Benzotriazole Removal Research Articles

Methanol-dispersed of ternary Fe3O4@γ-APS/graphene oxide-based nanohybrid for novel removal of benzotriazole from aqueous solution

A novel nanohybrid: Fe3O4 coated with γ-APS polymer deposited on graphene oxide (F@γ-A/G), to remove an emergent heterocyclic contaminant benzotriazole (BTA) from solution. F@γ-A/G was synthesized in methanol-dispersion via aminosilanization under ultra-sonication. We newly found that F@γ-A/G crystallite lattice has a 2D triangular-network intersection with angle of 60° in three types of d311, d220 and d111 planes with different interplanar spacings. Textural characteristics did not affect BTA adsorption, which was desired at high temperature (40 °C), neutral solution (pH = 6) and controlled by endothermic process. Considering the maximum BTA adsorption capacity of 312.5 mg/g, which was much higher than previously reported adsorbents, the plausible mechanism was attributed to hydrophobic, electrostatic and π-π interaction. Effects of pH and temperature are significant on BTA adsorption to F@γ-A/G. Methanol was the best solvent for multiple cycle regeneration with only 2% loss of BTA removal efficiency even after five cycles of F@γ-A/G.

Degradation of 1H-benzotriazole using ultraviolet activating persulfate: Mechanisms, products and toxicological analysis

Benzotriazoles have been widely used as additives in industrial products, and they are released or discharged along with sewage into wastewater treatment plants. Traditional wastewater treatment processes, especially biological methods, cannot completely eliminate BTAs. Developing cost-effective and environmental-friendly treatment methods for the removal of benzotriazoles is in urgent need. This study evaluated the degradation efficiency of 1H-benzotriazole (1H-BTA) with 280 nm ultraviolet activating persulfate (UV/PS). Degradation of 1H-BTA followed pseudo-first order kinetics with a rate constant at 0.226 min−1 when [1H-BTA]0 = 8.39 μM, [PS]0 = 420 μM, UV intensity = 0.023 mW cm−2. Scavenger experiments with ethanol and tert-butyl alcohol proved that both hydroxyl radical and sulfate radical contributed to the degradation of 1H-BTA. Reactions induced by these radicals were affected by pH value, anions and natural organic matters, implying that an incomplete mineralization of 1H-BTA by UV/PS would be ubiquitous in heterogeneous water matrix. As the reaction proceeded, 1H-BTA was transformed to a series of intermediate products. Simple hydroxylated product C6H5N3O was dominating in the initial stage (∼10 min), while further open-loop oxidative product C4H3N3O4 had a peak value in the later stage (∼45 min). Based on model organism proteomics and metabolic network analyses, down regulation of stress resistance proteins in Escherichia coli exposed to degradation products indicated that the toxicity of 1H-BTA was declined. To summarize, incomplete mineralization of 1H-BTA using UV/PS is likewise effective for its detoxification.

A novel combination of oxidative degradation for benzotriazole removal using TiO2 loaded on FeIIFe2IIIO4@C as an efficient activator of peroxymonosulfate

A heterogeneous photocatalyst, TiO2-functionalized magnetic activated carbon (T@MPAC), was fabricated as a novel peroxymonosulfate (PMS) activator for improving the oxidative degradation of benzotriazole (BTA) in aqueous media. For characterization of the features of the synthesized catalyst, XRD, FESEM, EDS, BET, TEM, PL and UV-vis DRS techniques were applied. Influence of operating parameters namely solution pH, reaction time and catalyst dosages, PMS and BTA was studied in a batch environment. A plausible oxidation mechanism and reaction pathway for BTA degradation was proposed. Potential catalytic, recyclability, durability and quenching studies were performed. The catalytic activity of T@MPAC in the activation of different oxidants also evaluated. Under optimized conditions, the degradation and mineralization rates of BTA were found to be 71.6 and 38.7%, respectively, after the fifth cycles. The catalytic activity of T@MPAC on BTA degradation was improved with the suitability in order of PMS>persulfate>ozone>H2O2. The trapping experiments confirmed the participation of OH, SO4−, O2− radicals as reactive species in the system. Among the reactive species (i.e. OH, SO4−, O2− and holes) included in T@MPAC/PMS/UV system, SO4− radicals had dominant role in controlling the oxidation reaction. Decreasing the degradation rate in the presence of scavenger agents was as IPA>BQ>t-BuOH>KI. The catalytic performance dropped in the presence of chloride ions, while it was less affected by phosphate, nitrate and sulfate anions. The catalyst showed a good recyclability and stability after five consecutive uses. To conclude, coupling of T@MPAC/UV and PMS can be successfully applied as a novel and effective technique to degrade organic substances in wastewater, due to easy recoverable, high catalytic activity and the cogeneration of different reactive species.

