KEYWORDS: Chemical species, Etching, Silicon, Anisotropic etching, Photomasks, Simulation of CCA and DLA aggregates, Semiconducting wafers, Crystals, Tin, Device simulation
A continuous cellular automaton (CCA) is presented for the simulation of anisotropic wet chemical etching in the fabrication of microstructures. Based on the step-flow model, the surface atoms are divided into categories according to the atom configurations on different crystal planes. An analytical solution for the dependence of the etch rate on orientation is derived, and the CCA approach makes a direct conversion of experimental macroscopic rates into calibrated microscopic parameters for realistic and reliable simulations. The presented model has been extended to a simulation system based on a CCA method. Linear search and variable time stepping are used to simulate a silicon wafer in various etching condition and mask shapes. The simulation results agree well with the experiments. This improved CCA makes possible for the realization of accurate simulations of anisotropic etching in engineering applications.
The silicon anisotropic wet chemical etching technique is widely employed for fabricating various microelectromechanical system structures for advantages such as simple etching equipment and its capability to fabricate special microstructures. In this paper, we consider one of the most frequently used equations of atomistic model of simulation of anisotropic wet etching. Then using a trial and error method we solve the mentioned equations and derive a new equation for calculating the microscopic etch rates of some surface atoms for a new range of concentrations and temperatures. Furthermore, a new equation is presented for the calculation of the microscopic activation energies for some typical surface atoms and a new comparison of activation energies between some atoms is made dividing atoms into three categories. This classification makes it easier to study microscopic etch rates and activation energies of other atoms. The results demonstrate a good agreement with the experimental results.
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