Ion source

Abstract

It prevents nozzle clogging and improves the lifespan of the vaporizer. [Solution] The ion sources IS1, IS2, and IS3 are equipped with vaporizers C1, C2, and C3 that supply gas generated in crucibles 2 and 32 to the plasma generation chamber 14 via nozzles 3 connected to hollow crucibles 2 and 32 that are elongated in one direction, and extract an ion beam IB containing aluminum ions from the plasma generation chamber 14. The ion sources IS1, IS2, and IS3 are also equipped with a control device C that controls the set temperature of vaporizers C1, C2, and C3 according to the temperature of the plasma generation chamber 14 or the value of a parameter correlated with the temperature of the plasma generation chamber 14, so that the temperature of the connection part P2 between the crucibles C1, C2, and C3 and the nozzle 3 is higher than the temperature of the central part P1 of the crucibles 2 and 32 in the longitudinal direction of the crucibles 2 and 32.

Description

Technical Field

[0001] Relates to an ion source having a vaporizer.

Background Art

[0002] Silicon carbide (SiC) devices are expected to be used in high-voltage and high-temperature applications such as electric vehicles, railways, and power plants. The manufacturing process of SiC devices uses an ion implantation process, similar to that of conventional silicon devices.

[0003] In the ion implantation process of SiC devices, when fabricating a PN junction, nitrogen ions or phosphorus ions are implanted as N-type dopants, and aluminum ions or boron ions are implanted as P-type dopants into a SiC wafer.

[0004] In the generation of nitrogen ions, phosphorus ions, and boron ions, generally, plasma is generated using a gas as a raw material. On the other hand, there is no optimal gas as a raw material for the generation of aluminum ions.

[0005] To generate a plasma containing aluminum ions, sputtering of an aluminum-containing solid material (aluminum nitride, alumina, etc.) has been used. Also, the method using a vaporizer described in Patent Document 1 has been used. Specifically, an aluminum-containing solid material (aluminum chloride) is placed in a crucible, and the crucible is heated to generate an aluminum-containing gas from the solid material. Based on the generated gas, a plasma containing aluminum ions is generated.

[0006] In recent years, new vaporizers described in Patent Document 2 and Patent Document 3 have been proposed. In the vaporizers disclosed in these documents, a reactive gas (such as chlorine gas or hydrogen chloride gas) is supplied to a crucible. A solid material (such as pure aluminum, aluminum nitride, or alumina) is placed in the crucible. Inside the crucible, the reactive gas reacts with the solid material to produce a reaction product (aluminum chloride) on the solid material. The generated reaction product is vaporized when the crucible is heated to a high temperature and supplied to the plasma generation chamber. In the plasma generation chamber, a plasma containing aluminum ions is generated from the supplied gas. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2004-359985 [Patent Document 2] Japanese Patent Publication No. 2023-154377 [Patent Document 3] Japanese Patent Publication No. 2023-172015 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the vaporizer-based methods described in Patent Documents 2 and 3, increasing the crucible temperature is desirable to improve the efficiency of aluminum ion generation. When the crucible temperature is increased, the amount of chlorine radicals generated due to the chlorine component in the reactive gas increases. Chlorine radicals readily combine with aluminum. As a result, the amount of AlCl generated increases.

[0009] To increase the volume of solid material when operating a vaporizer for extended periods, long, cylindrical crucibles are used. In such crucibles, a temperature distribution exists along the length of the crucible. The trend in temperature distribution is that the temperature is higher in the center of the crucible where the heater is located, and lower at the ends of the crucible compared to the center.

[0010] AlCl, which is generated in the relatively high-temperature central part of the crucible, reaches the relatively low-temperature ends of the crucible via a gas flow of reactive gas supplied into the crucible along its longitudinal direction, and is separated into Al and Cl due to the temperature difference.

[0011] The nozzle, fixed to the end of the crucible, is made of carbon material for its heat resistance. When AlCl is separated, Cl is released as a gas. Meanwhile, the separated Al remains in an active state at the crucible end and reacts with the crucible and nozzle made of carbon material to produce Al4C3.

