Apparatus for improving substrate temperature uniformity in a substrate processing chamber are provided herein. In some embodiments, a substrate support processing chamber may include a chamber body having a bottom portion and a sidewall having a slit valve opening to load and unload substrates, a pin lift mechanism, disposed in a pin lift mechanism opening formed in the bottom portion of the chamber body, having a plurality of substrate support pins coupled to the pin lift mechanism, a movable substrate support heater having substrate support portion and a shaft, and a cover plate disposed about the shaft of the movable substrate support, wherein the cover plate covers the pin lift mechanism and pin lift mechanism opening.