Understanding and controlling the role of ions during plasma-enhanced ALD and ALE*

As semiconductor devices continue to push the boundaries of traditional process technologies, atomic-scale processing methods are increasingly vital. Among these methods, atomic layer deposition (ALD) has emerged as a critical technique for creating ultrathin films on the demanding 3D geometries involved. Concurrently, atomic layer etching (ALE) processes are being integrated into state-of-the-art semiconductor manufacturing flows. ALE typically employs plasma-based techniques to achieve anisotropic etching, while ALD frequently incorporates plasma enhancement to reach the required results.

This contribution focuses on the significance of ions in plasma-enhanced ALD and ALE. Most prominently, it addresses the ion-surface interaction in plasma-enhanced ALD, an aspect that has not been widely considered to date. Topics that will be discussed are: (1) the role of low energy ions (< 30 eV) on the ALD process for, e.g., grounded substrates; (2) the tuning of the ion energy (up to 300 eV) during plasma-enhanced by rf substrate biasing and the beneficial and detrimental effects that can be achieved by highly energetic ions; and (3) the implementation of tailored-waveform biasing for reaching very narrow ion energy distributions (full-width half-maximum < 10 eV) and hence very accurately controlled surface reactions during ALD and ALE.