[0012] In a high-temperature crucible, aluminum is liquefied. The addition of Al4C3 improves the wettability of the liquefied aluminum. As wettability improves, the molten aluminum can rise to the nozzle. Since the temperature near the nozzle, which is the connection point between the crucible and the nozzle, is lower than in the center of the crucible, there is a concern that the molten aluminum may precipitate in this area, causing the nozzle to clog.

[0013] Regarding the nozzle clogging problem described above, it is a concern that, not only in the vaporizers described in Patent Documents 2 and 3, but also in the vaporizer described in Patent Document 1, the wettability of aluminum improves, and the molten liquefied aluminum enters the nozzle, causing it to clog. The primary objective of this invention is to suppress nozzle clogging and improve the lifespan of the vaporizer. [Means for solving the problem]

[0014] An ion source comprising a vaporizer that supplies gas generated in a crucible to a plasma generation chamber via a nozzle connected to a hollow crucible that is elongated in one direction, and which extracts an ion beam containing aluminum ions from the plasma generation chamber, A control device is provided that controls the set temperature of the vaporizer according to the temperature of the plasma generation chamber or the value of a parameter that has a correlation with the temperature of the plasma generation chamber, such that the temperature of the connection portion between the crucible and the nozzle becomes higher than the temperature of the central portion of the crucible in the longitudinal direction of the crucible.

Advantages of the Invention

[0015] Since the temperature of the connection portion between the crucible and the nozzle is made higher than the temperature of the central portion of the crucible, clogging of the nozzle is suppressed, and the life of the vaporizer can be improved.

Brief Description of the Drawings

[0016] [Figure 1] Schematic cross-sectional view of an ion source [Figure 2] Schematic cross-sectional view of another ion source [Figure 3] Simplified configuration diagram of the ion source described in FIGS. 1 and 2 [Figure 4] Flowchart showing an example of temperature control of the vaporizer [Figure 5] Flowchart showing another example of temperature control of the vaporizer [Figure 6] Schematic cross-sectional view of another ion source [Figure 7] Flowchart showing another example of temperature control of the vaporizer

Embodiments for Carrying Out the Invention

[0017] FIG. 1 is a schematic cross-sectional view of an ion source IS1. The ion source IS1 is an indirectly heated cathode (IHC) ion source. In this ion source IS1, a filament 16 heats a cathode 15. Since the heated cathode 15 emits ionizing electrons (thermoelectrons) inside the plasma generation chamber 14, the cathode 15 is also called a thermoelectron emission member. A reflecting electrode 17 is arranged facing the cathode 15. The reflecting electrode 17 repels the ionizing electrons (thermoelectrons) approaching the reflecting electrode 17 back toward the cathode 15 side. An electromagnet (not shown) is positioned outside the plasma generation chamber 14. This electromagnet generates a magnetic field inside the plasma generation chamber 14 along the direction in which the cathode 15 and the reflecting electrode 17 face each other.

[0018] A gas containing aluminum is supplied to the plasma generation chamber 14 from the vaporizer C1. In the plasma generation chamber 14, a plasma, as shown by the dashed line, is generated based on the aluminum-containing gas. The ion beam IB, which contains aluminum ions, is extracted from the ion extraction port 23 of the plasma generation chamber 14 by the extraction electrode E.

[0019] Figure 1 illustrates two extraction electrodes E having a passage for the ion beam IB. However, the number of extraction electrodes E shown in Figure 1 is illustrative. The number of electrodes constituting the extraction electrodes E may be three or more, and may be changed depending on the configuration of the ion source.

[0020] The vaporizer C1 includes a crucible 2 in which an aluminum-containing solid material 7 (for example, a solid material such as pure aluminum, aluminum nitride, or aluminum oxide, including powdered material) is placed.

[0021] The crucible 2 illustrated in Figure 1 is a hollow member that is elongated in one direction. For example, the axis of the crucible 2 extends along the Z-axis direction in Figure 1. An outlet 2b for supplying aluminum-containing gas to the plasma generation chamber 14 is provided at one end of the crucible 2 in the longitudinal direction. A gas inlet 2a for introducing a reactive gas, a chlorine-containing gas, into the crucible 2 is provided at the other end of the crucible 2 in the longitudinal direction. The chlorine-containing gas is a gas containing chlorine components, such as chlorine gas (Cl2) or hydrogen chloride gas (HCl).

