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Computer simulation and optimization of properties of porous low-k dielectrics

Elsner A., Hermann H.

Materials Science Poland

2007

Vol. 25, No. 4

1193--1202

Due to progressive miniaturization one of the current challenges in microelectronics is to find materials with very low electric permittivity. The model of dense random packed spheres is applied to generate model systems of porous dielectric materials. Pores are represented by dense packed spheres. By optimizing the parameters, the porosity and therefore the theoretical electric permittivity was reduced significantly. Another task is optimization of mechanical properties. Mechanical stability is an important criterion for the processability in industrial fabrication of microlectronics components. The mechanical stability is mostly negatively correlated to porosity. Simulated open pore and closed pore systems with high porosity were analyzed in terms of mechanical properties. Other methods like an adapted random walk algorithm were used to characterize further important properties like particle permeability. In porous materials, the so-called "random voiding" may appear. This happens when pores are larger than the layer thickness. Simulation of porous structures can show limitations in pore size and spatial distribution where the requirements of industrial processability are no longer satisfied. Advantageous parameters for porosity in dielectric materials are advised.

Influence of the packing effect on stability and transformation of nanoparticles embedded in random matrices

Hermann H., Elsner A., Gemming T.

Materials Science Poland

2005

Vol. 23, No. 2

541--549

The compression of random hard sphere systems does not lead to the formation of iscosahedral short - range order. Instead, icosahedral clusters embedded in a hard sphere system with a medium packing fraction are not stable against densification and they dissolve with an increasing packing fraction. Random homogeneous hard sphere models with equal spheres transform into nanometre scale composites of face-centred cubic nanocrystals embedded in a dense random packed matrix when the mean packing fraction of 0.64 is exceeded.