Paper PS-ThM5
Improving RF Power Delivery for Pulsed Operation

Thursday, October 25, 2018, 9:20 am, Room 104A

The increased reliance on pulsed RF power delivery for manufacturing applications has greatly expanded the process window and performance capability of state-of-the-art process equipment. Power delivery under pulsed conditions rely mainly on static impedance matching conditions, delivered power compensation, or optimization algorithms that minimize power reflection due to impedance mismatch over multiple pulse cycles. On time scales within the RF pulse, power delivery can significantly impact process performance, particularly as devices approach the sub 10nm regime, as it can impact electron temperature spikes at ignition and the formation of electric potentials in and around the plasma and substrate. Options to improve power delivery efficiency within the pulse can provide mechanisms to control or mitigate these conditions for process optimization, but have practical limitations due to the ms time scale response needed to capture electrical transients under pulsed conditions.

Using standard match topologies found in pulsed RF systems, methodologies for impedance matching optimization for plasma transient control are presented. Using a simple global plasma model with equivalent circuit module for capturing power delivery circuitry and a cylindrical ICP reactor, the interaction between power coupling (specifically impedance matching) and plasma conditions during the power-on transient of a pulsed ICP system are studied. Control of electron temperature spiking at the power onset as well as rate of rise of plasma density are demonstrated using a static p-type match topology. The impact of dissipative losses in the matching network are also explored, and suggest that the standard insertion loss, or “equivalent series resistance” characterization of impedance match power dissipation may present an incomplete picture of match performance under transient conditions and that dissipation in the shunt elements play a significant role with regard to the transient plasma conditions during the power on cycle of a pulsed RF system, and may provide a pathway for improving the efficiency of power delivery during pulsed operation. Finally, a synergistic approach where match topology, source antenna design, and plasma load are considered can provide pathways for within-pulse impedance matching and power delivery control. We will present examples where this approach may enable within-pulse active tuning of pulsed RF systems with existing technologies. This work is supported by the Samsung Mechatronics R&D Center.