Electrolyte and method for preparing nanotwinned copper

Abstract

The application provides an electroplating solution and an electroplating method for preparing nanotwinned copper, wherein the electroplating solution comprises copper sulfate, sulfuric acid, chloride ions, a polyether-type inhibitor, a sulfur-containing accelerator, a main twinning inducer and a stress biasing component, the stress biasing component comprises metal ions or metal complexes, the metal ions are not copper ions, and the metal complexes are not copper complexes. The electroplating solution of the application can regulate the dynamic adsorption layer on the cathode surface, the copper nucleation density, the local internal stress and the (111) plane preferred growth by adding the main twinning inducer and the stress biasing component and the like, so that the nanotwinned copper with a high volume fraction can be prepared under the direct current electroplating condition.

Description

Technical Field

[0001] This invention belongs to the field of copper electroplating technology, and relates to an electroplating solution and electroplating method for preparing nanotwinned copper. Background Technology

[0002] Nanotwinned copper (nt-Cu) is a special copper material with a unique microstructure containing high-density nanoscale twin lamellae (typically 5-100 nm thick, preferably 5-30 nm) within copper grains. Its crystal structure remains face-centered cubic (FCC-Cu), with numerous coherent twin boundaries within the grains, often exhibiting a strong Cu(111) preferred orientation. Compared to ordinary electroplated copper, nanotwinned copper significantly improves strength, electromigration resistance, and thermal stability while maintaining high conductivity, making it a highly promising material for advanced packaging and next-generation copper interconnect structures.

[0003] Currently, nanotwinned copper is mainly prepared through the following technical routes:

[0004] (1) Pulse electroplating method

[0005] Pulse electroplating promotes nanotwin formation by periodically altering the cathode current or potential, creating alternating high nucleation, high growth, and stress release processes during deposition. This method can easily achieve high-density columnar nanotwin structures by controlling the interlayer spacing of the twin wafers through pulse frequency, duty cycle, and peak current density. However, it has significant drawbacks: it requires a dedicated pulse power supply, the process is complex, the tooff stage reduces the average deposition rate, it has limited compatibility with existing large-scale DC electroplating lines, and it poses challenges to the uniformity and throughput of damask filling processes.

[0006] (2) DC electroplating + traditional additive method

[0007] DC electroplating boasts advantages such as mature equipment, high capacity, and strong compatibility. Existing research indicates that by using additives such as gelatin, sulfur-containing compounds, polyamino acids, and heterocyclic organic compounds, twinning of copper plating layers can be induced under DC conditions. This method utilizes existing DC power supplies, exhibits good compatibility with wafer electroplating systems, is suitable for industrial scale-up, and has low cost. However, it also has the following drawbacks: unstable twinning ratios, wide thickness distribution of twinned wafer layers, and the impact of additive aging and decomposition on long-term stability. Furthermore, it is susceptible to compatibility issues with SPS / MPS, PEG, and Cl... - The synergistic relationship of mature damascus additive systems is unclear, making it difficult to obtain high volume fraction nanotwins while ensuring no void filling.

[0008] (3) High-frequency pulse or special bath system method

[0009] Existing technologies include methods for preparing nanotwinned copper using high-frequency pulses, methanesulfonate systems, specific temperature control, segmented deposition, and multilayer structures. While these technologies can achieve good microstructures, they often suffer from problems such as insufficient compatibility with existing copper sulfate-sulfuric acid wafer electroplating systems, narrow process windows, high equipment modification costs, and difficulty in large-scale mass production for advanced packaging.

[0010] Therefore, existing preparation processes each have limitations: pulse electroplating is complex, has poor production line compatibility, and restricts mass production efficiency; conventional DC additive systems lack twin structure stability and are difficult to adapt to mature damascus plating solutions; special baths and high-frequency deposition technologies face industrialization challenges such as high modification costs and narrow process windows. Furthermore, the stability of additives in the electroplating solution is insufficient; natural polymers such as gelatin are prone to hydrolysis and aging, and exhibit significant batch-to-batch variations, while novel twinning promoters may disrupt PEG / SPS / Cl... - Filling balance and twinning layer control are difficult, and relying solely on the concentration of a single additive is insufficient. Furthermore, deep trench or micropore filling requires strong acceleration / inhibition synergy, while high twinning demands strong texture and stress regulation. Existing electroplating solutions cannot simultaneously achieve both filling and twinning. Currently, there is an urgent need for a fabrication technology that balances filling performance with a high proportion of nanotwinned structures within a mature acidic DC electroplating system.

