Ritalba Lamendola

FLUORINATED DIAMONDLIKE CARBON FILMS DEPOSITED FROM RADIO-FREQUENCY GLOW DISCHARGE IN A TRIODE REACTOR

Diamondlike carbon thin films have been deposited by H2–C2F6 fed rf‐glow discharges in a triode reactor. Raman spectroscopy and electron spectroscopy for chemical analysis have been utilized as diagnostic tools to investigate structural properties and chemical composition of deposited films. Transitions in film properties have been observed, from those typical of hydrogenated polymers to those of diamondlike and fluorinated polymers, by changing feed composition, substrate bias, and substrate temperature. In particular, it has been shown that the energy of the ions bombarding the growing films, as well as the fluorine contents in the films is the most critical parameter to obtain materials with diamondlike structure.

Ion‐beam sputtering deposition of fluoropolymer thin films

It is shown that it is possible to deposit thin films with various CFx composition (1.26≤x≤1.83) by ion‐beam sputtering. These materials with ‘‘teflon‐like’’ composition have been deposited at room temperature by Ar ion‐beam sputtering of a teflon target; the film chemical composition has been determined by electron spectroscopy for chemical analysis. The fluorine‐to‐carbon ratio of the films, as well as their crosslinking degree, is shown to depend on the energy of the ions impinging on the target.

Thin film deposition from hexamethyldisiloxane fed glow discharges

Hexamethildisiloxane-oxygen fed radiofrequency discharges have been studied under high power density and 0.05÷0.1 torr pressure, i.e., experimental conditions of high monomer fragmentation. Actinometric Optical Emission Spectroscopy of plasma phase, X-Ray Photoelectron Spectroscopy and Infrared Spectroscopy analyses of the deposited films allowed to set the basis of the first “semi-quantitative” mechanism of deposition of siloxane films which can reasonably account for both deposition rates and film compositions. A by-product of the research is the use of CH-to-Ar emission ratio as a probe of carbon content in the film, an important practical parameter for process control.

Dry etching of titanium nitride thin films in CF4–O2 plasmas

The dry etching of titanium nitride has been studied in fluorine containing glow discharges. Untreated samples are covered by an oxidized layer of titanium oxide and/or oxynitride. X‐ray photoelectron spectroscopy cannot be utilized to clarify the nature of these species that strongly influence surface reactivity. In agreement with some published data, it has been found that the component of the N 1s signal at low binding energy is due to interstitial nitrogen atoms and not to substoichiometric nitrides. An analysis of the effect of temperature and bias voltage variation is reported as well as the changes of surface composition due to the plasma action. Comparisons with the reactivity of metallic titanium are also discussed.

Modulated rf discharges as an effective tool for selecting excited species

Modulated NH3-fed rf glow discharges have been investigated; the emissions of the active species NH* and N2* have been collected during the modulation period (time on+time off). In this study, modulated discharges have been characterized by a constant time on of 7 ms and a tunable time off in the range of 0–1000 ms. It has been found that the power modulation represents an effective tool for selecting excited species: this procedure may be exploited in surface grafting treatments of polymers where high selectivity of chemical groups is requested, e.g., for preferentially grafting −NH2 groups onto polyethylene with respect to all other N-containing functionalities.

PECVD of SiOxNyCzHw thin films from hexamethyldisilazane containing feed. Investigation on chemical characteristics and aging behavior

The chemical characteristics and aging behavior of thin films obtained by HMDSN/NH3 or N2 containing plasmas have been studied by means of FT-IR spectroscopy as a function of feed composition, substrate temperature and bias voltage. Deposits obtained with low energy ion bombardment are polyphasic and contain a consistent fraction of polysilazane. Reactive polymeric SiH2 chains are formed when ammonia or nitrogen are added to the feed. Film aging is mainly due to the reactions of Si-H bonds and of linear polysilazane chains. Films with better stability are obtained by excluding ammonia or nitrogen from the feed and with bias superimposition.

Selective Grafting of Amine Groups on Polyethylene by Means of Modulated RF NH 3 Plasmas

Plasma treatments in power modulated NH 3 RF glow discharges have been performed for modifying the surface of polyethylene (PE). Time Resolved Optical Emission Spectroscopy (TR-OES) has been utilized for monitoring the emission of active species during the modulation period of the discharge, Electron Spectroscopy for Chemical Analysis (ESCA) has been used for studying the surface composition of PE before and after the derivatization of plasmagrafted -NH 2 groups. We present our preliminary results here, which show how modulated NH 3 plasmas can effectively improve the grafting selectivity of -NH 2 respect to all other N-containing groups.

Plasma-Enhanced Chemical Vapor Deposition

The basic principles of Plasma-Enhanced Chemical Vapor Deposition processes are examined along with reactor architectures. Emphasis is given to the chemistry of the discharge and to active species and deposition precursors with the aim of correlating film compositions with discharge internal parameters. The processes for the deposition of films of fluoropolymers, metal containing polymers, SiO2-likes and silicone-likes are examined as case studies.