Silver etching solution and preparation method and application thereof

Abstract

The present application relates to the field of flat panel display technology, and provides a silver etching solution and a preparation method and application thereof. The silver etching solution, based on the total weight of the silver etching solution being 100%, comprises the following components in the following weight percentages: 7-9% inorganic acid, 5-7% organic acid, 13-18.5% organic chelating agent, 8-10% chelating dispersant, 15-28% acid inorganic salt, and the balance being water. The silver etching solution has a low viscosity, a high proportion of components with a buffering effect in the silver etching solution, a stable etching rate, a better etching effect, and better uniformity; at the same time, an organic acid chelating agent and a chelating dispersant are added to improve the adsorption and re-adhesion of silver ions.

Description

Technical Field

[0001] The present application relates to the field of flat panel display technology, and in particular to a silver etching solution and a preparation method and application thereof. Background Art

[0002] In recent years, OLED displays have been widely used in mobile phones and flat panel displays. Metallic silver is widely used in the anode wiring (ITO / Ag / ITO) structure of OLED displays due to its excellent electrical conductivity and carrier mobility. In order to etch this, wet etching solutions based on phosphoric acid, nitric acid, acetic acid and nitrates are currently mainly used (for example, patent publication number CN107419270A), but these etching solutions all have problems such as silver residue, uneven etching, silver adsorption and re-staining, and unstable silver etching rate during the service life. In addition, the etching solutions in the prior art are also difficult to control the corrosion rate of non-metallic oxides and metallic titanium. Summary of the invention

[0003] The purpose of the present application is to provide a silver etching solution and a preparation method and application thereof, aiming to solve the problems of silver residue, uneven etching, silver adsorption and re-staining, and unstable silver etching rate during the service life of the existing silver etching solution.

[0004] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0005] In a first aspect, the present application provides a silver etching solution, which comprises the following components in the following weight percentages, based on the total weight of the silver etching solution being 100%:

[0006] Inorganic acid 7-9%, organic acid 5-7%, organic chelating agent 13-18.5%, chelating dispersant 8-10%, acid inorganic salt 15-28%, and the balance is water.

[0007] As a possible design, based on the total weight of the silver etching solution as 100%, the silver etching solution includes the following components in the following weight percentages:

[0008] Inorganic acid 8%, organic acid 6%, organic chelating agent 13-18.5%, chelating dispersant 9%, acid inorganic salt 15-28%, and the balance is water.

[0009] As a possible design, based on the total weight of the silver etching solution as 100%, the silver etching solution includes the following components in the following weight percentages:

[0010] Nitric acid 7-9%, acetic acid 5-7%, succinic acid 2.5-3.5%, citric acid 11-15%, polycarboxylic acid 8-10%, sodium bisulfate 22-28%, and the balance is water.

[0011] As a possible design, based on the total weight of the silver etching solution as 100%, the silver etching solution includes the following components in the following weight percentages:

[0012] Nitric acid 8%, acetic acid 6%, succinic acid 3%, citric acid 13%, polycarboxylic acid 9%, sodium bisulfate 25%, and the balance is water.

[0013] As a possible design, the organic chelating agent includes at least one of lactic acid, succinic acid, malic acid, citric acid, malonic acid and maleic acid.

[0014] As a possible design, the organic chelating agent is a mixture of at least two of succinic acid, malic acid, citric acid and malonic acid.

[0015] As a possible design, the inorganic acid includes nitric acid; preferably, the organic acid includes acetic acid; preferably, the chelating dispersant includes polycarboxylic acid; preferably, the acid inorganic salt includes sodium dihydrogen phosphate and / or sodium bisulfate.

[0016] In a second aspect, the present application provides a method for preparing a silver etching solution, comprising the following steps:

[0017] Adding inorganic acid, then adding organic chelating agent, chelating dispersant and acid inorganic salt to water in sequence, stirring until all are dissolved to form a solution;

[0018] adding an organic acid to the solution and stirring until all the solution is uniformly mixed to obtain a mixture;

[0019] The mixture was filtered.

[0020] As a possible design, the filtration involves two filtrations, the filter element diameter of the first filtration is 0.4-0.6 μm, and the filter element diameter of the second filtration is 0.2 μm.

