In situ particle monitors: a new process control technology for Digital Semiconductor's Fab 6

As part of the start-up strategy for Digital Semiconductor's Fab 6 facility, a project was implemented to use a new technology for monitoring particle levels in vacuum process tools. The current practice of running witness wafers to gauge surface defects has several drawbacks, including wafers cost and reduction of process tool throughput. A development project team was put into place to install, analyze, and implement vacuum In Situ Particle Monitors (ISPM) into Digital Semiconductor's Fab 6 manufacturing process. ISPM process sensors provide particle count information from inside a process tool in a real-time manner. ISPM sensors use light scattering techniques to detect particle levels within the vacuum system of a semiconductor process tool. By monitoring particle levels continuously, the ISPMs can quickly signal out of specification process events and monitor routine operations without impacting tool availability. This paper discusses the application of ISPM sensors onto both etch and deposition process tools. Specifically, data for an oxide etch process tool is presented. The ISPM data has shown correlation to tool conditions and been used to identify various process problems. Reduction of process monitor wafers has been achieved for the oxide etch process and is fully implemented in manufacturing. A crude ROI estimate shows a payback period of approximately 50 weeks. In all, the ISPM program in Fab 6 has demonstrated good results and is targeting other process applications.