Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 μm complementary metal–oxide–semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward success...

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High-κ gate dielectrics: Current status and materials properties considerations

Learn the basic properties and designs of modern VLSI devices, as well as the factors affecting performance, with this thoroughly updated second edition. The first edition has been widely adopted as a standard textbook in microelectronics in many major US universities and worldwide. The internationally-renowned authors highlight the intricate interdependencies and subtle tradeoffs between various practically important device parameters, and also provide an in-depth discussion of device scaling and scaling limits of CMOS and bipolar devices. Equations and parameters provided are checked continuously against the reality of silicon data, making the book equally useful in practical transistor design and in the classroom. Every chapter has been updated to include the latest developments, such as MOSFET scale length theory, high-field transport model, and SiGe-base bipolar devices.

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Fundamentals of Modern VLSI Devices

While there has been growing interest in two-dimensional (2-D) crystals other than graphene, evaluating their potential usefulness for electronic applications is still in its infancy due to the lack of a complete picture of their performance potential. The focus of this article is on contacts. We demonstrate that through a proper understanding and design of source/drain contacts and the right choice of number of MoS2 layers the excellent intrinsic properties of this 2-D material can be harvested. Using scandium contacts on 10-nm-thick exfoliated MoS2 flakes that are covered by a 15 nm Al2O3 film, high effective mobilities of 700 cm2/(V s) are achieved at room temperature. This breakthrough is largely attributed to the fact that we succeeded in eliminating contact resistance effects that limited the device performance in the past unrecognized. In fact, the apparent linear dependence of current on drain voltage had mislead researchers to believe that a truly Ohmic contact had already been achieved, a miscon...

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High Performance Multilayer MoS2 Transistors with Scandium Contacts

Electrically induced electron-spin polarization near the edges of a semiconductor channel was detected and imaged with the use of Kerr rotation microscopy The polarization is out-of-plane and has opposite sign for the two edges, consistent with the predictions of the spin Hall effect Measurements of unstrained gallium arsenide and strained indium gallium arsenide samples reveal that strain modifies spin accumulation at zero magnetic field A weak dependence on crystal orientation for the strained samples suggests that the mechanism is the extrinsic spin Hall effect

https://science.sciencemag.org/content/sci/306/5703/1910.full.pdf

Observation of the spin Hall effect in semiconductors.

Wide-band-gap oxides such as SrTiO3 are shown to be critical tests of theories of Schottky barrier heights based on metal-induced gap states and charge neutrality levels. This theory is reviewed and used to calculate the Schottky barrier heights and band offsets for many important high dielectric constant oxides on Pt and Si. Good agreement with experiment is found for barrier heights. The band offsets for electrons on Si are found to be small for many key oxides such as SrTiO3 and Ta2O5 which limit their utility as gate oxides in future silicon field effect transistors. The calculations are extended to screen other proposed oxides such as BaZrO3. ZrO2, HfO2, La2O3, Y2O3, HfSiO4, and ZrSiO4. Predictions are also given for barrier heights of the ferroelectric oxides Pb1−xZrxTiO3 and SrBi2Ta2O9 which are used in nonvolatile memories.

Band offsets of wide-band-gap oxides and implications for future electronic devices

A new approach to the application of the well-known charge pumping technique is proposed as a tool for the measurement of the energy distribution of interface traps in small area MOSFETs. In the classical procedure, the band gap is scanned by applying pulses with variable transition times to the gate of the transistor, defining different energy windows from which the charge pumping signal is measured. The new approach is spectroscopic in nature, i.e., only one energy window is defined and forced to move through the band gap by changing the sample temperature. This method has the advantages of addressing a larger part of the band gap as compared to the classical approach, to reduce complication in the processing of the data and to yield information about the hole and electron capture cross sections separately.

A new charge pumping procedure to measure interface trap energy distributions on MOSFETs

For sub-5 nm oxides there are two different stages for breakdown; soft breakdown (SBD) and hard breakdown (HBD). It has been shown that both SBD and HBD exhibit the same statistics. Therefore, the physical mechanism governing them is the same. The major difference between them is the energy transferred from the capacitor to the localized conducting path. In this paper, a simple equivalent circuit is proposed to explain the effect of the measurement technique, oxide thickness, and test structure area on the detection of soft breakdown. Also an inelastic quantum tunneling model is proposed to discuss the current-voltage characteristics after SBD. The model is also successful in explaining the temperature dependence of SBD IV characteristics.

Measurement technique, oxide thickness and area dependence of soft breakdown

A system of measuring a state density in a semi-conductor element and a method using this system. The system measuring a state density in a semi-conductor element comprises a pulse generator and a control unit for controlling size and shape of the pulses, such as to be able to measure state densities in the band gap of the semi-conductor element.

A system of measuring a state density in a semi-conductor element and a method using this system

Characteristics and Correlated Fluctuations of the Gate and Substrate Current after Oxide Soft-Breakdown

Micro-Raman measurements are performed with a focused laser beam. Because of its finite diameter ({approximately}1 {micro}m) and penetration depth, the laser beam samples a large volume of the sample. In a nonuniformly strained sample, spectra originating from different points are different. Therefore the observed spectrum depends on both the strain distribution in the sample and the adsorption coefficient of the laser light. The authors describe a method to calculate the Raman spectra taking these factors into account. The calculated spectra show excellent agreement with the experimental results.

Herman Maes

Papers

A new charge pumping procedure to measure interface trap energy distributions on MOSFETs

Measurement technique, oxide thickness and area dependence of soft breakdown

A system of measuring a state density in a semi-conductor element and a method using this system

Characteristics and Correlated Fluctuations of the Gate and Substrate Current after Oxide Soft-Breakdown

Measurement of nonuniform stresses in semiconductors by the micro-Raman method