[0021] The beneficial effects of the present invention are:

[0022] The silver etching solution disclosed by the invention has low viscosity, a high proportion of components with buffering effect in the silver etching solution, a stable etching rate, a better etching effect and better uniformity; and an organic acid chelating agent and a chelating agent dispersant are added at the same time to improve the situation of silver ion adsorption and re-adhesion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 is a scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in Example 1 of the present application;

[0025] Figure 2 is a scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in Example 2 of the present application;

[0026] Figure 3 is a scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in Example 3 of the present application;

[0027] Figure 4 is a scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in Example 4 of the present application;

[0028] Figure 5 is a scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in Example 5 of the present application;

[0029] Figure 6 is a scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in Example 6 of the present application;

[0030] Figure 7 is a scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in Example 7 of the present application;

[0031] Figure 8 is a scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in the comparative example of the present application;

[0032] Fig. 9 It is an explanatory diagram of the scanning electron microscope cross-sectional view after etching with the silver etching solution obtained in Examples 1-7 of the present application and the comparative example;

[0033] Fig.10 This is a cross-sectional view after etching with the silver etching solution obtained in Example 1 of the present application;

[0034] Fig.11 This is a cross-sectional view after etching with the silver etching solution obtained in the comparative example of this application. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0037] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0038] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0039] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0040] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0041] The term "PET" is the abbreviation of "Polyethylene terephthalate", which means polyethylene terephthalate; the term "PU" is the abbreviation of "polyurethane", which means polyurethane material and is the abbreviation of polyurethane.

[0042] The inventors found that the traditional formula is composed of phosphoric acid, nitric acid, acetic acid and some trace additives. The phosphoric acid system has a fast etching rate and a large CD-loss (Chinese meaning: line width loss). Moreover, for the phosphoric acid system, the etching solution has a large viscosity and the molecular ions diffuse slowly. Moreover, due to its faster etching rate, the etching is uneven and the etched cross-sectional morphology has poor uniformity. At the same time, in the solution, anions exist in a free state, and silver ions will stick back to the surface of the substrate in the state of metallic silver, showing problems such as silver metal residue and silver sticking back.

[0043] In view of the above problems, the present invention discloses a silver etching solution, which comprises the following components in the following weight percentages, based on the total weight of the silver etching solution being 100%:

[0044] Inorganic acid 7-9%, organic acid 5-7%, organic chelating agent 13-18.5%, chelating dispersant 8-10%, acid inorganic salt 15-28%, and the balance is water.

[0045] It should be noted that the two endpoint values ​​of the weight percentage of the above components and any value between the two endpoints all meet the requirements.

[0046] In the present invention, an organic chelating agent is added to replace phosphoric acid. The organic chelating agent provides hydrogen ions to play a buffering role, which can make the reaction more gentle and mild. In addition, the viscosity of the organic chelating agent is lower than that of phosphoric acid, the overall fluidity of the solution is large, and the molecular ion diffusion rate is fast, which improves the problem of uneven etching.

[0047] At the same time, adding an organic chelating agent, such as at least one of lactic acid, succinic acid, malic acid, citric acid, malonic acid and maleic acid, can chelate the silver ions in the etched system. The organic group is large in size, and the anions are completely wrapped, forming a steric effect, which cannot be completely ionized and plays a certain buffering role to avoid the problem of silver metal back-adhesion.

[0048] In the present invention, an organic acid, such as acetic acid, is added to reduce the surface tension of the liquid medicine and improve the wettability of the liquid medicine. Acetic acid can ionize hydrogen ions and play a buffering role. The etching process is smooth and not violent, so that the etched CD-Loss has better uniformity.

[0049] In the present invention, an inorganic acid, such as nitric acid, is added. Nitric acid is an oxidant in the system, and its main function is to oxidize metallic silver into anions to accelerate etching. At the same time, it is also the main component for providing acidic conditions.

[0050] In the present invention, a chelating dispersant, such as polycarboxylic acid, is added to have both adsorption and complexing effects on metal ions, and can effectively inhibit the adsorption of metal ions on the surface of the glass substrate, thereby avoiding problems such as metal residue and metal back-adhesion.

[0051] In the present invention, an acid inorganic salt is added, such as sodium bisulfate and / or sodium dihydrogen phosphate. The acid inorganic salt does not completely ionize hydrogen ions, and can effectively balance the concentration of hydrogen ions in the solution, maintain a stable etching rate, and in the presence of inorganic acid nitric acid, nitric acid oxidizes silver metal into silver oxide, phosphoric acid and sulfate, and dissolves silver oxide into hexasilver trioxide and silver phosphate.

[0052] In summary, the present invention achieves better etching effect and uniformity through the respective effects of the components and the synergistic effects between them, and improves the silver ion adsorption and re-adhesion.

[0053] As a preferred embodiment, based on the total weight of the silver etching solution being 100%, the silver etching solution comprises the following components in the following weight percentages:

[0054] Inorganic acid 8%, organic acid 6%, organic chelating agent 13-18.5%, chelating dispersant 9%, acid inorganic salt 15-28%, and the balance is water.

[0055] As a more preferred embodiment, based on the total weight of the silver etching solution as 100%, the silver etching solution includes the following components in the following weight percentages:

[0056] Nitric acid 7-9%, acetic acid 5-7%, succinic acid 2.5-3.5%, citric acid 11-15%, polycarboxylic acid 8-10%, sodium bisulfate 22-28%, and the balance is water.

