Trench etching method and trench isolation structure

Abstract

The invention provides a trench etching method and a trench isolation structure, and the method comprises the steps: sequentially depositing a first oxide layer, a first nitride layer, a second oxide layer, a second nitride layer and a third oxide layer on a metal layer, and enabling the thickness of the first oxide layer to be larger than the thickness of the third oxide layer; coating a photoresist layer on the surface of the third oxide layer, and exposing and developing the photoresist layer to obtain a patterned photoresist layer; executing an etching process to form a first groove, wherein the first groove extends from the surface of the third oxide layer to the surface of the first oxide layer; and performing an etching process to form a second groove, performing end point detection on the etching process, and stopping the etching process after a signal of the second nitride layer is detected, thereby preventing the etching gas from reacting with the metal layer to generate a polymer in the etching process of the first oxide layer. And the polymer pollutes an etching machine table in the etching process of the metal layer.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor devices, and particularly relates to a trench etching method and a trench isolation structure. BACKGROUND

[0002] In a key patterning process in the manufacturing process of a silicon-based liquid crystal display panel, photoresist and single-layer silicon oxide have limitations in etching durability and photolithography reflection interference, and in the prior art, the original single-layer 300A silicon oxide hard mask is generally replaced by an oxide-nitride-oxide (ONO) three-layer structure.

[0003] Figure 1 is a structural schematic diagram after each step of the trench etching method in the prior art, Figure 2 is an energy dispersive X-ray spectrogram after wet cleaning in the trench etching method in the prior art, Figure 3 is a schematic diagram of aluminum fluoride in the aluminum etching process polluting the etching machine in the aluminum film layer etching process after wet cleaning in the trench etching method in the prior art, please refer to Figures 1-3 The mask layer of the above-mentioned ONO three-layer structure is in the over-etching process of the bottom layer of silicon oxide, and the etching gas is carbon tetrafluoride. Since the over-etching amount of this step needs to be ensured to be more than 40%, the surface of the aluminum metal layer opened by the bottom layer will combine with the etching gas fluorine to generate aluminum fluoride polymer. This aluminum fluoride is difficult to remove completely by wet cleaning, and the aluminum fluoride polymer will be decomposed in the aluminum etching step, causing the aluminum etching machine to be polluted. SUMMARY

[0004] The purpose of the present application is to provide a trench etching method and a trench isolation structure, which can improve the problem of pollution of the etching machine in the manufacturing process of the trench isolation structure.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: the present application provides a grinding pad, which comprises: A first oxide layer, a first nitride layer, a second oxide layer, a second nitride layer and a third oxide layer are sequentially deposited on the metal layer, the material of the first oxide layer and the third oxide layer is the same, and the thickness of the first oxide layer is greater than the thickness of the third oxide layer; The photoresist layer is coated on the surface of the third oxide layer, and the photoresist layer is exposed and developed to obtain a patterned photoresist layer; An etching process is performed to form a first trench, the first trench extends from the surface of the third oxide layer to the surface of the first oxide layer; The etching process is performed to form a second trench, and endpoint detection is performed on the etching process, and the etching process is stopped after a signal of the second nitride layer is detected.

[0006] Further, the etching process is performed to form a first trench, and before the first trench extends from the surface of the third oxide layer to the surface of the first oxide layer, the etching process further includes: The etching process is performed to form a third trench, and the third trench extends from the surface of the third oxide layer to the surface of the first nitride layer.

[0007] Further, before the photoresist layer is coated on the surface of the third oxide layer, the etching process further includes: coating an anti-reflective coating layer on the surface of the third oxide layer.

[0008] Further, the etching process is performed to form a first trench, and before the first trench extends from the surface of the third oxide layer to the surface of the first oxide layer, the etching process further includes: The photoresist layer and the anti-reflective coating layer on the surface of the third oxide layer are removed.

[0009] Further, after the etching process is performed to form a second trench, endpoint detection is performed on the etching process, and the etching process is stopped after a signal of the second nitride layer is detected, the etching process further includes: The etching process is performed to form a fourth trench, and the fourth trench extends through the first oxide layer and the metal layer remaining in the process of forming the second trench.

