Composite ion sources based on heterogeneous metal-metal fluoride systems

Abstract

An ion source is provided that can include an ion chamber for generating an ion beam including a metal ion species, and a charge source including a charge mixture coupled to supply metal vapor to the ion chamber. The charge mixture can include a first portion including an elemental metal and a second portion including a dissimilar metal fluoride compound.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. non-provisional patent application Ser. No. 17 / 715,690, entitled "COMPOSITE ION SOURCE BASED UPON HETEROGENEOUS METAL-METAL FLUORIDE SYSTEM," filed on April 7, 2022, the entire contents of which are incorporated by reference into this specification.

[0002] The present embodiments relate to ion sources, and more particularly, to ion sources for beamline ion implanters. [Background technology]

[0003]

[0003] Ion sources are used to generate various ion species, including dopant ions used to implant into semiconductor substrates to control their electronic properties. Current ion sources for implanting species such as metal species can use a solid target etched by a plasma to generate metal-containing ions, or can use liquid metal contained in a crucible. These types of ion sources may generate only modest ion current output because of limitations in generating sufficient metal vapor to be ionized in the ion source. Handling materials in such ion sources can be challenging. For example, metal species (e.g., Ga, Ge, In, Al) exhibit relatively low melting points, but high vapor pressures make these materials difficult to manipulate with known vaporizers. Current approaches using pure metal dopants in ion sources require a retractable crucible that is passively heated by the ion source to obtain a high enough temperature to generate metal vapor, but still provide low vapor output and limit the resulting ion beam current.

[0004]

[0004] It is with respect to these and other considerations that the present disclosure is provided. Summary of the Invention

[0005] In one embodiment, an ion source is provided. The ion source can include an ion chamber for generating an ion beam including a metal ion species, and a charge source including a charge mixture coupled to provide metal vapor to the ion chamber. The charge mixture can include a first portion including an elemental metal and a second portion including a dissimilar metal fluoride compound.

[0006]

[0006] In another embodiment, an ion implanter is provided. The ion implanter may include an ion source configured to generate a metal ion beam including a plurality of metal ions. The ion source may include an ion chamber for generating an ion beam including the metal ion species, and a charge source including a charge mixture coupled to supply metal vapor to the ion chamber. The charge mixture may include a first portion including an elemental metal and a second portion including a heterogeneous metal fluoride compound formed from a heterogeneous metal element different from the elemental metal. The ion implanter may further include a mass filter disposed downstream of the ion source and configured to remove a set of impurity ions including the heterogeneous metal element from the metal ion beam.

[0007]

[0007] In a further embodiment, a method of operating a metal ion source is provided. The method can include providing a charge mixture in a charge source, the charge source including a vaporizer or a retractable crucible. The charge mixture can include a first portion including an elemental metal and a second portion including a dissimilar metal fluoride compound in solid form. The method can include heating the charge mixture to an operating temperature at which the charge source produces a metal vapor including at least one metal sub-fluoride species, and producing metal ions in an ion chamber of the metal ion source, the metal ions being derived from the metal vapor. [Brief description of the drawings]

[0008] [Figure 1]1 illustrates an ion implanter according to an embodiment of the present disclosure. [Diagram 2] 1 illustrates an ion source according to an embodiment of the present disclosure. [Figure 3A] 1 illustrates a side view of a charge source in an example of operation, according to an embodiment of the present disclosure. [Figure 3B] 3B illustrates a side view of the charge source of FIG. 3A during another example of operation, according to an embodiment of the present disclosure. [Figure 3C] 3B illustrates a side view of the charge source of FIG. 3A in a further example of operation, according to an embodiment of the present disclosure. [Figure 4] 1 illustrates an exemplary process flow. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009]

[0014] The present embodiments will now be described in more detail with reference to the accompanying drawings in which several embodiments are shown. The subject matter of the present disclosure can be embodied in many different forms and is not to be construed as being limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout.

