Masaaki Yoshida

Defect studies of resist process for 193nm immersion lithography

193nm immersion lithography is the most promising lithographic technology for the semiconductor device manufacturing of 65nm node and below. The advantage of 193nm immersion lithography is the possibility of wider depth of focus (DOF) and higher resolution through the hyper NA lens design greater than 1.0(1-3). In this paper, we investigated the topcoat material film characteristics and evaluated its performance to determine the chemical properties needed for a practical level. The stage scan speed capability evaluation, which is one of the best available method to test the suppression or generation of small water droplet remains on the topcoat film at high-speed stage scan during immersion exposure, was used. And finally we investigated the defectivity of topcoat process utilizing the Nikon EET. The static and dynamic contact angles of water droplet were investigated to characterize the topcoat material. The tilting sliding and receding angle, the contact angle of water droplet at the dynamic state, were important parameters to characterize the topcoat materials and have good correlation to wafer stage scan speed capability and immersion defect count reduction.

Resist development status for immersion lithography

Immersion lithography has already demonstrated superior performance for next generation semiconductor manufacturing, while some challenges with contact immersion fluids and resist still remain. There are many interactions to be considered with regards to the solid and liquid interface. Resist elusion in particular requires very careful attention since the impact on the lens and fluid supply system in exposure tool could pose a significant risk at the manufacturing stage. TOK developed a screening procedure to detect resist elution of ion species down to ppb levels during non and post exposure steps. It was found that the PAG cation elution is affected by molecular weight and structure while the PAG anion elution was dependent on the molecular structure and mobility. In this paper, lithographic performance is also discussed with the low elution type resist.