Misregistration metrology tool matching in a one-megabit production environment

Misregistration control in a large DRAM production facility requires careful selection, matching, and control of metrology equipment. Total metrology tool measurement error tolerances in advanced DRAM manufacturing are fast approaching 15 nm and below. The sources of error must be minimized and maintained at acceptable levels in order to accurately and precisely monitor the process. In a large production facility with many metrology tools, an additional source of error must be considered besides single tool precision and accuracy; this is the variation in measurement from tool to tool, or machine matching. This paper presents a method for calibrating multiple metrology tools in a fabrication facility that does not use one tool as a `golden standard,' but rather calibrates each machine for its own induced error. A procedure is then introduced that determines a matching error value for each machine based on a mean deviation from what is considered the correct value determined by all tools in the fabrication. This error is expressed as a mean and precision (3 sigma) value and is used to characterize each tool for its `matching error.' Data are then available so that as new machines are introduced into the fabrication they may be characterized for matching against the current tools without a complete investigation requiring a great amount of downtime for the current tools. Results are shown from an investigation using three KLA 5000 series metrology tools with matching measured over five layers (oxide, poly, nitride, WSi, and metal) using multiple wafers for each layer. A matching error is calculated for each tool for each layer. A method for determining total tool error for all machines in the fabrication is described.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.