| 摘要 |
PURPOSE:To detect exactly the end point of a surface treatment by deciding the time when the level of the signal detecting the quantity of the transmitted light exceeds no longer the prescribed threshold value within prescribed time and when the level of the signal detecting the quantity of the reflected light decreases below the prescribed threshold value as the end point of said treatment. CONSTITUTION:Whether the detection signal V1 corresponding to the quantity of the light transmitted through a plate-shaped body 1 to be treated exceeds a prescribed threshold value V2i in prescribed time during a treatment stage or not is detected. When said signal does not exceeds said value, a fresh threshold value 2i is successively set according to the progression of the surface treatment and is compared with the changing signal V1 by a comparator 19. Such comparison is repeated by said comparator. Then the signal V1 exceeds no longer the value V2i in the prescribed time TE in the final and the similar processing is accomplished with the detection signal v1 corresponding to the quantity of the reflected light as well. The point of the time when the signal attains finally the roughly specified detection value with the rapid decrease of the light quantity by the removal of metallic oxide film 2 is decided as the end point of the surface treatment. The end point of the surface treatment is exactly detected by such detecting method. |
