A copper etching solution for strengthening molybdenum-niobium alloy etching and an etching method

Abstract

The application discloses a copper etching solution for strengthening molybdenum-niobium alloy etching, and the main components of the copper etching solution are as follows in percentage by mass: 5-20% of hydrogen peroxide, 5-20% of organic acid, 3-12% of organic alkali, 0-0.25% of metal protective agent and 60-77% of deionized water; the pH value of the copper etching solution is 2.1-3.6; and the organic acid is a combination of at least two kinds of organic acids. The copper etching solution for strengthening molybdenum-niobium alloy etching accelerates the etching rate of the copper / molybdenum-niobium layer in two different regions of the same substrate, i.e., a region with uniform and dense photoresist distribution and a region with sparse photoresist distribution, especially the etching rate of the region with sparse photoresist distribution, by optimizing the content of the main components of the copper etching solution and the pH value range, so that the etching time of different regions in the same substrate tends to be consistent; the overall etching time of the substrate is shortened, and the etching efficiency and etching precision consistency of the copper / molybdenum-niobium metal laminated substrate are improved. The application further discloses an etching method based on the copper etching solution.

Description

Technical Field

[0001] This invention relates to the field of wet etching technology for metal films, and specifically to a copper etching solution and etching method for enhancing the etching of molybdenum-niobium alloys. Background Technology

[0002] In the structure of large-size display devices, metallic copper is typically used to fabricate the source, drain, and gate electrodes. However, copper has poor adhesion to the glass substrate. Therefore, a molybdenum layer or a molybdenum alloy layer, such as a molybdenum-niobium alloy layer, is placed between the copper and the glass substrate. The production of copper conductors in large-size display devices mainly includes the following steps: applying a predetermined pattern of photoresist to the surface of the copper layer; etching the areas of the copper layer and the molybdenum-niobium alloy layer not covered by the photoresist using a wet etching solution; and finally, stripping and cleaning to remove the photoresist.

[0003] In existing technologies, the main components of etching solutions for copper-molybdenum alloys are oxides, acids, alkalis, and corrosion inhibitors. Among them, oxides are used to oxidize metals to generate metal oxides, and acids are mainly used to dissolve metal oxides, stabilize hydrogen peroxide, and form stable complexes with metal ions generated in the etching system. The specific components and contents of oxides, acids, alkalis, and corrosion inhibitors in the etching solution are all factors affecting the etching rate. In addition, copper and molybdenum-niobium alloys exposed to the etching solution at the same time form a galvanic cell, which accelerates the corrosion of molybdenum-niobium alloys.

[0004] There are two main types of etched metal stacks containing copper and molybdenum-niobium alloy layers: one is a three-layer stack structure consisting of a molybdenum-niobium alloy surface layer, a copper layer, and a molybdenum-niobium alloy bottom layer; the other is a two-layer stack structure consisting of a copper layer and a molybdenum-niobium alloy bottom layer. Compared to a single copper layer, the etching rate of a single molybdenum-niobium alloy layer is slower. The etching time of the three-layer stack structure consists of three time periods: etching of the molybdenum-niobium alloy surface layer, etching of both the copper and molybdenum-niobium alloy surface layers after the copper layer is exposed, and etching of the stack structure after the molybdenum-niobium alloy bottom layer is exposed. The etching time of the two-layer stack structure consists of two time periods: etching of the copper layer and etching of the stack structure after the molybdenum-niobium alloy bottom layer is exposed. Based on the same thickness of copper and molybdenum-niobium alloy surface / bottom layers, the etching time of the three-layer stack structure is longer than that of the two-layer stack structure. With a 30% OE overcut, the overcut time of the three-layer stack structure is also correspondingly longer than that of the two-layer stack structure, indicating that the molybdenum-niobium bottom layer is etched more during the overcut time period in the three-layer stack structure. Based on the same over-etching time, the molybdenum-niobium bottom layer of the two-layer stacked structure has more residue, requiring an increase in over-etching to eliminate residue.

