Effect of target processing on CoCrPtTa thin-film media
S.D. Harkness IV,a) and W. Lewisb)
Intevac VSD, Santa Clara, California 94054
M. Bartholomeusz and M. Tsai
Heraeus MTD, Chandler, Arizona 85226
(Received 6 January 2000; accepted 13 September 2000)
The ensuing paper summarizes an investigation on the effect of target microstructural
morphology on resultant sputter deposited media magnetic performance. Significant
differences in media magnetic coercivity were obtained from Co–Cr–Pt–Ta targets
possessing the same chemistry, sputtered under identical conditions, but possessing
different microstructural phase and crystallographic texture characteristics. This result
was most likely caused by the difference in sputter yields for the Ta-containing phases
in the two distinct target microstructures. Results support enhanced chromium
segregation yielding a decrease in the intergranuler exchange energy field for the
deposited thin films.
I. INTRODUCTION
form, the Co matrix is allotropic and exhibits both FCC
and HCP crystallographies. Other phases formed via the
addition of elements such as Ta, B, Nb, and W are more
complex with significantly reduced packing densities.
Crystallite grain sizes of the various phases can vary
from submicron to several hundred microns. Depending
on the target material-processing route selected, a variety
of crystallographic textures, different for the different
phases, can be obtained. Therefore, for a given compo-
sition, distinct material processing routes can promote
profound microstructural and property differences in the
resultant target product. This paper describes a brief sys-
tematic study on revealing possible effects of target ma-
terial microstructure and processing on subsequent media
performance and properties for CoCrPtTa alloys.
Magnetron sputter processing has long been the domi-
nant technique for recording media production based in
terms of film quality and cost effectiveness. In pursuit of
improved recording performance, scientists have sought
to understand the role of process environment on typical
magnetic thin film structures. While many reports have
revealed important effects of vacuum level and micro-
contamination,1,2 the role of sputter target microstructure
has been largely ignored. Over the past several years,
empirical observations by the authors have revealed that
the microstructure and processing of target materials can
noticeably impact the properties of resultant thin-film
media. The multitude of interrelated factors involved in
the physical vapor deposition (PVD) formation of media
storage devices renders decoupling the target/media
property and process effects rather complex. These fac-
tors include the following: (i) the dependence of atomic
ejection on target material phase(s) packing density and
crystallography; (ii) the relatively small mean free path
of ejected atoms compared with the deposition distance
at current operative pressures; (iii) the prevalence of
complex shaped target erosion grooves; (iv) the relative
geometries of the magnetron, target, and media system.
The manifestation and magnitude of the target/media ef-
fects can vary considerably on the basis of the applica-
tion, sputter process tool, and alloy set utilized.
II. EXPERIMENT
Media samples were produced using an Intevac MDP
250-B magnetron-sputtering tool. Simple CoCrPtTa/CrV
bilayers on NiP/Al substrates with circumferential me-
chanical texture (Ra 2 nm) were formed with appropri-
ate CrV composition for lattice matching.3 This was done
in an effort to eliminate all mitigating effects on media
performance other than the associated magnetics of the
investigated materials. The process was optimized for
bicrystal media,4 and x-ray diffraction confirmed the
crystallite texture to be (11.0)//(200). Magnetic and elec-
trical data was collected with a vibrating-sample magn-
etometer (VSM) and Guzik 1701MP spinstand,
respectively. Microstructural analysis was conducted
with a scanning electron microscope fitted with back-
scattered electron imaging (SEM-BEI), and composi-
CoCrPt(Ta,B,Nb,W,X) alloys are thermodynamically
constrained to exhibit complex multiphasic microstruc-
tures depending on the specific composition. In bulk
a)Present address: Seagate RMO, Fremont, CA 94538.
b)Present address: Hambrecht & Quist, San Francisco, CA 94107.
J. Mater. Res., Vol. 15, No. 12, Dec 2000
© 2000 Materials Research Society
2811
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