EUV exposure apparatus with reflective elements having reduced influence of temperature variation

摘要

A projection lens of an EUV-lithographic projection exposure system with at least two reflective optical elements each comprising a body and a reflective surface for projecting an object field on a reticle onto an image field on a substrate if the projection lens is exposed with an exposure power of EUV light, wherein the bodies of at least two reflective optical elements comprise a material with a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures, and wherein the absolute value of the difference between the zero cross temperatures is more than 6K.

主权项

1. A projection lens of an EUV-lithographic projection exposure system including a reticle and an illumination system for illuminating the reticle, the projection lens comprising:
at least first and second reflective optical elements (Mm, Mn); said reflective optical elements (Mm, Mn) having respective bodies (MBm, MBn) defining respective reflective surfaces (MSm, MSn) for projecting an object field on said reticle onto an image field on a substrate when said projection lens is exposed with the exposure power of the EUV light reflected from said reticle when illuminated by said illumination system; said bodies (MBm, MBn) including a material having a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures (T0m, T0n); said zero cross temperatures (T0m, T0n) having a difference between each other of which the absolute value is greater than 6K, expressed as abs(T0m−T0n)>6K; and, said projection lens being configured to be exposed with an exposure power of more than 8 W of EUV light at a wavelength lying in a wavelength range of less than 50 nm.