JP6083260B2 - Ion source and ion beam irradiation apparatus equipped with the ion source - Google Patents

Description

  The present invention relates to an ion source having a cleaning function and an ion beam irradiation apparatus including the ion source.

  If the operation of the ion source is continued for a long time, components of ionized gas such as BF3 and PH3 adhere to the inner wall of the plasma chamber constituting the ion source and the extraction electrode system disposed adjacent to the plasma chamber. Will accumulate.

  If such a deposit is left unattended, the amount of the deposit gradually increases, and due to this, there is a gap between the plasma chamber and between the electrodes constituting the extraction electrode system disposed at the end of the plasma chamber and the plasma chamber. An abnormal discharge occurs. Generation of such an abnormal discharge makes the generation of plasma in the plasma chamber unstable, making it difficult to extract a desired ion beam from the ion source.

  In addition, when the ionized gas is switched by one ion beam irradiation device and a sample such as a silicon wafer or a glass substrate is irradiated with an ion beam of a different ion species, the deposit by the previously used ionized gas is removed from the plasma chamber. When the plasma is generated with the next different ionized gas, unnecessary ions are generated from the deposit by the previous ionized gas and mixed into the ion beam irradiated to the sample. . When the sample is irradiated with an ion beam in which unnecessary ions are mixed, the sample becomes defective in manufacture, and the sample must be discarded.

  In order to solve the problems of abnormal discharge and manufacturing defects described above, it is necessary to clean the inside of the ion source appropriately. In cleaning the inside of the ion source, in consideration of the time and labor required for cleaning, as described in Patent Document 1, cleaning is performed without opening the ion source to the atmosphere.

  The ion source described in Patent Document 1 is a high-frequency ion source used in an ion implantation apparatus, and generates hydrogen plasma in a plasma chamber by introducing hydrogen gas into the ion source at times other than during ion implantation. And the deposit of the extraction electrode system arranged adjacent to the inner wall of the plasma chamber and the plasma chamber is peeled off by utilizing the sputtering action by the plasma.

Japanese Patent No. 2956412

  In the ion source described in Patent Document 1, the potentials of the plasma chamber and the electrodes arranged at the ends of the plasma chamber are the same potential, and the output voltage of the high-frequency power source that determines these potentials changes periodically. Further, the potential of the hydrogen plasma generated in the plasma chamber also periodically changes due to the change in the output voltage of the high-frequency power source. When the plasma potential is sufficiently high with respect to the potential of the plasma chamber or the like, the plasma chamber or the like is strongly sputtered by the hydrogen plasma and cleaning can be performed effectively. When the potential of is not so high with respect to the plasma chamber or the like, the plasma chamber or the like is hardly sputtered. That is, although there is a difference in degree, in this case, the inside of the ion source is hardly cleaned.

  As described above, in the ion source of Patent Document 1, the inside of the ion source is periodically cleaned according to the change in the output voltage of the high-frequency power source, and the cleaning efficiency is poor.

  In view of the above points, the main object of the present invention is to improve the efficiency of cleaning performed by a high-frequency ion source.

  The ion source is an ion source that generates plasma in a plasma chamber using a high-frequency power source, and extracts an ion beam from the plasma using an extraction electrode system including a plurality of electrodes disposed adjacent to the plasma chamber, During cleaning, a cleaning gas is introduced into the plasma chamber, and the high-frequency power source is connected to the plasma chamber, and between the plasma chamber and any of the electrodes constituting the extraction electrode system Bias power supply is connected.

  Since a bias power source is provided between the plasma chamber and any electrode constituting the extraction electrode system, the potentials of both members can be made different. Therefore, even if the output voltage or output current of the high frequency power source changes, the inner wall of the plasma chamber or the surface of the electrode to which the bias power source is connected can be effectively cleaned.

  The bias power source is preferably connected to an electrode disposed at a position closest to the plasma chamber among a plurality of electrodes constituting the extraction electrode system.

