JP2017054707A - Ion source, ion source front slit voltage-setting device, and ion source front slit voltage-setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a time for cleaning an ion source.SOLUTION: An ion source 10 comprises: an ion source chamber 11 having a chamber main body 13, a front slit part 15 and an insulating part 16 interposed therebetween. The ion source further comprises, on the chamber main body 13, a front slit power source 17 for applying a voltage to the front slit part 15, and an ion source control part 18. The ion source control part 18 includes: a sputtering rate storage part for storing sputtering rate information representing the relation between the kinetic energy of ions and the rate of sputtering a front slit deposition by the ions in a plasma-generation space 12; an optimum voltage-decision part for deciding, based on the sputtering rate information, a set voltage Vs to apply to the front slit part 15 for cleaning the front slit part 15 on the chamber main body 13; and a power source control part for controlling the front slit power source 17 according to the set voltage Vs.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ion source, an ion source front slit voltage setting device, and an ion source front slit voltage setting method.

  When the operation of the ion source is continued, deposits adhere to the inner wall and extraction electrode of the plasma generation container. A cleaning method is known in which a cleaning gas is introduced into a plasma generation container to generate the plasma in the container, and deposits are removed by sputtering, chemical reaction, or the like using ions in the plasma.

JP 2012-38668 A Japanese Patent Laid-Open No. 3-64462

  One exemplary object of an aspect of the present invention is to provide a technique for shortening the ion source cleaning time.

  According to an aspect of the present invention, the ion source includes a chamber main body that surrounds the plasma generation space, a front slit portion that defines an ion extraction opening of the chamber main body, and the front slit portion is electrically insulated from the chamber main body. An ion source chamber comprising an insulating portion interposed between the front slit portion and the chamber body, and the chamber body and the front slit portion so as to apply a voltage to the front slit portion with respect to the chamber body. And a front slit power source electrically connected between the ion source control unit and the ion source control unit. The ion source control unit includes a sputtering rate storage unit that stores sputter rate information representing a relationship between a kinetic energy of ions in the plasma generation space and a sputtering rate of the front slit deposit by the ions, and cleaning of the front slit unit. For this purpose, an optimum voltage determining unit that determines a set voltage to be applied to the front slit unit with respect to the chamber body based on the sputtering rate information, and a power control unit that controls the front slit power source according to the set voltage Prepare.

  According to an aspect of the present invention, the ion source front slit voltage setting device provides sputter rate information representing a relationship between the kinetic energy of ions generated in the chamber body of the ion source and the sputter rate of the front slit deposit by the ions. A sputtering rate storage unit for storing, and an optimum voltage determination unit for determining a set voltage to be applied to the front slit unit with respect to the chamber body for cleaning the front slit unit of the ion source based on the sputtering rate information; .

  According to an aspect of the present invention, an ion source front slit voltage setting method includes: sputtering rate information representing a relationship between a kinetic energy of ions generated in a chamber body of an ion source and a sputtering rate of a front slit deposit by the ions. And generating a setting voltage to be applied to the front slit portion with respect to the chamber body for cleaning the front slit portion of the ion source based on the sputtering rate information.

  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.

  According to the present invention, the cleaning time of the ion source can be shortened.

It is a figure showing roughly the ion source concerning a certain embodiment of the present invention. It is a figure which shows schematically the ion source front slit voltage setting apparatus which concerns on one embodiment of this invention. It is a figure which shows schematically the ion source front slit voltage setting method which concerns on one embodiment of this invention. It is a graph which illustrates the sputtering rate information concerning an embodiment of the present 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. Moreover, the structure described below is an illustration and does not limit the scope of the present invention at all.

  FIG. 1 schematically shows an ion source 10 according to an embodiment of the present invention. The ion source 10 is used as an ion source of an ion irradiation apparatus such as an ion implantation apparatus or a particle beam therapy apparatus. The ion source 10 is a microwave ion source, for example. In the microwave ion source, a microwave is introduced into a vacuum plasma chamber. The source gas supplied to the plasma chamber is excited by microwaves, and plasma P is generated. Ions I are extracted from the plasma P. The ion source 10 may be another type of ion source such as an indirectly heated cathode type ion source.

  The ion source 10 includes an ion source chamber 11. The ion source chamber 11 includes a chamber body 13 that surrounds the plasma generation space 12, a front slit portion 15 that defines an ion extraction opening 14 of the chamber body 13, and an insulating portion 16 that is interposed between the front slit portion 15 and the chamber body 13. And comprising. The insulating part 16 electrically insulates the front slit part 15 from the chamber body 13. A part of the chamber body 13 may be a microwave introduction window for receiving the microwave in the ion source chamber 11.

