Semiconductors, Silicon Based

Abstract

Their unique properties have allowed silicon‐based semiconductor devices, especially metal/oxide/semiconductor field‐effect transistors (MOSFETs), to dominate the electronics industry. Exponentially increasing numbers of transistors on single chips of silicon have led to exponential improvements in chip performance. The properties of silicon as an electronic material, the dependence of carrier statistics on doping, and carrier transport are reviewed because they determine device behavior. The characteristics of transistors, both bipolar and MOSFET, depend on the properties of p ‐ n junctions. An abrupt p ‐ n junction places acceptor‐doped, p ‐type silicon next to donor‐doped n ‐type silicon. The performance of n ‐ p ‐ n bipolar transistors depends on minority electrons injected into the p ‐type base by the forward‐biased base‐emitter p ‐ n junction reaching the reverse‐biased base‐collector p ‐ n junction. n ‐Channel MOSFETs depend on electrons traveling between n + source and drain junctions through an n ‐type surface channel. This surface channel is induced by a voltage applied across the MOS capacitor formed by a polysilicon metal gate over an oxidized silicon surface. The unique low concentration of surface states, which can be achieved at a thermally oxidized Si–SiO 2 boundary, is the basis of MOSFET technology. The ability to shrink the dimensions of these devices without radically altering their behavior (scaling) has allowed the microelectronics industry to place exponentially increasing numbers of MOSFETs on a single chip. Generally speaking, the growth of the microelectronics industry has been the result of device scaling rather than fundamental changes in device physics. Variations of silicon technology are leading to devices with deep submicrometer dimensions or new applications such as thin‐film transistors for flat‐panel displays, flash memories, or power devices. Variations in silicon technology, eg, silicon on insulator, silicon–germanium alloys, or silicon carbide are briefly reviewed.