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.

Simulation Of Polycrystalline Silicon Growth By Pulsed Excimer Laser Annealing

2000 ◽  
Vol 617 ◽  
Author(s):  
Toshio Kudo ◽  
Daiji Ichishima ◽  
Cheng-Guo Jin
Keyword(s):  
Energy Density ◽  
Excimer Laser ◽  
Dynamic Simulation ◽  
Pulse Energy ◽  
Laser Annealing ◽  
Excimer Laser Annealing ◽  
Time Jitter ◽  
Grain Sizes ◽  
Pulse Energy Density ◽  
Pulsed Irradiation

AbstractThe dynamic simulation of poly-Si film synthesis has been fulfilled by means of the overlapping irradiation of single- and double-pulsed XeCl excimer lasers shaped into the line beam. A novel model applied to the dynamic simulation is based on the homogeneous nucleation, and the growth and shrinkage velocity of Si grains. The results simulated with the single-pulsed XeCl excimer laser has reproduced the super lateral growth (SLG) phenomenon which occurs in the very narrow range of energy density (the near complete melt regime). The actual energy density dispersion within 5.3% allows us to visualize the multiformity of grain sizes in the cross sectional texture. Standing on the reproduction of the SLG phenomenon by the single-pulsed irradiation, we have obtained the practical knowledge of the growth process of larger grains by the double-pulsed irradiation. We intend that the first pulse has charge of completely melting and the second pulse has charge of adjusting the number of nuclei. The adjustment of the first pulse energy density rather than that of the second pulse energy density leads to the growth of huge columnar grains much larger than the thickness of the Si layer. For the double-pulsed irradiation, the influence of the worst energy density dispersion (each of double pulses has the same fluctuation as the single pulse) is much larger than that of the actual delay time jitter (within 2.5ns) in a sense of the multiformity of grain sizes.

Experimental Analysis for Low-Temperature Poly-Si Films Produced by Using the Excimer Laser Annealing Method

2006 ◽  
Vol 505-507 ◽  
pp. 277-282 ◽  
Author(s):  
Yu Ru Chen ◽  
Long Sun Chao
Keyword(s):  
Grain Size ◽  
Excimer Laser ◽  
Glass Substrate ◽  
Laser Annealing ◽  
Pulse Number ◽  
Sio2 Layer ◽  
Excimer Laser Annealing ◽  
Melt Pool ◽  
Si Films ◽  
Annealing Method

This paper is to investigate the effects on grain size of different working conditions for making poly Si films by using the excimer laser annealing method. In this research, a KrF excimer laser of 248 nm in wavelength is used to irradiate a-Si films of 0.1 μm in thickness on glass substrate to produce poly-Si ones. The control parameters are laser intensity (200~500 mJ/cm2), pulse number (1~10 shots) and coverage fraction (0~100%). Besides, the effect of a SiO2 layer is also studied, which is utilized as a heat-isolated zone located between the Si film and glass substrate. Average grain sizes from SEM photos are used to analyze the effects of these parameters. Purely from the heat transfer view, the Si film obtains more energy would have the slower cooling or solidification rate, which results in the larger grain. From the experimental results, if the melt pool is within the range of Si film or does not contact its neighboring layer (SiO2 layer or glass substrate), the more absorbed energy from the higher energy intensity, the larger pulse number or the bigger coverage fraction can have the larger average grain size. However, with large enough energy, the melt pool could go through the Si film and touch the lower layer. This would induce much more nuclei due to the homogeneous nucleation in the pool and the heterogeneous nucleation near the interface between the film and the neighboring layer. The resulting grain size is much smaller than that of the former one. The transition points of these two cases for different control parameters can be obtained from the experimental results in this study. When the energy from the laser is small, the SiO2 layer acts like a heat absorber and makes the grain size smaller than that of not having the SiO2 layer. On the other hand, when the energy is large, the SiO2 layer becomes a heat insulator and makes the grain size larger.

Femtosecond and Nanosecond Laser Pulse Crystallization of Thin a-Si:H Films on Non-Refractory Glass Substrates

2007 ◽  
Vol 131-133 ◽  
pp. 479-484 ◽  
Author(s):  
Vladimir A. Volodin ◽  
M.D. Efremov ◽  
G.A. Kachurin ◽  
S.A. Kochubei ◽  
A.G. Cherkov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Energy Density ◽  
Laser Pulse ◽  
Raman Scattering ◽  
Pulse Energy ◽  
Laser Wavelength ◽  
Nanosecond Laser ◽  
Glass Substrates ◽  
Pulse Energy Density ◽  
Krf Laser

Thin (90 nm) a-Si:H films on Corning 7059 glass substrates have been crystallized by 120 fs pulses of Ti:sapphire and nanosecond pulse XeCl and KrF excimer lasers. Initial films were deposited using low-temperature plasma enhanced deposition technique. The structural properties of the films were characterized using the spectroscopy of Raman scattering, excited by the argon laser (line 514.5 nm) and using electron microscopy. For the femtosecond pulse treatments the ablation threshold was found to be some more than 65 mJ/cm2. When pulse energy density was lower than ~30 mJ/cm2 no structural changes were observed. In optimal regimes the films were found to be fully crystallized with needle grain structure, according to the Raman scattering and electron microscopy data. Estimates show the pulse energy density was lower than the Si melting threshold, so non-thermal “explosive” impacts may play some role. The main result in nanosecond XeCl and KrF laser pulse crystallization is the narrower window between beginning of crystallization and ablation for KrF laser (wavelength 248 nm) than for the XeCl laser (wavelength 308 nm). So, the possibility of the femtosecond and nanosecond laser pulses to crystallize a-Si films on non refractory glass substrates was shown. The results obtained are of great importance for manufacturing of polycrystalline silicon layers on non-refractory large-scale substrates for giant microelectronics.

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.

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.

Silicide Formation by Pulsed Excimer Laser Annealing

2001 ◽  
Vol 685 ◽  
Author(s):  
Connie Lew ◽  
Michael O. Thompson
Keyword(s):  
Excimer Laser ◽  
Laser Annealing ◽  
Interface Reaction ◽  
Silicide Formation ◽  
Metal Interface ◽  
Excimer Laser Annealing ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Si Films

AbstractSilicide formation may occur at the interface of metal and a-Si films upon annealing with a pulsed excimer laser (XeCl 308 nm; 30 ns). During laser-induced melting, the melt front reaches the Si/metal interface, where liquid phase kinetics allow reaction to occur to form a silicide, despite the <100 ns time-scale. It is thought that silicide reaction would occur if TM, metal ≍ TM, a-Si (1480 ± 50K). The a-Si/metal film stacks that have been investigated include a-Si/Al/Cr, a-Si/Ti, and a-Si/W on thermally oxidized Si. Samples were laser-annealed at varying energy densities in order to determine the onset of melt, and the fluence at which Si/metal interface reaction and film ablation occurs. Rutherford backscattering (RBS), optical inspection, cross-sectional scanning transmission electron microscopy (STEM), as well as parallel and serial electron energy loss spectroscopy (EELS) were used to analyze the films. For the a-Si/Al/Cr and a-Si/W films, no reaction is observed at the Si/metal interface. With a-Si/Ti, intermixing of Si and Ti at the interface is observed, as indicated by RBS and parallel EELS analysis. Laser annealing at higher fluences and further characterization is needed to determine if this mechanism does allow for silicide reaction to take place.

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
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