接觸點電阻轉換之研究: 電阻式記憶體及其應用

The Study of Contact Resistive Switching Behavior: RRAM and Its Application

沈文超(Wen-Chao Shen)

指導教授 ： 林崇榮

國立清華大學/電機資訊學院/電子工程研究所/博士(2014年)

https://doi.org/10.6843/NTHU.2014.00643

摘要

在過去數十年間，歸功於個人攜帶式設備及雲端科技的發展，爆炸性成長的儲存需求不斷刺激各種固態儲存的創新研發。快閃記憶體是現今應用於大量資料儲存的主流產品並且長期占據市場中的領先地位。然而，快閃記憶體也面臨著在製程微縮上各式各樣的挑戰與困難，包括高電壓電路設計、薄膜可靠度，已及日漸增加的製程複雜度。學術界及工業界都在引頸期盼一個泛用的解決方案作為未來固態儲存的技術。電阻式記憶體有著優異的特性包括快速寫入數度，製程簡易，元件結構單純以及高度相容於邏輯製程，似乎有望在未來固態儲存領域扮演救世主的角色。 在本論文中，一種新型的接觸點式電阻式記憶體已經被研究並且量測分析。此元件的電阻轉換特性可以在從0.18微米到28奈米的邏輯製程中實現並且觀測。隨著製程技術的演變，它展現了優異的微縮特性，在內嵌式系統單晶片應用上將可望是潛在的解決方案。除此之外，在邏輯製程發展下的垂直式雙極性電晶體將做為接觸點電阻式記憶體的選擇元件，藉此實現超高密度的記憶體陣列。 電阻轉換特性在過去幾年也被廣泛研究在非傳統儲存應用上面，譬如利用電阻式記憶體模擬腦內神經傳導，設計具有學習能力的仿神經電路，這些領域具有高度的創新性，並且在未來有著更龐大的發展潛能。本論文基於對於接點式電阻式記憶體的了解及研究經驗，發展一種非揮發性邏輯閘及隨機亂數產生器。利用順序性的輸入訊號配合共用接點的結構，非揮發性邏輯閘具備有計算AND或是OR能力，並且同時記憶輸出值的功能。而隨機亂數產生器則是利用簡單的比較電路，可以產生隨機零或壹數位訊號，而這些隨機亂數的數位訊號將可以作為通訊加密使用。 總歸而言，接點式電阻記憶體有著很多優異的元件特性，並且可以在純邏輯製程中製作完成，而垂直式新型雙極性電晶體則可以更進一步的縮小單一記憶位元的面積，最後，利用接觸點電阻式記憶體的特性，本論文發展兩種不同於傳統記憶體的應用

關鍵字

電阻式記憶體 ； 非揮發性邏輯閘 ； 隨機亂數產生器 ； 垂直式雙極性接面電晶體

並列摘要

Abstract During a past decade, the explosive increase on storage demand, including personal portable device and cloud technology, has spurred a kaleidoscope of investigation and development on solid state storage. The main-stream technology for fast and mass data storage nowadays, flash memory, has long-time occupied the leading position in the market. It, however, suffered a series of wide spectrums of scaling challenge, such as high voltage design, thin film reliability and process complexity. Scientists and industry are looking forward a universal solution as alternative for solid-state storage in the future. Resistive Random Access Memory, with the superior characteristic on writing speed, simplicity on structure and process, and highly compatible to CMOS process, seems like a promising savior in the future. In this dissertation, the Contact Random Access Memory (CRRAM) has been fully studied and characterized. The resistive switching behavior of CRRAM has been observed from 0.18m technology to advanced 28nm node in standard CMOS logic process. It shows the continuous scaling ability in both unit cell size and applied voltage, promising the CRRAM as a potential candidate in the field of embedded SOC application. Furthermore, ultra-high density CRRAM array can be realised by introduction of logic compatible vertical bipolar junction transistor (VBJT). With burying the NPN junction as conductive selector in the silicon substrate, single Contact RRAM (1C-RRAM) is demonstrated. Study of resistive switching phenomenon in the past few years reveals its widely application beyond memory. Including RRAM-base synapse to simulate and implement neuromorphic circuit and element-based logic operation. These areas are novel and attractive with infinity possibility in near future. Basing on the study and observation of CRRAM, this dissertation proposes two novel applications beyond conventional memory. Firstly, the share contact structure with properly input sequential signal to realise a non-volatile logic operation gate. Secondly, a novel true random number generator has been realised base on the strong random telegraph noise in CRRAM. In summary, CRRAM has several attractive advantage and superior cell performances including fully compatible with CMOS process and platform, ultra-small cell size, data retention and endurance. Its cell size can be further reduced by introduction of Vertical BJT as array selector. Finally, two unique inventions based on resistive switching behavior and strong noise in RRAM current are demonstrated. These shows the CRRAM could not only be a promising candidate for embedded memory, but also could implement as special circuit application.

並列關鍵字

RRAM ； NV Latch ； Random Number Generator ； Vertical BJT

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