DEVELOPMENT AND APPLICATION OF ON-WAFER SMALL ANGLE X-RAY SCATTERING FOR THE QUANTIFICATION OF PORE MORPHOLOGY IN LOW K POROUS SILK~(TM) SEMICONDUCTOR DIELECTRICS

摘要

The continual drive for faster interconnects requires the development of new interlayer dielectric materials with k values less than 2.1. Porous SiLK~(TM) semiconductor dielectric resin was developed to achieve these low dielectric constants by introducing nanometer-sized pores into the dense SiLK resin matrix. A quantitative description of the nano-porous morphology in low-k interlayer dielectrics can be difficult to achieve for many reasons, including: complexities in the porous structure (size range, geometry, pore/pore interaction), inadequate mathematical descriptors, limitations of existing metrology technology, and availability of "tailor-made" experimental samples with a wide range of pore morphologies. On-wafer quantification of pore morphology is even more difficult as data must be obtained from extremely limited sample volumes (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 small angle 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 quantification over the entire pore size range for these systems. Recently developed data acquisition, reduction and analysis tools will be described. Direct evaluation of the strengths and challenges of several models 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.