Thermochemical prediction of runaway energetic reactions involving organometallic (Al, In) and silane precursors in deposition tools

Abstract

In the manufacturing of integrated circuits (ICs), many deposition systems use solid, liquid, and gaseous precursors that can form potentially hazardous by-products in the exhaust lines. To assess the likelihood of an energetic reaction taking place, Gibbs free energy minimization was used to examine the reactions between chemical precursors, such as trimethylaluminum, trimethylindium, silane, and silane derivatives with H2O, O3, and Cl2. For the trimethyl-metal precursors, CH4 is a major by-product in both the O3 and H2O environments, and CH4, HCl, and CCl4 are possible products in the Cl2 environment. For silanes, a small H2O to silane ratio leads predominantly to the formation of H2 and siloxane while a large H2O to silane ratio leads primarily to the formation of H2 and more H2O. In addition to depositing reaction by-products, unreacted precursors may also deposit on the interior surfaces of the exhaust system, narrowing the cross-sectional area of the pipes. These narrowed regions can become temperature, pressure, and concentration hot spots where energetic reactions are more likely to occur. Results from this analysis may be helpful in designing a safer downstream exhaust system that minimizes the risk of energetic events.