  Of the electrodes that make up the extraction electrode system, the surface of the electrode arranged at the end of the plasma chamber has a high rate of contact with the ionized gas, so that deposits due to the ionized gas are deposited on the electrode surface compared to other electrodes. Easy to do. Therefore, if a bias power source is connected to such an electrode, the extraction electrode system can be effectively cleaned.

  The bias power source is preferably connected so that the plasma chamber side is a negative electrode.

  With such a configuration, a relatively large plasma chamber exposed to the ionized gas can be intensively cleaned.

  On the other hand, the bias power source may be connected so that the plasma chamber side is a positive electrode.

  With such a configuration, the surface of the electrode constituting the extraction electrode system can be intensively cleaned.

  The bias power source may be an AC power source.

  With such a configuration, the inner wall of the plasma chamber and the extraction electrode system can be cleaned alternately.

  In addition, the plasma chamber includes a back surface that is substantially orthogonal to the ion beam extraction direction and a side surface that is not substantially orthogonal to the ion beam extraction direction, and a plurality of permanent magnets are disposed along the periphery of the side surface. It is desirable that

  With such a configuration, it is possible to effectively clean the back surface constituting the plasma chamber.

  The ion beam irradiation apparatus includes the above-described ion source, a mass analysis electromagnet that deflects ions contained in the ion beam extracted from the ion source according to mass, and a specific one of the ions deflected by the mass analysis electromagnet And an analysis slit that allows only ions having a mass of 1 to pass therethrough.

  In such a mass spectrometry type ion implantation apparatus, when ion beam irradiation processing is performed on the sample by switching the ionization gas, the deposit of the ionization gas used in the previous ion beam irradiation processing is stored in the plasma chamber or Even if some amount remains on the electrode, ions generated from the deposit can be separated from the ion beam by mass separation, so that it is possible to prevent a defective production of the sample due to the mixing of unnecessary ions.

  A bias power source is provided between the plasma chamber and any electrode constituting the extraction electrode system, and the potentials of both members are made different. Therefore, even if the output voltage of the high frequency power source changes with time, the plasma chamber Either the inner wall or the extraction electrode system can continue to be effectively cleaned.

It is a top view showing the whole ion implantation apparatus. It is sectional drawing of the ion source which concerns on 1st Embodiment. It is sectional drawing of the ion source which concerns on 2nd Embodiment. It is sectional drawing of the ion source which concerns on 3rd Embodiment. It is sectional drawing of the ion source which concerns on 4th Embodiment. It is sectional drawing of the ion source which concerns on 5th Embodiment. It is sectional drawing of the ion source which concerns on 6th Embodiment. It is sectional drawing of the ion source which concerns on 7th Embodiment. It is sectional drawing of the ion source which concerns on 8th Embodiment.

  FIG. 1 is a plan view showing the entirety of an ion implantation apparatus IM as an example of an ion beam irradiation apparatus used in the present invention.

  The Z-axis direction shown represents the traveling direction of the ion beam IB, and the X-axis and the Y-axis are orthogonal to the Z-axis. The ion beam IB described in the example of FIG. 1 is a ribbon-like ion beam whose dimension in the X-axis direction is longer than that in the Y-axis direction, and when the ion beam IB is cut on the XY plane, the cross section thereof is substantially It has a rectangular shape. The description regarding each axis is the same in FIGS.

  In FIG. 1, the Y-axis direction and the Z-axis direction change in the path along which the ion beam IB is transported. Each axis shown in FIG. 1 is drawn with respect to an ion beam IB incident on a processing chamber 5 described later. Hereinafter, the ion implantation apparatus IM will be described with reference to FIG.

  Plasma is generated in the plasma chamber 1, and an ion beam IB is extracted from the ion source IS by an extraction electrode system 2 disposed adjacent to the plasma chamber 1.

  The ion beam IB extracted from the ion source IS enters the mass analysis electromagnet 3. The ion beam IB includes ions having various masses, and the deflection amount of each ion that has passed through the mass analysis electromagnet 3 differs depending on the mass of each ion. In the mass analysis electromagnet 3, the density of magnetic flux generated inside the electromagnet is adjusted so that only ions having a desired mass pass through the analysis slit 4 provided downstream (on the Z-axis direction side) of the mass analysis electromagnet 3. It has been broken. In FIG. 1, the trajectory of the ion beam IB containing ions having a desired mass is depicted.

