Plasma-enhanced atomic layer deposition of MgO thin films with superior fluorine plasma resistance

초록

Magnesium oxide (MgO) thin films were deposited by plasma-enhanced atomic layer deposition (PE-ALD) using bis(ethylcyclopentadienyl)magnesium and O-2 plasma, and their resistance to fluorine-based plasmas was evaluated. The films exhibited high density (3.30 g cm(-)(3)), smooth surfaces, and a non-stoichiometric composition with a O/Mg ratio less than 1. Under SF6-based mixed-mode and radical-mode plasmas, MgO showed low etch rates of 3.3 and 2.6 nm min(-)(1), respectively, substantially lower than those of sputtered Y2O3 used as a reference (5.9 and 6.8 nm min(-)(1)). Depth profiling revealed shallow fluorine incorporation (similar to 3 nm) after plasma etching and limited penetration (similar to 30 nm) even under aggressive fluorine-rich conditions at 400 degrees C. Structural analyses suggested preservation of the cubic rock-salt lattice, indicating that fluorine incorporation occurred primarily through substitution at oxygen sites rather than through major phase transformation. A practical test further confirmed that the films function effectively as protective coatings for AlN ceramics in CVD heaters at elevated temperature. The superior resistance was attributed to the close-packed anion framework of MgO, together with the high density and smooth morphology inherent to the PE-ALD process. These findings establish PE-ALD MgO as a promising next-generation protective coating for plasma-facing components in semiconductor manufacturing, offering enhanced durability, reduced particle contamination, and extended component lifetimes under harsh fluorine environments.

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