Etching solution for selectively removing tantalum nitride relative to silicon

Abstract

The invention relates to an etching solution for selectively removing tantalum nitride relative to silicon. The composition comprises the following components in percentage by mass: 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 to 1% of a surfactant; and the balance of high-purity water. The etching solution not only provides a method capable of efficiently removing a tantalum nitride film, but also can keep extremely high selectivity and excellent surface flatness for a substrate silicon material.

Description

Technical Field

[0001] The invention belongs to the field of electronic chemicals, and in particular relates to an etching solution for selectively removing tantalum nitride relative to silicon. Background Art

[0002] With the development of semiconductor technology, the requirements for chip integration are constantly increasing, and the device size has gradually shrunk from the 28nm node to the 14nm node, and then to the 7nm, 5nm and even 3nm node, which requires each step in the semiconductor manufacturing process to meet higher requirements. Therefore, in the semiconductor manufacturing process, the ability to accurately control the etching process of thin film materials is crucial to device performance. Tantalum nitride (TaN), as an excellent barrier layer material, is widely used in the manufacturing process of advanced integrated circuits (ICs), especially in the field of high-K gate dielectrics and metal gate technology. TaN can not only effectively prevent the diffusion between metal and silicon materials, but also improve the stability and reliability of the device.

[0003] At present, the etching solution used to remove TaN is mainly composed of an oxidant, an etchant, various additives and an organic solvent. For example, CN109423290B discloses an etching solution composed of a fluorine ion source, a phosphoric acid solution, an oxidant and a water-miscible organic solvent, and US10889757B2 discloses an etching composition containing hydrofluoric acid, a carboxylic acid, an oxidant, a complexing agent and an organic solvent. However, when the feature size reaches 10 nanometers or even smaller (such as 7 nanometers, 5 nanometers, 3 nanometers), these etching solutions are used to remove TaN. Not only will they cause a certain degree of erosion to the silicon substrate, resulting in damage to the edge structure and reducing the performance of the device, but they will also face greater challenges in etching uniformity, that is, at the nanoscale, even the slightest etching unevenness will significantly affect the electrical characteristics and reliability of the device, thereby limiting its application in high-precision, high aspect ratio feature manufacturing. In order to overcome the above difficulties, the present invention aims to provide an etching solution and a preparation method thereof for selectively removing tantalum nitride relative to silicon. The etching solution can not only efficiently etch tantalum nitride, but also maintain extremely high selectivity and excellent surface flatness for the underlying silicon substrate when the feature size is small. Summary of the invention

[0004] To solve the above problems, the present invention provides an etching solution for selectively removing tantalum nitride relative to silicon.

[0005] An etching solution for selectively removing tantalum nitride relative to silicon, the composition comprising the following components by mass fraction: 1-5% fluoride ion source; 20-50% oxidant; 1-5% organic acid; 0.01-1% silicon inhibitor; 0.01-1% leveling agent; 0.01-1% surfactant; The balance is high purity water.

[0006] Preferably, the fluoride ion source is hydrofluoric acid, ammonium fluoride, fluorosilicic acid or fluoroboric acid or a combination thereof.

[0007] Preferably, the oxidant is nitric acid, peroxide, persulfate, perborate, permanganate, periodate or potassium dichromate or a combination thereof.

[0008] 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.

[0009] 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 polyammonium acrylate (PAA) or a combination thereof.

[0010] Preferably, the leveling agent is neopentyl glycol ester (NGE), trimethylolpropane ester (TMPE), sorbitol ester (SE) or xylitol ester (XE) or a combination thereof. Preferably, the surfactant is a polyamine silane, 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.

[0011] The etching method of the etching solution for selectively removing tantalum nitride relative to silicon comprises the following steps: S1: First, add the silicon inhibitor into the organic acid and form a uniform and stable solution by ultrasonic stirring; S2: After the fluoride ion source, oxidant, leveling agent and surfactant are evenly mixed, the above-mentioned stabilizing solution is added, and water is added to adjust the total amount of the etching solution, and the etching solution is obtained after sufficient stirring.

[0012] Preferably, the method further comprises the step of drying the semiconductor device.

[0013] Preferably, the contacting step is carried out at a temperature of 25-50° C. and a stirring rate of 100 r / min-500 r / min. The contacting time may be 1 minute to 60 minutes.

[0014] The steps can be performed by any suitable means, such as dipping, spraying or a flow process.

[0015] The beneficial effects of the present invention are as follows: 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, and the silicon inhibitor can form a dense protective film on the surface of the silicon substrate to reduce the direct contact between the etching solution and the silicon substrate, thereby improving the selectivity of the silicon substrate. In addition, the two also act synergistically on the metal surface, which can not only evenly distribute the etchant to ensure the uniformity of the etching process and improve the surface quality after etching, but also control the etching rate at the same time, thereby improving the efficiency and controllability of the overall etching process.

[0016] 2. The leveling agent can guide the liquid flow to fill tiny bumps and depressions during the etching process, effectively reducing the occurrence of orange peel effect, pinholes and other surface defects, and can form a thin temporary protective film on the surface of the etching liquid to prevent surface problems caused by rapid evaporation of the liquid, such as shrinkage or bubbling, so that the stress inside the etching liquid is released, thereby promoting the formation of a smoother and flatter etching surface.

