Ion generation device and ion generation method

There is provided an ion generation device including a plasma generation chamber that generates a plasma for extracting an ion, and a heating device configured to heat the plasma generation chamber by irradiating a member that defines the plasma generation chamber or a member that is to be exposed to the plasma generated inside the plasma generation chamber with a laser beam.

RELATED APPLICATIONS

The content of Japanese Patent Application No. 2020-047762, on the basis of which priority benefits are claimed in an accompanying application data sheet, is in its entirety incorporated herein by reference.

BACKGROUND

Technical Field

Certain embodiments of the present invention relate to an ion generation device and an ion generation method.

Description of Related Art

In a semiconductor manufacturing process, a process of implanting ions into a semiconductor wafer (also referred to as an ion implantation process) is generally performed in order to change conductivity of a semiconductor, or in order to change a crystal structure of the semiconductor. A device used for the ion implantation process is generally called an ion implanter. The ion implanter includes an ion generation device for converting a source gas into a plasma to generate ions.

In the ion generation device, operation conditions of the ion generation device may be switched in order to change implantation conditions such as an ion species and/or an ion beam current. In a case of the ion generation device using an arc discharge, a chamber (also referred to as an arc chamber) surrounding the plasma is heated due to generation of the plasma by the arc discharge, and comes to have a high temperature (for example, several hundred degrees Celsius or higher). In the related art, when the operation condition such as an arc current is changed, a state of the plasma is changed, and a temperature of the arc chamber is also changed in response to a change in the state of the plasma.

SUMMARY

According to an embodiment of the present invention, there is provided an ion generation device including a plasma generation chamber that generates a plasma for extracting an ion, and a heating device configured to heat the plasma generation chamber by irradiating a member that defines the plasma generation chamber or a member that is to be exposed to the plasma generated inside the plasma generation chamber with a laser beam.

According to another embodiment of the present invention, there is provided an ion generation method. The method includes heating a plasma generation chamber by irradiating a member that defines the plasma generation chamber or a member that is to be exposed to a plasma generated inside the plasma generation chamber with a laser beam, and extracting an ion from the plasma generated inside the plasma generation chamber.

DETAILED DESCRIPTION

In order to stably generate a plasma, it is preferable to maintain an arc chamber at a suitable temperature in accordance with each of operation conditions of an ion generation device. However, the arc chamber has poor temperature responsiveness due to its relatively large heat capacity, and heat loss is significant due to thermal radiation in a high temperature state. Consequently, when the operation conditions are switched, it takes time especially in a case where a temperature of the arc chamber needs to be largely raised to a suitable temperature. In addition, even when the temperature of the arc chamber has been raised to the suitable temperature, a waiting time may be additionally required until plasma generation is stabilized. In this case, a time required for switching the operation conditions is lengthened, and productivity in an ion implantation process is degraded.

It is desirable to provide a technique for improving the productivity in the ion implantation process.

Any desired combination of the above-described components, and those in which the components or expressions according to the present invention are substituted from each other in methods, devices, or systems are effectively applicable as an aspect of the present invention.

Before the embodiments are described in detail, an outline will be described. The present embodiment relates to an ion implanter including an ion generation device. The ion generation device includes a plasma generation chamber that generates a plasma for extracting ions. In order to stably generate the plasma, it is necessary to raise a temperature of the plasma generation chamber to a suitable temperature (for example, 1,000° C. or higher). In the present embodiment, the plasma generation chamber is heated by irradiating a member that defines the plasma generation chamber or a member that is to be exposed to the plasma generated inside the plasma generation chamber with a laser beam. In this manner, temperature raising of the plasma generation chamber is promoted. In this manner, a waiting time required until the plasma generation is stabilized is shortened.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. In describing the drawings, the same reference numerals will be assigned to the same elements, and repeated description will be appropriately omitted. Configurations described below are merely examples, and do not limit the scope of the present invention in any way.

FIG.1is a top view schematically illustrating an ion implanter10according to an embodiment, andFIG.2is a side view illustrating a schematic configuration of the ion implanter10. The ion implanter10is configured to perform an ion implantation process into a surface of a workpiece W. For example, the workpiece W is a substrate, or is a semiconductor wafer. For convenience of description, the workpiece W may be referred to as a wafer W in the description herein. However, this is not intended to limit a target of implantation process to a specific object.

The ion implanter10is configured to irradiate a whole processing surface of the wafer W with the ion beam by performing reciprocating scanning using the beam in one direction and causing the wafer W to reciprocate in another direction perpendicular to the scanning direction. In the description herein, for convenience of description, a traveling direction of the ion beam which travels along a designed beamline A is defined as a z-direction, and a plane perpendicular to the z-direction is defined as an xy-plane. When the workpiece W is scanned with the ion beam, a scanning direction of the beam is defined as an x-direction, and a direction perpendicular to the z-direction and the x-direction is defined as a y-direction. Therefore, the reciprocating scanning using the beam is performed in the x-direction, and a reciprocating motion of the wafer W is performed in the y-direction.

The ion implanter10includes an ion generation device12, a beamline device14, an implantation process chamber16, and a wafer transfer device18. The ion generation device12is configured to provide the ion beam for the beamline device14. The beamline device14is configured to transport the ion beam from the ion generation device12to the implantation process chamber16. The implantation process chamber16accommodates the wafer W which is an implantation target, and performs an implantation process of irradiating the wafer W with the ion beam provided from the beamline device14. The wafer transfer device18is configured to load an unprocessed wafer before the implantation process into the implantation process chamber16, and unload a processed wafer after the implantation process from the implantation process chamber16. The ion implanter10includes a vacuum exhaust system (not illustrated) for providing desired vacuum environments for the ion generation device12, the beamline device14, the implantation process chamber16, and the wafer transfer device18.

