Method and system for reducing white pixel generation by f ion implantation on cis products

Abstract

The application discloses a method and system for reducing white pixel caused by F ion implantation on CIS products, wherein the method comprises the following steps: if the current machine implantation gas source is a predetermined gas source with reducing property, it is determined whether there is a batch of F ion implantation; if yes, the machine implantation gas is switched, and the first batch of F ion implantation is completed; it is continuously determined whether there is a second batch of F ion implantation; if yes, the machine switches the gas source, and the predetermined gas source with reducing property is implanted, and the corresponding product batch is processed; after the corresponding product batch is completed, the machine switches the gas source, and the second batch of F ion implantation is processed; the cycle is repeated until all batches of F ion implantation are completed. The application can effectively avoid the white pixel defect and improve the product quality.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and more particularly to a method and system for reducing the generation of white pixels on CIS products by F ion implantation. Background Technology

[0002] In CIS (CMOS Image Sensor) products, to reduce noise interference, F ions can be implanted into the polysilicon gate (Pixel Poly) formed in the CIS pixel area. During the annealing process, F ions diffuse from the polysilicon layer (poly) into the gate oxide layer (Gate Oxide). These F ions passivate the dangling bonds at the Si-SiO2 interface, thereby reducing defects in the gate oxide layer and improving the noise effect in CMOS devices.

[0003] During F-ion implantation, higher energy or concentration significantly improves upon POR (Plan of Record). However, in actual production (i.e., wafers entering the production line to complete semiconductor product manufacturing), it was found that while F-ion implantation improves noise, it also produces white pixels. Further analysis revealed that this is related to the duration of F-ion implantation during the production process; the longer the implantation time, the more white pixel defects are produced.

[0004] The F ion implantation time and ICPMS (metal element content analysis) were verified on two machines (e.g., machine 1 and machine 2). The results showed that the F ion implantation time of metal ions such as Fe, W, Cu, and Ni gradually increased with the F ion implantation time and then tended to stabilize after a certain period of time. Among them, the Fe / Ca ratio had the strongest correlation with the F IMP (ion implantation) time.

[0005] Based on experimental verification and relevant data analysis, Cu, Ni, Fe, W, and Mo are more prone to transition between the valence band and conduction band, leading to dark current deterioration (an abnormal increase in leakage current in devices under no-light conditions, resulting in decreased signal-to-noise ratio, increased image noise, or device performance degradation). Because the mass-to-charge ratio of F and Fe ions is close to 19, the 90 AMU (mass screening, which only allows ions with specific mass-to-charge ratios to pass through; different elements have different mass-to-charge ratios, resulting in different deflection radii in the magnetic field; here, it's a 90-degree deflection to achieve the screening purpose) cannot accurately screen out Fe ions (the root cause). Fe ions are then implanted into the wafer along with the ion beam, leading to white pixel defects.

[0006] Analysis of the source of Fe ions revealed that because the high-current ion implanter lacks graphite coating in the ion source and triaxial regions, the F ions generated during BF3 dissociation possess strong oxidizing properties. When the ion beam contacts the surface of the ion source and triaxial regions, it corrodes the component surface, forming Fe ions. Therefore, removing Fe ions is crucial. Summary of the Invention

[0007] The main objective of this invention is to provide a method and system for effectively removing Fe ions during the CIS product manufacturing process and reducing the generation of white pixels by F ion implantation on CIS products.

[0008] The technical solution adopted in this invention is:

[0009] A method for reducing white pixels generated by F ion implantation on CIS products is provided, comprising the following steps:

[0010] If the gas source injected by the current machine is a predetermined reducing gas source, then determine whether there is a batch of F ions to be injected. If so, switch the gas source injected by the machine to complete the first batch of F ion injection.

[0011] Continue to determine if there is a second batch of F ion implantation. If so, switch the gas source of the machine to a pre-determined reducing gas source and process the corresponding product batch.

[0012] After completing the corresponding batch of products, switch the gas source of the machine to process the second batch of F ion implantation; repeat this cycle until all batches requiring F ion implantation are completed.

[0013] According to the above technical solution, the difference in mass-to-charge ratio between the main ions and iron ions in the reducing gas source is higher than the preset value.

[0014] According to the above technical solution, when a certain batch is completed, if there is an urgent batch that needs to be processed first, the machine will switch to process the urgent batch.

[0015] Following the above technical solution, if there is no batch that requires F-ion implantation, the machine will process the product batch according to the established dispatching logic.

[0016] Following the above technical solution, in the established dispatching logic, product batches with the same injected gas are processed first.

[0017] Following the above technical solution, the reducing gas source is arsine or phosphine.

[0018] Following the above technical solution, arsine is the preferred reducing gas source.

[0019] According to the above technical solution, the mass-to-charge ratio of the main ion is at least twice that of the iron ion.