[0011] Based on this, the present invention proposes a composite additive synergistic regulation strategy to precisely regulate the nucleation behavior, crystal orientation and internal stress state of copper deposition on the basis of the existing copper sulfate electroplating system, and stably obtain a high volume fraction, (111) crystal plane preferred orientation nanotwin copper plating layer, thereby achieving a synergistic improvement of low resistivity and high structural reliability. Summary of the Invention

[0012] The purpose of this invention is to provide an electroplating solution and an electroplating method for preparing nanotwinned copper. The electroplating solution for preparing nanotwinned copper is prepared by adding a main twinning inducer and a stress biasing component, etc., so that the main twinning inducer, stress biasing component, chloride ions, polyether inhibitors and sulfur-containing accelerators work together to adjust the dynamic adsorption layer, copper nucleation density, local internal stress and (111) plane preferential growth on the cathode surface, thereby preparing high volume fraction nanotwinned copper under DC electroplating conditions.

[0013] To achieve this objective, the present invention adopts the following technical solution:

[0014] In a first aspect, the present invention provides an electroplating solution for preparing nanotwinned copper, wherein the electroplating solution for preparing nanotwinned copper includes copper sulfate, sulfuric acid, chloride ions, polyether inhibitors, sulfur-containing accelerators, main twinning inducers, and stress biasing components.

[0015] The main twinning inducer contains an X group (X is a copper surface adsorption group), an L linking chain, and a Y group (a water-soluble or weakly coordinating tail group). The X group is selected from any one of mercapto, thioether, disulfide, thiazolyl, benzothiazolyl, imidazolyl, pyridinyl, or triazolyl. The L linking chain is selected from any one of an alkyl chain, alkenyl chain, ether-containing chain, amide-containing chain, disulfide-containing chain, or aromatic ring-containing chain. The Y group is selected from any one of a sulfonic acid group, carboxylic acid group, hydroxyl group, quaternary ammonium salt group, or polyethylene glycol chain.

[0016] The stress bias component includes metal ions or metal complexes, wherein the metal ions are not copper ions and the metal complexes are not copper complexes.

[0017] The electroplating solution of this invention, with its specific composition, can achieve the preparation of high volume fraction nanotwinned copper under DC electroplating conditions by adjusting the dynamic adsorption layer, copper nucleation density, local internal stress, and (111) orientation preferential growth on the cathode surface. Specifically, this invention utilizes a main twinning inducing agent and a polyether inhibitor / sulfur-containing accelerator / Cl... - The synergistic effect makes Cu(111) orientation the dominant growth direction; on the other hand, by adjusting the stress bias component and the interface adsorption layer, a local stress state conducive to twin nucleation is formed. Therefore, through the synergistic effect of the above two aspects, the present invention enables the stable formation of nanotwinned copper under DC conditions.

[0018] The dynamic adsorption layer reconstruction mechanism of this invention includes the following six stages:

[0019] Stage 1: Formation of the basic inhibition layer: polyether inhibitors and Cl - An inhibitory layer is formed on the copper surface to reduce the reduction rate of copper ions and prevent excessively rapid deposition in the raised areas.

[0020] Stage 2: Local Acceleration Site Formation: Sulfur-containing Accelerators and Cu + Intermediate synergy weakens the inhibition layer formed in stage 1, creating accelerated deposition sites.

[0021] Stage 3: Selective adsorption of twinning inducers: The main twinning inducers are enriched at steps, crystal nucleus edges, high-energy crystal planes or specific Cu surface sites, regulating surface diffusion and crystal plane competition.

[0022] Stage 4: Stress bias and stacking fault formation: Stress bias components regulate local deposition stress and atomic stacking behavior, increasing the probability of stacking fault and twin embryo formation.

[0023] Stage 5: (111) Columnar crystal competitive growth: Under the above synergistic effect, the competitive growth advantage of Cu (111) oriented grains is enhanced, and non-(111) grains are suppressed, forming columnar (111) oriented grains.

[0024] Stage 6: Stable growth of nanotwin wafer layers: Under conditions of high nucleation density, restricted surface diffusion, and moderate internal stress, periodic or quasi-periodic nanotwin wafer layers are formed inside the grains.

