This one looked to me like a line of people, standing at attention.  It’s actually an edge-on view of a comb-like grating structure, seen here as it passes between two rectangular alignment markers.  The people-like shape is due to the weird way the plasma etcher ate away the semiconductor, which you can also see on the side of the alignment marker.  Ideally, the walls should be smooth and vertical - the weird shape here (and the ultra-thin region at the very top of the grating) was probably caused by etching for too long.

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