The development of EUV (extreme ultraviolet) resist materials is critical to producing semiconductor devices with the smallest feature sizes. Understanding the light-induced chemistry of EUV photoresist and its impact on the quality of EUV lithography would help engineers to optimize this important technology. Photo-induced Force Microscopy (PiFM), with its capability to detect nanoscale chemical properties, is well suited to study this important group of materials.
Visualizing Latent Images of Exposed EUV Photoresist via PiFM Imaging
A commercial EUV photoresist is exposed but not developed. PiFM can be used to visualize the latent image associated with the exposed region by using the reduction in the signal associated with the vibrational mode at 1760 cm-1. For the 45 nm feature size, PiFM provides a clearer image (compared to the AFM topography) due to the lack of background features. The resist was extremely under-exposed, causing only a minor change in the polymer. Due to the under-exposure, the 45 nm features are not defined in topography. It is significant that PiFM is able to detect the minor chemical changes from such small features.