3-dimensional modeling and simulation of surface and sidewall roughening during plasma etching

Line edge roughness (LER) on the sidewalls of gate electrodes in metal oxide semiconductor transistors is one of the most important issues in the manufacturing of modem integrated circuits (IC). The significance of LER increases tremendously as desired features miniaturize because the dimensions of the edge roughness become comparable to those of the features. A fundamental understanding of the origins of the surface roughness and LER formation during plasma etching process is thus necessary to optimize the IC manufacturing process and prevent device failure. To meet this challenge, a 3-D Monte Carlo simulator was developed to model the roughening of a surface as well as follow the macroscopic evolution of its profile during plasma etching. The simulator employs a cellular representation of the surface with Monte Carlo modeling of the mass transport and reaction kinetics. The local geometric properties of surface features were computed by fitting to a polynomial surface, which allowed for a more accurate description of the surface normal and local curvature. This numerical algorithm for simulating etching and deposition was validated by comparing with the theoretical advancement of a surface for the case of isotropic and anisotropic etching. The simulator was used to explore surface roughening during the physical sputtering of a blanket silicon surface by argon ion bombardment. The results showed that there is a significant change in its morphology with different off-normal angles of incidence. When the surface is etched at normal incidence, the surface becomes roughened with no preferred orientation. When etched with an off-normal ion incidence below 500, the surface develops ripples that are oriented perpendicular to the ion beam direction. For off-normal angles between 500 and 600, the surface remains smooth independent of the etch time.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Kawai, Hiroyo

Advisor dc:contributor.advisor

• Herbert H. Sawin.

• Chemical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/43201

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/43201