Multilayer mirror, method for manufacturing the same, and exposure equipment

• US 20090097104A1
• Filed: 09/12/2008
• Published: 04/16/2009
• Est. Priority Date: 10/15/2003
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Komiya, Takaharu, Shiraishi, Masayuki, Kandaka, Noriaki, Murakami, Katsuhiko
• Granted Patent: US 7,706,058 B2
• Time in Patent Office: Days
• US Class Current: 359/359
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G02B 5/0891 Ultraviolet [UV] mirrors apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06
• CPC Class Codes: G03F 7/70316 Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements
• CPC Class Codes: G03F 7/70958 Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties
• CPC Class Codes: G21K 1/062 Devices having a multilayer structure

Abstract

A multilayer mirror aims to reduce incidence angle dependence of reflectivity. A substrate is made of low thermal polished expansion glass with 0.2 nm RMS or less roughness of the surface. On the surface thereof formed is a Ru/Si multilayer having a wide full-width half maximum of peak reflectivity, and on the Ru/Si multilayer formed is a Mo/Si multilayer having a high peak reflectivity value. This enables higher reflectivity than when Ru/Si alone provided and a reflectivity peak having a wider full-width half maximum than when the Mo/Si multilayer alone provided. Since Ru absorbs EUV ray more than Mo does, higher reflectivity is obtainable than that of a structure having the Ru/Si multilayer formed on the Mo/Si multilayer. The multilayer with a wide full-width half maximum has small incidence angle dependence of reflectivity in spectral reflectivity, thereby achieving high imaging performance in projection optical system.

Claims

1. A multilayer mirror comprising a reflective multilayer in which a high refractive-index film and a low refractive-index film are laminated on a substrate by turns under a condition that a Bragg'"'"'s reflection condition holds that reflected light from a plurality of boundary surfaces of the high refractive-index film and low-refractive index film for EUV ray is put in phase, comprising:

an interposed layer having a thickness of half or more of a center wavelength of the EUV ray, wherein

a band of EUV ray wavelength or incidence angle having a relatively high EUV ray reflectively is widened.

2. The multilayer mirror according to claim 1, wherein part of layer pairs of the high refractive-index film and low refractive-index film is composed of two kinds of substances and another part thereof is composed of three or more kinds of substances.

3. The multilayer mirror according to claim 1, wherein each layer is laminated while the film thickness thereof is varied arbitrarily so that reflectivity for light having a wavelength of 13.1 nm to 13.9 nm is set to 45% or more.

4. The multilayer mirror according to claim 1, wherein the interposed layer is at least one layer of the high refractive-index film.

5. Exposure equipment which forms a pattern by selectively irradiating a sensitive substrate with EUV ray, comprising the multilayer mirror according to claim 1 in an optical system.