Photocatalytic degradation of acetaminophen in water via ultraviolet light and titanium dioxide thin films part II: chemical and kinetic aspects

Among the large family of emergent pharmaceutical contaminants, we find acetaminophen (ACE) that critically needs to be removed from wastewater. Advanced Oxidation Process (AOP) have proven effective in the degradation of large molecular contaminants from water. To the best of our knowledge this is the first study reported on the degradation of ACE based on immobilized TiO2 thin films. In an effort to increase the understanding of the efficiency of the degradation process, an in-depth investigation of the effects of the structure, i.e., coating layers and the amount of surface, i.e., number of coated slides used, is needed. Transparent, anatase-form TiO2 thin films were prepared via the sol-gel method (Rawal, S., S. Buer, J. R. Sanders, and P. E. Arce. 2021. “Photocatalytic Degradation of Acetaminophen from Water Solutions Via Thin Films. Part I: Synthesis and Characterization of TiO2 Thin Films.” International Journal of Reactor Engineering [Accepted]) and deposited onto glass microscope slides using a novel spraying technique, with coatings ranging from one to 10 layers. This contribution summarizes the effect of several key factors including initial concentration of the ACE, the number of coating layers (6, 8, and 10) on the glass slides and the number (4 and 6) of slides on the degradation levels for three selected media, e.g., acid, neutral and base. Comparisons studies, supported by statistical analysis between two different sets (4 and 6) of slides with discussion of potential physical-chemical reasons behind the behaviors are reported. Finally, global, first order kinetic rate constants are also reported for the different conditions used in the investigation. Although further research would be needed, in general the results are promising for the potential degradation of ACE in continuous flow systems by using immobilized TiO2 on surfaces as thin films.

Experimental Wafer Carrier Contamination Analysis and Monitoring in Fully Automated 300 mm Power Production Lines

Contamination control is essential in semiconductor manufacturing to ensure high yield and product quality. Latest power electronic devices are manufactured in fully automated 300 mm production lines, which utilize closed wafer containers called Front Opening Unified Pods (FOUPs). It has been observed, that FOUPs capture airborne molecular contaminants (AMC) outgassing from processed wafers or being transferred from the equipment minienvironment. These AMC might be released afterwards and can lead to defects causing yield and/or reliability issues of the power devices. Specific FOUP cleaning and exchange rules are already being utilized in the fab. But so far, these rules are not validated or adapted by actual concentration values in the FOUPs. In this paper, contamination levels in FOUPs are investigated to identify the sources of different AMC. The contamination data is analysed together with FOUP logistics data in order to establish an optimized FOUP management strategy. In the first part, in-line carrier contamination control is explained and a general overview of the AMC detected is given. In the second part, the data-driven FOUP-monitoring is described using the example of the root cause analysis of hydrofluoric acid (HF) contamination.

Transport Coefficients of Ammonia Gas in Thermoplastic Polymers and Nanocomposites Used for Microelectronic Substrates Containers

Polymeric plastic boxes (named Front Opening Unified Pods (FOUP)) were widely used in semiconductor manufacture to maintain the cleanliness of processed wafer substrates in a controlled mini-environment. Polymeric materials, however, are able to sorb airborne molecular contaminants (AMCs) and subsequently to outgas the sorbed AMCs backward to FOUP’s atmosphere, causing the transfer of AMCs to sensitive stored substrates, named cross-contamination. As a type of AMCs, the NH3 cross-contamination could cause a severe yield loss to integrated circuits (crystals (haze), resist-development defects (T-topping) or metallic corrosion). Experiments were carried out to establish the NH3 sorption and desorption kinetics in polyetherimide (PEI), Entegris Barrier Material (EBM)), and EBM/carbon nanotubes (EBMCNT) at NH3 concentration of 800-ppbv, 21°C, and relative humidity of 40%. The transport coefficients i.e. solubility and diffusivity (DNH3 and SNH3) were then determined. The study on NH3 provides an additional guideline to choose the best raw materials for FOUP formulation in taking into account the potential cross-contamination of AMCs. Numerical simulation model based on obtained solubility and diffusivity values was conducted to demonstrate NH3 concentration profiles in FOUP walls during contamination and FOUP decontamination, which are inaccessible by conventional experiments.

Diffusion and Solubility of Common Microelectronic Airborne Molecular Contaminants into PEI Thin Polymer Membranes and its Related Contamination Control Applications

Sorption and outgassing mechanisms of corrosive gases in relation with wafers lost yield due to polymer container Front Opening Unified Pod (FOUP), is crucial information to understand the cross contamination between FOUP and wafers. This occurs when FOUPs (made in polymers) outgas contaminants into the wafer surrounding minienvironment. Gas sorption is governed by surface adsorption, followed by diffusion and solubility and then, permeability appears as a key parameter to understanding these cross contamination phenomena. In this work, we present the transport coefficients obtained for gaseous HF and HCl at cleanroom conditions (Patm, 21 ± 2°C & 40% RH) at two different HX concentrations using the sorption kinetic method, based on Fick’s law, for thin films (≈50μm) of PEI. Finally, we establish the relationship between the sorption parameters of a polymer thin film and the potential contamination transfer from a FOUP whose main polymer material is similar.

ALD-Grown Metal Oxide Films for the Detection of Molecular Contaminants on Spacecraft

Mitigating molecular contamination during the assembly, integration, and testing of space systems requires quantitative and qualitative methods to detect the presence of molecular films on sensitive surfaces. Atomic layer deposition (ALD) is a self-limiting deposit of a variety of films layer by layer in the vapor phase on multiple types of substrates. The controlled layer-by-layer deposition enables the user to change orientation, morphology, and grain size in films, which directly impacts optical and electronic responses. In this study, the authors demonstrate the ability to use ALD-grown metal oxide thin films coupled with a Raman spectrometer to provide early detection of molecular films on witness surfaces during the assembly, integration, and testing of space flight hardware.