High-selectivity SiO2 etching solution without damaging Cu and Ta barrier layers
By adding specific components to the acidic SiO2 etching solution to form a protective film, the problem that it is difficult to quickly etch SiO2 under acidic conditions without damaging Cu, Ta and TaN structures is achieved, and a highly selective etching effect is achieved.
Patent Information
- Application Number
- CN202411739958.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-03-14
AI Technical Summary
In the acid etching liquid, it is difficult to achieve rapid etching of SiO2 without damaging Cu, Ta and TaN structures, especially due to the galvanic corrosion problem between Cu and Ta.
An acid SiO2 etching solution is provided, which contains components such as fluoride, solvent, ammonium salt, azoles and cucurbita. By forming an azole-metal-cucurbita mesh protective film structure, the Cu and Ta structure are protected, and the potential difference is regulated by ammonium salt to enhance the protection of Ta.
Rapid etching of SiO2 is achieved without damaging Cu, Ta and TaN structures, which significantly improves the selectivity of etching.
Smart Images
Figure CN119615164A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of semiconductor etching, and in particular relates to a highly selective SiO2 etching solution which does not damage Cu and Ta barrier layers and can be used for removing SiO2 from microelectronic devices. Background Art
[0002] In recent years, with the continuous development of integrated circuit technology at a higher speed and smaller size, the characteristic size of the back-end metal interconnects has shown a trend of rapid shrinkage. This leads to an increase in the capacitance between metal interconnects and a gradual increase in the interconnect RC delay, which seriously affects the circuit operation speed. To solve this problem, we can start from two aspects. On the one hand, we can use low-conductivity interconnect metal to reduce the resistance of the interconnect; on the other hand, we can use low-dielectric-constant interlayer dielectrics to reduce the capacitance value.
[0003] Compared with other metals and their compounds, Cu has become an important interconnect material for the back-end metal interconnect system due to its low resistance, good stress resistance and migration resistance. However, Cu is easy to diffuse in the dielectric layer, which is fatal to the performance of the device and the reliability of the dielectric. This diffusion will cause voltage attenuation between copper interconnects and even cause voltage breakdown between interconnect layers, seriously affecting the reliability of the circuit. An effective way to prevent Cu diffusion is to add a diffusion barrier layer between Cu and the dielectric. This barrier layer is usually TaN, and in order to improve the adhesion between Cu and TaN, Ta is generally used as an adhesion layer.
[0004] In order to further reduce the dielectric constant of the interlayer dielectric, it is sometimes necessary to etch the interlayer dielectric such as SiO2. In an alkaline system, the etching rate is too slow; in an acid system, due to the strong galvanic corrosion between Cu and Ta, it is difficult to protect the Ta and TaN structures. Under this condition, the art needs a highly selective SiO2 etching solution that can quickly etch SiO2 without damaging the Cu, Ta and TaN structures. Summary of the invention
[0005] The invention provides a highly selective SiO2 etching solution which does not damage Cu and Ta barrier layers. The etching solution does not damage Cu metal interconnection materials and Ta barrier layers and can quickly etch interlayer dielectric SiO2.
[0006] The technical solution of the present invention is to provide a highly selective SiO2 etching solution that does not damage Cu and Ta barrier layers. The etching solution is an acidic etching solution, which contains the following components by mass percentage: 1-15% fluoride, 5-45% solvent, 0.1-10% ammonium salt, 0.1-5% azole, 0.0005-0.05% cucurbituril, and the balance is water.
[0007] Further, the etchant is one or more of hydrogen fluoride (HF), ammonium bifluoride (NH4HF2), ammonium fluoride, ammonium hexafluorosilicate, triethanolammonium fluoride, tetrafluoroboric acid, ammonium tetrafluoroborate, methyldiethanolammonium fluoride, tetramethylammonium fluoride, triethylamine trihydrofluoride, fluoroboric acid, ammonium fluorosilicate, tetrabutylammonium tetrafluoroborate, fluoroacetic acid, ammonium fluoroacetate, trifluoroacetic acid, fluorosilicic acid, diglycolammonium fluoride and mixtures thereof.
