A semiconductor etching method based on plasma synergistic regulation

Abstract

The application relates to the technical field of semiconductor etching, in particular to a semiconductor etching method based on plasma synergistic control, which comprises the following steps: alternately using a first plasma and a second plasma on a semiconductor to be etched to obtain a plurality of groove structures with a preset aspect ratio, wherein the first plasma performs etching, and the second plasma performs sidewall residue cleaning; using a laser interference measurement method to detect to obtain an etching rate ratio and a sidewall angle corresponding to each groove structure; and determining corresponding processing according to the change of the etching rate ratio and the sidewall angle, including maintaining the etching and cleaning parameters of the current stage, or adjusting the corresponding parameters of the first plasma as required, or adjusting the corresponding parameters of the second plasma as required. The application performs synergistic control on the first plasma and the second plasma to adjust the groove structures in each stage, so that the uniformity of the groove structures is improved and the damage to the sidewall surface is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor etching technology, and in particular to a semiconductor etching method based on plasma synergistic control. Background Technology

[0002] Semiconductor manufacturing processes are the foundation of modern information technology, with etching being one of the core processes. Plasma etching is a core process in modern semiconductor manufacturing, and its precision directly determines the forming quality of microstructures and device performance. As semiconductor device dimensions continue to shrink to the nanometer scale, the requirements for etching precision are becoming increasingly stringent. However, existing etching techniques still produce significant inhomogeneities in the etching of trench structures. Therefore, it is urgent to address the inhomogeneities in trench structures during the etching process.

[0003] Chinese Patent Publication No. CN119340207A discloses a dry semiconductor etching process based on dual-frequency electric field control. This technology simultaneously applies a high-frequency electric field (first frequency) and a low-frequency electric field (second frequency) during the etching process, monitors plasma density and ion energy in real time, and dynamically adjusts the power output and phase relationship of the first and second frequency electric fields. The phase relationship adjustment optimizes the uniform distribution of plasma density. By adjusting the ion energy of the low-frequency electric field, the kinetic energy of ions bombarding the target material is controlled within the range of 10-100 eV. During the etching process, the plasma generation rate and ion energy distribution are also controlled by adjusting the frequency and power ratio of the first and second frequency electric fields based on the conductivity and dielectric constant of the material layer. Related technical solutions can change etching uniformity and reduce plasma damage by adjusting the ion energy of the low-frequency electric field and controlling the plasma generation rate and ion energy distribution; however, this technical solution only changes the sheath morphology on the wafer surface by adjusting the phase difference, and cannot affect the electric field distribution inside the deep hole, so it still cannot effectively improve the uniformity of the trench structure and reduce the sidewall surface loss layer during the etching process. Summary of the Invention

[0004] Therefore, the present invention provides a semiconductor etching method based on plasma synergistic control to overcome the problems in the prior art that cannot improve the uniformity of the trench structure and reduce the loss layer on the sidewall surface during the etching process.

[0005] To achieve the above objectives, the present invention provides a semiconductor etching method based on plasma-coordinated control, comprising:

[0006] A halogen gas is introduced to generate a first plasma, and an oxygen-containing gas is introduced to generate a second plasma;

[0007] The first plasma and the second plasma are used alternately to process the semiconductor to be etched, wherein...

[0008] The first plasma is used to etch the semiconductor to be etched to form a plurality of trench structures with a preset aspect ratio.

[0009] The second plasma is used to remove sidewall residues generated during the etching process from each of the trench structures;

[0010] Determine the etching rate ratio and sidewall angle corresponding to each trench structure in the current stage, wherein the etching rate ratio is the ratio of the bottom etching rate to the top etching rate, and the sidewall angle is the angle between the sidewall surface of the trench structure and the surface of the semiconductor substrate to be etched.

[0011] Based on the changes in the etching rate ratio and the sidewall angle, it is determined whether the etching process corresponding to each trench structure in the current stage meets the standard, including:

[0012] The incident angle of the second plasma is adjusted according to the comparison result of the sidewall angle and the sidewall angle threshold, and the flow rate of the halogen gas is adjusted according to the comparison result of the re-detected sidewall angle and the sidewall angle threshold after adjusting the incident angle of the second plasma.

[0013] Furthermore, the process of determining whether the etching process corresponding to each trench structure in the current stage meets the standard based on the etching rate ratio and the sidewall angle change includes:

[0014] Based on the comparison results of the etching rate ratio and the etching rate ratio threshold, combined with the comparison results of the sidewall angle and the sidewall angle threshold, it is determined whether the etching process corresponding to each trench structure in the current stage meets the standard.

[0015] If the etching rate ratio is greater than the first etching rate ratio threshold and less than or equal to the second etching rate ratio threshold, then the etching process corresponding to each trench structure in the current stage is determined to meet the standard by combining the comparison result of the sidewall angle and the sidewall angle threshold.

[0016] If the etching rate ratio is less than or equal to the first etching rate ratio threshold, the flow rate of the halogen gas in the first plasma is adjusted.

[0017] Furthermore, based on the comparison results between the sidewall angle and the sidewall angle threshold, a re-determination is made as to whether the etching process corresponding to each trench structure in the current stage meets the standard, including:

[0018] If the sidewall angle is less than or equal to the first sidewall angle threshold, it is determined that the longitudinal section of the trench structure is an inverted trapezoid, and the incident angle of the second plasma is increased based on the angle difference.

[0019] If the sidewall angle is greater than the second sidewall angle threshold, it is determined that the longitudinal section of the trench structure is a trapezoid, and the incident angle of the second plasma is reduced based on the angle offset value.

[0020] Wherein, the angle difference is the difference between the first sidewall angle threshold and the sidewall angle, and the angle offset is the difference between the sidewall angle and the second sidewall angle threshold.

