Pasquale Alfred Falcigno

Bilayer resist approach for 193-nm lithography

Tremendous efforts to extend optical lithography beyond the quarter micrometer boundary, which is currently achievable with KrF-excimer laser lithography, are ongoing. One-hundred- ninety-three nm lithography, using ArF-excimer lasers, is believed to be the technology of choice to approach the ambitious sub-0.2 micrometer resolution target. Single layer, positive tone resist systems, which can be developed with aqueous base, would be preferred. However, it might well turn out that the targeted requirements can only be fulfilled by resist systems which involve some type of dry etch steps. This paper focuses on a positive tone bilayer resist system, which is based on novel silicon containing methacrylate polymers bearing acid labile side groups. Due to a unique combination of monomeric building blocks, polymers with high silicon concentrations and, at the same time, high thermal flow stability are obtained. Hardbaked novolac is used as the planarizing layer. Resists systems based on the new silicon containing polymers demonstrated 0.175 micrometer resolution capability, a thermal flow stability greater than 120 degrees Celsius, and an etch selectivity ratio greater than 20.

Structural design of ketal and acetal blocking groups in two-component chemically amplified positive DUV resists

In the present study, protecting groups of moderate stability, such as acetals and ketals, were investigated as pendant blocking groups in polyvinyl phenols. Polymers were obtained by reacting enol ethers with the phenolic side groups to form acetal or ketal blocked phenols. Decomposition temperatures, glass transition temperatures, and molecular weights of the resulting polymers were monitored and correlated with the protecting group structure. Stability of the protecting groups can be explained by protonation occurring at either of the two oxygen sites, making two cleavage routes possible. Secondary reactions of the released protecting groups in the resist film were investigated and discussed. The structure of the protecting group was designed in order to meet basic resist properties such as resolution/linearity, DOF, post exposure delay latitude and thermal stability. A Canon FPA 4500 (NA equals 0.37) and a GCA XLS exposure tool (NA equals 0.53) were used for the optimization process. A preoptimized resist formulation based on the above criteria exhibits 0.23 micrometers line/space resolution, 0.8 micrometers focus latitude at 0.25 micrometers resolution and approximately two hours post exposure delay latitude.

Advanced positive photoresists for practical deep-UV lithography

New positive tone deep UV resists with enhanced post-exposure delay (PED) latitude and process latitude are presented. Additives and functionalized sulfone terpolymers are tailored to optimize the dissolution properties and process stability. Adjustment of the dissolution rate is used as a design criterion for optimizing the resist performance. RX 165 resist, optimized using the above criteria, exhibits 0.25 micron line/space resolution, 0.8 micrometers focus latitude at 0.275 micrometers resolution, and 1 hour post exposure delay latitude.