[0020] Following the above technical solution, when the machine completes other product batches between processing two batches that require F ion implantation, the energy, current, or duration of the ion beam injected with the reducing gas source is greater than a preset threshold.

[0021] The present invention also provides a system for reducing white pixels generated by F ion implantation on CIS products. The system includes a control switching module, which is used to determine whether there is a batch of F ion implantation when the current injection gas source of the machine is a predetermined reducing gas source. If so, the injection gas source of the machine is switched to complete the first batch of F ion implantation. Then, the system continues to determine whether there is a second batch of F ion implantation. If so, the system controls the machine to switch the gas source to inject the predetermined reducing gas source to process the corresponding product batch. After the corresponding product batch is completed, the system controls the machine to switch the gas source again to process the second batch of F ion implantation. This cycle is repeated until all batches requiring F ion implantation are completed.

[0022] The beneficial effects of this invention are as follows: When manufacturing CIS products, this invention breaks through the original machine's predetermined dispatching logic. Between two batches requiring F ion implantation, a batch of products with a pre-determined reducing gas source is inserted. The unexpected effect is that the pre-determined reducing gas source reduces the oxidized Fe ions, thereby reducing the number of Fe ions implanted into the wafer along with the ion beam, and effectively avoiding the generation of white pixel defects. Furthermore, under normal circumstances, the mass-to-charge ratio of the main ions in the reducing gas source during CIS product manufacturing is significantly different from that of iron ions, which can bombard Fe ions on the machine surface to a certain extent, and then filter them out by a quality screener, thereby further reducing Fe ions.

[0023] Furthermore, the difference between the mass-to-charge ratio of the main ions in the reducing gas source and iron is higher than the preset value, that is, it is desirable for the difference between the two to be as large as possible. For example, the mass-to-charge ratio of As ions is 75, which is much higher than the mass-to-charge ratio of Fe ions of 18.6. Its ion beam itself has high energy, so its bombardment capability is stronger and it can more effectively bombard the Fe elements on the surface of the instrument, and then filter them out by 90AMU.

[0024] Furthermore, in the present invention, when the machine completes other product batches between processing two batches that require F ion implantation, the energy, current, or duration of the ion beam injected with a reducing gas source is greater than a preset threshold, because the energy, current, and duration of the ion beam are all proportional to its ability to bombard the surface of the machine. Sufficient bombardment capability can more effectively bombard the Fe ions off the surface of the machine.

[0025] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of a method for reducing white pixels generated by F ion implantation on CIS products according to an embodiment of the present invention. Figure 1 ;

[0028] Figure 2 This is a flowchart of a method for reducing white pixels generated by F ion implantation on CIS products according to an embodiment of the present invention. Figure 2 . Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0031] In this invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0032] Furthermore, it should be noted that the features of the various embodiments of the present invention can be combined or integrated in whole or in part, and as those skilled in the art will understand, they can interact and operate in different ways. Each embodiment can be implemented independently of each other or in association with one another.

[0033] When processing CIS products, F-ion beams are required to reduce defects in the gate oxide layer and improve noise levels in CMOS devices. However, this process corrodes the machine surface, generating iron ions. These iron ions are then injected into the wafer along with the F-ion beam, leading to white pixel defects. To eliminate this defect, this invention breaks away from the original machine's predetermined dispatching logic during CIS product manufacturing. Between batches requiring F-ion implantation, a batch of products is processed using a pre-determined reducing gas source. This effectively removes iron ions and prevents the generation of white pixel defects.

[0034] like Figure 1 As shown, the method for reducing white pixels generated by F ion implantation on CIS products according to embodiments of the present invention mainly includes the following steps:

[0035] S102. Determine that the gas source injected into the current machine is a pre-determined reducing gas source;

[0036] S104. Determine if there is a batch that has been injected with F ions;

[0037] S106. If so, that is, there is a batch of F ions to be injected, then switch the injection gas of the machine to complete the F ion injection of one batch.

[0038] S108. Continue to determine if there are other batches of F ion implanted;

[0039] S110. If so, that is, there are other batches of F ion implantation, the machine switches the gas source to inject a pre-determined reducing gas source and processes the corresponding product batch; such as switching to a process that meets the conditions, such as As+ / P+ / B+, to prepare for the next batch that needs to be implanted with F ions.

[0040] S112. After completing the corresponding product batch, switch the machine gas source to process the F ion implantation batch.

[0041] This process is repeated until all batches requiring F-ion implantation are completed. Afterward, the machine processes the remaining product batches according to its predetermined dispatching logic.