[0025] Specifically, the functions of each component in the electroplating solution of the present invention are as follows: the polyether inhibitor and Cl... - The synergistic adsorption of the sulfur-containing accelerator onto the copper surface forms an inhibitory film, suppressing excessively rapid deposition in protruding areas, ensuring uniform damascus filling, and regulating lateral grain growth. + The intermediate synergistically disrupts or weakens the inhibition layer, enhancing copper deposition in recessed areas or at the bottom of trenches, improving filling capacity, and regulating grain nucleation rate. The mechanism of action of the master twinning inducer differs from traditional hydrolysis mechanisms; it can reversibly adsorb and react with Cu. + Coordination, crystal plane selective adsorption, restricted surface diffusion, induced stacking fault formation, and enhanced (111) preferred orientation. The stress bias component, acting as an interface modulation factor, can regulate the Cu on the cathode surface. + Intermediate concentration, altering the surface diffusion length of copper atoms, increasing the probability of stacking fault formation, providing local stress bias, increasing the probability of twin nucleation, suppressing excessively rapid growth of non-(111) crystal planes, and increasing the volume fraction of nanotwin structures. The chloride ions can form an inhibitory layer with polyether inhibitors and with Cu... + It forms surface intermediates, participates in the acceleration mechanism of sulfur-containing accelerators, regulates crystal face adsorption, and affects the interfacial adsorption of twinning inducers.

[0026] Preferably, the metal ion is selected from Ni. 2+ Co 2+ Zn 2+ Ag + Sn 2+ Bi 3+ In 3+ Mn 2+ Or any one or a combination of at least two of the iron ions, preferably Ni 2+ Ni 2+ With Co 2+ Combination or Ni 2+ With Zn 2+ The combination of .

[0027] The stress biasing component described in this invention is preferably a metal ion. Compared to metal complexes, metal ions can directly participate in cathode interface regulation in a free or weakly hydrated ionic state, reducing the impact of complexing ligands on Cu. 2+ Cu + Furthermore, it mitigates the competitive effects of the adsorption balance between polyether inhibitors, chloride ions, and sulfur-containing accelerators, reducing the interference of organic ligand accumulation on the stability of the electroplating solution and facilitating industrial control through conventional ion concentration detection methods.

[0028] Preferably, the iron ions include Fe. 2+ or Fe 3+ .

[0029] Preferably, the central metal ion in the metal complex is selected from Ni. 2+ Co 2+ Zn 2+ Ag + Sn 2+ Bi 3+ In 3 + Mn 2+ Or any one or a combination of at least two of the iron ions, wherein the ligand is selected from any one or a combination of at least two of the citrate, gluconate, lactate, glycinate, ethylenediamine or ethylenediaminetetraacetic acid ions.

[0030] Preferably, the metal complex comprises any one or a combination of at least two of nickel citrate, nickel gluconate, nickel lactate, nickel glycinate, nickel ethylenediamine, cobalt citrate, cobalt gluconate, zinc citrate, or zinc gluconate.

[0031] Preferably, the concentration of the stress bias component in the electroplating solution is 0.001ppm-100ppm, for example, it can be 0.001ppm, 0.01ppm, 0.1ppm, 1ppm, 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm or 100ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.05ppm-20ppm.

[0032] The electroplating solution of the present invention adds a trace amount of stress bias component. If the amount of stress bias component added is too much, it will increase the risk of co-deposition of non-copper metal impurities, cause excessive local deposition stress and destroy the preferential growth of Cu(111). At the same time, it may disturb the dynamic adsorption balance of polyether inhibitors / sulfur-containing accelerators / chloride ions, resulting in rough coating, nodules, pores or increased resistivity. However, if too little is added, it will affect its function.

[0033] Preferably, the stress bias component includes Ni. 2+ Co 2+ Zn 2+ or Ag + Any one or at least two of them, wherein Ni 2+The concentration in the electroplating solution is 0.01ppm-100ppm (preferably 0.1ppm-20ppm), for example, it can be 0.01ppm, 0.1ppm, 1ppm, 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm, or 100ppm. 2+ The concentration in the electroplating solution is 0.01ppm-50ppm (preferably 0.05ppm-10ppm), for example, it can be 0.01ppm, 0.1ppm, 1ppm, 10ppm, 20ppm, 30ppm, 40ppm or 50ppm, Zn 2+ The concentration in the electroplating solution is 0.01ppm-50ppm (preferably 0.05ppm-10ppm), for example, it can be 0.01ppm, 0.1ppm, 1ppm, 10ppm, 20ppm, 30ppm, 40ppm or 50ppm, Ag + The concentration in the electroplating solution is 0.001ppm-10ppm (preferably 0.005ppm-1ppm), for example, it can be 0.001ppm, 0.01ppm, 0.1ppm, 1ppm, 3ppm, 5ppm, 8ppm or 10ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the concentration of the main twinning inducer in the electroplating solution is 0.1ppm-100ppm, for example, it can be 0.1ppm, 1ppm, 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm or 100ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1ppm-30ppm.

