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28 May 2004 New double exposure technique using alternating phase-shifting mask with reversed phase
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We propose a new double exposure technique to obtain a balanced intensity profile through focus using an alternating phase-shifting mask (alt-PSM) with a reversed phase. To cancel the intensity imbalance caused by the mask topography and phase error, an additional alt-PSM which has a reversed phase is prepared and exposed at the same position on a wafer. In practical application, two alt-PSMs with reversed phase relative to each other are placed along the scan direction (y-direction) in a 4X-reticle. The imbalanced images are added in a complementary manner by repeating exposure at a half dose and step at a half pitch along the y-direction. The throughput loss can be minimized by using a chip layout with two alt-PSMs in one reticle. The impact of position error between two exposures on lithography performance is discussed, and a 20-nm position error is shown to be tolerable for 80-nm L/S patterns. Both theoretical discussions and experimental data show that even a no Cr-undercut design and a 10° phase error are acceptable. Also, this double exposure technique can lower the risk of defect printing. Such large tolerance regarding the topographical design, phase error, and phase defects is the key to the application of alt-PSM technology in low k1 lithography beyond the 65-nm node.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Shoji Hotta, Katsuya Hayano, Kazuyuki Kakuta, and Norio Hasegawa "New double exposure technique using alternating phase-shifting mask with reversed phase", Proc. SPIE 5377, Optical Microlithography XVII, (28 May 2004);

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