Microlithographic projection exposure apparatus and measuring device for a projection lens

Abstract

A microlithographic projection exposure apparatus includes a projection lens that is configured for immersion operation. For this purpose an immersion liquid is introduced into an immersion space that is located between a last lens of the projection lens on the image side and a photosensitive layer to be exposed. To reduce fluctuations of refractive index resulting from temperature gradients occurring within the immersion liquid, the projection exposure apparatus includes heat transfer elements that heat or cool partial volumes of the immersion liquid so as to achieve an at least substantially homogenous or at least substantially rotationally symmetric temperature distribution within the immersion liquid.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This is a continuation-in-part of International Patent Application PCT / EP2005 / 000246, which was filed on Jan. 13, 2005 and claims benefit of US provisional application Ser. No. 60 / 537,784 filed Jan. 20, 2004. The full disclosure of these earlier applications is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The invention relates to microlithographic projection exposure apparatuses as used for manufacturing highly-integrated electrical circuits and other microstructured components. In particular, the invention relates to projection exposure apparatuses configured for immersion operation. The invention further provides measuring devices for determining the imaging properties of projection lenses. [0004] 2. Description of Related Art [0005] Integrated electrical circuits and other microstructured components are usually manufactured by applying a plurality of structured layers to a suita...

AI Technical Summary

Benefits of technology

The invention is about improving a projection exposure apparatus and a measuring device for optical properties of projection lenses by reducing imaging defects caused by inhomogeneities of the refractive index in the immersion liquid. The invention achieves this by using a heat transfer element to control the temperature of the immersion liquid in a specific area. By doing so, the heat transfer element can be positioned to achieve a desired temperature distribution and minimize vibrations caused by the circulation of the immersion liquid. The heat transfer element can be an electrically heatable or cooled wire, or a conduit through which a heating or cooling medium flows. The invention also includes the use of optical elements to direct the thermal radiation from the heat transfer element to the immersion liquid.

Problems solved by technology

A difficulty with the immersion operation of projection exposure apparatuses is to keep the optical characteristics of the immersion liquid constant, at least where the liquid is exposed to the projection light.

Local fluctuations in the absorption, as can be produced, for example, by impurities, lead to undesired intensity fluctuations in the image plane.

Local fluctuations in the refractive index of the immersion liquid have an especially detrimental effect, since such fluctuations directly impair the imaging characteristics of the projection exposure apparatus.

If the refractive index of the immersion liquid is inhomogeneous within the volume of the immersion liquid exposed to the projection light, this causes distortions of the wave fronts passing through the immersion space.

Moreover, temperature fluctuations within the immersion liquid not only cause fluctuations of refractive index, but can also cause adjacent optical elements, in particular the last optical element of the projection lens on the image side, to be heated unevenly and therefore to be deformed in a manner that can hardly be corrected.

However, the homogenization of temperature distribution that can be achieved in this way is frequently not sufficient.

Relatively high flow velocities, which may lead to disturbing vibrations, are usually required.

In addition, high flow velocities promote the formation of gas bubbles which can also adversely affect the imaging properties.

Moreover, similar difficulties also arise in measuring devices with which the imaging characteristics of such projection lenses can be determined.

Because of the extremely high demands on the measuring accuracy of such devices, inhomogeneities of refractive index within the immersion liquid cannot be tolerated.

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