WO2024181225A1 - Ion source - Google Patents

Abstract

Provided is an ion source including: a plasma generation container that has an elongated shape having an internal space into which an ion source gas is introduced and that has an ion extraction port on a side wall along a longitudinal direction thereof; a plasma generation means for generating plasma in the internal space by ionizing the ion source gas; and an extraction electrode system that is provided outside the plasma generation container and that extracts an ion beam from the internal space through the ion extraction port, wherein the plasma generation means includes, outside the plasma generation container, an antenna provided along the longitudinal direction, a high-frequency power source that applies a high frequency to the antenna, and a magnetic field transmission window that is formed at a position facing the antenna in a side wall of the plasma generation container and that allows a high-frequency magnetic field generated at the antenna to be transmitted into the internal space therethrough.

Description

Ion source

The present invention relates to an ion source for use in, for example, an ion implantation device.

As shown in Patent Document 1, this type of ion source has a rectangular parallelepiped plasma generating vessel into which an ion source gas is introduced, a number of magnets arranged on the outer side of the plasma generating vessel to form a cusp magnetic field inside the plasma generating vessel, and a filament that emits electrons and is inserted into the plasma generating vessel from its side wall. In this ion source, the plasma generating vessel also serves as an anode, and electrons emitted from the filament are discharged inside the plasma generating vessel to ionize the ion source gas and generate plasma. An extraction electrode system arranged near an ion extraction port formed in one side wall of the plasma generating vessel is used to extract an ion beam from the plasma.

JP 2011-228044 A

In the above-mentioned ion source in which the filament is inserted into the plasma generating vessel from the side wall, a negative voltage is applied to the plasma generating vessel to generate plasma, and the filament is worn out due to sputtering by positive ions. In particular, when a halide ion source gas such as _BF3 is used to generate plasma, the filament is subjected to sputtering accompanied by a chemical reaction, and is more likely to be worn out. When the filament wears out, maintenance such as replacement is required, so in conventional ion sources, the life of the filament is the main factor that determines the maintenance cycle of the ion source.

Furthermore, to generate a roughly uniform plasma inside the plasma generating vessel, it is necessary to provide a large number of filaments, and a power supply must be provided for each filament, which increases the number of parts and makes the device larger. Furthermore, as the number of parts increases, the amount of processing required for installation also increases, and as the number of power supplies increases, the number of control points also increases proportionally, resulting in higher costs. Furthermore, since a large number of filaments are provided, the number of high-current cables used for connecting the filaments also increases, which complicates the wiring paths and causes problems with workability during maintenance.

The present invention was made to solve all of these problems at once, and its main objective is to provide an ion source that has a long maintenance cycle, is highly functional during maintenance, allows the overall device to be made smaller, and has low manufacturing costs.

In other words, the ion source according to the present invention is an elongated vessel having an internal space into which an ion source gas is introduced, and is equipped with a plasma generating vessel having an ion outlet formed on one side wall along the longitudinal direction thereof, plasma generating means for ionizing the ion source gas to generate plasma in the internal space, and an extraction electrode system provided outside the plasma generating vessel and extracting an ion beam from the internal space through the ion outlet, the plasma generating means comprising an antenna provided outside the plasma generating vessel along the longitudinal direction, a high frequency power source for applying high frequency to the antenna, and a magnetic field transmission window formed in a position facing the antenna on the side wall of the plasma generating vessel and allowing a high frequency magnetic field generated by the antenna to pass through to the internal space.

The present invention thus configured can provide an ion source that has a long maintenance cycle, is highly functional during maintenance, and allows the overall device to be made smaller, while keeping manufacturing costs down.

1 is a schematic diagram showing an overall configuration of an ion implantation apparatus according to an embodiment of the present invention; FIG. 2 is a cross-sectional view illustrating a schematic configuration of an ion source according to the embodiment. FIG. 2 is a vertical cross-sectional view illustrating a schematic configuration of an ion source according to the embodiment. 3A is a cross-sectional view of the window member according to the embodiment, FIG. 3B is a plan view of the window member as viewed from the antenna side, and FIG. 3C is a plan view of the window member as viewed from the internal space side. 5 is a graph showing a plasma density distribution of inductively coupled plasma using the ion source of the embodiment. 10A and 10B are diagrams illustrating a configuration of a window member according to another embodiment, in which FIG. 10A is a cross-sectional view and FIG. 10B is a plan view seen from the internal space side. 13A and 13B are diagrams for explaining a function of a current distribution monitor in an ion implantation apparatus according to another embodiment. FIG. 11 is a cross-sectional view showing a schematic configuration of an ion source according to another embodiment. FIG. 11 is a cross-sectional view showing a schematic configuration of an ion source according to another embodiment. FIG. 11 is a vertical cross-sectional view illustrating a schematic configuration of an ion source according to another embodiment.

