A method for improving carbon ion beam of ion implanter

Abstract

The present invention provides a method for improving the carbon ion beam of an ion implanter, which comprises the following steps: step S1, selecting an improved time node; step S2, improving the carbon ion beam of ion implantation; step S3, when the machine is idle, using argon to keep the ion source at a high temperature, rather than shutting down the beam to cool the ion source. The present invention uses a low-cost and easy-to-operate method for improving the carbon ion beam of an ion implanter to effectively solve the occurrence of beam instability, sparking and the like caused by deposits in carbon ion implantation, increase the stability of ion implantation production, and increase the service life of the ion source during carbon ion beam implantation. The present invention uses boron trifluoride (BF3) gas to adjust or improve operations, effectively solving the problem of deposits in the ion source.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor equipment, and in particular relates to a method for improving the carbon ion beam of an ion implanter. Background Art

[0002] In the current high-end chip manufacturing process, carbon ion implantation is an important step. The main purpose of carbon implantation is to amorphize the single crystal structure in the wafer and limit the diffusion and stress generated by other ions during the annealing process. However, during the carbon ion implantation process, carbon ions are prone to produce deposits in the ion source, causing beam instability, sparking and other adverse phenomena, affecting the ion implantation process and reducing the life of the ion source. For example, Figure 1 As shown in Figure 1, tungsten carbide forms near the hotter cathode in the ion source, and tungsten oxide forms at the cooler counter cathode. These deposits can degrade ion source performance and cause beam instabilities.

[0003] People are trying to find ways to solve the deposition problem caused by carbon ion implantation. In the case of the difficulty of hardware replacement of carbon ion implantation mechanism, people have thought of using other gases to improve the condition after carbon ion implantation to reduce the rate of deposition. Phosphine (PH3) is a gas commonly used for improvement after carbon ion implantation. It is used to remove carbon ions and carbon monoxide (CO) gas left in the ion source after carbon ion implantation and solve the generation of deposition in the ion source.

[0004] However, existing improvement methods have limited effects on solving the problem of carbon deposits in the ion source. At the same time, phosphorus ions produced in phosphine (PH3) will also be deposited at the absorption electrode of the ion implanter, resulting in the instability of the beam and sparking during carbon ion implantation. It is impossible to fundamentally improve the phenomenon.

[0005] Therefore, finding an improvement method that can effectively solve the generation of carbon deposits in the ion source without causing other adverse effects is of great significance for extending the service life of the ion source and increasing the production capacity of the ion implanter. Summary of the invention

[0006] Based on the problems existing in the prior art, the present invention provides a method for improving the carbon ion beam of an ion implanter, which is a low-cost and easy-to-operate method for solving the problem of deposits easily generated during carbon ion implantation.

[0007] According to the technical solution of the present invention, the present invention provides a method for improving the carbon ion beam of an ion implanter, which comprises the following steps:

[0008] Step S1, improved time node selection;

[0009] Step S2, improving the carbon ion beam for ion implantation;

[0010] Step S3, when the machine is in an idle state, argon gas is used to keep the ion source at a high temperature instead of turning off the beam to allow the ion source to cool down.

[0011] In the selection of the time node for improvement in step S1, the improvement operation is performed after the carbon ion beam runs for a set time period threshold. Further, the time period threshold is set to 1.5 hours to 4 hours.

[0012] Preferably, the time period threshold is set to 2 hours.

[0013] Further, step S2 of improving the carbon ion beam of ion implantation comprises the following steps:

[0014] Step S21, turning on the argon gas and adjusting the gas flow rate to a set flow rate value of the argon gas;

[0015] Step S22, closing the gas flow of phosphine used as auxiliary gas for ion implantation to 0 sccm, and closing the gas flow of carbon monoxide to 0 sccm;

[0016] Step S23, opening the boron trifluoride gas valve and adjusting the gas flow rate to 2.5 sccm;

[0017] Step S24, closing the gas flow rate of argon gas to 0 sccm;

[0018] Step S25, adjusting the boron trifluoride beam current and maintaining the boron trifluoride beam current for a specified time;

[0019] Step S26, turning on the argon gas and adjusting the gas flow to a set flow.

[0020] Preferably, the set flow rate value of the argon gas is based on an experimental verification value. More preferably, the set flow rate value of the argon gas is determined based on the amount of tungsten carbide generated near the cathode with a higher temperature in the ion source during the first three months of ion implantation, or the amount of tungsten oxide generated at the counter cathode with a lower temperature during the first three months of ion implantation.

