Positron annihilation lifetime spectroscopy (PALS) on advanced, self-assembled porous organosilicate glasses

摘要

The dielectric material, necessary for insulation and packaging of on-chip wiring in microelectronics, causes capacitances and signal delays, which ever increase with continuing minimization down to the nanoscale. The root cause for the capacitance is the permittivity, also called dielectric constant or k-value. The aim is to reduce the permittivity to a minimum in order to make further down-scaling possible and keep up the pace of structure integration. It seems that the only viable approach to decrease the k-value below 2.2 is to introduce a significant amount of porosity into the dielectric material. Porous organosilicate glasses (OSGs) are promising materials to serve these requests. Concurrent with the introduction of porosity, the mechanical properties substantially deteriorate and are a great concern for chip reliability. In this work, self-assembled organosilicate glasses with varying k-values down to 1.8 are investigated by positron annihilation lifetime spectroscopy (PALS) to assess the pore size. By self-assembly, the pore structure is ordered and allows higher mechanical strength at the same porosity level compared to non-ordered pores. For further characterization, the PALS study is accompanied with Monte Carlo simulation of the positronium trace in the pores of the OSGs.