Ag etching solution for relieving side etching and method of using the same

Abstract

The application provides an Ag etching solution for relieving side etching and a use method thereof, and relates to the technical field of metal film layer etching. The Ag etching solution is composed of nitric acid, weak organic acid, succinic acid, pimelic acid, 2-mercaptobenzimidazole, 1-phenyl-5-mercaptotetrazole, benzyltriethylammonium chloride and water. The Ag etching solution can effectively improve the problem of side etching, thereby effectively solving the problem of excessive etching of Ag in the traditional process.

Description

Technical Field

[0001] This invention relates to the field of metal film etching technology, and more specifically to an Ag etching solution for mitigating lateral etching and its application method. Background Technology

[0002] As flat panel display technology develops towards higher resolution, higher refresh rates, and greater flexibility, and as the demand for fine circuitry in advanced semiconductor packaging increases, silver, with its extremely low resistivity (volume resistivity of approximately 1.59 μΩ·cm) and excellent anti-electromigration properties, is gradually replacing traditional metals such as aluminum and molybdenum as a key interconnect material for the gate, source / drain of thin-film transistor liquid crystal displays (TFT-LCDs), the anode reflective layer of OLEDs (organic light-emitting diodes), and the under-bump metal layer (UBM) in heterogeneous integrated packaging.

[0003] In the fabrication of silver micro-nano circuits, wet etching is one of the core processes. An ideal silver wet etching solution must simultaneously meet the following requirements: (1) controllable and stable etching rate; (2) high lateral resolution, i.e., the smallest possible amount of lateral etching; (3) no damage to other metals or inorganic substrates (such as glass, silicon nitride, indium tin oxide, etc.) under the silver layer; and (4) no unwashable metal residues or polymer residues after etching, ensuring the interface cleanliness of subsequent processes.

[0004] Currently, the mainstream silver etching solutions widely used in industry are typically based on nitric acid, phosphoric acid, acetic acid, or a mixture thereof. They dissolve elemental silver by oxidizing it to silver ions using the strong oxidizing power of nitric acid. However, this traditional system has inherent drawbacks, such as the difficulty in achieving a balanced solution. First, severe lateral etching and linewidth loss occur. Nitric acid-based etchants etch silver at extremely high and mostly isotropic rates, resulting in typically low etch factors. Within a very short time of etching through the silver film, the etchant laterally etches into the edges of the linewidth covered by the photoresist, leading to a significant reduction in the final linewidth compared to the design value. Especially when fabricating precision circuits with a linewidth / spacing (L / S) ratio below 2μm / 2μm, the linewidth loss caused by lateral etching can exceed 20%, severely limiting the improvement of aperture ratio in high-precision panels and the limits of line density in advanced packaging.

[0005] Second, selective damage to dissimilar metals and multilayer film stacked substrates. In practical devices, silver electrodes are often deposited on barrier layers or seed layers composed of metals such as molybdenum (Mo), titanium (Ti), and aluminum (Al), or in a stacked structure with them. In nitric acid-based etching solutions, due to the significant galvanic corrosion potential difference between different metals, silver (high potential) and the underlying active metal (low potential) will immediately form a galvanic cell once they come into contact with the solution simultaneously. This leads to severe galvanic corrosion of the active metal layer without external field intervention, causing the barrier layer to be hollowed out, resulting in the detachment of the silver electrode or a sharp increase in contact resistance. Even with the addition of traditional corrosion inhibitors, it is difficult to passivate the active metal without completely affecting the etching rate and surface condition of silver. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an Ag etching solution that alleviates lateral etching and its application method, effectively improving the lateral etching problem and thus effectively solving the problem of excessive Ag etching in traditional processes.

[0007] To achieve the above objectives, the present invention provides the following technical solution: An Ag etching solution for mitigating lateral etching, the etching solution comprising the following raw materials in the indicated mass percentages: 10%-15% nitric acid (HNO3), 8%-12% weak organic acid, 0.2%-0.5% succinic acid, 0.12%-0.15% sebacic acid, 0.1%-0.5% 2-mercaptobenzimidazole (MBI), 0.05%-0.3% 1-phenyl-5-mercaptotetrazole (PMT), 0.02%-0.08% benzyltriethylammonium chloride (BTEAC), and water to make up to 100%; wherein the mass percentage ratio of nitric acid to 2-mercaptobenzimidazole is ≤100, and the mass percentage ratio of sebacic acid to benzyltriethylammonium chloride is ≥2.

