Les statistiques d’ordre superieur

Abstract

The aim of this work is to find the theoretical average based on an accurate numerical method in order to rebuilt, as nearly as possible, the doping profiles into polysilicon thin films. Doping profiles means the de concentration distribution C(x) of a given dopant as function of the material depth x. Controlled depth-concentration is seen very important when we realize deep junctions needed for high performance microelectronic components which will be integrated in very small sizes. We remember that the parameter of decreasing sizes under nanometer scale was became the most important feature in VLSI/ULSI technology. In this study, we have used boron profiles in polysilicon material, which first we have introduced nitrogen doped atoms carried out into LPCVD equipments. Then, a second step is made by ion implantation of boron at high concentration and low energy. This technique is often called SIMS procedure (secondary Ion mass Spectrometry, using an equipment CAMECA lMS-4f/6f) type. The only inconvenient is its destroying character, which means that the sample used is irrecoverable. So, we can see the interest of simulation process in this kind of works. The simulation step is based on high order statistics limited to the fourth rank for determining the key parameters of an ion implantation procedure. The results obtained, permit to say that it is now possible to rebuild the doping profiles of any experimental ion implantation even under various technical conditions. It is also possible to do that in the example of on in-situ doping case. At the end, the attentive analysis of the obtained results show an effect of slowing down diffusion mechanism when we use at the same time an in-situ nitrogen doping atom and a boron ion implantation ones. This is exactly what we have done when we have used a varied density  of the target that we have implanted in our computing program.