Synthesis and characterization of silica aerogel films for inter-metal dielectrics via ambient drying

Abstract

Low-dielectric silica aerogel films could be synthesized via solvent exchange-ambient drying of wet gel films that were obtained by spin-coating the isopropanol based silica sol on a p-Si (100) wafer. Using isopropanol as a drying solvent, the thickness and the dielectric constant of silica films significantly changed from 1100 nm to 350 nm and from 2.1 to 3.6, respectively, with the drying pressure of [8 MPa (270 °C)→2.6 MPa (200 °C)]. However, when isopropanol in pores was exchanged with n-heptane followed by ambient drying technique, the aerogel films had 1350 nm thickness, 80% porosity, and 2.0 dielectric constant, regardless of the drying pressure. The degree of planarization and the gap filling capability on 0.7 μm tungsten patterning wafer were excellent. It was proven that the ambient-dried aerogel films have a possibility of an application to IMD (inter-metal dielectrics) materials in the next generation of semiconductor devices beyond the giga level.