The etch characteristics of HfO 2 by atomic-layer etching ͑ALET͒ were investigated using a BCl 3 /Ar neutral beam. The effect of ALET on surface modification and etch-depth control was also examined. Self-limited etching of HfO 2 could be obtained using BCl 3 ALET. This was attributed to the absorption of BCl 3 by the Langmuir isotherm during the absorption stage and the vaporization of hafnium-chlorides/boron oxychlorides formed on the surface during the desorption stage. In addition, the surface composition of HfO 2 was not altered by etching during ALET.The downscaling of metal-oxide-semiconductor field-effect transistors ͑MOSFETs͒ has created the need for high-dielectric-constant ͑k͒ materials to replace SiO 2 for reducing the gate-leakage current while maintaining the gate-dielectric capacitance. Among the various high-k materials, hafnium oxide ͑HfO 2 ͒ is a potential material in next-generation MOSFETs due to its high-dielectric constant ͑25-30͒, wide bandgap, low leakage current, and superior thermal stability. 1,2 In order to apply HfO 2 to next-generation MOSFET devices, HfO 2 films should be patterned by dry etching, because the wet etching of HfO 2 has several disadvantages such as difficulty in controlling the etch rate, severe undercut, etc. Therefore, there have been many studies on the dry etching of HfO 2 using halogen-based plasma etching for applications to MOSFET devices. A precise etch rate is required in the plasma etching for HfO 2 instead of a high etch rate due to the low thickness of the material. Moreover, an extremely high etch selectivity over the underlayer material is required. In addition, the damage on the etched surface is intolerable. However, these conventional plasma-etching processes tend to physically damage the surface of the devices by creating surface defects, including structural disruption, an intermixing layer, or stoichiometry modification, and increasing surface roughness, due to use of energetic reactive ions to achieve vertical etch profiles. 3,4 In addition, these halogen-based plasma etchings showed finite etch selectivity between HfO 2 and the underlying materials. 5,6 These problems decrease the device performance.Atomic-layer etching ͑ALET͒ may be the most suitable method for etching HfO 2 in next-generation MOSFET devices because it may etch HfO 2 with no physical damage and with atomic-scale etch controllability. Generally, ALET is a cyclic process that consists of four sequential steps: ͑i͒ adsorption of reactant molecules on the surface, ͑ii͒ evacuation of the remaining reactant molecules, ͑iii͒ Ar + ion-beam irradiation to the reactant adsorbed surface for the desorption of chemisorbed species, and ͑iv͒ evacuation of the etch products. 7,8 However, during step ͑iii͒ with Ar + beam irradiation, the device can be damaged electrically due to the charged particles, such as positive ions generated in the plasma.In this article, ALET of HfO 2 was carried out using BCl 3 adsorption, followed by Ar neutral-beam irradiation instead of Ar + ionbeam irradiation to a...
X-ray photoelectron spectroscopy was used to determine the level of surface fluorination damage of Ge2Sb2Te5 (GST) etched by fluorocarbon gases at different F/C ratios. When blank GST was etched, the gas with a higher F/C ratio produced a thinner C–F polymer on the etched surface but fluorinated Ge, Sb, and Te compounds were observed in the remaining GST. When the sidewall of the etched GST features was investigated, a thicker fluorinated layer was observed on the GST sidewall etched by the higher F/C ratio gas, indicating more fluorination due to the difficulty in preventing F diffusion into the GST through the thinner C–F layer.
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