[0010] Further, the thickness of the third oxide layer is 300-400 angstroms, and the thickness difference between the first oxide layer and the third oxide layer is 200-300 angstroms.

[0011] Further, the thickness of the second nitride layer is greater than 200 angstroms.

[0012] Further, the thickness of the first nitride layer is less than 1000 angstroms.

[0013] Further, the etching process is a plasma etching process, and the endpoint detection method includes one of optical emission spectroscopy, optical reflection method, and gas analysis method. The materials of the first oxide layer, the second oxide layer, and the third oxide layer are all silicon oxide, and the materials of the first nitride layer and the second nitride layer are both silicon nitride or silicon carbide.

[0014] The second aspect of the present application provides a trench isolation structure, and the trench isolation structure is obtained by filling an isolation material in a target trench obtained by using the trench etching method.

[0015] The trench etching method provided by the application comprises sequentially depositing a first oxide layer, a first nitride layer, a second oxide layer, a second nitride layer and a third oxide layer on a metal layer, the first oxide layer and the third oxide layer are of the same material, and the thickness of the first oxide layer is greater than that of the third oxide layer; a photoresist layer is coated on the surface of the third oxide layer and is subjected to exposure and development to obtain a patterned photoresist layer; a first trench is formed by performing an etching process, and the first trench extends from the surface of the third oxide layer to the surface of the first oxide layer; a second trench is formed by performing an etching process, endpoint detection is performed on the etching process, and the etching process is stopped after the signal of the second nitride layer is detected; and the thickness of the first oxide layer corresponding to the endpoint of the etching process is the difference between the thicknesses of the first oxide layer and the third oxide layer. The trench etching method controls the residual thickness of the first oxide layer through the third oxide layer of the top layer, retains part of the first oxide layer in the hard mask etching process, and avoids the reaction between the etching gas and the metal layer to generate a polymer in the etching process of the first oxide layer, thereby avoiding the problem that the polymer pollutes the etching machine in the etching process of the metal layer. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0017] Figure 1 It is a structural schematic diagram after each step of the trench etching method in the prior art; Figure 2 It is an energy dispersive X-ray spectrum schematic diagram after wet cleaning of the trench etching in the prior art, wherein F is fluorine on the surface of the aluminum metal; Figure 3 It is a schematic diagram of the pollution of the etching machine by aluminum fluoride in the aluminum etching process after wet cleaning of the trench etching in the prior art, wherein ALxFy is aluminum fluoride; Figure 4 It is a flowchart schematic diagram of each step of the trench etching method provided by the embodiment of the present application; Figure 5 It is a structural schematic diagram after each step of the trench etching method provided by the embodiment of the present application; Figure 6 It is a structural schematic diagram after each step of the trench etching method provided by the embodiment of the present application.

[0018] In the drawings, various reference signs represent: 110 - glass substrate; 111 - metal layer; 112 - first oxide layer; 113 - first nitride layer; 114 - second oxide layer; 115 - second nitride layer; 116 - third oxide layer; 117 - black matrix; 118 - backlight; 119 - liquid crystal layer; A - first groove; B - second groove; C - third groove; D - fourth groove. DETAILED DESCRIPTION

[0019] To make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0020] In the description of the present application, it should be understood that the terms "include" and "have" and any variations thereof used herein are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units need not be limited to those clearly listed steps or units, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0021] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0022] In addition, the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. It should be understood that the term "and / or" used herein is only used to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. In the description of the present application, unless otherwise specified, the meaning of "multiple" is two or more.

