Single anti-reflection coating optimization with different polarizations for hyper numerical aperture immersion lithography

Abstract

Immersion lithography uses a hyper-numerical aperture (NA) to make smaller patterns and this hyper-NA imaging needs serious consideration of polarization effects. Immersion lithography using a hyper-NA affects the selection and optimization of various resolution enhancement techniques. Increasing the NA means a higher substrate reflectivity owing to a higher incidence angle. Thus, reflectivity should be considered with polarization in immersion lithography. Reflectivity at the resistsubstrate interface has been a concern in the fabrication of many devices. To control the critical dimensions and the swing curve, we usually use anti-reflection coating (ARC). Lithography has become increasingly dependent on ARC to reduce reflectivity. If ARC has optimum parameters such as refractive index and thickness, we can obtain reduced reflectivity through the destructive interference of light. We suggest that different polarization states require different thicknesses of ARC to control reflectivity. The consideration of reflectivity, based on a hyper-NA is also investigated. Different polarization states in terms of different ARC thicknesses for controlling reflectivity are also studied. The fidelity of different patterns is valid with different polarization states for reflectivity reduction. The substrate and resist reflectivity affect the line width swing curve. Therefore, we studied the effects of reflectivity on immersion lithography.