| CPC H01L 21/681 (2013.01) | 11 Claims |
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1. An overlay measurement device for measuring an error between a first overlay mark and a second overlay mark respectively formed on different layers of a wafer, the overlay measurement device comprising:
a light source;
an objective lens that concentrates a beam from the light source on a measurement position of the wafer, and gathers the beam being reflected in the measurement positon;
a lens focus actuator that adjusts a distance between the objective lens and the wafer such that a focus surface is placed at the first overlay mark or the second overlay mark;
an auto focus module that adjusts a focus by adjusting the lens focus actuator;
a detector for obtaining an image of the first overlay mark or an image of the second overlay mark;
a transmission and receipt part; and
a processor connecting to the transmission and receipt part electrically,
wherein the processor is configured to:
obtain data transmitted from a user terminal through the transmission and receipt part,
analyze a recipe included in the data,
perform optimization of measurement options of a wafer, based on the recipe, after the recipe is analyzed,
perform a focus scan at one site by controlling the auto focus module,
determine a focus measurement area based on the performed focus scan,
calculate statistical values for a plurality of parameters by moving the focus by one step within the determined focus measurement area for each site,
apply a weight respectively to the calculated statistical values, and
perform a focus optimization process of selecting a focus where a total of the statistical values to which the weight is applied respectively is a minimum value as a focus of the auto focus module.
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