High-performance buffer oxide etching solution and application thereof

Abstract

The invention discloses a high-performance buffer oxide etching solution and application thereof. The high-performance buffer oxide etching solution is prepared from the following raw materials in percentage by weight: 0.1-1 wt% of hydrofluoric acid, 15-22 wt% of ammonium fluoride, 0.05-0.2 wt% of organic alkali, 0.03-0.5 wt% of a compound surfactant and the balance of water, the organic alkali is a quinoline amine active agent, and the compound surfactant is composed of an anionic surfactant and a cationic surfactant according to a mass ratio of 1: 5-10: 1. The high-performance buffer oxide etching solution can completely etch the lateral annular silicon oxide, can inhibit the corrosion of the nickel-silicon layer, can meet the requirement of high selection ratio of the silicon oxide layer to the nickel-silicon layer in an advanced process, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of etching solutions, and in particular relates to a high-performance buffered oxide etching solution and application thereof. Background Art

[0002] Silicon oxide has the advantages of high dielectric constant, low leakage current and excellent controllability, and has very important applications in semiconductor processes, such as as gate oxide in MOSFET, or as dielectric layer in IC process, etc. Nickel silicon can form gate contact area and drain contact area with low contact resistance, and can also be used as metal wire and interlayer connection to realize the transmission of electrical signals inside and outside the device. Due to its excellent conductivity and thermal stability, it has been widely used in advanced semiconductor manufacturing processes.

[0003] Buffered oxide etchant (BOE) is often used for silicon oxide etching, and its main components are hydrofluoric acid, ammonium fluoride and water. Chinese patent CN117844485A discloses a buffered oxide etchant and its application in the modification of the sidewall of the gate oxide layer. The etchant includes hydrofluoric acid, ammonium fluoride, a surfactant, a thickener and ultrapure water; the surfactant is an isomeric alcohol polyoxyethylene ether; the thickener is a symmetrical polyol ether, which can effectively inhibit the lateral corrosion of the gate oxide layer while ensuring the integrity and smoothness of the sidewall.

[0004] Chinese patent CN117757477A discloses a formula of an etching solution and its application. The etching solution is composed of 30-35% ammonium fluoride, 4-8% hydrofluoric acid, 3-5% hydrogen chloride, 0.1-0.25% surfactant, and the balance is ultrapure water; the surfactant includes fluorine-containing alcohol and fluorine-containing carboxylic acid; it has the advantages of excellent wettability, low surface tension, and few bubbles, can evenly etch the silicon dioxide film under the photoresist, does not produce silicon dioxide residue, and has no effect on the photoresist, and has a good application prospect.

[0005] Chinese patent CN115232624B discloses a buffered oxide etching solution for etching nano-scale silicon oxide intermediate layers, including hydrofluoric acid, ammonium fluoride, surfactant, defoamer and ultrapure water. It has low surface tension and strong drilling ability for nano-scale holes, ensuring the integrity and uniformity of the structure in the holes after etching. It can meet the etching of intermediate oxide layers with pore sizes of less than 100nm in chip structure manufacturing and ensure the integrity of the structure in the layer.

[0006] However, conventional BOE etching liquid cannot meet the requirements of etching silicon oxide with annular structure, especially the drilling ability is low, and there are problems such as residues after etching and too fast corrosion of nickel silicon layer, which cannot meet the high selectivity requirements of special structures. Therefore, it is necessary to develop a BOE etching liquid that can meet the high selectivity requirements of silicon oxide layer to nickel silicon layer in advanced processes. Summary of the invention

[0007] In view of the above technical problems, the present invention provides a high-performance buffered oxide etching solution and its application. The etching solution can completely etch the lateral annular silicon oxide and inhibit the corrosion of the nickel silicon layer, thereby meeting the high selectivity requirement of the silicon oxide layer to the nickel silicon layer in advanced processes.

[0008] In order to achieve the above object, the present invention provides a high-performance buffered oxide etching solution, which is composed of the following raw materials in weight percentage: 0.1-1wt% of hydrofluoric acid, 15-22wt% of ammonium fluoride, 0.05-0.2wt% of organic base, 0.03-0.5wt% of compound surfactant, and the balance is water.

[0009] Preferably, the hydrofluoric acid is electronic grade and has a mass concentration of 48-50wt%.

