High-stability and high-safety cupric acid etching solution and preparation method thereof

Abstract

The application discloses a high-stability and high-safety cupric acid etching liquid and a preparation method thereof, and belongs to the etching technical field.The cupric acid etching liquid comprises the following raw materials in percentage by weight: hydrogen peroxide 5-24%; ammonium persulfate 0.5-6%; a chelating agent 0.5-8%; a main stabilizer 0.05-2%; an auxiliary stabilizer 0-3%; a main corrosion inhibitor 0.05-2%; an auxiliary corrosion inhibitor 0-0.4%; a pH regulator 0-1%; fluoride 0.1%; and the balance is water.Hydrogen peroxide is used as a main oxidant to oxidize exposed metal into metal oxide, and mainly influences etching rate and etching morphology.Ammonium persulfate is used to reduce the use amount of hydrogen peroxide, still maintain strong oxidizing capacity, and improve the safety of the etching liquid.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of etching, and particularly relates to a high-stability and high-safety cupric acid etching solution and a preparation method thereof. BACKGROUND

[0002] Thin film transistor liquid crystal display (LCD) process mainly includes a panel section and a backlight module section, the panel section mainly includes a color film substrate, a TFT substrate and liquid crystal medium filled in the two substrates, wherein the TFT substrate process is particularly important, an electric field is formed through the TFT substrate to control the deflection of liquid crystal molecules, so that a colorful picture is formed. The TFT substrate is composed of a plurality of metal film layers and non-metal film layers, and a target pattern is completed through a Dep->Mask->Etch process, the non-metal layer is generally etched by a dry method, and the metal is generally etched by a wet method; the progress of the times promotes the development of technology, and at present, high refresh rate and low delay are the development direction of LCD, so it is inevitable to use low-resistance and high-corrosion-resistant metal to make a circuit, therefore, the multi-layer metal of copper and molybdenum is widely used as Gate and SD, and the etching solution used in wet etching also needs to be adjusted accordingly, therefore, the development of new copper etching solution has become a hot direction in the industry. SUMMARY

[0003] The application aims to provide a high-stability and high-safety cupric acid etching solution and a preparation method thereof, so as to solve the problem of low safety of the cupric acid etching solution.

[0004] The object of the application can be achieved by the following technical solutions.

[0005] A high-stability and high-safety cupric acid etching solution comprises the following raw materials in percentage by weight:

[0006] Hydrogen peroxide 5-24%;

[0007] Ammonium persulfate 0.5-6%;

[0008] Chelating agent 0.5-8%;

[0009] Main stabilizer 0.05-2%;

[0010] Auxiliary stabilizer 1-3%;

[0011] Main corrosion inhibitor 0.05-0.5%;

[0012] Auxiliary corrosion inhibitor 0-0.4%;

[0013] pH regulator 0-2%;

[0014] Fluoride 0.1%;

[0015] The balance is water.

[0016] Preferably, the chelating agent has amino, carboxylic acid and the like groups, and the chelating agent is selected from one or more of amino diacetic acid, nitrilotriacetic acid, glycine, malonic acid, succinic acid, iminotetrasuccinic acid, polyepoxysuccinic acid, 2-hydroxypyridine, maleic acid, glutamic acid, mixed in any ratio.

[0017] Preferably, the main stabilizer is one of polyacrylamide, diglycolamine, triethanolamine, n-hexylamine, N,N-dimethylformamide, diethylaminoethanol.

[0018] Preferably, the auxiliary stabilizer is one of polyethylene glycol 400, t-butylaminoethoxyethanol, n-butanol, propylene glycol methyl ether, 1,4-butanediol.

[0019] Preferably, the main corrosion inhibitor is one or more of 2-mercapto benzimidazole, mercapto benzothiazole, hexadecylamine, methyl benzotriazole, polyaspartic acid, mixed in any ratio.

[0020] Preferably, the auxiliary corrosion inhibitor is one or two of sodium silicate, sodium nitrate, triethanolamine, sodium molybdate, mixed in any ratio.

[0021] Preferably, the pH adjuster is one or more of potassium phosphate, potassium dihydrogen phosphate, diammonium hydrogen phosphate and the like phosphate, and similar aminotri (methyl) phosphonic acid, polyamino polyether group methylene phosphonic acid, aminotri (methylene) phosphonic acid, ethylenediamine tetramethylene phosphonic acid, hydroxyethylene diphosphonic acid, mixed in any ratio.

