Electroplating copper solution and electroplating process

Abstract

The application discloses a kind of electroplating copper solution and electroplating process, belong to electroplating technical field, its technical scheme key points are a kind of electroplating copper solution, including following raw materials: copper sulfate 200-240g / L, sulfuric acid 35-55g / L, chloride ion 50-100mg / L, leveling agent 7-10g / L, brightener 3-6g / L, the brightener is at least one in formamide propane sulfonic acid sodium, 1,1-dimethyl guanidine sodium sulfate, the present application is accurately regulated by each component in electroplating copper solution, effectively improve the throwing power of electroplating solution and the bright performance of coating.

Description

Technical Field

[0001] This invention relates to the field of electroplating technology, and in particular to an electroplating copper solution and electroplating process. Background Technology

[0002] Electroplating, as a common metal surface treatment technology, plays an important role in the industrial field. It significantly enhances the corrosion resistance, wear resistance, and aesthetic appearance of metal products, and is therefore widely used in many industrial sectors such as automotive, hardware, and electronics. Particularly in semiconductor fabrication, the copper electroplating process in wafer circuitry is a key technology for achieving metal interconnects, playing a crucial role in constructing the internal circuit connections of chips and driving the continuous development of the semiconductor industry.

[0003] In the electroplating copper process for semiconductor fabrication, existing technologies typically employ electrolysis to reduce copper ions to metallic copper, which is then deposited in specific areas of the wafer to form conductive paths. This electrolytic method is a common practice in the industry. By applying current to the electroplating solution, copper ions undergo a chemical reaction on the wafer surface, gradually depositing to form a copper layer. Furthermore, the composition and concentration of the electroplating solution are carefully controlled to ensure the smooth progress of the electroplating process. During operation, process parameters such as current and temperature are also controlled to influence the electroplating effect.

[0004] However, existing copper plating processes have significant drawbacks. Conventional copper plating processes often result in uneven coating coverage and pitting, leading to an uneven wafer surface. These surface defects can negatively impact circuit reliability, potentially causing circuit failures and reducing the quality and performance of semiconductor products. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a copper plating solution and an electroplating process. By precisely controlling the components in the copper plating solution, this invention effectively improves the uniform plating ability of the plating solution and the brightness of the plating layer.

[0006] The present invention provides a copper plating solution and electroplating process using the following technical solution: A copper electroplating solution comprises the following raw materials: 200-240 g / L copper sulfate, 35-55 g / L sulfuric acid, 50-100 mg / L chloride ions, 7-10 g / L leveling agent, and 3-6 g / L brightener, wherein the brightener is at least one of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate.

[0007] By employing the above technical solution, copper sulfate, as the main source of copper ions, provides copper ions for the electroplating process to deposit and form a copper layer; sulfuric acid can adjust the pH of the electroplating solution, enhance the conductivity of the solution, and promote the movement of copper ions; chloride ions can form complexes with copper ions, which helps to uniformly deposit copper ions on the cathode surface; the leveling agent can be adsorbed on the cathode surface, inhibiting the deposition rate of copper ions on protruding parts and promoting deposition on recessed parts, making the plating surface smoother; the brightener can reduce the surface tension of the plating layer, improve the brightness and uniformity of the plating layer, and the leveling agent adsorbs in high current density areas (such as the orifice) to inhibit deposition, while the brightener is enriched and accelerates deposition in low current density areas (such as the bottom of the orifice). This differential adsorption forms a deposition rate gradient, making the filling rate at the bottom of the orifice higher than that at the orifice, achieving bottom-up filling and avoiding voids. The components work synergistically to solve the problems of uneven plating coverage and pitting leading to uneven surface in existing copper electroplating processes, thus improving circuit reliability.

[0008] In the above scheme, insufficient copper sulfate can easily lead to scorching, while excess copper sulfate can easily lead to crystallization, affecting electroplating performance; insufficient chloride ions can cause scorching and precipitation spots in high current areas, while excess chloride ions can easily cause darkening in low current areas; excessive leveling agent can cause spots to appear in high current areas.

[0009] In a preferred embodiment, the leveling agent consists of a quaternary ammonium salt compound and azathioprine.

[0010] In a preferred embodiment, the amount of the quaternary ammonium salt compound added is 10-40 g / L, and the amount of the azathioprine added is 20-60 mg / L.

[0011] In a preferred embodiment, the quaternary ammonium salt compound is obtained by the following preparation method: tetramethylhexanediamine and dichloroethyl ether are added to water, and the reaction is carried out at a temperature of 90-95°C for 6-7 hours. After adjusting the pH of the system to 3-4, the quaternary ammonium salt compound is obtained.

