具有空氣倉隔離和溝槽爲1T-DRAM應用之新型TFT

A New TFT with Trenched Body and Airgap-insulated Structure for Capacitorless 1T-DRAM Application

陳鉦欣 ； 林吉聰 ； 張子豐 ； 黃奕泉 ； 林勃劦 ； 張又哲

《國家奈米元件實驗室奈米通訊》 18卷2期 (2011/06) Pp. 8-13

https://doi.org/10.29913/NDLC.201106.0002

摘要

在本論文中，我們提出了一個具有溝槽且周圍為空氣倉隔離的新型薄膜電晶體(a New TFT with Trenched Body and Airgap-insulated Structure, AITFT)，並研究其在1T-DRAM的應用。同時我們也探討不同介電係數材料對於感應電流窗(Sensing Current Window)和資料保持時間(Retention Time)的影響。在此，元件的操作是利用碰撞游離(Impact Ionization)機制以及浮體效應(Floating Body E_ect)來改變臨限電壓(Threshold Voltage, V(下標 th))，造成讀取時狀態”1”與狀態”0”汲極電流的不同，藉此判斷位元(bit)的狀態。藉由ISE TCAD 10.0的模擬，我們設定在通道長度皆為150 nm且溫度為300 K的情況下與傳統TFT結構比較，由於有溝槽和空氣倉隔離的設計，AITFT的感應電流窗比傳統TFT大了212%，資料保持時間也比傳統TFT多了42%。此外，AITFT的非連續絕緣設計除了可抑制短通道效應外，元件操作時產生的熱可經由源汲極(Source/Drain)從基板排出，進而增加元件的可靠度。

關鍵字

薄膜電晶體 ； 單電晶體無電容式記憶體

並列摘要

In this study, we propose a new thin-film transistor with trenched body and airgap-insulated structure (AITFT) for one-transistor dynamic random access memory (1T-DRAM) applications and investigate the influence of different dielectric materials on the sensing current window and retention time. Its operation mechanisms are based on the impact ionization and floating body effects. Due to the generated holes stored in the pseudo neutral region, the threshold voltage (V(subscript th)) is lower, resulting in a high drain current for state ”1”. Therefore we can recognize the data by sensing the difference of the drain current. According to the ISE TCAD 10.0 simulations, owing to the design of trench and airgap-isolation structure, the AITFT can enhance about 212% sensing current window and 42% retention time compared with the conventional TFT at conditions of the channel length of 150 nm and temperature of 300 K. Also, owing to the source/drain-tie, the generated heat can be dissipated quickly through the source/drain to the substrate thus the thermal instability can be improved. In other words, the AITFT can improve the thermal reliability but without losing control of the short-channel effects.

並列關鍵字

Thin Film Transistor, TFT ； One Transistor Dynamic Random Access memory, 1T-DRAM