The beamline device14includes a mass analyzing unit20, a beam park device24, a beam shaping unit30, a beam scanning unit32, a beam parallelizing unit34, and an angular energy filter (AEF)36, sequentially from an upstream side of the beamline A. The upstream side of the beamline A means a side closer to the ion generation device12, and a downstream side of the beamline A means a side closer to the implantation process chamber16(or a beam stopper46).

The mass analyzing unit20is provided downstream of the ion generation device12, and is configured to select a required ion species from the ion beam extracted from the ion generation device12by performing mass analyzing. The mass analyzing unit20has a mass analyzing magnet21, a mass analyzing lens22, and a mass analyzing slit23.

The mass analyzing magnet21applies a magnetic field to the ion beam extracted from the ion generation device12, and deflects the ion beam to travel in different paths in accordance with a value of the mass-to-charge ratio M=m/q (m is mass, and q is charge) of the ions. For example, the mass analyzing magnet21applies the magnetic field in the y-direction (−y-direction inFIGS.1and2) to the ion beam so that the ion beam is deflected in the x-direction. Intensity of the magnetic field applied by the mass analyzing magnet21is adjusted so that the ion species having a desired mass-to-charge ratio M passes through the mass analyzing slit23.

The mass analyzing lens22is provided downstream of the mass analyzing magnet21, and is configured to adjust convergence/divergence power for the ion beam. The mass analyzing lens22adjusts a focusing position of the ion beam passing through the mass analyzing slit23in a beam traveling direction (z-direction), and adjusts a mass resolution M/dM of the mass analyzing unit20. The mass analyzing lens22is not an essential configuration, and the mass analyzing unit20may not have the mass analyzing lens22.

The mass analyzing slit23is provided downstream of the mass analyzing lens22, and is provided at a position away from the mass analyzing lens22. The mass analyzing slit23is configured so that a beam deflecting direction (x-direction) by the mass analyzing magnet21coincides with a slit width direction, and has an opening23ahaving a shape which is relatively short in the x-direction and relatively long in the y-direction.

The mass analyzing slit23may be configured so that the slit width is variable for adjusting the mass resolution. The mass analyzing slit23may be configured to include two blockade bodies that are movable in the slit width direction, and may be configured so that the slit width is adjustable by changing an interval between the two blockade bodies. The mass analyzing slit23may be configured so that the slit width is variable by switching any one of a plurality of slits having different slit widths.

The beam park device24is configured to cause the ion beam to temporarily retreat from the beamline A and to block the ion beam directed to the implantation process chamber16(or the wafer W) located downstream. The beam park device24can be disposed at any desired position in an intermediate portion of the beamline A. For example, the beam park device24can be disposed between the mass analyzing lens22and the mass analyzing slit23. A prescribed distance is required between the mass analyzing lens22and the mass analyzing slit23. Accordingly, the beam park device24is disposed between both of these. In this manner, a length of the beamline A can be shortened, compared to a case where the beam park device24is disposed at another position. Therefore, the whole ion implanter10can be reduced in size.

The beam park device24includes a pair of park electrodes25(25aand25b) and a beam dump26. The pair of park electrodes25aand25bfaces each other across the beamline A, and faces each other in a direction (y-direction) perpendicular to the beam deflecting direction (x-direction) of the mass analyzing magnet21. The beam dump26is provided on the downstream side of the beamline A than the park electrodes25aand25b, and is provided away from the beamline A in a facing direction of the park electrodes25aand25b.

The first park electrode25ais disposed on an upper side of the beamline A in a direction of gravity, and the second park electrode25bis disposed on a lower side of the beamline A in the direction of gravity. The beam dump26is provided at a position away to the lower side of the beamline A in the direction of gravity, and is disposed on the lower side of the opening23aof the mass analyzing slit23in the direction of gravity. For example, the beam dump26is configured on a portion where the opening23aof the mass analyzing slit23is not formed. The beam dump26may be configured to be separate from the mass analyzing slit23.

The beam park device24deflects the ion beam by using an electric field applied between the pair of park electrodes25aand25b, and causes the ion beam to retreat from the beamline A. For example, a negative voltage is applied to the second park electrode25bwith an electric potential of the first park electrode25aas reference. In this manner, the ion beam is deflected downward from the beamline A in the direction of gravity, and is incident into the beam dump26. InFIG.2, a trajectory of the ion beam directed toward the beam dump26is indicated by a dashed line. The beam park device24causes the ion beam to pass toward the downstream side along the beamline A by setting the pair of park electrodes25aand25bto have the same electric potential. The beam park device24is configured to be operable by switching between a first mode in which the ion beam passes toward the downstream side and a second mode in which the ion beam is incident into the beam dump26.

An injector Faraday cup28is provided downstream of the mass analyzing slit23. The injector Faraday cup28is configured to be movable into and out of the beamline A by an operation of an injector driving unit29. The injector driving unit29moves the injector Faraday cup28in a direction (for example, the y-direction) perpendicular to an extending direction of the beamline A. When the injector Faraday cup28is disposed on the beamline A as illustrated by a dashed line inFIG.2, the injector Faraday cup28blocks the ion beam directed toward the downstream side. On the other hand, when the injector Faraday cup28is removed from the beamline A as illustrated by a solid line inFIG.2, the blocking of the ion beam directed toward the downstream side is released.

The injector Faraday cup28is configured to measure a beam current of the ion beam subjected to mass analyzing by the mass analyzing unit20. The injector Faraday cup28can measure a mass analyzing spectrum of the ion beam by measuring the beam current while changing the intensity of the magnetic field applied by the mass analyzing magnet21. The mass resolution of the mass analyzing unit20can be calculated using the measured mass analyzing spectrum.