[0012] In a preferred embodiment, the molar ratio of tetramethylhexanediamine to dichloroethyl ether is (0.8-1.1):1.

[0013] By adopting the above technical solution, when the leveling agent is composed of the aforementioned quaternary ammonium salt compounds and thiazoline, the two work together to ensure a uniform and smooth coating surface at different scales, reducing pinholes and residual stress within the coating. The resulting coating exhibits excellent mechanical properties. The specific reasons are as follows: Quaternary ammonium salt compounds, as large molecular cations, have strong adsorption capacity on the cathode surface and preferentially adsorb in high current density areas (such as workpiece protrusions or blind hole openings). Through electrostatic interaction, they form an inhibition layer, hindering copper ion reduction and thus reducing the stress at protrusions. The deposition rate (inhibiting protrusion growth); as a nitrogen-containing heterocyclic compound, thiazoline can form coordination bonds between its heterocyclic nitrogen and sulfur atoms on the copper surface, enhancing adsorption stability. Furthermore, the adsorption of thiazoline tends to be more inclined towards microscopic uneven regions, further refining the surface profile by filling grain boundary defects. Therefore, when the two are combined, the strong electrostatic adsorption of quaternary ammonium salt compounds provides a more uniform adsorption interface for thiazoline, avoiding local over-inhibition. Thiazoline compensates for the weak adsorption of quaternary ammonium salts in low current density regions, ensuring full-area coverage and effectively improving the uniform plating ability of the electroplating solution.

[0014] In a preferred embodiment, the brightener is composed of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate.

[0015] In a preferred embodiment, the amount of sodium formamide propane sulfonate added is 3-12 g / L and sodium 1,1-dimethylguanidine sulfate is 5-10 g / L.

[0016] In a preferred embodiment, the brightener further includes 1-3 g / L of hydroxyethyl cellulose.

[0017] By adopting the above technical solution, the sulfonic acid groups of sodium formamide propane sulfonate are adsorbed on the cathode surface, destroying the copper ion hydration layer, accelerating the copper ion reduction reaction, reducing cathode polarization, promoting crystal nucleation and grain refinement, and ensuring a dense coating base; the guanidine groups in sodium 1,1-dimethylguanidine sulfate form temporary complexes with the copper ion hydration layer, slowing down the deposition rate and making the grain orientation more uniform. At the same time, it works synergistically with the sulfonic acid groups to expand the brightness range in the low current density region; the ether bonds in hydroxyethyl cellulose form a composite inhibition film with chloride ions, increasing cathode polarization, inhibiting disordered copper ion deposition, and promoting bubble detachment by reducing the surface tension of the solution, preventing hydrogen bubbles from accumulating and forming vacuum defects.

[0018] Therefore, when the three are used together, sodium formamide propane sulfonate accelerates deposition, sodium 1,1-dimethylguanidine sulfate regulates crystal orientation, and hydroxyethyl cellulose inhibits abnormal growth. The three work together to obtain a smooth and fine-grained coating, achieving a full-brightness effect.

[0019] A second aspect of the present invention is to provide an electroplating process using the copper plating solution described above, comprising the following steps: S1. Dissolve copper sulfate in water, and then add the prescribed amount of sulfuric acid while stirring. S2. After adding chloride ions, leveling agent, and brightener, stir and then electrolyze in air for 1-2 hours. S3. Begin operation, controlling the cathode current density to 1-10 A / dm². 2 The temperature of the copper plating solution is 20-30℃.

[0020] In summary, the present invention has the following beneficial effects: The synergistic effect of leveling agents and brighteners optimizes coating performance by regulating the deposition rate in different current density zones, thereby improving coating uniformity and reducing pinhole defects. In addition, sodium formamide propane sulfonate in the brightener promotes rapid crystal nucleus formation, resulting in a fine-grain strengthening effect. The increased number of grain boundaries hinders dislocation movement. The nitrogen-containing heterocycles of thiazolyl purine adsorb at the grain boundaries, inhibiting columnar crystal growth and promoting the formation of equiaxed crystals, thus enhancing the density of the coating. Hydroxyethyl cellulose inhibits excessive polarization and avoids internal stress concentration. The complexing effect of sodium 1,1-dimethylguanidine sulfate delays deposition, allowing copper atoms to be arranged in an orderly manner and reducing twin defects. Furthermore, the sulfuric acid content in the electroplating solution ensures conductivity and avoids brittleness caused by concentration difference polarization. Attached Figure Description

[0021] Figure 1 This is a photograph of the product obtained after electroplating in Example 1 of this application. Detailed Implementation

