Influence of porosity on dielectric breakdown of ultralow-k dielectrics

Abstract

The effect of porosity on the electrical properties of porogen-free ultralow-k dielectric materials was demonstrated using a special curing process that allows a separate control of porosity and matrix properties. It is shown that the leakage current was insensitive to porosity, suggesting a bulk conduction mechanism. On the other hand, higher porosity leads to lower breakdown voltage, indicating that porosity can degrade the electrical reliability performance of the dielectric material. The observed lower breakdown field is explained in terms of the amount of cage structure in the film, the exacerbation of strain in the Si–O–Si backbone structure by an external electric field, and local field enhancements near the pores, thereby making the Si–O bond highly susceptible to breakage.