International Conference on Enabling Science and Nanotechnology 2012 (ESciNano 2012)
5-7 January 2012, Persada Johor International Convention Center, Johor Bahru, MALAYSIA
ESciNano 2012 – http://www.fke.utm.my/mine/escinano2012
Study on the influence of oxygen/argon flow ratio toward the growth of TiO
2
film
in reactive magnetron sputtering plasma
Riyaz Ahmad Mohamed Ali *, Sharifah Amira Amir Shariffuddin, Salwa Omar and Nafarizal Nayan,
Microelectronic and Nanotechnology - Shamsuddin Research Centre (MiNT-SRC),
Faculty of Electrical and Electronic Engineering , Universiti Tun Hussein Onn Malaysia, Malaysia,
*riyaz@uthm.edu.my
Titanium dioxide (TiO
2
) material has attracted much attention due to its high refractive index,
high transparency in the visible and near – infrared wavelength region, a high dielectric constant and very
good wear resistance and chemical stability. Such properties have led homogenous TiO
2
thin film layer to
be used widely in optical coating, photovoltaic, sensor and electronics applications. Reactive magnetron
sputtering is one of most reliable and sophisticated technique to fabricate TiO
2
thin film. This technique
offers a strict controlled deposition process to growth high quality TiO
2
thin film at varies parameter
value. This includes parameter change in discharge power, working pressure, type of sputter target,
composition ambient and reactive gas ratio, substrate temperature and others [1].
Globally, many researchers have reported the formation of TiO
2
thin film under various
sputtering conditions. However, only handful study has been done focusing on the influence of reactive
oxygen (O
2
) gas in ambient Argon (Ar) gas ratio. Study shows that, sufficient amount of O
2
gas needed to
influence the formation of TiO
2
compound using Titanium (Ti) metal as the sputter target [1-3]. The
purpose of this study to clarify the critical amount of O
2
gas flow ratio needed for the optimum growth of
TiO
2
compound. We will be using an in-situ optical emission spectroscopy (OES) inspection technique.
Information gain through OES technique will help to understand the atomic distribution of excited Ti, Ar
and O atom under various O
2
/Ar+O
2
flow ratio and working pressure.
Series of sputtering plasma were produced by employing various O
2
/Ar+O
2
gas flow ratio from
0% till 20% at different working pressure of 5 ~ 30 mTorr. The metal Ti (99.995%) was used as sputter
target. The discharge power was fixed at 400 W using radio frequency (rf) of 13.56MHz automated
matching power supply. Single converging quartz lens is then tune position to focus light emission
spectrum that exits exactly 10cm downstream region of the plasma plume into optical fiber via quartz
view port. The experimental setup is as shown in the figure 1. Every change in sputtering parameter is
then recorded using OES system (Ocean Optic) which is connected to a computer.
Figure 2 shows optical emission spectrum of excited Ti atom measured at wavelength of
521.04nm in various working pressures. The Ti emission was observed clearly before the 7% ratio. The
measurement shows higher Ti emission was observed with increase in working pressure value. On the
other hand, the figure 3 and 4 consist of emission spectrum of excited Ar (811.53nm) and excited O
(777.2nm) respectively. Figure 3 and 4 show slight decrease of Ar and O emission with the increasing
working pressure, especially after 11% ratio. The decrease of Ar and O emission are due to smaller mean
path occur inside the plasma plume as the working pressure increases.
Figure 5 shows combination emission spectrum of Ti, Ar and O at 15mTorr working pressure
under various gas flow rate. From the figure 5, the Ti atomic emission spectrum shows a sudden drop of
Ti emission at over 7% O
2
/Ar+O
2
gas flow ratio. On the other hand, O emission increased at the same
O
2
/Ar+O
2
gas flow ratio. Such phenomena suggest the O
2
amount provided has surpassed the critical
value needed before target begins to oxides (also known as target poisoning). Thus, it is suggested that the
empirical growth of TiO
2
film has started at this point and resulting lower overall growth rate of film.
Investigations on plasma temperature and plasma density using Langmuir probe will be presented during
the seminar and further results on its effect on the growth of TiO
2
film will be discussed.
This work was supported by Ministry of Higher Education of Malaysia under Fundamental
Research Grant Scheme (FRGS vot0703) and Universiti Tun Hussein Onn Malaysia under Graduate
Incentive Scheme (GIS vot0672).
References
[1] G.S. Chen, C.C. Lee, H. Niu, Welson Huang, Robert Jann and T. Schütte, Thin Solid Films 516 (2008) 8473-8478.
[2] K. Takamura, Y. Abe and K. Sasaki, Vacuum 74 (2004) 397-401.
[3] M. Gaillard, N. Britun, Y.M. Kim and J.G. Han, J. Phys. D: Appl. Phys. 40 (2007) 809-817.
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