Cryogenic heat transfer systems and ion implantation systems

Abstract

A low temperature heat transfer system and an ion implantation system are provided. A low temperature heat transfer system includes a platen, a housing, the platen is supported by a rotatable shaft, the housing surrounds a portion of the rotatable shaft, the housing includes: an annular heat sink, surrounding the rotatable shaft and defining a heat transfer gap between the heat sink and the rotatable shaft, the heat sink including a fluid conduit extending through the heat sink to circulate a first cooling fluid through the heat sink; a first dynamic seal configuration extending from a first axial end of the heat sink and surrounding the rotatable shaft; and a second dynamic seal configuration extending from a second axial end of the heat sink opposite to the first axial end and radially surrounding the rotatable shaft; wherein the heat sink and the first and second dynamic seal configurations define a fluid sealing volume surrounding the rotatable shaft, the fluid sealing volume containing a second cooling fluid.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to the field of semiconductor processing equipment, and more particularly, to a cryogenic heat transfer system for cooling a rotatable platen used in an ion implantation process and an ion implantation system. Background Art

[0002] Ion implantation is a standard technique for introducing property-changing impurities into a substrate. During the ion implantation process, the desired impurity material ("dopant") is ionized in a source chamber and the ions are directed through an extraction aperture. The ions are accelerated to form an ion beam of a specified energy and directed onto the surface of a substrate, which is disposed on a rotatable platen in a process chamber. The energetic ions in the ion beam penetrate the subsurface of the substrate material and are embedded into the crystal lattice of the substrate material to form regions having the desired conductivity or material properties.

[0003] In some ion implantation processes, the desired implantation profile is achieved by implanting ions into the target substrate at low temperatures (e.g., between -100 degrees Celsius and -200 degrees Celsius). During the ion implantation process, cooling the target substrate to such a temperature can be achieved by supporting the substrate on a cooled platen. Typically, the platen is cooled by circulating a cooling fluid (e.g., helium or nitrogen) around the axis of the platen under high pressure and in direct contact with the axis. In the case of a rotatable platen, a dynamic fluid seal is implemented around the axis while allowing the axis to rotate to prevent the cooling fluid from leaking into the process environment of the substrate. Such seals are typically very complex, difficult to implement, and prone to leaking when facing the fluid under high pressure. Therefore, such seals actually limit the options for cooling fluids to those that are suitable for being sealed and have minimal or no significant risk of leakage. For example, although fluids and certain gases (e.g., helium) may be the best choice for use as cooling fluids, less efficient gases (e.g., nitrogen) are often selected because less efficient gases are easier to seal under high pressure.

[0004] With regard to these and other considerations, the present improvements may be useful. Summary of the invention

[0005] This Summary is provided to introduce a selection of concepts in a simplified form. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is this Summary intended to be an aid in determining the scope of the claimed subject matter.

[0006] An embodiment of a low-temperature heat transfer system according to the present disclosure may include a platen and a shell, wherein the platen is supported by a rotatable shaft, and the shell surrounds a portion of the rotatable shaft, the shell including: an annular heat sink surrounding the rotatable shaft and defining a heat transfer gap between the heat sink and the rotatable shaft, the heat sink including a fluid conduit extending through the heat sink to circulate a first cooling fluid through the heat sink; a first dynamic sealing configuration extending from a first axial end of the heat sink and surrounding the rotatable shaft; and a second dynamic sealing configuration extending from a second axial end of the heat sink opposite to the first axial end and radially surrounding the rotatable shaft, wherein the heat sink and the first and second dynamic sealing configurations define a fluid sealing volume surrounding the rotatable shaft, and the fluid sealing volume accommodates a second cooling fluid.