  The ion beam IB that has passed through the analysis slit 4 enters the processing chamber 5. A sample 6 to be ion-implanted is disposed in the processing chamber 5. In the X-axis direction, the dimension of the ion beam IB is longer than the dimension of the sample 6. In this example, the sample 6 is scanned across the ion beam IB along the direction of the arrow shown by a transfer mechanism (not shown). By this scanning, the entire surface of the sample 6 is irradiated with the ion beam IB, and an ion implantation process to the sample 6 is realized.

  When cleaning the ion source IS of such an ion implanter IM, the structure shown in FIGS. 2 to 9 is used. Hereinafter, a specific configuration of the ion source IS will be described.

  FIG. 2 is a cross-sectional view of the ion source IS according to the first embodiment. The ion source IS is an ion source that generates plasma P inside the plasma chamber 1 using capacitively coupled high-frequency discharge.

  In this example, the plasma chamber 1 of FIG. 1 includes a side wall 1a and a back plate 1b. An insulating member (a hatched member in the figure) is provided between the two members, and the two members are electrically separated from each other. A high-frequency power source Vh (the frequency of the high-frequency power is about 13.56 MHz to 100 MHz) is connected between the side wall 1a and the back plate 1b. It is introduced into the plasma chamber composed of the face plate 1b, and plasma P is generated in the plasma chamber. A matching circuit (not shown) is provided between the high-frequency power source Vh and the back plate 1b.

  An opening for extracting the ion beam IB from the plasma P is formed in the plasma chamber. In this example, an opening is formed at a position facing the back plate 1b in the Z-axis direction. An extraction electrode system 2 composed of a plurality of electrodes is disposed adjacent to the opening. In this example, the extraction electrode system 2 is composed of four electrodes, but may be two or three electrodes, for example. An insulating member is provided between each electrode constituting the extraction electrode system 2 and between the side wall 1a constituting the plasma chamber and the electrode disposed at the end of the side wall 1a so that each part is electrically separated. It is configured. A plurality of round holes or slits are formed on the surface of each electrode constituting the extraction electrode system 2.

  When cleaning the ion source IS, for example, a bias power source Vb is connected between the side wall 1a and the electrode of the extraction electrode system 2 disposed at the end of the side wall 1a as shown in the figure. During the normal operation of the ion source IS (when the ion implantation process is performed on the sample 6), the bias power source Vb may be removed. In addition, the output voltage of the bias power source Vb is variably switched, and during normal operation of the ion source IS, the output voltage is set to zero and the two members are short-circuited to be arranged at the end portions of the side wall 1a and the side wall 1a. It may be configured such that the potential difference from the other electrode becomes zero.

  In this example, the positive electrode of the bias power source Vb is connected to the electrode disposed at the end of the side wall 1a. Thereby, a positive voltage (for example, several tens of V to several tens of V) is applied to the electrode disposed at the end of the side wall 1a with respect to the side wall 1a.

  The potential of the plasma P is determined by the configuration and potential of the members constituting the plasma chamber 1 (in this example, the side wall 1a and the back plate 1b). As the output voltage of the high frequency power supply Vh changes, the potential of the plasma P also changes. If the potential of the plasma P is sufficiently higher than the potential of the side wall 1a, the deposit deposited on the side wall 1a can be removed by the sputtering action by the plasma P. However, when the potential difference between the plasma P potential and the side wall 1a becomes small due to the change in the output voltage of the high-frequency power source Vh, the side wall 1a is hardly sputtered.

  In the example of FIG. 2, a bias power source Vb is provided between the side wall 1a and the electrode constituting the extraction electrode system 2 disposed at the end of the side wall 1a, and a positive voltage is applied to the electrode disposed at the end of the side wall 1a. Thus, the potential of the plasma P is raised by the potential of the electrode and becomes high. As a result, the potential of the plasma P can always be sufficiently higher than the potential of the side wall 1a, so that the side wall 1a can always be sufficiently sputtered.

