Control of Two Types of Dielectric Relaxation Current for Ta2O5 Metal-Insulator-Metal Capacitors

Ta2O5 is the most promising high-k dielectric candidate for metal-insulator-metal (MIM) capacitors, but its dielectric relaxation (DR) currents may cause irrecoverable charge loss, although DR is a universal phenomenon of normal dielectrics. Therefore, the Ta2O5 MIM capacitors DR chasracteristics and their control were investigated. Ta2O5 DR is composed of two components. One component shows t-1-type time decay, which is assumed to be caused by nonuniformity of electron polarization and is almost of the same order as that of SiN. Thus, its influence on dynamic random access memory (DRAM) operation will be limited. The other component shows t-0.5-type time decay, which is caused by hydrogen deoxidation of Ta2O5, and is dominant in the case of deoxidized Ta2O5 DR. It causes about 16% charge loss. Namely, it will have an adverse influence on DRAM operation. N2 annealing is a possible solution for the reduction of this t-0.5-type DR.