LPP-based reflectometer for characterization of EUV lithography systems

Abstract

An EUV reflectometer, based on a laser-produced plasma (LPP) light source, has been developed for characterization of EUV lithography systems. The reflectometer consists of the LPP light source, a prefocusing toroidal mirror, a grating monochromator, a polarizer, a beam intensity monitor, a refocusing toroidal mirror and a sample stage. The LPP light source is driven by a Nd:YAG laser; the laser beam is focused onto a copper tape target. A debris mitigation system that uses a rotating shutter was developed. Higher-orders from the grating monochromator were suppressed to less than 0.2% of incident beam intensity by total reflection of three grazing incidence mirrors. In order to compensate for beam intensity instability, a beam intensity monitor using a grating beamsplitter was installed between the refocusing mirror and the sample. Beam intensity instability can be corrected to less than 0.1% by using the beam intensity monitor.

Схема VLS-монохроматора Высокого Разрешения Для Синхротронного Излучения

“…В настоящее время VLS-спектрометры и VLS-монохроматоры различного типа широко применяются в исследованиях в мягком рентгеновском (МР) диапазоне спектра [6,7]. Они используются в спектроскопии и диагностике лабораторной плазмы [8], астрофизике [9][10][11], рефлектометрии/метрологии с использованием лазерноплазменного источника МР излучения [12], рентгеновском флуоресцентном анализе с использованием СИ и эмиссионной спектроскопии, совмещенной с электронным микроскопом [13]. Пользовательские каналы МР/ВУФ-излучения на зарубежных синхротронах часто используют монохроматоры и спектрометры на основе VLS-решеток [14][15][16].…”

Manufacturing and Investigating Objective Lens for Ultrahigh Resolution Lithography Facilities

“…In Refs. (Loyen et al, 2003;Miyake et al, 2003;Gulikson et al, 1992) the specialized reflectometers for investigating multilayer optics in the range around 13.5 nm are described. As a source of the soft x-ray and EUV radiation the laser plasma is used, which arises due to the irradiation of solid-state targets by laser light with a power density about 10 9 W/cm 2 .…”