Microcolumn with variable axis lens for large scan fields and pixel numbers
A microcolumn is presented containing a variable axis lens optimized for large scan fields and pixel numbers with minimal probe sizes for the deflected beam. At beam energy of 1 keV and a working distance of 38 mm the magnifying column can address scan fields of more than 7 x 7 mm(2) employing dynamic correction. Simulations of the design predict a probe diameter of 75 nm on axis up to similar to 1 mu m for a beam being deflected 5 mm of axis, assuming a field emission source. Within a scan field of 3 x 3 mm(2) this microcolumn could address over 1 gigapixels of less than 100 nm in size. Tests of the column, using the 135 nm probe of a SEM as the source, resulted in a beam size of similar to 720 nm on axis and up to 1.1 mu m for a beam deflected 5 mm off axis, consistent with simulations. (C) 2011 Elsevier B.V. All rights reserved.