[0022] The following combination Figure 1 The present invention will be further described in detail below. All reagents, unless otherwise specified, are commercially available conventional reagent products. Preparation Example 1

[0023] A method for preparing a quaternary ammonium salt compound includes the following steps: adding tetramethylhexanediamine and dichloroethyl ether to water at a molar ratio of 0.8:1 to form a mixed solution with a total concentration of 30wt%, then reacting at 90℃ for 7h, and adjusting the pH of the system to 3.5 to obtain the quaternary ammonium salt compound. Preparation Example 2

[0024] A method for preparing a quaternary ammonium salt compound includes the following steps: adding tetramethylhexanediamine and dichloroethyl ether to water at a molar ratio of 1.1:1 to form a mixed solution with a total concentration of 30wt%, then reacting at 95℃ for 6 hours, and adjusting the pH of the system to 3.0 to obtain the quaternary ammonium salt compound.

[0025] In the following examples and comparative examples of this application, electronic-grade copper sulfate is used. Example 1

[0026] A copper plating solution comprises the following raw materials: 200 g / L copper sulfate, 35 g / L sulfuric acid, 50 mg / L chloride ions, 7 g / L leveling agent, and 3 g / L brightener; The brightener is sodium formamide propane sulfonate; The leveling agent is composed of the quaternary ammonium salt compound obtained in Preparation Example 1 and azathioprine, wherein the amount of the quaternary ammonium salt compound added is 10 g / L and the amount of the azathioprine added is 20 mg / L. Its electroplating process includes the following steps: S1. Dissolve copper sulfate in water. After dissolving, add the prescribed amount of sulfuric acid while stirring. Then add 2g / L of commercially available activated carbon. Stir for 1 hour and let stand for 1.5 hours to allow the activated carbon to settle and filter before use. S2. Add sodium chloride, leveling agent, and brightening agent, then stir. The mixture is stirred at a current density of 1 A / dm³. 2 Electrolysis under vacuum for 1 hour; S3. Begin operation, controlling the cathode current density to 1A / dm³. 2 The copper plating solution temperature is 20℃, the anode is a phosphor bronze ball, and the anode current density is 1 A / dm³. 2 Electroplating is performed. Example 2

[0027] A copper plating solution comprises the following raw materials: 220 g / L copper sulfate, 45 g / L sulfuric acid, 70 mg / L chloride ions, 8 g / L leveling agent, and 4 g / L brightener; The brightener is sodium formamide propane sulfonate; The leveling agent is composed of the quaternary ammonium salt compound obtained in Preparation Example 1 and azathioprine, wherein the amount of the quaternary ammonium salt compound added is 10 g / L and the amount of the azathioprine added is 20 mg / L. Its electroplating process includes the following steps: S1. Dissolve copper sulfate in water. After dissolving, add the prescribed amount of sulfuric acid while stirring. Then add 2g / L of commercially available activated carbon. Stir for 1 hour and let stand for 1.5 hours to allow the activated carbon to settle and filter before use. S2. Add sodium chloride, leveling agent, and brightening agent, then stir. The mixture is stirred at a current density of 1 A / dm³. 2 Electrolysis under vacuum for 1 hour; S3. Begin operation, controlling the cathode current density to 6A / dm. 2 The copper plating solution temperature is 25℃, the anode is a phosphor bronze ball, and the anode current density is 2 A / dm³. 2 Electroplating is performed. Example 3

[0028] A copper plating solution comprises the following raw materials: 240 g / L copper sulfate, 55 g / L sulfuric acid, 100 mg / L chloride ions, 10 g / L leveling agent, and 6 g / L brightener; The brightener is sodium formamide propane sulfonate; The leveling agent is composed of the quaternary ammonium salt compound obtained in Preparation Example 1 and azathioprine, wherein the amount of the quaternary ammonium salt compound added is 10 g / L and the amount of the azathioprine added is 20 mg / L. Its electroplating process includes the following steps: S1. Dissolve copper sulfate in water. After dissolving, add the prescribed amount of sulfuric acid while stirring. Then add 2g / L of commercially available activated carbon. Stir for 1 hour and let stand for 1.5 hours to allow the activated carbon to settle and filter before use. S2. Add sodium chloride, leveling agent, and brightening agent, then stir. The mixture is stirred at a current density of 1 A / dm³. 2 Electrolysis under vacuum for 2 hours; S3. Begin operation, controlling the cathode current density to 10A / dm². 2 The copper plating solution temperature is 30℃, the anode is a phosphor bronze ball, and the anode current density is 3 A / dm³. 2 Electroplating is performed. Example 4

