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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.Key word: CD SEM, 2D, AREA MEASUREMENT, MTT, UNIFORMITY INRODUCTIONBasically, the quality of a mask is determined by the degree of equality with design data, i.e. pattern shape and CD target of the mask should be the same as those of its design. Various proposals of Resolution Enhancement Technology (RET), however, were made and applied to the recent mask technology. With the RET know-how being developed, the mask pattern shape is getting complicated due to the deformed, shrunk and rounded patterns.In case of extremely narrow region of arbitrarily shaped patterns, the measured CD can easily be fluctuated depending on setting of Region of Interest (ROI) in a rounded area. It is very difficult to define real error budget and MTT of masks using the conventional CD SEM systems which are based on 1D measurement algorithm. To overcome these difficulties, it is needed to analyze the CD with a 2D method and interpret 2D data as 1D format.The conventional CD SEM systems supply area measurement function only for simple contact and dot patterns, but cannot support 2D function for complex and arbitrarily shaped patterns. In order to get 2D data of arbitrarily shaped patterns, we have shared ideas and concepts with system manufacturers. As a result, we construct a system that can measure the area of arbitrarily shaped patterns, and evaluate a method to analyze 2D data from the 1D point of view.This paper summarizes the evaluation results that compare error budget between 1D and 2D data using CD SEM and other optical metrology systems.

Inspection of aggressive Optical Proximity Correction (OPC) designs, improvement of usable sensitivity, and reduction of cost of ownership are the three major challenges for today's mask inspection methodologies. In this paper we will discuss using aerial-plane inspection and wafer-plane inspection as novel approaches to address these challenges for advanced reticles.Wafer-plane inspection (WPI) and aerial-plane inspection (API) are two lithographic inspection modes. This suite of new inspection modes is based on high resolution reflected and transmitted light images in the reticle plane. These images together with scanner parameters are used to generate the aerial plane image using either vector or scalar models. Then information about the resist is applied to complete construction of the wafer plane image. API reports defects based on intensity differences between test and reference images at the aerial plane, whereas WPI applies a resist model to the aerial image to enhance discrimination between printable and non-printable defects at the wafer plane.The combination of WPI and API along with the industry standard Reticle Plane Inspection (RPI) is designed to handle complex OPC features, improve usable sensitivity and reduce the cost of ownership. This paper will explore the application of aerial-plane and wafer-plane die-to-die inspections on advanced reticles. Inspection sensitivity, inspectability, and comparison with Aerial Imaging Measurement System (AIMS TM[1] ) or wafer-print-line will be analyzed. Most importantly, the implementation strategy of a combination of WPI and API along with RPI leading-edge mask manufacturing will be discussed.

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