[0007] Another embodiment of a low-temperature heat transfer system according to the present disclosure may include a platen, a drive mechanism, and a shell, wherein the platen is supported by a rotatable shaft, the drive mechanism is coupled to the rotatable shaft to rotate the rotatable shaft, the shell surrounds a portion of the rotatable shaft, the shell includes an annular heat sink, the annular heat sink surrounds the rotatable shaft and defines a heat transfer gap between the heat sink and the rotatable shaft, and the heat sink includes a fluid conduit extending through the heat sink to circulate a first cooling fluid through the heat sink. The housing may further include: a first dynamic seal configuration extending from a first axial end of the heat sink and surrounding the rotatable shaft, the first dynamic seal configuration comprising a first rotating support member and a first stationary support member, the first rotating support member being fixed to the rotatable shaft, the first stationary support member surrounding the first rotating support member and being fixed to the heat sink, wherein the first rotating support member and the first stationary support member cooperate with each other to form a fluid-tight seal, the fluid-tight seal surrounding the rotatable shaft while allowing the rotatable shaft to rotate; and a second dynamic seal configuration extending from a second axial end of the heat sink opposite the first axial end and radially surrounding the rotatable shaft, the second dynamic seal configuration comprising a second rotating support member and a second stationary support member, the second rotating support member being fixed to the rotatable shaft, the second stationary support member surrounding the second rotating support member and being fixed to the heat sink, wherein the second rotating support member and the second stationary support member cooperate with each other to form a fluid-tight seal, the fluid-tight seal surrounding the rotatable shaft while allowing the rotatable shaft to rotate. The heat sink and the first and second dynamic seal arrangements define a fluid-sealed volume surrounding the rotatable shaft, the fluid-sealed volume containing a second cooling fluid, and wherein a fluid pressure of the first cooling fluid is greater than a fluid pressure of the second cooling fluid.

[0008] An embodiment of an ion implantation system according to the present disclosure may include a process chamber defining a closed process environment, a platen, and a housing, wherein the process chamber defines a closed process environment, the platen is supported by a rotatable shaft disposed in the process chamber, the housing surrounds a portion of the rotatable shaft, the housing includes: an annular heat sink surrounding the rotatable shaft and defining a heat transfer gap between the heat sink and the rotatable shaft, the heat sink including a fluid conduit extending through the heat sink to circulate a first cooling fluid through the heat sink; a first dynamic seal configuration extending from a first axial end of the heat sink and surrounding the rotatable shaft; and a second dynamic seal configuration extending from a second axial end of the heat sink opposite the first axial end and radially surrounding the rotatable shaft. The heat sink and the first and second dynamic seal configurations define a fluid seal volume surrounding the rotatable shaft, the fluid seal volume containing a second cooling fluid. The ion implantation system may further include a chilling unit connected to the fluid conduit by a fluid line and adapted to cool the first cooling fluid, wherein the chilling unit, the fluid line, and the fluid conduit define a stationary closed-loop fluid circuit that is fluid-tight with respect to the process environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] By way of example, various embodiments of the disclosed system will now be described with reference to the accompanying drawings, in which:

[0010] Figure 1 is a schematic cross-sectional side view illustrating a cryogenic heat transfer system according to a non-limiting embodiment of the present disclosure. DETAILED DESCRIPTION

[0011] The present embodiment will now be described more fully below with reference to the accompanying drawings, in which some embodiments are shown. The subject matter of the present disclosure can be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. These embodiments are provided so that the present disclosure will be thorough and complete and will fully convey the scope of the subject matter to those skilled in the art. In all drawings, the same numerals refer to the same elements.

[0012] According to the present disclosure, a low temperature heat transfer system is provided and will be described in detail below. The low temperature heat transfer system of the present disclosure can facilitate the cooling of a rotatable platen in an ion implantation system while eliminating or greatly reducing the risk of leakage of high pressure cooling fluid into the process environment of the ion implantation system. The dynamic fluid seals of the provided low temperature heat transfer system only need to accommodate cooling fluid maintained at a low pressure, thereby reducing the difficulty and complexity associated with implementing dynamic fluid seals relative to dynamic fluid seals typically implemented in conventional cooled rotatable platens.

[0013] Reference Figure 1 , Figure 1 A cross-sectional side view of a cryogenic heat transfer system 10 (hereinafter “system 10”) according to a non-limiting exemplary embodiment of the present disclosure is shown. For convenience and clarity, terms such as “top,” “bottom,” “above,” “below,” “lower,” “upper,” “downward,” “upward,” “vertical,” “axial,” and “radial” may be used below to describe the relative placement and orientation of various components of system 10, all of which are intended to Figure 1 The geometry and orientation of the system 10 is depicted in FIG. 1. The terminology shall include the words specifically mentioned, derivatives thereof and words of similar import.

