Grain Boundary Location-Controlled Polt-Si Films for Tft Devices Obtained Via Novel Excimer Laser Process

1994 ◽  
Vol 358 ◽  
Author(s):  
H. J. Kim ◽  
James S. Im
Keyword(s):  
Grain Boundary ◽  
Excimer Laser ◽  
Crystallization Process ◽  
Critical Distance ◽  
Capping Layer ◽  
Complete Melting ◽  
Boundary Location ◽  
Si Films ◽  
Active Channel ◽  
Induced Crystallization

ABSTRACTBased on a previously acquired physical understanding of the excimer-laser-induced crystallization process, we have developed a new crystallization technique that produces controlled microstructures and possesses a wide processing window. A patterned oxide capping layer was used as an antireflective coating to induce complete melting of an Si film under an SiO2 pattern, and partial melting of the Si film in the areas not under the capping layer—allowing controlled super lateral growth to proceed from the incompletely melted portion of the film to the completely melted portion. For the simple stripes used in this investigation, when the width of the completely molten region is less than a critical distance (above which nucleation of solids occurs in the middle of the completely melted regions), the resulting microstructure has large and elongated grains with one precisely located grain boundary running parallel to the stripe In the middle of the oxide capped region.Arrangement of TFT devices on the resulting Grain boundary Location-Controlled (GLC) Si films with one (or zero) grain boundaries located perpendicular to the flow of electrons within the active channel portion of the TFT devices is illustrated. Such devices are expected to possess performance and uniformity characteristics that are superior to currently available poly-Si TFT devices.

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.

The Mechanism of Excimer Laser-Induced Amorphization of Ultra-Thin Si Films

1993 ◽  
Vol 321 ◽  
Author(s):  
T. Eiumchotchawalit ◽  
James S. Im
Keyword(s):  
Energy Density ◽  
Excimer Laser ◽  
Supercooled Liquid ◽  
Transformation Mechanism ◽  
Quenching Rate ◽  
Tem Analysis ◽  
Si Substrates ◽  
Complete Melting ◽  
Small Crystals ◽  
Si Films

ABSTRACTTo better understand the involved phase transformation Mechanism, we are studying the excimer laser-induced amorphization (ELA) of ultra-thin Si films on oxidized Si substrates. In this paper, we show that the onset of amorphization of hydrogen-free Si films on SiO2 substrates upon increases in the energy density is associated with the onset of complete melting of the film. Once complete melting occurs, further increases in the incident energy density and/or increases in the substrate temperature can lead to incomplete amorphization of the film. Planar view TEM analysis of nearly-amorphized Si films reveals a heterogeneous microstructure, which consists of a mixture of densely dispersed amorphous-like annular regions (∼20 to 40 μm−2), embedded within and typically separated by a region containing finegrained small crystals. Such a cellular microstructure strongly suggests that amorphization occurred not via a homogeneous but via a heterogeneous transformation. In particular, the microstructure paints a scenario in which amorphization proceeded via nucleation of solids, which is then followed by interfacial amorphization. The experimental results unambiguously reveal (1) that the previously proposed criteria of the melt duration and the vertical temperature gradient are irrelevant in determining amorphization of supercooled liquid Si films and (2) that the quenching rate, not surprisingly, is the important parameter.

Poly-Si Thin Film Transistors Fabricated By Employing Selective Si Ion-Implantation And Excimer Laser Annealing

2000 ◽  
Vol 609 ◽  
Author(s):  
Min-Cheol Lee ◽  
Jae-Hong Jeon ◽  
Jin-Woo Park ◽  
Min-Koo Han
Keyword(s):  
Grain Boundary ◽  
Ion Implantation ◽  
Excimer Laser ◽  
Laser Annealing ◽  
Defect Density ◽  
Mask Pattern ◽  
Excimer Laser Annealing ◽  
Boundary Location ◽  
Si Ion Implantation ◽  
Annealing Method

ABSTRACTA new excimer laser annealing method is proposed in order to produce the poly-Si film with low defect density and large grain, by combining the selective Si ionimplantation and excimer laser annealing. Selective Si ion-implantation is employed to form artificial nucleation seeds in a-Si film prior to excimer laser annealing in order to increase the nucleation probability. The grain boundary location in poly-Si film has been controlled through implantation mask, and the grain size around micrometer order is obtained without any other process. TEM result shows that grain boundary is controlled according to mask pattern and the crystallinity of the poly-Si film is improved.

