Ion generator

An ion generator includes an arc chamber which has a plasma generating region therein, a cathode configured to emit a thermoelectron toward the plasma generating region, a repeller which faces the cathode in an axial direction in a state where the plasma generating region is interposed between the cathode and the repeller, and a cage which is disposed to partially surround the plasma generating region at a position between an inner surface of the arc chamber and the plasma generating region.

RELATED APPLICATIONS

Priority is claimed to Japanese Patent Application No. 2017-041654, filed Mar. 6, 2017, the entire content of which is incorporated herein by reference.

BACKGROUND

Technical Field

Certain embodiments relate to an ion generator.

Description of Related Art

An ion generator is used as an ion source which is mounted on a device such as an ion implanter which irradiates ions to a workpiece. In the ion irradiation device, in general, in order to perform an irradiation process and another irradiation process with a different recipe (for example, a recipe having a different ion species and a different energy), switching of ion beam conditions between these processes is performed. In most cases, the switching of the ion beam conditions includes switching of ion generation conditions operated by the ion generator.

SUMMARY

According to an embodiment of the present invention, there is provided an ion generator, including: an arc chamber which has a plasma generating region therein; a cathode configured to emit a thermoelectron toward the plasma generating region; a repeller which faces the cathode in an axial direction in a state where the plasma generating region is interposed between the cathode and the repeller; and a cage which is disposed to partially surround the plasma generating region at a position between an inner surface of the arc chamber and the plasma generating region.

DETAILED DESCRIPTION

Immediately after ion generation conditions are switched, a quality of an ion beam is not necessarily stable enough. Therefore, it is necessary to wait for stabilization of ion beam for a while from a start of an operation of a new ion generation condition. In order to improve productivity of an ion irradiation device, it is desirable to shorten this waiting time.

It is desirable to provide an ion generator useful for improving the productivity of the ion irradiation device.

It is to be noted that any combination of the above constituent elements and any mutual substitution of constituent elements and expressions of the present invention among methods, devices, systems, or the like are also effective as aspects of the present invention.

According to the present invention, it is possible to provide an ion generator useful for improving the productivity of the ion irradiation device and a control method of the ion irradiation device.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In descriptions of the drawings, the same reference numerals are assigned to the same elements, and redundant descriptions thereof are appropriately omitted. The following configurations are only examples, and the scope of the present invention is not limited by the configurations.

FIG. 1is a view schematically showing an ion implanter10according to the embodiment. An upper portion inFIG. 1is a top view showing a schematic configuration of the ion implanter10, and a lower portion inFIG. 1is a side view showing the schematic configuration of the ion implanter10.

The ion implanter10is configured to implant ions to a surface of a workpiece in a vacuum. For example, the workpiece is a substrate W or a semiconductor wafer. Hereinafter, for convenience of explanation, the workpiece is referred to as the substrate W or the semiconductor wafer. However, this is not intended to limit an implantation target to a specific object.

The ion implanter10is configured to irradiate an ion beam B to the entire surface of the substrate W by at least one of a beam scan and a mechanical scan. In the present specification, for convenience of explanation, a traveling direction of the ion beam B on the design is defined as a z direction and a surface perpendicular to the z direction is defined as a xy surface. As described later, in a case where the workpiece is scanned with the ion beam B, a scanning direction is referred to as an x direction, and a direction orthogonal to the z direction and the x direction is referred to as a y direction. Accordingly, the beam scan is performed in the x direction and the mechanical scan is performed in the y direction.

The ion implanter10includes an ion generator12, a beamline unit14, and an implantation process chamber16. The ion generator12is configured to provide the ion beam B to the beamline unit14. The beamline unit14is configured to transport ions from the ion generator12to the implantation process chamber16. The ion implanter10includes an evacuation system (not shown) for providing a desired vacuum environment to the ion generator12, the beamline unit14, and the implantation process chamber16.

For example, as shown inFIG. 1, the beamline unit14includes amass analyzing magnet device18, abeam shaping device20, a deflection scanning device22, a beam parallelizing device24such as a P lens, and an angular energy filter26in order from the upstream side. In the present specification, the upstream side indicates a side close to the ion generator12and a downstream side indicates a side close to the implantation process chamber16.

The mass analyzing magnet device18is provided on the downstream side of the ion generator12and is configured to select necessary ion species out of the ion beam B extracted from the ion generator12by mass analysis. The beam shaping device20includes a focusing/defocusing lens such as a Q lens and is configured to shape the ion beam B into a desired sectional shape.

