Ion beam irradiation device and gas exhaust method

Abstract

To start ion source maintenance early after the ion source is shut down.SOLUTION: An ion beam irradiation device IM includes a plasma generation container 2 in which plasma is generated, a vaporizer S connected to the plasma generation container 2, a halogen gas supply path 13 that supplies halogen gas to the vaporizer S, an air supply path 16 that supplies air to the vaporizer S, and an exhaust path 11 that discharges a reaction product generated by the reaction between halogen gas and air to the outside of the device.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an ion beam irradiation apparatus that irradiates an object with an ion beam and a gas evacuation method used in the apparatus. [Background technology]

[0002] In the maintenance of an ion source used in an ion beam irradiation device, the inside of the device is changed from a vacuum atmosphere to an air atmosphere, the ion source is then removed from the ion beam irradiation device, and consumables that make up the ion source are replaced.

[0003] When the inside of the ion beam irradiation device is changed from a vacuum atmosphere to an atmospheric atmosphere, as described in Patent Document 1, the inside of the device is filled with a rare gas such as nitrogen, and the pressure inside the device is set to atmospheric pressure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 7-326320 Summary of the Invention [Problem to be solved by the invention]

[0005] There are various types of ion beams, and when the ion beam contains metal ions, a vaporizer is used to vaporize the metal material, plasma is generated from the vapor of the metal material, and an ion beam containing the metal ions is extracted from the plasma.

[0006] Recently, as research into vaporizers has progressed, the applicant of the present application has proposed a new vaporizer, which involves placing a metal material such as aluminum or tungsten in a crucible of the vaporizer, introducing a halogen gas such as chlorine or fluorine into the crucible, generating a reaction product through a chemical reaction between the metal material and the halogen gas, and heating the reaction product to supply vapor of the reaction product to a plasma generating vessel.

[0007] In an ion source equipped with the vaporizer, it is necessary to sufficiently reduce the concentration of toxic halogen gas remaining in the ion source before maintenance. As with conventional techniques, when the pressure of the ion source is adjusted to atmospheric pressure by supplying nitrogen gas, the inside of the ion source is alternately filled with nitrogen gas and evacuated. After the concentration of the remaining halogen gas is sufficiently reduced, nitrogen gas is again supplied to restore atmospheric pressure inside the ion source. This method is problematic because it takes a long time for the halogen gas concentration to be reduced, which means that it takes a long time to restore atmospheric pressure inside the ion source and start maintenance.

[0008] Therefore, a main object of the present invention is to provide a new ion beam irradiation apparatus and a new gas exhaust method that allow for early start of maintenance of the ion source. [Means for solving the problem]

[0009] The ion beam irradiation device a plasma generating vessel in which plasma is generated; a vaporizer connected to the plasma generating vessel; a halogen gas supply path for supplying a halogen gas to the vaporizer; an air supply passage for supplying air to the vaporizer; The apparatus is provided with an exhaust path for discharging reaction products generated by the reaction between the halogen gas and the air to the outside of the apparatus.

[0010] Since air is supplied instead of the conventional nitrogen gas supply, the water component in the supplied air reacts with the halogen gas remaining in the vaporizer, making it possible to quickly reduce the concentration of the halogen gas, and ultimately making it possible to start maintenance of the ion source early.

[0011] In order to reliably prevent oxidation of the components, it is desirable to provide a measuring device for measuring the temperature of the plasma generating chamber.

[0012] In order to start maintenance of the ion source as soon as possible, it is desirable to provide a nitrogen supply path for supplying nitrogen to the plasma generating chamber.

[0013] Similarly, in order to start maintenance of the ion source quickly, it is desirable to provide a cooling path for cooling the plasma generating vessel.

[0014] Specific gas exhaust methods include: a plasma generating vessel in which plasma is generated; a vaporizer connected to the plasma generating vessel; a halogen gas supply channel for supplying halogen gas into the vaporizer; an air supply passage for supplying air to the interior of the vaporizer; an exhaust path for discharging reaction products generated by the reaction of the halogen gas with the air to the outside of the apparatus, Before maintenance of the ion beam irradiation device, an air supply process for supplying air from the air supply path and an exhaust process for exhausting the reaction products from the exhaust path are carried out at least once, and then the air supply process is carried out last to bring the inside of the device to atmospheric pressure. [Effects of the Invention]

