Ion implanter and ion implantation method

An ion implanter includes a plasma shower device configured to supply electrons to an ion beam with which a wafer is irradiated. The plasma shower device includes a plasma generating chamber provided with an extraction opening, a first electrode which is provided with an opening communicating with the extraction opening and to which a first voltage is applied with respect to an electric potential of the plasma generating chamber, a second electrode which is disposed at a position facing the first electrode such that the ion beam is interposed between the first and second electrodes and to which a second voltage is applied with respect to the electric potential of the plasma generating chamber, and a controller configured to independently control the first voltage and the second voltage to switch operation modes of the plasma shower device.

RELATED APPLICATIONS

Priority is claimed to Japanese Patent Application No. 2017-064492, filed Mar. 29, 2017, the entire content of which is incorporated herein by reference.

BACKGROUND

Technical Field

Certain embodiment of the present invention relates to an ion implanter and an ion implantation method.

Description of Related Art

In a semiconductor manufacturing process, a process of implanting ions into a semiconductor wafer is normally performed in order to change conductivity of the semiconductor wafer, to change a crystal structure of the semiconductor wafer, or the like. In general, a device used in this process is referred to as an ion implanter and is configured to irradiate an ion beam toward a wafer in an implantation process chamber. A charge suppression device such as a plasma shower device is provided in the implantation process chamber in order to prevent a wafer surface from being charged by ion implantation. The plasma shower device supplies electrons to the wafer surface and thus, neutralizes an electric charge accumulated on the wafer surface.

SUMMARY

According to an embodiment of the present invention, there is provided an ion implanter, including: a plasma shower device configured to supply electrons to an ion beam with which a wafer is irradiated, in which the plasma shower device includes a plasma generating chamber provided with an extraction opening from which the electrons supplied to the ion beam are extracted, a first electrode which is provided with an opening communicating with the extraction opening and to which a first voltage is applied with respect to an electric potential of the plasma generating chamber, a second electrode which is disposed at a position facing the first electrode in a state where the ion beam is interposed between the first electrode and the second electrode and to which a second voltage is applied with respect to the electric potential of the plasma generating chamber, and a controller configured to independently control the first voltage and the second voltage to switch operation modes of the plasma shower device.

According to another embodiment of the present invention, there is provided an ion implantation method. This method uses an ion implanter including a plasma shower device configured to supply electrons to an ion beam with which a wafer is irradiated. The plasma shower device includes a plasma generating chamber provided with an extraction opening from which the electrons supplied to the ion beam are extracted, a first electrode which is provided with an opening communicating with the extraction opening and to which a first voltage is applied with respect to an electric potential of the plasma generating chamber, and a second electrode which is disposed at a position facing the first electrode in a state where the ion beam is interposed between the first electrode and the second electrode and to which a second voltage is applied with respect to the electric potential of the plasma generating chamber. In this method, the first voltage and the second voltage are independently controlled to switch operation modes of the plasma shower device according to a beam condition of the ion beam.

DETAILED DESCRIPTION

An electron supply amount required for a plasma shower device is changed according to a beam condition of an ion beam with which a wafer is irradiated. For example, if the beam is a high current beam of approximately 1 to 10 mA, more electron supply amount is required. Meanwhile, if the beam is a low/medium current beam of approximately 10 to 100 JA, the electron supply amount as much as that for the high current beam is not required. Accordingly, in general, in a high current implanter and a low/medium current implanter, plasma shower devices having different specifications are used, respectively. Meanwhile, in a case where one implanter is configured to be able to cover a range from a low/medium current region to a high current region, a plasma shower device capable of realizing an appropriate electron supply amount according to the beam condition is required.

It is desirable to provide a plasma shower device capable of dealing with a wide beam condition.

Aspects of the present invention include arbitrary combinations of the above-described elements and mutual substitutions of elements or expressions of the present invention among apparatuses, methods, systems, or the like.

According to the present invention, it is possible to a plasma shower device capable of dealing with a wide beam condition.

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 below-described configurations are only examples and the scope of the present invention is not limited by the configurations.

