JP5141732B2 - Ion source electrode cleaning method - Google Patents

Description

  The present invention relates to a cleaning method for removing deposits deposited on the surface of an electrode constituting an extraction electrode system of an ion source. In this specification, the simple ion refers to a positive ion.

  When the operation of extracting the ion beam from the ion source is continued, deposits are deposited (attached) on the electrodes constituting the extraction electrode system. If it is left unattended, it will cause problems such as abnormal discharge between the electrodes.

  Therefore, as an example of a method for cleaning the ion source electrode, a rare gas is supplied into the plasma chamber instead of the ionized gas, an ion beam of the rare gas is extracted, and either or both of the gas flow rate and the extraction voltage are set. Conventionally, a cleaning method has been proposed in which the beam diameter of the ion beam is adjusted to adjust the ion beam so that the ion beam collides with the deposit deposited on the electrode surface and the deposit is removed by sputtering (for example, patents). Reference 1).

Japanese Patent No. 4374487 (paragraphs 0024-0028, FIG. 1)

  In the conventional cleaning method, the deposit is removed by colliding the ion beam of the rare gas with the deposit on the electrode surface. The rare gas is supplied to the plasma chamber or applied to the extraction electrode system. Regardless of how the extraction voltage is adjusted, the area where deposits are removed is limited to the periphery of the electrode holes (ion extraction holes), so deposits deposited in other areas cannot be removed. . Therefore, the area where deposits can be removed is narrow.

  The upper limit value of the ion beam current extracted from the plasma in the plasma chamber and applied to each electrode is, in principle, about the maximum ion beam current of the ion source, and is at most several hundred mA at most. To a certain extent, and therefore high speed removal of deposits is difficult.

  Accordingly, the main object of the present invention is to provide a cleaning method capable of removing deposits at a high speed over a wide area of the electrode constituting the extraction electrode system of the ion source.

A cleaning method according to the present invention includes a plasma generation unit that introduces an ionized gas and ionizes the ionized gas to generate plasma, and an electrode system that extracts an ion beam from the plasma in the plasma generation unit by the action of an electric field. A method for cleaning an electrode constituting the extraction electrode system of an ion source comprising: an extraction electrode system having at least a first electrode , a second electrode, and a third electrode arranged in the ion beam extraction direction from the plasma side A switch for switching an electric circuit for applying a voltage to the ion source between a state in which an ion beam is drawn out and a state in which the electrode is cleaned is provided. It switched to a state side to perform, and leave grounding the third electrode via a resistor, the flop Instead of introducing the ionized gas into the zuma generating unit and extracting the ion beam, a cleaning gas is supplied between at least the first electrode and the second electrode constituting the extraction electrode system, and the first electrode In a state where the gas pressure between the second electrode and the second electrode is kept higher than the gas pressure at the time of extracting the ion beam, a voltage is applied from the power source through a series resistor between the first electrode and the second electrode. This is characterized in that glow discharge of the cleaning gas is generated between the two electrodes.

  In this cleaning method, a plasma of a cleaning gas is generated by glow discharge generated between the first electrode and the second electrode, sputtering by ions in the plasma, chemical reaction with active particles in the plasma, etc. Thus, the deposits deposited on the surfaces of both electrodes are removed. That is, both electrodes can be cleaned.

  In addition, since the glow discharge is generated almost entirely between the first electrode and the second electrode to which a voltage is applied, almost the entire electrode surface on the side where the plasma due to the glow discharge is generated becomes the plasma. Be exposed. Therefore, the deposit can be removed over a wide area of both electrodes without being limited to the periphery of the ion extraction hole.

  Furthermore, since the discharge current of the glow discharge can be easily set to a value much larger than the maximum ion beam current of the ion source, deposits can be removed at a higher speed than the conventional cleaning method.

  If the extraction electrode system has at least a first electrode, a second electrode, and a third electrode, the second electrode can be used instead of or in place of generating a glow discharge between the first electrode and the second electrode. Glow discharge may be generated between the electrode and the third electrode. Thereby, the second electrode and the third electrode can be cleaned.

  The voltage for generating the glow discharge may be a DC voltage with the electrode on the ion beam extraction direction side being the negative side or an AC voltage.

