Horizontally suspended carbon nanotube bundles patterned on silicon trench sidewalls

The strong interaction between horizontally aligned carbon nanotubes (CNTs) and the growth substrate has long been impeding the application of CNTs in micro/nano electronics, the shape and dimension of densely packed CNT bundles are also highly desirable in interconnects and sensor applications. In this paper, we report a method to grow horizontally suspended carbon nanotube (HSCNT) bundles patterned on selected silicon trench sidewalls. Semiconductor microfabrication technologies were employed to prepare the growth substrate, and the key process is to pattern an iron (Fe) catalyst layer onto selected silicon trench sidewalls via a shadow mask placed on top of silicon trenches by the tilted electron beam evaporation technique. The CNT growth process was conducted in a conventional thermal chemical vapour deposition (TCVD) furnace. The resultant CNTs are densely packed in bundles with very good horizontal alignment, their interactions with the silicon trench bottom are negligible since they are horizontally suspended from desired trench sidewalls. On the other hand, the dimension and shape of these HSCNT bundles were determined by the CNT growth duration, the deposition direction of the Fe catalyst relative to the substrate, and the open windows in the shadow mask. These results will facilitate the application of CNTs in micro/nano electronics.