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<sup>(1-3)</sup>. 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.
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.
The Electron Projection Lithography (EPL) has already presented high resolution capabilities and been developed as one of the candidates of post optical lithography. However, much discussion has not been made for resist chemistry, especially on outgassing during exposure, regardless of utilizing high acceleration voltage and applying vacuum system. Moreover, two types of resist system, positive and negative tones, are required for a complete device manufacturing due to its stencil mask structure. Both resist tones with chemically amplified system were experimentally formulated to examine the partial and total pressure changes after exposure. The mass number of outgassing species was also measured in vacuum. The positive tone resist sample indicated many peaks at high mass numbers, in contrary to that negative tone resist sample showed strong peaks at low mass numbers. In addition, it was found that there was a clear trend between the total exposure doses and the total pressure changes in a certain positive-tone resist formulation. The fact may suggest the necessity of high sensitivity resists for EPL from the different standpoint of high throughput in mass production. The dependency of resist base polymer backbone was also examined under an accelerated exposure condition. The resist comprising of methacrylate base polymer indicated high amount of outgassing than that of poly(hydroxystyrene) (PHS) base polymer, with the same resist formulation. The polymer decomposition other than deprotection was considered since the exposure energy in EPL was much greater than that of optical lithography. We developed a new resist adopting the low outgassing concepts such as high sensitivity, non-methacrylate part, and low protecting ratio. The resist presented 56nm 1:2 contact resolution with resist sensitivity of 5.7μC/cm<sup>2</sup>.