[0035] The concentration of the master twinning inducer described in this invention affects the selective adsorption at the cathode interface, the preferred orientation of Cu(111), the surface diffusion of copper atoms, and the formation of stacking faults / twin embryos. If the concentration of the master twinning inducer is too high, it will cause excessive adsorption at the interface or excessive local inhibition, which will disrupt the acceleration / inhibition balance between polyether inhibitors, sulfur-containing accelerators, and chloride ions, reduce deposition uniformity, and may cause organic inclusions, surface roughness, or increased resistivity. However, if the concentration of the master twinning inducer is too low, it will affect its function.

[0036] Preferably, the X group is selected from any one of mercapto, disulfide bond, thiazolyl, benzothiazolyl or imidazole.

[0037] Preferably, the L-linking chain is selected from any one of C3-C8 alkyl chains, C3-C8 sulfide chains, or hydrophilic chains containing 1-3 EO units (ethylene oxide units).

[0038] Preferably, the Y group is selected from any one of sulfonates, carboxylates, hydroxyl groups, or polyethylene glycol chains.

[0039] Preferably, the master twinning inducer comprises any one or a combination of at least two of the following: sodium 2-mercaptobenzothiazole-6-sulfonate, sodium 2-mercaptobenzimidazole-5-sulfonate, 1-(3-sulfopropyl)imidazolium inner salt, 1-(3-sulfopropyl)pyridinium inner salt, or sodium 3-mercapto-1,2,4-triazole.

[0040] Preferably, the polyether inhibitor includes any one or a combination of at least two of PEG (polyethylene glycol), PPG (polypropylene glycol), EO-PO block copolymer (ethylene oxide-propylene oxide block copolymer), or EO-PO end-group modifiers.

[0041] Preferably, the molecular weight of the PEG is 1000-10000, for example, it can be 1000, 3000, 5000, 7000, 9000 or 10000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 3000-8000.

[0042] Preferably, the molecular weight of the EO-PO block copolymer is 1,000-20,000, for example, it can be 1,000, 3,000, 5,000, 7,000, 9,000, 10,000, 15,000 or 20,000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the concentration of polyether inhibitor in the electroplating solution is 20ppm-500ppm, for example, it can be 20ppm, 100ppm, 150ppm, 200ppm, 300ppm, 400ppm or 500ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 50ppm-250ppm.

[0044] Preferably, the sulfur-containing accelerator includes SPS (bis-(3-sulfopropyl)-disulfide) and / or MPS (3-mercapto-1-propanesulfonic acid).

[0045] Preferably, the concentration of the sulfur-containing accelerator in the electroplating solution is 0.5ppm-50ppm, for example, it can be 0.5ppm, 1ppm, 5ppm, 10ppm, 20ppm, 30ppm, 40ppm or 50ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. Preferably, it is 2ppm-20ppm, more preferably 5ppm-15ppm.

[0046] Preferably, the copper sulfate is CuSO4·5H2O, and the concentration of CuSO4·5H2O in the electroplating solution is 25g / L-120g / L, for example, it can be 25g / L, 30g / L, 40g / L, 50g / L, 60g / L, 70g / L, 80g / L, 90g / L, 100g / L or 120g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 50g / L-90g / L.

[0047] Preferably, the concentration of sulfuric acid in the electroplating solution is 30g / L-250g / L, for example, it can be 30g / L, 50g / L, 100g / L, 150g / L, 200g / L or 250g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 120g / L-220g / L.

[0048] Preferably, the concentration of chloride ions in the electroplating solution is 20ppm-100ppm, for example, it can be 20ppm, 40ppm, 60ppm, 80ppm or 100ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 30ppm-70ppm.

[0049] Preferably, the electroplating solution further includes a leveling agent and deionized water.

[0050] The leveling agent described in this invention serves to inhibit deposition in raised areas, improve surface roughness, enhance film thickness uniformity, and assist in void-free filling of damascus steel.

[0051] Preferably, the concentration of the leveling agent in the electroplating solution is 0.1ppm-20ppm, for example, it can be 0.1ppm, 1ppm, 5ppm, 10ppm, 15ppm or 20ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5ppm-5ppm.

[0052] The concentration of the leveling agent in the electroplating solution described in this invention should be strictly controlled to avoid excessive inhibition and damage to the growth of nanotwins.

[0053] Preferably, the leveling agent comprises any one or a combination of at least two of nitrogen-containing heterocyclic polymers, pyridinium compounds, quaternary ammonium salts, Janus Green B compounds, or polyvinylpyridine.

[0054] In summary, the components and concentrations of the electroplating solution described in this invention are as shown in Table 1 below.