The deflection scanning device22is configured to provide the beam scan. The deflection scanning device22scans the ion beam B in the x direction. Accordingly, the ion beam B is scanned over a scanning range in the x direction, which is longer than a beam width in the y direction. InFIG. 1, the beam scanning direction and the scanning range thereof are exemplified by an arrow C, and the ion beams B on one end and the other end of the scanning range are respectively indicated by solid lines and dashed lines. For the sake of clarity, the ion beams B are shown to be hatched.

The beam parallelizing device24is configured to parallelize the traveling direction of the scanned ion beam B. The angular energy filter26is configured to analyze the energy of the ion beam B, deflect ions having a desired energy downward, and lead the ions to the implantation process chamber16. In this way, the beamline unit14supplies the ion beam B to be irradiated to the substrate W to the implantation process chamber16.

The implantation process chamber16includes an object holding unit (not shown) which is configured to hold one or a plurality of substrates W and provide a relative movement (so-called mechanical scan) with respect to the ion beam B in the y direction to the substrate W if necessary, for example. InFIG. 1, the mechanical scan is exemplified by an arrow D. The implantation process chamber16includes a beam stopper28at a termination of a beamline. In a case where the substrate W does not exist on a trajectory of the ion beam B, the ion beam B is incident into the beam stopper28.

In another embodiment, the ion implanter10may be configured to supply an ion beam having a cross section which is considerably long in one direction perpendicular to the z direction to the implantation process chamber16. For example, the ion beam has a width in the x direction which is longer than the width in the y direction. The ion beam having the elongated cross section maybe referred to as a ribbon beam. In still another embodiment, the ion implanter10may be configured to supply an ion beam having a spot-shaped cross section to the implantation process chamber16without scanning the ion beam.

FIG. 2is a sectional view schematically showing a configuration of the ion generator12according to the embodiment. The ion generator12is an ion source with an indirectly heated cathode and includes an arc chamber30, a thermoelectron emitting portion32, a repeller34, a first extraction electrode36, a second extraction electrode38, a cage72, and various power supplies.

The arc chamber30has an approximately rectangular parallelepiped box shape. The arc chamber30has an elongated shape in one direction, and hereinafter, the one direction is referred to as an axial direction of the arc chamber30. The axial direction is an up-down direction on a paper surface ofFIG. 2.

The arc chamber30is configured of a high melting point material, specifically, a high melting point metal such as tungsten (W), molybdenum (Mo), or tantalum (Ta), alloys thereof, graphite (C), or the like. Accordingly, the arc chamber is not easily melted even in an environment where a temperature inside the arc chamber is considerably high.

The thermoelectron emitting portion32is provided on one side in the axial direction of the arc chamber30. The repeller34is provided on the other side in the axial direction of the arc chamber30. The repeller34faces the thermoelectron emitting portion32. Hereinafter, for convenience of explanation, aside of the thermoelectron emitting portion32in the arc chamber30is referred to as an upper side, and a side of the repeller34in the arc chamber30is referred to as a lower side.

The descriptions such as the “upper side” and the “lower side” are merely used for the convenience of explanation, and this does not mean that the thermoelectron emitting portion32should be disposed on the upper side in the vertical direction and the repeller34should be disposed on the lower side in the vertical direction when the ion generator12is used. In the ion generator12, the thermoelectron emitting portion32may be disposed on the lower side in the vertical direction and the repeller34may be disposed on the upper side in the vertical direction. The ion generator12may be disposed such that the axial direction thereof becomes the horizontal direction or the axial direction thereof becomes inclined to the vertical direction and the horizontal direction.

A gas inlet40through which a material gas is introduced is provided on one side portion of the arc chamber30. A front slit42which is an opening through which the ion beam B is extracted is formed on the other side portion of the arc chamber30.

The material gas includes rare gas, or hydride such as hydrogen (H2), phosphine (PH3), or arsine (ASH3), or halide which is fluorides such as boron trifluoride (BF3) or germanium tetrafluoride (GeF4), chloride such as indiumtri chloride (InCl3), or the like. The material gas may include substances containing oxygen atoms (O) such as carbon dioxide (CO2), carbon monoxide (CO), or oxygen (O2).

