• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.92-96
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• 2019

In the presence of ${\mu}-tip$ embedded in a slot-die head for stripe coatings, there arises the capillary flow that limits an increase of the stripe density, which is required for the potential applications in organic light-emitting diode displays. With an attempt to suppress it, we have employed a computational fluid dynamics software and performed simulations by varying the ${\mu}-tip$ length and the contact angles of the head lip and ${\mu}-tip$. We have first demonstrated that such a capillary flow phenomenon (a spread of solution along the head lip) observed experimentally can be reproduced by the computational fluid dynamics software. Through simulations, we have found that stronger capillary flow is observed in the hydrophilic head lip with a smaller contact angle and it is suppressed effectively as the contact angle increases. When the contact angle of the head lip increases from $16^{\circ}$ to $130^{\circ}$, the distance a solution can reach decreases sharply from $256{\mu}m$ to $44{\mu}m$. With increasing contact angle of the ${\mu}-tip$, however, the solution flow along the ${\mu}-tip$ is disturbed and thus the capillary flow phenomenon becomes more severe. If the ${\mu}-tip$ is long, the capillary flow also appears strong due to an increase of flow resistance (electronic-hydraulic analogy). It can be suppressed by reducing the ${\mu}-tip$ length, but not as effectively as reducing the contact angle of the head lip.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.157-160
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• 2021

As an insulator for a thin film transistor(TFT) and an encapsulation material of organic light emitting diode(OLED), aluminum oxide (Al₂O₃) has been widely studied using several technologies. Especially, in spite of low deposition rate, atomic layer deposition (ALD) has been used as a process method of Al₂O₃ because of its low process temperature and self-limiting reaction. In the Al₂O₃ deposition by ALD method, Ar Purge had some crucial effects on the film properties. After reaction gas is injected as a formation of pulse, an inert argon(Ar) purge gas is injected for gas desorption. Therefore, the process parameter of Ar purge gas has an influence on the ALD deposited film quality. In this study, Al₂O₃ was deposited on glass substrate at a different Ar purge time and its structural characteristics were investigated and analyzed. From the results, the growth rate of Al₂O₃ was decreased as the Ar purge time increases. The surface roughness was also reduced with increasing Ar purge time. In order to obtain the high quality Al₂O₃ film, it was known that Ar purge times longer than 15 sec was necessary resulting in the self-limiting reaction.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.6
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• pp.17-23
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• 2000

In this study, we prepared red organic light-emitting-diode(OLED) with a fluorescent dye(Sq)-doped and inserted between emission and cathode layer 1,3-bis(5-p-t-butylphenyl)-1,3,4-oxadiazol-2-yl)benzene (OXD7) or/and tris(8-hydroxyquinoline) aluminum ($Alq_3$) layers for increasing electroluminescent(EL) efficiency. This inserting effect has been observed and EL mechanism characteristics have been examined. The hole transfer layer is a N,N'-diphenyl-N,N'-bis-(3-methyl phenyl)-1,1'-diphenyl-4,4'-diamine (TPD), and the host and guest materials of emission layer is $Alq_3$ and bis[1-methyl-3,3'-dimethyl-2-indorindiylmethyl] squaraine (Sq), respectively. For the inserting of $Alq_3$, emission efficiency increased. But we can not obtained highly pure red emission owing to the emission of inserting $Alq_3$ layer. The inserting of OXD7 makes hole block and accumulate. Because of increasing recombination probability of electron and hole, highly pure red color can be held. Simultaneously brightness characteristics and emission efficiency could improve.

• Journal of the Korean Society of Urban Environment
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• v.18 no.4
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• pp.503-509
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• 2018

In this study, a Proton-Transfer Reaction-Time-of-Flight Mass spectrometer (PTR-TOF-MS) was used for the continuous monitoring of Volatile Organic Compounds (VOCs) emitted from semiconductor workplace such as photolithography (PHOTO), flat panel display (FPD), organic light emitting diode (OLED), etching (WET) process. The averaged VOCs mixing ratio in the such workplace, PHOTO was 6.5 ppm, FPH was 6.4 ppm, WET was 2.0 ppm and OLED was 1.3 ppm, respectively. The abundance of VOCs in the workplace were methyl ethyl ketone (MEK) with 2.8 ppm (69%) and acetaldehyde with 0.5 ppm (13.2%). Depending on the semiconductor process characteristics, various VOCs have been observed in the workplace. The VOCs mixing ratio are lower than the workplace regulation standard (TWA), it is necessary to continuously monitor and effectively manage these VOCs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.878-885
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• 2008

The FPDs(Flat Panel Displays) such as LCD(Liquid Crystal Display) and PDP(Plasma Display Panel) and OLED(Organic Light Emitting Diode), recently, have been substituted for CRT(Cathode Ray Tube) displays because they have a convex surface, small volume, light weight and lower electric power consumption. The productivity of FPDs is greatly dependent on the area of thin glass panel with 0.6 - 0.8mm thickness because FPDs are manufactured by cutting a large-scaled thin glass panel with patterns to the required product dimensions. So FPD's industries are trying to increase the area of thin glass panel. For example, the thin glass panel size of the 8th generation is 2,200mm in width, 2,600mm in length and 0.7mm in thickness. The air flows both in the thin glass panel and in the porous PE-plate surface were modeled and analyzed, from which a working condition was estimated. The thin glass panel on the porous PE-plate surface with self-lubricating characteristics was investigated and compared with that on the square duct floating bar surface with many holes of 1mm diameter when the thin glass panel contacts the floating bar surface due to malfunction of electric power supply.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.351-359
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• 2015

