Effect of pulse phase lag in the dual synchronized pulsed capacitive coupled plasma on the etch characteristics of SiO2 by using a C4F8/Ar/O2 gas mixture

The characteristics of a synchronized pulse plasma using 60 MHz radio frequency as a source power and 2 MHz radio frequency as a bias power were investigated for the etching of SiO2 masked with an amorphous carbon layer (ACL) in a C4F8/Ar/O2 gas mixture. Especially, the effects of the pulse phase lag of the synchronized dual-frequency pulsing between source power and bias power on the characteristics of the plasma and SiO2 etching were investigated. The results showed that the etch rates of SiO2 was the highest and the etch profile was the most anisotropic when the pulse phase lag between the source power and bias power was 0° in the synchronized pulse plasma. Increasing the phase lag to 180° decreased the etch rates and degraded the etch anisotropy. The change in etch characteristics as a function of pulse phase lag was believed to be related to the difference in gas dissociation and fluorocarbon passivation caused by the variations in electron temperatures during the source pulse off-time.