Cleaning Solution Effect on Electrical and Reliability Properties of Dense and Porous Low Dielectric Constant Materials

The effects of different cleaning solutions and various immersion times on the electrical and reliability characteristics of the low-k dielectrics are investigated in this study. After immersing in a wet cleaning solution, both dense and porous low-k dielectrics are needed a post-baking process to remove the physically-adsorbed water. The experimental results indicate that the acid HF solution and basic NH₄OH solution have negative impact on low-k dielectrics. Moreover, the acid HF solution causes the low-k dielectrics to be modified and a longer immersion time have larger impact. The formation of chemically-adsorbed water and the increased pore size or porosity in the low-k dielectrics with HF solution immersion were observed. These phenomena become more obviously in the porous low-k dielectrics with a longer immersion time. Except the positive benefit in the reduction of the dielectric constant, these changes cause the degradation in electrical and reliability performance for low-k dielectrics.