Browsing by Author "Lee, Yih-Shing"

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Effects of Ga2O3 deposition power on electrical properties of cosputtered In-Ga-Zn-O semiconductor films and thin-film transistors
(2014-05-01)
Lee, Yih-Shing
;
Chang, Chih-Hsiang
;
Lin, Yuan-Che
;
Lyu, Rong-Jhe
;
Lin, Horng-Chih
In this study, we have successfully fabricated In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) with various Ga2O3 deposition powers prepared using a two radio-frequency (RF) (ceramics targets: In2O3 and Ga2O3) and one direct-current (DC) (metallic target: Zn) magnetron cosputtering system at room temperature. The carrier concentration for the IGZO films decreases to less than 3 x 10(16) cm(-3) when the Ga2O3 deposition power is 175W and Hall mobility decreases from 12.8cm(2)V(-1) s(-1) and saturates at 4.6 cm(2)V(-1) s(-1) with increasing Ga2O3 deposition power. The increase in the resistivity of the cosputtered films correlates with the decrease in the crystallinity of the InGaZn7O10 phase and the phase transformation from InGaZn7O10 to InGaZn2O5 with increasing Ga2O3 deposition power. With an optimum Ga2O3 deposition power of 150W, cosputtered IGZO TFTs with a higher, saturated drain current of 4.5 mu A, good saturation mobility, mu(sat) of 4.92cm(2)V(-1) s(-1), I-on/I-off of 10(9), a low subthreshold swing (SS) of 0.27V/decade, and R-SD of 30 k Omega have been successfully fabricated. (C) 2014 The Japan Society of Applied Physics
Electrical characteristics of amorphous In-Ga-Zn-O thin-film transistors prepared by radio frequency magnetron sputtering with varying oxygen flows
(2014-07-01)
Lee, Yih-Shing
;
Yen, Tung-Wei
;
Lin, Cheng-I
;
Lin, Horng-Chih
;
Yeh, Yun
This study investigates impacts of oxygen flow during the deposition of amorphous indium-gallium-zinc oxide (a-IGZO) channel layer with a radio frequency (r.f.) magnetron sputter on the electrical characteristics of the fabricated thin-film transistors (TFTs). Results indicate that as the film was deposited with a higher oxygen flow, the transfer curves are positively shifted while the field-effect mobility (mu(FE)) is significantly decreased. To get more insight about the effects, channel resistance (R-CH) and the parasitic source-to-drain resistance (R-SD) of the fabricated devices are extracted using the total resistance method. The extracted a-IGZO channel resistance per unit length (r(ch)) and R-SD are found to increase while the extracted effective mobility (mu(E)) is decreased with increasing oxygen flow during sputtering. These observations are postulated to be related the decrease in the In/(In + Ga + Zn) ratio and the increase in the Zn/(In + Ga + Zn) ratio of the a-IGZO films with increasing the oxygen flow rate which lead to higher resistivity and lower carrier concentration. The extracted R-SD can be comparable with R-CH for the devices prepared with high oxygen flow, resulting in the roll-off of mu(FE) as the channel length is shorter than 20 mu m. (C) 2014 Elsevier B.V. All rights reserved.
Electrical characteristics of amorphous In-Ga-Zn-O thin-film transistors prepared by radio frequency magnetron sputtering with varying oxygen flows
(2014-07-01)
Lee, Yih-Shing
;
Yen, Tung-Wei
;
Lin, Cheng-I
;
Lin, Horng-Chih
;
Yeh, Yun
This study investigates impacts of oxygen flow during the deposition of amorphous indium-gallium-zinc oxide (a-IGZO) channel layer with a radio frequency (r.f.) magnetron sputter on the electrical characteristics of the fabricated thin-film transistors (TFTs). Results indicate that as the film was deposited with a higher oxygen flow, the transfer curves are positively shifted while the field-effect mobility (mu(FE)) is significantly decreased. To get more insight about the effects, channel resistance (R-CH) and the parasitic source-to-drain resistance (R-SD) of the fabricated devices are extracted using the total resistance method. The extracted a-IGZO channel resistance per unit length (r(ch)) and R-SD are found to increase while the extracted effective mobility (mu(E)) is decreased with increasing oxygen flow during sputtering. These observations are postulated to be related the decrease in the In/(In + Ga + Zn) ratio and the increase in the Zn/(In + Ga + Zn) ratio of the a-IGZO films with increasing the oxygen flow rate which lead to higher resistivity and lower carrier concentration. The extracted R-SD can be comparable with R-CH for the devices prepared with high oxygen flow, resulting in the roll-off of mu(FE) as the channel length is shorter than 20 mu m. (C) 2014 Elsevier B.V. All rights reserved.
