Shielded gas inlet for an ion source

Abstract

This invention provides an ion source having an arc chamber having one or more radiation-generating features, an arc chamber body enclosing an internal volume, and at least one gas inlet aperture defined within the arc chamber body. A gas source provides a gas, such as a source gas or a halide, via the gas inlet aperture. The source gas may be an aluminum-based ion source material, such as dimethylaluminum chloride (DMAC). One or more shielding elements positioned near the gas inlet aperture provide fluid communication between the gas inlet aperture and the internal volume, minimizing line-of-sight from the one or more radiation-generating features to the gas inlet aperture, and substantially preventing thermal radiation from the one or more radiation-generating features to the gas inlet aperture.

Description

[Technical Field]

[0001] This invention generally relates to ion implantation systems, and more particularly to an ion source for an ion implantation system configured to generate an ion beam, wherein a shield is used to introduce source gas into the gas inlet of the ion source to mitigate degradation of the source material at high temperatures, such as when aluminum ions are formed from gaseous dimethylaluminum chloride (DMAC). Reference to related applications

[0002] This application claims the benefits of U.S. Provisional Application No. 63 / 273,338, filed on October 29, 2021, entitled “SHIELDED GAS INLET FOR AN ION SOURCE”, the contents of which are incorporated herein by reference in their entirety. [Previous Technology]

[0003] The demand for ion implants using metal ions is gradually increasing. For example, aluminum implants are crucial to the power device market, a small but rapidly growing segment of that market. For many metals, including aluminum, there are problems supplying the feed material to the ion source. Systems utilizing vaporizers, which are small ovens outside the arc chamber of the ion source, have previously been provided, in which metal salts are heated to generate sufficient vapor pressure to supply vapor to the ion source. However, the oven is located far from the arc chamber and takes time to heat to the required temperature, establish a vapor flow, start the plasma, and initiate the ion beam. Furthermore, if a change from one metallic material to another is required, time is spent waiting for the oven to cool sufficiently for this material change.

[0004] Another known technique involves placing a metallic material, such as aluminum or another metal, inside the arc chamber. For aluminum, the metallic material may include alumina, aluminum fluoride, or aluminum nitride, all of which can withstand temperatures of approximately 800°C within the plasma chamber. In such systems, ions are sputtered directly from the material in the plasma. Another technique involves using a plasma containing an etchant such as fluorine to achieve chemical etching of the metal. Although acceptable beam currents can be obtained using these various techniques, compounds of alumina, aluminum chloride, and aluminum nitride, which are all good electrical insulators, tend to deposit on electrodes adjacent to the ion source within a relatively short period (e.g., 5 to 10 hours). Therefore, various adverse effects are observed, such as high voltage instability and associated variations in the dose of implanted ions. [Summary of the Invention]

[0005] The present invention therefore provides a system and apparatus for generating ion beams using thermally unstable gases, such as forming ion beams comprising ions from gaseous dimethylaluminum chloride (DMAC), diborane, or other gases. Therefore, a simplified overview of the invention is presented below to provide a basic understanding of some aspects of the invention. This overview is not a comprehensive summary of the invention. It is not intended to identify key or essential elements of the invention, nor to describe the scope of the invention. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that follows.

[0006] According to one aspect of the present invention, an ion implantation system is provided. Broadly, the present invention relates to ion implantation and ion sources for implanting ions. In a particular example, a thermally unstable gas, such as a gaseous aluminum-based ion source material, is provided, wherein the ion source is configured to receive and ionize the gaseous aluminum-based ion source material and form an ion beam therefrom. A beamline assembly is configured to selectively transport the ion beam, and a terminal station is configured to receive the ion beam for implanting ions into a workpiece.

[0007] Gaseous aluminum-based ion source materials, for example, contain or are composed of dimethylaluminum chloride (DMAC). In one example, DMAC is stored as a liquid that transforms into a gaseous phase at room temperature under vacuum. For example, a pressurized gas cylinder is configured to contain DMAC and supply DMAC to the ion source. For example, the ion source includes an arc chamber in which a pressurized gas cylinder is configured to supply DMAC. One or more dedicated supply lines may be provided and configured to transfer DMAC from the pressurized gas cylinder to the arc chamber. For example, a low-pressure gas cylinder is configured to contain DMAC and supply DMAC as a gas to the arc chamber of the ion source via a primary gas line.

[0008] According to some examples of the present invention, an ion source is provided, wherein an arc chamber has one or more radiation-generating features defined therein. For example, the arc chamber includes an arc chamber body that substantially encloses an internal volume. For example, the arc chamber has at least one gas inlet aperture defined therein. For example, one or more shielding elements are positioned adjacent to the gas inlet aperture. For example, one or more shielding elements provide fluid communication between the gas inlet aperture and the internal volume. The one or more shielding elements are further configured to substantially prevent thermal radiation from the one or more radiation-generating features reaching the gas inlet aperture.

[0009] According to various embodiments of the invention, an ion source is provided, wherein an arc chamber has one or more radiation-generating features defined therein. The arc chamber comprises an arc chamber body that substantially encloses an internal volume, wherein the arc chamber body has a gas inlet aperture defined therein. For example, a gas source is configured to supply gas via the gas inlet aperture, and one or more shielding elements are positioned close to the gas inlet aperture. In one example, the gas comprises dimethylaluminum chloride (DMAC).

