JP2007242368A - Neutralizer, and film forming device equipped with this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a neutralizer capable of extracting much electron current and achieving a long lifetime. <P>SOLUTION: The neutralizer is provided with a discharge tube 4 which can extract electron current from one end part, a gas inlet tube 3 to introduce gas into the discharge tube 4, a high frequency induction coil 5 to generate plasma inside the discharge tube 4, a cathode electrode 6 arranged in the discharge tube 4, a first keeper electrode 7 arranged on the opening 4a side of the discharge tube 4, an extraction power source 13 to impress a voltage on the first keeper electrode 7 so as to become a positive potential more than the cathode electrode 6, a second keeper electrode 8 arranged separated from the first keeper electrode 7, and a capacitor 16 to impress a self bias voltage to become a positive potential more than the cathode electrode 6 on this second keeper electrode. Much electron current can be extracted by the self bias voltage of the second keeper electrode 8 and since the second keeper electrode 8 is hardly sputtered, a long lifetime can be achieved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a neutralizer and a film forming apparatus including the same, and more particularly to a neutralizer used for manufacturing a semiconductor device or an optical element and a film forming apparatus including the same.

Various film forming technologies such as plasma ion plating, plasma CVD, plasma sputtering, plasma etching, ion beam evaporation, and ion beam sputtering are used to manufacture semiconductor devices such as silicon wafers and optical elements such as optical lenses. It is done.
In these techniques, a neutralizer that irradiates an electron beam onto a substrate or a sample is used.

  For example, in an optical thin film manufacturing technique, a method is used in which a vapor deposition material is vapor-deposited on the surface of a substrate by an ion-assisted vapor deposition apparatus. The ion-assisted deposition apparatus includes a substrate dome that holds a substrate, a deposition source that deposits a deposition material source, and an ion gun that irradiates the substrate with a positive ion beam. In a film formation method using ion-assisted vapor deposition, a vapor deposition material is attached to a substrate using a vapor deposition source, and an ion beam is irradiated onto the substrate from an ion gun. The vapor deposition material adhering to the surface of the substrate is agglomerated by the collision energy when the positive ions contained in the ion beam collide with the substrate. Thereby, the denseness of the thin film formed on the surface of the substrate, the crystal orientation, the adhesion strength to the substrate, and the like can be improved.

  In the ion-assisted deposition apparatus, positive ions irradiated from an ion gun accumulate on the substrate, so that a phenomenon that the entire substrate is positively charged (so-called charge-up) occurs. When this charge-up occurs, abnormal discharge occurs between the positively charged substrate and other members, and there is a problem that the insulating film formed on the surface of the substrate is destroyed by an impact caused by the discharge. In addition, since the base is positively charged, collision energy due to positive ions supplied from the ion gun is reduced, so that the density and adhesion strength of the thin film are reduced. For this reason, the inconvenience that the physical and optical specification of the thin film formed falls.

  In order to prevent such charge-up, a neutralizer is used for the purpose of electrically neutralizing (also referred to as neutralization) positive charges accumulated in the substrate. A neutralizer is a device that generates plasma inside, draws electrons from the plasma, and irradiates an object as an electron beam. By irradiating the electron beam extracted from the neutralizer toward the substrate, the charge of the positively charged substrate can be neutralized.

  The inventors of the present invention can improve the conventional neutralizer and use it at a relatively low temperature, and can obtain an electron beam with low energy consumption and energy efficiency. A neutralizer has been developed (for example, Patent Document 1).

The conventional neutralizer will be described in detail below. FIG. 6 is an explanatory diagram showing electrical wiring of a conventional neutralizer.
The neutralizer 100 includes an electron gun body 101 that houses each component, a cylindrical discharge tube 102 that can extract an electron beam from one end, a gas introduction tube 103 that introduces gas into the discharge tube, A high-frequency induction coil 104 wound around the discharge tube 102, a cathode electrode 105 housed inside the discharge tube 102, and an anode electrode 106 (also referred to as a keeper electrode) provided on one end side of the discharge tube 102 And an extraction power supply 113 for applying a voltage to the anode electrode 106 so as to have a positive potential with respect to the cathode electrode 105.
When a high frequency current is passed from the high frequency power supply 111 to the high frequency induction coil 104 in a state where the gas is introduced into the discharge tube 102 through the gas introduction tube 103, a high frequency induction electric field is generated inside the discharge tube 102, and the gas is discharged Plasma is generated. When a voltage is applied to the anode electrode 106 so that the potential is higher than that of the cathode electrode 105 in a state where plasma is generated, electrons in the plasma are attracted toward the anode electrode 106 due to a potential difference between the two electrodes. The attracted electrons are extracted to the outside as an electron beam from an electron beam emission hole 106 a formed in the anode electrode 106. The extracted electron beam is irradiated toward a positively charged substrate, and this is electrically neutralized.

Japanese Patent No. 3606842

Since such a conventional neutralizer has only a single keeper electrode (the anode electrode 106 in FIG. 6), the electron current value of the electron beam extracted from the plasma is small. For this reason, the irradiation amount of the electron beam from the neutralizer cannot catch up with the irradiation amount of the ion beam, neutralization is not performed completely, and abnormal discharge occurs between the positively charged substrate and other members. There was an inconvenience of doing.
On the other hand, when the ion beam irradiation amount is reduced in order to catch up with neutralization, the film formation rate is lowered, and it is difficult to reduce the tact time required for manufacturing the product.