[0010]

[0015] The present embodiments provide a novel approach to forming a high current metal ion source, such as for ion implantation. In various embodiments, the metal ion source (sometimes simply referred to herein as an "ion source") uses a charge source, such as a vaporizer, with a charge formed from a complex mixture of dissimilar metal-metal fluoride systems that provide the source of metal ions for use in, for example, an ion implanter. As used herein, the term "dissimilar metal-metal fluoride system" can refer to a mixture of metal and metal fluoride, where the elements that form the metal fluoride are not the same as the elements that form the metal. Similarly, in the context of a given metal material of an ion source, a "dissimilar metal fluoride," "dissimilar metal fluoride compound," or "dissimilar metal fluoride portion" can refer to a metal fluoride material based on a metal element that is different from the given metal material. Similarly, a "dissimilar metal element" can refer to a metal element in a metal fluoride compound that is different from the given metal material of an ion source. Thus, in an aluminum metal ion source, CdF2 metal fluoride represents the foreign metal fluoride to aluminum, with Cd representing the foreign metal element to aluminum. In operation, this type of charge provides a suitable chemical reaction to reduce the vapor pressure by producing volatile subfluorides that are generated from the metals when they are heated and liquid. The reduction in vapor pressure of the liquid metals for use as a source of metal ions and the generation of volatile subfluorides can provide a better mechanism for controlling the vapor supply of implanted ion species, such as dopant metal ions. At the same time, the formation of volatile subfluorides of a given metal species can increase the metal ion beam current.

[0011]

[0016] In certain embodiments highlighted below, an aluminum metal ion source is formed using a charge formed from metallic aluminum and a foreign metal fluoride. As detailed below, certain foreign metal fluorides may be particularly suitable for enhancing the performance of aluminum metal ion sources. While various embodiments detailed below detail the benefits of using foreign metal fluoride additives with aluminum to enhance the performance of aluminum ion sources, additional embodiments are contemplated in which foreign metal fluorides are added to enhance the performance of other metal ion sources, such as La and Ga ion sources.

[0012]

[0017] In various embodiments, novel ion implanters and novel metal ion sources, as well as techniques for improving the operation of metal ion sources, are provided. FIG. 1 illustrates an ion implanter according to an embodiment of the present disclosure. The ion implanter 100 is configured as a beamline ion implanter and can include various beamline components as known in the art to direct an ion beam 104 from an ion source 101. The ion source 101 can operate as a metal ion source including a metal vapor source, shown as charge source 103, and an ion chamber, shown as ion chamber 102, which is coupled to receive the metal vapor from the charge source 103. In some non-limiting embodiments, the charge source 103 can be a vaporizer or a retractable crucible. The ion chamber 102 can be an indirectly heated cathode source, an arc source, a plasma chamber, or other known ion source configurations. In this manner, the ion chamber 102 is coupled to receive the metal vapor from the charge source 103, which provides a source of ion species for the ion beam 104.

[0013]

[0018] The ion beam 104 may be extracted from the ion source 101 as a metal ion beam that includes ion species containing the metal species received from the charge source 103, and the metal species is implanted into the substrate 116. The ion beam 104 may be directed along a beamline where the ion beam 104 is mass analyzed, accelerated, decelerated, shaped, and directed toward a substrate stage 114 that supports or holds the substrate 116. The components of the ion implanter 100 shown in FIG. 1 are merely exemplary, and other components and additional known components may be included in the ion implanter 100 according to different embodiments. As shown in the figure, the ion implanter 100 may include a mass analyzer 106 that may mass analyze and direct the ion beam 104, a mass resolving slit 108, and a scanner 110 for scanning the ion beam 104, particularly in embodiments where the ion beam 104 is initially generated as a spot ion beam. In other embodiments, the ion beam 104 may be generated as a ribbon ion beam, where the scanner 110 is omitted. The ion implanter 100 may further include a collimator 112 for receiving the scanned ion beam and directing the ion beam 104 as a ribbon ion beam 119 towards the substrate 116. In this manner, the ion energy of the ion beam 104 may be set to achieve a target implantation depth of the metal ions.