[0055] Table 1

[0056]

[0057] This invention optimizes different electroplating solution formulations for different systems:

[0058] (1) For Damascus compatible type (suitable for trench, through hole, micro blind hole and RDL filling)

[0059] CuSO4·5H2O: 60-80 g / L; H2SO4: 150-200 g / L; Cl - : 40-60 ppm; Polyether inhibitor (PEG-6000): 80-200 ppm; Sulfur-containing accelerator (SPS): 5-15 ppm; Principal twinning inducer: 2-20 ppm; Stress bias component (Ni 2+ Ni 2+ With Co 2+ (Combination of ingredients): 0.1-10 ppm; leveling agent: 0.5-3 ppm.

[0060] (2) High volume fraction nanotwin thin film type (suitable for blanket wafer, copper film, Cu-Cu bonding layer)

[0061] CuSO4·5H2O: 70-100 g / L; H2SO4: 120-180 g / L; Cl - 30-60 ppm; Polyether inhibitors (PEG-4000 / 8000): 50-150 ppm; Sulfur-containing accelerators: 5-20 ppm; Principal twinning inducers: 5-30 ppm; Ni 2+ 0.5-20 ppm; optional Co 2+ : 0.05-5 ppm.

[0062] Preferred Formulation 3: Low-Impurity Semiconductor Interconnect Type (Suitable for wafer interconnects that are extremely sensitive to metal contamination)

[0063] CuSO4·5H2O: 40-80 g / L; H2SO4: 150-220 g / L; Cl -: 40-70 ppm; Polyether inhibitor (PEG): 50-200 ppm; Sulfur accelerator: 2-15 ppm; Main twinning inducer: 2-20 ppm; Stress biasing agent: ≤1 ppm; Leveling agent: ≤2 ppm.

[0064] In a second aspect, the present invention provides an electroplating method, wherein the electroplating solution used in the electroplating method includes the electroplating solution for preparing nanotwinned copper as described in the first aspect.

[0065] Preferably, the current mode of the electroplating method is direct current electroplating.

[0066] Preferably, the current density used in the electroplating method is 1ASD-30ASD, for example, it can be 1ASD, 5ASD, 10ASD, 15ASD, 20ASD, 25ASD or 30ASD, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 2ASD-15ASD.

[0067] Preferably, the electroplating method uses a temperature of 15-45℃, such as 15℃, 20℃, 30℃, 40℃ or 45℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 20-35℃ being the preferred temperature.

[0068] Preferably, the electroplating method employs any one of the following stirring methods: circulating filtration, jetting, or wafer rotation.

[0069] Preferably, the electroplating method uses a pH < 1 (preferably a strong acid system), for example, 0.9, 0.7, 0.5 or 0.3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] The key control points of the electroplating method described in this invention are as follows:

[0071] (1) Clean and activate the seed layer before electroplating.

[0072] (2) Control Cl - Concentration fluctuations are within ±5 ppm.

[0073] (3) Control the ratio of sulfur-containing accelerator to main twinning inducer.

[0074] (4) Control the total carbon content of organic additives.

[0075] (5) Use CVS or electrochemical methods to monitor the effective concentrations of accelerators and inhibitors.

[0076] (6) Tissue stability was verified by sheet resistance, XRD and periodic TEM sampling.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] In the electroplating solution of the present invention, the main twinning inducer enhances the preferred orientation of Cu(111) through selective adsorption on the crystal plane, and the stress bias component adjusts the local stress through trace metal ions, thereby increasing the probability of twin nucleation. The two work synergistically to stably form a high volume fraction nano-twin copper plating layer under conditions of high nucleation density and limited surface diffusion. Therefore, the crystal structure of the twin copper obtained by using the electroplating solution of the present invention is FCC-Cu, with a nano-twin region area fraction ≥50% (preferably ≥70%, more preferably ≥85%), an average twin wafer thickness of 5-80nm (preferably 5-40nm, more preferably 5-25nm), a Cu(111) texture ratio ≥85% (preferably ≥95%, more preferably ≥98%), and a resistivity ≤2.2μΩ·cm (preferably ≤2.0μΩ·cm, more preferably ≤1.9μΩ·cm). Detailed Implementation

[0079] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0080] Example 1

[0081] This embodiment provides an electroplating solution for preparing nanotwinned copper, the composition of which is as follows:

[0082] CuSO4·5H2O: 80g / L; H2SO4: 170g / L; Cl - 50ppm; Polyether inhibitor (PEG-4000): 100ppm; Sulfur-containing accelerator (SPS): 10ppm; Main twinning inducer (specifically sodium 2-mercaptobenzothiazole-6-sulfonate): 20ppm; Stress bias component (Ni 2+ ): 10ppm; leveling agent (polyvinylpyridine): 3ppm; deionized water: balance.

