One Transistor Ferroelectric Memory Devices with Improved Retention Characteristics

概要

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We have fabricated Pb5Ge3O11 (PGO) MFMPOS (M: metal, F: ferroelectrics, P: polysilicon, O: oxide, S: silicon) memory transistor devices using metal organic chemical vapor deposition (MOCVD) selective deposition, damascene structure and chemical mechanical planarization (CMP) processes. These processes have no need to etch the ferroelectric material. As a result, etching-induced damages are avoided. The one-transistor memory devices show memory windows around 2–3 V. The memory windows are almost saturated from operation voltage of 3 V. For the one transistor memory device, after writing the “off” state ($-5$ V), the drain current ($I_{\text{D}}$) at a $V_{\text{D}}$ of 0.1 V and a $V_{\text{G}}$ of 0, 0.5, and 1 V is about $2\times 10^{-14}$ A. After writing the “on” state ($+5$ V), the drain current ($I_{\text{D}}$) at a $V_{\text{D}}$ of 0.1 V and a $V_{\text{G}}$ of 0, 0.5, and 1 V is about $1\times 10^{-5}$ A. The ratio of the “on” state current to the “off” state current is close to 9 order. The 1 T devices show very good memory characteristics. The one-transistor memory devices also show very good retention properties.
2002-11-30