[0014]

[0019] In various embodiments, the charge source 103 or a similar charge source serves as a charge-enhancing source of vapor species to increase the ion current and improve the operational stability of the ion source 101, as described in more detail below.

[0015]

[0020] FIG. 2 shows details of an ion source 200 according to an embodiment of the present disclosure. In this example, the ion chamber 102 is coupled to a charge source 103A that includes a charge mixture 202. The charge mixture 202 can include a first portion 204 that is an elemental metal and a second portion 206 that is a dissimilar metal fluoride. The portions can each be provided in a solid phase at room temperature when placed in the charge source 103A. For example, one or more of the first portion 204 and the second portion 206 can be provided in the form of a powder, can be provided in the form of a pellet, and in some cases, can be mixed together in the solid state to form a homogenous mixture. In a particular embodiment for an aluminum ion source, the first portion 204 can be elemental aluminum metal, while the second portion 206 can be a dissimilar metal fluoride, various dissimilar metal fluorides are described below.

[0016]

[0021] During operation, the charge source 103A can be heated to generate a series of reactions that serve to generate volatile (gas-phase) fluoride species of the metal species to be extracted from the ion chamber 102 to form the metal ion beam 210. As an example of an aluminum ion beam, when the charge source 103A is operating at an operating temperature, the charge mixture 202 can include aluminum and dissimilar metal fluorides that react to form aluminum vapor including gas-phase aluminum subfluorides. The aluminum vapor can then be transported to the ion chamber 102, ionized within the ion chamber 102, and extracted from the ion chamber 102 as the metal ion beam 210. As used herein, the terms "aluminum vapor" or "metal vapor" can refer to a vapor or gas-phase material or mixture that includes aluminum or a metal species, respectively. For example, aluminum vapor can refer to a gas-phase mixture of aluminum fluoride, aluminum subfluoride, and / or elemental aluminum vapor. By providing a suitable dissimilar metal fluoride material in the second portion 206, the charge source 103A can operate more stably and can help increase the overall current of aluminum ions extracted to form the metal ion beam 210.

[0017]

[0022] To further illustrate the operation of the charge source, FIG. 3A shows a side view of the charge source in one example of operation according to an embodiment of the present disclosure, FIG. 3B shows a side view of the charge source of FIG. 3A in another example of operation according to an embodiment of the present disclosure, and FIG. 3C shows a side view of the charge source of FIG. 3A in a further example of operation according to an embodiment of the present disclosure. The charge source 103B in this example includes a charge mixture 300 at the stage of FIG. 3A, which includes a solid metal portion 302 and a dissimilar metal fluoride portion 304 (which may also be in solid form). At this stage, the charge source 103B has been prepared and may not have previously been operated at an operating temperature. As such, the charge mixture 300 may be loaded into the charge source 103B prior to the performance of ion implantation.

[0018]

[0023] At the stage of Figure 3B, the charge source 103B is being heated and at least one reaction is occurring between the different components of the charge mixture 300 at the stage of Figure 3A. The reaction may form different combinations of materials present at the stage of Figure 3A. The nature of the combination of materials that may be formed at this stage of Figure 3B may depend on the chemical and thermodynamic properties of the solid metal portion 302 and the dissimilar metal fluoride portion 304, for example, the solid metal portion 302 may be in a liquid state at this stage.