[0005] In addition, wet etching of two-layer stacked structures has the following drawbacks: In workpieces where the photoresist is not uniformly distributed in the uncovered areas, the galvanic cell accelerates the corrosion after the molybdenum-niobium alloy underlayer is exposed, making the etching rate distribution more uniform; however, in some substrates that simultaneously have AA (effective display) areas and Fanout areas, the photoresist distribution in the AA area is uniform and dense, and the etched area size is small; the photoresist distribution in the Fanout area is sparse, and the etched area size is large. This directly leads to poor etching synchronization between the two areas when the etchant treats the substrate, that is, when the AA area is etched, a large area of ​​molybdenum-niobium alloy underlayer remains in the Fanout area (e.g., Figure 1 As shown, the etching time needs to be extended to complete the etching of the entire substrate. During the extended etching period, the copper etchant not only treats the residue in the Fanout area but also laterally etches the AA area, degrading the consistency of the substrate's conductive etching precision. Summary of the Invention

[0006] One of the objectives of this invention is to overcome the deficiencies in the prior art and provide a copper etching solution that enhances the etching of molybdenum-niobium alloys, effectively increasing the etching rate of metal stacks in areas with sparse or no photoresist distribution on the same substrate, thereby shortening the overall etching time of the substrate.

[0007] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows: a copper etching solution for strengthening the etching of molybdenum-niobium alloys, wherein, by mass percentage, the main components of the copper etching solution are: 5%–20% hydrogen peroxide, 5%–20% organic acid, 3%–12% organic alkali, 0%–0.25% metal protectant, and 60%–77% deionized water; the pH value of the copper etching solution is 2.1–3.6;

[0008] The organic acid is a combination of at least two organic acids.

[0009] Furthermore, based on the mass percentages of hydrogen peroxide, organic acid, and deionized water in the copper etching solution, the mass percentage of the metal protectant is 0.01% to 0.1%, more preferably 0.02% to 0.07%.

[0010] A preferred technical solution is that the copper etching solution contains less than 3.5% hydrogen peroxide stabilizer;

[0011] Furthermore, the copper etching solution contains less than 2% hydrogen peroxide stabilizer.

[0012] Specifically, the content of hydrogen peroxide stabilizer in the copper etching solution is 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 0.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.3%, and 3.5%, as well as the range between the two values ​​mentioned above as the maximum and minimum values.

[0013] A preferred technical solution is that the pH value of the copper etching solution is 2.3 to 3.4;

[0014] Furthermore, the pH value of the copper etching solution is 2.7–3.3.

[0015] Specifically, the pH values ​​of the copper etching solution are 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, and 3.4, as well as the range between the two values ​​mentioned above as the maximum and minimum values.

[0016] The preferred technical solution is that, by mass percentage, the main components of the copper etching solution are: 12.5%–18% hydrogen peroxide, 6%–13% organic acid, 5%–9% organic alkali, 0.02%–0.07% metal protectant, and 64%–76% deionized water.

[0017] The preferred technical solution is that the organic acid is a combination of α-hydroxy aliphatic monocarboxylic acid and organic acid A other than α-hydroxy aliphatic monocarboxylic acid;

[0018] Furthermore, organic acid A is selected from at least one of malic acid, citric acid, malonic acid, pyruvic acid, glutamic acid, glycine, threonine, tartaric acid, oxalic acid, and succinic acid.

[0019] The preferred technical solution is that, based on the total mass of organic acids being 100%, the mass percentage of the α-hydroxy aliphatic monocarboxylic acid is 84% ​​to 97%.

[0020] Specifically, the mass percentages of α-hydroxyaliphatic monocarboxylic acids are 84%, 85%, 87%, 89%, 91%, 93%, 95%, and 97%, as well as the ranges with the above two points as the maximum and minimum values. Further, the mass percentage of α-hydroxyaliphatic monocarboxylic acids ranges from 86% to 95%.

[0021] The preferred technical solution is that the organic base is a combination of a sterically hindered amine and an organic base A other than the sterically hindered amine; the mass percentage of the sterically hindered amine is 84% ​​to 97% based on the total mass of the organic bases being 100%.

[0022] Specifically, the mass percentage of the sterically hindered amine in the organic base is 84%, 85%, 87%, 89%, 91%, 93%, 95%, 97%, etc., and the range between these two points is taken as the maximum and minimum value. Further, the mass percentage of the sterically hindered amine is 86% to 94%.

