JP6052792B2 - Microwave ion source and operation method thereof - Google Patents

Description

  The present invention relates to a microwave ion source and a method for operating the same.

  Ion sources that use microwaves for plasma generation are known. Microwave is introduced into the vacuum plasma chamber. The source gas supplied to the plasma chamber is excited by microwaves to generate plasma. Ions are extracted from the plasma. The ions thus extracted from the ion source are used, for example, for an ion implantation process.

JP-A-5-109365 Japanese Patent Laid-Open No. 6-166865

  In some microwave ion sources, multiply charged ions are generated using a mirror magnetic field that has the effect of confining the plasma. This ion source is sometimes called an ECR ion source. Since the ECR ion source is optimized to efficiently generate multiply charged ions, it is not suitable for generating monovalent ions. Therefore, when the ion source owner performs a process requiring monovalent ions, another ion source suitable for generating monovalent ions must be used. Thus, the use of commonly available microwave ion sources is limited. Preparing different ion sources depending on the application leads to an increase in cost of ownership.

  One exemplary object of an aspect of the present invention is to provide a microwave ion source that can be used in a wide range of applications, and a method of operating such a microwave ion source.

  According to an aspect of the present invention, a plasma chamber, and a magnetic field generator for generating a magnetic field in the plasma chamber, the magnetic field generator includes a mirror magnetic field suitable for generating multivalent ions and monovalent ions. A microwave ion source is provided that is configured to switch between a non-mirror magnetic field suitable for generation.

  According to an aspect of the present invention, there is provided a method for operating a microwave ion source, wherein an operation mode of the microwave ion source is selected, and plasma is generated in a plasma chamber of the microwave ion source according to the selected operation mode. And the operation mode is a first operation mode suitable for the production of multivalent ions, or a second operation mode suitable for the production of monovalent ions.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the microwave ion source which can be utilized for a wide use and the operating method of such a microwave ion source can be provided.

1 is a diagram schematically showing an overall configuration of an ion implantation apparatus according to an embodiment of the present invention. It is a figure showing typically composition of a microwave ion source concerning a certain embodiment of the present invention. It is a figure which illustrates the axial direction magnetic field distribution which the magnetic field generator which concerns on one embodiment of this invention generates in a plasma chamber. It is a figure which shows another example of the non-mirror magnetic field which the magnetic field generator which concerns on one embodiment of this invention generates in a plasma chamber. It is a flowchart showing the operating method of the microwave ion source which concerns on an embodiment of this invention. It is a figure which shows typically the structure of the microwave ion source which concerns on other embodiment of this invention. It is a figure which shows typically the structure of the microwave ion source which concerns on other embodiment of this invention. It is a figure which shows typically the structure of the microwave ion source which concerns on other embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate.

  FIG. 1 is a diagram schematically showing an overall configuration of an ion implantation apparatus 100 according to an embodiment of the present invention. FIG. 1 shows typical components of the ion implantation apparatus 100. The ion implantation apparatus 100 ionizes atoms or molecules to generate an ion beam 20 and irradiates the substrate (for example, a semiconductor substrate) 104 to perform an ion implantation process for injecting the atoms or molecules into the substrate 104. Device.

  The ion implantation apparatus 100 includes a microwave ion source 10, a beam line assembly 110, and a processing chamber 112. The microwave ion source 10 is configured to ionize atoms or molecules to be implanted. The microwave ion source 10 will be described later with reference to FIG.

  The beam line assembly 110 transports, accelerates, and shapes the ion beam 20 and the mass analyzer 114 for selecting ions to be implanted into the substrate 104 among the ions ionized by the microwave ion source 10 according to mass. Or a beam transport system 116 for scanning. On the downstream side of the mass analyzer 114, a mass analysis slit 118 for passing the ion beam 20 made of ions having a predetermined mass to the beam transport system 116 is provided. The beam transport system 116 includes a beam scanner 120 for scanning the ion beam 20. A scannable range of the ion beam 20 by the beam scanner 120 is indicated by an arrow 138.

  The processing chamber 112 may include a contact ion beam detector (for example, a Faraday cup) 122. The ion beam detector 122 may output the measurement result to the ion implantation control unit 128. The ion beam detector 122 is disposed at a position (one side (in the case of illustration) or both sides) of the substrate 104 adjacent to the substrate 104 in the ion beam scanning direction. The ion beam detector 122 may be a detector that can be moved in and out of the beam line as necessary for measurement. In this case, the ion beam detector 122 may be provided at any location of the beam line assembly 110.

  The processing chamber 112 includes a substrate support portion 124 for supporting the substrate 104. The substrate 104 is supported by the substrate support portion 124 and is accommodated in the processing chamber 112. The substrate support unit 124 is configured as a so-called mechanical scan system for moving the substrate 104 with respect to the ion beam 20, and includes a table or platen for holding the substrate 104, and a drive mechanism for moving the table or platen. ,including. The substrate support unit 124 is configured to reciprocate the substrate 104 in a scanning range in a direction perpendicular to the traveling direction of the ion beam 20 and the scanning direction, for example.

