Annular motion enhanced ion source

Abstract

An IHC ion source having a high plasma potential is disclosed. In certain embodiments, the extraction plate is biased at a higher voltage than the body of the arc chamber to achieve the higher plasma potential. A shield electrode can be utilized to eliminate interaction between the biased extraction plate and the plasma. The cross section of the arc chamber can be circular or near-circular to facilitate rotation of electrons within the chamber. In another embodiment, biased electrodes can be positioned heightwise within the chamber on either side of the extraction opening. In some embodiments, only one of the electrodes is biased at a higher voltage than the body of the arc chamber.

Description

[Technical Field]

[0001] This application claims priority to U.S. Patent Application No. 17 / 551,849, filed December 15, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to ion sources, and more particularly to indirectly heated cathode ion sources in which at least one biased component is disposed within a chamber such that a plasma potential is elevated. [Background technology]

[0003] Various types of ion sources can be used to generate ions used in semiconductor processing equipment. For example, an indirectly heated cathode (IHC) ion source operates by supplying current to a filament positioned behind a cathode. The filament emits thermionic electrons, which accelerate toward the cathode, heating it and causing the cathode to emit electrons into the arc chamber of the ion source. The cathode is located at one end of the arc chamber. A repeller may be located at the end of the arc chamber opposite the cathode. The cathode and repeller may be biased to repel the electrons and return them toward the center of the arc chamber. In other embodiments, a cold cathode may be located at the opposite end of the arc chamber. In some embodiments, a magnetic field is used to further confine the electrons within the arc chamber. Side walls are used to connect the two ends of the arc chamber.

[0004] An extraction aperture is located along one of the sides adjacent the center of the arc chamber through which ions generated within the arc chamber can be extracted.

[0005] There are various parameters of interest in IHC ion sources, including extraction beam current, dopant fractionation, and plasma stability. However, optimizing all of these parameters can be difficult. For example, high extraction current can reduce plasma stability.

[0006] Therefore, it would be beneficial to have an IHC ion source that overcomes these problems, especially one that has improved plasma stability even at high extraction currents. Summary of the Invention

[0007] An IHC ion source having a high plasma potential is disclosed. In certain embodiments, to achieve the higher plasma potential, an extraction plate is biased at a higher voltage than the body of the arc chamber. A shield electrode can be utilized to reduce interaction between the biased extraction plate and the plasma. The cross section of the arc chamber can be circular or near-circular to facilitate electron rotation within the chamber. In another embodiment, biased electrodes can be positioned heightwise within the chamber on either side of the extraction opening. In some embodiments, only one of the electrodes is biased at a higher voltage than the body of the arc chamber.

[0008] According to one embodiment, an ion source is disclosed. The ion source includes a chamber. The chamber includes a body having a first end, a second end, a bottom, and multiple walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate including an extraction aperture having a width and a height through which ions are extracted, the extraction plate being electrically insulated from the body, and the body and the extraction plate forming a closed space; one or more shield electrodes disposed adjacent to the extraction plate within the closed space so as not to physically contact the extraction plate, the one or more shield electrodes being electrically connected to the body; and an extraction power supply communicating with the extraction plate, the extraction plate being positively biased relative to the body. In some embodiments, the one or more shield electrodes are disposed above and below the extraction aperture along the width of the extraction aperture. In some embodiments, the inner surfaces of the one or more shield electrodes are curved. In some embodiments, the bottom and multiple walls are a unitary piece having curved inner surfaces, whereby the inner surfaces of the unitary piece and the one or more shield electrodes form a circular or nearly circular cross section within the chamber along a portion of the chamber. In some embodiments, the circular or nearly circular cross-section extends along the width of the extraction opening. In certain embodiments, the bottom and the walls are separate pieces, and the ion source further comprises curved electrodes disposed in corners formed between the bottom and each wall. In this case, the curved electrodes are electrically connected to the body. In some embodiments, the bottom, the walls, the curved electrodes, and exposed portions of the inner surfaces of the one or more shield electrodes form a circular or nearly circular cross-section along a portion of the chamber. In some embodiments, the circular or nearly circular cross-section extends along the width of the extraction opening. In some embodiments, the extraction plate is biased at a voltage that is 10 V to 100 V higher than the voltage of the body.

[0009] According to another embodiment, an ion implantation system is disclosed, comprising an ion source, a mass analyzer, and an acceleration / deceleration stage as described above.

