Method for controlling CMP (chemical mechanical polishing) dish-shaped pits and corrosion pits of ruthenium barrier layer copper wiring

Abstract

The invention discloses a method for controlling CMP (chemical mechanical polishing) dish-shaped pits, corrosion pits and interface corrosion of ruthenium barrier layer copper wiring, which is suitable for a manufacturing process of integrated circuits of 14 nanometers and below. According to the method, a specifically synthesized TTAK corrosion inhibitor is introduced into a polishing solution system, the oriented adsorption characteristic of the molecular structure of the TTAK corrosion inhibitor is utilized, the corrosion reaction of copper is selectively inhibited, meanwhile, the normal material removal efficiency of a ruthenium barrier layer and a TEOS dielectric layer is maintained, and cooperative regulation and control of the removal rate of the Cu / Ru / TEOS material are achieved. By means of the method, dished pits, corrosion pits and Fang type interface defects generated in the fine polishing and barrier layer polishing process can be effectively eliminated, and copper / ruthenium interface corrosion is improved. According to the method, the global planarization quality of the copper interconnection ruthenium barrier layer is remarkably improved, the interface bonding strength and the electrical reliability of an interconnection circuit are enhanced, and an effective solution is provided for performance optimization of an advanced process integrated circuit device.

Description

Technical Field

[0001] This invention relates to the field of advanced technology node integrated circuit manufacturing, particularly to the field of chemical mechanical polishing (CMP), and more specifically, to a method for controlling CMP disc pits and etching pits and interface corrosion of ruthenium barrier layer copper wiring. Background Technology

[0002] With the development of integrated circuits, current integrated circuits typically employ multi-layer wiring to achieve interconnect structures, thereby reducing line length and improving processing speed. In the dual damascene process for multi-layer wiring, the photolithography process requires the consistency of the preceding planarization process to maintain a length that is eight orders of magnitude greater; chemical mechanical polishing (CMP) is currently the only technology for achieving planarization of multi-layer wiring in integrated circuits. Currently, in advanced technology nodes below 14nm using Cu interconnects, Ru is considered a highly promising barrier layer material due to its low impedance, high melting point, superior barrier properties, and good adhesion and wetting characteristics.

[0003] Nevertheless, during the CMP process, the differences in the physicochemical properties of different materials lead to uneven removal rates, which in turn form dishing and erosion defects on the wafer surface, such as... Figure 1 As shown, a dish pit refers to the height difference between copper and the surrounding dielectric in a wide-line region, while an etch pit is the height difference between the dielectric and the surrounding large-area dielectric in a narrow-line region. The appearance of these dish pits and etch pits creates depressions on the wafer surface, which is detrimental to focusing during photolithography, thus posing challenges to subsequent processes. One of the goals of barrier layer CMP is to correct the dish pits formed during copper CMP and prevent the formation of deep etch pits by selectively controlling the removal rates of different materials. This requires the removal rate of the barrier layer material to be slightly higher than that of the wiring material. Only in this way can the dish pit defects generated after copper CMP be corrected and the remaining barrier layer outside the trench be removed to achieve wafer surface planarization.

[0004] Meanwhile, edge-over-erosion (EOE) involves corrosion at material interfaces, including the effects of chemical reactions, galvanic corrosion, and mechanical stress, especially at the junction of copper conductors and barrier layers (such as ruthenium). Inconsistent removal rates between dissimilar materials can create sharp corners at the metal interface, i.e., sharp grooves on the sidewalls of the copper conductors. Figure 2These trenches are called "teeth." This defect, caused by the combined effects of mechanical stress and galvanic corrosion, leads to edge cracks in the wiring layer, reducing circuit performance and reliability. In the multilayer interconnect structure of integrated circuits, the metal Cu and the barrier layer Ru are in direct contact and are exposed to polishing solutions containing various corrosive chemicals during CMP (Chemical Metallurgy). Therefore, galvanic corrosion at the Cu / Ru interface is unavoidable and harmful. The standard electrode potentials for Cu and Ru are 0.337V and 0.450V, respectively (relative to the standard hydrogen electrode). During the CMP process of Cu interconnecting the Ru barrier layer, when galvanic corrosion occurs at the Cu / Ru interface, Cu acts as the anode, accelerating corrosion and leading to corrosion and dissolution of Cu at the trench sidewalls, significantly impacting device reliability. Summary of the Invention