  The ion source 10 controls the ion source 10 and a front slit power source 17 electrically connected between the chamber main body 13 and the front slit portion 15 so as to apply a voltage to the front slit portion 15 with respect to the chamber main body 13. An ion source control unit 18 configured as described above. The ion source control unit 18 may be configured to control other components of the ion irradiation apparatus on which the ion source 10 is mounted. Details of the ion source controller 18 will be described later.

  The ion source 10 includes a gas supply system (not shown) for supplying the plasma P source gas to the plasma generation space 12. By this gas supply system, for example, source gases such as diborane, boron trifluoride, arsine, and phosphine are supplied to the plasma generation space 12. The gas supply system may supply a cleaning gas (for example, argon) for cleaning the chamber body 13 and the front slit portion 15 to the plasma generation space 12.

  A magnetic field generator (not shown) such as a coil for generating a magnetic field along the central axis of the plasma generation space 12 may be provided outside the ion source chamber 11. In order to efficiently absorb the microwave into the source gas, a magnetic field in the electron cyclotron resonance condition or an axial magnetic field stronger than that is applied to the plasma generation space 12. In this way, high-density plasma may be generated in the plasma generation space 12.

  An extraction electrode system (not shown) for extracting the ions I out of the ion source chamber 11 is provided outside the ion extraction opening 14. The extraction electrode system corresponds to the most upstream part of a so-called beam line for carrying the ions I to the irradiated object. This beam line is also kept in a vacuum by an evacuation system (not shown) as in the plasma generation space 12.

  A mass spectrometer 20 is installed downstream of the ion source 10. The mass spectrometer 20 is disposed downstream of the front slit portion 15 so as to receive the ion beam B exiting from the ion extraction opening 14 and is configured to measure a mass spectrum of the ion beam B. The mass spectrometer 20 is disposed downstream of the above-described extraction electrode system. In this document, the mass spectrometer 20 may be regarded as a part of the ion source 10 or may be regarded as a component different from the ion source 10 in the ion irradiation apparatus.

  The mass spectrometer 20 includes a mass spectrometry controller 21 configured to control the mass spectrometer 20. The mass analysis control unit 21 performs mass analysis so that a mass spectrum measurement mode for controlling the mass spectrometer 20 so that the mass spectrum of the ion beam B is measured and a predetermined ion species are selected from the ion beam B. One operation mode is selected from a plurality of operation modes including a predetermined ion species selection mode for controlling the apparatus 20. The mass spectrometry control unit 21 may be provided separately from the ion source control unit 18. The mass spectrometry control unit 21 may be a part of the ion source control unit 18.

  FIG. 2 is a diagram schematically showing an ion source controller 18 or an ion source front slit voltage setting device according to an embodiment of the present invention. Such a control device is realized by hardware, software, or a combination thereof. FIG. 2 schematically shows a configuration of a part of the related ion source 10.

  The ion source control unit 18 includes an operation mode selection unit 30, a cleaning control unit 31, a storage unit 32, an input unit 34, and an output unit 36.

  The operation mode selection unit 30 is configured to select one operation mode from a plurality of operation modes including a cleaning operation mode for performing cleaning of the ion source 10 and a normal operation mode for extracting the ions I from the ion source 10. ing. The plurality of operation modes may include a simultaneous operation mode in which cleaning and ion extraction are performed simultaneously. The operation mode selection unit 30 may select one operation mode according to the input from the input unit 34.

  The cleaning control unit 31 is configured to control the ion source 10 in the cleaning operation mode. Although described in detail later, the cleaning control unit 31 controls the front slit power source 17 so that the front slit power source 17 outputs the set voltage Vs in the cleaning operation mode. The cleaning control unit 31 controls the front slit power supply 17 to output the set voltage Vs or any voltage different from the set voltage Vs in the normal operation mode (or the simultaneous operation mode). The cleaning control unit 31 includes an ion species specifying unit 38, a deposit specifying unit 40, a sputtering rate calculation unit 42, a sputtering rate storage unit 44, an optimum voltage determination unit 46, and a power supply control unit 48.

