Aluminum etching solution as well as preparation method and application thereof

Abstract

The invention discloses an aluminum etching solution and a preparation method and application thereof, the aluminum etching solution is composed of the following raw materials in percentage by mass: 55-75% of phosphoric acid, 1.5-8.5% of nitric acid, 2-10% of glacial acetic acid, 1-6% of an additive and the balance of deionized water, and the additive is composed of a surfactant accounting for 0.005-1% of the total mass of the aluminum etching solution and a buffering agent accounting for 1-5% of the total mass of the aluminum etching solution; all the raw materials can be used for etching aluminum-silicon-copper after being uniformly mixed, and the method has the advantages that the lateral erosion amount is small, the etching depth-to-width ratio can reach 2.23 or above, meanwhile, the etching taper angle is large, the etching rate is controlled between 5800-6200 / min, and the requirement of the market for the etching rate can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of etching liquids, and in particular relates to an aluminum etching liquid and a preparation method and application thereof. Background Art

[0002] The common metal interconnection layer structure in semiconductor devices is a two-layer structure of silicon dioxide and aluminum-silicon-copper. A small amount of silicon and copper is doped into the metal aluminum, which is beneficial to reduce the electron mobility and increase the service life of the semiconductor device. The thickness of the aluminum coating containing aluminum-silicon-copper is generally several microns, and a small amount of side etching and a large etching cone angle are required when etching aluminum. At present, the etching method for aluminum coating generally uses plasma for dry etching, but the dry etching cost is high, the production capacity is low, the material selectivity is low, and the plasma may cause electromagnetic radiation damage to the chip. Therefore, more and more fields choose wet etching with lower cost. Among them, aluminum etching liquid is a liquid generated by etching the surface of aluminum and its alloy metals with acid corrosive agents. It can be widely used in various surface treatment processes, especially in the manufacture of printed circuit boards, the manufacture of electronic parts, the manufacture of instrument parts and components, and the various stages of micro-exterior use of metals, and has important application value.

[0003] Chinese patent CN111334298B discloses a molybdenum-aluminum-molybdenum and ITO / Ag / ITO compatible etching solution and a preparation method thereof. The etching solution comprises 55-75% of inorganic acid phosphoric acid, 2.5-5% of nitric acid, 12-28% of acetic acid, 1-8% of surfactant, 0.1-5% of compound metal inhibitor, 0.1-5% of protective agent and the balance of pure water; the compound metal inhibitor is a compound mixture of at least two substances selected from molybdate, nitrate, mercaptobenzothiazole, lauric acid and mercaptobenzothiazole; by adding the compound metal inhibitor, the etching speed is controllable, the degradation of the anti-corrosion protective layer is effectively suppressed, and a metal film with a flat and smooth surface is obtained, which has important application value.

[0004] Chinese patent CN102925896B discloses a high-etching-rate, residue-free acidic aluminum etching solution and its preparation process, wherein the aluminum etching solution comprises phosphoric acid, acetic acid, nitric acid, an inorganic chlorine-based compound, an inorganic nitrate compound, a surfactant and pure water; the surfactant is a mixture of an anionic surfactant and a polyoxyethylene nonionic surfactant. The etching solution has a high etching rate for metal aluminum, a stable reaction, no residue, and basically no side etching phenomenon.

[0005] However, the current aluminum etching solution still has the problems of large side etching amount and small etching cone angle. The etching depth-to-width ratio is generally 0.7-0.9, or even below 0.7. This problem is more significant in the etching of aluminum-silicon-copper, thereby reducing the current transmission efficiency and process yield, and shortening the service life of the device. Summary of the invention

[0006] In view of the above technical problems, the present invention provides an aluminum etching solution and a preparation method and application thereof. The etching solution has small side etching amount after etching aluminum silicon copper, and the etching depth-to-width ratio can reach above 2.23. At the same time, the etching cone angle is large and the etching rate is controlled between 5800-6200 Å / min, which can meet the market requirements for etching rate.

