Novel method for dimensional measurements of nanorelief elements based on electron probe defocusing in a scanning electron microscope

Abstract

In this paper, we propose a new method of measuring parameters of features of relief nanostructures. The method is based on the dependence of the length of the control intervals between certain bend points on video signal curves on the effective diameter of an electron probe. These video signals are obtained in the secondary electron imaging mode of a scanning electron microscope. Variation of the effective diameter of the electron probe is achieved by changing the microscope focus. The above dependences can be approximated by linear functions for a number of relief nanostructures, including the pitch structures of single crystal silicon with various profiles of the relief features, resist masks, etc. For appropriate choice of control intervals, the use of a constant term in such linear functions enables one to determine the size of relief features.

Development and characterisation of a new line width reference material

“…Several CD reference materials or standards have been developed [13][14][15][16][17][18][19][20][21][22]. Many of them are made of crystal silicon [13][14][15][16][17][18][19], and some are made of CoG (Chrome-on-glass) or MoSi (molybdenum silicide) usually applied as reference photomask line width standards [20][21][22].…”

“…Several CD reference materials or standards have been developed [13][14][15][16][17][18][19][20][21][22]. Many of them are made of crystal silicon [13][14][15][16][17][18][19], and some are made of CoG (Chrome-on-glass) or MoSi (molybdenum silicide) usually applied as reference photomask line width standards [20][21][22]. The crystal silicon samples are usually fabricated by the anisotropic etching of monosilicon, which offers a well-defined orientation of the feature surface coinciding with crystallographic planes.…”

“…Remarkable progress in applying this idea is the development of SCCDRM (single crystal critical dimension reference material) by Dixson et al [13][14][15][16][17], where the specimen is fabricated using a lattice plane selective etch on (1 1 0) silicon, exhibiting near vertical sidewalls and high uniformity. Another sample to be mentioned is the MShPS-2.0 K developed by Rakov et al [18,19]. Their relief structure is formed by anisotropic etching of the silicon surface {1 0 0} along the {1 1 1} crystallographic plane.…”