[0021] More preferably, the set flow rate value of argon gas is inversely proportional to the time period of improvement of the subsequent specified flow rate of boron trifluoride gas.

[0022] Furthermore, the set flow value of the argon gas in step S21 is 1 sccm. The beam flow of boron trifluoride at the specified time in step S25 is associated with the argon gas flow rate adjusted to the set flow value of the argon gas in step S21.

[0023] Compared with the prior art, the method of improving the carbon ion beam of an ion implanter of the present invention has the following beneficial technical effects:

[0024] 1. The low-cost and easy-to-operate method for improving the carbon ion beam of the ion implanter effectively solves the beam instability and sparking caused by deposits during carbon ion implantation, increases the stability of ion implantation production, and improves the service life of the ion source during carbon ion beam implantation.

[0025] 2. The present invention uses boron trifluoride (BF3) gas to adjust or improve operation, effectively solving the problem of deposits in the ion source. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the deposit situation in the ion source after ion implantation using an existing carbon ion beam.

[0027] Figure 2 It is a logical flow chart of the method for improving the carbon ion beam of an ion implanter according to the present invention.

[0028] Figure 3 is a schematic diagram of a carbon beam flow before improvement according to the method of the present invention.

[0029] Figure 4 Schematic diagram of a first improved carbon beam flow according to the method of the present invention.

[0030] Figure 5 Schematic diagram of the second improved carbon beam flow according to the method of the present invention.

[0031] Figure 6 Schematic diagram of carbon beam flow after four days of multiple improvements according to the method of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0034] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0035] It should be noted that the modifications of "one" and "plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0036] The present invention provides a method for improving the carbon ion beam of an ion implanter. The present invention utilizes ions generated by boron trifluoride (BF3) gas to react with deposits such as tungsten carbide to generate non-deposits to reduce deposits generated during carbon ion implantation, while ensuring that high temperature conditions are maintained in the ion source to reduce the generation of deposits. The present invention solves the problem of easy generation of deposits during carbon ion implantation, and reduces the corrosion of the BF3 gas on the ion source cavity by controlling the improvement time, thereby achieving the purpose of protecting the ion source and extending the life of the ion source.

[0037] A method for improving the carbon ion beam of an ion implanter of the present invention comprises the following steps:

[0038] Step S1, selection of time node for improvement. The improvement operation is performed after the carbon ion beam runs for a set time period threshold, and the set time period threshold is preferably 1.5 hours to 4 hours, preferably 2 hours; if the set time period threshold is exceeded, a longer operation time and a larger carbon ion beam current will increase the ignition frequency and increase the adjustment time.

[0039] Step S2, detailed steps of improving the carbon ion beam for ion implantation:

[0040] Step S21, turn on the argon gas and adjust the gas flow to the set flow value of the argon gas. The set flow value of the argon gas is based on the experimental verification value; preferably, the set flow value of the argon gas is determined by the amount of tungsten carbide generated near the cathode with a higher temperature in the ion source during the previous three months of ion implantation, or the amount of tungsten oxide generated at the counter cathode with a lower temperature during the previous three months of ion implantation; further, the set flow value of the argon gas is inversely proportional to the time period of improvement of the subsequent specified flow rate of boron trifluoride (BF3) gas, that is, the shorter the duration of the specified flow rate of boron trifluoride (BF3) gas, the greater the required set flow value of the argon gas. In the present invention, the set flow value of the argon gas is preferably 1 sccm; (standard liter per minute flow value, volume flow unit, gas volume flow refers to the volume of gas flowing through the delivery pipeline per unit time);

[0041] Step S22, closing the gas flow of phosphine (PH3) used as an auxiliary gas for ion implantation to 0 sccm, and closing the gas flow of carbon monoxide (CO) to 0 sccm;

[0042] Step S23, open the boron trifluoride (BF3) gas valve and adjust the gas flow rate to 2.5 sccm;

[0043] Step S24, closing the gas flow rate of Argon to 0 sccm;

[0044] Step S25, adjusting the boron trifluoride (BF3) beam current and maintaining the boron trifluoride (BF3) beam current for a specified time, wherein the boron trifluoride (BF3) beam current for the specified time is associated with the argon (Argon) gas flow rate adjusted to the set flow rate value of the argon (Argon) gas in step S21; in a preferred embodiment of the present invention, maintaining the boron trifluoride (BF3) beam current for a specified time of 20 minutes, and the corresponding set flow rate value of the argon (Argon) gas is 1 sccm;