  Also, since a negative voltage is applied to the neutralizer anode electrode (that is, the keeper electrode), positive ions emitted from an ion gun or the like are attracted to and collide with the keeper electrode, so that the keeper electrode itself is Sometimes sputtered. Due to such a sputtering phenomenon, when the neutralizer is used for a long time at a high set electronic current value, there is a disadvantage that the deterioration rate of the keeper electrode is increased and the product life of the neutralizer is shortened.

An object of the present invention is to provide a neutralizer capable of increasing the electron current value of an extracted electron beam and extending the lifetime.
Another object of the present invention is to provide a film forming apparatus capable of stably forming a film with a high electron current for a long period of time using a neutralizer.

  According to the neutralizer of the present invention, the above-described problem is achieved by a discharge tube having an opening through which an electron beam can be drawn at one end, a gas introduction tube for introducing gas into the discharge tube, and the gas in the discharge tube. A plasma generating electrode for generating a plasma of the first electrode, a cathode electrode disposed in the discharge tube, a first keeper electrode disposed on the opening side of the discharge tube, and a positive potential than the cathode electrode. A drawing power source for applying a voltage to the first keeper electrode, a second keeper electrode spaced from the first keeper electrode on the opening side of the discharge tube, and the second keeper electrode This is solved by providing self-bias means for applying to the keeper electrode a self-bias voltage that is more positive than the cathode electrode.

Thus, according to the neutralizer of the present invention, the second keeper electrode is provided in addition to the first keeper electrode, and the second keeper electrode is connected to the self-biasing means. The second keeper electrode is more positive than the cathode electrode due to the self-bias voltage of the self-biasing means. For this reason, an electron beam can be extracted from the plasma generated in the discharge tube by this potential difference. Therefore, an electron beam having a higher electron current value can be extracted from the plasma as compared with a conventional neutralizer having a single keeper electrode.
Further, the self-bias voltage applied to the second keeper electrode changes depending on the ease of flow of the electron current from the electron beam extracted from the plasma. That is, the self-bias voltage is high when the electron current is likely to flow, but the self-bias voltage is low when the electron current is difficult to flow. When the self-bias voltage is low, positive ions such as an ion beam are unlikely to collide and thus are not easily sputtered. For this reason, the neutralizer of the present invention can reduce electrode deterioration due to sputtering, as compared with a conventional neutralizer in which a voltage is constantly applied from an extraction power supply. Therefore, it is possible to extend the life of the neutralizer.

The self-biasing means is preferably a capacitor having one terminal connected to the second keeper electrode and the other terminal connected to ground.
Thus, the neutralizer of the present invention has a configuration in which the second keeper electrode is connected to the ground via the capacitor. For this reason, a self-bias voltage is applied to the second keeper electrode due to a voltage drop across the capacitor.
That is, a simple configuration in which the capacitor is connected to the ground makes it possible to apply a self-bias voltage to the second keeper electrode. As a result, an electron beam having a high electron current value can be extracted and the lifetime of the neutralizer can be extended.

Further, it is preferable that the capacitor is configured to be capable of changing a capacity.
In this case, the capacitor is preferably a variable capacitor.
Alternatively, it is preferable that the capacitor includes a plurality of capacitors having different capacities and a switch for connecting any one of the plurality of capacitors to the second keeper electrode.

  In this way, the capacitor is configured so that the capacitance can be changed. Capacitors have characteristics that current does not flow until they are charged, and that capacitor charging time varies depending on the capacitance of the capacitor. Therefore, it is possible to immediately change the electron current value of the electron beam drawn from the neutralizer by changing the capacitance of the capacitor during the operation of the neutralizer.

  In addition, according to the film forming apparatus of the present invention, the above-described problem is directed toward a vacuum chamber capable of maintaining the inside in a vacuum, a substrate holding means disposed in the vacuum chamber and capable of holding a substrate, and the substrate. 6. A film forming apparatus comprising: an ion gun that irradiates an ion beam; and a neutralizer that extracts an electron beam from plasma and irradiates the substrate, wherein the neutralizer is any one of claims 1 to 5. This is solved by the neutralizer described in the above.

In the film forming apparatus of the present invention, a second keeper electrode is provided in addition to the first keeper electrode, and a self-biasing means is connected to the second keeper electrode. As described above, it is possible to extract an electron beam with a higher electron current value and extend the life of the neutralizer compared to a conventional neutralizer having a single keeper electrode. It becomes.
As described above, since an electron beam having a high electron current value can be extracted, the ion irradiation amount from the ion gun can be increased, and the film formation rate can be improved. Further, since it is possible to draw out an electron beam having a high electron current value, it is possible to prevent abnormal discharge from occurring on the substrate due to insufficient irradiation of the electron beam. Furthermore, since the lifetime of the neutralizer is long, the frequency of replacing the neutralizer during film formation decreases, and the time required for product manufacture can be reduced.
That is, in the film forming apparatus provided with such a neutralizer, film formation can be performed at a higher film formation rate while preventing the occurrence of abnormal discharge as compared with the case where a conventional neutralizer is used. For this reason, it becomes possible to improve the tact time of product manufacture.

