高介電常數材料(HfAlO)沉積前後表面處理之研究

Abstract

近年來很多研究致力於發展可替代二氧化矽介電層材料，用高介電常數取代二氧化矽的方法使得半導體的元件能夠持續發展下去，並且克服物理上縮小的限制，在高介電常數的材料中，二氧化鉿是較有潛力的高介電常數材料，它有較高的介電係數跟跟載子能障，且與矽反應所需能量較高，如果我們在沉積二氧化鉿時，參雜一些三氧化二鋁可以提高結晶溫度，增加熱穩定性，但由於鋁堆積在介電層與矽之間的介面，依然有固定負氧化物電荷的問題，使得遷移率下降。因此在介電層與矽基板之間的介面層就變得很重要，它的品質會影響到元件的特性還有可靠度等。所以在本論文中，我們比較用二氧化氮和紫外光加臭氧表面處理形成的一層薄膜類似二氧化矽，看哪種表面處理對元件的特性有較好的影響。 在另一方面，經過表面處理可能會改變介電層的主要鍵結，減少在金屬與介電層介面或介電層中的缺陷，我們用NH3 電漿與紫外光加臭氧兩種表面處理伴隨之後適當快速熱退火溫度來改變介電層中的主要鍵結，看是否對電性能有正面的影響。從磁滯效應，漏電流，電容，可靠度，等效二氧化矽厚度等特性來看，紫外光加臭氧的前處理以及NH3電漿伴隨800℃的後處理能夠達到較好的電性。

In recent years, a lot of research effort has been focused on developing alternative gate dielectric materials to replace SiO2. Using high dielectric constant provide the way to make the semiconductor roadmap go on, and overcome the present physical limits of semiconductor scaling down. Among High-k materials, HfO2 can be used due to its relatively high dielectric constant, its relatively high free energy of reaction with Si, and its relatively high band gap, and if we add Al during deposition process to form HfAlO can increase crystallization temperature, and have better thermal stability than HfO2, but HfAlO also introduces negative fixed oxide charges due to Al accumulation at the HfAlO-Si interface, resulting in mobility degradation, therefore the control of SiO2-like interface between high-□ dielectrics and silicon substrate pays more and more important, since the device performances and reliability characteristics are strongly affected by the interface quality. In this thesis we compare Nitridation of the Si surface using N2O and Oxidation of the Si surface using UV ozone prior to the deposition of high-□ gate dielectrics to see which is good for the electrical properties of devices. In the other hand the interface treatment can change the texture bonding, and reduce defects such as dangling bonds at the interface between metal gate and dielectric as well as incorporation of extra impurities. The changes of interface and incorporation will upset a balance within the primary interface, we use UV ozone and NH3. two treatment accompany with appropriate RTA temperature to change the texture bonding and see which improve the electrical properties effectively. In this thesis we find a suitable surface treatment before and after HfAlO deposition and appropriate annealing temperature to improve electrical characteristics. From the hysteresis , leakage current density, capacitance, reliability, EOT, etc. the UV ozone pre-treatment and NH3 post treatment with 800℃ RTA has excellent electrical characteristics.