An exemplary apparatus includes a metal furnace tube having an open first end and an opposite second end. The metal furnace tube includes an inner chamber, a fluid inlet to intake a fluid into the inner chamber, and a fluid outlet to exhaust the fluid from the inner chamber, the inner chamber to support a plurality of substrates within the metal furnace tube. The apparatus includes a first base plate or flange back plate coupling the fluid inlet to the inner chamber; a second base plate or flange back plate coupling the fluid outlet to the inner chamber; and a furnace includes a heater to heat the metal furnace tube, the metal furnace tube being mounted within the furnace and the heater being disposed outside the metal furnace tube.