Etching solution for selectively removing tantalum nitride relative to silicon

Abstract

The application discloses an etching solution for selectively removing tantalum nitride relative to silicon. The composition comprises the following components in terms of mass fraction: 1-5% of a fluorine ion source; 20-50% of an oxidizing agent; 1-5% of an organic acid; 0.01-1% of a silicon inhibitor; 0.01-1% of a leveling agent; 0.01-1% of a surfactant; and the balance of high-purity water. The etching solution not only provides a method for efficiently removing a tantalum nitride film, but also maintains high selectivity for a silicon substrate and excellent surface flatness.

Description

Technical Field

[0001] This invention belongs to the field of electronic chemicals, and specifically relates to an etching solution that selectively removes tantalum nitride relative to silicon. Background Technology

[0002] As semiconductor technology advances and demands for chip integration increase, device dimensions have shrunk from 28 nanometers to 14 nanometers, then to 7 nanometers, 5 nanometers, and even 3 nanometers. This necessitates that every step in the semiconductor manufacturing process meet higher requirements. Therefore, precise control of the etching process for thin film materials is crucial for device performance in semiconductor manufacturing. Tantalum nitride (TaN), as an excellent barrier layer material, is widely used in the manufacturing of advanced integrated circuits (ICs), especially in the fields of high-k gate dielectrics and metal gate technologies. TaN not only effectively prevents diffusion between metal and silicon but also improves device stability and reliability.

[0003] Currently, etching solutions used to remove TaN mainly consist of oxidants, etchants, various additives, and organic solvents. For example, CN109423290B discloses an etching solution composed of a fluoride ion source, phosphoric acid solution, oxidant, and a water-miscible organic solvent. US10889757B2 discloses an etching composition containing hydrofluoric acid, carboxylic acid, oxidant, complexing agent, and organic solvent. However, when feature sizes reach 10 nanometers or even smaller (e.g., 7 nanometers, 5 nanometers, 3 nanometers), these etching solutions, when used to remove TaN, not only cause some erosion of the silicon substrate, leading to damage to the edge structure and reducing device performance, but also face greater challenges in etching uniformity. At the nanoscale, even minute etching inhomogeneities can significantly affect the electrical characteristics and reliability of the device, thus limiting its application in high-precision, high aspect ratio feature manufacturing. To overcome the above difficulties, the present invention aims to provide an etchant for selectively removing tantalum nitride relative to silicon and a method for preparing the same. This etchant can not only efficiently etch tantalum nitride, but also maintain extremely high selectivity and excellent surface flatness on the underlying silicon substrate even with small feature sizes. Summary of the Invention

[0004] To address the aforementioned problems, the present invention provides an etching solution that selectively removes tantalum nitride relative to silicon.

[0005] An etchant for selectively removing tantalum nitride relative to silicon, the composition comprising the following components in mass fractions:

[0006] 1-5% fluoride ion source;

[0007] 20-50% oxidant;

[0008] 1-5% organic acids;

[0009] 0.01-1% silicon inhibitor;

[0010] 0.01-1% leveling agent;

[0011] 0.01-1% surfactant;

[0012] The remainder is high-purity water.

[0013] Preferably, the fluoride ion source is hydrofluoric acid, ammonium fluoride, fluorosilicic acid, or fluoroboric acid, or a combination thereof.

[0014] Preferably, the oxidant is nitric acid, peroxide, persulfate, perborate, permanganate, periodate, or potassium dichromate, or a combination thereof.

[0015] Preferably, the organic acid is citric acid (CA), acetic acid (HAc), propionic acid (PA), oxalic acid (OA), or lactic acid (LA) or a combination thereof.

[0016] Preferably, the silicon inhibitor is triethanolamine-triacetic acid (TTA), N-hydroxyethylenediamine-N,N'-diacetic acid (NTA), N,N-dicarboxymethyl-L-aspartic acid (DTPMP), ethylenedithiocarbamate (DTCs), N-(2-hydroxyethyl)-ethylenediamine-N,N,N'-triacetic acid (HEDTA), or ammonium polyacrylate (PAA) or a combination thereof.

[0017] Preferably, the leveling agent is neopentyl glycol ester (NGE), trimethylolpropane ester (TMPE), sorbitol ester (SE), or xylitol ester (XE) or a combination thereof.

