Atomic layer etching of silicon dioxide using alternating C4F8 and energetic Ar+ plasma beams

作者：Kaler Sanbir S; Lou Qiaowei; Donnelly Vincent M^*; Economou Demetre J

来源：Journal of Physics D: Applied Physics , 2017, 50(23): 234001.

DOI：10.1088/1361-6463/aa6f40

• atomic layer etching
• silicon dioxide
• argon ion beam
• fluorocarbon plasma
• fluorocarbon film
• quasi self-limiting

Atomic layer etching (ALE) of SiO2 was studied by alternating exposure of a 5 nm-thick SiO2 film on Si substrate to (1) a plasma beam emanating from a c-C4F8 inductively coupled plasma (ICP), to grow a fluorocarbon (FC) film composed mainly of CF2, and (2) an energetic (130 eV) Ar+ ion beam extracted from a separate Ar ICP. In situ x-ray photoelectron spectroscopy was used to analyze the chemical composition of the near-surface region, and to quantify the thickness of the FC and SiO2 films. A very thin (3-6 angstrom), near self-limiting thickness CF2-rich FC film was found to deposit on the SiO2 surface with exposure to continuous or pulsed power C4F8 plasma beams, under conditions that generated a large relative flux of CF2. Following this, a FC film of similar composition grew at similar to 10 times slower rate. Exposure of the thin film to the Ar+ beam led to removal of 1.9 angstrom SiO2. An estimated yield of 1.3 SiO2 molecules-per-Ar+ was found for a single ALE step. The rate of 1.9 angstrom/cycle persisted over multiple ALE cycles, but a carbon-rich residual film did build up. This film can be removed by a brief exposure to an O-2-containing plasma beam.

• 出版日期2017-6-14