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5. Applications

In order to demonstrate the functionality and the abilities of the Monte-Carlo ion implantation simulator MCIMPL several one-dimensional, two-dimensional and three-dimensional application have been selected, which cover hot topics in modern semiconductor technology. In case of the one-dimensional problems the results are also accessible by measurements, but the advantage of the simulation is that a rigorous analysis or optimization of a problem is much cheaper than a series of experiments. In case of two-dimensional and three-dimensional problems the simulation results additionally provide a deeper insight into a process than any measurement can do. Often only indirect measurements methods are available, like the measurement of the electrical properties after some process steps. Thereby, the influence of a certain process step can only be estimated. Contrary the simulation allows to study all effects directly. Therefore, simulation is a very useful tool in the development of new technologies.

In Sec. 5.1 the influence on the doping profile of layers made of various materials, covering a silicon substrate is studied in detail. The scattering properties of these materials are extensively analyzed and compared. Besides, the influence of a scattering layer on the doping distribution in the vicinity of a mask edge is demonstrated by a two-dimensional simulation.

Alternatively to covering the crystalline silicon substrate with a scattering layer the doping profile can be influenced by pre-amorphization of the substrate before the actual implantation of the electrical active dopants as demonstrated in Sec. 5.2. There the influence of the energy and the dose of a silicon implantation used for pre-amorphization on the doping profile of the dopant atoms is extensively analyzed.

In Sec. 5.3 it is shown that the implantation through a layer of silicon dioxide does not only yield positive effects as demonstrated in Sec. 5.1, but also results in a pollution of an area in the silicon substrate in the vicinity of the silicon-silicon dioxide interface with oxygen atoms. Since this area is a part of the electrical active area the pollution may influence the electrical behavior. The amount of pollution is studied dependent on the implantation energy.

In order to demonstrate that the simulator is capable to perform full three-dimensional simulation within an acceptable amount of simulation time three-dimensional applications are presented in Sec. 5.4. On the one hand side a threshold voltage adjust implantation with BF$ _2$ ions is simulated. Therefore the full molecular method is applied which allows the calculation of the boron and of the fluorine distribution in the simulation domain. On the other hand side a source/drain implantation with arsenic ions is performed. This example is used to demonstrate that the Monte-Carlo simulator can efficiently predict the formation of amorphous areas. For the simulation the Follow-Each-Recoil method is applied which is the most computational intensive but most accurate method of the simulator.

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A. Hoessiger: Simulation of Ion Implantation for ULSI Technology