[0021] Furthermore, the process of increasing the incident angle of the second plasma based on the angle difference includes:

[0022] The incident angle of the second plasma is increased based on the comparison result between the angle difference and the preset angle difference, wherein the increase in the incident angle of the second plasma is positively correlated with the angle difference.

[0023] Furthermore, after increasing the incident angle of the second plasma and removing the sidewall residue, the sidewall angle is re-detected to obtain the increased sidewall angle and compared with the first sidewall angle threshold.

[0024] If the increased sidewall angle is still less than or equal to the first sidewall angle threshold, the flow rate of the halogen gas is increased based on the comparison result between the increased angle difference and the preset increased angle difference, wherein the increase in halogen gas flow rate is positively correlated with the increased angle difference.

[0025] Wherein, the increased adjustment angle difference is the difference between the first sidewall angle threshold and the increased adjustment sidewall angle.

[0026] Furthermore, the process of reducing the incident angle of the second plasma based on the angle offset value includes:

[0027] The incident angle of the second plasma is reduced based on the comparison result between the angle offset value and the preset angle offset value, wherein the reduction in the incident angle of the second plasma is positively correlated with the angle offset value.

[0028] Furthermore, after reducing the incident angle of the second plasma and removing the sidewall residue, the sidewall angle is re-detected to obtain the reduced sidewall angle and compared with the second sidewall angle threshold.

[0029] If the reduced sidewall angle is still greater than the second sidewall angle threshold, the flow rate of the halogen gas is reduced based on the comparison result between the reduced angle difference and the preset reduced angle difference, wherein the reduction in the flow rate of the halogen gas is positively correlated with the reduced angle difference.

[0030] The reduced angle difference is the difference between the reduced sidewall angle and the second sidewall angle threshold.

[0031] Furthermore, determining the etching process corresponding to each trench structure in the current stage based on the comparison result of the etching rate ratio and the etching rate ratio threshold also includes:

[0032] If the etching rate ratio is less than or equal to the first etching rate ratio threshold, it is determined that the etching rate of the bottom of the hole corresponding to the trench structure is less than the etching expectation, and the flow rate of the halogen gas is increased based on the rate ratio difference.

[0033] If the etching rate ratio is greater than the second etching rate ratio threshold, it is determined that the etching rate of the bottom hole corresponding to the trench structure is greater than the etching expectation, and the flow rate of the halogen gas is reduced based on the rate ratio offset value.

[0034] Wherein, the rate ratio difference is the difference between the first etching rate ratio threshold and the etching rate ratio, and the rate ratio offset is the difference between the etching rate ratio and the second etching rate ratio threshold.

[0035] Furthermore, the process of increasing the flow rate of the halogen gas based on the rate ratio difference includes:

[0036] The flow rate of the halogen gas is increased based on the comparison result between the rate ratio difference and the preset rate ratio difference, wherein the increase in the halogen gas flow rate is positively correlated with the rate ratio difference.

[0037] Furthermore, the process of reducing the flow rate of the halogen gas based on the rate ratio offset value includes:

[0038] The flow rate of the halogen gas is reduced based on the comparison result between the rate ratio offset value and the preset rate ratio offset value, wherein the reduction in the halogen gas flow rate is positively correlated with the rate ratio offset value.

[0039] Compared with the prior art, the beneficial effect of the semiconductor etching method based on plasma synergistic control of the present invention is that by alternately using a first plasma and a second plasma on the semiconductor to be etched to obtain a number of trench structures, wherein the first plasma performs etching and the second plasma cleans the sidewall residues; laser interferometry is used to detect and obtain the etching rate ratio and sidewall angle corresponding to each trench structure; and the corresponding processing is determined according to the changes in the etching rate ratio and sidewall angle, including maintaining the etching and cleaning parameters of the current stage, or adjusting the corresponding parameters of the first plasma as needed, or adjusting the corresponding parameters of the second plasma as needed, thereby adjusting the trench structure at each stage, thereby improving the uniformity of the trench structure and reducing the damage to the sidewall surface.

[0040] Furthermore, this invention can analyze the etching process corresponding to several trench structures at the current stage by comparing the etching rate ratio with the etching rate ratio threshold, thereby determining whether the etching process is qualified. In addition, during the determination process, the etching process can be further determined based on the comparison result of the obtained sidewall angle with the sidewall angle threshold, thereby improving the accuracy of the determination process and accurately analyzing the etching process.

[0041] Furthermore, when the present invention determines that severe residue buildup has occurred on the sidewall based on the comparison between the sidewall angle and the sidewall angle threshold, it determines to increase the incident angle of the second plasma based on the comparison between the angle difference and the preset angle difference, thereby enhancing the directional cleaning capability of the residue at the bottom of the deep hole by increasing the ion bombardment angle; or when it determines that the sidewall cleaning is excessive, it determines to decrease the incident angle of the second plasma based on the comparison between the angle offset value and the preset angle offset value, thereby reducing sidewall damage and suppressing lateral etching by decreasing the ion bombardment angle.

[0042] Furthermore, after increasing the incident angle of the second plasma and removing sidewall residues, this invention re-determines the need to increase the flow rate of halogen gas in the first plasma based on a comparison of the adjusted sidewall angle with the first sidewall angle threshold. This directly increases the reactant concentration, promotes bottom etching, and reduces residue formation. Simultaneously, increasing the gas flow rate also raises the chamber pressure, which helps improve the transport of the second plasma, thus indirectly aiding in cleaning. Through the coordinated control of the first and second plasmas, the uniformity of the trench structure on the semiconductor to be etched is improved.