In addition to the first keeper electrode, the neutralizer of the present invention includes self-bias means for applying a self-bias voltage that is more positive than the cathode electrode to the second keeper electrode. For this reason, the electron beam can be extracted from the plasma not only by the first keeper electrode but also by the second keeper electrode. In addition, the self-bias voltage of the second keeper electrode varies depending on the electron current value. When the self-bias voltage is low, positive ions hardly collide and are not easily sputtered.
Therefore, it is possible to extract an electron beam having a higher electron current value from the plasma and to extend the lifetime of the neutralizer as compared with a conventional neutralizer having a single keeper electrode. Become.
In the film forming apparatus provided with the neutralizer of the present invention, an electron beam having a high electron current value can be extracted, and the life of the neutralizer can be extended. Therefore, it is possible to increase the ion beam irradiation amount and improve the film formation rate while preventing the occurrence of abnormal discharge due to insufficient electron beam irradiation. In addition, the neutralizer replacement frequency is reduced, and the time required for product manufacture can be reduced. Therefore, it is possible to improve the tact time of product manufacture.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. It should be noted that members, arrangements, and the like described below do not limit the present invention, and it goes without saying that various modifications can be made in accordance with the spirit of the present invention.

  1 to 3 are explanatory views of a neutralizer according to a first embodiment of the present invention and a film forming apparatus having the neutralizer, and FIG. 1 shows electrical wiring of the neutralizer according to the first embodiment. FIG. 2 is an explanatory view showing a longitudinal cross-sectional shape of the neutralizer according to the first embodiment, and FIG. 3 is an explanatory view showing an example in which the neutralizer of the first embodiment is used in an ion-assisted deposition apparatus. .

  As shown in FIGS. 1 and 2, the neutralizer 1 of the present embodiment includes a base 2, a gas introduction tube 3, a discharge tube 4, a high frequency induction coil 5, a cathode electrode 6, and a first keeper electrode. 7, a second keeper electrode 8, a trigger electrode 9, an extraction power source 13, and a capacitor 16 are provided as main components.

  The base 2 is a container for housing the discharge tube 4, the high frequency induction coil 5, the cathode electrode 6, and the trigger electrode 9. The base 2 is a substantially cylindrical body made of stainless steel, and a gas introduction pipe 3 for introducing gas is connected to one end face in a state of penetrating the inside of the base 2. In addition, a circular opening 2a for allowing the electron beam drawn from the inside of the base to pass through is formed at the center of the other end face. As shown in FIG. 2, the opening 2 a is formed in a tapered shape whose diameter increases toward the outside of the neutralizer 1 (upper side in FIG. 1). As shown in FIG. 1, a ground wire is connected to the outer peripheral surface of the base 2, whereby the base 2 is set to a ground potential. For this reason, it becomes possible to extract an electron beam from plasma generated inside the cathode electrode 6 described later. That is, the base 2 has a function as an anode electrode. The diameter of the opening 2a can be arbitrarily determined between 1 and 50φ (that is, 1 to 50 mm) according to the electron current value of the extracted electron beam. In particular, it is preferably between 5 and 20 mm.

The discharge tube 4 is a cylindrical container for generating plasma inside. The discharge tube 4 is formed of an insulating material that has resistance to sputtering and can transmit a high-frequency electric field. Examples of such an insulating material include alumina (Al ₂ O ₃ ), quartz (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), boron nitride (BN), and the like.
A gas introduction tube 3 is connected to one end face of the discharge tube 4 in a penetrating manner. In addition, a circular opening 4a for allowing an electron beam drawn from the inside of the base to pass through is formed at the center of the other end face of the discharge tube 4.

  The high frequency induction coil 5 is a radiator for high frequency radio waves and is a means for generating plasma inside the discharge tube 4. The high frequency induction coil 5 is spirally wound around the outer periphery of the side surface of the discharge tube 4 so as to be coaxial with the longitudinal direction of the discharge tube 4. As shown in FIG. 1, the high frequency induction coil 5 is connected to a high frequency power source 11. The high frequency power source 11 is a power source for flowing a high frequency current through the high frequency induction coil 5. A matching box 12 is provided between the high frequency induction coil 5 and the high frequency power source 11. The matching box 12 is current adjusting means for adjusting the current value flowing through the high frequency induction coil 5. The current from the high frequency power supply 11 flows through the high frequency induction coil 5 with the current value adjusted by the matching box 12.

  The cathode electrode 6 is an electrode for extracting an electron beam from plasma by a potential difference with a first keeper electrode 7 described later. The cathode electrode 6 is a cylindrical member having a U-shaped cross section with one end open, and a plurality of slits are formed on the side surface. The cathode electrode 6 is housed inside the discharge tube 4 and is connected to the end surface opposite to the open end in a state where the gas introduction tube 3 penetrates.

  The gas introduction tube 3 is a tubular member made of an insulating material, and one end portion thereof is inserted into the cathode electrode 6 as described above. A gas cylinder (not shown) is connected to the other end. A gas is introduced into the cathode electrode 6 from a gas cylinder through the gas introduction pipe 3. Examples of the gas introduced into the cathode electrode 6 include rare gases such as argon and helium. When a gas is introduced from the gas introduction tube 3 into the cathode electrode 6, a high-frequency current flows through the high-frequency induction coil 5, so that an induced electromotive force is generated in the high-frequency induction coil 5. Plasma is generated inside the tube 4.

The trigger electrode 9 is means for generating plasma by applying a high voltage inside the cathode electrode 6. As shown in FIG. 1, the trigger electrode 9 is electrically connected to the trigger power source 17. The trigger power source 17 is a power source that periodically applies a high voltage composed of a rectangular wave or a sine wave of 500 to 2000 V to the trigger electrode 9. By applying a voltage applied from the trigger electrode 9 to the introduced gas, an initial discharge is caused in the introduced gas to generate plasma.
The trigger electrode 9 and the trigger power source 17 are means for generating plasma more reliably by generating an initial discharge, but are not necessarily required for the present invention.