[0019]

[0024] According to various embodiments, the dissimilar metal fluoride portion 304 of the charge mixture 300 of FIG. 3A has a relative free energy of formation, ΔG, of the dissimilar metal fluoride relative to the free energy of formation of the fluoride compound of the metal of the solid metal portion 302. fIn various embodiments of the aluminum ion source in which the solid metal portion 302 is elemental aluminum, the dissimilar metal fluoride compound may be characterized by a free energy of formation that is greater than or less thermodynamically favorable than the free energy of formation of aluminum fluoride (i.e., AlF3). More specifically, in the designed operating temperature range of the charge source 103B, the free energy of formation of AlF3 may have a more negative value than the free energy of formation of the dissimilar metal fluoride. In general, for many metal fluorides, the free energy of formation is known as a function of temperature. This data may be derived from known thermodynamic data tables or may be presented in the well-known Ellingham diagram that shows the free energy of formation as a function of temperature for various fluorides, including AlF3. Examples of curves representing the free energy of formation of several metal fluorides that have a smaller free energy of formation than the curve for AlF3 are known, which show a curve with a free energy of formation of ΔG over a temperature range, such as between room temperature and 1800 K. f means that the negative value of is small. This temperature range may encompass the temperature range for operating a charge source such as charge source 103B. For example, metal fluorides such as CdF2 have a smaller free energy of formation than AlF3, i.e., the curve for CdF2 lies above the curve for AlF3 throughout the temperature range shown, in this case by about 50 kcal / gfw between 0 and 1040 K. This same conclusion can be reached by constructing a thermodynamic cycle using information obtained from thermodynamic tables such as those provided by the National Institute of Standards and Technology. The significance of this fact is that the compound AlF3 is more stable than CdF2, and therefore reacting elemental aluminum with a dissimilar metal fluoride such as CdF2 may tend to produce AlF3. The same is true for other dissimilar metal fluorides such as BiF3, AsF5, SbF5, all of which exhibit a smaller free energy of formation than AlF3.

[0020]

[0025] Returning to the example of FIG. 3B, the charge mixture 300 now includes a reactive portion 308 and a liquid portion 306. As described in more detail below, the reactive portion 308 may include a solid phase 307 or may include gaseous species. In an aluminum ion source embodiment, the reactive portion 308 may include an aluminum subfluoride, such as AlF or AlF2, generated directly from the reaction of the solid metal portion 302 with the dissimilar metal fluoride portion 304, and the liquid portion 306 may represent an alloy or other mixture of aluminum and the dissimilar metal obtained from the dissimilar metal fluoride portion 304. In some examples, the dissimilar metal fluoride portion 304 may be a difluoride or trifluoride and may react with aluminum metal to produce a metal-liquid mixture of the dissimilar metal element and aluminum, and a phase of AlF or AlF2. For example, when gallium-based heterometallic fluoride (GaF3) is mixed with aluminum metal at 1200 K, aluminum subfluoride AlF can be produced (ΔG° [A] =-19.88kJ). TIFF2025512909000002.tif5170In this same system, the reaction of GaF3 with Al at the same operating temperature of 1200K should not produce AlF2 according to the following equation (ΔG° [B] =+0.810kJ). In this exemplary system, co-generation of AlF and AlF2 is possible at a temperature of 1200 K (ΔG° [C] =-6.089kJ). TIFF2025512909000004.tif5170When the difluorine-containing aluminum subfluoride AlF2 is produced at a temperature of 1200 K, an additional reaction pathway for the production of AlF is opened according to the following equation (ΔG° [D] =-13.80kJ). TIFF2025512909000005.tif5170

[0021]

[0026] This process is advantageous because the reaction directly produces aluminum subfluoride, which has a lower vapor pressure than Al or GaF3, meaning that the Al charge vapor can be achieved at lower temperatures overall.

[0022]

[0027] In another example of a charge mixture initially using a dissimilar metal trifluoride (MeF3) and aluminum, the reaction can generally proceed as follows: TIFF2025512909000006.tif5170 Note that metal difluorides (MeF2) can also react with aluminum to produce AlF3+aluminum-heterometallic liquid mixtures. In this example, the reaction portion 308 can include AlF3 in the solid phase 307. TIFF2025512909000007.tif8170

[0023]

[0028] It should be noted that in the above example where the reaction portion 308 includes an aluminum subfluoride such as AlF or AlF2 generated directly from the reaction of the solid metal portion 302 with the dissimilar metal fluoride portion 304, the aluminum subfluoride can rapidly transform into a gas phase depending on the reaction temperature. This situation is depicted in Figure 3B, where the reaction portion 308 can include a gaseous species 310 representing AlF and a gaseous species 312 representing AlF2.