[0023] A preferred embodiment is that the sterically hindered amine is selected from at least one of tert-butylaminoethoxyethanol, tert-butylaminoisopropanol, tert-butylaminon-propanol, tert-butylaminoisopropanol, triisopropanolamine, isobutanolamine, and 3-diethylaminopropylamine; and the organic base A is selected from at least one of ethylenediamine, diethanolamine, triethanolamine, dimethylethylenediamine, diethylene glycolamine, and monoisopropanolamine.

[0024] Furthermore, the sterically hindered amine is selected from at least one of triisopropanolamine, isobutanolamine, and 3-diethylaminopropylamine;

[0025] Furthermore, organic base A is selected from at least one of ethanolamine and monoisopropanolamine.

[0026] A second objective of this invention is to provide an etching method that uses the aforementioned copper etching solution for strengthening molybdenum-niobium alloy etching to etch a substrate having a metal stack, wherein the metal stack includes a molybdenum-niobium alloy layer and a copper layer disposed on the surface of the molybdenum-niobium alloy layer.

[0027] A preferred technical solution is that the etching temperature of the substrate is 25–40°C;

[0028] Furthermore, the etching temperature of the substrate is 30–35°C;

[0029] Furthermore, the substrate includes a base material, and the copper layer is disposed on the surface of the molybdenum-niobium alloy layer opposite to the base material.

[0030] The advantages and beneficial effects of this invention are as follows:

[0031] This enhanced copper etching solution for molybdenum-niobium alloy etching accelerates the etching rate of copper / molybdenum-niobium layers in two different regions of the same substrate—one with uniform and dense photoresist distribution and the other with sparse photoresist distribution—by optimizing the content of the main components and the pH range of the copper etching solution. In particular, it improves the etching rate of the sparse photoresist distribution region, making the etching time of different regions in the same substrate tend to be consistent.

[0032] Shorten the overall etching time of the substrate and improve the etching efficiency and etching accuracy consistency of the copper / molybdenum-niobium metal stacked substrate. Attached Figure Description

[0033] Figure 1 This is a photograph of a substrate with AA and Fanout areas processed at a 1OE 30% ratio. The gray part of the Fanout area is the etching residue of the molybdenum-niobium alloy underlayer.

[0034] Figure 2 This is a photograph of a substrate with AA and Fanout areas processed at a ratio of 1OE 30%. There is no gray residue in either the AA or Fanout areas.

[0035] Figure 3 This is a cross-sectional photograph of the substrate treated with 30% OE in Example 1;

[0036] Figure 4 This is a photograph of the remaining Fanout area on the substrate treated with 30% OE in Example 1;

[0037] Figure 5 This is a cross-sectional photograph of a substrate processed at a 30% scale (3OE). The white unidirectional arrow indicates the undercut position.

[0038] Figure 6 This is a cross-sectional photograph of the substrate treated with 30% OE in Example 6. The white unidirectional arrow indicates the undercut position.

[0039] Figure 7 This is a cross-sectional photograph of the substrate treated with 30% OE in Example 9;

[0040] Figure 8 This is a photograph of the remaining Fanout area on the substrate treated with 30% OE in Example 9;

[0041] Figure 9 This is a cross-sectional photograph of the substrate treated with 30% OE in Example 11;

[0042] Figure 10 This is a photograph of the remaining Fanout area on the substrate treated with 30% OE in Example 11. Detailed Implementation

[0043] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0044] Other components of copper etching solution

[0045] In addition to hydrogen peroxide, organic acids, and organic bases, known additives include penetrants, wetting agents, and electrochemical modifiers. Furthermore, the sum of the mass percentages of hydrogen peroxide, organic acids, organic bases, hydrogen peroxide stabilizers, metal protectants, and deionized water is not less than 95%, and even further, not less than 98%, for example, 100%.

[0046] Furthermore, the copper etching solution does not contain fluorine or phosphorus sources.

[0047] Hydrogen peroxide and hydrogen peroxide stabilizers

[0048] Hydrogen peroxide oxidizes copper, molybdenum, and niobium to form corresponding metal oxides. Hydrogen peroxide participates in etching, having little effect on the pH of the etching system. Hydrogen peroxide is added to the etching system as a 30% hydrogen peroxide solution.

