Computer simulation of nanoporous low - k dielectrics for microelectronic applications

32 Driving the interconnect dimensions of microelectronic circuits to smaller sizes, the delay time caused by the electrical resistance of the Aluminium or Copper wires and the capacitors generated by neighbouring wires and the insulating material becomes the essential limiting factor of the performance of the circuits [1-3]. Fig. 1 shows the delay time as a function of the interconnect dimension for different combinations of metal and insulating material. With the introduction of Copper lines, the speed limit has been partially removed. It is, however, clear that in addition to the replacement of Aluminium by Copper the properties of the insulating material must now be improved. The conventional dielectric material is Silicon oxide with k = 4. This value has to be shifted towards the dielectric constant of the vacuum, k = 1. Trying to develop new dielectric materials with improved properties one may start on a molecular base. Fig. 2 illustrates the interplay of external electric field, and macroscopic and microscopic polarisation fields. The dipole p induced at the position of the considered molecule is given by p = αmol Eloc and depends both on the molecular polarisability αmol and the local electrical field Eloc. The simplest model which proHelmut Hermann Antje Elsner Michael Hecker Manfred Taut Andrei Touzik Kostya Zagorodniy