Comparison of ATHENA~(TM) and TTL Alignment Capability on Product Wafers

摘要

Semiconductor manufacturers using ASML exposure tools have traditionally used a zero layer mark approach and Through the Lens (TTL) alignment system to align all production layers of a device. Future ASML exposure tools will no longer have the TTL system and will exclusively employ ATHENA~(TM), which is an off-axis alignment system utilizing two wavelengths and higher diffraction orders. In anticipation of this conversion, an evaluation has been performed using IDT's standard alignment scheme to compare the performance of ATHENA~(TM) to that of TTL for the alignment of the Gate layer to the STI layer. Standard XPA and higher diffraction order enhanced XPA mark types were evaluated using the zero layer approach, as well as non-zero layer enhanced scribeline SPM marks. TTL alignment to both standard and enhanced XPA marks showed a good alignment capability, with enhanced marks showing a slight improvement over standard marks. ATHENA~(TM) alignment to XPA marks gave similar results, although the red wavelength was shown to be slightly more stable than the green. CMP and thin film stack splits showed no significant correlation to alignment capability for any mode or mark type.