Copper electroplating additive applied to semiconductor chip copper interconnection and preparation method

Abstract

The invention relates to the technical field of copper electroplating deposition, in particular to a copper electroplating additive applied to semiconductor chip copper interconnection and a preparation method. A compound containing a 1-fluorine-tetrafluoroalkene structural unit is adopted as a leveling agent of the copper electroplating liquid and is in synergistic effect with an accelerator and an inhibitor, so that the deposition speed of copper at the bottom of a blind hole and a channel of a wafer is higher than that of the top, inversion of the deposition speed is realized, bottom growth in the hole or the channel from bottom to top is completed, and the copper electroplating quality is improved. A plating layer obtained through electroplating is free of pores and holes, the surface roughness and the structural compactness of the plating layer are good, the impurity content of the plating layer is low, and the good wafer Damascus copper electroplating application effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of electroplated copper deposition, and in particular to an electroplated copper additive used for copper interconnection of semiconductor chips and a preparation method thereof. Background Art

[0002] The copper electroplating process for copper interconnection of ultra-large-scale integrated circuits is a very important link in the manufacture of integrated circuit chips, and is a key step in achieving the interconnection of the internal circuits of integrated circuit chips. With the development of integrated circuit technology, the reduction of feature size, the continuous improvement of packaging density and operating frequency, the line spacing and cross-sectional area of ​​the interconnection lines on the chip continue to decrease. The increased interconnection line resistance and parasitic capacitors have greatly increased the time constant of the interconnection line, and the proportion of the time constant of the interconnection line in the delay of the integrated circuit system is increasing, becoming the main factor limiting the speed of the integrated circuit system. The copper interconnection technology based on the Damascus structure is a revolutionary technological advancement, which realizes the simultaneous deposition of linking blind holes and interconnection leads, reduces the interconnection process steps and time, significantly improves the integration of integrated circuits, reduces interconnection delays, and also reduces manufacturing costs. The key technology of copper interconnection is achieved by electroplating copper, and the biggest challenge of the Damascus copper plating process is to form high aspect ratio filling channel lines without gaps, and the crystallization is dense and uniform.

[0003] The core of electrochemical deposition Damascus copper interconnect technology is to achieve defect-free filling of blind holes and trenches. To achieve this goal, the deposition rate of copper at the bottom of the blind hole and trench must be greater than that at the top, so as to achieve the reversal of the deposition rate and complete the bottom growth from bottom to top in the hole or trench. Since electric lines tend to concentrate at the hole mouth, this goal can generally be achieved through the synergistic effect of accelerators, inhibitors, and levelers. In addition, the electrochemical deposition copper interconnect process needs to meet other requirements. For example, the surface after electrodeposition can be as flat as possible to reduce the difficulty of subsequent chemical mechanical polishing. There are also strict requirements for the impurity content, uniform plating, surface roughness, resistivity, and coating stress in the coating. It is not easy to achieve. Today, the technology node of logic chips has reached below 14 nanometers, and the road to localization of such materials is more challenging. Summary of the invention

[0004] The purpose of the present invention is to provide a copper electroplating additive and a preparation method for copper interconnection of semiconductor chips, so as to solve the problems of voids, high impurity content in the coating, poor throwing power, high surface roughness and high stress in the coating that are easily occurred in the Damascus copper electroplating process.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: A leveling agent, wherein the leveling agent is a compound having a 1-fluoro-tetrafluoroene structural unit and has the following structural formula (1): ; Wherein, in the structural formula (1), R is an organic group having 1 to 6 carbon atoms, the organic group is an alkyl group, an alkoxy group, an alkyl group containing a hydroxyl group or an alkoxy group; the alkyl group is any one of a methyl group, an ethyl group, a n-propyl group and a n-butyl group.

[0006] The electroplating composition comprising the compound having 1-fluoro-tetrafluoroene structural unit in the structural formula (1) as a leveler can at least improve the void-free and crystalline properties compared with many conventional acid copper electroplating compositions, making it suitable for Damascus copper electroplating process.

[0007] A preparation method of a leveling agent, the preparation method comprising: Under nitrogen protection, 1-fluoro-tetrafluoroene and chlorinated compounds are added to deionized water, reacted at 80-90°C with constant stirring for 12-24 hours, then naturally cooled to room temperature, added with deionized water for dilution, and the pH is adjusted to neutral with dilute sulfuric acid to obtain a leveling agent.

[0008] As a limitation of the present invention, the chlorinated compound has the following structural formula (2): ; In the structural formula (2), R is an organic group having 1 to 6 carbon atoms, the organic group is an alkyl group, an alkoxy group, an alkyl group containing a hydroxyl group or an alkoxy group; the alkyl group is any one of a methyl group, an ethyl group, a n-propyl group and a n-butyl group.

