Fault tree analysis on kinematic accuracy of wafer stage using BDD and DFTA technique
Based on the structure and operation mechanism of the dual-stage lithographic system, fault tree analysis for the key subsystem, wafer stage, is performed. Since the system is very complexity, the BDD (binary decision diagram) and DFTA (dynamic fault tree analysis) technique are introduced to make up the disadvantages of the traditional static FTA (fault tree analysis) method. Event “The kinematic accuracy of wafer stage can't meet the goal” is installed as the top event of the fault tree. Central factors affecting the kinematic accuracy of the wafer stage is identified through the study.
BN formation from bombardment of boron with N2
Abstract Boron nitride formation from bombardment of boron with 0.5–4 keV N 2 + ions is studied by in situ XPS and AES measurements. A dynamic process of nitrogen implantation and surface sputtering leads to the formation of a BN layer whose thickness is comparable to the range of the nitrogen ions in the boron. The maximal nitrogen entrapment is determined by the stoichiometry of BN; excess nitrogen is released by sputtering and possibly diffusion. No diffusion of nitrogen to the bulk nor expansion of the BN layer is detected at room temperature for prolonged bombardment. The results are in accord with a simple collisional altered layer model that is presented.
An altered layer model for ion assisted deposition under net sputtering erosion conditions
Abstract A simplified three layer model is developed for prediction of the time dependent and steady state concentration ratios of impurity atomic species incorporated into substrates by either direct ion implantation or by atomic deposition and congruent ion irradiation induced intermixing under conditions of net sputtering erosion. The three layers considered are (1) a sputtering layer, (2) a radiation altered layer and (3) the bulk. The model predictions give guidance as to parameter selection for experimental study of this area of increasing importance in sputter depth profiling and ion assisted reactive gas etching.