[0014] The system 10 may include a generally flat, disk-shaped platen 12 adapted to hold a substrate 14 (e.g., a semiconductor wafer) in a process chamber 16 of an ion implantation system. The platen 12 may include an electrostatic chuck 15 disposed on or otherwise integrated with the platen 12 to facilitate securely clamping the substrate 14 to the platen 12. The electrostatic chuck 15 may be of any type familiar to one of ordinary skill in the art and is not germane to the present disclosure. In various alternative embodiments, a mechanical chuck may replace the electrostatic chuck 15. The present disclosure is not limited thereto. The platen 12 may be supported by a rotatable shaft 18 extending vertically from a bottom surface of the platen 12. In various embodiments, the platen 12 and the shaft 18 may be separate components mechanically coupled together, or may be part of a continuous, unitary structure (e.g., formed from a continuous piece of material). Platen 12 and shaft 18 may be formed of aluminum, alumina, stainless steel, or other materials having similarly good thermal conductivity (eg, thermal conductivity greater than 175 watts per meter Kelvin). The present disclosure is not limited in this regard.

[0015] The shaft 18 of the system 10 may be rotatably mounted within a housing 20 and may be coupled to a drive mechanism 21 (e.g., a rotary drive motor and pulley arrangement, a direct drive rotary motor, etc.) adapted to controllably rotate the shaft 18 and the platen 12 about a vertical axis 22. The housing 20 may be adapted to cool the shaft 18 and the platen 12 while allowing the drive mechanism 21 to rotate the shaft 18 and the platen 12. The housing 20 may include a generally annular, or cylindrical, heat sink 24 that radially surrounds the shaft 18 in a close clearance relationship with the shaft 18. The inner surface of the heat sink 24 may be generally coaxial with the outer surface of the shaft 18, and a heat transfer gap 26 may be defined between the inner surface of the heat sink 24 and the outer surface of the shaft 18. In various embodiments, the heat transfer gap 26 may have a width in a range of 25 microns to 150 microns. The present disclosure is not limited in this regard. The heat sink 24 may be formed of aluminum, alumina, stainless steel, or other material having similarly good thermal conductivity (e.g., thermal conductivity greater than 175 Watts per meter Kelvin). In various embodiments, the heat sink and shaft 18 may be formed of the same material (or a material having the same or similar coefficient of thermal expansion) to maintain the width of the heat transfer gap regardless of temperature.

[0016] The heat sink 24 may include a fluid conduit 28 extending through the heat sink 24 to circulate a first cooling fluid 30 through the heat sink 24, as further described below. The first cooling fluid 30 may be any fluid or gas suitable for cooling the heat sink 24. Such fluids and gases include, but are not limited to, liquid or gaseous nitrogen, liquid or gaseous helium, neon, and the like. The fluid conduit 28 may have a fluid inlet port 32 and a fluid outlet port 34, which are connected to a chilling unit 36 ​​through fluid lines 38 and 40, respectively. The chilling unit 36 ​​may cool the first cooling fluid 30 to a predetermined temperature and may pump the first cooling fluid 30 through the fluid conduit 28 at a high pressure (e.g., 2,500 torr to 10,000 torr) to cool the heat sink 24. In various embodiments, the chilling unit 36 ​​may be a commercial chiller (e.g., a Cold Helium Circulation System sold by CRYOMECH). The quench unit 36, fluid lines 38, 40, and fluid conduit 28 may define a stationary closed-loop fluid circuit that is fluid-tight with respect to a process environment 42 within the process chamber 16. Thus, the quench unit 36 ​​may circulate the first cooling fluid 30 at high pressure through the heat sink 24 without risk (or with very little risk) of the first cooling fluid 30 leaking into the process environment 42.

[0017] Although the fluid conduit 28 is Figure 1Although shown as being generally U-shaped, various alternative embodiments are contemplated in which the fluid conduit 28 may define a curvilinear, spiral, irregular, or tortuous path through the heat sink 24. Additionally, in some embodiments, the fluid conduit may extend completely around the axis 18 one or more times. Furthermore, although Figure 1 One fluid conduit 28 is depicted, but various alternative embodiments of the present disclosure are contemplated in which the heat sink 24 may include multiple fluid conduits extending through the heat sink 24. The present disclosure is not limited in this regard.

