Tetraethylammonium Hydroxide Research Articles

Preparation of Novel Hierarchical Catalysts by Simultaneous Generation of β-Zeolite and Mesoporous Silica for Catalytic Cracking.

The gel skeletal reinforcement (GSR) method was applied at the preparation stage of β-zeolite to prepare a novel hierarchical catalyst. A solution of hexamethyldisiloxane (HMDS) and acetic anhydride, a GSR reagent, was added to the mixture of colloidal silica, sodium aluminate, tetraethylammonium hydroxide, sodium hydroxide and water, and successive aging and hydrothermal treatment gave microporous β-zeolite surrounded by mesoporous silica like core-shell structure. Its properties were characterized by XRD, nitrogen adsorption and desorption, NH3-TPD, TEM, and TG-DTA measurements, and further characteristics of the catalysts produced were clarified by the catalytic cracking of n-dodecane. The hierarchical structure of microporous zeolite and mesoporous silica was shown from GSR-2.9HS-H-Beta to GSR-3.2HS-H-Beta, where the molar ratio of HMDS and silica source of β-zeolite was 2.9~3.2 : 100. It was found that in the catalytic cracking of n-dodecane, the relative activity (the conversion per the amount of zeolite crystals) increased with the increase in mesopore volume and surface area. The result indicated that the introduction of mesopores was effective even in catalytic cracking of small molecule of n-dodecane.

Directional Transport in Hierarchically Aligned ZSM-5 Zeolites with High Catalytic Activity.

Zeolites, the most technically important crystalline microporous materials, are indispensable cornerstones of chemical engineering because of their remarkable catalytic properties and adsorption capabilities. Numerous studies have demonstrated that the hierarchical engineering of zeolites can maximize accessible active sites and improve mass transport, which significantly decreases the internal diffusion limits to achieve the desired performance. However, the construction of hierarchical zeolites with ordered alignments and size-controlled substructures in a convenient way is highly challenging. Herein, we develop a facile procedure using two common structure-directing agents, tetrapropylammonium hydroxide (TPAOH) and tetraethylammonium hydroxide (TEAOH), to synthesize hierarchically aligned ZSM-5 (Hie-ZSM-5) crystals with a-axis alignment substructures of controllable size. The control of the substructure size (α) in the range of 10-60 nm and the corresponding similarity (r = α/β, where β is the size of Hie-ZSM-5) ranging from 0.004 to 0.033 can be tuned by varying the Si/Al ratios (40-120). A systematic investigation of the overall crystallization process, using time-dependent XRD, SEM, TEM, and solid-state magic-angle spinning NMR (13C, 27Al, 29Si) methods, enable us to construct a solid mechanism for the generation of Hie-ZSM-5. Most importantly, directional transport in the unique structures of Hie-ZSM-5 efficiently enhances mass diffusion, as well as catalytic activity and stability. These findings improve our understanding of the zeolite crystallization process and inspire novel methods for the rational design of hierarchical zeolites.

Preparation of TiO2 nanoparticles decorated porous carbon via a pseudo co-templating strategy and their application as substrates for high performance cathode of Li[sbnd]S batteries

