Ultra-Low Temperature Poly-Si Thin Film Transistor for Plastic Substrate

Takashi Noguchi,Do Young Kim,Hans S. Cho,Huaxing Yin,Hyuck Lim,권장연,Ji Sim Jung,Jong Man Kim,Kyung Bae Park,Xiaoxin Zhang 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.I

We studied the fabrication of poly-Si TFT (thin film transistor) by using excimer laser crystallization of sputtered a-Si film at below 200 C. We could obtain the precursor a-Si film with low impurity gas content of 0.39 % by using Xe sputtering and poly-Si film with maximum grain size of 1 μm. We successfully fabricated poly-Si TFT with a field-effect mobility of 70 cm2/V·sec on glass and 15 cm2/V·sec on plastic by using ultra low temperature process at below 200 C, respectively..

Effective Annealing and Crystallization of Si Film for Advanced TFT System

Noguchi, Takashi The Korean Infomation Display Society 2010 Journal of information display Vol.11 No.1

The effect of the crystallization and activated annealing of Si films using an excimer laser and the new CW blue laser are described and compared with furnace annealing for application in advanced TFTs and for future applications. Pulsed excimer laser annealing (ELA) is currently being used extensively as a low-temperature poly-silicon (LTPS) process on glass substrates as its efficiency is high in the ultra-violet (UV) region for thin Si films with thickness of 40-60 nm. ELA enables extremely low resistivity relating to high crystallinity for both the n- and p-type Si films. On the other hand, CW blue laser diode annealing (BLDA) enables the smooth Si surface to have arbitral crystal grains from micro-grains to an anisotropic huge grain structure only by controlling its power density. Both annealing techniques are expected to be applied in the future advanced TFT systems.

Poly-Si TFT Technology

Noguchi, Takashi,Kim, D.Y.,Kwon, J.Y.,Park, Y.S. The Korean Infomation Display Society 2004 인포메이션 디스플레이 Vol.5 No.1

Poly-Si TFT(Thin Film Transistor) technology are reviewed and discussed. Poly-Si TFTs fabricated on glass using low-temperature process were studied extensively for the application to LCD (Liquid Crystal Display) as well as to OLED(Organic Light Emitting Diode) Display. Currently, one of the application targets of the poly-Si TFT is emphasized on the highly functional SOG(System on Glass). Improvement of device characteristics such as an enhancement of carrier mobility has been studied intensively by enlarging the grain size. Reduction of the voltage and shrinkage of the device size are the trend of AM FPD(Active Matrix Flat Panel Display) as well as of Si LSI, which will arise a peculiar issue of uniformity for the device performance. Some approaches such as nucleation control of the grain seed or lateral grain growth have been tried, so far.

Influence of Grain Size Deviation on the Characteristics of Poly-Si Thin Film Transistor

Takashi Noguchi,HyunMo Koo,HongSock Choi 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.2

The influence of grain size deviation on the device characteristics of thin film transistors (TFTs) was investigated by using the defect and grain model. By varying the deviation of the grain size in poly-Si film relating to the channel size of the device, the deviations of the S factor, i.e., the gate voltage swing, which affects the threshold voltage and the drain current, were evaluated. From the calculation results, as the deviation of the grain size increases, the uniformity of the device characteristics degrades drastically. As the channel size decreases, the uniformity of the device characteristics degrades drastically even for the same deviation of grain size. If high-performance, uniform TFTs are realized, it is important to control the deviation of the grain size and the number of grains contained in a channel, as well as the grain size itself.

Electrical Activation of Boron in Si Film Using Excimer Laser Annealing

Takashi Noguchi,Masateru Sato,Tomoyuki Miyahira,Kenji Kawai,Toshiharu Suzuki 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1

After UV (ultra-violet) pulsed ELA (excimer laser annealing) for highly-boron doped Si films, the conductivity and the correlated crystallinity in the lm were evaluated by comparing them with the case of SPC (solid phase crystallization) in a furnace chamber at the temperature below 650 ℃. The sheet resistance decreases drastically with improving crystallinity by performing ELA. By optimizing the ELA conditions, ecient solidied activation after melting occurs and the Si film with a 50 nm thickness shows an extremely low sheet resistance of 50 ohm/□ at a dose of 5 × 10<SUP>15</SUP> cm<SUP>-2</SUP>. The analytical result from the Hall measurement suggests that the drastic activation after ELA is due to the high carrier concentration, which relates to the higher crystallinity. ELA activation for heavily-impurity-incorporated Si lms is eective not only for the formation of the source and the drain or the Si gate in CMOS (complementary metal oxide semiconductor) TFTs (thin-film transistors) but also for the electrode in pin photo-sensor diodes for SoP (system on panel) and solar cell applications.

Low-resistance phosphorus-doped Si films through blue laser diode annealing

Takashi Noguchi,Tatsuya Okada 한국정보디스플레이학회 2014 Journal of information display Vol.15 No.1

The effect of activated annealing on Si films using a new semiconductor blue laser was studied for application to the thin-film transistor (TFT) system on a panel. As a result of the blue laser diode annealing (BLDA) of the continuous-wave (CW) scanning mode at 500 mm/s for 50-nm-thick heavily phosphorus-doped Si films, drastic crystallization occurred while maintaining the surface’s smoothness. By irradiating the laser power between 5 and 8 W for chemical vapor deposition (CVD) films, the grain size was successively controlled by forming micrograins to large grains as well as to anisotropic long crystal grains. Correspondingly, the resistivity decreased depending on the increase in the electron mobility while the high carrier concentration values were retained for the various grained structures. The dopant activation rate was estimated to be 100% in the Si network in spite of the polycrystalline phase. The heavily doped Si film is expected to be applied to electrodes in high-performance TFTs as an advanced low-temperature polysilicon (LTPS) process on glass or flexible plastic sheets.