[0022] A first nozzle 3 is detachably attached to the crucible 2. In the configuration example shown in Figure 1, a second nozzle 4 for supplying reactive gas to the crucible 2 is integrally formed with the crucible 2. Various methods (e.g., fitting and / or screwing) can be used to attach the first nozzle 3 to the crucible 2. The first nozzle 3, the second nozzle 4, and the crucible 2 are made of carbon-containing materials (C, SiC, carbon fiber, etc.) for heat resistance.

[0023] In Figure 1, arrow J indicates the flow of chlorine-containing gas supplied to crucible 2. The chlorine-containing gas flows from the gas supply source 11 through valve 12, then sequentially through the second nozzle 4, crucible 2, and first nozzle 3 into the plasma generation chamber 14. When chlorine-containing gas flows into crucible 2, it reacts with the aluminum-containing solid material 7, which has been heated to a high temperature. This reaction produces reaction products such as aluminum chloride (AlCl3). The generated reaction products are vaporized inside the high-temperature crucible 2, producing an aluminum-containing gas containing aluminum particles. The aluminum-containing gas and chlorine-containing gas are supplied from crucible 2 to the plasma generation chamber 14 via the first nozzle 3.

[0024] In some embodiments, the aluminum-containing solid material 7 is pure aluminum with a purity of 99.90% or higher. Pure aluminum increases the proportion of aluminum in the aluminum-containing gas compared to other materials. By using pure aluminum, the ion beam current of the ion beam IB containing aluminum ions extracted from the ion source IS increases. However, the aluminum-containing solid material 7 is not limited to pure aluminum. In some embodiments, aluminum nitride, aluminum oxide, and / or other aluminum-containing solid materials may be used.

[0025] The supply of chlorine-containing gas to the second nozzle 4 may be performed via a connecting member 9 fitted inside the second nozzle 4. Alternatively, a mass flow controller may be connected to the piping 13 connecting the gas supply source 11 and the connecting member 9 to control the flow rate of the chlorine-containing gas. However, the specific configuration for gas supply is not particularly limited, as long as it can supply chlorine-containing gas to the connecting member 9.

[0026] The end 3a of the first nozzle 3, opposite to the end attached to the crucible 2, protrudes into the plasma generation chamber 14. The end 3a is provided with four orthogonal holes for supplying gas. This configuration makes it possible to diffusely supply aluminum-containing gas in multiple directions within the plasma generation chamber 14. However, the number of gas supply holes formed in the end 3a is not limited to four. There may be fewer than four or more than four.

[0027] A heater 5 is positioned around the outer periphery of the crucible 2. The heater 5 is, for example, a coil heater or a sheet heater. However, various other heaters may be used. A first heat shield 6a is positioned around the outer periphery of the heater 5 to block heat radiation from the heater 5. A second heat shield 6b is positioned between the plasma generation chamber 14 and the first nozzle 3 to suppress excessive heat transfer from the plasma generation chamber 14 to the crucible 2.

[0028] A flange 8 is provided to attach the vaporizer C1 to the ion source flange 18. In Figure 1, the ion source flange 18 indirectly supports the plasma generation chamber 14 and other components such as the filaments 16 and cathode 15 surrounding the plasma generation chamber 14 by supporting components not shown.

[0029] The second nozzle 4 has a large-diameter portion 4a. A coil spring 10 is provided between the flange 8 and the large-diameter portion 4a of the second nozzle 4. The coil spring 10 biases the vaporizer C1 against the side wall of the plasma generation chamber 14 in order to maintain airtightness between the first nozzle 3 and the plasma generation chamber 14 and to prevent the outflow of aluminum-containing gas and / or chlorine-containing gas from between the components. Furthermore, the elastic member that biases the vaporizer C1 against the side wall of the plasma generation chamber 14 is not limited to the coil spring 10; other alternative means such as a leaf spring may also be used.

