Solid State Phenomena Vol. 187

Abstract: Current work describes development, testing and verification of a single wafer megasonic cleaning method utilizing a transducer design that meets the extreme particle neutrality, Particle Removal Efficiency (PRE), and repeatability requirements of production scale wafer bonding and other applications requiring extremely low particle levels.

Abstract: Water purity is not taken for granted in the Semiconductor Industry. Ultra high purity water (UPW) is analyzed continuously in-line for particles and resistivity. Routine samples are automatically taken for total organic carbon (TOC), boron, silica and dissolved oxygen. Less routine analyses, such as metals, are done off-line. Metal content of UPW water is well below the detection limits of ICP-MS even with a pre-concentration step. As a result, metals content may vary in the water without being detected. These variations may affect device performance and yield while the root cause may go undetected.

Abstract: Mask cleaning remains as one of the major challenges in EUV lithography. Without the use of traditional pellicles, EUV masks demand high purity and effective but mild cleaning techniques for protection from defects. Recently, trends towards dilute chemistries and progress in megasonic cleaning have brought renewed interest in gasified DI water. In this paper, we describe the design and development of a point-of-use functional water treatment system, specifically for advanced mask cleaning applications. The system comprises two modules the purification module and the gasification module. The purification module provides treatment features including TOC reduction, sub-micron particle retention, and degassing, as well as thermal and pressure control. The gasification module employs micro-porous PFA membrane contacting technology to deliver ultra clean bubble-free DI water with various gases (O3, N2, H2, CO2, NH3, etc.) over a wide concentration range. The treatment system is also equipped with closed loop process control to maintain and regulate process temperature, pressure and dissolved gas concentration. This active control feature allows precise control and minimal process variations.

Abstract: Metallic contamination on silicon surfaces has a detrimental impact on ULSI device performance and yield. Surface metal impurities degrade gate oxide integrity, while metal impurities dissolved in silicon provide recombination centers, resulting in junction leakage. Surface metal impurities penetrate silicon by the collision with dopant during ion implantation and are also diffused in silicon by subsequent annealing [. If metal impurities are present around junctions, they can cause junction leakage. In order to avoid the junction leakage, metal impurities must be away from junction. It was reported that iron can be gettered in the region of dopants implanted at high energy [. On the other hand, little work has been reported on the behavior of metal impurities in shallow junction. In this study, the gettering behavior of various transition metals in low-energy and high-dose ion-implanted silicon has been demonstrated.

Abstract: Small amounts (~10¹⁰ atms of Fe) of metal-ion contamination remains on local spots on the backside of the wafer. During a thermal process step, 30% of this contamination is transferred to the front side of the wafer where it causes in some specific cases substrate degradation. The source of the contamination is stainless-steel wafer pins that are used in wafer handling on for example litho tracks. This contamination is printed onto the backside wafer surface where two cleaning steps were not able to remove it. Figure 1. Wafer test: 3 clusters of devices failing due to the tripod signal.

Abstract: The European Integrated Activity of Excellence and Networking for nanoand Micro-Electronics Analysis (ANNA), www.ANNA-i3.net, has addressed the further development and assessment of methodologies for the detection of low concentration inorganic contaminants on and in silicon as well as for novel materials. The comparison of various analytical techniques available to the ANNA partners helped to identify the degree of comparableness of results revealed at different installations. The assessment of improved methodologies as well as the reliability of quantification and calibration procedures of specific analytical techniques such as Total-Reflection X-ray Fluorescence (TXRF) analysis has been of particular interest.

Abstract: Reference samples were produced for development, benchmarking and comparison of analytical techniques based on mass spectroscopy as TD-GCMS and TOF-SIMS and x-ray analysis as TXRF-NEXAFS. Organic contaminants representing plasticizers, disinfectants and flame retardants were chosen. The contaminants were selected with respect to reliable detection using the above analytical techniques. The stability of the reference samples produced with dethylphtalate, triclosane, and tetrabrombisphenol A on silicon stripes or wafers with a diameter of 200 mm was found to be approx. 10 days. The comparison of the techniques showed that the mass spectroscopy methods allowed reliable qualification of organic surface contamination. TD-GCMS quantifies and identifies the volatile organic compounds whereas TXRF quantifies the carbon contamination, especially the non-volatile, on sample surfaces.

Abstract: The effectiveness of a FOUP (Front Opening Unified Pod) conditioning test bench was tested with respect to the reduction of outgassing materials from FOUP materials and cleanroom compatibility. The equipment uses vacuum and heat to reduce volatile organic compounds from construction material and wafers. Five different analysis methods were used to asses the performance of the equipment with respect to organic, ionic and metal contamination. The experiments showed that the use of heat and vacuum has a positive effect on the organic contamination from FOUPs, and that the equipment is suitable for semiconductor applications in cleanroom environments.

Abstract: The surface concentrations of organic compounds in a three-component (isopropanol-diethylphthalate-octanol) system were in situ measured using a quartz crystal microbalance. Additionally, the surface concentrations were calculated on the basis of the rate theory, to show that the surface concentration of organic compound was influenced by the other organic compounds. The net situation of airborne organic contamination may change, even when the total amount of organic compounds adsorbed on silicon surface seems to be in a steady state.

Abstract: A pH neutral formulation 3x to perform the in-line cleaning of resists/topcoats contaminated immersion assembly efficiently and effectively has been developed. It is environmentally benign with no halides, no individual component having a flash point above 38°C or known to cause cancer, birth defects or other reproductive harm.