臺灣博碩士論文加值系統

本論文旨在使用傳導式原子力顯微鏡研究高介電質係數氧化層氮氧化鉿在奈米尺度應力下的退化與崩潰情形。

氧化層的崩潰與退化是一局部之行為，其發生區域面積約為數百奈米平方，而傳統氧化層之可靠度分析是透過金氧半電容元件量測來進行，其所提供的是閘極面積下之空間的平均資訊，許多發生在氧化層中單一崩潰及退化情形將被整體行為所遮蔽或被誤視為雜訊。因此，為了更加了解氧化層之崩潰與退化機制，本論文使用擁有奈米等級解析度之傳導式原子力顯微鏡來進行微觀量測。

我們利用反應式濺鍍方式沉積氮氧化鉿氧化層，並利用傳導式原子力顯微鏡對氮氧化鉿施予連續斜坡電壓應力，觀察氧化層的退化情形及崩潰後的特徵。藉著對崩潰後的電流-電壓曲線作power-law fitting，我們可以發現到在高介電係數氮氧化鉿氧化層當中有可能發生三種不同的傳導模式。

在本論文中，我們嘗試以導電性的轉換(switch)與電荷的捕捉及反捕捉有關聯為基礎的傳導機制，來解釋這些崩潰後不同的傳導模式。

The main purpose of this thesis is to investigate the degradation and breakdown characteristics of high-k hafnium oxynitride oxide layer by using conductive atomic force microscopy（CAFM）。

The breakdown and degradation characteristics are highly localized phenomenon, typically in a range of several hundred nano-meter squares. Conventional method of analyzing oxide reliability use electrical tests such as I-V and C-V measurements that are made on MOS capacitor devices. Due to the larger area of the devices, these measurements provide spatially average information of the oxide electrical properties under the gate area. Many single breakdown and degradation characteristics are therefore masked by overall behavior of larger capacitors. Hence, to completely understand the breakdown and degradation mechanisms, conductive atomic force microscopy is more appropriate to use because of its probe tip area is in the same order of magnitude as the breakdown area.

In this work, we use reactive-sputter to deposit hafnium oxynitride, and applying repetitive ramped voltage stress (RVS) through CAFM to the hafnium oxynitride films. The degradation and post-breakdown characteristics were then investigated by measuring the I-V curves. From the power-law fitting of post-breakdown I-V characteristics, we found three different types of conduction mode that are possible in the high-k oxynitride films. Conduction mechanism based on conductivity switching in conjunction with charge trapping and detrapping was given to explain these different post-breakdown conduction mode.

目 錄
第一章 緒論-----------------------------------------1
1-1 研究動機與歷史背景--------------------------1
1-2 氧化層可靠度分析----------------------------------------------2
1-2-1 傳統氧化層可靠度分析（巨觀量測）----------------------------3
1-2-2 以掃描式探針技術分析氧化層可靠度（微觀量測）-----------------4
1-2-3 氧化層崩潰機制介紹-----------------------------------------6
1-3 以金屬鉿為基礎的各種高介電質材料------------------------------8
1-4 原子力顯微鏡工作原理與操作模式--------------------------------9
1-5 論文架構-----------------------------------------------------12
第二章 實驗步驟與樣品備製-----------------------------------------28
2-1 樣品備製-----------------------------------------------------28
2-2 傳導式原子力顯微鏡之量測設定---------------------------------29
2-3 實驗步驟-----------------------------------------------------30
第三章 結果與討論-------------------------------------------------33
3-1 前言---------------------------------------------------------33
3-2 電流─電壓特性曲線-------------------------------------------33
3-3 氧化層表面型態及電流影像-------------------------------------34
3-4 崩潰點擴散現象（BD spot propagation）------------------------35
3-5 崩潰前電流─電壓曲線之F─N fitting---------------------------35
3-6 崩潰後電流─電壓曲線----------------------------------------36
3-7 傳導路徑改變------------------------------------------------36
3-8 CV量測與TEM分析---------------------------------------------39
3-9 輻射對氧化層的影響------------------------------------------39
第四章 結論與未來展望--------------------------------------------70
4-1 結論--------------------------------------------------------70
4-2 未來展望----------------------------------------------------71
參考文獻---------------------------------------------------------72













