High-throughput SiN ALE: surface reaction and ion-induced damage generation mechanisms

Abstract

Atomic layer etching (ALE) has been practically implemented as a technique to achieve atomic/molecular level control. However, its main disadvantage is that it involves long process time. The surface reaction mechanism required to realize high-throughput (HT) SiN ALE was investigated. CH3F/Ar plasma was applied in the adsorption step, while Ar plasma was used in the desorption step. Finally, an additional O2 ashing step was applied. To reduce process time, HT ALE was performed at high ion energy, and the amount of etched SiN was evaluated. HT SiN ALE conducted at short time intervals and at high ion energy underwent a quasi-self-limited reaction, which is a characteristic of ALE, and the process time decreased. However, HT ALE using CH3F in the adsorption step caused an increase in the extent of the damage. Thus, the use of C4F8 (without H) can significantly reduce damage even under HT ALE conditions.