Low-temperature poly Si TFTs via BLDA for a Ne-sputtered Si film using sputtered gate SiO2

Takashi Noguchi,Tatsuya Okada 한국정보디스플레이학회 2018 Journal of information display Vol.19 No.4

Amorphous SiO2 and amorphous Si films were deposited on glass using radio frequency (RF) sputtering, and were subsequently poly-crystallized using blue-laser diode annealing (BLDA) scanned by a CWbeam. Ne, which has a smaller atomic radius than Ar, was used for the sputtering of the Si film. For the gate insulator, a small amount of O2 gas diluted with Ar was flown during the sputtering to optimize the SiO2 film with a low leakage current. A simple TFT structure with a metal source and drain (S/D) was adopted to realize a low-temperature process with a low fabrication cost. Furthermore, to confirm the effectiveness of the sputtered gate oxide, a poly-Si TFT adopting a Si film deposited using plasma-enhanced chemical vapor deposition (PE CVD) for the channel was fabricated and was compared with the TFT with a sputtered Si film for the channel. Reasonable Vg-Id characteristics were obtained for both poly-Si TFTs. The TFT structure with a metal S/D formed through a low-temperature sputtering-based process is expected to be applied to Si TFTs on an arbitrary flexible panel.

Effective Annealing and Crystallization of Si Film for Advanced TFT System

Takashi Noguchi 한국정보디스플레이학회 2010 Journal of information display Vol.11 No.1

The effect of the crystallization and activated annealing of Si films using an excimer laser and the new CW blue laser are described and compared with furnace annealing for application in advanced TFTs and for future applications. Pulsed excimer laser annealing (ELA) is currently being used extensively as a low-temperature poly-silicon (LTPS) process on glass substrates as its efficiency is high in the ultra-violet (UV) region for thin Si films with thickness of 40-60 nm. ELA enables extremely low resistivity relating to high crystallinity for both the n- and p-type Si films. On the other hand, CW blue laser diode annealing (BLDA) enables the smooth Si surface to have arbitral crystal grains from micro-grains to an anisotropic huge grain structure only by controlling its power density. Both annealing techniques are expected to be applied in the future advanced TFT systems.

Age-Related Prevalence of Periodontoid Calcification and Its Associations with Acute Cervical Pain

Takashi Kobayashi,Naohisa Miyakoshi,Norikazu Konno,Yoshinori Ishikawa,Hideaki Noguchi,Yoichi Shimada 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.6

Study Design: Prospective study. Purpose: To assess the prevalence of periodontoid calcification and its associations with acute cervical pain. Overview of Literature: Calcium pyrophosphate dihydrate (CPPD) deposition disease is a common rheumatological disorder that occurs especially in elderly patients. Although CPPD crystals induce acute arthritis, these crystals are not usually symptomatic. Calcification surrounding the odontoid process (periodontoid calcification) has been reported to induce inflammation, resulting in acute neck pain. This disease is called crowned dens syndrome. Whether calcification induces inflammation or whether the crystals are symptomatic remains unclear. Methods: The prevalence of periodontoid calcification at the atlas transverse ligament was examined by computed tomography of the upper cervical spine in patients suspected of brain disease but no cervical pain (control group, n=296), patients with pseudogout of the peripheral joints but no cervical pain (arthritis group, n=41), and patients with acute neck pain (neck pain group, n=22). Next, the correlation between the prevalence of periodontoid calcification and symptoms was analyzed. Results: In the control group, 40 patients (13.5%) showed periodontoid calcification with no significant difference in the prevalence with gender. The prevalence of calcification increased significantly with age (p =0.002). In the arthritis group, 26 patients (63.4%) reported periodontoid calcification. In the neck pain group, 14 patients (63.6%) reported periodontoid calcification. Multiple logistic regression analysis by age and group revealed that higher age, inclusion in the arthritis group, and inclusion in the neck pain group significantly affected the prevalence of calcification. Conclusions: Our results cumulatively suggest that periodontoid calcification is an aging-related reaction and that calcification per se does not always cause neck pain. Periodontoid calcification was observed more frequently in patients with pseudogout of the peripheral joints and in those with acute neck pain than in asymptomatic control patients.

Aerosol Deposition and Behavior on Leaves in Cool-temperate Deciduous Forests. Part 2: Characteristics of Fog Water Chemistry and Fog Deposition in Northern Japan

Takashi Yamaguchi,Izumi Noguchi,Yoko Watanabe,Genki Katata,Haruna Sato,Hiroshi Hara 한국대기환경학회 2013 Asian Journal of Atmospheric Environment (AJAE) Vol.7 No.1

The fog water chemistry and deposition in northern Japan were investigated by fog water and throughfall measurements in 2010. Fog water was sampled weekly by an active-string fog sampler at Lake Mashu from May to November. Throughfall measurements were conducted using rain gauges under three deciduous trees along the somma of the lake from August to October. The mean fog deposition rate (flux) was calculated using throughfall data to estimate the total fog water deposition amount for the entire sampling period. NH4+ and SO42- were the most abundant cation and anion, respectively, in the fog water samples. A mean pH of 5.08 in the fog water, which is higher than those in rural areas in Japan, was observed. The [NH4+]/[SO42-] equivalent ratio in fog water was larger than 1.0 throughout the study period, indicating that NH3 gas was the primary neutralizing agent for fog water acidity. The mean rate and total amount of fog water deposition were estimated as 0.15 mm h-1 and 164 mm, respectively. The amounts of nitrogen and sulfate deposition via fog water deposition were corresponded to those reported values of the annual deposition amounts via rainfall.