Evidence and understanding of ALD HfO2-Al2O3 laminate MIM capacitors outperforming sandwich counterparts

Abstract

Metal-insulator-metal capacitors with atomic-layer-deposited HfO2-Al2O3 laminated and sandwiched dielectrics have been compared, for the first time, for analog circuit applications. The experimental results indicate that significant improvements can be obtained using the laminated dielectrics, including an extremely low leakage current of 1 × 10-9 A/cm2 at 3.3 V and 125 °C, a high breakdown electric field of ∼3.3 MV/cm at 125 °C, good polarity-independent electrical characteristics, while retaining relatively high capacitance density of 3.13 fF / μm2 as well as voltage coefficients of capacitance as low as - 80 ppm/V and 100 ppm/V2 at 100 kHz. The underlying mechanism is likely due to alternate insertions of Al2O3 layers that reduce the thickness of each HfO2 layer, hereby efficiently inhibiting HfO2 crystallization, and blocking extensions of grain boundary channels from top to bottom as well as to achieve good interfacial quality. © 2004 IEEE.