Influence of Ion Bombardment and Annealing on the Structural and Optical Properties of TiO_x Thin Films Deposited in Inductively Coupled TTIP/O₂ Plasma

Abstract

TiO2 films were deposited in a low‐pressure inductively coupled rf plasma in O2/titanium tetraisopropoxide (TTIP). First, depositions were realized at floating potential using nitrogen as bubbling gas. The structural and optical properties of the films were studied, before and after annealing at 450 °C under air. As expected, as‐deposited films are amorphous, with a columnar structure. A post‐annealing under flowing air allows obtaining partially crystallized films in anatase phase. Secondly, films were deposited using nitrogen and oxygen as bubbling gas. In both cases, TiO2‐like films exhibit very similar structure and optical properties. Finally, the effect of biasing the substrate was investigated. An improvement of film properties has been found for a bias voltage of −15 V at T<100 °C: deposited TiO2 film is dense (3.7) with a high refractive index (n = 2.32 at 634 nm) and partially crystallized in rutile phase.

Effect of ion bombardment on the structural and optical properties of TiO2 thin films deposited from oxygen/titanium tetraisopropoxide inductively coupled plasma

“…For instance, reactive magnetron sputtering is a PVD plasma process which allows the deposition of columnar, amorphous or polycrystalline films (anatase and/or rutile phase) at relatively low substrate temperature (100 to 200 °C) [17][18]. At least, although much less studied, TiO 2 films can be grown by using chemical vapour deposition processes which are based on the dissociation of an inorganic (TiCl 4 ) or metallorganic (such as titanium tetraisopropoxide, TTIP, Ti-(OC 3 H 7 ) 4 ) precursor, by heating (conventional CVD) [19][20], atomic layer deposition (ALD) [21] or by plasma enhanced atomic layer deposition (PEALD) [22][23] and plasma enhanced chemical vapour deposition (PECVD) [24][25][26][27][28].…”

“…In addition, the low pressure radiofrequency inductively coupled plasma such as the one used in this study, offers the possibility to control independently the ion density (fixed by the power coupled to the plasma source) and the ion energy (by biasing the substrate). Since the ion energy actively influences the film growth through surface activation and densification, its control is crucial for tailoring the film structure [28,32].…”

In situ spectroscopic ellipsometry study of TiO2 films deposited by plasma enhanced chemical vapour deposition

“…), and to be compatible with silicon based semiconductor technologies. In addition, for high density inductively coupled plasma (ICP) reactors, such as helicon ones, one of the most important advantages is their ability to control the ion energy, independently on the plasma density [10][11][12].…”

Optimized ICPCVD-Based TiO2 for Photonics

“…We investigated the influence of the ICP source power, the table power, and the chamber pressure effects on the TiO 2 thin film properties. The radiofrequency (RF) power of the ICP source varied from 800 W to 1500 W, which was substantially higher than in previous studies [ 14 , 21 , 22 , 23 ]. Note that it is actually not straightforward to make a comparison since the source diameter and the exposed area of the lower electrode are probably not the same.…”