Advanced high-κ dielectric stacks with polySi and metal gates: Recent progress and current challenges
ABSTRACT The paper reviews our recent progress and current challenges in implementing advanced gate stacks composed of high-κ dielectric materials and metal gates in mainstream Si CMOS technology. In particular, we address stacks of doped polySi gate electrodes on ultrathin layers of high-κ dielectrics, dual-workfunction metal-gate technology, and fully silicided gates. Materials and device characterization, processing, and integration issues are discussed.
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ABSTRACT: This paper identifies and investigates a new source of random threshold voltage variation, which is referred to as Grain-Orientation-induced Quantum Confinement (GOQC) in emerging ultra-thin-body metal-gate complementary metal-oxide-semiconductor (CMOS) devices including FinFET, tri-gate, and nanowire field-effect transistors. Due to the dependence of the work function of the metal gates on their grain orientations, different parts of the gate in multigate CMOS devices can have different work functions, resulting in a high electric field in the channel (body) of these devices and, hence, in electrical confinement of the carriers. GOQC effect is shown to be the dominant source of the quantum threshold voltage variation in all emerging ultra-thin multi-gate devices including FinFETs. It is also highlighted for the first time that such variations can have significant implications for the performance and reliability of minimum-sized digital circuits such as static random-access memory cells.IEEE Transactions on Electron Devices 09/2011; · 2.06 Impact Factor
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ABSTRACT: The response to heavy-ion irradiation of FinFET and Multi-Channel Nanowire MOSFET (MC-NWFET) operated with independent gates is investigated by 3-D numerical simulation. The bipolar amplification and charge collection of devices with independent gates are particularly investigated and compared to those of conventional devices having a single surrounding gate. We show that the independent-gate operation of both FinFET and MC-NWFET degrades the device immunity to heavy-ion irradiation.IEEE Transactions on Nuclear Science 01/2012; 59(6):3249-3257. · 1.22 Impact Factor
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ABSTRACT: An overview is presented of total ionizing dose (TID) effects in MOS and bipolar devices from a historical perspective, focusing primarily on work presented at the annual IEEE Nuclear and Space Radiation Effects Conference (NSREC). From the founding of the IEEE NSREC in 1964 until ~1976, foundational work led to the discovery of TID effects in MOS devices, the characterization of basic charge transport and trapping processes in SiO2, and the development of the first generations of metal-gate radiation-hardened MOS technologies. From ~1977 until ~1985, significant progress was made in the understanding of critical defects and impurities that limit the radiation response of MOS devices. These include O vacancies in SiO2, dangling Si bonds at the Si/SiO2 interface, and hydrogen. In addition, radiation-hardened Si-gate CMOS technologies were developed. From ~1986 until ~1997, a significant focus was placed on understanding postirradiation effects in MOS devices and implementing hardness assurance test methods to qualify devices for use in space systems. Enhanced low-dose-rate sensitivity (ELDRS) was discovered and investigated in linear bipolar devices and integrated circuits. From ~1998 until the present, an increasing focus has been placed on theoretical studies enabled by rapidly advancing computational capabilities, modeling and simulation, effects in ultra-thin oxides and alternative dielectrics to SiO2, and in developing a comprehensive model of ELDRS.IEEE Transactions on Nuclear Science 01/2013; 60(3):1706-1730. · 1.22 Impact Factor