[0008] Preferably, the weak organic acid is any one or a combination of citric acid, salicylic acid, tartaric acid, lactic acid, and acetic acid.

[0009] Preferably, the weak organic acid is obtained by combining citric acid and acetic acid in a mass ratio of 1-1.5:7-10.5.

[0010] The preparation method of the above etching solution includes the following steps: A weak organic acid, 1-phenyl-5-mercaptotetrazole, and 2-mercaptobenzimidazole were mixed with water and stirred until homogeneous. Then, succinic acid, sebacic acid, benzyltriethylammonium chloride, and nitric acid were added in sequence and stirred until homogeneous to obtain the Ag etching solution.

[0011] Preferably, the etching solution is used by spraying.

[0012] Preferably, the spraying pressure used is 0.1-0.2 MPa, and the etching temperature is controlled at 35-45°C during spraying.

[0013] The above-mentioned Ag etching solution is used for wet etching of Ag.

[0014] This invention provides an Ag etching solution for mitigating lateral etching and its application method, which has the following advantages compared to existing technologies: This invention optimizes a non-phosphoric acid Ag etching solution by adjusting the addition of nitric acid, weak organic acids, succinic acid, and sebacic acid, and by incorporating components such as 2-mercaptobenzimidazole, 1-phenyl-5-mercaptotetrazole, and benzyltriethylammonium chloride. Through precise control of the chemical composition and reaction conditions, the side etching problem and Al damage problem are improved, effectively solving the problem of Ag over-etching in traditional processes. The prepared etching solution not only simplifies the etching process and improves production efficiency, but also significantly improves the manufacturing yield of OLED panels, providing strong technical support for the further development of OLED display technology. Attached Figure Description

[0015] Figure 1 This is a schematic diagram showing the etching process of the ITO / Ag / ITO substrate by the etching solution in the experimental group of this invention when the O / E ratio is 100%. Figure 2 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution in the experimental group of this invention when the O / E ratio is 150%. Figure 3 This is a schematic diagram showing the etching process of the ITO / Ag / ITO substrate by the etching solution in the experimental group of this invention when the O / E ratio is 200%. Figure 4 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 1 of the present invention when the O / E ratio is 100%. Figure 5 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 1 of the present invention when the O / E ratio is 150%. Figure 6 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 1 of the present invention when the O / E ratio is 200%. Figure 7 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution in control group 2 of this invention when the O / E ratio is 100%. Figure 8 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution in control group 2 of this invention when the O / E ratio is 150%. Figure 9This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution in control group 2 of this invention when the O / E ratio is 200%. Figure 10 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 3 of this invention when the O / E ratio is 100%. Figure 11 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 3 of this invention when the O / E ratio is 150%. Figure 12 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 3 of this invention when the O / E ratio is 200%. Figure 13 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the control group 4 etching solution of the present invention when the O / E ratio is 100%. Figure 14 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 4 of this invention when the O / E ratio is 150%. Figure 15 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the control group 4 etching solution of the present invention when the O / E ratio is 200%. Figure 16 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 5 of this invention when the O / E ratio is 100%. Figure 17 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 5 of this invention when the O / E ratio is 150%. Figure 18 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the etching solution of control group 5 of this invention when the O / E ratio is 200%. Figure 19 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the control group 6 etching solution when the O / E ratio is 100%. Figure 20 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the control group 6 etching solution of the present invention when the O / E ratio is 150%. Figure 21 This is a schematic diagram showing the etching of an ITO / Ag / ITO substrate by the control group 6 etching solution of the present invention when the O / E ratio is 200%. Figure 22 This is a schematic diagram of the U / C ratio after etching an ITO / Ag / ITO substrate with an O / E ratio of 150% using the etching solution in the experimental group of this invention. Figure 23This is a schematic diagram of the U / C image taken after etching an ITO / Ag / ITO substrate with the etching solution of control group 2 of this invention at an O / E ratio of 150%. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. 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.

