Ion source, ion implantation apparatus, and ion implantation method

Abstract

The present invention provides an ion source capable of rapidly increasing the current value of an Al ion beam to a predetermined value, and an ion implantation apparatus equipped therewith. [Solution] An ion source according to one embodiment of the present invention comprises a chamber, a cathode electrode, a raw material block, a filament, a repeller electrode, a gas supply unit, and a control unit. The raw material block and the repeller electrode are composed of an aluminum compound. The gas supply unit has a first gas introduction line for introducing a first reactive gas consisting of a fluorine-based gas that generates positively charged aluminum ions through reaction with the raw material block, and a second gas introduction line for introducing a second reactive gas consisting of a nitrogen-based gas that generates positively charged nitrogen ions. The control unit is configured to execute a first control mode for generating aluminum ions in the chamber and a second control mode for generating nitrogen ions in the chamber.

Description

Technical Field

[0001] The present invention relates to an ion source, an ion implantation apparatus, and an ion implantation method.

Background Art

[0002] An ion implantation apparatus for SiC power devices generates Al (aluminum) as a p-type dopant with an ion source and implants the generated Al ions into a SiC substrate. On the other hand, when generating N (nitrogen) ions as an n-type dopant, N2 gas is generally used.

[0003] When generating Al ions, a method of reacting AlN (aluminum nitride) with a fluorine-based gas (e.g., PF3 gas) to generate aluminum ions is known. For example, in Patent Document 1, an ion implantation apparatus including an ion source having a cathode electrode disposed at one end in the uniaxial direction in a chamber, a raw material block made of AlN disposed around the cathode electrode, a filament for heating the cathode electrode, and a repeller electrode disposed at the other end in the uniaxial direction in the chamber so as to face the cathode electrode is disclosed.

[0004] In the above ion source, the cathode electrode heated by the filament emits thermoelectrons toward the repeller electrode, and the thermoelectrons reciprocate between the cathode electrode and the repeller electrode to decompose the PF3 gas introduced into the chamber to generate plasma, and fluorine in the plasma reacts with the raw material block made of AlN to generate positively charged aluminum ions.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When irradiating a substrate with an Al ion beam and a N ion beam by switching between them using the ion source described in Patent Document 1, the ions generated in the ion source can be switched from Al ions to N ions, or from N ions to Al ions, by using different reactive gases, PF3 gas and N2 gas, introduced into the chamber of the ion source. By introducing Ar (argon) gas into the ion source instead of the reactive gas, the inside of the chamber can be cleaned.

[0007] However, there is a problem in that when the ion source operation is switched back to Al ion beam generation after switching from Al ion beam generation to N ion beam generation or Ar cleaning, the Al ion beam cannot be increased to a predetermined current value in a short time. This is thought to be because, with discharge using gases such as N2 or Ar, no reaction occurs with the AlN raw material block, and sputtering particles (typically particles of high-melting-point metals such as W, Mo, and Ta) mainly from the repeller electrode accumulate on the surface of the raw material block, and these deposits inhibit the reaction between the PF3 gas and the raw material block during Al ion generation.

[0008] In view of the above circumstances, the object of the present invention is to provide an ion source, an ion implantation apparatus, and an ion implantation method that can suppress the deposition of metal particles on the surface of a raw material block by discharge using a gas such as N2, and can quickly increase the Al ion beam to a predetermined current value after switching to an Al ion beam. [Means for solving the problem]

