Measurement of latent image in resist using scanning probe techniques

The most pressing issue facing extreme ultraviolet lithography (EUV) as a multi-node technology is the inability to effectively manage stochastic effects. Fundamentally linked to the discrete nature of absorbed light (photons) and photo or electron-active components in the photoresist, stochastic effects lead to non-idealities in printed features, which for lines manifests itself as line edge and width roughness, and in the extreme cases, line breaks and bridges. However, measurement of stochastic propagation in photoresist has been hampered by the lack of metrology capable of probing the resist at intermediate stages of the patterning process. Here we present the use of atomic force microscopy (AFM) to measure the image in resist prior to photoresist development. In particular, the method was used to analyze the role of bake time on important resist metrics such as critical dimension, edge roughness, and roughness correlation length.