Orientation dependence of linewidth variation in sub- Gaussian e-beam lithography and its correction
Primitive arrangements in the first quadrant of a zone plate pattern generated by custom software.
(a) Square pattern of dose variation as viewed in a SEM micrograph of a zone plate exposure. (b) A high magnification SEM micrograph shows the square patterns are collective angular dose/linewidth variations. [(c) and (d)] Differential interference contrast (DIC) micrographs of the zone plates exposed with the patterns generated by (c) custom software and (d) JEOL software.
(a) Trapezoid filling scheme of the JBX-9300FS. (b) Linewidth variation is due to the nonuniform filling near the primitive boundaries. (c) Correction of ODLWV effect by segmenting a parallelogram into three parts. The outer parts, whose widths are multiple of the shot pitch, are exposed at regular dose. The insert is exposed at a corrected dose which accounts for the missing spots. (d) Double-insert correction scheme, which is especially good for exposure of very thin lines. The dose for the two inserts (areas in boundaries BCFG with shadowed shots and IJKL with bold shots) is corrected by counting the excess shot spot area.
Linewidth in nanometers of the underdosed part of the lines drawn at various angles. This figure shows the effect with shot pitch in a address grid.
SEM micrograph of a zone plate pattern exposure and simulation of the same. The simulation is based on the data in Fig. 4.
DIC micrographs of the test exposure. All the patterns are exposed with a shot pitch, except (d) and (h), whose shot pitch is . The arrows in (b) and (f) show the locations of the imperfect correction.
Solution to increase the minimal dose of corrected pattern. (a) Original pattern. (b) Pattern corrected with single-insert scheme which cuts the minimal dose by half. (c) By broadening the insert by two shot pitches, the minimal dose is kept unchanged. (d) A modified double-insert scheme, which raises the minimal dose required by original double-insert scheme.
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