圖 表 目 錄
表1-1 常見高介電常數材料介電係數一覽表----------------------------13
表1-2 常見SPM技術------------------------------------------------14
表1-3 利用power law fitting所得到的a、b值-----------------------60
圖1-1 金屬─氧化物─半導體（MOS）電容基本結構圖-------------------15
圖1-2 Stair-case ramp voltage stress 電場與時間關係圖-------------16
圖1-3 Exponentially ramped current stress 電流密度與時間關係圖----17
圖1-4 Combined ramped/constant stress 電壓與時間關係圖------------18
圖1-5 傳統巨觀量測與掃描式探針微觀量測比較示意圖------------------19
圖1-6 氧化層退化與崩潰電流─電壓關係圖----------------------------20
圖1-7 Stress-induced leakage current（SILC）電流─電壓關係圖------21
圖1-8（a） 分別對不同厚度之閘極氧化層施加定電流應力所得閘極電壓─應力
施加時間關係圖-----------------------------------------22
圖1-8（b）圖1-8（a）中區域A之放大-------------------------------22
圖1-9 當氧化層發生軟崩潰後，電壓─時間關係曲線呈現一雜訊特徵------23
圖1-10 原子力顯微鏡基本架構圖與操作原理---------------------------24
圖1-11 距離與操作範圍之凡得瓦力關係圖-----------------------------25
圖1-12（a）原子力顯微鏡接觸式操作模式示意圖-----------------------26
圖1-12（b）原子力顯微鏡非接觸式操作模式示意圖---------------------26
圖1-12（c）原子力顯微鏡半接觸式或輕敲式操作模式示意圖-------------26
圖1-13 利用傳導式原子力顯微鏡進行氧化層可靠度分析示意圖-----------27
圖2-1 氮氧化鉿樣品製作流程圖--------------------------------------31
圖2-2 二氧化矽樣品製作流程圖--------------------------------------32
圖3-1（a）氮氧化鉿樣品經過十二次應力後之電流─電壓曲線------------41
圖3-1（b）二氧化矽樣品經過十二次應力後之電流─電壓曲線------------41
圖3-2 氮氧化鉿與二氧化矽臨界電壓比較圖----------------------------42
圖3-3 圖3-2之誤差線(error bar）----------------------------------43
圖3-4 RVS一次之後電流─電壓圖-------------------------------------44
圖3-5（a）施加十次RVS後所得到的表面形貌圖-------------------------45
圖3-5（b）施加十次RVS後所得到的電流影像圖-------------------------45
圖3-6崩潰誘發電荷與探針之間形成淨電力示意圖-----------------------46
圖3-7厚度5.6nm的二氧化矽氧化層崩潰後之TEM表面形貌圖-------------47
圖3-8（a）施加RVS 5次後所得到的表面形貌圖-------------------------48
圖3-8（b）施加RVS 10次後所得到的表面形貌圖------------------------48
圖3-8（c）施加RVS 20次後所得到的表面形貌圖------------------------48
圖3-8（b）施加RVS 40次後所得到的表面形貌圖------------------------48
圖3-9（a）施加RVS 5次後所得到的電流影像圖-------------------------49
圖3-9（b）施加RVS 10次後所得到的電流影像圖------------------------49
圖3-9（c）施加RVS 20次後所得到的電流影像圖------------------------49
圖3-9（d）施加RVS 10次後所得到的電流影像圖------------------------49
圖3-10 氮氧化鉿樣品之RVS施加次數與崩潰面積對應關係圖--------------50
圖3-11（a）RVS10次後將探針偏壓至0伏，所得到的表面形貌圖----------51
圖3-11（b）RVS10次後將探針偏壓至-2伏，所得到的表面形貌圖----------51
圖3-11（c）RVS10次後將探針偏壓至-4伏，所得到的表面形貌圖----------51
圖3-11（d）RVS10次後將探針偏壓至-5伏，所得到的表面形貌圖----------51
圖3-12 對施加一次RVS後的電流─電壓曲線做F-N plot------------------52
圖3-13 對施加一次RVS之電流─電壓曲線做F-N fitting----------------53
圖3-14 RVS一次之後對其電流─電壓曲線取對數後，其曲線呈現power law-54
圖3-15 傳導路徑發生改變前後的斜率相似（插圖為liner scale）---------55
圖3-16 電流峯值前後的傳導路徑呈現一至的現象（插圖為liner scale）----56
圖3-17 電流峯值與圖3-17發生的方式不同，但電流峯值發生前後其傳導路徑
呈現一至的現象---------------------------------------------57
圖3-18無發生傳導路徑改變之power law fitting-----------------------58
圖3-19（a）模式一傳導路徑改變的power law fitting------------------59
圖3-19（b）模式二傳導路徑改變的power law fitting------------------59
圖3-19（c）模式三傳導路徑改變的power law fitting------------------59
圖3-20 利用AFM只能觀測到單一傳導路徑示意圖------------------------61
圖3-21主要傳導路徑與其分支傳導路徑示意圖--------------------------62
圖3-22（a）分支傳導路徑上發生電子反捕捉示意圖-----------------------63
圖3-22（b）主要傳導路徑上發生電子反捕捉示意圖-----------------------63
圖3-23 分支路徑上發生電子反捕捉後，後捕捉到電子--------------------64
圖3-24 經由電子的捕捉產生一新分支路徑，之後在新形成之分支路徑上發生電
子的反捕捉------------------------------------------------65
圖3-25 發生傳導路徑改變與電壓關係圖-------------------------------66
圖3-26 高頻CV曲線------------------------------------------------67
圖3-27 TEM分析圖--------------------------------------------------68
圖3-26（a）未照輻射之電流影像圖-----------------------------------69
圖3-26（b）輻射劑量1M/rads之電流影像圖---------------------------69
圖3-26（c）輻射劑量10M/rads之電流影像圖--------------------------69

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