Positive Bias Stress Instability of In-Ga-Zn-O Thin-Film Transistors with Al2O3/TEOS Oxide Gate Dielectrics
(2017-01-01)
Lee, Yih-Shing
;
Wang, Yu-Hsin
;
Tien, Tsung-Cheng
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
The Vth shift (Delta Vth) of a-IGZO devices with gate dielectrics of Al2O3 and TEOS oxide after at a gate bias of +20V for 3600 s are +3.66V and -2.18V, respectively. Moreover, the V-th shift of two stacked dielectrics Al2O3 /TEOS oxide by using the equivalent capacitance with 100-nm-thick TEOS oxide. Two stacked dielectrics with a 10-nm-thick Al2O3 and a 96-nm-thick TEOS oxide, Delta Vth decreases to -0.42V after a gate bias of +20 V for 6400 s.
Relationships between the crystalline phase of an IGZO target and electrical properties of a-IGZO channel film
(2012-01-01)
Lee, Yih-Shing
;
Dai, Zuo-Ming
;
Lin, Cheng-I
;
Lin, Horng-Chih
;
電子工程學系及電子研究所
This study used powders containing different In2O3-Ga2O3-ZnO (IGZO) chemical compositions to manufacture targets using a metallurgical process. The resulting targets were used to deposit amorphous In-Ga-Zn-O (a-IGZO) channel films by a radio frequency magnetron sputtering process. This study examined the relationships between these target compositions and crystalline phases of the powders and the resulting material characterization, examining the impacts on electrical characteristics of a-IGZO films with varied O-2 flow rates. The ternary compound phase of ZnGa2O4 became stable at 1000 degrees C according to XRD diagrams at different calcining temperatures. An analysis of the XRD diagrams of different compositions of IGZO powders showed that the atomic ratio of ZnO is larger than that of In2O3 and Ga2O3, and that the main peaks (1 0 1) and (0 0 15) intensity of the respective InGaZnO4 and lnGaZnO6 phases intensity would increase. Ceramic targets with different compositions were used to deposit the a-IGZO films with varied O-2 flow rates. When the O-2 flow rate was zero, the results of a Hall measurement of a-IGZO films deposited from targets with higher Zn atomic ratio showed lower resistivity, higher carrier concentration, and lower mobility. Nevertheless, as the O-2 flow rate was more than 5 sccm, increasing the atom ratio of Zn in the IGZO ceramic target obviously increased the capability of capturing O-2 in the a-IGZO films, leading to higher resistivity, lower carrier concentration (<10(18) cm(-3)), and higher mobility. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Temperature Instability of Amorphous In-Ga-Zn-O Thin Film Transistors
(2013)
Lee, Yih-Shing
;
Fan, Sheng-Kai
;
Chen, Chii-Wen
;
Yen, Tung-Wei
;
Lin, Horng-Chih
In this paper, the temperature dependence of electrical behavior on amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) having plasma-enhanced chemical vapor deposition (PECVD) tetraethylorthosilicate (TEOS) oxide as the dielectric material was evaluated. Sub-threshold swing (SS) increases and Vth is negatively shifted as the temperature rises. Temperature-dependent sub-threshold characteristics were also observed for the fabricated a-IGZO TFTs. The increase in subthreshold current in a-IGZO TFTs is well described by the thermally activated electrons.