Grain Boundary Location Control by Patterned Metal Film in Excimer Laser Crystallized Polysilicon

1999 ◽  
Vol 67-68 ◽  
pp. 175-180 ◽  
Author(s):  
L. Mariucci ◽  
R. Carluccio ◽  
A. Pecora ◽  
G. Fortunato ◽  
F. Massussi ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Excimer Laser ◽  
Metal Film ◽  
Boundary Location

Optimization and Transformation Analysis of Grain-Boundary-Location-Controlled Si Films

1995 ◽  
Vol 397 ◽  
Author(s):  
H.J. Kim ◽  
James S. Im
Keyword(s):  
Grain Boundary ◽  
Surface Profile ◽  
Solidification Process ◽  
Lateral Growth ◽  
Cross Sectional ◽  
Experimental Parameters ◽  
Positive Volume ◽  
Boundary Location ◽  
Si Films

ABSTRACTBy optimizing various experimental parameters, we were able to extend the width of the microstructually optimized regions in grain-boundary-location-controlled (GLC) Si films up to 10 μm. In situ transient reflectance (TR) measurements during the solidification process reveal that the underlying GLC transformation sequence is consistent with the artificially controlled super-lateral growth (ACSLG) scenario, from which the GLC process was developed and is being optimized. A definite change in the slope of the TR signal was found to appear at the transition between the vertical-and-lateral -growth and lateral-growth-only modes. Protrusions at the center of the GLC Si microstructure, which are observed in cross-sectional TEM micrographs and surface profile measurements, are formed as a result of the positive volume change associated with freezing of Si.

Modeling Analysis of Excimer Laser Crystallization of a-Si Films with Nanosecond Temperature Response

2006 ◽  
Vol 505-507 ◽  
pp. 283-288 ◽  
Author(s):  
Chien Hung Chang ◽  
Long Sun Chao
Keyword(s):  
Melting Point ◽  
Partial Melting ◽  
Latent Heat ◽  
Excimer Laser ◽  
Maximum Temperature ◽  
Complete Melting ◽  
Melting Regime ◽  
Surface Reflectivity ◽  
Si Films ◽  
Temperature Responses

In the fabrication of a poly-Si film, an a-Si thin layer on glass substrate is melted by the irradiation of an excimer laser with the duration of nanosecond scale, and then is cooled down to form the poly-Si one. For analyzing the fabricating process, an efficient two-dimensional numerical model has been developed in this work, based on the finite difference method and the specific heat/enthalpy method used to handle the release of latent heat. The model can simulate the heat transfer, melt and solidification behavors of a-Si films subjected to the laser irradiation. Numerical analysis was performed by solving the heat flow equation which incorporates the material properties of temperature dependence, the surface reflectivity of silicon film, the variation of the incident power density with time and heat lose by the radiation and convection from the film surfaces into the surroundings. From the analysis of temperature responses for different laser intensities, the thresholds corresponding to the surface and full melting of the Si film can be found. The temperature responses are essentially different in the partial-melting and the complete-melting regimes. The Ft (surface melting threshold) and Fc (full-melt threshold) obtained from the simulation results of the proposed model in this study agree fairly well with those from the experimental data reported in the literature. In the partial-melting regime, the maximum temperature is close to the melting point of amorphous Si, since it is the point where solid a-Si is transformed into liquid state and the high latent heat can absorb extra energy to keep the temperature at the melting point. The fluence larger than Fc is the complete-melting regime, the maximum temperature increases with fluence. It is also found that the variation of the surface reflectivity gives a good way to observe the phase change and the melting duration. When the a-Si melts, the reflectivity rapidly goes up to a steady value which is consistent with the reflectivity of liquid silicon, and stays there until the melt silicon begins to solidify. As the irradiation energy of laser increases, the melting duration in the silicon layer is prolonged.

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