Semiconductor structure and forming method thereof
By adopting a multi-layer hard mask layer structure and selective etching in semiconductor manufacturing, the problem of inconsistent morphology when heterogeneous films are co-etched into trenches is solved, the continuity and consistency of etching depth and sidewalls are achieved, and device performance is improved.
Patent Information
- Application Number
- CN202510771944.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-10
- Publication Date
- 2025-09-09
AI Technical Summary
In the semiconductor manufacturing process, when etching heterogeneous films and etching trenches together, there are inconsistencies in the etching rates, etching uniformity and sidewall angles of different film qualities, resulting in irregular morphology of the etched trenches, which affects device performance.
A multi-layer hard mask layer structure is adopted, and by selecting the etching selectivity corresponding to different film qualities, the isolation trench filling layer and substrate material are etched successively to ensure the consistency of etching depth and sidewall.
The morphology of the trench is improved, the depth continuity and sidewall consistency at the interface of different materials are ensured, and the performance of the semiconductor device is improved.
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Figure CN120613262A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present application relate to the field of semiconductor manufacturing, and specifically to a semiconductor structure and a method for forming the same. Background Art
[0002] During the semiconductor manufacturing process, trench etching is often necessary due to design and functional requirements. In some semiconductor devices, trench etching may require the simultaneous etching of multiple film types, i.e., co-etching of heterogeneous films. For example, when etching trench structures, it is necessary to simultaneously etch both OX (Silicon Oxide) and SI (Silicon).
[0003] However, since the etching rate, etching uniformity, sidewall angle, etc. of different film qualities are different during dry etching, the morphology formed by etching has defects.
[0004] In this context, how to provide a method for forming a semiconductor structure to improve the morphology of the trenches formed by etching has become an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention
[0005] In view of this, an embodiment of the present application provides a semiconductor structure and a method for forming the same, which can ensure the morphology of the grooves formed when etching different film qualities, that is, ensure that the groove structure has depth continuity and sidewall consistency when crossing the interfaces of different materials, thereby improving the morphology of the grooves.
[0006] To achieve the above objectives, the embodiments of the present application provide the following technical solutions.
[0007] In a first aspect, an embodiment of the present application provides a method for forming a semiconductor structure, comprising:
[0008] Providing a substrate, wherein the substrate is made of a first material;
[0009] forming an isolation trench in the substrate, filling the isolation trench with a second material to form an isolation trench filling layer, and forming a multi-layer hard mask layer on the substrate, wherein the first material is different from the second material, and a material of some layers of the multi-layer hard mask layer is the second material;
[0010] Etching the multi-layer hard mask layer to form an opening, wherein the opening includes a first opening portion exposing a portion of a top surface of the isolation trench filling layer, and a second opening portion exposing a portion of a top surface of the substrate;
[0011] Using a first etching selectivity corresponding to etching the second material, etching the second material from the isolation trench filling layer starting from the exposed portion of the top surface of the isolation trench filling layer through the first opening, wherein the etching depth of the second material is less than the depth of the isolation trench filling layer;
[0012] Using a second etching selectivity corresponding to etching the first material, the substrate is etched from the exposed portion of the top surface of the substrate through the second opening portion, based on the etching depth of the second material of the isolation trench filling layer, to form an initial trench.
[0013] Optionally, also include:
[0014] The remaining second material of the exposed isolation trench filling layer and the exposed substrate are over-etched through the opening, and the etching is continued to reach a target depth to form a target trench.
[0015] Optionally, the first etching selectivity is a ratio of an etching rate of the second material to an etching rate of the first material, and in the first etching selectivity, the etching rate of the second material is greater than the etching rate of the first material;
[0016] The second etching selectivity is a ratio of an etching rate of the first material to an etching rate of the second material, and in the second etching selectivity, the etching rate of the first material is greater than the etching rate of the second material.
[0017] Optionally, the multi-layer hard mask layer includes: a first hard mask layer made of the second material, a second hard mask layer made of the third material above the first hard mask layer, and a third hard mask layer made of the second material above the second hard mask layer;
[0018] The first hard mask layer includes a second material layer covering the surface of the substrate and a second material trench formed in the isolation trench, wherein the second material layer is connected to the second material trench;
[0019] The isolation trench filling layer includes: a second material trench in the isolation trench, and a second material filling layer filled in the second material trench, wherein a height of the second material filling layer is aligned with a height of the second material layer.
