For evaluation of high-end photomasks for under 65 nm design rule wafers, Holon has developed EMU-Navi, optional software for Holon EMU-series mask Critical Dimension Scanning Electron Microscope (CD-SEM), which helps automated and accurate CD measurement on high-end masks with complicated patterns after optical proximity correction (OPC) processing. As CD measurement preparation, the user makes one file indicating points to measure and the other containing template bitmaps from Electron beam (EB) writing output format data, which are to be used for pattern matching to SEM images. During measurement, EMU-Navi compares each SEM image to the corresponding template bitmap in order to have EMU move its stage accurately to the point to measure where EMU measures the CD in the SEM image. This function is especially effective in positioning complicated features in SEM images. After measurement, the user can examine whether mask patterns have been precisely processed. In this manuscript, the flow of CD measurement procedure is described.
Recently, in Critical Dimension (CD) measurement on high-end masks, Optical Proximity Correction (OPC) pattern measurement is on increase and it has become important to measure angled lines. In CD searching on a CAD layout viewer, the exact CD values can be detected for the OPC patterns because they consist of a lot of rectangles. While, the CD values for angled lines have not been detected in it. Meanwhile the mask Critical Dimension Scanning Electron Microscope (CD-SEM) can measure angled lines, but measurement accuracy cannot be verified because there is no reference standard sample available for calibration of the CD values. In this study, we made the prototype of a standard sample for CD measurement with 0 degree and 45 degree angled lines by using VLSI Standards Inc. Nano Lattice Standard. The shape is the same as 6025 mask. We measured CDs of angled lines of the above sample using Holon EMU-260 and examined the calibration
method. We are going to discuss the CD marking method on a CAD layout viewer in order to automate measurement of angled lines in near future.