FIG. 1is a top view schematically showing an ion implanter10according to an embodiment andFIG. 2is a side view showing the schematic configuration of the ion implanter10.

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

The ion implanter10is configured to reciprocatingly perform scanning in one direction with a beam and reciprocatingly move the wafer W in a direction orthogonal to the one direction such that the entire wafer W is irradiated with an ion beam B. In the present specification, for convenience of explanation, a traveling direction of the ion beam B traveling along a designed beam trajectory is defined as a z direction and a plane perpendicular to the z direction is defined as an xy plane. In a case where the workpiece W 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 reciprocating scanning of the beam is performed in the x direction and the reciprocating movement of the wafer W is performed in the y direction.

The ion implanter10includes an ion source12, a beamline unit14, and an implantation process chamber16. The ion source12is configured to provide the ion beam B to the beamline unit14. The beamline unit14is configured to transport ions from the ion source12to the implantation process chamber16. The ion implanter10includes an evacuation system (not shown) for providing desired vacuum environments to the ion source12, the beamline unit14, and the implantation process chamber16.

For example, the beamline unit14includes a mass analyzer18, a variable aperture20, a beam shaping unit22, a first beam measurement instrument24, a beam scanner26, a parallelizing lens30or a beam parallelizing unit, and an angular energy filter (AEF)34in order from the upstream side. The upstream side of the beamline unit14indicates a side close to the ion source12, and a downstream side thereof indicates a side close to the implantation process chamber16(or beam stopper38).

The mass analyzer18is provided on the downstream side of the ion source12and is configured to select desired ion species from the ions extracted from the ion source12by mass analysis.

The variable aperture20is an aperture of which an opening width can be adjusted, and adjust a beam current of the ion beam B passing through the aperture by changing the opening width. For example, the variable aperture20may include aperture plates which are disposed in upper and lower positions in a state where a beam trajectory is interposed between the aperture plates and may adjust the beam current by changing a gap between the aperture plates.

The beam shaping unit22includes a focusing/defocusing lens such as a quadrupole focusing/defocusing unit (Q lens) and is configured to shape the ion beam B passing through the variable aperture20into a desired cross-sectional shape. The beam shaping unit22is an electric field type three-stage quadrupole lens (referred to as a triplet Q lens), and includes a first quadrupole lens22a, a second quadrupole lens22b, and a third quadrupole lens22cin order from the upstream side. The beam shaping unit22can adjust convergence or divergence of the ion beam B incident into the wafer W independently in each of the x direction and the y direction using the three lens units22a,22b, and22c. The beam shaping unit22may include a magnetic field type lens unit or may include a lens unit which shapes the beam using both an electric field and a magnetic field.

The first beam measurement instrument24is an injector flag Faraday cup which is disposed to be able to move into and out of the beam trajectory and measures a current of the ion beam. The first beam measurement instrument24is configured to be able to measure the beam current of the ion beam B which is shaped by the beam shaping unit22. The first beam measurement instrument24includes a Faraday cup24bwhich measures the beam current and a drive unit24awhich moves the Faraday cup24bvertically. As shown by a dashed line inFIG. 2, in a case where the Faraday cup24bis disposed on the beam trajectory, the ion beam B is blocked by the Faraday cup24b. Meanwhile, as shown by a solid line inFIG. 2, in a case where the Faraday cup24bis removed from the beam trajectory, the blocking of the ion beam B is released.

The beam scanner26is configured to supply the reciprocating scanning of the beam and is a deflector which performs scanning in the x direction with the shaped ion beam B. The beam scanner26includes a pair of scanning electrodes28which is provided to face each other in the x direction. The pair of scanning electrodes28is connected to a variable voltage power supply (not shown), which is periodically changes a voltage applied to the pair of scanning electrodes28to change an electric field generated between electrodes, and thus, the ion beam B is deflected in various angles. In this way, the scanning of the ion beam B is performed over a scanning range in the x direction. InFIG. 1, the scanning direction and the scanning range of the beam are exemplified by an arrow X, and a plurality of trajectories of the ion beam B in the scanning range are shown by chain lines.