[0010] Preferably, the ammonium fluoride is electronic grade and has a mass concentration of 39-41.8 wt%.

[0011] Preferably, the organic base is at least one of 2-quinolinemethylamine, 5-trifluoromethyl-8-quinolineamine, isoquinoline-6-amine, 2-hydrazinoquinoline, and 8-fluoro-2-methyl-4-quinolineamine.

[0012] Preferably, the compound surfactant consists of anionic surfactant and cationic surfactant.

[0013] Further preferably, the mass ratio of the anionic surfactant to the cationic surfactant is 1:5-10:1.

[0014] More preferably, the anionic surfactant is any one of disodium lauryl polyoxyethylene ether sulfosuccinate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium tetradecyl alcohol polyoxyethylene (3) ether sulfate monoester sodium salt, and sodium lauryl polyoxyethylene ether sulfate.

[0015] More preferably, the cationic surfactant is any one of tetradecyldimethylbenzyl ammonium chloride, dodecyltrimethylammonium chloride, heptadecyltrimethylammonium bromide and dioctadecylmethylbenzyl ammonium chloride.

[0016] Preferably, the water is ultrapure water having a resistivity of not less than 18 megohms at 25°C.

[0017] The present invention also provides a method for preparing a high-performance buffered etching solution, and the specific method is as follows: (1) mixing anionic surfactant and cationic surfactant to obtain a compound surfactant; (2) Place ultrapure water in a container, add hydrofluoric acid, ammonium fluoride, an organic base and a compound surfactant in sequence, and stir and mix for 2 hours to obtain a high-performance buffered oxide etching solution.

[0018] The invention also provides an application of a high-performance buffered oxide etching solution, which is used in etching silicon oxide films.

[0019] Preferably, the etching temperature is 25°C±5°C.

[0020] Preferably, the silicon oxide film is Thermal Oxide, TEOS, or BPSG.

[0021] The beneficial effects of the present invention are: 1. The hydrofluoric acid in the high-performance buffered oxide etchant is used to etch the silicon oxide layer, and ammonium fluoride is used to provide fluoride ions to stabilize the etching rate of the etchant; the organic base reacts with the metal ions on the surface of nickel silicon, and these reaction products can stabilize the surface structure of nickel silicon, forming a protective film layer, reducing the corrosion of BOE on the nickel silicon layer; quinoline amine active agents react with hydrofluoric acid to generate their salts, which can form a protective fluoride film on the surface of nickel silicon to prevent BOE from further corroding nickel silicon.

[0022] 2. Compound anionic surfactants and cationic surfactants, in which different functional groups work synergistically to reduce the surface tension of the etching solution and significantly reduce the contact angle of the solution on the silicon oxide film layer, so that the solution has a strong lateral drilling ability in the small-sized silicon oxide ring structure, so that it can etch without residue in the ring structure.

[0023] 3. The present invention provides a high-performance buffered oxide etching solution with high selectivity for silicon oxide layer and nickel silicon layer, and an etching rate selectivity ratio of ≥690. It has strong lateral drilling ability and can be applied to the etching of small-sized silicon oxide ring structures. It ensures that there is no silicon oxide residue after etching and reduces the corrosion of the nickel silicon layer. It has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of the annular silicon oxide structure sheet before etching.

[0025] Figure 2 Schematic diagram of the structure of a ring-shaped silicon oxide structure sheet with residues after etching.

[0026] Figure 3 This is a schematic diagram of the structure of a ring-shaped silicon oxide structure sheet with a lot of residue after etching.

[0027] Figure 4 This is a schematic diagram of the structure of a ring-shaped silicon oxide structure sheet without any residue after etching. DETAILED DESCRIPTION

[0028] 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.

[0029] Example 1 A high-performance buffered oxide etching solution, composed of the following raw materials in weight percentage: 0.8wt% hydrofluoric acid, 19wt% ammonium fluoride, 0.15wt% isoquinolin-6-amine (organic base), 0.2wt% compound surfactant, and the balance is ultrapure water; the compound surfactant is composed of disodium lauryl polyoxyethylene ether sulfosuccinate (anionic surfactant) and tetradecyl dimethyl benzyl ammonium chloride (cationic surfactant) in a mass ratio of 1:1; Preparation method: (1) Mixing anionic surfactant and cationic surfactant in proportion to obtain a compound surfactant; (2) According to the formula, ultrapure water is placed in a container, and hydrofluoric acid, ammonium fluoride, an organic base and a compound surfactant are added in proportion in sequence, and the mixture is stirred for 2 hours to obtain a high-performance buffered oxide etching solution.

