TCAD for MEMS
R. Paganini*, R. Ruehl*, J. Funk and H. Baltes Physical Electronics Laboratory, ETH Zurich, Switzerland +Integrated Systems Laboratory, ETH Zurich, Switzerland *ISE AG, Switzerland Introduction. We present key components of a technology CAD (TCAD) tool for inte¬ grated micro electro mechanical system (iMEMS) simulation. The TCAD capabilities augment the SOLIDIS device simulator [1], Key components are: Meshing interface to process simulation; Application-oriented solid modeler; Algorithms for iMEMS sensor and actuator device simulation using finite and boundary element compuational engines; Interface for mixed-signal system level simulation using SPICE. Meshing. We present an approach to boundary-to-mesh generation based on a Monte
Enhanced multipole acceleration technique for the solution of large Poisson computations
The solution of Poisson's simulations in large, geometrically complex domains with various boundary conditions are of interest in many physical computations. In this paper, we focus on electrostatic analysis. This is important for microactuator (MEMS) and interconnect modeling and also in the simulation of the electrostatic properties in VLSI chips, such as CCD sensors and DRAM cells. The computation of the static electric potential and field distribution involves the solution of the Poisson's equation, or in case of charge free space, Laplace's equation. The boundary element method has proven to be well suited for the solution of these partial differential equations in both 2- and 3-D. The required computational resources can be significantly reduced with the use of multipole acceleration techniques. An enhanced multipole (MP) acceleration technique is presented, allowing for reduced computational time and memory requirements in all stages of the computational process: the assembly of the global system of equations, the solution of the system and the evaluation of the potential and flux at specified internal positions. Contrary to previous applications of MP acceleration to Poisson's equation, the method allows the treatment of a wider class of boundary conditions, including Neumann and floating. The method is applicable both in two and three dimensions using a constant or high order boundary elements.
Intensification of Bubble Disintegration and Dispersion by Mechanical Stirring in Gas Injection Refining
Water model experiments were performed for establishing highly efficient gas injection refining processes. Mechanical stirring was applied to disintegrate the injected bubbles and to disperse them widely in the bath. The bubble disintegration and dispersion were investigated by changing rotation mode (direction of rotation), rotation speed, blade size of the impeller and gas flow rate. Forward rotation of the impeller induced a stable tangential flow and could not disperse bubbles in the bath due to formation of a vortex around the impeller shaft. The tangential flow could be suppressed by forward–interrupt rotation, which could reduce the vortex formation to some degree. However, forward–interrupt rotation could not disperse the bubbles widely in the bath. Forward–reverse rotation could prevent the vortex formation completely and create a strong shear stress field, which intensified the bubble disintegration and dispersion in the bath. Higher impeller rotation speed and larger blade length in forward–reverse rotation could enhance the bubble disintegration and make the dispersed bubbles smaller. The bubble dispersion zone became wider with larger blade length. The bubble size tended to be larger at higher gas flow rates. However, its dependence on the gas flow rate became smaller at higher impeller rotation speed.