膜リアクタ・デバイス 半導体層間絶縁膜としての周期構造ポーラスシリカ膜の合成

Abstract

Low-k dielectric materials have been in demand in order to solve the physical limits of interconnects for a new LSI technology system. Ordered mesoporous silica films are promising materials as low-k dielectrics because of their high porosity and high mechanical strength. Here, we show two preparation methods for thermally stable mesoporous silica films.First, a mesoporous silica film was prepared on a silicon substrate using a spin-coating process followed by a vapor treatment using tetraethyl orthosilicate (TEOS). The TEOS-treated mesostructured silica film did not contract during calcination, showing high structural stability. A flat mesoporous silica film about 250 nm thick was grown from the silicon substrate. No silica particle was deposited on the surface of film. FTIR studies suggested that the Si-OH groups in the film significantly decreased after the TEOS treatment. TEOS molecules penetrate into an originally deposited silicate film and react with the silanol groups. The densified silica wall has high structural stability and hardly contracts under a calcination process.Vapor-phase synthesis is another promising method for the preparation of thermally stable mesoporous silica film. We found nano-phase transition of an organic-inorganic nanocomposite under vapor infiltration of TEOS. The rearrangement into a hexagonal periodic structure implies high mobility of the surfactant-silicate composites in solid phase. The vapor infiltration method is a simpler process than conventional sol-gel techniques and attractive for mass production of a variety of organic-inorganic composite materials and inorganic porous films.