Comparison of sequential with intimate coupling of photolysis and biodegradation for benzotriazole

Benzotriazole (BTA) is an emerging contaminant that also is a recalcitrant compound. Sequential and intimate coupling of UV-photolysis with biodegradation were investigated for their impacts on BTA removal and mineralization in aerobic batch experiments. Special attention was given to the role of its main photolytic products, which were aminophenol (AP), formic acid (FA), maleic acid (MA), and phenazine (PHZ). Experiments with sequential coupling showed that BTA biodegradation was accelerated by photolytic pretreatment up to 9 min, but BTA biodegradation was slowed with longer photolysis. FA and MA accelerated BTA biodegradation by being labile electron-donor substrates, but AP and PHZ slowed the rate because of inhibition due to their competition for intracellular electron donor. Because more AP and PHZ accumulated with increasing photolysis time, their inhibitory effects began to dominate with longer photolysis time. Intimately coupling photolysis with biodegradation relieved the inhibition effect, because AP and PHZ were quickly biodegraded and did not accumulate, which accentuated the beneficial effect of FA and MA.

Mass loading and removal of benzotriazoles, benzothiazoles, benzophenones, and bisphenols in Indian sewage treatment plants

Little is known about the occurrence of emerging environmental contaminants, such as benzotriazoles (BTRs), benzothiazoles (BTHs), benzophenones (BzPs), and bisphenol analogues (BPs) in India. In this study, we determined the occurrence and removal of BTRs, BTHs, BzPs, and BPs in five Indian sewage treatment plants (STPs). The respective measured mean concentrations (N = 5) in influents and effluents were 370 and 57.4 ng L−1 for BTRs, 50800 and 20200 ng L−1 for BTHs, 351 and 163 ng L−1 for BzPs, and 98.0 and 9.6 ng L−1 for BPs. Among the target chemicals analyzed, BTHs were found at elevated levels, and the measured levels were some of the highest ever reported in the literature. The mean concentrations (N = 5) of BTRs, BTHs, BzPs, and BPs in sludge were 44.2, 51200, 124, and 200 ng g−1 dry wt, respectively. The removal efficiencies for BTRs, BTHs, BzPs, and BPs ranged as follows: 54.2–85.6%, 23.4–85.0%, 51.8–71%, and 76.0–97.0%, respectively, and were comparable to those reported for other countries. Elevated concentrations of BTHs in Indian STPs can be related to consumption of these chemicals in a wide range of products including paper, textile and rubber materials.

Removal of benzotriazole by Photo-Fenton like process using nano zero-valent iron: response surface methodology with a Box-Behnken design

Abstract In this paper, the removal of benzotriazole (BTA) was investigated by a Photo-Fenton process using nano zero valent iron (NZVI) and optimization by response surface methodology based on Box-Behnken method. Effect of operating parameters affecting removal efficiency such as H2O2, NZVI, and BTA concentrations as well as pH was studied. All the experiments were performed in the presence of ultraviolet radiation. Predicted levels and BTA removal were found to be in good agreement with the experimental levels (R2 = 0. 9500). The optimal parameters were determined at 60 min reaction time, 15 mg L-1 BTA, 0.10 g L-1 NZVI, and 1.5 mmol L-1 H2O2 for Photo-Fenton-like reaction. NZVI was characterized using X-ray diffraction (XRD), transmission electron microscope (TEM) images, and scanning electron microscope (SEM) analysis.

