Titanium alloy etching solution and preparation method thereof

Abstract

The application provides a titanium alloy etching liquid and a preparation method thereof, and belongs to the technical field of etching compositions, and comprises the following steps: S1, dissolving aminothiourea in anhydrous ethanol under continuous stirring, then adding 3-acetyl coumarin solution dropwise, mixing and stirring, adding concentrated acetic acid dropwise, refluxing under continuous stirring, cooling, filtering, taking out the solid, washing, and obtaining a coumarin-thiosemicarbazide hybrid; S2, adding the coumarin-thiosemicarbazide hybrid into anhydrous ethanol, heating, and ultrasonic treating to obtain a coumarin-thiosemicarbazide solution; and S3, uniformly mixing deionized water, citric acid, ammonium citrate, a hydroxyethylidene diphosphonic acid aqueous solution, hydrogen peroxide and the coumarin-thiosemicarbazide hybrid solution to obtain the titanium alloy etching liquid. The application can make etching be carried out efficiently and stably while avoiding the occurrence of side etching.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of etching compositions, in particular to a titanium alloy etching solution and a preparation method thereof. BACKGROUND

[0002] Copper bump technology is a new generation of chip interconnection technology, which is used for the connection of chips and substrates in the integrated circuit packaging process. Compared with the traditional solder bump packaging process, it has better electrical conductivity, thermal performance and reliability, better resistance to electromigration, and is more suitable for fine pitch to increase interconnection density, low cost and other advantages. In the bump manufacturing process, due to the poor adhesion of copper to silicon dioxide / silicon, a titanium-tungsten alloy is needed as an adhesion layer, and then copper is sputtered as an electroplating seed layer to form a bump under metalization layer as a conductive layer for bump electroplating. After the completion of bump electroplating, the exposed titanium-tungsten alloy adhesion layer must be etched and removed without affecting the bump and the metalization layer under the bump in the pattern area on the substrate.

[0003] The currently commonly used titanium-tungsten etching solution is a series of hydrofluoric acid etching solution or a series of alkaline etching solution containing hydrogen peroxide. However, the use of acid hydrofluoric acid series etching solution products has the problems of etching silicon and silicon dioxide substrates, and side etching of Cu and Al layers. The use of alkaline hydrogen peroxide series etching solution products has the problems of fast decomposition of hydrogen peroxide in the etching solution, slow etching rate, large etching rate variation, poor etching stability, poor selectivity, short service life, etc.

[0004] In addition, the titanium-tungsten alloy surface often has a layer of passivation film (titanium nitride), which is dense and chemically stable, hindering the etching process and making the etching efficiency low. The patent application file with publication number CN113802120A discloses an acidic titanium-tungsten etching solution for semiconductors, which is composed of the following components by mass percentage: 50-70wt% phosphoric acid, 5-10wt% strong oxidizing acid, 5-10wt% surface active ingredient, 1-5wt% titanium activator, and the balance deionized water. By adding a titanium activator to the formula to activate the titanium nitride layer, the etching efficiency is further improved, but the consumption of strong oxidizing acid may cause unstable etching rate and high temperature sensitivity. In addition, it has a large corrosion on other substrates, and cannot achieve high etching efficiency while protecting the copper layer and silicon substrate.

[0005] Therefore, it is necessary to provide a titanium alloy etching solution and a preparation method thereof to solve the problems existing in the prior art. SUMMARY

[0006] Therefore, the present application provides a titanium alloy etching solution and a preparation method thereof, which can make the etching process efficient and stable while avoiding the occurrence of side etching.

[0007] To achieve the above object, the application provides a preparation method of a titanium alloy etching solution, comprising the following steps:

[0008] S1, dissolving aminothiourea in anhydrous ethanol under continuous stirring, then adding 3-acetyl coumarin solution dropwise and mixing and stirring, adding concentrated acetic acid dropwise, refluxing under continuous stirring, cooling, filtering, taking out the solid, washing, and obtaining a coumarin-thiosemicarbazide hybrid;

[0009] S2, adding the coumarin-thiosemicarbazide hybrid into anhydrous ethanol, heating, and ultrasonic treating to obtain a coumarin-thiosemicarbazide solution;

[0010] S3, mixing deionized water, citric acid, ammonium citrate, a hydroxyethylidene diphosphonic acid aqueous solution, hydrogen peroxide, and the coumarin-thiosemicarbazide solution to obtain the titanium alloy etching solution.

