ABSTRACT
This chapter aims to investigate the possibility of fabricating thin silicon circuit substrates with closely-spaced through-chip connections. An alternative method aiming at the realization of high-density, high-aspect-ratio, closely spaced interconnects based on macroporous silicon formation is explored. Although silicon substrates can be thinned down to a fraction of a micrometre, this is only possible if they are bonded to a supporting, insulating substrate. It is important to know how thin, free-standing, silicon chips can be made and how flat they will be. A number of techniques that can be applied for through-wafer hole-forming in silicon substrates are readily available. The Alcatel 601 high-density plasma etching system installed at the Delft Institute of Microelectronics and Submicrontechnology has been used for the through-chip hole experiments. After the high-aspect-ratio trenches or holes are formed, an insulation layer has to be formed to avoid electrical connection through the semiconductive silicon substrate.
