Apply multiple target for advanced gate ADI critical dimension measurement by scatterometry technology

Scatterometry-based metrology measurements for advanced gate after-develop inspection (ADI) and after-etch inspection (AEI) structures have been well proven1. This paper discusses the metrology challenges encountered in implementing a production-worthy methodology for accurately measuring gate ADI middle CD (MCD) and sidewall angle (SWA) to monitor focus and exposure dose. A Multi-Target Measurement (MTM) methodology on KLA-Tencor's SpectraShape 8810 was evaluated on its ability to characterize and measure FEM (Focus Exposure Matrix) and EM (Exposure Matrix) wafers. The correlation of MCD and SWA to the focus and exposure dose was explored. CD-SEM measurements were used as a reference to compare the accuracy of scatterometry MCD measurements. While there was no reference tool available to compare scatterometry SWA measurements, the SWA and focus tracking on the FEM wafer were verified. In addition to the MTM methodology evaluation, a fleet of four SpectraShape 8810 tools was evaluated to measure the fleet's capability for in-line monitoring in high volume manufacturing. The final results confirmed that the Multi-Target Measurement approach on SpectraShape 8810 is an effective solution for gate ADI metrology and the robust fleet matching performance would enable in-line monitoring use.