Simulation of the variability in microelectronic capacitors having polycrystalline dielectrics

The scaling down of on-chip microelectronic capacitors presents a considerable challenge for future microelectronic devices. High-permittivity polycrystalline dielectrics such as Ta2O5, SrTiO3 (STO), or (Ba, Sr)TiO3 (BSTO), have been considered as potential replacement for conventional amorphous SiO2 and SiNx. The polycrystalline microstructure of these materials may lead to capacitor-to-capacitor variations in charge storage capacity and charge retention. In this letter, a Monte Carlo simulation is used to assess these variations. Results show that as the average crystalline grain size becomes greater than 1% of the capacitor size, variations of +/-10% in capacitance and between 3-150% in leakage should be expected.