The arc chamber30includes a chamber body44, a slit member46, and an insulating member48. The front slit42is formed in the slit member46. The chamber body44is a box member in which one side portion is open. The slit member46is a cover which is attached to the open side of the chamber body44and is fixed to the chamber body44via the insulating member48. By attaching the slit member46to the open side of the chamber body44, a plasma chamber of the ion generator12is formed. The thermoelectron emitting portion32, the repeller34, and the gas inlet40are provided in the chamber body44.

The slit member46is connected to a positive terminal of an extraction power supply60and a high positive voltage is applied to the slit member46by the extraction power supply60. The chamber body44is connected to a negative terminal of a chamber power supply62, and thus, a negative voltage is applied to the chamber body44with respect to the slit member46. For example, the chamber power supply62is configured to apply a voltage which is one to five times an arc power supply58described later to the chamber body44.

The front slit42is an elongated slit which extends from the upper side of the slit member46to the lower side thereof. This vertically long hole has a larger area than that of a small hole such as a circular hole, and thus, it is possible to increase an amount of the ion beams extracted from the ion generator12.

For convenience of explanation, a direction in which the front slit42extends is referred to as a slit longitudinal direction. The slit longitudinal direction corresponds to the axial direction of the arc chamber30. The slit longitudinal direction is orthogonal to a beam extraction direction of the ion generator12. A direction orthogonal to both the slit longitudinal direction and the beam extraction direction is referred to as a slit width direction. Accordingly, the cross section shown inFIG. 2is a cross section formed by a plane parallel to both the slit longitudinal direction and the beam extraction direction. In the paper surface ofFIG. 2, the slit longitudinal direction is the up-down direction, the beam extraction direction is a right-left direction, and a slit width direction is a direction perpendicular to the paper surface.

The cage72is provided inside the arc chamber30. The cage72is positioned between an inner surface of the arc chamber30and a region (referred to as a plasma generating region) in which plasma P is generated and is disposed to partially surround the plasma generating region. The cage72includes a plurality of wire members74which are arranged with intervals in the axial direction and is formed in a cage shape or a fence shape. Gaps76are provided between adjacent wire members74and the material gas introduced from the gas inlet40flows into the plasma generating region through the gaps76of the cage72. Accordingly, the cage72is configured such that a flow of gas crossing the cage72is generated in a radial direction orthogonal to the axial direction.

Similarly to the arc chamber30, the cage72is configured of a high melting point material, specifically, a high melting point metal such as tungsten (W), molybdenum (Mo), or tantalum (Ta), alloys thereof, graphite (C), or the like. Accordingly, the cage72is not easily melted in an environment where a temperature of the cage72is considerably high during the generation of the plasma P.

The cage72is provided along three side portions of the chamber body44and is disposed to partition a portion between the plasma generating region and an inner surface45of the chamber body44. The cage72is fixed to an inner surface66of the slit member46and is disposed to be away from the inner surface45of the chamber body44. The same positive voltage as the slit member46is applied to the cage72, and thus, the plasma P is confined in a space inside the cage72. The cage72is heated by the plasma P and the temperature of the cage72becomes a high temperature of several hundreds degree Celsius or more.

The thermoelectron emitting portion32emits thermoelectrons into the arc chamber30and includes a filament50and a cathode52. The thermoelectron emitting portion32is inserted into a cathode attachment hole of the chamber body44and is fixed in a state insulated from the arc chamber30. In association with the thermoelectron emitting portion32, a filament power supply54, a cathode power supply56, and the arc power supply58are provided.

The filament50is heated by the filament power supply54, and thus, thermoelectrons are generated from a tip of the filament50. Primary thermoelectrons generated from the filament50are accelerated by a cathode electric field formed by the cathode power supply56. The primary thermoelectrons collide with the cathode52, and thus, the cathode52is heated by heat generated at the time of the collision. The heated cathode52generates secondary thermoelectrons.

An arc voltage is applied between the cathode52and the cage72by the arc power supply58and the secondary thermoelectrons are accelerated by the arc voltage. The secondary thermoelectrons are emitted to the inside of the cage72as beam electrons with sufficient energy to ionize gas molecules. Since the beam electrons are within a range approximately limited by a magnetic field M, ions are mainly generated within the range. The beam electrons reach the inner wall of arc chamber30, slit member46, cathode52, repeller34, and cage72by diffusion, and are lost on the walls.

The repeller34includes a repeller plate68. The repeller plate68is provided to be approximately parallel to the cathode52so as to face the cathode52. The repeller plate68bounces electrons in the arc chamber30to accumulate the electrons in the plasma generating region so as to increase ion generation efficiency.