[0017] 3. The polyamine silane contains both organic amine groups and inorganic siloxane groups. This unique amphiphilic structure enables it to more effectively adjust the surface tension between the etching solution and different phases, promoting its wetting and spreading on the solid surface. In addition, the polyamine silane can also construct a physical barrier on the surface of the silicon substrate through a monolayer or multilayer structure formed by self-assembly, providing additional passivation protection, thereby further adjusting the selectivity of the etching solution in the tantalum nitride and silicon phases. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a 3D morphology image of the Si test piece synthesized under an atomic force microscope before reaction in Example 14 of the present invention; Figure 2 This is a 3D morphology image of the Si test piece synthesized under an atomic force microscope after the reaction in Example 14 of the present invention; Figure 3 This is a 3D morphology diagram of the Si test piece synthesized under an atomic force microscope after the reaction in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0019] The technical solutions in the present invention are described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0020] 1. Preparation method: According to the components and contents of the embodiments and comparative examples in Tables 1-3, the corresponding raw materials are weighed by percentage calculation, the silicon inhibitor is first added to the organic acid, and a uniform and stable solution is formed by ultrasonic stirring. After the fluoride ion source, oxidant, leveling agent and surfactant are evenly mixed, the stable solution is added and water is adjusted to the total amount of the etching solution. After sufficient stirring, a uniformly mixed etching solution is obtained, wherein the content unit is w%.

[0021] 2. Etching conditions: 25-50℃, 100-500r / min stirring and immersion.

[0022] 3. Etching rate detection method: The test pieces containing TaN and Si were cut into 1cm*1cm squares during the test, and the film thickness of TaN and Si before and after etching was detected using an ellipsometer. The difference between the initial thickness and the thickness after etching divided by the etching time is the etching rate.

[0023] Table 1 shows the formula ratios, etching rates and silicon surface roughness of Examples 1 to 8.

[0024] Table 2 shows the formula ratios, etching rates and silicon surface roughness of Examples 9 to 16.

[0025] Table 3 shows the formula ratios, etching rates and silicon surface roughness of Comparative Examples 1 to 6

[0026] It can be seen from Examples 1-8 in Table 1 that within the scope covered by the present invention, the prepared etching solutions all show excellent selectivity of up to 190 and above, and have excellent surface flatness. Examples 9-13 and Examples 14-16 are etching solutions obtained under different silicon inhibitors and different organic acids, respectively, and their selectivity can be as high as 210 and above. Taking Example 14 as a control, Comparative Examples 1 and 2 are etching solutions obtained under temperatures below and above the temperature range, and the selectivity under these conditions is only above 90; Comparative Example 3 has no silicon inhibitor, and fails to form a dense protective film on the surface of the silicon substrate, and the selectivity is only 108; Comparative Example 4 has no organic acid, and fails to cooperate with the silicon inhibitor to regulate the overall etching process and ensure the uniformity of etching, resulting in a selectivity of only 118, and the roughness is slightly higher than that of other embodiments; Comparative Example 5 has no polyamine silane as a surfactant, and cannot effectively adjust the surface tension between the etching solution and different phases, and provide additional passivation protection for the silicon substrate, and the selectivity is only 127; Comparative Example 6 has no leveling agent, and although the selectivity is not greatly affected, it is caused by Figure 1 and Figure 2It can be seen that the etching solution obtained in Example 14 has greatly improved the flatness of the Si surface after etching, while Comparative Example 6 has no leveling agent to guide the liquid flow to fill the tiny bumps and grooves to improve the surface flatness, resulting in poor roughness of the Si surface after etching.

[0027] In summary, the etching solution prepared in the present invention not only has an extremely high selectivity, up to 210 and above, but also can maintain excellent surface flatness. Among them, the silicon inhibitor, organic acid, polyamine silane and leveling agent each play an important role, ensuring the efficiency and uniformity of the etching process, especially the application of the leveling agent significantly improves the flatness of the silicon surface after etching. These results prove the superior performance of the etching solution of the present invention in practical applications.

[0028] The foregoing description is primarily for illustrative purposes. Although the present invention has been shown and described with respect to exemplary embodiments thereof, it will be appreciated by those skilled in the art that the foregoing and various other changes, omissions and additions may be made in its form and details without departing from the spirit and scope of the present invention.

Claims

1. An etching solution for selectively removing tantalum nitride relative to silicon, characterized in that: The composition comprises the following components by mass fraction: 1-5% fluoride ion source; 20-50% oxidant; 1-5% organic acid; 0.01-1% silicon inhibitor; 0.01-1% leveling agent; 0.01-1% surfactant; The balance is high purity water.

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 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.

6. The etching solution for selectively removing tantalum nitride relative to silicon according to claim 1, characterized in that: The leveling agent is neopentyl glycol ester, trimethylolpropane ester, sorbitol ester or xylitol ester or a combination thereof.

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

8. The etching method of any one of claims 1 to 7, wherein the etching solution selectively removes tantalum nitride relative to silicon. The following steps are involved: S1: First, add the silicon inhibitor into the organic acid and form a uniform and stable solution by ultrasonic stirring; S2: After the fluoride ion source, oxidant, leveling agent and surfactant are evenly mixed, the above-mentioned stabilizing solution is added, and water is added to adjust the total amount of the etching solution, and the etching solution is obtained after sufficient stirring.

9. The method according to claim 8, characterized in that The method further includes the step of drying the semiconductor device.

10. The method according to claim 8, characterized in that The contacting step is carried out at a temperature of 25-50° C. and a stirring rate of 100 r / min-500 r / min.

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