[0024]

[0029] 3C, in charge mixture 300, reactive portion 308 is still present, and liquid portion 306A represents liquid portion 306 at a later stage where the composition of liquid portion 306 may have changed. At this stage, more gaseous species have been generated in charge source 103B, which can be used as vapor for ionization in the ion chamber. In an aluminum ion source embodiment, the gaseous species can include aluminum subfluoride species, with gaseous species 310 representing AlF and gaseous species 312 representing AlF2, as described above. In addition to direct production by reaction of aluminum with dissimilar metal fluorides, as represented in FIG. 3B, gaseous species can also be produced as a result of aluminum in liquid portion 306 reacting with AlF3 (represented by solid phase 307) to produce aluminum subfluorides. For example, reaction of AlF3 with Al at a temperature of 1200 K can produce aluminum subfluoride AlF (ΔG°) according to the following equation: [F] =-9.79kJ). TIFF2025512909000008.tif5170In this same system, the reaction of AlF3 with Al at the operating temperature of 1200 K should not produce the difluorine-containing aluminum subfluoride AlF2 according to the following equation (ΔG° [G] =+10.895kJ). TIFF2025512909000009.tif8170Furthermore, the co-production of different subfluorides (AlF, AlF2) by the reaction of AlF3 with Al under the same operating conditions at 1200 K is characterized by a thermodynamic unfavorability (ΔG° [H] = +3.996kJ), this should not occur. TIFF2025512909000010.tif5170

[0025]

[0030] Thus, in the examples of Figures 3B and 3C, volatile aluminum subfluorides can be produced not only directly from the reaction of aluminum with dissimilar metal fluorides, but also from AlF 3(S) The reaction of aluminum with dissimilar metal fluorides to form AlF 3(S)It can also be produced indirectly from the reaction of ZnO with residual aluminum in the charge.

[0026]

[0031] Thus, providing a solid dissimilar metal fluoride and aluminum as a charge mixture for an ion source can directly lead to the production of aluminum vapor for the ion source in the form of a volatile aluminum subfluoride. The aim of this approach is to increase the overall ion current in the ion source over that obtained from a charge based on a pure metal such as pure aluminum. For example, it has previously been shown that the aluminum ion current in an ion source can be increased using a mixture of aluminum and AlF3 as the initial charge material.

[0027]

[0032] The advantage of using a mixture of aluminum and a dissimilar metal fluoride as the initial charge material, rather than aluminum and AlF3, is that more reaction pathways for the production of aluminum subfluorides become viable. Thermodynamic calculations indicate that the relative instability in the formation of certain metal fluoride compounds compared to AlF3, as measured by standard Gibbs free energy (G), provides sufficient thermodynamic driving force for reactions that would otherwise be unfavorable. Since the objective is to produce Al subfluorides for use as a volatile precursor to aluminum ions, this consideration means that a mixture of dissimilar metal fluorides and aluminum is more optimal than a mixture of AlF3 and Al.

[0028]

[0033] Another advantage of adding solid dissimilar metal fluorides to aluminum, for example, as a charge material for an aluminum ion source, is that the flexibility of operation of the charge source may be improved by the use of different metal species provided by the dissimilar metal fluoride. In particular, reacting the dissimilar metal fluoride with aluminum to produce a liquid portion may produce an alloy or multiphase mixture of metal elements from aluminum and the dissimilar metal fluoride, whose melting characteristics are at least partially determined by the metal elements of the dissimilar metal fluoride. For example, in an embodiment in which the dissimilar metal fluoride portion 304 is GaF3 or InF3, the melting temperature of the subsequently formed liquid portion (i.e., liquid portion 306) formed from a mixture of the respective dissimilar metal element with Al will be lower than the melting temperature of pure Al, according to the well-known binary phase diagrams of Ga-Al or In-Al. Thus, the useful temperature range of such charge sources formed with GaF3 or InF3 can be tailored and may generally be wider than the useful temperature range of a pure aluminum charge source.