[0007] In order to achieve the above object, the present invention provides an aluminum etching solution, which is composed of the following raw materials in percentage by mass: 55-75% phosphoric acid, 1.5-8.5% nitric acid, 2-10% acetic acid, 1-6% additives, and the balance is deionized water.

[0008] Preferably, the additive is composed of the following raw materials in percentage by total mass of the aluminum etching solution: 0.005-1% surfactant and 1-5% buffer.

[0009] Preferably, the mass concentration of the phosphoric acid is 80-90%, the mass concentration of the nitric acid is 70-75%, and the mass concentration of the acetic acid is >99%.

[0010] Further preferably, the surfactant is one or more of C8-C20 alkylphenol polyoxyethylene ether, C5-C24 fatty alcohol polyoxyethylene ether, 2-naphthol polyoxyethylene ether, allyloxy polyoxyethylene ether, isodecanol polyoxyethylene ether, polysorbate 40, polyoxyethylene (12) isooctylphenyl ether, distyrylphenol polyoxyethylene ether, polyoxyethylene (12) nonylphenyl ether and polyethylene glycol lauryl ether.

[0011] More preferably, the C8-C20 alkylphenol polyoxyethylene ether is one or more of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether and octadecylphenol polyoxyethylene ether; and the C5-C24 fatty alcohol polyoxyethylene ether is C5-C8 lauryl alcohol polyoxyethylene ether.

[0012] More preferably, the molecular weight of the allyloxy polyoxyethylene ether is 1000.

[0013] Further preferably, the buffer is obtained by mixing an ammonium salt and an organic phosphine in a mass ratio of 20-100:1.

[0014] More preferably, the ammonium salt is one or more of ammonium acetate, ammonium oxalate, ammonium citrate, ammonium tartrate, ammonium silicate, ammonium metasilicate and ammonium carbonate.

[0015] More preferably, the organic phosphine is one or more of cyclohexanehexol hexaphosphate, ammonium polyphosphate, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0016] The invention also provides a method for preparing an aluminum etching solution, which comprises adding phosphoric acid, nitric acid and acetic acid into deionized water, mixing well, adding additives, adding residual ion water, and mixing well to obtain the aluminum etching solution.

[0017] The invention also provides an application of the aluminum etching solution, which is used in etching a thick aluminum film layer; the thickness of the thick aluminum film layer is 1-10 μm.

[0018] The beneficial effects of the present invention are: 1. Add surfactants to the aluminum etching solution to increase the surface tension of the aluminum etching solution, thereby increasing the contact angle between the solution and the top of the aluminum, reducing the contact between the aluminum etching solution and the aluminum, reducing the etching rate, and reducing the amount of side etching on the top.

[0019] 2. A compound buffer is obtained by mixing ammonium salt and organic phosphine, and then the compound buffer is mixed with phosphoric acid, nitric acid and glacial acetic acid to prepare aluminum etching solution. The buffer reduces the mass transfer efficiency between the reaction interface of the solution and the aluminum film layer and the outside world, reducing the side etching amount of the top aluminum film layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the SEM image of the aluminum etching solution obtained in Example 1 after etching.

[0021] Figure 2 This is the SEM image of the aluminum etching solution obtained in Example 4 after etching.

[0022] Figure 3 This is the SEM image of the aluminum etching solution obtained in Comparative Example 5 after etching.

[0023] Figure 4 This is the SEM image of the aluminum etching solution obtained in Comparative Example 9 after etching. DETAILED DESCRIPTION

[0024] 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 construed as limiting the present invention. The protection scope of the present invention shall be subject to the contents recorded in the claims. Any modification or replacement made by a person 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.

[0025] In the following examples, the mass concentration of phosphoric acid is 90%, the mass concentration of nitric acid is 75%, and the mass concentration of acetic acid is 99.99%.

