Temperature-controlled electrodes to limit deposition rate and strain

Abstract

An apparatus for limiting electrode deposition and thermal strain is disclosed. The apparatus includes a fluid source connected to a cooling channel embedded in the electrode. By circulating the fluid through the cooling channel, a more uniform temperature can be maintained, thereby limiting thermal strain. Furthermore, the cooler temperature of the electrode can also limit the deposition rate. The cooling channel may be embedded using an additive manufacturing process.

Description

Technical Field

[0001] This application claims priority to U.S. Patent Application No. 17 / 975,016, filed October 27, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] Embodiments relate to an apparatus for limiting the thermal stress of an electrode proximate to an ion source, and more particularly to an electrode having an embedded cooling channel.

Background Art

[0003] Ions are used in a plurality of semiconductor processes such as implantation processes, amorphization processes, deposition processes, and etching processes. These ions can be created within an ion source chamber and extracted through an extraction aperture in the ion source chamber.

[0004] Those ions can be drawn through the extraction aperture by an optical system disposed outside of and proximate to the ion source chamber. General optical elements for an ion source include an extraction electrode, which can be a wall of the ion source chamber including the extraction aperture. Other optical elements include a suppression electrode and a ground electrode. The suppression electrode can be electrically biased to draw ions created within the ion source chamber. For example, the suppression electrode can be negatively biased to draw positive ions from within the ion source chamber. In some embodiments, by adding a focusing lens and an additional ground electrode, there can be up to five electrodes.

[0005] Those electrodes can each be a single conductive component having an aperture disposed therein. Alternatively, each electrode can be composed of two components, and those two components are spaced apart to create an aperture between the two components. In both embodiments, the ion beam passes through the aperture in each electrode. The portion of the electrode disposed proximate to the aperture is sometimes referred to as an optical edge. The portion of the electrode furthest from the aperture is sometimes referred to as a distal edge.

[0006] It is not uncommon for a portion of the ion beam extracted from the ion source chamber to strike the extraction electrode, suppression electrode, and ground electrode, causing each electrode to heat up along its optical edge. However, not all portions of these electrodes are equally affected by the extracted ions. Therefore, these electrodes may be heated unevenly by these extracted ions.

[0007] In some embodiments, uneven heating of the electrodes can be problematic. This problem can worsen as the length of the electrodes increases. Therefore, a device to limit the thermal strain caused by this uneven heating would be beneficial. [Overview of the Initiative]

[0008] An apparatus for limiting electrode deposition and thermal strain is disclosed. The apparatus includes a fluid source connected to a cooling channel embedded in the electrode. By circulating the fluid through the cooling channel, a more uniform temperature can be maintained, thereby limiting thermal strain. Furthermore, the cooler temperature of the electrode can also limit the deposition rate. The cooling channel may be embedded using an additive manufacturing process.

[0009] According to one embodiment, an apparatus for controlling the thermal strain of an electrode is disclosed. The apparatus comprises an ion source having extraction openings and having a plurality of chamber walls defining an ion source chamber, and an electrode disposed outside the ion source chamber and having openings aligned with the extraction openings, wherein the electrode has an embedded cooling channel. In some embodiments, the apparatus comprises a fluid source connected to the embedded cooling channel to allow fluid flow through the electrode. In some embodiments, the fluid source comprises a cooling device. In some embodiments, the fluid source comprises a heater. In some embodiments, the embedded cooling channel is lined with a thermally conductive material. In some embodiments, the thermally conductive material is copper. In some embodiments, the electrode includes a suppression electrode. In some embodiments, the electrode includes a ground electrode.

[0010] According to another embodiment, an apparatus for controlling thermal strain and / or deposition of an electrode is disclosed. The apparatus comprises an ion source having extraction openings and having a plurality of chamber walls defining an ion source chamber; an electrode disposed outside the ion source chamber and having openings aligned with the extraction openings, wherein the electrode has an embedded cooling channel; a fluid source connected to the embedded cooling channel; and a controller connected to the fluid source for controlling the flow rate and / or temperature of the fluid flowing through the embedded cooling channel. In some embodiments, the controller maintains the electrode within a predetermined temperature range to control thermal strain. In some embodiments, the apparatus comprises a thermal sensor, and the controller uses information from the electrode to maintain the predetermined temperature range. In some embodiments, the thermal sensor is disposed on the electrode. In some embodiments, the thermal sensor does not directly contact the electrode. In some embodiments, the fluid source comprises a cooling device. In some embodiments, the fluid source comprises a heater. In some embodiments, the controller controls the temperature of the fluid flowing through the embedded cooling channel based on the species ionized in the ion source to control deposition on the electrode.