[0010] According to another embodiment, an ion source is disclosed. The ion source includes a chamber. The chamber includes a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate electrically connected to the body, the extraction plate including an extraction opening having a width and a height through which ions are extracted, the body and the extraction plate forming a closed space; two electrodes disposed adjacent to the extraction plate within the closed space, one electrode disposed above the extraction opening in a height direction and the other electrode disposed below the extraction opening in a height direction; and an electrode power supply communicating with the first of the two electrodes, wherein the first electrode is electrically insulated from the body and is positively biased relative to the body, and the second electrode is electrically connected to the body. In some embodiments, the two electrodes include a plate having a planar inner surface and a planar back surface, the plate disposed parallel to the extraction plate. In some embodiments, the two electrodes comprise a plate having a planar inner surface and a planar rear surface, the plate being positioned at an angle relative to the extraction plate.

[0011] According to another embodiment, an ion source is disclosed. The ion source includes a chamber. The chamber includes a body having a first end, a second end, a bottom, and multiple walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate electrically connected to the body, the extraction plate including an extraction opening having a width and a height through which ions are extracted; the body and extraction plate forming an enclosed space; the extraction plate; one or more electrodes disposed within the enclosed space, the one or more electrodes disposed heightwise above and below the extraction opening; and an electrode power supply communicating with at least one of the one or more electrodes. In this case, the inner surfaces of the one or more electrodes are curved, and the one or more electrodes are disposed within or adjacent to a corner formed at a junction between the body and the extraction plate. In some embodiments, the bottom and multiple walls are a unitary piece having a curved inner surface, such that the inner surfaces of the unitary piece and the one or more electrodes form a circular or nearly circular cross-section along a portion of the chamber. In some embodiments, the bottom and the walls are separate components, and the ion source further includes a curved electrode disposed within a corner formed between the bottom and each wall. In this case, the curved electrode is electrically connected to the body. In some embodiments, the bottom, the walls, the curved electrode, and the exposed portions of the inner surfaces of the one or more electrodes form a circular or nearly circular cross-section along a portion of the chamber. In some embodiments, the one or more electrodes include two electrodes, and the two electrodes are biased at different voltages.

[0012] According to another embodiment, an ion implantation system is disclosed, comprising an ion source, a mass analyzer, and an acceleration / deceleration stage as described above.

[0013] For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is an indirectly heated cathode (IHC) ion source according to one embodiment. [Figure 2A]2 shows a perspective view of the IHC ion source of FIG. 1 according to one embodiment. [Figure 2B] 2 shows a perspective view of the IHC ion source of FIG. 1 according to another embodiment. [Figure 3A] 3A-3B show cross-sectional views of the IHC ion source of FIG. 1 according to two embodiments. [Figure 3B] 3A-3B show cross-sectional views of the IHC ion source of FIG. 1 according to two embodiments. [Figure 4] 1 is an indirectly heated cathode (IHC) ion source according to another embodiment. [Figure 5A] 5A-5E show cross-sectional views of the IHC ion source of FIG. 4 according to various embodiments. [Figure 5B] 5A-5E show cross-sectional views of the IHC ion source of FIG. 4 according to various embodiments. [Figure 5C] 5A-5E show cross-sectional views of the IHC ion source of FIG. 4 according to various embodiments. [Figure 5D] 5A-5E show cross-sectional views of the IHC ion source of FIG. 4 according to various embodiments. [Figure 5E] 5A-5E show cross-sectional views of the IHC ion source of FIG. 4 according to various embodiments. [Figure 6] 1 illustrates an ion implantation system utilizing the IHC ion source of FIG. 1 or FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Various embodiments of IHC ion sources are disclosed in which the plasma potential is manipulated by biasing one or more components in the arc chamber that are exposed to the plasma at a higher voltage than the rest of the body of the arc chamber.

[0016] FIG. 1 illustrates an IHC ion source 10 according to one embodiment. The IHC ion source 10 includes an arc chamber 100. The arc chamber 100 has a body with two opposing ends and a bottom and wall 101 connecting the ends. The direction between the two opposing ends is referred to as the X-direction. The direction between the walls 101 is referred to as the Y-direction. The direction between the bottom and the extraction plate 103 is referred to as the Z-direction. The ends of the arc chamber 100 and the walls 101 may be constructed of a conductive material and may be in electrical communication with each other. In some embodiments, a liner may be disposed proximate one or more of the walls 101. A cathode 110 is disposed within the arc chamber 100 at a first end 104 of the arc chamber 100. A filament 160 is disposed behind the cathode 110. The filament 160 is in communication with a filament power supply 165. The filament power supply 165 is configured to apply electrical current to the filament 160. The cathode bias power supply 115 may bias the filament 160 to have a voltage that is, for example, between 200 V and 1500 V more negative than the voltage of the cathode 110. The cathode 110 then emits thermionic electrons from its front surface into the arc chamber 100.

