A sealing device configured for use in a vacuum chamber between a reaction region of the vacuum chamber and an exhaust port includes a ring-shaped body with an upper surface and a lower surface. A distance between the upper surface and the lower surface of the sealing device is a thickness of the ring-shaped body. The thickness of the ring-shaped body differs along a circumference of the ring-shaped body such that the ring-shaped body has a wedge shape. The thickness of the ring-shaped body, around its circumference is dependent upon a structure of the exhaust port.