The parallelizing lens30is configured to cause the traveling directions of the scanned ion beam B to be parallel with the designed beam trajectory, respectively. The parallelizing lens30includes a plurality of arc-shaped P lens electrodes32having a passing slit for the ion beam which is provided in the center portion of each P lens electrode32. Each of the P lens electrodes32is connected to a high-pressure power supply (not shown) and applies an electric field generated by a voltage application to the ion beam B to parallelize the traveling direction of the ion beam B. The parallelizing lens30may be replaced by another beam parallelizing units, and the beam parallelizing unit may be configured of a magnet unit using a magnetic field. An AD (Acceleration/Deceleration) column (not shown) for accelerating or decelerating the ion beam B may be provided on the downstream side of the parallelizing lens30.

The angular energy filter (AEF)34is configured to analyze an energy of the ion beam B, deflect ions having a desired energy downward, and lead the ions to the implantation process chamber16. The angular energy filter34includes a pair of AEF electrodes36for deflecting by an electric field. The pair of AEF electrodes36is connected to the high-voltage power supply (not shown). InFIG. 2, by applying a positive voltage to the upper AEF electrode and a negative voltage to the lower AEF electrode, the ion beam B is deflected downward. The angular energy filter34may be configured of a magnet unit for deflecting by a magnetic field, or may be configured of a combination of the pair of AEF electrode for deflecting by the electric field and the magnet unit for deflecting by the magnetic field.

In this way, the beamline unit14supplies the ion beam B with which the wafer W is to be irradiated to the implantation process chamber16.

As shownFIG. 2, a platen drive mechanism50holding one or a plurality of wafers W is included in the implantation process chamber16. The platen drive mechanism50includes a wafer holding unit52, a reciprocating motion mechanism54, a twist angle adjustment mechanism56, and a tilt angle adjustment mechanism58. The wafer holding unit52includes an electrostatic chuck or the like for holding the wafer W. The reciprocating motion mechanism54reciprocates the wafer holding unit52in a reciprocating direction (y direction) orthogonal to the beam scanning direction (x direction), and thus, the wafer held by the wafer holding unit52is reciprocated in the y direction. InFIG. 2, the reciprocating motion of the wafer W is exemplified by an arrow Y.

The twist angle adjustment mechanism56is a mechanism which adjusts a rotation angle of the wafer W, and rotates the wafer W with a normal line of a wafer processed surface as a rotation axis so as to adjust 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, an orientation flat or the like which is provided on the outer peripheral portion of the wafer, and is a mark which serves as a reference for an angular position in a crystal axis direction of the wafer or in a circumferential direction of the wafer. As shown in the drawings, the twist angle adjustment mechanism56is provided between the wafer holding unit52and the reciprocating motion mechanism54and is reciprocated together with the wafer holding unit52.

The tilt angle adjustment mechanism58is a mechanism which adjusts an inclination of the wafer W and adjusts a tilt angle between the traveling direction of the ion beam B toward the wafer processed surface and the normal line of the wafer processed surface. In the present embodiment, among inclination angles of the wafer W, an angle having an axis in the x direction as a central axis of the rotation is adjusted as the tilt angle. The tilt angle adjustment mechanism58is provided between the reciprocating motion mechanism54and a side wall of the implantation process chamber16and is configured to rotate the entire platen drive mechanism50including the reciprocating motion mechanism54in an R direction so as to adjust the tilt angle of the wafer W.

The implantation process chamber16includes the beam stopper38. In a case where the wafer W does not exist on the beam trajectory, the ion beam B is incident into the beam stopper38. A second beam measurement instrument44for measuring a beam current or a beam current density distribution of the ion beam is provided in the implantation process chamber16. The second beam measurement instrument44includes side cups40R and40L and a center cup42.

The side cups40R and40L are disposed to be deviated in the x direction with respect to the wafer W and are disposed at positions at which the side cups40R and40L do not block the ion beam directed to the wafer during the ion implantation. The scanning of the ion beam B is performed beyond the range in which the wafer W is positioned, and thus, a portion of the scanning beam is incident into the side cups40R and40L during the ion implantation. Accordingly, the beam current is measured during the ion implantation. The measured values of the side cups40R and40L are sent to the second beam measurement instrument44.