[0042] In this embodiment, between processing two batches that require F ion implantation, the gas source is switched to a pre-determined reducing gas source, and the corresponding product batch is processed. The purpose is to reduce the oxidized Fe ions by using the pre-determined reducing gas source, thereby reducing the number of Fe ions implanted into the wafer along with the ion beam, and effectively avoiding the generation of white pixel defects. Under normal circumstances, the mass-to-charge ratio of the main ions in the reducing gas source during CIS product manufacturing is significantly different from that of iron ions, which can bombard the Fe elements on the surface of the machine to a certain extent, and then filter them out by 90AMU, thereby further reducing Fe ions.

[0043] Furthermore, such as Figure 1 As shown, this embodiment also includes the following steps:

[0044] S105. If there is no batch that needs to be injected with F ions, the machine will process the product batch according to the established dispatching logic, that is, dispatching according to priority of the same gas.

[0045] Suppose that the machine has 16 batches of goods to be processed, four batches each of As+ / F+ / P+ / B+, and the main gas sources used by the ion implanter are arsine (AsH3), phosphine (PH3), and borane (BF3), providing N-type and P-type ion implantation, as shown in Table 1 below.

[0046] Table 1. Main gas sources used in ion implanters

[0047]

[0048] The original gas-based processing method is shown in Table 2 below. First, batches 1-4 are processed sequentially, and the process conditions all require arsenic ions (the main gas source used in the ion implanter is arsine (AsH3)). Then, batches 5-8 are processed sequentially, and the process conditions all require fluoride ions (the main gas source used in the ion implanter is borane (BF3)). Next, batches 9-12 are processed sequentially, and the process conditions all require phosphine ions (the main gas source used in the ion implanter is phosphine (PH3)). Finally, batches 13-16 are processed sequentially, and the process conditions all require boron ions (the main gas source used in the ion implanter is borane (BF3)).

[0049] Table 2 Gas Dispatch Method

[0050]

[0051] However, in the original gas-based processing method, the continuous processing of multiple batches requiring fluorine ion injection can lead to white pixel defects due to the influence of Fe element. In order to reduce the F+ injection of products, the processing flow can be changed in this embodiment of the invention, as shown in Table 3 below. The processing order is batch 1-5-2-6-3-7-4-8. If there are no batches requiring F ion injection, the machine will process the product batches according to the original predetermined processing logic, that is, process batches 9-12 next, and finally process batches 13-16.

[0052] Table 3. Modified Dispatch Method

[0053]

[0054] When completing a batch, if there are urgent batches that need to be processed first, the machine will switch to processing the urgent batches. For example... Figure 2 As shown, before step S104 to implant F ions into the batch, step S103 is also included: determining if there are any urgent batches that need to be processed first. If so, step S114 is executed, and the machine switches to process urgent batches; otherwise, step S104 is executed. After the urgent batch is processed, the product batch can continue to be processed according to the machine's predetermined dispatching logic. When it is determined that the gas source injected by the current machine is a pre-determined reducing gas source (i.e., switching to an As+ / P+ / B+ process recipe that meets the conditions, preparing for the next F+IMP (ion implantation) lot dispatching), the process continues according to the predetermined dispatching logic. Figure 1 The method and steps are executed.

[0055] The gas sources for the ion beams typically used in the production of CIS products are arsine (AsH3), phosphine (PH3), and borane (BF3). As has an atomic mass of 75, much higher than Fe's atomic mass of 56. The ion beam itself has high energy, thus possessing a bombardment effect, knocking down surface Fe elements, which are then filtered out by 90 AMU (monovalent As ions have a mass-to-charge ratio of 75, much higher than trivalent Fe ions' mass-to-charge ratio of 18.6). The H ions in AsH3 and PH3 have reducing properties and can reduce oxidized Fe ions to a certain extent; therefore, AsH3 and PH3 are the most effective. The gaseous reaction products can be removed by the pump in the ion implanter. Therefore, the difference between the mass-to-charge ratio of the main ions and iron ions in the selected reducing gas source is higher than the preset value (the preset value is generally greater than 18.6, and the difference between the two is at least twice the mass-to-charge ratio of iron ions). That is, the mass-to-charge ratio of the main ions in the gas source is much greater than the mass-to-charge ratio of iron ions. This preset value is determined based on the additional metal ions generated during the production process, namely iron ions. Since the mass-to-charge ratio of trivalent Fe ions is 18.6, if it is to be much greater than this mass-to-charge ratio, it can be basically determined that the gas source is arsine (AsH3) and phosphine (PH3), with arsine (AsH3) being preferred.

[0056] To further optimize the final result, based on P + With B + With similar cleaning effects, the applicant studied the White Pixel (WP) effect by setting different gradients for duration and ion beam current in split (grouping) experiments. They found that longer duration or higher beam current resulted in better effects. Further analysis revealed that a preset threshold of duration × ion beam current is sufficient to meet the WP requirements. In essence, the ion beam energy, current, or duration of the injected reducing gas source can be adjusted to exceed preset thresholds. Higher ion beam energy, current, or duration result in stronger bombardment of the instrument surface, making it easier to knock down the generated iron ions, which are then filtered out by the 90 AMU. Therefore, setting all three to exceed preset thresholds achieves the desired effect.

