Methods and Apparatus for EUV Mask Defect Inspection

Tech ID: 25579 / UC Case 2016-082-0

Brief Description

Since the 1970s, the semiconductor industry has strived to shrink the cost and size of circuit patterns printed onto computer chips in accordance with Moore’s law, doubling the number of transistors on a computer’s central processing unit (CPU) every two years. The introduction of extreme ultraviolet (EUV) lithography, printing chips using 13-nm-wavelength light, opens the way to future generations of smaller, faster, and cheaper semiconductors. There are serious challenges with EUV masks as compared with conventional optical transmissive mask behavior including the multi-layer stack of silicon and molybdenum as a complex reflector of EUV light. Moreover, research into non-optical solutions (e.g. e-beam) is expected to take many years and $100Ms of dollars to reach market maturity. To address these problems, researchers at UC Berkeley and Berkeley Lab worked with the IMPACT+ research team to create a unique optical approach called Optimized Pupil Engineering (OPE) which can detect and characterize mask defects with an 80% enhancement on defect Signal-to-Noise Ratio (SNR) as compared to current systems. This significant improvement reduces false positives and includes pattern and multilayer defects, while it leverages optical-based reticle platforms on the market today. OPE could one day be also used to characterize a variety of semiconductor masks and not limited to EUV lithography.

Suggested uses

  • Semiconductor equipment e.g. EUV mask or photomask inspection tools


  • Demonstrated in silico improvement of mask defect sensitivity (reduces false positives)
  • Low power with efficient use of light means faster inspection times
  • Compatible with most computational algorithms which need strong reference/background signal
  • Leverages industry standard platforms

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  • Neureuther, Andrew R.

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