OXIDATION OF SEMICONDUCTOR DEVICE

摘要

PURPOSE:To eliminate variations in steam pressure upon alteration of water level in a water tank by providing a water level detecting mechanism in the water tank and operating a water supplying mechanism by a signal from the water level detecting mechanism. CONSTITUTION:An electronic switch 20 is provided at the upper position of a water tank 14, and a float 30 for generating an electric signal upon detection of water level in the tank 14 by driving the switch 20 is provided in the tank 14. An electric signal from the switch 20 is applied to a solenoid valve 10a to start or stop the water supply. The electric signal from the switch 20 is dispatched when the water level in the tank 14 is decreased lower than the reference value set in advance to open the solenoid valve 10a and to fill water in the tank 14. When the water level is recovered by the filling of water, the electric signal is stopped to close the valve 10a. In this manner the water level in the tank 14 is retained at constant level, and it accordingly eliminates the variation in the steam pressure upon alteration of the water level to reduce the irregularity in the thickness of an oxide film.