The ion source of the present invention is used in ion beam irradiation devices such as ion implantation devices and ion doping devices used in, for example, semiconductor manufacturing processes and flat panel display manufacturing processes. Below, an ion implantation device 400 equipped with an ion source 100 according to one embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the ion implantation device 400 of this embodiment is for irradiating an ion beam IB onto a target substrate W to implant ions. Specifically, the ion implantation device 400 includes an ion source 100 that extracts an ion beam IB in a predetermined extraction direction, a mass analysis section 200 that is provided downstream of the ion source 100 and performs mass analysis of the ion beam IB extracted from the ion source 100, and a processing chamber 300 in which the substrate W is placed. In the ion implantation device 400 of this embodiment, a ribbon-shaped ion beam IB is extracted from the ion source 100, whose width in the front-to-back direction of the paper surface of FIG. 1 is sufficiently greater than its thickness in the direction perpendicular thereto.

The mass analysis section 200 has a mass analysis magnet 210 and an analysis slit 220. The mass analysis magnet 210 bends the ion beam IB in the thickness direction to select and extract the desired ions. The analysis slit 220 is provided downstream of the mass analysis magnet 210 and cooperates with the mass analysis magnet 210 to select and pass the desired ions. A slit plate 211 that forms an entrance slit is provided at the entrance of the mass analysis magnet 210. This slit plate 211 limits the incidence angle and beam width of the ion beam IB when it enters the mass analysis magnet 210, thereby improving the analytical performance of the ion beam passing through the analysis slit 220.

In the processing chamber 300, the substrate W is held by the substrate drive device 310 with its processing surface facing the ion beam IB. This substrate drive device 310 is configured to hold the substrate W and to mechanically drive it back and forth in a direction along the thickness of the ion beam IB incident on the substrate W. The ion implantation device 400 can perform ion implantation by injecting the ion beam IB onto the entire surface of the substrate W through the back and forth drive of the substrate W by the substrate drive device 310 and the irradiation of the ribbon-shaped ion beam IB.

The configuration of the ion source 100 will be described in detail below. Note that each figure shows only the essential parts of the ion source 100 according to the embodiment of the present invention, and various components are omitted.

Specifically, as shown in Figures 2 and 3, this ion source 100 includes a plasma generating vessel 1 into which an ion source gas is introduced to generate plasma, a plurality of magnets 2 that are provided outside the plasma generating vessel 1 and form a magnetic field (specifically, a cusp magnetic field, or more strictly, a multicusp magnetic field, also called a multipole magnetic field) within the plasma generating vessel 1, a plasma generating means 3 that forms plasma within the plasma generating vessel 1, an extraction electrode system 4 that extracts an ion beam IB from the plasma generating vessel 1, and a gas source 5 that supplies an ion source gas to the plasma generating vessel 1 at a constant flow rate.

The plasma generating vessel 1 is an elongated vessel having, for example, a rectangular parallelepiped shape. The inner wall surface of this plasma generating vessel 1 forms an internal space 1s into which an ion source gas is introduced to generate plasma. This internal space 1s is an elongated space having a roughly rectangular parallelepiped shape formed to extend along the longitudinal direction of the plasma generating vessel 1, and is formed by being surrounded by a pair of inner wall surfaces facing each other along the withdrawal direction and a pair of inner wall surfaces facing each other along the width direction. The internal section is evacuated to a vacuum by a vacuum exhaust device (not shown).

An ion extraction port 1H, which is an opening for extracting the ion beam IB from the internal space 1s, is formed in one side wall (hereinafter referred to as the front wall 11a) of the plasma generating vessel 1 parallel to the longitudinal direction. The ion extraction port 1H is formed in the front wall 11a so as to extend along the longitudinal direction, similar to the internal space 1s. In this embodiment, the front wall 11a is formed so as to be perpendicular to the extraction direction of the ion beam IB. Hereinafter, the direction perpendicular to the extraction direction and the longitudinal direction is referred to as the width direction. Note that the term "elongated shape" refers to any shape formed so that, when viewed from the extraction direction, the length in one axial direction (i.e., the length in the longitudinal direction) is longer than the length in the other axial direction (i.e., the length in the width direction), in two axial directions perpendicular to each other, and is not limited to a rectangular parallelepiped shape.

In the two side walls (hereinafter also referred to as side walls 11c, d) facing each other (facing each other in the width direction) across an axis (hereinafter also referred to as ion extraction axis L1) extending in the extraction direction through the ion extraction outlet 1H when viewed from the longitudinal direction, a plurality of gas introduction holes 1g are formed which communicate with the gas source 5 and introduce an ion source gas into the internal space 1s via a gas flow regulator (not shown). The plurality of gas introduction holes 1g have approximately the same diameter and are provided at approximately equal intervals along the longitudinal direction of the plasma generating vessel 1 near the ion extraction outlet 1H in the side walls 11c, d (i.e., near the joint with the front wall 11a). An ion source gas such as _BF3 gas or _PH3 gas is introduced into the internal space 1s from the gas introduction holes 1g.

The gas introduction holes 1g may be formed in only one of the two side walls 11c, d, or may be provided in the side walls 11c, d near the joint between the front wall 11a and the opposing rear wall 11b (i.e., near the magnetic field transmission window 3w described later). The gas introduction holes 1g may be provided at approximately equal intervals, and the hole diameter at both ends along the longitudinal direction may be relatively larger than the hole diameter at the center. Alternatively, the gas introduction holes 1g may have approximately the same hole diameter, and the arrangement interval at both ends along the longitudinal direction may be relatively narrower than the arrangement interval at the center. Furthermore, the gas introduction holes 1g are provided to open on the inner surface of the side wall of the plasma generating vessel 1, but they may also be provided to open on the wall of a gas supply pipe arranged in the plasma generating vessel 1.

