The importance of in-die sampling using E-beam solution on yield improvement

As technology progress with scaling to meet the market requirements, the patterning characterization of dense features suffers a significant challenge for current optic tools, and measurement accuracy will be an important index and great challenge as well. Patterning can mostly be characterized with index of overlay (OVL) and CDU (critical dimension uniformity) measurement. When you break down the budget of the overlay error, one of the challenges is a gap of measurement results between scribe and device, where provides improper information to be used in overlay correction and causes process anomaly (excursion) detection, resulting in a low yield at the end of the production process. An eBeam tool, using high electron landing energies while utilizing the ElluminatorTM technology[1] for improvement backscattered electrons (BSE) imaging efficiency, can be utilized to directly capture OVL performance of device unit in-die, including local and global level, due to BSE function of eBeam tool[2]. In this paper, we demonstrate overlay measurement of M0 to Poly line in device for advanced logic node (only OVL X measurement), obtaining Overlay gap between in-die and scribe line to capture the actual behavior of device unit in-die. Massive OVL data is measured using eBeam tool with fast speed and high resolution, and local OVL results have been analyzed in detail. We’ve quantified what is the impact of overlay correction by different measurement ways whether it depends on optical tool or eBeam tool and benefits yield improvement.