[0017] Thus, filament power supply 165 provides current to filament 160. Cathode bias power supply 115 biases filament 160, making it more negative than cathode 110. As a result, electrons are attracted from filament 160 toward cathode 110. In certain embodiments, cathode 110 may be biased with respect to arc chamber 100, such as by bias power supply 111. In other embodiments, cathode 110 may be electrically connected to arc chamber 100 so that it is at the same voltage as walls 101 of arc chamber 100. In these embodiments, bias power supply 111 may not be employed, and cathode 110 may be electrically connected to walls 101 of arc chamber 100. In certain embodiments, arc chamber 100 is electrically grounded.

[0018] A repeller 120 may be disposed at a second end 105 opposite the first end 104. The repeller 120 may be biased relative to the arc chamber 100 by a repeller bias power supply 123. In other embodiments, the repeller 120 may be electrically connected to the arc chamber 100 so as to be at the same voltage as the walls 101 of the arc chamber 100. In these embodiments, the repeller bias power supply 123 may not be employed, and the repeller 120 may be electrically connected to the walls 101 of the arc chamber 100. In still other embodiments, the repeller 120 is not employed.

[0019] The cathode 110 and the reflective electrode 120 are each made of a conductive material such as metal or graphite. The center of the cathode 110 and the center of the reflective electrode 120 are arranged along the central axis 108.

[0020] All of the components that make up the body of the arc chamber 100 are electrically and mechanically coupled to one another. In other words, the first end 104, the second end 105, the bottom, and the walls 101 are all at the same electrical potential.

[0021] In certain embodiments, a magnetic field 190 is applied along the arc chamber 100 parallel to the X direction. This magnetic field 190 is intended to confine electrons along one direction. The magnetic field 190 typically runs parallel to the wall 101 from the first end 104 to the second end 105. For example, electrons may be confined in columns parallel to the direction from the cathode 110 to the repeller 120 (i.e., the X direction). Thus, electrons do not experience any electromagnetic force moving in the X direction. However, electrons moving in other directions may experience electromagnetic forces.

[0022] Additionally, the IHC ion source 10 also includes a gas inlet 106 through which a feed gas to be ionized can be introduced into the arc chamber 100 .

[0023] One side of the arc chamber 100 is called the extraction plate 103. The extraction plate 103 includes an extraction aperture 140. In FIG. 1 , the extraction aperture 140 is located on a side parallel to the X-Y plane (perpendicular to the page). The extraction plate 103 is made of a conductive material such as metal or graphite. In certain embodiments, the extraction aperture 140 may have a width (i.e., in the X direction) that is significantly greater than its height (i.e., in the Y direction).

[0024] The extraction plate 103 is electrically isolated from the body of the arc chamber 100 by using an insulator 141. In other words, the first end 104, the second end 105, the bottom, and the wall 101 are maintained at a common potential, which may be grounded. However, in other embodiments, these components may be biased using a power supply.

[0025] As mentioned above, the extraction plate 103 is electrically insulated from the body of the arc chamber 100 through the use of insulators 141. In particular, the insulators 141 may separate the extraction plate 103 from the two walls 101, the first end 104, and the second end 105. These insulators 141 may be constructed of a dielectric material such as boron nitride (BN) or alumina (Al2O3).

[0026] One or more shield electrodes 150 are disposed between the interior of the arc chamber 100 and the extraction plate 103. The one or more shield electrodes 150 may be adjacent to the extraction plate 103, but not in physical contact with the extraction plate 103. In this manner, the one or more shield electrodes 150 may block a portion of the extraction plate 103 from being exposed to the plasma.

[0027] As seen in FIG. 2A , one or more shield electrodes 150 may be positioned above and below the extraction opening 140 in the Y direction. The one or more shield electrodes 150 may extend across the entire width of the extraction opening 140. In some embodiments, the one or more shield electrodes 150 may extend beyond the extraction opening 140 in the X direction. In one embodiment shown in FIG. 2A , there may be two shield electrodes 150, one on each side of the extraction opening 140 in the height direction. In another embodiment shown in FIG. 2B , the shield electrode 150 may be an integral part with an opening corresponding to the extraction opening 140.

[0028] Although the above disclosure describes an extraction opening having a width significantly greater than its height, other extraction openings are possible. For example, the extraction opening 140 may be a round opening. In this example, one or more shield electrodes 150 of FIG. 2A may still be disposed on either side of the extraction opening 140 in the height direction. In one embodiment, there may be two shield electrodes 150, one on each side of the extraction opening in the height direction (i.e., the Y direction). These shield electrodes 150 may extend beyond the round opening in the X direction. In another embodiment, the shield electrode 150 may be an integral part. In that case, the hole corresponding to the extraction opening 140 is similar to that shown in FIG. 2B. For example, the integral part may be round, square, diamond-shaped, rectangular, or any other shape with a hole.

