ABSTRACT
Polycrystalline silicon (polysilicon) is widely used in several very large scale integrated (VLSI) circuit elements, for example as the gate material of metal-oxide-semiconductor (MOS) capacitances and transistors, as interconnect lines, in fuse and anti-fuse elements, and for filling deep isolation trenches and via plugs. In the present chapter the structural, electrical and technological properties of polysilicon deposited by low pressure chemical vapor deposition (LPCVD) are briefly reviewed. Different applications of polysilicon in VLSI technology are discussed and updated. Finally two sections are devoted to semi-insulating polysilicon (SIPOS) and to polycrystalline silicon/germanium alloys. Dry directional etching such as plasma reactive ion etching (RIE) is usually used to etch polysilicon. The combined carrier recombination in the grains and at the grain boundaries determine the effective minority carrier lifetime in polysilicon. Polysilicon is used in dynamic random access memory (DRAM) cells as the gate electrode of the access (switching) MOSFET and of the storage MOS capacitor.
