Vapor compression refrigeration chuck for ion implanters

• US 9,558,980 B2
• Filed: 03/17/2010
• Issued: 01/31/2017
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: Axcelis Technologies Incorporated
• Original Assignee: Axcelis Technologies Incorporated
• Inventors: Lee, William D., Purohit, Ashwin M., LaFontaine, Marvin R.
• Primary Examiner(s): Kim, Robert
• Assistant Examiner(s): OSENBAUGH-STEWAR, ELIZA W
• Application Number:
  US12/725,508
• Publication Number:
  US 20100171044A1
• Time in Patent Office: 2,512 Days
• Field of Search: 250/492.1, 250/492.21
• US Class Current: 1/1
• CPC Class Codes: H01J 2237/002 Cooling arrangements of objects being observed or treated H01J2237/2001
• CPC Class Codes: H01J 2237/2001 Maintaining constant desired temperature
• CPC Class Codes: H01J 2237/2007 Holding mechanisms
• CPC Class Codes: H01J 2237/20214 Rotation
• CPC Class Codes: H01J 2237/2065 Temperature variations maintaining constant desired temperature H01J2237/2001
• CPC Class Codes: H01J 2237/31701 Ion implantation
• CPC Class Codes: H01J 37/20 Means for supporting or positioning the objects or the material; Means for adjusting diaphragms or lenses associated with the support introducing the objects H01J37/18
• CPC Class Codes: H01J 37/3171 for ion implantation plasma immersion ion implantation H01J37/32412
• CPC Class Codes: H01L 21/67109 mainly by convection
• CPC Class Codes: H01L 21/6831 using electrostatic chucks

Abstract

Aspects of the present invention relate to ion implantation systems that make use of a vapor compression cooling system. In one embodiment, a thermal controller in the vapor compression system sends refrigeration fluid though a compressor and a condenser according to an ideal vapor compression cycle to help limit or prevent undesired heating of a workpiece during implantation, or to actively cool the workpiece.

Claims

1. An ion implantation system comprising:

a beamline assembly configured to steer an ion beam from an ion source towards an electrostatic chuck, wherein the electrostatic chuck includes an engagement region adapted to selectively retain a workpiece for implantation by the ion beam;

a compressor configured to receive vapor-phase refrigerant fluid from the electrostatic chuck and compress the vapor-phase refrigerant fluid to provide a compressed refrigerant fluid;

a condenser configured to condense the compressed refrigerant fluid to provide a condensed refrigerant fluid; and

a supply conduit to transport the condensed refrigerant fluid from the condenser to the electrostatic chuck, wherein the electrostatic chuck includes a cavity or recess to expand and vaporize the condensed refrigerant fluid to cool the engagement region of the electrostatic chuck, and wherein the cavity or recess comprises;

a flow restrictor which is defined in a body of the electrostatic chuck; and

a cooling channel which is disposed in the body of the electrostatic chuck and which is downstream of the flow restrictor, wherein the flow restrictor comprises;

first and second distal flow restrictor regions having respective sidewalls separated by a first flow restrictor width, wherein the first distal flow restrictor region is proximate to the supply conduit and the second distal flow restrictor region is proximate to the cooling channel; and

a central flow restrictor region separating the first and second distal flow restrictor regions and having sidewalls separated by a second flow restrictor width that is greater than the first flow restrictor width.

2. The ion implantation system of claim 1, wherein the compressor is configured to compress the vapor-phase refrigerant fluid though an isentropic temperature rise.

3. The ion implantation system of claim 1, wherein the condenser is configured to condense the compressed refrigerant fluid at a constant pressure by removing heat from the refrigerant fluid.

4. The ion implantation system of claim 1, wherein the electrostatic chuck comprises:

a first plate having first and second opposing face regions, the first face region corresponding to the engagement region; and

a second plate having third and fourth opposing face regions, wherein the third face region meets the second face region of the first plate and wherein the cavity or recess is disposed within a body of the second plate between the third and fourth opposing face regions.

5. The ion implantation system of claim 4, further comprising:

a clamping control system operably coupled to the first plate and configured to selectively retain a workpiece on an engagement region of the first plate.

6. The ion implantation system of claim 5, wherein the clamping system comprises:

a voltage source operably coupled to the electrostatic chuck;

a gas source and vacuum source that are in fluid communication with a cavity or recess arranged within the first plate and corresponding to the engagement region;

wherein the voltage, gas, and vacuum sources are configured to act under direction of a clamping controller to selectively retain and release the workpiece from the engagement region of the electrostatic chuck.