[0043] Furthermore, after reducing the incident angle of the second plasma and removing sidewall residues, this invention re-determines the reduction of the halogen gas flow rate in the first plasma based on a comparison of the adjusted sidewall angle with the second sidewall angle threshold. This reduces the concentration of reactant free radicals, thereby weakening the etching process on the sidewalls. Simultaneously, it lowers the chamber pressure and improves ion directionality, further reducing sidewall etching. Through the coordinated control of the first and second plasmas, the uniformity of the trench structure on the semiconductor to be etched is improved, and damage to the sidewall surface is reduced.

[0044] Furthermore, this invention determines that when the bottom etching rate of the trench structure is less than the expected etching rate based on the comparison between the etching rate ratio and the etching rate ratio threshold, it can determine to increase the flow rate of halogen gas in the first plasma based on the comparison between the rate ratio difference and the preset rate ratio difference, thereby increasing the free radical concentration per unit volume and allowing more reactants to diffuse to the bottom of the deep hole, thus accelerating the bottom etching efficiency; or, when the bottom etching rate of the trench structure is greater than the expected etching rate, it determines to decrease the flow rate of halogen gas in the first plasma based on the comparison between the rate ratio offset value and the preset rate ratio offset value, thereby decreasing the free radical concentration per unit volume. Since the bottom region is more sensitive to reactant concentration (transmission is limited), the decrease in the bottom etching rate is greater than the decrease in the orifice etching rate, thus preventing over-etching of the bottom. The uniformity of the trench structure is improved by adjusting the first plasma. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the semiconductor etching method based on plasma synergistic control in this embodiment;

[0046] Figure 2 This is a schematic cross-sectional view of the semiconductor to be etched and several trench structures during the etching process in this embodiment;

[0047] Figure 3 This is a flowchart illustrating the determination of whether the etching process meets the standard based on the etching rate ratio and sidewall angle, and the corresponding processing steps in this embodiment.

[0048] Figure 4 This is a flowchart illustrating the reasons for the abnormality in the etching process based on the sidewall angle in this embodiment, and the corresponding handling. Detailed Implementation

[0049] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0050] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0051] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0052] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] Please see Figure 1 and Figure 2 As shown, Figure 1 This is a schematic flowchart of the semiconductor etching method based on plasma synergistic control in this embodiment. Figure 2 This is a schematic cross-sectional view of the semiconductor to be etched and several trench structures during the etching process in this embodiment. The process in this embodiment includes at least the following steps:

[0054] S1: A first plasma is generated by introducing a halogen gas, and a second plasma is generated by introducing an oxygen-containing gas.

[0055] S2: Alternate use of the first plasma and the second plasma;

[0056] S3: Use a first plasma to etch the semiconductor to be etched to form a number of trench structures with a preset aspect ratio;

[0057] S4: Use a second plasma during the etching interval to remove sidewall residues generated during the etching process from each trench structure;

[0058] S5: After removing the sidewall residue, use laser interferometry to detect and determine the etching rate ratio and sidewall angle of each trench structure at the current stage. The etching rate ratio is the ratio of the bottom etching rate to the top etching rate, and the sidewall angle is the angle between the sidewall surface of the trench structure and the surface of the semiconductor substrate to be etched.

[0059] S6: Determine whether the etching process corresponding to each trench structure in the current stage meets the standard based on the changes in etching rate ratio and sidewall angle;

[0060] S7: Determine the incident angle of the second plasma based on the comparison result of the sidewall angle and the sidewall angle threshold, and adjust the flow rate of the halogen gas based on the comparison result of the re-detected sidewall angle and the sidewall angle threshold after adjusting the incident angle of the second plasma.

[0061] Specifically, for the semiconductor to be etched, a first plasma is first used for preliminary etching to obtain a preliminary trench structure. Then, the etching with the first plasma is temporarily stopped, and a second plasma is used to remove the sidewall residues from the preliminary trench structure (at this time, the etching is in the interval period). The first plasma and the second plasma are used alternately to obtain an etched semiconductor with the corresponding trench structure.

[0062] In this embodiment, the semiconductor to be etched is placed in a plasma etching apparatus, which also includes a first plasma chamber and a second plasma chamber. In the first plasma chamber, an inductively coupled plasma is generated through high-frequency electric field (e.g., 13.56 MHz) and magnetic field coupling. A halogen gas (e.g., CF4, Cl2) is then introduced. The halogen gas ionizes in the inductively coupled plasma to generate active free radicals (·F, ·Cl), which react with the silicon-based material to generate volatile products (e.g., SiF4, SiCl4), thus obtaining the first plasma. This plasma is then used in the second plasma etching process. A primary plasma is used for the main etching process to achieve anisotropic etching. In a second plasma chamber, microwaves (2.45 GHz ± 0.05 GHz) and a magnetic field resonate to accelerate electrons, generating electron cyclotron resonance plasma. Oxygen-containing gas (such as O2) is then introduced, decomposing into oxygen free radicals (·O) within the electron cyclotron resonance plasma. These free radicals react with silicon to form volatile SiO, thus obtaining the second plasma. This second plasma is used to remove organic residues and carbon polymers, assisting in cleaning sidewall residues to reduce etching byproduct accumulation and improve pattern fidelity. The combined use of the first and second plasmas improves the uniformity and etching efficiency of the trench structure during the etching process. The generation of inductively coupled plasma and electron cyclotron resonance plasma are existing technologies and will not be elaborated upon further.

[0063] Plasma etching equipment also includes in-situ optical emission spectroscopy and laser interferometers. By real-time monitoring of changes in the plasma emission spectrum (such as OES) or laser interference signals, the etching depth, bottom etching rate, orifice etching rate, and sidewall angle are determined. The etching rate ratio R is then calculated by determining the ratio of the bottom etching rate to the orifice etching rate. Changes in the etching rate ratio R reflect the etching rate distribution along the longitudinal direction of the deep hole / trench. The sidewall angle reflects the physical and chemical equilibrium state of the etching process. Here, the sidewall angle B is the angle between the sidewall surface of the trench structure and the substrate surface, i.e., Figure 2 In the diagram, α, the substrate surface, refers to the wafer surface of the semiconductor single crystal material (such as silicon, silicon carbide, etc.) that forms the basis for processing.