[0045] Step S26, turn on the argon gas to adjust the gas flow to a set flow, preferably 2.5 sccm; then turn off the boron trifluoride (BF3) gas, adjust the argon beam flow, and maintain the argon beam flow improvement for a specified time, preferably 20 minutes; in this step S26, the product of the argon gas adjustment gas flow and the argon beam flow improvement time is 50 sccm*minute; adjust or control according to actual needs;

[0046] In step S3, when the machine is in an idle state, argon gas is used to keep the ion source at a high temperature instead of turning off the beam to allow the ion source to cool down.

[0047] Further, by turning on the argon gas to maintain the ion source temperature, and then turning on the BF3 gas and adjusting the beam current, the BF3 is used for improvement (adjustment). After the improvement (adjustment) is completed, the argon gas is turned on again and the beam current is adjusted to maintain the ion source temperature and remove the BF3 residue, thus completing the improvement (adjustment).

[0048] like Figure 2 As shown, it shows a further schematic flow chart of the method for improving the carbon ion beam of the ion implanter of the present invention. It is embedded in the ion implantation process and is closely connected with the carbon ion implantation process. Figure 2 As shown, the method for improving the carbon ion beam of an ion implanter includes:

[0049] Step S1, selection of the time node for improvement. Whether the carbon ion implantation is completed is used as the basis for judgment. If the implantation time reaches 2 hours, the argon gas is turned on to maintain the ion source temperature, that is, the cycle step of improving the carbon ion beam of ion implantation is entered; the cycle step of improving the carbon ion beam of ion implantation is also the cycle step of improving the implantation quality of the carbon ion beam of the ion implanter. If the implantation time does not reach 2 hours, the ion implantation is continued and the judgment of the length of the ion implantation time is continued.

[0050] The cycle steps for improving the carbon ion beam of ion implantation start from turning on the argon gas to maintain the ion source temperature, that is, entering step S2. The detailed steps for improving the carbon ion beam of ion implantation are:

[0051] Step S21, turn on the argon gas and adjust the gas flow rate to 1 sccm; (standard liter per minute flow rate value, volume flow unit, gas volume flow rate refers to the volume of gas flowing through the delivery pipeline per unit time);

[0052] Step S22, closing the gas flow of phosphine (PH3) used as an auxiliary gas for ion implantation to 0 sccm, and closing the gas flow of carbon monoxide (CO) to 0 sccm;

[0053] Step S23, opening the boron trifluoride (BF3) gas valve and adjusting the gas flow rate, preferably to 2.5 sccm;

[0054] Step S24, closing the gas flow rate of Argon to 0 sccm;

[0055] Step S25, adjusting the boron trifluoride (BF3) beam current and maintaining the boron trifluoride (BF3) beam current for 20 minutes, and continuously improving and adjusting the carbon ion beam of the ion implanter;

[0056] Step S26, after judging that the beam of boron trifluoride (BF3) is maintained for 20 minutes, the argon gas valve is opened, and the argon gas flow rate is adjusted to 2.5 sccm, and then the boron trifluoride (BF3) gas is turned off; the argon beam is adjusted, and the argon beam is maintained to be continuously improved for 20 minutes; at this point, the continuous improvement and adjustment of the carbon ion beam of the ion implanter is basically completed;

[0057] Step S3, judging the idle state of the machine, which is used as a judgment condition for ending the carbon ion beam of the ion implanter; if the machine is in an idle state, the argon beam is maintained to maintain the temperature of the ion source to ensure continuous improvement of the carbon ion beam of the ion implanter; if the machine is occupied or not in an idle state, the beam is turned off to allow the ion source to cool down and enter the ion implantation stage.

[0058] The method for improving the carbon ion beam of an ion implanter using the present invention effectively solves the occurrence of beam instability, sparking and the like caused by deposits during carbon ion implantation, increases the stability of ion implantation production, and increases the service life of the ion source during carbon ion beam implantation. Furthermore, the present invention uses boron trifluoride (BF3) gas for adjustment or improvement of operation, effectively solving the problem of deposits in the ion source.

