High performance buffer oxide etching solution and its application

Abstract

The application discloses a high-performance buffer oxide etching liquid and application thereof, and is composed of 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 an organic base, 0.03-0.5 wt% of a compound surfactant, and the balance of water; the organic base is a quinoline amine active agent; and the compound surfactant is composed of an anionic surfactant and a cationic surfactant in a mass ratio of 1:5-10:1. The high-performance buffer oxide etching liquid in the application can completely etch a lateral annular silicon oxide, can inhibit corrosion of a nickel silicon layer, can meet the high selectivity requirement of a silicon oxide layer to the nickel silicon layer in an advanced process, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of etching solution technology, specifically relating to a high-performance buffered oxide etching solution and its application. Background Technology

[0002] Silicon oxide has advantages such as high dielectric constant, low leakage current, and excellent controllability, making it very important in semiconductor processes. For example, it is used as the gate oxide in MOSFETs or as the dielectric layer in IC manufacturing. Nickel-silicon can form gate and drain contacts with low contact resistance and can also be used as metal wires and interlayer interconnects to enable electrical signal transmission between the inside and outside of devices. Due to its excellent conductivity and thermal stability, it has been widely used in advanced semiconductor manufacturing processes.

[0003] Buffered oxide etchant (BOE) is commonly 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 sidewalls 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; and 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 sidewalls.

[0004] Chinese patent CN117757477A discloses an etching solution formulation and its application. The etching solution consists of 30-35% ammonium fluoride, 4-8% hydrofluoric acid, 3-5% hydrogen chloride, 0.1-0.25% surfactant, and the balance being ultrapure water. The surfactant includes fluorinated alcohols and fluorinated carboxylic acids. It has the advantages of excellent wettability, low surface tension, and few bubbles. It can uniformly etch silicon dioxide films under photoresist without producing silicon dioxide residue and without affecting the photoresist, showing great application prospects.

[0005] Chinese patent CN115232624B discloses a buffer oxide etching solution for etching nanoscale silicon oxide intermediate layers, comprising hydrofluoric acid, ammonium fluoride, surfactant, defoamer, and ultrapure water. It has low surface tension, strong drilling and etching ability for nanoscale pores, and ensures the integrity and uniformity of the internal structure of the pores after etching. It can meet the etching requirements of intermediate oxide layers with pore diameters <100nm in chip structure manufacturing and ensure the integrity of the internal structure.

[0006] However, conventional BOE etchants cannot meet the etching requirements for silicon oxide with ring-shaped structures, especially due to their low etching capability, residue after etching, and excessively rapid corrosion of the nickel-silicon layer, failing to achieve the high selectivity requirements for special structures. Therefore, it is necessary to develop a BOE etchant that can meet the high selectivity requirements of the silicon oxide layer for the nickel-silicon layer in advanced processes. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a high-performance buffered oxide etching solution and its application. The etching solution completely etches lateral annular silicon oxide while simultaneously inhibiting nickel-silicon layer corrosion, thus meeting the high selectivity requirements of silicon oxide layers for nickel-silicon layers in advanced processes.

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

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

[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 selected from 2-quinoline methylamine, 5-trifluoromethyl-8-quinolineamine, isoquinoline-6-amine, 2-hydrazinoquinoline, and 8-fluoro-2-methyl-4-quinolineamine.

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

[0013] More 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, and sodium lauryl polyoxyethylene ether sulfate.

[0015] More preferably, the cationic surfactant is any one of tetradecyl dimethyl benzyl ammonium chloride, dodecyl trimethyl ammonium chloride, heptadecanyl trimethyl ammonium bromide, and dioctadecyl methyl benzyl ammonium chloride.

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

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

[0018] The present invention also provides an application of a high-performance buffer oxide etching solution, wherein the application is in the etching of silicon oxide thin films.

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

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

[0021] The beneficial effects of this invention are as follows: 1. In the high-performance buffer oxide etching solution, hydrofluoric acid is used to etch the silicon oxide layer, and ammonium fluoride is used to provide fluoride ions to stabilize the etching rate of the etching solution; organic bases react with metal ions on the nickel-silicon surface, and these reaction products can stabilize the nickel-silicon surface structure, forming a protective film layer and reducing the corrosion of the nickel-silicon layer by BOE; quinoline amine surfactants react with hydrofluoric acid to generate their salts, which can form a protective fluoride film on the nickel-silicon surface, preventing further corrosion of the nickel-silicon by BOE.

