Molecular engineering for thin-film applications: Area-selective atomic layer deposition (ALD) and molecular-atomic layer deposition (MALD).

摘要

In this dissertation, two different approaches to employ organic molecules for thin-film applications will be discussed. One is based on modification of substrates using self-assembled monolayers (SAMs) to prevent (or enhance) nucleation of atomic layer deposition (ALD). We demonstrate area-selective deposition using electron-beam lithography (EBL) patterned octadecyltrichlorosilane (OTS) SAM as a nucleation inhibition layer followed by titanium oxide (TiO2) deposition using ALD. It was found that the e-beam dosage determined the resolution of individual line width, while the accelerating voltage dominated the minimum pitch dimension of dense line patterns achievable. Eventually, using the optimal e-beam parameters, nano-line patterns with sub-30 nm resolution and 50 nm pitch were achieved. This study offers a new approach to fabricate close-packed nano-patterns for IC devices without any challenging etching process. The other approach is direct implementation of small molecules as molecular precursors to deposit self-limiting organic multi-layers which eventually allows layer-by-layer deposition like ALD. Two types of organic molecules, 7-octenytrichlorosilane (7-OTS) and hydroquinone (HQ), were applied as backbones of these multi-layers. Conventional inorganic ALD precursors, such as trimethylaluminum (TMA) and diethylzinc (DEZ), were applied as linkers between the organic layers to form organic-inorganic hybrid thin films and nano-laminates. It was found that resulting materials characteristics can be varied from insulating to semi-conducting by altering the organic component from alkane to aromatic based molecules. This methodology provides a new route to build 2D nano-sheets with unique properties.