Initial Stages of Thermally and Hot-Wire Assisted CVD Copper on SiLK® and LTO Substrates Activated with Mercaptopropyl Triethoxysilane Self-Assembled Monolayers

Abstract

The initial stages of thermal and hot-wire assisted CVD (HWCVD) of copper were studied with atomic force and scanning electron microscopy. The substrates used were Si (100) wafers covered either with low-temperature silicon oxide (LTO) or with SiLK® on which self-assembled monolayers (SAMs) of (3-Mercaptopropyl)trimethoxysilane (MPTMS) were applied. CupraSelect® (commercial name of hexafluoroacetylacetonate Cu(I) trimethylvinylsilane) was used as precursor and delivered in the reactor with the aid of a direct-liquid injection system. Thermally grown Cu films follow the initial topography of the substrate thus amplifying the roughness of the initial topography. HWCVD yields smoother films because the growth of Cu is due to entire molecules of the precursor, similarly to thermal CVD, and to activated, easily dissociated, species produced near the hot filament in the gas phase. Once trapped on surface irregularities these species probably dissociate and the deposited metal smooth out the surface yielding smoother Cu films.