A New Double Laser Recrystallization Technique to Induce Ultra-Large Poly-Si Grains

2001 ◽  
Vol 685 ◽  
Author(s):  
Minghong Lee ◽  
Seungjae Moon ◽  
Mutsuko Hatano ◽  
Costas P. Grigoropoulos
Keyword(s):  
Grain Growth ◽  
Excimer Laser ◽  
Laser Fluence ◽  
Laser Power ◽  
Laser Flash ◽  
Process Window ◽  
Nanosecond Laser ◽  
Solidification Velocity ◽  
Laser Recrystallization ◽  
Nucleation Sites

AbstractA new double laser recrystallization technique that can produce lateral grains of tens of micrometers is presented. A nanosecond laser (excimer or Nd:YLF laser) and a pulse modulated Ar+ laser are used in the experiment. The effect of different parameters on lateral grain growth is investigated. These parameters include the time delay between the two lasers, the excimer laser fluence, the Ar+ laser power and the pulse duration. This process has wide process window and is insensitive to both the excimer laser fluence and the Ar+ laser power fluctuations. Preheating and melting of the a-Si film with the Ar+ laser before firing the excimer laser is found to be necessary for inducting lateral grain growth. The transient excimer laser irradiation is believed to generate nucleation sites for initiating the subsequent lateral grain growth. The solidification dynamics of the process is probed by high spatial and temporal resolution laser flash photography. A lateral solidification velocity of about 10 m/s is observed.

Effect of Excimer Laser Fluence Gradient on Lateral Grain Growth in Crystallization of a-Si Thin Films

2000 ◽  
Vol 621 ◽  
Author(s):  
Minghong Lee ◽  
Seungjae Moon ◽  
Mutsuko Hatano ◽  
Kenkichi Suzuki ◽  
Costas P. Grigoropoulos
Keyword(s):  
Grain Growth ◽  
Excimer Laser ◽  
Laser Fluence ◽  
Electrical Conductance ◽  
Solidification Velocity ◽  
Lateral Growth ◽  
High Fluence ◽  
Conductance Measurement ◽  
Substrate Heating ◽  
The Relationship

ABSTRACTIn order to clarify the relationship between excimer laser fluence gradient and the length of lateral grain growth, the laser fluence is modulated by a beam mask. The fluence distribution is measured by using a negative UV photoresist. The lateral growth length and the grain directionality are improved with increasing fluence gradient. Lateral growth length of about 1.5 [.proportional]m is achieved by using a single laser pulse without substrate heating on a 50 nm-thick a-Si film by enforcing high fluence gradient. Electrical conductance measurement is used to probe the solidification dynamics. The lateral solidification velocity is found to be about 7 m/s.

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.

High-Quality Polysilicon Thin Film Recrystallization by Laser Annealing

2011 ◽  
Vol 382 ◽  
pp. 26-29
Author(s):  
King Kung Wu ◽  
Wen Chung Chang
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Excimer Laser ◽  
Laser Power ◽  
Laser Annealing ◽  
Process Window ◽  
Excimer Laser Annealing ◽  
High Quality ◽  
Surface Ablation ◽  
Processing Ability

Amorphous silicon (a:Si) recrystalized to poly-silicon (poly:Si) in different gas environments by excimer laser annealing (ELA) is studied. Variations of threshold laser power for the generation of surface ablation in pure N2 gas and the mixture of N2:98% and O2:2% environments are also investigated, respectively. From experiments, it is found the combination of N2:98% and O2:2% gas can enhance the threshold laser power from 320mJ/cm2 to 390mJ/cm2 for the suppressing of surface ablation phenomenon. In the condition of average grain over 0.25um, the process window (i.e. laser power for processing ability) is 30mJ/cm2 for pure N2 only, but is 50mJ/cm2 for the combination of N2:98% and O2:2%.

Large Grain Creation and Destruction in Excimer Laser Crystallized Amorphous Silicon

1993 ◽  
Vol 321 ◽  
Author(s):  
J. B. Boyce ◽  
G. B. Anderson ◽  
D. K. Fork ◽  
R. I. Johnson ◽  
P. Mei ◽  
...  
Keyword(s):  
Grain Size ◽  
Excimer Laser ◽  
Laser Fluence ◽  
Laser Energy ◽  
Laser Crystallization ◽  
X Ray Scattering ◽  
Maximum Value ◽  
Nucleation Sites ◽  
Average Grain Size ◽  
Similar Peak

