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The intent of photomask metrology has always been to understand the relationship between the features on the photomask and the design data. This desire has been actuated by the necessity to close the loop between the photomask process steps and the wafer lithography. As the Si technology approaches 0.25 micron and beyond, and the employment of resolution enhancement techniques (OPC and phase shifting mask) to extend the capability of optical lithography, both the photomask critical dimension control and pattern fidelity become important and challenging.Describing the features accurately on the photomask is critical to ensure the quality of photomasks.In this paper, the image processing software is examined for measuring and characterizing key photomask parameters, such as edge roughness, edge defects, isolated defects, corner rounding, and contacts. With this image processing software, the effect of mask processing on those key mask parameters, and the impact of those key parameters on defect printability were characterized. Thus, the application of Image Processing Software will contribute immensely to photomask metrology.

This paper addresses the various issues of Critical Dimension (CD) measurement methodology for mask manufacturing today, and suggests a new approach for standardization of CD process monitors, process improvement/development, and process capability calculations. The sampling method -both number and location -used to measure CD performance has become more crucial to high density, fine line device fabrication.Unfortunately, most of the mask manufacturing industry still use either CD cells or a few special CDs located outside the device area to define how well the reticle's CDs meet the specifications. The number ofCDs in both cases is limited and the locations constant relative to the center of the reticle. This sampling method does not reflect the true range of the CDs due to process radial effects. Therefore, it does not meet customers' expectations of a measure of the reticle's CDs that represent all CDs on the reticle and could cause misinterpretation of product and process performance.As an alternative, for process monitoring, process improvement/development and process capability calculations, we suggest using an "Artifact," a specially designed test mask. This mask allows measurement of a large number of CDs in order to accurately calculate the mask CD control.Using an "Artifact," process engineers can characterize CD patterns in their processes and can make better informed decisions. Unusual patterns in the CDs are more easily recognized with Artifact data, and therefore, can be analyzed more effeciently. By measuring process capability with Artifact CD data, rather than with product CD data, customers and management can be provided with a more accurate measure ofthe CD performance ofa mask manufacturing line. In this paper, the application of Artifact CD data to measuring the capability of a process to meet a CD performance specification will be studied in detail. BACKGROUND

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