A memory of a control unit stores correction data indicating a relationship between a decrement in a measurement value of a film thickness by removal of organic contamination adsorbed onto a substrate and an amount of adsorbed organic contamination corresponding to a difference between a true film thickness and the measurement. The deceleration detecting device detects a vehicle deceleration in the longitudinal direction. A metal-flash layer is formed overlying the polysilicon layer, and then a tungsten nitride layer is formed overlying the titanium layer.