Technique for low-temperature ion implantation

• US 7,935,942 B2
• Filed: 08/15/2006
• Issued: 05/03/2011
• Est. Priority Date: 08/15/2006
• Status: Active Grant

• Current Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Original Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Inventors: England, Jonathan, Muka, Richard S., Liebert, Reuel B., Blake, Julian, Murphy, Paul J., Walther, Steven R.
• Primary Examiner(s): Kim; Robert
• Assistant Examiner(s): MASKELL, MICHAEL P
• Application Number:
  US11/504,367
• Publication Number:
  US 20080044938A1
• Time in Patent Office: 1,722 Days
• Field of Search: 250/492.1, 250/492.2, 250/492.21, 250/492.3, 250/443.1, 118/723.CB, 118/723.FI
• US Class Current: 250/492.21
• CPC Class Codes: H01L 21/26593 at a temperature lower than room temperature
• CPC Class Codes: H01L 21/67098 Apparatus for thermal treatment
• CPC Class Codes: H01L 21/67109 mainly by convection
• CPC Class Codes: H01L 21/67213 comprising at least one ion or electron beam chamber coating by ion implantation C23C; ion or electron beam tubes H01J37/00
• CPC Class Codes: H01L 21/67248 Temperature monitoring

Abstract

A technique for low-temperature ion implantation is disclosed. In one particular exemplary embodiment, the technique may be realized as an apparatus for low-temperature ion implantation. The apparatus may comprise a pre-chill station located in proximity to an end station in an ion implanter. The apparatus may also comprise a cooling mechanism within the pre-chill station. The apparatus may further comprise a loading assembly coupled to the pre-chill station and the end station. The apparatus may additionally comprise a controller in communication with the loading assembly and the cooling mechanism to coordinate loading a wafer into the pre-chill station, cooling the wafer down to a predetermined temperature range, and loading the cooled wafer into the end station where the cooled wafer undergoes an ion implantation process.

Claims

1. An apparatus for low-temperature ion implantation, the apparatus comprising:

a pre-chill station located in proximity to an end station in an ion implanter;

a cooling mechanism within the pre-chill station configured to cool a wafer from ambient temperature to a predetermined temperature range less than or equal to −

50°

C.;

a loading assembly with access to the pre-chill station and the end station; and

a controller in communication with the loading assembly and the cooling mechanism, the controller configured to coordinate loading the wafer into the pre-chill station, cooling the wafer down to the predetermined temperature range less than or equal to −

50°

C. before any ion implantation into the wafer, and loading the cooled wafer into the end station where the cooled wafer undergoes an ion implantation process.

2. The apparatus according to claim 1, wherein the pre-chill station encloses a first vacuum space, and the end station enclosing a second vacuum space separate from the first vacuum space.

3. The apparatus according to claim 1, wherein the ion implanter is a single-wafer ion implanter that processes one wafer at a time in the end station.

4. The apparatus according to claim 1, wherein the controller is further adapted to cause the loading assembly to remove the wafer from the end station immediately after the ion implantation process.

5. The apparatus according to claim 1, wherein the end station comprises a platen that holds the wafer during the ion implantation process, and wherein the wafer is thermally substantially isolated from the platen.

6. The apparatus according to claim 5, wherein the platen comprises a plurality of mesa structures that support the wafer, such that total contact area between the platen and the wafer is substantially smaller than the wafer surface.

7. The apparatus according to claim 5, wherein the platen facilitates tilting and rotation of the wafer.

8. The apparatus according to claim 1, wherein the pre-chill station comprises a fixed platen that holds the wafer for cooling.

9. The apparatus according to claim 8, wherein the fixed platen comprises lift pins to accommodate loading and unloading of the wafer by the loading assembly.

10. The apparatus according to claim 1, wherein the wafer is attached to an object to achieve a larger thermal mass such that the wafer experiences a smaller temperature increase during the ion implantation process.

11. The apparatus according to claim 10, wherein the object is a carrier plate that is heavier than the wafer.

12. The apparatus according to claim 11, wherein the wafer is attached to the carrier plate with carbon dioxide below its sublimation temperature.

13. The apparatus according to claim 11, wherein the carrier plate comprises at least one thermal sensor embedded therein.

14. The apparatus according to claim 11, wherein the carrier plate has embedded therein a cooling/heating mechanism.

15. The apparatus according to claim 1, wherein the cooling mechanism cools the wafer based on one or more techniques selected from a group consisting of:

gas cooling, coolant circulation, coolant phase change, Peltier heat transfer, and a built-in cryopump.

16. The apparatus according to claim 1, wherein an amount of temperature increase due to the ion implantation process is predicted for the wafer, and wherein the controller is further configured to cause the wafer to be cooled based at least in part on the predicted amount of temperature increase to avoid overheating the wafer during the ion implantation process.

17. The apparatus according to claim 1, wherein the pre-chill station is part of a loadlock coupled to the end station.

18. The apparatus according to claim 1, wherein at least part of the pre-chill station and the cooling mechanism is incorporated into the loading assembly.

19. An ion implanter comprising:

at least one end station;

at least one pre-chill station located in proximity to the at least one end station, the at least one pre-chill station having a cooling mechanism configured to cool a wafer from ambient temperature to a predetermined temperature range less than or equal to −

50°

C.;

a loading assembly with access to the at least one end station and the at least one pre-chill station; and

a controller configured to cause the wafer to be loaded into the at least one pre-chilled station and cooled to the predetermined temperature range less than or equal to −

50°

C. before the wafer is loaded into the end station to undergo any ion implantation process.