Molecular Dynamics Simulations of Nucleation and Crystallization Processes During Excimer-Laser Annealing of Amorphous Silicon on Glass

2003 ◽  
Vol 780 ◽  
Author(s):  
T. Motooka ◽  
S. Munetoh ◽  
Lee Byoung Min ◽  
K. Nisihira

AbstractWe have investigated atomistic processes of nucleation and crystallization in excimer-laser annealed thin Si films on glass based on molecular-dynamics (MD) simulations using the Tersoff potential. MD cells composed of up to approximately 50000 Si atoms were heated to produce melted Si, and then melted Si was quenched under various supercooled conditions with or without a temperature gradient and the corresponding nucleation processes were visualized. Lateral growth of thin Si crystalline films was also simulated by embedding a crystalline nano-particle with various crystal surfaces in melted Si. It has been found that the crystal surfaces become predominantly {111} during the lateral growth processes.

2006 ◽  
Vol 958 ◽  
Author(s):  
Shinji Munetoh ◽  
Takanori Mitani ◽  
Takahide Kuranaga ◽  
Teruaki Motooka

ABSTRACTWe have performed molecular-dynamics simulations of heating, melting and recrystallization processes in amorphous silicon (a-Si) thin films deposited on glass during excimer laser annealing. By partially heating the a-Si surface region with 2 nm depth and removing thermal energy from the bottom of the glass substrate, a steady-state temperature profile was obtained in the a-Si layer with the thickness of 15 nm and only the surface region was melted. It was found that nucleation predominantly occurred in the a-Si region as judged by the coordination numbers and diffusion constants of atoms in the region. The results suggest that nucleation occurs in unmelted residual a-Si region during the laser irradiation and then crystal growth proceeds toward liquid Si region under the near-complete melting condition.


2008 ◽  
Vol 1150 ◽  
Author(s):  
Tomohiko Ogata ◽  
Takanori Mitani ◽  
Shinji Munetoh ◽  
Teruaki Motooka

AbstractWe investigated crystallization processes of amorphous Si (a-Si) during the excimer laser annealing in the complete-melting and near-complete-melting conditions by using molecular dynamics simulations. The initial a-Si configuration was prepared by quenching liquid Si (l-Si) in a MD cell with a size of 50×50×150Å3 composed of 18666 atoms. KrF excimer laser (wavelength: 248nm) annealing processes of a-Si were calculated by taking account of the change in the optical constant upon melting during a laser pulse shot with the intensity Ioexp[−(t–t0)2/ς2] (Io: laser fluence, t: irradiation time). The refractive indices of a-Si and l-Si were set at n+ik=1.0+3.0i and n+ik=1.8+3.0i, respectively. The simulated results well reproduced the observed melting rate and the near-complete-melting and complete-melting conditions were obtained for Io = 160mJ/cm2 and 180mJ/cm2, respectively. It was found that larger grains were obtained in the near-complete-melting condition. Our MD simulations also suggest that nucleation occurs first in a-Si and subsequent crystallization proceeds toward l-Si in the near-complete-melting case.


1992 ◽  
Vol 283 ◽  
Author(s):  
Hiroshi Iwata ◽  
Tomoyuki Nohda ◽  
Satoshi Ishida ◽  
Takashi Kuwahara ◽  
Keiichi Sano ◽  
...  

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.


2006 ◽  
Vol 45 (5B) ◽  
pp. 4344-4346 ◽  
Author(s):  
Shinji Munetoh ◽  
Takahide Kuranaga ◽  
Byoung Min Lee ◽  
Teruaki Motooka ◽  
Takahiko Endo ◽  
...  

MRS Bulletin ◽  
2006 ◽  
Vol 31 (6) ◽  
pp. 461-465 ◽  
Author(s):  
P.C. van der Wilt ◽  
M.G. Kane ◽  
A.B. Limanov ◽  
A.H. Firester ◽  
L. Goodman ◽  
...  

AbstractLow-defect-density polycrystalline Si on flexible substrates can be instrumental in realizing the full potential of macroelectronics. Direct deposition or solid-phase crystallization techniques are often incompatible with polymers and produce materials with high defect densities. Excimer-laser annealing is capable of producing films of reasonable quality directly on polymer and metallic substrates. Sequential lateral solidification (SLS) is an advanced pulsed-laser-crystallization technique capable of producing Si films on polymers with lower defect density than can be obtained via excimer-laser annealing. Circuits built directly on polymers using these SLS films show the highest performance reported to date.


2006 ◽  
Vol 505-507 ◽  
pp. 277-282 ◽  
Author(s):  
Yu Ru Chen ◽  
Long Sun Chao

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.


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