[0010] For example, one or more shielding elements provide fluid communication between the gas inlet aperture and the internal volume, wherein the one or more shielding elements minimize the line of sight from one or more radiation-generating features to the gas inlet aperture and are configured to substantially prevent thermal radiation from one or more radiation-generating features to the gas inlet aperture.

[0011] For example, a gas inlet temperature may be defined at the gas inlet aperture, wherein one or more shielding elements are configured to maintain the gas inlet temperature below a predetermined maximum temperature, wherein the predetermined maximum temperature is based on the decomposition temperature of the gas. In another example, the ion source is configured to form plasma from a source material containing dopant within an arc chamber. For example, at least one of the one or more shielding elements may be made of a shielding material containing dopant, wherein the shielding material is configured to be chemically etched by a gas. In one example, the dopant contains aluminum, wherein the gas contains a halide. In another example, one or more shielding elements comprise a plurality of shielding elements, wherein at least one shielding element comprises the closest shielding element of the plurality of shielding elements that is adjacent to the gas inlet aperture and is made of dopant, and wherein the farthest shielding element of the plurality of shielding elements that is furthest from the gas inlet aperture is made of refractory metal, ceramic, or graphite.

[0012] For example, one or more radiation-generating features may include one or more of the following: a plasma column, a cathode, a reflector, an arc chamber body, and an arc slit plate defined within the internal volume. For example, one or more shielding elements are configured to substantially prevent plasma formation at the gas inlet aperture.

[0013] According to another example, one or more shielding elements comprise a plurality of rigid plates in a stacked configuration. For example, the plurality of rigid plates are positioned directly above the gas inlet aperture without contacting it. For example, the arc chamber body may further comprise one or more liners, wherein the plurality of rigid plates are recessed behind the innermost liner and the arc chamber body. For example, the plurality of rigid plates may be spaced apart from each other by a predetermined distance.

[0014] In another example, one or more shielding elements are composed of a plurality of shielding elements, wherein one or more of the plurality of shielding elements have one or more shielding apertures defined therein. For example, one or more shielding apertures are defined in two or more of the plurality of shielding elements and are offset from each other, thereby preventing the line of sight from one or more radiation-generating features to the gas inlet aperture from passing through one or more shielding apertures.

[0015] For example, one or more shielding elements are arranged symmetrically with respect to the main body of the arc chamber. In yet another example, one or more shielding elements are made of one or more refractory materials, ceramics, and graphite.

[0016] In another example, the arc chamber body includes one or more liners, and one or more shielding elements are operatively coupled to one or more liners. For example, one or more liners include one or more thermal breaks defined therein, wherein the one or more thermal breaks are configured to reduce heat transfer to the gas inlet aperture. For example, one or more thermal breaks may include one or more of the following: grooves defined in one or more liners; regions of one or more liners having a smaller cross-section than the rest of one or more liners; and machined peripheries defined around the gas inlet aperture, configured to limit heat conduction through one or more liners to the gas inlet aperture.

[0017] One or more fastening devices may be further provided, wherein the one or more fastening devices, for example, operatively couple one or more shielding members to one or more of the arc chamber body and one or more linings. For example, the one or more fastening devices include one or more screws and / or one or more supports. In another example, a plurality of slots are defined in one or more linings, wherein one or more shielding members are configured to slidably engage the plurality of slots, thereby operatively coupling one or more shielding members to one or more linings.

[0018] According to another example, an ion source is provided, wherein an arc chamber is configured to form a plasma column. For example, a gas inlet aperture is defined in the wall of the arc chamber, and one or more shielding elements are provided, wherein the one or more shielding elements substantially prevent a line of sight from the plasma column to the gas inlet aperture. For example, the one or more shielding elements substantially define one or more walls of the arc chamber.

[0019] In another example, the ion source further includes a cathode and a reflector located at opposite ends of an arc chamber, wherein the arc chamber is symmetrical and one or more shielding elements are configured to provide uniform corrosion of the cathode and reflector.

[0020] For example, one or more shielding elements are further configured to reduce the temperature near the gas inlet aperture while forming the plasma column. In another example, one or more shielding elements further minimize the decomposition and / or blockage of the gas inlet aperture while forming the plasma column.

[0021] According to another example, one or more of the size, shape, and number of one or more shielding elements are configured to prevent a line of sight from the plasma column to the gas inlet aperture, at least in part, based on the temperature sensitivity of the gas supplied via the gas inlet aperture. For example, one or more shielding elements are configured to reduce the temperature of the arc chamber while forming the plasma column.

[0022] To achieve the foregoing and related objectives, the present invention includes the features fully described below and particularly pointed out in the claims. Certain illustrative specific examples of the invention are set forth in detail below with reference to the accompanying drawings. However, these specific examples indicate several ways in which the principles of the invention may be employed. Other objectives, advantages, and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

Implementation Method

[0024] This invention is generally directed to an ion implantation system and an associated ion source material. More specifically, the invention is directed to components used in the ion implantation system when using highly reactive and / or thermally unstable gases, wherein high temperatures within the ion source increase the reactivity or reaction rate of the gas. For example, an ion source material is provided as a source gas for generating atomic ions to electrically dope silicon, silicon carbide, or other semiconductor substrates at various temperatures. Specifically, the invention advantageously minimizes the degradation of such source gases at high temperatures, such as when using dimethylaluminum chloride (DMAC) as the ion source material. Furthermore, when using highly reactive gases such as fluorine, a lower temperature is achieved at the gas inlet of the ion source according to the invention, thereby reducing the etching rate of components adjacent to or in contact with the gas inlet, such as in the case of NF3, thereby slowing its decomposition into nitrogen and fluorine.