[0049] Hydrogen peroxide stabilizers, also known as hydrogen peroxide stabilizers, can be either adsorbent-type or complexing-type stabilizers that are stable in the etching system. Preferably, the etchant matrix does not contain phosphorus-containing compounds, meaning that phosphates (including inorganic phosphates and organophosphonic acid compounds) are not selected as complexing stabilizers. Further, the hydrogen peroxide stabilizer is a stabilizer other than the organic acid component; preferably, the hydrogen peroxide stabilizer is at least one selected from phenylurea and ethylene glycol.

[0050] organic acids

[0051] The organic acid is a combination of two or more organic acids, specifically organic acids with different acidity coefficients (pKa). Preferably, the main component of the organic acid is an α-hydroxy aliphatic monocarboxylic acid and an organic acid A other than the α-hydroxy aliphatic monocarboxylic acid. The α-hydroxy aliphatic monocarboxylic acid is selected from glycolic acid and lactic acid, and organic acid A can be selected from at least one of malic acid, citric acid, malonic acid, pyruvic acid, glutamic acid, glycine, threonine, tartaric acid, oxalic acid, and succinic acid. Further, organic acid A is selected from at least one of malic acid, citric acid, malonic acid, and succinic acid. Even further, organic acid A is malic acid (the combination of lactic acid and malic acid is beneficial for optimizing the synchronization of the AA region and the Fanout region during the etching process).

[0052] In the etching results of a two-layer stacked structure of molybdenum-niobium alloy layer and copper layer, the use of a single acid, especially α-hydroxy aliphatic monocarboxylic acid, increases the probability of undercutting of the copper layer.

[0053] Organic bases

[0054] The organic base may be a single organic base or a mixture of two or more organic bases, preferably a mixture of organic bases. When the organic base is a single base, it is preferably a sterically hindered amine: triisopropanolamine and / or 3-diethylaminopropylamine, and the main component of the organic base is the sterically hindered amine and organic base A other than the sterically hindered amine. The preferred sterically hindered amine is triisopropanolamine and / or 3-diethylaminopropylamine, and more preferably triisopropanolamine.

[0055] Organic base A may be selected from ethylenediamine, ethanolamine, diethanolamine, triethanolamine, dimethylethylenediamine, diethylene glycolamine, or monoisopropanolamine. Preferably, organic base A is at least one selected from ethanolamine and monoisopropanolamine.

[0056] Metal protectant

[0057] The metal protectant is a copper protectant, primarily used to regulate the etching rate of copper. It can be a nitrogen-based heterocyclic compound corrosion inhibitor, specifically at least one selected from 3-amino-1,2,4-triazole, 2-aminopyrimidine, 5-aminotetrazolium, imidazole, 4-amino-1,2,4-triazole, and benzotriazole. Based on the preferred etching solution component mass percentage, the metal protectant is 0.01% to 0.1%, more preferably 0.02% to 0.07%. Excessive use of the metal protectant can lead to undercutting of the copper layer. Specifically, in the cross-sectional photograph of the etched structure of the molybdenum-niobium alloy layer and the copper layer, the interface between the molybdenum-niobium alloy layer and the copper layer protrudes towards the etched area, forming an angle. Undercutting distorts the pattern linewidth and increases the probability of abnormal conductivity.

[0058] Molybdenum Niobium Alloy

[0059] Molybdenum-niobium alloy is any alloy type that can be laminated with a copper layer in existing LCD substrates.

[0060] Example

[0061] I. Components and preparation of copper etching solution (except for the metal protectant, all reagents are commercially available analytical grade reagents):

[0062] Hydrogen peroxide – 30% hydrogen peroxide;

[0063] Organic acids—lactic acid, malic acid, malonic acid;

[0064] Organic bases—triisopropanolamine, 3-diethylaminopropylamine, monoisopropanolamine;

[0065] Hydrogen peroxide stabilizer – phenylurea;

[0066] Metal protectant – 3-amino-1,2,4-triazole;

[0067] Preparation of copper etching solution: Add hydrogen peroxide, hydrogen peroxide stabilizer, organic acid, ammonium fluoride, organic base and metal protectant to the mixing tank in proportion, add water to adjust to the predetermined component content, and mix evenly to obtain copper etching solution for strengthening the etching of molybdenum-niobium alloy.

[0068] 2. Preparation of the etched sample substrate: A molybdenum-niobium alloy layer with a thickness of 350 angstroms and a copper layer with a thickness of 5000 angstroms are sequentially deposited on the surface of the glass substrate; the spacing between adjacent photoresist lines in the AA region of the substrate is 50-300 μm, and there is no photoresist spacing in the Fanout region, which has a full photoresist layer.