[0030] Example 2 A high-performance buffered oxide etching solution is composed of the following raw materials in weight percentage: 0.5wt% hydrofluoric acid, 17wt% ammonium fluoride, 0.08wt% 2-quinolinemethylamine (organic base), 0.23wt% compound surfactant, and the balance is ultrapure water; the compound surfactant is composed of fatty alcohol polyoxyethylene ether sodium sulfate (anionic surfactant) and dodecyltrimethylammonium chloride (cationic surfactant) in a mass ratio of 15:8; the preparation method is the same as that of Example 1.

[0031] Example 3 A high-performance buffered oxide etching solution is composed of the following raw materials in weight percentage: 0.6wt% hydrofluoric acid, 20wt% ammonium fluoride, 0.12wt% 5-trifluoromethyl-8-quinolineamine (organic base), 0.1wt% compound surfactant, and the balance is ultrapure water; the compound surfactant is composed of tetradecyl alcohol polyoxyethylene (3) ether sulfuric acid monoester sodium salt (anionic surfactant) and tetradecyl dimethyl benzyl ammonium chloride (cationic surfactant) in a mass ratio of 1:4; the preparation method is the same as that of Example 1.

[0032] Example 4 A high-performance buffered oxide etching solution is composed of the following raw materials in weight percentage: 0.2wt% hydrofluoric acid, 22wt% ammonium fluoride, 0.1wt% 8-fluoro-2-methyl-4-quinolineamine (organic base), 0.1wt% compound surfactant, and the balance is ultrapure water; the compound surfactant is composed of sodium lauryl polyoxyethylene ether sulfate (anionic surfactant) and heptadecyl trimethylammonium bromide (cationic surfactant) in a mass ratio of 1:1; the preparation method is the same as that of Example 1.

[0033] Example 5 A high-performance buffered oxide etching solution is composed of the following raw materials in weight percentage: 0.9wt% hydrofluoric acid, 16wt% ammonium fluoride, 0.2wt% 2-hydrazinequinoline (organic base), 0.18wt% compound surfactant, and the balance is ultrapure water; the compound surfactant is composed of fatty alcohol polyoxyethylene ether sodium sulfate (anionic surfactant) and tetradecyl dimethyl benzyl ammonium chloride (cationic surfactant) in a mass ratio of 5:1; the preparation method is the same as that of Example 1.

[0034] Example 6 A high-performance buffered oxide etching solution is composed of the following raw materials in weight percentage: 0.4wt% hydrofluoric acid, 21wt% ammonium fluoride, 0.05wt% 8-fluoro-2-methyl-4-quinolineamine (organic base), 0.33wt% compound surfactant, and the balance is ultrapure water; the compound surfactant is composed of disodium lauryl polyoxyethylene ether sulfosuccinate (anionic surfactant) and dioctadecyl methylbenzyl ammonium chloride (cationic surfactant) in a mass ratio of 10:1; the preparation method is the same as that in Example 1.

[0035] Example 7 A high-performance buffered oxide etching solution is composed of the following raw materials in weight percentage: 0.3wt% hydrofluoric acid, 18wt% ammonium fluoride, 0.06wt% isoquinoline-6-amine (organic base), 0.09wt% compound surfactant, and the balance is ultrapure water; the compound surfactant is composed of tetradecyl alcohol polyoxyethylene (3) ether sulfuric acid monoester sodium salt (anionic surfactant) and heptadecyl trimethylammonium bromide (cationic surfactant) in a mass ratio of 1:2; the preparation method is the same as that of Example 1.

[0036] Comparative Example 1 An etching solution is composed of the following raw materials in weight percentage: 0.8wt% hydrofluoric acid, 20wt% ammonium fluoride, and the balance is ultrapure water.

[0037] Comparative Example 2 An etching solution is composed of the following raw materials in weight percentage: 0.6wt% hydrofluoric acid, 20wt% ammonium fluoride, 0.12wt% 5-trifluoromethyl-8-quinolineamine, and the balance is ultrapure water.

