The study of the selectivity of the plasma etching of functional materials with respect to the mask of a negative electron resist based on hydrogen-silsesquioxane (HSQ) has been carried out. The formation of nanostructures with sub-50 nm critical dimensions by the HSQ mask has been studied for a number of materials: single-crystal silicon, a metallic Ta layer, dielectric layers of SiO2, Al2O3, HfO2, Si3N4, as well as a porous low-k dielectric based on organosilicate glass (OSG) on silicon substrates. It has been found that HSQ resist masks can be used to manufacture prototypes of microand nanoelectronic devices with critical dimensions less than 10 nanometers using a large number of materials, including for creating structures with relatively high aspect ratios with an absolute thickness of layers of functional materials of tens of nanometers.
The process of atomic layer etching (ALE) studied for aluminum oxide and hafnium oxide. The process based on cyclic looping of stages 1) BCl3 adsorption and 2) Ar plasma activation of reaction between adsorbed molecules and surface. The approaches to perform the process on conventional plasma etching tool is considered. The self-saturation of etching process is shown and synergy is calculated. That allows estimating of process window with respect to DC bias and BCl3 dose. The processes were performed at subzero temperatures of wafer (-20°C) which enhance adsorption of BCl3 on the sample, while the walls of reactor were kept at elevated temperature (+40°C) to reduce adsorption of chlorine-containing gases on walls. Such an approach, first used in this work, made it possible to increase the reproducibility of atomic layer etching processes, despite the fact that the work was performed in a conventional tool.
Basic properties of cyclic discrete etching process for Silicon dioxide were studied in conventional plasma etching tool. Process under consideration is based on consequent deposition of fluorocarbon polymer film from plasma of C4F8, and following activation of etching reaction between surface Silicon and Fluorine contained in the film by ion flux from plasma. Deposition rate of polymer film and its etching rate were measured by means of spectral ellipsometry at different wafer temperatures. Atomic layer etching process was demonstrated with usage of Oxygen and Argon plasma. Saturation of per cycle etching rate was achieved with respect to duration of deposition step.
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