Patent ID: 7328881

Claim:
An evacuating valve, comprising: a chamber port structure for connection with a vacuum vessel within which a plasma is produced to create a plasma atmosphere; the chamber port structure having at least two expanded parts that are configured as steps, formed from expanding an end part of an inside upper surface of the chamber port structure; a pump port structure for connection with a vacuum pump; a valve casing defining a passage connecting the chamber port structure and the pump port structure; a valve mechanism for opening and closing the chamber port structure, including a valve seat on an end surface of the chamber port structure that faces the passage; a valve element that is substantially configured as multi-stepped disk, moving along an axis of the chamber port structure for opening and closing the chamber port structure, the valve element comprising: a large part that forms a first section of the multi-stepped disk having substantially non-tapered, straight lateral and horizontal surfaces; the large part is pressed against the valve seat when the valve element is in a closed position, with a sealing member held between the large part and the valve seat for creating a non-leaking union between the valve seat and the valve element; at least two small parts that form a second section of the multi-stepped disk, having substantially non-tapered, straight lateral and horizontal surfaces that commensurately fit within the at least two expanded parts of the chamber port structure that form the steps; and a substantially non-tapered, straight, and flat bottom surface that faces the chamber port structure; the non-tapered, straight surfaces of the valve element that form the multi-stepped disk isolate the sealing member within the passage from the plasma atmosphere within the chamber port structure, preventing a deterioration of the sealing member by the plasma atmosphere; the number of the small parts of the valve element is equal to that of the expanded parts of the chamber port structure, with each of the expanded parts having a first surface substantially parallel to the axis of the chamber port structure, and a second surface substantially perpendicular to the axis of the chamber port structure, with the entire valve element on the side of the passage with respect to the second surface of the expanded part directly continuous with the inside surface of the chamber port structure when the valve element is seated on the valve seat to close the evacuating valve.