[0083] Example 2

[0084] This embodiment provides an electroplating solution for preparing nanotwinned copper, the composition of which is as follows:

[0085] CuSO4·5H2O: 50g / L; H2SO4: 120g / L; Cl -70 ppm; Polyether inhibitor (PEG-8000): 50 ppm; Sulfur-containing accelerator (SPS): 20 ppm; Main twinning inducer (specifically sodium 2-mercaptobenzimidazole-5-sulfonate): 1 ppm; Stress bias component: 0.05 ppm Ni 2+ and 0.05 ppm Co 2+ Leveling agent (polyvinylpyridine): 5 ppm, deionized water: balance.

[0086] Example 3

[0087] This embodiment provides an electroplating solution for preparing nanotwinned copper, the composition of which is as follows:

[0088] CuSO4·5H2O: 90g / L; H2SO4: 220g / L; Cl - 30ppm; Polyether inhibitor (PEG-4000): 250ppm; Sulfur-containing accelerator (MPS): 2ppm; Master twinning inducer (specifically 1-(3-sulfopropyl)imidazolium inner salt): 30ppm; Stress bias component (Ni 2+ ): 20ppm; leveling agent (polyvinylpyridine): 0.5ppm; deionized water: balance.

[0089] Example 4

[0090] This embodiment provides an electroplating solution for preparing nanotwinned copper, the composition of which is as follows:

[0091] CuSO4·5H2O: 120g / L; H2SO4: 30g / L; Cl - 20ppm; Polyether inhibitor (PEG-4000): 20ppm; Sulfur-containing accelerator (SPS): 50ppm; Main twinning inducer (specifically sodium 2-mercaptobenzothiazole-6-sulfonate): 20ppm; Stress bias component (Ni 2+ ): 10ppm; Deionized water: balance.

[0092] Example 5

[0093] This embodiment provides an electroplating solution for preparing nanotwinned copper, the composition of which is as follows:

[0094] CuSO4·5H2O: 25g / L; H2SO4: 250g / L; Cl - : 100ppm; Polyether inhibitor (PEG-4000): 500ppm; Sulfur-containing accelerator (SPS): 0.5ppm; Main twinning inducer (specifically sodium 2-mercaptobenzothiazole-6-sulfonate): 10ppm; Stress bias component (Ni 2+): 5ppm; Deionized water: balance.

[0095] Example 6

[0096] This embodiment provides an electroplating solution for preparing nanotwinned copper. Except for the concentration of the main twinning inducer being 0.1 ppm, the electroplating solution is the same as that in Example 1.

[0097] Example 7

[0098] This embodiment provides an electroplating solution for preparing nanotwinned copper. Except for the concentration of the main twinning inducer being 100 ppm, the electroplating solution is the same as that in Example 1.

[0099] Example 8

[0100] This embodiment provides an electroplating solution for preparing nanotwinned copper. Except for the concentration of the stress bias component being 0.001 ppm, the electroplating solution is the same as that in Example 1.

[0101] Example 9

[0102] This embodiment provides an electroplating solution for preparing nanotwinned copper. Except for the concentration of the stress bias component being 100 ppm, the electroplating solution is the same as that in Example 1.

[0103] Example 10

[0104] This embodiment provides an electroplating solution for preparing nanotwinned copper, wherein the electroplating solution contains, except for the stress bias component, Zn. 2+ Except for the above, everything else is the same as in Example 1.

[0105] Example 11

[0106] This embodiment provides an electroplating solution for preparing nanotwinned copper, wherein the electroplating solution contains, except for the stress bias component, Mn. 2+ Except for the above, everything else is the same as in Example 1.

[0107] Comparative Example 1

[0108] This comparative example provides an electroplating solution for preparing nanotwinned copper. The electroplating solution is the same as in Example 1, except that the main twinning inducer is replaced with gelatin at the same concentration.

[0109] Comparative Example 2

[0110] This comparative example provides an electroplating solution for preparing nanotwinned copper, which is identical to that in Example 1 except that it does not contain stress bias components.

[0111] Electroplating was performed using the electroplating solutions described in the above embodiments and comparative examples. The specific operation process of the electroplating is as follows:

[0112] (1) Weigh copper sulfate, sulfuric acid, chloride ion source, polyether inhibitor, sulfur-containing accelerator, main twin inducer, stress bias component and optional leveling agent according to the formulation of each embodiment or comparative example, add deionized water to prepare electroplating solution, stir until completely dissolved, filter with 0.22μm filter membrane, and stabilize the temperature of electroplating solution to 25℃.

[0113] (2) A silicon wafer or copper substrate with a copper seed layer on the surface is used as the cathode and a phosphorus copper anode is used as the anode. Before electroplating, the cathode is cleaned with deionized water, activated with 5wt% sulfuric acid aqueous solution for 30s-60s and rinsed with deionized water in sequence to remove the surface oxide layer.

