Tungsten and titanium nitride / titanium selective etching solution

Abstract

The invention provides a tungsten and titanium nitride / titanium selective etching solution which comprises the following components in percentage by mass: 5%-30% of an oxidizing agent, 0.5%-10% of an alkaline etching agent, 0.1%-1% of a tungsten corrosion inhibitor, 0.01%-0.05% of a surfactant and the balance of deionized water. According to the etching solution disclosed by the invention, the etching on W can be reduced while the high etching rate of TiN / Ti is maintained.

Description

Technical Field

[0001] The invention belongs to the field of electronic chemicals and relates to a metal etching liquid, in particular to a selective etching liquid for tungsten and titanium nitride / titanium. Background Art

[0002] The composite structure of titanium nitride / titanium (TiN / Ti) combines low resistivity, excellent thermal stability and high chemical stability, making it an indispensable high-end material for manufacturing electrodes and buffer layer barriers in semiconductor devices.

[0003] The film structure composed of TiN / Ti and metal tungsten (W) and their alloys plays a fundamental and key role in devices such as MEMS, CMOS and DRAM, and is an important material for promoting the advancement of semiconductor technology. W is used as a filling material for the intercalation layer of deep holes and slits to form a reliable conductive path, and TiN / Ti can be used as a barrier layer to prevent copper from diffusing into the surrounding insulating materials, ensuring the stability and electrical performance of the device.

[0004] However, tungsten generates tungsten oxide under the action of oxidant, which is then etched by alkaline solution at a too fast rate. This not only consumes the oxidant content and shortens the life of the etching solution, but also causes severe side erosion of the metal tungsten layer, seriously affecting the subsequent process.

[0005] The solution to the above problems involves incorporating a tungsten corrosion inhibitor into the alkaline etching solution system, aiming to achieve a dual goal: to significantly reduce the etching loss of metal tungsten while minimizing the impact on the etching rate of the TiN / Ti layer, and to simultaneously increase the service life of the etching solution, thereby enhancing the economy and sustainability of the overall process. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a selective etching solution of tungsten and titanium nitride / titanium, which comprises the following components by mass fraction: an oxidant content of 5% to 30%, an alkaline etchant content of 0.5% to 10%, a tungsten corrosion inhibitor content of 0.1% to 1%, a surfactant content of 0.01% to 0.05%, and the balance is deionized water.

[0007] The oxidant is hydrogen peroxide.

[0008] The alkaline etchant is at least one of ammonia water, potassium hydroxide, sodium hydroxide, sodium carbonate, sodium bicarbonate, tetramethylammonium hydroxide, diglycolamine, diethanolamine, triethanolamine, isopropanolamine, and NN dimethylformamide.

[0009] The tungsten corrosion inhibitor is at least one of pyrazine, 2-aminopyrazine, piperazine, N-(2-hydroxyethyl)piperazine, 1-(2-aminoethyl)piperazine, thiazole, 2-aminothiazole, 2-aminobenzothiazole, 2-mercaptobenzothiazole, 2-acetylthiazole, and 2-mercapto-1,3,4-thiadiazole.

[0010] The surfactant is at least one of 1-hydroxyethyl-2-oleyl imidazoline, 2-naphthol polyoxyethylene, S-carboxyethyl isothiourea betaine and polyethylene glycol.

[0011] A method for preparing a selective etching solution for tungsten and titanium nitride / titanium comprises weighing an oxidant, an alkaline etching agent, a tungsten corrosion inhibitor, a surfactant and deionized water in proportion, preparing the etching solution in any order of addition, and cooling the solution to room temperature after the mixture is uniformly mixed.

[0012] The invention discloses an application of a selective etching liquid of tungsten and titanium nitride / titanium in etching semiconductor materials containing tungsten and titanium nitride / titanium.

[0013] The etching of titanium nitride / titanium is carried out in two steps. First, titanium nitride / titanium is oxidized into titanium dioxide under the action of hydrogen peroxide, and then dissolved into titanate under the action of hydroxide ions. The main function of the oxidant is to oxidize titanium nitride / titanium into titanium dioxide, while the alkaline etchant mainly provides an alkaline environment and hydroxide ions required for etching to promote the reaction. The tungsten corrosion inhibitor added in the present invention forms a dense protective layer on the surface of tungsten to prevent the oxidant from oxidizing the metal tungsten, thereby inhibiting the corrosion of the metal tungsten.

