1. Field of the Invention
The present invention relates to a cleaning method of an immersion liquid, an immersion liquid cleaning composition, and a substrate.
2. Discussion of the Background
In manufacture of semiconductor devices, microfabrication by lithography carried out using a chemically amplified resist composition has been conventionally carried out. A pattern formation method used in the microfabrication generally includes: a step of forming a resist film on a substrate; a step of exposure by irradiating the resist film with an actinic ray such as ultraviolet ray through a mask; a step of development of the exposed resist film; and a step of etching using the obtained resist pattern as a protective film.
In recent years, enhanced integration of semiconductor devices has progressed, and thus further miniaturization of resist patterns in lithography has been demanded. Accordingly, as a method for forming a resist pattern that meets such demands, a liquid immersion lithography process in which a liquid immersion medium (immersion liquid) such as e.g., ultra pure water or a fluorine based inert liquid is filled between an exposure lens and the resist film to carry out the exposure (see, Japanese Unexamined Patent Application, Publication No. H10-303114) has been increasingly utilized. The liquid immersion lithography process is advantageous in that the numerical aperture (NA) of the lens can be increased, whereas the focal depth is less likely to be decreased even if NA is increased, and a high resolving ability can be attained.
Furthermore, in techniques for improving the liquid immersion lithography process, providing a liquid immersion upper layer film on the resist film for the purpose of suppressing elution of the resist film components into the immersion liquid, and the like, is proposed (see Japanese Unexamined Patent Application, Publication No. 2006-91798, and PCT International Publication No. 2008/47678 and 2009/41270).
However, also when the liquid immersion upper layer film is provided, the immersion liquid may be contaminated with slight amounts of resist film components and liquid immersion upper layer film components, or with dust present in the liquid immersion lithography apparatus during a formation step of a resist pattern carried out using a liquid immersion lithography process. Thus, due to the contaminants immixed in the immersion liquid, the exposure may be defective, and the resolving ability of the formed resist pattern may be deteriorated; therefore, development of a cleaning method of an immersion liquid, a composition for cleaning an immersion liquid, and a substrate which enable an immersion liquid containing such contaminants to be readily and efficiently cleaned to permit reuse has been desired.
USPTO Backgrounds
USPTO Backgrounds