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

Telephone (617) 253-8912
Email: jujin@mit.edu

Ju Jin An

Graduate Research Assistant

Research Interests

Synergistic effect of the mixed gases on the downstream cleaning chamber 

Even with the semiconductor device market rapidly expanding, industry fabricators are feeling the heated competition for market share and are seeking to squeeze advantage from semiconductor production. To gain an edge, all elements of the fabrication process are being re-scrutinized. One such crucial area for examination has become chamber cleaning after the CVD (chemical vapor deposition) of the semiconductor wafer. Conventional practice has been to combine a high inlet flow rate of etchant gas with high plasma power : this approach has been the easiest way to clean the PECVD (plasma enhanced chemical vapor deposition) chamber. The combination of high flow rate and high power however can be exceedingly costly. Our effort seeks to understand better the physical science behind the chamber cleaning so as to indicate a less expensive but still effective regime for this stage of fabrication.

The goal of my project aims to determine the surface kinetics on the nitride and oxide films when these films are etched by a certain combination of gases in the cleaning chamber. Using a toroidal plasma source, a heat exchanger and a cleaning chamber downstream from the plasma source, we are using mainly nitrogen trifluoride gas to test the etching phenomenon and then analyzing the etch with FT-IR (Fourier transform infrared spectrometry), an XPS (X-ray photoelectron spectroscopy), an interferometer and using actinometery and mass spectrometry.

So far we have found several interesting phenomena. Two such discoveries have been the enhancement of etching rate with certain gas mixtures and the dependence of etching rate on inlet fluorine flow rate relatively independent of pressure (see figure). Our current effort seeks to understand these dependencies and model the kinetics of the etch surface within the plasma.