[0057] To implement the above method embodiments, the present invention also provides a system for reducing the generation of white pixels on CIS products by F ion implantation. This system adds a control switching module to the existing machine processing system. When the current machine's injection gas source is a predetermined reducing gas source, the module determines whether there is a batch requiring F ion implantation. If so, it controls the machine to switch the injection gas source to complete the first batch of F ion implantation. It then continues to determine whether there is a second batch requiring F ion implantation. If so, it controls the machine to switch the gas source to the predetermined reducing gas source to process the corresponding product batch. After completing the corresponding product batch, it controls the machine to switch the gas source again to process the second batch of F ion implantation. This cycle continues until all batches requiring F ion implantation are completed.

[0058] The specific implementation function of the control switching module can be referred to the detailed steps of the above method embodiment, which will not be repeated here.

[0059] This invention has identified the causes of white pixels through research and proposed a better solution, namely an improved dispatching method. It has also found the optimal ion beam cleaning element and combined it with preset thresholds for ion beam energy, current, and duration, thereby providing a more flexible run dispatching method, further avoiding the generation of white pixels, improving product quality, and increasing product yield.

[0060] In summary, this invention breaks through the original machine's predetermined dispatching logic when manufacturing CIS products. Between two batches requiring F ion implantation, a batch of products with a pre-determined reducing gas source is inserted. An unexpected effect is that the pre-determined reducing gas source reduces oxidized Fe ions, thereby reducing the number of Fe ions implanted into the wafer along with the ion beam and suppressing white pixels caused by transit time during ion implantation. Furthermore, under normal circumstances, the mass-to-charge ratio of the main ions in the reducing gas source during CIS product manufacturing differs significantly from that of iron ions, which can bombard Fe elements from the machine surface to a certain extent. These Fe elements are then filtered out by a 90AMU, further reducing Fe ions and thus reducing white pixel generation, improving product quality.

[0061] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0062] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0063] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for reducing white pixels generated by F ion implantation on CIS products, characterized in that, Includes the following steps: If the gas source injected by the current machine is a predetermined reducing gas source, then determine whether there is a batch of F ions to be injected. If so, switch the gas source injected by the machine to complete the first batch of F ion injection. Continue to determine if there is a second batch of F ion implantation. If so, switch the gas source of the machine to a pre-determined reducing gas source and process the corresponding product batch. After completing the corresponding batch of products, switch the gas source of the machine to process the second batch of F ion implantation; repeat this cycle until all batches requiring F ion implantation are completed.

2. The method for reducing white pixels generated by F ion implantation on CIS products according to claim 1, characterized in that, The difference in mass-to-charge ratio between the main ions and iron ions in the reducing gas source is higher than the preset value.

3. The method for reducing white pixels generated by F ion implantation on CIS products according to claim 1, characterized in that, When a batch is completed, if there is an urgent batch that needs to be processed first, the machine will switch to process the urgent batch.

4. The method for reducing white pixels generated by F ion implantation on CIS products according to claim 1, characterized in that, If there are no batches requiring F-ion implantation, the machine will process the product batches according to the established dispatching logic.

5. The method for reducing white pixels generated by F ion implantation on CIS products according to claim 4, characterized in that, In the established dispatching logic, product batches with the same injected gas are processed first.

6. The method for reducing white pixels generated by F ion implantation on CIS products according to claim 1, characterized in that, The reducing gas source is arsine or phosphine.

7. The method for reducing white pixels generated by F ion implantation on CIS products according to claim 1, characterized in that, Arsine is the preferred reducing gas source.

8. The method for reducing white pixels generated by F ion implantation on CIS products according to claim 2, characterized in that, The mass-to-charge ratio of the major ion is at least twice that of the iron ion.

9. The method for reducing white pixels generated by F ion implantation on CIS products according to any one of claims 1-8, characterized in that, Between processing two batches requiring F-ion implantation, while the machine is completing other product batches, the energy, current, or duration of the ion beam injected from the reducing gas source exceeds a preset threshold.

10. A system for reducing white pixels generated by F ion implantation in CIS products, characterized in that, The system includes a control switching module, which determines whether there is a batch of F ions to be injected when the current injection gas source of the machine is a predetermined reducing gas source. If so, it controls the machine to switch the injection gas source to complete the first batch of F ion injection. Then, it continues to determine whether there is a second batch of F ion injection. If so, it controls the machine to switch the gas source to the predetermined reducing gas source to process the corresponding product batch. After the corresponding product batch is completed, it controls the machine to switch the gas source again to process the second batch of F ion injection. This cycle continues until all batches requiring F ion injection are completed.

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