[0029] The one or more shield electrodes 150 may be shaped to form a curved inner surface that faces the arc chamber 100. The curved inner surface may be concave. Additionally, the shield electrodes 150 are electrically isolated from the extraction plate 103, such as by using insulators 143 or gaps between the one or more shield electrodes 150 and the extraction plate 103. These insulators 143 may be constructed of a dielectric material such as boron nitride (BN) or alumina (Al2O3).

[0030] The one or more shield electrodes 150 may be constructed from a high-melting-point metal and are electrically conductive. The one or more shield electrodes 150 may be biased at the same potential as the body of the arc chamber 100. In certain embodiments, the one or more shield electrodes 150 contact the body of the arc chamber 100 when the arc chamber 100 is assembled. The term "body of the arc chamber" refers to the first end 104, the second end 105, the bottom, and the walls 101. The one or more shield electrodes 150 may be in physical and / or electrical contact with the body so as to have the same voltage as the body. In one embodiment, the one or more shield electrodes 150 are in physical contact with the body. In another embodiment, the one or more shield electrodes are electrically connected to the body, such as by a wire or conductive material 144, as shown in FIGS. 3A and 3B.

[0031] In certain embodiments, such as those shown in Figures 2A, 2B, and 3A, a portion of the body, in particular the bottom and the walls, constitutes a one-piece part 151 having a bottom (facing the extraction plate 103) and two walls. The direction between the bottom and the extraction plate 103 is referred to as the Z direction. In this embodiment, the one-piece part 151 may have a U-shaped inner surface.

[0032] 3A, the U-shaped inner surface of the one-piece part 151 and the inner surface of the shield electrode 150 may form a circular or nearly circular cross-section in the Y-Z plane along a portion of the arc chamber 100. This circular or nearly circular cross-section may extend along the X direction for the entire width of the extraction aperture 140. The term "nearly circular" is defined as a configuration in which the shortest distance from the central axis 108 to any point on the inner surface of the one-piece part 151 or the shield electrode 150 varies by less than 30%.

[0033] FIG. 3B shows a second configuration. In this embodiment, the wall 101 may be constructed from separate pieces, such as a bottom 152 and two walls 153. To create a circular or nearly circular cross-section, a curved electrode 154 may be placed in the corner between the bottom 152 and each of the walls 153. The inner surface of the curved electrode 154 may be concave. The curved electrode 154 may be electrically connected to the bottom 152 and the walls 153. In one embodiment, the curved electrode 154 may rest against the bottom 152 and / or the walls 153. In another embodiment, as shown in FIG. 3B, the curved electrode 154 is electrically connected to the body, such as by a wire or conductive material 144.

[0034] The curved electrode 154 may extend from the first end 104 to the second end 105. In another embodiment, the curved electrode 154 extends the entire width of the extraction opening 140. The curved electrode 154 may be electrically connected to the body of the arc chamber 100.

[0035] The exposed portions of the bottom 152, walls 153, curved electrode 154, and one or more shield electrodes 150 form a circular or nearly circular cross-section in the Y-Z plane along a portion of the arc chamber 100. In this embodiment, the term "nearly circular" is defined as a configuration in which the shortest distance from the central axis 108 to any point on the exposed inner surface of the bottom 152, walls 153, curved electrode 154, or shield electrode 150 varies by less than 30%.

[0036] In operation, when assembled, the extraction plate 103 and body of the arc chamber 100 form an enclosed volume. A feed gas enters the enclosed volume through the gas inlet 106. The feed gas introduced into the IHC ion source 10 is ionized to form a plasma. This plasma has an electric potential, referred to as the plasma potential, which is related to the electric potential of the walls that form the enclosed volume.

[0037] In this embodiment, the extraction plate 103 is independently biased using an extraction power supply 145. In certain embodiments, the extraction power supply 145 is referenced to the body of the arc chamber 100. The extraction power supply 145 can provide a positive voltage to the extraction plate 103 relative to the body of the arc chamber 100. These voltages can be between 5V and 100V more positive than the body, although other values ​​are possible.

[0038] A positively biased extraction plate 103 relative to the body of the arc chamber 100 provides an efficient ion source operating at higher plasma densities. In this mode, the extraction plate 103 is biased to a higher potential than the body of the arc chamber 100, so the plasma potential is at a higher voltage than that of the body of the arc chamber 100. Particularly near the extraction aperture 140, the plasma potential can be equal to or greater than the voltage applied to the extraction plate 103. Along the central axis 108, the plasma potential is higher than the voltage of the arc chamber 100 and can be approximately 50% to 75% of the voltage applied to the extraction plate 103.