Chemical Mechanical Planarization of Ruthenium Using Sodium Hypochlorite Based Titania Slurry

In the present work, chemical mechanical planarization (CMP) of Ru and Cu was carried out using titania based slurry containing sodium hypochlorite (NaOCl) as oxidizer with and without benzotriazole (BTA) as corrosion inhibitor. The CMP results reveal that in the absence of BTA, Ru removal rate (RR) increases with pH until pH 7 and then decreases gradually in the alkaline region, while Cu RR decreases with increase in pH. In the presence of BTA, both Cu and Ru removal rates decreased while the same trend in RR was observed with change in pH. RR selectivity between Ru and Cu of 1 was obtained at pH 9 which is preferred in industries. In the presence of NaOCl, Ru oxidizes to form RuO4, in the acidic and neutral pH and RuO4− and RuO42− in alkaline pH, which aids in the formation of RuO3/RuO2. The electrochemical techniques were also employed to understand the removal mechanism of Ru and Cu in electrolyte containing NaOCl with and without BTA. The Icorr values of Ru and Cu, obtained from the extrapolation of Tafel curves, follow the CMP removal rate trend. An electrical equivalent circuit was proposed to explain the results obtained in electrochemical impedance spectroscopy studies.

Adsorption of benzotriazole and benzimidazole from water over a Co-based metal azolate framework MAF-5(Co)

Benzotriazole (BTA) and benzimidazole (BZI) are regarded as water pollutants because of their extensive uses in industry and appreciable water solubility. The adsorption of both BTA and BZI from water over a newly synthesized metal-organic framework, MAF-5(Co), was investigated and compared with zeolitic imidazole frameworks (ZIFs), such as ZIF-8(Zn) and ZIF-67(Co), as well as commercial activated carbon. MAF-5(Co) had the highest adsorption capacities for both BTA and BZI. The maximum adsorption capacities of MAF-5(Co) for BTA and BZI were 389 and 175mgg−1, respectively. Hydrophobic and π-π interactions between the aromatic adsorbate BTA and MAF-5(Co) were suggested as a plausible mechanism. Based on the zeta potential of MAF-5(Co) and effects of pH on the BTA adsorption, electrostatic interactions between the MAF-5(Co) and BTA species might also affect the adsorption of BTA over MAF-5(Co). MAF-5(Co) can be recycled for adsorptive removal of BTA by simple ethanol washing. Therefore, MAF-5(Co) is suggested as a promising adsorbent for the removal of BTA and BZI from water.

Degradation of benzotriazole and benzothiazole in treatment wetlands and by artificial sunlight

Laboratory-scale experiments were performed using unsaturated subsurface-flow treatment wetlands and artificial sunlight (with and without TiO2) to study the efficiency of benzotriazole and benzothiazole removal and possible integration of these treatment methods. Transformation products in the effluent from the treatment wetlands and the artificial sunlight reactor were identified by high performance liquid chromatography coupled with tandem mass spectrometry. The removal of benzothiazole in the vegetated treatment wetlands was 99.7%, whereas the removal of benzotriazole was 82.8%. The vegetation positively affected only the removal of benzothiazole. The major transformation products in the effluents from the treatment wetlands were methylated and hydroxylated derivatives of benzotriazole, and hydroxylated derivatives of benzothiazole. Hydroxylation was found to be the main process governing the transformation pathway for both compounds in the artificial sunlight experiment (with and without TiO2). Benzotriazole was not found to be susceptible to photodegradation in the absence of TiO2. The integration of the sunlight-induced processes (with TiO2) with subsurface-flow treatment wetlands caused further elimination of the compounds (42% for benzotriazole and 58% for benzothiazole). This was especially significant for the elimination of benzotriazole, because the removal of this compound was 96% in the coupled processes.

Synergetic effect of chelating agent and nonionic surfactant for benzotriazole removal on post Cu-CMP cleaning**Project supported by the Natural Science Foundation of Hebei Province, China (No. F2015202267) and the Scientific Innovation Grant for Excellent Young Scientists of Hebei University of Technology (No. 2015007).

