Metal Capping Layer Research Articles

Theory of evanescent mode atomic mirrors with a metallic layer

Dielectric atomic mirrors are considered in which the repulsive force field owes its existence to an evanescent mode in the presence of a metallic capping layer. The theory of such an atomic mirror is constructed, assuming a finite thickness of the metallic layer with a finite plasma frequency and adopting the field-dipole orientation picture. The Rabi frequency together with the reflectivity for the light incident from within the substrate are evaluated, and their variations with the type of metal and layer thickness analyzed as useful indicators of the effectiveness of the system as an atomic mirror. A number of interesting features are pointed out, including a desirable enhancement. Solutions of the equation of motion for a given atom, subject to given initial conditions, lead to trajectories exhibiting reflection. The leading force fields controlling the dynamics include the average dipole image force plus the average light-induced forces due to the evanescent field. The parameters used to compute the trajectories are similar to those in recent experiments in which Rb atoms incident on a silver film deposited on a glass substrate have been shown to experience enhanced mirror action. The factors controlling the enhancement in general are pointed out and discussed.

Electron injection and transport in 8-hydroxyquinoline aluminum

We have measured the current–voltage characteristics and device efficiency of organic light emitting diodes (OLEDs) based on 8-hydroxyquinoline aluminum (Alq 3) in combination with several cathode layer setups. The electron injection properties of cathode metals evaporated under high vacuum (HV) and ultra-high vacuum (UHV) conditions are compared. Further, cathodes incorporating a thin layer of lithium fluoride, which is covered with a metal capping layer, are investigated. It will be shown that aluminum is an outstanding capping metal and significantly improves both electron injection and device efficiency. Quasi-static and transient current–voltage measurements on single-layer devices will be presented. It will be demonstrated that cathodes, comprising 0.2 nm LiF and aluminum, are able to sustain space charge limited currents in Alq 3. Additionally, the efficiency and lifetime data of multi-layer devices using this cathode layer setup are discussed.

Magnetoresistance in Magnetic Tunnel Junctions with Nonmagnetic Metallic Spacers and Cap Layers

In a free-electron approximation, transport properties of magnetic tunnel junctions with nonmagnetic metallic spacers and cap layers were studied. The magnetoresistance is oscillatory functions of the thicknesses of nonmagnetic metallic spacers and ferromagnets, their period is determined by the Fermi surface properties of the metals, and magnetoresistances (up to about 103%) much greater than those predicted by the Julliere's model are obtained. The results indicate that this structure has potential in designing spin-polarized tunneling devices.

Analysis of Copper and Low-K Dielectric Interconnect System for 0.18-μm Technology

ABSTRACTAs the interconnect RC delay plays an increasingly dominant role in the performance of deep submicron ULSI devices, Cu and low-k dielectric materials are deemed necessary to replace the traditional Al and SiO2 system to lower both the resistance and capacitance of metallization. This paper presents a systematic simulation method to assess the impact of Cu and low-k dielectric to the system speed and cross-talk noise for 0.18-μm design rules (0.6 μm pitch), and determine the practical process windows for metal line aspect ratio and the structural configuration of dielectrics. It was found that the high performance requirements for 0.18-μm devices (600 MHz and cross-talk <0.3 on a 2×2 cm2 chip) cannot be met by simply replacing Al with Cu or SiO2 with low-k dielectric (k=3), without any change in the interconnect architecture. By reverse scaling the metal pitch to 2× at upper levels, on the other hand, one can easily find a manufacturable process window, even with the Al and SiO2 system. Case studies on R and C of various structural configurations and boundary conditions have been performed, including Cu barrier layer thickness, metal gap fill and capping layer thickness of low-k dielectrics, as well as the influence of the lower and upper metal plates. The significance of the results on the strategy of implementing Cu/low-k interconnects versus extending Al/SiO2 will be discussed.

Enhancement of MR ratios with Ag capping layer in (100) oriented Ni-Fe/Cu/Co trilayers

This paper reports enhancement of magnetoresistance in spin-valve trilayers by improving specular reflectivity of conduction electrons at the film surface of the metal capping layer. The samples were epitaxially grown on MgO(100) by ultrahigh vacuum deposition. The MR ratio of the MgO/Pt(10 nm)/Cu(5 nm)/Ni-Fe(5 nm)/Cu(2.8 nm)/Co(5 nm)/Cu(1.2 nm) film increased from 3.9% to 5.4% by the addition of a 3 nm-thick-Ag capping layer. The enhancement of MR ratio may be attributed to the increase of specular reflection of conduction electrons at the Ag surface. Co layer thickness dependence of the MR ratio in the spin-valves also supports this interpretation.

Study of Arsenic Evolution During RTA of Au-Based Ohmic Contacts to GaAs

ABSTRACTWe report on the formation of AuZn/p-GaAs ohmic contacts by short time annealing either in open or closed configuration with a dielectric or metallic capping layer. Quantitative determination of the amount of arsenic losses was of primary concern. This was studied using the Cr-collector method, applying three types of collectors all of them using 100 nm thick Cr film for seizing evaporative As losses. In the first type, the Cr film was deposited onto oxidized Si substrate. In the second type - quartz substrate was used for the deposition of chromium film while the third collector used natural mica as a substrate for the Cr film. The obtained results show that the loss of arsenic is reduced below 2×1014 atom/cm2 using thin 20 nm Au/10 nm Zn/60 nm Au metallization annealed with a capping layer at 440°C for 15 sec. Electrical measurements indicate that under these conditions good ohmic contacts are obtained.