To investigate the origin of DRAM variable retention time (VRT), we use test structures and carefully measure the time dependence of leakage current in DRAM. Consequently we find for the first time that the junction leakage current fluctuates just like random telegraph signal. We analyze the leakage current fluctuation in detail and find it the origin of VRT.

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The variable retention time phenomenon has recently been highlighted as an important issue in dynamic random access memory (DRAM) technology. Based on electrically detected magnetic resonance and simulation studies, we suggest that a single Si vacancy-oxygen complex defect is responsible for this phenomenon, when the defect is embedded in the near surface drain-gate boundary of a DRAM cell.

Articles you may be interested inMicroscopic origins of dry-etching damages in silicon large-scaled integrated circuits revealed by electrically detected magnetic resonance Appl. Phys. Lett.Effects of ion implantation on electron centers in hydrogenated amorphous carbon films J. Appl. Phys. 93, 5905 (2003); 10.1063/1.1564280Boron penetration in p-channel metal-oxide-semiconductor field-effect transistors enhanced by gate ionimplantation damageWe used electrically detected magnetic resonance to study the microscopic structure of ion-implantation-induced point defects that remained in large-scale Si integrated circuits ͑Si LSIs͒. Two types of defects were detected in the source/drain (n ϩ -type͒ region of 0.25-m-gate-length n-channel metal oxide semiconductor field-effect-transistors on LSIs: ͑i͒ a spin-1 Si dangling-bond ͑DB͒ pair in divacancy-oxygen complexes ͑DB-DB distance, RϷ0.6 nm); and ͑ii͒ a series of larger Si vacancies involving distant Si DBs (Rу1.4 nm). These vacancy-type defects were much more thermally stable in Si LSIs than those in bulk Si crystals. We suggested two physical mechanisms for this enhanced stability: internal mechanical stress and oxygen incorporation in the active regions of LSIs. After examining the relationship between the defects and current-voltage characteristics, we concluded that these defects are distributed in the near-surface n ϩ -type region close to the gate and that they are the source of the gate-induced drain leakage currents.

An electron paramagnetic resonance ͑EPR͒ study on fluorine-vacancy defects ͑F n V m ͒ in fluorine-implanted silicon is demonstrated. Fluorine implantation is an important technology for Si microdevices and EPR measurements showed that this process created a variety of F n V m defects of different sizes ͑V 2 , V 4 , and V 5 ͒. In F n V m , a Si-F bond exhibited a different chemical nature compared to a Si-H bond in hydrogen-vacancy complexes. The most primitive defect was FV 2 ͑F0 center͒ and the final types were F n V 5 ͑F1 center͒ and F n V 2 ͑F2 center͒ which increased in annealing processes as low temperature as 200°C.