The cage72is disposed to avoid a position between the plasma generating region and the cathode52and a position between the plasma generating region and the repeller34so as not to hinder reciprocating motions of the beam electrons between the cathode52and the repeller34. Accordingly, the cage72is formed so as not to have a partition which is configured in a plane orthogonal to the axial direction.

The cage72is disposed to avoid a position between the plasma generating region and the front slit42so as not to hinder the extraction of the ion beam B from the front slit42. Therefore, the cage72is formed so as not to have a partition configured along the inner surface66of the slit member46.

A magnetic field generator70is provided in the ion generator12. The magnetic field generator70is disposed outside the arc chamber30. The magnetic field generator70includes a pair of magnetic-field coils, one thereof is positioned above the arc chamber30, and the other thereof is positioned below the arc chamber30. The magnetic field M is applied to the inside of the arc chamber30by the magnetic field generator70. The magnetic field M is applied in the axial direction of the arc chamber30.

The beam electrons emitted from the cathode52to the arc chamber30reciprocate between the cathode52and the repeller34along the magnetic field M. The reciprocating beam electrons collide with molecules of the material gas introduced to the arc chamber30and ionize the molecules of the material gas to generate ions, and thus, the plasma P is generated in the arc chamber30. Since the arc chamber30is elongated, the plasma P is also elongated.

A cooling device80is provided outside the arc chamber30. The cooling device80is attached to outside of the chamber body44and cools the chamber body44heated during the generation of the plasma. By providing the cooling device80, the temperature of the inner surface45of the chamber body44is decreased, and thus, substances disposed on the inner surface45due to the generation of the plasma P are not easily emitted from the inner surface45. In other words, the substances disposed on the inner surface45of the chamber body44are easily accumulated by decreasing the temperature of the chamber body44.

The first extraction electrode36is provided to be adjacent to the outside of the arc chamber30. The first extraction electrode36is disposed with a gap from the slit member46in the beam extraction direction. The second extraction electrode38is provided to be adjacent to the first extraction electrode36on a side opposite to the slit member46. The second extraction electrode38is disposed with a gap from the first extraction electrode36in the beam extraction direction.

As shown in the drawings, in each of the first extraction electrode36and the second extraction electrode38, an opening corresponding to the front slit42is provided to cause the ion beam B to pass through the opening. Similarly to the front slit42, the openings have a vertically long shape. For example, each of the first extraction electrode36and the second extraction electrode38is formed of stainless steel, graphite, molybdenum, or tungsten.

The first extraction electrode36is connected to a suppression power supply64. The suppression power supply64is provided to apply a negative electric potential to the first extraction electrode36with respect to the second extraction electrode38. The second extraction electrode38is grounded. The first extraction electrode36is referred to as a suppression electrode. The second extraction electrode38is referred to as a ground electrode.

Beam extraction is performed by an electric field which is generated in the vicinity of the front slit42according to a voltage applied to a portion between the first extraction electrode36and the slit member46. The ion beam B is extracted from the plasma through the front slit42by this electric field. The ion beam B passes through the openings of the first extraction electrode36and the second extraction electrode38and is transported to the implantation process chamber16by the beamline unit14, and thus, the substrate W is irradiated with the ion beam B.

FIG. 3is a sectional view schematically showing the configuration of the cage72and shows a cross section of the inside of the arc chamber30when viewed from the axial direction. As shown inFIG. 3, the cage72has a squared U shape (channel shape) when viewed from the axial direction and is disposed to be parallel to each of three side portions44a,44b,and44cof the chamber body44. Both ends74aand74bof the wire member74configuring the cage72are attached to the inner surface66of the slit member46.

The cage72is disposed so as to partition the inside of the arc chamber30into the first space82and the second space84. The first space82includes a plasma generating region in which the plasma P is generated and communicates with the front slit42. The second space84is a region along the inner surface45of the chamber body44and is a portion of which a distance from the inner surface45of the chamber body44is within a predetermined range.

