Fluorination of SiC with NF_3 by Plasma Assisted Reaction and Thermally Chemical Reaction

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 11650864
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 無機工業化学
• Research Institution: Doshisha University
• Principal Investigator: TASAKA Akimasa Doshisha University, Faculty of Engineering, Professor, 工学部, 教授 (90066275)
• Co-Investigator(Kenkyū-buntansha): INABA Minoru Kyoto University, Graduate School of Engineering, Associated Professor, 工学研究科, 助教授 (80243046)
• Project Period (FY): 1999 – 2000
• Keywords: Nitrogen Trifluoride / Silicon Carbide / Plasma Etching / Anisotropic Etching / Smoothing / Spike / Optical Emission Spectroscopy

Research Abstract

In the reactive ion etching (RIE) of SiC with NF_3, the etching rate was minimum at NF_3 pressure of 3 Pa. The surface of polished SiC specimen with treatment by RIE under conditions such as NF_3 pressure of 1 Pa and RF power of 100 W remained smooth in the scale of nm within 30 minutes, whereas it became rough in scale of 20 nm over 60 minutes. In contrast, the SiC surface became carbon-rich by RIE under NF_3 pressures higher than 3 Pa, because of the reaction of F radicals with Si on the SiC surface, and the carbon-rich part of SiC surface acted as a micromask to form spikes on it. The species such as N_2^+, N_2, and F radicals were observed in NF_3 plasma by optical emission spectroscopy. The physical etching by N_22^+ ion under lower NF_3 pressures and the chemical etching by F radicals under higher NF_3 pressures were preferentially occurred, respectively. Therefore, it is considered that the etching rate of 87 nm/min was obtained at NF_3 pressure of 0.5 Pa with RF power of 100 W, and that the depth of 2 μm was etched anisotropically with the smooth SiC surface in scale of nm. Analysis on the spike formation mechanism on the poly-SiC and SiC(111) specimens during RIE treatment revealed that the growth orientation of spike was independent of the critical face and the grain boundery on the SiC surface. The etching rates of the lattice planes such as (311) and (220) on the poly-SiC surface during Down Flow Etching (DFE) were small compared with those of (111), (200), and (222) lattice planes. On the other hand, the each etching rate for lattice planes mentioned above by sputtering with Ar^+ ion was almost equal to each other.