[0011] The application forms a coumarin-thiosemicarbazide hybrid as a copper-specific corrosion inhibitor component by condensation of 3-acetyl coumarin and aminothiourea, which has selective adsorption properties on the metal surface; under the framework of hard-soft acid-base theory, Ti 4+ , W 6+ are more inclined to form stable complexes with oxygen-containing ligands, and copper ions have stronger affinity to nitrogen-containing and sulfur-containing ligands, so the N and S coordination sites in the hybrid molecule can preferentially form Cu-N and Cu-S coordination bonds with the copper surface, are adsorbed on the copper surface, and form a dense and relatively stable protective film, effectively blocking the direct contact between the etching solution and the copper surface, avoiding side etching, and having little influence on the normal etching of the titanium-tungsten alloy. 2+ Meanwhile, the coumarin-thiosemicarbazide hybrid can also chelate Cu 2+ ions produced by trace dissolution of copper in the solution, reduce the catalytic decomposition of hydrogen peroxide by Cu + , and further improve the stability of the main component hydrogen peroxide in the etching solution, thereby prolonging the service life of the etching solution and keeping the etching rate stable.

[0012] The application introduces citric acid and ammonium citrate as pH buffers in the etching solution, so that the pH of the system is stabilized in the weak acid interval of 3-4, and under this condition, hydrogen peroxide is mainly in the form of molecules, and has moderate oxidizability, which can effectively oxidize the titanium-tungsten surface to generate soluble or easily complexed oxides, and avoid the corrosion risk of the substrate caused by excessive acidity; the buffer reduces the local pH fluctuation by balancing the concentration of H 4+ , reduces the tendency of the titanium-tungsten surface to form a dense passivation film again, and thus ensures the uniform etching rate. In addition, the hydroxyethylidene diphosphonic acid has the dual functions of hydrogen peroxide stabilizer and metal ion chelating agent in the system, and the phosphonic acid groups can chelate Ti 6+ , W 2+The metal ions form stable complexes, inhibit the catalytic decomposition of hydrogen peroxide by these metal ions, greatly reduce the self-decomposition rate of hydrogen peroxide, and prolong the life of hydrogen peroxide. At the same time, it can also complex with the metal ions produced by etching to prevent precipitation and ensure surface cleaning.

[0013] Optionally, the 3-acetyl coumarin solution is obtained by adding 3-acetyl coumarin to anhydrous ethanol and stirring for 5-10 min.

[0014] Optionally, the 3-acetyl coumarin solution comprises the following raw materials: 1.5-2 parts by mass of 3-acetyl coumarin and 15-20 parts by volume of anhydrous ethanol.

[0015] Optionally, in step S1, 1-1.5 parts by mass of aminothiourea is dissolved in 20 parts by volume of anhydrous ethanol under continuous stirring, then the 3-acetyl coumarin solution is added dropwise and stirred for 10-15 min, 0.1-0.2 parts by volume of concentrated acetic acid is added dropwise, and then refluxing is carried out under continuous stirring for 6-8 h, cooling to room temperature, vacuum filtration separation, taking out the solid, washing with 0-4℃ anhydrous ethanol for 3-5 times to obtain the coumarin-thiosemicarbazone hybrid.

[0016] In this step, the obtained solid product is washed with 0-4℃ anhydrous ethanol. The solubility of the hybrid in anhydrous ethanol at low temperature (0-4℃) decreases significantly, while the solubility of unreacted monomers and by-products is still strong. Therefore, by differential solubility at low temperature, unreacted raw materials and by-products are selectively removed, while the loss and oxidative degradation of the target hybrid are avoided.

[0017] Optionally, the mass fraction of aminothiourea is 1-1.5 parts, the volume fraction of anhydrous ethanol is 20 parts, and the volume fraction of concentrated acetic acid is 0.1-0.2 parts.

