AVS 51st International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoA

Paper PS1-MoA2
3-Dimensional Feature Scale Simulation of Polysilicon Sidewall Roughening

Monday, November 15, 2004, 2:20 pm, Room 213A

Session: Plasma Surface Interactions in Etching
Presenter: H. Kawai, MIT
Authors: H. Kawai, MIT
W. Jin, MIT
H.H. Sawin, MIT
Correspondent: Click to Email
The line edge roughening has become an important factor as the features shrink. Although there are 2-dimensional simulators that can simulate the artifacts such as faceting and microtrenching, they can not simulate the surface roughness since it is inherently 3-D in nature. Therefore, a 3-dimensional simulator was developed to study the physics of surface and line edge roughening. 2 ½ -dimensional simulator, that had been developed before, applied Monte Carlo model to model the surface kinetics. Although 3-D simulator also used Monte Carlo model, many changes were made to convert the simulator from 2 ½ -D to 3-D. These include a new algorithm for the computation of surface normals and fluxes on sidewalls. In addition, since 3-D simulator is more computationally intensive, it is necessary to optimize the simulator by minimizing the computation time while maintaining the accurate results. Simulation domain was discretized into cubic cells with the side of 2.5 nm, and when a particle strikes a surface cell, the local surface conformation was determined. The algorithm was based the fitting of the local region of the surface cells with a polynomial. The cell size of 2.5 nm had been used since the cell size corresponds to the ion induced mixing length. Since the grooved striations formed in line edge roughening have minimum radius of curvatures of about 25 nm, the appropriate degree of polynomial and number of cells to be fitted were selected to allow the representation of surface curvatures of 25 nm or less. This fitted surface is then used to compute the surface normal, scattering angle, and flux on the 3-D surface. The surface normal was used to determine the movement of the surface with material etching or deposition by selecting the appropriate cell for cell addition or collapse.