The problem of quantifying LER in the semiconductor industry has become critical with sub-lOOnm node manufacturing. However, routine methods for LER measurement to meet the needs of industry have not been reported. Even the definition for LER has not been defined unambiguously. Also, the length ofthe photoresist structure, on which LER is measured, has not been standardized.Meanwhile, demands for precision in LER calculations have been put forward without accounting for the statistical nature of this parameter. In addition, the algorithms used for feature edge localization when performing LER measurements frequently have free parameters [1] which makes LER estimation ambiguous and does not allow LER comparisons of the same feature. In particular, without taking into account the influence of signal noise in the SEM video, the LER measurements obtained will have contributions from both the measured feature and measuring tool (SEM). The manner in which this measurement is done results in LER values that exceed the true LER. Moreover, when measured objects have aspect ratios exceeding three, it is not clear where along the cross-section height of the object-bottom, top, or some intermediate position-correspond to the measured values. The above issues make the interpretation of obtained results very difficult, and significantly reduces the reliability and value of LER measurement results present in the referenced literature.Nanometrology has developed a new concept for LER measurements that is free of many of the disadvantages mentioned above. It is based on the definition ofLER as "a standard deviation ofthe factual edge position on SEM scan lines from an approximated straight line". Nanometrology's use of a patented algorithm for edge localization of 3D objects results in the measurement of the bottom CD of photoresist structures. Our algorithms do not have free parameters. These algorithms have been incorporated into a CD measurement software package called CD-LER.

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Nanometrology LLC has developed a unique set of solutions for optimizing CD-SEM metrology by improving signal to noise ratio and quantifying scan non-linearity. Examples of Nanometrology's solutions for improved CD-SEM magnification calibration are demonstrated using CD-SEMs from a variety of user sites. To our knowledge, this is the first time that a method to quantify CD-SEM scan non-linearity with precision 0. 1% has been reported. Calibration precision of 0. 1% or better can be achieved on both cross-section and CD-SEMs to enable them to meet or exceed the requirements ofthe ITRS roadmap beyond 2014.