強誘電体メモリ

Ferroelectric memory

Abstract

(57)【要約】 【課題】 非対称ヒステリシス曲線をもつ強誘電体薄膜 を使用した場合において、読み出し電圧の極性が、動作 上どのような影響があるかを明らかにし、読み出し手段 を改良する。 【解決手段】ヘテロエピタキシャル成長させた強誘電体 薄膜に残留分極として書き込まれたデジタル情報を、上 部電極に負の電圧をかけることによって読み出すことを 特徴とし、これにより、読み出し時間の高速化、誤動作 の防止、長時間保持後の信号レベルの劣化の低減などの 効果を得ることができる。
PROBLEM TO BE SOLVED: To provide a ferroelectric memory which can read out an information stored in a ferroelectric thin-film capacitor by applying a negative voltage to an upper electrode. SOLUTION: An SrRuO3 lower electrode 2 is formed on a substrate 1 made of single crystal of SrTiO3 whose surface is flat and smooth, by the rf magnetron sputtering method at 600 deg.C of substrate temperature and 0.6 Pa of a mixing gas atmosphere of Ar gas and O2 gas in a manner that it has a tetragonal crystal symmetricity and a (001) plane exposes. Next, a BaTiO3 thin film as a dielectric thin film 3 is formed thereon by two steps so as to form the dielectric thin film 3, and an SrRuO3 thin film is formed and then it is patterned by etching to form an upper electrode 4. Therefore, a nagative electric charge is applied to an upper electrode by using the potential of the lower electrode as a reference so as to read out an information, thereby shortening the read-out time, eliminating incorrect operation and minimizing an effect of reduction of signal voltage due to gradation of polarization after long holding time.

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    JP-2008085194-AApril 10, 2008Univ Of Tokyo, 国立大学法人 東京大学強誘電体デバイス