Phase Defect Observation Using Extreme Ultraviolet Microscope

Abstract

An aerial image mask inspection system for extreme ultraviolet lithography (EUVL) is developed. This system consists of microscopes using the same wavelength of light as is used for the exposure and produces a magnified image of defects on a mask. Using this microscope, amplitude defects on finished masks and phase defects on glass substrates are observed. A phase defect was formed by a multilayer coated on a line pattern with 5 nm high and 90 nm wide on a glass substrate. Although the defect detected is made beforehand, it is detected by reflection of the light which penetrated the multilayer. These results show that it is possible to detect the internal reflectivity distribution without depending on surface perturbations. We tried to observe “pit defects”, but it was not possible to observe these at this time. The pit defects, such as scratches on glass substrates may not become defects depending on the process of formation of the multilayer.

Imaging of extreme-ultraviolet mask patterns using coherent extreme-ultraviolet scatterometry microscope based on coherent diffraction imaging

“…The repair of the defect feature is also important. As a bright-field microscope, we have developed an EUV microscope using Schwarzschild optics and an x-ray zooming tube 8,9 that is installed at the NewSUBARU synchrotron facility. An EUV mask consists of a glass substrate (150 Â 150) mm 2 in size, a Mo/Si multilayer, and absorber patterns.…”

Demonstrating 30-nm spatial resolution of three-multilayer-mirror objective for extreme ultraviolet microscopy: Imaging test by observing lithography mask

“…The Schwarzschild objective, 1,2) a representative mirror objective for microscopy, can be configured to have a NA of over 0.2, 3) which is greater by one order of magnitude than that of diffraction zone plates commonly used in the soft X-ray region. 4,5) The Schwarzschild design incorporating two concentric mirrors has thus been applied to microscopy for tissue imaging [6][7][8] and lithography mask inspection, [9][10][11] where a high spatial resolution close to the diffraction limit is required. This high-NA system is also useful for the formation of a brighter image using a laboratory-based light sourcea laser produced plasma (LPP), 12,13) with relatively low luminance, since the system can collect light over a large solid angle.…”

The Photopolymer Science and Technology Award

“…SC 30X optics was employed as an imaging optics. In this program the phase defect (which is a defect inside the Mo/Si multilayer) is observed world first, and evaluated by the threshold of the defect-height and -width of the programmed defects which are printable and nonprintable [31][32][33][34][35][36].…”