Dimitri BOIVIN: Study and development of a method to monitor and control TiO2 thin layers thickness deposited with R-HiPIMS process...

Abstract:
The growth of thin layers in reactive-high power impulse magnetron sputtering (R-HiPIMS) process is the general framework of this PhD. The coating industry needs a simple and reliable method to track the evolution of deposits over time because, among other reasons, the racetrack shape certainly changes during the sputtering process. The main goal of this PhD is to develop a reliable tool devised to control TiO2 thin layer thickness in R-HiPIMS deposition process. Preliminary studies of the influence of O2 content in the Ar/O2 gas mixture, the mean pulse power, the pulse width and the substrate-holder temperature were performed. The plasma was characterized by optical emission spectroscopy (OES), mass spectrometry and current-voltage characteristics of the discharge. Thin films were analysed by XRD, SEM and profilometry. From combined analyses of Ti emission line intensity, integrated discharge current and deposited TiO2 coating thickness, it is established that plasma diagnostics can be used effectively to control the deposition rate. Indeed, dividing the time average emission line intensity (TA_OES) by the integrated current (Iint) leads to obtain the TA_OES signal(Ti)/Iint ratio, which allows eliminating the effect of any variation of the electron energy distribution function. In all our investigated conditions (% O2, pulse width, the target erosion profile and the substrate-holder temperature), the TA_OES signal(Ti)/Iint ratio seems to be in good agreement with the thickness. Thus, it seems that this ratio well reflects the titanium species density which contributes to the deposits.

Keywords:
control of TiO2 film thickness, HiPIMS deposition process, optical emission spectroscopy, mass spectrometry, XRD, SEM, profilometry.

Composition of the jury:
> Reporters:
- Sédina TSIKATA, Chargée de recherche, CNRS, ICARE
- Stéphane BECHU, Directeur de recherche, CNRS, LPSC
> Examiners:
- Angélique BOUSQUET, Maîtresse de conférences, Université Clermont Auvergne, ICCF
- Tiberiu MINEA, Professeur, Université Paris-Saclay, LPGP
- David HORWAT, Professeur, Université de Lorraine, IJL
> Direction of thesis:
- Ludovic DE POUCQUES, Maître de conférences, IJL, Université de Lorraine, Directeur de thèse
- Stéphane CUYNET, Chargé de recherche, CNRS, IJL, Co-encadrant de thèse