Very brief Introduction to Ion Implantation for Semiconductor Manufacturing

Gerhard Spitzlsperger

Abstract:

The key feature of semiconductors, that makes them so successful in modern electronic devices, is the possibility to alter their conductivity several orders of magnitude by introducing small quantities of dopant atoms.

Ion implantation is the method of choice in state of the art semiconductor manufacturing to bring the dopants into the substrate material, mainly due to its ability to accurately control the number of implanted dopants and and to place them at the desired depth.

Ion implantation works by ionizing the required atoms, accelerating them in an electric field, select only the species of interest by an analyzing magnet and direct this beam towards the substrate. When entering the substrate material the energy of the dopants decreases, while they interact with the target material. After some time the atoms come to rest at some depth depending on their initial energy. This depth has some distribution as the collisions with the target atoms are random.

So one important point for the device design is to know which initial energy is necessary to place the dopants at the required depth and what will be their spread. Several methods and theories exist to answer this question. Within this text expecially the LSS (Lindhard, Scharff, Schiøtt) theory is briefly reviewed as a background for the SIMPIMPLANT program which allows to draw one-dimensional distributions of the typical dopants in silicon technology.