Process control approaches using real time harmonic impedance measurements

As semiconductor processing requirements evolve to meet the demands of decreasing geometries, new approaches in plasma metrology will be needed to monitor the performance of the equipment and its processes. This performance has traditionally been monitored via Statistical Process Control (SPC) on output parameters such as etch rate and uniformity. These measurements are typically taken on single film wafers which may not be an accurate representation of product. With emerging, non-intrusive, RF sensor technology, equipment and process engineers have access to signals which provide better resolution in determining the health of the equipment. This paper will discuss the relationships between machine settings, real-time RF sensor measurements and the etch rate and uniformity metrics typically used in machine/process qualifications. Run to run control algorithms using the RF sensor measurements will also be presented. Finally, the implications of using RF sensor measurements to provide real-time closed loop control of machine settings will be discussed.