# Microelectronics

| Microelectronics is an inexhaustible topic in itself; it fills many books and we will encounter it in its own lectures. A taste of it is offered in the Hyperscript "Electronic Materials". At the very heart of microelectronics is the Si wafer and the structures integrated into it or on top of the the Si.
|  | How is it done? By defect engineering - and there is the connection to defects! However, here this expression is used in a totally different context from that of an process engineer in a "wafer fab" i.e. a factory that makes chips (= integrated circuits) by processing wafers.
|  | A process engineer considers "defect engineering" to be everything related to what produces "defective" chips, e.g. embedded particles, short-circuits etc.
| We, however, mean defects in the sense of this lecture, i.e. point defects, dislocations, etc. "Defect engineering" then comprises:
|  | Growth of a Si single crystal with no grain boundaries or dislocations whatsoever, and very small and preferably very few point defect agglomerates and impurity precipitates.
|  | Keeping that crystal clean and dislocation free - despite the fact that during the many high temperature processes necessary to make a chip, a lot of impurity atoms would like to diffuse into the Si. Temperature gradients, in addition, introduce mechanical stress which tends to relax by generation and movement of dislocations.
|  | Get the right amount of dopant atoms in the right positions. This always involves defects - either generated by ion-implantation of the dopant, or the ones necessary for the diffusion. Still, they must be gone again in the end.
|  | Have the right interface reactions, e.g. for forming an oxide. This involves point defects, too - oxidation, e.g., injects Si interstitials. Avoid, at all costs, to have those interstitials agglomerate into stacking faults!
| In summary: Chip making is indeed an exercise in defect engineering - as well as in equipment engineering, electrical engineering and so on.

With frame

3.1.1 Diffusion and Point Defects

Optoelectronics

© H. Föll (Defects - Script)