20 May 2004 Techniques for directly measuring the absorbance of photoresists at EUV wavelengths
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Abstract
Absorbance is a key characteristic of photoresists that can limit resolution, wall angle, and practical resist film thicknesses. Currently, however, there is limited data for absorbance of resists at EUV (13.5 nm) wavelengths. The most common way of estimating the absorbance of materials at EUV wavelengths is to use an experimentally measured value of density along with stoichiometric chemical information of the material in a theoretical calculation such as that available through the Center for X-Ray Optics at Lawrence Berkeley National Laboratory website.1 However, there is limited validation of these estimates for photoresists. The paper will compare calculations using density measurements of EUV-2D by a variety of methods: traditional weight measurements and Specular X-ray reflectivity (SXR) to determine density; and against grazing incidence and normal incidence reflectivity measurements to determine absorbance directly. It will be shown that inaccurate density measurements can result in 10% or greater absorbance estimates from the calculations. Based on the results, recommendations will be made for measurement techniques and accurate density based calculations of photoresist absorbance.
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Manish Chandhok, Manish Chandhok, Heidi Cao, Heidi Cao, Wang Yueh, Wang Yueh, Eric M. Gullikson, Eric M. Gullikson, Robert L. Brainard, Robert L. Brainard, Stewart A. Robertson, Stewart A. Robertson, } "Techniques for directly measuring the absorbance of photoresists at EUV wavelengths", Proc. SPIE 5374, Emerging Lithographic Technologies VIII, (20 May 2004); doi: 10.1117/12.535959; https://doi.org/10.1117/12.535959
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