[0011] According to another embodiment, an apparatus for controlling thermal strain of an extraction electrode is disclosed. The apparatus comprises an ion source having a plurality of chamber walls defining an ion source chamber and an extraction electrode, wherein the extraction electrode has an extraction opening, and an electrode disposed outside the ion source chamber and having an opening aligned with the extraction opening, wherein the extraction electrode has an embedded cooling channel. In some embodiments, a fluid source is connected to the embedded cooling channel to allow fluid flow through the extraction electrode. In some embodiments, the fluid source comprises a cooling device or heater. In some embodiments, the embedded cooling channel is lined with a thermally conductive material.

[0012] References to the accompanying drawings, incorporated herein by reference, are made for a better understanding of this disclosure. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an apparatus for controlling thermal strain according to one embodiment. [Figure 2A] This figure shows the inhibitory electrode before extraction. [Figure 2B] This figure shows the suppression electrode after being affected by the extracted ion beam. [Figure 3] This is a cross-sectional view of an electrode with an implanted channel. [Figure 4] Figure 3 is a perspective view of the electrode shown. [Figure 5] This figure shows a control system for controlling thermal strain according to one embodiment. [Modes for carrying out the invention]

[0014] Figure 1 shows one embodiment of a device that may be used to control the thermal strain of an extraction electrode 112, a suppression electrode 200, or a ground electrode 210. In this embodiment, an RF ion source 100 is shown. The RF ion source 100 comprises a plurality of chamber walls 111 defining an ion source chamber 110. An RF antenna 120 may be disposed within the ion source chamber 110. The RF antenna 120 may be made of a conductive material such as copper. The RF antenna 120 may be placed in a hollow tube 125, which may be made of a dielectric material such as quartz. An RF power supply 130 is in electrical communication with the RF antenna 120. The RF power supply 130 may supply an RF voltage to the RF antenna 120. The power supplied by the RF power supply 130 may be between 0.5 kW and 60 kW and may be at any preferred frequency, such as between 5 MHz and 15 MHz. Furthermore, the power supplied by the RF power supply 130 may be pulsed.

[0015] The figure shows an RF antenna 120 placed in a hollow tube 125 within an ion source chamber 110, but other embodiments are possible. For example, one of the chamber walls 111 may be made of a dielectric material, and the RF antenna 120 may be positioned outside the ion source chamber 110, close to the dielectric wall. In other embodiments, the plasma may be generated in different ways, such as by a Bernas ion source or an indirectly heated cathode (IHC). The modes in which the plasma is generated are not limited by this disclosure.

[0016] In some embodiments, the chamber walls 111 may be conductive and may be constructed from metal. In some embodiments, these chamber walls 111 may be electrically biased. In some embodiments, the chamber walls 111 may be grounded. In other embodiments, the chamber walls 111 may be biased at a certain voltage by a bias power supply 140. In some embodiments, the bias voltage may be a constant (DC) voltage. In other embodiments, the bias voltage may be pulsed. The bias voltage applied to the chamber walls 111 establishes the potential of the plasma in the ion source chamber 110. The difference between the plasma potential and the potential of the suppression electrode 200 may determine the energy of the extracted ions.

[0017] One chamber wall, called the extraction electrode 112, includes an extraction opening 115. The extraction opening 115 may be an opening through which ions generated in the ion source chamber 110 are extracted and directed toward the workpiece 10. The extraction opening 115 may be of any preferred shape. In some embodiments, the extraction opening 115 may be oval or rectangular, having one dimension called length, through which the length may be much larger than a second dimension called height. In some embodiments, the length of the extraction opening 115 may be as large as 2 meters or more. In some embodiments, only the extraction electrode 112 is conductive and connected to a bias power supply 140. The remaining chamber walls 111 may be made of dielectric material. In other embodiments, the extraction electrode 112 and all of the chamber walls 111 may be conductive. The bias power supply 140 may bias the extraction electrode 112 at a voltage between 1 kV and 5 kV, but other voltages are also within the scope of this disclosure.

[0018] The suppression electrode 200 is disposed outside and adjacent to the extraction opening 115. The suppression electrode 200 may be a single conductive component in which the suppression opening 205 is disposed. Alternatively, the suppression electrode 200 may consist of two conductive components, which are spaced apart to create a suppression opening 205 between them. The suppression electrode 200 may be a metal such as titanium. The suppression electrode 200 may be electrically biased using a suppression power supply 220. The suppression electrode 200 may be biased to be more negative than the extraction electrode 112. In some embodiments, the suppression electrode 200 is negatively biased by the suppression power supply 220 at a voltage between -3kV and -15kV, for example, but other voltages are also within the scope of this disclosure.

