JP5409470B2 - Neutralizer and ion beam apparatus provided with the same - Google Patents

Description

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

  Ion beams are often used for applications such as space development, observation technology, and microfabrication of devices. Usually, an electron source (hereinafter referred to as “neutralizer”) is used together to maintain electrical neutrality. It is common.

  Neutralizers include thermionic emission type, hollow cathode (hollow cathode) type, and high-frequency discharge type, etc., depending on the electron generation mechanism, but the hollow cathode type has the advantage that high-density electron current can be obtained. It is adopted by the device.

  FIG. 3 is an explanatory diagram showing electrical wiring of a conventional hollow cathode type neutralizer (with plasma ignition maintaining component) (see Patent Document 1). The conventional neutralizer 1 of FIG. 3 includes a gas introduction tube 3, a discharge tube 4, a cathode electrode 6, a first keeper electrode 7, a second keeper electrode 8, an extraction power source 13, a capacitor 16, As a major component. As shown in FIG. 4, an electron beam emission hole 7 a is provided at the center of the keeper electrode 7 so that electrons are drawn out, and an electron beam 32 is emitted toward the ion beam 33 therefrom. In FIG. 3, 7a is an electron beam emission hole, 8a is an electron beam emission hole, 14 is a keeper power supply, 15 is a cathode power supply, and 16a to 16c are capacitors (self-biasing means). In Patent Document 1, the trigger electrode 9 and the trigger power source 17 are used as means for improving the ignitability, and the high frequency induction coil 5, the high frequency power source 11, the matching box 12, and the base 2 are used as means for maintaining the plasma. It has.

  Next, the operation of the conventional neutralizer will be described. First, a discharge gas is supplied into the discharge tube 4. Next, a high voltage is applied to the trigger electrode 9 from the trigger power source 17 to perform initial discharge. Further, when a high frequency current is passed through the high frequency induction coil 5 by the high frequency power source 11 at the same time as the trigger power source 17 is turned on, an induction electric field is generated in the discharge tube 4. The electrons existing in the initial discharge repeatedly accelerate and decelerate by this induction electric field, and excite the gas for discharge, so that the plasma 31 is finally generated. When a voltage of several hundred volts is applied between the keeper electrode 7 and the cathode electrode 6 by the extraction power supply 13 in a state where plasma is generated inside the discharge tube 4 as described above, the electron beam 32 is extracted from the electron beam emission hole 7a. It will function as an electron source.

  Depending on the usage environment and pressure zone, even when the plasma 31 is not generated inside the discharge tube 4, it is only necessary to apply a voltage of several hundred volts between the keeper electrode 7 and the cathode electrode 6 by the extraction power supply 13. The plasma 31 can be generated and maintained, and at the same time, the electron beam 32 is extracted from the electron beam emission hole 7a and can function as an electron source. In such a case, the trigger electrode 9 and the trigger power source 17 which are necessary means for generating the initial discharge, and the high frequency induction coil 5 and the high frequency power source which are necessary means for generating and maintaining the plasma 31 are used. 11, the matching box 12 and the base 2 are not required, and the configuration is simple as shown in FIG. Since the difference between FIG. 3 and FIG. 4 is only whether or not a means for igniting and maintaining the plasma is provided, the mechanism of extraction of the electron beam, and the problem that arises therewith, is the same.

  When trying to draw a higher electron current, it is realized by increasing the number of multiplied electrons by increasing the voltage of the cathode power supply 15.

  Such a conventional neutralizer has a technical problem in that the lifetime of the neutralizer is determined by the following phenomenon, and it is necessary to frequently replace the neutralizer. This point will be described with reference to FIGS. FIG. 4 is a cross-sectional view of a conventional neutralizer (with no plasma ignition maintenance component) and an explanatory diagram showing electrical wiring, and FIG. 5 is an explanation showing problems with the conventional neutralizer (with or without a plasma ignition maintenance component). FIG.

