Solid State Phenomena Vol. 314

Abstract: Organic optoelectronic devices such as light-emitting diodes and solar cells present unique challenges for surface cleaning and preparation because of their large area and the ‘soft’, thin film nature of the materials involved. This paper gives an introduction to this class of semiconductor devices and covers a recent example of how surface cleaning impacts the long-term reliability of organic light-emitting diodes being commercialized for solid-state lighting.

Abstract: Metallic contamination is a major challenge in multiple semiconductor processes, including photolithography and wet etch and cleans (WEC). Though there are several contributors to metallic contamination, significant efforts have focused on improving the incoming quality of process chemicals, especially commodity chemicals. Another key contributor to on-wafer metallic contamination is water (H2O), which is used to dilute most aqueous chemicals. Single Particle Inductively Coupled Plasma Mass Spectroscopy (SP-ICP-MS), a technique relying on time-based resolution of pulses generated during a standard ICP-MS analysis, is used to aid the understanding of metal particle contamination in water and process chemicals.In this paper, we studied water and 30% Hydrogen Peroxide (H2O2), two of the most widely used chemicals across all WEC processes. We used a high purity grade of 30% H2O2, further diluted to a typical use concentration (5% by volume) using two grades of Deionized Water (unfiltered and filtered) where the concentration of metallic particles was the key variable. The metals studied included Iron (Fe), Chromium (Cr), Zinc (Zn), Titanium (Ti), Nickel (Ni) and Aluminum (Al), representing some of the most commonly observed metallic contaminants in H2O2 and water. After analyzing the distribution of contaminants in the chemicals, filters were introduced into the system to observe the impact of filtration on metal removal. The importance of filtration on the overall quality of the diluted process chemical was demonstrated by using a Polysulfone (PS) membrane to filter the lower grade Deionized Water (DIW).

Abstract: Gas Exchange Device (GED) was integrated with Inductively Coupled Plasma Mass Spectrometry(ICP-MS) for analysis of metallic particles in NH3 and HCl gases used in semiconductormanufacturing. A single pg/kg (ppq) level of metallic impurities in these gases could be determinedwithout any sample preparation.

Abstract: Technological control over ultra-trace level contaminants is important for semiconductor development. Despite technological developments, defects remain in the single wafer wet cleaning process. In this paper, the source of the contamination is explained via trace analytical methods. Fluorine resin materials of polytetrafluoroethylene (PTFE) and ethylene tetrafluoroethylene (ETFE) are commonly used in semiconductor equipment. Isopropyl alcohol (IPA) oxidation reactions occur at high temperature below the boiling point due to impurities. IPA changed to different alcohol forms from gas chromatography (GCMS) analysis. The oxygen concentration in the X-ray photoelectron spectroscopy (XPS) results increased and formed new bonds in IPA with fluorine resin. These reactions confirmed that cations were a catalyst from the time-of-flight secondary ion mass spectrometry (TOF-SIMS) results. Representative ions were Fe+, K+, and Na+ with different concentrations for each material.

Abstract: One of the critical process steps in the assembly of integrated circuits is the making of the connection between the silicon chip and the outside world. This is done by a thermo-sonic welding process of sometimes more than 800 copper wires to the aluminum bond pads. The Al-Cu intermetallic compound formed during this process is sensitive for trace amount of chloride from the environment. It is found that Cl-containing microplastics are the source of this chloride and further analyzing these particles helps to identify the origin of these particles.

Abstract: 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.

Abstract: The focus of the study was to understand the behavior of airborne molecular contaminations (AMC) within the 300 mm wafer containers called front-opening unified pods (FOUPs) in a high-volume fabrication facility for power semiconductors of Infineon Technologies Dresden. A main goal was to implement new concepts and strategies to prevent the different power semiconductors from any yield losses driven by AMC. It could be shown, that there is a strong dependency of the concentration and the type of the determined contaminations on the investigated process steps.

Abstract: The steam oxidation of SiGe shows a transition from Si-like to Ge-like oxidation behavior depending on Ge concentration and oxidation temperature. Ge-like oxidation is described by the generation of oxygen vacancies (VO) at the interface between the oxide and SiGe virtual substrate. [1] Due to the different oxidation behavior, the presence of a Ge-oxide-free interfacial layer (IL) can suppress SiGe oxidation. [2] Here we show how a passivating interfacial layer can be grown using low-pressure oxidation and highlight the importance of SiGe surface preparation prior to low-pressure oxidation.

Abstract: Thin organic self-assembled monolayer films are used to promote adhesion and seal the pores of metal oxides as well as direct the deposition of layers on patterned surfaces. Defects occur as the self-assembled monolayer forms, and the number and type of defects depend on surface preparation, deposition solvent, temperature, time and other parameters. Particles commonly deposit during organosilane self-assembly on metal oxide surfaces. The particles are defects because they are prone to react in subsequent processing, which may not be desirable if the organosilane serves as a pore sealant or passivation layer. Cleaning the organosilane by solvent extraction to remove non-polar agglomerates followed by an aqueous mixture of ammonium hydroxide and hydrogen peroxide, which is Standard Clean 1, a common particle removal step for silicon surfaces, produced monolayers with few agglomerates based on atomic force microscopy without etching the layer. The combined cleaning sequence contained fewer particles than separate cleaning steps, showing that the cleans removed particles with different compositions. The thickness and contact angle of cleaned monolayers was comparable to those made using a costlier solvent.