[0026] Example 1 An aluminum etching solution, which is formulated in terms of mass percentage to be 75% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 2.1% additives, and the remainder is deionized water, wherein the additives include the following raw materials in terms of the total mass percentage of the aluminum etching solution: 2% ammonium citrate (ammonium salt), 0.04% cyclohexanehexol hexaphosphate (organic phosphine), and 0.06% octylphenol polyoxyethylene ether (surfactant); Preparation method: (1) Add phosphoric acid to deionized water, stir and mix, then add acetic acid and nitric acid and mix to obtain a mixed solution; (2) Add additives (surfactant and buffer) to the mixed solution, mix well, add the remaining deionized water to make up to 100%, and mix well again to obtain aluminum etching solution.

[0027] Example 2 An aluminum etching solution, wherein the formula by mass percentage is 55% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 2.1% additives, and the balance is deionized water, wherein the additive formula is the same as that in Example 1; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0028] Example 3 An aluminum etching solution, comprising 68% phosphoric acid, 8.5% nitric acid, 7% acetic acid, 2.1% additives in terms of mass percentage, and the balance being deionized water, wherein the additive formula is the same as in Example 1; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0029] Example 4 An aluminum etching solution, comprising 68% phosphoric acid, 1.5% nitric acid, 7% acetic acid, 2.1% additives in terms of mass percentage, and the balance being deionized water, wherein the additive formula is the same as in Example 1; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0030] Example 5 An aluminum etching solution, comprising 75% phosphoric acid, 3.6% nitric acid, 10% acetic acid, 2.1% additives in terms of mass percentage, and the balance being deionized water, wherein the additive formula is the same as in Example 1; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0031] Example 6 An aluminum etching solution, wherein the formula by mass percentage is 68% phosphoric acid, 3.6% nitric acid, 2% acetic acid, 2.1% additives, and the balance is deionized water, wherein the additive formula is the same as that in Example 1; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0032] Example 7 An aluminum etching solution, comprising 68% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 2.1% additives in terms of mass percentage, and the balance being deionized water, wherein the additive formula is the same as in Example 1; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0033] Example 8 An aluminum etching solution, having the same formula as in Example 7, except that the ammonium salt is replaced by ammonium acetate (ammonium salt); The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0034] Example 9 An aluminum etching solution, having the same formula as in Example 7, wherein the ammonium salt is replaced by ammonium tartrate, and the organic phosphine is replaced by 2-phosphonobutane-1,2,4-tricarboxylic acid; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0035] Example 10 An aluminum etching solution, having the same formula as in Example 7, wherein the ammonium salt is replaced by ammonium silicate, and the surfactant is replaced by 2-naphthol polyoxyethylene ether; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0036] Embodiment 11 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the surfactant is replaced by allyloxy polyoxyethylene ether; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0037] Example 12 An aluminum etching solution, having the same formula as in Example 10, wherein the organic phosphine is replaced by ammonium polyphosphate, and the surfactant is replaced by polysorbate 40; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0038] Embodiment 13 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the mass percentage of the additive is changed to 4.1%, wherein the mass percentage of ammonium citrate (ammonium salt) is changed to 4%; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0039] Embodiment 14 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the mass percentage of the additive is changed to 1.1%, wherein the mass percentage of ammonium citrate (ammonium salt) is changed to 1%; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0040] Embodiment 15 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the mass percentage of the additive is changed to 2.16%, wherein the mass percentage of cyclohexanehexol hexaphosphate (organic phosphine) is changed to 0.1%; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0041] Example 16 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the mass percentage of the additive is changed to 2.09%, wherein the mass percentage of cyclohexanehexol hexaphosphate (organic phosphine) is changed to 0.03%; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0042] Embodiment 17 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the mass percentage of the additive is changed to 3.04%, wherein the mass percentage of octylphenol polyoxyethylene ether (surfactant) is changed to 1%; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0043] Embodiment 18 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the mass percentage of the additive is changed to 2.045%, wherein the mass percentage of octylphenol polyoxyethylene ether (surfactant) is changed to 0.005%; The preparation method is the same as that in Example 1 to prepare an aluminum etching solution.

[0044] Comparative Example 1 An aluminum etching solution is prepared by stirring and mixing 68% phosphoric acid, 3.6% nitric acid, 7% acetic acid, and the remainder deionized water in terms of mass percentage.

