Toward accurate characterization of nitrogen depth profiles in ultrathin oxynitride films

Good accuracy in depth profile analyses of nitrogen in ultrathin oxynitride films is desirable for process development and routine process monitoring. Low energy SIMS is one of the techniques that has found success in the accurate characterization of thin oxynitride films. This work investigated the artifacts in a typical depth profile analysis of nitrogen with the current SIMS technique and the ways to improve the accuracy by selecting optimal analytical conditions. It was demonstrated that surface roughness developed rapidly in a SiO₂/Si stack when it was bombarded with an O₂⁺ beam at 250 eV and angle of incidence from 70 to 79° . The roughness caused distortion in the measured depth profiles of nitrogen and the major component elements. However, the above roughness and the distortion in the depth profiles can be eliminated by using a 250 eV O₂⁺ beam at an angle of incidence above 80° . Depth profile analyses with a 250 eV 83° O₂⁺ beam exhibited minimal surface roughening and insignificant variation in the secondary ion yield of SiN^? from SiO₂ bulk to the SiO₂/Si interface, facilitating an accurate analysis of nitrogen distribution in a SiO₂/Si stack. In addition, depth profiles of the major component elements such as ¹⁸O^? and ²⁸Si^? delivered clear information on the location of the SiO₂/Si interface. Using the new approach, we compared nitrogen distribution in thin SiNO films with the decoupled‐plasma nitridation (DPN) at various powers. Copyright © 2008 John Wiley & Sons, Ltd.     

Continuation and shooting methods for boundary value problems of Bernstein type

Fixed point continuation methods and shooting methods are combined to produce an effective numerical procedure for solving boundary value problems for nonlinear ordinary differential equations. Typical numerical solution schemes involve an iteration procedure. Continuation methods systematically generate good initial guesses and, when combined with a shooting method and an appropriate update procedure, give systematic means for the numerical solution of nonlinear boundary value problems. This paper concentrates on problems of Bernstein type, which arise naturally in the calculus of variations and in steady-state heat conduction.     

ChemInform Abstract: Hexatellurium Rings in Coordination Polymers and Molecular Clusters: Synthesis and Crystal Structures of [M(Te6)]X3 (M: Rh,Ir; X: Cl,Br, I) and [Ru2(Te6)] (TeBr3)4(TeBr2)2.

Black crystals of [Rh(Te₆)]Br₃ (I), [Rh(Te₆)]I₃ (II), [Ir(Te₆)]Cl₃ (III), [Ir(Te₆)]Br₃ (IV), and [Ir(Te₆)]I₃ (V) are prepared from stoichiometric mixtures of Rh or Ir, Te, and TeX₄ (X: Cl, Br, I; evacuated silica tube, 300—350 °C, 7 d).