Kinetics modeling and 3-dimensional simulation of surface roughness during plasma etching

The control of feature profiles in directional plasma etching processes is crucial as critical dimension, line-edge roughening, and other artifacts affect device performance and process yields. A profile simulator is necessary to predictively model the etching processes as well as roughness transfer and artifact evolution. The development of profile simulators has been inhibited by the limited knowledge of the surface kinetic processes and rate coefficients. A mixing-layer surface kinetic model was developed to account for plasma-surface interactions. The simplified reaction set was carefully chosen to reflect the overall etching characteristics and the rate coefficients were fitted to experimental data. After the model was tested for accuracy using poly-Si etching in Cl2 gas plasma, it was incorporated into the 3-Dimensional (3-D) Monte Carlo profile simulator with a cell-based representation. The good match between the profile simulation and the kinetics modeling results verified the capability of incorporating complex chemical processes into the 3-D simulator. The angular dependence on etching yield was modeled based upon the mixing layer kinetics model. All the rate coefficients fitted previously at normal ion incidence were kept constant without any further optimization. The angular curves were assigned to all ion-initiated reactions based upon their characteristics and the overall etching yield was calculated with a combination of individual etching yields. The variation of etching yield with ion bombardment angle for poly-Si in Cl2 plasma was modeled and showed quantitative agreement with the experimental measurements, indicating the angular curves for all the fundamental reactions are sufficient to account for the etching behavior at off-normal angles at different operating conditions. With the modeling of angular dependence, the kinetics model is complete and can be used to explore the surface roughness in the 3-D profile simulator. The roughening of the SiO2 surface in fluorocarbon plasma was explored using the 3-D Monte Carlo profile simulator.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Guo, Wei, Ph. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Herbert H. Swain.

• 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/1721.1/46600

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/46600