Full-wafer 3D metrology solution based on imaging ellipsometry for process uniformity control

As semiconductor manufacturing technology becomes more complex, process control becomes more important, and in particular, technologies for discovering and controlling structural defects become more important. However, considering the productivity of manufacturing, it is impossible to achieve full coverage measurement with existing measurement technologies. Here, we propose imaging ellipsometry-based full wafer coverage metrology (IFM) that acquires spectra of all cell blocks of DRAM devices using large-area imaging ellipsometry measurements with a 22 mm x 22 mm field of view (FOV) and 6.5 μm spatial resolution. A prediction model learned from tens to hundreds of reference data points and the acquired spectra helps generate a massive amount of measurement data exceeding 12 million points per wafer. The vast amount of data generated allows us to extend the spatial coverage of existing thickness measurements, which typically cover only 0.001%, to up to 47%. The proposed method can play a critical role in detecting suspected equipment failures, especially when repetitive and periodic patterns indicating problems appear in the fault map. This novel approach identified and mitigated equipment-induced distributions that negatively impacted product yield that were difficult to observe using conventional metrology. The effectiveness of this approach was verified through measurements performed over 100 steps on the DRAM device.