[0064] In this embodiment, non-contact real-time monitoring can be achieved through laser interferometry, avoiding the physical damage risk of traditional mechanical probes. Based on the data obtained by laser interferometry, an etching structure-plasma parameter mapping model is constructed. Based on the model, the etching rate ratio threshold R0 and sidewall angle threshold B0 corresponding to each trench structure at different etching stages are determined. By measuring the changes in the etching rate ratio R and sidewall angle B, it can be determined whether the etching process of each trench structure on the semiconductor at the current stage meets the standard. If it meets the standard, the current etching parameters and cleaning parameters are maintained. If it does not meet the standard, the cause of the abnormality can be determined and the relevant parameters of the first plasma or the second plasma can be adjusted as needed to adjust the etching rate ratio R and sidewall angle B, thereby improving the uniformity of the trench structure and reducing damage to the sidewall surface.

[0065] In this embodiment, the preset aspect ratio has different preset ranges depending on the application scenario; for example, when manufacturing channel holes in 3D NAND flash memory, the aspect ratio is extremely high, and the corresponding preset aspect ratio is 60:1 to 80:1; for example, when manufacturing deep trench capacitors in DRAM cells, the aspect ratio is high, and the corresponding preset aspect ratio is 30:1 to 50:1; for example, when manufacturing contact holes in logic chips that connect transistors and back-end interconnects, the aspect ratio is medium, and the corresponding preset aspect ratio is 15:1 to 20:1.

[0066] Please see Figure 3 The diagram shows a flowchart illustrating the process of determining whether the etching process meets the standard based on the etching rate ratio and sidewall angle in this embodiment, along with the corresponding processing. The process of determining whether the etching process corresponding to each trench structure in the current stage meets the standard based on the changes in the etching rate ratio and the sidewall angle includes: determining whether the etching process corresponding to each trench structure in the current stage meets the standard based on the comparison result of the etching rate ratio and the etching rate ratio threshold, combined with the comparison result of the sidewall angle and the sidewall angle threshold; wherein, if the etching rate ratio is greater than a first etching rate ratio threshold and less than or equal to a second etching rate ratio threshold, then the etching process corresponding to each trench structure in the current stage is re-determined based on the comparison result of the sidewall angle and the sidewall angle threshold.

[0067] In this embodiment, the corresponding properties of the semiconductor material to be etched are determined, and the values ​​of subsequent preset or critical parameters are set in combination with historical measurement data and relevant industry standards. An etching rate ratio threshold R0 corresponding to the etching rate ratio R is set. In order to analyze the judgment process more accurately, the etching rate ratio threshold R0 can be divided into a first etching rate ratio R1 and a second etching rate ratio R2. The ideal value corresponding to the etching rate ratio R is 1, so R1=0.86 and R2=1.14 can be set. The comparison process between R and R1 and R2 is as follows:

[0068] If R is less than or equal to R1, it means that the etching rate at the bottom of the hole is much less than the etching rate at the top of the hole, indicating that the etching at the bottom of the hole is seriously insufficient per unit time and the etching efficiency at the bottom of the hole needs to be improved. At this time, the difference between R1 and R is calculated and recorded as the rate ratio difference A. Based on the rate ratio difference A, the intervention method to improve the etching efficiency at the bottom of the hole is determined.

[0069] If R is greater than R2, it means that the etching rate at the bottom of the hole is much greater than the etching rate at the top of the hole, indicating that the bottom of the hole is being over-etched per unit time and the etching rate at the bottom of the hole needs to be suppressed. At this time, the difference between R and R2 is calculated and recorded as the rate ratio offset value V. Based on the rate ratio offset value V, the intervention method to suppress the etching rate at the bottom of the hole is determined.

[0070] If R is greater than R1 and less than or equal to R2, it indicates that the etching process is in a critical state. In order to more accurately determine whether the uniformity of the trench structure meets the standard at the current stage, further judgment can be made by combining the change of the new parameter sidewall angle B. This will accurately determine whether there is an anomaly and generate the corresponding processing method after the anomaly is determined. By introducing a new parameter, we can avoid relying on a single-dimensional analysis and analyze from multiple dimensions to improve the accuracy of the judgment process. At this time, the sidewall angle B becomes the key criterion for judging the etching uniformity of the trench structure.

[0071] Please see Figure 4 The diagram shows a flowchart illustrating the reasons for and corresponding processing of abnormalities in the etching process based on the sidewall angle in this embodiment. The process of re-determining the etching process corresponding to each trench structure in the current stage, based on the comparison between the sidewall angle and the sidewall angle threshold, includes: if the sidewall angle is less than or equal to the first sidewall angle threshold, the longitudinal section of the trench structure is determined to be an inverted trapezoid, and the incident angle of the second plasma is increased based on the angle difference; if the sidewall angle is greater than the second sidewall angle threshold, the longitudinal section of the trench structure is determined to be a regular trapezoid, and the incident angle of the second plasma is decreased based on the angle offset value; the angle difference is the difference between the first sidewall angle threshold and the sidewall angle, and the angle offset is the difference between the sidewall angle and the second sidewall angle threshold.

