(163bt) High-Yield Approach of Zeolite Nanocrystal Synthesis

As the feature size of microprocessors decreases, low dielectric constant (low-k) insulators are highly desired. Pure silica zeolites (PSZs) are promising candidates because of their uniform micro-porosity, high heat conductivity, superior mechanical strength as well as high hydrophobicity. We have developed two film deposition processes — in-situ crystallization and spin-on of zeolite nanoparticle suspension. For spin-on process, the crystallinity and crystal size are very important parameters to control the film properties. Once the crystal size is reduced while keeping high yield, the inter-particle mesopores will become smaller and more uniform, which will result in higher modulus and heat conductivity as well as smoother film. In this presentation, a new high yield approach of zeolite nanocrystal synthesis is reported. Two-stage method was used in the first batch to synthesize PSZ MFI nanocrystals. After the reaction, nanocrystals were removed by centrifugation and the rest of reaction gels was recycled. For the latter batches, the reaction time was much shorter than the first batch because of the presence of precursors in the synthesis solutions. Based on this method, PSZ MFI nanocrystal size was controlled at 30~35nm, 40~50nm, 53~58nm with the accumulative yields of 23%, 48% and 62% respectively. Moreover, after compensating to the synthesis solution every cycle, we obtained stable output 28nm nanocrystals with average yield of 2.13% for each batch.