[0018] Optionally, in step S2, the coumarin-thiosemicarbazone hybrid is added to anhydrous ethanol, heated to 60-80℃, and ultrasonically treated for 10-20 min to obtain a coumarin-thiosemicarbazone solution.

[0019] In this step, the coumarin-thiosemicarbazone hybrid is fully dissolved and dispersed by heating and ultrasonic treatment, which not only avoids the agglomeration and sedimentation of the hybrid in the etching solution, but also enhances the exposure of the active groups, thereby improving the selective adsorption and corrosion inhibition performance on the copper surface and maintaining the transparency and stability of the etching solution system.

[0020] Optionally, in step S3, deionized water, citric acid, and ammonium citrate are mixed, magnetically stirred for 10-20 min, and then hydroxyethylidene diphosphonic acid aqueous solution is added and stirred for 8-10 min. Under continuous stirring, hydrogen peroxide and coumarin-thiosemicarbazone hybrid solution are added in sequence, and stirring is continued for 15-20 min to obtain a titanium alloy etching solution.

[0021] Optionally, the mass concentration of the aqueous hydroxyethylidene diphosphonic acid solution is 60%, and the volume concentration of the hydrogen peroxide is 30%.

[0022] In the present application, the hydrogen peroxide with a volume concentration of 30% is selected to be used. The hydrogen peroxide with this concentration has moderate oxidizing ability and good chemical stability under acidic conditions, which can effectively oxidize the surface of titanium tungsten to form a soluble complex and improve the etching rate, and also avoids the violent decomposition and bubble generation caused by high-concentration hydrogen peroxide, thereby ensuring the transparency and stability of the etching solution. In combination with the stabilizing effect of hydroxyethylidene diphosphonic acid, the service life of the etching solution can be significantly prolonged, and a stable, controllable and highly selective titanium tungsten etching effect can be achieved.

[0023] Optionally, in the step S3, 0.1-0.5 parts by mass of nitrilotriacetic acid is further added when the aqueous hydroxyethylidene diphosphonic acid solution is added.

[0024] In the system of the present application, nitrilotriacetic acid (NTA) is further added as a titanium activator, which can coordinate with the Ti 4+ complex on the surface to break the dissolution-repassivation balance on the surface of the passivation film, thereby continuously promoting the dissolution and rupture of the TiO2 / TiN layer; at the same time, hydroxyethylidene diphosphonic acid (HEDP) can strongly chelate with Ti 4+ and W 6+ under acidic conditions, further weakens the structural stability of the passivation film through the competitive coordination of the phosphonic acid group with the metal oxygen bond (Ti–O–Ti, Ti–O–W), and inhibits the redeposition or repassivation of free Ti 4+ and W 6+ in the solution, so as to ensure that the etching interface maintains a high degree of activation throughout the etching process, the metal surface is fully exposed, and the hydrogen peroxide can directly react with the substrate, thereby maintaining a stable and controllable etching rate.

[0025] The present application also provides a titanium alloy etching solution, which comprises the following raw materials in parts by mass: 600-700 parts of deionized water, 70-80 parts of citric acid, 70-80 parts of ammonium citrate, 16.2-20.3 parts of hydroxyethylidene diphosphonic acid, 50-66.6 parts of hydrogen peroxide, and 0.1-0.15 parts of coumarin-thiosemicarbazide hybrid; and further comprising 5 parts by volume of anhydrous ethanol.

[0026] In the present application, the formula in parts by mass enables the etching solution to have stable buffering property in the pH 3.0-4.0 interval, the hydrogen peroxide to be effectively stabilized by HEDP in an acidic environment, and copper to be highly selectively passivated by coumarin-thiosemicarbazide, thereby achieving efficient, uniform and repeatable TiW etching while ensuring the transparency and service life of the solution.