[0072] In this embodiment, a sidewall angle threshold B0 corresponding to the sidewall angle B is set. To more accurately analyze the secondary determination process, the sidewall angle threshold B0 can be divided into a first sidewall angle threshold B1 and a second sidewall angle threshold B2. B1 = 88° and B2 = 92° can be set. The comparison process between B and B1 and B2 is as follows:

[0073] If B is less than or equal to B1, it indicates that there is a serious accumulation of residue on the sidewall, which means that the second plasma cleaning is incomplete. This residue blocks the deposition of the passivation layer, resulting in the longitudinal section of the trench structure being an inverted trapezoid that is wider at the top and narrower at the bottom. In this case, the incident angle of the second plasma can be increased to enhance the directional cleaning capability of the residue at the bottom of the deep hole by increasing the ion bombardment angle. The difference between B1 and B is calculated and recorded as the angle difference M. The increase in the incident angle of the second plasma is determined based on the change in the angle difference M. The increase in the incident angle refers to the rotation of the original incident angle towards the sidewall of the trench structure.

[0074] If B is greater than B1 and less than or equal to B2, it indicates that the sidewall angle is within the acceptable range, meaning that the current etching and cleaning process is temporarily stable and the current etching and cleaning parameters can be maintained.

[0075] If B is greater than B2, it indicates that the sidewall cleaning is excessive, causing the longitudinal section of the trench structure to present a trapezoidal shape that is narrow at the top and wide at the bottom. At this time, the incident angle of the second plasma can be reduced. By reducing the ion bombardment angle, the sidewall damage can be reduced and the lateral etching can be suppressed. The difference between B and B2 is calculated and recorded as the angle offset value K. Based on the change of the angle offset value K, the reduction of the incident angle of the second plasma is determined. The reduction of the incident angle refers to the original incident angle rotating away from the sidewall of the trench structure.

[0076] Specifically, the process of increasing the incident angle of the second plasma based on the angle difference includes: increasing the incident angle of the second plasma based on the comparison result between the angle difference and a preset angle difference, wherein the increase in the incident angle of the second plasma is positively correlated with the angle difference.

[0077] In this embodiment, the smaller the sidewall angle B, the more severe the accumulation of residue on the sidewall, and the greater the increase in the incident angle of the second plasma needs to be. When the sidewall angle B is smaller, the corresponding angle difference M is larger. Therefore, the increase in the incident angle of the second plasma is positively correlated with the angle difference M. The initial setting range of the original incident angle is typically 3° to 5°. A preset angle difference M0 corresponding to the angle difference M is set. To more accurately determine the increase in the incident angle of the second plasma, the preset angle difference M0 can be divided into a first preset angle difference M1 and a second angle difference M2. M1 = 5° and M2 = 7° can be set. The comparison process between M and M1 and M2 is as follows:

[0078] If M is less than or equal to M1, a corresponding first incident angle adjustment command is generated, and the second plasma is controlled to increase by 3° based on the original incident angle. If M is greater than M1 and less than or equal to M2, a corresponding second incident angle adjustment command is generated, and the second plasma is controlled to increase by 4.5° based on the original incident angle. If M is greater than M2, a corresponding third incident angle adjustment command is generated, and the second plasma is controlled to increase by 5° based on the original incident angle.

[0079] Understandably, the increase in the incident angle can also be set to other values ​​that meet the requirements. For example, when M is greater than M2, the incident angle can be increased by 5.5° based on the original incident angle. It should be noted that increasing the incident angle of the second plasma will not have a negative impact on the semiconductor etching uniformity.

[0080] Specifically, after increasing the incident angle of the second plasma and removing the sidewall residue, the sidewall angle is re-detected to obtain the increased sidewall angle, which is then compared with the first sidewall angle threshold. If the increased sidewall angle is still less than or equal to the first sidewall angle threshold, the halogen gas flow rate is increased based on the comparison between the increased angle difference and a preset increased angle difference. The increase in halogen gas flow rate is positively correlated with the increased angle difference. The increased angle difference is the difference between the first sidewall angle threshold and the increased sidewall angle.

[0081] In this embodiment, after increasing the incident angle of the second plasma and removing the sidewall residue again, the increased sidewall angle G is compared with the first sidewall angle threshold B1. If the increased sidewall angle G is still less than or equal to the first sidewall angle threshold B1, it indicates that the sidewall residue is too stubborn or the aspect ratio is too high, so even increasing the incident angle of the second plasma cannot effectively deliver the cleaning particles to the bottom sidewall of the hole. In this case, it is necessary to increase the flow rate of halogen gas in the first plasma, thereby directly increasing the reactant concentration, which can promote the etching of the bottom of the hole and reduce the formation of residue. At the same time, increasing the gas flow rate can also increase the chamber pressure, which helps to improve the transmission of the second plasma, thereby indirectly helping the cleaning. The smaller the increased sidewall angle G is, the more sidewall residue there is, and the greater the increase in the halogen gas flow rate needs to be. When the increased sidewall angle G is smaller, the corresponding increased angle difference Q is larger. Therefore, the increase in halogen gas flow rate is positively correlated with the increased angle difference Q.

[0082] The initial setting range for the original halogen gas flow rate is 90-110 sccm. A preset angle difference value Q0 corresponding to the increased angle difference value Q is set. To more accurately determine the increase in halogen gas flow rate, Q0 can be divided into a first preset angle difference value Q1 and a second preset angle difference value Q2. Q1 can be set to 2.5° and Q2 to 3.5°. The comparison process between Q and Q1 and Q2 is as follows:

[0083] If Q is less than or equal to Q1, a first gas flow rate regulation command is generated, which controls the halogen gas flow rate to increase by 7% based on the original gas flow rate; if Q is greater than Q1 and less than or equal to Q2, a second gas flow rate regulation command is generated, which controls the halogen gas flow rate to increase by 8% based on the original gas flow rate; if Q is greater than Q2, a third gas flow rate regulation command is generated, which controls the halogen gas flow rate to increase by 9% based on the original gas flow rate.

