Boron fluoride mixed gas and application thereof in ion implantation system

Abstract

The invention relates to boron fluoride mixed gas and application thereof in an ion implantation system, a fluid supply container is filled with mixed gas in sequence, the mixed gas is composed of doped gas and hydrogenated gas, the doped gas is boron fluoride, the volume percentage of the boron fluoride is 90%-95%, the volume percentage of the hydrogenated gas is 5%-10%, and the volume percentage of the doped gas is 5%-10%. By introducing the hydrogenated gas and optimizing the ratio of the hydrogenated gas to boron fluoride, higher and more stable boron ion beam output can be realized under the condition of lower gas flow when the device is applied to an ion implantation system, and the stable operation time is remarkably prolonged.

Description

Technical Field

[0001] This invention relates to a mixed gas, and more particularly to a boron fluoride mixed gas and its application in an ion implantation system. Background Technology

[0002] In the semiconductor manufacturing field, ion implantation is a key doping process for precisely controlling the electrical properties of wafers. This process involves ionizing specific dopant gases (such as fluorine- or hydrogen-containing compounds) in an ion source to form a high-energy ion beam, which is then implanted into the wafer substrate to alter its conductivity.

[0003] Currently, fluorine-containing gases are widely used as doping sources in ion implantation processes; for example, boron trifluoride (BF3) is used for boron doping, and germanium tetrafluoride (GeF4) is used for germanium doping. However, these fluorine-containing gases generate a large number of fluoride ions (F) in the high-energy plasma environment of the ion source. + ) or fluorine radicals (F). These highly reactive fluorines can cause severe chemical corrosion to key components of the ion source (usually the chamber walls, filament, or anode made of tungsten or tungsten alloys), generating volatile tungsten fluoride (WF). X The corrosion process of tungsten fluoride (WF) compounds triggers a vicious cycle known as the "halogen cycle": the volatilization of tungsten fluoride (WF) compounds leads to the release of halogenated compounds. X The ion source is dissociated again in the plasma, releasing tungsten (W) which deposits on other surfaces of the chamber, while fluorine (F) continues to participate in the corrosion reaction. This cycle not only significantly shortens the ion source lifespan, increases maintenance frequency and cost, but the deposited tungsten can also contaminate the wafer, leading to a decrease in device yield.

[0004] To mitigate this issue, the current mainstream technology involves mixing a certain proportion of hydrogen (H2) into the fluorine-doped gas. The principle is that hydrogen reacts with active fluorine in the plasma to generate relatively stable hydrogen fluoride (HF) gas, which is discharged with the process exhaust gas, thus interrupting the "halogen cycle" to some extent and reducing direct corrosion of tungsten components. However, this mainstream approach still has significant drawbacks in practical applications. The generated hydrogen fluoride (HF) itself is still highly corrosive and may cause secondary corrosion to non-tungsten components downstream of the ion source, such as cooling pipes and vacuum pump valves. The hydrogen ratio needs precise control; insufficient ratio results in poor protection, while excessive ratio may over-consume the highly active fluorine in the plasma, negatively impacting the target dopant ions (such as B). + The low generation efficiency of hydrogen leads to beam instability or poor doping uniformity. Furthermore, hydrogen has a high compressibility factor, greater than 1 at room temperature. This makes it difficult to compress hydrogen during filling, limiting the amount of boron fluoride that can be filled. Increasing the amount of hydrogen will raise the pressure inside the cylinder, causing germanium tetrafluoride or boron trifluoride to liquefy under higher pressure. This could lead to serious quality incidents downstream when using cylinderd gases. Summary of the Invention

[0005] In view of this, in order to overcome the above problems, the present invention provides a boron fluoride mixed gas and its application in an ion implantation system, by optimizing the ratio parameters of the mixed gas to solve the problems existing in the application of the ion implantation system.

[0006] A boron fluoride mixed gas, characterized in that the mixed gas is sequentially filled into a fluid supply container, the mixed gas being composed of a dopant gas and a hydrogenated gas, wherein the dopant gas is boron fluoride, the volume percentage of the boron fluoride is 90%~95%, and the volume percentage of the hydrogenated gas is 5%~10%.

[0007] Furthermore, the hydrogenating gas is selected from at least one of NH3, B2H6, and SiH4, or any combination thereof.

[0008] Furthermore, the hydrogenated gas consists only of ammonia.

[0009] Furthermore, the boron fluoride is selected from at least one of boron trifluoride and boron tetrafluoride.

[0010] Furthermore, the boron fluoride is boron trifluoride and boron tetrafluoride, wherein the boron trifluoride accounts for 80% to 90% of the total mixed gas volume percentage, and the boron tetrafluoride accounts for 6% to 15% of the total mixed gas volume percentage.

[0011] Furthermore, the boron tetrafluoride accounts for 6% to 10% of the total volume of the mixed gas.

