• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.187-187
• /
• 2012

Solution-processed metal-alloy oxides such as indium zinc oxide (IZO), indium gallium zinc oxide (IGZO) has been extensively researched due to their high electron mobility, environmental stability, optical transparency, and solution-processibility. In spite of their excellent material properties, however, there remains a challenging problem for utilizing IZO or IGZO in electronic devices: the supply shortage of indium (In). The cost of indium is high, what is more, indium is becoming more expensive and scarce and thus strategically important. Therefore, developing an alternative route to improve carrier mobility of solution-processable ZnO is critical and essential. Here, we introduce a simple route to achieve high-performance and low-temperature solution-processed ZnO thin film transistors (TFTs) by employing alkali-metal doping such as Li, Na, K or Rb. Li-doped ZnO TFTs exhibited excellent device performance with a field-effect mobility of $7.3cm^2{\cdot}V-1{\cdot}s-1$ and an on/off current ratio of more than 107. Also, in case of higher drain voltage operation (VD=60V), the field effect mobility increased up to $11.45cm^2{\cdot}V-1{\cdot}s-1$. These all alkali metal doped ZnO TFTs were fabricated at maximum process temperature as low as $300^{\circ}C$. Moreover, low-voltage operating ZnO TFTs was fabricated with the ion gel gate dielectrics. The ultra high capacitance of the ion gel gate dielectrics allowed high on-current operation at low voltage. These devices also showed excellent operational stability.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.05a
• /
• pp.13.1-13.1
• /
• 2009

Transparent electronics has attracted many interests, for it can open new applications for consumer electronics, transportation, business, and military. Among them, display backplane, thin film transistor (TFT) array would be the most attractive application. Many researchers have been investigating oxide semiconductors for transparent channel material of TFT since the report for transparent amorphous oxide semiconductor (TAOS) TFT by Hosono group and ZnO TFT by Wager group. Especially, oxide TFTs have been intensively investigated during a couple of years since the first demonstration of ZnO-TFT driving AM-OLED. Many papers regarding the fabrication and performance of oxide TFTs, and active matrix display driven by oxide TFTs have been reported. Now lots of people have confidence in the competitiveness of oxide TFTs for the backplane of AM-Display. Especially, high mobility, uniformity, fairly good stability, and low cost process make oxide TFTs applied even to a large size AM-OLED. Last year, Samsung mobile display, former SID, reported 12" AM-OLED driven by IZGO-TFT and it seems that the remained issue for the mass production is the bias temperature stability. Here, we will introduce the application of oxide TFT and important issue for oxide TFT to be used for the direct printing.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.7
• /
• pp.1489-1496
• /
• 2009

Amorphous indium-gallium-zinc-oxide thin-film-transistors (TFTs) were modeled successfully. Dependence of TFT characteristics on structure, thickness, and equilibrium electron-density of the active layer was studied. For mono-active-layer TFTs, a thinner active layer had higher field-effect mobility. Threshold voltage showed the smallest absolute value for the 20 nm active-layer. Subthreshold swing showed almost no dependence on active-layer thickness. For the double-active-layer case, better switching performances were obtained for TFTs with bottom active layers with higher equilibrium electron density. TFTs with thinner active layers had higher mobility. Threshold voltage shifted in the minus direction as a function of the increase in the thickness of the layer with higher equilibrium electron-density. Subthreshold swing showed almost no dependence on active-layer structure. These data will be useful in optimizing the structure, the thickness, and the doping ratio of the active layers of oxide-semiconductor TFTs.

• Journal of Information Display
• /
• v.13 no.2
• /
• pp.61-66
• /
• 2012

The double-layered Ti/Si barrier metal is demonstrated for the source/drain Cu interconnections in oxide semiconductor thin-film transistors (TFTs). The transmission electromicroscopy and ion mass spectroscopy analyses revealed that the double-layered barrier structure suppresses the interfacial reaction and the interdiffusion at the interface after thermal annealing at $350^{\circ}C$. The underlying Si layer was found to be very useful for the etch stopper during wet etching for the Cu/Ti layers. The oxide TFTs with a double-layered Ti/Si barrier metal possess excellent TFT characteristics. It is concluded that the present barrier structure facilitates the back-channel-etch-type TFT process in the mass production line, where the four- or five-mask process is used.