  According to the first aspect of the present invention, since the glow discharge of the cleaning gas is generated between the first electrode and the second electrode constituting the extraction electrode system, it is not limited to the periphery of the ion extraction hole. Deposits can be removed over a wide area of both electrodes.

In addition, since the discharge current of the glow discharge can be easily set to a value much larger than the maximum ion beam current of the ion source, deposits can be removed at a higher speed than the conventional cleaning method.
Furthermore, if a glow discharge is generated with deposits on the first electrode and the second electrode, abnormal discharge is likely to occur between the two electrodes, which may cause a failure of the power source for generating the glow discharge. However, by applying a voltage between the two electrodes from the power source via the series resistor, a sudden increase in current when an abnormal discharge occurs between the two electrodes can be suppressed by the series resistor.

And according to invention of Claim 1, there exists the following further effect. That is, the extraction electrode system has at least a first electrode, a second electrode, and a third electrode, and a voltage is applied between the first electrode and the second electrode to generate a glow discharge between the two electrodes . When you clean the electrode and the second electrode, the advance of the third electrode is grounded through a resistor, the plasma between the second electrode and the third electrode can be prevented from occurring, the Glow discharge can be preferentially generated between the first electrode and the second electrode.

It is the schematic which shows an example of the ion source apparatus which implements the cleaning method concerning this invention, and shows the state at the time of ion beam extraction. It is the schematic which shows an example of the ion source apparatus which implements the cleaning method which concerns on this invention, and shows the state at the time of cleaning. It is the schematic which shows the other example of the ion source apparatus which implements the cleaning method concerning this invention, and shows the state at the time of cleaning. It is the schematic which shows the further another example of the ion source apparatus which implements the cleaning method concerning this invention, and shows the state at the time of cleaning. It is the schematic which shows the further another example of the ion source apparatus which implements the cleaning method concerning this invention, and shows the state at the time of cleaning. It is the schematic which shows the other example of the introduction method of cleaning gas.

  An example of an ion source apparatus for carrying out the cleaning method according to the present invention is shown in FIGS. FIG. 1 shows a state during extraction of an ion beam, and FIG. 2 shows a state during cleaning.

  The ion source 2 constituting the ion source device includes a plasma generation unit 4 that introduces an ionized gas 38 and ionizes the ionized gas 38 to generate plasma 6, and an electric field action from the plasma 6 in the plasma generation unit 4. And an extraction electrode system 10 for extracting the ion beam 20.

  In this example, the plasma generation unit 4 emits thermoelectrons from a filament 8 provided in the plasma generation container 5 and discharges (arc discharge) between the filament 8 and the plasma generation container 5 that also serves as an anode. The ionized gas 38 is ionized to generate the plasma 6. A filament power supply 50 for heating is connected to the filament 8, and an arc power supply 52 for generating arc discharge is connected between one end of the filament 8 and the plasma generation vessel 5 with the former as the negative electrode side.

  However, the plasma generation unit 4 is not limited to this type. The number of filaments 8 is not limited to one as in the illustrated example. For example, a plurality of filaments 8 may be provided. Moreover, the type etc. which ionize the ionized gas 38 by high frequency discharge and produce | generate plasma 6 may be used.

  In this example, the ionized gas 38 is introduced from the ionized gas source 32 into the plasma generation container 5 via the flow rate regulator 34, the valve 36, and the gas inlet 7.

The ionized gas 38 is a gas containing a desired dopant, such as boron (B), phosphorus (P), or arsenic (As). For example, boron fluoride gas (BF ₃ ), hydrogen diluted diborane gas (B ₂ H ₆ / H ₂ ), hydrogen diluted phosphine gas (PH ₃ / H ₂ ), hydrogen diluted arsine gas (AsH ₃ / H ₂ ), or the like.

  In this example, the extraction electrode system 10 includes four electrodes arranged from the most plasma side to the ion beam extraction direction, that is, a first electrode (also referred to as a plasma electrode) 11 and a second electrode (also referred to as an extraction electrode). 12, a third electrode (which is also referred to as a suppression electrode) 13, and a fourth electrode (which is also referred to as a ground electrode) 14. Although 16 is an insulator, illustration of other insulators is omitted. The number of electrodes is not limited to four, but may be two, three, or the like. Each of the electrodes 11 to 14 has an ion extraction hole 15. The ion extraction hole 15 may be, for example, a plurality of (many) holes or one or more slits.