Lithium‑sulfur batteries (LSBs) with a high theoretical specific capacity are considered as one of the most promising energy storage devices for next-generation. However, issues such as the insulation of pristine sulfur, the shuttle effect of polysulfides (LiPSs), and the volume change of sulfur cathode during cycling hinder their commercial applications. In this work, composite microspheres of TiO2@p-C consisting of porous carbon decorated with TiO2 nanoparticles, have been designed and synthesized aiming to confine and trap the polysulfides inside the porous substrates and to improve the kinetics of the electrochemical reaction therein. TiO2 particles with size of a few nanometers are prepared by a tetraethyl ammonium hydroxide assisted sol-gel method. Composite microspheres of TiO2@p-C are created through spray drying technique using chitosan as carbon source, and nanoparticles of SiO2 with TiO2 as co-template while selectively etching of the former. The confinement effects via the pores in the TiO2@p-C microspheres and the affinity between the polar TiO2 moieties and the polysulfide species work synergistically, alleviating the effusion of the polysulfides and promoting the conversion reaction of them as well. As a result, the shuttle effect of polysulfides can be inhibited obviously. Significantly, the S@TiO2@p-C-2 composite cathode exhibits excellent cyclic performance of 1263 mAh g−1 at 0.2C and maintains still a discharge capacity of 809 mAh g−1 after 100 charge and discharge cycles. At a current density of 2C, it still delivers an outstanding specific capacity of 772 mAh g−1. In the case of high sulfur load up to 90 wt%, the discharge capacity of S@TiO2@p-C-2 composite electrode could still maintain at 469.5 mAh g−1 after 100 cycles under current density of 0.2C.

Solvent-free synthesis of lamellar SAPO-18/34 intergrowth zeolite and the catalytic performance for 1-butene cracking

Lamellar SAPO-18/34 intergrowth zeolite has been successfully synthesized by solvent-free method employing N,N-diisopropylethylamine and tetraethylammonium hydroxide as co-template. Different framework structures (SAPO-34 or SAPO-18) could also be crystallized from identical gels under the guidance of a single template agent. The differences in structure, morphology, pore characteristics, chemical composition, and acidity of the prepared zeolite SAPO samples were investigated by XRD, SEM, N2 adsorption–desorption, XRF, and NH3-TPD. In comparison to SAPO-18 and SAPO-34, the lamellar SAPO-18/34 intergrowth zeolite with suitable acidity exhibited better catalytic conversion and enhanced catalytic stability in the cracking of 1-butene.

Microwave-assisted synthesis of solketal from glycerol and acetone in the presence of SAPO-34 and SAPO-5

Solketal is one of the most promising additives improving the properties of motor fuels. Investigations related to process intensification of synthesis of solketal from glycerol and acetone is gaining importance. The present work illustrates the use of the microwave mode for intensification of this process in the presence of silicoaluminophosphates (SAPO) as catalysts. The main focus of the study was placed on tuning the textural, acidic, and catalytic properties of SAPO-34 and SAPO-5 via variation of the synthesis parameters, such as the nature of Al and Si sources and the structure-directing agent. The catalytic properties of SAPO materials were investigated in the synthesis of solketal from glycerol and acetone under microwave assistance at the acetone/glycerol molar ratio of 2.4 in a methanol solution (glycerol/methanol: 1 g/1 mL) and 56 °C. It was demonstrated that the selectivity towards solketal was 91.1–98.6 % in the presence of the studied materials. The activities of mesoporous SAPO-34 and SAPO-5 prepared in the presence of triethylamine were higher as compared with microporous SAPO-34 prepared in the presence of tetraethylammonium hydroxide due to the high mesoporosity and a larger content of acid sites. The 90.4 % conversion of glycerol and 98.6 % selectivity towards solketal were observed in the presence of mesoporous 7.6%SAPO-34 for 90 min. The advantage of using microwave technology is shown. The solketal yield in the reaction under microwave irradiation was 3 times higher than that in the process performed under thermal heating conditions.

Enhanced particle removal ability of two representative nonionic surfactants: A reasonable interpretation based on DFT and coarse-grained molecular dynamics methods