[0022] Preferably, the fluoride is one of hydrofluoric acid, ammonium fluoride, potassium hydrogen fluoride, ammonium hydrogen fluoride, potassium fluoride.

[0023] A preparation method of a high-stability and high-safety copper acid etching solution comprises the following steps: weighing raw materials according to a formula to obtain a high-stability and high-safety copper acid etching solution.

[0024] The present application has the following beneficial effects:

[0025] The hydrogen peroxide used in the present application is used as a main oxidizing agent to oxidize exposed metal into metal oxide, mainly affecting the etching rate and etching morphology. The content of this component is mainly controlled within the range of 5% to 24%. When the content of hydrogen peroxide is less than 5%, the etching solution will not have enough oxidation ability, which cannot meet the etching requirements. When the content of hydrogen peroxide is greater than 24%, the etching rate will be too fast, which will lead to the incoordination of etching between the copper metal layer and other metal layers, making it difficult to accurately control the etching process, resulting in the failure to meet the etching requirements, and also facing the high risk of unstable and easy decomposition of hydrogen peroxide.

[0026] The ammonium persulfate is used in the application to reduce the use amount of hydrogen peroxide, and still maintain strong oxidation ability. Furthermore, the safety of the etching solution is improved. The ammonium persulfate is dissolved in water, and a reversible reaction occurs in water to generate hydrogen peroxide, but the forward reaction is inhibited in an acidic condition. In the copper acid etching solution system, the ammonium persulfate mainly supplements the oxidation ability of the etching solution under the condition that the copper ion content increases, the pH of the solution increases, and the hydrogen peroxide is consumed.

[0027] The content of the ammonium persulfate is mainly controlled in the range of 0.5% to 6%. When the content of the ammonium persulfate is less than 0.5%, the auxiliary oxidation ability is not obvious, and the etching requirement cannot be met. When the content of the ammonium persulfate is greater than 6%, the etching rate is too fast, and a better etching morphology cannot be formed. According to different customer requirements, the content of the ammonium persulfate is adjusted corresponding to the high-concentration and low-concentration hydrogen peroxide, and needs to be coordinated with the content of the hydrogen peroxide. When the content of the hydrogen peroxide is low, the content of the ammonium persulfate can be appropriately increased to make up for the insufficient oxidation ability caused in the etching process.

[0028] In the application, under an acidic condition, the oxidized metal generates metal ions which are combined with a chelating agent to form a stable chelate, thereby avoiding the decomposition of hydrogen peroxide itself and strengthening the stability of the copper acid etching solution. If the chelating agent is absent in the etching solution, a large amount of free metal ions generated in the etching process will catalyze the activation of hydrogen peroxide, accelerate the decomposition of hydrogen peroxide, and cause safety problems such as sudden boiling.

[0029] The content of the chelating agent is mainly controlled in the range of 0.5% to 8%. When the content of the chelating agent is less than 0.5%, the complexing ability of the chelating agent to the metal ions is weak, and the chelating agent cannot inhibit the activity and stability of hydrogen peroxide. If the content of the component is higher than 8%, the chelating ability is saturated, and the strong chelating effect cannot be maintained under a high copper content. The continuous addition not only increases the cost, but also does not significantly improve the stability.

[0030] In the application, the main stabilizer used is an alcohol amine or an equivalent compound. The alcohol amine can be used to adjust the pH of the solution to form a buffer system, prevent the pH of the solution from fluctuating greatly in the etching process, and affect the stability of hydrogen peroxide. Meanwhile, the alcohol amine can also be combined with metal ions to make up for the chelating ability and improve the etching stability of the solution.

[0031] The content of the main stabilizer is mainly controlled in the range of 0.05% to 2%. When the content of the main stabilizer is less than 0.05%, the main stabilizer cannot provide enough buffer material to form a buffer system in the solution, and the etching stability is weak. When the content of the component is higher than 2%, the pH of the copper acid etching solution will be close to 6 or above. At this time, the activity of hydrogen peroxide increases, and the decomposition accelerates, which will lead to the need to supplement a large amount of organic acid, inorganic acid or pH regulator, and increase the cost.

[0032] In the present application, the auxiliary stabilizer used is an alcohol compound with surface activity, which is not only beneficial to the wettability of the interface between the copper etching solution and the exposed copper surface during the etching process, to maintain the etching uniformity and etching precision, but also can better disperse the chelate formed by the chelating agent and Cu ions, thereby maintaining the stability of the etching solution, controlling the decomposition of hydrogen peroxide, and improving the safety in use. Compared with the copper etching solution, the auxiliary stabilizer can be contained in an amount of 0 to 0.4%.