[0084] Understandably, the increase in halogen gas flow rate can also be set to other acceptable values. For example, when Q is greater than Q2, the flow rate can be increased by 8.5% based on the original flow rate. It should be noted that increasing the halogen gas flow rate in the first plasma will not cause the etching rate ratio R to exceed the range of (R1, R2) and will not have a negative impact on the etching process.

[0085] Specifically, the process of reducing the incident angle of the second plasma based on the angle offset value includes: reducing the incident angle of the second plasma based on the comparison result between the angle offset value and the preset angle offset value, wherein the reduction in the incident angle of the second plasma is positively correlated with the angle offset value.

[0086] In this embodiment, the larger the sidewall angle B, the more severe the over-cleaning of the sidewall, and the greater the reduction in the incident angle of the second plasma needs to be. When the sidewall angle B is larger, the corresponding angle offset value K is larger. Therefore, the reduction in the incident angle of the second plasma is positively correlated with the angle offset value K. A preset angle offset value K0 is set to correspond to the angle offset value K. To more accurately determine the reduction in the incident angle of the second plasma, the preset angle offset value K0 can be divided into a first preset angle offset value K1 and a second preset angle offset value K2. K1 = 4° and K2 = 6° can be set. The comparison process between K and K1 and K2 is as follows:

[0087] If K is less than or equal to K1, a corresponding fourth incident angle adjustment command is generated, which controls the second plasma to decrease by 2.5° from the original incident angle. If K is greater than K1 and less than or equal to K2, a corresponding fifth incident angle adjustment command is generated, which controls the second plasma to decrease by 3° from the original incident angle. If K is greater than K2, a corresponding sixth incident angle adjustment command is generated, which controls the second plasma to decrease by 4° from the original incident angle.

[0088] Understandably, the reduction in the incident angle can also be set to other values ​​that meet the requirements. For example, when K is greater than K2, the incident angle can be reduced by 4.5° from the original angle. It should be noted that the reduction in the incident angle of the second plasma will not have a negative impact on the semiconductor etching uniformity.

[0089] Specifically, after reducing the incident angle of the second plasma and removing the sidewall residue, the sidewall angle is re-detected to obtain the reduced sidewall angle and compared with the second sidewall angle threshold. If the reduced sidewall angle is still greater than the second sidewall angle threshold, the flow rate of the halogen gas is reduced based on the comparison result between the reduced angle difference and the preset reduced angle difference. The reduction in halogen gas flow rate is positively correlated with the reduced angle difference. The reduced angle difference is the difference between the reduced sidewall angle and the second sidewall angle threshold.

[0090] In this embodiment, after reducing the incident angle of the second plasma and removing the sidewall residue, the reduced sidewall angle Z is compared with the second sidewall angle threshold B2. If the reduced sidewall angle Z is still greater than the second sidewall angle threshold B2, it indicates that even with the reduced incident angle of the second plasma, excessive etching is still occurring on the sidewall of the trench structure. In this case, the flow rate of halogen gas in the first plasma needs to be reduced to decrease the concentration of reactant free radicals, thereby weakening the etching process on the sidewall. Simultaneously, the chamber pressure is reduced to improve ion directionality (reducing scattering and making ions more perpendicular to the incident surface), thus reducing sidewall etching. A larger reduced sidewall angle Z indicates a deeper degree of excessive etching on the sidewall, requiring a greater reduction in the halogen gas flow rate. A larger reduced sidewall angle corresponds to a larger angle difference P; therefore, the reduction in halogen gas flow rate is positively correlated with the angle difference P.

[0091] Set a preset angle difference P0 corresponding to the angle difference after reduction adjustment. To more accurately determine the reduction range of halogen gas flow rate, P0 can be divided into a first preset angle difference P1 and a second preset angle difference P2. P1 can be set to 3° and P to 4°. The comparison process between P and P1 and P2 is as follows:

[0092] If P is less than or equal to P1, a corresponding fourth gas flow regulation command is generated, which controls the halogen gas flow rate to decrease by 6.5% based on the original gas flow rate; if P is greater than P1 and less than or equal to P2, a corresponding fifth gas flow regulation command is generated, which controls the halogen gas flow rate to decrease by 7.5% based on the original gas flow rate; if P is greater than P2, a corresponding sixth gas flow regulation command is generated, which controls the halogen gas flow rate to decrease by 8.5% based on the original gas flow rate.

[0093] Understandably, the reduction in halogen gas flow rate can also be set to other acceptable values. For example, when P is less than or equal to P1, the flow rate can be reduced by 6% based on the original flow rate. It should be noted that reducing the halogen gas flow rate in the first plasma will not cause the etching rate ratio R to exceed the range of (R1, R2), nor will it have a negative impact on the etching process.

[0094] Specifically, determining the etching process corresponding to each trench structure at the current stage based on the comparison result of the etching rate ratio and the etching rate ratio threshold further includes: if the etching rate ratio is less than or equal to the first etching rate ratio threshold, then it is determined that the bottom etching rate of the trench structure is less than the expected etching rate, and the flow rate of the halogen gas is increased based on the rate ratio difference; if the etching rate ratio is greater than the second etching rate ratio threshold, then it is determined that the bottom etching rate of the trench structure is greater than the expected etching rate, and the flow rate of the halogen gas is decreased based on the rate ratio offset value; the rate ratio difference is the difference between the first etching rate ratio threshold and the etching rate ratio, and the rate ratio offset value is the difference between the etching rate ratio and the second etching rate ratio threshold.

