阅读说明：本技术 液态金属离子源 (Liquid metal ion source ) 是由 尼尔·巴瑟姆 尼尔·科尔文 哲-简·谢 迈克尔·阿米 于 2020-03-19 设计创作，主要内容包括：离子源配置成形成离子束并且具有电弧室,电弧室围封电弧室环境。储集器装置可以配置为推斥极并且向电弧室环境提供液态金属。偏置电源相对于电弧室对储集器装置进行电偏置,以使液态金属在电弧室环境中蒸发形成等离子体。储集器装置具有杯体和封盖,杯体和封盖限定用于液态金属的储集器环境,储集器环境通过封盖中的孔与电弧室环境流体联接。部件从杯体延伸到储集器中并接触液态金属,以通过毛细作用将液态金属朝向电弧室环境馈送。结构、表面积、粗糙度和材料改变毛细作用。该部件可以是延伸到液态金属中的环形圈、杆或管。(The ion source is configured to form an ion beam and has an arc chamber enclosing an arc chamber environment. The reservoir arrangement may be configured to repel poles and provide liquid metal to the arc chamber environment. A bias power supply electrically biases the reservoir arrangement relative to the arc chamber to vaporize the liquid metal in the arc chamber environment to form a plasma. The reservoir apparatus has a cup and a lid defining a reservoir environment for the liquid metal, the reservoir environment being fluidly coupled with the arc chamber environment through an aperture in the lid. A member extends from the cup into the reservoir and contacts the liquid metal to wick the liquid metal toward the arc chamber environment. Structure, surface area, roughness, and material change the capillarity. The component may be an annular ring, rod or tube extending into the liquid metal.)

1. An ion source configured to form an ion beam, the ion source comprising:

an arc chamber substantially enclosing an arc chamber environment;

a reservoir device configured to provide liquid metal to the arc chamber environment; and

a bias power supply configured to electrically bias the reservoir device relative to the arc chamber.

2. The ion source of claim 1, wherein the reservoir arrangement comprises a cup having a recess configured to substantially contain the liquid metal therein.

3. The ion source of claim 2, wherein the cup is configured to substantially contain the liquid metal therein by gravity.

4. The ion source of claim 2, wherein the reservoir arrangement further comprises a lid, wherein the lid selectively engages with the cup and substantially encloses a top portion of the reservoir arrangement in which a reservoir environment associated with the liquid metal is defined.

5. The ion source of claim 4, wherein the liquid metal resides in the reservoir environment, wherein the reservoir arrangement is further configured to selectively vaporize at least a portion of the liquid metal therein.

6. The ion source of claim 5, wherein the reservoir arrangement is configured to selectively evaporate the at least a portion of the liquid metal by selectively heating the reservoir arrangement via a heat source.

7. The ion source of claim 6, wherein the heat source comprises one or more of: a plasma generated within the arc chamber, energy associated with ions from the plasma impacting the reservoir device, an auxiliary heater.

8. The ion source of claim 4 wherein the cover comprises one or more apertures defined therein, wherein the one or more apertures provide fluid communication between the reservoir environment and the arc chamber environment.

9. The ion source of claim 8, wherein the lid further comprises one or more components extending into the recess, wherein the one or more components are configured to contact the liquid metal within the recess and feed the liquid metal toward the arc chamber environment via capillary action.

10. The ion source of claim 9, wherein the one or more components comprise one or more of: a surface material configured to provide said capillary action, a surface roughness, a predetermined surface area.

11. The ion source of claim 9, wherein the one or more components comprise one or more of: an annular member extending from the cover into the recess, a reservoir member extending from the recess toward the cover, an elongated member extending from a central portion of the cover into the liquid metal within the recess.

12. The ion source of claim 1, wherein the liquid metal is comprised of one of aluminum, gallium, and indium.

13. An arc chamber for forming an ion beam, the arc chamber comprising:

a housing substantially enclosing an arc chamber environment;

a reservoir device positioned within the arc chamber environment, wherein the reservoir device is configured to contain a liquid metal in the arc chamber environment; and

a bias power supply configured to electrically bias the reservoir device and form a plasma within the arc chamber environment.

14. The arc chamber of claim 13 wherein the reservoir arrangement comprises a cup and a lid, wherein the cup has a groove configured to at least partially contain the liquid metal therein, wherein the lid is selectively engaged with the cup and substantially encloses a top portion of the reservoir arrangement in which a reservoir environment associated with the liquid metal is defined, wherein the liquid metal resides in the reservoir environment, wherein the reservoir arrangement is further configured to selectively vaporize at least a portion of the liquid metal therein.

15. The arc chamber of claim 14 wherein the reservoir device is configured to selectively vaporize the at least a portion of the liquid metal by selectively heating the reservoir device via a heat source, wherein the heat source comprises one or more of a plasma generated within the arc chamber, energy associated with the ion beam, and an auxiliary heater.

16. The arc chamber of claim 15 wherein the cover comprises one or more apertures therein, wherein the one or more apertures provide fluid communication between the reservoir environment and the arc chamber environment, wherein the one or more apertures have one or more diameters, wherein the one or more apertures are oriented such that plasma in the arc chamber is not in direct contact with the liquid metal in the groove.

17. The arc chamber of claim 15 wherein the lid comprises one or more components extending into the cup, wherein the one or more components are configured to contact the liquid metal within the groove and feed the liquid metal toward the arc chamber environment via capillary action.

18. The arc chamber of claim 17 wherein the one or more components comprise one or more of an annular ring defined in the cover, wherein the annular ring extends from a main portion of the cover into the liquid metal within the groove.

19. The arc chamber of claim 17 wherein the one or more components comprise an elongated component that extends from a main portion of the cover into the liquid metal within the groove.

20. A method for forming an ion beam, comprising:

heating the elemental metal to a liquid state into an internal environment of the arc chamber;

evaporating the elemental metal; and

energizing the elemental metal to form metal ions within the arc chamber.