[0025] Therefore, the invention will now be described with reference to the accompanying drawings, in which similar reference numerals are always used to refer to similar elements. It should be understood that such descriptions are merely illustrative and should not be interpreted in a limiting sense. In the following description, numerous specific details are set forth for purposes of explanation to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without such specific details. Furthermore, the scope of the invention is not intended to be limited to the specific examples or embodiments described below with reference to the accompanying drawings, but is intended to be limited only to the appended claims and their equivalents.

[0026] It should also be noted that the drawings are provided to illustrate certain aspects of specific embodiments of the invention, and therefore should be considered illustrative only. Specifically, according to specific embodiments of the invention, the elements shown in the drawings are not necessarily drawn to scale, and the placement of the various elements in the drawings is chosen to provide a clear understanding of the respective specific embodiments and should not be construed as necessarily representing the actual relative positions of the components in the implementation. Furthermore, unless otherwise specifically indicated, the features of the various specific embodiments and examples described herein can be combined with each other.

[0027] It should also be understood that, in the following description, any direct connection or coupling between functional blocks, devices, components or other entities or functional units shown in the figures or described herein may also be implemented by indirect connection or coupling. Furthermore, it should be understood that a functional block or unit shown in the figures may be implemented as a separate feature in one specific instance, and may also be implemented wholly or partially as a common feature in another specific instance. For example, several functional blocks may be implemented in the form of software running on a general-purpose processor such as a signal processor.

[0028] Ion implantation is a physical process used in semiconductor device manufacturing to selectively implant dopants into semiconductor and / or wafer materials. Therefore, the implantation action does not depend on the chemical interaction between the dopant and the semiconductor material. For ion implantation, dopant atoms / molecules from an ion source in an ion implanter are ionized, accelerated, formed into an ion beam, analyzed, and swept across the wafer, or the wafer is translated through the ion beam. Dopant ions physically bombard the wafer, penetrate the surface, and remain below the surface at a depth related to their energy.

[0029] The ion source in an ion implantation machine typically generates an ion beam by means of a source material in an ionized arc chamber, wherein the composition of the source material is the desired dopant element. The desired dopant element is then extracted from the ionized source material in the form of an ion beam.

[0030] To gain a general understanding of the invention, and according to one embodiment of the invention, FIG1 illustrates an exemplary vacuum system 100. The vacuum system 100 in this example includes an ion implantation system 101, but also encompasses various other types of vacuum systems, such as plasma processing systems or other semiconductor processing systems. For example, the ion implantation system 101 includes terminals 102, a beamline assembly 104, and a terminal station 106.

[0031] Generally, the ion source 108 in terminal 102 is coupled to power supply 110 to ionize the dopant gas into a plurality of ions to form an ion beam 112. Individual electrodes adjacent to the extraction electrode can be biased to suppress the backflow of neutralized electrons to the source or back to the extraction electrode.

[0032] In this embodiment of the invention, an ion beam 112 is guided through a beam deflector 114 and directed toward a terminal station 106 through an aperture 116. At the terminal station 106, the ion beam 112 bombards a workpiece 118 (e.g., a semiconductor such as a silicon wafer, a display panel, etc.), which is selectively clamped or mounted to a chuck 120 (e.g., an electrostatic chuck or ESC). Once embedded in the lattice of the workpiece 118, the implanted ions alter the physical and / or chemical properties of the workpiece. Thus, ion implantation is used in various applications in semiconductor device manufacturing and metal surface treatment, as well as in materials science research.

[0033] The ion beam 112 of the present invention may take any form, such as a pencil or dot beam, a band beam, a scanning beam, or any other form that guides ions toward the terminal station 106, and all such forms are intended to be within the scope of the present invention.

[0034] According to one exemplary embodiment, terminal station 106 includes a processing chamber 122, such as a vacuum chamber 124, wherein a processing environment 126 is associated with the processing chamber. The processing environment 126 is typically located within the processing chamber 122 and, in one example, includes a vacuum generated by a vacuum source 128 (e.g., a vacuum pump) coupled to and configured to substantially evacuate the processing chamber. Furthermore, a controller 130 is provided for the overall control of the vacuum system 100.

[0035] This invention has found that a workpiece 118 on which a silicon carbide-based device is formed has better thermal and electrical properties compared to a silicon-based device, particularly in applications such as high-voltage and high-temperature devices like electric trains. However, implanting ions into silicon carbide utilizes a different class of implanting dopants than those used for silicon workpieces. In silicon carbide implantation, aluminum, phosphorus, and nitrogen implantation are typically performed. For example, nitrogen implantation is relatively simple because nitrogen can be introduced as a gas and provides relatively easy conditioning and cleaning. However, aluminum is more difficult because there are currently few known good gaseous aluminum solutions.

[0036] The present invention contemplates, for example, providing ion source material 132 to the arc chamber 134 of ion source 108 for forming ion beam 112. To date, no material exists that can be safely and efficiently delivered to ion source 108 in gaseous form to generate ion beam 112 for subsequent implantation of aluminum ions. In the past, solid source material (not shown) was placed in a heated vaporizer assembly (not shown), thereby feeding the resulting gas into arc chamber 134, or solid high-temperature ceramics such as Al₂O₃ or AlN (not shown) were placed in the arc chamber, wherein the ceramics were etched by a fluorine-based gas.

