Control of subthreshold swing using an in situ PEALD nano-laminated IGZO/Al₂O₃ multi-channel structured TFT

Figures & data

Figure 1. Schematic of (a) the stacked TFT with IGZO/Al₂O₃ using in situ PEALD (1S, 3S, 5S, and 10S TFTs), (b) representative transfer curve, and (c) trend of the electrical parameters of the devices based on the number of stacking layers.

Table 1. Device parameters (V_th, µ_FE and SS) for the 1S, 3S, 5S, and 10S TFTs.

Annealed at 350^oC	1S TFT	3S TFT	5S TFT	10S TFT
Vth [V]	0.22 ± 0.02	0.19 ± 0.05	0.13 ± 0.04	0.16 ± 0.03
μFE [cm^2/Vs]	1.34 ± 0.21	2.40 ± 0.19	2.94 ± 0.10	4.33 ± 0.08
S·S [V/decade]	0.31 ± 0.01	0.31 ± 0.02	0.36 ± 0.02	0.45 ± 0.02

Figure 2. (a) STEM image, (b) EDS mapping image (2-D) of Al and In, (c) vertical EDS line scan (1-D) of Al, In, Ga and Zn in a 10-stack IGZO/Al₂O₃ layer.

Figure 3. (a) 2-D and (b) 1-D distributions of the simulated current density under the operational state (V_GS: 10 V, V_DS: 0.1 V) based on multi-channel TFT (1S, 3S, 5S and 10S TFTs).

Figure 4. Energy band and enlarged conduction band edge in the gate insulator (SiO₂) and IGZO/Al₂O₃ under the operational state (V_GS: 10 V, V_DS: 0.1 V) for (a) 1S, (b) 3S, (c) 5S, and (d) 10S TFTs.

Table 2. Potential decomposition under the operational state (V_GS: 10 V and V_DS: 0.1 V) in the gate insulator (SiO₂) and multilayer (IGZO and Al₂O₃).

VGS: 10 V	1S TFT	3S TFT	5S TFT	10S TFT
$V_{\text{Si}{\text{O}}_2}$ (V)	9.97	9.90	9.87	9.48
VIGZO (V)	0.03	0.06	0.09	0.11
$V_{\text{A}{\text{l}}_2{\text{O}}_3}$ (V)	0.00	0.04	0.04	0.41

Figure 5. Changes in V_th with stress time under PBS evaluation (V_GS: 2 MV/cm, time: 3600 s).