The beam shaping unit30includes a focusing/defocusing device such as a focusing/defocusing quadrupole lens (Q-lens), and is configured to shape the ion beam which has passed through the mass analyzing unit20into a desired cross-sectional shape. For example, the beam shaping unit30is configured as an electric field type three-stage quadrupole lens (also referred to as a triplet Q-lens), and has three quadrupole lenses30a,30b, and30c. The beam shaping unit30adopts the three lens devices30ato30c. Accordingly, the beam shaping unit30can independently adjust converging or diverging of the ion beam in the x-direction and the y-direction, respectively. The beam shaping unit30may include a magnetic field type lens device, or may include a lens device that shapes the beam by using both an electric field and a magnetic field.

The beam scanning unit32is a beam deflection device configured to provide reciprocating scanning using the beam and to perform scanning using the shaped ion beam in the x-direction. The beam scanning unit32has a scanning electrode pair facing in a beam scanning direction (x-direction). The scanning electrode pair is connected to variable voltage power supplies (not illustrated), and a voltage applied between the scanning electrode pair is periodically changed. In this manner, an electric field generated between the electrodes is changed so that the ion beam is deflected at various angles. As a result, a whole scanning range is scanned with the ion beam in the x-direction. InFIG.1, the scanning direction and the scanning range of the ion beam are indicated by an arrow X, and a plurality of trajectories of the ion beam in the scanning range are indicated by one dot chain lines.

The beam parallelizing unit34is configured so that the traveling directions of the ion beam used for the scanning become parallel to the trajectory of the designed beamline A. The beam parallelizing unit34has a plurality of arc-shaped parallelizing lens electrodes in each of which an ion beam passing slit is provided in a central portion in the y-direction. The parallelizing lens electrodes are connected to high-voltage power supplies (not illustrated), and apply an electric field generated by voltage application to the ion beam so that the traveling directions of the ion beam are parallelized. The beam parallelizing unit34may be replaced with another beam parallelizing device, and the beam parallelizing device may be configured to serve as a magnet device using a magnetic field.

An acceleration/deceleration (AD) column (not illustrated) for accelerating or decelerating the ion beam may be provided downstream of the beam parallelizing unit34.

The angular energy filter (AEF)36is configured to analyze energy of the ion beam, to deflect ions having necessary energy downward at a prescribed angle, and to guide the ions to the implantation process chamber16. The angular energy filter36has an AEF electrode pair for deflection by an electric field. The AEF electrode pair is connected to high-voltage power supplies (not illustrated). InFIG.2, the ion beam is deflected downward by applying a positive voltage to the upper AEF electrode and applying a negative voltage to the lower AEF electrode. The angular energy filter36may be configured to include a magnet device for deflection by a magnetic field, or may be configured to include a combination between the AEF electrode pair for electric field deflection and the magnet device.

In this way, the beamline device14supplies the ion beam to be used for irradiating the wafer W to the implantation process chamber16.

The implantation process chamber16includes an energy slit38, a plasma shower device40, a side cup42, a center cup44, and the beam stopper46, sequentially from the upstream side of the beamline A. As illustrated inFIG.2, the implantation process chamber16includes a platen driving device50that holds one or more wafers W.

The energy slit38is provided downstream of the angular energy filter36, and analyzes the energy of the ion beam incident into the wafer W together with the angular energy filter36. The energy slit38is an energy defining slit (EDS) configured as a slit that is horizontally long in the beam scanning direction (x-direction). The energy slit38causes the ion beam having a desired energy value or a desired energy range to pass toward the wafer W, and blocks other ion beams.

The plasma shower device40is located downstream of the energy slit38. The plasma shower device40supplies low-energy electrons to the ion beam and a surface of the wafer W (wafer processing surface) in accordance with a beam current of the ion beam, and suppresses charge-up of positive charges on the wafer processing surface which occurs due to ion implantation. For example, the plasma shower device40includes a shower tube through which the ion beam passes, and a plasma generation device that supplies electrons into the shower tube.

The side cup42(42R or42L) is configured to measure the beam current of the ion beam during the ion implantation process into the wafer W. As illustrated inFIG.2, the side cups42R and42L are disposed to be shifted to the right and left (x-direction) with respect to the wafer W disposed on the beamline A, and are disposed at positions at which the side cups42R and42L do not block the ion beam directed toward the wafer W during the ion implantation. The ion beam is subject to scanning in the x-direction beyond a range where the wafer W is located. Accordingly, a portion of the beam for the scanning is incident into the side cups42R and42L even during the ion implantation. In this manner, the beam current during the ion implantation process is measured by the side cups42R and42L.

The center cup44is configured to measure the beam current on the wafer processing surface. The center cup44is configured to be movable by an operation of a driving unit45, is retreated from an implantation position where the wafer W is located during the ion implantation, and is inserted into the implantation position when the wafer W is not located at the implantation position. The center cup44measures the beam current while moving in the x-direction. In this manner, the center cup44can measure the beam current over the whole beam scanning range in the x-direction. As the center cup44, a plurality of Faraday cups may be aligned in the x-direction to be formed in an array so that the beam currents can be simultaneously measured at a plurality of positions in the beam scanning direction (x-direction).

At least one of the side cup42and the center cup44may include a single Faraday cup for measuring the beam current, or may include an angle measurement device for measuring angle information of the beam. For example, the angle measurement device includes a slit and a plurality of current detectors provided away from the slit in the beam traveling direction (z-direction). For example, the angle measurement device can measure an angle component of the beam in the slit width direction by causing the plurality of current detectors aligned in the slit width direction to measure the beam which has passed through the slit. At least one of the side cup42and the center cup44may include a first angle measurement device capable of measuring angle information in the x-direction and a second angle measurement device capable of measuring angle information in the y-direction.

