US Patent 7464941 Sealing mechanism for sealing a vacuum chamber

A sealing mechanism comprises a support member forming part of the semiconductor producing apparatus which has a vacuum chamber, a rotation shaft rotatably received in the support member, and at least three seal rings axially spaced apart from each other between the support member and the rotation shaft to form a first fluid chamber close to the atmosphere and a second fluid chamber close to the vacuum chamber. The first fluid chamber is vacuumized to have a first pressure, and the second fluid chamber is also vacuumized to have a second pressure which is lower than the first pressure. The first and second fluid chambers work together to enhance the sealing performance of the sealing mechanism.