[0005] The purpose of this invention is to provide a novel polishing slurry containing the corrosion inhibitor TTAK. Utilizing TTAK's selective and strong corrosion inhibition effect (significantly suppressing the corrosion rate of copper while having negligible inhibitory effect on ruthenium and TEOS), the Cu surface is effectively protected, resisting aggressive ions in the corrosive environment. This reduces Cu corrosion and makes the Cu surface more uniform and smooth. It significantly improves the control of dish-shaped pits and etching pits during fine polishing (P2) and the correction of dish-shaped pits during the barrier layer CMP (P3) process. Furthermore, it effectively reduces the formation of "tooth" defects, improves the stability of copper conductors, and provides a new solution for improving the performance and yield of electronic devices.

[0006] The technical problem solved by this invention is achieved by the following technical solution.

[0007] This application provides a method for controlling CMP (Continuous Machining) pits, etching pits, and interface corrosion in ruthenium barrier layer copper wiring, including the following steps:

[0008] A polishing slurry containing the corrosion inhibitor TTAK was prepared; the polishing slurry was then added to a polishing machine to polish the Cu interconnect Ru barrier layer pattern of the integrated circuit multilayer wiring to obtain the finished product;

[0009] The polishing conditions are as follows: working pressure is 1-5 Psi, polishing head speed is 88-108 r / min, polishing disc speed is 100-110 r / min, and polishing fluid flow rate is 200-300 ml / min.

[0010] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0011] This invention uses a polishing slurry containing the corrosion inhibitor TTAK to polish the Cu interconnect Ru barrier layer patterned wafer of advanced technology node integrated circuits. This can control the CMP (Continuous Polishing) pits and etching pits in the copper wiring of the Ru barrier layer, as well as interface corrosion. The principle is as follows:

[0012] TTAK exhibits an adsorption effect on copper surfaces, encompassing both physical and chemical adsorption. The introduction of TTAK significantly inhibits copper corrosion, while its inhibitory effect on ruthenium and TEOS is negligible. This precise control of selectivity between heterogeneous materials is attributed to the strong selective corrosion inhibition of TTAK, effectively protecting the Cu surface and resisting aggressive ions in the corrosive environment. This reduces Cu corrosion and makes the Cu surface more uniform and smooth. This is because TTAK hinders the oxidation reaction, effectively suppressing the corrosion process on the Cu surface. Furthermore, during adsorption on the Cu surface, TTAK molecules effectively displace water molecules, enhancing their adsorption capacity on the metal surface and thus improving the adsorption efficiency of the corrosion inhibitor. Therefore, the addition of TTAK has a significant effect on controlling dish-shaped pits and etching pits during fine polishing and on correcting dish-shaped pits during the CMP process of the barrier layer. It can also effectively reduce the formation of "tooth" defects, improve the stability of copper wires, and provide a new perspective for improving the performance and yield of electronic devices. By utilizing the selective etching mechanism of the polishing slurry on the Cu interconnect Ru barrier layer pattern, the removal rate selectivity of heterogeneous materials is effectively improved, thereby enhancing the planarization of integrated circuits and improving the electrical performance of the circuits. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 Schematic diagrams of (a) dish-shaped pits and (b) corrosion pits caused by Cu CMP;

[0015] Figure 2 Teeth in images with different line widths / spacings under an atomic force microscope;

[0016] Figure 3 This is a schematic diagram of the molecular structure of the corrosion inhibitor TTAK.

[0017] Figure 4 Comparative figures show the roughness and surface condition of Example 1, Comparative Example 1, and Comparative Example 2 after polishing.

[0018] Figure 5 The diagram shows the effect of TTAK on the control of dish-shaped pit erosion in process P2 and the correction of dish-shaped pit erosion in process P3.

[0019] Figure 6 The image shows the effect of TTAK on improving corrosion at the Cu / Ru interface.