The multiple magnets 2 are provided externally along the outer surfaces of the side walls other than the front wall 11a (specifically, the side walls 11c, d), and form a cusp magnetic field near the inner surfaces of the side walls 11c, d. In this embodiment, each magnet 2 is a permanent magnet, but electromagnets may also be used. The multiple magnets 2 are arranged at approximately equal intervals with different polarities along a direction perpendicular to the ion extraction direction. Note that the arrangement of the multiple magnets 2 is not limited to this and can be changed as appropriate.

The plasma generating means 3 ionizes the ion source gas by supplying a high-frequency magnetic field to the internal space 1s of the plasma generating vessel 1 to generate plasma.

The extraction electrode system 4 is provided near the ion extraction port 1H of the plasma generating vessel 1, and accelerates and extracts the ion beam IB by applying a potential difference between the extraction electrode system 4 and the plasma generating vessel 1. Specifically, the extraction electrode system 4 has a plurality of plate-shaped electrodes 41 to 44 in which slits 4x are formed. More specifically, as shown in Figures 2 and 3, the extraction electrode system 4 has a plasma electrode 41, an extraction electrode 42, a suppression electrode 43, and a ground electrode 44, which are arranged in order from the plasma generating vessel 1 toward downstream along the ion extraction direction. Each of these electrodes has a slender slit 4x formed in the center thereof, which penetrates in the thickness direction and extends along the longitudinal direction. Each electrode is arranged so that the slit 4x formed in the center faces the ion extraction port 1H of the plasma generating vessel 1. The electrodes are electrically insulated from each other by, for example, an insulator (not shown). It is preferable that the slit width of the electrode (here, the plasma electrode 41) closest to the plasma generating vessel 1 in the extraction electrode system 4 is variable. In this way, the gas pressure in the plasma chamber can be made variable, allowing freedom in setting the pressure in the plasma generating vessel 1 and the degree of vacuum in the extraction electrode area, which allows for a margin in the withstand voltage applied between the electrodes.

The ion source 100 of this embodiment is configured such that the plasma generating means 3 generates an inductively coupled plasma in the internal space 1s of the plasma generating vessel 1, and includes an antenna 31 provided outside the plasma generating vessel 1, a high frequency power supply 32 that applies high frequency to the antenna 31, and a magnetic field transmission window 3w formed in a position facing the antenna 31 on the side wall of the plasma generating vessel 1 and allowing the high frequency magnetic field generated from the antenna 31 to pass through to the internal space 1s. In this configuration, by applying high frequency from the high frequency power supply 32 to the antenna 31, a high frequency current flows through the antenna 31, an induced electric field is generated in the plasma generating vessel 1, and an inductively coupled plasma is generated.

The antenna 31 is linear (specifically cylindrical) with a length of several tens of centimeters or more when viewed from the outside. This antenna 31 is arranged so as to be straight along the longitudinal direction of the plasma generating vessel 1 with a gap from the magnetic field transmission window 3w outside the plasma generating vessel 1. That is, the antenna 31 is arranged so as to be straight along the longitudinal direction of the ion extraction outlet 1H and the slit 4x of the extraction electrode system 4. When viewed from the ion extraction direction, the antenna 31 is arranged at a position facing the ion extraction outlet 1H, and more specifically, on the ion extraction axis L1 described above. A high-frequency power source 32 is connected to one end of the antenna 31, which is the power supply end, via a matching circuit 321.

The high-frequency power supply 32 can pass a high-frequency current through the antenna 31 via the matching circuit 321. The frequency of the high-frequency current is, for example, a typical 13.56 MHz, but is not limited to this and may be changed as appropriate.

The magnetic field transmission window 3w is formed in the side wall (referred to as the rear wall 11b) facing the front wall 11a of the plasma generating vessel 1. Specifically, as shown in Figures 4(a) to (c), this magnetic field transmission window 3w is formed by an opening 1x provided in the rear wall 11b of the plasma generating vessel 1 and a window member 33 attached to the plasma generating vessel 1 so as to close the opening 1x.

When viewed from the ion extraction direction, this opening 1x has a rectangular shape whose length along the longitudinal direction of the plasma generating vessel 1 is greater than its length along the width direction. This opening 1x is formed in the rear wall 11b at a position facing both the antenna 31 and the ion extraction port 1H, and more specifically, is formed so as to be located on the line connecting the antenna 31 and the ion extraction port 1H.

The window member 33 includes a slit plate 331 that blocks the opening 1x formed in the rear wall 11b of the plasma generating vessel 1 from the outside, and a dielectric plate 332 that blocks the slit 331x formed in the slit plate 331 from the outside of the plasma generating vessel 1.

The slit plate 331 allows the high-frequency magnetic field generated by the antenna 31 to pass into the plasma generating vessel 1, and prevents an electric field from entering the inside of the plasma generating vessel 1 from the outside. Specifically, the slit plate 331 is a flat plate with multiple slits 331x formed along the longitudinal direction of the antenna 31, penetrating the plate in the thickness direction. The slit plate 331 preferably has a higher mechanical strength than the dielectric plate 332 described below, and preferably has a larger thickness dimension than the dielectric plate 332. The multiple slits 331x are parallel to each other when viewed from the thickness direction, and are formed so as to intersect with the antenna 31 (specifically, so as to be perpendicular). All of the multiple slits 331x have the same shape (specifically, a rectangular shape when viewed from above).

