Varying susceptor emissivity to manage beam power efficacy

Abstract

A workpiece mounting system including a chuck and a base is disclosed. The emissivity of the base is increased to enable more heat to be transferred from the chuck to the base. In some embodiments, the emissivity of the susceptor may be controllable such that the emissivity remains low for an ion beam having a lower power level, thereby enabling the chuck to quickly reach a desired temperature. For ion beams with higher power levels, the emissivity may be increased to enable more heat to be transferred to the susceptor, thereby enabling the chuck to maintain a desired temperature. A high emissivity coating may be applied to the top surface of the susceptor. In other embodiments, a set of movable shields may be disposed between the chuck and the base. The position of the shield may be a function of the power level of the incident ion beam.

Description

[0001] This application claims priority to U.S. patent application serial number 17 / 943,753 filed on September 13, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] The disclosed embodiments are directed to a system for varying the emissivity of a pedestal to improve heat transfer from an electrostatic chuck to the pedestal and enable higher power implants. Background Art

[0003] The manufacture of semiconductor devices involves multiple discrete and complex processes. Semiconductor workpieces typically undergo many processes during the manufacturing process. When the workpiece is processed, the workpiece is typically clamped to a chuck. This clamping can be mechanical or electrostatic in nature. Electrostatic chucks are traditionally composed of multiple layers. The top layer, also known as the top dielectric layer, contacts the workpiece and is made of an electrically insulating material or a semiconductor material so that the top layer generates an electrostatic field without forming a short circuit. To form an electrostatic force, a plurality of electrodes can be arranged below the top dielectric layer. The plurality of electrodes are composed of a conductive material (e.g., a metal).

[0004] In certain applications (e.g., fabrication of power devices), it may be beneficial to perform implantation at elevated temperatures. To increase the temperature of the workpiece, the workpiece is typically heated, for example, by contact (e.g., by using a gas trapped between the workpiece and the chuck) while the workpiece is held in place by electrostatic forces. The workpiece may also be heated directly through the chuck. In both embodiments, heat is applied to the lower surface of the workpiece through the chuck. To achieve these elevated temperatures, the chuck is typically maintained at elevated temperatures by using embedded resistive heating elements.

[0005] At lower beam power levels, the chuck is able to dissipate heat at a faster rate than the rate at which heat is provided by the ion beam. At these beam power levels, a heating element is used to maintain the desired temperature of the chuck. However, at higher beam power levels, the chuck cannot dissipate heat quickly enough to control the temperature of the workpiece. This phenomenon is called thermal runaway and may limit the beam power level that can be used. By using a beam power level lower than the desired level, the implant time is extended, resulting in reduced yield.

[0006] Therefore, it would be advantageous to provide a system that can dissipate the energy provided by the ion beam so that higher beam power levels can be utilized. Furthermore, it would be beneficial to have such a system applicable to both low power levels and high power levels. Summary of the invention

[0007] A workpiece mounting system including a chuck and a pedestal is disclosed. The emissivity of the pedestal is increased so that more heat can be transferred from the chuck to the pedestal. In some embodiments, the emissivity of the pedestal can be controllable so that for ion beams with lower power levels, the emissivity remains low, allowing the chuck to quickly reach a desired temperature. For ion beams with higher power levels, the emissivity can be increased so that more heat can be transferred to the pedestal, allowing the chuck to maintain a desired temperature. A high emissivity coating can be applied to the top surface of the pedestal. In other embodiments, a set of movable shields can be set between the chuck and the pedestal. The position of the shield can be a function of the power level of the incident ion beam.

[0008] According to one embodiment, a system for mounting and heating a workpiece is disclosed. The system includes: an electrostatic chuck; and a pedestal, separate from the electrostatic chuck; wherein a material having an emissivity different from that of the pedestal is disposed on a top surface of the pedestal. In some embodiments, the material includes a high emissivity coating. In certain embodiments, the high emissivity coating has an emissivity of 0.4 or greater than 0.4. In certain embodiments, the high emissivity coating has an emissivity of 0.6 or greater than 0.6. In some embodiments, the high emissivity coating includes at least one of anodized aluminum, anodized titanium, SiC, aluminum oxide, graphite, silicon, silicon dioxide, nickel-chromium alloy, and a ceramic coating. In certain embodiments, the material includes an electrochromic material. In some embodiments, the electrochromic material includes electrochromic glass. In certain embodiments, the electrochromic glass has a transmittance that varies by at least 30% depending on a voltage applied to the electrochromic glass.