[0009] As a limitation of the present invention, the molar ratio of the 1-fluoro-tetrafluoroene to the chlorinated compound is 1:4, and the chlorinated compound is one of 2-chloroethanol, 2-chloroethoxyethanol, chloropropane, 1-chlorobutane, and 2-chloroethyl propyl ether.

[0010] A copper electroplating additive applied to copper interconnection of semiconductor chips, the copper electroplating additive at least comprising the above-mentioned leveling agent, the dosage of the leveling agent is 1-10 mL / L.

[0011] As a limitation of the present invention, the electroplating copper additive also includes an accelerator and an inhibitor. The amount of the accelerator is 0.5 to 100 ppm, and the amount of the inhibitor is 50 to 1500 ppm.

[0012] As a limitation of the present invention, the accelerator is sodium polydisulfide propane sulfonate or sodium 3-mercapto-1-propane sulfonate; the inhibitor is one or more compounds having the following structural formulas (3) to (8): ; Wherein, in the structural formula (3), a is an integer from 10 to 500; ; Wherein, in the structural formula (4), a is an integer from 10 to 500; ; Wherein, in the structural formula (5), a, b, and c are each an integer between 10 and 100; ; Wherein, in the structural formula (6), a, b, and c are each an integer between 10 and 100; ; Wherein, in the structural formula (7), a and b are integers between 10 and 100 respectively; ; In the structural formula (8), n is an integer from 10 to 500.

[0013] A copper electroplating solution, comprising any one of the above copper electroplating additives.

[0014] Any copper ion soluble in the electroplating solution is applicable, and suitable copper ions include but are not limited to: copper sulfate, copper chloride, copper nitrate, copper sulfamate, copper methanesulfonate, copper sulfate and copper methanesulfonate are preferred; suitable acidic electrolytes in the electroplating solution include but are not limited to: sulfuric acid, acetic acid, methanesulfonic acid, sulfuric acid is preferred; the electrolyte contains a halogen ion source, and the preferred halogen ion source is chloride ion, which is generally added to the acid copper plating solution using copper chloride or hydrochloric acid.

[0015] As a limitation of the present invention, the contents of the components of the copper electroplating solution are: 20-50 g / L copper ions, 80-200 g / L sulfuric acid, 10-100 ppm chloride ions, 0.5-100 ppm accelerator, 50-1500 ppm inhibitor, and 1-10 mL / L leveler.

[0016] If the content of accelerator in the acid copper plating solution is less than 0.5ppm, it is difficult to ensure that a bright coating is formed on the surface of the integrated circuit chip, resulting in problems such as copper powder and pinholes; if the content of inhibitor is less than 50ppm, the wetting effect of the plating solution will be reduced, resulting in a large number of pinholes on the surface of the coating.

[0017] As a limitation of the present invention, the contents of the components of the copper electroplating solution are: 30-40 g / L copper ions, 100-130 g / L sulfuric acid, 50-60 ppm chloride ions, 0.5-10 ppm accelerator, 200-800 ppm inhibitor, and 3-7 mL / L leveler.

[0018] The electroplating copper additive applied to the copper interconnection of semiconductor chips can be used to electroplate copper metal on the integrated circuit chip by any method known in the prior art and literature. Typically, the copper metal is electroplated by conventional electroplating processes using electroplating equipment commonly used in the field of wafer manufacturing. These electroplating processes are well known in the art. The current density and electrode surface potential can vary depending on the specific substrate to be plated.

[0019] An application of the copper electroplating solution in copper interconnection of semiconductor chips, wherein the electroplating process of the copper electroplating solution is: Step 1: Current density is 0.3~0.8A / dm 2 , the electroplating time is 3 to 20 seconds, and the electroplating temperature is 20 to 30°C; Step 2: Current density is 0.5~1.5A / dm 2 , the electroplating time is 30-50s, and the electroplating temperature is 20-30℃; Step 3: Current density is 1-10A / dm 2 The electroplating time is 30 to 50 seconds and the electroplating temperature is 20 to 30°C.

[0020] As a limitation of the present invention, the electroplating process of the copper electroplating solution is: Step 1: Current density is 0.65A / dm 2 , the electroplating time is 5s, and the electroplating temperature is 25℃; Step 2: Current density is 1.0A / dm 2 , the electroplating time is 45s, and the electroplating temperature is 25℃; Step 3: Current density is 6.0A / dm 2 , the electroplating time is 38s, and the electroplating temperature is 25℃.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts a compound containing a 1-fluoro-tetrafluoroene structural unit as a leveler of a copper electroplating solution, and cooperates with an accelerator and an inhibitor to make the deposition rate of copper at the bottom of a wafer blind hole and a trench greater than that at the top, thereby realizing a reversal of the deposition rate and completing bottom growth from bottom to top in the hole or the trench. The electroplated coating has no pores or holes, has good surface roughness and structural density, and has a low impurity content in the coating, thereby showing a good wafer Damascus copper electroplating application effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The synthetic route of the leveling agent in Example 1 of the present invention; Figure 2 The figure shows the plating effect of the copper electroplating solution 1 of Example 3 of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the present invention, polyethyleneimine (MW=600) is provided by Shanghai Aladdin, and the other reagents are industrial products and can be purchased on the market.