[0029] An electroplating copper solution differs from Example 2 in that it uses the quaternary ammonium salt compound obtained in Preparation Example 2, with an addition amount of 30 g / L for the quaternary ammonium salt compound and an addition amount of 40 mg / L for the azathioprine. All other aspects are the same as in Example 2. Example 5

[0030] An electroplating copper solution differs from Example 2 in that it uses the quaternary ammonium salt compound obtained in Preparation Example 2, with an addition amount of 40 g / L of the quaternary ammonium salt compound and an addition amount of 60 mg / L of the azathioprine. All other aspects are the same as in Example 2. Example 6

[0031] An electroplating copper solution differs from Example 4 in that the total amount of brightener remains unchanged. The brightener is composed of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate. The amount of sodium formamide propane sulfonate added is 3 g / L and sodium 1,1-dimethylguanidine sulfate is 5 g / L. All other aspects are the same as in Example 4. Example 7

[0032] An electroplating copper solution differs from Example 4 in that the total amount of brightener remains unchanged. The brightener is composed of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate. The amount of sodium formamide propane sulfonate added is 8 g / L and the amount of sodium 1,1-dimethylguanidine sulfate added is 8 g / L. All other aspects are the same as in Example 4. Example 8

[0033] An electroplating copper solution differs from Example 4 in that the total amount of brightener remains unchanged. The brightener is composed of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate. The amount of sodium formamide propane sulfonate added is 12 g / L and sodium 1,1-dimethylguanidine sulfate is 10 g / L. All other aspects are the same as in Example 4. Example 9

[0034] An electroplating copper solution, which differs from Example 7 in that the brightener also includes hydroxyethyl cellulose at an addition amount of 1 g / L, while all other aspects are the same as in Example 7. Example 10

[0035] An electroplating copper solution, which differs from Example 7 in that the brightener also includes hydroxyethyl cellulose at an addition amount of 3 g / L, while all other aspects are the same as in Example 7. Comparative Example 1

[0036] An electroplating copper solution differs from Example 2 in that the leveling agent is added at a rate of 15 g / L, while all other aspects are the same as in Example 2. Comparative Example 2

[0037] An electroplating copper solution differs from Example 2 in that the amount of copper sulfate added is 180 g / L, while all other aspects are the same as in Example 2. Comparative Example 3

[0038] An electroplating copper solution, which differs from Example 2 in that an equal amount of imidazoline quaternary ammonium salt is used instead of the quaternary ammonium salt compound obtained in Example 1 of this application, while all other aspects are the same as in Example 2. Comparative Example 4

[0039] An electroplating copper solution differs from Example 2 in that an equal amount of sodium polydithiopropane sulfonate is used instead of sodium formamide propane sulfonate; otherwise, they are the same as in Example 2. Comparative Example 5

[0040] An electroplating copper solution differs from Example 2 in that an equal amount of sodium 1-butyl-3-methylimidazolium trifluoromethanesulfonate is used instead of sodium formamide propanesulfonate; otherwise, they are identical to Example 2. Performance testing

[0041] The coatings obtained in the above embodiments and comparative examples were tested for gloss, tensile strength, elongation and uniform coating ability. The test results are shown in Table 1.

[0042] Glossiness: The projection angle is 60° during testing.

[0043] Tensile strength and elongation were tested using a tensile testing machine at a tensile rate of 10 mm / min.

[0044] Table 1. Test Results of Various Properties of the Coating project Gloss (60°) Tensile strength / MPa Elongation / % Plating uniformity / % Example 1 240 345 3.5 65.9 Example 2 242 358 3.8 67.3 Example 3 245 360 3.7 66.8 Example 4 255 367 4.1 68.8 Example 5 252 366 4.0 68.5 Example 6 264 386 4.5 70.2 Example 7 268 391 4.6 71.8 Example 8 269 389 4.6 71.2 Example 9 272 406 4.8 73.4 Example 10 275 410 5.1 75.6 Comparative Example 1 228 313 2.6 55.8 Comparative Example 2 198 295 1.6 38.6 Comparative Example 3 234 339 2.9 58.1 Comparative Example 4 235 341 2.7 55.4 Comparative Example 5 237 345 2.9 58.6 Based on the test data in Table 1: The coatings obtained from the electroplating copper solutions in Examples 1-3 of this application have a gloss of 240 or higher, a tensile strength of 345 MPa or higher, an elongation of 3.5% or higher, and a plating uniformity of more than 65%, indicating that the coatings obtained in the examples of this application have good mechanical properties and electroplating uniformity.

[0045] Compared with Example 2, in Examples 4-5, with the increase of quaternary ammonium salt compounds and thiazoline content in the leveling agent, the brightness, tensile strength and elongation of the coating obtained in Examples 4-5 were significantly increased, and the plating uniformity was slightly increased.