[0009] According to another embodiment, a system for mounting and heating a workpiece is disclosed. The system includes: an electrostatic chuck; a pedestal, separate from the electrostatic chuck; and a controller configured to modify the amount of heat transfer between the electrostatic chuck and the pedestal based on the power level of the incident ion beam. In some embodiments, the electrochromic material is disposed on the top surface of the pedestal, and the system also includes an electrochromic power supply in communication with the electrochromic material and the controller, wherein the controller controls the voltage supplied to the electrochromic material by the electrochromic power supply. In some embodiments, the emissivity of the electrochromic material is greater than the emissivity of the top surface of the pedestal. In some embodiments, the transmittance of the electrochromic material is at a first value when a low-power ion beam is used, and is at a second value lower than the first value when a high-power ion beam is used. In certain embodiments, when the transmittance is the second value, the amount of heat transfer between the electrostatic chuck and the pedestal is greater than the amount of heat transfer when the transmittance is the first value. In some embodiments, the system also includes a movable shield, which is disposed between the electrochromic chuck and the pedestal. In some embodiments, the top surface of the pedestal is coated with a high emissivity material, the high emissivity material having an emissivity of 0.4 or greater. In some embodiments, the movable shield is made of a material having an emissivity lower than that of the high emissivity material. In some embodiments, the movable shield is in a closed position when a low-power ion beam is used and in an open position when a high-power ion beam is used, wherein in the closed position, the movable shield is positioned so that the top surface of the movable shield is parallel to the bottom surface of the electrostatic chuck. In some embodiments, the movable shield is in a closed position when a low-power ion beam is used and in an open position when a high-power ion beam is used, wherein in the closed position, the movable shield is positioned so that more than 80% of the heat radiated by the electrostatic chuck is blocked by the movable shield so that the heat does not propagate directly from the electrostatic chuck to the top surface of the pedestal. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a better understanding of the present disclosure, reference is made to the accompanying drawings which are incorporated herein by reference and wherein:

[0011] Figure 1 is a side view of a chuck and a base according to one embodiment.

[0012] Figure 2 is a side view of a chuck and a base according to another embodiment.

[0013] Figure 3A -B is a side view of the chuck and the base in the closed position and the open position respectively according to the third embodiment. DETAILED DESCRIPTION

[0014] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0015] As described above, in many applications, it may be advantageous to heat a workpiece while it is clamped to an electrostatic chuck. Traditionally, this heating is performed using conduction, where the heat contained in the electrostatic chuck is often transferred to the workpiece using a backside gas.

[0016] Various embodiments of a system for mounting and heating a workpiece are disclosed. Figure 1 A first embodiment is shown in FIG.

[0017] The chuck (which may be an electrostatic chuck 100) may include one or more electrodes 110 disposed in the chuck. The electrodes 110 are in communication with an electrode power supply 120. The electrode power supply 120 may supply a direct current (DC) voltage or an alternating current (AC) voltage to the electrodes 110. The frequency and amplitude of the voltage supplied to the electrodes 110 may be determined by design and are not limited by the present disclosure. In certain embodiments, the electrodes 110 may be arranged in pairs, wherein voltages of opposite polarity are provided to the pair of electrodes 110.

[0018] The electrostatic chuck 100 may also include heaters 130 embedded in the electrostatic chuck 100. These heaters 130 may be used to heat the electrostatic chuck 100 to a desired temperature. These heaters 130 may be resistive elements, wherein an electric current is passed through the heaters 130 to increase the temperature of the heaters 130. The heaters 130 may be in communication with a heating power source 135.

[0019] The backside gas passages may pass through the electrostatic chuck 100 and terminate on the top surface of the electrostatic chuck 100. The backside gas passages 150 may be in communication with a backside gas source. This backside gas is capable of conducting heat between the electrostatic chuck 100 and the workpiece 10.