[0057] As a most preferred embodiment, the silver etching solution comprises the following components in the following weight percentages, based on the total weight of the silver etching solution being 100%:

[0058] Nitric acid 8%, acetic acid 6%, succinic acid 3%, citric acid 13%, polycarboxylic acid 9%, sodium bisulfate 25%, and the balance is water.

[0059] The present invention also discloses a method for preparing the aforementioned silver etching solution, comprising the following steps:

[0060] S1. Adding an inorganic acid to water in sequence, then adding an organic chelating agent, a chelating dispersant and an acidic inorganic salt, stirring until completely dissolved to form a solution;

[0061] If the solid raw materials you choose are prone to caking, you need to break them into small pieces before adding them.

[0062] S2. Add an organic acid to the solution and stir until all are mixed to obtain a mixture;

[0063] S3. Filter the mixture.

[0064] The filtration can be carried out in multiple stages, and the mixture can be filtered using filter screens with different mesh sizes or apertures to obtain a silver etching solution with a uniform texture.

[0065] In the present invention, two-stage filtration is taken as an example. In the first filtration, the pore size of the filter is about 0.5 μm; in the second filtration, the pore size of the filter is 0.2 μm.

[0066] The following describes the invention in conjunction with specific embodiments.

[0067] It should be noted that the specific use method of the silver etching solution prepared in the following embodiments is as follows.

[0068] 1. Prepare the Etched Panel

[0069] Using glass as substrate, sputtering thickness ITO layer, thickness Silver layer and thickness The ITO layer is coated with a resist, exposed through a transfer pattern mask, and then developed to form a wiring pattern.

[0070] 2. Etching process

[0071] Heat the etching solution in a water bath to 40°C, put the glass substrate into the silver etching solution under insulation conditions, shake the glass substrate at a constant speed, and observe the etching time t when the panel just becomes transparent with the naked eye. EPD = 2*t, and the total etching time is T = 1.5*2t (OE 50%). Rinse the board surface taken out of the etching solution with pure water for 30s and blow dry with a nitrogen gun.

[0072] Among them, EPD is the abbreviation of Just Etch Time, which means just etching time in Chinese. OE is the abbreviation of Over Etch, which means transition etching in Chinese.

[0073] The weight percentages of the various substances in the following examples are shown in Table 1.

[0074] Table 1

[0075]

[0076] It should be noted that in Examples 1-7, except for the mass percentages of the components in Table 1, the rest is water, and the total mass percentage is 100%.

[0077] Comparative Example

[0078] The proportion of the silver etching solution in this comparative example is: 5% nitric acid, 50% phosphoric acid, 12% acetic acid, and the balance is water.

[0079] It should be noted that Examples 1-7 are implemented with reference to the above method. The preparation method of the silver etching solution in the comparative example is: uniformly mix the raw materials.

[0080] The effects of the silver etching solutions of Examples 1-7 and Comparative Examples after a certain time were tested, as follows:

[0081] Scanning electron microscope was used to observe the etched panel, observe the cross-sectional morphology and measure the etched CD-Loss. Under the same over-etching amount, the CD-Loss is getting smaller and smaller, controlled within 0.5μm on a single side, and no metal residue is the best.

[0082] Results comparison

[0083] Result judgment criteria:

[0084] Uniformity: ① After etching and removing the photoresist, observe the SEM surface image and observe the boundary lines after etching. If the boundary lines are jagged, it is NG, and if the boundary lines are smooth and without jagged, it is OK. ② Compare the changes in CD-LOSS when the silver ion concentration of the solution is 0ppm and 300ppm. If the difference is greater than 0.2μm, it is judged that the uniformity is poor, and if the difference is less than 0.1μm, it is judged that the uniformity is good.

[0085] Metal residue: After etching and removing the photoresist, SEM surface image is taken to observe whether there are any dot-shaped metal residues at the position after etching.

[0086] Metal back-adhesion: After etching and removing the photoresist, observe the metal back-adhesion on the surface of the glass substrate under a microscope.

[0087] The results are shown in Table 2.

[0088] Table 2

[0089] / t EPD T CD-Loss / μm Etching morphology uniformity Metal Residue Example 1 37 74 111 0.40 OK OK Example 2 35 70 105 0.52 OK OK Example 3 30 60 90 1.00 OK OK Example 4 60 120 180 0.64 NG NG Example 5 40 80 120 0.35 OK OK Example 6 38 76 114 0.55 NG NG Example 7 45 90 135 0.64 OK NG Example 8 20 40 60 1.10 NG NG

[0090] Note: In Table 2, the Chinese explanation of CD-Loss is line width loss.

