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Abstract:
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The focus of this work is to study the feasibility , reliability and applicability of advanced dielectrics in both Metal Oxide Semiconductor Field Effect Transistor (MOSFET ) gate oxide and device level packaging for Microelectromechanical Systems (MEMS ) . The scaling of silicon based MOSFET is approaching physical limits imposed by atomic structure . This continuous scaling trend of complementary MOSFET technologies introduces new challenges relating to power , heat and device behavior . To overcome the power dissipation and heating problems arising from gate leakage , high dielectric constant (high -k ) materials are proposed . Hafnium based high -k dielectric layers and metal gate electrodes have been extensively investigated as alternative gate materials . Successful incorporation of these materials into the MOSFET gate stack with minimum feature size of 45nm has recently been reported . Here , the low frequency noise characteristics of MOSFETs with differently nitrided HfSiO gate dielectric materials are studied . To evaluate the high -k MOSFET performance using low frequency noise as a characterization tool , the devices were also subjected to different stress induced degradation . Device performance of differently nitrided samples is also compared with the control , pure HfSiO MOSFET sample . This work reports , for the first time , the low frequency noise performance of 2nm high -k gate dielectric material for the sub 45nm technology node . The advantages of the MEMS packaging approach described here compared to other MEMS packaging techniques are that it is a CMOS compatible low temperature method . Different MEMS devices can be used for vacuum encapsulation using this method . It does not require a high temperature deposition and etching of sacrificial materials and is stiction -free . Removal of the sacrificial layer is performed through openings , called trench cuts , and later the openings are sealed for encapsulation . For the MEMS packaging application , Al₂O₃ (alumina ) is chosen as a resonator beam and sealing material . The primary reasons for choosing this material is due to the hard and stiff material property with high Young's modulus . Alumina can also be used in high temperature and under harsh environment . On top of that , packages with optical transparent window can be made with this material . For the first time this work was reported the use of alumina as a packaging material in MEMS .Extensive RF and reliability measurements were performed on the packaged resonators including evaluation of the package permeability , stress and cavity pressure . Long term and accelerated life testing on the packaged resonators indicated the robustness of the package . |