  As shown in FIG. 1, the ion implantation apparatus 100 includes an evacuation system 126 so that the microwave ion source 10, the beam line assembly 110, and the processing chamber 112 have a desired vacuum environment for the ion implantation process. To be kept. The vacuum exhaust system 126 includes, for example, a high vacuum pump such as a cryopump or a turbo molecular pump, and a roughing pump for roughing up to the operating pressure of the high vacuum pump.

  The ion implantation apparatus 100 includes an ion implantation control unit 128. The ion implantation control unit 128 is configured to execute an ion implantation process by controlling the microwave ion source 10, the mass analyzer 114, the beam transport system 116, the substrate support unit 124, the vacuum exhaust system 126, and other components. Has been. The ion implantation control unit 128 comprehensively controls the ion implantation apparatus 100 in accordance with input signals from the beam measurement system including the ion beam detector 122, various data stored in the memory, input commands from the operator, and the like. To do.

  The ion implantation control unit 128 includes, for example, arbitrary hardware including a CPU that executes various arithmetic processes, a ROM that stores various control programs, a RAM that is used as a work area for data storage and program execution, and various arithmetic operations. Or software such as a program for executing control. The ion implantation control unit 128 may include input means such as a mouse and keyboard for receiving input from an operator, communication means for communicating with other devices, and output means such as a display and a printer.

  Under the control of the ion implantation control unit 128, the substrate 104 is irradiated with, for example, a spot-like ion beam 20 having a cross section. The ion beam 20 is scanned in one direction by the beam scanner 120 (also called a beam scan), and the substrate 104 is mechanically scanned in the orthogonal direction (also called a mechanical scan). By coordinating beam scanning and mechanical scanning, the ion beam irradiation region (for example, the entire surface of the substrate 104) on the substrate 104 can be irradiated with the ion beam 20 in accordance with a given scanning sequence. Such a scanning method that combines a beam scan in one direction and a mechanical scan in the vertical direction is sometimes called a hybrid scan.

  The ion implantation apparatus 100 is not limited to the hybrid scan method. For example, the ion implantation apparatus 100 may employ a scanning method in which a so-called ribbon beam extending in a uniaxial direction and a mechanical scan in the orthogonal direction are combined. Alternatively, the ion implantation apparatus 100 may adopt a method of performing two-dimensional mechanical scanning in a plane perpendicular to the beam traveling direction with respect to the spot beam.

  The ion implantation apparatus 100 shown in FIG. 1 is configured as a so-called single wafer type. That is, the ion implantation apparatus 100 is a type in which one substrate 104 is held at a time on the substrate support portion 124 and ion implantation processing is performed one by one. Note that the processing is not necessarily limited to processing one by one, and the substrate support unit 124 may be configured to provide two or more sheets simultaneously and provide mechanical scanning in at least one direction. Further, the ion implantation apparatus 100 may be configured as a so-called batch type in which a large number of substrates are placed on a rotatable table and rotated while simultaneously performing ion implantation on the large number of substrates.

  FIG. 2 is a diagram schematically showing the configuration of the microwave ion source 10 according to an embodiment of the present invention. A microwave ion source 10 generates high-density plasma by inputting microwave power in the direction of magnetic field into a plasma chamber 12 to which a magnetic field satisfying electron cyclotron resonance (ECR) or a magnetic field higher than the magnetic field is applied to generate ions with high density. Ion source to be extracted. The microwave ion source 10 is configured to generate a plasma of a source gas by the interaction between a magnetic field and a microwave, and to extract ions from the plasma to the outside of the plasma chamber 12.

  As is well known, the strength of the magnetic field that satisfies the ECR condition is uniquely determined with respect to the microwave frequency used, and a magnetic field of 87.5 mT (875 gauss) is required when the microwave frequency is 2.45 GHz. It is. Hereinafter, for convenience, a magnetic field that satisfies the ECR may be referred to as a resonance magnetic field.

  The microwave ion source 10 includes an ion source body 14. The ion source body 14 includes a plasma chamber 12, a magnetic field generator 16, and a vacuum vessel 18.

  The plasma chamber 12 has a cylindrical shape having both ends. Hereinafter, the direction from one end to the other end of the plasma chamber 12 may be referred to as an axial direction for convenience. In addition, a direction orthogonal to the axial direction may be referred to as a radial direction, and a direction surrounding the axial direction may be referred to as a circumferential direction. However, these do not necessarily mean that the plasma chamber 12 has a rotationally symmetric shape. In the illustrated example, the plasma chamber 12 has a cylindrical shape, but the plasma chamber 12 may have any shape as long as it can appropriately accommodate plasma. The axial length of the plasma chamber 12 may be longer or shorter than the radial length of the end portion of the plasma chamber 12.

