Some integrated circuits

Abstract

A wide variety (about 2000 different models) of integrated circuits (ics) are available commercially. From the constructional point of view there are two main kinds of monolithic integrated circuit: (a) the planar bipolar silicon transistor type and (b) those based on metal-oxide-semiconductor transistors (mosts or mosfets). Both kinds (a) and (b) are formed within the surface of a silicon chip (or slice) which has dimensions of typically 1.25 × 1.25 × 0.25 mm. The kind (a) comprises bipolar transistors and semiconductor diodes (if needed) formed by diffusion usually within an epitaxial surface layer of n-type or p-type silicon (not more than 12 µm thick) on the silicon chip together with the (usually vacuum-deposited) metallic interconnections and lands (terminals) necessary to form the circuit required. Type (b) involves a silicon oxide (SiO2) film grown on the surface of a chip (usually of n-type silicon) and also contains the required (usually vacuum-deposited) metallic interconnections and lands. In the treatment of logic circuits (Chapter 7) an example of ics involving planar bipolar transistors is the TTL, whereas CMOS logic circuits exemplify the oxidized silicon chip integrated circuit.