Cleaning of copper surfaces after chemical mechanical polishing is indispensable for removing particle residues, which is a critical step in integrated circuits manufacturing. This paper introduces two nonionic surfactants, coconut oil diethanolamine (CDEA) and fatty alcohol polyoxyethylene ether (AEO-9), into a basic alkaline cleaning solution comprising tetraethyl ammonium hydroxide and lysine to investigate their abilities to enhance particle removal performance. Cleaning performance was measured with scanning electron microscopy, which showed that the two surfactants achieved excellent particle removal efficiency (above 95 %), with CDEA performing slightly better in all tested concentrations. Concerning critical micelle concentration, surface tension tests showed that CDEA (at 1500 ppm) had superior wettability and dispersive capacity compared with AEO-9 (at 2000 ppm) and could prevent particle redeposition more effectively. Using density functional theory, CDEA was found to have more polar groups to form hydrogen bonds with the hydrophilic surface of colloidal silica particles or bond with the copper substrate, explaining CDEA’s ability to lower the surface tension of the cleaning solution and improve the zeta potential between particles and the copper substrate. Finally, based on the Martini forcefield, simulations of coarse-grained molecular dynamics provided valuable theoretical insights into the different dispersion abilities of the two nonionic surfactants that CDEA had a more significant diffusion coefficient (0.073 Å2/ps) and was able to form micelles more efficiently in solution compared with that of AEO-9 (0.066 Å2/ps).

Dissolution dynamics of poly(4-hydroxystyrene) partially protected with t-butoxycarbonyl group in alkyltrimethylammonium hydroxide aqueous developers

Novel developers with low biotoxicity have attracted considerable attention with respect to ensuring environmental sustainability. In this study, the dissolution dynamics of poly(4-hydroxylstyrene) (PHS) partially protected with a t-butoxycarbonyl (t-Boc) group in alkyltrimethylammonium hydroxide and tetraethylammonium hydroxide aqueous solutions (0.26 N) were investigated by the quartz crystal microbalance method. One of the methyl groups of tetramethylammonium hydroxide (TMAH) was substituted by ethyl, propyl, and butyl groups. Depending on the developer used, the dissolution dynamics of PHS and t-Boc-protected PHS (t-Boc PHS) films showed different tendencies. The dissolution rate of PHS was higher in the TMAH developer than in the butyltrimethylammonium hydroxide (B-TMAH) developer, whereas that of the t-Boc PHS (30 mol%-protected) film was higher in the B-TMAH developer than in the TMAH developer. The elongation of one of the alkyl chains is beneficial for the penetration of the developer and the separation of nonpolar molecular interactions among t-Boc PHS molecules.

Investigation of a liquid-mediated defect-healing treatment in zeolite beta

We report the application of a liquid-mediated defect-healing treatment based on tetraethylammonium (TEA+) hydroxide and ammonium fluoride, and variants thereof, to the H+ form of zeolite beta. Through comparison between H-beta of high (730) and lower (28.6) SiO2: Al2O3 ratios, and characterisation of the treated samples before and after calcination, insights into the interaction of TEA+ and F− with H-beta under hydrothermal conditions were gained. In general, the treatments resulted in the loss of crystallinity and the generation of relatively large mesopores in the more siliceous samples, but improvements in long-range order and the development of relatively small mesopores in the less siliceous samples. The healing of silanol defects was observed for most of the treatments. A partial mechanism is proposed to explain the action of defect-healing treatments based on pore-occupying cations and F−; fluorine may be essential in some cases because it balances the charge of the organic cations, preventing the “trapping” of silanol groups as charge-balancing silanolate groups which resist healing.

Synthesis‐structure‐catalysis relations in CHA zeolites applied for selective catalytic reduction of NOx with ammonia

Microporous aluminosilicate zeolites are useful industrial catalysts. However, their hydrothermal synthesis is a multistep process with complicated and unclear reactions, limiting their rational functional design. Herein, we compare the formation pathway and the structural and catalytic properties of several CHA zeolites to obtain fundamental knowledge for intentionally controlling the catalytic function of zeolites. Three CHA zeolites were synthesized using different starting silica/alumina sources in the presence of tetraethylammonium hydroxide as an inexpensive organic structure‐directing agent. FAU zeolite and an amorphous synthesis gel prepared using two different methods were used as starting materials. The obtained CHA zeolites were applied for exhaust gas purification (selective catalytic reduction of NOx with ammonia, NH3‐SCR), and their structural characteristics and formation pathways were investigated using a combination of analytical methods. Stepwise gel preparation (SGP), which divides the compositional control of the amorphous synthesis gel, promotes the decomposition of the initial additive (zeolite seed), resulting in the formation of CHA zeolites with abundant micropores and paired Al sites. This structural feature obtained using the SGP method improves the catalytic durability of the NH3‐SCR reaction. The present relationship, including different crystallization phenomena, structures, and catalytic abilities, provides useful insights into rational zeolite synthesis and its application.

