Reflection masks, microlithography apparatus using same, and integrated circuit manufacturing methods employing same
AssigneeNikon Corporation
InventorKatsuhiko Murakami
Life of this patent
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Abstract
Reflection masks are disclosed for use in microlithography (especially soft-X-ray microlithography) in which the linewidth of a circuit pattern defined by such a mask is transferred onto a wafer with reduced adverse effects from reflectance non-uniformities of the mask. A representative reflection mask includes a multilayer mirror that reflects soft X-rays of a prescribed wavelength and a soft-X-ray-absorber layer defining pattern elements. The multilayer mirror is configured to have a thickness period that varies through the thickness dimension of the multilayer mirror.
Claims11
A reflection mask for use in microlithography, the reflection mask comprising:
- a multilayer mirror that reflects incident electromagnetic radiation of a prescribed wavelength;
- and
- an absorptive layer superposed on the multilayer mirror, the absorptive layer defining elements of a pattern defined by the mask, wherein the multilayer mirror has a thickness period, through a thickness dimension of the multilayer mirror, that varies through the thickness dimension.
A microlithography apparatus, comprising:
- an illumination-optical system situated and configured to irradiate electromagnetic radiation from a source onto a reflection mask, the reflection mask defining a pattern to be projected onto a substrate;
- an imaging-optical system situated and configured to direct portions of the electromagnetic radiation reflected from the reflection mask to the substrate so as to form an image of the pattern on the substrate;
- and
- the reflection mask comprising a multilayer mirror that reflects a prescribed wavelength of the electromagnetic radiation and an absorber layer, superposed on the multilayer mirror, that absorbs the electromagnetic radiation and defines elements of the pattern, the multilayer mirror having a thickness period, through a thickness dimension of the multilayer mirror, that varies through the thickness dimension.
In a method for manufacturing an integrated circuit, a microlithography step in which a circuit pattern, defined on a mask, is transferred to a wafer to form the circuit pattern on the wafer, the microlithography step being performed using a reflection mask comprising a multilayer mirror that reflects a prescribed wavelength of electromagnetic radiation and an absorber layer, superposed on the multilayer mirror, that absorbs the electromagnetic radiation and defines elements of the pattern, the multilayer mirror having a thickness period, through a thickness dimension of the multilayer mirror, that varies through the thickness dimension.
Dependencies are inferred from the claim text.