[0020] The system also includes a pedestal 180, which is typically cooled. The pedestal 180 may be made of metal (e.g., aluminum). The pedestal 180 may be water-cooled. The pedestal 180 may be maintained at a lower temperature than the electrostatic chuck 100. The electrostatic chuck 100 may be separated from the pedestal 180 using a support or another mechanism, particularly for high temperature implantation, where proper thermal management is critical. The support enables reasonable temperature gradients and acceptable thermal stresses to be maintained in the electrostatic chuck 100 while keeping the wafer at a high temperature (e.g., for example, greater than 300° C.). In some embodiments, the electrostatic chuck 100 is separated from the pedestal 180 by a distance in a range of, for example, between 0.5 mm and 50 mm. In certain embodiments, the distance between the electrostatic chuck 100 and the pedestal 180 may be between 1.0 mm and 10 mm. Of course, other sizes may also be used.

[0021] The controller 190 may be in communication with the electrode power supply 120 and the heating power supply 135. The controller 190 has a processing unit and an associated memory device. This memory device contains instructions that enable the system to implement the functions described herein when executed by the processing unit. This memory device may be a non-volatile memory, such as a flash read-only memory (ROM) (FLASH ROM), an electrically erasable ROM, or other suitable devices. In other embodiments, the memory device may be a volatile memory, such as a random access memory (RAM) or a dynamic random access memory (DRAM). In certain embodiments, the controller 190 may be a general-purpose computer, an embedded processor, or a specially designed microcontroller. The actual implementation of the controller 190 is not limited by the present disclosure.

[0022] The heat transfer (Q) between electrostatic chuck 100 and pedestal 180 is determined by the following equation:

[0023]

[0024] where σ is the Stefan-Boltzmann constant, is the effective emissivity between the electrostatic chuck and the base, ε 卡盘 is the emissivity of the electrostatic chuck, and ε 基座 is the emissivity of the surface of the pedestal 180, assuming that the view factor between the electrostatic chuck and the pedestal is 1. A is the surface area of ​​the top surface of the pedestal, and T 卡盘 and T 基座 are the temperature of the electrostatic chuck 100 and the temperature of the susceptor 180 , respectively.

[0025] As described above, the base 180 is typically aluminum, and the emissivity of the base 180 is approximately 0.1 to 0.2 depending on the surface finish. Therefore, if the emissivity of the base 180 increases, more heat will be transferred to the base 180. Figure 1 In the embodiment shown in FIG, the top surface of the pedestal 180 has been coated with a high emissivity coating 181. This high emissivity coating 181 can be any material that controls the surface emissivity and also meets the semiconductor processing constraints, such as anodized aluminum, anodized titanium, SiC, aluminum oxide, graphite, silicon, silicon dioxide, nickel chromium alloy, ceramic coatings (such as Cerablak TM )) and other materials. The coating method may be, but is not limited to, atomic layer deposition (ALD), plasma vapor deposition (PVD), chemical vapor deposition (CVD), thermal spraying, and other methods. To achieve higher emissivity, the coating thickness may be 2 μm or greater, as long as good adhesion can be achieved between the high emissivity coating 181 and the base 180. The high emissivity coating 181 may be any coating having an emissivity of at least 0.4 that can be applied to the top surface of the base 180. Depending on the emissivity of the chuck, such a coating may approximately double the amount of heat transferred to the base 180. In some embodiments, the high emissivity coating has an emissivity of at least 0.6. Depending on the emissivity of the chuck, such a coating may approximately triple the amount of heat transferred from the electrostatic chuck 100 to the base 180. The emissivity of the high emissivity coating 181 may be customized by changing the material selection or chemical composition of the coating to control the emission and absorption of thermal energy. The coating emissivity is then controlled accordingly. The energy absorption of the pedestal 180 can also be further controlled by changing the surface roughness of the pedestal 180 (e.g., Ra>0.5 μm), which is an effective way to increase the surface area A, as described in equation (1). The increased roughness also has the additional benefit of increasing the adhesion between the high emissivity coating 181 and the pedestal 180.

[0026] Figure 2 In this embodiment, the electrostatic chuck 100 is connected to the Figure 1The same. The distance between the electrostatic chuck 100 and the base 180 can be as described above. In this embodiment, the electrochromic material 182 is applied to the top surface of the base 180. Although other thicknesses are possible, the electrochromic material 182 may have a thickness between 0.1 μm and 10 μm. The electrochromic material 182 may be connected to the electrochromic power supply 183. In operation, the transmittance of the electrochromic material 182 changes based on the voltage provided by the electrochromic power supply 183. The electrochromic material 182 may be a switchable glass (also known as smart glass) or may be a different material. The electrochromic material 182 may include an oxide of a transition metal, such as NbO x , WO3, MoO3, IrO2, NiO and V2O5. In one embodiment, the electrochromic material 182 may be tin-doped indium (ITO) nanocrystals in niobium oxide glass. It is reported that the transmittance of glass containing ITO nanocrystals can be changed from about 60% to about 95% by changing the applied voltage from 1.5V to 4V. In other words, the transmittance can be changed by at least 30% depending on the voltage applied to the electrochromic material 182. Of course, different voltages can also be used. In addition, the electrochromic material 182 generally has a much higher emissivity than aluminum, for example 0.9.