[0017] Example 1: Prepare different Ag etching solutions according to the formulas in Table 1 below, expressed as a percentage by mass, with the remainder being water: Table 1

[0018] The preparation method is as follows: Acetic acid, citric acid, 1-phenyl-5-mercaptotetrazole, 2-mercaptobenzimidazole, and water were mixed and stirred until homogeneous. Then, succinic acid, sebacic acid, benzyltriethylammonium chloride, and nitric acid were added in sequence and stirred until homogeneous to obtain Ag etching solution.

[0019] Etching effect inspection: 1. Testing method: Etching substrate: ITO / Ag / ITO (150 / 950 / 75A); Etching conditions: Spray (small etching machine), test temperature 40℃, spray pressure 0.1Mpa, EPD (End Point Detection), O / E 100% (after EPD, an additional 100% etching time is added), O / E 150% (after EPD, an additional 150% etching time is added), O / E 200% (after EPD, an additional 200% etching time is added). The etching results are shown in Table 2 below (T / E / T is the total etching time; S / E is the lateral etching amount): Table 2

[0020] For each group of etched substrates, determine whether to proceed with the next step of U / C (side etching) measurement. When making the determination, compare with the Reference (baseline data, S / E is 0.25 at 100% OE, 0.30 at 150% and 0.35 at 200%). S / E that is too large or too small is not acceptable, and it should also conform to the rule that the larger the OE, the larger the S / E. In terms of morphology, the S / E is uniform on both sides of the line, and there are no large residual areas. After meeting the above conditions, proceed with the U / C imaging operation. The conditions after etching of each group are as follows Figures 1-21 (1 in the figure represents S / E) and as shown in Table 2 above, the experimental group and control group 2 meet the standard for U / C morphology imaging; the S / E value in control group 1 is too high, the S / E value in control group 3 is too low, the etching is incomplete, and there are large particles remaining; the S / E value in control group 4 is uneven, the etching is incomplete, and there are large particles remaining; the S / E value trend in control group 5 is inconsistent, and large particles remain; the S / E value in control group 6 is too low and uneven. Therefore, considering all factors, only the U / C morphology of the experimental group and control group 2 should be imaged, specifically the U / C morphology with 150% O / E, as shown in Table 3 below. Figure 22 , Figure 23 As shown.

[0021] Table 3

[0022] That is, the U / C value of the experimental group was significantly lower than that of the control group, meaning that the experimental group was able to effectively reduce corrosion.

[0023] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An Ag etching solution for mitigating lateral etching, characterized in that, The etching solution is composed of the following raw materials in the indicated mass percentages: 10%-15% nitric acid, 8%-12% weak organic acid, 0.2%-0.5% succinic acid, 0.12%-0.15% sebacic acid, 0.1%-0.5% 2-mercaptobenzimidazole, 0.05%-0.3% 1-phenyl-5-mercaptotetrazole, 0.02%-0.08% benzyltriethylammonium chloride, and water to make up to 100%. The mass percentage ratio of nitric acid to 2-mercaptobenzimidazole is ≤100, and the mass percentage ratio of sebacic acid to benzyltriethylammonium chloride is ≥2. The weak organic acid is any one or a combination of citric acid, salicylic acid, tartaric acid, lactic acid, and acetic acid.

2. The Ag etching solution for mitigating lateral etching according to claim 1, characterized in that: The weak organic acid is obtained by combining citric acid and acetic acid in a mass ratio of 1-1.5:7-10.

5.

3. The Ag etching solution for mitigating lateral etching according to claim 1, characterized in that, The method for preparing the etching solution includes the following steps: A weak organic acid, 1-phenyl-5-mercaptotetrazole, and 2-mercaptobenzimidazole were mixed with water and stirred until homogeneous. Then, succinic acid, sebacic acid, benzyltriethylammonium chloride, and nitric acid were added in sequence and stirred until homogeneous to obtain the Ag etching solution.

4. The Ag etching solution for mitigating lateral etching according to claim 1, characterized in that: The etching solution is applied by spraying.

5. The Ag etching solution for mitigating lateral etching according to claim 4, characterized in that: The spraying pressure used is 0.1-0.2 MPa, and the etching temperature is controlled at 35-45℃ during spraying.

6. The application of the Ag etching solution as described in any one of claims 1-5 in Ag wet etching.

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