CMOS compatible alignment marks for the SCALPEL proof of lithography tool

SCALPEL alignment marks have been fabricated in a SiO2/WSi2 structure using SCALPEL lithography and plasma processing. The positions of the marks were detected through e-team resist in the SCALPEL proof of lithography (SPOL) tool by scanning the image of the corresponding mask mark over the wafer mark and detecting the backscattered electron signal. Single scans of line space patterns yielded mark positions that were repeatable within 30 nm 3 sigma with a dose of 0.4 mu C/cm(2) and signal-to-noise of 16 dB. An analysis shows that the measured repeatability is consistent with a random noise limited response. The mark detection repeatability limit, that can be attributed to SPOL machine factors, was measured to be 20 nm 30. By using a digitally sequenced mark pattern, the capture range of the mark detection was increased to 13 mu m while maintaining 36 nm 30 precision. The SPOL machine mark detection results are very promising considering that they were measured under electron optical conditions that were not optimized.