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P: Plasmaphysik

P 10: Poster II

P 10.45: Poster

Dienstag, 18. März 2003, 17:30–19:15, Foyer

Evolution of Si roughness in a Ar⁺/XeF₂ beam etching experiment — •Alquin Stevens and Herman Beijerinck — Eindhoven University of Technology

Plasma processing is the single most important semiconductor device manufacturing technique. The need for smaller feature sizes in ICs but also the high aspect ratios required in a new field of research, photonic bandgap materials, introduces a new challenge. The surface roughness caused by the etch process becomes a critical parameter regarding the quality of these devices. Ellipsometry has been applied to study the fundamentals of the etch process of silicon in a multiple-beam etching experiment by well-defined beams of Ar⁺ ions and XeF₂ etch precursor gas. The ellipsometric properties of Si during spontaneous etching by XeF₂ and ion-assisted etching have revealed basic information regarding the reaction layer dynamics and composition. Spontaneous etching by XeF₂ is found to cause a rough reaction layer up to 25 nm thick that can be thought of as a rough and partially fluorinated silicon (Si_xF_y) surface. Ion-assisted etching is a combination of sputtering by Ar⁺ ions and etching by XeF₂, which resembles the actual etch process in plasmas. The reaction layer in this case is a Bruggemann mixture of rough a-Si and Si_xF_y layer of less than 1 nm on top of a thicker a-Si layer due to the keV ion bombardment. In order to obtain more detailed information regarding the surface layer composition from ellipsometry measurements and simulations, the surface roughness has been verified by atomic force microscopy.