[0019] The ground electrode 210 can be disposed close to the suppression electrode 200. Like the suppression electrode 200, the ground electrode 210 can be a single conductive component in which a ground aperture 215 is disposed therein, or can be composed of two components, and these two components are separated so as to create a ground aperture 215 between the two components. The ground electrode 210 can be electrically connected to ground. Of course, in other embodiments, the ground electrode 210 can be biased using a separate power source. The extraction aperture 115, the suppression aperture 205, and the ground aperture 215 are all aligned. The ground electrode 210 is arranged such that the suppression electrode 200 is located between the extraction electrode 112 and the ground electrode 210.

[0020] The workpiece 10 is located downstream from the ground electrode 210. In some embodiments, the workpiece 10 is located immediately after the ground electrode 210. In other embodiments, additional components, such as a mass spectrometer, a collimating magnet, acceleration stages, and deceleration stages, can be disposed between the ground electrode 210 and the workpiece 10.

[0021] During operation, the feed gas from the gas storage container 150 is introduced into the ion source chamber 110 through the gas inlet 151. The RF antenna 120 is energized by the RF power source 130. This energy excites the feed gas and causes the creation of a plasma. The ions in the plasma are generally positively charged. Since the suppression electrode 200 is biased more negatively than the extraction electrode 112, the ions exit through the extraction aperture 115 in the form of an ion beam 1. The ion beam 1 passes through the extraction aperture 115, the suppression aperture 205, and the ground aperture 215 and proceeds towards the workpiece 10.

[0022] The portion of the suppression electrode 200 disposed close to the suppression aperture 205 in the height dimension may be referred to as an optical edge. The portion of the suppression electrode 200 furthest from the suppression aperture 205 in the height dimension may be referred to as a distal edge.

[0023] Similarly, a portion of the ground electrode 210 disposed close to the ground aperture 215 in the height dimension may be called an optical edge. A portion of the ground electrode 210 farthest from the ground aperture 215 in the height dimension may be called a distal edge.

[0024] Ions from the ion beam 1 extracted through the extraction aperture 115 can generally strike the suppression electrode 200 close to the optical edge. Further, ions from the ion beam 1 can also generally strike the ground electrode 210 close to the optical edge.

[0025] As the optical edge of the suppression electrode 200 is heated by the impact of ions, the length of the suppression electrode 200 can increase. This increase in length can be determined based on the coefficient of thermal expansion of the material used to create the suppression electrode 200. However, the increase in length may not be equal across the entire suppression electrode 200. For example, due to the thermal resistance of the material used to construct the suppression electrode 200, the distal edge of the suppression electrode 200 that is not directly struck by ions may not be as hot as the optical edge of the suppression electrode 200. This causes the optical edge of the suppression electrode 200 to expand more than the distal edge, causing the suppression electrode 200 to warp or bend.

[0026] FIG. 2A shows a suppression electrode 200 made from two components 201a, 201b. The space between the two components 201a, 201b defines a suppression aperture 205. Before the ion beam 1 is extracted, these two components 201a, 201b are not distorted, and thus, the optical edges 202a, 202b of the two components 201a, 201b are parallel to each other, respectively.

[0027] When the ion beam 1 is extracted, the ions strike the optical edges 202a and 202b of components 201a and 201b, causing these optical edges to expand. However, as described above, the distal edges 203a and 203b of components 201a and 201b may not expand to the same extent due to temperature differences. Therefore, the suppression electrode 200 is distorted as shown in Figure 2B. This distortion is exaggerated for illustrative purposes. In this figure, the optical edges 202a and 202b are expanded, causing each component 201a and 201b to bend. In some embodiments, the middle portion of each optical edge 202a and 202b in the length dimension bends toward the other optical edge 202a and 202b. This causes the shape of the suppression opening 205 to become irregular, such that the suppression opening 205 may be narrower in the middle portion than in the outer portion in the length dimension. Therefore, the beam current of ion beam 1 becomes non-uniform with respect to its length, which can be problematic. Furthermore, as the length of the suppression electrode 200 increases, the strain caused by thermal expansion may worsen.

[0028] The extraction electrode 112 and the ground electrode 210 may be similarly distorted by the ion beam 1.

[0029] To compensate for this unwanted strain, the cooling channel 310 may be embedded in the suppression electrode 200. Similarly, the cooling channel 310 may be embedded in the ground electrode 210 or the extraction electrode 112. Furthermore, in systems employing three or more electrodes, the cooling channel 310 may be embedded in any or all of these electrodes.