[0027] The controller 190 may be in communication with the electrochromic power source 183. Thus, the controller 190 is able to cause the transmittance of the electrochromic material 182 to change.

[0028] In this embodiment, the heat exchange between the chuck and the base can be written as:

[0029]

[0030] where τ is the transmittance, and is the effective emissivity between the electrostatic chuck and the electrochromic material 182 .

[0031] Therefore, the first part of the equation represents the heat transfer between the electrostatic chuck and the base, while the second part of the equation represents the heat transfer between the electrostatic chuck and the electrochromic material 182. When a high voltage (which may be, for example, 4V) is applied, the electrochromic material 182 becomes nearly transparent, i.e., τ→1, and equation (2) is equivalent to equation (1). If the base maintains the natural surface of the base (which may be ε 基座 =0.2), then this configuration will represent a low emissivity configuration. When the voltage is reduced, the transmittance τ can be reduced to 60%. In this scenario, equation (2) becomes towards a lower emissivity base (ε 基座 = 0.2) and heat transfer to high emissivity surfaces (ε 玻璃 =0.9) for mixed case of heat transfer.

[0032] Therefore, in Figure 1-2 In the illustrated embodiment, the top surface of the base 180 is covered with a material having an emissivity different from that of the base 180. This material may be a high emissivity coating 181, such as Figure 1 Alternatively, the material may be an electrochromic material 182, such as Figure 2 This material may have a higher emissivity than the top surface of the base 180.

[0033] Figure 3A-3B In this embodiment, the electrostatic chuck 100 is connected to the Figure 1 The distance between the electrostatic chuck 100 and the base 180 may be as described above. In this embodiment, one or more movable shields 185 are disposed between the base 180 and the electrostatic chuck 100. The movable shields 185 may be made of metal or another suitable material. Each of the movable shields 185 has a Figure 3A is defined as the horizontal width in Figure 3A , is defined as the thickness in the vertical direction and the length in the direction into the page. The length of each of the movable shields 185 may be such that each movable shield 185 is at least as long as the portion of the electrostatic chuck below which the movable shield 185 is disposed. In addition, the width of each of the movable shields 185 may be such that when the plurality of movable shields are placed adjacently in the width direction, the combined width is at least as wide as the electrostatic chuck 100. The thickness of the movable shield may be substantially less than the width of each shield. For example, in some embodiments, the ratio of the width to the thickness of the movable shield 185 may be at least 5:1. In other embodiments, the ratio may be 10:1 or greater.

[0034] Furthermore, the movable shielding member 185 is configured such that the movable shielding member 185 can pivot about an axis, such as Figure 3B In some embodiments, the movable shielding member may be capable of pivoting at least 90°. The pivot motor 186 may be in communication with the movable shielding member 185 so that the movable shielding member 185 can be moved from Figure 3A Rotate to the closed position shown in Figure 3B The controller 190 may be in communication with the pivot motor 186 .

[0035] Additionally, the emissivity of the top surface of the movable shield (which is the surface closest to the electrostatic chuck 100) can be different from the emissivity of the bottom surface. In some embodiments, the emissivity of the top surface can be greater than the emissivity of the bottom surface. In other embodiments, the emissivity of the two surfaces is the same.

