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Measurement of critical dimensions and vertical shape of features in semiconductor manufacturing is a critical task. Optical scatterometry proved capable of providing such measurements. In this paper, a software tool to model scatterometry was developed. Rigorous coupled wavelength analysis (RCWA) is used as a physical model. This software does not use fitting coefficients of any specific equipment and therefore is useful in understanding, analysis and optimization of measurements of specific patterns and potential sensitivity of methods and systems to process variation. Special attention was given to improve the accuracy and throughput of simulation; results of comparison to another software proved advantages of the developed software.

As device feature size reduction continues, requirements for Critical Dimension (CD) metrology tools are becoming stricter. For sub-32 nm node, it is important to establish a CD-SEM tool management system with higher sensitivity for tool fluctuation and short Turn around Time (TAT). We have developed a new image sharpness monitoring method, PG monitor. The key feature of this monitoring method is the quantification of tool-induced image sharpness deterioration. The image sharpness index is calculated by a convolution method of image sharpness deterioration function caused by SEM optics feature. The sensitivity of this methodology was tested by the alteration of the beam diameter using astigmatism. PG monitor result can be related to the beam diameter variation that causes CD variation through image sharpness. PG monitor can detect the slight image sharpness change that cannot be noticed by engineer's visual check. Furthermore, PG monitor was applied to tool matching and long-term stability monitoring for multiple tools. As a result, PG monitor was found to have sufficient sensitivity to CD variation in tool matching and long-term stability assessment. The investigation showed that PG monitor can detect CD variation equivalent to ~ 0.1 nm. The CD-SEM tool management system using PG monitor is effective for CD metrology in production.

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