Characterization and modeling of the metal diffusion from deep ultravioletphotoresist and silicon-based substrate

The radioactive tracer technique was applied to investigate the out-diffusi on of the transition metals (Cu, Fe and Co) from deep ultraviolet (DUV) pho toresist into underlying substrate. Two important process parameters, viz., baking temperatures and substrate types (i.e., bare silicon, polysilicon, silicon oxide and silicon nitride), were evaluated. Results indicate that t he out-diffusion of Co is insignificant, irrespective of the substrate type and baking temperature. The Out diffusion of Cu is significant for substra tes of bare silicon and polysilicon but not for silicon oxide and nitride; for Fe, the story is reversed. The substrate type appears to strongly affec t the diffusion, while the baking temperature does not. Also, the effect of solvent evaporation was found to play an important role in impurity diffus ion. Using the method of numerical analysis, a diffusion profile was depict ed in this work to describe the out-diffusion of metallic impurities from p hotoresist layer under Various baking conditions. In addition, the effectiv eness of various wet-cleaning recipes in removing metallic impurities such as Cu, Fe and Co was also studied using the radioactive tracer technique. A mong the six cleaning solutions studied, SC2 and SPM are the most effective in impurity removal. An out-diffusion cleaning model was first proposed to describe the cleaning process. A new cleaning coefficient, h(T), was sugge sted to explain the cleaning effect. The cleaning model could explain the t racer results. (C) 2001 Elsevier Science Ltd. All rights reserved.