A method of reducing metal contamination in ion implantation

Abstract

The application provides a method for reducing metal contamination in ion implantation, comprising the following steps: adjusting a source magnetic field current, obtaining a plurality of groups of source magnetic field currents and corresponding ion beam currents; fitting to obtain a first fitting curve; determining a target source magnetic field current according to the source magnetic field current corresponding to the highest point of the first fitting curve; obtaining a plurality of groups of source gas flow corresponding to the ion beam current; fitting to obtain a second fitting curve; determining a target source gas flow according to the source gas flow corresponding to the highest point of the second fitting curve; obtaining a plurality of groups of cathode-heater currents and corresponding ion beam currents; fitting to obtain a third fitting curve; determining a target cathode-heater current according to the cathode-heater current corresponding to the highest point of the third fitting curve; and performing ion implantation by using the target source magnetic field current, the target source gas flow and the target cathode-heater current. The method can make the ion beam current meet the requirements, the arc current is small, and the metal contamination caused by the source cavity is reduced from the source.

Description

Technical Field

[0001] This invention relates to the field of ion implantation technology, and in particular to a method for reducing metal contamination during ion implantation. Background Technology

[0002] Semiconductor devices require ion implantation during the manufacturing process. For example, CIS (CMOS image sensor) requires the use of an implanter to implant pixel zones during the manufacturing process.

[0003] like Figure 1 and Figure 2 As shown, the implantation device includes a source chamber for generating an ion beam 5. The source chamber includes a chamber wall 1, a repeller 2, a cathode 3, and a filament 4. These components are typically made of tungsten. During collisions with these components, electrons and ions in the source chamber cause the tungsten material to dissociate into tungsten ions. These tungsten ions leave the source chamber with the ion beam 5 and enter... Figure 2 The magnetic field screening unit shown in the diagram, during the screening process, due to the difference in atomic mass and charge ratio between tungsten ions and ion beam 5, will cause tungsten ions to concentrate on one side of ion beam 5. After ion beam 5 passes through the beamline (ion beam region), the impact of ion beam 5 on the inner metal wall of the ion beam region will further increase metal contamination. During the implantation of ion beam 5 into the wafer, metal ions will be implanted at the edge of the wafer, resulting in poor white pixel quality in the product due to metal contamination. Figure 3 As shown, since ion implantation involves four steps, the wafer needs to be rotated 90° counterclockwise when switching steps. After the four steps are completed, a square pattern (map) can be formed. The pattern is located in the uncontaminated area 6. The uncontaminated area 6 is usually located in the middle of the wafer, while the contaminated area 7 is usually located at the edge of the wafer. White pixels are usually concentrated in the contaminated area 7.

[0004] To reduce metal contamination, current solutions primarily involve installing a Metals Reduction Kit (MRK) in the ion beam region. This involves placing graphite or a coating on the inner wall of the ion beam region to reduce metal contamination. However, this does not reduce metal contamination from the source cavity at its source. Summary of the Invention

[0005] This invention provides a method for reducing metal contamination in ion implantation, thereby addressing the technical problem that existing solutions cannot reduce metal contamination from the source cavity at its source.

[0006] To address the aforementioned technical problems, this invention provides a method for reducing metal contamination during ion implantation, comprising the following steps:

[0007] Adjust the source magnetic field current to obtain multiple sets of source magnetic field currents and corresponding ion beam currents; fit the multiple sets of source magnetic field currents and corresponding ion beam currents to obtain a first fitting curve; determine the target source magnetic field current based on the source magnetic field current corresponding to the highest point of the first fitting curve;

[0008] Keeping the source magnetic field current constant at the same level as the target magnetic field current, the source gas flow rate is adjusted to obtain multiple sets of source gas flow rates and corresponding ion beam currents; a second fitting curve is obtained by fitting the multiple sets of source gas flow rates and corresponding ion beam currents; the target source gas flow rate is determined based on the source gas flow rate corresponding to the highest point of the second fitting curve.