[0027] The above technical solutions of the present application at least include the following beneficial effects:

[0028] 1. The present application utilizes the selective adsorption characteristics of coumarin-thiosemicarbazide hybrid on the copper surface, forms a dense protective film through Cu-N and Cu-S coordination, effectively blocks the etching solution from contacting the copper, avoids side etching, and simultaneously chelates Cu 2+ in the solution, inhibits its catalytic decomposition of hydrogen peroxide, thereby realizing effective corrosion inhibition of copper and stability of hydrogen peroxide, ensuring stable etching rate of titanium alloy and prolonging the service life of the etching solution.

[0029] 2. The present application adopts a citric acid-ammonium citrate buffer system to stabilize the etching solution in the weak acid range of pH 3-4, maintains the stable existence of hydrogen peroxide and promotes the dissolution of titanium tungsten oxide, and hydroxyethylidene diphosphonic acid inhibits the decomposition of hydrogen peroxide by chelating metal ions, thereby improving the stability of hydrogen peroxide. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The cross-sectional electron microscope image of the Cu bump TiW / Si test piece after etching by the etching solution prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. The described embodiments are part of the embodiments of the present application, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present application belong to the scope of protection of the present application.

[0032] Example 1

[0033] 1.8g 3-acetylcoumarin was added to 15mL anhydrous ethanol and mixed and stirred for 10min to obtain a 3-acetylcoumarin solution; 1.5g aminothiourea was dissolved in 20mL anhydrous ethanol under continuous stirring, then the 3-acetylcoumarin solution was added dropwise and mixed and stirred for 15min, 0.15mL concentrated acetic acid was added dropwise, and then refluxed under continuous stirring for 8h, cooled to room temperature, separated by vacuum filtration, and the solid was washed with 0℃ anhydrous ethanol for 5 times to obtain a coumarin-thiosemicarbazide hybrid; 0.12g coumarin-thiosemicarbazide hybrid was added to 5mL anhydrous ethanol, heated to 70℃, and ultrasonically treated for 20min to obtain a coumarin-thiosemicarbazide solution.

[0034] Mix 600 mL of deionized water, 80 g of citric acid, 80 g of ammonium citrate in a beaker, magnetically stir for 20 min, add 25 mL of hydroxy ethylene diphosphonic acid aqueous solution with a mass concentration of 60% and 0.5 g of amino triacetic acid, mix and stir for 10 min, add 200 mL of hydrogen peroxide solution with a volume concentration of 30% and coumarin thiourea hydrazine hybrid solution in sequence under continuous stirring, continue to stir for 20 min, and get titanium alloy etching solution.

[0035] Example 2

[0036] Mix 1.5 g of 3-acetyl coumarin into 20 mL of anhydrous ethanol, stir for 5 min to get 3-acetyl coumarin solution; dissolve 1 g of aminothiourea in 20 mL of anhydrous ethanol under continuous stirring, then add 3-acetyl coumarin solution dropwise, mix and stir for 10 min, add 0.1 mL of concentrated acetic acid, and reflux for 6 h under continuous stirring, cool to room temperature, separate by vacuum filtration, take out the solid, wash with 4 ℃ anhydrous ethanol for 3 times, get coumarin-thiourea hydrazine hybrid; add 0.1 g of coumarin-thiourea hydrazine hybrid to 5 mL of anhydrous ethanol, heat to 60 ℃, ultrasonic treatment for 10 min to get coumarin-thiourea hydrazine solution.

[0037] Mix 700 mL of deionized water, 70 g of citric acid, 70 g of ammonium citrate in a beaker, magnetically stir for 10 min, add 20 mL of hydroxy ethylene diphosphonic acid aqueous solution with a mass concentration of 60% and 0.1 g of amino triacetic acid, mix and stir for 8 min, add 150 mL of hydrogen peroxide solution with a volume concentration of 30% and coumarin thiourea hydrazine hybrid solution in sequence under continuous stirring, continue to stir for 15 min, and get titanium alloy etching solution.

