Ion source and its operating method

Abstract

To reduce a time required for switching between ion species.SOLUTION: An ion source IS includes: a vaporizer S that generates a reaction product produced by supplying a reactive gas that reacts with a fixing material 4 via a first gas supply path 14 to a crucible 3 in which the fixing material 4 is provided, and converts the reactive material produced by heating the crucible 3 by a heater 5 into steam; a plasma generation container 2 in which vapor V is supplied via a vapor supply path 12 from the vaporizer S; and a second gas supply path 11 that is connected to the plasma generation container 2 in addition to the vapor supply path 12. During the supply of the gas to the plasma generation container 2 from the second gas supply path 11, the crucible 3 is heated by the heater 5, and the supply of the reactive gas to the crucible 3 from the first gas supply path 14 is stopped.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an ion source used in an ion beam irradiation apparatus and a method for operating the same. [Background technology]

[0002] In an ion implantation system, ion species are switched depending on the processing content. To switch ion species, the type of gas or vapor introduced into the plasma generating chamber is switched, plasma is generated for each switched gas or vapor, an ion beam is extracted from the generated plasma, and the extracted ion beam is adjusted to have a desired beam current.

[0003] Among ion sources, there is one equipped with an oven for solid samples, as described in Patent Document 1. In this ion source, gas from a gas source and vapor from the oven are selectively supplied to a plasma generation unit as ion species, but when the ion species is switched from vapor to gas, the oven is heated by radiant heat from the plasma generation unit, causing a temperature rise even though the power supply to the oven heater is turned off, and vapor is released into the plasma generation unit and mixed into the gas supplied from the gas source, which has been a problem.

[0004] As a countermeasure to this problem, it has been proposed to use a cooling mechanism to keep the temperature of the oven low so that when an ion beam is generated based on gas from a gas source, heat from the plasma generation unit is transferred to the oven and unnecessary steam is not supplied from the oven. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 8-36983 Summary of the Invention [Problem to be solved by the invention]

[0006] In the configuration of Patent Document 1, when switching ion species, the oven temperature is switched from low to high or from high to low so that the oven temperature reaches a predetermined temperature. This oven temperature control takes time, which is believed to be the reason why switching ion species takes a long time. The time required to control the oven temperature increases depending on the number of times the ion species is switched, so if the ion species is switched frequently, this becomes a major obstacle to improving the productivity of the ion implantation system.

[0007] The main object of the present invention is to reduce the time required to switch ion species. [Means for solving the problem]

[0008] The ion source is operated as follows: a vaporizer that generates a reaction product by supplying a reactive gas that reacts with the solid material through a first gas supply path to a crucible containing the solid material, and vaporizes the reaction product by heating the crucible with a heater; a plasma generating vessel into which vapor is supplied from the vaporizer through a vapor supply path; an ion source having a second gas supply path connected to the plasma generating chamber in addition to the vapor supply path, While the gas is being supplied from the second gas supply line to the plasma generating chamber, the crucible is heated by the heater, and the supply of the reactive gas from the first gas supply line to the crucible is stopped.

[0009] By stopping the supply of reactive gas, no reaction products are generated, and if there are no reaction products, their vapor will not be supplied to the plasma generating chamber even if the crucible is heated. By using a configuration in which the heater heats the crucible while the gas is being supplied to the plasma generating chamber from the second gas supply line and the supply of reactive gas to the crucible from the first gas supply line is stopped, it is possible to set the crucible temperature to a high temperature before switching the ion species from gas to vapor, thereby shortening the time required for the crucible temperature to reach the set temperature. Furthermore, when switching the ion species from vapor to gas, it is sufficient to stop the supply of reactive gas from the first gas supply line and start the gas supply from the second gas supply line, so there is no need to lower the crucible temperature, and the time required to switch the ion species can be shortened. This reduces the time required to switch ion species from gas to vapor or from vapor to gas.

[0010] It is desirable that the output of the heater is constant while the gas is being supplied from the second gas supply path to the plasma generating chamber.

[0011] With the above configuration, it is not necessary to control the temperature of the heater in response to switching of ion species.

[0012] While gas is being supplied from the second gas supply path to the plasma generating chamber, it is desirable to switch the output of the heater to the output when vapor is being supplied to the plasma generating chamber.

[0013] With the above configuration, it is possible to reduce the power consumption of the heater and to mitigate deterioration of the heater due to long-term use at high output.

