ECR PLASMA DEVICE

PURPOSE:To control the acceleration of ion beams while enabling a substrate with large diameter to be processed by a method wherein a space in a divergence magnetic field leading-in the ion beams from a plasma production chamber and expanding the diameter of ion beams is provided between the plasma production chamber and a grid. CONSTITUTION:A space 30 is provided on a divergence magnetic field. A microwave reflecting sheet 11 is made of a metallic net with fairly fine mesh and high aperture rate, the diameter of ion beams coming out of the metallic net is notably expanded in the space 30 of divergence magnetic field reaching a grid 32 at a floating potential; and the beams, after being accelerated by another grid 33 at earth potential, irradiate a substrate 8 on a substrate holder 7. In such a constitution, a conical metallic shielding sheet 34 connected to the room walls of a plasma production chamber 1 together with the grid 32 at floating potential prevent the ion beams 31 expanding the diameter thereof from being disturbed by an intensive electric field as well as the surface processing of substrate 8 from becoming uneven.