[0030] To maintain airtightness between the first nozzle 3 and the plasma generation chamber 14, one or more gaskets (not shown) may be provided between the vaporizer C1 and the side wall of the plasma generation chamber 14. Furthermore, a damper (e.g., a spring clip) may be attached to the first nozzle 3 to avoid excessive pressure due to the elastic force of the coil spring 10. Similarly, a damper (e.g., a spring clip) may be provided between the large-diameter portion 4a of the second nozzle 4 and the inner wall of the first heat shield 6a to prevent excessive pressure due to the elastic force of the coil spring 10.

[0031] If the crucible 2 is cylindrical, the cross-section of the aluminum-containing solid material 7 in the XY plane is semicircular. Furthermore, the height of the aluminum-containing solid material 7 is such that it does not block the gas inlet 2a and outlet 2b. With such an aluminum-containing solid material 7, the chlorine-containing gas flows along the surface of the aluminum-containing solid material 7, allowing for an efficient reaction between the chlorine-containing gas and the solid material 7.

[0032] In the fabrication of PN junctions in SiC devices, ionic species other than aluminum ions are also used. For the generation of these other ionic species, gases such as PH3, PF3, BF3, and N2 are supplied to the plasma generation chamber 14. The supply path for these gases used to generate ionic species other than aluminum ions may be shared with the flow path for chlorine-containing gas. However, since mixing with residual gas may cause unexpected problems such as discharge, a separate gas supply path may be provided for generating ion species other than aluminum ions, separate from the chlorine-containing gas flow path. In Figure 1, a gas inlet 22 for supplying gas to generate ion species other than aluminum ions is provided on the wall of the plasma generation chamber 14 on the X-axis side.

[0033] In the embodiment shown in Figure 1, an IHC ion source is exemplified as the configuration of the ion source IS, but other configurations such as a Vernus type or high-frequency type may also be used.

[0034] Instead of having the end portion 3a of the first nozzle 3 protrude into the plasma generation chamber 14, the tip of the end portion 3a provided on the first nozzle 3 may be made flush with the wall of the plasma generation chamber 14. In this case, the number of gas supply holes formed at the end 3a of the first nozzle 3 is one in the Z-axis direction.

[0035] In crucible 2, which is heated to a high temperature, a large amount of chlorine radicals are generated from the chlorine-containing gas. These chlorine radicals readily combine with aluminum to form AlCl. AlCl, generated in the relatively high-temperature central part of crucible 2 (indicated by the dashed line P1 in Figure 1), reaches the relatively low-temperature end of crucible 2 (the connection point between the first nozzle 3 and crucible 2, indicated by the dashed line P2 in Figure 1) due to the gas flow of reactive gas supplied to crucible 2 along its longitudinal direction. There, due to the temperature difference, it is separated into Al and Cl.

[0036] When AlCl is separated, Cl is released as a gas. Meanwhile, the separated Al remains in an active state at the end of crucible 2 and reacts with the carbon components of crucible 2 and the first nozzle 3 to produce Al4C3.

[0037] In crucible 2, which is heated to a high temperature, the aluminum is liquefied. When Al4C3 is mixed in, the wettability of the liquefied aluminum is improved. The aluminum with improved wettability travels through the crucible and reaches the vicinity of the first nozzle 3. Since the temperature near the first nozzle 3, which is the connection point P2 between the crucible 2 and the first nozzle 3, is lower than the central part P1 of the crucible 2, there is a concern that molten aluminum may precipitate in this area, causing clogging of the first nozzle 3.

[0038] To address this clogging, the temperature at the crucible end, which is the connection point P2 between the first nozzle 3 and the crucible 2, is set higher than the temperature at the central part P1 in the longitudinal direction (Z-axis direction) of the crucible 2. During operation of the ion source IS1, the formation of Al4C3 can be suppressed by maintaining the above-described temperature relationship between the central part P1 and the connection part P2 of the crucible 2. As a result, the wettability of the liquefied aluminum in the crucible 2 does not improve, making it difficult for the liquefied aluminum to reach the vicinity of the first nozzle 3, and thus improving the lifespan of the vaporizer C1.

