JP3498405B2 - Ion source - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an ion beam apparatus such as an ion implantation apparatus, and converts an ion species gas introduced into a plasma generation chamber into plasma to convert ions. It relates to the generated ion source. 2. Description of the Related Art In recent years, ion sources for converting an element into plasma and extracting ions in the plasma as an ion beam have been used in various fields such as ion implantation, ion plating, crystal growth, and ion processing. It's being used. [0003] The above-mentioned ion source is a low-voltage arc discharge type such as a Freeman type ion source or a Bernas type ion source.
There are high frequency type such as ECR ion source and various types, but basically, arc discharge or microwave while supplying ion species gas from a gas supply source into a high vacuum plasma generation chamber. This is a configuration in which the introduced gas is converted into plasma using discharge or the like. [0004] A gas introducing pipe for introducing an ion species gas such as BF ₃ or a cleaning gas such as an argon gas into the chamber is connected to the plasma generation chamber of the ion source. When the ion species is arsenic, phosphorus, or another metal, the solid sample is vaporized by heating,
Some ion sources need to be introduced into the plasma generation chamber, and are provided with an oven for heating the solid sample outside the plasma generation chamber. Here, a configuration of a conventional ion source capable of ionizing a solid sample is shown in FIG. In this type of ion source, an oven 51 and a plasma generation chamber 52 are connected by a gas introduction pipe 53 made of metal such as stainless steel.
The sample gas vaporized in the oven is introduced into the plasma generation chamber 52 through the oven. The amount of gas introduced from the oven into the plasma generation chamber 52 is adjusted by adjusting the temperature of the oven 51 and adjusting the temperature of the sample 5.
4 by changing the amount of vaporization. [0006] In the conventional ion source,
Gas introduction pipe 53 connecting between oven 51 and plasma generation chamber 52, and adapter 5 for attaching the tip of gas introduction pipe 53 to plasma generation chamber 52.
5 is formed of a metal such as stainless steel in consideration of heat resistance, strength, workability, and the like. Therefore, a large amount of heat is transmitted (conducted) between the plasma generation chamber 52 and the oven 51 via the metallic gas introduction pipe 53 having a relatively high thermal conductivity. For example, in a Freeman-type or Bernas-type ion source, a current is supplied to a filament provided inside the plasma generation chamber 52 to heat the filament, and an arc voltage is applied between the filament and the plasma generation chamber 52. The temperature of the plasma generation chamber 52 is set to 100
The temperature becomes higher than 0 ° C. In other types of ion sources, the plasma generation chamber 52 is also formed by air discharge or the like.
Temperature rises. For example, after the solid sample such as phosphorus is vaporized using the oven 51 to operate the ion source, the oven 5
The plasma generation chamber 52 with argon gas with a cooling and cleaning a predetermined time, followed by BF ₃
When the ion source is operated using an ion species gas such as that described above, the heat of the plasma generation chamber 52 is transmitted to the oven 51 via the gas introduction pipe 53, whereby the solid sample remaining in the oven 51 is vaporized. And is introduced into the plasma generation chamber 52. [0009] Even during the operation of the ion source using the oven 51, heat exchange between the plasma generation chamber 52 and the oven 51 affects each other. For example, the plasma density in the plasma generation chamber 52 is adjusted by changing the arc voltage. When the temperature of the plasma generation chamber 52 changes in accordance with the adjustment, the temperature change affects the heating temperature of the oven 51. , The amount of vaporization of the sample in the oven 51 changes. As a result, inconveniences such as an unstable gas introduction amount from the oven 51 to the plasma generation chamber 52 occur. In the above-mentioned ion source, the plasma generation chamber 52 is thermally affected not only by the oven 51. As shown in FIG. 7, the plasma generation chamber 52 includes a metal support plate member 58 attached to the tip of four metal support bars 57, such as stainless steel, erected on a base plate 56. , Fixed by bolts and the like. In such a conventional support structure, the heat of the plasma generation chamber 52, which has become high temperature, escapes to the outside via the metal receiving plate member 58 and the support rods 57, and the temperature of the plasma generation chamber 52 decreases. Resulting in. For example, when an ion source is operated by evaporating a solid sample having a high melting point such as phosphorus using the oven 51,
When the temperature of the plasma generation chamber 52 is low, the amount of the solid sample (or the compound of the solid sample and any substance) remaining in the chamber increases, and thereafter, the ion source is operated by switching to another ion species. In this case, there is an inconvenience that the time required for the cleaning process (the process of operating the ion source using an argon gas or the like until another ion species remaining in the plasma generation chamber 52 becomes equal to or less than the reference amount) becomes long. [0012] [0013] [0014] Means for Solving the Problems] ion source according to the invention of claim 1 comprises a plasma generation chamber into plasma the gas introduced into the chamber, the plasma generation chamber And a support member for supporting and fixing at a predetermined position, wherein the following means are taken in order to solve the above-mentioned problems. That is, at least a part of the supporting member is made of a heat insulating material (for example, Al) having lower thermal conductivity than metal.
