Three-dimensional simulation of surface topography evolution in the Bosch process by a level set method

Abstract

There have been a number of researches focusing on the simulation of silicon anisotropic wet etching (Kakinaga et al. 2004;Zhou et al. 2007Zhou et al. , 2009). All the simulation results have contributed to improving and optimizing the practical process. However, the ICP process itself has a vast number of process variables as pressure, gas flow rates, and input power that influence the process result (Läermer and Schilp 1994). Modeling of the ICP process is much more difficult than that of silicon anisotropic wet etching. The Bosch process consists of multiple cycles of alternating etching and deposition steps, advancing the trenches formed in small increments until the expected aspect ratio is reached. Each phase lasts several seconds. An attempt has been made to model the Bosch process (Zhang et al. 2005;Chen et al. 2013;Zhou et al. 2004; Radjenovic and Radmilovic-Radjenovic 2012; Ertl and Selberherr 2010). A two-dimensional (2-D) simulator by using a string-cell hybrid method for tracking surface evolution with a particle transport model was developed (Zhou et al. 2004), which is suitable for simulations in geometries with translational symmetry in one direction. 3-D simulations of the Bosch process have been reported recently (Radjenovic and Radmilovic-Radjenovic 2012; Ertl and Selberherr 2010). A simplified 3-D model has been developed that uses the etching rates of silicon and polymer as input parameters (Radjenovic and Radmilovic-Radjenovic 2012), which significantly reduces computational time while it is incapable of simulating several phenomena such as the lag effect (Gottscho et al. 1992). A Monte Carlo method was used to calculate local particle fluxes and etching and deposition rates (Ertl and Selberherr 2010), which incorporates higher order re-emissions of particles, but demands long computational time and memory consumption. Based on the particle transport model (Zhou et al. 2004) and the level set method (Osher and Sethian 1988; Sethian and Adalsteinsson 1997), Abstract A deep reactive ion etching (DRIE) process (Bosch process) is used extensively in the fabrication of microelectromechanical systems (MEMS). Modeling and simulation studies have helped improve our understanding and process design. The Bosch process consists of multiple cycles of alternating etching and deposition steps. Based on a narrow band level set method, by integrating etching simulation and deposition simulation modules, a simulation system is proposed for three-dimensional (3-D) simulation of the Bosch process with arbitrarily complex mask shapes. To verify the simulation system, a series of simulations and experiments have been performed. The simulation results are in good agreement with the experiments. The method may be used to optimize the practical Bosch process and to design and control the profile of high-aspect ratio microstructures.

Three-Dimensional Simulation of DRIE Process Based on the Narrow Band Level Set and Monte Carlo Method

“…However, the extension to 3-D is difficult. Later Li et al presented a simplified geometric model which used visible angles to calculate the flux [ 6 ]. This simulator is fast, but not so accurate.…”