Low Temperature Crystallization of Amorphous Silicon Films Using an Excimer Laser

1989 ◽  
Vol 149 ◽  
Author(s):  
S. E. Ready ◽  
J. B. Boyce ◽  
R. Z. Bachrach ◽  
R. I. Johnson ◽  
K. Winer ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Excimer Laser ◽  
Laser Energy ◽  
Amorphous Material ◽  
Surface Region ◽  
Silicon Films ◽  
Starting Material ◽  
Near Surface ◽  
Silicon Thin Films ◽  
Crystallite Sizes

ABSTRACTIn an effort to enhance the electrical properties of silicon thin films, we have performed recrystallization experiments on a variety of amorphous silicon films using an excimer laser. The intense, pulsed UV produced by the laser (308nm, using XeCl gas) is highly absorbed by the amorphous material and thus provides intense localized heating in the near surface region. Two types of starting films were studied: plasma CVD a-Si:H and LPCVD a-Si. The subsequent modification produces crystallites whose structure and electrical characteristics vary due to starting material and laser scan parameters. The treated films have been characterized using Raman, x-ray diffraction, TEM, SIMS and transport measurements. The results indicate that crystallites nucleate in the surface region. The degree of crystallization near the surface increases dramatically as a function of deposited laser energy density and less so as a function of laser shot density. The hall mobility of the highly crystallized samples exhibit an increase of 2 orders of magnitude over the amorphous starting material. In the PECVD material, the rapid diffusion of hydrogen causes voids to be formed at intermediate laser energy densities and removal of film at higher energy densities. The LPCVD material withstands the high laser energies to produce well crystallized films with crystallite sizes greater then 1000Å.

Nucleation Process During Excimer Laser Annealing of Amorphous Silicon Thin Films on Glass: A Molecular-dynamics Study

2006 ◽  
Vol 958 ◽  
Author(s):  
Shinji Munetoh ◽  
Takanori Mitani ◽  
Takahide Kuranaga ◽  
Teruaki Motooka
Keyword(s):  
Thin Films ◽  
Molecular Dynamics ◽  
Amorphous Silicon ◽  
Excimer Laser ◽  
Laser Annealing ◽  
Surface Region ◽  
Excimer Laser Annealing ◽  
Silicon Thin Films ◽  
Steady State Temperature ◽  
Dynamics Simulations

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.

ArF Excimer Laser Assisted Solution Based Metal Induced Crystallization of Amorphous Silicon Films

2015 ◽  
Vol 1096 ◽  
pp. 45-49
Author(s):  
Wen Yun Dai ◽  
Jing Jin ◽  
Chao Xian Hui ◽  
Can Liu ◽  
Zhi Jun Yuan ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Excimer Laser ◽  
Salt Solution ◽  
Volume Fraction ◽  
Laser Energy ◽  
Silicon Films ◽  
Coated Sample ◽  
Crystalline Fraction ◽  
Metal Induced Crystallization ◽  
Arf Excimer Laser

Amorphous silicon films with and without spin-coating aluminum-salt-solution are treated by 193nm ArF excimer laser with different laser energies. It is observed that the crystalline fraction increases along with the laser energy. By comparation, with the help of Al, higher crystalline volume fraction and lower in-plane stress can be achieved at the same laser energy (2.9mJ). Large grain size of 200~300nm and maximum crystalline fraction of 82.3% are obtained in Al-salt-solution spin-coated sample, which is treated with laser energy of 3.2mJ,and its carrier mobility is 56.3cm2/Vs.