  Since the cathode electrode 6 has a negative potential, sputtering occurs due to positive ions in the plasma 31 during discharge. Therefore, the cathode electrode 6 is scraped with the operation time, the discharge efficiency is deteriorated, and finally the discharge cannot be maintained. Therefore, in order to extend the life, it is necessary to make the discharge voltage as small as possible. With respect to this problem, in Patent Document 2, the discharge voltage is lowered by covering the inside of the cathode electrode 6 with an electron emitter, and in Patent Document 3 by changing the shape of the cathode electrode 6, thereby extending the life of the cathode electrode 6. I am trying.

JP 2007-242368 A JP 2000-130316 A JP 59-228338 A

  However, when the hollow cathode type neutralizer described in Patent Document 1 is used, the cathode material released by sputtering is repeatedly sputtered and reattached, and finally on the side of the keeper electrode 7 facing the cathode electrode 6. Adhere to. When the amount of adhesion increases, the electric field intensity around the electron beam emission hole 7a becomes weak and the electron beam 32 is not emitted (FIG. 5).

  In addition, since the film attached to this portion tends to be a film having a low density and a weak adhesive force, troubles such as abnormal discharge caused by the peeled film are likely to occur (FIG. 5).

  In FIG. 3, since a negative voltage is applied to the keeper electrode 7, some of the positive ions in the ion beam are attracted and sputtering occurs. This sputtering acts particularly strongly around the electron beam emission hole 7a, and the hole diameter of the electron beam emission hole 7a gradually expands according to the operation time. On the other hand, the internal pressure of the discharge tube 4 is determined by the flow rate of the discharge gas and the hole diameter of the electron beam emission hole 7a. If the hole diameter of the electron beam emission hole 7a is increased, the pressure in the discharge tube 4 is reduced. Causes a drop. When the pressure in the discharge tube becomes lower than a predetermined value, the plasma 31 cannot be generated and the electron source does not operate.

  With respect to this problem, Patent Document 1 attempts to improve the problem by installing the second keeper electrode 8 via a capacitor 16. Since the second keeper electrode 8 is electrically insulated from the outside, its potential takes a certain value determined by the balance between the inflow of electrons and positive ions. Since this potential is higher than the potential of the first keeper electrode 7, it is expected that the amount and energy of positive ions flying from the outside are reduced, and the wear speed of the keeper electrode is suppressed.

  However, this method is expected to reduce the amount of current of the electron beam 32. That is, the value [cm−2s−1] of the electron current per unit area is determined by the density and electron temperature of the plasma 31, the conductance determined by the shape near the electron beam emission hole 7a, and the electric field generated near the electron beam emission hole 7a. On the other hand, in Patent Document 1, since the number of keeper electrodes is increased to two, ie, the first keeper electrode and the second keeper electrode, the conductance is reduced, and the plasma 31 and the second keeper electrode are used. Since the distance 8 becomes larger, the electric field intensity near the electron beam emission hole 7a becomes smaller, and as a result, the current value of the electron beam 32 decreases.

  Further, positive ions are constantly incident on the surface of the second keeper electrode 8, but since the second keeper electrode 8 is electrically insulated, in order to keep its potential, that is, the total amount of charges, constant. The same amount of electrons as positive ions are electrically sucked into the second keeper electrode 8. This further reduces the net electron current emitted towards the ion beam 33. Thus, even if the wear of the keeper electrode can be suppressed, the current value of the obtained electron beam 32 becomes small, so that it is considered difficult to achieve a practical effect. Further, in Patent Document 1, since the number of keeper electrodes is increased to two, there is a problem that the neutralizer is enlarged and cannot be provided in a small apparatus.