[0018] The housing 20 may further include a first dynamic seal arrangement 44 and a second dynamic seal arrangement 46 disposed on opposite axial sides of the heat sink 24 (ie, as shown in FIG. Figure 1 2 and 3. The first and second dynamic seal configurations 44 and 46 are shown in FIGS. 1 and 10 (a top side and a bottom side of the heat sink 24 shown in FIG. 1 ) and radially surround the shaft 18. The first and second dynamic seal configurations 44 and 46 may be substantially identical, mirror images of each other (i.e., vertically inverted relative to each other). Therefore, for the sake of brevity, the first dynamic seal configuration 44 will be described in detail below, and this description should also apply to the second dynamic seal configuration 46. Reference numbers assigned to various components of the first dynamic seal configuration 44 should also refer to corresponding components of the second dynamic seal configuration 46.

[0019] The first dynamic seal configuration 44 may include a rotating support member 48 fixed to the shaft 18 and a stationary support member 50 radially surrounding the rotating support member 48. The rotating support member 48 may include an annular first thermal insulator 52 directly coupled to the outer surface of the shaft 18. In various examples, the first thermal insulator 52 may be coupled to the shaft 18 by welding, brazing, various thermal insulating adhesives, various mechanical fasteners (e.g., screws, bolts, etc.), clamps, etc. The first thermal insulator 52 may be formed of ceramic, plastic, or other materials having similarly poor thermal conductivity (e.g., thermal conductivity less than 20 watts per meter Kelvin). The present disclosure is not limited in this regard.

[0020] The rotation support member 48 may further include a rotation support 54 that radially surrounds the first thermal insulator 52 and is coupled to the first thermal insulator 52. The rotation support 54 may be formed of, for example, stainless steel, and may be coupled to the first thermal insulator 52 by welding, brazing, various thermal insulation adhesives, various mechanical fasteners, etc. In alternative embodiments, the rotation support 54 and the first thermal insulator 52 may be parts of a continuous integral structure (e.g., formed from a continuous piece of material). The present disclosure is not limited thereto.

[0021] The stationary support member 50 of the first dynamic seal configuration 44 may extend axially from the heat sink 24 and may radially surround the rotating support member 48. The stationary support member 50 may include an annular second thermal insulator 58 coupled to an axial end face 60 of the heat sink 24. In various examples, the second thermal insulator 58 may be coupled to the heat sink by welding, brazing, various thermal insulating adhesives, various mechanical fasteners (e.g., screws, bolts, etc.), clamps, etc. Like the first thermal insulator 52, the second thermal insulator 58 may be formed of ceramic, plastic, or other materials having similarly poor thermal conductivity (e.g., thermal conductivity less than 20 watts per meter Kelvin). The present disclosure is not limited in this regard.

[0022] The stationary support member 50 may further include a stationary support 62 extending axially from and coupled to the second thermal insulator 58. Like the rotating support 54, the stationary support 62 may be formed of, for example, stainless steel, and may be coupled to the second thermal insulator 58 by welding, brazing, various thermal insulating adhesives, various mechanical fasteners, etc. In alternative embodiments, the stationary support 62 and the second thermal insulator 58 may be part of a continuous unitary structure (e.g., formed from a continuous piece of material). The present disclosure is not limited in this regard.

[0023] The radially inwardly facing surface of the stationary bearing support 62 may be disposed in a parallel, spaced-apart, facing relationship with the radially outwardly facing surface of the rotating bearing support 54 to define a gap 68 between the radially inwardly facing surface of the stationary bearing support 62 and the radially outwardly facing surface of the rotating bearing support 54. A bearing 70 may be disposed within the gap 68 and the bearing 70 may engage the radially facing surfaces of the stationary bearing support 62 and the rotating bearing support 54 (e.g., may be "sandwiched" between the radially facing surfaces of the stationary bearing support 62 and the rotating bearing support 54). In various embodiments, the bearing 70 may be disposed within complementary grooves formed in the radially facing surfaces of the stationary bearing support 62 and the rotating bearing support 54, such as Figure 1As will be appreciated by one of ordinary skill in the art, the bearing 70 may facilitate smooth, relatively low-friction rotation of the rotating bearing member 48 and the attached shaft 18 relative to the stationary bearing member 50. An annular dynamic fluid seal 72 may be disposed within the gap 68 radially inward (i.e., closer to the heat sink 24 relative to the bearing 70) of the bearing 70. The dynamic fluid seal 72 may provide a fluid-tight seal between radially facing surfaces of the stationary bearing support 62 and the rotating bearing support 54 while allowing the rotating bearing member 48 to rotate relative to the stationary bearing member 50. In various embodiments, the dynamic fluid seal 72 may be or may include any type of dynamic sealing configuration, including but not limited to a ferrofluid rotary seal, a mechanical lip seal, and the like. The present disclosure is not limited thereto.