[0037] However, both of these technologies may have significant limitations. For example, the time required for the vaporizer to reach the temperature necessary to convert solid materials into a gaseous phase can exceed 30 minutes, thus affecting tool productivity. Furthermore, when different dopant gases need to be introduced into the arc chamber, the time required to subsequently lower the vaporizer temperature so that the source material is no longer in a gaseous phase can exceed 30 minutes. This is commonly referred to as the transition time between substances, which can reduce the productivity of ion implantation machines.

[0038] Furthermore, when fluorine-based dopant gases (e.g., BF3, NF3, PF3, PF5) are used to etch alumina (Al2O3) or aluminum nitride (AlN) ceramics, the resulting reaction byproducts (e.g., AlFx, Al, N, and neutral AlN and Al2O3 compounds) can form an insulating coating on the extraction electrode (e.g., under negative voltage). This can then cause charge accumulation and subsequent discharge to the ion source arc slit optics plate (e.g., under positive voltage), thus further reducing the productivity of the tool.

[0039] To overcome limitations or prior art, the ion implantation system 101 of the present invention provides gaseous dimethyl aluminum chloride (C4H10AlCl, also known as DMAC) as ion source material 132 to advantageously deliver aluminum-based materials in gaseous form into the arc chamber 134 of the ion source 108. For example, providing DMAC in gaseous form to the arc chamber 134 advantageously achieves a faster transition time between substances (e.g., less than 5 minutes), no waiting time for material heating and cooling, and no formation of insulating material on the extraction electrode as seen in conventional systems. For example, the ion source material 132 (e.g., DMAC) is selectively delivered to the arc chamber 134 via a dedicated primary gas line 136 because it is a highly reactive (ignitable) material. A fluorinated gas source 138 (e.g., BF3, PF3, etc.) is selectively supplied to the arc chamber 134 via a secondary gas line 140, wherein the primary gas line 136 and the secondary gas line are separate and isolated gas lines. For example, the fluorinated gas source 138 is a molecule or premixture of gas, wherein at least one component is fluorine.

[0040] Using gases such as DMAC as source materials to generate aluminum ion beams has advantages in terms of rapid switching and stability of the ion source; however, DMAC gas exposed to temperatures above 400°C tends to decompose DMAC. For example, Figure 2 illustrates a photograph 200 of the sidewall 202 of a conventional arc chamber of an ion source, in which contaminants 204 can be formed at the gas inlet channel 206 used to introduce DMAC gas into the arc chamber, whereby the gas inlet channel is conventionally exposed to high temperatures (e.g., above 400°C) within the arc chamber, and whereby the gas inlet channel can be blocked by decomposed DMAC or otherwise contaminated.

[0041] Therefore, the present invention provides several devices, systems, and methods for generally preventing such blockage, fouling, or contamination of gas inlet apertures associated with an ion source. Accordingly, according to one exemplary embodiment of the invention, FIG3 illustrates an exemplary ion source 300, wherein an arc chamber 302 is provided having one or more radiation-generating features 304 defined therein. The arc chamber 302 includes an arc chamber body 306 that generally encloses or otherwise defines an internal volume 308. For example, one or more radiation-generating features 304 include one or more of a cathode 310, a reflector 312 (also referred to as a counter cathode), a wall 314 of the arc chamber 302, an arc slit 316, and a plasma column 318 defined within the internal volume 308 during operation of the ion source 300. The arc slit 316 is illustrated by a dashed line and defined within the arc slit plate (not shown for clarity) that generally encloses the internal volume 318.

[0042] For example, the arc chamber body 306 may further include one or more liners 320, wherein the one or more liners are typically used to protect the arc chamber body 306 thermally, chemically, or otherwise. For example, the one or more liners 320 may comprise or be constituted of a material such as graphite or other protective material. In one example, the arc chamber 302 includes at least one gas inlet aperture 322 for introducing gas from a gas source 324 into the internal volume 308, as will be further discussed below. For example, the gas inlet aperture 322 (e.g., a hole, channel, or other opening) is defined in or through one or more of the arc chamber body 306 and one or more of the liners 320.

[0043] According to one embodiment of the invention, one or more shielding elements 326 are positioned near the gas inlet aperture 322, wherein the one or more shielding elements provide fluid communication between the gas inlet aperture and the internal volume 308, while shielding the gas inlet aperture from thermal radiation associated with the internal volume. For example, one or more shielding elements 326 illustrated in FIG. 3 are configured to substantially limit thermal radiation associated with the plasma column 318 or other of the one or more radiation-generating features 304 from reaching the gas inlet aperture 322. In one embodiment, one or more shielding elements 326 are operatively coupled to one or more of the arc chamber body 306 and one or more of the liners 320 via one or more fastening devices 328. In this embodiment of the invention, the one or more fastening devices 328 include one or more screws 330 and / or one or more supports 332, thereby selectively positioning one or more shielding elements 326 relative to the arc chamber body 306 via the one or more fastening devices. For example, one or more shielding elements 326 substantially reduce or prevent the line of sight from one or more radiation-generating features 304 (e.g., plasma columns 318) to the gas inlet aperture 322, and are expected to have various configurations. For example, one or more shielding elements 326 are expected to have a wide variety of sizes and shapes, such as one or more of rectangular, oval, circular or irregular shapes.