The cage72is provided to be away from the inner surface45of the chamber body44. A distance d1between the cage72and the inner surface45of the chamber body44needs to be large enough to ensure insulation between the cage72and the chamber body44having electric potentials different from each other. Meanwhile, in order to secure the plasma generating region having a certain size, it is preferable that distance d1between the cage72and the inner surface45of the chamber body44is as small as possible. Preferably, the distance d1between the cage72and the inner surface45of the chamber body44is set to 30% or less of an internal dimension d0of the arc chamber30, and for example, the distance d1is approximately 5%, 10%, 15%, or 20% of the internal dimension d0. Here, the internal dimension d0of the arc chamber30is not a dimension in the longitudinal direction of the arc chamber30but a dimension of the arc chamber30in the lateral direction (slit width direction or beam extraction direction) orthogonal to the longitudinal direction.

FIG. 4is a sectional view schematically showing the configuration of the cage72and is a view corresponding to a portion ofFIG. 2. InFIG. 4, a range in the axial direction in which the cage72is provided is shown in detail. The cage72is provided over at least a first section C1in the axial direction in which the front slit42is provided. Preferably, the cage72is provided to be positioned in at least a portion of a second section C2between the front slit42and the cathode52and at least a portion of a third section C3between the repeller34and the front slit42. Accordingly, a length l1of the cage72in the axial direction is longer than a length l0of the front slit42in the axial direction (slit longitudinal direction).

The cage72may be provided to be positioned in only a portion of the second section C2and the third section C3or may be provided to be positioned over the entirety of at least one of the second section C2and the third section C3. The cage72may be provided to be positioned in at least a portion of a fourth section C4in which the cathode52is positioned or may be provided to be positioned in at least a portion of a fifth section C5in which the repeller34is positioned. In a case where the cage72is provided in the fourth section C4, the cage72is disposed to be positioned outside the thermoelectron emitting portion32in the radial direction such that the cage72and the thermoelectron emitting portion32do not come into contact with each other. Similarly, in a case where the cage72is provided in the fifth section C5, the cage72is disposed to be positioned outside the repeller34in the radial direction such that the cage72and the repeller34do not come into contact with each other. The cage72is disposed to be away from an upper portion and a lower portion of the chamber body44so as not to come into contact with the upper portion and the lower portion of the chamber body44.

As described above, the arc voltage is applied between the cage72and the cathode52, and the cage72functions as an anode for generating the plasma in the plasma generating region. A positive voltage is applied to the cage72with respect to the chamber body44, and thus, the cage72has a function which confines the plasma P inside the cage72to increase the ion generation efficiency. The functions are realized by the wall of the electric field (potential) generated by the cage72, and thus, ideally, it is preferable that the cage72is configured of a plate-shaped member and the gaps76are not provided. However, if the gaps76are not provided in the cage72, it is impossible to sufficiently provide the material gas for the plasma P to the inside of the cage72, and thus, a stable plasma formation is hindered.

From the above-described viewpoint, preferably, a pitch p of the wire members74configuring the cage72is as small as possible. For example, the pitch p is ⅕ or less of the length l1of the cage72in the axial direction. More preferably, the pitch is 1/10 or less of the length l1. Accordingly, preferably, the number of the plurality of wire members74is five or more, or ten or more.

In order to effectively supply the material gas to the inside of the cage72, preferably, a ratio occupied by the gaps76in the cage72, that is, an opening ratio is 30% or more. Here, the “opening ratio” means an area ratio occupied by the gaps76per unit area in a plan view when the cage72is viewed from the radial direction. For example, in order to set the opening ratio of the cage72to 30% or more, a width w1of the wire member74and a width w2of the gap76satisfy a relation of w1/w2≤2.

Meanwhile, if the opening ratio of the cage72increases, the width w1of the wire member74has to be decreased, and thus, it is difficult to provide the wire member74having a sufficient strength. If the width w1of the wire member74is decreased, the function as the wall of the electric field (potential) generated by the cage72is decreased. Accordingly, preferably, the opening ratio of the cage72is 91% or less. In order to set the opening ratio of the cage72to 91% or less, for example, the width w1of the wire member74and the width w2of the gap76satisfy a relation of w1/w2≥0.1.

Next, effects of the ion generator12according to the present embodiment will be described. First, a state change of the inner wall of the arc chamber will be described in a case where ion generation conditions are switched in an ion generator according to Comparative Example. In Comparative Example, the above-described cage72and the cooling device80are not provided, and the same arc voltage is applied to the arc chamber body and the slit member.

