An apparatus for loading semiconductor wafers into a cantilever diffusion tube includes a cantilever paddle supporting a boatload of wafers. The paddle is moved into alignment with the open end of the cantilever diffusion tube. The open end portion of cantilever diffusion tube is moved to surround the paddle and boat load of wafers. The paddle is lowered slightly, causing the boat load of wafers to be supported on an inside surface of the cantilever diffusion tube and providing clearance around the paddle. The cantilever tube is withdrawn from the paddle, which then is withdrawn from the path of the cantilever diffusion tube. The cantilever tube and the boatload of wafers is moved into the hot zone of the furnace. After a heat treating operation, the cantilever diffusion tube is withdrawn from the furnace, and the reverse operation is performed to unload the boatload of wafers. In one embodiment of the invention, a plug is inserted into the open end of the cantilever diffusion tube after the boat load of wafers is loaded therein. In another embodiment, a tube passes through the plug and communicates with an external coupling to an external gas source.