The center cup42measures the beam current or the beam current density distribution on the surface of the wafer W (wafer processed surface). The center cup42is movable, is retracted from a wafer position during the ion implantation, and is inserted into the wafer position when the wafer W is not positioned at an irradiation position. The center cup42measures the beam current while moving the x direction and measures the beam current density distribution in the beam scanning direction. The measured value of the center cup42is sent to the second beam measurement instrument44. The center cup42may be formed in an array shape in which a plurality of Faraday cups are arranged in the x direction such that ion irradiation amounts at a plurality of positions in the beam scanning direction can be measured at the same time.

A plasma shower device60which supplies electrons to the ion beam B is provided in the implantation process chamber16. The plasma shower device60includes a plasma generating chamber62and a shower tube70. The plasma shower device60is configured to generate plasma in the plasma generating chamber62, extract the electrons from the plasma, and supply the electrons into the shower tube70through which the ion beam B passes toward the wafer W.

FIGS. 3 and 4are sectional views showing a configuration of the plasma shower device60according to an embodiment.FIG. 3shows a cross section when viewed from the x direction andFIG. 4shows a cross section when viewed from the y direction. The plasma shower device60includes the plasma generating chamber62, a suppression electrode68, the shower tube70, a controller86, and various power supplies.

The plasma generating chamber62has an approximately rectangular parallelepiped box shape and has an elongated shape in the scanning direction of the ion beam B (x direction). An antenna66to which a radio frequency (RF) voltage is applied is provided inside the plasma generating chamber62. A source gas is introduced to the inside of the plasma generating chamber62and plasma P is generated by a radio frequency electric field caused by the antenna66. A magnet unit (not shown) for generating a cusp magnetic field which confines the plasma P is provided in a wall of the plasma generating chamber62. An extraction opening64is provided in the plasma generating chamber62and the electrons are extracted from the plasma P through the extraction opening64.

The shower tube70is provided to be adjacent to the extraction opening64of the plasma generating chamber62. The shower tube70has a rectangular tube shape and is disposed such that the ion beam B passes through the inside of the rectangular tube. The shower tube70includes a first electrode71which has an opening74communicating with the extraction opening64, a second electrode72which faces the first electrode71in the y direction in a state where the ion beam B is interposed between the first electrode71and the second electrode72, and third electrodes73(73L and73R) which face each other in the x direction in a state where the ion beam B is interposed between the third electrodes73. As shown inFIG. 4, the opening74provided in the first electrode71is formed to extend in the x direction over the scanning range of the ion beam B. The extraction opening64of the plasma generating chamber62is similar to the opening74.

The suppression electrode68is provided on the upstream side of the shower tube70. Similarly to the shower tube70, the suppression electrode68has a rectangular tube shape and is disposed such that the ion beam B passes through the inside of the rectangular tube. The suppression electrode68is connected to a suppression power supply78, and a negative voltage is applied to the suppression electrode68with respect to an electric potential of the plasma generating chamber62. The suppression electrode68prevents the electrons extracted from the plasma generating chamber62from escaping to the upstream side from the plasma shower device60.

The plasma generating chamber62is connected to an extraction power supply80and an extraction voltage is applied to the plasma generating chamber62by the extraction power supply80. The first electrode71is connected to a first power supply81and a first voltage is applied to the first electrode71with respect to the electric potential of the plasma generating chamber62. The second electrode72is connected to a second power supply82and a second voltage is applied to the second electrode72with respect to the electric potential of the plasma generating chamber62. The third electrode73is connected to a third power supply83and a third voltage is applied to the third electrode73with respect to the electric potential of the plasma generating chamber62.

FIG. 4shows the scanning range of the ion beam B in the x direction. As shown inFIG. 4, an irradiation region C1in which the wafer W is positioned and non-irradiation regions C2outside the irradiation region C1are scanned with the ion beam B. Beams B1directed to the irradiation region C1are implanted into the wafer W. Meanwhile, beams B2directed to the non-irradiation regions C2are incident into the side cups40L and40R on the downstream side of the shower tube70.