[0020] Optionally, forming an isolation trench in the substrate, filling the isolation trench with a second material to form an isolation trench filling layer, and forming a plurality of hard mask layers stacked sequentially on the substrate includes:
[0021] Filling the surface of the substrate and the isolation trench with a second material to form a second material layer covering the surface of the substrate and a second material trench in the isolation trench;
[0022] Continue filling the second material on the second material trench in the isolation trench to form a second material filling layer with the same height as the second material layer;
[0023] forming a second hard mask layer made of a third material on the second material layer and the second material filling layer;
[0024] A third hard mask layer made of the second material is formed on the second hard mask layer.
[0025] Optionally, the etching depth of the second material of the isolation trench filling layer is the same as the depth of the second material filling layer.
[0026] Optionally, the first etching selectivity ratio is greater than or equal to 2, and the second etching selectivity ratio is greater than or equal to 10.
[0027] Optionally, the process of etching the second material includes: a first dry etching process, wherein process parameters of the first dry etching process include: etching gas including one or more of C4F6, C4F8, O2, and one or more of He and Ar, wherein the gas flow rate of C4F6 and / or C4F8 is 15 sccm to 50 sccm, the gas flow rate of O2 is 3 sccm to 20 sccm, and the gas flow rate of He and / or Ar is 50 sccm to 500 sccm;
[0028] The process of etching the first material includes: a second dry etching process, and the process parameters of the second dry etching process include: the etching gas includes one or more of HBr, Cl2, one or more of O2, SF6, CF4, CHF, CH2F2, CH3F, and one or more of He, Ar, wherein the gas flow rate of O2 is 3sccm to 50sccm, and the gas flow rate of He and / or Ar is 50sccm to 500sccm.
[0029] Optionally, the isolation trench has an inverted trapezoidal shape, and a depth of the isolation trench is 1500 angstroms to 4000 angstroms;
[0030] The target groove has a rectangular shape and a depth of 2000 angstroms to 5000 angstroms.
[0031] In a second aspect, an embodiment of the present application provides a semiconductor structure, which is formed based on the method for forming a semiconductor structure as described in the first aspect.
[0032] It can be seen that the method for forming a semiconductor structure provided by an embodiment of the present application includes: providing a substrate, wherein the material of the substrate is a first material; forming an isolation trench in the substrate, filling the isolation trench with a second material to form an isolation trench filling layer, and forming a multi-layer hard mask layer on the substrate, wherein the first material is different from the second material, and the material of some layers of the multi-layer hard mask layer is the second material; etching the multi-layer hard mask layer to form an opening, wherein the opening includes a first opening portion exposing a portion of the top surface of the isolation trench filling layer, and a second opening portion exposing a portion of the top surface of the substrate; using a first etching selectivity corresponding to etching the second material, starting from the exposed portion of the top surface of the isolation trench filling layer through the first opening portion, etching the isolation trench The trench filling layer is etched with a second material, and the etching depth of the second material is less than the depth of the isolation trench filling layer; a second etching selectivity corresponding to the etching of the first material is adopted, and starting from the exposed top surface of the substrate through the second opening portion, the substrate is etched with the first material based on the etching depth of the second material of the isolation trench filling layer to form an initial trench; that is, when etching two different film qualities to form a trench structure, the embodiment of the present application can successively etch the two different materials by respectively adopting different etching selectivities corresponding to etching the two materials, and thus can control the etching depths when etching different materials to remain consistent, that is, ensure that the trench structure has depth continuity and sidewall consistency when crossing the interface of different materials, thereby improving the morphology of the trench. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.
[0034] Figures 1 to 11 It is a structural schematic diagram corresponding to each step in the method for forming a semiconductor structure provided in an embodiment of the present application. DETAILED DESCRIPTION
[0035] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.