[0114] (3) Place the cathode and anode in the electroplating tank, control the pH of the electroplating solution to <1, use circulating filtration or jet stirring, and control the Cl... - Concentration fluctuations are within ±5 ppm.

[0115] (4) Deposition was carried out using DC electroplating mode, with a current density of 10 ASD, an electroplating temperature of 25℃, and an electroplating time of 5 min-30 min controlled according to the target film thickness.

[0116] (5) After electroplating, the cathode is removed and rinsed with deionized water and dried with nitrogen to obtain a nano-twinned copper coating.

[0117] (6) The resistivity, Cu(111) texture ratio, nanotwin area fraction and average twin layer thickness of the coating were tested by sheet resistance test, XRD and TEM / TKD.

[0118] The area fraction of nanotwinned regions, average twin layer thickness, Cu(111) texture ratio, and resistivity of the electroplated twinned copper are shown in Table 2.

[0119] Table 2

[0120]

[0121] As can be seen from Table 2 above:

[0122] As shown in Table 2, Examples 1-3, using a preferred range of basic acid copper system, main twinning inducer, and stress biasing component, resulted in copper coatings with a nanotwin region area fraction exceeding 85%, an average twin layer thickness of 18nm-22nm, a Cu(111) texture ratio exceeding 96%, and a resistivity below 1.90μΩ·cm. This indicates that the main twinning inducer and stress biasing component described in this invention can synergistically promote the formation of high-volume-fraction nanotwinned copper under DC electroplating conditions. Compared to Example 1, Examples 4-5 used a non-preferred basic formulation, resulting in a decrease in the nanotwin region area fraction, Cu(111) texture ratio, and resistivity. This indicates that the concentrations of the basic acid copper system, polyether inhibitors, sulfur-containing accelerators, and chloride ions need to be matched with the main twinning inducer and stress biasing component. As shown in Examples 1 and 6-7, when the concentration of the main twinning inducer is too low, interfacial selective adsorption and orientation induction are insufficient; when the concentration is too high, excessive interfacial adsorption or excessive local inhibition occurs, both of which are detrimental to obtaining the preferred nanotwinned structure. As shown in Examples 1 and 8-9, when the concentration of the stress bias component is too low, it is difficult to sufficiently increase the probability of twin nucleation; when the concentration is too high, it increases the risk of impurity co-deposition and stress imbalance, leading to a decrease in coating performance. As shown in Examples 1 and 10-11, using Zn... 2+ or Mn 2+ Preferred alternative Ni 2+ It can still provide stress offset, but its overall performance is lower than that of Ni. 2+ System. As can be seen from Example 1 and Comparative Examples 1-2, after replacing the main twinning inducer with gelatin or omitting the stress bias component, the area fraction of the nanotwinned region and the proportion of Cu(111) texture are significantly reduced, and the resistivity is increased. This indicates that the synergistic effect of the main twinning inducer and the stress bias component is the key to obtaining high volume fraction nanotwinned copper in this invention.

[0123] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An electroplating solution for preparing nanotwinned copper, characterized in that, The electroplating solution used to prepare nanotwinned copper includes copper sulfate, sulfuric acid, chloride ions, polyether inhibitors, sulfur-containing accelerators, main twinning inducers, and stress biasing components. The master twinning inducer contains an X group, an L linker chain, and a Y group, wherein the X group is selected from any one of mercapto, thioether, disulfide, thiazolyl, benzothiazolyl, imidazolyl, pyridinyl, or triazolyl; the L linker chain is selected from any one of alkyl, alkenyl, ether-containing, amide-containing, disulfide-containing, or aromatic ring-containing chains; and the Y group is selected from any one of sulfonic acid, carboxylic acid, hydroxyl, quaternary ammonium salt, or polyethylene glycol chains. The stress bias component includes metal ions or metal complexes, wherein the metal ions are not copper ions and the metal complexes are not copper complexes.

2. The electroplating solution for preparing nanotwinned copper according to claim 1, characterized in that, The metal ions are selected from Ni. 2+ Co 2+ Zn 2+ Ag + Sn 2+ Bi 3+ In 3+ Mn 2+ Or any one or a combination of at least two of the iron ions, preferably Ni 2+ Ni 2+ With Co 2+ Combination or Ni 2+ With Zn 2+ The combination; Preferably, the iron ions include Fe. 2+ or Fe 3+ ; Preferably, the metal complex comprises a water-soluble metal complex of an organic acid anion, amino acid, amine, or hydroxycarboxylic acid ligand; Preferably, the central metal ion in the metal complex is selected from Ni. 2+ Co 2+ Zn 2+ Ag + Sn 2+ Bi 3+ In 3+ Mn 2 + Or any one or at least two of the iron ions, the ligands being selected from any one or at least two of the citrate, gluconate, lactate, glycinate, ethylenediamine or ethylenediaminetetraacetic acid ions; Preferably, the metal complex comprises any one or a combination of at least two of nickel citrate, nickel gluconate, nickel lactate, nickel glycinate, nickel ethylenediamine complex, cobalt citrate, cobalt gluconate, zinc citrate, or zinc gluconate. Preferably, the concentration of the stress bias component in the electroplating solution is 0.001ppm-100ppm, and more preferably 0.05ppm-20ppm.