[0023] In the key patterning process of the manufacturing process of a silicon-based liquid crystal display panel, the photoresist and the single-layer silicon oxide have limitations in etching durability and photolithography reflection interference, and in the prior art, the originally single-layer 300A silicon oxide hard mask is generally replaced by an oxide-nitride-oxide (ONO) three-layer structure. Figure 1 is a structural schematic diagram after each step of the prior art trench etching method, Figure 2 is an energy dispersive X-ray spectroscopy diagram after wet cleaning in the prior art trench etching, Figure 3 is a schematic diagram of aluminum fluoride contaminating an etching machine in the aluminum etching process after wet cleaning in the prior art trench etching process, please refer to Figures 1-3 The mask layer of the above-mentioned ONO three-layer structure is in the over-etching process of the bottom oxide layer, and the etching gas is carbon tetrafluoride. Since the over-etching amount of this step needs to be ensured to be more than 40%, the surface of the aluminum metal layer opened by the bottom layer will combine with the etching gas fluorine to generate aluminum fluoride polymer. This aluminum fluoride is difficult to remove completely by wet cleaning, and the aluminum fluoride polymer will be decomposed in the aluminum etching step, causing the aluminum etching machine to be contaminated. Based on the above reasons, the present application provides a trench etching method and a trench isolation structure.

[0024] The trench etching method and the trench isolation structure provided by the present application will be described in detail below in combination with specific embodiments.

[0025] Figure 4 is a flowchart of the trench etching method provided by the embodiment of the present application, Figure 5 is a structural schematic diagram after each step of the trench etching method provided by the embodiment of the present application, please refer to Figure 4 、 Figure 5 The first aspect of the embodiment provides a trench etching method, comprising: S101, sequentially depositing a first oxide layer, a first nitride layer, a second oxide layer, a second nitride layer and a third oxide layer on a metal layer, the material of the first oxide layer and the third oxide layer is the same, and the thickness of the first oxide layer is greater than the thickness of the third oxide layer; Specifically, the metal layer 111 of the embodiment is formed on a substrate 110, which can be made of semiconductor material, insulating material, conductor material or any combination of the material types. For example, the substrate 110 can be a silicon (Si) substrate 110, a silicon germanium (SiGe) substrate 110, a silicon germanium carbon (SiGeC) substrate 110, a silicon carbide (SiC) substrate 110, a gallium arsenide (GaAs) substrate 110, an indium arsenide (InAs) substrate 110, an indium phosphide (InP) substrate 110. Alternatively, for example, the substrate 110 can be a stack including Si and SiGe, a stack including Si and SiC, etc. The metal layer 111 of the embodiment is an aluminum film layer, and the surface of the aluminum film layer is formed with a first oxide layer 112, a first nitride layer 113, a second oxide layer 114, a second nitride layer 115 and a third oxide layer 116 stacked in sequence. The oxide layer of the embodiment can be silicon oxide, and the nitride layer of the embodiment can be silicon nitride. For example, the first oxide layer 112, the second oxide layer and the third oxide layer of the embodiment are all made of silicon oxide, and the first nitride layer 113 and the second nitride layer 115 are both made of silicon nitride or silicon carbide. The first oxide layer 112 of the embodiment can relieve the stress between the metal layer 111 (e.g., the aluminum film layer) and the upper nitride layer, and prevent metal damage. Silicon nitride or silicon carbide generally has high residual stress (especially tensile stress), and the stress accumulation will increase significantly with the increase of thickness. When the stress exceeds the adhesion between the metal layer 111 and the substrate 110, local or overall peeling will occur, resulting in device failure. The high stress of the first nitride layer 113 of the embodiment can be partially offset by the reverse stress of the first oxide layer 112 and the second oxide layer 114, reducing the risk of warping or cracking of the overall structure. The thickness of the first oxide layer 112 of the embodiment is greater than the thickness of the third oxide layer 116.

[0026] S102, coating a photoresist layer on the surface of the third oxide layer and performing exposure and development on the photoresist layer to obtain a patterned photoresist layer; Specifically, a uniform and defect-free photoresist layer 117 is formed on the surface of the third oxide layer 116, providing a basis for subsequent exposure and development. The trench pattern is transferred to the photoresist layer 117 through a mask, and a latent image is formed by photochemical reaction. The pattern is transferred to the third oxide layer 116 by dry etching (e.g., CF4 / CHF3 plasma) using the photoresist layer 117 as a mask.