Specifically, the slit plate 331 is made of metal, and is manufactured by rolling (e.g., cold rolling or hot rolling) a metal material such as one metal selected from the group including Cu, Al, Zn, Ni, Sn, Si, Ti, Fe, Cr, Nb, C, Mo, W, or Co, or an alloy thereof (e.g., stainless steel alloy, aluminum alloy, etc.).

This slit plate 331 is larger than the opening 1x of the plasma generating vessel 1 in a plan view, and blocks the opening 1x while supported by the rear wall 11b (i.e., while placed on the rear wall 11b), and is at the same potential as the plasma generating vessel 1. A sealing member such as an O-ring or gasket is interposed between the slit plate 331 and the rear wall 11b, and a vacuum seal is formed between them.

The dielectric plate 332 is placed on the outward surface of the slit plate 331 that faces the outside of the plasma generating vessel 1 (the reverse side of the inward surface that faces the inside of the plasma generating vessel 1) and closes the slits 331x of the slit plate 331. A seal member is interposed between the dielectric plate 332 and the slit plate 331, and the space between them is vacuum sealed.

The dielectric plate 332 is a flat plate made entirely of a dielectric material, such as ceramics such as alumina, silicon carbide, and silicon nitride, inorganic materials such as quartz glass and non-alkali glass, and resin materials such as fluororesin (e.g., Teflon).

With this configuration, the slit plate 331 and the dielectric plate 332 function as a magnetic field transmission window 3w that transmits the magnetic field generated by the antenna 31. In other words, when a high frequency is applied to the antenna 31 from the high frequency power supply 32, the high frequency magnetic field generated by the antenna 31 passes through the magnetic field transmission window 3w consisting of the slit plate 331 and the dielectric plate 332 and is formed (supplied) inside the plasma generating vessel 1. As a result, an induced electric field is generated in the space inside the plasma generating vessel 1, and an inductively coupled plasma is generated.

In the plasma processing apparatus of this embodiment, the window member 33 further includes a mask plate 333 that covers each slit 331x formed in the slit plate 331 from the inside of the plasma generating vessel 1 with a gap therebetween.

To explain more specifically, the mask plate 333 is a flat plate with multiple slits 333x formed along the longitudinal direction of the antenna 31, penetrating through the mask plate 333 in the thickness direction. When viewed from the thickness direction, the multiple slits 333x are parallel to each other and to the multiple slits 331x formed in the slit plate 331. Here, each slit 333x is formed so as to intersect with the antenna 31 (specifically, so as to be perpendicular). All of the multiple slits 333x are formed to have the same shape (specifically, rectangular in a plan view).

Between adjacent slits 333x in the mask plate 333, beam-shaped regions 333z are formed parallel to each slit 333x. A plurality of beam-shaped regions 333z are formed to correspond to the plurality of slits 331x formed in the slit plate 331, and each beam-shaped region 333z covers each slit 331x of the slit plate 331. Here, the length (width) of the beam-shaped region 333z along the longitudinal direction of the antenna 31 is approximately the same as the width of the slit 331x of the slit plate 331, and each beam-shaped region 333z covers approximately the entirety of each slit 331x of the slit plate 331. Each beam-shaped region 333z may be formed to cover only a portion of each slit 331x. The mask plate 333 is connected to the inner surface of the slit plate 331 and is at the same potential.

Specifically, the mask plate 333 is made of a metal material such as one metal selected from the group including Cu, Al, Zn, Ni, Sn, Si, Ti, Fe, Cr, Nb, C, Mo, W, or Co, or an alloy thereof (e.g., stainless steel alloy, aluminum alloy, etc.). It is preferable that the thickness of the mask plate 333 is smaller than the thickness of the slit plate 331.

In addition, in this embodiment, a flow path 331r is formed in the slit plate 331, through which a cooling medium such as water flows. This flow path 331r is formed along the longitudinal direction of the antenna 31 near the connection area of the mask plate 333 in the slit plate 331. Here, the flow path 331r is formed so as to be located directly above the connection area along the thickness direction of the slit plate 331.

In the ion source 100 of this embodiment, the electrode (plasma electrode 41) in the extraction electrode system 4 closest to the plasma generating vessel 1 is preferably provided near the position where the plasma density peaks when plasma is generated to the position where the plasma density is half of the peak. The change in the peak position of the plasma density distribution is small relative to the pressure of the ion source gas supplied and the density of the applied high-frequency power, and therefore providing the plasma electrode 41 near the position where the plasma density peaks is preferable in terms of efficient extraction of the ion current. On the other hand, the vicinity of this peak position is an area where a strong high-frequency magnetic field is generated, and so overheating due to induced current may occur. Therefore, from the viewpoint of suppressing overheating due to induced current, the plasma electrode 41 is preferably provided in the plasma diffusion region up to the position where the plasma density is half of the peak.

