Influence of interface and Al structure on layer exchange during aluminum-induced crystallization of amorphous silicon

Abstract

Aluminum-induced crystallization of amorphous silicon (a-Si) is studied using various microscopy techniques and x-ray photoelectron spectroscopy. During the isothermal annealing of subsequently deposited aluminum and a-Si films on glass, a layer exchange process is induced, while a continuous polycrystalline silicon film (poly-Si) on glass is formed within the initial metal layer and therefore displaces it. This crystallization process is conducted at temperatures ranging from 350 °C to 500 °C, significantly below the eutectic temperature of the Si–Al binary system of 577 °C. The results presented focus on the influences of the polycrystalline structure of the evaporated Al, the Si–Al layer sequence, and the interface layer between the Al and Si films on the overall crystallization process. They reveal that the larger the Al grain size of the initial polycrystalline Al layer, the larger the grain size of the final poly-Si film and the slower the entire layer exchange process. It is further shown that the layer sequence, although influencing the speed of the poly-Si formation, has little impact on the overall layer exchange process. Additionally, evidence is given that an Al oxide interface layer separates the continuous poly-Si layer from the Al, independent of the original layer sequence. The analyzed oxide interface layer remains at its position throughout the entire Al and Si layer exchange process. An existing phenomenological model of the diffusion-controlled crystallization during the layer exchange is extended to embrace the role of the parameters discussed in this paper.

On the Mechanisms Governing Aluminum-Mediated Solid-Phase Epitaxy of Silicon

“…This is in agreement with the results previously reported by Nast and co-authors 24,25 for a layer-exchange aluminum-induced crystallization mechanism on glass substrates. During the SPE process, the Al film is segregated above the SPE-Si and forms an amorphous-like film like the one shown in Fig.…”

“…4 A generally accepted mechanism of crystallization based on a-Si/Al layer exchange has been used to describe the growth of polycrystalline Si on foreign substrates in this situation. [5][6][7] In previous studies, 8,9 we reported a sub-500°C selective Si solid-phase epitaxy (SPE) process using Al as a transport medium. On both patterned and nonpatterned crystalline Si substrates this process produced high-quality monocrystalline Si (c-Si) islands, which are uniformly doped with Al.…”

Superhydrophobic surfaces produced by applying a self-assembled monolayer to silicon micro/nano-textured surfaces

“…AIC of a-Si is an MEMS fabrication process compatible technique which has been studied extensively for production of large continuous polysilicon grains for electronic and photovoltaic applications [18 23]. For example, Nast et al improved our fundamental understanding of the mechanism of AIC of a-Si by their discovery of the layer exchange phenomenon ocurring during the AIC of a-Si processes [18]. Schneider et al investigated the influence of annealing temperature profiles on AIC of a-Si in order to improve the resulting silicon polycrystalline fi lms [19].…”

Tin-induced crystallization of amorphous silicon assisted by a pulsed laser irradiation

“…These experimental results interpreted by the new MIC mechanism proposed in the papers [20][21][22]. It differs significantly from those known for other metals [13,[15][16][17]. According to this mechanism, silicon nanocrystals are formed due to cyclic repetition of formation and decomposition of a supersaturated silicon in tin solution on the narrow eutectic layer at a-Si/Sn interface of tin micro-droplets in amorphous Si volume.…”

“…One of promising ways in this direction is the use of metal-induced crystallization (MIC) of amorphous silicon [13][14][15][16][17]. In particular, the possibility to form Si nanocrystals in amorphous Si matrix at 2 to 5 nm sizes and the phase volume fraction up to 80% was shown by means of tin-stimulated crystallization of amorphous Si at low temperatures [18][19][20].…”