FIG. 5is a view showing a state change of an inner wall of an arc chamber130in a case were the ion generation conditions are switched according to Comparative Example. The ion generation conditions are the operating conditions of the ion generator and include parameters such as a type of gas used, a flow rate of the gas, input power (for example, arc current and arc voltage) for plasma excitation, and an applied magnetic field. When the ion generation conditions are switched, at least one of the parameters is changed. Hereinafter, for convenience of explanation, a condition before switching is appropriately referred to as “a current ion generation condition” from the fact that the condition is currently operated ion generation condition, and condition after switching is appropriately referred to as “a new ion generation condition” from the fact that the condition is an ion generation condition to be used next.

A left upper portion ofFIG. 5shows a state of the inner wall of the arc chamber130when the ion generator according to Comparative Example is continuously operated during a sufficient time in the current ion generation condition. A center upper portion ofFIG. 5shows a state of the inner wall of the arc chamber130immediately after the conditions are switched from the current ion generation condition to the new ion generation condition, and a right upper portion ofFIG. 5shows a state of the inner wall of the arc chamber130when the ion generator is continuously operated during a sufficient time in the new ion generation condition after the switching. The lower portion ofFIG. 5shows a change of a substance formation amount (for example, thickness of substance layer) on the inner wall of the arc chamber130when the conditions are switched from the current ion generation condition to the new ion generation condition.

According to the consideration of the present inventor, different substances maybe formed on the inner wall of the arc chamber130depending on the ion generation condition. For example, as shown in the left upper portion of theFIG. 5, a first plasma Pa is generated in the arc chamber130in the current ion generation condition, and thus, a first substance α is formed on the inner wall. If the conditions are switched from the current ion generation condition to the new ion generation condition, as shown in the center upper portion ofFIG. 5, a second plasma Pb different from the first plasma Pa is formed in the arc chamber130. Since it is immediately after the switching, the first substance α still remains on the inner wall of the arc chamber130. As shown in the right upper portion ofFIG. 5, if a sufficient time has elapsed from the start of the operation of the new ion generation condition, a second substance β is formed on the inner wall of the arc chamber130by the second plasma Pb.

In this way, the switching of the ion generation conditions involves a state transition of the inner wall of the arc chamber130. As shown in the lower portion ofFIG. 5, the first substance α formed in the current ion generation condition is gradually removed from the inner wall, and the second substance β is gradually formed on the inner wall in the new ion generation condition. It is considered that the first substance α removed from the inner wall is evacuated to the outside of the arc chamber130together with the ion beam. If the second substance β is formed on the inner wall to some extent, the amount of the second substance β is saturated.

In the transition state shown in the center portion ofFIG. 5, a quality of the ion beam extracted from the ion generator12is not sufficiently stable. Therefore, it is necessary to wait for stabilization of the ion beam for a while from the start of the operation of new ion generation conditions. This waiting time ΔT'may be considerably long depending on a combination of the current ion generation condition and the new ion generation condition. Implantation processing of the ion implanter10is not started until the waiting time ΔT1elapsed. Accordingly, in order to improve productivity of ion implanter10, it is desired to shorten the waiting time for ion beam stabilization required with the switching of the ion generation conditions.

According to the consideration of the present inventor, in Comparative Example, the reason why the above-described waiting time ΔT'is lengthened is because the temperature of the arc chamber inner wall is relatively high, and thus, the accumulation substances α and β are not easily accumulated and are easily emitted. Typically, the arc chamber130is heated by the plasma P and reaches several hundreds Celsius or more. However, from the viewpoint of replacing and stabilizing the accumulation substances α and β on the inner wall of the arc chamber130in order to switch the ion generation conditions, it is preferable that the temperature of the arc chamber130is low. Accordingly, the present inventor considers that the waiting time caused by the switching of the ion generation conditions can be shortened by disposing the cage72inside the arc chamber and dividing functions into the cage72having a relatively high temperature for heating the plasma P and the arc chamber30having a relatively low temperature for early stabilizing the accumulation substances.

FIG. 6is a view showing a state change of the inner wall of the arc chamber30when the ion generation conditions are switched according to the present embodiment and corresponds toFIG. 5according to the above-described Comparative Example. In the present embodiment, the cage72is provided between the plasma and the inner wall of the arc chamber30, and the temperature of the inner wall of the arc chamber30is lower than that of the cage72. As a result, compared to the case of Comparative Example, the accumulation substances α and β are easily accumulated on the inner wall of the arc chamber30, and the substances accumulated once are difficult to be emitted.

