System and methods for a radiant heat cap in a semiconductor wafer reactor

A reaction apparatus for contacting a process gas on a semiconductor wafer during a wafering process, the semiconductor wafer defining a center region, the reaction apparatus comprising:

• an upper dome;
• a lower dome attached to the upper dome, the upper dome and the lower dome defining a reaction chamber;
• a susceptor for supporting the semiconductor wafer within the reaction chamber, wherein the susceptor is supported by a shaft;
• a cap positioned on the shaft within the reaction chamber for reducing heat absorbed by the center region of the semiconductor wafer, the cap attached to a first end of the shaft, the cap comprising:
• a tube defining a tube outer diameter and a tube inner diameter larger than a shaft diameter of the shaft, wherein the tube circumscribes the first end of the shaft;
• and
• a disc attached to the tube, the disc defining a disc outer diameter, the disc outer diameter being greater than the tube outer diameter, wherein the disc is generally opaque to absorb radiant heat and is positioned to block the radiant heat from heating the center region of the semiconductor wafer, wherein the disc is positioned a distance below the center region of the semiconductor wafer and the susceptor;
• and
• a temperature sensor mounted on the reaction chamber, the temperature sensor being separate from the cap, the cap being free of temperature sensors.