[0036] In some embodiments, the movable shield 185 may have a low emissivity. In some embodiments, the movable shield 185 may have an emissivity of 0.4 or less. In other embodiments, the movable shield 185 may have an emissivity of 0.2 or less. In other embodiments, the movable shield 185 may have an emissivity of 0.1 or less. When in the closed position, such as Figure 3A As shown in , most of the heat radiated by the electrostatic chuck 100 is reflected back to the chuck, allowing the chuck to retain more heat of the chuck. In the closed position, the top surface of the movable shield 185 can be arranged in a plane parallel to the bottom surface of the electrostatic chuck 100. When in the closed position, the top surface of each movable shield is defined as the side closest to the chuck. In the closed position, more than 80% of the heat radiated by the electrostatic chuck can be blocked by the movable shield 185 so that the heat does not spread directly from the chuck to the top surface of the base 180. In other embodiments, more than 90% of the heat is blocked. Since almost all of the heat is first transferred to the movable shield and then transferred from the movable shield to the base, the effective emissivity between the electrostatic chuck 100 and the base 180 becomes:

[0037]

[0038] If ε 屏蔽件 is maintained in the range of <0.1 and the base has a high emissivity coating so that the emissivity is at least 0.4, then the effective emissivity ε eff，sh is much lower than the configuration without the movable shield 185. For example, under the following assumptions, ε 卡盘 =0.9,ε 基座 =0.9,ε 屏蔽件 = 0.1, the effective emissivity when the shield is closed is given by:

[0039]

[0040] This represents a low emissivity configuration.

[0041] When in the open position, Figure 3BAs shown in , the heat radiated by the electrostatic chuck can be directly transmitted to the top surface of the base 180. This is because the thickness of the movable shield 185 is much smaller than the width of the shield. In some embodiments, in the open position, the movable shield 185 can be rotated so that the top surface of the movable shield 185 is perpendicular to the bottom surface of the electrostatic chuck 100. This configuration minimizes the effectiveness of the movable shield 185 on the heat transfer between the electrostatic chuck 100 and the base 180. Of course, in other embodiments, the movable shield 185 can be rotated less than 90°. In the open position, more than 80% of the heat radiated by the electrostatic chuck can be directly transmitted from the chuck to the top surface of the base 180. In other embodiments, more than 90% of the heat is directly transmitted to the top surface of the base 180.

[0042] In this configuration, the base 180 may be coated with a high emissivity coating. Assuming the same emissivity as given above, the effective emissivity may be given by:

[0043]

[0044] This represents a high emissivity configuration.

[0045] Of course, other emissivities may also be utilized. For example, if a high emissivity coating on the base has an emissivity of 0.5, the emissivity is 0.047 when the shield is closed and 0.473 when the shield is open. In some embodiments, the emissivity of the top surface of the base 180 is greater than the emissivity of the movable shield 185.

[0046] Thus, in some embodiments, a material having a different emissivity than the base 180 may be applied to the top surface of the base 180. For example, a high emissivity coating 181 (e.g., Figure 1 Alternatively, an electrochromic material 182 may be applied to the top surface (e.g., Figure 2 The electrochromic material described in 182).

[0047] Figure 2 The embodiment shown in -3 makes the rate of heat transfer from the chuck adaptive.

[0048] For example, assume that an ion beam with a low power level is to be utilized. The low power level is defined as a power level at which the electrostatic chuck 100 is able to dissipate heat through radiative heat transfer faster than the ion beam transfers heat to the chuck. In these embodiments, a heater 130 in the chuck is used to maintain the electrostatic chuck 100 at a high temperature. In some embodiments, the low power beam may represent a beam power of less than 100 W. The high power level is defined as a power level at which the thermal energy supplied by the ion beam in a conventional chuck cannot be dissipated through the chuck, resulting in thermal runaway. In some embodiments, the high power level is defined as a beam power greater than 100 W. In other embodiments, the high power level may be defined as greater than 500 W. In still other embodiments, the high power level may be greater than 1000 W.

[0049] exist Figure 2 In the illustrated embodiment, the controller 190 can control the electrochromic power supply 183 to set the transmittance of the electrochromic material 182 to a first value. This first value can be close to 100%. In this mode, the electrochromic material 182 is close to transparent, and therefore the system operates similarly to a system that does not utilize the electrochromic material 182. When a high power level ion beam is used, the controller 190 can control the electrochromic power supply 183 to set the transmittance of the electrochromic material 182 to a second value lower than the first value, for example, less than 70%. Since the emissivity of the electrochromic material 182 is higher than the emissivity of the base 180, more heat is transferred from the electrostatic chuck when a high power ion beam is used.

[0050] Similar techniques can be applied to Figure 3A-3B 180. When a low power level ion beam is used, the controller 190 can control the pivot motor 186 to close the movable shield 185. This allows heat to be reflected back to the electrostatic chuck 100. When a high power level ion beam is used, the controller 190 can control the pivot motor 186 to move the movable shield 185 to an open position. In this position, heat can be reflected from the bottom surface of the shield to the base 180, and can also be directly transferred to the base 180. This increases the heat transfer between the electrostatic chuck 100 and the base 180 when a high power ion beam is used.

