[0037] Example 12 An alkaline stripping solution for silicon-based surface composite films, comprising 14% tetramethylammonium hydroxide (alkaline substance), 0.1% oxidant (composed of 0.02% hydrogen peroxide and 0.08% ammonium persulfate), 0.1% composite chelating agent, 0.01% lauramide propyl betaine (surfactant), and the remainder deionized water; wherein the composite chelating agent is composed of ethylenediaminetetraacetic acid (aluminum chelating agent) and potassium citrate (molybdenum chelating agent) in a mass ratio of 1:1.

[0038] Comparative Example 1 A stripping solution having a formula of 16% potassium hydroxide (alkaline substance) and the balance being deionized water.

[0039] Comparative Example 2 A stripping solution, the formula of which is 16% potassium hydroxide (alkaline substance), 0.1% hydrogen peroxide (oxidant), and the balance is deionized water.

[0040] Comparative Example 3 A peeling solution, wherein the formula is 16% potassium hydroxide (alkaline substance), 0.1% hydrogen peroxide (oxidant), 0.01% lauramide propyl betaine (surfactant), and the balance is deionized water.

[0041] Comparative Example 4 A peeling solution, the formula of which is 16% potassium hydroxide (alkaline substance), 0.1% hydrogen peroxide (oxidant), 0.1% potassium citrate (molybdenum complexing agent), 0.01% lauramide propyl betaine (surfactant), and the balance is deionized water.

[0042] Comparative Example 5 A peeling solution, the formula of which is 16% potassium hydroxide (alkaline substance), 0.1% hydrogen peroxide (oxidant), 0.1% ethylenediaminetetraacetic acid (aluminum complexing agent), 0.01% lauramide propyl betaine (surfactant), and the balance is deionized water.

[0043] Comparative Example 6 A stripping solution, the formula and preparation method are the same as those in Example 1, except that the mass ratio of the aluminum complexing agent to the molybdenum complexing agent is changed to 2:1.

[0044] Comparative Example 7 A stripping solution, the formula and preparation method are the same as those in Example 1, except that the mass ratio of the aluminum complexing agent to the molybdenum complexing agent is changed to 1:2.

[0045] Comparative Example 8 A stripping solution, the formulation and preparation method are the same as those in Example 1, except that the content of the alkaline substance is changed to 10%.

[0046] Comparative Example 9 A stripping solution, the formulation and preparation method are the same as those in Example 1, except that the content of the alkaline substance is changed to 20%.

[0047] Comparative Example 10 A stripping solution, the formulation and preparation method are the same as those of Example 1, except that the oxidant content is changed to 0.2%.

[0048] Example 13 Stripping method (1) Take a composite film layer containing scandium-doped aluminum nitride, aluminum nitride, and molybdenum on a silicon substrate, with a film thickness of 1 μm and a size of 1.6*1.6 cm as a test piece; (2) Soak the test piece in anhydrous isopropanol for 1 min, take it out and blow dry it with nitrogen to obtain a clean test piece; (4) The clean test pieces were placed in the alkaline stripping solution prepared in the above-mentioned embodiment and comparative example, respectively, and stripped at room temperature. After 1 hour, the test pieces were taken out and rinsed with deionized water to complete the stripping. Then, the test pieces after stripping were subjected to super depth of field characterization to detect the stripping conditions. The results are shown in Table 1. (4) The composite film layers containing one or more of scandium-doped aluminum nitride, aluminum nitride, and molybdenum on the silicon substrate were respectively washed and placed in the alkaline stripping solution prepared in Example 1. The stripping conditions were tested after stripping at room temperature. The results are shown in Table 2.

[0049] Table 1 Effect of stripping solution formulation on the stripping effect of the test piece

