Grain Quality Enhancement of Nickel-Crystallized Polysilicon Film in Quantum-Wire-Like Structures

Methods for forming high quality re-crystallizing polysilicon films are being actively studied due to their ability to provide significant improvement to polysilicon Thin-Film-Transistors (TFT). Recently, a simple Metal-Induced-Lateral-Crystallization (MILC) method with nickel, together with high temperature annealing, can result in single crystal like polysilicon film [1]. TFTs fabricated on this so-called Large-grain Silicon-On-Insulator (LPSOI) can achieve SOI MOSFET performance especially for making small dimension devices. This paper reports that the polysilicon grain quality can be further enhanced by crystallizing the polysilicon film into the shape of long-wire.The crystallization procedure started with a regular Nickel-Induced-Lateral-Crystallization (NILC) process at 560 °C as described in [1]. The film was then etched into narrow wires, which were parallel to the direction of nickel propagation. The NILC second anneal at 900 °C was then performed on these silicon wire. Through surface energy anisotropy stimulated grain expansion in the NILC high-temperature second annealing, enhanced grain quality beyond that on planar polysilicon film.Transistor fabricated on these wire is similar to gate-all-around structure as that of FinFET [2]. Much better scalability to the deep submicron region was observed for these wire transistors than regular planar TFTs formed on the same NILC film. Experimental results showed that a wide transistor formed by the parallel combination of the quantum wire transistors much higher current drive than a TFT on the same NILC film with equivalent width.