低溫成長介電層與堆疊垂直閘極對於無接面電荷儲存式快閃記憶體元件之特性研究

Low-Temperature Formed Dielectrics and Stacked Vertical Gate on Characteristics of Junctionless Charge Trapping Flash Memory Devices

李東諺(Li, Dong Yan)

指導教授 ： 張廖貴術

國立清華大學/原子科學院/工程與系統科學系/碩士(2015年)

摘要

近在元件日漸微縮的趨勢下，平面式元件微縮空間有限，使得元件的密度難以再提升而且製程上也變的棘手。因此要增加元件密度以及使電特性提高是目前重要的課題。而目前已經有許多解決方法被提出，像是使用高介電常數材料的應用、奈米線通道的結構、無接面快閃記憶體元件的應用及三維堆疊陣列等等。本篇論文以使用了低溫的二氧化矽當作穿隧層用在奈米線通道結構以及可堆疊式電荷捕捉式快閃記憶體元件，以及高介電常數材料做能帶工程的應用，目的是為了減少熱預算與增加單位面積之元件密度。
第一個實驗室使用了較低溫的感應耦合電漿化學氣相沉積(ICPCVD)成長出來的氧化層來當我們的穿隧層(Tunneling Layer)，以及使用高介電常數材料做能帶工程應用來當我們的電荷捕捉層，而結構上都是使用奈米線通道式的結構，可以發現使用低溫的感應耦合電漿化學氣相沉積(ICPCVD)成長出來的氧化層與使用急速升溫退火爐(KORONA)成長出來的氧化層擁有差不多好的電特性，而使用二氧化鉿/氮化矽堆疊的電荷捕捉層比單層的氮化矽擁有較快的寫入抹除速度，在可靠度上面也有所改善，因此能帶工程對元件的特性的確有所改善。
第二個實驗也是使用了較低溫的感應耦合電漿化學氣相沉積(ICPCVD)成長出來的氧化層來當我們的穿隧層(Tunneling Layer)，以及使用高介電常數材料做能帶工程應用來當我們的電荷捕捉層，而結構上則是使用了無接面奈米線通道式的結構，可以看到無接面式元件它的確都擁有不錯的寫入特性，能帶工程在寫入特性、記憶窗大小及可靠度特性上都有所改善，因此希望可以將ICPCVD成長的電荷穿隧層應用到未來3-D堆疊結構上。
第三個實驗就是將ICPCVD成長的電荷穿隧層應用到可堆疊式閘極元件上面，並且探討能帶工程在這種可堆疊式閘極元件上是否能有特性的改善，可以發現能帶工程在這種可堆疊式閘極元件上的確改善了他的寫抹速度、電荷保持力及電荷耐久力的特性，但發現到所有元件在可靠度上的表現並不是很好，雖然ICPCVD成長的二氧化矽應用在奈米線結構元件上特性表現得不錯，但是在這種可堆疊式閘極元件上ICPCVD成長的二氧化矽還有很大的改善空間。

關鍵字

堆疊垂直閘極快閃記憶體 ； 奈米線快閃記憶體

並列摘要

The scaling trend of flash device is limited by the dimension of planar device, which makes the process flow more complex. How to improve the operational characteristics and increase the device density at the same time become two of the most important issues. Some approaches have been reported such as high-k material, nanowire channel structure, junctionless (JL) channel and 3D array flash memory devices. In this thesis, a low temperature formed SiO2 is proposed as tunneling layer for nano-wire and stacked vertical gate structure charge trapping (CT) flash memory devices. The purposes are to reduce thermal budget and increase device density.
In the first study, a low temperature formed SiO2 is proposed to replace conventional high temperature SiO2 as tunneling layer. HfO2/Si3N4 stacked trapping layers are implemented to improve the operational characteristics of nano-wire inversion mode flash device. It is found that operational characteristics such as program/erase (P/E) speed、retention and endurance characteristics of low temperature formed SiO2 are as good as those with high temperature formed SiO2. HfO2/Si3N4 stacked trapping layers device has better P/E speed and good reliability characteristics truely.
In the second study, a low temperature formed SiO2 is used as tunneling layer and HfO2/Si3N4 stacked trapping layers to improve the operational characteristics of nano-wire junctionless device. It is found that HfO2/Si3N4 stacked trapping layers device has good P/E speed、memory window and reliability characteristics. Therefore, low temperature formed SiO2 is promising to be applied to 3-D stacked device.
In the last study, low temperature formed SiO2 is applied to stacked vertical gate structure. Effect of HfO2/Si3N4 stacked trapping layers on operational characteristics of the stacked vertical gate device is also studied. It is found that HfO2/Si3N4 stacked trapping layers device improves its P/E speed、retention and endrance characteristics truly. However, the reliability characteristics of all devices are not good enough. Therefore, improvement of ICPCVD formed SiO2 is necessary on such a stacked vertical gate structure.

並列關鍵字

Stacked Vertical Gate Junctionless Flash Memory ； Nano-wire Flash Meemory

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