The cleaning of copper interconnects after chemical mechanical planarization (CMP) process is a critical step in integrated circuits (ICs) fabrication. Benzotriazole (BTA), which is used as corrosion inhibitor in the copper CMP slurry, is the primary source for the formation of organic contaminants. The presence of BTA can degrade the electrical properties and reliability of ICs which needs to be removed by using an effective cleaning solution. In this paper, an alkaline cleaning solution was proposed. The alkaline cleaning solution studied in this work consists of a chelating agent and a nonionic surfactant. The removal of BTA was characterized by contact angle measurements and potentiodynamic polarization studies. The cleaning properties of the proposed cleaning solution on a 300 mm copper patterned wafer were also quantified, total defect counts after cleaning was studied, scanning electron microscopy (SEM) review was used to identify types of BTA to confirm the ability of cleaning solution for BTA removal. All the results reveal that the chelating agent can effectively remove the BTA residual, nonionic surfactant can further improve the performance.

(Invited) Quantification and Characterization of Adsorbed BTA on Copper Surfaces Under Conditions Relevant to Barrier CMP

In the formation of copper interconnects by CMP, barrier polishing is typically carried out using alkaline slurries containing copper corrosion inhibitors. Benzotriazole (BTA) has been the inhibitor of choice in such slurries. The effect of BTA on copper corrosion has been extensively studied in the past few decades, and there is general agreement that the adsorbed film formed in acidic solutions is a multilayer film with a chemisorbed first layer. However, simultaneous real time measurement of the amount of BTA adsorbed and characterization of nature of the adsorbed film (rigid/viscoelastic) has received very little attention. The objective of this work was to measure the extent of BTA adsorption onto PVD Cu films and characterize the nature of the adsorbed film in real time using a quartz crystal microbalance with dissipation monitoring (QCMD) capability. Quartz crystals (fundamental frequency of 5 MHz) coated with ~300 nm PVD copper layer were used in the experiments. To mimic the conditions during barrier polishing, BTA dissolved in alkaline solutions was pumped through the flow cell containing the crystal, and the change in crystal oscillation frequency and dissipation data were collected at a time resolution of fraction of a second for several minutes. This was followed by rinsing with DI or solutions containing selected surfactants to determine extent of desorption of BTA. As an example, adsorption of BTA from a solution of pH 10 is shown in figure 1. The measured frequency shift (Δf) and dissipation shift (ΔD) at different overtones (multiples) of crystal fundamental frequency are plotted as a function of time. At the time marked with t1, a sharp decrease of frequency may be seen, which indicates rapid adsorption of BTA. The data points for all frequencies fall on one curve indicating that the adsorbed BTA film on copper is quite rigid in nature. This is confirmed by very little measured change in the ΔD values. At the end of adsorption marked with t2, deionized water was introduced into the system, and the positive shift of frequency is indicative of BTA removal and/or etching of copper in DI water. In the presentation, results of adsorption and desorption experiments carried out under different experimental conditions will be presented. The disruption of adsorbed BTA layer by selected chemicals will be addressed. Figure 1

Photoperoxi-coagulation using activated carbon fiber cathode as an efficient method for benzotriazole removal from aqueous solutions: Modeling, optimization and mechanism

In this research, benzotriazole (BTA) was removed from aqueous solution using photoperoxi-coagulation (PPC) in which activated carbon fiber (ACF) was used as a cathode. Box-Behnken design was used to optimize and analyze four parameters i.e. time, applied current, initial BTA concentration and UV light power. According to the results, the R-squared and adjusted R-squared were 0.982 and 0.964, respectively, implying that the model was statistically suitable. It was shown that under the optimal condition for BTA removal i.e. 60 mg/L initial BTA concentration, 50 min time, 200 mA applied current and UV light power of 12W, the efficiency of the PPC process was maximum (97.8%). The removal mechanisms were determined and their results showed that the oxidation mechanism of photoperoxi-coagulation process had a more contribution in BTA removal in comparison with coagulation mechanism. The results of scavenging experiments also confirmed the determined removal mechanisms. Synergistic effect was observed in PPC while first order rate constant of PPC was 2.7 fold more than that of sum of each mechanism. The removals of TOC and COD were 64.5% and 76.3% respectively. Average oxidation state and carbon oxidation state of BTA solution were increased after PPC process indicating biodegradability improvement indirectly.