[0038] Comparative Example 3 An etching solution is composed of the following raw materials in weight percentage: 0.8wt% hydrofluoric acid, 19wt% ammonium fluoride, 0.4wt% sodium lauryl polyoxyethylene ether sulfate (anionic surfactant), and the balance is ultrapure water.

[0039] Comparative Example 4 An etching solution is composed of the following raw materials in weight percentage: 0.5wt% hydrofluoric acid, 17wt% ammonium fluoride, 0.3wt% dodecyltrimethylammonium chloride (cationic surfactant), and the balance is ultrapure water.

[0040] Comparative Example 5 An etching solution is composed of the following raw materials in weight percentage: 0.7wt% hydrofluoric acid, 19wt% ammonium fluoride, 0.02wt% compound surfactant, and the balance is ultrapure water, wherein the compound surfactant is composed of disodium lauryl polyoxyethylene ether sulfosuccinate (anionic surfactant) and heptadecanyl trimethyl ammonium bromide (cationic surfactant) in a mass ratio of 1:1.

[0041] Comparative Example 6 An etching solution is composed of the following raw materials in weight percentage: 0.6wt% hydrofluoric acid, 17wt% ammonium fluoride, 0.01wt% 2-quinolinemethylamine, 0.12wt% compound surfactant, and the balance is ultrapure water, wherein the compound surfactant is composed of tetradecyl alcohol polyoxyethylene (3) ether sulfuric acid monoester sodium salt (anionic surfactant) and heptadecyl trimethyl ammonium bromide (cationic surfactant) in a mass ratio of 1:1.

[0042] Comparative Example 7 An etching solution is composed of the following raw materials in weight percentage: 0.8wt% hydrofluoric acid, 19wt% ammonium fluoride, 0.15wt% isoquinoline-6-amine, 0.1wt% disodium lauryl polyoxyethylene ether sulfosuccinate, and the balance is ultrapure water.

[0043] Comparative Example 8 An etching solution is composed of the following raw materials in weight percentage: 0.8wt% hydrofluoric acid, 19wt% ammonium fluoride, 0.15wt% isoquinoline-6-amine, 0.1wt% tetradecyl dimethyl benzyl ammonium chloride, and the balance is ultrapure water.

[0044] Comparative Example 9 An etching solution is composed of the following raw materials in weight percentage: 0.8wt% hydrofluoric acid, 19wt% ammonium fluoride, 0.15wt% methylethanolamine, 0.2wt% compound surfactant, and the balance is ultrapure water; the compound surfactant is composed of disodium lauryl polyoxyethylene ether sulfosuccinate (anionic surfactant) and tetradecyl dimethyl benzyl ammonium chloride (cationic surfactant) in a mass ratio of 1:1.

[0045] Result detection: Take the etching solution prepared in the above embodiments and comparative examples, put it in a PFA bottle, put it in a low-temperature thermostatic bath (25°C) for 3 hours, put the silicon oxide thin film wafer, nickel silicon wafer, and annular silicon oxide structure wafer into the etching solution and slowly stir and etch. After the etching is completed, take out the three materials, use an ellipsometer to detect the thickness of silicon oxide and nickel silicon before and after etching, and calculate the corresponding etching rate, then use SEM to observe the morphology of the annular structure before and after etching, use a contact angle meter to detect the contact angle of the etching solution on the silicon oxide film layer; use a surface tension meter to detect the surface tension of the etching solution; the etching rate is calculated as follows: etching rate = (thickness before etching - thickness after etching) / etching time; the results are shown in Table 1: Table 1 Etching conditions of etching solution

[0046] Note: Silicon oxide / nickel silicon etching selectivity = silicon oxide etching rate / nickel silicon etching rate.

[0047] As shown in Table 1, the mass ratio of anionic surfactant to cationic surfactant in the composite surfactant in the etching solution in Examples 1-7 is 1:5-10:1, the surface tension is in the range of 25-30 mN / m, the contact angle @ silicon oxide is <10°, and there is no residue after the annular structure is etched ( Figure 4 ), silicon oxide / nickel silicon etching selectivity ratio>690, and the organic base content of about 0.15% has the best effect on inhibiting nickel silicon corrosion.

