3-D Simulator of Laser Crystallization for Polycrystalline-Silicon Thin-Film Transistors
A 3-D simulator of laser crystallization for polycrystalline-silicon thin-film transistors has been developed. Random nucleation, crystal growth velocity, latent heat emission, and partial crystallization are modeled, and a 2-D algorithm is extended to a 3-D algorithm. The <formula formulatype="inline"><tex Notation="TeX">$\mu$</tex></formula>-Czochralski technique is analyzed using the 3-D simulator, and it is found that the grain size becomes large when the initial temperature is high after the laser irradiation.
Laser pulse shape dependence of poly-Si crystallization
Poly-Si crystallization mechanism is examined by conducting numerical simulations, combining the thermal diffusion equation with a rigorous coupled wave analysis method. The ripples at the boundary of poly-Si grains are modeled as a grating surface structure. Under laser beam irradiation, the melting front profiles are accurately analyzed by including surface diffraction, polarization of the laser, and laser energy density. For two different lasers, XeCl excimer laser (λ = 308 nm) and Yb:YAG solid state laser (λ= 343 nm), the energy density range at which poly-Si grains are gradually ordered was determined. Furthermore, the energy density window of the Yb:YAG laser is found to be four times larger than that of XeCl laser. On the other hand, the Yb:YAG laser may produce amorphous-Si phase after completing the crystallization process. It is suggested that this amorphous-Si phase could be avoided, if a double pulse laser is used.
Structural and photoelectrical properties of a third‐order twin boundary (Σ = 27) in silicon
A comparison of structural and photoelectrieal properties of a third order twin boundary (Σ = 27) and a tetrajoint comprising this boundary is made. In contrast to the joint the boundary displayed structural instability. On annealing it faceted and dissociated forming lower energy defects: twin boundaries of first and second orders. The electrical properties of the boundaries and the joint are determined by following methods: light beam induced current (LBIC), photovoltage (PV), and spreading resistance (SB). The Σ = 27 boundary is found to be of high electrical activity in the symmetrical {552}/{552} and faceted (parallel to the plane {111} of one of the grains) orientations. Surface recombination velocities (s) equal 6.6 × 105 and 1.3 × 106 em s−1 at 300 K, respectively. The value s increases approximately twice during faceting which agrees with geometrical models for the Σ = 27 boundary in a diamond lattice. The electrical activity of the tetrajoint and the regions of the intersection of electrically inactive first order twin boundaries is revealed. 
 
 
 
Es wird ein Vergleich der strukturellen und photoelektrischen Eigenschaften einer Zwillingsgrenze dritter Ordnung (Σ = 27) und einer Vierfachbindung, die diese Grenze enthalt, durchgefuhrt. Im Gegensatz zur Bindung zeigt die Grenze eine strukturelle Instabilitat. Bei Temperung facettiert und dissoziiert sie und bildet Defekte niedrigerer Ordnung: Zwillingsgrenzen erster und zweiter Ordnung. Die elektrischen Eigenschaften der Grenzen und der Bindung weiden mit folgenden Methoden bestimmt: Lichtinduzierter Strom (LBIC), Photospannung (PV) und “spreading-resistance” (SR). Es wird gefunden, das die Σ = 27-Grenze in den Symmetrieorientierungen {552}/{552} und facettierten (parallel zur {111}-Ebene ernes der Korner) Orientierungen von hoher elektrischer Aktivitat ist. Die Oberflachenrekombinationsgeschwindigkeiten (s) betragen 6,6 × 105 bzw. 1,3 × 106 cm s−1 bei 300 K. Der Wert s nimmt wahrend der Facettierung naherungsweise um den Faktor zwei zu, was mit geometrischen Modellen fur die σ = 27-Grenze in einem Diamantgitter ubereinstimmt. Die elektrische Aktivitat der Vierfachbindung und der Bereiche der uberschneidung von elektrisch inaktiven Zwillingsgrenzen erster Ordnung wird aufgedeckt.