[0009] Keeping the source gas flow rate constant at the target source gas flow rate, the cathode-filament current between the cathode and the filament is adjusted to obtain multiple sets of cathode-filament currents and corresponding ion beam currents; based on the multiple sets of cathode-filament currents and corresponding ion beam currents, a third fitting curve is obtained; the target cathode-filament current is determined based on the cathode-filament current corresponding to the highest point of the third fitting curve.

[0010] Ion implantation is performed using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current.

[0011] Optionally, the step of determining the target source magnetic field current based on the source magnetic field current corresponding to the highest point of the first fitting curve specifically includes the following steps: taking the source magnetic field current corresponding to the highest point of the first fitting curve as the target source magnetic field current.

[0012] Optionally, the step of determining the target source gas flow rate based on the source gas flow rate corresponding to the highest point of the second fitting curve specifically includes the following steps: taking the source gas flow rate corresponding to the highest point of the second fitting curve as the target source gas flow rate.

[0013] Optionally, the step of determining the target cathode-filament current based on the cathode-filament current corresponding to the highest point of the third fitting curve specifically includes the following steps: taking the cathode-filament current corresponding to the highest point of the third fitting curve as the target cathode-filament current.

[0014] Optionally, between the step of using the cathode-filament current corresponding to the highest point of the third fitted curve as the target cathode-filament current and the step of performing ion implantation using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current, the following step is further included:

[0015] Determine whether the ion beam current corresponding to the target cathode-filament current is equal to a preset threshold. If the ion beam current corresponding to the target cathode-filament current is equal to the preset threshold, then perform the step of ion implantation using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current. If the ion beam current corresponding to the target cathode-filament current is greater than the preset threshold, then decrease the target cathode-filament current. If the ion beam current corresponding to the target cathode-filament current is less than the preset threshold, then increase the target source gas flow rate, and then perform the step of adjusting the cathode-filament current between the cathode and the filament to obtain multiple sets of cathode-filament currents and corresponding ion beam currents.

[0016] Optionally, the expression for the first fitted curve is y1 = a6x 6 +a5x 5 +a4x 4 +a3x 3 +a2x 2 +a1x+a0, where y1 represents the ion beam current, x represents the source magnetic field current, and a6, a5, a4, a3, a2, a1, and a0 represent the fitted coefficients.

[0017] Optionally, the expression for the second fitted curve is y2 = b6x 6 +b5x 5 +b4x 4 +b3x 3 +b2x 2 +b1x+b0, where y2 represents the ion beam current, x represents the source gas flow rate, and b6, b5, b4, b3, b2, b1, and b0 represent the fitted coefficients.

[0018] Optionally, the expression for the third fitted curve is y3 = c6x 6 +c5x 5 +c4x 4 +c3x 3 +c2x 2 +c1x+c0, where y3 represents the ion beam current, x represents the cathode-filament current, and c6, c5, c4, c3, c2, c1, and c0 represent the fitted coefficients.

[0019] Optionally, while performing the step of acquiring multiple sets of source magnetic field currents and corresponding ion beam currents, the following step is also performed: acquiring multiple sets of source magnetic field currents and corresponding arc currents.

[0020] Optionally, while performing the step of obtaining multiple sets of source gas flow rates and corresponding ion beam currents, the following step is also performed: obtaining multiple sets of source gas flow rates and corresponding arc currents.

[0021] This invention provides a method for reducing metal contamination during ion implantation. Through theoretical and statistical analysis, it is determined that the magnitude of the arc current is affected by three parameters: the source magnetic field current, the source gas flow rate, and the cathode-filament current. Therefore, by using the target source magnetic field current, target source gas flow rate, and target cathode-filament current for ion implantation, an unexpected technical effect is that the ion beam current can meet the requirements to complete the ion implantation; furthermore, the arc current is smaller. Due to the smaller arc current, the frequency of collisions between ions and electrons and the cavity wall is lower, which can reduce metal contamination from the source cavity at the source. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the source cavity structure of an implantation device in the prior art.