[0036] As described in the background technology, during the semiconductor manufacturing process, due to design and functional requirements, in some semiconductor devices, when etching the trench structure, it may be necessary to etch multiple film types at the same time, that is, the situation of co-etching the trench with heterogeneous films, such as the need to etch OX (Silicon Oxide) and SI (Silicon) at the same time. However, since the etching rates, etching uniformity, sidewall angles, etc. of different film types are different in the dry etching process, the grooves formed by etching have defects, such as inconsistent depths and morphologies on both sides of a single trench, resulting in an irregular shape, which in turn affects the performance of the semiconductor device.
[0037] In view of this, an embodiment of the present application provides a method for forming a semiconductor structure, which can ensure the morphology of the groove formed when etching different film qualities, that is, ensure that the groove structure has depth continuity and sidewall consistency when crossing the interface of different materials, thereby improving the morphology of the groove. The method for forming a semiconductor structure includes: providing a substrate, wherein the material of the substrate is a first material; forming an isolation trench in the substrate, filling the isolation trench with a second material to form an isolation trench filling layer, and forming a multi-layer hard mask layer on the substrate, wherein the first material is different from the second material, and the material of some layers of the multi-layer hard mask layer is the second material; etching the multi-layer hard mask layer to form an opening, wherein the opening includes a first opening portion exposing a portion of the top surface of the isolation trench filling layer, and a second opening portion exposing a portion of the top surface of the substrate; using a first etching selectivity corresponding to etching the second material, starting from the exposed portion of the top surface of the isolation trench filling layer through the first opening portion, etching the isolation trench filling layer with the second material, the etching depth of the second material being less than the depth of the isolation trench filling layer; using a second etching selectivity corresponding to etching the first material, starting from the exposed portion of the top surface of the substrate through the second opening portion, etching the substrate with the first material based on the etching depth of the second material of the isolation trench filling layer to form an initial trench.
[0038] The following describes in detail the method for forming a semiconductor structure provided by the embodiment of the present application with reference to the accompanying drawings. Figures 1 to 11 It is a structural schematic diagram corresponding to each step in a method for forming a semiconductor structure provided in an embodiment of the present application.
[0039] Reference Figure 1 , providing a substrate 100.
[0040] In the embodiment of the present application, the material of the substrate 100 is a first material, and the first material can be silicon, that is, the substrate in the embodiment of the present application can be a silicon substrate. In other embodiments, the substrate 100 can also be a germanium silicon substrate, a III-V group element compound substrate, a silicon carbide substrate or a stacked structure thereof, or other semiconductor material substrates known to those skilled in the art, and the present invention does not make specific limitations on this.
[0041] refer to Figure 2 , an isolation trench 200 is formed in the substrate 100 .
[0042] In an embodiment of the present application, an isolation trench etched in AA (Active Area) can be used to isolate adjacent devices (such as the source / drain region of a transistor), and the process for forming the isolation trench can be an etching process, wherein the etching process can be a dry etching process, a wet etching process, or a combination of dry etching and wet etching processes.
[0043] The shape, depth and number of the isolation trenches 200 can be adjusted according to specific process requirements.
[0044] In an optional embodiment, if Figure 2 As shown, the isolation trench may have an inverted trapezoidal shape. The design of the inverted trapezoidal inclined sidewalls can avoid mechanical stress problems, optimize stress distribution, and facilitate uniform filling of the subsequent isolation trench filling layer to prevent void formation.
[0045] In an optional embodiment, the depth of the isolation trench 200 may be 1500 angstroms to 4000 angstroms.
[0046] Reference Figures 3 to 5 , filling the isolation trench 200 with a second material to form an isolation trench filling layer, and forming a multi-layer hard mask layer on the substrate, wherein the first material is different from the second material, and the material of some layers of the multi-layer hard mask layer is the second material.
[0047] During the subsequent multiple etching processes, the multi-layer hard mask layer can be used to achieve pattern conversion and alignment, maintaining the accuracy of the pattern and alignment; and can also protect the underlying substrate to prevent it from being over-etched.
[0048] In the embodiment of the present application, the first material may be silicon Si, and the second material may be silicon oxide OX.
[0049] The multi-layer hard mask layer includes: a first hard mask layer made of the second material OX, a second hard mask layer made of the third material above the first hard mask layer, and a third hard mask layer made of the second material OX above the second hard mask layer.