₂ O ₃ ). According to the structure of the first aspect of the present invention, at least a part of the support member supporting the plasma generation chamber is formed of a heat insulating material having a lower thermal conductivity than metal. Therefore, the amount of heat escaping to the outside of the plasma generation chamber via the support member is smaller than that of the related art (where the support member is made of metal). Accordingly, the temperature of the plasma generation chamber during operation of the ion source rises higher than before, and even when the ion source is operated using a gas of a substance having a high melting point (for example, phosphorus or the like), plasma generation is not performed. The amount of the substance (or the compound of the substance) remaining in the chamber becomes smaller than before, and the cleaning time required when the ion source is operated by switching the ion species can be shorter than before. [Embodiment 1] FIGS. 1 to 3 show an embodiment of the present invention.
This will be described below. As shown in FIG. 1, the ion source according to the present embodiment heats and vaporizes an arc chamber (plasma generation chamber) 1 for generating plasma and a solid sample 5 such as phosphorus or arsenic. An oven (evaporation source) 2, a gas introduction pipe 3 for introducing the sample vaporized in the oven 2 into the arc chamber 1, and a tip for connecting the tip of the gas introduction pipe 3 to the arc chamber 1. And an adapter 4. Here, the gas introduction member described in the claims is constituted by the gas introduction pipe 3 and the adapter 4. The ion source is a gas introduction pipe (not shown) for introducing an ion species gas such as BF ₃ or a cleaning gas such as an argon gas from a gas box (not shown) into the arc chamber 1. ), And can operate with a sample in either solid or gas state. FIG. 1 shows a Freeman type ion source as an example. The ion source is an arc chamber 1
Is provided with a linear cathode filament (hereinafter, simply referred to as a filament) 1a, and both ends thereof are supported by insulating caps 1b provided in the arc chamber 1. The arc chamber 1 has a positive terminal of an arc power supply 1c and the filament 1a.
Are connected to the negative terminals of the arc power supply 1c, respectively. Between the arc chamber 1 and the filament 1a,
A predetermined potential difference required for arc discharge is generated. Further, a filament power supply 1 for supplying a current to the filament 1a is provided at both ends of the filament 1a.
The terminals d are connected to each other. Outside the arc chamber 1, a magnet (not shown) that forms an external magnetic field parallel to the axis of the filament 1a is provided. A slit-shaped outlet for extracting an ion beam is formed on the wall surface of the arc chamber 1 in parallel with the axis of the filament 1a. The arc chamber 1 is provided with a gas inlet 1e, to which the tip of a gas inlet tube 3 is connected via an adapter 4. Specifically, an adapter 4 is screwed into the arc chamber 1, and has a mounting structure in which the distal end portion of the gas introduction tube 3 is fitted to the adapter 4. In the present embodiment, the gas introduction pipe 3 and the adapter 4 are both formed of alumina (aluminum oxide: Al ₂ O ₃ ) having a lower thermal conductivity than metal, so that the arc chamber 1 Thermal insulation with the oven 2 is achieved. In the above configuration, when the arc power supply 1c and the filament power supply 1d are turned on, the filament 1
When a current flows through the filament 1a, the filament 1a generates heat, and due to a potential difference between the arc chamber 1 and the filament 1a (voltage of the arc power supply 1c), electrons are emitted from the heated filament 1a to cause arc discharge.
