The effect of nitrogen on the properties of rf-sputtered tantalum nitride thin
films
G. Stavrinidis
(*,1)
, S. Georgakis
(1,2)
, A. Kostopoulos
(1)
, K. Tsagaraki
(1)
, M. Androulidaki
(1)
,
M. Kayambaki
(1)
, V. Kontomitrou
(1)
, M. Modreanu
(2)
, G. Konstantinidis
(1)
and E. Aperathitis
(1)
(1)
Microelectronics Research Group, Institute of Electronic Structure & Laser, Foundation
for Research and Technology–FORTH-Hellas, P.O. Box 1385, Heraklion 70013, Crete,
Greece.
(2)
Physics Department, University of Crete, P.O. Box 2208, 71003 Heraklion, Crete, Greece.
(3)
National Institute, Lee Maltings, Prospect Row, Cork, Ireland.
* Corresponding & Presenting Author: G. Stavrinidis,
Transition metal nitrides are materials which have attracted considerable importance in
recent years due to their outstanding mechanical, chemical and electrical properties like
chemically inert, resistance to corrosion, hard and conductivity. Tantalum nitride (TaN) is
one of them and it has been used as thin film resistor since it is considered to be more
thermally stable resistor than others, like NiCr or SiCr, and it can cover resistivity range from
few ohms to kohms, as diffusion barrier in Cu-based metallizations for monolithic microwave
and millimeter wave integrated circuits (MMICs and MIMICs) as well as low-deviation and
low-variability terminator resistor in silicon optical bench transmitters. Generally, TaN thin
films have been fabricated by CVD and PVD deposition techniques and the properties of the
films have been shown to depend greatly on their stoichiometry and microstructure.
Furthermore, conductivity and transparency of TaN films depend on the nitrogen content in
the film which make TaN possible candidate for applications in transparent optoelectronics.
Thus, controllable and reliable TaN requires precise control over the deposition parameter of
the film.
In this work TaN thin films were fabricated by R.F. sputtering from Ta target in plasma
containing mixture of N
2
and Ar gases. The RF power was varied up to 500W while the total
pressure was 5mTorr. The sputtering system was capable of applying the rf power, and thus
creating plasma, on both the target (anode) and the substrate (cathode). The substrates were
fused silica glass, Si and thermally oxidized SiO
2
/Si. The surface morphology of the films
was examined by AFM and SEM while compositional analysis was made by EDX. The
structural properties were studied by grazing incidence X-ray diffraction. The optical
properties of the films were examined by the following spectroscopic techniques: UV-VIS-
NIR transmittance, Raman and variable angle ellipsometry. The carriers’ concentration of
TaN films was investigated employing Hall-effect measurements, whereas its resistivity was
determined by using gate-like patterns. The patterning was made by employing standard
photolithographic technique including reactive ion etching in SF
6
/Ar mixtures. The optimum
TaN film will be used as thin film resistor and incorporated in the processing procedure for
the fabrication and testing of MMIC (HPA & LNA)) based on AlGaN/GaN high electron
mobility transistors (HEMTs).
PS2 20
-214-
