Preventing deposition on pedestal in semiconductor substrate processing

A heat shield structure for a substrate support in a substrate processing system, the heat shield structure comprising:

• an outer shield configured to surround a stem of the substrate support, wherein the outer shield is further configured to define an inner volume between (i) the outer shield and the stem of the substrate support and (ii) the outer shield and a lower surface of the substrate support;
• at least one heat shield plate configured to be arranged below the substrate support in the inner volume between the outer shield and the lower surface of the substrate support;
• and
• an edge guard extending upward from the outer shield, wherein the edge guard is configured to (i) surround an outer perimeter of the substrate support and (ii) define a gap between the edge guard and the substrate support.