[0014] The present invention has the following beneficial effects: 1. The present invention provides an etching solution that is selective for titanium nitride / titanium and metal tungsten, which can rapidly etch titanium nitride / titanium while inhibiting the etching of tungsten, thereby increasing the etching rate ratio of titanium nitride / titanium to metal tungsten.

[0015] 2. The surfactant contained in the present invention can improve the surface tension of the solution, so that the tungsten corrosion inhibitor can be evenly attached to the surface of the metal tungsten, further reducing the etching rate of the metal tungsten. DETAILED DESCRIPTION

[0016] The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Example 1 A selective etching solution for tungsten and titanium nitride / titanium, wherein the mass content of hydrogen peroxide as an oxidant is 20%, the mass content of potassium hydroxide as an alkaline etchant is 2%, the mass content of 2-aminopyrazine as a tungsten corrosion inhibitor is 0.1%, the mass content of S-carboxyethyl isothiourea betaine as a surfactant is 0.01%, and the balance is deionized water.

[0018] Example 2 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.2%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0019] Example 3 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor N-(2-hydroxyethyl) piperazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0020] Example 4 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor 2-acetylthiazole is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0021] Example 5 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor 2-aminobenzothiazole is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0022] Example 6 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor piperazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0023] Example 7 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor 1-(2-aminoethyl)piperazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0024] Example 8 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the tungsten corrosion inhibitor is 0.05% 2-aminopyrazine + 0.05% 2-aminobenzothiazole, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0025] Example 9 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the tungsten corrosion inhibitor is 0.05% 2-aminopyrazine + 0.05% piperazine, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0026] Example 10 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the tungsten corrosion inhibitor is 0.05% 2-aminopyrazine + 0.05% 1-(2-aminoethyl)piperazine, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0027] Embodiment 11 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 1%, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0028] Example 12 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 5%, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0029] Example 13 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 8%, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0030] Embodiment 14 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant is 1.5% NN dimethylformamide + 0.5% potassium hydroxide, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0031] Embodiment 15 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant is 1% NN dimethylformamide + 1% potassium hydroxide, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0032] Example 16 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the alkaline etchant is 1.5% NN dimethylformamide + 0.5% potassium hydroxide, the tungsten corrosion inhibitor is 0.05% 2-aminopyrazine + 0.05% piperazine, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0033] Embodiment 17 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant 1-hydroxyethyl-2-oleyl imidazoline is 0.01%, and the balance is deionized water.

[0034] Embodiment 18 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant 2-naphthol polyoxyethylene ether is 0.01%, and the balance is deionized water.

[0035] Embodiment 19 A selective etching solution for tungsten and titanium nitride / titanium, specifically as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the alkaline etchant potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant polyethylene glycol is 0.01%, and the balance is deionized water.

[0036] Comparative Example 1 A selective etching solution for tungsten and titanium nitride / titanium, without the addition of alkaline etchants, is as follows: The mass content of the oxidant hydrogen peroxide is 20%, the mass content of the tungsten corrosion inhibitor 2-aminopyrazine is 0.1%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0037] Comparative Example 2 A selective etching solution for tungsten and titanium nitride / titanium, without the addition of tungsten corrosion inhibitor, is as follows: The mass content of the oxidizing agent hydrogen peroxide is 20%, the mass content of the alkaline etching agent potassium hydroxide is 2%, the mass content of the surfactant S-carboxyethyl isothiourea betaine is 0.01%, and the balance is deionized water.

[0038] Comparative Example 3 A selective etching solution for tungsten and titanium nitride / titanium, without the addition of surfactant, is as follows: The mass content of the oxidizing agent hydrogen peroxide is 20%, the mass content of the alkaline etching agent potassium hydroxide is 2%, the mass content of the tungsten corrosion inhibitor 2-aminobenzothiazole is 0.1%, and the balance is deionized water.

[0039] The titanium nitride / titanium monolith on the silicon substrate was etched at 60°C using the etching solution configured in proportion to the above embodiment and the comparative example, and the titanium nitride / titanium monolith was cut into regular squares of 2cm*2cm in size. In order to avoid inaccurate measurement caused by oxidation of titanium nitride / titanium in the air, the titanium nitride / titanium monolith was first pretreated in a low-concentration alkaline solution and soaked for 10s to remove the oxide layer on the surface. The metal thickness was obtained by four-probe test. The four-probe selected four center points of the metal film for testing and calculated the average of the thickness of the four points. The average is the thickness of the titanium nitride / titanium monolith, and the titanium nitride / titanium monolith etching rate can be calculated.

