Local purge within metrology and inspection systems

An apparatus comprising:

• an optical metrology or inspection head that produces a light beam that is incident on a substrate to be optically measured and is received by the optical metrology or inspection head after interacting with the substrate;
• a chuck for holding the substrate, wherein at least one of the chuck and the optical metrology or inspection head is movable to position the substrate at a plurality of measurement positions with respect to the optical metrology or inspection head;
• a purge gas distribution manifold coupled to a purge gas source, the purge gas distribution manifold having at least one port through which the light beam is transmitted, wherein there is relative motion between the purge gas distribution manifold and the substrate when the at least one of the chuck and the optical metrology or inspection head is moved to position the substrate at the plurality of measurement positions with respect to the optical metrology or inspection head, the purge gas distribution manifold having a plurality of apertures through which purge gas is expelled over a top surface of the substrate, wherein the plurality of apertures are distributed over a surface area that is larger than a surface area of the top surface of the substrate to distribute the purge gas over an entirety of the top surface of the substrate at all measurement positions of the substrate with respect to the optical metrology or inspection head.

An apparatus comprising:

• an optical metrology or inspection head that produces a light beam that is incident on a substrate to be optically measured and is received by the optical metrology or inspection head after interacting with the substrate;
• a chuck for holding the substrate, wherein at least one of the chuck and the optical metrology or inspection head is movable to position the substrate at a plurality of measurement positions with respect to the optical metrology or inspection head;
• a ceiling having at least one port through which the light beam is transmitted, the ceiling having a bottom surface that is 25 mm or less from a top surface of the substrate;
• and
• a fence surrounding the substrate on the chuck, wherein the fence is held linearly stationary with respect to the substrate when the at least one of the chuck and the optical metrology or inspection head is moved to position the substrate at the plurality of measurement positions with respect to the optical metrology or inspection head, the fence having one or more apertures below the top surface of the substrate and through which purge gas is expelled over the top surface of the substrate to distribute the purge gas over an entirety of the top surface of the substrate at all measurement positions of the substrate with respect to the optical metrology or inspection head.