具不同通道結構薄膜電晶體 SONOS記憶體之研究

Abstract

在本篇論文中，我們提出兩種新穎的薄膜電晶體之SONOS型記憶體結構:「閘極環繞式多晶矽奈米通道結構」與「類鰭式通道結構」來改善傳統平面薄膜電晶體之非揮發性SONOS型記憶體的寫入抹除特性。此兩種結構在製程上與最新穎的COMS製程有高度的相容性並且無需任何先進的微影系統便可以產生新穎通道結構，一方面使得製程成本相對降低且相當有潛力運用於三維積體電路整合技術。 另一方面在電特性表現上，藉由此兩種特殊通道結構有較佳的閘極控制能力以及電場在通道結構中的提昇，可以改善傳統平面薄膜電晶體結構之SONOS型記憶體在抹除時所遇到的抹除飽和現象(Erase Saturation)。在操作上我們選擇FN 穿隧注入 (FN Tunneling) 作為寫入抹除的操作條件。與一般SONOS記憶體不容易利用FN 穿隧注入抹除記憶體中的載子相互比較，此兩種新穎的結構明顯的得到極為出色的抹除表現並且沒有抹除飽和現象。 進一步比較兩種新穎的通道結構，閘極環繞式多晶矽奈米通道結構應用於薄膜電晶體結構之SONOS型非揮性記憶體(non-volatile memory)元件具有極佳的特性表現如：較大的記憶體窗(memory window)、較低的操作電壓、快速的寫入/抹除速度、長時間的載子保存性(data retention)與耐久度(endurance)。 有鑑於我們所提出的新穎結構具有相當優異的寫入抹除特性，我們預期新穎的「閘極環繞式多晶矽奈米通道結構」以及「類鰭式通道薄膜電晶體結構」之SONOS型記憶體元件在薄膜電晶體之SONOS型記憶體元件於閘極長度持續微縮的過程中與應用於未來的三維積體電路與記憶體整合的市場將更具吸引力以及潛力。

In this thesis, we proposed two novel SONOS-type thin film transistor memory channel structures to improve the conventional planar thin film transistor SONOS-type non-volatile memory program and erase characteristics. The novel channel structure processes we demonstrated are not using any advanced lithographic tools. Compared with general SONOS processes, the memory processes of our novel channel structures are lower cost and high level compatibility of COMS process for future 3D IC’s application. The novel memory channel structures which we successfully demonstrated are thin film transistor SONOS-type memory with “Fin-like channels” and “gate all around Si nanowire channels”. Both of two structures has better gate controllability contrast with convention thin film transistor SONOS-type memory. Furthermore, the electric field in the specific channel structures will be enhanced and improve the erase saturation phenomenon. The program and erase operations are performed by FN tunneling mechanism here. As opposed to the conventional SONOS, the erasing behavior in our novel structures shows great erase characteristics and can erase smoothly. To compare two novel memory channel structure, Gate all around Si nanowire SONOS memory exhibit a significantly improved performance with a large memory window, low operating voltage, high P/E speed, good retention time and excellent endurance performance. According the novel structures exhibits superior electric performance, it’s promising for SOP and future 3D IC’s applications and also has the large application potential for flash memory market.