[0008] Furthermore, the solvent is one or more of isopropyl alcohol (IPA), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone, ethylene glycol, propylene glycol, butyl diglycol, 1,4-butanediol, tripropylene glycol methyl ether, propylene glycol propyl ether, diethylene glycol monobutyl ether, hexamethylphosphoric triamide, dimethylformamide and N-methyl-2-pyrrolidone.
[0009] Further, the ammonium salt is one or more of ammonium acetate (NH4OAc), ammonium bromide (NH4Br), ammonium citrate, triammonium citrate, ammonium chloride, ammonium tartrate, hexadecyltrimethylammonium bromide, ammonium sulfate, ammonium carbamate, ammonium benzoate, ammonium malonate, ammonium adipate, ammonium lactate, dodecyltrimethylammonium bromide, tetraammonium ethylenediaminetetraacetate and ammonium succinate.
[0010] Furthermore, the azole is one or more of 2-mercaptobenzothiazole (2-MBT), benzimidazole (BZI), pyrazole, 4-aminopyrazole, pyrazole-3-carboxylic acid, 2-amino-1,3,4-thiadiazole, imidazole, imidazolidinone, 1H-1,2,3-triazole, 1,2,4-triazole-3-carboxylic acid, 1,2,4-triazole, 1-methyl-1,2,4-triazole, benzotriazole (BTA), 5-carboxy-benzotriazole, tetrazole, 1H-tetrazole-5-acetic acid, 5-methyltetrazole, 5-phenyl-1H-tetrazole and 5-amino-1H-tetrazole.
[0011] Furthermore, the Ta inhibitor is cucurbituril. The structure of cucurbituril is as follows:
[0012]
[0013] Cucurbituril preferably accounts for 0.001% to 0.05% of the etching solution, more preferably 0.001% to 0.02%, most preferably 0.001% to 0.01%.
[0014] The invention also relates to the application of the etching solution in etching SiO2 of microelectronic devices.
[0015] The present invention has the following beneficial effects:
[0016] The cleaning solution provided by the present invention contains azoles and cucurbituril as inhibitors of Cu and Ta, which can form an azole-metal-cucurbituril mesh protective film structure, and can well protect the metal material. The ammonium salt can repair the defects of the protective film, and can also regulate the potential difference between Cu and Ta, further increasing the protection of Ta. In addition, the solvent reduces the surface tension of the etching solution, which is conducive to the dissolution of the etchant. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a microelectronic structural layer containing SO2, Cu, Ta and TaN.
[0018] Figure 2 This is the SEM image of the untreated structure containing SO2, Cu, Ta and TaN layers.
[0019] Figure 3 This is a SEM image of the SiO2 etching solution used in Example 2.
[0020] Figure 4 This is a SEM image of the SiO2 etching solution used in Comparative Example 11. DETAILED DESCRIPTION
[0021] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.
[0022] The SiO2 cleaning solution provided by the invention contains at least one fluoride, one solvent, one ammonium salt, one azole, cucurbituril and deionized water.
[0023] In some embodiments, the fluoride preferably accounts for 1-15% of the etching solution, more preferably 1% to 12.5%, and most preferably 1% to 10%. The specific fluoride can be hydrogen fluoride (HF), ammonium bifluoride (NH4HF2), ammonium fluoride, ammonium hexafluorosilicate, triethanolammonium fluoride, tetrafluoroboric acid, ammonium tetrafluoroborate, methyldiethanolammonium fluoride, tetramethylammonium fluoride, triethylamine trihydrofluoride, fluoroboric acid, ammonium fluorosilicate, tetrabutylammonium tetrafluoroborate, fluoroacetic acid, ammonium fluoroacetate, trifluoroacetic acid, fluorosilicic acid, diglycolammonium fluoride and combinations thereof. Among them, the HF metal content is low and easy to obtain, preferably HF. Under the presence of the fluoride of the present application, the etching solution of the present application is an acidic etching solution component, wherein the acidic condition is a pH content of any value below pH 6, or pH below 5H, or pH below 4, or pH below 3.