[0091] The electron microscope cross-sectional images after scanning of Examples 1-8 and Comparative Examples are shown as follows: Figure 1-8 As shown, it should be noted that Figure 1-8 The right picture in the figure is a partial enlarged picture of the left picture. It should be noted that Figure 1-8 The upper part of the middle left picture is photoresist, the lower part is glass, and the part between the two is the metal layer ITO / Ag / ITO, such as Fig. 9 shown.

[0092] Figure 4 In the right picture, the middle position is the etched position, and both sides are unetched metal layers. From the picture, we can see that the etched position is dotted with stars and there is metal residue. The etched boundary metal lines are smooth, the etched morphology is flat, and the uniformity is good.

[0093] Depend on Figure 1 , 2 As can be seen from the right figures in , 3 and 5, when the silver etching solution of Examples 1, 2, 3 and 5 is used, no metal remains at the etched position, the boundary metal lines after etching are smooth, the etched morphology is smooth, and the uniformity is good.

[0094] Depend on Figure 6-8 As can be seen from the right figure in the figure, with the silver etching solutions of Examples 6, 7 and the comparative example, the etched positions are dotted with stars, with metal residues, and the boundary metal lines after etching are jagged, and the etched morphology is jagged, with poor uniformity, especially the silver etching solution of the comparative example;

[0095] The following conclusions can be drawn from Table 2:

[0096] 1. Comparison between Examples 1 to 7 and the comparative example: non-phosphoric acid system, good uniformity, small loss, and less metal residue.

[0097] 2. Comparison between Example 2 and Example 1: Sodium dihydrogen phosphate is more acidic and has a faster etching rate.

[0098] 3. Comparison between Example 3 and Example 1: Malonic acid has stronger acidity and a faster etching rate.

[0099] 4. Comparison of Example 4 and Example 1; Malic acid is less acidic than citric acid and has poor uniformity.

[0100] 5. Comparison of Example 5 and Example 1: Without adding succinic acid, the etching rate is reduced.

[0101] 6. Comparison between Example 6 and Example 1: less polycarboxylic acid is added, and the uniformity becomes worse.

[0102] 7. Comparison between Example 7 and Example 1: When the sodium bisulfate content is reduced, the etching rate is reduced and the uniformity is deteriorated.

[0103] It can be seen from this that the silver etching solution obtained in Example 1 has the best etching effect.

[0104] Fig.10 The cross-sectional view after the silver etching solution obtained in Example 1 is shown in FIG. Fig.10 It can be seen that the metal does not stick back in the cross section after etching. Fig.11 The cross-sectional view after the silver etching solution etching obtained in the comparative example is shown in FIG. Fig.10 It can be seen that metal back-adhesion occurs in the cross section after etching.

[0105] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A silver etching solution, characterized in that Taking the total weight of the silver etching solution as 100%, the components selected from the following weight percentages are included: Nitric acid 8%, acetic acid 6%, succinic acid 3%, citric acid 13%, polycarboxylic acid 9%, sodium bisulfate 25%, and the balance is water.

2. A silver etching solution, characterized in that: Taking the total weight of the silver etching solution as 100%, the components selected from the following weight percentages are included: Nitric acid 8%, acetic acid 6%, succinic acid 3%, citric acid 13%, polycarboxylic acid 9%, sodium dihydrogen phosphate 25%, and the balance is water.

3. A silver etching solution, characterized in that Taking the total weight of the silver etching solution as 100%, the components selected from the following weight percentages are included: Nitric acid 8%, acetic acid 6%, malonic acid 13%, polycarboxylic acid 9%, sodium bisulfate 25%, and the balance is water.

4. A silver etching solution, characterized in that Taking the total weight of the silver etching solution as 100%, the components selected from the following weight percentages are included: Nitric acid 8%, acetic acid 6%, citric acid 13%, polycarboxylic acid 9%, sodium bisulfate 25%, and the balance is water.

5. A method for preparing the silver etching solution according to any one of claims 1 to 4, characterized in that: The following steps are involved: Adding inorganic acid, then adding organic chelating agent, chelating dispersant and acid inorganic salt to water in sequence, stirring until all are dissolved to form a solution; adding an organic acid to the solution and stirring until all the solution is uniformly mixed to obtain a mixture; The mixture was filtered.

6. The preparation method according to claim 5, characterized in that: The filtration involves two filtrations, the filter element diameter of the first filtration is 0.4-0.6 μm, and the filter element diameter of the second filtration is 0.2 μm.

7. A silver etching solution according to any one of claims 1 to 4 or a silver etching solution prepared by the preparation method according to claim 5 or 6, used in a flat panel display OLED, characterized in that: The silver etching solution is used to etch the OLED anode layer.

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