The magnetic field generator 16 is provided to apply a magnetic field to the plasma chamber 12 . The magnetic field generator 16 is configured to generate a magnetic field along the central axis of the plasma chamber 12, and the direction of the magnetic force lines is indicated by an arrow M in FIG. The magnetic field generator 16 is configured to generate a resonance magnetic field or a magnetic field having a higher strength than that in at least a part on the axis of the plasma chamber 12. The magnetic field generator 16 can also generate a magnetic field lower than the resonance magnetic field in at least a part of the axis of the plasma chamber 12.

  As will be described later, the magnetic field generator 16 is configured to switch between a mirror magnetic field suitable for generating multivalent ions and a non-mirror magnetic field suitable for generating monovalent ions. Multivalent ions are divalent or higher ions. The magnetic field generator 16 includes a plurality of magnetic field generation units arranged in the axial direction, and each magnetic field generation unit includes an electromagnet such as a coil (for example, a solenoid coil 76) and / or a permanent magnet. The magnetic field generator 16 switches the magnetic field under the control of the control unit C or manually.

  The magnetic field generator 16 may include a drive mechanism for adjusting the relative positions of the plurality of magnetic field generation units. The at least one magnetic field generation unit may include an electromagnet and a permanent magnet, and the electromagnet and the permanent magnet may be configured to generate magnetic fields in opposite directions (the direction of arrow M and the opposite direction). One magnetic field generation unit and another magnetic field generation unit may be configured to generate magnetic fields in opposite directions.

  The vacuum container 18 is a housing for accommodating the plasma chamber 12 in a vacuum environment. The vacuum vessel 18 is also a structure for holding the magnetic field generator 16. The plasma chamber 12 has a vacuum window 24 for receiving microwaves therein. The plasma chamber 12, the magnetic field generator 16, and the vacuum vessel 18 will be described in more detail later.

  The microwave ion source 10 includes a microwave supply system 26. The microwave supply system 26 is configured to input microwave power to the plasma chamber 12 through the vacuum window 24. The microwave supply system 26 includes a microwave source 28, a waveguide 30, and a matching section 32. The microwave source 28 is, for example, a magnetron. The microwave source 28 outputs a microwave having a frequency of 2.45 GHz, for example. The waveguide 30 is a three-dimensional circuit for transmitting the microwave output from the microwave source 28 to the plasma chamber 12. One end of the waveguide 30 is connected to the microwave source 28, and the other end is connected to the vacuum window 24 via the matching section 32. A matching section 32 is provided for microwave matching.

  In this way, microwaves are introduced from the microwave supply system 26 into the plasma chamber 12 through the vacuum window 24. The introduced microwave propagates inside the plasma chamber 12 toward the end of the plasma chamber 12 facing the vacuum window 24. The propagation direction of the microwave is indicated by an arrow P in FIG. The propagation direction P of the microwave is the same as the magnetic force line direction M by the magnetic field generator 16, and the propagation direction P of the microwave coincides with the axial direction of the plasma chamber 12.

  The microwave ion source 10 includes a gas supply system 34. The gas supply system 34 is configured to supply a plasma source gas to the plasma chamber 12. The gas supply system 34 includes a gas cylinder 36 that is a gas source and a gas flow rate controller 38. The front end of the gas pipe 40 of the gas supply system 34 is connected to the plasma chamber 12 through the vacuum vessel 18. For example, the gas pipe 40 is connected to the side wall 64 of the plasma chamber 12. The gas flow rate controller 38 includes an on-off valve for connecting or blocking the gas cylinder 36 to or from the plasma chamber 12 or a flow rate control valve for adjusting the gas flow rate from the gas cylinder 36 to the plasma chamber 12. In this way, the source gas is supplied from the gas cylinder 36 to the plasma chamber 12 at a controlled flow rate and / or pressure.

  The ion source body 14 includes an extraction electrode system 42. The extraction electrode system 42 is configured to extract ions from the plasma through the ion extraction opening 66 of the plasma chamber 12. The extraction electrode system 42 includes a first electrode 44 and a second electrode 46. The first electrode 44 is provided between the plasma chamber 12 and the second electrode 46. The terminal portion 62 having the ion extraction opening 66 and the first electrode 44 are arranged with a gap therebetween, and the first electrode 44 and the second electrode 46 are arranged with a gap therebetween. Each of the first electrode 44 and the second electrode 46 is formed, for example, in an annular shape, and has an opening at the center for allowing ions extracted from the plasma chamber 12 to pass therethrough.

  The first electrode 44 is provided to extract positive ions from the plasma and prevent electrons from returning from the beam line upstream portion 52 to the plasma chamber 12. Therefore, a negative high voltage is applied to the first electrode 44. In order to apply a negative high voltage to the first electrode 44, a first extraction power supply 48 is provided. The second electrode 46 is grounded. A positive high voltage is applied to the vacuum vessel 18. In order to apply a positive high voltage to the vacuum vessel 18, a second extraction power source 50 is provided. In this manner, a positive ion beam 20 is extracted from the plasma chamber 12. The extraction direction of the ion beam 20 from the plasma chamber 12 is the same as the microwave propagation direction P and the magnetic force line direction M.