Hydroxide Ion Conduction through Viologen-Based Covalent Organic Frameworks (vCOFs): An Approach toward the Advancement.

Alkaline fuel cells rely on the movement of hydroxide anions (OH-) for their operation, yet these anions face challenges in efficient conduction due to their limited diffusion coefficient and substantial mass compared to proton (H+) transport. Within the covalent organic framework structure, ordered channels offer a promising solution for the OH- ion transport. Herein, we synthesized a cationic covalent organic framework (vTAPA) via the solvothermal-assisted Zincke reaction. vTAPA showcases excellent stability in harsh basic solution (12 M) and a wide range of pH. This framework facilitates OH- conduction through its one-dimensional network through the anion exchange process. We employed various tertiary ammonium salts (tetramethyl, tetraethyl, and tetrabutyl ammonium hydroxide) to exchange trapped anionic chloride ions inside the vTAPA structure with OH- ions. The density functional theory (DFT) study exhibited that the anion exchange process is very favorable, as the vTAPA framework offers preferable interaction sites for OH- ions. The impact of steric hindrance from these tertiary ammonium salts on the OH- conduction performance was extensively investigated. Butyl@vTAPA exhibited a high OH- ion conductivity of 1.05 × 10-4 S cm-1 at 90 °C under 98% relative humidity (RH). Our uniquely designed cationic covalent organic frameworks (COF) created a platform for a preferential transport network of hydroxide ions, and this is the first report of directly used COFs for hydroxide ion conduction without any vigorous postsynthetic modification.

Synthesis of Al-containing Sn-beta with tunable brønsted and lewis acidity for conversion of glucose to 5-hydroxymethylfurfural

Sn–Al-Beta zeolites with less silanol defects were synthesized in fluoride media. The effects of the amount of organic template (tetraethylammonium hydroxide, TEAOH), mineralizer (NH4F), Al and Sn on the synthesis, acidity and catalytic performance were systematically studied. The synthesized Sn–Al-Beta zeolites were characterized by XRD, SEM, 27Al MAS NMR, UV–vis DRS and FT-IR spectroscopy of hydroxy region and pyridine adsorption. The optimum values of nTEAOH/nSi and nF-/nSi were same (0.3) for synthesizing Sn–Al-Beta with high crystallinity at 140 °C for 7 d. Moreover, decreasing nF-/nSi facilitated the incorporation of Al into the framework. The crystallization rate of Sn–Al-Beta is similar with that of Sn-Beta. Sn was promoted to enter the framework with the increase of Al content, while elevating Sn content has no effect on the incorporation of Al into the framework. The catalytic performance of Sn–Al-Beta was investigated for conversion of glucose to 5-hydroxymethylfurfural in water-containing solvent. Sn–Al-Beta synthesized in fluoride media is more stable than the post-synthesized sample.

The dry-gel conversion synthesis of the lithium sodium borosilicate jadarite, LiNaSiB3O7(OH)