[0012] Furthermore, the mixed gas is not additionally filled with hydrogen.

[0013] The mixed gas is filled into a fluid supply container. The filling sequence is to first fill the container with boron fluoride gas, then fill it with hydrogen gas. After filling, the container is removed and rotated to ensure thorough mixing.

[0014] The mixed gas is delivered to the arc chamber of the ion source device, where it is ionized to form an ion beam. The collision of the ion beam with lattice atoms enables the directional insertion of impurities.

[0015] Furthermore, when the mixed gas is delivered from a container to the arc chamber at a flow rate of 1-2 sccm, the boron ion beam current generated by the gas components is 5-6 mA.

[0016] Beneficial effects: On the one hand, by introducing hydrogen gas and optimizing its ratio in a boron fluoride-based mixed gas system, a higher and more stable boron ion beam output can be achieved at a lower gas flow rate, and the stable operating time can be significantly extended. On the other hand, adding a small amount of boron tetrafluoride to the system can directly replenish boron atoms and boron-containing groups to the plasma, effectively increasing the boron concentration in the plasma. + With BF2 + The concentration of plasma, in conjunction with the effect of hydrogenation gas, further enhances the intensity of the boron ion beam. Attached Figure Description

[0017] Figure 1 A simplified diagram of the ion implantation process;

[0018] Figure 2 This is a diagram showing the relationship between beam current and flow rate.

[0019] Labeling: 1. Ion source; 2. Plasma; 3. Extraction assembly; 4. Analytical magnet; 5. Ion beam; 6. Accelerator tube; 7. Process chamber; 8. Gas container. Detailed Implementation

[0020] To explain in detail the possible application scenarios, technical principles, specific feasible solutions, and the objectives and effects that this application can achieve, the following detailed description is provided in conjunction with the specific embodiments listed.

[0021] The embodiments described in this invention are only used to illustrate the technical solutions of this application more clearly, and are therefore only examples and should not be used to limit the scope of protection of this application.

[0022] In this invention, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0023] Unless otherwise defined, the technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms in this invention is merely for describing specific embodiments and is not intended to limit this application.

[0024] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, in this invention, the character " / " generally indicates that the preceding and following objects have an "or" logical relationship.

[0025] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0026] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0027] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0028] A boron fluoride mixed gas, wherein the mixed gas is sequentially filled into a fluid supply container, the mixed gas being composed of a dopant gas and a hydrogenated gas, the dopant gas being boron fluoride, wherein the volume percentage of the boron fluoride is 90% to 95%, and the volume percentage of the hydrogenated gas is 5% to 10%.

[0029] Furthermore, the hydrogenating gas is selected from at least one of NH3, B2H6, and SiH4, or any combination thereof.

[0030] In some embodiments, the hydrogenation gas consists only of ammonia. First, in an ion source, the ammonia plasma is ionized, resulting in nitrogen and hydrogen ions. These ions react with fluoride ions ionized from boron fluoride to generate NF. X(i.e., polyfluorinated nitrogen) and HF hydrogen fluoride are used to remove fluorine from the reaction system, thereby increasing the service life of the ion implanter. Secondly, ammonia has a compressibility factor of 0.9 at room temperature and can remain in a gaseous state under high pressure without liquefying, thus ensuring that the cylinder is entirely in a gaseous phase. During ion implantation, this ensures uniform gas output, maximizing the degree of ionization. The power output of the ion source matches the uniform gas phase, resulting in electron resonance absorption, increased electron energy and ion density, reduced ion beam scattering, and a more parallel and focused beam. Finally, uniform gas output avoids uneven gas output from the cylinder due to partial liquefaction of the filling material, preventing large fluctuations in the final beam current of the ion implanter.

[0031] Ammonia has high compressibility. When it is mixed with boron fluoride in an optimized ratio and filled into the same gas cylinder, the actual amount of boron fluoride filled in a unit container can be significantly increased within a safe pressure range. This is equivalent to storing more effective dopant raw materials in a single gas cylinder, thereby directly increasing the overall gas usage, extending the gas supply time of a single cylinder, and helping to improve the continuity of process operation and production efficiency.

[0032] As described above, in some embodiments, the ammonia volume percentage is controlled at 5% to 10%. When the ammonia filling is too low, the halogen cycle cannot be effectively interrupted, and excessive F corrodes the tungsten, forming volatile tungsten fluoride, which redeposites in the cold zone of the cavity, damaging the components. When the ammonia filling is too high, a large amount of N is introduced. + N2 + H + Non-target ions dilute and interfere with the target boron ion beam, causing the beam current to fluctuate and decrease.

