Preparation and characterization of low dielectric methyl silsesquioxane (MSSQ) thin films

As feature sizes in integrated circuits approach 0.18 mum and below, proble ms such as interconnect RC delay and crosstalk become more serious. Materia ls with low dielectric constants are needed to solve these problems. We app lied methyl silsesquioxane (MSSQ) as a low dielectric material and studied the film formation condition and the electrical properties of MSSQ films. M SSQ dissolved in a propylene glycol methyl ether acetate (PGMEA) and MSSQ/P CMEA solution was spun on glass substrates at various concentrations. Spinn ing at 2,500 rpm for 30 sec resulted in films with thicknesses of 6.500 Ang strom. Then, we cured the films by heating and measured the electrical prop erties of samples sandwiched between Al electrodes. The dielectric constant was: similar to 2.7. the breakdown strength was about 2.3 MV/cm. and the l eakage current was 5.4 x 10(-10) A/cm(2) Dynamic Mechanical Analysis (DMA) indicated that the curing reaction started at about 200 degreesC and procee ded very fast up to 250 degreesC. The structural change in the MSSQ films d uring curing was monitored by following the Fourier Transform Infrared (FTI R) absorption intensity of the Si-O stretching vibration, which showed that the Si-O structure became more asymmetric during curing and/or network for mation.