Localized Excimer Laser Energy Modulation in the Crystallization Of Poly-Si Film On Stepped Substrate

2000 ◽  
Vol 617 ◽  
Author(s):  
Kee-Chan Park ◽  
Sang-Hoon Jung ◽  
Woo-Jin Nam ◽  
Min-Koo Han
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Excimer Laser ◽  
Thermal Gradient ◽  
Laser Energy ◽  
Vertical Wall ◽  
Energy Difference ◽  
Deep Trench ◽  
Laser Recrystallization ◽  
Horizontal Bottom

AbstractAnew excimer laser recrystallization method of a-Si film to increase the grain size of poly-Si film has been proposed. Excimer laser energy was locally modulated by being irradiated on stepped substrate with 500 nm deep trench on which a-Si film was deposited. Fairly large poly-Si grains (over 1 µm) were obtained due to lateral thermal gradient which resulted from the laser energy difference on the vertical wall and on the horizontal bottom plane of the trench without altering laser energy density elaborately.

scholarly journals Electrical and Structural Characteristics of Excimer Laser-Crystallized Polycrystalline Si1−xGex Thin-Film Transistors

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1739 ◽  
Author(s):  
Kyungsoo Jang ◽  
Youngkuk Kim ◽  
Joonghyun Park ◽  
Junsin Yi
Keyword(s):  
Thin Film ◽  
Grain Size ◽  
Energy Density ◽  
Excimer Laser ◽  
Density Of States ◽  
Silicon Germanium ◽  
Structural Characteristics ◽  
Thin Film Transistor ◽  
Electrical Characteristics ◽  
Starting Point

We investigated the characteristics of excimer laser-annealed polycrystalline silicon–germanium (poly-Si1−xGex) thin film and thin-film transistor (TFT). The Ge concentration was increased from 0% to 12.3% using a SiH4 and GeH4 gas mixture, and a Si1−xGex thin film was crystallized using different excimer laser densities. We found that the optimum energy density to obtain maximum grain size depends on the Ge content in the poly-Si1−xGex thin film; we also confirmed that the grain size of the poly-Si1−xGex thin film is more sensitive to energy density than the poly-Si thin film. The maximum grain size of the poly-Si1−xGex film was 387.3 nm for a Ge content of 5.1% at the energy density of 420 mJ/cm2. Poly-Si1−xGex TFT with different Ge concentrations was fabricated, and their structural characteristics were analyzed using Raman spectroscopy and atomic force microscopy. The results showed that, as the Ge concentration increased, the electrical characteristics, such as on current and sub-threshold swing, were deteriorated. The electrical characteristics were simulated by varying the density of states in the poly-Si1−xGex. From this density of states (DOS), the defect state distribution connected with Ge concentration could be identified and used as the basic starting point for further analyses of the poly-Si1−xGex TFTs.

Considerations for Large Area Fabrication of Integrated a-Si and Poly-Si TFTs

1994 ◽  
Vol 336 ◽  
Author(s):  
P. Mei ◽  
G. B. Anderson ◽  
J. B. Boyce ◽  
D. K. Fork ◽  
M. Hack ◽  
...  
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Laser Energy ◽  
Gate Insulator ◽  
Laser Energy Density ◽  
Laser Crystallization ◽  
Large Area ◽  
Low Leakage ◽  
Threshold Voltages ◽  
Excellent Method

ABSTRACTThe combination of a-Si low leakage pixel TFTs with poly-Si TFTs in peripheral circuits provides an excellent method for reducing the number of external connections to large-area imaging arrays and displays. To integrate the fabrication of the peripheral poly-Si TFTs with the a-Si pixel TFTs, we have developed a three-step laser process which enables selective crystallization of PECVD a-Si:H. X-ray diffraction and transmission electron microscopy show that the polycrystalline grains formed with this three-step process are similar to those crystallized by a conventional one step laser crystallization of unhydrogenated amorphous silicon. The grain size increases with increasing laser energy density up to a peak value of a few Microns. The grain size decreases with further increases in laser energy density. The transistor field effect mobility is correlated with the grain size, increasing gradually with laser energy density until reaching its maximum value. Thereafter, the transistors suffer from leakage through the gate insulators. A dual dielectric gate insulator has been developed for these bottom-gate thin film transistors to provide the correct threshold voltages for both a-Si and poly-Si TFTs.

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.

Fast-Pulse Excimer-Laser-Induced Processes in a-Si:H

1989 ◽  
Vol 164 ◽  
Author(s):  
K. Winer ◽  
R.Z. Bachrach ◽  
R.I. Johnson ◽  
S.E. Ready ◽  
G.B. Anderson ◽  
...  
Keyword(s):  
Energy Density ◽  
Excimer Laser ◽  
Impurity Concentration ◽  
Laser Annealing ◽  
Laser Energy ◽  
Laser Energy Density ◽  
Excimer Laser Annealing ◽  
Near Surface ◽  
Pulse Excimer Laser ◽  
Fast Pulse

AbstractThe effects of fast-pulse excimer laser annealing of a-Si:H were investigated by measurements of electronic transport properties and impurity concentration depth profiles as a function of incident laser energy density. The dc dark conductivity of laser-annealed, highly-doped a-Si:H increases by a factor of ∼350 above a sharp laser energy density threshold whose magnitude increases with decreasing impurity concentration and which correlates with the onset of hydrogen evolution from and crystallization of the near-surface layer. The similarities between the preparation and properties of laser-crystallized a-Si:H and pc-Si:H are discussed.

