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Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.
Ryan J Gasvoda1, Alex W van de Steeg2, Ranadeep Bhowmick3
1Department of Chemical and Biological Engineering, Colorado School of Mines , 1613 Illinois Street, Golden, Colorado 80401, United States.
ACS Applied Materials & Interfaces
|August 11, 2017
Summary
Atomic layer etching (ALE) of silicon dioxide (SiO2) involves sequential deposition and Ar plasma activation of fluorocarbon (CFx) films. This process forms an atomically thin mixing layer, enabling precise etching at a few monolayers per cycle.
Area of Science:
- Materials Science
- Plasma Physics
- Surface Chemistry
Background:
- Atomic Layer Etching (ALE) is crucial for precise semiconductor fabrication.
- Understanding surface phenomena in ALE is key to controlling etch rates and selectivity.
- Plasma-assisted deposition and activation are common steps in ALE processes.
Purpose of the Study:
- To investigate the surface phenomena during atomic layer etching (ALE) of silicon dioxide (SiO2).
- To elucidate the role of fluorocarbon (CFx) film deposition and Ar plasma activation in the ALE process.
- To understand the formation and impact of interfacial layers on etch rates.
Main Methods:
- In situ surface infrared spectroscopy to analyze surface chemistry.
- Ellipsometry to measure film thickness and etch depth.
- Sequential plasma-assisted CFx deposition and Ar plasma activation cycles.
Main Results:
- An atomically thin mixing layer forms between CFx and SiO2 during deposition.
- Ar+ bombardment removes CFx and SiO2, with etch rates of a few monolayers per cycle.
- Etching extends beyond CFx removal due to radical release, leading to etch rate increase over time.
Conclusions:
- The atomically thin interfacial mixing layer is critical for achieving monolayer-level control in SiO2 ALE.
- Fluorocarbon radical release from reactor walls influences the overall etch process and etch rate.
- Optimizing CFx deposition and Ar plasma conditions is essential for stable and predictable ALE of SiO2.