  The present invention has been made in view of the above-described problems, and is capable of extracting a large number of electron beams, and a small neutralizer that operates stably over a long period of time, and an ion beam apparatus including the same. The purpose is to provide.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a discharge tube having an opening through which an electron beam can be drawn out at one end, a gas introduction tube for introducing a gas into the discharge tube, A cathode electrode disposed on the discharge tube, a keeper electrode disposed on the opening side of the discharge tube, a cathode power source for applying a voltage to the cathode electrode , a keeper power source for applying a voltage to the keeper electrode,
The cathode power supply and the keeper power supply are connected to an inversion mechanism that inverts the voltage polarity of the cathode electrode and the keeper electrode. .
According to a second aspect of the present invention, in the neutralizer according to the first aspect, the reversing mechanism includes a forward relay and a reverse relay .
The invention according to claim 3 is the neutralizer according to claim 2, wherein the forward relay is composed of a first forward relay and a second forward relay, and the reverse relay is The first reverse relay and the second reverse relay are configured, and the input side of the first forward relay and the input side of the first reverse relay are connected to the negative side of the cathode power supply. The input side of the second forward relay and the input side of the second reverse relay are connected to the positive side of the cathode power supply, and the output side of the first forward relay and the second side The output side of the reverse relay is connected to the cathode electrode, and the output side of the second reverse relay and the output side of the first reverse relay are connected to the keeper electrode. Features.
According to a fourth aspect of the present invention, in the neutralizer according to the first aspect, when discharging is performed with the voltage polarity of the keeper electrode and the cathode electrode reversed, the reversing mechanism causes the cathode electrode to be positive. The keeper electrode is a negative electrode.
According to a fifth aspect of the present invention, in the neutralizer according to the third aspect, when the electron beam is generated, the first forward relay and the second forward relay are closed, When the reverse relay and the second reverse relay are opened and discharging is performed with the voltage polarity of the keeper electrode and the cathode electrode reversed, the first forward relay and the second forward relay Is switched from closed to open, and the first reverse relay and the second reverse relay are switched from open to closed.
According to a sixth aspect of the present invention, there is provided a vacuum chamber capable of maintaining the inside thereof in a vacuum, a substrate holding means disposed in the vacuum chamber and capable of holding the substrate, and ions for irradiating an ion beam toward the substrate. source and, an ion beam device including a neutralizer, an irradiated to the substrate is pulled out of the electron beam from the plasma, the neutralizer is neutralizer according to any one of claims 1 5 It is characterized by being.

  In the present invention, since the reversing mechanism for reversing the voltage polarity of the cathode electrode and the keeper electrode is provided, there is no need for an electron source, for example, while the substrate is being transported or while the ion beam 33 is being adjusted. It is now possible to perform discharge with the voltage polarity of the keeper electrode 7 and the cathode electrode 6 of the neutralizer reversed (hereinafter referred to as “reverse discharge”). For this reason, the side of the keeper electrode 7 facing the cathode electrode 6 is usually covered with a sputtered cathode material 34 and covered with a film, but ions are discharged while the voltage polarity is reversed. Sputtered by By this action, the effect of slowing the growth rate of the film on the side of the keeper electrode 7 facing the cathode electrode 6 can be obtained, and the time until electrons are not emitted can be lengthened. Moreover, since the neutralizer in this invention refills the part which was worn by use again, it becomes possible to reduce the wear speed of a neutralizer significantly. Therefore, in the apparatus equipped with the neutralizer of the present invention, the frequency of replacement of the neutralizer can be lowered compared with the case where the conventional neutralizer is used, thereby improving the throughput compared to the conventional case. In addition, it is possible to reduce the running cost associated with parts replacement.

It is a figure which shows the cross section of the neutralizer (without plasma ignition maintenance component) by embodiment of this invention, and an electrical circuit. It is explanatory drawing which shows the example which used the neutralizer by the embodiment of this invention (regardless of the presence or absence of a plasma ignition maintenance component) for the ion beam etching apparatus. It is a figure which shows the cross section of the conventional neutralizer (Plasma ignition maintenance component existence, patent document 1). It is a figure which shows the cross section and electric circuit of a conventional type neutralizer (without plasma ignition maintenance components). It is a figure which shows the subject which arises with the conventional neutralizer (The presence or absence of a plasma ignition maintenance component is not ask | required).

  Below, the operation method of the neutralizer which concerns on this invention is demonstrated with an Example.

  FIG. 1 is a cross-sectional view of a neutralizer (with no plasma ignition maintenance component) according to an embodiment of the present invention and an explanatory diagram showing electrical wiring. The same members as those in FIG. 3 are given the same numbers.