[0025] Embodiment 1: A method for preparing a leveling agent, specifically: Under nitrogen protection, 50 mmol of 1-fluoro-tetrafluoroene, 200 mmol of 2-chloroethanol and 30 mL of deionized water were mixed, heated to 85°C, and reacted for 20 hours. After the reaction was completed, it was naturally cooled to room temperature, and methanol and water were removed by vacuum distillation to obtain compound R1. The obtained compound R1 was dissolved in 5.7 L of deionized water and stirred evenly. The pH value of the solution was adjusted to 7 with 20% dilute sulfuric acid to obtain leveling agent 1.

[0026] 1 H NMR (400 MHz, CDCl3), 4.24 (s, 4H), 3.97 (t, 8H), 3.68 (s, 8H), 3.43 (t, 8H), 3.30 (s, 12H), 3.22 (t, 8H), 2.17 (m, 4H).

[0027] Example 2: Using the preparation method in Example 1, leveling agent 2, leveling agent 3, leveling agent 4, and leveling agent 5 were prepared, specifically:

[0028] Embodiment 3: A copper electroplating solution 1, the components of which are as follows: , ;

[0029] Example 4: copper electroplating solution 2, copper electroplating solution 3, copper electroplating solution 4 and copper electroplating solution 5 containing different levelers in Example 2.

[0030]

[0031] Based on Example 3, a control experiment was carried out, specifically Comparative Example 1, as described below: Comparative Example 1: This comparative example relates to a copper electroplating solution, which is different from Example 3 only in that this comparative example uses polyethyleneimine as a leveling agent, and its components are as follows: , ; Detection experiment: The copper electroplating solution 1 in Example 3, the copper electroplating solution 2, copper electroplating solution 3, copper electroplating solution 4 and copper electroplating solution 5 in Example 4 and the copper electroplating solution in the comparative example are respectively used for patterning wafers of PVD seed layers, and a layer of silicon dioxide is vapor-deposited on the surface of the wafer, photoresist is coated, exposed, developed, dry-etched grooves, ashed, and cleaned. Then, a layer of copper is deposited on the surface of the etched wafer by magnetron sputtering to form a copper seed layer. The magnetron sputtering parameters are as follows: the sputtering temperature during magnetron sputtering is room temperature, the working gas pressure is 1 Pa, the argon gas flow rate is 20 sccm, the working voltage is 300 V, the working current is 0.10 A, the sputtering power is 48 W, and the sputtering thickness is 1 micron.

[0032] The prepared magnetron wafer was placed in a Haring cell for electroplating test. The opening width feature on the patterned wafer was 45nm, and the electroplating process parameters were: Step 1: Current density is 0.6A / dm 2 , the electroplating time is 5s, and the electroplating temperature is 25℃; Step 2: Current density is 1A / dm 2 , the electroplating time is 50s, and the electroplating temperature is 25℃; Step 3: Current density is 5A / dm 2 , the electroplating time is 40s, and the electroplating temperature is 25℃.

[0033] Determination of impurity content in the coating: The coatings electroplated with the copper electroplating solutions of Example 3, Example 4, and Comparative Example 1 were measured using a secondary ion mass spectrometer (SIMS) to analyze the contents of C, N, S, O, and Cl in each coating as well as their total.

[0034] Observation of coating surface: A scanning electron microscope (SEM) was used to observe the coating pores and holes of the wafers electroplated with the copper plating solutions of Example 3, Example 4, and Comparative Example 1, whether there was sealing after the second step of electroplating, the roughness of the coating surface, and the structural density.

[0035]

[0036] Conclusion: From the above experiments, it can be seen that the state and parameters of the coating plated with the copper electroplating solution 1 of Example 3 are better than those of the coating plated with the copper electroplating solution of Comparative Example 1. The copper electroplating solution using the compound of the 1-fluoro-tetrafluoroene structural unit involved in the present invention as a leveler has no pores or holes in the coating, and no sealing phenomenon occurs after the second step of electroplating. The surface roughness and structural density of the coating are good, and the impurity content of the coating is low. Its parameter indicators are better than the comparative example results using polyethyleneimine as a leveler, showing a good application effect of wafer Damascus copper plating.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A leveling agent, characterized in that: The leveling agent is a compound having a 1-fluoro-tetrafluoroene structural unit and has the following structural formula (1): ； Wherein, in the structural formula (1), R is an organic group having 1 to 6 carbon atoms, the organic group is an alkyl group, an alkoxy group, an alkyl group containing a hydroxyl group or an alkoxy group; the alkyl group is any one of a methyl group, an ethyl group, a n-propyl group and a n-butyl group.