[0033] In some embodiments, the boron fluoride is at least one of boron trifluoride and boron tetrafluoride, more preferably boron trifluoride and boron tetrafluoride, wherein the boron trifluoride accounts for 80% to 90% of the total mixed gas volume percentage, and the boron tetrafluoride accounts for 6% to 15% of the total mixed gas volume percentage, more preferably boron tetrafluoride accounts for 6% to 10% of the total mixed gas volume percentage.

[0034] Boron tetrafluoride contains two boron atoms. Combining it with boron trifluoride directly increases the supply of boron in the plasma, significantly enhancing B. + and BF2 + The beam current intensity; BF3 is a stable molecule that requires high electron energy to effectively ionize and ultimately produce the desired B. +Ions. The BB bonds in the B2F4 molecule are relatively weak, making B2F4 more prone to ionization and decomposition than BF3 in the plasma environment of an ion source. However, an excessively high proportion of B2F4 increases the complexity and cost of storage, transportation, and process control, while also reducing the proportion of boron trifluoride, altering the optimized reaction equilibrium of the mixed gas, and consequently affecting the B... + and BF2 + The beam intensity. Conversely, too low a filling ratio will not achieve the desired effect.

[0035] In some embodiments, the mixed gas is not additionally filled with hydrogen.

[0036] The mixed gas is filled into a fluid supply container. The filling sequence is to first fill the container with boron fluoride gas, then fill it with hydrogen gas. After filling, the container is removed and rotated to ensure thorough mixing.

[0037] As shown in Figure 1, the mixed gas in the gas container (8) is transported to the arc chamber of the ion source (1) device. The mixed gas is ionized in the arc chamber to form ions. The extraction component (3) extracts the ions to form a preliminary beam. Then, the magnet causes ions of different masses to be deflected in different ways, and the desired ions are selected. High pressure is applied through the acceleration tube (6) to provide kinetic energy for the ions to collide with the lattice atoms of the wafer in the process chamber (7) to achieve directional embedding.

[0038] In some embodiments, when the mixed gas is delivered from a container to the arc chamber at a flow rate of 1 to 2 sccm, the boron ion beam current generated by the gas components is 5 to 6 mA.

[0039] The following are specific implementation experimental examples for verification, which are only used as preferred options to illustrate and verify the process and technical effects of the above preparation process.

[0040] Comparative Example 1: Accurately calculate the required mass or partial pressure for filling with 70% boron trifluoride and 30% hydrogen, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first fill the container with boron trifluoride at a low and steady flow rate. After filling is complete, continue to introduce hydrogen as a buffer component until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for about 10-20 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0041] Comparative Example 2: Accurately calculate the required mass or partial pressure for filling with 80% boron trifluoride and 20% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first fill the container with boron trifluoride at a low and steady flow rate. After filling is complete, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for about 10-20 molecules to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0042] Comparative Example 3: Accurately calculate the required mass or partial pressure for filling 75% boron trifluoride, 22% boron tetrafluoride, and 3% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first, fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0043] Comparative Example 4: Accurately calculate the required mass or partial pressure for filling 84% boron trifluoride, 8% boron tetrafluoride, and 8% silane (SiH4), and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first, fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia gas until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0044] Example 1: Accurately calculate the required mass or partial pressure for filling 90% boron trifluoride and 10% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0045] Example 2: Accurately calculate the required mass or partial pressure for filling 95% boron trifluoride and 5% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0046] Example 3: Accurately calculate the required mass or partial pressure for filling 88% boron trifluoride, 6% boron tetrafluoride, and 6% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first, fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0047] Example 4: Accurately calculate the required mass or partial pressure for filling 85% boron trifluoride, 6% boron tetrafluoride, and 9% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first, fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0048] Example 5: Accurately calculate the required mass or partial pressure for filling 84% boron trifluoride, 8% boron tetrafluoride, and 8% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first, fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0049] Example 6: Accurately calculate the required mass or partial pressure for filling 82% boron trifluoride, 9% boron tetrafluoride, and 9% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first, fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0050] Example 7: Accurately calculate the required mass or partial pressure for filling 80% boron trifluoride, 10% boron tetrafluoride, and 10% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first, fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0051] Example 8: Accurately calculate the required mass or partial pressure for filling 86% boron trifluoride, 9% boron tetrafluoride, and 5% ammonia, and calibrate the relevant high-precision pressure gauges and weighing instruments; then, first, fill the container with boron trifluoride and boron tetrafluoride in sequence at a low and steady flow rate. After filling is completed, continue to introduce ammonia until the pressure reaches the preset total filling pressure; finally, place the gas cylinder horizontally on a rolling machine or rotating frame and roll it at a low speed for at least 30 minutes to ensure uniform mixing. After mixing is complete, let it stand vertically.

[0052] The above examples were subjected to ion implantation cathode weight change tests, with the following basic test conditions: Flow rates: 1 sccm, 1.5 sccm, 2 sccm; Ion source: 25 mA; Arc voltage: 90V; Lead-out voltage: 30 kV; Suppression voltage: 3.5 kV; Experimental mode: Fixed ion source; Test duration: 10 hours.

