Advanced Process Control (APC) for Selective EPI process in 300mm Fab

Abstract

An advanced in-line process controller, which combines 4 new features with the traditional statistical process control (SPC) feedback control, has been developed and applied to the selective epitaxial growth of phosphorous doped Si (Si:P) process in a 300mm Fab to improve incoming lot to lot variation, Cp, Cpk, and tool throughput. An automatic pilot split feature has been added to the controller by integrating Real Time Dispatching (RTD) to replace manual splitting for improved throughput and elimination of human errors; a damping factor has also been introduced to further adjust the feedback sensitivity as an extra knob to accommodate incoming upstream variations. As the deposited EPI layer thickness is also affected by the patterned wafer loading effect, a product dependent APC control group has been created and embedded within the controller to adjust the deposition time based on the Si open ratio and/or reticle pattern density. Finally, a phantom target concept has been introduced and applied for fine tuning of the fleet thickness mean down to the Ångstrom scale to overcome the slow drifting of deposition rate due to tool aging. The application of this new controller resulted in an improved Cp and Cpk of 15% for the key inline parameter and an 8% capacity increase while also reducing the wafer OOC (out of control) rate and scrap event rate.