[0048] When the content of each raw material component in the high-performance buffered oxide etching solution prepared in Examples 1-7 fluctuates, the silicon oxide / nickel silicon etching selectivity can reach more than 690, and there is no residue after etching the annular silicon oxide structure, meeting the requirements for etching the annular structure. However, in Comparative Example 1, which does not contain an organic base and a compound surfactant, its surface tension is large, the contact angle @ silicon oxide is large, the lateral drilling ability of the etching solution is weak, the annular structure is not completely etched, and the corrosion inhibition effect on the nickel silicon layer is small, and the etching rate selectivity is low ( Figure 3 ). Comparative Example 2 contains an organic base but no compound surfactant, so the contact angle @ silicon oxide is large, the lateral drilling ability of the etching solution is weak, and the annular structure is not completely etched ( Figure 3), but it has an inhibitory effect on the corrosion of the nickel-silicon layer. In Comparative Example 3, there is no organic base, but an anionic surfactant is contained, the contact angle @ silicon oxide is large, the lateral drilling ability of the etching solution is weak, and the nickel-silicon layer is corroded too quickly. In Comparative Example 4, there is no organic base, but a cationic surfactant is contained, the contact angle @ silicon oxide is large, the lateral drilling ability of the etching solution is weak, and the nickel-silicon layer is corroded too quickly. In Comparative Example 5, there is no organic base, and when the content of the composite surfactant is too low, the contact angle @ silicon oxide is high, the lateral drilling ability of the etching solution is weak, and the annular structure is not completely etched ( Figure 2 ), which corrodes the nickel-silicon layer too quickly. Comparative Example 6 contains a composite surfactant, the organic base content is too low, the contact angle @ silicon oxide is small, the etching solution has a strong lateral drilling ability, and the annular structure is completely etched ( Figure 4 ), but the corrosion inhibition effect on the nickel silicon layer is small. Comparative Examples 7 and 8 contain organic bases and single anionic / cationic surfactants, the contact angle @ silicon oxide is large, the lateral drilling ability of the etching solution is weak, and the annular structure is not completely etched ( Figure 3 ), but it has an inhibitory effect on the corrosion of the nickel silicon layer. Comparative Example 9 contains a composite surfactant, replaces the organic base, the contact angle @ silicon oxide is small, the etching liquid has a strong lateral drilling ability, and the annular structure is completely etched ( Figure 4 ), but the corrosion inhibition effect on the nickel-silicon layer is small.

Claims

1. A high performance buffered oxide etching solution, characterized in that: The invention is composed of the following raw materials in weight percentage: 0.1-1.0 wt % of hydrofluoric acid, 15-22 wt % of ammonium fluoride, 0.05-0.2 wt % of organic base, 0.03-0.5 wt % of compound surfactant, and the balance is water.

2. A high performance buffered oxide etching solution according to claim 1, characterized in that: The hydrofluoric acid is electronic grade and has a mass concentration of 48-50 wt%.

3. A high performance buffered oxide etching solution according to claim 1, characterized in that: The ammonium fluoride is electronic grade and has a mass concentration of 39-41.8 wt %.

4. A high performance buffered oxide etching solution according to claim 1, characterized in that: The organic base is at least one of 2-quinolinemethylamine, 5-trifluoromethyl-8-quinolineamine, isoquinoline-6-amine, 2-hydrazinoquinoline, and 8-fluoro-2-methyl-4-quinolineamine.

5. A high performance buffered oxide etching solution according to claim 1, characterized in that: The compound surfactant consists of anionic surfactant and cationic surfactant.

6. A high performance buffered oxide etching solution according to claim 5, characterized in that: The mass ratio of the anionic surfactant to the cationic surfactant is 1:5-10:

1.

7. A high performance buffered oxide etching solution according to claim 6, characterized in that: The anionic surfactant is any one of disodium lauryl polyoxyethylene ether sulfosuccinate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium tetradecyl alcohol polyoxyethylene (3) ether sulfate monoester sodium salt, and sodium lauryl polyoxyethylene ether sulfate.

8. A high performance buffered oxide etching solution according to claim 6, characterized in that: The cationic surfactant is any one of tetradecyl dimethyl benzyl ammonium chloride, dodecyl trimethyl ammonium chloride, heptadecyl trimethyl ammonium bromide and dioctadecyl methyl benzyl ammonium chloride.

9. An application of the high performance buffered oxide etching solution according to any one of claims 1 to 8, characterized in that: The application is the application in etching silicon oxide thin films.

10. The use according to claim 9, characterized in that: The etching temperature is 25°C±5°C.

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