[0015] Since air is supplied instead of the conventional nitrogen gas supply, the water component in the supplied air reacts with the halogen gas remaining in the vaporizer, making it possible to quickly reduce the concentration of the halogen gas, and ultimately making it possible to start maintenance of the ion source early. [Brief explanation of the drawings]

[0016] [Figure 1] Schematic cross-sectional view showing the ion source in operation [Figure 2] Schematic plan view of the ion beam irradiation device in the XY plane of FIG. [Figure 3] Air supply diagram [Figure 4]Exhaust diagram [Figure 5] Nitrogen supply diagram [Figure 6] Flowchart showing an example of a gas exhaust method [Figure 7] 10 is a flowchart showing another example of a gas exhaust method. [Figure 8] 10 is a flowchart showing another example of a gas exhaust method. [Figure 9] 10 is a flowchart showing another example of a gas exhaust method. [Figure 10] 10 is a flowchart showing another example of a gas exhaust method. DETAILED DESCRIPTION OF THE INVENTION

[0017] Figure 1 is a schematic cross-sectional view of an ion beam irradiation system IM showing the ion source IS in operation. The ion beam irradiation system IM is, for example, a system that irradiates an ion beam onto an object to introduce impurities into the object, or a system that modifies or cuts the surface of the object using ions contained in the ion beam. More specifically, this system includes an ion implantation system, an ion beam etching system, etc.

[0018] The ion source IS mainly includes a plasma generating vessel 2 in which plasma P is generated, a vaporizer S having one end connected to the plasma generating vessel 2, a halogen gas supply path 13 for supplying halogen gas to the vaporizer S from the other end side of the vaporizer S, and an extraction electrode E for extracting an ion beam IB from the plasma P in the plasma generating vessel 2.

[0019] Around the plasma generating vessel 2, there are arranged a cathode for generating plasma P inside, a filament for heating the cathode, a reflective electrode arranged opposite the cathode inside the plasma generating vessel 2 and reflecting electrons emitted from the cathode toward the cathode, an electromagnet for generating a magnetic field inside the plasma generating vessel 2 along the opposing direction of the cathode and reflective electrode, etc., but these components are not shown in the figure.

[0020] A block including the plasma generating vessel 2 and vaporizer S of the ion source IS is supported as an ion source head part by an ion source flange 1 via a structure not shown. The ion source flange 1 is fixed to a vacuum vessel C by fasteners such as bolts not shown. The ion source flange 1 is provided with a cooling path R for cooling the ion source head part. This cooling path R is a circulation path for a refrigerant and air.

[0021] The extraction electrode E consists of a suppression electrode 7 for preventing electrons from flowing into the plasma generating vessel 2 and a ground electrode 8 for fixing the ground potential. A DC power supply (not shown) with the plasma generating vessel 2 side positive is connected between the plasma generating vessel 2 and the suppression electrode 7, and a positively charged ion beam IB is extracted from the plasma P through the ion extraction port 6 of the plasma generating vessel 2 due to the potential difference between the components.

[0022] A first on-off valve 21 is provided in the Z direction, which is the ion beam extraction direction of the extraction electrode E. The first on-off valve 21 is an openable valve element that separates the spaces of the vacuum vessel C before and after the first on-off valve 21 in the Z direction, and is open (in an open state) while the ion source IS is in operation.

[0023] A vaporizer S is connected to the plasma generating vessel 2. The vaporizer S includes a crucible 3 in which a pellet, powder, or lump of metal material 4 is placed, a heater 5 that raises the temperature of the crucible 3, a shield 9 that blocks heat emission from the heater 5, and a thermocouple TC (temperature measuring device) that measures the temperature of the crucible 3. The vaporizer S also includes a halogen gas supply path 13 for supplying a halogen gas such as chlorine or fluorine to the crucible 3.

[0024] A halogen gas bottle 15 is attached to the halogen gas supply line 13 via a second on-off valve 14. When the ion source IS is operated, the second on-off valve 14 is in an open state, and when halogen gas is supplied from the halogen gas bottle 15 to the crucible 3, the halogen gas chemically reacts with the metal material 4. When the crucible 3 is heated by the heater 5 and the temperature of the crucible 3 rises, the reaction product of the halogen gas and the metal material 4 vaporizes and is supplied as vapor V from the crucible 3 to the plasma generating vessel 2. The vapor V then becomes plasma P in the plasma generating vessel 2 and is extracted as an ion beam IB.