[0024] In some embodiments, the solvent preferably accounts for 5% to 45% of the etching solution, more preferably 10% to 40%, and most preferably 20% to 30%. The solvent is isopropyl alcohol (IPA), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone, ethylene glycol, propylene glycol, butyl diglycol, 1,4-butanediol, tripropylene glycol methyl ether, propylene glycol propyl ether, diethylene glycol monobutyl ether, hexamethylphosphoric acid triamide, dimethylformamide and N-methyl-2-pyrrolidone and combinations thereof. A combination of DMAC and IPA is preferred.
[0025] In some embodiments, the ammonium salt preferably accounts for 0.1% to 10% of the etching solution, more preferably 0.5% to 5%, and most preferably 0.5% to 4%. The ammonium salt is ammonium acetate (NH4OAc), ammonium bromide (NH4Br), ammonium citrate, triammonium citrate, ammonium chloride, ammonium tartrate, hexadecyltrimethylammonium bromide, ammonium sulfate, ammonium carbamate, ammonium benzoate, ammonium malonate, ammonium adipate, ammonium lactate, dodecyltrimethylammonium bromide, tetraammonium ethylenediaminetetraacetate, and ammonium succinate, and combinations thereof. The preferred ammonium salt may be ammonium acetate.
[0026] In some embodiments, the azoles preferably account for 0.1 to 5% of the etching solution, more preferably 0.3 to 2%, and most preferably 0.5 to 1%. The azoles are 2-mercaptobenzothiazole (2-MBT), benzimidazole (BZI), pyrazole, 4-aminopyrazole, pyrazole-3-carboxylic acid, 2-amino-1,3,4-thiadiazole, imidazole, imidazolidinone, 1H-1,2,3-triazole, 1,2,4-triazole-3-carboxylic acid, 1,2,4-triazole, 1-methyl-1,2,4-triazole, benzotriazole (BTA), 5-carboxy-benzotriazole, tetrazole, 1H-tetrazolyl-5-acetic acid, 5-methyltetrazole, 5-phenyl-1H-tetrazole and 5-amino-1H-tetrazole and combinations thereof.
[0027] In some embodiments, cucurbituril preferably accounts for 0.001% to 0.05% of the etching solution, more preferably 0.001% to 0.02%, and most preferably 0.001% to 0.01%.
[0028] The following examples and comparative examples are provided to further illustrate the etching solution of the present invention. See Table 1 for details. Unless otherwise indicated, all percentages are by weight.
[0029] The SiO2 etching solution of the present invention is composed of the components described in Table 1, and the balance is deionized water. Deionized water is added first, then the solvent is added, then the ammonium salt is added, then the cucurbituril is added, then the azoles are added, and finally the fluoride is added. After all the components are added, the solution is stirred evenly using a glass rod.
[0030] Table 1
[0031]
[0032]
[0033] The etching solution in the above examples and comparative examples is prepared by first adding deionized water, then adding solvent, then adding ammonium salt, then adding cucurbituril, then adding azoles, and finally adding fluoride. After all components are added, the solution is stirred evenly using a glass rod.
[0034] The cleaning solutions obtained in the above-mentioned embodiments and comparative examples were used in the cleaning test of SiO2.
[0035] 1)Cu, Ta, TaN and SiO2 etching rates
[0036] After chemically treating SiO2 film sheets for 5 minutes at 25°C, the SiO2 etching rate evaluation was implemented. After chemically treating Cu, Ta, and TaN film sheets for 20 minutes at 25°C, the etching rate evaluation of Cu, Ta, and TaN was implemented. The thickness of Cu, Ta, and TaN was measured using Four Dimensions Four Point Probe Meter 333A, and the impedance of the film was related to the film thickness remaining after contacting the composition of the present invention. The SiO2 thickness was measured using the Auto SE Spectroscopic Ellipsometer from HORIBA JOBIN YVON. The etching rate was calculated as the thickness change (before and after chemical treatment) divided by the chemical treatment time.
[0037] 2) Electrochemical corrosion assessment
[0038] After chemical treatment of the Cu / Ta / TaN / SiO2 laminate at 25°C for 5 minutes, the electrochemical corrosion was evaluated by FIB and SEM, where A was severe electrochemical corrosion, B was general electrochemical corrosion, C was slight electrochemical corrosion, and D was almost no electrochemical corrosion.
[0039] Specific test data are shown in Table 2.
