Early defect detection for EUV self-aligned litho-etch litho-etch patterning with EPE

Abstract

We demonstrate the use of EPE (Edge Placement Error) as an early defect detection metric in an EUV self-aligned litho-etch-litho-etch (eSALELE) patterning process. Pitch 21nm test structures were investigated on an eSALELE flow consisting of 4 EUV exposures, 2 of which are lines-spaces while the other 2 exposures are for block patterns that defines the tip-to-tip. An HMI eP5 SEM with large field-of-view (8x8 mu m FOV) was used to measure critical dimension (CD) on wafer at each critical processing step while the overlay between multiple exposures were measured optically on uDBO marks using a YieldStar (YS). On top of CD metrology, patterning defects were measured at the final patterning transfer into dielectric material using an eP5 SEM and built-in defect inspection capability. Line-break defects are reported. Although each metric like CD, LWR or OVL is expected to contribute to the defect performance of the final pattern transfer, using only one information or another is not fully descriptive. Combining these information into an EPE metric on this complicated patterning process showed better correlation to the defect rates at dielectric transfer.