Observation of EUVL mask using coherent EUV scatterometry microscope with high-harmonic-generation EUV source

In extreme ultraviolet (EUV) lithography, development of review tools for EUV mask pattern and phase defect at working wavelength of 13.5 nm is required. The EUV mask is composed of an absorber pattern (50 – 70 nm thick) and Mo/Si multilayer (280 nm thick) on a glass substrate. This mask pattern seems three-dimensional (3D) structure. This 3D structure would modulate EUV reflection phase, which would cause focus and pattern shifts. Thus, EUV phase imaging is important to evaluate this phase modulation. We have developed coherent EUV scatterometry microscope (CSM), which is a simple microscope without objective optics. EUV phase and intensity image are reconstructed with diffraction images by ptychography with coherent EUV illumination. The high-harmonic-generation (HHG) EUV source was employed for standalone CSM system. In this study, we updated HHG system of pump-laser reduction and gas-pressure control. Two types of EUV mask absorber patterns were observed. An 88-nm lines-and-spaces and a cross-line patterns were clearly reconstructed by ptychography. In addition, a natural defect with 2-μm diameter on the cross-line was well reconstructed. This demonstrated the high capability of the standalone CSM, which system will be used in the factories, such as mask shops and semiconductor fabrication plants.

[1]  Iwao Nishiyama,et al.  Analysis of Printability of Scratch Defect on Reflective Mask in Extreme Ultraviolet Lithography , 2006 .

[2]  J. Miao,et al.  Extending the methodology of X-ray crystallography to allow imaging of micrometre-sized non-crystalline specimens , 1999, Nature.

[3]  Toshihiko Tanaka,et al.  Actinic Phase Defect Detection for Extreme Ultraviolet Lithography Mask with Absorber Patterns , 2010 .

[4]  Kenichi Takahara,et al.  A novel defect detection optical system using 199-nm light source for EUVL mask , 2010, Advanced Lithography.

[5]  Takeo Watanabe,et al.  EUV mask observations using a coherent EUV scatterometry microscope with a high-harmonic-generation source , 2015, Other Conferences.

[6]  Takeo Watanabe,et al.  Phase imaging of EUV masks using a lensless EUV microscope , 2013, Photomask and Next Generation Lithography Mask Technology.

[7]  Katsumi Midorikawa,et al.  Development of coherent EUV scatterometry microscope with high-order harmonic for EUV mask inspection , 2013, Optics & Photonics - Optical Engineering + Applications.

[8]  Naoya Hayashi,et al.  Direct phase-shift measurement of thin and thick absorber EUV masks , 2012, Other Conferences.

[9]  Iacopo Mochi,et al.  Assist features: placement, impact, and relevance for EUV imaging , 2016, SPIE Advanced Lithography.

[10]  J. Miao,et al.  Phase retrieval from the magnitude of the Fourier transforms of nonperiodic objects , 1998 .

[11]  Kenneth A. Goldberg,et al.  Quantitative evaluation of mask phase defects from through-focus EUV aerial images , 2011, Advanced Lithography.

[12]  M. Murnane,et al.  Tabletop nanometer extreme ultraviolet imaging in an extended reflection mode using coherent Fresnel ptychography , 2013, 1312.2049.

[13]  Farhad Salmassi,et al.  EUVL alternating phase shift mask , 2011, Advanced Lithography.

[14]  C. Winterfeldt,et al.  Colloquium: Optimal control of high-harmonic generation , 2008 .

[15]  Katsumi Midorikawa,et al.  Dramatic enhancement of high-order harmonic generation. , 2007, Physical review letters.

[16]  Takeo Watanabe,et al.  Characterization of small phase defects using a micro-coherent extreme ultraviolet scatterometry microscope , 2014 .

[17]  J. Rodenburg,et al.  A phase retrieval algorithm for shifting illumination , 2004 .

[18]  K. Midorikawa,et al.  Single-shot spatial-coherence measurement of 13 nm high-order harmonic beam by a Young's double-slit measurement. , 2007, Optics letters.

[19]  J. Rodenburg,et al.  Ptychographic electron microscopy using high-angle dark-field scattering for sub-nanometre resolution imaging , 2012, Nature Communications.

[20]  Katsumi Midorikawa,et al.  10mJ class femtosecond optical parametric amplifier for generating soft x-ray harmonics , 2008 .

[21]  Takeo Watanabe,et al.  Study of Critical Dimensions of Printable Phase Defects Using an Extreme Ultraviolet Microscope , 2009 .

[22]  O. Bunk,et al.  High-Resolution Scanning X-ray Diffraction Microscopy , 2008, Science.

[23]  Takeo Watanabe,et al.  Phase Imaging of Extreme-Ultraviolet Mask Using Coherent Extreme-Ultraviolet Scatterometry Microscope , 2013 .

[24]  M. Ware,et al.  Direct observation of laser filamentation in high-order harmonic generation. , 2006, Optics letters.

[25]  Kenneth A. Goldberg,et al.  Printability of native blank defects and programmed defects and their stack structures , 2011, Photomask Technology.

[26]  Naoya Hayashi,et al.  Phase-shifting effect of thin-absorber EUV masks , 2011, Photomask Technology.

[27]  T. Last,et al.  Experimental verification of AI decomposition-based source optimization for M1 two-bar building blocks in 0.33NA EUVL , 2016, Photomask Technology.

[28]  Osamu Suga,et al.  Impact of mask absorber properties on printability in EUV lithography , 2007, SPIE Photomask Technology.