Our goal is to develop measurement methods with sufficiently high spatial resolution to uncover the materials limitations in the resolution of state-of-the-art photoresist formulations. Photolithography, the process used to fabricate integrated circuits, has been the key enabler for performance advances in the microelectronics industry. However, as the lithographically patterned features decrease towards length scales of 32 nm, challenges arise because photoresists appear to be reaching their resolution limits. Our measurements help define these limits and enable the development of higher resolution photoresists and lithographic processes.
- With more that $43 Billion in exports in 2005, the semiconductor industry is the leading U.S. exporter and provides more than240,000 domestic jobs.
- NIST successfully completed a two-year contract with SEMATECH on quantifying the materials sources of line-edge roughness which causes excess chip power consumption and process speed variation.
- NIST developed and transferred FTIR based reaction-kinetics tools and modeling software to Intel.This method is being used by Intel to independently benchmark photoacid diffusion length for advanced photoresist formulations and optimize parameters for their manufacturing processes.
- World's first measurement of the buried in-plane reaction-diffusion profile and latent-image swelling by neutron reflectivity and diffuse scattering methods provided critical data on how resist processing contributes to line-edge roughness, a measure of ultimate resolution.
- CRADA with Intel to develop quartz-crystal microbalance methods to characterize photoresist swelling which impacts resolution of model and commercial photoresists.
Additional Technical Details
Latent Image Formation:
Metrology for Immersion Lithography:
Next-generation lithography will use an immersion fluid between the lens and photoresist.This leads to undesirable leaching of critical components that will cause undesirable defect formation.The change in component distribution, such as photoacid generators, within the top 8 nm at the surface of the thin film may be observed by examining the near-edge X-ray spectra of light elements such as carbon, oxygen, fluorine, and nitrogen.In this way, changes in the surface chemistry relative to the bulk film can be investigated as a function of lithographic processing steps. We have found that fluorinated PAG molecules preferentially segregate to the film surface.
The relative amount of segregation is dependent upon the specific polymer chemistry and PAG size (TPS-triflate< TPS-PFBS <TPS-PFOS). NEXAFS measurements quantify the influence of water immersion on the depth profile and loss of these critical components. When combined with liquid chromatography/mass spectrometry, the equilibrium water solubility of PAGs with varying perfluoroalkyl length does not serve as the appropriate criteria for selecting PAGs for immersion lithography; rather the segregation of PAGs to the top few nanometers provides the majority of leaching.
Intel CRADA 1893
NIST Center for Neutron Research
NIST Office of Microelectronics Programs