[0050] Among them, in an embodiment of the present application, the third material can be silicon nitride SiN, that is, the multi-layer hard mask layer in the present application can be a silicon oxide-silicon nitride-silicon oxide (ONO) structure. Using the ONO structure as the hard mask layer can further ensure that the subsequent photoresist pattern can be accurately transferred to the lower layer.
[0051] Furthermore, in an embodiment of the present application, the first hard mask layer may include a second material layer covering the surface of the substrate, and a second material trench formed within the isolation trench, wherein the second material layer is connected to the second material trench. The isolation trench filling layer may include a second material trench within the isolation trench, and a second material filling layer filling the second material trench, wherein the height of the second material filling layer is aligned with the height of the first hard mask layer.
[0052] In an embodiment of the present application, the steps of filling the isolation trench 200 with a second material to form an isolation trench filling layer, and forming a multi-layer hard mask layer on the substrate may include the following.
[0053] Reference Figure 3 The second material OX is filled on the surface of the substrate 100 and in the isolation trench 200 to form a second material layer 101 covering the surface of the substrate 100 and a second material trench 202 in the isolation trench 200 .
[0054] The second material layer 101 and the second material trench 202 are connected to form the first hard mask layer 300 , and the first hard mask layer 300 conformally covers the isolation trench 200 .
[0055] In the embodiment of the present application, the process of forming the first hard mask layer can be a chemical vapor deposition (CVD) process. The deposited first hard mask layer 300 can evenly cover the surface of the substrate 100 and the isolation trench 200, maintaining consistency in thickness in each region.
[0056] Reference Figure 4 , the second material trench 202 in the isolation trench is continuously filled with the second material OX to form a second material filling layer 404 whose height is flush with the second material layer 101 .
[0057] The second material trench 202 in the isolation trench and the second material filling layer 404 filled in the second material trench constitute the isolation trench filling layer 400 . The height of the second material filling layer 404 is aligned with the height of the second material layer 101 .
[0058] In the embodiment of the present application, the second material filling layer 404 and the first hard mask layer 300 are both made of the second material silicon oxide OX. OX serves as an insulating medium to isolate adjacent structures (eg, to prevent leakage current) and provide insulation protection.
[0059] Reference Figure 5 A second hard mask layer 501 made of the third material is formed on the second material layer 101 and the second material filling layer 404 ; and a third hard mask layer 502 made of the second material is formed on the second hard mask layer 501 to form a multi-layer hard mask layer.
[0060] In an embodiment of the present application, the first hard mask layer 300 is a second material, silicon oxide OX, the second hard mask layer 501 is a third material, silicon nitride SiN, and the third hard mask layer 502 is a second material, silicon oxide OX. That is, the multi-layer hard mask layer in the present application can be a silicon oxide-silicon nitride-silicon oxide (ONO) structure. Using the ONO structure as the hard mask layer can further ensure that the subsequent photoresist pattern can be accurately transferred to the lower layer.
[0061] After the deposition of multiple hard mask layers is completed, an etching process may be started to form target trenches.
[0062] First, the multi-layer hard mask layer is etched to form an opening, wherein the opening exposes a first opening portion that exposes a portion of the top surface of the isolation trench filling layer, and a second opening portion that exposes a portion of the top surface of the substrate.
[0063] For details, please refer to Figure 6 After forming the multi-layer hard mask layer, a patterned photoresist layer 600 is formed on the multi-layer hard mask layer.
[0064] In the embodiment of the present application, a photoresist (PR) may be used as a mask to etch the multi-layer hard mask layer below the photoresist layer, namely, an ONO structure.
[0065] Reference Figure 7 Using the patterned photoresist layer 600 as a mask, the multi-layer hard mask layer is etched to form an opening, wherein the opening includes a first opening portion K1 exposing a portion of the top surface of the isolation trench filling layer, and a second opening portion K2 exposing a portion of the top surface of the substrate 100.
