I. Reid

Electronic structure of the organic semiconductor Alq3 (aluminum tris-8-hydroxyquinoline) from soft x-ray spectroscopies and density functional theory calculations

The element-specific electronic structure of the organic semiconductor aluminum tris-8-hydroxyquinoline (Alq(3)) has been studied using a combination of resonant x-ray emission spectroscopy, x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and density functional theory (DFT) calculations. Resonant and nonresonant x-ray emission spectroscopy were used to measure directly the carbon, nitrogen and oxygen 2p partial densities of states in Alq(3), and good agreement was found with the results of DFT calculations. Furthermore, resonant x-ray emission at the carbon K-edge is shown to be able to measure the partial density of states associated with individual C sites. Finally, comparison of previous x-ray emission studies and the present data reveal the presence of clear photon-induced damage in the former.

Influence of plasma parameters on the chemical composition of steady-state fluorocarbon films deposited on carbon-doped low-k dielectric layers during etching

This study investigates the fluorocarbon-based plasma etching (FBPE) of low dielectric constant (ULK) carbon-doped oxide (CDO) films, which have a dielectric constant (k) value of 2.4. The effects of different ion density and ion energy power settings on the chemical composition of the fluorocarbon layer deposited during the etch process were investigated. X-ray photoelectron spectroscopy (XPS) was used to analyse the chemical composition of the post-etched low-k CDO films while spectroscopic ellipsometry (SE) was used to determine the overall film thickness. XPS spectra of the C1s core levels reveal that the relative concentration of CFx species in the fluorocarbon films reduced as ion density source power and ion energy power levels were increased, and this can be correlated with a higher etch rate and thinner fluorocarbon layer. Plasma conditions which led to the deposition of a thick fluorocarbon film significantly inhibited the etch rate. This work demonstrates that the chemical composition and the thickness of the fluorocarbon film can be controlled by the plasma power parameters, and this has implications for the etching of ULK CDO layers.

Investigation of varying C4F8/O2 gas ratios on the plasma etching of carbon doped ultra-low-k dielectric layers

This study investigates the fluorocarbon-based plasma etching for ultra-low-k carbon doped oxide (CDO) dielectric layers which have a k value of 2.4; the CDO film is made up of SiOCH. The thickness of fluorocarbon layers deposited on the surface of the underlying CDO was controlled by independently varying the flow of C4F8 and O2 feed gases into the chamber. X-ray photoelectron spectroscopy and spectroscopic ellipsometry have been used to analyse the post-etched low-k CDO films. These studies have identified the conditions that lead to the formation of the thinnest fluorocarbon layers compatible with efficient etching, but that do not result in carbon depletion from the CDO layer. The results indicate that once the plasma gas mixture results in the presence of an extremely thin fluorocarbon layer, the carbon depletion is significantly suppressed. The thickness of the fluorocarbon film can be controlled by the C4F8/O2 gas ratio and the presence of this film has a large impact on the etch rate.