  As can be seen from the comparison between FIG. 4 and FIG. 1, the characteristic features of the present invention are components related to electrical wiring such as the keeper power supply 14, the cathode power supply 15, the forward relays 35 and 36, and the reverse relays 37 and 38, and In the configuration method, the vacuum components such as the cathode electrode 6, the keeper electrode 7, the electron beam extraction hole 7a, the gas introduction tube 3 and the discharge tube 4 are exactly the same as those of the conventional neutralizer.

  The neutralizer of the present embodiment includes a gas introduction tube 3, a discharge tube 4, a cathode electrode 6, a keeper electrode 7, and an electron beam extraction hole 7a, as in the conventional neutralizer.

  The discharge tube 4 and the keeper electrode 7 are made of a conductive material, and a negative potential is applied by a keeper power source 14. Since the surface of the keeper electrode 14 is struck by ions and gradually scatters into the vacuum, a metal having high sputter resistance such as Mo and Ti is preferable in view of contamination in the vacuum.

  The cathode electrode 6 is made of a conductive material and has a cylindrical shape with one side open. The hollow cathode thus means a “negative electrode with a depression”, and is characterized in that a high plasma density can be obtained by trapping electrons in this cylinder. Since the cathode electrode 6 is also struck by ions and scattered in the vacuum, a metal having high sputtering resistance such as Mo and Ti is preferable.

  The cylindrical container composed of the discharge tube 4 and the keeper electrode 7 is made highly airtight, and the discharge gas enters the cylindrical container through the gas introduction tube 3 and is vacuumed from the electron beam extraction hole 7a. To be released. The internal pressure of the discharge tube 4 is determined by the flow rate of the discharge gas and the conductance of the electron beam extraction hole 7a. Since the electron beam extraction hole 7a in this embodiment is as small as about 1 mm in diameter, the internal pressure of the discharge tube 4 is relatively high at several tens of Pa, and the mean free path at that time is also very short at 0.1 m or less. Yes. Thus, by performing discharge under high pressure, a high-density plasma 31 is obtained, and an electron beam 32 of about 1 ampere at most is obtained. From the experiment, if the diameter of the beam extraction hole 7a is smaller than 0.7 mm, the electron beam 32 cannot be extracted, and if the diameter of the beam extraction hole 7a is larger than 2 mm, the internal pressure of the discharge tube 4 is lowered and the plasma 31 is reduced. I know it ca n’t be maintained.

Next, the drawer power supply 13 will be described. As shown in FIG. 1, the drawer power supply 13 includes a keeper power supply 14 and a cathode power supply 15. As the keeper power source 14 and the cathode power source 15, a general DC power source was used.
Since the cathode power source 15 is responsible for plasma ignition and discharge maintenance, a relatively high voltage is required. In this embodiment, the rated voltage is 600 volts. Regarding the current, a rated current of 1 ampere was used in consideration of the maximum value of the electron beam. Since the cathode power supply 15 is basically controlled by a current value, a cathode power supply capable of current control is used.
The keeper power supply 14 only needs to maintain a voltage of several tens of volts in order to extract electrons. In this embodiment, the rated voltage is 50 volts and the rated current is 1 ampere. The keeper power supply 14 is capable of voltage control.

Next, a procedure for generating the electron beam 32 will be described.
First, a discharge gas (for example, Ar) is flowed, and the pressure in the discharge tube 4 is set to a predetermined pressure (for example, 30 Pa). Next, the entire system including the gas introduction tube 3, the discharge tube 4, the cathode electrode 6, the keeper electrode 7, and the cathode power source 15 (power is in an off state) is lowered to a negative potential by the keeper power source 14. This is because the plasma 31 is generated unless the potential of the entire system is lowered, but the electron beam 32 is not generated. In the present embodiment, the potential of the entire diameter system is set to −30 volts.

  When generating the electron beam 32, a voltage of several hundred volts is applied between the cathode electrode 6 and the keeper electrode 7 by the cathode power supply 15. The free field is accelerated by the electric field generated at this time, and plasma 31 is generated by causing collision and ionization with the gas. At the same time, electrons are extracted from the electron emission hole 7a toward the vacuum device 21 shown in FIG. 2, and an electron beam 32 is generated. When it is desired to stop the electron beam 32, the cathode power supply 15 is turned off so that the plasma 31, and thus the electron beam 32, disappears.

