The continual drive for faster interconnects requires the development of new interlayer dielectricmaterials with k values less than 2.1. Porous SiLKTM semiconductor dielectric resin wasdeveloped to achieve these low dielectric constants by introducing nanometer-sized pores intothe dense SiLK resin matrix. A quantitative description of the nano-porous morphology in low-kinterlayer dielectrics can be difficult to achieve for many reasons, including: complexities in theporous structure (size range, geometry, pore/pore interaction), inadequate mathematicaldescriptors, limitations of existing metrology technology, and availability of “tailor-made” experimental samples with a wide range of pore morphologies. On-wafer quantification of poremorphology is even more difficult as data must be obtained from extremely limited samplevolumes (thin films of ∼100-500 nm) residing on thick silicon (Si) wafer substrates.
This paper will focus on the design, development and successful application of on-wafer smallangle x-ray scattering (SAXS) technology to characterize the morphology of porous SiLK resin.It will be demonstrated, by example, that this technology is able to deliver rapid quantificationover the entire pore size range for these systems. Recently developed data acquisition, reductionand analysis tools will be described. Direct evaluation of the strengths and challenges of severalmodels used to generate average pore size and pore size distribution will be reviewed. Finally,additional capabilities offered by this technology (wafer mapping and detection of “killer” pores)will also be discussed.