[0023] Figure 2 This is a schematic diagram of the magnetic field screening unit of an implantation device in the prior art.

[0024] Figure 3 This is a schematic diagram of the structure of a metal-contaminated wafer in the prior art.

[0025] Figure 4 This is a flowchart of a method for reducing metal contamination in ion implantation according to an embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram of the source cavity structure of an implantation device provided in an embodiment of the present invention.

[0027] Figure 6 These are three electron movement paths corresponding to three different magnitudes of source magnetic field current provided in one embodiment of the present invention.

[0028] Figure 7 This is a graph showing the relationship between arc current and the number of white pixels, provided in an embodiment of the present invention.

[0029] Figure 8 This is a diagram showing the relationship between arc current and ion beam current and source magnetic field current, respectively, provided by an embodiment of the present invention.

[0030] Figure 9 This is a graph showing the relationship between arc current and ion beam current and source gas flow rate, provided by an embodiment of the present invention.

[0031] Figure 10 This is a diagram showing the relationship between arc current and ion beam current and cathode-filament current, respectively, provided by an embodiment of the present invention.

[0032] Figure 11 This is a comparison image of the number of white pixels on a wafer before and after optimization, provided by an embodiment of the present invention.

[0033] [The annotations in the attached figures are explained below]:

[0034] Cavity wall-1, reflector-2, cathode-3, filament-4, ion beam-5, uncontaminated area-6, contaminated area-7;

[0035] Arc current - I1, cathode-filament current - I2. Detailed Implementation

[0036] To make the objectives, advantages, and features of the present invention clearer, a method for reducing metal contamination during ion implantation, as proposed by the present invention, will be further described in detail below with reference to the accompanying drawings. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0037] In the description of this invention, the terms "first," "second," and other qualifiers are added for convenience of description and reference, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with qualifiers such as "first" and "second" may explicitly or implicitly include one or more of that feature.

[0038] like Figure 4 As shown, this embodiment provides a method for reducing metal contamination during ion implantation, including the following steps:

[0039] S1, such as Figure 8 As shown, by adjusting the source magnetic field current, multiple sets of source magnetic field currents and corresponding ion beam currents are obtained, such as... Figure 8 As shown, each dot represents a set of source magnetic field currents and corresponding ion beam currents, with a one-to-one correspondence between the source magnetic field currents and ion beam currents. Based on the multiple sets of source magnetic field currents and corresponding ion beam currents, a first fitting curve is obtained, which can be shown as follows: Figure 8 The dashed line indicating the midpoint is shown; optionally, the expression for the first fitted curve is y1 = a6x. 6 +a5x 5 +a4x 4 +a3x 3 +a2x 2+a1x+a0, where y1 represents the ion beam current, x represents the source magnetic field current, and a6, a5, a4, a3, a2, a1, and a0 represent the fitted coefficients; optionally, y1 = 0.1024x 6 -1.3605x 5 +6.8789x 4 -16.344x 3 +16.997x 2 -2.4289x + 5.0479, the goodness of fit R at this point is... 2 =0.9778, indicating a high degree of agreement between the experimental data and the first fitting function; the target source magnetic field current is determined based on the source magnetic field current x1 corresponding to the highest point of the first fitting curve; optionally, the source magnetic field current x1 corresponding to the highest point of the first fitting curve can be used as the target source magnetic field current; in other embodiments, the value of the adjacent source magnetic field current x1 can be used as the target source magnetic field current; wherein, such as Figure 5 and Figure 6 As shown, the source magnetic field current refers to Source Magnet I, i.e., the magnetic field current applied across the source cavity. The source magnetic field current can adjust the magnitude of the magnetic force between the magnetic poles N and S. This magnetic force affects the electron's rotation radius in the magnetic field, and consequently, the collision frequency between the electron and cavity wall I. The electron's rotation radius in the magnetic field is r = mv / qB, where m represents the electron's mass, v represents its velocity, q represents its charge, and B represents the magnetic field strength. Figure 6 As shown, if the source magnetic field current is zero, electrons move along path A, moving in a straight line from filament 4 to cavity wall 1. If the source magnetic field current is within the normal range, electrons move along path B, rotating from filament 4 to reflector 2 with a normal radius of rotation. If the source magnetic field current is too large, electrons move along path C, rotating from filament 4 to reflector 2 with a very small radius of rotation. A suitable radius of rotation can increase the collision frequency between electrons and gas, facilitating gas dissociation. When the gas is fully dissociated, the beam current is at its maximum, at which point the collision frequency between electrons and cavity wall 1 is relatively low, and the arc current I1 is relatively small. Figure 5 and Figure 8 As shown, the arc current I1 refers to the current formed by electrons between the cavity wall 1 and the cathode 3, which is affected by the number of electrons in the source cavity, the magnitude of the magnetic field, and the source gas flow rate. The arc current I1 is a minimum value; the smaller the value, the lower the collision frequency between ions and electrons and the cavity wall 1, and the less metal contamination may occur. For example, as... Figure 7 As shown, the inventors determined through theoretical and statistical analysis that the smaller the arc current I1, the smaller the number of white pixels. Therefore, as Figure 8As shown, the source magnetic field current x1 corresponding to the highest point of the first fitted curve is the optimal source magnetic field current.