A novel compound cleaning solution for benzotriazole removal after copper CMP**Project supported by the Special Project Items No.2 in National Long-Term Technology Development Plan, China (Nos. 2009ZX02308-003, 2014ZX02301003-007).

After the chemical mechanical planarization (CMP) process, the copper surface is contaminated by a mass of particles (e.g. silica) and organic residues (e.g. benzotriazole), which could do great harm to the integrated circuit, so post-CMP cleaning is essential. In particular, benzotriazole (BTA) forms a layer of Cu-BTA film with copper on the surface, which leads to a hydrophobic surface of copper. So an effective cleaning solution is needed to remove BTA from the copper surface. In this work, a new compound cleaning solution is designed to solve two major problems caused by BTA: one is removing BTA and the other is copper surface corrosion that is caused by the cleaning solution. The cleaning solution is formed of alkaline chelating agent (FA/O II type), which is used to remove BTA, and a surfactant (FA/O I type), which is used as a corrosion inhibitor. BTA removal is characterized by contact angle measurements and electrochemical techniques. The inhibiting corrosion ability of the surfactant is also characterized by electrochemical techniques. The proposed compound cleaning solution shows advantages in removing BTA without corroding the copper surface.

Photocatalysis assisted by peroxymonosulfate and persulfate for benzotriazole degradation: effect of pH on sulfate and hydroxyl radicals.

Recently, notable attempts have been devoted to removing emerging pollutants from water resources. Benzotriazole (BTA) as an emerging pollutant has widely been detected in the aquatic environment and water resources. In the current work, peroxymonosulfate (PMS) and persulfate (PS) were added to a TiO2/UV system for BTA degradation, as electron acceptors to overcome recombination of hole and electron. Additions of PMS and PS to the photocatalysis process considerably increased removal efficiency. The rate constants of UV/TiO2/PMS, UV/TiO2/PS and UV/TiO2 were 0.0217 min(-1), 0.0152 min(-1) and 0.0052 min(-1) respectively. The results showed that pH significantly affected the UV/TiO2/PMS system while it marginally affected UV/TiO2/PS. Scavenging experiments using alcohols indicated that in acidic pH, the dominant oxidant was sulfate radical in both systems. The contribution of hydroxyl radical in BTA degradation was boosted at alkaline and neutral conditions especially in the UV/TiO2/PMS system. Moreover, other scavenging experiments implied that reaction of radicals occurred at both the catalyst surface and in solution. The mineralization results showed that PMS and PS significantly increased chemical oxygen demand and total organic carbon removal efficiencies. In general, presence of PMS in the photocatalysis process had a better performance compared to PS in terms of BTA removal and mineralization.

Effect of Dissolved Oxygen on the Removal of BTA from Cu By Tetra Methyl Ammonium Hydroxide