Abstract The lithium sodium borosilicate jadarite, LiNaSiB3O7(OH), was first identified in 2007 in the Jadar basin, Serbia, where it forms the principal ore mineral of one of Europe's largest Li deposits. We report the successful application of the dry-gel conversion technique (DGC) to synthesise a jadarite analogue, via a dry-gel precursor made using sol-gel synthesis and the inclusion of the structure directing agent tetraethylammonium hydroxide (TEAOH). Pawley refinement of powder X-ray diffraction (PXRD) data collected on the synthetic sample was carried out using a monoclinic unit cell in space group P21/c (Whitfield et al., 2007), and gave refined unit cell parameters of a = 6.824(3) Å, b = 13.882(5) Å, c = 7.735(3) Å and β = 124.37(1)° (Rwp = 9.22). Inductively-coupled plasma optical emission spectroscopy (ICP–OES) on the synthetic sample confirmed an empirical formula of Li1.07Na1.40Si0.79B3O7.32(OH), based on three B atoms per formula unit (apfu). The synthetic product was found to be deficient in Si compared to natural jadarite from analysis of PXRD and ICP–OES data. Fourier-transform infrared spectroscopy (FTIR) showed that synthetic jadarite has peaks at 1415 and 1342 cm–1 and between 1180 and 900 cm–1, which are attributed to the presence of trigonal (BO3) and tetrahedral (BO4) borate groups characteristic of the natural jadarite structure, as well as a broad peak at 3441 cm–1 due to the presence of residual TEAOH. Scanning electron microscopy showed similarities in the morphologies between synthetic and natural jadarite particles.

Synthesis, characterization, and evaluation of the CO2 adsorption capacities of beta, ZSM-12, ZSM-48, and silicalite-1 zeolites obtained in the presence of tetraethylammonium hydroxide and 1,6-diaminohexane as organic structure-directing agents

Synthesis, characterization, and evaluation of the CO2 adsorption capacities of beta, ZSM-12, ZSM-48, and silicalite-1 zeolites obtained in the presence of tetraethylammonium hydroxide and 1,6-diaminohexane as organic structure-directing agents

Synthesis and Crystallization Mechanism for SAPO-34 Zeolite Derived from Magadiite.

In this work, we explored the hydrothermal synthesize and crystallization process of SAPO-34 zeolites from two-dimensional layered silicate magadiite by using tetraethylammonium hydroxide (TEAOH) as a templating agent. Comprehensive characterization was conducted by XRD, SEM, FTIR, Raman, and BET. Time-resolved PXRD analysis revealed that SAPO-34 zeolite exhibited a steep growth curve when the crystallization time was 30 h, and the crystallinity reached 98.65 % at 48 h. Specifically, the disruption of the magadiite layer exposed charged silanol groups on the surface, fostering an affinity for AlO4 and PO4 species, thereby initiating the nucleation process. Under the guidance of TEAOH, these nucleation sites transformed into SAPO-34 nuclei, gradually advancing towards crystallization. FTIR and Raman analyses affirmed the presence of 6Rs, followed by D6R and 4Rs SBUs, along with the characteristic CHA structure. Combined with 29Si NMR established that disaggregated silicate minerals served as zeolite synthesis "seeds", enhancing nucleation sites and overall crystallization efficiency.

MOR nanosheets with tunable c-axis thickness and their catalytic performance in DME carbonylation

Controlling the anisotropic growth of crystals to achieve desired morphology is a challenge in zeolite crystallization, which often requires the use of bulky organic surfactants or additional crystal growth modifiers. Here, MOR crystals with tunable c-axis thickness (12-MR channel direction) were readily synthesized with commercial tetraethylammonium hydroxide (TEAOH) as an organic-structure directing agent (OSDA). It is revealed that the relative growth rates of different crystal faces of MOR zeolite can be tuned by the crystallization temperature and TEAOH amount in the developed gel system. Higher temperature and lower TEAOH concentration can effectively retard the growth of MOR crystals along the c-axis, yielding MOR nanosheets with short c-axis thickness (ca. 40 nm). Investigation on the crystallization process demonstrates that the crystal growth follows a particle attachment mechanism. Theoretical calculation was further employed to elucidate the c-axis thickness variation of MOR zeolite under different conditions. A kilogram-scale synthesis of MOR nanosheets has been realized with a 10 L autoclave, achieving high solid yield of 92 %. The MOR nanosheets, offering short 12-MR diffusion path, exhibit substantially enhanced catalytic activity and stability in the dimethyl ether (DME) carbonylation to methyl acetate reaction.