[0039] To raise the temperature of the connection point P2 above the temperature of the central part P1 of the crucible 2, the ion source IS1 is equipped with a control device C. The control device C includes an arithmetic processing unit and a memory unit. The arithmetic processing unit is a microprocessor, a central processing unit, a microcontroller, or hardware control logic, or a combination thereof. The arithmetic processing unit may also be provided as multiple arithmetic processing units. The memory unit can store program code for realizing various functions, such as a storage function for storing data, an arithmetic function for processing data, a control function for controlling each part of the ion source IS1 based on the calculation results, and a control function for controlling each part of the ion source IS1 based on input data, as well as reference values ​​used in the comparison processing described later. The arithmetic processing unit of the control device C accesses the program code and reference values ​​stored in the memory unit of the control device C and executes each function.

[0040] During operation of the ion source IS1, the temperature of the plasma generation chamber 14, or a parameter correlated with the temperature of the plasma generation chamber 14, is input to the control device C. The control device C compares the reference value stored in the memory unit with the input data and changes the set temperature of the vaporizer C1 according to the comparison result. The set temperature of the vaporizer C1 is determined by the output of the heater 5 of the crucible 2.

[0041] The temperature of the plasma generation chamber 14 changes depending on the operating conditions of the ion source IS1. For example, when the beam current of the ion beam IB drawn from the ion source IS1 is high, the temperature of the plasma generation chamber 14 becomes relatively high. Conversely, when the beam current of the ion beam IB drawn from the ion source IS1 is low, the temperature of the plasma generation chamber 14 becomes relatively low.

[0042] Since the first nozzle 3 is located near the plasma generation chamber 14, it is affected by temperature changes in the plasma generation chamber 14. Specifically, when the set temperature of the vaporizer C1 is constant, the temperature of the connection part P2 changes via the first nozzle 3 as the temperature of the plasma generation chamber 14 changes. On the other hand, the central part P1 of the crucible 2 is spaced apart from the connection part P2, and the central part P1 of the crucible 2 is hardly affected by the temperature change of the plasma generation chamber 14. Therefore, the temperature of the central part P1 of the crucible 2 is determined taking into consideration its relationship with the set temperature of the vaporizer C1.

[0043] When the temperature of the plasma generation chamber 14 is relatively high, the temperature of the first nozzle 3 also becomes relatively high, and the temperature of the connection part P2 becomes higher than the central part P1 of the crucible 2. In this temperature relationship, the wettability of the liquefied aluminum inside the crucible 2 is not improved, making it difficult for it to penetrate the first nozzle 3. On the other hand, when the temperature of the plasma generation chamber 14 is relatively low, the temperature of the first nozzle 3 is also relatively low, and the temperature of the connection part P2 is lower than that of the central part P1 of the crucible 2. In this temperature relationship, the wettability of the liquefied aluminum improves, which could cause clogging of the first nozzle 3.

[0044] Therefore, in order to suppress the improvement in the wettability of the liquefied aluminum, the control device C sets the output of the heater 5 to a lower level so that the temperature of the connection part P2 is higher than the central part P1 of the crucible 2. As a result, it becomes difficult for the liquefied aluminum to reach the vicinity of the first nozzle 3, and the lifespan of the vaporizer C1 is improved. Furthermore, when the control device C described here sets the output of the heater 5 to a low level, it means that the output is reduced compared to the output of the heater 5 that is set when the temperature of the plasma generation chamber 14 is relatively high.

[0045] Figure 2 is a schematic cross-sectional view of another ion source, IS2. The same reference numerals are used for the same components as in ion source IS1 in Figure 1. In ion source IS2, the crucible 32 and the aluminum-containing material 24 differ from the configuration of ion source IS1. Crucible 32 does not have the gas inlet 2a that crucible 2 had. The aluminum-containing material 24 contains solid materials such as aluminum chloride and pure aluminum, as well as liquid materials such as aluminum iodide and dimethylaluminum chloride.

[0046] In the ion source IS2 shown in Figure 2, the aluminum-containing material 24 is vaporized by heating the crucible 32 with the heater 5, and the aluminum-containing gas is supplied to the plasma generation chamber 14. Even with an ion source IS2 equipped with such a vaporizer C2, there is a concern that clogging of the first nozzle 3 may occur due to improved wettability of the liquefied aluminum, similar to the ion source IS1.