[0040] The tungsten monolith on the silicon substrate was etched at 60°C with the etching solution configured in the above ratio, and the tungsten monolith was cut into regular squares of 2cm*2cm. In order to avoid inaccurate measurement caused by oxidation of tungsten in the air, the titanium nitride / titanium monolith was first pretreated in a low-concentration acid solution and soaked for 10s to remove the oxide layer on the surface. The thickness was obtained by four-probe test. The four-probe selected four center points of the metal film for testing and calculated the average of the thickness of the four points. The average is the thickness of the metal tungsten sheet, and the etching rate of the tungsten sheet can be calculated.

[0041] The etching data of the above embodiments and comparative examples are shown in Table 1. It can be concluded from the data in Table 1 that in Comparative Example 1, no alkaline etchant is added compared to Example 1, and the etching rate of TiN / Ti is significantly reduced, indicating that the alkaline etchant can effectively improve the etching rate of TiN / Ti, which is a key factor in TiN / Ti etching. Comparative Example 2 does not add tungsten corrosion inhibitor compared to Example 1, so the etching rate of W is too fast, while the rate of TiN / Ti does not change significantly, resulting in a significant decrease in the selectivity of the two. Comparative Example 3 does not add surfactants compared to Example 1. During the etching process, the tungsten corrosion inhibitor cannot be well divided on the surface of the W layer, resulting in an excessively high etching rate of the W layer and a reduced selectivity. In Example 1, the alkaline etchant potassium hydroxide keeps the TiN / Ti etching rate at a high value, and 2-aminopyrazine, as a tungsten corrosion inhibitor, controls the etching rate of tungsten at a low level to ensure a high etching selectivity. The subsequent examples adjusted the types and ratios of oxidants, alkaline etchants, tungsten corrosion inhibitors, and surfactants within a certain range, and the etching selectivity was greater than 200.

[0042] Table 1 Data and selectivity of etching experiments of Examples 1-19 and Comparative Examples 1-3

[0043] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A selective etching solution for tungsten and titanium nitride / titanium, characterized in that: The invention comprises the following components: an oxidant content of 5% to 30%, an alkaline etchant content of 0.5% to 10%, a tungsten corrosion inhibitor content of 0.1% to 1%, a surfactant content of 0.01% to 0.05%, and the balance is deionized water.

2. A selective etching solution for tungsten and titanium nitride / titanium according to claim 1, characterized in that: The oxidant is hydrogen peroxide.

3. A selective etching solution for tungsten and titanium nitride / titanium according to claim 1, characterized in that: The alkaline etchant is at least one of ammonia water, potassium hydroxide, sodium hydroxide, sodium carbonate, sodium bicarbonate, tetramethylammonium hydroxide, diglycolamine, diethanolamine, triethanolamine, isopropanolamine, and NN dimethylformamide.

4. A selective etching solution for tungsten and titanium nitride / titanium according to claim 1, characterized in that: The tungsten corrosion inhibitor is at least one of pyrazine, 2-aminopyrazine, piperazine, N-(2-hydroxyethyl)piperazine, 1-(2-aminoethyl)piperazine, thiazole, 2-aminothiazole, 2-aminobenzothiazole, 2-mercaptobenzothiazole, 2-acetylthiazole, and 2-mercapto-1,3,4-thiadiazole.

5. A selective etching solution for tungsten and titanium nitride / titanium according to claim 1, characterized in that: The surfactant is at least one of 1-hydroxyethyl-2-oleyl imidazoline, 2-naphthol polyoxyethylene, S-carboxyethyl isothiourea betaine and polyethylene glycol.

6. A method for preparing a selective etching solution for tungsten and titanium nitride / titanium according to any one of claims 1 to 5, characterized in that: The oxidant, alkaline etchant, tungsten corrosion inhibitor, surfactant and deionized water are weighed respectively in proportion, and the etching solution is prepared in any order of addition. After the mixture is mixed evenly, it is cooled to room temperature.

7. Use of a selective etching solution for tungsten and titanium nitride / titanium according to any one of claims 1 to 5, characterized in that: Applications in etching of tungsten and titanium nitride / titanium semiconductor materials.

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