[0045] Comparative Example 2 An aluminum etching solution is prepared by stirring and mixing the following ingredients in percentage by weight: 68% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 2% ammonium citrate, and the remainder is deionized water.

[0046] Comparative Example 3 An aluminum etching solution is prepared by stirring and mixing the following ingredients in percentage by mass: 68% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 0.04% cyclohexanehexol hexaphosphate, and the remainder is deionized water.

[0047] Comparative Example 4 An aluminum etching solution is prepared by stirring and mixing the following ingredients in percentage by mass: 68% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 0.06% octylphenol polyoxyethylene ether, and the remainder deionized water.

[0048] Comparative Example 5 An aluminum etching solution is prepared by stirring and mixing the following ingredients in percentage by mass: 68% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 2% ammonium citrate, 0.04% cyclohexanehexol hexaphosphate, and the remainder is deionized water.

[0049] Comparative Example 6 The invention discloses an aluminum etching liquid, which is prepared by stirring and mixing the following ingredients in percentage by mass: 68% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 2% ammonium citrate, 0.06% octylphenol polyoxyethylene ether, and the balance is deionized water.

[0050] Comparative Example 7 The invention discloses an aluminum etching liquid, which comprises 68% phosphoric acid, 3.6% nitric acid, 7% acetic acid, 0.04% cyclohexane hexaphosphate, 0.06% octylphenol polyoxyethylene ether and the balance of deionized water, and is stirred and mixed uniformly.

[0051] Comparative Example 8 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the amount of phosphoric acid is changed to 79%, and the preparation method is the same as that of Example 1 to prepare the aluminum etching solution.

[0052] Comparative Example 9 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the amount of phosphoric acid is changed to 50%, and the preparation method is the same as that of Example 1 to prepare the aluminum etching solution.

[0053] Comparative Example 10 An aluminum etching solution, having the same formula as Example 7, except that the amount of nitric acid is changed to 8%, and a preparation method is the same as Example 1 to prepare the aluminum etching solution.

[0054] Comparative Example 11 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the amount of nitric acid is changed to 1%, and the preparation method is the same as that of Example 1 to prepare the aluminum etching solution.

[0055] Comparative Example 12 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the amount of acetic acid is changed to 15%, and the preparation method is the same as that of Example 1 to prepare the aluminum etching solution.

[0056] Comparative Example 13 An aluminum etching solution, the formula of which is the same as that of Example 7, except that the amount of acetic acid is changed to 1%, and the preparation method is the same as that of Example 1 to prepare the aluminum etching solution.

[0057] Comparative Example 14 An aluminum etching solution has the same formula as Example 7, except that octylphenol polyoxyethylene ether is replaced by potassium molybdate, and the preparation method is the same as Example 1 to prepare the aluminum etching solution.

[0058] Comparative Example 15 An aluminum etching solution has the same formula as Example 7, except that 0.06% of octylphenol polyoxyethylene ether is replaced by 0.03% of octylphenol polyoxyethylene ether and 0.03% of sodium dodecylbenzene sulfonate (anionic surfactant). The preparation method is the same as Example 1 to prepare the aluminum etching solution.

[0059] Comparative Example 16 An aluminum etching solution has the same formula as Example 7, except that 0.06% of octylphenol polyoxyethylene ether is replaced by 0.03% of octylphenol polyoxyethylene ether and 0.03% of potassium molybdate. The preparation method is the same as Example 1 to prepare the aluminum etching solution.

[0060] Embodiment 19 An aluminum etching solution has the same formula as Example 7, except that octylphenol polyoxyethylene ether is replaced by sodium dodecylbenzene sulfonate. The preparation method is the same as Example 1 to prepare the aluminum etching solution.