[0025] An air supply line 16 is connected to the ion source flange 1. Air is supplied to the air supply line 16 from an air supply source 18 via a third on-off valve 17. The air supply source 18 may be a bottle filled with air, or may be an air supply line installed in a factory where the ion beam irradiation device IM is installed. The third on-off valve 17 is closed (in a closed state) while the ion source IS is in operation.

[0026] Fig. 2 is a schematic plan view of the ion beam irradiation device IM in Fig. 1 in the XY plane. An end of an ion source flange 1 is attached to a vacuum vessel C. An air supply line 16 is connected to the ion source flange 1, and a halogen gas supply line 13 is attached to the crucible 3 in Fig. 1 via the ion source flange 1. Vacuum seals (not shown), such as O-rings, are provided between the components so that the inside of the vacuum vessel C is sealed. It is also possible to prepare a flange for attaching the vaporizer S to the ion source flange 1, and have the crucible 3 supported by this flange, and also to connect the halogen gas supply path 13 to this flange.

[0027] During operation of the ion source IS, the inside of the vacuum vessel C is evacuated to maintain a constant degree of vacuum. This evacuation is performed via an exhaust path 11 connected to the vacuum vessel C. A fourth on-off valve 12 is attached to the exhaust path 11, and is kept open during operation of the ion source IS. In addition, a concentration measuring device D for measuring the halogen gas concentration is provided in the exhaust path 11. The exhaust path 11 is connected to a vacuum pump (not shown) or an exhaust line provided in a factory where the ion beam irradiation device IM is installed.

[0028] Before maintenance of the ion source IS is performed, the operation of the ion source IS is stopped and air is supplied into the apparatus. Figure 3 is an explanatory diagram of the air supply. When air is supplied to the vacuum vessel C, the first on-off valve 21, the second on-off valve 14, and the fourth on-off valve 12 are all closed, and only the third on-off valve 17 is open. The supplied air is supplied to each part in the flow indicated by the arrows in the figure, and is finally supplied to the inside of the vaporizer S (crucible 3).

[0029] When the operation of the ion source IS is stopped, the halogen gas supplied to the vaporizer S, plasma generating chamber 2, etc. remains inside the device. When air is supplied to each part, the residual gas reacts with the water component in the air, generating a reaction product (gas).

[0030] After a predetermined time has elapsed since the air supply, or after the pressure in the vacuum vessel C has reached a predetermined pressure, the gas in the vacuum vessel C is exhausted to the outside of the device. This state is illustrated in Figure 4. Note that the outside of the device refers to the outside of the ion beam irradiation device IM, and more specifically, the outside of the vacuum vessel C.

[0031] 4, the first on-off valve 21, the second on-off valve 14, and the third on-off valve 17 are in a closed state, and the fourth on-off valve 12 is in an open state. In this state, gas inside the vacuum vessel C is exhausted through the exhaust path 11. The arrows drawn inside the vacuum vessel C indicate the flow of the exhausted gas. At this time, the halogen gas concentration in the gas exhausted through the exhaust path 11 is measured by the concentration measuring device D.

[0032] As in conventional technology, when the pressure of the ion source IS is adjusted to atmospheric pressure by supplying nitrogen gas, it takes a long time to reduce the halogen gas concentration. However, by supplying air instead of nitrogen, the water component in the supplied air reacts with the residual halogen gas, allowing the halogen gas concentration in the device to be reduced quickly.

[0033] Finally, when the halogen gas concentration reaches a predetermined concentration or less, air is supplied again as described in Fig. 3 to restore atmospheric pressure inside the vacuum vessel C. This makes it possible to reduce the halogen gas concentration to a low concentration earlier than in the configuration of the prior art, and ultimately makes it possible to start maintenance of the ion source IS earlier.

[0034] If the amount of residual halogen gas is large and the halogen gas concentration cannot be sufficiently reduced by supplying air once, the step of supplying air (air supply step) described in FIG. 3 and the step of evacuating the reaction product (evacuation step) described in FIG. 4 may be repeated multiple times before the step of bringing the inside of the vacuum vessel C to atmospheric pressure in order to remove the ion source IS.

[0035] When supplying air, there is a concern that the oxygen contained in the air may oxidize the components of the ion source IS. During operation of the ion source IS, the plasma generating vessel 2 reaches a relatively high temperature compared to the other components of the ion source IS. Metal components (high-melting-point metals such as tungsten and molybdenum) such as the cathode and repeller attached to the periphery of the plasma generating vessel 2 react with oxygen at high temperatures. If these components are oxidized, it will interfere with the operation of the ion source IS. Therefore, it is desirable to start supplying air a predetermined time after the operation of the ion source IS is stopped. The predetermined time here is the time derived from past experience and is the time required for the temperature of the plasma generating vessel 2 to drop below a predetermined temperature.

