| 摘要 |
A scatterometer is used to measure a property of structures on a substrate. A target grating comprises lines arranged periodically over an distance gp in a first direction, each line individually extending a distance gL in a second direction. The grating is illuminated with a spot of radiation and diffracted radiation is detected and used to calculate a measurement of CD, side wall angle and the like. The spot defines a field of view customized to the grating such that an extent fP of the spot in said first direction is greater than distance gp while an extent fL of the spot in said second direction is less than distance gL- The grating may be smaller than conventional gratings. The calculation can be simplified and made more robust, using a mathematical model that assumes that the grating is finite in the first direction but infinite in the second direction. |
