Paper PS-WeM1
Examination of Atomistic Etching Control of SiO₂-Si-SiO₂ Multi-Layers Stacks Using Cyclic Ar/C₄F₈ Plasma

Wednesday, October 30, 2013, 8:00 am, Room 104 C

There is great interest in establishing directional etching methods capable of atomic scale resolution for fabrication of highly scaled electronic devices. We report on controlled etching of sub-nm thick layers of silicon and SiO₂ using cyclic Ar/C₄F₈ plasma. The work was performed in an inductively coupled plasma reactor. Use of SiO₂-Si-SiO₂ multi-layers on a Si substrate enables precise examination of selectivity, etch stop, and modification using in situ ellipsometry. Controlled etching is based on deposition of a thin (<1 nm) reactive fluorocarbon (FC) layer on SiO₂-Si-SiO₂ layers using p ulsed C₄F₈ flow. Subsequent Ar⁺ ion bombardment removes the FC layer along with SiO₂ from the surface. Ar⁺ ion bombardment energies were selected so that once the FC layer had been removed, etching ceased. If ion energies are too high, significant SiO₂ etching takes place and a self-limited process cannot be achieved. The impact of deposited FC layer thickness on SiO₂ etching and etch selectivity relative to Si is examined and quantified. Additionally, x-ray photoemission spectroscopy (XPS) studies are used to investigate surface chemistry at various stages of the cyclic surface etching and will be reported. We found that chamber condition, especially inadvertent fluorocarbon deposition on the chamber walls concurrent with ultra-thin FC layer deposition on the substrate surface, can have a strong impact on the etch characteristics. The authors gratefully acknowledge financial support from National Science Foundation award CBET-1134273.