[0009] An ion source according to one embodiment of the present invention comprises a chamber, a cathode electrode, a raw material block, a filament, a repeller electrode, a gas supply unit, and a control unit. The cathode electrode is positioned at one end of the chamber in a uniaxial direction. The raw material block is positioned around the cathode electrode, but not in contact with the cathode electrode or the chamber, and is made of an aluminum compound. The filament is positioned on the back side of the cathode electrode, and by heating the cathode electrode, thermionic electrons are emitted from the surface of the cathode electrode. The repeller electrode is positioned at the other end of the chamber in the uniaxial direction so as to face the surface of the cathode electrode. The repeller electrode is made of an aluminum compound and causes thermionic electrons emitted from the surface of the cathode electrode to reciprocate in the uniaxial direction within the chamber. The gas supply unit has a first gas introduction line and a second gas introduction line. The first gas introduction line introduces a first reactive gas, consisting of a fluorine-based gas, into the chamber to generate positively charged aluminum ions through reaction with the raw material block. The second gas introduction line introduces a second reactive gas, consisting of a nitrogen-based gas, into the chamber to generate positively charged nitrogen ions. The control unit is configured to perform a first control mode in which aluminum ions are generated by introducing the first reactive gas into the chamber, and a second control mode in which nitrogen ions are generated by introducing the second reactive gas into the chamber.

[0010] Because the repeller electrode of the above ion source is made of an aluminum compound, it can suppress the deposition of metal particles on the surface of the raw material block during N2 gas discharge compared to cases where the repeller electrode is made of metal. As a result, the Al ion beam can be rapidly increased to a predetermined current value after switching to the Al ion beam.

[0011] The first reactive gas is, for example, phosphorus trifluoride gas. The second reactive gas is, for example, nitrogen trifluoride gas, or a mixture of nitrogen and nitrogen trifluoride gas.

[0012] The aluminum compound is typically aluminum nitride.

[0013] The gas supply unit may further include a third gas introduction line for introducing argon gas into the chamber. The control unit may be configured to perform a third control mode in which the chamber is cleaned by introducing argon gas into the chamber.

[0014] An ion implantation apparatus according to one embodiment of the present invention comprises an ion source, an extraction electrode for drawing out ions generated in the ion source, a mass spectrometer for mass spectrometry of the ions drawn out from the ion source, and an implantation chamber capable of accommodating a substrate to which the mass-spectr'd ions are irradiated. The ion source comprises a chamber, a cathode electrode, a raw material block, a filament, a repeller electrode, a gas supply unit, and a control unit. The cathode electrode is positioned at one end of the chamber in a uniaxial direction. The raw material block is positioned around the cathode electrode, but not in contact with the cathode electrode or the chamber, and is made of an aluminum compound. The filament is positioned on the back side of the cathode electrode, and by heating the cathode electrode, thermionic electrons are emitted from the surface of the cathode electrode. The repeller electrode is positioned at the other end of the chamber in the uniaxial direction so as to face the surface of the cathode electrode. The repeller electrode is made of an aluminum compound and causes thermionic electrons emitted from the surface of the cathode electrode to reciprocate in the uniaxial direction within the chamber. The gas supply unit has a first gas introduction line and a second gas introduction line. The first gas introduction line introduces a first reactive gas, consisting of a fluorine-based gas, into the chamber to generate positively charged aluminum ions through reaction with the raw material block. The second gas introduction line introduces a second reactive gas, consisting of a nitrogen-based gas, into the chamber to generate positively charged nitrogen ions. The control unit is configured to execute a first control mode in which the aluminum ions are generated by introducing the first reactive gas into the chamber, and a second control mode in which the nitrogen ions are generated by introducing the second reactive gas into the chamber.

[0015] An ion implantation method according to an embodiment of the present invention is an ion implantation method using the ion source, execute a first control mode in which the aluminum ions are generated by introducing the first reactive gas into the chamber, execute a second control mode in which the nitrogen ions are generated by introducing a mixed gas of nitrogen and nitrogen trifluoride gas as the second reactive gas into the chamber, execute the first control mode again by introducing the first reactive gas into the chamber.

[0016] In the second control mode, the nitrogen ions may be generated by introducing nitrogen as the second reactive gas, and the mixed gas of nitrogen and nitrogen trifluoride gas may be introduced into the chamber immediately before switching from the second control mode to the first control mode.

Advantages of the Invention

[0017] According to the present invention, it is possible to suppress the deposition of metal particles on the surface of the raw material block due to discharge using a gas such as N2 or Ar. Thereby, after switching to the Al ion beam, the Al ion beam can be quickly increased to a predetermined current value.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic configuration diagram showing the whole of an ion implantation apparatus provided with an ion source according to an embodiment of the present invention. [Figure 2] It is a schematic side sectional view for explaining the internal structure of the chamber constituting the ion source.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0020] [Ion Implantation Device] FIG. 1 is a schematic configuration diagram showing the overall ion implantation device 100 including an ion source 10 according to an embodiment of the present invention.