The platen driving device50includes a wafer holding device52, a reciprocating mechanism54, a twist angle adjusting mechanism56, and a tilt angle adjusting mechanism58. The wafer holding device52includes an electrostatic chuck or the like for holding the wafer W. The reciprocating mechanism54causes the wafer holding device52to reciprocate in a reciprocating direction (y-direction) perpendicular to the beam scanning direction (x-direction). In this manner, the wafer held by the wafer holding device52is caused to reciprocate in the reciprocating direction (y-direction). InFIG.2, a reciprocating movement of the wafer W is indicated by an arrow Y.

The twist angle adjusting mechanism56adjusts a rotation angle of the wafer W. The twist angle adjusting mechanism56rotates the wafer W around a normal line of the wafer processing surface as an axis. In this manner, the twist angle adjusting mechanism56adjusts a twist angle between an alignment mark provided on an outer peripheral portion of the wafer and a reference position. Here, the alignment mark of the wafer means a notch or an orientation flat provided on the outer peripheral portion of the wafer, and means a mark that serves as a reference for an angular position in a crystal axis direction of the wafer or in a circumferential direction of the wafer. The twist angle adjusting mechanism56is provided between the wafer holding device52and the reciprocating mechanism54, and is caused to reciprocate together with the wafer holding device52.

The tilt angle adjusting mechanism58adjusts inclination of the wafer W, and adjusts a tilt angle between the traveling direction of the ion beam directed toward the wafer processing surface and the normal line of the wafer processing surface. In the present embodiment, out of inclination angles of the wafer W, an angle at which an axis in the x-direction is a rotation center axis is adjusted as the tilt angle. The tilt angle adjusting mechanism58is provided between the reciprocating mechanism54and an inner wall of the implantation process chamber16, and rotates the whole platen driving device50including the reciprocating mechanism54in an R-direction. In this manner, the tilt angle adjusting mechanism58is configured to adjust the tilt angle of the wafer W.

The platen driving device50holds the wafer W so that the wafer W is movable between the implantation position where the wafer W is irradiated with the ion beam and a transfer position where the wafer W is loaded or unloaded between the platen driving device50and the wafer transfer device18.FIG.2illustrates a state where the wafer W is located at the implantation position, and the platen driving device50holds the wafer W so that the beamline A and the wafer W intersect with each other. The transfer position of the wafer W corresponds to a position of the wafer holding device52when the wafer W is loaded or unloaded through a transfer port48by a transfer mechanism or a transfer robot provided in the wafer transfer device18.

The beam stopper46is provided on the most downstream side of the beamline A, and is mounted on the inner wall of the implantation process chamber16, for example. When the wafer W does not exist on the beamline A, the ion beam is incident into the beam stopper46. The beam stopper46is located close to the transfer port48that connects the implantation process chamber16and the wafer transfer device18to each other, and is provided at a position vertically below the transfer port48.

The ion implanter10further includes a control device60. The control device60controls an overall operation of the ion implanter10. The control device60is realized in hardware by elements such as CPUs and memories of a computer or mechanical devices, and in software by computer programs. Various functions provided by the control device60can be realized by cooperation between the hardware and the software.

FIG.3is a sectional view schematically illustrating a configuration of the ion generation device12according to the embodiment. The ion generation device12includes a plasma generation device70and a heating device90.

The plasma generation device70includes an arc chamber72that defines the plasma generation chamber78, and generates a plasma P containing ions inside the plasma generation chamber78. The ions generated by the plasma generation device70are extracted by an extraction electrode82as an ion beam IB. The heating device90heats the arc chamber72by irradiating an outer surface72aof the arc chamber72with a laser beam LB, and adjusts a temperature of the arc chamber72.

The plasma generation device70is disposed in an inner portion102of a vacuum chamber100. The heating device90is disposed in an outer portion104of the vacuum chamber100. The arc chamber72is irradiated with the laser beam LB generated by the heating device90through a vacuum window106provided on a wall of the vacuum chamber100. The vacuum window106is provided with a cooling flow path108through which a fluid (cooling water or the like) for cooling the vacuum window106passes.

The plasma generation device70includes the arc chamber72, a cathode74, and a repeller76. The arc chamber72has a substantially rectangular parallelepiped shape. The arc chamber72defines the plasma generation chamber78in which the plasma P is generated. A slit80for extracting the ion beam IB is provided on a front surface of the arc chamber72. The slit80has an elongated shape extending in a direction from the cathode74toward the repeller76.

The arc chamber72is formed of a refractory material, and for example, is formed of refractory metal such as tungsten (W), molybdenum (Mo), or tantalum (Ta), an alloy thereof, or graphite (C). In this manner, it is possible to suppress damage caused by the heat of the arc chamber72in an environment where the inside of the plasma generation chamber78has a high temperature (for example, 700° C. to 2000° C.)

A reflector86is disposed outside the arc chamber72. The reflector86is disposed to face an outer surface72aof the arc chamber72. The reflector86may be formed of the refractory material same as that of the arc chamber72, or may be formed of a material different from that of the arc chamber72. For example, as a material of the reflector86, tungsten, molybdenum, graphite, stainless steel, or a ceramic material can be used. The reflector86functions to suppress temperature lowering in the arc chamber72due to thermal radiation by reflecting the thermal radiation from the outer surface72aof the arc chamber72toward the arc chamber72. The reflector86may function as a muffle for suppressing the heat loss from the arc chamber72. The reflector86is provided with an irradiation port86athrough which the laser beam LB for irradiating the outer surface72aof the arc chamber72passes. The reflector86may not be provided.

The cathode74emits thermal electrons into the plasma generation chamber78. The cathode74is a so-called indirectly heated cathode (IHC), and has a filament74aand a cathode head74b. The filament74ais heated by a filament power supply88ato generate primary thermal electrons. A cathode power supply88bis connected between the filament74aand the cathode head74b, and the primary thermal electrons generated by the filament74aare accelerated by a cathode voltage. The cathode head74bis heated by the accelerated primary thermal electrons from the filament74a, and supplies secondary thermal electrons into the plasma generation chamber78. An arc power supply88cis connected between the arc chamber72and the cathode74, and the secondary thermal electrons generated by the cathode head74bare accelerated by an arc voltage.