[0066] In an embodiment of the present application, the first opening portion K1 exposes a portion of the top surface of the isolation trench filling layer, and the isolation trench filling layer is made of the second material OX, that is, the first opening portion K1 exposes the second material OX; the second opening portion K2 exposes a portion of the top surface of the substrate, and the substrate is made of the first material Si, that is, the second opening portion K2 exposes the first material Si; therefore, in the process of etching the trench structure, it is necessary to etch two different film qualities, OX and Si, at the same time. Since the etching rates, etching uniformities, sidewall angles, etc. of different film qualities are different in the etching process, the trench structure formed by etching may have inconsistent depths and morphologies on both sides, and may be irregular in shape, which may affect the performance of the semiconductor device.
[0067] To solve the above problems, the embodiment of the present application can etch two types of films by separately selecting gases with relatively high selectivity for the two types of films, thereby achieving separate etching of the two types of films in sequence to ensure that the depth and angle of the two sides of the etched grooves remain consistent, thereby improving the morphology of the grooves.
[0068] The etching process of the two film types will be described in detail below with reference to the accompanying drawings.
[0069] First, a portion of the top surface of the exposed isolation trench filling layer is etched, that is, the OX film is etched first.
[0070] For details, please refer to Figure 8 , continue to use the photoresist layer 600 as a mask, adopt the first etching selection ratio corresponding to etching the second material OX, through the first opening portion K1, start from the exposed portion of the top surface of the isolation trench filling layer, and etch the second material of the isolation trench filling layer. The etching depth of the second material is less than the depth of the isolation trench filling layer.
[0071] In the process of etching the isolation trench filling layer, a certain thickness of OX needs to be retained to protect part of the substrate below OX, so as to prevent the substrate below the first opening part K1 (i.e., the substrate below the second material groove 202) from being over-etched when the part of the substrate exposed by the second opening part K2 is subsequently etched, resulting in inconsistent trench depth.
[0072] In an optional embodiment, the etching depth of the second material of the isolation trench filling layer may be the depth of the second material filling layer 404. That is, during the etching of the isolation trench filling layer, the second material filling layer 404 may be etched away along the first opening portion K1, leaving the second material trench 202 below the second material filling layer 404. That is, the retained area OX of a certain thickness may be the portion of the second material trench 202 exposed by the first opening portion K1.
[0073] Furthermore, to ensure that in the etching step, only the isolation trench filling layer made of the second material is etched without affecting part of the substrate made of the first material, etching can be performed using a first etching selectivity ratio corresponding to etching the second material.
[0074] In an embodiment of the present application, the first etching selectivity is the ratio of the etching rate of the second material to the etching rate of the first material, and the etching rate of the second material in the first etching selectivity is greater than the etching rate of the first material; therefore, in the process of etching the second material, the first etching selectivity, that is, a gas with a high OX / Si selectivity ratio can be selected for etching, which tends to remove the second material with a higher etching rate, thereby avoiding etching of the first material.
[0075] In an optional embodiment, the first etching selectivity ratio may be greater than or equal to 2.
[0076] In an embodiment of the present application, the process of etching the second material may include: a first dry etching process, the process parameters of the first dry etching process include: the etching gas includes one or more of C4F6, C4F8, O2, and one or more of He, Ar, wherein the gas flow rate of C4F6 and / or C4F8 is 15sccm to 50sccm, the gas flow rate of O2 is 3sccm to 20sccm, and the gas flow rate of He and / or Ar is 50sccm to 500sccm.
[0077] Further, refer to Figure 9 After removing the portion of the isolation trench filling layer exposed by the first opening portion K1 , the photoresist layer 600 is removed.
[0078] After removing the photoresist layer, the third hard mask layer 502 may be used as a mask to etch the exposed portion of the substrate, that is, the first material may be etched first.
[0079] For details, please refer to Figure 9 and 10 , using a second etching selectivity corresponding to etching the first material, starting from the exposed top surface of the substrate through the second opening portion K2, the substrate is etched of the first material based on the etching depth of the second material of the isolation trench filling layer to form an initial trench.
[0080] After removing the portion of the isolation trench filling layer, the portion of the substrate exposed by the second opening portion is etched. To ensure that in this etching step, only the portion of the substrate of the second material exposed by the second opening portion is etched, and the portion of the substrate below the second material trench is not affected, the second etching selectivity corresponding to etching the first material can be used for etching.
