| 摘要 |
PROBLEM TO BE SOLVED: To detect thermal deformation of a reaction tube without fail by projecting light on a wafer or wafer boat and receiving reflected light from the wafer or boat. SOLUTION: A wafer boat 30, having a wafer 32 mounted thereon, is set at a specified position in a reaction tube 10, an emitting-means 24 is actuated to emit light and to project it on the wafer 32, and receiving-means receives normally the reflected light from the wafer. If the tube is thermally deformed, the receiving-means will not receive the reflected light or the received light quantity will decrease because of the boat 30 being inclined in the tube 10. Thus it is possible to easily and sufely detect the thermal deformation of the tube 10 and prevent the reduction in the production yield, due to the characteristic change of a semiconductor device. |