The repeller76is provided at a position facing the cathode74. The repeller76repels the secondary thermal electrons supplied into the plasma generation chamber78and electrons generated by ionization of source gas molecules inside the plasma generation chamber78, and retains both of the electrons in the plasma generation chamber78so that generation efficiency of the plasma is improved.

A gas introduction port84is provided on a side wall of the arc chamber72. The gas introduction port84supplies the source gas into the plasma generation chamber78from a gas cylinder or the like (not illustrated). As the source gas, rare gas, hydrides such as hydrogen (H2), phosphine (PH3), or arsine (AsH3), or fluorides such as boron trifluoride (BF3) or germanium tetrafluoride (GeF4) are used. In addition, as the source gas, materials containing oxygen atoms (O) such as carbon dioxide (CO2), carbon monoxide (CO), or oxygen (O2) are also used.

A magnetic field B is applied to the plasma generation chamber78in a direction (or a direction opposite thereto) from the cathode74toward the repeller76. The magnetic field B is generated by an electromagnet (not illustrated), and intensity of the magnetic field B is adjusted by changing a magnet current flowing in the electromagnet. The thermal electrons moving inside the plasma generation chamber78are restrained by the magnetic field B applied to the plasma generation chamber78, and spirally moves along the magnetic field B. The electrons spirally moving in the plasma generation chamber78collide with the source gas molecules introduced into the plasma generation chamber78, ionize the source gas molecules to generate the ions and new electrons, and generate the plasma P in the plasma generation chamber78. By causing the electrons to

move spirally in the plasma generation chamber78, the generation efficiency of the plasma can be improved.

The heating device90includes a laser beam source92and an irradiation optical system94. The laser beam source92generates a laser beam LB for heating the plasma generation device70. The irradiation optical system94propagates the laser beam LB generated by the laser beam source92toward the plasma generation device70.

The laser beam source92and the irradiation optical system94are disposed in the outer portion104of the vacuum chamber100. At least a portion of the irradiation optical system94may be disposed in the inner portion102of the vacuum chamber100, or the whole irradiation optical system94may be disposed in the inner portion102of the vacuum chamber100. In addition, both the laser beam source92and the irradiation optical system94may be disposed in the inner portion102of the vacuum chamber100. In this case, the vacuum chamber100may not be provided with the vacuum window106. Alternatively, instead of providing the vacuum window106, the laser beam LB may be propagated into the inner portion102of the vacuum chamber100by using an optical fiber extending from the outer portion104of the vacuum chamber100toward the inner portion102of the vacuum chamber100.

The laser beam source92is configured to generate the laser beam LB of ultraviolet, visible, or near-infrared light included in a wavelength range from 200 nm to 2,000 nm, for example. A type of the laser beam source92is not limited, and for example, a small and easy-to-handle semiconductor laser can be used. The laser beam LB may be continuous light, or may be pulsed light. For example, a power of the laser beam source92is approximately 0.1 kW to 10 kW. As an example of the laser beam source92, a semiconductor laser that emits the continuous light of 1 kW at a wavelength of 450 nm can be used. A metal material or graphite forming the arc chamber72has a high absorptivity of the light having a relatively short wavelength. Accordingly, the arc chamber72can be effectively heated by using the laser beam LB of the ultraviolet or visible (blue or green) light.

FIGS.4A to4Care views schematically illustrating configuration examples of the irradiation optical systems94. The irradiation optical system94may include at least one of optical systems94a,94b, and94cfor adjusting beam characteristics such as an irradiation range, a beam diameter, and cross-sectional intensity distribution of the laser beam LB.

FIG.4Aillustrates a scanning optical system94afor scanning and irradiating the outer surface72aof the arc chamber72with the laser beam LB. The scanning optical system94ahas a first mirror96aand a second mirror96bfor scanning with the laser beam LB. The laser beam LB from the laser beam source92is reflected by the first mirror96aand the second mirror96b, and is incident into the outer surface72aof the arc chamber72. The first mirror96ais driven to change a reflection angle of the laser beam LB by the first mirror96a. In this manner, scanning with the laser beam LB can be performed as illustrated by an arrow S. In this manner, an irradiation range C of the laser beam LB can be widened, and a larger region on the outer surface72aof the arc chamber72can be more uniformly heated. Scanning with the laser beam LB may be performed by driving the second mirror96binstead of the first mirror96a. Scanning with the laser beam LB may be performed in one dimension, or may be performed in two dimensions. For example, both the first mirror96aand the second mirror96bare driven respectively in two directions perpendicular to each other. In this manner, the outer surface72aof the arc chamber72can be scanned in two dimensions, and a larger region on the outer surface72aof the arc chamber72can be more uniformly heated. Instead of driving a reflective optical element such as the mirror, scanning with the laser beam LB may be performed by driving a refractive optical element such as a prism.

FIG.4Billustrates a magnification optical system94bfor magnifying the beam diameter of the laser beam LB and irradiating the outer surface72aof the arc chamber72with the laser beam LB, of which the beam diameter is magnified. For example, the magnification optical system94bhas a first lens96cand a second lens96d. By using the magnification optical system94b, the laser beam LB having a small beam diameter D1which is emitted from the laser beam source92can be converted into the laser beam LB having a large beam diameter D2. In this manner, a larger region on the outer surface72aof the arc chamber72can be irradiated with the laser beam LB, and the arc chamber72can be more uniformly heated. A reflective optical element such as a convex mirror or a concave mirror may be used instead of the refractive optical element such as the lens. The irradiation optical system94may include a reduction optical system for reducing the beam diameter. The irradiation optical system94may include a magnification-reduction optical system for magnifying or reducing the beam diameter.

