The continuing drive by the semiconductor industry to fabricate smaller structures with photolithography will soon require dimensional control at length scales, (2 to 5) nm, comparable to the size of the polymeric molecules in the materials used to pattern them. The current technology, chemically amplified photoresists, utilizes a complex reaction-diffusion process to delineate patterned areas soluble in a developer solution with high spatial resolution. However, nanometer level control of this critical process is limited by the lack of direct measurements of the reaction front. In this work, we demonstrate the use of x?ray (XR) and neutron reflectometry (NR) as a general methodology to measure the spatial evolution of the reaction-diffusion process in chemically amplified photoresists with nanometer resolution.Measuring compositional profiles, provided by deuterium-labeled reactant groups for neutron scattering contrast, we show that the reaction front within the material is broad rather than sharply defined and the compositional profile is altered during development. Measuring the density profile, we directly correlate the developed film structure with that of the reaction front. This spatial detail provides quantitative data critically needed to understand, design, and control lithographic materials and processes at nanometer length scales.
Issue: No. 5580
Pub Type: Journals
nanofabrication, neutron reflectometry, photolithography, photoresist, polymer thin film, reaction front profile, x-ray reflecto