Mechanism for pillar-shaped surface morphology of polysilicon prepared by excimer laser annealing

Abstract

Surface morphology of polycrystalline silicon prepared by excimer laser annealing has been investigated. It was found that when a thin amorphous Si film is irradiated by excimer laser, pillars are formed on the surface of the crystallized polysilicon. To find out the mechanism, various preparation parameters such as laser power densities, shot numbers and the thickness of the amorphous Si have been studied. Several intermediate patterns have been found which illustrate the sequential formation of pillars. A surface tension model is proposed to explain these patterns. This mechanism can be applied to prepare the self-assembled silicon quantum dots, whose average size and height are 14.2 and 3.7 nm, respectively.

Surface morphology and recrystallization behavior of amorphous Si after ArF laser irradiation

“…Whether to induce the adequate grain size of poly-Si film or to form hillocks on the film surface resulting in a rougher surface, affecting the manufacturing of thin-film transistor displays, are dependent on the vertical solidification speed of molten silicon involved during laser irradiation process. Early investigations on the laser crystallization of a-Si films have mainly attributed the surface roughness dependent on the evolution of the surface morphology to the differences in latent heat and thermal conduction between the interface of poly-Si/a-Si and a-Si/glass substrate, to the hydrogen formed in plasma-enhanced chemical vapor deposition a-Si film, to the positive feedback of optical interference effects in multi-shots crystallization, to the capillary wave excited by the volume change at the silicon-melt transition resulting in the viscous damping and the agglomeration of the molten silicon and also to the adhesion force between molten silicon and unmelted microcrystalline Si greater than the agglomeration force of the molten silicon, leading to the formation of the surface hillocks [13].…”

“…The other model explained that the micro-hillocks were formed during laser annealing process due to larger adhesion force occurred between the molten Si and unmelted silicon clusters than the agglomeration force of the molten Si. However, the micro-hillocks were not always shown to be formed on the grain boundary areas [13]. This paper focuses on the experimental investigation of the evolution of surface morphology and recrystallization behaviour involved during 193nm-ArF excimer laser annealing of a-Si film deposited on glass using PECVD technique.…”

Large-Scale and Localized Laser Crystallization of Optically Thick Amorphous Silicon Films by Near-IR Femtosecond Pulses

“…In recent decades, laser annealing was recognized as a flexible technique to locally crystallize -Si with high control [ 11 ]. In particular, the use of excimer laser with ultraviolet (UV) radiation was previously justified to efficiently drive transition of amorphous Si to its polycrystalline phase allowing to produce high-quality films [ 12 , 13 , 14 , 15 ]. However, ultra-low penetration depth of UV light to silicon limits the thickness of -Si film, which can be processed with such an approach.…”

Polysilicon Thin Film Developed on Flexible Polyimide for Biomedical Applications

“…GFs as high as 50 [17] with a TCR close to 0%/K have been reported for polysilicon. To lower the crystallization temperature of polysilicon and accommodate its use with plastic substrate, approaches such as PECVD [18], laser annealing [19] and metal-induced crystallization [20]- [22] have been reported. Nast et al [22] proposed the technique of Aluminum induced crystallization (AIC), in which the crystallization process occurred at a temperature under the eutectic temperature of 577°C.…”