High quality ZnO rotary and planar ceramic sputtering targets for related transparent
conductive films
Ye Yang
a,b
, Pinjun Lan
a,b
, Jia Li
a
, Yanling Wen
b
, Dongmiao Qi
b
, Weijie Song
a,b
a
Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences,
Ningbo 315201, PR China
b
Ningbo Sunlit Electronic Materials Co., LTD, Ningbo 315171, PR China
Email:
Recently, ZnO transparent conductive oxide (ZnO-TCO) films, such as Al doped ZnO
(AZO), Ga doped ZnO (GZO) and In doped ZnO (IZO), have been widely used in the field of
low-E coating, thin-film solar cells, display device, transparent heater and electrochromic
glass. Benefit from the advantage of large area deposition, relatively low cost and higher film
uniformity, the magnetron sputtering (MS) has became a mainstream technology in massive
ZnO-TCO film production. During the MS process, the ZnO ceramic target plays a major role
in achieving high-quality films. In order to meet the requirement of uniform, stable film
deposition with a high deposition rate, the ceramic target should be made with a character of
high density, finer grain size and better conductance. As far as the target shape and structure
be concerned for large area coating, the target manufacturers should supply not only the
bonded planar targets but also the new generation bonded rotary targets as well as large size.
For the bonded targets, the bonding ratio between ceramic target segment and backing tube or
plate is another important parameter for high powder sputtering.
In this paper, we choose the mostly used AZO target (2wt% Al
2
O
3
doping) as a
representative to introduce our commercialized developments in high quality ZnO rotary and
planar ceramic sputtering targets. The high purity ZnO and Al
2
O
3
nano-sized powers used as
starting materials are mixed and highly dispersed by a high energy ball milling process, then
formed into rotary or planar green body in a custom-made mold by a special forming method
with the aid of cold isostatic pressing machine. This kind of forming method is helpful of
enhancing the relative density of AZO green body to exceed 70% (AZO theoretical density:
5.58g/cm
3
), and also making large size green body fabrication more easily. The maximum
rotary and planar green body sizes are 200OD×150ID×400H and 480L×420W×20H,
respectively. The formed green bodies are transferred into an electric furnace and sintered in
air at the temperature of ranging from 1,300°C to 1,450°C. After machining and polishing,
the sintered bodies will transformed into the AZO target segments. The typical AZO target
has a density of 5.56 g/cm
3
(99.6% of theoretical density) with a grain size of about 10μm
and a bulk resistivity of 1.78 × 10
−3
Ω·cm. The AZO target segments are bonded on backing
tubes or plates using indium metal solder, and the bonding ratio is more than 95%.
References:
[1] Junhua Zhao, et al., J. Am. Ceram. Soc., 2011,94 [3]: 725–728
[2] Yang et al., Nanoscale Research Letters, 2012,7: 481
[3]
Yulong Zhang et al.,
Int. J. Appl. Ceram. Technol., 2012,9 [5]: 960–967
PS2 9
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