20 May 2004 Modeling for sub-50-nm x-ray application with phase masks
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The CNTech Advanced Lithography Toolset uses a beam propagation method to calculate the intensity profile as it propagates through the mask and into the photoresist. One can construct the membrane, absorber, gap, and resist, each as a series of n-slices to achieve unusually precise calculations. Here a clear X-ray phase mask is modeled with silicon nitride in a configuration called a Bright Peak Enhanced X-ray Phase Mask (BPEXPM). For the optimized structure of this mask, which relies on both diffraction and phase shifting to produce the reduced wafer image, four factors must be controlled; these are: absorber thickness - material and wavelength dependent, absorber wall slope, gap, and resist threshold. A central composite experimental design showed that a 100 nm mask would print a wafer at 35 nm CD using the 70% maximum intensity threshold when the wall slope was 0.5° from the vertical. Additionally: 1) a 100 nm increase in absorber thickness decreased the CD by 1.0 nm; 2) every 1.0 um increase in gap decreased the CD 0.8 nm; and 3) every 1.0 nm increase in mask CD increased the linewidth only 0.1 nm. Other mask processing materials were examined in addition to the 180° (π) phase-shift absorber thickness. Experimental verifications of the modeling results are in progress to demonstrate device construction for devices with lower wafer coverage than would be required for memory devices.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
James W. Taylor, James W. Taylor, Daniel H. Malueg, Daniel H. Malueg, Franco Cerrina, Franco Cerrina, Mumit Khan, Mumit Khan, Don Thielman, Don Thielman, } "Modeling for sub-50-nm x-ray application with phase masks", Proc. SPIE 5374, Emerging Lithographic Technologies VIII, (20 May 2004); doi: 10.1117/12.535422; https://doi.org/10.1117/12.535422

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