[0018] Preferably, the surfactant is a polyamine silane, and more preferably, the surfactant is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (AEAPTMS), bis(3-triethoxysilylpropyl)amine (BIS-TESPA), N-(6-aminohexyl)-γ-aminopropyltrimethoxysilane (AHAPS), or diethylenetriaminesilane (DETS) or a combination thereof.

[0019] The etching method for selectively removing tantalum nitride relative to silicon using an etchant includes the following steps:

[0020] S1: First, add the silicon inhibitor to the organic acid and stir it with ultrasound to form a uniform and stable solution;

[0021] S2: After mixing the fluoride ion source, oxidant, leveling agent and surfactant evenly, add the above stable solution, and add water to adjust to the total amount of etching solution. After stirring thoroughly, the etching solution is obtained.

[0022] Preferably, the process further includes a step of drying the semiconductor device.

[0023] Preferably, the contact step is carried out at a temperature of 25-50°C and a stirring rate of 100-500 r / min. The contact time can be from 1 minute to 60 minutes.

[0024] The steps can be performed in any suitable manner, such as soaking, spraying, or a flow process.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. The organic acid and silicon inhibitor play multiple roles in the etching solution. The organic acid provides a buffering effect by adjusting the pH to maintain the stability of the etching solution, while the silicon inhibitor can form a dense protective film on the silicon substrate surface to reduce direct contact between the etching solution and the substrate, thereby improving the selectivity of the silicon substrate. Furthermore, the two work synergistically on the metal surface, which not only ensures uniform distribution of the etchant to guarantee the uniformity of the etching process and improves the surface quality after etching, but also controls the etching rate, thereby improving the overall efficiency and controllability of the etching process.

[0027] 2. The leveling agent can guide the liquid flow during the etching process to fill tiny uneven areas, effectively reducing the occurrence of orange peel effect, pinholes and other surface defects. It can also form a thin temporary protective film on the surface of the etching solution to prevent surface problems caused by rapid evaporation of the liquid, such as craters or bubbles, thereby releasing the stress inside the etching solution and promoting the formation of a smoother and flatter etched surface.

[0028] 3. The polyamine silane contains both organic amine groups and inorganic siloxane groups. This unique amphiphilic structure enables it to more effectively regulate the surface tension between the etchant and different phases, promoting its wetting and spreading on solid surfaces. Furthermore, the polyamine silane can construct a physical barrier on the silicon substrate surface through self-assembly forming a monolayer or multilayer structure, providing additional passivation protection, thereby further regulating the selectivity ratio of the etchant between the tantalum nitride and silicon phases. Attached Figure Description

[0029] Figure 1 This is a 3D morphology image of the Si sample synthesized under an atomic force microscope before reaction in Example 14 of this invention;

[0030] Figure 2 This is a 3D morphology image of the Si sample synthesized under an atomic force microscope after the reaction in Example 14 of this invention; Figure 3 This is a 3D morphology image of the Si sample synthesized under an atomic force microscope after the reaction in Comparative Example 6 of this invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] 1. Preparation method: According to the components and contents of the examples and comparative examples in Tables 1-3, weigh the corresponding raw materials by percentage calculation. First, add the silicon inhibitor to the organic acid and stir with ultrasound to form a uniform and stable solution. After the fluoride ion source, oxidant, leveling agent and surfactant are mixed evenly, add the stable solution and adjust the water to the total amount of etching solution. After stirring thoroughly, a uniformly mixed etching solution is obtained, where the content is in units of w.

[0033] 2. Etching conditions: 25-50℃, 100-500r / min stirring and soaking.

[0034] 3. Etching rate detection method: The test pieces containing TaN and Si were cut into 1cm*1cm squares during the test. The film thickness of TaN and Si before and after etching was detected by an elliptic polarization spectrometer. The difference between the initial thickness and the thickness after etching was divided by the etching time to obtain the etching rate.

[0035] Table 1 shows the formulation ratios, etching rates, and silicon surface roughness of Examples 1 to 8.

[0036]

[0037] Table 2 shows the formulation ratios, etching rates, and silicon surface roughness for Examples 9 to 16.

[0038]

[0039] Table 3 shows the formulation ratios, etching rates, and silicon surface roughness for Comparative Examples 1 to 6.