[0050] Table 2 Peeling effect of Example 1 on different test pieces

[0051] The results show that by comparing the roughness of the test pieces of Example 1 and Example 2 in Table 1, it can be found that the roughness of the silicon-based surface is reduced after the oxidant is added to the stripping solution, and the stripping rate is greatly improved in the same time, which also shows that the oxidant has a great promoting effect on the stripping of the composite film layer. Comparing the data of Table 1 of Examples 3-5 with Example 1, it can be found that the aluminum complexing agent, molybdenum complexing agent, and surfactant are indispensable. The roughness of the test pieces of Examples 3-5 is large and cannot achieve a good stripping effect. Comparing the data of Examples 6-10 in Table 1 with Example 1, it can be found that the ratio of each component of the stripping solution must be within a certain ratio range. Exceeding the range will cause the stripping rate of the test piece to decrease or the roughness to increase, resulting in a poor effect of the stripping solution. Comparison between Example 8 and Example 1 shows that when the mass percentage of the alkaline substance is low, the stripping rate is significantly reduced and the roughness is significantly increased; comparison between Example 9 and Example 1 shows that when the mass percentage of the alkaline substance is high, the stripping rate is high and similar to that of Example 1, but the roughness is significantly increased compared to Example 1. Therefore, the alkaline substance must be within an appropriate mass percentage range to ensure a good stripping effect. Comparison between Example 10 and Example 1 shows that an oxidant mass percentage beyond the range will also cause an increase in roughness, indicating that a high oxidant content will lead to a decrease in the smoothness of the silicon-based surface. Observe the ultra-depth image of the test piece after stripping of Example 1-2 ( Figure 1-2 ) surface, it can be found that there is no residue on the surface, and the scandium-doped aluminum nitride, aluminum nitride, and molybdenum composite film on the silicon substrate are successfully stripped. The same is true for other embodiments; however, after the stripping solution prepared in Comparative Examples 1-4 is stripped, there are residues on the surface to varying degrees, and the roughness is relatively high ( Figure 3-6 ). The stripping solutions of Examples 1-12 ensured the smoothness of the silicon-based surface (roughness below 20 nm) on the basis of a good stripping rate, and all of them could successfully strip the test pieces.

[0052] From the data in Table 2, it can be found that Example 1 has a good stripping effect on the four test pieces. Among them, the scandium-doped aluminum nitride layer is more difficult to strip, but the stripping rate can reach 100% in 40 minutes, and the roughness is below 20 nm, indicating that the stripping solution has a good stripping effect on various silicon-based composite film layers.

Claims

1. An alkaline stripping solution for silicon-based surface composite films, characterized in that: The invention is composed of the following raw materials in percentage by mass: 12-17% alkaline substance, 0.08-0.15% oxidant, 0.02-0.1% complexing agent, 0.01-0.05% surfactant, and the balance is water.

2. The alkaline stripping solution for silicon-based surface composite membrane according to claim 1, characterized in that: The composite complexing agent is composed of an aluminum complexing agent and a molybdenum complexing agent in a mass ratio of 1:

1.

3. The alkaline stripping solution for silicon-based surface composite film according to claim 2, characterized in that: The aluminum complexing agent is one or more of ethylenediaminetetraacetic acid, ethylenediaminetetrapropionic acid, ethylenediaminetetraacetic acid potassium, ethylenediaminetetraacetic acid ammonium, ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraacetic acid dianhydride, diethylenetriaminepentaacetic acid, diethylenetriaminepentaacetic acid pentasodium, common chelating agent of sodium tripolyphosphate, and polyvinyl alcohol ammonium phosphate.

4. The alkaline stripping solution for silicon-based surface composite film according to claim 2, characterized in that: The molybdenum complexing agent is one or more of citric acid, sodium citrate, ammonium citrate, potassium citrate, choline citrate, quinoline-4-amine, 5-quinolinic acid, isoquinoline, 7-quinolinecarboxylic acid, 4-quinolineacetic acid, and 6-quinolineacetic acid.

5. The alkaline stripping solution for silicon-based surface composite membrane according to claim 1, characterized in that: The alkaline substance is one or more of potassium hydroxide, sodium hydroxide, ammonia water, tetramethylammonium hydroxide and tetraethylammonium hydroxide.

6. The alkaline stripping solution for silicon-based surface composite membrane according to claim 1, characterized in that: The oxidant is one or more of hydrogen peroxide, ammonium persulfate, potassium persulfate, potassium permanganate, sodium hypochlorite, potassium iodide, catechol, potassium iodate, sodium iodate, potassium dichromate, and sodium dichromate.

7. The alkaline stripping solution for silicon-based surface composite film according to claim 1, characterized in that: The surfactant is one or more of lauryl amide propyl betaine, dodecyl dimethyl hydroxypropyl sulfobetaine, octyl sulfobetaine, lauryl dimethyl sulfobetaine, and cocamidopropyl betaine.

8. A method for stripping a silicon-based surface composite film, characterized in that: The stripping method comprises stripping the silicon-based surface composite film using the alkaline stripping solution described in any one of claims 1 to 7.

9. A method for stripping a silicon-based surface composite film according to claim 8, characterized in that: The stripping method comprises cleaning the silicon-based surface composite film, placing it in an alkaline stripping solution, reacting it at room temperature for 0.5-2 hours, taking it out for cleaning, and completing the stripping.

10. A method for stripping a silicon-based surface composite film according to claim 8 or 9, characterized in that: The silicon-based surface composite film is one or more of scandium-doped aluminum nitride, aluminum nitride and molybdenum.

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