Effect of Substrate Heating During Excimer Laser Annealing on Poly-Si TFT

1995 ◽  
Vol 403 ◽  
Author(s):  
T. Noguchi ◽  
A. J. Tang ◽  
J. A. Tsai ◽  
R. Reif
Keyword(s):  
Energy Density ◽  
Laser Annealing ◽  
Single Pulse ◽  
Single Shot ◽  
Excimer Laser Annealing ◽  
Substrate Heating ◽  
Amorphous Si ◽  
Voltage Swing ◽  
Si Films ◽  
Low Temperature Process

AbstractSingle-shot ELA was performed on 45nm-thick amorphous Si films. With an increase in pulse energy density, the cystallinity improved drastically for both samples without heating and with heating at 400°C. Correspondingly, the characteristics of TFT fabricated using a low temperature process improved distinctly. The threshold voltage decreased depending on the decrease in gate voltage swing due to the improvement in crystallinity of Si films. Efficient single-pulse ELA of less than 250MJ/cm2 as the optimum condition for poly Si TFT has been attained as a result of saving an energy amount of 100mJ/cm2 by heating the substrate. Moreover, a uniform distribution of TFT characteristics across the wafer was obtained.

Microstructures of Luminescent nc-Si by Excimer Laser Annealing of a-Si:H

1996 ◽  
Vol 452 ◽  
Author(s):  
Xinfan Huang ◽  
Wei Wu ◽  
Honghui Shen ◽  
Wei Li ◽  
Xiaoyuan Chen ◽  
...  
Keyword(s):  
Energy Density ◽  
Pulse Energy ◽  
Laser Annealing ◽  
Laser Wavelength ◽  
Pulse Number ◽  
Excimer Laser Annealing ◽  
Pulse Energy Density ◽  
Transmission Electron ◽  
Ion Laser ◽  
Si Films

AbstractWe have reported for the first time on visible photoluminescence (PL) in crystallized a-Si:H/a-SiNx:H multilayer structures by CW Ar ion laser annealing treatments. In this paper we present new results on visible PL from crystallized a-Si:H by using KrF excimer pulse laser (wavelength 248 nm) irradiating treatments. The transmission electron microscopy and Raman scattering studies reveal the microstructures of crystallized Si films, which depend on the pulse number and the pulse energy density of KrF laser. When the laser pulse energy density is higher than 520 mJ/cm2, the nanosized Si crystallites (nc-Si) can be formed from a-Si:H layers with a thickness of 100 nm and strong PL with a peak wavelength of 610 nm has been observed at room temperature.

Excimer Laser Annealed Poly-Si TFT Technologies

1995 ◽  
Vol 377 ◽  
Author(s):  
Fujio Okumura ◽  
Kenji Sera ◽  
Hiroshi Tanabe ◽  
Katsuhisa Yuda ◽  
Hiroshi Okumura
Keyword(s):  
Energy Density ◽  
Leakage Current ◽  
Excimer Laser ◽  
Laser Annealing ◽  
Laser Energy ◽  
Gate Insulator ◽  
Excimer Laser Annealing ◽  
Threshold Voltage Shift ◽  
Si Films ◽  
Current Reduction

ABSTRACTThis paper describes the excimer laser annealed (ELA) poly-Si TFT technologies in terms of excimer laser annealing of Si films, the leakage current, and the TFT stability. A laser energy density and a shot dependencies of TFT characteristics was analyzed by TEM, SEM, and Raman. The mobility increases with increasing not only the energy density but also the shot density. The mobility increase with the energy density is due to the grain size enlargement. On the other hand, the mobility increase up to 10 to 20 shots is due to a decrease of defects, including small grains, grain boundaries and defects inside grains. The contribution of grain-growth is small. The ELA TFT has a micro-offset structure to reduce the leakage current. Moreover, we have proposed a dynamic leakage current reduction structure. The combination of these technologies provides a sufficiently small leakage current for AMLCDs. The stability of the gate insulator was analyzed. The TFT shows negative threshold voltage shift under gate bias stress. This is due to water penetration and the subsequent field activated chemical reaction in the gate insulator. The dissociation of Si-OH bonds with hydrogen-bonded water was a fundamental contributor. The shift was suppressed sufficiently by hydrogen passivation. Obtained ELA TFTs;s have mobilities of over 100 cm2/Vsec, threshold voltages of less than 3 V, effective leakage currents of less than 10−13 A, and are stable more than 10 years.

Large-Grain Doped Poly-Si Films Fabricated Using New Excimer Laser Annealing Technique

1992 ◽  
Vol 283 ◽  
Author(s):  
Hiroshi Iwata ◽  
Tomoyuki Nohda ◽  
Satoshi Ishida ◽  
Takashi Kuwahara ◽  
Keiichi Sano ◽  
...  
Keyword(s):  
Grain Size ◽  
Sheet Resistance ◽  
Excimer Laser ◽  
Laser Annealing ◽  
Solidification Velocity ◽  
Excimer Laser Annealing ◽  
Arf Excimer Laser ◽  
Si Films

ABSTRACTThe grain size of phosphorous (P)-doped poly-Si film has been enlarged to about 5000 Å by controlling the solidification velocity of molten Si during ArF excimer laser annealing. The drastically enlarged grain has few defects inside the grain. It has been confirmed that control of the solidification velocity is effective for P-doped poly-Si similar to the case of non-doped poly-Si films. In addition, a sheet resistance of 80 Ω/□ (ρ = 4 × 10-4 Ω · cm) has been achieved for very thin (500 Å) films by recrystallizing PECVD P-doped a-Si films.

