Improvement of total quality on EUV mask blanks toward volume production

Abstract. Influences of phase defect structures on extreme ultraviolet (EUV) microscope images were examined. Phase defects on the bottom of a multilayer (ML) do not always propagate vertically upward to the ML's top surface. For this study, two types of masks were prepared. One was an EUV blank with programmed phase defects made of lines in order to analyze the inclination angle of the phase defects. The other was an EUV mask that consists of programmed dot type phase defects 80 nm wide and 2.4 nm high with absorber patterns of halfpitch 88-nm lines-and-spaces. The positions of the phase defects relative to the absorber lines were designed to be shifted accordingly. Transmission electron microscope observations revealed that the line type phase defects starting from the bottom surface of the ML propagated toward the ML's top surface, while inclined toward the center of the EUV blank. At the distances of 0 and 66 mm from the center of the EUV blank, the inclination angles varied from 0 to 4 deg. The impacts of the inclination angles on EUV microscope images were significant even though the positions of the phase defect relative to the absorber line, as measured by a scanning probe microscope, were the same. © 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.

Section: Introductionmentioning

confidence: 99%

Observation of phase defect on extreme ultraviolet mask using an extreme ultraviolet microscope

Amano¹,

Terasawa²,

Watanabe³

et al. 2014

“…However, the path to establish the EUVL is not without technical difficulties. For example, a lack of sufficient light-source power, particle-free mask handling, defect-free and flat mask blanks, [1][2][3][4][5] and resist material development 6,7 all need to be addressed. From the viewpoint of EUV mask fabrication, mask pattern defect inspection [8][9][10][11] and repair [12][13][14] are some of the most demanding tasks to be dealt with.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the phase defect size using a scanning probe microscope and at-wavelength inspection tool

Amano¹,

Abe

2015

Abstract. Predicting the lithography impact of a phase defect embedded in a mask used for extreme ultraviolet lithography on the printed image on wafer is a challenging task. In this study, two types of measurement tools were employed to characterize the phase defects. The prior measurement tool was a scanning probe microscope used for measuring the surface topography of phase defects, and the second was an at-wavelength darkfield inspection tool capable of capturing a phase defect and then calculating the defect detection signal intensity (DSI) from those images. A programmed phase defect mask with various lateral sizes and depths was prepared. The sizes and DSIs were then measured. The measured data indicated that the DSIs did not directly correlate with the phase defect volumes. The influence of the phase defects on the printed image on a wafer was also calculated using a lithography simulator. The simulation results indicated that the printed critical dimensions (CDs) were strongly correlated with the DSIs rather than with the phase defect volumes. As a result, the influence of the phase defect on the printed CD can be predicted from the values of the DSIs. © 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.

“…However, the path to establish the EUVL is not without technical difficulties. For example, the lack of sufficient light-source power, particle-free mask handling, defect-free and flat mask blanks, [1][2][3][4][5] and resist material development 6,7 need to be resolved. From the viewpoint of EUV mask fabrication, mask pattern defect inspection [8][9][10] and repair [11][12][13] are some of the most demanding tasks to be addressed.…”

Section: Introductionmentioning

confidence: 99%

Phase defect detection signal analysis: dependence of defect size variation

Amano¹,

Watanabe²,

Abe

2015

Abstract. The influence of the size or volume of the phase defect embedded in the extreme ultraviolet mask on wafer printability by scanning probe microscope (SPM) is well studied. However, only a few experimental results on the measurement accuracy of the phase defect size have been reported. Therefore, in this study, the measurement repeatability of the phase defect volume using SPM and the influence of the defect volume distribution on defect detection signal intensity (DSI) using an at-wavelength dark-field defect inspection tool were examined. A programmed phase defect mask was prepared, and a defect size measurement repeatability test was conducted using an SPM. As a result, the variation of the measured volume due to the measurement repeatability was much smaller than that of the defect-to-defect variation. This result indicates that measuring the volume of each phase defect is necessary in order to evaluate the defect detection yield using a phase defect inspection tool and wafer printability. In addition, the images of phase defects were captured using an at-wavelength dark-field inspection tool from which the defect DSIs were calculated. The DSI showed a direct correlation with the defect volume. © 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.