[0022] 2. By combining anionic and cationic surfactants, the synergistic effect of different functional groups reduces the surface tension of the etching solution and significantly reduces the contact angle of the solution in the silicon oxide film layer. This gives the solution a strong lateral drilling capability in small-sized silicon oxide ring structures, allowing it to etch without residue in the ring structure.

[0023] 3. This invention provides a high-performance buffered oxide etchant with high selectivity for silicon oxide and nickel-silicon layers and an etch rate selectivity ratio ≥690. It has strong lateral drilling capability, can be applied to the etching of small-sized silicon oxide ring structures, ensures no silicon oxide residue after etching, and reduces corrosion of the nickel-silicon layer, showing good application prospects. Attached Figure Description

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

[0025] Figure 2 This is a schematic diagram of a ring-shaped silicon oxide structure sheet with residual material after etching.

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

[0027] Figure 4 This is a schematic diagram of a ring-shaped silicon oxide structure sheet that has no residue after etching. Detailed Implementation

[0028] The technical solution of the present invention will be further explained and described below with reference to 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 construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0029] Example 1 A high-performance buffer oxide etching solution is composed of the following raw materials by weight percentage: 0.8 wt% hydrofluoric acid, 19 wt% ammonium fluoride, 0.15 wt% isoquinoline-6-amine (organic base), 0.2 wt% compound surfactant, and the balance being ultrapure water; wherein 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) Mix anionic surfactants and cationic surfactants in a certain proportion to obtain a compound surfactant; (2) According to the formula, place ultrapure water in a container, add hydrofluoric acid, ammonium fluoride, organic base and compound surfactant in sequence according to the proportion, stir and mix for 2 hours to obtain high performance buffer oxide etching solution.

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

[0031] Example 3 A high-performance buffer oxide etching solution is composed of the following raw materials by weight percentage: 0.6 wt% hydrofluoric acid, 20 wt% ammonium fluoride, 0.12 wt% 5-trifluoromethyl-8-quinolinamine (organic base), 0.1 wt% compound surfactant, and the balance being ultrapure water; the compound surfactant is composed of tetradecyl alcohol polyoxyethylene (3) ether sulfate 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 in Example 1.

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

[0033] Example 5 A high-performance buffer oxide etching solution is composed of the following raw materials by weight percentage: 0.9 wt% hydrofluoric acid, 16 wt% ammonium fluoride, 0.2 wt% 2-hydrazinoquinoline (organic base), 0.18 wt% compound surfactant, and the balance being ultrapure water; the compound surfactant is composed of sodium fatty alcohol polyoxyethylene ether 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 in Example 1.

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

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

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

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

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

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

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

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

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

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

[0044] Comparative Example 9 An etching solution is composed of the following raw materials by weight percentage: 0.8 wt% hydrofluoric acid, 19 wt% ammonium fluoride, 0.15 wt% methylethanolamine, 0.2 wt% compound surfactant, and the balance being ultrapure water; wherein 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] Results Detection: The etching solutions prepared in the above examples and comparative examples were placed in PFA bottles and kept in a low-temperature constant temperature bath (25℃) for 3 hours. Silicon oxide thin film wafers, nickel-silicon wafers, and ring-shaped silicon oxide structure wafers were then slowly etched by stirring in the etching solution. After etching, the three materials were removed, and the thicknesses of silicon oxide and nickel-silicon before and after etching were measured using an elliptic polarization spectrometer. The corresponding etching rates were calculated. The morphology of the ring structure before and after etching was observed using SEM. The contact angle of the etching solution on the silicon oxide film layer was measured using a contact angle meter, and the surface tension of the etching solution was measured using a surface tension meter. The etching rate was calculated using the formula: Etching rate = (Thickness before etching - Thickness after etching) / Etching time. The results are shown in Table 1. Table 1. Etching performance of the etching solution

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

[0047] As shown in Table 1, in Examples 1-7, the mass ratio of anionic to cationic surfactants in the etching solutions was 1:5-10:1, the surface tension was all within the range of 25-30 mN / m, the contact angle @silicon oxide was all <10°, and there was no residue in the etching of the ring structure. Figure 4 With a silicon oxide / nickel-silicon etching selectivity ratio >690, an organic alkali content of around 0.15% provides the best inhibition of nickel-silicon corrosion.