In the fabrication of copper interconnects, chemical mechanical polishing (CMP) is used to remove excess copper and barrier layers. Because of its ability to form a protective layer, Benzotriazole (BTA) is used as Cu corrosion inhibitor during CMP as well as post-CMP cleaning [1, 2]. It is desirable to remove this protective layer between multiple copper deposition and CMP steps. Investigations on the removal of chemisorbed BTA by tetra methyl ammonium hydroxide (TMAH), hydroxylamine and organic acid have been reported [2-4]. These studies have used 0.1 wt % and lower concentration of BTA at natural pH ( < 7) or alkaline pH (11) to form adsorbed layers [3-5]. The effect of dissolved oxygen content on the adsorption of BTA and subsequent removal by TMAH is not yet reported. In this work, removal of BTA adsorbed on Cu at a pH value of ~10, which is close to the conditions that exist during barrier CMP, using a quartz crystal microbalance (QCM) technique. Since the study focussed only on the BTA removal, particles were not included in the test solution. A thin layer of Cu was first electrodeposited on Au electrodes of a quartz crystal in an electrolyte containing 10 mM CuSO4 and 100 mM H2SO4. The electrodeposition was carried out at – 150 mV vs. Ag/AgCl for 300 s. An SRS QCM-200 model quartz crystal microbalance (QCM) was used to monitor the changes in mass of the Cu coated crystal, during BTA adsorption and removal. A freshly prepared surface was used for each run. The dissolved oxygen level was controlled by bubbling either nitrogen or air before and during the experiments. During the adsorption and removal experiments, the temperature was maintained at 30 ± 0.1 °C using a circulating bath. After the completion of each experimental run, the Cu layer was stripped by maintaining the electrode at +600 mV vs.Ag/AgCl in the same solution. In the first part of investigation, a Cu sample was immersed in KOH solution of pH 10 without BTA for 200 s. After this conditioning time, the solution was switched to 1 wt% TMAH. The changes in the crystal resonance frequency were converted to changes in mass per unit area, using Sauerbrey equation as Δm = -17.67(ng/cm2/Hz) Δf and reported in Figure 1. Figure 1(a) shows that when air is bubbled in the KOH solution, the mass increases over time and this is probably due to the formation of oxides and hydroxides of Cu. Upon switching the solution to TMAH, the mass decreases and goes below the original value. This indicates that TMAH removes Cu oxides, hydroxides and Cu. When the sample is immersed in KOH solution with nitrogen bubbling, the mass remains relatively constant, but switching the solution to TMAH causes a reduction in mass. This confirms that TMAH etches bare Cu. In the second part of the investigation, a Cu sample was immersed in KOH solution of same pH but containing 0.1 wt% BTA for 200 sec. The results are presented in Figure 1 (b). The mass increases to roughly the same extent regardless of whether air or nitrogen is bubbled in the solution. When the solution was switched to aerated TMAH solution, the mass decreases rapidly indicating that BTA and possibly the oxides of Cu are removed. On the other hand, when nitrogen deaerated (nitrogen saturated) TMAH was used, the mass continues to increase suggesting that BTA is not removed. These results indicate that BTA adsorbed on oxide free Cu surface is not attacked by TMAH to the same extent as that adsorbed on oxide free surface.

Benzotriazole removal on post-Cu CMP cleaning**Project supported by the Major National Science and Technology Special Projects (No. 2009ZX02308).

This work investigates systematically the effect of FA/O II chelating agent and FA/O I surfactant in alkaline cleaning solutions on benzotriazole (BTA) removal during post-Cu CMP cleaning in GLSI under the condition of static etching. The best detergent formulation for BTA removal can be determined by optimization of the experiments of single factor and compound cleaning solution, which has been further confirmed experimentally by contact angle (CA) measurements. The resulting solution with the best formulation has been measured for the actual production line, and the results demonstrate that the obtained cleaning solution can effectively and efficiently remove BTA, CuO and abrasive SiO2 without basically causing interfacial corrosion. This work demonstrates the possibility of developing a simple, low-cost and environmentally-friendly cleaning solution to effectively solve the issues of BTA removal on post-Cu CMP cleaning in a multi-layered copper wafer.

Identification of selected microorganisms from activated sludge capable of benzothiazole and benzotriazole transformation.

Benzothiazole (BT) and benzotriazole (BTA) are present in the environment - especially in urban and industrial areas, usually as anthropogenic micropollutants. BT and BTA have been found in the municipal and industrial wastewater, rivers, soil, groundwater, sediments and sludge. The origins of those substances' presence in the environment are various industry branches (food, chemical, metallurgical, electrical), households and surface runoff from industrial areas. Increasingly strict regulations on water quality and the fact that the discussed compounds are poorly biodegradable, make them a serious problem in the environment. Considering this, it is important to look for environmentally friendly and socially acceptable ways to remove BT and BTA. The aim of this study was to identify microorganisms capable of BT and BTA transformation or/and degradation in aquatic environment. Selected microorganisms were isolated from activated sludge. The identification of microorganisms capable of BT and BTA removal was possible using molecular biology techniques (PCR, DNA sequencing). Among isolated microorganisms of activated sludge are bacteria potentially capable of BT and BTA biotransformation and/or removal. The most common bacteria capable of BT and BTA transformation were Rhodococcus sp., Enterobacter sp., Arthrobacter sp. They can grow in a medium with BT and BTA as the only carbon source. Microorganisms previously adapted to the presence of the studied substances at a concentration of 10 mg/l, showed a greater rate of growth of colonies on media than microorganisms unconditioned to the presence of such compounds. Results of the biodegradation test suggest that BT was degraded to a greater extent than BTA, 98-100% and 11-19%, respectively.

