A six-band k⋅p model has been used to study the mobility of holes in Si inversion layers for different crystal orientations, for both compressive or tensile strain applied to the channel, and for a varying thickness of the Si layer. Scattering assisted by phonons and surface roughness has been accounted for, also comparing a full anisotropic model to an approximated isotropic treatment of the matrix elements. Satisfactory qualitative (and in several cases also quantitative) agreement is found between experimental data and theoretical results for the density and temperature dependence of the mobility for (001) surfaces, as well as for the dependence of the mobility on surface orientation [for the (011) and (111) surfaces]. Both compressive and tensile strain are found to enhance the mobility, while confinement effects result in a reduced hole mobility for a Si thickness ranging from 30 to 3 nm.
In the next decade, advances in complementary metal-oxide semiconductor fabrication will lead to devices with gate lengths (the region in the device that switches the current flow on and off) below 10 nanometers (nm), as compared with current gate lengths in chips that are now about 50 nm. However, conventional scaling will no longer be sufficient to continue device performance by creating smaller transistors. Alternatives that are being pursued include new device geometries such as ultrathin channel structures to control capacitive losses and multiple gates to better control leakage pathways. Improvement in device speed by enhancing the mobility of charge carriers may be obtained with strain engineering and the use of different crystal orientations. Here, we discuss challenges and possible solutions for continued silicon device performance trends down to the sub-10-nm gate regimes.
We discuss novel multi-level write algorithms for phase change memory which produce highly optimized resistance distributions in a minimum number of program cycles. Using a novel integration scheme, a test array at 4bits/cell and a 32kb memory page at 2bits/cell are experimentally demonstrated. Introduction Phase change memory (PCM) is widely considered to be a potential next-generation non-volatile solid-state memory [1-3]. In addition to its superior write speed compared to 0.2pm -flash, PCM offers a large signal margin between its -crystalline and amorphous states. This wide dynamic range Fig. 2: TEM image of phase-change element (PCE), with underlying also opens the door for multi-level cells (MLC). In this paper, TiN heater on top of W contact. The phase-change material and the we explore MLC write algorithms for up to 16 levels in small o T test arrays, and then demonstrate a 4-level, 32kbit page being overln Tiner are coNnected ubinEs thr a via.part of an experimental memory chip. transferred into the TiN layer using RIB. After strip, oxide isolation is deposited and planarized, exposing the top of the Integration Scheme pillar electrode. The Ge2Sb2Te5 and TiN top electrode layers The memory cell consists of a pillar-heater phase change are then deposited, patterned into islands and encapsulated element (PCE) in series with an access nMOSFET (180nm with dielectric. Top contacts and metallization lines are CMOS technology). As shown in Fig. 1, the 50nm bottom formed using a standard Cu damascene process. Fig. 2 shows electrode heater is fabricated in a subtractive process from a a TEM cross-section of the finished pillar-heater PCE. 75nm thick TiN layer directly deposited over the W contacts.
This study examined the electrical properties of Ti/MnO2/Pt devices with stable and reproducible bipolar resistive switching behavior. The dependency of the memory behavior on the cell area and operating temperature suggest that the conducting mechanism in the low resistance states is due to the locally conducting filaments formed. X-ray photoelectron spectroscopy showed that nonlattice oxygen ions form at the MnO2 surface. The mechanism of resistance switching in the system examined involves the generation and recovery of oxygen vacancies with the nonlattice oxygen ions.
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