  The storage unit 32 is configured to store information related to the control of the ion source 10. The sputtering rate storage unit 44 may be provided in the storage unit 32. The input unit 34 is configured to receive an input related to the control of the ion source 10 from a user or another device. The input unit 34 includes, for example, an input unit such as a mouse and a keyboard for receiving input from the user, and / or a communication unit for communicating with other devices. The output unit 36 is configured to output information related to the control of the ion source 10 and includes output means such as a display and a printer. The storage unit 32, the input unit 34, and the output unit 36 are connected to the cleaning control unit 31 so as to communicate with each other.

  The mass spectrometry control unit 21 may select the selection of the mass spectrum measurement mode when the operation mode selection unit 30 selects the cleaning operation mode. The mass spectrometry control unit 21 may select the predetermined ion species selection mode when the operation mode selection unit 30 selects the normal operation mode (or the simultaneous operation mode).

  The mass spectrometry control unit 21 may include a mass spectrum monitor 22. The mass spectrum monitor 22 is configured to output the mass spectrum MS of the ion beam B measured in the mass spectrum measurement mode to the ion source control unit 18. The ion source control unit 18 may provide the input mass spectrum MS to the operation mode selection unit 30 and the cleaning control unit 31 as necessary. Alternatively, the ion source control unit 18 may store the mass spectrum MS in the storage unit 32 and / or output it to the output unit 36.

  FIG. 3 is a diagram schematically showing an ion source front slit voltage setting method according to an embodiment of the present invention. This method includes an ion I and front slit deposit D identification step (S1), a sputtering rate calculation step (S2), and an optimum voltage determination step (S3). After the optimum voltage determination step (S3), a cleaning step (S4) may be included as necessary.

  In the specifying step (S1), the ion species specifying unit 38 specifies one or more ion species generated in the plasma generation space 12. The ion species identification unit 38 may store information representing the identified ion species in the storage unit 32 and / or output the information to the output unit 36.

  For example, the ion species identification unit 38 may identify one or more ion species included in the ion beam B from the measured mass spectrum MS of the ion beam B. Alternatively, the ion species specifying unit 38 may specify one or more ion species generated from the gas species (raw material gas or cleaning gas) supplied to the plasma generation space 12. Information representing the gas type supplied to the plasma generation space 12 may be input from the input unit 34 and stored in the storage unit 32 in advance. The ion species specifying unit 38 may read out such information from the storage unit 32 and use it.

  In the specifying step (S1), the deposit specifying unit 40 specifies one or more types of front slit deposits D. The deposit specifying unit 40 may store information representing the specified front slit deposit D in the storage unit 32 and / or output the information to the output unit 36.

  For example, the deposit specifying unit 40 may specify one or more types of deposits on the front slit unit 15 from the deposit specifying database. The deposit identification database includes the source gas species supplied to the plasma generation space 12 in the previous operation and, if necessary, the material of the ion source chamber 11 exposed to the plasma generation space 12 as a result of the operation. It has information representing things. For example, when phosphine is used as the source gas, red phosphorus can be deposited on the front slit portion 15. When arsine is used as the source gas, arsenic solid can be deposited on the front slit portion 15. When boron trifluoride is used as the source gas and the exposed surface of the chamber body 13 is boron nitride, polycrystalline boron nitride can be deposited on the front slit portion 15. The deposit specifying database representing such deposit information may be created in advance and stored in the storage unit 32.

  In the sputtering rate calculation step (S2), the sputtering rate calculation unit 42 calculates the sputtering rate and generates sputtering rate information. Here, the sputtering rate information represents the relationship between the kinetic energy of the ions I in the plasma generation space 12 and the sputtering rate of the front slit deposit D by the ions I. Further, as is known, the sputtering rate represents the number of atoms bounced from an object when one ion I collides with the object.

  For example, the sputtering rate calculation unit 42 calculates the sputtering rate for each of a plurality of different kinetic energy values, and generates sputtering rate information. The sputtering rate calculation unit 42 may sequentially calculate the sputtering rate corresponding to each kinetic energy value while changing the kinetic energy value over a range of a certain kinetic energy value. Such calculations can be performed using commonly available software (eg, SRIM). The sputtering rate calculation unit 42 may store the generated sputtering rate information in the sputtering rate storage unit 44 and / or output it to the output unit 36.

  The sputtering rate calculation unit 42 may select one ion species from one or more ion species identified by the ion species identification unit 38. The sputtering rate calculation unit 42 may select one type of deposit from one or more types of front slit deposits D specified by the deposit specifying unit 40. The sputter rate calculation unit 42 generates sputter rate information representing the relationship between the ion kinetic energy of the selected one ion species and the sputter rate of the selected one type of deposit by the one ion species. Also good. The sputtering rate calculation unit 42 includes a plurality of (for example, all of the one or more ion species specified by the ion species specifying unit 38 and one or more types of front slit deposits D specified by the deposit specifying unit 40. ) Sputtering rate information may be generated for the combination.

