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...

/pdf/high-k-gate-dielectrics-current-status-and-materials-zjvba0c4u8.pdf

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

Transparent conductors—A status review

We review work on In2O3:Sn films prepared by reactive e‐beam evaporation of In2O3 with up to 9 mol % SnO2 onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10−4 Torr. Optimized coatings have crystallite dimensions ≳50 nm and a C‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐μm range, by X‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10−4 Ω cm. The corre...

Evaporated Sn‐doped In2O3 films: Basic optical properties and applications to energy‐efficient windows

An overview of the state of art in ferroelectric thin films is presented. First, we review applications: microsystems' applications, applications in high frequency electronics, and memories based on ferroelectric materials. The second section deals with materials, structure (domains, in particular), and size effects. Properties of thin films that are important for applications are then addressed: polarization reversal and properties related to the reliability of ferroelectric memories, piezoelectric nonlinearity of ferroelectric films which is relevant to microsystems' applications, and permittivity and loss in ferroelectric films-important in all applications and essential in high frequency devices. In the context of properties we also discuss nanoscale probing of ferroelectrics. Finally, we comment on two important emerging topics: multiferroic materials and ferroelectric one-dimensional nanostructures. (c) 2006 American Institute of Physics.

/pdf/ferroelectric-thin-films-review-of-materials-properties-and-rc7umdkxk5.pdf

Ferroelectric thin films: Review of materials, properties, and applications

The scaling of complementary metal oxide semiconductor transistors has led to the silicon dioxide layer, used as a gate dielectric, being so thin (14?nm) that its leakage current is too large It is necessary to replace the SiO2 with a physically thicker layer of oxides of higher dielectric constant (?) or 'high K' gate oxides such as hafnium oxide and hafnium silicate These oxides had not been extensively studied like SiO2, and they were found to have inferior properties compared with SiO2, such as a tendency to crystallize and a high density of electronic defects Intensive research was needed to develop these oxides as high quality electronic materials This review covers both scientific and technological issues?the choice of oxides, their deposition, their structural and metallurgical behaviour, atomic diffusion, interface structure and reactions, their electronic structure, bonding, band offsets, electronic defects, charge trapping and conduction mechanisms, mobility degradation and flat band voltage shifts The oxygen vacancy is the dominant electron trap It is turning out that the oxides must be implemented in conjunction with metal gate electrodes, the development of which is further behind Issues about work function control in metal gate electrodes are discussed

https://iopscience.iop.org/article/10.1088/0034-4885/69/2/R02/pdf

High dielectric constant gate oxides for metal oxide Si transistors

Historical Perspective (H. Hughes). Electron--Hole Generation, Transport, and Trapping in SiO2 (F. McLean, et al.). Radiation--Induced Interface Traps (P. Winokur). Radiation Effects on MOS Devices and Circuits (P. Dressendorfer). Radiation--Hardening Technology (P. Dressendorfer). Process--Induced Radiation Effects (T. Ma). Source Considerations and Testing Techniques (K. Kerris). Transient--Ionization and Single--Event Phenomena (S. Kerns). Index.

Ionizing radiation effects in MOS devices and circuits

Recently, black phosphorus (BP) has joined the two-dimensional material family as a promising candidate for photonic applications due to its moderate bandgap, high carrier mobility, and compatibility with a diverse range of substrates. Photodetectors are probably the most explored BP photonic devices, however, their unique potential compared with other layered materials in the mid-infrared wavelength range has not been revealed. Here, we demonstrate BP mid-infrared detectors at 3.39 μm with high internal gain, resulting in an external responsivity of 82 A/W. Noise measurements show that such BP photodetectors are capable of sensing mid-infrared light in the picowatt range. Moreover, the high photoresponse remains effective at kilohertz modulation frequencies, because of the fast carrier dynamics arising from BP’s moderate bandgap. The high photoresponse at mid-infrared wavelengths and the large dynamic bandwidth, together with its unique polarization dependent response induced by low crystalline symmetry,...