[0030] Since these electrodes are placed within the processing chamber, the choice of materials that can be used to create the embedded cooling channels may be limited. For example, conventional brazing techniques employ materials that are unsuitable for the processing chamber. Therefore, conventional manufacturing techniques may be unacceptable.

[0031] However, newer additive manufacturing techniques may be useful. For example, in one embodiment, ultrasonic additive manufacturing (UAM) may be used. In this embodiment, a conventional electrode is manufactured. In some embodiments, a portion of the electrode may be machined to create a channel on the exposed surface of the electrode. Then, UAM can be used to continuously add a thin layer of material to the electrode, effectively covering the channel and creating an embedded channel. Figure 3 shows one such embedded cooling channel 310 that can be created in an electrode 300 using this technique. Note that the material 320 above the cooling channel 310 may be added using UAM.

[0032] Alternatively, other additive manufacturing techniques, such as direct melting laser sintering (DMLS), selective laser sintering (SLS), and direct energy deposition (DED), can be used to create electrodes with embedded cooling channels.

[0033] Therefore, in this disclosure, the term “embedded cooling channel” refers to a cooling channel that is at least partially disposed within the body of the electrode. Accordingly, a cooling channel that is brazed, soldered, swaged, or possibly fixed to the outer surface of the electrode is not considered an embedded cooling channel.

[0034] The use of additive manufacturing also allows the embedded cooling channel to be lined with a more thermally conductive material. For example, as shown in Figure 3, a liner 330 may be disposed around the embedded cooling channel 310. In some embodiments, copper may be used to line the embedded cooling channel 310. Since the copper is completely contained within the electrode, there is no risk of contamination of the processing chamber.

[0035] Figure 4 shows a perspective view of an electrode 300 having an embedded cooling channel 310. In this figure, an external connector 340 is attached so that the embedded cooling channel 310 can be connected to a fluid.

[0036] In some embodiments, the embedded cooling channel may be a single channel having a constant cross-section similar to the cross-section shown in Figure 3. However, other embodiments are also possible. For example, the embedded cooling channel may have a meandering shape. Furthermore, Figure 3 shows an embedded cooling channel 310 positioned near the center of the electrode in the width direction. However, in other embodiments, the embedded cooling channel 310 may be offset in the height direction. For example, the embedded cooling channel 310 may be positioned closer to the optical edge. Furthermore, although Figure 3 shows a single embedded cooling channel, it should be understood that two or more embedded cooling channels may be positioned within the electrode. These multiple channels may be integrated with each other within the electrode or connected externally.

[0037] In some embodiments, the embedded cooling channel 310 is fluidly connected to one or more fluid sources. The fluid sources may contain water or another fluid, including liquids or gases. In one embodiment shown in Figure 5, the fluid source 400 may be a cooling device. The embedded cooling channel 310 of the electrode 300 is connected to the cooling device via two conduits 410, 420. In this way, the fluid is cooled so that the electrode 300 is kept at or below ambient temperature. For example, the fluid may be water and be cooled to a temperature below room temperature. In some embodiments, a controller 450 may be utilized. The controller 450 may include a processing unit and a storage element. The storage element may be any suitable non-temporary memory device, such as semiconductor memory (i.e., RAM, ROM, EEPROM, flash RAM, DRAM, etc.), magnetic memory (i.e., disk drive), or optical memory (i.e., CD-ROM). The storage element may be used to include instructions that, when executed by a processing unit in the controller 450, enable the fluid source 400 to control the thermal strain of the electrode 300. In detail, the controller 450 may control the fluid flow rate and / or temperature to maintain the electrode 300 within a predetermined temperature range.

[0038] In some embodiments, a thermal sensor 460 may be positioned on or near the electrode 300 to measure the temperature of the electrode 300. In some embodiments, the thermal sensor 460 is positioned near both the optical edge and the distal edge. In other embodiments, the thermal sensor 460 is positioned near only one of these two edges. These thermal sensors 460 may be a thermocouple, a resistance temperature detector (RTD), or other type of thermal sensor. In another embodiment, the thermal sensor 460 may not be positioned on the electrode 300. For example, the thermal sensor 460 may be an infrared camera, which may be positioned in a location where the temperature of the electrode 300 can be measured remotely. The infrared camera may be used interchangeably with an RTD or thermocouple in any of these embodiments.

[0039] Based on this information, the controller 450 can control the temperature and / or flow rate of the fluid in the cooling device or other fluid source.

[0040] In other embodiments, the fluid source 400 may include a heater that maintains the fluid at a temperature above the ambient temperature. For example, in some embodiments, the material from the RF ion source 100 is less likely to be deposited on the electrode 300 if its temperature is higher. Therefore, it should be understood that although these channels are called cooling channels, they can also be used to heat the electrode.