  The microwave ion source 10 is connected to a beam line upstream portion 52 for transporting the ion beam 20 extracted by the extraction electrode system 42. The beam line upstream portion 52 is a part of the beam line assembly 110 (see FIG. 1) connected to the ion source main body 14 on the side opposite to the microwave supply system 26. The beam line upstream portion 52 is insulated from the vacuum vessel 18 of the ion source body 14 and attached to the vacuum vessel 18. For this purpose, a bushing 54 is provided between the beam line upstream portion 52 and the vacuum vessel 18.

  The bushing 54 maintains the withstand voltage between the vacuum vessel 18 and the ground side while maintaining the vacuum in the beam line upstream portion 52 and the vacuum vessel 18. The bushing 54 is made of an insulating material. The bushing 54 has an annular shape and surrounds the extraction electrode system 42. The bushing 54 is attached by being sandwiched between the mounting flanges of the beam line upstream portion 52 and the ion source main body 14.

  A vacuum exhaust device 56 for providing a vacuum environment to the vacuum vessel 18 and the plasma chamber 12 is provided. The evacuation device 56 is provided in the beam line upstream portion 52 and constitutes a part of the evacuation system 126 shown in FIG. Since the beam line upstream portion 52 communicates with the vacuum vessel 18 and the plasma chamber 12, the vacuum exhaust device 56 can evacuate the vacuum vessel 18 and the plasma chamber 12.

  The microwave ion source 10 may include a control unit C for controlling the ion beam 20. The control unit C controls each component of the microwave ion source 10 to control the plasma generated in the plasma chamber 12, thereby controlling, for example, the amount of ion current. The control unit C is configured to control the operations of the microwave supply system 26, the gas supply system 34, the first coil power supply 77, the second coil power supply 79, and the third coil power supply 81, for example. For example, the controller C may control the ion beam 20 by adjusting at least one of the flow rate and / or pressure of the source gas, the microwave power, and the magnetic field strength in the plasma chamber 12. The control unit C may be a part of the ion implantation control unit 128 described above, or may be provided separately from the ion implantation control unit 128.

  The plasma chamber 12 is configured to generate and maintain plasma in its internal space. Hereinafter, the internal space of the plasma chamber 12 may be referred to as a plasma accommodating space 58.

  The plasma chamber 12 includes a start end portion 60, a termination end portion 62, and a side wall 64. The start end portion 60 and the end end portion 62 face each other with the plasma accommodating space 58 interposed therebetween. The side wall 64 surrounds the plasma storage space 58 and connects the start end 60 and the end end 62. In this way, the plasma storage space 58 is defined inside the vacuum vessel 18 by the start end portion 60, the end end portion 62, and the side wall 64. When the plasma chamber 12 has a cylindrical shape, the start end portion 60 and the end portion 62 have a disk shape, the side wall 64 has a cylindrical shape, and the ends of the side walls 64 are fixed to the outer peripheral portions of the start end portion 60 and the end portion 62. Yes.

  The start end 60 has a vacuum window 24. The vacuum window 24 may occupy the entire start end 60 or may be formed at a part (for example, the center) of the start end 60. One side of the vacuum window 24 faces the plasma accommodating space 58, and the other side of the vacuum window 24 is directed to the microwave supply system 26. The vacuum window 24 seals the inside of the plasma chamber 12 to a vacuum. The propagation direction P of the microwave is perpendicular to the vacuum window 24. The vacuum window 24 is formed of a dielectric having a low dielectric loss (for example, alumina or boron nitride). The portions other than the vacuum window 24 of the plasma chamber 12 and the vacuum vessel 18 are made of, for example, a nonmagnetic metal material.

  At least one ion extraction opening 66 is formed in the end portion 62. The ion extraction opening 66 is formed at a position facing the vacuum window 24 with the plasma accommodating space 58 interposed therebetween. That is, the vacuum window 24, the plasma accommodating space 58, and the ion extraction opening 66 are arranged along the axial direction of the plasma chamber 12.

  The vacuum vessel 18 has a double cylinder structure in which the plasma chamber 12 is integrally formed. That is, the plasma chamber 12 is an inner cylinder of the vacuum vessel 18, and an outer cylinder 68 that accommodates the plasma chamber 12 is provided outside the plasma chamber 12. The outer cylinder 68 may have a cylindrical shape that is coaxial with the plasma chamber 12. There is a gap between the outer cylinder 68 and the side wall 64 of the plasma chamber 12, and the tip of the gas pipe 40 of the gas supply system 34 enters the gap and is attached to the side wall 64.

  The vacuum vessel 18 may not be formed integrally with the plasma chamber 12. The vacuum vessel 18 and the plasma chamber 12 may be separate and separable. Further, the vacuum vessel 18 itself may form the plasma chamber 12. Thus, when the vacuum vessel 18 also serves as the plasma chamber 12, an end plate having an ion extraction opening 66 may be attached to the beam line upstream portion 52 side of the outer cylinder 68.