Technical Field

The present invention relates generally to ion implantation systems, and more particularly to apparatus, systems, and methods for providing source materials for an ion source.

Background

There is an increasing demand for ion implants using metal ions. For example, aluminum implantation is important to the power device market, which is a small but very rapidly growing market segment. For many metals, including aluminum, supplying feed materials to the ion source is problematic. Although gas molecules containing aluminum or other metals may be used, metal atoms tend to attach to carbon and/or hydrogen, which can cause problems with the ion source. Systems have previously been provided which utilize a vaporizer, which is a small oven located outside the arc chamber of the ion source, whereby the metal salt is heated to generate sufficient vapor pressure to supply the vapor to the ion source. However, the oven is remote from the arc chamber and requires time to heat to a desired temperature, generate a vapor stream, initiate a plasma, initiate an ion beam, and the like. Furthermore, if a change from one metallic substance to some other substance is required, it takes time to wait for the oven to cool sufficiently for this change of substance.

Another conventional technique is to place a metal-containing material, such as aluminum or another metal, within the arc chamber. For aluminum, the metal-containing material may include aluminum oxide, aluminum fluoride, or aluminum nitride, all of which may withstand temperatures of about 800 ℃ of the plasma chamber. In such systems, ions are sputtered directly from the material in the plasma. Another technique is to use a plasma containing an etchant such as fluorine to effect chemical etching of the metal. While acceptable beam currents can be obtained using these various techniques, compounds of alumina, aluminum chloride and aluminum nitride, all of which are good electrical insulators, tend to deposit on electrodes adjacent the ion source in a relatively short period of time (e.g., 5-10 hours). Thus, various adverse effects can be seen, such as high voltage instability and associated variations in the ion dose being implanted.

Disclosure of Invention

Aspects of the present disclosure facilitate ion implantation processes for increasing the length of time an ion source of an ion implantation system is used between preventative maintenance periods, thereby increasing the overall productivity and lifetime of the ion implantation system.

According to one example, an ion source configured to form an ion beam is provided, wherein the ion source comprises an arc chamber that substantially encloses an arc chamber environment. A reservoir apparatus configured to provide liquid metal to the arc chamber environment is also provided. A bias power supply is also configured to electrically bias the reservoir device relative to the arc chamber. The reservoir device, for example, includes a cup configured to substantially contain a liquid metal therein. For example, the cup is configured to substantially contain the liquid metal therein by gravity.

In one exemplary aspect, the reservoir apparatus further includes a lid, wherein the lid selectively engages the cup and substantially encloses a top portion of the reservoir apparatus, in which a reservoir environment associated with the liquid metal is defined. For example, the liquid metal resides in a reservoir environment, wherein the reservoir device is further configured to selectively vaporize at least a portion of the liquid metal therein. For example, the reservoir device is configured to selectively vaporize at least a portion of the liquid metal by selectively heating the introduction device via the heat source.

In one example, the heat source includes one or more of: a plasma generated within the arc chamber, energy associated with ions from the plasma striking the reservoir device, an auxiliary heater.

In another example aspect, the cover includes one or more apertures defined therein, wherein the one or more apertures provide fluid communication between the reservoir environment and the arc chamber environment. In one example, the lid further comprises one or more components extending into the reservoir, wherein the one or more components are configured to contact the liquid metal within the reservoir and wick the liquid metal toward the arc chamber environment. For example, the one or more components include one or more of: a surface material configured to provide capillary action, a surface roughness, a predetermined surface area. In another example, the one or more components include one or more of: an annular member extending from the lid into the reservoir, a reservoir member extending from the reservoir to the lid, an elongated member extending from a central portion of the lid into the liquid metal within the reservoir.

According to another aspect of the present disclosure, an arc chamber for forming an ion beam is provided, wherein the arc chamber includes a housing substantially enclosing an arc chamber environment. Within the arc chamber environment, for example, a reservoir device is provided, wherein the reservoir device is configured to contain liquid metal within the arc chamber environment. Further, a bias power supply is provided that is configured to electrically bias the reservoir device and form a plasma within the arc chamber environment.

In one example, a reservoir apparatus includes a cup configured to at least partially contain liquid metal therein and a lid, wherein the lid selectively engages with the cup and substantially encloses a top portion of the reservoir apparatus in which a reservoir environment associated with the liquid metal is defined. The liquid metal resides, for example, in a reservoir environment, wherein the reservoir device is further configured to selectively vaporize at least a portion of the liquid metal therein.

In another example, the reservoir apparatus is configured to selectively vaporize at least a portion of the liquid metal by selectively heating the reservoir apparatus via a heat source, wherein the heat source comprises one or more of a plasma generated within the arc chamber, energy associated with the ion beam, and an auxiliary heater.

For example, the lid may include one or more apertures therein, wherein the one or more apertures provide fluid communication between the reservoir environment and the arc chamber environment, and the one or more apertures have one or more diameters, and the one or more apertures are oriented such that the plasma in the arc chamber is not in direct contact with the liquid metal in the reservoir.

In another example, the lid may further include one or more components extending into the cup, wherein the one or more components are configured to contact the liquid metal within the reservoir and wick the liquid metal toward the arc chamber environment. For example, the one or more components may include one or more of an annular ring defined in the lid, wherein the annular lip extends from a main portion of the lid into the liquid metal within the reservoir. In another example, the one or more components include an elongated component that extends from a main portion of the cover into the liquid metal within the reservoir.

In yet another example aspect of the present disclosure, a method for forming an ion beam is provided in which an elemental metal is provided to an internal environment of an arc chamber and heated to a liquid state. Further vaporizing the elemental metal and energizing the elemental metal to form metal ions within the arc chamber.

The above summary is intended only to give a brief overview of some features of some embodiments of the disclosure, and other embodiments may include additional and/or different features than those described above. In particular, this summary should not be construed as limiting the scope of the application. Thus, to the accomplishment of the foregoing and related ends, the disclosure comprises the features hereinafter described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the disclosure. These embodiments are indicative, however, of but a few of the various ways in which the principles of the disclosure may be employed. Other objects, advantages and novel features of the disclosure will become apparent from the following detailed description of the disclosure when considered in conjunction with the drawings.

