Substrate processing chamber having heated showerhead assembly

A substrate processing chamber, comprising:

• a chamber body;
• an electrically conductive top plate disposed above the chamber body to define interior volume within the chamber body and the electrically conductive top plate;
• a substrate support disposed in a lower portion of the interior volume, wherein the substrate support includes a first heater;
• a gas distribution plate disposed in an upper portion of the interior volume opposite the substrate support, wherein the electrically conductive top plate and the gas distribution plate at least partially define an inner volume of a showerhead assembly;
• a heating apparatus having a second heater and disposed between and spaced apart from the gas distribution plate and the electrically conductive top plate, wherein the second heater is configured to force all gases introduced into the inner volume of the showerhead assembly to flow from above the heating apparatus, around the heating apparatus along an uppermost surface and an outermost sidewall of the heating apparatus, and beneath the heating apparatus into the gas distribution plate, wherein the second heater includes, embedded in a heater plate, one or more second resistive heater elements or one or more second heating lamps;
• a holder having a wall, a flange extending radially inwardly from a lower portion of the wall and coupled to the gas distribution plate, and a flange extending radially outwardly from an upper portion of the wall and disposed between the chamber body and the electrically conductive top plate, wherein the electrically conductive top plate includes an annular channel having two adjacent annular legs on either side of the annular channel which sits atop the flange extending radially outward of the holder;
• a lid plate disposed atop walls of the chamber body and configured to couple a chamber lid to the chamber body;
• an isolator ring disposed about the gas distribution plate, the isolator ring having a body, a first portion extending radially outwardly from an upper portion of the body and disposed atop a portion of the lid plate, and a second portion extending radially inwardly from a lower portion of the body, wherein the second portion is adjacent the gas distribution plate, and wherein a gap is disposed between the gas distribution plate and the second portion to accommodate thermal expansion of the gas distribution plate;
• a washer ring disposed between the holder and the isolator ring to support the holder;
• a radio frequency (RF) power source electrically coupled to the electrically conductive top plate to deliver RF energy to the substrate processing chamber, wherein the electrically conductive top plate is formed of an electrically conductive material;
• and
• an RF gasket disposed between the flange extending radially outwardly and the electrically conductive top plate to facilitate coupling of RF energy from the electrically conductive top plate, through the holder, and into the gas distribution plate.