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17 December 2003 Implementing AAPSM in 90-nm product with practical image imbalance correction
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Abstract
Each new technology node tests the limits of optical lithography. As exposure wavelength is reduced, new imaging techniques are needed to maximize resolution capabilities. The phase shift mask (PSM) is one such technique that is utilized to push the limits of optical lithography. Altering the optical phase of the light that transmits through a photo mask can increase the resolution of a lithographic image significantly. There are several types of phase shift mask and each has a general charateristic in which some transparent area of the mask are given 180° shift in optical phase relative to other nearby transparent areas. The interaction of the aerial images between two features with a relative phase difference of 180° create interference regions that can be used to printed images much closer together and with an increased depth of focus than that of a standard chrome-on-glass mask. An AAPSM is fabricated using a subtractive process in which the quartz substrate is etched to a given depth to produce the desired phase shift. However, intensity imbalances between the etched and non-etched regions due to sidewall scattering can cause resolution, phase and placement errors on the wafer. One method to balance the transmission is 40 nm undercut with 16 nm shifter width bias. Based on our previous study, 40 nm undercut with 16 nm shifter width bias showed an improved balance of intensities between the etched and non-etched regions. The object of this experiment is to implement the AAPSM with 40 nm undercut and 16 nm shifter width bias in SRAM product and the exposure wavelength is 193 nm. The main purpose is to proof the technology of AAPSM with 40 nm undercut and 16 nm shifter width bias in real product. Also verifying all issue of AAPSM in production. In this study, the image imbalance has been corrected via 40 nm undercut and 16 nm shifter width bias, and the DOF of AAPSM for wafer print performance is larger than binary mask. The DOF of AAPSM is about 0.5 μm and the conventional binary mask is 0.3μm.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Benjamin Szu-Min Lin, Shu-hao Hsu, I. H. Huang, Kunyuan Chen, Frank Hsieh, Tony Hsu, Hua-Yu Liu, Armen Kroyan, Freeman Hsu, and Jason Huang "Implementing AAPSM in 90-nm product with practical image imbalance correction", Proc. SPIE 5256, 23rd Annual BACUS Symposium on Photomask Technology, (17 December 2003); https://doi.org/10.1117/12.518029
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