The first keeper electrode 7 is an electrode for extracting an electron beam from plasma generated inside the discharge tube 4 due to a potential difference with the cathode electrode 6 described above. The first keeper electrode 7 is a disk-like member made of a conductive material, and an electron beam emission hole 7a for extracting an electron beam and emitting it to the outside is formed in the center portion thereof. The diameter of the 1st keeper electrode 7 can be arbitrarily set in the range of about 20-100 (phi) (namely, 20-100 mm).
The diameter of the electron beam emission hole 7a can be arbitrarily determined between 1 and 50φ (that is, 1 to 50 mm) according to the electron current value of the extracted electron beam. In particular, it is preferably between 5 and 20 mm. As shown in FIG. 2, the electron beam emission hole 7 a is formed in a tapered shape whose diameter is increased toward the outside of the neutralizer 1.
Examples of the material of the first keeper electrode 7 include stainless steel (SUS), titanium (Ti), tungsten (W), molybdenum (Mo), and carbon (C). Of these, stainless steel (SUS), tungsten (W), molybdenum (Mo), etc., which have high sputtering resistance, are particularly suitable.
The first keeper electrode 7 is provided on the opening 2 a side of the base 2 and outside the base 2. The opening 2a of the base 2 and the electron beam emission hole 7a of the first keeper electrode 7 are arranged so as to be coaxially arranged.

Next, the extraction power supply 13 for generating a potential difference between the cathode electrode 6 and the first keeper electrode 7 will be described. As shown in FIG. 1, in this embodiment, the drawer power supply 13 is mainly composed of a keeper power supply 14 and a cathode power supply 15. In FIG. 1, this drawing power supply 13 is shown surrounded by a one-dot chain line.
The keeper power supply 14 is provided outside the neutralizer 1, and the first keeper electrode 7 is connected to the negative terminal side thereof. Further, the positive terminal side of the keeper power supply 14 is grounded. The keeper power supply 14 is a DC power supply whose voltage value can be changed, and can generate a voltage of 10 to 50V. For this reason, a potential of about −10 to −50 V can be applied to the first keeper electrode 7. Here, it is assumed that the keeper power supply 14 can generate a voltage of Vk volts (Vk> 0). In this case, as shown in FIG. 1, a potential of −V k volts (the first keeper potential in the figure) can be generated at the first keeper electrode 7.
Similarly, the cathode power supply 15 is also provided outside the neutralizer 1. The negative terminal side of the cathode power supply 15 is electrically connected to the cathode electrode 6. Further, the positive terminal side of the cathode power supply 15 is connected to a wiring connecting the first keeper electrode 7 and the keeper power supply 14. The cathode power supply 15 is also a DC power supply that can change the voltage value in the same manner as the keeper power supply 14, and can generate a voltage of 10 to 50V. Since the cathode power source 15 and the keeper power source 14 are connected in series to the cathode electrode 6, a potential of −20 to −100 V can be applied to the cathode electrode 6. Here, it is assumed that the cathode power supply 15 can apply a voltage of Vc volts (Vc> 0). In this case, as shown in FIG. 1, a potential of −Vk−Vc volts (the cathode potential in the drawing) can be generated at the cathode electrode 6.

  Due to such a circuit configuration, when a voltage is applied from the keeper power supply 14 and the cathode power supply 15, a potential of −Vk volts is generated in the first keeper electrode 7, and −− A potential of Vk-Vc volts is applied. That is, a fixed bias is applied between the first keeper electrode 7 and the cathode electrode 6, and the first keeper electrode 7 has a positive potential about Vc volts than the cathode electrode 6. Due to this potential difference, electrons are attracted from the plasma generated inside the cathode electrode 6 and emitted as an electron beam.

Among the wires connecting the first keeper electrode 7 and the keeper power supply 14, an ammeter A <b> 1 is provided closer to the first keeper electrode 7 than the contact with the cathode power supply 15. The ammeter A1 is a device for measuring a current value input from the keeper power supply 14 to the first keeper electrode 7. An ammeter A2 is also provided between the contact between the first keeper electrode 7 and the keeper power supply 14 and the positive terminal of the cathode power supply 15. The ammeter A2 is a device for measuring the value of the current flowing between the keeper power supply 14 and the cathode power supply 15. Further, an ammeter A3 is also provided between the positive terminal side of the keeper power supply 14 and the ground. The ammeter A3 is a device for measuring a current value between the keeper power supply 14 and the ground.
By observing the current values of these ammeters A1 to A3 during the film formation process, it can be determined whether a stable extraction voltage is applied between the cathode electrode 6 and the first keeper electrode 7.

Next, the second keeper electrode 8 and the capacitor 16 which are characteristic components in the present invention will be described.
The second keeper electrode 8 is disposed on the opening 4 a side of the discharge tube 4 and at a position farther from the cathode electrode 6 than the first keeper electrode 7. The second keeper electrode 8 is a disk-like member made of a conductive material like the first keeper electrode 7 and has an electron beam emission hole for emitting an electron beam to the outside at the center. 8a is drilled. The electron beam emission hole 8a can be arbitrarily determined between 1 and 50φ (that is, 1 to 50 mm) according to the electron current value of the extracted electron beam. In particular, it is preferably between 5 and 20 mm. As shown in FIG. 2, the electron beam emission hole 8 a is formed in a tapered shape whose diameter is increased toward the outside of the neutralizer 1.
Similarly to the first keeper electrode 7, the second keeper electrode 8 is preferably formed of a conductive metal material. Examples of such materials include stainless steel (SUS), titanium (Ti), tungsten (W), molybdenum (Mo), carbon (C), and the like. Of these, stainless steel (SUS), tungsten (W), molybdenum (Mo), etc., which have high sputtering resistance, are particularly suitable.

