A buffered oxide etching solution for preventing corrosion of aluminum

Abstract

The present invention provides a buffered oxide etching solution for preventing aluminum from being corroded, wherein the main components of the etching solution are hydrofluoric acid, ammonium fluoride, additives, organic solvents and ultrapure water. The etching solution of the present invention is used for etching and cleaning of oxide layer films, and can prevent corrosion of aluminum layers. The additive has a high solubility in the etching solution and is easy to disperse, and can form a stable protective effect on the surface of the aluminum film; the organic solvent has good solubility in the HF system, and can promote the dissolution of the additive in the etching solution, avoiding precipitation at low temperatures to cause surface residues, and a certain viscosity increase can improve the flatness of the aluminum film surface, making the surface roughness lower. The etching solution of the present invention greatly improves the etching selectivity of the oxide layer to the aluminum layer, and can meet the etching selectivity requirements in the construction of PCB circuit board leads.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductors, and in particular to a buffered oxide etching solution for preventing aluminum from being corroded. Background Art

[0002] Electronic chemicals refer to special chemicals used in the electronics industry. Specific wet electronic chemicals with high quality requirements and strong functionality are often required in the manufacturing processes of integrated circuits, discrete devices and circuit boards.

[0003] In the process of PCB circuit board lead construction, silicon dioxide layer is often used as a buffer layer or electrical isolation layer. In the subsequent process, the excess silicon oxide layer needs to be completely removed. Dry removal process is usually adopted, but dry etching takes a long time, and there will be obvious residues on the surface, which needs further cleaning, which greatly increases the time consumption of the whole process; wet removal usually uses buffered oxide etching liquid to etch and clean silicon oxide. Buffered oxide etching liquid (BOE) is a common wet chemical used for etching and cleaning silicon dioxide film. Its main components are hydrogen fluoride (HF), ammonium fluoride (NH4F) and water, and the etching rate is controlled by adjusting the content of hydrogen fluoride and ammonium fluoride. However, the conventional BOE etching liquid often has a very low selectivity of silicon dioxide to aluminum etching rate, which cannot achieve the same effect as dry removal. At this time, additives are introduced to improve the selectivity, which greatly reduces the corrosion of the etching liquid to aluminum. The addition of organic solvents further increases the viscosity of the etching liquid, which can not only increase the solubility of the additives in the etching liquid, but also clean the burrs on the aluminum surface, greatly reducing the roughness of the aluminum surface. The effect of dry etching followed by cleaning can be achieved through a one-step wet etching process, which greatly reduces the manufacturing time. Summary of the invention

[0004] The present invention provides a buffered oxide etching solution for preventing aluminum from being corroded. The one-step wet etching can achieve the effect of protecting aluminum and reduce the surface roughness. Meanwhile, the cleaning process after dry etching is eliminated, and the process requirements of PCB circuit boards are fully met.

[0005] The technical scheme of the invention is a buffered oxide etching solution for preventing aluminum from being corroded. The etching solution contains 0.1-10% hydrofluoric acid, 10-30% ammonium fluoride, 0.01-0.3% additives and 10-50% organic solvents by mass percentage, and the rest is ultrapure water.

[0006] Furthermore, the hydrofluoric acid in the etching solution is electronic grade, with a mass concentration of 48-50%.

[0007] Furthermore, the ammonium fluoride in the etching solution is electronic grade, with a mass concentration of 38-40%.

[0008] Furthermore, the additive is an alkane or a structure in which a functional group is connected to benzenesulfonic acid.

[0009] Furthermore, the additive is any one of 4-hydroxybenzenesulfonic acid, p-aminobenzenesulfonic acid, phenylhydrazine-4-sulfonic acid, 4-ethylbenzenesulfonic acid, 4-isopropylbenzenesulfonic acid and dodecylbenzenesulfonic acid.

[0010] Furthermore, the organic solvent is a high polyol, including any one of polyethylene glycol, polyvinyl alcohol and polypropylene glycol.

[0011] Furthermore, the resistivity of the ultrapure water at 25° C. is not less than 18 megohms.

[0012] The invention also relates to the application of the etching solution in etching and / or cleaning of oxide layer films.

[0013] Furthermore, the oxide layer film is BPSG, TEOS or SiO film.

[0014] The present invention has the following beneficial effects:

[0015] The etching solution of the present invention comprises hydrofluoric acid for etching a silicon dioxide film; ammonium fluoride for providing fluoride ions to stabilize the etching rate of the etching solution; the special structure of the additive makes it easy to form adsorption on the surface of the nitrogen aluminum film, and the additive is arranged in a directional manner to form a steric hindrance, thereby improving the protective effect on the aluminum; the organic solvent increases the viscosity of the solution, further smoothes the burrs on the aluminum surface, greatly reduces the roughness of the aluminum film, effectively protects the metal aluminum film, is used for etching the silicon dioxide film, and can also meet the index requirements of high-selectivity etching in the process of PCB circuit boards.

[0016] The etching solution of the present invention can achieve the effect of a two-step process of dry etching followed by cleaning by one-step wet etching while meeting the requirements of the PCB circuit board manufacturing process, thereby greatly reducing the working time and cost. DETAILED DESCRIPTION

[0017] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0018] Example 1

[0019] The composition of Example 1: 2.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 0.1 wt% 4-hydroxybenzenesulfonic acid, 25% polyethylene glycol, and the balance is water.

[0020] Example 2

[0021] The composition of Example 2: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 0.1 wt% 4-hydroxybenzenesulfonic acid, 25% polyethylene glycol, and the balance is water.