  In the state in which the plasma 31 is generated, positive ions are constantly drawn into the cathode electrode 6 from the plasma 31, so that a very large potential difference is generated between the cathode electrode 6 and the plasma 31 due to the cathode drop. On the other hand, a potential difference also occurs between the keeper electrode 5 and the plasma 31 due to the anode drop, but its value is very small compared to that of the cathode drop. As a result, the plasma 31 and the keeper electrode 7 have substantially the same potential of −30 volts, and only the cathode electrode 6 has a very low potential of minus several hundred volts. As can be seen, since the potential of the plasma 31 is about −30 volts, which is lower than the ground, electrons are extracted toward the vacuum device 21 that is the ground potential, and an electron beam 32 is generated. I understand that Further, since the potential of the cathode electrode 6 is as low as minus several hundred volts with respect to the potential of the plasma 31, the cathode electrode 6 is worn away by sputtering with positive ions. It can be seen that the scraped cathode material repeatedly diffuses and reattaches in the plasma, and eventually adheres and accumulates on the back side of the keeper electrode 1 that is not hit by ions.

  Next, forward relays 35 and 36, reverse relays 37 and 38, which are characteristic components in the present invention, and an operation method thereof will be described with reference to FIG.

Four relays with 1a contacts that are commonly used were used. The contact 1a is normally open, but is closed only while a signal is applied from the outside. Since the contact is loaded with a maximum of 600 volts and 1 ampere, it is necessary to select a contact that satisfies the contact capacity. Although the relay is used this time, the method is not limited as long as the power source configuration can reverse the electrodes of the cathode electrode 6 and the keeper electrode 7.
Actual wiring was performed as shown in FIG. That is, the negative side of the cathode power supply 15 is input to the input side of the forward relay 35 and the reverse relay 37, and the positive side of the cathode power supply 15 is input to the input side of the forward relay 36 and the reverse relay 38. Connected to the side. On the other hand, the cathode electrode 6 was connected to the output side of the forward relay 35 and the reverse relay 38, and the keeper electrode 7 was connected to the output side of the forward relay 36 and the output side of the reverse relay 37.

  When the electron beam 32 is generated (hereinafter referred to as “normal time”), the forward relays 35 and 36 are closed and the reverse relays 37 and 38 are opened. The electrical wiring in this state is exactly the same as the conventional type in FIG. Accordingly, when the power supply is turned on in the order of the keeper power supply 16 and the cathode power supply 15 with the discharge gas flowing, the plasma 31 and the electron beam 32 are generated and operate as an electron source.

  Next, when reverse discharge is performed, first, the cathode power supply 15 and the keeper power supply 14 are turned off, and the plasma 31 and the electron beam 32 are once extinguished. Then, after switching the forward relays 35, 36 from closed to open and the reverse relays 37, 38 from open to closed, when the cathode power supply 15 is turned on, plasma 31 is generated. Absent). The discharge at this time is different from the normal case in that the polarity of the electrode is reversed, and the cathode electrode 6 is set to the positive electrode (ground) and the keeper electrode 7 is set to the negative electrode (minus several hundred volts). Therefore, in this state, the cathode material 34 deposited on the cathode side of the keeper electrode 7 is hit and repeatedly diffused and reattached in the plasma, and finally deposited on the surface of the original cathode electrode 6. Go. As a result, the growth speed of the cathode material 34 deposited on the cathode side of the keeper electrode 7 can be reduced, and the wear speed of the cathode electrode 6 can also be reduced.

  For comparison, a sample in which normal discharge was performed for 2500 minutes and a sample in which normal discharge for 5 minutes and reverse discharge for 5 minutes were repeated for a total of 2500 minutes were prepared, and the inside of the neutralizer was confirmed.

  Regarding the cathode electrode 6, there is no significant difference in the state. That is, since the inside of the cylinder was shaved by positive ions in the plasma 31, a clean metal surface (SUS material in this embodiment) was exposed. However, in terms of the degree of wear, the one that was subjected only to normal discharge was worn quickly and the tip of the cathode electrode 6 was shaved and rounded, whereas the one that repeated normal discharge and reverse discharge was This phenomenon is not observed, and the wear speed is thought to be decreasing.

