Controlling gas partial pressures for process optimization

• US 20060118178A1
• Filed: 12/02/2005
• Published: 06/08/2006
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Alcatel SA (Nokia Corporation)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Puech, Michel, Desbiolles, Jean-Pierre
• Granted Patent: US 7,793,685 B2
• Time in Patent Office: Days
• US Class Current: 137/565.300
• CPC Class Codes: F04D 19/04 specially adapted to the production of a high vacuum, e.g. molecular pumps
• CPC Class Codes: F04D 27/00 Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
• CPC Class Codes: Y10T 137/0396 Involving pressure control
• CPC Class Codes: Y10T 137/86002 Fluid pressure responsive
• CPC Class Codes: Y10T 137/86083 Vacuum pump
• CPC Class Codes: Y10T 137/86139 Serial
• CPC Class Codes: Y10T 137/87917 Flow path with serial valves and/or closures

Abstract

Apparatus for establishing and controlling a low pressure gas mixture in a vacuum enclosure (8) comprises at least one secondary pump (9) of the molecular, turbomolecular, or hybrid type, followed by at least one primary pump (10), with first control and adjustment means (22) such as a regulation valve (24) for controlling and adjusting the total gas pressure of the mixture of gases in the vacuum enclosure (8) as a function of a total pressure setpoint (27). The apparatus further comprises second control and adjustment means (28) such as a second regulation valve (29a) downstream from the secondary pump (9). The second regulation valve (29a) is controlled as a function of a delivery pressure setpoint (32) to modify the delivery pressure of the secondary pump (9) and thus to adapt its pumping capacity in selective manner. This makes it possible to adjust the proportions of the gases in the mixture of gases in the vacuum enclosure, independently of the total pressure which is controlled by the first regulation valve (24).

Claims

1. Apparatus for establishing and controlling an appropriate low pressure gas mixture in a vacuum enclosure, the apparatus comprising:

at least one secondary pump of a molecular, turbomolecular, or hybrid type;

at least one primary pump adapted to deliver to atmospheric pressure;

a first pipe having an inlet connected to an outlet of the vacuum enclosure and an outlet connected to a suction inlet of the secondary pump;

an intermediate pipe having an inlet connected to a delivery outlet of the secondary pump and an outlet connected to a suction inlet of the primary pump;

first control and adjustment means adapted to controlling and adjusting the total gas pressure of the mixture of gases in the vacuum enclosure as a function of a total pressure setpoint; and

second control and adjustment means distinct from the first control and adjustment means, disposed downstream from the secondary pump, and acting on the delivery pressure from the secondary pump in the range of pressures in which changes of pressure lead to significant variations in the selective pumping speeds of different gases of the mixture, so as to adapt the pumping capacity of the secondary pump selectively, thereby adjusting the proportions of the gases in the mixture of gases in the vacuum enclosure.

2. Apparatus according to claim 1, in which the first control and adjustment means are disposed upstream from the secondary pump, and comprise a regulation valve interposed in the first pipe and/or means for controlled injection of gas into the vacuum enclosure.

3. Apparatus according to claim 1, in which the second control and adjustment means comprise a regulation valve interposed in the intermediate pipe.

4. Apparatus according to claim 1, in which the second control and adjustment means comprise a gas injection device for injecting an inert gas into the intermediate pipe.

5. Apparatus according to claim 1, in which the second control and adjustment means comprise speed control means for controlling the speed of the primary pump.

6. Apparatus according to claim 1, further comprising:

partial pressure sensors suitable for determining the partial pressure(s) of one or more gases in the mixture of gases in the vacuum enclosure, and for producing partial pressure data; and

a partial pressure controller, receiving the partial pressure data produced by the partial pressure sensors, comparing said data with partial pressure setpoints, searching for differences between the measured proportions of the gases and the proportions corresponding to the partial pressure setpoints, and generating an output signal controlling the second control and adjustment means to adapt the pumping capacity of the secondary pump selectively in the direction that reduces the difference between the measured proportions of the gases and the proportions corresponding to the partial pressure setpoints.

7. Apparatus according to claim 6, in which:

the partial pressure controller generates on its output a delivery pressure setpoint;

a delivery pressure sensor measures the delivery pressure in the intermediate pipe and generates delivery pressure measurement data; and

a delivery pressure controller receives the delivery pressure setpoint and the delivery pressure data, and controls the delivery pressure regulation means to reduce the difference between the delivery pressure setpoint and the measured delivery pressure data.

8. Apparatus according to claim 1, including a control unit controlling the second control and adjustment means in application of a specific program for adapting the pumping capacity of the secondary pump selectively to the various successive steps of a treatment process taking place in the vacuum enclosure.

9. A method of establishing and controlling an appropriate low pressure mixture of gases in a vacuum enclosure using apparatus according to claim 1, by acting on the delivery pressure of the secondary pump to adapt its pumping capacity selectively, thereby adjusting the proportions of the gases in the gas mixture.

10. A method according to claim 9, in which action is taken on the delivery pressure by modifying the conduction of the intermediate pipe.

11. A method according to claim 9, in which action is taken on the delivery pressure by injecting an inert gas into the intermediate pipe.

12. A method according to claim 9, in which action is taken on the delivery pressure by modifying the speed of the primary pump.

13. A method according to claim 9, in which action is taken on the delivery pressure of the secondary pump as a function of successive steps in a treatment process taking place in the vacuum enclosure.

14. A method according to claim 9, in which action is taken on the delivery pressure of the secondary pump in the direction appropriate for increasing the pumping of moisture during a process of controlled evacuation of the vacuum enclosure.

15. A method according to claim 9, in which action is taken on the delivery pressure of the secondary pump in the direction appropriate for keeping the partial pressure of at least one gas in the vacuum enclosure constant.

16. The use of apparatus according to claim 1 to compensate for variations in the pumping characteristics of a secondary pump.

17. The use of apparatus according to claim 1 to compensate drift in a system for pumping gas from a vacuum enclosure.

18. The use of apparatus according to claim 1 to increase the speed of a dry etching process by increasing the delivery pressure of the secondary pump.

19. The use of apparatus according to claim 1 to control the quality of chemical vapor deposition (CVD) by acting on the delivery pressure of the secondary pump.