Modeling and experimentation in the chemical vapor deposition of silicon in a single wafer rapid thermal system

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7020457

Toprac, A J

The chemical vapor deposition of polysilicon from thermally activated silane in a cold wall, single wafer rapid thermal system was studied by both experimentation and mathematical modeling. Experimental deposition rates were obtained at a variety of conditions, including very high temperatures. While there is no practical benefit from polysilicon films produced at such high temperatures, the deposition data at these conditions produced insight into the nature of the silane surface reactions. As temperature increased, the apparent activation energy of polysilicon deposition decreased, as has been observed by other investigators in measurements of the silane reactive sticking coefficient. In addition to this previously reported effect, at very high temperatures a decrease in deposition rate with temperature increase was observed. This new finding, coupled with an experimental observation of polysilicon film decomposition at high temperature in inert ambient, allowed a fundamental insight of polysilicon deposition as the net result of competing forward and reverse silane surface reaction rates. Based on this insight, classic chemical engineering methods of characterizing catalytic surface reactions were used to produce an empirical fit which describes very well the complex behavior seen in the deposition data. A model of mass transfer in polysilicon deposition was developed using the new silane surface reaction rate expression. This model gave excellent predictions of polysilicon deposition data both in absolute rates and deposition uniformity across the wafer. The model was formulated with an absence of gas phase reactions, which were definitively shown to be negligible in contributing to the overall deposition rate by a separate model of the gas phase chemistry. Finally, modeling of the flow field in the reactor chamber furnished insight into principles of good single wafer reactor chamber design.

• Research Organization: Texas Univ., Austin, TX (United States)
• OSTI ID: 7020457
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360601* -- Other Materials-- Preparation & Manufacture
CHEMICAL COATING
CHEMICAL VAPOR DEPOSITION
DEPOSITION
ELEMENTS
HYDRIDES
HYDROGEN COMPOUNDS
MATHEMATICAL MODELS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
SEMIMETALS
SILANES
SILICON
SILICON COMPOUNDS
SURFACE COATING
THERMAL ANALYSIS