  Next, the keeper electrode 7 is compared. In the case where only normal discharge was performed, the cathode material 34 adhered to the cathode side of the keeper electrode 7 and grew in a columnar shape, and because the adhesion was weak, it peeled off when scratched. On the other hand, in the case where the normal discharge and the reverse discharge were repeated, the cathode material 34 was also adhered to the cathode side of the keeper electrode 7, but it was dense and high in adhesion force and its amount was small.

  Here, the reason why the film quality is changed by the reverse discharge will be considered. During normal discharge, the potential of the keeper electrode 7 is only a few volts lower than the potential of the plasma 31, so that the cathode material diffused into the plasma adheres to the keeper electrode 7 with almost no energy. In this situation, diffusion on the surface does not proceed, and a brittle columnar crystal with a low density grows. Now stop normal discharge and switch to reverse discharge. Since only the keeper electrode 7 drops to minus several hundred volts, the keeper electrode 7 starts to be struck by Ar ions in the plasma. Then, the cathode material 34 adhering to the keeper electrode 7 is scraped little by little while repeating sputtering and reattachment. However, at this time, since atoms having high energy exist on the surface of the keeper electrode 7, an amorphous strong film having a low density is formed on the surface when the reverse discharge is stopped. Conceivable. Thus, it can be seen that reverse discharge has the effect of inhibiting the brittle columnar crystal growth that occurs in normal discharge and resetting the film quality once.

  Next, the electron extraction hole 7a is compared. In the case where only the normal discharge is performed, the hole diameter of the electron emission hole 7a is increased, whereas in the case where the normal discharge and the reverse discharge are repeated, on the contrary, The hole diameter was small. This is because, during normal discharge, positive ions are attracted from the ion beam 33 toward the electron emission hole 7a and the hole diameter increases due to the sputtering phenomenon, whereas the keeper electrode 7 becomes a negative electrode during reverse discharge. Therefore, although it is sputtered by ions in the plasma 31, the sputtered material 34 is also emitted obliquely forward in the vicinity of the electron emission hole 7a, and this is considered to be reattached as a film to the inner wall of the electron beam emission hole 7a. It is done.

  From the above comparative experiments, it was confirmed that the use of reverse discharge together has the effect of slowing the wear speed of the cathode electrode 6 and extending its life. As for the keeper electrode 7, it was found that the amount of the film adhering to the side facing the cathode is reduced, and the film quality is also strong and difficult to peel off. Further, it has been found that the speed of the electron beam emission hole 7a, which is a major factor for shortening the life of the keeper electrode, can be slowed.

  This time, the evaluation was performed by repeating the normal discharge for 5 minutes and the reverse discharge for 5 minutes. This is because the apparatus operation example referred to was that the substrate processing time was 5 minutes and the time during which the apparatus was not used for transporting the substrate was about 5 minutes, and various combinations are actually conceivable.

  The wear speed is determined by the ratio of normal discharge and reverse discharge. Increasing the reverse discharge ratio decreases the wear speed, but if the reverse discharge ratio increases too much, the compensation effect increases and electron beam emission increases. Conversely, the hole diameter of the hole 7a becomes smaller. In the case of this example, it is considered that the life is further extended if the percentage of reverse discharge is further reduced.

  The wear speed of the cathode electrode 6, the keeper electrode 7, and the electron emission hole 7 a varies depending on the material and shape, the use conditions such as the discharge power and pressure, and the intensity of the ion beam 33. It seems to be wise to find the optimal ratio by gradually increasing the percentage of, and confirming the state of wear.

Next, an etching apparatus provided with the neutralizer of the present invention will be described.
FIG. 2 is an explanatory diagram showing an example in which the neutralizer (with or without the plasma ignition maintaining component) of this embodiment is used in an ion beam etching apparatus. The ion beam etching apparatus 39 includes a vacuum chamber 21 that can maintain the inside in a vacuum state, a hemispherical stage 40 that holds the substrate S, a rotation motor 23 that rotates the stage, and ions toward the substrate S. Main components are an ion beam source 41 that emits, a neutral laser 1 that neutralizes positive charges on the substrate S, and a potential sensor 42 that measures the potential on the stage.