Drawings

FIG. 1 is a block diagram of an exemplary vacuum system according to several aspects of the present disclosure.

Fig. 2 is a schematic diagram of an ion source according to one example of the present disclosure.

Fig. 3A is a perspective view of a reservoir device for containing liquid metal according to various examples of the present disclosure.

Fig. 3B is a partial cross-sectional view of the reservoir device of fig. 3A, according to various examples of the present disclosure.

Fig. 4 is a partial cross-sectional view of an arc chamber of an ion source according to various examples of the invention.

Fig. 5A is a perspective view of a reservoir device with a closure according to various examples of the present disclosure.

Fig. 5B is a side view of the reservoir device of fig. 5A, according to various examples of the present disclosure.

Fig. 5C is a cross-sectional view of the reservoir device of fig. 5A, according to various examples of the present disclosure.

Fig. 6A is a perspective view of another reservoir device with a lid according to various examples of the present disclosure.

Fig. 6B is a side view of the reservoir device of fig. 6A, according to various examples of the present disclosure.

Fig. 6C is a cross-sectional view of the reservoir device of fig. 6A, according to various examples of the present disclosure.

Fig. 7A is a perspective view of a closure for a reservoir device according to various examples of the present disclosure.

Fig. 7B is a side view of the closure of fig. 7A, according to various examples of the present disclosure.

Fig. 7C is a cross-sectional view of the closure of fig. 7A, according to various examples of the present disclosure.

Fig. 8 is a flow chart illustrating an example method for forming ions from a liquid metal source according to another example of the present disclosure.

Detailed Description

The present disclosure relates generally to various apparatuses, systems, and methods associated with implanting ions into a workpiece. More particularly, the present disclosure relates to an ion source configured to provide liquid metal within an arc chamber to extract ions therefrom.

Accordingly, the present invention is now described with reference to the drawings, wherein like reference numerals may be used to refer to like elements throughout. It should be understood that the description of these aspects are merely illustrative and should not be construed in a limiting sense. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details. Furthermore, the scope of the present invention is not limited by the embodiments or examples described below with reference to the drawings, but is only limited by the appended claims and equivalents thereof.

It should also be noted that the figures are provided to give an illustration of some aspects of embodiments of the invention and should therefore be considered as merely schematic. In particular, the elements shown in the figures are not necessarily to scale relative to each other, and the arrangement of the various elements in the figures is intended to provide a clear understanding of the respective embodiments and should not be construed as necessarily representing actual relative positions of the various components in implementations consistent with embodiments of the invention. Furthermore, the features of the various embodiments and examples described herein may be combined with each other, unless specifically noted otherwise.

It should also be understood that in the following description, any direct connection or coupling between functional blocks, devices, components, circuit elements or other physical or functional units shown in the figures or described herein may also be achieved through an indirect connection or coupling. Furthermore, it should be understood that the functional blocks or units shown in the figures may be implemented as separate features or circuits in one embodiment, and may also or alternatively be implemented in whole or in part in a common feature or circuit in another embodiment. For example, several of the functional blocks may be implemented as software running on a common processor, such as a signal processor. It should also be understood that any connection described in the following specification as being wire-based may also be implemented as wireless communication, unless specified to the contrary.

In the fabrication of semiconductor devices, ion implantation is used to dope semiconductors with impurities. Ion implantation systems are commonly used to dope workpieces, such as semiconductor wafers, with ions from an ion beam to form passivation layers or to produce n-type or p-type material doping during the fabrication of integrated circuits. Such beam processing is commonly used for: during the fabrication of integrated circuits, a workpiece is selectively implanted with impurities of a particular dopant material at a predetermined energy level and controlled concentration to produce a desired semiconductor material. For example, when used to dope semiconductor wafers, ion implantation systems implant a selected species of ions into the workpiece to produce the desired extrinsic material. For example, implanting ions generated from source materials such as antimony, arsenic or phosphorus results in "n-type" extrinsic material wafers, whereas "p-type" extrinsic material wafers are typically generated from ions generated using source materials such as boron, gallium or indium.

An ion implanter includes an ion source, an ion extraction apparatus, a mass analysis apparatus, a beam transport apparatus, and a workpiece processing apparatus. The ion source generates ions of a desired atomic or molecular dopant species. These ions are extracted from the ion source by an extraction system, such as a set of electrodes that excite and direct a stream of ions from the ion source, thereby forming an ion beam. In a mass analysis apparatus (e.g., a magnetic dipole that performs mass dispersion or separation on the extracted ion beam), desired ions are separated from the ion beam. A beam transport apparatus, such as a vacuum system comprising a series of focusing apparatuses, transports the ion beam to workpiece processing equipment while maintaining desired properties of the ion beam. Finally, workpieces, such as semiconductor wafers, are transferred into and out of the workpiece handling apparatus by a workpiece handling system, which may include one or more robotic arms for placing workpieces to be processed in front of the ion beam and removing processed workpieces from the ion implanter.

For example, the present disclosure provides advantages over conventional ion sources that use aluminum or other metallic elements or compounds as a sputtering target within conventional ion sources or as a feed in a vaporizer using aluminum iodide, aluminum chloride, or other metallic compounds, wherein such conventional methods have low beam currents and introduce atoms other than the desired dopant into the plasma within conventional ion sources.

Conventionally, ion implanters are used to implant a wide variety of species. Such precursors are generally preferred if gaseous precursors can be used, as they provide relatively fast switching between species and minimize deposition of materials within the arc chamber that can lead to cross-contamination when other species are operated. However, for some materials, such as gallium, indium, and aluminum, convenient gaseous precursors are generally not available. In this case, a vaporizer system is used to supply vapor containing target atoms to the ion source. The material is selected to have a vapor pressure of about 1mTorr to 1Torr at a temperature of about 100 ℃ to 800 ℃, and the material is typically heated in an oven outside of the arc chamber of the ion source. The oven communicates with the arc chamber through a nozzle so that the vapor flows from the oven to the arc chamber. However, because of the relatively high thermal mass and long settling time of oven and nozzle systems, such systems tend to exhibit a relatively long time to switch between the substances being evaporated.