[0040] S2, such as Figure 9 As shown, keeping the source magnetic field current constant at the same level as the target magnetic field current, the source gas flow rate is adjusted to obtain multiple sets of source gas flow rates and corresponding ion beam currents. Based on the multiple sets of source gas flow rates and corresponding ion beam currents, a second fitting curve is obtained. The second fitting curve can be shown as follows: Figure 9 The dashed line indicating the midpoint is shown; optionally, the expression for the second fitted curve is y2 = b6x. 6 +b5x 5 +b4x 4 +b3x 3 +b2x 2 +b1x+b0, where y2 represents the ion beam current, x represents the source gas flow rate, and b6, b5, b4, b3, b2, b1, and b0 represent the fitted coefficients; optionally, y2 = 0.2049x 6 -1.0688x 5 -4.2592x 4 +44.775x 3 -129.66x 2 +163.51x-72.646, the goodness of fit R at this point is... 2 =0.9952, indicating a high degree of agreement between the experimental data and the second fitting function; the target source gas flow rate is determined based on the source gas flow rate x2 corresponding to the highest point of the second fitting curve; optionally, the source gas flow rate x2 corresponding to the highest point of the second fitting curve can be used as the target source gas flow rate; in other embodiments, the value of the adjacent source gas flow rate x2 can be used as the target source gas flow rate; wherein, the source gas flow rate refers to the amount of gas flowing into the source cavity, which affects the magnitude of the ion beam current and the frequency of electron collisions with the cavity wall 1. Because the number of electrons in the source cavity is fixed, increasing the source gas flow rate can reduce the frequency of electron collisions with the cavity wall 1, thereby reducing the arc current I1. When the source gas flow rate reaches a certain critical value, further increasing the source gas flow rate will increase the number of gas molecules, which will instead inhibit gas dissociation. Therefore, the source gas flow rate x2 corresponding to the highest point of the second fitting curve is the optimal source gas flow rate.