[0039] This creates an electric field within the arc chamber 100 that extends radially outward from the central axis 108. In other words, a voltage gradient exists in the radial direction because the plasma potential is higher than the voltage on the body and shield electrodes 150 of the arc chamber 100. Additionally, as previously mentioned, there may be a magnetic field 190 that is parallel to the central axis 108.

[0040] The radial electric field and axial magnetic field 190 result in a rotational force, indicated by the arrows in FIGS. 3A-3B. This rotational force can be optimized by minimizing the surface area of ​​the interior surfaces exposed to the plasma and at a higher voltage than the body. Therefore, the use of one or more shield electrodes 150 serves two functions. First, the one or more shield electrodes 150 help to create a circular or near-circular cross-section of the arc chamber 100 in the Y-Z plane along a portion of the arc chamber 100. Second, the one or more shield electrodes 150 also reduce the surface area of ​​the interior surfaces exposed to the plasma and at a different potential than the body of the arc chamber 100. In certain embodiments, it may be advantageous to minimize the ratio of the surface area of ​​the extraction plate 103 (acting as an anode) exposed to the plasma to the total surface area within the arc chamber 100 exposed to the plasma. In one embodiment shown in FIG. 3A , this total surface area includes the exposed inner surface of one or more of shield electrode 150, the exposed inner surface of unitary piece 151, first end 104, second end 105, and exposed portions of extraction plate 103. In one embodiment shown in FIG. 3B , this total surface area includes the exposed inner surface of one or more of shield electrode 150, the exposed inner surface of curved electrode 154, the exposed inner surface of wall 153, the exposed inner surface of bottom 152, first end 104, second end 105, and exposed portions of extraction plate 103. In certain embodiments, the ratio of the surface area of ​​extraction plate 103 exposed to the plasma to the total surface area within arc chamber 100 can be between 0.01 and 0.3. In certain embodiments, this ratio can be between 0.01 and 0.2. In some embodiments, this ratio can be between 0.01 and 0.1.

[0041] Figure 4 shows an IHC ion source 10 according to another embodiment. In this figure, components that are identical to those in Figure 1 are given the same reference numerals. In this embodiment, an extraction plate 103 is electrically connected to the body of the arc chamber 100. The extraction aperture 140 can be a slit having a width that is significantly greater than its height.

[0042] Thus, one or more electrodes 300 are positioned within the arc chamber 100 to increase the plasma potential. In this embodiment, the electrodes 300 may be biased using an electrode power supply 310. In certain embodiments, the electrode power supply 310 is referenced to the body of the arc chamber 100. The electrode power supply 310 may provide a positive voltage to the electrodes 300 relative to the body of the arc chamber 100. These voltages may be between 5 V and 100 V more positive than the body, although other values ​​are possible. In this manner, one or more of the electrodes 300 may act as an anode.

[0043] The one or more electrodes 300 may be positioned at a variety of different locations within the arc chamber 100. Each location is adjacent to at least a portion of the extraction plate 103. As shown in FIGS. 5A-5B , the one or more electrodes 300 may be positioned adjacent to the extraction plate 103 on either side of the extraction opening 140 in the height direction or width direction. In certain embodiments, the electrode 300 may have a plasma-exposed surface area that is between 3% and 50% of the inner surface area of ​​the extraction plate 103. In some embodiments, the plasma-exposed surface area of ​​the electrode 300 may be between 3% and 30% of the inner surface area of ​​the extraction plate 103. In some embodiments, the plasma-exposed surface area of ​​the electrode 300 may be between 3% and 20% of the inner surface area of ​​the extraction plate 103. In some embodiments, the plasma-exposed surface area of ​​the electrode 300 may be between 3% and 10% of the inner surface area of ​​the extraction plate 103. The body of the arc chamber 100 can be a unitary piece 151, as shown in Figure 5A. Alternatively, the body of the arc chamber 100 can include separate pieces that make up the bottom 152 and walls 153, as shown in Figure 5B. The electrode 300 can be a plate having a planar inner surface facing the plasma and a planar back surface facing the extraction plate 103. In these embodiments, the electrode 300 can be positioned parallel to the extraction plate 103.

[0044] 5C shows another position for electrode 300. In this embodiment, electrode 300 is a plate, as described above. Additionally, electrode 300 is positioned at an angle relative to extraction plate 103. In one embodiment, electrode 300 may form a 45 degree angle with extraction plate 103, although other angles are possible. Note that this position for electrode 300 may be used with a unitary part 151, as shown in FIG. 5C, or with a body constructed from separate parts, as shown in FIG. 5B.

