MONTE-CARLO LOW-PRESSURE DEPOSITION PROFILE SIMULATIONS

The models and algorithms used for simulation of chemical vapor deposition (CVD) profiles in Stanford profile emulator for etching and deposition in integrated circuit engineering are described. In the CVD simulation direct deposition, re-emission, and surface diffusion are considered as the mechanisms for near surface mass transport. The re-emission process is characterized by a single surface reaction coefficient (or sticking coefficient) which condenses the complex physico-chemical mechanisms (physisorption, chemisorption, desorption) in a single probability that defines the final attachment of a reactive to a surface. For desorption process, different desorption models can be selected (cosine re-emission, specular reflection). Surface diffusion is modeled with a gaussian distribution function characterized by the diffusion length. A Monte Carlo approach is used to determine the deposition rates in arbitrary topologies and a string algorithm is used for the evolution of the surface. Iteration between them allows taking into account self-shadowing effects. Comparisons of experimental versus simulation results for SiO2 trench filling, that can be characterized by direct deposition and re-emission with a pure cosine desorption law and no surface diffusion are included.