[0044] For example, one or more shielding elements 326 are configured to substantially not interfere with the plasma column 318 within the arc chamber 302. For example, one or more shielding elements 326 include shielding elements 334A, 334B, and 334C shown in FIG. 3, wherein the innermost shielding element 334A has the greatest direct exposure to the plasma column 318. Thus, for example, at least the innermost shielding element 334A is configured such that it is substantially symmetrical with respect to the arc slit 316 and generally provides symmetry within the internal volume 308. For example, the innermost shielding element 334A can therefore be positioned within the arc chamber 302 such that its position relative to one or more of the cathode 310, reflector 312, liner 320, and arc slit 316 substantially does not interfere with the formation of the plasma column 318. For example, the innermost shield 334A may be substantially coplanar with or slightly recessed from the inner surface 336 of the sidewall 338 of the arc chamber 302 associated with the gas inlet aperture 322 (e.g., the surface of one or more liners 320). While the innermost shield 334A is illustrated in this example as extending partially along the sidewall 338 of the arc chamber 302, the invention further encompasses at least one of the shields 326 (e.g., the innermost shield 334A) extending substantially entirely between the end sidewalls 340 of the arc chamber 302 having the cathode 310 and the reflector 312. In the example illustrated in FIG. 3, the shields 326 are substantially uniform in size and shape.

[0045] For example, Figures 4 and 5 illustrate another exemplary arc chamber 350, wherein one or more shielding members 326 include shielding plates 352A to 352C configured to slidably engage with one or more of the arc chamber body 306 and one or more of the liners 320. For example, the shielding plates 352A to 352C of Figure 5 slidably engage with slots 354A to 354C defined in a side member 356 (e.g., one or more of the liners 320 or the arc chamber body 306), and the cover member 358 shown in Figure 4 is operatively coupled to the side member to selectively secure the shielding plates in place. Thus, the slidable engagement between the shielding plates 352A to 352C and the slots 354A to 354C, together with the cover member 358, generally defines one or more fastening devices 328. In an example of the invention, for instance, the innermost shielding plate 352A is slightly recessed from the inner surface 336 of the sidewall 338 of the arc chamber 302, thus again providing general symmetry of the internal volume 308. The sidewall 338 of the arc chamber 302 further defines an exposure aperture 360 ​​that exposes at least the innermost shielding plate 352A to the internal volume 308.

[0046] The present invention therefore understands that while there may be an operational advantage here of providing a generally symmetrical internal volume 308 associated with one or more shields 326 and the arc chamber 302, as illustrated in the examples shown in Figures 3 to 5, various other configurations of the one or more shields are contemplated within the scope of the present invention. According to another example illustrated in Figure 6, another arc chamber 370 is shown, wherein one or more shields 326 comprise a plurality of shields 372A to 372C having varying geometries, whereby the plurality of shields are illustrated as generally stepped relative to the gas inlet aperture 322. For example, the plurality of shields 372A to 372C may be symmetrical about the plasma column 318, or offset from the plasma column, or otherwise asymmetrical about the arc chamber 302.

[0047] Referring again to FIG. 3, according to another exemplary embodiment of the invention, a gas source 324 is configured to supply gas (e.g., process gas, companion gas, or other gas) to or through a gas inlet aperture 322 via one or more conduits 374 selectively fluid-coupled to the gas source and gas inlet apertures. It should be further noted that while the gas inlet aperture 322 is described as a single aperture in one example, it also encompasses multiple apertures, orifices, or channels to which one or more conduits 374 are configured to selectively supply gas.

[0048] For example, during operation of any of the arc chambers 302, 350, and 370 in Figures 3 to 6, a gas inlet temperature is defined at the gas inlet aperture 322, wherein one or more shields 326 are further configured to maintain the gas inlet temperature below a predetermined maximum temperature. For example, the predetermined maximum temperature may be based on or associated with the decomposition temperature of the gas at which it begins to substantially decompose due to this high temperature. In one example, the gas contains dimethylaluminum chloride (DMAC), and the predetermined maximum temperature is about 400°C. Therefore, a predetermined configuration of the number, size, shape, thickness, position along the sidewall 338, or other characteristics associated with one or more shields 326 can be advantageously provided based on the predetermined maximum temperature associated with the gas. Additionally, the predetermined configuration of one or more shields 326 may be based on the desired flow rate of the gas from the gas inlet aperture 322 to the internal volume 308. Therefore, gas can be provided between or through a predetermined interval or flow path of one or more shields 326 to generate the desired flow rate of gas from the gas inlet aperture 322 to the internal volume 308.

[0049] According to another example, one or more shielding elements 326 are further configured to substantially prevent plasma formation at or near the gas inlet aperture 322. For example, at least one of the one or more shielding elements 326 may be positioned directly above the gas inlet aperture 322 of any of Figures 3, 5, and 6, without contacting the gas inlet aperture. For example, one or more shielding elements 326 may include one or more rigid plates 380, as illustrated in Figure 7. For example, one or more rigid plates 380 may be made of one or more of a variety of refractory materials, ceramics, and graphite. For example, one or more rigid plates 380 may be substantially planar, as illustrated in Figure 7, or may include curved plates (not shown). For example, one or more shielding elements 326 may be further configured to conform to various features of the arc chamber, such as conforming to the arc chamber body 306 of any of Figures 3 to 6. For example, one or more rigid plates 380 are configured to be mounted in various positions relative to the innermost lining and the arc chamber body 306, as described above. For example, one or more rigid plates 380 may be spaced apart from each other by one or more fastening devices 328, thereby allowing the gas described above to be transferred between the plates from the gas inlet aperture 322 to the internal volume 308 of the arc chamber body 306.