At this time, a gas (or an ion species gas such as BF ₃ ) obtained by evaporating a solid sample 5 such as phosphorus or arsenic in the oven 2 is supplied to the gas introduction tube 3 (or a gas introduction tube (not shown) for introducing the ion species gas). When the gas is introduced into the arc chamber 1 through the gas chamber, the particles of the introduced gas collide with the electrons, thereby ionizing the gas particles and generating plasma. Thereby, the temperature of the arc chamber 1 becomes high during the operation of the ion source. The plasma density in the arc chamber 1 is adjusted by changing the voltage of the arc power supply 1c, and the temperature of the arc chamber 1 changes with this adjustment. Conventionally, there has been a problem that the temperature of the oven 2 is not constant due to the influence of the temperature change of the arc chamber 1, but the gas introduction pipe 3 and the adapter 4 are formed of alumina as described above. To provide thermal insulation between the arc chamber 1 and the oven 2
The temperature of the oven 2 can be kept constant. As a result, the amount of gas introduced from the oven 2 is stabilized. After the solid sample 5 such as phosphorus is vaporized by using the oven 2 and the ion source is operated by the above-mentioned thermal insulation, the ion source is subsequently operated by using an ion species gas such as BF _3. Even in such a case, there is no inconvenience that the solid sample 5 remaining in the oven 2 is vaporized and introduced into the arc chamber 1 as in the related art. The test results are shown below. In this test, the above-mentioned ion source was incorporated into an ion implantation apparatus. First, the oven 2 was operated under the following operating conditions with respect to each of the conventional ion source and the ion source of the present embodiment.
The operation using was performed. Solid sample: Phosphor oven temperature: 340 ° C. Arc voltage: 60 V Arc current: 1.0 A Extraction current: 4 mA The extraction current is the beam current of all ions extracted from inside the arc chamber 1. . In addition, the ion beam extracted from the ion source was subjected to mass analysis by an analysis magnet arranged at the subsequent stage of the ion source, and the conditions were set so that a P ²⁺ beam with a beam current of 30 μA and 100 kV was obtained in the target. After the operation of the ion source under the above conditions, the oven 2 is rapidly cooled, and the conventional ion source and the ion source of the present embodiment are continuously operated without using the oven 2 under the following operating conditions. Was done. Gas: BF ₃ Gas flow rate: 0.74 cc / min Arc voltage: 60 V Arc current: 1.5 A Extraction current: 10 mA Further, beam current 150 μA, 80 at the target
The conditions were such that a kV B ⁺ beam was obtained. When a conventional ion source is used, the gas from the oven (phosphorus remaining in the oven is heated and gasified by the heat from the arc chamber) even after 20 minutes from the rapid cooling of the oven. As a result, there was a residual beam of phosphorus of about 400 μA in the target.
