Large ferroelectric polarization of TiN/Hf0.5Zr0.5O2/TiN ...
Transcript of Large ferroelectric polarization of TiN/Hf0.5Zr0.5O2/TiN ...
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[Supplementary material]
Large ferroelectric polarization of TiN/Hf0.5Zr0.5O2/TiN capacitors due to
stress-induced crystallization at low thermal budget
Si Joon Kim1, Dushyant Narayan1, Jae-Gil Lee1, Jaidah Mohan1, Joy S. Lee1, Jaebeom Lee1,
Harrison S. Kim1, Young-Chul Byun1, Antonio T. Lucero1, Chadwin D. Young1, Scott R.
Summerfelt2, Tamer San2, Luigi Colombo2, and Jiyoung Kim1,*
1Department of Materials Science and Engineering, The University of Texas at Dallas,
800 West Campbell Road, Richardson, Texas 75080, United States
2Texas Instruments,
13121 TI Blvd, Dallas, Texas 75243, United States
Keywords
Ferroelectric random access memory, Hf0.5Zr0.5O2, Atomic layer deposition, Stress-induced
crystallization, Low thermal budget process
*Electronic mail: [email protected]
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For the pulse write/read measurement (see Fig. S1(a)),1 a series of write and read trapezoidal
voltage pulses with a pulse width of 4 μs, a rising/falling time of 1 μs, and a delay time of 10 μs
were applied to the Hf0.5Zr0.5O2 (HZO) samples using a pulse generator (Agilent 81110A). The
subsequent voltage drop on the internal resistor of 50Ω (shunt resistor) was measured using an
oscilloscope (Tektronix DPO7104). The load current was calculated from the load voltage using
Ohm's law and the load current of each pulse was integrated over time to extract the polarization.
Figure S1(b) and (c) show an example of the pulse write/read result of the HZO sample
according to the pulse sequence.
In the write/read sequence, the write pulse is applied such that the switching and non-
switching polarization can be extracted from the read pulse. For example, applying +2.5 V write
pulse and -2.0 V read pulse can help us extract the switching polarization at -2.0 V from the read
pulse. Similarly, applying -2.5 V write pulse and -2.0 V read pulse can help us extract the non-
switching polarization at -2.0 V from the read pulse. Hence, the applied write voltage was fixed
at ±2.5 V and the read voltage varied from -2.5 V to 2.5 V with 0.1 V step as shown in Fig. S1(c).
It takes around 5 s to initialize the pulse generator and the oscilloscope between each write/read
sequence, which gives the domains sufficient time to relax. By subtracting the integrated current
values of the switching and non-switching read pulses, the real ferroelectric switching
polarization (Psw) were extracted. The slope of the integrated current values of non-switching
read pulses can be also used to extract the dielectric constant of the HZO sample as shown in Fig.
S1 and Fig. S2(a).
We can see two different slope regions in non-switching pulse write/read results (see Fig.
S2(a) inset). Therefore, two dielectric constants in two different read voltage operation regions
are extracted from non-switching pulse write/read results, respectively. The dielectric constant in
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the first region (when read voltage is much lower than coercive voltage) and the second region
(when read voltage is coercive voltage or higher) are about 45.3 and 67.2, respectively. The
dielectric constant extracted from the first region is similar to the dielectric constant obtained
from the small signal capacitance-voltage (C-V) measurement at 2.5 MV/cm (higher than
coercive field) where the ferroelectric switching effect is minimized (at a frequency of 10 kHz
with an amplitude of 50 mV using an Agilent 4284A) as shown in Fig. S2(b). Meanwhile, the
extracted dielectric constant at or above the coercive voltage is close to the maximum dielectric
constant in small signal C-V measurement at the coercive voltage. These extracted values are
shown in Table I of the manuscript.
[1] S. J. Kim, D. Narayan, J.-G. Lee, J. Mohan, J. S. Lee, J. Lee, C. D. Young, J. Kim, S. R.
Summerfelt, T. San, and L. Colombo, in Proc. 9th IEEE International Memory Workshop
(IMW), (2017).
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FIG. S1. (a) Schematic diagram of pulse write/read measurement. (b) Pulse write/read result of
the HZO sample annealed at 400°C after TiN TE deposition. (c) The sequence of pulse
write/read measurement: for example, the write voltage was fixed at ±2.5 V and the read voltage
varied (-2.0 V, -1.5 V, -0.5 V, 0.5 V, 1.5 V, and 2.0 V).