[0033] In the present application, in order to obtain better etching morphology and strict and accurate etching parameters, control the etching rate of the etching solution, and reduce the amount of expensive corrosion inhibitor, the azole metal corrosion inhibitor and the related metal salt with synergistic effect are selected. The complexing effect of the two improves the organic adsorption effect, and the two form an adsorption layer on the surface of the copper layer, promote each other, and improve the adsorption stability. The preferred ones can be polyaspartic acid, methyl benzotriazole, molybdate, etc.

[0034] Polyaspartic acid has a synergistic effect with phosphine compounds and other compounds in the system, and is compounded with phosphine compounds and other compounds into a high-efficiency and multifunctional corrosion and scale inhibitor. Polyaspartic acid also has a chelating effect on metal ions.

[0035] In the present application, the pH regulator plays a role in adjusting the pH value of the etching solution during the etching process, and improves the profile of the etching. Organic phosphonic acid has excellent chelating ability for Cu and other metal ions, forms a stable complex, and has strong inhibiting ability to inhibit the catalytic decomposition activity of hydrogen peroxide under the condition of high content of Cu ions. One or a mixture of the above preferred organic phosphonic acid and phosphate can be used.

[0036] In the present application, the fluoride used is mainly aimed at effectively reducing the adverse effects of bottom tailing, avoiding the brightness influence caused by tailing, and the residual influence of the bottom substrate on short circuit, lack of brightness and other adverse effects; for Mo or MoNb metal layer, a small amount of fluorine can achieve effective residue removal effect without damage to the bottom ITO / substrate; but for Ti or MoTi composite metal and special Array process layer, the content of fluorine needs to be increased to enhance the etching of the copper etching solution on the metal layer or the substrate.

[0037] In the present application, the temperature of the copper etching solution can be controlled between 30-35℃, 30℃ can obtain higher safety and longer storage safety time under high copper content, but the etching time is slower than 33℃, and the additives need to be adjusted to meet the requirements. BRIEF DESCRIPTION OF DRAWINGS

[0038] The present application will be further described below in conjunction with the drawings.

[0039] Figure 1 (a-e) are SEM images of etching performance test of Example 1 of the present application.

[0040] Figure 2 (a-e) are SEM images of etch performance testing of the present application Example 2;

[0041] Figure 3 (a-e) are SEM images of etch performance testing of the present application Example 3;

[0042] Figure 4 (a-e) are SEM images of etch performance testing of the present application Comparative Example 3;

[0043] Figure 5 (a-e) are SEM images of etch performance testing of the present application Comparative Example 7.

[0044] Figure 6 SEM images of etch performance testing of the present application Example 4;

[0045] Figure 7 SEM images of etch performance testing of the present application Example 5;

[0046] Figure 8 SEM images of etch performance testing of the present application Example 6;

[0047] Figure 9 SEM images of etch performance testing of the present application Example 7;

[0048] Figure 10 SEM images of etch performance testing of the present application Example 8;

[0049] Figure 11 SEM images of etch performance testing of the present application Comparative Example 1;

[0050] Figure 12 SEM images of etch performance testing of the present application Comparative Example 2;

[0051] Figure 13 SEM images of etch performance testing of the present application Comparative Example 4;

[0052] Figure 14 SEM images of etch performance testing of the present application Comparative Example 5;

[0053] Figure 15 SEM images of etch performance testing of the present application Comparative Example 6. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0055] Examples 1-8

[0056] The raw materials were weighed according to the formulations in Table 1 below and mixed to prepare the samples to be tested:

[0057] Table 1

[0058]

[0059] Comparative Examples 1-9

[0060] The raw materials were weighed according to the formulations in Table 2 below and mixed to prepare the samples to be tested:

[0061] Table 2

[0062]

[0063] Examples 1-8 and Comparative Examples 1-9 were tested, and a laboratory mini etching machine was used to etch a TFT substrate with a copper / molybdenum-niobium film thickness of 7000 / 150. The test results are shown in Tables 3-4 below:

[0064] Table 3

[0065]

[0066] Table 4

[0067]

[0068] From the etching experimental results recorded in Tables 3 and 4, it can be found that the ammonium persulfate added in the present application has a significant effect on the etching rate. If the amount of the added ammonium persulfate is too high, the etching rate is fast, which results in a large CD bias and no adverse effects such as tailing and residue on the bottom layer. Comparative Example 9 without the addition of an auxiliary oxidizing agent has adverse effects such as Mo layer tailing and residue.

