27 August 1999 Silicide sheet resistivity and metal film stress measurements as emissivity-independent techniques for RTP temperature monitoring
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Abstract
Transfer of semiconductor process steps from one Rapid Thermal Processing (RTP) system to another may cause severe problems due to non-matching pyrometers. Resulting temperature differences of alternatively used RTP machines despite identical process recipes can lead to process and yield problems. In this study we present two emissivity-independent methods for comparing and adjusting wafer temperatures of different RTP systems, one by monitoring titanium silicide (TiSix) sheet resistivities and the other by titanium film stress measurements. We perform sheet resistivity measurements on various titanium sputtered silicon wafers. TiSix formation is induced by RTP on an AST SHS 1000 and an AG HEATPULSE 4100 system in the temperature range between 680 degrees Celsius and 800 degrees Celsius, which is of particular interest for RTP nitridation of titanium as a diffusion barrier. Prior to resistivity measurement the unreacted titanium is selectively etched. We show how temperature differences of the two RTP systems can be deduced from different sheet resistivity values of AST and AG wafers processed at the same nominal temperatures as read on the respective pyrometer scales. Comparison of mechanical stress imposed on the wafers by titanium deposition and the subsequent RTP induced silicidation yield exactly the same temperature difference. Both methods offer fast, reliable and sensitive tools to observe and correct for potential temperature differences of different RTP systems and therefore comprise efficient means to avoid process and yield problems and enhance throughput.
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Ingrid Jonak-Auer, Ingrid Jonak-Auer, } "Silicide sheet resistivity and metal film stress measurements as emissivity-independent techniques for RTP temperature monitoring", Proc. SPIE 3884, In-Line Methods and Monitors for Process and Yield Improvement, (27 August 1999); doi: 10.1117/12.361338; https://doi.org/10.1117/12.361338
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