[0041] In other words, the controller 450 can control the temperature of the electrode 300 based on the species ionized in the RF ion source 100 to minimize electrode deposition. The controller 450 can do this by controlling the temperature of the fluid from the fluid source that flows through the embedded cooling channel.

[0042] This device has many advantages.

[0043] Firstly, the fluid flow through the embedded cooling channel can help maintain a uniform temperature throughout the electrode. This reduces the potential for thermal strain on the electrode, as shown in Figure 2B.

[0044] Secondly, the ability to control the electrode temperature can be useful in reducing the rate of deposition on the electrode. For example, some species are more likely to deposit on the electrode when the electrode is at a high temperature. In the case of these species, the electrode can be kept at a lower temperature. Conversely, other species may be more likely to deposit on the electrode when the electrode is at a colder temperature. In the case of these species, the fluid can be heated to keep the electrode at a higher temperature.

[0045] Thirdly, in some embodiments, the ion implantation system may not be usable until the electrode reaches its steady-state temperature. By passing a fluid at that temperature through an embedded cooling channel, the electrode can reach its steady-state temperature more rapidly, allowing for an increased operating time.

[0046] This disclosure should not be limited in scope by the specific embodiments described herein. In fact, various other embodiments and modifications of this disclosure, in addition to those described herein, will be apparent to those skilled in the art from the above description and the accompanying drawings. Accordingly, such other embodiments and modifications will fall within the scope of this disclosure. Furthermore, while this disclosure has been described herein in the context of a specific implementation in a specific environment for a particular purpose, those skilled in the art will recognize that the usefulness of this disclosure is not limited thereto, and that this disclosure can be usefully implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be interpreted in light of the entire scope and spirit of this disclosure as described herein.

Claims

1. A device for controlling the thermal strain of electrodes, An ion source having multiple chamber walls defining the ion source chamber and having extraction openings, An electrode disposed outside the ion source chamber and having an opening aligned with the extraction opening, wherein the electrode has an embedded cooling channel. A device equipped with the following features.

2. The apparatus according to claim 1, further comprising a fluid source connected to the embedded cooling channel to enable the flow of fluid through the electrode.

3. The apparatus according to claim 2, wherein the fluid source is equipped with a cooling device.

4. The apparatus according to claim 2, wherein the fluid source is equipped with a heater.

5. The apparatus according to claim 1, wherein the embedded cooling channel is lined with a thermally conductive material.

6. The apparatus according to claim 5, wherein the thermally conductive material is copper.

7. The apparatus according to claim 1, wherein the electrode includes a suppression electrode.

8. The apparatus according to claim 1, wherein the electrode includes a ground electrode.

9. An apparatus for controlling thermal strain and / or deposition of electrodes, An ion source having multiple chamber walls defining the ion source chamber and having extraction openings, An electrode disposed outside the ion source chamber and having an opening aligned with the extraction opening, wherein the electrode has an embedded cooling channel, A fluid source connected to the aforementioned embedded cooling channel, A controller connected to the fluid source for controlling the flow rate and / or temperature of the fluid flowing through the embedded cooling channel. A device equipped with the following features.

10. The apparatus according to claim 9, wherein the controller maintains the electrode within a predetermined temperature range to control thermal strain.

11. The apparatus according to claim 10, comprising a thermal sensor, wherein the controller uses information from the electrodes to maintain the predetermined temperature range.

12. The apparatus according to claim 11, wherein the thermal sensor is disposed on the electrode.

13. The apparatus according to claim 11, wherein the thermal sensor does not come into direct contact with the electrode.

14. The apparatus according to claim 9, wherein the fluid source is equipped with a cooling device.

15. The apparatus according to claim 9, wherein the fluid source is equipped with a heater.

16. The apparatus according to claim 9, wherein the controller controls the temperature of the fluid flowing through the embedded cooling channel based on the species ionized in the ion source in order to control the deposition on the electrode.

17. A device for controlling the thermal strain of an extraction electrode, An ion source having a plurality of chamber walls defining an ion source chamber and the extraction electrode, wherein the extraction electrode has an extraction opening, An electrode disposed outside the ion source chamber and having an opening aligned with the extraction opening, wherein the extraction electrode has an embedded cooling channel. A device equipped with the following features.

18. The apparatus according to claim 17, further comprising a fluid source connected to the embedded cooling channel to enable the flow of fluid through the extraction electrode.

19. The apparatus according to claim 18, wherein the fluid source comprises a cooling device or a heater.

20. The apparatus according to claim 17, wherein the embedded cooling channel is lined with a thermally conductive material.

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