[0027] S103, performing an etching process to form a first trench extending from the surface of the third oxide layer to the surface of the first oxide layer; Specifically, after the substrate 110 with the patterned photoresist layer 117 is obtained, step S103 is performed to form a plurality of first grooves A on the substrate 110 by using a dry etching process, such as a reactive ion etching process. Compared with a wet etching process, the dry etching process can provide higher selectivity. Specifically, the substrate 110 with the patterned photoresist layer 117 after the S102 step can be placed in a plasma reaction chamber, and then etching reaction gas is introduced into the plasma reaction chamber, and radio frequency power generated by a radio frequency power source is fed between upper and lower electrodes of the plasma reaction chamber to ionize the reaction gas to generate plasma. Commonly used reaction gases include mixed gases such as SF6, CF4, O2 and / or Ar. Different reaction gases can be selected according to the material of the substrate 110, the first nitride layer 113, the second oxide layer 114, the second nitride layer 115 and the third oxide layer 116, and the parameters of the device, so as to obtain the desired etching speed and depth. In the present application, the first grooves A extend from the surface of the third oxide layer 116 to the surface of the first oxide layer 112, as shown in FIG. 1C. Figure 5 The size of the opening of the first groove A can be determined according to the width of the target groove to be obtained. It should be noted that, in combination with the following description, it should be understood that the third groove C in the S105 step is an initially formed groove.

[0028] S104, performing an etching process to form a second groove, and performing end point detection on the etching process, and stopping the etching process after detecting a signal of the second nitride layer 115.

[0029] Specifically, the etching process of this step can be a reactive ion etching (RIE) process. The substrate 110 with the first trench A formed in the step S103 can be put into a plasma reaction chamber, and then etching reaction gas is introduced into the chamber, and radio frequency power generated by a radio frequency power source is fed between the upper and lower electrodes of the chamber to ionize the reaction gas to generate plasma. In the etching process of this step, the plasma mainly acts on the lower part of the first trench A, so that the depth of the first trench A is increased to form a first trench B. This embodiment monitors the etching process in real time, and stops etching as soon as the signal of the second nitride layer 115 is detected. The thickness of the first oxide layer 112 corresponding to the end point of the etching process is the difference between the thicknesses of the first oxide layer 112 and the third oxide layer 116. This embodiment uses the difference between the thicknesses of the first oxide layer 112 and the third oxide layer 116 to indirectly ensure that the thickness of the remaining first oxide layer 112 meets the design requirements. For example, this step monitors the etching rate in the initial etching stage to ensure uniformity, and reduces the etching rate when the etching approaches the second nitride layer 115. At this time, the remaining thickness of the first oxide layer 112 approaches the design value. By monitoring a specific wavelength through plasma emission spectroscopy, the etching is immediately terminated when the signal strength suddenly increases (indicating that the second nitride layer is exposed). Assuming that the initial thickness of the first oxide layer 112 is 500 A, and the thickness of the third oxide layer 116 is 200 A, the difference between the thicknesses of the first oxide layer 112 and the third oxide layer 116 is equal to 300 A. The etching needs to be stopped when the first oxide layer 112 remains 300 A, at which time the second nitride layer is just exposed, and the etching end detection system signal is triggered. Among them, Figure 5 The part outlined by the dashed line in the middle is the remaining first oxide layer 112 after the etching end detection system detects the etching signal of the second nitride layer 115.

[0030] The trench etching method provided by the embodiment comprises sequentially depositing a first oxide layer 112, a first nitride layer 113, a second oxide layer 114, a second nitride layer 115 and a third oxide layer 116 on the metal layer 111, the first oxide layer 112 and the third oxide layer 116 are of the same material, and the thickness of the first oxide layer 112 is greater than that of the third oxide layer 116; coating a photoresist layer 117 on the surface of the third oxide layer 116 and performing exposure and development on the photoresist layer 117 to obtain a patterned photoresist layer 117; performing an etching process to form a first trench A, the first trench A extending from the surface of the third oxide layer 116 to the surface of the first oxide layer 112; performing an etching process to form a second trench B, endpoint detection is performed on the etching process, and the etching process is stopped after the signal of the second nitride layer 115 is detected, and the thickness of the first oxide layer 112 corresponding to the endpoint of the etching process is the difference between the thicknesses of the first oxide layer 112 and the third oxide layer 116. The trench etching method controls the residual thickness of the first oxide layer 112 through the third oxide layer 116 of the top layer, and part of the first oxide layer 112 is reserved in the hard mask etching process, so that the metal layer 111 no longer contacts the fluorine-containing gas, thereby avoiding the problem that the polymer generated by the reaction between the etching gas and the metal layer 111 in the first oxide layer 112 etching process pollutes the etching machine in the metal layer 111 etching process.