[0014] The ion source is a vaporizer that generates a reaction product by supplying a reactive gas that reacts with the solid material through a first gas supply path to a crucible in which a solid material is placed, and vaporizes the reaction product by heating the crucible with a heater; a plasma generating vessel into which vapor is supplied from the vaporizer through a vapor supply path; a second gas supply path connected to the plasma generating chamber separately from the vapor supply path; and a control device that heats the crucible with the heater while gas is being supplied from the second gas supply path to the plasma generating chamber, and stops the supply of the reactive gas from the first gas supply path to the crucible. [Effects of the Invention]

[0015] The crucible temperature can be set to a high temperature before switching the ion species from gas to vapor, thereby shortening the time required for the crucible temperature to reach the set temperature. Furthermore, when switching the ion species from vapor to gas, it is sufficient to stop the supply of reactive gas from the first gas supply line and start the gas supply from the second gas supply line, so there is no need to lower the crucible temperature, and the time required to switch the ion species can be shortened. This reduces the time required to switch ion species from gas to vapor or from vapor to gas. [Brief explanation of the drawings]

[0016] [Figure 1] Schematic cross-sectional view of the ion source [Figure 2] Schematic cross-sectional view of the ion source of FIG. 1 as seen from another plane. [Figure 3] An explanatory diagram of an example of control of each part when switching ion species [Figure 4] An explanatory diagram of another example of control of each part when switching ion species. [Figure 5] An explanatory diagram of another example of control of each part when switching ion species. DETAILED DESCRIPTION OF THE INVENTION

[0017] Fig. 1 is a schematic cross-sectional view of an ion source IS. Fig. 2 is a schematic cross-sectional view of the ion source IS of Fig. 1 as viewed from another plane. The configuration of the ion source IS of the present invention will be described with reference to these figures.

[0018] The ion source IS mainly includes a plasma generating vessel 2 in which plasma P is generated inside, an extraction electrode E that extracts an ion beam IB from the plasma P generated in the vessel through an ion extraction port 6 of the plasma generating vessel 2, a second gas supply path 11 that supplies a gas that will become the source of the plasma to the plasma generating vessel 2, and a vaporizer S that supplies a vapor V that will become the source of the plasma to the plasma generating vessel 2.

[0019] Around the plasma generating vessel 2, there are provided a cathode that emits electrons to ionize the gas or vapor supplied into the vessel, a reflecting electrode that reflects the electrons emitted from the cathode toward the cathode, an electromagnet that generates a magnetic field in the direction opposite the cathode and reflecting electrode, etc., but these are not shown in the figure to simplify the drawing. The extraction electrode E is composed 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.

[0020] The vaporizer S supplies a reactive gas that chemically reacts with the solid material 4 (including various shapes such as pellets, powder, and blocks) to a crucible 3 through a first gas supply path 13, thereby generating a reaction product on the surface of the solid material 4, and vaporizes the generated reaction product by heating the crucible 3 with a heater 5.

[0021] To give a specific example, the solid material 4 is an aluminum-containing material such as pure aluminum or aluminum fluoride, and the reactive gas is a halogen gas such as chlorine gas or fluorine gas. When the first on-off valve 14 is open (in an open state), a reactive gas is supplied from the first gas supply bottle 16 to the crucible 3 through the first gas supply path 13. When the reactive gas is supplied to the crucible 3, a chemical reaction occurs between the reactive gas and the solid material 4, and a reaction product is generated on the surface of the solid material 4. For example, if the reactive gas is chlorine gas and the solid material 4 is pure aluminum, aluminum chloride is generated as a reaction product on the surface of the pure aluminum. Also, if the reactive gas is fluorine gas and the solid material 4 is pure aluminum, aluminum fluoride is generated as a reaction product on the surface of the pure aluminum.

[0022] Around the crucible 3, a heater 5 (for example, a coil heater) for heating the crucible 3 and a thermocouple TC for measuring the temperature of the crucible 3 are arranged. When the heater 5 heats the crucible 3 to a predetermined temperature or higher, the reaction product generated on the surface of the solid material 4 is vaporized. After that, the vapor V of the reaction product is supplied to the plasma generating vessel 2 through the vapor supply path 12.

[0023] When the temperature of the crucible 3 is heated to a predetermined temperature or higher, the predetermined temperature is a temperature that allows the reaction product to be vaporized and is lower than the melting point of the solid material 4 . Specifically, if the reaction product is aluminum chloride, the temperature required to vaporize it is approximately 180°C, although this may vary slightly depending on the degree of vacuum within the crucible 3. On the other hand, if the solid material 4 is pure aluminum, the melting point of pure aluminum is approximately 660°C. Therefore, the predetermined temperature can be any temperature between approximately 200°C and 500°C, but it does not need to be set to a specific temperature, as long as it falls within a certain range.

[0024] Gas is supplied to the plasma generating vessel 2 through a supply path separate from the steam. This gas is sealed in a second gas supply bottle 17, and when the second on-off valve 15 is opened (opened), the gas is supplied to the plasma generating vessel 2 through the second gas supply path 11. At this time, the first on-off valve 14 is closed, and the supply of reactive gas is stopped.

[0025] The opening and closing operations of the first on-off valve 14 and the second on-off valve 15 and the adjustment of the output of the heater 5 may be performed manually, or a control device C as shown in the figure may be provided and each part may be controlled using control signals S1 to S3.

[0026] 3 to 5 are explanatory diagrams of the opening and closing operations of the first on-off valve 14 and the second on-off valve 15 and the output adjustment of the heater 5. Using these diagrams, the control of each part when switching ion species will be described below.

