Department of Chemical and Biological Engineering, Colorado School of Mines , 1613 Illinois Street, Golden, Colorado 80401, United States.
Applied Physics Department, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
ACS Appl Mater Interfaces. 2017 Sep 13;9(36):31067-31075. doi: 10.1021/acsami.7b08234. Epub 2017 Aug 28.
Surface phenomena during atomic layer etching (ALE) of SiO were studied during sequential half-cycles of plasma-assisted fluorocarbon (CF) film deposition and Ar plasma activation of the CF film using in situ surface infrared spectroscopy and ellipsometry. Infrared spectra of the surface after the CF deposition half-cycle from a CF/Ar plasma show that an atomically thin mixing layer is formed between the deposited CF layer and the underlying SiO film. Etching during the Ar plasma cycle is activated by Ar bombardment of the CF layer, which results in the simultaneous removal of surface CF and the underlying SiO film. The interfacial mixing layer in ALE is atomically thin due to the low ion energy during CF deposition, which combined with an ultrathin CF layer ensures an etch rate of a few monolayers per cycle. In situ ellipsometry shows that for a ∼4 Å thick CF film, ∼3-4 Å of SiO was etched per cycle. However, during the Ar plasma half-cycle, etching proceeds beyond complete removal of the surface CF layer as F-containing radicals are slowly released into the plasma from the reactor walls. Buildup of CF on reactor walls leads to a gradual increase in the etch per cycle.
使用原位表面红外光谱和椭圆光度法研究了 SiO 原子层刻蚀（ALE）过程中，等离子体辅助氟碳（CF）薄膜沉积的连续半循环和 CF 薄膜的 Ar 等离子体激活过程中的表面现象。来自 CF/Ar 等离子体的 CF 沉积半循环后的表面红外光谱表明，在沉积的 CF 层和下面的 SiO 薄膜之间形成了原子级薄的混合层。Ar 等离子体循环期间的刻蚀是通过 CF 层的 Ar 轰击激活的，这导致表面 CF 和下面的 SiO 薄膜同时被去除。ALE 中的界面混合层很薄，因为在 CF 沉积过程中离子能量较低，再加上极薄的 CF 层，确保了每个循环的蚀刻速率为几个单层。原位椭圆光度法表明，对于约 4 Å 厚的 CF 薄膜，每个循环约蚀刻 3-4 Å 的 SiO。然而，在 Ar 等离子体半循环期间，由于从反应器壁缓慢释放到等离子体中的含 F 自由基，蚀刻会在完全去除表面 CF 层之后继续进行。CF 在反应器壁上的积累导致每个循环的蚀刻逐渐增加。