7. An ion implantation system comprising:

an ion source configured to provide an ion beam;

a beamline assembly configured to steer the ion beam from the ion source towards an electrostatic chuck, wherein the electrostatic chuck includes a body made up of first and second plates;

a clamping control system operably coupled to the first plate and configured to selectively retain a workpiece on an engagement region of the first plate; and

a vapor compression cooling system operably coupled to the second plate and including one or more cooling channels in the second plate in which a vapor phase refrigerant is provided to cool the engagement region and thereby cool the workpiece, wherein the vapor compression cooling system comprises;

a compressor configured to receive vapor-phase refrigerant fluid from the electrostatic chuck and compress the vapor-phase refrigerant fluid to provide a compressed refrigerant fluid;

a condenser configured to condense the compressed refrigerant fluid to provide a condensed refrigerant fluid; and

a supply conduit to transport the condensed refrigerant fluid from the condenser to the electrostatic chuck, wherein the electrostatic chuck includes a flow restrictor and cooling channel defined in a body thereof, wherein the flow restrictor and cooling channel expand the condensed refrigerant fluid to vapor-phase to cool the engagement region of the electrostatic chuck, and wherein the flow restrictor comprises;

first and second distal flow restrictor regions having respective sidewalls separated by a first flow restrictor width, wherein the first distal flow restrictor region is proximate to the supply conduit and the second distal flow restrictor region is proximate to the cooling channel; and

a central flow restrictor region separating the first and second distal flow restrictor regions and having sidewalls separated by a second flow restrictor width that is greater than the first flow restrictor width.

8. The ion implantation system of claim 7, wherein the compressor is configured to compress the vapor-phase refrigerant fluid though an isentropic temperature rise.

9. The ion implantation system of claim 8, wherein the condenser is configured to condense the compressed refrigerant fluid at a constant pressure by removing heat from the refrigerant fluid.

10. The ion implantation system of claim 7, wherein the clamping system comprises:

a voltage source operably coupled to the electrostatic chuck;

a gas source and vacuum source that are in fluid communication with a cavity or recess corresponding to the engagement region of the first plate;

wherein the voltage, gas, and vacuum sources are configured to act under direction of a clamping controller to selectively retain and release the workpiece from the engagement region of the electrostatic chuck.

11. The ion implantation system of claim 7, wherein the first plate comprises:

an annulus region configured to make surface to surface contact with the workpiece; and

a central region circumscribed by the annulus region and being recessed relative to the annulus region by a predetermined distance;

wherein a cavity is defined between the central region and a backside of the workpiece when the workpiece is retained on the engagement region of the first plate.

12. The ion implantation system of claim 11, wherein the annulus region and central region comprise a semiconductor dielectric material having a bulk resistivity between 1×

10⁸ to 1×

10¹² ohm-cm.

13. The ion implantation system of claim 11, wherein the central region comprises one or more gas supply orifices and one or more gas return orifices to provide a fluid path by which a cushion of gas is to be provided between the central region and the backside of the workpiece, wherein the gas return orifices have an average diameter ranging from 2 millimeters and 500 microns.

14. A method comprising:

placing a workpiece on an engagement region of an electrostatic chuck;

receiving vapor-phase refrigerant fluid at a first temperature from the electrostatic chuck and compressing the vapor-phase refrigerant fluid to provide a compressed refrigerant fluid;

condensing the compressed refrigerant fluid to provide a condensed refrigerant fluid;

transporting the condensed refrigerant fluid to the electrostatic chuck; and

cooling the engagement region of the electrostatic chuck by expanding the condensed refrigerant fluid within the electrostatic chuck to vaporize the condensed refrigerant to exhibit a second temperature, which is less than the first temperature, wherein the condensed refrigerant fluid is vaporized within the electrostatic chuck via a flow restrictor that is defined within a body of the electrostatic chuck.

15. The method of claim 14, wherein the vapor-phase refrigerant fluid is compressed though an isentropic temperature rise.

16. The method of claim 14, wherein the compressed refrigerant fluid is condensed at a constant pressure by removing heat from the compressed refrigerant fluid.

17. The method of claim 14, wherein the flow restrictor comprises a central region having sidewalls separated by a first distance and distal regions having sidewalls separated by a second distance that is greater than the first distance.