Alternatively, a solid target containing atoms may be placed inside the arc chamber at the repeller extremity and/or on the sidewalls so that the plasma formed within the arc chamber sputters material from the solid target into the plasma. This sputtering can be enhanced by chemical effects by introducing a fluorine-containing gas or other reactive gas into the plasma. However, the range of materials available is limited because they should be able to withstand temperatures in the arc chamber of 600 ℃ to 1000 ℃ without melting or sublimating. For example, most of these materials, particularly the gallium and aluminum metals of technical interest, are oxides, fluorides or nitrides. These materials, when combined with reactive gases, may cause insulating compounds to deposit on the high voltage electrodes used to extract and shape the ion beam exiting the ion source. Such deposition can lead to shortened lifetime and high voltage instability of the ion source. Furthermore, even when other substances are extracted, the solid target is exposed to the plasma, leading to contamination of the extracted beam and wear of the solid target. However, the present disclosure presently recognizes advantages in providing a pure source of dopant species to the plasma to provide a relatively short time to turn the ion source on and off.

In accordance with one aspect of the present disclosure, fig. 1 illustrates an exemplary vacuum system 100. The vacuum system 100 in this example includes an ion implantation system 101, however various other types of vacuum systems are also contemplated, such as plasma processing systems or other semiconductor processing systems. For example, the ion implantation system 101 includes a terminal 102, a beamline assembly 104, and an end station 106.

Generally, the ion source 108 in the terminal 102 is coupled to a power supply 110, whereby source material 112 (also referred to as dopant material) is supplied to an arc chamber 114 and ionized into a plurality of ions to form an ion beam 116 and the ion beam 116 is extracted through an extraction aperture 117. The ion beam 116 in this example is directed through a beam steering device 118 (also referred to as a source magnet) and out an aperture 120 toward the end station 106. In the end station 106, the ion beam 116 bombards a workpiece 122 (e.g., a semiconductor, such as a silicon wafer, a display panel, etc.), which is selectively clamped or mounted to a chuck 124 (e.g., an electrostatic chuck or ESC). Once embedded into the crystal lattice of the workpiece 122, the implanted ions change the physical and/or chemical properties of the workpiece. Therefore, ion implantation is used in semiconductor device fabrication and metal finishing, as well as in various applications in material science research.

The ion beam 116 of the present disclosure may take any form, such as a pencil or spot beam, a ribbon beam, a scanned beam, or any other form that directs ions toward the end station 106, all of which are considered to be within the scope of the present disclosure.

According to one exemplary aspect, the end station 106 includes a process chamber 126, such as a vacuum chamber 128, wherein a processing environment 130 is associated with the process chamber. The processing environment 130 is generally present within the processing chamber 126 and, in one example, includes a vacuum generated by a vacuum source 132 (e.g., a vacuum pump), the vacuum source 132 being coupled to the processing chamber and configured to substantially evacuate the processing chamber. In addition, a controller 134 is provided for overall control of the vacuum system 100 and its components.

It should be understood that the apparatus of the present disclosure may be implemented in other semiconductor processing tools, such as CVD, PVD, MOCVD, etching tools, and various other semiconductor processing tools, all of which are considered to fall within the scope of the present disclosure. The apparatus of the present disclosure advantageously increases the length of time that the ion source 108 is used between preventative maintenance cycles, thus increasing the overall productivity and lifetime of the vacuum system 100.

For example, the ion source 108 (also referred to as an ion source chamber) may be constructed using refractory metals (W, Mo, Ta, etc.) and graphite to provide suitable high temperature performance, whereby these materials are generally accepted by semiconductor chip manufacturers. In accordance with the present disclosure, the source material 112 includes or consists of a metal (e.g., aluminum, gallium, indium, or other metal) that is advantageously provided in liquid form within the ion source 108 (e.g., in the arc chamber 114).

For example, an arc chamber 114 of the ion source 108 is schematically illustrated in fig. 2, whereby the ion source of the present disclosure may be configured to provide an ion beam 116 having a high beam current by using evaporation from a metal source material 136, such as aluminum, indium, gallium, antimony, or other metals. The metal source material 136 is heated within the arc chamber 114 to form or otherwise remain in a liquid state, thereby defining a liquid metal 138, wherein the liquid metal is further vaporized within the arc chamber to form a plasma 140. For example, the liquid metal 138 may be directly exposed to an arc chamber environment 142 in which a plasma 140 is formed. Alternatively or additionally, the present disclosure may provide a capillary action to draw the liquid metal 138 into the plasma 140, where the liquid metal 138 is incorporated into the plasma by a physical or chemical action, as discussed further below. For example, the metal source material 136 (e.g., the liquid metal 138) may be retained or otherwise contained or contained in the reservoir device 144. For example, the reservoir arrangement 144 includes a cup 146 defined in a repeller 148 of the ion source 108, whereby the cup is negatively biased with respect to the arc chamber 114 by a bias voltage 150 (e.g., 0 to 500V) provided by a repeller power supply 152. For example, the bias voltage 150 (e.g., the repeller supply voltage) may change in response to changes in arc current, extraction current, or other factors for control purposes. Fig. 3A-3B illustrate an example reservoir assembly 144 in which the metal source material 136 may be contained within a recess 154 of the cup 146. In one example, the geometry of the arc chamber 114 of the ion source 108 of fig. 2 is such that the liquid metal 138 is held in the cup 146 by gravity and does not tilt or spill during operation of the ion source 108.