FIG. 4 is a graph illustrating sputtering rate information according to an embodiment of the invention. The vertical axis in FIG. 4 represents the sputtering rate, and the horizontal axis represents the kinetic energy of the ions I. The kinetic energy corresponds to the voltage of the front slit power supply 17. FIG. 4 shows, as an example, the sputtering rate calculated when the ion I is Ar ⁺ (argon) and the deposit is B (boron).

  In the optimum voltage determination step (S3), the optimum voltage determination unit 46 determines the set voltage Vs to be applied to the front slit portion 15 to the chamber body 13 for cleaning the front slit portion 15 based on the sputtering rate information. To do. The optimum voltage determination unit 46 may read the sputtering rate information from the sputtering rate storage unit 44 and use it. The optimum voltage determination unit 46 may store information representing the set voltage Vs in the storage unit 32 and / or output the information to the output unit 36.

  As illustrated in FIG. 4, the optimum voltage determination unit 46 may determine the set voltage Vs from the ion kinetic energy value E that gives the maximum sputtering rate Smax derived from the sputtering rate information. Alternatively, the optimum voltage determination unit 46 may determine the set voltage Vs from a certain kinetic energy value that gives a certain ratio or more (for example, 95% or more or 90% or more) of the maximum sputtering rate Smax.

  As described above, when the sputtering rate information is prepared for each of a plurality of combinations of ion species and deposits, the maximum sputtering rate Smax is obtained for each sputtering rate information. When there are a plurality of maximum sputtering rates Smax as described above, the optimum voltage determination unit 46 may select the maximum sputtering rate by comparing them and determine the set voltage Vs based on the selected sputtering rate, for example. Or the optimal voltage determination part 46 may determine the weighting average of the setting voltage based on each of the some maximum sputtering rate Smax to the setting voltage Vs actually used.

  Note that the generation of the sputtering rate information by the sputtering rate calculation unit 42 is not always performed every time the set voltage Vs is determined. That is, the specific step (S1) and the sputtering rate calculation step (S2) can be omitted. In this case, the cleaning control unit 31 may execute a step in which the sputtering rate storage unit 44 stores the sputtering rate information prepared in advance and the above-described optimum voltage determination step (S3). When the sputtering rate information prepared in advance can be used, the optimum voltage determination unit 46 may read it from the sputtering rate storage unit 44 and use it to determine the set voltage Vs.

  Since the above-described specific step (S1), sputtering rate calculation step (S2), and optimum voltage determination step (S3) are preparations for cleaning, the cleaning control unit 31 performs steps S1 to S3 by the ion source 10. Executed when not in the cleaning operation mode. For example, the cleaning control unit 31 may execute steps S1 to S3 in the normal operation mode or when the operation of the ion source 10 is stopped.

  In the cleaning step (S4), the operation mode selection unit 30 switches from another operation mode (for example, the normal operation mode) to the cleaning operation mode, and starts the cleaning operation mode. In response to this, the power supply control unit 48 controls the front slit power supply 17 according to the set voltage Vs. The power supply control unit 48 may read the set voltage Vs from the storage unit 32 and use it. Thus, the front slit power source 17 applies the set voltage Vs to the front slit portion 15 with respect to the chamber body 13. Therefore, the front slit deposit D can be removed at the maximum or near sputtering rate.

  When a predetermined cleaning end condition is satisfied, the operation mode selection unit 30 switches from the cleaning operation mode to another operation mode (for example, the normal operation mode), and ends the cleaning operation mode. For example, the operation mode selection unit 30 may determine whether or not to end the cleaning based on the mass spectrum MS. When most or all of the deposit is removed, the front slit portion 15 itself is sputtered. Therefore, the material of the front slit portion 15 can be included in the ion beam B. Cleaning may be completed by detecting this from the mass spectrum MS.

  When the cleaning operation mode is terminated, the power supply control unit 48 may control the front slit power supply 17 so that the chamber body 13 and the front slit unit 15 have the same potential. In this way, it is possible to prevent the potential difference between the chamber main body 13 and the front slit portion 15 from affecting the subsequent normal operation. Alternatively, the power supply control unit 48 may control the front slit power supply 17 so that a voltage smaller than the set voltage Vs is applied to the front slit unit 15 with respect to the chamber body 13. In this way, a certain amount of cleaning can be continued in the subsequent normal operation.

