Ultra-precision alignment based on differential moiré technique

An ultra-precision alignment technique based on differential moiré technique is presented for room-temperature imprint lithography. The Moiré signal generated by a pair of special slant gratings is detected by a set of photoelectric detectors then the detected signals are used to estimate the magnitudes of misalignment in x, y directions. The test results conformed that differential moiré signal is more sensitive than simple moiré signal. Additionally, a Chebyshev digital filter is adopted in control system to reduce the noise from the differential moiré signals. As a result, the repeatable alignment accuracy can reach ± 20 nm and meet the requirement of alignment accuracy for sub-100 nm imprint lithography.