• Transactions on Electrical and Electronic Materials
• /
• v.17 no.3
• /
• pp.143-145
• /
• 2016

In order to find suitable source and drain (S/D) electrodes for amorphous InGaZnO thin film transistors (a-IGZO TFTs), the specific contact resistance of interface between the channel layers and various S/D electrodes, such as Ti/Au, a-IZO and multilayer of a-IGZO/Ag/a-IGZO, was investigated using the transmission line model. The a-IGZO TFTs with a-IGZO/Ag/a-IGZO of S/D electrodes had good performance and low contact resistance due to the homo-junction with channel layer. The stability was measured with different electrodes by a positive bias stress test. The result shows the a-IGZO TFTs with a-IGZO/Ag/a-IGZO electrodes were more stable than other devices.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.14 no.5
• /
• pp.594-600
• /
• 2014

A threshold voltage compensation pixel circuit was developed for active-matrix organic light emitting diodes (AMOLEDs) using amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO-TFTs). Oxide TFTs are n-channel TFTs; therefore, we developed a circuit for the n-channel TFT characteristics. The proposed pixel circuit was verified and proved by circuit analysis and circuit simulations. The proposed circuit was able to compensate for the threshold voltage variations of the drive TFT in AMOLEDs. The error rate of the OLED current for a threshold voltage change of 3 V was as low as 1.5%.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1027-1029
• /
• 2004

In this paper, we have fabricated pentacene thin film transistors (TFTs) using polyvinylphenol (PVP) copolymer and cross-linked PVP as gate insulator on glass and plastic (PET) substrate. Depending on the density of PVP and cross-link material the performance has been changed. We obtained the best device performance with the mobility of 0.32cm2/V${\cdot}$sec and the on/off current ratio of 1.19${\times}$106 for the case of 10wt% PVP copolymer mixed with 5wt% poly (melamine-co-formaldehyde). Additionally using pentacene TFTs with the above PVP gate insulator, we fabricated the integrated circuits including inverter which produced the gain of 9.7.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.172-172
• /
• 2003

It has been known that Pd-MILC shows much faster and lower temperature crystallization than Ni-MILC but it can not be put into practice due to the quality issue of thus fabricated poly crystals. In this study, addition of Pd into Ni-MILC has been attempted in order to take advantages of the Pd-MILC without sacrificing of the Ni-MILC TFTs. It turns out that when 5% of Pd has been added to Ni for MILC, MILC growth rate increases two - three times faster than pure Ni-MILC. The MILC growth rate shows monotonic increase with increase the amount of Pd in Ni up to 50%. Even when small amount of Pd was added to Ni like 5%, crystallization phenomenon already follows the way of Pd-MILC. The Poly-W thus fabricated shows lower leakage current than pure Ni-MILC TFT without losing any amount of on-current This fact is very important in low temperature poly-TFTs because MILC-TFTs, especially suffer from the relatively high leakage current

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1216-1219
• /
• 2007

We have been developing printed organic TFTs for flexible displays. In this study, we have pay attention to the operation stability improvement of the organic TFTs, and studied several factors especially depending on the dielectric layers. From the detailed analysis of the effects of dielectric layers, we have proposed a new printed dielectric layer which is mainly consisting of metal oxide and gives high operation stability

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1172-1175
• /
• 2007

We have investigated the threshold voltage shifts(${\Delta}Vth$) and drain current level shift (${\Delta}Ids$) in subthreshold region of a-Si:H TFTs induced by DC Bias (Vgs and Vds) - Temperature stress (BTS) condition. We plotted the transfer curves and the ${\Delta}Vth$ contour maps as Vds-Vds stress bias and Temperature to examine the severe damage cases on TFTs. Also, by drawing out the time-dependent transfer curve (Ids-Vgs) in the region of $10^{-8}\;{\sim}\;10^{-13}$ (A) current level, we can estimate the failure time of TFTs in a operating condition.