Fitting leakage current property

Form the physics of semiconductor devices, there are six different basic conduction processes in semiconductors: Schottky emission, Frenkel-Poole emission, tunneling or field emission, space-charge-limited, Ohmic and Ionic conduction.

To understand and explain the conduction mechanisms, the current fitting of both H-state and L-state for I-V curve is performed. We consider that H-state is Frenkel-Poole emission as Pd/HfOx/TiN device, as showed in Fig. 3-41, which is reasonable to be considered that L-state switching to H-state is the process of forming the current paths between the top electrode and bottom electrode. The current paths could be related to the arranging the order of point defects, such as oxygen vacancies and ionic defects associated with Hafnium atoms replaced. Electrons hop through the defects within the doped HfOx films. It is that the defects, composing the current paths, trap the electrons causes some ruptures of the current paths. However, at the same time, other current paths have chances to be formed again, which increase the conduction current within the transition region. Excessive of the nitrogen flow and without nitrogen treatment current fitting is Frenkel-Poole emission. The Frenkel-Poole emission equation is 2 )

Vexp(

As showed in Fig.3-42, that L-state is Ohmic conduction. I - V characteristics exhibiting the I V correlation is Ohmic (slope = 1). Which is reasonable to be considered that H-state switching to L-state is the process of ruptured the current paths between the top electrode and bottom electrode. The conduction mechanisms dominating in the H-state is Frenkel-Poole emission and L-state is Ohmic conduction.

Fig 3-43 show the different thermal treatment at H-state, as the without thermal treatment and thermal treatment current fitting is Frenkel-Poole emission, switching conduction mechanisms with the structure which has changed by thermal treatment.

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Fig 3-44 show L-state through thermal treatment changed switching conduction mechanisms from Ohmic conduction. The Pd/HfOx/TiN device whether thermal treatment or nitrogen flow treatment, the H-state is dominated by Frenkel-Poole emission, the L-state is dominated by Ohmic conduction. Fig 3-45 shows as different nitrogen flow treatment before deposition Al interface layer H-state changed switching conduction mechanisms, the switching conduction mechanisms is same from Pd. The switching conduction current fitting is Frenkel-Poole emission. Fig 3-46 show deposition Al layer H-state without nitrogen flow treatment and nitrogen flow treatment is dominated by Ohmic conduction. Fig 3-47 show deposition Al layer H-state different thermal treatment, the switching conduction mechanisms is Frenkel-Poole emission. Whether it is nitrogen flow or thermal treatment H-state is Frenkel-Poole emission. Fig 3-48 show deposition Al layer L-state different thermal treatment is Ohmic conduction. The thermal treatment does not influence the transfer characteristic.

It is proved again that the H-state dominated by forming of the current paths.

While a current path is formed, the electrons prefer to pass through the new-formed current path, which causes other paths to be formed with little chance. The small variation of the resistance of the H-state could be explained clearly. But, the larger variation of the resistance of the L-state is relative to the random electron-trapping in the turn-off process.

From the I-V curve that has been shown, the leakage current density of the OFF/ON state shows at both positive and negative voltage. As the same reason, the mechanism of the device was conjectured due to interface. Besides, at the high temperature, the current of the L-state significantly increases more than that of the H-state. It may be due to the electrons more difficult to be trapped at the higher temperature during the OFF process, which leads the fewer current paths to be

ruptured. Have proved the Al, nitrogen, thermal treatment will change and switching conduction mechanisms to the attitude characteristic.

Fig 3-1 SEM cross-sectional structure of as deposited HfOx film

Fig 3-2 AFM step height of HfOx/TiN film

(a)

(b)

Fig 3-3 AFM image of as deposited HfOx film (a) 2d image (b) rms image

Fig 3-4 SEM top view of as deposited HfOx film

Fig 3-5 XPS cross-sectional structure of as deposited HfOx film

Fig 3-6 X-ray photoelectron spectra of the Hf 4f region of as deposited HfOx films in surface layer

Fig 3-7 X-ray photoelectron spectra of the Hf 4f region of as deposited HfOx films in interface region

Fig 3-8 X-ray diffraction patterns of as-deposited HfOx films

Fig 3-9 X-ray diffraction patterns of as-deposited HfOx films and RTA process

Fig 3-10 I-V curve of the Pd/HfOx/TiN device

Fig 3-11 switch cycle vs. voltage of Pd/HfOx/TiN device

Fig 3-12 I-V curve of the Pd/HfOx/TiN device after RTA 400℃ for 30s for negative switch on positive switch off

Fig 3-13 I-V curve of the Pd/HfOx/TiN device after RTA 400℃ for 30s for positive switch on negative switch off

