Clean SiO₂ atomic layer etching based on physisorption of high boiling point perfluorocarbon

Area of Science:

• Materials Science
• Chemical Engineering
• Semiconductor Manufacturing

Background:

• Atomic Layer Etching (ALE) is crucial for precise semiconductor fabrication.
• Achieving high selectivity in etching different materials like SiO2 and Si3N4 remains a challenge.
• High boiling point perfluorocarbons (HBP PFCs) offer potential for selective physisorption-based etching.

Purpose of the Study:

• To evaluate an SiO2 ALE process selective to Si3N4 using HBP PFCs.
• To investigate the effect of substrate temperature on etch depth and selectivity.
• To optimize desorption conditions and address challenges in achieving anisotropic etching.

Main Methods:

• Utilized HBP PFCs (C5F8, C7F14, C6F6, C7F8) for SiO2 ALE.
• Varied substrate temperature between 20 °C and -20 °C.
• Optimized desorption time and ion bombardment energy.
• Incorporated an O2 descumming step.

Main Results:

• Lowering temperature to -20 °C significantly increased SiO2 etch depth per cycle (EPC).
• Near-infinite SiO2/Si3N4 etch selectivity was achieved.
• Anisotropic SiO2 etching was enabled by adding an O2 descumming step, preventing sidewall adsorption.

Conclusions:

• HBP PFCs enable highly selective SiO2 ALE over Si3N4.
• Temperature control and an O2 descumming step are key for anisotropic etching.
• This ALE process offers stability and reliability for semiconductor manufacturing.