Degradation rates of benzotriazoles and benzothiazoles under UV-C irradiation and the advanced oxidation process UV/H2O2

Benzotriazoles (BTs) and benzothiazoles (BTHs) are extensively used chemicals found in a wide range of household and industrial products. They are chemically stable and are therefore ubiquitous in the aquatic environment. The present study focuses on the potential of ultraviolet (UV) irradiation, alone or in combination with hydrogen peroxide (H2O2), to remove BTs and BTHs from contaminated waters. Six compounds, three out of each chemical class, were investigated using a low-pressure mercury lamp (main emission at 254 nm) as the radiation source. Initially, the direct phototransformation kinetics and quantum yield in dilute aqueous solution was studied over the pH range of 4–12. All BTs and BTHs, except for benzothiazole, exhibited pH-dependent direct phototransformation rate constants and quantum yields in accordance to their acid−base speciation (7.1 < pKa < 8.9). The direct phototransformation quantum yields (9.0 × 10−4−3.0 × 10−2 mol einstein−1), as well as the photon fluence-based rate constants (1.2–48 m2 einstein−1) were quite low. This suggests that UV irradiation alone is not an efficient method to remove BTs and BTHs from impacted waters. The second-order rate constants for the reaction of selected BTs and BTHs with the hydroxyl radical were also determined, and found to fall in the range of 5.1–10.8 × 109 M−1 s−1, which is typical for aromatic contaminants. Finally, the removal of BTs and BTHs was measured in wastewater and river water during application of UV irradiation or the advanced oxidation process UV/H2O2. The latter process provided an efficient removal, mostly due to the effect of the hydroxyl radical, that was comparable to other aromatic aquatic contaminants, in terms of energy requirement or treatment costs.

Effect of chelating agent on benzotriazole removal during post copper chemical mechanical polishing cleaning

During the chemical mechanical polishing (CMP) process of copper, benzotriazole (BTA) is the most commonly used inhibitor, especially in acidic slurry. The post CMP cleaning process is mainly removal of slurry particles and organic residues. The presence of BTA results in a hydrophobic surface of copper, which leads to difficulty in cleaning, and BTA is the main organic residue. The BTA on the copper surface should be removed by using an effective cleaning solution. In this paper, a novel alkaline chelating agent with functionalities of BTA removal was designed for advanced post CMP cleaning solution. The alkaline chelating agent was used as main composition of cleaning agent. When the chelating agent concentration is 100–150ppm, it can effectively remove Cu–BTA. The removal of BTA is characterized by contact angle measurement, electrochemical methods and static etching rate (SER) measurement. The corrosion protection ability of the cleaning solutions was quantified by potentiodynamic polarization studies. Atomic force microscopy (AFM) measurement was used to monitor the surface quality of copper after cleaning.

Characterization of non-amine-based post-copper chemical mechanical planarization cleaning solution

Copper surfaces can become contaminated by slurry particles and organic residues during chemical mechanical planarization (CMP). Silica particles are widely used as abrasives, while benzotriazole (BTA) is widely used as corrosion inhibitor, in copper CMP slurries. The contaminated copper surface needs to be cleaned by using an effective cleaning solution. These material contaminate the copper surface during CMP and need to be removed by using an effective cleaning solution. The objectives of this work were to develop a non-amine-based alkaline cleaning solution and characterize the solution based on the benzotriazole (organic residue) removal and particle removal efficiency. Cesium hydroxide and potassium hydroxide were used as cleaning agents and ethylene glycol was used as a corrosion inhibitor. Ethylene glycol acts as a chelating agent as well in the cleaning composition. BTA removal was characterized using contact angle measurements, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy (EIS) techniques. The corrosion protection ability of the cleaning solutions was quantified by potentiodynamic polarization studies. Both potassium hydroxide- and cesium hydroxide-based solutions exhibited high BTA and silica particle removal. When compared to a potassium hydroxide based cleaning solution, cesium hydroxide based cleaning solutions were found to be more effective in terms of low surface roughness and low etch rate.