This resource about ASICs is the pages that went into the “ASICs… the book”. When you get to Mass Production or want to pack a lot of electronics into a small size, an ASIC is inevitable. It improves reliability and consistency in the manufactured gadgets. It is a justified process, when a device is needed in large numbers. For smaller numbers use Flash Programmable Embedded Devices.
by Michael John Sebastian Smith – Addison-Wesley Publishing Company – VLSI Design Series
“ICs are made on a thin (a few hundred microns thick), circular silicon wafer , with each wafer holding hundreds of die (sometimes people use dies or dice for the plural of die). The transistors and wiring are made from many layers (usually between 10 and 15 distinct layers) built on top of one another. Each successive mask layer has a pattern that is defined using a mask similar to a glass photographic slide. The first half-dozen or so layers define the transistors. The last half-dozen or so layers define the metal wires between the transistors (the interconnect ).”