Pressure control system

• US 20050279454A1
• Filed: 06/17/2004
• Published: 12/22/2005
• Est. Priority Date: 06/17/2004
• Status: Active Grant

• Current Assignee: ASM International NV
• Original Assignee: ASM International NV
• Inventors: Snijders, Gert Jan
• Granted Patent: US 7,253,107 B2
• Time in Patent Office: Days
• US Class Current: 156/345.290
• CPC Class Codes: C23C 16/4412 Details relating to the exhausts, e.g. pumps, filters, scrubbers, particle traps
• CPC Class Codes: G05D 16/208 using a combination of controlling means as defined in G05D16/2013 and G05D16/2066 G05D16/2073 takes precedence
• CPC Class Codes: H01L 21/67017 Apparatus for fluid treatment H01L21/67126, H01L21/6715 take precedence
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring

Abstract

A pressure control system allows gas to be evacuated out of a semiconductor process chamber at a substantially constant rate of mass flow. A gas line connects the process chamber to a vacuum pump. A controllable valve having a variable sized opening is positioned between the process chamber and the vacuum pump. A pressure sensor is in turn positioned between the valve and the vacuum pump, proximate the inlet to the vacuum pump. The size of the variable sized opening is regulated based upon the pressure in the gas line measured by the pressure sensor. The size of the valve opening is varied to maintain the pressure measured by the pressure sensor at a constant value. As a result, because the quantity of gas flowing through the gas line is proportional to the gas pressure, a substantially constant mass flow of gas out of the chamber and into the pump can be achieved.

Claims

1. A semiconductor processing system, comprising:

a process chamber;

a vacuum pump;

a gas line connecting the process chamber and the vacuum pump;

a valve in the gas line between the process chamber and the vacuum pump, wherein the valve has a variable size opening;

a pump pressure sensor configured to measure a pump gas pressure in the gas line between the valve and the pump; and

a valve controller connected to the valve and the pump pressure sensor, wherein the valve controller is configured to regulate a size of the opening based upon the pump gas pressure.

2. The system of claim 1, wherein the valve is a proportional opening valve.

3. The system of claim 1, wherein the valve is a pneumatically operated valve.

4. The system of claim 1, further comprising an additional valve allowing gas communication between the chamber and the pump, wherein the additional valve has a constant-sized opening.

5. The system of claim 4, wherein the additional valve by-passes the valve having the variable size opening.

6. The system of claim 1, wherein the valve controller is configured to control the size of the opening to maintain the pump gas pressure at a substantially constant value to maintain a mass flow of gas out of the chamber at a substantially constant value.

7. The method of claim 6, wherein the mass flow is within 50 percent of a reference value.

8. The method of claim 7, wherein the mass flow is within 10 percent of the reference value.

9. The system of claim 1, wherein the valve controller is selected from the group consisting of a PID controller, an H∞

controller, a model based controller and an adaptive controller.

10. The system of claim 1, wherein the valve controller is a nested loop controller.

11. The system of claim 10, wherein the nested loop controller comprises an inner loop and an outer loop, wherein the outer loop is configured to output a valve opening signal based upon a difference between a desired pump gas pressure set-point and the pump gas pressure and wherein the inner loop is configured to receive the valve opening signal and a signal corresponding to the size of the opening and to calculate another signal to set the size of the opening.

12. The system of claim 1, wherein the valve controller is separate from a process controller for controlling processing of the substrate.

13. The system of claim 1, wherein the gas line pressure sensor is located between the valve and the pump.

14. The system of claim 1, further comprising a chamber pressure sensor in the process chamber for measuring a process chamber gas pressure, wherein, during processing of a substrate in the chamber, the valve controller is configured to receive a chamber pressure from the chamber pressure sensor and to output instructions to the valve to set the size of the opening based upon the chamber pressure and wherein, during pump-down of the chamber, the valve controller is configured to output instructions to the valve based upon the pump gas pressure.

15. The system of claim 14, further comprising a software switch for switching the valve controller between using the chamber pressure during processing of a substrate in the chamber and using the pump gas pressure during pump-down of the chamber.

16. The system of claim 15, wherein the software switch is provided within the valve controller.

17. The system of claim 1, wherein the process chamber is a batch reactor.

18. The system of claim 1, wherein the gas line does not comprise a mass flow controller.

19. A semiconductor processing system, comprising:

a gas compartment having an entrance and an exit to an inlet of a pump, wherein the entrance has a controllable variable size; and

a pressure sensor proximate the inlet of the pump, wherein the pressure sensor is configured to sense a gas pressure at the inlet and wherein the system is configured to regulate the size of the gas compartment entrance based upon the gas pressure at the inlet to maintain the gas pressure substantially at a desired set point.

20. The system of claim 19, wherein the entrance is an opening of a variable opening valve.

21. The system of claim 20, wherein the entrance connects the gas compartment to a process chamber.

22. The system of claim 19, further comprising a controller connected to the entrance and the pressure sensor, wherein the controller is configured to receive an input from the pressure sensor and to produce an output for setting the size of the entrance.