Optimization and performance evaluation of a fluorescent sensor for residual sulfonamide antibiotics in honey samples

AbstractIn the quest to address the mounting concerns over sulfonamide antibiotic residues in food, which pose significant threats to public health and food safety, this study introduces a cutting‐edge detection method. Surface molecular imprinting on silicon nanoparticles is harnessed to fabricate a novel fluorescent sensor that exploits the luminescent properties of cadmium telluride (CdTe) quantum dots. This innovative approach aims to detect residual sulfonamide antibiotics with high specificity and sensitivity. At the heart of this research is the development of a core‐shell nanostructure, where silicon dioxide serves as the core, and a molecularly imprinted polymers (MIPs) layer, tailored to recognize sulfamethazine (SM2), forms the shell. The pivotal advancement in this sensor design is the integration of highly fluorescent CdTe quantum dots within the MIPs layer, which significantly enhances the signal response, enabling the detection of SM2 with remarkable precision. The synthesis of this sensor employs a novel strategy, utilizing 3‐aminopropyltriethoxysilane as the functional monomer, while tetraethyl orthosilicate and ammonium hydroxide act as catalysts to facilitate the polymerization reaction. This meticulous process yields a stable core‐shell structure with active fluorescent properties. Experimental results reveal that under optimal conditions, the sensor exhibits a robust linear response to SM2 concentrations ranging from 10 to 60 μmol L−1, with a detection limit as low as 0.78 μmol L−1. Furthermore, when applied to real food samples, such as honey, the sensor not only demonstrates high recovery rates of 92.3%–98.1%, but also maintains a low relative standard deviation of less than 2.5%. The implications of this study are far‐reaching, offering a promising avenue for the rapid and reliable monitoring of antibiotic residues in the food supply chain, thereby safeguarding consumer health and upholding food safety standards.

Sustainable Synthesis of Zeolitic Imidazolate Frameworks at Room Temperature in Water with Exact Zn/Linker Stoichiometry.

Zeolitic imidazolate frameworks (ZIFs) are widely used MOFs because of certain characteristics, but also because they can be prepared at room temperature using water as the unique solvent. However, these a priori sustainable conditions inevitably entail a huge and somehow unusable excess of linker. Here, we present the formation of ZIFs at room temperature in water, starting from mixtures with a linker/metal ratio of two, that is, coinciding with the stoichiometry found in the final MOFs, in the presence of amines. ZIF-8 can be prepared with triethylamine (TEA), giving a yield of Zn of 96.6%. Other bases, like NaOH, tetraethylammonium hydroxide or ammonium hydroxide, do not lead to ZIF-8 under the same conditions. The so-obtained ZIF-8 contains TEA inside its cavities, making it less porous than its conventionally prepared counterparts. Amine can be removed by mild thermal treatments (200-250 °C). Such thermal treatments induce the generation of g-C3N4-like species which could give added value to these materials as potential photocatalysts, increasing their affinity to CO2, as proved in this work. This methodology can be successfully extended to other amines, like N,N-dicyclohexylmethylamine, as well as to other prepared ZIFs, like Co-based ZIF-67, isostructural to ZIF-8.