  In addition, the space | interval between each electrode 11-14 which comprises the extraction electrode system 10 is expanded and shown in figure for convenience of illustration. The same applies to the other drawings.

  The front part of the plasma generation unit 4 (more specifically, the plasma generation container 5) is attached to ion source chambers 22 and 23 that are evacuated by a vacuum evacuation device 30 through a valve 28. 10 is accommodated in the ion source chambers 22 and 23. The ion source chambers 22 and 23 are insulated by an insulator 24 in order to insulate a voltage corresponding to the output voltage of the acceleration power source 58. In the ion source chamber 23, a valve (gate valve) 26 is provided at a position downstream of the extraction electrode system 10 and the valve 28 to partition the ion source 2 for maintenance and inspection. .

  The first electrode 11 of the extraction electrode system 10 is connected to the negative electrode side of the arc power source 52 in this example. An acceleration power source 58 that mainly determines the energy of the ion beam 20 is connected between the plasma generation vessel 5 and the ground potential portion, with the former being on the positive electrode side. Between the second electrode 12 and the plasma generation vessel 5, an extraction power source 54 for mainly extracting ions from the plasma 6 is connected via the changeover switch 71 described later with the former set to the negative electrode side. Between the third electrode 13 and the ground potential portion, a suppression power source 56 for suppressing backflow electrons mainly from the downstream side is connected via the changeover switch 72 described later with the former set to the negative electrode side. The fourth electrode 14 is grounded.

  This ion source device further includes the following configuration so that the cleaning method described below can be performed instead of introducing the ionized gas 38 into the plasma generating unit 4 and extracting the ion beam 20.

  That is, the cleaning gas source 42, the flow rate regulator 44, and the valve 46 are provided, and in this example, the cleaning gas 48 (see FIG. 2) can be supplied into the plasma generation vessel 5 through the gas introduction port 7. I can do it. The cleaning gas 48 is diffused between the electrodes of the extraction electrode system 10 through the ion extraction holes 15 of the first electrode 11 and the like by helping to be evacuated by the evacuation device 30 provided at the position. It is also supplied between the electrodes.

  As the cleaning gas 48, it is preferable to use a gas that hardly generates deposits on the electrode surface when glow discharge described later is generated. For example, the cleaning gas 48 is an inert gas (also referred to as a rare gas) such as hydrogen gas or argon, or a mixed gas thereof. The inert gas may be He, Ne, Kr, or Xe other than Ar. When hydrogen gas is used as the cleaning gas 48, there is an advantage that the deposit removed from the electrode surface is easily discharged to the outside by the vacuum exhaust device 30 by combining with hydrogen to form a hydrogen compound.

  At the time of cleaning, in order to exhaust the inside of the ion source chambers 22 and 23 by the vacuum exhaust device 30 at a lower exhaust speed than that at the time of extraction of the ion beam, the opening area is smaller than the valve 28 in parallel with the valve 28 and conductance is reduced. A small valve 29 is provided.

  A DC voltage is applied between the first electrode 11 and the second electrode 12 so that the second electrode 12, which is the electrode on the ion beam extraction direction side, is on the negative side. A direct current glow discharge power source 60 for generating a glow discharge 80 (see FIG. 2) is provided. The output voltage of the glow discharge power source 60 is, for example, about several hundred V to several kV, more specifically about 100 V to 1 kV.

  Switches 70 to 73 are provided to switch between extraction of the ion beam 20 and electrode cleaning. The changeover switch 71 switches the second electrode 12 between the drawing power supply 54 side and the glow discharge power supply 60 side via the resistor 64. The changeover switch 72 switches the third electrode 13 between the suppression power supply 56 side and the ground side via the resistor 66.

  The switches 70 and 73 are for bringing the plasma generation container 5, the first electrode 11 and the like to the ground potential. When the switches 70 and 73 are closed, the output voltages of the power sources 52 and 58 are naturally set to 0 in advance.

  FIG. 1 shows a state when the ion beam 20 is extracted. In this case, the valve 26 is kept open. Then, the valve 29 is closed and the valve 28 is opened, and the inside of the ion source chambers 22 and 23 is evacuated by the evacuation apparatus 30. With the valve 46 closed and the valve 36 opened, the ionized gas 38 is introduced into the plasma generation vessel 5. The switches 70 and 73 are opened, the changeover switch 71 is switched to the drawer power supply 54 side, and the changeover switch 72 is switched to the suppression power supply 56 side.

