AVS 53rd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuM

Paper PS2-TuM11
3-Dimensional Feature Scale Profile Simulation of Surface Roughness in Physical Sputtering Process

Tuesday, November 14, 2006, 11:20 am, Room 2011

Session: Plasma Surface Interactions I: Joint AVS-AIChE Session
Presenter: H. Kawai, Massachusetts Institute of Technology
Authors: H. Kawai, Massachusetts Institute of Technology
W. Guo, Massachusetts Institute of Technology
H.H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
One of the most important issues in the microfabrication process today is the line edge roughness (LER) on the sidewalls of gate electrodes in metal oxide semiconductor transistors. LER becomes more important as the feature size decreases because the variation in width becomes comparable to the minimum feature dimension. Sidewall roughening is also important in back-end processing, such as contact holes formation. A fundamental understanding of surface roughness and LER formation is necessary to optimize the IC manufacturing process. To promote this understanding, we have developed a 3-dimensional feature scale profile simulator to model and simulate the surface and sidewall roughening during the etching process of polysilicon and silicon dioxide in chlorine, hydrogen bromide and argon plasmas. A dynamic Monte Carlo model is used to simulate the etching process, where the simulation domain is discretized into an array of cubic cells with a unit cell length of 2.5 nm. The local surface conformation is determined by fitting the local region of the surface cells with a polynomial, which is used to compute the surface normal, scattering angle, and flux on the 3-D surface. Our simulator has been utilized to examine the physical sputtering of a smooth polysilicon surface with argon ions at different off-normal ion incidence angles. Our results show that the root-mean square (RMS) roughness increases with the off-normal incident angle. In addition, at a normal ion incidence angle, the RMS roughness remained constant as the material was etched, but at grazing ion incidence angles, RMS roughness increased with the amount of materials etched. At high enough off-normal ion incidence angles, such as 75 degrees, the striations formed are aligned with the ion beam direction due to ion channeling. These results capture many of the qualitative trends observed in experimental measurements.