[0081] In the embodiment of the present application, the second etch selectivity is the ratio of the etching rate of the first material to the etching rate of the second material, and in the second etch selectivity, the etching rate of the first material is greater than the etching rate of the second material. Therefore, when etching the first material, the second etch selectivity, i.e., a gas with a high Si / OX selectivity, can be selected for etching, which tends to remove the first material with a higher etching rate, thereby avoiding etching the second material.
[0082] In an optional embodiment, the second etching selectivity ratio may be greater than or equal to 10.
[0083] In an embodiment of the present application, the process of etching the first material may include: a second dry etching process, and the process parameters of the second dry etching process include: the etching gas includes one or more of HBr, Cl2, one or more of O2, SF6, CF4, CHF, CH2F2, CH3F, and one or more of He, Ar, wherein the gas flow rate of O2 is 3sccm to 50sccm, and the gas flow rate of He and / or Ar is 50sccm to 500sccm.
[0084] Among them, in the process of etching the first material, it is necessary to etch the first material of the substrate based on the etching depth of the second material of the isolation trench filling layer, so as to ensure that the depth and angle of both sides of the initial trench formed after etching the two materials are consistent, so as to improve the morphology of the trench structure.
[0085] Further, refer to Figure 10 and Figure 11 , continue etching along the opening, over-etch the remaining second material of the exposed isolation trench filling layer and the exposed substrate through the opening, and continue etching to reach the target depth to form a target trench 1100.
[0086] During the etching process, a certain amount of over-etching needs to be ensured to ensure that the remaining second material and the first material are completely removed to form a target trench of a desired depth.
[0087] In an optional embodiment, the target trench may have a rectangular shape, and a depth of the target trench is 2000 angstroms to 5000 angstroms.
[0088] It can be seen that the method for forming a semiconductor structure provided by an embodiment of the present application includes: providing a substrate, wherein the material of the substrate is a first material; forming an isolation trench in the substrate, filling the isolation trench with a second material to form an isolation trench filling layer, and forming a multi-layer hard mask layer on the substrate, wherein the first material is different from the second material, and the material of some layers of the multi-layer hard mask layer is the second material; etching the multi-layer hard mask layer to form an opening, wherein the opening includes a first opening portion exposing a portion of the top surface of the isolation trench filling layer, and a second opening portion exposing a portion of the top surface of the substrate; using a first etching selectivity corresponding to etching the second material, starting from the exposed portion of the top surface of the isolation trench filling layer through the first opening portion, etching the isolation trench The trench filling layer is etched with a second material, and the etching depth of the second material is less than the depth of the isolation trench filling layer; a second etching selectivity corresponding to the etching of the first material is adopted, and starting from the exposed top surface of the substrate through the second opening portion, the substrate is etched with the first material based on the etching depth of the second material of the isolation trench filling layer to form an initial trench; that is, when etching two different film qualities to form a trench structure, the embodiment of the present application can successively etch the two different materials by respectively adopting different etching selectivities corresponding to etching the two materials, and thus can control the etching depths when etching different materials to remain consistent, that is, ensure that the trench structure has depth continuity and sidewall consistency when crossing the interface of different materials, thereby improving the morphology of the trench.
[0089] Correspondingly, an embodiment of the present application further provides a semiconductor structure, which is formed based on the method for forming a semiconductor structure as described in the above embodiment.
[0090] The above describes multiple embodiment schemes provided by the embodiments of the present application. The various optional methods introduced in each embodiment scheme can be combined and cross-referenced with each other without conflict, thereby extending a variety of possible embodiment schemes, which can all be considered as embodiment schemes disclosed and open in the embodiments of the present application.
[0091] Although the embodiments of the present application are disclosed above, the present application is not limited thereto. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims.