[0069] The polyaspartic acid added in the present application also has a good effect of inhibiting the etching rate. After the amount of the main corrosion inhibitor is reduced, the addition of sodium silicate and sodium molybdate salt still has a good corrosion inhibition effect, meets the requirements of customers, and the single-sided loss is less than 0.75 um and the Taper angle is 30-55°.

[0070] It can also be found from the above etching experimental data that the content of the chelating agent and the content of the auxiliary stabilizer have a greater impact on the safety time of 10000 ppm of the etching solution, and the safety time of the etching solution is reduced by 10-18 h. The low content of the chelating agent has a great impact on etching. The low content of the chelating agent has weak binding capacity with metal ions, the etching speed is reduced, and the chelate cannot be efficiently formed, so that the etching cannot be accurately performed and the safety cannot be improved.

[0071] The copper acid etching solution life performance test was performed on example 1, example 2, example 3, comparative example 3 and comparative example 7.

[0072] The etching performance test was performed on example 1:

[0073] The copper powder was added to 300 ppm, and the sample was etched at 300 ppm, and the SEM image was taken, as shown in Figure 1 (a); the copper powder was added to 3000 ppm, and the sample was etched at 3000 ppm, and the SEM image was taken, as shown in Figure 1 (b); the copper powder was added to 5000 ppm, and the sample was etched at 5000 ppm, and the SEM image was taken, as shown in Figure 1 (c); the copper powder was added to 7000 ppm, and the sample was etched at 7000 ppm, and the SEM image was taken, as shown in Figure 1 (d); the copper powder was added to 10000 ppm, and the sample was etched at 10000 ppm, and the SEM image was taken, as shown in Figure 1 (e).

[0074] The etching performance test was performed on example 2:

[0075] The copper powder was added to 300 ppm, and the sample was etched at 300 ppm, and the SEM image was taken, as shown in Figure 2 (a); the copper powder was added to 3000 ppm, and the sample was etched at 3000 ppm, and the SEM image was taken, as shown in Figure 2 (b); the copper powder was added to 5000 ppm, and the sample was etched at 5000 ppm, and the SEM image was taken, as shown in Figure 2 (c); the copper powder was added to 7000 ppm, and the sample was etched at 7000 ppm, and the SEM image was taken, as shown in Figure 2 (d); the copper powder was added to 10000 ppm, and the sample was etched at 10000 ppm, and the SEM image was taken, as shown in Figure 2 (e).

[0076] The etching performance test was performed on example 3:

[0077] Copper powder was added to increase to 300 ppm, etching sample at 300 ppm concentration, sample preparation and SEM photos were taken, see Figure 3 (a); Copper powder was added to increase to 3000 ppm, etching sample at 3000 ppm concentration, sample preparation and SEM photos were taken, see Figure 3 (b); Copper powder was added to increase to 5000 ppm, etching sample at 5000 ppm concentration, sample preparation and SEM photos were taken, see Figure 3 (c); Copper powder was added to increase to 7000 ppm, etching sample at 7000 ppm concentration, sample preparation and SEM photos were taken, see Figure 3 (d); Copper powder was added to increase to 10000 ppm, etching sample at 10000 ppm concentration, sample preparation and SEM photos were taken, see Figure 3 (e).

[0078] Etching performance test was carried out with Comparative Example 3:

[0079] Copper powder was added to increase to 300 ppm, etching sample at 300 ppm concentration, sample preparation and SEM photos were taken, see Figure 4 (a); Copper powder was added to increase to 3000 ppm, etching sample at 3000 ppm concentration, sample preparation and SEM photos were taken, see Figure 4 (b); Copper powder was added to increase to 5000 ppm, etching sample at 5000 ppm concentration, sample preparation and SEM photos were taken, see Figure 4 (c); Copper powder was added to increase to 7000 ppm, etching sample at 7000 ppm concentration, sample preparation and SEM photos were taken, see Figure 4 (d); Copper powder was added to increase to 10000 ppm, etching sample at 10000 ppm concentration, sample preparation and SEM photos were taken, see Figure 4 (e).

[0080] Etching performance test was carried out with Comparative Example 7:

[0081] Copper powder was added to increase to 300 ppm, etching sample at 300 ppm concentration, sample preparation and SEM photos were taken, see Figure 5 (a); Copper powder was added to increase to 3000 ppm, etching sample at 3000 ppm concentration, sample preparation and SEM photos were taken, see Figure 5 (b); Copper powder was added to increase to 5000 ppm, etching sample at 5000 ppm concentration, sample preparation and SEM photos were taken, see Figure 5 (c); Copper powder was added to increase to 7000 ppm, etching sample at 7000 ppm concentration, sample preparation and SEM photos were taken, see Figure 5 (d); Copper powder was added to increase to 10000 ppm, etching sample at 10000 ppm concentration, sample preparation and SEM photos were taken, seeFigure 5 (e).

