in the picture below six furnaces can be seen (some are used for annealing, some for oxidation, some for diffusion)

the temperature inside is maintained constant (800oC for oxidation furnace), and it can be increased until 1200oC

gases are introduced from the back of the furnace

the boats with the wafers are introduced in front, as shown below for the middle furnace

the system is automatic and controlled by panels

in the back, the gas can pass through DI water, for example, in case of wet oxidation (the lower picture)