[0053] Table 1 Different flow rates B + Beam current

[0054] Table 2 shows the weight loss before and after the cathode.

[0055] Comparative Example 1 involved boron trifluoride filled with 30% hydrogen gas. The high proportion of hydrogen gas diluted the relative concentration of effective boron in the dopant gas, resulting in a decrease in the concentration of B... + The ion beam current is too low, which significantly prolongs the injection time.

[0056] In Comparative Example 2, boron trifluoride was filled with 20% ammonia. Similarly, the higher proportion of ammonia resulted in a dilution of the relative concentration of effective boron in the doped gas and a significant decrease in beam intensity, thus prolonging the injection time.

[0057] In Comparative Example 3, which contained 75% boron trifluoride, 22% boron tetrafluoride, and 3% ammonia, the high boron fluoride content resulted in a higher beam current. However, considering the low hydrogen content, a small amount of contaminant deposition occurred at the cathode of the ion source.

[0058] In Comparative Example 4, which contained 84% boron trifluoride, 8% diboron tetrafluoride, and 8% silane (SiH4), silane was used as the hydrogenation gas. No phenomenon was observed in silane that could increase the current in the stream.

[0059] In Examples 1 and 2, 90%~95% boron trifluoride was filled with 5%~10% ammonia. On the one hand, the ammonia promoted the increase of flow rate and current, and on the other hand, the reaction electrode controlled by fluorine free radicals was protected. Therefore, the test weight before and after the cathode was slightly reduced.

[0060] In Examples 3-8, the plasma is sequentially filled with 80%-90% boron trifluoride, 6%-10% boron tetrafluoride, and 5%-10% ammonia. The difference from the previous examples is that the boron fluoride used is boron trifluoride and boron tetrafluoride. The boron tetrafluoride molecule contains two boron atoms; combining it with boron trifluoride increases the supply of boron in the plasma. Furthermore, the BB bond in the B2F4 molecule is relatively weak; in the plasma environment of the ion source, B2F4 is more easily ionized and decomposed than BF3, significantly increasing the boron supply. + and BF2 + The beam current intensity was improved, and by optimizing and controlling the filling ratio of ammonia to boron tetrafluoride to 1:1, it was found that the synergistic effect of ammonia and boron tetrafluoride further improved the beam current, while also effectively reducing the etching rate of fluorine free radicals on the tungsten cathode electrode, controlling the cathode loss within the range of 0 to -0.012g, with only a slight reduction in weight, thus extending the service life of the electrode.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A boron fluoride mixed gas, characterized in that, The mixed gas is sequentially filled into a fluid supply container. The mixed gas consists of a dopant gas and a hydrogenated gas. The dopant gas is boron fluoride, with a volume percentage of 90% to 95% and a volume percentage of 5% to 10% for the hydrogenated gas.

2. The boron fluoride mixed gas according to claim 1, characterized in that, The hydrogenation gas is selected from at least one of NH3, B2H6, and SiH4, or any combination thereof.

3. The boron fluoride mixed gas according to claim 2, characterized in that, Hydrogenated gas consists of only ammonia.

4. The boron fluoride mixed gas according to claim 1, characterized in that, The boron fluoride is selected from at least one of boron trifluoride and diboron tetrafluoride.

5. The boron fluoride mixed gas according to claim 4, characterized in that, The boron fluoride is boron trifluoride and boron tetrafluoride, wherein boron trifluoride accounts for 80% to 90% of the total mixed gas volume percentage, and boron tetrafluoride accounts for 6% to 15% of the total mixed gas volume percentage.

6. The boron fluoride mixed gas according to claim 5, characterized in that, The boron tetrafluoride accounts for 6% to 10% of the total volume of the mixed gas.

7. The boron fluoride mixed gas according to claim 1, characterized in that, The mixed gas does not contain hydrogen.

8. The boron fluoride mixed gas according to claim 1, characterized in that, The mixed gas is filled into a fluid supply container. The filling sequence is to first fill the container with boron fluoride gas, then fill it with hydrogen gas. After filling, the container is removed and rotated to ensure thorough mixing.

9. The application of the boron fluoride mixed gas according to any one of claims 1 to 8 in an ion implantation system, characterized in that, The mixed gas is delivered to the arc chamber of the ion source device, where it is ionized to form an ion beam. The collision of the ion beam with lattice atoms enables the directional insertion of impurities.

10. The application of the boron fluoride mixed gas according to claim 9 in an ion implantation system, characterized in that, When the mixed gas is delivered from a container to the arc chamber at a flow rate of 1 to 2 sccm, the boron ion beam current generated by the gas components is 5 to 6 mA.

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