[0069] The copper etching solution sample was heated and kept at 32-34°C using etching equipment to etch the sample substrate; after etching, it was rinsed with pure water and dried.

[0070] The etching time of the substrate was set according to 30% of the OE in the AA region; the etching of the same substrate sample was performed in parallel for 4 groups.

[0071] III. Etching Time and Result Detection in Examples and Comparative Cases:

[0072] 1. Take SEM photos after etching, and calculate the residual area of ​​the fanout region based on the photos (with the area of ​​the fanout region as 100%).

[0073] 2. Obtain the etching tilt angle and CD-loss (single-sided linewidth loss) of the copper / molybdenum-niobium alloy layer from the SEM image of the etched workpiece cross section, and calculate the average etching tilt angle and the average CD-loss.

[0074] 3. Technical standards: Etching angle 20-50°; CD-loss 0.5-1.0μm.

[0075] IV. Examples and Comparative Examples

[0076] 1. The compositions of Examples 1-4 and Comparative Examples 1-2 regarding pH values ​​are shown in the table below. All components in the table are expressed as mass percentages:

[0077]

[0078] The metrological test results of Examples 1-4 and Comparative Example 2 are shown in the table below:

[0079]

[0080] Photograph of the etched substrate in Example 1 is shown below. Figure 3 , 4 As shown.

[0081] The residual area of ​​the fanout region in Comparative Example 1 accounts for 45.5% of the total area of ​​the fanout region, indicating that there is a large difference in etching rate between the fanout region and the AA region, and that the CD-loss exceeds the technical standard.

[0082] Examples 1, 2, 3, and 4: In Examples 2-4, where the pH value is 2.7 to 3.3, the percentage of the residual area of ​​the fanout region to the total area of ​​the fanout region is smaller than that in Example 1.

[0083] Example 1 and Comparative Example 3: Comparative Example 3 used lactic acid alone as the organic acid. Although the percentage of the residual area in the fanout region to the total fanout region was lower than in Example 1, and the etching tilt angle and CD-loss were within the technical standard range, the copper layer showed obvious undercut (e.g. Figure 5 (As shown), it does not meet the technical standards.

[0084] 2. The composition of Examples 5-7 regarding the corrosion inhibitor content is shown in the table below. All components in the table are expressed as a percentage by mass:

[0085]

[0086] The measurement test results for Examples 3 and 5-7 are shown in the table below:

[0087]

[0088] Examples 3, 5-7: 3-Amino-1,2,4-triazole is mainly used as a copper protectant. The etching synchronization of Example 5 is better than that of Example 3.

[0089] Example 6 shows copper layer undercut (e.g.) Figure 6 (As shown); Excessive copper protectant leads to an increased etching time in the AA region, reaching 130s for OE%30, resulting in a smaller percentage of the fanout region's residual area compared to the total fanout region area. In copper etching solutions, excess copper protectant can be used in combination with other components that accelerate the copper layer etching rate.

[0090] In Example 7, no 3-amino-1,2,4-triazole was added. The percentage of the residual area of ​​the fanout region to the total area of ​​the fanout region increased compared to Example 3, and the CD-loss exceeded the technical standard.

[0091] 3. The compositions of the organic acids and organic bases in Examples 8-13 are shown in the table below. All components in the table are expressed as mass percentages:

[0092]

[0093]

[0094] The measurement test results for Examples 3 and 8-13 are shown in the table below:

[0095]

[0096] As can be seen from Examples 3, 8, and 9, compared with the use of triisopropanolamine alone in Example 3, the combination of sterically hindered amine and organic base A in the organic base is beneficial to reducing the percentage of the residual area of ​​the fanout region to the total area of ​​the fanout region, and the etching tilt angle and CD-loss both meet the technical standards.

[0097] like Figure 7 , 8 As shown, the hindering amine used in Example 9 is 3-diethylaminopropylamine, and the sum of the mass percentages of organic amines in Example 9 is less than the sum of the mass percentages of organic amines in Example 8. Based on the similar synchronous etching effect in the two regions, Example 9 consumes less organic base.

