On the Mechanism of the Step Coverage of Blanket Tungsten Chemical Vapor Deposition

In this study, computer modeling of the contact fill process with chemical vapor deposition, (CVD) of tungsten is usedto show the importance of several details on the quality of the fill process. The effect of surface curvature on the stepcoverage of CVD-W has been investigated. It is shown that for contacts with an aspect ratio smaller than one, the effect ofsurface curvature is substantial and actually improves step coverage. Therefore, surface curvature for features with aspectratios smaller than one, should be accounted for in computer simulations of the fill process. For contacts with aspect ratioslarger than one the effect of surface curvature is negligible. It is shown that the size of the void (which will be formed incases of step coverage less than 100%) is a better way to describe the quality of the deposition and the repercussions of thevoid on subsequent process steps such as tungsten etch back. In addition, the size of the void depends for a given set ofdeposition conditions solely on the depth of the contact rather than the contact diameter (for aspect ratios larger than 1.0)

Green Technology in Developing Countries: Creating Accessibility Through a Global Exchange Forum

As they pursue economic development, developing countries possess high demand for processes and technologies that have climate-friendly methods or alternatives. However, these nations currently face barriers to entry because of trade policies and intellectual property regulations that render procurement of these technologies cost-prohibitive. In light of the recent breakdown in negotiations at the United Nations climate conference in Bali to remove tariffs on green technology, a new approach to green technology diffusion should be considered in order to balance the demand among developing nations for fluid technology transfers with the profit-driven needs and intellectual property considerations of technology holders. A potential solution to overcome the high fixed costs of technology diffusion could involve the creation of a global exchange forum in which transnational green technology holders, green venture capitalists, and developing country entrepreneurs could broker for efficient allocation of investment, resources, and technologies

In Situ Growth Rate Measurement of Selective LPCVD of Tungsten

The reflectance measurement during the selective deposition of W on Si covered with an insulator grating is proven tobe a convenient method to monitor the W deposition. The reflectance change during deposition allows the in situ measurementof the deposition rate. The influence of surface roughening due to either the W growth or an etching pretreatmentof the wafer is modeled, as well as the effect of selectivity loss and lateral overgrowth

A test chip for automatic reliability measurements of interconnect vias

A test circuit for electromigration reliability measurements was designed and tested. The device under test (DUT) is a via-hole chain. The test circuit permits simultaneous measurements of a number of DUTs, and a fatal error of one DUT does not influence the measurement results of the other DUTs. Measurements require only a few measurement instruments. Comparing the measurement results of a single DUT io the measurement results of the test circuit shows that the test circuit may be used for reliability measurements

Shell Model Description of Isotope Shifts in Calcium

Isotope shifts in the nuclear charge radius of even and odd calcium isotopes are calculated within the nuclear shell model. The model space includes all configurations of nucleons in the $2s, 1d_{3/2}, 1f_{7/2}, {\rm and} ~2p_{3/2}$ orbits. The shell model describes well the energies of the intruder states in Sc and Ca, as well as the energies of the low-lying $2^+$ and $3^-$ states in the even Ca isotopes. The characteristic features of the isotope shifts, the parabolic dependence on $A$ and the prominent odd-even staggering, are well reproduced by the model. These features are related to the partial breakdown of the $Z = 20$ shell closure caused by promotion, due to the neutron-proton interaction, of the $ds$ shell protons into the $fp$ shell.Comment: 4 pages, 4 figures include