29 March 2006 New 193nm top antireflective coatings for superior swing reduction
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Abstract
Reflectivity caused by topography on wafer stacks is very difficult to reduce with the use of thin antireflective bottom layers. A coating of top antireflective layer, with 1/4n wavelength of exposure source (193nm in this case), will create destructive interference between incident and reflected light. This destructive interference reduces the variation of energy deposited in resist of different thicknesses, which in turns, reduces the CD variation over topography. The optimum refractive index of this TARC layer, when coated over a resist with n value of 1.69, is around 1.3. Most currently available commercial TARCs, which are based on fluoropolymers, have an n value of 1.47 or higher. Even for TARCs with n value in this range, the swing amplitude is still in the >20% range. Besides the required low n value necessary for swing reduction, the TARC also should not affect resist image profiles. In this paper, we will discuss a newly developed TARC system which is different from the traditional approach in new TARC design. This new absorbing TARC system has demonstrated a superior capability of reducing CD swing, to less than 5%, without impacting resist image profile. This TARC system can provide a solution to the concern of CD variation over different topography on a wafer in device manufacturing.
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Wu-Song Huang, Wu-Song Huang, William H. Heath, William H. Heath, Ranee Kwong, Ranee Kwong, Wenjie Li, Wenjie Li, Kaushal Patel, Kaushal Patel, Pushkara Rao Varanasi, Pushkara Rao Varanasi, } "New 193nm top antireflective coatings for superior swing reduction", Proc. SPIE 6153, Advances in Resist Technology and Processing XXIII, 61530S (29 March 2006); doi: 10.1117/12.656641; https://doi.org/10.1117/12.656641
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