As shown in FIG. 5, when high-frequency plasma was ignited through the magnetic field transmission window 3w using the ion source 100 according to this embodiment, it was confirmed that the plasma density distribution peaked at a position of about 45 mm and was halved at a position of about 140 mm. It was also confirmed that the change in the peak position of the plasma density was small with respect to changes in the pressure of the ion source gas supplied and the density of the applied high-frequency power. For this reason, it is preferable that the distance between the inward surface of the magnetic field transmission window 3w (specifically, the inward surface of the slit plate 331) and the surface of the electrode in the extraction electrode system 4 closest to the plasma generation vessel 1 be set in the range of about 45 mm to about 140 mm.

<Effects of this embodiment>
According to the ion source 100 of the present embodiment thus configured, plasma is generated in the internal space 1s by the antenna 31 provided outside the plasma generating vessel 1 without using a filament protruding into the internal space 1s of the plasma generating vessel 1, so that the number of parts that are consumed by sputtering in the plasma generating vessel 1 can be reduced, and the maintenance cycle can be extended. Moreover, since the antenna 31 is provided along the longitudinal direction of the plasma generating vessel 1, a substantially uniform plasma can be generated in the internal space 1s by one antenna 31 extending along the ion extraction port 1H and one high frequency power source 32, so that the number of parts can be significantly reduced, the device can be made compact, and the number of processing steps required for installation and the number of control points of the power source can be reduced, so that the manufacturing cost can be suppressed. Furthermore, by reducing the number of power sources, the number of wires for power supply and the control lines for the equipment can be significantly reduced, and the wiring work during assembly and the detachment work during maintenance can be simplified, improving the workability.

<Other Modified Embodiments>
The present invention is not limited to the above-described embodiment.

For example, the ion source 100 of another embodiment may include a distance adjustment mechanism 6 for adjusting the distance between the antenna 31 and the magnetic field transmission window 3w, as shown in FIG. 6(a). This distance adjustment mechanism 6 is configured to partially adjust the distance between the antenna 31 and the magnetic field transmission window 3w by adjusting the positions of multiple points on the antenna 31, and specifically, is configured to be able to adjust the position of one or multiple parts along the longitudinal direction of the antenna 31.

More specifically, the distance adjustment mechanism 6 is provided on the upper surface of the window member 33 and includes an antenna support member 61 that supports both ends of the antenna 31, a number of gripping parts 62 that grip multiple locations of the antenna 31 and displace the gripped parts relative to the magnetic field transmission window 3w (specifically, the dielectric plate 332), and a drive source (not shown) such as a motor that moves these gripping parts 62 independently.

The multiple gripping parts 62 are insulators that are electrically insulated from the antenna 31. One of these gripping parts 62 is located directly above the center of the opening 1x of the plasma generating vessel 1, and another gripping part 62 is provided at a symmetrical position along the longitudinal direction of the antenna 31 relative to this gripping part 62. In this embodiment, the multiple gripping parts 62 are arranged at equal intervals, and all of them are provided inside the opening 1x when viewed from a direction perpendicular to the opening 1x of the plasma generating vessel 1.

Specifically, the gripping portion 62 includes a pressing tool 621 that presses the side of the antenna 31 toward the window member 33, and a gap adjustment tool 622 that is provided so as to be braced between the antenna 31 and the window member 33. The pressing tool 621 is configured to constantly press the antenna 31 toward the window member 33, for example, by using a spring material or the like. The gap adjustment tool 622 is configured so that its length along the thickness direction of the window member 33 can be adjusted. Here, the gap adjustment tool 622 is a tool with an elliptical cross section, and is configured so that its length along the thickness direction can be changed by rotating, thereby adjusting the distance between the antenna 31 and the window member 33.

In the ion source 100 of the above embodiment, the mask plate 333 has a plurality of slits 333x formed therein, and the slits 331x of the slit plate 331 are covered by the beam-shaped regions 333z formed between the plurality of slits 333x, but this is not limited thereto. In other embodiments, the mask plate 333 may be made of a metal plate having a rectangular shape, as shown in FIG. 6(b). In this case, one or more mask plates 333 may be provided at positions facing each of the plurality of slits 331x formed in the slit plate 331. When multiple mask plates 333 are provided for one slit 331x, it is preferable to arrange them so that they are staggered from each other in the thickness direction.

In another embodiment, the ion implantation device 400 may be configured to adjust the distance between the antenna 31 and the magnetic field transmission window 3w and the output of the high frequency power supply 32 according to the current value of the extracted ion beam IB. Specifically, as shown in FIG. 7, the ion implantation device 400 may be configured to include a current distribution monitor 7 that monitors the current distribution of the ion beam IB along the longitudinal direction, downstream of the mass analysis magnet 210, to compare the monitored current distribution of the ion beam IB with the target values of the average current density and uniformity using a comparison calculator, and to adjust the distance between the antenna 31 and the magnetic field transmission window 3w and the output of the high frequency power supply 32 according to the comparison result.

In the above embodiment, the magnetic field transmission window 3w is formed in the rear side wall 11b of the plasma generating vessel 1, but this is not limited to the above. For example, in other embodiments, the magnetic field transmission window 3w may be formed in one or both of the two side walls (lateral side walls 11c, d) that face each other across the ion extraction axis L1 when viewed from the longitudinal direction. In this case, the lateral side walls 11c, d of the plasma generating vessel 1 may be inclined so that their inner wall surfaces face the ion extraction port 1H as shown in FIG. 8, or may be straight along the extraction direction as shown in FIG. 9.