Claims
1. A method for forming a semiconductor structure, characterized in that: include: Providing a substrate, wherein the substrate is made of a first material; forming an isolation trench in the substrate, filling the isolation trench with a second material to form an isolation trench filling layer, and forming a multi-layer hard mask layer on the substrate, wherein the first material is different from the second material, and a material of some layers of the multi-layer hard mask layer is the second material; Etching the multi-layer hard mask layer to form an opening, wherein the opening includes a first opening portion exposing a portion of a top surface of the isolation trench filling layer, and a second opening portion exposing a portion of a top surface of the substrate; Using a first etching selectivity corresponding to etching the second material, etching the second material from the isolation trench filling layer starting from the exposed portion of the top surface of the isolation trench filling layer through the first opening, wherein the etching depth of the second material is less than the depth of the isolation trench filling layer; Using a second etching selectivity corresponding to etching the first material, the substrate is etched from the exposed portion of the top surface of the substrate through the second opening portion, based on the etching depth of the second material of the isolation trench filling layer, to form an initial trench.
2. The method for forming a semiconductor structure according to claim 1, wherein: Also includes: The remaining second material of the exposed isolation trench filling layer and the exposed substrate are over-etched through the opening, and the etching is continued to reach a target depth to form a target trench.
3. The method for forming a semiconductor structure according to claim 1, wherein: The first etching selectivity is a ratio of an etching rate of the second material to an etching rate of the first material, and in the first etching selectivity, the etching rate of the second material is greater than the etching rate of the first material; The second etching selectivity is a ratio of an etching rate of the first material to an etching rate of the second material, and in the second etching selectivity, the etching rate of the first material is greater than the etching rate of the second material.
4. The method for forming a semiconductor structure according to claim 1, wherein: The multi-layer hard mask layer includes: a first hard mask layer made of the second material, a second hard mask layer made of the third material above the first hard mask layer, and a third hard mask layer made of the second material above the second hard mask layer; The first hard mask layer includes a second material layer covering the surface of the substrate and a second material trench formed in the isolation trench, wherein the second material layer is connected to the second material trench; The isolation trench filling layer includes: a second material trench in the isolation trench, and a second material filling layer filled in the second material trench, wherein a height of the second material filling layer is aligned with a height of the second material layer.
5. The method for forming a semiconductor structure according to claim 4, wherein: The steps of forming an isolation trench in the substrate, filling the isolation trench with a second material to form an isolation trench filling layer, and forming a plurality of hard mask layers stacked sequentially on the substrate include: Filling the surface of the substrate and the isolation trench with a second material to form a second material layer covering the surface of the substrate and a second material trench in the isolation trench; Continue filling the second material on the second material trench in the isolation trench to form a second material filling layer with the same height as the second material layer; forming a second hard mask layer made of a third material on the second material layer and the second material filling layer; A third hard mask layer made of the second material is formed on the second hard mask layer.
6. The method for forming a semiconductor structure according to claim 5, wherein: The etching depth of the second material of the isolation trench filling layer is equal to the depth of the second material filling layer.
7. The method for forming a semiconductor structure according to claim 3, wherein: The first etching selectivity ratio is greater than or equal to 2, and the second etching selectivity ratio is greater than or equal to 10.
8. The method for forming a semiconductor structure according to claim 7, wherein: The process of etching the second material includes: a first dry etching process, wherein the process parameters of the first dry etching process include: etching gas including one or more of C4F6, C4F8, O2, and one or more of He and Ar, wherein the gas flow rate of C4F6 and / or C4F8 is 15 sccm to 50 sccm, the gas flow rate of O2 is 3 sccm to 20 sccm, and the gas flow rate of He and / or Ar is 50 sccm to 500 sccm; The process of etching the first material includes: a second dry etching process, and the process parameters of the second dry etching process include: the etching gas includes one or more of HBr, Cl2, one or more of O2, SF6, CF4, CHF, CH2F2, CH3F, and one or more of He, Ar, wherein the gas flow rate of O2 is 3sccm to 50sccm, and the gas flow rate of He and / or Ar is 50sccm to 500sccm.
9. The method for forming a semiconductor structure according to claim 2, wherein: The isolation trench has an inverted trapezoidal shape and a depth of 1500 angstroms to 4000 angstroms; The target groove has a rectangular shape and a depth of 2000 angstroms to 5000 angstroms.
10. A semiconductor structure, characterized in that The semiconductor structure is formed based on the method for forming a semiconductor structure according to any one of claims 1 to 9.