FIG.4Cillustrates a beam shaping optical system94cfor adjusting the cross-sectional intensity distribution of the laser beam LB. The beam shaping optical system94cconverts the laser beam LB having a Gaussian type intensity distribution P1emitted from the laser beam source92into the laser beam LB having a top-hat-like intensity distribution P2. For example, the beam shaping optical system94chas an aspherical lens96ecalled a homogenizer. The beam shaping optical system94cmay be configured to include any desired optical element, and may be configured to include a combination of a plurality of lenses and/or mirrors. The outer surface72aof the arc chamber72is irradiated with the laser beam LB having the top-hat-like intensity distribution P2. In this manner, it is possible to prevent damage to the arc chamber72which is caused by local heating.

The irradiation optical system94may include two of the scanning optical system94a, the magnification optical system94b, and the beam shaping optical system94c, or may include all three of the systems. For example, scanning with the laser beam LB whose beam diameter is magnified by the magnification optical system94band whose cross-sectional intensity distribution is made more uniform by the beam shaping optical system94cmay be performed by using the scanning optical system94a. By combining the three optical systems94ato94cwith each other, a larger region on the outer surface72aof the arc chamber72can be irradiated with the laser beam LB having a more uniform intensity distribution. In this manner, the outer surface72aof the arc chamber72can be still more uniformly heated.

FIGS.5A to5Care views schematically illustrating a configuration example of the laser beam source92, and illustrates a case where the heating device90includes two laser beam sources92aand92b. In the illustrated example, the two laser beam sources92aand92bare both disposed in the outer portion of the vacuum chamber. However, at least one of the two laser beam sources92aand92bmay be disposed in the inner portion of the vacuum chamber.

FIG.5Aillustrates a case where mutually different irradiation ranges C1and C2are irradiated respectively with a first laser beam LB1emitted from the first laser beam source92aand a second laser beam LB2emitted from the second laser beam source92b. Therefore, mutually different regions on the outer surface72aof the arc chamber72are irradiated respectively with the two laser beams LB1and LB2emitted from the two laser beam sources92aand92b. The mutually different irradiation ranges C1and C2are irradiated respectively with the laser beams LB1and LB2by using the two laser beam sources92aand92b. In this manner, a larger region on the outer surface72aof the arc chamber72can be heated.

FIG.5Billustrates a case where mutually overlapping irradiation ranges C3and C4are irradiated respectively with the first laser beam LB1emitted from the first laser beam source92aand the second laser beam LB2emitted from the second laser beam source92b. Therefore, the same region on the outer surface72aof the arc chamber72is irradiated with at least a portion of the laser beam LB1emitted from the laser beam sources92aand at least a portion of the laser beam LB2emitted from the laser beam source92bin an overlapping manner. The overlapping range is irradiated with the laser beams LB1and LB2by using the two laser beam sources92aand92b. Accordingly, for example, it is possible to efficiently heat a part where the temperature is likely to be lowered due to thermal radiation.

FIG.5Cillustrates a case where the outer surface72aof the arc chamber72is irradiated with the first laser beam LB1emitted from the first laser beam source92athrough the vacuum window106, and the outer surface72aof the arc chamber72is irradiated with the second laser beam LB2emitted from the second laser beam source92bthrough an optical fiber96f. In this configuration, for example, the first laser beam LB1can be used to heat a relatively large region on the outer surface72aof the arc chamber72, and the second laser beam LB2can be used to heat a relatively small region on the outer surface72aof the arc chamber72.

A part other than the outer surface72aof the arc chamber72may be irradiated with the laser beam LB emitted from the heating device90. Any desired member that defines the plasma generation chamber78may be irradiated with the laser beam LB, or any desired member exposed inside the plasma generation chamber78may be irradiated with the laser beam LB. An inner wall78aof the plasma generation chamber78may be irradiated with the laser beam LB. At least one of the cathode74and the repeller76may be irradiated with the laser beam LB. The arc chamber72may have an irradiation port for irradiating an inner portion of the plasma generation chamber78with the laser beam LB. An optical fiber may be introduced into an inner portion of the arc chamber72, and the cathode74and the repeller76may be irradiated with the laser beam LB through the optical fiber.

FIG.6is a view schematically illustrating a functional configuration of the control device60according to the embodiment. The control device60includes an ion generation control unit61for controlling an operation of the ion generation device12. The ion generation control unit61includes a power supply control unit62, an electromagnet control unit63, a gas flow rate control unit64, a heating control unit65, a condition storage unit66, and a monitor unit67.

The power supply control unit62controls current values and voltage values of various power supplies such as the filament power supply88a, the cathode power supply88b, and the arc power supply88cwhich are connected to the plasma generation device70. The electromagnet control unit63controls intensity of the magnetic field B by adjusting the current value flowing through the electromagnet that applies the magnetic field B to the plasma generation chamber78. The gas flow rate control unit64controls a flow rate of the source gas supplied from the gas introduction port84.

The heating control unit65controls an operation of the heating device90. The heating control unit65controls turning on/off of the laser beam source92and a power of the laser beam LB. For example, the heating control unit65turns on the laser beam source92when the temperature of the plasma generation chamber78needs to be raised, and turns off the laser beam source92when the temperature of the plasma generation chamber78does not need to be raised. The heating control unit65may control an operation of the irradiation optical system94.

The condition storage unit66stores various parameters for determining operation conditions of the ion generation device12. The condition storage unit66stores operation parameters for realizing implantation conditions such as an ion species, an ion charge state, an ion energy, and an ion current. For example, the condition storage unit66stores the operation parameters such as a filament current, a cathode current, a cathode voltage, an arc current, an arc voltage, a gas flow rate, and an electromagnet current. The power supply control unit62, the electromagnet control unit63, and the gas flow rate control unit64are operated in accordance with the operation parameters stored in the condition storage unit66.