[0021] As shown in FIG. 1, the ion implantation device 100 of the present embodiment includes an ion source 10, a traveling chamber 2, a mass spectrometer 3, an accelerator 4, a scanner 5, an implantation chamber 6, and a control unit 15. The ion implantation device 100 is configured such that the ion source 10, the traveling chamber 2, the mass spectrometer 3, the accelerator 4, the scanner 4, and the implantation chamber 6 are connected in this order.

[0022] The ion source 10 has a chamber 11 and a gas supply unit 12. The chamber 11, the traveling chamber 2, the accelerator 4, and the implantation chamber 6 are evacuated by vacuum exhaust devices 9a to 9d so as to be able to maintain a predetermined reduced-pressure atmosphere respectively.

[0023] The ion source 10 generates positively charged ions using the gas supplied by the gas supply unit 12. The ion source 10 generates different ions depending on the type of gas supplied from the gas supply unit 12. As will be described later, the ion source 10 is configured to be able to generate positively charged aluminum ions and positively charged nitrogen ions.

[0024] The positively charged ions generated in the ion source 10 are drawn into the inside of the traveling chamber 2, travel inside the traveling chamber 2, and enter the inside of the mass spectrometer 3. The positively charged ions that enter the inside of the mass spectrometer 3 are mass-analyzed when passing through the mass spectrometer 3, and only the ions having a desired mass-to-charge ratio enter the accelerator 4. The ions that enter the accelerator 4 are accelerated to a predetermined energy to form an ion beam, and the traveling direction is controlled by the scanner 5 and enters the inside of the implantation chamber 6.

[0025] Inside the injection chamber 6, multiple (two in this case) substrates 8 are arranged. The substrates 8 are, for example, SiC substrates. The ion beam is scanned by the scanner 5 toward one of the multiple substrates 8 and irradiated onto the surface of that substrate 8, thereby implanting ions into the surface of the substrate 8.

[0026] The control unit 15 comprehensively controls each part of the ion implanter 100. As will be described later, the control unit 15 is configured to selectively execute a first control mode that generates aluminum ions (hereinafter also referred to as Al ions) as p-type dopants in the chamber 11, and a second control mode that generates nitrogen ions (hereinafter also referred to as N ions) as n-type dopants.

[0027] The control unit 15 can be implemented using hardware elements used in computers, such as a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory), as well as the necessary software. Instead of the CPU, or in addition to it, a PLD (Programmable Logic Device) such as an FPGA (Field Programmable Gate Array), a DSP (Digital Signal Processor), or other ASICs (Application Specific Integrated Circuits) may be used.

[0028] (Ion source) Next, we will describe the details of the ion source 10. Figure 2 is a schematic side cross-sectional view illustrating the internal structure of the chamber 11.

[0029] As described above, the ion source 10 includes a chamber 11 and a gas supply unit 12. The chamber 11 is located inside a container 13 that is maintained in a vacuum atmosphere and connected to the traveling chamber 2. The chamber 11 forms a reaction chamber R that generates ions corresponding to the type of reactive gas supplied from the gas supply unit 12. The inside of the chamber 11 and the container 13 that houses it are evacuated to a vacuum atmosphere by the vacuum evacuation device 9a shown in Figure 1.

[0030] Chamber 11 has a first end face 31 and a second end face 32 that face each other in a uniaxial direction (vertical direction in Figure 2). Inside the chamber 11, the filament 20 is located near the first end face 31, and the repeller electrode 23 is located near the second end face 32. The filament 20 is located in a vacuum atmosphere outside the chamber 11.

