Abstract: Flow of processing gas is controlled by one valve from the atmospheric pressure to a substantial vacuum pressure. The valve body includes a first disc-shaped valve body portion to be pressed against a flange portion of a valve seat and a second disc-shaped valve body portion which is screwed on an end surface of the first valve body portion and adjusted its alignment. The second valve body portion is provided with an O-ring fitted thereon in such a slanting state that a plane including a circular line passing a cross-sectional center of the O-ring forms a specified angle with a plane perpendicular to the direction in which the second valve body portion slides back and forth against the valve seat. When the second valve body portion slides in the valve seat, a gap produced between them varies its size by the effect of the O-ring and hence a cross-sectional area of the passage correspondingly changes.

Abstract: Flow of processing gas is controlled by one valve from the atmospheric pressure to a substantial vacuum pressure. A valve body is disposed in a valve chamber having an inlet to be connected with a reaction chamber and an outlet to be connected with an evacuation pump. The valve body includes a first disc-shaped valve body portion to be pressed against a flange portion of a valve seat and a second disc-shaped valve body portion which is screwed on an end surface of the first valve body portion and adjusted its alignment. The second valve body portion is inserted into a valve hole of the valve seat. The first valve body portion has a circular groove at one of its surfaces to be brought into contact with the flange portion and an O-ring in the groove so as to choke fluid flow when in contact with the valve seat. The second valve body portion has tapered notches of which depths are gradually decreased from downstream to upstream.

Abstract: A throttle valve is provided with a heater for keeping an external surface of a valve disc and an adjacent thereto internal surface of a flange portion at high temperature to prevent deposition of fine particles contained in etching gas, and thereby the said valve may provide smooth and reliable adjustment of the valve opening over the long period of its operation.The valve controls the flow of gas along a pipe by changing the open area of a fluid passage formed therein through the valve disc 2 which is turned by driving shaft 3 from driving means provided in a driving portion 4. The valve disc 2 is heated with a heating rod 6 mounted therein. Plate-like heaters 20.sub.1 and 20.sub.2 are mounted on the flange portion 1b of the valve 1 to heat the flange portion 1b and valve disc 2. The external surface of the valve disc 2 and the internal surface of the flange portion are heated to prevent adhesion of dust particles thereto. Therefore, the valve disc 2 can smoothly move with no obstruction.