The monitor unit67acquires a measurement value which indicates an operation state of the ion generation device12. For example, the monitor unit67acquires an arc current value of the arc chamber72, a temperature of the arc chamber72, an ion current value of the ion extracted from the ion generation device12. For example, the measurement value acquired by the monitor unit67is used for the heating control unit65to control the operation of the heating device90.

The ion generation control unit61controls density (also referred to as plasma density) of the plasma P generated in the plasma generation chamber78in order to generate the ions having the ion species, the ion charge state, and the ion current in accordance with the implantation conditions. For example, the ion charge state and the ion current of the generated ions can be increased by increasing the plasma density, and the ion charge state and the ion current of the generated ions can be decreased by decreasing the plasma density. In addition, optimum plasma density to realize a desired ion charge state and a desired ion current may vary, in accordance with a kind of the source gas and a kind of the ion to be extracted.

The plasma density inside the plasma generation chamber78is mainly controlled by the arc current, the arc voltage, the gas flow rate, and the magnetic field intensity. For example, the plasma density can be increased by increasing the values of them. Out of these, a magnitude of the arc current generated by the arc discharge inside the plasma generation chamber78and the plasma density inside the plasma generation chamber78substantially correspond to each other. Accordingly, the plasma density is controlled by mainly adjusting the arc current. The magnitude of the arc current can be adjusted by the filament current, the cathode current, the cathode voltage, the arc voltage, the gas flow rate, and the magnetic field intensity. However, in many cases, the magnitude of the arc current is controlled by the cathode voltage having better responsiveness. The plasma density can be controlled also by adjusting the gas flow rate. However, when the gas flow rate is too small or too large, the plasma generation becomes unstable. Therefore, in order to stably generate the plasma, it is necessary that the gas flow rate falls within a predetermined range. Accordingly, it is relatively difficult to adjust the plasma density by changing the gas flow rate.

When the plasma is generated by using the arc discharge, a relatively large amount of electric power needs to be applied to the arc chamber72. Therefore, the arc chamber72has a high temperature (for example, 1,000° C. or higher). The temperature of the arc chamber72is mainly determined by a total amount of the input powers of the filament power supply88a, the cathode power supply88b, and the arc power supply88c. Therefore, when the operation conditions are changed to control the plasma density so that the current values and the voltage values of various power supplies are changed, the temperature of the arc chamber72is also changed in response to a change in an input power amount. Heat capacity of the arc chamber72is relatively large. Accordingly, temperature responsiveness of the arc chamber72is low, and it takes time until the arc chamber72reaches a thermal equilibrium state. Especially in a high temperature state, the heat loss is significant due to the thermal radiation. Accordingly, a required time until the temperature of the arc chamber72is stabilized is lengthened in an operation condition of raising the temperature of the arc chamber72. When the temperature of the arc chamber72is not stabilized, the plasma is also not stably generated in the plasma generation chamber78, and stability of the ions extracted from the ion generation device12is also lowered. Therefore, in the present embodiment, the time until the arc chamber72reaches the thermal equilibrium state is shortened by using the heating device90to promote the temperature raising of the plasma generation chamber78.

When the operation condition of the ion generation device12is switched from a low arc condition to a high arc condition, the heating control unit65turns on the laser beam source92so that the arc chamber72is irradiated with the laser beam LB. Here, the “low arc condition” means an operation condition in which the plasma density in the plasma generation chamber78is relatively low, and means an operation in which the arc chamber72in the thermal equilibrium state has a relatively low temperature since the input power amount is relatively low. On the other hand, the “high arc condition” means an operation condition in which the plasma density in the plasma generation chamber78is relatively high, and means an operation in which the arc chamber72in the thermal equilibrium state has a relatively high temperature since the input power amount is relatively high.

It may be relatively judged that a specific operation condition is either the low arc condition or the high arc condition. For example, it is conceivable to realize a case as follows. As a first operation condition, the plasma density is set to first density. As a second operation condition, the plasma density is set to second density higher than the first density. As a third operation condition, the plasma density is set to third density higher than the second density. In this case, when the operation condition is switched from the first operation condition to the second operation condition, the first operation condition is the “low arc condition” and the second operation condition is the “high arc condition”. On the other hand, when the operation condition is switched from the second operation condition to the third operation condition, the second operation condition is the “low arc condition” and the third operation condition is the “high arc condition”. Judgement that a specific operation condition is either the low arc condition or the high arc condition may be determined by whether or not the input power amount is equal to or higher than a predetermined threshold value.

When the operation condition is switched from the low arc condition to the high arc condition, the heating control unit65may change the operation of the heating device90in accordance with a difference between the operation conditions of the low arc condition and the high arc condition. For example, output power of the laser beam source92may be adjusted in accordance with a difference between the input power amount under the low arc condition and the input power amount under the high arc condition. For example, the power of the laser beam LB may be increased when the difference in the input power amounts is large, and the power of the laser beam LB may be decreased when the difference in the input power amounts is small. The heating control unit65may adjust an irradiation time of the laser beam LB in accordance with the difference in the input power amounts. For example, the heating control unit65may lengthen the irradiation time of the laser beam LB when the difference in the input power amounts is large, and may shorten the irradiation time of the laser beam LB when the difference in the input power amounts is small.

The heating control unit65may control the irradiation condition of the laser beam LB to be variable with a lapse of time, based on the measurement value acquired by the monitor unit67. For example, the power of the laser beam LB may be gradually reduced in response to an increase in the plasma density in the plasma generation chamber78or an increase in the temperature of the plasma generation chamber78. The heating control unit65may reduce the power of the laser beam LB as the arc chamber72approaches the thermal equilibrium state. In this manner, the heating control unit65may prevent the arc chamber72from being overheated. The heating control unit65may turn off the laser beam source92when the ion current of the ion extracted from the ion generation device12is stabilized.