  As a result, the ionization gas 38 is ionized in the plasma generation unit 4 (more specifically, the plasma generation vessel 5) to generate the plasma 6, and the extraction beam system 10 extracts the ion beam 20 from the plasma 6. it can.

  FIG. 2 shows the state when the electrodes are cleaned. In this case, the valve 26 is closed. Then, the valve 28 is closed and the valve 29 is opened, and the inside of the ion source chambers 22 and 23 is exhausted by the vacuum exhaust device 30 at a low exhaust speed. Further, instead of closing the valve 36, the valve 46 is opened, and the cleaning gas 48 is introduced into the plasma generation container 5. Accordingly, as described above, the cleaning gas 48 introduced into the plasma generation container 5 is supplied at least between the first electrode 11 and the second electrode 12. At this time, the gas pressure between the first electrode 11 and the second electrode 12 is extracted by adjusting the flow rate of the cleaning gas 48 introduced into the plasma generation vessel 5 and the exhaust speed by the vacuum exhaust device 30. Keep higher than the time gas pressure (for example, less than 1 Pa). More specifically, the gas pressure that is convenient for generating the glow discharge 80 of the cleaning gas 48 is maintained. For example, it is maintained at about 1 Pa to 1000 Pa.

  Further, the changeover switch 71 is switched to the glow discharge power source 60 side (specifically, the resistor 64 side), and the switch 70 is closed, and the latter is placed between the first electrode 11 and the second electrode 12 on the negative side. Then, a DC voltage is applied from the glow discharge power source 60 to generate a glow discharge (DC glow discharge) 80 of the cleaning gas 48 between the electrodes 11 and 12. The changeover switch 72 is switched to the resistor 66 side, and the switch 73 is closed.

  A plasma of the cleaning gas 48 is generated by the glow discharge 80 generated between the first electrode 11 and the second electrode 12, and sputtering with ions in the plasma and chemistry with active particles such as radicals in the plasma are performed. Deposits deposited on the surfaces of both electrodes 11 and 12 are removed by reaction or the like. That is, both electrodes 11 and 12 can be cleaned.

  Moreover, since the glow discharge 80 is generated almost entirely between the first electrode 11 and the second electrode 12 to which a voltage is applied, the electrode surface on the side where the plasma due to the glow discharge 80 is generated (that is, Nearly the entire back surface 11b of the first electrode 11 and the front surface 12a) of the second electrode 12 are exposed to plasma. Therefore, the deposit can be removed over a wide area of both the electrodes 11 and 12 without being limited to the periphery of the ion extraction hole 15.

  Furthermore, since the discharge current of the glow discharge 80 can be easily set to a value much larger than the maximum ion beam current of the ion source, deposits can be removed at a higher speed than the conventional cleaning method. .

  This will be explained in more detail. The higher the density of the glow discharge plasma, the higher the density of ions and active particles in the plasma, so that the deposit removal rate becomes faster. Accordingly, the larger the glow discharge current that is an index of plasma density, the faster the deposit removal rate. For example, according to an experiment using an ion source device for an ion doping apparatus for manufacturing a flat panel display (FPD), when an ion beam is made to collide with the second electrode 12 by a method corresponding to the conventional cleaning method described above. The ion beam current at that time was limited to about 200 mA. On the other hand, the glow discharge current in the case of this cleaning method was able to achieve 2000 mA.

  By the way, the amount of deposits deposited on the electrodes 11 and 12 is much larger on the front surface 12a, which is the surface on which the ion beam strikes, than on the back surface 11b of the electrode 11 facing it. Therefore, when the voltage for generating the glow discharge 80 is a DC voltage with the second electrode 12 that is the electrode on the ion beam extraction direction side as the negative side as in the example shown in FIG. Since ions are incident on and collide exclusively with the negative electrode, that is, the front surface 12a of the second electrode 12, it is possible to preferentially remove the deposit on the front surface 12a where a large amount of deposit is deposited. Therefore, cleaning can be performed more efficiently.