[0031] In the above embodiment, referring to Figure 5 , the etching process further comprises the following steps before forming the first trench A extending from the surface of the third oxide layer 116 to the surface of the first oxide layer 112: S105, performing an etching process to form a third trench, the third trench extending from the surface of the third oxide layer to the surface of the first nitride layer.

[0032] Specifically, a dry etching process is used to form a plurality of third trenches C on the substrate 110. Specifically, the substrate 110 with the patterned photoresist layer 117 after the S102 step can be placed in a plasma reaction chamber, and then etching reaction gas is introduced, and radio frequency power generated by a radio frequency power supply is fed between the upper and lower electrodes of the plasma reaction chamber to ionize the reaction gas to generate plasma. Commonly used reaction gases include SF6, CF4, O2 and / or Ar mixed gas, etc. In the embodiment, the third trench C extends from the surface of the third oxide layer 116 to the surface of the first nitride layer 113, as shown in Figure 5 The size of the opening of the third trench C can be determined according to the width of the target trench to be obtained In the above embodiment, before the third oxide layer 116 is coated with a photoresist layer 117, the method further comprises: S106, coating the third oxide layer 116 with an anti-reflective coating 118.

[0033] In semiconductor manufacturing, the core role of coating the oxide layer with an anti-reflective coating 118 (ARC) is to reduce the interference of reflected light on the photoresist layer 117, thereby ensuring pattern accuracy. Reflection of ultraviolet light by the base material (such as the oxide layer) can cause abnormal exposure of the photoresist layer 117, resulting in standing wave effects that cause pattern edges to blur and distort. ARC eliminates reflected light through destructive interference, ensuring uniform exposure of the photoresist layer 117. ARC can fill the small bumps and pits on the surface of the substrate, providing a uniform coating basis for the photoresist layer 117 and reducing the risk of pattern distortion caused by uneven substrate. If the oxide layer is made of high-reflectivity materials such as glass or metal, ARC can also reduce the impact of reflectivity differences on critical dimension uniformity, further ensuring the accuracy of semiconductor chip structures.

[0034] Further, after the etching process is performed to form the second trench B, before endpoint detection of the etching process, the method further comprises: S107, removing the photoresist layer 117 and the anti-reflective coating 118 on the surface of the third oxide layer 116.

[0035] After the circuit pattern on the mask is transferred to the substrate surface to form a protective layer through exposure and development, the area will not be etched in subsequent processes. After removing the ARC and the photoresist layer 117, the etching process can more accurately act on the target oxide layer. The presence of ARC can cause reflection interference, affecting etching uniformity, and the presence of photoresist can hinder the complete removal of the oxide by chemical / physical etching. After both the photoresist layer 117 and the ARC are removed, the third oxide layer 116 is more fully exposed, and etching selectivity and efficiency can be improved.

[0036] Figure 6 For the structure schematic diagram of each step of the trench etching method provided by the embodiment of the present application, please refer to Figure 5 and Figure 6 Further, after the etching process is performed to form the second trench B, after endpoint detection of the etching process, and after the signal of the second nitride layer is detected, the method further comprises: S108, performing an etching process to form a fourth trench D, the fourth trench D penetrating through the first oxide layer 112 and the metal layer 111 remaining during the formation of the second trench B.

[0037] Exemplarily, the metal layer 111 is an aluminum film layer, and the first oxide layer 112 remaining before etching the aluminum film layer is removed by plasma etching. In this embodiment, after the fourth groove D is formed, the isolation material 119 is filled, and then the second oxide layer 114, the second nitride layer 115, and part of the first nitride layer 113 are removed by chemical mechanical polishing to obtain a groove isolation structure.