[0059] Figure 3 is a schematic diagram of a carbon beam flow before improvement according to the method of the present invention. Figure 4 Schematic diagram of a first improved carbon beam flow according to the method of the present invention. Figure 5 Schematic diagram of the second improved carbon beam flow according to the method of the present invention. Figure 6 Schematic diagram of carbon beam flow after four days of multiple improvements according to the method of the present invention.

[0060] like Figure 3-Figure 6 As shown, Figure 3 This is the beam current condition when no improvement (adjustment) is performed after carbon ion beam implantation. Figure 3 The figure above shows the beam size feedback value, Figure 3 The following figure shows the absorption electrode current feedback value, from Figure 3 From the above figure, we can see that the carbon ion beam is unstable after ion implantation, and there are many sparking phenomena with high frequency. The change of the absorption electrode current corresponds to it, indicating that the quality of the carbon ion beam and the ion source are poor at this time, and it is not suitable for further ion implantation.

[0061] Figure 4 To perform an improved (adjusted) carbon ion beam, Figure 4 The figure above shows the beam size feedback value, Figure 4 The following figure shows the absorption electrode current feedback value, from Figure 4 It can be seen that after an improvement (adjustment), the frequency of sparking has decreased.

[0062] Figure 5 This is the carbon ion beam after two improvements (adjustments). Figure 5 The figure above shows the beam size feedback value, Figure 5 The following figure shows the absorption electrode current feedback value, from Figure 5 It can be seen that the frequency of sparking phenomenon is further reduced.

[0063] Figure 6 To improve (adjust) the carbon ion beam condition after 4 days using the method of the present invention, Figure 6 It can be seen that the beam stability has been significantly improved, the sparking phenomenon has disappeared, and the quality of the carbon ion beam has been greatly improved.

[0064] from Figure 3-Figure 6 It can be seen from the comparison that after using the method of the present invention for improvement (adjustment), the quality of the carbon ion beam is significantly improved, the beam current is more stable, the ignition frequency is significantly reduced, and the ion beam is more suitable for ion implantation production. The improvement (adjustment) method has a significant effect.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the carbon ion beam of an ion implanter, characterized in that: It includes the following steps: Step S1, selecting a time node for improvement; in the selection of the time node for improvement in step S1, the improvement operation is performed after the carbon ion beam runs for a set time period threshold, and the set time period threshold is 1.5 hours to 4 hours; Step S2, improving the carbon ion beam for ion implantation; Step S3, when the machine is in an idle state, argon gas is used to keep the ion source at a high temperature instead of turning off the beam to allow the ion source to cool down; Step S2 improves the carbon ion beam for ion implantation and includes the following steps: Step S21, turning on the argon gas and adjusting the gas flow rate to a set flow rate value of the argon gas; Step S22, closing the gas flow of phosphine used as auxiliary gas for ion implantation to 0 sccm, and closing the gas flow of carbon monoxide to 0 sccm; Step S23, opening the boron trifluoride gas valve and adjusting the gas flow rate to 2.5 sccm; Step S24, closing the gas flow rate of argon gas to 0 sccm; Step S25, adjusting the boron trifluoride beam current and maintaining the boron trifluoride beam current for a specified time; Step S26, turning on the argon gas and adjusting the gas flow to a set flow.

2. The method for improving the carbon ion beam of an ion implanter according to claim 1, characterized in that: Set the time period threshold to 2 hours.

3. The method for improving the carbon ion beam of an ion implanter according to claim 1, characterized in that: The set flow value of argon gas is based on the experimental verification value.

4. The method for improving the carbon ion beam of an ion implanter as claimed in claim 3, characterized in that: The set flow value of the argon gas is determined based on the amount of tungsten carbide generated near the higher temperature cathode in the ion source during the first three months of ion implantation, or the amount of tungsten oxide generated at the lower temperature counter cathode during the first three months of ion implantation.

5. The method for improving the carbon ion beam of an ion implanter as claimed in claim 3, characterized in that: The set flow rate value of the argon gas is inversely proportional to the time period for improvement of the subsequent specified flow rate of the boron trifluoride gas.

6. The method for improving the carbon ion beam of an ion implanter as claimed in claim 3, characterized in that: The set flow rate value of the argon gas in step S21 is 1 sccm.

7. The method for improving the carbon ion beam of an ion implanter as claimed in claim 3, characterized in that: The beam flow of boron trifluoride at the specified time in step S25 is associated with the argon gas flow rate adjusted to the set flow value of the argon gas in step S21.

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