  If such a configuration is used when cleaning the ion source IS, cleaning of the inner wall of the plasma chamber 1 (side wall 1a in the example of FIG. 2) is continued even if the output voltage of the high-frequency power source Vh changes. Therefore, cleaning can be performed more efficiently than the conventional configuration. In addition, since the cleaning efficiency is improved, the cleaning can be completed early and the ion source IS can be restarted in a short time, and the productivity of the ion implantation apparatus IM can be improved.

  FIG. 3 shows a cross-sectional view of an ion source IS according to the second embodiment. The difference from the example of FIG. 2 is that the polarity direction of the bias power supply Vb is different. Since other configurations are the same as those in the example of FIG. 2, the description of the same configurations is omitted.

  If the positive electrode of the bias power source Vb is connected to the side wall 1a as in the example of FIG. 3, the surface of the electrode constituting the extraction electrode system 2 disposed at the end of the side wall 1a is cleaned by the sputtering action by the plasma P. can do. When such a configuration is used, the potential of the electrode of the extraction electrode system 2 can be kept sufficiently low with respect to the potential of the plasma P regardless of the change in the output voltage of the high-frequency power source Vh. Thus, instead of cleaning the plasma chamber 1, the electrode surface of the extraction electrode system 2 can be intensively cleaned.

  In the example of FIG. 3, the bias power source Vb is connected to the electrode disposed at the end of the side wall 1a among the electrodes constituting the extraction electrode system 2, but the bias power source Vb is connected to a different electrode. You can keep it clean. For example, the bias power supply Vb may be connected to the second electrode counted from the end of the side wall 1a.

  Further, based on the example of FIG. 2 or the example of FIG. 3, cleaning of the side wall 1a and the electrodes arranged at the end of the side wall 1a may be performed alternately. For example, if the cleaning time is determined in advance, the tendency of contamination of the ion source IS may be confirmed by experiment, and time may be allocated so as to intensively clean the severely contaminated one. . In this case, the connection of the bias power supply Vb is reconnected for each cleaning place, or the bias power supply Vb is a bipolar power supply, and the polarity of the bias power supply Vb is appropriately switched to change the cleaning place. You can keep it.

  FIG. 4 shows a cross-sectional view of an ion source IS according to the third embodiment. When the place to be cleaned is switched, the bias power source Vb connected between the side wall 1a and the electrode disposed at the end of the side wall 1a may be configured with an AC power source as shown in FIG. . Other configurations are the same as those in FIG.

  Considering the time and labor for changing the connection, the configuration shown in FIG. 5 may be used. FIG. 5 shows a cross-sectional view of an ion source IS according to the fourth embodiment.

  In the example of FIG. 5, three circuits are connected in parallel between the side wall 1a and the electrode disposed at the end of the side wall 1a. Each circuit is configured such that any one of the circuits is selected based on electrical signals S1 to S3 from the control device 8. By using such a configuration, the trouble of changing the connection between the normal operation and the cleaning of the ion source IS can be omitted.

  The example of the ion source IS described so far has been the capacitively coupled ion source IS. However, instead of this, an inductively coupled ion source IS may be used. FIG. 6 shows an example of an inductively coupled ion source IS as a fifth embodiment.

  In the ion source IS of FIG. 6, a coil L is introduced into the plasma chamber 1 via an insulating member (a hatched member in the figure). The tip portion of the coil L is wound, for example, in a spiral shape. When a high frequency current flows through the coil L from the high frequency power source Vh, an induction electric field is generated in the plasma chamber 1 and the cleaning gas introduced from the gas bottle 7 is turned into plasma by the action of the induction electric field.

  The high frequency power source Vh is connected to the plasma chamber 1 when the ion source IS is cleaned. A bias power source Vb is connected between the plasma chamber 1 and the electrodes constituting the extraction electrode system 2 disposed at the end of the plasma chamber 1 with the electrode side as a positive electrode. Even with such a configuration, the plasma chamber 1 can be efficiently cleaned as in the example described with reference to FIG.