On the other hand, when the ion source of this example was used, the residual beam of phosphorus was approximately 0 μA. In the above description, both the gas introduction pipe 3 and the adapter 4 are made of alumina. However, even if either the gas introduction pipe 3 or the adapter 4 is made of alumina, the arc chamber 1 and the oven 2 Is possible, and the same effect as above can be obtained. Alternatively, as shown in FIG. 2, a part of the gas introducing pipe 3 'may be formed of alumina. That is, in the figure, the adapter 4 'is made of metal such as stainless steel,
The same effect as described above can be obtained even if the gas introducing pipe 3 'is configured by connecting the heat insulating part 3a made of alumina and the non-heat insulating part 3b made of metal. If the wall thickness of the arc chamber 1 has a certain thickness, a configuration without using an adapter is also possible as shown in FIG. That is, the adapter enables the gas inlet tube 3 to be connected to the arc chamber 1 without causing gas leakage even when the wall thickness of the arc chamber 1 is small. If there is, the adapter can be omitted. in this case,
As shown in the figure, an alumina gas introduction pipe 3 may be directly fitted to a gas introduction port 1e formed in the arc chamber 1. Although not shown, only a part of the gas introduction pipe 3 may be formed of alumina. By the way, as the material used for the ion source, it is necessary to consider the melting point, strength, reactivity with gas, and the like. Alumina has been described above as a preferred material having a lower thermal conductivity than metals. However, the material is not limited to alumina, and other materials such as 3Al ₂ O ₃ .2SiO ₂ , zirconia (zirconium oxide), and sialon (SIALON) can also be used. Embodiment 2 The following will describe another embodiment of the present invention with reference to FIGS. 4 and 5. Note that members having the same functions and configurations as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and description thereof will be omitted. In the ion source according to the present embodiment, as shown in FIG. 4, the arc chamber 1 is mounted on a receiving plate member 8 attached to the upper ends of four support rods 7 standing on a base plate 6. It has a support structure for the arc chamber 1 fixed by bolts. Here, the support members described in claims are constituted by the support rods 7 and the receiving plate member 8. The upper end of each of the support rods 7 forms a heat insulating portion 7a made of alumina, and the other portion 7b is made of metal such as stainless steel. Also, the receiving plate member 8
Is also made of metal such as stainless steel. FIG. 5 shows a connection structure between the receiving plate member 8 and the support rod 7.
Shown in As shown in the figure, the receiving plate member 8 is screwed to the upper end of the support rod 7 by a metal bolt 9. When the receiving plate member 8 is made of metal, the heat of the arc chamber 1 is transmitted to the receiving plate member 8 and the temperature of the receiving plate member 8 becomes high. In this case, the bolt 9 is used to prevent the heat of the receiving plate member 8 from being transmitted to the metal portion 7b of the support rod 7 via the bolt 9.
A heat insulating member 10 made of alumina is interposed between the support member 8 and the receiving plate member 8. In the above configuration, the temperature of the arc chamber 1 becomes high during the operation of the ion source as described above. However, the heat is not released to the outside through the support rod 7 as in the prior art, so that the arc chamber 1 is made of alumina. Thermal insulation is achieved by the thermal insulation part 7a. Thereby, the arc chamber 1 during operation is
Of the solid sample (or the solid sample and some other substance) inside the arc chamber 1 when the ion source is operated by evaporating the solid sample having a high melting point such as phosphorus using an oven and operating the ion source. And the remaining amount of the compound becomes smaller than before. The test results are shown below. Note that this test was also performed by incorporating the ion source into the ion implantation apparatus as described above. First, each of the conventional ion source and the ion source of the present embodiment was operated using an oven under the following operating conditions. Solid sample: Phosphor oven temperature: 395 ° C. Arc voltage: 60 V Arc current: 1.0 A Extraction current: 4 mA The conditions were such that a P ²⁺ beam with a beam current of 30 μA was obtained in the target. After the operation under the above conditions for 2 to 3 days, heating by the oven was stopped (set at 0 ° C. in the oven), and the ion source was operated under the following conditions while supplying the cleaning gas to the arc chamber 1 from the gas box. Then, the inside of the arc chamber 1 was cleaned for 20 minutes. Cleaning gas: Ar Ar gas flow rate: 0.2 cc / min Arc voltage: 75 V Arc current: 0.85 A Extraction current: 6 mA After the above-described cleaning step, the conventional ion source and the ion source of the present embodiment were used. Each was subsequently operated under the following operating conditions, and a B ⁺ beam was emitted. Gas: BF ₃ Gas flow rate: 0.74 cc / min Arc voltage: 60 V Arc current: 1.6 A Extraction current: 7 mA When using a conventional ion source, 200
There was a residual beam of phosphorus of about μA (a beam extracted by ionizing phosphorus remaining in the arc chamber 1 and measured by a target after mass analysis). On the other hand, when the ion source of the present embodiment is used, the above-mentioned residual phosphorus beam is 40 μm, which is 1/5 of the conventional one.