  One end of the vacuum vessel 18 is closed by an end plate 70, and the other end is opened toward the beam line upstream portion 52. A starting end 60 of the plasma chamber 12 is formed at the center of the end plate 70. The outer peripheral portion of the end plate 70 extends to the outside of the outer cylinder 68 in the radial direction. An attachment flange 72 for the bushing 54 is provided at the end of the vacuum vessel 18 on the beam line upstream portion 52 side. The mounting flange 72 extends radially outward from the outer cylinder 68. The vacuum vessel 18 and the plasma chamber 12 have the same axial length, and the mounting flange 72 and the end portion 62 of the plasma chamber 12 have the same axial position. The vacuum vessel 18 and the plasma chamber 12 may have different axial lengths.

  A magnet holder 74 for holding the magnetic field generator 16 is formed in the vacuum container 18. For example, the magnet holding part 74 is formed on the outer surface of the outer cylinder 68 of the vacuum vessel 18. In this embodiment, the magnetic field generator 16 is provided outside the vacuum vessel 18 (that is, in the atmosphere). The magnetic field generator 16 is disposed so as to surround the vacuum vessel 18. However, in another example, the vacuum vessel 18 may include a magnet holding unit 74 for holding the magnetic field generator 16 inside the vacuum vessel 18 (that is, in a vacuum). In this case, the same effect as in this example can be obtained. In this way, the magnetic field generator 16 is arranged so as to surround the plasma accommodating space 58.

  The magnetic field generator 16 includes a plurality of coils arranged in the axial direction, specifically, a first solenoid coil 76, a second solenoid coil 78, and a third solenoid coil 80. Each of these three coils is disposed so as to surround the plasma chamber 12 and is configured to generate a magnetic field directed in the axial direction of the plasma chamber 12. The first solenoid coil 76 surrounds the start end 60 of the plasma chamber 12, and the third solenoid coil 80 surrounds the end 62 of the plasma chamber 12. The second solenoid coil 78 is provided between the first solenoid coil 76 and the third solenoid coil 80 and surrounds the central portion of the side wall 64 of the plasma chamber 12. In the present embodiment, the plasma chamber 12 and the vacuum vessel 18 are cylindrical, and each coil is formed in an annular shape, and a conducting wire is wound around the plasma chamber 12 in the circumferential direction. There is a gap in the axial direction between adjacent coils. Each coil may be provided with a yoke.

  The magnetic field generator 16 includes a coil power source corresponding to each coil. That is, the magnetic field generator 16 supplies a first coil power source 77 for flowing current to the first solenoid coil 76, a second coil power source 79 for flowing current to the second solenoid coil 78, and a third solenoid coil 80. And a third coil power supply 81 for supplying a current.

  The control unit C individually controls the first coil power source 77, the second coil power source 79, and the third coil power source 81. Thereby, the control unit C applies different currents to the first solenoid coil 76, the second solenoid coil 78, and the third solenoid coil 80. The magnitude of the current correlates with the magnitude of the resulting magnetic field. Therefore, the magnetic field generator 16 generates axial magnetic fields having different magnitudes at the respective axial positions of the plasma chamber 12 corresponding to the first solenoid coil 76, the second solenoid coil 78, and the third solenoid coil 80. Since the coil power supplies are individually controlled, it is naturally possible to apply the same magnitude of current to the plurality of coil power supplies and generate the same magnitude of magnetic fields in the plurality of coils.

FIG. 3 is a diagram illustrating an axial magnetic field distribution generated in the plasma chamber 12 by the magnetic field generator 16 according to an embodiment of the invention. The upper part of FIG. 3 schematically shows the main part of the microwave ion source 10 shown in FIG. In the center and the lower part of FIG. 3, a mirror magnetic field B1 and a non-mirror magnetic field B2 generated in the plasma chamber 12 by the magnetic field generator 16 are illustrated. In FIG. 3, the vertical axis represents the axial magnetic flux density B on the central axis of the plasma chamber 12, and the horizontal axis represents the axial position L of the plasma chamber 12. The resonance magnetic field B _ECR is indicated by a broken line. In addition, axial positions corresponding to the first solenoid coil 76, the second solenoid coil 78, and the third solenoid coil 80 are denoted by reference numerals L1, L2, and L3, respectively.

As illustrated, the mirror magnetic field B1 has a bimodal axial magnetic field distribution with two peaks. The mirror magnetic field B1 has a first peak at an axial position L1 corresponding to the first solenoid coil 76, and a second peak equivalent to the first peak at an axial position L3 corresponding to the third solenoid coil 80. The first peak and the second peak give the maximum value of the axial magnetic field of the plasma chamber 12. The magnetic field strength of the first peak and the second peak is larger than the resonance magnetic field B _ECR . Further, the mirror magnetic field B1 has the minimum value of the axial magnetic field between the axial position L1 and the axial position L3 at the axial position L2 corresponding to the second solenoid coil 78. This minimum value is smaller than the resonance magnetic field B _ECR in the illustrated example, but may be larger than the resonance magnetic field B _ECR . Such a mirror magnetic field B1 has an effect of confining electrons and is suitable for the generation of multiply charged ions in the plasma chamber 12.

