Search

In this paper, the impact of charge transfer doping on the variability of multiwalled carbon nanotube (MWCNT) local interconnects is studied by experiments and simulations. We calculate the number of conducting channels of both metallic and semiconducting carbon nanotubes as a function of Fermi level shift due to doping based on the calculation of transmission coefficients. By using the MWCNT compact model proposed in Part I of this paper, we study the charge transfer doping of MWCNTs employing Fermi level shift to reduce the performance variability due to changes in diameter, chirality, defects, and contact resistance. Simulation results show that charge transfer doping can significantly improve MWCNT interconnect performance and variability by increasing the number of conducting channels of shells and degenerating semiconducting shells to metallic shells. As a case study on an MWCNT of 11 nm outer diameter, when the Fermi level shifts to 0.1 eV, up to ~80% of performance and standard deviation improvements are observed. Furthermore, a good match between experimental data and simulation results is observed, demonstrating the effectiveness of doping, the validity of the MWCNT compact model and proposed simulation methodology. [ABSTRACT FROM AUTHOR]

In this paper, an enhanced compact model of multiwalled carbon nanotube (MWCNT) interconnects while considering defects and contact resistance is proposed. Based on the atomistic-level simulations, we have found that defect densities impact MWCNT resistance and ultimately their electrical performance. Furthermore, we have computed by atomistic-level simulations, the end-contact resistance between single-wall carbon nanotube and palladium (Pd) electrode to mimic the Pd–CNT end-contact resistance of each CNT shell in MWCNT. We have developed an advanced shell-by-shell model to include various parameters, such as shell diameter, shell chirality, defects on each shell, and connectivity of each shell to end contacts. We run Monte Carlo simulations to perform variability studies on each of these parameters to understand the electrical performance variation on MWCNT interconnects. We present the simulation results to convey the critical impact of variations. The impact of doping on MWCNT variability in the form of Fermi level shift will be addressed in Part II of this paper. [ABSTRACT FROM AUTHOR]

In this letter, we report a quantum transport simulation study of the impact of random discrete dopants (RDDs) on Si-InAs nanowire p-type Tunnel FETs. The band-to-band tunneling is simulated using the non-equilibrium Green’s function formalism in effective mass approximation, implementing a two-band model of the imaginary dispersion. We have found that RDDs induce strong variability not only in the OFF-state but also in the ON-state current of the TFETs. Contrary to the nearly normal distribution of the RDD-induced ON-current variations in conventional CMOS transistors, the TFET’s ON-currents variations are described by a logarithmic distribution. The distributions of other figures of merit (FoM) such as threshold voltage and subthreshold swing are also reported. The variability in the FoM is analyzed by studying the correlation between the number and the position of the dopants. [ABSTRACT FROM AUTHOR]

This paper presents experimental and simulation analysis of an $\Omega $ -shaped silicon junctionless nanowire field-effect transistor (JL-NWT) with gate lengths of 150 nm and diameter of the Si channel of 8 nm. Our experimental measurements reveal that the ON-currents up to 1.15 mA/ $\mu \text{m}$ for 1.0 V and 2.52 mA/ $\mu \text{m}$ for the 1.8-V gate overdrive with an OFF-current set at 100 nA/ $\mu \text{m}$. Also, the experiment data reveal more than eight orders of magnitude ON-current to OFF-current ratios and an excellent subthreshold slope of 66 mV/dec recorded at room temperature. The obtained experimental current–voltage characteristics are used as a reference point to calibrate the simulations models used in this paper. Our simulation data show good agreement with the experimental results. All simulations are based on drift-diffusion formalism with activated density gradient quantum corrections. Once the simulations methodology is established, the simulations are calibrated to the experimental data. After this, we have performed statistical numerical experiments of a set of 500 different JL-NWTs. Each device has a unique random distribution of the discrete dopants within the silicon body. From those statistical simulations, we extracted important figures of merit, such as OFF-current and ON-current, subthreshold slope, and voltage threshold. The performed statistical analysis, on samples of those 500 JL-NWTs, shows that the mean ${I}_{D} - {V}_{\text {Gs}}$ characteristic is in excellent agreement with the experimental measurements. Moreover, the mean ${I}_{D} - {V}_{\text {Gs}}$ characteristic reproduces better the subthreshold slope data obtained from the experiment in comparison to the continuous model simulation. Finally, performance predictions for the JL transistor with shorter gate lengths and thinner oxide regions are carried out. Among the simulated JL transistors, the configuration with 25-nm gate length and 2-nm oxide thickness shows the most promising characteristics offering scalable designs. [ABSTRACT FROM AUTHOR]

Using a state-of-the-art quantum transport simulator based on the effective mass approximation, we have thoroughly studied the impact of variability on Si x Ge 1 − x channel gate-all-around nanowire metal-oxide-semiconductor field-effect transistors (NWFETs) associated with random discrete dopants, line edge roughness, and metal gate granularity. Performance predictions of NWFETs with different cross-sectional shapes such as square, circle, and ellipse are also investigated. For each NWFETs, the effective masses have carefully been extracted from s p 3 d 5 s ∗ tight-binding band structures. In total, we have generated 7200 transistor samples and performed approximately 10,000 quantum transport simulations. Our statistical analysis reveals that metal gate granularity is dominant among the variability sources considered in this work. Assuming the parameters of the variability sources are the same, we have found that there is no significant difference of variability between SiGe and Si channel NWFETs. [ABSTRACT FROM AUTHOR]