New ways of looking at masks with the SHARP EUV microscope

Extreme ultraviolet (EUV) microscopy is invaluable for the development of EUV photomasks, providing detailed information for the creation of new mask processes, and reliable feedback for comparison with printing studies. The SHARP microscope at Lawrence Berkeley National Laboratory is dedicated to photomask research. It was developed with forward-looking specifications that make it well suited to the emulation of current EUV lithography tools and a variety of possible future directions. Some recent examples include (1) the demonstration of imaging with 4x numerical aperture values up to 0.625, measuring patterns with feature sizes down to 30-nm half-pitch, created with a tin-based photoresist serving as the absorber. (2) The emulation of complex, free-form illuminators used in source-mask optimization, including grayscale pupil fills. (3) Point by point phase measurement from aerial image measurements using several techniques. (4) Direct observation of non-telecentric, through-focus imaging effects that arise from the angular-dependence of the mask’s multilayer coating properties. In addition, we are preparing to extend SHARP imaging to include anamorphic optics, an emerging area of EUV lithography research.

[1]  Shalin B. Mehta,et al.  Quantitative phase-gradient imaging at high resolution with asymmetric illumination-based differential phase contrast. , 2009, Optics letters.

[2]  Takeshi Isogawa,et al.  Learning from native defects on EUV mask blanks , 2014, Photomask and Next Generation Lithography Mask Technology.

[3]  Patrick P. Naulleau,et al.  Zernike phase contrast microscope for EUV mask inspection , 2014, Advanced Lithography.

[4]  Kenneth A. Goldberg,et al.  Broader view on extreme ultraviolet masks: adding complementary imaging modes to the SHARP microscope , 2015 .

[5]  Kenneth A. Goldberg,et al.  Status of EUV micro-exposure capabilities at the ALS using the 0.3-NA MET optic , 2004, SPIE Advanced Lithography.

[6]  R. Horstmeyer,et al.  Wide-field, high-resolution Fourier ptychographic microscopy , 2013, Nature Photonics.

[7]  Iwao Nishiyama,et al.  Impact of the EUV mask phase response on the asymmetry of Bossung curves as predicted by rigorous EUV mask simulations , 2001, SPIE Advanced Lithography.

[8]  Iacopo Mochi,et al.  Actinic mask imaging: recent results and future directions from the SHARP EUV microscope , 2014, Advanced Lithography.

[9]  Eric M. Gullikson,et al.  Understanding EUV mask blank surface roughness induced LWR and associated roughness requirement , 2015, Advanced Lithography.

[10]  Kenneth A. Goldberg,et al.  Actinic imaging and evaluation of phase structures on EUV lithography masks , 2010 .

[11]  Kenneth A. Goldberg,et al.  Phase-enhanced defect sensitivity for EUV mask inspection , 2014, Photomask Technology.

[12]  Kannan Ramchandran,et al.  Multiplexed coded illumination for Fourier Ptychography with an LED array microscope. , 2014, Biomedical optics express.

[13]  G. Vandenberghe,et al.  Freeform illumination sources: an experimental study of source-mask optimization for 22-nm SRAM cells , 2010, Advanced Lithography.

[14]  L. Tian,et al.  3D differential phase-contrast microscopy with computational illumination using an LED array. , 2014, Optics letters.

[15]  Kenneth A. Goldberg,et al.  A Synchrotron‐Based Fourier‐Synthesis Custom‐Coherence Illuminator , 2004 .

[16]  K. Goldberg,et al.  Actinic imaging and evaluation of phase structures on extreme ultraviolet lithography masks , 2010 .

[17]  Takeshi Isogawa,et al.  Screening EUV mask absorbers for defect repair , 2014, Photomask and Next Generation Lithography Mask Technology.

[18]  Farhad Salmassi,et al.  The SEMATECH high-NA actinic reticle review project (SHARP) EUV mask-imaging microscope , 2013, Photomask Technology.

[19]  Bernhard Kneer,et al.  EUV lithography optics for sub-9nm resolution , 2015, Advanced Lithography.

[20]  Judon Stoeldraijer,et al.  From performance validation to volume introduction of ASML's NXE platform , 2012, Advanced Lithography.

[21]  Sudhar Raghunathan,et al.  Imaging impact of multilayer tuning in EUV masks, experimental validation , 2014, Photomask Technology.

[22]  Takeshi Isogawa,et al.  Repairing native defects on EUV mask blanks , 2014, Photomask Technology.

[23]  Paul van Adrichem,et al.  EUV source-mask optimization for 7nm node and beyond , 2014, Advanced Lithography.

[24]  Pei-yang Yan,et al.  Understanding Bossung curve asymmetry and focus shift effect in EUV lithography , 2002, SPIE Photomask Technology.

[25]  Sascha Migura,et al.  EUV lithography scanner for sub-8nm resolution , 2015, Advanced Lithography.

[26]  Robert John Socha,et al.  An innovative Source-Mask co-Optimization (SMO) method for extending low k1 imaging , 2008, Lithography Asia.

[27]  Kenneth A. Goldberg,et al.  An EUV Fresnel zoneplate mask-imaging microscope for lithography generations reaching 8 nm , 2011, Advanced Lithography.

[28]  Johannes Ruoff.  Impact of mask topography and multilayer stack on high NA imaging of EUV masks , 2010, Photomask Technology.

[29]  Emily Gallagher,et al.  Through-focus EUV multilayer defect repair with nanomachining , 2013, Advanced Lithography.

[30]  Martin Burkhardt,et al.  Best focus shift mechanism for thick masks , 2015, Advanced Lithography.

[31]  Robert Socha,et al.  Simultaneous source mask optimization (SMO) , 2005, Photomask Japan.

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

[33]  Kenneth A. Goldberg,et al.  Enhancing defect detection with Zernike phase contrast in EUV multilayer blank inspection , 2015, Advanced Lithography.

[34]  Kenneth A. Goldberg,et al.  Commissioning an EUV mask microscope for lithography generations reaching 8 nm , 2013, Advanced Lithography.

[35]  Kenneth A. Goldberg,et al.  Experimental measurements of telecentricity errors in high-numerical-aperture extreme ultraviolet mask images , 2014 .