Porosity Characterization Of Porous Silk (Tm) Dielectric Films

The continual drive for faster interconnects in integrated circuits requires the development of new interlayer dielectric materials with k values less than 2.2. Porous SiLK semiconductor dielectric resin was developed to achieve this low dielectric constant by introducing nanometer-sized pores into the SiLK matrix. The development of metrology to characterize the pores in porous SiLK dielectric films is critical for successful adoption of the material in the industry, both to ensure the film attains the desired dielectric properties and to monitor pore characteristics that may impact the integration process. Due to the complex nature of the porous structure, multiple on-wafer methods were investigated to quantify the porosity in porous SiLK dielectric films. The use of ellipsometry, small angle X-ray scattering and atomic force microscopy to measure void fraction, pore size, size distribution, pore morphology and their uniformity across a porous SiLK film are described. Advances in these techniques and commercialization of fab-quality X-ray scattering tools indicates significant progress has been made in the availability of porosity metrology for porous SiLK resin films.