Synthesis of mesoporous thin silica films with ultra low dielectric constant

Vapor phase treatment with tetraethyl orthosilicate (TEOS) was used to improve the performance of methylated mesoporous silica films spin-coated on silicon wafers. Subsequent calcination treatment led to formation of methyl-functionalized-silica films with high structural stability and hydrophobicity. XRD, FTIR results show that the films have high structural stability and hydrophobicity. SEM images indicate that TEOS treatment favors the formation of flat and integrated non-crack films. Dielectric constant (k) value of the films is ultra low, k approximate to 1.74, and remains as low as 1.81 after aging in 25 degrees C and 50% similar to 60% -relative-humidity environment for over 15 days. Mechanical strength (elastic modulus and hardness) is high enough to withstand the stresses that occur during the chemical mechanical polishing and wire bonding process (E=10.9 GPa). Effects of the methyl group introduction and the TEOS vapor treatment on the structural stability and hydrophobicity have been studied.