第12卷 第2期 太赫兹科学与电子信息学报 Vo1.12,No.2
2014 年 4 月
Journal of Terahertz Science and Electronic Information Technology Apr.,2014
文章编号:2095-4980(2014)02-0315-06
A PMOS multipled LVTSCR device for ESD protection
with a higher holding voltage
JIANG Tong-quan
a,b
,WANG Yang
a,b
,HUANG Wei
a,b
,LUO Qi-yuan
a,b
,JIN Xiang-liang*
a,b
(a.Faculty of Materials,Optoelectronics and Physics;b.Hunan Engineering Laboratory for Microelectronics,Optoelectronics and System
on A Chip,Xiangtan Hunan 411105,China)
Abstract:A novel LVTSCR structure for 5 V on-chip protection against Electrostatic Discharge(ESD)
stress at input or output pads is presented. Silvaco 2D TCAD software is used to simulate the device
including electrical and thermal characteristics. The new device exchanges the diffusion region of N+ and
P+ in N-WELL and introduces a PMOS-like structure to discharge ESD current before Low Voltage
Triggering SCR(LVTSCR) starting to work. And the device simulation results show that it obtains a higher
holding voltage(10.51 V) and a faster turn on speed(1.05×10
-10
s) compared with LVTSCR, with the
triggering voltage only increasing slightly from 12.45 V to 15.35 V. Also, in order to make sure that the
PMOS structure will trigger first and will not cause thermal breakdown problem, nearly the same channel
length as NMOS should be chosen for PMOS structure.
Key words:electrostatic discharge;Low Voltage Triggering SCR;PMOS trigger;Silvaco
CLC number:TN248.6 Document code:A
doi:10.11805/TKYDA201402.0315
In recent CMOS and BiCMOS technologies, ESD protection has a practical problem for the demand of a lower triggering
voltage and a higher holding voltage within a small layout area. SCR could be used for ESD protection because of its high
second breakdown current(It2) and low
-capacitance
[1]
. But its high switching voltage has limited the use of SCR-based
devices in on
-chip ESD protection
[2]
. In order to trigger SCR at a low voltage, an NMOS structure is included in LVTSCR
[3]
shown in Fig.1 and Table 1. When it comes to the application of
mixed-voltage interface ESD, Complementary-LVTSCR could have a
good performance
[4]
. Also, modified lateral SCR(MLSCR) and
Capacitance Coupling Triggering SCR(CCTSCR) were designed based
on a lower triggering voltage strategy
[5-6]
. And the PMOS trigger
structure is also suitable for ESD protection
[7-8]
. Although a lower
triggering voltage is important, a higher holding voltage within an
acceptable triggering voltage is more practical to avoid Latch
-Up Effect.
Transforming the LVTSCR at the diffusion region of N+ and P+ in
N
-WELL, shown in Fig.2 and Table1, can raise its holding voltage, but
the triggering voltage(Vt1) will increase either. The LVTSCR and
transformed LVTSCR have a same working process. First, the NMOS is
brokendown and triggers the SCR structure starting to work, shown in
Fig.3 and Fig.5. Then the device will reach its holding point since
current rising, shown in Fig.4 and Fig.6. So another pre
-triggering
mechanism is needed to lower Vt1 of the transformed LVTSCR, in order
to design an ESD device with better performance based on a higher
holding voltage. These features about LVTSCR and PMOS are combined
together with a novel multiplexed PMOS in the PMOS multipled LVTSCR(PMLVTSCR).
Received date:2013-05-24;Revised date:2013-07-05
This work is supported by the National Natural Science Foundation of China (Grant No.61274043), by the State Key Program of National Natural Science o
China (Grant No.61233010) and the Key Project of Chinese Ministry of Education(Grant No.212125) and Creative Project in Xiangtan University.
*Corres
ondin
autho
:JIN Xian
-lian
, email:
inxl@xtu.edu.cn
Fig.1 Structure of normal LVTSCR
PAD
D5 D3 D4 D4 D3
N+ P+ P+N+ N+
D1
D1
D2
D1 D1
R
w
N-WELL
P-SUB
PAD
D5 D3 D4 D4 D3
N+ P+ P+N+ N+
D1
D1
D2
D1 D1
R
w
N-WELL
P-SUB
Fig.2 Structure of the transformed LVTSCR