  The controller C controls the first coil power supply 77 and the third coil power supply 81 so as to apply a large current to the first solenoid coil 76 and the third solenoid coil 80, and applies a small current to the second solenoid coil 78. The second coil power source 79 is controlled. In this way, the control unit C controls the magnetic field generator 16 so as to generate the mirror magnetic field B1 in the plasma chamber 12. Note that the control unit C may stop supplying power to the second solenoid coil 78 instead of applying a small current.

The non-mirror magnetic field B2 has a single-peak axial magnetic field distribution having one peak. The non-mirror magnetic field B <b> 2 has a maximum value of the axial magnetic field at the axial position L <b> 2 corresponding to the second solenoid coil 78. This maximum value is larger than the resonance magnetic field B _ECR . Further, the non-mirror magnetic field B _< b _{> 2 is} larger than the resonance magnetic field B _ECR over the entire axial direction of the plasma chamber 12. Thus, the non-mirror magnetic field B2 helps to generate and maintain the plasma, but has no effect of confining electrons. Such a non-mirror magnetic field B2 is suitable for generation of monovalent ions in the plasma chamber 12.

  The control unit C controls the first coil power source 77 and the third coil power source 81 so as to apply a small current to the first solenoid coil 76 and the third solenoid coil 80, and applies a large current to the second solenoid coil 78. The second coil power source 79 is controlled. In this way, the control unit C controls the magnetic field generator 16 so as to generate the non-mirror magnetic field B2 in the plasma chamber 12.

FIG. 4 is a diagram showing another example of a non-mirror magnetic field generated in the plasma chamber 12 by the magnetic field generator 16 according to an embodiment of the present invention. The non-mirror magnetic field B2 shown in FIG. 3 is symmetrical with respect to the axial position L2 at the center of the plasma chamber 12, whereas the non-mirror magnetic field B2 ′ shown in FIG. The non-mirror magnetic field B2 ′ has the maximum value of the axial magnetic field at the axial position L1 corresponding to the first solenoid coil 76. The non-mirror field B2 'is the axial position L2 that corresponds to the second solenoid coil 78 as a boundary, the vacuum window 24 side larger than resonance magnetic field _{B ECR,} the ion extracting opening 66 side is smaller than the resonance magnetic field _{B ECR.}

  In this case, the control unit C controls the first coil power source 77 so as to give a large current to the first solenoid coil 76, and controls the second coil power source 79 so as to give a medium current to the second solenoid coil 78. The third coil power supply 81 may be controlled so as to apply a small current to the third solenoid coil 80. In this way, the control unit C may control the magnetic field generator 16 so as to generate the non-mirror magnetic field B <b> 2 ′ in the plasma chamber 12.

  By changing the peak position and / or the magnetic field strength of the non-mirror magnetic field in this way, the plasma distribution and plasma density in the plasma chamber 12 can be adjusted, and the amount of ion current drawn from the plasma chamber 12 can be controlled. Therefore, the microwave ion source 10 can control the ion current amount of monovalent ions extracted from the plasma chamber 12 by adjusting the non-mirror magnetic field in the plasma chamber 12.

  Similarly, the control unit C may adjust the magnetic field generator 16 so as to change the peak position and / or the magnetic field strength of the mirror magnetic field B1. Thus, the microwave ion source 10 can control the ion current amount of multiply charged ions extracted from the plasma chamber 12 by adjusting the mirror magnetic field in the plasma chamber 12.

  FIG. 5 is a flowchart showing a method of operating the microwave ion source 10 according to an embodiment of the present invention. This method is executed by the control unit C, for example. As shown in FIG. 5, the method includes an operation mode selection step (S10) and a plasma generation step (S20).

  The controller C selects one of the operation modes from the plurality of operation modes of the microwave ion source 10 (S10). The plurality of operation modes include a first operation mode suitable for the production of multiply charged ions and a second operation mode suitable for the production of monovalent ions.

  The control unit C switches between the first operation mode and the second operation mode based on the magnitude of energy required for the ion beam 20 according to the process. The control unit C selects the first operation mode in order to obtain the ion beam 20 having an energy exceeding the set energy threshold value, and the second operation mode in order to obtain the ion beam 20 having the energy equal to or lower than the threshold value. Select the operation mode. In this way, a low energy ion beam can be generated using monovalent ions, and a high energy ion beam can be generated using multivalent ions. Therefore, the microwave ion source 10 covering a wide energy region can be provided.

  The first operation mode is set to generate a mirror magnetic field in the plasma chamber 12. Further, the first operation mode is set so that a relatively large first microwave power is applied to the plasma chamber 12. Further, the first operation mode is set so that a relatively low first pressure is generated in the plasma chamber 12 (in other words, a low-concentration source gas is supplied to the plasma chamber 12).