If the ion generation conditions are switched in the present embodiment, as shown in the center upper portion ofFIG. 6, the inner wall state is transferred to a state where both of the first substance α and the second substance β are accumulated on the first substance α accumulated on the inner wall of the arc chamber30. The reason is because the first substance α is not easily emitted, the second substance β is easily accumulated, and thus, the second substance β covers the first substance α before the first substance α is completely removed. As a result, as shown in the right upper portion ofFIG. 6, the second substance β is accumulated and saturated in a state where the first substance α remains on the inner wall of the arc chamber30. In the present embodiment, the first substance α is completely covered with the second substance β, and thus, a stable state is realized in the new ion generation condition.

In the present embodiment, the first substance α finishes being emitted before the first substance α is completely removed, and thus, the time until the first substance α finishes being emitted is shorter than that of the above-described Comparative Example. Because the temperature of the inner wall of the arc chamber30is relatively low, the time until the second substance β is accumulated and saturated on the inner wall is shorter than that of the above-described Comparative Example. As a result, as shown in the lower portion ofFIG. 6, a waiting time ΔT2until the ion generation conditions are switched and stabilized is shorter than that of the above-described Comparative Example. According to the present embodiment, in this way, the waiting time caused by the switching of the ion generation conditions is shortened, and thus, it is possible to improve productivity of the ion implanter10.

FIG. 7is a view showing a change of a beam current when the ion generation conditions are switched, and shows the change of the beam current of a phosphorus ion beam (P beam) in a case where the conditions are switched from a generation conditions for phosphorus (P) ions to a generation condition for argon (Ar) ions. A solid line indicates a beam current change for the present embodiment in which the cage72is provided in the arc chamber30and a dashed line indicates a beam current change for Comparative Example in which the cage72is not provided in the arc chamber. As shown in the drawings, compared to Comparative Example, in the present embodiment, a time until the P beam is sufficiently decreased after the ion generation conditions are switched is short, and a time integrated value of the beam current of the P beam output after the switching is small. In this way, according to the present embodiment, it is possible to shorten the waiting time caused by the switching of the ion generation conditions.

FIG. 8is a view showing the change of the beam current when the ion generation conditions are switched, and in contrast with the case ofFIG. 7,FIG. 8shows the change of the beam current of the P beam in a case where the conditions are switched from a generation conditions of argon (Ar) ions to a generation conditions of phosphorus (P) ions. A solid line indicates beam current change for the present embodiment in which the cage72is provided in the arc chamber30and a dashed line indicates a beam current change for Comparative Example in which the cage72is not provided in the arc chamber. As shown in the drawings, compared to Comparative Example, in the present embodiment, a time until the P beam current is substantially stabilized after the ion generation conditions are switched is short. In this way, according to the present embodiment, it is possible to shorten the waiting time caused by the switching of the ion generation conditions.

MODIFICATION EXAMPLE 1

FIGS. 9A to 9Care sectional views schematically showing configurations of cages72a,72b,and72caccording Modification Example 1 and show cross sections when the inside of the arc chamber30is viewed in the axial direction.FIG. 9Ashows the cage72awhich is formed in a U shape when viewed in the axial direction.FIG. 9Bshows the cage72bwhich is formed in a C shape when viewed in the axial direction.FIG. 9Cshows the cage72cwhich is formed in a V shape when viewed in the axial direction. In the shown Modification Example 1, each of the cages72a,72b,and72cis disposed to partition a portion between the region in which the plasma P is generated and the inner surface45of the arc chamber30and is attached to the slit member46. The shape of the cage is not limited to those of the shown cages, and an arbitrary shape can be adopted as long as it partially surrounds the plasma generating region.

MODIFICATION EXAMPLE 2

FIG. 10is a sectional view schematically showing a configuration of a cage72daccording to Modification Example 2 and shows a cross section when the inside of the arc chamber30is viewed in the slit width direction. In the cage72daccording to Modification Example 2, a plurality of second wire members75extending in the axial direction are provided in addition to the plurality of wire members (first wire members)74which are disposed with intervals in the axial direction. The second wire members75are disposed at intervals in the direction in which the first wire members74extend. The cage72daccording to Modification Example 2 is formed in a mesh shape by using a combination of the first wire members74and the second wire members75. That is, the cage72dincludes a mesh member. Preferably, in Modification Example 2, the opening ratio of the gaps76of the mesh is 30% or more and 90% or less.

