微縮化氧化鋯鉿鐵電電容及 電晶體的面積和電壓關聯性研究

Investigation of the characteristics in scaling ferroelectric HfZrO2 MOSCAPs and Ferroelectric FETs with area and bias dependencies

阮竹蘼(Truc My Nguyen)

指導教授 ： 吳添立

國立交通大學/國際半導體產業學院/國際半導體產業學院/碩士(2020年)

摘要

在此篇論文當中，探討鐵電特性隨著薄膜微縮趨勢的改變。當薄膜厚度縮減時，電容值會隨之上升，但同時鐵電的效應會反之下降。然而，為了增強元件效能，超薄薄膜常被拿來使用，如:在手持電子產品工業中，低操作電壓、快速開關等應用。
為了元件的微縮，高漏電流成了一個探討的因素。基於鋁參雜的特性，讓薄膜有較小的晶粒，進而降低漏電流，我們設計不同種沉積材料順序在原子層沉積的步驟，包含了:二氧化鉿鋯、二氧化鉿鋯參雜鋁和二氧化鉿。在相同的製程條件下，我們發現二氧化鉿鋯參雜鋁的薄膜使用，可以限制漏電流的大小，同時降低元件跟元件之間的差異性，但鐵電的特性相較二氧化鉿鋯作為薄膜來的較弱。
在鐵電的電性量測上，我們使用了三角波型和正-上-負-下四波型(PUND, positive-up negative-down)去量測元件效能。兩者之中，三角波型的量測有較大的剩餘極化(remnant polarization)，然而正-上-負-下四波型(PUND, positive-up negative-down)量測可以去除傳導電流的影響，得到更純粹的極化值。
同時，在二氧化鉿鋯鐵電場效電晶體(Ferroelectric material HfZrO2 field effect transistor (FeFET))的章節，我們也探討了元件尺寸與偏壓大小對於亞閾值斜率和臨界電壓的影響。發現亞閾值斜率和閘極的大小與偏壓施加的方向有所相關。再者，二氧化鉿鋯鐵電場效電晶體(HZO FeFET)和二氧化鉿鋯參雜鋁鐵電場效電晶體(Al-doped HZO FeFET)在薄膜沉積後退火處理與金屬層沉積後退火處理後有不同的電性呈現和機制，一同在此研究中作分析跟討論。

關鍵字

鐵電體 ； 極化 ； 場效應晶體管 ； MOSCAPs ； 縮小比例 ； 漏電流

並列摘要

In this thesis, the dependency of scaled film thickness on ferroelectric characteristics is investigated. When down-scaling film thickness, the capacitance will be increased, while the ferroelectricity will be also decreased. However, ultra-thin films are used to enhance performance, fast-switching and low-voltage operation for mobile device industry.
From above scaling motivation, high leakage current is serious consequent. In the hope the leakage current decreases from small grain size due to Al-doped, the different atomic layer deposition (ALD) deposit sequences of Hf0.5Zr0.5O2 (HZO), Al-doped HZO (HAZO) and HfO2 are designed. When HZO and HAZO are compared under same conditions, HAZO can limit leakage current and reduce device-to-device variation, however, ferroelectricity is reduced comparing to the pure HZO.
For ferroelectricity measurement, triangle pulse and perform pulsed measurements (called PUND, which stands for positive-up, negative-down) that are two typical methods. Therein, the triangle pulse shows higher polarization (Pr) compared to the PUND pulse. However, the PUND pulse can eliminate conduction current, which shows more accuracy polarization of samples.
We also investigated the dependency of devices’ dimensions and bias on sub-threshold slope (SS) and threshold voltage (VTH) hysteresis, which is systematically studied in Hf0.5Zr0.5O2-based ferroelectric-field-effect transistors (FeFETs). It is found that SS is dependent on both the gate size and sweeping directions. Moreover, Al-doped HZO and pure HZO FeFET under PMA (post deposition annealing) and PDA (post metallization annealing) conditions are also studied, that is found that has different effects on ferroelectricity of devices.

並列關鍵字

Ferroelectric ； Polarization ； Field effect transistor ； MOSCAPs ； down scaling ； leakage current

參考文獻

Reference

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