[0045] 5D-5E illustrate several embodiments in which the electrode 300 is positioned within or adjacent to a corner formed at the junction between the body and the extraction plate 103, more specifically, at the junction between the wall and the extraction plate 103. Furthermore, the electrode 300 may also have a curved inner surface. This curved inner surface may be concave. In one embodiment shown in FIG. 5D, the bottom and wall are a single piece 151. The single piece 151 and the electrode 300 thereby form a circular or nearly circular cross-section in the Y-Z plane along a portion of the arc chamber 100. The term "nearly circular" is defined as a configuration in which the shortest distance from the central axis 108 to any point on the inner surface of the single piece 151 or the electrode 300 varies by less than 30%. In one embodiment shown in FIG. 5E, the body of the arc chamber 100 is formed from separate pieces, such as the bottom 152 and the wall 153. In this embodiment, a curved electrode 154 electrically connected to the body may be utilized. In this manner, the cross section of the arc chamber 100 is circular or nearly circular in the Y-Z plane along a portion of the arc chamber 100. In this embodiment, the term "nearly circular" is defined as a configuration in which the shortest distance from the central axis 108 to any point on the bottom 152, wall 153, curved electrode 154, or exposed inner surface of electrode 300 varies by less than 30%. This circular or nearly circular cross section may extend along the entire width of the extraction aperture 140.

[0046] In the embodiments shown in FIGS. 5D-5E, the curved inner surface promotes rotation of the electrons, similar to the operation of the IHC ion source of FIG.

[0047] 5D-5E, one or more electrodes 300 may be positioned above and below the extraction opening 140 in the Y direction. The electrodes 300 may extend across the entire width of the extraction opening 140. In some embodiments, the electrodes 300 may extend beyond the extraction opening 140 in the X direction. In one embodiment, there may be two electrodes 300, one on each side of the extraction opening 140 in the height direction. In another embodiment where the electrodes are commonly biased, the electrodes 300 may be a unitary part with an opening corresponding to the extraction opening 140.

[0048] In some embodiments shown in FIGS. 5D-5E, one or more electrodes 300 may be positively biased with respect to the body of the arc chamber 100 using a common electrode power supply 310. In another embodiment, two electrodes 300 are utilized, and only one of the two electrodes 300 may be biased, with the other being electrically connected to the arc chamber 100. In another embodiment, the two electrodes 300 may be biased using two different electrode power supplies. For example, the second electrode may be biased at the same voltage as the first electrode, at a greater voltage than the first electrode, or at a lesser voltage than the first electrode. Furthermore, in certain embodiments, one of the electrodes 300 may be negatively biased with respect to the arc chamber 100. In particular, when one or more of the electrodes 300 is biased at a different voltage than the body, it may be electrically insulated from the extraction plate 103 by the use of a gap or by the use of an insulator 142. In particular, the insulator 142 may separate the extraction plate 103 from the electrode 300 or may separate the body from the electrode 300. These insulators 142 may be constructed of a dielectric material such as boron nitride (BN) or alumina (Al2O3). If one of the electrodes 300 is at the same voltage as the body, it may be in physical and / or electrical contact with the body or extraction plate 103, such as by a wire or conductive material 144, as shown in Figures 5D and 5E.

[0049] The curved electrode 154 may be electrically connected to the bottom 152 and the wall 153. In one embodiment, the curved electrode 154 may rest against the bottom 152 and / or the wall 153. In another embodiment, the curved electrode 154 is electrically connected to the body, such as by a wire or conductive material 144, as shown in FIG.

[0050] While the above disclosure describes an extraction opening having a width significantly greater than its height, other extraction openings are possible. For example, the extraction opening 140 may be a round opening. In this example, one or more electrodes 300 of FIGS. 5A-5E may still be positioned on either side of the extraction opening 140 in the height direction. In one embodiment, there may be two electrodes 300, one on each side of the extraction opening in the height direction (i.e., the Y direction). These electrodes 300 may extend beyond the round opening in the X direction. In another embodiment in which the electrodes 300 are commonly biased, the electrodes 300 may be a unitary part with holes corresponding to the extraction openings 140. For example, the unitary part may be round, square, diamond, rectangular, or any other shape with holes.

[0051] In certain embodiments, the ratio of the surface area of ​​the one or more electrodes 300 that are positively biased and exposed to the plasma to the total surface area within the arc chamber 100 can be between 0.01 and 0.3. In certain embodiments, this ratio can be between 0.01 and 0.2. In some embodiments, this ratio can be between 0.05 and 0.2.

[0052] Figure 6 shows an ion implantation system using the IHC ion source 10 of Figure 1 or Figure 4. As shown in Figures 1 and 4, one or more extraction electrodes 200 are positioned outside and near the extraction aperture of the IHC ion source 10. The one or more extraction electrodes 200 may be biased using an electrode power supply 201.