  Similarly to the examples of FIGS. 3 to 5, in the example of FIG. 6, the polarity of the bias power supply Vb is reversed, the bias power supply Vb is configured with a bipolar power supply, the AC power supply is configured, A plurality of circuits may be prepared so that these can be switched automatically.

  Furthermore, as a modification of the inductively coupled ion source IS, the ion source IS shown in FIG. 7 may be used. FIG. 7 shows a cross-sectional view of an ion source IS according to the sixth embodiment.

  The ion source IS of FIG. 7 includes a plurality of coils L, and a window W (insulating member) made of a dielectric is disposed at a position where the back plate 1b is provided in the example of FIG. Through this window W, an induction electric field is generated in the chamber (plasma chamber 1 shown in FIG. 1) constituted by the side wall 1a and the window W, and the cleaning gas introduced from the gas bottle 7 is turned into plasma.

  When cleaning the ion source IS, one of the high-frequency power sources Vh connected to each coil L is connected to the side wall 1a. A bias power source Vb is connected between the side wall 1a and the electrode disposed at the end of the side wall 1a with the electrode side as a positive electrode. By using such a configuration, the plasma chamber 1 can be efficiently cleaned. In the example of FIG. 7 as well, various configurations described in the examples of FIGS. 3 to 5 may be applied as in the description of FIG. Further, a matching circuit may be provided between the high frequency power supply Vh and the coil L shown in FIGS.

  Moreover, in order to clean the surface of the window W, you may use the structure as shown to Fig.8 (a)-(c). 8A to 8C are sectional views of an ion source according to the seventh embodiment.

  In this example, the bias power source Vb is composed of a high frequency power source. With such a configuration, the positive electrode included in the plasma P is generated by repulsive force by making the potential of the electrode constituting the extraction electrode system 2 positive with respect to the ground potential with this bias power source Vb in a certain time zone. Charged ions collide with the surface of the window W. In another time zone, the potential of the electrodes constituting the extraction electrode system 2 is set to a negative potential with respect to the ground potential, so that electrons having a negative charge in the plasma P collide with the window W due to repulsive force. It is configured as follows. As a result, the surface of the window W can be cleaned. If only the window W is to be cleaned, it is not necessary to connect the high-frequency power source Vh to the side wall 1a. The side wall 1a is simply electrically grounded and arranged at the end of the side wall 1a and the side wall 1a. A bias power source Vb made of a high frequency power source may be provided between the formed electrodes.

  Further, as shown in FIG. 8A, a plurality of permanent magnets 10 may be provided along the periphery of the side wall 1a. FIG. 8B and FIG. 8C illustrate a cross-sectional state of the side wall 1a illustrated in FIG. 8A in the XY plane. The permanent magnet 10 may be arranged so that the polarity on the side wall 1a side changes alternately along the side wall 1a as depicted in FIG. 8B. On the other hand, as illustrated in FIG. 8C, the polarities of the permanent magnets adjacent along the side wall 1 a may be in the same direction.

  Such a permanent magnet 10 generates a cusp magnetic field as depicted by an arrow inside the side wall 1a. By this magnetic field, it is possible to prevent ions and electrons pushed out from the electrode side constituting the extraction electrode system 2 to the window W side from colliding with the side wall 1a and disappearing. Therefore, by using such a configuration, the surface of the window W can be more effectively cleaned.

  In the example shown in FIG. 7 or FIG. 8A, the plasma chamber 1 shown in FIG. Expressing this generally, the plasma chamber 1 includes a back surface (in this example, a window W) that intersects the extraction direction of the ion beam (in this example, the Z-axis direction shown in the figure) and the extraction direction of the ion beam. If a side surface (in this example, the side wall 1a) that does not intersect is provided and a plurality of permanent magnets 10 are provided around the side surface, cleaning of the back surface using an electric repulsive force is effective. Can be done.

  Note that the shape of the side wall 1a may be a rectangular cross-sectional shape on the XY plane as shown in FIGS. 8B and 8C, or a shape different from this. Also good. For example, it may be circular or polygonal. Moreover, the groove | channel for holding the permanent magnet 10 may be provided in the outer periphery of the side wall 1a, and it may be comprised so that the special holder for holding the permanent magnet 10 can be attached to the side wall 1a. .