When providing a magnetic field transmission window 3w in the inclined lateral side walls 11c, d as shown in FIG. 8, it is preferable to configure the axis connecting the antenna 31 and the center of the magnetic field transmission window 3w (center of the opening 1x) (hereinafter also referred to as the magnetic field transmission axis L2) to pass near the ion extraction outlet 1H. It is also preferable that the magnetic field transmission axes L2 of the two magnetic field transmission windows 3w intersect on the ion extraction axis L1. It is also preferable that the angle between the magnetic field transmission axis L2 and the electrode surface of the plate-shaped electrode that constitutes the extraction electrode system is approximately 20° or more and approximately 45° or less.

In this case, it is preferable that a cooling flow passage 1c is formed on the outer wall side of the rear side wall 11b directly facing the ion extraction port 1H. This cooling flow passage 1c is preferably formed so as to pass through the ion extraction axis L1 and extend along the longitudinal direction of the plasma generating vessel 1. By providing a cooling flow passage along the ion extraction axis L1 in this way, heating due to backflow electrons can be efficiently cooled. Also, in this embodiment, it is preferable that the magnet 2 is provided on the outer surface of each lateral side wall 11c, 11d so as to sandwich the magnetic field transmission window 3w from both sides when viewed from the longitudinal direction.

As shown in Fig. 9, when the side walls 11c and 11d of the plasma generating vessel 1 are made straight along the extraction direction, the extraction electrode system 4 (specifically, the plasma electrode 41) can be brought closer to the ion extraction port 1H without considering the peak position of the plasma density. That is, in the configurations shown in Fig. 2 and Fig. 8, the magnetic field transmission window 3w is installed so as to face the ion extraction port 1H, so that the magnetic field in the vicinity of the ion extraction port 1H becomes strong, and it is necessary to install the plasma electrode 41 while taking into consideration overheating due to induced current. In contrast, in the configuration shown in Fig. 9, the magnetic field transmission window 3w does not face the ion extraction port 1H, so that the magnetic field at the ion extraction port 1H is weaker than that in Fig. 2 and Fig. 8, so that the plasma electrode 41 can be installed without taking into consideration overheating due to induced current.
In addition, in the inner wall of the plasma generating vessel 1, the portion facing the ion outlet 1H is easily heated by the backflow of electrons in the plasma, but by forming the magnetic field transmission window 3w at a position not facing the ion outlet 1H as shown in Fig. 9, it is possible to reduce contamination of the window member 33 (particularly the dielectric plate 332), and to suppress the decrease in the transmittance of the magnetic field and stabilize the operation, compared to Figs. 2 and 8 in which the magnetic field transmission window 3w is formed at a position facing the ion outlet 1H. In addition, it is possible to avoid problems such as the dielectric plate 332 itself heating up or being damaged.

Also, in the embodiment shown in FIG. 9, as in the embodiment in FIG. 8, a cooling passage 1c may be formed on the ion extraction axis L1 on the outer wall side of the rear wall 11b directly facing the ion extraction port 1H. In this way, the heating caused by backflow electrons can be effectively cooled.

In addition, in the ion source 100 of the above embodiment, the high frequency power supply 32 and the matching circuit 321 are installed in the high voltage section, but this is not limited to the above. In the ion source 100 of another embodiment, as shown in FIG. 10, the high frequency power supply 32 and the matching circuit 321 may be installed at ground potential. This contributes to reducing the capacity of the insulating transformer for supplying power to the high voltage section, and can also contribute to miniaturization and cost reduction of the entire system, and to avoiding equipment failures when discharge problems occur due to high voltage.

The antenna 31 may also have a hollow structure with a flow path formed inside through which the coolant can flow. The antenna 31 may also be a so-called LC antenna 31 that includes at least two conductor elements and a capacitor that is a fixed element electrically connected in series with adjacent conductor elements. For example, the antenna 31 may include three conductor elements and two capacitors, and each conductor element may be of the same shape, forming a straight tube shape (specifically, a circular tube shape) with a linear flow path formed inside through which the coolant flows. The material of each conductor element may be, for example, copper, aluminum, an alloy of these, or a metal such as stainless steel.

By configuring the antenna 31 in this way, the combined reactance of the antenna 31 is, simply put, the inductive reactance minus the capacitive reactance, so the impedance of the antenna 31 can be reduced. As a result, even if the antenna 31 is lengthened, the increase in impedance can be suppressed, making it easier for high-frequency current to flow through the antenna 31, and efficiently generating inductively coupled plasma in the internal space 1s.

It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the invention.

The disclosure of this specification may further include the following aspects 1-10.

(Mode 1) An ion source comprising: a plasma generating vessel which is an elongated vessel having an internal space into which an ion source gas is introduced and in which an ion outlet is formed on one side wall along the longitudinal direction of the vessel; plasma generating means which ionizes the ion source gas to generate plasma in the internal space; and an extracting electrode system which is provided outside the plasma generating vessel and extracts an ion beam from the internal space through the ion outlet, the plasma generating means comprising: an antenna provided outside the plasma generating vessel along the longitudinal direction; a high frequency power source which applies high frequency to the antenna; and a magnetic field transmission window which is formed in a position facing the antenna on the side wall of the plasma generating vessel and which allows a high frequency magnetic field generated from the antenna to pass through the internal space.