[0027] 3 to 5 show an example in which an ion beam is extracted from a gas-derived plasma and an ion beam irradiation process is performed on an irradiated object, and an ion beam is extracted from a vapor-derived plasma and an ion beam irradiation process is performed on an irradiated object, are performed alternately.

[0028] The horizontal axis of each graph in each figure represents elapsed time, and the time axes of each graph are the same. The vertical axis of each graph represents the amount of gas or steam flowing through each supply path, or the heater output. At the origin where the vertical axis intersects with the horizontal axis, the amount of gas or steam is zero, and the heater output is stopped.

[0029] After the supply of gas from the second gas supply path 11 is stopped, the supply of steam is started from the vaporizer S. This point is the same as the prior art cited in Patent Document 1, but due to the difference in the steam supply method, the output control of the heater 5 differs between the present invention and the prior art.

[0030] In the vaporizer S of the present invention, if the supply of reactive gas is stopped, no reaction products are generated by chemical reaction with the solid material 4. If there are no reaction products, no vapor of the reaction products is generated even if the output of the heater 5 is maintained. Therefore, by controlling the supply of reactive gas, it is possible to control the vapor supply to the plasma generating chamber 2.

[0031] When switching ion species, the time required to adjust the temperature of the crucible 3 is longer than the time required to control the on / off of the gas supply. In the present invention, when switching between ion species, it is only necessary to control the on / off of the reactive gas from the first gas supply path 13 and the gas from the second gas supply path 11, which makes it possible to shorten the time required to switch between ion species compared to conventional configurations.

[0032] 3, the output of the heater 5 is kept constant. If the output is kept constant, there is no need to control the temperature of the heater 5 in response to switching of ion species, which simplifies the control.

[0033] On the other hand, if the power consumption of the heater 5 and wear due to long-term use are taken into consideration, the output of the heater 5 may be kept low while gas is being supplied from the second gas supply line 11 to the plasma generating chamber 2, and the output of the heater 5 may be switched to the output for supplying steam shortly before the ion species is switched, as in the embodiment shown in Fig. 4. With this configuration, it is possible to reduce the power consumption of the heater 5 and reduce deterioration due to long-term use of the heater at high output.

[0034] Furthermore, as in the embodiment shown in FIG. 5, when gas is supplied from the second gas supply path 11 to the plasma generating chamber 2 for a long period of time, the output of the heater 5 may be temporarily set to zero, and then the output of the heater 5 may be switched to the output for supplying steam shortly before the ion species is switched.

[0035] In either embodiment shown in FIG. 4 or FIG. 5, the crucible 3 is heated by the heater 5 while the gas is being supplied from the second gas supply path 11 to the plasma generating chamber 2, so that the time required for switching the ion species can be shortened compared to the conventional configuration.

[0036] The solid material 4 depicted in FIG. 1 is about half the size of the crucible 3 , but it may be the same size as the internal space of the crucible 3 .

[0037] The ion source IS of the present invention can be used not only in an ion implantation apparatus but also in various other ion beam irradiation apparatuses that use an ion beam to treat an object to be irradiated. Examples of ion beam irradiation apparatuses other than ion implantation apparatuses include an ion beam etching apparatus and a surface modification apparatus that uses an ion beam.

[0038] 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]

[0039] 2. Plasma generating vessel 3. Vaporizer 4 solid materials 5 Heater 11 Second gas supply line 12 Steam supply line 13 First gas supply line C Control device IS ion source S vaporizer

Claims

1. a vaporizer that generates a reaction product by supplying a reactive gas that reacts with the solid material through a first gas supply path to a crucible in which a solid material is placed, and vaporizes the reaction product by heating the crucible with a heater; a plasma generating vessel into which vapor is supplied from the vaporizer through a vapor supply path; an ion source having a second gas supply path connected to the plasma generating chamber in addition to the vapor supply path, a heater for heating the crucible while supplying gas from the second gas supply line to the plasma generating chamber, and stopping supply of the reactive gas from the first gas supply line to the crucible.

2. 2. The method for operating an ion source according to claim 1, wherein the output of said heater is constant while gas is being supplied from said second gas supply line to said plasma generating chamber.

3. 2. The method for operating an ion source according to claim 1, wherein an output of the heater is switched to an output when vapor is supplied to the plasma generating chamber while gas is being supplied from the second gas supply line to the plasma generating chamber.

4. a vaporizer that generates a reaction product by supplying a reactive gas that reacts with the solid material through a first gas supply path to a crucible in which a solid material is placed, and vaporizes the reaction product by heating the crucible with a heater; a plasma generating vessel into which vapor is supplied from the vaporizer through a vapor supply path; a second gas supply path connected to the plasma generating chamber separately from the vapor supply path; a control device that heats the crucible with the heater while gas is being supplied from the second gas supply line to the plasma generating chamber, and stops the supply of the reactive gas from the first gas supply line to the crucible.

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