有機金屬合成製備之鉭酸鍶鉍薄膜在非揮發性鐵電記憶體之研究

Abstract

隨著個人攜行裝置逐漸盛行，非揮發性記憶體的需求越益增加。在現今所有非揮發記憶體技術中，鐵電記憶體以其優越的特性，廣受各界矚目與研究，可望成為下一代記憶體的主流。本論文以有機金屬合成法製備鉭酸鍶鉍(SBT)鐵電薄膜，研究其在鐵電記憶體上的應用。首先，以白金為上、下電極製備MFM電容，探討退火條件對SBT鐵電特性的影響，實驗結果在大於750oC退火後可得多晶的鈣鈦礦鐵電相， 值約為12.2 □C/cm2。接著，以微影製程製作MFIS與MFMIS電容結構，探討SBT應用在非破壞性讀取記憶體方面的特性。這兩種結構中的絕緣層採用濺鍍沉積法製備的二氧化鈰(CeO2)薄膜取代傳統的二氧化矽。在MFIS結構方面，以6V的電壓作C-V量測可以得到記憶窗寬為0.95V。而在MFMIS方面，隨著面積比減少(AF:AI)，在固定的電壓下可以得到更大的記憶窗寬。在最小的面積比(1:16)，以5V作C-V量測可得記憶窗寬為2.7V。最後考慮元件的持續性(retention)，MFM結構可以得到很好的持續時間，但若將鐵電膜沉積在閘極絕緣層上，持續時間會變的很短，很多文獻皆有相同的結果，我們亦將可能的原因列在文中。

As portable electronic devices become more and more popular nowadays, there is a confirmed increase in the demand for nonvolatile memory (NVRAM). Among all current NVRAM, ferroelectric memory (FRAM) is the most promising candidate. In this thesis, we investigated SrBi2Ta2O9 (SBT) films derived by metal organic decomposition (MOD) method for NVRAM applications. A well-shaped hysteresis loop with of 12.2 □C/cm2 is obtained using Pt as top and bottom electrodes. The physical and electrical properties of SBT films associated with annealing conditions are also studied using the same MFM structure. As for nondestructive readout FRAM, MFIS and MFMIS capacitors have been fabricated by our three-mask lithography process. A suitable memory window width of the value 0.95V under a sweeping voltage 6V can be obtained from our MFIS capacitors using CeO2 films as insulator (I) layers. As the area ratio (AF:AI) of MFMIS capacitors decreases, the memory windows can increase up to 2.7V under a sweeping voltage 5V. The retention characteristics of MFIS and MFMIS capacitors are poor in our experiments. The reasons are discussed in the text.