[0024] In various embodiments, the stationary support member 50 may further include one or more heaters 74 coupled to the stationary support support 62. The heater 74 may adjust the temperature of the first dynamic seal configuration 44 to prevent cooling from the heat sink 24 and / or the shaft 18 from interfering with the operation of the dynamic fluid seal 72. In various embodiments, the heater 74 may be any type of resistive heater suitable for implementation in the process environment 42, including but not limited to conventional surface heaters. Alternative embodiments of the present disclosure are contemplated in which the heater 74 may be omitted.

[0025] As described above, the second dynamic seal configuration 46 can be substantially the same as the first dynamic seal configuration 44 (but vertically inverted relative to the first dynamic seal configuration 44). Therefore, the first dynamic seal configuration 44, the heat sink 24, and the second dynamic seal configuration 46 can together define a fluid-sealed volume 80 surrounding the shaft 18. The volume 80 can contain a second cooling fluid 82, which is maintained at a relatively low fluid pressure compared to the fluid pressure of the first cooling fluid 30 circulating through the heat sink 24. For example, the second cooling fluid 82 can be maintained at a fluid pressure in the range of 20 torr to 60 torr. The present disclosure is not limited in this regard. The second cooling fluid 82 can be the same as or different from the first cooling fluid 30, and can be any liquid or gas suitable for providing an effective thermally conductive medium for transferring heat from the shaft 18 to the heat sink 24. In various embodiments, the second cooling fluid 82 can be liquid or gaseous nitrogen, liquid or gaseous helium, neon, etc. The present disclosure is not limited in this regard.

[0026] During normal operation of the system 10, the quenching unit 36 ​​may pump the first cooling fluid 30 through the fluid conduit 28 to cool the heat sink 24 as described above. In various embodiments, the heat sink 24 may be cooled to a temperature of -150 degrees Celsius or less. The present disclosure is not limited thereto. The cooled heat sink 24 may in turn cool the second cooling fluid 82 in the adjacent volume 80 surrounding the shaft 18, and the cooled second cooling fluid 82 may in turn cool the shaft 18 and the platen 12, and in turn cool the substrate 14 disposed on the platen 12. Specifically, heat may be transferred from the substrate 14 to the platen 12 and the shaft 18, and then from the shaft 18 through the second cooling fluid 82 in the narrow heat transfer gap 26 to the heat sink 24, where the first cooling fluid 30 then carries the heat to the quenching unit 36. At the same time, the housing 20, and specifically the first dynamic seal configuration 44 and the second dynamic seal configuration 46, may allow the drive mechanism 21 to freely rotate the shaft 18 and the platen. Since the pressure of the second cooling fluid 82 is relatively low, the dynamic fluid seals 72 of the first dynamic sealing configuration 44 and the second dynamic sealing configuration 46 can effectively retain the second cooling fluid 82 within the volume 80 without the risk (or very small risk) of the second cooling fluid 82 leaking into the process environment 42.

[0027] In various embodiments, the system 10 may further include a temperature sensor 86 (e.g., a thermocouple, a thermistor, etc.) for measuring the temperature of the substrate 14. The measured temperature may be transmitted to a controller 88 (e.g., a programmable logic controller, a microcontroller, etc.), which is operably connected to the chilling unit 36. The controller 88 may specify various operating parameters of the chilling unit 36 ​​based on the measured temperature to control the cooling provided by the chilling unit 36 ​​to achieve a predetermined temperature in the substrate 14. Such parameters may include, but are not limited to, the cooling temperature and flow rate of the chilling unit 36.

