Vacuum pumping system and method of controlling the same

{
  "publication_number": "US2004126244A1",
  "country": "US",
  "kind": "A1",
  "title": "Vacuum pumping system and method of controlling the same",
  "abstract": "A vacuum pump system (10; 36; 46) for pumping gas from an enclosure (12) comprises: a vacuum pump unit (14) having a pump inlet (16) connectable with an outlet (18) of such an enclosure and a pump outlet (20) for exhausting gas; and a chamber (22; 50) selectively connectable with the pump inlet and the pump outlet, such that, in use, in a first state gas can be pumped from the chamber to the pump inlet by the vacuum pump unit and in a second state gas can be evacuated from the pump outlet to the chamber to reduce pressure at the pump outlet. A method of controlling the vacuum pump system (10; 36; 46) comprises a first step of pumping gas from the chamber to the pump inlet using the vacuum pump unit and a second step of allowing gas to be evacuated from the pump outlet to the chamber to reduce pressure at the pump outlet.",
  "claims": [
    "1. A vacuum pump system for pumping gas from an enclosure, the system comprising: a vacuum pump unit having a pump inlet connectable with an outlet of such an enclosure and a pump outlet for exhausting gas; and a chamber selectively connectable with the pump inlet and the pump outlet, such that, in use, in a first state gas can be pumped from the chamber to the pump inlet by the vacuum pump unit and in a second state gas can be evacuated from the pump outlet to the chamber to reduce pressure at the pump outlet. 2. A system as claimed in claim 1, wherein the chamber is selectively connectable with the pump inlet and the pump outlet by first valve means and second valve means, respectively, and during use in said first state said first valve means is opened and during use in said second state said second valve means is opened. 3. A system as claimed in claim 1, wherein said vacuum pump unit exhausts through an exhaust valve means for preventing gas flow therethrough during use in said second state. 4. A system as claimed in claim 3, wherein the second state valve means and the exhaust valve means is constituted by a single valve. 5. A system as claimed in claim 1, wherein the chamber has a first use to reduce pressure at the pump outlet and a further use in the vacuum pump system. 6. A system as claimed in claim 5, wherein the further use is as an exhaust silencer. 7. A system as claimed in claim 1, wherein chamber is annular and formed about a portion of a duct of the system. 8. A system as claimed in claim 1, wherein the volume of said chamber is selected to reduce pump outlet pressure by a predetermined amount thereby to reduce by a predetermined amount power requirement of the system when operating at ultimate. 9. A method of controlling a vacuum pump system for pumping gas from an enclosure, said system comprising: a vacuum pump unit having a pump inlet connectable with an outlet of such an enclosure and a pump outlet for exhausting gas; and a chamber selectively connectable with the pump inlet and the pump outlet, the method comprising a first step of pumping gas from the chamber to the pump inlet using the vacuum pump unit and a second step of allowing gas to be evacuated from the pump outlet to the chamber to reduce pressure at the pump outlet. 10. A method as claimed in claim 9, wherein the system comprises a first valve means which is opened during said first method step and a second valve means which is opened during said second method step. 11. A method as claimed in claim 10, wherein during said first method step gas is pumped from the chamber by said vacuum pump unit and exhausted through an exhaust valve means and during said second step, said exhaust valve means prevents gas flow from downstream thereof from entering said chamber to allow gas at said pump outlet to be evacuated to the chamber. 12. A method as claimed in claim 11, wherein said first method step is effected during an initial evacuation stage of said enclosure. 13. A vacuum pump system for pumping gas from an enclosure, the system comprising: a vacuum pump unit having a pump inlet connectable with an outlet of such an enclosure and a pump outlet for exhausting gas; and a chamber selectively connectable with the pump inlet by a first valve and with the pump outlet by a second valve, such that, in use, in a first state said first valve is open and said second valve is closed and gas can be pumped from the chamber to the pump inlet by the vacuum pump unit and in a second state said first valve is closed and said second valve is open and gas can be evacuated from the pump outlet to the chamber to reduce pressure at the pump outlet."
  ],
  "description_excerpt": "1. Field of the Invention [0001]\n\nThe present invention relates to a vacuum pump system for pumping gas from an enclosure and to a method of controlling the system. [0002]\n\n2. Background of the Related Art [0003]\n\nA vacuum pump system may be used for pumping gas from an enclosure, such as a load lock chamber or transfer chamber of a semiconductor processing assembly. The system may comprise a vacuum pump unit having a pump inlet connectable with an outlet of such an enclosure and a pump outlet for exhausting gas, usually to atmosphere. [0004]\n\nProcessing of semiconductor wafers, for instance, takes place at low pressures close to vacuum which for brevity hereinafter will be referred to as vacuum. Transferral of wafers at atmospheric pressure to processing chambers at vacuum is achieved by the use of an intermediate chamber, or load lock chamber, which is adjustable between atmosphere and vacuum. Unprocessed semiconductor wafers are deposited in a load lock chamber and processed wafers are removed therefrom when the chamber is at atmospheric pressure. Wafers can be transferred between the load lock chamber and the processing chambers when the load lock chamber has been evacuated to vacuum. [0005]\n\nIt is desirable to be able to reduce the load lock chamber from atmosphere to vacuum quickly to increase efficiency of the semiconductor processing assembly. When the load lock chamber has been evacuated to vacuum, there is little or no mass flow rate through the vacuum pump unit the unit is maintaining inlet and outlet pressure, or is holding back outlet pressure downstream thereof.",
  "cpc": [
    "F04C 28/24",
    "F04B 37/14",
    "F04C 2220/10",
    "F04C 2220/30",
    "F04C 2270/02",
    "F04C 25/02",
    "F04C 28/065",
    "Y10T 137/86083"
  ],
  "ipc": [
    "F04B 19/00",
    "F04B 37/16",
    "F04B 49/06",
    "F04C 28/24",
    "C23C 14/00",
    "E03B 5/00",
    "F04B 49/22"
  ],
  "assignees": [
    "BOC Group Ltd"
  ],
  "inventors": [
    "Derek Savidge",
    "Neil Turner",
    "Graeme Huntley"
  ],
  "filing_date": "2003-05-15",
  "publication_date": "2004-07-01",
  "priority_date": "2002-05-31",
  "application_number": "US-43842703-A",
  "family_id": "9937904",
  "cited_by_count": 7,
  "citations": [
    "US5088895A",
    "US5228838A",
    "US5788825A",
    "US6149729A",
    "US6446651B1"
  ]
}