[0031] The cathode electrode 22 is positioned inside the chamber 11, between the filament 20 and the repeller electrode 23, and close to the filament 20. In other words, the cathode electrode 22 is positioned on the first end face 31 side. The filament 20 is positioned on the back side of the cathode electrode 22, and the repeller electrode 23 is positioned on the second end face 32 side, facing the surface of the cathode electrode 22. The cathode electrode 22 and the repeller electrode 23 are flat or columnar in shape, and their opposing surfaces are parallel. In this embodiment, the repeller electrode 23 is made of an aluminum compound, as will be described later.

[0032] A base plate 30 is positioned outside the chamber 11, near the first end face 31 close to the filament 20. The base plate 30 is insulated from the chamber 11 and fixed to the chamber 11 by a support mechanism (not shown). The base plate 30 is an annular plate member having hollow portions 30a that allow both ends of the filament 20 to be drawn out to the outside.

[0033] The base plate 30 is electrically conductive and is integrally connected to the raw material support 26 that supports the raw material block 28 (described later) and the electrode support 33 that supports the cathode electrode 22. The raw material support 26 and the electrode support 33 are electrically conductive cylindrical members and are inserted through a through hole 47 provided in the first end face 31 of the chamber 11. The cathode electrode 22 is attached to the tip of the electrode support 33. The electrode support 33 and the cathode electrode 22 may be an integrated structure.

[0034] The second end face 32 is provided with a through hole 48 through which a support rod 36 supporting the repeller electrode 23 is inserted. The tip of the support rod 36 is positioned inside the chamber 11, and the repeller electrode 23 is fixed to it. The end of the support rod 36 opposite to the tip is positioned outside the chamber 11. The support rod 36 is fixed to the chamber 11 by an insulator 41, and the support rod 36 and the chamber 11 are insulated. As a result, the repeller electrode 23 is at a floating potential.

[0035] The raw material support 26 is positioned between the edge of the through-hole 47 and the electrode support 33, in a non-contact manner with the chamber 11 and the electrode support 33. A raw material block 28, formed from a solid aluminum compound in a predetermined shape, is attached to the tip of the raw material support 26. In this case, the aluminum compound is aluminum nitride (AlN). The electrode support 33 and the raw material support 26 are electrically conductive and are at the same potential as the base plate 30, so the cathode electrode 22 and the raw material block 28 are also at the same potential as the base plate 30.

[0036] The raw material block 28 is positioned between the side surface of the cathode electrode 22 and the inner surface 25 of the chamber 11, without contact with either the cathode electrode 22 or the chamber 11. Of the surface of the raw material block 28, the evaporation surface 28a, which is the surface facing the repeller electrode 23 spaced apart from the raw material block 28, is flat and formed parallel to the mutually parallel surfaces of the cathode electrode 22 and the repeller electrode 23.

[0037] If we call the surface of the cathode electrode 22 facing the repeller electrode 23 the electron emission surface 22a, then the plane on which the evaporation surface 28a of the raw material block 28 is located is situated between the surface of the repeller electrode 23 facing the cathode electrode 22 and the electron emission surface 22a of the cathode electrode 22. In other words, the evaporation surface 28a is positioned such that the distance between the plane on which the evaporation surface 28a is located and the repeller electrode 23 is smaller than the distance between the electron emission surface 22a and the repeller electrode 23.

[0038] The raw material block 28 is ring-shaped with a window hole 28b formed in the center. The electron emission surface 22a of the cathode electrode 22 is positioned inside the window hole 28b so as to be exposed toward the repeller electrode 23. Here, the shape of the window hole 28b is circular, the shape of the cathode electrode 22 is disc-shaped, and the diameter of the window hole 28b is larger than the diameter of the cathode electrode 22.

[0039] Outside the chamber 11 are a discharge power supply 52, a cathode heating power supply 53, and a filament heating power supply 54. The discharge power supply 52, cathode heating power supply 53, and filament heating power supply 54 are all DC power supplies.

[0040] The chamber 11 is electrically connected to the positive voltage terminal of the discharge power supply 52. ​​The raw material support 26 is electrically connected to the negative voltage terminal of the discharge power supply 52, and the negative voltage terminal of the discharge power supply 52 is connected to the base plate 30 and the electrode support 33 via this raw material support 26. Therefore, when the discharge power supply 52 is operating, a negative voltage is applied to the cathode electrode 22 and the raw material block 28 relative to the chamber 11.

