Impact of long-period line-edge roughness (LER) on accuracy in critical dimension (CD) measurement and a new guideline for cd metrology

Line-edge roughness (LER) has been characterized for various lithography and etching processes, and its impact on device performance has been discussed. [1-3]. We have investigated characteristics of the spatial-frequency of LER and shown that the long-period components of LER significantly affects the variation in gate length of MOSFET, namely, transistor performances. To evaluate the LER influence described above, a new guideline for LER metrology has been introduced [4]4. However, influence of long-period LER on CD measurement has not been discussed. Long-period LER causes long-period line-width roughness (LWR), which means deviation of local CD (ΔCD) from the average CD(Fig. 1).