Full Field Adaptive Tolerance Analysis of Extreme Ultraviolet Lithography Objective

The relationship between structural parameters and aberrations in large field of view extreme ultraviolet lithography objective systems is very complex and the requirements for tolerances are extremely strict. It is not only necessary to select the image quality compensator reasonably, but also to relax the tolerance values to ensure the manufacturability of the lithography system. In this paper, a full-field adaptive tolerance analysis method is proposed for the extreme ultraviolet lithography objective system. The method firstly analyzes the sensitivity of system structural parameters to full-field distortion, astigmatism, coma and spherical, and selects different image quality compensators for different image aberrations. Then, by analyzing the influence of the full-field tolerance on the system image quality, an automatic tolerance accuracy model is constructed, through which the tolerance can be automatically relaxed to the allowed limit value under the condition of meeting the system image quality requirements, and the tolerance value can be adjusted efficiently and precisely. In order to verify the advanced effect of the method, the compensator selection and manufacturing tolerance analysis were carried out for a set of extreme ultraviolet projection objectives with a numerical aperture of 0.33, which were designed independently at an early stage. Five image quality compensators were firstly determined by the above method, and tolerance allocation and full-field adaptive tolerance accuracy analysis were carried out by CODEV software. The results showed that the root-mean-square (RMS) value of the system waveform aberration was less than 0.6 nm with 97.7% confidence probability.