As shown in FIG. 2, a keeper shield 19 is crowned on the opening 2 a side of the base 2. The first keeper electrode 7 and the second keeper electrode 8 are accommodated between the keeper shield 19 and the end surface of the base 2.
Between the base 2 and the first keeper electrode 7, between the first keeper electrode 7 and the second keeper electrode 8, and between the second keeper electrode 8 and the keeper shield 19, insulation such as an insulator is used. A spacer 18 formed of a member is disposed. Thereby, the insulation between the base 2 and the first keeper electrode 7, between the first keeper electrode 7 and the second keeper electrode 8, and between the second keeper electrode 8 and the keeper shield 19, respectively. Maintained. The distance between the first keeper electrode 7 and the second keeper electrode 8 can be arbitrarily set between 0.1 and 10 mm. In particular, it is preferably between 0.5 and 3 mm.

As shown in FIG. 1, the second keeper electrode 8 is connected to one terminal of the capacitor 16. The other terminal of the capacitor 16 is grounded. An ammeter A4 is provided between the capacitor 16 and the ground.
As the type of the capacitor 16, a known capacitor such as an aluminum electrolytic chip capacitor, a fixed tantalum chip capacitor, a ceramic capacitor, an electric double layer capacitor, or a mica capacitor can be used.
Further, the capacitance of the capacitor 16 can be arbitrarily set between about 50 pF to 10 μF.

  The capacitor 16 is an element that accumulates a predetermined amount of charge. The capacitor 16 has a role of applying a self-bias voltage to the second keeper electrode 8. That is, the capacitor 16 corresponds to the self-bias means of the present invention. One terminal of the capacitor 16 is connected to the second keeper electrode 8, and the other terminal is grounded. The second keeper electrode 8 is not connected to other members such as the base 2 and is in an electrically floating state. Accordingly, a part of the electron current drawn from the plasma inside the discharge tube 4 flows into the capacitor 16 through the second keeper electrode 8 and charges it. This charging time varies depending on the capacity of the capacitor 16. For example, in the case of a capacitor having a large capacity, the charging time becomes long, whereas in the case of a capacitor having a small capacity, the charging time is short.

As described above, the second keeper electrode 8 is applied with a self-bias voltage due to a voltage drop of the capacitor 16 due to an electron current drawn from the plasma inside the discharge tube 4 flowing. The self-bias voltage varies depending on the electron current value of the extracted electron beam, but is generally 0 to 100 V under normal film forming conditions. The self-bias voltage applied to the second keeper electrode 8 is Vm volts.
The second keeper electrode 8 has a higher potential than the cathode electrode 6 and the first keeper electrode 7. For this reason, electrons in the plasma generated inside the discharge tube 4 cause a potential difference between the cathode electrode 6 and the second keeper electrode 8 and between the first keeper electrode 7 and the second keeper electrode 8. It is extracted by the potential difference and emitted to the outside of the neutralizer 1 through the electron beam emission hole 8a.

As described above, the neutralizer 1 of the present invention is characterized in that in addition to the first keeper electrode 7, the second keeper electrode 8 to which the self-bias voltage Vm is applied is provided. That is, as compared with a conventional neutralizer that extracts an electron beam with a single keeper electrode, the neutralizer 1 of the present invention includes the second keeper electrode 8 in addition to the first keeper electrode 7, It is possible to draw out an electron beam having a higher electron current value than the electron current drawn out when a single keeper electrode is provided.
Therefore, when the neutralizer 1 of the present invention is used for an ion-assisted deposition apparatus or the like, it is possible to increase the total electron current value of the electron beam irradiated on the substrate, and neutralize the positive charge charged on the substrate. Speed can be increased. For this reason, the film formation rate is increased, and the tact time can be improved.

  Neutralizers are often used in film forming apparatuses such as ion-assisted vapor deposition apparatuses. Since ion guns and electron guns are placed near the neutralizer in the ion-assisted vapor deposition system, conventional neutralizers can be damaged by spattering the keeper electrode with positive ions from the ion gun or emitted from the electron gun. There is a disadvantage that the electron current value of the electron beam drawn from the neutralizer is lowered by the reflected electrons.

  However, in the conventional neutralizer, since a constant voltage is always applied to the keeper electrode, positive ions always collide. For this reason, while the voltage was applied to the keeper electrode, the keeper electrode was always sputtered by the collision of positive ions. For this reason, the damage speed of the keeper electrode is large, and it has been difficult to extend the life of the neutralizer.

On the other hand, in the neutralizer 1 of the present invention, since the second keeper electrode 8 is grounded via the capacitor 16, the potential of the second keeper electrode 8 changes according to the electron current value of the extracted electron beam. . That is, when the capacitor 16 is hardly charged and the electronic current easily flows, the voltage drop due to the capacitor 16 is large, and the value of the self-bias voltage applied to the second keeper electrode 8 becomes large. That is, the potential of the second keeper electrode 8 is greatly shifted to plus, and the collision frequency of positive ions is reduced.
On the contrary, when the capacitor 16 is charged and the electronic current hardly flows, the voltage drop due to the capacitor 16 is small, so that the self-bias voltage applied to the second keeper electrode 8 becomes almost zero. In the case of the circuit of FIG. 1, the potential of the second keeper electrode 8 is substantially equal to the ground potential. In this case, the frequency of collisions with positive ions increases.