[0050] Figure 8 illustrates another example, in which one or more of the shielding elements 326 include one or more slot-shaped apertures 382 defined therein. For example, one or more slot-shaped apertures 382 are further disposed in the respective shielding plates 352A to 352C in the exemplary arc chamber 350 illustrated in Figures 4 and 5. Although only shielding plate 352A is visible in Figure 4, shielding plates 352B and 352C shown in Figure 5 may have a similar configuration. Thus, gas is configured to pass through each of the slot-shaped apertures 382 in the respective shielding plates 352A to 352C, while thermally protecting the gas inlet aperture 322 of Figure 5 from exposure to the plasma formed within the internal volume 308 of the arc chamber body 306.

[0051] Figures 9A to 9C illustrate another example, wherein one or more shielding elements 326 are composed of a plurality of shielding elements 384A, 384B, and wherein one or more of the plurality of shielding elements has one or more shielding apertures 386 defined therein. In Figure 9A, the plurality of shielding elements 384A, 384B are illustrated as being installed in an ion source, whereby the shielding elements are stacked and spaced apart in the y-direction, and whereby the plurality of apertures are offset from each other when viewed from the y-direction. For example, one or more shielding apertures 386 are defined in two or more of the plurality of shielding elements 384A, 384B, wherein the one or more shielding apertures are offset from each other when two or more of the plurality of shielding elements are stacked on top of each other, to substantially prevent the line of sight between the plasma column 318 shown in Figures 3 and 6 and the gas inlet aperture 322. It should be understood that the present invention covers one or more shielding apertures 386 in any of a variety of shapes, such as circular as illustrated in Figures 9A to 9C, slotted as illustrated by the slotted aperture 382 in Figure 8, or other shapes such as curved, polygonal, labyrinthine, or other shapes not specifically described, wherein a configuration combining one or more shielding apertures 386 stacked with two or more of the shielding elements generally prevents the line of sight between the plasma column 318 or other radiation generating feature 304 shown in Figures 3 and 6 and the gas inlet aperture 322.

[0052] According to another example, as illustrated in Figures 3 and 6, one or more liners 320 include one or more thermal breaks 388 defined therein, wherein the one or more thermal breaks are configured to reduce heat transfer to the gas inlet aperture 322. For example, one or more thermal breaks 388 include one or more recesses defined in one or more liners 320. Alternatively or additionally, for example, one or more thermal breaks 388 include a region of one or more liners 320 having a cross-section smaller than the rest of one or more liners (e.g., a thinned cross-section), as illustrated in the example of Figure 5. For example, one or more thermal breaks 388 may include a machined periphery defined around the gas inlet aperture 322, wherein heat conduction to the gas inlet aperture is reduced.

[0053] According to another illustrative example of various embodiments of the present invention, the ion source 300 of FIG3 is configured to form a plasma from a predetermined source material, wherein one or more shields 326 are made of a predetermined material compatible with the source material, and wherein one or more shields maintain structural integrity during plasma formation. For example, one of the shields 326 closest to the gas inlet aperture 322 (e.g., shield 334C) may have a lower melting temperature than the shield furthest from the gas inlet aperture (e.g., shield 334A). In the example where the source material is a halide, shield 334C may be made of a doped metal or a ceramic containing a dopant, and one or more of the remaining shields (e.g., shields 334A, 334B) may be made of a refractory metal, ceramic, or graphite.

[0054] Therefore, the present invention understands that by positioning one or more shields 326 above or near the gas inlet aperture 322 (e.g., based on the temperature sensitivity of the source gas or molecules), the surface or region near the gas inlet aperture is thus protected from the thermal effects associated with the plasma column 318, the cathode 310 (e.g., an indirect heating cathode or IHC), the arc chamber body 306, or the reflector 312. For example, one or more shields 326 also substantially prevent the formation of plasma at or near the gas inlet aperture 322 due to localized high voltage in the region, thereby reducing the temperature of the region or area surrounding the gas inlet aperture and / or preventing plasma intrusion into the inlet aperture. For example, one or more shields 326 may comprise or be made of a refractory metal with low thermal conductivity, such as tantalum. Alternatively, one or more shields 326 may comprise or be made of various other materials such as tungsten, molybdenum, graphite, aluminum nitride, and alumina.

[0055] According to another example, the configuration of one or more shielding elements 326 (e.g., length, width, height, shape, etc.) may be at least partially based on the temperature sensitivity of the gas introduced into the ion source 300 via the gas inlet aperture 322. The one or more shielding elements 326 may be planar or any non-planar shape, such as curved or bell-shaped. In another example, the width and height of the one or more shielding elements 326 may be staggered or stepped to cover or substantially prevent the line of sight from the plasma column 318 to the gas inlet aperture 322.

[0056] For example, one or more shielding elements 326 are coupled to the arc chamber body 306 or one or more liners 320 via one or more fastening devices 328, such as one or more screws, supports, clamps, interference-fit components, slots, etc. For example, the one or more fastening devices 328 comprise or are made of one or more of refractory metals, ceramics, or graphite, thereby being configured to withstand high temperatures, reactive gases such as fluorine, and having low impurity content. For example, the one or more fastening devices 328 are made of a material with low thermal conductivity (such as tantalum), thereby preventing heat from easily transferring to the arc chamber body 306 or one or more liners 320.