[0038] Example 3

[0039] Mix 2 g of 3-acetyl coumarin into 20 mL of anhydrous ethanol, stir for 8 min to get 3-acetyl coumarin solution; dissolve 1.5 g of aminothiourea in 20 mL of anhydrous ethanol under continuous stirring, then add 3-acetyl coumarin solution dropwise, mix and stir for 12 min, add 0.2 mL of concentrated acetic acid, and reflux for 7 h under continuous stirring, cool to room temperature, separate by vacuum filtration, take out the solid, wash with 2 ℃ anhydrous ethanol for 3-5 times, get coumarin-thiourea hydrazine hybrid; add 0.14 g of coumarin-thiourea hydrazine hybrid to 5 mL of anhydrous ethanol, heat to 80 ℃, ultrasonic treatment for 15 min to get coumarin-thiourea hydrazine solution.

[0040] Mix 650 mL of deionized water, 75 g of citric acid, 75 g of ammonium citrate in a beaker, magnetically stir for 15 min, add 22 mL of hydroxy ethylene diphosphonic acid aqueous solution with a mass concentration of 60% and 0.2 g of amino triacetic acid, mix and stir for 9 min, add 170 mL of hydrogen peroxide solution with a volume concentration of 30% and coumarin thiourea hydrazine hybrid solution in sequence under continuous stirring, continue to stir for 18 min, and titanium alloy etching solution is obtained.

[0041] Example 4

[0042] Mix 1.6 g of 3-acetyl coumarin into 18 mL of anhydrous ethanol, stir for 6 min to obtain a 3-acetyl coumarin solution; dissolve 1.2 g of aminothiourea in 20 mL of anhydrous ethanol under continuous stirring, then add the 3-acetyl coumarin solution dropwise, mix and stir for 14 min, add 0.12 mL of concentrated acetic acid, and reflux under continuous stirring for 6.5 h. Cool to room temperature, separate by vacuum filtration, take out the solid, and wash with 3 ℃ anhydrous ethanol 4 times to obtain a coumarin-thiourea hydrazine hybrid; add 0.15 g of coumarin-thiourea hydrazine hybrid to 5 mL of anhydrous ethanol, heat to 65 ℃, and ultrasonic treat for 18 min to obtain a coumarin-thiourea hydrazine solution.

[0043] Mix 680 mL of deionized water, 78 g of citric acid, 78 g of ammonium citrate in a beaker, magnetically stir for 16 min, add 24 mL of hydroxy ethylene diphosphonic acid aqueous solution with a mass concentration of 60% and 0.3 g of amino triacetic acid, mix and stir for 9 min, add 180 mL of hydrogen peroxide solution with a volume concentration of 30% and coumarin thiourea hydrazine hybrid solution in sequence under continuous stirring, continue to stir for 18 min, and titanium alloy etching solution is obtained.

[0044] Example 5

[0045] Mix 1.7 g of 3-acetyl coumarin into 16 mL of anhydrous ethanol, stir for 7 min to obtain a 3-acetyl coumarin solution; dissolve 1 g of aminothiourea in 20 mL of anhydrous ethanol under continuous stirring, then add the 3-acetyl coumarin solution dropwise, mix and stir for 10 min, add 0.1 mL of concentrated acetic acid, and reflux under continuous stirring for 6 h. Cool to room temperature, separate by vacuum filtration, take out the solid, and wash with 2 ℃ anhydrous ethanol 4 times to obtain a coumarin-thiourea hydrazine hybrid; add 0.13 g of coumarin-thiourea hydrazine hybrid to 5 mL of anhydrous ethanol, heat to 80 ℃, and ultrasonic treat for 15 min to obtain a coumarin-thiourea hydrazine solution.

[0046] Mix 620 mL of deionized water, 72 g of citric acid, 72 g of ammonium citrate in a beaker, magnetically stir for 13 min, add 23 mL of hydroxyethylenediphosphonic acid aqueous solution with a mass concentration of 60% and 0.4 g of amino triacetic acid, mix and stir for 9 min, add 180 mL of hydrogen peroxide solution with a volume concentration of 30% and the coumarin thiosemicarbazone hybrid solution in sequence under continuous stirring, continue to stir for 18 min, and titanium alloy etching solution is obtained.

