Apparatuses for annealing semiconductor substrates, such as a batch processing chamber, are provided herein. The batch processing chamber includes a chamber body enclosing an internal volume, a cassette moveably disposed within the internal volume and a plug coupled to a bottom wall of the cassette. The chamber body has a hole through a bottom wall of the chamber body and is interfaced with one or more heaters operable to maintain the chamber body at a temperature of greater than 290° C. The cassette is configured to be raised to load a plurality of substrates thereon and lowered to seal the internal volume. The plug is configured to move up and down within the internal volume. The plug includes a downward-facing seal configured to engage with a top surface of the bottom wall of the chamber body and close the hole through the bottom wall of the chamber body.