高介電常數材料作為低溫複晶矽快閃記憶體電荷捕捉層之研究

Abstract

本篇論文主要著眼於低溫複晶矽薄膜電晶體(LTPS-TFT)於非揮發性快閃記憶體之電性及可靠度研究，包括寫入/抹除速度、於寫入狀態之資料保存能力(Retention)、重複寫入/抹除之耐操度(Endurance)以及寫入時造成的非理想擾動(Disturbance)。首先於N型通道元件中改變不同介電常數的材料作為記憶體之電荷捕捉層(Charge Trapping Layer)，分別為氮化矽(SiNx)、氧化鋁(Al2O3)以及鉿矽酸鹽(Hf-silicate)。可發現所製作之記憶體元件表現出良好的資料保存性以及擾動特性，這主要導因於較厚的底部氧化層。在三種電荷捕捉層材料當中氧化鋁在各方面表現皆最為良好。接下來將同樣三種介電常數材料用於製作P型通道快閃記憶體元件，此P型通道記憶體比較於N型通道記憶體表現出較快速的寫入速度、較低的寫入電壓以及較好的資料保存能力，這使得元件之能量消耗得以減少。在所有的P型通道記憶體中，氧化鋁同樣表現出最好的特性。最後將N型通道記憶體再加以氨氣電漿(NH3 plasma)處理，處理過後元件於耐操度以及電荷保存能力上皆表現出明顯的進步。

In this thesis, electrical characteristic and Reliability of low temperature poly- silicon thin film transistor nonvolatile flash memory have studied, including programming/erasing speed, retention, endurance, retention after cycling and programming disturbances. First, three kinds of high-k materials, SiNx, Al2O3 and Hf-silicate, respectively, were applied for charge trapping layer of n-channel TFT memories. The fabricated memory devices show great retention and disturbance characteristics, attributed to the thick tunneling oxide. Among these three materials, Al2O3 performs best. Then, the same three kinds of materials as mentioned above were applied for p-channel TFT flash memories. The p-channel memory devices show better programming speed, programming voltage and data retention ability than n-channel ones, result in the lowering of power dissipation. Among all p-channel memory devices, Al2O3 performs best, also. Last, the n-channel devices after NH3 plasma treatment show obviously improvement on endurance and data retention.