[0047] Therefore, similar to the ion source IS1, the ion source IS2 is equipped with a control device C that controls the set temperature of the crucible 32 according to the temperature of the plasma generation chamber 14, or a parameter correlated with the temperature of the plasma generation chamber 14. By incorporating such a control device C, it becomes possible to suppress clogging of the first nozzle 3 due to the improvement in the wettability of the liquefied aluminum.

[0048] Figure 3 is a simplified diagram of the ion source configuration, showing the configurations of ion source IS1 described in Figure 1 and ion source IS2 described in Figure 2. In Figure 3, some components of the crucible 32, such as the gas inlet 2a and the reflecting electrode 17, are not shown. During operation of the ion source, the temperature of the plasma generation chamber 14 is measured by a thermometer T. The measurement results are transmitted to the control device C. This thermometer T may be, for example, a contact thermocouple, a non-contact thermograph, or a radiation thermometer. As described in the embodiment of the ion source IS1, the control device C compares the temperature of the plasma generation chamber 14 with a reference value stored in the memory unit. Subsequently, the control device C controls the output of the heater 5 according to the comparison result.

[0049] The data transmitted to the control device C may include parameters correlated with the temperature of the plasma generation chamber 14, in addition to the temperature of the plasma generation chamber 14. The control device C compares the value of the parameter with a reference value stored in the memory unit and controls the output of the heater 5. An example of a parameter correlated with the temperature of the plasma generation chamber 14 is the density of the plasma generated in the plasma generation chamber 14. A higher plasma density results in a higher temperature in the plasma generation chamber 14. Conversely, a lower plasma density results in a lower temperature in the plasma generation chamber 14. To measure the plasma density, a probe for measuring plasma density is installed inside the plasma generation chamber 14. Alternatively, a measuring instrument for measuring electromagnetic waves emitted from the generated plasma may be placed near the plasma generation chamber 14.

[0050] Various power sources are provided around the plasma generation chamber 14. A filament power supply Vf is connected between the terminals of the filament 16. A cathode power supply Vc is connected between the filament 16 and the cathode 15. An arc power supply Va is connected between the plasma generation chamber 14 and the cathode 15. Of these power sources, the value of the arc current flowing through the arc power source Va is correlated with the plasma density generated in the plasma generation chamber 14, and therefore also correlated with the temperature of the plasma generation chamber 14.

[0051] The arc current may be measured by an ammeter 25 and transmitted to the control device C, which may then control the output of the heater 5. Alternatively, the control device C may control the output of the heater 5 according to the power value, which is the product of the arc current and the arc voltage. In the case of a Vernus-type ion source configuration, there is no cathode 15, and thermionic electrons are directly emitted from the filament 16 into the plasma generation chamber 14. In this case, the filament 16 becomes a thermionic electron emitting member that supplies thermionic electrons to the plasma generation chamber 14.

[0052] In the longitudinal direction of crucibles 2 and 32, if the length of the first nozzle 3 is sufficiently longer than the length of crucibles 2 and 32, there is a concern that the central part of the first nozzle 3 will become cold, causing the gas passing through it to precipitate. Furthermore, the sufficiently long first nozzle 3 excessively obstructs heat transfer from the plasma generation chamber 14 to the crucibles 2 and 32. There is concern that the temperature of the connection point P2 will drop despite the plasma generation chamber 14 being at a relatively high temperature.

[0053] Taking the above concerns into consideration, the relationship between crucibles 2 and 32 is set such that the length L1 of crucibles 2 and 32 in the longitudinal direction is at least twice the length L2 of the first nozzle 3.