The shower tube70is disposed to cover both of the irradiation region C1and the non-irradiation regions C2, and is configured to be able to supply the electrons to both of the beams B1toward the wafer W and the beams B2toward the side cups40L and40R. Outer cases of the side cups40L and40R are connected to a fourth power supply84and a fourth voltage is applied to the outer cases with respect to the electric potential of the plasma generating chamber62.

The controller86is configured to independently control the voltages of the various power supplies of the plasma shower device60so as to switch operation modes of the plasma shower device60. The controller86switches the operation mode according to a beam condition such as a current value, an energy, and an ion species of the ion beam B with which the wafer W is irradiated.

Preferably, the amount of the electrons supplied from the plasma shower device60to the ion beam B is adjusted according to an amount of a positive electric charge on the wafer W accumulated by the irradiation of the ion beam B. For example, in a case where the current of the ion beam B is large, the amount of the positive electric charge accumulated on the wafer W increases, and thus, it is necessary to supply more electrons from the plasma shower device60. Meanwhile, in a case where the current of the ion beam B is small, if a large amount of electrons is supplied from the plasma shower device60, a negative electric charge is accumulated on the wafer W, and thus, it is preferable to decrease the electron supply amount.

For example, the ion implanter10according to the present embodiment is configured to be able to cover a range from a low current of approximately 10 μA to a high current of approximately 10 mA. Therefore, it is preferable that the electron supply amount generated by the plasma shower device60can be adjusted over a large range in accordance with a change in the beam current which extends over approximately three-digit range. For example, if the density of the plasma P generated in the plasma generating chamber62can be freely adjusted, the electron supply amount may be adjusted flexibly. However, in general, it is not easy to greatly change the density of the plasma P. This is because it is necessary to keep a certain degree of the density of the plasma P in order to stably generate the plasma P and it is difficult to stably supply electrons while extremely reducing the density of the plasma P.

The plasma shower device60supplies not only the electrons from the plasma P but also ions included in the plasma P. Some of the ions extracted from the plasma shower device60flow into the side cups40L and40R and affect measurement results. If the current of the ion beam B is large and the inflow of the ions due to the plasma shower device60is small enough to be negligible, there is no particular problem. However, in a case where the current of the ion beam B is low, the influx of ions extracted from the plasma shower device60affects the measurement results, and deteriorates measurement accuracy of the beam current.

Accordingly, in the present embodiment, the operation modes can be switched between a first mode in which the electron supply amount generated by the plasma shower device60increases and a second mode in which the ion flowing from the plasma shower device60into the side cups40L and40R decreases. Particularly, in the second mode for a low/medium e current, the electrons can be supplied while the ion supply from the plasma shower device60is minimized, and thus, it is possible to prevent the measurement accuracy from being deteriorated due to the ions from the plasma shower device60while suppressing charging of the wafer W.

FIG. 5is a view schematically showing the plasma shower device60which is operated in the first mode. In the first mode, the first voltage, the second voltage, the third voltage and the fourth voltage are controlled to be negative. The magnitude (absolute value) of each of the first voltage, the second voltage, the third voltage, and the fourth voltage is 0.1 V to 50 V, and, for example, is 1 V to 20 V. In an example, the extraction voltage applied by the extraction power supply80is −5 V, and each of the first voltage, the second voltage, the third voltage, and the fourth voltage is −3 V. A suppression voltage applied by the suppression power supply78is approximately −40 V to −50 V, and for example, is −48 V. The voltages of the first voltage, the second voltage, the third voltage, and the fourth voltage need not be the same, and at least one voltage of them may be different from the other voltages.

The electrons supplied to the ion beam B are extracted from the plasma P in the plasma generating chamber62mainly by a beam potential of the ion beam B. Since the ion beam B consists of ions having a positive electric charge, the electrons are extracted from the plasma P by a positive space charge generated by the ion beam B. In the first mode, a negative voltage is applied to the shower tube70based on the electric potential of the plasma generating chamber62, and thus, the electrons are repelled by an inner surface of the shower tube70, and the extracted electrons are efficiently supplied to the ion beam B. A negative voltage is also applied to the outer cases of the side cups40, and thus, the electrons can be prevented from flowing into the outer cases of the side cups40, and the electrons can be efficiently supplied to the beams also at both ends of the beam scanning in the x direction.

