Some applications of new generation of CAD tools to micro and nanosystems

The need for a new generation of Technology CAD tools based on atomic scale modelling to meet the future needs of the microelectronic industry for the sub micron devices and the Microsystems design has been described. It is stated how a cascade of different types of modeling going from the basic atomistic level to macroscopic continuum can be linked together, each feeding parameters into the higher level modeling. Four examples of fields in which we have been involved are given. The heteroepitaxial growth where the strain induced by lattice mismatch leads to the formation of facetted islands and interface defects. Comparison with experimental in situ characterization techniques such as RHEED and photoemission are emphasized. The diffusion of impurities and their subsequent reactions to form extended defects such as dislocation loops are reported. The statistical and geometrical characteristics of the defects are discussed and compared with results of kinetic modeling. The wet chemical etching of silicon is shown to be reliably modeled by introducing a few atomic scale parameters. A global etching diagram in good agreement with experimental data is found and can be fed into macroscopic tools. Preliminary results of oxygen interaction with silicon surface are presented. It is shown that the reaction leads, from the beginning, to the roughening of the silicon surface and to the formation of near crystalline oxide.