Study on TSV isolation liners for a Via Last approach with the use in 3D-WLP for MEMS

This paper discusses approaches for the isolation of deep high aspect ratio through silicon vias (TSV) with respect to a Via Last approach for micro-electro-mechanical systems (MEMS). Selected TSV samples have depths in the range of 170…270 µm and a diameter of 50 µm. The investigations comprise the deposition of different layer stacks by means of subatmospheric and plasma enhanced chemical vapour deposition (PECVD) of tetraethyl orthosilicate; Si(OC₂H₅)₄ (TEOS). Moreover, an etch-back approach and the selective deposition on SiN were also included in the investigations. With respect to the Via Last approach, the contact opening at the TSV bottom by means of a specific spacer-etching method have been addressed within this paper. Step coverage values of up to 74 % were achieved for the best of those approaches. As an alternative to the SiO₂-isolation liners a polymer coating based on the CVD of Parylene F was investigated, which yields even higher step coverage in the range of 80 % at the lower TSV sidewall for a surface film thickness of about 1000 nm. Leakage current measurements were performed and values below 0.1 nA/cm² at 10 kV/cm were determined for the Parylene F films which represents a promising result for the aspired application to Via Last MEMS-TSV.     

Towards inverse modeling of turbidity currents: The inverse lock-exchange problem

A new approach is introduced for turbidite modeling, leveraging the potential of computational fluid dynamics methods to simulate the flow processes that led to turbidite formation. The practical use of numerical flow simulation for the purpose of turbidite modeling so far is hindered by the need to specify parameters and initial flow conditions that are a priori unknown. The present study proposes a method to determine optimal simulation parameters via an automated optimization process. An iterative procedure matches deposit predictions from successive flow simulations against available localized reference data, as in practice may be obtained from well logs, and aims at convergence towards the best-fit scenario. The final result is a prediction of the entire deposit thickness and local grain size distribution. The optimization strategy is based on a derivative-free, surrogate-based technique. Direct numerical simulations are performed to compute the flow dynamics. A proof of concept is successfully conducted for the simple test case of a two-dimensional lock-exchange turbidity current. The optimization approach is demonstrated to accurately retrieve the initial conditions used in a reference calculation.     

Anatomical structure modeling from medical images

Some clinical applications, such as surgical planning, require volumetric models of anatomical structures represented as a set of tetrahedra. A practical method of constructing anatomical models from medical images is presented. The method starts with a set of contours segmented from the medical images by a clinician and produces a model that has high fidelity with the contours. Unlike most modeling methods, the contours are not restricted to lie on parallel planes. The main steps are a 3D Delaunay tetrahedralization, culling of non-object tetrahedra, and refinement of the tetrahedral mesh. The result is a high-quality set of tetrahedra whose surface points are guaranteed to match the original contours. The key is to use the distance map and bit volume structures that were created along with the contours. The method is demonstrated on computed tomography, MRI and 3D ultrasound data. Models of 170,000 tetrahedra are constructed on a standard workstation in approximately 10s. A comparison with related methods is also provided.     

The semigroups of linearly realizable finite automata. I

Summary First the problem is solved how one can decide whether an arbitrary finite semigroup H is linearly A-realizable, i.e., whether there exists a linearly realizable finite automaton having a semigroup isomorphic to H. This leads to a question about the existence of certain generating subsets of H. The determination of these subsets is rather complicated in case H-HH=Ø and very simple in case H-HH#Ø. But in the first case we are able to clear up completely the structure of the semigroups which are linearly A-realizable: These are exactly the finite right groups which have maximal subgroups of the type described by Ecker in [4]. In the second case we get only necessary structure conditions. Among other things we shall see: If a semigroup H is linearly A-realizable one can define a congruence relation on it having the property, that H is isomorphic to a semigroup of a strongly connected and linearly realizable automaton iff the so-called index of H equals the index of H/. Developing these results about semigroups we obtain at the same time many structure theorems about linearly realizable automata.     

On parsing two-level grammars

Summary Making use of the fact that two-level grammars (TLGs) may be thought of as finite specification of context-free grammars (CFGs) with infinite sets of productions, known techniques for parsing CFGs are applied to TLGs by first specifying a canonical CFG G — called skeleton grammar — obtained from the cross-reference of the TLG G. Under very natural restrictions it can be shown that for these grammar pairs (G, G) there exists a 1 — 1 correspondence between leftmost derivations in G and leftmost derivations in G. With these results a straightforward parsing algorithm for restricted TLGs is given.     

Self-consistent-phonon,random phase,and transfer-integral methods for a linear chain with anharmonic potential

The transfer-integral (TI) method, developed especially for hard-core potentials, is tested with anx ² + ₃x³ + ₄x⁴ potential by a comparison with other methods: In the harmonic approximation the improvement of the TI method over the self-consistent phonon (SCP) method is about as great as that of the SCP method over the random phase approximation (RPA).     

Correlations and effective potential in the ground state of a one-dimensional model for solid helium and deuterium

The ground-state energyE can be calculated exactly by the transfer-integral method if the total wave function is assumed to be a product of single-particle functions and nearest-neighbor correlation functionsf. The variation ofE with respect tof for fixed leads to a Schrödinger equation for the relative motion of two particles which is coupled to the transfer integral equation by an effective potential V. For the case of a Gaussian the optimalf, the one- and two-particle probability amplitudes, and other quantities are computed by iteration of the Schrödinger equation with the transfer integral equation until self-consistency is achieved. The minimum ofE as a function of the Gaussian width is obtained for different values of the lattice parameter. The shape of V andf is discussed. The self-consistentf describes both short- and long-range correlations.     

Selecting scientific excellence through committee peer review - A citation analysis of publications previously published to approval or rejection of post-doctoral research fellowship applicants

Summary We investigated committee peer review for awarding long-term fellowships to post-doctoral researchers as practiced by the Boehringer Ingelheim Fonds (B.I.F.) - a foundation for the promotion of basic research in biomedicine. Assessing the validity of selection decisions requires a generally accepted criterion for research impact. A widely used approach is to use citation counts as a proxy for the impact of scientific research. Therefore, a citation analysis for articles published previous to the applicants' approval or rejection for a B.I.F. fellowship was conducted. Based on our model estimation (negative binomial regression model), journal articles that had been published by applicants approved for a fellowship award (n = 64) prior to applying for the B.I.F. fellowship award can be expected to have 37% (straight counts of citations) and 49% (complete counts of citations) more citations than articles that had been published by rejected applicants (n = 333). Furthermore, comparison with international scientific reference values revealed (a) that articles published by successful and non-successful applicants are cited considerably more often than the “average” publication and (b) that excellent research performance can be expected more of successful than non-successful applicants. The findings confirm that the foundation is not only achieving its goal of selecting the best junior scientists for fellowship awards, but also successfully attracting highly talented young scientists to apply for B.I.F. fellowships.     

Predicting change for individual psychotherapy clients on the basis of their nearest neighbors.

This study extended client-focused research by using the nearest neighbor (NN) approach, a client-specific sampling and prediction strategy derived from research on alpine avalanches. Psychotherapy clients (N = 203) seen in routine practice settings in the United Kingdom completed a battery of intake measures and then completed symptom intensity ratings before each session. Forecasts of each client's rate of change and session-by-session variability were computed on the basis of that client's NNs (n = 10-50 in different comparisons). Alternative forecasts used linear or log-linear slopes and were compared with an alternative prediction strategy. Results showed that the NN approach was superior to the alternative model in predicting rate of change, though the advantage was less clear for predicting variability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)