  When the cleaning gas 48 is supplied as in the example shown in FIG. 1, there is an advantage that the gas introduction port 7 can also be used as the ionized gas 38, but between the first electrode 11 and the second electrode 12. In order to supply the cleaning gas 48, the cleaning gas 48 may be introduced into the inside of the ion source chamber 22 (or 23) from the wall surface, for example, as shown in FIG. The same applies to the examples shown in FIGS.

  Further, in order to adjust the gas pressure between the first electrode 11 and the second electrode 12 so as to be convenient for the generation of the glow discharge 80, the valves 26 and 28 are closed as in the example shown in FIG. Although it is practical and preferable to exhaust at a low exhaust speed by the vacuum exhaust device 30 via the valve 29, of course, the gas pressure between the first electrode 11 and the second electrode 12 is adjusted by other methods. You may do it.

  If the glow discharge 80 is generated with deposits on the electrodes 11, 12, abnormal discharge is likely to occur between the electrodes 11, 12, which may cause the glow discharge power supply 60 to fail. . Therefore, as in the example shown in FIG. 2, it is preferable to provide the series resistor 64, and by doing so, the resistor 64 can suppress a rapid increase in current during abnormal discharge. That is, the resistor 64 functions as a current limiting resistor.

  When the third electrode 13 is grounded via the changeover switch 72, a voltage is also applied between the second electrode 12 and the third electrode 13 from the glow discharge power source 60. Therefore, in order to preferentially generate the glow discharge 80 between the electrodes 11 and 12, it is preferable to ground the third electrode 13 via a high-resistance resistor 66 as in the example shown in FIG. . As a result, if plasma is generated between the second electrode 12 and the third electrode 13, electrons having a higher mobility than ions in the plasma are incident on the third electrode 13, and the third electrode. As a result of the negative charging of 13, the potential difference between the second electrode 12 and the third electrode 13 decreases, so that the generation of plasma between the electrodes 12 and 13 can be suppressed.

  Instead of providing the glow discharge power source 60, the second switch 12 is configured to be connected to the extraction power source 54 through the resistor 64 by the changeover switch 71 as in the example shown in FIG. May also be used as a power source for generating glow discharge 80. In such a case, the cleaning can be performed without adding a power supply dedicated to glow discharge. In this case, the glow discharge current is limited by the maximum output current of the extraction power supply 54.

  Further, instead of providing the DC glow discharge power source 60, an AC glow discharge power source 62 is provided as shown in FIG. 4, and the glow discharge 80 (in this case, AC glow discharge) is applied by applying an AC voltage. ) May be generated.

  When the voltage for generating the glow discharge 80 is an AC voltage, ions in the plasma generated by the glow discharge 80 are incident on and collide with both electrodes 11 and 12 sandwiching the glow discharge 80 according to the polarity inversion of the applied voltage. Therefore, the deposits deposited on both the electrodes 11 and 12, that is, both the front surface 12 a of the second electrode 12, which is an electrode on the ion beam extraction direction side, and the back surface 11 b of the first electrode 11 opposed thereto are efficiently removed. be able to.

  Further, the AC glow discharge power source 60 is usually configured mainly with a transformer and is less likely to fail than a DC power source using a semiconductor element, so that abnormal discharge occurs between the electrodes 11 and 12. There is also an advantage that it is difficult to break down.

  Each of the above cleaning methods is a cleaning method for generating a glow discharge 80 between the first electrode 11 and the second electrode 12, so that the extraction electrode system 10 has at least the first electrode 11 and the second electrode 12. If applicable.

  In addition, since the third electrode 13 is on the downstream side of the second electrode 12, the amount of deposit on the third electrode 13 due to extraction of the ion beam is smaller than the amount deposited on the second electrode 12. In the same manner as the cleaning method in which the glow discharge 80 is generated between the first electrode 11 and the second electrode 12, the glow discharge 80 is generated between the second electrode 12 and the third electrode 13. 13 cleaning may be performed.

  An example of this cleaning method will be described with reference to FIG. The difference from the example shown in FIG. 2 will be mainly described. The glow discharge power source 60 and the resistor 64 are connected to the changeover switch 72 side, and the changeover switch 72 is connected to the glow discharge power supply 60 side (when cleaning). Specifically, switching to the resistor 64 side). Further, a switch 74 for setting the second electrode 12 to the ground potential is provided and is closed during cleaning. At this time, naturally, the output voltage of the drawing power supply 54 is set to 0 in advance.