[0041] The positive voltage terminal of the cathode heating power supply 53 is electrically connected to the negative voltage terminal of the discharge power supply 52. ​​The negative voltage terminal of the cathode heating power supply 53 is electrically connected to one end of the filament 20. When the cathode heating power supply 53 is operating, a negative voltage is applied to the filament 20 relative to the cathode electrode 22. In addition, the aforementioned one end of the filament 20 is electrically connected to the negative voltage terminal of the cathode heating power supply 53 and the negative voltage terminal of the filament heating power supply 54, and the other end of the filament 20 is electrically connected to the positive voltage terminal of the filament heating power supply 54.

[0042] The cathode electrode 22, repeller electrode 23, and filament 20 are placed in a vacuum atmosphere. When the filament heating power supply 54 is activated and the filament 20 is energized in the vacuum atmosphere, the filament 20 generates heat. In this state, when a negative voltage is applied to the filament 20 relative to the cathode electrode 22 by the cathode heating power supply 53, thermionic electrons are emitted from the filament 20 toward the cathode electrode 22. When these thermionic electrons collide with the cathode electrode 22, the cathode electrode 22 is heated.

[0043] The cathode electrode 22 is made of a high-melting-point metal and is heated to a temperature of approximately 2200°C by the filament 20. The raw material block 28 is positioned near the cathode electrode 22 but not in contact with it, and also not in contact with the chamber 11. Therefore, the raw material block 28 is heated and its temperature rises by the heat rays emitted from the cathode electrode 22, without heat flowing into the chamber 11.

[0044] As described above, of the surfaces of the raw material block 28, the evaporation surface 28a facing the spaced-apart repeller electrode 23 is positioned closer to the repeller electrode 23 than the electron emission surface 22a of the cathode electrode 22. In addition to means for adjusting the temperature of the cathode electrode 22, the raw material block 28 is heated to a temperature range of 1200°C to 1700°C by adjusting the distance between the evaporation surface 28a facing the repeller electrode 23 and the electron emission surface 22a of the raw material block 28 in the direction perpendicular to the electron emission surface 22a, the distance between the raw material block 28 and the side surface of the cathode electrode 22, and the distance between the raw material block 28 and the inner surface 25 of the chamber 11.

[0045] With a negative voltage applied to the cathode electrode 22 relative to the chamber 11 by the discharge power supply 52, when the cathode electrode 22 is heated, thermionic electrons are emitted from the electron emission surface 22a of the cathode electrode 22 toward the repeller electrode 23 and accelerated. The repeller electrode 23, which is at a floating potential, has the same negative potential as the cathode electrode 22, and thermionic electrons (hereinafter referred to as primary electrons) emitted and accelerated from the cathode electrode 22 have their direction of flight reversed by electrostatic force and fly toward the cathode electrode 22. Primary electrons that have gone toward the cathode electrode 22 also have their direction of flight reversed by the cathode electrode 22 and reverse toward the repeller electrode 23. In this way, primary electrons repeatedly move back and forth between the cathode electrode 22 and the repeller electrode 23 along the axial direction (up and down direction) of the chamber 11.

[0046] Outside the chamber 11, a first magnet 58 is positioned with one of its two magnetic poles (N pole and S pole) pointed towards the chamber 11, and a second magnet 59 is positioned with the other magnetic pole pointed towards the chamber 11. The first magnet 58 and the second magnet 59 are positioned so that the magnetic field lines formed between their N and S poles penetrate the cathode electrode 22 and the repeller electrode 23. As a result, primary electrons move back and forth while spiraling around the magnetic field lines. These actions increase the probability of collisions between the gas introduced into the chamber 11 and the electrons moving back and forth between the cathode electrode 22 and the repeller electrode 23, thereby increasing the plasma generation efficiency.

[0047] The side of the chamber 11 is provided with a gas inlet 34 and an ion outlet 35.

