Extreme ultraviolet mask defect inspection with a half pitch 16-nm node using simulated projection electron microscope images

Abstract

Abstract. According to an International Technology Roadmap for Semiconductors (ITRS-2012) update, the sensitivity requirement for an extreme ultraviolet (EUV) mask pattern inspection system is to be less than 18 nm for half pitch (hp) 16-nm node devices. The inspection sensitivity of extrusion and intrusion defects on hp 64-nm line-andspace patterned EUV mask were investigated using simulated projection electron microscope (PEM) images. The obtained defect images showed that the optimization of current density and image processing techniques were essential for the detection of defects. Extrusion and intrusion defects 16 nm in size were detected on images formed by 3000 electrons per pixel. The landing energy also greatly influenced the defect detection efficiency. These influences were different for extrusion and intrusion defects. These results were in good agreement with experimentally obtained yield curves of the mask materials and the elevation angles of the defects. These results suggest that the PEM technique has a potential to detect 16-nm size defects on an hp 64-nm patterned EUV mask. © The Authors.Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Impact of B4C capping layer for extreme ultraviolet mask on the sensitivity of patterned mask inspection using a projection electron microscope

“…[4][5][6][7] In order to accelerate this development program, the optimal inspection condition was investigated by using a computer simulation. [8][9][10][11] We already reported that 16-nm-sized defect on hp 64-nm mask pattern was detectable with a 10-times higher signal intensity than that of the standard deviation of the background intensity level by using the PEM technique when the Ru capped multilayer (ML) was used in EUV mask, 9 and the simulated detectability was found to be in good agreement with experimental results. 7 It was also found that the sensitivity of defect detection was predictable by measuring the secondary electron yield curves of a Ta-based absorber layer and Ru-capped ML.…”

“…The authors had already reported that a similar phenomenon was observed in the case of Ru-capped ML. 9 In the case of the intrusion defect, because the aspect ratio of the smaller defect becomes higher, the elevation angle of the defect becomes narrower as defect size gets smaller. Therefore, the signal from the bottom of the intrusion defect becomes weaker as shown in Fig.…”

“…Image processing operations were applied to the simulated image to enhance the detect signal intensities. 6,9 The detailed simulation conditions were described earlier. shows the experimental SEEC difference (which is calculated by subtracting the SEEC of these MLs from that of the absorber layer) as a function of incident beam energy.…”

“…This result suggests that the EUV mask structure affects the optimal inspection condition. 9,10 As a capping layer, nondoped Si, 11-nm thick, had been investigated. However, because of its disadvantages, such as prone to oxidation, low chemical resistance, and low etch selectivity, 2.5-nm-thick Ru has been used to replace Si.…”

Investigation of defect detectability for extreme ultraviolet patterned mask using two types of high-throughput electron-beam inspection systems

“…[5][6][7][8] In the pattern inspection system, the signal-to-noise ratio (SNR) is another critical parameter as it affects the defect detection sensitivity and minimizes false defect detection. 9 At higher illumination beam current densities, where a larger number of electrons per pixel is obtained on the detector, a higher SNR is achieved. However, high current densities of a focused illumination beam degrade the resolution due to blurring caused by the space charge effect.…”