Spin chuck including edge ring

Apparatus for treating a substrate includes a stationary plate assembly including liquid nozzles to direct liquid at an edge of the substrate during treatment. A chuck assembly includes a chuck body arranged below and radially outside of the stationary plate assembly and rotatable relative to the stationary plate assembly. An edge ring is attached to the chuck body and defines a radially inner surface extending in an axial direction above and below a plane including the substrate. The edge ring is located radially outside of a radially outer edge of the substrate along an entire surface of the edge ring. A plurality of pins is movable between a clamping position to engage the radially outer edge of the substrate and an idle position.