[0098] Compared with Example 8, based on the organic acid mass of 100%, the lactic acid accounted for 80% of the organic acid mass in Example 10, the OE 30% was significantly shortened, and the percentage of the fanout area residue to the total fanout area was significantly increased. This indicates that the copper etching solution containing this organic acid combination is more conducive to promoting the etching of the AA area, and also indicates that the composition of organic acid has a greater impact on the etching synchronization of the two areas of the substrate.

[0099] like Figure 9 , 10 As shown, compared to the organic acid combination of lactic acid and malonic acid in Example 8, the combination of lactic acid and malic acid is beneficial for further improving the synchronization of the AA region and the fanout region of the substrate. In Example 11, the time required for both the AA region and the fanout region of the substrate to be etched was 118 seconds.

[0100] Examples 11-13 show that, within the range of 80%-90% mass percentage of hindered amine in organic bases, the lower the content of hindered amine in organic bases, the greater the percentage of residual area of ​​the OE30% fanout region relative to the total area of ​​the fanout region.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A copper etching solution for enhancing the etching of molybdenum-niobium alloys, characterized in that, By mass percentage, the main components of the copper etching solution are: hydrogen peroxide 5%–20%, organic acid 5%–20%, organic base 3%–12%, metal protectant 0%–0.25%, and deionized water 60%–77%; the pH value of the copper etching solution is 2.1–3.

6. The organic acid is a combination of at least two organic acids, and the copper etching solution contains less than 3.5% hydrogen peroxide stabilizer. The organic acid is a combination of α-hydroxy aliphatic monocarboxylic acid and organic acid A other than α-hydroxy aliphatic monocarboxylic acid; The α-hydroxy aliphatic monocarboxylic acid is glycolic acid and / or lactic acid; the organic acid A is at least one selected from malic acid, citric acid, malonic acid, pyruvic acid, glutamic acid, glycine, threonine, tartaric acid, oxalic acid, and succinic acid. The α-hydroxy aliphatic monocarboxylic acid has a mass percentage of 84% to 97%, based on the total mass of organic acids being 100%. The organic base is a combination of a sterically hindered amine and an organic base A other than the sterically hindered amine; the sterically hindered amine has a mass percentage of 84% to 97% based on the total mass of the organic bases being 100%. The sterically hindered amine is at least one selected from triisopropanolamine and 3-diethylaminopropylamine; the organic base A is at least one selected from ethanolamine and monoisopropanolamine.

2. The copper etching solution for enhancing molybdenum-niobium alloy etching according to claim 1, characterized in that, The copper etching solution contains less than 2% hydrogen peroxide stabilizer.

3. The copper etching solution for enhancing molybdenum-niobium alloy etching according to claim 1, characterized in that, The pH value of the copper etching solution is 2.3 to 3.

4.

4. The copper etching solution for enhancing molybdenum-niobium alloy etching according to claim 3, characterized in that, The pH value of the copper etching solution is 2.7 to 3.

3.

5. The copper etching solution for enhancing molybdenum-niobium alloy etching according to claim 1, characterized in that, By mass percentage, the main components of the copper etching solution are: hydrogen peroxide 12.5%–18%, organic acid 6%–13%, organic alkali 5%–9%, ​​metal protectant 0.02%–0.07%, and deionized water 64%–76%.

6. The copper etching solution for enhancing molybdenum-niobium alloy etching according to claim 1, characterized in that, The mass percentage of α-hydroxyaliphatic monocarboxylic acids is 86%–95%.

7. The copper etching solution for enhancing molybdenum-niobium alloy etching according to claim 1, characterized in that, The sterically hindered amine has a mass percentage of 86% to 94%.

8. An etching method, characterized in that, A substrate having a metal stack is etched using a copper etching solution for enhanced molybdenum-niobium alloy etching as described in any one of claims 1 to 7, wherein the metal stack comprises a molybdenum-niobium alloy layer and a copper layer disposed on the surface of the molybdenum-niobium alloy layer.

9. The etching method according to claim 8, characterized in that, The etching temperature of the substrate is 25–40°C.

10. The etching method according to claim 9, characterized in that, The etching temperature of the substrate is 30-35°C.

11. The etching method according to claim 9, characterized in that, The substrate includes a base material, and the copper layer is disposed on the surface of the molybdenum-niobium alloy layer opposite to the base material.

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