An apparatus for reticle sub-field thermal control in a lithography system is disclosed. The apparatus includes a clamp configured to fix an object. The clamp includes a plurality of gas distribution features that are spatially arranged in a pattern. The apparatus further includes a gas pressure controller configured to individually control a gas flow rate through each of the plurality of gas distribution features to spatially modulate a gas pressure distribution in a space between the clamp and the object. The gas distribution features include a plurality of trenches or holes arranged in an array form.
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