26 March 2008 Improvement of 90nm technology VIA photo alignment through TiN hard mask removing above previous photo alignment mark area
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As the IC product scribe line of logic 90nm (L90) technology shrinks from 80µm to 62μm, the wafer quality (W.Q.), will become weak and less distinguishable during the subsequent ASML scanner stepper's photo mask aligning. Many wafers having photo mask aligning errors will eventually lead to wafer scrapping. In order to improve the photo alignment signal (W.Q.) acquired from the relatively smaller 62μm scribe-line's alignment mark while proceeding with the VIA layer photo aligning directly to its previous metal layer, it is found that removing the TiN hard mask (H.M.) just above the previous inter-metal dielectric (IMD) and alignment mark area can help the deep ultra-violet (DUV) 193nm wavelength ASML scanner stepper successfully acquires a better alignment signal and alignment accuracy (A.A.). However, due to copper (Cu) residues and CMP dishing after metal copper CMP, it has been found that both large area "half size open" and "full size open" approaches for TiN removing in the scribe-line alignment area can not be used. Hence, for safer photolithography aligning margin the "sizing + 0.25μm" mark on the scribe line's photo alignment area is suggested for better signal acquiring, whose experimental results in UMC shows that around 90% of the alignment signal (W.Q.) can be verified. The alignment accuracy (A.A.) can also be improved through using this technique and is accurate enough as compared to the conventional scanner alignment method used for above 0.13μm generation technology.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Wen-Shiang Liao, Wen-Shiang Liao, Hsin-Hung Lin, Hsin-Hung Lin, Yu-Huan Liu, Yu-Huan Liu, Mao-Chyuan Tang, Mao-Chyuan Tang, Sheng-Yi Huang, Sheng-Yi Huang, Cheng-Han Wu, Cheng-Han Wu, Yue-Gie Liaw, Yue-Gie Liaw, Tung-Hung Chen, Tung-Hung Chen, Tommy Shih, Tommy Shih, Kun-Ming Chen, Kun-Ming Chen, "Improvement of 90nm technology VIA photo alignment through TiN hard mask removing above previous photo alignment mark area", Proc. SPIE 6923, Advances in Resist Materials and Processing Technology XXV, 69233Y (26 March 2008); doi: 10.1117/12.772286; https://doi.org/10.1117/12.772286

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