Metal induced lateral crystallization of amorphous silicon nanowires
Résumé
Thanks to their integration properties and their high surface to volume ratio, silicon nanowires (SiNWs) offer great potential in the fields of high integration electronics or highly sensitive sensors in a fully compatible silicon technology.
In our study, SiNWs are formed with the sidewall spacer method using classical lithographic tools. In this method an amorphous silicon (a-Si) layer is deposited on a SiO2 step. An anisotropic Reactive Ion Etching of the a-Si layer allows sidewall spacer formation of nanometric size used as nanowires. However, such SiNWs show poor electrical properties due to their crystal quality.
The solution studied here to improve SiNWs crystal quality is the Metal Induced Lateral Crystallization (MILC) method. This approach involves the use of a metallic catalyst to create oriented crystals. A thin layer of metal, in our case nickel, is deposited locally on the surface of amorphous silicon and the sample is then annealed. The nickel creates a crystallization front which is parallel to the limit of the deposited metal and spreads, creating needle-like crystals in its path. Those crystals are oriented in the direction of the spread of the crystallization front.
First measurements were done on silicon nanowires crystallized with the MILC method and used as resistors. Comparisons with SPC crystallized nanowires and amorphous ones have shown that MILC devices present a good ohmicity but lower current levels than classically crystallized ones as of yet.