本研究以RuxZr1-x和WxZr1-x兩組合金薄膜作為金屬閘極，並以950℃熱氧化形成的SiO2當作介電材料，形成兩套MOS電容器。在金屬閘極部分，RuxZr1-x和WxZr1-x金屬薄膜分別以鋯靶材跟釕靶材共濺鍍，和以鋯靶材跟鎢靶材共濺鍍形成，兩者皆利用不同濺鍍功率調變薄膜中的金屬成分比例。研究內容主要是探討不同成分比例金屬閘極電極之材料性質與電性表現，藉以評估其做為閘極電極層之可行性。
實驗中使用電子微探儀分析RuxZr1-x和WxZr1-x合金薄膜成分比例；利用低掠角X光繞射儀對RuxZr1-x和WxZr1-x合金薄膜進行晶體結構分析；使用穿透式電子顯微鏡來觀察RuxZr1-x/SiO2/Si之MOS結構電容器之橫截面影像，並且鑑定950℃生長之SiO2厚度以及RuxZr1-x金屬薄膜結晶性；利用X光光電子能譜儀對初鍍不同成分比例之RuxZr1-x/SiO2/Si之MOS結構電容器進行縱深分析，觀察由薄膜表面至RuxZr1-x/SiO2界面的化學鍵結變化；使用附加於原子力顯微鏡上之表面電位顯微鏡來獲得試片表面功函數；MOS結構電容器之電容-電壓(C-V)曲線乃使用電感電容電阻計量儀(Agilent 4284)進行量測，並萃取出其有效功函數。
低掠角X光繞射儀分析結果顯示，初鍍RuxZr1-x和WxZr1-x只有Ru> 90 at%和W > 80 at%的試片才會有明顯結晶產生，其餘試片呈現非晶質結構。RuxZr1-x/SiO2/Si之MOS結構在穿透式電子顯微鏡分析下，並沒有看到明確中介層產生於界面。然而，X光光電子能譜儀分析結果顯示，Zr成分≧23at%的試片容易在表面產生ZrOx，而富含Zr成分(≧67 at%)的試片也會在RuxZr1-x/SiO2 、WxZr1-x/SiO2界面產生界面反應。
電性量測顯示，初鍍的純Zr所量得有效功函數約為4.0 eV，隨著Ru含量的添加，Ru0.20Zr0.80、Ru0.33Zr0.67增加到4.37、4.46eV，但隨後Ru0.46Zr0.54的有效功函數卻下降到4.15eV。當Ru含量再添加越來越多時，RuxZr1-x金屬閘極功函數也有越來越大的趨勢。初鍍純Ru所量測到的有效功函數大約為5.16 eV。對於WxZr1-x金屬閘極而言，隨著W含量添加，W0.22Zr0.78有效功函數增加到4.5eV，但隨後W0.52Zr0.48卻下降到4.22eV。當W含量再添加越來越多時，WxZr1-x金屬閘極有效功函數也會越來越大，W0.97Zr0.03可增加到4.63 eV。但對於純W金屬閘極而言，功函數卻下降到4.49 eV。
在表面電位量測分析中，對於RuxZr1-x和WxZr1-x金屬閘極系統，當Ru或W含量小於80 at%時，所量得表面功函數並不會隨成分改變而有明顯變化，其功函數值大約落在4.3 ~ 4.5eV。對於C-V磁滯曲線掃描分析，不管金屬閘極電極是RuxZr1-x或WxZr1-x ，其氧化層捕獲電荷數值皆約為同一個級數，1×1011 ~ 9×1011 (#/cm2)，且其電荷捕捉型態也都為負電荷。

In this study, metal gates of RuxZr1-x and WxZr1-x alloyed films are deposited on n-type Si with thermally grown SiO2 to form two types of metal-oxide-semiconductor (MOS) capacitors. For the metal gates, both RuxZr1-x and WxZr1-x thin films were fabricated by co-sputtering ruthenium and zirconium targets, and by co-sputtering tungsten and zirconium targets, respectively. Compositions of RuxZr1-x and WxZr1-x alloyed films were controlled by adjusting the sputtering power. Material and electrical characteristics for alloyed metal gates of different compositions are investigated to assess their feasibility as metal gate materials.
Compositions of RuxZr1-x and WxZr1-x thin films are examined by electron probe X-ray microanalyzer (EPMA). Crystal structures of RuxZr1-x and WxZr1-x thin films are identified by grazing incident angle x-ray diffractometer (GIAXRD). Transmission electron microscopy (TEM) is employed to examine the cross- sectional microstructure of RuxZr1-x/SiO2/Si MOS capacitors, crystal quality of RuxZr1-x alloyed films, and to identify the thickness of thermally grown SiO2. X-ray photoelectron spectroscopy (XPS) depth profiling spectra are applied for chemical bonding analysis of RuxZr1-x/SiO2/Si structures. Surface potential microscopy is used to measure the work function on sample surface. The C-V curves of MOS structure capacitors are measured by LCR meter (Agilent 4284A) to extract the effective work function of RuxZr1-x and WxZr1-x metal gates.
According to the X-ray diffraction patterns, only the RuxZr1-x films of Ru>90 at% and WxZr1-x films of W>80 at% exhibit distinct diffraction peaks. All others are amorphous as deposited. TEM micrographs indicate that there is no obvious interlayer observed at the interface between RuxZr1-x and SiO2. However, XPS depth profiling spectra reveal that the samples with composition of ≧23 at% Zr oxidize to form ZrOx on the surface and the Zr-rich RuxZr1-x (≧67 at% Zr) react with SiO2 at the interface between RuxZr1-x and SiO2.
For RuxZr1-x metal gate electrodes, the effective work function of the as-deposited pure Zr is 4.0 eV, and then it increases to 4.37 and 4.46 eV for Ru0.20Zr0.80 and Ru0.33Zr0.67 with increasing Ru content. But the work function of Ru0.46Zr0.54 decreasing to 4.15 eV. Further addition of Ru will again increase the work function of RuxZr1-x and the effective work function is about 5.16 eV for pure Ru. For WxZr1-x metal gates, the work function is 4.5 eV for W0.22Zr0.78 and then it reduces to 4.22 eV for W0.52Zr0.78. The more W content leads to the higher the work function. The work function for W0.97Zr0.03 is 4.63 eV but it decreases to 4.49 eV for pure W.
In the analysis of surface potential microscopy, the surface work function has no remarkable change with composition for RuxZr1-x and WxZr1-x alloyed films when Ru or W content is smaller than 80 at%. The value is about 4.3~4.5 eV. The oxide trapped charge density extracted from C-V hysteresis curves is about 1×1011 ~ 9×1011 (#/cm2) and the trapped charges are negative for both RuxZr1-x and WxZr1-x metal gates.

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