It was about A. As described above, a cleaning step required when the ion source is operated by switching the ion species (a cleaning gas such as an argon gas or the like until the other ion species remaining in the arc chamber 1 becomes equal to or less than the reference amount). The time required for the operation of the ion source using the method can be shortened as compared with the conventional case (for example, the cleaning time, which conventionally took one hour, can be reduced to 30 minutes or less). That is, the switching time of the ion species can be reduced to less than half of the conventional one, and the use efficiency of the apparatus can be improved. Even if the cleaning step is not performed sufficiently, the amount of ion species used in the previous operation included in the beam as contamination is reduced. ,
It is possible to reduce the amount of contamination injected into an ion irradiation target such as a wafer. Further, since the amount of the solid sample (or its compound) remaining in the arc chamber 1 is smaller than in the prior art, cleaning (maintenance) of the inside of the arc chamber 1 by a person becomes easy. In the above description, a part of the support rod 7 is formed of alumina, but the entire support rod 7 may be formed of alumina. Further, even if the receiving plate member 8 is formed of alumina, thermal insulation from the outside is possible (in this case, the support rod 7 can be made of metal), and the same effect as above can be obtained. Alternatively, a heat insulating plate made of alumina (which constitutes a part of the supporting member) may be interposed between the arc chamber 1 and the receiving plate member 8 (in this case, the supporting rod 7 and the receiving plate member 8 are made of metal). Can be used), and the same effect as above can be obtained. In the above description, alumina is shown as a material suitable for thermal insulation. However, the material is not limited to alumina.
As other materials, for example, 3Al ₂ O ₃ .2SiO
₂ , zirconia, sialon, etc. can be used. In each of the embodiments described above, the freeman type ion source is shown as an example.
It can be applied to various other types of ion sources such as an R ion source. Each of the above embodiments is merely for clarifying the technical contents of the present invention, and should not be construed as being limited to such specific examples in a narrow sense. Can be implemented with various changes within the scope of the above. As described above, in the ion source according to the first aspect of the present invention, at least a part of the support member that supports the plasma generation chamber and fixes it at a predetermined position is made of metal. This is a configuration formed of a heat insulating member having lower thermal conductivity than that of the first embodiment. Therefore, even when the temperature of the plasma generation chamber rises during operation of the ion source as compared with the conventional case, and the ion source is operated using a gas of a substance having a high melting point (for example, phosphorus or the like), the plasma generation chamber is operated. The amount of the substance (or the compound of the substance) remaining in the chamber becomes smaller than before. Therefore, the cleaning time required when the ion source is operated by switching the ion species can be shortened as compared with the conventional case, and the effect of improving the use efficiency of the ion source can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows one embodiment of the present invention, and is a schematic longitudinal sectional view showing a configuration of a main part of an ion source. FIG. 2 is a schematic longitudinal sectional view showing a modification of the ion source. FIG. 3 is a schematic longitudinal sectional view showing another modification of the ion source. FIG. 4 is a schematic perspective view showing another embodiment of the present invention and showing a support structure of an arc chamber of an ion source. 5 is a schematic longitudinal sectional view showing a connection structure between a receiving plate member and a support rod of the ion source of FIG. 4; FIG. 6 is a schematic longitudinal sectional view showing a configuration of a main part of a conventional ion source. FIG. 7 is a schematic perspective view showing a support structure of a plasma generation chamber in a conventional ion source. [Description of Signs] 1 arc chamber (plasma generation chamber) 2 oven (evaporation source) 3 gas introduction pipe (gas introduction member) 4 adapter (gas introduction member) 5 solid sample 7 support rod (support member) 8 receiving plate member ( Support member)

──────────────────────────────────────────────────続 き Continued on the front page (56) References JP-A 1-1112556 (JP, U) JP-A 4-49448 (JP, U) JP-A 64-12363 (JP, U) JP-A 64-64 12362 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 37/08 H01J 27/02

Claims (1)

(57) Claims 1. An ion comprising: a plasma generation chamber for converting a gas introduced into a chamber into plasma; and a support member for supporting the plasma generation chamber and fixing the same at a predetermined position. An ion source according to claim 1, wherein at least a part of said support member is formed of a heat insulating material having a lower thermal conductivity than metal.