| 摘要 |
PURPOSE:To measure accurate film thickness in plasma by arranging the following base plate for detection in a vacuum tank wherein two conductive films are separately provided on an insulated base plate and connecting a bypass filter and a measuring device for DC resistance between the films to both conductive films. CONSTITUTION:As plasma is generated and a-Si or the like is deposited on a base plate 5 to be stuck, a-Si or the like is also deposited between two conductive films 1, 2 provided on a base plate 6 for detection and resistance value is gradually reduced. A high frequency component is excited by plasma between conductive films 1, 2 provided on the base plate 6 for detection but a bypass filter circuit 15 is constituted by connecting the connection points of two capacitors 13, 14 to a vacuum tank 4 and grounding it. The high frequency component is grounded by this filter and potential of the base plate 6 for detection is nearly made equal to potential of the vacuum tank 4. The high frequency component is cut off by coils 9, 10 and a DC component between the conductive layers is detected by an ammeter 12 of an ohmmeter 16.
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