Black Phosphorus Mid-Infrared Photodetectors with High Gain

In principle, a memory field-effect transistor (FET) based on the metal-ferroelectric-semiconductor gate stack could be the building block of an ideal memory technology that offers random access, high speed, low power, high density and nonvolatility. In practice, however, so far none of the reported ferroelectric memory transistors has achieved a memory retention time of more than a few days, a far cry from the ten-year retention requirement for a nonvolatile memory device. This work will examine two major causes of the short retention (assuming no significant mobile ionic charge motion in the ferroelectric film): 1) depolarization field and 2) finite gate leakage current. A possible solution to the memory retention problem will be suggested, which involves the growth of single-crystal, single domain ferroelectric on Si. The use of the ferroelectric memory transistor as a capacitor-less DRAM cell will also be proposed.

Why is nonvolatile ferroelectric memory field-effect transistor still elusive?

To extend the scaling limit of thermal SiO/sub 2/ in the ultrathin regime when the direct tunneling current becomes significant, members of this author's research team at Yale University, in collaboration with the Jet Process Corporation, embarked on a program to explore the potential of silicon nitride as an alternative gate dielectric. In this paper, high-quality silicon nitride (or oxynitride) films made by a novel jet vapor deposition (JVD) technique are described. The JVD process utilizes a high-speed jet of light carrier gas to transport the depositing species onto the substrate to form the desired films. The film composition has been determined to consist primarily of Si and N, with some amounts of O and H. Metal-nitride-Si (MNS) capacitors based on the JVD nitride films deposited directly on Si exhibit relatively low densities of interface traps, fixed charge, and bulk traps. The interface traps at the nitride/Si interface exhibit different properties from those at the SiO/sub 2//Si interface in several aspects. In contrast to the conventional CVD silicon nitride, the high-field I-V characteristics of the JVD silicon nitride fit the Fowler-Nordheim (F-N) tunneling theory over four to five orders of magnitude in current, but do not fit at all the Frenkel-Poole (F-P) transport theory. This is consistent with the much lower concentration of electronic traps in the JVD silicon nitride. Results from the carrier separation experiment indicate that electron current dominates the gate current with very little hole contribution. Both theoretical calculation and experimental data indicate that the gate leakage current in JVD silicon nitride is significantly lower than that in silicon dioxide of the same equivalent oxide thickness. The breakdown characteristics of the JVD nitride are also respectable. Compared to their MOSFET counterparts, MNS transistors exhibit reduced low-field transconductance but enhanced high-field transconductance, perhaps due to the presence of border traps. As expected, the JVD silicon nitride films exhibit very strong resistance to boron penetration and oxidation at high temperatures. These properties, coupled with its room-temperature deposition process, make JVD silicon nitride an attractive candidate to succeed thermal SiO/sub 2/ as an advanced gate dielectric in future generations of ULSI devices.

Making silicon nitride film a viable gate dielectric

Based on the experimental results of the temperature dependence of gate leakage current and Fowler-Nordheim tunneling characteristics at 77 K, we have extracted the energy band diagrams and current transport mechanisms for metal/HfO/sub 2//Si structures. In particular, we have obtained the following quantities that will be useful for modeling and simulation: i) HfO/sub 2//Si conduction band offset (or barrier height): 1.13 /spl plusmn/ 0.13 eV; ii) Pt/HfO/sub 2/ barrier height: /spl sim/ 2.48 eV; iii) Al/HfO/sub 2/ barrier height: /spl sim/ 1.28 eV; iv) electron effective mass in HfO/sub 2/: 0.1 m/sub o/, where m/sub o/ is the free electron mass and v) a trap level at 1.5 /spl plusmn/ 0.1 eV below the HfO/sub 2/ conduction band which contributes to Frenkel-Poole conduction.

Tso-Ping Ma

Papers

Ionizing radiation effects in MOS devices and circuits

Black Phosphorus Mid-Infrared Photodetectors with High Gain

Why is nonvolatile ferroelectric memory field-effect transistor still elusive?

Making silicon nitride film a viable gate dielectric

Current transport in metal/hafnium oxide/silicon structure