TEAOH-assisted cost-effective preparation of SSZ-13 using L zeolite as Al source

Developing an economical and high-efficiency synthesis pathway of SSZ-13 zeolite is of great significance for the ammonia selective catalytic reduction of nitrogen oxides (NH3-SCR of NOx) reactions. Herein, SSZ-13 zeolite were synthesized using L zeolite as the aluminum source in the presence of a mixed structure directing agent (SDA) composed of N,N,N, trimethtyl-1-adamantammonium hydroxide (TMAdaOH) and tetraethylammonium hydroxide (TEAOH). This synthesis strategy aims to accelerate the crystallization rate through interzeolite transformation, while less expensive TEAOH can play a cooperative structure-directing role, thus reducing the consumption of expensive TMAdaOH template. The results showed that pure SSZ-13 zeolites with high crystallinity can be obtained from L zeolite within 12 h at 160 ℃ under low TMAdaOH/SiO2 ratio of 0.05 (too low to carry out the synthesis on its own in the current synthesis system) in the presence of TEAOH. Moreover, the crystallization mechanism was also investigated by XRD, FT-IR, SEM and TG-DTG techniques. It was proposed that the crystallization of SSZ-13 occurs through the formation of SSZ-13 nuclei under the direction of TMAdaOH and promotion of TEAOH, subsequently TMAdaOH was incorporated in the framework to further induce the crystal growth of SSZ-13. Especially, the zeolite crystal size can be modulated by the amount of TEAOH added. In addition, After Cu2+ exchange, the obtained Cu-SSZ-13 sample exhibits superior catalysis performance in the NH3-SCR of NOx reaction, and the NOx conversion rate remained over 90 % across a broad range from 200 to 600 °C, demonstrating its significant application potentials in NOx removal from diesel vehicle exhausts.

Effects of two mild amino acids on benzotriazole residue desorption during cobalt post-chemical mechanical polishing cleaning: Experimental and theoretical studies

During the polishing process of the cobalt (Co) interconnect layer, the corrosion inhibitor in the polishing solution will leave an organic residue on the polished cobalt surface, which needs to be removed by the post-chemical mechanical polishing (CMP) cleaning process. However, given the active chemical properties of cobalt, the potent and corrosive complexing agents in traditional cleaning solutions have the drawback of generating new corrosion defects on the cobalt surface. In this study, an eco-friendly cleaning solution is developed utilizing tetraethyl ammonium hydroxide (TEAH), deionized water, and either sarcosine or serine, thereby ensuring the absence of any additional introduction of metal impurities. The removal effect of the cleaning solution on BTA was tested using atomic force microscopy (AFM) and X-ray photoelectron spectrometer (XPS). The results demonstrate that post-CMP cleaning with either sarcosine or serine yielded a cobalt surface with reduced roughness (2.78 nm and 2.63 nm), diminished Co-BTA content (10.6% and 9.5%), and a lowered contact angle (44.3° and 37.9°). To elucidate the mechanism of post-CMP cleaning, electrochemical measurements and molecular dynamics were employed. Initially, in the cleaning solution with a pH of 10.4, the adsorption of BTA and cobalt is minimized. Subsequently, as serine permeates through the BTA residue layer, the desorption of BTA is expedited through competitive adsorption. These findings contribute valuable insights into the mechanism of residue removal in post-CMP cleaning processes.

Synergistic Effect of Composite Complex Agent on BTA Removal in Post-Cu-CMP: Experimental and Theoretical Analysis

Nowadays the development of nanoscale-interconnected integrated circuit chips makes the chemical mechanical polishing (CMP) and post-CMP cleaning more challenging. In general, organic residues such as benzotriazole (BTA) can adsorb on the wafer surface after CMP process and form thin films to prevent the contact between cleaning solution and the wafer surface, which thus can seriously affect the post-CMP cleaning process. And the efficient removal of BTA remains problematic due to the potential introduction of additional impurities. Therefore, a new alkaline cleaning solution based on citric acid (CA) was proposed to improve the removal efficiency of BTA. Results exhibit that the cleaning efficiency of BTA residues can reach 98.86% with 400 ppm tetraethyl ammonium hydroxide (TEAH) and 0.6 wt% CA (pH = 10.5). X-ray photoelectron spectroscopy (XPS) measurements show that the cleaning solution can coordinate with copper ions to break the ionization balance of Cu-BTA. In addition, the electronic properties and reaction sites on copper surface were determined by quantum chemical calculation and density functional theory (DFT). The theoretical analysis indicates that CA has hydroxyl and carboxyl functional groups, and its presence with TEAH can promote the complexation of Cu ions, which accelerates the breakage of Cu-BTA and the desorption of BTA from the copper surface.