Study of Crystal Growth Mechanism for Poly-Si Film Prepared by Excimer Laser Annealing

Abstract

Recrystallization of polycrystalline silicon (poly-Si) film by excimer laser annealing (ELA) is discussed by considering the experimental results that the three stages of nucleation, textured grain growth and secondary grain growth were observed. Although the phenomenon of nucleation in the amorphous silicon (a-Si) is understood by considering crystallization from the super cooled liquid, the growth mechanisms of the textured grain and secondary grain are not understood by this, because the melting point of poly-Si which has already been formed on the entire surface during these growth stages is higher than that of a-Si. The recrystallization mechanism considering the dislocation movement is introduced to investigate the present phenomenon. It also clarifies the reason why secondary grain growth occurs under the critical conditions of laser irradiation energy and shot number. The feasibility of nucleation through the super cooled liquid is also discussed.

Influence of Post Excimer Laser Annealing on Crystallinity of Precursor Polycrystalline Si Film Formed by Solid Phase Crystallization

“…This phenomenon coincides with the result 11) that the ELA process after SPC increased the grain size. From the viewpoint of secondary grain growth, 15) it is observed with ELA, ELA followed by SPC, and SPC followed by ELA. Although partial secondary grain growth occurs for SPC, textured grains are predominantly observed.…”

Stress Relaxation of Poly-Si Film Formed by Excimer Laser Annealing

“…It is found that, firstly, the tensile stress of the polySi film is released with a progress of secondary grain growth, and secondly, the stress relaxation becomes marked as the hydrogen concentration decreases. Stress Relaxation of Poly-Si Film Formed by Excimer Laser Annealingwhich we previously proposed, 18) in the point that secondary grain growth leads to tensile stress relaxation by the release of strain energy. The origin of the strain energy is thought to be the field of elastic stress around the dislocations at the grain boundary.…”

“…In our group, the mechanism of secondary grain growth by ELA has been examined to provide a high-quality large-grained film. [15][16][17][18][19][20][21][22][23][24][25][26] Here, the secondary grain is defined as having a grain size larger than the film thickness. It was found by electron spin resonance (ESR) measurement that most of the crystal defects were located at the grain boundary of poly-Si film and that hydrogen in a-Si film influenced the crystallinity of the poly-Si.…”

“…16,17) On the basis of these results, a new crystal growth model was presented. [18][19][20][21] The purpose of this paper is to review the characteristics of the poly-Si film recrystallized by the ELA method. [22][23][24][25][26] First, the influence of the secondary grain growth on the stress relaxation of poly-Si film is explained.…”

Excimer Laser Annealing of Hydrogen Modulation Doped a-Si Film

“…Such polySi films prepared by the crystallization of amorphous silicon (a-Si) by excimer laser annealing (ELA) have been examined. [1][2][3][4] It is known that hydrogen in a-Si film causes the film exfoliation, and therefore, the H concentration is decreased to below 1 at% by thermal treatment at 500 C for several hours. However, hydrogen desorption does not occur for lowtemperature processes.…”