Patent ID: 7942425

Claim:
A plasma resistant seal comprising: a plasma seal made entirely of a material provided with a plasma resisting performance, the plasma seal being provided in on a plasma irradiating side of a packing, the packing being made of a plasma resistant FKM rubber containing no mineral component and serving as a main seal, said plasma seal being made entirely of a non-filler type of polytetrafluoroethylene and said packing being an O-ring, a diameter of said packing in a height direction of said packing being larger than a height of said plasma seal as measured in the height direction of said packing, the packing being attached to a packing installation groove provided in one of two installation members, and the plasma seal being attached to a plasma irradiation side of the installation groove, the packing installation groove being formed in an approximately quadrangular cross section shape in the one installation member, a side wall portion of the packing installation groove being formed at a right angle with respect to an end surface of the one installation member in on the plasma irradiating side, and the plasma seal being compressed between the side wall portion of the packing installation groove and the packing, both of the plasma seal and the packing being compressed between the two installation members to provide a pinching of the plasma seal and the packing between each other and with the two installation members so that the plasma seal and the packing receive a reaction force under compression from the two installation members, the height direction of the packing being in a direction along the side wall portion; the plasma seal having an arch cross sectional shape with a concave surface engaging the packing and having a convex surface engaging the side wall portion of the packing installation groove, and the convex and concave surfaces of the plasma seal being arranged along a direction generally orthogonal to a plasma irradiation direction so that the packing is prevented from protruding into a gap extending from the plasma irradiation direction.