次世代非揮發性記憶體技術之研究-電荷捕捉型NAND型快閃記憶體及低溫鐵電記憶體製程之研究

A Study of Future Non-volatile Memory Technologies - Charge Trapping NAND Flash Memory and Low Temperature Processed FeRAM

賴昇志(Sheng-Chih Lai)

指導教授 ： 吳泰伯

國立清華大學/工學院/材料科學工程學系/博士(2008年)

https://doi.org/10.6843/NTHU.2008.00147

摘要

隨著行動電子產品需求的快速成長，非揮發性半導體記憶體也越來越受到重視。在本論文裡，將針對最新型SONOS-type快閃記憶體的抹除機制及性能做深入的探討。此外，一種藉由延長雷射脈衝時間的低溫退火技術也將在本篇中討論，此低溫技術適用於將鐵電電容置於導線之上的鐵電記憶體，以作為系統單晶片之應用。
在新型SONOS-type快閃記憶體的研究中，我們提出並驗證了MANOS元件的抹除機制是一種電子由缺陷跳脫的行為。此外，藉由一種暫態分析的分法，MONOS、 MANOS及BE-SONOS三種元件的抹除機制及電荷儲存能力將可被公平的比較。藉由對抹除機制的了解，一種具創新性的BE-MANOS結構也在本論文中首次提出，此結構具有抑制抹除飽和及加大記憶窗之能力。然而，BE-MANOS之電荷儲存能力卻遠不及BE-SONOS，此問題主要是導因於氧化鋁薄膜無法有效阻絕電荷流失。因此，我們導入一層二氧化矽緩衝層，介於氧化鋁及氮化矽之間，此具二氧化矽緩衝層的BE-MANOS結構不但具有良好的性能，而且改善了電荷流失的問題。另外，在此研究中，我們也釐清了氧化鋁薄膜及二氧化矽緩衝層在電荷阻障層中所扮演的角色。
延長雷射脈衝時間的退火技術將可以提供較多的能量及充分的時間，給予PZT薄膜作為結晶之用，然而，底層的塊材卻依然可以保持在低溫之中。在此研究中，我們針對雷射退火的熱模擬也有所著墨，藉由熱模擬不但可以得知試片中溫度的分佈，也可以了解使用延長脈衝雷射的好處。因此，此新型低溫雷射退火技術，將適用於嵌入式鐵電電容在導線上的鐵電記憶體，以作為系統單晶片之應用。

關鍵字

NAND型快閃記憶體 ； 鐵電記憶體 ； 高介電薄膜 ； 雷射退火

並列摘要

Non-volatile semiconductor memories have attracted much attention due to the fast growing demand of portable electronic devices. In this thesis, the erase mechanism and the performance of the state of the art SONOS-type flash memories are critically examined, and a low temperature extended-pulse laser annealing for COI FeRAM is also studied.
In the study of innovative SONOS-type flash memories, a de-trapping model for the erase mechanism of MANOS device is proposed and demonstrated. In addition, the erase and retention characteristics for MONOS, MANOS and BE-SONOS devices are fairly compared by using the transient analysis method. Moreover, an innovative BE-MANOS is proposed to overcome the erase saturation and to enlarge the memory window. However, the retention of BE-MANOS is not as good as BE-SONOS owing to the charge leakage through Al2O3 film. By inserting a SiO2 buffer layer between Al2O3 and SiN storage layer, the oxide-buffered BE-MANOS shows good performance and good reliability, and the roles of high-k Al2O3 and SiO2 buffer layer are also clarified in this work.
An extended-pulse laser annealing is used to provide sufficient thermal energy and time into the PZT film to complete the crystallization, while the bulk of materials remains at low temperature. In this work, the thermal simulation is also presented to illustrate the temperature distribution in the specimen and the benefits of the extended pulse. This new low temperature process is suitable for embedded COI FeRAM for SoC applications.

並列關鍵字

NAND Flash ； FeRAM ； High-k film ； Laser annealing

參考文獻

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