FIG. 6is a view schematically showing a behavior of ions supplied from the plasma shower device60in the first mode. In the first mode, a negative voltage is applied to the shower tube70, and thus, the first electrode71functions as an extraction electrode which extracts the ions from the plasma P in the plasma generating chamber62. As a result, not only the electrons but also the ions are extracted from the plasma generating chamber62. In a case where the ions are extracted together with the electrons from the plasma generating chamber62, the space charge in the vicinity of the extraction opening64is neutralized by the ions, and thus, the electrons can be effectively extracted. In this way, in the first mode, the electron supply amount to the ion beam B can be maximized. Meanwhile, some of the extracted ions flow into the side cups40, and thus, in a situation where the ion beam B detected by the side cups40is relatively small, they affects the measurement accuracy of the side cup40, and the measurement accuracy of the side cup40deteriorates.

FIG. 7is a view schematically showing the plasma shower device60which is operated in the second mode. In the second mode, while the first voltage of the first electrode71, the third voltage of the third electrodes73, and the fourth voltage of the outer cases of the side cups40are controlled to be positive, the second voltage of the second electrode72is controlled to be negative. In an example, the extraction voltage applied by the extraction power supply80is −7 V, and each of the first voltage, the third voltage, and the fourth voltage is +10 V, and the second voltage is −10 V. The suppression voltage applied by the suppression power supply78is approximately −40 V to −50V, and for example, is −48 V. The voltages of the first voltage, the third voltage, and the fourth voltage need not be the same, and at least one voltage of them may be different from the other voltages.

In the second mode, the first electrode71is positive with respect to the electric potential of the plasma generating chamber62, and thus, the extraction of the ions from the plasma generating chamber62is suppressed. Even in a case where some ions are extracted through the extraction opening64, the second electrode72has a negative voltage, and thus, the extracted ions mainly flow into the second electrode72. The outer cases of the side cups40have a positive voltage, and thus, the extracted ions are not easily directed to the side cups40. As a result, the amount of the ions directed from the plasma shower device60toward the side cups40decreases, and thus, it is possible to suppress the deterioration in the measurement accuracy of the ion beam B.

In the second mode, the current of the ion beam B is relatively small, and thus, the amount of the electrons extracted from the plasma P by the beam potential becomes small. The ions are not easily extracted from the plasma P, and thus, the electrons are easily accumulated in the vicinity of the extraction opening64, and an extraction amount of the electrons decreases by the space charge effect. Accordingly, in the second mode, even in a state where the plasma P is stably generated, the electron supply amount can be much smaller than that in the first mode, and it is possible to supply the amount of the electrons matched to the low/medium current beam.

In the present embodiment, the first voltage to be applied to the first electrode71can be determined from the viewpoints of the ion supply from the plasma generating chamber62, the electron supply from the plasma generating chamber62, and the prevention of the inflow of the electrons into the shower tube70. The ion supply amount and the electron inflow prevention effect tend to increase when the first electrode71is set to have a negative voltage and tend to decrease when the first electrode71is set to have a positive voltage. The electron supply amount tends to increase when the first electrode71is set to have a negative voltage having a small absolute value and tends to decrease when the first electrode71is set to have a negative voltage having a large absolute value or a positive voltage. It is preferable that the first voltage of the first electrode71is determined taking these factors into consideration.

The second voltage to be applied to the second electrode72can be determined from the viewpoints of the prevention of the inflow of the electrons into the shower tube70and ion absorption into the shower tube70. The electron inflow prevention effect and the ion absorption capability increases when the second electrode72is set to have a negative voltage and decreases when the second electrode72is set to have a positive voltage. Accordingly, it is preferable that a negative voltage is applied to the second electrode72and that the magnitude of the negative voltage is determined according to required levels of electron inflow prevention effect and the ion absorption capacity.