MODIFICATION EXAMPLE 3

FIG. 11is a sectional view schematically showing a configuration of a cage72eaccording to Modification Example 3, and similarly toFIG. 10, shows a cross section when the inside of the arc chamber30is viewed in the slit width direction. The cage72eaccording to Modification Example 3 is configured of plate members77having a plurality of openings78. The cage72ehas a squared U shape when viewed in the axial direction and includes three plate members77which are disposed to respectively face the three side portions of the chamber body44. The plurality of openings78are formed in an array on the plate member77, and, for example, are arranged in a trigonal lattice alignment or a tetragonal lattice alignment. In Modification Example 3, preferably, the opening ratio of the plurality of openings78is 30% or more and 90% or less.

MODIFICATION EXAMPLE 4

FIGS. 12A and 12Bare sectional views schematically showing internal configurations of the arc chamber30according to Modification Example 4, and show cross sections when the inside of the arc chamber30is viewed in the axial direction. Modification Example 4 is different from the above-described embodiment in that the cage72fis not fixed to the slit member46and is fixed to the chamber body44. The cage72fis disposed to be away from the inner surface66of the slit member46and is attached to the inner surface45of the chamber body44via insulating members91or92. In Modification Example 4 shown inFIG. 12A, the cage72fis fixed to two side portions44aand44cof the chamber body44facing each other in the slit width direction via the insulating members91. In Modification Example 4 shown inFIG. 12B, the cage72fis fixed to one side portion44bof the chamber body44facing the slit member46via the insulating members92.

In Modification Example 4, the cage72fis electrically insulated from the chamber body44, and thus, the cage72fmay have an electric potential different from that of the chamber body44. For example, similarly to the above-described embodiment, the cage72fis configured to have the same electric potential as that of the slit member46. The cage72fmay be electrically insulated from the slit member46and may have an electric potential different from that of the slit member46. In this case, a voltage may be applied to the cage72fby using another power supply which is not shown inFIG. 2. The cage72fmay be configured to have a floating electric potential.

MODIFICATION EXAMPLE 5

FIGS. 13A and 13Bare sectional views schematically showing internal configurations of the arc chamber30according to Modification Example 5, and show cross sections when the inside of the arc chamber30is viewed in the axial direction. Modification Example 5 is similar to Modification Example 4 in that cage72gor72his fixed to the chamber body44. However, Modification Example 5 is different from Modification Example 4 in that the cages72gand72hare directly fixed to the chamber body44. Accordingly, in Modification Example 5, the cage72gor72his configured to have the same electric potential as that of the chamber body44.

In Modification Example 5 shown inFIG. 13A, the cage72gis fixed to the two side portions44aand44cof the chamber body44facing each other in the slit width direction. The cage72gincludes a partitioning portion94gwhich is disposed to partially surround the plasma generating region and an attachment portion96gwhich protrudes from the partitioning portion94gtoward the side portions44aand44cof the chamber body44. In Modification Example 5 shown inFIG. 13B, the cage72his fixed to the one side portion44bof the chamber body44facing the slit member46. The cage72hincludes a partitioning portion94h which is disposed to partially surround the plasma generating region and an attachment portion96hwhich protrudes from the partitioning portion94htoward the side portion44bof the chamber body44.

In another Modification Example, the cage72may not be fixed to the side portions of the chamber body44and may be fixed to the upper portion and/or the lower portion of the chamber body44. In this case, the cage72maybe directly fixed to the chamber body44or may be fixed to the chamber body44via an insulating member.

It should be understood that the invention is not limited to the above-described embodiments, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.

In the above-described embodiment, the case where the voltage generated by the chamber power supply62is applied between the chamber body44and the slit member46is shown. In still another Modification Example, the chamber power supply62may not be provided, and the chamber body44and the slit member46maybe configured to have the same electric potential as each other. In this case, the cage72may be configured to have the same electric potential as those of the chamber body44and the slit member46, and the cage72may be configured to have an electric potential different from those of the chamber body44and the slit member46. In the latter case, the cage72may be configured to have a floating electric potential with respect to the chamber body44and the slit member46.

The above descriptions are made with reference to the ion generator with indirectly heated cathode. However, the present invention is not limited to this and may be applied to another arbitrary ion generator such as an RF ion generator, a microwave ion generator, or a Bernas type ion generator, in which a reactive material gas is supplied to a plasma chamber and react with an inner wall of the plasma chamber. In this case, the term “arc chamber” mentioned in the above description can be replaced by the term “plasma chamber” used as a more generalized expression.