[0036] Instead of waiting for a predetermined time to elapse, the temperature of the plasma generating chamber 2 may be measured, and air supply may be started according to the measured value. The temperature of the plasma generating vessel 2 may be measured directly by attaching a thermocouple to the plasma generating vessel 2. Also, instead of the thermocouple, a radiation thermometer or a thermograph may be used for temperature measurement. Furthermore, the temperature of the vaporizer S connected to the plasma generating vessel 2 may be measured using a thermocouple TC, and the temperature of the plasma generating vessel 2 may be indirectly derived by taking into account the correlation between the temperatures of the vaporizer S and the plasma generating vessel 2.

[0037] The temperature of the plasma generating vessel 2 may be lowered by natural cooling, but it is preferable to use a refrigerant to reduce the cooling time. For example, as in the embodiment shown in Figures 1 to 4, if a cooling path R is formed in the ion source flange 1 and a refrigerant or air is circulated through the cooling path R, the plasma generating vessel 2 supported by the ion source flange 1 can be cooled.

[0038] 5 may be adopted for cooling the plasma generating vessel 2. The embodiment of FIG. 5 differs from the other embodiments in that nitrogen gas is supplied into the vacuum vessel C. One end of the nitrogen supply line 23 is connected to the ion source flange 1, and the other end of the nitrogen supply line 23 is connected to a nitrogen supply bottle 24 via a fifth on-off valve 22. In this embodiment, prior to supplying air into the vacuum vessel C, nitrogen is introduced from the nitrogen supply line 23 to cool the plasma generating vessel 2. By carrying out the step of cooling the plasma generating vessel 2 by supplying nitrogen (nitrogen supply step) before the start of the air supply step, it is possible to further shorten the waiting time until air is supplied.

[0039] After the nitrogen supply, before the air supply is started, the nitrogen inside the apparatus is exhausted to the outside of the apparatus through the exhaust path 11. This supply and exhaust of nitrogen may be carried out multiple times to lower the temperature of the plasma generating vessel 2.

[0040] 5, the nitrogen supply path 23 and the air supply path 16 are individually connected to the ion source flange 1, but the supply paths connected to the ion source flange 1 may be partially shared. In this case, the supply paths branch off from the common supply path midway.

[0041] During maintenance work on the ion source IS, if the temperature of the vaporizer S is high and it takes time to remove the vaporizer S, air from the air supply path 16 or nitrogen from the nitrogen supply path 23 may be blown onto the vaporizer S. Furthermore, in addition to the air supply path 16 and the nitrogen supply path 23 shown in the figure, a gas supply path for cooling the vaporizer S may be provided.

[0042] The method for exhausting the residual halogen gas described above will be described in detail with reference to FIGS.

[0043] 6 is a flowchart of one embodiment of a gas exhaust method. In step S1, the operation of the ion source IS is stopped. At this time, the voltage application to the extraction electrode E, the voltage application to the plasma generating chamber 2, the current supply to the heater 5 of the vaporizer S, and the supply of halogen gas to the vaporizer S are stopped. Meanwhile, the circulation of the refrigerant and air in the cooling path R of the ion source flange 1 continues. Furthermore, with the operation of the ion source IS stopped, the first on-off valve 21, the second on-off valve 14, and the fourth on-off valve 12 are closed.

[0044] After that, in step S2, the time elapsed since the operation of the ion source IS was stopped is counted, and the next step is put on hold until a predetermined time (for example, several tens of minutes) has elapsed. As time passes, when the temperature of the plasma generating chamber 2 drops below a predetermined temperature, in step S3, the third on-off valve 17 is opened and air is supplied.

[0045] Air is supplied in step S3, and after a predetermined time has elapsed or after the inside of the device reaches a predetermined pressure, the inside of the device is evacuated in step S4. This exhaust causes gas, which is a reaction product of moisture in the air and halogen gas remaining in the device, to be discharged to the outside of the device.

[0046] Depending on the volume of the apparatus, if it is difficult to reduce the concentration of halogen gas remaining in the apparatus to a predetermined concentration or less by a single evacuation, the supply of air in process S3 and the evacuation in process S4 may be repeated. In step S5, the number of repetitions is set in advance, and it is determined whether the air supply in step S3 and the exhaust in step S4 have been performed a predetermined number of times.