[0020] Figure 7 Schematic diagram of the principle of selective adsorption of corrosion inhibitor TTAK on copper surface Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0023] This invention provides a method for controlling CMP (Continuous Processing) pits, etching pits, and interface corrosion in ruthenium barrier layer copper wiring, comprising the following steps:

[0024] A polishing slurry containing the corrosion inhibitor TTAK was prepared; the polishing slurry was then added to a polishing machine to polish the Cu interconnect Ru barrier layer pattern of the integrated circuit multilayer wiring to obtain the finished product;

[0025] The polishing conditions are as follows: working pressure is 1-5 Psi, polishing head speed is 88-108 r / min, polishing disc speed is 100-110 r / min, and polishing fluid flow rate is 200-300 ml / min.

[0026] In the above embodiments, the selective etching mechanism of the polishing slurry on the Cu interconnect Ru barrier layer pattern effectively improves the removal rate selectivity of heterogeneous materials, thereby improving the planarization of the integrated circuit and enhancing the electrical performance of the circuit.

[0027] In some embodiments of the present invention, the TTAK preparation method is as follows: The potassium methylbenzotriazole (TTAK) salt is prepared by mixing methylbenzotriazole (TTA) and potassium hydroxide (KOH) in a molar ratio of 1:1, adding them to a 42wt% solution prepared in deionized water, and obtaining the corrosion inhibitor TTAK after the reaction is complete. Specifically, the deionized water is continuously stirred in the same direction with a glass rod, and then KOH powder is slowly poured into the deionized water. After the KOH powder is completely dissolved, methylbenzotriazole (TTA) powder is added to the solution. Simultaneously, the mixture is stirred evenly while mixing, and stirred for at least 3 minutes after pouring to ensure uniform mixing. After the reaction is complete, the corrosion inhibitor TTAK is obtained. Furthermore, due to the acid-base neutralization reaction between the two, TTA has excellent solubility, reducing the complexity of the preparation process.

[0028] In some embodiments of the present invention, the components of the polishing liquid, by mass percentage, are as follows: 3-10% silica sol, 0.02-2% complexing agent, 0.1-2% oxidant, 0.001-1% corrosion inhibitor TTAK, 0.03-2% bactericide, 0.0001-3% surfactant, and the balance being deionized water.

[0029] In some embodiments of the present invention, the pH value of the polishing solution is 7.0-11.5. This is because acidic environments easily generate toxic RuO4 gas, which poses a threat to the environment and human health; therefore, Ru CMP polishing solutions should preferably be alkaline.

[0030] In some embodiments of the present invention, the particle size of the aforementioned silica sol is 30 nm-200 nm. Nanoscale silica sol abrasives primarily provide mechanical action during the CMP process. Abrasives with suitable particle size play an important role in polishing rate, surface roughness, and surface defects.

[0031] In some embodiments of the present invention, the complexing agent is triammonium triacetate (NTA(NH4)3), glycine (C2H5NO2, Gly), ethylenediaminetetraacetic acid (C... 10 H 16 Organic carboxylic acids and their salts, such as citric acid (C6H8O7, CA), tartaric acid (C4H6O6, TA), and oxalic acid (H2C2O4, OA); and organophosphonic acids and their salts, such as ethylenediaminetetramethylphosphonic acid (C6H8O7, CA), tartaric acid (C4H6O6, TA), and oxalic acid (H2C2O4, OA); 20 N2O 12 One or more of the following: P4 (EDTMP), hydroxyethyl diphosphonic acid (C2H8O7P2, HEDPA), etc.

[0032] The surfactants mentioned above are one or more of cationic, anionic, and nonionic surfactants mixed in a certain proportion. Surfactants can improve the dispersion of silica sol, prevent gelation of the polishing slurry, reduce the possibility of large particle agglomeration, reduce surface roughness, avoid scratches and other defects caused by large particles, and improve the surface quality after polishing.

[0033] In some embodiments of the present invention, the bactericide is one or a mixture of methylisothiazolinone, Kathon, potassium sorbate, benzoic acid, 5-chloro-2-methyl-4-isothiazolin-3-one, and 1-2-benzisisothiazolin-3-one. The bactericide can sterilize the polishing solution and effectively extend its service life.

[0034] In some embodiments of the present invention, the preparation method of the above-mentioned polishing slurry includes the following steps: taking silica sol, diluting it with deionized water to obtain a silica sol solution; mixing a complexing agent, an oxidizing agent, a corrosion inhibitor TTAK, a bactericide, and a surfactant, diluting them with deionized water, adding the silica sol solution, and stirring evenly to obtain the polishing slurry. This preparation method is simple and can produce a polishing slurry with good stability, which is suitable for the needs of large-scale industrial production.