Excimer Laser Induced Crystallization of Amorphous Silicon Near Threshold

1989 ◽  
Vol 157 ◽  
Author(s):  
R.Z. Bachrach ◽  
K. Winer ◽  
J.B. Boyce ◽  
F.A. Ponce ◽  
S.E. Ready ◽  
...  
Keyword(s):  
Energy Density ◽  
Laser Beam ◽  
Amorphous Silicon ◽  
Excimer Laser ◽  
Laser Energy ◽  
Laser Energy Density ◽  
Square Root ◽  
Threshold Behavior ◽  
Sharp Threshold ◽  
Induced Crystallization

ABSTRACTUsing a suitably homogenized excimer laser beam, we have shown that the threshold for crystallization of amorphous silicon is well defined and exhibits a square root dependence on the laser energy density above threshold. This sharp threshold behavior can be exploited in a number of ways.

scholarly journals Effect of Laser Energy Density on the Microstructure andTexture Evolution of Hastelloy-X Alloy Fabricated by Laser Powder Bed Fusion

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4305
Author(s):  
Shuzhe Zhang ◽  
Yunpei Lei ◽  
Zhen Chen ◽  
Pei Wei ◽  
Wenjie Liu ◽  
...  
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Electron Backscatter Diffraction ◽  
Laser Energy ◽  
Primary Dendrite ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Hastelloy X ◽  
Powder Bed ◽  
Average Grain Size

It is of great importance to study the microstructure and textural evolution of laser powder bed fusion (LPBF) formed Hastelloy-X alloys, in order to establish a close relationship between the process, microstructure, and properties through the regulation of the Hastelloy-X formation process parameters. In this paper, components of a Hastelloy-X alloy were formed with different laser energy densities (also known as the volume energy density VED). The densification mechanism of Hastelloy-X was studied, and the causes of defects, such as pores and cracks, were analyzed. The influence of different energy densities on grain size, texture, and orientation was investigated using an electron backscatter diffraction technique. The results show that the average grain size, primary dendrite arm spacing, and number of low angle grain boundaries increased with the increase of energy density. At the same time, the VED can strengthen the texture. The textural intensity increases with the increase of energy density. The best mechanical properties were obtained at the VED of 96 J·mm−3.

2-Dimensional Controlled Large Lateral Grain Growth on the Floating Amorphous Silicon Film by Excimer Laser Recrystallization

2003 ◽  
Vol 762 ◽  
Author(s):  
In-Hyuk Song ◽  
Su-Hyuk Kang ◽  
Woo-Jin Nam ◽  
Min-Koo Han
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Excimer Laser ◽  
Thermal Gradient ◽  
Laser Annealing ◽  
Silicon Film ◽  
Excimer Laser Annealing ◽  
Active Structure ◽  
Current Path ◽  
Laser Recrystallization

AbstractWe have successfully obtained large lateral grains with well-controlled grain boundary. The proposed excimer laser annealing (ELA) method produces 2-dimensionally controlled grain growth because the temperature gradient is induced in two directions. Along the channel direction, the floating active structure produces large thermal gradient due to very low thermal conductivity of the air-gap. Along the perpendicular direction to the channel, the surface tension effect also produces thermal gradient. The proposed ELA method can control the grain boundary perpendicular and parallel to current path with only one laser irradiation.

Considerations for Large Area Fabrication Of Integrated a-Si and Poly-Si TFTs

1994 ◽  
Vol 345 ◽  
Author(s):  
P. Mei ◽  
G. B. Anderson ◽  
J. B. Boyce ◽  
D. K. Fork ◽  
M. Hack ◽  
...  
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Laser Energy ◽  
Gate Insulator ◽  
Laser Energy Density ◽  
Laser Crystallization ◽  
Large Area ◽  
Low Leakage ◽  
Threshold Voltages ◽  
Excellent Method

AbstractThe combination of a-Si low leakage pixel TFTs with poly-Si TFTs in peripheral circuits provides an excellent method for reducing the number of external connections to large-area imaging arrays and displays. To integrate the fabrication of the peripheral poly-Si TFTs with the a-Si pixel TFTs, we have developed a threestep laser process which enables selective crystallization of PECVD a-Si:H. X-ray diffraction and transmission electron microscopy show that the polycrystalline grains formed with this three-step process are similar to those crystallized by a conventional one step laser crystallization of unhydrogenated amorphous silicon. The grain size increases with increasing laser energy density up to a peak value of a few microns. The grain size decreases with further increases in laser energy density. The transistor field effect mobility is correlated with the grain size, increasing gradually with laser energy density until reaching its maximum value. Thereafter, the transistors suffer from leakage through the gate insulators. A dual dielectric gate insulator has been developed for these bottom-gate thin film transistors to provide the correct threshold voltages for both a-Si and poly-Si TFTs.

Characteristics of XeCI Excimer-Laser Annealed Insulator

1996 ◽  
Vol 424 ◽  
Author(s):  
Keun-Ho Jang ◽  
Hong-Seok Choi ◽  
Jae-Hong Jun ◽  
Jhun-Suk Yoo ◽  
Minkoo Han
Keyword(s):  
Energy Density ◽  
Metal Oxide ◽  
Excimer Laser ◽  
Laser Annealing ◽  
Laser Energy ◽  
Breakdown Field ◽  
Oxide Interface ◽  
Annealing Effects ◽  
Silicon Structures ◽  
Tetra Ethyl Ortho Silicate

AbstractThe laser annealing effects on the TEOS (Tetra-Ethyl-Ortho-Silicate) oxide of MOS (Al/TEOS/n+ Silicon ) structures was investigated with different initial oxide conditions, such as breakdown field. The breakdown field increased upto the 170 mJ/cm2 with increasing laser energy density and decreased at 220 mJ/cm2. It is considered that the increase of breakdown field is originated from the restore of strains which exist mainly at the metal/oxide interface.

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