[0022] Example 3

[0023] The composition of Example 3: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 0.05 wt% 4-hydroxybenzenesulfonic acid, 20% polyvinyl alcohol, and the balance is water.

[0024] Example 4

[0025] The composition of Example 4 is: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 0.1 wt% p-aminobenzenesulfonic acid, 25% polypropylene glycol, and the balance is water.

[0026] Example 5

[0027] The composition of Example 5: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 0.1 wt% phenylhydrazine-4-sulfonic acid, 25% polypropylene glycol, and the balance is water.

[0028] Example 6

[0029] The etching solution comprises: 4.0 wt % hydrofluoric acid, 25 wt % ammonium fluoride, 0.005 wt % 4-hydroxybenzenesulfonic acid, 25 wt % polyethylene glycol, and the balance is water.

[0030] Example 7

[0031] The composition of the etching solution: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 0.5 wt% dodecylbenzene sulfonic acid, 25% polyvinyl alcohol, and the balance is water.

[0032] Example 8

[0033] The composition of the etching solution: 4.0wt% hydrofluoric acid, 25wt% ammonium fluoride, 0.1wt% p-aminobenzenesulfonic acid, 5% polypropylene glycol, and the balance is water.

[0034] Comparative Example 9

[0035] The composition of Comparative Example 9: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 0.1 wt% p-aminobenzenesulfonic acid, and the balance is water.

[0036] Comparative Example 10

[0037] The composition of Comparative Example 10: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 0.1 wt% p-aminobenzenesulfonic acid, 60% polypropylene glycol, and the balance is water.

[0038] Comparative Example 11

[0039] The composition of Comparative Example 11: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, 25 wt% polyvinyl alcohol, and the balance is water.

[0040] Comparative Example 12

[0041] The composition of Comparative Example 12: 4.0 wt% hydrofluoric acid, 25 wt% ammonium fluoride, and the balance water.

[0042] After the etching solution is prepared, stir and mix evenly first, then put the PFA bottle containing the etching solution into a low-temperature constant temperature bath and heat it to 23°C. After the temperature stabilizes for a period of time, put the silicon dioxide film wafer and the copper-doped aluminum film wafer into the etching solution and let them etch statically. The thickness of the silicon dioxide film wafer before and after etching is detected by an ellipsometer, and the thickness of the copper-doped aluminum film wafer before and after etching is detected by a four-point probe resistance meter. The corresponding etching rate is calculated according to the thickness difference before and after etching / etching time. Finally, the surface roughness of the copper-doped aluminum film is tested by an atomic force microscope.

[0043] The etching rate, etching selectivity and roughness in the above embodiments and comparative examples are shown in Table 1 below.

[0044] Table 1

[0045]

[0046]

[0047] As shown in Table 1, the etching rate of aluminum by the etching solution in Examples 1-5 is kept at a very low level, the etching rate selectivity of silicon dioxide to aluminum is all >13, and the surface roughness of the aluminum film after etching is very low, Ra is all <4nm; in Example 6, the amount of additive added is too low, and adsorption protection cannot be formed on the surface of the aluminum film, so the etching rate of aluminum is very fast, but the presence of organic solvent can still keep the surface roughness of the aluminum film very low; in Example 7, due to the long carbon chain length of dodecylbenzenesulfonic acid, the solubility is poor, and the solution is turbid. Although the etching selectivity is very high, it will cause uneven etching of the aluminum film surface and increase the roughness. In Example 8 and Comparative Example 9, since the amount of organic solvent added is very low or absent, the surface of the aluminum film cannot be effectively smoothed, and the roughness is also very high; in Comparative Example 10, the amount of organic solvent added is too high, the fluidity of the solution is greatly reduced, the mass transfer efficiency is slowed down, and the etching rate of silicon dioxide is seriously affected, which does not meet the use requirements; Comparative Example 11 has no additives, cannot effectively inhibit the corrosion of aluminum, and does not meet the use requirements; in Comparative Example 12, the conventional buffered oxide etching solution has a very high corrosion rate on the aluminum film, and cannot effectively improve the roughness of the aluminum film surface, which is completely unable to meet the use requirements in the wet etching of PCB circuit boards.

[0048] Obviously, the above embodiments and comparative examples are only examples for clear demonstration, and are not limited to the above embodiments. For those skilled in the art, the above embodiments have many variations or combinations, and it is not necessary and impossible to cite all the embodiments here. Therefore, the changes or modifications based on the above embodiments are still within the protection scope of the present invention.

Claims

1. A buffered oxide etching solution for preventing aluminum from corroding, characterized in that: The etching solution contains, by mass percentage, 0.1-10% hydrofluoric acid, 10-30% ammonium fluoride, 0.01-0.3% additives and 10-50% organic solvent, with the remainder being ultrapure water; The additive is 4-hydroxybenzenesulfonic acid, p-aminobenzenesulfonic acid or phenylhydrazine-4-sulfonic acid; the organic solvent is a high polyol, including any one of polyethylene glycol, polyvinyl alcohol and polypropylene glycol.

2. The etching solution according to claim 1, characterized in that: The hydrofluoric acid in the etching solution is electronic grade, and the mass concentration is 48-50%.

3. The etching solution according to claim 1, characterized in that: The ammonium fluoride in the etching solution is electronic grade, and the mass concentration is 38-40%.

4. The etching solution according to claim 1, characterized in that: The resistivity of the ultrapure water at 25° C. is not less than 18 megohms.

5. Use of the etching solution according to any one of claims 1 to 4 in etching and / or cleaning of oxide layer films.

6. The use according to claim 5, characterized in that: The oxide layer film is BPSG, TEOS or SiO film.

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