[0095] In this embodiment, the etching expectation refers to the initial compliance of the first plasma with the bottom etching of the trench structure at the current stage, i.e., the current stage is within the warning range where R∈(R1, R2) during the etching process. When the etching rate ratio R is less than or equal to the first etching rate ratio threshold R1, or when the etching rate ratio R is greater than the second etching rate ratio threshold R2, it indicates that R at the current stage exceeds the warning range, and the corresponding parameters of the first plasma need to be adjusted.

[0096] When R is less than or equal to R1, the halogen gas flow rate in the first plasma can be increased based on the change in the rate ratio difference A, thereby increasing the free radical concentration per unit volume. This allows more reactants to diffuse to the bottom of the deep hole, accelerating the bottom etching efficiency. When R is greater than R2, the halogen gas flow rate in the first plasma can be decreased based on the change in the rate ratio offset V, thereby decreasing the free radical concentration per unit volume. Since the bottom region is more sensitive to reactant concentration (transport is limited), the decrease in the bottom etching rate is greater than that at the orifice, thus preventing over-etching of the bottom.

[0097] Specifically, the process of increasing the flow rate of the halogen gas based on the rate ratio difference includes: increasing the flow rate of the halogen gas based on the comparison result between the rate ratio difference and a preset rate ratio difference, wherein the increase in the halogen gas flow rate is positively correlated with the rate ratio difference.

[0098] In this embodiment, the etching rate ratio R represents the ratio of the etching rate at the bottom of the hole to the etching rate at the top of the hole. A smaller etching rate R indicates a greater degree that the etching rate at the bottom of the hole is less than the etching rate at the top of the hole, thus requiring a greater increase in the halogen gas flow rate in the first plasma. Conversely, a smaller etching rate ratio R results in a larger rate ratio difference A. Therefore, the increase in halogen gas flow rate is positively correlated with the rate ratio difference A. A preset rate ratio difference A0 is set to correspond to the rate ratio difference A. To more accurately determine the increase in halogen gas flow rate when the etching rate ratio R is less than or equal to the first etching rate ratio threshold R1, the preset rate ratio difference A0 can be divided into a first preset rate ratio difference A1 and a second preset rate ratio difference A2, with A1 = 0.2 and A2 = 0.3. The comparison process between A and A1 and A2 is as follows:

[0099] If A is less than or equal to A1, a corresponding seventh gas flow regulation command is generated, which controls the halogen gas flow rate to increase by 10% based on the original gas flow rate; if A is greater than A1 and less than or equal to A2, a corresponding eighth gas flow regulation command is generated, which controls the halogen gas flow rate to increase by 11.5% based on the original gas flow rate; if A is greater than A2, a corresponding ninth gas flow regulation command is generated, which controls the halogen gas flow rate to increase by 12.5% ​​based on the original gas flow rate.

[0100] Understandably, the increase in halogen gas flow rate can also be set to other acceptable values. For example, when A is greater than A2, the flow rate can be increased by 12% based on the original flow rate. It should be noted that increasing the halogen gas flow rate can improve the etching rate ratio R to be greater than the first etching rate ratio threshold R1, without negatively impacting the etching process.

[0101] Specifically, the process of reducing the flow rate of the halogen gas based on the rate ratio offset value includes: reducing the flow rate of the halogen gas based on the comparison result between the rate ratio offset value and a preset rate ratio offset value, wherein the reduction in the halogen gas flow rate is positively correlated with the rate ratio offset value.

[0102] In this embodiment, a larger etching rate ratio R indicates a greater degree of difference between the bottom etching rate and the orifice etching rate, thus requiring a greater reduction in the halogen gas flow rate in the first plasma. A larger etching rate ratio R also results in a larger rate ratio offset value V. Therefore, the reduction in halogen gas flow rate is positively correlated with the rate ratio offset value V. A preset rate ratio offset value V0 is set to correspond to the rate ratio offset value V. To more accurately determine the reduction in halogen gas flow rate when the etching rate ratio R is greater than the second etching rate ratio threshold R2, the preset rate ratio offset value V0 can be divided into a first preset rate ratio offset value V1 and a second preset rate ratio offset value V2, with V1 = 0.15 and V2 = 0.25. The comparison process between V and V1 and V2 is as follows:

[0103] If V is less than or equal to V1, a corresponding tenth gas flow rate regulation command is generated, which controls the halogen gas flow rate to decrease by 11% based on the original gas flow rate; if V is greater than V1 and less than or equal to V2, a corresponding eleventh gas flow rate regulation command is generated, which controls the halogen gas flow rate to decrease by 12% based on the original gas flow rate; if V is greater than V2, a corresponding twelfth gas flow rate regulation command is generated, which controls the halogen gas flow rate to decrease by 13% based on the original gas flow rate.

[0104] Understandably, the reduction in halogen gas flow rate can also be set to other acceptable values. For example, when V is less than or equal to V1, the flow rate can be reduced by 11.5% from the original flow rate. It should be noted that reducing the halogen gas flow rate can reduce the etching rate ratio R in the direction of being less than or equal to the second etching rate ratio threshold R2, without having a negative impact on the etching process.

[0105] It is understood that no specific limitation is made to any preset parameter or critical parameter in the embodiments of the present invention, and the above values ​​are not limited thereto. Those skilled in the art can make corresponding adjustments to the preset parameters or critical parameters according to actual needs, analysis of historical data, or equipment usage.

