Scatterfield microscopy of 22 nm node patterned defects using visible and DUV light

Smaller patterning dimensions and novel architectures are fostering research into improved methods of defect detection in semiconductor device manufacturing. This experimental study, augmented with simulation, evaluates scatterfield microscopy to enhance defect detectability on two separate 22 nm node intentional defect array wafers. Reducing the illumination wavelength nominally delivers direct improvements to detectability. Precise control of the focus position is also critical for maximizing the defect signal. Engineering of the illumination linear polarization and incident angle are shown to optimize the detection of certain highly directional defects. Scanning electron microscopy verifies that sub 15 nm defects can be measured experimentally using 193 nm wavelength light. Techniques are discussed for taking advantage of the complexities inherent in the scattering of highly directional defects within unidirectional patterning. Although no one single set of parameters can be optimized to detect all defects equally, source optimization is shown to be a realistic path towards improved sensitivity.