[0047] In process S5, it is determined that the air supply in process S3 and the exhaust in process S4 have been performed a predetermined number of times, and then finally, in process S6, air is supplied to make the inside of the device atmospheric pressure. By using such a gas exhaust method, the concentration of the remaining halogen gas can be reduced early, which in turn makes it possible to start maintenance work on the ion source IS early.

[0048] In the embodiment of Fig. 6, the number of times to supply air in process S3 and exhaust in process S4 is determined in process S5, but the concentration of halogen gas exhausted through exhaust path 11 may be actually measured, and whether this is a reference concentration may be determined to determine the number of times to supply air in process S3 and exhaust in process S4. In the embodiment of Fig. 7, process S7, which is a process of comparing the halogen gas concentration with the reference concentration, is added instead of process S5 of Fig. 6.

[0049] In the embodiment of FIG. 6, after the ion source is stopped, the process waits for a predetermined time until the temperature of the plasma generating vessel 2 drops in step S2. However, as in the embodiment of FIG. 8, the process may be replaced with step S8 in which the temperature of the plasma generating vessel 2 is actually measured and compared with a reference value.

[0050] Also, a configuration may be adopted in which a rare gas is supplied after the operation of the ion source IS is stopped in step S1 in order to effectively reduce the temperature of the plasma generating chamber 2. Specifically, as shown in Fig. 9, after the operation of the ion source IS is stopped in step S1, and before step S3 in which air is supplied, step S9 in which a rare gas such as nitrogen gas or argon gas is supplied, step S10 in which the rare gas is exhausted from the inside of the apparatus after the rare gas is supplied, and step S11 in which it is determined whether these steps have been performed a predetermined number of times are performed.

[0051] Furthermore, instead of the process S11 in which the supply and exhaust of the rare gas are carried out a predetermined number of times as in the embodiment of FIG. 10, after the supply of the rare gas in the process S9 and the exhaust of the inside of the apparatus in the process S10, the temperature of the plasma generating vessel 2 may be measured directly or indirectly, and the measured temperature may be compared with a reference temperature in the process S12.

[0052] Furthermore, in the embodiment of Figures 8 to 10, the processing after air supply is the same as that in the embodiment of Figure 6, but this processing may be the same as that in the embodiment of Figure 7.

[0053] In the embodiment of FIGS. 1 to 5, the exhaust path 11 is described as one that exhausts the inside of the apparatus while the ion source IS is in operation. However, the exhaust path 11 for exhausting the reaction products of the air and the halogen gas does not necessarily have to have such a function. A separate exhaust path may be provided and used to exhaust the inside of the apparatus while the ion source IS is in operation.

[0054] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0055] 2. Plasma generating vessel 3 Crucible 11 Exhaust duct 13 Halogen gas supply line 16 Air supply line R cooling path S vaporizer C Vacuum container TC measuring instrument IB ion beam IS ion source IM Ion Beam Irradiation Equipment

Claims

1. a plasma generating vessel in which plasma is generated; a vaporizer connected to the plasma generating vessel; a halogen gas supply path for supplying a halogen gas to the vaporizer; an air supply passage for supplying air to the vaporizer; an exhaust path for discharging reaction products produced by the reaction between the halogen gas and the air to the outside of the ion beam irradiation device;

2. 2. The ion beam irradiation apparatus according to claim 1, further comprising a measuring device for measuring the temperature of the plasma generating chamber.

3. 2. The ion beam irradiation apparatus according to claim 1, further comprising a nitrogen supply passage for supplying nitrogen to said plasma generating chamber.

4. 2. The ion beam irradiation apparatus according to claim 1, further comprising a cooling path for cooling said plasma generating vessel.

5. a plasma generating vessel in which plasma is generated; a vaporizer connected to the plasma generating vessel; a halogen gas supply channel for supplying halogen gas into the vaporizer; an air supply passage for supplying air to the interior of the vaporizer; an exhaust path for discharging reaction products generated by the reaction of the halogen gas with the air to the outside of the apparatus, A gas exhaust method in which, before maintenance of the ion beam irradiation device, an air supply process for supplying air from the air supply path and an exhaust process for exhausting the reaction products from the exhaust path are performed one or more times, and then the air supply process is performed last to make the inside of the device atmospheric pressure.

Images