| 摘要 |
The specification describes a spatial autocorrelation technique for measuring ultrafine linewidths of the order of tens of nanometers and less. Two beams of actinic radiation are used to draw parallel lines in a resist material. Each beam is adjusted to deliver a dose below the threshold for printing a feature, but when combined the dose is sufficient to print a line feature. During exposure the separation between beams is changed in controlled spatial steps until the beams cross one another. During some of the steps at least a portion of the beams will be coincident thus producing printable features. The resist is developed to print the features where the beams are coincident. The lines are below the resolving power of an optical microscope but their presence is discernible. The width of the line is determined from the number of lines printed and the size of the spatial steps.
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