[0035] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0036] Example 1

[0037] A method for improving the rate of ruthenium CMP in multilayer wiring of integrated circuits includes the following steps:

[0038] Preparation of 10 kg polishing slurry: Take 5% by mass of silica sol with a particle size of 60 nm, dilute with deionized water to 5 kg to obtain a silica sol solution; mix 0.04% by mass of complexing agent NTA(NH4)3, 0.15% by mass of hydrogen peroxide, 0.04% by mass of corrosion inhibitor TTAK, 0.5% by mass of bactericide and 0.06% by mass of surfactant, dilute with deionized water to 5 kg, add the above silica sol solution, stir evenly to obtain polishing slurry, adjust the pH of polishing slurry to 9, and set aside for use;

[0039] The molecular formula of the aforementioned corrosion inhibitor TTAK is shown in the appendix. Figure 3 ;

[0040] The above-mentioned bactericide is a mixture of methylisothiazolinone, Kathon, potassium sorbate, and benzoic acid;

[0041] The surfactant mentioned above is a mixture of sodium dodecyl sulfate, dodecylbenzene sulfonic acid, and fatty acid methyl ester ethoxylate.

[0042] Polishing: Add polishing slurry to the Universal-300Plus polishing machine produced by Huahai Qingke, and polish under the following conditions: working pressure Z1: 4.76Psi, Z2: 2.01Psi, Z3: 1.82Psi, Z4: 1.92Psi, Z5: 1.63Psi; polishing head speed 98r / min; polishing disc speed 105r / min; polishing slurry flow rate 250ml / min.

[0043] Comparative Example 1

[0044] Compared with Example 1, the polishing fluid in Comparative Example 1 was a commercially available polishing fluid.

[0045] Comparative Example 2

[0046] Compared with Example 1, Comparative Example 2's polishing solution did not contain the corrosion inhibitor TTAK.

[0047] Experimental Example 1

[0048] The 300mm graphic sheet was polished using the methods of Example 1, Comparative Example 1, and Comparative Example 2. After cleaning, the surface roughness and surface condition were compared, and the results are shown in Table 1 and Table 2. Figures 4-6 As shown.

[0049] From Table 1 and Figure 4 It can be seen that the blank sample ( Figure 4 b) Comparison with CMP results using commercial liquid ( Figure 4 Compared to a), the peak-to-valley difference in surface roughness and linear roughness both increased significantly, exhibiting the largest root-mean-square surface roughness (Sq = 14.1 nm) and the largest peak-to-valley difference in linear roughness (PV = 69.9 nm). Simultaneously, the Cu surface underwent severe corrosion, resulting in an uneven and rough surface with deep, large pits. This is typically associated with the formation of porous and rough oxides and is related to the corrosive dissolution of Cu and its surface oxides by the complexing agent. When TTAK was added ( Figure 4 c) The surface roughness of Cu was effectively reduced, resulting in a more uniform and smooth surface with minimal surface roughness (Sq = 1.038 nm). The height profile of the linear roughness also showed the same phenomenon, with a peak-to-valley difference (PV) of 2.99 nm, the smallest among the three samples. This indicates that TTAK can effectively reduce the corrosion degree of the Cu surface.

[0050] Table 1

[0051] Group Root mean square roughness (Sq) Example 1 1.038 nm Comparative Example 1 10.7 nm Comparative Example 2 14.1 nm

[0052] TTAK's control over disc-shaped pits and etch pits in graphics is as follows: Figure 5 As shown in (a): During the P2 process, the depth of the dish-shaped pit after CMP varies depending on the line width / spacing of the graphic region. Lower left and right to Left and right, while in the narrow line area, the depth of the erosion pits is from Reduce to The left and right sides indicate that the introduction of TTAK can effectively control the formation of dish-shaped pits / erosion pits during the P2 process.

[0053] TTAK's effect on correcting disc-shaped pits and etched pits in graphics is as follows: Figure 5 As shown in (bg): During the P3 process, the introduction of TTAK can effectively correct the depth of the dish-shaped pits and erosion pits, and the correction effect is better as the concentration of TTAK increases.

