非晶態氧化銦鎵鋅電阻式記憶體特性之研究

Abstract

近年來非揮發性記憶體廣泛地運用在各種可攜式的消費性電子產品中。 而當今市場上非揮發性記憶體的主流是快閃式記憶體 (Flash memory),但 其存在操作電壓大、存取速度慢的缺點;此外隨著元件尺寸不斷的縮小, 快閃式記憶體也面臨到尺寸微縮後的可靠度問題。電阻式記憶體是下一代 非揮發性記憶體的熱門候選之一,因為其具有低功率消耗、高儲存密度、 元件結構簡單等優點。 本論文以非晶態氧化銦鎵鋅 (a-InGaZnO) 做為電阻轉換層的材料。在 室溫下製做成 TiN/Ti/IGZO/Pt 以及 TiN/IGZO/Pt 的結構。在TiN/Ti/IGZO/Pt 結構下,元件可呈現穩定的電阻轉態。其耐久性 (endurance) 可達一萬次,我們藉由材性分析的方式,探討鈦夾層提升電 阻轉換穩定性的原因。此外,我們利用控制限流達到不同電阻態,因其各 阻態分布較集中,適合做多階操作。另外也測試原件在高溫 (攝氏 100 度) 下的穩定性,並藉由變溫量測、改變沈積 IGZO 時氧氣的分壓以及將其電壓 電流曲線做導電機制分析,進一步建立其電阻轉換機制。 最後,由於元件的所有製程都是在室溫下完成,適合應用於軟性電子技 術。此技術擁有輕薄、可撓曲及易隨身攜帶等特性,為近年相當受矚目的 一項技術。我們將原件製作在可撓曲的不鏽鋼基板上,以測試元件在不同 彎曲程度以及多次撓曲後的電特性。

Recently, nonvolatile memory (NVM) has been widely used in electronic devices. Nowadays, the prevailing NVM is Flash memory. However, it is generally believed that the conventional Flash memory will approach its scaling limit within about a decade. The resistive random access memory (RRAM) is emerging as one of the potential candidates for future memory replacement because of its high storage density, low power consumption as well as simple structure. The purpose of this thesis is to develop a reliable a-InGaZnO based resistive switching memory. We investigate the resistive switching characteristics of TiN/T i/IGZO/Pt structure and TiN/IGZO/Pt structure. The device with TiN/Ti/IGZO/Pt structure exhibits stable bipolar resistive switching. The impact of inserting a Ti interlayer is studied by material analyses. The device shows excellent resistive switching properties. For example, the DC sweep endurance can achieve over 1,000 times; and the pulse induced switching cycles can reach at least 10,000 times. In addition, we demonstrate the possibility of MLC operation for the device. By controlling the compliance current, multi-level operation can be achieved. Furthermore, the impact of different sputtering ambient, the temperature instability, and the conduction mechanisms are also investigated. According to our experiments, we propose a model to explain the resistive switching phenomenon observed in our devices. Finally, because the whole fabricating process of the RRAM device is under room temperature, it holds the potential for flexible electronics applications. The TiN/Ti/IGZO/Pt RRAM device is fabricated on flexible stainless steel to test its flexibility and mechanical endurance.