  The second operation mode is set so that a non-mirror magnetic field is generated in the plasma chamber 12. Further, the second operation mode is set so that the second microwave power lower than the first microwave power is applied to the plasma chamber 12. Further, the second operation mode is set so that a second pressure higher than the first pressure is generated in the plasma chamber 12 (in other words, a high-concentration source gas is supplied to the plasma chamber 12).

  The control unit C generates plasma in the plasma chamber 12 according to the selected operation mode (S20). When the first operation mode is selected, the control unit C controls the magnetic field generator 16 so as to generate a mirror magnetic field in the plasma chamber 12. Further, the control unit C controls the microwave supply system 26 so as to supply the first microwave power to the plasma chamber 12. Further, the control unit C controls the gas supply system 34 so as to generate the first pressure in the plasma chamber 12. Thus, the plasma chamber 12 is supplied with a low-pressure source gas and high microwave power under a mirror magnetic field. Multivalent ions are efficiently generated by confinement of plasma by a mirror magnetic field. The ion beam 20 containing a large amount of multivalent ions is extracted from the plasma chamber 12 through the ion extraction opening 66 by the extraction electrode system 42. The extracted ion beam 20 is supplied to the beam line upstream portion 52.

  On the other hand, when the second operation mode is selected, the control unit C controls the magnetic field generator 16 so as to generate a non-mirror magnetic field in the plasma chamber 12. Further, the control unit C controls the microwave supply system 26 so as to apply the second microwave power to the plasma chamber 12. Further, the control unit C controls the gas supply system 34 so that the second pressure is generated in the plasma chamber 12. Thus, the plasma chamber 12 is supplied with a high-pressure source gas and low microwave power under a non-mirror magnetic field, and mainly generates monovalent ions. The ion beam 20 containing a large amount of monovalent ions is extracted from the plasma chamber 12 through the ion extraction opening 66 by the extraction electrode system 42. The extracted ion beam 20 is supplied to the beam line upstream portion 52.

  Therefore, according to this embodiment, the function of both a monovalent ion source and a multivalent ion source can be provided by a single microwave ion source 10.

  Moreover, the microwave ion source 10 which can be used over a wide energy region from low energy to high energy is provided. For example, considering the configuration in which monovalent to pentavalent ions can be generated and the extraction voltage can be up to 100 kV, the energy region of the extracted ions is 0 to 500 keV. Further, a wider energy range can be realized by combining post-stage acceleration such as tandem acceleration and high-frequency acceleration. For example, an energy region of 0 to 5 MeV can be obtained by combining post acceleration that can accelerate to 1 MeV.

  An ion implanter comprising such a microwave ion source can be used in processes for manufacturing most semiconductor devices (eg, power transistors, memories, logic, etc.). Since it can be used for a wide range of applications, the microwave ion source and the ion implantation apparatus including the microwave ion source according to the present embodiment are particularly useful for research applications, small-scale lines, and high-mix low-volume production.

  FIG. 6 is a diagram schematically showing a configuration of a microwave ion source 10 according to another embodiment of the present invention. The magnetic field generator 16 of the microwave ion source 10 includes a first solenoid coil 82 and a second solenoid coil 85. Each of the first solenoid coil 82 and the second solenoid coil 85 is disposed so as to surround the plasma chamber 12 and is configured to generate a magnetic field directed in the axial direction of the plasma chamber 12.

  The first solenoid coil 82 is provided with a first yoke 83 surrounding the outer side in the axial direction and the outer side in the radial direction. Similarly, the second solenoid coil 85 has a second yoke 86 surrounding the outer side in the axial direction and the outer side in the radial direction. Is provided. In the initial state shown in FIG. 6, the first solenoid coil 82 and the second solenoid coil 85 are adjacent in the axial direction, and no yoke is provided in the adjacent portion. Corresponding coil power sources (not shown) are provided for the first solenoid coil 82 and the second solenoid coil 85, respectively.

  The magnetic field generator 16 includes a first drive mechanism 84 and a second drive mechanism 87 configured to adjust the distance between the first solenoid coil 82 and the second solenoid coil 85. The first drive mechanism 84 is configured to move the first solenoid coil 82 and the first yoke 83 in the axial direction. The axial movable range of the first solenoid coil 82 by the first drive mechanism 84 is, for example, from the central portion of the plasma chamber 12 (see FIG. 6) to the vacuum window 24 (see FIG. 7). Similarly, the second drive mechanism 87 is configured to move the second solenoid coil 85 and the second yoke 86 in the axial direction. The movable range of the second solenoid coil 85 by the second drive mechanism 87 is, for example, from the central portion (see FIG. 6) of the plasma chamber 12 to the ion extraction opening 66 (see FIG. 7).

  The position of one of the first solenoid coil 82 and the second solenoid coil 85 may be fixed, and the distance between the two coils may be adjusted by providing an axial drive mechanism on the other. Further, at least one of the first solenoid coil 82 and the second solenoid coil 85 may be configured to be manually positioned.

