Ph.D Thesis


Ph.D StudentIlia Platzman
SubjectSelf-Assembly of Organic Thin Films as Interactive, Bridging
and Conductive Layers for Nanoelectronic
Applications
DepartmentDepartment of Chemical Engineering
Supervisors Prof. Tannenbaum Rina
Prof. Haick Hossam
Full Thesis textFull thesis text - English Version


Abstract

State-of-the-art surface mount technology (SMT) involves the use of the stencil-printing process, in which a thin layer of solder-paste is deposited on copper (Cu) pads, followed by positioning of the components onto their designated places. While this technology can be applied successfully in the macro- and micro-regimes, it fails when either the lateral and/or horizontal dimensions of the devices approach the nanometric scale, because the placement accuracy would be seriously affected by height, area or volume of the solder-paste bricks. Moreover, the formation of relatively rough Cu surfaces (~5 nm roughness) and Cu-oxide layers upon exposure to air will hinder the reliability of this application. Hence, the goal of this research was to develop and study a "bottom up" design of a conductive adhesive layer through the use of molecules with "tailored" properties and functions. Each of these molecules would have two functional groups (X) with an overall structure of the type X-(R)-X, where R is a p-conjugated organic group. These molecules could form “smart,” selective, self-assembled monolayer (SAM) adhesives, which could essentially operate at the molecular/nanoscale level, and could form protective and conductive bridges between pads and components.

            We initially conducted a qualitative and quantitative investigation of the oxidation behaviour of polycrystalline copper (Cu) thin films upon exposure to ambient air conditions for long periods (on the order of several months). Based on the results, we proposed an overall Cu oxidation mechanism, and observed that the different stages of oxide growth mechanism were found to be strongly dependent on the microstructure and morphology of the Cu surfaces. In order to improve the Cu surface stability for long periods against oxidation and corrosion, there is a need to improve the surface conditions of the deposited Cu surfaces. Hence, we proposed a simple way to prepare high-quality, defect free ultra-smooth polycrystalline Cu surfaces by means of simple annealing of Cu thin film. Morphological properties, oxidation behaviour, and coating applications by SAM on annealed Cu surfaces were also examined. The conductive properties of molecularly modified surfaces were characterized by developing a novel parallel plate junction (PPJ) method. The results have shown that the tunnelling was the dominant mechanism of charge transport.

            Our findings imply that the SAMs used in this study can serve as protective coatings for annealed Cu and, furthermore, as conductive molecular bridges that can potentially bind circuital pads/components in a selective manner in micro- and nano-electronic applications.