三維NAND快閃記憶體隨機電報雜訊之特性探討

Abstract

本篇論文主要著重在研究以隨機電報雜訊與缺陷位置對於不同操作電壓所影響之讀取電流於三維NAND快閃記憶體之特性研究。首先，我們製備了平面NAND快閃記憶體來比較不同通道之材料對於讀取電流擾動之影響。由實驗結論我們發現在多晶矽材料之通道的確有較多的讀取電流擾動之影響。接著，我們再針對三維NAND快閃記憶體每一個單位元件作測試，研究發現，在同一串連元件中，單一缺陷可造成不同擾動之影響於單位元件讀取操作下。缺陷位置與讀取電流之關係藉由讀取各個元件可辨別缺陷位置與讀取電流之關係，進而判定缺陷的確切位置及對可靠度之影響。藉由簡單的操作偏壓測試,我們可以由相關之證據發現於三維NAND快閃記憶體中單一缺陷可影響同一串連元件的讀取電流特性。

We investigate the dependence of random telegraph noise (RTN) on a poly-silicon trap position in a 3D vertical channel and charge-trapping NAND flash cell string. First, we characterize the read current of a planar 32-cell NAND string with different channel material. There indeed has different feature in bulk Si and poly Si channel material. We characterize RTN in read current of each cell of a string at different read and pass voltages. Measured RTN characteristics can be explained by current-path percolation and channel carrier screening effects. By using different combination of operation voltages, we could find that RTN is induce by how many traps in a string and the rough position in a string. In addition, a single trap could cause RTN in each cell in a string.