[0028] In view of the foregoing, the cryogenic heat transfer system of the present disclosure provides advantages in the art by facilitating cooling of a rotatable platen in an ion implantation system while eliminating or greatly reducing the risk of high pressure cooling fluid being leaked into the process environment of the ion implantation system. The cryogenic heat transfer system of the present disclosure provides a further advantage by allowing a selection of a variety of different cooling fluids to circulate about the axis of the rotatable platen, because such cooling fluids are maintained at a low fluid pressure and thus can be easily and effectively sealed from the process environment using dynamic fluid seals. As a further advantage, and also because the cooling fluid surrounding the axis is maintained at a low fluid pressure, the difficulties and complexities associated with implementing dynamic fluid seals are reduced relative to dynamic fluid seals typically implemented in conventional cooled, rotatable platens.

[0029] As used herein, an element or step described in the singular and followed by the word "a" or "an" will be understood to not exclude multiple elements or steps, unless such exclusion is explicitly described. In addition, reference to "one embodiment" of the present disclosure is not intended to be interpreted as excluding the existence of additional embodiments that include the described features.

[0030] The scope of the present disclosure is not limited by the specific embodiments described herein. In fact, by reading the foregoing description and the accompanying drawings, various other embodiments of the present disclosure and various modifications to the present disclosure other than the embodiments and modifications described herein will be apparent to those of ordinary skill in the art. Therefore, these other embodiments and modifications are intended to fall within the scope of the present disclosure. In addition, the present disclosure has been described herein in the context of specific embodiments in a specific environment for a specific purpose, but those of ordinary skill in the art will recognize that its applicability is not limited thereto. The embodiments of the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Therefore, the claims set forth above should be interpreted in light of the full breadth and spirit of the present disclosure described herein.

Claims

1. A low temperature heat transfer system comprising: a table supported by a rotatable shaft; as well as A housing surrounding a portion of the rotatable shaft, the housing comprising: an annular heat sink surrounding the rotatable shaft and defining a heat transfer gap between the heat sink and the rotatable shaft, the heat sink including a fluid conduit extending through the heat sink to circulate a first cooling fluid through the heat sink; a first dynamic seal configuration extending from a first axial end of the heat sink and surrounding the rotatable shaft, the first dynamic seal configuration comprising a first rotating support member fixed to the rotatable shaft and a first stationary support member surrounding the first rotating support member and fixed to the heat sink; and a second dynamic seal arrangement extending from a second axial end of the heat sink opposite the first axial end and radially surrounding the rotatable shaft, the second dynamic seal arrangement comprising a second rotating support member fixed to the rotatable shaft and a second stationary support member surrounding the second rotating support member and fixed to the heat sink; The heat sink and the first and second dynamic seal arrangements define a fluid-sealed volume surrounding the rotatable shaft, the fluid-sealed volume containing a second cooling fluid. 2 . The low temperature heat transfer system of claim 1 , wherein the heat transfer gap has a width in the range of 25 microns to 150 microns. 3 . The low temperature heat transfer system of claim 1 , wherein a fluid pressure of the first cooling fluid is greater than a fluid pressure of the second cooling fluid.

4. The low temperature heat transfer system of claim 3, wherein the fluid pressure of the first cooling fluid is in the range of 2,500 Torr to 10,000 Torr and the fluid pressure of the second cooling fluid is in the range of 20 Torr to 60 Torr.

5. The cryogenic heat transfer system of claim 1, wherein the first cooling fluid is one of nitrogen, helium, and neon.

6. The cryogenic heat transfer system of claim 1, wherein the second cooling fluid is one of nitrogen, helium, and neon.

7. The cryogenic heat transfer system of claim 1, further comprising a chilling unit connected to the fluid conduit and adapted to cool the first cooling fluid.

8. The low temperature heat transfer system of claim 1, wherein the rotatable shaft and the heat sink are formed of the same material.

9. The low temperature heat transfer system of claim 1, wherein the rotatable shaft is formed of a first material and the heat sink is formed of a second material different from the first material, wherein a coefficient of thermal expansion of the first material is equal to a coefficient of thermal expansion of the second material.

10. The cryogenic heat transfer system of claim 1, wherein the first rotating support member cooperates with the first stationary support member to form a fluid-tight seal that surrounds the rotatable shaft while allowing the rotatable shaft to rotate.