23. The system of claim 22, further comprising a selector switch and an additional pressure sensor in the process chamber, wherein the selector switch is configured to switch the input to the controller between the output from the pressure sensor during evacuation of the process chamber in the process chamber and another output from the additional pressure sensor during processing of a substrate.

24. The system of claim 23, wherein the pressure sensor is a low pressure sensor.

25. The system of claim 24, wherein the additional pressure sensor is a high pressure sensor.

26. The system of claim 23, wherein the additional pressure sensor is configured to measure a pressure of the process chamber.

27. The system of claim 26, configured to maintain the pressure of the process chamber constant during processing of a substrate.

28. The system of claim 19, wherein the pump is a configured to displace a constant volume of gas at a substantially constant rate.

29. The system of claim 28, wherein the pump is a rotating vane vacuum pump.

30. The system of claim 19, configured to maintain the pressure within about 50 percent of the desired set-point.

31. The system of claim 30, configured to maintain the mass flow within about 50 percent of a reference mass flow value.

32. The system of claim 30, configured to maintain the pressure within about 10 percent of the desired set-point.

33. The system of claim 32, configured to maintain the pressure within about 2 percent of the desired set-point.

34. A method for fabricating an integrated circuit, comprising:

providing a semiconductor process chamber having a gas outlet;

providing a pump having a gas inlet;

providing a gas line connecting the gas outlet to the gas inlet, wherein a variable size opening is located within the gas line; and

pumping down the chamber, wherein pumping down the chamber comprises varying the size of the opening depending upon a pressure of gas downstream of the opening, wherein varying the size of the opening maintains a mass flow of gas out of the chamber at a substantially constant rate.

35. The method of claim 34, wherein the process chamber is a batch reactor.

36. The method of claim 34, wherein the opening is an opening of a proportional opening valve.

37. The method of claim 34, wherein the pump is a rotating vane vacuum pump.

38. The method of claim 37, wherein a rotating vane of the rotating vane vacuum pump rotates at a substantially constant speed.

39. The method of claim 34, further comprising processing a substrate in the chamber.

40. The method of claim 39, wherein processing the substrate comprises low pressure chemical vapor deposition.

41. The method of claim 39, further comprising measuring a gas pressure in the chamber and switching between using the gas pressure in the chamber to control the size of the gas line opening during processing of the substrate and using the gas pressure downstream of the opening to control the size of the gas line opening during pump down of the chamber.

42. The method of claim 41, wherein the size of the gas line opening is controlled during processing of the substrate to maintain the pressure in the chamber substantially constant.

43. The method of claim 34, wherein varying the size of the opening maintains the gas pressure in the gas line downstream of the opening at a substantially constant value at least during a period between a start and an end of pumping down the chamber.

44. The method of claim 43, wherein varying the size of the opening further comprises maintaining the gas pressure substantially constant at a value lower than the substantially constant value during another period between the start and the end.

45. The method of claim 43, wherein pumping down the chamber comprises maintaining the mass flow within about 50 percent of a reference rate.

46. The method of claim 45, wherein the mass flow is maintained within about 10 percent of the reference rate.

47. The method of claim 34, further comprising providing a bypass gas line for bypassing the opening, wherein pumping down the chamber comprises flowing gas through the bypass gas line during an initial stage of pumping down the chamber and then flowing gas through the opening.

48. A method for semiconductor processing, comprising:

loading a substrate into a semiconductor processing chamber, wherein the chamber is connected to a pump; and

evacuating the chamber using the pump, wherein a mass flow of fluid from the chamber into the vacuum pump is controlled by regulating a pressure of the fluid proximate an entrance to the pump.

49. The method of claim 48, wherein evacuating the chamber comprises maintaining the mass flow at a substantially constant rate by maintaining the pressure at a substantially constant value.

50. The method of claim 49, wherein evacuating the chamber comprises maintaining the pressure within about 50 percent of a desired set-point pressure.

51. The method of claim 50, wherein evacuating the chamber comprises maintaining the pressure within about 10 percent of the set-point pressure.

52. The method of claim 51, wherein evacuating the chamber comprises maintaining the pressure within about 2 percent of the set-point pressure.

53. The method of claim 48, wherein a gas line connects the chamber and the pump and wherein regulating the pressure of the fluid proximate the entrance to the pump comprises varying an opening size of a valve upstream of the pump entrance in the gas line.

54. The method of claim 53, wherein varying the opening size of the valve comprises measuring a pressure in the gas line between the pump and the chamber and calculating a size of opening based upon the measured pressure in the gas line.

55. The method of claim 48, further comprising performing a low pressure chemical vapor deposition after evacuating the chamber.

56. The method of claim 48, wherein the mass flow of fluid from the chamber into the vacuum pump is controlled without use of a mass flow controller.

57. The method of claim 48, wherein the pump displaces a substantially constant volume of gas at a substantially constant rate.