[0082] The lifetime performance of the copper acid etching solution was tested for Examples 4-8, Comparative Examples 1-2, and Comparative Examples 4-6.

[0083] Copper powder was added to a concentration of 300 ppm, and the sample was etched at this concentration. The resulting film was then prepared and SEM images were taken. The test SEM image for Example 4 is shown below. Figure 6 See the test SEM image of Example 5. Figure 7 See the test SEM image of Example 6. Figure 8 The test SEM image of Example 7 is shown below. Figure 9 See the test SEM image of Example 8. Figure 10 The test SEM image for Comparative Example 1 is shown below. Figure 11 The test SEM images for Comparative Example 2 are shown below. Figure 12 The test SEM image for Comparative Example 4 is shown below. Figure 13 The test SEM image for Comparative Example 5 is shown below. Figure 14 The test SEM image for Comparative Example 6 is shown below. Figure 15 .

[0084] The copper ion loading capacity of the sample prepared in Example 1 was tested, and the results are shown in Table 5 below:

[0085] Table 5

[0086]

[0087] The copper ion loading capacity of the samples prepared in Example 2 was tested, and the results are shown in Table 6 below:

[0088] Table 6

[0089]

[0090] The copper ion loading capacity of the sample prepared in Example 3 was tested, and the results are shown in Table 7 below:

[0091] Table 7

[0092]

[0093] As can be seen from Tables 5-7, Examples 1-3 all demonstrated the ability to dissolve high copper concentrations. The etching was stable even when copper ions reached 10,000 ppm, and the CD Bias and Taper values ​​obtained from the etching were stable with small fluctuations, meeting the etching requirements.

[0094] The copper ion loading capacity of the sample prepared in Comparative Example 3 was tested, and the results are shown in Table 8 below:

[0095] Table 8

[0096]

[0097] The sample prepared in Comparative Example 7 was subjected to copper ion loading capacity test, and the results are shown in Table 9 below:

[0098] Table 9

[0099]

[0100] From Table 8 and Table 9, it can be seen that Comparative Example 3 and Comparative Example 7 are stable in etching at a copper ion content of 5000 ppm. Comparative Example 3 shows a fast etching rate and a large CD bias at 7000 ppm, and a deviation of 0.3 um at 10000 ppm. Comparative Example 7, which contains less hydroxyethylidene diphosphonic acid, shows a reduced CD bias at 7000 ppm, indicating a slower etching rate and weaker etching ability, which cannot meet the etching precision requirement.

[0101] It should be noted that the relational terms herein such as first and second, and the like, are used solely to distinguish one from another entity or action, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0102] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, alternatives, and variations can be made in the embodiments without departing from the spirit and scope of the present application as defined by the appended claims and their equivalents.

Claims

1. A highly stable and safe copper acid etching solution, characterized in that, Including the following raw materials by weight percentage: Hydrogen peroxide 5-24%; Ammonium persulfate 0.5-6%; Chelating agent 5-8%; Primary stabilizer 0.05-2%; 1-3% auxiliary stabilizer; Primary corrosion inhibitor 0.1-0.5%; Auxiliary corrosion inhibitor 0-0.4%; pH adjuster 0.4-2%; Fluoride 0.1%; The remainder is water; The chelating agent is a mixture of glycine and aminodiacetic acid in any proportion; The main stabilizer is diethylaminoethanol; The auxiliary stabilizer is polyethylene glycol 400; The main corrosion inhibitor is one or two of methylbenzotriazole and polyaspartic acid, mixed in any proportion; The auxiliary corrosion inhibitor is one or two of sodium silicate and sodium molybdate mixed in any proportion; The pH adjuster is hydroxyethylidene diphosphonic acid.

2. The highly stable and safe copper acid etching solution according to claim 1, characterized in that, Fluorides are one of hydrofluoric acid, ammonium fluoride, potassium hydrogen fluoride, and potassium fluoride.

3. The method for preparing a highly stable and safe copper acid etching solution according to claim 1, characterized in that, The process includes the following steps: weighing and mixing raw materials according to the formula to obtain a highly stable and safe copper acid etching solution.

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