Two-mirror telecentric optics for soft x-ray reduction lithography

Abstract

A two-mirror telecentric optic has been designed for soft x-ray reduction lithography with high throughput using synchrotron radiation. A resolution of 0.1 μm is achieved at a wavelength of 130 Å with a 15-mm ring field. In the design, aberrations, including distortion, are reduced using aspherical concave and convex mirrors with an ellipsoid surface at a numerical aperture of 0.07. Telecentric imaging is obtained by illuminating a reflection mask using focusing toroidal mirrors. The designed optics achieves a modulation transfer function (MTF) value of over 40% at a spatial frequency of 5000 lines/mm capable of resolving 0.1-μm lines and spaces. The depth of focus is ±1 μm. The distortion is <0.01 μm in the image field. The imaging field is a 12.5-mm radius ring field which enables a 15×15-mm field exposure by the ring-field scanning method. The reduction ratio is 1/5.

The Early Days of R&D on EUV Lithography and Future Expectations

“…To suppress any image shift due to defocusing, the telecentricity on the wafer was taken into account. Thus, the design was completed for a telecentric optical system with a reduction ratio of 1/5 and a resolution of 0.1μm with a numerical aperture (NA) of 0.1 and two aspherical mirrors [23,24]. Based on this system design, we designed and fabricated a two-aspherical-mirror system with an NA of 0.1 [23,24].…”

“…Thus, the design was completed for a telecentric optical system with a reduction ratio of 1/5 and a resolution of 0.1μm with a numerical aperture (NA) of 0.1 and two aspherical mirrors [23,24]. Based on this system design, we designed and fabricated a two-aspherical-mirror system with an NA of 0.1 [23,24]. Figure 1 shows a schematic of the EUVL system employing a system with two aspherical mirrors.…”

Euv Lithography for Semiconductor Manufacturing and Nanofabrication

“…Figure 4 illustrates a two-aspherical-mirror system for the replication of 0.06 µm patterns in a large exposure area demonstrated by NTT. 3,5 The incident angle to the optics is nearly normal (∼ 2 • ). The focused beam strikes the wafer perpendicularly; that is, the optics is telecentric with respect to the plane of a wafer.…”

Design of beamline optics for EUVL

“…The mask pattern can be replicated onto a wafer through the imaging optics, which consist of multilayer-coated mirrors. EUVL employs multilayer-coated-mirror imaging optics at a wavelength of 13 nm (Kurihara et al, 1991;Kinoshita et al, 1993Kinoshita et al, , 1997Cook, 1981;Mashima, 1997;Watanabe et al, 1997;Namioka et al, 1995). The collimating optics are employed in the collection of X-rays from a very wide aperture and to provide an image, in combination with the imaging optics, that is matched to the requirements of the exposure system.…”