<Other variations>
In the above-described embodiment, the example in which a porous or a plurality of slits are formed on the surface of the electrode constituting the extraction electrode system 2 has been described, but the configuration to which the present invention is applied is not limited thereto. FIG. 9A shows a cross-sectional view of an ion source IS according to the eighth embodiment. As described in FIG. 9A, a large single hole may be formed on the surface of each electrode constituting the extraction electrode system 2. As a specific configuration, as shown in FIG. 9B, when each electrode surface is viewed along the Z-axis direction, the shape of the hole formed in the electrode has a substantially square shape. ing.

  The configuration of the ion implantation apparatus IM shown in FIG. 1 is a so-called non-mass separation type ion implantation apparatus that includes the mass analysis electromagnet 3 and the analysis slit 4 but does not include these members. It ’s okay. However, in the case of a mass spectrometry type ion implantation apparatus, when an ionization gas is switched to perform an ion implantation process on a sample, a deposit by another ionization gas adhered inside the ion source IS is ionized, and this is an ion beam. Even if it is mixed in, it can be removed by mass spectrometry.

  Furthermore, although ion source IS was described in embodiment mentioned above, ion source IS to which this invention is applied is not restricted only to what is used in order to extract an ion beam. For example, there is an apparatus called a plasma doping apparatus. In this apparatus, plasma is generated in a plasma chamber, ions are extracted from the plasma by an extraction electrode disposed adjacent to the plasma chamber, and ion implantation is performed on a sample. In such an apparatus, an ion source is used. The name of the plasma source is used instead of the name of the plasma source, but since the mechanism for extracting ions from such a plasma source is the same as that of the ion source described so far, of course, the ion source of the present invention is Such plasma sources are also included.

  In the embodiment described above, the configuration of the ion implantation apparatus is described as an example of the ion beam irradiation apparatus. However, the ion beam irradiation apparatus to which the present invention is applied is not limited thereto. Any material can be used as long as the sample is processed by irradiation with an ion beam. For example, an ion doping apparatus or an ion beam alignment apparatus may be used.

  In addition to the above, it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Plasma chamber 1a Side wall 1b Back plate 2 Extraction electrode system 3 Mass analysis electromagnet 4 Analysis slit 5 Processing chamber 6 Sample 7 Gas bottle IM Ion implantation apparatus IS Ion source IB Ion beam Vb Bias power supply Vh AC power supply P Plasma L Coil

Claims (7)

Plasma is generated in a plasma chamber using a high-frequency power source, and an ion beam is generated from the plasma using an extraction electrode system that is arranged adjacent to the plasma chamber and is electrically insulated from the plasma chamber. An ion source to be extracted;
At the time of cleaning, a cleaning gas is introduced into the plasma chamber, and one end of the high-frequency power source is conductively connected to the plasma chamber, and the plasma chamber and any electrode constituting the extraction electrode system An ion source with a bias power supply in between.   2. The ion source according to claim 1, wherein the bias power source is connected to an electrode disposed at a position closest to the plasma chamber among a plurality of electrodes constituting the extraction electrode system.   The ion source according to claim 1, wherein the bias power source is connected so that the plasma chamber side is a negative electrode.   The ion source according to claim 1, wherein the bias power source is connected so that the plasma chamber side is a positive electrode.   The ion source according to claim 1, wherein the bias power source is an AC power source.   The plasma chamber includes a back surface that intersects with the extraction direction of the ion beam and a side surface that does not intersect with the extraction direction of the ion beam, and a plurality of permanent magnets are disposed along the periphery of the side surface. 5. The ion source according to 5. An ion source according to any one of claims 1 to 6;
A mass analyzing electromagnet for deflecting ions contained in an ion beam extracted from the ion source according to mass;
An ion beam irradiation apparatus comprising: an analysis slit that allows passage of only ions having a specific mass among ions deflected by the mass analysis electromagnet.

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