[0061] Take the aluminum etching solution prepared in the above embodiment and comparative example, heat it to 50°C, immerse a thick aluminum film (97% aluminum) with a thickness of 50000Å into it for etching, until the thick aluminum film changes from silvery white to dark gray, record the time as EPD, take it out, wash it with water, blow it dry with nitrogen, and calculate the etching rate (unit: Å / min) according to the following formula: etching rate = 50000 / EPD; use a scanning electron microscope to take pictures of the structure layer, measure the side etching amount of the top of the thick aluminum film layer (referring to the distance between the end of the photoresist and the top of the metal, unit: Å), and calculate the etching depth-to-width ratio according to the following formula: etching depth-to-width ratio = 50000 / top side etching amount (the etching depth-to-width ratio is preferably greater than 2); the etching results are shown in Table 1: Table 1 Etching performance of aluminum etching solutions with different ratios

[0062] As can be seen from Table 1, the contents of phosphoric acid, nitric acid and acetic acid in Examples 1-6 are within the limit values ​​of the concentration range. After etching, the etching depth-to-width ratio can reach above 2.23, and the etching rate is 5800-6200Å / min. The contents of phosphoric acid, nitric acid and acetic acid in Comparative Examples 8-13 exceed the range, and the etching cone angle is obviously small, the top side etching amount is large, and the etching rate is unstable, indicating that the contents of phosphoric acid, nitric acid and acetic acid have beneficial effects within the range.

[0063] In addition, adding a certain amount of surfactant and buffer at the same time can slow down the etching rate, increase the surface tension of the solution, reduce the mass transfer efficiency between the reaction interface of the solution and the aluminum film layer and the outside world, and significantly improve the etching depth-to-width ratio. Comparative Examples 14-17 introduce potassium molybdate and sodium dodecylbenzene sulfonate surfactants, but the etching rate is low and the etching depth-to-width ratio is small, which cannot meet the etching requirements.

Claims

1. An aluminum etching solution, characterized in that: The invention is composed of the following raw materials in percentage by mass: 55-75% phosphoric acid, 1.5-8.5% nitric acid, 2-10% glacial acetic acid, 1-6% additives, and the balance is deionized water.

2. An aluminum etching solution according to claim 1, characterized in that: The additive is composed of the following raw materials accounting for the total mass percentage of the aluminum etching solution: 0.005-1% of a surfactant and 1-5% of a buffer.

3. An aluminum etching solution according to claim 1, characterized in that: The mass concentration of the phosphoric acid is 80-90%, the mass concentration of the nitric acid is 70-75%, and the mass concentration of the glacial acetic acid is >99%.

4. An aluminum etching solution according to claim 2, characterized in that: The surfactant is one or more of C8-C20 alkylphenol polyoxyethylene ether, C5-C24 fatty alcohol polyoxyethylene ether, 2-naphthol polyoxyethylene ether, allyloxy polyoxyethylene ether, isodecanol polyoxyethylene ether, polysorbate 40, polyoxyethylene (12) isooctylphenyl ether, distyrylphenol polyoxyethylene ether, polyoxyethylene (12) nonylphenyl ether and polyethylene glycol lauryl ether.

5. An aluminum etching solution according to claim 4, characterized in that: The C8-C20 alkylphenol polyoxyethylene ether is one or more of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether and octadecylphenol polyoxyethylene ether; the C5-C24 fatty alcohol polyoxyethylene ether is C5-C8 lauryl alcohol polyoxyethylene ether.

6. An aluminum etching solution according to claim 2, characterized in that: The buffer is obtained by mixing ammonium salt and organic phosphine in a mass ratio of 20-100:

1.

7. An aluminum etching solution according to claim 6, characterized in that: The ammonium salt is one or more of ammonium acetate, ammonium oxalate, ammonium citrate, ammonium tartrate, ammonium silicate, ammonium metasilicate and ammonium carbonate.

8. An aluminum etching solution according to claim 6, characterized in that: The organic phosphine is one or more of cyclohexane hexol hexaphosphate, ammonium polyphosphate, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

9. A method for preparing an aluminum etching solution as described in any one of claims 1 to 8, characterized in that: Phosphoric acid, nitric acid and acetic acid are added to deionized water, and after mixing, additives are added, and then the remaining ionized water is added and mixed to obtain an aluminum etching solution.

10. An application of the aluminum etching solution according to any one of claims 1 to 8, characterized in that: The application is in etching of thick aluminum film layers.

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