[0054] Figures 4 and 5 are flowcharts related to the temperature control of vaporizers C1 and C2, as described above. The same symbols are used for processes common to both figures. The ion source is started (S1). At this time, the operating parameters of each part of the ion source IS1 and IS2, including the output of the heater 5, are set to initial values ​​(initial settings) determined for each operating condition of the ion source. In the flowchart of Figure 4, during the operation of ion sources IS1 and IS2, the temperature of the plasma generation chamber 14 is monitored and compared with a reference temperature A (reference value) stored in the memory of the control device C (S2). Based on the comparison results, if the temperature of the plasma generation chamber 14 is below the reference temperature A, the output of the heater 5 is reduced from the initial setting value to lower the set temperatures of the vaporizers C1 and C2 (S3). On the other hand, if the temperature of the plasma generation chamber 14 exceeds the reference temperature A, the output of the heater 5 is not changed from the initial setting value, and the set temperatures of the vaporizers C1 and C2 are maintained (S4).

[0055] In the flowchart of Figure 5, during the operation of ion sources IS1 and IS2, the arc current is monitored and compared with the reference current B (reference value) stored in the memory of the control device C (S5). The same process as in the flowchart of Figure 4 is performed, except that the comparison target in the control device C is different.

[0056] In the flowcharts in Figures 4 and 5, after the operation of ion sources IS1 and IS2 has started and stabilized, each parameter is measured, and a comparison process is performed by control device C. However, unlike the flowcharts in Figures 4 and 5, before starting operation of ion sources IS1 and IS2, the values ​​of the target parameters (temperature of the plasma generation chamber 14, arc current, or plasma density, etc.) may be inferred from the operating conditions set at the start of operation, and the comparison and judgment process in each flowchart may be performed. Then, when starting operation of ion sources IS1 and IS2, vaporizers C1 and C2 are operated at an appropriate set temperature. This series of processes is performed by the control device C.

[0057] For example, the control device C stores the relationship between the operating conditions and target parameters during ion source operation in its memory. After the operating conditions are determined, the data is read from the memory, and vaporizers C1 and C2 are operated at the appropriate set temperature. Concerns include the possibility of differences in the values ​​of target parameters occurring over time after the ion source has been in operation, even when the ion source is operated under the same operating conditions, and that the target parameters may fluctuate during the operation of the ion source. To address these concerns, the control device C may control the set temperatures of vaporizers C1 and C2 both before and after the ion source starts operation.

[0058] Figure 6 is a schematic cross-sectional view of another ion source, IS3. The difference from ion source IS1 in Figure 1 lies in the method of generating an aluminum-containing gas from an aluminum-containing solid material 7. In the vaporizer C3 of the ion source IS3, the heat generated when the reactive gas (chlorine-containing gas) introduced into the crucible 2 reacts with the aluminum-containing solid material 7 is used to vaporize the reaction product, aluminum chloride. Furthermore, in order to promote the reaction between the reactive gas and the solid material 7, a heater 5 may be provided and used, similar to the vaporizers C1 and C2.

[0059] The temperature setting in the vaporizer C3 is changed by cooling the crucible 2 with a cooling member R. The cooling member R is a straight cylindrical member and is positioned around the crucible 2 in a state of non-contact with the crucible 2. The cooling member R covers the outer circumference of the crucible 2, specifically the area corresponding to the central part P1 of the crucible 2. Specific examples of the cooling element R include conventionally known cooling methods such as water-cooled and air-cooled chillers.

[0060] Figure 7 is a flowchart related to the control of the set temperature in vaporizer C3. The same symbols are used for processes common to Figures 4 and 5. The ion source is started (S1). At this time, the operating parameters of each part of the ion source IS3, including the output of the heater 5, are set to initial values ​​determined for each operating condition.

[0061] The flowchart in Figure 7 assumes that the cooling element R is disabled during the initial operation of the ion source IS3. Furthermore, the flow rate of the reactive gas remains constant during the operation of the ion source IS3. During operation of the ion source IS3, the arc current value is monitored and compared with the reference current B (reference value) stored in the memory of the control device C (S5). Based on the comparison results, if the arc current value is less than or equal to the reference current B (reference value), the cooling element R is activated and the set temperature of the vaporizer C3 is lowered (S6). On the other hand, if the arc current value exceeds the reference current B, the function of the cooling element R is kept stopped and the set temperature of the vaporizer C3 is maintained (S7).

[0062] The flowchart in Figure 7 illustrates the processes performed after the ion source IS3 starts operation. However, as explained in the flowchart embodiments in Figures 4 and 5, the control device C may also control the set temperature of the vaporizer C3 before the ion source IS3 starts operation, or before and after the ion source IS3 starts operation.

