Substrate pedestal including backside gas-delivery tube

A substrate pedestal, comprising:

• a platen comprising a ceramic material and having an upper surface configured to support a substrate during processing;
• a stem comprising a ceramic material and having an upper-stem flange upon which the platen is mechanically coupled, the stem having an interior portion;
• and
• a backside gas-delivery tube comprising a ceramic material, the backside gas-delivery tube being is located in the interior portion of the stem, the backside gas-delivery tube including an upper gas-tube flange that is located between a lower surface of the platen and an upper surface of the upper-stem flange, the backside gas-delivery tube being configured to be in fluid communication with at least one backside-gas passage of the platen, the backside gas-delivery tube being configured to supply a backside gas to a region below and in fluidic contact with at least a central portion of a lower surface of the substrate during processing, the backside gas-delivery tube further including a plurality of openings in the upper gas-tube flange having a plurality of respective electrical connections that extend through the upper gas-tube flange.