According to one example, by varying the bias voltage 150, input parameters of the source magnet 118 of fig. 1, and/or other parameters associated with the plasma 140 of fig. 2, the amount of power from the plasma may be controlled and provided to the liquid metal 138 to raise its temperature sufficiently to enable a vapor pressure to reach the plasma maintained within the arc chamber 114. For example, a support gas 156 may optionally be introduced into the arc chamber 114 to further sustain the plasma 140, wherein the support gas may be inert (e.g., argon) or may chemically react with the source material 136 (e.g., fluorine, chlorine). For example, the bias voltage 150 may also be used to provide direct sputtering of the source material 136, such as by bombardment with a supporting gas 156. For example, the support gas 156 may further increase the efficiency of the ion source 108 by sputtering material that condenses on one or more walls 158 (also referred to as sidewalls), which walls 158 substantially enclose the arc chamber 114 and convert the sputtered material back to the plasma 140. For example, the bias voltage 150 may be further provided, controlled or enhanced by an arc voltage 160 (e.g., 0 to 150V) applied to a cathode 162 of the ion source 108, or may alternatively be provided by a cathode power supply 164.

Accordingly, the reservoir apparatus 144 (e.g., crucible) of the present disclosure provides advantages over conventional systems whereby, for example, a reservoir apparatus may be provided in one or more of the repeller position 166 associated with the repeller 148 and the sidewall 158 of the arc chamber 114 of the ion source 108, wherein the reservoir apparatus is configured to substantially retain or contain the source material 136 in the form of the liquid metal 138 described above.

Fig. 4 illustrates another example of an arc chamber 114 in accordance with another aspect of the present disclosure. In the example shown in fig. 4, the reservoir arrangement 144 within the arc chamber 114 also includes a lid 168 (also referred to as a lid) that substantially covers the cup 146, wherein the reservoir arrangement is located in the repeller position 166 of the arc chamber. For example, the reservoir device 144 shown in fig. 4 may be used as the repeller pole 148 as discussed above with reference to fig. 2, or alternatively, the reservoir device may be implemented without being coupled to a power source, but only in the repeller pole location 166 of the arc chamber 114. For example, the arc chamber 114 of fig. 4 may be advantageously implemented in a "purify" ion implantation system manufactured by Axelis Technologies, beverly, ma, whereby the reservoir arrangement 144 may be vertically oriented at the bottom of a vertically aligned ion source. For example, the lid 168 includes one or more apertures 170, whereby the apertures are configured and oriented such that the plasma 140 in the ion source 108 of fig. 2 is not in direct contact with the source material 136 held in the cup 146.

For example, fig. 5A-5C illustrate a reservoir device 200, wherein the reservoir device may be configured in a manner similar to the reservoir device 144. The reservoir device 200 of fig. 5A-5C, for example, includes a cup 202 having a lid 204 operatively coupled thereto, wherein a recess 206 shown in fig. 5C is configured to substantially retain or confine the liquid metal 138 shown in fig. 2 (e.g., initially in a solid form, such as solid aluminum in powder form). For example, the lid 204 of fig. 5A-5C may rest on the cup 202 or otherwise be secured to the cup 202, e.g., via one or more fastening components 208 (e.g., one or more slots, pins, clips, etc.) associated with one or more of the cup and the lid, thereby substantially covering the recess 206. The groove 206 may have a varying diameter. The reservoir device 200, for example, can be filled or otherwise contain the one or more source materials 136 of fig. 2 in a liquid state, whereby the one or more source materials have a low vapor pressure (e.g., <1mTorr) at the temperature experienced by the repeller 148 (e.g., approximately 800 ℃). Also, such materials may include, but are not limited to, aluminum, gallium, and indium, for example.

For example, the cover 204 of fig. 5A-5C may further include one or more apertures 210 defined therein, wherein the one or more apertures are configured to expose the recess 206 to the arc chamber environment 142 of fig. 2. For example, the layout and configuration of the one or more apertures 210 in the lid 204 of fig. 5A-5C may be selected to be any number, location, and size, such as having one or more diameters 212 shown in fig. 5C, whereby the layout and configuration may be based on the desired amount of vapor that may be delivered through the one or more apertures. The reservoir apparatus 200 may, for example, be configured such that the metal source material 136 of fig. 2 is maintained substantially at a level 214 such that the liquid metal 138 substantially fills the recess 206 in the cup 202 to that level. Thus, for example, the cavity 216 shown in fig. 5C above the level 214 of the metal source material 136 may be configured to provide a headspace for a vapor pressure that is generated and subsequently diffused out of the one or more holes 210 on the lid 204 to form the plasma 140 of fig. 2. The respective cup 202 and lid 204, for example, are also configured to provide wicking along the sidewalls 218, 220 and/or evaporation within the cavity 216.

In another example shown in fig. 6A-6C, another example of a reservoir device 300 is shown, wherein the reservoir device may again be configured in a manner similar to the reservoir device 144 of fig. 2. For example, the reservoir device 300 of fig. 6A-6C may be implemented as the repeller pole 148 of fig. 2, whereby the metallic source material 136 is liquefied and subsequently converted to a gas phase. For example, the reservoir device 300 of fig. 6C is shown as including a cup 302 and a lid 304, wherein the lid includes one or more apertures 306. The one or more apertures 306 shown in the example of fig. 6C are further angled. In addition, the lid 304 includes, for example, one or more features 308 that extend into a recess 310 of the cup 302. In the example shown in fig. 6C, one or more components 308 extend below a level 312 substantially maintained by the metal source material 136 of fig. 2 such that the one or more components extend into the liquid metal 138. The one or more members 308 include, for example, an annular ring 316. Although not shown, the annular ring or cylinder 316 can, for example, extend to the bottom 318 (or near the bottom) of the cup 302, and can optionally include radial holes (not shown) in the cylinder so that as the level 312 of liquid metal in the cup decreases, contact continues with the lid for additional capillary action, as discussed below.