[0063] The flowcharts in Figures 4, 5, and 7 show a configuration in which one reference value is compared with a measured value, but it is also possible to compare multiple reference values ​​with measured values. For example, multiple reference values ​​may be set in stages, and the output of the heater 5 may be changed in stages according to the number of reference values. Alternatively, the control device C may control the set temperatures of vaporizers C1, C2, and C3 by comparing multiple parameters with reference values. Specifically, the temperature of the plasma generation chamber 14 and the arc current are compared with their respective reference values, and if the results of both comparisons fall below the reference values, the output of the heater 5 is reduced by a predetermined amount. Furthermore, the reference value data stored in the memory unit of the control device C may be updated to change the reference value according to the usage status of the ion sources IS1, IS2, and IS3.

[0064] In the above embodiment, the initial settings of the vaporizers C1, C2, and C3 are assumed to be high. Under this assumption, for example, the flowchart in Figure 4 states that if the temperature of the plasma generation chamber 14 is below a reference value, the output of the heater 5 is reduced. However, the initial temperature settings for vaporizers C1, C2, and C3 may be set to low temperatures. In this case, the processing performed after the comparison and judgment process between the reference value and the target parameter will differ from the processing described in the flowcharts in Figures 4, 5, and 7.

[0065] Specifically, in the flowcharts of Figures 4 and 5, if the conditions are met in the comparison decision process, the output of heater 5 is not changed. Conversely, if the conditions are not met in the comparison decision process, the output of heater 5 is increased.

[0066] The cooling element R shown in the flowchart of Figure 7 is not a means of raising the temperature of the vaporizer C3. Therefore, a heater 5 is separately attached to the ion source IS3, and as explained as a modified example of the flowcharts in Figures 4 and 5, if the conditions are met in the comparison judgment process, the output of the heater 5 is not changed. Conversely, if the conditions are not met in the comparison judgment process, the output of the heater 5 is increased.

[0067] In the above embodiment, it was explained that in the ion sources IS1 and IS2, the output of the heater 5 is reduced when the conditions are met through a comparison and judgment process between the target parameter and a reference value. However, the cooling member R described in Figure 6 may be provided in the ion sources IS1 and IS2, and the temperature of the vaporizer C1 may be lowered by operating the cooling member R. Furthermore, although a non-contact configuration was given as an example for the cooling element R, a cooling element R that physically contacts the crucible 2 may also be used.

[0068] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Explanation of symbols]

[0069] 2, 32 crucible 3. First Nozzle 5 Heater 14 Plasma generation chamber 15. Cathode (thermionic emission component) 23 Ammeter VA Arc Power Supply R Cooling component C Control device T Thermometer P1 central part P2 connection point C1, C2, C3 vaporizers IS1, IS2, IS3 Ion Sources

Claims

1. An ion source comprising a vaporizer that supplies gas generated in a crucible to a plasma generation chamber via a nozzle connected to a hollow crucible that is elongated in one direction, and which extracts an ion beam containing aluminum ions from the plasma generation chamber, An ion source comprising a control device that controls the set temperature of the vaporizer according to the temperature of the plasma generation chamber, or the value of a parameter correlated with the temperature of the plasma generation chamber, such that the temperature of the connection between the crucible and the nozzle is higher than the temperature of the central part of the crucible in the longitudinal direction of the crucible.

2. The aforementioned vaporizer is, The crucible is equipped with a heater for heating the crucible, The ion source according to claim 1, wherein the control device controls the output of the heater.

3. A thermionic emission member that emits thermionic electrons is placed inside the plasma generation chamber, An arc power supply that applies a voltage between the plasma generation chamber and the thermionic emission member, The system further comprises an ammeter for measuring the arc current flowing through the aforementioned arc power supply, The ion source according to claim 1, wherein the parameter is the arc current.

4. The ion source according to claim 1, wherein the crucible has a length of at least twice the length of the nozzle in the longitudinal direction of the crucible.

5. The ion source according to any one of claims 1 to 4, wherein the nozzle is made of a carbon-containing material.

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