Phase field modeling of excimer laser crystallization of thin silicon films on amorphous substrates

Abstract

Excimer laser crystallization processing of thin silicon films on amorphous silicon oxide substrates was simulated by means of phase field modeling. The quantitative phase field model was derived from the Gibbs-Thompson equation coupled with energy conservation. Because the adaptive mesh scheme was adopted, the present calculations could accommodate both two-dimensional superlateral growth ͑SLG͒ phenomena and the realistic interface thickness ͑in the order of 10 −10 m͒. The vertical growth of fine-grained nucleation structures was simulated using one-dimensional calculations, and the results are consistent with those obtained in previous experiments. Two cases of SLG were also simulated, and the evolution of the interface and thermal fields was determined. Based on our simulation results, we conclude that SLG crystallization does not achieve steady growth because of the extremely fast heat dissipation from the substrate. To obtain very uniform electric characteristics for device fabrication, the layout design and the device position should take the SLG laser mask into consideration.

Pulsed Laser Heating and Melting

“…The phase field method was originally proposed for equilibrium solidification and has been very successful in predicting the large scale structure, such as the growth of dendrites, often seen in such systems. It has also been applied to rapid solidification (Kim & Kim, 2001), including excimer laser processing of silicon (La Magna, 2004;Shih et al, 2006;Steinbach & Apel, 2007). Despite its success in replicating many experimentally observed features in solidification (see for example, Pusztai, 2008, and references therein) and the phase field itself is not necessarily associated with any physical property of the interface (Qin & Bhadeshia, 2010).…”

P-6: Analysis of Microscopic Crystallization of Two-Shot SLS Process and Its Dependence on Performance of LTPS Devices

“…To realize the basic phase transformation during the excimer laser crystallization, the authors have developed a 2D (the crosssectional plane) numerical code based on the phase field methodology [6]. The detailed numerical and physical studies have shown elsewhere [6].…”

“…To realize the basic phase transformation during the excimer laser crystallization, the authors have developed a 2D (the crosssectional plane) numerical code based on the phase field methodology [6]. The detailed numerical and physical studies have shown elsewhere [6]. Here, a 100nm thin amorphous-Si The evolution of interfaces in Figure 1 clearly indicates that both energy densities can totally melt the a-Si region inside the transparent part of SLS mask.…”

“…As the laser pulse decays with time such that the temperature of interface is lower than the melting point of a-Si (for the first shot) or p-Si (for the second shot), the re-crystallization starts. Since the direction of crystal growth is vertical to the one of heat dissipation, many simulation results have pointed out that the very high supercooling exists on the interface and the solidification speed is in the order of 10m/s [6,7]. The degree of supercooling during crystallization mainly depends on the evolution of thermal fields, while lower supercooling can induces slower solidification and better crystallinity.…”

“…In this paper, we have analyzed microscopic crystallization of TS-SLS films under high (900mJ/cm2) and low (700mJ/cm2) energy densities by using the phase field modeling [6]. Because the non-equilibrium model is embedded, the degree of supercooling during solidification is clearly illustrated to realize the crystallinity of SLS films.…”