[0057] In one example, one or more liners 320 may be configured such that two end pieces can be bridged together via one or more radiation shields. For example, one or more of the liners 320 may include at least one thermal break 388 machined on or otherwise defined in one or more sides of the gas inlet aperture 322. In another example, the thermal break 388 may be machined around the gas inlet aperture 322. One or more liners 320 may also be thinned near the gas inlet aperture 322 to further reduce mass and subsequent heat conduction. Although not shown, one or more liners 320 may include a one-piece U-shaped liner (e.g., combining two side liners and a rear liner to form a U-shaped liner), and one or more of the shields 326 may be positioned above the gas inlet aperture 322. For example, one or more liners 320 may be flat or shaped to conform to various profiles of the shield closest to the plasma. Various underlying U-shaped liners may be spaced apart to further reduce heat conduction to the arc chamber body.

[0058] For example, the present invention therefore provides one or more thermal shields to reduce the temperature of various components near the gas inlet aperture, and / or substantially prevent plasma flow into the gas inlet aperture, which may be a region with a higher pressure than the remainder of the arc chamber. The present invention is therefore particularly suitable for introducing various thermally unstable stable gases into the arc chamber, such as dimethylaluminum chloride (DMAC), diborane, halides, or other such gases. For example, DMAC can be used as an aluminum source for implanting aluminum ions in high-power devices.

[0059] It should be noted that the present invention is also applicable to various applications of introducing highly reactive gases into an arc chamber. In these applications, the present invention improves upon previously observed problems where high temperatures and highly reactive gases, such as fluorine reacting with tungsten to form volatile WFx, are present. For example, highly reactive gases such as fluorine, XeF2, or other reactive gases can be supplied via a gas inlet orifice, thereby advantageously protecting the area of ​​the gas inlet orifice with one or more shielding elements of the present invention.

[0060] Figure 10 illustrates an exemplary method 400 for implanting aluminum ions into a workpiece. It should be further noted that although the exemplary method is described herein as a series of actions or events, it will be understood that the invention is not limited to the described order of such actions or events. As with the invention, some steps may occur and / or simultaneously in a different order than other steps shown and described herein. Furthermore, not all described steps are required to implement the method according to the invention. In addition, it will be understood that these methods can be implemented in combination with the systems described herein as well as with other systems not described.

[0061] According to an exemplary embodiment, in action 402 of FIG4, gas is supplied to the arc chamber of the ion source via a gas inlet orifice. In one example, the gas may contain a gaseous ion source material in the form of dimethylaluminum chloride (DMAC). For example, the gaseous ion source material may be provided in a low-pressure bottle (e.g., about 10 to 15 Torr), wherein DMAC flows as gas from the low-pressure bottle to the arc chamber via the gas inlet orifice. In action 404, the gas inlet orifice is shielded. For example, as discussed above, one or more shields are provided in the arc chamber. In action 406, the ion source material is ionized in the ion source to generate ions. In action 408, ions are extracted from the ion source to form an ion beam containing ions, and in action 410, aluminum ions are implanted into the workpiece.

[0062] Although the present invention has been shown and described with respect to one or more specific examples, it should be noted that the specific examples described above serve only as examples of embodiments of some specific examples of the invention, and the application of the invention is not limited to these specific examples. In particular, with regard to the various functions performed by the components (assemblies, devices, circuits, etc.) described above, unless otherwise indicated, the terminology used to describe such components (including references to "component") is intended to correspond to any component that performs the specified function of the described component (i.e., is functionally equivalent), even if the disclosed structure is not structurally equivalent to the function described in the exemplary specific examples of the invention herein. Furthermore, although a particular feature of the invention may have been disclosed with respect to only one of several specific examples, such feature may be combined with one or more other features of other specific examples to be desirable and advantageous for any given or particular application. Therefore, the invention is not limited to the specific examples described above, but is intended to be limited only to the appended claims and their equivalents. [Simplified Explanation of the Diagram]

[0023] [Figure 1] is a block diagram of an exemplary vacuum system according to several embodiments of the present invention. [Figure 2] is a photograph of a conventional gas inlet to an arc chamber having a packing material blocking the gas inlet. [Figure 3] is a schematic representation of an ion source according to several embodiments of the present invention. [Figure 4] is a perspective view of an exemplary arc chamber according to various embodiments of the present invention. [Figure 5] is a partial cross-sectional view of the exemplary arc chamber of Figure 4 according to various embodiments of the present invention. [Figure 6] is a schematic representation of another ion source according to several embodiments of the present invention. [Figure 7] illustrates a front perspective view of an exemplary shielding member according to an embodiment of the present invention in which an aperture is not defined. [Figure 8] illustrates a front perspective view of an exemplary shielding member according to an embodiment of the present invention in which a slot is defined. [Figures 9A] to [Figure 9C] illustrate front and rear views of an exemplary plurality of shielding members according to an embodiment of the present invention in which a plurality of offset holes are defined. [Figure 10] illustrates an exemplary method for implanting aluminum ions into a workpiece using dimethylaluminum chloride as a gaseous ion source material.

Claims

1. An ion source comprising: an arc chamber having one or more radiation-generating features defined therein, wherein the arc chamber includes an arc chamber body that substantially encloses an internal volume, and wherein the arc chamber body has a gas inlet aperture defined therein; a gas source configured to provide a gas via the gas inlet aperture; and one or more shielding members positioned adjacent to the gas inlet aperture, wherein the one or more shielding members provide fluid communication between the gas inlet aperture and the internal volume, and wherein the one or more shielding members minimize line-of-sight from the one or more radiation-generating features to the gas inlet aperture and are configured to substantially prevent thermal radiation from the one or more radiation-generating features to the gas inlet aperture.