  Thus, since the potential of the first keeper electrode 8 changes depending on the ease of flow of the electron current (that is, the degree of charging), the collision frequency of positive ions changes. Since the capacitor 16 is repeatedly charged and discharged while the electronic current is flowing, the state where it is easily sputtered and the state where it is difficult to be sputtered are alternately repeated. Therefore, compared to the case where the sputtering is always performed as in the conventional neutralizer, the deterioration rate of the keeper electrode due to sputtering is reduced, and the lifetime of the neutralizer can be extended.

  Furthermore, since the neutralizer 1 of the present invention includes the capacitor 16, the reflected electrons from the electron gun can be trapped in the capacitor 16. For this reason, the change in the electron current value due to the influence of the reflected electrons can be reduced.

In the above-described embodiment, an example in which a capacitor is used as the self-bias means has been described. However, as the self-bias means, for example, other elements such as resistors can be used.
For example, by using a resistor instead of the capacitor 16 in FIG. 1, a self-bias voltage is applied to the second keeper electrode 8 due to a voltage drop of the resistor.
As such a resistance, a known resistance can be used. Also, the resistance value can be arbitrarily set in the range of about 25Ω to 20 kΩ.
When a resistor is used as the self-biasing means, heat is generated by the flow of an electron current from the electron beam. For this reason, if a high electron current continues to flow, the resistance itself may be damaged due to burnout. However, when a capacitor is used, such heat generation hardly occurs. For this reason, it is possible to efficiently draw out an electron beam having a high electron current value.

Next, a film forming apparatus provided with the neutralizer of the present invention will be described. In the following example, an example in which an ion-assisted deposition apparatus is used as a film forming apparatus will be described.
FIG. 3 is an explanatory diagram showing an example in which the neutralizer of this embodiment is used in an ion-assisted deposition apparatus. The ion-assisted deposition apparatus 20 includes a vacuum chamber 21 that can maintain the inside in a vacuum state, a dome-shaped substrate dome 22 that holds the substrate S, a rotation motor 23 that rotates the substrate dome 22, and a deposition material source. The main component is an evaporation source 24 that evaporates and emits toward the substrate S, an ion gun 25 that irradiates an ion beam toward the substrate S, and the neutralizer 1.

The vacuum chamber 21 is a container that forms a film inside. A vacuum pump (not shown) is connected to the vacuum chamber 21, and the vacuum pump exhausts the inside of the vacuum chamber 21 so that the inside of the vacuum chamber 21 is in a high vacuum state of 10 ⁻² to 10 ⁻⁵ Pa. Become.
The substrate dome 22 is a member for holding the substrate S provided in the vacuum chamber 21. The substrate dome 22 is composed of a dome-shaped member having a predetermined curvature, and a plurality of substrates S are held on its inner peripheral surface by fastening members such as screws.
The rotation motor 23 is a device for rotating the substrate dome 22. The rotation motor 23 is provided outside the vacuum chamber 21. The output shaft of the rotation motor 23 is connected to the center of the substrate dome 22, and the substrate dome 22 is rotated by the rotation output of the rotation motor 23.

The evaporation source 24 is an apparatus for attaching a vapor deposition material to the substrate S, which is disposed inside the vacuum chamber 21. The evaporation source 24 includes an evaporation boat 26 provided with a depression for placing a deposition material source thereon, an electron gun 27 that irradiates the deposition material source with an electron beam to evaporate, and a deposition material directed from the evaporation boat 26 toward the substrate S. And a shutter 28 which is rotatably provided at a position where the shutter is cut off as a main component.
When an evaporation source is irradiated with an electron beam from the electron gun 27 in a state where a vapor deposition material source as a raw material of the vapor deposition material is placed on the evaporation boat 26, the vapor deposition material source is heated and evaporated. When the shutter 28 is opened in this state, the vapor deposition material evaporated from the evaporation boat 26 moves toward the substrate S in the vacuum chamber 21 and adheres to the surface of the substrate S.

The ion gun 25 is a device that irradiates positive ions toward the substrate S. A known ion gun can be used as the ion gun.
The vapor deposition material moving from the evaporation source 24 toward the substrate S adheres to the surface of the substrate S with high density and strength due to the collision energy of positive ions irradiated from the ion gun 25. At this time, the substrate S is positively charged by positive ions contained in the ion beam.
The neutralizer 1 is used during ion beam irradiation. The charge of the positively charged substrate S is neutralized by the electron beam emitted from the neutralizer 1.

Next, the operation of the neutralizer 1 will be described.
In order to operate the neutralizer 1, first, argon gas is introduced into the discharge tube 4 through a gas introduction tube 3 from a gas cylinder (not shown). The flow rate of the introduced argon gas is about 5 to 20 sccm.
When the inside of the discharge tube 4 reaches a predetermined gas pressure, the high-frequency power supply 11 is turned on to conduct a high-frequency current of 13.56 MHz to the high-frequency induction coil 5. An induction electric field is generated inside the discharge tube 4 by this high-frequency current. Furthermore, simultaneously with turning on the high-frequency power supply 11, a rectangular wave high voltage is continuously applied to the trigger electrode 9 from the trigger power supply 17 at an interval of 1200 V at intervals of 1 second to perform initial discharge. By performing this initial discharge, plasma is generated.