  The operation of the ion source 10 having the above configuration will be described. As the ion source 10 is operated, solid matter derived from the source gas or the like can be deposited in the ion source chamber 11. Excess deposits on the front slit portion 15 can block the ion extraction opening 14. In that case, the ion source 10 cannot continue operation. Therefore, the ion source 10 is periodically cleaned. The cleaning operation of the ion source 10 is started in response to a user input or automatically. At this time, the front slit power supply 17 applies a set voltage Vs to the front slit portion 15 with respect to the chamber body 13.

  As described, the set voltage Vs is prepared in advance so as to realize the maximum sputtering rate or a sputtering rate close thereto. By optimizing the sputtering voltage, deposits can be efficiently removed from the front slit portion 15. Therefore, the cleaning time of the ion source 10 can be shortened.

  During operation of the ion source 10, the ion source chamber 11 can be heated to a high temperature of at least several hundred degrees by the plasma P. For example, a microwave ion source can be heated to about 300 ° C. to 400 ° C. The indirectly heated cathode type ion source can be heated to about 1000 ° C. Since the heating temperature of the microwave ion source is relatively low, deposits tend to adhere to the plasma chamber of the microwave ion source. For this reason, the optimum voltage setting according to the embodiment and the efficient cleaning thereby are particularly suitable for the microwave ion source.

  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.

  DESCRIPTION OF SYMBOLS 10 Ion source, 11 Ion source chamber, 12 Plasma production space, 13 Chamber main body, 14 Ion extraction opening, 15 Front slit part, 16 Insulation part, 17 Front slit power supply, 18 Ion source control part, 30 Operation mode selection part, 31 Cleaning control unit, 32 storage unit, 38 ion species identification unit, 40 deposit identification unit, 42 sputter rate calculation unit, 44 sputter rate storage unit, 46 optimum voltage determination unit, 48 power supply control unit, Smax maximum sputtering rate, Vs setting Voltage.

Claims (6)

A chamber body surrounding the plasma generation space; a front slit portion defining an ion extraction opening of the chamber body; and the front slit portion and the chamber body between the front slit portion and the chamber body so as to electrically insulate the front slit portion from the chamber body. An ion source chamber comprising an intervening insulation;
A front slit power source electrically connected between the chamber main body and the front slit portion so as to apply a voltage to the front slit portion with respect to the chamber main body;
An ion source controller,
A sputtering rate storage unit for storing sputtering rate information representing a relationship between the kinetic energy of ions in the plasma generation space and the sputtering rate of the front slit deposit by the ions;
An optimum voltage determining unit that determines a setting voltage to be applied to the front slit portion with respect to the chamber body for cleaning the front slit portion based on the sputtering rate information;
An ion source comprising: an ion source control unit comprising: a power source control unit that controls the front slit power source according to the set voltage.   The ion source according to claim 1, wherein the optimum voltage determination unit determines the set voltage from an ion kinetic energy value that gives a maximum sputtering rate derived from the sputtering rate information.   The ion source according to claim 1, wherein the ion source control unit includes a sputtering rate calculation unit that calculates the sputtering rate for each of a plurality of different kinetic energy values and generates the sputtering rate information. The ion source control unit includes an ion species identifying unit that identifies one or more ion species generated in the plasma generation space, and a deposit identifying unit that identifies one or more types of front slit deposits,
The sputter rate information includes one kind of ion kinetic energy of one ion species selected from the one or more ion species and one kind of front slit deposit selected from the one or more kinds of front slit deposits. The ion source according to claim 1, wherein the ion source represents a relationship with a sputtering rate of the deposit. A sputtering rate storage unit for storing sputtering rate information representing a relationship between the kinetic energy of ions generated in the chamber body of the ion source and the sputtering rate of the front slit deposit by the ions;
An optimum voltage determining unit that determines a set voltage to be applied to the front slit portion with respect to the chamber main body for cleaning the front slit portion of the ion source based on the sputtering rate information. Ion source front slit voltage setting device. Generating sputter rate information representing the relationship between the kinetic energy of ions generated in the chamber body of the ion source and the sputter rate of the front slit deposit by the ions;
Determining a set voltage to be applied to the front slit portion of the chamber body for cleaning the front slit portion of the ion source based on the sputtering rate information. Slit voltage setting method.

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