2. The ion source of claim 1, wherein a gas inlet temperature is defined at the gas inlet aperture, and wherein the one or more shields are configured to maintain the gas inlet temperature below a predetermined maximum temperature, and wherein the predetermined maximum temperature is based on one of the decomposition temperatures of the gas.

3. The ion source of claim 1, wherein the ion source is configured to form a plasma from a source material containing a dopant substance within the arc chamber, and wherein at least one of the one or more shielding elements is composed of a shielding material containing the dopant substance, wherein the shielding material is configured to be chemically etched by the gas.

4. The ion source of claim 3, wherein the dopant material comprises aluminum and wherein the gas comprises a halide.

5. The ion source of claim 3, wherein the one or more shielding elements comprise a plurality of shielding elements, and wherein the at least one shielding element comprises the closest shielding element among the plurality of shielding elements that is closest to the gas inlet aperture and is made of the dopant material, and wherein the farthest shielding element among the plurality of shielding elements that is furthest from the gas inlet aperture is made of a refractory metal, a ceramic or graphite.

6. The ion source as claimed in claim 2, wherein the gas contains dimethylaluminum chloride (DMAC).

7. The ion source of claim 1, wherein the one or more radiation-generating features include one or more of a plasma column, a cathode, a reflector, the arc chamber body, and an arc slit plate defined within the internal volume.

8. The ion source of claim 7, wherein the one or more shielding elements are configured to substantially prevent the plasma column from forming a plasma at the gas inlet aperture.

9. The ion source of claim 1, wherein the one or more shielding members comprise a plurality of rigid plates in a stacked manner.

10. The ion source of claim 9, wherein the plurality of rigid plates are positioned directly above the gas inlet aperture without contacting the gas inlet aperture.

11. The ion source of claim 10, wherein the arc chamber body comprises one or more liners, wherein the plurality of rigid plates are recessed behind an innermost liner and the arc chamber body.

12. The ion source of claim 11, wherein the plurality of rigid plates are spaced apart from each other by a predetermined distance.

13. The ion source of claim 1, wherein the one or more shielding elements are composed of a plurality of shielding elements, wherein one or more of the plurality of shielding elements have one or more shielding apertures defined therein.

14. The ion source of claim 13, wherein the one or more shielding apertures are defined in two or more of the plurality of shielding elements and offset from each other, thereby preventing the line of sight from the one or more radiation generation features to the gas inlet aperture from passing through the one or more shielding apertures.

15. The ion source of claim 1, wherein the one or more shielding elements are symmetrically arranged relative to the main body of the arc chamber.

16. The ion source of claim 1, wherein the arc chamber body comprises one or more liners, and wherein the one or more shielding elements are operatively coupled to the one or more liners.

17. The ion source of claim 16, wherein the one or more liner includes one or more thermal breaks defined therein, wherein the one or more thermal breaks are configured to reduce heat transfer to one of the gas inlet orifices.

18. The ion source of claim 17, wherein the one or more thermal fractures comprise one or more of the following: a groove defined in one or more of the liner; a region of the one or more liner having a cross-section smaller than the remainder of one or more liners; and a processing periphery defined around the gas inlet aperture, configured to limit thermal conduction through the one or more liners to the gas inlet aperture.

19. The ion source of claim 16 further includes one or more fastening devices, wherein the one or more fastening devices operatively couple the one or more shielding elements to one or more of the arc chamber body and one or more of the one or more linings.

20. The ion source of claim 19, wherein the one or more fastening devices comprise one or more screws and / or one or more supports.

21. The ion source of claim 16 further includes a plurality of slots defined in the one or more liner, wherein the one or more shields are configured to engage the plurality of slots in a sliding manner, thereby operatively coupling the one or more shields to the one or more liner.

22. The ion source of claim 1, wherein the one or more shielding elements are composed of one or more refractory materials, ceramics and graphite.

23. An ion source comprising: an arc chamber configured to form a plasma column; a gas inlet aperture defined in a wall of the arc chamber; and one or more shielding elements, wherein the one or more shielding elements substantially prevent a line of sight from the plasma column to the gas inlet aperture.

24. The ion source as claimed in claim 23, wherein the one or more shielding elements substantially define one or more walls of the arc chamber.

25. The ion source of claim 24 further includes a cathode and a reflector respectively located at opposite ends of the arc chamber, wherein the arc chamber is symmetrical, and thereby the one or more shielding elements are configured to provide uniform corrosion of the cathode and the reflector.

26. The ion source of claim 23, wherein the one or more shielding elements are configured to reduce a temperature near the gas inlet aperture while forming the plasma column.

27. The ion source of claim 23, wherein the one or more shielding elements further minimize the decomposition and / or blockage of one of the gas inlet orifices while forming the plasma column.

28. The ion source of claim 23, wherein one or more of the size, shape and number of the one or more shielding elements are configured to prevent the line of sight from the plasma column to the gas inlet aperture based at least in part on the temperature sensitivity of a gas provided via the gas inlet aperture.

29. The ion source of claim 23, wherein the one or more shielding elements are configured to reduce the temperature of one of the arc chambers while forming the plasma column.

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