[0029]

[0034] According to certain embodiments of the present disclosure, the dissimilar metal fluoride compound used in the charge source may be one of CdF2, InF3, and GaF3. These particular materials may meet several criteria that favor their use as charge source materials in combination with elemental aluminum for aluminum ion sources. In these embodiments, after reaction with elemental aluminum, the resulting liquid portion generally contains Al x Ga 1-x , Al x In 1-x , or Al x CD 1-x The liquid phase may be one or more phases that are aluminum-containing metallic liquid phase mixtures represented by the formula: Again, according to the above description, the accompanying solid phase that is expected to form with this liquid phase is AlF3. Since AlF3 is solid up to its melting temperature of 1290°C, the charge source can operate stably over a relatively wide range of temperatures below the melting temperature of this AlF3 and above the melting temperature of the mixture of aluminum and dissimilar metallic elements.

[0030]

[0035] Among the useful properties of a charge source formed from a mixture of dissimilar metal fluorides and aluminum is the melting temperature of the dissimilar metal fluoride. Table I lists exemplary melting properties of suitable dissimilar metal fluorides. As shown in TIFF2025512909000011.tif53170 Table I, all of the listed fluorides have melting temperatures of 800°C or higher, which may be significantly higher than the operating temperature of the charge source. Since alloy mixtures of aluminum with the metallic elements of the listed dissimilar metal fluorides all exhibit melting temperatures lower than the melting temperature of aluminum (660°C), charge sources containing dissimilar metal fluorides and aluminum can operate to form melts at a temperature range much lower than the melting temperature of a given dissimilar metal fluoride. This property is useful in that it avoids the loss of fluorine when the charge source is heated before it reaches the operating temperature. In other words, if the dissimilar metal fluoride melts before the aluminum reaches a temperature sufficient to start melting, fluorine can be expected to evolve from the liquid dissimilar metal fluoride and cause a loss of control of the charge process.

[0031]

[0036] Additionally, while elements such as Ga, Cd, and In may be considered undesirable when implanted into a substrate, in ion implantation embodiments using aluminum as a dopant source for implantation into semiconductors, elements such as Ga, Cd, and In can be easily removed from the ion beam and do not pose a risk to the Al implantation process. This ability to remove such species is illustrated in Table II, which shows the mass / charge (m / q) ratios of the ionized species of these elements compared to the m / q ratio of aluminum ions. TIFF2025512909000012.tif119170

[0032]

[0037] Because there is no overlap in the m / q ratios of these foreign metal ions and aluminum ions, the mass analyzer can easily remove such foreign metal ions downstream of the ion source when a volatile vapor containing the foreign metal species enters the ion chamber from the charge source and is then ionized and extracted.

[0033]

[0038] 4 illustrates an exemplary process flow 400. At block 402, a charge is provided in a charge source, where the charge is formed of a charge mixture including an elemental metal, such as aluminum, and a dissimilar metal fluoride compound. The various materials of the charge may all be in a solid state at room temperature. As such, the charge mixture may be conveniently placed in any suitable charge source, including a vaporizer or retractable crucible source.

[0034]

[0039] In block 404, the charge in the charge source is heated to an operating temperature and the charge source generates a metal vapor. In one embodiment of the aluminum charge source, aluminum vapor is produced that includes at least one aluminum subfluoride vapor species, such as AlF or AlF2. In one example where the dissimilar metal fluoride is trifluoride (MeF3), the aluminum subfluoride vapor species AlF (G) can be produced in a series of reactions as generally shown below: TIFF2025512909000013.tif15170Similarly, there is the following series of reactions: TIFF2025512909000014.tif5170 and TIFF2025512909000015.tif15170

[0035]

[0040] The element aluminum, represented by formula [2], is a liquid mixture of aluminum and other metallic elements (Al x Me 1-x(Liquid) ) and aluminum vapor is obtained from Al x Me 1-x(Liquid) Note that this may also include elemental aluminum vapor species emanating from the material.