Next-generation displays should be transparent and flexible as well as having high resolution and frame number. The main factor for active matrix organic light emitting diode and next-generation displays is the development of TFTs (thin-film transistors) with high mobility and large area uniformity. The TFTs used for transparent displays are mainly oxide TFT that has oxide semiconductor as channel layer. Zinc-oxide based substances such as indium-gallium-zinc-oxide has attracted attention in the display industry. In this paper, the mobility improvement of low cost oxide TFT is studied for fast operating next-generation displays by overcoming disadvantages of amorphous silicon TFT that has low mobility and poly silicon TFT that requires expensive equipment for complex process and doping process.

• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.63-68
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• 2011

The investigation is directed to lead free (Pb-free) frits that can be used for organic light emitting diode, plasma display screen devices and other sealing materials. $P_2O_5$-SnO system glasses have been prepared for Pb-free low temperature glass frit. Structure and properties of the glasses with the composition SnO-$xB_2O_3-(60-x)P_2O_5$ (x=0, 5, 10, 15, 20, 25, 30, 35, 40 mol%) were characterized by infrared spectra (IR), X-ray diffraction(XRD), Density, Molar volume, Thermo mechanical analysis(TMA) and weight loss after immersion test. Glass transition temperature($T_g$), dilatometric softening temperature($T_d$) and chemical durability increased, and coefficient of thermal expansion($\alpha$) decrease with the substitution of $B_2O_3$ for $P_2O_5$ in the range of 0~25 mol%.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.519-525
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• 2015

Positive bias stress-induced instability in amorphous indium-gallium-zinc-oxide (a-IGZO) bottom-gate thin-film transistors (TFTs) was investigated under high $V_{GS}$/low $V_{DS}$ and low $V_{GS}$/high $V_{DS}$ stress conditions through incorporating a forward/reverse $V_{GS}$ sweep and a low/high $V_{DS}$ read-out conditions. Our results showed that the electron trapping into the gate insulator dominantly occurs when high $V_{GS}$/low $V_{DS}$ stress is applied. On the other hand, when low $V_{GS}$/high $V_{DS}$ stress is applied, it was found that holes are uniformly trapped into the etch stopper and electrons are locally trapped into the gate insulator simultaneously. During a recovery after the high $V_{GS}$/low $V_{DS}$ stress, the trapped electrons were detrapped from the gate insulator. In the case of recovery after the low $V_{GS}$/high $V_{DS}$ stress, it was observed that the electrons in the gate insulator diffuse to a direction toward the source electrode and the holes were detrapped to out of the etch stopper. Also, we found that the potential profile in the a-IGZO bottom-gate TFT becomes complicatedly modulated during the positive $V_{GS}/V_{DS}$ stress and the recovery causing various threshold voltages and subthreshold swings under various read-out conditions, and this modulation needs to be fully considered in the design of oxide TFT-based active matrix organic light emitting diode display backplane.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.281-285
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• 2020

Oxide semiconductor devices have become increasingly important because of their high mobility and good uniformity. The channel length of oxide semiconductor thin film transistors (TFTs) also shrinks as the display resolution increases. It is well known that reducing the channel length of a TFT is detrimental to the current saturation because of drain-induced barrier lowering, as well as the movement of the pinch-off point. In an organic light-emitting diode (OLED), the lack of current saturation in the driving TFT creates a major problem in the control of OLED current. To obtain improved current saturation in short channels, we fabricated indium gallium zinc oxide (IGZO) TFTs with single gate and double gate structures, and evaluated the electrical characteristics of both devices. For the double gate structure, we connected the bottom gate electrode to the source electrode, so that the electric potential of the bottom gate was fixed to that of the source. We denote the double gate structure with the bottom gate fixed at the source potential as the BGFP (bottom gate with fixed potential) structure. For the BGFP TFT, the current saturation, as determined by the output characteristics, is better than that of the conventional single gate TFT. This is because the change in the source side potential barrier by the drain field has been suppressed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.5
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• pp.12-18
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• 2008

Ag paste was employed for source and drain electrode of OTFTs and for the data metal lines of OTFT-OLED array on PC(polycarbonate) substrate. We tested two kinds of Ag-pastes such as pastes for 325 mesh and 500 mesh screen mask to examine the pattern ability and electrical performance for OTFTs. The minimum feature size was 60 ${\mu}m$ for 325 mesh screen mask and 40 ${\mu}m$ for 500 mesh screen mask. The conductivity was 60 $m{\Omega}/\square$ for 325 mesh and 133.1 $m{\Omega}/\square$ for 500 mesh. For the OTFT performance the mobility was 0.35 $cm^2/V{\cdot}sec$ and 0.12 $cm^2/V{\cdot}sec$, threshold voltage was -4.7 V and 0.9 V, respectively, and on/off current ratio was ${\sim}10^5$, for both screen masks. We applied the 500 mash Ag paste to OTFT-OLED array because of its good patterning property. The pixel was composed of two OTFTs and one capacitor and one OLED in the area of $2mm{\times}2mm$. The panel successfully worked in active mode operation even though there were a few bad pixels.