[0048] The gas inlet 34 is connected to the gas supply unit 12. The gas supply unit 12 has a first gas inlet line L1, a second gas inlet line L2, and a third gas inlet line L3.

[0049] The first gas introduction line L1 is configured to allow the introduction of a fluorine-based gas (first reactive gas) from the first gas source 121 into the chamber 11, which generates positively charged aluminum ions through a reaction with the raw material block 28. The second gas introduction line L2 is configured to allow the introduction of a nitrogen-based gas (second reactive gas) from the second gas source 122 into the chamber 11, which generates positively charged nitrogen ions. The third gas introduction line L3 is configured to allow the introduction of argon gas from the third gas source 123 into the chamber 11.

[0050] For the first reactive gas, a fluorine-based gas such as phosphorus trifluoride (PF3) gas is used. For the second reactive gas, a nitrogen-based gas such as nitrogen trifluoride (NF3) gas or a nitrogen compound gas such as a mixture of nitrogen and nitrogen trifluoride gas is used.

[0051] A flat extraction electrode 24 is positioned near the ion emission hole 35 outside the chamber 11, to which a negative voltage is applied to the chamber 11. Positively charged ions generated inside the chamber 11 are attracted to the extraction electrode 24 by the electric field formed by the extraction electrode 24, extracted to the outside of the chamber 11 through the ion emission hole 35, and enter the interior of the aforementioned traveling chamber 2 after passing through the central hole 24a of the extraction electrode 24.

[0052] (Control unit) The control unit 15 is configured to execute a first control mode in which aluminum ions are generated by introducing a first reactive gas (fluorine-based gas) into the chamber 11, and a second control mode in which nitrogen ions are generated by introducing a second reactive gas (nitrogen-based gas) into the chamber 11.

[0053] In the first control mode, the control unit 15 introduces a first reactive gas (fluorine compound gas) from a first gas source 121 to the chamber 11 at a predetermined flow rate via a first gas introduction line L1. The fluorine compound gas introduced into the chamber 11 is decomposed by primary electrons reciprocating inside the chamber 11, generating a plasma containing fluorine ions and fluorine radicals. The generated plasma comes into contact with the evaporation surface 28a of the raw material block 28 made of aluminum nitride. The aluminum nitride reacts with fluorine, such as fluorine ions and fluorine radicals in the plasma, to generate aluminum fluoride (AlFx).

[0054] Aluminum fluoride is heated to a high temperature and turns into a gas, which is released into the chamber 11 from the evaporation surface 28a of the raw material block 28. The released aluminum fluoride is decomposed by primary electrons reciprocating within the chamber 11, producing aluminum ions (Al + ) is generated. The generated aluminum ions are drawn out by the extraction electrode 24 into the traveling chamber 2, and an Al ion beam is generated which is irradiated onto the surface of the substrate 8 placed in the injection chamber 6.

[0055] In the second control mode, the control unit 15 introduces a second reactive gas (nitrogen compound gas) from a second gas source 122 into the chamber 11 at a predetermined flow rate via a second gas introduction line L2. The nitrogen compound gas introduced into the chamber 11 is decomposed by primary electrons reciprocating inside the chamber 11, generating a plasma containing nitrogen ions. The generated nitrogen ions are extracted into the travel chamber 2 by the extraction electrode 24, generating an N-ion beam that irradiates the surface of the substrate 8 placed in the injection chamber 6.

[0056] The control unit 15 of this embodiment is configured to execute a third control mode for cleaning the chamber by introducing argon gas into the chamber 11 at a predetermined flow rate from a third gas source 123 via a third gas introduction line L3. The argon gas introduced into the chamber 11 is decomposed by primary electrons reciprocating inside the chamber 11, generating a plasma containing argon ions. As a result, various reactive materials deposited inside the chamber 11 are removed by sputtering action caused by argon ions.

