Invited Paper AP+2D+EM+PS+TF-MoM10
Surface Chemistry during Plasma-Assisted ALE: What Can We Learn from ALD?

Monday, October 21, 2019, 11:20 am, Room A214

Due to ever decreasing device dimensions and the introduction of 3D device architectures, it is challenging to operate within a narrow processing window using conventional plasma etching. One method to address the demands of the next-generation of devices is atomic layer etching (ALE) which provides high fidelity, selectivity, and directionality, and layer-by-layer removal. Plasma-assisted ALE has been extensively studied for a variety of materials, including Al₂O₃, HfO₂, Si, and Si‑based dielectrics. Plasma-assisted ALE of SiO₂ or SiN_x typically uses two sequential steps in a cyclic fashion: CF_x deposition from a C₄F₈/Ar plasma followed by an Ar plasma activation step. However, the surface chemistry during plasma ALE is not well understood. In this study, we used in situ attenuated total reflection Fourier transform infrared (ATR‑FTIR) spectroscopy and in situ four-wavelength ellipsometry during ALE to monitor the surface reactions, film composition, as well as the net film thickness. Similar to area-selective atomic layer deposition, we show that surface functionalization prior to ALE can be used to alter the etch per cycle. Using this methodology, I will discuss how selective functionalization of SiO₂ or SiN_x can be used to alter the selectivity during plasma-assisted ALE.