Journal of University of Science and Technology Beijing
Volume 11, Number 1, February 2004, Page 30
Corresponding author: Fengping Wang, E-mail: wfp2002@hotmail.com
Materials
Structural and physical properties of permalloy thin films prepared
by DC magnetron sputtering at different substrate temperature
Fengping Wang
1,2)
, Ping Wu
1,2)
, Hong Qiu
1,2)
, Liqing Pan
1,2)
, Huanping Liu
1)
, Yue Tian
1,2)
, and Sheng Luo
1)
1) Department of Physics, University of Science and Technology Beijing, Beijing 100083, China
2) Beijing Keda-Tianyu Microelectronic Materials Technology Development Co. Ltd., Beijing 100083, China
(Received 2003-04-01)
Abstracts: Permalloy Ni
80
Fe
20
films have been grown on thermal oxidized Si (111) wafers by magnetron sputtering at
well-controlled substrate temperatures of 300, 500, 640 and 780 K in 0.65 Pa argon pressure. The base pressure was about 110
4
Pa.
The deposition rate was about 5 nm/min for all the films. The structure of the films was studied using X-ray diffraction, scanning
electron microscopy and atomic force microscopy. The composition of the films was analyzed using scanning Auger microprobe.
The resistance and magnetoresistance of the films were measured using four-point probe technique. The results show that the content
of oxygen in the films decreases gradually with raising substrate temperature. In addition, the surface morphology of the films
presents notable change with the increasing of the substrate temperature; the residual gases and defects decrease and the grains have
coalesced evidently, and then the grains have grown up obviously and the texture of (111) orientation develops gradually in the
growing film. As a result, the resistivity reduces apparently and magnetoresistance ratio increases markedly with raising substrate
temperature.
Key words: permalloy film; substrate temperature; residual gases; resistance and magnetoresistance
[This work was financially supported by National Natural Science Foundation of China (No.19974005).]
The anisotropic magnetoresistive (AMR) effect is
widely utilized in sensor applications, related with the
detection of weak magnetic fields [1], for example,
detecting the orientation of the earth magnetic field.
Permalloy film is a kind of very important soft mag-
netic material. A good anisotropic magnetoresistive
effect has been found in Ni
80
Fe
20
films and has been
applied for magnetoresistive sensors [2,3]. At the
same time, permalloy is also the important material
made of GMR heads [4], spin valves [5,6] and tunnel
junctions [7]. Thus, investigating for permalloy thin
film has been the extensive interesting of people ever
since. The magnetic properties strongly depend on
microstructure and phase composition. It is thus
worthwhile to establish the possible connections be-
tween structure and magnetic properties. In this work,
the structural characterization and magnetic behavior
of Ni
80
Fe
20
thin films deposited at different substrate
temperature were analyzed.
1
Experimental
Permalloy Ni 80% Fe 20% films (about 40 nm
thick) were prepared using magnetron sputtering on
thermal oxidized Si(111) wafers at well-controlled
substrate temperatures of 300, 500, 640 and 780 K in
0.65 Pa argon pressure. The base pressure was about
110
4
Pa. The deposition rate was about 5 nm/min
for all the films.
The resistance and magnetoresistance were meas-
ured by a four-point probe technique. The magnetore-
sistance measurements were made in two configura-
tions: (a) magnetic field applied was parallel to the
current direction (longitudinal magnetoresistance) and
(b) magnetic field perpendicular to the current direc-
tion (transverse magnetoresistance).
The structure of Ni
80
Fe
20
films, the grain orienta-
tion, cross section morphology, granule size and sur-
face roughness were characterized using X-ray dif-
fraction (XRD), scanning electron microscopy (SEM),
scanning Auger microprobe (SAM) and atomic force
microscopy (AFM). The temperature coefficient of re-
sistance (TCR) of the films were measured using
four-point probe technique in the range of 77-300 K.
2 Results and discussion
2.1 Structure and composition