[0057] (Details of the ion source) In this case, when a discharge is performed using nitrogen gas or argon gas in the chamber 11, no reaction occurs with the AlN raw material block 28, and sputtering particles mainly from the repeller electrode 23 accumulate on the surface (evaporation surface 28a) of the raw material block 28. If the repeller electrode 23 is made of a high-melting-point metal such as tungsten, sputtering particles of that metal will accumulate on the surface (evaporation surface 28a) of the raw material block 28. Therefore, at the start of aluminum ion generation (start of execution of the first control mode), the accumulation of metal particles on the surface of the raw material block 28 inhibits the reaction between the PF3 gas (fluorine compound gas) and the raw material block 28. This resulted in the problem that the Al ion beam could not be increased to a predetermined current value in a short time.

[0058] In contrast, in the ion source 11 of this embodiment, the repeller electrode 23 is made of an aluminum compound. As a result, when discharge is performed using nitrogen gas or argon gas, sputtered particles consisting of the aluminum compound or its decomposition products are deposited on the surface of the raw material block 28. Therefore, even when switching to the aluminum ion generation mode (first control mode), it is possible to generate aluminum ions early without inhibiting the reaction between the raw material block 28 and PF3 gas (fluorine compound gas). This makes it possible to shorten the switching time of the ion species generated in the chamber 11, thereby improving productivity.

[0059] The aluminum compound constituting the repeller electrode 23 is preferably the same material as the aluminum compound constituting the raw material block 28, and is typically aluminum nitride (AlN).

[0060] Furthermore, when discharging using nitrogen gas or argon gas, sputtered particles of the metal material (typically high-melting-point metals such as tungsten) that constitutes the cathode electrode 22 (electron emission surface 22a), in addition to the repeller electrode 23, may accumulate on the surface of the raw material block 28, and these deposits may inhibit the reaction between the raw material block 28 and the PF3 gas.

[0061] Therefore, in this embodiment, instead of nitrogen gas alone, a nitrogen compound gas consisting of NF3 gas or a mixture of N2 and NF3 is used as the reactive gas (second reactive gas) used to generate nitrogen ions. Fluoride ions or fluoride radicals in the NF3 gas plasma react with the sputtered particles made of the above-mentioned metal material deposited on the surface of the raw material block 28, and remove them. The removed deposits either accumulate on the inner wall surface of the chamber 11 or become tungsten fluoride (WFx) and are released to the outside of the chamber 11.

[0062] When using a mixture of N2 and NF3 gas as the nitrogen compound gas (second reactive gas), the mixing ratio of NF3 gas is not particularly limited, but it is sufficient that the mixture contains at least an amount of NF3 gas that provides the aforementioned reaction removal effect of metal particles. Alternatively, the amount of NF3 gas that can shorten the ion species switching time to the desired time may be determined experimentally in advance.

[0063] Alternatively, in the second control mode for generating N ions, nitrogen may be introduced as the second reactive gas to generate N ions, and a mixture of nitrogen and nitrogen trifluoride gas may be introduced into the chamber just before switching to the first control mode for generating Al ions. In this case, for example, the mixing ratio of NF3 gas may be gradually increased from 0, or all at once, to reach the desired mixing ratio, just before switching from N ion generation to Al ion generation.

[0064] As described above, according to this embodiment, the deposition of metal particles on the surface of the raw material block by discharge using gases such as nitrogen and argon is suppressed, and after switching to the Al ion beam, the Al ion beam can be rapidly increased to a predetermined current value, thereby improving productivity.

[0065] Although embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the embodiments described above and can be modified in various ways.

[0066] For example, in the embodiments described above, an ion source for an ion implantation apparatus was used as an example, but the present invention is not limited to this and can also be applied to ion sources for other surface treatment devices such as plasma doping apparatuses.

[0067] In the embodiments described above, PF3 gas was used as an example of a fluorine compound gas (first reactive gas) for generating aluminum ions, but it is also possible to use, for example, boron trifluoride (BF3) gas.