Again, for example, the cavity 314 shown in fig. 6C above the level 312 of the metal source material 136 may be further configured to provide a headspace for vapor pressure for generation and subsequent diffusion out of the one or more apertures 306 on the lid 304. The respective covers 304 are further configured to provide wicking or wicking along the sidewalls 320 and/or evaporation within the cavity 314, for example.

Fig. 7A-7C illustrate another example of a closure 400, wherein the closure includes a plurality of apertures 402 having different diameters 404A, 404B, and one or more members 406 (e.g., annular rings 408) configured to extend below the level of the liquid metal, as described above. As seen in the example of fig. 6C and 7C, respective lids 304, 400 are configured to cover cup 302 and provide wicking along side walls 409 and/or evaporation within the cavity between the tops of the liquid metal in the cup.

Referring again to the example of fig. 4, when the source material 136 (e.g., initially in solid or powder form) is heated to melt into the liquid metal 138, the liquefied metal source material is allowed to wick via capillary action to one or more holes 170 in the cap 168 of the repeller pole 148. The present disclosure contemplates capillary action, for example, to help transfer the liquefied metal source material to one or more apertures 170 in the cap 168, whereby the metal source material is further converted to a gas phase. For example, the cap 168 becomes the hottest surface of the reservoir device 144 by means of ion current caused by the negative bias on the repeller pole 148, thereby effecting a transition to the gas phase.

For example, the present disclosure provides an introduction device configured to introduce the liquid metal into the arc chamber 114 (e.g., proximate to or in lieu of the repeller electrode) and apply an electrical bias to the liquid metal to control the amount of electricity applied to the liquid metal. At temperatures of about 800 c in the arc chamber 114, for example, the vapor pressure is typically too low to sustain a plasma of certain metals. However, if the metal is heated to 1000 ℃ to 1200 ℃, the vapor pressure may be sufficient that the plasma can be obtained directly from the pure metal (e.g., elemental metal rather than the metal in molecular form). Thus, better beam current can be obtained compared to conventional techniques because, in contrast to various other compositions of metal sources provided in molecular form, only metal ions (or metal ions when used with gases such as argon) are in the plasma. Such devices thus provide faster response for turning the system on and off, because the vapor pressure versus temperature curve is generally exponential, and the repulsion pole-like structures of the present disclosure have a much smaller thermal mass than conventional evaporators. Thus, the temperature variation can be reduced by only 30 to 50 ℃ with sufficient vapour pressure, for example, whereby the vapour pressure is thus reduced by one or two orders of magnitude, thus quickly "shutting down" the evaporation of metal in the arc chamber 114. This rapid transition can further minimize contamination and has other benefits.

The present disclosure presently recognizes that when the surface of a liquid metal is directly exposed to a plasma, it tends to operate in an unstable manner, where a vertically higher plasma density at a location on the liquid metal locally heats the metal at that location, releasing more vapor and making the plasma denser, and further feeds back to itself, thus resulting in rapid and unstable heating.

Accordingly, the present disclosure provides a reservoir device having a cup or crucible of liquid metal with a lid or lid located above the cup, wherein the lid has one or more apertures formed therein such that a region for forming ions is provided between the liquid metal inside the reservoir device and the space of the arc chamber. Thus, the liquid metal source of the present disclosure can operate stably for more than 40 hours, rather than only 5 to 10 hours as previously seen with ion sources of aluminum implants; while further providing greater beam current than conventional systems.

The present disclosure contemplates two potential mechanisms of evaporation and plasma formation; one mechanism provides pure evaporation of the liquid metal, while the other mechanism provides a wicking effect that may occur between the liquid metal and the inner surface of the cup (e.g., formed of tungsten). By wicking or drawing the liquid metal up the side wall or component of the cup and out of the hole in the lid by capillary action, once the liquid metal passes through the hole (or a little earlier), the liquid metal encounters the plasma and is evaporated and enters the plasma. The present disclosure provides both evaporation and wicking as a reactive effect, and recognizes that the interaction between the vapor and capillary action may be different for various parameters, such as the material composition of the cup and/or lid, the metal source material, the surface treatment of the cup and/or lid, and/or the temperature of the reservoir device, and thus the parameters may be tailored for various injectate species. For example, variations in surface structure, texture, material composition, and area available for wicking, etc., may be modified to control evaporation and wicking of the material to control the plasma, and all such modifications are considered to fall within the scope of the present disclosure.

For example, the lid 400 of fig. 7C may be configured to resemble a candle, whereby a central region 410 of the lid includes one or more elongated members 412 that protrude into a liquid metal (not shown) contained in the cup such that the liquid metal (e.g., liquid aluminum) may be drawn over the one or more elongated members. The one or more elongated member structures may include, for example, one or more of a post, tube, rod, or other structure.

The respective annular rings 316, 408 of fig. 6C and 7C and/or the one or more elongated members 412 of fig. 7C may extend near the bottom of the recess in the cup such that as the level of liquid metal in the cup drops, contact with the lid continues to occur to create additional capillary action. With this capillary effect, capillary effects such as modification of the grooves, changes in material composition, or providing sintered material, etc. may be further increased or otherwise altered. In addition, the size and number of holes in the cup or lid may be modified to provide various degrees of exposure of the liquid metal or vapor to the plasma. For example, capillary action can occur on the sidewall of the cup into a hole in the lid, along with one or more posts (e.g., a central structure like a candle or a plurality of posts) extending between the lid and the cavity of the reservoir device and into the liquid metal, the cylinder defined in the lid having a lip configured to extend into the cavity and/or angled holes in the lid, whereby the geometry and configuration of the lid and cup exposes the liquid metal through the hole (e.g., wicks up through the hole). In addition, the liquid metal can also reach the gas phase in the cavity.

The closure 400 of fig. 7A-7C, for example, further includes a crown 414 whereby the crown causes any excess material wicked through the apertures 402 to flow toward the central region 410 whereby the excess material may advantageously evaporate due to the higher temperature at the central region. For example, by providing the peaks 414, excess material wicked through the apertures 402 is substantially prevented from dripping or flowing down the sides 416 of the lid 400, thereby substantially preventing short circuits between the lid and other components.

