Chin. Phys. B Vol. 22, No. 7 (2013) 078501
Lead zirconate titanate behaviors in an LDMOS
∗
Zhai Ya-Hong(翟亚红)
†
, Li Wei(李 威), Li Ping(李 平), Li Jun-Hong(李俊宏),
Hu Bin(胡 滨), Huo Wei-Rong(霍伟荣), Fan Xue(范 雪), and Wang Gang(王 刚)
State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
(Received 19 December 2012; revised manuscript received 4 February 2013)
The behaviors of lead zirconate titanate (PZT) deposited as the dielectric for high-voltage devices are investigated
experimentally and theoretically. The devices demonstrate not only high breakdown voltages above 350 V, but also excellent
memory behaviors. A drain current–gate voltage (I
D
–V
G
) memory window of about 2.2 V is obtained at the sweep voltages
of ±10 V for the 350-V laterally diffused metal oxide semiconductor (LDMOS). The retention time of about 270 s is
recorded for the LDMOS through a controlled I
D
–V
G
measurement. The LDMOS with memory behaviors has potential to
be applied in future power conversion circuits to boost the performance of the energy conversion system.
Keywords: laterally diffused metal oxide semiconductor (LDMOS), lead zirconate titanate, memory behavior,
retention
PACS: 85.30.De, 85.50.–n, 77.55. df DOI: 10.1088/1674-1056/22/7/078501
1. Introduction
Lead zirconate titanate (Pb(Zr,Ti)O
3
, PZT) has been
widely investigated and integrated in ferroelectric random ac-
cess memories and ferroelectric field effect transistors due to
large remnant polarization and high permittivity.
[1–7]
In these
applications, the PZT has mainly been used in low-voltage
device fields.
[8–14]
Recently, high-permittivity dielectrics for
power electronic applications have been extensively applied to
realize high breakdown voltages and low on-resistance (R
on
).
However, most of these studies still remain at the simulation
and theoretical analysis stages.
[15–19]
In our previous work,
[20]
we have successfully fabricated
a laterally diffused metal oxide semiconductor (LDMOS) cov-
ered by the PZT with high dielectric constants. The breakdown
voltage is about 350 V, which is three times larger than that for
the LDMOS covered by SiO
2
, suggesting that the PZT is a po-
tential candidate for future power applications. However, the
behaviors of PZT in power applications have rarely been re-
ported, thus making it an interesting and necessary research
task.
Our experimental results show that the PZT LDMOS also
has a memory characterization, which has not been reported.
With the memory behavior, the LDMOS allows impulse driv-
ing instead of switching driving, which can be potentially used
to design novel DC–DC circuit and improve the performance
of the energy conversion system. The present work focuses
mainly on the analysis of its memory performance.
2. Device structure and fabrication
Figure 1 shows the schematic cross section of the LD-
MOS, where a 600-nm PZT film covers a 20-nm SiO
2
insula-
tor layer. The gate is also the field plate for the device. The
channel length and width are 2 µm and 6000 µm, respectively.
The N
−
drift region is 80 µm. The n-channel LDMOS de-
vice was fabricated on a p-type Si (100) substrate. After the
ion implantation into N
+
drain and source regions, the SiO
2
insulator layer was thermally grown. Then, the PZT film was
deposited using radio-frequency magnetron sputtering. Sub-
sequently, the PZT film was etched and contact windows were
opened. Finally, the aluminum was deposited and patterned.
We also fabricated counterparts with a SiO
2
dielectric for com-
paring with the novel devices. The current–voltage character-
istics of the LDMOS were measured with an Agilent 4155B
semiconductor parameter analyzer.
source
P
+
N
+
N
+
P well
Psub
Ndrift
SiO
2
drain
600 nmPZT
2 mm
80 mm
gate
Fig. 1. Schematic cross section of the LDMOS with PZT.
3. Results and discussion
Figure 2(a) shows the drain current–gate voltage (I
D
–V
G
)
characteristics of the LDMOS with PZT. The gate voltages
∗
Project supported by the National Basic Research Program of China (Grant No. 50772019) and the National Natural Science Foundation of China (Grant
No. 61204084).
†
Corresponding author. E-mail: yhzhai@uestc.edu.cn
© 2013 Chinese Physical Society and IOP Publishing Ltd http://iopscience.iop.org/cpb http://cpb.iphy.ac.cn
078501-1