Hyung-Joo Lee

The study on quantifiable analysis for complex OPCed patterns based on Mask CD SEM contour information

As the design rule becomes continuously smaller, the Hard OPC is being applied to pattern design in semiconductor production. Controllability of hard OPCed pattern’s quality directly affects to the performance of the device and yields of production. Critical Dimension Scanning Electron Microscopy (CD-SEM) is used to accurately confirm the Critical Dimension (CD) quality of the photomask. CD-SEM makes the pattern’s shape image by using secondary electrons information directly from the Mask surface and can measure CD values. Classically the purpose of CD-SEM measurement was to get one dimensional CD values. However it is difficult to guarantee complex hard OPCed pattern’s quality by using only one dimensional CD values because complexity of pattern design has been increased. To confirm and control the quality of hard OPCed pattern, the quality of pattern fidelity must be measured quantitatively. In order to overcome this difficulty we developed a new method to quantitatively evaluate the quality of pattern fidelity using EPE (Edge Placement Error) distance from the overlay between Target Design GDS and SEM GDS contour which is extracted from CD-SEM image. This paper represents how to define and analyze quantitatively the quality of complex hard OPCed pattern.

Novel CD-SEM measurement methodology for complex OPCed patterns

As design rules of lithography shrink: accuracy and precision of Critical Dimension (CD) and controllability of hard OPCed patterns are required in semiconductor production. Critical Dimension Scanning Electron Microscopes (CD SEM) are essential tools to confirm the quality of a mask such as CD control; CD uniformity and CD mean to target (MTT). Basically, Repeatability and Reproducibility (R and R) performance depends on the length of Region of Interest (ROI). Therefore, the measured CD can easily fluctuate in cases of extremely narrow regions of OPCed patterns. With that premise, it is very difficult to define MTT and uniformity of complex OPCed masks using the conventional SEM measurement approach. To overcome these difficulties, we evaluated Design Based Metrology (DBM) using Large Field Of View (LFOV) of CD-SEM. DBM can standardize measurement points and positions within LFOV based on the inflection/jog of OPCed patterns. Thus, DBM has realized several thousand multi ROI measurements with average CD. This new measurement technique can remove local CD errors and improved statistical methodology of the entire mask to enhance the representativeness of global CD uniformity. With this study we confirmed this new technique as a more reliable methodology in complex OPCed patterns compared to conventional technology. This paper summarizes the experiments of DBM with LFOV using various types of the patterns and compares them with current CD SEM methods.

2D measurement using CD SEM for arbitrarily shaped patterns

As the design rule of lithography becomes smaller, accuracy and precision in Critical Dimension (CD) and controllability of pattern-shape are required in semiconductor production. Critical Dimension Scanning Electron Microscope (CD SEM) is an essential tool to confirm the quality of the mask such as CD control, CD uniformity and CD mean to target (MTT). Unfortunately, in the case of extremely rounded region of arbitrary enclosed patterns, CD fluctuation depending on Region of Interest (ROI) is very serious problem in Mask CD control, so that it decreases the yield. In order to overcome this situation, we have been developing 2-dimensonal (2D) method with system makers and comparing CD performance between mask and wafer using enclosed arbitrary patterns. In this paper, we summarized the results of our evaluation that compare error budget between 1-dimensonal (1D) and 2D data using CD SEM and other optical metrology systems.