For example, the present disclosure provides two mechanisms to introduce one or more source materials from a reservoir device into an arc chamber or ion source; namely evaporation and capillary action. In the first case, the temperature of the reservoir device can be raised to the vapor range (e.g., 1000 ℃ to 1200 ℃) by adjusting parameters associated with the plasma (e.g., arc current, parameters associated with the source magnet, etc.) or by applying an electrical bias to the repeller pole to provide a vapor pressure sufficient to adequately operate the ion source. The reservoir device of the present disclosure also advantageously provides: when the input power to the ion source is reduced, for example, the temperature of the reservoir device is rapidly reduced, whereby a temperature drop of only a few tens of degrees is sufficient to reduce the vapor pressure time by an order of magnitude or more, minimizing loss of material and eliminating cross-contamination. Thus, for example, evaporation may be controlled by controlling heat input and loss to the reservoir arrangement and conduction between the reservoir arrangement and the arc chamber of the ion source.

According to another example of the present disclosure, capillary action may be utilized such that the liquid material is drawn onto a sidewall or component associated with the reservoir device, whereby the liquid material passes through the aperture in the cover, thereby exposing the liquid material to the plasma, whereby the liquid material is vaporized by the plasma. For example, the rate of such capillary action or "wicking" may be influenced or otherwise controlled by: an inner surface area of the reservoir device; the presence or absence of a component (such as a post, tube, or central core or other component associated with the closure); surface treatment of one or more of the cup and lid, for example providing grooves or striations in the surface thereof; and the material selection of the various components of the cup and lid.

For example, the interaction between evaporation and capillary action associated with one or more of the cup and lid may thus be varied by geometry, material selection, surface treatment, or other considerations, such as the lid being formed with a central region and an outer region having different thermal properties. Reservoir devices constructed of (or containing) tungsten may be well suited for use with metal source materials such as liquid aluminum. The present disclosure further contemplates other refractory materials, such as molybdenum, graphite, boron nitride, aluminum nitride, alumina, and tantalum, which may alternatively be used to form the reservoir device.

For example, the volume of metal source material that may be held or retained within the reservoir means inside the arc chamber is typically limited by the geometry of the arc chamber. For example, the volume of source material provided within the reservoir device may be increased or supplemented by providing an auxiliary supply (e.g., an accessory reservoir, tank, or other volume) in fluid communication with the reservoir device within the arc chamber, wherein the auxiliary supply provides a greater volume of metal source material to the cup of the reservoir device through a conduit, such as a pipe. For example, the secondary supply is configured to maintain the temperature of the metal source material above the melting point of the metal source material by heat collected from the plasma chamber and/or the external heater.

According to another example, the reservoir apparatus of the present disclosure is adapted to provide a Ga + ion beam current of 10mA and Al + ion beam currents of >2mA and Al + + of 1mA in the ion source for a period of time exceeding 40 hours, whereby the ion source utilizing the reservoir apparatus may advantageously operate for more than 40 hours without substantial maintenance. In contrast, operation of conventional ion sources using AlN sputtering targets within the arc chamber provides a typical lifetime of about 10 hours, where lifetime is generally limited by deposits formed on the ion source extraction electrodes.

In another example, the ion source of the present disclosure may be configured for implantation of gallium ions, whereby a metal source material containing liquid gallium is contained in a reservoir device provided as a repeller in the ion source. For example, the repeller is biased more negative than the cathode so that the energy transferred from the plasma to the metal source material can be increased and controlled. Thus, the temperature of the metal source material can be advantageously increased to 1300K to 1400K, which for gallium will result in a sufficiently high vapor pressure to sustain the plasma. The present disclosure further recognizes that various other metal source materials may benefit from such heating of the repeller cup, and all such materials are contemplated as falling within the scope of the present disclosure.

For example, calculations indicate that gallium has a vapor pressure of about 1mTorr at 1200K and 10mTorr at 1320K. In an isolated repeller structure, for example, temperatures of about 1000 ℃ may be reached, whereby further biasing the repeller more negative than the cathode may reach these elevated temperatures to achieve the desired vapor pressure.

For the required gallium area, if the source and target are in equilibrium at 1300K, then according to kinetic theory, for a pressure of 8 mTorr:

gas number density of gallium atom 5.9 × 10¹⁹m^-3。

Wherein, the flux is 9.2 multiplied by 10²¹Atom/m²S, which is equal to 5.5X 10²³Atom/m²/min、0.92mol/m²Per min or 20600sccm/m². Thus, to maintain a flow rate of 5sccm for the exemplary implant, 2.4×10^-4m²Is considered reasonable, or a square of 15mm on each side.

For example, for next generation PMOS S/ds, it is understood that low contact resistance can be achieved by using gallium doping. For example, gallium-69 is a metal with a melting point of 302.91 ° K (29.76 ℃ or 85.57 ° f). For example, gallium-69 is typically in a liquid state at a temperature slightly above room temperature. For example, a gas such as argon may be used as a source gas to generate the temperature required to vaporize gallium.

For example, the liquid metal in the reservoir device may remain liquid as it is heated by the plasma in the arc chamber, and the amount of heating may be varied by varying or controlling the density of the plasma, varying or controlling the arc current, and/or by varying or controlling the parameters of the source magnet. In the case of the lid and cup in the form of repeller electrodes, such control may focus the plasma on the repeller electrodes to further control heating thereof. In addition, a radiation shield (not shown) may be used around the lid and cup to make them hotter or otherwise control heating. Additionally, notches and/or slots may be implemented in a stem portion extending from the cup to reduce heat loss, wherein the stem is retained in a clamp having a cross-section that may be similarly configured to reduce or control heat transfer.

