A novel approach to the characterization of dynamic interactions of gases with solid surfaces is developed. A model is developed to represent the simultaneous adsorption and desorption processes in these systems. The model can simulate properties of nonequilibrium adsorption and desorption processes as well as the equilibrium state (isotherms and isobars). It also provides information on the distribution of loading of tightly bound molecules as the first layer on the surface as well as loosely bound physisorbed molecules as the upper layers during a transient process and at the equilibrium state. The model is validated and applied to the adsorption of moisture on oxides (ZrO2 and HfO2). Practical application of this work is shown by optimizing the purge recipes for removal of moisture from ZrO2 film. Optimization helps in lowering gas and energy consumption as well as reducing the purge times.

The interactions of moisture with spin-on porous methylsilsesquioxane ͑p-MSQ͒ low-k dielectric films are investigated by on-line and real-time measurement of the rates of moisture uptake and removal. A process model is developed that provides information on the dynamics of moisture adsorption and desorption processes. The process model can be used to find optimum purge temperature and gas purity condition for cleaning and drying of low-k films. The cured p-MSQ films are compared with the partially etched and N 2 H 2 ashed films. The results show that these two films have similar moisture solubilities; however, the moisture diffusivity in the patterned film is considerably higher. Transmission electron microscope results show that the etching and ashing processes not only decrease the overall film thickness but also increase the film porosity. The process model also provides information on moisture distribution within the film; this information is important in characterizing residual moisture and interfacial adhesion. The results for a wide range of diffusivity show that thin cap layers with low moisture solubility effectively block moisture penetration into the p-MSQ film without slowing down the outgassing and moisture removal during the purge.

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