Third voltage to be applied to the third electrodes73can be determined from the viewpoints from the ion supply from the plasma generating chamber62, the electron supply from the plasma generating chamber62, the prevention of the inflow of the electrons into the shower tube70, and the ion absorption into the shower tube70. The relationship between the third voltage and these effects is similar in the cases of the first electrode and second electrode described above. It is preferable that the third voltage of the third electrodes73is determined taking the factors described above into consideration.

The fourth voltage to be applied to the outer cases of the side cups40can be determined from the viewpoints of the prevention of the inflow of the electrons into the outer cases of the side cups40and the prevention of the inflow of the ions into the side cups40. The electron inflow prevention effect increases when the fourth voltage is set to have a negative voltage and decreases when the fourth voltage is set to have a positive voltage. Meanwhile, the ion inflow prevention effect increases when the fourth voltage is set to have a positive voltage and decreases when the fourth voltage is set to have a negative voltage. Accordingly, it is preferable that the fourth voltage to be applied to the outer cases of the side cups40is determined taking these factors into consideration.

In the above-described embodiment, the case is described, in which separate power supplies are respectively connected to the first electrode71, the second electrode72, the third electrodes73, and the outer cases of the side cups40. In a modification example, the same power supply may be used for electrodes with common applied voltages. For example, the first power supply81may be connected to the first electrode71, the third electrodes73, and the outer cases of the side cups40, and the second power supply82may be connected to the second electrode72.

In the above-described embodiment, the case is described, in which some power supplies are connected between the plasma generating chamber62and the shower tube70and the other power supply is connected between the plasma generating chamber62and the outer cases of the side cups40with respect to the electric potential of the plasma generating chamber62to which the extraction power supply80is connected. In a modification example, one end of each of the first power supply81, the second power supply82, and the third power supply83connected to the shower tube70and one end of the fourth power supply84connected to the outer cases of the side cups40may be connected to the ground, and the voltage of each electrode of the shower tube70and the voltage of the outer cases of the side cups40may be controlled with respect to the ground electric potential. Also in this case, it is preferable that a positive or a negative voltage is controlled to be applied to each electrode of the shower tube70and the outer cases of the side cups40with respect to the electric potential of the plasma generating chamber62.

In the above-described embodiment, the case is described, in which a negative voltage is applied to the third electrode73in the first mode and a positive voltage is applied to the third electrode73in the second mode such that polarities of the voltages of the first electrode71and the third electrodes73are the same as each other. In a modification example, polarities of the voltages of the second electrode72and the third electrodes73may be the same as each other, a negative voltage may be applied to the third electrodes73also in the first mode, and a negative voltage may be applied to the third electrode73in the second mode.

In the above-described embodiment, the first electrode71and the third electrode73may be configured to be electrically connected to each other, and for example, the first electrode71and the third electrode73may be integrally configured. Meanwhile, the second electrode72and the third electrodes73are electrically insulated, and insulating members are provided between the second electrode72and the third electrodes73. In a modification example, the second electrode72and the third electrodes73may be configured to be electrically connected to each other, and insulating members may be provided between the first electrode71and the third electrodes73. Insulating members may be provided between the first electrode71and the third electrodes73and between the second electrode72and the third electrodes73.

The shower tube70may not have the third electrodes73while having the first electrode71and the second electrode72.

The side cups40may be provided to be separated away from the shower tube70. Different voltages according to the operation modes may not be applied to the outer cases of the side cups40, and the voltage may be fixed to be a ground electric potential, for example.

In the above-described embodiment, the case is described, in which the voltage of each electrode of the shower tube70is set to have a positive voltage or a negative voltage with respect to the plasma generating chamber62. In a modification example, the voltage of at least one of electrodes may be the same as that of the plasma generating chamber62in an operation mode.

The controller86may control a voltage of another structure disposed in the vicinity of the shower tube70. For example, the another structure disposed in the vicinity of the shower tube70may be set to have a negative voltage in the first mode and may be set to have a positive voltage in the second mode, with respect to the electric potential of the plasma generating chamber62is.