  An induction electric field generated by the high frequency induction coil 5 is introduced into the cathode electrode 6 through a slit provided in the cathode electrode 6. Electrons ionized in the argon gas move along the induction electric field and collide with other argon atoms. The collided argon atoms are ionized into electrons and ions. Electrons generated by ionization collide with other argon atoms to ionize them. By repeating this, high-density plasma inside the discharge tube 4 is generated.

When a potential difference is generated between the cathode electrode 6 and the first keeper electrode 7 by the extraction power supply 13 in a state where plasma is generated inside the discharge tube 4, electrons in the plasma are directed toward the first keeper electrode 7. And pulled out from the electron beam emission hole 7 a formed in the first keeper electrode 7 toward the inside of the vacuum chamber 21.
Specifically, when voltages of Vk volts and Vc volts are applied to the keeper power supply 14 and the cathode power supply 15 constituting the extraction power supply 13, respectively, -Vk-Vc volts are applied to the cathode electrode 6, and -Vk is applied to the first keeper electrode 7. A voltage of volts is applied, and a potential difference of Vc volts is generated between both electrodes.
Further, since the second keeper electrode 8 is grounded via the capacitor 16, a self-bias voltage is applied. For this reason, electrons in the plasma are also attracted by the potential difference between the cathode electrode 6 and the second keeper electrode 8 and between the first keeper electrode 7 and the second keeper electrode 8. The attracted electrons are extracted from an electron beam emission hole 8 a provided in the second keeper electrode 8.

The extracted electron beam travels along a trajectory toward the member having the highest potential in the vacuum chamber 21, that is, the positively charged substrate S, and is irradiated onto the substrate S. When the substrate S is irradiated with the electron beam, the positive charges accumulated on the substrate S and the electrons of the electron beam are combined to neutralize the positively charged substrate S.
After the film formation is completed, the vacuum state of the vacuum chamber 21 is released, and the internal substrate S is taken out.

In the above embodiment, the capacitance of the capacitor 16 is fixed. However, the capacitance of the capacitor 16 may be changed during the film formation process so that the capacitor 16 can respond quickly to load fluctuations. The neutralizer of the second embodiment will be described below.
FIG. 4 is an explanatory diagram showing electrical wiring of the neutralizer according to the second embodiment. Unlike the first embodiment, the neutralizer 1 of this embodiment is characterized in that a plurality of capacitors 16 a to 16 c having different capacities are provided in parallel, and the capacitors can be switched by the switch 30.

As described above, switching capacitors having different capacities has the following advantages.
As described above, the neutralizer 1 is often used for the purpose of neutralizing a positively charged substrate by an ion beam irradiation apparatus such as an ion gun. Therefore, in order to perform the neutralization process stably, it is necessary to irradiate the substrate with an amount of electrons commensurate with the amount of positive ions emitted from the ion gun.
However, in an ion-assisted deposition apparatus or the like, the amount of ion beam emitted from the ion gun may rapidly decrease due to a cause such as deposition material adhering to the inside of the ion gun as film formation progresses. In such a case, if the electron current value of the electron beam extracted from the neutralizer 1 is not immediately reduced, the entire substrate may be in an excessive electron state and may be negatively charged.
In order to avoid such an excessive electron state, when the supply amount of the ion beam fluctuates, it is necessary to quickly reduce the electron current value drawn from the neutralizer 1 in accordance with the fluctuation.

  In the conventional neutralizer, in order to cope with such fluctuation, the high-frequency voltage applied to the high-frequency induction coil from the high-frequency power supply is changed to reduce the amount of plasma generated or the cathode electrode applied by the extraction power supply 13. The extracted electron current value is reduced by reducing the potential difference between the keeper electrode and the keeper electrode. However, in any of the methods, it takes a certain amount of time for the extracted electron current value to change, and thus the electron current supplied from the neutralizer to the substrate may temporarily become excessive.

In such a case, by providing a plurality of capacitors 16a to 16c having different capacities as in this embodiment and switching the load when there is a change, it is possible to quickly cope with the change. Become. Here, it is assumed that the capacitance of the capacitor is 16a>16b> 16c.
A capacitor with a large capacity has a long charge / discharge time for an electron current, and a capacitor with a small capacity has a short charge / discharge time for an electron current.
A part of the electron current drawn from the plasma flows into the capacitor via the second keeper electrode 8 and charges it. During this charging, the value of the electron current drawn out of the neutralizer 1 decreases. That is, the operation of the neutralizer 1 can be delayed by this charging time. This charging time is longer for a capacitor having a larger capacity and shorter for a capacitor having a smaller capacity.

Therefore, for example, when the ion beam irradiation amount decreases due to a sudden load change, the capacitor is changed to a capacitor having a large capacity. Specifically, in the state where the capacitor 16b is connected to the second keeper electrode 8, in order to reduce the electron current value of the electron beam drawn out due to a sudden load change, the capacitor 16a having a larger capacity is connected. Thus, the delay time of the operation of the neutralizer 1 is lengthened. Thereby, it is possible to prevent the electron current value supplied to the substrate from rapidly decreasing, thereby preventing an excessive electron state.
On the contrary, in a state where the load fluctuation is small and the operation is stable, the operation delay time of the neutralizer 1 can be shortened and the electronic current can be stably extracted by connecting the capacitor 16c having a small capacity. .

