An apparatus for reducing by-product formation in a semiconductor wafer-processing chamber. In a first embodiment, the apparatus comprises a chuck having a chucking electrode and a radially extending peripheral flange. A collar is disposed over the peripheral flange defining a first gap therebetween, and circumscribes the chuck. A heater element is embedded within the collar and adapted for connection to a power source. In a second embodiment, the apparatus comprises a chuck having a chucking electrode and a radially extending peripheral flange, and a collar having a heater element embedded therein. The collar is disposed over the peripheral flange to define a gap therebetween, and circumscribes the chuck. Moreover, a pedestal having a gas delivery system therein is disposed below the chuck and collar. In a third embodiment, the apparatus comprises a chuck having a chucking electrode and a radially extending peripheral flange, a collar, and a waste ring having a heater element embedded therein. The waste ring is disposed over the peripheral flange defining a gap therebetween, and circumscribes the chuck. The collar is chucked to the waste ring, and the waste ring is chucked to a pedestal support. Moreover, the waste ring and pedestal each have a gas delivery system therein for regulating the temperature of the collar.