3. The electroplating solution for preparing nanotwinned copper according to claim 1, characterized in that, The stress bias component includes Ni. 2+ Co 2+ Zn 2+ or Ag + Any one or at least two of them, wherein Ni 2+ The concentration of Co in the electroplating solution is 0.01ppm-100ppm. 2+ The concentration of Zn in the electroplating solution is 0.01ppm-50ppm. 2+ The concentration of Ag in the electroplating solution is 0.01ppm-50ppm. + The concentration in the electroplating solution is 0.001ppm-10ppm; Preferably, the stress bias component includes Ni. 2+ Co 2+ Zn 2+ or Ag + Any one or at least two of them, wherein Ni 2+ The concentration of Co in the electroplating solution is 0.1ppm-20ppm. 2+ The concentration of Zn in the electroplating solution is 0.05ppm-10ppm. 2 + The concentration of Ag in the electroplating solution is 0.05ppm-10ppm. + The concentration in the electroplating solution is 0.005ppm-1ppm.

4. The electroplating solution for preparing nanotwinned copper according to claim 1 or 2, characterized in that, The concentration of the main twinning inducer in the electroplating solution is 0.1ppm-100ppm, preferably 1ppm-30ppm.

5. The electroplating solution for preparing nanotwinned copper according to claim 1 or 2, characterized in that, The X group is selected from any one of mercapto, disulfide bond, thiazolyl, benzothiazolyl or imidazolyl; Preferably, the L-linking chain is selected from any one of C3-C8 alkyl chains, C3-C8 sulfide chains, or hydrophilic chains containing 1-3 EO units; Preferably, the Y group is selected from any one of sulfonates, carboxylates, hydroxyl groups, or polyethylene glycol chains; Preferably, the master twinning inducer comprises any one or a combination of at least two of the following: sodium 2-mercaptobenzothiazole-6-sulfonate, sodium 2-mercaptobenzimidazole-5-sulfonate, 1-(3-sulfopropyl)imidazolium inner salt, 1-(3-sulfopropyl)pyridinium inner salt, or sodium 3-mercapto-1,2,4-triazole.

6. The electroplating solution for preparing nanotwinned copper according to claim 1 or 2, characterized in that, The polyether inhibitors include any one or a combination of at least two of PEG, PPG, EO-PO block copolymers or EO-PO end-group modifiers; Preferably, the concentration of polyether inhibitor in the electroplating solution is 20ppm-500ppm, more preferably 50ppm-250ppm; Preferably, the sulfur-containing accelerator comprises bis-(3-sulfopropyl)-disulfide and / or 3-mercapto-1-propanesulfonic acid; Preferably, the concentration of the sulfur-containing accelerator in the electroplating solution is 0.5ppm-50ppm, more preferably 2ppm-20ppm, and even more preferably 5ppm-15ppm.

7. The electroplating solution for preparing nanotwinned copper according to claim 1 or 2, characterized in that, The copper sulfate is CuSO4·5H2O, and the concentration of CuSO4·5H2O in the electroplating solution is 25g / L-120g / L, preferably 50g / L-90g / L; Preferably, the concentration of sulfuric acid in the electroplating solution is 30 g / L-250 g / L, more preferably 120 g / L-220 g / L; Preferably, the concentration of chloride ions in the electroplating solution is 20ppm-100ppm, and more preferably 30ppm-70ppm.

8. The electroplating solution for preparing nanotwinned copper according to claim 1 or 2, characterized in that, The electroplating solution also includes a leveling agent and deionized water; Preferably, the concentration of the leveling agent in the electroplating solution is 0.1ppm-20ppm, and more preferably 0.5ppm-5ppm.

9. An electroplating method, characterized in that, The electroplating method uses an electroplating solution including the electroplating solution for preparing nanotwinned copper as described in any one of claims 1-8.

10. The electroplating method according to claim 9, characterized in that, The electroplating method uses a current density of 1ASD-30ASD, preferably 2ASD-15ASD; Preferably, the electroplating method uses a temperature of 15-45℃, more preferably 20-35℃; Preferably, the electroplating method uses a pH < 1.

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