研究生: |
張佑安 Chang, Yu-An |
---|---|
論文名稱: |
金氧半元件中堆疊式高介電層與界面層之製程研究 Process Study of Higher-k Gate Stack Dielectrics and Interfacial layer for MOS Devices |
指導教授: |
張廖貴術
Chang-Liao, Kuei-Shu |
口試委員: | |
學位類別: |
碩士 Master |
系所名稱: |
原子科學院 - 工程與系統科學系 Department of Engineering and System Science |
論文出版年: | 2010 |
畢業學年度: | 98 |
語文別: | 中文 |
論文頁數: | 116 |
中文關鍵詞: | 閘極 、介電層 、高介電常數 、界面層 |
外文關鍵詞: | high-k, higher-k, Gate Stack, Interfacial layer, Dielectrics |
相關次數: | 點閱:3 下載:0 |
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VLSI製程技術持續以元件微縮為目標,在CMOS等效氧化層厚度上以被要求微縮至1nm以下。然而,由於以二氧化矽做為介電層微縮到1.5nm以下會導致嚴重的漏電流問題,為了元件持續微縮,改採用高介電常數材料取代二氧化矽做為介電層,但高介電材料與矽基板為非理想接面、界面氧化層的增生使EOT微縮不易與載子遷移率下降,皆是使用高介電材料介電層所帶來的一些新挑戰。
第一部分以鈦薄膜搭配高介電層形成閘極介電層,藉此提高介電層之介電係數,觀察經過不同 PDA與PMA溫度退火對鈦擴散深度的影響,而鈦擴散的深度將對元件電性造成影響。實驗結果發現,在high-k與metal gate中間加入一層Ti cap,經過高溫的退火後,雖然介電層中的介電常數上升,但由於interfacial layer的增生使得EOT無法微縮,如經由低溫的退火控制Ti擴散到介電層當中,而不使之擴散至介面層,則可提高介電層當中的介電常數且避免interfacial layer的增生,進而達到EOT的微縮,但是在遲滯量與元件可靠度方面,也因參雜入Ti而有變差的趨勢。而ZrO2經過PDA後堆疊Ti在做低溫PMA退火,EOT向下微縮,而漏電流卻無明顯的上升,在遲滯量與元件可靠度方面,參雜Ti在Zr-base的介電層中,遲滯量並無急遽上升,這是參雜Ti在Zr-base的介電層中的優點,但而在元件可靠度方面加入Ti還是有變差的趨勢。
第二部分以鋯金屬薄膜搭配化學氧化層,經高溫退火形成高品質氧化矽鉻作為介電層,並以鈦薄膜提氧化矽鉻之介電常數,觀察不同鈦薄膜厚度與不同 PMA退火溫度對電性所造成的影響。實驗結果發現,以Zr/chemical oxide 退火形成ZrSixOy作為介電層,隨著不同的PDA退火溫度,會有不同的介電層品質,以經PDA800℃所形成之介電層品質較佳。而PDA700℃雖然EOT較低但漏電流較大,這可能是因為Zr尚未和chemical oxide反應完全,所以介電層較薄所造成。PDA900℃漏電流漏電流更為劇烈,猜測在經過900℃退火之後Zr已穿過chemical oxide,在矽基本中產生大量的缺陷,所以其介面品質極差。進一步在此高品質的ZrSixOy介電層上堆疊Ti cap經不同溫度的PMA退火後發現,以PMA 600℃提升介電層介電常數效果較佳,PMA 700℃因為Ti擴散至介電層當中的量較多且較為靠近矽接面,造成漏電流上升過於劇烈,不符合微縮上漏電流增加的趨勢,而PMA 500℃則因退我溫度較低,Ti擴散至介電層提高介電常數的教果較不顯著。在ZrSixOy介電層上堆疊不同厚度之Ti cap經相同溫度的PMA退火後發現,以cap10□提升介電層介電常數效果較佳,cap 5□因Ti擴散的量太少提升效果較不顯著,而cap 15□過多的Ti cap擴散入介電層中以無法再提升介電常數,反而使漏電流劇烈上升,特性變差。
第三部分本章節以化雙氧水形成學氧化層經高溫退火,再以400:1稀釋之氫氟酸蝕刻至不同厚度形成高品質介面層,討論不同厚度之二氧化矽界面氧化層堆疊高介電材料介電層,對電性所造成的影響。再者討論化學氧化層有無經高溫退火,作為界面層,對電性所造成的影響。實驗結果發現,經高溫退火之後的化學氧化層有較佳的品質,在遲滯與元件可靠度上皆有較佳的特性,並且微縮此品質較佳的界面氧化層厚度,可使EOT有效微縮。
Process Study of Higher-k Gate Stack Dielectrics and Interfacial layer for MOS Devices.Introduction of high-k ,exotic higher-k gate dielectric ,interfacial layer of chemical oxide and stress relieved preoxide.
Three chapters of Experiment and Results.
Increased dielectric constant of HfO2 and ZrO2 gate dielectrics by Ti cap.Ti cap increased HfO2 dielectric constant from 25 to 34 and no extra IL growth after PMA 600 ℃.The devices with Ti cap have poor hysteresis and reliability .The device with Ti cap will increase dielectric thickness by PDA.The devices with PIII nitridation has better hysteresis property.
Effects of Ti cap on ZrSixOy gate dielectric.
Zr metal layer will react with SiO2 after PDA.
The devices with Ti cap 5 □ and PMA500 ℃ enhance
dielectric constant not very much.The devices with Ti cap 15 □ and PMA700 ℃ havelarge leakage current.
The effects of interfacial engineering between high-k gate dielectrics and Si substrate.EOT scaling by reducing SRPO thickness.SRPO has better interface property.
The devices with SRPO have better hysteresis and reliability properties.IL can not be reduced by Zr metal layer and chemical oxide reacting.
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