High selectivity copper etching liquid composition and use thereof

Abstract

The present application relates to the technical field of metal etching liquid, in particular to a high-selectivity copper etching liquid composition and application thereof.The components include organic acid 1-5%, inorganic acid 0.5-4%, fluorine compound 0.01-0.5%, alcohol ether stabilizer 0.5-3%, amine stabilizer 0.1-1%, azole inhibitor 0.2-2%, amide alloy etching inhibitor 0.01-0.8%, hydrogen peroxide 3-20% and deionized water to make up the rest by weight percentage.The present application introduces amide inhibitor containing amide structure into the etching liquid, which is compounded with azole inhibitor and fluorine compound, so as to greatly reduce the alloy layer etching rate under the premise of ensuring the normal etching rate of copper, and realize the high selectivity effect of copper etching and alloy layer protection.

Description

Technical Field

[0001] This invention relates to the field of metal etching solution technology, and more specifically, to a high selectivity copper etching solution composition and its application. Background Technology

[0002] With the rapid development of industries such as 5G communication and flexible displays, microelectronic devices continue to evolve towards higher density, multilayering, and refinement. The stacked structure composed of copper wiring and alloy barrier / adhesive layers such as molybdenum, molybdenum-niobium, and molybdenum-titanium (MoTi) has become the mainstream design in the industry. In the patterning etching process, the etching solution needs to completely remove the copper layer in the exposed areas while leaving the underlying alloy barrier layer untouched, in order to ensure the structural accuracy, electrical performance, and long-term reliability of the device.

[0003] Currently, hydrogen peroxide-based copper etching solutions are widely used in the industry. However, while etching copper, these solutions generally exhibit high etching rates on alloy layers such as molybdenum and molybdenum-titanium, easily leading to problems such as over-etching of alloy layers, barrier layer failure, excessive linewidth deviation, and decreased device yield, failing to meet the process requirements of advanced manufacturing processes. For example, Chinese invention patent application CN115418642A discloses a copper-molybdenum etching solution and its preparation method. This solution constructs an etching system using hydrogen peroxide, inorganic acid, chelating agent, and thiazole inhibitors, primarily achieving simultaneous etching of copper and molybdenum to meet the process requirements of copper-molybdenum co-etching. However, it cannot be applied to selective etching scenarios that only etch copper while retaining alloy layers. Meanwhile, some existing technologies slow down alloy etching by reducing the oxidant content and increasing the chelating agent ratio, but this directly leads to a decrease in copper etching rate and production efficiency. It also easily results in increased post-etching residue and reduced copper ion loading capacity, failing to balance copper etching efficiency with alloy layer protection. Furthermore, existing etching inhibitors are mostly azole compounds, which have a stronger inhibitory effect on copper etching than on alloys, making it difficult to achieve selective inhibition of the alloy layer and failing to fundamentally solve the industry pain point of over-etching of the alloy layer during copper etching. Therefore, developing an etching solution that combines high copper etching efficiency and high alloy etching selectivity has significant industrial application value. Summary of the Invention

[0004] The first aspect of the present invention provides a high-selectivity copper etching solution composition, comprising, by weight percentage, 1-5% organic acid, 0.5-4% inorganic acid, 0.01-0.5% fluorine compound, 0.5-3% alcohol ether stabilizer, 0.1-1% amine stabilizer, 0.2-2% azole inhibitor, 0.01-0.8% amide alloy etching inhibitor, 3-20% hydrogen peroxide, and deionized water to make up the balance.

[0005] Existing copper etching systems mostly use azole compounds as single inhibitors combined with fluorine sources to regulate etching activity. Azole compounds preferentially adsorb onto the copper surface to control the etching rate, exhibiting weak selectivity and limited protective effect on molybdenum-based alloy layers such as molybdenum-titanium and molybdenum-niobium. They cannot effectively block the corrosion of the alloy by oxidants, acidic components, and fluoride ions, easily leading to simultaneous over-etching, morphological degradation, and functional failure of the alloy barrier layer during copper etching. This makes it difficult to meet the process requirements of high-density multilayer processes for high-selectivity etching of copper and alloys. This invention introduces amide inhibitors containing amide structures into the etching solution. The polar amide groups in the amide molecules can selectively chemically adsorb onto the alloy surface, forming a dense protective adsorption film that prevents oxidants, hydrogen ions, and fluoride ions from contacting the alloy surface. Simultaneously, it is combined with azole inhibitors and fluorine compounds. The azole compounds regulate the etching rate of the copper surface to ensure etching uniformity, while the fluorine compounds maintain appropriate etching activity to avoid copper layer residue. Ultimately, while ensuring a normal copper etching rate, the etching rate of the alloy layer is significantly reduced, achieving a high-selectivity effect for both copper etching and alloy layer protection.