In another example, the center of the cap may have a greater thickness where ion bombardment occurs. For example, the most dense portion of the plasma column is where most of the ions strike and sputter, whereby the repeller may be further biased to different voltages to increase or decrease the energy with which the ions strike their surface, thereby further controlling the heating of the repeller. For example, by biasing the lid by the repeller power supply shown in fig. 2, the power can be nearly instantaneously electrically controlled to control the amount of power applied to the repeller and the lid and/or cup.

The configuration, size, number, location, etc. of the holes in the closure can be modified, as can the number and configuration of cylinders, posts or other components, to suit the particular needs of a particular injectate. As described above, the present disclosure, for example, provides for wicking of liquid metal from the cup to the location where the liquid metal meets the plasma. For example, by controlling the material temperature, the flow rate of wicking of the liquid metal can be adjusted so that a constant source of liquid metal can be provided into the plasma to maintain or control the plasma. For example, the metal may wick from the cup to the hole and to the outer surface of the lid, and then evaporate by the full force of the plasma facing.

The present disclosure further recognizes that direct evaporation can be achieved, for example, for gallium implants, whereby a temperature of about 1100 ℃ allows the vapor pressure to withstand the plasma alone. In this case, while wicking may still be achieved, this may not be necessary as evaporation of the liquid metal in the cup may allow the evaporated metal to "leak" through the pores. For example, as shown in fig. 9A-9C, showing the lid over the sidewall (with no components extending into the cup), the volume within the cup increases as much as possible with the sidewall, whereby the cavity defined therein has a headspace to contain some of the evaporated metal.

In some experiments, run times of over 100 hours have been obtained using the liquid metal apparatus described herein. Furthermore, gravity may provide a further advantage when, for example, repeller means (e.g. cup and lid) are provided at the bottom of the ion source arc chamber in the vertical orientation shown in figure 2, as the cup may be supported directly at the bottom of the arc chamber by conventional techniques, thereby providing a reservoir of sufficient size for the liquid metal. However, the present disclosure further contemplates providing an external reservoir that is operatively coupled or connected to a cap-like structure within the arc chamber, such as by a pipe or other conduit. For example, liquid metal may be fed into the arc chamber in a variety of ways so long as the external reservoir remains above the melting point of the metal, thereby further potentially extending the life of the components of the arc chamber. Similarly, a constant level of liquid metal may be further retained in the cup by archimedes' principle, whereby liquid metal may be fed into the reservoir arrangement to prolong the operating time of the arc chamber. For example, an auxiliary reservoir may be provided around the arc chamber (e.g. maintained at 600 to 700 ℃) and maintained at a temperature to maintain the metal in the liquid phase. The present disclosure recognizes that gallium melts at room temperature, while indium melts at 130 ℃, and thus may also provide varying degrees of active heating.

The present disclosure further recognizes that liquid metal may be provided to the arc chamber in other ways, without necessarily being introduced via the repeller electrode. For example, the present disclosure contemplates any biasing or non-biasing structure in the arc chamber configured to provide liquid metal to the interior of the arc chamber. For example, in some ion sources, the ion source arc chamber is set in a horizontal position whereby the apparatus of the present disclosure may effect wicking to supply liquid metal and/or heating liquid metal to provide metal vapor. For example, such a device may be positioned on one side of the ion source (e.g. when the arc chamber is oriented horizontally) whereby the device may be provided with a heat source (e.g. heaters may be provided around the device). Further, if a horizontal configuration is provided, the cup may be oriented such that gravity holds the liquid metal in the cup, for example, whereby the lid may be angled relative to the cup (e.g., at 90 degrees or other angles), whereby wicking and/or direct evaporation may also be achieved. A showerhead type or other configuration may similarly be provided on the sides of the arc chamber.

Again, although the repeller pole is provided in several examples of the present disclosure, the concepts of the present disclosure are not limited to the repeller pole. Furthermore, by controlling the material selection, temperature, and configuration discussed herein, the liquid metal does not have to be exposed to the plasma at all times. If a bath of liquid metal is placed along the side of the ion source, the liquid metal may be exposed to the plasma whenever the plasma is activated. The present disclosure also provides the ability to turn on and off exposure of the liquid metal to the plasma. For example, the present disclosure thus provides a reservoir or other means for supplying liquid metal to an interior region of an ion source.

According to another exemplary aspect, a method 500 for providing liquid metal to an ion source to form an ion beam for implanting ions into a workpiece is provided in fig. 8. It should be noted that while exemplary methods are illustrated and described herein as a series of acts or events, it will be appreciated that the present disclosure is not limited by the illustrated ordering of such acts or events, as some steps may occur in different orders and/or concurrently with other steps apart from that shown and described herein, in accordance with the disclosure. Moreover, not all illustrated steps may be required to implement a methodology in accordance with the present disclosure. Further, it should be understood that the methods may be implemented in association with the systems illustrated and described herein as well as in association with other systems not illustrated.

It should be noted that the controller 134 of FIG. 1 may be configured to perform the method 500 of FIG. 8, whereby control of the various components described above may be implemented in the manner described herein. As shown in fig. 8, the exemplary method 500 begins at act 502, where a metal, e.g., in elemental form, is provided to an ion source in solid form. The metal may be in powder or other solid form. For example, metal is provided to a cup of a reservoir device positioned within the arc chamber, as described in several examples above.

In act 504, the metal is heated to a liquid state and in act 506, liquefied metal is provided to an interior region of the arc chamber. Acts 504 and 506 may be performed sequentially or simultaneously in various orders. In one example, the metal may be heated to a liquid state outside the arc chamber in act 504 and then provided to an interior region of the arc chamber in act 506. In act 508, the liquid metal is evaporated to form a plasma.

Although the invention has been shown and described with respect to one or more particular embodiments, it should be noted that the above-described embodiments are merely illustrative of implementations of some embodiments of the invention, and the application of the invention is not limited to these embodiments. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.), the terms (including a reference to a "means") used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application. Accordingly, the present invention is not limited to the above-described embodiments, but is intended to be defined only by the following claims and equivalents thereof.