11. A low temperature heat transfer system comprising: a table supported by a rotatable shaft; a drive mechanism coupled to the rotatable shaft to rotate the rotatable shaft; as well as A housing surrounding a portion of the rotatable shaft, the housing comprising: an annular heat sink surrounding the rotatable shaft and defining a heat transfer gap between the heat sink and the rotatable shaft, the heat sink including a fluid conduit extending through the heat sink to circulate a first cooling fluid through the heat sink; a first dynamic seal configuration extending from a first axial end of the heat sink and surrounding the rotatable shaft, the first dynamic seal configuration comprising a first rotating support member and a first stationary support member, the first rotating support member being fixed to the rotatable shaft, the first stationary support member surrounding the first rotating support member and fixed to the heat sink, wherein the first rotating support member and the first stationary support member cooperate to form a fluid-tight seal around the rotatable shaft while allowing the rotatable shaft to rotate; as well as a second dynamic seal configuration extending from a second axial end of the heat sink opposite the first axial end and radially surrounding the rotatable shaft, the second dynamic seal configuration comprising a second rotating support member and a second stationary support member, the second rotating support member being fixed to the rotatable shaft, the second stationary support member surrounding the second rotating support member and fixed to the heat sink, wherein the second rotating support member and the second stationary support member cooperate to form a fluid-tight seal around the rotatable shaft while allowing the rotatable shaft to rotate; The heat sink and the first and second dynamic seal configurations define a fluid-sealed volume surrounding the rotatable shaft, the fluid-sealed volume containing a second cooling fluid, and wherein a fluid pressure of the first cooling fluid is greater than a fluid pressure of the second cooling fluid.

12. An ion implantation system comprising: Process chamber, which defines a closed process environment; a platen supported by a rotatable shaft disposed within the process chamber; A housing surrounding a portion of the rotatable shaft, the housing comprising: an annular heat sink surrounding the rotatable shaft and defining a heat transfer gap between the heat sink and the rotatable shaft, the heat sink including a fluid conduit extending through the heat sink to circulate a first cooling fluid through the heat sink; a first dynamic seal configuration extending from a first axial end of the heat sink and surrounding the rotatable shaft, the first dynamic seal configuration comprising a first rotating support member fixed to the rotatable shaft and a first stationary support member surrounding the first rotating support member and fixed to the heat sink; and a second dynamic seal arrangement extending from a second axial end of the heat sink opposite the first axial end and radially surrounding the rotatable shaft, the second dynamic seal arrangement comprising a second rotating support member fixed to the rotatable shaft and a second stationary support member surrounding the second rotating support member and fixed to the heat sink; wherein the heat sink and the first and second dynamic seal arrangements define a fluid-tight volume surrounding the rotatable shaft, the fluid-tight volume containing a second cooling fluid; and A chilling unit is connected to the fluid conduit by a fluid line and is adapted to cool the first cooling fluid, wherein the chilling unit, the fluid line and the fluid conduit define a stationary closed-loop fluid circuit that is fluid-tight with respect to the process environment.

13. The ion implantation system of claim 12, wherein the heat transfer gap has a width in a range of 25 microns to 150 microns.

14. The ion implantation system of claim 12, wherein a fluid pressure of the first cooling fluid is greater than a fluid pressure of the second cooling fluid.

15. The ion implantation system of claim 14, wherein a fluid pressure of the first cooling fluid is in a range of 2,500 Torr to 10,000 Torr and a fluid pressure of the second cooling fluid is in a range of 20 Torr to 60 Torr.

16. The ion implantation system of claim 12, wherein the first cooling fluid is one of nitrogen, helium, and neon.

17. The ion implantation system of claim 12, wherein the second cooling fluid is one of nitrogen, helium, and neon.

18. The ion implantation system of claim 12 wherein said rotatable shaft and said heat sink are formed of the same material.

19. The ion implantation system of claim 12, wherein the rotatable shaft is formed of a first material and the heat sink is formed of a second material different from the first material, wherein a coefficient of thermal expansion of the first material is equal to a coefficient of thermal expansion of the second material.

20. The ion implantation system of claim 12, wherein the first rotating support member cooperates with the first stationary support member to form a fluid-tight seal that surrounds the rotatable shaft while allowing the rotatable shaft to rotate.

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