The vacuum chamber 21 is a container that performs etching 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 ⁻³ to 10 ⁻⁶ Pa. Become.
The stage 40 is a member for holding the substrate S provided in the vacuum chamber 21. The substrate S is held on the stage by a restraining jig provided on the surface of the stage 40 or a method such as electrostatic adsorption.
The rotation motor 23 is a device for tilting the stage 40 and is provided outside the vacuum chamber 21. The output shaft of the rotation motor 23 is connected to the side surface of the stage 38, and the rotation of the rotation motor 23 causes the stage 40 to rotate about the substrate. As a result, the ion beam 9 and the substrate S can be set at an arbitrary angle and the etching process can be performed.

The ion beam source 41 is a device that irradiates positive ions toward the substrate S. A well-known thing can be used as an ion beam source. The ion beam 33 emitted from the ion beam source 41 collides with the substrate S while having high kinetic energy, and etching of the surface of the substrate S proceeds. At this time, the substrate S is positively charged by positive ions contained in the ion beam 33.
The neutral laser 1 is used during irradiation of the ion beam 33. The charges of the positively charged substrate S are neutralized by the electron beam 32 irradiated from the neutralizer 1.
The potential sensor 42 is a sensor that measures the potential on the stage 40. By feeding back the value of the sensor to the electron beam 11, the potential on the stage 38 can be kept constant. For example, when the value of the potential sensor 42 is positive, it means that neutralization is insufficient, so the amount of the electron beam 11 is increased and the neutralization is strengthened.
After the etching process is completed, the ion beam 33 and the electron beam 32 are stopped, and the substrate S is taken out using a vacuum robot (not shown).

  In the above embodiment, a hollow cathode is shown as means for generating electrons, but the invention is not limited to this. For example, a thermionic emission electron source or a high-frequency electron source is possible.

  In the above embodiment, the keeper power supply is used to lower the potential of the entire discharge system in order to extract electrons. However, the present invention is not limited to this. For example, the effect of the present invention is also achieved in a method of extracting electrons by applying a positive electric field in front of the keeper electrode.

  When trying to extend the life of a hollow cathode, the conventional technology generally changed the material and shape of the cathode electrode 6 or provided a new electrode. The invention differs from the prior art in that discharge is performed by reversing the voltage polarity of the electrodes.

  As described above, according to the present invention, the voltage of the keeper electrode 7 and the cathode electrode 6 of the neutralizer is not necessary when the electron source is required, for example, while the substrate is being transported or while the ion beam 33 is being adjusted. Reverse discharge is performed with the polarity reversed. Thereby, the following actions and effects are exhibited.

  The side of the keeper electrode 7 facing the cathode electrode 6 is usually covered with a sputtered cathode material 34 and is covered with a film, but is sputtered by ions while discharging with a reverse voltage polarity. The By this action, the effect of slowing the growth rate of the film on the side of the keeper electrode 7 facing the cathode electrode 6 can be obtained, and the time until electrons are not emitted can be lengthened.

  The cathode electrode 6 is usually scraped by the action of sputtering because of a negative potential, but while the cathode material 34 generated in the above item is deposited again while the voltage polarity is reversed, the actual scraping speed is reduced. Can slow down.

  When the voltage polarity of the keeper electrode 7 and the cathode electrode 6 of the neutralizer is reversed to generate the plasma 31, the cathode material 34 is repeatedly attached and sputtered on the side of the keeper electrode 7 facing the cathode electrode 6. At this time, since the sputter speed is increased at a portion where the film is growing rapidly, an effect of making the attached film flat and dense is produced. By this action, the adhered film is strong and difficult to peel off, and the occurrence of discharge troubles due to the film peeling can be suppressed.