  The cleaning gas 48 may be introduced into the plasma generation vessel 5 in the same manner as in the example of FIG. 2, or is introduced into the interior of the ion source chamber 22 (or 23) from the wall surface as in the example shown in FIG. You may do it. In this way, the cleaning gas 48 is supplied at least between the second electrode 12 and the third electrode 13, and the gas pressure between the second electrode 12 and the third electrode 13 is changed to the ion beam as described above. A DC voltage is applied between the second electrode 12 and the third electrode 13 from the glow discharge power source 60 in a state where the gas pressure is maintained higher than the gas pressure at the time of extraction, and the cleaning gas 48 is applied between the electrodes 12 and 13. A glow discharge 80 is generated.

  Thus, deposits can be removed over a wide area of both electrodes 12 and 13 without being limited to the periphery of the ion extraction hole 15 by the same action as in the example shown in FIG.

  Moreover, since the discharge current of the glow discharge 80 can be easily set to a value much larger than the maximum ion beam current of the ion source, deposits can be removed at a higher speed than in the conventional cleaning method. .

  Further, when the voltage for generating the glow discharge 80 is a DC voltage with the third electrode 13, which is an electrode on the ion beam extraction direction side, set to the negative side, the ions in the plasma by the glow discharge 80 are negatively charged, that is, the first electrode. Since only the front surface 13a of the three electrodes 13 is incident and collides, it is possible to preferentially remove the deposit on the front surface 13a where a large amount of deposits are deposited. Therefore, cleaning can be performed more efficiently.

  However, as in the example shown in FIG. 4, an AC glow discharge power source 62 may be provided instead of the DC glow discharge power source 60. By doing so, deposits deposited on both the electrodes 12 and 13, that is, on both the front surface 13 a of the third electrode 13 that is an electrode in the ion beam extraction direction side and the back surface 12 b of the second electrode 12 that faces the electrode 13 and 13. It can be removed efficiently.

  When the extraction electrode system includes at least the first electrode 11, the second electrode 12, and the third electrode 13, (a) the first electrode 11 and the second electrode 12, as in the example shown in FIG. A glow discharge 80 may be generated between them, or (b) a glow discharge 80 may be generated between the second electrode 12 and the third electrode 13 as in the example shown in FIG. c) Glow discharge generation (cleaning) in (a) and glow discharge generation (cleaning) in (b) above are performed by appropriately switching the connections of the glow discharge power sources 60, 62, etc. And may be switched.

  Since the amount of deposits on the fourth electrode 14 is usually small, the need to clean the fourth electrode 14 is not so high, but if necessary, the third electrode 13 and Cleaning may be performed by supplying a cleaning gas 48 to the fourth electrode 14 and applying a glow discharge voltage to generate a glow discharge between the electrodes 13 and 14.

  After cleaning, the ion beam 20 can be extracted by returning to the state shown in FIG.

2 ion source 4 plasma generation unit 10 extraction electrode system 11 first electrode 12 second electrode 13 third electrode 14 fourth electrode 20 ion beam 38 ionized gas 48 cleaning gas 60, 62 glow discharge power source 80 glow discharge

Claims (1)

A plasma generation unit that introduces an ionized gas and ionizes the ionized gas to generate plasma, and an electrode system that extracts an ion beam from the plasma in the plasma generation unit by the action of an electric field, and in the ion beam extraction direction from the plasma side A method for cleaning an electrode constituting the extraction electrode system of an ion source comprising: an extraction electrode system having at least a first electrode , a second electrode, and a third electrode arranged;
A switch for switching an electric circuit for applying a voltage to the ion source between a state of drawing out an ion beam and a state of cleaning an electrode is provided,
When cleaning the electrode, switch the switch to the state to be cleaned,
And the third electrode is grounded through a resistor ,
Instead of introducing the ionized gas into the plasma generation unit and extracting the ion beam, a cleaning gas is supplied between at least the first electrode and the second electrode constituting the extraction electrode system, and the first electrode In a state where the gas pressure between the first electrode and the second electrode is kept higher than the gas pressure at the time of extracting the ion beam,
A voltage is applied between the first electrode and the second electrode through a series resistor from a power source to generate a glow discharge of the cleaning gas between the two electrodes. Cleaning method.

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