[0036]

[0041] At block 406, metal ions are generated in an ion chamber of the ion source, the metal ions being derived from metal vapor generated in the charge source. As previously described, the metal vapor, such as aluminum vapor, can include elemental metal vapor species as well as metal subfluorides. The charge source can be coupled to the ion chamber, and the elemental metal vapor generated during heating of the charge source as well as the metal subfluorides are transported to the ion chamber. Thus, the density of the metal ions, such as aluminum ions, can be higher than the density of metal ions generated from a charge made of pure elemental metal.

[0037]

[0042] In block 408, the ion beam is extracted from the ion chamber, the ion beam comprising metal ions. It should be noted that during the generation of aluminum subfluoride vapor, other gas phase species comprising dissimilar metal elements may be generated in the charge source, introduced into the ion source, and subsequently ionized in the ion source.

[0038]

[0043] In block 410, filtering (removal) of foreign metal ions from the ion beam is performed using a mass analysis component located downstream of the ion source. The mass analysis component may be a known magnetic device in which different ions with different m / q ratios are deflected along different arcs, transmitting only selected ions of the selected m / q ratio. Thus, the elemental metals of the group of foreign metal fluorides selected for the charge mixture can be selected such that the metal ions of any given charge state of the foreign metal element do not have m / q ratios that overlap with the m / q ratios of the various metal ion charge states of the metal ions ionized singly, doubly, triply, etc. Thus, a pure metal ion beam, such as an aluminum ion beam, can be transported to a substrate for implantation while the foreign metal ions are selected and removed.

[0039]

[0044] The present embodiment offers several advantages over current approaches to metal source ion implantation. First, the use of a dissimilar metal fluoride additive in a metal charge, such as an aluminum charge material, in a charge source can actually produce a higher overall yield of metal-containing vapor and therefore a higher metal ion beam current in the ion chamber compared to using a pure elemental metal charge. Second, a charge source operating according to the charge mixture of the present embodiment can be operated at a lower overall temperature, providing more consistent ion source performance, fewer failures, and better overall control of metal vapor generation.

[0040]

[0045] The present disclosure is not limited in scope by the specific embodiments described herein. Indeed, in addition to those described herein, various other embodiments and modifications of the present disclosure will be apparent to those skilled in the art from the foregoing description and the accompanying drawings. Accordingly, such other embodiments and modifications are intended to be included within the scope of the present disclosure. Furthermore, although the present disclosure has been described herein in the context of specific implementations in specific environments for specific purposes, those skilled in the art will recognize that the usefulness is not limited thereto, and the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Therefore, the claims set forth below should be construed in light of the full scope and spirit of the present disclosure as described herein.

Claims

1. an ion chamber for generating an ion beam comprising a metal ion species; a charge source coupled to supply metal vapor to the ion chamber; 1. An ion source comprising: a charge source comprising a charge mixture, the charge mixture comprising: a first portion comprising an elemental metal; a second portion comprising a different metal fluoride compound; an ion source comprising:

2. the metal ion species is aluminum; the dissimilar metal fluoride compound is characterized by a first curve defining a free energy of formation as a function of temperature over a charge source operating temperature range; Aluminum fluoride (AlF ３ 2. The ion source of claim 1, wherein the charge source is characterized by a second curve that defines a free energy of formation as a function of temperature over the charge source operating temperature range, the second curve being below the first curve.