[0054] TTAK's effectiveness in preventing corrosion at the Cu / Ru interface of patterned wafers is as follows: Figure 6 Figure 7 As shown: the depth of the "tooth" corner on the wafer surface is significantly reduced after adding the corrosion inhibitor TTAK. Reduce to This indicates a positive correlation between increased TTAK concentration and reduced interfacial corrosion. This comparison clearly demonstrates the effectiveness of TTAK in mitigating the "tooth" effect in interfacial corrosion.

[0055] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for controlling CMP (Continuous Processing) pits, etch pits, and interface corrosion in ruthenium barrier layer copper wiring, characterized in that, Includes the following steps: A polishing slurry containing potassium methylbenzotriazole (TTAK) was prepared; the polishing slurry was then used to polish the ruthenium barrier layer pattern of copper interconnects in integrated circuits below 14nm. The polishing conditions are as follows: working pressure is 1-5 Psi, polishing head speed is 88-108 r / min, polishing disc speed is 100-110 r / min, and polishing fluid flow rate is 200-300 ml / min.

2. The method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 1, characterized in that, The method for preparing the potassium salt of methylbenzotriazole (TTAK) is as follows: methylbenzotriazole (TTA) and potassium hydroxide (KOH) are mixed in a molar ratio of 1:1 and added to a 42wt% solution prepared in deionized water. After the reaction is completed, the corrosion inhibitor TTAK is obtained.

3. The method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 1, characterized in that, The polishing solution also includes silica sol, oxidant, bactericide, inhibitor, surfactant, pH adjuster, and deionized water.

4. The method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 3, characterized in that, The polishing solution comprises, by mass percentage: 3-10% silica sol, 0.02-2% TTAK corrosion inhibitor, 0.1-2% oxidant, 0.001-1% complexing agent, 0.03-2% bactericide, 0.0001-3% surfactant, and the balance being deionized water.

5. A method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 4, characterized in that, The pH value of the polishing solution is 7.0-11.

5.

6. A method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 4, characterized in that, The particle size of the silica sol is 30nm-200nm.

7. A method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 4, characterized in that, The oxidant is one or more of the following: peroxides, transition metal salts, nitric acid and nitrates, halogen oxyacids, etc.

8. A method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 4, characterized in that, The complexing agent is triammonium triaminotriacetate (NTA(NH4)3), glycine (C2H5NO2, HGly), and ethylenediaminetetraacetic acid (C... 10 H 16 Organic carboxylic acids and their salts, such as citric acid (C6H8O7, CA), tartaric acid (C4H6O6, TA), and oxalic acid (H2C2O4, OA); and organophosphonic acids and their salts, such as ethylenediaminetetramethylphosphonic acid (C6H8O7, CA), tartaric acid (C4H6O6, TA), and oxalic acid (H2C2O4, OA); 20 N2O 12 P4, EDTMP), hydroxyethyl diphosphonic acid (C6H 20 N2O 12 One or more mixtures of P4, EDTMP, etc.

9. A method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 4, characterized in that, The bactericide is one or a mixture of methylisothiazolinone, Kathon, potassium sorbate, benzoic acid, 5-chloro-2-methyl-4-isothiazolin-3-one, and 1-2-benzisothiazolin-3-one.

10. A method for controlling CMP disc-shaped pits, etching pits, and interface corrosion of ruthenium barrier layer copper wiring according to claim 4, characterized in that, The surfactant is one or more of cationic surfactants, anionic surfactants, and nonionic surfactants.

11. A method for controlling CMP disc-shaped pits and etching pits and interface corrosion of ruthenium barrier layer copper wiring according to claim 4, characterized in that, The pH adjuster is one or more commonly used inorganic acids and bases such as KOH and boric acid.

12. The method for improving the ruthenium CMP rate of multilayer wiring in integrated circuits according to claim 1, characterized in that, The preparation method of the polishing slurry includes the following steps: take silica sol, dilute it with deionized water to obtain silica sol solution; mix oxidant, complexing agent, inhibitor TTAK, bactericide and surfactant and dilute with deionized water, then add silica sol solution, adjust the pH value to the required value with pH adjuster, and stir evenly to obtain polishing slurry.

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