2. A method for preparing a leveling agent, characterized in that: The preparation method is: Under nitrogen protection, 1-fluoro-tetrafluoroene and chlorinated compounds are added to deionized water, reacted at 80-90°C with constant stirring for 12-24 hours, then naturally cooled to room temperature, added with deionized water for dilution, and the pH is adjusted to neutral with dilute sulfuric acid to obtain a leveling agent.

3. The method for preparing a leveling agent according to claim 2, characterized in that: The chlorinated compound has the following structural formula (2): ； In the structural formula (2), R is an organic group having 1 to 6 carbon atoms, the organic group is an alkyl group, an alkoxy group, an alkyl group containing a hydroxyl group or an alkoxy group; the alkyl group is any one of a methyl group, an ethyl group, a n-propyl group and a n-butyl group.

4. The method for preparing a leveling agent according to claim 3, characterized in that: The molar ratio of 1-fluoro-tetrafluoroene to the chlorinated compound is 1:4, and the chlorinated compound is one of 2-chloroethanol, 2-chloroethoxyethanol, chloropropane, 1-chlorobutane, and 2-chloroethyl propyl ether.

5. An electroplating copper additive for copper interconnection of semiconductor chips, characterized in that: The electroplating copper additive comprises at least the leveling agent according to claim 1, and the dosage of the leveling agent is 1 to 10 mL / L.

6. The electroplating copper additive for copper interconnection of semiconductor chips according to claim 5, characterized in that: The electroplating copper additive also includes an accelerator and an inhibitor. The amount of the accelerator is 0.5 to 100 ppm, and the amount of the inhibitor is 50 to 1500 ppm.

7. The electroplating copper additive for copper interconnection of semiconductor chips according to claim 6, characterized in that: The accelerator is sodium polydisulfide propane sulfonate or sodium 3-mercapto-1-propane sulfonate; the inhibitor is one or more compounds having the following structural formulas (3) to (8): ； Wherein, in the structural formula (3), a is an integer from 10 to 500; ； Wherein, in the structural formula (4), a is an integer from 10 to 500; ； Wherein, in the structural formula (5), a, b, and c are each an integer between 10 and 100; ； Wherein, in the structural formula (6), a, b, and c are each an integer between 10 and 100; ； Wherein, in the structural formula (7), a and b are integers between 10 and 100 respectively; ； In the structural formula (8), n is an integer from 10 to 500.

8. A copper electroplating solution, characterized in that: The copper electroplating solution comprises the copper electroplating additive according to any one of claims 5 to 7.

9. A copper electroplating solution according to claim 8, characterized in that: The contents of the components of the copper electroplating solution are: 20-50 g / L copper ions, 80-200 g / L sulfuric acid, 10-100 ppm chloride ions, 0.5-100 ppm accelerator, 50-1500 ppm inhibitor, and 1-10 mL / L leveler.

10. A copper electroplating solution according to claim 9, characterized in that: The contents of the components of the copper electroplating solution are: 30-40 g / L copper ions, 100-130 g / L sulfuric acid, 50-60 ppm chloride ions, 0.5-10 ppm accelerator, 200-800 ppm inhibitor, and 3-7 mL / L leveler.

11. Use of the copper electroplating solution according to claim 9 in copper interconnection of semiconductor chips, characterized in that: The electroplating process of copper electroplating solution is: Step 1: Current density is 0.3~0.8A / dm 2 , the electroplating time is 3 to 20 seconds, and the electroplating temperature is 20 to 30°C; Step 2: Current density is 0.5~1.5A / dm 2 , the electroplating time is 30-50s, and the electroplating temperature is 20-30℃; Step 3: Current density is 1-10A / dm 2 The electroplating time is 30 to 50 seconds and the electroplating temperature is 20 to 30°C.

12. The use according to claim 11, characterized in that: The electroplating process of copper electroplating solution is: Step 1: Current density is 0.65A / dm 2 , the electroplating time is 5s, and the electroplating temperature is 25℃; Step 2: Current density is 1.0A / dm 2 , the electroplating time is 45s, and the electroplating temperature is 25℃; Step 3: Current density is 6.0A / dm 2 , the electroplating time is 38s, and the electroplating temperature is 25℃.

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