[0106] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for semiconductor etching based on synergistic regulation of plasma, characterized in that, The method comprises: introducing halogen gas to generate a first plasma and introducing oxygen-containing gas to generate a second plasma; alternately using the first plasma and the second plasma to treat a semiconductor to be etched, wherein using the first plasma to etch the semiconductor to be etched to form a plurality of trench structures with a preset aspect ratio; using the second plasma to remove sidewall residues generated in the etching process of each of the trench structures; determining an etching rate ratio and a sidewall angle of each of the trench structures in the current stage, wherein the etching rate ratio is a ratio of a bottom hole etching rate to an opening etching rate, and the sidewall angle is an included angle between a sidewall surface of the trench structure and a substrate surface of the semiconductor to be etched; judging whether the etching process of each of the trench structures in the current stage meets a standard based on changes in the etching rate ratio and the sidewall angle, comprising adjusting an incident angle of the second plasma according to a comparison result of the sidewall angle and a sidewall angle threshold, and adjusting a flow rate of the halogen gas after adjusting the incident angle of the second plasma according to a comparison result of a re-detected sidewall angle and the sidewall angle threshold; determining whether the etching process of each of the trench structures in the current stage meets the standard based on a comparison result of the etching rate ratio and an etching rate ratio threshold in combination with a comparison result of the sidewall angle and the sidewall angle threshold, wherein if the etching rate ratio is greater than a first etching rate ratio threshold and less than or equal to a second etching rate ratio threshold, determining whether the etching process of each of the trench structures in the current stage meets the standard in combination with the comparison result of the sidewall angle and the sidewall angle threshold; if the etching rate ratio is less than or equal to the first etching rate ratio threshold, determining to adjust the flow rate of the halogen gas in the first plasma.

2. The method of claim 1, wherein the plasma synergistically controlled semiconductor etching is characterized by, rejudging whether the etching process of each of the trench structures in the current stage meets the standard in combination with the comparison result of the sidewall angle and the sidewall angle threshold, comprising if the sidewall angle is less than or equal to a first sidewall angle threshold, determining that a longitudinal section of the trench structure is an inverted trapezoid, and increasing the incident angle of the second plasma based on an angle difference value; if the sidewall angle is greater than a second sidewall angle threshold, determining that the longitudinal section of the trench structure is a trapezoid, and decreasing the incident angle of the second plasma based on an angle offset value; wherein the angle difference value is a difference between the first sidewall angle threshold and the sidewall angle, and the angle offset value is a difference between the sidewall angle and the second sidewall angle threshold.

3. The method of claim 2, wherein the plasma synergistically modulated semiconductor etching is characterized by, The process of increasing the incident angle of the second plasma based on the angle difference value comprises: increasing the incident angle of the second plasma based on a comparison result of the angle difference value and a preset angle difference value, wherein an increasing amplitude of the incident angle of the second plasma and the angle difference value have a positive correlation.

4. The method of claim 3, wherein the plasma synergistically controlled semiconductor etching is characterized by, After completing the adjustment of increasing the incident angle of the second plasma and removing the sidewall residues, the sidewall angle is re-detected to obtain an increased sidewall angle and compared with the first sidewall angle threshold. If the increased-adjusted sidewall angle is less than or equal to the first sidewall angle threshold, the flow of the halogen gas is increased based on a comparison result of the increased-adjusted angle difference value and a preset increased-adjusted angle difference value, wherein the increase amplitude of the halogen gas flow is positively correlated with the increased-adjusted angle difference value. The increased-adjusted angle difference value is a difference value between the first sidewall angle threshold and the increased-adjusted sidewall angle.

5. The method of claim 2, wherein the plasma synergistically controlled semiconductor etching is characterized by, The process of decreasing the incident angle of the second plasma based on the angle offset value comprises: The incident angle of the second plasma is decreased based on a comparison result of the angle offset value and a preset angle offset value, wherein the decrease amplitude of the incident angle of the second plasma is positively correlated with the angle offset value.

6. The method of claim 5, wherein the plasma synergistically controlled semiconductor etching is characterized by, After the incident angle of the second plasma is decreased and the sidewall residue is removed, the sidewall angle is re-detected to obtain a decreased-adjusted sidewall angle and compared with the second sidewall angle threshold; If the decreased-adjusted sidewall angle is greater than the second sidewall angle threshold, the flow of the halogen gas is decreased based on a comparison result of the decreased-adjusted angle difference value and a preset decreased-adjusted angle difference value, wherein the decrease amplitude of the halogen gas flow is positively correlated with the decreased-adjusted angle difference value. The decreased-adjusted angle difference value is a difference value between the decreased-adjusted sidewall angle and the second sidewall angle threshold.

7. The method of claim 1, wherein the plasma synergistically controlled semiconductor etching is characterized by, The process of determining the etching process of each of the trench structures in the current stage based on a comparison result of the etching rate ratio and the etching rate ratio threshold comprises: If the etching rate ratio is less than or equal to the first etching rate ratio threshold, it is determined that the hole bottom etching rate corresponding to the trench structure is less than the etching expectation, and the flow of the halogen gas is increased based on a rate ratio difference value; If the etching rate ratio is greater than the second etching rate ratio threshold, it is determined that the hole bottom etching rate corresponding to the trench structure is greater than the etching expectation, and the flow of the halogen gas is decreased based on a rate ratio offset value; The rate ratio difference value is a difference value between the first etching rate ratio threshold and the etching rate ratio, and the rate ratio offset value is a difference value between the etching rate ratio and the second etching rate ratio threshold.

8. The method of claim 7, wherein the plasma synergistically modulated semiconductor etching is characterized by, The process of increasing the flow of the halogen gas based on the rate ratio difference value comprises: The flow of the halogen gas is increased based on a comparison result of the rate ratio difference value and a preset rate ratio difference value, wherein the increase amplitude of the halogen gas flow is positively correlated with the rate ratio difference value.

9. The method of claim 7, wherein the plasma synergistically modulated semiconductor etching is characterized by, The process of decreasing the flow of the halogen gas based on the rate ratio offset value comprises: The flow of the halogen gas is decreased based on a comparison result of the rate ratio offset value and a preset rate ratio offset value, wherein the decrease amplitude of the halogen gas flow is positively correlated with the rate ratio offset value.

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