In this configuration, plasma is generated in the internal space by an antenna installed outside the plasma generating vessel, without using a filament protruding into the internal space of the plasma generating vessel, thereby reducing the number of parts inside the plasma generating vessel that are subject to wear due to sputtering and lengthening the maintenance cycle.
Moreover, since the antenna is provided along the longitudinal direction of the plasma generating vessel, a substantially uniform plasma can be generated in the internal space by one antenna extending along the ion extraction direction opening and one high frequency power source, the number of parts can be significantly reduced, the device can be made smaller, the number of processing steps required for installation and the number of control points for the power source can be reduced, and the manufacturing cost can be suppressed. Furthermore, by reducing the number of power sources, the number of power supply wires and device control wires can be significantly reduced, and the wiring work during assembly and the removal and attachment work during maintenance can be simplified, improving the workability.

(Aspect 2) The ion source according to aspect 1, wherein the extraction electrode system includes one or more plate-shaped electrodes provided at a position facing the ion extraction port, and a slit penetrating the electrode in its thickness direction is formed along the longitudinal direction at a position of each electrode corresponding to the ion extraction port, and the direction in which the slit extends coincides with the direction in which the antenna extends.
In this configuration, the slit formed in the electrode constituting the extraction electrode and the antenna extend in the same direction, making it possible to extract an ion beam with a substantially uniform current density along the longitudinal direction.

(Aspect 3) An ion source according to aspect 1 or 2, wherein the magnetic field transmission window comprises an opening formed in a side wall of the plasma generating vessel, a slit plate that covers the opening, and a dielectric plate that covers the slit formed in the slit plate from the outside of the plasma generating vessel.
In this embodiment, for example, a slit formed in a metal slit plate and a dielectric plate placed on the slit plate form a magnetic field transmission window that transmits the high frequency magnetic field generated from the antenna into the internal space. Since a part of the member forming the magnetic field transmission window can be made of a metal material that has higher toughness than a dielectric material such as ceramics, the thickness of the magnetic field transmission window can be made smaller than when the magnetic field transmission window is made of only a dielectric material. In addition, since the dielectric plate is supported in contact with the metal plate, deformation of the dielectric plate during vacuum processing can be reduced, and bending stress generated in the dielectric plate can be reduced. Therefore, the thickness of the dielectric plate itself can be made smaller. This allows the distance from the antenna to the internal space to be shortened, and the high frequency magnetic field generated by the antenna can be efficiently supplied into the plasma generating vessel.

(Aspect 4) The ion source according to aspect 3, wherein the magnetic field transmission window further comprises a mask plate that covers the slit formed in the slit plate from the inside of the plasma generating vessel with a gap therebetween.
In this embodiment, the antenna to which high-frequency power is applied is optically and electrically shielded by the mask plate, so that the high-frequency voltage of the antenna can be shielded, and the ion energy and its energy width in the generated plasma can be reduced. This reduces the influence on the mass separation of ions extracted from the ion source. This effect is particularly effective when extracting low-energy ions.
In the ion source, while ions are extracted from the plasma by the extraction electrode, electrons flow back from the extraction electrode into the plasma generating vessel. However, by using a structure in which the magnetic field transmission window is shielded by a mask plate, it is possible to prevent the electron flow from entering the dielectric plate that constitutes the magnetic field transmission window. This reduces the possibility of the dielectric plate being damaged by heating, charging, or discharge. Furthermore, if a high-melting-point metal is used in this part, thermal deformation can be reduced, enabling stable operation.
Furthermore, if a conductive coating generated by plasma passes through the slits and adheres to the dielectric plate, the transmittance of the high-frequency magnetic field decreases, resulting in a decrease in the efficiency of plasma generation, and the heat generated by the deposited coating may damage the components that make up the magnetic field transmission window. However, by providing a mask plate that covers the slits, the adhesion of the conductive coating to the dielectric plate can be prevented.

(Aspect 5) The ion source according to any one of aspects 1 to 4, further comprising a distance adjustment mechanism that partially adjusts the distance between the antenna and the magnetic field transmission window.
In this configuration, the distance adjustment mechanism partially adjusts the distance between the antenna and the magnetic field transmission window, making it possible to finely adjust the plasma density distribution along the longitudinal direction of the antenna by simply adjusting the output of a single high-frequency power supply, thereby enabling adjustment of the average current density of the ion beam along the longitudinal direction with a simple configuration.

(Aspect 6) The ion source according to aspect 5, wherein the distance adjustment mechanism displaces the position of the antenna at multiple points along the longitudinal direction.
In this manner, the plasma density distribution along the longitudinal direction of the antenna can be adjusted more precisely.

