Minimum contact area wafer clamping with gas flow for rapid wafer cooling

• US 8,033,771 B1
• Filed: 12/11/2008
• Issued: 10/11/2011
• Est. Priority Date: 12/11/2008
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Original Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Inventors: Gage, Christopher, Kalyanasundaram, Nagarajan, Cohen, David, Pomeroy, Charles E.
• Primary Examiner(s): LOWE, MICHAEL S
• Application Number:
  US12/333,239
• Time in Patent Office: 1,034 Days
• Field of Search: 414/217, 414/805, 414/935, 118/715, 438/758
• US Class Current: 414/217
• CPC Class Codes: H01L 21/67109 mainly by convection
• CPC Class Codes: H01L 21/67201 characterized by the construction of the load-lock chamber
• CPC Class Codes: H01L 21/68735 characterised by edge profile or support profile
• CPC Class Codes: H01L 21/6875 characterised by a plurality of individual support members, e.g. support posts or protrusions
• CPC Class Codes: Y10S 414/135 Associated with semiconductor wafer handling

Abstract

Apparatuses and methods for cooling and transferring wafers from low pressure environment to high pressure environment are provided. An apparatus may include a cooling pedestal and a set of supports for holding the wafer above the cooling pedestal. The average gap between the wafer and the cooling pedestal may be no greater than about 0.010 inches. Venting gases may be used to increase the pressure inside the apparatus during the transfer. In certain embodiment, venting gases comprise nitrogen.

Claims

1. A load lock for cooling wafers after processing, the load lock comprising:

(a) an inlet transfer port for receiving the wafers after processing;

(b) an outlet transfer port for removing the wafers after cooling;

(c) a pedestal having a surface for absorbing heat from the wafers, said surface being structured to prevent a venting gas from passing through the pedestal while absorbing heat from the wafers;

(d) a venting non-process gas port for delivering a venting gas above the pedestal surface to increase pressure inside the load lock, the venting gas port shaped as a ring and comprising an opening facing a center of the ring, the opening configured to direct the venting non-process gas above and parallel to front surfaces of the wafers upon leaving the opening, wherein a diameter of the ring is smaller than a diameter of the wafers; and

(e) at least three supports provided on the pedestal surface, wherein said supports have heights which provide an average gap between one of the wafers and the pedestal surface of no greater than about 0.010 inches, when the one of the wafers is supported by the supports.

2. The load lock of claim 1, wherein the average gap is no greater than about 0.005 inches.

3. The load lock of claim 1, wherein the average gap is no greater than about 0.002 inches.

4. The load lock of claim 1, wherein the venting gas port has a venting gas port opening having a diameter of between about 4 inches and 8 inches.

5. The load lock of claim 4, wherein the venting gas port opening has a diameter of between about 6 inches and 6.5 inches.

6. The load lock of claim 4, wherein the venting gas port opening has a width of between about 0.010 inches and 0.100 inches.

7. The load lock of claim 4, further comprising a load lock lid and a load lock body, and wherein the venting gas port opening is defined by the load lock lid and the load lock body.

8. The load lock of claim 1, further comprising a venting gas source coupled to the venting gas port, wherein the venting gas is substantially free of helium.

9. The load lock of claim 1, wherein the venting gas comprises nitrogen.

10. The load lock of claim 1, wherein the pedestal surface has a convex shape.

11. The load lock of claim 1, wherein a difference between an edge gap and a center gap is between about 0.001 inches and 0.010 inches.

12. The load lock of claim 1, wherein a difference between an edge gap and a center gap is between about 0.001 inches and 0.003 inches.

13. The load lock of claim 1, wherein at least ten supports are provided.

14. The load lock of claim 1, wherein the supports are arranged within at least a first ring and a second ring on the pedestal and wherein the first ring is positioned between about 4 inches and 6 inches from a center of the pedestal and wherein the second ring is positioned between about 1 inch and 3 inches from the center of the pedestal.

15. The load lock of claim 14, wherein at least six supports are provided within the first ring and at least three supports are provided within the second ring.

16. The load lock of claim 1, wherein tips of the supports provide a flat plane above the surface of the pedestal.

17. The load lock of claim 1, wherein the supports have rounded tips.

18. The load lock of claim 1, wherein the supports have diameter of between about 0.020 and 0.125 inches.

19. The load lock of claim 1, wherein the supports comprise a thermally insulating material.

20. The load lock of claim 1, wherein the supports comprise an electrically conductive ceramic material.

21. The load lock of claim 1, further comprising a controller comprising program instructions for:

(a) providing the wafer to the load lock;

(b) positioning the wafer on the supports;

(c) closing the inlet transfer port;

(d) controlling pressure inside the load lock to keep the wafer in contact with at least 70% of the supports; and

(e) opening the outlet transfer port and removing the wafer.

22. The load lock of claim 1, wherein the wafer comprises an outer edge and a center and wherein the pedestal surface forming a gap with the wafer during absorbing heat from the wafers, the gap being filed with the venting gas passing through the gap from the outer edge to the center.

23. A method of cooling and transferring a wafer from a low pressure side to a high pressure side using a load lock, the method comprising:

(a) providing the wafer into the load lock;

(b) positioning the wafer on supports provided on a pedestal having a surface for absorbing heat from the wafers, said surface being structured to prevent a venting gas from passing through the pedestal while absorbing heat from the wafers;

(c) closing an inlet transfer port;

(d) increasing pressure inside the load lock by delivering a venting non-process gas through a venting gas port shaped as a ring and comprising an opening facing a center of the ring, wherein a diameter of the ring is smaller than a diameter of the wafer and wherein the venting non-process gas is delivered parallel above and parallel to a front side of the wafer and to keeps the wafer in contact with at least 70% of the supports by creating pressure differential at a center of the wafer such that pressure at the front side of the wafer is greater than pressure at a back side of the wafer forcing at least the center of the wafer towards the supports; and

(e) opening an outlet transfer port and removing the wafer.

24. The method of claim 23, wherein controlling the pressure comprises providing the venting gas, and wherein the venting gas is substantially free of helium.

25. The method of claim 23, wherein controlling the pressure comprises increasing the pressure inside the load lock at a rate of at least 30 Torr per seconds.

26. The method of claim 23, wherein controlling the pressure comprises providing the venting gas at a flow rate between about 10 and 50 standard liters per minute.

27. The method of claim 23, wherein controlling the pressure is performed in less than 15 seconds, and wherein a temperature of the wafer decreases by at least 200 degrees Centigrade during this time.

28. The method of claim 23, wherein controlling the pressure creates a pressure differential on opposite sides of the wafers creating a downward force directed towards the supports and forcing the wafer against the supports.