THE development of new semiconductor devices depends strongly on the aid of process and device simulation. The miniaturization of today's semiconductor devices suggests a change from the common two-dimensional layout to three-dimensional structures to increase the amount of devices on the same wafer area. Therefore modern process simulators must be capable of modeling these realistic three-dimensional structures accurately.
Currently, the most important technique for doping the wafer is the ion implantation. Subsequently, to activate the dopants a thermal treatment is necessary. With the increasing density of devices per area it becomes more and more important that the original profile is not modified too much by this annealing or diffusion step. Therefore special techniques, as for instance rapid thermal annealing (RTA), were developed. Consequently, the accurate determination of implantation profiles has become a very important task. Therefore, the exact simulation of ion implantation gained in significance tremendously.
In most simulation programs for semiconductor fabrication steps only simple, analytical models based on distribution functions for the determination of implantation profiles are incorporated. In this work such a module is described, too. Such programs give results quickly, but they can not be applied to complex structures. The restriction of an analytic description of the Ion-Implantation is also documented in this work. The main goal was the development of a computer simulation program for realistic three-dimensional structures based on the Monte-Carlo method. This technique has the advantage that there are no limitations as to the geometries or the ion/target-combinations which can be handled. The only drawback is the high CPU-time consumption. The result of this research work is a program which is not only suitable for such cases where other methods fail, but it can also be applied to standard problems due to its small demands on computation time.
Despite today's computer power the determination of realistic three-dimensional implantation profiles based on this technique is fairly impossible, without special considerations concerning the necessary geometric checks. For the point location problem a method from the graphical image processing - the discretization of the structure using an octree - has been applied. With this technique it is possible for the first time ever to apply the simulation of ion implantation based on the Monte-Carlo method to realistic three-dimensional structures with a reasonable amount of CPU-time.
By use of the simulation program which was developed during this work it is possible to save both time and money in the future development of new process technologies. Before realizing new structures and performing experiments computer simulations can estimate their functioning.