FILM FORMING DEVICE

PURPOSE:To control film thickness accurately, easily and automatically by a method wherein reaction gas supply is controlled by a detecting means and reaction gas controller corresponding to the balancing status of a scale within a film growing process. CONSTITUTION:A scale 13 comprising a fulcram 2 and arms 3 is installed in a chamber 1 while a wafer placing base 5 is arranged on one end of the arms 3 and a weight 6 equivalet to the total weight of wafer including the weight of grown film with specific thickness is arranged on the other end of the arms 3. When the film starts to be grown, the weight 6 is lower than the wafer 4 due to heavier weight but the weight of wafer 4 increases in proportion to the weight of growing film lifting the weight 6 in the arrow direction (a) while the wafer 4 is gradually moved downward in the arrow direction (b) to keep the horizontal position represented by a wave line 12. The balancing status may be detected by a detector 10 giving no shock to the arms 3 at all to stop gas supply by means of gas controller 11 actuated by detecting signals transmitted from the detector 10.