When the operation conditions are switched, the ion generation control unit61may perform a cleaning operation to remove substances accumulated on the inner wall78aof the plasma generation chamber78. The substances corresponding to a kind of the source gas supplied to the plasma generation chamber78is accumulated on the inner wall78aof the plasma generation chamber78as the ion generation device12is operated. When the kind of the source gas is changed to switch the ion species, the substances accumulated on the inner wall78abefore the switching are removed, and the substances corresponding to the kind of the source gas after the switching are accumulated. Accordingly, the substances accumulated on the inner wall78aare replaced. Until the substances accumulated on the inner wall78aare stabilized, a state of the plasma inside the plasma generation chamber78can be changed. Therefore, the ions cannot be stably extracted. By operating the ion generation device12under a cleaning condition, the removal of the substances accumulated on the inner wall78abefore the switching can be promoted, and the time until the substances accumulated on the inner wall78aafter the switching are stabilized can be shortened.

The condition storage unit66may store a cleaning operation condition as one of the operation conditions. Under the cleaning operation condition, in order to promote the removal of the substances accumulated on the inner wall78aof the plasma generation chamber78, the operation parameters are determined for the high arc condition. The cleaning operation condition may be determined so that the plasma density is higher than the other operation conditions. The high density plasma is generated in the plasma generation chamber78under the cleaning operation condition. Accordingly, the plasma can strongly affect the substances accumulated on the inner wall78ato promote the removal of the accumulated substance. In addition, since the cleaning is performed under the high arc condition, the temperature of the plasma generation chamber78can be raised, and the removal of the substances accumulated on the inner wall78acan be promoted by means of evaporation or decomposition. Under the cleaning operation condition, as the source gas, it is desirable to use rare gas (for example, Ar or Xe) or highly reactive fluoride (for example, BF3). When the rare gas is used, it is possible to prevent unnecessary substances from being accumulated on the inner wall78a. In addition, when the highly reactive fluoride is used, the removal of the substances accumulated on the inner wall78acan be promoted.

When the cleaning operation is performed, the heating control unit65may turn on the laser beam source92so that the arc chamber72is irradiated with the laser beam LB. The arc chamber72is heated by using the laser beam LB during the cleaning operation. In this manner, the temperature raising of the plasma generation chamber78can be promoted, and the removal of the substances accumulated on the inner wall78acan be further promoted.

In a state where the plasma is not generated inside the plasma generation chamber78, the heating control unit65may turn on the laser beam source92so that the arc chamber72is irradiated with the laser beam LB. For example, in a state where the plasma generation is stopped, the heating device90may be used to perform the cleaning operation for removing the substances accumulated on the inner wall78a. In this case, the plasma generation may be stopped by stopping the supply of the source gas, or by turning off various power supplies.

In a state where plasma is generated inside the plasma generation chamber78, the heating control unit65may turn on the laser beam source92so that the arc chamber72is irradiated with the laser beam LB. For example, when the operation condition is switched from the low arc condition to the high arc condition, the arc chamber72may be heated by the laser beam LB in a state where the plasma is generated under the high arc condition. In addition, the arc chamber72may be heated by the laser beam LB in a state where the plasma is generated under the cleaning operation condition.

The heating control unit65may control the operation of the heating device90to suppress fluctuations in the temperature of the plasma generation chamber78which are caused by the difference in the arc conditions. For example, the power of the laser beam LB may be increased when the plasma is generated under the low arc condition, and the power of the laser beam LB may be decreased when the plasma is generated under the high arc condition. In this manner, a difference between the temperature of the plasma generation chamber78under the low arc condition and the temperature of the plasma generation chamber78under the high arc condition may be reduced.

When the ion generation device12is started up from a non-operation state to an operation state, the heating control unit65may heat the arc chamber72by irradiating the arc chamber72in a low temperature state having an approximate room temperature with the laser beam LB. In this case, the arc chamber72may be irradiated with the laser beam LB in a state where the plasma is not generated inside the plasma generation chamber78. The plasma generation chamber78is irradiated with and heated by the laser beam LB. In this manner, it is possible to promote the switching from a state where the plasma is not generated inside the plasma generation chamber78to a state where the plasma is generated inside the plasma generation chamber78.

According to the present embodiment, the plasma generation chamber78is heated by using the laser beam LB. In this manner, it is possible to promote the temperature raising of the plasma generation chamber78regardless of the arc condition for generating the plasma. It is possible to intentionally increase the input power amount to the plasma generation chamber78to give priority to the temperature raising of the plasma generation chamber78. However, the input power amount has an upper limit. In addition, when the input power amount is unnecessarily increased, there is a possibility of an adverse effect in that components forming the plasma generation device70may deteriorate. In the present embodiment, the temperature of the plasma generation chamber78can be more flexibly controlled by providing the heating device90independent of various power supplies88ato88cconnected to the plasma generation device70. For example, even when the input power amount optimized from a viewpoint of stably generating the plasma is maintained, the temperature raising of the plasma generation chamber78can be promoted by using the heating device90, and it is possible to shorten a waiting time until a desired operation state is realized. In this manner, it is possible to shorten a non-operation time of the ion implanter10, and to improve productivity of the ion implanter10.

Hitherto, the present invention has been described with reference to the above-described respective embodiments. However, the present invention is not limited to the above-described respective embodiments. Those in which configurations of the respective embodiments are appropriately combined or replaced with each other are also included in the present invention. Based on the knowledge of those skilled in the art, the respective embodiments can be combined with each other, the processing sequences can be appropriately rearranged, or various changes such as design changes can be added to the embodiment. The embodiment having such modifications can also be included in the scope of the present invention.