[0046] Compared with Example 4, Examples 6-8, by optimizing the addition amounts of quaternary ammonium compounds and azathioprine, and using a combination of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate as brighteners, showed significantly higher gloss, uniform plating ability, tensile strength, and elongation of the coatings obtained in Examples 6-8 compared to Example 4. This demonstrates that the combined use of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate with quaternary ammonium compounds and azathioprine leveling agents results in finer grain size and significantly improved tensile strength of the coating. Furthermore, the competitive adsorption between the two brighteners and the two leveling agents leads to better uniformity of the coating.

[0047] Compared with Example 7, when hydroxyethyl cellulose was added to the brightener, the brightness, tensile strength, elongation and uniform plating ability of the coating were further improved in Examples 9-10. It can be seen that the addition of hydroxyethyl cellulose can not only stabilize the cathode diffusion layer and enable other additives to be evenly distributed, but also reduce the retention of hydrogen bubbles by stabilizing the cathode film, thus effectively reducing vacuum defects on the coating surface.

[0048] Compared with Example 2, when the leveling agent is added in excess, the excess leveling agent molecules are tightly adsorbed on the cathode surface, forming an excessively thick barrier layer. This causes the reduction of copper ions to overcome an extremely high energy barrier, which causes the selective adsorption advantage of the leveling agent at micro-depressions to disappear. Both protrusions and depressions are strongly suppressed, resulting in a loss of balance. Consequently, the uniformity of the coating is poor, the internal stress of the coating increases sharply, and the tensile strength and elongation decrease.

[0049] Compared with Example 2, when the amount of copper sulfate added is too low, a violent hydrogen evolution side reaction occurs on the cathode surface due to a severe lack of copper ions, which fundamentally destroys the coating structure. The coating is brittle, has low tensile strength, and hydrogen evolution leads to abnormally coarse coating crystals.

[0050] Compared with Example 2, when other imidazoline quaternary ammonium salts were used instead of the quaternary ammonium salt compounds prepared in Example 1 of this application, sodium polydisulfide dipropane sulfonate was used instead of sodium formamide propane sulfonate of this application, or sodium 1-butyl-3-methylimidazolium trifluoromethanesulfonate was used instead of sodium formamide propane sulfonate of this application, the properties of the coatings obtained in Comparative Examples 3-5 were significantly reduced compared with those in Example 2. This further illustrates that the synergistic effect between the components in this application effectively improves the mechanical properties of the coating while also effectively improving the uniform plating ability of the electroplating solution.

[0051] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A copper plating solution, characterized in that: It includes the following raw materials: 200-240 g / L copper sulfate, 35-55 g / L sulfuric acid, 50-100 mg / L chloride ions, 7-10 g / L leveling agent, and 3-6 g / L brightener, wherein the brightener is at least one of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate.

2. The copper plating solution according to claim 1, characterized in that: The leveling agent is composed of quaternary ammonium salt compounds and thiazopurine.

3. The copper plating solution according to claim 2, characterized in that: The amount of the quaternary ammonium salt compound added is 10-40 g / L, and the amount of the azathioprine added is 20-60 mg / L.

4. The copper plating solution according to claim 2, characterized in that: The quaternary ammonium salt compounds are obtained by the following preparation method: tetramethylhexanediamine and dichloroethyl ether are added to water, and the reaction is carried out at a temperature of 90-95℃ for 6-7 hours. After adjusting the pH of the system to 3-4, the quaternary ammonium salt compounds are obtained.

5. The copper plating solution according to claim 4, characterized in that: The molar ratio of tetramethylhexanediamine to dichloroethyl ether is (0.8-1.1):

1.

6. The copper plating solution according to claim 1, characterized in that: The brightener is composed of sodium formamide propane sulfonate and sodium 1,1-dimethylguanidine sulfate.

7. The copper plating solution according to claim 6, characterized in that: The amount of sodium formamide propane sulfonate added is 3-12 g / L and sodium 1,1-dimethylguanidine sulfate is 5-10 g / L.

8. The copper plating solution according to claim 1, characterized in that: The brightener also includes 1-3 g / L of hydroxyethyl cellulose.

9. An electroplating process using the copper plating solution according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Dissolve copper sulfate in water, and then add the prescribed amount of sulfuric acid while stirring. S2. After adding chloride ions, leveling agent, and brightener, stir and then electrolyze in air for 1-2 hours. S3. Begin operation, controlling the cathode current density to 1-10 A / dm². 2 The temperature of the copper plating solution is 20-30℃.

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