Method and apparatus for improved processing with a gas-cluster ion beam

1. An apparatus for generating a gas-cluster ion beam with a modified gas-cluster ion energy distribution, comprising:

a reduced-pressure chamber having a reduced-pressure;

a gas-cluster ion beam source within the chamber, for generating an energetic gas-cluster ion beam having a gas-cluster ion beam path; and

a pressure-controlled region within the reduced-pressure chamber having an average pressure greater than the reduced-pressure;

wherein at least a portion of the gas-cluster ion beam path traverses the pressure-controlled region so as to be modified by the greater pressure of the pressure-controlled region.

2. The apparatus of claim 1 , wherein the gas-cluster ion beam source further comprises:

a pressurized gas source;

a nozzle for expanding pressurized gas from the pressurized gas source into the reduced-pressure chamber to form gas-clusters;

an ionizer for ionizing the gas-clusters to form a gas-cluster ion beam; and

an accelerator for accelerating the gas-cluster ion beam to form the energetic gas-cluster ion beam.

3. The apparatus of claim 1 , wherein the portion of the gas-cluster ion beam path that traverses the pressure-controlled region has a pressure-distance integral along the path within the pressure-controlled region that is greater than about 5×10 −4 torr-cm.

4. The apparatus of claim 1 , further comprising a control system for controlling the average pressure in the pressure-controlled region.

5. The apparatus of claim 1 , wherein the energetic gas-cluster ion beam comprises gas-cluster ions, at least a fraction of which are multiply ionized.

6. The apparatus of claim 4 , wherein the pressure-controlled region comprises a region within a pressure chamber.

7. The apparatus of claim 1 , wherein:

the reduced-pressure chamber further comprises an ionizing/acceleration chamber including the gas-cluster ion beam source;

the pressure-controlled region comprises a pressure chamber; and

the pressure chamber has a higher pressure than the ionizing/acceleration chamber.

8. The apparatus of claim 7 , wherein:

the reduced-pressure chamber further comprises a processing chamber; and

the pressure chamber has a higher pressure than the processing chamber.

9. The apparatus of claim 1 , wherein the pressure-controlled region comprises a region within a pressure cell.

10. The apparatus of claim 9 , wherein the gas-cluster ion beam source further comprises:

an ionizer for ionizing said gas-clusters to form a gas-cluster ion beam; and

an accelerator for accelerating said gas-cluster ion beam to form an energetic gas-cluster ion beam.

11. The apparatus of claim 9 , further comprising a control system for controlling a pressure in the pressure cell.

12. The apparatus of claim 9 , wherein the energetic gas-cluster ion beam comprises gas-cluster ions, at least a fraction of which are multiply ionized.

13. The apparatus of claim 9 , wherein the pressure cell has a higher pressure than the reduced-pressure chamber.

14. A method of processing a workpiece with a gas-cluster ion beam, comprising the steps of:

generating a gas-cluster ion beam with a gas-cluster ion beam source within a reduced-pressure chamber;

accelerating via an accelerator the gas-cluster ion beam to form an energetic gas-cluster ion beam having a beam path;

holding a workpiece within the reduced-pressure chamber;

providing an increased-pressure region between the accelerator and the workpiece, wherein at least a portion of the beam path traverses the increased-pressure region.

15. The method of claim 14 , wherein the generating step further comprises:

providing a pressurized gas source;

providing a nozzle

flowing pressurized gas through said nozzle for expanding the gas from said pressurized gas source into said reduced-pressure chamber to form gas-clusters;

providing an ionizer; and

ionizing said gas-clusters to form the gas-cluster ion beam.

16. The method of claim 14 , further comprising the steps of:

providing a control system for controlling a pressure in the increased-pressure region; and

controlling a pressure in the increased-pressure region with the control system.

17. The method of claim 14 , wherein the at least a portion of the beam path that traverses the increased-pressure region has a pressure-distance integral along the path within the increased-pressure region that is greater than about 5×10 −4 torr-cm.

18. The method of claim 14 , wherein the energetic gas-cluster ion beam comprises gas-cluster ions, at least a fraction of which are multiply ionized.

19. A method of modifying the gas-cluster ion energy distribution in an accelerated gas-cluster ion beam comprising the steps of:

generating a gas-cluster ion beam with a gas-cluster ion beam source within a reduced-pressure chamber;

accelerating with an accelerator within the reduced-pressure chamber the gas-cluster ion beam to form an energetic gas-cluster ion beam having a beam path and a gas-cluster ion energy distribution;

providing an increased-pressure region in the reduced-pressure chamber;

directing the energetic gas-cluster ion beam path so as to traverse the increased-pressure region with at least a portion of the gas-cluster ion beam path, producing a gas-cluster ion beam with a modified gas-cluster ion energy distribution.

20. The method of claim 19 , wherein the at least a portion of the gas-cluster ion beam path that traverses the increased-pressure region has a pressure-distance integral along the path within the increased-pressure region that is greater than about 5×10 −4 torr-cm.

21. The method of claim 19 , further comprising the steps of:

providing a control system for controlling a pressure in the increased-pressure region; and

controlling a pressure in the increased-pressure region.

22. The method of claim 21 , wherein the controlling step controls a pressure within the increased-pressure region such that the pressure-distance integral along the path is greater than about 5×10 −4 torr-cm.

23. The method of claim 19 , wherein the energetic gas-cluster ion beam comprises gas-cluster ions, at least a fraction of which are multiply ionized.