[0038] It should be understood that the numbering of the above steps S101-S107 is for the convenience of technicians to understand the implementation sequence of the trench etching method, and the implementation can not be performed in the numbered order in actual production, for example, S104 is implemented first and then S103 is implemented. The numbering order of steps S101-S108 in the above embodiment should not be understood as a limitation on the implementation order.

[0039] In the above embodiment, in the method for detecting the etching endpoint of the etching process for forming the second groove B, the etching endpoint detection method mainly includes the following methods: first, optical emission spectroscopy, which detects the etching endpoint by analyzing the spectral changes of the plasma excited substance. This method is suitable for full wafer detection and has low cost, but it needs to rely on a stop layer or different layer structures. Second, optical reflection method, which detects the etching process by detecting the change of reflected light intensity, suitable for detection of different materials and structures. Third, gas analysis method, which monitors the change of active component concentration or product concentration of etching gas to indirectly judge the endpoint. The technician can stop the etching process after detecting the signal of the second nitride layer by using one of the above endpoint detection methods.

[0040] In a specific embodiment, referring to Figure 5 , the thickness of the third oxide layer 116 is 300-400A, and the thickness difference between the first oxide layer 112 and the third oxide layer 116 is 200-300A. In this embodiment, the thickness of the third oxide layer 116 cannot be too thick, and the thickness of the third oxide layer 116 is controlled to be 300-400A, and the thickness difference between the first oxide layer 112 and the third oxide layer 116 is 200-300A. During the etching process for forming the second groove B, the residual amount of the first oxide layer 112 at the etching endpoint is 200-300A, and the etching endpoint can be captured by the film layer change between the first oxide layer 112 and the metal layer 111 during the etching of the metal layer 111. In the etching process, the residual thickness of the first oxide layer 112 at the bottom will directly affect the accuracy of the endpoint detection system. If the residual amount of the first oxide layer 112 is too small (e.g., <200A), the optical signal change relied on by the endpoint detection system will become weak, resulting in that the system cannot clearly identify the etching endpoint.

[0041] In the above embodiment, referring to Figure 5, the thickness of the second nitride layer 115 is greater than 200A, and when endpoint detection is performed on the etching process for forming the second trench B, the endpoint detection system determines the endpoint by monitoring the interface reflection signal (such as light intensity or wavelength change) of the third oxide layer 116 and the second nitride layer 115. If the second nitride layer 115 is too thin, the signal change amplitude is small, and it is easy to be covered by noise, leading to over-etching (damaging the second nitride layer 115).

[0042] In the above embodiments, please refer to Figure 5 The thickness of the first nitride layer 113 is less than 1000A, and the first nitride layer 113 in the embodiment is silicon nitride. Silicon nitride has high tensile stress, and a too thick layer (such as >1000A) is easy to cause substrate warping or film peeling. A thin layer can relieve stress accumulation and improve device reliability. In a step in which silicon nitride needs to be removed (such as STI or gate process), a thin layer can be quickly removed by dry etching (such as CF4 plasma), reducing damage to the underlying material.

[0043] The trench etching method provided by the embodiment of the present application comprises sequentially depositing a first oxide layer, a first nitride layer, a second oxide layer, a second nitride layer and a third oxide layer on a metal layer, the material of the first oxide layer and the third oxide layer is the same, and the thickness of the first oxide layer is greater than the thickness of the third oxide layer; coating a photoresist layer on the surface of the third oxide layer and performing exposure and development on the photoresist layer to obtain a patterned photoresist layer; performing an etching process to form a first trench, the first trench extending from the surface of the third oxide layer to the surface of the first oxide layer; performing an etching process to form a second trench, and stopping the etching process after detecting the signal of the second nitride layer, and the thickness of the first oxide layer corresponding to the endpoint of the etching process is the difference between the thickness of the first oxide layer and the thickness of the third oxide layer. The trench etching method controls the residual thickness of the first oxide layer through the third oxide layer on the top layer, and retains part of the first oxide layer in the hard mask etching process. The metal layer no longer contacts the fluorine-containing gas, avoiding the problem that the polymer generated by the reaction between the etching gas and the metal layer in the first oxide layer etching process pollutes the etching machine table.

