A substrate support assembly includes a plate structure and an insulator structure. The plate structure includes an upper plate and a lower plate. The lower plate includes a lower plate structure surface. The insulator structure is disposed beneath the plate structure. The insulator structure includes a lower insulator structure surface and an upper insulator structure surface. A first portion of the upper insulator structure surface is recessed with respect to a second portion of the upper insulator structure surface. The first portion of the upper insulator structure surface forms an interior volume with the lower plate structure surface.