Metrology methods for quantifying edge roughness II

Advanced scanning electron and atomic force microscopy techniques have been developed to quantify line-edge and sidewall roughness in patterned resist and silicon features with nanometer scale accuracy. Both techniques are able to follow small changes in the line-edge roughness. The measurement repeatability of the scanning electron and atomic force microscope was characterized and is 0.1 and 0.6 nm, respectively. Any roughness measured in the single layer resist mask (both low-frequency period >100 nm and high-frequency period <5-10 nm) transfers to the underlying silicon throughout a range of pattern transfer conditions. Within the measurement precision, silicon pattern transfer does not appear to decrease or increase the sidewall or line-edge roughness. An attempt to quantify the edge-roughness spatial frequency is discussed. The scanning electron microscope is still recommended over the atomic force microscope for line-edge roughness measurements based on sample throughput.