[0006] By weight percentage, the components include 2-4% organic acids, 0.5-3% inorganic acids, 0.05-0.3% fluorine compounds, 1-3% alcohol ether stabilizers, 0.3-1% amine stabilizers, 0.5-1% azole inhibitors, 0.01-0.6% amide inhibitors, 5-10% hydrogen peroxide, and the balance is made up with deionized water.

[0007] The weight ratio of the fluorinated compounds, azole inhibitors, and amide inhibitors is 0.1:(0.5-0.8):(0.05-0.3).

[0008] The weight ratio of the fluorinated compounds, azole inhibitors, and amide inhibitors is 0.1:(0.55-0.75):(0.05-0.3).

[0009] The weight ratio of the organic acid to the inorganic acid is (2-4):(1.5-2.5).

[0010] The weight ratio of the alcohol ether stabilizer to the amine stabilizer is (1-2):(0.5-1).

[0011] The organic acid includes at least one of iminodiacetic acid, hypozinotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, carbamic acid (methylenephosphonic acid), 1-hydroxyethane-1,1-diphosphonic acid, ethylenediaminetetraacetic acid (methylenephosphonic acid), diethylenetriaminepentamethylenephosphonic acid, alanine, aminobutyric acid, acetic acid, formic acid, butyric acid, citric acid, glycolic acid, oxalic acid, malonic acid, malic acid, valeric acid, propionic acid, tartaric acid, gluconic acid, succinic acid, glutamic acid, hydroxyethylidene diphosphonic acid, phenolsulfonic acid, and fumaric acid.

[0012] The inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, and at least one of sulfate, nitrate, hydrochloride, and phosphate.

[0013] The fluorine compounds include at least one of hydrofluoric acid, sodium fluoride, potassium fluoride, aluminum trifluoride, fluoroboric acid, ammonium fluoride, ammonium hydrogen fluoride, sodium hydrogen fluoride, and potassium unsymmetrical dihydrofluorate.

[0014] The amine stabilizers include at least one of the following: n-hexylamine, cyclohexylamine, triisopropanolamine, isopropanolamine, diisopropanolamine, diethylene glycolamine, hydroxyethyl ethylenediamine, hydroxyethylamine, N-methylaminoethanol, diethanolamine, triethanolamine, 2-[2-(2-aminoethoxy)(ethoxy)]ethanol, N-aminoethyl-N'-hydroxyethyl ethylenediamine, and N,N'-dihydroxyethyl-ethylenediamine.

[0015] The alcohol ether stabilizers include at least one of polyethylene glycol, polybutylene glycol, polypropylene glycol, polytetramethylene ether glycol, 1,3-propanediol, and ethylene glycol butyl ether.

[0016] The azole inhibitors are at least one of 5-methyltetrazole, oxazole, imidazole, pyrazole, triazole, tetrazolium, 5-aminotetrazole, and methyltetrazole.

[0017] The amide inhibitors include at least one of nicotinamide, isonicotinamide, 2-methylnicotinamide, N-methylnicotinamide, and 6-methylnicotinamide.

[0018] A second aspect of the present invention provides an application of an etching solution composition for etching copper alloy stacks.

[0019] The copper alloy stack includes at least one of Cu-MoTi, Cu-MTD (doped molybdenum-titanium alloy), Cu-Mo, and Cu-MoNb.

[0020] Beneficial effects 1. This invention introduces amide inhibitors containing amide structures into the etching solution, which are then combined with azole inhibitors and fluorine compounds to significantly reduce the etching rate of the alloy layer while ensuring the normal etching rate of copper, thereby achieving a high selectivity effect between copper etching and alloy layer protection.

[0021] 2. The weight ratio of fluorine compounds, azole inhibitors and amide inhibitors is limited to 0.1:(0.5-0.8):(0.05-0.3) to stabilize the copper layer cone angle at 55-62° after etching, control the linewidth loss within a reasonable range, and meet the process requirements of high-density and high-precision patterning.

[0022] 3. The weight ratio of alcohol ether stabilizer to amine stabilizer is limited to (1-2):(0.5-1), which can improve the uniformity and wettability of the etching solution, promote the uniform etching reaction, avoid local insufficient etching and copper residue, and ensure that there are no residues on the surface after etching.

[0023] 4. The etching solution of this invention does not require significant adjustments to the formula based on the type of alloy, and can be widely adapted to etching processes of different types of copper / alloy stacked structures.

[0024] 5. The copper loading of the etching solution of this invention can reach 5000ppm. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the etching solution in Example 1 obtained by etching electron microscopy. Detailed Implementation

[0026] Examples 1-10 A high selectivity copper etching solution composition, the components of which are shown in Table 1, with blank spaces indicating no additions.