[0040] Table 2
[0041]
[0042]
[0043] Figure 2 This is the SEM image of the untreated structure containing SO2, Cu, Ta and TaN layers.
[0044] The SEM image of the SiO2 etching solution using Example 2 is as follows Figure 3 As shown, it can be seen that the Cu, Ta, and TaN structures are intact, while SiO2 is etched.
[0045] The SEM image of the SiO2 etching solution of Comparative Example 11 is as follows Figure 4 As shown, it can be seen that Cu has some damage, Ta and TaN structures are completely etched, and SiO2 is etched.
[0046] It can be seen from the experimental results of the above embodiments that the SiO2 etching solution provided by the present invention can quickly remove SiO2, while inhibiting the etching of Cu, Ta, and TaN, and has high selectivity for SiO2.
[0047] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A highly selective SiO2 etching solution that does not damage Cu and Ta barrier layers, characterized in that: The etching solution contains the following components in percentage by mass: 1-15% of fluoride, 5-45% of solvent, 0.1-10% of ammonium salt, 0.1-5% of azoles, 0.001-0.05% of cucurbituril, and the balance is water.
2. The highly selective SiO2 etching solution according to claim 1 that does not damage the Cu and Ta barrier layers, characterized in that: The fluoride is one or more of hydrogen fluoride, ammonium bifluoride, ammonium hexafluorosilicate, triethanolammonium fluoride, tetrafluoroboric acid, ammonium tetrafluoroborate, methyldiethanolammonium fluoride, tetramethylammonium fluoride, triethylamine trihydrofluoride, fluoroboric acid, ammonium fluorosilicate, tetrabutylammonium tetrafluoroborate, fluoroacetic acid, ammonium fluoroacetate, trifluoroacetic acid, fluorosilicic acid, diglycolammonium fluoride and mixtures thereof.
3. The highly selective SiO2 etching solution according to claim 1 that does not damage the Cu and Ta barrier layers, characterized in that: The solvent is one or more of isopropanol, dimethylacetamide, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, ethylene glycol, propylene glycol, butyl diglycol, 1,4-butanediol, tripropylene glycol methyl ether, propylene glycol propyl ether, diethylene glycol monobutyl ether, hexamethylphosphoric triamide, dimethylformamide and N-methyl-2-pyrrolidone.
4. The highly selective SiO2 etching solution according to claim 1 that does not damage the Cu and Ta barrier layers, characterized in that: The ammonium salt is one or more of ammonium acetate, ammonium bromide, ammonium citrate, triammonium citrate, ammonium chloride, ammonium tartrate, hexadecyltrimethylammonium bromide, ammonium sulfate, ammonium carbamate, ammonium benzoate, ammonium malonate, ammonium adipate, ammonium lactate, dodecyltrimethylammonium bromide, tetraammonium ethylenediaminetetraacetate and ammonium succinate.
5. The highly selective SiO2 etching solution according to claim 1 that does not damage the Cu and Ta barrier layers, characterized in that: The azoles are one or more of 2-mercaptobenzothiazole, benzimidazole, pyrazole, 4-aminopyrazole, pyrazole-3-carboxylic acid, 2-amino-1,3,4-thiadiazole, imidazole, imidazolidinone, 1H-1,2,3-triazole, 1,2,4-triazole-3-carboxylic acid, 1,2,4-triazole, 1-methyl-1,2,4-triazole, benzotriazole (BTA), 5-carboxy-benzotriazole, tetrazole, 1H-tetrazole-5-acetic acid, 5-methyltetrazole, 5-phenyl-1H-tetrazole and 5-amino-1H-tetrazole.
6. The highly selective SiO2 etching solution according to claim 1 that does not damage the Cu and Ta barrier layers, characterized in that: The Ta inhibitor is cucurbituril, the structural formula is Cucurbituril preferably accounts for 0.001% to 0.02% of the etching solution, and more preferably 0.001% to 0.01%.
7. Use of the highly selective SiO2 etching solution according to any one of claims 1 to 6 that does not damage Cu and Ta barrier layers in cleaning and removing SiO2 from microelectronic devices.
8. The use according to claim 7, characterized in that: In the process of cleaning the microelectronic device, the Cu, Ta and TaN structures are not damaged and SiO2 is etched.