ABSTRACTFor fast-pulse laser-crystallized thin-film Si on non-crystalline substrates, the average grain size exhibits a peak as a function excimer laser energy density at a characteristic laserfluence FM. The average grain size increases with increasing laser fluence and can reach a maximum value on the order of 10 pm or about 100 times the film thickness. The grain size then decreases with further increases in fluence. This peak in grain size is accompanied by a similar peak in the Hall electron mobility and x-ray scattering intensity. Our experiments have investigated as-deposited and ion-implanted samples, using a double-scan laser crystallization process. Devices have also been fabricated and studied. The results are consistent with the increase in grain size occurring because of the destruction of nucleation sites with increasing laser fluence (i.e., increased heating and complete Melting). But substrate damage occurs in the vicinity of FM, creating nucleation sites which give rise to small grain sizes in the solidified film. The disruption of the interface causes substantial current leakage through the dielectric of bottom-gate transistors, implying that devices should be laser fabricated below Fm.

Laser Crystallized Polysilicon Thin Films and Applications

1995 ◽  
Vol 403 ◽  
Author(s):  
J. B. Boyce ◽  
P. Mei ◽  
D. K. Fork ◽  
G. B. Anderson ◽  
R. I. Johnson
Keyword(s):  
Grain Size ◽  
Amorphous Silicon ◽  
Grain Growth ◽  
Excimer Laser ◽  
Laser Fluence ◽  
Polycrystalline Silicon ◽  
Grain Structure ◽  
Large Area ◽  
Materials Properties ◽  
Average Grain Size

AbstractPulsed excimer-laser crystallization of amorphous silicon on non-crystalline substrates is an important processing technique for large-area polycrystalline silicon films and devices. Interest stems, in large part, from proposals to use polycrystalline silicon on glass in large-area electronic applications, such as flat-panel active matrix displays and two-dimensional imaging systems. The polycrystalline silicon is envisioned to increase the functionality and reduce costs over the current circuits that use amorphous silicon. Also, it is found that laser-crystallized polycrystalline silicon exhibits some interesting materials properties, such as a sharp peak in the average grain size with large lateral grain growth as a function of excimer laser energy density. The average grain size increases with increasing laser fluence and peaks on the order of several microns or two orders of magnitude larger than the film thickness. The grain size then decreases with further increases in laser fluence. This peak in grain size is accompanied by a similar peak in the Hall electron mobility. This is a significant relationship for devices since the grain structure has a substantial influence on electrical properties. But to the detriment of device parameters, this large lateral grain growth occurs over a very arrow range of laser fluences and is accompanied by a corresponding peak in the surface roughness of the films. These relationships between laser processing conditions, materials properties, and device parameters force a compromise between large grain size for high mobility and homogeneity of material for uniformity of device characteristics. A window does exist in process parameter space where good-quality devices with uniform characteristics have been obtained. In addition, these attributes have been achieved under conditions that yield good polycrystalline silicon and good amorphous silicon devices on the same wafer within a mm of one another, allowing for hybrid polycrystalline and amorphous silicon circuits.

New Excimer Laser Recrystallization of Poly-Si for Effective Grain Growth and Grain Boundary Arrangement

2000 ◽  
Vol 39 (Part 1, No. 4B) ◽  
pp. 2012-2014 ◽  
Author(s):  
Jae-Hong Jeon ◽  
Min-Cheol Lee ◽  
Kee-Chan Park ◽  
Min-Koo Han
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Excimer Laser ◽  
Laser Recrystallization

High Resolution Displacement of Functional Groups onto Fluorocarbon Resin Surface by Using ArF Excimer Laser

1996 ◽  
Vol 451 ◽  
Author(s):  
T. Shimizu ◽  
M. Murahara
Keyword(s):  
Contact Angle ◽  
High Resolution ◽  
Laser Beam ◽  
Thin Layer ◽  
Functional Groups ◽  
Excimer Laser ◽  
Laser Fluence ◽  
Large Area ◽  
Three Solutions ◽  
Arf Excimer Laser

ABSTRACTA Fluorocarbon resin surface was selectively modified by irradiation with a ArF laser beam through a thin layer of NaAlO2, B(OH)3, or H2O solution to give a hydrophilic property. As a result, with low fluence, the surface was most effectively modified with the NaAlO2 solution among the three solutions. However, the contact angle in this case changed by 10 degrees as the fluence changed only 1mJ/cm2. When modifying a large area of the surface, high resolution displacement could not be achieved because the laser beam was not uniform in displacing functional groups. Thus, the laser fluence was successfully made uniform by homogenizing the laser beam; the functional groups were replaced on the fluorocarbon resin surface with high resolution, which was successfully modified to be hydrophilic by distributing the laser fluence uniformly.

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.

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