[0051] The above embodiments in the present application may have many advantages. In one simulation, the emissivity of the pedestal 180 was increased from 0.2 to 0.8. The maximum ion beam current that could be implanted without causing thermal runaway was increased by 50%. This simulation was verified by testing in which a high emissivity coating was applied to the pedestal 180. As predicted, the maximum ion beam current that did not cause thermal runaway was increased by 50%. By increasing the maximum allowable ion beam current, the throughput of the implant system can be increased. In addition, as Figure 2As shown in Figure 3, the ability to adaptively vary the heat transfer rate enables the same chuck and pedestal combination to be used for ion beams having both low and high power levels.

[0052] The scope of the present disclosure is not limited by the specific embodiments described herein. In fact, through the above description and the accompanying drawings, it will be apparent to those of ordinary skill in the art that, in addition to the embodiments and modifications described herein, various other embodiments of the present disclosure and various modifications to the present disclosure will also be apparent. Therefore, these other embodiments and modifications are intended to fall within the scope of the present disclosure. In addition, although the present disclosure has been described herein in the context of a specific embodiment in a specific environment for a specific purpose, it will be recognized by those of ordinary skill in the art that the utility of the present disclosure is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Therefore, the claims described above should be interpreted in light of the full scope and spirit of the present disclosure described herein.

Claims

1. A system for mounting and heating a workpiece, comprising: Electrostatic chuck; as well as a base, separate from the electrostatic chuck; A material having a different emissivity than the base is disposed on a top surface of the base.

2. The system of claim 1, wherein the material comprises a high emissivity coating.

3. The system of claim 2, wherein the high emissivity coating has an emissivity of 0.4 or greater.

4. The system of claim 2, wherein the high emissivity coating has an emissivity of 0.6 or greater.

5. The system of claim 2, wherein the high emissivity coating comprises at least one of anodized aluminum, anodized titanium, SiC, alumina, graphite, silicon, silicon dioxide, nickel-chromium alloy, and a ceramic coating.

6. The system of claim 1, wherein the material comprises an electrochromic material.

7. The system of claim 6, wherein the electrochromic material comprises electrochromic glass.

8. The system of claim 7, wherein the electrochromic glass has a transmittance that varies by at least 30% depending on a voltage applied to the electrochromic glass.

9. A system for mounting and heating a workpiece, comprising: Electrostatic chuck; a base, separate from the electrostatic chuck; as well as A controller is configured to modify an amount of heat transfer between the electrostatic chuck and the pedestal based on a power level of an incident ion beam.

10. The system of claim 9, wherein an electrochromic material is disposed on a top surface of the base, and further comprising an electrochromic power supply in communication with the electrochromic material and the controller, wherein the controller controls a voltage supplied by the electrochromic power supply to the electrochromic material.

11. The system of claim 10, wherein the emissivity of the electrochromic material is greater than the emissivity of the top surface of the base.

12. The system of claim 10, wherein the transmittance of the electrochromic material is at a first value when a low power ion beam is used, and is at a second value lower than the first value when a high power ion beam is used.

13. The system of claim 12, wherein the amount of heat transfer between the electrostatic chuck and the pedestal when the transmittance is the second value is greater than the amount of heat transfer when the transmittance is the first value.

14. The system of claim 9, further comprising a movable shield disposed between the electrostatic chuck and the pedestal.

15. The system of claim 14, wherein a top surface of the base is coated with a high emissivity material having an emissivity of 0.4 or greater.

16. The system of claim 15, wherein the movable shield is made of a material having an emissivity lower than the emissivity of the high emissivity material.

17. The system of claim 14, wherein the movable shield is in a closed position when a low power ion beam is used and in an open position when a high power ion beam is used, wherein in the closed position, the movable shield is positioned such that a top surface of the movable shield is parallel to a bottom surface of the electrostatic chuck.

18. The system of claim 14, wherein the movable shield is in a closed position when a low power ion beam is used and in an open position when a high power ion beam is used, wherein in the closed position, the movable shield is positioned such that more than 80% of the heat radiated by the electrostatic chuck is blocked by the movable shield so that the heat does not propagate directly from the electrostatic chuck to the top surface of the pedestal.

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