Sawin Squad People

Department of Chemical Engineering
Room 66-217
Massachusetts Institute of Technology
77 Massachusetts Avenue
Cambridge, MA 02139-4307 USA

Telephone (617) 253-6586

Bo Bai

Graduate Research Assistant

(Co-Advisor: Prof. Miklos Porkolab)

B.S., Physics, University of Science & Technology, Hefei, PRC, 1998
M.S., Physics, University of Science & Technology, Hefei, PRC, 2001

Research Interests

Modeling of Surface Kinetics and Feature Profiles of Directional Plasma Etching 

Directional plasma etching is widely used in the fabrication of microelectronics. In this technique, the control of etching feature profiles (measured by profile aspects such as line-edge roughening among others) remains crucial for good fabrication process yields and device performance. And to predict feature profiles well, any simulator further requires a thorough understanding of the physical surface kinetics. Our work aims to create a surface kinetics model that could quantitatively predict ion enhanced etching, ion enhanced deposition, and the dependence of etching/deposition yield on the ion energy, ion incident angle, and neutral-to-ion flux ratio. This model could be used in various scenarios such as polysilicon etched by halogen plasmas, polysilicon etched by fluorocarbon plasmas, silicon oxide etched by fluorocarbon plasmas, and low-k dielectrics etched by fluorocarbon plasmas. Furthermore, incorporating the surface kinetics model into the feature profile simulator will enable better understanding and control of the directional plasma etching.

Transformer Coupled Toroidal Plasmas for Remote Plasma Processing

The transformer coupled toroidal plasma (TCTP) source is an emerging tool for such semiconductor processing as remote chamber cleaning and remote photo-resist stripping. Presently the feed gases usually employed to produce fluorine atoms for remote chemical vapor deposition chamber cleaning with a TCTP source, such as nitrogen trifluoride, are very expensive and toxic. One goal of my research is to find alternative feed gas mixtures which are nontoxic and less expensive, but have comparable etching rate and no other negative side effects. The other goal of my research is to gain a scientific understanding of TCTP by setting up a hydrodynamic plasma model coupled with complicated plasma chemistry at high neutral gas temperature. The model is going to be verified by multiple diagnostics of plasma parameters like electron temperature, electron density, neutral temperature and concentration of plasma species. The model may then help predict optimal operation conditions for different feed gases.

Personal Interest

I was originally attracted to plasma physics just because of the glorious color that plasmas give off. Later, when I learned of the possible endless energy that fusion may provide, I became very enthused with both magnetically confined plasmas used in fusion research and inertially confined fusion. More recently my research interests have shifted to those low temperature plasmas that are used for integrated circuit processing. I find that studying low temperature plasma and its interactions with different materials provides more intriguing physical problems and more challenges for me as well.

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