Fig 3-14 I-V curve of the Pd/HfOx/TiN device after RTA 400℃ for 1min

Fig 3-15 I-V curve of the Pd/HfOx/TiN device after RTA 400℃ 1min for positive switch on negative switch off

Fig 3-16 comparison thermal treatment of the Pd/HfOx/TiN device

Fig 3-17 comparison sample of thermal treatment as Pd initial forming

Fig 3-18 comparison sample of thermal treatment at various RTA times

Fig 3-19 I-V curve as N2 0.5sccm 20s before deposition Pd layer

Fig 3-20 I-V curve as N2 12sccm 20s before deposition Pd layer

Fig 3-21 comparison nitrogen different flow with deposition Pd initial forming

Fig 3-22 comparison sample as N2 0.5sccm 20s of thermal treatment at various RTA times

Fig 3-23 comparison sample as N2 12 sccm 20s of thermal treatment at various RTA times

Fig 3-24 comparison Al layer of thickness

Fig 3-25 I-V curve of the Pd/Al/HfOx/TiN device for positive switch on negative switch off

Fig 3-26 I-V curve of the Pd/Al/HfOx/TiN device as different thermal treatment time

Fig 3-27 I-V curve of the Pd/Al/HfOx/TiN device

Fig 3-28 switch cycle vs. voltage of Pd/Al/HfOx/TiN device

Fig 3-29 Retention properties of RLow and RHigh at room temp.

Fig 3-30 comparison nitrogen flow 0.5sccm different time at deposition 35Å Al

Fig 3-31 comparison nitrogen different flow at deposition 35Å Al

Fig 3-32 I-V curve of the Pd/AlN/HfOx/TiN device

Fig 3-33 I-V curve as N2 6sccm 20s of the Pd/Al/HfOx/TiN device

Fig 3-34 I-V curve as N2 12sccm 20s of the Pd/Al/HfOx/TiN device

Fig 3-35 comparison nitrogen different flow 20s with deposition 35Å Al

Fig 3-36 comparison nitrogen different flow with deposition 35Å Al RTA 30s

Fig 3-37 comparison nitrogen different flow with deposition 35Å Al RTA 1min

Fig 3-38 comparison Al 35 RTA resistance state

Fig 3-39 I-V curve of the Pd/Al/HfOx/TiN device as N 12sccm 20s after RTA 400℃ for 1min

Fig 3-40 Retention properties of RLow and RHigh at room temp

Fig. 3-41 the current fitting of H-state as Pd/HfOx/TiN device as different nitrogen flow I-V curve

Fig. 3-42 the current fitting of L-state as Pd/HfOx/TiN device as different nitrogen flow I-V curve

Fig. 3-43 the current fitting of H-state as Pd/HfOx/TiN device as different thermal treatment time I-V curve

Fig. 3-44 the current fitting of L-state as Pd/HfOx/TiN device as different thermal treatment I-V curve

Fig. 3-45 the current fitting of H-state as Pd/Al/HfOx/TiN device as different nitrogen flow I-V curve

Fig. 3-46 the current fitting of L-state as Pd/Al/HfOx/TiN device as different nitrogen flow I-V curve

Fig. 3-47 the current fitting of H-state as Pd/Al/HfOx/TiN device as different thermal treatment I-V curve

Fig. 3-48 the current fitting of L-state as Pd/Al/HfOx/TiN device as different thermal treatment I-V curve

Table 3-1 comparison Pd/HfOx/TiN sample different treatment negative switch on

Origin RTA 30s RTA 1min N₂0.5sccm 20s N₂ 12sccm 20s Current 200μA 500μA 1mA 500μA 1mA

Voltage >2V ~1.5V ~1V <1.5V ~1V

Table 3-2 comparison Pd/HfOx/TiN sample different treatment positive switch on

Table 3-3 comparison Pd/Al/HfOx/TiN sample different treatment negative switch on

Origin RTA 30s RTA 1min N20.5sccm 20s N26sccm 20s N2 12sccm 20s Current ~1mA ~500μA ~50μA ~500μA ~500μA ~500μA Voltage <1V <1.5v ~3.5v <2V <2V <2v

Table 3-4 comparison Pd/Al/HfOx/TiN sample different treatment positive switch on

Origin RTA 30s RTA 1min N2 0.5sccm 20s N2 6 sccm 20s N2 12sccm 20s Current ~1mA ~500μA ~50μA ~500μA ~500μA ~500μA Voltage <1V <1.5v ~3.5v <2V <2V <2v

Endurance 1500 75 13 30 5 75

ratio 10 150 2x104 103 103 4x104