[0040]

[0041] As shown in Examples 1-8 of Table 1, within the scope of this invention, the prepared etching solutions all exhibit excellent selectivity ratios of 190 and above, and possess excellent surface smoothness. Examples 9-13 and Examples 14-16 are etching solutions obtained under different silicon inhibitors and different organic acids, respectively, and their selectivity ratios can all reach 210 and above. Taking Example 14 as a control, Comparative Examples 1 and 2 are etching solutions obtained below and above the temperature range, respectively, and the selectivity ratio under these conditions only reaches 90 or above; Comparative Example 3 has no silicon inhibitor and failed to form a dense protective film on the silicon substrate surface, with a selectivity ratio of only 108; Comparative Example 4 has no organic acid and failed to synergistically work with the silicon inhibitor to regulate the overall etching process and ensure etching uniformity, resulting in a selectivity ratio of only 118, and the roughness is also slightly higher than other examples; Comparative Example 5 has no polyamine silane as a surfactant and cannot effectively regulate the surface tension between the etching solution and different phases, nor provide additional passivation protection for the silicon substrate, with a selectivity ratio of only 127; Comparative Example 6 has no leveling agent, and although the selectivity ratio is not significantly affected, due to... Figure 1 and Figure 2 It can be seen that the etching solution obtained in Example 14 greatly improves the surface smoothness of Si after etching, while Comparative Example 6 does not have a leveling agent to guide the liquid flow to fill the tiny bumps and depressions to improve the surface smoothness, resulting in very poor surface roughness of Si after etching.

[0042] In summary, the etching solution prepared in this invention not only possesses an extremely high selectivity, reaching up to 210 or higher, but also maintains excellent surface smoothness. The silicon inhibitor, organic acid, polyamine silane, and leveling agent each play crucial roles, ensuring the efficiency and uniformity of the etching process. In particular, the application of the leveling agent significantly improves the smoothness of the silicon surface after etching. These results demonstrate the superior performance of the etching solution of this invention in practical applications.

[0043] The foregoing description is primarily for illustrative purposes. Although the invention has been shown and described with respect to exemplary embodiments thereof, those skilled in the art will understand that various other changes, omissions, and additions in form and detail may be made without departing from the spirit and scope of the invention.

Claims

1. An etching solution for selectively removing tantalum nitride relative to silicon, characterized in that, The etching solution comprises the following components by mass fraction: 1-5% fluoride ion source; 20-50% oxidant; 1-5% organic acids; 0.01-1% silicon inhibitor; 0.01-1% leveling agent; 0.01-1% surfactant; The remainder is high-purity water; The silicon inhibitor is triethanolamine-triacetic acid, N-hydroxyethylenediamine-N,N'-diacetic acid, N,N-dicarboxymethyl-L-aspartic acid, ethylenedithiocarbamate, N-(2-hydroxyethyl)-ethylenediamine-N,N,N'-triacetic acid, or ammonium polyacrylate or a combination thereof. The leveling agent is neopentyl glycol ester, trimethylolpropane ester, sorbitol ester or xylitol ester or a combination thereof; The surfactant is a polyamine silane.

2. The etching solution for selectively removing tantalum nitride relative to silicon according to claim 1, characterized in that, The fluoride ion source is hydrofluoric acid, ammonium fluoride, fluorosilicic acid, or fluoroboric acid, or a combination thereof.

3. The etching solution for selectively removing tantalum nitride relative to silicon according to claim 1, characterized in that, The oxidant is nitric acid, peroxide, persulfate, perborate, permanganate, periodate, or potassium dichromate, or a combination thereof.

4. The etching solution for selectively removing tantalum nitride relative to silicon according to claim 1, characterized in that, The organic acid is citric acid, acetic acid, propionic acid, oxalic acid, or lactic acid, or a combination thereof.

5. The etching solution for selectively removing tantalum nitride relative to silicon according to claim 1, characterized in that, The surfactant is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, bis(3-triethoxysilylpropyl)amine, N-(6-aminohexyl)-γ-aminopropyltrimethoxysilane or diethylenetriaminesilane or a combination thereof.

6. The etching method for selectively removing tantalum nitride relative to silicon using an etchant according to any one of claims 1-5, characterized in that, Includes the following steps: S1: First, add the silicon inhibitor to the organic acid and stir it with ultrasound to form a uniform and stable solution; S2: After mixing the fluoride ion source, oxidant, leveling agent and surfactant evenly, add the above stable solution, and add water to adjust to the total amount of etching solution. After stirring thoroughly, the etching solution is obtained.

7. The method according to claim 6, characterized in that, The etching conditions for the etching solution are: a temperature of 25-50℃ and a stirring rate of 100 r / min. Performed at 500 r / min.

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