[0047] Example 6

[0048] Mix 2 g of 3-acetylcoumarin into 20 mL of anhydrous ethanol, stir for 5 min to obtain a 3-acetylcoumarin solution; under continuous stirring, dissolve 1 g of aminothiourea in 20 mL of anhydrous ethanol, then add the 3-acetylcoumarin solution dropwise, mix and stir for 12 min, add 0.15 mL of concentrated acetic acid, then reflux under continuous stirring for 8 h, cool to room temperature, separate by vacuum filtration, take out the solid, wash with 4 ℃ anhydrous ethanol 3 times, and coumarin-thiosemicarbazone hybrid is obtained; add 0.12 g of coumarin-thiosemicarbazone hybrid to 5 mL of anhydrous ethanol, heat to 60 ℃, and ultrasonic treatment for 10 min to obtain a coumarin-thiosemicarbazone solution.

[0049] Mix 600 mL of deionized water, 70 g of citric acid, 70 g of ammonium citrate in a beaker, magnetically stir for 10 min, add 20 mL of hydroxyethylenediphosphonic acid aqueous solution with a mass concentration of 60%, mix and stir for 8 min, add 150 mL of hydrogen peroxide solution with a volume concentration of 30% and the coumarin thiosemicarbazone hybrid solution in sequence under continuous stirring, continue to stir for 20 min, and titanium alloy etching solution is obtained.

[0050] The present application also carries out comparative examples and related tests.

[0051] Comparative Example 1

[0052] Compared with Example 1, the only difference is that the coumarin-thiosemicarbazone hybrid is not prepared, and the other preparation methods and components are completely consistent, and finally titanium alloy etching solution is obtained.

[0053] Comparative Example 2

[0054] Compared with Example 1, the only difference is that citric acid and ammonium citrate are not added, and the other preparation methods and components are completely consistent, and finally titanium alloy etching solution is obtained.

[0055] Comparative Example 3

[0056] Compared with Example 1, the only difference is that the hydroxyethylenediphosphonic acid aqueous solution is not added, and the other preparation methods and components are completely consistent, and finally titanium alloy etching solution is obtained.

[0057] Performance detection test

[0058] The Cu bump TiW / Si test pieces used in this test were commercially available. The initial TiW layer thickness was recorded as H0 (nm). The test pieces were immersed in 100 mL of the titanium alloy etching solutions prepared in Examples 1-6 and Comparative Examples 1-3, respectively. The solutions were continuously stirred at 200 rpm at 20°C. The corresponding test pieces were taken out at 30 s, 60 s, and 120 s, respectively, and immediately rinsed three times with a large amount of deionized water and dried with N2. The film thickness Ht (nm) was measured, and the etching rate (nm / s) at 0~30 s, 0~60 s, and 0~120 s was calculated according to the following formula to evaluate the etching efficiency and etching stability. The results are shown in Table 1.

[0059] Etching rate =

[0060] Table 1: Etching Rate Results

[0061]

[0062] As shown in Table 1, Examples 1-6 of the present invention all exhibited good etching stability, with minimal decay within a 2-minute experimental period. Example 6, due to the absence of aminotriacetic acid, had a slightly lower initial etching rate, but its stability was significantly better than Comparative Examples 1-3. Comparative Example 1, due to the absence of coumarin-thioaminourea hybrid, had a high initial etching rate, but subsequently, due to the corrosion of copper, Cu... 2+ The strong catalysis of hydrogen peroxide decomposition caused a sharp drop in etching rate; the absence of a pH buffer system (citric acid and ammonium citrate) in Comparative Example 2 resulted in pH loss of control in the system, which also significantly reduced the etching rate in the later stages; the lack of hydroxyethylidene diphosphonic acid in Comparative Example 3 accelerated the failure rate of hydrogen peroxide, shortened the overall lifespan of the etching solution, and also significantly reduced the etching rate in the later stages.

[0063] After the above sample has been etched for 120 seconds, take it out and put 5 mL of the etched sample into a clean centrifuge tube. Use ICP-OES to measure the Cu dissolution amount (ppm) to evaluate the etching effect of the etchant on copper. The specific test results are shown in Table 2.

