PURPOSE: To eliminate the need for interrupting film forming work and cleaning a microwave transmission window by providing a thin film forming device with a deposition preventive plate which can transmit microwaves freely exchangeably so as to face the microwave transmission window disposed at the microwave reaction tube of a plasma reaction plasma reaction tube.
CONSTITUTION: The microwaves through a waveguide are introduced through the microwave transmission window 2a of the plasma reaction tube 2 to which reactive gases are supplied. The plasma is then excited and cyclotron resonance is induced by the magnetic field by a coil 3 for ECR. The film formation by plasma CVD is thus executed. The reaction tube 2 is internally freely exchangeably provided with the deposition preventive plate 4 which is supplied from a deposition preventive plate holder 5 via push rods 6, 9 and is discharged to a deposition preventive plate recovering pocket 13 so as to face the window 1a, thereby, the deposition of carbon, etc., accompanying the CVD work on the deposition preventive plate 4 is prevented. Accordingly, the need for interrupting the film forming work, removing the window 2a from the reaction tube 2 and cleaning the window is eliminated. The continuation of the good CVD film forming work without interruption is thus made possible.
SHIGA AKIRA
MIZUNOYA HIROHIDE
