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SEMI M60-0305 © SEMI 2005 16 0 5 10 15 01 0 2 0 TDDB defect density(cm-2) TZDB B-mode defe ct density(cm-2) Figure R1-1 Correlation of Defect Densities of TZDB and TDDB Measurements Q b d Weib ull I n i t i a l B r e a k…

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R1-4 Dependence of Stress Current Density
R1-4.1 In this TDDB measurement, the stress electric field was applied so as to keep the oxide leakage current
constant. The applied voltage was monitored at the constant time interval. A stress current of 0.001 A/cm
2
or less
leads to uselessly long measurement time.
R1-4.2 On the other hand, too high a current density leads to nonuniform application of the stress voltage to the
gate oxide. That is, the reliability of the measurement is reduced.
R1-4.3 In this round robin, the applied stress condition is shown in Table R1-1.
R1-4.4 The Weibull plot obtained in this round robin is shown in Figure R1-5. The Q
bd
values and the accidental
failure rates are shown in Table R1-2. The Q
bd
clearly depended on the stress current in the stress range of this
round robin. The Q
bd
decreased with increasing stress current density, though the difference of the failure rates is
slight. The failure rates in this result were defined by the sum of the accidental initial and intermediate modes in
Figure R1-2. The classification between intermediate (A-B mode) and wearout (W mode) breakdowns was
performed at the injected charge density of 2C/cm
2
.
R1-4.5 The total accidental failure rates, that is, the sum of the A-A and A-B modes, were not influenced by the
current density in this round robin condition. Therefore, the recommended stress current density range is from 0.1 to
0.01A/cm
2
.
R1-5 Dependence of Measurement Temperature
R1-5.1 On the other hand, in this TDDB measurement, the stress temperature is an important parameter. The Q
bd
depended on the stress temperature. Too high a temperature degrades the measurement system. In the stress
temperature range of room temperature to 125ºC, systematic TDDB data were obtained. The recommended stress
temperature is 125ºC or less.
R1-5.2 The stress conditions in this round robin are shown in Table R1-1. In this table, the accidental failure rate
was defined by the sum of the initial and intermediate breakdowns in Figure R1-2. In this case, the classifications of
the A-B and W modes were defined as follows:
125ºC–2C/cm
2
85ºC–5C/cm
2
25ºC (r.t.)–10C/cm
2
R1-5.3 The Q
bd
depended on the stress temperature in this round robin condition. However, the sum of the
accidental A-A and A-B breakdown modes was independent of stress temperature. Therefore, taking into
consideration the above practical factors, the reasonable stress temperature range is from room temperature to
125ºC.
SEMI M60-0305 © SEMI 2005 16
0
5
10
15
01020
TDDB defect density(cm-2)
TZDB B-mode defect density(cm-2)
Figure R1-1
Correlation of Defect Densities of TZDB and TDDB Measurements
Qbd
Weibull
I
n
i
t
i
a
l
B
r
e
a
k
d
o
w
n
We
a
ro
u
t
B
r
e
a
k
d
o
w
n
I
n
t
e
r
m
e
d
i
a
t
e
B
r
e
a
k
d
o
w
n
Q
a
log Q
BD
Qbd
Weibull
I
n
i
t
i
a
l
B
r
e
a
k
d
o
w
n
We
a
ro
u
t
B
r
e
a
k
d
o
w
n
I
n
t
e
r
m
e
d
i
a
t
e
B
r
e
a
k
d
o
w
n
Q
a
Qbd
Weibull
I
n
i
t
i
a
l
B
r
e
a
k
d
o
w
n
We
a
ro
u
t
B
r
e
a
k
d
o
w
n
I
n
t
e
r
m
e
d
i
a
t
e
B
r
e
a
k
d
o
w
n
Q
a
log Q
BD
Figure R1-2
Classification of TDDB Breakdown Mode
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1.00
2.00
3.00
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02
Qbd (C/cm
2
)
Ln(-Ln(1-F))
1mm2
1mm2
1mm2
5mm2
5mm2
5mm2
10mm2
10mm2
10mm2
Figure R1-3
Capacitor Area Dependence of Q
BD
. J=0.1A/cm
2
, 125ºC.
Table R1-1 Measurement Condition of Constant Current Stress
TDDB for Round Robin.
J
stress
(A
･
cm
2
)
Temp.(ºC)
0.1 RT/80/125
0.05 125
0.01 125
Figure R1-4
Gate Area Dependence of CCS-TDDB Measurement at 125ºC, 100mA/cm
2
in the W-mode Range of 2C/cm
2
or more. High Linearity in All TDDB Results Was Obtained in the W-mode Region.
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-2.00
-1.00
0.00
1.00
2.00
3.00
0.1110
Q bd (C /cm 2)
L n (- L n (1 - F ))
1m m 2
1m m 2
1m m 2
5m m 2
5m m 2
5m m 2
10m m 2
10m m 2
10m m 2