[0048] When the content of each raw material component in the high-performance buffer oxide etching solution prepared in Examples 1-7 fluctuates, the silicon oxide / nickel-silicon etching selectivity ratio can reach over 690, and there is no residue after etching the annular silicon oxide structure, meeting the requirements for annular structure etching. However, Comparative Example 1 does not contain organic alkali or compound surfactant, resulting in high surface tension, a large contact angle @ silicon oxide, weak lateral drilling ability of the etching solution, incomplete etching of the annular structure, and little inhibition of nickel-silicon layer corrosion, leading to a low etching rate selectivity ratio. Figure 3 Comparative Example 2 contains organic alkali but no compound surfactant, has a larger contact angle @ silicon oxide, weak lateral etching ability of the etchant, and incomplete etching of the ring structure. Figure 3However, it has an inhibitory effect on the corrosion of the nickel-silicon layer. Comparative Example 3 does not contain organic alkali but contains anionic surfactant, resulting in a larger contact angle @silicon oxide, weak lateral etching ability of the etchant, and excessively rapid corrosion of the nickel-silicon layer. Comparative Example 4 does not contain organic alkali but contains cationic surfactant, resulting in a larger contact angle @silicon oxide, weak lateral etching ability of the etchant, and excessively rapid corrosion of the nickel-silicon layer. Comparative Example 5 does not contain organic alkali, but when the content of the compound surfactant is too low, the contact angle @silicon oxide is too high, the lateral etching ability of the etchant is weak, and the etching of the ring structure is incomplete. Figure 2 The etching process caused excessively rapid corrosion of the nickel-silicon layer. Comparative Example 6 contained a compound surfactant, but the organic alkali content was too low, resulting in a small contact angle @ silicon oxide. This led to strong lateral etching ability of the etchant, but ultimately resulted in complete etching of the ring structure. Figure 4 However, it has little effect on inhibiting the corrosion of nickel-silicon layers. Comparative Examples 7 and 8 contain organic bases and single anionic / cationic surfactants, resulting in a larger contact angle @ silicon oxide, weak lateral etching ability of the etchant, and incomplete etching of the ring structure. Figure 3 However, it inhibits the corrosion of the nickel-silicon layer. Comparative Example 9 contains a compound surfactant; replacing the organic alkali results in a smaller contact angle @ silicon oxide, stronger lateral etching ability of the etching solution, and complete etching of the ring structure. Figure 4 However, it has little effect on inhibiting corrosion of nickel-silicon layers.

Claims

1. A high-performance buffered oxide etching solution, characterized in that: It is composed of the following raw materials by weight percentage: 0.1-1.0 wt% hydrofluoric acid, 15-22 wt% ammonium fluoride, 0.05-0.2 wt% organic base, 0.03-0.5 wt% compound surfactant, and the balance being water; The compound surfactant is composed of anionic surfactant and cationic surfactant in a mass ratio of 1:5-10:1; The organic base is at least one of 2-quinoline methylamine, 5-trifluoromethyl-8-quinolineamine, isoquinoline-6-amine, 2-hydrazinoquinoline, and 8-fluoro-2-methyl-4-quinolineamine; 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, and sodium lauryl polyoxyethylene ether sulfate; the cationic surfactant is any one of tetradecyl dimethyl benzyl ammonium chloride, dodecyl trimethyl ammonium chloride, heptadecanyl trimethyl ammonium bromide, and dioctadecyl methyl benzyl ammonium chloride.

2. The high-performance buffer 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. The 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. An application of the high-performance buffered oxide etching solution as described in any one of claims 1-3, characterized in that: The application is in the etching of silicon oxide thin films.

5. The application according to claim 4, characterized in that: The etching temperature is 25℃±5℃.

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