PROCEEDINGS ARTICLE | September 9, 2013
Proc. SPIE. 8880, Photomask Technology 2013
KEYWORDS: Imaging systems, Sensors, Inspection, Image acquisition, Transmittance, Extreme ultraviolet, Integrated optics, Extreme ultraviolet lithography, Modulation transfer functions, EUV optics
In order to realize EUV mask pattern defect inspection in 16nm node, we have developed new optics on a novel
projection electron microscopy (PEM) and a new inspection system with the new optics and a new mask handling and
imaging units, e.g., a high precision stage, an imaging detector, an imaging processing system, and so. on. This
inspection system enables us to make the inspection in high resolution and high speed as compared with conventional
DUV and EB inspection systems. The new optics on the novel PEM comprises an exposure and an imaging electron
beam optics (EOs). The optics is based on the new design concept to meet the required progress for 1Xnm EUV mask
inspection as compared to the current inspection system for 2Xnm node; The concept employs new techniques to
achieve the features: high energetic electron imaging optics to have low aberration, high transmittance efficiency, e.g.,
on the ratio of exposure current/emitted current, in the exposure and the imaging optics, respectively. The new handling
and imaging system are also based on the design concept of imaging in high resolution by combination operation among
the new optics on the novel PEM, the stage, and the detector. In this paper, we describe the basic performance evaluation
as concerning these features and the operation: 1) MTF inclination in hp44~100nm L/S pattern of the developed
imaging optics. 2) Secondary electron imaging by the integrated optics, i.e., both of the exposure and the imaging EOs,
on the novel PEM, 3) Secondary electron image acquisition operation in still mode on the new inspection system
assembled with the new optics on the novel PEM, the high precision stage, the detector, and so. on.. The results show the
new optics on the novel PEM is capable to meet the required progress for 1Xnm EUV mask inspection and the new
inspection system with the novel PEM operates in much feasibility in the electron image acquisition.