[0041] S3, such as Figure 5 and Figure 10 As shown, keeping the source gas flow rate constant at the target source gas flow rate, the cathode-filament current I2 between the cathode 3 and the filament 4 is adjusted to obtain multiple sets of cathode-filament currents I2 and corresponding ion beam currents; based on the multiple sets of cathode-filament currents I2 and corresponding ion beam currents, a third fitting curve is obtained, which can be shown as follows: Figure 10The dashed line indicating the midpoint is shown; optionally, the expression for the third fitted curve is y3 = c6x. 6 +c5x 5 +c4x 4 +c3x 3 +c2x 2 +c1x+c0, where y3 represents the ion beam current, x represents the cathode-filament current, and c6, c5, c4, c3, c2, c1, and c0 represent the fitted coefficients; optionally, y3 = -8014.4x 6 +135458x 5 -952021x 4 +4E+06x 3 -7E+06x 2 +8E+06x-4E+06, at this point the goodness of fit R 2 =0.9973, indicating a high degree of agreement between the experimental data and the third fitting function; the target cathode-filament current is determined based on the cathode-filament current x3 corresponding to the highest point of the third fitting curve; optionally, the cathode-filament current x3 corresponding to the highest point of the third fitting curve can be used as the target cathode-filament current; in other embodiments, the value of the nearest cathode-filament current x3 can be used as the target cathode-filament current; wherein, as... Figure 5 As shown, the cathode-filament current I2 refers to the current between the cathode 3 and the filament 4, which affects the magnitude of the ion beam current and the arc current I1. Increasing the cathode-filament current I2 increases the number of electrons in the source cavity, raising the frequency of electron-gas collisions to facilitate gas dissociation, thereby increasing the ion beam current. If the number of electrons continues to increase beyond a certain critical value, the collisions of the electrons themselves will actually affect the collisions with the gas, hindering gas dissociation and leading to a decrease in the ion beam current. Therefore, the cathode-filament current x3 corresponding to the highest point of the third fitted curve is the optimal cathode-filament current.

[0042] S4. Ion implantation is performed using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current. After determining these three parameters, the ion implantation machine can use them to perform ion implantation on the wafer. For example... Figure 11 As shown, when performing ion implantation using the method for reducing metal contamination during ion implantation provided in this embodiment, the number of white pixels is significantly reduced compared to before optimization.

[0043] This embodiment provides a method for reducing metal contamination during ion implantation. Through theoretical and statistical analysis, it is determined that the magnitude of the arc current I1 is affected by three parameters: the source magnetic field current, the source gas flow rate, and the cathode-filament current I2. Therefore, by using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current for ion implantation, an unexpected technical effect is that the ion beam current can meet the requirements to complete the ion implantation. Furthermore, a smaller arc current I1 results in a lower frequency of collisions between ions and electrons and the cavity wall 1, which can reduce metal contamination from the source cavity at the source.

[0044] Optional, see reference Figure 10 As shown, between steps S3 and S4, there is an additional step: between the step of using the cathode-filament current corresponding to the highest point of the third fitting curve as the target cathode-filament current and the step of performing ion implantation using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current, there is an additional step: determining whether the ion beam current corresponding to the target cathode-filament current is equal to a preset threshold; if the ion beam current corresponding to the target cathode-filament current is equal to the preset threshold, then performing the step of performing ion implantation using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current; if the ion beam current corresponding to the target cathode-filament current is greater than the preset threshold, then decreasing the target cathode-filament current; if the ion beam current corresponding to the target cathode-filament current is less than the preset threshold, then increasing the target source gas flow rate, and then performing the step of adjusting the cathode-filament current between the cathode and the filament to obtain multiple sets of cathode-filament currents and corresponding ion beam currents.