[0053] Located downstream from the extraction electrode 200 is a mass analyzer 210. The mass analyzer 210 uses a magnetic field to guide the path of the extracted ions 1. The magnetic field influences the flight path of the ions according to their mass and charge. A mass resolving device 220 having a resolving aperture 221 is located at the output (i.e., distal end) of the mass analyzer 210. By appropriately selecting the magnetic field, only ions 1 having a selected mass and charge will be guided through the resolving aperture 221. Other ions will collide with the walls of the mass resolving device 220 or the mass analyzer 210 and will not be able to travel further within the system.

[0054] A collimator 230 may be positioned downstream from the mass resolving device 220. The collimator 230 accepts ions 1 that have passed through the resolving aperture 221 and generates a ribbon ion beam made up of multiple parallel or nearly parallel beamlets. The output (i.e., distal end) of the mass analyzer 210 and the input (i.e., proximal end) of the collimator 230 may be separated by a fixed distance. The mass resolving device 220 is positioned in the space between these two components.

[0055] Downstream from the collimator 230, an acceleration / deceleration stage 240 may be located. The acceleration / deceleration stage 240 may be referred to as an energy purity module. An energy purity module is a beamline lens component configured to independently control the deflection, deceleration, and focusing of the ion beam. For example, the energy purity module may be a vertical electrostatic energy filter (VEEF) or an electrostatic filter (EF). Downstream from the acceleration / deceleration stage 240, a workpiece 250 is located.

[0056] The embodiments described above in this application may have many advantages. The IHC ion sources of FIGS. 3A-3B and 5A-5E allow electrons to drift E×B in a rotational manner, thereby reducing the number of electrons lost to the body of the arc chamber 100. By increasing the number of available electrons, more ionization can occur. Therefore, plasma density can be increased compared to conventional IHC ion sources. Furthermore, each embodiment increases the plasma potential. Increasing the plasma potential can result in greater plasma density. In one experiment, the use of a 10 V biased electrode 300 or extraction plate 103 increased the plasma potential along the central axis 108 by approximately 7 V compared to a conventional IHC ion source, resulting in an approximately 300% increase in plasma density along the central axis 108. Higher plasma density can result in higher extraction currents, better fractionation, and lower plasma noise.

[0057] The present disclosure is not limited in scope by the specific embodiments described herein. Indeed, various other embodiments and modifications of the present disclosure, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description and accompanying drawings. Accordingly, such other embodiments and modifications are intended to be included within the scope of the present disclosure. Moreover, while the present disclosure has been described herein in the context of particular implementations in particular environments for particular purposes, those skilled in the art will recognize that its utility is not limited thereto, and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in accordance with the broadest possible scope and spirit of the disclosure as described herein.

Claims

1. 1. An ion source comprising a chamber, the chamber comprising: a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate including an extraction aperture having a width and a height through which ions are extracted, said extraction plate being electrically insulated from said body, said body and said extraction plate forming a closed space; one or more shield electrodes disposed within the enclosed space adjacent to the extraction plate and not in physical contact with the extraction plate, the one or more shield electrodes being electrically connected to the body; and an extraction power supply in communication with the extraction plate, the extraction plate being positively biased with respect to the body; An ion source wherein the body and the one or more shield electrodes form a circular or nearly circular cross-section within the chamber along a portion of the chamber.

2. An ion source comprising a chamber, the chamber comprising: a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate including an extraction aperture having a width and a height through which ions are extracted, said extraction plate being electrically insulated from said body, said body and said extraction plate forming a closed space; one or more shield electrodes disposed within the enclosed space adjacent to the extraction plate and not in physical contact with the extraction plate, the one or more shield electrodes being electrically connected to the body; and an extraction power supply in communication with the extraction plate, the extraction plate being positively biased with respect to the body; an inner surface of the one or more shield electrodes being curved, and the bottom and the plurality of walls being a unitary piece having a curved inner surface, whereby the inner surfaces of the unitary piece and the one or more shield electrodes form a circular or nearly circular cross-section within the chamber along a portion of the chamber.

3. The ion source of claim 2 , wherein the circular or nearly circular cross-section extends along the width of the extraction aperture.

4. An ion source comprising a chamber, the chamber comprising: a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate including an extraction aperture having a width and a height through which ions are extracted, said extraction plate being electrically insulated from said body, said body and said extraction plate forming a closed space; one or more shield electrodes disposed within the enclosed space adjacent to the extraction plate and not in physical contact with the extraction plate, the one or more shield electrodes being electrically connected to the body; and an extraction power supply in communication with the extraction plate, the extraction plate being positively biased with respect to the body; an inner surface of the one or more shield electrodes being curved, the bottom and the walls being separate pieces, the ion source further comprising a curved electrode disposed within a corner formed between the bottom and each wall, the curved electrode being electrically connected to the body.

5. 5. The ion source of claim 4, wherein the bottom, the walls, the curved electrode, and exposed portions of the inner surfaces of the one or more shield electrodes form a circular or nearly circular cross-section along a portion of the chamber.