Time-Resolved Reflectivity Measurements of Silicon And Germanium Using A Pulsed Excimer Laser

1985 ◽  
Vol 51 ◽  
Author(s):  
G. E. Jellison ◽  
D. H. Lowndes ◽  
D. N. Mashburn ◽  
R. F. Wood
Keyword(s):  
Excimer Laser ◽  
Surface Region ◽  
Finite Energy ◽  
Time Resolved ◽  
Model Calculations ◽  
Near Surface ◽  
Maximum Reflectivity ◽  
Liquid Phases ◽  
Silicon And Germanium ◽  
Melt Duration

ABSTRACTTime-resolved reflectivity measurements of silicon and germanium have been made during pulsed KrF excimer laser irradiation. The reflectivity was measured simultaneously at both 1152 and 632.8 nm wavelengths, and the energy density of each laser pulse was monitored. The melt duration and the time of the onset of melting were measured and compared with the results of melting model calculations. For energy densities just above the melting threshold, it was found that the melt duration was never less than 20 ns for Si and 25 ns for Ge, while the maximum reflectivity increased from the value of the hot solid to that of the liquid over a finite energy range. These results, along with a reinterpretation of earlier time-resolved ellipsometry measurements, indicate that, during the melt-in process, the near-surface region does not melt homogeneously, but rather consists of a mixture of solid and liquid phases. The reflectivity at the onset of melting and in the liquid phase have been measured at both 632.8 and 1152 nm, and are compared with the results found in the literature.

Amorphous Silicon Crystallization For Tft Applications

1993 ◽  
Vol 321 ◽  
Author(s):  
J. Yi ◽  
R. Wallace ◽  
N. Sridhar ◽  
D. D. L. Chung ◽  
W. A. Anderson
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Leakage Current ◽  
Excimer Laser ◽  
Delay Time ◽  
Solid Phase ◽  
Laser Energy ◽  
Silicon Film ◽  
Rapid Thermal Anneal ◽  
Laser Anneal

ABSTRACTThin film hydrogenated Amorphous silicon (a-Si:H) was deposited on Molybdenum (Mo) substrates by d.c. glow discharge. We investigated the a-Si:H crystallization using four anneal techniques; nitrogen atmosphere furnace, vacuum, rapid thermal anneal (RTA), and excimer laser anneal. Anneal temperature ranged from 100 to 1200 °C. Excimer laser energy per pulse ranged from 90 to 340 M.J. Transmission electron Microscopy (TEM) revealed microstructure of crystallized Si film with grain size over 0.5 μm. X-ray diffraction (XRD) and Raman spectroscopy were employed to determine the degree of crystallization. The a-Si:H started to crystallize at temperatures over 600 °C. An 850 °C anneal reduced film resistivity to 10s (ω-cm) for intrinsic and 1 (ω-cm) for n-type. Coplanar type thin film transistors (TFT) with gate channel length of 25 μm and width of 220 μm were fabricated with various insulating layers; if sputtered SiO2, Si3N4, BaTiO3, MgO, and evaporated SiO. The first two exhibited the least leakage current. The as-grown intrinsic a-Si:H field effect mobility was around 0.03 (cmVV.s) and delay time was 5×10−7 s. The solid phase crystallized silicon film exhibited high leakage current. The delay time of an excimer laser anneal treated TFT was reduced to 2.5×10−7 s. Crystallized Si film mobility was improved to 15 (cm2 /V.s).

Crystallization of Tin-Implanted Amorphous Silicon Thin Films

1992 ◽  
Vol 279 ◽  
Author(s):  
Fuyu Lin ◽  
Miltiadis K. Hatalis
Keyword(s):  
Amorphous Silicon ◽  
Crystallization Process ◽  
Silicon Films ◽  
Grain Structure ◽  
Crystallization Time ◽  
Silicon Thin Films ◽  
Fine Grain ◽  
Annealing Conditions ◽  
Transmission Electron ◽  
Si Films

ABSTRACTThe crystallization of Sn-implanted amorphous silicon was studied as a function of tin implant dose and annealing conditions by transmission electron microscopy. The films were implanted at an energy of 110 keV with a dose in the range of 5 × 1014 to 5×1016 cm−2 and were annealed at a temperature in the range of 450°C to 550°C. An enhanced rate of crystallization in amorphous Si-Sn films compared to the non-implanted amorphous silicon films during thermal annealing was observed. The crystallization process of Si films implanted with tin at a dose of 2.5×1016 cm−2 or less is very similar to unimplanted silicon films except higher nucleation rates and shorter crystallization time were observed with increasing tin dose. Films implanted with tin at a dose of 2.5×1016 cm−2 or more display extremely rapid crystallization (3 hours at 450°C) and very fine grain structure (10 nm); no substantial grain growth has been observed during lurther annealing, but some single crystal-like areas were formed. In-situ annealing of silicon implanted to 5×1016 cm−2 showed that the crystallization process is enhanced by the formation of the liquid tin phase.