[0045] During ion implantation, the ion beam current sometimes needs to be adjusted to a preset, suitable value. If the ion beam current corresponding to the target cathode-filament current determined in step S3 above is equal to the preset threshold, step S4 above can be executed directly. If the ion beam current corresponding to the target cathode-filament current determined in step S3 above is greater than the preset threshold, the target cathode-filament current can be reduced. Reducing the target cathode-filament current can reduce the magnitude of the ion beam current and the arc current I1. Reducing the arc current I1 can reduce metal contamination from the source cavity at the source. If the ion beam current corresponding to the target cathode-filament current determined in step S3 above is less than the preset threshold, the target source gas flow rate can be increased, and then the step of adjusting the cathode-filament current I2 between the cathode and filament can be executed to obtain multiple sets of the cathode-filament current I2 and the ion beam current, so as to obtain an updated third fitting curve. Then, the updated target cathode-filament current is determined based on the updated third fitting curve. Increasing the target source gas flow rate can increase the ion beam current corresponding to the updated target cathode-filament current, thereby making the ion beam current meet the requirements.

[0046] Optional, such as Figure 8 As shown, while performing the step of acquiring multiple sets of source magnetic field currents and corresponding ion beam currents, the following step is also performed: acquiring multiple sets of source magnetic field currents and corresponding arc currents. The arc current is as follows... Figure 8 As shown in the triangle diagram, by measuring multiple sets of source magnetic field currents and corresponding arc currents, a fitting curve between the source magnetic field current and the arc current can be obtained. This fitting curve is shown in the diagram. Figure 8 As shown by the dashed line containing the middle triangle, the changing trends of this fitted curve and the first fitted curve can further verify the rationality of using the target source magnetic field current for ion implantation. Optionally, as... Figure 9 As shown, while performing the step of acquiring multiple sets of source gas flow rates and corresponding ion beam currents, the following step is also performed: acquiring multiple sets of source gas flow rates and corresponding arc currents. The arc current is as follows... Figure 9 As shown in the triangle, by measuring multiple sets of source gas flow rates and corresponding arc currents, a fitting curve between the source gas flow rate and arc current can be obtained. This fitting curve is shown in the figure. Figure 9 As shown by the dashed line containing the triangle, the changing trends of the fitted curve and the second fitted curve can further verify the rationality of using the target source gas flow rate for ion implantation.

[0047] Optional, such as Figure 10 As shown, while performing the step of acquiring multiple sets of cathode-filament currents and corresponding ion beam currents, the following step is also performed: acquiring multiple sets of cathode-filament currents and corresponding arc currents. The arc current is as follows... Figure 10As shown in the triangle, by measuring multiple sets of cathode-filament currents and corresponding arc currents, a fitting curve between the cathode-filament current and the arc current can be obtained. This fitting curve is shown in the figure. Figure 10 As shown by the dashed line containing the middle triangle, the changing trends of this fitting curve and the third fitting curve can further verify the rationality of using the target cathode-filament current for ion implantation.

[0048] In summary, the present invention provides a method for reducing metal contamination during ion implantation. Through theoretical and statistical analysis, it has been determined that the magnitude of the arc current I1 is affected by three parameters: the source magnetic field current, the source gas flow rate, and the cathode-filament current I2. Therefore, by using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current for ion implantation, an unexpected technical effect is that the ion beam current can meet the requirements to complete the ion implantation. Furthermore, a smaller arc current I1 results in a lower frequency of collisions between ions and electrons and the cavity wall 1, which can reduce metal contamination from the source cavity at the source.

[0049] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the present invention.