(Aspect 7) An ion source according to any one of aspects 1 to 6, wherein the plasma generating vessel has a plurality of gas inlet holes provided along the longitudinal direction for introducing an ion source gas into the internal space, and the plurality of gas inlet holes have a hole diameter at both ends along the longitudinal direction that is relatively larger than the hole diameter at a central portion, or the arrangement spacing at both ends along the longitudinal direction is relatively narrower than the arrangement spacing at the central portion.
When plasma is generated by an external antenna, the plasma density tends to be relatively lower at both ends along the longitudinal direction of the antenna in the internal space than at the center. Therefore, by making the diameter of the gas inlet holes for introducing the ion source gas larger at both ends along the longitudinal direction than at the center, or by making the spacing between the gas inlet holes at both ends along the longitudinal direction narrower than that at the center, the pressure of the ion source gas in both longitudinal end regions is increased, thereby increasing the plasma density in the both end regions, and thus an ion beam with good uniformity can be extracted. In this state, for example, by adjusting the distance between the antenna and the magnetic field transmission window, an ion beam with an increased average current density can be extracted.

(Aspect 8) An ion source according to any one of aspects 1 to 7, wherein, when viewed from the longitudinal direction, the magnetic field transmission window is formed in a side wall of the plasma generating vessel that faces the side wall in which the ion extraction port is formed.
With this configuration, a peak of the plasma distribution can be generated in the vicinity of the ion extraction port in the width direction perpendicular to the longitudinal direction and the ion extraction direction, and plasma can be efficiently generated in the vicinity of the ion extraction port, making it possible to extract an ion beam with an increased average current density.

(Aspect 9) An ion source according to any one of aspects 1 to 7, wherein, when viewed from the longitudinal direction, the magnetic field transmission window is formed in one or both of two side walls of the plasma generating vessel that face each other across an ion extraction axis that passes through an ion extraction port and extends in the extraction direction of the ion beam.
In this embodiment, it is possible to prevent the backflow electrons flowing from the extraction electrode side into the plasma generating vessel from entering the magnetic field transmission window, and the plasma generation operation can be stabilized. In addition, if the magnetic field transmission window is provided on both of the two side walls, it is possible to increase the plasma density in the vicinity of the ion extraction port.

(Aspect 10) An ion source according to aspect 9, wherein, when viewed from the longitudinal direction, the two side walls in which the magnetic field transmission window is formed are inclined with respect to the ion extraction axis so that their inner wall surfaces face the ion extraction port.
In this embodiment, the plasma density in the vicinity of the ion outlet can be further increased.

The present invention described above can provide an ion source that has a long maintenance cycle, is highly functional during maintenance, and allows the overall device to be made smaller, while keeping manufacturing costs down.

100: Ion source 1: Plasma generating vessel 1s: Internal space 11a: Side wall (front wall)
1H: Ion extraction port 3: Plasma generating means 31: Antenna 32: High frequency power source 3w: Magnetic field transmission window 4: Extraction electrode system W: Substrate IB: Ion beam

Claims (10)

a plasma generating vessel which is an elongated vessel having an internal space into which an ion source gas is introduced and in which an ion extraction port is formed on one side wall along the longitudinal direction of the vessel;
a plasma generating means for ionizing the ion source gas to generate plasma in the internal space;
an extraction electrode system provided outside the plasma generating vessel and extracting an ion beam from the internal space through the ion extraction port;
The plasma generating means is
an antenna provided outside the plasma generating chamber along the longitudinal direction;
a high frequency power source that applies a high frequency to the antenna;
an ion source comprising: a magnetic field transmission window formed in a side wall of the plasma generating vessel at a position facing the antenna, the magnetic field transmission window allowing a high frequency magnetic field generated from the antenna to pass through the internal space; the extraction electrode system includes one or more plate-like electrodes provided at a position facing the ion extraction port, and a slit penetrating the electrode in a thickness direction is formed along the longitudinal direction at a position of each electrode corresponding to the ion extraction port,
2. The ion source according to claim 1, wherein the extending direction of the slit coincides with the extending direction of the antenna. The ion source according to claim 1, wherein the magnetic field transmission window comprises an opening formed in the side wall of the plasma generating vessel, a slit plate that closes the opening, and a dielectric plate that closes the slit formed in the slit plate from the outside of the plasma generating vessel. The ion source according to claim 3, wherein the magnetic field transmission window further comprises a mask plate that covers the slits formed in the slit plate from the inside of the plasma generating vessel with a gap. The ion source of claim 1 further comprising a distance adjustment mechanism for partially adjusting the distance between the antenna and the magnetic field transmission window. The ion source according to claim 5, wherein the distance adjustment mechanism displaces the position of the antenna at multiple points along the longitudinal direction. the plasma generating chamber is provided with a plurality of gas inlet holes along the longitudinal direction for introducing an ion source gas into the internal space,
2. The ion source according to claim 1, wherein the plurality of gas introduction holes have a hole diameter at both ends along the longitudinal direction that is relatively larger than a hole diameter at a central portion, or an arrangement interval at both ends along the longitudinal direction that is relatively narrower than an arrangement interval at the central portion. The ion source according to claim 1, wherein, when viewed from the longitudinal direction, the magnetic field transmission window is formed in a side wall of the plasma generating vessel that faces the side wall in which the ion extraction port is formed. The ion source according to claim 1, wherein, when viewed from the longitudinal direction, the magnetic field transmission window is formed on one or both of two side walls of the plasma generating vessel that face each other across an ion extraction axis that extends through an ion extraction port in the extraction direction of the ion beam. The ion source according to claim 9, wherein, when viewed from the longitudinal direction, the two side walls in which the magnetic field transmission window is formed are inclined with respect to the ion extraction axis so that their inner wall surfaces face the ion extraction port.

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