6. The ion source of claim 5 , wherein the circular or nearly circular cross-section extends along the width of the extraction aperture.

7. 5. The ion source of claim 1, wherein the one or more shield electrodes are positioned above and below the extraction aperture along the width of the extraction aperture.

8. The ion source of claim 1 , wherein an inner surface of the one or more shield electrodes is curved.

9. 5. The ion source of claim 1, wherein the extraction plate is biased at a voltage between 10V and 100V higher than the voltage of the body.

10. 10. The ion source according to claim 1, 2 or 4, Mass spectrometers, and An ion implantation system comprising an acceleration / deceleration stage.

11. 1. An ion source comprising a chamber, the chamber comprising: a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate electrically connected to the body, the extraction plate including an extraction aperture having a width and a height through which ions are extracted, the body and the extraction plate forming a closed space; two electrodes arranged adjacent to the extraction plate in the closed space, one electrode being arranged above the extraction opening in the height direction and the other electrode being arranged below the extraction opening in the height direction; and an electrode power supply in communication with a first of the two electrodes, the first electrode being electrically isolated from the body and positively biased with respect to the body, and a second electrode being electrically connected to the body.

12. An ion source comprising a chamber, the chamber comprising: a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate electrically connected to the body, the extraction plate including an extraction aperture having a width and a height through which ions are extracted, the body and the extraction plate forming a closed space; two electrodes arranged adjacent to the extraction plate in the closed space, one electrode being arranged above the extraction opening in the height direction and the other electrode being arranged below the extraction opening in the height direction; and an electrode power supply in communication with a first of the two electrodes, the first electrode being electrically isolated from the body and positively biased with respect to the body, and a second electrode being electrically connected to the body; The two electrodes comprise plates having planar inner and rear surfaces, the plates being positioned at an angle relative to the extraction plate.

13. 12. The ion source of claim 11, wherein the two electrodes comprise plates having planar inner and rear surfaces, the plates being positioned parallel to the extraction plate.

14. 1. An ion source comprising a chamber, the chamber comprising: a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate electrically connected to the body, the extraction plate including an extraction aperture having a width and a height through which ions are extracted, the body and the extraction plate forming a closed space; one or more electrodes arranged in the closed space, the one or more electrodes being arranged above the extraction opening and below the extraction opening in a height direction; and an electrode power supply in communication with at least one of the one or more electrodes, the inner surface of the one or more electrodes being curved, the one or more electrodes being positioned within or adjacent to a corner formed at a junction between the body and the extraction plate; An ion source wherein the body and the one or more electrodes form a circular or nearly circular cross-section within the chamber along a portion of the chamber.

15. An ion source comprising a chamber, the chamber comprising: a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate electrically connected to the body, the extraction plate including an extraction aperture having a width and a height through which ions are extracted, the body and the extraction plate forming a closed space; one or more electrodes arranged in the closed space, the one or more electrodes being arranged above the extraction opening and below the extraction opening in a height direction; and an electrode power supply in communication with at least one of the one or more electrodes, the inner surface of the one or more electrodes being curved, the one or more electrodes being positioned within or adjacent to a corner formed at a junction between the body and the extraction plate; the bottom and the walls are a unitary piece having a curved inner surface, whereby the inner surfaces of the unitary piece and the one or more electrodes form a circular or nearly circular cross-section along a portion of the chamber.

16. An ion source comprising a chamber, the chamber comprising: a body having a first end, a second end, a bottom, and a plurality of walls; an indirectly heated cathode disposed at the first end of the chamber; an extraction plate electrically connected to the body, the extraction plate including an extraction aperture having a width and a height through which ions are extracted, the body and the extraction plate forming a closed space; one or more electrodes arranged in the closed space, the one or more electrodes being arranged above the extraction opening and below the extraction opening in a height direction; and an electrode power supply in communication with at least one of the one or more electrodes, the inner surface of the one or more electrodes being curved, the one or more electrodes being positioned within or adjacent to a corner formed at a junction between the body and the extraction plate; the bottom and the walls are separate pieces, the ion source further comprising a curved electrode disposed in a corner formed between the bottom and each wall, the curved electrode electrically connected to the body.

17. 17. The ion source of claim 16, wherein the bottom, the walls, the curved electrode, and exposed portions of the interior surfaces of the one or more electrodes form a circular or nearly circular cross-section along a portion of the chamber.

18. 17. The ion source of claim 14, wherein the one or more electrodes include two electrodes, the two electrodes being biased at different voltages.

19. 17. An ion source according to any one of claims 14 to 16. mass spectrometer, and An ion implantation system comprising an acceleration / deceleration stage.

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