Metal Alloys and Gate Stack Engineering for CMOS Gate Electrode Application
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Published: 2004
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DOWNLOAD EBOOKThe purpose of this research has been to search for proper metallic gate electrodes for CMOS devices. This dissertation covers several binary alloy metal gate research topics. First, intermetallic binary alloy RuY was investigated. From C-V analysis we obtained the effective work function of Ru-Y thin films to range from 5.0eV to 3.9eV which is suitable for dual metal gate CMOS. The rich Y film was found to be not stable on SiO2 dielectrics because of the high oxygen affinity of Y. RuxYy thin film may still be a candidate for low temperature process, especially due to its large range of work function. More over, RuY has smaller grain size than Ru which demonstrates one of the advantages of alloy by reducing grain size to achieve more uniform gate film and more uniform effective work function for the nano-size device applications. Chapter 3 presents MoxTay as a potential candidate for dual metal CMOS applications. The electrical characterization results of MoTa alloy indicates that the effective work function can be controlled to around 4.3 eV on SiO2 and is suitable for NMOS gate electrode application. The MoTa alloy forms a solid solution instead of an intermetallic compound. We report that the MoTa solid solution can achieve low work function values and is stable up to 900 & deg;C. X-ray diffraction results indicated only a single MoTa alloy phase. Moreover, from Auger electron spectroscopy and Rutherford backscattering spectroscopy analysis, MoTa was found to be stable on SiO2 under high temperature anneals and no metal diffusion into substrate Si channel was detected. This indicates that MoxTay is a good candidate for CMOS metal gate applications. Chapter 4 evaluates Ru and W capping layer for MoTa metal gate electrodes in Metal Oxide Semiconductor capacitor applications. We report that the oxygen diffusion from the capping layer plays an important role in determining the MoTa alloy effective work function value on SiO2. MoTa alloy metal gate with Ru capping exhib.