  When the voltage polarity of the keeper electrode 7 and the cathode electrode 6 of the neutralizer is reversed to generate the plasma 31, the cathode material 34 formed before inverting the voltage polarity of the keeper electrode 7 and the cathode electrode 6 is replaced with the keeper electrode. 7 and the cathode electrode 6 are reversed by reversing the voltage polarity. At this time, most of the sputtered cathode material 34 is emitted toward the plasma 31 and the cathode electrode 6 side, but in the vicinity of the electron emission hole 7a, the cathode material 34 is also emitted obliquely forward. The cathode material 34 emitted obliquely forward is reattached as a film to the inner wall of the electron beam emission hole 7a. By this action, the speed at which the inner diameter of the electron beam emission hole 7a expands is suppressed, and the time until the plasma 31 cannot be generated can be lengthened.

  Originally, in the ion beam apparatus, since the wear speed of the neutralizer is fast, the frequency of replacement of parts is high, and as a result, there is an operational problem that the overall operation rate of the apparatus cannot be increased. In addition, in recent years, in order to increase the throughput, there is an increasing situation in which a large current ion beam must be used. As the ion beam current increases, the electron beam current value that neutralizes the ion beam current inevitably increases, so the wear of the neutralizer is accelerating further. In such a situation, the neutralizer according to the present invention refills the portion worn by use again, so that the wear speed of the neutralizer can be greatly reduced. Therefore, in the apparatus equipped with the neutralizer of the present invention, the frequency of replacement of the neutralizer can be lowered compared with the case where the conventional neutralizer is used, thereby improving the throughput compared to the conventional case. In addition, it is possible to reduce the running cost associated with parts replacement. Moreover, it can be used by applying the present invention to the application of high electron current, which has so far been fast and practically difficult to use.

DESCRIPTION OF SYMBOLS 1 Neutralizer 2 Base 3 Gas introduction tube 4 Discharge tube 5 High frequency induction coil 6 Cathode electrode 7 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 Drawer power supply 14 Keeper power supply 15 Cathode power supply 16 Capacitor (self-biasing means)
16a to 16c capacitors (self-biasing means)
17 Trigger power supply 21 Vacuum chamber 23 Rotating motor 31 Plasma 32 Electron beam 33 Ion beam 34 Cathode material 35 Forward relay 36 Forward relay 37 Reverse relay 38 Reverse relay 39 Ion beam etching apparatus 40 Stage 41 Ion beam source 42 Potential sensor S substrate

Claims (6)

A discharge tube having an opening at one end through which an electron beam can be extracted;
A gas introduction tube for introducing gas into the discharge tube;
A cathode electrode disposed in the discharge tube;
A keeper electrode disposed on the opening side of the discharge tube;
A cathode power source for applying a voltage to the cathode electrode ;
A keeper power source for applying a voltage to the keeper electrode;
A neutralizer comprising:
The neutralizer, wherein the cathode power source and the keeper power source are connected to an inversion mechanism for inverting the voltage polarity of the cathode electrode and the keeper electrode . The neutralizer according to claim 1, wherein the reversing mechanism includes a forward relay and a reverse relay. The forward relay is composed of a first forward relay and a second forward relay,
The reverse relay is composed of a first reverse relay and a second reverse relay,
The input side of the first forward relay and the input side of the first reverse relay are connected to the negative side of the cathode power supply;
The input side of the second forward relay and the input side of the second reverse relay are connected to the positive side of the cathode power supply;
An output side of the first forward relay and an output side of the second reverse relay are connected to the cathode electrode;
The neutralizer according to claim 2, wherein an output side of the second reverse relay and an output side of the first reverse relay are connected to the keeper electrode. 2. The neutral according to claim 1, wherein when discharging is performed in a state in which the voltage polarity of the keeper electrode and the cathode electrode is reversed, the reversing mechanism sets the cathode electrode to a positive electrode and the keeper electrode to a negative electrode. Riser. When generating the electron beam, the first forward relay and the second forward relay are closed, the first reverse relay and the second reverse relay are opened,
When discharging with the voltage polarity of the keeper electrode and the cathode electrode reversed, the first forward relay and the second forward relay are switched from closed to open, and the first reverse relay and 4. The neutralizer according to claim 3, wherein the second reverse relay is switched from open to closed. 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 source that irradiates an ion beam toward the substrate;
An ion beam apparatus comprising: a neutralizer that extracts an electron beam from plasma and irradiates the substrate;
The ionizer according to claim 1, wherein the neutralizer is a neutralizer according to claim 1.