Toshiro Ishiyama

Nikon projection lens update

This paper describes various kinds of technological improvements in ArF projection lenses for success in very low-k1 and high NA lithography. This paper covers optical design, lens manufacturing, aberration characterization, aberration manipulation, flare control, and linear polarizing illumination. Actual lens performance of the Nikon NSR-S307E (0.85NA ArF Optics) is also reviewed.

A hyper-NA projection lens for ArF immersion exposure tool

Resolution enhancement in ArF dry lithography is limited by the numerical aperture (NA), which cannot be extended past the physical limit of 1.0. Immersion lithography is proposed as a candidate to overcome this limitation as resolution can be enhanced with a hyper-NA immersion projection lens. In addition, depth of focus (DOF) can be extended owing to the small incident angle for marginal rays onto the image plane. Our development of immersion optics can be divided into three phases. First, the initial evaluation has successfully been conducted in the engineering evaluation tool (EET), in which the projection optics is converted from dry-use to wet-use while retaining the same NA, 0.85. Second, the projection optics with 1.07NA has been developed aiming at devices with 50-55nm half-pitch (hp) patterns. The optics, comprising only the refractive elements, is exclusively dedicated to immersion usage. Third, catadioptric optics with 1.3NA targeting at 45nm hp devices is intensively studied. This paper will focus on the second and the third phases of the development.

High-NA projection lens design for exposure tools

In the history of the semiconductor industry, exposure tools have been improved in resolution. This paper describes how to increase NA of projection lens up to more than 0.7 without increasing lens diameter or deteriorating the aberrations.