Heat Transfer and Phase Transformations in Laser Annealing of Thin a-Si Films

2001 ◽  
Author(s):  
Seung-Jae Moon ◽  
Minghong Lee ◽  
Costas P. Grigoropoulos
Keyword(s):  
Laser Annealing ◽  
Thermal Emission ◽  
Electrical Conductance ◽  
Nanosecond Laser ◽  
Solidification Velocity ◽  
Emission Measurement ◽  
Excimer Laser Annealing ◽  
In Situ Experiments ◽  
Si Films

Abstract The liquid-solid interface motion and the temperature history of thin Si films during excimer laser annealing are observed by in situ experiments combining time-resolved (∼lns) thermal emission measurements, optical reflectance and transmittance at near-IR wavelengths and electrical conductance measurements. The spontaneous nucleation temperature in the supercooled liquid melt is studied from the thermal emission measurement A new double laser recrystallization technique using a temporally modulated CW Ar+ laser in conjunction with a superposed nanosecond laser pulse produces lateral grain growth at the irradiated spot. The laser melting process is numerically simulated. High-resolution laser flash photography enabled in-situ direct visualization of the resolidification process. The images reveal lateral solidification velocity of about 10 m/s.

scholarly journals Crystal Growth of Low-Temperature Processed Poly-Si by Excimer Laser Annealing. Dependences of Poly-Si Grain on Energy Density and Shot Number.

Shinku ◽  
2000 ◽  
Vol 43 (12) ◽  
pp. 1120-1125 ◽  
Author(s):  
Naoto MATSUO ◽  
Hisashi ABE ◽  
Naoya KAWAMOTO ◽  
Ryouhei TAGUCHI ◽  
Tomoyuki NOUDA ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Energy Density ◽  
Low Temperature ◽  
Excimer Laser ◽  
Laser Annealing ◽  
Excimer Laser Annealing ◽  
Shot Number

Multiple Pulse Irradiation Effects in Excimer Laser-Induced Crystallization of Amorphous Si Films

1993 ◽  
Vol 321 ◽  
Author(s):  
H. J. Kim ◽  
James S. Im
Keyword(s):  
Excimer Laser ◽  
Single Pulse ◽  
Pulse Irradiation ◽  
Multiple Pulse ◽  
Melting Phenomenon ◽  
Irradiation Energy ◽  
Crystallization Experiments ◽  
Amorphous Si ◽  
Si Films ◽  
Induced Crystallization

ABSTRACTWe have experimentally Investigated the effects that are associated with Multiple-pulse irradiation in the excimer laser processing of thin Si films on SiO2. Double-pulse irradiation experiments revealed results, which are consistent with that which is known from single-pulse crystallization experiments, and these experiments confirm the applicability of the transformation scenarios, which were derived from single pulse-induced crystallization experiments [1,2]. The results from the Multiple-pulse irradiation experiments clearly show that gradual and substantial grain enlargement can occur — and only occurs — when the irradiation energy density is close to but less than the level that is required to melt the film completely. Based on these findings, we argue that the grain enlargement effect is a near-complete melting phenomenon that is associated with polycrystalline Si films, and we present a grain boundary melting model to account for this phenomenon. A brief discussion on the apparent similarities and physical differences between the observed phenomenon and the solid state grain growth processes is provided herein.

Excimer Lasbr Induced Crystallization of thin Amorphous Si Films on SiO2: Implications of Crystallized Microstructures for Phase Transformation Mechanisms

1992 ◽  
Vol 283 ◽  
Author(s):  
H. J. Kim ◽  
James S. Im ◽  
Michael O. Thompson
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Laser Energy ◽  
High Energy ◽  
High Energy Density ◽  
Laser Energy Density ◽  
Single Shot ◽  
Average Grain Size ◽  
Si Films ◽  
Density Regime

ABSTRACTUsing planar view transmission electron microscope (TEM) and transient reflectance (TR) analyses, we have investigated the excimer laser crystallization of amorphous silicon (a-Si) films on SiO2. Emphasis was placed on characterizing the microstructures of the single-shot irradiated materials, as a function of the energy density of the laser pulse and the temperature of the substrate. The dependence of the grain size and melt duration as a function of energy density revealed two major crystallization regimes. In the low energy density regime, the average grain size first increases gradually with increases in the laser energy density. In the high energy density regime, on the other hand, a very fine grained microstructure, which is relatively insensitive to variations in the laser energy density, is obtained. In addition, we have discovered that at the transition between these two regimes an extremely small experimental window exists, within which an exceedingly large grain-sized polycrystalline film is obtained. We suggest a liquid phase growth model for this phenomenon, which is based on the regrowth of crystals from the residual solid islands at the oxide interface.

Sign in / Sign up

Export Citation Format

Share Document