[0064] Table 2: Cu dissolution results

[0065]

[0066] From Table 2, the Cu dissolution amount of Examples 1-6 is less than 10 ppm, and the copper-specific corrosion inhibition effect is excellent. The absence of the coumarin-thiosemicarbazone hybrid in Comparative Example 1 significantly increases the Cu dissolution amount, indicating that the coumarin-thiosemicarbazone hybrid prepared in the present application has a significant effect on inhibiting Cu dissolution. The absence of the pH buffer system (citric acid and ammonium citrate) in Comparative Example 2 and the absence of hydroxyethylidene diphosphonic acid in Comparative Example 3 also exhibit higher Cu dissolution, which further indicates that the buffer system and the metal chelating agent also play an auxiliary role in the overall selective protection.

[0067] From Figure 1 The cross-sectional electron microscope image of the TiW / Si test piece of the Cu bump etched by the etching solution prepared in Example 1 can also be clearly seen. The TiW layer is selectively removed after etching by the etching solution prepared in Example 1 of the present application, and the copper layer and the silicon base layer are not excessively damaged. In summary, the titanium alloy etching solution prepared in the present application has a high and stable etching effect on the titanium tungsten layer, and can alleviate the side etching phenomenon of the upper copper layer.

[0068] The above is the preferred embodiment of the present application, and those skilled in the art can make several improvements and refinements without departing from the principles of the present application. These improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for preparing a titanium alloy etching solution, characterized in that, Includes the following steps: S1. Under continuous stirring, dissolve aminothiourea in anhydrous ethanol, then add 3-acetylcoumarin solution dropwise and stir for 10-15 min. After adding concentrated acetic acid dropwise, reflux for 6-8 h under continuous stirring, cool to room temperature, separate by vacuum filtration, take out the solid, and wash 3-5 times with anhydrous ethanol at 0-4℃ to obtain coumarin-thioaminourea hybrid. S2. Add 0.14g of coumarin-thioaminourea hybrid to 5mL of anhydrous ethanol, heat, and sonicate to obtain coumarin-thioaminourea solution. S3. Mix 650 mL of deionized water, 75 g of citric acid, 75 g of ammonium citrate, 22 mL of 60% hydroxyethylidene diphosphonic acid aqueous solution, 0.2 g of aminotriacetic acid, 170 mL of 30% hydrogen peroxide and coumarin-thioaminourea hybrid solution to obtain titanium alloy etching solution.

2. The method for preparing a titanium alloy etching solution according to claim 1, characterized in that, The 3-acetylcoumarin solution was obtained by adding 3-acetylcoumarin to anhydrous ethanol and mixing and stirring for 5-10 minutes.

3. The method for preparing a titanium alloy etching solution according to claim 1, characterized in that, The 3-acetylcoumarin solution comprises the following raw materials: 1.5 to 2 parts by mass of 3-acetylcoumarin and 15 to 20 parts by volume of anhydrous ethanol.

4. The method for preparing a titanium alloy etching solution according to claim 1, characterized in that, The aminothiourea is present in a mass fraction of 1 to 1.5 parts, anhydrous ethanol in a volume fraction of 20 parts, and concentrated acetic acid in a volume fraction of 0.1 to 0.2 parts.

5. The method for preparing a titanium alloy etching solution according to claim 1, characterized in that, In step S2, 0.14g of coumarin-thioaminourea hybrid is added to 5mL of anhydrous ethanol, heated to 60~80℃, and ultrasonically treated for 10~20min to obtain a coumarin-thioaminourea solution.

6. The method for preparing a titanium alloy etching solution according to claim 1, characterized in that, In step S3, 650 mL of deionized water, 75 g of citric acid, and 75 g of ammonium citrate are mixed and magnetically stirred for 10-20 min. Then, 22 mL of a 60% (w / w) aqueous solution of hydroxyethylidene diphosphonic acid and 0.2 g of aminotriacetic acid are added and stirred for 8-10 min. While stirring continuously, 170 mL of a 30% (w / w) hydrogen peroxide and a coumarin-thioaminourea hybrid solution are added sequentially, and stirring is continued for 15-20 min to obtain the titanium alloy etching solution.

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