Claims

1. A method for reducing metal contamination during ion implantation, characterized in that, Includes the following steps: Adjust the source magnetic field current to obtain multiple sets of source magnetic field currents and corresponding ion beam currents; Based on the multiple sets of source magnetic field currents and the corresponding ion beam currents, a first fitting curve is obtained; The target source magnetic field current is determined based on the source magnetic field current corresponding to the highest point of the first fitted curve. Keeping the source magnetic field current constant at the target source magnetic field current, the source gas flow rate is adjusted to obtain multiple sets of source gas flow rates and corresponding ion beam currents; Based on the multiple sets of source gas flow rates and corresponding ion beam currents, a second fitting curve is obtained; The target source gas flow rate is determined based on the source gas flow rate corresponding to the highest point of the second fitted curve. Keeping the source gas flow rate constant at the target source gas flow rate, the cathode-filament current between the cathode and the filament is adjusted to obtain multiple sets of cathode-filament currents and corresponding ion beam currents; based on the multiple sets of cathode-filament currents and corresponding ion beam currents, a third fitting curve is obtained; the target cathode-filament current is determined based on the cathode-filament current corresponding to the highest point of the third fitting curve. Ion implantation is performed using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current. Between the step of using the cathode-filament current corresponding to the highest point of the third fitted curve as the target cathode-filament current and the step of performing ion implantation using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current, the following steps are also included: Determine whether the ion beam current corresponding to the target cathode-filament current is equal to a preset threshold. If the ion beam current corresponding to the target cathode-filament current is equal to the preset threshold, then perform the step of ion implantation using the target source magnetic field current, the target source gas flow rate, and the target cathode-filament current. If the ion beam current corresponding to the target cathode-filament current is greater than the preset threshold, then the target cathode-filament current is reduced; if the ion beam current corresponding to the target cathode-filament current is less than the preset threshold, then the target source gas flow rate is increased, and then the steps of adjusting the cathode-filament current between the cathode and the filament are performed to obtain multiple sets of cathode-filament currents and corresponding ion beam currents are executed.

2. The method for reducing metal contamination during ion implantation as described in claim 1, characterized in that, The step of determining the target source magnetic field current based on the source magnetic field current corresponding to the highest point of the first fitting curve specifically includes the following steps: taking the source magnetic field current corresponding to the highest point of the first fitting curve as the target source magnetic field current.

3. The method for reducing metal contamination during ion implantation as described in claim 1, characterized in that, The step of determining the target source gas flow rate based on the source gas flow rate corresponding to the highest point of the second fitting curve specifically includes the following steps: taking the source gas flow rate corresponding to the highest point of the second fitting curve as the target source gas flow rate.

4. The method for reducing metal contamination during ion implantation as described in claim 1, characterized in that, The step of determining the target cathode-filament current based on the cathode-filament current corresponding to the highest point of the third fitting curve specifically includes the following steps: taking the cathode-filament current corresponding to the highest point of the third fitting curve as the target cathode-filament current.

5. The method for reducing metal contamination during ion implantation as described in claim 1, characterized in that, The expression for the first fitted curve is y1=a6x 6 +a5x 5 +a4x 4 +a3x 3 +a2x 2 +a1x+a0, where y1 represents the ion beam current, x represents the source magnetic field current, and a6, a5, a4, a3, a2, a1, and a0 represent the fitted coefficients.

6. The method for reducing metal contamination during ion implantation as described in claim 1, characterized in that, The expression for the second fitted curve is y2=b6x 6 +b5x 5 +b4x 4 +b3x 3 +b2x 2 +b1x+b0, where y2 represents the ion beam current, x represents the source gas flow rate, and b6, b5, b4, b3, b2, b1, and b0 represent the fitted coefficients.

7. The method for reducing metal contamination during ion implantation as described in claim 1, characterized in that, The expression for the third fitted curve is y3=c6x 6 +c5x 5 +c4x 4 +c3x 3 +c2x 2 +c1x+c0, where y3 represents the ion beam current, x represents the cathode-filament current, and c6, c5, c4, c3, c2, c1, and c0 represent the fitted coefficients.

8. The method for reducing metal contamination during ion implantation as described in claim 1, characterized in that, While performing the step of acquiring multiple sets of source magnetic field currents and corresponding ion beam currents, the following step is also performed: acquiring multiple sets of source magnetic field currents and corresponding arc currents.

9. The method for reducing metal contamination during ion implantation as described in claim 1, characterized in that, While performing the step of acquiring multiple sets of source gas flow rates and corresponding ion beam currents, the following step is also performed: acquiring multiple sets of source gas flow rates and corresponding arc currents.

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