Mask and wafer evaluation of Sigma7500 pattern generator applied to 65nm Logic metal and via layers

摘要

As pattern density and OPC complexity grow, photomask write times on electron beam tools increase in proportion. Reducing the write time would decrease mask-making costs, but the performance of any alternative mask writer must meet all of the technical requirements on both mask and wafer. In addition, it is desirable to use existing OPC models in order to avoid the costs of developing and maintaining separate OPC models for each writer. The Sigma7500 deep-UV pattern generator provides the highest resolution available from a laser-based tool, and it has the advantage of maintaining about a 3 hour write time even as the feature count increases.rnIn this study, the Sigma7500 and a variable shaped e-beam (VSB) tool are compared on 65nm metal 1 and vial layers. In the first phase, the Sigma pattern positioning was matched to a SMIC reference grid and a registration value of 10 nm (3s) was achieved with scales removed. In the second phase, M1 and V1 masks were printed with both laser and e-beam writers using the same pattern data and compared on CD uniformity, linearity and proximity. The Sigma7500 met all of the photomask requirements for these layers. The masks were then printed on wafers and the wafer data was evaluated. The results were comparable to those for the e-beam masks and were within the requirements, indicating that the Sigma7500 can handle these layers without the need to revise the e-beam mask OPC models.