3. The different metal fluoride compound is CdF ２ , InF ３ , and GaF ３ The ion source of claim 2 , comprising one of:

4. The elemental metal comprises Ga, and the heterogeneous metal fluoride compound comprises AlF ３ or InF ３ The ion source of claim 1 , comprising:

5. The elemental metal includes La, and the heterogeneous metal fluoride compound includes AlF ３ , CdF ２ , or InF ３ The ion source of claim 1 , comprising:

6. In operation, the charge source comprises Al ｘ G １－ｘ , Al ｘ In １－ｘ , or Al ｘ Cd １－ｘ 2. The ion source of claim 1, comprising an aluminum-containing metal liquid phase comprising:

7. The ion source of claim 6 , wherein during operation, the charge source further comprises at least one aluminum subfluoride.

8. 1. An ion source configured to generate a metal ion beam comprising a plurality of metal ions, the ion source comprising: an ion chamber for generating an ion beam comprising a metal ion species; a charge source coupled to supply metal vapor to the ion chamber; the charge source comprises a charge mixture, the charge mixture comprising: a first portion comprising an elemental metal; a second portion including a dissimilar metal fluoride compound formed from a dissimilar metal element different from the elemental metal; an ion source comprising: a mass filter disposed downstream of the ion source and configured to remove a set of impurity ions containing the different metal element from the metal ion beam; An ion implantation apparatus comprising:

9. The elemental metal comprises aluminum and the heterometallic fluoride compound comprises CdF ２ , InF ３ , and GaF ３ 9. The ion implanter of claim 8, comprising one of:

10. 10. The ion implanter of claim 9, wherein during operation, the charge mixture comprises an aluminum-containing metallic liquid phase.

11. The aluminum-containing metal liquid phase is Al ｘ G １－ｘ , Al ｘ In １－ｘ , or Al ｘ Cd １－ｘ The ion implanter of claim 10 , comprising:

12. The ion implanter of claim 11 , wherein during operation, the charge source further comprises at least one aluminum subfluoride.

13. 13. The ion implanter of claim 12, wherein the metal ions comprise elemental aluminum ions having a set of mass / charge ratios of aluminum, and the impurity ions comprise elemental metal ions of the dissimilar metal element having a set of mass / charge ratios of impurity ions, the set of mass / charge ratios of aluminum being non-overlapping with the set of mass / charge ratios of impurity ions.

14. The heterogeneous metal fluoride compound is AlF ３ 9. The ion implanter of claim 8, comprising:

15. 1. A method of operating a metal ion source, comprising: providing a charge mixture in a charge source, the charge source including a vaporizer or a retractable crucible, the charge mixture including a first portion including an elemental metal and a second portion including a dissimilar metal fluoride compound in solid form; heating the charge mixture to an operating temperature, the charge source producing a metal vapor comprising at least one metal subfluoride species; generating metal ions in an ion chamber of the metal ion source, the metal ions being derived from the metal vapor; The method includes:

16. The elemental metal comprises aluminum and the heterometallic fluoride compound comprises CdF ２ , InF ３ , and GaF ３ 16. The method of claim 15, comprising one of:

17. The metal vapor is AlF and AlF ２ and wherein during heating the charge mixture, the metal vapor is generated at least in part directly from reacting the dissimilar metal fluoride compound with aluminum.

18. The metal vapor is AlF and AlF ２ during heating of the charge mixture, the metal vapor first reacts with the dissimilar metal fluoride compound to form AlF ３ A solid and an aluminum-containing liquid are produced, and then the AlF ３ 17. The method of claim 16, at least in part produced from reacting a solid with the aluminum-containing liquid to produce the metal vapor.

19. During heating of the charge mixture, the metal vapor is converted into AlF ３ The metal vapor is produced from the reaction of the material with an aluminum-containing metal liquid phase, the metal vapor being AlF and AlF ２ The method of claim 15 , comprising at least one of:

20. 16. The method of claim 15, wherein the metal ions comprise elemental aluminum ions having a set of aluminum mass / charge ratios, the set of aluminum mass / charge ratios not overlapping with a set of impurity ion mass / charge ratios characteristic of a set of impurity ions derived from metal elements of the heterogeneous metal fluoride compound, the method further comprising removing the set of impurity ions using a mass analyzer disposed downstream of the metal ion source.

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