[0068] Furthermore, although the above embodiments have described ion implantation apparatuses using a first and second reactive gas as examples, it is also possible to use general raw material gases used in semiconductor manufacturing, such as phosphine (PH3) gas for doping with phosphorus (P) as an impurity element. [Explanation of Symbols]

[0069] 3...Mass spectrometer 6…Injection chamber 8... Circuit board 10…Ion source 11... Chamber 12…Gas Supply Department 15…Control Unit 20… Filament 22... Cathode electrode 23... Repeller electrode 24…Extraction electrode 26… Raw material block 100... Ion implantation device L1…First gas introduction line L2…Second gas introduction line L3…Third gas introduction line

Claims

1. Chamber and, A cathode electrode positioned at one end in one axial direction within the chamber, A raw material block made of an aluminum compound is arranged around the cathode electrode, not in contact with the cathode electrode and the chamber. A filament is positioned on the back side of the cathode electrode and emits thermionic electrons from the surface of the cathode electrode when the cathode electrode is heated, A repeller electrode made of an aluminum compound is positioned at the other end of the chamber in the uniaxial direction so as to face the surface of the cathode electrode, and causes thermionic electrons emitted from the surface of the cathode electrode to reciprocate in the uniaxial direction within the chamber. A gas supply unit having: a first gas introduction line for introducing a first reactive gas consisting of a fluorine-based gas that generates positively charged aluminum ions by reaction with the raw material block into the chamber; and a second gas introduction line for introducing a second reactive gas consisting of a nitrogen-based gas that generates positively charged nitrogen ions into the chamber; A control unit configured to alternately execute a first control mode, which generates aluminum ions by introducing the first reactive gas into the chamber, and a second control mode, which generates nitrogen ions by introducing the second reactive gas into the chamber. An ion source equipped with the following features.

2. An ion source according to claim 1, The first reactive gas is phosphorus trifluoride gas. The second reactive gas is nitrogen trifluoride gas, or a mixture of nitrogen and nitrogen trifluoride gas. Ion source.

3. The ion source according to claim 2, The aforementioned aluminum compound is aluminum nitride. Ion source.

4. An ion source according to claim 1, The gas supply unit further includes a third gas introduction line for introducing argon gas into the chamber. The control unit is configured to perform a third control mode, which involves introducing argon gas into the chamber to clean the inside of the chamber. Ion source.

5. Ion source, An extraction electrode for drawing out ions generated in the ion source, A mass spectrometer for mass spectrometry of ions extracted from the aforementioned ion source, An injection chamber capable of housing a substrate to be irradiated with mass-spectrometry-analyzed ions, It is equipped with, The aforementioned ion source is Chamber and, A cathode electrode positioned at one end in one axial direction within the chamber, A raw material block made of an aluminum compound is arranged around the cathode electrode, not in contact with the cathode electrode and the chamber. A filament is positioned on the back side of the cathode electrode and emits thermionic electrons from the surface of the cathode electrode when the cathode electrode is heated, A repeller electrode made of an aluminum compound is positioned at the other end of the chamber in the uniaxial direction so as to face the surface of the cathode electrode, and causes thermionic electrons emitted from the surface of the cathode electrode to reciprocate in the uniaxial direction within the chamber. A gas supply unit having: a first gas introduction line for introducing a first reactive gas consisting of a fluorine-based gas that generates positively charged aluminum ions by reaction with the raw material block into the chamber; and a second gas introduction line for introducing a second reactive gas consisting of a nitrogen-based gas that generates positively charged nitrogen ions into the chamber; A control unit configured to alternately execute a first control mode, which generates aluminum ions by introducing the first reactive gas into the chamber, and a second control mode, which generates nitrogen ions by introducing the second reactive gas into the chamber. An ion implantation device having the following features.

6. An ion implantation method using the ion source described in claim 1, A first control mode is executed in which the aluminum ions are generated by introducing the first reactive gas into the chamber. A second control mode is executed in which nitrogen ions are generated by introducing a mixed gas of nitrogen and nitrogen trifluoride as the second reactive gas into the chamber. The first control mode is executed again by introducing the first reactive gas into the chamber. Ion implantation method.

7. The ion implantation method according to claim 6, In the second control mode, nitrogen is introduced as the second reactive gas to generate nitrogen ions, and immediately before switching from the second control mode to the first control mode, a mixed gas of nitrogen and nitrogen trifluoride is introduced into the chamber. Ion implantation method.

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