  As shown in FIG. 6, the non-mirror magnetic field B <b> 2 described with reference to FIG. 3 is formed in the plasma chamber 12 by arranging the first solenoid coil 82 and the second solenoid coil 85 in the center of the plasma chamber 12. Can do. Further, by arranging the first solenoid coil 82 and the second solenoid coil 85 at both ends of the plasma chamber 12 as shown in FIG. 7, the mirror magnetic field B1 described with reference to FIG. 3 can be formed. As shown in FIG. 8, the first solenoid coil 82 and the second solenoid coil 85 are arranged at one end of the plasma chamber 12 (in the vicinity of the vacuum window 24), so that the non-mirror magnetic field B2 ′ described with reference to FIG. Can be formed.

  In this way, even if two coils at least one of which is movable are used, the function of both the monovalent ion source and the multivalent ion source can be provided by a single microwave ion source 10. This embodiment is suitable when the axial length of the plasma chamber 12 is short because the number of coils arranged in the axial direction is small.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way.

  The microwave ion source according to the embodiment of the present invention is not limited to an ion implantation apparatus, but other ion generation apparatus or ion irradiation apparatus, such as a medical accelerator, a particle beam therapy apparatus, a flat panel manufacturing apparatus, and a solar cell manufacturing apparatus. It can also be applied.

  10 microwave ion source, 12 plasma chamber, 16 magnetic field generator, 26 microwave supply system, 34 gas supply system, 76 first solenoid coil, 78 second solenoid coil, 80 third solenoid coil, 82 first solenoid coil, 84 1st drive mechanism, 85 2nd solenoid coil, 87 2nd drive mechanism, 100 ion implantation apparatus, B1 mirror magnetic field, B2 non-mirror magnetic field, C control part.

Claims (9)

A plasma chamber;
A magnetic field generator for generating a resonance magnetic field satisfying an electron cyclotron resonance condition or an axial magnetic field having a higher intensity in at least a part of the axis of the plasma chamber;
Wherein the magnetic field generator is configured to switch between mirror magnetic field and non-mirror field,
The mirror magnetic field has an axial magnetic field distribution with two peaks, the magnetic field strength of the two peaks being greater than the resonance magnetic field,
The microwave ion source , wherein the non-mirror magnetic field has an axial magnetic field distribution having one peak, and the magnetic field intensity of the one peak is larger than the resonance magnetic field . When the magnetic field generator generates the mirror magnetic field, an ion beam having energy exceeding a set energy threshold can be extracted from the plasma chamber, and the magnetic field generator generates the non-mirror magnetic field. 2. The microwave ion source according to claim 1, wherein an ion beam having an energy equal to or lower than the energy threshold can be extracted from the plasma chamber.   The microwave ion source according to claim 1 or 2, wherein the magnetic field generator includes three coils each generating an axial magnetic field in the plasma chamber.   The magnetic field generator comprises two coils each for generating an axial magnetic field in the plasma chamber, and a drive mechanism configured to adjust the distance between the two coils. The microwave ion source according to 1 or 2.   A first operation mode of a microwave ion source that controls the magnetic field generator to generate the mirror magnetic field in the plasma chamber, and the magnetic field generator to control to generate the non-mirror magnetic field in the plasma chamber. The microwave ion source according to any one of claims 1 to 4, further comprising a control unit configured to switch between a second operation mode of the microwave ion source. Further comprising a microwave supply system configured to provide microwave power to the plasma chamber;
The first operation mode is set to give a first microwave power to the plasma chamber,
6. The microwave ion source according to claim 5, wherein the second operation mode is set to apply a second microwave power lower than the first microwave power to the plasma chamber. A gas supply system configured to supply a plasma source gas to the plasma chamber;
The first operation mode is set to generate a first pressure in the plasma chamber by the source gas supplied from the gas supply system,
The second operation mode is set so that a second pressure higher than the first pressure is generated in the plasma chamber by a source gas supplied from the gas supply system. 6. The microwave ion source according to 6.   An ion implantation apparatus comprising the microwave ion source according to claim 1. A method of operating a microwave ion source,
Selecting an operation mode of the microwave ion source;
Generating a plasma in a plasma chamber of the microwave ion source according to a selected mode of operation,
Generating the plasma includes generating a resonance magnetic field satisfying an electron cyclotron resonance condition or an axial magnetic field having a higher intensity in at least a part on an axis of the plasma chamber;
The operation mode, Ri Oh in the second operation mode to generate a non-magnetic mirror field in the first operation mode or the plasma chamber to generate a mirror field on the plasma chamber,
The mirror magnetic field has an axial magnetic field distribution with two peaks, the magnetic field strength of the two peaks being greater than the resonance magnetic field,
The non-mirror magnetic field has an axial magnetic field distribution with one peak, and the magnetic field strength of the one peak is larger than the resonance magnetic field .

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