Microstructural Control of Amorphous Silicon Films Crystallized using an Excimer Laser

1997 ◽  
Vol 472 ◽  
Author(s):  
J.W. Viatella ◽  
R.K. Singh
Keyword(s):  
Laser Annealing ◽  
Laser Energy ◽  
Single Crystal Silicon ◽  
Silicon Films ◽  
Crystal Silicon ◽  
Intimate Contact ◽  
Fine Grained ◽  
Silicon Thin Films ◽  
Fine Mesh ◽  
Microstructural Control

ABSTRACTThe results of experiments using two techniques for microstructural control of laser-annealed silicon thin films on SiO2 substrates are given. In the first set, photolithographically fabricated single-crystal silicon seed wafers in intimate contact with the silicon films are used to show that it is possible to control nucleation location during laser annealing. Laser energy density was varied from 250–450 mJ/cm2 and the resultant microstructure was characterized using transmission electron microscopy (TEM). It was found to consist of four distinct regions. Areas adjacent to the seed consisted of grains with dimensions ∼ 0.5 μm. The surrounding region consisted of larger (∼ 1 μm) rectangular grains. A third region was observed sporadically and consisted of large (∼ 1.5 μm) rectangular grains adjacent to the latter region. The fourth region occurred several microns away from the contact and consisted of a fine-grained microstructure. In the second set, fine mesh (19 μm) masks were used to selectively crystallize regions in laser-annealed films. The resultant microstructure was characterized using TEM and was found to consist of large (∼ 1.5 μm) edge grains with smaller (∼ 0.8 μm) grains just inside of the edge grains. A theoretical discussion is presented to explain the observed phenomena in both experiment sets.

Microstructural control of amorphous silicon films crystallized using an excimer laser

1998 ◽  
Vol 13 (8) ◽  
pp. 2105-2109
Author(s):  
John Viatella ◽  
Rajiv K. Singh
Keyword(s):  
Excimer Laser ◽  
Annealed Film ◽  
Silicon Films ◽  
Theoretical Discussion ◽  
Intimate Contact ◽  
Silicon Thin Films ◽  
Grain Structures ◽  
Transmission Electron ◽  
Etched Silicon ◽  
Microstructural Control

A technique for microstructural control of excimer laser-annealed silicon thin films on SiO2 substrates has been developed. By using single-crystal photolithographically etched silicon seed wafers in intimate contact with the silicon films, we have shown that it is possible to spatially control nucleation. Transmission electron micrographs show the resultant microstructure to consist of large (∼1 µm) grain structures in the area surrounding the seed contact, with distinct organization not previously observed. A theoretical discussion is presented to explain the observed phenomena. Also, results from a numerical simulation are given which outline the effects of the seed wafer on the resultant microstructure of the laser-annealed film, as compared to nonseeded areas.

A Current Conduction Mechanism in Laser Recrystallized Silicon Metal-Oxide-Semiconductor Transistors

1983 ◽  
Vol 23 ◽  
Author(s):  
Han-Sheng Lee
Keyword(s):  
Conduction Mechanism ◽  
Single Crystal Silicon ◽  
Silicon Films ◽  
Oxide Semiconductor ◽  
Silicon Substrates ◽  
Mos Transistors ◽  
Crystal Silicon ◽  
Ion Laser ◽  
Argon Ion ◽  
A Current

ABSTRACTN-channel MOS transistors were fabricated on silicon films that had been recrystallized by an argon ion laser at different power levels. These transistors showed electrical characteristics similar, but somewhat inferior to those devices fabricated on single crystal silicon substrates. These differences are attributed to the presence of trapping states at the grain boundaries of the crystallites in the recrystallized silicon. A coulombic scattering model is presented to explain these differences. In the case of films annealed at low laser power, an additional factor of nonuniform trap state distribution is invoked to explain device characteristics. This model provides an adequate explanation for the observed transport properties of transistors fabricated from recrystallized silicon films.

Residual stresses in a SiC whisker-reinforced alumina composite by high-temperature X-ray diffraction

1994 ◽  
Vol 9 (1) ◽  
pp. 50-53 ◽  
Author(s):  
Benjamin L. Ballard ◽  
Paul K. Predecki ◽  
Camden R. Hubbard
Keyword(s):  
Residual Stress ◽  
Single Crystal Silicon ◽  
Linear Extrapolation ◽  
X Ray Diffraction ◽  
Crystal Silicon ◽  
X Ray ◽  
Fine Grained ◽  
Silicon Carbide Whiskers ◽  
Alumina Composite ◽  
Residual Strains

Residual strains and microstresses are evaluated for both phase of a hot-pressed, fine-grained α-alumina reinforced with 25 wt% (29 vol%) single-crystal silicon carbide whiskers at temperatures from 25 to 1000 °C. The sample was maintained in a nonoxidizing environment while measurements of the interplaner spacing of alumina (146) and SiC (511 + 333) were made using X-ray diffraction methods. The residual strains were profiled at temperature increments of 250 °C from which the corresponding microstresses were calculated. Linear extrapolation of the SiC ε33 profile indicates that the strains are completely relaxed at a temperature of approximately 1470 °C. These residual stress relaxation results suggest that elevated temperature toughness and fracture strength of this composite may result from cooperative mechanisms.

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.

Thermal conduction in doped single-crystal silicon films

2002 ◽  
Vol 91 (8) ◽  
pp. 5079-5088 ◽  
Author(s):  
M. Asheghi ◽  
K. Kurabayashi ◽  
R. Kasnavi ◽  
K. E. Goodson
Keyword(s):  
Single Crystal ◽  
Thermal Conduction ◽  
Single Crystal Silicon ◽  
Silicon Films ◽  
Crystal Silicon
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