Excimer Laser Crystallized Amorphous Silicon Films: Effects of Shot Density and Substrate Temperature

1991 ◽  
Vol 219 ◽  
Author(s):  
R. I. Johnson ◽  
G. B. Anderson ◽  
S. E. Ready ◽  
J. B. Boyce
Keyword(s):  
Energy Density ◽  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Laser Energy ◽  
Silicon Films ◽  
Laser Energy Density ◽  
Laser Crystallization ◽  
Average Grain Size ◽  
Substrate Temperatures

ABSTRACTLaser crystallization of a-Si thin films has been shown to produce materials with enhanced electrical properties and devices that are faster and capable of carrying higher currents. The quality of these polycrystalline films depends on a number of parameters such as laser energy density, shot density, substrate temperature, and the quality of the starting material. We find that the average grain size and transport properties of laser crystallized amorphous silicon films increase substantially with laser energy density, increase only slightly with laser shot density, and are unaffected by substrate temperatures of up to 400°C. The best films are those processed in vacuum but films of fair quality can also be obtained in air and nitrogen atmospheres.

ArF Excimer Laser Doping into Amorphous Silicon thin films

1991 ◽  
Vol 219 ◽  
Author(s):  
M. Elliq ◽  
A. Slaoui ◽  
E. Fogarassy ◽  
H. Pattyn ◽  
R. Stuck ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Excimer Laser ◽  
Polycrystalline Silicon ◽  
Surface Concentration ◽  
Silicon Thin Film ◽  
Molten Layer ◽  
Silicon Thin Films ◽  
One Step ◽  
Arf Excimer Laser ◽  
Rate Limiting

ABSTRACTDoping of amorphous silicon (a-Si or a-Si:H) coated by a spin-on oxide film containing the dopant (phosphorus or boron) using an ArF excimer laser has been investigated as a function of laser fluence, number of pulses and dopant film thickness. From these results, it is found that the surface concentration and the junction depth vary with the number of pulses, and that the doping process is rate limiting. Sheet resistance lower than 10 kΩ/□ have been obtained. It is also shown that for a-Si:H films, laser irradiation produces exodiffusion of hydrogen from the molten layer resulting in rough surface. This one-step process seems suitable for polycrystalline silicon thin film transistors (TFT's) fabrication.

Low-Energy, Pulsed-Laser Irradiation of Amorphous Silicon: Melting and Resolidification at Two Fronts

1984 ◽  
Vol 35 ◽  
Author(s):  
W. Sinke ◽  
F.W. Saris
Keyword(s):  
Amorphous Silicon ◽  
Laser Irradiation ◽  
Surface Segregation ◽  
Crystalline Silicon ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Surface Region ◽  
Low Energy ◽  
Double Peak Structure ◽  
Pulsed Laser Irradiation

ABSTRACTAfter low-energy pulsed-laser irradiation of Cu-implanted silicon, a double-peak structure is observed in the Cu concentration profile, which results from the occurrence of two melts. From Cu surface segregation we calculate the depth of the surface melt. Cu segregation near the position of the amorphous-crystalline interface gives evidence for a self-propagating melt, moving from the surface region towards the crystalline substrate. Measurements of As-redistribution and of sheet resistance as a function of laser energy density in As-implanted silicon are consistent with the crystallization model which is derived from the effects as observed in Cu-implanted silicon.The results imply a large difference in melting temperature, heat conductivity and heat of melting between amorphous silicon and crystalline silicon.

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