[0044] The second aspect of the embodiment provides a trench isolation structure, which is obtained by using the trench etching method described in the above embodiment, and the trench isolation structure is obtained by filling an isolation material in the target trench.

[0045] For example, the trench etching method comprises: sequentially depositing a first oxide layer, a first nitride layer, a second oxide layer, a second nitride layer and a third oxide layer on a metal layer, the material of the first oxide layer and the third oxide layer is the same, and the thickness of the first oxide layer is greater than the thickness of the third oxide layer. coating a photoresist layer on the surface of the third oxide layer and performing exposure and development on the photoresist layer to obtain a patterned photoresist layer; performing an etching process to form a first trench, the first trench extending from the surface of the third oxide layer to the surface of the first oxide layer; performing an etching process to form a second trench, endpoint detection is performed on the etching process, and the etching process is stopped after a signal of the second nitride layer is detected.

[0046] In the process of manufacturing the target trench, the residual thickness of the first oxide layer is controlled by the third oxide layer of the top layer in the trench isolation structure of the embodiment, which improves the problem that the polymer generated by the reaction between the etching gas and the metal layer in the etching process of the first oxide layer contaminates the etching machine in the etching process of the metal layer.

[0047] In the above description, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0048] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the above embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A trench etching method, characterized in that: include: Depositing a first oxide layer, a first nitride layer, a second oxide layer, a second nitride layer, and a third oxide layer in sequence on the metal layer, wherein the first oxide layer and the third oxide layer are made of the same material, and the thickness of the first oxide layer is greater than that of the third oxide layer; coating a photoresist layer on the surface of the third oxide layer and exposing and developing the photoresist layer to obtain a patterned photoresist layer; performing an etching process to form a first trench, wherein the first trench extends from a surface of the third oxide layer to a surface of the first oxide layer; An etching process is performed to form a second trench, and an endpoint detection is performed on the etching process. The etching process is stopped after a signal of the second nitride layer is detected. The thickness of the first oxide layer corresponding to the endpoint of the etching process is the difference between the thicknesses of the first oxide layer and the third oxide layer.

2. The trench etching method according to claim 1, wherein: Performing an etching process to form a first trench, wherein the first trench extends from the surface of the third oxide layer to the surface of the first oxide layer, further comprises: An etching process is performed to form a third trench, where the third trench extends from a surface of the third oxide layer to a surface of the first nitride layer.

3. The trench etching method according to claim 2, wherein Before coating the photoresist layer on the surface of the third oxide layer, the method further includes coating an anti-reflective coating on the surface of the third oxide layer.

4. The trench etching method according to claim 3, wherein: Performing an etching process to form a second trench, and before performing endpoint detection on the etching process, further comprising: The photoresist layer and the anti-reflective coating on the surface of the third oxide layer are removed.

5. The trench etching method according to claim 1, wherein: The method further comprises: performing an etching process to form a second trench, performing endpoint detection on the etching process, and stopping the etching process after detecting a signal of the second nitride layer; An etching process is performed to form a fourth trench, where the fourth trench penetrates the first oxide layer and the metal layer remaining in the second trench formation process.

6. The trench etching method according to any one of claims 1 to 5, characterized in that: The thickness of the third oxide layer is 300-400 Å, and the difference in thickness between the first oxide layer and the third oxide layer is 200-300 Å.

7. The trench etching method according to claim 6, wherein: The thickness of the second nitride layer is greater than 200 Å.

8. The trench etching method according to claim 6, wherein: The thickness of the first nitride layer is less than 1000 Å.

9. The trench etching method according to claim 6, wherein: The etching process is a plasma etching process, and the endpoint detection method includes one of optical emission spectroscopy, optical reflection method, and gas analysis method; The first oxide layer, the second oxide layer, and the third oxide layer are all made of silicon oxide, and the first nitride layer and the second nitride layer are all made of silicon nitride or silicon carbide.

10. A trench isolation structure, characterized in that: A target trench is obtained by adopting the trench etching method according to any one of claims 1 to 9, and an isolation material is filled in the target trench to obtain the trench isolation structure.

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