[0027] A method for preparing a high-selectivity copper etching solution composition includes the following steps: mixing all components evenly and setting aside.

[0028] Table 1

[0029] Comparative Examples 1-8 A copper etching solution composition, the components of which are shown in Table 2, with blank spaces indicating no addition.

[0030] A method for preparing a copper etching solution composition includes the following steps: mixing all components evenly and setting aside for later use.

[0031] Table 2

[0032] Performance testing methods and data The etching solutions prepared in the examples and comparative examples were used for Cu-MoTi alloy stack etching. The etching conditions and etching data are listed in Tables 3 and 4, where Table 3 corresponds to the etching data of the examples and Table 4 corresponds to the etching data of the comparative examples.

[0033] Table 3

[0034] Table 4

[0035] As shown in Tables 3-4, under the uniform test conditions of a copper layer thickness of 6500 Å, a MoTi alloy layer thickness of 350 Å, an etching temperature of 32℃, and an etching time of 130 s, Examples 1-10 with added amide-based alloy etching inhibitors showed significant performance differences compared to Comparative Examples 1-8 without such inhibitors. Figure 1 The etching solution of Example 1 demonstrates excellent etching performance. Regarding core etching selectivity, the MoTi tail length in the examples was in the range of 0.50-0.75 μm, far exceeding the 0.05-0.22 μm level of the comparative examples. This indicates that amide inhibitors can effectively block the erosion of the MoTi alloy by the etching components, significantly reduce the alloy etching rate, and achieve high selectivity etching of copper and alloy. In terms of etching morphology and surface quality, no residue was found after etching in all examples, the lateral etching loss (CD-loss) was stable at 0.75-0.86 μm, and the etching cone angle could be controlled at 55-62°. The morphology uniformity and process stability were excellent. In contrast, the groups in the comparative examples with unbalanced formulation components and excessive oxidant content showed obvious etching residue, and the overall lateral etching loss and cone angle fluctuated more widely, resulting in a narrower process window. In terms of solution lifespan, the highest copper load in the examples could reach 5000 ppm, which was significantly better than the copper load capacity of some comparative examples. This comprehensively verifies the comprehensive technical advantages of the etching solution composition of the present invention in terms of high selective etching, morphology accuracy control, process yield improvement, and extended solution lifespan.

Claims

1. A high-selectivity copper etching solution composition, characterized in that, By weight percentage, the components include 1-5% organic acids, 0.5-4% inorganic acids, 0.01-0.5% fluorine compounds, 0.5-3% alcohol ether stabilizers, 0.1-1% amine stabilizers, 0.2-2% azole inhibitors, 0.01-0.8% amide alloy etching inhibitors, 3-20% hydrogen peroxide, and deionized water to make up the balance.

2. The etching solution composition according to claim 1, characterized in that, The etching solution composition comprises, by weight percentage, 2-4% organic acid, 0.5-3% inorganic acid, 0.05-0.3% fluorine compound, 1-3% alcohol ether stabilizer, 0.3-1% amine stabilizer, 0.5-1% azole inhibitor, 0.01-0.6% amide alloy etching inhibitor, 5-10% hydrogen peroxide, and deionized water to make up the balance.

3. The etching solution composition according to claim 1 or 2, characterized in that, The weight ratio of the fluorinated compounds, azole inhibitors, and amide inhibitors is 0.1:(0.5-0.8):(0.05-0.3).

4. The etching solution composition according to claim 3, characterized in that, The weight ratio of the fluorine compounds, azole inhibitors, and amide alloy etching inhibitors is 0.1:(0.55-0.75):(0.05-0.3).

5. The etching solution composition according to claim 1, characterized in that, The weight ratio of the organic acid to the inorganic acid is (2-4):(1.5-2.5).

6. The etching solution composition according to claim 1, characterized in that, The weight ratio of the alcohol ether stabilizer to the amine stabilizer is (1-2):(0.5-1).

7. The etching solution composition according to claim 1, characterized in that, The fluorine compounds include at least one of hydrofluoric acid, sodium fluoride, potassium fluoride, aluminum trifluoride, fluoroboric acid, ammonium fluoride, ammonium hydrogen fluoride, sodium hydrogen fluoride, and potassium unsymmetrical dihydrofluorate.

8. The etching solution composition according to claim 1, characterized in that, The amide-based alloy etching inhibitor includes at least one of nicotinamide, isonicotinamide, 2-methylnicotinamide, N-methylnicotinamide, and 6-methylnicotinamide.

9. An application of the etching solution composition according to any one of claims 1-8, characterized in that, Etching for copper alloy stacks.

10. The application of the etching solution composition according to claim 9, characterized in that, The copper alloy stack includes at least one of Cu-MoTi, Cu-MTD, Cu-Mo, and Cu-MoNb.

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