Effect of resist surface characteristics on film-pulling velocity in immersion lithography

Abstract

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“…5). This conclusion does not hold for the more recent introductions of immersion and double patterning technologies, which achieved rates of NA eq improve- and additive technology, 10 and immersion top coats 11,12 to enable defect-free high scan speeds, this development has not led to significant increases in resolution capability: 193 nm immersion resists do not show significant resolution improvements versus dry resists when imaged on a non-immersion tool. The linear increase of NA eq as a function of time is an entirely empirical relationship; while it holds for multiple technologies over long time scales, its origin is unknown (although it has been speculated that it may result from characteristics of the materials development infrastructure, e.g.…”

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“…To study the fundamental interaction of water with immersion surfaces, contact angle measurements are made using commercially available systems. − In the tilting sessile drop method shown in Figure , for example, a droplet of water is placed on a coated substrated that is tilted until the droplet begins to slide. The static advancing contact angle (SACA, θ s,a ) and static receding contact angle (SRCA, θ s,r ) are determined just before the drop begins to slide.…”

“…Fluid loss has been found to occur via two mechanisms: film pulling and inertial instability (as shown in Figure ). ,− Film pulling occurs when the dynamic receding contact angle approaches zero and a thin layer of fluid is pulled out behind the receding meniscus . The film pulling velocity (υ fp ) can be modeled by υ fp = C 1 υ ̅ ca θ s , r 3 wherein C 1 is an empirical constant, θ s,r is the static, receding contact angle, and the capillary velocity υ̅ ca is defined as υ ̅ ca = γ μ wherein γ is the surface tension and μ is the dynamic viscosity of the fluid. ,, Film pulling of water is frequently observed at low velocities on hydrophilic surfaces (i.e., those with low SRCA values).…”

“…Fluid loss by inertial instability occurs when the fluid surface tension is insufficient to counteract the inertial force imposed by the fluid at the receding meniscus. ,,, In this case, bulk fluid loss occurs when droplets of fluid break off from the extended receding meniscus. Failure by inertial instability is frequently observed at high wafer accelerations and velocities on more hydrophobic surfaces (i.e., those with higher SRCA values).…”

“…Failure by inertial instability is frequently observed at high wafer accelerations and velocities on more hydrophobic surfaces (i.e., those with higher SRCA values). The inertial instability velocity (υ in ) can be modeled by υ in = C 2 υ ̅ in 3 / 4 υ ̅ ca 1 / 4 sin 3 / 4 true( θ s , r 2 true) wherein C 2 is an empirical constant and υ̅ in is given by υ ̅ in = γ ρ κ − 1 wherein ρ is the density of the fluid and κ −1 is κ − 1 = γ ρ g wherein g is the acceleration due to gravity. , …”