A wafer carrier includes a body defining a central axis, a generally planar top surface perpendicular to the central axis, and pockets recessed below the top surface for receiving wafers. The body can include a lip projecting upwardly around the periphery of the top surface. The lip can define a lip surface sloping upwardly from the planar top surface in a radially outward direction away from the central axis. The body can be adapted for mounting on a spindle of a processing apparatus so that the central axis of the body is coaxial with the spindle. The lip can improve the pattern of gas flow over the top surface of the wafer carrier.