Switching of the capacitors 16a to 16c by the switch 30 may be performed manually when an operator operating the ion assist vapor deposition apparatus observes a load fluctuation and a predetermined fluctuation occurs, but a computer, an automatic switching circuit, or the like may be used. May be used to switch automatically.
In this case, as a method of observing the load fluctuation, it can be measured by a known method such as providing a probe for measuring the amount of ions from the ion gun in the vicinity of the substrate. For example, when the amount of ions from the ion gun drops to 90% or less of the normal value, the switch 30 is switched to switch from the capacitors 16b to 16a. By performing such feedback control, it is possible to quickly respond to load fluctuations and to reduce the labor required for film formation.

In the second embodiment, a plurality of capacitors 16a to 16c are connected in parallel, and the capacitance of the capacitor is changed by switching the connection with the switch 30. For example, as shown in FIG. The capacity may be changed by 16d. FIG. 5 is an explanatory diagram showing electrical wiring of the neutralizer according to the third embodiment.
A variable capacitor can be used as the type of the variable capacitor 16d. As the type of the variable capacitor, a known one such as a polyvaricon or an air variable condenser can be used.

  In the second embodiment, a plurality of capacitors 16a to 16c are provided in parallel and the capacitors are switched by the switch 30, but a single capacitor is connected by a clip or the like to change the load. Depending on the condition, another capacitor having a different capacity may be manually replaced by the operator.

  In each of the above embodiments, a method is shown in which plasma is generated by the high-frequency power source 11 and the high-frequency induction coil 5 and electrons in the plasma are extracted as an electron beam. However, as means for generating electrons, It is not limited to such a high frequency induction system. For example, a thermoelectron emission type that generates thermoelectrons using a coiled electrode may be used.

In each of the above embodiments, a single keeper electrode is provided as an electrode to which a self-bias voltage is applied. However, two or more keeper electrodes are arranged along the trajectory of the electron beam, A configuration in which a bias voltage is applied may be employed. By providing such a plurality of keeper electrodes, the electron current value of the extracted electron beam is further improved.
In this case, it is preferable to apply a self-bias voltage so as to generate a potential gradient in each keeper electrode along the irradiation trajectory of the electron beam. By providing such a potential gradient, the electron beam is smoothly irradiated toward the object.

It is explanatory drawing which shows the electrical wiring of the neutralizer which concerns on 1st embodiment. It is explanatory drawing which shows the longitudinal cross-sectional shape of the neutralizer which concerns on 1st embodiment. It is explanatory drawing which shows the example which used the neutralizer of 1st embodiment for the ion assist vapor deposition apparatus. It is explanatory drawing which shows the electrical wiring of the neutralizer which concerns on 2nd embodiment. It is explanatory drawing which shows the electrical wiring of the neutralizer which concerns on 3rd embodiment. It is explanatory drawing which shows the electrical wiring of the conventional neutralizer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Neutralizer 2 Base 2a Opening 3 Gas introduction tube 4 Discharge tube 4a Opening 5 High frequency induction coil 6 Cathode electrode 7 First keeper electrode 7a Electron beam emission hole 8 Second keeper electrode 8a Electron beam emission hole 9 Trigger electrode 11 High frequency Power supply 12 Matching box 13 Lead electrode 14 Keeper power supply 15 Cathode power supply 16 Capacitor (self-biasing means)
16a to 16c capacitors (self-biasing means)
16d variable capacitor (self-biasing means)
Reference Signs List 17 Trigger Power Supply 18 Spacer 19 Keeper Shield 20 Ion Assist Deposition Device 21 Vacuum Chamber 22 Substrate Dome 23 Rotating Motor 24 Evaporation Source 25 Ion Gun 26 Evaporation Boat 27 Electron Gun 28 Shutter 30 Switch 100 Neutralizer 101 Electron Gun Body 102 Discharge Tube 103 Gas Introduction tube 104 High frequency induction coil 105 Cathode electrode 106 Anode electrode (keeper electrode)
106a Electron beam emission hole 111 High frequency power supply 113 Drawer power supply A1 to A4 Ammeter S Substrate

Claims (6)

A discharge tube having an opening at one end through which an electron beam can be drawn; and
A gas introduction tube for introducing gas into the discharge tube;
A plasma generating electrode for generating a plasma of the gas in the discharge tube;
A cathode electrode disposed in the discharge tube;
A first keeper electrode disposed on the opening side of the discharge tube;
An extraction power source for applying a voltage to the first keeper electrode so as to have a positive potential with respect to the cathode electrode;
A second keeper electrode disposed apart from the first keeper electrode on the opening side of the discharge tube;
A self-bias means for applying a self-bias voltage that is more positive than the cathode electrode to the second keeper electrode;
A neutralizer characterized by comprising   The neutralizer according to claim 1, wherein the self-biasing means is a capacitor having one terminal connected to the second keeper electrode and the other terminal connected to ground.   The neutralizer according to claim 2, wherein the capacitor is configured to be capable of changing a capacitance.   The neutralizer according to claim 3, wherein the capacitor is a variable capacitor.   4. The neutralizer according to claim 3, wherein the capacitor includes a plurality of capacitors having different capacities and a switch that connects any one of the plurality of capacitors to the second keeper electrode. A vacuum chamber capable of maintaining a vacuum inside;
A substrate holding means disposed in the vacuum chamber and capable of holding the substrate;
An ion gun that irradiates an ion beam toward the substrate;
A neutralizer that draws an electron beam from the plasma and irradiates the substrate, and a film forming apparatus comprising:
The film forming apparatus according to claim 1, wherein the neutralizer is the neutralizer according to claim 1.

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